NOTICES

OF THK

PROCEEDINGS

AT THE

MEETINGS OF THE MEMBERS

OF THE

3^o^al institution of (^reat 3Srttain,

WITH

ABSTRACTS OF THE DISCOURSES

DELIVERED AT

THE EVENING MEETINGS.

VOLUME XL

1884—1886.

LONDON:

PBINTED BY WILLIAM CLOWES AND SONS, LIMITED,

STAMFOKD STREET AND CHARING CROSS.

1887.

patron.

HER MOST GRACIOUS MAJESTY

QUEEN VICTOKIA.

HIS ROYAL HIGHNESS

THE PKINCE OF WALES, E.G. F.K.S.

President — The Duke of Northumberland, E.G. D.C.L. LL.D.

Treasurer — Henry Pollock, Esq. — V.P.

Honorarij Secretary — Sir Frederick Bramwell, D.G.L. F.R.S.— 7.P.

Managers. 1886-87.

F.R.S.

LL.D.

M.D.

M.A.

M.A.

Sir Frederick Abel, C.B. D.C.L,

— V.P,
Sir William Bowman, Bart,

F.R.S.— F.P.
Joseph Brown, Esq. Q.C.
Sir James Crichton Browne,

LL.D. F.R.S.
William Crookes, Esq. F.R.S.
Henry Doulton, Esq.
Sir William Witliey Gull, Bart, M.D.

D.C.L. F.R.S.
Right Hon. The Lord Hal sbury.— F.P.
William Huggins, Esq. D.C.L. LL.D.

F.R.S.— F.P.
Alfred Brav Kempe, Esq. M.A. F.R.S.
Sir John Lubbock, Bart. M.P. D.C.L.

LL.D. F.R.S.— F.P.
Hugo W. MuUer, Esq. Ph.D. F.R.S.
Sir Frederick Pollock, Bart.

V.P.
John Rae, M.D. LL.D. F.R.S.
Lord Arthur Russsell.

professors.

Professor of Natural Philosophy— J OR^ Tyndall, Esq. D.C.L. LL.D. F.R.S. &c.
Fuller ian Professor of Chemistry— James Dewar, Esq. M.A. F.R.S. Jacksonian

Professor of Natural Experimental Philosophy, Univ. Cambridge.
FuUerian Professor of Physiology— Artrvr Gamgee, M.D. F.R.S.

Visitors. 1886-87.

Shelford Bidwell, Esq. M.A. F.R.S.
Stephen Busk, Esq.
Michael Carteighe, Esq. F.C.S.
Arthur Herbert Church, Esq.

F.C.S.
Vicat Cole, Esq. R.A.
William Henry Domville, Esq.
James Edmunds, M.D. F.C.S.
Charles Hawksley, Esq. M.I.C.E.
Alfred G utter esHenriques, Esq. F.G.S.
David Edward Hughes, Esq. F.R.S.
George Matthey, Esq. F.R.S.
John W. Miers, Esq.
Lachlan Mackintosh Rate, Esq. M.A.
William Chandler Roberts- Austen, Esq.

F.R.S.
Alexander Siemens, Esq.

Keeper of the Library and Assistant Secretary— Mr. Benjamin Vincent.

Assistant in the Library— Mr. Henry Young.

Clerk of Accounts and Collector— Mr. Henry C. Hughes.

Assistant in the Chemical Laboratory— Mr. R, N. Lennox.

CONTENTS.

1884.

Page
Feb. 8. — George J. Eomanes, Esq. — The Darwinian Theory

of Instinct .. .. .. .. - .. 131

,j 29. — Professor D. E. Hughes. — Theory of Magnetism 1

March 3.— General Monthly Meeting 11

„ 7. — C. Vernon Boys, Esq. — Bicycles and Tricycles in

Theory and Practice .. .. .. .. 13

„ 14. — J. N. Langley, Esq. — The Physiological Aspect of

Mesmerism .. .. .. .. ..25

„ 21. — Matthew Arnold, Esq. — 'Emerson (no Abstract) .. 43

„ 28. — Professor Osborne Eeynolds. — The Two Manners

of Motion of Water .. 44

April 4. — Professor T. G. Bonney. — The Building of the

Alps 53

„ 7. — General Monthly Meeting .. .. .. .. 68

„ 25.— Walter Besant, Esq. — The Art of Fiction .. 70

May 1. — Annual Meeting ,. ., ., .. .. 84

„ 2. — Professor J. W. JuDD. — Krakatoa.. .. .. 85

„ 5. — General Monthly Meeting ., .. ,. .. 88
„ 9. — Professor W. Robertson Smith. — Mohammedan

Mahdis .. 147

40142

iv CONTENTS.

1884. Page

May 16. — Professor W. Odling. — The Dissolved Oxygen of

Water (no Abstract) .. .. .. ,. 90

„ 23. — David Gill, Esq. — Eecent Researches on the
Distances of the Fixed Stars, and Some Future
Problems in Sidereal Astronomy .. .. 91

„ 30. — Monsieur E. Mascart. — Sur Les Couleurs. (In

French.) 107

June 2.— General Monthly Meeting .. .. .. ..116

^^ 6. — WiLLOUGHBY Smith, Esq. — Volta - Electric and

Magneto-Electric Induction .. . .. 119

„ 13. — (Extra Evening.) — Professor Dewar. — Researches

on Liquefied Gases .. .. .. ..148

July 7.— General Monthly Meeting 153

Nov. 3.— General Monthly Meeting 155

Dec. 1.— General Monthly Meeting 159

1885.

Jan. 16. — Professor Tyndall. — On Living Contagia .. 161

„ 23. — Professor H. N. Moselet. — The Fauna of the Sea-
shore .. .. .. .. .. .. 168

„ 30. — Professor Ernst Pauer. — A short review of the

works of Living Composers for the Pianoforte ., 171

Feb. 2.— General Monthly Meeting 175

„ 6. — G. Johnstone Stoney, Esq. — How Thought presents

itself in Nature 178

„ 13. — Sir John Lubbock, Bart. M.P. — The Forms of

Leaves .. .. .. .. .. .. 197

„ 20. — William Huggins, Esq. — The Solar Corona ., 202

„ 27. — Professor E. Eay Lankester. — A Marine Bio-
logical Laboratory .. .. .. .. 215

CONTENTS. V

1885. Page

March 2.— General Monthly Meeting 216

„ 6. — Charles T. Newton, C.B. — The German Dis-
coveries at Pergamus (wo J.6s^mc<) .. .. 217

„ 13. — Sir Frederick Abel, C.B. — Accidental Explosions

produced by non-explosive Liquids ,. .. 218

„ 20. — Professor A. W. Kucker. — Liquid Films . . . . 243

„ 27. — Victor Horsley, Esq. — The Motor Centres of the

Brain, and the Mechanism of the Will .. .. 250

Ajml 6.— General Monthly Meeting 263

„ 17. — Professor S. P. Langley. — Sunlight and the

Earth's Atmosphere. .. .. .. .. 265

„ 24. — William Carruthers, Esq. — British Fossil Cycads

and their relation to Living Forms (no Abstract) 283

May 1.— Annual Meeting 283

„ 1. — The Eight Hon. Lord Eayleigh. — Water Jets and

Water Drops (»iO ^&s/mc/) .. .. .. 284

„ 4.— General Monthly Meeting 285

„ 8. — W. F. K. Weldon, Esq. — On Adaptation to Sur-
roundings as a Factor in Animal Development
(no Abstract) 287

„ 15. — Professor Burdon Sanderson. — Cholera : its Cause

and Prevention .. .. .. .. .. 288

„ 22. — Walter H. Pollock, Esq. — Garrick as an Actor.. 304

„ 29. — J. J. Coleman, Esq. and Professor J. G.
McKendrick. — The Mechanical Production of
Cold, and the Effects of Cold on Microphytes .. 305

June 1.— General Monthly Meeting 317

„ 5. — Professor Dewar. — Liquid Air and the Zero of

absolute Temperature (no J.&sirac^) .. .. 318

July 6.— General Monthly Meeting 319

Nov. 2.— General Monthly Meeting 321

VI CONTENTS.

1885. Page

Dec. 7.— General Monthly Meeting 325

„ 29. — Notes on Professor Dewar's Lectures on the

et seq. Story of a Meteorite .. .. .. .. 328

1886. ,

Jan. 22. — Professor Ttndall. — Thomas Young .. .. 553

„ 29. — Sir William Thomson. — Capillary Attraction ,. 483

Feb. 5. — T. Pridgin Teale, Esq. — The Principles of

Domestic Fire-place Construction .. .. 338

„ 12. — Professor Osborne Eeynolds. — Experiments show-
ing Dilatancy, a property of Granular Material,
possibly connected with Gravitation .. .. 354

„ 19. — Professor W. H. Flower.— The Wings of Birds .. 364

„ 26. — A. A. Common, Esq. — Photography as an Aid to

Astronomy .. ,. .. .. .. 367

March 1.— General Monthly Meeting 376

„ 5. — Professor Alexander Macalister. — Anatomical

and Medical Knowledge of Ancient Egypt .. 378

„ 12. — Keginald Stuart Poole, Esq. — The Discovery of

the Biblical Cities of Egypt 384

^^ 19.— W. H. M. Christie, Esq.— Universal Time .. 387

„ 26. — W. Chandler Eoberts-Austen, Esq. — On Certain

Properties common to Fluids and Solid Metals .. 395

April 2. — Howard Grubb, Esq. — Telescopic Objectives and

Mirrors: their Preparation and Testing ,. 413

„ 5.— General Monthly Meeting 433

^^ 9. — William Anderson, Esq. — New Applications of

the Mechanical Properties of Cork to the Arts .. 436

„ 16. — Professor Sir Henry E. Roscoe, M.P. — Recent

Progress in the Coal Tar Industries .. .. 450

CONTENTS. VU

1886. Page

May 1. — Annual Meeting .. .. .. .. .. 467

„ 3.— General Monthly Meeting .. 468

„ 7. — Frederick Siemens, Esq. — Dissociation Tempera-
tures .. .. .. .. .. .. 471

„ 14. — Professor John Millar Thomson. — Suspended

Crystallisation .. .. .. .. ..508

„ 21. — Sir John Lubbock, Bart. M.P. — The Forms of

Seedlings: the causes to which they are due .. 517

,5 28. — Professor Oliver Lodge. — Electrical Deposition

of Dust and Smoke ... .. .. .. 520

June 4. — Walter H. Gaskell, M.D. — The Sympathetic

Nervous System .. .. .. .. .. 530

„ 7.— General Monthly Meeting .. 538

„ 11. — Professor Dewab. — Recent Eesearches on Meteorites 541

July 5. — General Monthly Meeting 589

Nov. 1. — General Monthly Meeting 591

Dec. 6. — General Monthly Meeting .. .. ,. ..594

Index to Volume XI 597

( viii )

PLATES

Page
Distribution of Solar Energy 279

On Dissociation Temperatures .. .. .. .. 475, 481

Apparatus for Solidifying Oxygen .. .. .. .. 550

l^ogal Jn^titution of OSreat IS

WEEKLY EVENING MEETING
Friday, February 29, 1884.

SiE William Bowman, Bart. LL.D. F.E.S. Honorary Secretary and
Vice-President, in the Chair.

Professor D. E. Hughes, F.E.S. M.B.I.

Theory of Magnetism.

The theory of magnetism, which I propose demonstrating this evening,
may be termed the mechanical theory of magnetism, and, like the
now well-established mechanical theory of heat, replaces the assumed
magnetic fluids and elementary electric currents by a simple, sym-
metrical, mechanical motion of the molecules of matter and ether.

That magnetism is of a molecular nature has long been accepted,
for it is evident that, no matter how much we divide a magnet, we
still have its two poles in each separate portion, consequently we can
easily imagine this division carried so far that we should at last
arrive at the molecule itself possessing its two distinctive poles, con-
sequently all theories of magnetism attempt some explanation of the
cause of this molecular polarity, and the reason for apparent neutrality
in a mass of iron.

Coulomb and Poisson assume that each molecule is a sphere
containing two distinct magnetic fluids, which in the state of neutrality
are mixed together, but when polarised are separated from each other
at opposite sides ; and, in order to explain why these fluids are kept
apart as in a permanent magnet, they had to assume, again, that each
molecule contained a peculiar coercive force, whose functions were to
prevent any change or mixing of these fluids when separated.

There is not one experimental evidence to prove the truth of this
assumption ; and as regards coercive force, we have direct experi-
mental proof opposing this view, as we know that molecular rigidity
or hardness, as in tempered steel, and molecular freedom or softness,
as in soft iron, fulfil all the conditions of this assumed coercive force.
Ampere's theory, based upon the analogy of electric currents,
supposes elementary currents flowing around each molecule, and that
in the neutral state these molecules are arranged hap-hazard in all
directions, but that magnetisation consists in arranging them sym-
metrically.

The objections to Ampere's theory are numerous. 1st. We have

no knowledge or experimental proof of any elementary electric

currents continually flowing without any expenditure of energy.

2nd. If we admit the assumption of electric currents around each

Vol. XI. (No. 78.) b

2 Professor D. E. Hughes [Feb. 29,

molecule, tlie molecule itself would then be electro-magnetic, and the
question still remains. What is polarity ? Have the supposed electric
currents separated the two assumed magnetic fluids contained in the
molecule, as in Poisson's theory ? or are the electric currents them-
selves magnetic, independent of the iron molecule ?

In order to produce the supposed heterogeneous arrangement of
neutrality, Ampere's currents would have either to change their
position upon the molecule, and have no fixed axis of rotation, or else
the molecule, with its currents and polarities, would rotate, and thus
be acting in accordance with the theory of De la Kive. 3rd. This
theory does not explain why (as in the case of soft iron) polarity
should disappear whenever the exciting cause is removed, as in the
case of transient magnetisation. It would thus require a coercive force
in iron to cause exactly one-half of the molecules to instantly reverse
their direction, in order to pass from apparent external polarity to
that of neutrality.

The influence of mechanical vibrations and stress upon iron in
facilitating or discharging its magnetism, as proved by Matteucci,
1847, in addition to the discovery by Page, 1837, of a molecular
movement taking place in iron during its magnetisation, producing
audible sounds, and the discovery by Dr. Joule, 1842, of the elonga-
tion of iron when magnetised, followed by the discoveries of
Guillemin, that an iron bar bent by a weight at its extremity would
become straight when magnetised ; also that magnetism would tend to
take off twists or mechanical strains of all kinds — together with the
researches of Matteucci, Marianini, De la Rive, Sir W. Grove, Faraday,
Weber, Wiedemann, Du Moncel, and a host of experimenters, in-
cluding numerous published researches by myself — all tend to show
that a mechanical action takes place whenever a bar of iron is
magnetised, and that the combined researches demonstrate that the
movement is that of molecular rotation.

De la Rive was the first to perceive this, and his theory, like those
of Weber, Wiedemann, Maxwell, and others, is based upon molecular
rotation. Their theories, however, were made upon insufficient data,
and have proved to be wrong as to the assumed state of neutrality,
and right only where the experimental data clearly demonstrated
rotation.

I believe that a true theory of magnetism should admit of
complete demonstration, that it should present no anomalies, and that
all the known effects should at once be exj^lained by it.

From numerous researches I have gradually formed a theory of
magnetism entirely based upon experimental results, and these have
led me to the following conclusions : —

1. That each molecule of a piece of iron, as well as the atoms of
all matter, solid, liquid, gaseous, and the ether itself, is a separate and
independent magnet, having its two poles and distribution of magnetic
polarity exactly the same as its total evident magnetism when noticed
upon a steel bar-magnet.

1884.] on the Theory of Magnetism. 3

2. That each molecule can be rotated in either direction upon its
axis by torsion, stress, or by physical forces such as magnetism and
electricity.

3. That the inherent polarity or magnetism of each molecule is a
constant quantity like gravity ; that it can neither be augmented nor
destroyed.

4. That when we have external neutrality, or no apparent mag-
netism, the molecules arrange themselves so as to satisfy their mutual
attraction by the shortest path, and thus form a complete closed
circuit of attraction.

5. That when magnetism becomes evident, the molecules and
their polarities have all rotated symmetrically, producing a north
pole if rotated in a given direction, or a south pole if rotated in the
opposite direction. Also, that in evident magnetism we have still
a symmetrical arrangement, but one whose circles of attraction are
not completed except through an external armature joining both
poles.

6. That we have permanent magnetism when the molecular
rigidity, as in tempered steel, retains them in a given direction, and
transient magnetism whenever the molecules rotate in comparative
freedom, as in soft iron.

Experimental Evidences.

In the above theory the coercive force of Poisson is replaced by
molecular rigidity and freedom ; and as the effect of mechanical
vibrations, torsion, and stress upon the apparent destruction and
facilitation of magnetism is well known, I will, before demonstrating
the more serious parts of the theory, make a few experiments to prove
that molecular rigidity fulfils all the requirements of an assumed
coercive force.

I wdll now show you that if I magnetise a soft iron rod, the
slightest mechanical vibration reduces it to zero ; whilst in tempered
steel or hard iron, the molecules are comparatively rigid, and are but
slightly affected. The numerous experimental evidences which I
shall show prove that whilst the molecules are not completely rigid
in steel, they are comparatively rigid when compared with the
extraordinary molecular freedom shown in soft iron. {Experiments
shown.)

If I now take a bottle of iron filings, I am enabled to show how
completely rigid they appear if not shaken ; but the slightest motion
allows these filings to rotate and short circuit themselves, thus pro-
ducing apparent neutrality. Now I will restore the lost magnetism
by letting the filings slowly fall on each other under the influence
of the earth's magnetic force ; and here we have an evident proof of
rotation producing the result, as we can ourselves perceive the
arrangement of the filings. {Experiment shoivn.')

If I take this extremely soft bar of iron, you notice that the

B 2

4 Professor D. E. Hughes [Feb. 29,

slightest mechanical tremor allows molecular rotation, and conse-
quent loss or change of polarity ; but if I put a slight strain on this
bar, so as to fasten each molecule, they cannot turn with the same
freedom as before, and they now retain their symmetrical polarity like
tempered steel, even when violently hammered. {Experiment shown.)
We can only arrive at one conclusion from this experiment, viz.
that the retention of apparent magnetism is simply due to a frictional
resistance to rotation ; and whenever this frictional resistance is
reduced, as when we take off a mechanical strain, or by making the
bar red hot, the molecules then rotate with an almost inconceivable
freedom from frictional resistance.

Conduction.

You notice that if I place this small magnet at several inches*
distance from the needle, it turns in accordance with the pole pre-
sented. How is the influence transmitted from the magnet to the
needle? It is through the atmosphere and the ether, which is the
intervening medium. I have made a long series of researches on the
subject, involving new experimental methods, the results of which are
not yet published. One result, however, I may mention. We know
that iron cannot be magnetised beyond a certain maximum, which
we call its saturation point. It has a well-defined curve of rise to
saturation, agreeing completely with a curve of force produced by
the rotation of a bar magnet, the force of which was observed from
a fixed point. I have completely demonstrated by means of my
magnetic balance (shown in the Library') that our atmosphere, as well
as Crooke's vacuum, has its saturating point exactly similar in every
respect to that of iron : it has the same form through every degree.
We cannot reduce nor augment the saturating point of ether; it is
invariable, and equals the finest iron. We may, however, easily
reduce that of iron by introducing frictional resistance to the free
motion of its molecules.

From consideration of the ether having its saturating point, I am
forced to the conclusion that it could only be explained by a similar
rotation of its atoms as demonstrable in iron.

Eeflection would teach us that there cannot be two laws of mag-
netism, such as one of vibrations in the ether and rotations in iron.
We cannot have two correct theories of heat, light, or magnetism ;
the mode of motion in the case of magnetism being rotation, and not
vibration.

Let us observe this saturation point of the atmosphere compared
with iron. I pass a strong current of electricity in this coil. The
coil is quite hot, so we are very near its saturation. I now place this
coil at a certain distance from the needle (8 inches) ; we have now a
deflection of 45° on the needle. I now introduce this iron core, exactly
fitting the interior previously filled by the ether and atmosphere. Its
force is much greater, so I gradually remove this coil to a distance,

1884.] on tJie Theory of Magnetism. 5

where I find the same deflection as before (45°). This happens to be
at twice the distance, or 16 inches, so we know, according to the law of
inverse squares, that the iron has four times the magnetic power of
the atmosphere. But this is only true for this piece of iron : with
extremely fine specimens of iron I have been enabled to increase the
force of the coil forty times, whilst with manganese steel containing
10 per cent, of manganese it was only 30 per cent, superior. We see
here that the atmosphere is extremely magnetic. Let us replace
the solid bar by iron filings. We now only have twice the force.
Replace this by a bottle of sulphate of iron in a liquid state : it is
now a mere fraction superior to the atmosphere ; and if we were still
further to separate the iron molecules, as in a gaseous state, it is
reasonable to suppose that if we could isolate the iron gas from that
of ether, that iron gas would be strongly diamagnetic, or have far
less magnetic capacity than ether, owing to the great separation of its
molecules. These are assumptions, but they are based upon experi-
mental evidences, which give it value.

Let us quit the domain of assumption to enter that of demonstra-
tion. Here I have a long bar of neutral iron. If I place this small
magnet at one end, we notice that its pole has moved forward three
inches, having a consequent point at that place. Let us now vibrate
this rod, and you notice the slow but gradual creeping of the con-
duction until at the end of two seconds it has reached 14 inches.
The molecules have been freed from frictional resistance by the
mechanical vibrations, and have at once rotated all along the bar.
(Experiment shown.) Let us repeat this experiment by heating the
rod to red heat. You notice the gradual creeping or increased con-
duction as the heat allows greater molecular freedom. (Experiment
shoivn.) Let us now again repeat this experiment by sending a
current of electricity through the bar. You notice the instant
that I touch the bar with this wire, conveying the current
through it, that we have identically the same creeping forwards, no
matter what direction of the current. (Experiment shown.) If you
simply looked at the effects produced, you could not tell which
method I had employed ; either mechanical vibrations, heat vibra-
tions, or electrical currents. Consequently, knowing the two first to
be modes of motion, it is fair to assume that an electrical current is
a mode of motion, the manner of which is at present unknown ; but
that there is a molecular disturbance in each case is evident from the
experiments shown.

Neutrality.

If I take this bar of soft iron, introduce it in the coil, and pass a
strong electric current though the coil, you notice that it is intensely
magnetic, holding up this large armature of iron and strongly deflect-
ing the observing needle. I now interrupt the current, the armature
falls, and the needle only shows traces of the previous intense
magnetisation. What has become of this polarity? or what has

6 Professor D. E. Hughes [Feb. 29,

caused this sudden neutrality ? Coulomb supposes tliat the magnetic
fluids have become mixed in each molecule, thus neutralising each
other. Ampere supposes that the elementary currents surrounding
each molecule have become heterogeneous. De la Rive, Wiedemann,
Weber, Maxwell, and all up to the present time have accounted for
this disappearance as a case of mixture of polarities or heterogeneous
arrangement.

My researches proved to me that neutrality was a symmetrical
arrangement ; I stated this in my paper upon the theory of magnetism
to the Royal Society last year. I have since made a long series of
researches upon this question, and my paper upon this subject wdll
shortly be read at the Royal Society. This paper will demonstrate
beyond question — 1. That a bar of iron under the influence of a
current or other magnetising force is more strongly polarised on the
outside than in the interior ; that its degree of penetration follows the
well-defined law of inverse squares, up to the saturation point of
each successive layer. 2. The instant that the current ceases, a
reaction takes place, the stronger outside reacting upon the weaker
inside, completely reversing it, until its reversed polarity exactly
balances the external layers.

We might here suppose that there existed two distinct polarities
at the same end of a neutral bar, but this is only partially true, as
the rotation of the molecules from the inside to the exterior is a
gradual, well-defined curve, perfectly marked, as shown in the
diagrams. (Diagrams explained.) We see from these that in a large
solid bar the reversed polarity would be in the interior, but in a thin
bar under an intense field, the reversed polarity would be on the
outside. Thus a bar which had previously strong north polarity
under an external influence would, the instant it formed its neu-
trality, have a north polarity in the interior covered or rendered
neutral by an equal south exterior, the sum of both giving the
apparent neutrality that we notice. I must refer all interested
upon this question to my paper shortly to be read, but I will make
a few experiments to demonstrate this important fact.

If I take this piece of soft steel and magnetise it strongly, it has a
strong remaining magnetism, or only partial neutrality. If I now
heat this steel to redness, or put it into a state of mechanical vibra-
tion, the remaining magnetism almost entirely disappears, and we
have apparent neutrality. This piece of steel being thin (^ millimetre),
I know that the outside is reversed to its previous state. I place this
piece of steel in a glass vase near the observing needle, and at present
there seems no polarity. I now pour dilute nitric acid upon it, filling
up the vase. The exterior is now being dissolved, and in a few
minutes you will see a strong polarity in the steel, as the exterior
reversed polarity is dissolved in the acid. (Experiment sJwivn.)

Let us observe this by a difierent method. I take two strij)s of
hard iron, and magnetise them both in the same direction.

If I place them together and then separate them, there seems no

1884.] on the Theory of Magnetism. 7

change, although in reality the mere contact produced a commence-
ment of reversal. Let us vibrate them whilst together, allowing the
molecules greater freedom to act as they feel inclined ; and now on
separating we see that one strip has exactly the opposite polarity
to the other, both extremely strong, but the sum of which, when
placed together, is zero, or neutrality. {Experiment shown.)

Let us take two extremely soft strips placed together, and mag-
netised whilst together. On withdrawal of the inducing force, the
rods are quite neutral. (Experiment shoicn.^

We now separate these strips, and find that one is violently
polarised in one direction, whilst the other is equally strong in the
reversed ; the sum of both being again zero.

We might suppose that the reaction is due to having separate
bars. I will now demonstrate that this is not the case by magnetising
this large j-inch bar with a magnetising force just sufficient to render
the rod completely neutral when held vertically or under the earth's
magnetic influence. [Experiment shoion.)

You notice that it is absolutely neutral, all parts as well as the
ends showing not the slightest trace of polarisation. I reverse this
bar, and you perceive that it is now intensely polarised. This is due
to the fact that the earth's influence uncovers or reverses the
outside molecules, and consequently they are now of the same polarity
as its interior. Upon reversing this rod, the magnetism again dis-
appears, and re-appears if turned as previously. We have thus a
rod which appears intensely magnetic when one of its ends is lower-
most, whilst if that same end is turned upwards all traces of mag-
netism disap23ear. These and several other demonstrations which I
shall now show you (proving the enormous influence which thickness
of a bar has in the production of neutrality or its retention of mag-
netism) are simple lecture demonstrations. For the complete proof of
my discovery of neutral curves I must refer you to my forthcoming
paper upon this subject. {Experiments shown proving the great influence
of a thickness of a har upon its retentive and neutral powers.)

Inertia.

I have remarked in my researches that the molecules have true
inertia, that they resist being put in motion, and if put in motion will
vanquish an opposing resistance by their simple momentum. To
illustrate this, I take this large J-inch bar, magnetise it so that
its south pole is at the lowest end. We know that the earth's
influence is to make the lower end north. I now gently strike it with
a wooden mallet, and the rod immediately falls to zero. I continue
these blows, but the rod obstinately refuses to pass the neutral line to
become north, the reason being in so doing it would have to change
the whole internal reversed curve that I have discovered. It requires
now extremely violent and repeated blows from the mallet to make it
obey the earth's influence.

8 Professor D. K Hughes [Feb. 29,

Let us repeat this experiment by starting the molecule rapidly in
the first instance. The rod is now magnetised south as before. I
give one single sharp tap; the molecules run rapidly round, pass
through neutrality, breaking up its curve, and arrive at once to strong
north polarity. [Experiment shoivn.)

A very extraordinary effect is shown if we produce this effect by
electricity ; it then almost appears as if electricity itself had inertia.
I take this bar of hard iron and magnetise it to a fixed degree. On
the passage of the current, you notice that the magnetism seems to be
increased as the needle increases its arc, but this is caused by the
deflection of the electric current in the bar. The current is now
obliged to travel in spirals, as my researches have proved to me that
electricity can only travel at right angles to the magnetic polar
direction of a molecule, consequently in all permanent magnets the
current must pass at right angles to the molecule, and its path will
be that of a spiral. Let us replace this bar by one from a similar
kind of iron well annealed. The molecules here are in a great state
of freedom. We now magnetise this rod to the same degree as in the
previous case; the electric current now, instead of being deflected,
completely rotates the molecules, and the needle returns to zero, all
traces of external magnetism having ceased. The electricity on
entering this bar should have been forced to follow a tortuous circular
route ; its momentum was, however, too great for the molecules, and
they elected to turn, allowing the electricity to pass in a straight line
through the bar. Thus, in the first instant, magnetism was the master
directing the course of the current ; in the last, it became its servant,
obeying by turning itself to allow a straight path to its electric
master. (Experiment shown.)

Superposed Magnetism.

It is well known that we can superpose a weak contrary polarity
upon an internal one of an opposite name. I have been enabled thus
to superpose twenty successive stratas of opposite polarities upon a
single rod, by simply diminishing the force at each reversal. I was
anxious to prepare a steel wire so that in its ordinary state it would
be neutral, but that in giving it a torsion to the right one polarity
would appear, whilst a torsion to the left would produce the opposite
polarity. This I have accomplished by taking ordinary soft steel
drill wire and magnetising it strongly whilst under a torsion to the
right, and more feebly with an opposite polarity when magnetised
under torsion to the left.

The power of these wires, if properly prepared, is most remarkable,
being able to reverse their polarity under torsion, as if they were
completely saturated ; and they preserve this power indefinitely if
not touched by a magnet. It would be extremely difiicult to explain
the action of the rotative effects obtained in these wires under any
other theory than that which I have advanced; and the absolute

188-1.] on the Theory of Magnetism. 9

external neutrality that we obtain in them when the polarities are
changing we know, from their structure, to be perfectly symmetrical.

I was anxious to show some mechanical movement produced by
molecular rotation, consequently I have arranged two bells that are
struck alternately by a polarised armature put in motion by the
double polarised rod I have already described, but whose position, at
three centimetres distant from the axis of the armature, remains
invariably the same. The magnetic armature consists of a horizontal
light steel bar suspended by its central axle ; the bells are thin wine-
glasses, giving a clear musical tone loud enough, by the force with
which they are struck, to be clearly heard at some distance. The
armature does not strike these alternately by a pendulous movement,
as we may easily strike only one continuously, the friction and inertia
of the armature causing its movements to be perfectly dead-beat when
not driven by some external force, and it is kept in its zero position
by a strong directive magnet placed beneath its axle.

The mechanical power obtained is extremely evident, and is
sufiScient to put the sluggish armature in rapid motion, striking the
bells six times per second, and with a power sufficient to produce
tones loud enough to be clearly heard in all parts of the hall of the
Institution.

There is nothing remarkable in the bells themselves, as they
evidently could be rung if the armature was surrounded by a coil,
and worked by an electric current from a few cells. The marvel,
however, is in the small steel superposed magnetic wire producing
by slight elastic torsions from a single wire, 1 millimetre in dia-r
meter, sufficient force from mere molecular rotation to entirely replace
the coil and electric current. {Experiment shoivn hy ringing the
hells hy the torsion of a small ^^-inch wire placed 4 inches distant from
hell-hammer.)

Correlation of Forces.

There is at present a tendency to trace all physical forces to one,
or rather a variation of modes of motion. In my last experiment
the energy of my arm was transformed in the wire to molecular
motion, producing evident polarity; this, again, acted upon the
ether, putting the needle-hammer into mechanical motion. This by
its impact upon the glass bells transformed its motions into sonorous
vibrations; but this does not mean that we can convert directly
sonorous vibrations into magnetism, or vice versa.

Let us take this soft iron rod ; it seems quite neutral, although
we know that the earth's magnetism is trying to rotate its molecules
to north polarity at its lowest extremity. We now put it in mecha-
nical vibration by striking it gently with a wooden mallet; the
molecules at once rotate, and we have the expected strong north
polarity. Let us repeat this experiment by employing heat, and here,
again, at red heat an equally strong north polarity appears.

Again we repeat, and simply pass an electric current of no matter

10 Professor Hughes on the Theory of Magnetism. [Feb. 29,

what direction ; again the same north pole appears. Thus these forces
must be very similar in nature, and may be fairly presumed to be
vibrations, or modes of motion, having no directive tendency except a
slight one, as in the case of electricity. For the same three forces
render the rod perfectly neutral, even when previously magnetised,
when placed in a longitudinally neutral field, as east and west.

Motion of the molecules gives rise to external magnetism to a rod
previously neutral, or renders it neutral when previously magnetised ;
in other words, it simply allows the molecules to obey an external
directing influence; the only motion, therefore, is during a change
of state or polarity. If there is constant polarity, there is no con-
sequent motion of the molecules : in fact, the less motion of any kind
that it can receive, the more perfect its retention of its previous
position ; consequently, constant magnetism cannot be looked upon
as a mode of motion, neither vibratory nor rotatory ; it is an inherent
quality of each molecule, similar in its action to its chemical affinity,
cohesion, or its polar power of crystallisation. A molecule of all
kinds of matter has numerous endowed qualities ; they are inherent,
and special in degree to the molecule itself. I regard the magnetic
endowed qualities of all matter or ether to be inherent, and that they
are rendered evident by rotation to a symmetrical arrangement in
which their complete polar attractions are not satisfied.

Time will not allow me to show how completely this view explains
all the phenomena of electro-magnetism, diamagnetism, earth cur-
rents— in fact, all the known efi'ects of magnetism — up to the original
cause of the direction of the molecules of the earth. To explain the
first cause of the direction of the molecules of the earth would rest
altogether upon assumption as the first cause of the earth's rotation,
and of all things down to the inherent qualities of the molecule itself.

The mechanical theory of magnetism which I have advocated
seems to me as fairly demonstrable as the mechanical theory of heat,
and it gives me great pleasure to have been allowed to present you
with my views on the theory of magnetism.

[D. E. H.]

1884.] General Monthly Meeting.. 11

GENERAL MONTHLY MEETING,

Monday, March 3, 1884.

Sir Frederick Pollock, Bart. M.A. Manager and Vice-President,
in the Chair.

Major-General William Howell Bejnon,

Frederick William Blunt, Esq.

John Griffin Bristow, Esq. M.A.

Mrs. R. Brudenell Carter,

Mrs. J. T. Clover,

Frank M. Gowan, Esq.

Wynnard Hooper, Esq.

John Charles Medd, Esq.

Robert Muir, Esq.

Bonamy Mansell Power, Esq.

Mrs. William Crookes,

P. Donovan, Esq. J.P.

Lewis H. Edmunds, Esq. B.A.

Miss J. L. Reynolds,

Shirley Harris Salt, Esq.

George Nelson Strawbridge, Esq. F.Z.S.

were elected Members of the Royal Institution.

The Presents received since the last Meeting were laid on the
table, and the thanks of the Members returned for the same, viz. : —

FROM

The Governor-General of India — Geological Survey of India: Palseontoloo-ia

ludica : Series X. Vol. II. Part 6. 4to. 1884, °

The Trustees of the British 3Iuseum— Catalogue of Romances in MSS. By H L D

Ward. Vol. 1. 8vo. 1883.
Accademia dei Lincei, Beale, Boma — Atti, Serie Terza : Transunti Vol VllI

Fasc. 2, 3. 1883-4.
Academy of Natural Sciences, Philadelphia — Proceedings, 1883, Part 2 Svo

1883.
Alpine Club — The Alpine Journal, Nos. 1 to 16 and Nos. 21 to 83. Svo. 1863-84.
American Academy of Arts and Sciences — Proceedings, Vol. XVIII. Svo. 1883.
American Philosophical Society — Proceedings, No. 113. Svo. 1883

Transactions, Vol. XVI. Part 1. 4to. 1883.
Astronomical Society, Boijal — Monthly Notices, Vol. XLIV. No. 3. Svo. 1884.
Bankers, Institute o/— Journal, Vol. V. Parts 1, 2. Svo. 1884.
Boston Society of Natural History — Memoirs, Vol. III. Nos. 6, 7. 4to. 1883.

Proceedings, Vol. XXI. Part 4; Vol. XXII. Part 1. Svo. 1883.
British Architects, Boyal Institute of — Proceedings, 1883-4, Nos. 8, 9. 4to.
Canada Geological and Natural History Survey — Report of Progress for 1880-2

with Maps. Svo. 1883. '

Catalogue of Canadian Plants. Part 1, Polypetalse. By J. Macoun Svo

1883.
Chief Signal 0{Jicer, U.S. ^rjny— Professional Papers of the Signal Service

Nos. 8 to 12. 4to. 1882.

12 General Monthly Meeting. [March 3,

Chemical Society — Journal for P''eb. 1884. 8vo.

Index, Vols. XLIII. and XLIV. 8vo. 1883.
Crisp, Frank, Esq. LL.B. F.L.S. &c. M.R.I, {the Editor)-~3omxvQ\ of the Koyal

Microscopical Society, Series II. Vol. IV. Part 1. 8vo. 1884.
Editors — American Journal of Science for Feb. 1884. 8vo.
Analyst for Feb. 1884. 8vo.
Athenseum for Feb. 1884. 4to.
Ctiemical News for Feb. 1884. 4to.
Engineer for Feb. 1884. f..l.
Horological Journal for Feb. 1884. 8vo.
Ironfor Feb. 1884. 4to.
Nature for Feb. 1884. 4to.

Eevue Scientifique and Revue Politique et Litterairc for Feb. 1884. 4to.
Science Monthly, Illustrated, for Feb. 1884.
Telegraphic Journal for Feb. 1884. 8vo.
Franklin Institute— J om-nal, No. 698. 8vo. 1884.
Geographical Society, Boyal— 'Proceedings, New Series, Vol. VI. No. 2. Svo.

1884.
Geological Society — Quarterly Journal, No. 157. Svo. 1884.
Glasgow University Observatory — Catalogue of 6115 Stars for 1870. Bv R. Grant.

4to. 1883.
Johns Hopkins University — American Chemical Journal, Vol. V. No. 6. Svo.

1883.
Liverpool Literary and Philosophical Society — Proceedings, Vols. XXXV. XXXVI.

and XXXVII. Svo. 1880-3.
Medical and Chirurgical 8oc/e%— Proceedings, New Series, No. 4. Svo. 1SS3.
North of England Institute of Mining and Mechanical Engineers — Transactions,

Vol. XXXIII. Part 2. Svo. 1884.
Pharmaceutical Society of Great Britain — Journal, Feb. 1884. Svo.
Photograpjhic Society — Journal, New Series, Vol. VIII. No. 4. Svo. 1884.
Plateau, Madame — Expe'riences sur les Lames Liquides Minces. 2^ Note. Par
J. Plateau. (Bui. Acad. Roy. de Belgique, t. VI.) 1883.
Sur rObservation des Mouvements tres Rapides. Par J. Plateau. (Bui. Acad.

Roy. de Belgique, t. VI.) 1883.
Bibliographic Analytique des Principaux Phenomenes Subjectifs de la Vision.
Par J. Plateau. (Mem. de I'Acad. Roy. de Belgique, t. XLV.) 1883.
Pogson, Miss E. Isis (the Repjorter) — Report of the Meteorological Reporter to the

Government of Madras, 1881-3. Svo. 1882-3.
Preussische Akademie der Wissenschaften — Sitzungsberichte, XXXVIII.-LIII.

4to. 1883.
Secretary of State for the Colonies — Report on the Agricultural Resources of the

Island of St. Helena. By D. Morris. Svo. 1884.
Society of ^r^s— Journal, Feb. 1884. Svo.

Telegraph Engineers, Society of — Journal, Vol. XII. No. 50. Svo. 1884.
The Editor— 'EAeeincmu' 8 Directory, 1884. Svo.
Tohin, W. B. Esq. — Report and Collections of the Nova Scotia Historical Society,

Vols. I. II. and III. Svo. 1878-83.
United Service Institution, Royal — Journal, No. 122. Svo. 1883.
United States Geological Survey— The Tertiary History of the Grand Cafion
District. With Atlas. By C. E. Dutton. 4to and fol. 1882.
Second Annual Report, 1880-1. 4to. 1882.
Hayden's Twelfth and Final Report, 1878. 3 vols. Svo. 1883.
Bulletin I : on Hypersthene Andesite. By W. Cross. Svo. 1883.
Vereins zur Beforderung des Gewerbfleisses in Preussen — Verhandlungen, 1884:

Heft 1. 4to.
Wild, Dr. H. {the Director) — Annalen des Physikalischen Central-Observatoriums,
1882, Theil I. 4to. 1883.
Eepertorium fiir Meteorologie, Band VIII. 4to. 1883.

1884.] Mr. G. V. Boys on Bicycles and Tricycles. 13

WEEKLY EVENING MEETING

Friday, March 7, 1884.

Henry Pollock, Esq. Manager, in the Chair.

C. Vernon Boys, Esq. A.R.S.M.

Bicycles and Tricycles in Theory and in Practice.

When I was honoured by the invitation to give this discourse on
bicycles and tricycles, I felt that many might think the subject to be
trivial, altogether unworthy of the attention of reasonable or scientific
people, and totally unfit to be treated seriously before so highly
cultured an audience as usually assembles in this Institution. On the
other hand, I felt myself that this view was entirely a mistaken one,
that the subject is one of real and growing importance, one of great
scientific interest, and, above all, one of the most delightful to deal
with that a lecturer could wish to have suggested to him.

It is quite unnecessary for me to bring forward statistics to show
how great a hold this so-called new method of locomotion has taken
upon people of all classes. The streets of London, the roads and
lanes in all parts of the country testify more forcibly than any words
of mine can do to what enormous numbers there are who now make
use of cycles of one sort or another for pleasure or for the purposes
of business.

Not only has the newly developing trade brought prosperity to
towns whose manufactures were dying a natural death, but the re-
quirements of cyclists have given rise to a series of minor industries
themselves of great importance. Riders of bicycles and tricycles
come along so silently that instruments of warning have been devised.
There are bells that jingle, bells that ring, whistles, bugles, and a
fiendish horn on which all the noises of the farmyard can be imitated,
and which will utter anything from a gentle remonstrance to a wild,
unearthly shriek. Lamps, tyres, saddles, seats, springs, &c., are made
in unending variety. These form the endless subject of animated
conversation in which the cyclist so frequently indulges. Cyclometers,
or instruments for measuring the distance run, are also much used.
Some show the number of revolutions made by the wheel, from which
the distance can be found by a simple calculation, others indicate the
distance in miles. There is on the table a home-made one of mine
with a luminous face, which at the end of every mile gives the rider
a word of encouragement; it now indicates that a mile is nearly
complete : in another turn or two you will all hear it speak.

Cyclists have a literature of their own. There are about a dozen
papers wholly or largely devoted to the sport. They can even insure

14 3Ir. C. Vernon Boys [Marcli 7,

themselves and their machines against injury by accident in a company
of their own.

The greatest, and by far the most important, growth is the Cyclists*
Touring Club, a gigantic club to which every right-minded rider in
the country belongs. This club has done more to make touring
practically enjoyable than could have been thought possible when it
began its labours. Railway companies have, with few exceptions,
consented to take cycles at a fixed and reasonable rate ; in almost
every town in the country an agreement has been made with the
leading or at any rate a first class hotel, in virtue of which the
touring member may be sure of meeting with courtesy and attention
for himself, and with clean quarters and an intelligent groom for his
horse, instead of finding himself, as hitherto, a strange being in a
strange place, at the mercy of some indifferent or exorbitant landlord.
In consequence of this, thousands now spend their holidays riding
over and admiring the beauties of our own country, instead of being
dragged with a party of tourists through the streets and buildings of a
foreign town. Of the delightful nature of a cycling tour I can speak
from grateful experience ; last autumn alone I travelled nearly 1500
miles, meeting on my way with almost every variety of beauty that
the scenery of this country affords. Wherever I went I felt the bene-
ficial influence of the C.T.C., as the touring club is called. At all the
hotels — our headquarters — at which I stopped I found the most
sanguine wishes of the club amply fulfilled, our wants understood and
provided for.

The C.T.C. have done a great service in providing us wath a
uniform which has been proved to be as near perfection as possible.
They have also designed a lady's cycling dress, which can be seen in
the library.

Though touring in the country is the perfection of our art, town
riding has its advantages. I, in common with a fair number, ride
daily to and from my work, no matter what the weather may be.
Eain, snow, wind or hail, cycling affords the pleasantest means of
crossing Loudon. Instead of waiting in draughty railway stations,
or catching cold outside or being stewed inside omnibuses, or of being
smoked in the underground railway, we, the regular cyclists, look
forward to our daily ride with pleasure ; for the healthy exercise, the
continuous necessity of watching the traffic and avoiding every
approaching danger form between them a relief from mental worry
or business anxiety which we alone can appreciate.

Of the dangers of the streets I have little to say : the regulation of
the traffic by the police, and the consideration of drivers, though they
are not in general too fond of us, make danger in the quarter from
which it might be expected very remote. Our chief difficulty is due
to the irregular and utterly unaccountable movements of pedestrians,
whose carelessness keeps us in a continual state of anxiety.

There remains one point of the utmost importance, on which I
would say a few words : I refer to the effect of cycling on our general

1884.] on Bicycles and Tricycles in Theory and in Practice. 15

health. About a year ago there appeared in the Lancet an article
condemning in no measured terms the evils likely to result from the
development of this new craze, in which, as far as I remember, it was
stated that we are now sowing the seeds of a series of new diseases,
the symptoms of which will only appear possibly in years to come. I
would not for a moment question the accuracy of opinion held by any
professional man : whether this is or is not the case I cannot tell ;
however, I may mention that the only symptoms which I have so far
discovered in myself are an improved appetite, increased weight, and
a general robustness to which I was formerly a perfect stranger.

Having, I trust, succeeded in showing that the advantages offered
to riders are sufficient to account for the rapid development of cycling —
that it is, in fact, no mere temporary craze — I shall now proceed to
consider the theory and construction of the various machines at
present known.

From the hobby-horse to the bone-shaker, and from the bone-
shaker to the bicycle, the steps are so simple and obvious that it is
quite unnecessary for me to trace them. It is also needless for me to
describe the modern bicycle : every one must be familiar with it, every
one must have seen the ridiculous zig-zag of the beginner, and have
admired the graceful gliding of an accomplished rider. Of the theory
of the balance little need be said ; anything supported on a mere line,
in unstable equilibrium, as it is called, must fall one way or the other.
The machine and rider would of necessity capsize if some action of
recovery were not possible. To whichever side the machine shows
any inclination, to that side the rider instinctively directs it ; by this
means the tendency to fall to one side is balanced by the property of
the rider to continue moving in a straight line and so to go over on
the other side. This action of recovery is always overdone, so that a
second turn in the opposite direction must follow. Hence the extra-
ordinary path traced by the beginner. Even with the most skilful
rider, though he appears to travel in a perfectly straight line, a
slightly sinuous course is essential, as the highly characteristic track
left on the road indicates. If anything should happen to check this
slightly serpentine motion — as, for instance, occurs when the driving-
wheel drops in the groove of a tram line — the balance at once becomes
impossible, and the rider is compelled to dismount.

The extraordinary stability of the bicycle at a high speed depends
largely on the gyroscopic action of the wheels. On the table is a top
supported in a ring which is free to move how it pleases. So long
as the top is spinning the ring is as rigid as a block ; on stopping it
the freedom of the support is at once apparent.

It is a marvel to many how anything so light, how anything so
delicate, can carry the weight, or can travel at the speed so common,
without utterly collapsing. The wheels especially attract attention.
In a hoop no one part can be pushed in unless some other part can
go out. A bicycle wheel is a hoop in which every part is jDrevented
from going out by the tension of the spokes. To give the wheel

16 Mr. C. Vernon Boys [March 7,

lateral stability, the spokes are carried not to the centre, but to the
two ends of the hub, thus lying on two cones. Such a wheel is
abundantly strong in its own plane : it can withstand the jars and
shocks of a bad road without a groan, but once subject it to a serious
side strain, such as I can with ease put upon it with a jerk of my
wrists, and the wheel will crumple up like an umbrella in a storm.
Till this year there has been no change in the principle of construc-
tion, though in detail many improvements have been carried out and
are largely adopted. By the use of hollow rims a stiffer and lighter
wheel can be made ; thick-ended, crossed, and laced spokes are em-
ployed, and other details modified. Essentially, however, the " spider "
wheel as a structure is the same as it was when first introduced.
Suddenly, two radical changes are presented to us. Mr. Otto, whose
great work I shall describe in its projDer place, has devised a wheel
on a new system, in which the spokes that form the structure lie in
the plane of the rim, in which position they are best able to withstand
direct shocks. Such a wheel would be unstable, but requires very little
to keep it true. Delicate spokes not screwed up very tight are therefore
placed on either side, so that a side strain is met by the whole
strength of the spokes on one side, which are not, as hitherto, weakened
by the pull of the spokes on the other. On this system much nar-
rower wheels can be made than was possible before. The other
change, due to the same inventor, is still more striking. He has
found, contrary to the opinion of every one, that wheels, either of his
narrow type or of the usual form, can be made and will remain true
when the spokes are made elastic by being bent into a wavy
or slightly spiral form. If only these wheels will stand the
test of time — and I see no reason why they should not — one of the
greatest discomforts and probable causes of injury from which the
cyclist suffers, the vibration and jolting due to a bad road, will have
been removed.

The bearings in a bicycle are perhaps more to be admired than
any single part. Instead of allowing the axle to slide round in its
bearings, hard steel rollers or balls are introduced, so that the parts
which are pressed together roll over and do not slide upon one
another. Any one who has trodden on a roller or a marble must have
found in a possibly unpleasant manner the great difference between
rolling and sliding friction. I can now give for the first time the
result of an experiment, only completed this morning, which shows
the extraordinary perfection to which this class of work has attained.
I have observed how much a new set of balls, which I obtained direct
from the well-known maker Mr. Bown, has lost in weight in travelling
1000 miles in my machine. Every 200 miles I cleaned and weighed
the balls with all the care and accuracy that the resources of a
physical laboratory will permit. The set of twelve when new weighed
25-80400 grms., after 1000 miles they weighed 25*80088 grms., the
loss being 3 "12 milligrams, which is equal to ~ grain, that is in
running 1000 miles each ball lost -J- grain. This corresponds to a

1884. J on Bicycles and Tricycles in Tlieory and in Practice.

17

wear of only ^^- inch off tlie surface. At this rate of wear —
3-12 mgms. per 1000 miles — tbe balls would lose only J- of their
weight in travelling as far as from here to the moon.

The twelve balls, after the first 200 miles, each weighed in grammes
as follows. The loss of each in running 600 miles is appended ; —

Weight in grms.

Loss in 600 miles.

Weight in grms.

Loss in 600 x\

2-16605

-00050

2-14725

•00020

2-16180

-00025

2-14725

•00020

2 15500

•00035

2-14700

-00020

2-15480

•00015

2-14500

-00020

2-15000

•00015

2-14280

-00025

2 14730

-00015

2-13875

•00020

miles.

I did not weigh each ball on the first and last occasion ; however,
the wonderfully uniform wear in the intermediate 600 miles speaks
well for the equal hardness of the balls.

The wear of the dozen during each journey of 200 miles was as
follows : —

Miles.

Wear in grms.

Oto 200

•00055

200 „ 400

-00070

400 „ 600

-00055

600 „ 800

•00075

800 „ 1000

-00062

I have given the results of these experiments at length, for I do
not think that accurate and systematic observations of the kind have
been made before.

We may consider, then, that the balls are practically inde-
structible. Knowing this, Mr. Trigwell has applied the ball bearing
to the construction of the " head " of the bicycle, not so much with the
view of diminishing the friction there, but of preventing wear in a
place where any shake is highly objectionable. One of his ball
heads is en the table.

The frame of the bicycle, consisting merely of the fork and Lack-
bone, is made of thin steel tube, the type of all that is light and
strong, Indiarubber, besides being used for the tyres of all machines,
has been worked into every part of the structure, to diminish, so far
as is possible, that perpetual and wearying vibration of which all
bicyclists so bitterly complain. The number of improvements in
every detail is so great that any attempt to enumerate them is out of
the question. Suf&ce it to say that the modern bicycle is the per-
fection of all that is perfect ; as a machine for racing, as a machine
for hurrying over good and level roads, nothing can approach it.
Unfortunately, however, there is ever present danger, and danger of
the most objectionable sort, for the most skilful rider knows too well
that should he strike a stone of even an ordinary size, he must expect
to be pitched over the handles and come with a crash to the ground.

Vol. XI. (No. 78.) o

18 Mr. C. Vernon Boys [Marcli 7,

It is true that in general no harm is done, but such a fall may bring
any one to a sudden and horrible end.

Many have attempted, while still retaining the advantage of the
bicycle, to make these involuntary headers impossible by modifying
in some way its construction. One of the earliest attempts in this
direction is well named the " Extraordinary." On it the rider is placed
much further behind the main wheel, but can still employ his weight
to advantage, as the treadles are placed below him and are connected
by levers with the cranks. In another safety bicycle a third wheel
is carried in front just above the ground, so as to resist at once any
tendency to tilt forward. In another type much smaller wheels are
employed, and the feet, now nearer the ground, are connected with
the cranks by levers in the " Facile," or by a hanging pedal in the " Sun
and Planet." There is a bicycle with two large wheels, one in front
of the other, which two can ride, which should be both safe and
rapid.

By far the most curious and utterly unintelligible of all machines
of the bicycle type is Mr. Burstow's " Centre-cycle." So incompre-
hensible did this machine seem to me that I took the trouble one after-
noon last week to ride to Horsham to see it in its native place. A
careful examination has convinced me that it is not only correct in its
design but that it is in many respects the most wonderful cycle at
present made.

There is on the table a model Plympton skate. When this is level
it runs straight, when inclined either way it wheels around in a
manner that was so familiar a few years ago. The four wheels of the
Centre-cycle are a counterpart of the four wheels of the skate :
when the frame leans either way tbey turn in an appropriate manner,
or, conversely, when they turn the machine leans in the proper
direction. It might be thought that a thing with five wheels was
more nearly allied to a tricycle than to a bicycle, but this is not so,
for the Centre-cycle, when ridden skilfully, has rarely more than
one wheel on the ground. The leaning to one side in turning a
corner (tricycles, unfortunately, must remain upright) and the general
action is essentially that of a bicycle. The great peculiarity of this
machine is the power that the rider possesses of raising or lowering
any wheel he pleases. Now that I have mounted it you will see that
I can rest on one, three, four or five wheels, as I please. In conse-
quence of this power of lifting the wheels, a rider can travel over an
umbrella without touching it, lifting the wheels as they approach and
dropping them as they pass, after the manner of a caterpillar.

Till a few years ago the bicycle was the only velocipede which
was worthy of the name. Inventive genius and mechanical skill have
given rise to a series of machines on three wheels on which any one
can at once sit at ease, and which require but little skill in their
management. Men who do not care to risk their necks at the giddy
height of the bicyclist, ladies, to whom the ordinary bicycle presents
difficulties which they cannot well surmount, each find in the tricycle

1884.] on Bicycles and Tricycles in Theory and in Practice. 19

the means of obtaining healthy and pleasant exercise and of enjoying
to a certain extent the advantages which the bicycle affords. Thanks
to the perfection of the modern tricycle, cycling has become one of
the most popular institutions of the day.

Whatever difficulty I may have had in doing justice to the
bicycle, the corresponding difficulty in the case of tricycles is far
greater. The number of makers and the variety of their work is so
great that it would be sheer madness on my part to attempt to
describe all that has been done. Those who wish to see the great
variety of detail which chiefly constitutes the difference between one
make and another must go to one of the exhibitions of these things
which are now so common.

All I shall attempt will be an explanation of the leading principles
which are involved in the design of a tricycle. For this purpose it
will be necessary for me to mention occasionally some particular
machine ; but, in justice to the hundreds to which I cannot even refer,
I wish it to be understood that those named, though typical, are not
of necessity better than any other.

It is first necessary to know what combinations of three wheels
will and what will not roll freely round a curve. The few possible
arrangements determine the general forms which a tricycle can take.
A wheel can only travel in its own dii*ection : no side motion is possible
without the application of considerable force, entailing strain and
friction of a most injurious kind. In any combination, then, of three
wheels each must be able, in spite of the united action of the other two,
to move in its own direction. There is on the table a model in which
the three wheels can take every possible position. To begin with, two
large ones are placed opposite but independent of one another and
parallel, and a small one parallel to the others is mounted between
them at one end. This arrangement rolls along in a straight line
with perfect freedom ; on twisting the plane of the third wheel it is
also free to roll round a curve whether the little wheel is before or
behind. If I shift the position of one of the large wheels so that
though still parallel to, it is no longer opposite, the other, then, though
they can freely move in a straight line, they can by no possibility be
induced to roll round a curve. It is clear, then, that two wheels which
are parallel cannot be employed in a tricycle unless they are opposite
one another. The only class of people who frequently appear to be
familiar with this fact are nursemaids, who always tip up the front of
a perambulator in turning a corner. If one wheel is in front of and
another behind a third, the combination can only freely turn a
corner w^hen the front and rear wheels are turned to proportionate
extents in opposite directions. The model is so arranged ; now, if either
of the little wheels is not turned to exactly the right amount they can
no longer roll, they can only be dragged round a curve. It is not
sufficient that two parallel wheels should be opposite one another : they
must be able to turn at different speeds. I have now the two large
wheels keyed on the same axle, so that they must of necessity turn

c 2

20 Mr. C. Vernon Boyg [March 7,

together ; this combination is ready enough to go straight, but no amount
of encouragement by the steering wheel will induce it to go in any
other direction.

Bearing these facts in mind it will not be difficult to follow the
development of the tricycle. It would seem impossible in the first
arrangement (that with two wheels opposite one another, and a third
or steering wheel before or behind between them) to drive both sides,
for the wheels must be able to turn at different speeds ; let, therefore,
one be free to go as it pleases, if the other only is driven, we have at
once a very common form of tricycle in which one wheel drives, one
steers, and one is idle. Machines of this class have many defects. The
feeble steering power, combined with their unsymmetrical driving,
render them altogether untrustworthy. If much power is applied to
the driver, which can only have its share of the weight upon it, it
slips on the ground : if the machine is quickly stopped, owing to the
small weight on the steering wheel it is apt to swing round and upset;
nevertheless, those who are content with pottering about on our wood
pavement and gravel roads find this class of machine answer their
purpose, and owing to its cheapness and simplicity they do not care
to get a better. The second arrangement of the model, in which
riders must have recognised the " Coventry rotary," is free from most of
the defects of the form just described : there is more weight on the
driver but not enough to prevent its being made to slip round ; there
are two steering wheels a long way apart with plenty of weight upon
them, so that the guiding power in this type of tricycle is all that
can be desired.

Let me now return to the first arrangement, in which two parallel
wheels are opposite one another. If by any possibility both wheels
could be driven and yet be free to go at different speeds, then, there
being so large a weight on the drivers, they could not be made to slip ;
the driving being symmetrical most of the twisting strain would be
taken off the steering wheel and still the machine would be capable
of rolling round a curve with perfect freedom.

All the methods of solving the problem of double driving come
under two heads, one depending on the action of a clutch and the
other on differential or balance gear.

The clutch action being the simplest, I shall describe that first.
In going round a corner the inner wheel must lag behind or the outer
wheel must run ahead of the other ; as either wheel must be inner or
outer, according to the direction of the curve, each must be able to
lag behind or each must be able to run ahead. If both were able to
lag behind, the machine could not be driven forward and it would be
of little use ; if both were able to run ahead, the machine could not
be driven backwards, a matter of small importance. There is on the
table a large working model showing how a four-sided wheel is free
to revolve in a ring, but is instantly seized when turned the other
way owing to a jambiug action of one or more of four rollers. The

1884.] on Bicycles and Tricycles in Theory and in Practice. 21

four-sided wheel, tlieu, can be employed to drive the ring one way
but not the other. One of these " clutches " or " friction grips "
is placed at each end of the crank-shaft in the " Cheylesmore " tricycle,
and a chain round the ring of each drives the corresponding wheel.
The machine named is a rear steerer. The clutch is also employed in
some front steerers.

The other method of double-driving depends on the use of the
well-known gear of three bevil wheels, or of some equivalent mechanism.
If the axle of the middle of the three wheels is turned round the
common axle of the other two, the applied force is divided between
those two wheels, yet the pair are free to move relatively. Let, then,
the chain drive a wheel carrying the middle bevil and let the side bevils
be connected with the two drivers ; whatever happens, the power of the
rider will be equally divided between them, yet the machine will be
free to roll round a curve.

There are a great number of devices which are exactly equivalent
to this, the simplest of all which is known as Starley's gear. There
is on the table a beautiful model of the gear used in the Sparkbrook
tricycle which has been lent me by the makers of that machine, Bown's
differential gear, and some others ; but time will not allow me to
describe them. There is one gear, however, which presents many
peculiarities, which I have devised, and which may be of interest.
A large working model is on the table. Between the conical edges
of two wheels which are connected to the drivers, lie a series of balls
outside which is a ring with sloping recesses. If the ring is turned
by a chain or otherwise, the balls jamb in the recesses as the rollers do
in the clutch gear. Nevertheless, they are free to turn about a radial
axis, and so allow the two driven cone wheels independent motion.
The bursting strain on the ring and the side thrust on the cones
acting on another set of rolling balls, balance one another. With this
gear the rider can cause the balls to jamb one way or both ways, and
so have or avoid the " free pedal " as he pleases.

Having spoken of the differential gear and the clutch, I had better
show the comparative advantages and disadvantages of the two
methods of double driving. With the differential gear the same force
is always applied to each wheel, so in turning a corner the outer one,
which travels furthest, has most work exjDended upon it (work = force
X distance). In this respect the differential gear is superior. On
the other hand, when one wheel meets wdth much resistance from mud
or stones and the other with hardly any, the latter has still half the
strength of the rider spent upon it, which is clearly a mistake. With
a clutch-driven machine running straight, the wheels take such a
share of the rider's power as is proportional to the resistance they
individually meet. When the machine is describing a curve — that is,
generally — only the inner wheel is driven and the machine is for the
time only a single driver with the driver on the wrong side.

In almost all good designs of front-steering tricycles, the power

22 Mr. a Vernon Boys [March 7,

applied to the cranks is transmitted to a differential gear by a chain.
The crank and connecting rod have also been used to transmit the
power, but then the clutch is necessary.

There is, however, another type of tricycle in which the use of
cranks is avoided, among which may be mentioned the " Omnicycle,"
the " Merlin," and that highly ingenious machine the " Oarsman "
tricycle. On the table there is the Omnicycle gear. In all these
the power is applied direct to the circumference of a wheel or sector,
and so dead points are avoided, which is a point in their favour when
meeting with much resistance. On the other hand, the sudden starting
and stopping of the feet at every stroke in the two former machines
and of the body in the latter makes this type utterly unsuitable for
obtaining anything more than a moderate speed. In the Omnicycle
ingenious expanding drums are employed so that the power may be
applied with different degrees of leverage according to circumstances.

There remains one type of tricycle which for rapid running sur-
passes many : I refer to what is known as the Humber pattern. So
excellent is this form in this respect that the leading manufacturers
have, by turning out machines on the same lines, paid the original
makers a compliment which is not altogether appreciated. This
pattern departs less from the ordinary bicycle than any other ; it is
one, in fact, in which, instead of one, there are two great wheels, giving
width to the machine, between which the power is divided by the
usual differential gear.

I must now describe some devices which are attracting much
attention at the present time, the speed and power gears. Let us
suppose there are two machines with wheels of different sizes, but in
other respects alike. Then each turn will take the larger-wheeled
machine further than the smaller. In going up a hill the larger
wheel will take its machine up a greater height than the other in one
revolution, which involves more work and therefore more strength.
If on the large wheel the chain pulley were increased in size, then
for the same speed of the treadles it would not turn so quickly : it
would not take the machine so far up the hill as before : it would, in
fact, be equivalent to a smaller wheel, so that less strength than before
would be necessary. This diminution of speed, though of great
advantage when climbing a hill, is the reverse on the level, for there
very rapid pedalling would be necessary to maintain even a moderate
speed. To obtain the advantage of high wheels or high gearing on
the level, and at the same time low wheels or low gearing on the
hills, some highly ingenious devices are employed. On the table is
a well-known example, the " Crypto-dynamic," which by a simple
movement changes the relative speed of wheel and treadle. Time
will not permit me to describe the details of this arrangement, but it
contains an epicyclic gear, which is or is not in action, according as
the rider desires power or speed. There are several other devices
having the same object, some depending on an epicyclic gear in a
pulley, others on the use of two chains, only one of which is active at

1884.] on Bicycles and Tricycles in Theory and in Practice. 23

a time. These arrangements have the further advantage of enabling
the rider to disconnect the treadles from the wheels whenever he
pleases. Tricycles on which two, three, or a whole family can go out
for a ride together involve few new principles, and I shall not, for
this reason, have a word to say about them.

There remains one machine forming a class by itself more distinct
from all others than they are from one another. It is not a bicycle
in the ordinary sense of the word ; it is not a tricycle, for it has only
two wheels. This machine is from a scientific and therefore from
your 2)oint of view more to be admired than any other. It is called,
after its inventor, the " Otto." The Otto bicycle and the Otto gas-
engine will be lasting memorials to the ingenuity of the brothers
who invented them.

No machine appears so simple but is so difficult to understand as
this. Tricyclists who have been in the habit of managing any machine
at once are surprised to find in this something which is utterly beyond
them. They cannot sit upon it for an instant, for so soon as they are
let alone it politely turns them off. When at length, after much
coaxing, they can induce it to let them remain upon it, they find it
goes the way they do not want. Riding the Otto, like any other
accomplishment, must be learnt. Some seem at home on it in half an
hour, others take a week or more. It is not surprising that that quick
perception in which ladies have so much the advantage of men
enables them to quickly overcome the apparently insurmountable
difficulties which this machine presents to the beginner.

The rider, when seated, is above the axle of two large equal wheels,
being then apparently in unstable equilibrium : he would of necessity
fall forwards or backwards if some movement of recovery were not
possible. The Otto rider maintains his balance in the same way as
the pedestrian. If he is too far forward, pressure on the front foot
will push him back ; if too backward in position, pressure on the rear
foot will urge him forward. That this must be so is clear, for what-
ever turning power he applies to the wheels, action and reaction being
equal and opposite, they will produce an equal turning effect upon
him. The steering of this machine is quite peculiar. In the ordinary
way both wheels are driven by steel bands at the same speed : so long
as this is the case the Otto of necessity runs straight ahead. When
the rider desires to turn he loosens one of the bands, which causes the
corresponding wheel to be free ; if then he touches it with the brake
or drives the other wheel on, it will lag behind and the machine will
turn. It is even possible to make one wheel go forwards and one
backwards at the same time, when the machine will spin like a top
within a circle a yard in diameter.

There being no third wheel the whole weight is on the driver, the
whole weight is on the steerers ; the frame, which is free to swing,
compels the rider to take that position which is most advantageous,
making him upright when climbing a hill and comfortably seated
when on tlie level. Owing to a curious oscillation of the frame which

24 Mr. C. V. Boys on Bicycles and Tricycles. [March 7,

occurs in hill-climbing the dead points are eliminated, so the rider
need not waste his strength at a position where labour is of no
avail.

Though it has been impossible for me to do more than indicate in
the most imperfect manner how numerous and beautiful are the
principles and devices employed in the construction of cycles, I trust
I have disappointed those who were shocked and horrified that so
trivial a suhiect should be treated seriously in this Institution.

[0. V. B.]

1884.] 3Ir. J. N. Langley on the Physiological Asiject of Mesmerism. 25

WEEKLY EVENING MEETING,

Friday, March 14, 1884.

Sib Frederick Pollock, Bart. M.A. Manager anr] Vice-President,

in the Chair.

J. N. Langley, Esq. M.A. F.E.S.

The Physiological Aspect of Mesmerism,

Scattered about in the literature of the seventeenth and eighteenth
centuries are many records of the cure of divers human maladies in
simple and mysterious-seeming ways.

Valentin Greaterakes, in Charles II.'s reign, was, we are told,
" famous for curing various diseases and distempers by a stroak of
the hand only." His power, he thought, was a special gift from
heaven. Many people, however, were not slow to say that he had
dealings with the devil. In some cases wonders were wrought by
touching the affected parts of the patient with a magnet. Maxwell,
w^ho in 1679 published a short treatise on magnetic medicine,
attributed the cures brought about by this, and by some other un-
usual forms of medical practice, to the accumulation of a subtile fluid
in the body of the patient. This subtile fluid was diffused through
all things in nature ; a fortunate few amongst men had an inborn
power of controlling its distribution. Such men could cure all
diseases ; they could indeed, he says, by adding to their own proper
quantum of fluid, make themselves live for ever, were not the
influence of the stars adverse.

In 1775 the theory of animal magnetism was put forward in
Vienna by Friedrich Anton Mesmer Neither his theories nor his facts
differ very greatly from those of some of his predecessors. There
exists, he said, in nature a universal fluid; in virtue of this, the
human body possesses " properties analogous to those of a magnet ;
there are to be distinguished in it poles equally different and
opposite, which may even be communicated, changed, destroyed, and
restored ; even the phenomenon of inclination is observed therein."
By means of this magnetic fluid all the maladies of man could be
healed. A few years later Mesmer left Vienna for Paris. At first
he magnetised his patients by gazing steadily at them, or by means of
" passes " ; but as patients became more numerous, he brought them
into a proper magnetic condition by other methods, often of a very
fantastic nature. The patients did not, when magnetised, all show
the same symptoms ; some passed into a heavy sleep, some became in-
sensible to touch, or even to stimuli ordinarily painful ; some became
cataleptic, some were seized with local or general convulsions. This
last condition was called a crisis, and was the triumph of the mes-

26 Mr. J. K Langley [March 14,

meriser, the moment when the disease was considered to be forcibly-
expelled from the system. Now-a-days it is the last state a physician
would care to produce in a patient.

For a time Mesmer's success was enormous. His admirers sub-
scribed for him a sum of nearly 350,000 francs, receiving in return
details as to the method of magnetisation. In Paris the belief in the
power of Mesmer to cure diseases soon waned ; but by this time he
had made a stir in the world, and had drawn attention to a number
of facts which were either only locally known, or largely disregarded.
Mesmer devoted himself chiefly to curing patients, and it must be
added, to receiving fees ; but about ten years after the time of his
coming to Paris it was found that a state resembling somnambulism,
or sleep-walking, could be produced in some persons by magnetising
them. This gave a stimulus to the investigation of what I may call
the magical side of the phenomena. This magical side had always
been present, but in the height of Mesmer's power had not been much
regarded. Of the magic of animal magnetism I will say one word
more presently.

The term animal magnetism lingered long, but has now happily
fallen into disuse, either mesmerism or hypnotism being used in its
stead. " Hypnotism " we owe to Dr. Braid of Manchester, who, from
1841 to the time of his death in 1860, subjected all the phenomena
said to be produced in the magnetic state to a searching investigation.
Braid is the founder of mesmerism in its scientific aspect. Hypnotism
and mesmerism, as commonly used now, are synonymous terms ; it
would be advantageous, I think, if we could make a distinction
between them. We might, for example, use the term hypnotism to
embrace all those phenomena which are proven, and the term mes-
merism to embrace all those phenomena which are not proven.
Mesmerism would then mean what I have called its magical side
and would embrace those phenomena which are sometimes called the
higher phenomena of mesmerism. These are of various kinds. It
is said, for instance, that one person can, at any time he wishes,
mesmerise another who is at a distance, and who is in perfect
ignorance of the intentions of the mesmeriser ; that a mesmerised
person can perceive the thoughts and sensations of the mesmeriser,
without receiving any indications from the known organs of sense ;
that a clairvoyant can see with parts of the body other than the
eyes, for example with the back of the head, or with the pit of the
stomach ; that a clairvoyant can describe places and persons which
he has never read of, or heard of, or seen. Those observers who
have done most to elucidate the subject, such as Braid, have failed
to observe any of these and other similar higher phenomena. They
are unproven. It would be convenient, 1 say, to include such
phenomena only, under the heading of mesmerism ; but this I cannot
yet venture to do. The facts I have to mention I shall call those
of hypnotism or mesmerism indifferently. The magical side of the
subject may, I think, at present be fairly left out of account.

1884.] on the Physiological Aspect of Mesmerism. 27

Primarily, the hypnotic or mesmeric state is one in which the
will is partially or wholly paralysed by certain sensory impressions ;
but there is no distinct line of demarcation between this and
various other conditions, such as occur in sleep, somnambulism,
and in some diseases of the central nervous system, such as hysteria.
In each there is a typical state, but between them are many transition
states.

Before discussing the mesmeric condition, I must say one or two
words about the action of the central nervous system. I trust you
will forgive me if, as very well may be the case, you find that part of
what I say seems too simple to need saying, and part too complex and
uncertain to be said without reservation. The one for the sake of
clearness must needs be stated ; the other for the sake of brevity must
needs be dogmatic.

Here is a diagram of the brain and of the spinal cord of the frog.
In this, all the chief structures of the brain of man are represented.
For my present purpose it is only necessary to distinguish three
divisions.

First there is the spinal cord. If a frog be decapitated, the brain
is of course removed and the spinal cord is the only part of the central
nervous system left. Yet if any part of the body of the brainless frog
be gently stimulated, a particular movement results — a reflex action is
produced. If, for instance, the right hind leg is gently pinched, this
leg and this only is kicked out ; if the left fore leg is gently pinched,
this and this only is moved. Diagrammatically we may represent any
one of these movements as being brought about in the following way.
Pinching the skin stimulates the nerve endings of a sensory nerve,
£0 that a nerve impulse — analogous to, but not identical with, an
electric current passing along a wire — travels up the nerve to a
sensory nerve cell in the spinal cord. In this nerve cell certain
changes take place which result in an impulse being sent along
another nerve to a motor nerve cell in the spinal cord. This is, in
consequence, stimulated to activity and sends out a third impulse along
a motor nerve to a muscle. The muscle then contracts, and the limb
is moved.

If the brainless frog be pinched somewhat sharply, the movements
which result are more extensive than when it is gently pinched, a
spasm of the whole body may result. Referring to the diagram, we
may represent this in the following way. The sensory cell being
more strongly aifected, sends out impulses to a number of other
sensory cells on the opposite side of the spinal cord, and above and
below it ; these send impulses to their motor centres, and thus a more
or less widely-spread movement results. This spreading out of im-
pulses from the part immediately affected is called the irradiation of
exciting impulses. When any part of the skin is stimulated, many
sensory and many motor cells are affected ; a collection of cells
serving a common purpose is called a nerve centre. The spinal
cord, then, consists of a collection of nerve centres. By appropriate

28 3Ir. J. N. LangJeij [March 14,

stimulation, any one, or all of these nerve centres can be set in
activity.

The second division of the central nervous system is the pos-
terior part of the brain — the brain minus the cortex of the cerebral
hemispheres. This, like the spinal cord, consists of a collection of
nerve centres, but the function of these nerve centres is much more
complex than that of the centres of the spinal cord. A stimulus to
the skin, which, when the spinal cord is the only part of the central
nervous system left, will produce either a local movement or no
movement at all, will, when the posterior part of the brain is also
present, produce a general co-ordinated movement such as occurs in
walking, jumping, swimming. In fact, all the co-ordinated movements
of which the body is capable can be brought about by the activity of
one or more of the lower centres of the brain. Moreover, these centres
can be set in action by events which have no effect when the spinal
cord only is present. Here a flash of light or a sudden noise sets in
activity a nerve centre in a manner strictly comparable to the way in
which a pinch applied to the foot sets in activity a nerve centre in the
spinal cord ; and just as in the spinal cord the active sensory centre
may excite to activity a motor centre, and this may cause the foot to
be moved, so in the lower centres of the brain the activity of the
visual or auditory centre may excite to activity a motor centre and
lead to a complicated movement such as shrinking or jumping, A frog
with these two divisions only of the central nervous system does
nothing of itself; it is without will and consciousness, in the same
way that the frog with a spinal cord only, is without will and con-
sciousness ; it is a complicated machine, any part of which can be
put in action by using the proper means.

The last division of the central nervous system is the cortex of
the cerebral hemisf)heres. This part of the brain is concerned with
ideas, with will, and with consciousness in the sense in which that
term is usually employed, that is, speaking generally, it is con-
cerned with the higher psychical functions.* In saying that this
part of the brain is concerned with the higher psychical functions,
I mean that every higher psychical act is accompanied by some
definite change in the cortex of the cerebral hemisphere. I mean
that every emotion, every idea, every effort of will is accompanied
by an activity of nerve cells in this part of the brain and that
this activity is comparable to the activity which takes place in
definite cells of the spinal cord when a leg or arm of a brainless
frog is pinched.

Here we touch the much disputed question of the localisation
of the functions of the brain. Eoughly speaking, this question
is whether there are nerve centres in the cortex corresponding to
those which exist in the rest of the brain and in the spinal cord : —

♦ It is not possible within the limits of this lecture to give the reservations
that wonlrl be nccoHsary in a full discussion of the subject.

1884.] on the Physiological Aspect of Mesmerism. 29

whether, for example, visual sensation and ideas are accompanied by
an activity of one part of the cortex, and auditory sensation and ideas
are accompanied by an activity of a different part of the cortex ; or
whether visual and auditory sensation and ideas may occur in any
part of the cortex, the mode of activity of the cells being different in
the two cases.

Happily, it is not necessary to enter into this question in order to
gain a fair idea of the chief features of mesmerism. The idea which
we gain lacks no doubt definiteness in detail, and we must be prepared
to express it in different language according as we find later, that the
cortex of the cerebral hemispheres consists of one nerve centre with
many functions, or of many nerve centres with different functions, or
again as we find — and this is most probable — that the truth is between
these two extreme theories.

But whilst we may put in the background the question of localisa-
tion of function for the cortex of the brain, we must linger a little to
consider its mode of action. I will take a particular instance.

The changes which occur in the retina of the eye when rays of
light from an external object fall upon it give rise to nervous impulses
which eventually produce in the cortex of the brain a certain activity ;
this activity leads to our forming an idea of the object. Now in
some cases the formation of the idea is all that takes place : often,
however, impulses are sent out from the active cells of the cortex to
a motor centre in the lower part of the brain, and a movement is
made. This is a reflex action from the cerebral cortex. Here the
active sensory centre excites a motor centre, just as happens in the
spinal cord of a frog the leg of which is pinched. Our actions are
often of this nature, though in many cases of course it is very difficult to
say how far the will is exercised in the action. If you give a child
a sweetmeat, the child sometimes no doubt deliberates what to do with
it ; in others the rapid transference of the sweetmeat to the mouth
seems to be simply a reflex action entirely independent of any effort
of will, though accompanied by consciousness.

Dr. Carpenter has introduced the useful term unconscious cerebra-
tion into physiological-psychology. By this is meant that the cortex
may be active without our knowing anything about it. An instance
which Dr. Carpenter gives, is that of trying to remember a name
which for the moment we have forgotten, in such cases it is often
best to give up consciously thinking, but the fundamental activities
in the brain which accompany thinking go on nevertheless, so that
presently without farther conscious effort, the name is remembered, is
as it were thrown up into consciousness.

I said a moment ago that reflex actions not infrequently occur in
which a conscious idea forms part of the reflex chain. But conscious-
ness is not necessary to the reflex action ; that is, the changes in the
cortex which are the physical basis of the idea may be carried out
without giving rise to consciousness. Here we want a term to imply
that state in which everything necessary for an idea is present except

30 Mr. J. N. Langley [March 14,

consciousness. Sometimes tliis is called an "unconscious idea,"
which would be convenient enough but that " idea " is generally taken
to imply consciousness. It is an act of unconscious cerebration.

Eeflex actions in which an unconscious cerebration forms part of
the chain occur to all of us. Some time ago, whilst walking up and
down the laboratory at Cambridge thinking intently on the result of
an experiment, I noticed that the pipe which I had been smoking had
gone out. Making up my mind to light it again, I walked to the
place where the matches were kept, which happened to be close to
a water-tap. As I went I began thinking again of my experiment.
In a moment or two I was disturbed by a rush of cold water over my
hand. I found that I had turned the water-tap, and let the stream of
water run full into the bowl of my pipe. This was a reflex action
from the cerebral cortex. The sight of the tap had given rise to what
for this once I will call an unconscious idea, which had led to the
somewhat complex movements of turning the tap and collecting the
water in the pipe-bowl.

The central nervous system consists, then, of a vast number of
nerve centres, each of which can be set in activity by an appropriate
nerve impulse reaching it either by a peripheral nerve or from some
other nerve centre. The action of these nerve centres is normally
controlled by the will.

Here, at last, we come to mesmerism; the primary point in
mesmerism is the paralysis of the will ; the nervous system is then
out of the control of the subject, whether animal or man, and by
appropriate stimulation, any one or more of his nerve centres can
be set in activity. I shall consider first the behaviour of the lower
animals when mesmerised : in these the phenomena, as far as at
present observed, are much simpler than they are in man. If a frog
be turned over on its back, it at once regains its normal position ;
if, however, it be prevented from doing so, and its struggles are
for a short time gently suppressed, it becomes hypnotised. Then,
although it be left at liberty to regain its normal position, it will not
attempt to do so. Apart from the movements it makes in breathing,
it lies motionless. If it has been held for a short time only, the
hypnotic state does not last long, usually from one to five or ten
minutes ; but, if the movements it makes, say at the end of one minute,
of five minutes, and so on, are suppressed, it will not infrequently
happen that the frog will then stay without farther movement for a
considerable time, sometimes even for many hours. During the first
part of this time a slight pinch, a sudden flash of light, or a loud
noise, will usually cause it to turn over and sit up in its normal
manner. For a moment or two it looks a little dull and confused, but
rapidly regains its normal activity. During the latter part of this
time it responds less and less to external stimuli. Reflex actions are
less readily obtained, or may not be produced at all by stimuli
ordinarily effective. Within certain limits, the longer the frog
remains hypnotised, the more marked becomes its general insensi-

1884.] on the Fhjsiological Aspect of Mesmerism. 31

bility, the decrease in reaction being earliest distinct in the centres of
special sense. When it is in this state, it may be propped up against
a support with its legs crossed under it, or placed so that it rests on
its head, or placed on its side with its legs arranged in this or that
fashion, without offering the least resistance. Strong stimuli, or
certain apparently lesser ones, for example a dash of water, cause it
to recover its position slowly ; it then usually sits for several minutes
motionless, and only after some time regains its normal sensitiveness
and activity. I show you here a frog in the early hypnotic state.

I have spoken of the frog as being hypnotised or mesmerised.
Let us consider what is meant by this. I think it is obvious that the
animal does not remain passive from any astuteness on its part ; it is
incredible that the frog, finding its efforts to escape ineffective, should
make up its mind to remain quiet, and should, although at liberty to
move, stay still for hours, becoming more and more determined as
time goes on to take no notice of noises, of flashes of light, and of
pinching of its skin. On the contrary, it is, I think, obvious that in
some way its will has become paralysed. In order to attempt to
explain how this is brought about, we must consider another aspect
of reflex action, an aspect which is very little understood.

You remember that a brainless frog will, when its leg is gently
pinched, kick out the leg ; but if just previously some other part of the
body has also been pinched, one of two opposite things may take place :
the leg may be kicked out more quickly and vigorously, or it may not
be kicked out at all. In both cases the nerve centre involved in pro-
ducing the movement of the leg receives an additional impulse from
another nerve centre, but in one case the additional impulse increases
the activity of the nerve centre involved in the reflex action, in the
other case it annuls this activity — there is, to use the physiological
term, an inhibition of the " reflex " nerve centre.

To take another instance, a frog without its cerebral hemispheres,
but with the rest of its nervous system, will croak when its sides are
gently touched ; but if at the moment of touching it, its leg be
pinched, it moves or jumps, but does not croak. Here the motor
centre which causes the movements of the muscles in croaking, receives
nervous impulses from two sensory centres ; one of these being set in
activity by touching the sides of the frog, the other from pinching its
leg. The impulses from the former tend to make the motor centre
active, and so produce a croak ; but the exciting effect of these
impulses is annulled by the impulses coming from the latter centre ;
in other words the nerve centre involved in croaking is inhibited.
Inhibition by impulses proceeding from the cortex of the brain occurs
every day of our lives. The " will " is perpetually being brought
into play to inhibit some nerve centre or other. For example, you
may be on the verge of yawning, when it suddenly occurs to you that
it will be better not to do so ; you suppress the yawn without moving
a muscle. What happens is this. An inhibitory nerve impulse is
sent from the cortex, and puts a stop to the indiscreet activity of a

32 Mr. J. N. Langley [March 14,

nerve centre elsewhere in the brain. Further, when the cortex is set
in activity in a particular way by one impulse, another impulse
reaching it may inhibit the first activity, or, in terms of the localisa-
tion theory, one nerve centre in the cortex may send out inhibitory
imj^ulses to any other nerve centre of the cortex.

I need not farther multiply instances of inhibition. I wish,
however, to lay stress on this, that it is highly probable that
impulses travelling from any peripheral nerve-ending to a nerve
centre, or from any one nerve centre to any other, may, under certain
circumstances, diminish or annul the functional activity of the nerve
centre, that is, may inhibit it. And there is equal reason to believe
that, under certain other circumstances, the effect produced will not
be inhibition, but an increase of activity of the centre. The exact
conditions which determine whether one effect or the other takes
place, have not as yet been made out. For the present the facts must
suffice us. We may now return to the mesmerised frog.

Whatever the will may be, its action is accompanied by a certain
activity of the cortex of the brain ; if this activity is prevented from
taking place, the will can no longer act. From the physiological
standpoint, then, the mesmerised frog lies motionless because an
inhibition of a particular activity of the nerve cells of the cortex has
taken plaoe. We may distinguish two chief causes of this inhibition.

The tactile stimuli sent to the central nervous system when the
frog lies on its back are obviously different from those sent when
the frog is in its normal position. The unusual nerve impulses
travelling from the skin in the unusual position of the frog are
inhibitory nerve impulses. There is reason to believe that they act
first on some lower centre of the brain, and that from this, impulses
are sent which diminish or annul the activity of the cortical nerve
ceils which is necessary for the exercise of will.

The second chief cause of inhibition is in the cortex itself.
Handling the frog in the way which is done when it is mesmerised,
produces a certain emotional condition which we may call fright.
But when the animal is frightened, the nerve cells of the cortex are
set in activity in a special manner. This mode of activity inhibits
other modes of activity, and the will is paralysed.* We cannot at
present, I think, put in any more definite form the effect of one state
of the cortex of the brain upon its other possible states. We do not
know enough of the relations of the cortex of the brain to the
psychical functions to say more. In some cases fright seems to play
a very small 2)art, if any, in producing the effect. That it is not an
essential factor is, to some extent, confirmed by the fact that a frog
without the cerebral hemispheres can be easily mesmerised ; it is

* The term " paralysis of the will " is here used to include the state in which
there is an effort of will, but in wliicli the effort is not followed by a despatcii of
nervous impulses from the cerebral hemispheres to the lower nervous centres.

1884.] on the Physiological Aspect of Mesmerism. 33

difficult to conceive of the animal in this state being very much
frightened.

It will be remembered that reflex action from all parts of the
body is diminished in the mesmerised frog. After a time, then, there
is a marked inhibition of activity of the whole nervous system.
Now in the brainless frog placed on its back there is no such diminu-
tion of reflex action ; hence in the intact hypnotised frog the spinal
cord must be inhibited by impulses coming from the brain; from
which we may conclude that centres inhibited in their own proper
actioD, nevertheless send out inhibitory impulses to other centres.
There appears then to be an irradiation of inhibitory impulses, just
as we have seen that there is an irradiation of exciting impulses.

There are two other features in the hypnotised frog which I
must mention, although time will not allow me to discuss them.
It sometimes happens that soon after a frog has been hypnotised,
reflex actions, instead of being more difficult to obtain than normally,
are obtained more easily. Preceding the condition of reflex decrease
there is a condition of reflex increase. Further, it sometimes happens
that the hypnotised frog, instead of lying with its muscles flaccid,
passes into a cataleptic state, so that its limbs tend to remain in any
condition in which they are placed. Both the condition of reflex
increase and that of catalepsy are more marked in man.

Before passing to mesmerism in man I will show you two
other instances of hypnotism in the lower animals. The alligator
which you see here behaves very much like the frog. It has, how-
ever, less tendency to become cataleptic. After a brief struggle, it
becomes quiescent and its limbs slowly relax ; its mouth may then
be opened, and a cork placed between its teeth, without giving rise to
any voluntary movement on its part. It may be kept for a consider-
able time in this limp condition by gently stroking the skin close to
its eyes.

So far as I have observed, the hypnotic condition in birds and in
lower mammals is not capable of any great development. It may
last ten minutes, but rarely longer. In these animals, too, the
emotional condition is probably the chief factor in producing the
inhibition. Of impulses from peripheral sense organs, tactile im-
pulses seem to be most effective in the lower mammals, as in the
rabbit and guinea-pig, and visual impulses in the bird. The pigeon
which I have here, remains longest quiescent when, after it has been
held for a minute or two, I bring my hand slowly up and down over
its head.

In man the phenomena of mesmerism are of a very much more
striking character than they are in the lower animals. Speaking
generally, this seems to be due to a greater interdependence of the
various parts of the nervous system in the lower animals. In these,
when any one centre is stirred up by exciting impulses, an irradiation
of exciting impulses is apt to take place to all other centres, and the
mesmeric state is in consequence apt to be broken. And on the other
(Vol. XI. No. 78.) d

34 Mr, J. N, Langley [March 14,

hand, when a centre is inhibited, an irradiation of inhibitory impulses
is apt to take place, and the whole nervous system is in consequence
apt to be inhibited. Hence the activity or suppression of activity
of particular parts of the central nervous system, which forms so
conspicuous a feature of mesmerism in man, can be only partially
produced in the lower vertebrates. Even in man there is very con-
siderable difference, in different individuals, in the ease with which par-
ticular nerve centres can be excited or inhibited without other centres
being similarly affected. But apart from this the fundamental
features are the same, whether a man or a frog be mesmerised. The
primary point is, as I have said, the paralysis of the will, that is, the
inhibition of a certain activity of the nerve cells of the cortex of the
cerebrum.

In man, as in the frog, this inhibition may be brought about either
by impulses proceeding from the peripheral organs of sense, or by
impulses originating in the cortex itself. Of the former class, tactile
and visual impulses are most effective, although the mesmeric state
may be produced by auditory and probably by other impulses. A
man may, then, be mesmerised by passing the hands over or close
to the skin, or by making him look steadily at an object, or listen
intently to a sound.

Whether the inhibitory impulses so set up produce inhibition or
not, depends upon the condition of the whole of the nervous system.
The effect of the inhibitory impulses may be counteracted by exciting
impulses coming from other parts of the central nervous system. In
many people the exciting impulses are always sufficiently strong to
overpower the inhibitory ones, and such people cannot be mesmerised.
In others, the inhibitory impulses must be kept up for a long time,
and repeated on successive days, before they acquire sufficient force
to overcome the exciting ones. Such people are mesmerised with
great difficulty.

The great majority of people cannot be mesmerised unless they
consent to fix their attention on some particular object. This fixing
of the attention, speaking generally, seems to be a voluntary exclusion
of exciting impulses, leaving thus the inhibitory ones an open field.
Idiots, who, on account of the lack of co-ordination of their nerve
centres, cannot fix their attention for any length of time on any one
object, cannot as far as I know be mesmerised. Now this, now that part
of the brain becomes active, and exciting impulses are sent out which
overpower the inhibitory ones.* Inhibition from impulses arising in
the cortex itself are rare unless the patient has been previously mes-
merised. Some such cases, however, do occur. But in people who
have been previously mesmerised inhibition in this manner is of not
unfrequent occurrence ; within limits, the more often the changes in

* It is said tliat some persons, whilst they arc sleeping, can be brought by
means of passes into the mesmeric state. It would be interesting to observe if
this can also be done with insane people.

1884.] on the Physiological Aspect of Mesmerism, 35

the cells accompanying inhibition have been produced, the easier
they are to reproduce. Those who have often been mesmerised may
fall again into this condition at any moment, if the idea crosses their
minds that they are expected to be mesmerised.

Thus if a sensitive subject be told that the day after to-morrow at
half-past nine he will be mesmerised, nothing more need be done ; the
day after to-morrow at half-past nine he will remember it, and in so
doing will mesmerise himself.

An instance sent by M. Eicher to Dr. Hake Tuke, presents, it
seems to me, an example of inhibition from the cortex which is of a
somewhat different class, and more allied to that which occurs in birds
and lower mammals. A patient was suspected of stealing some
photographs from the hospital, a charge which she indignantly denied.
One morning M. Richer found this patient with her hand in the drawer
containing the photographs, having already transferred some of them
to her pocket. There she remained motionless. She had been mes-
merised by the sound of a gong struck in an adjoining ward. Here,
probably, the changes in the cortex accompanying the emotion which
was aroused by the sudden sound at the moment when she was
committing the theft, produced a widespread inhibition — she was
instantaneously mesmerised.

I will show you the method of mesmerising which is, perhaps, on
the whole, most effective ; it is very nearly that described by Braid.
I have not time to attempt a mesmeric experiment to-night, it is the
method only which I wish to show you. With one hand a bright object,
such as this facetted piece of glass, is held thus, eight to twelve inches
from the subject, so that there is a considerable convergence of the
eyes, and rather above the level of the eyes, so that he is obliged to look
upwards. The subject is told to look steadily at the piece of glass,
and to keep his whole attention fixed upon it. This position is kept
up for five to ten minutes ; during this time the pupils will probably
dilate considerably, often assuming a slight rhythmic contraction and
dilation ; when this is the case the free hand is moved slowly from
the object towards the eyes. If the subject is sensitive, the eyes will
usually close with a vibratory motion. In some cases the subject is
then unable to open them, and the usual mesmeric phenomena can be
obtained. If when the operator brings his hand near the eyes of the
subject, the subject instead of closing them follows the movements
of the fingers, the whole proceeding is repeated, but the subject is told
to close his eyes when the fingers are brought near them, but to keep
them fixed in the same direction as before, and to continue to think
of the object and that only. The operator then for some minutes
makes " passes," bringing his warm hands over and close to the face
of the subject in one direction. When the subject is inclined to pass
into the cataleptic state, an indication of his condition may be obtained
by gently raising his arm ; if he is beginning to be mesmerised, the
arm remains in the position in which it is placed. If the arm
falls, the mesmeric state may not infrequently be hastened on by

D 2

36 Mr. J. N. Langleij [March 14,

telling the subject to keep his arm extended whilst he is still gazing
at the object, or whilst the passes are being made. And that is the
whole of the process. The man thus mesmerised sinks from manhood
to a highly complicated piece of machinery. He is a machine which
for a time is conscious, and in which ideas can be excited by appro-
priate stimulation ; anyone acquainted with the machinery can set it
in action.

The distinguishing feature of the earlier stages of mesmerism
in man is that by slight stimulation any one centre can be easily
set in violent activity, and its activity easily stopped, without the
activity spreading to other distant centres. It is on this that the
mesmeric j^henomena usually exhibited depend ; with most of these
phenomena you are no doubt familiar, so that I need mention one or
two only.

Complicated reflexes may be produced in various ways, just as we
have seen is the case with a frog even when without its cerebral
hemispheres. Thus Braid mentions that on one occasion an old
lady who had never danced, and who indeed considered it a sinful pas-
time, when mesmerised began to dance as soon as a waltz tune was
played.

A statement made to a subject will often produce implicit belief
notwithstanding the evidence of his senses. I remember telling a
subject that I was about to bring a hot body near his face, and he was
to tell me when it was painful. I put my finger on his cheek, upon
which he cried out violently that I was burning him. When he was
awakened he remembered that I had touched him with something
very hot. The idea I had given him was remembered, the evidence
of his sense of touch was disregarded. Even in ordinary, apparently
wakeful, life an idea may produce a belief in no way borne out by
the evidence of the senses. Dr. Beard narrates that once when
crossing the Atlantic, the steamer he was in ran into a sailing-
vessel. It was at night, and amidst the roar of the wind, the shrieks,
and cries, and prayers of the passengers, the cry went forth that the
steamer was stove in and the bow sinking; straightway all eyes
were turned to the bow, and to every eye it seemed to be sinking.
" I sha,ll never forget," he says, " how it gradually lowered in the
darkness." In fact, however, the vessel was uninjured, and the bow
did not sink at all. Here probably tht? majority of the people present
passed simultaneously into a condition resembling the mesmeric con-
dition ; the idea presented to them by the cry " the bow is sinking "
being more powerful than the ideas aroused by the objects actually
seen.

But even in the absence of strong emotion, it may happen that an
idea suggested by a statement may be more powerful than the proper
sensory impression. There are some persons, apparently perfectly
trustworthy, who nevertheless, if they were told to look closely at the
top of this bell jar and sec the faint flame coming from it, would very
soon see the flame quite distinctly. In health, as well as in disease.

1884.] on the Physiological Aspect of Mesmerism. 37

there are many partial revelations of the condition produced by
mesmerism.

In some subjects the sensibility of the skin to variations of
temperature is very greatly increased, so that the contour and size of
an object which is brought near the skin can be recognised by the
alteration in the feeling of temperature of the part. The size and
contour of an object such as a book or a coin being thus known, the
subject may of course be able to guess that a book or coin is being
held before him.

There are certain attitudes which we usually assume under the
influence of certain moods or ideas ; from each of the muscles con-
cerned in bringing about any one attitude, impulses travel up to the
brain, and give rise to a definite muscular sensation which comes
therefore to be associated with a particular mental mood. In mes-
merised people the production of a definite muscular sensation not
infrequently produces in the mind the mood with which it is, in the
wakeful state, associated. At the same time ideas may be produced
corresponding to the mood, and the ideas may give rise to particular
actions, such as laughing, crying, fighting.

If the head is pushed back and the shoulders opened out, the
face assumes a look full of pride or haughtiness, and if the subject be
asked what he is thinking about, he will give some answer indicating
what a fine fellow he fancies himself to be. If, then, the head is
bowed and the shoulders contracted, the aspect of the face changes
to one of humility and i)ity. Occasionally it happens that a slight
pressure on a single muscle, which causes it to contract, will by an
irradiation of nerve imj)ulses produce the muscular sensations proper
to a group of muscles, and this will give rise to the associated frame
of mind. Thus very different feelings may be made to rapidly
succeed one another in the mind of the subject by simply pressing on
various muscles of the head and neck. At first sight such an experi-
ment looks like a revival of the now happily forgotten phrenology.

I have said that in a frog which remains mesmerised for any time,
there is a considerable reflex depression, i. e. inhibition of the whole
of the central nervous system — that there is an irradiation of inhibitory
impulses. In man a similar irradiation of inhibitory impulses appears
to take place ; usually a mesmerised person if left alone passes
gradually, but often rapidly, into a state of torpor ; consciousness
disappears, memory is lost, reflex action becomes difficult to obtain,
finally, it may be, there is complete anaesthesia, a limb may be cut off
without producing any movement or any pain ; since this torpor comes
on without anything farther being done to the subject, we may con-
clude that here, as in the frog, but to a much more marked degree,
there is an irradiation of inhibitory impulses. The primarily
inhibited centres send out inhibitory impulses to all other nerve
centres. Up to a certain stage, possibly throughout, any one or more
centres may be brought back to a condition of activity by certain
exciting stimuli, but when these cease the inexcitable condition is

38 Mr. J. 'N. Langley [March 14,

soon brotiglit back by the inhibitory impulses streaming to them from
other nerve centres.

The extent to which the torpid condition develops itself, varies in
different individuals. It depends upon the condition of the nervous
system, upon the relative intensities of the inhibitory and exciting
impulses. As far as our present knowledge goes, it would appear
that a few only of those who can be mesmerised, can be made to pass
into a condition of complete anaesthesia. It is possible, however,
that this may be due to the passes which give rise to inhibitory
impulses not being continued long enough. Dr. Esdaile, who in
India was accustomed to mesmerise his patients before performing
surgical operations upon them, used to continue the passes for one to
two hours, and often to repeat this for several days in succession.

In different people the order in which different centres are
inhibited varies, as we should expect from the unequal development
of different centres in different people. This is no doubt of influence
in determining whether the general state is cataleptic, somnambulistic,
or lethargic, and here probably the method used to mesmerise is also
of considerable importance ; it would seem that the cataleptic condi-
tion is more likely to be developed when the process of mesmerisation
involves a strain on the eyes of the subject, than when he is mes-
merised by passes. Not much attention, however, has as yet been
directed to this point.

There can, I think, be no doubt that mesmerism may help,
and sometimes cure, persons suffering from certain diseases of the
nervous system. It is not in our power to make any accurate state-
ment of the way in which this is brought about ; but since disease
may be the result of either an over-activity or of an under-activity of
any part of the central nervous system, it is reasonable to suppose
that a beneficial effect will follow the employment of a method
which allows us to diminish or increase these activities as we will.
This is a side of the question which is of the greatest interest both
to physicians and to physiologists — to physiologists, since it bears
directly upon the problem of the influence of the nervous system on
nutrition. There is good reason to believe that by directing attention
strongly to any particular part of the body, the nutritive state of
that part of the body may be altered. The determination of the
actual way in which this is brought about is full of difficulties, but
the following way is at least theoretically possible. It may be that
the nerve centres connected with the tissue in question are made
unusually active, and that they send out nerve impulses of a trophic
nature, that is, impulses which directly control the nutrition of the
tissue. The alteration in the tissue caused by its changed nutritive
state — its changed metabolism — may conceivably be either beneficial
or detrimental to the whole organism ; it may give rise to a diseased
state, or get rid of an existing one.

The modern miracles of healing, wrought in persons in a state of
religious enthusiasm, offer a field for investigating this problem ; the

1884.] on the Physiological Aspect of Mesmerism. 39

field, however, is a particularly bad one, and chiefly because so many
people concerned regard any careful examination of the subject as
impious. But in mesmerised j)ersons it seems probable that such
investigations could be made on a fairly satisfactory basis. Men
when mesmerised gradually lose remembrance of those things which
they remember when they are awake, but not infrequently other
things are remembered which are forgotten in the waking state.*
This is normally the case with a person who has been previously and
recently mesmerised. He may then remember little else than what
took place in the corresponding stage of his previous mesmerisation.
In a certain state, then, an event or a command will produce in the
central nervous system those changes which are necessary for the
event or the command to be remembered later, without ever rising to
consciousness in the waking condition. Thus a command to do a
particular thing, given to a subject in this mesmeric stage, may be
carried out when he awakes, although he is quite unconscious why he
does it. We may say that such an act is one of unconscious memory.
But it is, I think, something more than this. The subject is usually
uneasy and preoccupied until the thing is done ; he is to a greater
or less extent unable to fix his attention on other things ; he is, in
fact, in a state of unconscious attention to an unconscious memory.
This brings us to our point. It suggests that if a subject in a
certain stage of mesmerisation be told that in a few days a sore will
appear upon his hand, or conversely that a sore already there will
disappear, the conditions which accompany conscious expectation and
attention, will to a certain degree be established; and the trophic
influence of the nervous system on the tissues may be tested in a
manner which puts the experiment fairly within the control of the
observer, and to a certain degree excludes imposture. Such an
experiment has obviously some "drawbacks, it would probably only
succeed, if it succeeded at all, with a person whose nervous system
was in a state of unstable equilibrium ; and it can hardly be expected
that the effects would be so striking as when conscious expectation
is also concerned. Still observations of this kind are well worth
attention, on account of the medical, the physiological, and the
psychological issues involved in the results.

A lightly mesmerised subject can be easily brought back to a
normal condition by a sudden slight shock, by sprinkling water in the
face, or by a current of cold air. These give rise to exciting impulses
which arouse to normal activity the inhibited parts of the brain ; just
as we have seen that any other part of the central nervous system can

* A case is recorded by Braid, of a woman who, during natural somnam-
bulism— which is almost identical with a state that can be produced by mes-
merism—could repeat correctly long passages from the Hebrew Bible, and from
books in other languages, although she had never studied any of these languages,
and was quite ignorant of them wlien slie was awake. At length, however, it was
discovered that she had learnt the passages when she was a girl, by hearing a
clergyman with whom she lived read them out aloud.

40 Mr. J. N. Langley [March 14,

be aroused to activity by slight exciting impulses. There is no
mystery in this, beyond the mystery which lies in the relative action
of all exciting and inhibitory impulses. The power of responding in
strikingly diiferent ways to weak stimuli differing in kind, or to stimuli
apparently of the same kind, but differing in intensity, is not peculiar
to the nervous system of man ; it is a jDOwer possessed by the nervous
system of all animals, and indeed, not improbably by all living
substance. This has already been touched upon in what I have said
of inhibition, but I will give you one or two other instances of the dis-
similar effects produced by slight, and apparently not very dissimilar,
stimuli, instances which are especially pertinent to the subject of
mesmerism. These we owe to Heidenhain.

When morphia is given to a dog, and the animal is left undis-
turbed, it passes into a condition resembling sleep ; but a little
investigation usually shows that the condition differs in certain
notable respects from sleep. Whilst consciousness, as far as can be
told, is gone, and voluntary movement is abolished, many reflex
actions can be obtained much more readily than in the waking state ;
moreover, there is a tendency for the muscles which contract in a
reflex action to remain contracted, the nerve centres when set in
activity remain active for a considerable time, and continue to send
out impulses to the muscles, which in consequence are kept con-
tracted ; in other words the reflex contraction produced by a slight
stimulus applied to the skin is of a tonic instead of a tetanic
nature. Now this tonic contraction can be brought to an end by
various slight stimuli, for instance by lightly stroking the skin
over the contracted muscles, by gently tapping the contracted
part, by blowing in the face of the animal, or by stimulating
the cortex of the brain by a weak electric current. Nevertheless,
the acts just mentioned may, when the muscles are not contracted,
cause or help to cause, their contraction. I will give an instance of
this. Electrical stimulation of a definite part of the cortex of the
brain causes a tonic contraction of certain muscles of the leg, in con-
sequence of which, let us say, the leg is bent and remains so. Now wo
have seen that passing the hand over the skin of the leg will cause it
to unbend ; well, if the cortex of the brain be stimulated with an
electric current, not quite strong enough to produce of itself bending
of the leg, the bending may at once be produced by gently stroking the
leg at the same time as the cortex is being stimulated. Of a similar
nature is the effect of electrical currents of different strengths.
When a limb has been brought into a state of tonic contraction by
electrical stimulation of a certain part of the cortex of the brain, a
weaker electrical stimulation of the same spot of the cortex will bring
the tonic contraction to an end.

The phenomena just described as occurring in a dog under the
influence of morphia, closely resemble those often observed in human
beings when mesmerised. Commonly in a mesmerised person the
arm, let us say, may be made to bend by gently stroking the skin over

1884.] on the Physiological Aspect of Mesmerism. 41

the appropriate muscles ; give a slight tap on the arm, and it relaxes.
Braid observed in some subjects that if a limb was made rigid by-
passing the hands over it, and if it was left extended for a short time,
then the repetition of the same act of passing the hands over the limb
caused the rigidity to disappear. It is unnecessary, I think, to con-
sider in detail the corresponding states in the narcotised dog and the
mesmerised man ; enough has been said to show that in both certain
slight stimuli produce, sometimes excitation, sometimes inhibition.

It must, however, be noted, that our conception of inhibition is not
rendered clearer by these facts ; for it would appear from them that a
nerve centre may be excited or be inhibited by the same nerve impulse,
the result depending upon the condition of the nerve centre. This
is not a necessary inference, but it is perhaps at present the most
convenient working hypothesis. A certain group of facts, indeed, may
be held together and receive a provisional explanation by saying that
in some conditions of the central nervous system, a stimulus excites a
nerve centre if it is quiescent, and inhibits it if it is active.

It seems to me probable that what is called the " transference of
contracture " and the " transference of sensation " are of the same
order of facts. These phenomena are exceedingly curious. Suppose
that the left biceps of a mesmerised person be gently stroked or pressed,
so that it contracts and remains so. The continuous contraction of
the muscle is called contracture. In consequence of the contracture,
the arm is kept bent. Suppose that the biceps of the other arm be gently-
stimulated, we may get a transference of the contracture, i. e. the right
biceps becomes contracted and the right arm bent, whilst the left arm
which previously was bent, falls flaccid. Similarly there may be a
transference of sensation ; thus the right arm say is rendered insensi-
tive, so that pricking it with a needle does not give rise to any sensa-
tion ; on the back of the right hand, a piece of metal, such as a two-
shilling piece, is now placed, and left for a short time. On removing
it, it is found that the spot of skin which was in contact with the metal
has become sensitive, so that the prick of a needle is at once felt, but
that the corresponding part of the other hand has become insensitive,
so that pricking it with a needle produces no sensation.

The observations of this kind have hitherto been made almost,
though not quite exclusively, upon patients suffering from certain
diseases of the nervous system, and the facts have been described as
occurring both in the wakeful and in the mesmeric state. The
proximate explanation appears to be, to take the case of transference
of sensation just mentioned, that the gentle tactile stimuli caused by
the pressure of the coin on the skin, reaching an inhibited centre
sets it in activity, and the sensibility of that part of the skin is
restored, but the stimulus passes on to the corresponding and hitherto
active centre of the opposite side of the body, and this is inhibited.

Here I must leave the subject. I have not attempted to give
an account of all the phenomena of mesmerism ; I have taken
those phenomena which seemed to me to be the least easy to

42 Mr. J. N. tangley [March 14,

understand, the most liable to misconception, and have attempted to
show that they resemble fundamentally certain simpler phenomena
which can be observed in lower animals. I have further attempted to
string together the various facts upon a thread of theory, which may
be briefly summed up as follows : —

Tlie primary condition of mesmerism is an inhibition of a particular
mode of activity of the cortex of the brain, in consequence of which the
will can no longer be made effective.

This inhibition may be brought about by nervous impulses coming
from certain sensory nerves, as those of sight, touch, hearing.

It may also be brought about by impulses or changes arising in the
cortex itself.

The inhibited cortex, and probably also inhibited lower centres of the
brain, send out inhibitory impulses to all other parts of the central
nervous system, so that the mesmerised man or animal gradually passes
into a state of torpor, or even of complete ancesthesia.

The phenomena of the excitable stage of mesmerism are proximately
determined by the possibility of exciting any particular centre alone,
without exciting at the same time other centres by which its activity is
normally controlled. In lower animals this stage is less marked in
consequence of a greater interdependence of the various parts of the
central nervous system.

I would expressly state that I regard this theory only as pro-
visional. Further, I am quite conscious that it is very imperfect.
A complete explanation of the phenomena of mesmerism and of its
allied states can only be given when we have a complete knowledge
of the structure and functions of all parts of the central nervous
system. But I have not much doubt that the explanation of the main
features of mesmerism will be found when we are able to answer the
question — What is inhibition ? And it is some comfort to think that
the answer awaits us in the comparatively simple nervous system of
the lower animals. I would not be understood to mean that varia-
tion of blood supply and various other events are of no influence in
producing mesmeric phenomena ; I think, however, that these events
are of secondary importance only.

Finally, I would say a word about the attitude of physiologists to
animal magnetisers and mesmerists. It has sometimes been made a
subject of reproach to physiologists that they have not concerned
themselves more actively in investigating mesmeric phenomena.
The reproach has very little foundation. The knowledge which has
been gained on the subject has been gained almost entirely by
medical practitioners and by physiologists, and it must be remembered
that until lately most physiologists were also medical practitioners ;
the division of labour is of recent date.

It is, however, true that in the beginning and middle part of this
century there were many scientific men who regarded the subject
with a contempt which intrinsically it did not deserve. But in my

1884.] on the Physiological Aspect of Mesmerism. 43

opinion they had much justification. A scientific man has always
before him some problems which he knows he can solve, or help to
solve. He has always before him a road which he knows leads
somewhither. Mesmerism was long mixed up with assertions of the
transmission of cerebral fluid, with impossible notions which had
been banished from physiology, and with charlatanism. The scientific
man of that day may, I think, be readily pardoned for supposing
that the facts which were given as not more true than the theories,
might be equally false. Why should he leave the fruitful work his
hand had found to do for that which to all appearance would be barren.
Dr. Esdaile, who although himself not altogether free from blame
for mystifying the subject, yet did much to advance it, expresses
what must have been a general feeling : — " The ignorance and pre-
sumption of man ; his passion for the mysterious and marvellous ; his
powers of self-delusion, with the pranks of knaves and the simplicity
of fools, have so mystified the subject, that the artificial difficulties
cost us more trouble to remove than the natural ; and a mass of
rubbish must be got rid of before we can reach the foundation stone
of truth."

[J. N. L.]

WEEKLY EVENING MEETING,

Friday, March 21, 1884.

Sir William Bowman, Bart. LL.D. F.E.S. Honorary Secretary and
Vice-President, in the Chair.

Matthew Arnold, Esq.

Emerson.

[For Abstract see Maemillan's Magazine for May, 1883.]

44 Professor Osborne Beynolds [March 28,

WEEKLY EVENING MEETING,

Friday, March 28, 1884.

Sir Frederick Pollock, Bart. M.A. Vice-President, in the Chair.

Professor Osborne Reynolds, M.A. F.R.S.

The Two Manners of Motion of Water.

In commencing this discourse the author said : —

It has long been a matter of very general regret with those who
are interested in natural jDhilosophy, that in spite of the most strenuous
efforts of the ablest mathematicians the theory of fluid motion fits
very ill with the actual behaviour of fluids ; and this for unexplained
reasons. The theory itself appears to be very tolerably complete
and affords the means of calculating the results to be expected in
almost every case of fluid motion, but while in many cases the
theoretical results agree with those actually obtained, in other cases
they arc altogether different.

If we take a small body such as a raindrop moving through the
air, the theory gives us the true law of resistance ; but if we take a
large body such as a ship moving through the water, the theoretical
law of resistance is altogether out. And what is the most unsatis-
factory part of the matter is that the theory affords no clue to the
reason why it should apply to the one class more than the other.

When, seven years ago, I had the honour of lecturing in this room
on the then novel subject of vortex motion, I ventured to insist that the
reason why such ill success had attended our theoretical efforts was
because, owing to the uniform clearness or opacity of water and air,
we can see nothing of the internal motion ; and while exhibiting
the phenomena of vortex rings in water rendered strikingly a^Dparent
by partially colouring the water, but otherwise as strikingly invisible,
I ventured to predict that the more general application of this method,
which I may call the method of colour-bands, would reveal clues
to those mysteries of fluid motion which had baffled philosophy.

To-night I venture to claim what is at all events a partial verifi-
cation of that prediction. The fact that we can see as far into fluids
as into solids naturally raises the question why the same success
should not have been obtained in the case of the theory of fluids as
in that of solids? The answer is plain enough. As a rule, there
is no internal motion in solid bodies ; and hence our theory based
on the assumption of relative internal rest applies to all cases. It
is not, however, impossible that an, at all events seemingly, solid
body should have internal motion, and a simple experiment will show

1884.] on the Tivo Manners of Motion of Water. 45

that if a class of such bodies existed they would apparently have
disobeyed the laws of motion.

These two wooden cubes are apparently just alike, each has a
string tied to it. Now, if a ball is suspended by a string you all
know that it hangs vertically below the point of suspension or swings
like a pendulum. You see this one does so. The other you see
behaves quite differently, turning up sideways. The effect is very
striking so long as you do not know the cause. There is a heavy
revolving wheel inside which makes it behave like a top.

Now what I wish you to see is, that had such bodies been a work
of nature so that we could not see what was going on — if, for

instance, apples were of this nature while pears were what they are

the laws of motion would not have been discovered ; if discovered for
pears they would not have applied to apples, and so would hardly
have been thought satisfactory.

Such is the case with fluids : here are two vessels of water which
appear exactly similar — even more so than the solids, because you
can see right through them — and there is nothing unreasonable in
supposing that the same laws of motion would apply to both vessels.
The application of the method of colour-bands, however, reveals a
secret : the water of the one is at rest, while that in the other is in
a high state of agitation.

I am speaking of the two manners of motion of water — not
because there are only two motions possible ; looked at by their
general appearance the motions of water are infinite in number • but
what it is my object to make clear to-night is that all the various
phenomena of moving water may be divided into two broadly distinct
classes, not according to what with uniform fluids are their apparent
motions, but according to what are the internal motions of the fluids
which are invisible with clear fluids, but which become visible with
colour-bands.

The phenomena to be shown will, I hope, have some interest in
themselves, but their intrinsic interest is as nothing compared to
their jDhilosophical interest. On this, however, I can but slightly touch.

I have already pointed out that the problems of fluid-motion may
be divided into two classes: those in which the theoretical results
agree with the experimental, and those in which they are altocrether
different. Now what makes the recognition of the two manners of
internal motion of fluids so important, is that all those problems to
which the theory fits belong to the one class of internal motions.

The point before us to-night is simple enough, and may be well
expressed by analogy. Most of us have more or less familiarity with
the motion of troops, and we can well understand that there exists a
science of military tactics which treats of the best manoeuvres and
evolutions to meet particular circumstances.

Suppose this science proceeds on the assumption that the
discipline of the troops is perfect, and hence takes no account of such
moral effects as may be produced by the presence of an enemy.

46 Professor Osborne Reynolds [March 28,

Such a theory would stand in the same relation to the movements
of troops as that of hydrodynamics does to the movements of water.
For although only the disciplined motion is recognised in military
tactics, troops have another manner of motion when anything disturbs
their order. And this is precisely how it is with water : it will move
in a perfectly direct disciplined manner under some circumstances,
while under others it becomes a mass of eddies and cross streams
which may be well likened to the motion of a whirling, struggling mob
where each individual particle is obstructing the others.

Nor does the analogy end here : the circumstances which deter-
mine whether the motion of troops shall be a march or a scramble,
are closely analogous to those which determine whether the motion of
water shall be direct or sinuous.

In both cases there is a certain influence necessary for order :
with troops it is discipline ; with water it is viscosity or treacliness.

The better the discipline of the troops, or the more treacly the
fluid, the less likely is steady motion to be disturbed under any
circumstances. On the other hand, speed and size are in both cases
influences conducive to unsteadiness. The larger the army, and the
more rapid the evolutions, the greater the chance of disorder ; so with
fluid the larger the channel, and the greater the velocity, the more
chance of eddies.

With troops some evolutions are much more difficult to effect with
steadiness than others, and some evolutions which would be perfectly
safe on parade, would be sheer madness in the presence of an enemy.
So it is with water.

One of my chief objects in introducing this analogy of the troops
is to emphasise the fact, that even while executing manoeuvres in a
steady manner there may be a fundamental difference in the condition
of the fluid. This is easily realised in the case of troops. Difficult and
easy manoeuvres may be executed in equally steady manners if all
goes well, but the conditions of the moving troops are essentially
different. For while in the one case any slight disarrangement would
be easily rectified, in the other it would inevitably lead to a scramble.
The source of such a change in the manner of motion under such
circumstances, may be ascribed either to the delicacy of the manoeuvre,
or to the upsetting disturbance, but as a matter of fact, both of these
causes are necessary. In the case of extreme delicacy an indefinitely
small disturbance, such as is always to be counted on, will eftect the
change.

Under these circumstances we may well describe the condition of
the troops in the simple manoeuvre as stable, while that in the
delicate manoeuvre is unstable, i. e. will break down on the smallest
disarrangement. The small disarrangement is the immediate source
of the break-down in the same sense as the sound of a voice is
sometimes the cause of an avalanche ; but if wc regard such dis-
arrangement as certain to occur, then the source of the disturbance is
a condition of instability.

1884.J on the Two Manners of Motion of Water. 47

All this is exactly true for the motion of water. Supposing no
disarrangement, the water would move in the manner indicated in
theory just as, if there is no disturbance, an egg will stand on its end ;
but as there is always slight disturbance, it is only when the condi-
tion of steady motion is more or less stable that it can exist. In
addition then to the theories either of military tactics or of hydro-
dynamics, it is necessary to know under what circumstances the
manoeuvres of which they treat are stable or unstable. And it is in
definitely separating these conditions that the method of colour-bands
has done good service which will remove the discredit in which
the theory of hydrodynamics has been held.

In the first place, it has shown that the property of viscosity or
treacliness, possessed more or less by all fluids, is the general influence
conclusive to steadiness, while, on the other hand, space and velocity
are the counter influence ; and the effect of these influences is subject
to one perfectly definite law, which is that a particular evolution
becomes unstable for a definite value of the viscosity divided by the
product of the velocity and space. This law explains a vast number of
phenomena which have hitherto aj)peared paradoxical. One general
conclusion is, that with sufficiently slow motion all manners of motion
are stable.

The effect of viscosity is well shown by introducing a band of
coloured water across a beaker filled with clear water at rest. Now
the water is quite still, I turn the beaker round about its axis. The
glass turns but not the water, except that which is close to the glass.
The coloured water which is close to the glass is drawn out into
what looks like a long smear, but it is not a smear, it is simply a
colour-band extending from the point in which the colour touched
the glass in a spiral manner inwards, showing that the viscosity was
slowly communicating the motion of the glass to the water within.
To prove this I have only to turn the beaker back, and the colour
band assumes its radial position. Throughout this evolution the
motion has been quite steady — quite according to the theory.

When water flows steadily it flows in streams. Water flowing
along a pipe is such a stream bounded by the solid surface of the
pipe, but if the water be flowing steadily we can imagine the water
to be divided by ideal tubes into a fagot of indefinitely small streams,
any of which may be coloured without altering its motion, just as
one column of infantry may be distinguished from another by colour.

If there is internal motion, it is clear that we cannot consider the
whole stream bounded by the pipe as a fagot of elementary streams,
as the water is continually crossing the pipe from one side to the
other, any more than we can distinguish the streaks of colour in a
human stream in the corridor of a theatre.

Solid walls are not necessary to form a stream : the jet from a
fire hose, the falls of Niagara, are streams bounded by a free surface.

A river is a stream half bounded by a solid surface.

Streams may be parallel, as in a pipe ; converging, as in a conical

48

Professor Osborne Bepiolds

[March 28,

mouth-piece ; or when the motion is reversed, diverging. Moreover,
the streams may be straight or curved.

All these circumstances have their influence on stability in a
manner which is indicated in the accompanying diagram : —

Circumstances conducive to

Direct or Steady Motion.

1. Viscosity or fluid friction which

continually destroys disturb-
ances.
(Treacle is steadier than water.)

2. A free surface.

3. Converging solid boundaries.

4. Curvature with the velocity

greatest on the outside.

Sinuous or Unsteady/ Motion.

5. Particular variation of velocity

across the stream, as when a
stream flows through still
water.

6. Solid bounding walls.

7. Diverging solid boundaries.

8. Curvature with tlie velocity

greatest on the inside.

It has for a long time been noticed that a stream of fluid through
fluid otherwise at rest is in an unstable condition. It is this insta-
bility which gives rise to the talking-flame and sensitive-jet with
which you have been long familiar in this room. I have here a glass
vessel of clear water in front of the lantern, so that any colour-bands
will be projected on the screen.

You see the ends of two vertical tubes one above the other.
Nothing is flowing through these tubes, and the water in the vessel
is at rest. I now open two taps, so as to allow a steady stream of
coloured water to enter at the lower pipe, water flowing out at the
upper. The water enters quite steadily, forms a sort of vortex ring
at the end which proceeds across the vessel, and passes out at the
lower tube. Now the coloured stream extends straight across the
vessel, and fills both pipes. You see no motion ; it looks like a glass
rod. The water is, however, flowing slowly along it. The motion
is so slow, that the viscosity is paramount, and hence the stream is
steady.

I increase the speed, you see a certain wriggling sinuous action
in the column ; faster, the column breaks up into beautiful and well-
defined eddies, and spreads out into the surrounding water, which,
becoming opaque with colour, gradually draws a veil over the
experiment.

The same is true of all streams bounded by standing water. If
the motion is sufficiently slow, according to the size of the stream
and the viscosity of the fluid, it is steady and stable. At a certain
critical velocity, the which is determined by the ratio of the viscosity
to the diameter of the stream, the stream becomes unstable. Under
any conditions, then, which involve a stream flowing through sur-
rounding water, the motion will be unstable if the velocity is sufficient.

Now, one of the most marked facts relating to experimental
hydrodynamics is the difference in the way in which water flows along
contracting and expanding channels ; these include an enormously
large class of the motions of water, but the typical phenomenon is
shown by the simple conical tubes. Such a tube is now projected on

1884.] on the Two Manners of Motion of Water. 49

the screen ; it is surrounded with clear still water. The mouth of
the tube at which the water enters is the largest part, and it contracts
uniformly for some way down the channel, then the tube expands
again gradually until it is nearly as large as at the mouth, and then
again contracts to the tube necessary to discharge the water. I draw
water through the tube, but you see nothing as to what is going on.
I now colour one of the elementary streams outside the mouth ;
this colour-band is drawn in with the surrounding water, and will
show us what is going on. It enters quite steadily, preserving its
clear streak-like character until it has reached the neck where con-
vergence ceases ; now the moment it enters the expanding tube it is
altogether broken up into eddies. Thus the motion is direct in the
contracting tube, sinuous in the expanding.

The hydrodynamical theory affords no clue to the cause why ; and
even by the method of colour-bands the reason for the sinuosity is
not at once obvious. If we start the current suddenly, the motion
is at first the same in both tubes, its change in the expanding pipe
seemed to imply that here the motion was unstable. If so, this ought
to appear from the equations of motion. With this view this case
was studied, I am ashamed to say how long, without any light. I
then had recourse to the colour-bands again, to try and see how the
phenomena came on. It all then became clear: there is an inter-
mediate stage. When the tap is opened, the immediately ensuing
motion is nearly the same in both parts ; but while that in the con-
tracting portion maintains its character, that in the expanding portion
changes its character. A vortex ring is formed which, moving for-
ward, leaves the motion behind that of a parallel stream through the
surrounding water.

If the motion be sufficiently slow, as it is now, this stream is
stable, as already explained. We thus have steady or direct motion
in both the contracting and expanding parts of the tube, but the two
motions are not similar : the first being one of a fagot of similar
elementary contracting streams, the latter being that of one parallel
stream through the surrounding fluid. The first of these is a stable
form ; the second an unstable form, and, on increasing the velocity,
the first remains, while the second breaks down ; and we have, as
before, the exj)anding part filled with eddies.

This experiment is typical of a large class of motions. Wherever
fluid flows through a narrow, as it approaches the neck it is steady,
after passing, it is sinuous. The same effect is produced by an
obstacle in the middle of a stream ; and very nearly the same thing
by the motion of a solid object through the water.

You see projected on the screen an object not unlike a ship. Here
the ship is fixed, and the water flowing past it ; but the effect would
be the same if we had the ship moving through the water. In the
front of the ship the stream is steady, and so till it has passed the
middle, then you see the eddies formed behind the ship. It is these
eddies which account for the discrepancy between the actual and

Vol. XI. (No. 78.) e

50 Professor Osborne Beynolds [March 28,

theoretical resistance of ships. We see, then, that the motion in the
expanding channel is sinuous because the only steady motion is that
of a stream through water. Numerous cases in which the motion is
sinuous may be explained in the same way, but not all.

If we have a perfectly parallel channel, neither contracting nor
expanding, the steady moving stream will be a fagot of perfectly
steady parallel elementary streams all in motion, but moving fastest
at the centre. Here we have no stream through steady water. Now
when this investigation began it was not known, or imperfectly
known, whether such a stream was stable or not, but there was a
well-known anomaly in the resistance to motion in parallel channels.
In rivers, and all pipes of sensible size, experience had shown that
the resistance increased as the square of the velocity, whereas in very
small pipes, such as represent the smaller veins in animals, Poiseuille
had proved the resistance increased as the velocity.

Now since the resistance would be as the square of the velocity
with sinuous motion, and as the velocity, if direct, it seemed that the
discrepancy could be accounted for if the motion could be shown to
become unstable for a sufficiently large velocity. This suggested
the experiment I am now about to produce before you.

You see on the screen a pipe with its end open. It is surrounded
by clear water and by opening a tap I can draw water through it.
This makes no difference to the appearance until I colour one of the
elementary streams, when you see a beautiful streak of colour extend
all along the pipe. The stream has so far been running steadily,
and appears quite stable. I now merely increase the speed ; it is
still steady, but the colour-band is drawn down fine. I increase the
colour and then again increase the speed. Now you see the colour-
band at first vibrates and then mixes so as to fill the tube. This is
at a definite velocity ; if the velocity be diminished ever so little the
band becomes straight and clear ; increase it again, it breaks up.
This critical speed depends on the size of the tube in the exact
inverse ratio; the smaller the tube, the greater the velocity; also,
the more viscous the water the greater the velocity.

We have then not only a complete explanation of the difiference in
the laws of resistance generally experienced and that found by
Poiseuille, but also we have complete evidence of the instability of
parallel streams flowing between or over solid surfaces. The cause
of the instability is as yet not explained, but this much can be shown,
that whereas lateral stiffness in the walls is unimportant, inextensibility
or tangential rigidity is essential to the creation of eddies. I cannot
show you this because the only way in which we can produce the
necessary conditions without a solid channel is by a wind blowing over
water. When the wind blows over water it imparts motion to tlie
surface of the water just as a moving solid surface ; moving in this
■way, however, the water is not susceptible of eddies. It is unstable,
but the result of disturbance is waves. This is proved by an experi-
ment long known, but which has recently attracted considerable notice.

1884.] on the Tioo Manners of Motion of Water. 51

If oil be put on the surface it spreads out into an indefinitely thin
sheet which possesses only one of the characteristics of a solid surface,
it offers resistance, very slight, but still resistance to extension and
contraction. This, however, is sufficient to entirely alter the character
of the motion. It renders the water unstable internally, and instead
of waves, what the wind does is to produce eddies beneath the sur-
face. This has been proved, although I cannot show you the experi-
ments.

To those who have observed the phenomena of oil preventing
waves, there is probably nothing more striking throughout the
region of mechanics. A film of oil so thin that we have no means
of illustrating its thickness, and which cannot be perceived except by
fts effect — which possesses no mechanical properties that can be made
apparent to our senses — is yet able to entirely prevent an action
which involves forces the strongest we can conceive, which upset our
ships and destroy our coasts. This, however, becomes intelligible
when we perceive that the action of the oil is not to calm the sea by
sheer force, but merely, as by its moral force, to alter the manner of
motion produced by the action of the wind from that of the terrible
waves upon the surface into the harmless eddies below. The wind
throws the water into a highly unstable condition, into what morally
we should call a condition of great excitement. The oil by an
influence we cannot perceive directs this excitement.

This influence, though insensibly small, is however now proved of
a mechanical kind, and to me it seems that the phenomenon of one
of the most powerful mechanical actions of which the forces of nature
are capable, being entirely controlled by a mechanical force so
slight as to be otherwise quite imperceptible, does away with every
argument against the strictly mechanical sources of what we may
call mental and moral forces.

But to return to the instability in parallel channels. This has
been the most complete, as well as the most definite result of the
colour-bands.

The circumstances are such as to render definite experiments
possible. These have been made, and reveal a definite law of the
instability, which law has been tested by reference to all the nume-
rous and important experiments on the resistance in channels by
previous observers ; whereupon it is found that waters behave in
exactly the same manner whether the channel, as in Poiseuille's experi-
ment, is of the dimensions of a hair or whether it be the size of a
water main or of the Mississippi ; the only difference being that
in order that the motions may be compared, the velocity must be
inversely as the diameter of the pipe. But this is not the only
point explained if we consider other fluids than water. Some fluids,
like oil or treacle, apparently flow more slowly and steadily than
water. This, however, is only in smaller channels ; the critical
velocity increases with the viscosity of the fluid. Thus, while water
in comparatively large streams is always above its critical velocity,

E 2

62 Prof. 0. Beynolds on the Tivo Manners of Motion of Water. [March 28,

and the motion always sinuous, the motion of treacle in streams
of such size as we see is below its critical velocity, and the motion
direct. But if nature had produced rivers of treacle the size of the
Thames, for instance, the treacle would have flowed just like water.
Thus, in the lava streams from a volcano, although looked at close
the lava has the consistence of a pudding, in the large and rapid
streams down the mountain sides the lava flows as freely as water.

I have now only one circumstance left to which to ask your
attention. This is the effect of curvature of the stream on the
stability of the fluid.

Here again we see the whole effect altered by very slight causes.

If water be flowing in a bent channel in steady streams, the
question as to whether it will be stable or not turns on the variation
in the velocity from the inside to the outside of the stream.

In front of the lantern is a cylinder with glass ends, so that the
light passes through in the direction of the axis. The disk of light
on the screen being the light which passes through this water, and is
bounded by the circular walls of the cylinder.

By means of two tubes temporarily attached, a stream of coloured
water is introduced right across the cylinder extending from wall to
wall ; the motion is very slow, and the taps being closed, and the tubes
removed, the colour-band is practically stationary. The vessel is now
caused to revolve about its axis. At first, only the walls of the cylinder
move, but the colour-band shows that the water gradually takes up
the motion, the streak being wound off at the ends into a spiral
thread, but otherwise remaining still and vertical. When the spirals
meet in the middle, the whole water is in motion, but the motion is
greatest at the outside, and is therefore stable. The vessel stops, and
gradually stops the water, beginning at the outside. If the motion
remained steady, the spirals would unwind, and the streak be restored.
But the motion being slowest at the outside against the surface, you
will see eddies form, breaking up the spirals for a certain distance
towards the middle, but leaving the middle revolving steadily.

Besides indicating the effect of curvature, this experiment really
illustrates the action of the surface of the earth on the air moving
over it ; the varying temperature having much the same influence as
the curvature of the vessel on stability. The air is unstable for a few
thousand feet above the surface, and the motion is sinuous, resulting
in the mixing of the strata, and producing the heavy cumulus clouds ;
but above this the influence of temperature predominates, and clouds,
if there are any, are of the stratus-form, like the inner spirals of
colour. But it was not the intention of this lecture to trace the two
manners of motion of fluids in the phenomena of Nature and Art, so
I thank you for your attention. [0. E.]

1884.] Professor T. 0. Bonney on the Building of the Alp,

WEEKLY EVENING MEETING,\/5^

Friday, April 4, 1884.

Sir Frederick Bramwell, F.E.S. Manager and Vice
in the Chair.

Professor T. G. Bonney, D.Sc. F.R.S. Pres. G.S.

The Building of the Alj)s.

When were the Alps upraised, and what is the age of their building
stones ? On the former of these questions there is less diversity of
opinion than on the latter ; yet, notwithstanding all that has been
■written on both, I am not without hope that I may find a few things
sufficiently novel to be of interest to a general audience.

The subject, indeed, is so vast that I must crave your indulgence for
leaving some gaps in my reasoning unfilled, and presenting you with
little more than an outline. To save time I shall assume a know-
ledge of the simpler geological terms, asking you only to remember
that I always use the word " schist," as I maintain it ought to be
used, to denote a more or less fissile rock the constituents of which
have undergone so much mineral change that, as a rule, their original
nature is almost wholly a matter of conjecture. I must also ask you
to remember that, though I have seldom mentioned the names of other
workers, I am really doing little more than giving an epitome of the
labours of a host of geologists, conspicuous among whom are Heim,
Baltzer, Von Hauer, Gastaldi, Lory, Favre, Eenevier, and many more,
both Continental and English ; I select however those facts with which
I have myself become familiar during many visits to different districts
of the Alps, from the Viso on the south to the Dachstein on the east.
It is needless, I assume, to explain that mountain chains are the
result of lateral thrust rather than of vertical upheaval, and their
contours are mainly due to the sculpturing action of heat and frost,
rain and rivers, acting upon rocks bent into various positions, and of
various degrees of destructibility. There are, however, three prin-
ciples which are less familiar, but which I must ask you to bear in
mind throughout this lecture : (1) That when a true schist is asserted
to be the metamorphosed representative of a post- Archaean rock, the
onus prohandi lies with him who makes the assertion ; (2) that rocks
composed of the detritus of older rocks may often readily be mistaken
for them ; (3) that great caution is needful in applying the principles
of lowland stratigraphy to a mountain region. The first of these is,

64 Professor T. G. Bonney [April 4,

I know, disputed, but there can be little doubt as to its accuracy, the
second is indisputable ; so is the third ; but I will briefly illustrate
what I mean by the statement.

[Attention was then directed to diagrams of folds and reversals of
strata in the Alps.]

The first section to which I invite your attention is in the neigh-
bourhood of the Lake of Lucerne. There are few travellers to
whom the cliffs of the Eigi are not familiar. Those great walls of
rock, along and beneath which the Rigibahn now takes its audacious
way, are mainly composed of enormous masses of conglomerate, an
indurated gravel of Miocene age, called the nagelflue. These pebble
beds may be traced in greater or less development along the north-
western margin of the Swiss Alps ; they attain in the Eigi and the
fatal crags of the adjoining Eossberg a thickness of not less than
2000 feet. The structure and nature of this nagelflue show that it
has been deposited by rivers, possibly at their entry into lakes, but
more probably, as suggested by my friend Mr. Blanford, on beginning
a lowland course at the very gates of the mountains. In this great
mass there are indeed pebbles of doubtful derivation ; but we need
not hesitate to refer the bulk of them to the mountains which lie
towards the east, and we may regard the great pebble beds of the
Eigi and the Eossberg as built of the ruins of Miocene Alps by the
streams of a Miocene Eeuss. Now, when we scrutinise the pebbles of
this nagelflue we are at once struck by a remarkable fact. The
Eeuss, at the present day, only passes through mesozoic rocks when
it apin'oaches the neighbourhood of the Lake of Lucerne. It is
within the mark to say that quite three-fourths of its drainage area
consists of crystalline rocks. Hence schists and gneisses abound
among its pebbles, and the same rocks are no less frequent among the
erratics which have been deposited by the vanished glaciers of the
Great Ice Age on the flanks of the Eigi to a height of 2000 feet above
the Lake of Lucerne. Yet, on examining the nagelflue, we find that,
while pebbles of grit, and limestone, and chert — specimens of the
Alpine mesozoic rocks — abound, pebbles of schist and gneiss are ex-
tremely rare. I had searched for hours before I found a single one.
The matrix also of the nagelflue — the mortar which makes this natural
concrete — when examined beneath the microscope, tells the same
story. We do not see in it the frequent quartz grains, the occasional
pieces of felspar, the mica flakes, which are records of the detrition
of gneissic rocks, but it consists of fragments similar to those which
form tlie larger pebbles. It is therefore a legitimate inference that,
in this part of the Alps at least, the protective covering of mesozoic
rock in the Miocene age had not generally been stripped away from
the crystalline schists of the Upper Eeuss, and that since then the
mountains may have been diminished and the valleys deepened by at
least a mile vertically. I have spoken only of the valley of the
Eeuss, but a little consideration will show that my remarks may be
extended to a much larger area of the Oberland Alps.

1884.] on the Building of the Alps. 55

I pass now to two other sections: of these the first is in the
neighbourhood of Pontresina. Most of the peaks in this region
consist of igneous rocks, of gneisses, and of schists, but some of later
date are not wanting — as, for example, may be seen in the flanks of
well-known Heuthal. These last are limestones of Triassic age.
Here they overlie unconformably a coarse gneiss — in other places
they rest on schists presumably of later date ; in fact, the series of
mesozoic rocks of which the above limestone is the lowest member —
though now to a great extent removed by denudation — has clearly
once passed transgressively over the whole series of gneisses and
schists of the Engadine.

The second section, or rather group of sections, is some distance
away to the south-east, in the region of the Italian Tyrol. Those
magnificent crags of the Dolomite mountains, the serrate teeth of the
Eosengarten and the Langkofel, the towers of the Cristallo and the
Drei Zinnen, the precipitous masses of the Blattkogel and the
Marmolata, are built up of rocks of Triassic age, not of a very
difierent date from the soft red marls which occupy so large an area
in the Midlands of England. Follow me for one moment by the
mountain road from Predazzo to Primiero. At the former place —
classic ground for geologists — we are surrounded by great masses of
igneous rocks, the roots, it may be, of long-vanished cones, although
we refuse to recognise a crater in the valley about Predazzo. As we
ascend towards the beautiful Alps of Paneveggio, we pass for a
considerable distance over a great mass of red felstone. This belongs
to a group of igneous rocks which extend to the westward even
beyond the Etsch. It is overlain by the beds of the Trias, commenc-
ing with the red Grodner sandstone and passing up soon into the vast
masses of Dolomite which form the wild crags of the Cimon della
Pala and its attendant summits. But as we descend on the other side
of the pass towards Primiero we see the Triassic rocks, without the
intervention of the felstone, resting upon mica schists, similar to those
which occur in many other parts of the Alps. Sections of the above
kind, were it needful, might be multiplied indefinitely to prove that
between the base of the Trias and the Alpine schists and gneisses
there is an enormous break, but we may content ourselves with one
other, interesting not only for the completeness of the demonstration
but also for the mode in which it illustrates Alpine structure.

[Attention was then directed to the section of the Mont Blanc
Eange, after Favre.]

The Aiguilles Rouges are composed of coarse gneisses and crystal-
line schists, but on the highest summit there remains a fragmental
outlier of stratified and unaltered rock. The upper part of this is
certainly Jurassic. Below this comes a representative of the Trias —
much attenuated, as it is generally in this western region, with possibly
a remnant of a deposit of Carboniferous age. Be that as it may, there
is undoubtedly here a great break between the crystalline series and
the succeeding mesozoic or palaeozoic rock.

66 Professor T. G. Bonney [April 4,

There remains yet one other section to wliich I wish to direct your
attention ; it is near Vernayaz, in the vicinity of the famous gorge of
the Trient. Where the Ehone bends, at Martigny, from a south-west
to a north-west course, the crystalline massif of the Mont Blanc region
of which we have just spoken crosses the river, and is lost to sight
as it plunges beneath the mesozoic rocks of the western summits of
the Oberland. The gorge of the Trient is cut through hard and
moderately coarse gneiss ; the same rock occurs at the Sallenche
waterfall. Between the two is a mass of rock of a totally different
character — in part a dark slate, like some in Britain of Lower Silurian
age ; in part a conglomerate or breccia in a micaceous matrix, proved
by its plant remains to be a member of the Carboniferous series.
Omitting some minor details, not without interest, it may suffice to
say that we have in this place the end of an almost vertical loop,
formed by the folding of beds of Carboniferous age between the
crystalline rocks, which are the foundation-stones of the district.
The conglomerate is at the base of the Carboniferous series, and its
matrix so closely resembles a mica schist, that it has been claimed as
indicating metamorphism, and as linking together the Carboniferous
slates and the crystalline schists. But, in the first place, the fragments
in the conglomerate are not only gneisses and schists, but also
ordinary slaty rocks, no more altered than those of Llanberis. How,
we may well ask, could the latter escape unchanged when all the
surrounding matrix was converted into mica schist? Further,
when we apply the test of the microscope — that Ithuriel spear by
which the deceits of rocks are so often revealed — we find that this
seeming mica schist is only the consolidated debris of micaceous
rocks. Its composition, and that of the conglomerate, justifies us in
asserting that when the Carboniferous rocks of the Valorsine were
deposited there were land surfaces of gneiss and schist in the western
region of the Alps, and that these rocks were substantially identical
with those through which the Trient has sawn its ravine.

It would be easy to multiply instances similar to one or the other
of those quoted above from this or that district of the Alpine region,
from the south of Monte Viso to the north of the Adriatic, to speak
only of those districts of which I have a personal knowledge ; but I
should speedily weary you, and will ask you to regard these as typical
cases, single samples of a great collection. They justify, as I think you
will agree, the following inferences : (1) That there has been one epoch,
at least, of mountain-making posterior to the deposition of the
Miocene nagclflue, which has given to many parts of the Alpine chain
an uplift sometimes not less than a mile in vertical elevation ; (2)
that prior to this there was an earlier epoch of mountain-making,
which affected all the rocks of older date, including at any rate a
portion of middle Eocene age — for wc find marine strata of this date
crowning the summit of the Diablerets, now more than 10,000 feet
above the sea, and bent back, as at the Rigi Scheideck, over the beds
of the nagelflue ; (3) that there was a pre-Triassic land surface of great

1884.] on the Building of the Alps. 67

extent, largely composed of crystalline rocks, and that with this
geological age commenced a long continuous period of depression,
lasting into Tertiary times ; (4) that a land surface of considerable
extent existed at a yet earlier period, and that this in the Carbo-
niferous age was watered by streams and clothed with vegetation —
whether there were mountains then it is impossible to say, but the
evidence certainly points to the conclusion that the ground was hilly ;
(5) that anterior to the last-named period there is a great gap in our
records ; the older rocks, whose stratigraphical position can be ascer-
tained, being much metamorphosed, so that we appear justified in con-
cluding that all the more important mineral changes which they had
undergone occurred in pre-Carboniferous times — namely, that the later
Pala3ozoic land surfaces consisted of gneiss and schists in all important
respects identical with those which now exist.

I have thus led you step by step — by processes, I trust, of cautious
induction — to the result that the Alps, as an irregular land surface,
are a very ancient feature in the contour of the earth, and that the
gneisses and crystalline schists, whereof they so largely consist, are
rocks of very great antiquity. Let us now attempt to advance a
step further by attacking the problem from another side. Hitherto
we have been working downwards from the newer to the older, from
the rocks of known towards those of unknown date. Beginning
now in the unknown, beginning with the most remote that we can
find, let us proceed onwards toward the more recent and more
recognisable.

This is a task of no slight difficulty. The ordinary rules of strati-
graphical inference frequently fail us ; nay, if blindly followed, would
lead us to the most erroneous conclusions. In the apparent succes-
sion of strata in a mountain range the last may be first and the first
last in the literal sense of the words. Beds may be repeated again and
again by great folds, now in the direct, now in the inverse order of their
superposition. They may have been faulted and then folded, or
folded and then faulted, and the difficulty is augmented by the vast
scale on which these earth movements have taken place, by the frequent
impossibility of scaling the crags or pinnacles where critical sections
are disclosed, and by the masking of large areas of surface by snow and
glacier, or by debris and vegetation. Yet more, the consciousness of
these difficulties produces in the mind — I speak for myself — a sort of
hesitation and scepticism, which are most unfavourable for inductive
reasoning. Knowing not what features are of importance, one is per-
plexed by the variety of facts that seem to call for notice ; knowing
how easily one may be deceived, one hesitates to draw conclusions. I
am often painfully conscious of how much I have lost in a previous
journey from not having remarked some fact to which a fortunate
accident has just compelled my attention. In this part, therefore, I
must be pardoned if I speak with considerable hesitation and do not
attempt more than to state those inferences which seem to me
warranted by facts.

58 Professor T. G. Bonney [April 4,

I shall again ask permission to conduct you to a series of typical
sections, which, however, I shall describe with less minuteness.

Let us place ourselves in imagination on the great ice-j6.eld at the
upper part of the Gross Aletsch Glacier — the Place de la Concorde of
Nature, as it has been happily termed. We are almost hemmed in by
some of the loftiest peaks of the Bernese Oberland : the Aletschhorn,
the Jungfrau, the Monch, and several others. We find the rocks
which rise immediately round the glacier — as, for example, near the
well-known Concordia hut — to be coarse gneisses, with difficulty dis-
tinguishable from granites. As the eye travels up any one of the
mountain ridges, the rock evidently becomes less massive and more dis-
tinctly foliated. We note the same sequence as we retrace our steps
towards the Ehone valley — speaking in general terms, the ridges and
the flanks of the Eggischhorn consist of more finely granulated
gneisses and of strong micaceous schists, which alternate more fre-
quently one with another. Further to the west, in the region around
the Oberaletsch Glacier and on the slopes of the Bell Alp, we find the
same succession — coarse granitoid gneisses in the relatively lower part
of the heart of the chain, finer grained and more variable gneisses and
schists on the upper ridges and the southern flanks.

Let us change our position to a spot considerably to the east, to
the great section of the crystalline series made by the valley of the
Keuss below Andermatt.

From the spot where the rocks close in suddenly upon the torrent
near the Devil's Bridge, to a considerable distance below Wasen, ex-
tends an almost unbroken mass of coarse granitoid gneiss. This, how-
ever, becomes more distinctly bedded and schistose before it entirely
disappears beneath the secondary deposits that border the Bay of Uri.
Similarly, if from Wasen, where the gneiss is barely distinguishable
from granite, we ascend the wild glen which leads up to the Susten
Pass, and descend on the other side by the grand scenery of the Stein
Alp to the beautiful Gadmenthal, thus passing obliquely outwards
along the apparent strike of the rocks to the point where, as in the
neighbourhood of Imhof, they finally disappear beneath mesozoic
deposits, we again find that we are among rocks which are rather
more variable in their mineral character, oscillating between
moderately coarse gneisses, sometimes porphyritic, and strong mica
schists. Near Miihlestalden, in the Gadinenthal, even a bed of white
crystalline dolomitic limestone is interstratified with the gneissic
rocks.

Leaving for a brief space the vicinity of the St. Gothard road, and
returning to the upper valley of the Ehone, let us place ourselves on
such an outlook as we can obtain from Professor Tyndall's chalet on
the Bel Alp, and fix our eyes on the magnificent panorama of the
Pennine chain, with whose geology we will suppose ourselves to
have become familiar in frequent traverses from the northern to the
southern side of the watershed of Central Europe. Facing us, and
forming the lower slopes and crags of the great mountain chain

1884.] on the Building of the Alps. 59

of the Pennines, we see an enormous mass of distinctly bedded rock,
of a brownish tint, of which at this distance we should hesitate to
say whether we ought to regard it as a member of the metamorphic
or of the ordinary sedimentary series. In an E.N.E. direction we see
it gradually rising to form the peak of the Ofenhorn and the upper
part of the mountains about the Gries Pass. In the opposite direc-
tion it forms the lower slopes of the Simplon Pass and the portals
of the valley of the Yisp. Hence, could we follow it, the area
occupied by this rock broadens out into the spurs which enclose
the Einfischthal and the Eringerthal, and crosses the watershed
towards the south, to the east of the St. Bernard Pass. In more
than one locality in the region of the Binnenthal a band, of no
great vertical thickness, of a white crystalline dolomite is conspicu-
ously present. A very similar group of rocks occurs in the Val
Piora, in some bands of which black garnets are very abundant.
The same mineral also occurs in a similar rock near the summit of
the Gries Pass. Andalusite or staurolite also occurs occasionally ;
the group, in short, is well characterised, and for reference I will
call it the Lustrous Schists.

I pass now to the neighbourhood of the St. Gothard. The coarse
gneiss, which is pierced by the northern entrance of the great tunnel,
ends abruptly at the Urnerloch. The basin of the Urserenthal is
excavated from satiny slates with dark limestones, very possibly of
Jurassic age, and from some underlying rather variable schists. The
first rock visible on the eastern side as we approach Andermatt is a
schistose crystalline limestone, associated with mica schists; and a
series of rather variable schists, evidently very different from the
coarse gneisses of the gorge below, apj)ears to cross the valley, and
form the slopes leading to the Oberalp Pass. These may be traced
for some distance up the Furka road above Realp, when they are
abruptly succeeded by the slaty group mentioned above. I am con-
vinced that they are much more ancient than the latter, being probably
members of the Lustrous Schist group, if not older. It is obvious
that the newer rocks are only a fragment of a loop of a huge fold, over
which on either hand the fragments of the enveloping older meta-
morphic rocks tower up in mountain peaks. On the ascent of the St.
Gothard Pass from Hospenthal a series of somewhat variable micaceous
schists continues till the top of the first step in the ascent is reached,
about 800 feet above the valley, when gneiss sets in, generally rather
coarse and sometimes very porphyritic, occasionally interbanded with
dark, rather friable mica schists. The upper plateau of the pass
consists of a porphyritic rock, often called granite, but with a
gneissose aspect and rather more friable in character than the rock of
the Wasen district. On the first steep descent on the south side this
rock appears to pass into a normal coarse gneiss, occasionally banded
with mica schist, resembling that in a similar position on the northern
flank, which is succeeded for a short space by a remarkably well-
banded gneiss. To this succeeds — it must be remembered that

GO Professor T. G. Bonney [April 4,

tlie series is inverted in order — the great group of hornblendic
and garnetiferous mica schists, which continue along the Val Tremola
and the lower slopes of the mountain to the neighbourhood of Airolo,
where some calcareous rock occurs, being probably an infold of much
later date.

Through the kindness of Mr. Fletcher and Mr. Davis, of the British
Museum, I have been allowed to examine the series of specimens from
the St. Gothard tunnel in that collection. They correspond in
general with the succession above indicated, except that I have failed
to identify the granitoid rock of the summit plateau. Leaving,
however, for a moment the question of correlation, we see that the
St. Gothard section presents us with an instance of folding on a
gigantic scale, and of the fan structure, doubtless with many minor
flexures and faults.

In the neighbourhood of the Val Piora we get an important
succession. The ascent to the hotel from the Val Bedretto passes in
the main over a series of micaceous schists, and rather friable gneisses,
which are a prolongation of an axis exposed in the mountains south
of Airolo and fairly correspond with much of the rock (excepting the
granitoid) forming the upper part of the St. Gothard Pass. To this
succeeds a series which, though more calcareous, clearly represents
the garnetiferous actinolitic series of the southern slopes, and to this a
group closely resembling the Lustrous Schists.

I pass now to the section of the Simplon. On the southern side,
deep in the glen of the Doveria, in the vicinity of the gorge of Gondo,
we find a mass of granitoid gneiss, which recalls to mind that already
described from the wildest portion of the upper valley of the Eeuss.
We may, I think, with confidence affirm that, whatever be the true nature
of this rock, we are again touching the foundation-stones of the rock
masses of the Alps. As we approach Algaby, the granitoid gneiss
becomes more distinctly bedded and variable, a thin band of
micaceous crystalline limestone is passed, and presently the more
rapid ascent of the pass begins. Hence to beyond the summit we
traverse, so far as can be seen, a great series of bedded gneisses,
often coarse and even porphyritic, and of schists. The same are displayed
in the crags of Monte Leone on the east and of the Eossbodenhorn on
the west. As shown in Professor Renevier's valuable section, bands
of crystalline Dolomitic limestone, and of hornblendic and garneti-
ferous schists occur in various places on either side of the Simplon
road. Then, after descending about half way to Brieg, we strike
the group of the Lustrous Schists, with the usual calcareous zone in
the lower part. Professor Renevier does not attempt to unravel the
complexities of the strata which compose this portion of the central
ridge of the Alps, and I feel that my slighter knowledge makes caution
y et more imperative ; but I think we are justified in asserting that we
have evidence of an upward succession from the coarse granitoid
fundamental gneisses, through more variable and bedded gneisses, to
a group which recalls the garnetiferous schists, so finely developed on

1884.] on the Building of the Alps. 61

the southiern flanks of the St. Gothard — a group also traceable in the
upper portion of the Binnenthal, though apparently far less perfectly
developed. I think also that in the gigantic anticlinal of the
Simplon we have evidence of sharp flexures on a great scale ; and
that these garnetiferous schists are only here and there preserved as
the lower ends of enfolded loops, so that the bulk of the massif, and so
far as I can tell the actual summit ridges of the Rossbodenhorner and
Monte Leone, are composed of the bedded gneisses and strong schists,
and perhaps of the more friable gneisses which have been already
described in the mountains further to the east.

The mountains further west — the aspiring peaks which rise
around the two branches of the Visp, including among them some
of the highest summits of the Alps, such as Monte Rosa, the Mischa-
belhorner, the Matterhorn, and the Weisshorn — offer indeed magnifi-
cent sections, but are full of difficulty. The fundamental gneiss,
if I mistake not, is occasionally exposed — as, for example, in the
rocks of Auf der Platte, at the base of Monte Rosa; and in parts
of the Mischabelhorner blocks of coarse granitoid rock, often very
porphyritic, which I refer to the same series, are brought down by
the glaciers. There are also mica schists in plenty, such as the
summit rocks of Monte Rosa and the backbone — if the phrase be
permitted — of the Mischabel- and Saaser- horner, which I refer to
the second zone already described — that of the bedded gneisses and
strong mica schists. I have also seen specimens which closely resemble
the garnetiferous schists of the St. Gothard district, but we meet in
this district with a group of rocks which, if not altogether unknown
before, appears now to be developed to an exceptional extent, and to
become an important factor in the Alpine crystalline series.

Those who are familiar with the environs of Saas and Zermatt
will remember how frequently schists or schistose rocks of a greenish
colour occur. Sometimes they are interbedded with strong mica schists,
or schisty quartzites ; sometimes they form homogeneous masses of
considerable extent. It is possible that some of the latter are in-
trusive masses of serpentine, to which subsequent pressure has given
a schistose aspect; certainly there are occasional masses of coarse
gabbro, which I think undoubtedly an intrusive igneous rock ; but
still, making all allowance for such cases, there is in this region a
considerable mass of greenish hornblendic, talcose, and serpentinous
rocks which appears to be non-igneous in origin. We find these all
around Zermatt. They form the ridges of the Gorner Grat and of the
Hornli. They break out through the snows of the Breithorn and
Little Mont Cervin, and constitute no inconsiderable portion of the
mighty obelisk of the Matterhorn. The whole of that peak, according
to the investigations of Sgr. Giordano — and with this my own recol-
lections correspond — consists of an apparently regularly bedded series
of serpentinous and micaceous schists, and of greenish gneisses, with
the exception of a gabbro, developed on the western side, which I have
no doubt is an intrusive rock. Can we trust these indications ? Are

62' Professor T. G. Bonney [April 4,

we justified in assigning to this zone, with those characteristics, a verti-
cal thickness of more than a mile ? To these questions I can give at
present no answer, further than to state that I am convinced that, not-
withstanding the apparent regularity of the bedding in this and
the neighbouring peaks, there are really great folds which patient
scrutiny may at length unravel, and that this zone of greenish rocks —
for which Alpine geologists have proposed the name of Pietra Verde
group, appears to underlie the garnetiferous series of silvery mica
schists, and either to overlie or replace the upper portions of the
banded gneiss series which succeeds to the fundamental series.

I do not propose to weary you further with the details of Alpine
sections, except that I must add a few words upon the extent of this
remarkable series to which I have now introduced you. On the
northern side of the watershed in the Swiss Alps, so far as I am
aware, it is not generally strongly developed, except in certain
localities in the southernmost of the three ranges which make up the
whole chain, but in parts of the Tyrol it is well displayed. It
borders — the mica schists sometimes dominating — the fundamental
gneiss in the Oetzthal massif; it forms the peak of the Gross Glockner ;
it meets us on the Brenner Pass and elsewhere overlain by and
folded up with rocks which, if my memory do not mislead me, are the
equivalents of the Lustrous Schists of more western districts.

Again, it is finely developed, seemingly in succession to bedded
coarser gneiss, in some of the peaks of the Bernina range, and it
occupies a considerable tract about the heads of the valleys to the
south. It may be traced, indeed, over a great zone, and with but slight
interruption all along the southern slopes of the Alps, even to the
south of the head waters of the Po, forming many of the grandest
peaks in the Graian, Tarentaise, Maurienne, and Cottian Alps ; and
we find traces of it overlying the coarse granitoid series in the massif
of the Alps of Dauphine.

Sections, indeed, in the neighbourhood of Biella, according to
Gastaldi and Sterry Hunt, exhibit the Pietra Verde group overlying
the upper or more bedded portion of the great gneissic or basal series,
and succeeded by the group of friable gneisses, described above as
closely associated with the garnetiferous schists, in a manner that
suggests an unconformity. TJnder ordinary circumstances we should
not hesitate to admit that there is considerable evidence in favour of
this break, and some for one between the Pietra Verde group and the
stronger gneisses and schists below ; but in mountain regions we fear
to trust our eyes. The evidence, however, in certain districts in favour
of a break at the base of the Lustrous Schists is yet stronger. If I am
right in regarding the Lustrous Schists as forming one group with
the older part of the Bundnerschiefer of the Grisons region, and of
the Thonschiefcr of Von Hauer in the Eastern Alps, a study of the
geological map will show that it is difficult to explain the relation of
these beds to the underlying gneisses and schists without such an
hypothesis. What I have myself seen in regard to the Lustrous Schists

1884.] on the Building of the Alps. G3

is strongly in favour of a great break in some localities. On tho south
side of the St. Gothard we have in the Val Piora the Lustrous Schists
apparently in true succession with the representatives of the garneti-
ferous group of the Val Tremola, yet on the northern side, in the
Urseren thai, the latter series is wanting, and the gneisses which underlie
it appear to be immediately succeeded by the Lustrous Schists. This,
however, might be explained by a complication of faulting and folding.
What I have seen in the Binnenthal is harder to explain. At the
head of the Hohsand Glacier, just below the peak of the Ofenhorn, we
have a coarse but bedded gneiss, which I should correlate with the
series immediately overlying the granitoid gneiss so often mentioned
as the lowest rock of all. Glancing towards the north, across the snow-
field, we see this rock in the base of the Strahlgrat distinctly over-
lain by the Lustrous series, with its characteristic band of limestone
or dolomite. This series swoops down for some 2000 feet, and we cross
it in the upper basin of the valley below, while yet further down the
valley I detected the characteristic garnetiferous schist, of which,
however, there is no great development. If this be the result of
faulting and folding only, it is certainly very remarkable.

But I must linger no longer over details. The passing time
warns me that I must attempt briefly to describe the general process
of the building of this great mountain group of Europe. I have, I
hope, proved that the metamorphic rocks of the Alps, if we may trust
mineral similarity and mineral and lithological sequence, are vastly
older than the Carboniferous period, and that in this ancient series a
certain succession may be made out. If we may reason from the
analogy of other regions, we may assign to the whole of their latest
group (the Lustrous Schists) an antiquity greater than the earliest
rocks in which indisputable traces of organic life have been found. One
point, however, I should notice before proceeding further. It might
perhaps be said — it has indeed been said — that the crystalline schists
and gneisses of the Alps are the result of the great earth movements
by which the mountains were upraised, when heat and pressure changed
mud into schists and felspathic sandstone into gneiss. I have shown
you that we can trace a mineral succession in the crystalline series of
the Alpine chain, and that some at least of these are earlier than the
Carboniferous period ; but I can add to the proofs that these great rock
masses had assumed in the main their present mineral structure when
these movements occm-red. We meet indeed with some rock masses
whose structure is doubtless due to the pressure which they have
undergone. This is the case with all cleaved rocks, as was lucidly
explained, twenty-eight years since, by Professor Tyndall in this very
room. We meet also with schists, where, from the arrangement of
the mineral constituents, we have good reason for supposing that they
were developed when the rock mass was exposed to a pressure definite
in direction. Here the lines of difierent minerals, which we believe
indicative of an original structure in the rock, are often wrinkled ; the
more flaky minerals commonly lie with their broader planes parallel,

64 Professor T. G. Bonney [April 4,

but, notwitlistanding this, there is no very definite cleavage in the rock
mass, nor tendency to separate easily along the different mineral
layers. Specimens of such rocks may be obtained in the Alps, but there
are others in v^^hich the layers have evidently been crumpled up
after the period of mineral change : the bands of quartz and felspar
have been, as it were, crushed together, the flakes of mica are some-
times crumbled and sometimes twisted round into new positions.

The subject is a technical one, so I must ask you to accept my
statement, without the long details of microscopic work on which it is
founded, that the older Alpine rocks frequently testify to having
undergone an extraordinary amount of crushing. In the middle of
coarse gneisses, for example, streaks and thin bands of a mica schist
may be found, which are not due to an original difference of materials,
but to the fact that here and there the original rock has yielded to
enormous pressure, and has been crushed in situ into lenticular bands
of rock dust, from which some new mineral developments have taken
place. You may notice also in some regions, where you would classify
the rocks at first sight as mica schists, that a close examination of the
broken surfaces at right angles to what appear to be planes of foliation
reveals a structure resembling a coarsish gneiss. The microscope
shows that the rock is really a gneiss, somewhat crushed, and that
the micaceous layers are of extreme tenuity — mere films, which do not
seem to have been original constituents. The gneissic mass has been
crushed, cleaved, and on the cleavage planes films of a hydro-mica
have been developed. We cannot fail to be struck, when once our
eyes have been opened to it, by the frequency of a slabby structure
in the more central parts of the Alpine ranges, the surfaces of these
slabs being coated with minute scales or films of mica. These i "^
really records of a rude cleavage which has been impressed upon the
more central and less flexible portions of the Alps during the great
earth movements which they have undergone since they were first
metamorphosed.

Thus in the building of the Alps our thoughts are carried very
far back in the earth's history, far beyond the earliest strata of the
Palaeozoic age. Under what conditions were these great homogeneous
granitoid masses of the fundamental gneisses formed ? They differ on
the one hand from granites, on the other from the ordinary gneisses ;
from the former their differences are but slight, and of uncertain value,
yet into the latter they appear to graduate. There is nothing like to
them in any subsequent rock group, and, so far as our knowledge at
present goes, they appear to be the records of a period unique in the
world's history. This may well be. When the dry land first ap-
peared, when the surface of the earth's crust had not long ceased to
glow, when the bulk of the ocean yet floated as a vapour in the heated
atmosphere, when many gases now combined were free, we can well
imagine that the earliest sediments would be deposited under con-
ditions which have never been reproduced. In the later schists, with
their more frequent mineral changes, their distinct stratification, and

1884.] on the Building of the Alps. &5

their beds of quartzite and of limestone, we may mark the gradual
approach to a more normal condition of things. Some, such as the
Lustrous Schists, may indeed be contemporaneous with our earliest
Palaeozoic rocks ; but I confess that to myself the evidence appears
more favourable to the idea that all are more ancient than the period
which we call Cambrian, and that the majority are so I feel little
doubt.

Supposing, then, that I am right in considering all the Aljjine
schists, even the Lustrous group, to be pre- Cambrian, we have a vast
interval of time which has left no record in those districts of the
Alps of which I have been speaking. It is not till we come to the
Carboniferous period that we can identify any pages in the life history
of the earth. We are justified with regard to these in the following
conclusions : —

That in the place of the Alps there was at that time an up-
land district, composed of gneisses and schists, in substantially the
same mineral condition as they are at present, together with slaty
beds in a comparatively unaltered condition, which district was
fringed by a lowland covered by a luxuriant vegetation. Prior to
this time, also, the metamorphic rocks of the Alps had been so far
folded and denuded that the coarser gneisses were in many places
laid bare, and contributed the materials which we now find in such
beds as the Val Orsine Pudding stone. Whether there was a pre-
Triassic mountain chain occupying some part of the present Alpine
region we cannot venture to say, but I think we may unhesitatingly
affirm that there were pre-Triassic highlands.

After the close of the Carboniferous period, and anterior to the
middle part of the Trias, there were volcanic outbursts on a large scale
in more than one region of the Alps — notably in the district near and
to the east of Botzen. After this commenced a period of subsidence
and of continuous deposition of sediment. This seems to have begun
earlier and to have been at first more rapid in the eastern than in the
western area. Since in the former the Triassic beds are generally much
thicker and more calcareous than in the latter, one is tempted to
imagine that the eastern area quickly became a coraliferous sea, with
an occasional atoll or volcanic island. Henceforward to the later part
of the Eocene the record is generally one of subsidence and of deposit
of sediment. Pebble beds are rare : the strata are grits, shales (or
slates), and limestones. Whence the inorganic constituents of these
were derived I cannot at present venture to suggest, but though con-
glomerates are rare, there are occasional indications that land was not
very distant. In the eastern Alps, however, the position of some of
the Cretaceous deposits and the marked mineral differences between
these and the Jurassic seem to indicate disturbances during some
part of the Neocomian, but I am not aware of any marked trace of
these over the central and western areas. The mountain-making of
the existing Alps dates from the later part of the Eocene. Beds of
about the age of our Bracklesham series now cap such summits as
Vol. XL (No. 78.) f

66 Professor T. Q. Bonney [April 4,

the Diablerets, or help to form the mountain masses near the Todi,
rising in the Bifertenstock to a height of 11,300 feet above the sea.
Still there are signs that the sea was shallowing and the epoch of
earth movements commencing. The Eocene deposits of Switzerland
include terrestrial and fluviatile, as well as marine remains. Beds of
conglomerate occur, and even erratics of a granite from an unknown
locality, of such a size as to suggest the aid of ice for their transport.
For the present I prefer, for sake of simplicity, to speak of the uprais-
ing of the Alps as though it were the result of a few acts of compres-
sion, though I am by no means sure that this is the case. Thus
speaking we find that in Miocene times a great mountain chain existed
which covered nearly the same ground as the present Alpine region of
mesozoic and crystalline rocks. To the north, and probably to the
south, lay shallow seas, between which and the gates of the hills was
a level tract traversed by rivers, perhaps in part occupied by lakes.
Over this zone, as it slowly subsided — in correspondence, probably, with
the uplifting of the mountain land — were deposited the pebble beds of
the nagelflue and the sandstones of the molasse.

Then came another contraction of the earth's crust ; the solid moun-
tain core was no doubt compressed, uplifted, and thrust over newer
beds, but the region of the softer border land, at any rate on the north,
was apparently more affected, and the subalpine district of Switzerland
was the result. I may here call your attention to the fact that, whether
as a consequence of this or of subsequent movements, the miocene
beds occur on the northern flank of the Alps at a much greater height
above the sea than on the southern, and have been much more
upraised in the central than in the western and eastern Alps. Further,
between the Lago Maggiore and the south of Saluzzo mesozoic rocks
are almost absent from the southern flank of the Alps, and the miocene
beds are but slightly exposed and occupy a comparatively lowland
country. I think it therefore probable that the second set of move-
ments produced more effect on the German than on the Italian side of
the Alps, causing in the latter a relative depression. In support of this
view we may remark that the rivers which flow from the Alps towards
the north or the west start, as a rule, very far back, so that the water-
shed of the Alps is the crest of the third range reckoning from the
north, and the great flat basin of the Po is the receptacle for a series
of comparatively short mountain rivers. These also take a fairly
straight course to the gates of the hills, while the others change not
seldom from the lines of outcrop to the lines of dip of the strata — a
fact I think not without significance. To this rule the valley of the
Adige in the eastern region is an exception. May not this be due to
the remarkable series of minor flexures indicated by the strike of the
rocks (secondary and earlier) immediately to the west of it, which
probably influences the course of the Adda and can, I think, be traced
at intervals along the chain as far as Dauphine ? Be this as it may, it
is obvious that the generally uniform E.N.E. to W.S.W. strike of tho
rocks which compose the Alpine chain is materially modified as wo

1884.] on the Building of the Alps. 67

proceed south of the lake of Geneva, changing rapidly in the neighbour-
hood of Grenoble from a strike N.E. to S.W. to one from N.W. to S.E.
This subject, however, is too complicated to be followed further on the
present occasion. I will only add that the singular trough-like
upland valleys, forming the upper parts of some of the best-known
road passes — as, for instance, the Maloya — which descend so gently to
the north, and are cut off so abruptly on the south, seem to me most
readily explained as the remnants of a comparatively disused drainage
system of the Alps.

It remains only to say a few words on the post-tertiary history of
the Alps. We enter here upon a troubled sea of controversy, upon
which more than the time during which I have spoken might easily be
spent; so you will perhaps allow me to conclude with a simple
expression of my own opinion, without entering into the arguments.
That the glaciers of the Alps were once vastly greater than at the
present time is beyond all dispute ; they covered the fertile lowlands of
Switzerland, they welled up against the flanks of the Jura above Neuf-
chatel, they crept over the orange gardens of Sirmio, and projected
into the plains of Piedmont. By their means great piles of broken
rock must have been transported into the lowlands; but did they
greatly modify the peaks, deepen the valleys, or excavate the lake
basins ? My reply would be, " To no very material extent." I regard
the glacier as the file rather than as the chisel of nature. The Alpine
lakes appear to be more easily explained, as the Dead Sea can only bo
explained — as the result of subsidence along zones roughly parallel
with the Alpine ranges, athwart the general directions of valleys
which already existed and had been in the main completed in pre-
glacial times. To produce these lake basins we should require earth
movements on no greater scale than have taken place in our own
country since the furthermost extension of the ice-fields. This
opinion as to the origin of the lakes is, I believe, generally held
to be a heresy, but it is a heresy which has been ingrained in me by
some twenty years of study of the physiography of the Alps.

[T. G. B.]

F 2

68 General Monthhj Meeting. [April 7,

GENERAL MONTHLY MEETING,
Monday, April 7, 1884.

George Busk, Esq. F.R.S. Treasurer and Vice-President,
in the Chair.

Robert Ellis Dudgeon, M.D.
David John Eussell Duncan, Esq.
Willoughby Smith, Esq.

were elected Members of the Eoyal Institution.

Four Candidates for Membership were proposed for election.

The Fullerian Professorship of Physiology became vacant by the
resignation of Professor McKendrick on March 5th, on account of
ill health.

The following arrangements for the Lectures after Easter were
announced : —

Edward E. Klein, M.D. F.E.S. and Professor Arthur Gamgee, M.D. F.R.S.
— Seven Lectures on The Anatomy and Physiology of Nerve and Muscle.
Dr. Klein.— Two Lectures on The Anatomy of Nerve and Muscle ; on Tuesdays,
April 22 and 29. Professor Gamgee. — Five Lectures on The Physiology of
Nerve and Muscle ; on Tuesdays, May 6 to June 3.

Professor Dewar, M.A. F.R.S. MM.I. — Seven Lectures on Flame and
Oxidation ; on Thursdays, April 24 to June 5.

HoDDER M. Westropp, Esq. — Three Lectures on Recent Discoveries in
Roman Archeology : I. The Colosseum ; 11. The Forum ; III. The Palatine
Hill ; on Saturdays, April 26 to May 10.

Professor T. G. Bonney, D.Sc. F.R.S. Pres. G.S. — Four Lectures on The
Bearing of Microscopical Research upon some large Geological Problems;
on Saturdays, May 17 to June 7.

The Presents received since the last Meeting were laid on the
table, and the thanks of the Members returned for the same, viz. : —

TJie Governor- General of India — Geological Survey of India: Palseontologia
Indica: Series X. Vol. HI. Part 1. 4to. 1884.
Records, Vol. XVII. Part 1. 8vo. 1884.
Accademia dei Lincei, Beale, Roma— Att\, Serie Terza: Transunti. Vol. VIII.

Fasc. 4-6. 4to. 1884.
Asiatic Society of Bengal — Proceedings, No. 9. 8vo. 1883.

Journal, Vol. LII. Part I. Nos. 3, 4 ; Part II. Nos. 2-4. 8vo. 1883.
Astronomical Society, Royal— Monthly Notices, Vol. XLIV. No. 4. 8vo. 1884.
Bankers, Institute o/— Journal, Vol. V. Part 3. 8vo. 1884.

1884.J General Monthly Meeting, 69

Chemical Society — Journal for March 1884. 8vo.
Editors — American Journal of Science for March 1884. 8vo.
Analyst for March 1884. 8vo.
Athenaeum for March 1884. 4to.
Chemical News for March 1884. 4to.
Engineer for March 1884. fol.
Horological Journal for March 1884. 8vo.
Iron for March 1884. 4to.
Nature for March 1884. 4to.

Kevue Scientifique and Eevue Politique et Litte'raire for March 1884. 4to.
Science Monthly, Illustrated, for March, 1884.
Telegraphic Journal for March 1884. 8vo.
Franklin Institute — Journal, No. 699. 8vo. 1884.
Geographical Society, Royal — Proceedings, New Series, Vol. VI. No. 3. 8vo.

1884.
Geological Institute, Imperial, Vienna — Jahrbuch, Band XXXIV. No. 1. 8vo.

1884.
Johns Hopkins University — American Chemical Journal, Vol. VI. No. 1. 8vo.
1884.
American Journal of Philology, No. 16. 8vo. 1883.
Linnean Society — Journal, No. 102. 8vo. 1884.

Lisbon, Sociedade de Geographia— Bulletin, 4^ Serie, Nos. 4, 5. 8vo. 1883.
Manchester Geological >S'oae<«/— Transactions, Vol. XVII. Parts 13, 14. 8vo.

1883-4.
Mechanical Engineers' Institution — Proceedings, No. 1. 8vo. 1884.
MiddlesexHospital— ReipOTta for 1881. 8vo. 1884.
Miller, W. J. C. Esq. (the Registrar)— The Medical Register. 8vo. 1884.

The Dentists' Register. 8vo. 1884.
Newlands, John A. R. Esq. F.I.C. F.C.S. (the Author) — The Periodic Law. 8vo.

1884.
North of England Institute of Mining and Mechanical Engineers — Transactions,

Vol. XXXIII. Part 3. 8vo. 1884.
Numismatic Society — Chronicle and Journal, 1883, Part 4. 8vo.
Pharmaceutical Society of Great Britain — Journal, March 1884. 8vo.
Photographic Society— J omnai. New Series, Vol. VIII. No. 5. 8vo. 1884.
Radcliffe Observatory — Radcliflfe Observations for 1858-80. 8vo.

Radcliffe Catalogue of Stars. 2 vols. 8vo. 1860.
Rio de Janeiro, Observatoire Imperiale — Bulletin, No. 10. fol. 1883.
Royal College of Surgeons of England — Catalogue of Specimens illustrating the
Osteology of Vertebrated Animals in the Museum. By W. H. Flower.
Vol. 2, Mammalia. 8vo. 1884.
Royal Society of London — Proceedings, No. 229. 8vo. 1884.
St. Petersbourg, Academic des Sciences — Memoires, Tome XXXI. No. 9. 4to.

1883.
Saxon Society of Sciences, iJovaZ— Philologisch-historische Classe: Abhandlungen :
Band VIII. Nos. 5, 6; Band IX. No. 1. 8vo. 1883.
Verhandlungen, 1882. 8vo. 1883.
Mathematisch-physische Classe : Abhandlungen : Band XII. No. 9. 8vo.

1883.
Verhandlungen, 1882. 8vo. 1883.
Society of Arts — Journal, March 1884. 8vo.
Tokio University— Memoiis, No. 9. 8vo. 1884.

Upsal University— 'NoYSi Acta, Ser. III. Vol. XI. Fasc. 2. 4to. 1883.
Vereins znr JBef order ung des Gewerbfleisses in Preussen — Verhandlungen, 1884 :

Heft 2. 4to.
Yorkshire Archxological and Topographical Association — Jouraal, Part 31. 8vo.

70 Mr. Walter Besant [April 25,

WEEKLY EVENING MEETING,

Friday, April 25, 1884.

Sir Frederick Pollock, Bart. M.A. Manager and Vice-President,
in the Chair.

Walter Besant, Esq.

The Art of Fiction*

I DESIRE, this evening, to consider Fiction as one of the Fine Arts.
In order to do this, and before doing it, I have first to advance
certain propositions. They are not new, they are not likely to be
disputed, and yet they have never been so generally received as to
form part, so to speak, of the national mind. These propositions
are three, though the last two directly spring from the first. They
are: —

1. That Fiction is an Art in every way worthy to be called the
sister and the equal of the Arts of Painting, Sculpture, Music and
Poetry ; that is to say, her field is as boundless, her possibilities as
vast, her excellences as worthy of admiration, as may be claimed for
any of her sister Arts.

2. That it is an Art which, like them, is governed and directed
by general laws ; and that these laws may be laid down and taught
with as much precision and exactness as the laws of harmony, per-
spective, and proportion.

3. That, like the other Fine Arts, Fiction is so far removed from
the mere mechanical arts, that no laws or rules whatever can teach it
to those who have not already been endowed with the natural and
necessary gifts.

These are the three propositions which I have to discuss. It
follows as a corollary and evident deduction, that, these propositions
once admitted, those who follow and profess the Art of Fiction must
be recognised as artists, in the strictest sense of the word, just as
much as those who have delighted and elevated mankind by music
and painting ; and that the great Masters of Fiction must be placed
on the same level as the great Masters in the other Arts. In other
words, I mean that where the highest point, or what seems the
highest point, possible in this Art is touched, the man who has
reached it is one of the world's greatest men

The general — the Philistine — view of the* Profession, is, first of
all, that it is not one which a scholar and a man of serious views

* The full discourse is published by Messrs. Cliatto and Windus.

1884.] on the Art of Fiction. 71

should take up : the telling of stories is inconsistent with a well-
balanced mind; to be a teller of stories disqualifies one from a
hearing on important subjects

With these people must not be confounded another class, not so
large, who are prepared to admit that Fiction is in some qualified
sense an Art ; but they do this as a concession to the vanity of its
followers, and are by no means prepared to allow that it is an Art of
the first rank. How can that be an Art, they might ask, which has
no lecturers or teachers, no school or college or Academy, no recog-
nised rules, no text-books, and is not taught in any University?
Even the German Universities, which teach everything else, do not
have Professors of Fiction, and not one single novelist, so far as I
know, has ever pretended to teach his mystery, or spoken of it as a
thing which may be taught. Clearly, therefore, they would go on to
argue, such art as is required for the making and telling of a story
can and must be mastered without study, because no materials exist
for the student's use. It may even, perhaps, be acquired uncon-
sciously, or by imitation. This view, I am sorry to say, largely
prevails among the majority of those who try their chance in the field
of fiction. Anyone, they think, can write a novel ; therefore, why
not sit down and write one ? I would not willingly say one word
which might discourage those who are attracted to this branch of
literature ; on the contrary, I would encourage them in every possible
way. One desires, however, that they should approach their work
at the outset with the same serious and earnest appreciation of its
importance and its difficulties with which they undertake the study of
music and painting. I would wish, in short, that from the very begin-
ning their minds should be fully possessed with the knowledge that
Fiction is an Art, and, like all other Arts, that it is governed by certain
laws, methods, and rules, which it is their first business to learn.

It is, then, first and before all, a real Art. It is the oldest, because
it was known and practised long before Painting and her sisters were
in existence or even thought of ; it is older than any of the Muses
from whose company she who tells stories has hitherto been excluded ;
it is the most widely spread, because in no race of men under the sun
is it unknown, even though the stories may be always the same, and
handed down from generation to generation in the same form ; it is
the most religious of all the Arts, because in every age until the
present the lives, exploits and sufferings of gods, goddesses, saints
and heroes have been the favourite theme ; it has always been the
most popular, because it requires neither culture, education, nor
natural genius to understand and listen to a story ; it is the most
moral, because the world has always been taught whatever little
morality it possesses by way of story, fable, apologue, parable, and
allegory. It command's the widest influence, because it can be carried
easily and everywhere, into regions where pictures are never seen
and music is never heard ; it is the greatest teaching power, because
its lessons are most readily apprehended and understood. All this.

72 Mr. Walter Besant [April 25,

which might have been said thousands of years ago, may be said to
day with even greater force and truth. That world which exists not,
but is an invention or an imitation — that world in which the shadows
and shapes of men move about before our eyes as real as if they were
actually living and speaking among us, is like a great theatre acces-
sible to all of every sort, on whose stage are enacted, at our own
sweet will, whenever we please to command them, the most beautiful
plays : it is, as every theatre should be, the school in which manners
are learned : here the majority of reading mankind learn nearly all
that they know of life and manners, of philosophy and art ; even of
science and religion. The modern novel converts abstract ideas into
living models ; it gives ideas, it strengthens faith, it preaches a higher
morality than is seen in the actual world ; it commands the emotions
of pity, admiration, and terror ; it creates and keeps alive the sense
of sympathy ; it is the universal teacher ; it is the only book which
the great mass of reading mankind ever do read ; it is the only way
in which people can learn what other men and women are like ; it
redeems their lives from dulness, puts thoughts, desires, knowledge,
and even ambitions into their hearts ; it teaches them to talk, and
enriches their speech with epigrams, anecdotes and illustrations. It
is an unfailing source of delight to millions, happily not too critical.
Why, out of all the books taken down from the shelves of the public
libraries, four-fifths are novels, and of all those that are bought nine-
tenths are novels. Compared with this tremendous engine of popular
influence, what are all the other Arts put together? Can we not
alter the old maxim, and say with truth, Let him who pleases make
the laws if I may write the novels ?

As for the field with which this Art of Fiction occupies itself, it
is, if you please, nothing less than the whole of Humanity. The
novelist studies men and women ; he is concerned with their actions
and their thoughts, their errors and their follies, their greatness and
their meanness ; the countless forms of beauty and constantly varying
moods to be seen among them ; the forces which act upon them ; the
passions, prejudices, hopes and fears which pull them this way and
that. He has to do, above all and before all, with men and women.
No one, for instance, among novelists, can be called a landscape
painter, or a painter of sea-pieces, or a painter of fruit and flowers,
save only in strict subordination to the group of characters with
whom he is dealing

It is, therefore, the especial characteristic of this Art, that, since
it deals exclusively with men and women, it not only requires of its
followers, but also creates in readers, that sentiment which is destined
to be a most mighty engine in deepening and widening the civiliza-
tion of the world. We call it Sympathy, but it means a good deal
more than was formerly understood by the word. It means, in fact,
what Professor Secley once called the Enthusiasm of Humanity, and it
first appeared, I think, about a hundred and fifty years ago, when
the modern novel came into existence. You will find it, for instance,

1884.J on the Art of Fiction. 73

conspicuous for its absence in Defoe. The modern Sympathy
includes not only the power to pity the sufferings of others, but also
that of understanding their very souls ; it is the reverence for man,
the respect for his personality, the recognition of his individuality, and
the enormous value of the one man, the perception of one man's
relation to another, his duties and responsibilities. Through the
strength of this newly-born faculty, and aided by the guidance of a
great artist, we are enabled to discern the real indestructible man
beneath the rags and filth of a common castaway, and the possibilities
of the meanest gutter child that steals in the streets for its daily
bread. Surely that is a wonderful Art which endows the people —
all the people — with this power of vision and of feeling. Painting
has not done it, and could never do it ; Painting has done more for
nature than for humanity. Sculpture could not do it, because it
deals with situation and form, rather than action. Music cannot do
it, because Music (if I understand rightly) appeals especially to the
individual concerning himself and his own aspirations. Poetry
alone is the rival of Fiction, and in this respect it takes a lower place,
not because Poetry fails to teach and interpret, but because Fiction is,
and must always be, more popular.

Again, this Art teaches, like the others, by suppression and
reticence. Out of the great procession of Humanity, the Comedie
Humaine, which the novelist sees passing ever before his eyes, single
figures detach themselves one after the other, to be questioned,
examined, and received or rejected. This process goes on perpe-
tually. Humanity is so vast a field, that to one who goes about
watching men and women, and does not sit at home and evolve
figures out of inner consciousness, there is not and can never be any
end or limit to the freshness and interest of these figures. It is the
work of the artist to select the figures, to suppress, to copy, to group,
and to work up the incidents which each one offers. The daily life
of the world is not dramatic— it is monotonous ; the novelist makes it
dramatic by his silences, his suppressions, and his exaggerations. No
one, for example, in fiction behaves quite in the same way as in real
life ; as on the stage, if an actor unfolds and reads a letter, the simple
action is done with an exaggeration of gesture which calls attention to
the thing and to its importance, so in romance, while nothing should
be allowed which does not carry on the story, so everything as it occurs
must be accentuated and yet deprived of needless accessory details.
The gestures of the characters at an important juncture, their looks,
their voices, may all be noted if they help to impress the situation.
Even the weather, the wind, and the rain, with some writers, have been
made to emphasize a mood or a passion of a heroine. To know
how to use these aids artistically is to the novelist exactly what to
the actor is the right presentation of a letter, the handing of a chair,
even the removal of a glove.

A third characteristic of Fiction, which should alone be sufficient
to give it a place among the noblest forms of Art, is that, like

74 Mr. Walter Besant [April 25,

Poetry, Painting, and Music, it becomes a veliicle, not only for the
best thoughts of the writer, but also for those of the reader, so that a
novelist may write truthfully and faithfully, but simply, and yet be
understood in a far fuller and nobler sense than was present to his
own mind. This power is the very highest gift of the poet. He has
a vision and sees a thing clearly, yet perhaps afar off ; another who
reads him is enabled to get the same vision, to see the same thing,
yet closer and more distinctly. For a lower intellect thus to lead
and instruct a higher is surely a very great gift, and granted only to
the highest forms of Art. And this it is which Fiction of the best
kind does for its readers. It is, however, only another way of saying
that Truth in Fiction produces effects similar to those produced by
Truth in every other Art

We come next to speak of the Laws which govern this Art. I
mean those general rules and principles which must necessarily be
acquired by every writer of Fiction before he can even hope for success.
Rules will not make a man a novelist, any more than a knowledge
of grammar makes a man know a language, or a knowledge of musical
science makes a man able to j)lay an instrument. Yet the Rules must
be learned. And, in speaking of them, one is compelled, so close is
the connection between the sister Arts, to use not only the same
terms, but also to adopt the same rules, as those laid down by
painters for their students. If these Laws appear self-evident, it is a
proof that the general principles of the Art are well understood.
Considering, however, the vast quantity of bad, inartistic work which
is every week laid before the public, one is inclined to think that a
statement of these principles may not be without usefulness.

First, and before everything else, there is the Rule that everything
in Fiction which is invented and is not the result of personal
experience and observation is worthless. In some other Arts, the
design may follow any lines which the designer pleases : it may be
fanciful, unreal, or grotesque; but in modern Fiction, whose sole
end, aim, and purpose is to portray humanity and human character,
the design must be in accordance with the customs and general
practice of living men and women under any proposed set of circum-
stances and conditions. That is to say, the characters must be real,
and such as might be met with in actual life, or, at least, the natural
developments of such people as any of us might meet ; their actions
must be natural and consistent ; the conditions of place, of manners,

and of thought must be drawn from personal observation

Remember that most of the people who read novels and know
nothing about the art of writing them, recognise before any other
quality that of fidelity : the greatness of a novelist they measure
chiefly by the knowledge of the world displayed in his pages;
the highest praise they can bestow upon him is that he has drawn the
story to the life

This being so, the first thing which has to be acquired is the art
of description. It seems easy to describe ; anyone, it seems, can set

1884.] on the Art of Fiction. 75

down what he sees. But consider. How much does he see ? There
is everywhere, even in a room, such a quantity of things to be seen :
far, far more in field and hedge, in mountain and in forest, and beside
the stream are there countless things to be seen ; the unpractised eye
sees nothing, or next to nothing. Here is a tree, here is a flower,
there is sunshine lying on the hill. But to the observant and trained
eye, the intelligent eye, there lies before him everywhere an inexhaus-
tible and bewildering mass of things to see. Eemember how Mr.
Jefferies sits down in a coppice with his eyes wide open to see what
the rest of us never dreamed of looking for. Long before he has
half fiuished telling us what he has seen — behold ! a volume, and one
of the most delightful volumes conceivable. But then, Mr. Jefferies
is a profound naturalist. We cannot all describe after his manner ;
nor should we try, for the simple reason that descriptions of still life
in a novel must be strictly subordinated to the human interest. But
while Mr. Jefferies has his hedge and ditch and brook, we have our
towns, our villages, and our assemblies of men and women. Among
them we must not only observe, but we must select. Here, then, are
two distinct faculties which the intending novelist must acquire; viz.
observation and selection. As for the power of observation, it may
be taught to anyone by the simple method adopted by Eobert
Houdin, the French conjuror. This method consists of noting down
continually and remembering all kinds of things remarked in the
course of a journey, a walk, or the day's business. The learner must
carry his note-book always with him, into the fields, to the theatre,
into the streets — wherever he can watch man and his ways, or Nature
and her ways. On his return home he should enter his notes in his
commonplace-book. There are places where the production of a note-
book would be embarrassing — say, at a dinner-party, or a street fight ;
yet the man who begins to observe will speedily be able to remember
everything that he sees and hears until he can find an opportunity to
note it down, so that nothing is lost.* The materials for the novelist,
in short, are not in the books upon the shelves, but in the men and
women he meets with everywhere ; he will find them, where Dickens
found them, in the crowded streets, in trains, tramcars and omnibuses,
at the shop- windows, in churches and chapels: his materials are
everywhere — there is nothing too low, nothing too high, nothing
too base, nothing too noble, for the novelist. Humanity is like a
kaleidoscope, which you may turn about and look into, but you will

* I earnestly recommend those who desire to study this Art to begin by daily
practice in the description of things, even common things, that they have
observed, by reporting conversations, and by word portraits of their friends.
They will find that the practice gives them firmness of outline, quickness of
observation, power of catching important details, and, as regards dialogue, readi-
ness to see what is unimportant. Preliminary practice and study of this kind
will also lead to the saving of a vast quantity of valuable material, wJiich is
only wasted by being prematurely worked up into a novel written before tlie
elements of the Art have been acquired.

76 Mr. Walter Besant [April 25,

never get the same picture twice — it cannot be exhausted. But it
may be objected, that the broad distinctive types have been long
since all used. They have been used, but the comfort is that they
can never be used up, and that they may be constantly used again and
again. Can we ever be tired of them when a master hand takes one
of them again and gives him new life ? . . . .

Fidelity, therefore, can be only assured by acquiring the art of
observation, which further assists in filling the mind with stored
experience. I am quite sure that most men never see anything at all.
I have known men who have even gone all round the world and seen
nothing — no, nothing at all. Emerson says, very truly, that a
traveller takes away nothing from a place except what he brought
into it. Now, the observation of things around us is no part of the
ordinary professional and commercial life ; it has nothing at all to
do with success and the making of money ; so that we do not learn
to observe. Yet it is very easy to shake people and make them open
their eyes. Some of us remember, for instance, the time when
Kingsley astonished everybody with his descriptions of the wonders
to be seen on the seashore and to be fished out of every pond in
the field. Then all the world began to poke about the seaweed
and to catch tritons and keep water-grubs in little tanks. It was
only a fashion, and it presently died out ; but it did people good,
because it made them understand, perhaps for the first time, that
there really is a good deal more to see than meets the casual eye. At
present the lesson which we need is not that the world is full of the
most strange and wonderful creatures, all eating each other perpetu-
ally, but that the world is full of the most wonderful men and women,
not one of whom is mean or common, but to each his own personality
is a great and awful thing, worthy of the most serious study.

There are, then, abundant materials waiting to be picked up by any-
one who has the wit to see them lying at his feet and all around him.
"What is next required is the power of Selection. Can this be taught ?
I think not, at least I do not know how, unless it is by reading. In
every Art, selection requires that kind of special fitness for the Art
which is included in the much-abused word Genius. In Fiction, the
power of selection requires a large share of the dramatic sense.
Those who already possess this faculty will not go wrong if they
bear in mind the simple rule that nothing should be admitted which
does not advance the story, illustrate the characters, bring into
stronger relief the hidden forces which act upon them, their emotions,
their passions, and their intentions. All descriptions which hinder
instead of helping the action, all episodes of whatever kind, all
conversation which does not either advance the story or illustrate
the characters, ought to be rigidly suppressed.

Closely connected with selection is dramatic presentation. Given
a situation, it should be the first care of the writer to present it as
dramatically, that is to say, as forcibly as possible. The grouping
and setting of the picture, the due subordination of description

1884.] on the Art of Fiction. 77

to dialogue, the rapidity of the action, those things which naturally
suggest themselves to the practised eye, deserve to be very carefully
considered by the beginner. In fact, a novel is like a play : it may
be divided into scenes and acts, tableaux and situations, separated by
the end of the chapter instead of the drop scene : the writer is the
dramatist, stage-manager, scene-painter, actor, and carpenter, all in
one : it is his single business to see that none of the scenes flag or fall
flat : he must never for one moment forget to consider how the piece
is looking from the front.

The next simple Rule is that the drawing of each figure must be
clear in outline, and, even if only sketched, must be sketched without
hesitation. This can only be done when the writer himself sees his
figures clearly. Characters in fiction do not, it must be understood,
spring Minerva-like from the brain. They grow : they grow some-
times slowly, sometimes quickly. From the first moment of concep-
tion, that is to say, from the first moment of their being seen and
caught, they grow continuously and almost without mental effort. If
they do not grow and become every day clearer, they had better be
put aside at once, and forgotten as soon as may be, because that is a
proof that the author does not understand the character he has himself
endeavoured to create. To have on one's hands a half-created being
vrithout the power of finishing him must be a truly dreadful thing.

The only way out of it is to kill and bury him at once

On the other hand, how possible, how capable of development, how
real becomes a true figure, truly understood by the creator, and truly
depicted ! Do we not know what they would say and think under all
conceivable conditions ? We can dress them as we will ; we can
place them in any circumstances of life : we can always trust them,
because they will never fail us, never disappoint us, never change,
because we understand them so thoroughly. So well do we know
them that they become our advisers, our guides, and our best friends,
on whom we model ourselves, our thoughts, and our actions. The
writer who has succeeded in drawing to the life, true, clear, distinct,
60 that all may understand, a single figure of a true man or woman,
has added another exemplar or warning to humanity. Nothing, then,
it must be insisted upon as of the greatest importance, should be
begun in writing until the characters are so clear and distinct in the
brain, so well known, that they will act their parts, bend their dia-
logue, and suit their action to whatever situations they may find
themselves in, if only they are becoming to them. Of course, clear
outline drawing is best when it is accomplished in the fewest strokes,
and the greater part of the figures in Fiction, wherein it differs from
Painting, in which everything should be finished, require no more
work upon them, in order to make them clear, than half-a-dozen bold,
intelligible lines.

As for the methods of conveying a clear understanding of a
character, they are many. The first and the easiest is to make it clear
by reason of some mannerism or personal peculiarity, some trick of

78 Mr, Walter Besant [April 25,

speech or of carriage. This is the worst, as may generally be said of
the easiest way. Another easy method is to describe your character at
length. This also is a bad, because a tedious, method. If, however,
you read a page or two of any good writer, you will discover that he
first makes a character intelligible by a few words, and then allows
him to reveal himself in action and dialogue. On the other hand,
nothing is more inartistic than to be constantly calling attention in a
dialogue to a gesture or a look, to laughter or to tears. The situation
generally requires no such explanation : in some well-known scenes
which I could quote, there is not a single word to emphasize or
explain the attitude, manner, and look of the speakers, yet they are as
intelligible as if they were written down and described. That is the
highest art which carries the reader along and makes him see, with-
out being told, the changing exj)ressions, the gestures of the speakers,
and hear the varying tones of their voices. It is as if one should
close one's eyes at the theatre, and yet continue to see the actors on
the stage as well as hear their voices. The only writer who can do
this is he who makes his characters intelligible from the very outset,
causes them first to stand before the reader in clear outline, and then
with every additional line brings out the figure, fills up the face, and
makes his creatures grow from simple outline more and more to the
perfect and rounded figure.

Clearness of drawing, which includes clearness of vision, also
assists in producing directness of purpose. As soon as the actors in
the story become real in the mind of the narrator, and not before, the
story itself becomes real to him. More than this, he becomes straight-
way vehemently impelled to tell it, and he is moved to tell it in the
best and most direct way, the most dramatic way, the most truthful
way possible to him. It is, in fact, only when the writer believes
his own story, and knows it to be every word true, and feels that he
has somehow learned from everyone concerned the secret history of
his own part in it, that he can really begin to write it.* We know
how sometimes, even from a practised hand, there comes a work
marred with the fatal defect that the writer does not believe in his
own story. When this is the case, one may generally find on investi-
gation that one cause at least of the failure is that the characters, or
some of them, are blurred and uncertain.

Again, the modern English novel, whatever form it takes, almost
always starts with a conscious moral purpose. When it does not, so

* Hardly anytliing is more important than this — to believe in your own story.
Wherefore let the student remember that unless the cluiraeters exist and move
about in his brain, all separate, distinct, living, and perpetually engaged in the
action of the story, sometimes at one part of it, sometimes at another, and that in
scenes and places which must be omitted in the writing, he lias got no story to tell
and had better give it up. I do not think it is generally understood that there are
th«MiSiinds of scenes which belong to the story and never get outside the writer's
brain at all. Some of these may be beautiful and touching ; but there is not
room for all, and the writer has to select.

1884.] on the Art of Fiction. .79

much are we accustomed to expect it, that one feels as if there has been
a debasement of the Art. It is, fortunately, not possible in this
country for any man to defile and defame humanity and still be called
an artist ; the development of modern sympathy, the growing rever-
ence for the individual, the ever-widening love of things beautiful and
the appreciation of lives made beautiful by devotion and self-denial,
the sense of personal responsibility among the English-speaking
races, the deep-seated religion of our people, even in a time of doubt,
are all forces which act strongly upon the artist as well as upon his
readers, and lend to his work, whether he will or not, a moral purpose
so clearly marked that it has become practically a law of English
Fiction. We must acknowledge that this is a truly admirable thing,
and a great cause for congratulation. At the same time, one may be
permitted to think that the preaching novel is the least desirable of
any, and to be unfeignedly rejoiced that the old religious novel,
written in the interests of High Church or Low Church or any other
Church, has gone out of fashion.

Next, just as in Painting and Sculpture, not only are fidelity,
truth, and harmony to be observed in Fiction, but also beauty of
workmanship. It is almost impossible to estimate too highly the
value of careful workmanship, that is, of style. Every one, without
exception, of the great Masters in Fiction, has recognised this truth.
You will hardly find a single page in any of them which is not care-
fully and even elaborately worked up. I think there is no point on which
critics of novels should place greater importance than this, because it
is one which young novelists are so very liable to ignore. There
ought not to be in a novel, any more than in a poem, a single sentence
carelessly worded, a single phrase which has not been considered.
Consider, if you please, any one of the great scenes in Fiction — how
much of the effect is due to the style, the balanced sentences, the very
words used by the narrator ! This, however, is only one more point
of similarity between Fiction and the sister Arts. There is, 1 know,
the danger of attaching too much attention to style at the expense of
situation, and so falling a prey to priggishness, fashions, and man-
nerisms of the day. It is certainly a danger ; at the same time, it
sometimes seems, when one reads the slipshod, careless English which
is often thought good enough for story-telling, that it is almost
impossible to overrate the value of style. There is comfort in the
thought that no reputation worth having can be made without attend-
ing to style, and that there is no style, however rugged, which cannot
be made beautiful by attention and pains

In fact, every scene, however unimportant, should be completely
and carefully finished. There should be no unfinished places, no sign
anywhere of weariness or haste — in fact, no scamping. The writer
must so love his work as to dwell tenderly on every page and be
literally unable to send forth a single page of it without the finishing
touches. We all of us remember that kind of novel in which every
scene has the appearance of being hurried and scamped.

80 Mr. Walter Besant [April 25,

To sum up these few preliminary and general laws. The Art of
Fiction requires first of all the power of description, truth, and fidelity,
observation, selection, clearness of conception and of outline, dramatic
grouping, directness of purpose, a profound belief on the part of the
story-teller in the reality of his story, and beauty of workmanship.
It is, moreover, an Art which requires of those who follow it seriously
that they must be unceasingly occupied in studying the ways of man-
kind, the social laws, the religions, philosophies, tendencies, thoughts,
prejudices, superstitions of men and women. They must consider as
many of the forces which act upon classes and upon individuals as
they can discover ; they should be always trying to put themselves
into the place of another ; they must be as inquisitive and as watchful
as a detective, as suspicious as a criminal lawyer, as eager for knowledge
as a physicist, and withal fully possessed of that spirit to which
nothing appears mean, nothing contemptible, nothing unworthy of
study, which belongs to human nature.

I repeat that I submit some of these laws as perhaps self-evident.
If that is so, many novels which are daily submitted to the reviewer
are written in wilful neglect and disobedience of them. But they
are not really self-evident ; those who aspire to be artists in Fiction
almost invariably begin without any understanding at all of these
laws. Hence the lamentable early failures, the waste of good
material, and the low level of Art with which both the novel-writer
and the novel-reader are too often contented. I am certain that if
these laws were better known and more generally studied, a very
large proportion of the bad works of which our critics complain
would not be produced at all. And I am in great hopes that one
effect of the establishment of the newly founded Society of Authors
will be to keep young writers of fiction from rushing too hastily into
print, to help them to the right understanding of their Art and its
principles, and to guide them into true practice of their principles
while they are still young, their imaginations strong, and their
personal experiences as yet not wasted in foolish failures.

After all these preliminary studies there comes the most im-
portant point of all — the story. There is a school which pretends
that there is no need for a story : all the stories, they say, have been told
already ; there is no more room for invention : nobody wants any longer
to listen to a story. One hears this kind of talk with the same wonder
which one feels when a new monstrous fashion changes the beautiful
figure of woman into something grotesque and unnatural. Men say
these things gravely to each other, especially men who have no
story to tell : other men listen gravely ; in the same way women put
on the newest and most preposterous fiishions gravely, and look upon
each other without either laughing or hiding their faces for shame.
It is indeed, if we think of it, a most strange and wonderful theory,
that we should continue to care for Fiction and cease to care for the
story. We have all along been training ourselves how to tell the
story, and here is this new school which stops in like the needy

1884.] CM the Art of Fiction. 81

knife-grinder, to explain that there is no story left at all to tell.
Why, the story is everything. I cannot conceive of a world going on
at all without stories, and those strong ones, with incident in them,
and merriment and pathos, laughter, and tears and the excitement of
wondering what will happen next. Fortunately, these new theorists
contradict themselves, because they find it impossible to write a
novel which shall not contain a story, although it may be but a puny
bantling. Fiction without adventure — a drama without a plot — a
novel without surprises — the thing is as impossible as life without
uncertainty.

As for the story, then. And here theory and teaching can go no
farther. For every Art there is the corresponding science which
may be taught. We have been speaking of the corresponding
science. But the Art itself can neither be taught nor communicated.
If the thing is in a man he will bring it out somehow, well or badly,
quickly or slowly. If it is not, he can never learn it. Here, then,
let us suppose that we have to do with the man to whom the inven-
tion of stories is part of his nature. We will also suppose that he
has mastered the laws of his Art, and is now anxious to apply them.
To such a man one can only recommend that he should with the
greatest care and attention analyze and examine the construction of
certain works which are acknowledged to be of the first rank in
fiction. Among them, not to speak of Scott, he might pay especial
attention from the constructive point of view, to the truly admirable
shorter stories of Charles Reade, to George Eliot's ' Silas Marner,*
the most perfect of English novels, Hawthorne's 'Scarlet Letter,*
Holmes's ' Elsie Venner,' Blackmore's ' Lorna Doone,' or Black's
* Daughter of Heth.' He must not sit down to read them " for the
story," as uncritical people say : he must read them slowly and care-
fully, perhaps backwards, so as to discover for himself how tho
author built up the novel, and from what original germ or conception
it sprang

One thing more the Art student has to learn. Let him not only
believe his own story before he begins to tell it, but let him
remember that in story-telling, as in almsgiving, a cheerful counte-
nance works wonders, and a hearty manner greatly helps the teller
and pleases the listener. One would not have the novelist make
continual efforts at being comic ; but let him not tell his story with
eyes full of sadness, a face of woe and a shaking voice. His story
may be tragic, but continued gloom is a mistake in Art, even for a
tragedy. If his story is a comedy, all the more reason to tell it
cheerfully and brightly. Lastly, let him tell it without apparent
effort : without trying to show his cleverness, his wit, his powers of
epigram, and his learning. Yet let him pour without stint or
measure into his work all that he knows, all that he has seen, all
that he has observed, and all that he has remembered : all that there
is of nobility, sympathy, and enthusiasm in himself. Let him spare
nothing, but lavish all that he has, in the full confidence that the

Vol. XI. (No. 78.) G

82 Mr. Walter Besant [April 25,

wells will not be dried up, and that the springs of fancy and imagina-
tion will flow again, even though he seem to have exhausted himself

in this one effort

Let me say one word upon the present condition of this most
delightful Art in England. Eemember that great Masters in every
Art are rare. Perhaps one or two appear in a century : we ought not
to expect more. It may even happen that those modern writers of
our own whom we have agreed to call great Masters will have to take
lower rank among posterity, who will have great Masters of their own.
I am inclined, however, to think that a few of the nineteenth-century
novelists will never be suffered to die, though they may be remem-
bered principally for one book — that Thackeray will be remembered
for his ' Vanity Fair,' Dickens for ' David Copperfield,' George
Meredith for the ' Ordeal of Richard Feverel,' George Eliot for
' Silas Marner,' Charles Eeade for the ' Cloister and the Hearth,' and
Blackmore for his ' Lorna Doone.' On the other hand, without
thinking or troubling ofirselves at all about the verdict of posterity,
which matters nothing to us compared with the verdict of our con-
temporaries, let us acknowledge that it is a bad year indeed when we
have not produced some good work, work of a very high kind, if not
immortal work. An exhibition of the year's novels would generally
show two or three, at least, of which the country may be, say reason-
ably proud. Does the Royal Academy of Arts show every year more
than two or three pictures — not immortal pictures, but pictures of
which we may be reasonably proud ? One would like, it is true, to
see fewer bad novels published, as well as fewer bad pictures exhi-
bited ; the standard of the work which is on the borderland between
success and failure should be higher. At the same time I am very
sure and certain that there never has been a time when better works
of Fiction have been produced, both by men and women. That Art
is not declining, but is advancing, which is cultivated on true and
not on false or conventional principles. Ought we not to be full of
hope for the future, when such women as Mrs. Oliphant and Mrs.
Thackeray Ritchie write for us — when such men as Meredith, Black-
more, Black, Payn, Wilkie Collins, and Hardy are still at their best,
and such men as Louis Stevenson, Christie Murray, Clark Russell and
Herman Merivale have just begun ? I think the fiction, and, indeed,
all the imaginary work of the future will be far fuller in human in-
terest than in the past ; the old stories — no doubt they will still be
the old stories — will be fitted to actors who up to recently were only
used for the purposes of contrast ; the drama of life which formerly
was assigned to kings and princes will be played by figures taken as
much from the great struggling, unknown masses. Kings and great
lords are chiefly picturesque and interesting on account of their
beautiful costumes, and a traditional belief in their power. Costume
is certainly not a strong point in the lower ranks, but I thiulc we
shall not miss that, and wherever we go for our material, whether to
the higher or the lower ranks, we may be sure of finding everywhere

1884.] on the Art of Fiction. 83

love, sacrifice, and devotion for virtues, with selfishness, cunning, and
treachery for vices. Out of these, with their endless combinations
and changes, that novelist must be poor indeed who cannot make a
story.

Lastly, I said at the outset that I would ask you to accord to
novelists the recognition of their place as artists. But after what has
been said, I feel that to urge this further would be only a repetition
of what has gone before. Therefore, though not all who write novels
can reach the first, or even the second, rank, wherever you
find good and faithful work, with truth, sympathy, and clearness of
purpose, I pray you to give the author of that work the praise as
to an Artist — an Artist like the rest — the praise that you so readily
accord to the earnest student of any other Art. As for the great
Masters of the Art — Fielding, Scott, Dickens, Thackeray, Victor
Hugo — I, for one, feel irritated when the critics begin to appraise,
compare, and to estimate them : there is nothing, I think, that we can
give them but admiration that is unspeakable, and gratitude that is
silent. This silence proves more eloquently than any words how
great, how beautiful an Art is that of Fiction.

[W. B.]

o 2

84

Annual Meeting.

[May 1,

ANNUAL MEETING.

Thursday, May 1, 1884.

George Busk, Esq. F.R.S. Treasurer and Vice-President,
in the Chair.

The Annual Report of the Committee of Visitors for the year
1883, testifying to the continued prosperity and efficient management
of the Institution, was read and adopted. The Real and Funded
Property now amounts to above 85,400Z., entirely derived from the
Contributions and Donations of the Members.

Thirty-seven new Members paid their Admission Fees in 1883.

Sixty-three Lectures and Nineteen Evening Discourses were
delivered in 1883.

The Books and Pamphlets presented in 1883 amounted to about
236 volumes, making, with 558 volumes (including Periodicals bound)
purchased by the Managers, a total of 794 volumes added to the
Library in the year.

Thanks were voted to the President, Treasurer, and the Honorary
Secretary, to the Committees of Managers and Visitors, and to the
Professors, for their valuable services to the Institution during the
past year.

The following Gentlemen were unanimously elected as Officers
for the ensuing year :

President — The Duke of Northumberland, D.C.L. LL.D.

Treasitrer — George Busk, Esq. F.R.S.

Secretary — Sir William Bowman, Bart. LL.D. F.R.S.

Managers.

George Berkley, Esq. M.I C.E.

Sir Frederick J. Bramwell, F.R.S.

Joseph Brown, Esq. Q.C.

Warren De La Rue, Esq. M.A. D.C.L. F.R.S.

Captain Douglas Galton, C.B. D.C.L. F.R.S.

Colonel James Augustus Grant,C.B.C.S.L F.R.S.

The Hon. Sir Wm. Robt. Grove, M.A. D.C.I.

LL.D. F.R.S.
Right Hon. The Lord Claud Hamilton, J.P.
Sir John Hawkshaw, F.R.S. F.G.S.
Sir John Lubbock, Bart. M.P. D.C.L. LL.D.

F.R.S.
Hugo W. Miiller, Esq. Ph.D. F.R.S.
Sir Frederick Pollock, Bart. M.A.
John Rae, M.D. LL.D. F.R.S.
The Earl of Rosse, D.C.L. LL.D. F.R.S.
The Hon. Rollo Russell, M.A. F.M.S.

Visitors.

John Birkett, Esq. F.L.S. F.R.C.S.

Charles James Busk, Esq.

Stephen Busk, Esq.

George Frederick Chambers, Esq. F.R.A.S.

William Crookes, Esq. F.R.S.

Rear-Admiral Herbert P. De Kantzow,

R.N.
William Henry DomA'ille, Esq.
Alexander John Ellis, Esq. B.A. F.S.A.

F.R.S.
Rev. John Macnaught, M.A.
Robt. Jas. Mann, M.D. F.R.C.S. F.R.A.S.
Sir Thomas Pycroft, M.A. K.C.S.L
Lachlan Mackintosh Rate, Esq. M.A,
John Bell Sedgwick, Esq. F.R.G.S.
Basil Woodd Smith, Esq. F.R.A.S.
Charles Meymott Tidy, Esq. M.B F.C.S.

1884.] Professor J. W. Jiidd on KraJcatoa, 85

WEEKLY EVENING MEETING,

Friday, May 2, 1884.

The Duke of Nobthumbebland, D.C.L. LL.D. President,
in the Chair.

PfiOFESSOK J. W. JuDD, F.R.S. Scc, G.S.

Krakatoa.

The great subterranean convulsions which during the last few-
years have visited Croatia, Ischia, and Asia Minor, culminated in
the autumn of 1883 in the grand volcanic outburst of Krakatoa, the
most terrible and destructive event of its kind which has occurred
within the memory of the present generation. It is not, however, true,
as has been asserted, that this manifestation of volcanic energy was
of altogether unparalleled magnitude or of unprecedented character ;
for within the last 120 years at least two paroxysmal volcanic out-
bursts on an equally grand scale have occurred in the same district —
those namely of Papandayang in 1772, and of Tomboro in 1815.

Situated as it is in the middle of the Sunda Strait, one of the great
highways of commerce, Krakatoa has been the subject of more exact
observation — before, during, and since the eruption — than was possible
in the case of any other volcano in equally violent activity. In spite
of this, however, the first accounts brought to Europe concerning the
great outburst were singularly inaccurate, and we are only now
beginning to glean from the vast mass of conflicting reports the true
story of the terrible event. Certain it was, however, that on the 26th
and 27th of August, 1883, the shores of Java and Sumatra were swept
by a great sea-wave which desolated considerable tracts of country and
destroyed the lives of more than 35,000 human beings, and that this
sea-wave was one of the most striking accompaniments of a paroxysmal
outburst of Krakatoa.

The volcano of Krakatoa lies at the intersection of two great
fissures — indicated by numerous volcanic vents — in that part of
the earth's crust where we have the most abundant indication of
subterranean energy. The group of four small islands in the midst
of the Sunda Strait was evidently the " basal-wreck " of a grand
volcanic cone, which had been destroyed by a paroxysmal outburst in
prehistoric times. It is not improbable that the subsidence accom-
panying this great outburst gave rise to the depression which forms the
strait now separating Java and Sumatra. About 200 years ago the
volcano is known to have been in eruption for a period of eighteen
months, but since that time it has remained perfectly dormant.

During the last few years numerous earthquakes have indicated

86 Professor J. W. Judd [May 2,

that the district of which Krakatoa is the centre was likely to again
become the scene of volcanic disturbance, and on the 20th of May, 1883,
Krakatoa again burst into activity. This eruption, wHch was of
moderate violence, continued for about three months, resulting in the
formation of two cinder-cones of considerable size, and the scattering
of large quantities of pumice over the surface of the ocean. The
materials of Krakatoa and the neighbouring volcanoes are almost
entirely pumiceous in character, being formed through Ihe distension
by gases of a hypersthene-augite-andesite with an exceptionally large
proportion of a highly vitreous base.

On the afternoon of August 26th, the volcano passed from the stage
of continued moderate activity, to a paroxysm of great violence.
During this paroxysm, the whole district for 100 miles around the
volcano was enveloped in intense darkness, produced by the enormous
clouds of volcanic dust thrown into the atmosphere, some of which fell
at distances of over 1000 miles from Krakatoa. Our knowledge of what
took place during this terrible outbreak is derived from the reports of
the few survivors in the towns on the shores of the strait, from the
logs of various ships, three of which were actually within the strait at
the time of the eruption, from the indication afforded by self-recording
instruments at Batavia and more distant localities, and by a comparison
of the condition of tbe volcano before and after the eruption.

It appears that during the height of the eruption the detonations of
the volcano increased in number and violence till they blended in a
continuous roar, and that enormous quantities of steam with pumice and
dust were flung to very great heights in the atmosphere. The result
of this action was the blowing away, not only the two cones recently
formed, but of the greater part of the old volcano, leaving a vast
crateral hollow more than 1000 feet in depth. As to the earthquake
shocks accompanying this paroxysm, the accounts are very con-
flicting. There was unfortunately no seismograph at Batavia, but the
magnetograph-records seem to indicate that considerable seismic dis-
turbance took place during the whole time of the eruption. The
precisely similar instrument at Kew Observatory recorded in the same
w^ay the small earthquake of April 22nd, 1884.

No doubt exists, however, as to the nature and magnitude of the
sea-waves produced by these great concussions. During the whole
time of the eruption, the ocean was thrown into a state of violent oscil-
lations, the oscillations increasing in height as the eruptive action
became more intense. In the narrow and shallow eastern throat of
the Sunda Strait, and in the deep gulfs of Lampong, Semangka, and
Welcome Bay, these vibratory movements of the water were converted
into waves of translation of great height and destructiveness. West-
ward, however, they were propagated across the Indian Ocean, like
the ordinary oceanic tidal wave, at rates varying from 350 to 500
miles per hour, recording themselves on the tide-gauges all over the
world. At Mauritius and Port Elizabeth, at Aden and the principal
Indian ports, and even as far away as Australia, New Zealand, San

1884.] on KraJcatoa. 87

Francisco and Alaska, these disturbancies of the ocean were felt and
recorded.

Still more striking were the vibrations propagated through the
more mobile material of the atmosphere. The effects produced on
the atmosphere in the vicinity of Krakatoa by the violently up-rushing
columns of vapour, and by its condensation, were indicated by frequent
and sudden changes in the height of the barometric column, and by a
terrible storm, of a strictly local character, which raged during the
whole time of the eruption. The investigations of Mr. Scott and
General Strachey have demonstrated that these disturbances were pro-
pagated in a series of waves, which, travelling at the rate of 700 miles
per hour, passed three-and-a-half times round the globe, recording
themselves on the barographs of meteorological stations all over the
world.

The vibrations producing sound, whether carried by the land, the
ocean, or the air, made themselves felt over a circle with a radius of
2000 miles.

The electrical disturbances, resulting in vivid lightning " fire-
balls," corposants, and a phosphorescent condition of the ejected
materials, were of the most startling character.

The careful surveys undertaken since the eruption by the officers
of the Dutch Government, have shown that the whole of the island of
Krakatoa, except the high ridge on its southern side, was blown away
during the eruption, but that two adjoining smaller islands were
increased in size. To the north and north-east of Krakatoa, at a
distance of 7 miles from the centre of activity, two new islands
were formed where the sea had before a depth of about 20 fathoms.
As these new islands are entirely composed of loose fragmentary
materials, it has been thought that they were formed by the accumu-
lation of the ejecta from the central vent. There are strong grounds
however for the belief that lateral eruptions causing submarine
volcanoes accompanied the outburst from the central crater of
Krakatoa. The quantity of pumice thrown out during the eruption
was so great as to impede the navigation of the strait, and to cover
the ocean for thousands of square miles.

Comparing the outburst of Krakatoa with that of Tomboro in 1815
we find that the quantity of material ejected in the latter was
according to Verbeek, from eight to eleven times as great as in that
of the former, while the area of darkness produced by the dust was
no less than nine times as great. On the other hand, it must be
remembered that the duration of the Tomboro eruption was more
than thirty days, while that of the Krakatoa was less than that
number of hours. Hence we are led to conclude that the Krakatoa
eruption, though of short duration, was of exceptional violence a
conclusion borne out by the fact that it was heard at distances twice
as great as the outburst of Tomboro.

Of the interesting atmospheric effects, and especially the beautiful
sunsets, following the Krakatoa eruption, which have with a great

88 Professor J. W. Judd on Krdkatoa. [May 2,

show of probability been thought to have resulted from it, it is the
province of the physicist and meteorologist, rather than of the
geologist, to speak. Without attempting to discuss any of the diffe-
rent explanations that have been offered to account for these strikingly
beautiful phenomena, it is only just to remark that the basis of all
such explanations will probably be found in the experiments carried
on by Faraday at the Eoyal Institution, which demonstrated the
excessive divisibility of matter and the effect of finely divided
particles on light, with others, subsequently made by Professor
Tyndall, which suggested the application of these principles to the
explanation of the colours of the atmosphere.

[J. W. J.]

GENERAL MONTHLY MEETING,

Monday, May 5, 1884,

Warren De La Eue, Esq. M.A. D.C.L. F.R.S. Manager,
in the Chair.

Rookes Evelyn Crompton, Esq.
Ernest George Mocatta, Esq.
Ernest Robert Moon, Esq.
John Lawrence Tatham, Esq.

were elected Members of the Royal Institution.

John Tyndall, Esq. D.C.L. LL.D. F.R.S. was re-elected Professor
of Natural Philosophy.

The Presents received since the last Meeting were laid on the
table, and the thanks of the Members returned for the same, viz. : —

FROM

The Governor- General of India — Memoirs, Vol. XX. Parts 1 and 2. 8vo. 1883.
T//e Secretary of State for India — Report on Public Instruction in Bengal, 1882-3.

fol. 1883.
The Trustees of the British Museum — Catalogue of Birds, Vol. IX. 8vo. 1884.
Academy of Natural Sciences, Philadelphia — Proceedings, 1883, Part 3. 8vo.

1883.
Accademia dei Lincei^ Beale, Roma — Atti, Serie Terza; Transunti. Vol. VIII.

Fuse. 7-10. 4to. 1884.
Agricultural Society of England, Royal — Journal, Second Series, Vol. XX. Part 1.

8vo. 1884.
Asiatic Society, Royal— Journal, Vol. XVI. Part 2. 8vo. 1884.
Banlters, Institute o/— Journal, Vol. V. Part 4. 8vo. 1884.

1884.] -"^ General Monthly Meeting. 89

Birmingham Philosophical Society — Proceedings, Vol. III. Parts 1 and 2. 8vo.

1881-3.
British Architects, Royal Institute of — Proceedings, 1883-4, No. 11. 4to.
Browne, Lennox, Esq. (the Author) — Science and Singing. 8vo. 1884.
Burt, Major Thomas Seymour, F.R.S. (the Tramlator) — The .^neid, Georgics,
and Eclogues of Virgil. In English Blank Verse, with Latin Text. 3 vols.
8vo. 1883.
Chemical Society— 3 onxnol for April 1884. 8vo.
Civil Engineers' Institution — Minutes of Proceedings, Vol. LXXV. 8vo. 1884.

Applications of Electricity, 1882-3. 8vo. 1884.
Crisp, Frank, Esq. LL.B. F.L.S. <Scc. M.R.I, {the Editor)— 3 onruoX of the Royal

Microscopical Society, Series II. Vol. IV. Part 2. 8vo. 1884.
Dax: Societe de Borda — Bulletins, 2'' Serie Neuvieme Anne'e: Trimestre 1. 8vo.

1884.
East India Association — Journal, Vol. XVI. No. 2. 8vo- 1884.
Editors — American Journal of Science for April 1884. 8vo.
Analyst for April 1884. 8vo.
AthensBum for April 1884. 4to.
Chemical News for April 1884. 4to.
Engineer for April 1884. fol.
Horological Journal for April 1884. 8vo.
Iron for April 1884. 4to.
Nature for April 1884. 4to.

Revue Scientifique and Revue Politique et Litt^raire for April 1884. 4to.
Science Monthly, Illustrated, for April 1884. 8vo.
Telegraphic Journal for April 1884. 8vo.
Franklin Institute — Journal, No. 700. 8vo. 1884.
Geological Institute, Imperial, Vienna — Jahrbuch, Band XXXIII. No. 4. 8vo,

1883.
Grey, Henry ^ Esq. (the Author) — A Bird's Eye View of English Literature. 12mo.

1884.
Hanks, Henry G. Esq. (State Mineralogist) — California State Mining Bureau,

Annual Report. 8vo. 1883.
Hungarian Academy of Sciences — Mathematische und Naturwissenschaftliche

Berichte aus Ungarn. Band I. Svo. 1883.
Inwards, Richard, Esq. F.R.A.S. (the Author)— The Temple of the Andes. 4to.

1884.
Iron atid Steel Institute — Journal, 1883, No. 2. Svo.
Johns Hopkins University — University Circulars, No. 29. 4to. 1884.
Marks, W. Dennis, Esq. (the Author) — The Law of Condensation of Steam in

Cylinders. (Jour, of Franklin Inst. 1884.) 8vo.
Medical and Chirurgical Society — Proceedings, New Series, No. 5. Svo. 1884.
Meteorological Society, Royal — Quarterly Journal, No. 49. Svo. 1884.

Meteorological Record, No. 11. Svo. 1883.
National Association for Social Science — Transactions, Huddersfield, 1883. Svo.
1884.
Proceedings, Vol. XVII. No. 1. Svo. 1884.
Pharmaceutical Society of Great Britain — Journal, April 1884. Svo.
Photographic Society — Journal, New Series, Vol. VIII. No. 6. Svo. 1S84.
Richardson, B. W. M.D. F.R.S. (the Author)— The Asclepiad. Vol. I. No. 2.

Svo. 1884.
Rio de Janeiro, Observatoire Imperiale — Bulletin, Nos. 3, 11. fol. 1881-3.
Society of Arts — Journal, April 1884. Svo.
Statistical Society— Soux^dl, Vol. XLVII. Part 1. Svo. 1884.
Telegraph Engineers, Society of — Journal, Vol. XIII. No. 51. Svo. 1884.
University of London — Calendar, 1884-5. Svo.
Vereins zur Beforderung des Gewerhfleisses in Preussen — Verhandlungen, 1884:

Heft 3. 4to.
Victoria Institute — Journal, No. 68. Svo. 1884.

90 General Montldij Mcetlwj. L-^^^J ^5

Westropp, Hodder M. Esq. (the Author)— Hie Age of Homer. 8vo. 1884.
Williams, Charles J. B. M.D. F.K.S. (the Author) -demons of Life and Work.

8vo. 1884.
Williamson, B. Esq. 31. A. F.R.S. (the Author) — Elementary Treatise on tiie

Integral Calculus. 4th ed. 8vo. 1884.
Zoological ^oce'e/;/— Proceedings, 1883, Part 4. 8vo.
Catalogue of the Library, Supplement. 8vo. 1883.

WEEKLY EVENING MEETING,

Friday, May 9, 1884.

The Duke op Northumbeuland, D.C.L. LL.D. President,
in the Chair.

Professor W. Robertson Smith, M.A. LL.D.

Mohammedan MaJidis.

(Abstract deferred.)

WEEKLY EVENING MEETING,

Friday, May 16, 1884.

Sir Fredeuick Bramwell, F.E.S. Manager and Vice-President,
in the Chair.

Professor W. Ocling, M.A. F.R.S. M.B.L

The Dissolved Oxygen of Water.

(Abstract deferred.)

1884.] Mr. David GUI on the Distances of the Fixed Stars. 91

WEEKLY EVENING MEETING,

Friday, May 23, 1884.

The Earl of Rosse, D.C.L. LL.D. F.R.S. Manager aud Vice-
President, in the Chair.

David Gill, Esq. LL.D. F.R.S.

Her Majesty's Astronomer at the Cape of Good Hope.

Recent Besearclies on the Distances of the Fixed Stars, and some Future
Problems in Sidereal Astronomy.

There has ever been a desire to burst aside the constraints im-
posed upon our research by the distances of space ; to pass from the
study of the planets of our solar system to that of the suns and
galaxies that surround us ; to determine the position and relative
importance of our own system in the scheme of the universe, and the
whence we have come and the whither we are drifting through the
realms of space.

The galaxy or Milky Way — what is it? Is our sun one of
its members ? What is the shape of that galaxy ? What are its
dimensions ? What is the position of our sun in it ?

The star-clusters — what are they ? Are these clusters galaxies ?
Have these suns real dimensions comparable with those of our sun,
and is it distance alone that renders their light and dimension so
insignificant to the naked eye ? Or are the real dimensions of the
clusters small as compared with our galaxy ? Are their component
suns but the fragments of some great sun that has been shattered by
forces unknown to us, or have they originated from chaotic matter,
which, instead of forming one great whirlpool and condensing by
vortex action into one great sun, has been thrown into numerous
minor vortices, and so become rolled up into numerous small suns ?

The nebulaB — what are they ? Are they, too, condensing into
clusters or stars, or will their ghost-like forms remain for ever
unchanged amongst the stars? or do they play some part in the
scheme of nature of which we have as yet no conception ?

These and many others are the questions which press on the
ardent mind that contemplates the subject ; and there arises the
intense desire to answer such questions, and, where facts are wanting,
to supply facts by fancy. The history of deep and profound thought
in some of these subjects goes back through 2000 years, but the
history of real progress is but as of yesterday. The foundation of
sidereal astronomy may be said to have begun with the art of accurate
observation. Bradley's meridian observations at Greenwich about
1750, his previous discovery of the aberration of light in 1727, and
Herschel's discovery of the binary nature of double stars, his surveys
of the heavens, and bis catalogues of double stars — these are solid

92 Mr. David Gill [May 23,

facts, facts that have contributed more to the advancement of sidereal
astronomy than all the speculations of preceding centuries. They
point to us the lesson that " art is long and life is short," that human
knowledge, in the slow developing phenomena of sidereal astronomy,
must be content to progress by the accumulating labours of successive
generations of men, that progress will be measured for generations
yet to come more by the amount of honest, well-directed and systema-
tically-discussed observation than by the most brilliant speculation,
and that in observation concentrated systematic effort on a special
thoughtfully-selected problem will be of more avail than the most
brilliant but disconnected work.

I hope that no one present thinks from what I have said that I
undervalue the imaginative fervid mind that longs for the truth, and
whose fancy delights to speculate on these great subjects. On the
contrary, I think and I believe that without that fervid mind, with-
out that longing for the truth, no man is fitted for the work required
of him in such a field — for it is such a mind and such desires that
alone can sweeten the long watches of the night, and transform such
work from drudgery into a noble labour of love.

It is for like reasons that I ask you to leave with me the
captivating realms of fancy this evening, and to enter the more
substantial realms of fact.

We suppose ourselves, then, face to face with all the problems of
sidereal astronomy to which I have hastily referred — the human mind
is lost in speculation, and we are anxious to establish a solid
groundwork of fact.

Now what in such circumstances would be the instinct of the
scientific mind ?

The answer is unquestionable — viz. to measure — and no sooner
were astronomical instruments made of reasonable exactness than
astronomers did begin to measure, and to ask, are the distances of the
fixed stars measurable ?

I should like to have given a short history of the early attempts
of astronomers to measure the distance of a fixed star. But I must
come at once to the time when the long baffled labours of astronomers
began to be crowned with success.

Before I begin, it will save both time and circumlocution if I
define a word that we must frequently use — viz. the word " parallax."
It may be defined as the change in the apparent place of a star
produced by viewing it from a point other than that of reference.
[The lecturer here gave some practical illustrations of parallax.]
Our point of reference for stars is the sun, and as we view the stars
now from one side of the sun, and six mouths afterwards from a point
on the opposite side of the sun — that is, from two points 186 millions
of miles apart — we might expect to find a considerable change in
their apparent places.

But previous to 1832 astronomers could not discover with any
certainty that such changes were sensible — or, putting it another way,
the stars were so distant that the diameter of the earth's orbit viewed

1884.] <m the Distances of the Fixed Stars. 93

from the nearest star subtended a smaller angle than their instru-
ments could measure. Bradley felt sure that if the star y Draconis
were so near that its parallax amounted to 1" of arc he would have
detected it — that is, if the earth's orbit viewed from y Draconis
measured 2" in diameter (or as big as a globe 1 foot in diameter
would look if viewed at 40 miles distant) he would have detected it.
But the real distances of the stars were greater than that.

The time at last arrived when the two great masters of modem
practical astronomy, Bessel and Struve, were preparing by elaborate
experiment and study for the researches which led to ultimate
success. After vain attempts to obtain conclusive results by endea-
vours to determine the apparent changes in the absolute direction
of a star at different seasons of the year, both astronomers had
recourse to a method which, originally proposed by Galileo in 1632,
was carried out first on a large scale by Sir William Herschel. I
shall refer in the first place to the researches of the great Kussian
astronomer Struve.

Astronomers had sufficiently demonstrated that the distances of
the stars were very great, and it was reasonable to argue that as a
rule the brighter stars would be those nearest to us. If, therefore,
two stars are apparently near each other — the one bright, the other
faint — the chances are that in reality they are far apart, though
accidentally nearly in a line.

If two such stars are represented by S s in Diagram I., they would

Diagram I.

appear near each other viewed from one side of the earth's orbit at A,
but not so near each other viewed from B — the opposite side of the
earth's orbit, the red lines obviously indicating the apparent angle
between the stars when they are viewed from A, and the black lines
the apparent angle when they are viewed from B. Struve selected
for the star S the bright star Vega (a Lyrae). From its brilliancy he
considered it probably one of our nearest neighbours amongst the
stars, and a faint star apparently near it seemed to afford a suitable
representative of the really distant star s. Struve was careful to
ascertain that this comparison star was not physically connected with
a Lyrte, and he was able to prove this from the fact that whilst
a Lyrae has a small annual motion relative to all neighbouring stars,
this motion is not shared by the faint comparison star. Struve was

94 Mr. David Gill [May 23,

provided with a telescope driven by clockwork to follow the diurnal
motion of a star, and thus the hands of the observer were free to make
the necessary measures. These were accomplished by an instrument,
such as I hold in my hands, applied to the telescope. This micro-
meter contains two parallel spider-webs each attached to a slide, one
slide being moved by one screw, the other by the other screw. The
screws are provided with drum-heads divided into 100 parts. One
web was placed on the image of a Lyrae, the other upon that of the
faint comparison star, and the angle between the stars was thus read
off in terms of the number of revolutions and decimals of a revolution
of the screws. A number of such observations was made on each
night, and the result for each night depended on the mean of the
numerous observations made each night.

By observations on ninety-six nights between November 1835 and
August 1838, he showed that the distance between a Lyrae and the
faint comparison star changed systematically with a regular annual
period, and that the maxima and minima of those distances corre-
sponded with the times of the year at which these maxima and
minima should occur if the brighter star were really much nearer
than the fainter one.

Assuming that the fainter star is at a practically immeasurable
distance, Struve showed that a Lyrae had a parallax that amounted to
about a quarter of a second of arc, which is equivalent to the state-
ment that a globe whose diameter is equal to that of the earth's orbit
— that is, to 186 millions of miles — would at the distance of a Lyrae
present an apparent diameter of half a second of arc. If you wish to
realise this angle, place a globe 1 foot in diameter at a distance of
80 miles, or look at a coin half the diameter of a silver threepenny-
piece at a distance of 1 mile from the eye, and try to measure it.

The great German astronomer, Bessel, was simultaneously
en^^aged in like work at Konigsberg. He selected as the object of his
researches a very remarkable double star — 61 Cygni.

This star had already been the subject of similar researches on
his part with much inferior means. He now attacked the problem
with the splendid heliometer which had been made for him by
Frauenhofer for the purpose. The principle of this instrument I
shall presently explain. His reasons for choosing 61 Cygni were
that the two components of this star, though not remarkable for
brightness — they are just visible to the naked eye — yet have this
peculiarity, that they have a remarkably large proper motion, the
largest then known, though now known to be surpassed by that of
two other stars which I shall afterwards mention. The components
of 61 Cygni have an apparent angular motion relative to other stars
of more than five seconds of arc per annum.

Struve had argued that if the stars were on the average of similar
brightness, those stars which were brightest would probably be those
nearest to us, and Bessel, in like manner, argued that if the absolute
motions of the stars were similar on the average, those motions which
appeared the largest belonged to stars which on the average were

188i.] on the Distances of the Fixed Stars. 95

nearest to us — ^just as the motion of a snail could be easily watched
at the distance of two or three feet from the eye, but could not be
detected except after a long interval if the animal were a good many
yards distant.

Bessel employed two faint comparison stars at right angles to
each other with respect to 61 Cygni, and he made two separate series
of observations, the first extending from August 1837 to October 1838,
the second from October 1838 to March 1840.

Both series confirm each other, and the results deduced separately
from the measures of the two comparison stars also agree within very
narrow limits. From all the observations combined Bessel found the
parallax of 61 Cygni to be 35/100 of a second — a quantity which has
been shown by the modern researches of Prof. Auwers and Dr. Ball
to be more nearly half a second of arc. Thus at 61 Cygni the
diameter of the earth's orbit round the sun would appear of the same
size as a globe a foot in diameter viewed at 40 miles distance, or of a
silver threepenny-piece a mile ofi". But whilst these great masters of
astronomy — Struve and Bessel — had been exhausting the resources of
their skill in observation, and that of the astronomical workshops of
Europe in supplying them with the most refined instruments, a quiet
and earnest man had been at work at the Cape of Good Hope, and,
without knowing it at the time, had really made the first observations
which afforded strong presumptive evidence of the existence of the
parallax of any fixed star.

Henderson occupied the post of Her Majesty's Astronomer at
the Cape of Good Hope in 1882 and 1833, and during his brief and
brilliant tenure of ofiice there, he made, amongst many others, a fine
series of meridian observations of a Centauri — a bright and other-
wise remarkable double star. When, after his return to England,
Henderson reduced these observations, and compared them with the
earlier observations of other astronomers, he found that a Centauri
had a large proper motion ; he was therefore led to examine and see
whether his observations gave any indication of an annual parallax.
He found that they did so, and not of a small parallax but of one
amounting to nearly a second of arc. But it was not till this was
confirmed, not only by the observations with the mural circle but by
those of the transit instrument also, not only by his own observations
but by those of Lieut. Meadows, his assistant, that Henderson ventured
to publish his remarkable result.

In the year 1842 it was felt by the astronomical world at large
that the problem which hitherto had baffled astronomers had begun to
yield, that some approximation to the truth had at last been arrived
at with regard to the distance of a fixed star, and it was fit and proper
that the Koyal Astronomical Society of London should acknowledge
the labours of him who had most effectually contributed to this end.

Henderson's results seemed sufficiently convincing, but they de-
pended upon determinations of the absolute place of a Centauri.
The experiences of the skilful astronomer Brinkley at Dublin were
still fresh in the minds of astronomers. He had arrived by similar,

96

Mr. David Gill

[May 23,

though less perfect, means at results like those of Henderson ; but
his results had been proved to be fallacious, though the causes of
their being so still remain somewhat inexplicable. In the case of
Struve's observations the weight of evidence which he produced and
the excellence of his method were admitted, but men were not pre-
pared by experience for accepting as accurate the minute changes of
angle which Struve had to measure ; nor was the proof afforded by
his series of observations so entirely convincing as that afforded by the
series of Bessel. Therefore, to Bessel the well-earned medal was given,
but the labours of Struve and Henderson received high and honour-
able mention. I quote from the speech of Sir John Herschel in award-
ing that medal. He says of Henderson's researches on a Centauri : —

" Should a different eye, and a different circle continue to give the
same result, we must of course acquiesce in the conclusion ; and the
distinct and entire merit of the first discovery of the parallax of a
fixed star will rest indisputably with Mr. Henderson. At present,
however, we should not be justified in anticipating a decision which
time alone can stamp with the seal of absolute authority."

So much for Sir John Herschel's ofiicially expressed opinion. I
can state now, and as Henderson's successor I do so with pride and
pleasure, that a different eye (that of his able and sympathetic
successor, Sir Thomas Maclear) fully confirmed Henderson's result
with another circle ; and further, that Henderson's result has been
still further confirmed by additional researches of which I shall
presently speak.

I must now pass over briefly the history of succeeding researches,
and indeed it has been so admirably and so recently told within
these walls by Dr. Ball, that it is quite unnecessary I should enter
upon it in detail. The most reliable values arrived at for the
parallaxes of the stars of the northern hemisphere are given in the
following table, and to these results I shall afterwards refer : —

Table I. — Parallaxes of Stabs which have been determined in the
Northern Heavens with considerable Accuracy.

61 Cygni .. ..
Lalande 21185..
a Tauri

34 Groombridge
Lalande 21258..
O. Mg. 17415 ..
<r Draconis
a Lyrso
jp Ophiuehi
o Bootis ..
Grooiiibrid^e 1830
Bradley 3077 ..
85 Pfxasi . . . .

Magnitude. Proper Motion. ParaUax

6

n
I

8

8^

9

5|

1

1
7
G
G

514

0-.50

4-75

0-50

0-19

0-52

2-81

0-29

4-40

0-26

1-27

0-25

1-87

0 25

0-31

0-20

10

0-17

2-43

0-13?

7-05

0-09

209

007

1-38

005

1884.] on the Distances of the Fixed Stars. 97

The recent researches referred to in the title of this evening's
lecture are some investigations which, in conjunction with a young
American friend, Dr. Elkin, who was my guest for two years, I have
recently carried out at the Cape of Good Hope.

The instrument employed was a heliometer — my own property —
the good qualities of which I had previously tested at Mauritius in
1874, and at the Island of Ascension in 1877.

[The lecturer. here described the heliometer, and illustrated the
method of its use.]

I have said that the angle between the stars is measured in
terms of the scale of the heliometer, but the scale-value, in
seconds of arc, may change by the effects of temperature and from
other causes.

Bessel in his researches on the parallax of 61 Cygni, determined by
independent means the effect of temperature on his scale-value, and
applied corresponding corrections to his observations. But he also
took the precaution to employ two stars of comparison situated at
right angles to each other with respect to the principal star, so that
the effect of parallax would be at a maximum for one comparison star
at the season of the year when it was at zero for the other, and vice
versa.

But in the course of previous researches I found that there were
sources of error other than mere change of the temperature of the air,
viz. differences of temperature in different parts of the instrument,
and changes in the normal focus of the observer's eye, which exercised
a very sensible influence on the results. It was necessary to devise
some method by which these should also be eliminated.

There is a very simple means of doing this. Instead of taking
two comparison stars at right angles, take two comparison stars
situated nearly symmetrically on opposite sides of the star whose
parallax is to be determined — such, for example, as the stars a and
p in Diagram II. Now observe these distances in the order a, (3,
/?, a, on each night of observation ; so that on each night the observa-
tions at both distances are practically made at the same instant.
Then, whatever causes have combined to create a systematic error in
the measurement of one of- these distances, precisely the same causes
must create precisely similar systematic error in the measurement of
the other distance. Thus if, by the regular or irregular effects of
temperature or by changes in the normal condition of the observer's
eye, we measure the distance a too great, so for the simultaneous
observations of the distance /3 we shall, from precisely the same
causes, measure that distance too great also.

But the difference of the distances will be entirely free from all
errors of the kind ; and if the distances are not quite equal, it is very
easy to apply a correction on the assumption that the sum of the
distances is a constant.

In Diagram II. the circle represents a radius of 2° surrounding
the star a Centauri. The distance of the component stars a^ and ag
Centauri in the diagram is enormously exaggerated for the sake of

YoL. XI. (No. 78.) H

98 ^ Mr. David GUI [May 23,

clearness. Guided by the principles jnst explained, search was made
for comparison stars in pairs symmetrically situated with respect to
a Centauri, and otherwise favourably situated for measurement of
parallax.

Diagram II.

-%

Showing comparison stars employed in determining the parallax of a Centauri.

You will remember that from the effects of parallax all stars
appear to describe small ellipses about a mean position ; stars near
the pole of the ecliptic describing nearly circles, and those near the
ecliptic very elongated ellipses. Obviously, then, those pairs of stars
are most favourable — other conditions being equal — which lie near
the major axis of the parallactic ellipse. The dotted ellipse in
Diagram II. represents the form of the parallactic ellipse ; that is to
say, the form of the apparent path which a Centauri must describe if
it is affected by parallax. Of course the size of the ellipse is exagge-
rated— in fact in the diagram nearly 5000 times — therefore, remember
that the diagram represents only that which we can compute before
we have observed, viz. the shape of the ellipse, or the relations of the
lengths of the two axes ; the absolute size has to be determined
from the observations.

The most favourable couple of comparison stars in our drawing is
that marked a and (3 — they are nearest to the major axis of the
parallactic ellipse, and they are very symmetrically situated with
respect to a Centauri.

Now turn to Diagram III. Here is exhibited the results of my

measures on a very large scale — in a manner similar to that in which

the height of the barometer for different hours of the day, or the com-

V. parative price of wheat at different seasons of the year or in different

1884.1

on the Distances of the Fixed Stars.

99

H 2

100 Mr. David Gill [May 23,

years, is now exhibited in the daily papers. Imagine the star a about
a mile immediately below any point of that curve, and the star /3
rather over three-quarters of a mile immediately above the same point,
and you would then have a diagram to scale.* The middle horizontal
line represents the mean difference of these two distances, and each
dot or mark on Fig. 1 of the diagram represents the variation of that
distance according to each successive observation. The different
kinds of dot represent measures made at different hour angles, or
when the relation of the direction of measurement to the line joining
the observer's eye is different. These different kinds of personal
errors were separately investigated, and they were then allo^ved for
and the observations were corrected accordingly.

The observations so corrected are represented in Fig. 2, where
each black dot expresses the result of the observations of a single
night, and the curve is the commuted curve resulting from the
mathematical discussion of the observations.

You must be careful to understand that this is not simply the kind
of curve which best represents the observations. The curve is limited
by purely geometrical conditions to have its maximum on March 7, and
its minimum on September 10, and to follow a precise form of curve
according to a simple law. The observations only determine the
range from maximum to minimum, and yet you see how perfectly the
maximum of the observations agrees with the maximum of the curve,
and the minimum of the observations with the minimum of the curve,
and how closely the law is followed throughout.

The result was that from these observations the parallax of a
Centauri was 0" • 747, or practically three-quarters of a second of arc.

But I was not content with this result alone. I wished further
confirmation, and selected another pair of stars, a and /3', shown in
Diagram II.

From similar observations with these comparison stars I obtained
for the parallax of a Centauri 0" • 760, a result which is identical
with the last within the limits of the probable error of either.

My friend Dr. Elkin selected the stars a h and a b' as his com-
parison stars, and in a precisely similar way he obtained as the mean
of his results a parallax of 0"*762, a result identical with my own, so
that we may conclude as one of the most certainly established facts
of astronomy that the parallax of a Centauri relative to an average
star of the seventh or eighth magnitude is three-quarters of a second
of arc.

It is therefore beyond all doubt that Henderson's discovery was a
real one. Herschel's verdict must therefore bo confirmed, and the
palm for first breaking down the barriers tliat separated us from any
knowledge of the distances of the fixed stars be accorded to the
memory of the Cape Astronomer, Henderson.

In the wall diagram one second of arc wns represented by about fifteen inches.

1884.]

on tlte Distances of the Fixed Stars.

101

So far as all existing researches go, a Centauri is the nearest of
the fixed stnrs. Regarding the faint comparison stars as practically
infinitely distant, let us try to realise how near or how far distant
a Centauri really is.

If we wish to deal with distance so immense, we must alopt a
more convenient unit of measure.

The most convenient unit for our purpose is the number of
years that light would take to reach us. Light takes almost exactly
500 seconds of time to come from the sun; this is a figure easy
to remember, and is probably exact to a single unit. The sun is
93 millions of miles distant, and this figure I believe to be exact
within 200,000 miles.

Quite recently the accuracy of these figures has been confirmed in
a very remarkable way by different kinds of investigations by
different observers ; otherwise I should not have quoted them with so
much confidence.

The parallax of a Centauri is three-quarters of a second of arc ;
therefore its distance is 275,000 times the distance of the earth from
the sun, and therefore light, which travels to the earth from the sun
in 500 seconds (i. e. in 8^ minutes) would take 4*36, or a little more
than 4^- years to come from a Centauri.

You will find in the accompanying table a specific account of the
other results which were arrived at by Dr. Elkin and myself by
precisely similar means, and you will find on the wall diagrams
representing my own detailed observations in the case of Sirius and
c Indi. (See Diagrams IV. and V.;

Table II. — Kesults of Recent Researches on the Parallax of Stars
IN the Southern Hemisphere.

Name of Star.

Observer.

Star's
magnitude.

Annual
proper

motion
in arc.

Parallax.

Star's distance
in light units, or
number of years

in which light
from star would
reach the earth.

Velocity of star's
motion in miles

per second at
right angles to

line of sight.

o Centauri , .

G. &E.

1

3-67

0-75

4-36

14-4

Sirius

G. &E.

1

1-24

0-38

8-6

9-6

Lacaille9352

G.

n

6-95

0-28

11-6

73

t Indi

G. (teE.

5i

4-68

0-22

15

63

02 Eridani . .

G.

H

4-10

0-17

19

69

€ Eridani ..

E.

n

3-03

0 14

23^

64

CTucanse ..

E.

6

2-05

0-06

54

101

Canopus . .

E.

1

0-00

Insensible

—

—

/3 Centauri

G.

1

—

Insensible

Time does not permit me to go into more detail as to each of
these separate results, full of interest though they are, and each of
them representing months of labour.

102 . Mr. David Gill [May 23,

My object now is to generalise, to put out the conclusions that
must be drawn from these two tables of parallax (Tables I. and II.),
and to see what are the broad lessons that they teach us.

A glance is sufficient to show that neither apparent magnitude
nor apparent proper motion can afford a definite criterion of the
distance of any fixed star — that different stars really differ greatly in
absolute brightness and in absolute motion.

And now what is the work before us in the future ?

The great cosmical problem that we have to solve is not so much
what is the parallax of this or that particular star, but we have to
solve the much broader questions —

1. What are the average parallaxes of stars of the first, second,
third, and fourth magnitudes, compared with those of fainter
magnitude ?

2. What connection does there subsist between the parallax of a
star and the amount and direction of its proper motion, or can it be
proved that there is no such relation or connection ?

With any approximate answer to these questions we should pro-
bably be able to determine the law of absorption of star-light in space,
and be provided with the data at present wanting for determining
with more precision the constant of precession and the amount and
direction of the solar motion in space. And who can predict what
hitherto unknown cosmical laws might reveal themselves in the course
of such an investigation ?

It is important to consider whether such a scheme of research is
one that can be realised in the immediate future, or one that can
only be carried to completion by the accumulated labours of succes-
sive astronomers.

I have very carefully considered this question from a practical
point of view, and I have prepared a scheme, founded on the results
of my past experience. I have submitted that scheme for the opinion
of the most competent judges, and in their opinion, as well as my
own, the work can be done, with honest hard work for one hemi-
sphere, within ten years. I have offered to do that work for the
southern hemisphere with my own hands, and a proposal for the
necessary instruments and appliances is now under the consideration
of my Lords Commissioners of the Admiralty. I need hardly add
that in this matter I look confidently for that complete consideration
and that efficient support which I have never failed to receive at their
hands since I have had the honour to serve them.

The like work will be undertaken for the northern hemisphere by
my friend Dr. Elkin, who is now in charge of the heliometer at Yale
College in America. It is at present the finest instrument of the
kind in the world, and a photograph of it you have already seen
upon the screen.

I most earnestly trust that we may be granted health and
strength for this work, and that no unforeseen circumstances will
prevent its complete accomplishment.

1884."

on ilie Distances of the Fixed Star,

103

104 Mr. David Gill [May 23,

Before closing this lecture I wish briefly to allude to another
engine of research in sidereal astronomy which quite recently has
received an enormous development, and whose application appears
to oflfer a rich harvest of results. I refer to the application of
photography to astronomical observation.

Your respected member, Mr. De la Eue, is the father of this
method. Time does not permit me to dwell on his early endeavours
and his successful results, but they are well known to you all. He
opened up the field, and he cleared the way for his successors.

The recent strides in the chemistry of photography and the pro-
duction of dry plates of extreme sensibility, have permitted the
application of the method to objects that formerly could not be
photographed. Here, on the screen, are the spectra of stars photo-
graphed directly from the stars by Dr. Huggins, the lines which tell
of the chemical constitution and temperature of the star's atmosphere
being sharply defined.

Here are photographs of the great comet of 1882, which, with the
co-operation of Mr. Allis of Mowbray, I obtained at the Cape, by
attaching his ordinary camera to an equatorially mounted telescope,
and with its aid following the comet exactly for more than two hours.
Each one of the thousands of points of light that you see is the
picture of a fixed star. The photograph suggests the desirability
of producing star maps by direct photography from the sky.

Here on the screen is a photograph of the great nebula of Orion,
or rather a series of photographs of it, made by Mr. Common of Ealing.
You will note the gradual development of detail by increase of ex-
posure, and the wonderful amount of detail at last arrived at. Here
are photographs from drawings of the same, and you will note the
discrepancies between them. And here is a photograph of a star
cluster, also by Mr. Common.

No hand of man has tampered with these pictures. They have a
value on this account which gives them a distinct and separate claim
to confidence above any work in which the hand of fallible man has
had a part.

The standpoint of science is so different from that of art. A picture
which is a mere copy of nature, in which we do not recognise some-
what of the soul of the artist, is nothing in an artistic point of view ;
but in a scientific point of view the more absolutely that the indivi-
duality of the artist is suppressed, and the more absolutely a rigid
representation of nature is obtained, the better.

Here is a volume compiled by one of the most energetic and able of
American astronomers — Prof. Holden. It contains faithful reproduc-
tions of all the available drawings that have been made by astronomers
of this wo-.derful nebula of Orion from the year 1656 to recent
times.

If now we were to suppose one hundred years to elapse, and no
further observation of the nebula of Orion to be made in the interval ;
if in some extraordinary way all previous observations were lost, but

ISS^l.] on the Distances of the Fixed Stars. 106

that astronomers were offered the choice of recovering this photograph
of Mr. Common's, or of losing it and preserving all the previous
observations of the nebula recorded in Prof. Holden's book — how
would the choice lie ? I venture to say that the decision would be
— Give us Mr. Common's photograph.

Is it not therefore now our duty to commence a systematic
photographic record of the present aspect of the heavens ? Will not
coming generations expect this of us ? Does not photography offer
the only means by which, so far as we know, man will be able to
trace out and follow some of the more slowly developing phenomena
of sidereal astronomy ?

Huggins has shown how the stars may be made to trace in the
significant cipher of their spectra the secrets of their constitution and
the story of their history. Common has shown us how the nebulae
and clusters may be separately photographed, and it is not difficult to
see how that process may be applied, not only to special objects, but
piece by piece to the whole sky, till we possess a photographic
library of each square half-degree of the heavens. But such a work
can only be accomplished by consummate instruments, and with a
persistent systematic continuity which the unaided amateur is unable
to procure and to employ. It is a work that must be taken up and
dealt with on a national scale, on lines which Huggins and Common
have so well indicated, and which has already been put in a practical
form by a proposal of Norman Lockyer's at a recent meeting of the
Eoyal Astronomical Society.

I would that I had the power to urge with due force our duty as
a nation in this matter, but my powers are inadequate to the task.

I employ rather the words of Sir John Herschel, because no words
of mine can equal those of him who was the prose-poet of our science,
whose glowing language was always as just as it was beautiful, and whose
judgment in such matters has never been excelled. They were spoken
in the early days of exact sidereal astronomy, when the strongholds of
space were but beginning to yield the secret of their dimensions to
the untiring labour and skill of Bessel, of Struve, and of Henderson.
Think what they would have been noio when they might have told
how Huggins' spectroscope had determined the kinship of the stars
with our sun, how it had so far solved the mysteries of the constitution
of the nebulsB, and pointed out the means of determining the absolute
velocity of the celestial motions in the line of sight. Think what
Herschel would have said of those photographs by Common that we
have seen to-night of that nebula that Herschel himself had so
laboriously studied, and whose mysterious convolutions he had in
vain endeavoured adequately to portray ; and think of the lessons
of opportunity and of duty that he would have drawn from such
discoveries, as you listen to his words spoken forty-two years ago : —

" Such results are among the fairest flowers of civilisation.
They justify the vast expenditure of time and talent which have led
up to them ; they justify the language which men of science hold, or

106 Mr. David Gill on the Distances of the Fixed Stars. [May 23,

ought to hold, when they appeal to the Governments of their respective
countries for the liberal devotion of the national means in furtherance
of the great objects they propose to accomplish. They enable them
not only to hold out but to redeem their promises, when they profess
themselves productive labourers in a higher and richer field than that
of mere material and physical advantages.

" It is then, when they become (if I may venture on such a figure
without irreverence) the messengers from heaven to earth of such
stupendous announcements as must strike every one who hears them
with almost awful admiration, that they may claim to be listened to
when they repeat in every variety of urgent instance that these are
not the last of such announcements which they shall have to com-
municate, that there are yet behind, to search out and to declare, not
only secrets of nature which shall increase the wealth or power of
man, but truths which shall ennoble the age and country in which
they are divulged, and, by dilating the intellect, react on the moral
character of mankind. Such truths are things quite as worthy of
struggles and sacrifices as many of the objects for which nations
contend and exhaust their physical and moral energies and resources.
They are gems of real and durable glory in the diadems of princes,
and conquests which, while they leave no tears behind them, continue
for ever unalienable."

ID. G.]

1884.1 Monsieur E. Mascart siir les Couleurs. 107

WEEKLY EVENING MEETING,

Friday, May 30, 1884.

Warren De La Rue, Esq. M.A. D.C L. F.R.S. Manager and
Vice-President, in the Chair.

Monsieur E. Mascart,

PROFE6SEUK AU COLLKGE DE FRANCE.

Sur les Couleurs.

Mesdames, Messieurs, —

C'est une entreprise tres hasardee de vous entretenir dans une
langue etrangere d'un sujet qui ne vous menage aucune surprise et
dans une salle ou vous etes habitues a entendre les plus grands
esprits exposer leurs decouvertes. Vous trouverez, sans doute, bien
legitime que je reclame toute votre indulgence, dans la crainte
surtout que mes honorables amis n'aient a regretter I'invitation qu'ils
m'ont fait I'honneur de m'adresser.

Une lumiere est definie par deux qualites, I'eclat et la couleur.
La comparaison de deux lumieres ayant la meme couleur pourrait etre
faite sans le secours de nos organes et par des moyens physiques,
mais il est impossible de comparer des couleurs diflferentes sans faire
intervenir I'impression physiologique.

On sait depuis les travaux de Newton que la lumiere blanche, ou,
pour preciser davantage, la lumiere du soleil, est formee d'un grand
nombre de couleurs differentes, et que la reunion de toutes ces
couleurs dans la meme proportion, agissant sur I'ceil, soit d'une
maniere simultanee, soit a des intervalles tres raj)proches, reproduit
exactement I'impression du blanc.

En partant d'une analogic precon9ue avec les notes de la gamme,
Newton a partage le spectre solaire, c'est-a-dire I'image obtenue en
decomposant la lumiere blanche par un prisme refringent, en sept
couleurs diflferentes. En realite, cette division est arbitraire, les
couleurs passent de I'un a Tautre par des transitions insensibles,
et chacune d'elles pent etre caracterisee, soit par sa refraction dans
un prisme, soit plutot par la longueur des ondulations auxquelles
elle correspond.

Quand on reunit en un point une partie des rayons du spectre, on
obtient, soit une des couleurs primitives plus on moins pure, soit une
teinte nouvelle. Si on divise le spectre en deux parties arbitraires
reunies separement, on obtient deux couleurs distinctes dont la super-
position reproduit encore la lumiere blanche. L'experience pent etre

108 Monsiciw E. Mascart [May 30,

realisee a I'aide d'un spectre ordiuaire que Ton divise en deux parties
arbitraires; elle s'effectue pour ainsi dire naturellement dans les
phenomenes de polarisation rotatoire, ou Ton peut obtenir les teintes
les plus eclatantes.

Nous ne rappelons ces proprietes generales que pour en deduire
deux conclusions. On remarque d'abord que le melange des lumieres
simples ou homogenes dans une proportion quelconque produit
toujours sur I'oeil une impression unique, celle d'une seule couleur ;
tandis que I'oreille peut distinguer toutes les notes qui constituent
une harmonie, I'oeil ne saisit jamais qu'une couleur, sans pouvoir
distinguer si elle est reellement simple ou formee de lumieres
diflferentes.

En second lieu, le melange des couleurs ne provoque qu'une im-
pression nouvelle, celle du pourpre que Ton peut obtenir, par exemple,
en melangeant du rouge et du violet, les varietes de rose n'etant
d'ailleurs que des melanges de pourpre et de blanc.

Le blanc peut etre reproduit par deux couleurs simples seulement,
telles que le rouge et le vert; d'une maniere plus generale, si Ton
isole dans le spectre trois couleurs convenablement choisies, telle que
certaines nuances de rouge, de vert et de violet, on peut par leurs
melanges en differentes proportions, imiter les impressions produites
par toutes les couleurs. Les couleurs artificielles, formees par des
rayons pris dans un spectre par exemple, peuvent etre simples ou
composees, sans que I'ceil en soit informe, sauf peut-etre quand elles
ont une nuance de pourpre ou de rose, parce que nous savons que ces
couleurs n'existent pas a I'etat simple.

-II en est de meme pour les couleurs de la nature ou de
I'industrie. Un objet nous parait colore parce qu'il nous renvoie une
partie seulement de la lumiere qu'il emprunte a I'eclairage general.
Le partage se fait soit par transmission, comme dans les verres de
couleur, soit par reflexion, comme pour les metaux, soit par diffraction,
comme pour les ailes de certains papillons ou les couronnes que I'on
distingue quelquefois autour de la lune ; la portion de la lumiere
qui n'arrive pas a I'oeil est absorbee ou renvoyee dans une direction
differente. Si on laisse a part les effets de fluorescence, on voit
qu'un objet n'a pas de couleur par lui-meme, il ne fait qu'em-
prunter a la lumiere generale les teintes qui lui conviennent et I'aspect
qu'il presente est tres different suivant la mode d'eclairage. Un ruban
rouge, par exemple, place successivement dans les differentes couleurs
du spectre parait noir, sauf dans la region rouge du spectre; il
renvoie done par reflexion une lumiere presque homogene. Un ruban
rose parait lumineux d'une maniere tres inegale dans toutes les
parties du spectre ; la lumiere qu'il reflechit est done tres complexe.

On peut se demander alors ce que deviendrait la nature, si la
lumiere qui nous eclaire etait absolument homogene. Certains corps
I'absorberaient completement, ils paraitraient obscurs comme du
velours noir ; d'autres la reflechiraient plus ou moins activement, ils
seraient lumineux avec plus ou moins d'cclat. Comme il n'existerait

1884. J sur les Conleurs. 109

plus aiicnn terme de comparaison, I'oeil ne conscrvcrait que la sensa-
tion du blanc, du noir et des gris intermediaires.

II ne semble pas necessaire d'en faire lepreuve, mais une experience
n'est jamais inutile et elle revele presque toujours des idees imprevues.

Pascal disait que rien ne fait mieux comprendre les proprietes
de Fair que ce qui se passe la oil il n'existe plus ; de meme, rien ne
fera mieux comprendre les proprietes des couleurs que 1 'aspect du
monde dans un eclairage de lumiere homogene. La volatilisation d'un
sel de soude dans la flamme d'un bee de Bunsen realise cette condition
d'une maniere presque parfaite.

Avec un pareil eclairage les ^toffes teintes des plus riches couleurs
ne presentent plus que du blanc, du noir et du gris; I'art de la
peinture n'existe plus. Voici un superbe tableau d'Ed. W. Cooke,
que Sir W. Bowman a eu I'obligeance de me confier, et qui represente
un aspect de Venise au soleil coucbant ; il n'est plus qu'une gravure :
voici maintenant deux paysages dessines a la lumiere de la soude par
un artiste qui croyait n'employer que des crayons noirs et gris : il se
servait en realite de couleurs tres eclatantes, et vous en verrez I'aspect
a la lumiere ordinaire; ce bouquet do fleurs n'est plus qu'une
collection de taches blanches et grises sur un feuillage noir ; la figure
humaine prend un aspect cadaverique, etc. II faut subir pendant
quelque temps I'impression d'un tel spectacle pour saisir completement
ce qu'il a de monotone, de triste et de sepulcral. Ce serait assurement
un etrange supplice que d'etre oblige a vivre dans un pareil milieu
et on eprouverait une joie indescriptible si la baguette d'une fee
rendait immediatement leur eclat a tons les objets qui nous entourent,
comme je le fais en enflammant un fil de magnesium, et je suis sur
que vous eprouvez vous-memes une sorte de soulagement en voyant la
fin de cette experience lugubre.

Le jugement de la couleur etant lie a I'impression produite sur
la retine, il est a prevoir que I'oeil humain ne remplira pas toujours
egalement bien cette fonction.

Deja les difi'erentes points de la retine sent inegalement aptes a
apprecier les couleurs. Pour distinguer les details d'un objet, il faut
diriger son regard vers cet objet, c'est-a-dire produire une image sur
la region centrale de la retine ou I'acuite de la perception physiolo-
gique est beaucoup plus grande. II en est de meme pour les couleurs.
Quand on maintient le regard dans une direction determinee, et qu'on
place un corps colore dans le champ visuel de fa^on que son image se
produise lateralement, on remarque que la notion de la couleur
s'affaiblit de plus en plus a mesure qu'on s'ecarte de la vision centrale,
pour disparaitre aux limites du champ.

Mais le fait le plus important consiste en ce que les difi'erentes
vues ne distinguent pas les couleurs les unes des autres avec une egale
facilite, et meme que Ton arrive quelquefois a confondre les couleurs
qui nous paraissent les plus discordantes, telles que le vert et le rouge.
La decouverte de cette forme particuliere d'infirmite est due a Dalton,
pui en etait affecte a un tres haut degre, et qui a analyse les erreujs

110' Monsieur E. Mascart [May 80,

de son jngement avec le plus grand soin. Nous avons I'habitude
d'appeler Daltonisme le defaut que vous appelez " colour-blindness,"
et c'est peut-etre abuser du nom d'un savant qui a tant d'autres titres
pour passer a la posterite. Ce defaut si longtemps inaper9U est
en realite tres frequent ; il y a bien 10 personnes sur 100 qui com-
mettent dans la comparaison des couleurs des erreurs assez marquees
pour qu'on puisse les mettre en evidence par un examen attentif.
En general, cette imperfection de la vue n'a pas d'inconvenients graves,
et on la corrige d'une maniere inconsciente, par I'habitude, le souvenir
des objets et le jugement d'autrui ; mais la gene devient extreme
quand on ne pent distinguer, par exeraple, le rouge du vert, une cerise
ou une f raise mure au milieu du feuillage, un feu vert d'un feu rouge
dans les signaux des chemins de fer ou de navigation. Les artistes
ont quelquefois une predilection marquee pour certaines couleurs.
Lesueur mettait le bleu a profusion dans tons ses tableaux ; votre
grand peintre Turner semble avoir recherche de plus en plus les tons
rouges. II y aurait lieu peut-etre de chercher si le choix de couleurs,
pour certains peintres, est absolument intentionnel ou bien s'il est la
consequence d'un etat physiologique.

On est presque toujours daltonien de naissance, mais cette affec-
tion pent se produire aussi a la suite d'un accident; dans certaines
affections nerveuses elle se manifesto quelquefois d'une maniere
temporaire et sous les formes les plus bizarres.

Plus que les autres sens, la vue pent etre ainsi I'occasion d'erreurs
et d'illusions nombreuses. Pour ne parler que de celles qui ont trait
aux couleurs, je rappellerai les effets de contraste de deux couleurs
voisines, ou ceux qui suivent I'impression d'une image, ou encore
les couleurs subjectives que Ton voit les yeux fermes, par suite
d'une action mecanique sur I'oeil, et je me bornerai a vous rendre
teraoins de quelques experiences relatives au relief apparent des
couleurs.

Quand on examine sur un ecran I'image d'un spectre, produit par
un pri6«me a vision directe, les couleurs successives semblent bien
situees dans un meme plan ; mais si Ton fait tourner lentement la
fente ou le prisme, on a de suite I'illusion d'une lame coloree en
relief, dont I'extremite rouge est en avant. L'effet est plus sensible
encore quand la fente a la forme d'un V, le spectre parait etre une
veritable gouttiere. En rempla^ant la fente par le mot DAVY en
lettres transparentes, on croirait voir sur le tableau, avec une exa-
geration extreme, les lettres en relief que Ton rencontre sur certaines
enseignes de magasins.

En dehors des couleurs que nous voyons habituellement, le spectre
solaire renferme encore d'autres radiations, les unes moins refrangibles
que le rouge, qui se manifestent par leurs projirietes calorifiques, les
autres plus refrangibles que le violet, remarquables par leurs effets
photographiques, et par Taction qu'ellcs cxercent sur les substances
fluoresccntes. Le spectre solaire ultra-violet produit par refraction
dans un prisme occupe une etenduc a pen pres egale a celle du

1884.] sur lea Couleurs. Ill*

spectre lumineiix, et Mr. Stokes a montre que Tare electrique donne «
un spectre ultra-violet 5 ou 6 fois plus etendu.

On peut etre etonne que la vue humaine soit restreinte a une si
faible partie des radiations qu'emet une source de lumiere. Nous
remarquerons d'abord qu'il en est de meme pour les autres sens : le
toucher ne peut donner une idee de la temperature d'un corps qu'entre
des limites tres resserrees ; Toreille ne percoit pas les sons tres graves
ni les sons tres aigus, et les plus eleves qu'elle puisse entendre pro-
duisent une impression penible. Du cote des rayons infra-rouges, le
spectre visible s'arrete presque brusquement, et les efforts de Brewster
n'ont guere recule la limite des rayons que I'ceil peut percevoir ; nous
devons attendre que des procedes ingenieux, comme ceux que M. le
Capitaine Abney a employes avec tant de succes, nous donneut
I'histoire complete de cette region.

De I'autre cote, la visibility persiste d'une maniere remarquable.
M. Helmholtz avait reconnu deja qu'avec quelques precautions on peut
voir le spectre solaire ultra-violet tout entier, tel qu'il est revele par
la photographic. Ayant eu I'occasion d'etudier la lumiere emise
par les vapeurs metalliques, j'ai constate d'abord qu'avec un prisma
de spath d'Islande une vue ordinaire peut distinguer un spectre ultra-
violet 3 ou 4 fois aussi etendu que le spectre lumineux ; un de mes
collaborateurs voyait meme beaucoup plus loin et dessinait d'avance
toutes les raies brillantes qu'il m'etait possible de photographier. Si,
au lieu de considerer la refraction de ces rayons, laquelle varie avec la
nature des substances, on les definit par leur longueur d'onde ou la
duree de vibration, on peut dire que le spectre lumineux ordinaire
comprend I'intervalle d'une octave et qu'il est possible de percevoir
une seconde octave plus aigue.

En rappelant ces difft^rentes proprietes de la lumiere, je voudrais
y ajouter quelques remarques. Sir W. Thomson a exprime sa surprise
que la Nature ait oublie de nous donner un sens particulier pour
percevoir les phenomenes magnetiques, au milieu desquels nous
vivons. Ici, au contraire, nous sommes en presence de radiations qui
n'existent pas dans la lumiere du soleil, ou du moins qui n'arrivent
pas jusqu'a nous, qui sont energiquement absorbees par la plupart
des milieux transparents et en particulier par les humeurs de I'ceil,
dont nous nous desinteressons absolument dans la vie courante et qui
neanmoins agissent sur la retine ; la couche nerveuse retinisnne est
done extremement sensible a leur action. Ne semble-t-il pas que
nous possedions sous ce rapport une sensibilite superflue et qu'il y ait la
un defaut d'harmonie entre la structure de I'organe et les besoins
auxquels il doit repondre ?

On a souleve encore, a ce sujet, une question qui presente le plus
grand interet au point de vue philosophique, celle de savoir si
I'homme est susceptible d'un perfectionnement orgauique, et s'il est
possible de saisir la trace d'un progres accompli dans la vision des
couleurs, et par suite dans la structure de I'oeil. Un des hommes
eminents de I'Angleterre n'a pas dedaigne de s'occuper de cette

112 Monsieur E. Mascart [May 80,

question. Mr. Gladstone a fait un depouilleraent complet des ex-
pressions employees par Homere pour designer la couleur des objets ;
il parait bien en resulter que les epithetes d'Homere sont appliquees
d'une maniere fort incertaine, que le grand poete semble confondre
le vert avee le jaune, le bleu avee le noir.

Avant de conclure, de cette curieuse observation, que le sentiment
de la couleur etait alors pen developpe, on pourrait remarquer peut-
etre que I'intervalle qui nous separe d'Homere est peu de cbose dans
I'histoire de I'huraanite, que les Grecs, quelque temps apres, faisaient
un grand usage des couleurs dans leurs tableaux et dans les statuettes
peintes dont on possede de si nombreux specimens, que les fresques
de Pompeii presentent les couleurs les plus varices, et qu'enfin
I'examen attentif des auteurs modernes risquerait de conduire aux
memes conclusions que celles qu'on tire des ecrits d'Homere. Au
milieu du 17"^ siecle, a I'epoque ou Lesueur faisait un tel usage du
bleu dans la peinture, n'est-il pas singulier qu'un poete naturaliste
par excellence, La Fontaine, n'ait pas employe une seule fois
I'expression de " bleu " pour designer un objet colore ou la couleur
du ciel ? Le moindre roman d'aujourd'hui fournirait une recolte de
couleurs autrement importante. La litterature avait autrefois pour
but de raconter les faits de I'histoire ou les passions de I'homme, afin
de produire une impression voulue sur I'esprit du lecteur ; la peinture
seule se servait du dessin et de la couleur. Depuis quelque temps,
au moins en France, il semble que les roles soient intervertis, la
litterature abuse de pittoresque, la peinture devient impressioniste ;
sans recourir a une modification des nos organes, le cbangement des
idees et le besoin de trouver du nouveau suffiraient pour expliquer le
langage colore des litterateurs contemporains.

i)'ailleurs. si I'humanite etait capable d'un perfectionnement si
rapide, on doit bien admettre que les peuples qui sont restes pour
ainsi dire a I'age de pierre, comme les naturels du Cap Horn, n'ont
pas participe au progres general. L'expedition frangaise qui vient
de sejourner pendant une annee a la Terre de Feu, a eu I'heureuse
idee d'etudier les indigenes sous ce rapport. La langue fuegienne
n'a d'expressions que pour designer deux couleurs, I'un pour le rougO
et les teintes analogues, I'autre pour le bleu et le vert ; mais cette
pauvrete du langage tient seulement a ce que les couleurs ne jouent
pas de role important dans I'existence des Fuegiens, car on a reconnu
qu'avec un peu d'exercice ils arrivaient a distinguer et a classer les
couleurs et leur difie rentes nuances avee autant d'exactitude que
I'Europeen le plus civilise ; le developpement organique de leur
appareil visuel ne laisse done rien a desirer.

La vision des animaux est-elle la meme que celle de rhorame,
ou bien quelques-uns d'entre eux au moins ont-ils la faculty d'aper-
cevoir des radiations auxquelles nous sommes insensibles? Pour
repondre a cette question, nous repeterons d'abord une curieuse
experience de M. Paul Bert. Dans un cuve en verre on a place de
I'eau renfermant une grande quantit6 de petits crustaces d'eau douce

1884.] sur les Coideurs. 113

appartenant a lafamille des Daphnies. Quand on eclaire un point de
la cuve, les daphnies s'y precipitent et elles se deplacent avec le
rayon de lumiere ; la plupart des animaux sent dans le meme cas,
et cherchent la lumiere a moins qu'elle ne soit trop eclatante. Quand
on projette un spectre sur la cuve, on voit encore les daphnies couvrir
tome la region eclairee, mais avec des particularites tres remar-
quables. Les plus petites se repandent dans tout le spectre, rares
dans le rouge, abondantes dans le jaune et le vert, plus nombreuses
dans le bleu et le violet et disseminees encore dans I'ultra-violet.
Les plus grosses, au contraire, sent presque exclusivement localisees
sur une bande etroite situee entre le vert et le bleu. Ces animaux
voient done les meme rayons que nous, malgre la distance qui separe
I'homme des crustaces dans I'echelle zoologique, et ils paraissent
meme partager nos infirmites, puisque quelques-uns se comportent
comme s'ils etaient aflfectes de daltonisme. Sir John Lubbock a fait,
dans le laboratoire meme de I'lnstitution Royale, une belle serie de
recherches sur la vision des fourmis, des abeilles et des guepes, d'ou
resulte en particulier ce fait curieux, que les rayons ultra-violets
paraissent aux fourmis plus eclatants que le spectre lumineux
ordinaire. L'histoire des animaux sous ce rapport serait done du
plus haut interet.

Nous n'avons considere jusqu'a present les couleurs que comme
une decoration de la nature, mais leur injfluence sur le developpement
des etres vivants s'exerce dans les conditions les plus variees.

La lumiere et les couleurs agissent sans aucun doute sur I'etat de
notre esprit, et cette impression morale ne peut etre que la traduction
d'une action physiologique.

Dans certains etablissements sanitaires, relatifs aux aberrations
mentales, on fait sojourner les malades dans une lumiere jaune-doree
qui parait exercer une heureuse influence sur leur caractere et les
amene a des sentiments de douceur. Ce n'est certes pas la lumiere
jaune de la sonde qui peut produire un pareil resultat, mais une sorte de
lumiere blanche dont on a attenue les rayons extremes bleus et rouges
de maniere a faire dominer les tons roses et jaunes.

La predilection des animaux pour certaines couleurs n'est pas le
resultat d'une preference artistique. Si les daphnies recherchent la
lumiere verte et les fourmis la lumiere ultra-violette, c'est sans doute
qu'elles y trouvent de meilleures conditions d'existence.

Les plantes se pretent mieux a ce genre d'etudes. Une plante
ordinaire, comme celles que nous avons habituellement sous les yeux,
grandit, se developpe en tons sens, augmente de poids, produit des
feuilles, des fleui-s et des fruits, et respire, c'est-a-dire qu'il existe
un echange continuel entre les elements qu'elle contient et les gaz de
de I'atmosphere. Ces differents actes de la vie vegetative s'effec-
tuent tres inegalement sous I'influence des diverses radiations
lumineuses ou calorifiques.

La croissance de la plante, par I'allongement et la multiplication
des cellules, se fait surtout sous I'influence des rayons calorifiques, et

Vol. XI. (No. 78.) i

114 Monsieur E. Mascart [May 30,

il existe pour cliacune d'elles une temperature preferee. Si une plante
ne revolt de chaleur que d'un cote, elle s'y developpe d'avantage et
se courbe dans la direction opposee ; c'est le phenomene du thermo-
tropisme.

A la lumiere, une plante s'accroit moins vite que dans
I'obscurite, mais au benefice de sa nutrition generale et de son
developpement transversal. Ici les differentes couleurs ont une
action specifique tres marquee. Avec un bon eclairage, Taction
retardatrice, insensible pour les rayons obscurs, presente un premier
maximum vers I'extremite rouge, un minimum dans le jaune, oil la
lumiere est le plus intense, et un grand maximum dans le violet.
Ce sent done les rayons a courte longueur d'onde qui sent les plus
actifs.

II en resulte I'explication tres simple de I'heliotropisme, c'est-a-
dire de la tendance marquee des plantes a se courber vers la lumiere.
Quand une plante est exposee a une lumiere laterale, les portions
eclairees s'allongent moins vite que celles qui restent dans I'ombre et
la plante inflechit la tete vers la lumiere. En mesurant cette in-
flexion dans les differentes regions du spectre, on a reconnu d'ailleurs
que I'effet est insensible dans le jaune, plus marque dans le rouge et
qu'il est maximum dans le bleu et le violet.

Nous pouvons entrer plus avant encore dans le mecanisme de la
nutrition. En dehors de la perte d'eau par evaporation, les plantes
ont deux sortes de respirations : I'une qui est continuelle, le jour et la
nuit, et qui degage de I'acide carbonique, c'est une sorte de com-
bustion correlative de la vie et tout a fait analogue a la respii*ation
des animaux ; I'autre est intermittente et ne se fait qu'a la lumiere,
elle a pour resultat d'emprunter a I'acide carbonique de I'air le
carbone dont la plante fait du sucre et du bois, et de degager I'oxygene.
La matiere colorante des feuilles, la chloropbylle, jouo le role
principal dans cette respiration nutritive. Or, la chloropbylle doit
se fabriquer d'abord, puis exercer ses fonctions respiratoii*es, et ici
les differentes couleurs agissent encore tres inegalement.

Si Ton examine la formation de chlorophylle dans la plante avec
un eclairage moyen, on reconnait qu'elle se produit dans toute
I'etendue du spectre, tres faiblement dans I'infra-rouge, avec un
maximum dans le jaune intense et une diminution reguliere jusque
dans le spectre solaire ultra-violet. La courbe de cette action a un
allure tout-a-fait analogue a celle qu'a donnee Frauenbofer pour la
distribution de I'eclat lumineux dans le spectre, mais elle se prolonge
davantage vers les rayons plus refrangibles. Ici encore il y a une
intensite preferee, au-dela de laquelle la chlorophylle se forme moins
facilement, pour se detruire ensuite, comme il arrive pour les plantes
exposees en plein soleil.

L'experience montre aussi que la production d'oxygene ne se fait
que la oil existent les grains de chlorophylle. Si Ton fiiit traverser
une dissolution de chlorophylle par un rayon de lumiere blanche
qu'on analyse ensuite par un prisme, on remarque une bande d'absorp-

1884.] sur les Couleurs. 115

tion energique dans le rouge et deux autres dans le bleu et le violet.
Or, ce sont precisement ces rayons absorbes par la substance verte
qui agissent pour la reduction de I'acide carbonique, et je ne resiste
pas au desir de vous indiquer la methode ingenieuse employee par
M. Engelmann pour mettre ce fait en evidence.

Dans ses experiences sur ses fermentations, auxquelles M. Tyndall
a apporte un appui si autorise, M. Pasteur distingue les petits etres
microscopiques en aerobies et anaerohies ; les uns respirent et se
developpent en presence de I'oxygene de I'air, I'oxygene tue les autres.
Si on examine au microscope des bacteries aerobies nageant dans un
liquide, on les voit se concentrer autour des buUes d'air oil elles trou-
vent Toxygene. Si le liquide est prive de bulles d'air et renferme un
filament d'algue verte, les bacteries se promenent indifferemment
dans le milieu tant qu'on les eclaire avec une lumiere tres faible, ou
mieux avec une lumiere qui a filtre a travers une dissolution de
chlorophylle. A la lumiere blanche, on voit aussitot les bacteries se
precipiter sur tons les grains de chlorophylle pour y saisir les traces
d'oxygene degage ; elles constituent done un reactif tres delicat.

Pour voir I'effet des differentes couleurs, il suffit maintenant de
faire tomber un spectre microscopique sur un filament de conferve ou
une coupe transversale de feuille. Les bacteries s'accumulent sur la
plante dans le rouge, juste au point ou se trouve le maximum d'absorp-
tion de la chlorophylle, puis dans le bleu, et la densite de la popula-
tion, pour ainsi dire, reproduirait a pen pres la courbe d'absorption de
la matiere colorante.

Je ne puis pas insister trop longuement sur ces faits d'histoire
naturelle ; je dois ajouter cependant qu'il y a sous ce rapport de
grandes differences specifiques, en relation avec la couleur propre des
differentes plantes, comme cela doit resulter de I'inegale absorption de
leurs matieres colorantes. II me suffira d'en citer un exemple.
L'eau de mer a une couleur diJBferente suivant I'epaisseur au travers
de laquelle on I'observe, a cause de I'inegale absorption des differentes
radiations ; suivant la profondeur du sol sur lequel elle repose, une
plante marine trouvera done des conditions plus ou moins favorables,
et elle sera plus ou moins bien armee dans sa lutte pour I'existence.
Quand on examine une plage que vient de quitter la maree, on trouve
des algues bleues sur le bord des plus grandes eaux, plus bas des algues
vertes, puis des algues brunes, et enfin des algues rouges dans les
regions qui sont rarement decouvertes. Du haut d'une falaise, on
apercoit ainsi une serie de bandes concentriques de couleurs differentes
qui dessinent les limites ou chacune des especes, mieux appropriee aux
conditions physiques, a elimine et vaincu les especes voisines ; et ce
n'est pas une question de profondeur, parce qu'on retrouve les algues
rouges a fleur d'eau dans les endroits abrites, les creux des rochers,
les grottes profondes, comme celle de Capri, oil la lumiere ne pent
penetrer qu'affaiblie. En citant des faits de cette nature, je suis assure
que vous avez tons sur les levres le nom d'une des gloires de
I'Angleterre et de I'humanite — du naturaliste Darwin.

I 2

116 General Monthly Meeting, [June 2,

La lumiere est done une source inepuisable a laquelle les etres
vivants empruntent I'energie sous toutes les formes et dans les con-
ditions les plus imprevues, et je vous demanderai la permission de
terminer cette conference en citant quelques paroles de Lavoisier,
qui, en raison de leur date, paraitront peut-etre une sorte de divina-
tion : —

" L'organisation, le sentiment, le mouvement spontane, la vie
n'existent qu'a la surface de la terre, et dans les lieux exposes a la
lumiere. On dirait que la fable du flambeau de Prometliee etait
Texpression d'une verite philosopbique qui n'avait pas ecbappe aux
anciens. Sans la lumiere, la nature etait sans vie, elle etait morte et
inanimee; un Dieu bienfaisant en apportant la lumiere, a repandu
sur la surface de la terre l'organisation, le sentiment et la pensee."

[E. M.]

GENERAL MONTHLY MEETING,

Monday, June 2, 1884.

SiE Feederick Pollock, Bart. M.A. Manager and Vice-President,
in the Chair.

The following Vice-Presidents for the ensuing year were
announced :

Sir Frederick Bramwell, F.R.S.

Warren De La Rue, Esq. M.A. D.C.L. F.R.S.

The Hon. Sir William R. Grove, M.A. D.C.L. LL.D. F.R.S.

Sir John Lubbock, Bart. M.P. D.C.L. LL.D. F.R.S.

Sir Frederick Pollock, Bart. M.A.

The Earl of Rosse, D.C.L. LL.D. F.R.S.

George Busk, Esq. F.R.S. Treasurer.

Sir William Bowman, Bart. LL.D. F.R.S. Honorary Secretary.

James Mansergh, Esq. M.LC.E.

was elected a Member of the Royal Institution.

The Presents received since the last Meeting were laid on the
table, and the thanks of the Members retui'ned for the same, viz. : —

FROM

The Governor- General of India — Geological Survey of India : PalaBontologia
Indica : Series XIV. Vol. I. Part 3, Fasc. 3. 4to. 1884.
Records, Vol. XVII. Part 2. 8vo. 1884.

1884.] General Monthly Meeting, H7

The French Government — Documents Inedits sur I'Histoire de France :
Melanges Historiques, Tome IV. 4to. 1882.
Lettres de Jean Chapelain. Par P. Tamizey de Labroque. Tome II. 4to.

1883.
Inscriptions de la France. Par F. de Guilhermy et K. de Lasteyrie. Tome V.

4to. 1883.
Monoo;raphie de Notre Dame de Chartres. Explication des Planches par

P. Durand. 4to. 1881.
Lettres du Cardinal Mazarin. Par A. Cheruel. Tome III. 4to. 1883.
American PJiUosophical Society — Proceedings, No. 114. 8vo. 1883-4.
Asiatic Society of Bengal — Proceedings, 1883, No. 10 ; 1884, No. 1. 8vo.
Astronomical Society, Boyal — Monthly Notices, Vol. XLIV. No. 6. 8vo. 1884.
Ateneo Fewefo— Rivista Mensile, Serie VII. Nos. 3-6 ; Serie VIII. Nos. 1, 2. 8vo.

1883-4.
Auhertin, J. J. Esq. M.B.I, (the Translator') — The Lusiads of Camoens. Trans-
lated into English Verse. 2 vols. 8vo. 1884.
Bagot, Alan, Esq. M.I.C.E. (the Author) — Application of Electricity to the Work-
ing of Coal Mines. (Proc. Inst. Mech. Engineers, 1883). 8vo.
Bankers, Institute o/— Journal, Vol, V. Part 5. 8vo. 1884.
British Architects, Royal Institute of — Proceedings, 1883-4, Nos. 12-14. 4to.
British Association for the Advancement of Science — Report of Meeting at South-
port, 1883. 8vo. 1884.
Chemical Society— Journal for May 1884. 8vo.
East India Association — Journal, Vol. XVI. No. 3. 8vo. 1884.
Editors — American Journal of Science for May 1884. 8vo.
An alyst for May 1884. 8vo.
Athenaeum for May 1884. 4to.
Chemical News for May 1884. 4to.
Engineer for May 1884. fol.
Horological Journal for May 1884. 8vo.
Iron for May 1884. 4to.
Nature for May 1884. 4to.

Revue Scientitique and Revue Politique et Litteraire for May 1884. 4to.
Science Monthly, Illustrated, for May 1884.
Telegraphic Journal for May 1884. 8vo.
Franklin Institute— J omnsd, No. 701. 8vo. 1884.
Geddes, Patrick, Esq. (the Author) — A Re-Statement of the Cell Theory. (Proc.

Roy. Soc. of Edin. XII.) 8vo. 1884.
Geographical Society, Boyal — Proceedings, New Series, Vol. VI. No. 5.. 8vo.

1884.
Geological Society — Quarterly Journal, No. 158. 8vo. 1884.
Gordon, Surgeon- General C. A. M.D. C.B. M.B.I, (the Compiler) — Medical Reports

of the Chinese Customs Service, 1871-1882. 4to. 1884.
Harlem, Societe Hollandaise des Sciences — Archives Neerlandaises, Tome XVIII.
Liv. 2, 3, 4, 5 ; Tome XIX. Liv. 1. 8vo. 1883-4.
Natuurkundige Verhandelingen. 3de Verz. Deel IV. 3de Stuk. 4to. 1883.
Programme for 1882, 1883. 4to.
Johns Hopkins University —Amencan Chemical Journal, Vol. VI. No. 2. Svo.
1884.
University Circulars, No. 30. 4to. 1884.
Linnean Society — Journal, Nos. 130, 131. Svo. 1884.

Manchester Geological Society — Transactions, Vol. XVII. Part 15. 8vo. 1883-4.
Manchester Literary and Philosophical Society — Memoirs, 3rd Series, Vols. VII.
and IX. 8vo. 1882-3.
Proceedings, Vols. XX. XXI. XXII. 8vo. 1880-3.
Meteorological O^ce— Barometer Manual for Seamen. 8vo. 1884.

Report of -Meteorological Council, R.S. to 31st March, 1883. 8vo. 1884.
Monthly Weather Report for January 1884. 4to.
National Association for Social Science — Proceedings, Vol. XVII. No. 2. Svo. 1884.

118 General Monthly Meeting. [June 2,

National Lifeboat Institution, Eo?/aZ— Annual Eeport for 1884. 8vo.

Pharmaceutical Society of Great Britain— Journal, May 1884. 8vo.

Photographic Society— J omnsA, New Series, Vol. VIII. No. 7. Svo. 1884.

Physical Society— Fioceedinga, Vol. V. Part 5. Svo. 1884.

Preussische Akademie der Wissenschaften — Sitzungsberichte, I.-XVII. 4to. 1884.

Boyal Society o/ I/ttera^wre— Transactions, Vol. XIII. Part 1. Svo. 1883.

Boyal Society of London— Proceedings, No. 230. Svo. 1884.

Boyal Society of New South TFaZes— Journal of Proceedings, Vol. XVI. Svo. 1883.

Society o/^rfs— Journal, May 1884. Svo.

Society for Psychical Besearch—Troceedings, Vol. I. Part 5. Svo. 1884.

Teyler Museurtir— Archives, Serie II. 4^ Partie. 4to. 1883.

Toronto Observatory — Report of the Canadian Observations of the Transit of

Venus, 6th Dec. 1884. Svo.
United Service Institution, Boyal — Journal, No. 123. Svo. 1884.
Vereins zur Beforderung des Gewerbfleisses in Prewssen— Verhandlungen, 1884 :

Heft 4. 4to.
Wild, Dr. H. (the Director)— Annsden des Physikalischen Central-Observatoriums,

1882, Theil 11. 4to. 1883.

1884.] Mr. WillougJihy Smith on Electric Induction. 119

WEEKLY EVENING MEETING,
Friday, June 6, 1884.

Waeren De La Eue, Esq. M.A. D.C.L. F.R.S. Manager and
Vice-President, in the Chair.

WiLLOUGHBY Smith, Esq. M.B.I.

Volta-Electric and Magneto-Electric Induction.

Tbe subject which I shall bring before your notice this evening is
" \olta-Electric and Magneto-Electric Induction " ; and I propose to
describe some of my experiments in connection with this phenomenon
in dectricity and magnetism, which was discovered, named, and for
fortr years fostered within this very building by our universally
esteemed and beloved Michael Faraday.

It is now thirty years ago that Faraday gave me my first lesson in
Voltt-Electric Induction, at the same time impressing upon me the
fact taat physical science must ever be progressive and corrective, and
that hs was always pleased to learn that his experiments had been
repeated by others, with a view to their verification or correction. In
the remembrance of this, I have felt encouraged in coming before you
this evening.

Doubtless all present are familiar with the fact, that about 1819
Professor Oersted made a discovery which has done much to advance
our knowledge with regard to electricity and magnetism. This
disccvery arose from a very simple experiment, but it is none the less
valuable on that account. I will now repeat this experiment, as the
result obtained will lead up to, and enable you to better understand
what I nay show later on. Here is a length of copper wire, from the
top surfac^e and centre of which projects a metal pin, having, balanced
on its point, a magnet. The position of the steel magnet is, as you
perceive, parallel with the wire ; and that position being north and
south, it will thus remain until, by pressing down this spring, the
length of copper wire is placed in metallic circuit with this battery,
and you observe that the magnet immediately has a tendency to place
itself at right angles to the copper wire, remaining thus displaced
until the current ceases to flow, when the needle again obeys the
influence of terrestrial magnetism, and returns to its former position.
This was Oersted's exjDeriment which led to the discovery that all
bodies possess the qualities of a magnet whilst a current is passing
through them. From this fact Faraday conceived the idea that, if a
similar length of copper wire were placed parallel with the former

120 Mr. Willoughhy Smith [June 6,

one, and close to it, each time the circuit was made or unmade there
would be an induced current flowing in this wire, provided it was part
of a closed metallic or other conducting circuit. The first experiment
was not successful, for the simple reason that the galvanometer was
not sufficiently sensitive to be visibly affected by the very small
current induced in so short a length of wire as that with which he
made the experiment; nor was he prepared to find that induced
currents were of such momentary duration. But failures with Faraday
were merely stepping-stones to success ; he repeated the experiments
with spirals of insulated wire, instead of straight wires parallel to eacl
other, thus getting comparatively long lengths in close proximity. B7
these means he gained the object of his search, the result of which
he called " Volta-Electric Induction." Through the kindness of Tr.
Tyndall, I have here the identical spirals which were made and uffid
by Faraday on that memorable occasion. One of these Faraday con-
nected in circuit with a galvanometer, and placed it on top of the otler
spiral, through which intermittent currents from a battery were gent
at fixed intervals. On " making " the battery circuit, he noticed :hat
the needle of the galvanometer was deflected in one direction, anc on
breaking the circuit, the needle was again deflected, but in the opposite
direction. Faraday saw, in his mind's eye, each particle of the circuit
through which the current was passing, acting as a centre of force,
emitting its lines far from it, yet each of these lines returning ^0 its
own source ; he in consequence made a series of experiments, by
placing various substances in the path of the lines of force, to ascer-
tain whether they would in any way be affected or intercepted by the
substances so placed. For instance, he found that they were sensibly
affected by iron, but with copper no satisfactory effects were perceived,
although he felt sure the copper did in some way influence theai, but
so imperceptibly that he was unable to detect it. It was this con-
viction, and the doubt by Faraday of the result of his experiment
with regard to copper, which led me to experiment in this direction.
My apparatus and its arrangements being somewhat different from
Faraday's, I will more fully describe them. Here are two flat spirals
of fine silk-covered copper wire, about twelve inches in diameter,
suspended spider-web fashion in separate frames, the two ends of each
spiral being attached to terminals at the base of its own frame. These
two spirals, which are marked respectively A and B, will now be
placed a definite distance apart, and comparatively slow reversals from
a battery of ten cells sent through spiral A. You will see the amount
of the current induced in B by observing the deflection on the scale of
the mirror reflecting galvanometer, which is in circuit with that spiral.
These inductive effects vary inversely as the square of the distance
between the two spirals when parallel to each other ; the induced
current in B being also proportional to the number of reversals of
the battery current passing through spiral A, and also to the strength
of the inducing current. Spiral A is so connected that reversed
currents, at any desired speed per minute, can be passed through it

1884.] on Volta-Electric and Magneto-Electric Induction. 121

from a battery ; B is so connected to the galvanometer and a reverser
as to show the deflections caused by the induced currents, which are
momentary in duration, and, in the galvanometer circuit, all on the
same side of zero ; for, as the battery current, on making contact,
produces an induced current in the reverse direction to itself, but in
the same direction when broken, of course the one would neutralise
the other, and the galvanometer remain unaffected. To obviate this,
the galvanometer connections are reversed with each reversal of the
battery current, and thus a steady deflection is produced.

Perhaps, for the information of those not acquainted with the con-
struction of a galvanometer, I ought to explain it more fully. The
one I am about to use consists of a coil of very fine silk-covered
wire, in the centre of which is suspended a very small magnet ; the
ends of the coil of wire and the ends of spiral B are connected re-
spectively together, thus forming a metallic circuit, one part of which
is wound into a coil and the other into this spiral. Call to mind
Oersted's experiment, and it will be readily understood that when a
current of electricity is flowing in this metallic circuit, the magnet
will be influenced in magnitude according to the amount of current
thus flowing. The movements of the magnet, however, would be too
small to be seen unless watched very closely ; therefore fixed to it is
a very small concave mirror, on to which a beam of light from the
lamp is thrown, and the mirror reflecting this on to the scale, will, I
hope, enable a]l to see that somewhat broad beam move in accord-
ance with tlie movements of the magnet. Reversed currents at the
speed of 100 per minute will now be passed through spiral A, and
you will observe that the induced currents in B give about 28
divisions on the scale of the galvanometer : we will note this on the
black-board. Now, we place this plate of iron midway between the
two spirals, and you observe the deflection on the scale is reduced to
about one-half, or in round numbers to 15, showing clearly that the
presence of the iron plate has in some way influenced the previous
effects. We now remove the iron, when you see the deflection re-
turns to its original amount of 28 divisions ; and if I now interpose
a similar sheet of copjDer, the interposition does not alter the deflec-
tion. The results of this experiment are therefore as follows : —

Speed = 100 reversals per minute.
Induced current = 28° deflection.
Iron interposed = 15° „
Copper „ = 28°

I may here state that, up to this point, the results of my experiments
confirm those of Faraday, viz. that all dielectrics and diamagnetic
metals appear in no way to interrupt or interfere with the lines of
force.

Now, let us repeat this experiment with the speed of the reversals
increased ten times, or to 1000 per minute ; the spirals are in the same
position as before, and the deflection is now about 86. I have already

122 Mr. Willoughhy Smith [June 6,

said tliat the induced current is in direct proportion to the speed of
the reversals, the battery and spirals remaining the same. It might
therefore cause confusion were I not to explain that the deflection
would be ten times as great as it was with the lower speed of reversals,
but that the scale of the galvanometer not being sufficiently long to
record this high deflection, we have what is termed " shunted " a part
of the current ; that is to say, between the two ends of the galvano-
meter coil we have inserted a length of copper wire, so that the
current, on arriving at one terminal of the coil, divides, part going
through the coil of the galvanometer, and the rest through the shunt ;
the two currents reunite at the other terminal of the galvanometer.
By varying the resistance of the shunt, therefore, the desired amount
of the current can be sent through the galvanometer. In this case
sufficient current passes to keep the beam of light just on the scale at
about 86 divisions. We now interpose the sheet of iron as before,
and you see the deflection falls as before to about one-half. We with-
draw the iron and the deflection returns to its former amount of 86.
We now interpose the copper, when the deflection, instead of remain-
ing stationary, as in the former experiment, actually falls to 17.
We now obtain the following results, viz. : —

Speed = 1000 reversals per minute.
Induced current = 86° deflection.
Iron interposed = 40° „
Copper „ = 17°

Now, the question arose, why does copper, at the low speed of the
reversals, apparently have no efi:ect, while at the higher speed it plays
so important a part in intercepting the lines of force ? The only
solution of the phenomenon which suggested itself to me was that
the lines of force have first to polarise the molecules of substances
placed in their path before they can pass through them, and in this
process time is a very important element to be considered ; for in-
stance, at the slow speed there is sufficient time between the reversals
for the copper to polarise before the next reversal takes place;
whereas at the high speed the copper plate is unable to fully polarise
before the next reversal arrives, and then the two induced effects
partly blend, and being opposite in direction tend to cancel each
other. Now, if this really be the case, the higher the speed the less
should be the proportional deflection when experimenting with copper.
The time at our disposal this evening will not allow of accurate
measurements, or of other substances being experimented upon, but
careful and reliable measurements have been made, the results of
which are shown on the sheet before you marked 1. It will be seen
by reference to these results that the percentage of inductive energy
iutercepted does not increase for different speeds of the revcrser in
the same rate with different metals, the increase with iron being very
slight, whilst with co])pcr the induced current set up is so long in

1884.] on Volta-Eleciric and Magneto-Electric Induction.

123

duration that when the speed of the reverser is at all rapid, the cur-
rent not having time to exhaust itself before the galvanometer is
reversed, tends to produce a lower deflection. If the speed of the

100

Plate 1.

90

i,

COPPER

80

/^^

^ ^

ZINC.

70

t—

/

^

J

^

^

^

TIN.

60

C— **

IRON.

50
40
30

/

^^

/

/

20

/ y^ i ^--^

LEAD.

1 ^\ ^^^'^^

100

500 1000 1500

REVERSALS PER MINrTE.

2000

reverser is further increased, the induced current is received on the
opposite terminal of the galvanometer, and thus a negative result is
obtained.

My next object was to verify, if possible, by a different system of
experiment, the correctness of this theory, and I could think of no
better arrangements than those used by Faraday in some of his
experiments on Magneto-Electric Induction. I was not, however,
encouraged to proceed in that direction ; for if my theory were
correct, the results published by Faraday could not be so ; and know-
ing what a careful experimentalist he was, I could not doubt that
he was right. After long and careful thought on the subject, I
ventured, however, to repeat some of his experiments, and I will
again repeat them before you presently.

About sixty years ago Arago made the discovery in Electrical
Science, that if a plate of copper be revolved close to a magnetic needle,
or magnet suspended in such a way that the latter may rotate in a plane
parallel to the former, the magnet tends to follow the motion of the
plate ; or if the magnet be revolved the plate tends to follow its motion.
This simple apparatus will better illustrate the experiment. Here
is a copper plate one-tenth of an inch thick, and seven and a half
inches in diameter, fixed to a vertical spindle and enclosed in a
wooden case having a glass cover; beneath the copper plate is a
small grooved pulley around which passes an endless band ; the band
also passing round this horizontal wheel to which a handle is fixed,
so that it may be conveniently revolved. A small brass disc is here
provided, in the centre of which is fixed a pointed steel pin, and on

124 Mr. Willoughby Smith [June 6,

this pin is balanced a steel magnet. I will place this on the glass
cover over the centre of the copper plate. Now, if the copper plate
be made to revolve, you will see that the magnet will revolve also in
the direction of the copper disc. There it goes! No doubt you
observed how sluggish its movements were at first, and that it was
some time before it followed the movements of the disc ; this was
owing to the attraction of the earth's magnetism on the magnet, which
held it in bondage until the speed of the disc was sufficient to over-
come its attraction, then, once released, how merrily it appeared to
obey the influence of a superior power. The disc now being at rest,
the needle has returned into bondage ; but if I judiciously use the
influence of this magnet to partially neutralise the influence of the
earth's attraction, you will observe how much more quickly it obeys
the influence of the mysterious power of the revolving disc. There
it goes ! Apparently more readily than before. Were I lecturing on
moral philosophy, I certainly should make use of the similes which
might be drawn with advantage from experiments with this simple
instrument ; but my subject being of a different nature, I will resume
without further digression. If the order were reversed and the magnet
revolved, the copper disc would act in the same way as the magnet
has just done. This is the phenomenon discovered by Arago, who
also asserted that the effect takes place, not only with all metals, but
with all substances. On this latter point there has always been a
difference of opinion between experimentalists who have endeavoured
to verify Arago's statement. As far as my experiments have gone, I
have only obtained reliable results from good conductors of electricity ;
but I believe that, theoretically, Arago is right ; for as all substances
are, in a certain degree, conductors of electricity, it, I think, neces-
sarily follows that we only want sufficiently sensitive instruments to
develop the phenomenon, as Arago asserts, in every substance. It
has been stated that all substances when subjected to a sufficiently
strong magnetic force are found to give indications of polarity, and
also, when magnetic force acts on any medium, whether magnetic,
diamagnetic, or neutral, it produces within it a phenomenon called
magneto-induction. If this be the case it materially strengthens the
correctness of Arago's assertion. Arago's discovery that copper, a
non-magnetic metal, was influenced by a rotating magnet, or that
a magnet was, in the same way, affected by a rotating disc of copper,
was looked upon at the time as a remarkable and new phenomenon in
induced magnetism by philosophers both in England and other
countries ; but it was Faraday who, by the assistance of his know-
ledge of the evolution of electricity from magnetism, gave the true
solution, by proving it to be the effect of electrical currents induced
in the disc on account of its motion in a magnetic field. He not only
proved by simple experiments the correct interpretation of the phe-
nomenon, but he saw the way to making the discovery of Arago a
new source of electricity, not despairing, by the aid of his knowledge
of teirestrial-magneto-induction, of being able to construct a new

1884.] on Volta-Electric and Magneto-Electric Induction. 125

magneto-electric machine. For this purpose he arranged an apparatus
similar to the one I have here, which is simply a permanent magnet,
so fixed that discs of metal or other substances can be rotated
between its poles. Two wires leading one from each terminal of a
galvanometer were applied to any desired part of the revolving disc,
and the deflections on the galvanometer noted. The first experiments
were made with a very large compound permanent magnet, and with
what would now be termed a quantity astatic galvanometer. His
discs of metal were twelve inches in diameter, and about one-fifth of
an inch in thickness, fixed upon a brass axis. He experienced diffi-
culty in making contact between the terminals of the galvanometer
and the edge and other parts of the revolving disc, as also in main-
taining uniform velocity of rotation. With a much smaller magnet
and a more sensitive galvanometer, the results were more striking.
Thus, with his accustomed simplicity, he demonstrated the production
of a permanent current of electricity from an ordinary magnet, at the
same time asserting that with powerful magnets and rapid rotation of
a copper disc, very strong currents would be produced. What a
wonderful lesson this apparently simple machine teaches, for it is
able to exert the power, which has its origin within itself, on external
matter, without in any way exhausting or diminishing that power !

The apparatus that I employed for my experiments is the same
that I shall use this evening. On this stand is fixed an electro-
magnet, the poles of which are so placed that the rim of the disc
under experiment can be freely revolved between them. The cores
of the electro-magnet are 1*75 inch in diameter, and are wound
with twelve layers of silk-covered copper wire of high conductivity,
• 028 of an inch in diameter, each layer having sixty-one turns ; each
core has 732 turns, making a total of 1464 turns on the two poles.
The total resistance of the wire is 13 • 75 Ohms, and through this flows
the current from twelve Leclanche cells. The same galvanometer is
used as in the other experiments, being brought in circuit with the
disc by means of the axis on which the disc revolves, and a metal
brush which forms a rubbing contact on the rim of the disc ; this,
working on a fixed centre, can be readily shifted to any part of the
circumference of the revolving disc. The disc is revolved by this
cone-shaped pulley, worked lathe fashion, and connected by an endless
band to a small grooved pulley fixed on the same axis as the metal
disc. We will now make a few experiments with the copper disc,
which is now revolving at the speed of 1000 revolutions per minute,
and the connections are so made that the current will be taken from
the rim of the disc just as it passes between the poles of the magnet.
On pressing this spring the circuit is completed, and you observe the
effect of the current on the scale of the galvanometer ; it is about
100 divisions. We will now remove the contact to about one-fourth
of the diameter of the disc or top position, so that the current will
be taken at that distance from the poles of the magnet as the disc is
approaching the poles ; now, on completing the circuit, you observe

126 Mr. Willoughby Smith [June 6,

the deflection is reduced to about fifteen divisions. The contact will
now be removed to the opposite side, or bottom position of the disc,
so that the current will be taken at the same distance from the poles,
but after that part of the disc has just passed between them; on
completing the circuit you see the deflection has increased to 33
divisions. Let us note these results as follows : —

Copper.

We will now replace the copper disc with one of iron, and repeat
precisely the same experiment. We find that the current from
position A is so great that it is necessary to insert a resistance of
500 Ohms in the circuit to bring the beam of light on to the galvano-
meter scale : as before shown, by means of inserted resistance we can
obtain any desired deflection. It is now about 98, and that we will
take as the right measure at A. We take the top position, or B, and
you observe that the deflection is only 7 divisions ; the connection is
now placed at position C, or bottom part, and we get but very little
more current as the deflection is only increased by one division. The
r esults with iron are therefore as follows : —

Iron,
500 Ohms ill circuit.

8

If we compare the results of these experiments with those obtained
with the same metals in volta-clcctric induction, we see that iron
remains fairly uniform in its results in both cases, but that copper
behaves dilferently. You must not, please, take the figures given as

1884.] on Volta-Electric and Magneto-Electric Induction.

being absolutely correct, the
experiments having been
somewhat hurriedly made,
and merely given with the
view of enabling you to
understand the results of
carefully-made experiments
with various metals. These
results are graphically
shown on the large sheet
suspended before you,
marked 2 ; and, as the
measurements are to scale,
they can be compared
directly with each other.
The large circles represent
the revolving discs, the
small ones show the position
of the poles of the electro-
magnet, and the arrows the
direction of rotation. The
coloured portions show the
electro - motive force at
every point round the re-
volving disc ; thus in every
case the strongest point is,
as might be expected,
directly in front of the
poles of the exciting mag-
net, the strength gradually
fading from thence on either
side. The blue portions
show the excess of inductive
effect there produced, rela-
tively to a point equidistant
from the magnetic poles, but
on the opposite side. If the
current set up in the metal
simply depended upon the
intensity of that part of
the magnetic field through
which the metal was passing,
then equidistant points on
either side of the magnetic
poles should produce equal
deflections, because the
magnetic intensity is equal ;
on inspecting the diagrams,

127

128

Mr. Willoughhy Smith

[June 6,

however, it appears as if a very sluggish inductive effect were produced
in the diamagnetic metals of high conductivity, the sluggishness
increasing with the conductivity of the metal, as though the atoms
took a comparatively long time to accommodate themselves to the
changes in the magnetic field through which they were passing.
This, I think, confirms the theory I have ventured to advance with
respect to copper while under the influence of induction.

If, as in the case of volta-electric induction, the lines of force are
generated too quickly; or, as in the case of magneto-electric induction,
the diamagnetic body passes too quickly through the magnetic field ;
the atoms of the substance, in each case, have not time to polarise with
sufficient rapidity to radiate in the same time or place as when
influenced more slowly by this force. This would account for the
apparent interruption of the lines of force by the copper plate in the
volta-electric experiments, and also for the " drag " or retardation on
the disc of the same metal, as shown by the blue colour in the diagram
whilst part of it is passing quickly through a magnetic field. That
being the case, it is easy to perceive that a speed of the copper disc
might be attained at which the current would be nil, through the
atoms being unable to polarise in the allotted time. Not so with
magnetic metals, as iron or nickel, in each of which the atoms appear
to be very susceptible to magnetic influences, and to polarise very
quickly, as shown by the way in which part of the disc is affected
just before entering the poles, as indicated by the blue colour in the

diagram marked 3.

Plate 3.

The atoms must as quickly depolarise, as you perceive there is but
very little of what I have termed "drag " in those metals. The con-
sequence of this is, that with iron the amount of current is nearly in
direct i)roportion to the speed of the disc ; whereas with copper the

1884.] on Volta- Electric and Magneto- Electric Induction. 129

increase is very small, the current produced by the two metals being
as 1 to 7, at a speed of about 1300 revolutions per minute. The
higher the specific conductivity of the diamagnetic metal, the greater
the " drag," and consequently the less the current at the poles, this
being more manifest at the high speeds, which does not, however,
agree with the results obtained by Faraday, for he found that the
currents were proportionate in strength to the conducting power of
the bodies experimented with, or, in other words, that the higher the
conductivity the greater the current, whereas I find the reverse to be
the case, as shown on the diagram before you.

Faraday also obtained much better results from copper than from
iron, and thus he recommended copper for his new magneto-electric
machine. Here, again, my results do not agree with his, for I find
that iron gives much better results than copper, as shown on the
diagram ; and also that iron has the advantage that the current in-
creases almost in direct proportion to the speed, whereas copper does
not ; in fact, as already stated, a speed might be obtained at which
copper would give no current.

Faraday, in summing up the results of his experiments on Arago's
phenomenon, says : " Nothing can be more clear, therefore, than that
with iron and bodies admitting of ordinary magnetic induction,
opposite poles on opposite sides of the edge of the plate neutralise
each other's effects, while similar poles exalt the action. But with
copper, and substances not sensible to ordinary magnetic impressions,
similar poles on opposite sides of the plate neutralise each other, and
opposite poles exalt the action." Perhaps you will more readily grasp
the subject by reference to the diagram marked 4, in which P repre-
sents the plates of metal, and the other letters the respective poles of
the magnet and their position.

Plate 4.
faraday. results of my experiments.

nIs nIn sis si nI n|s n|n s|s s| n|

IRON I I I I I IRON

NIL MAXIMUM ^ ' 624 0 0 192 L 192 R

nIs nIn sis si nI nIs nIn sis

COPPER I i I I I COPPER III

MAXIMUM ^""HiC^ ^ GOOD*^ '30 0 0 48L 48R

Here again it will be seen that the results obtained by me are opposed
to those given by Faraday. I have given the actual figures obtained
in my experiments, and it will be seen that the only difference between
Vol. XI. (No. 78.) k

130 Mr. Willoughhy Smith on Electric Induction. [June 6,

the metals copper and iron is that iron gives the higher current of the
two, as it has done in all my experiments.

I have no doubt that we should be able to get approximately
near for all practical purposes to the relative conductivity of metals
by revolving discs of the metal under test in a magnetic field, and
measuring the amount of current between the poles or the amount of
•'drag." The results given on diagram 5 show how suitable the
method also is for obtaining the saturation point of the cores of electro-
magnets, whether of ditferent qualities of iron or different metals.

Plate 5.

IRON

NICKEL

3-5

Very recently an Electrical Congress, held in Paris, agreed to an
universal system of electrical units. I believe the value of some of
the units to be adopted was determined by passing masses of metal at
varying velocity through a magnetic field of uniform intensity, and
noting the amount of current so produced. I understand that the
results obtained by different experimentalists did not agree, and from
what I have shown you this evening, you will readily understand the
reason of the discrepancy. To obtain accurate results the influence
of what I have called " drag " must certainly be taken into the calcu-
lations as an important factor. There are other matters to which I
attach importance connected with the experiments I have endeavoured
to make clear to you, especially with those on magneto-electric induc-
tion, which I publish for the first time this evening ; but of the many
good rules of this Institution, there is one which does not allow me
to tax your patience for more than one hour, and, as I have already
exhausted that time, I must not detain you longer, except to thank
you, which I do most sincerely, for the kind attention you have given
to my humble endeavours to advance our knowledge of volta-electric
and magneto-electric induction.

[W. S.]

1884.] Mr. G. J. Romanes on the Darwinian Theory of Instinct. 131

WEEKLY EVENING MEETING,

Friday, February 8, 1884.

Sir William Bowman, Bart. LL.D. F.R.S. Honorary Secretary and
Vice-President, in the Chair.

Gkoege J. EoMANES, Esq. M.A. LL.D. F.R.S.

The Darwinian Theory of Instinct.

" Gayest thou the goodly wings unto the peacocks ? or wings and
feathers unto the ostrich ? which leaveth her eggs in the earth, and
warmeth them in dust, and forgetteth that the foot may crush them,
or that the wild beast may break them. . . . Because God hath
deprive^J her of wisdom, neither hath He imparted to her under-
standing."

This is the oldest theory of instinct. The writer of that sublime
monument of literary power in which it occurs observed a failure of
instinct on the part of the ostrich, and forthwith attributed the fact
to neglect on the part of the Deity ; the implication plainly being
that in all cases where instinct is perfect, or completely suited to the
needs of the animal presenting it, the perfection is to be attributed to
a God-given faculty of wisdom. This, I say, is the oldest theory of
instinct, and I may add that until within the past twenty-five years
it has been the only theory of instinct. I think, therefore, I ought
to begin by explaining that this venerable and time-honoured theory
is a purely theological explanation of the ultimate source of instinct,
and therefore cannot be affected by any scientific theory as to the
proximate causes. It is with such a theory alone that we shall here
be concerned.

" When giants build, men must bring the stones." For the past
eight or ten years I have been engaged in elaborating Mr. Darwin's
theories in the domain of psychology, and I cannot allude to my own
work in this connection without expressing the deep obligations under
which I lie to his ever ready and ever generous assistance — assist-
ance rendered not only in the way of conversation and correspondence,
but also by his kindness in making over to me all his unpublished
manuscripts, together with the notes and clippings which he had
been making for the past forty years in psychological matters. I have
now gone carefully through all this material, and have published
most of it in my work on ' Mental Evolution in Animals.' I allude
to this work on the present occasion in order to observe that, as it has
so recently come out, I shall feel myself entitled to assume that few
have read it ; and therefore I shall not cramp my remarks by seeking
to avoid any of the facts or arguments therein contained.

K 2

132 Mr. George J. Romanes [Feb. 8,

As there are not many words within the compass of our language
which have had their meanings less definitely fixed than the word
" instinct," it is necessary that I should begin by clearly defining the
sense in which I shall use it.

In general literature and conversation we usually find that instinct
is antithetically opposed to reason, and this in such wise that while
the mental operations of the lower animals are termed instinctive, those
of man are termed rational. This rough and ready attempt at psycho-
logical classification has descended to us from remote antiquity, and
like kindred attempts at zoological classification, is not a bad one so
far as it goes. To divide the animal kingdom into beasts, fowls, fish,
and creeping things, is a truly scientific classification as far as it goes,
only it does not go far enough for the requirements of more careful
observation ; that is to say, it only recognises the more obvious and
sometimes only superficial differences, while it neglects the more
hidden and usually more important resemblances. And to classify
all the mental phenomena of animal life under the term " instinct,"
while reserving the term " reason " to designate a mental peculiarity
distinctive of man, is to follow a similarly archaic method. It is
quite true that instinct preponderates in animals, while reason pre-
ponderates in man. This obvious fact is what the world has always
seen, just as it saw that flying appeared to be distinctive of birds,
and creeping of reptiles. Nevertheless, a bat was all the while a
mammal, and a pterodactyl was not a bird ; and it admits of proof as
definite that what we call instinct in animals occurs in man, and that
what we call reason in man occurs in animals. This, I mean, is the
case if we wait to attach any definition to the words which we employ.
It is quite evident that there is some difference between the mind of
a man and the mind of a brute, and if without waiting to ascertain
what this difference is, we say that it consists in the presence or
absence of the faculty of reason, we are making the same kind of
mistake as when we say that the difference between a bird and a
mammal consists in the presence or absence of the faculty of flying.
Of course, if we choose, we may employ the word " reason " to signify
all the differences taken together, whatever they may be ; and so, if
we like,' we may use the word " flying." But in either case we should
be talking nonsense, because we should be divesting the words of
their meaning, or proper sense. The meaning of the word " reason "
is the faculty of ratiocination — the faculty of drawing inferences
from a perceived equivalency of relations, no matter whether the
relations involve the simplest mental perceptions, or the most abstruse
mathematical calculations. And in this, the only real and proper
sense of the word, reason is not the special prerogative of man, but
occurs through the zoological scale at least as far down as the
articulata.

What then is to be our definition of instinct ?
First of all, instinct involves mental operation, and therefore
implies consciousness. This is the point which distinguishes instinct

1884.] on the Darwinian Theory of Instinct. 133

from reflex action. Unless we assume that a new-born infant, for
example, is conscious of sucking, it is as great a misnomer to term
its adaptive movements in the performance of this act instinctive, as
it would be similarly to term the adaptive movements of its stomach
subsequently performing the act of digestion.

Next, instinct implies hereditary knowledge of the objects and
relations with respect to which it is exercised; it may therefore
operate in full perfection prior to any experience on the part of the
individual. When the pupa of a bee, for instance, changes into an
imago, it passes suddenly from one set of experiences to another — the
diiference between its previous life as a larva and its new life as an
imago being as great as the difference between the lives of two
animals belonging to two different sub-kingdoms ; yet as soon as its
wings are dry it exhibits all the complex instincts of the mature
insect in full perfection. And the same is true of the instincts of
vertebrated animals, as we know from the researches of the late
Mr. Douglas Spalding and others.

Again, instinct does not imply any necessary knowledge of the
relation between means employed and ends attained. Such know-
ledge may be present in any degree of distinctness, or it may not be
present at all ; but in any case it is immaterial to the exercise of
the instinct. Take, for example, the instinct of the Bembex. This
insect brings from time to time fresh food to her young, and
remembers very exactly the entrance to her cell, although she has
covered it with sand, so as not to be distinguishable from the sur-
rounding surface. Yet M. Fabre found that if he brushed away
the earth and the underground passage leading to the nursery,
thus exposing the contained larva, the parent insect " was quite
at a loss, and did not even recognise her own offspring. It seemed
as if she knew the doors, nursery, and the passage, but not her child."

Lastly, instinct is always similarly manifested under similar cir-
cumstances by all the individuals of the same species. And, it may
be added, these circumstances are always such as have been of frequent
occurrence in the life-history of the species.

Now in all these respects instinct differs conspicuously from every
other faculty of mind, and especially from reason. Therefore to
gather up all these differentioe into one definition, we may say that
instinct is the name given to those faculties of mind which are con-
cerned in consciously adaptive action, prior to individual experience,
without necessary knowledge of the relation between means employed
and ends attained; but similarly performed under similar and fre-
quently recurring circumstances by all the individuals of the same
species.

Such being my definition of instinct, I shall now pass on to con-
sider Mr. Darwin's theory of the origin and development of instincts.

Now, to begin with, Mr. Darwin's theory does not, as many suppose
that it does, ascribe the origin and development of all instincts to natural
selection. This theory does, indeed, suppose that natural selection

134 Mr, Oeorge J. Romanes [Feb. 8,

is an important factor in the process ; but it neither supposes that it
is the only factor, nor even that in the case of numberless instincts
it has had anything at all to do with their formation. Take, for
example, the instinct of wildness, or of hereditary fear as directed
towards any particular enemy — say man. It has been the experience
of travellers w^ho have first visited oceanic islands without human
inhabitants, and previously unvisited by man, that the animals are
destitute of any fear of man. Under such circumstances the birds
have been known to alight on the heads and shoulders of the new-
comers, and wolves to come and eat meat held in one hand while a
knife was held ready to slay them with the other. But this primitive
fearlessness of man gradually passes into an hereditary instinct of
wildness, as the special experiences of man's proclivities accumulate ;
and as this instinct is of too rapid a growth to admit of our attributing
it to natural selection (not one per cent, of the animals having been
destroyed before the instinct is developed), we can only attribute itis
growth to the effects of inherited observation. In other words, just
as in the lifetime of the individual, adjustive actions which were
originally intelligent may by frequent repetition become automatic,
so in the lifetime of the species, actions originally intelligent may,
by frequent repetition and heredity, so write their effects on the
nervous system that the latter is prepared, even before individual ex-
perience, to perform adjustive actions mechanically which, in previous
generations, were performed intelligently. This mode of origin of
instincts has been called by Mr. Lewes the " lapsing of intelligence,"
and it was fully recognised by Mr. Darwin as a factor in the formation
of instinct.

The Darwinian theory of instinct, then, attributes the evolution
of instincts to these two causes acting either singly or in combination
— natural selection and lapsing intelligence. I shall now proceed to
adduce some of the more important facts and considerations which,
to the best of my judgment, support this theory, and show it to be
by far the most comprehensive and satisfactory explanation of the
phenomena which has hitherto been propounded.

That many instincts must have owed their origin and develop-
ment to natural selection exclusively is, I think, rendered evident by
the following general considerations : —

(1) Considering the great importance of instincts to species, we
are prepared to expect that they must be in large part subject to the
influence of natural selection. (2) Many instinctive actions are per-
formed by animals too low in the scale to admit of our supposing
that the adjustments which are now instinctive can ever have been
intelligent. (3) Among the higher animals instinctive actions are
performed at an age before intelligence, or the power of learning by
individual experience, has begun to assert itself. (4) Many instincts,
as we now find them, are of a kind which, although performed by in-
telligent animals at a matured age, yet can obviously never have been
originated by intelligent observation. Take, for instance, the instinct

1884.] on the Darwinian Theory of Instinct. 135

of incubation. It is quite impossible that any animal, prior to
individual or ancestral experience, can have kept its eggs warm with
the intelligent purpose of developing their contents ; so we can only
suppose that the incubating instinct began in some such form as we
now see it in the spider, where the object of the process is protection,
as distinguished from the imparting of heat. But incidental to such
protection in the case of a warm-blooded animal is the imparting of
heat, and as animals gradually became warm-blooded, no doubt this
latter function became of more and more importance to incubation.
Consequently, those individuals which most constantly cuddled their
eggs would develop most progeny, and so the incubating instinct
would be developed by natural selection without there ever having
been any intelligence in the matter.

From these four general considerations, therefore, we may conclude
(without waiting to give special illustrations of each) that one mode
of origin of instincts consists in natural selection, or survival of the
fittest, continuously preserving actions which, although never intelli-
gent, yet happen to have been of benefit to the animals which first
chanced to perform them. Among animals, both in a state of nature
and domestication, we constantly meet with individual peculiarities
of disposition and of habit, which in themselves are utterly meaning-
less, and therefore quite useless. But it is easy to see that if among
a number of such meaningless or fortuitous psychological variations,
any one arises which happens to be of use, this variation would be
seized upon, intensified, and fostered by natural selection, just as in the
analogous case of structures. Moreover there is evidence that such
fortuitous variations in the psychology of animals (whether useless or
accidentally useful) are frequently inherited, so as to become distinc-
tive, not merely of individuals, but of races or strains. Thus, among
Mr. Darwin's manuscripts I find a letter from Mr. Thwaites under
the date 1860, saying that all his domestic ducks in Ceylon had quite
lost their natural instincts with regard to water, which they would
never enter unless driven, and that when the young birds were thus
compelled to enter the water they had to be quickly taken out again
to prevent them from drowning. Mr. Thwaites adds that this pecu-
liarity only occurs in one particular breed. Tumbler pigeons in-
stinctively tumbling, pouter-pigeons instinctively pouting, &c., are
further illustrations of the same general fact.

Coming now to instincts developed by lapsing intelligence, I have
already alluded to the acquisition of an hereditary fear of man as an
instance of this class. Now not only may the hereditary fear of man
be thus acquired through the observation of ancestors — and this even
to the extent of knowing by instinct what constitutes safe distance
from fire-arms ; but, conversely, when fully formed it may again be
lost by disuse. Thus there is no animal more wild, or difficult to
tame, than the young of the wild rabbit ; while there is no animal
more tame than the young of the domestic rabbit. And the same
remark applies, though in a somewhat lesser degree, to the young of

136 Mr. George J. Romanes [Feb. 8,

the wild and of the domestic duck. For, according to Dr. Rae, " If
the eggs of a wild duck are placed with those of a tame duck under a
hen to be hatched, the ducklings from the former, on the very day
they leave the egg, will immediately endeavour to hide them-
selves, or take to the water, if there be any water, should anyone
approach, whilst the young from the tame duck's eggs will show
little or no alarm." Now, as neither rabbits nor ducks are likely to
have been selected by man to breed from on account of tameness, we
may set down the loss of wildness in the domestic breeds to the un-
compounded effects of hereditary memory of man as a harmless
animal, just as we attributed the original acquisition of instinctive
wildness to the hereditary memory of man as a dangerous animal; in
neither case can we suppose that the principle of selection has operated
in any considerable degree.

Thus far, for the sake of clearness, I have dealt separately with
these two factors in the formation of instinct — natural selection and
lapsing intelligence — and have sought to show that either of them
working singly is sufficient to develop some instincts. But, no
doubt, in the case of most instincts intelligence and natural selection
have gone hand in hand, or co-operated, in producing the observed
results — natural selection always securing and rendering permanent
any advances which intelligence may have made. Thus, to take one
case as an illustration. Dr. Kae tells me that the grouse of North
America have the curious instinct of burrowing a tunnel just below
the surface of the snow. In the end of this tunnel they sleep
securely, for when any four-footed enemy approaches the mouth of
the tunnel, the bird, in order to escape, has only to fly up through
the thin covering of snow. Now in this case the grouse probably
began to burrow in the snow for the sake of warmth, or concealment,
or both ; and, if so, thus far the burrowing was an act of intelligence.
But the longer the tunnel the better would it serve in the above-
described means of escape ; therefore natural selection would tend to
preserve the birds which made the longest tunnels, until the utmost
benefit that length of tunnel could give had been attained.

And similarly, I believe, all the host of animal instincts may be
fully explained by the joint operation of these two causes — intelli-
gent adjustment and survival of the fittest. For now, I may draw
attention to another fact which is of great importance, viz. that
instincts admit of being modified as modifying circumstances may
require. In other words, instincts are not rigidly fixed, but are
plastic, and their plasticity renders them capable of improvement or
of alteration, according as intelligent observation requiies. The
assistance which is thus rendered by intelligence to natural selection
must obviously be very great, for under any change in the surround-
ing conditions of life which calls for a corresponding change in the
ancestral instincts of the animal, natural selection is not left to wait,
as it were, for the required variations to arise fortuitously ; but is from
the first furnished by the intelligence of the animal with the particular
variations which are needed.

1884.] on the Darwinian Theory of Instinct. 137

In order to demonstrate this principle of the variation of instinct
under the guidance of intelligence, I may here introduce a few

Huber observes, " How ductile is the instinct of bees, and how
readily it adapts itself to the place, the circumstances, and the needs
of the community." Thus, by means of contrivances which I need
not here explain, he forced the bees either to cease building combs, or
to change their instinctive mode of building from above downwards,
to building in the reverse direction, and also horizontally. The bees
in each case changed their mode of building accordingly. Again, an
irregular piece of comb, when placed by Huber on a smooth table,
tottered so much that the bumble bees could not work on so unsteady
a basis. To prevent the tottering, two or three bees held the comb
by fixing their front feet on the table, and their hind feet on the comb.
This they continued to do, relieving guard, for three days, until they
had built supporting pillars of wax. Some other bumble bees, when
shut up and so prevented from getting moss wherewith to cover
their nests, tore threads from a piece of cloth, and " carded them with
their feet into a fretted mass," which they used as moss. Lastly,
Andrew Knight observed that his bees availed themselves of a kind
of cement made of rosin and turpentine, with which he had covered
some decorticated trees — using this ready-made material instead of
their own propolis, the manufacture of which they discontinued ; and
more recently it has been observed that bees, " instead of searching
for pollen, will gladly avail themselves of a very different substance,
namely, oatmeal." Now in all these cases it is evident that if, from
any change of environment, such accidental conditions were to occur
in a state of nature, the bees would be ready at any time to meet
them by intelligent adjustment, which, if continued sufficiently long
and aided by selection, would pass into true instincts of building
combs in new directions, of supporting combs during their construc-
tion, of carding threads of cloth, of substituting cement for propolis
and oatmeal for pollen.

Tui'ning to higher animals, Andrew Knight tells us of a bird
which, having built her nest upon a forcing-house, ceased to visit it
during the day when the heat of the house was sufficient to incubate
the eggs ; but always returned to sit upon the eggs at night when the
temperature of the house fell. Again, thread and worsted are now
habitually used by sundry species of birds in building their nests,
instead of wool and horse-hair, which in turn were no doubt originally
substitutes for vegetable fibres and grasses. This is especially
noticeable in the case of the tailor-bird, which finds thread the best
material wherewith to sew. The common house-sparrow furnishes
another instance of intelligent adaptation of nest-building to circum-
stances, for in trees it builds a domed nest (presumably, therefore, the
ancestral type), but in towns avails itself by preference of sheltered
holes in buildings, where it can afford to save time and trouble by
constructing a loosely-formed nest. Moreover, the chimney- and
house-swallows have similarly changed their instincts of nidification.

138 Mr. George J. Bomanes [Feb. 8,

and in America this change has taken place within the last two or
three hundred years. Indeed, according to Captain Elliott Cones, all
the species of swallow on that continent (with one possible exception)
have thus modified the sites and structures of their nests in accord-
ance with the novel facilities afibrded by the settlement of the
country.

Another instructive case of an intelligent change of instinct in
connection with nest-building is given from a letter by Mr. Haust,
dated New Zealand, 1862, which I find among Mr. Darwin's manu-
scripts. Mr. Haust says that the Paradise duck, which naturally or
usually builds its nest along the rivers on the ground, has been
observed by him on the east of the island , when disturbed in their
nests upon the ground, to build " new ones on the tops of high trees,
afterwards bringing their young ones down on their backs to the
water ; " and exactly the same thing has been recorded by another
observer of the wild ducks of Guiana. Now if intelligent adjustment
to peculiar circumstances is thus adequate, not only to make a whole
breed or species of bird transport their young upon their backs — or,
as in the case of the woodcock, between their legs — but even to make
web-footed water-fowl build their nests in high trees, I think we can
have no doubt that if the need of such adjustment were of sufficiently
long continuance, the intelligence which leads to it would eventually
produce a new and remarkable modification of their ancestral instinct
of nest-building.

Turning now from the instinct of nidification to that of incuba-
tion, I may give one example to show the plasticity of the instinct in
relation to the observed requirements of progeny. Several years ago
I placed in the nest of a sitting Brahma hen, four newly-born ferrets.
She took to them almost immediately, and remained with them for
rather more than a fortnight, when I made a separation. During the
whole of the time the hen had to sit upon the nest, for the young
ferrets were not able to follow her about, as young chickens would
have done. The hen was very much puzzled by the lethargy of her
offspring, and two or three times a day she used to fly off the nest
calling on her brood to follow ; but, on hearing their cries of distress
from cold, she always returned immediately, and sat with patience
for six or seven hours more. I found that it only took the hen one
day to learn the meaning of these cries of distress ; for after the first
day she would always run in an agitated manner to any place where
I concealed the ferrets, provided that this place was not too far
away from the nest to prevent her from hearing their cries. Yet
I do not think it would be possible to imagine a greater contrast
between two cries than the shrill piping note of a young chicken, and
the hoarse growling noise of a youug ferret. At times the hen used
to fly off the nest with a loud scream, which was doubtless due to the
unaccustomed sensation of being nipped by the young ferrets in their
search for the traditional source of mammalian nutriment. It is
further worthy of remark that the hen showed so much anxiety when

1884.] on the Darwinian Theory of Instinct. 139

the ferrets were taken from the nest to be fed, that I adopted the plan
of giving them the milk in their nest, and with this arrangement the
hen seemed quite satisfied ; at any rate she used to chuck when she saw
the milk coming, and surveyed the feeding with evident satisfaction.

Thus we see that even the oldest and most important of instincts
in bees and birds admit of being greatly modified, both in the indi-
vidual and in the race, by intelligent adaptation to changed conditions
of life ; and therefore we can scarcely doubt that the principle of
lapsing intelligence must be of much assistance to that of natural
selection in the origination and development of instinct.

I shall now turn to another branch of the subject. From the
nature of the case it is not to be expected that we should obtain a
great variety of instances among wild animals of new instincts
acquired under human observation, seeing that the conditions of
their life, as a rule, remain pretty uniform for any periods over which
human oljservation can extend. But from a time before the begin-
ning of history, mankind, in the practice of domesticating animals,
has been making what we may now deem a gigantic experiment upon
the topic before us.

The influences of domestication upon the psychology of animals
may be broadly considered as both negative and positive — negative
in the obliteration of natural instincts ; positive in the creation of
artificial instincts. I shall consider these two branches separately,
and here I may again revert to the obliteration of natural wildness.
We all know that the horse is an easily breakable animal, but his
nearest allies in a state of nature, the zebra and the quagga, are the
most obstinately unbreakable of animals. Similar remarks apply to
the natural wildness of all wild species of kine, as contrasted with
the innate tameness of our domesticated breeds. Consider again the
case of the cat. The domesticated animal is sufficiently tame, even
from kittenhood ; whereas its nearest cousin in a state of nature, the
wild cat, is perhaps of all animals the most untameable. But of
course it is in the case of the dog that we meet with the strongest
evidence on this point. The most general and characteristic features
in the psychology of all the domesticated varieties are faithfulness,
docility, and sense of dependence upon a master ; whereas the most
usual and characteristic features in the psychology of all the wild
species are fierceness, treachery, and self-reliance. But, not further
to pursue the negative side of this subject, let us now turn to the
positive, or to the power which man has shown himself to possess of
implanting new instincts in the mental constitution of animals. For
the sake of brevity I shall here confine myself to the most conspicuous
instance, which is of course furnished by the dog, seeing that the dog
has always been selected and trained with more or less express
reference to his mental qualities. And here I may observe that in
the process of modifying psychology by domestication exactly the
same principles have been brought into operation as those to which
we attribute the modification of instincts in general ; for the processes

140 Mr. George J. Bomanes [Feb. 8,

of artificial selection and training in successive generations are
precisely analogous to the processes of natural selection and lapsing
of intelligence in a state of nature.

Touching what Mr. Darwin calls the artificial instincts of the dog,
I may first mention those which he has himself dilated upon — I mean
the instincts of pointing, retrieving, and sheep-tending ; but as Mr.
Darwin has already fully treated of these instincts, I need not go
over the ground which he has traversed, and so shall confine myself
to the consideration of another artificial instinct, which, although not
mentioned by him, seems to me of no less significance — I mean the
instinct of guarding property. This is a purely artificial instinct,
created by man expressly for his own purposes : and it is now so
strongly ingrained in the intelligence of the dog that it is unusual to
find any individual animal in which it is wholly absent. Thus, we
all know, that without any training a dog will allow a stranger to
pass by his master's gate without molestation, but that as soon as the
stranger passes within the gate, and so trespasses upon what the dog
knows to be his master's territory, the animal immediately begins to
bark in order to give his master notice of the invasion. And this
leads me to observe that barking is in itself an artificial instinct,
developed, I believe, as an offshoot from the more general instinct of
guarding property. None of the wild species of dog are known to
bark, and therefore we must conclude that barking is an artificial
instinct, acquired by the domestic dog for the purpose of notifying to
his master the presence of thieves or enemies. I may further observe
that this instinct of guarding property extends to the formation of an
instinctive idea on the part of the animal, of itself as constituting part
of that property. If, for instance, a friend gives you temporary charge
of his dog, even although the dog may never have seen you before,
observing that you are his master's friend and that his master intends
you to take charge of him, he immediately transfers his allegiance
from his master to you, as to a deputed owner, and will then follow
you through any number of crowded streets with the utmost confidence.
Thus, whether we look to the negative or to the positive influences of
domestication upon the psychology of the dog, we must conclude that
a change has been wrought, so profound that the whole mental con-
stitution of the animal now presents a more express reference to the
needs of another, and his enslaving animal, than it does to his own.
Indeed, we may say that there is no one feature in the whole
psychology of the dog which has been left unaltered by the influence
of man, excepting only those instincts which, being neither useful nor
harmful to man, have never been subject to his operation — such, for
instance, as the instinct of bmying food, turning round to make a
bed before lying down, &c.

I will now turn to another branch of the subject, and one which,
although in my opinion of the greatest importance, has never before
been alluded to ; I mean the local and specific variations of instinct.
By a local variation of instinct, I mean a variation presented by a
species in a state of nature over some particular area of geographical

1884.] on the Darwinian Theory of Instinct. 141

distribution. It is easy to see the importance of such local variations
of instinct as evidence of the transmutation of instinct, if we reflect
that such a local variation is obviously on its way to becoming a new
instinct. For example, the beavers in California have ceased to make
dams, the hyasnas in South Africa have ceased to make burrows, and
there is a squirrel in the neighbourhood of Mount Airy which has
developed carnivorous tastes — running about the trees, not to search
for nuts, but to search for birds, the blood of which it sucks. In
Ohinitahi there is a mountain parrot which before the settlement of
the place was a honey-eater, but when sheep were introduced the birds
found that mutton was more palatable to them than honey, and
quickly abandoned their ancestral habits, exchanging their simple
tastes of honey-eaters for the savageness of tearers of flesh. For the
birds come in flocks, single out a sheep,' tear out the wool, and when the
sheep, exhausted by running about, falls upon its side, they bore into
its abdominal cavity to get at the fat which surrounds the kidneys.

These, I think, are sufficient instances to show what I mean by
local variations of instinct. Turning now to the specific variations,
I think they constitute even stronger evidence of the transmutation
of instinct; for where we find an instinct peculiar to a species, or
not occurring in any other species of the genus, we have the strongest
possible evidence of that particular instinct having been specially
developed in that particular species. And this evidence is of parti-
cular cogency when, as sometimes happens, the change of instinct is
associated with structures pointing to the state of the instincts before
the change. Thus, for example, the dipper belongs to a non-aquatic
family of birds, but has developed the instinct, peculiar to its species,
of diving under water and running along the bottoms of streams.
The species, however, has not had time, since the acquisition of this
instinct, to develop any of the structures which in all aquatic families
of birds are correlated with their aquatic instincts, such as webbed
feet, &c. That is to say, the bird retains all its structural affinities,
while departing from the family type as regards its instincts. A
precisely converse case occurs in certain species of birds belonging to
families which are aquatic in their affinities, these species, however,
having lost their aquatic instincts. Such is the case, for example,
with the upland geese. These are true geese in all their affinities,
retaining the webbed feet, and all the structures suited to the display
of aquatic instincts ; yet they never visit the water. Similarly, there
are species of parrots and tree frogs, which, while still retaining the
structures adapted to climbing trees, have entirely lost their arboreal
habits. Now, short of actual historical or palseontological informa-
tion— which of course in the case of instincts is unattainable, seeing
that instincts, unlike structures, never occur in a fossil state — short,
I say, of actual historical or palaeontological information, we could
have no stronger testimony to the fact of transmutation of instincts
than is furnished by such cases, wherein a particular species while
departing from the instinctive habits of its nearest allies, still retains
the structures which are only suited to the instincts now obsolete.

142 Mr. George J. Romanes [Feb. 8,

This last head of evidence — that, namely, as to local and
specific variations of instincts — differs in one important respect from
all the other heads of evidence which I have previously adduced. For
while these other heads of evidence had reference to the theory
concerning the causes of transmutation, this head of evidence has
reference to the fact of transmutation. Whatever, therefore, we
may think concerning the evidence of the causes, it is quite distinct
from that on which I now rely as conclusive proof of the fact.

I shall now, for the sake of fairness, briefly allude to the more
important cases of special difficulty which lie against Mr. Darwin's
theory of the origin and development of instincts. For the sake
of brevity, however, I shall not allude to those cases of special
difficulty which he has himself treated in the * Origin of Species,'
but shall confine myself to considering the other and most formidable
cases which, after surveying all the known instincts presented by
animals, I have felt to be such.

First, we have the alleged instinct of the scorpion committing
suicide when surrounded by fire. This instinct, if it really exists,
would no doubt present a difficulty, because it is clearly an instinct
which, being not only of no use, but actually detrimental both to the
individual and the species, could never have been developed either by
natural selection or by lapsing intelligence. I may, however, dismiss
this case with a mere mention, because as yet the evidence of the
fact is not sufficiently precise to admit of our definitely accepting it
as a fact.

There can be no such doubt, however, attaching to another
instinct largely prevalent among insects, and which is imquestionably
detrimental, both to the individual and to the species. I allude to
the instinct of flying through flame. This is unquestionably a true
instinct, because it is manifested by all individuals of the same
species. How then are we to explain its occurrence ? I think we
may do so by considering, in the first place, that flame is not a suffi-
ciently common object in nature to lead to any express instinct for
its avoidance; and in the next place by considering that insects
unquestionably manifest a disposition to approach and examine
shining objects. Whether this disposition is due to mere curiosity,
or to a desire to ascertain if the shining objects will, like flowers,
yield them food, is a question which need not here concern us. We
have merely to deal with the fact that such a general disposition is
displayed. Taking then this fact, in connection with the fact that
flame is not a sufficiently common object in nature to lead to any
instinct expressly directed against its avoidance, it seems to me that
the difficulty we are considering is a difficulty no longer.

The shamming-dead of insects appears at first sight a formidable
difficulty, because it is impossible to understand how any insect can
have acquired the idea of death or of its intentional simulation.
This difficulty occurred to Mr. Darwin thirty or forty years ago, and
among his manuscripts I find some very interesting notes of experi-
ments upon the subject. He procured a number of insects which

1884.] on the Barwinian Theory of Instinct. 143

exhibited the instinct, and carefully noted the attitude in which
they feigned death. Some of these insects he then killed, and he
found that in no case did the attitude in which they feigned death
resemble the attitude in which they really died. Consequently we
must conclude that all the instinct amounts to is that of remaining
motionless, and therefore inconspicuous, in the presence of danger ;
and there is no more difficulty in understanding how such an instinct
as this should be developed by natural selection in an animal which
has no great powers of locomotion, than there is in understanding
how the instinct to run away from danger should be developed in
another animal with powers of rapid locomotion. The case, however,
is not, I think, quite so easy to understand in the feigning death of
higher animals. From the evidence which I have I find it almost
impossible to doubt that certain birds, foxes, wolves, and monkeys,
not to mention some other and more doubtful cases, exhibit the
peculiarity of appearing dead when captured by man. As all these
animals are highly locomotive, we cannot here attribute the fact to
protective causes. Moreover, in these animals this behaviour is not
truly instinctive, inasmuch as it is not presented by all, or even most
individuals. As yet, however, observation of the facts is insufficient
to furnish any data as to their explanation, although I may remark
that possibly they may be due to the occurrence of the mesmeric or
hypnotic state, which we know from recent researches may be induced
in animals under the influence of forcible manipulation.

The instinct of feigning injury by certain birds presents a peculiar
difficulty. As we all know, partridges, ducks, and plovers, when they
have a brood of young ones, and are alarmed by the approach of a
carnivorous quadj-uped, such as a dog, will pretend to be wounded,
flapping along the ground with an apparently broken wing in order
to induce the four-footed enemy to follow, and thus to give time for
the young brood to disperse and hide themselves. The difficulty here,
of course, is to understand how the birds can have acquired the idea
of pretending to have a broken wing, for the occasions must be very
rare on which any bird has seen a companion thus wounded followed
by a carnivorous quadruped ; and even if such observations on their
part were of frequent occurrence, it would be difficult to accredit the
animals with so high a degree of reasoning power as would be re-
quired for them intentionally to imitate such movements. When I
consulted Mr. Darwin with reference to this difficulty, he gave me a
provisional hypothesis by which it appeared to him that it might be
met. He said that anyone might observe, when a hen has a brood
of young chickens and is threatened by a dog, that she will alternately
rush at the dog and back again to the chickens. Now if we could
suppose that under these circumstances the mother bird is sufficiently
intelligent to observe that when she runs away from the dog, she is
followed by the dog, it is not impossible that the maternal instinct
might induce her to run away from a brood in order to lead the dog
away from it. If this happened in any cases, natural selection would
tend to preserve those mother birds which adopted this device. I

144: Mr. George J, Bomanes [Feb. 8,

give this explanation as the only one which either Mr. Darwin or
myself has been able to suggest. It will be observed, however, that
it is unsatisfactory, inasmuch as it fails to account for the most pecu-
liar feature of the instinct — I mean the trailing of the apparently
wounded wing.

The instinct of migration furnishes another case of special diffi-
culty, but as I have no space to dwell upon the sundry questions
which it presents for solution, I shall now pass on to the last of the
special difficulties which most urgently call for consideration. The
case to which I refer deserves, I think, to be regarded as the most
extraordinary instinct in the world. There is a species of wasp-like
insect, called the Sphex. This insect lays its eggs in a hole excavated
in the ground. It then flies away and finds a spider, which it stings
in the main nerve-centre of the animal. This has the effect of para-
lysing the spider without killing it. The sphex then carries the now
motionless spider to its nursery, and buries it with the eggs. When
the eggs hatch out the grubs feed on the paralysed prey, which is
then still alive and therefore quite fresh, although it has never been
able to move since ^he time when it was buried. Of course the diffi-
culty here is to understand how the sphex insect can have acquired
so much anatomical and physiological knowledge concerning its prey
as the facts imply. We might indeed suppose, as I in the first in-
stance was led to suppose, that the sting of the sphex and the nerve-
centre of the spider being both organs situated on the median line
of their respective possessors, the striking of the nerve-centre by
the sting might in the first instance have been thus accidentally
favoured, and so have supplied a basis from which natural selection
could work to the perfecting of an instinct always to sting in one
particular spot. But more recently the French entomologist, M.
Fabre, who first noticed these facts with reference to the stinging of
the spider, has observed another species of sphex which preys upon
the grasshopper, and as the nervous system of a grasshopper is more
elongated than the nervous system of a spider, the sphex in this case
has to sting its prey in three successive nerve-centres in order to in-
duce paralysis. Again, still more recently, M. Fabre has found
another species of sphex, which preys upon a caterpillar, and in this
case the animal has to sting its victim in nine successive nerve-
centres. On my consulting Mr. Darwin in reference to these
astonishing facts, he wrote me the following letter : —

" I have been thinking about Pompilius and its allies. Please take
the trouble to read on perforation of the corolla, by Bees, p. 425, of
my ' Cross-fertilisation,' to end of chapter. Bees shows so much
intelligence in their acts, that it seems not improbable to me that the
progenitors of Pompilius originally stung caterpillars and spiders,
&c., in any part of their bodies, and then observed by their intelli-
gence that if they stung them in one particular place, as between
certain segments on the lower side, their prey was at once paralysed.
It does not seem to me at all incredible that this action should then

1884.] 071 the Darwinian TJieory of Instinct. 145

become instinctive, i. e. memory transmitted from one generation to
another. It does not seem necessary to suppose that, when Pompilius
stung its prey in the ganglion it intended, or knew, that the prey
would keep long alive. The development of the larvaB may have been
subsequently modified in relation to their half-dead, instead of wholly
dead prey ; suj)posing that the prey was at first quite killed, which
would have required much stinging. Turn over this in your mind, &c."

I confess that this explanation does not appear to me altogether
satisfactory, although it is no doubt the best explanation that can be
furnished on the lines of Mr. Darwin's theory.

In the brief time at my disposal, I have endeavoured to give an
outline sketch of the main features of the evidence which tends to
show that animal instincts have been slowly C3volved under the influ-
ence of natural causes, the discovery of which we owe to the genius
of Darwin. And, following the example which he has set, I shall
conclude by briefly glancing at a topic of wider interest and more
general importance. The great chapter on Instinct in the ' Origin of
Species ' is brought to a close in the following words : —

" Finally it may not be a logical deduction, but to my imagination
it is far more satisfactory to look at such instincts as the young
cuckoo ejecting its foster-brothers, ants making slaves, the larvae of
ichneumonidse feeding within the live bodies of caterpillars, not as
specially endowed or created instincts, but as small consequences of
one general law leading to the advancement of all organic beings,
namely, multiply, vary, let the strongest live, and the weakest die."

This law may seem to some, as it has seemed to me, a hard one
— hard, I mean as an answer to the question which most of us must
at some time and in some shape have had faith enough to ask, " Shall
not the Judge of all the earth do right ? " For this is a law, rigorous
and universal, that the race shall always be to the swift, the battle
without fail to the strong ; and in announcing it the voice of science
has proclaimed a strangely new beatitude — Blessed are the fit, for
they shall inherit the earth. Surely these are hard sayings, for in the
order of nature they constitute might the only right. But if we are
thus led to feel a sort of moral repugnance to Darwinian teaching, let
us conclude by looking at this matter a little more closely, and in the
light that Darwin himself has flashed upon it in the short passage
which I have quoted.

Eighteen centuries before the publication of this book — the
* Origin of Species ' — one of the founders of Christianity had said,
in words as strong as any that have been used by the Schopeuhauers
and Hartmanns of to-day, " the whole creation groaneth in pain and
travail." Therefore we did not need a Darwin to show us this terrible
truth ; but we did need a Darwin to show us that out of all the evil
which we see, at least so much of good as we have known has come ;
that if this is a world of pain and sorrow, hunger, strife, and death, at
least the sufiering has not been altogether profitless ; that whatever
may be " the far-off divine event to which the whole creation moves,"

Vol. XI. (No. 78.) l

14:6 Mr. G. J. Bomanes on Darwinian Theory of Instinct. [Feb. 8,

the whole creation, in all its pain and in all its travail, is certainly
moving, and this in a direction which makes, if not for " righteous-
ness," at all events for imiDrovement. No doubt the origin of evil has
proved a more difficult problem to solve than the origin of species ;
but, thus viewed, I think that the Darwinian doctrine deserves to be
regarded as in some measure a mitigation of the difficulty : certainly
in no case an aggravation of it. I do not deny that an immense
residuum of difficulty remains, seeing that, so far as we can judge,
the means employed certainly do not appear to be justified by the ends
attained. But even here we ought not to lose sight of the possibility
that, if we could see deeper into the mystery of things, we might find
some further justification of the evil, as unsuspected as was that which,
as it seems to me, Darwin has brought to light. It is not in itself
impossible — perhaps it is not even improbable — that the higher
instincts of man may be pointing with as true an aim as those lower
instincts of the brutes which we have been contemplating. And,
even if the theory of evolution were ever to succeed in furnishing
as satisfactory an explanation of the natural development of the
former as it has of the natural development of the latter, I think that
the truest exponent of the meaning — as distinguished from the causa-
tion— of these higher instincts would still be, not the man of science,
but the poet. Here, therefore, it seems to me, that men of science
ought to leave the question of pain in Nature to be answered, so far
as it can be answered, by the general voice of that humanity which
we all share, and which is able to acknowledge that at least its own
allotment of suffering is not an unmitigated evil.

" For clouds of sorrow deepness lend
To change joy's early rays,
And manhood's eyes alone can send
A grief-ennobled gaze ;

" While to that gaze alone expand
Those skies of fullest thought,
Beneath whose star-lit vault we stand,
Lone, wondering, and untaught."

" We look before and after,
And pine for what is not.
Our sincerest laughter
With some pain is fraught."

Yet still,—

" Our sweetest songs are those that tell of saddest thought."

[G. J. R]

1884.] Professor W. Bohertson Smith on Mohammedan Mahdis. 147

WEEKLY EVENING MEETING,

Friday, May 9, 1884.

The Duke of Northumberland, D.O.L. LL.D. President,
in the Chair.

Professor W. Robertson Smith, M.A. LL.D.

Mohammedan Mahdis.

1. The nameMahdi. Al-Mahdi is not a corruption of Al-muhdi,
and does not mean " the spiritual guide," as has been lately asserted
by scholars both in England and in the East, but as can be proved by
the metre of poems in which it occurs is a passive form (Al-Mahdiyu,
" the rightly-guided one"). The idea of the Mahdi is therefore that of
a chief of Islam who is himself infallibly guided by God.

2. This idea does not belong to the original doctrine of Islam, which
makes Mohammed the seal of the prophets and regards the Koran as
all-suf&cient for the future. Source of Mohammed's theory of revela-
tion by a hook ; its inadequacy to sustain and inspire the Moslems
after his death except in their first career of victory ; the empire of
the Caliphs did not realise the ideal of a theocracy guided wholly by
the Koran even for the Arabs and much less for the Persians.

3. Rise of Messianic ideas ; i:)oints of resemblance to and distinction
from such ideas in Judaism. The Messianic idea takes shape among
the Persians in conformity with their high-flown notions of Kingship
as almost divine. The tragedy of Ali and his family leads the Shia
to accept his family as legitimate and expect the golden age from its
restoration.

4. The doctrine of the hidden Imam arises, on the failure of
successive attempts at religious revolution in favour of the Alidae. In
the darkest times God's sovereignty on earth is rejDresented by a hidden
leader w^ho in due time will appear in victory. The hidden Imam is
the Mahdi, and both names appear together for the first time in
connection with Mohammed ibn al Hanafiya.

5. The Shiite doctrine of the Imam modified so as to become
influential outside the Shia circle : the Ismailis. Abdullah al Kaddah
and his secret society ; the Carmathians ; the Fatimites.

6. Ultimately the doctrine of the Mahdi becomes a stereotyped
element in all popular risings within Islam against oppression, and is
not limited to the Shia. A typical example is found in Ibn Tumert
the Almohade Mahdi. His history proves him to have been an
impostor, not an enthusiast, and this is almost always found to be the
case with political Mahdis. Of unpolitical and unselfish Mahdis the
chief type is the Persian religious teacher Bab.

L 2

148 Professor Dewar [June 1^

WEEKLY EVENING MEETING,

Friday, June 13, 1884.

Warren De La Rub, Esq. M.A. D.C.L. F.R.S. Manager and Vice-
President, in the Chair.

Professor James Dewar, M.A. F.R.S. M.B.L

Researches on Liquefied Gases.*

The two Russian chemists, MM. Wroblewski and Olzewski, who have
recently made such a splendid success in the production and main-
tenance of low temperature, have used in their researches an enlarged
form of the well-known Cailletet apparatus ; but for the purposes of
lecture demonstration, which necessarily involves the projection on a
screen of the actions taking place, the apparatus represented in the
annexed woodcut is more readily and quickly handled, and enables
comparatively large quantities of liquid oxygen to be produced. The
arrangements will be at once understood on looking at the figure,
which is taken from a photograph. The oxygen- or air-reservoir, C,
is made of iron ; it contains gas compressed for convenience to 150
atmosi)heres. A is the stopcock for regulating the pressure of the
gas in the glass tube F, and D is the pressure-manometer, the fine
copper tube which connects the gas-reservoir and the glass tube, F,
being shown at I. The air-pump gauge is marked J, the tube leading
to the double oscillating Bianchi being attached at H. The glass
test-tube G, which contains the liquid ethylene, solid carbonic acid, or
liquid nitrous oxide, which is to be boiled in vacuo, is placed in the
middle of a larger tube. It has holes, shown at E, in the upper part,
so that the cool vapours in their course to the air-pump are forced to
pass round the outside of the vessel and help to guard it from external
radiation. The lower part of the outer cylinder is covered with pieces
of chloride of calcium, shown at K. If a thermometer is used and a
continuous supply of ethylene maintained, the indiarubber cork
through which the tube F passes has two additional apertures for
the purpose of inserting the respective tubes. When the pump has
reduced the pressure to 25 mm., the ethylene has a temperature of
about —140^ C. ; a pressure of between 20 and 30 atmospheres is then
sufficient to produce liquid oxygen in the tube F. The tube F is
5 mm. in diameter and about 3 mm. thick in the walls, and when

* See Professor Dewar's discourse on the Liquefaction of Gases. — ' Proceedings '
of the Royal Institution, vol. viii. p. 657.

1884.J

on Liquefied Gases.

149

filled with fluid oxygen (for projection) holds at least 1-5 cubic
centim. With such a quantity of fluid oxygen it is easy to show its
ebullition at ordinary pressures, and by means of a thermo-junction
to demonstrate the great reduction of temperature which is attendant
on its change of state at atmospheric pressure.

Provided a supply of liquid ethylene can be had, there is no
difficulty in repeating all the experiments of the Eussian observers ;
but as this gas is troublesome to make in quantity, and cannot be
bought like carbonic acid or nitrous oxide, such experiments neces-
sitate a considerable sacrifice of time. It was therefore with con-
siderable satisfaction that I observed the production of liquid oxygen

by the use of solid carbonic acid, or preferably liquid nitrous oxide.
When these substances are employed and the pressure is reduced to
about 25 mm., the temperature of —115° 0, may be taken as that of
the carbonic acid, and — 125° C. as that of the nitrous oxide. As the
critical point of oxygen, according to the Eussian observers, is about
— 113° C., both these cooling agents may be said to lower the tempera-
ture sufficiently to produce liquid oxygen, provided a pressiu'e of the
gas above the critical pressure, which is 50 atmospheres, is at
command. In any case, however, the temperature is near that of the
critical point ; and as it is difficult to maintain the pressure below
about an inch of mercury, the temperature is apt to be rather above

150 Professor Dewar [June 13,

the respective temperatures of -115° C. and -125° C. In order to
get liquefaction conveniently with either of these agents, it is neces-
sary to work at a pressure of oxygen gas from 80 to 100 atmospheres,
and to have the means of producing a sudden expansion when the
compressed gas is cooled to the above-mentioned temperatures. This
is brought about by the use of an additional stopcock, represented in
the fif^ure at B. During the expansion the stopcock at A is closed
and the pressure-manometer carefully observed. No doubt liquid
nitrous oxide is the most convenient substance to use as a cooling
agent ; but as it is apt to get superheated during the reduction of
pressure and boil over with explosive bursts of vapour, it is well to
collect the fluid in a small flask of about 250 cub. centim. capacity,
and to change it into the solid state by connecting the flask with the
air-pump, and then to use the substance in this form. The addition
of alcohol or ether to the solid nitrous oxide makes the body more
transparent, and thereby favours the observations.

It is evident that this apparatus enables the observer to determine
the density of the fluid gases condensed in tbe tube F ; since he has
only to measure the volume of fluid in F, and to collect, by means of
the stopcock B, the whole volume of gas given by the fluid and
condensed vapour, which gives an accurate determination of the total
weight of substance distributed between fluid and vapour in the whole
apparatus. The amount of substance which is required to produce
the vapour is easily found by observing the vapour-pressure of the
liquid gas before expanding it into gas for the volume measurement ;
and while keeping shut the stopcock B, by opening A suddenly until
tliis pressure is just reached and then instantly shutting off the
receiver. If this volume of gas is now measured by opening B as
before, the difference between the two volumes thus collected will
correspond to the real w^eight of substance in the liquid state. A
rough experiment with oxygen near the critical point gave the
density 0*65.

As to the most convenient substance for use as a cooling agent, I
am still of opinion that marsh-gas would be the best ; and I may
take the opportunity of pointing out that the employment of this
body was suggested by me in a communication made to the Chemical
Section of the British Association in 1883. The following extract
from 'Nature,' of October 4, 1883, will prove that my experiments
with liquid marsh-gas were made a year in advance of those made
recently by M. Cailletet * and M. Wroblewski f : —

" Professor Dewar pointed out an important relation between the
critical temperatures and pressures of volatile liquids and their
molecular volumes. The ratio of the critical temperature to the

* " Sur I'emploi du Formeiic pour la production de3 trijs basses temperatures,"
C'imptes Rendus, June 30, 1884.

t " Sur les proprietes du gaz des niarais liquide, et sur son emploi commo
rdfrigeraut," Conqdes liendus, July 21, 1884.

1884.]

on Liquefied Gases.

151

critical pressure is proportional to the molecular volume, so that the
determination of the critical temperature and pressure of a substance
gives us a perfectly independent measure of the molecular volumes.
Prof. Dewar pointed out the great advantage of employing a liquid of
low critical temperature and pressure such as liquid marsh-gas for
producing exceedingly low temperature. He hoped to be able to
approach the absolute zero by the evaporation of liquefied marsh-gas
whose critical temperature was less than — 100° C, and whose
critical pressure was only 39 atmospheres."

I ought to mention that the marsh-gas used in my experiments was
made by the action of water on zinc methyl, and was therefore very
pure, and that the observed critical pressure was not 39 atmospheres,
but 47*6. The following table gives the values of the ratio of the
absolute critical temperature to the critical pressure in the case of a
number of substances. The values for ammonia, sulphuretted hydrogen,
cyanogen, marsh-gas, and hydride of ethyl are new.

Chlorine Clg

Hydrochloric acid HCl

Oxygen Oj

Water H2O

Nitrogen Nj

Hydrogen sulphide .. .. H2S

Ammonia .. " .. .. H3N

Diethylaraine (C2H5)2HN

Nitrous oxide NgO

Sulphurous acid SO.,

Marsh-gas CH,

Acetylene C2H2

Ethylene CjH^

Ethyl hydride C.Hg

Amylene ^sHio

Benzol OgHg

Chloroform CHCI3

Carbon chloride CCI4

Carbonic acid CO2

Bisulphide of carbon . . . . CSg

Cyanogen C2N2

T.

Critical

P.

Critical

T^

temperature.

pressure.

P

0
141-0

83-9

5-0

52-3

860

3-7

-113-0

50-0

3-2

370-0

195-5

3-3

-146-0

35-0

3-6

100-2

92-0

4-0

130-0

115-0

3-5

220-0

38-7

15-4

35-4

75-0

4-1

155-4

7S-9

5-4

- 99-5

50-0

3-5

37-0

68-0

4-5

10-1

51-0

5-5

35-0

45-2

6-8

191-6

33-9

13-7

291-7

60-4

9-3

268-0

54-9

9-9

282-0

57-6

9-6

31-9

77-0

4-0

277-7

78-1

7-0

124-0

61-7

6-4

A glance at the last column of the table shows that a large number
of substances have at their respective critical temperatures simple
volume relations. Thus hydrochloric acid, water, ammonia, and
marsh-gas, the four chemical substances from which the great majority
of chemical compounds may be derived by processes of substitr.tion,
have nearly the same volume ; while the more complex derivatives
show an increased volume which bears a simple ratio to that of the
typical body. As the critical pressures are not known with any great

152

Professor Dewar

[June 13,

accuracy at present, it would be useless to discuss the results with any
severity. All that can be inferred is that the subject is worthy of
farther investigation and promises important generalisation. Sarrau
{Comjjf. Hend. 1882) deduced the critical temperatures and pressures
of hydrogen, oxygen, and nitrogen by the application of Clausius'
formula to the experiments of Amagat ; and it is interesting to
compare his results with the experimental values.

Sarrau's Calculated Values.

Hydrogen

Oxygen

Nitrogen

T.

Critical
temperature.

P.

Critical
pressure.

T
P'

-m

98-9

1-0

-105-4

48-7

3-4

-124

421

3-5

It will be observed that the calculated critical temperatures of
oxygen and nitrogen are remarkably near the truth, being respectively
8° and 22° too high. On the other hand, the values of the ratios of
the calculated critical temperatures and pressures are almost identical
with those obtained by direct experiment. The only peculiarity to
be noted is in the case of hydrogen, which has such a high critical
pressure, and therefore leads to a remarkably small molecular volume
at the critical point. If the values of the T-f-P ratio be taken as
proportional to the molecular volumes, then it is easy to infer the
densities of the fluids at their respective critical temperatures, pro-
vided the density of one standard substance is known by experiment.
The simple formula thus stated is

S' ^ W' V

s w w

where S and S' are the specific gravities of two bodies, W and W
their molecular weights, and V and V their molecular volumes. It
will be convenient to take the density of carbonic acid at the critical
])oint as the standard density to which the others can be referred.
The density of carbonic acid under such conditions may be taken as
0-65. Calculating with the above formula, the density of acetylene
would be 0-32, whereas the experimental number of Ansdell is 0'36.
In the same way the density of hydrochloric acid is found to be
0 • 6, the true value being 0-61. The density of oxygen would be 0 • G3,
and that of nitrogen 0 • 45. The calculated density of hydrogen at its
critical point would be 0 12, if we assume the correctness of Sarrau's
values for the critical temperature and pressure. A\'e may compare
these values with the numbers obtained by Caillctct and Hautcfeuille
for the densities of oxygen, nitrogen, and hydrogen from their

1884.] on Liquefied Gases. 153

experiments on the density of liquid carbonic acid obtained from
mixtures of this body with these gases. At the temperature of 0° C.
the experiments found for oxygen, nitrogen, and hydrogen the
respective values of 0 * 65, 0 • 37, and 0 * 025. It seems that the calculated
values for oxygen and nitrogen are not very far wrong ; but hydrogen
is clearly incorrect. The explanation of this anomaly is probably to
be found in the fact that the calculated molecular volume of hydrogen
is wrong, and that instead of being unity on our scale it ought to be
3 • 5 like oxygen and nitrogen. In fact, the chemist would infer that,
as the difference in the complexity of the molecular structure of
hydrochloric acid, water, ammonia, and marsh-gas does not affect the
molecular volume under the coLditions we are discussing, in all
probability the value for hydrogen would be identical with that of the
above-mentioned bodies. If we adopt this view and change the value
of the T,-J-Pc to 3-5, then the density of the fluid would become 0 • 034,
which is in accordance with the experimental number of Cailletet and
Hautefeuille. An accurate determination of the critical temperature
and pressure of hydrogen, for which, judging from the success of the
experiments of M. Olzewski, chemists will not have to wait long, will
thus be of great interest.

[J.D.]

GENERAL MONTHLY MEETING,

Monday, July 7, 1884.

The Hon. Sir William R. Grove, M.A. D.C.L. LL.D. F.R.S.
Manager and Vice-President, in the Chair.

James Wimnshurst, Esq.

was elected a Member of the Eoyal Institution.

The decease of The Right Hon. Lord Claud Hamilton, a Manager,
was announced from the Chair.

The Managers, at their Meeting this day, appointed Professor
Arthur Gamgee, M.D. F.R.S. Fullerian Professor of Physiology for
three years.

154 General Monthly Meeting. [July 7,

The Presents received since the last Meeting were laid on the
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Academy of Natural Sciences, Philadelphia— Fvoceedrngs, 1884, Part 1. 8vo.

1884.
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Journal, Vol. LIII. Part I. No. 1. 8vo. 1884.
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Ottawa, 1884.
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Civil Engineers' Institution — Minutes of Proceedings, Vol. LXXVI. 8vo. 1884.
Cornwall Polytechnic Society, Royal — Fifty-first Annual Eeport. 8vo. 1883.
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M.U.I the {Authors) — Recherches Expe'rimentales sur la Decharge Electrique
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8vo. 1883.
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1884.
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1884.] General Monthly Meeting. 155

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GENERAL MONTHLY MEETING,

Monday, November 3, 1884.

The Hon. Sir William R. Grove, M.A. D.C.L. LL.D. F.R.S.
Manager and Vice-President, in the Chair.

Charles Hartree, Esq.
Robert Wilson, Esq. C.E.

were elected Members of the Royal Institution.

William Miller Ord, M.D. was elected a Manager in the room
of the late Right Hon. the Lord Claud Hamilton.

The Presents received since the last Meeting were laid on the
table, and the thanks of the Members returned for the same, viz. : —

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156 General Monthly Meeting. [Nov. 3,

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1884.] General Monthly Meeting. 157

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Expedi^ao Scientitica a Serra da Estrella em. 1881. 4to. 1883.
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1884.
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Communications from the International Polar Commission, Part 6. fol. 1884.
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158 General Monthly Meeting. [Nov. 3,

Middlesex Hospital— "Reports for 1882. 8vo. 1884.

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United Seroice Institution, Boyal — Journal, Nos. 124, 125. Svo. 1884.
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1884.
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1884. r

Zoological Society — Proceedings, 1884, Parts 2, 3. Svo,
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1884.] General 3Iontldy Meeting. 159

GENEEAL MONTHLY MEETING,

Monday, December 1, 1884.

The Hon. Sir William R. Grove, M.A. D.C.L. LL.D. F.R.S.

Manager and Vice-President, in the Chair.

Sir Frederick A. Abel, K.C.B. D.C.L. F.R.S.

George Andrews, Esq. J.P.

George Mann Carfrae, M.D.

Rogers Field, Esq.

James P. Harper, M.D.

Samuel Page, Esq.

Boverton Redwood, Esq. F.C.S. F.LC.

Thomas Alfred Routh, Esq.

J. Graham Smith, Esq.

were elected Members of the Royal Institution.

A Report from the Managers was read stating that it had been
found necessary to reconstruct the whole of the drainage system of
the Institution, which had been effected upon the most approved
principles under the advice and supervision of Mr. Rogers Field,
the eminent sanitary engineer.

The following Lecture Arrangements were announced : —

Peofessok Tyndall, D.C.L. F.R.S. ilf.i?. 7.— Six Lectures (adapted to a
Juvenile Auditory) on The Sources of Electricity : Friction-electricity,
Volta-electricity, Pyro-electricity, Thermo-electricity, Magneto-electricity • on
Dec. 27 (Saturday), Dec. 30, 1884 ; Jan. 1, 3, 6, 8, 1885.

Professor Henry N. Moseley, M.A. F.R.S. — Five Lectures on Colonial
Animals : their Structure and Life Histories ; on Tuesdays, Jan. 13, 20, 27,
Feb. 3, 10.

Professor Sidney Colvin, M.A. — Two Lectures on Museums and National
Education ; on Tuesdays, Feb. 17, 24.

Professor Arthur Gamgee, M.D. F.R.S. — Four Lectures on Digestion (the
Subject to be continued after Easter) ; on Tuesdays, March 3, 10, 17, 24.

Professor Dewar, M.A. F.R.S. M.R.I. — Eleven Lectures on The New

Chemistry ; on Thursdays, Jan. 15, 22, 29, Feb. 5, 12, 19, 26, March 5, 12, 19, 26.

Charles Waldstein, Ph.D. Heidelberg, Hon. M.A. Cantab. — Three Lectures on

Greek Scllpture from Pheidias to the Roman Era ; on Saturdays, Jan. 17,

24, 31.

George Johnstone Stoney, Esq. F.R.S. — Three Lectures on The Scale on
■which Nature works, and the Character of some of hek Operations • on
Saturdays, Feb. 7, 14, 21.

Carl Armbruster, Esq. — Five Lectures on The Life, Theory, and Work
of Richard Wagner (with Illustrations, Vocal and Instrumental) ; on Saturdays,
Feb. 28, March 7, 14, 21, 28.

The Presents received since the last Meeting were laid on the
table, and the thanks of the Members returned for the same, viz. : —

160 General Monthly Meeting. [Dec. 1,

The French Government— T>ici\oTmQ\xe Topographique du Departement des Hautes
Alpes. Par J. Roman, ito. 1884.

Inventaire des MSS. de la Bibliotheque Natiouale. Fonds de Cluni. Par
L. Delisle. Svo. 1881.
The Lords of the ^cZin/m%— Nautical Almanac for 1888. Svo. 1884.
Agricultural SocieUj of England, Royal — Journal, Vol. XX. Part 2. 8vo. 1884.
Asiatic Society of Bengal — Proceedings, Nos. G, 7. 8vo. 1884.

Journal, Vol.LlII. Part II. No. 2. Svo. 1884.
Astronomical Society, 2?o?/aZ— Monthly Notices, Vol. XLIV. No, 9. 8vo. 1884.
Bankers, Institute o/— Journal, Vol. V. Part 8. Svo. 1884.
Bell, L Lowthian, Esq. F.R.S. (the Author) — Manufacture of Iron and Steel. Svo.

1884.
British Architects, Royal Institute of — Proceedings, 1884-5, Nos. 2, 3. 4to.
Canada Meteorological Office — Report, 1882. Svo.
Chemical Society — Journal for November, 1884. Svo.

Civil Engineers^ Institution— 'Mmnie^ of Proceedings, Vol. LXXVIII. Svo. 1884.
Devonshire Association for the Advancement of Science, Literature, and Art — Report
and Transactions, Vol. XVI. Svo. 1884.

The Devonshire Domesday, Part 1. Svo. 1884.
Editors — American Journal of Science for November, 1884. Svo.

Analyst for November, 1884. Svo.

Athenseum for November, 1884. 4to.

Chemical News for November, 1884. 4to.

Engineer for November, 1884. fol.

Horological Journal for November, 1884. Svo.

Iron for November, 1884. 4to.

Nature for November, 1884. 4to.

Revue Scientifique and Revue Politique et Litte'raire for November, 1884. 4to.

Science Monthly, Illustrated, for November, 1884.

Telegraphic Journal for November, 1884. Svo.
FranMin Institute— J oumsil, No. 707. Svo. 1884.

Geographical Society, Royal — Proceedings, New Series, Vol. VI. No. 11. Svo. 1884.
Geological Society — Quarterly Journal, No. 160. Svo. 1884.
Harlem, Sociite Hollandaise des Sciences — Archives Neerlandaises, Tome XIX,

Liv. 3. Svo. 1884.
Iron and Steel Institute — Journal for 1884, No. 1. Svo.
Madrid Scientific and Literary Athenxum — Discurso leido por D. S. M. Y. Pren-

dergast. Svo. 1884.
Manchester Geological Society — Transactions, Vol. XVIII. Parts 1 and 2. Svo. 1884.
Meclianiccd Engineers' Institution — Proceedings, No. 3. Svo, 1884.
Medical and Chirurgical Society, Royal — Transactions, Vol, LXVII. Svo. 1884.
Meteorological Office — INIonthly Weather Report, August 1884. 4to.
Meteorological Society, Royal — Quarterly Journal, No. 51. Svo. 1884.

Meteorological Record,'No. 13. Svo. 1884.
Norfolk and Norwich Naturalists' Society — Transactions, Vol. III. Parts 4 and 5.

Svo. 18S3-4.
Odonlological Society of Great Britain — Transactions, Vol. XVII. No. 1. New

Series. Svo. 1884.
Pharmaceutical Society of Great Britain — Journal, November, 1884. Svo.
Royal Society of London — Proceedings, No. 233. Svo. 1884.
Royal Society of New South TFaZes— Journal and Proceedings, Vol. XVII. Svo. 1884.
Society of Arts — Journal, November, 1884. Svo.

St. Pelershourg, Academic des Sciences — Bulletins, Tome XXIX. No. 3. 4to. 1884.
Teyler Museum— AxchWes, Se'rie II. Vol. 2. Part 1. 4to. 1884.
United States Geological Survey — Mineral Resources of the United States. By

A. Williams. Svo. 1883.
Verei)is zur Beforderung des Gewerhjleisses in Preussen — Verliaiidlungen, 1884 :
Hefts. 4to.

ISogal Jfttgtitution of ©reat 13rttam,

WEEKLY EVENING MEETING,

Friday, January 16th, 1885.

The Duke of Northumbebland, D.C.L. LL.D. President, in the

Chair.

Professor Tyndall, D.C.L. LL.D. F.R.S. M.B.I.

On Living Contagia.

By desire of our excellent Honorary Secretary, Sir William Bowman,
to all of whose requests I wish to pay dutiful attention, I have
incurred the risk of standing before you here to-night. I speak thus,
because the time at my disposal, since the conclusion of the Christmas
lectures, has been far from adequate to the preparation of this
discourse. Its subject will, in the main, be a review of the labours of
Pasteur. Before he was born, Arago and Biot had discovered that
rock crystal, cut in a certain direction, possessed the extraordinary
power of rotating the plane of polarized light. Some samples of the
crystal turned the plane of polarization to the right, and others to the
left ; they were therefore called respectively, right-handed and left-
handed crystals. The power disappeared when the crystal was
dissolved, and did not therefore reside in the molecule or unit-brick
of the crystal. Biot afterwards discovered that many liquids possessed
this power of rotation ; and in these cases the rotary force must have
resided in the molecule. Two compounds of tartaric acid had been
discovered which, in solution, turned the plane of polarization, the
one to the right, and the other to the left. The left-handed tartrate
was discovered by Pasteur. Prompted by an observation made in
Germany, Pasteur mixed the pure, right-handed, tartrate of ammonia
with some albumenoid substances, and exposing the mixture to a
gentle heat, found that it fermented. The solution, at first limpid,
became turbid, and this turbidity was proved to be due to the multipli-
cation in the liquid of a minute microscopic fungus. A solution was
then prepared, wherein the right-handed and left-handed tartrates
were so equally balanced that they completely neutralized each other.
The solution had at first no power over polarized light. But
immediately after fermentation had begun, or in other words, after
the fungus had begun to multiply, a rotation to the left was observed.
This increased until it reached a maximum, when it was found that
all the right-handed tartrate had disappeared from the liquid, leaving
the left-handed tartrate behind. Now the two tartrates were alike in
chemical composition ; they possessed the same atoms and the same
proportion of atoms ; but owing to a difference in the structure of
their molecules, one of them turned the plane of polarization to the
Vol. XI. (No. 79.) m

162 Professor Tyndall [Jan. 16,

right and the other to the left. This self-same molecular peculiarity
enabled the little fungus to live and thrive upon the one class of
molecules, while leaving the other class intact.

In making these extremely curious observations, Pasteur found
himself confronted by the general question of fermentation. In 1837,
Cagniard - Latour and Schwann had independently proved the
alcoholic ferment to be a budding microscopic vegetable. Spui-red by
this discovery and strengthened by his own, Pasteur rapidly closed
witb the idea that all ferments were living organisms, and that the
substances usually regarded as ferments were in reality the food of
the! ferments. Thus the sugar of the wort in the manufacture of beer,
the sugar of the grape in the manufacture of wine, the sugar of the
cherry in the manufacture of kirsch, the sugar of the apple in the
manufacture of cider, and, it might perhaps be added, the sugar of
the gooseberry in the manufacture of champagne, is decomposed by
the little organism which derives from the sugar the oxygen necessary
for its existence. One of the products of this decomposition is our
familiar alcohol.

When I studied at the University of Marburg, one of the luxuries
of student life consisted of pancakes and sour milk. Whence this
pleasant acidity? It was proved by Pasteur to be due to living
microscopic rods — the lactic acid ferment — which grew and multiplied
in the milk. The butyric acid ferment was also proved to be an
organism. The acidity of sour wines was proved to be due to a
minute microscopic plant called Mycoderma aceti. By the action of
this plant, wine is transformed into vinegar, the vast industries of
Orleans and other places being based upon its operations. Ruinous
losses had frequently been incurred by the souring of French wines,
but Pasteur proved to the wine-grower that by simply heating his
wine to a temperature of 122*^ Fahrenheit — a temperature which in no
way alters the quality of the wine— the injurious organisms are all
destroyed, the wine being thereby permanently protected.

The sourness, putridity, and other maladies of beer were traced
by Pasteur to special organisms — ferments of disease, as he rightly
calls them— which, mingling with the torula or true yeast plant,
added their offensive products to the pure alcohol. Vast losses were
frequently incurred by the use of bad yeast, where five minutes'
examination with the microscope would have revealed to the brewer
the cause of the badness, and prevented him from using the yeast.
Under the head of fermentation, Pasteur rightly placed the phe-
nomena of putrefaction, which he studied with admirable thorough-
ness and skill. All the objectionable odours of putrefying flesh
result from decompositions set up by microscopic organisms. Keep
your meat free from such organisms — kill them by heat or deaden
them by cold — and you can have no putrefaction. Schwann, whom I
have already mentioned, was the first to upset the doctrine propounded
by Gay Lussac, that putrefaction was caused by atmospheric oxygen,
and to prove that it was not the air, but living germs suspended in

1885.] on Living Contagia. 163

the air which caused flesh to putrefy. To his succeeded the far more
elaborate labours of Pasteur. Note the unlooked-for issues to which
these labours have led. With the boldness and penetration which
belong to genius, Lister extended to living matter the generalisation
established by Schwann and Pasteur in regard to dead matter. With
admirable clearness of vision, he pictured the atmospheric germs
falling upon the wounds in our hospitals and setting at nought, by
subsequent mortification, the skill of the best operator. ' Lister
insisted that the treatment after the operation was quite as important
as the operation itself. He devised effectual means for destroying
these putrefactive organisms, and thus established that antiseptic
system of surgery which is one of the greatest and most beneficent
achievements of the age in which we live.

We now stand upon the margin of a new field which invited the
activity of Pasteur. In 1865, owing to a plague among the worms,
the silk husbandry of France had fallen into ruin. The worms
sickened and died wholesale ; and, because of the spots upon their skin,
the malady was called Pebrine. A minute corpuscular organism,
called Micrococcus ovatuSj had been discovered by Cornalia in the blood
and organs of the diseased worms, and, acquainted as he was with the
action of living ferments, Pasteur was prepared to see in the corpuscles
the cause of the plague. He followed them through all the phases of
the insect's life — through the egg, through the worm, through the
chrysalis, through the moth. He proved that the germ of the malady
might be present in the egg, and still escape observation. In the
worm also it might elude the search of the microscope. But in the
moth it reached a development so distinct as to render its detection
inevitable. From healthy moths, healthy eggs were sure to spring ;
from healthy eggs vigorous worms, from vigorous worms fine cocoons ;
so that the great problem of restoring to France its silk industry was
reduced by Pasteur to the separation of the healthy from the un-
healthy moths, the destruction of the latter and the exclusive employ-
ment for breeding of the eggs of the former.

While discovering the cause of pebrine and the way to combat it,
Pasteur inquired how the disease was spread ; pursuing in this inquiry
the only way open to the investigator. He infected healthy worms
by smearing with corpusculous matter the mulberry leaves on which
they fed. He infected them by inoculation, and showed how they
infected each other by the wounds and scratches of their own claws.
Bringing together healthy and diseased worms, the healthy ones, like
their smitten companions, soon sickened and died. He produced
infection at a distance, by wafting corpusculous dust through the air.
All the modes by which infection is spread among human beings were
thus illustrated. Was it cruel to treat the healthy silkworms in this
fashion ? It may have been for the moment ; but Pasteur's investiga-
tion swept a deadly epidemic from the soil of France ; and, for the
units slain during the inquiry, millions have been preserved.

In May 1876, there appeared in Cohn's ' Beitrage zur Pflanzen-

M 2

164 Professor Tyndall [Jan. 16,

Zoologie ' a memoir on a disorder called by the French charhon. by the
Germans Milzhrand, and by tlie English, woolsorters' disease, malig-
nant pustule, or S2)lenic fever. This memoir seemed to me to mark
an epoch in the history of a most deadly malady, and also in the
history of the germ theory itself. The coutagium of splenic fever is
an organism which apj^ears as rods in the blood and tissues of men
and auimals smitten by the fever. The name of the organism is
Bacillus anthracis, and with consummate skill, patience, and penetra-
tion, in the memoir referred to, its life-history was completely
followed out. It was easy to predict that the author of the paper,
who at that time held a small appointment in the neighbourhood of
Breslau, would soon find himself transferred to a hioher postion.
The admirable worker to wliom I here refer was Dr. Koch, and the
next time I heard of him he was head of the Imperial Sanitary
Institute of Berlin.

Koch was not the discoverer of the parasite of sjDlen^'c fever. As
early as 1850, Davaine and Eeyer had observed the microscopic rods
in the blood of animals that had died of the disease. But they were
at the time unconscious of the significance of their observation, and
for thirteen years allowed the matter to drop. Eoused by the
researches of Pasteur, Davaine returned to the subject in 1863, and
then affirmed the rods to be the contagium of the fever. He was
opposed by some of his own countrymen, and hot discussions on the
subject were carried on in the Academy of Sciences and elsewhere.
PoUender, Brauell, and Burden Sanderson made important contribu-
tions to the etiology of the disease; but knowledge was contradictory,
uncertain, and incomplete till Koch grasped the subject in 1876,
and, with the ardour of a youth and the caution of a veteran in
microscopic research, cultivated the organism, reconciled contradic-
ti(ms, and placed beyond the possibility of doubt the parasitic
character of splenic fever. This result again was achieved by the
only means open to the investigator ; namely, by the inoculation of
healthy animals with a living virus derived either from artificial
cultivations or from other animals smitten with the disease. An
interval of twenty- six years from the first observation of Davaine, was
closed by Koch's memorable investigation.

Pasteur long held himself aloof from any direct examination of
the germ theory. But he must have been profoundly impressed
by his own experiments on silkworms, and he was at length made
aware of the vast promise of the field of inquiry which his own
researches and those of others had opened up. Attacking the subject
of splenic fever, he soon gave evidence of the genius which charac-
terised his former work. Take an illustration. Koch had proved that
while mice and guinea pigs were infallibly killed by Bacillus anthracis,
birds were able to defy it. Why ? Here is the answer given by Pasteur.
The higher limit of temperature which arrests the multiplication
of the bucillus in infusions is 44° Cent. (111° Eahr.) The tempera-
ture of the blood of birds is from 41° to 42^ Cent. It is therefore

1885.] on Living Contagia. 165

close to the prohibitary temperature. Now the bloorl-corpuscles of a
living fowl are sure to offer a certain resistance to any attempt to
deprive them of tlitir oxygen. But close to its prohibitory tempera-
ture, the anthrax ctntagiiim may be expected to be enfeebled, and the
question arises : May not the blood-corpuscles in those circumstances
be ahle successfully to combat the organism? Experiment al(»ne
could decide, and Pasteur made the experiment. He lowered, by
chilling in cold water, the temperature of a fowl 4P \ and while in
this condition inoculated it with the splenic fever parasite. In
twenty-four hours the fowl was dead. Inoculating another fowl
similarly chilled, he permitted the fever to come to a head, and then
transferred the fowl to a warm chnmber. The career of the parasite
was soon stopped, and in a few hours the health of the fowl was
restored. Tlie issues of this experiment, as suggesting the application
of heat or cold in the fevers which afflict humanity, are incalculable.

Pasteur next attacked the fatal malady of chicken cholera. The
parasite of this disease had been discovered before him ; but, by a
method now universally applied, he rendered the solution of the
problem sure. Into chicken broth, boiled sufficiently long to destroy
all germs with which it may be contaminated, let a minute drop of
the blood of a fowl suffering from chicken cholera be introduced.
The organisms of the bluod increase and multiply, until they finally
invade the whole of the nutritive liquid. With the point of a needle,
let a speck of this liquid be introduced into a second sterilised
infusion. As before, the organisms multiply until the liquid becomes
thick with them. Let a speck, taken on the needle-point from this
second cultivation, be communicated to a third sterilised infusion.
A similar result will be observed. In this way any number of
generations of the organism may be cultivated, and whatever foreign
matter, chemical poison, or otherwise, might attach itself to the drop
of blood first taken from the animal, is thus washed away. This is
the method oi " pure culture" now pursued. After fifty cultures, let
a speck of the infected infusion be introduced into the blood of a
healthy fowl. Cholera and death are the consequence. The organism
is as virulent as at first. But here we come to a point of supreme
importance. The virulence is maintained on one condition. The
cultures must rapidly succeed each other. When the infusion with
its swarming organisms is allowed to remain for a week, for a
fortnight, fur a month, for two months, without renewal, the power of
the organism gradually diminishes, and after a certain time, though
it may be able to produce malaise, it is not able to produce death. It
thus becomes what Pasteur calls an attenuated virus — a true vaccine.
For, if with the organism in this condition, a fowl be inoculated, the
subsequent malaise passes away, and the fowl is afterwards proof
against the organism in its most virulent form.

Pasteur next laid hold of the murderous virus of splenic fever,
and succeeded in rendering it not only harmless to life, but a sure
protection against the assaults of the disease. It was soon noised

166 Professor Tyndall [Jan. 16,

abroad among the sheep and cattle dealers of France that he had
overcome this contagium. In various districts of France the disorder
was very deadly. He confined himself for a time, to what might be
called laboratory experiments ; but believing that a principle which
had proved true in small things would also prove true in large, he had
the boldness to accept an invitation from the President of the
Agricultural Society of Melun, to make an experiment publicly, on
what might be called an agricultural scale.

He had placed at his disposal a flock of sheep which he divided
into two groups. The members of one group were all vaccinated with
the " attenuated " virus of splenic fever, while the members of the
other group were left un vaccinated. A number of cows were similarly
treated. The question to be decided was : Would the mild virus act
as a protection ? Experiment alone could answer this question.
Fourteen days subsequent to the first inoculation, all the sheep and
all the cows, vaccinated and unvaccinated, were inoculated with a
highly virulent virus. Three days afterwards, more than two hundred
persons, including among them journalists, farmers, lawyers, and
public men, assembled to witness the result. Pasteur is capable of
elation, and he must have felt elated at the shout of admiration which
hailed the success of his exiDeriment. Of 25 sheep inoculated with a
virulent virus, but unprotected by vaccination, 21 were already dead,
while the remaining 4 were dying. The 25 vaccinated sheep, which
had also received the deadly virus into their blood, were in full
health and gaiety. The unvaccinated cows showed tumours at the
place of inoculation, and were so prostrate with fever as to be unable
to eat. The vaccinated cows remained perfectly well, showing neither
tumours nor fever, nor even any rise of temperature, and consumed
their food with appetites unimpaired. Pasteur was soon overwhelmed
with applications for this " benign vaccine." At the end of 1881,
close upon 34,000 animals had been vaccinated, while in 1883 the
number rose to nearly 500,000.

Malignant pustule is a very loathsome disease, and the sufferings
of animals dying from it are obviously very great. An account of the
symptoms which precede death would be by no means pleasant read-
ing. Imagine then one of those tender-hearted gentlemen who write
about torture and cruelty in the Times, entering the laboratory of
Pasteur and seeing him sow this malady among his unprotected
victims! Some years ago, accompanied by my wife, I visited the
laboratory of the Ecole Normale, and we were shown there by Pasteur
himself, the formidable organism in the investigation of which he was
then engaged. It was curious to reflect how a thing so mean could
exercise such deadly power over man and brute. Both Pasteur and
his assistants had to be very wary in dealing with this organism, for
either the adult bacillus, or one of its spores, entering the blood by
tlie sliglitest scratch on the skin, would have proved fatal to the
individual infected by it. In a room adjacent to the laboratory stood
a large cage, containing guinea-pigs and rabbits, some sprightly, and

1885.] on Living Contagia. 167

munching their food ; some drowsy and languid ; some mortally sick,
some in the last agony, and some in the rigor of death. It was
subsequent to these experiments that Pasteur operated on larger
animals, subjecting them to the " tortures " I have just described.
"What would a tender-hearted bishop * have said under these circum-
stances ? Were it in his power to do so, would he not have invoked
the arm of the law to stay such damning cruelty ? Most assuredly he
would. And yet, in doing so, he would have affixed the brand of
cruelty upon himself. In lieu of the few animals saved from the
operations of the man of science, he would have handed over tens ol
thousands of the same animals to the fearful ravages of splenic fever.

[J. T.]

* The Bishop of Oxford had been just writing to the Times on the cruelties
of experimental physiology.

168 Frojessor H. N. Moseley [Jan. 23,

WEEKLY EVENING MEETING,

Friday, January 23, 1885.

8iB Febdeeiok Beamwell, F.R.S. Manager and Vice-President,
in the Chair.

Peofessor H. N. Moseley, M.A. F.E.S.

The Fauna of the Seashore.

The marine fauna of the globe may be divided into the littoral, the
deep-sea, and the pelagic faunas. Of the three regions inhabited by
these faunas, the littoral is the one in which the conditions are most
favourable for the development of new forms through the working of
the principle of natural selection. As Professor Loven writes, " The
littoral region comprises the favoured zones of the sea where light
and shade, a genial temperature, currents changeable in power and
direction, a rich vegetation spread over extensive areas, abundance of
food, of prey to allure, of enemies to withstand or evade, represent an
infinitude of agents competent to call into ]}laj the tendencies to vary
which are embodied in each species, and always ready by modifying
its parts to respond to the influences of external conditions." It is
consequently in this littoral zone, where the water is more than
elsewhere favourable for respiration, and where constant variation of
conditions is produced by the tides, that all the main groups of the
animal kingdom first came into existence ; and here also, probably,
where the first attached and branching plants were developed, thus
establishing a supply of food for the colonisation of the region by
animals.

The animals inhabiting the littoral zone are most variously modi-
fied, to enable them to withstand the peculiar physical conditions
which they encounter there. Hence the origin of all hard shells
and skeletons of marine invertebrata, various adaptations for boring
in sand, the adoption of the stationary fixed condition, and similar
arrangements. Almost all the shore forms of animals, however
inert in the adult condition, pass through in embryological develop-
ment free-swimming larval stages which are closely alike in form for
very widely difierent groups of animals. Thus the oyster and most other
mollusca of all varieties and shapes when adult, develop from a free-
swimming pelagic trochosphere larva, and so do many annelids. Such
larvae cannot be of subsequent origin to the adults of which they are
phases. If such were the case, they would not have become so closely
alike in structure. In reality they represent the common ancestors
from which all the forms in which they occur were derived, and as
all these larvjo are pelagic in habits and structure, it follows that the

1885. J on the Fauna of the Seashore. 169

inhabitants of the shores were derived from pelagic ancestors. The
earliest plants were also probably free-swimming.

In the case of the cirripedia there can be no doubt, from the
history of their development, that they were originally pelagic, and
have become specially modified for coast life ; and in the case of the
echiuoderms the only possible explanation of the remarkable simi-
larity of the larval forms of the various, groups of widely differing
adults is that these pelagic larvae represent a common ancestor of the
group. The madreporarian corals all spring from a pelagic larva.
The colonial forms probably owe their origin and that of their
skeletons to the advantage gained by them in the formation of reefs,
and the increase in facilities of respiration consequent on the
production of surf. In the deep sea they are very scarce.

The vertebrata are sprung from a very simple free-swimming
ancestor, as shown by the ciliated gastrula stage of Amphioxus.
The ascidians afford another evident instance of the extreme
modification of pelagic forms for littoral existence.

The peculiar mode of respiration of vertebrata by means of gill-
slits occurs in no other animal group except in Balanoglossus, which
will probably shortly be included amongst vertebrata. Possibly gill-
slits as a respiratory apparatus first arose in a littoral form, such as
Balanoglossus, and hence their presence at the anterior end of the
body, that nearest to the surface in an animal buried in sand. The
connection of Balanoglossus witli the echinoderms through Tornaria is
very remarkable. Possibly Amphioxus once had a Tornaria stage,
and has lost it just as one species of Balanoglossus has lost it, as
Mr. Bateson has lately discovered.

The littoral zone has given off colonists to the other three
faunal regions. The entire terrestrial fauna has sprung from
colonists contributed by the littoral zone. Every terrestrial verte-
brate bears in its early stages the gill-slits of its aquatic ancestor.
All organs of aerial respiration are mere modifications of apparatus
previously connected with aquatic respiration, excepting, perhaps,
in the case of Tracheata, tracheae being most likely modifications of
skin-glands, as appears probable from their condition in Peripatus.
The oldest known air-breathing animals are insects and scorpions,
which have lately been found in Silurian strata. Prof. Pay Lan-
kester believes the lungs of scorpions to be homogenous with the
gill-plates of Limulus. Birds were possibly originally developed
in connection with the seashore, and were fish-eaters like the tooth-
bearing Hesperornis.

The fauna of the coast has not only given rise to the terrestrial
and fresh-water fauna ; it has from time to time given additions to the
pelagic fauna in return for having thence derived its own starting-
points. It has also received some of these pelagic forms back again, to
assume afresh littoral existence.

The deep-sea fauna has probably been formed almost entirely
from the littoral, not in the remotest antiquity, but only after food

170 Professor H. N. Moseley on the Fauna of the Seashore. [Jan. 23,

derived from the debris of the littoral and terrestrial faunas and
floras became abundant.

It is because all terrestrial and deep-sea ainmal forms have passed
through a littoral phase of existence, and that the littoral animals
retain far better than those of any other faunal region the recapitu-
lative larval phases by means of which alone the true histories of
their origins can be recovered, that marine zoological laboratories on
the coast have made so many brilliant discoveries in zoology during
late years.

The lecturer concluded by appealing for assistance, in the way of
subscriptions to the funds ol the Marine Biological Association of
Great Britain, the object of which is to construct a marine labora-
tory on the English coast for the purpose of researches such as
those referred to. England is at present without any such laboratory,
although nearly all Continental countries possess them.

[H. N. M.]

1885.] Professor Ernst Paiier on Living Composers, dc. 171

WEEKLY EVENING MEETING,

Friday, January 30, 1885.

Sir Frederick Pollock, Bart. M.A. Manager and Vice-President,

in the Chair.

Professor Ernst Pauer.

A short review of the Woi'hs of Living Composers for the Pianoforte.

The Musical Illustrations were given by Mr. Max Pauer.

The lecturer began by observing that it is a matter of great difficulty
to become acquainted with new musical works ; with musicians it is
not like with authors, whose works are reported and criticised in the
different magazines, and are afterwards perused by an eager public
through the means of the circulating libraries. It requires a great
amount of technical efficiency and musical knowledge to execute and
read satisfactorily a new pianoforte piece — and even when such
physical and mental powers are possessed, it is generally only a very
small circle which can profit by it.

In the public concerts a very strong feeling of conservatism exists
with regard to the composition of concert-programmes, the general
public really and truly not caring to listen to new works of composers
whose names are not yet universally accredited. In this respect, the
painters and sculptors enjoy a most decided advantage — their works
are to be seen either in the great annual Exhibition of the Eoyal
Academy or in one or the other of the numerous smaller galleries,
and thus the public is able to become acquainted with the talent and
genius of English, French, Belgian, German, Italian, Eussian,
Norwegian, &c., painters ; excellent notices are written by competent
critics and appear in the principal daily papers, enabling the public
who are fond to be guided in such matters, to detect what is to be
admired and praised, and what on the other hand may be treated with
comparative indifference. To hold a similar small exhibition of
musical cabinet-pictures and to add some verbal critical notes is
attempted this evening. The chosen works show the individuality
and characteristic talent of the composers. Several well-known and
justly famous composers — still living — have been omitted — for
instance Franz Liszt, Wilhelm Taubert, Stephen Heller, Adolph
Henselt, Niels Gade — all these musicians have attained an age
ranging between 65 and 75 years, and thus belong more to the past
than to the present generation. It is also necessary to leave out

172 Professor Ernst Pauer [Jan. 30,

several highly esteemed younger composers, such as Friedrich Gerns-
heim, Woldemar Bargiel, Salomon Jadassohn, Julius Schulhoff,
Camille St. Saens, Heinrich Hofmann — but their turn may come on
a future occasion.

The spirit and expression of our present pianoforte-music is
decidedly that of elegance, more cleverness than feeling, and a very
carefully considered refinement. None of the present composers
possesses the genius of a Mozart, Beethoven or Schubert; but they may
lav claim to a talent of the highest order, and have by earnest study,
undaunted perseverance, and accomplishment certainly attained a
high degree of artistic excellence. All the present composers have
more or less been influenced by Mendelssohn, Chopin, Schumann, and
Richard Wagner. Some of the works are made up from apparently
very insignificant material, but the cleverness with which this
material is handled is so conspicuous that to the less experienced ear
it sounds like the product of a great genius. We begin our review
with the celebrated

1. Anton Rubinstein
(Born November 30, 1830, at Wechwotynez, near Jassy).

(a) Nocturne in G.

(b) Capriccio in E flat.

The Nocturne is full of sweet expression, slightly tinged with
exquisite melancholy ; it is more remarkable for the euphony of its
tone effect than for the richness and solidity of its content. The
Capriccio is a crisp, interesting and sparkling Scherzo, which exhibits
greater care in thematic work than Rubinstein generally devotes to
his compositions. The characteristic qualities of the celebrated
composer are a strong and impulsive feeling, a certain amount of
elegance, and undoubted energy.

No. 2. — Johannes Brahms
(Born May 7, 1833, at Hamburg).

(a) Intermezzo in A flat.

(b) Capriccio in B Minor.

The same high position Richard Wagner holds in the domain of
dramatic music, Brahms occupies in the realm of instrumental music ;
the basis on which Brahms's works rest is a scientific one, but it is
a science suffused with modern feeling and the harmonies which
complete the scientific matter are such as derive their origin from
the romantic phase of our art. There is an intellectual agency in his
pieces which will perhaps not strike the listener at once, but which
is found out by degrees. The Intermezzo is actually a mere sketch,
which however, is complete in itself, full of charm, and showing a

1885.] on Worlcs of Living Composers for the Pianoforte. 173

rare cleverness in handling a phrase of singular nobility and beauty.
In the Cap'iccio we admire ingenuity and spirit, humour and fresh-
ness of invention, it is a piece full of caprice and obstinacy but also
of gentleness and amiability.

No. 3. — Joseph Rheinberger

(Born March 17, 1839, at Vaduz, Lichtenstein).

Toccata, op. 12.

This composer is an exceedingly clever, thoroughly instructed,
and experienced artist; the chief qualities of his works are a natural
and fresh healthy expression, an agreeable unpretentiousness, and
decided strength. The Toccata is a truly excellent and spirited
composition, full of fire, variety, and enthusiasm.

No. 4. — Peter Tschaikowsky
(Born December 25, 1840, at Wotkinski, Government of Perm).

(a) Chanson sans paroles in F.

(b) Trn^a, inE.

This composer represents the national Russian element; his works
surprise us by their staitling changes of harmony, while their fresh,
pulsating rhythmical life offers a decided charm, and the construc-
tion of his melodies excites our interest by their quaintness and
simplicity.

No. 5. — Edvaed Grieg
(Born June 15, 1843, at Bergen, Norway).

(a) " On the Mountains."

(b) " Norwegian Bridal Procession passing hy."

E. Grieg's pianoforte-pieces take hold at once of the attention and
favour of the amateurs; their striking originality and individuality
cannot fail to excite ioterest; his works are eminently influenced by
Norwegian melodies, and thus they represent in a most pleasant
manner Norwegian life and character. The first piece possesses a
rugred, sturdy, healthy force and vigour ; the second may be justly
considered as one of the most delicious musical genre-pictures.

No. 6. — Xaver Scharwenka

(Born January 6, 1850, at Samter, Posen).

Polish Dances, op. 3.

In Scharwenka we possess one of the most richly gifted composers
of the present time ; his melodies are fresh, genuine, and well

174 Professor Ernst Pauer on Living Composers, &c. [Jan. 30,

constructed, his harmonies bokl and vigorous, and the moduhitions
natural and nowhere forced ; in his rhythmical expression he is
generally happy, and offers a good deal of variety. Scharwenka has
been reproached for writing his Polish dances in the style of Chopin,
but in as far as a national Polish dance, like the Mazurka (Masur,
Mazurek), possesses certain rhythmical and harmonious features,
which make it actually the Polish dance and not a Russian or German
dance, and in as far as Chopin has repeatedly employed these features
in his Mazurkas, there is no reason why another composer — also
writing Mazurkas — should not employ the same means. The dif-
ference between Chopin's and Scharwenka's Polish dances consists in
the first having a rather feminine, plaintive, and melancholy ex-
pression, whilst the latter (Scharwenka's) are expressive of manly-
vigour, chivalrous energy, and decided firmness.

No. 7. — Jean Loms Nicode
(Born August 12, 1853, at Jerezik, near Posen).

(a) Canzonetta.

(b) Tarentella.

Nicode's pieces (only published since a few years) struck at once
a sympathetic chord in the hearts of the public, for some of his
shorter pieces already enjoy a great, genuine, and well -deserved
popularity. He is peculiarly happy in his modulations, and his
harmonies are singularly euphonious. The '■'-Canzonetta" is a genre-
piece of a remarkably happy conception and of most refined work-
manship. The " Tarentella " introduces a national Neapolitan air,
which lends great charm to it, and produces a decided effect.

No. 8. MORITZ MOSZKOWSKI

(Born August 23, 1854, at Breslau).

(a) Germany ) ^^.^^ ^^^ g^.^^ « ^^^^ Foreign Parts," op. 23.

(b) Hungary ) o j i

The great beauty and the delightful freshness and rhythmical
charm of Moszkowski's Spanish Dances, op. 12, Album cspagnol, op.
21, and the Suite '' From Foreign Parts," op. 23, at once caught the
public ear, and found their way into the libraries of British amateurs.
Moszkowski is undoubtedly a highly talented composer, and is able
to invent beautiful melodies, which he understands to surround with
exc[uisito harmonies.

[E. P.]

1885.1 General Monthly Meeting. 175

GENERAL MONTHLY MEETING,

Monday, February 2, 1885.

The Hon. Sir William R. Grove, M.A. D.C.L. F.R.S. Manager and
Vice-President, in the Chair.

Arthur Edward Durham, Esq. F.R.C.S.
James Love, Esq. F.E.A.S. F.G.S. F.Z.S.

were elected Members of the Royal Institution.

With reference to the report of the Managers read at the previous
meeting, a Resolution was unanimously passed authorizing the Sale
of a part of the New Three per Cent. Consols belonging to and
standing in the name of the Royal Institution of Great Britain, suffi-
cient to raise a sum of not exceeding £2000 cash.

The Special Thanks of the Members were returned for the
following donations to the Fund for the Promotion of Experimental
Research : —

Warren de la Rue, Esq £100

Sir Frederick Bram well . . . . £50

The Special Thanks of the Members were returned to Miss Julia
Moore, for her present, on behalf of her sister, the late Miss Harriet
Jane Moore, M.R.L, of a fine copy of Dante's 'Divina Commedia,'
printed in 1564 ; and also two Water-Colour Drawings of the Old
Laboratory of the Royal Institution, including Portraits of Professor
Faraday, and his Assistant, Mr. Anderson, painted by Miss
H. J. Moore in 1852.

The Presents received since the last Meeting were laid on the
table, and the thanks of the Members returned for the same, viz. :—

FROM

The Governor-General of India — Geolo,2:ical Survey of India: Palaeontologia

Indica : Series X. Vol. III. Part 5 ; Series XIV. Vol. I. Part 3, Fasc. 4. 4to.

1884.
Records, Vol. XVII. Part 4. 8vo. 1884.
The Secretarij of State for India— Lists of the Antiquarian Remains in Madras.

By R. Sewell. Vol. II. 4to. 1884.
Accademia del Lincei, Reale, Roma — Atti, Serie Terza : Transunti. Vol. VIII.

Fasc. 16. 4to. 1884.
Academy of Natural Sciences, Philadelphia — Proceedings, 1884, Part 2. 8vo.
Amsterdam Royal Society of Zoology — Bijdrageu tot de Dierkuude. Afl. 10. 4to.

1884.
Tijdschrift voor de Dierkuude. Jaar. 5, Afl. I. and II. 8vo. 1884.

176 General Monthly Meeting. [Feb. 2,

Antiquaries, Society of — Proceedings, Second Series, Vol. X. No. 1. 8vo. 1884.
Asiatic Society, Royal — Journal, Vol. XVII, Part 1. 8vo. 1885.
Asiatic Society of Bengal — Proceedings, Nos. 8, 9. 8vo. 1884.

Journal, Vol. LIIL Part 1, No. 2. 8vo. 1884.
Astronomical Society, Royal — Monthly Notices, Vol. XLV. Nos. 1, 2. 8vo,

1884.
Basel Naturforschende Gesellschaft — Verb and lungen, 7te Thiel, 2te8 Heft. 1884.
Birmingham Fhilosopliical Society — Proceedings, Vol. IV. Part 1. 8vo. 1884.
British Architects, Royal Institute of — Proceedings, 1884-5, Nos. 4, 5, 6, 7. 4to.
Chemical Society — Journal for December 1884, January 1885. 8vo.
Chief Signal Officer, U. S. Army — Professional Papers, No. 14. 4to. 1884.
Crisp, Frank, Esq. LL.B. F.L.S. &c. M.R.I, (the Editor)— Jomnal of the Royal

Microscopical Society, Series II. Vol. IV. Part 6. 8vo. 1884.
Daz : Societe de Borda — Bulletins, 2*^ Serie Neuvieme Annee : Trimestre 4. 8vo.

1884.
Buha, Surgeon-Major Theodore, MD. F.R.C.S M.R.I, {the ^wf/ior)— Remarks on

the Life and Labours of A. C-'oma de Koros. (Journ. Asiatic See. 1884.)
East India Association — Journal, Vol. XVII. No. 1. 8vo. 1885.
Editors — American Journal of Science for December 1884, January 1885. Svo,
Analyst for December 1884, January 1885. 8vo.
Angler's Note Book, No. 5. 4to. 1884.
Athenaeum for December 1884, January 1885. 4to.
Chemical News for December 1884, January 1885. 4to.
Eastward Ho! Vols. L and IL No. 7. 8vo. 1884.
Engineer for December 1884, January 1885. fol.
Horological Journal for December 1884, January 1885. 8vo.
Iron for December 1884, January 1885. 4to.
Nature for December 1884, January 1885. 4to.
Revue Scientifique and Revue Politique et Litteraire for December 1884,

January 1885. 4to.
Science Monthly, Illustrated, for December 1884, January 1885. Svo.
Telegraphic Journal for Deceujber 18^4, January 1885. '8vo.
Franklin Institute — Journal, Nos. 708, 709. 8vo. 1884.
Eraser, Lieut- Colonel A. T. R.E. i¥.E.J,— Atharva Veda Sanhita. Edited by

Sewaklal Kaisandas. Svo. Bombay, 1884.
Gallovoy, R. Esq. F.C.S. {the Author) — Reforms in the Mode of Conducting

Chemical Examinations. (Journal of Science, 1885.)
Geographical Society. Royal — Proceedings, New Series, Vol. VI. No. 12 ; Vol. VII.

No. 1. 8vo. 1884-5.
Geoloqiad and Natural History Survey of Canada — Vocabularies of the Indian
tribes of British Columbia. By W. F. Tolmie and G. M. Dawson. With
Maps. 8vo. 1884.
Descriptive Sketch of the Physical Geography and Geology of Canada. By
A. R. C. Selwyn and G.M. "Dawson 8vo. 1884.
Goldsmid, Lady — Memoir of Sir Francis Henry Goldsmid. 2nd edition. Svo.

1882.
Hamilton Association— Journal and Proceedings, Vol. I. Part 1. Svo. 1884.
Iron and Steel Institute — Journal for 1884, No. 2. 8vo.

Jolms Hopkins University — American Chemical Journal, Vol. VI. Nos. 4, 5. Svo,
1884.
American Journal of Philology, No. 19. Svo. 1884.
Kew Observatory — Report, 1884. Svo.
Linnean Society — Journal, Nos. 106, 1.S5. Svo. 1884.
Macnaught, Rev. John, M.A. M.R.I, {the Author) — The Confessional in the Mission.

A Lecture. Svo. 18S5.
Manchester Geological -Soc/e/?/— Transactiftns, Vol. XVIII. Part 3. Svo. 18S5.
Mechanical Engineers^ Institution — Proceedings, No. 4. Svo. 1884.
Menshru<i<jhe, M. G. Van der {the Author) — Notice Biographique de Joseph A, F.
Plateau, Hon. M.R.I. 12ino. Bruxelles, 1884.

1885.] General MontJthj Meeting. 177

Meteorological Office — Monthly Wtather lleportsj for October, 1884. 4to.

Quarterly Weather Reports for 1877, Part 1. ito. 1884.
Meteorological Society, Royal— Quavieviy Journal, No. 52. Svo. 1884.

Meteorological Record, No. 14. Svo. 1884.
Michael, William H. Esq. Q.C MM. I. and J. S. Will, Esq. Q.C. (the Authors)—
The Law relating to Gas and Water. 3rd edition. By M. J. Michael. Svo
1884.
Newton, A. V. Esq. {the ^wf/ior)— Analysis of the Patent and Copyright Laws.

Svo. 1884.
Numismatic Society — Chronicle and Journal, 1884, Part 3. Svo.
Odontological Society of Great ^n7am— Transactions, Vol. XVII. Nos. 2, 3. New

Series. Svo. 1884-5.
Pharmaceutical Society of Great Britain — Journal, December 1S84, and January
1885. Svo.
Calendar for 1885. Svo.
Vhotographic Society — Journal, New Series, Vol. IX. Nos. 2, 3. Svo. 1884.
Physical Society of London — Proceedings, Vol. VI. Part 3. Svo. 1884.
The Scientific Papers of James Prescott Joule. Vol. I. Svo. 1884.
Polloch, Frederick, Esq. M.A. LL.D. (the Editor)— Law Quarterly Review, Vol I.

No. 1. Svo. 1885.
Richardson, B. W. M.D. F.R.S. (the Author)— The Asclepiad. Vol. II. No. 5.

Svo. 1885.
Rio de Janeiro, Ohservafoire Imperial de — Annales, Tome II. 4to. 1884.
Rogers, G. A. Esq. (the Author)— The Art of Wood Carving. Svo. 1879.
Royal Society of London — Proceedings, No. 234. Svo. 1884.

Philosophical .Transactions, Vol. CLXXIV. Part 3 ; Vol. CLXXV. Part 1 .
4to. 1883-4.
Sanitary Imtitute of Great Britain — Transactions, Vol. V. Svo. 1884.
Saxon Society of Sciences, Royal — Philologisch-Historische Classe :
Abhandlungen : Band IX. Nos. 2-6. 4to. 1884.
Berichte, 18S3. Svo. 1884.
Mathematische-Physische Classe :
Abhandlungen: Band XIII. No. 1. 4to. 18S4.
Berichte, 1883. Svo. 1884.
Scottish Society of Arts, i^oyoZ— Transactions, Vol. XL Part 2. Svo. 1884.
Society of Arts — Journal, December 1884, and January 1885. Svo.

Indexes to Journal, Vols. XI. to XXX. Svo. 1873 and 1884.
Statistical Society — Journal, Vol. XL VII. Part 5, Appendix. Svo. 1884.
St. Bartholomeio s IfosptYaZ— Statistical Tables, 1888. Svo. 1884.
St. Petersbourg, Academic des Sciences — Memoires, Tome XXXII. Nos. 4-12. 4to.

1884.
Telegraph Engineers, Society o/— Journal, Vol. XIII. No. 54. Svo, 1885.
Tohio University— Memohs, No. 4. Svo. 1884.
United Service Institution, Royal — Journal, No. 126. Svo. 1884.
Vereins zur Beforderung des Gewerhjleisses in Preussen — Verhandlungen, 1884 :

Heft 9, 10. 4to.
Victoria Institute — Journal, No. 71. Svo. 1884.

Woolnough, C. W. Esq. (the Author)— The whole Art of Marbling. Svo. 1881.
Yorkshire Archaeological and Topographical Association— J ommil, Part 33. Svo.
1885.

Vol. XI. (Xo. 79.)

178 Mr. G. Johnstone Stoney • [Feb. 6,

WEEKLY EVENING MEETING,

Friday, February 6, 1885.

Sir Frederick Beam well, F.R.S. Manager and Vice-President,
in the Chair.

G. Johnstone Stoney, Esq. M.A. D.So. F.R.S.

How Thought presents itself in Nature.

All the main steps in the great progress which man has been able to
make in understanding the universe in which we live and of which
we form a part have consisted in ascertaining that there is more
simi^licity in what occurs than had before been known to prevail. It
is the aim of the present discourse to endeavour to follow this
simplification up to the stage to which scientific inquiry has now
succeeded in carrying it, and to point out a further simplification,
which is suggested and rendered probable by that which has been
thus ascertained, although we are not yet in a position to speak con-
fidently about this further step.

Sound is Motion.

A very important discovery was made when it was found that
while we are listening to sound what is really occurring in the outer
world is merely a motion of materials all of which were there before.
Thus in playing a piano the strings are made to vibrate by the per-
former ; this sets up a quivering motion in the sounding-board
corresponding to the motion of the strings, and the sounding-board
in its turn transmits an undulation through the air, some very small
part of which occurs within the outer passage of our ear. It here
encounters the membrane which separates the outer from the middle
chamber of the ear, and through it communicates the motion to the
air of the middle chamber and to three delicate little bones which
finally carry the motion forward to the inner chamber where the
true auditory apparatus suspended in a liquid is operated upon by
the vibratory motion, and in its turn acts upon the multitudinous
filaments of the elaborate fringe in which our nerve of hearing
terminates.

The whole of the phenomenon then so far as it exists in the
outer world consists entirely of motions, and it becomes sound only
at Some stage beyond the portals of our ears. \\'hen this was found
out, a very important discovery was made respecting the actual
operations of nature. This discovery was followed up by investiga-
tions, through which a multitude of details have been brought to
light, as, for example, that the pitch of the sound as we hear it

1885.] on how Thought p-esents itself in Nature. 179

depends ou the periodic time of the waves that occur outside us, that
the quality of the tone depends on the form of the wave, and so on.
The character also of the imdulation in different materials has been
ascertained. For instance, in air it consists at each point of a rapid
succession of little winds blowing alternately forwards and back-
wards. The length of the waves in various media, the rapidity of
their advance, and a multitude of other particulars about them, have
been carefully measured. It has thus been ascertained that in air the
longest waves we can hear are about twelve or fourteen metres from
each point of compression to the next, the shortest about a centi-
metre ; that the length of the air waves produced by the middle E of
the piano is about one metre, and so on.

Light is Motion.

Another and a most important advance in our knowledge of
nature was made when discovery after discovery confirmed the truth
of the undulatory theory of light and radiant heat, and justified us in
accepting it. These and discoveries in molecular physics certify to
us that we see objects because periodic motions in their molecules
generate an undulation around that pulsates in harmony with them.
A very small portion of this great undulation obtains access to our
eyes through the pupils, and produces a change in some substance or
substances of the black pigment that lies under the retina at the
back of the eye. What this change is we do not yet fully know, but
it is probably a fugitive change of the nature of the more permanent
chemical change which occurs in photography. Of whatever kind it
is, the altered pigment gains for the time the power, through an
intricate apparatus of rods, cones, and bulbs, of exciting the optic
nerve to act upon the brain. However, we are not just at present
engaged in following up the series of events through our organs of
sense to the brain and mind, but are only inquiring what part of the
series takes place in the outer world. This part is simply motions :
anything else that is in the series of events known to us comes in at
some subsequent stage.

What a Scientific Explanation is.
In order to keep our conceptions clear, it will be convenient to
take a general survey here of what would constitute a complete
explanation of a phenomenon from the scientific naturalist's point of
view. We may select any phenomenon — for example the green colour
we see when we look at the foliage of a particular plant, let us
suppose of a geranium. The perception of green in certain situa-
tions, which is, so long as we are looking at the plant, a part of the
great complex thought which we call our mind, is the known element
of this inquiry — equally known before the investigation as after it.
It may be called the a or known part of our problem ; and, adoptinc^
the practice of mathematicians, we will assign the last letters of the
alphabet z, y, x, and lo to those unknown parts which the scientific

N 2

180 Mr. G. Johnstone Stoney [Feb. 6,

man endeavours to ascertain. His first inquiry is as to what has
occurred in the outer world. This in the case we have taken he finds
to be motions with ascertainable periodic times within and between
molecules of the gerauium, followed up by an undulation around that
has the same periodic time as those motions, a very small part of
which reaches the black pigment of the eye through the pupil. This
is the first or z part of a scientific explanation of the phenomenon. It
is the explanation of what is going on in the outer world, and the z
of the problem would be considered by the scientific man as having
been fully discovered if these motions and all that relates to the laws
under which they occur had been made out.

The next, or y part of the investigation, is to discover what change
this z produces within our organs of sense on those parts of them
which stand in a direct functional relation with the associated
nerves. This, in the example we have taken, would consist in ascer-
taining— 1st. What new substances ay)pear in consequence of the
(probably three) photographic effects which the incident light has on
the pigmentum nigrum ; 2nd. What effect these have upon the appa-
ratus of rods and cones which keeps tapping against the pigmentiun
nigrum; 3rd. What is the connection between this last change and the
excitation of the nerve. The next in order would bo the x part of
the inquiry. It would be an inquiry into the j^hysical change which
the presence of these substances produces in the retina and along the
optic nerve. If all these, and all about them, were fully made out
the y and x parts of the explanation would be comj^lete. And, finally,
if it could be discovered what physical change ensues in the brain
itself the lo part of the problem would be solved, and the whole
scientific exj)lanation would be then complete.

In order of time the z part of the phenomenon first occurs in the
outer world. Some excessively small part of this gains access to our
organs of sense and produces in them the y part of the phenomenon,
which acting on the nerves, and developing in them the x part of the
phenomenon, excites them in turn to make that stir within the brain
which is the iv part of the phenomenon, along with which the a part of
the phenomenon presents itself and the percej^tion of green at certain
situations in space comes to form for the time a part of our mind.

We are, however, as yet only concerned with the z part of the
phenomenon — that part which takes place in the outer world, and
with which science has been up to the present able most fully to
deal. As we have seen, it consists entirely in motions. It has been
found possible to measure many of these motions in various ways ;
and, to give some notion of what the universe really is, I will state
the results of some of these determinations.

Metrets.

Scientific measures are now made in metres and divisions of the
metre. The metre itself is a few inches more than a yard long, and
is divided into metrets, a convenient name for its decimal subdivi-

1885.] on how Thought present itself in Nature. 181

sions, that is subdivisions each of which is the tenth part of the one
before it in the series, and ten times the next after it. The decimetre,
or tenth part of a metre, is the first of these metrets ; it is about a
hand-breadth. The next metret is the centimetre, the hundredth part
of a metre, and is about a nail-breadth. The third-metret is the
millimetre, about the distance across a small pin's head. The fourth-
metret is the tenth of this, and is about the thickness of a sheet of
paper. The tifth-metret is microscopical ; it is intermediate in size
between the diameters of the red and white disks that float in human
blood. The tenth of this, the sixth-metret, would be a very small
object in the microscope, and no microscope is able to show the
seventh-metret, which is the next of the series. However the study
of nature has obliged us to go farther than the microscope can pene-
trate, and leads us on to, at all events, the tenth and eleventh of this
series of metrets. The tenth-metret is so small that a child during
the years of its most vigorous growth is growing at the averao^e rate
of between thirty and forty of them every second, and the eleventh-
metret is the tenth part of this again. This is about as far as the
scientific examination of nature has as yet obliged us to go.

Quantitative Determinations — Light and Sound.

Now the waves of light as they travel between the objects we are
looking at and our eye, are of various lengths, but all shorter than
the sixth-metret. The shortest are about four and the longest about
eight of the seventh-metrets, but none so long as ten seventh-metrets,
which would make up the whole of a sixth-metret. They must there-
fore take rank with microscopic objects so small that they can only
be seen with a tolerably high power. Small as they are, these tiny
waves advance with extraordinary speed, travelling a distance of
thirty quadrants of the earth in a second of time, meaning by a
quadrant the distance along a meridian from the earth's equator to
the pole, a distance which measures ten millions of metres. The
vibratory motion at each point of space is transverse to the direction
in which the waves are travelling, a kind of motion with which we
are familiar in the waves that run along the surface of water. The
range of this transverse motion is about a tenth-metret, the very
minute quantity to which I drew attention a while ago; and the
rapidity with which it is repeated varies with the colour of the light,
and for green light has about its mean value : in a ray which pro-
duces this colour the oscillatory movement is repeated about as often
every second as there are seconds in nineteen millions of years.

This short sketch will, I hope, give a picture that will suffice for
our present purpose, of the kind of motion in the outer world that
affects us through our organ of sight. It stands in very broad
contrast to that great coarse kind of motion which acts upon us
through our ears, and which for the middle E of the piano is repeated
only 330 times in a second. The direction of motion also is different,
for in the sound waves of air it is backwards and forwards along the

182 Mr. G. Johnstone Stoney | FeK 6,

direction in which the waves are propagated, while in light it is
transverse to that direction. But the greatest difterence is one to
which I have not yet drawn attention, viz. : that the motions in sound
and light belong to different orders of motion. To understand this, it
will be necessary to examine first other motions that are going on in
nature.

Gases.

We have gained more knowledge of the motions that go on in gases
than in either solids or liquids. A gas consists of separate little
missiles called its molecules, darting about in every conceivable
direction. In gas so perfect as the air about us at the surface of the
earth there is room enough between these molecules for each in its
flight usually to pass several of its fellows before its motion is
interfered with by its encountering any of them. When the encounter
takes place the two molecules that come together grapple with one
another in a peculiar way, sometimes exchanging part of their
contents, and always shaking up the internal motions that go on
within them both. After they get free from each other they dart off
in new directions, to be again turned aside when they encounter other
molecules. In this way the course of each is an irregular zig-zag,
consisting of little straight pieces corresponding to the free paths of
the molecule between its encounters. The rapidity of its flight is
liable to change at each encounter : by some encounters it is increased,
by others diminished, by a very excej)tional encounter it may possibly
be left the same as before. The length of each little free path will
of course depend upon how long the little traveller chances to avoid
its neighbours.

The details of the motions cannot be separately traced, but never-
theless a good deal of valuable information about them has been
obtained and many useful averages have been determined. For ex-
ample, in the air about us, at the pressure and temperature which
prevail in this room, there are about a unit-eighteen, or 1 with
eighteen O's after it (1,000000,000000,000000, a million times a
million millions) of these molecules in each cubic millimetre, i. e. in
about the volume of a pin's head. If at any instant they could be
kept from darting about, and if their distances asunder were then
measured, the average of all these various little distances would be
about a ninth-metret, about as much as a child grows in the third of a
second. They dash about at various rates, some more others less
than 500 metres per second, but on the average at about that speed.
This is about the quickest speed with which modern ordnance can
launch their projectiles. It is not far short of a third of a mile in a
second.

Of the available energy that is in the gas somewhat less than
two-thirds takes the form of this great activity ; the rest, which as
more than one-third, is occupied in maintaining internal motions that
go on within the molecules of the gas. About these internal motions
we have much information given to us through observations made with

1885.] on how ThoiigJd presents itself in Nature. 183

the spectroscope, but it comes to us in an exceedingly fragmentary
form, and it is difficult to get definite information out of it. Perhaps
the most precise information we as yet possess is in the case of a
periodic motion which occurs within the molecules of a vapour called
chlorochromic anhydride, which motion has been found to be repeated
about 809,520,000000 of times every second, and to be of such a kind
as to bear a close analogy to the motion of a point on a violin string
which is nearly but not quite two-fifths of the length of the string
from one end.

To return to the air about us, in which the molecules are at about
a ninth-metret asunder: it is only when they happen to get much
nearer together than this ninth-metret that they can interfere with
each other's motions, and the mean length of their free paths, the
average distance to which they are able to make their way between
their encounters is somewhere about three-quarters of a seventh-
metret ; from which and from the speed with which they are moving
it is computed that each molecule usually is subjected to about
7000,000000 encounters in each second.

Accordingly we may get some picture of the path pursued by a
molecule within one second of time by imagining a line 500 metres
long (the length of Grosvenor Place or Portland Place, or twice the
length of Albemarle Street) crumpled up till it has 7000 millions of
angles upon it ; the little straight bits will be of various lengths, all
small, and on the average about three-quarters of a seventh-metret
long, i. e. about one-third of the diameter of the smallest spec that
can be seen with the best microscope.

But I do not know of a contrivance by which we can form any
adequate conception of the far more dainty little motions within the
molecules, upon which one-third of their energy is expended.

Liquids and Solids.

When the gas is condensed into a liquid or frozen into a solid,
the molecules are forced close together. In the liquid state they can
still jostle about among one another though there is not room for
free paths : in fact they are always in a state of encounter. And if
the liquid is frozen into a solid the molecules become so much
restrained that they cannot get past each other and are unable to
travel away from the place assigned to them. However, the delicate
and almost immeasurably rapid internal motions still go on, either
in the same form as before, or, as more usually happens, in a modified
form. It is these which start vibrations around, the waves of light
and radiant heat, with various periodic times, the swiftest that have
been measured by the spectroscope in the ultra-violet rays being
repeated about as often each second as there are seconds in 50 millions
of years, the slowest that are visible to our eyes being repeated as
often as there are seconds in 12 millions of years, and still slower
ones affecting us as heat though we have not such substances in the
pigment of our eyes as would be influenced by them as light.

184 3Ir. G, Johnstom Stonetj [Fob. 6,

Primary and Secondary Motions.

This will be a convenient place in wliicli to draw attention to a
distinction of importance in the study of nature : the radical distinction
which exists between primary motions and secondary. Secondary
motion exists wherever there is a transference from place to place of
other underlying motions. Primary motions are those that have no
other more subtile motions underlying them. None of the senses
with which man is furnished, even when aided to the utmost by the
microscope, have ever reached primary motions, nor have they indeed
been able to penetrate beyond coarse forms of secondary motion ; and
it should be observed that the science of dynamics deals exclusively
with this class of motions.

When the spore of a mushroom is hurried along by the wind, the
vast accumulation of molecular motions that are going on within its
small volume is being drifted forwards, and constitutes the visible
motion of the spore a secondary motion. In what enormous numbers
underlying motions are here present may be judged from considering
that comx^lex motions go on within every chemical atom, that there
are within the most minute organic spec that has ever been seen with
a microscope enough of chemical atoms to make up from 10,000 to
100,000 of the most comj^lex organic molecules known to chemists,
allowing thousands of chemical atoms for each of these complex
molecules, and that a vast number of such organic specs would be
needed to make up a very tiny spore. It will thus be perceived that
the motions that go on within a spore are in inconceivable numbers
and of extraordinary complexity. The motion of a spore, then, when
drifted by the wind is a rather coarse secondary motion, i. e. it is?
the travelling forwards of a complicated mass of underlying motions.

A far less coarse motion is taking place in the molecules of gas
as they dash about among each other in the way described above.
Yet here again the motion is secondary, for within each molecule
there are the motions going on that originate the lines seen with
the spectroscope. Whether these internal motions are primary or
secondary we do not yet know, but the probability seems to be that
even they are secondary and that underlying them there are still
more subtile motions. There is in fact some reason to susj^ect that
chemical atoms may be likened to the vortex rings of which an im-
perfect illustration is shown in the beautiful experiment in which
smoke rings are shot across a room. Two or more chemical atoms
unite to form a molecule of the gas. The advance of the vortex ring-
across the room will stand for the travelling motion wdiicli carries an
atom of the gas along as part of its molecule, the pulsation which is
often seen passing round the vortex ring may represent the heat and
light vibrations wliicli take place within each atom of the molecule,
and underlying both of these is the vortex motion itself, which may
perhaps correspond to the real primary motion in the molecule.
However, in the present state of science wc do not know certainly

1885.] on hoiu Thought presents itself in Nature. 185

that these last underlying motions exist, though we have reason to
suspect them. If they do exist, then the heat motions are secondary ;
if they do not exist, then the heat motions are the primary motions.

A similar doubt exists in regard to the undulations of which light
and radiant heat consist. In the present state of our knowledge it
continues undecided whether they are primary motions, or whether
they are waves transmitted through still more subtile motions under-
lying them, and if this be the case then they are secondary motions.
But whether primary or secondary these etherial motions are mani-
festly of quite a diiferent order from the motions which take place in
sound. They are to be classed along with the subtile internal motions
that go on icithin the molecules of bodies, and are very different from
that general shifting backwards and forwards of vast accumulations
of molecules which we hear as sound. This is that fundamental
difference between light and sound of which I spoke earlier in this
discourse.

ExTEENAL Source of our other Sensations.

When we extend this scrutiny to those events in the outer world
which act on us through our other senses, we find motions throughout
the material universe, motions everywhere, motions underlying every
phenomenon; and no phenomenon has yet been met with in the
material universe that when adequately examined does not resolve
itself entii-ely into motions and the relations between motions. If a
chemist comes across an object surrounded by those light waves which
would give it to his eyes the appearance of being of the steel grey of
sodium ; if on approaching a knife to it he finds he can divide it, and-
that the molecular motions of the edge of his knife are made to
retreat inwards to the small extent which causes him to feel the
amount of resistance which sodium offers ; if he allows it to drop and
finds that it moves towards the earth as ponderable matter does ; if
he places it in the pan of his balance and finds that the upper mole-
cular motions of the pan approach those beneath in the degree which
requires a counterpoise corresponding to the weight of sodium to be
moved into the other scale to prevent the rest of the pan from
descending ; if he sees the motions of combustion arise when he
throws it on warm water, and ascertains by his spectroscope that the
motion ensues in the surrounding space which occasions the charac-
teristic lines of sodium ; if on applying some of its salts to his tongue
those motions occur in that organ which result in his perceiving a
saline taste ; if on approaching chemical tests to it he finds all the
alterations of molecular motion arise which are manifested when a
compound of sodium is j^i'ocluced : would any chemist hesitate one
moment to pronounce that the object with which he has been dealing
is sodium ? Yet at every step he has done nothing but move objects
about, and it has been motions and nothing hut motions and their changes
which he has really observed.

186 3Ir. G. Johnstone Stoney [Feb. 6,

What Fouce is.

Many persons suppose that force, mass, energy and so on have an
independent existence in nature. In reality they are functions of the
motions that occur in nature, and of relations between these motions.
These j^articular functions are so constantly presenting themselves in
our dynamical calculations, that it is most convenient to have definite
names and symbols for them, but it is a grave error to mistake them
for the real agents, and not to recognise that they really are merely
contrivances, most useful contrivances, for simplifying the description
of complex phenomena, so as to enable us to grasj) sufficiently those
parts of a problem that are essential for the purpose we may happen
to have in view.

It is sometimes said — " Force is the cause, motion the effect."
This statement needs much amendment. Force is not any existing
thing. When we speak of so much force as acting in any particular
case, we only mean to indicate that some sufficient cause of accelera-
tion is present acting up to that particular degree which is capable of
producing a change of motions of a specified amount ; and the con-
venience of the term is that it successfully avoids the necessity of
paying attention to what the cause is.

The reason why a stone falls is not, as is sometimes supposed,
that an agent which can be called the force of gravitation is acting
upon it. The real cause is that the great mass of molecular motions
called the earth is in sufficient proximity to that other mass of
motions called the stone. The cause why a bolt is projected from a
cross-bow is that by the action of the bow the molecular motions on
the front of the string have been brought into sufficiently close
relation to the molecular motions at the back of the bolt. The word
force expresses that one or other of these causes, or some other cause
capable of producing the effect, is present ; with the great convenience
that it relieves us from the necessity of determining which of the innu-
merable possible causes is the one acting in the case we are dealing
with — a problem unnecessary, and often too difficult for solution.
The term and its mathematical symbol are therefore most useful by
enabling us to get on with our work, when we want to find out lioio
much effect will arise, and do not care whether the real agent is a
cord pulling, a spring urging, a magnet attracting, or any other.
But in every case treated of in the science of dynamics (i. e. in every
case in which we are studying the drifting about of masses of mole-
cular motions), the real cause is that certain motions (whether that
vast accumulation of motions called the earth, the end motions of the
cord, the front motions of the spring, or wliatever they may be) have
come into the requisite position with relation to that other aggregation
of motions that is moved.

What Mass is.

Similarly the symbol used by mathematicians and called by them
the mass of an object, suppose of a stone, is the convenient con-

1885.] on hoiv Thought presents itself in Nature. 187

trivance by which they take notice of the fact that in every such case
the drifting motion of both the bodies is affected, both of the body
acting on the stone and of the stone. What is called the mass of the
stone is really the measure of the acceleration received by the other
body while it and the stone are acting on each other, so that the
ratio of t]ie two masses is the ratio of the accelerations taken in
reverse order ; or if we wish to make the statement general, the mass
of the stone is the measure of all the changes of drifting motions
going on elsewhere throughout the material universe which have
relation to the simultaneously existing motions which we call the
stone. The real cause that is operating is the proximity of the
molecular motions in the stone to the molecular motions of some other
body ; one part of the effect is a change in the molar motions of both
bodies, i. e. in the drifting about of their masses of molecular motions.
Other effects also arise, but this is the part of the effects which the
science of dynamics investigates. In fact dynamics does not concern
itself in the least with the motions going on within the molecules of
the bodies with which it is dealing. It is the science of the transfer-
ence from place to place of underlying motions. The symbols for
force and mass express vaguely the presence of adequate causes, while
in terms of the effects these symbols are, in the science of dynamics,
quite definite.

The proper description of the law of gravitation is that towards
each particle of ponderable matter, i. e. towards the molecular motions
within a small compact volume, all the other molecular motions that are
going on in the universe are being drifted with accelerations that are
inversely as the squares of their distances from that centre ; and the
ratio of the acceleration thus impressed by one particle on another
when comj)ared with the amount received by the first from the
second is that ratio which is called the ratio of their masses. The .
resultants of these accelerations may properly be called things, in
the sense that we find them really existing in nature : all the rest
are contrivances of the mind to enable it sufficiently to grasn the
phenomena.

Of Substance.

Another prevalent impression is that, in addition to the motions
we find existing in nature, there is a mysterious entity which is
spoken of under the name of substance. Now Science has never
found, and therefore knows nothing of, any object devoid of internal
motions such as that often supposed under this name, added to
external nature by the mind, not found by it in nature. Whence,
then, comes it that there is an almost universal persuasion that under-
lying every motion there must be some thing to be moved ? We need
not search far to find the answer to this question. It has arisen from
experience, from abundant experience : from our experience and the
experience of the whole series of our progenitors down from the dawn
of such organised thought upon the earth as we possess. Neither we
nor any member of this long series ever felt or saw a primary motion

188 Mr. G. Johnstone Stoneij [Feb. 6,

at all, nor even a molecular motion, althougli some of these are
secomlary. The only motions that until in recent times any man
could ascertain to be motion were the coarser forms of secondary
motion, and even still every motion that our senses are competent to
perceive to be motion has a very considerable thing that is moved,
namely, vast aggregations of subsidiary motions, of kinds which
science can show to be present, which we can conceive as motions, but
which we are unable to perceive except under forms so disguised that
they seem stationary. Until the discoveries of science were made,
masses of molecular motions, such as clubs, boats, stones, grains of
dust, &c., were mistaken by everybody for objects that might be
brought to absolute rest. This is the only class of objects that
any one ever felt or saw in motion, and so there grew up the sup-
2)osition that wherever there is motion there is something moving
which might be brought to rest. This conclusion, however, went beyond
^hat the experience really warranted. The conclusion it warrants
is that wherever we men, with certain limited senses, cdiU. perceive that
there is motion by the special senses that we happen to possess,
whether unassisted or with the best aid we can obtain from micro-
scopes or other appliances, there is always something moving. This
more guarded statement is perfectly correct ; for since a sufficient
scientilic investigation became possible, the very important discovery
has been made that in all the cases covered by the correct statement,
there is a vast accumulation of subsidiary motions being drifted along.
Anything else -which any one supposes to be present, is really not
what he knows to exist, but what he imagines.

Experiments consist of Motions.

Every experiment man can make consists altogether of motions.
A chemist pours one of his solutions upon another. This bringing of
them together is a rough secondary motion. This is followed by
another motion, the mixing of the two solutions till the molecules get
into such close apposition that they can act on each other. The
next stage is again motion, when atoms of the one are exchanged for
atoms of the other, and new compounds are formed. So also when
in theii" new positions the motions of which the atoms consist, or with
which they twine amongst one another, are subjected by their new
neighbours to new constraints and new influences, and the motions
become altered — when perhaps a new colour appears, betraying the
fact that a periodic time has changed. In fact, in every part of the
process, nothing but motions has ever been traced.

Take another example. We magnetise a piece of steel and alter
some of its internal motions, yet how completely has this changed
some of its dynamical relations to several other bodies of the
universe ! So when we electrify a conductor. Here wo have altered
motions, probably motions in the surrounding dielectric, and we have
by doing so profoundly changed the relations of the system to the
rest of the universe. So again, when wc spin a gyroscope contained

1885.] on hoio Thought presents itself in Nature. 189

within a box, and by this very coarse internal motion have done
enough to alter the inertia of the system, i. e. the way it behaves
under impressed forces ; and that not merely as respects its quantity
but its kind. By an equally rough contrivance we can create by
motions a property resembling elasticity ; and so in other cases.

Conclusions — I. The External Source of Sensation is Motion.
The general outcome of all such inquiries is that we are con-
fronted with the fact revealed to us by science, that every phenomenon
of the outer world which we can perceive by any of our souses, is
simply a mass of motions. The z of our inquiry is entirely motion.

II. So ALSO IS WHAT OCCURS WITHIN OUR BoDIES.

So also is the y, which means that part of the phenomenon which
although still outside the nerves, is in more immediate relation to
them. Nerves are not directly acted upon by what goes on outside
our organs of sense, but by the change within our organs of sense
which the external events occasion. For example, the molecular
motions that are going on in the object we look at, do not reach
our optic nerve. What they do is to produce luminous undulation
around that body. Nor is it even this undulation, the light, that
acts on our optic nerve. What it does is to make a change in the
black pigment of the eye, and it is the new chemical substances thus
evolved which are what act upon an apparatus of rods, cones, and
bulbs in such a way that the latter become able to operate on the
nerve. The new series of events that occur within the eye would, if
fully understood, constitute the y part of the scientific naturalist's
explanation ; and although the details are imperfectly understood,
they are all of those kinds that consist of changes of motion.

So again of the next, or x part of the scientific exi^lanation. This
is what occui's within the nerve fibres while they are receivino- the
impression from without, and exercising the j^ower to act upon the
brain which that stimulus has conferred upon them. Much is not
yet known about what occurs within the nerve, but in consequence of
the processes that go on, the nerve wastes and requires nourishment ;
it undergoes change, and the change which it undergoes advances
inwards towards the brain at a rate that can be measured, and which
is about the speed of the fastest railway train, a moderate sjDced com-
pared with many others we meet with in nature. Here all that has
been made out betokens that what occurs within the nerves is entirely
made up of motions.

And, finally, the same is true of the brain itself. The motions
that go on within that most wonderful organ are probably the most
intricate that are known anywhere to prevail. But tliou<Th un-
fortunately very little is understood about the operations that are
going forward, there is nothing to raise the most distant suspicion
that if an adequate examination could be made, the scientific naturalist

190 Mr. G. Johnstone Stoney [Feb. 6,

would find any change going on in my brain while I am thinking
that is not of those kinds which on ultimate analysis resolve them-
selves into motions and the relations between motions.

The Universe One.

And here, after our survey of the material universe let us pause
for an instant to reflect what all this really means. Some of the
motions that are going forward in nature we call ponderable matter,
others we call the ether ; and again, within the range of ponderable
matter we think of individual bodies each separate from the others.
Now all this is very convenient, not only convenient but indeed
essential to our making an intelligent use of the great world that lies
around us — but it is not an accurate presentation of what really
takes place. The motion that pervades the universe is not many
motions but one motion, indescribably complex, but not divisible into
parts that exist separate from one another. All the parts, if they can
be called parts, mutually interpenetrate each other ; and we do not
view them correctly when we think of any one of them as having an
existence independent of the rest. The motions that went on yester-
day in the table at which I stand are succeeded by those that are
going on there now, but these are not the only offspring of those
former motions, neither are those the sole progenitors of these present
motions. Those motions of yesterday also gave rise to an undulation
around, some of which having escaped through the skylight is at this
moment urging its rapid flight over an ever widening area -to the
distant stars ; other parts of the undulation enabled this table to be
seen by every member of the audience which was in this room yester-
day ; much of it fell upon the walls, the ceiling, the floor, bearing to
them heat, light, electricity, which have made their motions, the
motions in the rooms beyond them, in the street, all over London,
different now from what they otherwise would have been. The earth
as it darted forwards on its course has borne all the molecular motions
of that table along with it, and changed their distance and direction
from the other bodies of the universe : and, as a consequence, the sun
himself, the planets, the most distant stars have recognised its
influence, have ceased to bend towards its former position, and are at
this moment inclining a little towards that it now occupies. All
these motions and multitudes of others are the lineal descendants of
the molecular motions which yesterday constituted this table ; and,
correspondingly, those which are now going on in the table have not
wholly sprung from the motions in it yesterday, but the entire of the
rest of the universe has contributed to them.

Many will be disposed to say, " These effects are trifling, too small
to deserve notice." This is not so, though some are small, not one of
them is one whit the less real ; neither are they in their own nature
small, and some of them are conspicuous even to the few and slender
moans which men possess of becoming acquainted with tliem. Bring
even one candle into this room at night, and in an instant its small

1885.] 071 how Thought presents itself in Nature. 191

flame excites molecular motions in the walls and furniture, and rouses
them so strenuously that they maintain a great complex motion filling
the entire space, one ten-millionth part of which entering our eyes is
enough to enable us to see them all. And when it so effectually sets
up motions near the surfaces of those bodies, these in their turn
react on motions beyond, and so none of the motions within those
bodies are quite what they were before, nor indeed can any part of
the whole universe remain unchanged. There is no one body about
us which would be what it is, if any one of all the other bodies of the
universe had been other than what it was. The universe then is one,
and is not made up of parts that exist separately.

In each part of which there is material for information
about all the rest.

This is one reflection to which our inquiries naturally give rise.
Another, which is closely allied to it, is that in each part of this
great universe there is information about all the rest, which only
requires an adequate interpreter to be brought conspicuously out.
Such an interpreter, organised to deal with one small part of the
information really contained in the motions that are dealt with, is
our eye, with our optic nerve, our brain and our mind behind it.
And what are the motions that it analyses? They are a small
selection from those going on in the little circular disk of space
which lies beyond the eye immediately in front of its cornea, with a
diameter equal to the pupil of the eye and which may be very thin.
When we stand in the country and see every blade of grass beneath
our feet, birds and insects on the wing, the leaves upon a thousand
trees, clouds, mountains, hedges and fields — what is really occurring
is that molecular motions in all those objects have been brought to
such activity by the undulation which has spread towards them from
the sun, that they in turn have been able to send abroad motions
in all directions, some of which have reached the tiny patch described
above in front of each of our eyes. None of all that motion beyond
conveys information to us except by being the cause why those two
tiny patches are moving as they are ; and the meaning of a small
part of the motion that has been thus excited within those two little
disks is in one particular way interpreted for us by the eye, and
contains within it all the information given to us through that organ,
and indeed contains vastly more. An equal amount of information
about what is going on elsewhere is contained within every similar
patch of space throughout the whole universe.

Outcome of the Scientific Inquiry.

Thus we may extend the statement made before, and say that
scientific inquiry finds motion pervading the material universe ;
motion everywhere, motions underlying every phenomenon, and it
finds nothing existing outside the mind excepting motions.

192 3Ir. G. Johnstone Stone y [Feb. G,

Outcome of a further Inquiry.

Here we miglit rest and be content with the assurance that there
are at most only two kinds of existence known to us, thought and
motion — all that is within the mind being thought, all that is with-
out it motion. To this conclusion science inevitably leads ; and of
its truth, as of all other scientific conclusions, reasonable minds with
a sufficient training can fully satisfy themselves. However, it is not
possible to be content to stop here, and the further step to which we
feel almost impelled, unfortunately falls not within the domain of
science but of metaphysics. I say " unfortunately," because the rea-
soning which is at our disposal in metaphysics, unlike that of science,
is in reality not an appeal to every trained human mind of sufficient
capacity, but to those which have a leaning towards one particular
school of thought. That this is the case we are forced to recognise,
when in metaphysics we find able and well-instructed minds taking
opposite sides, even where their opposition is as great as it is between
Realists and Idealists.

What then is that motion to which science reduces every material
phenomenon? The conception of motion is a thought within our
minds. This conception exists, but it exists internally; it has no
non-egoistic or external existence. It however has its source in part
in something existing outside us. This something (in any particular
instance) acts uj)on something else, that upon something further,
that again upon another something, and so on, till, at the end of a
long series of this kind, the last of these somethings is a sensation or
sensations which form part of our mind for the time being. These
sensations are worked up with what else is then in the mind in such
a way that the general outcome of the whole is what we call the per-
ception or conception of a motion. But in reality all we know of the
original external source is that it is at the farther end of this long
series of causes and effects, and that thoughts of which we are con-
scious, and which therefore we really know, are at the nearer end.
Though we have spoken of intermediate steps of the series, of the y, x,
and 10 steps, of chemical or other material changes that occur within
our organs of sense, nerves, and brain, the meaning of what we have
said is only this, that if what is here going on loere placed at the
farthest end of such a series, if in fact made a z and examined as such
by some human mind through its organs of sense, nerves, and brain,
that under these circumstances what is going on would rouse in that
mind sensations which science has succeeded in referring to motions
as the z part of the cause. But it is only if reaching the mind by
that special circuitous course that motions, whether inside or out-
side our bodies, are known to elicit sensations. What they are in
themselves we know not ; what their effect within the mind would be
if they approached it in any other way we know not ; we only know
that they produce, with uniform certainty, this particular series of
events when operating in this particular way. We ought therefore

1885.] on liow Thought presents itself in Nature. 193

to be in readiness to accept any evidence as to what they really are,
for in all we know there is nothing to be set against that evidence.
Now there is some evidence, and even considerable evidence, that
that external cause is thought, not our thought, but thought that is
going on elsewhere than in our consciousness. For this hypothesis,
the simplest that can be entertained, quite gets rid of what is else
an oppressive difficulty, the abrupt appearance of thought along
with that one particular organisation which we call a brain, although
the whole train of physical causes and effects is complete without it,
and leaves no room for it. On the hypothesis now put forward the
thought which is associated with a brain would be no " Jack in the
box," springing up suddenly before us, but would be in full conso-
nance with the ordinary course of nature. The weight of these
considerations will be found to be very considerable when they are
carefully pondered over, and I think warrant us —

1st. In being confident that all existence known to us is at

most of two kinds, thought and whatever is the external source

of our conceptions of motion ; and

2nd. In regarding it as probahle that the latter existence is

thought — not our thoughts, but the thought of the great

" Anima," or rather Animus " Mundi."

Other Considerations Support this Conclusion.

Every simplification of nature which can be effected recommends
itself to our scientific judgment, and w^e are justified in esteeming
very highly the evidence upon which we may carry the simplifica-
tion of nature to this farthest point. What we have already adduced
is sui^ported by other considerations. The hypothesis calls upon
us to admit that the thoughts of which we are conscious as our mind,
and are aware of as minds in our fellow-men and in other animals
are in reality very small swirls in an illimitable ocean of thought.
Moreover, our mind, the cerebration of which we are conscious, can
be but a small portion even of the thought going on inside our own
brain, the rest being as much outside our consciousness as are the
thoughts of our fellow-men. We may judge how much lies beyond our
consciousness by reflecting that we have no thoughts at all with such
time relations as the original molecular motions of our brains, so that
all these, though they are present, lie utterly remote from the grasp
of such a consciousness as ours. Our consciousness is in fact very
much more restricted on this side. Every one must have noticed that
as we become expert in any art, in walking, speaking, reading, playing
from music, riding a bicycle, it comes to be done more and more
outside our consciousness, and partly because the separate acts of
the process then succeed one another too promptly to be consciously
followed. While the habit is being formed it is found to hang for a
long time on the boundary between consciousness and unconsciousness,
passing inside that boundary when we give special attention to what
we are doing, passing outside when we otherwise occupy our thoughts.

Vol. XI. (No. 79.) o

194 Mr. G, Johnstone Stoney [Feb. 6,

This is intimately connected with another shortcoming of our
minds, that the quantity of thought which can come wdthin our con-
sciousness at any one time is limited. We find that by what we call
attending we can exercise a choice amid such suitable materials as
are present within the brain ; but that by choosing some we exclude
others. In a large assembly a babel of sounds may reach our brain :
by attention we can bring more emphatically within our conscious-
ness some of these sounds, and thereupon the rest pass partially
beyond consciousness. Before we make our choice we hear a confused
and much louder noise. After we set ourself to listen to one speaker
out of many, to the rustle of a particular silk dress, or to any other of
the tangle of sounds that assail us, those w^e have directed our atten-
tion to become more distinctly heard, the rest less heard, those we
have selected are brought far within the boundary of consciousness
and will be long remembered, the others pass partly beyond and if
heard at all are soon forgotten — indeed they may pass entirely beyond
our consciousness and be wholly unnoticed, if our attention to the
selected sounds is sufiiciently intense.

A very curious phenomenon closely related to the foregoing
occurs when the clock strikes w^hile we are so preoccupied, that
though we hear that it is striking, we do not know what o'clock has
struck. If just after it has struck, " with the sound still ringing in
our ears," we wish to know the hour, it is generally possible to go
over in memory what has recently been heard and to count the strokes,
the number of which was until then unknown.

We often avail ourselves of these jDroperties of our minds. The
way in which we dismiss a thought from our mind is by vigorously
devoting our attention to something else. It is in fact the only way
we have of doing so.

By carefully observing matters of this kind we may satisfy our-
selves that the thought of w^hich we are conscious is a portion of a
larger body of thought of the same kind lying close to our conscious-
ness, in fact within our brain. The considerations brought forward
in the earlier part of this discourse, give us reason strongly to suspect
that there is also present within the brain a vastly more extensive
body of thought differing, at all events in time relations, from any
thought of which we can be conscious ; and further that the thought
that is present in the brain, whether the little that we are conscious
of or the rest, is but one (hoy) of a boundless ocean.

Here I must end. I dwelt chiefly on the first part of my subject
as being the most appropriate to be fully discussed in the hall in
which we are here assembled, and this has left little time for expound-
ing the second. If time had allowed, the second part would have
led us through considerations of supreme interest, and its issue is to
reveal to us a vision of the universe of unsurpassed sublimity.

[G. J. S.]

1885.] on how Thought presents itself in Nature. 195

Postscript.

It may be useful to give a recapitulation of tlie main steps of the
argument.

A small j)art of what takes place in the outer world affects my
senses, and througli them indirectly affects me.

The result of a successful scrutiny of what is going on in the
outer world may for convenience be called the z part of the scientific
explanation of what I vvitness.

The result of a successful scrutiny of the change which the z
occasions within my organs of sense would be the y part of the
explanation.

The result of a successful scrutiny of the changes that ensue
along the associated nerves would be the x part of the explanation.

And, finally, the result of a successful scrutiny of the physical
changes which this x produces within my brain would be the iv part
of the explanation ; and the explanation of the phenomenon from the
naturalist's point of view would be then complete.

The state of my own mind while I am witnessing what is going
forward consists of sensations, perceptions, and conceptions, or some
combination of these with reflections, reminiscences, associations,
feelings, emotions, and so on, and may be called the a part of the
inquiry, as it is the known part, known as fully before as after the
investigation.

The whole of a scientific inquiry starts with this a, and is concerned
in discovering the z, the ?/, the x, and the ii\

We now know enough of this class of investigation to assure us
that the whole of the z explanation, the y exj)laiiation, the x and the iv,
would, if we could fully explore them, turn out to be motions, and
the laws that govern changes of motion. That, for example, the
geranium 1 am now looking at, is a mass of molecular motions
(whether with, as many people suppose, or Avithout, as I suppose, that
'something else' which they call substance); that the molecular
motions in the geranium modify the ether motions going on around
it in the room ; that the etherial motions when thus altered produce
new motions in the back of my eye ; that this event next alters motions
in the associated nerve ; and, finally, that the disturbance in the nerve
produces an effect upon the motions going on in my brain. Here, if
all the details were ascertained, as to what particular motions arc
occurring at each step, ' and what laws regulate their occurrence,
Natural Science would have said her whole say. It has, however,
then to be added that although this series is self ccmtained and com-
plete, there occurs another event alongside of it without any traceable
place in the sequence of causes and effects, viz. the change within my
mind which I call perceiving the geranium. Herein lies the great
difficulty of the dualistic hypothesis, from which the monistic hypo-
thesis is free.

Motion throughout this statement has meant, not my perception

o 2

196 Mr. G. J, Stoney on hoio Tlioiigld p-esents itself in Nature. [Feb. 6,

or conception of motion, but the factor in the outer world whatever
it is, which, co-operating with factors within my mind produces that
perception or conception. It is this outside factor which there seems
reason to suspect is thought going on beyond my consciousness. When
put into the language of this hypothesis, the result of the scientific
inquiry would be expressed thus : the geranium consists of eminently
complex thoughts going on outside my consciousness, which are in
fact a part of the great Animus Mundi. These act on other thoughts,
commonly regarded as waves of light, which again alter part of that
vast assemblage of thoughts called one of my organs of sense. These,
in theii' turn, act on another group of thoughts called the associated
nerve, and finally, the thoughts which constitute the nerve bring
about a modification within that other vast assemblage of thoughts
called my brain ; out of which last assemblage a few small pinnacles
rise within my consciousness, i. e. have a special interaction and
include special relations to preceding states, and so become parts of
one complex thought, my mind.

That there is one great consciousness extending through the whole
Animus Mundi, is I think suggested by the known fact that each part
of material nature acts on and is acted on by every other.

On so abrupt a statement of the drift of an hypothesis which lies
outside men's usual highways of thought, it will necessarily seem
fanciful ; but just as what is at first sight plausible may prove to be
not true, so what on a fii'st view strikes us as fanciful may turn out
to be sober fact.

[G. J. S.]

APPENDIX.

This Friday Evening discourse was accompanied by three
afternoon lectures at the Eoyal Institution, in which the lecturer
endeavoured to explain how some of the determinations referred to
in the discourse had been effected. For accurate determinations of
wave-lengths of light the reader may refer to Angstrom's ' Spectre
Normal du Soleil ' ; for the motions in gases to Maxwell's ' Heat,'
pp. 297 and 299, and to a paper* by the lecturer on the internal
motions of gases in the ' Philosophical Magazine ' for August, 1868 ;
for the motions in chlorochromic anhydride to a paper by the lecturer
and Professor J. Emerson Eeynolds in the ' Philosophical Magazine '
for July 1871. Most of the other determinations are in the text-
books.

* Keaders of that paper arc requested to change the square of 16 into the
square-root of 16, at the eud of the second paragraph.

1885.] Sir John Luhhoch on the Forms of Leaves. 197

WEEKLY EVENING MEETING,
Friday, February 13, 1885.

Sib Frederick Pollock, Bart. M.A. Manager an 1 Vice-President,
in the Chair.

Sir John Lubbock, Bart. M.P. D.C.L. F.R.S. M.BJ.

The Forms of Leaves.

Greatly as we all appreciate the exquisite loveliness of flowers, it
must be admitted that the beauty of our woods and fields is quite as
much due to the marvellous grace and infinite variety of foliage. How
is this inexhaustible richness of forms to be accounted for ? Does it
result from an innate tendency of the leaves in each species to assume
some particular shape ? Has it been intentionally designed to delight
the eyes of man? Or has it reference to the structure and organisation
— the wants and requirements of the plant itself ?

Size.

Now, if we consider firstly the size of the leaf we shall find
that it stands in close relation to the thickness of the stem, and
that when strict proportion is departed from the difference can
generally be accounted for. This was shown, for instance, by a table
giving the leaf area and the diameter of stem of the Hornbeam,
Beech, Elm, Lime, Spanish Chestnut, Ash, Walnut, and Horse
Chestnut.

The size, once determined, exercises much influence on the form.
For instance, in the Beech the leaf has an area of about 3 square
inches. The distance between the buds is about IJ inch, and the
leaves lie in the general plane of the branch, which bends slightly at
each internode. The basal half of the leaf fits the swell of the twig,
while the upper half follows the edge of the leaf above; and the
form of the inner edge, being thus determined, decides that of the
outer one also. In the Lime the internodes are longer, and the leaf
consequently broader. In the Spanish Chestnut the stem is nearly
three times as stout as that of the Beech, and consequently can carry
a larger leaf-surface. But the distances between the buds are often
little greater than those in the Beech. This determines, then, the
width, and, by compelling the leaf to lengthen itself, leads to the
peculiar form which it assumes.

198 Sir John Luhhock [Feb. 13,

Arrautjement.

Moreover, not only do the leaves on a single twig admirably fit
one another, but they are also adapted to the ramification of the twigs
themselves, and thus avail themselves of the light and air, as we can
see by the shade they cast without large interspaces or much over-
lapping. In the Sycamores, Maples, and Horse Chestnuts, the
arrangement is altogether different. The shoots are stiff and upright,
with leaves placed at right angles to the plane of the branch, instead
of being parallel to it. The leaves are in pairs, and decussate with
one another, while the lower ones have long petioles, which bring
them almost to the level of the upper pairs, the whole thus forming a
beautiful dome.

For leaves arranged as in the Beech, the gentle swell at the base
is admirably suited, but in a crown of leaves, such as those of the
Sycamore, space would be thereby wasted, and it is better that they
should expand at once, as soon as their stalks have carried them free
from the upper and inner leaves ; hence we see how beautifully the
whole form of these leaves is adapted to the mode of growth and
arrangement of the buds in the jDlants themselves.

In the Black Poplar the arrangement of the leaves is again quite
different. The leaf-stalk is flattened from side to side, so that the
leaves hang vertically. In connection with this it will be observed
that while in most leaves the upper and under surfaces are quite un-
like, in the Black Poplar, on the contrary, they are very similar.
The stomata, or breathing holes, moreover, which in the leaves of
most trees are confined to the under-surface, are in this species nearly
equally numerous on both. The " Compass Plant " of the American
prairies, a yellow Composite not unlike a small Sunflower, is another
plant with upright leaves, which, growing in the wide open prairies,
tend to poiut north and south, thus exposing both surfaces equally to
the light and heat. It was shown by diagrams that this position also
affected the internal structure of the leaf.

In the Yew the leaves are inserted close to one another, and are
long and linear; while in the Box they are further apart and broader.
In the Scotch Fir the leaves are linear, and 1^ inch long, while in
other Pines, as, for instance, the Weymouth, the stem is thicker and
the leaves longer.

In the plants hitherto mentioned, one main consideration a^Dpears
to be the securing of as much light as possible ; but in tropical
countries the sun is often too powerful, and the leaves, far from
courting, avoid the light. The typical Acacias have jnnnate leaves,
but in many Australian species the true leaves are replaced by a
vertically flattened leaf-stalk. It will be found, however, that the
seedlings have leaves of the form typical in the genus. Gradually
the leaf becomes smaller and smaller, until nothing is left but the
flattened leaf-stalk or phyllode. * In one species the plant throughout

1885.] on the Forms of Leaves. 199

life produces both leaves and phyllodes, which give it a very curious
and interesting appearance. In Eucalyptus, again, the young plant
has horizontal leaves, which in older ones are replaced by scimitar-
shaped phyllodes. Hence the different appearance of the young and
old trees which must have struck every visitor to Algiers or the
Riviera.

Evergreens.

We have hitherto been considering mainly deciduous trees. In
evergreens the conditions are in many respects different. It is
generally said that leaves drop off in the autumn because they die.
This, however, is not strictly correct. The fall of the leaf is a vital
process, connected with a change in the cellular tissue at the base of
the leaf-stalk. If the leaves are killed too soon they do not drop off.
Sir John illustrated this by some twigs which he had pui'posely
broken in the summer ; below the fracture the leaves had been thrown
off, above they still adhered, and so tightly that they could support a
considerable weight. In evergreen trees the conditions are in many
respects very different. It is generally supposed that the leaves last
one complete year. Many of them, however, attain a much greater
age ; for instance, in the Scotch Fir, two or three years ; in the
Spruce and Silver, six or seven ; in the Yew even longer. It appears
from this that they require a tougher and more leathery texture.
When we have an early fall of snow our deciduous trees are often
much broken down ; glossy trees have a tendency to throw it off, and
thus esca]3e ; hence evergreen leaves are very generally smooth and
glossy. Again, evergreen leaves often have special protection, either
in an astringent or aromatic taste, which renders them more or less
inedible ; or by thorns and spines. Of this the Holly is a familiar
illustration ; and it was j)oiiited out that in old plants, above the
range of browsing quadrupeds, the leaves tend to lose their spines,
and become unarmed. The hairs on leaves are another form of pro-
tection ; on herbs, the j)resence of hairs is often associated with that
of honey, as they protect the plants from the visits of creeping
insects ; hence perhajDS the tendency of water species to become
glabrous, Polygonum amjphihium being a very interesting case, since
it is hairy when growing on land, and smooth when in water. Sir
John then dealt with cases in which one sjpecies mimics another, and
exhibited a striking photograph of a group of Stinging Nettles and
Dead Nettles, which were so much alike as to be hardly distinguish-
able. No one can doubt that the Stinging Nettle is protected by its
poisonous hairs, and it is equally clear that the innocuous Dead
Nettle must profit by its similarity to its dangerous neighbour. Other
similar cases were cited.

He had already suggested one consideration which in certain
cases determined the width of leaves, but there were others in which
it was due to other causes, one being the attitude of the leaf itself.

200 Sir John Luhhoch [Feb 13,

In many genera witli broad and narrow leaved species, Drosera and
Plantago, for instance, the broad leaves formed a horizontal rosette,
\vhile the narrow ones were raised upwards. Fleshy leaves were
principally foimd in hot and dry countries, where this peculiarity had
the advantage of offering a smaller surface, and therefore exposing
the plant less to the loss of water by evaporation.

Water Plahts,

Many of the acquatic plants have two kind of leaves — one more
or less rounded, which floats on the surface, and others cut up into
narrow filaments, which remain below; the latter thus present a
greater extent of surface. In air, however, such leaves would be
unable to support even their own weight, much less to resist any
force such as that of the wind. In perfectly still air, for the
same reason, finely divided leaves may be an advantage, while in
comparatively exjDOsed situations more compact leaves may be more
suitable. It was pointed out that finely cut leaves are common among
low herbs, and that some families which among the low and herb-like
species have such leaves, in shrubby or ligneous ones have leaves
more or less like those of the Laurel or Beech.

An interesting part of the subject is connected with the light
thrown by the leaves of seedlings. Thus the Furze has at first
trifoliate leaves, which gradually pass into spines. This shows that
the Furze is descended from ancestors which had trifoliate leaves, as
so many of its congeners have now. Similarly in some species,
which when mature have palmate leaves, those of the seedling are
heart-shaped. Could it be possible that the palmate form was
derived from the heart-shaped, and that when in any genus we find
heart-shaped and lobed leaves, the former may represent the earlier
or ancestral condition ? He then pointed out that if there was some
definite form told off for each species then surely a similar rule ought
to hold good for each genus. The species of a genus might well
differ more from one another than the varieties of any particular
species ; the generic type might be, so to say, less closely limited ;
but still there ought to be some type characteristic of the genus. He
took then one genus, that of Senecio (the Groundsel). Now, in
addition to Senecios more or less resembling the common Groundsel,
there were species with leaves like the Daisy, bushy species with
leaves like the Privet and the Box, small trees with leaves like the
Laurel and- the Poplar, climbing species like the Tamus and Bryony.
In fact, the list is a very long one, and showed that there is no
definite type of leaf, but that the form in the various species depends
on the condition of the sj^ecies. From these and other considerations
he concluded that the form of leaves did not depend on any inherent
tendency, but on the structure and organisation, the habits and
requirements of the plant. Of course it might be that the present

1885.] on tlie Forms of Leaves. 201

form had reference to former and not to present conditions. This
rendered the problem all the more complex and difficult. The lecture
was illustrated by numerous diagrams and specimens, and Sir John
concluded by saying the subject presented a very wide and interesting
iield of study, for if he were correct in his contention every one o1
the almost infinite forms of leaves must have some cause and
explanation.

[J. L.]

202 Mr. William Huggins [Feb. 20,

WEEKLY EVENING MEETING,

Friday, February 20, 1885.

Sir Frederick Bramwell, F.R.S. Manager and Vice-President,
in the Chair.

William Huggins, Esq. D.C.L. LL.D. F.E.S. M.B.L

On the Solar Corona.

If it were usual to prefix a motto to these evening discourses, I might
have selected such words as " Seeing the Invisible," for I have to
describe a method of investigation by which wliat is usually unseeable
may become revealed. We live at the bottom of a deep ocean of air,
and therefore every object outside the earth can be seen by us only as it
looks when viewed chrough this great depth of air. Professor Langley
has shown recently that the air mars, colours, distorts, and therefore
misleads and cheats us to an extent much greater than was sui3j)osed.
Langley considers that the light and heat absorbed and scattered by
the air and the particles of matter floating in it amount to no less than
40 per cent, of the light falling upon it. In consequence of this want of
transparency and of the presence of finely divided matter always more
or less suspended in it, the air, when the sun shines upon it, becomes
itself a source of light. This illuminated aerial ocean necessarily
conceals from us by overpowering them any sources of light less bril-
liant than itself which are in the heavens beyond. From this cause
the stars are invisible at midday. This illuminated air also conceals
from us certain surroundings and a|)pendages of the sun, which become
visible on the very rare occasions when the moon coming between us
and the sun cuts ofi" the sun's light from the air where the eclipse is
total, and so allows the observer to see the surroundings of the sun
through the cone of unilluminated air which is in shadow. It is only
when the aerial curtain of light is thus withdrawn that we can become
spectators of what is taking place on the stage beyond. The mag-
nificent scene never lasts more than a few minutes, for the moon
passes and the curtain of light is again before us. On an average,
once in two years this curtain of light is lifted for from three to six
minutes. I need not say how difficult it is from these glimpses at
long intervals even to guess at the plot of the drama which is being
played out about the sun.

The purjiose of this discourse is to describe a method by which it
is possible to overcome the barrier presented to our view by the
bright screen of air, and so watch from day to day the changing
scenes taking place behind it in the sun's surroundings.

1885.] on the Solar Corona. 203

The object of our quest is to be found in the glory of radiant
beams and bright streamers intersected by darker rifts which appears
about the sun at a total solar eclipse. The corona possesses a struc-
ture of great complexity, which is the more puzzling in its intricate
arrangement because though we seem to have a flat surface before us,
it exists really in three dimensions. If we were dwellers in Flatland
and the corona were a sort of glorified catherine-wheel, the task of
interpretation would seem less difiicult. But as we are looking at an
object having thickness as well as extension, the forms seen in the
corona must appear to us more or less modified by the effect of
perspective. This consideration tells us also that the intrinsic bright-
ness of the corona towards the sun's limb is much less than its
apparent brightness as seen by us, of which no inconsiderable part
must be due to the greater extent of corona in the line of sight as the
sun is approached. The corona undergoes great and probably con-
tinual change, as the same coronal forms are not present at different
eclipses.

The attempts which have been made from time to time to see the
corona without an eclipse have been based mainly upon the hoj)e that
if the eye were protected from the intense direct light of the sun, and
from all light other than that from the sky immediately about the
sun, then the eye might become sufficiently sensitive to perceive the
corona. These attempts have failed because it was not possible to
place the artificial screen where the moon comes, outside our atmo-
sphere, and so keep in shadow the part of the air through which the
observer looks. The latest attempts have been made by Professor
Laiigley at Mount Whitney, and Dr. Copeland, assistant to Lord
Crawford, on the Andes. Professor Langley says, "I have tried
visual methods under the most favourable circumstances, but with
entire non-success." Dr. Copeland observed at Puno, at a height of
12,040 feet. He says : " It ought to be mentioned that the appearances
produced by the illuminated atmosphere were often of the most
tantalising description, giving again and again the impression that
my efforts were about to be crowned with success."

There are occasions on which the existence of the brighter part of
the corona near the sun's limb can be detected without an eclipse.
The brightness of the sky near the sun's limb is due to two distinct
factors, the air-glare and the corona behind it, which M. Janssen
considers to be brighter than the full moon. When Venus comes
between us and the sun, it is obvious that the planet as it ai^proaches
the sun, comes in before the corona, and shuts off the light which is
due to it. To the observer the sky at the place where the planet
is appears darker than the adjoining parts, that is to say, the with-
drawal of the coronal light from behind has made a sensible diminu-
tion in the brightness of the sky. It follows that the part of the
sky behind which the corona is situated must be brighter in a small
degree than the adjoining parts, and it would perhaps not be too much
to say that the corona would always be visible when the sky is clear.

204 Mr. William Huggins [Feb. 20,

if our eyes were more sensitive to small differences of illumination of
adjacent areas. My friend Mr. John Brett, A.E.A. tells me that he
is able to see the corona in a telescope of low power.

The spectroscopic method by which the prominences can be seen
fails because a part only of the coronal light is resolved by the prism
into bright lines, and of these lines no one is sufficiently bright, and
co-extensive with the corona, to enable us to see the corona by its
light, as the prominences may be seen by the red, the blue, or the
green line of hydrogen.

The corona sends to us light of three kinds. (1) Light which the
prism resolves into bright lines, which has been emitted by luminous
gas. (2) Light which gives a continuous spectrum, which has come
from incandescent liquid or solid matter. (3) Reflected sunlight,
which M. Janssen considers to form the fundamental part of the
coronal light.

The problem to be solved was how to disentangle the coronal
light from the air-glare mixed up with it, or in other words how to
give such an advantage to the coronal light that it might hold its
own sufficiently for our eyes to distinguish the corona from the bright
sky.

When the report reached this country in the summer of 1882
that photographs of the spectrum of the corona taken during the eclipse
in Egypt showed that the coronal light seen from the earth, as a whole
is strong in the violet region, it seemed to me probable that if by some
method of selective absorption this kind of light were isolated, then
when viewed by this kind of light alone the corona might be at a suffi-
cient advantage relatively to the air-glare to become visible. Though
this light falls within the range of vision, the eye is less sensitive to
small differences of illumination near this limit of its power. This
consideration and some others led me to look to photography for aid,
for it is possible by certain technical methods to accentuate the
extreme sensitiveness of a photographic plate for minute differences of
illumination. [A cardboard on which a corona had been painted by
so thin a wash of Chinese white that it was invisible to the audience,
had been photographed. The photograph thrown upon the screen
showed the corona plainly.] This cardboard represents the state of
things in the sky about the sun. The painted corona is brighter than
the cardboard, but our eyes are too dull to see it. In like manner the
part of the sky near the sun where there is a background of corona, is
brighter than the adjoining parts where there is no corona behind, but
not in a degree sufficiently great for our eyes to detect the difference.

A photographic plate i^ossesses another and enormous advantage
over the eye, in that it is able to furnish a permanent record of the
most complex forms from an instantaneous exposure.

In my earlier experiments the necessary isolation of violet light
was obtained by interposing a screen of coloured glass or a cell
containing potassic permanganate. The possible coming of false
light upon the sensitive plute from the glass sides of the cell, as well

1885.] on the Solar Corona. 205

as from precipitation due to the decomposition of the potassic per-
manganate under the sun's light, led me to seek to obtain the necessary
light-selection in the film itself. Captain Abney had shown that
argentic bromide, iodide, and chloride, differ greatly in the kind of
light to which they are most sensitive. The chloride is most strongly
affected by violet light from h to a little beyond K. It was found
possible by making use of this selective action of argentic chloride
to do away with an absorptive medium. To prevent reflected light,
the back of the plate was covered with asphaltum varnish, and fre-
quently a small metal disc a little larger than the sun's image was
interposed in front of the plate to cut off the sun's direct light.

The next consideration was as to the optical means by which an
image of the sun, as free as possible from imperfections of any kind,
could be formed upon the plate. For several obvious reasons the use
of lenses was given up, and I turned to reflection from a mirror of
speculum metal. My first experiments were made with a Newtonian
telescope by Short. With this instrument, during the summer of
1882 about twenty plates were taken on different days, in all of which
coronal forms are to be seen about the sun's image. After a very
critical examination of these plates, in which I was greatly helped by
the kind assistance of Professor Stokes and Captain Abney, there
seemed to be good ground to hope that the corona had really been
obtained on the plates. [One of these negatives, obtained in August
1882, was shown upon the screen.]

In the spring of the following year, 1883, the attack upon the
corona was carried on with a more suitable apparatus. The Misses
Lassell were kind enough to lend me a seven-foot Newtonian
telescope made by Mr. Lassell which possesses great perfection of
figure and retains still its fine polish. For the purpose of avoiding
the disadvantage of a second reflection from the small mirror, and
also of reducing the aperture to Sh inches, which gives a more
manageable amount of light, I adopted the arrangement of the
instrument which is shown in the following woodcut.

SHUTTER

7?

The speculum b remains in its place at the end of the tube a, a,
by which the mechanical inconvenience of tilting the speculum
within in the tube as in the ordinary form of the Herschelian tele-
scope is avoided.

The small plane speculum and the arm carrying it were removed.
The open end of the tube is fitted with a mahogany cover. In this

206 Mr. William Hiujgins [Feb. 20,

cover at one side is a circular bole/, 3;^ iucbes diameter, for tbe ligbt
to enter ; below is a similar bole over wbieb is fitted a framework to
receive tbe " backs " containing tbe pbotograpbic plates, and also to
receive a frame witb fine-ground glass for putting tbe apparatus into
position. Immediately below, towards tbe speculum, is fixed a
sbutter witb an opening of adjustable widtb, wbicb can be made to
pass across more or less rapidly by tbe use of indiarubber bands of
different degrees of strengtb. In front of tbe opening / is fixed a
tube c, six feet long, fitted witb diapbragms, to restrict as far as
possible tbe ligbt wbicb enters tbe telescoj)e to tbat wbicb comes from
tbe sun and tbe sky immediately around it. Tbe telescope-tube a, a,
is also fitted witb diapbragms, wbicb are not sbown in tbe diagram,
to keep from tbe plate all ligbt, except that coming directly from tbe
speculum. It is obvious tbat, wben tbe sun's ligbt entering tbe tube
at / falls upon tbe central part of tbe speculum, tbe image of tbe sun
will be formed in tbe middle of tbe second opening at d, about two
incbes from tbe position it would take if tbe tube w^ere directed
axially to tbe sun. Tbe exquisite definition of tbe pbotograpbic
images of tbe sun sbows, as was to be expected, tbat tbis small devia-
tion from tbe axial direction, two incbes in seven feet, does not affect
sensibly tbe performance of tbe mirror. Tbe wbole apparatus is
firmly straj^ped on to tbe refractor of tbe equatorial in my observa-
tory, and carried wdtb it by tbe clock motion.

Tbe performance of tbe aj^paratus is very satisfactory. Tbe
pbotograpbs sbow tbe sun's image sbar^^ly defined ; even small spots
are seen. Wben tbe sky is free from clouds, but presents a wbity
appearance from tbe large amount of scattered ligbt, tbe sun's image
is well defined upon a uniform background of illuminated sky, with-
out any sudden increase of illumination immediately about it. It is
only wben tbe sky becomes clear and blue in colour tbat coronal
appearances present tbemselves witb more or less distinctness.
[Several negatives taken during tbe summer of 1883 were sbown on
the screen.] In our climate tbe increased illumination of tbe sky
where there is a background of coronal ligbt is too small to permit
the pbotograpbs which show tbis difference to be otherwise than very
faint. A small increase of exposure, or of develoj^ment, causes it to
be lost in the strong pbotograpbic action of tbe air-glare. For this
reason, the negatives should be examined under carefully arranged
illumination. They are not, therefore, well adapted for projection on
a screen. [A negative taken with a wbity sky, showed a well-defined
image of the sun, with a sensibly uniform surrounding of air-glare,
but without any indication of the corona. In the case of the other
negatives exhibited, which were taken on clearer days, an ai^i^earance,
very coronal in character, was to be seen about the sun.J

On May 6, the corona was photographed during a total eclipse at
Caroline Island by Messrs. Lawrence and Woods. Tbis circum-
stance furnished a good opportunity of subjecting the new method to
a crucial test, namely, by making it possible to compare tbe photo-

1885.] on the Solar Corona. 207

graphs taken in England where there was no eclipse, with those taken
at Caroline Island of the undoubtedly true corona during the eclipse.
On the day of the eclipse the weather was bad in this country, but
plates were taken before the eclipse, and others taken later on. These
plates were j)laced in the hands of Mr. Wesley, who had had great
experience in making drawings from the photograjihs taken during
former eclipses. Mr. Wesley drew from the plates before he had any
information of the results obtained at Caroline Island, and he was
therefore wholly without bias in the drawings which he made from
them. [Photographs of Mr. Wesley's drawings were projected on the
screen, and then a copy of the Caroline Island eclipse photograph.
The general resemblance was unmistakable, but the identity of the
object photographed in England and at Caroline Island was placed
beyond doubt by a remarkably formed rift on the east of the north
jDole of the sun. This rift, slightly modified in form, was to be seen
in a plate taken about a solar rotation period before the eclipse, and
also on a plate taken about the same time after the eclipse. The
general permanence of this great rift certainly extended over some
months, but no information is given as to whether the corona rotates
with the sun. For from the times at which the plates were taken, one
about a rotation period before and the other a rotation period after
the eclipse, it is obvious the rift might have gone round with the
sun, but there is no positive evidence on this point.*]

As the comparison of the English plates with those taken at
Caroline Island possesses great interest, I think it well to put on
record here a letter written by Mr. Lawrence to Professor Stoke?:,
dated September 14, 1883:—

" Dr. Huggins called upon Mr. Woods this morning and showed us
the drawings Mr. Wesley has made of his coronas. He told us that
he particularly did not wish to see our negatives, but that he would
like us to compare his results with ours. We did so, and found that
some of the strongly marked details could be made out on his drawings,
a rift near the north pole being especially noticeable ; this was in a
photograj)h taken on April 3, in which the detail of the northern
hemisphere is best shown, while the detail of our southern hemi-
sphere most resembles the photograph taken on June 6 ; in fact,
our negatives seem to hold an intermediate position. Afterwards I
went with Dr. Huggins and Mr. Woods to Burlington House to see
the negatives. The outline and distribution of light in the inner
corona of April 3 is very similar to that on our plate which had the
shortest exposure; the outer corona is, however, I think, hidden by
atmospheric glare. As a result of the comparison, I should say that
Dr. Huggins's coronas are certainly genuine as far as 8' from the
limb."

Though the plates which were obtained during the summer of 1883
appeared to be satisfactory to the extent of showing that there could

* See Plates XI. and XIa, British Association Eeport, 1883, p. 348.

208 Mr. William Hurjgins [Feb. 20,

be little doubt remaining but that the corona had been photographed
without an eclipse, and therefore of justifying the hope that a suc-
cessful method for the continuous investigation of the corona had
been j)laced in the hands of astronomers, yet as the photographs were
taken under the specially unfavourable conditions of our climate, they
failed to show the details of the structure of the corona.

The next step was obviously to have the method carried out at
some place of high elevation, where the large part of the glare which
is due to the lower and denser j)arts of our atmosphere would no
longer be present. I ventured to suggest to the Council of the Eoyal
Society that a grant from the fund placed annually by the Govern-
ment at the disposal of the Royal Society, should be put in the
hands of a small committee for this purpose. This suggestion was
well received, and a committee was appointed by the Council of the
Royal Society. The committee selected the Rififel near Zermatt in
Switzerland, a station which has an elevation of 8500 feet, and the
further advantages of easy access, and of hotel accommodation. The
committee was fortunate in securing the services, as photographer, of
Mr. Ray Woods, who as assistant to Professor Schuster had photo-
graphed the corona during the eclipse of 1882 in Egypt, and who in
1883, in conjunction with Mr. Lawrence, had photographed the eclipse
of that year at Caroline Island.

Mr. Woods arrived at the Riffel in the beginning of July 1884,
with an apparatus, similar to one shown in the woodcut on a former
page, constructed by Mr. Grubb.

Captain Abney who had made observations on the Rififel in former
years, had remarked on the splendid blue-black skies which were
seen there whenever the lower air was free from clouds or fog.
But unfortunately during the last year or so a veil of finely
divided matter of some sort has been put about the earth, of which
we have heard so much in the accounts from all parts of the earth of
gorgeous sunsets and afterglows. This fine matter was so per-
sistently present in the higher regions of the atmosphere during last
summer, that Mr. Woods did not get once a really clear sky. On the
contrary, whenever visible cloud was absent, then instead of a blue-
black sky there came into view a luminous haze, forming a great
aureole about the sun, of a faint red colour, which passed into bluish
white near the sun. Mr. Woods found the diameter of the aureole
to measure about 44^. This appearance about the sun has been seen
all over the world during last summer, but with greatest distinctness
at places of high elevation.

The relative position of the colours, blue inside and red outside,
shows that the aureole is a diffraction phenomenon due to minute
particles of matter of some kind. Mr. Ellery, Caj^tain Abney, and
some others consider the matter to be water in the form probably of
minute ice spicules ; others consider it to consist of particles of
volcanic dust projected into the air during the eruption at Krakatoa ;
but whatever it is, and whencesoever it came, it is most certainly

1885. J on the Solar Corona. 209

matter iu the wroug place so far as astrouomical observations are
concerned, and iu a peculiar degree for success in j^liotographing
the corona. We are only beginning to learn tbat wbetber in our
persons or in our works, it is bj minimised matter chiefly tbat we are
undone. So injurious was tbe effect of this aureole tbat it was not
possible to obtain any pbotograi^bs of tbe corona at my observatory
near London. Tbis great diffraction aureole went far to defeat tbe
object for which Mr. Woods had gone to tbe Eiffel, but fortunately
tbe great advantage of being free from the effects of the lower
8000 feet of denser air told so strongly, that notwithstanding the
ever-present aureole Mr. Woods was able to obtain a number of
plates on which the corona shows itself with more or less distinct-
ness. [Three untouched photographic copies of the plates taken at
the Eiffel were shown upon the screen.] From the presence of the
aureole the negatives show less detail than we have every reason to
believe would have been the case if the sky had been as blue and clear
as in some former years. This circumstance makes great care neces-
sary in the discussion of these plates, and it would be premature to
say what information is to be obtained from them.

[As an illustration of the differences of form which the corona has
assumed at different eclipses, photographs taken in 1871, 1878, 1882,
and 1883 were projected on the screen. Attention was called to the
equatorial extension seen in the photograph taken in 1878, and to
the suggestion which had been put forward that this peculiar cha-
racter was connected with the then comparative state of inactivity of
the sun's surface, at a period of minimum sun-spot action, especially
as an equatorial extension was observed in 1867.]

It is now time that something should be said of the probable
nature of the corona.

Six hypotheses have been suggested : —

1. That the corona consists of a gaseous atmosphere resting upon
the sun's surface and carried rouud with it.

2. That the corona is made up, wholly or in part, of gaseous and
finely divided matter which has been ejected from the sun, and is in
motion about the sun from the forces of ejection, of tlie sun's rotation,
and of gravity, — and possibly of a rejDulsion of some kind.

3. That the corona resembles the rings of Saturn, and consists of
swarms of meteoric particles revolving with suf&cient velocity to
prevent their falling into the sun.

4. That the corona is the appearance presented to us by the
unceasing falling into the sun of meteoric matter and the debris of
comets' tails.

5. That the coronal rays and streamers are, at least in part,
meteoric streams strongly illuminated by their near ajDj^i'oacb to the
sun, neither revolving about nor falling into the sun, but permanent
in position and varying only in richness of meteoric matter, wdiich
are parts of eccentric comet orbits. This view has been supported by

Vol. XI. (No. 79.) p

210 Mr. William Euggins [Feb. 20,

Mr. Proctor, on the gronnd tliat there must be such streams crowding
richly together in the sun's neighbourhood.

6. The view of the corona suggested by Sir William Siemens in
his solar theory.

It has been suggested, even, that the corona is so complex a
phenomenon that there may be an element of truth in every one of
these hypotheses. Any way this enumeration of hypotheses more or
less mutually destructive, shows how great is the difficulty of ex-
plaining the appearances which present themselves at a total solar
eclipse, and how little we really know about the corona.

An American philosopher, Professor Hastings, has revived a prior
and altogether revolutionary question : Has the corona an objective
existence ? Is it anything more than an optical appearance depending
upon diffraction ? Professor Hastings has based his revival of this
long discarded negative theory upon the behaviour of a coronal line
which he saw, in his spectroscope, change in length east and west of
the sun during the progress of the eclipse at Caroline Island. His
view appears to rest on the negative foundation that Fresnel's theory
of diffraction may not apply in the case of a total eclipse, and that
at such great distances there is a possibility that the interior of the
shadow might not be entirely dark, and so to an observer might cause
the appearance of a bright fringe around the moon.*

Not to speak of the recent evidence of the reality of the corona
from the photographs which have been taken when there is no inter-
veninfi- moon to produce diffraction, there is the adverse evidence
afforded by the peculiar spectra of different parts of the corona and by
the complicated and distinctly peculiar structure seen in the photo-
graphs taken at eclipses. The crucial test of this theory appears
to be, that if it be true, then the corona would be much wider
on the side where the sun's limb is least deeply covered, that is to
say the corona would alter in width on the two sides during the
progress of the eclipse. Not to refer to former eclipses where photo-
graphs taken at different times and even at different places have been
found to agree, the photographs taken during the eclipse at Caroline
Island show no such changes. M. Janssen ssijs : " Les formes de
la couronno ont ete absolument fixes pendant toute la duree do la
totalite." The photographs taken by Messrs. Lawrence and Woods
also go to show that the corona suffered no such alterations in width
or form as would be required by Professor Hastings' theory during
the passage of the moon.

We have therefore, I venture to think, a right to believe in an
objective reality of some sort about the sun corresponding to the
appearance which the corona presents to as. At the same time some
very small part of what we see must be due to a scattering of the

* Koport of tlic Eclipse Expedition to Caroline Islaml, May 1883. Memoir
of the National Academy of Sciences, Wasbington.

1885.] on the Solar Corona. 211

coronal light itself by onr air, but tbe amount of this scattered light
over the corona must be less than what is seen over the dark moon.

That the sun is surrounded by a true gaseous atmosphere of rela-
tively limited extent there can be little doubt, but many considera-
tions forbid us to think of an atmosphere which rises to a height
which can afford any exiDlanation of the corona, which streams several
hundred thousand miles above the photosphere. For example, a gas
at that height, if hundreds or even thousands of times lighter than
hydrogen, w^ould have more tlian metallic density near the sun's
surface, a state of things wliich spectroscopic and other observations
show is not the case. The corona does not exhibit the rapid con-
densation towards the sun's limb which such an atmosphere would
present, especially when we take into account the effect of perspective
in increasing the apparent brightness of the lower regions of the
corona. There is, too, the circumstance that comets have passed
through the upper part of the corona without being burnt up or
even sensibly losing velocity.

There can scarcely be doubt that matter is present about the sun
wherever the corona extends, and further that this matter is in the
form of a fog. But there are fogs and fogs. The air we breathe,
when apparently pure, stands revealed as a dense swarming of millions
of motes if a sunbeam passes through it. Even such a fog is out of
the question. If we conceive of a fog so attenuated that there is only
one minute liquid or solid particle in every cubic mile, we should still
have matter enough, in all probability, to form a corona. That the
coronal matter is of the nature of a fog is shown by the three kinds of
light which the corona sends to us. Eeflected solar light scattered
by particles of matter solid or liquid, and secondly light giving a
continuous spectrum, which tells us that these solid or liquid particles
are incandescent, while the third form of spectrum of bright lines,
fainter and varying greatly at different parts of the corona and at
different eclipses, shows the presence also of light-emitting gas. This
gas existing between the particles need not necessarily form a true
solar atmosj)here, which the considerations already mentioned make
an almost impossible supposition, for we may w^ell regard this thin
gas as carried up with the particles, or even to some extent to be
furnished by them under the sun's heat.

It will be better to consider first the probable origin of this
coronal matter, and by wdiat means it can find itself at such enormous
heights above the sun.

There is another celestial phenomenon, very unlike the corona
at first sight, which may furnish us possibly with some clue to its
true nature. The head of a large comet presents us with luminous
streamers and rifts and curved rays, which are not so very unlike,
on a small scale, some of the appearances which are peculiarly
characteristic of the corona.* We do not know for certain the con-

* See " Comets," Eoyal Institutiou Procfcdingr--, vol. x. p. 1 .

p 2

212 3Ir, William Hiigrjins [Feb. 20,

ditions under wliicli these cometary appearances take place, but the
hypothesis which seems on the way to become generally accepted,
attributes them to electrical disturbances, and especially to a re-
pulsive force acting from the sun, possibly electrical, which varies as
the surface and not like gravity as the mass. A force of this nature
in the case of highly attenuated matter can easily master the force
of gravity, and as we see in the tails of comets, blow away this thin
kind of matter to enormous distances in the very teeth of gravity.

If such a force of repulsion is experienced in comets, it may well
be that it is also present in the sun's surroundings. If this force be
electrical it can only come into play when the sun and the matter
subjected to it have electric potentials of the same kind, otherwise the
attraction on one side of a particle would equal the repulsion on
the other. On this theory, the coronal matter and the sun's surface
must both be in the same electrical state, the repelled matter negative
if the sun is negative, positive if the sun is positive.

The grandest terrestrial displays of electrical disturbance, as seen
in lightning and the aurora, must be of a small order of magnitude
as compared with the electrical changes taking place in connection
with the ceaseless and fearful activity of the sun's surface, but we do
not know how far these actions, or the majority of them, may be in
the same electrical direction, or what other conditions there may be,
so as to cause the sun's surface to maintain a high electrical state,
whether positive or negative. A permanence of electric potential of
the same kind would seem to be required by the phenomena of
comets' tails.

If such a state of high electric potential at the photosphere be
granted as is required to give rise to the repulsive force which the
phenomena of comets appear to indicate, then considering the gaseous
irruptions and fiery storms of more than Titanic proportions which
arc going on without ceasing at the solar surface, it does not go
beyond what might well be, to suppose that portions of matter
ejected to great heights abave the photosphere and often with velo-
cities not fa removed from that which would bo necessary to set it
free from the sun's attraction, and very probably in the same electric
state as the photosphere, might so come under this assumed electric
repulsion as to be blown upwards and to take on forms such as those
seeu in the corona : the greatest distances to which the coronal
streamers have been traced are small as compared with the extent of
the tails of comets, but then the force of gravity which the electrical
repulsion would have to overcome near the sun would be enormously
greater.

It is in harmony with this view of things that the positions of
greatest coronal extension usually correspond with the spot zones
where the solar activity is most fervent ; and also that a careful
examination of the structure of the corona suggests strongly that the
forces to which this comjikx and varying structure is due have their
seat iu the sun. Matter repelled upwards would rise with the smaller

1885.] on the Solar Corona. 213

rotational velocity of the photosphere, and lagging behind would give
rise to curved forms ; besides, the forces of irruption and subsequent
electrical repulsion might well vary in direction and not be always
strictly radial, and under such circumstances a structure of the
character which the corona presents might well result. The sub-
permanency of any great characteristic coronal forms, as, for ex-
ample, the great rilt seen in the photographs of the Caroline Island
eclipse and also in those taken in England a month before the eclipse
and about a month afterwards, must probably be explained by the
maintenance for some time of the conditions upon which the forms
depend, and not to an unaltered identity of the coronal matter ; the j)er-
manency belonging to the form only, and not to the matter, as in the
case of a cloud over a mountain top, or of a flame over the mouth of
a volcano. If the f(n'ces to which the corona is due have their seat
in the sun, the corona would probably rotate with it ; but if the corona
is produced by conditions external to the sun, then the corona might
not be carried round with the sun.

We have seen that the corona consists probably of a sort of incan-
descent fog, which at the same time scatters to us the photospheric
light. Now we must bear in mind the very different behaviour of a
gas, and of liquid or solid particles in the near neighbourhood of the
sun. A gas need not be greatly heated, even when near tlie sun, by
the radiated energy ; heated gas from the photosphere would rapidly
lose heat ; but on the other hand liquid or solid particles, whether
originally carried uj) as such, or subsequently formed by condensation,
would absorb the sun's heat, and at coronal distances would soon rise
to a temperature not very greatly inferior to that of the photosphere.
The gas which the spectroscope shows to exist along with the incan-
descent particles of the coronal stuff, may therefore have been carried
up as gas, or have been in part distilled from the coronal particles
under the enormous radiation to which they are exposed. Such a view
would not be out of harmony with the very different heights to which
different bright lines may be traced at different parts of the corona
and at different eclipses. For obvious reasons, gases of different vapour
density would be differently acted upon by a repulsive force which
varies as the surface and would to some extent be winnowed from
each otber; the lighter the gas the more completely would it come
under the sway of repulsion, and so would be carried to a greater
height than the gas more strongly held down by gravity. The
relative proportions, at different heights of the corona, of the gases
which the spectroscope shows to exist there (and recently Captain
Abney and Professor Schuster have shown that in addition to the
bright lines already known, the spectrum of the corona of 1882 gave
the rhythmical group of the ultra-violet lines of hydrogen which are
characteristic of the photographic sj^ectra of the white stars, and some
other lines also) would vary from time to time, and depend in ynvt
upon the varying state of activity of the photosphere, and so probably
establish a connection with the spectra of the prominences. This

214 Mr. William Euggins on the Solar Corona, [Feb. 20,

view of the corona would bring it within the charmed circle of inter-
action which seems to obtain among the phenomena of sun-sjiots
and terrestrial magnetic disturbances and auroras.

Many questions remain unconsidered ; among others, whether the
light emitted by the gaseous part of the corona is due directly to the
sun's heat, or to electrical discharges taking place in it of the nature
of the aurora. Further, what becomes of the coronal matter on the
theory which has been suggested ? Is it permanently carried away
from the sun, as the matter of the tails of comets is lost to them?
Amoncy other considerations it may be mentioned that electric re-
pulsion can maintain its sway only so long as the repelled particle
remains in the same electrical state : if through electric discharges it
ceases to maintain the electrical potentiarl it possessed, the repulsion
has no more power over it, and gravity will be no longer mastered.
If, when this takes place, the particle is not moving away with a
velocity sufficiently great to carry it from the sun, the particle will
return to the sun. Of course, if the effect of any electric discharges
or other conditions has been to change the potential of the particle
from positive to negative, or the reverse, as the case may be, then the
repulsion would be changed into an attraction acting in the same
direction as gravity. In Mr. Wesley's drawings of the corona,
especially in those of the eclipse of 1871, the longer rays or streamers
appear n-t to end, but to be lost in increasing faintness and diffusion,
but certain of the shorter rays are seen to turn round and to descend
to the sun.*

It is difficult for us living in dense air to conceive of the state of
attenuation probably present in the outer parts of the corona. Mr,
Johnstone Stoney has calculated that more than twenty figures are
needed to express the number of molecules in a cubic centimetre of
ordinary air, and Mr. Crookes shows us in his tubes that matter,
even wdien reduced to one-millionth part of the density of ordinary
air, can become luminous under electrical excitement. [A glass bulb
about 4 inches in diameter, kindly lent to me by Mr. Crookes, was
exhibited, in which a metal ball about half an inch in diameter
formed the negative pole. Under a suitable condition of the induc-
tion current, this ball was seen to be surrounded by a corona of
blueish-grey light which was sufficiently bright to be seen from all
parts of the theatre.] Yet it is probable that these tubes must be
looked upon as crowded cities of molecules as compared with the
sparse molecular population of the great coronal wastes.

I forbear to speculate further, as we may expect more information
as to the state of things in the corona from the daily photographs
which will be shortly commenced at the Cape of Good Hoj^e by Mr.
Kay Woods under the direction of Dr. Gill. [W. H.]

* For a history of opinion of the nature of the corona, see Papers by Prof.
Norton, Prof. Young, and Prof. Langky in the 'American Journal of Science';
also 'The Sun/ by Prof. Young; and 'The Sun the liulcr of the Pliiuetary
Syateni,' and various essays by Mr. R. A. Proctor.

1885.] Prof. Lanhester on a Marine Biohxjical Lahoratory. 215

WEEKLY EVENING MEETING,

Friday, February 27, 1885.

Henry Pollock, Esq. in tlie Chair.

Professor Eay Lankester, M.A. LL.D. F.R.S.

A Marine Biological Laboratory,

The lecturer stated that he had been invited, as Secretary of the
Marine Biological Association, of which Professor Huxley was
President, H.R.H. the Prince of Wales, Patron, and all our leading
naturalists members, to explain the objects of the Association. The
immediate purpose of the Association was to erect a laboratory
on the sea-coast where naturalists might resort for the purpose of
studying, with the aid of the best possible ajiparatus and other
facilities, the structure and life-history of marine })lants and animals.

This study was not only important as a rapidly growing branch
of science, but had value for the practical man, in that the proper
management of our sea-fisheries must dei)end on the knowledge gained
in such laboratories as that about to be erected.

The lecturer then gave some account of an investigation made by
him into the causes of the colour of the " green beard " oysters, or
huitres de Marenne, as an example of the kind of work which would
be carried on in a marine laboratory, and of the ap^jaratus needed for
such work.

He then mentioned what had been done by other countries in the
way of providing laboratories on the sea-coast. The governments of
France and the United States were especially signalised as having
recognised the commercial and national imj^ortance of a thorouo-]ily
scientific study of sea-fishes and shell-fish, the latter giving now a
yearly grant of seventy tliousand jjounds to Professor Baird for the
jmrpose of laboratories and experiments in fisli-culture. The admir-
able marine laboratory organised at Naples by Dr. Dolirn, and tho
smaller institutions at Trieste, at Newport and Beaufort, US. A.
were described. Drawings of the Naples laboratory and of that at
Wood's Holl, U.S.A. were exhibited.

A map of Plymouth Sound was then referred to, and the
advantages of Plymouth as a site for a marine laboratory were
explained — being these, viz. the occurrence of a varied and abundant
faima in the waters of the Sound and the presence of a large fleet of
fishing boats. The Marine Biological Association had obtained per-
mission to erect a laboratory upon an admirable site on the Citadel

216 Prof. Lankester on a Marine Biological Lahoratory. [Marcli 2,

Hill at Plymoutli — a sketch of wliicli was exhibited. Five thousand
pounds had been raised by the Association by subscriptions from
scientific men and their friends, and from important bodies interested
in the enterprise as one of a national character tending to develop
commercial and industrial resources— such as the Corporation of the
City of London, the Clothworkers', Mercers', Skinners' and Gold-
smiths' Companies. The Association required another five thousand
23ounds before commencing to build its laboratory — and this the
lecturer hoped to see soon provided.

[K.L.J

GENERAL MONTHLY MEETING,

Monday, March 2, 1885.

SiK FiiEDEiiiCK Pollock, Bart. M.A. Manager and Vice-President,

in the Chair.

A. Noel Agnew, Esq.

Alfred Barnard Basset, Esq. M.A.

Richard H. Beauchamj), Esq.

Charles Harrison, Esq.

James Hole, Esq.

Tliomas John Maclagan, M.D.

"William Haynes Smith, Esq.

Richard Everard Webster, Esq. Q.C.

were elected Members of the Royal Institution.

The Pkesents received since the last Meeting were laid on the
table, and the thanks of the Members returned for the same, viz. : —

FROM

The Governor-General of Jw(7ia— Geological Survey of India: Pah\3ontolt)giii

Indica : Series IV. Voh I. Part 4. 4to. 1885.
The Neio Zealand Government— iHatist'ics of the Colony of New Zealand, 1883.

ful. 1884.
The Corporation of the City of Loudon — London's Roll of Fame, 1757-1884. 4to.

1884.
Accademia dei Lincei, Eeale, lioma — Atti Seric Quarta : Rendieonti. Vol. I.

Fasc. 1-4. 8vo. 1884-5.
Asiatic Society of Bengal — Proceedings, No. 10. 8vo. 1884.

Journal, Vol. LII. Part 11. 8vo. 1883.
Astronomical Society, lioy<d — Montldy Notices, Vol. XLV. No. 3. 8vo. 1885.
Bagot, Alan, Esq. {the ylMf/<or)— Principles of Civil Engineering as applied to

Agriculture and Estate Management. Vlmo. 1885.
Bankers, Institute o/— Journal, Vol. V. Part 9; Vol. VI. Parts 1 and 2. 8vo.

1884-5.
Bo.^lon Society of Natural H/sf or y— Memoirs, Vol. 111. Nos. 8-10. 4to. 1884.
Proceedings, Vol. XXII. Parts 2, 3. 8vo. 1883-4.

1885.] General MontJili/ Meeting, 217

British Architects, Royal Institute o/— Proceedings, 1884-5, Nos. 8, 9. 4to.
Brussels, University of — Notice Historique. Par L. Vanderkindere [1831-1884].

8vo. 1884.
Cambridge Philosophical Society — Proceedings, Vols. I. and II. 1813-1876. 8vo.
Chemical Society — Journal for Februnvv, 1885. 8vo,

Index to Journal, Vols. XLV. and XLVI.
Dilettanti Society — An Account of the Portraits. 8vo. 1885.
F.ast India Association— 3 onxnal. Vol. XVII. No. 2. 8vo. 1885.
Editors — Ame\\Q2i\\ Journal of Science for February, 1885. 8vo.

Analyst for February, 1885. 8vo.

Athenaeum for February, 1885. 4to.

Chemical Newd for February, 1885. 4to.

Engineer for February, 1885, fol.

Horological Journiil for February, 1885. 8vo.

Iron for February, 1885. 4to.

Nature for February, 18S5. 4to.

Revue Scientifique and Revue Politique et Littc'rairc for February, 1885. 4to.

Science Munthly, Illustrated, for February, 1885.

Telegrapliic Journal for February, 1885. 8vo.
FranUin Institute— Jommd], No. 710. 8vo. 1885.
Geograj)hical Society, Boyal — Proceedings, New Series, Vol. VII. No. 2. 8vo.

1885.
Geological Society — Quarterly Journal, No. 161. 8vo. 1885.
Johns Ilopliitis University — University Circular, No. 36. 4to. 1884,
Linnean Society — Transactions: Botany, Vol. II. Part 8; Zoology, Vol. II.

Parts 11, 13, 14; Vol. III. Part 2. 4to. 1884.
Meteorological Office — Monthly AVeather Report, November, 1884. 4to.

Principles of Forecasting. By R. Abercromby. 8vo. 1885.
National Association for Social Science — Proceedings, Vol. XVII. No. 4. 8vo.

1884.
North of England Institute of Mining and Mechanical Engineers — Transactions,

Vol. XXXIV. Part 1. 8vo. 1885.
Odontological Society of Great Britain — Transactions, Vol. XVII. No. 4. New
Series. 8vo. 1885.

Supplementary Catalogue of the Museum. 8vo. 1884,
Pharmaceutical Society of Great Britain — Journal, February, 1885. 8vo.
Photographic Society — Journal, New Series, Vol. IX. No, 4. 8vo. 1885.
Seismologicfd Society of Japan — Transactions, Vol. VII. Part 2. 8vo. 1884.
Smith, iVilloughhy, Esq. M.R.I. (the ^?t//wr)— Induction and Conduction. 8vo.

1885.
Society of Arts — Journal, February, 1885. 8vo.
St. Bartholomew's Hospital— ^ei>OTts, Vol. XX. 8vo. 1884.
St. Pttershourg, Academic des Sciences — Bulletins, Tome XXIX. No. 4. 4to. 1884.
United Service Institution, i?o//aZ— Journal, No. 127. 8vo. 1885.
Vereins zur Beforderung des Gewerbfleisses in Prenssen — Verhandlungen, 1885 :
Heft 1. 4to.

WEEKLY EVENING MEETING,

Friday, March 6, 1885.

Joseph Brown, Esq. Q.C. Manager, in tlie Chair.

Charles T. Newton, C.B..LL.D. M.A.

The German Discoveries at Pergamus.
(No Abstract.)

218 Sir Frederick Abel [March 13,

WEEKLY EVENING MEETING,

Friday, March 13, 1885.

Sill Fredekick Bramwell, F.R.S. Manager and Vice-Presidcut,
in the Chair.

Sir Frederick Abel, C.B. D.C.L. F.R.S. M.B.L

Accidental Explosions produced by Non-explosive Liquids.

Ten years ago the lecturer discussed in some detail the various
causes of the continually recurring casualties which are classed under
the head of accidental explosions, and he then had occasion to com-
jiare the causes of coal-gas explosions, the occurrence of which is
as deplorably frequent now as it was then, with those of accidents
connected with the transport, storage, and use of volatile inflammable
liquids which are receiving extensive ajDplication, chiefly as solvents
and as illuminating agents.

Within the last few years he has had occasion to devote special
attention to the investigation of instances of this class of accident,
and to examine more particularly into the probable causes of frequent
casualties connected with the employment of lamps in which the
various products included under the general designations of jDctroleum
and paraffin oil are burned. The latter branch of these inquiries,
which is still in progress, has been conducted in association with Mr.
Bovcrton Redwood, the talented Secretary and Chemist of the Petro-
leum Association, and with the valuable aid of Dr. W^. Kellner,
Assistant- Chemist of the War Department. Although it may be
hoped that their continuation will lead to farther data and con-
clusions of practical and public importance, it is thought that some
account of facts ah'eady elicited may interest the members of the
Royal Institution, and j^ossess some general value.

Ever since liquids which, more or less rapidly, evolve inflammable
vapour when freely exj^osed to air, or partially confined, have been in
extensive use, casualties have occurred from time to time through
tlie accidental or thoughtless ignition of the mixtures of vapour
and air thus formed, whereby more or less violent and destructive
explosions have been produced, often followed by the ignition of the
exposed liquid which is the source of the explosive mixture, and by
the consequent frequent development of disastrous conflagrations.

Many instances are on record of explosions, sufficiently violent to
produce effects destructive or injurious to life and property, resulting
from the application of flame to vessels which had contained cither
the more volatile coal-tar or petroleum products, or strong spirituous

1885. J on Accidental Explosions by Non-explosive Liquids. 219

liquids, and which, though they had been entirely or nearly emptied
of their contents, still contained, or retained by absorption within their
body, some of the volatile liquid, this having, by evajioration into the
air in the emptied receptacle, produced with it a more or less violently
explosive mixture. Thus, a loud explosion occurred at the entrance
of a lamp-maker's shop in Whitecross Street, which was found to have
been caused by a boy throwing a piece of lighted paper into a cask
standing under the gateway, which had contained benzoline ; two
boys were very seriously injured by the blast of flame which was
projected from the barrel. A perfectly analogous accident was soon
afterwards reported in the papers as having occurred at Sheffield,
with serious injury to the author of the catastroj)he and another boy ;
and a very similar case occurred at Exeter during the removal of
some empty benzoline barrels, consequent upon a boy applying a
lighted match to the hole of one of them. Again, at Spaxton in
Somersetshire, a young man applied a light to the hole of a benzoline
cask described as nearly empty which was standing in the road, when
three young men were blown across the road, one of them being so
seriously injured about the head that he died.

Explosions with similarly disastrous results have also been
publicly recorded as having resulted from the application of a light
to rum puncheons and whisky casks, even some time after they
have been emptied of their contents, the evaporation of the alcohol
absorbed by the wood having sufficed to convert the confined air into
a violently explosive mixture.

The readiness or extent to which inflammable vapour is evolved
from those j^i'oducts of the distillation of petroleum, or of shale or
coal, which are used for illuminating purposes, dififers of course
considerably with the character of these liquids. Those which are
classed as petroleum spirit (known as gasoline, benzine, benzoline,
nai3htha,japanners' spirit, &c.), and in regard to which there exist very
special precautionary enactments, are, it need scarcely be said, of far
more dangerous character than those classed as burning oils, which
include the paraffin oils obtained from shale and the so-called flashing
points of which range from 73^ to above 140° Fahrenheit. The
rapidity with which the vapours, evolved by the more volatile products
on exposure to air, or by their leakage from casks or barrels, diffuse
themselves through the air, producing with it more or less violent
explosive mixtures, has been a fruitful source of disaster, sometimes
of great magnitude. The lecturer had occasion to refer, in his
discourse of 1875, to an accident at the Eoyal College of Chemistry
of which he was a witness, in 1847, when the lamented Mr. C B.
Mansfield was engaged in the conversion of a quantity of benzol into
nitrobenzol in a capacious glass vessel, which suddenly cracked,
allowing the warm liquid hydrocarbon to escape and flow over a large
surface. This occurred in an apartment 38 feet long, about 30 feet
wide, and 10 feet high ; there was a gas jet burning at the extremity
of the room opposite to that where the heated liquid was spilled, and

220 Sir Frederick Abel [March 13,

within a very brief space of time after the vessel broke, a sheet of
flame flashed from the gas jet along the upper part of the room, to
the spot where the fluid lay scattered.

The origin of a fire which occurred at some mineral oil stores at
Exeter in 1882, affords another striking illustration of the great
rapidity with which the vapour of petroleum spirit will diffuse itself
throuf^h the air. The store which caught fire, and which contained
both petroleum oil and spirit, or benzoline, was one of a range of
arched caves upon the bank of a canal, being separated from it by a
roadway about 50 feet wide. It was a standing rule at the stores
that no light should be taken to any one containing benzoline. The
benzoline casks were to be removed from this store, and the foreman,
desirous of beginning the work early, and forgetful of the rule, went
to the store shortly before daylight, carrying a lighted lantern, which
he placed upon the ground at a distance of several feet from the doors.
He then proceeded to open these. As he did so, he noticed a very
powerful odour of benzoline and, almost immediately, he saw a flash
of flame proceed from the lantern to the store. He had just turned
to escape, when an explosion occurred which blew the doors and the
lantern across the canal ; the benzoline in the store was at once inflamed,
and flowed out into the road and upon the surface of the water, firing
a small vessel which lay against the quay, and setting fire to the
stores of benzoline contained in two neighbouring caves.

Many exemplifications might be cited of the danger arising from
the accidental spilling or escape of petroleum spirit (or even of oils of
very low flashing point) in the ordinary course of dealing w4th these
liquids, as in stores where there is but very imperfect ventilation,
and in some part of which a flame exists, or is carelessly introduced;
or, from the escape of spirit or its vapour from stores or receptacles
to adjacent spaces where, its existence being unsuspected, the ignition
of the resulting explosive mixture of vapour and air may be at any
time brought about.

Without referring to accidents which have been due to flagrant
carelessness in introducing a flame or striking a light in a store where
petroleum vapour is likely to exist in the air, or where some form of
spirit has been accidentally spilled, a few instances may be quoted
which illustrate the magnitude of casualties liable to arise from the
causes just referred to. Some years ago an explosion productive of
much damage occurred in a sewer at Greenwich, and was clearly
traced to the entrance into the sewer of some petroleum products
(from a neighbouring patent gas factory) ; the vapours from these had
diffused themselves through the air in tlic sewer to a considerable
distance, forming with it an explosive mixture which must have been
accidentally ignited at one of the sewer openings in the street above.
Last spring a similar accident occurred at Newport in Monmouth-
shire, a quantity of benzoline having escaped into a sewer from a
neighbouring store ; the ignition of the resulting explosive mixture
of vapour and air, with which a considerable length of the sewer

1885.] on Accidental Explosions by Non-explosive Liquids. 221

became filled, tore u]) tlie roadway to some distance, several persons
being thrown down. A terrific disaster of the same class was re^iorted
from San Francisco in November 1879. During the driving of a
tunnel in the San Jose Santa Cruz Eailway, a vein of petroleum
became exposed by the excavators, who were of course working with
naked lights. Three violent explosions occurred in consequence, in
rapid succession, resulting in the death of twenty-five Chinamen and
in the injury of seventeen others and two w^hite men.

Another accident, which occurred near Coventry nearly five years
ago, may be quoted in illustration of the unsuspected manner in which
explosive gas-mixtures may exist in localities which, to the superficial
observer, may appear to have no connection with a neighbouring
locality where volatile liquids are liable to escape confinement.

A dealer in benzoline spirit kept his small store of that liquid
(from 20 to 80 gallons) in an apartment of his house, upon the base-
ment, the floor of the room being paved with red bricks. At a
distance of about three feet from the store room there was a well,
the depth of which to the surface of the water was 20 feet. The
well was closed in almost entirely wdth planks covered with earth.
The water in the well being found foul, the owner had the latter
uncovered, with a view to its being cleared out. The workman in
charge of the operation, after having been engaged for three hours in
pumping out a large quantity of the water, lowei-ed a lighted candle
into the well according to the usual practice to see whether he could
descend with safety, when, while bending over the opening, he per-
ceived a blue flame shooting upwards, and was violently thrown back
and badly burnt, a woman who was watching him being similarly
injured. The benzoline which had been spilled from time to time in
small quantities in filling the cans of customers had readily passed
through the porous brick upon which it fell, and gradually permeating
the soil beneath had, in course of time, drained into the adjacent well.
That this must occur under the circumstances described would have
been self-evident to any one acquainted with the behaviour of these
liquids and with the attendant circumstances. In localities where
large quantities have for some time been stored in the usual casks or
barrels, there is no difficulty in " striking oil " by sinking a well in
the immediately adjacent ground, in consequence of the large amount
of leakage of the spirit or oil which must unavoidably occur. Even
in the absence of leakage from the openings of the barrels or from
any accidental imperfection, considerable difi'usion of the volatile
liquid and consequent escape by evaporation through the wood itself^
must occur in large petroleum stores especially if much exposed to
the sun, and in the holds of ships where the temperature is generally
more or less high. Even the precaution adopted of rinsing the barrels
before use with a stiff solution of glue is not effectual in preventing
the escape of the spirit from these causes, as the effect of alternations
of temperature ujDon the barrels must tend to re-open any unsound
places temporarily closed by the glue. Even at very extensive

222 Sir Fredenclc Ahel [March 13,

depots, where special arrangements were adopted to maintain the
stores uniformly at a very moderate average temperature, the loss of
petroleum sj^irit from leakage and evaporation was estimated, ten
years ago, to amount to about 18 per cent, of the total stored, while
the average loss from the same causes upon petroleum oil was about
9 per cent. By the introduction from time to time of improvements
of the arrangements, the loss of spirit by leakage and evaporation
has been very considerably reduced, amounting to less than 8 per
cent, in well-constructed stores, while at some petroleum stores, more
especially in Germany, the loss of oil from leakage is now said not to
exceed 1 per cent.

As in the case of the loss of coal-laden ships by explosions on the
high seas, such loss has probably in many cases been due to the
development of gas from the cargo, and to its diffusion into the air of
parts of the ship more or less distant from the coal, producing an
explosive atmosi)here which might become ignited by the convey-
ance or existence of a light or fire, where its presence was not
deemed dangerous; so also it is not improbable that the supposed loss
by effects of weather, of missing petroleum-laden vessels, may have
occasionally arisen from fire caused in the first instance by the
diffusion of vapour, escaping from the cargo, through the air in
contiguous parts of the ship, and the accidental ignition of the
explosive atmosphere thus produced.

The possibility of such disasters has been demonstrated by the
repeated occurrence of accidents of this class in ports or their
vicinity. A very alarming instance of the kind occurred in 1871 on
the Thames at Erith. Two brigantines had nearly completed the
discharge of their cargoes of petroleum spirit (" na2)htha "), when
another vessel, the Muth, from Nova Scotia, containing upwards of
2000 barrels of the same material, together with other inflammable
cargo, anchored alongside them. This ship had encountered very
severe weather, and it had been necessary to batten down the hatches ;
the cargo in the hold had consequently become enveloped in the
vapour which had escaj^ed from the casks. On the removal of the
hatches, an explosive mixture was speedily produced by access of
air, and, through some unexplained cause, became ignited shortly
after the vessel anchored. A violent explosion followed, and the vessel
was almost instantly in flames, the fire being rapidly communicated to
the other two ships, which were with difiiculty saved after sustaining
considerable injury, while the Ruth, in which the fire raged uncon-
trollably, was after a time towed to a spot where she could burn
herself out and sink, without damage to the other shipi^ing. Three
of the crew were seriously injured by the explosion, and the mate
was blown to some distance into the water.

In June 1873 a vessel (the Maria Lee), laden with 300 barrels
of petroleum and other inflammable cargo, was destroyed by fire on
the Thames near the Purflcct powder magazines, consequent upon

1885.] on Accidental Explosions hy Non-explosive Liquids. 223

the explosion in her of a mixture of i)etrolenm vapour and air, and a
similar accident occurred about the same time in Glasgow harbour.
In the case of the Maria Lee it was clearly proved that the vapour
resulting from leakage and evaporation of the spirit in the hold had
diffused itself through the ship during the night, which was very hot,
the hatches having been kept closed and covered with tarpaulin, in
consequence of the occurrence of a thunderstorm. Upon the captain
entering his cabin in the after-part of the ship early in the morning
(and probably striking a light) a loud explosion took place, and
flame was immediately seen issuing from the fore-part of the ship.

A very similar casualty to the foregoing occurred at Liverpool
four years afterwards, in a small vessel laden with petroleum spirit,
which proved not to have been at all adapted by internal construction
for the safe carriage of such a freight. The cargo of 214 barrels of
spirit had been stowed on board, and the hatches were put down and
covered with tarpaulin. The cabin and forecastle of the smack were
below deck, and were only separated by a thin partition from the
hold. The loading had been completed between 6 and 7 o'clock in
the evening, and at about 8 o'clock the captain went into the cabin
and kindled a lamp. A man upon deck, who with another was in-
jured by the explosion and fire, saw the light burning in the forecastle,
and almost immediately afterwards the deck was lifted and the man
was thrown some distance, while flame issued from the hold. The
captain was terribly burned, and died shortly afterwards. In vessels
which are constructed for the American petroleum trade, the cabins
and forecastles are all upon deck, that part of the vessel which carries
the freight, between decks, being as completely as possible separated
from the other parts of the shij).

In some instances, ships laden with petroleum oil have become
inflamed, in an unexplained manner, without the occurrence of any
noticeable explosion, as was the case last year with a large vessel (the
Aurora) in the port of Calcutta, after she had discharged more
than half her cargo of 59,000 cases. The vessel burned for nine
hours, the river becoming covered with burning oil as she gradually
filled with water ; the direction of the wind and the condition of the
tide at the time of her sinking fortunately prevented the fire from
reaching the shipping higher up the river.

There is no doubt that, while with cargoes of the more volatile
petroleum products, classed as spirit, the greatest precautions are
necessary to guard against the possible ignition of more or less ex-
plosive mixtures of vapour and air which will be formed in the
stowage spaces of ships, and which may extend to other parts of the
vessels unless very efficient ventilation be maintained, ships laden
with the oils produced for use in ordinary petroleum- or paraffin-
lamps, and which, yielding vapours at temperatures above the standard
fixed as a guarantee of safety, incur comparatively very little risk of
accident, ijrovided simple precautions be observed. If moreover, by
yome act of carelessness, or some accident not guarded against by the

224 Sir Frederick Abel [March 13,

prescribed precautions, a part of such a cargo does become ignited, the
prompt and, as far as practicable, complete exclusion of air from the
seat of the fire, by the secure battening down of the hatches, will most
probably save the ship from destruction. There are numerous records
of vessels having discharged cargoes of petroleum oil, many barrels of
which have been found greatly charred on the outside, occasionally
even to such an extent that the receptacle has scarcely sufficient
strength remaining to retain its contents. A remarkable illustration
of the controllable nature of fire in a petroleum-laden ship was
furnished by the ship Joseph Fish, laden with refined petroleum,
lubricating oil, and turpentine, which, a fortnight after leaving New
York (in September 1879), was struck by lightning during a heavy
squall, the hatches being closed at the time. Smoke at once issued
from below, and the force-pumps were set to work directly to keep
the fire down. The hatches were removed for examination as the fire
appeared to gain ground, but were immediately rej)laced, and, after
further pumping, as the fire appeared to increase, and an explosion
w^as feared, the crew took to their boats, remaining near the ship.
Eight hours afterwards they were picked up by a passing ship, which
remained near the Joseph Fish until daylight. Her captain then
returned on board, and as he found that the fire aj)peared to be out,
the crew returned and the ship resumed her voyage, reaching the port
of London without further incident, except that during the use of the
pumps for removing the water, considerable quantities of petroleum
and turpentine were pumped up with it from the hold. When the
cargo was discharged, a large number of the barrels bore evidence of
the great heat to which they had been exposed ; several casks had
gone to pieces and the staves of others were charred quite half-w\n,y
through, although they still retained their contents.

The lecturer had occasion, ten years ago, to dwell upon the
recklessness with which fearful risks were incurred, in some cases no
doubt ignorantly, but in others scarcely without a knowledge on the
part of those who were responsible, of the nature of the materials
dealt with, by transporting volatile and highly inflammable liquids
together with explosive substances in barges or other craft, and in
doing so, moreover, without the adoption of even the most obvious
j)recautions for guarding against access of fire to the contents of those
vessels. The instance of the explosion in 1864 of the Lottie Sleigh
at Liverpool, laden with 11 J tons of gunpowder, inconsequence of the
accidental spilling andignifion of some paraffin oil in the cabin of the
ship, illustrated the danger incurred in permitting these materials to
bo together on board a vessel, and should have furnished some
warning by the publicity it received ; but the explosion ten years later,
on the Kegent's Park canal, of the barge Tilbury, revealed the
continued prevalence of the same reckless disregard of all dictates of
common prudence in dealing with the joint transport of explosives
and vfjlatile inflammable liquids.

The efficient laws and Government inspection to wliich all traffic

1885.] on Accidental Explosions by Non-explosive Liquids. 226

in exiHosives has since then been subject, has rendered the recurrence
of that identical kind of catastrophe almost out of the question, but
an illustration has not been wanting quite recently of the fact that,
but for the respect commanded by the rigour of the law, barges passing
through towns would probably still carry freights composed of
petroleum spirit and powder or other explosives, being at the same
time provided with a stove, lamp and matches for the convenient
production of explosions. In August 1883 an explosion occurred on
the canal at Bath, in a barge which sank immediately, the master
being slightly injured ; the freight of the vessel consisted of petroleum,
benzoline, and lucifer-matches.

The last four years have furnished several very remarkable illus-
trations of great injuries inflicted on ships by explosions, the origin of
which was traced to the existence on board of only small quantities of
some preparation containing petroleum spirit, or benzoline, with the
nature of which the men who had charge of them were not properly
acquainted. These materials had consequently been so dealt with as
to become the means of filling more or less confined spaces in the ships
with an explosive atmosphere which, when some portion of it reached
a flame, was fired throughout, with violently destructive effects.

The first authenticated case of an accident due to this cause
occurred in June 1880, on board the Pacific Steam Navigation
Company's steamer Coquimho shortly after her arrival in the
morning at Valparaiso from Coquimbo. A violent explosion took
place, without any warning or apparent cause, in the fore-peak of the
vessel, blowing out several plates of the bow and doing other structural
damage, besides killing the ship's carpenter; the explosion could
only be accounted for by the circumstance that a small quantity of a
benzoline preparation used for painting purposes (probably as
"driers") was stored in the fore-peak and that a mixture of the
vapour from this with the air had become ignited. The sufferer was
the only person who could have thrown light upon the precise cause
of the accident, but there was no other material whatever in that part
of the ship to which the explosion could have been in any way
ascribed.

In May 1881 an explosion of a trifling character occurred on
board H.M.S. Cockatrice in Sheerness Dockyard, in consequence
of a man going into the store-room with a naked light and holding it
close to a small can which was uncorked at the time, and which
contained a preparation recently introduced into the naval service as
a " driers " for use with paint, under the name of Xerotine Siccative.
This preparation, which was of foreign origin, appears to have been
adopted for use in the naval service and to have been issued to
H.M. ships generally without any knowledge of its composition, and
without attention being directed to the fact that it consisted very
largely of the most volatile petroleum spirit, which would evaporate
freely if the liquid were exposed to air at ordinary temperatures, and
the escape of which from a can, jar or cask, placed in some confined
Vol. XI. (No. 79.) ' q

226 Sir Frederick Abel [March 13,

and non-ventilated space, must speedily diffuse itself througli the air,
and render the latter more or less violently explosive.

When attention was directed to the highly inflammable character
of this xerotine siccative by the slight accident referred to, official
instructions were issued by the Admiralty, in June 1881, to ships and
dockyards that the preparation should be stored and treated with the
same precautions as turpentine and other highly inflammable liquids or
preparations.

The following November, however, telegraphic news was re-
ceived of a very serious explosion on board H.M.S. Triumpli, then
stationed at Coquimbo, due to the xerotine siccative. The explosion
took place early in the evening of the 23rd November, and originated
in one of the paint-rooms of the ship ; the painter and a marine
who was assisting him were in the upper j)aint-room at the time ;
the former received severe internal injuries and afterwards died, the
latter was killed at once. One man standing at the open door of the
sick bay furthest from the explosion was instantaneously killed, others
in close proximity receiving only superficial injuries. Altogether there
were two killed, two dangerously wounded — of whom one died, and
six injured, by the explosion.

The results of the official inquiry held at Callao led to the con-
clusion that the explosion was caused by the ignition of an explosive
gas-mixture produced by xerotine siccative which had leaked from a tin
kept in a compartment under the paint-room and quite at the bottom
of the ship, usually termed the " glory hole " ; that locality having
been considered by the captain of the ship as the safest place in
which to keep this material, to the dangerous nature of which his atten-
tion had been recently called by the receipt of the Admiralty Circular.
It transpired that the painter had sent his assistant down to this
compartment from the paint-room to fetch some paint. The man,
who had a hand-lantern with him, while unscrewing the hatch
which had not been opened for three days, made the remark that there
was a horrible smell; the chief painter told him to return, as he
thought the smell was due to foul air, and immediately afterwards
the explosion occurred.

The tin can which had contained six gallons of the liquid was
found, after the accident, to have received injury as though some heavy
body had fallen, or been placed, upon it ; this appeared to have been
done before the explosion, and there is no doubt that the liquid had
leaked out of the can, and had evaporated into the air in the compart-
ment beneath the paint-room, and probably also to some extent in the
adjoining spaces. The damage done was very considerable. An iron
ladder leading from one paint-room to the other was so twisted up as
to have lost all semblance of originality, the wooden bulkhead separa-
ting the upper paint-room and sick bay was completely blown away,
the framing of the ship's side in the sick bay was blown inwards and
broken, the furniture in the latter was completely shattered, and the
bedding and clothes of the me^ near the explosion were much

1885.] on Accidental Explosions hij Non-explosive Liquids. 227

burned. The inqiuries which followed upon this deplorable accident
showed that, while due precautious were taken to store the supplies of
mineral oil used for burning purposes, of turpentine and of spirit,
which were sent to diiferent naval stations for supply to the fleet, in
special parts of the ships or on deck, this highly inflammable liquid,
which was far more dangerous than other stores of this class, had
been sent in freight-ships as common cargo, being stored in the hold
without any precautions. A stone jar which was advised as contain-
ing a supply had arrived at its destination in the Pacific quite empty,
the contents having leaked out and evaporated on the passage out, so
that the vessel carrying it had been unsuspectedly exposed to very
great danger.

The disaster on board the Triumph, combined with the fact that
this xerotine siccative had been issued to H.M. ships generally, the
authorities and officers of the navy having been in ignorance as to
its dangerous nature, re-directed official attention to the loss of the
Voter el on April 26, 1881, while at anchor off Sandy Point, by an
explosion, or rather by two distinct exjjlosions following each other
in very rapid succession, which caused the death of eight officers and
135 men, there being only twelve survivors of the crew. The
inquiry by court-martial into the catastrophe had led to the conclusion
that the primary cause of the destruction of that vessel was an
explosion of gas in the coal bunkers, caused by disengagement of fire-
damp from the coal with which these were in jDart filled. Its distri-
bution through the air in the bunkers and in air-spaces adjoinino- the
ship's magazine, was believed to have taken place to such an extent
as to produce a violently explosive mixture, and that this had become
accidentally inflamed, causing a destructive explosion, which was
followed within half a minute by the much more violent explosion of
the shij)'s magazine containing four or five tons of powder, to which
the flame from the exploding gas-mixture had penetrated.

The circumstances elicited by the inquiry, coupled with the
information, relating to explosions known to have occurred in coal-
laden ships, which had been collected by a Eoyal Commission in
1876 (of which the lecturer was a member), combined to lend a con-
siderable amount of probability to the view adopted by the court-
martial in exj)lanation of an accident for which there appeared to be
no other reasonable mode of accounting.

The conclusion arrived at led to the appointment of a committee
under the presidency of Admiral Luard (of which Professor Warino--
ton Smyth and the lecturer were members) to inquire into the
probabilities of coal-gas being evolved, and of an exj^losive gas-
mixture accumulating in consequence in the coal-bunkers of ships of
war, and into the possible extent and nature of damage which might
be inflicted upon ships of war by explosions due to the ignition of
such accumulations. The committee were also instructed, in the
event of their finding that H.M. ships were liable to exposure to
danger from such causes, to consider and devise the means best

Q 2

228 - Sir Frederick Abel [March 13,

suited for preventing dangerous accumulations of gas in the coal-
bunkers as distributed over the various parts of the ship in the different
classes of vessels composing the Eoyal Navy.

The committee instituted a very careful inquiry, and a series of
experimental investigations, including the firing of explosive gas-
mixtures, in large wrought-iron tanks in the first instance, and
afterwards in one of the large bunkers, empty of coal, in an old man-of-
war which afforded some comparison with the condition, as regards
the relative strength or powers of resistance of the surroundings, and
with the position, relatively to the ship's magazine, of the par-
ticular bunker in the Doterel in which it was thought the explosion
might have originated. The results of these experiments could not
be said to do more than lend some amount of support to the belief
that effects of the nature of those ascribed to the first explosion in
the Doterel might have been produced by the ignition of a power-
fully explosive gas-mixture, contained in the middle- or athwart-shij^'s
bunker of the ship. The committee's experimental investigations
for ascertaining the best general method of securing the efficient
ventilation of the coal-bunkers in different classes of men-of-war
was, however, of considerable advantage in leading to the general
adoption of arrangements in H.M. ships whereby the X30ssible accumu-
lation in the bunkers of gas which may be liable to be occluded from
coal after its introduction into them is effectually prevented, and the
occurrence of the kind of accident guarded against, of which there
are several on record, due to the ignition of explosive mixtures
which have been produced in coal-bunkers.

Although the inquiry instituted by the court-martial in August
1881, into the loss of the Doterel was apparently very exhaustive,
some significant facts connected with the existence of a supply of
xerotine siccative in the ship, which appear to have had a direct
bearing upon the occurrence of the disaster, only came to light acci-
dentally in January 1882. A caulker formerly on the Doterel, but
then employed in the Indus, recognised, while some painting was being
done in that ship, a peculiar odour (as he called it, " the old smell ")
which he had noticed in the lower part of the Doterel the night before
the explosion ; on inquiry as to the material which gave rise to it, he
learned that it was due to some of the same material, xerotine siccative,
that had caused the explosion in the Triumph. Upon this being com-
municated to the authorities, an official inquiry was directed to be
held, and it was then elicited that the very offensive smell due to
the crude petroleum spirit of which this xerotine siccative mainly
consisted had been observed not only by this man (who in his
evidence before the court-martial had not alluded to the circumstance),
but also by several others in the Doterel, between decks, the night
before the explosion ; that, on the following day, a search was made
for the cause of the odour, and that a jar containing originally about
a gallon of the fluid, which was kept in a space at the bottom of the
foremast together with lieavy stores of various kinds, was found to

1885.J en Accidental Exjjlosions by Non-explosive Liquids. 229

have been cracked, the principal portion of its contents having leaked
out into the bottom of the ship. The cracked jar was handed iij) to
the lower deck with the siccative still leaking from it, and orders
were given to throw it overboard on account of the bad smell which
it emitted ; this was done within a very few minutes after the jar had
been removed, and the first explosion occurred almost directly after-
wards. Instructions had been given to clear up the leakage from the
jar after the hatch of the mast-hole had been left off a little time, and
it appeared that a naked candle had been given to the man who handed
the jar up out of the small store-hold described by that name. There
appears very little room for doubt that an exj^losive mixture of the
vapour and air had not only been found in the j)articular space where
the jar was kept, but tliat it had also extended through the air-spaces
at the bottom of the shijD towards and underneath the powder-
magazine, so that even the air in the latter may have been in an
explosive condition, as many hours had elapsed between the time
when the smell of the petroleum spirit-vapour was first noticed and
when the first explosion occurred.

The special committee which had inquired into the jDossibility of
the occurrence of a violent gas explosion in the coal-bunkers of the
Doterel, was directed to institute experiments with a view of ascer-
taining whether the vapour evolved by this xerotine siccative would,
in the circumstances indicated by the official inquiry, have furnished
an explosive gas-mixture possessing sufficient power to have produced
the effects resulting from the first explosion on the Doterel, and
to have exploded the powder magazine. A preliminary experiment
showed that when a small quantity of the liquid was spilled at one
extremity of a wooden channel 7 feet long and 2*5 inches by 3 inches
in section, the vapour had diffused itself in the space of three minutes
throughout the channel to such an extent, that, on a light being applied
at one end, the flame travelled along very rapidly to the other end,
igniting a heap of gunpowder which had been placed there. Some of
the liquid was. also spilled upon the bottom of a very large sheet-iron
tank, and after this had remained closed for about twenty-four hours,
being exposed on all sides to the cool air of an autumn night, and there-
fore not under conditions nearly so favourable to evaporation as those
obtaining in the hold of a ship, the application of flame produced an
explosion of such violence as to tear open the tank. Experiments
were also made with the liquid in an old man-of-war, under conditions
somewhat similar to those which existed in the Doterel, and destructive
effects were obtained of a nature to warrant the conclusion that the
first explosion in the Doterel might have been due to the ignition of
an explosive mixture of the air in the confined space at the bottom of
the ship, with spirit vapour furnished by the liquid which had leaked
out of the jar.

It is very instructive, as indicating the manner in which volatile
liquids of this class may, if their nature be unsuspected, be the causes
of grave disasters, to note that, while stringent regulations apply and

230 Sir Frederick Abel [March 13,

are strictly enforced in our men-of-war in connection with the
storage and treatment of explosives [|and inflammable bodies carried
in the shij), the introduction into the service of this highly vola-
tile liquid, and its supply to ships in small quantities, was
speedily followed by two most calamitous accidents because the
material was only known under the disguise of a name affording no
indication of its character. Its dangerous nature had consequently
escaped detection by the officials through whose hands it had passed,
the makers of the preparation having, in a reprehensible manner
which cannot but be stigmatised as criminal, withheld the information
which most j^robably would have, at the outset, acted as a prohibition
to the adoption of this material by the Admiralty for use in ships,
or which would, at any rate, have led to the adoption of very special
precautions in dealing with this material.

Although not initiated, nor attended, by an exjDlosion, the accident
which in December 1875 caused the loss, by fire, of the training-ship
Goliath off Grays (near Gravesend) and the death of several of the
boys by drowning, claims notice as an illustration of the facility with
which, by heedlessness, or inattention to obvious precautions, accidents
may be brought about in the use as an illuminating agent of mineral
oil or petroleum, even where these are of such low volatility, or high
" flashing point," as to entitle them to be considered as safe, under
all ordinary conditions, as vegetable or animal oils. The evidence
elicited at the coroner's inquest showed that one of the boys of the
Goliath, whose duty it was, at the time, to trim the lamps used in the
ship, to place them in position and remove and extinguish them in
the morning, and to whom this work had been but recently allotted,
let fall a lamp which, after having lowered the flame, he had carried
from its assigned position into the lamp- or trimming-room, and which
he could hold no longer on account of its heated state. The heated
oil was scattered upon the floor and was aj^parently at once
inflamed by the burning wick of the lamp ; the floor of the room
was, it ai^pears, much im23regnated with oil which had been let drop
from time to time by lads employed upon the work of lamp trim-
ming ; hence the flame attacked the apartment generally with con-
siderable rapidity, and a wind blowing at the time caused the fire to
spread through the vessel so very quickly as to compel many of
those composing the crew to jump overboard, and to render the
rescue of the boys from burning or drowning a difficult matter. The
occurrence of this accident was made the occasion, in some of the
public papers, to decry petroleum oil as a dangerous illuminating
agent, although it was proved that the particular oil used at the time
when the fire occurred had so unusually high a flashing point that the
consequent inferiority of its burning quality had been made the
subject of complaint. This low volatility of the oil has been
occasionally regarded as one very important element of safety in
reference to its employment in lamps, but the lecturer wdll pre-
sently have to refer to circumstances which do not altogether sub-

1885.] on Accidental Explosions by Non-explosive Liquids. 281

stantiate this view. At any rate, however, although the heated oil
which was spilled on to the floor from the lamp was in a condition
favourable to immediate ignition by the burning wick, it is not at
all likely that the fire would have extended almost at once with
uncontrollable violence, especially in face of the excellent disci-
pline and arrangements in case of fire which were shown to have
existed in the Goliath, if the scrupulous cleanliness and care had
been enforced which were essential in a room where lamp filling
and trimming were regularly carried out, and where it was necessary
to keep some supply of oil for current consumption. Instead of this,
the floor and probably therefore other parts of the room appear to have
been in a condition most favourable to the rapid propagation of the
flame ; moreover, the evidence as to proper care having been taken
to keep the S'apj)ly of oil required for current use in such a way as
to guard against its being accidentally spilled, or to impress the
boys employed upon the work with the great importance of care
and cleanliness, was by no means satisfactory, and there can be little
doubt that this catastrophe has to be classed among the numerous
accidents of a readily avertible kind which have coi^tributed to
lead tbe public to form an exaggerated estimate of the dangerous
character of petroleum oil as an illuminant.

The employment of liquid hydrocarbons as competitors with animal
and vegetable oils in lamps for domestic use is of comparatively
recent origin, although petroleum or mineral naphtha in its crude or
native conditions was used at a very early date in Persia and in
Japan, in lamps of primitive construction, while in Italy it was
similarly employed about a century ago.

The application of the most volatile products of coal distillation
to illuminating purposes in a crude way appears to have originated,
so far as Great Britain is concerned, with the working of a patent
taken out by Lord Dundonald in 1781, for the distillation of coal,
not with a view to producing gas, but for the production of naphtha,
brown or heavy oil, and tar.

In 1820, at about the time when gas-lighting was being estab-
lished in London, his successors sold coal-naphtha in the metropolis
for illuminating purposes ; but the first really successful introduction
of naphtha as an illuminating agent was made by Mr. Astley shortly
afterwards, through the agency of the so-called Founders blast-lamp,
which came into use for workshops and yards in factories, and of the
naphtha lamp of Bead Holliday of Huddersfield, with which we are
well acquainted to this day, as, although it never became a success,
for internal illumination of houses, it still continues in extensive use
almost in its original form, by itinerant salesmen and showmen.

In the Founders lamp a current of air, artificially established, was
made to impinge upon the flame and thus to greatly assist the com-
bustion of the crude heavy oil used in it.

In the Holliday naphtha lamp the spirit finds its way slowly from

232 Sir Frederick Abel [March 13,

the reservoir through a capillary tube to a small chamber placed at a
lower level, which has a number of circumferential perforations, and
is in fact at the same time the burner of the lamp and the vapour-
producer which furnishes the continuous supply of illuminaut, the
liquid supplied to the chamber being vaporised by the heat of the
jets of flame which are fed by its production.

Between 1830 and 1850 the knowledge of the production not only
of oils but also of paraffin, by the distillation of coal or shale, became
considerably developed by Eeichenbach, Christison, Mitscherlich,
Kane, du Boisson and others, and the practical success attained by
the latter was soon eclipsed by that of Mr. James Young, who
after establishing oil distillation at Alfreton from the Derbyshire
petroleum, began to distil oils from the Bathgate mineral in 1850,
and soon developed this industry to a remarkable extent.

The first lamps for burning liquid hydrocarbon which competed
for domestic use, in this country, with the superior kinds of lamps,
introduced after 1835, in which animal or vegetable oils were burned
(solar lamps and moderator lamps), were the so-called camj^hine
lamps (known as the Vesta and Paragon lamps) in which carefully
rectified oil of turpentine was used. They gave a brilliant light, but
soon acquired an evil reputation as being dangerous and liable, upon
the least provocation, especially if exposed to slight draughts, to fill
the air with adhesive soot-flakes.

After a time Messrs. George Miller & Co. of Glasgow (who
lield for a time the concession of the products manufactured by
Mr. Young) tried with some amount of success to use the lighter
products from the boghead mineral in the camj)hine lamp, but the
chief aim of Mr. Young appears to have been to produce the heavier
oil suitable for lubricating purposes, the light oil or naphtha meeting
with an indifterent demand as a solvent, in competition with coal-tar
naj)htha, in the manufacture of iudiarubber goods. He, however,
himself used the mineral oil produced at Alfreton in Argand lamps
in the earliest days of his operations ; a small sale of the Bathgate
oil took place about 1852-3 for use in Argand lamps, and the earliest
description of lamp employed in Germany, where the utilisation of
mineral oil as a domestic illuminant was first developed, appears to
have been of the Argand type.

In 1853 a demand Sj)rang up for the lighter parafiin oils in
Germany. For three or four years previously, a burning oil was
distilled from schist or brown coal at Hamburg by a Frenchman
named Noblee, who gave it the name of photor/erie. The existence in
Glasgow of a considerable supply of the oils became known to a
German agent, and after they had been exp;)rted from Glasgow to
Hamburg for a considerable time it was found tliat the chief purchaser
was Mr. C. H. Stobvvasser of Berlin, who appears to have originated
the really successful employment of mineral oils in lamps for
domestic use, and to have been the first to bring out the flat-wick
burners for these oils. After a time Messrs. Young discovered the

1885.] on Accidental Explosions hy Non-explosive Liqaids. 233

destinatiou of their oil, and, having brought over a number of
German lamps, for which a ready sale was found, commenced the
lamp manufacture upon a large scale, and rapidly developed tlie
trade in mineral (or paraffin) oil for burning purposes, which
attained to great importance some time before the American
petroleum oils entered the market. In 1859 a firm in Edinburgh
supplied Young's company with nearly a quarter of a million
burners for lamps, and it was not until 1859 that the foundation of
the United States' petroleum industry was laid by Colonel G. L. Drake,
who first struck oil (in Pennsylvania) at a depth of 71 feet, obtaining
at once a supply of 1000 gallons per day. The lamps first used in
America were probably of German make, but it need hardly be said
that the lamj) manufacture was speedily developed to a gigantic extent
in that countr3^ Some of the earliest lamps for burning mineral oil
in dwellings which were produced in Germany and in Scotland
possess considerable interest as ingenious devices for promoting the
perfect and steady combustion of the oil, and as attempts to dispense
with the necessity of the chimney for the production of a steady
light. In one of these a small lamp was introduced into the base or
stand of the lamp proper, and a tube 2)assed from over this little
lamp, through the oil reservoir into the burner, so as to supply the
latter with heated air. In another, a small fan or blower with simple
clockwork attached, to keep it in rapid motion, is placed in the stand,
and supplies the flame with a rapid current of air. Among other
workers at the perfection of mineral oil lamps was the late Dr. Angus
Smith, who produced a double-wick lamp some years before the
beautiful duplex lamps were first manufactured by Messrs. Hinks.
Some of the more recent American lamps exhibit decided improve-
ments in the details of construction of the oil reservoirs, the wick-
holders, and elevators, the arrangements for extinguishing the lamps,
&c.

It does not come within the province of this discourse to deal with
the marvellous development of the petroleum industry in America,
where the region of Western Pennsylvania now furnishes about 70,000
barrels of oil per day, having up to the 1st January, 1884, yielded a
total of 250,000,000 barrels. Nor would it be relevant to enter upon
the equally interesting topic of the recent extraordinary progress of
the same industry in the Caucasus, which is chiefly due to Messrs.
Nobel Brothers, further than to refer to the fact that the Baku
petroleum lamp oil, which supplies the entire wants of Eussia, and is
gradually obtaining a footing in Germany and even here, appears,
notwithstanding its high sj)ecific gravity, to be suitable for mineral
oil-lamps of the ordinary construction. This seems to be partly owing
to the comparatively small proj^ortion of lamp oil that is extracted
from the crude Baku petroleum, in consequence of which the variety
of hydrocarbons composing that product of distillation w^hich is
used for illuminating purposes, presents a narrower range than is
the case in the ordinary American petroleum oil of commerce. It

234 Sir Frederick Abel [Marcli 13,

has also been established by careful observations which Beilsteiu
has instituted, that some American oil which is specifically lighter
than the Baku oil is not so readily carried up to the flame as
the latter, by the capillary action of the wick. Mr. Boverton Eed-
wood has carried out some instructive exjDcriments, employing
different kinds of wick as siphons, and measuring the quantity of
different descriptions of oil drawn over in corresponding periods of
time by the different wicks. These showed that the Baku kerosine was
drawn over with decidedly greater rapidity than samples of American
petroleum of ordinary quality, but that on the other hand, a sample of
American kerosine of the highest quality exhibited a corresponding
superiority over the Baku oil experimented with. The nature and
behaviour of the wick plays a most important part in determining the
efficiency and also the safety of a mineral oil- or petroleum-lamp, as
will be presently pointed out.

Ever since paraffin or petroleum oils, w^hich may be included
under the general designation of mineral oils, first assumed im-
portance as illuminating agents, accidents connected with their use
have continued to claim prominence among those casualties of a
domestic character, which tend to cast suspicion on the safety of the
material dealt with, or of the method of employing it, under the
ordinary conditions fulfilled by its careful use.

The employment as an illuminant of the most volatile portions
of petroleum which are classed as spirit or naj)htha has been chiefly
limited to the wickless Holliday lamp, in which a small continuous
supply to a chamber heated by the lamp flame which surrounds it,
furnishes the vapour which maintains that flame, and to the small so-
called sj^onge lamps or benzoline lamps, of which the body is filled
with fragments of sponge, and which is intended to be charged only
with as much spirit as the sponge will hold thoroughly absorbed ; the
small flame at the toji of the wick-tube being fed by the gradual
abstraction of the liquid from the soaked sponge, by the wick of
sponge or asbestos which fills the tube. An ingenious application
of naphtha as an illuminant consists in filling a reservoir with
sponge fragments, kept soaked with the spirit, the vapour of which
descends by its own gravity through a narrow tube at the base of the
reservoir, and issues from a fish-tail burner under sufficient pressure
to produce a steady flame for some time.

The only real danger which may attend the use of the little
sponge lamps arises from accidental spilling of spirit used for filling
them in the neighbourhood of a flame, or from carrying out the
operation of filling in the vicinity of a light. Indeed, such casualties
as have been attendant upon the use of petroleum spirit as an
illuminant have been mainly connected with the keeping and handling
of the supplies of this very volatile liquid, and are largely attributable
to want of caution or to forgetfulness. The salutary regulation pre-
scribed by law, that vessels containing the f2^^'^"i^ sliall bear a
conspicuous label indicating its dangerous character, lias undoubtedly

1885.] on Accidental Explosions hy Non-explosive Liquids. 235

operated very beneficially in diminishing the frequency of accidents
with it, by constantly admonishing to caution. It is a matter for
much siu'prise and regret that the manufacturers of a class of miners'
safety lamps, consisting of modifications of well-known types, with the
ordinary oil lamp replaced by the sponge lamp, in which petroleum-
spirit is burned, should have allowed trade interests to induce them
to mislead those who use these lamps with regard to the nature of
the illuminant supplied with them, by devising a name for it which
gives a false indication of its nature, being designed to create the
belief that it is an article of special manufacture, allied in cliaracter
to a comparatively very safe oil largely used in miners' lamjDs, while in
reality it is a well-known article of commerce, the safe storage and
use of which demand special precautions and vigilance.

The lecturer took occasion to point out here, ten years ago, that a
large proportion of the accidents arising out of the employment of
petroleum- or paraf&n-lamps were not actually due to the occurrence
of explosions. Thus the incautious carrying of a lamp, whereby the
liquid is brought into contact with the warm portion of the lamp close
to the burner, may give rise to a liberation of vapour which in
escaping from the lamp may be ignited, causing an outburst of flame
which may alarm a nervous person and cause the dropping or overturn-
ing of the lamp. The accident which occurred in some apartments in
Hampton Court Palace, in December 1882, andl'gave rise to a some-
what alarming fire, appeared almost beyond doubt to have originated
from the employment by a domestic servant of a contrivance in which
petroleum sjjirit was used for heating water ; but, as petroleum-
lamps were used in the particular residence \vhere the fire actually
occurred, public correspondence ensued regarding the dangers
attending the use of such lam|)S, although all which were known to
have been on the premises were forthcoming after the fire and found to
be intact. There was, at any rate, no evidence whatever adduced in
support of an assumption that the casualty was due to the explosion
of a lamp, and other instances might be quoted in which the break-
ing out of a fire, or the destruction of or injury to life, which had
evidently been caused by upsetting or allowing to fall a petroleum-
lamp, has been erroneously ascribed to an explosion.

There are, however, numerous casualties which have been un-
questionably caused by the occurrence of explosions in lamps, and
which have in many cases been followed by the ignition of the
oil, and the consequent loss of life or serious injury to those in the
immediate vicinity of the accident. Careful inquiries have of late
been instituted into casualties of this kind, and in many instances
the explosions have been distinctly traceable to some immediate
cause. In the great majority of cases they occur some considerable time
after the lamp was first kindled, and when the supply of oil remaining
in the reservoir has been but small. Occasional examples of the
reverse are however met with. Thus, last sj)ring^ a man and his
young son were sitting at a table reading, his wife being also close

236 Sir Frederklc Ahel [Marcli 13,

at hand, wlien a paraffin lamp which had just been lighted exploded,
and the room was at once set on fire by the burning oil which
escaped. The husband and wife fled from the room, both being
slightly injured, but the child was unable to. escape from the
flame, and. was burned to death. The oil used in the lamp was of a
well-known brand, having a flashing point ranging from 73° to
86° F., and assuming that the recently lighted lamp had been
filled with oil, and was untouched at the time of the explosion, no
satisfactory explanation can be given of the accident, unless perhaps
the reservoir had been so completely filled with oil that the expan-
sion of the liquid, on its becoming slightly warm, exerted sufficient
force to determine the fracture of the glass at some part where a flaw
or crack existed.

A lamp accident which occurred last July at Barnsbury, causing
the death of a woman and her husband, appears, on the other hand,
distinctly traceable to the production of an explosion in the reservoir
of the lamp. The latter was stated to have been alight but a short
time, when, the husband being already in bed, the wife, in her night-
dress, attempted to blow out the flame of the lamp ; the man heard a
report, and looking towards the lamp, saw his wife in flames. He
proceeded at once to her rescue and was severely burnt in extinguishing
the flames in which she was enveloped. The woman died in a few
hours, and the man succumbed three days later to the injuries received.
There being no witness to the accident, there is no evidence against
the supposition that, on the occurrence of a slight explosion in the
reservoir in the lamp, the woman, having hold of it when attempting
to blow it out, may have upset it, or tilted it so as to cause the oil to
flow out and become inflamed. The lamp may have become fractured
by the explosion ; but whenever such a result has been produced the
lamp had always been burning some time, so that there was considera-
able air-space which could be filled by an explosive atmosphere,
whereas, in this case, the evidence appears positive as to the lamp
having been full of oil when lighted.

In another fatal case of a lamp explosion in the same month, at
Mile End, the accident was also caused by the attempt on the part
of a woman to blow out the lamp before going to bed. In this
case the lamp had been burning for three hours; the husband
of the sufferer was in bed asleep in the room at the time, and, the
woman being unable to give any account of the occurrence, the only
information elucidating it w^as furnished by the daughter, to the effect
that the lamp had been burning for three hours, and that it was the
habit of her mother to extinguish the lamp by first lowering the wick
and then blowing down the chimney.

Another fatal accident, caused by the explosion of a lamp, took place
at Camber well last January, and was brought about, as in the two
preceding cases, by attempts to extinguish the lamp by blowing down
the chimney. The husband and two sons of the sufferer were
witnesses of this accident; the lamp had been burning for six or

1£85.] on Accidental Explosions by Non-explosive Liquids. 237

seven hours, when the woman took it in her hand, and having
partially turned it down, proceeded to blow down the chimney ; an
explosion at once occurred, the glass reservoir was broken, and the
inflamed oil flowed upon her dress, burning her most severely.

A lamp explosion which occurred last December, in a van used as
a bedroom by an itinerant showman, at the so-called World's Fair
held at the Agricultural Hall, Islington, and which caused the death
of an infant, was of a somewhat different character to the foregoing.
The lamj), which was of the duplex form and was attached to a
bracket, had been alight for some hours, when a woman went, from a
neighbouring van used as the dwelling room, to extinguish it. She
observed that while the lamp, or wick, was only burning faintly, the
oil in the reservoir was alight. She placed her ajDron over the top of
the chimney to extinguish the lamp, when it at once appeared to
explode, and the bui-ning oil set the interior of the van on fire. The
woman ran out for help, and a lad, protecting his head with his coat
rushed in and brought out the infant which was lying upon the bed,
and which died from injuries received. The oil used in the lamp was
believed to be of high flashing point, being obtained by the retailer who
supplied it, from a firm dealing in a Scotch shale oil manufactured
by the Walkinshaw Company (known as an " electric light " brand).
A sample of the oil, as supj)lied by the wholesale dealers, had a
flashing point of 114:° F., but a portion of the oil actually purchased
by the owner of the lamp had a flashing point of only 63° F., and
evidently consisted of a mixture of the heavy oil and of benzoline.
The oil in question would naturally become exhausted of the volatile
spirit after the lamp had burned for some time, and the flame would
then have burned low in consequence of the heavy character of the
residual oil ; the lamp and its contents would have thus become
highly heated, and some accidental disturbance of the surrounding air
must have caused vapour generated from the heated oil and contained
in the air-space of the reservoir, to become inflamed ; the oil itself
being thereby ignited. By placing her apron hastily upon the top
of the chimney, the woman forced air into the reservoir, and thus
either caused a slight explosion to take place, or determined the
breaking of the glass by the sudden change of temperature. A lamp-
accident, apparently due to the same cause, occurred quite re-
cently in the cabin of a small steam-launch on the Medway, near
Chatham.

Several cases of undoubted lamp explosions, fortunately un-
attended by serious consequences, have come to the lecturer's know-
ledge as having occurred in the billiard-rooms of barracks where
petroleum or paraffin oil was employed as the illuminant. These lamj)s
are fixed over the billiard tables, and generally speaking the rooms
have top- or sky-lights. In every instance the lamp had been burn-
ing for several hours and had probably become more or less heated,
especially as shades of sheet tin weie placed over them as reflectors.
In each case a portion of the glass reservoir was blown out by the

238 Sir Frederick Abel - [March 13,

explosion, and the oil, becoming ignited, burnt portions of the table
on which it fell.

A careful investigation of accidents of which the foregoing are
illustrations,* together with a critical examination of the construction
of various lamps, and the results of many experiments have, up to the
present time, led the lecturer and Mr. Eedwood to arrive at several
definite conclusions with respect to the immediate causes of lamp-
explosions and to certain circumstances which may tend to favour the
production of such exi^losions.

If the lamp of which the reservoir is only partly full of oil, be
carried, or rapidly moved from one place to another, so as to agitate
the liquid, a mixture of vapour and air may make its escape from the
lamp in close vicinity to the flame, and, by becoming ignited, deter-
mine the exj^losion of the mixture existing in the reservoir. This
escajje may occur through the burner itself, if the wick does not fit
the holder properly, or through openings which exist in some lamps
in the metal work, close to the burner, of sufficient size to allow flame
to pass them readily. A sudden cooling of the lamp, by its exposure
to a draught or by its being blown upon, may give rise to an inrush
of air, thereby increasing the explosive j)roperties of the mixture of
vaj^our with a little air contained in the reservoir, and the flame
of the lamp may at the same time be drawn or forced into the air-
space filled with that mixture, especially if the flame has been turned
down, as the latter is thereby brought nearer to the reservoir. The
sudden cooling of the glass, if it had become heated by the burning
of the lamp, may also cause it to crack if it is not well annealed,
and this cracking, or fracture, which may allow the oil to escape,
may convey the idea that an explosion has taken place. If the
evidently common practice is resorted to of blowing down the
chimney with a view to extinguish the lam]), the efi'ects above in-
dicated as produceable by a sudden cooling may be combined with
the sudden forcing of the flame into the air-sj)ace, and an exj^losion
is thus pretty certain to ensue, especially if that air-space is con-
siderable. If the flashing point of the oil used be below the
minimum (73° Abel) fixed by law, and even if it be about that
point or a little above it, vapour will be given off comparatively freely
if the oil in the lamp be agitated, by carrying the latter or moving it
carelessly ; the escape of a mixture of vapour with a little air from
the lamp, and its ignition, will take place more readily, but on the
other hand it will probably be feebly explosive, because the air will
have been expelled in great measure by the generation of petroleum
vapour. If the flashing point of the oil be high, the vapour will be
less readily or copiously produced, under the conditions above in-
dicated, but, as a natural consequence, the mixture of vapour and

* Mr. Alfred Spencer, of the Metropolitan Board of Works, has obligingly
furnished me with the official details of several of the accidents above referreil to.
— F. A. A.

1885.] on Accidental Explosions by Non-exjplosioe Liquids. 239

air existing in tlie lamp may be more violently explosive, because the
proi)ortion of the former to the latter is likely to be lower and nearer
that demanded for the production of a powerfully explosive mixture.
If the quantity of oil in the lamp reservoir be but small, and the
air-space consequently large, the ignition of an exjilosive mixture
produced within the lamp will obviously exert more violent effects
than if there be only space for a small quantity of vapour and air,
because of the lamp being comparatively full. If the wick be lowered
very much, or if for some other reason the flame becomes very low,
so that it is burning beneath the metal work which surrounds and
projects over the wick-holder, the lamp will become much heated at
those parts, and the tendency to the production of an explosive
mixture within the space of the lamp will be increased, while, at the
same time, heat will be transmitted to the glass, and it will be corre-
spondingly more suscejDtible to the effects described as being exerted
by its sudden exposure to a draught. Experiments have demon-
strated that a lamp containing an oil of high flashing point is more
liable to become heated than a comparatively light and volatile oil,
in consequence of the much higher temperature developed by the
combustion, and of the comparative slowness with which the heavy oil
is conveyed by the wick to the flame. It therefore follows that safety
in the use of mineral oil lamps is not to be secured simply by the
employment of oils of very high flashing point (or low volatility),
and that the use of very heavy oils may even give rise to dangers
which are small, if not entirely absent, with oils of comparatively low
flashing points. The occurrence of such an accident as that in the
training-ship Goliath, already referred to, which was brought about
by a boy letting fall a lamp which had been alight all night, and which
was so hot that he could no longer hold it, appears to be primarily
ascribable to the use of an oil of very high flashing point ; and the
accident at the Agricultural Hall furnished another illustration of the
kind of danger attending the use of such an oil.

The character of the wick very materially afiects not only the
burning quality of the lamp, but also its safety. A loosely plaited
wick of long staple cotton draws up the oil to the flame regularly
and freely, and so long as the oil be not very heavy or of very higji
flashing point, and therefore difticultly volatisable or convertible
into vapour (by so-called destructive distillation), the flame will con-
tinue to burn brightly and uniformly, with but little charring
effect upon the wick ; that is to say, the extremity of the latter will
only be darkened and eventually charred to a distance of much
less than a quarter of an inch downwards, and it will not be until
the partial exhaustion of the oil-sui3j)ly diminishes the size of the
flame and induces the user to raise the wick, that the latter will
become more considerably charred. But, if the wick be very tightly
plaited, and made, as is not unfrequently the case, of a short staple
cotton of inferior cajDillary power, the oil will be less copiously
drawn up to the flame ; as a consequence, the length of exposed wick

240 Sir Frederick Ahel [March 13,

will be increased by the user of the lamp, and as the evaporation of
the oil will take place more slowly from each portion of the wick
which furnishes the flame, the heat to which the cotton is exposed
will be greater, and the charring, which is fatal to the jDroper feeding
of the flame by destroying the porosity of the end of the wick, will
take place more rapidly and to a mucli greater extent.

Even with wicks of the higher qualities, considerable differences
exist in the rapidity with which the oil is raised to the flame. In Mr.
Eedwood's experiments, conducted with a specimen of English wick
of good quality and with a very superior American wick, of corre-
sponding dimensions, the quantity of oil sijDhoned over by the latter
in a given time, was from 35 to 47 per cent, greater (according to the
nature of oil experimented with) than that carried over by the English
wick.

If the wick be at all damp when taken into use, its power of
conveying the oil to the flame will be decidedly diminished, the
capillaries of the fibre being more or less filled with moisture, and
similarly, if the oil accidentally contain any water, the latter, passing
into the wick, will interfere with the j)roper feeding of the flame. As
the oil is very thoroughly filtered or strained during its transmission
through the body of the wick to the flame, it is obvious that any
impurities suspended in the liquid will be deposited within the wick
and will gradually diminish its porosity. For this reason the same
wick should not be used for a great length of time, and it is decidedly
objectionable to use a much greater length of wick than is necessary
to reach to the bottom of the reservoir, and to continue its use until
it has become too greatly shortened by sucessive trimmings. On the
other hand, the wick should always be of sufficient length to be
immersed to a considerable distance in the oil. It is evident that
the copious supj^ly of oil to the flame will become reduced as the
column of liquid which covers the wick in the reservoir becomes
reduced in height ; hence the supply of oil in the lamp should never
be allowed to get very low, not only because it is undesirable to have
a large air-space which may be filled with vapour and air, but also
because the burning of the lamp is injuriously affected thereby.

Some lamj)s, of patterns first constructed in the United States, are
provided with what may be called a feeding wick in addition to the
wick, or wicks, which furnish the flame. This wick is generally
simply suspended from the lower surface of the burner, and reaches
nearly to the bottom of the reservoir, being so placed that it hangs
against one flat side of the regular wick, and thus aids considerably
the copious and uniform absorption of oil by the latter. In certain
lamps of recent construction the reservoir which contains the main
supply of oil is so arranged (upon the principle of the old study-
or Queen's oil-lamp), that it regularly maintains at a uniform level
the supply of oil, which surrounds the wick in a small central reser-
voir or cylinder, separated from the main reservoir (excepting as
regards a small channel of communication) by an air-space, which

1885.] OH Accidental Explosions by Non-explosive Liquids. 241

presents the additional advantage of preventing the transmission of
heat to the oil-vessel. This kind of lamp is constructed entirely
of metal ; this is the case now with a very large proportion of the
lamps in use, and unquestionably adds greatly to the safety of
lamps, which, if constructed of glass or porcelain, are always liable
to accidental fracture, quite apart from the question of possible
explosion.

It has been proved experimentally that if the reservoir of a
burning lamp be warmed, so as to favour the emission of vapour into
the space above the oil, and a small ojDcniug in the top of the reser-
voir be then uncovered, air will be drawn into the latter and form
an explosive mixture with the vapour, which, escaping from the lamp
close to the wick-holder, will be fired and produce an explosion in the
lamp. It is an interesting illustration of the very imperfect apjDre-
ciation, by some lamp designers, of the conditions which, in the
construction of a lamp, secure safety or determine danger, that the
reservoirs of some petroleum lamps are actually furnished with an
opening in the upper surface, which is closed with a more or less
badly fitting metal ax-p, and is intended to be used for filling the
lamp with oil. Independently of the great element of danger which
this fitment presents, in consequence of the obvious temptation to the
users to replenish the reservoir while the lamp is actually burninfy, it
is very likely sooner or later to be the means of admitting to the
reservoir, in the manner above indicated, the suj^ply of air necessary
to determine the explosion of vapour therein existing.

Another source of danger introduced in the construction of lamps
which should be sufficiently obvious, and to which reference was
made when first discussing the causes of lamp explosions, consists in
the provision in many lamps, of oi^enings of considerable size close
to the burner, apparently Avith the object of affording a passage for
the air, or vapour, in the reservoir which may expand as the lamp
becomes somewhat warm. Other devices with the same object in
view, consisting of small channels or shafts brought up from the
top of the reservoir to the seat cf the lamj) flame, are ado23ted
in some American lamps. If these openings or channels were
protected, in accordance with the well-known principles which
govern the construction of miners' safety lamps, so as to preclude the
possibility of flame passing them, they would obviously be unobjec-
tionable, and indeed in one or two instances of modern lamps the
openings which have been provided for the escape of expanding air
or vapour are of such dimensions that flame could not pass. A
simple arrangement which would efiect the desired object with
perfect safety, and would at the same time protect the lamp wdcks
from deterioration by the grosser im2:)urities sometimes contained in
portions of a supply of oil, is to attach to the bottom of the burner a
cylinder of wire gauze of the requisite fineness (28 meshes to the
inch) which w^ould contain the wicks, and would allow the passage of
air or vapour through it towards the burner, while it would effectually

Vol. XI. (No. 79.) r •

242 Sir Frederick Abel on Accidental Explosions, &c. [March 13,

j)revent the transmission of fire from the lamp flame to the air-space
of the reservoir.

Some of the more prominent points elicited by the inquiry in
progress, as to the causes of explosions in petroleum lamps, and the
conditions which regulate their efficiency and safety, having now
been noticed, it remains to otfer a few simple suggestions, the atten-
tion to which cannot but serve to reduce the risks of accident which
attend the use of petroleum and paraffin oil.

1. It is desirable that the reservoir of the lamp should be of
metal. It should have no opening or feeding place in the reservoir,
nor should there be any opening or channel of communication to the
reservoir at or near the burner, unless protected by fine wire gauze,
or packed with wire, or unless it is of a diameter not exceeding 0 • 04
inch.

2. The wick used should be of soft texture and loosely plaited ;
it should fill the entire space of the wick-holder, and should not be
so broad as to be compressed within the latter ; it should always
be thoroughly dried before the fire, when required for use. The
fresh wick or wicks should be but little longer than sufficient to
reach to the bottom of the reservoir, and should never be immersed to
a less depth than about one-third the total depth of the reservoir.

3. The reservoir or lamp should always be almost filled before use.

4. If it be desired to lower the flame of the lamp for a time, this
should be carefully done, so as not to lower it beneath the metal-
work deeper than is absolutely necessary ; but it should be borne in
mind that even then the combustion of the oil will be imperfect, and
that vapour of unconsumed petroleum will escape, and render the
lamp very unpleasant in a room.

5. When the lamp is to be extinguished, and is not provided with
an extinguishing arrangement (of which many excellent forms are
now applied to lamps) the flame should be lowered until there is only a
flicker ; the mouth should then be brought to a level with the top of the
chimney, and a sharp puff of breath should be projected across the
opening. The lamp should remain on a firm support when it is being
extinguished.

The lecturer hopes that, pending the more thorough treatment of
this subject by Mr. Redwood and himself when these investigations
are completed, the points dealt with in this discourse which relate to
accidents with petroleum lamps may, on the one hand, tend to
dispel groundless alarm as to the dangerous nature of petroleum and
paraffin oil as illuminants, and may, on the other hand, serve to convey
some useful information resi)ecting the causes which lead to accidents
with lamps and the readiness with which they may be avoided.

[F. A. A.]

1885.] Professor A. W. BiicJcer on Liquid Films. 243

WEEKLY EVENING MEETING,

Friday, March 20, 1885.

Sir Fredeuick Bramwell, F.R.S. Manager and Vice-President,
in the Chair.

Professor A. W. Piijcker, M.A. F.R.S.

Liquid Films.

The molecules in the interior of a liquid are surrounded on all sides
by others which they attract, and by which they are themselves
attracted, while those on the surface have neighbours on one side
only. In consequence of this difference in their surroundinorg there
is in all probability a difference in the grouping of the interior and
exterior molecules which is attended by corresponding variations in
the physical properties of the liquid of which they are constituent
parts. Thus it was shown by M. Plateau that the viscosity of the
surface of a liquid is in general different from that of its interior.
The most striking example of this phenomenon is afforded by a
solution of sajjonine. Two per cent, of this substance dissolved in
water does not effect any marked change in the properties of the
great mass of the liquid, but produces a most remarkable increase in
the surface viscosity, so that forces which suffice to create rapid
motion in bodies which are completely immersed, fail to produce any
ajjpreciable movement if they lie in the exterior sui-face. The first
attem23t to obtain a numerical estimate of the difference of the resist-
ances experienced by a body oscillating in turn in the interior and in
the surface of the liquid was made about two years ago by Messrs.
Stables and Wilson, students in the Yorkshire College. In the case
of a horizontal disc suspended in water, the logarithmic decrement
diminishes to about one-half as the surface is approached. In a
saponine solution, on the other hand, it is 125 times greater in the
sui'face than in the interior, and about 38 times greater in the surface
than at a depth of 0*1 mm. below it. Even in the latter case the
greater part of the resistance is due, not to the friction between the
disc and the liquid, but to that experienced by the supporting rod in
the surface, so that in all jDrobability the surface viscosity is more
than 600 times greater than that of the mass of the liquid.

The immense change in the resistance which takes place when the
disc is immersed to a depth of O'l mm. only confirms the general
opinion that any peculiarity of grouping or arrangement due to
proximity to the surface extends to a very small depth. A liquid
must thus be conceived as surrounded bv a very thin layer or skin,

R 2

244 Professor A. W. Bikher [March 20,

the properties of which are different from that of the liquid in the
interior, and to which rather than to any ideal geometrical boundary
the term surface might be applied. It may, however, prevent con-
fusion if it is called the surface-lmjer.

Many attempts have been made to measure the thickness of the
surface-layer. In particular, M. Plateau studied a thinning soap film
with the view of determining whether or no the pressure exerted on
the enclosed air by the film when very thin is the same as when it is
comparatively thick. Had any such difference been observed it might
but have been taken as prima fade evidence that the tenuity was so
great that all the interior portions of the film had drained away, and
that the thickness did not exceed that of the two surface-layers.

This experiment has been criticised by Prof. Eeinold and mys.elf,
but it is not intended in this lecture to enter upon the general question
of the thickness of the surface-layer, or the interesting theoretical
problems w^hich are closely connected with it, as we are at present
engaged in an investigation which we hope may throw further light
upon the subject. There are, however, two preliminary questions on
which we have arrived at definite conclusions.

In any experiments which have for their object the detection of
small changes in the properties of a soap film as it becomes thinner, it
is essential that we should be able to assert with certainty that no
causes other than the increasing tenuity have been in play, by w^hich
the effect looked for might either be produced or masked. Changes
in the temperature or composition of the film, must especially be
prevented.

The liquid ordinarily employed for such investigations is the
" liquide glycerique " of M. Plateau. In dry air some of the water of
which it is in part composed would evaporate, while in moist air, in
consequence of the hygroscopic properties of the glycerine, additional
water would be absorbed. Though these facts were well known, and
though they are evidently possible sources of error, no attempt (as
far as I am aware) had been made before our own to determine
what precautions it was necessary to take to prevent the results ol
experiments such as M. Plateau's being affected by them. The first
question then that we set ourselves to answer, was — to what extent is
the composition of a soap film altered by changes in the temperature
or hygroscopic state of the air which surrounds it ?

The method adopted in answering this inquiry was to measure the
electrical resistance of soaj) films formed in an inclosed space con-
taining a thermometer and hair hygrometer. If the observations led
to the conclusion that the resistance of film varied inversely as its
thickness, they would jirove that no change in composition had taken
place, and that the film at the thinnest had afforded no evidence of an
approach to a thickness equal to that of the surface-layers. If the
specific resistance was found to vary according to some regular law as
the thickness altered, there would be a strong presumption, that the
thickness was not much greater than, and was i)0hsibly even less than

1885.] on Liquid Filmfi. 245

that of the two surface-layers. If, lastly, tlic changes were irregular,
they might safely be ascribed to alterations in temperature or consti-
tution.

To obtain the desired facts it was necessary (1) to devise a method
of forming the films in a closed chamber, (2) to measure their thick-
ness, and (3) to determine their electrical resistance.

The films were formed in a glass box at the lower extremity of a pla-
tinum ring which communicated by means of a tube with the out-
side. In the earlier experiments a cup of the liquid was raised by
rackwork to the ring and then withdrawn, leaving a film behind it.
The latter was blown out by air which had been dried and passed
through tubes containing " liquide glycerique." When large enough
it adhered to a second platinum ring placed vertically below the first,
and on some of the air being withdrawn it assumed the cylindrical
form.

The thickness was measured by means of the colours displayed,
two independent determinations being obtained by two beams of light
incident at different angles. Newton's Table of Colours was re-
vised, and it was found that the differences between the thicknesses
given by him and those determined by new experiment were far greater
than the error of experiment of a single observer. Hence, if accu-
rate measurements are required by means of Newton's scale, every
experimenter must reconstruct that scale for himself.

At first the electrical resistance was determined by means of
Wheatstone's Bridge. The edges of the film where it is close to its
solid supports are often, however, the seat of j)henomena which might
afl"ect the results. Thin rings of white or black appear which alter
the resistance considerably, and which introduce errors for which it is
almost impossible to make any accurate allowance. This fact, com-
bined with the advantage of avoiding errors due to polarisation, and
of being able to select any particular part of the film for examination
instead of the whole, led us to adopt a different method. Gold wires
attached to a movable support were thrust into the film, and the
difference of potential between these when a current was passing
through the film was compared with that between the extremities of a
known resistance included in the same circuit.

The result of these observations was to prove that the specific
resistance of the films altered in an irregular manner, varying between
200 and 137 ohms per cubic cm. A closer inspection showed that
abnormal results were always accomj)anied by abnormal variations in
the thermometer or hygrometer. When those films were selected which
had been observed when such variations were especially small, it was
found that the range of variation of the specific resistances was only
between 137 and 146, and that the mean value was 143, that of the
liquid in mass being 140*5 (at the same temperature). It was also
proved that between thicknesses varying from 1370 to 374 millionths
of a millimetre, no regular change in specific resistance could be
detected, the actual variations lying within 2*5 per cent.

246

Profer^sor A. W. Bilcler

[Marcli 20,

The coiiclnsion was thus arrived at that the specific resistance of
the liquid of which a soaji film is formed does not difier from that of
the same liquid in mass, at all events when the thickness is greater
than 374 x 10"'^ mm, and that comparatively small changes in the
temperature or hygroscopic state of the air in contact with the film
are attended with great alterations in the specific resistance, which
indicate a considerable change in composition.

The method of experiment made it possible to determine the
amoimt of this change. Solutions were made up representing
" liquide glycerique " which had lost or gained given percentages of
water, their specific resistances were determined at various tempera-
tures, and approximate formulae obtained by which the percentage of
water present could be calculated if the specific resistance and
tempei'ature were known.

The results of the application of this method of analysis to a film
are shown in the accompanying figure. The abscissae represent time,
the ordinates of curve I. represent the average thickness of the film.

Fig. 1,

It will be observed that the film continued to get thinner during the
whole time that it was under observation. The electrical observations
however, proved that at first the jiroduct of the resistance and thick-
ness steadily increased, indicating a continuous loss of water. Curve II.
shows the numl)cr of parts of water in 100 of the solution lost at the

1885.] on Liquid Films. 247

times indicated by the abscissae. After a while a piece of blotting-
paper which had been hung up inside the case was moistened with
water. While this was being done the observations were interrupted.
On their renewal it was found that although the film thinned as steadily
as before, the j)roduct of the resistance and thickness diminished in-
stead of increasing. Curve III. shows the steady absorption of water
which follow^ed the moistening of the air. These experiments proved
that it is possible for a film to undergo great changes in composition
without any indication of the fact being afforded by the colours it dis-
plays. They show^ that if the composition of the " liquide glycerique "
is to be kept constant, all change in the temperature and hygrometric
state of the air must be as far as possible prevented. In later experi-
ments this condition has been secured by placing the film box in the
centre of a water tank, and by keeping an endless band of linen hung
up within the case, and which dips into the liquid, continually
moistened. Observations made with this apparatus show that these
precautions wliich are certainly necessary are also sufficient.

The second point to which special attention has hitherto been
given by Prof. Reinold and myself is the measurement of the thick-
ness of very thin films. If the thickness is less than a certain magni-
tude, the films appear black, and thus their colour gives only a limit
to and not a measure of their thickness. Black films display many
remarkable properties. In general there is a sudden change in thick-
ness at the edge of the black indicated by the omission of several
colours, or sometimes of one or two orders of colours. It is only
under rare conditions that a gradual change in thickness can be
observed from the white to the black of the first order.

To determine the thickness of the black its resistance was
measured, and the thickness calculated on the assum/ption that the
specific resistance loas the same as that of the liquid in mass.

The observations were made in several different ways and proved
that the thickness of the black portion remains constant in any given
film, liowever much its area may alter. Thus, in the case of a group
of films measured by Wheatstone's bridge, the average resistance of a
black ring 1 mm. in breadth was 1'761 megohms when the total
breadth was 2 mm., and 1-760 megohms when the total breadth lay
between 10 and 12 mm.

Again, the resistance of the part of the film between the needles
used in the electrometer method was practically the same when
the black had extended over the whole film (40 mm. long) as it had
been when only the upper 11 mm. were black. The final measure-
ment differed from the mean by only 0 • 1 per cent. Again, in another
film the resistance of the black per millimetre remained the same to
within 2 • 5 per cent, for an hour and a half.

On the other hand the experiments also proved that the thickness
of the black was different in difierent films. The values found varied
between 7*2 x 10 ""^ and 14-2 x 10"*^ mm. These differences are
quite outside the possible error of experiment. If they were due to

218 Professor A. W. Biiclcer [Marcli 20,

changes in the coilstitution of the liquid of which the films were
formed, it is very improbable that the specific resistance of individual
films would not have shown progressive changes. As has been stated,
none such were observed. The mean thickness of the five films made
of "liquide glycerique " which w^ere observed was 11-9 X 10 ""^ mm.,
while that of 13 films made of soap solution without any glycerine
was 11-74 X 10"^ mm.

The assumption made in these calculations that the specific
resistance of a film, the thickness of which is ten or twelve millionths
of a millimetre, is the same as that of the liquid in mass, is not justi-
fied by the previous experiments, which had proved it to hold good
only to the much greater thickness of 370 X 10 ~*^ mm. It was there-
fore desirable to check the results by an independent method. For
this purpose 50 or 60 plane films were formed side by side in a glass
tube which was placed in the path of one of the interfering beams in
a Jamin's Interferential Kefractometer. The compensator was ad-
justed so that it had to be moved through a large angle to cause one
interference band to occupy the position previously held by its neigh-
bour, i. e. to alter the difference of the paths of the interfering rays
by one wave length. This angle was determined for the red light of
known wave length transmitted by glass coloured with copper oxide.
When the films had thinned to the black they were broken by means
of a needle which had been included in the tube along with them, and
which was moved, without touching the tube, by a magnet. The
rupture of the films produced a movement of the interference fringes
which was measured by the compensator, and from which, in accordance
with well-known principles, the thickness of the films could be
deduced.

The mean thickness given by seven experiments on films made of
" liquide glycerique" was 10"7 X 10~^ mm., that obtained from nine
experiments on films made of soap solution was 12-1 x 10 ~^ mm.
The mean of these, or 11*4 X 10 ""^ mm., differed only by
0'4 X 10 ~^ mm. from the mean thickness deduced from the electrical
experiments.

The last point to which reference is necessary is one which lies
outside the main line of the enquiries above described, but w^hich is
nevertheless not without interest. In the course of the observations it
was noticed that the rate of thinning of a film seemed to be affected
by the passage of the electric current through it. Some experiments
made on this point last year proved the fact beyond the possibility of
doubt. The current appears to carry the matter of the film with it,
so that it thins more rapidly if the current runs down, and less
rapidly if the current runs up than if no current is passing. This
may be shown as a lecture experiment.

A vertical rod which can be moved up and down by rackwork is
passed through the centre of the cover of a glass film-box. To the
lower extremity is attachefl a horizontal platinum wire, from which
another similar horizontal wire is suspended by two silk fibres. A

1885.] on Liquid Films. 24'J

film is formed by lowering tlie whole into the liquid with which the
lower part of the vessel is flooded. The light reflected from the
film is passed through a lens, and au image formed upon a screen.
When the bands of colour are seen descending from the upper part of
the film a current from 50 Grove's cells is passed through it. If the
current flows downwards the bands of colour move more quickly than
before ; if it flows upwards their motion is checked and they begin
to ascend. The cause of this curious fact is still unknown. It may
either be analogous to the j^benomenon known as the "migration of
the ions," or it may be a secondary effect" due to a change in the sur-
face tension.

The general relation of the results attained in these investigations
as to the question of the size of molecules is interesting. Sir William
Thomson has expressed the opinion that 2 X 10~^ mm. and
0.01 X 10~'^mm. are superior and inferior limits respectively to
the diameter of a molecule. Van der Waals has been led, from con-
siderations founded on the theory of gases, to give 0* 28 X lO""*^ mm.
as an approximate value of the diameters of the molecules of the
gases of which the atmosphere is composed. The number of mole-
cules which could be plnced side by side within the thickness of the
thinnest soap film would, according to these various estimates, be
4, 26, and 720 respectively. The smallness of the first of these
numbers, especially when it is remembered that the liquid used on
some occasions w^as of a highly complex character, containing water,
glycerine and soap, points to the conclusion that the diameter of a
molecule is considerably less than 2 x 10 ~^ mm.

[A. W. E.]

250 Mr. Vidor Horsley [March 27,

WEEKLY EVENING MEETING,

Friday, March 27, 1885.

Sir Frederick Bramwell, F.E.S. Manager and Vice-President,
in the Chair.

Victor Horsley, Esq. F.E.C.S.

The Motor Centres of the Brain, and the Mechanism of the Will.

Feeling deei)ly as I do the responsibility I have incurred in under-
taking to address you to-night, I desire to express my regret that I
cannot instead share with you the pleasure of listening to the dis-
tinf^uished man who has been prevented by a most painful bereave-
ment from addressing you to-night.

My subject being the mechanism of the will, it might be asked,
" What has a surgeon to do with psychology ? " To which I would
answer, " Everything." For without sheltering myself behind Mr.
Jonachan Hutchinson's trite saying that "a surgeon should be a
physician who knows how to use his hands," I would remind you that
pure science has proved so good a foster-mother to surgery, that diseases
of the brain which were formerly considered to be hopeless, are now
brought within a measurable distance of the knife, and therefore a
step nearer towards cure. Again, I would remind you that surgeons
rather than physicians see the experiments which so-called Nature is
always providing for us, — experiments which, though horribly clumsy,
do on rare occasions, as I shall presently show you to-night, lend us
powerful aid in attempting to solve the most obscure problems ever
presented to the scientist.

The title I have chosen may possibly be objected to as too com-
prehensive ; but until we are ready to admit a new terminology wo
must employ the old in order to convey our meaning intelligibly,
although there may be coupled therewith the risk of exjjressing more
than we desire. Thus when I speak of the mechanism of the will
and the motor centres of the brain, I do not intend (as indeed must
be obvious) to discuss the existence of the so-called freedom of the
will, or the source of our consciousness of voluntary power.

I shall rather describe to you first the general plan of the
mechanism which convoys information to our biain, the thinking
ort^an • next the arrangement of those parts in it which are concerned
wi'tli voluntary phenomena; and finally I shall seek to show by
means of experiment that tlie consciousness of our existing as single
beings, the consciousness of our possessing but one will as people
say, wliile at the same time we know that we possess a double nervous

1885.] on the Motor Centres of the Brain, dc. 251

s\'stem, is due to the fact tliat miro volition is dcjicndent entirely on
the exercise of the attention which connotes the idea of singleness.
Consequently that it is impossible to carry out two totally distinct
ideas at one and the same moment of time, when the attention must
of course be fully engaged upon each.

I fear that in making my argument consecutive, T shall have to
pass over very well-beaten paths, and so I must ask your patience for
a few moments while I make good my premisses.

The nervous system, which in man is com^iosed of brain, spinal
cord, nerves, and nerve-endings, is arranged upon the simplest plan,
although the details of the same become highly complex when we
arrive at the top of the brain.

At the same time, while we have this simple plan of structure, we
find that there is also a fundamental mode of action of the same — a
mode which is a simple exposition of the principle, no effect without
a cause — a mode of action which is known as the phenomenon of
simjile reflex action.

The general plan of the whole nervous system is illustrated by
this model. Imbedded in the tissues all over the body, or highly
specialised and grouped together in separate organs, such as the eye
or ear, we find large numbers of nerve-endings, that is, small lumps
of protoplasm from which a nerve fibre leads away to the spinal cord
and so ujd to the brain.

These nerve-endings are designed for the reception of the different
kinds of vibration by which energy presents itself to us. As the
largest example of these nerve-endings, let me here show you one of
the so-called Pacinian bodies, or more correctly Marshall's corpuscles,
for Mr. John Marshall discovered these bodies in England before
Pacini published his observations in Italy. Here you see one of
these small oval bodies arranged on the ends of one of the nerves of
the fingers, and here you see the nerve fibre ending in the little
protoplasmic bulb which is protected by a number of concentric
sheaths.

Pressure or any form of irritation of this body at the end of the
nerve fibre causes a stream of nerve energy to travel through the
spinal cord to the brain, and so we become conscious that something
is happening to the finger.

Here in this section of the sensitive membrane of the back of the
eye, the retina, you see a similar arrangement, only more complicated,
namely, nerve fibres leading away from small protoplasmic masses
which possess the property of absorbing light and transforming it
into nerve energy. It is this transformation into nerve energy of
heat, light, pressure, &c., which it seems to me should alone be called
a sensation, irrespective of consciousness. And in fact we habitually
say we feel a sensation. The terms feeling and sensation, however,
are frequently used as interchangeable expressions, although, as I
shall show you directly, "feeling " is the conscious disturbance of a
sensory centre in the surface of the brain, and in fact feeling is the

252 Mr. Victor Ilon^leij [March 27,

conscious perception of sensations. This distinction between feeling
and sensation, if dogmatic, will save us from dispute as to the meaning
of the word sensation ; and further, the distinction is one, as I have
just shown, which is justified by custom.

Now the nerve fibre which conveys the energy of the sensation is
a round thread of protoi)lasm which in all probability connects the
nerve-ending with a sensory corpuscle in the spinal cord. These
nerve fibres running in nerves are white, whereas, as you know,
protoplasm is grey. They are white because each is insulated from
its fellow by a white sheath of fatty substance, just as we protect
telegraph wires with coatings. It is not stretching analogy too far
to say that nerve force may probably escape unless properly insulated.

In consequence of the fibres being covered with these white
sheaths, they form what is called the white matter of the brain ; while
the nerve centres are greyish, and therefore form what is called the
grey matter of the brain, so that the grey matter receives and records
the messages conveyed to it by the white insulated fibres.

From the sensory corpuscle, which is a small mass of protoplasm
provided with branches connecting it to neighbouring corpuscles, the
nerve energy if adequate passes along a junction thread of protoplasm
to a much larger corpuscle, which is called a motor corpuscle, and
the energy of which when liberated by the nerve impulse from the
sensory corpuscle is capable of exciting muscles into active contrac-
tion. These two cv:)rpuscles form what is called a nerve centre.

Not only are the motor corpuscles fewer as well as much larger
than the sensory ones, but also the nerve fibres wdiich go out fi-om
them are larger too. In fact, it would seem as if we had another close
analogy to electrical phenomena ; for here, where we want a sudden
discharge of a considerable intensity of nerve force, we find to hand a
large accumulator mechanism and a large conductor, the resistance of
which may justly be supposed to be low. Finally, the motor nerve-
fibre terminates in a protoi^lasmic mass which is firmly united to a
muscle fibre, and which enables the muscle fibre to contract and so
cause movement of one or more muscles. Now, with this idea of the
general plan on which the whole nervous system is constructed, you
will understand that muscular action, i. e. movement, will occur in
proportion to (1) t! e intensity of the stimulation of the sensory
corpuscle, and (2) the resistance in the different channels. When a
simple flow through the whole apparatus occurs, it is called a simple
reflex action, and this was discovered in England by Dr. Marshall
Hall.

To recapitulate : a nerve centre, theoretically speaking, we find to
consist of a sensory corpuscle on the one hand and a motor corpuscle
on the other, both these being united by junction threads or com-
missures. To such a centre come sensations or impressions from the
nerve-endings, and from such a centre go out impulses which set the
muscles in action.

I have dwelt thus at length ou this most elementary point, because

1885.] on the Motor Centres of the Brain, de, 253

it a2)i)cars to mo that in consequence of tlic rapidity with wliicli
function is being demonstrated to be definitely localised in various
l)ortions of tLe cerebral lieinisphercs, we are in danger of losing
siglit of Dr. Hnglilings Jackson's grand generalisations on nerve
function, and that we are gradually inclining to the belief that the
function of each part is very distinct, and therefore can most readily
act without disturbing another part.

In fact, we are perhaps drifting towards the quicksands of spon-
taneity, and disregarding entirely the facts of every-day life which
show that every cycle of nerve action includes a disturbance of the
sensory side as well as the active motor agency. Did we in fact
admit the possibility of the motor corpuscle acting per se, and in the
absence of any sensory stimulation, we should again be placed in the
position of believing that an eifect could be produced in the absence
of a cause.

For these reasons such a centre has been termed kinsesthetic or
sensori motor, and such centres exist in large quantities in the spinal
cord, and they perform for us the lower functions of our lives with-
out arousing our consciousness or only the substrata of the same.

But now, turning to the brain, although I am extremely anxious
to maintain the idea just enunciated that when discussing the abstract
side of its functions we should remember the sensori motor arrange-
ment of the ideal centre, I shall have to show you directly that the
two sides, namely, the sensory and motor in the brain are separated
by a wide interval, and that in consequence we have got into the
habit of referring to the groups of sensory and motor corpuscles in
the brain as distinct centres. I trust you will not confuse these ex-
pressions, this unfortunately feeble terminology, and that you will
understand, although parts may be anatomically separated and only
connected by commissural threads, that functionally they are closely
correlated.

In consequence of the bilateral symmetry of our bodies we possess
a double brain — a practically symmetrical arrangement of two in-
timately connected halves or hemispheres which, as you know, are
concerned with opposite sides of the body, for the right hemisphere
moves the left limbs, and vice versa.

For my purj)ose it will be sufficient if we regard the brain as com-
posed of two great collections of grey matter or nerve corpuscles
which are connected with sensory nerve-endings, with muscles, and
intimately with one another.

In this transverse section of a monkey's brain, which is stained
dark blue to show up its comjDonent parts, you will see all over the
surface a quantity of dark grey matter, which is simply the richly
convoluted surface of the brain cut across. Observe it is about
J inch deep, and from it lead downwards numerous white fibres down
towards the si)inal cord. The surface of the brain, the highest and
most complicated part of the thinking organ, is called the cortex, bark,
or rind, and in it are arranpred the motor centres I am about to

254 Mr. Victor llorsl'n [Marcli 27,

describe. These white fibres coming away from it to the cord, not
only are channels convoying messages down to the muscles, but also
carrying messages from the innumerable sense corpuscles all over the
body.

So much for one grey mass of centres. Now down here at the base
of the brain you see two lumps or masses of the same nature, and
these are called therefore the basal ganglia or grey masses. Since they
are placed at the side of the paths from the cortex, and undoubtedly
do not interfere with the passage of impulses along those paths, we
may put them aside, remembering that they i)robably are concerned
with low^ actions of the nervous system, such as eating, &c., which are
pojmlarly termed automatic functions.

In this photograph of a model made by Professor Aeby, of Berne,
you see represented from the front the two cerebral hemisj^heres with
the centres in the cortex as little masses on the surface, and the basal
ganglia as darker ones at the bottom, while leading from them down
into the spinal cord are wires to indicate the channels of commu-
nication.

Note in passing that both hemispheres are connected by a thick
band of fibres called the corpus callosum. It is, I believe, the close
union thus produced between the two halves that leads in a great
measure (though not wholly) to consonance of ideas.

The arrangement of the fibres will be rendered still clearer by this
sclieme, in which the cortex is represented by this concave mass, and
the fibres issuing from the same by these threads.

The basal ganglia would occupy this position, and they have their
own system of fibres.

I will now leave these generalisations, and ex[)lain at once the
great advance in our knowledge of the brain that has been made
during the last decade. The remarkable discovery that the cortex or
surface of the brain contained centres which governed definite groups
of muscles, was first made by the German observers Hitzig and
Fritsch ; their results were, however, very incomplete, and it was
reserved for Professor Ferrier to produce a masterly demonstration of
the existence and exact position of these centres, and to found an
entirely new sclieme of cerebral physiology.

The cortex of the brain, although it is convoluted in this exceed-
ingly complex manner, fortunately show^s great constancy in the
arrangement of its convolutions, and we may therefore readily grasp
the main features of the same without much trouble.

From this photograph of the left side of an adult human brain,
you will see that its outer surface or cortex is deeply fissured by a
groove running backward just below its middle, which groove is
called the fissure of Sylvius, after a distinguished med:a)val anatomist.
This fissure if carried upwards would almost divide the brain into a
motor half in front and a sensory half behind.

Of equal practical importance is another deep fissure which runs
at an open angle to the last, and which is called the fissure of Kolando,

1885.] on the Motor Centres of the Brain, &c. 255

Rolando being another pioneer of cerebral topograi)hy. Now it is
around this fissure of Rolando that tlie motor side of the centres for
voluntary movement is situated ; and when this portion of the cortex
is irritated by gentle electrfc currents, a constant movement follows
according to the part stimulated.

Because of their upward direction, the convolutions bounding the
fissure of Rolando are called respectively the ascending frontal and
ascending parietal convolutions.

Now here, at the lowest end of the fissure of Rolando, we find
motor areas for the movement of both sides of the face, that is to say,
that as regards this particular piece of the cortex, it has the power of
moving not only its regular side of the face, the right, but also the
left — that in fact both sides of the face move by impulse from it.

Higher up we find an area for movement of the oj^posite side of
the face only. I reserve for a moment the description of this portion
of the brain, and jDass on to say that above these centres for the face
we find the next is for the ujDper limb, and most especially the common
movement of the upper limb, viz. grasping, indeed the only forward
movement which the elbow is capable of, namely flexion. The
grasping and bringing of an object near to us is the commonest
movement by far, and we find here that this centre is mainly con-
cerned in it. Behind the fissure of Rolando, Dr. Ferrier placed the
centres for the fingers.

Next above the arm area is a portion of the cortex which moves
the lower limb only, and in front of this again is an area for consonant
action of the opposite arm and leg.

Let me here remind you that this being the left hemisphere, these
are the centres for movement of the opposite, that is the right limbs,
and that in the other hemisjDhere there are corresponding areas for the
left limbs.

Thus here we have majDped out those portions of the cortex which
regulate the voluntary movement of the limbs. So far I have
omitted mention of the muscles of the trunk, namely, those which
move the shoulders, the hips, and bend and straighten the back.
Dr. Ferrier had shown that there existed on the outer surface of the
cortex, here, a small area for the movement of the head from side to
side.

Professor Schafer and myself have found that the large trunk
muscles have special areas for their movement, ranged along the
margin of the hemisphere, and dipj)ing over into the longitudinal
fissure. Thus all the muscles of the body are now accoimted for, and
I will first draw special attention to the fact that they are arranged
in the order, from below upwards, of face, arm, leg, and trunk.

The consideration of this very definite arrangement led Dr.
Lander Brunton to make the ingenious suggestion that it followed as
a necessary result of the progressive evolution of our fac-ulties. For
premising in the first place from well- ascertained broad generalisa-
tions that the highest centre, physically speaking, is also the highest

256 Mr. Victor Horsleij [March 27,

functionally aud most recent in acquirement, we find tliat the lowest
is the face, and then we remember that the lowest animals simply
grasp their food with their mouth. I imagine it is scarcely necessary
for me to repeat the notorious confession that our faculties are
arranged for the jmrpose of obtaining food as the primary object of
what is called bare existence.

Proceeding upwards in the scale of evolution, we next find animals
which can grasp their prey and convey it to the mouth, and so we
find next to the face area evolved that for the arm.

And so on, the next step would be the development of the legs to
run after the prey, and here is the leg centre ; while finally, the
trunk muscles are dragged in to help the limbs more effectually.

To my mind this idea receives overwhelming support from the
consideration of the fact that the higher our centres are, the more they
require education ; the infant, for instance, in a few days shapes its
face quite correctly to produce the food-inspiring yell, yet takes
months or years to educate its upper limbs to aid it in the same
laudable enterprise. Finally, what terrible probation some people
pass through at the hands of dancing-masters before their trunk
muscles will bend into the bow of politeness.

Now to return to the lower end of the fissure of Eolando, to the
areas for movements of the face, it was long ago pointed out by the
two Dax's and Professor Broca that when this portion of the brain
immediately in front of the face area was destroyed, that the person
lost the power of articulate speech, or was only capable of uttering
interjections and customary " strange oaths."

In fact this small portion of the left side of our brains (about IJ
square inches) is the only aj)paratus for expressing our thoughts by
articulating sounds, and note particularly that it is on the left side.
The corresponding piece on. the right side cannot talk as it were.
This remarkable state of things is reversed in left-handed people.
In these the right hemisphere predominates ; and so we find that
when this portion was diseased, there followed aphasia, as it is called.
While, however, the right side customarily says nothing, it can be
taught to do so in young peoj^le, though not in the aged.

P)efore leaving these motor areas, let me repeat, by way of recapitu-
lation, that the only truly bilaterally acting areas are tliose for the
lower facial and throat muscles. This is a most important fact, for
tlie idea has recently been propounded that both sides of the body are
represented in each motor region of each hcmisjihere. That is to say,
each motor area has to do with the movements of both upper limbs, for
example. In support of my contention that this is not in accordance
with clinical facts, let me here show you photographs of the brain of
a man who was unfortunate enough to suffer destruction of the fibres
leading from one motor area. Here you see a puncture in the brain
which has caused ha3morrhage beneath the fissure of Rolando and tlie
motor convolutions in front and behind it.

In this transverse section of tlic same spot you see that the

1885.] on the Motor Centres of the Brain, the. 257

haemorrhage has ploughed up the interior of the brain. Here is tlie
cortical grey matter, but its fibres leading down to the muscles are all
destroyed.

Now in examining this patient I asked him to move his left arm
or leg ; he was perfectly conscious, and understanding the question,
made the effort as we say, but no movement occurred.

Now if both sides of the body are represented in each hemisphere,
it seems to me that such a case would be impossible, or at least that
a little practice would enable the other hemisphere to do the work ;
but all clinical facts say that, once destroyed, the loss is never
recovered.

If we examine this motor region of the cortex with the microscope,
we of course find these large corpuscles, which we have learnt are
those which alone give energy to the muscles.

But you must not imagine that the motor region consists solely of
these corpuscles. On the contrary, as you see in this diagram, we
have several layers of corpuscles. I shall return to this arrangement
of the corpuscles directly.

Looking back at the surface of the brain, you notice that I have
only accounted for but a small portion of the cortex. Dr. Ferrier
was the first to show that the portion of cortex which perceived (and
I use the word in its strictest sense) the sensation of light was this
part, and it is therefore called the visual centre or area. From
recent researches it would appear that we must give it the limits
drawn on this diagram. Below it we find the centre for hearing.

Thus we know where two sense percej^tive centres are situated.

Microscopical investigation shows that this sensorial portion of
the cortex is very deficient in large corpuscles, and is correspondingly
rich in small cells. Here in this diagram you see these two kinds
of structure in the cortex cerebri. Note the greater number and
complication of the small corpuscles in the sensory part of the cortex,
and the comparatively fewer though much larger corpuscles in the
motor region.

It seems to me that several beliefs are justified by these facts.

In the first place, the movements produced by the action of these
motor centres are always the same for the same centre; consequently
it has only one thing to do, one idea as it were. Thus, for instance,
bending of the arm ; this action can only vary in degree, for the elbow
will not permit of other movements. Hence we may look upon it as
one idea. Now observe that where one idea is involved, we have but
few corpuscles.

Next consider the multitude of ideas that crowd into our mind
when we receive a sensation. One idea then rapidly calls up another,
and so we find anatomically that there are a corres^Donding much
greater number and complication of nerve corpuscles.

To sum up, I believe we are justified in asserting that where in
the nervous system a considerable intensity of nerve energy is re-
quired (e. g. for the contraction of muscles) you find a few large cor-

VoL. XI. (No. 79.) s

258 Mr. Victor Horsley [March 27,

puscles and fibres provided, and that where numerous ideas have to
be functionalised, there numerous small corpuscles are arranged for
the purpose.

But now the special interest attaching to the sensory perceptive
areas is that they, unlike the motor areas, tend to be related to both
sides of the body. With our habit of constantly focussing the two
eyes on one object, it will strike you at once that habitually we can
only be attentively conscious of one object at a time, since both eyes
are engaged in looking at it, and as you know we cannot as a matter
of fact look at two things at once.

Hence I take it, both sensory perceptive centres are always fully
occupied with the same object at the same moment, and that therefore
we have complete bilateral representation of both sides of the body in
each hemisphere. As a further consequence, each sensory perceptive
area will register the idea that engaged it; in other words, both
centres will remember the same thing. Thus it happens that each
sensory area can perform the duty of the other, and therefore it is a
matter of comparative indiflference whether one is destroyed or not,
and as a matter of fact when this happens we find that the person or
animal recognises objects as they actually are, and in fact has no
doubt as to their nature. Here you see anatomically the reason of
this peculiarity is found to be that the optic or seeing nerves cross
one another incompletely in going to each hemisphere, and thus
each sensory centre represents half of each eyeball.

I must pass rapidly to the description of the rest of the surface of
the brain — the hinder and front ends. At the outset I must admit
that all our knowledge concerning them is very hypothetical in the
absence of positive experimental results.

This much we can say, that they are probably the seats of in-
tellectual thought, for many reasons which I have not time to detail.
Further we know that these intellectual areas are dependent for their
activity entirely on the sensory perceptive centres, for the dictum
that there is no consciousness in the absence of sensory stimulation is
very well established, as I shall now show you, however astounding
it may appear. In the first place, you will remember that when we
wish to encourage that natural loss of consciousness which we call
sleep, we do all we can to deprive our sense organs and areas of
stimulation ; thus we keep ourselves at a constant temperature, we
shut off the light, and abolish all noises if we can. But a most
valuable observation was made a few years ago by Dr. Striitnpell, of
Leipzig, who had under his care a youth, the subject of a disease of
the brain, &c., which while destroying the function of one eye and
ear, besides the sensibility to touch over the whole body, still left
him when awake quite conscious and able to understand, &c., using
his remaining eye and ear for social intercourse. Now when these
were carefully closed he became unconscious immediately, in fact
slept, and slept until he was aroused again, or woke naturally as wc
nay after some hours.

1885.] on the Motor Centres of the Brain, dr. 259

Hence the higher functions of the braiu exercised when that
organ is energising the reasoning of the mind, are absolutely de-
pendent ujion the reception of energy from the sense perceptive areas.

But my only point with reference to this part of the brain is to
attempt to determine how far they are connected with the motor
centres in the performance of a voluntary act. With the mechanism
of choice and deliberate action I have nothing to do, but there can be
no doubt that the part of the brain concerned in that process of the
mind is directly connected with the motor region, as indicated on
this diagram, to which I would now return. From what I have here
written you read, arranged schematically, the psychical processes
which for the sake of argument vv^e may assume are carried on by the
mind in these portions of the cortex.

I wish to point out that we have structurally and pliysiologically
demonstrated with great probability the paths and centres of these
psychical actions. There is no break ; the mere sight of an object
causes a stieam of energy to travel through our sense areas, expanding
as it goes by following the widening sensory paths were represented,
and at the same time we feel our intellect learns that new ideas are
rising up and finally expand into the process of deliberate thought,
concerning which, all we know is from that treacherous support,
namely introspection.

Then comes impulses to action, and these follow a converse path
to the receptive one just described ; the nerve energy is concentrated
more and more until it culminates in the discharge of the motor
corpuscles. We might represent the whole process of the voluntary
act by two fans side by side, and the illimitable space above their
arcs would serve very well to signify the darkness in which we sit
concerning the process of intellectual thought.

What I have hastily sketched is the outline of the process of an
attentive or voluntary act. I say attentive advisedly, for I wish now
to put forward the view that the proper criterion of the voluntary
nature of an act is not the mere effort that is required to perform it,
but is the degree to ivMch the attention is involved. The popular view
of the volitional character of an act being decided by the effort to
keep the action sustained is surely incomplete, for in the first place
we are not seeking to explain our consciousness of an effort, we
endeavour to discover the causation of the effort. Our sense of effort
only comes when the will has acted, and that same sense is no doubt
largely due to the information which the struggling muscle sends to
the brain, and possibly is a conscious appreciation of how much energy
this motor corpuscle is giving out.

Now to give you an example. I see this tambour and decide to
squeeze it, and do so. Now this was a distinctly voluntary act ; but
the volitionary part of it was not the effort made, it was the deliberate
decision to cause the movement.

I may now point out that in this whole process we say, and say
rightly, that our attention is involved so long as we are deliberating

s 2

260 Mr. Victor Horsley [March 27,

over the object, that as soon as another object is brought to us our
attention is distracted, that is to say, turned aside.

All writers are agreed that the attention cannot be divided, that
we really only attend to one thing at once.

It seems to me that this is so obvious as not to require experi-
mental demonstration, but I have led up to this point because I now
wish to refer to the third part of my subject, namely, the question as
to whether we have a really double nervous system or not ; but by
way of preface let me repeat that although we may have a subcon-
sciousness of objects and acts, that that subconscious state is true
automatism, and that such automatic acts are in no sense voluntary
until the attention has been concentrated upon them. For example,
again I press this tambour because I desire to raise the flag, and I
keep that raised while I attend to what I am saying to you. My
action of keeping the flag raised is only present to my consciousness
in a slight or subordinate degree, and does not require my attontion, ,
deliberate thought or choice, and therefore I repeat is not a voluntary
action, in fact it could be carried on perfectly well by this lower
sensori motor centre, which only now and then sends up a message to
say it is doing its duty, in the same way as a sentry calls out " All
well " at intervals.

But to return. In consequence of the obvious fact that we have
two nerve organs, each more or less complete, some writers have
imagined that we have two minds ; and to the Rev. Mr. Barlow, a
former Secretary of this Institution, is due the credit of recognising
the circumstances which seem to favour that view. It was keenly
taken up, and the furor culminated in a German writer (whose name [
am ashamed to say has escaped me) postulating that we possess two
souls.

Now the evidence upon which this notion rests, that the two
halves of the brain might occasionally work independently of one
another at the same moment, was of two kinds. In the first place it
was asserted that we could do two different things at once, and in the
second place evidence was produced of people acting and thinking as
if they had two minds.

Now, while of course admitting that habitually one motor centre
usually acts at one moment by itself, I am prejiared to deny in toto
that two voluntary acts can be performed at the same time, and I have
already shown what is necessary for the fulfilment of all the con-
ditions of volition, and that these conditions are summed up in the
word attention.

Further, I have already shown tliat when an idea comes into the
mind owing to some object catching the eye, that both sensory areas
are engaged in considering it. It seems to me I might stop here, and
say that here was an a priori reason why two simultaneous voluntary
acts are impossible ; but as my statements have mot with some oppo-
sition, I prefer to demonstrate the fact by some ex[)eriments.

The problem, stated in physiological terms, is as follows :

1885.] on the Motor Centres of the Brain, &c. 261

Can this right motor region act in the process of volition, while
at the same time this other m(jtor area is also engaged in a different
act of volition ?

Some say this is possible ; but in all cases quoted I have found
that subconscious or automatic actions are confused with truly volun-
tary acts. I mean that such automatic acts as playing bass and treble
are not instances of pure volition, as the attention is not engaged on
both notes at once.

Consider for a moment the passage of the nerve impulses through
the brain that would have to occur. At the outset we find that the
sensory perceptive centres would have to be engaged with two different
ideas at once ; but Lewes showed long ago that introspection tells us
this is impossible, that " consciousness is a seriated change of feelings,"
he might equally well have said ideas. And again, we know that when
two streams of energy of like character meet one another, they
mutually arrest each other's progress by reason of inteifering with
the vibration waves.

I will show directly that this is actually the case in the action of
the cortex when t ;e above-mentioned dilemma is presented to it.

The experiment I have devised for this purj^ose is extremely
simple.

A person who is more or less ambidextrous, and who has been
accustomed for a long time to draw with both hands, attempts to
describe on a flat surface a triangle and circle at the same moment.
I chose these figures after numerous trials as being the most opposite,
seeing that in a triangle there are only three changes of movement,
while in a circle the movement is changing direction every moment.
To ensure the attempt to draw these figures simultaneously
succeeding, it is absolutely necessary that the experimenter should
be started by a signal.

\Vhen the effort is made, there is a very definite sensation in the
mind of the conflict that is going on in the cortex of the brain. The
idea of the circle alternates with that of the triangle, and he result
of this confusion in the intellectual and sensorial portions of the
brain is that both motor areas, though remembering as it were the
determination of the experimenter to draw distinct figures, produce a
like confused effect, namely, a circular triangle and a triangular
circle. If the drawing is commenced immediately at the sound of
the signal, it will be found that the triangle predominates ; thus if I
determine to draw a triangle with my left hand and a circle with my
right, the triangle (though with all its angles rounded off) will be
fairly drawn, while the circle will be relatively more altered, of
course made triangular. On the other hand, if the two figures are not
commenced simultaneously, it will be found that usually the one
begun last will ajDpear most distinct in the fused result, in fact will
very markedly j^redominate.

Now the course of events in such an experiment appears to be
clear.

262 3Ir. V. Eorslfiij on the Motor Centres of the Brain, d-c. [March 27,

The idea of a triangle aud circle having been presented to the
intellect by the sensory centres, the voluntary effort to reproduce these
is determined upon. Now, if we Ijad a dual mind, and if each
hemisphere was capable of acting ^^^r se, then we should have each
intellectual area sending a message to its own motor area, with the
result that the two figures would be distinct and correct, not fused.

The other evidence that I referred to above, which is adduced in
favour of the synchronously independent action of the two hemispheres,
is from the account of such cases ss the following. Professor Ball, of
Paris, records the instance of a young man who one morning heard
himself addressed by name, and yet he could not see his interlocutor.
He re2>lied, however, and a conversation followed, in the course of
which his ghostly visitant informed him that his name was M.
Gabbage.

After this occurrence he frequently heard M. Gabbage speaking to
him. Unfortunately M. Gabbage was always recommending him to
perform very outrageous acts, such as to give an overdose of
chlorodyne to a friend's child, and to jump out of a second-floor
window. This led to the patient being kept under observation, and
it was found that he was suffering from a one-sided hallucination.

Similar cases have been recorded in w^hich disease of one sensory
perceptive area has produced unilateral hallucination.

I cannot see that these cases in any way supj)ort the notion of the
duality of the mind. On the contrary, they go to show tliat while as
a rule the sensory percej)tive areas are simultaneously engaged upon
one object, it is still possible for one only to be stimulated, and for
the mind to conclude that the information it receives in this unusual
way must be supernatural, and at any rate proceeding from one side
of the body.

To conclude, I have endeavoured to show that as a rule both
cerebral hemisidieres are engaged at once in the receiving and con-
sidering one idea. That under no circumstances can two ideas either
be considered or acted U2)on attentively at the same moment. That
therefore the brain is a single instrument.

It now appears to me that one is justified in suggesting that our
ideas of our being single individuals is due entirely to this single
action of the brain.

Laycock showed that the Ego was the sum of our experience, and
every writer since confirms him. But our experience means (1) our
perception of ideas transmitted and elaborated by the sensory paths of
the brain, and (2) our consciousness of the acts we perform. If now
these things are always single, the idea of the Ego surely must also be
single.

[V. H.]

1885.] General Monthly Meetimj. 263

. GENERAL MONTHLY MEETING,

Mouday, April 6, 1885.

The Hon. Siii William R. Giiove, M.A. D.C.L. F.R.S. Manager and
Vice-President, in the Chair.

James Stewart Hodgson, Esq.
Henry W. Wimshurst, Esq.

were elected Members of the Royal Institution.

The following arrangements for the Lectures after Easter were
announced : —

Professor Arthur Gamgee, jM.D. F.K.S. — Eight Lectures on Digestion ani>
Nutrition ; on Tuesdays, April 14 to June 2.

Professor Tyndall, D.C.L. LL.D. F.E.S. M.R.I. — Five Lectures on Xatlral
Forces and Energies; on Thursdays, April 16 to May 14.

Professor C. Meymott Tidy, M.B. F.C.S. M.R. I.— Three Lectures on
Poisons in relation to their Chemical Constitution and to Vital
Functions; on Tliursdays, May 21, 28, June 4.

William Carruthers, Esq. F.H.S. — Four Lectures on Fir-trees and their
Allies, in the Present and in the Past ; on Saturdays, April 18, 25, May 2, 9.

Professor William Odling, M.A. F.R.S. M.R.I. — Two Lectures on Organic
Septics and Antiseptics; on Saturdays, IMay 16, 23.

Rev. C. Taylor, D.D.— Two Lectures on A lately discovered Document,
POSSIBLY of the First Century, entitled ' The Teaching of the Twelve
Apostles,' with Illustrations from the Talmud ; on Saturdays, May 30,
June 6.

The Presents received since the last Meeting were laid on the
table, and the thanks of the Members returned for the same, viz. : —

FROM

The Governor- General of India — Geological Survey of India : Palseontologia
Indica : Series XII. Vol. I. Part 4, Fasc. 3, 4. 4to. 1884.

Memoirs, Vol. XXI. Parts 1, 2. 8vo. 1884.

Records, Vol. XVIII. Part 1. 8vo. 1885.
Tlie British Museum — Catalogue of Early English Books to 1640. 3 vols. 8vo.
18S4.

Catalogue of Oriental Coins, Vol. VIII. 8vo. 1883.

Catalogue of Greek Coins : Central Greece. 8vo. 1884.

Guide to WyclifFe Exhibition. 8vo. 1884.

Guide to Reading Room and Libraries. 12mo. 1884.
The British Museum (Natural History Department) — Catalogue of Fossil Sponges.
By G. J. Hinde. 4to. 1883.

Catalogue of Lizards. 2nd edition. By G. A. Boulenger. Vol. I. 8vo. 1885.

Catalogue of Fossil Mammalia. Part 1. By R. Lydekker. 8vo. 1885.

Guide to tlie Mineral Gallery. 8vo. 1884.

Guide to the Galleries of Mammalia. 8vo. 1885.

Guide to the Galleries of Geology and Palseontology. 8vo. 1884.

Guide to the Collection of Fossil Fishes. 8vo. 1885.

264 General Monthly Meeting. [April 6,

Accademia del Lincei, Iteale, Roma— Atti, Seiie Terza: Rcndiconti. Vol. I.

Fasc. 5, G. 4to. 18S5.
Astronomical Society, i/oj/aZ— Monthly Notices, Vol. XLV. No. 4. 8vo. 1885.
Bankers, Institute o/— Journal, Vol. VI Part 3. 8vo. 1885.
Bavarian Academy of Sciences, i?o?/a? -S.tzung«berichte, 1883, Heft 3; 1884,

Heft 1, 2, and 3. 8vo. 1884,
British Architects, Royal Institute o/— Proceedings, 1884-5, Nos. 10, 11. 4to.
Chemical Society— Somwol for March, 1885. 8vo.
Civil Engineers' Institution— 'iiiaTne-linl ex to Minutes of Proceedings, Vols.

I.-LVIII. (1837-187'J).' 8vo. 1885.
Dax: Soclete de ^orda— Bulletins, 2" Serie Dixieme Aunee: Trimestre 1. 8vo.

1885.
East India Association— Jouma], Vol. XVII. No. 3. 8vo. 1885.
Editors — American Journal of Science for March, 1885. 8vo.
Analyst for March, 1885. 8vo.
Athena3um for March, 1885. 4to.
Chemical News for March, 1885. 4to.
Engineer for March, 1885. fol.
Horological Journal for March, 1885. 8vo.
Iron for March, 1885. 4to.
Nature for March, 1885. 4to.

Eevne Sciei.tifique and E( vue Politique et Litte'rairo for March, 1885. 4 to.
Science Monthly, Illustrated, for March, 1885. 8vo,
Telegraphic Journal for March, 1885. 8vo.
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Geddes, Fair id:, Esq. (the Author) — An Analysis of the Principles of Economics.

Part 1. 8vo. 1885.
Geneva: Societe' de Physique et d'Histoire Naturelle — Memoires, Tome XXVIII.

Partie 2. 4to. 1884.
Geographi( al Society, Royal — Proceedings, New Series, Vol. VII. No. 3. 8vo. 1885.
Geoloqiral Institule, Inqjerial, Vienna— J ahrhuch : Band XXXIV. Heft 4. 8vo.
1884.
Verhandlungen, 1884, Nos. 1-18. 8vo. 1884.
Hanhs, Henry G. Esq. (State Mineralogist)— C-Aifornisi State Mining Bureau,

A. nual Keport. 8vo. 1884.
Johns Uo^jhins University— Vnwcrs^ty Circular, Nos. 37, 38. 4to. 1S85.

American Journal of Philology, No. 20. 8vo. 1884.
Kerslahe, Thomas, Esq. (the Author)— The Liberty of Independent Historical

Reseaich. 8vo. 1885.
Manchester Steam Users' Association — Boiler Explosions Act, 1882. Board of

Trade Reports, Nos. 46 to 86. fol. 1884.
Mechanical Engineers Institution — Proceedings, No. 1. 8vo. 1885,
Medical and Chirurgical Society, Royal — Proceedings, Vol. I. No. 7. 8vo. 1885.
Meteorological O^'ce;— Report of Meteorological Council, R. S. to 31 March, 1884.

8vo. 1885.
Miller, W. J. C. Esq. (the Registrar)— The Medical Register. 8vo. 1885.

The Dentist's Register. 8vo. 1885.
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Royal Soriity of London — Proceedings, No. 235. 8vo. 1884-5.
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Telegraph Engineers, Society o/— Journal, Vol. XIV. No. 55. 8vo. 1885.
Vereins zur Biforderung des Geicerhfleisses in IVeusseyi— Verhandlungen, 1885 :

Heft 2. 4to.
Vernon-IIarcourt, Leveson Francis, Esq. M.A. (the Author) — Harbours and Docks.
2 vols. 8vo. 1885.

1885.] Professor S. P. Laivjleij on Sunlhjht, dc. 265

WEEKLY EVENING MEETING,

Friday, April 17, 1885.

Sir William Bowman, Bart. LL.D. F.E.S. Honorary Secretary
and Vice-President, in the Chair.

Professor S. P. Langley.

Sunlight and the Earth's Atmosphere.

There is, we may remember, a passage in which Plato inquires what
would be the thoughts of a man who, having lived from infancy under
the roof of a cavern, where the light outside was inferred only by its
shadows, was brought for the first time into the full splendours of
the sun.

We may have enjoyed the metaphor without thinking that it has
any physical application to ourselves who appear to have no roof over
our heads, and to see the sun's face daily ; while the fact is that if
we do not see that we have a roof over our heads in our atmosphere,
and do not thiuk of it as one, it is because it seems so transparent
and colourless.

Now, I wish to ask your attention to-night to considerations in
some degree novel, which appear to me to show that it is not trans-
parent as it appears, and that this seeming colourlessness is a sort of
delusion of our senses, owing to which we have never in all our lives
seen the true colour of the sun, which is in reality blue rather than
white, as it looks, so that this air all about and above us is acting
like a coloured glass roof over our heads, or a sort of optical sieve,
holding back the excess of blue in the original sunlight, and letting
only the white sift down to us.

1 will first ask you, then, to consider that this seeming colourless-
ness of the air may be a delusion of our senses, due to habit, which
has never given us anything else to compare it with.

If that cave had been lit by sunshine coming through a reddish glass
in its roof, would the perpetual dweller in it ever have had an idea
but that the sun was red ? How is he to know that the glass is
"coloured" if he has never in his life anything to compare it with?
How can he have any idea but that this is the sum of all the sun's
radiations (corresponding to our idea of white or colourless light) ;
will not the habit of his life confirm him in the idea that the sun is
red ; and will he not think that there is no colour in the glass so
long as he cannot go outside to see ? Has this any suggestion for us,
who have none of us ever been outside our crystal roof to see ?

We must all acknowledge in the abstract, that habit is equally
strong in us whether we dwell in a cave or under the sky, that what

2G6 Professor S. P. LanjUij [April 17,

WG have thought from infancy will probably appear the sole possible
explanation, and that, if we want to break its chain, we should put
ourselves, at least in imagination, under conditions where it no longer
binds us.

The ' Challenger ' has dredged from the bottom of the ocean fishes
wliich live habitually at great depths, and \Yhose enormous eyes tell
of the correspondingly faint light which must liave descended to them
through the seemingly transparent water. It wdll not be as futile a
speculation as it may at fi)-st seem, to put ourselves in imagination in
the condition of creatures under the sea, and ask what the sun may
appear to be to them ; for if the fish who had never risen above the
ocean floor w^ere an intelligent being, might he not plausibly reason
that the dim greenish light of his heaven — which is all he has ever
known — was the full splendour of the sun, shining through a medium
wliich all his ex^Dcrience shows is transparent?

We ourselves are, in very fact, living at the floor of a great aerial
sea, whose billows roll hundreds of miles above our heads. Is it not
at any rate conceivable that we may have been led into a like fallacy
from judging only by what we see at the bottom ? May we not, that is,
have been led into the fallacy of assuming that the intervening
medium above us is colourless because the light which comes through
it is so ?

I freely admit that all men, educated or ignorant, appear to have
the evidence of their senses that the air is colourless, and that pure
sunlight is white, so that if I venture to ask you to listen to con-
siderations which have lately been brought forward to show that it is
the sun which is blue, and the air really acts like an orange veil or
like a sieve which picks out the blue and leaves the white, I do so in
the confidence that I may appeal to you on other grounds than those
I could submit to the primitive man who has his senses alone to trust
to ; for the educated intelligence possesses those senses equally, and
in addition the ability to interpret them by the light of reason,
and before this audience it is to that interpretation that I address
myself.

Permit me a material illustration. You see through this glass,
which may typify the intervening medium of air or water, a circle of
white light, which may represent the enfeebled disk of the sun when
so viewed. Is this intervening glass coloured or not? It seems
nearly colourless ; but have we any right to conclude that it is so
because it seems so r Are we not faking it for granted that the
original light which we see through it is white, and that the glass is
colourless, because the light seems unaltered, and is not an appeal to
be made here from sense to reason, which, in the educated observer,
recalls that white light is made of various colours, and that whether
the original light is really white and the glass transi^rent, or the
glass really coloured and so making the white, is to be decided only
by experiment, by taking away the possibly deceptive medium ? I
can take away this glass, wliich was not colourless, but of a deep

1885. J on Sunlight and the Earth's Atmosphere. 267

orange, and you see that the original light was not whito, but intensely
blue. If we couLl take the atmosphere away between us and the sun,
how can we say that the same result might not follow ? To make
the meaning of our illustration clearer, observe that this blueness is
not a pure spectral blue. It has in it red, yellow, blue, and all the
colours which make up white, but blue in superabun lance ; so that,
though the white is, so to say, latent there, the dominant effect is
blue. The glass coloured veil does not put anything m, but acts I
repeat like a sieve straining out the blue, and letting through to us
the white light which was there in the bluishness, and so may not our
air do so too ?

I think we already beghi to see that it is at any rate conceivable
tliat we may have been hitherto under a delusion about the true
colour of the sun, though of course this is not proving that wi; have
been so, and it will at any rate, I hope, be evident that here is a
question raised which ought to be settled, for the blueness of the sun,
if proven, evidently affects our present knowledge in many ways, and
will modify our present views in optics, in meteorology, and in
numerous other things. In oj^tics, because we should find that white
light is not the sum of the sun's radiations, but only of those dregs of
them which have filtered down to us ; in meteorology because it is
snggeste 1 that the temperature of the globe and the condition of man
on it, depend in part on a curious selective action of our air, which
picks out parts of the solar heat (for instance, that connected with its
blue light), and holds them back, letting other selected portions come
to us, and so altering the conditions on which this heat by which we
live, depends ; in otlier ways, innumerable, because, as we know, the
sun's heat and light are facts of such central imj^ortance, that they
affect almost every part of scientific knowledge.

It may be asked what suggested the idea that the sun may be blue
rather than any other colour.

My ow^n attention was first directed this way many years ago
when measuring the heat and light from different parts of the sun's
disk. It is known that the sun has an atmosj^here of its own which
tempers its heat, and, by cutting off certain radiations and not others,
produces the spectral lines we are all familiar with. These lines we
customarily study in connection with the absorbing vapours of sodium,
iron, and so forth, which produce them ; but my own attention was
^particularly given to the regions of absorption, or to the colour it
caused, and I found that the sun's body must be deeply bluish, and
that it would shed blue liglit except for this apparently colourless
solar at UK sphere, which really plays the part of a reddish veil, letting
a little of the blue appear on the centre of the sun's disk where it is
thinnest, and staining the edge red, so that to delicate tests the centre
of the sun is a pale aqua-marine, and its edge a garnet. The eflect I
found to be so important, that if this all but invisible solar atmosphere
were diminished by but a third part, the temperature of the British
islands would rise above that of the torrid zone, and this directed my

268 Professor S. P. Langley [April 17,

attention to the great practical importance of studying the action of
our own terrestrial atmosiDhere on the sun, and the antecedent pro-
bability that our own air was also and independently making the really
blue sun into an apparently white one. We actually know then,
beyond conjecture, by a comparison of the sun's atmosphere, where it
is thickest, and where it is thinnest, that an apparently colourless
atmosphere can have such an effect, and analogous observations which
I have carried on for many years, but do not now detail, show that the
atmosj^here of our own planet, this seemingly clear air in which we
exist like creatures at the bottom of the sea, does do so.

We look up through our own air as through something so limpid
in its purity that it aj^pears scarcely matter at all, and we are apt to
forget the enormous mass of what seems of such lightness, but which
really presses with nearly a ton to each square foot, so that the
weight of all the buildings in this great city, for instance, is less than
that of the air above them.

I hope to shortly describe the method of proof that it too has been
acting like an 023tical sieve, holding back the blue ; but it may naturally
be asked, " Can our senses have so entirely deceived us that they give
no hint of this truth, if it be one ? is the appeal wholly to recondite
scientific methods, and are there no indications, at least, which we
may gather for ourselves ? " • I think there are, even to our unaided
eyes, indications that the seemingly transparent air really acts as an
orange medium, and keeps the blue light back in the upper sky.

If I hold this piece of glass before my eyes, it seems colourless
and transparent, but it is jDroved not to be so by looking through it
edgewise, when the light, by traversing a greater extent, brings out
its true colour, which is yellow. Everyone knows this in every-day
experience. We shall not get the colour of the ocean by looking at
it in a wine-glass, but by gazing through a great depth of it ; and so
it is with the air. If we look directly up, we look through where it
is thinnest; but if we look horizontally through it towards the
horizon, through great thicknesses, as at sunrise or sunset, is it not
true that this air, where we see its real coloui* most plainly, makes
the sun look very plainly yellow or orange.

We not only see here, in humid English skies, the " orange sunset
waning slow," but most of us in these days of travel can perfectly
testify that the clearest heavens the earth affords, the rosy tint on the
snows of Mont Blanc, forerunning the dawn, or the warm glow of the
sun as he sets in Egyptian skies, show this most clearly — show that
the atmosphere holds back the blue rays by preference, and lets the
orange through.

If, next, we ask, " What has become of the blue that it has stopped ? "
does not that very blue of the midday sky relate the rest of the story
— that blue which Prof. Tyndall has told us is due to the presence of
innumerable fine particles in the air, which act selectively on the solar
waves, diffusing the blue light towards us ? I hope it will be under-
stood that Prof. Tyndall is in no way responsible for my own

1885.] on Sunlujht and the Earth's Atmosphere. 269

inferences ; but I think it is safe at least to say tliat the sky is not
self-luminous, and that, since it can only be shining blue at the
expense of the sun, all the light this sky sends us has been taken by
our atmosphere away from the direct solar beam, which would grow
both brighter and bluer if this were restored to it.

If all tliat has been said so far renders it jDossible that the sun may
be blue, you will still have a right to say that "possibilities" and
" maybes " are not evidence, and that no chain of mere hypotheses
will draw truth out of her well. We are all of one mind hero, and
I desire next to call your attention to what I think is evidence.

Remembering that the case of our supposed dweller in the cave
who could not get outside, or that of the inhabitants of the ocean-floor
who cannot rise to the surface, is really like our own, over whose
heads is a crystalline roof which no man from the beginning of time
has ever got outside of, an upper sea to whose surface we have never
risen ; we recognise that if we could rise to the surface, leaving the
medium whose effect is in dispute wholly beneath us, we should see
the sun as it is, and get proof of an incontrovertible kind ; and that,
if we cannot entirely do this, we shall get nearest to proof under our
real circumstances by going as high as we can in a balloon, or by
ascending a very high mountain. The balloon will not do, because
we have to use heavy apparatus requiring a solid foundation. The
proof to which I ask your kind attention, then, is that derived from
the actual ascent of a remarkable mountain by an expedition under-
taken for that purpose, which carried a whole j)hysical laboratory up
to a point where nearly cme-half the whole atmosphere lay below us.
I wish to describe the difference we found in the sun's energy at the
bottom of the mountain and at the top, and then the means we took
to allow for the eflfect of that part of the earth's atmosphere still over
our heads even here, so that we may be said to have virtually got
outside it altogether.

Before we begin our ascent, let me explain more clearly what we
are going to seek. We need not expect to find that the original sun-
light is a pure monochromatic blue by any means, but that though its
rays contain red, orange, blue, and all the other spectral colours, the
blue, the violet and the allied tints were originally there in disjDro-
portionate amounts, so that, though all which make white were present
from the first, the refrangible end of the spectrum had such an excess
of colour that the dominant effect was that of a bluish sun. In the
same way, when I say briefly that our atmosphere has absorbed this
excess of blue and let the white reach us, I mean, more strictly
speaking, that this atmosphere has absorbed all the colours, but,
selectively, taking out more orange than red, more green than orange,
more blue than green ; so that its action is wholly a taking out — an
action like that which you now see going on with this sieve, sifting a
mixture of blue and white beads, and holding back the blue while
letting the white fall down.

This experiment only rudely typifies the action of the atmosphere,

270 Professor S. P. Lamjley [April 17,

which is discriminating and selective in an amazing degree, and as
there are really an infinite number of shades of colour in the spectrum,
it would take for ever to describe the action in detail. It is merely
for brevity, then, that we now unite the more refrangible colours
under the general word " blue," and the others under the corresponding
terms " orange " or " red."

All that I have the honour to lay before you, is less an announce-
ment of absolute novelty than an appeal to your already acquired
knowledge and to your reason as superior to the delusions of sense.
I have, then, no novel experiment to offer, but to ask you to look at
some familiar ones in a new light.

AVe are most of us familiar, for instance, with that devised by
Sir Isaac Newton to show that white light is compounded of blue,
red, and other colours, where, by turning a coloured wheel rapidly, all
blend into a greyish white. Here you see the " seven colours " on
the screen ; but, though all are here, I have intentionally arranged
them, so that there is too much blue, and the combined result is a very
bluish white which may roughly stand for that of the original sun-ray.
I now alter the proportion of the colours so as to virtually take out
the excess of blue, and the result is colourless or white light. White,
then, is not necessarily made by combining the " seven colours," or
any number of them, unless they are there in just proportion (which
is in effect what Newton himself says) ; and white, then, may be made
out of such a bluish light as we have described, not by putting any-
thing to it, but by taking away the excess which is there already.

Here, again, are two sectors — one blue, one orange-yellow with
the blue in excess, making a bluish disk where they are revolved. I
take out the excess of blue, and now what remains is white.

Here is the spectrum itself on the screen, but a spectrum which
has been artificially modified so that the blue end is relatively too
strong. I recombine the colours (by Prof. Eood's ingenious device of
an elastic mirror), and they do not make a pure white, but (me tinted
with blue. I take out the original excess of blue, and what remains
combines into a pure white. Please bear in mind that when we " put
in " blue here, we have to do so by straining out other light through
some obscuring medium, which makes the spectrum darker ; but that,
in the case of the actual sunlight, introducing more blue, introduces
more light, and makes the spectrum brighter.

The spectrum on the screen ought to be made still brighter in the
blue tljan it is — far, far brighter— and then it might represent to us
the original solar spectrum before it has suffered any absorj-tion either
in the sun's atmosphere or our own. The Frauenhofer lines do not
appear in it, for these, when found in the solar spectrum, show that
certain individual rays have been stopped, or selected for absorjition
by the intervening atmospheres ; and though even the few yards of
atmosphere between the lamj) and the screen absorb, it is not enough
to show.

Our spectrum, as it appears before absorption, might be compared

1885.] on Sunlight and the Earth's Atmosphere, 271

to an army divided into numerous brigades, eacli wearing a distinct
uniform, one red, one green, one blue, so that all the colours are
represented each by its own body. If, to re2)resent the light absorbed
as it progresses, we suj^posed that the army advances under a fire
which thins its numbers, we should have to consider that (to give the
case of nature) this destructive fire was directed chiefly against those
divisions which were dressed in blue, or allied colours, so that the
army was thinned out unequally, many men in blue being killed otf
for one in red, and that by the time it has advanced a certain distance
under fire the proportion of the men in each brigade has been altered,
the red being comparatively unhurt. Almost all absorption is thus
selective in its action, and often in an astonishing degree, killing off,
so to speak, certain rays in jDreference to others, as though by an
intelligent choice, and destroying most, not only of certain divisions
(to continue our illustration), but even picking out certain files in
each company. Every ray, then, has its own individuality, and on
this I cannot too strongly insist ; for just as two men retain their
personalities under the same red uniform, and one may fall and the
other survive, though they touch shoulders in the ranks, so in the
spectrum certain parts will be blotted out by absorption, while others
next to them may escape.

To illustrate this selective absorption, I put a piece of didymium
glass in the path of the ray. It will, of course, absorb some of the
light, but instead of dimming the whole spectrum, we might almost
say it has arbitrarily chosen to select one narrow part for action, in
this particular case choosing a narrow file near the orange, and letting
all the rest go unharmed. In this arbitrary way our atmosphere
operates, but in a far more complex manner, taking out a narrow file
here and another there, in hundreds of j^laces, all through the spectrum,
but on the whole much the most in the blue, the Frauenhofer lines
being merely part of the evidence of this wonderful quasi-intelligent
action which bears the name of selective absorption.

Before we leave this spectrum, let us recall one most important
matter. We know that here beyond the red is solar energy in the
form of heat which we cannot see, but not on that account any less
important. More than half the whole power of the sun is here
invisible, and if we are to study completely the action of our atmo-
sphere, we shall have to pay great attention to this part, and find out
some way of determining the loss in it, which will be difficult, for the
ultra-red end is not only invisible, but compressed, the red end being
shut up like the closed pages of a book, as you may notice by com-
paring the narrowness of the red with the width of the blue.

Now refraction by a prism is not the only way of forming a
spectrum. Nature furnishes us colour not only from the rainbow,
but from non-transparent substances like mother-of-pearl, where the
iridescent hues are due to microscopically fine lines. Art has lately
surpassed nature in these wonderful "gratings," consisting of pieces
of polished metal, in which we see at first nothing to account for the

272 Professor S. P. Lanr/Iey | April 17,

spleudid play of colour apparently pouring out from them like light
from an opal, but which, on examination with a powerful microscope,
show lines so narrow that there are from 50 to 100 in the thickness
of a fine human hair, and all spaced with wonderful precision.

This grating is equal in defining power to many such prisms as
we have just been looking at, but its light does not show well upon
the screen. You will see, liowever, that its spectrum differs from
that of the prism, in that in this case the red end is expanded, as
compared with the violet, and the invisible ultra-red is expanded still
more, so that this will be the best means for us to use in exploring
that " dark continent " of invisible heat found not only in the spec-
trum of the sun, but of the electric light, and of all incandescent
bodies, and of whose existence we already know from Herschel and
Tyndall.

Now we cannot reproduce the actual solar spectrum on the screen
without the sun itself, but here are photographs of it, which show
parts of the losses the different colours have suffered on their way to
us. We have before us the well-known Frauenhofer lines, due, you
remember, not only to absorption in the sun's atmosj)here, but also to
absorption in our own. We have been used to think of tliem in
connection with their cause, one being due to the absorption of iron-
vapour in the sun, another to that of water- vapour in our own air,
and so forth ; but now I ask you to think of them only in connection
with the fact that each is due to the absorption of some part of the
original ligJit, and that collectively they tell much of the story of
wliat has happened to that light on its way down to us. Observe,
for instance, how much thicker they lie in the blue end than in the
red — another evidence of the great proportionate loss in the blue.

If WG could restore all the lost light in these lines, we should get
back partly to the original condition of things at the very fount, and,
so far as our own air is concerned, that is what we are to ascend the
mountain for — to see, by going up through nearly half of the atmo-
sphere, what the rate of loss is in each ray by actual trial ; then,
knowing this rate, to be able to allow for the loss in the other part
still above the mountain-top, and, finally, by recombining these rays
to get the loss as a whole. Remember, however, always, that the
most important part of the solar energy is in the dark spectrum which
we do not see, but which, if we could see, we should probably find to
have numerous absorj)ti(m-spaces in it corresponding to the Frauen-
hofer lines, but where heat has been stopped out rather than light.
To make our research thorough, then, we ought not to trust to the
eye only, or even chiefly, but have some way of investigating the
whole spectrum ; the invisible in which the sun's power chiefly lies,
as well as the visible, and both with an instrument that would dis-
criminate the energy in these very narrow spaces, like an eye to sec
in the dark ; and if science possesses no such instrument, then it may
be necessary to invent one.

The linear thermopile is nearest to it of any, and we all hero

1885.] on Sunlight and the Earth's Atmosphere. 273

know what good work it has done, but even that is not sensitive
enough to measure in the grating spectrum, in some parts of which
the heat is four hundred times weaker than in that of a prism, and we
want to observe this invisible heat in very narrow spaces. Something
like this has been provided since by Captain Abney's most valuable
researches, but these did not at the time go low enough for my
purpose, and I spent nearly a year before ascending the mountain in
inventing and perfecting the new instrument for measuring these,
which I have called the "bolometer" or "ray-measurer." The
principle on which it is founded is the same as that employed by my
late friend. Sir Wm. Siemens, for measuring temperatures at the bottom
of the sea, which is that a smaller electric current flows through a
warm wire than through a cold one.

One great difficulty was to make the conducting wire very thin,
and yet continuous, and for this purpose almost endless experiments
were made, among other substances pure gold having been obtained
by chemical means in a plate so thin that it transmitted a sea-green
light through the solid substance of the metal. This proving un-
suitable, I learned that iron had been rolled of extraordinary thinness
in a contest of skill between some English and American ironmasters,
and, procuring some, I found that 15,000 of the iron plates they had
rolled, laid one on the other, would make but one English inch.
Here is some of it, rolled between the same rolls which turn out plates
for an iron-clad, but so thin that, as I let it drop, the iron plate
flutters down like a dead leaf. Out of this the first bolometers were
made, and I may mention that the cost of these earlier experiments
was met from a legacy by the founder of the Royal Institution, Count
Eumford. The iron is now replaced by platinum, in wires or rasher
tapes from 1-2000 to 1-20, 000th of an inch thick, one of which is
within this button, where it is all but invisible, being far finer than a
human hair. I will project it on the screen, placing a common small
pin beside it as a standard of comparison. This button is placed in
this ebonite case, and the thread is moved by this micrometer screw,
by which it can ^e set like the spider line of a reticule ; but by means
of this cable, connecting it to the galvanometer, this thread acts as
though sensitive, like a nerve laid bare to every indication of heat and
cold. It is then a sort of sentient thing : what the eye sees as light
it feels as heat, and what the eye sees as a narrow band of darkness
(the Frauenhofer line) this feels as a narrow belt of cold, so that when
moved parallel to itself and the Frauenhofer lines do wn the spectrum
it registers their presence.

It is true we can see these in the visible spectrum, but you
remember we propose to explore the invisible also, and since to this
the dark is the same as the light, it will feel absorption lines in the
infra-red which might remain otherwise unknown.

I have spent a long time in these preliminary researches ; in
indirect methods for determining the absorption of our atmosphere,
and in experiments and calculations which I do not detail, but it is so

Vol. XI. (No. 79.) t

274 Professor S. P. Langley [April 17,

often supposed that scientific investigation is a sort of happy guessing,
and so little is realised of the labour of preparation and proof, that I
have been somewhat particular in describing the essential parts of the
apparatus finally employed, and now we must pass to the scene of
their use.

We have been compared to creatures living at the bottom of the
sea, who frame their deceptive traditional notions of what the sun is
like from the feeble changed rays which sift down to them. Though
such creatures could not rise to the surface, they might swim up to-
wards it ; and if these rays grew hotter, brighter, and bluer as they
ascended, it would be almost within the capacity of a fish's mind to
guess that they are still brighter and bluer at the top.

Since we children of the earth, while dwelling on it, are always
at the bottom of a sea, though of another sort, the most direct method
of proof I spoke of, is merely to group as far as we can and observe
what happens, though as we are men, and not fishes, something more
may fairly be expected of our intelligence than of theirs.

We will not only guess, but measure and reason, and in particular
we will first, while still at the bottom of the mountain, draw the
light and heat out into a spectrum, and analyse every part of it by some
method that will enable us to explore the invisible as well as record
the visible. Then we will ascend many miles into the air, meeting
the rays on the way down, before the sifting process has done its
whole work, and there analyse the light all over again, so as to be
able to learn the different proportions in which the different rays
have been absorbed, and by studying the action on each separate ray,
to prove the state of things which must have existed before this sifting
— this selective absorption — began.

It may seem at first that we cannot ascend far enough to do much
good, since the surface of our aerial ocean is hundreds of miles over-
head ; but we must remember that the air grows thinner as we ascend,
the lower atmosphere being so much denser, that about one-half the
whole substance or mass of it lies within the first four miles, which is
a less height than the tops of some mountains. Every high mountain,
however, will not do, for ours must not only be very high but very
steep, so that the station we choose at the bottom may be almost
under the station we are afterwards to occupy at the top.

Besides, we are not going to climb a lofty, lonely summit like
tourists to spend an hour, but to spend weeks ; so that we must have
fire and shelter, and above all we must have dry air to get clear
skies. First I thought of the Peak of Teneriffe, but afterwards some
point in the territories of the United States seemed preferable, par-
ticularly as the Government offered to give the Expedition, through
the Signal Service, and under the direction of its head, General
Hazen, material help in transportation and a military escort, if needed,
anywhere in its own dominions. No summit in the eastern part of
the United States rises much over 7000 feet ; and though the great
Kocky Mountains reach double this, their tops- are the home of fog

1885.] on Sunlight and the Earth's Atmosphere. 275

and mist, so that the desired conditions, if met at all, could only be
found on the other side of the continent in Southern California, where
the summits of the Sierra Nevadas rise precipitously out of the dry
air of the great wastes in lonely peaks, which look eastward down
from a height of nearly 15,000 feet upon the desert lands.

This remote region was, at the time I speak of, almost unexplored,
and its highest peak, Mount Whitney, had been but once or twice
asceaded, but was represented to be all we desired could we onco
climb it. As there was great doubt whether our apparatus, weighing
several thousand pounds, could possibly be taken to the top, and we had
to travel 3000 miles even to get where the chief difficulties would
begin, and make a desert journey of 150 miles after leaving the cars,
it may be asked why we committed ourselves to such an immense
journey to face such unknown risks of failure. The answer must be
that mountains of easy ascent and 15,000 feet high are not to be found
at our doors, and that these risks were involved in the nature of our
novel experiment, so that we started out from no love of mere adven-
ture, but from necessity, much into the unknown. The liberality of
a citizen of Pittsburgh, to whose encouragement the enterprise was
due, had furnished the costly and delicate apparatus for the exj)edition,
and that of the trans-continental railroads, enabled us to take this
precious freight along in a private car, which carried a kitchen, a
steward, a cook, and an ample larder besides.

In this we crossed the entire continent from ocean to ocean, stopped
at San Francisco for the military escort, went 300 miles south so as
to get below the mountains, and then turned eastward again on to
the desert, with the Sierras to the north of us, after a journey which
would have been unalloyed pleasure except for the anticipation of
what was coming as soon as we left our car. I do not indeed know
that one feels the triumphs of civilisation over the opposing forces of
Nature anywhere more than by the sharp contrasts which the marvel-
lous luxury of recent railroad accommodation gives to the life of the
desert. When one is in the centre of one of the great barren regions
of the globe, and, after looking out from the windows of the flying
train on its scorched wastes for lonely leagues of habitless desolation,
turns to his well-furnished dinner-table, and the fruit and ices of his
dessert, he need not envy the heroes of Oriental story, who were
carried across dreadful solitudes in a single night on the backs of
flying genii. Ours brought us over 3000 miles to the Mojave Desert.
It was growing hotter and hotter when the train stopped in the midst
of vast sand wastes a little after midnight. Eoused from our sleep,
we stepped on to the brown sand, and saw our luxurious car roll away
in the distance, experiencing a transition from the conditions of civi-
lisation to those almost of barbarism, as sharp as could well be imagined.
We commenced our slow toil northward with a thermometer at 110^
in the shade, if any shade there be in the shadeless desert, which
seemed to be chiefly inhabited by rattlesnakes of an ashen-grey colour,
and a peculiarly venomous bite. There is no water save at the rarest

T 2

276 Professor S. P. Langley [Ai^ril 17,

intervals, and the soil at a distance seems as though strewed with
sheets of salt, which aids the delusive show of the mirage. These
are, in fact, the ancient beds of dried-up salt lakes or dead seas, some
of them being below the level of the ocean ; and such a one on our
right, though only about twenty miles wide, has earned the name of
" Death Valley," from the number of human beings who have perished
in it. Formerly an emigrant train, when emigrants crossed the con-
tinent in caravans, had passed through the great Arizona deserts in
safety until, after their half-year's journey, their eyes were gladdened
by the snowy peaks of the Sierras looking delusively near. The goal
of their long toil seemed before them ; only this one more valley lay
between, and into this they descended, thinking to cross it in a day —
but they never crossed it. Afterwards the long line of wagons was
found with the skeletons of the animals in the harness, and by them
those of men, women, and little children dead of thirst, and some relics
of the tragedy remained at the time of our journey. I cite this as an
indirect evidence of the phenomenal dryness of the region— a dryness
which, so far, served our object, which was, in part, to get rid as much
as possible of that water vapour which is so well known to be a
powerful absorber of the solar heat.

Everything has an end, and so had that journey, which finally
brought us to the goal of our long travel, at the foot of the highest
peak of the Sierras, Mount Whitney, which rose above us in
tremendous precipices, that looked hopelessly insurmountable and
wonderfully near. The whole savage mountain region in its slow
rises from the west, and its descent to the desert plains in the east, is
more like the chain called the Apennines, in the moon, than anything
I know on the earth. The summits are jagged peaks like Alpine
" needles," looking in the thin air so delusively near, that, coming on
such a scene unprepared, one would almost say they were large grey
stones a few fields ofi^, with an occasional little white patch on the
top, that might be a handkerchief or a sheet of paper dropped
there. But the telescoj^e show^ed that the seeming stones were of
the height of many Snowdons piled on one another, and the white
patches occasional snow-fields, looking how invitingly cool, from the
torrid heat of the desert, where we were encamped by a little rivulet
that ran down from some unseen ice-lake in that upj)er air. Here
we pitched our tents and fell to work (for you remember we must
have two stations, a low and a high one, to compare the results), and
here we laboured three weeks in almost intolerable heat, the instru-
ments having to be constantly swept clear of the red desert dust
which the hot wind brought. Close by these tents a thermometer
covered by a single sheet of glass, and surrounded by wool, rose to
237° in the sun, and sometimes in the tent, which was darkened for
the study of separate rays, the heat was absolutely beyond human
endurance. Finally, our aj^i^aratus was taken apart and packed in
small pieces on the backs of mules, who were to carry it by a ten
days' journey through the mountains to the other side of the rocky

1885.] on Sunlight and the Earth's Atmosphere. 277

wall which, though only ten or twelve miles distant, arose miles
above our heads ; and, leaving these mule trains to go with the escort
by this longer route, I started with a guide by a nearer way to those
white gleams in the upper skies, that had daily tantalised us below
in the desert with suggestions of delicious, unattainable cold. That
desei't sun had tanned our faces to a leather-like brown, and the
change to the cooler air as we ascended was at first delightful. At
an altitude of 5000 feet we came to a wretched band of nearly naked
savages, crouched around their camp fire, and at 6000 found the first
scattered trees ; and here the feeble suggestion of a path stopped, and
we descended a ravine to the bed of a mountain stream, up which we
forced our way, cutting through the fallen trees with an axe, fighting
for every foot of advance, and finally passing what seemed impassable.
It was interesting to speculate as to the fate of our siderostat mirrors
and other precious freight, now somewhere on a similar road, but
quite useless. We were committed now, and had to make the best
of it — and, besides, I had begun to have my attention directed to a
more personal subject. This was, that the colder it grew the more
the sun burnt the skin — quite literally burnt, I may say, so that by
the end of the third day my face and hands, case-hardened, as I
thought, in the desert, began to look as if they had been seared with
red-hot irons, here in the cold where the thermometer had fallen to
freezing at night; and still as we ascended the paradoxical effect
increased ; the colder it grew about us, the hotter the sun blazed
above.

We have all heard probably of this curious effect of burning in
the midst of cold, and some of us may have experienced it in the
Alps, where it may be aided by reflection from the snow, which we
did not have about us at any time except in scattered patches, but
here by the end of the fourth day my face was scarcely recognisable,
and it almost seemed as though sunbeams up here were different
things, and contained something which the air filters out before they
reach us in our customary abodes. Eadiation here is increased by
the absence of water vapour too, and on the whole this intimate
personal experience fell in almost too well with our anticipations
that the air is an even more elaborate trap to catch the sunbeams
than had been surmised, and that this effect of selective absorption
and radiation was intimately connected with that change of the
primal energies and primal colour of the sun which we had climbed
towards it to study.

On the fourth day, after break-neck ascents and descents, we
finally ascended by a ravine, down which leaped a cataract, till, at
nightfall, we reached our upper camp, which was pitched by a little
lake, one of the sources of the waterfall, at a height of about
12,000 feet, but where we seemed in the bottom of a valley, nearly
surrounded as we were by an amphitheatre of rocky walls which
rose perpendicularly to the height of Gibraltar from the sea, and cut
off all view of the desert below or even of the peak above us.

278 Professor S. P. Langley [April 17,

The air was wonclerfuUy clear, so that the sun set in a yellow
rather than an orange sky, which was reflected in the little ice-
rimmed lakes and from occasional snow-fields on the distant waste of
lonely mountain summits on the west.

The mule train sent off before by another route, had not arrived
when we got to the mountain camp, and w^e realised that we were far
from the aj^pliances of civilisation by our inability to learn about
our chief apparatus, for here, without post or telegraph, we were as
completely cut off from all knowledge of what might be going on
with it in the next mountain ravine as a ship at sea is of the fate of
a vessel that sailed before from the same port. During the enforced
idleness we ascended the peak nearly 3000 feet above us, with our
lighter aj^paratus, leaving the question of the ultimate use of the
heavy ones to be settled later. There seemed little prospect of
carrying it uj), as we climbed where the granite walls had been split
by the earthquakes, letting a stream of great rocks, like a stone river,
flow down through the interstices by which we ascended, and, in
fact, the heavier apparatus was not carried above the mountain camp.

The view from the very summit was over numberless peaks on
the west to an horizon fifty miles away, of unknown mountain-tops,
for, with the exception of the vast ridge of Mount Tyndall, and
one or two less conspicuous ones, these summits are not known to
fame, and, wonderful as the view may be, all the charm of association
with human interest which we find in the mountain landscape of older
lands is here lacking.

It was impossible not to be impressed with the savage solitude of

this desert of the upper air, and our remoteness from man and his

works, but I turned to the study of the special things connected with

my mission. Down far below the air seemed filled with reddish dust

that looked like an ocean. This dust is really present everywhere (I

have found it in the clear air of Etna), and though we do not realise

its presence in looking up through it, to one who looks down on it,

the dwellers on the earth seem indeed like creatures at the bottom of

a troubled ocean. We had certainly risen towards the surface, for

about us the air was of exquisite purity, and above us the sky was of

such a deep violet blue, as I have never seen in Egypt or Sicily, and

yet even this was not absolutely pure, for separately invisible, the

existence of fine particles could yet be inferred from their action on

the liglit near the sun's edge, so that even here we had not got

absolutely above that dust shell which seems to encircle our whole

planet. But we certainly felt ourselves not only in an upper, but a

diflcrent region. We were on the ridge of the continent, and the

winds which tore by had little in common with the air below, and

were bearing past us (according to the geologists) dust which had

once formed part of the soil of China, and been carried across the

Pacific Ocean ; for here we were lifted into the great encircling

currents of the globe, and, "near to the sun in lonely lands," were

ill the right conditions to study the differences between his rays at

'iwr^TVYiiifr- III " "'i "iiijirtiiiiMii^^ ^'° ^'° ^*° ''' ''' ^'

H F 0 B A

DiSTIUBUTION OF Soi.AR EXEIIGY AT

E;ili:i.:illBll:!iil;iffi,i,iillliiii!iliii|il!illllllM

Al.EVEL AND AT VARIOUS ALTlTtlDES.

1885.] on Sunlight and the Earth's Atmosphere. 279

the surface and at the bottom of that turbid sea where we had left
the rest of mankind. We descended the peak and hailed with joy
the first arrival of our mule trains with the requisite apparatus at the
mountain camp, and found that it had suffered less than might be
expected, considering the pathless character of the wilderness. We
went to work to build piers and mount telescopes and siderostats, in
the scene shown by the next illustration on the screen, taken from a
sketch of my own, where these rocks in the immediate foreground
rise to thrice the height of St. Paul's. We suffered from cold (the
ice forming 3 inches deep in the tents at night) and from mountain
sickness, but we were too busy to pay much attention to bodily
comfort, and worked with desperate energy to utilise the remaining
autumn days, which were all too short.

Here, as below, the sunlight entered a darkened tent, and was
spread into a spectrum, which was explored throughout by the bolo-
meter, measuring, on the same separate rays which we had studied
below in the desert, all of which were different uj) here, all having
grown stronger, but in very different proportions. On the screen is
the spectrum as seen in the desert, drawn on a conventional scale,
neither prismatic nor normal, but such that the intensity of the energy
shall be the same in each part, as it is represented here by these equal
perpendiculars in every colour. Fix your attention on these three
as types, and you will see better what we found on the mountain, and
what we inferred as to the state of things still higher up, at the
surface of the aereal sea.

You will obtain, perhaps, a clearer idea, however, from the follow-
ing statement, where I use, not the exact figures used in calculation,
but round numbers, to illustrate the process employed. I may premise
that the visible spectrum extends from H (in the extreme blue) to A
(in the deepest red), or from near 40 (the ray of 40-100, OOOths of a
millimetre in wave-length) to near 80. All below 80, to the right, is
the invisible infra-red spectrum.

Now, the shaded curve above the spectrum represents the amount
of energy in the sun's rays at the foot of the mountain, and was
obtained in this way : — Fix your attention for a moment on any single
part of the spectrum, for instance, that whose wave-length is 60. If
the heat in this ray, as represented by the bolometer at the foot of
the mountain, was (let us suppose j 2°, on any arbitrary scale we draw
a vertical line, 2 inches, or 2 feet high over that part of the spectrum.
If the heat at another point, such as 40, were but a 4-°, a line would
be drawn there a quarter of an inch high, and so on, till these vertical
lines mark out the shaded parts of the drawing, the gaps and de-
pressions in whose outline correspond to the " cold bands " already
spoken of. Again, if on top of the mountain we measure all these
over once more, we shall find all are hotter, so that we must up there
make all our lines higher, but in very different proportions. At 60,
for instance, the heat (and light) may have grown from 2° to 3^, or
increased one-half, while above 40 the heat (and light) may have

280 Professor S. P. Langley [April 17,

grown from i° to 1°, or increased five times. These mountain
measurements give another spectrum, the energies in each part of
which are defined by the middle dotted line, which we see indicates
very much greater energy whether heat or light in the blue end than
below. Next, the light or heat which would be observed at the surface
of the atmosphere is found in this way. If the mountain top rises
through one-half the absorbing mass of this terrestrial atmosphere (it
does not quite do so, in fact), and by getting rid of that lower half,
the ray 60 has grown in brightness from two to three, or half as much
again ; in going up to the top it would gain half as much more, or
become 4J, while the ray near 40, which has already increased to five
times what it was, would increase five times more, or to 25. Each
separate ray increasing thus nearly in some geocentric progression
(though the heat, as a whole, does not), you see how we are able, by
repeating this process at every point, to build up our outer or highest
curve, which represents the light and heat at the surface of the
atmosphere. These have grown out of all proportion at the blue end,
as you see by the outer dotted curve, and now we have attained, by
actual measurement, that evidence which we sought, and by thus re-
producing the spectrum outside the atmosj^here, and then recombining
the colours by like methods to those you have seen on the screen, we
finally get the true colour of the sun, which tends, broadly speaking,
to blue.

It is so seldom that the physical investigator meets any novel fact
quite unawares, or finds anything except that in the field where he is
seeking, that he must count it an unusual experience to come un-
expectedly on even the smallest discovery. This experience I had on
one of the last days of work on the spectrum on the mountain. I was
engaged in exploring that great invisible heat region, still but so
partially known, or, rather, I was mapping in that great " dark
continent " of the spectrum, and by the aid of the exquisite sky and
the new instrument (the bolometer) found I could carry the survey
further than any had been before. I substituted the prism for the
grating, and measured on in that unknown region till I had passed
the Ultima Thule of previous travellers, and finally came to what
seemed the very end of the invisible heat spectrum beyond what had
previously been known. This was in itself a return for much trouble,
and I was about rising from my task when it occurred to me to advance
the bolometer still farther, and I shall not forget the surprise and
emotion with which I found new and yet unrecognised regions below
— a new invisible spectrum beyond the farthest limits of the old one.

I will anticipate here by saying that after we got down to lower
earth again the explorations and mapping of this new region was
continued. The amount of solar energy included in this new extension
of the invisible region is much less than that of the visible spectrum,
while its length upon the wave-length scale is equal to all that pre-
viously known, visible and invisible, as you will see better by this
view, having the same thing on the normal as well as the prismatic

1885.] on Sunlight and the Earth's Atmosphere. 281

scale. If it be asked which of these is correct, the answer is " both
of them." Both rightly interpreted mean just the same thing, but in
the lower one we can more conveniently comi^are the ground of the
researches of others with these. These great gaps I was at first iu
doubt about, but more recent researches at Alleghany make it probable
that they are caused by absorption in our own atmosphere, and not in
that of the sun.

We would gladly have stayed longer, in spite of physical discom-
fort, but the formidable descent and the ensuing desert journey were
before us, and certainly the reign of perpetual winter around us grew
as hard to bear as the heats of the desert summer had been. On
September 10 we sent our instruments and the escort back by the
former route, and, ourselves unencumbered, started on the adventurous
descent of the eastern precipices by a downward climb, which, if
successful, would carry us to the plains in a single day. I at least
shall never forget that day, nor the scenery of more than Alpine
grandeur which we passed in our descent, after first climbing by
frozen lakes in the northern shadow of the great peak, till we crossed
the eastern ridges, through a door so narrow that only one could pass
it at a time, by clinging with hands and feet as he swung round the
shoulder of the rocks — to find that he had passed in a single minute
from the view of winter to summer, the prospect of the snowy peaks
behind shut out, and instantly exchanged for that below of the glow-
ing valley and the little oasis where the tents of the lower camp were
still pitched, the tents themselves invisible, but the oasis looking like
a green scarf dropped on the broad floor of the desert. We climbed
still downward by scenery unique in my recollection. This view of
the ravine on the screen is little more than a memorandum made by
one of the party in a few minutes' halt part-way down, as we followed
the ice-stream between the tremendous walls of the defile which rose
2000 feet, and between which we still descended, till, toward night,
the ice-brook had grown into a mountain torrent, and, looking up the
long vista of our day's descent, we saw it terminated by the Peak of
Whitney, once more lonely in the fading light of the upper sky.

This site, in some respects unequalled for a physical observatory,
is likely, I am glad to say, to be utilised, the President of the United
States having, on the proper representation of its value to science,
ordered the reservation for such j)urposes of an area of 100 square
miles about and inclusive of Mount Whitney.

There is little more to add about the journey back to civilisation,
where we began to gather the results of our observation, and to reduce
them — to smelt, so to speak, the metal from the ore we had brought
home — a slow but necessary process, which has occupied a large part
of two years.

The results stated in the broadest way mean that the sun is blue
— but meaji a great deal more than that ; this blueness in itself being
perhaps a curious fact only, but in what it implies, of practical
moment.

282 Professor S. P. Langley on Sunlight, &c. [April 17,

We deduce in connection with it a new value of the solar heat, so
far altering the old estimates that we now find it capable of melting a
shell of ice sixty yards thick annually over the whole earth, or, what
may seem more intelligible on its practical bearings, of exerting over
one horse-power for each square yard of the normally exposed surface.
We have studied the distribution of this heat in a spectrum whose
limits on the normal scale our explorations have carried to an extent
of rather more than twice what was previously known, and we have
found that the total loss by absorption from atmosphere is nearly
double what Las been heretofore supposed.

We have found it probable that the human race owes its existence
and preservation even more to the heat-storing action of the atmosphere
than has been believed.

The direct determination of the effect of water vapour in this did
not come within our scope ; but that the importance of the blanketing
action of our atmospheric constituents has been in no way overstated,
may be inferred when I add that we have found by our experiments
that if the planet were allowed to radiate freely into space without
any protecting veil, its sunlit surface would probably fall, even in the
tropics, below the temperature of freezing mercury.

I will not go on enumerating the results of these investigations,
but they all flow from the fact, which they in turn confirm, that this
apparently limpid sea above our head, and about us, is carrying on a
wonderfully intricate work on the sunbeam, and on the heat returned
from the soil, picking out selected parts in hundreds of places, sorting
out incessantly at a task which would keej) the sorting demons of
Maxwell busy, and as one result, changing the sunbeam on its way
down to us in the way we have seen.

I have alluded to the practical utilities of these researches, but
practical or not, I hope we may feel that such facts as we have been
considering about sunlight and the earth's atmosphere may be stones
useful in the future edifice of science, and that if not in our own
hands then in those of others, when our day is over, they may find
the best justification for the trouble of their search, in the fact that
they prove of some use to man.

May I add an expression of my personal gratification in the oppor-
tunity with which you have honoured me of bringing these researches
before the Eoyal Institution, and of my thanks for the kindness with
which you have associated yourselves for an hour, in retrospect at
least, with that climb toward the stars which we have made together,
to find, from light in its fulness, what unsuspected agencies are at
work to produce for us the light of common day.

[S. p. L.]

1885.] Annual Meeting. 283

WEEKLY EVENING MEETING,

Friday, April 24, 1885.

Sib William Bowman, Bart. LL.D. F.R.S. Honorary Secretary and
Vice-President, in the Chair.

William Carruthers, Esq. F.E.S.

British Fossil Cijcads and their relation to Living Forms.

(Abstract deferred.)

ANNUAL MEETING
Friday, May 1, 1885.

The Duke of Northumberland, D.C.L. LL.D. President,
in the Chair.

The Annual Report of the Committee of Visitors for the year
1884, testifying to the continued prosperity and efficient management
of the Institution, was read and adopted. The Real and Funded
Property now amounts to above 85,400Z., entirely derived from the
Contributions and Donations of the Members.

Forty-four new Members paid their Admission Fees in 1884.

Sixty-three Lectures and Twenty Evening Discourses were
delivered in 1884.

The Books and Pamphlets presented in 1884 amounted to about
276 volumes, making, with 506 volumes (including Periodicals bound)
purchased by the Managers, a total of 782 volumes added to the
Library in the year.

Thanks were voted to the President, Treasurer, and the Honorary
Secretary, to the Committees of Managers and Visitors, and to the
Professors, for their valuable services to the Institution during the
past year.

284

Annual Meeting,

[May 1,

The following Gentlemen were unanimously elected as Officers for
the ensuing year :

President — The Duke of Northumberland, D.C.L, LL.D.
Treasurer — George Busk, Esq. F.R.S.
Secretary— Sir Frederick J. Bramwell, F.R.S.

Managers. Visitors.

Sir Frederick Abel, C.B. D.C.L. F.R.S.

George Berkley, Esq. M.I.C.E.

Sir William Bowman, Bart. LL.D. F.R.S.

Joseph Brown, Esq. Q.C.

William Crookes, Esq. F.R.S.

Warren de la Rue, Esq. M.A. D.C.L. F.R.S.

Captain Douglas Galton, C.B. D.C.L. F.R.S.

The Hon. Sir Wm. Robt. Grove, M.A. D.C.L.

LL.D. F.R.S.
Sir J. D. Hooker, K.C.S.L C.B. M.D. D.C.L.

LL.D. F.R.S.
William Huggins, Esq. D.C.L. LL.D. F.R.S.
Hugo W. Miiller, Esq. Ph.D. F.R.S.
The Right Hon. Earl Percy, M.P.
Henry Pollock, Esq.
John Rae, M.D. LL.D. F.R.S.
The Right Hon. Lord Rayleigh, M.A. D.C.L.

F.R.S.

The Lord Brabazon.

Stephen Busk, Esq.

Arthur Herbert Church, Esq. M.A.

Frank Crisp, Esq. LL.B. B.A. F.L.S.

Henry Herbert Stephen Croft, Esq. M.A.

Rear-Admiral Herbert P. De Kantzow, R.N.

William Henry Domville, Esq.

Alfred Gutteres Henriques, Esq. F.G.S.

Rev. John Macnaught, M.A.

Robert James Mann, M.D. F.R.C.S.

John W. Miers, Esq.

William Henry Preece, Esq. F.R.S.

Lachlan Mackintosh, Rate, Esq. M.A.

William Chandler Roberts, Esq. F.R.S.

Basil Woodd Smith, Esq. F.R.A.S.

WEEKLY EVENING MEETING,

Friday, May 1, 1885.

Sir William Bowman, Bart. LL.D. F.R.S. Manager and
Vice-President, in the Chair.

The Right Hon. Lord Rayleigh, M.A. D.C.L. LL.D. F.R.S. M.B.L

Water Jets and Water Drops.

(No Abstract.)

1885.] General Monthly Meeting. 285

GENEEAL MONTHLY MEETING,

Monday, May 4, 1885.

Sir William Bowman, Bart. LL.D. F.R.S. Manager and
Vice-President, in the Chair.

The following Vice-Presidents for the ensuing year were
announced : —

Sir William Bowman, Bart. LL.D. F.R.S.

Warren de la Eue, Esq. M.A. D.C.L. F.R.S.

The Hon. Sir William R. Grove, MA. D.C.L. LL.D. F.R.S.

Sir Joseph D. Hooker, K.C.S.L C.B. M.D. D.C.L. LL.D. F.R.S.

William Huggins, Esq. D.C.L. LL.D. F.R.S.

The Right Hon. Lord Rayleigh, M.A. D.C.L. F.R.S.

George Busk, Esq. F.R.S. Treasurer.

Sir Frederick J. Bramwell, F.R.S. Secretary.

His Royal Highness Prince Albert Victor Christian Edward, E.G.
His Royal Highness Prince George Frederick Ernest Albert, K.G.

were elected Honorary Members of the Royal Institution.

The Managers reported, that at their Meeting held this day the
following Resolution was unanimously agreed to : —

*' The Managers of the Royal Institution in accepting Sir William Bowman's
resignation of the office of Honorary Secretary, desire to express to him their
most cordial appreciation of the manner in which he accepted that post, and of
the admirable way in which he has discharged its duties durino- the time for
which he has been so good as to fill it.

" Sir William's own scientific distinctions, and the interest he has always
taken in the prosperity of the Institution, pointed him out as one eminently
fitted to occupy a foremost place among its officials. His extensive professional
engagements alone seemed to piesent an objection to his undertaking the
additional labours thus imposed upon him. This consideration was not alTowed
by Sir William to stand in the way ; he generously assumed the further burden,
and has acquitted himself in the execution of the important and multifarious
functions of the honorary Secretaryship in a mode thoroughly worthy of the
Institution and of himself— and has earned the lasting gratitude and thanks of
the Managers which they now resolve should be tendered to him along with iheir
deeply felt regret upon his retirement."

Montague Cookson, Esq. Q.C. D.C.L.
William Richard Minter Glasier, Esq.
Ernest Kiimpers, Esq.
William Robertson, Esq.

were elected Members of the Royal Institution.

286 General Monthly Meeting. [May 4,

The Presents received since the last Meeting were laid on the
table, and the thanks of the Members returned for the same, viz. :—

The Secretary of State for India—'Re^oYi on Public Instruction in Bengal, 1883-4,

fol. 1884.
Academy of Natural Sciences, Philadelphia— Pioceedings, 1884, Part 3. 8vo. 1885.
Accademia dti Lincei, Beale, Boma—Atti, Serie Quarta : Kendiconti. Vol. I.

Fasc. 7, 8. 8vo. 1884-5.
Asiatic Society of Bengal— Proceedings, No. 11. 8vo. 1884.

Journal, Vol. LIII. Parti. 8vo. 1884.
Asiatic Society, Boyal-Jomua\, Vol. XVII. Part 2. 8vo 1885.
Astronomical Society, iZoyaZ— Monthly Notices, Vol. XLV. No. 5. 8vo. 1885.
Atheneo do Por/o— Kevista Scientifica, Nos. 1-3. 8vo. 18S5.
Bankers, Institute o/— Journal, Vol. VI. Part 4 8vo. 1885.
Behnhe, Emil, Esq. and Lennox Browne, Esq. F.B.C.S. (the Authors)— The Child's

Voice. 12mo. 1885.
British Architects, Boyal Institute o/— Proceedings, 1884-5, No. 12. 4to.
British Museum (Natural History)— Catalogue of Birds. Vol. X. 8vo. 1885.

Guide to the Gallery of Reptilia. 8vo. 1885.
Broime, Lennox, Esq. F.B.C.S. {the Author)— Yoice Use and Stimulants. 12mo.

1885
Brymner, Douglas, Esq. (Archivist)— Be-port on Canadian Archives, 1884. Svo.

1885
Cambridge Philosophical Society—Pvoceedmgs, Vol. V. Parts 1-3. 8vo. 1884-5.

Transactions, Vol. XIV. Part I. 4to. 1885. ,. ^ , , . ^. .,. ^

Carhoni-Grio, Sigr. D. (the Author)— I Terremoti di Calabria e Sicilia. Svo.

Napoli, 1885.
C7iem?c/? ;Soae<.V— Journal for April, 1885. 8vo.

Chief Signal Officer, U.S. Army— Annual Eeport for 1 883. Svo. 1884.
CoUms, Louis, Esq: (the Author)— The Advertisers' Guardian. Svo. 1885,
Crisp Franh Esq. LL.B. F.L.S. &c. M.B.I, (the Editor)— Journal of the Royal

Microscopical Society, Series II. Vol. V. Part 2. Svo. 1885.
Dawson George M. Esq. F.G.S. (the ^Mi/ior)— Superficial Deposits and Glaciation

of the District in the Vicinity of the Bow and Belly Rivers. Svo. 1885.
Editors— American Journal of Science for April, 1885. Svo.

Analyst for April, 1885. Svo.

Athenseum for April, 1885. 4to.

Chemical News for April, 1885. 4to.

Engineer for April, 1885. fol.

Horological Journal for April, 1885. Svo.

Iron for April, 1885. 4to.

Nature for April, 1885. 4to.

Science Monthly, Illustrated, for April, 1885.

Telegraphic Journal for April, 1885. Svo.
Franklin Institute-Journal, No. 712. Svo. 1885
Geographical Society, jRoyaZ— Proceedings, New Series, Vol. VII. No. 4. Svo.

1885
Johns Hopkins University— 'Local Institutions of Virginia. By E. Ingle. Svo.

1885
Johnson, G. S. Esq. (the ^Mf/ior)— Elementary Nitrogen. Svo. 1885.
Linnean Society— Journal, Nos. 107, 136. Svo. 1885.

Lisbon Sociedade de Geographia—Boletim: 4« Serie, Nos. 10, 11. Svo. 1SS3.
Manchester Geological Society —Transactions, Vol. XVIII. Parts 4-7. Svo. 1885.
Medical and Chirurgical Society, Boyal— Proceedings, New Series, Nos. 8, 9,

Svo. 1885.
Meteorological O^ce— Monthly Weather Report, December 1884, January 1885.

4to.
Meteorological Society, i?oya?— Quarterly Journal, No. 53. Svo. 1885.
Meteorological Record, No. 15. Svo. 1885.

1885.] General Monthly Meeting. 287

National Association for Social Science^ Transactions, Birmingham, 1884. 8vo.

1885.
North of Enqland Institute of Mining and Mechanical Engineers — Transactions,

Vol. XXXIV. Part 2. 8vo. 1885.
Account of the Strata of Northumberland and Durham. F to K. 8vo. 1885.
Odontological Society of Great Britain — Transactions, Vol. XVII. No. 5. New

Series. 8vo. 1885.
Pharmaceutical Society of Great Britain — Journal, April, 1885. 8vo.
Photographic Society — Journal, New Series, Vol. IX. Nos. 5, 6. 8vo. 1885.
Preus'slsche Akademie der Wiesenschaften^ Sitzungsberichte, XL.-LIV. 8vo.

1884-5.
Royal Society of I(07ic?on— Philosophical Transactions, Vol. CLXXV. Part 2.

4to. 1885.
Society of Jr<s— Journal, April, 1885. 8vo.

St. F'e/erfibourg, Academic des Sciences — Memoir.^ Tome XXXII. No. 13. 4to. 1884.
United States Geological Survey— Third Annual Report, 1881-2. 4to. 1883.
Geoloijy of the Comstock Lode and the Washoe District. With Atlas. By

G. F. Becker. 4to. 1882.
Vereins zur Beforderung des Gewerhfleisses in Preussen — Verhandlungen, 1885 :

Heft 3. 4to.
Victoria Institute — Journal No. 72. 8vo. 1885.
Wild, Br. H. (the Director) — Annalen des Physikalischen Central-Observatoriums,

1882. 4to. 1883.
Zoologic.d Society— Froceedings, 1884, Part 4. 8vo. 1885.

WEEKLY EVENING MEETING,

Friday, May 8, 1885.

Sir William Bowman, Bart. LL.D. F.R.S. Manager and

Vice-President, in the Chair.

W. F. R. Weldon, Esq.

On Adaptation to Surroundings as a Factor in Animal Development.

(Abstract deferred.)

288 Professor J. Bur don Sanderson [May 15,

WEEKLY EVENING MEETING,

Friday, May 15, 1885.

Sir Frederick Abel, C.B. D.C.L. F.R.S. Manager, in the Chair.

Professor J. Burdon Sanderson, M.D. LL.D. F.R.S.

Cholera : its Cause and Prevention.

The interest excited in cholera by its presence in Europe during
last summer and autumn was reawakened in the spring by the
prospect of a war which might have brought us face to face with an
enemy much more formidable than the armies of Russia. War is no
longer in immediate prospect, so that for the present we need not
think of cholera in connection with Asia Minor or the Black Sea.
But the epidemic which is now raging with such pitiless fury in the
Mediterranean provinces of Spain makes us all feel that the threat
of 1884 may be fulfilled in 1885. There is probably no serious
ground for apprehending that we shall have to do with cholera in
England this year ; the chance, however, is sufficiently near to make
it reasonable to inquire whether any useful information as to the
causes of cholera, or the way in which it can best be guarded against,
has been gained since the last time that the disease visited our
shores.

In dealing with cholera, as in other matters in respect of which
conduct must be guided by knowledge of some kind, the question
what sort of knowledge is best and most valuable comes prominently
to the front, and is one on which those who profess to follow the
scientific method, and those who profess to be guided by what they
are pleased to call common sense, are apt to entertain difi'erent
opinions. The question is in reality not between two kinds of
knowledge, but between tw^o ways of acquiring the same kind of
knowledge. Those of us who have studied cholera at home in the
hospital ward or in the laboratory approach the subject on one side.
Those whose lives, like that of my friend Dr. J. M. Cunningham, the
Sanitary Commissioner with the Government of India, have for the
most part been spent in a prolonged encounter with cholera year after
year, as it presents itself in prisons and armies and among the multi-
tudinous populations of our Indian Empire, from another. But we
are all seeking the same kind of knowledge, and what is more, we
all tend to the same conclusions. If, for example, a comparison be
made of the recent work published by Dr. Cunningham, "Cholera:
What can the State do to prevent it ? " in which he professes to con-
fine himself to considerations of common sense and deprecates the
interference of science with practical questions, w^th the lecture

1885.] , on Cholera : its Cause and Prevention. 289

given a few months ago to tlie people of Munich by Professor von
Pettenkofer, who is acknowledged to be one of the highest scientific
authorities on the etiology of cholera, it will be found that the
German Gelehrter and the English administrator say practically the
same thing.

As this paper is intended for the perusal of persons who do not
specially concern themselves with pathology, I will enter as little as
possible upon subjects of controversy, regarding it as of much more
importance that those notions as to the cause and nature of cholera,
about which there is no dispute, should be generally understood,
than that the claims of rival investigators should be vindicated. In
the slow process by which new knowledge is acquired, strife is a
necessary and unquestionably a productive element. Burning ques-
tions arise wherever and whenever scientific investigation bears, or
appears to bear, on practical action. Eventually they find their
solution ; but in the meantime it is almost impossible for those who
are immediately concerned in discussing them to guard against the
influence of personal antagonisms and predilections. As regards all
recent questions of this kind, I think that I am myself in a position
to look at them from a distance, for I have had no direct concern
with cholera since 1866. I will therefore ask the reader to regard
me neither as a contagiouist nor as a localist, and to dismiss the
" comma-bacillus " from his mind until we have had time to take a
general view of the tendencies which this great world plague has
manifested in its dealings with mankind since it first found its way
into Euroi3e.

It is agreed by all authorities that cholera is native in India, and
particularly in the district where it is now " endemic " — namely, in the
district which corresponds roughly to the deltas of the Gauges and
Brahmaputra and the district of Cuttack. As, however, it for the
most part confined its ravages to the native populations, with whom
at that time our relations were much less direct and intimate than
they are now, it excited no general interest, and was indeed so little
known to medical men that when in 1817 the disease broke out at
Jessore, near Calcutta, it was believed to be an entirely new malady.
Even now there are some writers who speak of Jessore as the " cradle
of cholera " and the year 1817 as the starting-point of its history,
notwithstanding that the enquiries which were then initiated showed
not only that in Bengal the disease was an annual visitor, but that
in Calcutta itself it was fatally prevalent in the native town several
weeks before Dr. Tytler was called to see the first case at Jessore.

The great epidemic of 1817 and 1818 was distinguished from
previous ones by its extent and destructiveness, but chiefly by the
circumstance that in this year it became for the first time a serious
obstacle to English conquest. How or when it began it is probably
impossible to determine, for evidence exists of its presence in July
1817 within a few weeks at places so distant from one another as
Patna and Dacca. Two months later it was at Benares, Allahabad,
Vol. XI. (No. 79.) u

290 Professor J. Bur don Sanderson [May 15,

and Mirzapore ; and in October of the same year an event occurred
wliich at once gave the disease a significance it had not before
possessed. The Marquis of Hastings, with an army of over 10,000
Europeans and a much larger native force, was in the Bundelcund,
not far from Aliababad, where cholera was then raging. Cholera
had on several previous occasions interfered with military operations,
but this time it attacked Hastings' European troops with a violence
of which there had before been no example. The pestilence con-
tinued for several weeks with unabated destructiveness, until early in
November the army was withdrawn from the Bundelcund and moved
westwards in its march towards Gwalior, on which the mortality at
once subsided. Thousands of dead and dying were left behind, but
cholera was left behind with them, and a lesson was learned which
has since been often repeated in Indian experience — that when a
military force is encountered by cholera, removal from the infected
locality is the only effectual way of checking it.

In 1818 cholera overspread the whole Indian Peninsula. West-
ward it extended up the Ganges valley to Delhi and Agra, and
eventually found its way across the Sutlej to Lahore. Southwards
it flanked the line of the Yindhya, attacked Nagpore, and thence
spread to other places in Central India. Along the east coast there
were destructive epidemics at Vizagapatam, in the deltas of the
Godavery and Kistnah, at Madras and Pondicherry, and various other
places further south. In 1819 Ceylon, which had been similarly
invaded in 1804 and probably often previously, suffered very severely ;
The spread of cholera in the island was naturally enough attributed
to the commercial intercourse between Trincomalee and the infected
ports on the coast of Coromandel. Whatever may be said for or
a<^ainst this belief as regards Ceylon, it is difficult to offer any other
explanation of the outbreak which occurred the same year in
Mauritius than the obvious one that it w^as carried over the sea by
trading ships ; for even though the evidence which exists that the
Mauritius epidemic took its start from the arrival, with cholera on
board, of the ship Topaze, were proved to be defective, it could
scarcely be accounted for in any other way than as a result of com-
mercial intercourse. From Mauritius cholera spread to Madagascar
and the Portuguese settlements on the east coast of Africa.

In the course of 1820 cholera seems to have spread over Asia.
In that year it was at Canton and Nankin, and travelled up the
Yang-tse-kiang into the interior of China, and finally reached the
capital. In the same year it is said that 150,000 persons died of it
in the island of Java. Celebes, the Moluccas, and the Philippines
were invaded at the same time. Burmah, Siam, and Singapore had
been ravaged the previous year, and it was believed that the latter
place, where so many streams of commercial movement meet, was the
source whence the infection was distributed over China and the
Malay Archipelago. The explanation was probably correct. By the
universal infection of all the ports of our Indian dependencies in

1885.] on Cliolera : its Cause and Prevention. 291

1819 the channels of EurojDean commerce in the East were more
thoroughly contaminated than they had ever been before. Modern
experience teaches us that though cholera is very unapt to spread
in this way, it may do so ; and I confess it appears to me quite
impossible to doubt that in those early years of its history it did so.

From 1820 onwards we have evidence that cholera has never been
absent from Bengal, and has behaved throughout in the same way
that it does now. The best general idea of the extent of its influence
and of the differences which subsist between years of great epidemic
prevalence and others, may be gained by an examination of the series
of maps which have been published by the Indian Government. The
conclusions which these maps suggest, and which are confirmed by
the more minute and exhaustive study of cholera statistics which
has been made by Dr. Bryden,* may be summarily stated as
foUov/s.

Within certain areas, the limits of which comprise the alluvial
plains adjoining great rivers, and particularly in the deltas of such
rivers, cholera is always present. Outside these so-called endemic
areas some places are distinguished by their liability to the epidemic
prevalence of the disease, others by their special immunity, and in
general no relation can be traced between liability to epidemic pre-
valence and personal intercourse with infected districts; so that,
however clear it may be that the infection of cholera is capable,
under certain conditions, of being conveyed from place to place,
Indian experience affords no ground for attributing any importance
to such conveyance as a means of the spread of cholera in that
country.

Let me now try to give an account of the circumstances which led
to the escape of cholera, if such an expression may be used, from its
Indian home into Europe. As probably every reader knows, the first
European country invaded by cholera was Russia, and the first
European town of any importance was Orenburg, on the Ural, one of
the great feeders of the CasjDian. How did cholera find its way from
the Indian Peninsula to the Caspian ? The only answer that can be
given is that the communication took place by way of Persia, and that
Persia itself was invaded not, as has been sometimes said, by Afghan-
istan, but by the Persian Gulf. In 1821 — that is, a year after the
epidemic of Zanzibar — there was a destructive outbreak of cholera at
Muscat in Arabia and at the Persian port of Bushire, and a little
later at Bagdad. From these littoral beginnings the epidemic spread
during the next year (1822) over the whole of Persia and great part
of Asia Minor. In 1823 it was in Damascus and Aleppo, having at
the same time or previously existed in Iskanderoon and other places
on the Mediterranean. It is usually stated that in 1822 cholera

* See ' Epidemic Cholera in the Bengal Presidency.' By James L. Bryden,
M.D. Calcutta. 1869.

U 2

292 Professor J. Bur don Sander soil [May 16,

crossed the Caucasus for the first time, the only ground for the state-
ment being that in that year it jDrevailed at about the same time at
Tiflis and at Astrachan. In reality, cholera seems to Lave reached
Astrachan, not over the Caucasus, but by creeping along the Caspian
shores from Kesht, which was the first place invaded. In the Caspian,
as in India, it found a suitable soil in the deltas of the Terek and the
Volga, and finally ascended the Ural, as has been already noted, to
Orenburg. Beyond these limits cholera failed to penetrate further
into Europe either by the Mediterranean, the Black Sea, or the
Caspian, its disappearance in Syria and in Astrachan being simul-
taneous. There seems good reason for believing that it was entirely
absent for six years (1823 to 1829), but in August 1829 it reappeared
in Orenburg without its being possible to ascertain with any certainty
whence it came. All that can be asserted is, that it was at the same
time widely scattered over Central Asia, in Afghanistan, at Teheran,
at Khiva and Bokhara, as well as on the shores of the Caspian, and
that in consequence it was on this occasion believed to have rather
come by Central Asia than from Persia.

In 1830, the year after the Orenburg epidemic, cholera made its
first great advance into Europe. In August of that year there were
destructive epidemics at Astrachan (where there is good reason for
believing that the cholera had wintered), at Zaritzin, at Saratov, at
Kasan, and finally at Penza — all, with the exception of the last, on
the Volga. A few weeks later it was at Taganrog, Kertch, Sebastopol,
Cherson and Odessa, and finally, in September 1830, began the
epidemic of Moscow, which was rendered memorable by the self-
sacrifice and devotion of the Eussian Emperor. In 1831 cholera
for the first time spread over Central Europe. Beyond the broad
fact that Eussia was first invaded, it is quite impossible to say how
this momentous result was brought about, as the reader may at once
satisfy himself by comparing the following dates, which are derived
from Dr. Peters' ' History of the Travels of Asiatic Cholera,'
published in the Eeports of the United States War Department : —
Moscow, September 1830 to March 1831 ; and in the latter year,
Petersburg, June ; Warsaw and Cracow, April ; Dantzic, March ;
Berlin, August; Hamburg, October. In October 1831 cholera
appeared at Sunderland and became epidemic there and in the
neighbouring towns, Newcastle, Gateshead, Shields ; but it was not
until a large number of persons had been attacked and died that it
was admitted to be Asiatic. There is evidence that during the
preceding summer the disease had been introduced into the port of
London, and had even spread among the maritime population ; but
notwithstanding that no special precautions apiear to have been
taken, London itself remained exempt until early in the spring of
1832.

In tlie summer of that year it prevailed in most of the seaport
towns of England and Ireland, and was carried across the Atlantic
by Irish emigrants. For when, in June 1832, the disease broke out

1885.] on Cholera : its Cause and Prevention. 293

in a lodging-house in Quebec* wliicli had received a number of these
emigrants, destroyed fifty-six lives, and in the next fortnight spread
everywhere in the town, it is impossible to doubt that these persons
brought with them to their new home the seeds of cholera. The
history of the invasion of Montreal, which occurred about simulta-
neously, was but a repetition of the experience of Quebec. During
the autumn of 1832 and the year following, cholera ascended the
St. Lawrence to Chicago, and thence found its way to the Upper
Mississippi, where it very seriously interfered with the military
operations against the Indians. In 1833 it appeared in Cuba, whence
it spread later in the same year to Mobile, New Orleans, Tampico,
and other ports on the Gulf of Mexico, and eventually to Mexico and
Vera Cruz. Epidemics continued to occur in the Spanish-speaking
countries of the New World until 1834-35, in the former of which
years Spain itself was for the first time invaded. The great epi-
demics of Madrid and Barcelona were followed by a general exten-
sion along the Mediterranean coast — Cette, Marseilles, Toulon, Nice,
Genoa, and Naples being attacked in the order in which they have
been mentioned. As there was an interval between the Mediterranean
spread and the great wave which had alffected England in 1832, it
seemed as if the disease, which was communicated to the New World
from the Old, had been returned back to it from the West Indies.
Whether this was so or not is scarcely wortli inquiry. It w^ould be
much more interesting if we could explain how it was that the Medi-
terranean, which was in 1832 exposed to every conceivable chance of
infection, was not invaded until 1834 ; and why, having seized upon
such ports as Marseilles and Genoa, it showed no tendency to travel
northwards to the country it had previously invaded. Let me add
that cholera did not leave Euroj)e until 1837, after which the Western
World was free from it for a decade.

Cholera reached the Caspian for the third time in April 1847, its
arrival being the outcome of a general spread of the disease in Persia
and Central Asia. It soon found its way into the interior of Russia and
broke out for the second time in Moscow, two months after it had
appeared, almost simultaneously, at Astrachan and Constantinople.
By the winter of 1847-8 it was at Riga, and spread, during the
following summer, just as it had done before, along the Baltic coast,
reaching Hamburg in September.

The conveyance of cholera into England, and from England to
America, was but a repetition of what had happened in 1832 ; and
the same sort of evidence existed at New Orleans and at New York,
in which j)laces the epidemic began simultaneously (December 1848)
of importation by emigrants. From 1847 Western Europe was again
free from cholera for six years, notwithstanding that it was always
present somewhere in the East. 1853 was a cholera year : it was
marked by a fearful epidemic in St. Petersburg, which again spread

* Dr. Peters, he. cit. p. 564.

294 Professor J. Burdon Sanderson [May 15,

along the Baltic coast, reacliing London and Liverpool in July, but
not becoming epidemic until the following year.

After a dozen years of immunity,- cholera again appeared in Europe
in 1865. On this occasion it was generally believed that the pesti-
lence reached Europe, not as before by the Caspian and Black Sea,
but by the Mediterranean. There is no doubt that cholera was rife
at Jedda and Mecca in the spring of 1865, also that it prevailed from
the beginning of June in Alexandria, and appeared in Malta on the
20th of that month, and about the same time at Marseilles, and
subsequently on the Coast of Spain (Valencia). As was the case last
summer, the seed was conveyed to Paris, and on that occasion bore
fruit in the deaths of about 7000 persons in five months. There
was also, as many readers will remember, a small epidemic at South-
ampton, the origin of which was traced by Dr. Parkes to the arrival
of ships with cholera on board from Alexandria ; but with this excep-
tion Western Europe remained free until the following year. Nor
in all probability would England have ever suffered as it did in 1866,
had the sporadic spread of cholera from the Mecca pilgrims been
our only risk. At the time that all these events were going on
about the Mediterranean a new storm was brewing in the old quarter
— in North Germany. The appearance of cholera on August 29,
1865, at Altenburg, a place situated in the very middle of Germany,
was one of the strangest events which is on record in relation to
cholera in Europe. The epidemic in that district, which is exclu-
sively watered by tributaries of the Elbe, lasted for four months
(i.e. until the very middle of winter), culminating in October, and
destroying 500 people. All of these deaths occurred in some half-
dozen towns lying to the southward of Leipsic. This was followed
by a general dissemination of cholera in Germany. By July 1866
it was already at London and Liverpool. The Prussians in their
march into Bohemia passed through the country that had been the
seat of the epidemic in the previous year, and on their return from
their short but victorious campaign encountered it at Halle and
Leipsic, in which places by that time it had gained headway, and
suffered so severely that more soldiers' lives were lost by cholera
than by the weapons of the Austrians. Since 1866 we in England
have again had a long period of immunity, notwithstanding that we
have been repeatedly threatened. In Germany a succession of epi-
demics occurred between 1873 and 1875, none of which reached
England. Although these, from the completeness with which they
were investigated, afford materials for a very instructive study of the
subject, I must for the present content myself with the sketch already
given of the epidemics which have affected this country.* It may,
perhaps, suffice to enable the reader to see that in these successive

* See Gunther, ' Die indische Cholera in Sachsen im Jahre 18G5,' Leipzig,
1866; and Pettenkofer, 'Die Sachsischen CLolera-Epidemien des Jahrcs 1865.'
Ztsch. f. Biol., 1866.

1885.] on Cholera : its Cause and Prevention. 295

spreads of cholera over the civilised world it follows certain general
laws — as, for example, that it loves great rivers, and particularly their
deltas and estuaries, and that it is capable of being conveyed over
sea and land, following for the most 2)art the lines of commercial in-
tercourse. On either side of this general view which the unbiassed
intelligent reader of cholera history finds himself compelled to take,
range the opjDosite oj)inions of contagionists on the one hand, who
believe that cholera came to Europe in 1830, because the materies
morhi accidentally escaped from India ; and on the other, the believers
in the siDontaueous origin of cholera, who think that they mean some-
thing when they say that the cause of cholera is " atmospheric " or
" telluric."

Let us now see what can be learned by looking at the subject
from the consideration of its pathological nature. With this view
we will take as our starting-point the assumption that cholera is a
" specific " disease, which means simply that it has a particular or
proper cause — a cause which is peculiar to it, and without which it
cannot come into existence. In each of the diseases known as
smallpox, glanders, diphtheria, cattle plague, the cause presents itself
as a tangible material which can be obtained from the body of any
human being or animal afi'ected with it, and may thus be subjected
to experimental investigation. In the case of the affection called
woolsorters' disease, or splenic fever, to which persons engaged in
manipulating particular kinds of wool imported from the East are
liable, we know that the material cause not only exists in the body of
the sufferer, but also in the wool by which he is infected. Cholera
we believe to have a similar material and tangible cause, but no
one as yet has been able to seize upon it. It has been sought for
both diligently and skilfully, but it has hitherto eluded investigation.
It will therefore be convenient to speak of it as the unknown entity x.

In the search after the x of cholera which now occupies so many
minds, the method which the pathologist ought to follow — the only
one he can follow with reasonable prospect of success — is that of
proceeding step by step from the known to the unknown. Conjecture
must lead the way to discovery, but those conjectures only are likely
to be productive which are founded on the comparison of unknown
with known relations.

The fact which we have to explain is that cholera has spread
from India all over the world, and is always spreading somewhere.
The knowledge we have to guide us in seeking for an explanation
is that in other spreading diseases the spread consists in the convey-
ance of a something tangible from the infected person or thing to
a healthy person at a greater or less distance; and the legitimate
guiding conjecture is, that whatever may be known as to the nature
of the conveyable something in the cases in which it can be investi-
gated, is likely also to be true in those cases in which, as in cholera,
it is for the present beyond our reach.

In the current language of pathology, the conveyable something

296 Professor J. Burdon Sanderson [May 15,

by which infectious diseases are projDagated is called contagium^ a
word which may be conveniently used, provided that it is not
allowed to carry any suggestion that the disease to which it is
applied spreads by personal contact or intercourse. Like other
scientific terms, its use is to serve as a label for certain knowledge.
Under the heading contagium, the pathologist says (1) that all
contagia consist of organised (not merely organic) matter ; (2) that
this matter must, in order to be disseminated, be in a state of fine
division (particulate) ; (3) that the particles of which it consists
are living ; (4) that they derive their life (not as having been
themselves bits of the living substance of the diseased man or
animal, but) from parents like themselves. With reference to all of
these 2:)ropositions, excepting the last, there is agreement of opinion.
It is now eighteen years since it was proved by the investigations
of Chauveau that all the best known contagia (which are liquids of
the character of vaccine lymph) owe their activity to the minute,
almost ultra-microscopical, particles which float in them ; and no
one doubts that these particles are organised, and that their power
of producing disease depends on their organisation. Further, we
know, with reference to one or two diseases — namely, wcolsorters'
disease, or splenic fever, tuberculosis, leprosy, and one form of
septicaemia, that the particles in question are not only organised,
but themselves organisms — i. e. living individuals deriving their
life from parents like themselves. But from the moment that the
pathologist begins to infer that because in these particular instances,
which can be experimentally investigated, infection occurs by
organisms, it must be so in the case, for example, of cholera, of
which the behaviour is very different indeed from that of any of
the infectious diseases above enumerated, he leaves certainty behind
him and passes into the region of more or less probable conjecture.
With reference to the special question which now interests us, he
has to compare the mode of operation by which cholera spreads
with the modes of operation of those diseases which are propagated
by self- multiplying contagia — first, with a view to the estimation
of the antecedent probability that they are essentially identical ;
and secondly, to the testing of the estimate arrived at by such
experimental investigations as circumstances place within his reach.

The antecedent probabilities may be stated as follows: — If the
reader will approach the subject with a mind freed for the moment
from metaphysical considerations, he will see that the spread of
cholera over the world must be due either to the dispersion of
infected persons, or of things with which such persons have been
in contact, or to the dissemination through the air of what may be
called " cholera-dust." The question whether there is such a thing
as cholera-dust rests on the teaching of experience as to whether
cholera can or cannot jump from one place to another at a distance
without the aid of personal intercourse. If this does occur it can
only be by dust. — i. e. minute particles of infective material sus-

1885.] on Cholera : its Cause and Prevention. 297

pended in the air. If it is not so, it remains to be determined
whether such events as the conveyance of cholera from Ceylon to
Mauritius in 1819, from Astrachan up the Volga in 1830, from
Hamburg to Sunderland in 1831, frorh Dublin to Montreal in 1832,
and from Havre to Halifax in 1849, in all of which immigration
from infected places of men with their belongings led to the appear-
ance of cholera where it was before unknown, should be attributed
exclusively to the introduction into these places of persons actually
suffering from cholera, or to the circumstance that these persons,
whether themselves infected or not, brought with them an infected
environment. Experience all over the world is in favour of the
latter alternative, for on the one hand it teaches that cholera is not
" catching," so that attending on the sick is in itself unattended
with any risk ; and, on the other hand, that cholera has such a
power of haunting localities, that a house, street, town, or district
where cholera prevails to-day becomes thereby more liable to a
second visitation next year than it would otherwise be. Now the
only way in which such a fact as this can be explained is by sup-
posing that the material cause of cholera is capable of existing in
human belongings for a length of time independently of the human
body from which it sprang. But in addition it suggests something
as to the nature of that cause. That the contagium of cholera is
capable, after many months of quiescence, of recovering its activity
whenever the conditions of that activity come into existence, is a
fact which, while it is otherwise unintelligible, is very easy explained
on the supposition that the contagium itself is endowed wdth life ;
for it is characteristic of living things that they have the power
of sleeping and waking — of hibernating, and reviving under the
influence of summer warmth. In addition to this, we are led in the
same direction by the consideration, which applies to cholera in
common with all other spreading diseases, that whatever the x may
be, it certainly possesses another essential property of organisms—
namely, that it is capable of self-multij)lication ; for however incon-
sideralDle may be the weight of material which is wanted for the infec-
tion of a single individual, it is clear that when cholera invades a
country for the first time, the increase of that material, in the body
of the first case, then in the bodies of the thousands subsequently
affected, must be enormous.

The conjecture therefore that cholera, like other epidemic diseases,
owes its power of spreading to a living and self-multiplying organ-
ism is so well founded that we are justified in taking it as a starting-
point from which we may at once proceed to inquire — first, where
this self-multiplication takes place ; and secondly, how it is brought
about. The first question, I think, I can best answer by stating
to you the view on the subject which has received the most general
acceptance.

In splenic fever, as we have seen, there is no doubt whatever that
the disease of which the human being or the animal affected with it

298 Professor J. Burdon Sanderson [May 15,

dies, proceeds pari passu with the development of the disease-pro-
ducing organism x ; for in the hours, be they few or many, which
intervene between the sowing of the seed in the body of a living
animal and the maturation of the harvest — that is, between inocula-
tion and death — the whole of the living body of the affected animal
becomes so thoroughly infested that in many instances no fragment
of tissue, no single drop of circulating blood, can be found which
does not contain thousands and tens of thousands of the character-
istic rods (or bacilli), each of which individually is capable of com-
municating the disease if sown into the body of a healthy animal.
So also in another well-investigated instance, that of relapsing fever,
we have evidence that the multiplication of x takes place in the cir-
culation, and that the presence there of the characteristic spirilla is
so associated with the appearance of the fever itself, that the one
never manifests itself without the other having preceded it.

But as regards cholera, nothing of the kind can be observed. As
yet no one has been able to find the organism, either in the blood
or in any living tissue, notwithstanding that the research has been
conducted with every possible care. Nor has it been found either
that the bodies of persons affected with cholera, or that any part of
them, possessed the power of infecting other healthy persons. Con-
sequently the opinion first arrived at and formulated by Professor
Pettenkofer has come to be very generally adopted — that in cholera
the multiplication of x takes place, not in the tissues of the sick
person, but in his environment. Let us examine a little more closely
what this means.

Under the term environment is included everything which is in
relation with the external surface of the body, including the air we
breathe and the water and other material which we use as food.
And inasmuch as no multiplication can take place otherwise than in
a suitable soil consisting of organic matter, and no such soil exists in
the air, we may limit the possible seats of multiplication to tbe
moist organic substances of various kinds which exist at or near the
surface of the earth. Putting this into plainer language, it means
that when the cholera x invades a previously uninfected locality in
which it is about to become epidemic, the first thing it does is not to
find a home for itself (as the x of smallpox, of cattle-plague, or of
splenic fever w^ould do) in the body of some healthy j)erson, but to
sow itself in ivliatever material at or near the surface is Jit for its
reception and vegetation.

Now, in our study of the laws of diffusion of cholera we have seen
that, although cholera may be repeatedly introduced by personal
intercourse into an uninfected locality without result, it finally, after
a shorter or longer latency, bears fruit ; and this we exjslain on the
hypothesis that, of the two conditions which are essential to the
fructification of the germ — namely, the presence of the organism
itself, and the presence of a soil suitable for its growth, the latter is
of more importance than the former ; that, in short, the reason why

1885.] on Cholera: its Cause and Prevention. 299

a given town or country remains exempt from cholera — is not that
the seed of infection fails to reach it, but that those local conditions
which are necessary for its vegetation are wanting. If we call the
environment y, then the cause of cholera is not x4-y, but xy, so that
whatever value we assign to x, the product disappears as y vanishes.*

If the cholera organism multi])lies in the soil, not in the indivi-
dual, it must, in order to exercise its disease-jDroducing function,
attack the human body by one of two channels, either by air or food ;
it must be taken in either by breathing or swallowing, for the skin
has so little power of absorj^tion that it need not be considered. It
seems to be extremely probable that in either case x enters the
organism by the same portal — namely, by the process of intestinal
absorption ; that is, by the same channel by which the nutritious part
of our food is assimilated — i. e. that even if it were introduced by the
breath, it would still act by localising itself in the alimentary canal.
Consequently, if we want to engage in the search for it, there are
two places where we should exj^ect and seek to find it — namely, first,
in the soil ; and secondly, in the intestine of infected persons.
Hitherto attention has been exclusively given to the investigation
of the absorbing apparatus of the alimentary canal as the spot in
which X would be likely to be caught as it were flagrante delicto.

In illustration of this, let me now refer to the eflforts which have
been made at various periods to carry out this inquiry. Without
going back to the attempts made by Dr. Snow in the epidemic of
1854, I will content myself wdth a rapid survey of what has been
done in more recent times, premising that there is no necessary
connection between the notion which I am now advocating — namely,
that the cholera x resides in the soil, and produces cholera by finding
its way into the intestine, and the belief that the intestinal contents of
persons suffering from cholera are directly pernicious and infecting.

In 1870 a morphologist of great distinction (Professor Hallier)
published a remarkable series of observations, in which he endea-
voured to show, on purely morphological grounds, that the birth-
place (or rather the nursery) of cholera is the rice-plant — that a
parasite which grows on this plant, so essential to the populations of
the endemic area of Bengal, becomes in the course of successive
transformations the cholera fungus; that this fungus throws off
spores which are the immediate producers of cholera ; and that by
means of the endurance and extreme levity of these spores, they
serve as agents by which cholera is spread all over by the wind ; and
so on. Of Hallier it is sufiicient to say that, however distinguished he
might be as a botanist, he was a bad pathologist, and that his method
was fundamentally wrong, inasmuch as he proceeded throughout on
the assumption that the morphological characters of an organism
supposed to be infective may be taken as evidence of its infective

* In desiguating the seed, germ, coutagium, or miteries morhi of cholera x, and
the soil or environment y, I follow Professor v. Pettenkofer.

300 Professor J. Bunion Sanderson [May 15,

nature ; whereas pathology admits nothing to be a contagium unless
it can be observed in action as such. For one thing, at all events,
we may be grateful to the Jena botanist. It was for the purpose of
investigating his theory that those indefatigable cholera workers, Drs.
Lewis and .(Cunningham, were sent to India, where, although they spent
more time and labour in correcting Hallier's mistakes than it took
Hallier himself to fall into them, they were thereby aflbrded opportunity
of acquiring information of the highest practical and scientific value.
It would take too long to refer to other efforts in the same direction,
but it may be readily understood that the question of the material
cause of cholera was too important to be neglected, and that as soon
as cholera seemed once more to threaten Europe it again urgently
claimed the attention of scientific pathologists. Accordingly, in
1883, Dr. Koch, who is the author of two of the greatest discoveries
of modern times in relation to spreading diseases, was deputed by
the German Imperial Government to proceed to Egypt, and then to
India, to investigate cholera.

Stated in few words, the result of Dr. Koch's inquiries were —
(1) That the x in cholera has the form of a curved rod, which
Dr. Koch likens to a comma (as written, not as printed) ; and (2)
That the disease (cholera) is caused by the presence, growth, and multi-
plication of this organism in the apparatus for absorption contained
in the lower part of the small intestine, and by the consequent
formation there of an animal poison which produces the collapse and
the other fatal effects of cholera.

These statements, as soon as they became publicly known, assumed
a very great importance, because they appeared to afford support to
a doctrine with which they have no necessary connection — namely,
that of the communicability of cholera by direct personal intercourse
with the sick. The mere fact of the existence of countless myriads
of organisms of a particular form in the intestinal liquid, although
very interesting in itself, affords no evidence that they are tlie
culprits, unless two other things can be proved respecting them —
namely, that they possess the power of producing cholera wherever
they exist, and that they are capable of maintaining their life, not
merely within the intestine, but also in the soil: for, as we have
seen the evidence that the material cause of cholera is capable of
existing outside of the body and of spreading over the world inde-
pendently of the presence of persons affected with the disease, is so
conclusive, that no explanation of cholera can be accepted which
does not take this into account.

Now in India the question of the prevention of cholera is a very
practical one. Here, cholera is chiefly a question of preserving life ;
in India it is one of commerce, and consequently of national
prosperity. If it were believed in India that the cholera patient is
himself a source of infection, that each individual comma is a source
of danger, India would be compelled to adopt prophylactics of the
same kind as tliose which were adopted last year by the ignorant

1885.] on Cholera : its Cause and Prevention. 301

and short-sighted administrators of Italy and France. And it was,
I believe, on this ground judged necessary by her Majesty's Indian
Government to send out a special Commission for the purpose of
reporting generally on the practical bearing of the German investiga-
tions. The Commission was under the general guidance of Dr. Klein,*
who was selected on the recommendation of the highest scientific
authority in this country, as being the person who in England,
by his previous researches, had shown himself facile p'incejjs in
inquiries of this nature. The finding of the Commission was, that
although Dr. Koch was perfectly accurate in his statement of fact,
he had gone too far in inference. In other words, that although the
so-called cholera bacillus swarms in the intestine of every person
afl'ected with cholera, it does not there play the part which is
attributed to it.

I shall, I think, most usefully conclude this paper by stating as
clearly as I can in what way the knowledge and experience already
obtained as regards the cause of the spread of cholera by the two
methods of inquiry which are available for the purpose (and which
for the moment I will call the epidemiological and the bacteriological)
may be brought to bear on practical questions. And here I will ask
the reader to note once more amid the apparent differences of opinion
which exist at the present moment, as regards some questions which
have lately come prominently to the front, between persons whose
competency cannot be denied, that such j^jersons are nevertheless
•in agreement, not only with respect to the sources of danger and the
means of guarding against them, but also as to the most fundamental
theoretical questions. Thus, for example, while we hesitate to admit
that the particular organisms which Dr. Koch has so carefully inves-
tigated have anything to do with the causation of cholera, the conclu-
sions arrived at nearly twenty years ago by the two leading autho-
rities of that time — Simon in England and Pettenkofer in Germany
— that cholera depends on an organism, and that its spread cannot
be accounted for in any other way, are as certainly true now as they
were then. But this certainty arises not from any direct evidence
which has up to this time been offered with reference to a jDarticular
bacillus, but from the various facts which go to show that in places
inftcted or haunted by cholera something else exists besides the
infected persons. So that if we could imagine all the infected
persons in such a locality to be removed by some act of absolute
power, such an act would not stop the j)rogress of the epidemic, for
cholera would still be there.

Of the two methods of inquiry above referred to, the bacterio-
logical api^lies to the nature of the contagium itself, and the
epidemiological to the nature of the environing conditions which

* The Commission consisted of Dr. Klein, F.R.S., and Dr. Heneage Gibbes.
The Report has onlj^ just been published, but the scientific results of the inquiry
were coinmunicHted by Dr. Klein to the Royal Society in February last.

302

Professor J. Burclon Sanderson

[May 15,

favour its development. Hitherto the investigation of the latter has
been by far the most successful. But it would be a great mistake
to allow the apparent failure of such researches as those of Dr. Koch
in Egypt and in India to discourage the efforts which are now being
made everywhere by earnest and devoted workers to accomplish
what has baffled so able an investigator. Whenever the discovery is
made, it will not only serve as a key to the understanding of
cholera as a disease, and thereby tend to render its treatment a little
less hopeless than it is at present, but it will serve as the necessary
completion of the knowledge we have gained from the combined
experience of the medical profession in India, in Europe, and in
America, with reference to the behaviour of cholera as an epidemic
disease. To make this clear, all that is necessary is to summarise
statements which have been already placed before the reader in the
course of this article. What we have learned is that the liability of
a locality to cholera depends, first, on the physical characters of the
soil; and secondly, on certain changes which it undergoes in the
course of the seasons. The peculiarity of the soil which favours
cholera is unquestionably want of natural or artificial drainage, con-
bined with the presence in the liquid with which it is soaked of such
organised material, derived from the tissues of plants or animals, as
render it a fit soil for the development and vegetation of microphytes.
The seasonal change w^hich favours cholera is that which expresses
itself in the drying of such a soil under the influence of summer
temperature. In Europe this takes place in July, August, and*
September, in which last month, as the following table * strikingly
shows, cholera attains its maximum of destructiveness : —

Month . . .
Mortality .

April.
112

Mav.
446

June.
4,392

July.

8,480

Aug.
33,640

Sept.
56,561

Month . . .

Mortality .

Oct.
35,271

Nov.
17,630

Dec.
7,254

Jan.
2,317

Feb.

842

March.
214

But be it ever remembered that these two liabilities of time and
place do not explain everything. No combination of soil and season,
however favourable, will produce a harvest unless the seed has been
sown. It holds as true now as it ever did, that " if we possessed
the requisite knowledge, the disease could always be traced back in
lineal descent to its origin in some poor Hindoo on the banks of the
Ganges, as certainly as the pedigree of a horse or dog can be fol-
lowed to his remote ancestors."

* The numbers express the mortality from cholera in Prussia during the
thirteen years, 1848-1860.

1885.] on Cholera : its Cause and Prevention. 303

Notwitlistancling the overwliclming evidence wliich now exists in
proof of the harmlessness of the so-called " rice-water evacuations,"
it is not the less certain that the mechanism by which the infection
of the soil takes place (i. e. by which the disease from being epidemic
becomes epichthonic) is its contamination by the discharges of sick
persons. For there is no other possible way by which the soil can
acquire the morbific property which facts compel us to attribute to
it. Similarly, it may be regarded as absolutely certain that the in-
fluence of the soil on those who are infected by it is due to the
penetration into their bodies of infective material, either by respira-
tion or swallowing ; that, in the absence of proof of " cholera-dust,"
it is a matter of urgent necessity to avoid the use of water which
contains such material as from its chemical nature may be reason-
ably considered capable of harbouring infective microphytes.

Id this country and in our Indian possessions experience has led
us to do the very things which science, were her opinion asked,
would approve as of primary importance. In Calcutta, the
measures of sanitary improvement, particularly drainage works,
which have been carried out under the highly efiicient sanitary
administration there, have during the last dozen years led to a
diminution of the cholera mortality to something like a third
of its previous average, and similar good results have been obtained
elsewhere in India, in so far as it has yet been possible to bring
about the necessary reforms. In London we have been lavish
m ' our underground expenditure. Our water supply is good and
abundant, and our subsoil is dry, so that dwellers in the west and
north need not feel much apprehension even though cholera were
again to fix itself in the east. But we may, I think, venture to
anticipate that this year, at least, we shall not be tried. Cholera, had
it intended to attack us this season, would already have been on the
march. The eastern provinces of Spain are suffering severely, and
it can scarcely be hoped that other parts of the Mediterranean will
remain exempt ; but Central Europe is free. Hitherto cholera has
come to us from Holland or Germany, not from southern Europe, so
that until the Ehine, the Elbe, the Oder, or the Vistula are threat-
ened we need be in no immediate apprehension as to the Thames or
the Mersey. But in venturing on this favourable forecast, I would
beg the reader to understand that I speak with no authority, and
recognise his competence to judge as well as I can of its value.
Neither science nor experience affords a key to the reasons why
cholera now follows one course, now another, in its wanderings over
the world.

I J. B. S.]

304 Mr. Walter H. Pollock on Garrich as an Actor. [May 22,

WEEKLY EVENING MEETING,

Friday, May 22, 1885.

Sir William Bowman, Bart. LL.D. F.R.S. Manager and
Vice-President, in the Chair.

Walter H. Pollock, Esq. M.A.

Garrich as an Actor.

The lecturer began by a brief reference to Garrick's brilliant place
amid a crowd of persons distinguished in all kinds of ways who
flourished at the same time with him, and to the brilliant career with
the main features of which his audience was no doubt acquainted.
He proposed to dwell not on them, but on the curious and minute
accounts of Garrick's acting in certain parts preserved by eye-
witnesses of skill and experience. Lichtenberg on Abel Drugger, on
Sir John Brute, and on Hamlet, was quoted in a translation, and his
account was compared with that given by Davies, the friend of
Johnson, who was an actor and a bookseller, a man of singular talent,
reading, and judgment, and the biographer of Garrick as well as the
author of a book full of interest called ' Dramatic Miscellanies,' fiiom
which many passages were quoted. Other authorities were referred
to in the same way and with the same kind of illustration that was
given to these two. Garrick's dramatic alterations of Shakspeare
were referred to and passages given from one of the worst of them,
the Borneo and Juliet. It was at the same time pointed out that
Garrick had done much for other plays of Shakspeare in the way of
restoring the original text to the stage. The lecturer concluded by
citint^ passages from the Garrick Correspondence, which seemed to
prove conclusively that Garrick was what we now call a " mannered "
actor— and he devoted the last part of his lecture to arguing that so-
called " mannerism," in other words individuality, is not necessarily
a bar to the faculty of impersonation of a very various kind ; that it
is, on the contrary, when allied with genius, in other arts as in acting,
the very quality which engages and keeps attention. " Out of being
nothing but yourself" the lecturer said, " nothing can come. Out of
being everything but yourself nothing can come. Genius hits the
mark between the two and commands success and admiration."

[W. H. P.]

1885.] Mr. Coleman and Prof. McKendricJc on Cold, dc. 305

WEEKLY EVENING MEETING,

Friday, May 29, 1885.

William Huggins, Esq. D.C.L. LL.D. F.R.S. Manager and
Vice-President, in the Chair.

J. J.. Coleman, Esq. F.C.S. F.I.C. and Professor J. G. McKendrick,
M.D. LL.D. F.E.S.

The Mechanical Production of Cold and the Effects of Cold upon
3Iicrophytes.

This discourse was delivered by Mr. J. J. Coleman, and embraced
two parts, viz. 1st, a description of his own researches and their
application in the construction of cold-producing machines ; and
2nd, a description of a joint research undertaken by Professor
McKendrick and himself upon the effects of very low temperatures
upon microphytes.

Mr. Coleman pointed out that in the first place the title of the
discourse might be objected to, inasmuch as it was scarcely correct
to speak of the " production of cold." As, however, long usa«e had
made the phrase conventional it would be used in the sense of
meaning production of a state of coldness.

A close examination of all known methods of producing cold by
artificial means involved the employment of some volatile liquid
or compressed vapour capable of spontaneously expanding. Thus,
commencing with water, its spontaneous evaporation produced the
state of coldness of the domestic water-cooler.

The evaporation of ether, as in the spray used by surgeons ; also
the evaporation of liquid sulphurous acid, which boiled at — 10° C. •
of liquid carbonic acid, which boiled at — 78° C. ; of liquid nitrous
oxide, which boiled at — 86° C; of liquid ethylene, which boiled at
~ 102° C. ; or of liquid air, which boiled at - 191° C, were all
perfectly analogous to the spontaneous expansion of compressed air,
when released from pressure by opening the cock of a vessel
containing it.

The nearer the compressed vapour is to the state of a perfect
gas, or of a hypothetical perfect gas, the more exactly is the heat
absorbed by expansion balanced by the heat generated by the friction
of the molecules before coming to rest. This followed from the
joint researches of Sir William Thomson and Dr. Joule conducted
thirty years ago.* These eminent men, in a classical series of
experiments, the description of which occupies 122 pao-es of Sir

* " On the Thermal Effects of Fluids in Motion." See collected papers of Sir
W. Thomson, vol. i. Cambridge University Press, 1882.

Vol. XL (No. 79.) ' x

306 Mr. Coleman and Prof. McKendrick [May 29,

William Thomson's researches, and involved upwards of 1000 obser-
vations collected in 50 tables, demonstrated among other things
that air having a pressure of 100 lb. per square inch, when passed
through a porous plug so as to reduce its pressure to that of the
atmosphere, only becomes cooled to the extent of 1 • 6^ C, hydrogen
gas similarly expanded being heated 0* 116° C.

Free expansion of atmospheric air under pressure through a
small orifice of any kind was similar in its results, which Mr.
Coleman demonstrated by expanding a cubic foot of air of several
atmospheres pressure into a glass reservoir or chamber containing
a delicate air thermometer, which was not in the least affected,
although the result was thrown upon the screen magnified and
illumined by a beam of electric light.

It was otherwise, however, when the experiment was made as
originally conducted by Gay Lussac and Dr. Joule, in which case
the vessel containing the air being expanded became cold, and the
vessel into which the air flowed became hot, the one phenomenon
neutralising the other.

Mr. Coleman showed by an arrangement of his air thermometer,
the index of which was projected upon the screen, that the vapour
which exists in an ordinary bottle containing a little liquid ether has
sufficient tension to cause friction and production of heat in escaping
through a narrow orifice.

In this case the heat abstracted from the evaporating liquid was
compensated by the latent heat absorbed in conversion of the ether
liquid into ether gas + the heat caused by the vis-viva of the escaping
molecules coming into contact with the walls of the orifice and
afterwards with the external atmosphere.

The apparatus used was called a " Tripatmoscope " and was con-
structed as follows: —

a is a bottle of say i of a cubic foot capacity containing a small
quantity of liquid ether, and into the neck of which was fitted by an
indiarubber cork a glass funnel, c is a plug of boxwood cemented
into the funnel bowl, and having an annular aperture barely sufficient
to admit the thin copper cylindrical bulb d of an air thermometer say
J-inch diameter and 6 inches long and packed tight into the boxwood
by making the bulb a little sticky with mastic varnish and winding
round it fine cotton thread. On opening the cock x at intervals of a
few minutes, a marked fall of the water index lo occurred which was
magnified and illumined by a beam of electric light — indicating nearly
1° F. produced by friction of escaping vapour.*

The statement that is met with in some text-books, that no cold
can be produced by exjianding air without mechanical work being
performed, is not strictly correct, as one fraction of a given volume of
air can be cooled by blowing the other fraction into the atmosphere ;
but all such methods of producing cold are, however, from an engi-

* This instrument works best in an atmosphere of about 70° F., but with a
slight occasional agitation of the liquid ether gives good results at 60°.

1885.]

on the Mechanical Production of Cold^ dc.

307

neering point of view, wasteful, for to make an economical machine
energy must be abstracted from the expanding medium (generally

308 Mr. Coleman and Prof. McKendrick [May 29,

in the form of mechanical power, but not necessarily, as for instance
in the ammonia absorption machine) before the ivhole volume of
the gaseous medium can be reduced in temperature, and not only
is this necessary, but in order to enable the medium, when it has
arrived at atmospheric temperature, to be employed for a fresh cycle of
operations, energy must be introduced and then rejected.

In the case of atmospheric air the energy used in compression
appears as heat every cycle which has to be rejected, and this is
accomplished either by washing the air with injected water or by
passing it through tubes surrounded by water.

Some idea of the heat required to be removed each cycle is afforded
by the fact that compression of air to the extent of 65-86 lb. per
square inch above the atmosphere increases its temperature by 332^ F.

It is now about five years since machinery of this kind came into
extensive use, and for a long time there was a curious controversy
amongst engineers as to the two methods of removing the heat pro-
duced by compression. It was maintained that the water injection
would wet the air, but the lecturer showed by expanding a cubic foot
of air at 100 lb. pressure per square inch standing over water in the
theatre of the Institution, that on emerging from the iron bottle
containing it, it was exceedingly dry, which indeed followed from the
fact discovered by Dalton that saturated vapour is liquefied by com-
pression at a constant temperature, in direct proportion to the degree
of compression. In practice, however, especially at sea, the air pressure
is kept about 50 lb., and the dryness of the air is further ensured
by passing it, on its way to the expansion cylinder, through an inter-
changer, around the outside of which the partially cold air flowing
to the compressor is made to circulate.

A number of large diagrams and a complete model were shown,
showing the general construction of the cold-air machines used
for imj)orting meat into Great Britain, all of which were now manu-
factured after the general designs introduced by the lecturer a few
years ago and described to the Institution of Civil Engineers in his
paper read there in February 1882.

By means of these machines Australian, Eiver Plate and New
Zealand mutton comes into Great Britain at the rate of 18,000 sheep
or 400 tons per week, which represents a weekly procession a mile
long and ten abreast. The quantity of American meat carried by the
machines is still larger, so that the British householder is now
supplied by them with meat to the value of between 4,000,000/. and
5,000,000Z. j9er annum, calculated at the price of meat in retail shops.*

These machines, in an ordinary way, supply streams of atmo-
spheric air cooled to about 80° below zero F. ( - 63° C.) ; but, by
certain modifications, tliey can be adjusted to deliver the air cooled

* According to the Smithfield Market reports, 27,007 tons of mechanically
cooled meat arrived from U. S. America in 1884, and 5500 tons Australian,
New Zealand, and River Plate frozen mutton in first three months of 1885.

1885.] on the Mechanical Production of Cold, dc. 309

much lower, and, in point of fact, to as low temperatures as have
yet been produced in physical researches.

For the purposes of the conjoint experiments with Professor
McKendrick, a machine, worked by a gas motor engine, capable of
delivering 30 cubic feet of air (-84 cub. metre) per minute, was
employed, the cold air being made to pass upward in a square vertical
shaft of wood, in the sides of which were apertures regulated by
valves, and by means of which about a dozen chambers, each of 3 cubic
feet capacity ( • 084 cub. metre), could be maintained at any particular
temperature desired. These tem23eratures were carefully taken by
an absolute alcohol thermometer, made by Negretti and Zambra,
and checked by a special air thermometer devised by Mr. Coleman.

The experiments consisted in exposing for hours to low tempera-
tures putrescible substances in hermetically sealed tins or bottles, or in
flasks plugged with cotton wool ; the tins or flasks were then allowed
to thaw, and were kept in a warm room, the mean temperature of
which was about 80^ F. (27° C.) ; they were then opened and the con-
tents submitted to microscopical examination with magnifying powers of
from 250 to 1000 diameters. The general results were as follows : —

1. Meat in tins (4 J inches in diameter, and 1 inch in depth),
exposed to 80^ below zero F. ( - 63^ C.) for six hours, underwent
putrefaction with generation of gases.*

2. Whilst these experiments were going on, comparative experi-
ments were made with tins and bottles containing meat, but not
exposed to cold. Under such circumstances, the efiects of storing
them in the warm room for even the short period of a fortnight, was
to develop such large quantities of extremely foetid gas, and very
active bacteria and vibrios, that there was no doubt whatever but
that exposure to a cold of 80° below zero (63° C.) had checked their
development to some extent in the subsequent exposure to a warm
temperature.

3. On the 24th of December, 1884, thirty samples of fresh meat
were placed in 2-oz. white glass phials. These were carefully corked
with corks previously steeped in mastic varnish, and the necks of the
corked bottles were then immersed in melted sealing-wax. These
bottles were divided into five sets, and marked A, B, C, D, and E,
and they were treated as follows : —

A. 6 samples were exposed to zero F. (- 17° C.) for 65 hours.

B. 6 „ „ - 20° F. ( - 29° C.)

C. 6 „ „ - 30° F. (- 34° C.)
r>. 6 „ „ -40°F. (-40°C.)
E. 6 „ „ -80°F. (-62°C.)

* July 1885. — At this date, which is eight months from the commencement
of the experiment, several of the sealed -up tins are on hand ; the bulging of
the tins and apparently the generation of gases ceased after the first month
the organisms being apparently rendered inactive by their own effluvia, or
from want of oxygen. There is now very little smell on opening the tins,
but a large number of organisms are visible with a |-iuch object-glass— alive
and active. — [J. J. C]

310 Mr. Coleman and Prof. McKendrich [May 29,

These experiments ended on 28th December. On the 29th one
bottle from each group was again exposed to — 80° F. ( — 63° C.) for
six hours, then again frozen for six hours at — 80° F. ( — 63° C). The
whole of those were removed to the room, but in the meantime it
was noticed that at temperatures below zero, and particularly so
low as — 80°F. (— 63° C), the meat assumed a peculiar dirty-brown
appearance. In the course of a few hours, however, the whole
of the samples assumed at normal temperatures the well-known
reddish colour of meat. In all cases, however, in the course of ten
or twelve hours after removal to the warm room, signs of putrefac-
tion were visible, and in the course of a few days, the putrefactive
process was fully established. It is important to notice that the
temperature reached in these experiments, namely, from — 70° to — 80°
F. (— 56° to — 63° C), is about the minimum degree of cold hitherto
observed in Polar expeditions.*

4. It is well known that freezing muscle taken from a newly-
killed animal, prevents the coagulation of muscle-plasma, and that
the plasma can, on partial thawing, be squeezed out of the muscle and
allowed to coagulate. It occurred to the lecturers that if muscle were
suddenly exposed to extreme cold, before cadaveric rigidity had set
in, some change might be observed in the putrefactive process.
Accordingly a rabbit was instantaneously killed, portions of its
muscles were at once placed in stoppered bottles and transferred to
the cold chamber, then having a temperature of about — 80° F.
They were kept there for ten hours ; then allowed to thaw partially
in the cold chamber, whilst the cold-air machine was not at work ;
then again frozen for twelve hours; and finally transferred to the
warm room. In these circumstances, they underwent rapid putrefac-
tion. The samples seemed to be more moist than other specimens
of ordinary butcher meat, and they certainly underwent more rapid
putrefaction.

5. A further set of experiments with meat was carried out, in
which the samples were continuously exposed to a temperature of
from - 90° to - 120° F. ( - 83° C.) for 100 consecutive hours; the
bottles were then removed to the warm room, with the result that
in ten or twelve hours the putrefactive process seemed to be fully
established.

5a. It has been shown by Pasteur | that if putrescent or ferment-

* The lecturers have been favoured with the following remarks by Mr.
Alexander Buchan, the eminent meteorologist, to whom they applied for infor-
mation. " So far as I am aware, or can discover, the temperature of - 73*7° F.
registered on board the Alert in March 1876, is the lowest temperature yet
observed anywhere in the free atmosphere. The lowest mean monihJi) tempera-
ture known is — 55 8° F.for January, at Werchojansk (lat. G7° 3i' N., and long.
133° 51' E.), in north-eastern Siberia." It is possible that one or more of the
individual observations tliat make up this low mean may have given a reading
lower than - 73-7° F.

t Comptes^Rendus, Ivi., 734-1189. See also article " Fermentation," Watt's
* Dictionary of Chemistry,' First Supplement, p. 612.

1885.] on the Mechanical Production of Cold, &c. 311

ing substances are sealed up in a comparatively small space contain-
ing air, the processes are arrested when all the oxygen has been used
up, and the products of putrefaction may undergo no further altera-
tion. In these circumstances, in such experiments as ours, the
apparent arrest of putrefaction in sealed vessels might have been
attributed to the action on the organisms of the low temperature to
which they had been exposed, instead of to the real cause — the
removal of all the oxygen from the confined air. To meet this
difficulty the importance was seen of testing the effect of cold on
putrescible substances placed in test tubes and flasks firmly plugged
with cotton-wool, through which there might be a free play between
the gases in the tube or flask and the surrounding atmosphere. Nor
was it necessary in such experiments to sterilise the cotton- wool by'
heat, as must be done in all researches on the effects of high
temperatures, because if a low temperature were fatal to micro-
organisms, it would kill those in the cotton-wool as well as those
in the putrescible substances. Many experiments were made with
tubes and flasks stopped with cotton-wool plugs instead of being
hermetically sealed, but there was no difference in the general
result.

6. Six flasks were filled with fresh urine, and plugged with
cotton- wool, on the 10th of December. The first one plugged with
wool was exposed to the temperature of the engineering shop where
the experiments were carried on (about 50^ F.), and on the 13th the
urine was muddy ; on the 18th it was found to be swarming with
bacteria and vibrios. The second was exposed for eight hours to
zero F. ; on the 13th it showed slight muddiness, and on the 18th it
was swarming with bacteria. The third was exposed to a tempera-
ture of — 10^ F. for eight hours, and on the 18th it was also
swarming with bacteria. The fourth was exposed to — 20° F. with
the same result. The fifth was exposed to — 30° F. with a like
result. The sixth was exposed to — 80° F., and it did not become
muddy until the 22nd, that is, twelve days after the beginning of
the experiment. These results showed that freezing at very low
temperatures delayed the appearance of the alkaline fermentation
due to organisms, but a temperature of — 80° for eight hours did
not sterilise the urine.

7. Samples of fresh milk, exposed to temperatures of from zero to
— 80° F. for eight hours, curdled, and showed the well-known
bacterium lactis, and, so far as could be observed, freezing did not
delay the process after the flasks were kept at a temperature of about
50° F.

8. Samples of Prestonpans beer (containing about 2 per cent, of
alcohol) were similarly treated. Exposed to the air of the shop, a
scum of torulae made its appearance in three days- Freezing un-
doubtedly delayed the appearance of these in flasks plugged with
cotton-wool, and the delay corresponded to the fall of temperature,
so that the sample exposed to — 80° F. did not show the scum for

312 Mr. Coleman and Prof. McKendrick [May 29,

twenty-two days after its removal from the cold chamber. Still it
could not be said that this degree and duration of cold sterilised the
fluid.

9. Samples of sweet ale behaved in a precisely similar manner.

10. Samples of meat juice, made by boiling lean meat, filtering,
and carefully neutralising, were also operated on, both in flasks
hermetically sealed and having the necks stuffed with cotton-wool.
Exposed to temperatures of from zero to - 80^ F. for eight hours,
all of these in due time showed, under the microscope, numerous
bacteria, but the freezing process undoubtedly delayed their appear-
ance, and this was most marked in the samples exposed to the
lowest temperatures.

11. Samples of neutralised vegetable infusion behaved in a
similar way.

12. Many experiments were made with putrefying fluids, full of
bacteria and other micro-organisms. The method followed was to
examine the fluid with the microscope, and to note the appearances of
the organisms. Then portions of the fluid were placed either in a
flask plugged with cotton-wool or in a hermetically-sealed flask, and
exposed to the lowest temperature attainable —namely, — 120^ F.
In one set of experiments such organisms were exposed to — 120^ F.
for 100 consecutive hours. The thawed fluid was again examined
microscopically, with the result of showing that the organisms were
motionless. Still it could not be asserted that they, or at all events
their spores, were dead, as, after exposure to a temj)erature of 80° F.
for a few hours, the fluid was found to be again teeming with
organisms in active movement. The conclusion arrived at was that
such prolonged exposure to cold did not kill them all, probably
leaving spores unaffected.

13. It was also attempted, by repeated freezings and thawings, to
kill micro-organisms, as it was conceivable that cold might kill the
adults only, leaving the spores unaffected. If, then, the spores were
killed as they approached maturity, and before they had produced
new spores, it might be possible to sterilise the fluid. All attempts
in this direction were unsuccessful.

14. Experiments were also made with gelatinous infusions of meat,
to which grape sugar had been added. Exposure to low tempera-
tures and thawing did not destroy the gelatinous character of the
substance, but putrefaction was not prevented. Such gelatinous
masses, after exposure for 100 consecutive hours to — 120^ F.,
and subsequently for fifteen to twenty hours in a warm room of 80°
F., became filled with bubbles of imprisoned gas, each bubble being
the outcome of one or more organisms.

15. It is a striking consideration that freezing at low tempera-
tures makes a mass of organic matter solid throughout, so that it
can only be broken to pieces by violent blows of a hammer. Beef
has then a fractured surface like a piece of rock. Mutton is friable.

1885.] on the Mechanical Production of Cold, &c, 313

Still, when such a mass — say a piece of muscle — is thawed, its micro-
scopical structure seems to be unaltered. All that can be said is that
it is moister than ordinary fresh muscle. It is probable, therefore,
that the bodies of micro-organisms are also frozen solid, and yet
they apparently may live for a long time in this condition. One
cannot suppose that in these circumstances any of the phenomena of
life take place ; the mechanism is simply arrested, and vital changes
may again occur when the conditions of a suitable temperature
return. Such considerations led the lecturers to examine whether
any of the vital phenomena of higher animals might be retained at
such low temperatures. It was ascertained that a live frog may be
frozen quite solid throughout at a temperature of from ~ 20° F. to
— 30^ F. in about half an hour. On thawing slowly, in two instances,
the animal completely recovered. When kept in the cold chamber
longer than half an hour, the animal did not recover, but the
muscles and nerves were still irritable to electricity, responding to
weak induction shocks. Keflex action, however, was abolished. In
two cases, frogs were exposed for twenty minutes to a temperature
of — 100^ F. On thawing, they did not recover, but the muscles
still feebly responded to electrical stimulation, showing that their
irritability had not disappeared. The probability is that longer
exposure to this temperature, or exposure for a shorter time to a
lower temperature, would destroy muscular and nervous irritability,
but it is a striking fact that irritability can survive to any degree a
transition through a state of solidity produced by cold.*

16. One experiment was performed on a warm-blooded animal —
a rabbit. Before the experiment, the temperature of the rectum
was 99 "2° F., pulse 160 per minute, respirations about 45 per minute.
At 10 '80 A.M. it was placed in the cold chamber, the thermometer
of which stood at — 93^ F. At 11 a.m. it was removed for a minute
or two ; it did not seem to be affected, but the temperature of the
rectum was now 94 • 2^, a fall of 5° in half an hour. It was then re-
introduced into the cold chamber, the temperature of which was read
off at — 100^ F. It was taken out at 12 noon ; it seemed to be
comatose ; reflex action was abolished ; there were jerking movements
of the limbs ; its rectal temperature was now 43^ F., a fall of 51°
during the hour ; its pulse was 40 per minute, being a fall of 120 ;
and its respirations were barely perceptible. It was placed in a warm
place, and it began slowly to recover. In fifteen minutes its tem-
perature had risen to 72° F., in ten minutes more to 89° F. Its
pulse beats when removed from the chamber were 40 per minute, in
fifteen minutes they had risen to 60 per minute, and in fifteen
minutes more to 100 per minute. The animal completely recovered.
When removed from the chamber at 12 noon, although reflex action

* Kuhne observed that a frozen frog's muscle will contract after thawing, but
the temperatures he reached were not low.

314 M)\ Coleman and Prof. McKenclrich [May 29,

was abolished, the muscles were still irritable to electrical stimula-
tion, and on placing the wires over the sciatic nerve without cutting
the skin, strong spasms of the muscles of the leg were caused, showing
that the nerve was still irritable. It follows, therefore, that some
of the effects of the extreme cold were due to inactivity of the nerve
centres. Consciousness and reflex action were abolished, owing to
inactivity of the grey matter of the encephalon and of the spinal
cord.

The effect of the extreme cold on the warm-blooded or homoio-
thermal animal, as contrasted with its effect on the cold-blooded or
poikilothermal animal, is very striking. The cold-blooded frog
became as hard as a stone in from ten to twenty minutes, and the
temperature of its body was probably the mean temperature of the
chamber ; the warm-blooded animal produced in itself so much heat
as enabled it to remain soft and comparatively warm during exposure
of an hour's duration to — 100° F. Still its production of heat
was unequal to make good the loss, and every instant it was losing
ground, until, at the end of the hour, its bodily temperature had fallen
about 56° F. below its natural temperature. Had it been left in
the chamber long enough, its bodily temperature would have fallen
until it reached the temperature of the cold chamber, and it would
then have become as hard as the frozen frog. It is remarkable, how-
ever, that even at the end of an hour's exposure to — 100° F., its
bodily temperature was 143° above — 100° F. As blood freezes and
the haemoglobin crystallizes at about 25° F., had the temperature of
the body fallen below that point, the animal would not have re-
covered, as its blood would have been destroyed.

The lecturer observed that several researches had been made, prior
to those of himself and Professor McKendrick on the influence of
cold, none of them, however, very decisive as regards the microphytes
concerned in the putrefactive processes. Thus, before 1872, we find
Dr. Ferdinand Cohn ^ stating that he had subjected bacteria to low
temperatures without destroying their activity. He gives the
temperatures as follows : — Exposure for 12 hours 30 minutes to a
temperature 0° C. ; for Ih. 30m. to- 16° C. ; for Ih. 45m. to
- 17° C. ; for 3h. 30m. to - 18° C. ; for 4h. 30m. to - 18° C. ; for 5h.
to - 17-5° C. ; for 6h. to - 14° C. ; and for 7h. 30m. to - 9° C. He
produced the cold by freezing mixtures, and the lowest temperature
he obtained was - 18° C. = 0° F. In 1870-71, M.Melsens exposed
yeast and vaccine lymph to very low temperatures ( — 78° C), by means
of solid carbonic acid, without destroying the power of fermentation
or inoculation.f

Klein J states that " Freezing destroys likewise most bacteria,

* Cohn's Beitrage zur Biologie der Pflanzcn, 1870, Zweites Heft, p. 221.
t Melsens, Comptes Rendus, Todjg Ixx., 1870, p. G20 ; also Coniptes Rendus,
Tome Ixxi., p. 325.

X Klein, Micro-organisms, p. 35.

1885.] on the Mechanical Production of Cold, dc. 315

except the spores of bacilli, which survive exposure to as low a
temperature as — 15^ C, even when exposed for an hour or more."
Again, in another place, * he says : " Exposing the spores of anthrax-
bacillus to a temperature of 0° to — 15^ C. for one hour did not kill
them."

In 1884 a remarkable series of experiments were described to the
French Academy, by MM. R. Pictet and E. Yung.-f These observers
sealed up in small glass tubes fluids containing various kinds of
microphytes, and placed them in a wooden box. The box was in the
first place submitted for 20 hours to a cold of -- 70^ C, produced by
the evaporation of liquid sulphurous acid in vacuo. The box was
then surrounded by solid carbonic acid for 89 hours, and a cold of from
■- 70° to — 76° C. was thus obtained. Finally, the box was subjected for
a third period of 20 hours to a cold produced by the evaporation of
solid carbonic acid in vacuo — the temperature being estimated at from
— 76^ to — 130° C. — that is, a minimum temperature of 202° below
zero F. They sum up by stating that the organisms were acted
on by a cold of — 70° C. for 109 hours, followed by a tempera-
ture of — 130° for 20 hours. The organisms tested were Bacillas
anthracis, Bacillus suhtilis, Bacillus ulna, Micrococcus luteus, and a
micrococcus not determined. Bacillus anthracis retained its virulence
when injected into a living animal. The vitality of the others was
not affected. Experiment showed that, whilst cold seemed to kill
some of the micrococci, a great number resisted it. Yeast showed no
alteration under the microscope, but it had lost its powers of fermen-
tation. Vaccine lymph exposed to the low temperatures did not pro-
duce a pustule on the left arm of an infant, whilst another samj)le of
the same lymph introduced into the right arm of the same child pro-
duced a pustule. Pictet and Yung conclude, from their experiments,
that, in the conditions of cold indicated, many of the lower organisms
were not destroyed.^

From this concensus of evidence, Mr. Coleman observed, it then
appears that any hope of permanently sterilising meat by cold (the
counterpart of Appert's process by heat) must be abandoned, but it is
quite possible that at some point near absolute zero the vitality of all
microphytes may be destroyed.

The persistency, however, of their vitality between great extremes
of temperature, ranging in fact through 400° F. is very remarkable,
and is in marked contrast to their susceptibility to destruction by

* Klein, op. cit, p. 73.

t Comptes Eendiis, Tome xcviii., No. 12 (24 Mars, 1884), p. 747.

j lu a letter to Dr. McKendrick, Professor Arthur Gamgee states that some
months ago lie exposed putrescible fluids to moderate degrees of cold without
thereby preventing putrefaction, and that he abandoned the research as unlikely
to lead to any important result with the temperature he had at command. It is
also stated in Landois' Physiology, translated by Stirling, vol. i., p. 456, on the
authority of Frisch, that " bacteria survive a temperature of — 87° C. ; yeast
eveu - 100° C."

316 Mr. Coleman and Prof. McKendricJc on Cold, &c. [May 29,

moist ozone, peroxide of hydrogen, and by sunlight or diffused
daylight.*

There can be no doubt about disease germs being pestiferous, but
it is quite possible the function of many microphytes is beneficent,
preventing the undue accumulation of dead organic matter, though it
is not quite clear that they are absolutely essential as a preliminary
to its oxidation, and on this and kindred subjects there is much work
yet to be done by the united labour of the physicist, chemist, and
physiologist.

[J. J. C]

* ' Researches on the Effect of Light upon Bacteria and other Organisms,' by
Arthur Downes, M.D., and J. P. Blunt, M.A., Proc. Roy. Soc. xxvi. 1877.

1885.] Genei-al Monthly Meeting. 317

GENERAL MONTHLY MEETING
Monday, June 1, 1885.

The Duke of Northumberland, D.C.L. LL.D. President,
in the Chair.

Raphael Meldola, Esq. E.C.S. F.I.C.
Colonel George Swinton, R.E.

were elected Members of the Royal Institution.

The following Letter was read : —

Maelbo ROUGH House,

Pall Mall, S.W.,

Dear Sir, n ^ay, i885.

I am desired by Prince Albert Victor and Prince George of Wales to
acknowledge the receipt of your letters of the 4th instant, and to request you to
be good enough to convey to the Members of the Koyal Institution of Great
Britain their Koyal Higlmesses' best thanks for having elected them Honorary
Members of the Institution.

I remain, dear Sir,

Yours very faithfully,

M. HOLZMANN.

Sir Frederick Bramwell, F.E.S.

Honorary Secretary, R.I.

The Presents received since the last Meeting were laid on the
table, and the thanks of the Members returned for the same, viz. —

FROM

The French Government — Documents Inedits sur I'Histoire de France :
Lettres de Catherine de Medicis. Par Comte H. de la Ferriere. Tome II.

1563-6. 4to. 1885.
Receuil des Chartres de FAbbaye de Cluny. Par A. Bruel. Tome III.

987-1027. 4to. 1884.
Ministry of Public Works, jRo?we— Giomale del Genio Civile, Serie Quarta,

Vols. I.-IV. and V. Nos. 1-4. 8vo. And Disegni. fol. 1881-5.
Accademia' dei Lincei, Reale, Roma — Atti, Serie Terza: Rendiconti. Vol. I.

Fasc. 9, 10, 11. 4to. 1885.
Academy of Natural Sciences, Philadelphia — Proceedings, 1885, Part 1. 8vo. 1885.
Agricultural Society of England, Royal— Jomnol, Second Series, Vol. XXI. Part 1.

8vo. 1885.
American Philosophical Society — Proceedings, No. 116. 8vo. 1884.
Register of Papers in Transactions and Proceedings. 8vo. 1884.
Astronomical Society, Royal— 'Monthly Notices, Vol. XLV. No. 6. 8vo. 1885.
Atheneo do Po/-^o— Revista Scientifica, No. 4. 8vo. 1885.
Banhers, Institute of— Journal, Vol. VI. Part 5. 8vo. 1885.
British Architects, Royal Institute o/— Proceedings, 1884-5. Nos. 13, 14. 4to.
British Association for the Advancement of Science — Report of Meeting at Montreal,

1884. 8vo. 1885.
Chemical Society— Journal for May, 1885. 8vo.
Civil Engineers' Institution— Minutes of Proceedings, Vol. LXXIX. 8vo. 1885.

318 General Monthly Meeting. [June 1,

Duka, Theodore, M.D. F.R.C.S. M.R.L Qlie Aunwr)—h\ie and Works of Alex-
ander Csoma de Koros. 8vo. 1885.

Declaration by Soldiers of the Hungarian Army (1848-9). Translated by
A. J. Patterson. 8vo. 1884.
Editors— A.me\'\ca.n Journal of Science for May, 1885. 8vo.

Analyst for May, 1885. 8vo.

Athenaeum for May, 1885. 4to.

Chemical News for May, 1885. 4to.

Engineer for May, 1885. fol.

Horological Journal for May, 1885. Svo.

Iron for May, 1885. 4to.

Nature for Mny, 1885. 4to.

Revue Scientifique for May, 1885. 4to.

Science Monthly, Illustrated, for May, 1885. 8vo.

Telegraphic Journal for May, 1885. 8vo.
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Geographical Society, Royal — Proceedings, New Series, Vol. VII. No. 5. Svo. 1885.
Geological Society — Quarterly Journal, No. 162. Svo. 1885.
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American Chemical Journal, Vol. VII. No. 1. Svo. 1885.

Studies in Historical and Political Science, Third Series, No. 4. Svo. 1885.
Linnean Society — Journal, No. 137. Svo. 1885.
Mechanical Engineers Institution — Proceedings, No. 2. Svo. 1885.
Meteorological Office — Meteorological Observations at Stations of the Second Order
for 1880. 4to. 1885.

Quarterly Weather Report, 1877, Part 2. 4to. 1885.

Hourly Readings, 1882, Part 4. 4to. 1885.
Numismatic Society— Gh-xomcle and Journal, 1885, Part 1. Svo.
Odontological Society of Great 5ntom— Transactions, Vol. XVII. Nos. 6, 7. New

Series. Svo. 1885.
Pharmaceutical Society of Great Britain— Journal, May, 1885. Svo.
Photographic Society — Journal, New Series, Vol. IX. No. 7. Svo. 1885.
Royal Dublin ;Soc/e<t/— Transactions, Vol. III. Nos. 4-6. 4to. 1884-5.

Proceedings, Vol. IV. Parts 5, 6. Svo. 1884-5.
Royal Society of ioncZow— Proceedings, No. 236. Svo. 1885.
Smithsonian Institution— Second Report of the Bureau of Ethnology, 1880-1. By

J. W. Powell. 4to. 1883.
Society o/ ^r^s— Journal, May, 1885. Svo.
Tasmania Royal Society— Bepovt for 1884. Svo. 1885.
Telegraph Engineers, Society o/— Journal, Vol. XIV. No. 56. Svo. 1885.
United Service Institution, i?o?/aZ— Journal, No. 128. Svo. 1885.
University of London — Calendar for 1885-6. Svo.
Vereins zur Beforderung des Gewerhfleisses in Preussen — Verhandlungeu, 1885:

Heft 4. 4to.
Victoria Institute— J omno], No. 73. Svo. 1885.

WEEKLY EVENING MEETING,

Friday, June 5, 1885.

The Duke of Northumberland, D.C.L. LL.D. President,
in the Chair.

Professor Dewar, M.A. F.R.S. MMJ.

Liquid Ail' and tJie Zero of absolute Temperature.

(Abstract deferred.)

1885.] General Monthly Meeting. 319

GENERAL MONTHLY MEETING,

Monday, July 6, 1885.

William Huggins, Esq. D.C.L. LL.D. F.R.S. Manager and Vice-
President, in the Chair.

Sir Isaac Lowthian Bell, Bart. F.K.S. F.C.S. M.I.C.E.

Edwin Drew, M.D. B.Sc.

John Montague Spencer Stanhope, Esq. J.P.

were elected Members of the Royal Institution.

The Special Thanks of the Members were returned for the follow-
ing donation to the Fund for the Promotion of Experimental
Research : —

The Hon. Sir William E. Grove, 25Z.

The Peesents received since the last Meeting were laid on the
table, and the thanks of the Members returned for the same, viz. :

The Governor-General of India — Geological Survey of India : Records, Vol. XVIII.

Part 2. 8vo. 1885.
Accademia dei Lincei, Reale, Roma — Atti, Serie Quarta: Rendiconti. Vol. I.

Fasc. 12. 8vo. 1884-5.
Memorie della Classe di Scienze Morali, Storiche e Filologiche. Serie 3^^,

Vols. 8, 10, 11. 4to. 1883
Memorie della Classe di Scienze Fisiche, Mathematiche e Naturali. Vols. 14-17.

4to. 1883-4.
Antiquaries, Society of — Archseologia, Vol. XL VIII. Part, 2. 4to. 1885.
Astronomical Societij, Royal — Monthly Notices, Vol. XLV. No. 7. 8vo. 1885.
Bankers, Institute of — Journal, Vol. VI. Part 6. 8vo. 1885.
Berdoe, Edward, Esq. {the Author) — Browning as a Scientific Poet. 8vo. 1885.
British Architects. Royal Institute of — Proceedings, 1884-5, No. 15. 4to.

L'Institut Koyal des Architectes Britanniques. 7^ Conference, 1884. Cantor-

beiy-Londres. Par 0. Lucas. 8vo. 1885.
British Museum {Natural History) — List of Cetacea. 8vo. 1885.
Canada, Geological and Natural History Survey of — Reports of Progress. With

Maps, &c. 1882-4. 8vo. 1885.
Catalogue of Canadian Plants, Part II. By J. Macoun. 8vo. 1884.
Chemical Society — Journal for June, 1885. 8vo.
Crisp, FranJc, Esq. LL.B. F.L.S. &c. M.R.I. (the Editor)— J ourmil of the Royal

Microscopical Society, Series II. Vol. V. Part 3. Svo. 1885.
Dax: Societe'de Borda — Bulletins, 2" Serie, Dixierae Anne'e, Trimestre 2. 8vo.

1885.
East India Association — Journal, Vol. XVII. No. 4, Svo. 1885.

320 General Monthly Meeting. [July 6,

Editors — American Journal of Science for June, 1885. 8vo.
Analyst for June, 1885. 8vo.
Athenaeum for June, 1885. 4to.
Chemical News for June, 1885. 4to.
Engineer for June, 1885. ful.
Horological Journal for June, 1885. 8vo.
Iron for June, 1885. 4 to.
Nature for June, 1885. 4to.
Revue Scientifique for June, 1885.
Science Monthly, Illustrated, for June, 1885.
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FrcmUin Institute— J ournsi\, No. 714. 8vo. 1885.
Geographical Society, i?02/aZ— Proceedings, New Series, Vol. VII. No. 6. 8vo.

1885.
Geological Institute, Imperial, FteMna— Abhandlungen, Band XI. Abtheilung 1.
fol. 1885.
Jahrbuch: Band XXXV. Heft 1. 8vo. 1885.
Verhandlungen, 2-7. 8vo. 1885.
Jahlonowslci'scheGesellschaft, Leipzig, Furstliche—Vrtis&chrih,'i^o. 25. 4to. 1885.
Johns Hopkins University — Studies in Historical and Political Science, Third
Series, Nos. 5-7. 8vo. 1885.
American Journal of Philology, No. 21. 8vo. 1885.
Linnean Society — Journal, No. 108. 8vo. 1885.

Manchester Geological /S'oc^ef?/— Transactions, Vol. XVIII. Parts 8, 9. 8vo. 1885.
Medical and Chirurgical Society, i^o^/aZ— Catalogue of the Library, Supplement III.

8vo. 1885.
Meteorological Office — Monthly Weatlier Report, February, 1885. 4to.
Meteorologiccd Society, Eoyal — Quarterly Journal, No. 54. 8vo. 1885.

Meteorological Record, No. 16. 8vo. 1885.
Ministerio da Marinha e C/ZZmmar— Cartas das Colonias Portuguezas : Angola.

1885.
North of England Institute of Mining and Mechanical Engineers-— Transactions,

Vol. XXXIV. Part 8. 8vo. 1885.
Oaldey, B. Esq. {the Author) -Favfect Ventilation, fol. 1885.
Pennsylvania, Second Geological Survey o/— Reports. 8vo. 1873-1884.
Pharmaceutical Society of Great Britain— J ouvivdl, June, 1885. 8vo.
Photographic Society — Journal, New St-ries, Vol. IX. No. 8. 8vo. 1885.
Physical Society of London — Proceedings, Vol. VI. Part 4. 8vo. 1885.
Robins, Edward C Esq. F.S.A. (the Author)— Papers on Technical Education,

Applied Science Buildings, Fittings, and Sanitation. 4to. 1885.
Society of ^rZs— Journal, June, 1885. 8vo.
Statistical Society -3 o\una\, Vol. XLVIII. Part 1. 8vo. 1885.
Thorn, Adam, Esq. LL.D. (the Author) — Emmanuel : the Scriptural Alphabets,

and the Metallic Image. (Pentaglot.) 8vo. 1885.
United Service Institution, Boyal — Journal, No. 129. 8vo. 1885.
United States Geological Survey— Coppei-Beaiing Rocks of Lake Superior. By

R. D. Irving. 4to. 1883.
Vereins zur Beforderung des Geiverhfleisses in Prewsseii— Veihandlungen, 1885:

Heft 5. 4to.
Wilson, W. E. Esq. M.R.I.— Thoughts on Science, Theology, and Ethics. By J.

Wilson. 12mo. 1885.
Zoological Society— Proceedings, 1885, Part 1. 8vo. 1885.

1885.] General Monthly Meeting. 321

GENERAL MONTHLY MEETING,

Monday, November 2, 1885.

Warren de la Rue, Esq. M.A. D.C.L. F.R.S. Manager and
Vice-President, in the Chair.

Joseph Wilson Swan, Esq.

Mrs. J. W. Swan,

General J. F. Tennant, R.E. F.R.S.

were elected Members of the Royal Institution.

The Special Thanks of the Members were offered to the President,
His Grace The Duke of Northumberland, for his gracious offer to
defray the cost of supplementing the electric lighting installation
of the Institution by the requisite number of accumulators.

The Presents received since the last Meeting were laid on the
table, and the thanks of the Members returned for the same, viz. : —

FROM

The Governor-General of India — Geological Survey of India: PalaQontulogia
Indica : Series X. Vol. III. Part 6 ; Series XIII. Vol. I. Part 4, Fasc. 5 ;
Series XIV. Vol. I. Part 8, Fasc. 5. 4to. 1885.
Memoirs, Vol. XXI. Parts 3-4. Svo. 1885.
Records, Vol. XVIII. Part 3. 8vo. 1885.
Ministry of Public TForAs, i?o)ue— Giornale del Genio Civile, Serie Quarta,

Vol. V. Nos. 5-8. Svo. And Disegni. fol. 1885.
Accademia dei Lincei, Eeale, Roma — Atti, Serie Quarta ; Eendiconti. Vol. I.

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Part 2, No. 1. 4 to. 1874-85.
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American Association for the Advancement of Science — Proceedings, Vol. V.-XVI.

XXII.-XXVI. XXVIII.-XXXII. Svo. 1851-85..
American Fhilosophiccd Society — Proceedings, Xos. 117-119. Svo. 1884.
Amsterdam Boyal Society of Zoology — Bijdragen tot de Dierkuude. Afl. 12. 4to.

1885.
Ashhicrner, Charles A. Esq. (the Author) — Anthracite Coal Fields of Pennsylvania,
Svo. 1884.
Publications of Second Geological Survey of Pennsylvania. Svo. 1884.
Asicdic Society, Eoycd—Jomnal, Vol. XVII. Part 3. Svo. 1885.
Asiatic Society of Bengcd — Proceedings, Nos. 1 -5. Svo. 1885.
Journal, Vol. LIII. Part 2, No. 3 ; Vol. LIV. Part 1, Nos. 1, 2. Svo. 1884.
Centenary Review, 1784 to 1883. Svo. 1885.
Astronomical Society, Boyal — Monthly Notices, Vol. XLV, No. 8. Svo. 1885.

Memoirs, Vol. XLVIII. Part 2. 4to. 1884.
Australian Museum, Sydney— Catalogne of the Australian Hydroid Zoophytes.

By W. M. Bale. Svo. 1884.
Bankers, Institute o/— Journal, Vol. VI. Part 7. Svo. 1885.

Vol. XI. (No. 79.) y

322 General Montlihj Meeting. [Nov. 2,

Basel Naturforschencle GeseUschaft—Vevlmndlnx^gen, 7te Thiel, Btes Heft. 1885.
Batavia Observatory— R?i\nU\\ iii the East Indian Archipelago, 1884. 8vo, 1885.
Belqique Acad^mie des Sciences, J-c. — Memoires, Tome XLV. 4to. 1884.

Me'moires Coiironnees, Tome XLVI. 4to. 1884. Tome XXXVI. 8vo. 1884.
Bulletins, 3^ Serie, Tomes VI. VII. VIII. 8vo. 1883-4.
Annuaires, 1884 and 1885. 16to.
British Architects, Boyal Institute ©/—Proceedings, 1884-5, No. IG ; 1885-G, No. 1.
4to.
Kalendar. 1885-6. 8vo.

Transactions, New Series, Vol. I. 4to. 1885.
Chemical ^oc/ef?/— Journal for July-Oct. 1885. 8vo.
Chief Signal Officer, U.S. ^rm?/— Professional Papers of the Signal Service, No. 15.

4to. 1884.
Civil Engineers' Institution — Minutes of Proceedings, Vol. LXXX. LXXXI.
LXXXII. 8vo. 1885.
List of Members. 8vo. 1885.

Heat in its Mechanical Applications. Lectures, 1883-4. 8vo. 1885.
Cornimll Polytechnic Society, Royal — Fifty-second Annual Report. 8vo. 1884.
Corporation of the City of London— Qolen&QX of Letters, 1350-1370. Edited by

B. R. Sharpe. 8vo. 1885.
Craicford and Balcarres, The Earl of, F.R.S. 3I.R.I.— Dim Edit Observatory
Publications: Vol. III. Mauritius Expedition, 1874, Division 2. 4to. 188.%
Criqy, Frank, Esq. LL.B. F.L.S. &c. M.E.I, {the Editor)— Sowan^X of the Royal

Microscopical Society, Series IT. Vol. V. Parts 4, 5. 8vo. 1885.
Bax : Socie'te' de Borda — Bulletins, 2« Serie, Dixieme Anne'e, Trimestre 3. Svo,

1885.
Department of the Interior, Z7./Sf.— Land Laws of the United States. 3 vol. Svo.
1884.
The Public Domain. Its History, with Statistics. By T. Donaldson. 8vo.
1884.
Devonshire Association for the Advancement of Science, Literature, and Art — Roi)ort
and Transactions," Vol. XVII. 8vo. 1885.
The Devonshire Domesday, Part 2. 8vo. 1885.
Dunant, H. Esq. {the Author)— The Pyrophone. (M 9) 4to. 1885.
East India Association- J omnal. Vol. XVII. No. 5. 8vo. 1885.
Editors — American Journal of Science for July-Oct. 1885. Svo.
Analyst for July-Oct. 1885. Svo.
Athenffium for July-Oct. 1885. 4to.
Chemical News for July-Oct. 1885. 4to.
Engineer for July-Oct. 1885. fol.
Horological Journal for July-Oct. 1885. 8vo.
Iron for July-Oct. 1885. 4to.
Journal of Science for July-Oct. 1885. Svo.
Nature for July-Oct. 1885. 4to.
Eevue Scientifique for July-Oct. 1885. 4to.
Science Monthly, Illustrated, for July-Oct. 1885. Svo.
Telegraphic Journal for July-Oct. 1885. Svo.
Fatigati, Professor E. S. (the Author) — Reacciones quimicas en el campo del

Microscopio. (O 19) (With Photographs) MS. 1885.
Franklin Institute— J omu^l, Nos. 715, 71G, 717, 718. Svo. 1885.
Eraser, Lieut.- Col. A. T. R.E. M.B.I, {the ^uf/ior)— Darkness in the Land of

Egypt. (K 107) Svo. 1885.
Geographical Society, Boyal — Proceedings, New Series, Vol. VII. Nos. 7, 8, 9, 10.

Svo. 1885.
Geological Institute, Imperial, Ftewna— Jahrbuch : Band XXXV. Heft 2, 3. Svo.
1885.
Verhandlungen, S, 9. Svo. 1885.
Geological Society— Qunrtorly Journal, No. 1G3. Svo. 1885.
GUmjoif Philosophical Society — Proceedings, Vol. XVI. Svo. 1884-5.

1885.] General Monthly Meeting 323

Gordon, Surgeon- General C. A. M.D. C.B. M.R.I, (the ^?<</<or)— Analysis of

Correspoudcnce, &c. on Vivisection. (K 107) 8vo. 1885.
Gould, George, Esq. (the AutJwr) — Shuksperian Coirigenda. (K 107) 8vo. 1884.

Greek Plays in relation to Dramatic Unities. (K 107) 8vo. 1883.
Harlem, Societe Hollandaise des Sciences — Archives Ne'erlandaises, Tome XIX.

Liv. 4, 5; Tome XX. Liv. 1, 2. 8vo. 1884-5.
Birth, F. Esq. Ph.D. (the Author) — China and the Roman Orient: their Ancient

and Mediaeval Relations. 8vo. 1885.
Iron and Steel Institute— J ourna\ for 1885, No. 1. Svo.

Johiis Hopicins University — Studies in Historical and Political Science, Third
Series, Nos. 8, 9, 10. Svo. 1885.
American Journal of Philology, No. 22. Svo. 1885.
University Circular, Nos. 40, 41. 4to. 1885.
American Chemical Journal, Vol. VII. No. 2. Svo. 1885.
Kramer, F. H. Esq. (the Author) — Die Radikalheilung der Diptheritis. Svo. 1885.
Langley, S. P. Esq. (the Author) — The Temperature of the Surface of the Moon.

(M9) 4to. 1885.
Liveing, Professor G. D. 3LA. F.B.S. (the Author) — Chemical Equilibrium the

Result of the Dissipation of Energy. 12mo. 1885.
Linnean Society— Journal, Nos. 109, 138, 139. Svo. 1885.
Lisbon, Sociedade de Geographie — Boletim, 4* Serie, No. 12; 5^ Serie, Nos. 1, 2.

Svo. 1883.
Liverpool Literary and Philosophical Society — Proceedings, Vol. XXXVIII. Svo.

1884.
Lubbock, Sir John, Bart. M.P, F.B.S. M.B.I, (the Aidhor) —Representation. Svo.

1885.
Madras Government — Telegraphic Longitude Determinations in India. 4to. 1884.
Madras Magnetical Observations, 1851-1855. 4to. 1884.
Singapore Magnetical Observations, 1841-5. 4to. 1851.
Manchester Geological Society — Transactions, Vol. XVIII. Part 10. Svo. 1885.
Mechanical Engineers^ Institution — Proceedings, Nos. 3, 4. Svo. 1885.
Medical and Chirurgical Society, Boyal — Proceedings, New Series, Vol. I. No. 10.

Svo. 1885.
Mensbrugghe, M. G. Van der (the Author) — Theorie Mecanique de la Tension

Superficielle. (K 107) Svo. 1885.
Meteorological Society, Boyal — Quarterly Journal, No. 55. Svo. 1885.

Meteorological Record, No. 17. Svo. 1885.
Meteorological Oyice — Contributions to our Knowledge of the Meteorology of the
Arctic Regions, Part 4. fol. 1885.
Quarterly Weather Report, 1877, Part 3. 4to. 1885.
Monthly Weather Report for March, April, 1885. 4to.
Hourly Readings, 1883, Parts 1, 2. 4to. 1885.
Middlesex Hospital— B^epoits for 1883. Svo. 1885.
Montpellier Academie des Sciences et des Lettres — Memoires, Tome X. Fasc. 3.

4to. 1884.
Munchen, Sternwarte bei — Annalen, Supplementband, X. XIV. Svo. 1871-84.
North of England Institute of Mining and Mechanical Engineers — Transactions,

Vol. XXXIV. Parts 4, 5. Svo. 1885.
Norwegischen Commission der Europaischen Gradmessung — Geodatische Arbeiten,
Heft 4. 4to. 1885.
Vandstandsobservationer, Heft 3. 4to. 1885.
Numismatic Society— Chvonicle and Journal, 1885, Part 2. Svo.
Odontological Society of Great Britain — Transactions, Vol. XVII. No. 8. New

Series. Svo. 1885.
Pennsylvania, Second Geological Survey of — Reports. Svo. 1S74-1SS4.

Geological Hand Atlas of Pennsylvania. By J. P. Lesley. Svo. 1885.
Perry, Bev. S. J. F.B.S. (the ^w^/ior)— Results of Meteorological and Magnetical

Observations, 1884. 12mo. 1885.
Pharmaceutical Society of Great Britain — Journal, July-Oct. 1885. Svo.

Y 2

324 General Monthly Meeting. [Nov. 2,

Photographic SociefTj—Jomnai, New Series, Vol. IX. No. 9 ; Vol. X. No. 1. 8vo.

1885.
Physical Society of London— Troceedings, Vol. VII. Parts 1, 2. 8vo. 1885.
Pogson, Miss E. Isis (the Beporter)—Iiti:)ort of tlie Meteorological Reporter to the

Government of Madras, 1884-5. 8vo. 1885.
Pole, William, Esq. F.R.S. (the Author) — Further Data on Aerial Navigation.

(Proc. Inst. Civil Engineers, Vol. 81.) 8vo. 1885.
Preussische Akademie der Wissenschaften — Sitzungsberichte, I.-XXXIX. 8vo.

1885.
Prince, C. Leeson, Esq. (the Author) — The Topography and Climate of Crow-
borough Hill, Sussex. [Privately Printed] Svo. 1885.
Real y Pontificia Universidad de Sto. Tomas de Manila — Discurso por R. Arias.

8vo. 1885.
Richardson, B. W. M.D. F.R.S. (the Author)— The Asclepiad. Vol. II. Nos. 7, 8.

8vo. 1885.
Royal Society of London— Proceedings, Nos. 237, 288. 8vo. 1885.
Saunders, Laurence, Esq. (the Author) — Robert Boyle. A Biographical Sketch.

(O 19) 12mo. 1885.
Saxon Society of Sciences, Royal — Philologisch-Historische Classe :

Abhandlungen : Band X. Nos. 1, 2. 4to. 1885.

Berichte, 1884 and 1885. Svo.
Mathematische-Physische Classe :

Abhandlungen : Band XIII. Nos. 2, 3, 4. 4to. 1884-5.

Berichte, 1884 and 1885. 8vo.
Sibson, Mrs. M.R.I, (the Author) — Collected Works of Francis Sibson. Edited by

W. M. Ord. 4 vols. 8vo. 1881.
Smithsonian Institution— Qonixihuiious to Knowledge, Vol. XXIV. XXV. 4to.

1885.
Society of ^r^s— Journnl, July-Oct. 1885. 8vo.
Spratt, Vice- Admiral T. A. B. C.B. F.R.S. (the Author)— Uej^ovt on Navigation

of the River Mersey, 1884. 8vo. 1885.
Statistical Society— Jourufi], Vol. XLVIII. Parts 2, 3. 8vo. 1885.
St. Bartholomew's Hospital — Index to Reports, Vols. I.-XX. Svo. 1885.
St. Pe'tershourg, Acade'mie des Sciences— BuWetin, Tome XXXI. No. 2. 4to. 1885.
Swedish Academy of Sciences, J?02/aZ— Handlingar (Me'moires), Band 18, 19. 4to.

1880-1.
Bihang (Supplement aux Me'moires), Band 6, 7, 8. Svo. 1882-4.
Ofversigt (Bulletin), 1881, 1882, 1883.

Lefnadsteckningar (Biographies des Membres), Band 2, Heft 2. Svo. 1883.
Telegrapth Engineers, Society o/— Journal, Vol. XIV. Nos. 57, 58. Svo. 1885.
Teyier Museum— Axdnves, Serie II. Vol. II. 2^' Partie. 4to. 18S5.
Tokio University — Memoirs, No. 5 (Appendix). Svo. 1885.
Topley, William, Esq. F.G.S. (the Author) — The National Geological Surveys of

Europe. (Brit. Assoc. Reports.) Svo. 1885.
Trinity House — Report on Lighthouse Illuminants, Part 1. (P 14) fol. 1885.
United Service Institution, Royal — Journal, No. 130. Svo. 1885.
United States Geological Survey— Monogrd-phs, Vol. VI.-VIII. 4to. 1883-4.

Bulletins, Nos. 2-fi. Svo. 1883-4.
Upsal University — Bulletin Mensuel de TObservatoire de I'Universit^ d'Upsal,

Vol. XVI. 4to. 1884-5.
Nova Acta, Ser. III. Vol. XII. Fasc. 2. 4to. 1885.
Vereins zxir Beforderung des Gewerhfleisses in Preussen — Verhandlungen, 1885:

Heft G, 7. 4to.
Victoria Institute— J ourna}, No. 74. Svo. 1885.
Vincent, Benjamin, Esq. Assist. Sec. and Librarian R.I. (the Editor) — Haydn's

Dictionary of DatfS. 18th ed. Svo. 1885.
Yorkshire Archseological and Topographical Association— SomuoX, Part 34. Svo.

1885.
Zoolo(iiral Society— Vroceedinga, 1S85, Parts 2, 3. Svo. 1885.
Transactions, Vul. XI. Part 10. 4to. 1885.

1885.] General Monthly Meeting. 325

GENERAL MONTHLY MEETING,

Monday, December 7, 1885.

George Busk, Esq. F.R.S. Treasurer and Vicc-Presideut,
in the Chair.

James Butcher, Esq.

Charles Bell Eustace Ford, Esq.

were elected Members of the Royal Institution.

The following Lecture Arrangements were announced :

Professor Dewar, M.A. F.R.S. M.R.I. Fullerian Profe.ssor of Chemistry,
R.I. Six Lectures (adapted to a Juvenile Auditory) on The Story of a
Meteorite. On Dec. 29 {Tuesday), Dec. 31, 1885; Jan. 2, 5, 7, 9, 1886.

Robert Stawell Ball, Esq. LL.D. F.R.S. Andrews Professor of Astronomy
in the University of DubHn, and Royal Astronomer of Ireland. Three Lectures
on The Astronomical Theory of the Great Ice Age. On Ttiesday, Jan. 19,
Thursday, Jan. 21, Saturday, Jan. 23.

Reginald Stuart Poole, Esq. LL.D. of the British Museum, Corresp.
Inst. France. Tiiree Lectures on Naucratis : (1) Relations of the Greeks
WITH Egypt from the heroic age to Psammetichus ; (2) The Emporium of
Naucratis; (3) The Egyptian Sources of Greek Art. On Tuesday!^, Jan. 26,
Feb. 2, 9.

Charles T. Newton, C.B. LL.D. M.A. Three Lectures on The Un-
exhibited Portion of the Greek and Roman Sculptures in the British
Museum (illustrated by Drawings and Casts). On Tuesdays, Feb. 16, 23, March 2.

Professor Arthur Gamgee, M.D. F.R.S. Fullerian Professor of Physiology,
R.I. Six Lectures on The Function of Circulation. On Tuesdays, March 9,
16, 23, 30, April 6, 13.

W. Chandler Roberts-Austen, Esq. F.R.S. M.R.I. Chemist of the Mint.
Four Lectures on Metals as affected by small quantities of Impurity. On
Thursdays, Jan. 28, Feb. 4, 11, 18.

Professor W. Boyd Dawkins, M.A. F.R.S. F.G.S. Four Lectures on The
Ancient Geography of Britain. On Thursdays, Feb. 25, March 4, 11, 18.

Professor Tyndall, D.C.L. LL.D. F.R.S. M.R.I. Four Lectures on Light.
On Thursdays, March 25, April 1, 8, 15.

Archibald Geikie, Esq. LL.D. F.R.S. Director-General of the Geological
Survey of the United Kingdom, Four Lectures on The History of Volcanic
Action in the British Isles. On Saturdays, Jan. 30, Feb. 6, 13, 20.

Rev. C. Taylor, D.D. Master of St. John's College, Cambridge. Two
Lectures on The History of Geometry : the Greeks and the Moderns. On
Saturdays, Feb. 27, March 6.

Edward B. Poulton, Esq. M.A. Two Lectures on The Nature and
PROTEcaiVE U.^E OF CoLOUR IN Catekpillars. On Saturdays, March 13, 20,

326 General MontJdy Meeting, [Dec. 7

HowAKD Grubb, Esq. F.R.S. Two Lectures on The Astronomical Tele-
scope. On Saturdays, March 27, April 3.

Professor Outer Lodge, D.Sc. Two Lectures on Fuel and Smoke. On
Saturdays, April 10, 17.

The Presents received since tlie last Meeting were laid on the
table, and the thanks of the Members returned for the same, viz. : —

The Lords of the Admiralty— 'NaMtical Almanac for 1889. 8vo. 1885.

Greenwich Observations for 1883. 4to. 1885.

Greenwich Spectroscopic and Photographic Eesults for 1883. 4to. 1885.

Cape Catalogue of Stars for 1850. 8vo. 1883.
Ministry of Public Works, Rome — Giornale del Genio Civile, Serie Quarta,

Vol. V. No. 9. 8vo. AndDisegni. fol. 1885.
Abel, Sir Frederich, C.B. D.C.L. F.E.S. M.R.L (the Author)— AddvesB to the

Society of Arts (Explosions in Coal Mines). 8vo. 1885.
Accademia del Lincei, Beale, Roma — Atti, Serie Quarta: Rendiconti. Vol. I.

Fasc. 23, 24. 8vo. 1884-5.
Academy of Natural Sciences, Philadelphia — Proceedings, 1885, Part 2. 8vo.
Agricultural Society of England, Royal— Journal, Second Series, Vol. XXI.
Part 2. 8vo. 1885.

General Index to Second Series of Journal, Vols. XI.-XX. 8vo. 1885.
Antiquaries, Society o/— Proceedings, Vol. X. No. 2. 8vo. 1885.
Astronomical Society, Royal — Monthly Notices, Vol. XLV. No. 9, Sup. 8vo. 1885.
Bankers, Institute o/— Journal, Vol. VI. Part 8. 8vo. 1885.
Birmingham Philosoijhical Society — Proceedings, Vol. IV. Part 2. 8vo. 1884-5.
Birt, William, Esq.— Poppy Land. By Clement Scott. 12mo. 1885.
British Architects, Royal Institute of — ^Proceedings, 1885-6, Nos. 2, 3. 4to.
Cambridge Philosophical Society — Proceedings, Vol. V. Part 4. 8vo. 1885.
Chapman, Henry, Esq. M.Inst.C.E. {the ^m^/^o?-)— Compound Locomotives, fol.

1885.
Chemical Society — Journal for November, 1885. 8vo.
Civil Engineers' Institution — Theory and Practice of Hydro-Mechanics (Lectures).

8vo. 1885.
^fZi^ors— American Journal of Science for November, 1885. Svo.

Analyst for November, 1885. Svo.

Athenseum for November, 1885. 4to.

Chemical News for November, 1885. 4to.

Engineer for November, 1885. fol.

Horologicnl Journal for November, 1885. Svo.

Iron for November, 1885. 4to.

Nature for November, 1885. 4to.

Eevue Scientifique for November, 1885.

Science Monthly, Illustrated, for November, 1885.

Telegraphic Journal for November, 1885. Svo.
Franklin Institute— J oinnol, No. 719. Svo. 1885.
General Medical Council — Report of Statistical Committee. Svo. 1885.
Geographical Society, jRoyaZ— Proceedings, New Series, Vol. VII. No. 11. Svo.

1885.
Geological Society— Quarteily Journal, No. 1G4. Svo. 1885.
Johns Hopkins tlniversity-Vniyersity Circular, Nos. 42-44. 4to. 1885.

American Chemical Journal, Vol. VII. No. 3. Svo. 1885.
Kew Observatory— Hisiory. By R. H. Scott. (Proc. Royal Soc.) 1885.
Lisbon, Socieda'de de Geogra2)hie—Bo\ei\m, .I" Serie, No8. 3-5. Svo. 1885.
Madrid Literary and Scientific Athenxtim — La Cuestion Ferian en cl Ateuco.

12mo. 1885.
Manchester Geological Society — Transactions, Vol. XVIII. Part 11. Svo. 1885.

1885.] General Monthly Meeting. 327

Mechanical Engineers' Institution — Proceedmo;s, Index, 1874-1884. 8vo. 1885.
Melbourne Public L/&rar^— Map of Early Melbourne. By K. Kussell. 1885.
Meteorological (9^ce— IMonthly Weather Keport, May, 1885. 4to.
North of England Institute of Mining and Mechanical Engineers — Transactions,

Vol. XXXIV. Part 6. 8vo. 1885.
Pharmaceutical Societij of Great Britain — Jonrnal, November, 1885. 8vo.
Photographic Societij— Jour nsil. New Series, Vol. X. No. 2. 8vo. 1885.
Eoyal College of Surgeons of England — Calendar. 8vo. 1885.
Royal Society of New South Wales — Journal and Proceedings, Vol. XVIII. 8vo.

1884-5.
Royal Society of Tasmania — Catalogue of the Library. Svo. 1885.
Smithsonian Institution —'Report, 1883. Svo. 1885.
Society of Arts — Journal, November, 1885. Svo.
Startin, James, Esq. (the Author)— SyphUitic Eruptions of the Skin. Svo. 1885.

Lecture on a Healthy Skin. Svo. 1885.

Lecture on the Diseases of the Skin and Hair. 12mo. 1885.
St. Pelershourq, Academic des Sciences — Memoires, Tome XXXII. Nos. 14-18;

Tome XXXIIL Nos. 1, 2. 4to. 1885.
United Service Institution, Royal — Journal, No. 131. Svo. 1885.
Vercins zur Beforderuag des Geicerhjleisses in Preussen — Verhandluugen, 1885:
Hefts. 4to.

328 Professor Dewar [1885-6.

NOTES RELATING TO PROFESSOR DEWAR'S LECTURES
OlSr THE STOI^Y OF A METEORITE.

Delivered on December 29 and 31, 1885, and January 2, 5, 7, 9, 1886.

Account of the Dhurmsala Meteorite.

Beport to Punjab Government, dated Dhurmsala, 28 July, 1860.

On the afternoon of Saturday, the litli of July, 1860, between the
hours of 2 and 2 . 30 p.m., the station of Dhurmsala was startled by a
terrific bursting noise, which was supposed at first to proceed from
a succession of loud blastings or from the explosion of a mine in the
upper part of the station ; others, imagining it to be an earthquake
or very large landslip, rushed from their houses in the firm belief
that they must fall upon them.

It soon became apparent that this was not the case. The first
report, which was far louder in its discharge than any volley of
artillery, was quickly followed by another and another, to the
number of fourteen or sixteen. Most of the latter reports grew
gradually less and less loud. These were probably but the rever-
berations of the former, not among the hills but amongst the clouds,
just as is the case with thunder. It was difiicult to say which were
the reports and which the echoes. There could certainly not have
been fewer than four or five actual reports. During the time that
the sound lasted the ground trembled and shook convulsively.

From the diff'erent accounts of three eye-witnesses there appears
to have been observed a flame of fire, described as about 2 feet in
depth and 9 feet in length, darting in an oblique direction above the
station after the first explosion had taken place.

The stones as they fell buried themselves from a foot to a foot and
a half in the ground, sending up a cloud of dust in all directions.

Most providentially no loss of life or property has occurred.

Some coolies, passing by where one fell, ran to the sj)ot to j)ick
up the pieces ; before they had held them in their hands half a
minute they had to drop them owing to the intensity of the cold
which benumbed their fingers.

This, considering the fact that they were apparently but a
moment before in a state of ignition, is very remarkable. Each
stone that fell bore unmistakable marks of partial fusion,

The morning and afternoon preceding the occurrence had been
particularly dull and cloudy. Temperature was close, sultry, and
oppressive. The thermometer was above 80° of Fahrenheit, and no
rain had fallen. I had no barometer by me at the time ; I am there-
fore unable to state what was the precise pressiu'c of the atmosphere.

1885-6.] on the Story of a Meteorite. 329

The clouds, which were of the form technically called cumuliis and
cirrhus, were hanging low at the time, and the atmosphere heavily
charged with electricity.

Such are simply the facts of the case as they occurred.

There are of course all sorts of conjectures as to the probable
cause of the occurrence. Some state the stones to be of volcanic
origin; others that they were hurled from the heights above the
station or projected from the moon ; but I am inclined to regard
them as real hond-fide meteorolites. Their weight seems to indicate
that they are semi-metallic substances, composed probably of meteoric
iron alloyed with nickel and mixed with silica and magnesia or some
other earthy substance. They are nearly double the weight of a
piece of ordinary stone of similar dimensions.

Another very singular phenomenon was witnessed at Dhurmsala
on the evening of the same day that the aerolite fell. This appears
to have been a succession of igneous meteors, such as fire-balls, or
falling or shooting stars. This singular sight did not attract the
attention of most people. I quote the account from the writer who
describes it verbatim.

" I think it was on the evening of the same day that the meteor
fell that I observed lights in the air. They commenced to appear
about 7 P.M., and lasted for about three hours till 10 ; they appeared
for about one minute, some for longer, then went out again, other
lights appearing in their places ; sometimes three or four lights
appeared in the same place together, and one or two moved off, the
others remaining stationary, they looked like fire - balloons, but
appeared in places where it was impossible for there to have been
any houses or any roads, where people could have been. Some were
high up in the air moving like fire-balloons, but the greater part of
them were in the distance, in the direction of the lower hills, in
front of my house, others closer to our house, and between Sir A.
Lawrence's and the Barracks. I am sure from some which I observed
closely that they were neither fire-balloons, lanterns, nor bonfires, or
any other thing of that sort, but hond-fide lights in the heavens.
Though I made enquiries amongst the natives the next day, I have
never been able to find out what they were or the cause of their
appearance."

Another Account.

About 2 P.M. on Saturday, the 14th of July, a tremendous mid-air
explosion was heard at Dhurmsala, Kangra, Dalhousie, Madhoopoor
and Goordaspoor. The vapour or smoke following the explosion
was distinctly seen at Dalhousie about thirty miles, and at Kangra
ten miles from Dhurmsala, where the explosion, said to have
resembled the discharge of an 84-pounder, was followed by the
descent in various parts of the station, some two miles apart, of
large masses of aerolite. One piece that fell near the Dhurmsala

330 Professor Deivar [1885-6.

Police Battalion Lines, was ascertained to have been when entire,
one foot in diameter, but it was broken into several fragments.

I was at the time, reading wdth my Moonshi in my study, and
heard an extraordinary noise like that of thunder at a short distance.
There could be no doubt that it was near, and I immediately supposed
it was something else than thunder. The steady rattling noise which
appeared to be travelling in a horizontal direction gradually increased
to one tremendous majestic clap ; after which the former steady
rattling noise continued perhaps for a minute, till at last it died off
very gradually. The noise appeared to be so low that I thought a
volcano or something like it would immediately appear somewhere
in our valley. A servant of mine happened just to return from the
Post Office, and told me that above the hill on which our house is
situate he had seen a fire travelling towards Dhurmsala, till at last it
disappeared. The sky was cloudy, yet there were no such clouds as
w'ould justify the opinion that lightning and thunder had issued
from them.

Chemical Analysis of a Meteoric Stone from BJiurmsala.
By Br. C. T. Jackson.

The most curious fact alleged in the report is, that the pieces,
which were picked up immediately after they fell, when held in the
hand for half-a-minute, were so cold as to benumb the fingers, and
this is mentioned as very remarkable, since a few moments before the
surface of the meteorite was in a state of ignition, and still bears
evident marks of partial fusion.

The temperature of the day was 80° F., and the cold could not
have been occasioned by the soil in that climate. Indeed, the
temperature required to produce the effect alleged must have been
far bulow zero.

Now, supposing the fact to be true, that it was intense cold that
was produced by the stone, may it not have been owing to the low
temperature of the region from which the meteorite fell? the
interplanetary spaces, according to Baron Fourier's estimate, being
about — 50° Centigrade, or nearly 100° Fahr. below freezing point.

Allowing that the meteoric mass came from those regions, the
matter being a very slow conductor of heat, we can easily conceive
that when the mass entered the earth's atmosphere, it might become
heated and inflamed on the surface by condensing the air before it,
in its descent towards the earth ; and since it would have to fall
through about eighty miles of the atmosphere, the density of which
increases as it approaches the earth, the inflammation would take
place only where the air had sufficient density, and not in the highest
regions. Such being the case, the expansion of the exterior of the
meteorite, the surface being incandescent, while the interior was very
cold, would cause the mass to fly to pieces with violent detonations,
and this, too, quite near to the earth.

1885-6.] on the Story of a Meteorite. 331

The surfiice of so imperfect a conductor of lieat might be ignited,
while the interior of the mass remained intensely cold. We know
that imperfect conductors of heat, when heated to redness, and plunged
into cold water, so that they can be momentarily handled, will again
become nearly red hot on the surface, by heat derived from the
interior. Thus, specimens of lavas, which I collected in the crater of
Vesuvius, handled freely, and wrapped up in paper, frequently set
fire to the paper in a short time after they were so enveloj)ed. I
brought home many specimens which had browned and charred the
paper.

It is also known to all assayers and chemists, that a crucible full
of melted flux, if cooled on the surface by plunging the crucible into
water, will soon become hot again on the surface, and that the interior
of the flux will remain red hot, while the surface of the crucible may
be held in the hand for a short time.

Therefore, mutatis mutandis, there is no inherent improbability
that these masses of meteoric stone really would produce the sensation
of intense cold, if they were originally cold in the interior, and only
rapidly heated on the surface. If the facts are as alleged, this is the
first recorded recognition by the human senses of the cold of the
interplanetary regions. It would have been a curious and instructive
experiment, to have placed one of these stones, soon after it fell, in
water, when the formation of a crust of ice on the surface would have
visibly demonstrated the fact of intense cold ; and an estimate of the
degree of cold could also have been made, by similar means, ascer-
taining how much the temperature of a given quantity of water was
reduced by it, and computing the degrees of cold thereby.

The weight of the fragment presented to the Society is 4J- ounces.
It is 2 J inches long, 1:^ inches wide, and 1 inch in average thickness.

Its specific gravity is 3-456 at 68"^ Fahr., Barom. 29 • 9. Its struc-
ture is imperfectly granular, but not crystallised, and there are small
black specks of the size of a pin's head, and smaller, of malleable
meteoric iron, which is readily removed from the crushed stone by
the magnet. The colour of the mass is ash grey. A portion of the
surface is black and is scorified by fusion.

Its hardness is not superior to that of olivine or massive chrysolite.
Chemical analysis shows that its composition is that of a ferruginous
olivine.

One gramme of the stone, crushed in an agate mortar, and acted
on by a magnet, yielded 0*43 grm. of meteoric iron, which was
malleable. After the removal of this a qualitative analysis was made
of the residual powder. Another gramme was also taken, without
picking out the metallic iron, and was tested for chlorine and for
phosphoric acid. The results of the qualitative analysis were that
the stone contains silica, magnesia, a little alumina, oxide of iron and
nickel, a little tin, an alloy of iron and nickel, phosphoric acid, and a
trace of chlorine.

These ingredients being determined, the plan for a quantitative

332 Professor Dewar [1885-6.

analysis was laid out, and was duly executed by the usual and approved
methods. The following are the results of this analysis, per centum :

Silica, with traces of tin 40*000

Magnesia 26-600

Per-oxide of iron 27*700

Metallic iron 3*500

Metallic nickel 0*800

Alumina 0*400

Chlorine 0*049

Phosphoric acid .. .. not weighed —

99-049

Analysis of Gases in Meteorite (Ansdell and Dewar).

Carbonic acid 61*29

Carbonic oxide 7*52

Hydrogen 30*96

Nitrogen 0*23

100*00

The meteorite contains about three times its volume of gas.

Chladni's Theory (Nicliol).

" This theory, first proposed by Chladni in 1794, may be best
put in the following general form : —

Through the interplanetary spaces, and it may be, through the
interstellar spaces also, vast numbers of small masses of solid matter
may be moving in irregular orbits; and these, as they approach any
planet of powerful gravitation — such as the earth — will be disturbed,
and may fall towards its surface.

Chladni's hypothesis certainly explained much, but one essential
part of the phenomenon it did not explain.

For instance, it was quite consistent with the fact that some of
these bodies fall to the earth as aerolites, and that others escape as
mere falling stars ; but Chladni could, in his day, give no account
whatever of the heat of the stones that do fall, and the apparent
inflammation of those that only pass through our atmosphere, and
appear as falling stars.

The desideratum, however, has been supplied by modern physics.

No compression of the atmosphere certainly, by any body
moving through it, could evolve heat enough to produce such results ;
but the recent and apparently established conception regarding heat,
viz. that it must be evolved as an equivalent for any destroyed
mechanical effect, wholly removes the difficulty.

1885-6.] on the Story of a Meteorite. 333

The velocity of a sufficient number of these falling stars, for
instance, has been ascertained within due limits by Brandes and
others ; and M. Joule has shown conclusively, that in regard of the
greater number of these bodies — the heat, equivalent to the mechanical
effect due to their original vis viva, and destroyed by the resistance
of the atmosphere — is such as would melt the body and dissipate it
into fragments.

In case of smaller velocities, nothing beyond inflammation or
white heat might ensue ; but far oftener than we imagine, these
falling stars are utterly dissijjated by the agency now spoken of, and
reach the earth in the form of mere meteoric dust.

This special difficulty removed from Chladni's cosmical theory,
other problems remained. First, Have these stones, or meteoric
planets, a special or assignable origin ?

The lunar hypothesis of Laplace has frequently found favour.
But it ought not to be judged by the form in which it was proj)osed
by its founder.

The idea that these meteors are directly shot towards us by
lunar volcanoes in present action, is consistent neither with existing
observation of the condition of the moon, nor with the dynamical
essentialia of the problem.

But it does not follow that those vast lunar craters — such as
Tycho — the result evidently of enormous cataclysms, have not con-
tributed their part in driving among the interplanetary spaces, masses
of broken rock, that may on occasion come within the range of the
sjDecial attraction of our globe. But secondly, is it necessary to
search for any confined or special origin ? Is it not manifest, on
the contrary, that masses of such bodies are most widely diffused, and
may form an essential part — not of our solar system merely — but of
the material universe, in so far as man can discern it ? "

Joule's Explanation of the Heating of Meteorites.

" Behold, then, the wonderful arrangements of Creation. The
earth, in its rapid motion round the sun, possesses a degree of living
force so vast that, if turned into the equivalent of heat, its temperature
would be rendered at least 1000 times greater than that of red-hot
iron, and the globe on which we tread would in all probability be
rendered equal in brightness to the sun itself.

And it cannot be doubted that if the course of the earth were
changed, so that it might fall into the sun, that body, so far from
being cooled down by the contact of a comparatively cold body,
would actually blaze more brightly than before, in consequence of
the living force with which the earth struck the sun being converted
into its equivalent of heat. Here we see that our existence depends
upon the maintenance of the living force of the earth.

On the other hand, our safety equally depends in some instances
upon the conversion of living force into heat.

334 Professor Dewar on the Story of a Meteorite. [1885-6.

You have, no doubt, frequently observed what are called shoot-
ing stars, as they apj^ear to emerge from the dark sky of night,
pursue a short and rapid course, burst, and are dissipated in shining
fragments.

From the velocity with which these bodies travel, there can be
little doubt that they are small planets which, in the course of their
revolution round the sun, are attracted and drawn to the earth.

Eeflect for a moment on the consequences which would ensue,
if a hard meteoric stone were to strike the room in which we are
assembled with a velocity sixty times as great as that of a cannon-
ball.

The dire effects of such a collision are effectually prevented by
the atmosj)here surrounding our globe, by which the velocity of the
meteoric stone is checked, and its living force converted into heat,
which at last becomes so intense as to melt the body and dissipate it
into fragments too small probably to be noticed in their fall to the
ground.

Hence it is that, although multitudes of shooting stars appear
every night, few meteoric stones have been found, those few corrobo-
rating the truth of our hypothesis by the marks of intense heat which
they bear on their surface.

The average result of the experiments of Joule and Thomson
showed that the wire was warmed 1° Cent, by moving at the velocity
of 175 feet per second.

The highest velocity obtained was 872 feet per second, which
gave a rise of 5° -3 Cent. ; and there was no reason to doubt that the
thermal effect would go on continually increasing with the square of
the velocity. Thus at a mile per second the rise of temperature
would be, in round numbers, 900° Cent. ; and at twenty miles per
second, which may be taken as the average velocity with which
meteorites strike the atmosphere of the earth, 360,000°.

The temperature due to the stoppage of air at the velocity of
143 feet per second is 1° Cent. Hence we may infer that the rise
observed in the experiments was that due to the stoppage of air, less
a certain quantity, of which probably the greater part is owing to
loss by radiation. It beiug also clear that the effect is independent
of the density of the air, there remains no doubt as to the real nature
of ' shooting stars.'

These are small bodies which come into the earth's atmosphere
at velocities of twenty miles per second and upwards.

The instant they touch the atmosphere their surfaces become
heated far beyond the point of fusion — even of volatilisation — and
the consequence is that they are speedily and, for the most part, com-
pletely burnt down and reduced to impalpable oxides. It is thus that,
by the seemingly feeble resistance of the atmosphere, Providence
secures us effectively from a bombardment which would destroy all
animated nature exposed to its influence."

[J. D.J

lSoi)al Cngtitution of ©reat Britain.

WEEKLY EVENING MEETING,

Friday, January 22, 1886.

Sir William Bowman, Bart. LL.D. F.R.S. Vice-President, in the

Chair.

Professor Tyndall, D.C.L. LL.D. F.R.S. M.B.L

Thomas Young and the Wave Theory,
(Abstract deferred.)

WEEKLY EVENING MEETING,

Friday, January 29, 1886.

William Huggins, Esq. D.C.L. LL.D. F.R.S. Vice-President, in the

Chair.

Sir William Thomson, D.O.L. LL.D. F.R.S.

Capillary Attraction.

(Abstract deferred.)

GENERAL MONTHLY MEETING,

Monday, February 1, 1886.

Warren de la Rue, Esq. M.A. D.C.L. F.R.S. Vice-President,
in the Chair.

William Anderson, Esq. M. Inst. C.E.

Henry Arthur Blyth, Esq,

James Blyth, Esq.

James Crowdy, Esq.

Brownlow D. Knox, Esq.

Mrs. Shepherd,

W. F. R. Weldon, Esq. M.A.

were elected Members of the Royal Institution,

Vol. XL (No. 80.) z

336 General Monthly Meeting. [Feb. 1,

The Special Thanks of the Members were returned to Mr. James
WiMSHUEST, 3LB I. for his valuable present of two Electrical
Influence Machines.

The Presents received since the last Meeting were laid on the
table, and the thanks of the Members returned for the same, viz. : —

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1886.] General Monthly Meeting. 337

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338 Mr. T. Pridgin Teale [Feb. 5,

WEEKLY EVENING MEETING,

Friday, February 5, 1836.

Sir Frederick Bramwell, LL.D. F.R.S. Honorary Secretary and
Vice-President, in the Chair.

T. Pridgin Teale, Esq. M.A. F.R.C.S.

The Principles of Domestic Fireplace Construction.

If there be a place in the kingdom in which a lecture on the subject
selected for to-night could appropriately be given, surely it is the
theatre in which we are assembled. Some of ray hearers may be
aware of the mutual fitness of subject and place. Many, perhaps, are
not aware, as, indeed, was the case with myself three months ago, that
the principles of fireplace construction which will be laid before you
to-night, and which I have been working out and teaching for the last
three or four years, were urged, written about, and acted upon at the
end of the last century by your Founder, Count Enraford, and that a
great portion of his time, his writings, and his work was devoted to
this very question.

Hardly any subject would be more in harmony with the aims
which he set before him in founding this Society, as we may learn
from the following quotation from the "Prospectus of the Royal
Institution," published at the end of the 5th volume of Rumford's
Works : — " But if it should be proved, as in fact it may, that in the
applications of fire, in the management of heat, and in the production
of light, we do not derive half the advantage from combustion which
might be obtained, it will readily be admitted that these subjects must
constitute a very important part of the useful information to be con-
veyed in the public lectures of the Royal Institution." (V. p. 784.)

And why should it be necessary, at the end of this nineteenth
century, to give a lecture on " The princijdes of fireplace construc-
tion " ? Why should such a title draw together an audience ? Clearly
from the fact that correct principles have been habitually, and, until
the last few years, almost universally violated, and because the rules
so ably worked out, so earnestly and forcibly advocated by Rumford,
have lain dormant, lingering here and there, chiefly in old-fashioned
houses, and almost forgotten.

Again, why should a layman, whose profession lies outside that of
the architect, the builder, and the manufacturer, take upon himself to
teach principles that are to guide other professions than his own ?

1886.] on the Principles of Domestic Fireplace Construction. 339

Mainly for two reasons : one, that there are priuciijles which a medical
man may work out without reproach, as tending to contribute to the
happiness, the comfort, and the health of mankind; the other, that
when principles have to be insisted upon, and to be made a subject of
public instruction, they can be urged with more effect by those who
are hampered by no relations to any patents, and have no pecuniary
interest in the success or failure of the ajjj^lication of the jDrinciples
in question. On this point we have a good example in Count Eumford,
who says in a note : — " The public in general and particularly those
tradesmen and manufacturers whom it may concern, are requested to
observe, that, as the author does not intend to take out any patent for
any invention of his which may be of public utility, all persons are at
full liberty to imitate them, and vend them for their own emolument,
when, and where, and in any way they may think proper." (III. 527.)

Three evils result from the prevalence of bad principles in con-
struction : — 1. Waste of fuel and loss of heat. 2. Excessive production
of soot and smoke. 3. Large addition to ashj^it refuse by cinders,
which are really unburnt, and therefore wasted fuel. These are
matters of national concern, and it has been the main object of my
labours on this question during the last four years to endeavour to
convince the public that it is the interest no less than the duty of
every householder, to burn his fuel on correct principles, and to do
his part towards the diminution of these evils.

On the first point, " Waste of fuel and heat," let us listen to
Eumford, whose words areas true to-day as when written eighty years
ago. " Though it is generally acknowledged that there is a great
waste of fuel in all countries, arising from ignorance and carelessness
in the management of fire, yet few — very few, I believe— are aware of
the real amount of this w\aste." (IV. 5.) " From the result of all
my inquiries upon this subject, I have been led to conclude that not
less than seven-eightlis of the heat generated, or which ivith proper
management might he generated, from the fuel actually consumed, is
carried up into the atmosphere with the smoke, and totally lost."
(IV. 6.) " And with regard to the economy of fuel, it has this in
particular to recommend it, that whatever is saved by an individual is
at the same time a positive saving to the whole community." (IV. 4.)

Heat is wasted in three ways — either by combustion under the
impulse of strong draught, which means rapid escape of heat up the
chimney ; or by imperfect combustion of the gases which are generated
during the burning of the coals ; or by escape of heat through the iron
sides and back into the space between the range and the brickwork,
and so into the chimney. The greatest offenders are the ordinary
register grates. Iron all over, back, and sides, and roof, they are
usually set in a chamber open above to the chimney, and imperfectly
filled in, or not filled in at all, with brickwork. The heat escapes
through the iron to this chamber, and thence is lost. Another fault
is that the " register opening," in other words the " throat of the
chimney," being immediately above the coal, submits the burning fuel

340 Mr, T. Prldgin Teale [Feb. 5,

to the full concentrated force of the current to the chimney, convert-
ing the fire into a miniature blast-furnace. On this point Rumford
says : — " But there are, I am told, persons in this country who are so
fond of seeing what is called a great roaring fire, that even with its
attendant inconveniences, of roasting and freezing opposite sides of
the body at the same time, they prefer it to the genial and equable
warmth which a smaller fire, properly managed, may be made to pro-
duce, even in an open chimney fireplace." (III. 569.)

The second result of faulty construction in fireplaces is " Undue
production of smoke and soot." Smoke and soot imply imperfect
combustion, and to this two defects in a fire mainly contribute, one,
too rapid a draught through the fire which hurries away and
chills below burning jioint the gas rising from the heated fuel. The
other defect is too cold a fire, i. e, too small a body of heat in and
around the fuel, so that the temperature of the gases is not raised to
a point at which they will burn. On the smoke question Eumford
waxes eloquent : — " The enormous waste of fuel in London may be
estimated by the vast dark cloud which continually hangs over this
great metropolis, and frequently overshadows the whole country, far
and wide ; for this dense cloud is certainly composed almost entirely
of unconsumed coal, which, having stolen wings from the innumerable
fires of this great city, has escaj)ed by the chimneys, and continues to
sail about in the air till, having lost the heat which gave it volatility,
it falls in a dry shower of extremely fine black dust to the ground,
obscuring the atmosphere in its descent, and frequently changing the
brightest day into more than Egyptian darkness."

A few years ago the prevalence of unusually dense fogs roused
the metropolitan public to a sense of this great evil. The Smoke
Abatement Society was formed, and under its auspices exhibitions of
smoke-consuming apj^aratus and improved fireplaces were held in
London and Manchester. Beyond the fact that certain grates were
pronounced to be good in point of economy, and moderate in the
production of smoke, and that the public has been led to take an
interest in and enquire into the relative value and economy of
various patent fireplaces, there has been but little advance in the
education of the public in the principles which lie at the root of the
whole question.

A third result of bad construction is the " Production of cinders."
With good coal, cinders are inexcusable. They are unconsumed
carbon — coke — and imply a faulty fireplace. If thrown into the
ashi)it, as is the case in 99 times out of 100, they are shameful
waste, and more than waste, for they entail a great cost for their
removal. The town of Leeds pays about 14,000Z. a year for the
scavenging of the streets and the emptying of ashpits. Nearly
every house in Leeds sujiplies in the way of cinders at least twice
as much ashj^it refuse as it might do, were the fireiilaces projierly
constructed. The ashpit refuse of Leeds is burned in a " Destructor,"
and the cinders in the refuse provide, not only heat enough for its

1886.] on the Princijples of Domestic Firejjlace Construction, 341

reduction to a mineral residue, but spare heat for driving two
60-liorse power engines, and for consuming a reasonable amount
of pigs, &c., killed by or on account of disease.

These three great evils, evils affecting not only individuals, but
the community, waste of fuel and heat, production of soot, production
of cinders, are a direct result of the violation of the correct principles
in fireplace construction.

Let us next enquire what are the principles which promote good
combustion in an open firej)lace — i. e. what are the conditions which
are essential to enable fuel to give out to a room " good money's
worth in heat." That such a result may be obtained, fuel must
burn ivell but not rapidly. Two things in combination are essential
to the combustion of fuel — a supply of oxygen, and a high tempera-
ture— i. e. plenty of heat around the fuel. If fuel be burned with
a hot jacket around it, a very moderate amount of oxygen will
sustain combustion, and if the supply of oxygen be moderate, com-
bustion is slow. Burn coal with a chilling jacket around it, a
rapid conductor like iron, and it needs a fierce draught of oxygen to
sustain combustion, and this means rapid escape of actual heat, and
also of potential heat in unburnt gases and smoke, up the chimney.
This is the key to the whole position ; this is the touchstone by
which to test the principles of fireplace construction.

Few people probably realise the exact conditions of combustion,
which may be well illustrated from the process of manufacture of
coal gas. In coal we have three kinds of constituents. One mineral,
incombustible, seen in the ash residue, which for good coal amounts
to barely 3 per cent. The second, volatile, and which, under the
influence of heat becoming gaseous, appears in an open fire as tall
flame and smoke, and, where combustion is imperfect, produces soot.
The third constituent is carbon or charcoal, familiarly known as
coke or cinder, and when burning gives a short shallow blueish
flame. The carbon and the volatile portions can be raised to a high
temperature, and still will not burn unless oxygen be brought into
contact with them.

In the manufacture of gas, coal is raised to a high temperature,
and the gases are driven off by roasting the coal in an oven from
which air, i. e. oxygen, is shut out. The gases are conducted away,
cooled, purified, and stored for future use in a gasometer ; the com-
bined carbon and mineral residue, being non-volatile, is cooled down
before being exposed to the air, and is sold as coke. Here we have
a striking proof of the fact that high temperature in fuel does not of
itself involve combustion. If air were admitted to the red-hot coke,
or to the gases as they escape in their heated condition from the
furnace, they would burn. But when coke has become cold, and the
gases are cold, as in a gasometer, no amount of oxygen will of
itself start combustion.

The deduction from all this is, that complete oxydation, i. e.
good combustion, is possible only when the fuel and gases are at a

342 Mr. T. Pridgin Teale [Feb. 5,

high temperature, and that high temj^erature of fuel does not pro-
duce combustion until oxygen is introduced, — therefore we can have
a high temperature of fuel, without rapid combustion, provided we
control and limit the supply of oxygen. If we have thoroughly
grasped these elementary facts, we shall be in a position to under-
stand the points to be aimed at in the construction of a fireplace.

My attention was first directed to the question of waste of fuel
at the time of the coal famine some twelve years ago. I read in the
* Times,' and acted upon the suggestion, made, I believe, by the late
Mr. Mechi, to economise coal by inserting an iron plate on the grid
under the fuel so as to cut off all draught through the fire. This
undoubtedly induced slow combustion, and economised fuel, but the
fire was dull, cold, and ineffective. The plan w^as abandoned. It
taught me, however, the fact that combustion could be controlled by
cutting off the underdraught, but I did not then see why combustion
was spoiled. The reason was that the under surface of the fire was
chilled, and the fuel lost its incandescence owing to the rapid loss of
heat through the iron towards the open hearth chamber. To some
persons even now " Slow combustion stoves " are an abomination,
and are supposed to be synonymous with bad combustion.

The next stage in my firejjlace education was the adoption of
the Abbotsford grate. I thereby learnt that the reason why an
Abbotsford grate was an advance upon the iron plate lay in the fact
that the solid firebrick bottom stored up heat and enabled the fuel
to burn more brightly resting upon a hot surface — not upon a
cooling iron plate. But Abbotsford grates, and the other class of
grates w^ith solid firebrick bottoms, the Parson's grates, have dis-
advantages. They are apt to become dull and untidy towards the
end of the day, and do not burn satisfactorily with inferior coal.
There is a better thing than a solid firebrick bottom, and that is the
chamber under the fire closed in front by an " Economiser."

The history of the next, the most important stage of my fireplace
education, was as follows : —

Some five years ago I made, somewhat accidentally, the discovery
that the burning of coal in an ordinary fireplace could be controlled
and retarded by the adoption of a very simjjle and inexpensive
contrivance, applicable to nearly every existing grate, and that this
result could be attained without impairment of, and often with
increase of, the heating power of the fire. This contrivance, which
I have named an " Economiser," was simply a shield of iron, standing
on the hearth, and rising as high as the level of the grid at the
bottom of the grate, converting the hearth space under the fire into a
chamber closed by a movable door.

The effect was twofold. The stream of air, which usually rushes
through the bottom of the fire, and causes for a short time rapid
combustion at a white heat, was thereby cut off, and the air under the
fire was kept stagnant, the heated coal being dependent for its com-
bustion on the air jmssing over the front and the ii^per surface. The

1886.] on the Principles of Domestic Fireplace Construction. 343

second point was that this boxing up rendered the chamber hotter,
and this increased temperature beneath the fire-grate, i. e. under the
fuel, added so materially to the temperature of the whole, even of
the cinders coming into contact with the iron grid, that the very
moderate supply of oxygen reaching the front and upper surface of
the fuel was sufficient to maintain every portion in a state of incan-
descence. Moreover, I observed that combustion was going on at an
orange, not at a icliite, heat.

Let us contrast a white with the orange heat. A icliite heat in a
fire means rapid combustion, oiduij to the strong current of air, oxyjen,
which passes under the grate, through the centre of the fire, and up the
chimney. As soon as the heart of the fire has been rapidly burnt
away at a white heat, the fuel cools ; the iron grid cools also ; and
the cinders in contact with the grid are chilled below combustion
point. They then cease to burn, and the bottom of the fire becomes
dead and choked. The poker must now be brought into play to
clear away the dead cinders, and to re-open the slits in the choked
grid. New coal is added to the feeble remnant of burning embers,
with no reserve of heat in the iron surroundings ; and in time, and
perhaps very slowly, the fire revives, and rapid combustion sets in
afresh under the influence of the renewed current of oxygen passing
through the heart of the fire. An orange heat means that the coke,
i. e. the red-hot cinder, is burning with a slowly applied stream of
oxygen, a degree of combustion which is only possible ivhen the coal is
kept w-arm by the hot chamber beneath, and by a reasonable limitation
of loss of heat at the back and sides by firebrick, either in contact
with the fuel, or at least close behind the iron surrounding it. This
effect is seen, partially, in the grates with solid firebrick bottom, but
far more perfectly in the grates with the chamber closed by the
" Economiser."

This hot chamber has the following effects: — The incandescent
coal remains red-hot from end to end of the grate, until nearly all is
consumed, thus maintaining a larger body of the fuel in a state to
radiate effective heat into a room. The cinders on coming into
contact w^th the iron grid also remain red-hot, and so continue to
burn away until they fall through the grid as a fine powder. This
allows the fire to burn clearly all day long almost without poking.
When the fire is low, and new coal is added, the reserve of heat in
the hot chamber is such that the addition of cold fresh fuel does not
temporarily quench the embers, and the fire is very quickly in a
blaze after being mended.

Having made the discovery by the observation of a grate supplied
to me with an " Economiser," the value of which, I suspect, was
hardly appreciated by the makers, I applied " Economisers " one by
one to all my grates, kitchen included. The result surpassed my
expectations. There was a saving of at least a fourth of my coal.
The experience of many friends, who at my advice adopted the
system, confirmed my own results. It was therefore clear to me that

344 Mr. T. Pridghi Teale [Feb. 5,

I was bound to make widely known a discovery which was fraught
with such benefit to myself, and was likely to prove a great boon to
the public.

My chief aim hitherto has been to persuade the public to apply
the " Economiser " to existing fireplaces. After steady exertions for
four years, some impression has been made on the inertia of the
public, and extensive trials of the " Economiser " are taking place in
many parts of the country. To-day, however, my aims are more
complete. It is my wish to advocate not one principle alone,
although that is the cardinal one, but to urge all the best principles
which enter into the construction of a really effective firei)lace, and
to induce those whom it may concern to replace bad by an entirely
new construction, right in every point.

The rules of construction which I shall lay down have been
arrived at entirely by my own observation of what appeared to be the
best points in various fireplaces. It was, therefore, no less a satisfac-
tion to me than a surprise to discover, on reading Eumford's work in
preparation for this lecture, that nothing which I have to advocate is
new, but that every princij)le, and the " Economiser " is hardly an
exception, was advocated no less enthusiastically by him at the very
commencement of this century.

Having considered the principles that should guide us, we are
now prepared to lay down strict rules which should be acted upon in
the construction of fireplaces. I trust that what I have said has so
far commended itself to your judgment that the thirteen rules here
drawn up will command your hearty assent, and in due time will win
their way into the confidence of our architects, our builders, and
the public.

PiULE I. "As little iron as possihle." — The only parts of a fire-
place that are necessarily made of iron are the grid on which the coal
rests, and the bars in front. The " Economiser," though usually
made of iron, from convenience in construction, might be of earthen-
ware, and so would be more perfectly in harmony with this rule. On
this point Eumford speaks most emphatically : — " Those (grates)
whose construction is the most simple, and which, of course, are the
cheapest, are beyond comparison the best, on all accounts. Nothing
being wanted in these chimneys but merely a grate for containing
coals, and, additional apparatus being not only useless but very
pernicious, all complicated and expensive grates should be laid aside,
and such as are simple substituted in their stead. In the choice of a
grate beauty and elegance may easily be united with perfect simpli-
city. Indeed, they are incompatible with everything else." (III. 517.)
Again he says, " Iron, and in general metals of all kimjs, are to bo
reckoned amongst the very worst materials that it is possible to
employ in the construction of a fireplace."

EuLE II. " The hack and sides of the fireplace slioiild he of
hriclc, or firehricJc." — Brick retains, stores, and accumulates heat, and
radiates it back into the room, and keeps the fuel hot. Iron lets

1886.] on the Principles of Domestic Fireplace Construction. 346

heat slip tliroiigli it up the chimney, gives very little back to the
room, and chills the fuel. On this point also Rumford speaks very
strongly. " The best materials I have hitherto been able to discover
are firebrick and common bricks and mortar." " The fuel, instead
of being employed to heat the room directly or by the direct rays
from the fire, should be so disposed or placed as to heat the back and
sides of the grate, which must always be constructed of firebrick or
firestone, and never of iron or any other metal." (III. 345.)

EuLE III. " The firebrick back shoidd lean over the fire, not lean
away from it," as has been the favourite construction throughout the
kingdom. The lean-over not only increases the power of absorbing
heat from rising flame — otherwise lost up the chimney — but the
increased temperature accumulated in the firebrick raises the tempera-
ture of gases to combustion point, which would otherwise pass up
the chimney unconsumed, and thus be lost. Eumford discovered
accidentally the value of this " lean-over," and at once realised its
immense importance. He does not, however, seem to have carried out
his intention of working out for general adoption this form of back.

He first of all condemns to alteration all firebacks which lean
away from the fire. " It frequently happens that the iron backs of
grates are not vertical, but inclined backwards. Where the grates
are wide, and can be filled up with firebrick, the inclination of the
back will be of little consequence, since, by making the firebrick in
the form of a wedge, the front may be made perfectly vertical, the
iron back being hid in the solid work of the fireplace. If the grate
be too shallow to admit of any diminution, it will be best to take
away the iron back entirely, and cause the vertical back of the
fireplace to serve as the back to the grate." (III. 521.)

He next describes his discovery of the value of the " lean-over": —
" In this case I should increase the depth of the fireplace at the
hearth to 12 or 13 inches, and should build the back perpendicular
to the height of the top of the burning fuel, and then, sloping the
back by a gentle inclination forward, bring it to its proper place,
that is to say, perpendicularly under the back part of the throat of the
chimney. This slope (which will bring the back forward 4 or 5
inches, or just as much as the depth of the fireplace is increased),
though it ought not to be too abrupt, yet it ought to be quite finished
at the height of 8 or 10 inches above the fire, otherwise it may
perhaps cause the chimney to smoke.

" Having been obliged to carry backward the fireplace in the
manner here described, in order to accommodate it to a chimney
whose walls in front were remarkably thin, I was surprised to find,
upon lighting the fire, that it ajDpeared to give out more heat into
the room than any fireplace I had ever constructed. This effect was
quite unexpected ; but the cause of it was too obvious not to be
immediately discovered. The flame rising from the fire broke
against the part of the back w^hich sloped forward over the fire,
and this part of the back being soon very much heated, and in

346 Mr. T. Pruhjin Teale [Feb. 5,

consequence of its being very hot (and when the fire burned bright
it was frequently quite red-hot), it threw off into the room a great
deal of radiant heat. It is not possible that this oblique surface
(the slope of the back of the fireplace) could have been heated red-
hot merely by the radiant heat projected by the burning fuel ; for
other parts of the fireplace nearer the fire, and better situated for
receiving radiant heat, were never found to be so much heated ; and
hence it appears that the combined heat in the current of smoke and
hot vapour which rises from an open fire may he, at least in part,
stopped in its passage up the chimney, changed into radiant heat,
and afterwards thrown into the room.

" This opens a new and very interesting field for experiment,
and bids fair to lead to important improvements in the construction

of fireplaces But, as I mean soon to publish a particular

account of these fireplaces, with drawings and amide directions for
constructing them, I will not enlarge further on the subject in this
place. It may, however, not be amiss just to mention here, that
these new invented fireplaces not being fixed to the walls of the
chimney, but merely set down upon the hearth, may be used in any
open chimney ; and the chimneys altered or constructed on the
principles here recommended are particularly well adapted for
receiving them." (III. 526.)

Of receut years " lean-over " backs have been re-invented and
sparingly used. The " Milner " back, invented by a Lincolnshire
clergyman, and adopted by Barton and Co., is excellent. It burns
fuel well, and gives out a great heat. But it is extravagant in
consumption unless controlled by the " Economiser."

Captain Douglas Gallon saw the virtue of the " lean-over," and
adopted it in the grate which goes by his name. The "Bee-hive"
back was the same in principle and very good, and having a very
small grid, was economical.

The " Kifle " back, adopted by Nelson and Sons, of Leeds, gives
an admirable fire, little short of perfection ; but observation shows
that the "tall" flame extends far beyond the bend, and is therefore
soon lost as a heating factor, the heat being wasted in the chimney.

From the commencement of my study of the fireplace question
the value of the " lean-over " has not only taken firm hold of my
fancy, but my sense of its importance has been growing in intensity,
until I saw that the best construction must show the greatest possible
extent of " lean-over " that could be obtained without sacrifice of
otlier important details of construction. How to accomplish this
will appear in considering the Fifth Rule.

Rule IV. " Tlie bottom of the fire, or grating, should be deep
from before backwards, probably not less than 9 inches for a small room,
nor more than 11 inches for a large room.'' — This is a corollary to
Rule III. We cannot i)0ssibly have the back of the fireplace over-
hanging the fire when there is a shallow grid. If for no other
reason than the demands of tlie " lean-over," depth of fire space is

1886.] on the Principles of Domestic Fireplace Construction. 347

essential. But there is gain, thereby, in another direction. It
affords plenty of room for the burning fuel to lie down close to the
grid, and away from swift air currents, and prevents the tendency of
the fire to burn hollow.

On this point Eumford has a word to say : — " But as many of the
grates now in common use will be found too large when the fireplaces
are altered and improved, it will be necessary to diminish their
capacities by filling up with pieces of firebrick. But in diminishing
the capacities of grates, care must be taken not to make them too
narrow, i. e. too shallow.

" The proper depth for grates for rooms of middling size will be
from six to eight inches. But where the width (i.e. depth) is not
more than five inches, it will be very difficult to prevent the fire going
out." (III. 520.)

"Where grates designed for rooms of middling size are longer
(and broader) than 14 or 15 inches, it will always be best to diminish
their length by filling them up at their two ends by firebrick."
(III. 522.)

Rule V. " The sides or ' covings ' of the fireplace should be inclined
to one another as the sides of an equilateral triangle " (Fig. 2, p, 350). —
The working out of this rule has cost me much thought and experi-
ment. It was worked out more or less emjiirically with a view to
attain certain objects, and, having attained them, I discovered that I
had unwittingly selected the sidos of an equilateral triangle. It is of
some importance, and may be of interest, to tell how the question
arose. In my earlier fireplaces the sides or " covings " were parallel
to each other, and had the defect that they radiated most of their
heat from one to the other, not into the room, with the probable result
that much of such heat would eventually escape up the chimney.

It was clear then that the sides must be set at an angle with the
back, so as to face towards the room. But at what angle ? My first
experiments were determined by the shape of the corner bricks which
were in the market. These determined the inclination of the sides to
be such that, if prolonged, they would meet at a right angle. This is
the angle laid down by Eumford as the angle of selection, but as the
largest angle admissible in a good fireplace. This angle, however,
brought me into difficulties with my " lean-over " back. The of)en-
ness of the angle made the back, as it ascended, spread out so rapidly
that what was gained in width was lost in height. Moreover, my
critics objected to its appearance as ugly. What then should deter-
mine the inclination of the sides ? The point was thus determined.
Seeing that a heated brick throws off the greatest amount of radiant
heat at a right angle with its surface, the " covings " should be at such
an inclination to each other that the perpendicular line from the inner
margin of one "coving" should just miss the outer margin of the
opposite " coving." Where the " covings," as in my earlier attempts
and in Count Rumford's fireplaces, are at a right angle to each other,
this perpendicular line misses the opposite margin by several inches.

348 Mr. T. Pridgin Teale [Feb. 5,

It was clear, therefore, tliat the inclination might be made more
acute. Guided by this idea, and having determined the principle on
which the shape of the grate should depend, an inclination was
arrived at which turned out to be an angle of 60^, i. e. the inclination
of the sides of an equilateral triangle.

Count Rumford came very nearly to the same conclusions : — " I
have said, in my essay on chimney fireplaces, that where chimneys
are well constructed and well situated, and have never been apt to
smoke, in altering them the ' covings ' may be placed at an angle of
135 degrees with the back ; but I have expressly said that they should
never exceed that angle, and have stated at large the bad consequences
that must follow from making the opening of a fireplace very wide,
when its depth is very shallow." (V. p. 610.)

Rule VI. " The ' lean-over ' at the hack should he at an angle
of 70° " (Fig. 1). — Commencing at a level (A) corresponding with
the top of the front bars, and leaning forward at an angle of 70°
with the horizontal line of the hearth, the back should rise to such
a point that the angle where it returns towards the chimney (B)
should be vertically over the insertion (C) of the cheeks of the fire-
grate. This angle (B) will be about 28 inches from the hearth, or
16 inches from the top of the fire, and about 3 J to 4 J inches from
the front line of the fireplace, according to the size of the grate.
These points will be obvious from the vertical section of the fireplace
here shown, and from C, Fig. 2.

Note. — So far, in the fireplaces built after my rules, the height
of the grid from the hearth has been taken at two bricks, or 6 inches,
and the height of the bars from the grid also at two bricks, or 6
inches. It follows, therefore, that the lean-over commences at 12
inches from the hearth. It is possible that a better angle than 70°
may eventually be found — such as an angle of 60° — but commencing
a few inches above the fire so as not to loiver the angle B where the
lean-over returns to the chimney.

Rule VII. " The shape of the grate should he hased upon a square
described within an equilateral triangle, the size to vary in constant pro-
portion to the side of the square " (Fig. 2). — The shape of the grate, or
grid, is arrived at in the following way : — Describe a square D, of which
the sides shall be 8, 9, or 10 inches, according to the size of the
room, within an equilateral triangle E, the two sides of which shall
represent the " covings " of the fireplace, and the base the front line
of the fireplace. From each front angle of the square carry a line
from D to C, to the " covings " or sides of the triangle, at an angle
of 45° with the front line of the fireplace. These two lines, with
the side of the square from which they are drawn, form the front of
the grid. The back line of the grid does not correspond with the
corresponding side of the square, but is carried IJ inches further
back, so as to give greater depth to the grate, and allow the firebrick
back to overhang the back of the grid to the extent of IJ inches (see
A, Fig. 1) before it ascends as the "lean-over."

1886.] on the Principles of Domestic Fireplace Construction. 349

Tlie diagram of the grate, with the square and triangle on which
it is based in dotted lines, will, I hope, make this description suf-

Fio. 1.

, I « J f J rf 7 8 9 /• " li^^ iociUi.

L_. ■ / . ■ 1 ■ , ■ ■ « . I

^ I M -^

ficiently intelligible. Whenever a grate on this principle proves too
hot for a room, and in summer when a smaller fire is needed, the size

350

Mr. T. Pridgin Teale

[Feb. 5,

should be reduced in ividtli by triangular firebricks at each side, which
reduce the fire space to a square, with the addition of the IJ-inch
space under the back. This rule secures sufficient depth from front
to back, and a constant proportion between depth and width, whatever
be the size of grate.

Rule VIII. " The slits in the grating, or grid, should he narrow,
perhaps ^ inch for a sitting-room grate and good coal, f for a kitchen
grate and had coal." — When the slits are larger, small cinders fall
through and are wasted.

Rule IX. " The front hars should he vertical, that ashes may not
lodge and look untidy ; narrow, perhaps ^-inch in thickness, so as not to
ohstruct heat ; and close together, perhaps ^-inch apart, so as to prevent
coal and cinder from falling on the hearth" (Fig. 3). — It is too soon to

Fig. 2.

INCHfS

judge as to the lasting powers of \-m. bars. Those in one of my
own grates are round, and after 4J months' daily wear, show no sign
of burning away.

Flat bars, J in. X J in,, or even by |- in., might perhaps resist fire
better, if the ^-in. round bars burn away. The bars are so arranged
that if one fails, it can easily ,be renewed. I have round bars about
-^- in. in diameter at present on trial in my kitchen range.

Rule X. " There should he a rim 1 inch or IJ inch in depth
round the lower insertion of the vertical hars" (Fig. 8). — The object of
this is to conceal the ash at the bottom of the fire, and to enable
the front cinders to burn away completely by protecting them from
the cold air. This rim (F) contributes greatly to tidiness, and as a
rule will prevent the need of any sweeping up of the hearth during
the day.

1886.] 071 the Frind])les of Domestic Fireplace Construction. 351

Rule XI. " The chamber lender the fire should he closed hj a
shield or ' Economiser ' " (G, Figs. 1 and 3). — This has been ah-eady
spoken of, and described as the central principle which enhances
greatly the value of all the rest.

Fig. 3.

\ Z 3 k. s i f q^

INCHES
Front View of Fireplace.

^ Rule XII. " Whenever a fireplace is constructed on these
principles, it must he home in mind that a greater body of heat is
Vol. XI. (No. 80.) * 2 a

352 Mr. T. Pridgin Teale [Feb. 5,

accumulated about the hearth than in ordinary fireplaces. If there he
the least doubt ivhetlier loooden beams may possibly run under the
hearthstone, then an ashpan should be added, loith a double bottom, the
space between the two plates being filled with artificial asbestos,
* slagwool,' 2 inches in thickness."

EuLE XIII. " A fireplace on this construction must not be put up in
a party wall, ivhere there is no projecting chimney breast, lest the heated
back should endanger woodwork in a room at the other side."

Having now worked up Eules for the construction of an effective
fireplace, let us consider what benefits result.

1. — Economy of Fuel. I have already stated that my own
experience of the application of the " Economiser " to all my
original fireplaces, including kitchen and scullery, was a saving of
more than one-fourth. Friends who have followed my advice report
variously from a sixth to one-third. The saving in the Leeds
Infirmary, according to returns supplied to me by Mr. Blair, the
General Manager, has been nearly a sixth, amounting to nearly 100
tons in the year. What the saving in the fireplaces constructed on
the best rules may be I cannot say, probably about the same degree
of saving, with a large increase of heat given into the room. My
conviction is that such fireplaces make one ton of coal give out as
much heat into a room as two tons would yield if burnt in the worst
forms of the nearly obsolete register stove. Need more be said about
economy of fuel ?

2. — Reduction of Soot. This is, perhaps, from a national point
of view, the most important point in connection with our subject —
and yet it is the portion of it in which my evidence is the most
defective. I can only offer you my general impression that there is
a very important reduction in the amount of soot, an impression
based upon observation of the smoke issuing from chimneys where
" Economisers " are in use, and of the diminution of soot falling
about my own house, which is confirmed by the testimony of Miss
Gordon, Lady Superintendent of the Leeds Infirmary, as to the
lessened amount of soot which finds its way into the wards.

3. — Beduction of Ashjnt Befuse. This point is clearly proved by
the fine snuff-like powder, free from cinders, which I show ; and by
the fact that the whole produce in the ashpit of my kitchen fireplace
for one week was contained in one ashpan, and weighed 15 lbs.
Surely this is a fact for our local authorities to grasp.

Danger of Fire. — Seeing that improved fireplace construction
involves increased heat about the hearth, an actual danger of fire
will be created where the hearthstone rests on wood, unless the
hearth itself be protected. It was therefore my duty to find out a
means of protecting the hearth. With this view, experiments have
been made with ashpans with double bottoms and a small air-space
between the ashpan and the hearth. The results are shown in the
specimens of cotton wool, wood, &c., which have been exposed under
ashpans of various constructions. My conclusion is that two inches

1886.] on the Principles of Domestic Fireplace Construction, 353

of artificial asbestos at the bottom of an asbpan would render any
heartb safe. Sucb an asbpan may be named a " Hearth Protector."
Another caution should be given against erecting one of these im-
proved fireplaces where there is no projecting chimney breast, lest
there should be insufficient depth of brick between the back of the
fire and the woodwork of a room at the other side.

" Kitchen Refuse.'' — In some households there are certain portions
of kitchen refuse which are apt to find their way into the dust-bin,
instead of the pig-tub. You here see the remains of refuse, con-
sisting of celery stalks, potato parings, &c., which have been roasted
in a wire cage underneath my kitchen fire in the chamber closed by
the " Economiser." The wire cage is necessary to allow the heat to
reach the under surface of the refuse.

Having now for four years done my best to persuade the public
to take measures in reference to fireplaces which will confer upon
them a saving in the cost of fuel, a saving in the labour of servants,
an increase in the warmth and comfort of rooms, a lessening of the
soot in the atmosphere of towns, and a i)ossibility of reduction of
scavsr ging rates, it is no little satisfaction to feel that my views are
at last making way, and acquiring a momentum of their own ; and I
an encouraged to hope that the time is not far distant when the
Committees of Public Institutions, and the Directors of Eailway
Companies, following the example of the Weekly Board of the
Leeds Infirmary, will feel it their duty to weigh their value, and, if
they prove true, to adopt them; and perhaps even the Smoke Abate-
ment Society may be induced, as discharging a function for which it
exists, to put them to the test of scientific experiment.

It only remains for me now to bring my address to a conclusion
with the words of the Eoman Shakespeare, —

" Nonfumim exfulgore, seel ezfumo dare luceni."

HoR. Aks, Poet.

— which I will translate in the words of one of our greatest Latin
scholars, the late Professor Conington,

" Not smoke from fire my object is to bring,
But fire from smoke, a very different thing

[T. P. T.]

354 Professor Osborne Reynolds [Feb. 12,

WEEKLY EVENING MEETING,
Friday, February 12, 1886.

The Eight Hon. Lord Eayleigh, M.A. D.C.L. LL.D. F.E.S. Manager
and Vice-President, in the Chair.

Professor Osborne Eetnolds, M.A. F.E.S.

Experiments shoioing Dilatancy, a property of Granular Material,
possibly connected icith Gravitation.

In commencing this discourse, the author said, My principal object to-
night is to show you certain experiments which I have ventured to
think wouhl interest you on account of their novelty, and of their
paradoxical character. It is not, however, solely or chiefly on account
of their being curious that I venture to call your attention to them.
Let them have been never so striking, you would not have been
troubled with them had it not been that they afford evidence of a fact
of real importance in mechanical philosophy.

This newly recognised property of granular masses which I have
called dilatancy will, it may be hoped, be rendered intelligible by
the experiments, but it was not by these experiments that it was
discovered.

This discovery, if I may so call it, was the result of an attempt to
conceive the mechanical properties a medium must possess in order
that it might fulfil the functions of an all-pervading aether — not only
in transmitting waves of light, and refusing to transmit waves like
those of sound, but in causing the force of gravitation between distant
bodies, and actions of cohesion, elasticity, and friction between adjacent
molecules, together with the electric and magnetic properties of
matte r, and at the same time allowing the free motion of bodies.

It will be well known to those who attend the lectures in this
room, that although a vast increase has been achieved in knowledge of
the actions called the physical properties of matter, we have as yet
no satisfactory explanation as to the prima causa of these actions them-
selves ; that to explain the transmission of light and heat it has been
found necessary to assume space filled with material possessing the
properties of an elastic jelly, the existence of which, though it
accounts for the transmission of ligbt, has hitherto seemed inconsistent
with the free motion of matter, and failed to afford the slightest
reason for the gravitation, cohesion, and other physical properties of
matter. To explain these, other forms of nsther have been invented,
as in the corpuscular theory and the celebrated hypothesis of La Sage,
the impossibilities of which hypotheses have been finally proved by

1886.'] on Experiments shoioing Dilatancy. 355

the late Professor Maxwell, to whom we owe so much of our definite
knowledge of the fundamental physics. Maxwell insisted on the
fact, that even if each of the physical properties could be explained by
a special tether, it would not advance philosophy, as each of these
aethers would require another aether to explain its existence, ad in-
finitum. Maxwell clearly contemplated the existence of one medium,
but it was a medium which would cause not one but all the physical
properties of matter. His writings are full of definite investigations
as to what the mechanical properties of this aether must be to account
for the laws of gravitation, electricity, magnetism, and the trans-
mission of light, and he has i)roved very clear and definite jn'operties,
although, as he distinctly states, he was unable to conceive a mecha-
nism which should possess these properties.

As the result of a long-continued effort to conceive a mechanical
system possessing the properties assigned by Maxwell, and further,
which would account for the cohesion of the molecules of matter,
it became apparent that the simplest conceivable medium — a mass of
rigid granules in contact with each other — would answer not one but
all the known requirements, provided the shape and mutual fit of the
grains were such, that while the grains rigidly j)reserved their shape,
the medium should possess the apparently paradoxical or anti-sponge
jiroperty of swelling in bulk as its shape was altered.

I may here remark, that if aether is atomic or granular, that it should
be a mass of grains holding each other in position by contact like
the grains in the sack of corn is one of only two jjossible con-
ceptions ; the other being that of La Sage, or the corpuscular theory
that the grains are free like bullets moving in space in all directions.

Nor, in spite of its paradoxical sound, is there any great difficulty
of conceiving the swelling in bulk. When the grains are in contact,
it ajjpears at once that the mechanical projjerties of the medium must
be to some extent afi'ected by the shape and fit of the grains. And
having arrived at the conclusion that in order to act the part of
aether, this shape and fit must be such that the mass could not
change its shape without changing its volume or space occupied, the
next thing was to see what possible shape could be given to the
grains, so that while these rigidly preserved theii* shape, the medium
might possess this property of dilatancy.

It was obvious that the grains must so interlock, that when any
change of shape of the mass occurred, the interstices between the
grains should increase. This would be possessed by grains shaped to
tit into each other's interstices in one particular arrangement.

In an ordinary mass of brickwork or masonry well bonded without
mortar, the blocks fit so as to have no interstices ; but if the pile be in
any w^ay distorted, interstices appear, which shows that the sjDace
occupied by the entire mass has increased (slioivu hy a model).

At first it appeared that there must be something special and sys-
tematic, as in the brick wall, in the fit of the grain of aether, but
subsequent consideration revealed the striking fact, that a medium

356 Professor Osborne Reynolds \^^^' 12,

composed of grains of any possible shape possessed tliis property of dila-
tancy so long as one important condition was satisfied.

This condition is that the medium should be continuous, infinite
in extent, or that the grains at the boundary should be so held as to
prevent a rearrangement commencing. All that is wanted is a mass
of hard smooth grains, each grain being held by the adjacent grains,
and the grains on the outside prevented from rearranging.

Smooth hard spheres arranged as an ordinary pile of shot are in
their closest order, the interstices occupying a space about one-third
that occupied by the spheres themselves. By forcing the outside shot
so as to give the pile a different shape, the inside spheres are forced
by those on the outside, and the interstices increase. Thus by shaping
the outside of the pile, the interstices may be increased to any extent
until they occupy about nine-tenths the volume of the spheres : this is
the most open formation. A further change of shape in the same direc-
tion causes a contraction of the interstices until a minimum volume
is reached, and then again an expansion, and so on. The point to be
realised is that in any of these arrangements if the whole of the
spheres on the outside of the group are fixed, those inside will be
fixed also. {Shown by a model.)

An interior portion of a mass of smooth hard spheres therefore
cannot have its shape changed by the surrounding spheres without
altering the room it occupies, and the same is true for any granular
mass, whatever be the shape of the grains.

Considering the generality of this conclusion, the non-discovery of
this property as existing in tangible matter requires a word of
explanation.

The physical properties of elasticity, adhesion, and friction so far
render the molecules of ordinary matter incapable of behaving as a
system of parts with the sole property of keeping their shape, and so
prevents evidence of dilatancy in solids and fluids. This is quite
consistent with dilatancy in the sether, for the properties of
elasticity, cohesion, and friction in tangible matter are due to the
presence of the sether, so that it would be illogical for the elementary
atoms of the aether to possess these properties.

This although a sufficient reason why dilatancy has not been
recognised as a property of solid and fluid matter, does not explain
its non-existence in masses of solid, hard, free grains, as of corn, shot,
and sand. To understand why it has not been observed in these, it
must be remembered that to ordinary observation these present only
an outside ajipearance, and that the condition essential for dilatancy,
that the outside grains should not be free to rearrange, is seldom ful-
filled. Also these granular forms of matter, though commonplace,
have not been the subjects of physical research, and hence such
evidence as they do afford has escaped detection.

Once, however, having recognised dilatancy as a universal pro-
perty of granular masses, it was obvious that if evidence of it was
to be sought from tangible matter, it must be sought in what have

1886.] on Experiments sJiowing Dilatancy. 357

hitherto been the most commonplace and least interesting arrange-
ments. That an important geometrical and mechanical property of
a material system should have been hidden for thousands of years,
even in sand and corn, is such a striking thought that it required no
little faith in mechanical principles to undertake the search for it,
and although finding nothing but what was strictly in accordance
with the conclusions previously arrived at, the evidence obtained of
this long-hidden property was as much a matter of visual surprise to
the lecturer as it can be to any of the audience.

To render the dilatancy of a granular mass evident, it was neces-
sary to accomplish two things : (1) the outside grains must be con-
trolled so that they could not rearrange, and this without preventing
change of shape and bulk of the mass ; (2) the changes of bulk or
volume of the mass, or of the interstices between the grains, must be
rendered evident by some method of measurement which did not de-
pend on the shape of the mass.

A very simple means — a thin indiaruhher envelope or boundary —
answered both these purposes to perfection. The thin indiarubber
closed over the outside grains sufficiently to prevent their change of
position, and the impervious character of the bag allowed of a con-
tinuous measure of the volume of the contents, by measuring the
quantity of air or water necessary to fill the interstices.

Taking an indiarubber bag which will hold six pints of water,
without stretching, and having only a small tubular aperture, getting
it quite dry, and putting into it six pints of dry sea sand, such as will
run in an hour-glass, sharp river sand, dry corn, shot, or glass
marbles, it presents no very striking appearance, but all the same
when filled with any of these materials, it cannot have its form
changed as by squeezing between two boards without changing its
volume. These changes of volume are not sufficient to be noticeable
while the squeezing is going on, but they may be rendered apparent.
It is sufiicient to do this with the bag full of clean dry Calais sand,
such as is used in an hour-glass.

The tube from the bag is connected with a mercurial pressure-
gauge, so that the bag is closed by the mercury.

The actual volume occupied by the quartz grains is four and a
half pints. The remaining space, one and a half pints, is occupied by
the interstices between the grains in their closest order ; these inter-
stices are full of air, so that three-quarters of the bag are occupied by
quartz, and one-quarter by air. Since the bag is closed and no more
air can get in if interstices are increased from one pint and a half to
two pints, the air must expand, and its pressure will fall from that of
the atmosphere to three-quarters of an atmosphere. As soon as
squeezing begins, the mercury rises on the side connected with the
bag, and steadily rises as the bag flattens until it has risen seven inches,
showing that the bag has increased in capacity by half a pint or one-
twelfth of its initial capacity.

That by squeezing a porous mass like sand we should diminish

858 Professor Osborne Beynolds [Feb. 12,

the pressure of tlie air in the pores is paradoxical, and shows the
anti-sponginess of the granular material ; had there been a sponge in
the bag, the pressure of the air would have increased with the
squeezing.

This experiment has been mainly introduced to prevent a possible
impression that the fluid filling the interstices has anything to do with
the dilation besides measui'ing it.

Water affords a more definite measure of volume than air.

Taking a small indiarubber bottle with a glass neck full of shot
and water, so that the water stands well into the neck. If instead of
shot the bag were full of water or had anything of the nature of a
sponge in it, when the bag was squeezed the water would be forced
up the neck. With the shot the opposite result is obtained; as I
squeeze the bag, the water decidedly shrinks in the neck.

This experiment, which you see is on a very small scale, was not
designed to show to an audience ; it was the original experiment
which was made for my own satisfaction, when the idea of dilatancy
first presented itself. The result but for the knowledge of dilatancy
would appear paradoxical, not to say magical. When we squeeze a
sponge between two planes, water is squeezed out ; when we squeeze
sand, shot, or granular material, water is drawn in.

Taking a larger apparatus, a bag which holds six pints of sand,
the interstices of which are full of water without any air — the glass
neck being graduated so as to measure the water drawn in. On
squeezing the bag with a large pair of pincers, a pint of water is
drawn from the neck into the bag. This is the maximum dilation ;
the grains of sand are now in the most open order into which they
can be brought by this squeezing ; further squeezing causes them to
take closer order, the interstices diminish, and the water runs out into
the vessel, and for still further squeezing is drawn back again, show-
ing that as the change of form continues, the medium passes through
maximum and minimum dilations.

This experiment may be repeated with granules of any size or
shape, provided only they are hard, and shows the universality of
dilatancy.

Although not more definite, perhaps more striking evidence of
dilatancy is afforded by the means which the non-expansibility of
water affords of limiting the volume of the bag. An impervious bag
full of sand and water without air cannot have its contents enlarged
without creating a vacuum inside it — the interstices of the sand are
therefore strictly limited to the volume of the water inside it, unless
forces are brought to bear sufficient to overcome the pressure of the
atmosphere and create a vacuum. Since then, owing to this property
of dilatancy, the shape of a granular mass at its greatest density cannot
change without enlarging the interstices, preventing this enlargement
by closing the bag we prevent change of shape.

Taking the same bag, the sand being at its closest order —
closing the neck so that it cannot draw more water. A severe pinch

\

1886.] on Experiments showing Dilatancy. 359

is put on tliG bag, but it does not change its sliai^c at all ; tlie shape
cannot alter without enlarging the interstices, these cannot enlarge
without drawing more water, and this is prevented. To show that
there is an effort to enlarge going on, it is only necessary to open a
communication with a pressure-gauge, as in the exj)eriment with air.
The mercury rises on the side of the bag, showing when the pinch is
hardest (about 200 lbs. on the planes) that the pressure in the bag is
less by 27 inches of mercury than the pressure of the atmosphere ; a
little more squeezing and there is a vacuum in the bag. Without a
knowledge of the property of dilatancy such a method of producing
a vacuum would sound somewhat paradoxical. Opening the neck to
allow the entrance of water, the bag at once yields to a slight pressure,
changing shape, but this change at once stops when the sujDply is cut
off, preventing further dilation.

In these experiments neither the thickness of the bag nor the
character of the fluid has anything to do with the dilation of the con-
tents considered as forming an interior group of a continuous medium,
the bag merely controlling the outside members as they would be
controlled by surrounding grains, and the fluid merely measuring or
limiting the volume of the interstices.

It has, however, been absence of such control of the outside grains
and such means of measuring the volume of the interstices that has
lire vented the dilatancy revealing itself as a general mechanical
property of granular material, as a mechanical property, because
dilatancy has long been known to those who buy and sell corn. It
is seldom left for the philosopher to discover anything which has a
direct influence on pecuniary interests ; and when corn was bought and
sold by measure it was in the interest of the vendor to make the
interstices as large as possible, and of the vendee to make them as
small ; of the vendor to make the corn lie as lightly as possible, and
of the vendee to get it as dense as possible. These interests are
obvious ; but the methods of getting corn dense and light are para-
doxical when compared with the methods for other material. If we
want to get any elastic material light we shake it up, as a pillow or a
feather bed, or a basket of dried fruit; to get these dense we
squeeze them into the measure. With corn it is the reverse ; it is no
good squeezing it to get it dense ; if we try to press it into the measure
we make it light — to get it dense we must shake it — which owing to
the surface of the measure being free, causes a rearrangement in
which the grains take the closest order.

At the present day the measure for corn has been replaced by the
scales, but years ago corn was bought and sold by measure only,
and measuring was then an art which is still preserved. It is under-
stood that the corn is to be measured light, and the method
employed is now seen to have made use of the property of dilatancy.
The measure is filled over full and the toj) struck with a round pin
called the strake or strickle. The universal art is to put the strake end
on into the measure before commencing to fill it. Then when heaped

360 Professor Osborne Beynolds [Feb. 12,

full, to pull the strake gently out and strike the top ; if now the
measure be shaken it will be seen that it is only nine-tenths full.

Sand presents many striking phenomena well known but not
hitherto explained, which are now seen to be simply evidence of
dilatancy.

Every one who walks on the strand must have been painfully
struck with the difference in the firmness and softness of the sand at
different times ; letting alone when it is quite dry and loose. At
one time it will be so firm and hard that you may walk with high
heels without leaving a footprint ; while at others, although the sand is
not dry, one sinks in so as to make walking painful. Had you noticed
you would have found that the sand is firm as the tide falls, and
becomes soft again after it has been left dr}^ for some hours. The
reason for this difference is exactly the same as that of the closed
bags with water and air in the interstices of the sand. The tide
leaves the sand, though apparently dry on the surface, with all its
interstices perfectly full of water which is kept up to the surface of
the sand by capillary attraction ; at the same time the water is perco-
lating through the sand from the sands above where the capillary
action is not sufiicient to hold the water. "When the foot falls on this
water-saturated sand, it tends to change its shape, but it cannot do
this without enlarging the interstices — without drawing in more
water. This is a work of time, so that the foot is gone again before
the sand has yielded. If you stand still, you will find that your feet
sink more or less, and that when you move, the sand becomes wet all
round the space you stood on, which is the excess of water you have
drawn in, set free by the sand regaining its densest form.

One phenomenon attending walking on firm sand is very striking ; as
the foot falls, the sand all round appears to shoot white or dry
momentarily, soon becoming dark again. This is the suction into
the enlarging interstices below the foot, which for the moment
depresses the capillary surface of the water below that of the sand.

After the tide has left the sand for a sufiicient time, the greater
part of the water has run out of the interstices, leaving them full of
air, which by expanding allows the interstices to enlarge, and the
foot to sink in far enough to make walking unpleasant.

If we walk on sand under water, it is always more or less soft, for
the interstices can enlarge, drawing in water from above.

The firmness of the sand is thus seen to be due to the interstices
being full of water, and to the capillary action or surface tension of
the water at the surface of the sand. Tliis capillary action will hold
the water up in the sand for some inches or feet, according to the
fineness of the sand. This is shown by a somewhat striking experi-
ment. If sand running in a stream from a small hole in the bottom
of a vessel, as in an hour-glass, fall into a vessel containing a slight
depth of water, the sand at first forms an island, which rises above
the water. The sand which then falls on the top of this island is dry
as it falls, but capillary action draws up the water which fills the

1886.] on Experiments showing Dilatancij. 361

interstices ancl gives the sand colierence. The island grows vertically,
very fast, and assumes the form of a column, sometimes with branches
like a tree or a fern, some inches or even a foot high. The strength
of these consists in the surface tension of the water preventing air
from being drawn in to enlarge the interstices, which therefore
cannot change shape ; it is therefore another evidence of dilatancy.

By substituting an impervious envelope for the surface of water,
firmness of sand saturated with water may be rendered very striking.

Thin indiarubber balloons, which may be easily expanded with the
mouth, afford an almost transparent envelope.

Taking one with about six pints of sand and water closed without
air, there being more water than will fill the interstices at the densest,
but not enough to allow them to enlarge to the full extent. When
standing on the table, the elasticity of the envelope given is a rounded
shape. The sand has settled down to the bottom, and the excess of
water appears above the sand, the surface of which is free. The bag
may be squeezed and its shape altered, apparently as though it had
no firmness, but this is only so long as the surface is free. But taking
it between two vertical plates and squeezing, at first it submits,
apparently without resistance, when all at once it comes to a dead
stop. Turning it on to its side, a 56-lb. weight produces no further
alteration of shape ; but on removing the weight, the bag at once
returns to its almost rounded shape.

Putting the bag now between two vertical plates, and slightly
shaking while squeezing, so as to keep the sand at its densest, while
it still has a free surface, it can be pressed out until it is a
broad flat plate. It is still soft as long as it is squeezed, but the
moment the pressure is removed, the elasticity of the bag tends to
draw it back to its rounded form, changing its shape, enlarging the
interstices, and absorbing the excess of water ; this is soon gone, and
the bag remains a flat cake with peculiar properties. To j)ressures
on its sides it at once yields, such pressures having nothing to over-
come but the elasticity of the bag, for change of shape in that
direction causes the sand to contract. To radial pressures on its rim,
however, it is perfectly rigid, as such pressures tend further to dilate
the sand ; when placed on its edge, it bears one cwt. without
flinching.

If, however, while supporting the weight it is pressed sufficiently
on the sides, all strength vanishes, and it is again a rounded bag of
loose sand and water.

By shaking the bag into a mould, it can be made to take any
shape ; then, by drawing off the excess of water and closing the bag,
the sand becomes perfectly rigid, and will not change its shape without
the envelope be torn ; no amount of shaking will effect a change. In
this way bricks can be made of sand or fine shot full of water
and the thinnest indiarubber envelope, which will stand as much
pressure as ordinary bricks without change of shape ; also permanent
casts of figures may be taken.

362 Professor Osborne Beynolds [Feb. 12,

I have now shown as fully as time will allow, the exi:>eriments
which afford evidence of the existence of the property of dilatancy, and
how it exi)lains natural phenomena hitherto but little noticed.

Beyond affording evidence of the existence of the property of
dilatancy, these experiments have no direct connection with gravi-
tation or the physical properties of matter.

These properties cannot be deduced by direct experiment on
granular material, for the simple reason that the grains of the
medium which constitutes the aether must be free from friction,
while the grains with which we work are subject to friction. These
properties can only be deduced by mathematical reasoning, into
which I will not drag you to-night. I will merely show you one
or two or three facts which may serve to convey an idea of how
dilatancy should have such a bearing on the foundation of the
universe.

If you look at this diagram, you see it represents a ball surrounded
by a continuous mass of grain, the density of the grains being indi-
cated by the depth of colour. If that ball were to grow in volume,
it would have to push out the medium on all sides, and in that way
it would distort the groups of grains or change their form, causing
the interstices to increase ; those nearer the ball would be dis-
torted more than those further away. Then the interstices of these
would grow the most rapidly, and those adjacent to the ball would
first come to their openest order for further growth ; these would
contract somewhat, those a little further away would reach the
openest order, and if the process of growth steadily continued,
we should have a series of undulations of density commencing
at the ball and moving outwards ; the first of these waves of open
order would not, however, get beyond half the diameter of the
ball away. The diagram represents the interstices that would
result if a single grain of the material had grown to the size of the
ball, pushing the medium out before it. It is not necessary that the
ball should have grown, to produce this result ; however the ball
were originally placed, if it were moved away from its original place
it would assume this arrangement, and with this arrangement it
would be free to move. Now, although I cannot attempt to enter
upon the relation between the density of the medium and the force
of attraction between two bodies in it, I may call your attention
to this fact, that the dilation as calculated varies exactly as the
force of gravitation, inversely as the square of the distance from an
infinite distance till close to the ball, and then goes through several
undulations, corresponding exactly to tlie variations in the attraction
of bodies necessary to explain the elasticity and cohesion of mole-
cules. As is shown in the other diagrams, these undulations in
density, which may be experimentally produced, not only appear to
afford a clear explanation of cohesion, but arc the only suggestion
of an explanation ever made. And further, similar undulations have
been found necessary to explain one of the phenomena of light. My

1886.] o?» Experiments showing Dilatancy. 363

reason for calling your attention to them was partly an experiment,
which, although not the most striking, is the most advanced experi-
ment in the direction of dilatancy.

The apparatus is that represented in the diagram ; the medium is
contained in the large elastic bag ; in the middle of this bag is a
small hollow elastic ball, which can be expanded by water forced in
through a tube passing through the medium and outside ball ; the
quantity of water which passes in is measured by a mercury gauge,
the water being forced in by the pressure of the mercury. The
medium between the two balls is sand and water, and is connected
with a gauge, the water drawn from which measures the dilation.

The full pressure of 30 inches is on the interior ball, but produces
no expansion, because the medium outside cannot dilate as the supply
of water is now cut off; opening the tap to admit water to the outer
ball, it at once draws water. It has now drawn 3 oz. ; in the mean-
time the mercury has fallen, showing that an ounce and a half was
admitted to the interior ball, the expansion of which drew the water
into the outer envelope. This experiment is not striking, but it is
definite, and enables us to measure the dilation consequent on a given
distortion.

It is impossible for me to go further into this exjDlanation, so I
will merely state that the ability of the grains of a medium to slide
over a smooth surface has been experimentally shown to produce
phenomena closely resembling the conduction of electricity, to com-
plete which it is only necessary to construct the medium of two
different sorts of grains, different in size or different in shape, the
separation of which would afford the two electricities and be a
simple way out of the difficulty hitherto found in explaining the
non-exhaustibility of the electricity in a body. Hitherto the
two electric fluids have been supposed to reside together in
the matter of the machine, which, however much has been with-
drawn, has never shown signs of exhaustion. In the dilatant hypo-
thesis these electricities are the two constituents of the a3ther which
the machine separates, and it is worth noticing that the ordinary
electrical machine resembles in all essential particulars the machines
used by seedsmen for separating two kinds of seed, trefoil and rye-
grass, which grow together : as long as there is a supply of the mixture,
the machine is never exhausted.

This dilatant hypothesis of aether is very promising, although it
cannot be pat forward as proved until it has been worked out in
detail, which will take long. In the meantime it is put forward
mainly to excite interest in the property of dilatancy to the discovery
of which it has led. This property, now that it has once been recog-
nised, is quite independent of any hypothesis, and offers a new field
for philosophical and mathematical research quite independent of the
sether.

[0. E.]

364 Professor W. E. Flotver [Feb. 19,

WEEKLY EVENING MEETING,

Friday, February 19, 1886.

Sir William Bowman, Bart. LL.D. F.K.S. Manager and Vice-
President, in tbe Chair.

Professor W. H. Flower, LL.D, F.K.S. Director of tlie British
Natural History Museum.

The Wings of Birds.

The power of flying through the air is one of the principal
characteristics of the cLass of Birds. Although some members of the
other great divisions of the Vertebrates— the bats among Mammals, the
extinct pterodactyle among Keptiles, the flying fishes among Pisces —
possess this power in a greater or less degree, these are all exceptional
forms, whereas in birds the faculty of flight is the rule, its absence
the exception. Among Invertebrates this power is possessed in a very
complete degree by the greater number of insects.

In the normal structure of the vertebrate animals there are two
pairs of limbs, anterior and posterior, never more. It often happens,
however, that one pair, and sometimes both, are suiDpressed, being
rudimentary, functionless, or entirely absent. Flight is always per-
formed by the anterior or pectoral pair, more or less modified for the
purpose. The super-addition of wings to arms, as in the pictorial
representations of angels, has no counterpart in nature. The wings of
the bird, the bat, the pterodactyle, and flying fish, are the homologues
of the arms of man, the fore-legs of beasts. In the flying fish the
power is gained simply by an enlargement of the pectoral fin, and the
function is very imperfect ; in the pterodactyle, by immense elonga-
tion of one (the outer) finger, and extension of the skin between
it and the side of the body; in the bats, by elongation of the
four outer fingers, and extension of a web of skin between them and
the body. In the bird the flying organ is constructed mainly of
epidermic structures, peculiar outgrowths from the surface, called
feathers — modifications of the same tissue which constitutes the hair,
horns, scales, or nails of other animals. Feathers are met with only
in birds, and are found in all the existing members of the class, con-
stituting the general covering of the surface of the body.

The framework to which the broad expanse formed by the feathers
is attached is composed of bones, essentially resembling those of the
fore-limb of other vertebrates. The distal segment, manus, or hand,
in the vast majority of birds, has three metacarpal bones ^nd digits,
the former being more or less united together in the adult state. The

1886.J on the Wings of Birds. 365

digits appear to correspond with tlie pollex, index, and mediiis of tlie
typical pentadactyle manus ; the second is always the longest. Both
it and the pollex frequently bear small horny claws at their extremity,
concealed among the feathers and functiouless, but very significant
in relation to the probable original condition of the avian wing. These
claws are altogether distinct from the large, and often functional, spurs
developed in many species from the edge of the metacarpal bones,
resembling both in use and situation the corresponding weapons in
the hind feet. The thii'd digit does not bear a second phalanx or
claw in any existing bird.

The quills, remiges, or flight feathers attached to the bones of the
manus (called " primaries "), never exceed twelve in number, and are
(as has been recently shown by Mr. Wray) in the very great
majority of birds distributed as follows : — Six, or in some few cases
(flamingo, storks, grebes, &c.), seven to the metacarj)us ; of the
remainder or digital feathers, one {ad-digital) is attached close to the
metacarpo-phalangeal articulation, and rests on the phalanx of the
third digit ; two (mid-digital) have their bases attached to the broad
dorsal surface of the basal phalanx of the second digit, which is
grooved to receive them ; the remainder {p'se-digital) are attached
to the second phalanx of the same digit. These last vary greatly
in development, in fact their variations constitute the most important
structural differences of the wing. In most birds there are two ; the
proximal one well developed, the distal always rudimentary ; but the
former may show every degree of shortening, until it becomes quite
rudimentary, or even altogether absent, as in Fringillidse and other
" nine-primaried " birds, in which there are six metacarpal remiges,
one ad-digital, two mid-digital, and no prsedigitals, or only a very
rudimentary one. The smaller feathers at the base of the quills, called
upper and under coverts, have an equally regular arrangement. The
webs or vanes of all the flight-feathers are made up of a series of
parallel " barbs " which cohere together by means of minute hook-
lets, and so present a continuous, solid, resisting surface to the air.

Such is the characteristic structure of the wing in almost all
carinate birds, whether powerfully developed for flight, as in the
eagles, albatrosses, or swifts, or whether reduced in size and power
to practically useless organs, as in the extinct great auk, the dodo
and its kindred, weka rail, notornis, cnemiornis, &c., most of
which, being inhabitants of islands containing no destructive land
mammals, appear to have lost the principal inducement, and with
it the power, to fly.

In the penguins (S;p'heniscomorplise) the feathery covering of the
wing entirely departs from the normal type. Each feather is like a
flattened scale frayed out at the edges, the barbs are non-coherent
and have no booklets. They form an imbricated covering of both
surfaces of the wing, including the broad patagium which extends from
the cubital side of the limb, but appear to have no definite relation to
the bones, and cannot be divided into distinct groups, corresponding

366 Professor W. H. Flower on the Wings of Birds. [Feb. 19,

to those described above. The structure of the wing separates the
penguins sharply from all the other carinate birds.

The Ratitae, or birds without keel to the sternum, form another very-
distinct group, distinguished by the rudimentary or imperfect con-
dition of the remiges or quills, which never have coherent barbs and
are therefore unfitted to the purpose of flight. In the ostrich and
rhea the bones, though comparatively small, are distinct and complete,
and the feathers large and definitely arranged. The emu, cassowary,
and apteryx show various degrees of degeneration, which apparently
culminated in the dinornis, no trace of a wing-bone of which bird
has ever been found. The question which naturally presents itself
with regard to these birds is, whether they represent a stage through
which all have j)assed before acquiring perfect wings, or whether
they are descendants of birds which had once such wings, but which
have become degraded by w^ant of use. In the absence of palteonto-
logical evidence it is difficult to decide this point. The complete
structure of the bony framework of the ostrich's wing, with its two
distinct claws, rather points to its direct descent from the reptilian
hand, without ever having passed through the stage of a flying organ.
The function of locomotion being entirely performed by powerfully
developed hind-legs, and the beak mounted on the long flexible neck
being sufficient for the offices commonly performed by hands, the
fore-limbs appear to have degenerated or disappeared, just as the
hind-limbs of the whales disappeared when their locomotory functions
were transferred to the tail. This view is strengthened by the great
light that has been thrown on the origin of the wings of the flying
birds by the fortunate discovery of the Arcliseopteryx of the Solenhofen
beds of Jurassic age, as in this most remarkable animal, half lizard and
half bird, the process of modification from hand to perfect flying bird is
clearly demonstrated. The three digits which in the existing forms
are more or less pressed together and imperfect, still retain their free-
dom and complete number of phalanges, and are each armed with
terminal claws, while the flight feathers and remiges of the cubital,
metacarpal, and digital series are fully developed and evidently
functional. The earlier stages in which the outer digits were still
present, and the feathers imperfectly formed or merely altered scales,
are not yet in evidence.

Some conception of the process by wliich a wing may have been
formed may also be derived from the study of the growth of feathers
on the feet* of some domestic varieties of pigeons and poultry, illustra-
tions of which were shown at the lecture.

[W. H. F.]

1886.] Mr. A. A. Common on Photography, &c. 3G7

WEEKLY EVENING MEETING,

Friday, February 26, 1886.

William Huggins, Esq. D.C.L. LL.D. F.R.S. Vice-President,
in the Chair.

A. A. Common, Esq. F.R.S. M.B.l.

Photography as an Aid to Astronomy.

In many kinds of astronomical work the old method of direct observa-
tion seems likely to be superseded by the use of jDhotography ; and
the astronomer of the near future, instead of examining with eye
and telescope the various objects of the heavens, will prefer to deal
with the automatic records they leave on the sensitive plate. In some
work this state of things already exists, and its extension to all kinds
seems but a matter of time. It appears strange that any indirect
way of seeing an object can be better than the direct way, but in
some cases we shall certainly find it to be so. Between the construc-
tion of the eye and of the apparatus of the photographer there are
many points of great similarity. Both have optical means of produc-
ing an image, a camera, or dark chamber to keep out other light than
that going to form this image ; and both have a similar screen on
which this image is received. It is when we come to consider the
action of the screen in dealing with the image that the distinctive
diiference becomes apparent. In the eye the retina receives this
image, and in some occult way the impressions are carried to the
brain. With the sensitive plate the varying amount of light that
makes up the images produces corresponding changes in the chemical
nature of the film which allows the reproduction of this image in a
visible form afterwards.

As I understand the action of the eye, the retina acts only as a
transmitter of the sensations produced on its delicate structure by the
image ; and the brain records these sensations in a more or less per-
fect manner according to its capacity to deal with all those sensations
that are transmitted ; hence the power of the eye is limited by the
power of the brain to record, and this is evidently in many cases less
than that of the eye to perceive, whilst the power of the eye itself is
limited in more than one important point as regards our subject, the
retina becoming insensible to an image however perfect if insufficiently
illuminated. With the sensitive plate the measure of the eflective
light of an image is not, as in the eye, the amount going to form the
image, but the total amount that can be accumulated by a sufficiently
long exj)osure. Hence, we have the remarkable fact that I have else-
where before mentioned, that a certain object such as a star or nebula,

Vol. XI, (No. 80.) 2 b

368 Mr. A. A. Common [Feb. 26,

that would be just beyond the power of the eye, however long the
gazing was continued, could be photographed with a sufficiently long
exposure ; and this holds good whatever optical power be employed
to increase the amount of light brought to the eye ; as with the same
optical power, the power of the sensitive plate, if allowed sufficient
exposure, will always be greater. There is from this another conse-
quen^e: — The enlargement of an image produced by a telescope is
limited in one direction by the light, faint objects becoming too faint
to be seen if greatly enlarged, the sensitive plate, however, may still
utilise this image. There are other points of difference between the
action of the retina and of the sensitive plate. The power of the
latter is greater to record rays of light of quicker vibration, and it
may be possible to obtain photographs of celestial objects radiating
light that the eye is not adapted to receive ; and it is also quite
possible that plates may be prepared that will be sensitive to the
visual rays so that the magnitudes of stars in stellar photographs
would agree with magnitudes as obtained by the eye.

Though the image seems to be clearly formed in the eye over a
large angular extent, the central parts only are clearly seen, and the
image has to be traversed across this central part piece by piece to be
IH'operly examined.

With the sensitive plate, the image, no matter how complex, acts
equally over its extent and records itself with fidelity.

As was well said many years ago by Dr. de la Eue, who has been
rightly called the father of astronomical j)hotography, " the sensitive
film is a retina that never forgets."

I will try and show to-night how important the difference between
the ordinary eye observations and the work done by photography
may become ; not only in cases where the ordinary visual observa-
tions have been used, but in cases where the use of the micrometer
attached to the telescope has been the only means of accurate observa-
tions. Looking for a moment at the history of our subject, it appears
that the earliest application of photography to a celestial object was
made by Professor J. W. Draper in 1840 within one year of the
announcement by Daguerre of the details of the photographic j^rocess
with which his name will always be associated. Professor Draper
obtained a picture of the moon in twenty minutes, using a lens and a
heliostat.

An extract from the minutes of the New York Lyceum of Natural
History was to this effect : —

" March 23, 1840. — Dr. Draper announced that he had succeeded
in getting a representation of the moon's surface by the daguerreo-
ty})e. The time occupied was twenty minutes, and the size of the
figure about one inch in diameter. Daguerre had attempted the same
thiug but did not succeed. This is the first time tliat anything like
a distinct representation of the moon's surface has been obtained. —
Signed, Kobert U. Brownne, Secretary."

Kememberiug that this entry was made less than one year after

1886.] on Photographj as an Aid to Astronomy. 369

the publication of Daguerre's process, tlie negative statement that
Daguerre had failed where Draper had succeeded, is strange ; and the
allusion to the distinct representation of the moon's surface rather
implies that other representations existecl. It is, however, the earliest
record I can find, and we may consider it the starting-point.

Beyond experimental work little seems to have been done with the
daguerreotype.

Some astronomers, notably G. P. Bond in America, assisted by
two skilful photographers, with the 15-inch refractor of the Harvard
College Observatory, obtained photographs of some of the brighter
stars, and also some very fair pictures of the moon, that were
exhibited at the 1851 Exhibition in London, and also at a meeting of
the R.A.S. in May of that year ; and some solar and spectroscoj^ic
work was also done in Europe.

The important fact of the possibility of thus getting pictures of
the heavenly bodies was established, so that with the introduction
of the collodion process in 1851, with its great advantages over
the difficult and costly daguerreotype, astronomical photography
was taken up and soon became firmly established. From this
time its history became a record of continual advance, delayed, it is
true, from time to time by the want of improvement in instrument or
method, when further extensions of the art were attempted, in every
case with ultimate success.

Of the early workers with the collodion process, and the more
recent workers with the modern gelatine or dry plate process, and the '
persevering and skilful way they have dealt with the difficulties that
always surround a new art, I do not propose to speak, excej)t inci-
dentally. Time would not allow me to do so here, nor is it part of
my purpose ; my object being rather to deal with the results obtained,
to speak of this new art or method of astronomical observation and
record, than to give an account of the labours of those who have made
it what it now is. I propose to exhibit by the electric lantern such
specimens of early and recent work as I have been able to obtain for
this purpose,* and from which I think you may form an idea as to the
present value of photography as an aid to astronomy, and the probable
greater aid it may in future become.

Before doing so, however, although the art of photography is now
known to almost every one, I should like to say a few words about the
three processes I have mentioned, the daguerreotype, the collodion,
and the gelatine or dry plate process, and also to give very shortly
a general idea of the instruments and methods in use by the astrono-
mical photographer.

For an account of the daguerreotype one has to refer to the text
w^orks, as it is not now in general use. Shortly it may be described

* For the loan of some of the photographs exhibited I ata indebted to the
kindness of Mr. Crookes, Dr. de la Rue, Mr. Lockyer, and Caj^tain Abney, and
also to tlie Brothers Henry of Paris for specimens of their recent work.

2 B 2

370 Mr. A. A. Common [Feb. 26,

as the use of a polished surface of silver (usually supported by a thin
backing of copper) that has been exposed to the action of iodine so as to
form a film of sensitive iodide of silver, that may be acted upon by light,
and afterwards developed by the vapour of mercury. Although not
now used for astronomical work, it may be that owing to the intimate
connection between the image formed by the silver compound and the
backing that supports it, it will be found to have advantages in cases
where delicate measurements are required, that the other processes
may not have.

The collodion and gelatine (or dry plate) processes are so called
from the nature of the medium that is used to carry the sensitive
salts of silver during exposure to the action of light. The chief
difference between them, beyond the greater sensitiveness of the
latter, is that with the collodion plate the process of preparation,
exposure, and develoj)ment must be part of a continuous operation
taken in due order and time, with all the necessary apparatus,
and the chemicals in a proper state of efficiency, ready to hand,
conditions not easy to attend to in astronomical photography, and
when long exposures are to be given, hardly to be fulfilled.

With the gelatine process the plates can be prepared beforehand
under the best conditions, and almost any time may elapse before
use. The exposure of the plate may take place for any length of
time, and the development made at any suitable time afterwards ; all
advantages for astronomical work that are obvious ; and in addition,
there is the important advantage of the greatest sensitiveness, on
which, more than anything else, success so much depends when it
becomes a question of dealing with a small amount of light. Each
process has its particular advantages of w^hich the specialist may avail
himself; but the gelatine dry plate is far beyond the others for
nearly every class of astronomical work.

With regard to the instruments and methods of work, while the
main principles are adhered to, modifications have to be made to
suit different classes of work. These will be briefly mentioned in
speaking of the photographs. In all cases there must be an image of
the object, and this image must fall exactly on the sensitive plate,
and be kept there during exposure.

The image produced by a telescope reflecting or refracting is
generally used direct ; indeed, with the exception of the sun, where
the large amount of light rendered enlargement advantageous, until
quite recently the primary image v/as always used, it being thought
that with the small amount of light generally at disposal it was better
to get a picture thus and then enlarge it afterwards than to enlarge
the first image and so increase the time of exposure and all the
trouble that comes from atmospheric and instrumental tremors, and
, other causes.

We shall see how much has been gained by departing from this
old plan and using an enlarged imago when we come to examine the
photographs of the planets.

1886.] 071 Photography as an Aid to Astronomy. 371

In the method of working there is one important difference between
that followed by the terrestrial and celestial photographer. \Yithout
exception, everything that the latter has to photograph is in continual
apparent motion, owing to the rotation of the earth, and in some cases
to the proper motion of the object itself. This necessitates the use
of an equatorial mounting to carry the photographic apparatus, with
clockwork to give it a regular motion in a direction contrary to that
of the earth. Even then the difficulties of keeping the telescope
moving for one or more hours without allowing deviation of the
image on the sensitive j)late of a yoVo ^^ ^^ mah. during this time,
taxes very severely the powers of the observer ; for, every such long
exposure must be watched not only to correct irregularities of the
clock, but other slight though important movements, due to change
of refraction and other causes, which, if not immediately corrected,
would spoil the picture. These mechanical difficulties, however, are
not insurmountable, as will be seen from some of the photographs I
shall show ; and as instruments improve and workers gain experience
they will become less.

There are many technical details of extreme interest to the worker,
which it is hardly necessary to name to-night.

The light from the different celestial bodies varies greatly in
intensity. Between that from our sun and that from the faintest
nebula or star that can be seen, there is such an immense difference,
that their relative amounts can hardly be expressed by figures.

Dr. Huggins estimates the light of the faintest nebula that can
be seen with a moderately large instrument as equal to ^ooq-q ^^ *^®
light of a single standard candle viewed at a distance of a quarter of
a mile, that is, that such a candle a quarter of a mile off is 20,000 times
more brilliant than the nebula.

The astronomer, who deals with both, has therefore need of all his
art to reduce the light in the one case to that suitable for his pur-
pose ; and to utilise every ray he can get in the other, regulating the
exposure for the one to a minute fraction of a second, and extending
for the other to hours.

Between these two extremes of light-giving power are comprised
all other celestial objects.

For the purpose of convenience I will take the photograiDhs,
which I propose to show you, in the following order : — (1) those
of the sun ; (2) the moon ; (3) the stars ; (4) planets ; (5) nebulae ;
and (6) comets ; giving in nearly every case an early photograph and
a recent one for comparison ; and, where I can, a specimen of the work
of eye and hand that may be directly compared with a photograph of
the same object.

With the sun there are two distinct phenomena to observe:
(1) the physical aspect of his surface, with the remarkable spots
and markings that are frequently visible; and (2) the wonderful
prominences and corona that surrounds the sun and becomes visible
when he is eclipsed.

372 3Ir. A. A. Common [Feb. 26,

The first important photograpli of the surface of the sun seems
to have been obtained by Dr. de La Rue, July 24th, 1861.

The j^hotograph I show is one copied from a picture, itself a
reproduction, without retouch, of the original negative.

(Photographs of the surface of the sun, by Janssen, were also
shown.)

Berkowski, in the eclipse of the 28th July, 1851, took by the
daguerreotype the first photograph showing the corona and promi-
nences, and Dr. de la Eue in 1860 took the first good photographs
of the ^prominences, and obtained traces of the corona, using the
collodion process.

In 1869, Professor Stephen Alexander obtained at Ollumwa the
first good photograjdjs of the corona.

(Photographs of the corona and prominences, by General Tennaut,
Dr. de la Pue, and Captain Abney were shown.)

Since this time, photography has been used at every total eclipse
that has been observed, with increasing success.

In speaking of these corona photographs, I must not forget to
mention the important work of Dr. Huggins in photographing the
uneclipsed corona. He himself has lately given an account of the
methods he employs, and I have no doubt that under his skilful
direction we shall see the same successful advances as those we can
mark in every branch of astrcmomical photography ; although it is a
work which many of those who know the great difiiculties to be
encountered would hardly have dared to attempt.

Photographs of the moon are so easy to obtain that she has
received more attention than any other celestial object ; yet, strange
to say, with less improvement, the j)ictures taken by Rutherford
more than twenty years ago, not being yet surpassed.

Now, however, that we can safely enlarge the primary image
without unduly prolonging the exposure we may soon expect photo-
graphs of portions of the moon that will be far beyond anything
hitherto done, or possible, where the whole image is attempted.

[Photographs of the moon, by Mr. Crookes, Dr. de la Rue, and
others, were shown.]

With the stars photography has recently been most successful.

Rutherford, in 1864, completed a photographic objective of
11 J inches aperture and 14 feet focal length, with which he obtained
some very fine photograi^hs. Some of his remarks, written in 1864,*
in connection with the future of astronomical photography, are so
interesting at the present time that I will repeat them. " Since
the completion of the photograjihic objective, but one night has
occurred (the 6th of March) with a fine atmosphere, and on that
occasion the instrument was occujued with the moon ; so that as yet
I have not tested its powers upon the close double stars, 2" being

American Journal of Science anil Art,' 2nd series, vol. xxxix. p. 308.

1886.] on Photography as an Aid to Astronomy. 373

the nearest pair it has been tried ujoon. This distance is quite
manageable provided the stars are of nearly equal magnitude.

" The power to obtain images of the ninth magnitude stars with so
moderate an aperture promises to develop and increase the application
of ijhotography to the mapping of the sidereal heavens and in some
measure to realise the hopes which have so long been deferred and
disappointed.

" It would not be difficult to arrange a camera-box capable of
exposing a surface sufficient to obtain a map of two degrees square,
and with instruments of large aperture we may hope to reach much
smaller stars than I have yet taken. There is also every probability
that the chemistry of photography will be very much improved and
more sensitive methods devised."

In the light of recent work these words are almost prophetic.
The sensitive methods have been devised, and the result is that the
anticipations formed by Kutherford in 1864 are in 1886 not only
fulfilled but exceeded. It is in stellar photograj)hy that the
astronomer will be most benefited by the immense saving of labour
in making charts ; a single plate taken in one hour showing in their
proper relative place and in their relative photographic magnitudes,
all the stars down to the fifteenth magnitude over an area of about six
degrees— a result that it would be hardly possible to obtain by the
usual method of eye observation and measure.

[Photographs of the stars round Altair, taken in 1883, of part of
Orion, taken in 1884 by the speaker, and some of the recent plates of
stars and double stars, by the Brothers Henry of Paris, were shown,
with a companion plate of similar parts of the sky as shown on
Argelander's maj)s, showing the enormous increase in the number
of stars shown by one hour's exj)0sure, in one case ten times as many
stars being on the photographic plate as on the same area of the map.]

The i)lanets J upiter and Saturn were photographed by Dr. de la Eue
and others in the early days of photography. I have not been able
to obtain copies, or even a sight of any of these earlier ones, but I
have some of my own work that will enable you to see the improve-
ment that has been made since 1876.

[Photographs of Saturn from 1877 and of Jupiter from 1878 were
shown, including some of the recent work of the Brothers Henry of
Paris, showing the great advance obtained by the enlargement of the
primary image.]

With nebulae, although the work has been all done within the last
few years, the results have been very satisfactory.

Dr. Draper, in 1880, obtained a very promising picture of the
Orion nebula, and I was able in 1883 (after trials commencing in 1879)
to get, with a three-foot reflector, some very fair photographs. ^ A com-
parison with the last drawing will show the chief points of difi'erence.

Other nebulae have been photographed by myself and others, and
the power of the j)hotograph to portray these mysterious shapes has
been thoroughly demonstrated.

374 Mr. A. A. Common [Feb. 26,

In a recent pliotograpli of tlie Pleiades, wbicli the MM. Henry
have taken, they have obtained a picture of a nebula near Maia that
has not been seen before, and which has since been seen with the great
telescope at Pulkowa in Russia — a telescope very much larger than
that with which the photograph was taken.

On this plate part of the nebula near Merope is also shown.

[Photographs of Orion with exposures of from 1 to 80 minutes
were shown, and also photographs of the drawings made by the Bonds,
Lord Rosse, Trouvelot, and others, for comparison.]

Of comets, I have here copies of two of the photograi^hs taken
at the Cape of Good Hope, in 1882. These pictures may be called
I)hotographs of stars from the immense number that have impressed
themselves on the plate.

To others as well as to myself, these photographs came as a revela-
tion of the power of photography in this direction, and it is probably
to them that the increased attention lately given to stellar photo-
graphy is due.

Thei'e are other applications of photography to the work of the
astronomer besides those I have mentioned.

By the analysis of the light that comes to us from the heavenly
bodies the spectroscope tells us what elementary substances exist in
those bodies and in this most delicate research photography has
played a most important part, especially in dealing with that part of
the spectrum that the eye is not able to grasp.

The fleeting image that requires all the care that the mind can
give to interpret is recorded by means of photography, and can then
be studied under the most favourable conditions.

Such photographs cannot be shown in the same way as those I
have shown you to-night, nor can they be rendered intelligible except
to the very few who have made the consideration their study.

The recording of the passage of a star past the wires of a transit
instrument has always hitherto been done by the eye, but it is quite
possible that here photography may come in for this purpose, and
render such observations free from personal equation, as the allowance
that has to be made for different powers of different brains to record
an event is called by astronomers.

There is also a possibility that photograi^hy will be available to
record the paths of meteors and thus aid in a research that is engag-
ing more attention every day.

The discovery of minor planets by means of photography cannot
be helped when such photographs of the heavens as those taken by
the MM. Henry are produced consecutively, a comparison from time
t(j time being sufficient to detect the disi^lacement in position that
they must undergo, and it is not too much to say that if Uranus had
not been discovered by Herschel, and in consequence of the disagree-
ment between the position this planet should have occupied, and those
it did occupy owing to the attraction of Neptune, and the subsequent
discovery of this planet by the entirely theoretical investigations of

188G.] on Phoiograjphy as an Aid to Astronomy. 375

Professors Adams and Leverricr, both would have been discovered
eventually by photography. And if there is now, as some suppose
there is — and there is nothing against such a snjiposition — another
major planet beyond Nej^tune, it is most probable that it will be
thus discovered.

In thus bringing before you all these wonderful things that can be
done by photography I do not wish to imply that it is quite a new
thing. Astronomers have knov/n and valued it, but the immense step
it has lately taken through the great sensitiveness of the dry plate
process has not, I believe, been fully realised.

For many years the art of photography as applied to astronomy
has remained very nearly in the state it was when Eutherford wrote
those remarks I have quoted. At a bound it has gone far beyond
anything that was ex23ected from it, and bids fair to overturn a good
deal of the practice that has hitherto existed among astronomers.
I hope soon to see it recognised as the most potent agent of research
and record that has ever been within the reach of the astronomer ; so
that the records that the future astronomer will use, will not be the
M'ritten impressions of dead men's views, but veritable images of the
different objects of the heavens recorded by themselves as they
existed.

[A. A. C]

376 General Montlily Meeting. [March 1,

GENERAL MONTHLY MEETING,

Monday, March 1, 1886.

Warren de la Rue, Esq. M.A. D.C.L. F.R.S. Manager and
Vice-President, in the Chair.

John Abercrombie, Sen. M.D. F.R.C.P.

William Henry Barlow, Esq. F.R.S. M. Inst. C.E.

Alfred Carpmael, Esq.

Henry Doetsch, Esq,

John Piggin Fearfield, Esq.

R. Gent-Davis, Esq. M.P.

John Hopkinson, Esq. M.A. F.R.S.

John Inglis, Esq.

Major E. Cecil Johnson.

Mrs. T. C. Leitch.

Mrs. S. Joshua.

George Palmer, Esq.

Sir Ughtred Kay-Shuttle worth, Bart. M.P.

Silvauus P. Thompson, Esq.

Sir William Thomson, D.C.L. LL.D. F.R.S.

Walter Tomlinson, Esq. M.A.

were elected Members of the Royal Institution.

At a Meeting of the Managers held this day, the Actonian Prize
of one hundred guineas was awarded to Professor G. G. Stokes,
Pres. R.S. for his lectures on Light, in conformity with the Acton
Endowment Trust Deed.

The Presents received since the last Meeting were laid on the
table, and the thanks of the Members returned for the same, viz. : —

The Secretary of State for India — Keport on Public Instruction in Bengal, 1884-5.

fol. 1885.
Ministry of Fuhlic Worhs, Rome — Giornale del Genio Civile, Serie Quarta,

Vol. V. No. 12. 8vo. And Disegni. fol. 1885.
Accademia dei Lincei, Reale, Roma — Atti, Serie Quarta : Eendiconti. Vol. II.

Fasc. 1. 8vo. 1885-6.
Asfronomiccd Society, i?o?/aZ— Monthly Notices, Vol, XLVI. No. 3. 188G.
Hankers, Institute o/— Journal, Vol. VII. Part 2. 8vo. 188G.
British Architects, Royal Institute o/— Proceedings, 1885-6, Nos. 8, 9. -Ito.
Chemical Society — Journal for Februaiy, 1886. 8vo.
Chief Signal Officer, United Slides ^r/»7/— Professional Pajicrs of the Signal

Service, Nus. 16 and 18. 4 to. 1885.

1886.] General Mvnthhj Meeting. 377

Crisp, Fravli, Esq. LL.B. F.L.S. d-c. M.E.I. (the Editor)— J oumix\ of the Royal

Microscopical Society, Series II. Vol. VI. Part 1. 8vo. 1886.
Editors — American Journal of Science for February, 1886. Svo.
Analyst for February, 1886. 8vo.
Atheuseum for February, 1886. 4to.
Chemical News for February, 1886. 4to.
Engineer for February, 1886. fol.
Horologicnl Journal for February, 1886. Svo.
Iron for February, 188G. 4to.
Nature for February, 1886. 4to.
Revue Scientifique for February, 1886.
Science Monthly, Illustrated, for February, 1886. 8vo.
Telegraphic Journal for February, 1886. Svo.
Ellis, Alexander John, Esq. B.A. F.R.S. M.R I. (the Author)— Sensations of Tone.
By H. L. F. Hclmholtz. 2nd English edition. Svo. 1885.
Musical Scales of Various Nations. ( Journ. of Soc. of Arts.) Svo. 1885.
Franldin Institute — Journal, No. 722. Svo. 1886.
Geographical Society, Royal — Proceedings, New Series, Vol. VIII. No. 2. Svo.

1886.
Geoloqical Institute, Imperial, Vienna — Jahrbuch : Band XXXV. Heft 4 Svo

1885.
Geological Society — Quarterly Journal, No. 165. Svo. 1886.
Geological Society of Ireland, Royal — Journal, Vol. XVI. Part 3. Svo. 1886.
Iron and Steel Institute — Journal, 1885. Part 2. Svo.
Johns HoxMns University— Vniyevshy Circular, No. 46. 4to. 1886.

Studies in Historical and Political Science, Fourth Series, No. 1. Svo. 1886.
3Iann, Robert James, MD. F.R.C.S. il/.i?.!.— Lightning Conductors. By R.

Anderson. 3rd edition. Svo. 1885.
Marvin, C. Esq. (the Author) — Russia's Power of Attacking India. Svo. 1886.
Maryland Medical and Chirurgical Faculty — Transactions, 87th Session Svo

1885.
Meteorological O/^jce— Report of Meteorological Council, R. S. to 31st March. 1885.

Svo. 1886.
North of England Institute of Mining and Mechanical Engineers — Transactions,

Vol. XXXV. Part 1. Svo. 1886.
Odontological Society of Great Britain — Transactions, Vol. XVIII. No. 4. New

Series. Svo. 1886.
Pharmaceutical Society of Great Britain — Journal, February, 1886. Svo.
Photographic Society— Jonrnal, New Series, A^'ol. X. No. 4. Svo. 1886.
Preussische Ahademie der Wissenschaften—Sitzxingshevichte XL.-LII. Svo.

1885-6.
Richardson, B. W. M.B. F.R.S. (the Author)— The Asclepiad, Vol. III. No. 9.

Svo. 1886.
Royal Society of London — Proceedings, No. 240. Svo. 1885.
Scottish Society of Arts, Royal — Transactions, Vol. XI. Part 3. Svo. 1885.
Smithsonian Institution — Third Report of the Bureau of Ethnology, 1881-2. 4to.

1884.
Society of Arts — Journal, February, 1886. Svo.
Statistical Society— J omna], Vol. XLVIII. Part 4. Svo. 1885.

Jubilee Volume, June, 1885. Svo.
St. Bartholomew'' s Hospital — Reports, Vol. XXI. Svo. 1885.
St. Petershourg, Academic des Sciences — Me'moires, Tome XXXIII. Nos. 3, 4.

4to. ■ 1885.
United Service Institution, Royal — Journal, No. 132. Svo. 1886.
University College, North Wales — Calendar, 1885-6. 12mo.

Vereins zur Beforderung des Gewerhfleisses in Preussen — Verhaudlungen, 1886 ;
Heft 1. 4to.

378 ^rof. Alexander Macalister [March 6,

WEEKLY EVENING MEETING,

Friday, Marcli 5, 1886.

Sir Frederick Bramwell, F.E.S. Honorary Secretary and Vice-
President, in the Chair.

Professor Alexander Macalister, M.D. F.E.S.

Anatomical and Medical Knowledge of Ancient Egypt (^Abstract').

The surviving fragments of the early literature of Egyj^t are mainly
of a religious character ; but this is not to be wondered at, for the
genius of the peoj^le wds essentially religious, and their doctrine of
the future state leavened their national life in almost every particular ;
to them the body was an integral part of the immortal humanity,
therefore it must not be permitted to turn to decay, but it must be
preserved from corrujDtion that it may be a fit receptacle for the soul
to dwell in through eternity.

Their treatment of the body is thus dependent on their belief of
its relation to the soul, and this, we learn from their religious writings,
was a relationship of eternal interdependence.

To secure perpetual preservation the body must be proj)erly em-
balmed. The cavities must be opened and subjected to the action of
antiseptics. Even though the body is sacred, under the special pro-
tection of the god Thoth, though each part is under the guardianship)
of a special divinity, yet this sacredness does not preclude careful
inspection and the processes necessary for preservation, for all parts
have to be perpetuated.

Embalming is a religious rite, to be performed by the priests of
the cultus, and the historian Herodotus has preserved for us what is
doubtless a substantially accurate account of the different methods
whereby it was done, in the later times in which he lived.

There is, in Diodorus Siculus, an account of an episode in the
operation of embalming, which has long passed current as authentic.
He says that when the sacred scribe inspected the body, he marked on
its left side how much it was lawful to cut. Then the paraschistes,
holding in his hand a knife of Ethioj^ian stone, dissected the flesh as
far as the law permitted; then, turning suddenly, he fled away as fast
as he was able to run, pursued by the execrations of the bystanders,
often pelted with stones and otherwise maltreated. Then the tari-
clieuta3 enter, and passing their hands through the incisions into the
body, remove therefrom the digestive organs, the heart, the kidneys,
and other viscera. 'Jlien they wash out the cavities with palm wine
and aromatics, and finally replace the j>arts which have been anointed
with antiseptics.

While some portions of this description agree both with the earlier

1886.] on Anatomical and Medical Knowledge of Ancient Egypt. 379

account given by Herodotus, and with the national literature, yet the
first part I believe to be purely fictitious. There is no confirmation
in Egyptian literature of that portion which relates to the ill-treat-
ment of the outcast j^araschistes. There is no trace of any such
popular commotion in any of the pictures representing the stages of
the process. Nay, we have direct testimony on the subject, for it is
written in the Rhind papyrus, concerning the embalming of. the Lady
Ta-ani, " they made the incisions by the hand of a ;^ar-heb in the place
of opening, at the eighth hour." It was this grade of priests who
began and who carried out the work of embalming. M. Eevillout
has proved conclusively that the paraschistes and taricheutde are two
Greek names for the same functionaries, whose native name is ;)(ar-heb.
In the Rhind papyrus before quoted, it is written, " preserved is the
body by the ;)(ar-heb, who is thoroughly acquainted with the science
of embalming." From other passages in Egyj)tian writing we learn
that these ;)(ar-hebs were priests, sacred scribes, men of high character,
physicians, to whom even magical powers are ascribed, for the breath
from the mouth of a ^'^^r-heb has power to dissipate disease of the
heart. Further, we learn from several records that the incisions were
not all made at once, but in at least two series ; for the perfect pre-
servation of a mummy was accomplished gradually, the process
spreading over seventy days. .

The _)(ar-hebs were men with no civil disabilities ; they bought
and sold land, they made contracts, they drew up formal marriage
settlements for their wives, and received payment in money, vegetables,
wine, and other articles.

The organs removed from the bodies of persons of the better classes
were not returned into the body, but were i^reserved in vases of
alabaster or stone, surmounted by the heads of the four divinities of
Hades, the sons of Horus and Isis. The vessel which contained the
stomach and colon bore the human head of Amset ; that which held
the lungs and heart was under the protection of the jackal-head of
Tuaut-mutef; that which contains the small intestine was beneath
the baboon-head of Hapi ; while the liver was guarded by the hawk-
head of Kabhsenuf.

During the ascendancy of Greek influence in Egypt, Alexandria
earned the reputation of being the chief school of anatomy and
medicine in the world. Erasistratus, who lived in the days of Ptolemy
Soter, B.C. 285, was an anatomist of such enthusiasm, that he and his
disciples receiving from the king criminals condemned to death,
" vivos inciderint considerarintciue etiam, sjnrita remanente, ea qiise natura
ante clqusisset, eorumque posituram, colorem, figuram, magnitiidinem,
ordinem, duritiem, inollitiem, Isevorem, contactum, processus deinde singu-
loriim et recessus et sive quid inseritur cdteri sive quid partem alterius in
se recipit.^' It is recorded of Herophilus, the successor of Erasi-
stratus, by Tertullian, that he dissected 600 bodies.

But this Alexandrian school, although upon Egyptian soil, was
essentially Greek in spirit ; even Herophilus had learned some of his

380 Frof. Alexander Macallster [March 5,

anatomy from Praxagoras of Cos, althoiigli, as the anatomy of the
earlier Greek school was originally derived from Egyj^t, it was but
returning to the mother-country the traditions of culture derived
therefrom. It was in Egypt Democritus of Abdera studied, and so
was fitted to teach anatomy to Hippocrates, the father of medicine.
The three pithy and graphic letters on anatomy which are extant,
which it is supposed Democritus sent to Hippocrates, may well have
been the result of his Egyptian training. At a later period, it was
at Alexandria that Galen pursued his study of anatomy under Hera-
clianus, and the anatomical school of Alexandria survived until the
Mohammedan invasion of Amru in a.d, 640. That much even of the
earlier Greek medicine, anatomy, and pathology was derived from
Egypt, we learn, both directly and indirectly. Most of the vegetable
drugs in use in Greece were natives of Egypt ; and Galen, speaking
of one prescription called Epigonos, tells us that it was obtained from
the adytum of the temple of Ptah, at Memphis. He quotes it, and
other Egyptian prescriptions from the book Narthex, written by Hera
of Kappadokia.

Medical colleges of far greater antiquity than that of Alexandria
existed in the priestly schools of Memphis, Heliopolis, Sais, and
Thebes. These were much more faithful exponents of the purely
Egyptian system of the art of physic. .

It was natural that Memphis should have been the centre of
medical training in Egypt, as Imhotep, the patron god of medicine,
was son of Ptah the creator, the great god of the Memphite triad.
Here was the great library wherein students of the medical priesthood
could learn their traditional lore. Even as late as the time of
Clement of Alexandria, we read of the " TesseraJconta ai ixinu anaglmiai
to Herme gegonasi Bihlioi,'" which these pastophori studied ; and of
these, six were purely medical books which were respectively on
Anatomy, on Disease, on Drugs, on Ophthalmology, on Surgical
Instruments, and on Gynaecology. It is interesting to note that
Clement gives to Anatomy the first place in the curriculum, as
the foundation of medicine. Possibly the treatise Ambres, whose
title has been preserved by Horapollo, may have been one of
these. It was a sacred book whose rules were used by the
physicians to make their prognosis, whether a jiatient was caj)able of
recovery or no. It is probably from the title of this book that
Hesychius has framed the verb Ambrizein, which he defines as
Therapeuein en tois ierois. I cannot, however, find this verb in use
by any author, and it has not obtained a place in Liddell and Scott.
Such a book might well be the peri Noson of Clement. The name is
strictly not a proper one, but is the Greek transliteration of the first
words of one of these medical works.

Scant remains are left of these once famous seats of learning. Of
the city of Memphis itself nothing remains but heaps which can
scarcely be dignified as ruins, and of its medical library only a few
fragments have been preserved.

188G.] on Anatomical and Medical Knowledge of Ancient Egypt. 381

Of the ancient medical literature of Egypt, two nearly complete
treatises are still extant, and six or seven fragments of others. These
vary in date and in perfection. The most complete are the Papyrus
Ebers, and the Medical Papyrus of Berlin. The fragments which
are noteworthy are: — The British Museum Pa|)yrus, formerly the
property of the Royal Institution, the Papyrus VI. of Boulaq, the
Magical Papyri of Turin and Paris, the Coj^tic Medical Manuscript
in the Borgia Library, and the Greek Papyri 383 and 384 of Leyden.

In the very brief sketch which the time at our disposal allows of the
contents of these works, I cannot enter into the analysis of all these
works, nor into discussion of disiDuted points of translation, but I hope
soon to be in a position to publish a detailed and critical study of this
medical literature at fuller length. We shall confine ourselves prin-
cipally in our survey to the first and second.

The most complete of all these papyri is that which is known by the
name Papyrus Ebers, said to have come from a tomb at El Assassif ;
and this is not improbable, as the Medical Papyrus VI. of Boulaq is
from that place. It is in good preservation, written in a clear hieratic
script, the characters resemble those of the earlier manuscript of the
18th dynasty ; and its text presents few difficulties to the reader excej)t
those arising from the difficulty of ascertaining the precise diseases
referred to, and the exact nature of the remedies prescribed. Unlike
the Berlin PajDyrus, it is perfect at its begiiming, and it consists of 110
pages, each of twenty-one or twenty-two lines. A fac-simile copy has
been 23ublished by Prof. Ebers, with a short synopsis of his reading of
the contents. A brief notice of its contents has been published by
Chabas, and it has partly been translated into Norwegian by Prof.
Lieblein, but no complete translation has as yet been made public.

The work is really a series of treatises on difierent branches of me-
dicine, and from its introductory paragraph seems to be the embodiment
of Heliopolitan medical lore, probably dating from about 1550 B.C.

The first page, and the first five lines of the second, consist of an
introductory preface and prayer : — " Beginning of the treatise on the
administration of medicine to all parts of a person. I have come from
Heliopolis, from the authorities of the great Temple, from the rulers
of thought, the eternal governors of safety. I come from Sais with
the mother goddesses as a protector to me ; I speak for them ; I do it
from the Lord of the assembly conquering evil, the god slaying the
slayers, whose several sections are from this my head, from this my
neck, from these my arms, from these my limbs, from these my organs,
to destroy the magical power of the ruler who influences my flesh,
who sickens in these my limbs, and penetrates into my flesh, into my
head, into my arms, into my body," &c.

After this prefatory adjuration follows a section on hygienic
measures, cathartics, diuretics, and other remedies of the kind, which
occupies the following sixteen pages. This is followed by a short section
on the effects of the j^arasite Bilharzia haematobia, still a very common
cause of disease in the Nile valley, and the pages from this to the

382 Prof. Alexander Macalister [Marcli 5,

twenty-third are taken iii? with prescriptions for parasites. Three
prescriptions follow for u;i(et and others for ubaii, whose treatment
takes up the following four pages. Diseases of the colon, rectum,
and heart are next prescribed for, and diseases of the head follow ;
one prescription is given as a quotation from another medical treatise,
described as " the Old Scripture of the Wisdom of Men." Eenal and
gastric diseases follow, and a long section on oiDhthalmology, beginning,
" Treatise on the sufferings in the eye, means for the cure of inflamma-
tion, and determination of blood to the eye." Diseases of the eye appear
to have been as rife in Egypt then as they are still, and the author
names twenty-two distinct diseases, some of which are briefly and
graphically characterised. We can recognise among these, conjunc-
tival inflammation, choroiditis, amaurosis, cataract, oimcities of the
cornea, as well as fistula lachrymalis, and others not so easily identified.
One ointment for the eye, whose formula he gives, was invented by
Chui, the president of the college ; another is a foreign prescrijDtion in
use among the Phoenicians at Byblus.

Nor were serious maladies alone attended to, but those which
interfere with the apj)earance' also claimed the physician's care.
Twenty-four prescrij)tions of hair-washes, oils, dej)ilatories, and dyes,
are given, and some of them are characterised as very good. One of
these prescriptions, found on p. 66, line 15, is entitled, "Another
prescription to stimulate the growth of hair, prepared for the Lady
Sesh, the mother of his Majesty King of Upper and Lower Egypt,
Teta the blessed." This paragraph carries us back to the beginning
of time, for Teta was the second king of the first dynasty, about
4000 B.C. The Egyptian priest Manetho notes in regard t^ him that
he wrote books on human anatomy, for he was a physician-

After several smaller sections concerning diseases of the liver,
there begins on p. 70 a treatise on the surgery of wounds, ulcers,
erysipelas, cutaneous diseases, and diseases of the ear, nose, &c.

The section of this papyrus, which begins on the ninety-ninth page,
is a treatise on the vascular system, entitled " The beginning of the
mystbiy of medicine, knowledge of the motions of the heart, and
knowledge of the heart." " There are vessels from it to all parts,
which the physician Nebse;!(t, priest and Lord of Healing, describes.
All these he points out with his fingers to the head, to the neck, to
the hand, to the epigastrium, to the arms, to the legs ; all he enume-
rates from the heart, because the vessels are from it to all parts ; as
he describes, it is the beginning of the vessels to each organ."

The author then proceeds to enumerate the distribution of these
vessels from the heart, and first gives those ascending to the head.

Digressing from the vessels to the animal sj)irits, Nebse;^t tells us
that these vital spirits enter one nostril, 2)cnetrate to the heart througli
the tube which carries them into the body-cavity. A little farther
on he states another singular hypothesis concerning these vital
spirits ; for, speaking of the ears, he says, " Tliere are four vessels
going to the two cars together, two on the right side, two on the left

1886.] on Anatomical and Medical Knowledge of Ancient Egypt. 383

side, carrying the vital spirit into the one right ear, the breath of
death into the left ear, that is, it enters on the right-hand side, the
breath of death enters on the left-hand side."

]N'ebse;i(t next describes the vessels of the upper and lower limbs,
and the arteries of the viscera.

The anatomical description is followed by a series of aphorisms
regarding the pathology of vascular disease, arranged in separate
sentences ; protasis and apodosis beginning respectively with Ar and
pu, reminding us of the -qv fxe of HipiDOcrates ; indeed, there is such a
Hippocratic aspect about these that one cannot resist the conviction
that we have reached here the source of much of the Hippocratic
learning. It is possible that the earlier phrase may be interrogative,
and the latter an answer ; but it is more likely that the protasis is
conditional than interrogative. They relate to such conditions as
syncope, cardiac disturbance from abdominal distension, enlargement
of the heart, pericardiac adhesion and effusion, dilatation, and enlarge-
ment of the heart, &c. There are twenty-two such queries, and some
of them point to careful pathological observation ; thus there is an
allusion to valvular stenosis in one, which says, " If the orifice of the
heart be turned back, then constricted is the mouth of the heart."

Of the Berlin papyrus a fac-simile has been published, and it has
been discussed by three eminent scholars, Brugsch, Eenouf, and
Chabas. It is also written in hieratic characters, which are clear and
legible, and was executed in the reign of Kameses II., the Pharaoh of
the oppression, who reigned about 1300 B.C. The document consists
of twenty-one leaves, two of which are written on both sides. The
text is for the most part easily read ; the chief difficulty presented by
it, as by the other, is that of understanding the names of diseases and
of remedies, to which no cognate words in Coptic, nor derivative
words in other languages, have come down to us.

The other fragments are of literary rather than of medical
interest. They abound in mystical formulae, and seem to have been
magical and occult rather than scientific. Of the Coptic MS. a
transcript was published by Zoega, and it is evidently a fragment of
a larger work; it deals chiefly with eruptive fevers and similar
diseases.

[A. M.]

Vol. XI. (No. 80.) 2 c

384 Mr. Beginald Stuart Poole [March 12,

WEEKLY EVENING MEETING,

Friday, March 12, 1886.

The Duke of Northumberland, E.G. D.C.L. LL.D. President,

in the Chair.

Reginald Stuart Poole, Esq. LL.D. of the British Museum.

The Discovery of the Biblical Cities of Egypt.

Biblical criticism has been pursued by three schools. The Old School
was eminently conservative, and by too defensive an attitude had
produced the strong reaction of the New School, whose tendency was
in the opposite direction. Kejecting traditional authority, this school
based all its arguments on the text itself. The appearance of the
text, as redacted by the Masoretes in the sixth century of our era,
seemed to it to favour the idea of the latest date in all cases,
especially in that of the major part of the Pentateuch. The weak
jjoint in the researches of a body of scholars who had rendered the
greatest services to verbal criticism was their failure to pay due
consideration to historical evidence outside the record. Thus the
Moabite Stone, a document of the ninth century before our era,
reversed a canon of their criticism. Aramaic forms are now shown
to be consistent with antiquity, and no longer a proof of late date.
Again, existence of the Levitical body as generally understood, and
the arrangement of the Levitical cities, is denied by Prof. Wellhausen ;
yet the list of the conquests of Shishak, Jeroboam's ally, enumerates
ten Israelite cities, seven or eight of which belong to the Levitical
list, thus explaining the statements of Chronicles that the Levites
supported Rehoboam and were driven out by Jeroboam. This docu-
ment, fully explained twenty-two years ago, was wholly ignored by
Prof. Wellhausen. Such instances justified the existence of the Third
or Historical School, which devotes itself to bringing all historical
evidence to the elucidation of Biblical history. The chief weapon of
this school is the spade of the excavator.

The Egypt Exploration Fund, desirous of finding monumental
evidence of the history of the Hebrews in Egypt, succeeded, in 1883,
in obtaining the services of Mr. Kaville, one of the first living
Egyptologists. On reaching Cairo, Mr. Naville asked the advice of
Prof. Maspero, Director of the Museums and Excavations of Egypt.
He was recommended to try the great mound of Tel-el-Maskhutah,
on the Sweet-water Canal leading to Ismailia. This mound was sup-
posed by Lepsius to cover the remains of Kaamses or Rameses, one of
the two store-cities built by the Israelites during the great oppression.
Mr. Naville's excavation revealed not Rameses, but the sister store-city

1886.] on the Discovery of the Biblical Cities of Egypt, 385

Pithom. Pithom was at once a fortress and a place of stores, in
extent not larger than Lincoln's Inn Fields, outside which a later
town had grown. The walls of Pithom were 24 feet thick, of unburnt
brick. A sixth of its area was found to be filled by store-chambers
of massive construction, entered from above. Probably these occupied
a still larger space, and there was also a temple built by Eameses II.,
founder of the town, a colossal hawk bearing whose name was brought
thence by Mr. Naville, and is now in the British Museum. The
bricks are also of the period of the same sovereign.

The first deduction from this evidence was the identification of
Eameses II. as the great oppressor of the Hebrews. This view was
started by Algernon, Duke of Northumberland, in Wilkinson's
' Ancient Egyptians ' (i. p. 77 seqq.), with the modification that the first
oppressor was Eameses I., and the founder of Pithom and Eameses was
Eameses IT. It was revived by Prof. Lepsius in the form first stated,
and had already received the support of all leading Egyptologists.
Equally Meneptah, the son of Eameses II., had been considered the
Pharaoh of the Exodus. Their two reigns covered a period of eighty-
six years, and as Eameses was already founded in the fifth year of
the king who gave it his name, we had at least eighty-two years for
the great oppression, to which the Bible allows at least eighty. The
two Pharaohs correspond in the general portraiture of the Egyptian
records and the lively descriptions of the Book of Exodus. Eameses
is a proud, ruthless despot ; Meneptah, with no less pretension, weak
and vacillating. In consequence of this identification, the date of
the Exodus in Egyptian evidence would be about B.C. 1320, and this
date agrees with the most satisfactory scheme of Hebrew chronology,
that of Lord Arthur Hervey (the Bishop of Bath and Wells), who,
reckoning by the Hebrew genealogies, arrives at about the same date.

Pithom, the store-city, was so called by a sacred name Pi-tum,
the abode of Tum, the setting sun ; it had, as usual, a civil name
also, Thekut, identified by Mr. Naville and Dr. Brugsch with Succoth,
the second station of the Exodus, now one fixed point on the line of
march. It was the centre of the Land of Succoth, each station being,
as Mr. Naville contends, a country, not a place, a conclusion rendered
necessary by the historical circumstances. The route was therefore
along the Wadi-t-tumeylat, the narrow valley of the Sweet- water Canal.

In 1885 Mr. Naville had the good fortune to discover the town of
Kesem, Goshen (LXX. Pecre/x), near Zagazig, at the western extremity
of the valley just mentioned. The position of the Land of Goshen
was thus at last fixed as extending around this town and stretching
southwards towards Heliopolis and eastwards to Pithom. The Land
of Goshen is called in Scripture alternately the Land of Eameses,
later known as the Arabian Nome. This Mr. Naville argues is due
to the first organisation of this border-land into a settled district of
Egypt by Eameses II., which led to the enslaving of the Hebrews as
a necessary consequence. The town of Eameses as capital must have
either been identical with the town of Goshen or close to it, and thus

2 c 2

386 Mr. B. S. Poole on Bibical Cities of Egypt. [Mai-cli 12,

the eminent explorer has found the starting-point of the route of the
Exodus.

It is important to observe that the religion of Goshen, as shown
by a very important monument of Nectanebo, the last native Pharaoh,
which is consistent with much earlier indications, yet far fuller in
its extent, has no relation whatever to the Hebrew religion. The
monument mentioned, a monolithic shrine, will be published in
Mr. Naville's ' Memoir on Goshen,* the fourth annual volume of the
Egypt Exploration Fund.

Mr. Naville's work was carried on by Mr. Petrie, and since by
Mr. Griffith, at the site of Zoan, probably the capital of Joseph's
Pharaoh. Amid a multitude of interesting discoveries made in this
field, where, and in the adjacent country, the work is now being carried
on, the most curious as bearing on the present subject was the discovery
by Mr. Petrie, of the almost regal power of the viziers of the age of
Joseph, one of whom put his name on a sphinx, a class of monument
representing the king as a type of the sun, and elsewhere strictly
limited to royal inscriptions.

Very curious light had been thrown on the obscure two centuries
and a half, roughly, between the death of Joseph and the birth of
Moses, when the Hebrews were subjugated rather than oppressed.
Mr. Groff, a young Egyptologist of Paris, had recently identified two
names of cities and tribes conquered by Thothmes III. B.C. cir. 1550,
at the battle of Megiddo, fought against a great Canaanite and Syrian
confederacy. These names are Jaakeb-el and Jeshep-el, which he
held to be Jacob and Joseph in full form, as Nathaniel for Nathan.*
If so, the Hebrews during this obscure period were engaged in border
wars and even in military service abroad. This is consonant with
the story of the death of Ephraim^s sons in a border foray (1 Chron.
vii. 20, 21), and the fact that the Israelites marched out of Egypt in
battle array (Exod. xiii. 18).

Such were the consequences of historical criticism aided by dis-
covery. They showed the essential antiquity of the part of Genesis
and Exodus relating to the Hebrews in Egypt, and entitled the Egypt
Exploration Fund to the sympathy of all lovers of research for the
sake of truth.

[R. S. P.]

♦ See ' Kev. Egyptologique,' 1885, p. 95.

1886.1 Mr. W. H, M. Christie on Universal Time. 387

WEEKLY EVENING MEETING

Friday, March 19, 1886.

Sir William Bowman, Bart. LL.D. F.K.S. Manager and Vice-
President, in the Chair.

W. H. M. Christie, Esq. M.A. F.E.S. Astronomer Royal.

Universal Time.

Considering the natural conservatism of mankind in the matter of
time-reckoning it may seem rather a bold thing to propose such a
radical change as is involved in the title of my discourse. But in
the course of the hour allotted to me this evening, I hope to bring
forward some arguments which may serve to show that the proposal
is not by any means so revolutionary as might be imagined at the
first blush.

A great change in the habits of the civilised world has taken place
since the old days when the most rapid means of conveyance from
place to place was the stage-coach, and minutes were of little im-
portance. Each town or village then naturally kept its own time,
which was regulated by the position of the sun in the sky. Sufficient
accuracy for the ordinary purposes of village life could bo obtained
by means of the rather rude sun-dials which are still to be seen on
country churches, and which served to keep the village clock in
tolerable agreement with the sun. So long as the members of a
community can be considered as stationary, the sun would naturally
regulate, though in a rather imperfect way, the hours of labour and
of sleep and the times for meals, which constitute the most important
epochs in village life. But the sun does not really hold a very
despotic sway over ordinary life, and his own movements are
characterised by sundry irregularities to which a v/ell-ordered clock
refuses to conform.

Without entering into detailed explanation of the so-called '* Equa-
tion of Time," it will be sufficient here to state that, through the
varying velocity of the earth in her orbit, and the inclination of that
orbit to the ecliptic, the time of apparent noon as indicated by the
sun is at certain times of the year fast and at other times slow, as
compared with 12 o'clock, or noon by the clock. [The clock is sup-
posed to be an ideally perfect clock going uniformly throughout the
year, the uniformity of its rate being tested by reference to the fixed
stars.] In other words, the solar day, or the interval from one noon
to the next by the sun, is at certain seasons of the year shorter than
the average, and at others longer, and thus it comes about that by
the accumulation of this error of going, tlie sun is at the beginning

388 Mr. W. H. M. Christie [March 19,

of November more than 16 minutes fast, and by the middle of
February 14 J minutes slow, having lost 31 minutes, or more than
half-an-hour, in the interval. In passing it may be mentioned as a
result of this that the afternoons in November are about half-an-hour
shorter than the mornings, whilst in February the mornings are
half-an-hour shorter than the afternoons. In view of the importance
attached by some astronomers to the use of exact local time in
civil life, it would be interesting to know how many villagers have
remarked this circimistance.

It is essential to bear these facts in mind when we have to consider
the extent to which local time regulates the affairs of life, and the
degree of sensitiveness of a community to a deviation of half-an-hour
or more in the standard reckoning of time. My own experience is
that in districts which are not within the influence of railways the
clocks of neighbouring villages commonly differ by half-an-hour or
more. The degree of exactitude in the measurement of local time in
such cases may be inferred from the circumstance that a minute-hand
is usually considered unnecessary. I have also found that in rural
districts on the Continent arbitrary alterations of half-an-hour fast
or slow are accepted not only without protest but with absolute
indifference.

Even in this country where more importance is attached to
accurate time, I have found it a common practice in outlying parts of
Wales (where Greenwich time is about twenty minutes fast by local
time) to keep the clock half-an-hour fast by railway (i. e. Greenwich)
time, or about fifty minutes fast by local time. And the farmers
appeared to find no difficulty in adapting their hours of labour and
times of meals to a clock which at certain times of the year differed
more than an hour from the sun.

There is a further irregularity about the sun*s movements which
makes him a very unsafe guide in any but tropical countries. He is
given to indulging in a much larger amount of sleep in winter than
is desirable for human beings who have to work for their living and
cannot hibernate as some of the lower animals do. To make up for
this he rises at an inconveniently early hour in summer and does
not retire to rest till very late at night. Thus it would seem that
a clock of steady habits would be better suited to the genius of
mankind.

Persons whose employment requires daylight must necessarily
modify their hours of labour according to the season of the year,
whilst those who can work by artificial light are practically indepen-
dent of the vagaries of the sun. Those who work in collieries,
factories, or mines, would doubtless be unconscious of a difference of
half-an-hour or more between the clock and the sun, whilst agri-
culturists would practically be unaffected by it, as they cannot have
fixed hours of labour in any case.

Having thus considered the regulating influence of the sun on
ordinary life within the limits of a small community, we must now

1886.] on Universal Time. 389

take account of tlie effect of business intercourse between different
communities separated by distances which may range from a few miles
to half the circumference of our globe. So long as the means of
communication were slow, the motion of the traveller was insignificant
compared wath that due to the rotation of the earth, which gives us
our measure of time. But it is otherwise now, as I will proceed to
explain.

Owing to the rotation of the earth about its axis, the room in which
we now are is moving eastward at the rate of about 600 miles an hour.
If we were in an express train going eastward at a speed of sixty
miles an hour (relatively to places on the earth's surface), the velocity
of the traveller due to the combined motions would be 660 miles an
hour, whilst if the train were going westward it would be only 540
miles. In other words, if local time be kept at the stations, the
apparent time occupied in travelling sixty miles eastward would be
54 minutes, whilst in going sixty miles westward it would be 66
minutes. Thus the journey from Paris to Berlin would apparently
take an hour and a half longer than the return journey, supposing
the speed of the train to be the same in botb cases.

In Germany, under the influence of certain astronomers, the system
of local time has been developed to the extent of placing posts along
the railways to mark out each minute of difference of time from
Berlin. Thus there is an alteration of one minute in time reckoning
for every ten miles eastward or westward, and even with the low rate
of speed of German trains, this can hardly be an unimportant quantity
for the engine-drivers and guards, who would find that their watches
appeared to lose or gain (by the station clocks) one minute for every
ten miles they have travelled east or west. This would seem to be
the reductio ad ahsurdum of local time.

In this country the difficulty as to the time-reckoning to be used
on railways was readily overcome by the adoption of Greenwich time
throughout Great Britain. The railways carried London (i. e. Green-
wich) time all over the country, and thus local time was gradually
displaced. The public soon found that it was important to have
correct railway time, and that even in the west of England, where
local time is about 20 minutes behind Greenwich time, the discord-
ance between the sun and the railway clock was of no practical con-
sequence. It is true that for some years both the local and the
railway times were shown on village clocks by means of two minute-
hands, but the complication of a dual system of reckoning time
naturally produced inconvenience, and local time was gradually
dropped. Similarly in France, Austria, Hungary, Italy, Sweden, &c.,
uniform time has been carried by the railways throughout each country.
It is noteworthy that in Sweden the time of the meridian one hour
east of Greenwich has been adopted as the standard, and that local
time at the extreme east of Sweden differs from the standard by
about 36^ minutes.

But in countries of great extent in longitude, such as the United

390 Mr. W. H. M. Christie [March 19,

States and Russia, tlie time-question was not so easily settled. It was
in the United States and Canada that the complication of the numer-
ous time standards then in use on the various railways forced atten-
tion to the matter. To Mr. Sandford Fleming, the constructor of the
Inter-Colonial Eailway of Canada and engineer-in-chief of the Pacific
Railway, belongs the credit of having originated the idea of a universal
time to be used all over the world. In 1879 Mr. Fleming set forth
his views on time-reckoning in a remarkable paper read before the
Canadian Institute. In this he proposed the adoj)tion of a universal
day, commencing at Greenwich mean noon or at midnight of a place
on the anti-meridian of Greenwich, i.e. in longitude 180° from Green-
wich. The universal day thus proposed would coincide with the
Greenwich astronomical day, instead of with the Greenwich civil day
which is adopted for general use in this country.

The American Metrological Society in the following year issued
a report recommending that, as a provisional measure, the railways
in the United States and Canada should use only five standard times,
4, 5, 6, 7, and 8 hours respectively later than Greenwich, a suggestion
originally made in 1875 by Prof. Benjamin Pierce. This was pro-
posed as an improvement on the then existing state of aflfairs, when
no fewer than seventy-five different local times were in use on the
railroads, many of them not differing more than 1 or 2 minutes. But
the committee regarded this merely as a step towards unification, and
they urged that eventually one common standard should be used as
railroad and telegraph time throughout the North American continent,
this national standard being the time of the meridian 6 hours west of
Greenwich, so that North American time would be exactly 6 hours
later than Greenwich time.

Thanks to the exertions of Mr. W. F. Allen, Secretary of the
General Eailw^ay Time Convention, the first great practical step
towards the unification of time was taken by the managers of the
American railways on November 18, 1883, when the five time
standards above mentioned were adopted. Mr. Allen stated in
October 1884, that these times were already used on 97 J per cent, of
all the miles of railway lines, and that nearly 85 per cent, of the total
number of towns in the United States of over 10,000 inhabitants had
adopted them.

I wish to call particular attention to the breadth of view thus
evinced by the managers of the American railways. By adopting a
national meridian as the basis of their time-system, they might have
rendered imj^racticable the idea of a universal time to be used by
Europe as well as America. But they rose above national jealousies,
and decided to have their time-reckoning based on the meridian which
was likely to suit the convenience of the greatest number, thus doing
their utmost to promote uniformity of time throughout the world by
setting an example of the sacrifice of human suscej^tibilities to general
expediency.

Meanwhile Mr. Sandford Fleming's proposal had been discussed

1886.] m Universal Time. 391

at the Geographical Congress at Venice in 1881, and at a meeting of
the Geodetic Association at Eome in 1883. Following on this a
special Conference was held at Washington in October 1884, to fix on
a meridian proj)er to be employed as a common zero of Jongitude and
standard of time-reckoning throughout the globe. As the result of
the deliberation it was decided to recommend the adoption of the
meridian of Greenwich as the zero of longitude, and the Greenwich
civil day (commencing at Greenwich midnight and reckoned from 0
to 24 hours) as the standard for time-reckoning. In making this
selection the delegates were influenced by the consideration that the
meridian of Greenwich was already used by an overwhelming majority
of sailors of all nations, being adopted for purposes of navigation by
the United States, Germany, Austria, Italy, &c. Further, the United
States had recently adopted Greenwich as the basis of their time-
reckoning, and this circumstance in itself indicated that this was the
only meridian on which the Eastern and Western Hemispheres were
likely to agree.

The difficulties in the way of an agreement between the two
hemispheres may be appreciated by the remarks of the Superinten-
dent of the American Ephemeris on Mr. Sandford Fleming's scheme
for universal time (which was subsequently adopted in its essentials
at the Washington Conference) : — " A capital plan for use during the
millennium. Too perfect for the present state of humanity. See no
more reason for considering Europe in the matter than for consider-
ing the inhabitants of the planet Mars. No ; we don't care for other
nations, can't help them, and they can't help us." *

As a means of introducing universal time, it has been proposed by
Mr. Sandford Fleming, Mr. W. F. Allen, and others, that standard
times based on meridians differing by an exact number of hours from
Greenwich should be used all over the world. In some cases it may
be that a meridian differing by an exact number of half-hours from
Greenwich would be more suitable for a country like Ireland,
Switzerland, Greece, or New Zealand, through the middle of which
such a meridian would pass, whilst one of the hourly meridians would
lie altogether outside of it.

The scheme of hourly meridians, though valuable as a step towards
uniform time, can only be considered a provisional arrangement, and
though it may work well in countries like England, France, Italy,
Austria, Hungary, Sweden, &c., which do not extend over more than
one hour of longitude, in the case of such an extensive territory as the
United States difficulties arise in the transition from one hour-section
to the next which are only less annoying than those formerly ex-
perienced, because the number of transitions has been reduced from
seventy-five to five, and the change of time has been made so large
that there is less risk of its being overlooked. The natural inference
from this is that one time-reckoning should be used throughout the

* ' Proceedings ' of the Canadian Institute, Toronto, No. 143, July 1885.

392 Mr. W. H. M. Christie [March 19,

whole country, and thus we are led to look forward to the adoption
in the near future of a national standard time, six hours slow by
Greenwich, for railways and telegraphs throughout North America.

We may then naturally expect that by the same process which
we have witnessed in England, France, Italy, Sweden, and other
countries, railway time will eventually regulate all the affairs of
ordinary life. There may of course be legal difficulties arising from
the change of time-reckoning, and probably in the first instance local
time would be held to be the legal time unless otherwise specified.

It seems certain that when a single standard of time has been
adopted by the railways throughout such a large tract of country
as North America, where we have a difference of local times ex-
ceeding five hours, the transition to universal time will be but a
small step.

But it is when we come to consider the influence of telegraphs on
business life, an influence which is constantly exercised, and which
is year by year increasing, that the necessity for a universal or world
time becomes even more apparent. As far as railways are concerned,
each country has its own system, which is to a certain extent complete
in itself, though even in the case of railways the rapidly increasing
inter-communication between different countries makes the transition
in time-reckoning on crossing the frontier more and more inconvenient.
Telegraphs, however, take no account of the time kept in the countries
through which they pass, and the question, as far as they are con-
cerned, resolves itself into the selection of that system of time-reckon-
ing which will give least trouble to those who use them.

For the time which is thus proposed for eventual adoption through-
out the world, various names have been suggested. But whether we
call it Universal, Cosmic, Terrestrial, or what seems to me best of
all. World Time, I think we may look forward to its adoption for
many purposes of life in the near future.

The question, however, arises as to the starting-point for the
universal or world day. Assuming that, as decided by the great
majority of the delegates at Washington, it is to be based on the
meridian of Greenwich, it has still to be settled whether the world
day is to begin at midnight or noon of that meridian. The astro-
nomers at Rome decided by a majority of twenty-two to eight in
favour of the day commencing at Greenwich noon, that is, of making
the day throughout Europe begin about midday. However natural
it might be for a body of astronomers to propose that their own
peculiar and rather inconvenient time-reckoning should be imposed
on the general public, it seems safe to predict that a World Day
which commenced in the middle of their busiest hours would not be
accepted by business men. In fact, the idea on which this proposal
was founded was that universal time would be used solely for the
internal administration of railways and telegraphs, and that accurate
local time must be rigidly adhered to for all other purposes. It was
conceded, however, that persons who travelled frequently might with

1886.] on U7i{versal Time. 393

advantage use universal time during railway journeys. This attempt
to separate the travelling from the stationary public seems to be one
that is not likely to meet with success even temporarily, and it is
clear that in the future we may expect the latter class to be com-
pletely absorbed in the former. Another argument that influenced
the meeting at Rome was the supposed use of the astronomical day
by sailors. Now it appears that sailors never did use the astronomical
day, which begins at the noon following the civil midnight of that
date, but the nautical day which begins at the noon preceding, i. e.
twenty-four hours before the astronomical day of the same date, end-
ing w'hen the latter begins. And the nautical day itself has long
been given up by English and American sailors, who now use a sort
of mongrel time-reckoning, employing civil time in the log-book and
for ordinary purposes, whilst, in working up the observations on
which the safe navigation of the ship depends, they are obliged to
change civil into astronomical reckoning, altering the date where
necessary, and interpreting their a.m. and p.m. by the light of nature.
It says something for the common-sense of our sailors that they are
able to carry out every day without mistake this operation, which is
considered so troublesome by some astronomers.

In this connection I may mention that the Board of Visitors of
Greenwich Observatory have almost unanimously recommended that,
in accordance with the resolution of the Washington Conference, the
day in the English ' Nautical Almanac ' should be arranged from the
year 1891 (the earliest practicable date) to begin at Greenwich mid-
night (so as to agree with civil reckoning, and remove this source of
confusion for sailors), and that a committee appointed by them have
drawn up the details of the changes necessary to give effect to
this resolution without causing inconvenience to the mercantile
marine.

The advantage of making the world day coincide with the Green-
wich civil day is that the change of date at the commencement of a
new day falls in the houi'S of the night throughout Europe, Africa, and
Asia, and that it does not occur in the ordinary office hours (10 a.m. to
4 p.m.) in any important country except New Zealand. In the United
States and Canada the change of date would occur after four in the
evening, and in Australia before ten in the morning. This arrange-
ment would thus reduce the inconvenience to a minimum, as the part
of the world in which the change of date would occur about the
middle of the local day is almost entirely water, whilst on the opposite
side we have the most populous continents.

The question for the future seems to be whether it will be found
more troublesome to change the hours for labour, sleep, and meals
once for all in any particular place, or to be continually changing
them in communications from place to place, whether by railway,
telegraph, or telephone. When universal or world time is used for
railways and telegraphs, it seems not unlikely that the public may
find it more convenient to adopt it for all purposes. A business man

394 Mr. W. H. M. Cliristie on Universal Time. [March 19,

who daily travels by rail, and constantly receives telegrams from all
parts of the world, dated in universal time, would probably find it
easier to learn once for all that local noon is represented by 17h. U.T.
and midnight by 5h. (as would be the case in the Eastern States of
North America), and that his ofiice hours are 15h. to 21h. U.T., than
to be continually translating the universal time used for his telegrams
into local time.

If this change were to come about, the terms noon and midnight
would still preserve their present meaning with reference to local
time, and the position of the sun in the sky, but they would cease to
be inseparably associated with twelve o'clock.

The introduction of Universal Time would practically involve
the adoption of the system of counting the hours in one series from
0 to 24, instead of in the two series 0 to 12 a.m. and p.m., for as
apj)lied to Universal Time the terms ante-meridiem and post-meridiem
would be meaningless, except for places on the meridian of Green-
wich. The use of the 24 hour system on railways and telegraphs
would naturally assist in breaking the spell of habit which associates
noon and midnight with 12 o'clock.

It may be mentioned that the Eastern and Eastern Extension
Telegraph Companies already use the 24 hour system throughout
their extensive lines of telegraph to avoid mistakes of a.m. and p.m.,
and to save telegraphing these unnecessary letters. In this connection
the President of the Western Union Telegraph Company in the
United States has stated that the adoption of the 24 hour mode of
reckoning would, besides materially reducing the risk of error, save at
least 150 million letters annually on the lines of his company. It
is also noteworthy that 98 per cent, of the railway managers in the
United States, representing 60,000 miles of railway, have expressed
themselves in favour of the adoption of the simple notation from
0 to 24 hours.

Considering that the only change which we are called on, in
accordance with the Washington Resolutions, to make in our time-
reckoning on railways is the adoption of the 24 hour system, it may
be hoped that our railway companies will not be behind those of the
United States in appreciating the simplification in railway time-tables,
which would result from this reform.

[W. H. M. C]

1886.] Professor W. CJiaudler Boherts- Austen on Metals, 395

WEEKLY EVENING MEETING,

Friday, Marcli 26, 1886.

Sir William Bowman, Bart. LL.D. F.R.S. Vice-Presideat, in the

Chair.

Professor W. Chandler Roberts- Austen, F.R.S. M.B.I,

CHEMIST OF THE MINT, PROFESSOR OF METALLURGY, NORMAL SCHOOL OF SCIENCE AND
ROTAL SCHOOL OF MINES.

On Certain Properties common to Fluids and Solid Metals,

In one of the beautiful discourses, delivered in the early part of the last
century, which grace the annals of the French Academy of Sciences,*
Reaumur observes that industrial art, like nature, has its marvels,
which we often fail to notice because they are constantly before us.

The extraordinary ductility of metals aj)peared to him to involve
one of the deepest secrets of nature, and although he held that in
his time science was hardly in a position to explain more fully
than the old philosophers did, the cause of this property of bodies,
it was nevertheless possible to see better than they, what advantage
art has gathered from the power of leading and guiding metals by
hammering or by traction, and from this point of view, both art and
nature seem, he says, to rival each other in furnishing us with
remarkable facts. Reaumur then, with singular clearness, defines
the conditions under which metals prove to be ductile. The rela-
tion between the behaviour of solid metals and fluids has long been
recognised, not merely in the sense that atomic motion is common to
solids and fluids, and that therefore " everything moves and nothing
remains," but apart from theory there is much experimental evidence
as to the properties that are common to fluids and solid metals,
the characteristics of which, at first sight, seem widely separated.
Let me remind you of the elementary definition of the two states,
solid and liquid. A solid has a definite external form which either
does not change, or only changes with extreme slowness when left
to itself, and, in order to change this form rapidly, it is necessary
to exert a more or less energetic effort. A liquid, on the other
hand, can be said to have no form of its own, as it always assumes
that of the containing vessel, the mobility of its particles is extreme,
its resistance to rupture is very small, and its free surface is always
a plane when the mass is left at rest. Then there is the colloid
condition, which intervenes between the liquid and crystalline solid
state, extending into both, and probably affecting all kinds of solid

Histoire de FAcademie Royale des Sciences,' 1713 [vol. for 1739, p. 199].

396 Professor W. Chandler Roberts- A listen [March 26,

and liquid matter in a greater or less degree. The colloid or jelly-
like body does present a certain amount of resistance to change of
BhajDC. Such a substance is well imitated by a skin of thin india-
rubber filled with water. Another illustration is probably afforded
by iron and other substances which soften under heat, and may be
sup230sed to assume, at the same time, a colloid condition. Lastly,
there is the gaseous condition of matter, with which we have but
little to do at present.

We are in the habit of regarding metals as typical solids. I hope
to trace this evening the analogies of their behaviour under certain
conditions with that of fluids, and the following list shows the order
in which I propose to group the proj)erties common to fluids and
solid metals :

1. Rejection of impurities on solidification.

2. Snr fusion.

3. Flow under pressure.

4. Changes due to compression.

5. Absorption of gases.

6. „ liquids.

7. Diffusion.

8. Vaporisation.

9. Surface tension.

The transition from the liquid to the solid state is marked by the
same phenomena in the case of many metals, as is observed in certain
fluids, and I must dwell on this very briefly as leading up to the
relations between solid metals and fluids, which come more definitely
within the title of the lecture.

Water on passing from the liquid to the solid state undergoes a
partial purification, the ice first formed being sensibly more free from
colouring matter or suspended particles than the water from which it
separates.

Many metals on freezing similarly eject impurities. In the case
of alloys, saturated solutions, of one metal in another, appear to be
formed, and excess of metal ejected, a fact which is being studied
with much care by my colleague, Dr. Guthrie. The prominent facts
are perhaps best illustrated by reference to a frozen mixture of
copper, antimony, and lead. The results of some experiments con-
ducted in my laboratory by my assistant, Dr. E. J. Ball, show that
when a molten mixture of these metals is solidified, a definite atomic
alloy of copper and antimony, which possesses a beautiful violet tint,
first forms, and, after saturating itself with lead, up to a certain
point, it ejects the rest of the lead, driving it to the centre of the
mass so as to form a sharp line of demarcation, as is shown in the
engraving. Fig. 1, the outer circle of which represents violet, and the
inner grey, presenting a direct analogy to the ice, which is compara-
tively colourless, first forming from coloured water. Then there is
another remarkable analogy between the freezing of certain fluids
iind the solidification of some metals. Water may, as is well known,

188G.] on Properties common to Fluids and Solid Metals. 397

be cooled down to —8^ Cent., without solidification, but agitation

immediately determines the formation of ice, and at the same time a

thermometer plunged in the water rises to zero. Faraday stated, in

1858, that fused acetic acid, sulj)hur, phosphorus, many metals and

many solutions,* would exhibit the same effect.

Tin also may be cooled to several degrees below

its solidifying point without actually freezing,

and Dr. Van Eiemsdijk,"!' of Utrecht, has observed

that a globule of gold or silver, in a fused state,

will pass below its solidifying point without

actually solidifying, but the slightest touch

with a metallic point will cause the metal to

solidify, and the consequent release of its latent

heat of fusion is sufficient to raise the globule

to the melting point again, as is indicated by

a brilliant glow which the button emits, a beautiful effect which I

hope to show you. [The exjDeriment was then made.]

It may be well also to remind you incidentally that a minute
variation in composition is sometimes sufficient to lower the melting
point of a metal or alloy, as is instanced by the addition of y^- per
cent, of silicon to standard gold, which, as you will observe in the case
of this strip of the alloy, softens in the flame of a candle, or at about
the melting point of zinc, 412° Cent., although the melting point of
standard gold, free from silicon, would be over 1000^ Cent.

Now to pass to solid metals. It is the common experience of us
all, that a counterfeit shilling, consisting j)rincipally of lead, does not
" ring " when thrown on a wooden surface. In 1726, Louis Lemery
observed that lead is under certain conditions almost as sonorous as
bell-metal. | He communicated the fact to l^eaumur, who, being
much struck by it, investigated the conditions under which lead
becomes sonorous, and submitted the results to the French Academy.§
He pointed out that in describing a body which is not sonorous, it
is usual to say that it is as " dull as lead," an expression which has
become proverbial. " Nevertheless," he adds, " under certain con-
ditions, lead has a proj^erty both novel and remarkable, for it emits
surprisingly sharp notes when struck with another piece of lead."
He showed that it was necessary that the lead should be formed
by casting into a segment of a sphere, that is, mushroom shaped, as
in the sj)ecimens of lead exhibited. The lead must be free from
prominences, and must be neatly trimmed. The effect is less
marked, if the lead be very pure, than if ordinary commercial lead
be used, but it is only a question of degree.

* Faraday, ' Experimental Researches in Chemistry and Physics,' p. 379.
t Dr. Van Rienisdijk, ' Ann. de Chim. et de Phys.' t. xx. 1880, p. 66.
X Hoefer, ' Histoire de la Chimie,' t. ii. p. 374.

§ ' Histoire dc I'Academie Royale des Sciences,' Anne' 1726 [vol. for 1728.
V, 243].

398 Professor W. Chandler Bdberts- Austen [March 26,

[A mass of inire lead cast into tlie shai^e shown in the sketch,
Fig. 2, was struck with a piece of lead, and it emitted a sharp, clear

note.] /. 1 •

I have shown you the experiment mainly for the sake of being

able to quote Eeaumur's observations upon

it. He showed that the sonorous lead

'^^^^^ might be rendered dull by hammering it.

I. .ZZ'^^g^tZ^.:^.:^SP{ Here is lead from the same samj)le of metal

as that from which the sonorous mass was
cast, but it has been flattened out, and you will observe that it is
" dull." I think his remarks have been overlooked in late years. He
was led to the belief that in cast lead there must be an arrange-
ment of the interior of the mass which the hammer cannot impart,
because lead fashioned by hammering into the same form as the
sonorous cast mass, is dull, and, more important still, he held that the
fibrous and granular structure of the lead is modified in a manner
which makes it probable that the sound is due to the shape of the
grains, and to the " way in which they touch each other " ;
further, the blows of the hammer not only change the arrange-
ment of the fibres, but they alter the shape of the grains, "the
round grains are rendered flat, they are comj)elled to elongate and
fill the interstitial spaces which previously existed between them.
The particles are no longer free to vibrate, hence the lead is dull."
These remarks derive additional interest, if we compare them with
the observations in Professor Osborne Keynolds' most important lec-
ture on " Dilatancy in Granular Matter " recently delivered here.
We shall also, I think, see that this description of Eeaumur's shows
that he fully appreciated the theoretical importance of the kind of
facts depending on the transfer of metallic matter from one position
to another, which we now consider to be characteristic of the
" flow " of metals ; at any rate I have thought it well to make
L emery's experiment the starting point of the rest of the remarks
I have to offer you.

A solid may be very brittle, and may yet, if time be given to it,
flow from one point to another. This stick of sealing-wax was sup-
ported at its ends, and it has in a few weeks bent at the ordinary
atmosj)heric temperature, although at any given point of its flow it
would have been easy to snap it with a slight application of force.
This much thinner strip of pure lead of the same breadth as the
sealing-wax, also bends at the ordinary temperature with its own
weight, the ends being supported. Sir William Thomson has
pointed out that a gold wire sustaining half the weight which would
actually break it, would probably not rupture in a thousand or
even a million years, that is to say, there would be no " flow "
ending in disruption ; if, however, force be suitably applied, metals
will flow readily. First, let us examine the case of a metal under
force applied so as to compel it to flow through a hole, and I would
point to the analogy of an ordinary viscous fluid. This vessel con-

1886. J on Properties common to Fluids and Solid Metals.

399

taining treacle is provided with a cylindrical hole in its base, and on
the removal of the plug which now closes it, the treacle will flow
out, the end of the stream being rounded. If a similar vessel be
filled with lead it will, at the ordinary pressure, remain there, but if
pressure be applied the lead will prove by its behaviour that it is
really a viscous solid, as it flows readily through the orifice ; the end
of the jet is rounded, and, as has been shown by the beautiful
researches of the late M. Tresca, of Paris,* all the molecules which
compose the original block place themselves in the jet absolutely
as the molecules of a flowing jet of a viscous fluid would. If the
metal has a constant " head," as it would be termed in the case of
water, that is, if the vessel be kept filled with solid lead up to a
certain level, then you have a continuous stream, the length de-
pending on the constancy with which the " head " and the pressure
are maintained. If, on the other hand, the head is diminished so
that nearly all the solid lead has been allowed to flow away, you
have a folding of the jet, and vertical corrugations, exactly such as
would characterise the end of the flow of cei'tain other viscous fluids,
and finally the jet forms a distinct funnel-shaj)ed tube, concentric
with the jet. It is also seen that when the formation of these
cavities takes place, the jet is no longer equal to the full diameter
of the orifice, as is shown in Fig. 3, the formation of the contracted

Fig. 3.

vein is manifest, and a new analogy is thus obtained between the flow
of solids and liquids. The application of this fact, that solid metals
flow like viscous fluids, is of great importance in industry, and the

* These researches extend through a long series of memoirs ; those relating
to the flow of metals are well summarised in tlie 'Proc. Inst. Mech. Engineers,'
1867, p. 114, and in the report of tlie Science Conferences held in connection with
the Loan Collection of Scientific Apparatus (Phvsics and Mechanics), London,
1876, p. 252. ff ~

Vol. XL (No. 80.) 2 d

400

Professor W. Chandler Roberts- Attsten [March 26,

production of complicated forms by forging or by rolling iron and
steel and other metals, entirely dej)ends on the flow of the metal
when suitably guided by the artificer. The lines of flow in iron
may be well shown by polishing a surface of the metal, and by
submitting it to the action of a solution of bichloride of mercury,
which etches the surface, or better, to the slow action of chromic
acid solution, as suggested by Sir Frederick Abel, the result in
either case being, that any difference in the hardness of the metal
or in the chemical composition, or want of continuity, caused by
the presence of traces of entangled slag, reveals the manner in
which the metal has flowed. The engravings illustrate the direc-
tion of flow in the following cases. Fig. 4 is a section of a

Fig. 4.

forged crosshead, kindly sent me by Mr. Webb of Crewe. Fig. 5
represents the top, planed and etched, of a hemisphere of mild
steel, of the form and dimensions shown in the sectional view,
Fig. 6, I in. thick, " dished " cold by forcing a plate through a
circular orifice. The convolutions of the etched portions afford
evidence of the struggle sustained by the flowing particles of the
metal. The experiments of M. Tresca were not made on " cinder-
free " metal ; it is therefore interesting to compare the etched
section of the old rail. Fig. 7, the result of the complicated
welding of puddled iron, with a basic -Bessemer rail, rolled from
steel Avhich has been cast, and which is therefore free from entangled
slag. Fig. 8 represents a section of such a rail presented to mo
by Mr. P. C. Gilchrist.

A very striking illustration of the importance of the flow of
metals, when used in construction, is afforded by some observations

1886.] on Properties common to Fluids and Solid Metals.

401

of Mr. B. Baker, in a recent paper on the Forth Bridge.* He
says, " If the thing were practicable, what I should choose as the
material for the compression members of a bridge, would be 34
to 37-ton steel, which had been previously squeezed endwise, in the

Fig. 5.

Fig. 6.

direction of the stress, to a pressure of about 45 tons per square
inch, the steel plates being held in suitable frames to prevent
distortion." He adds, " My experiments have proved that 37-ton
steel so treated will carry as a column as much load as 70-ton

Fig. 7.

Fig. 8,

steel in the state in which it leaves the rolls, that is to say, not

previously pressed endwise At least one half of the 42,000

tons of steel in the Forth Bridge is in compression, and the same
proportion holds good in most bridges, so the importance of
gaining an increased resistance of 60 per cent, without any sacrifice

■ Jonrn. Iron and Steel Inst.' vol, ii. 1885, p. 497.

2 D 2

402 Professor W. Chandler Boherts- Austen [March 26,

in the facility of working, and safety belonging to a highly ductile
material can hardly be exaggerated." I need not point to the
extreme interest, in connection with my subject, of these remarks
from so distinguished an authority.

The very ancient mechanical art of striking coin is wholly
dependent on the flow of metals. There is a popular belief that
the impression imparted to discs of metal during coinage, is merely
the result of a permanent compression of the metal of which the
disc is made. Striking a coin, however, presents a case of moulding
a plastic metal, and of the true flow of metal, under pressure, into
the sunk portions of the die. I once heard Mr. Euskin say : "You
stamp the figure of the cow on a pat of butter ; why do you not
impress the bee on honey ? " Simjjly because honey is not plastic
and is too viscous, and it flows at the ordinary atmospheric pressure.
This medal, struck from a series of discs, will serve to show, when
the discs are separated, the way the metal flows into the deepest
portion of the die. If the alloy used be too hard, or if the thickness
of the metal required to flow be insufficient, the impression will
always be defective, no matter how many blows may be given by
the press. In Mr. Browning's well-known poem, " The King and
the Book," there is a subtle recognition of the viscous nature of very
pure gold, which he characterises as " the oozing of the mine," while,
with regard to the manufacture of the ring, he shows :

" Since hammer needs must widen out the round
And file emboss it fine with hly fiowers,"

that this is only possible because gold behaves like the honey to
which he comj)ares it. I have chosen this reference to Browning
because I happen to have a coin of " the great Twelfth Innocent,"
the Pope of the poem I have cited, and this coin has scars on its
surface which prove that there was not quite enough metal to flow
into the depths of the die.

If one side of a coin be ground away so as to leave a flat surface,
and if the disc be then struck between plain polished dies surrounded
by a steel collar, so as to prevent the escape of the metal, the
impression on the disc will be driven through the thickness of the
metal, and will then appear on both sides. In industrial art the
property of flow of metals is very important. The " spinning " of
articles in pewter is a familiar instance, and one which I propose to
illustrate.

[A disc of pewter was spun, on a lathe, into a vase, the shadow
being projected on the screen during the operation.]

The production of complicated forms, like a jelly mould, from a
single sheet of copper under the combined drawing and compressing
action of the hammer, is a still more remarkable case.

The flow of metals is illustrated very curiously in one phase of
Japanese art metal work, of which, however, it is now so difficult
to obtain native examples, that I have been obliged to prepare,

1886.] on Properties common to Fluids and Solid Metals. 403

with the aid of skilful artificers in the Mint, the few specimens I
have to submit to you. I allude to the metal work in banded
alloys to which the Japanese give the name of Moku-me, or " wood-
grain." In its preparation thin layers of coj)per, precious metals,
and various alloys, are soldered in superposition like the leaves of a
book ; through these layers, as is shown in Fig. 9, holes are drilled

Fig. 9.

to varying depths in the thickuusw ui tuu mcLtii, ur utiuches are
cut in it. The mass is then hammered flat until the hole or trenches
disapx^ear, and the result is contorted bands, of some complexity,
and often possessing much beauty, especially when the colour of
the metal is developed by suitable chemical treatment and polishing.
A similar effect may be produced by beating up the metal from one
side, and filing the other flat, as is shown in Fig 10. The structure
depends on the flow of the respective metals of which the mass is
composed, and behaviour of the components of the system, and
suggests one of the most marked facts in experimental hydrodyna-
mics, namely, the difference in the way in which water flows along
contracting and expanding channels. The sinuous lines the metal
assumes in the preparation of Moku-me, resemble the beautiful illus-
trations devised by Professor Osborne Eeynolds, to show the flow of
water.

We have hitherto only considered the flow of metals when sub-
mitted to compression, let us now examine the effect of traction.
When a viscous metal, such as iron or soft steel, is submitted to stress
by pulling its ends in oi>posite directious, it stretches uniformly

404

Professor W. Chandler Boherts- Austen [March 26,

tlirougliout its length ; there is in such a solid, a limit in the appli-
cation of the stress up to which the metal, if released, will return to

Fig. 10.

^!j^^^?5^h>c"----*t^r^2^^^

Fig. 11.

S ^ i 2

'y

T

1

1

V

A

y

/

^

i

10

15

ZO

LOAD
25'*

its normal length; this point is the limit of elasticity. Directly,
however, this limit is reached, the metal begins to stretch, and at

1886.] on Properties common to Fluids and Solid Metals.

405

TOIVS

f£ft D INCH

20,

Fig. 12.

first it stretches in a very singular way, without an increase of load,
as is shown by the curve, Fig. 11 ; when the limit of elasticity has
been passed, the metal continues to stretch with increased load until
it gives up resisting and breaks. The limit of elasticity of a solid
body marks the moment at which the body begins to " flow " under
the influence of the force to which it is submitted. There are many
materials which do not stretch when their limit of elasticity is
reached : in very hard steel, for instance, the breaking point and the
limit of elasticity practically coincide. Further, it must be observed
that every minute variation in composition is sufficient to change
the property of a body, and to cause what was a viscous body to break
close to the limit of elasticity. A most remarkable instance is pre-
sented by certain alloys of gold and copper. Standard gold, such as
is employed for British gold coin, which contains 9167 parts of gold
in 10,000 parts, breaks with a load of
18 tons to the square inch. Its limit of
elasticity is reached at Ij tons per
square inch, but it elongates 34 per cent,
before it breaks. If this standard gold
has only the o oVo*^ P^^'^ ^^ Iq^l^l added
to it, it becomes very brittle, and
breaks, as is shown by the diagram,
Fig. 12, with a stress of about 5J tons
to the square inch, instead of 18 tons
borne by the original pure standard
gold, and as it does not elongate
sensibly it cannot be said to flow at all.
A remarkable difference in the property
of the alloy, standard gold, is therefore
caused by the addition of only the
2oVo*^ P^^t ^^ ^^^^' 111 order to
understand this it will be necessary to
trace the analogy between fluids and
solid metals still further, and to
ascertain what takes place when metals,
in a roughly granular state, are sub-
mitted to compression, under conditions
in which the escape of the comj)ressed
metal is, as far as possible, restrained.
I must, therefore, turn to what I believe

to be the most important work relative to the molecular constitution
of metals, which has been done for many years, namely, the researches
of Professor Walthere Spring, of the University of Liege, whose
labours have since 1878 been devoted to the study of the effect of
compression on various bodies.* The particles of a metallic powder

.7-7

UfUa

Vs4

Percentage of Lead.

* * Bull, de I'Acad. Koyal de Belgique,' [2] t. xlv. No. 6, 1878. [2] t. xlix.
No. 5, 1880. See also subsequent papers in the same publicatiou, iu the ' Bull.
Soc. Chhu.' Paris, and in the 'Deutsche Ohemische Gcscllschaft ' (Bilduug von
Logirungcn durch Druck), b. xv. p. 595.

406

Professor W. Chandler Boherts- Austen. [March 26,

left to itself at the ordinary atmospheric pressure, will not unite ;
by " augmenting the number of points of contact in a powder," the
result may be very different. The powders of metals may weld into
coherent blocks. Let us appeal to his own experiments. The
section, Fig. 13, shows the general form of the compression apparatus
employed by Spring.

Under a pressure of 2000 atmospheres on the piston, or 13 tons
to the square inch, lead in the form of filings becomes compressed

Fig. 13.

The metallic powder is placed under a short cylinder of steel in a cavity in a
Bteel block divided vertically, held together by a collar, and placed in a chamber
of gun-metal, which may be rendered vacuous. The pressure is applied to a
cylindrical rod passing through the stufiSng-box.

into a solid block in which it is impossible to detect the slightest
vestige of the original grains, so that lead filings weld into a block
identical with that obtained by fusion. Under a pressure of 5000
atmospheres the lead no longer resists the pressure, but flows as if it
were liquid through the cracks of the apparatus, and the piston of the
compressor descends to the base of the cylindrical hole driving the
" flowing " lead before it. This result in the case of lead is hardly
unexpected, for BoUey* showed in 1849, that lead prepared in a
particular way, so as to be in a state of fine division, may be con-
verted under a powerful press into a flexible plate, or may be made
to receive a sharp impression. The more interesting results were

* 'Licbig u. Kopp. Jahresb.' 1849, p. 278, quoted by Dr. Percy, 'Metallurgy
of Lead, 1870, p. 9.

1886.] 071 Properties common to Fluids and Solid Metals. 407

obtained by Spring with crystalline metals. Bismutb is, as is well
known, very brittle and crystalline, yet fine powder of bismuth unites
under a pressure of 6000 atmospheres into a block very similar to
that obtained by fusion, having a crystalline fracture. The density
of compressed bismuth is 9*89, identical with that of metal which has
been fused. The table shows the amount of pressure required to
unite the powders of the respective metals :

Tons per
sq. inch.

Lead unites at 13

Tin „ 19

Zinc „ 38

Antimony unites at 38

Aluminium „ 38

Bismuth „ 38

Copper „ 33

Lead flows at 33

Tin „ 47

We will endeavour to repeat M. Spring's results in the case of
bismuth. It is necessary that the powder be perfectly clean and dry,
if it be then submitted in vacuo to a pressure of 6000 atmos^Dheres, it
will weld into a crystalline mass.

We know that combinations are produced when certain bodies in
solution are submitted to each other's action. But do solids combine ?
Is the alchemical aphorism that bodies do not react unless they are
in solution, true ? Experiment proves that such solution is not
necessary. I have here two anhydrous salts, iodide of potassium and
corrosive sublimate, and they are at the same time dry ; when they
are mixed together in this mortar, they unite, as is shown by the
vermilion colour which is produced.

My colleague, Professor Thorpe, called attention to the import-
ance of this fact at the meeting of the British Association at York,
1881. But do solid metals combine in the sense, that is, in which
chemical combination is possible between metals, when submitted to
each other's action? We know that metals do combine if they
be fluid, and the extraction of gold and silver from their ores by
amalgamation is moreover easy. It occurred to M. Spring that if
there be a true union between the particles of a metallic powder,
when submitted to great pressure, it ought to be possible to build up
alloys by compressing the powders of their constituent metals, and
he urged that the formation of alloys by pressure would afford the
most conclusive proof that there is a true union between the particles
of metals in the cold, when they are brought into intimate contact.
Experiment proved that this reasoning was correct, for by com-
pressing, in a finely divided state, fifteen parts of bismuth, eight
parts of lead, four parts of tin, and three parts of cadmium, an alloy
is produced which fuses at 100^ Cent. It is necessary, however, to
compress the mixed powders twice, crushing or filing up the block
obtained in the first compression, because the mechanical mixture of

408 Pwfessor W. Chandler Boherts- Austen [March 26,

the constituent metals is not sufficiently intimate to enable a uniform
alloy to be obtained by a single compression. The alloy we have
thus produced fuses, you will observe, in boiling water, actually at
9»° Cent., although the melting point of the most fusible of its con-
stituents, the tin, is 228^ Cent. I agree with Professor Spring in
thinking that the formation of alloys by pressure affords the most
complete proof which can be given of the accuracy of the views he
has adduced. The formation of fusible-metal by compression leads
me to deal with an objection which may, no doubt, have suggested
itself to many of us. It may be urged that by compressing these
metallic powders heat is evolved, and that this heat may be
sufficient to produce incipient fusion in the metallic powders, or,
at all events, may exert a material influence on the result obtained.
This objection has been experimentally anticipated by Professor
Sirring. First, the compression is effected with extreme slowness,
and therefore there can be no question as to the sudden evolution
of heat, as would be the case if the powders were compressed
by impact instead of by a slow squeeze ; and to sum the matter
up briefly. Spring calculates, taking an extreme case, that, if it
be granted that all the work done in compressing the powders
were actually translated into heat, it would only serve to heat a
cylinder of iron 10 mm. in height and 8 mm. in diameter (the dimen-
sions of cylinder produced in his apparatus), 40 * 64° Cent. In order
that direct experimental evidence might not be wanting. Spring took
the organic body phorone, a hard crystalline substance which melts at
28° Cent., and compressed it exactly as in the case of the metallic
powders.* He took the precaution to place a shot of lead on the top
of the powder before submitting it to compression : only imperfect
union of the particles of phorone resulted. The conclusion of the
experiment proved that the shot remained where it had been placed
at the top of the column, and therefore the 28° necessary to melt the
substance had not been evolved, for if it had the shot must have fallen
through the fluid mass. I think, then, it is absolutely safe to conclude
that, in the compression of bismuth, for instance, there can be no
question of the evolution of the heat necessary for the fusion of the
metal. There is, however, other evidence to which I may incidentally
appeal. M. Spring has shown that by compressing powders together,
chemical combination may be induced, and he has in this way produced
arsenide and sulphide of zinc, sulphide of load, and of bismuth, and
arsenide of lead. These are not merely intimate mechanical mixtures.
Take, for instance, the sulphide of magnesium produced by com-
pression ; it is soluble in hot water ; treatment with dilute hydro-
chloric acid evolves sulphuretted hydrogen, which is not the case
with mere mixtures of magnesium and sul2)hur. Further, Sju-ing has
shown that by pressure a body may be made to pass from one allo-
tropic state to another. Plastic sulphur is, under a pressure of 6000

Bull. Soc. Chim.' Paris, 1884, t. xli. p. 488.

1886.] on Properties common to Fluids and Solid Metals. 409

atmospheres, compelled to pass into the condition of octahedral
sulphur, an allotropic state which possesses a greater density. And
he points out that a solid metal (not powders of metals) may have
cavities obliterated by pressure, but that matter cannot be permanently
comj)ressed by pressure, unless it can assume an allotropic state of
greater density than the one it possesses at the moment of com-
pression.* Now let me point to the evidence these experiments afford
as to the relation between solid metals and fluids. Members of the
Royal Institution will know that Faraday discovered, in 1850, that
two fragments of ice pressed against each other will unite, tendency
to their union being considerable when the fragments are near their
melting point. We also know what splendid service the regelation
of ice has afforded in the hands of Dr. Tyndall, in explaining the
formation of glaciers. Ice owes its movement, not to viscosity, but
to regelation, and the union of fragments of ice under compression is
also due to regelation. The facts which have been aj)j)ealed to, and
the theories which have been formed, respecting the regelation of ice,
are too well known to you to demand lengthy notice from me. I will
only observe that bismuth, like ice, expands on solidifying, and
although Faraday failed to establish the existence of a property
similar to regelation in bismuth, an eminent engineer, Mr. Thomas
Wrightson, to whom we owe a series of experiments on the fluid
density of metals, has satisfied himself by experimental evidence,
that regelation exists in bismuth. Now, in explaining Spring's
results we are met by this difficulty ; the union of the particles of the
metals cannot, in all cases, be due to viscosity, because viscous bodies
are always capable of being stretched, and we find the welding taking
place between the compressed powders of bodies such as zinc and
bismuth, which, when submitted to traction, will not stretch. Spring
therefore asks, " Is it possible that regelation may have something to
do with the union of the powders ? " and he urges, " Is it safe to con-
clude that regelation is peculiar to water alone ? " " It is difficult to
believe," he adds, "that in the large number of substances which
nature presents to us, but one exists possessing a property of which
we can find only minute traces in other bodies. The sum of our
chemical and physical knowledge is against such a belief, and there-
fore the phenomenon of regelation may be pronounced in ice without
being absolutely wanting in other bodies. To ascertain whether this
is so, it is necessary to submit various bodies to the conditions under
which the phenomena can be produced." "What," he asks, "are
these conditions ? " and he answers, " The pressure supported by the
body, a certain degree of temperature, and time."

Helmholtz and Tyndall have shown that when the pressure is
weak, the regelation of ice is effected slowly. Spring points out that
nitrate of sodium and phosphate of sodium, in powder, left to them-

* " Sur I'elasticite parfaite des corps solides chemiquement definis." ' Bull.
Acad. Roy. Belgique,' [3] t. vi. 1883.

410 Professor W. Chandler Boherts- Austen [March 26,

selves in bottles become coherent, and if the coherence in these and
other chemical compounds is but weak, it is simply because the points
of contact between the i^articles of powder are but few. If, on the
other hand, metallic or other powder be submitted to strong com-
pression, the spaces between the fragments become filled with the
debris of the crushed particles, and a solid block is the result.
Finally, it may be urged that this union of powders of solid metals
under the influence of pressure, that is to say, the close approximation
of the particles, can be compared to the liquefaction of gases by
pressure. At the first view this comparison may appear rash or
strained, but it is nothing if we accept the views of Clausius on the
nature of gases and liquids. In a gas the molecules are free, but if
by pressure at a suitable temperature the molecules are brought
within the limits of their mutual attraction, the gas may be liquefied,
and under suitable thermal conditions solidified. The mechanical
pulverisation of a metal merely detaches groups of molecules from
other groups, because the mechanical treatment is imperfect, but the
analogy between the solid and a gas has, in a sense, been established ;
filing has coarsely gasified the mass, but pressure will solidify it as
you have already seen.

It is possible that in some of these metallic blocks, the particles
are not actually united by the pressure, which may, nevertheless,
develop the kind of "mutual attraction" contemplated by Sir W.
Thomson as existing between two pieces of matter at distances of less
than 10 micro-millimetres.

There are two other properties which solid metals possess, in
common with certain fluids, to which I must briefly allude. The
first is the power of dissolving gas, which metals in the solid colloid
condition possess. I will not offer any experimental illustration on
this point, because the work of Graham has been fully dealt with in
this theatre by Dr. Odling, and I have, in a course of lectures recently
delivered here, shown that just as solid palladium occludes hydrogen,
so the alloy of rhodium and lead occludes oxide of nitrogen, which it
gives up with explosive violence on heating in vacuo, suggesting an
analogy with fluid nitro-glycerine. The last property I have to
submit to you, is the power which certain solid metals possess of
taking up fluids, sometimes with a rapidity which suggests the
miscibility of ordinary fluid substances. In reference to this I have
found an interesting paper published so long ago as 1713, by the
Dutch chemist Homberg,* " On Substances which penetrate and
which pass through Metals without melting them." He enumerates
several substances which will pass through the pores of metals with-
out disturbing the particles, and he points out that mercury penetrates
metals without destroying them. Few of us are, I think, familiar
with the rapidity with which mercury will pass through tin. Here
is a bar, one inch wide and half inch thick ; if a little mercury be

* ' Mem. de I'Acad. Royalc dcs Sciences,' 1713 [vol. for 1739, p. 30G].

1886.] on Properties common to Fluids and Solid Metals. 411

rubbed liglitly on it the mercury will in 30 seconds penetrate the
mass, so that it breaks readily, although before the addition of the
mercury, the bar would bend double without any sign of fracture.

With regard to the vaporisation of solid metals, time will only
permit me to remind you that Demar9ay * has shown that in vacuo
metals evaporate at much lower temiDcratures than they do at the
ordinary atmospheric pressure, and he suggests that even metals of
the platinum grouj) will be found to be volatile at comparatively low
temperatures. Merget f has shown that the solidification of mercury
by extreme cold does not prevent the solid metal evaporating into the
atmosphere surrounding it.

With regard to the remaining properties on my list, you will say,
surely solids do not show any tendency to diffusion ? I have shown J
that in the case of molten metals the interdiffusion may be extremely
rapid, but, with regard to solid metals, some experiments conducted
by Sir Frederick Abel prove that carbon can pass from a plate of
richly carburised iron to one of iron free from carbon, against which
it is tightly pressed. This passage of carbon takes place at the
ordinary temperature, and it is difficult to exj^lain the transference of
matter without admitting the presence of some action closely allied
to the diffusion of liquids.

Finally, can we offer any evidence of surface tension in solid
metals ? There is only one experiment to submit to you illustrating
a j)oint I am still investigating. Some months since Mr. F. W.
Fletcher, manager of the works of Messrs. C. Ash and Sons, the well-
known dealers in the precious metals, pointed out to me an interesting
property of a hard-drawn rod or thick wire of 13-carat gold ; the gold
being alloyed with silver and copper in the following proportions : —

Gold 54-17

Copper 33-33

Silver 12-53

100-00

If such a rod be touched with a solution of chloride of iron or
certain other soluble chlorides, it will, in a short time, varying from
Sk few seconds to some minutes, break away, as is shown in the

Fig. 14.

A

diagram, Fig. 14, the fracture rapidly extending for a distance of
some inches.

[The image of the rod was projected on the screen, and in a few

* ' Comptes Eendus,' xcv. p. 183 [1882].

t ' Ann. de Chim. et de Pbys.' [4], xxv. p. 121.

X 'British Association Report/ 1883. p. 402.

412 Prof. W. Chandler Uoberts- Austen on Metals. [March 26,

seconds after the rod was touched with chloride of iron, it split close
to the point of contact with the solution.]

This result may be attended with the absorption of gas, but, in
any case, it would appear that in the hard-drawn rod the surface is in
a state of tension, which is released by the action of the chloride.

The facts we have considered afford additional evidence as to
continuity in the properties of all kinds of matter, and serve as a
connecting link with the work of the past, the importance of which is
too often overlooked. I trust it will be evident that the analogy of
solid metals to fluids has an important bearing on the labours of
those who are striving to advance science, to develoj) art, or to
promote the industrial well-being of this country.

[W. C. K.-A.]

1886.] 3Ir. H, Gruhh on Telescopic Objectives and Mirrors. 413

WEEKLY EVENING MEETING,

Friday, April 2, 1886.

William Huggins, Esq. D.C.L. LL.D. F.R.S. Vice-President,
in the Chair.

Howard Grubb, Esq. F.R.S. F.R.A.S.

Telescopic Objectives and Mirrors : their Preparation and Testing.

It would probably lend an additional interest to a technical subject
such as I have to bring before you to-night, could I preface my de-
scription of the processes now employed in the construction of tele-
scopic objectives by a short historical account of what has been
attempted and achieved in the past, but time will not permit.

A very few words, however, on the history of glass manufacture are
necessary.

As I pointed out last Saturday afternoon, Dollond's brilliant
discovery, which afforded a means of achromatising objectives, ren-
dered possible their construction of greater size and perfection than
formerly, provided suitable material could be obtained. But the
chromatic errors being removed, faults in the material hitherto
masked by them, were detected, and it was not until after many
years that Guinand, a lowly but gifted Swiss peasant, succeeded in
producing glass discs of a considerable size and free from these
defects.

The secrets of his process have been handed down in his own
family to Mens. Foil, of Paris (one of his descendants), and also
through M. Bontemps, who for a time was associated with Guinand's
son, and afterwards accepted an invitation from Messrs. Chance Bros.
& Co., of Birmingham, to assist them in an endeavour to improve
that branch of their manufacture. Only these two houses, so far as I
am aware, have succeeded in manufacturing optical discs of large
size.

Testing op Optical Glass.

Let me here say a few words respecting the testing of optical
glass ;. I mean of the material of the glass, quite apart from the
optician's work in forming it into an objective. When received from
the glass manufacturer it is sometimes in this state, roughly polished
on both sides, and sometimes in this, in which as you see there are
small windows only, facets as they are called, polished on the edges.
In case of lenses for telescopic objectives, it is always well to have

414 3Ir. Howard Gruhh [April 2,

them roughly polished on the sides, to avoid the chance of having to
throw away a lens after much trouble and labour has been spent
on it.

There are only three distinct points to be looked to in the testing
of optical glass ; (1) General clearness and freedom from air-
bubbles, specks, pieces of "dead metal," &c. ; (2) Homogeneity;
(3) Annealing.

The first is the least important, and needs no instructions for
detection of defects, any one can see these. The second is much more
important, and much more difficult to test.

The best test for homogeneity is one somewhat equivalent to
Foucault's test for figure of concave mirrors.

The disc of glass should be either ground and polished to form a
convex lens, or if that be not convenient, it should be placed in juxta-
position with a convex lens of similar or larger size, and whose
excellence has been established by previous experience.

The lens or disc is then placed opposite some small brilliant
light — a small gas flame generally suffices — and at such a distance
that a conjugate focus is formed at other side and at a convenient
distance. When the exact position of this focus is found, the eye
is placed as nearly as possible so that the image of flame is formed
on the pupil. On looking at it with the eye in this position, the
whole lens should appear to be " full of light " ; but at the slightest
movement to one side the light will disappear and the lens appear
quite dark. If the eye be now passed slowly backwards and forwards
between the position showing light and darkness, any irregularity of
density will be most easily seen.

Of course, like everything else, some experience is necessary.

The rationale of this is very obvious. When the eye is placed
exactly at the focus of a perfect lens, the image formed on the pupil
is very small, and the slightest movement of the eye will cause the
light to appear and disappear. If the eye be not at the focus, the
pencil of light will be larger, and consequently it will require a
much greater movement of the eye to cause the light to disappear.
Now if any portion of the lens be of a difi'erent density to the
general mass, that portion will have a longer or a shorter focus ;
consequently while the light flashes off the general area of the lens
quickly, it still remains on the defective portions.

By imitating this arrangement and substituting a camera for the
eye and forming the focus of a small point of light on the stop of the
lens, I have succeeded in ^photographing veins in glass, and sometimes
have found this useful as a record.

The third point — that of proper annealing — is easily tested by
the polari scope.

For small discs the usual plan is to hold them between the eye
and a polarizing plane, such as a piece of glass blackened at back or
a japanned surface, and look at them through the facets, using as an
analyser a Nichols prism.

1886.] on Telescopic Objectives and Mirrors. 415

Larger sizes, which are polished on the surfaces, can be more
easily examined. It is difficult to describe the appearances, but I will
put a few discs into the lantern polariscope and endeavour to point
out what amount of polarization may safely be permitted in discs of
glass to be used for objectives.

The composition of metallic mirrors of the present day differs
very little from that used by Sir Isaac Newton. Many and different
alloys have been suggested, some including silver or nickel or arsenic ;
but there is little doubt that the best alloy, taking all things into
account, is made with 4 atoms of copper and 1 of tin, which gives the
following proportions by weight : copper 252, tin 117*8.

Calculation op CtrEVES.

Having now obtained the proper material to work upon, the first
thing necessary is to calculate the curves to give to the lenses, in
order that the objective, when finished may be of the required
focus, and be properly corrected for the chromatic and spherical
aberrations.

As this lecture is intended to deal principally with the technical
details of the process, I do not intend to occuj^y your time for more
than a few moments on this head, nor indeed is it at all necessary.
In my lecture last Saturday I explained the principles of achro-
matism, and in many published works full and complete particulars
are given as to the calculation of the curves — particulars which are
sufficient, and more than sufficient, for the purpose.

Much has been discussed and written concerning the calculation
of curves of objectives, and much care and thought has been be-
s^^owed by mathematicians on this subject, and so far as the actual
constructors are concerned, a certain amount of veil is thrown over
this part of the undertaking, as if there were a secret involved, and
as if each had discovered some wonderful formulas by which he was
enabled to calculate the curves much more accurately than others.

I am sorry to have to dispel this illusion. Practically the case
stands thus. The calculation of the curves which satisfy the con-
ditions of achromatism and desired focus is a most simple one, and can
be performed by any one having a very slight algebraical knowledge
in a few minutes, provided the refractive indices and dispersive power
of the glass be known. Both Messrs. Chance and Feil supply these
data quite sufficiently accurately for small-size objectives. Speaking
for myself, I am quite content to take the figures as given by these
glass manufacturers for any discs up to 10 inches in diameter. If over
that size, I grind and polish facets on the disc and measure the re-
fractive and dispersive powers myself.

The calculations of the curves required to satisfy the conditions of
spherical aberration are very troublesome, but fortunately these may
be generally neglected.

Some years ago the Royal Society commissioned one of its mem-
VoL. XI. (No. 80.) 2 E

416 Mr. Howard Grubh [April 2,

bers to draw up tables for the use of opticians, giving the curves
required to satisfy the conditions of both corrections for all refractive
and dispersive indices.

A considerable amount of labour was expended on this work, but
in the end it was abandoned, for it was found that the calculation of
these curves was founded on the supposition that all surfaces produced
by the opticians were truly spherical ; while the fact is, a truly
spherical curve is the exception, not the rule. The slightest variation
in the form or figure of the curve will produce an enormous variation
in the correction for spherical aberration, and it •was soon apparent
that the final correction for spherical aberration must be left to the
optician and not to the mathematician. Object-glasses cannot he
made on pa'per. When I tell you that a sensible difference in cor-
rection for spherical aberration can be made by half an hour's
polishing, corresponding probably to a difference in the first place
of decimals in radii of the curves, you will see that it is practically
not necessary to enter upon any calculation for spherical aberration.
We know about what form gives an approximate correction ; we adhere
nearly to that, and the rest is done by figuring of the surface.

To illustrate what I mean. I would be quite willing to undertake
to alter the curves of the crown or flint lens of any of my objectives by
a very large quantity, increasing one and decreasing tlae other so as
to still satisfy the conditions of achromatism, but introducing theo-
retically a large amount of positive or negative spherical aberration,
and yet to make out of the altered lens an object-glass perfectly
corrected for spherical aberration.

I am now speaking of ordinary sizes. For very large sizes it is
usual to go more closely into the calculations ; but I may remark
that it is sometimes possible to make a better objective by deviating
from the curves which give a true correction for spherical aberration
and correcting that aberration by figuring, rather than by strictly
adhering to the theoretical curves. So far then as any calculation
is required, the ordinary formulae given in the text-books may be
considered amply sufficient.

Having now determined on the curves, we have to consider the
various processes which the glass has to undergo from the time it
is received in this form from the glass manufacturer to the time when
it is turned out a finished objective.

The work divides itself into five distinct operations : — (1) Eough
grinding; (2) Fine grinding; (3) Polishing; (4) Centering;
(5) Figuring and testing.

1. The rough grinding or approximate shaping of the glass is a
very simple process. The glass is cemented on a holder, and is held
against a revolving tool supplied with sand and water, and of a
shape which will tend to abrade whatever portions are necessary to
be removed to produce the required curves. These diagrams will
illustrate the various operations.

2. Fine grinding. The tools used for fine grinding are of this

188G.] on Telescopic Objectives and Mirrors. 417

form, and are made of either brass or cast iron. I prefer cast iron,
except for very small sizes. They are grooved on the face, in the
manner suggested by the late Mr. A. Eoss, in order to allow the
grinding material to properly distribute itself.

If two spherical surfaces be rubbed together they will, as may be
supposed, tend to keep spherical ; for the spherical is the only curve
which is the same radius every part of its surface. If fine dry
abrading powder be used between, the same result will be obtained ;
but if wet powder be used, the surface will no longer continue
spherical, but will abrade away more on the centre and edge than in
the zone between. It was to meet this difficulty that the late Mr."^A.
Ross devised the idea of the distributing grooves. The fine grinding
process is the first of the series which calls for any skill on the part
of the operator.

That the modus operandi of the grinding be the more easily under-
stood, let me explain the principle of the process in a few words.

When two surfaces of unequal hardness are rubbed together with
emery powder and water between the two, each little particle of the
powder is at any given moment in either of these conditions : —
(a) Imbedded into the softer surface ; (b) Rolling between the two
surfaces ; (c) Sliding between the two surfaces.

Those particles which become imbedded in the softer material
do no work in abrading it, and but little in abrading the harder.
They generally consist of the finer particles, and are kept out of
action by the coarser which are rolling or sliding between the surfaces.
Further, those that are purely rolling do little or no work. The
greater part of the work is performed by those particles which are
facetted and which slide between the two surfaces.

As the grinder is always of a much softer material than the
glass, there is much more friction between the grinder and these par-
ticles than between the glass and the same particles, and therefore
they partially adhere to the grinder and are carried by it across the
face of the glass. This being so, it is now easy to jDerceive w^hat
the best conditions for rapid grinding are. Not too little emery,
for then there will not be enough of abrading particles ; not too
much, for then the particles will roll on each other and tend to
crush and disintegrate each other instead of abrading the glass,
but just sufficient to form a single layer of particles between the
grinder and the glass surface.

In the grinding of the small lenses, I mean up to five or six inches
diameter, it is usual to carry out the entire grinding processes by hand ;
above that size by machinery. Surfaces up to 12 or even 15 inches
can be ground by hand ; but the labour becomes severe, and for my
part I am gradually reducing the size for which the hand grinding
is used, as I find the machine work more constant in its eftects.

The machinery used is the same as that emjDloyed for the polishing
operation, and I shall describe it under that head further on.

In the fine grinding operation by hand, the glass is usually

2 E 2

418 Mr. Howard Gruhb [April 2,

cemented on to a holder of this form, having (for smaller sizes) three
pieces of cork, to which the lens is attached, this holder being
screwed to a spud or nose on top of a post screwed to the floor. The
operator having applied the proper quantity of moist emery powder
between the grinder and the glass, proceeds to work the former over the
latter in a set of peculiar strokes, the amplitude and character of which
ho varies according to circumstances, at the same time that he changes
his position round the post every few seconds.

******

Although, as I have shown, the harder material is abraded very
much more than the softer, yet the softer (the grinder) suffers consi-
derable abrasion as well as the glass, and the skill of the operator is
shown by the facility with which he is able to bring the glass to the
curve of the grinder without altering the curve or figure of the
latter.

It is even possible for a skilled operator to take a lens of one
curve and a grinder of say a deeper curve, and by manipulation to
produce a pair of surfaces fitting together and of shallower curves
than either.

Measurement of the Curves.

In the early stages of grinding, gauges of the proper radius, cut
out of sheet brass or sheet steel, are used for roughly testing the
curves of the lenses ; but when we get to the finer grinding process,
it is necessary to have something much more accurate.

For this purpose a spherometer is used. It is made in various
forms, generally with three legs terminating in three hardened steel
points, which lie on the glass, and a central screw with fine thread, the
point of which can be brought down to bear on the centre of the glass.
In this way the versed sine of the curve for a chord equal to diameter
of circle formed by these points is measured, and the radius of curve
can be easily calculated from this.

I do not find the points satisfactory for regular work. They are
apt to get injured or worn, and for ground surfaces are a little
uncertain as one or other of the feet may find its way into a deep
pit. This particular spherometer has three feet, of about half an
inch long, which are hardened steel knife-edges forming three portions
of an entire circle. In using this it is laid on the surface to be
measured, and the screw with micrometer head is turned till the point
is felt to touch the surface of glass. This scale and head can then be
read off. The screw in this instrument has fifty threads to the inch,
and the head is divided into 100 parts, so that each division is equal to
sjyoo of an inch. With a little practice it is easy to get determinate
measures to y^^ of this, or -^-^q^ of an inch, and by adopting special
precautions even more delicate measures can be taken, as far probably
^^ Ju-Q^j^-uu ^^ T^oV^iF ^^ ^^ inch, which I have found to be prac-
tically the limit of accuracy of mechanical contact.

1886.] on Telescopic Objectives and Mirrors. 419

To give an idea of the delicacy of the instrument, I bring the
screw firstly into contact with the glass. Now the screw is in good
contact ; but there is so much weight still on the three feet, that if
I attempt to turn it round, the friction on the feet oppose me, and it
will not stir except I apply such force as will cause the whole instru-
ment to slide bodily on the glass. Now, however, I raise the whole
instrument, taking care that my hands touch none of the metal-work,
and that the screw be not disturbed. I lay my hands for a moment on
part of the glass where centre screw stood, and thus raise its tempera-
ture slightly, and on laying the spherometer back in the same place, you
now see that it spins on the centre screw, showing how easily it
detects what to it is a large lump, caused by expansion of the glass from
the momentary contact of my hand.

Flexure.

One of the greatest difficulties to be contended with in the
polishing of large lenses is that of flexure during the process.

It may appear strange that in discs of glass of such considerable
thickness as are used for objectives, any such difficulty should occur ;
but a simple experiment will demonstrate the ease with which such
pieces of glass can be bent, even under such slight strain as their own
weight.

We again take our spherometer and set it upon a polished
surface of a disc of glass of about 7 J inches diameter and J inch
thick. I set the micrometer head as in the former experiment to bear
on the glass, but not sufficiently tight to allow the instrument to spin
round. This has now been done while the glass as you see is sup-
ported on three blocks near its periphery. I now place one block
under the centre of disc and remove the others thus, and you see the
instrument now spins round on centre screw.

It is thus evident that not only is this strong plate of glass
bending under its own weight, but it is bending a quantity easily
measurable by this instrument, which as I shall presently show is quite
too coarse to measure such quantities as we have to deal with in
figuring objectives.

After this experiment, no surprise will be felt when I say that it
is necessary to take very special precautions in the supporting of discs
during the process of polishing, to prevent danger of flexure ; of
course, if the discs are polished while in a state of flexure the
resulting surface will not be true when the cause of flexure is
removed.

For small-sized lenses no very special precautions are necessary,
but for all sizes over 4 inches in diameter I use the equilibrated
levers devised by my father, and utilised for the first time on a large
scale in supporting the 6-foot mirror of Lord Eosse's telescope.
These have been elsewhere frequently described, but I have a small
set here as an example.

I have also sometimes polished lenses while floating on mercury.

420 Mr, Howard Gruhh [Aj^ril 2,

This gives a very beautiful support, but it is not so convenient, as it is
difficult to keep the disc sufficiently steady while the polishing opera-
tion is in progress, without introducing other chances of strain.

So far I have spoken of strain or flexure during the process of
working the surface ; but even if the surface be finished absolutely
perfectly, it is evident from the experiment I showed you that very
large lenses when placed in their cells must suffer considerable
flexure from their own weight alone, as they cannot then be sup-
ported anywhere except round the edge.

To meet this, I proposed many years ago to have the means of
hermetically sealing the tube, and introducing air at slight pressure
to form an elastic support for the objective, the pressure to be regu-
lated by an automatic arrangement according to the altitude. My
attention was directed to this matter very pointedly a few years ago
from being obliged to use for the Vienna 27-inch objective a crown
lens which was according to ordinary rules much too thin.

I had waited some years for this disc, and none thicker could be
obtained at the time. This disc was very pure and homogeneous, but so
thin that if offered to me in the first instance I would certainly have
rejected it. Great care was taken to avoid flexure in the working,
but to my great surprise I found no difficulty whatever with it in
this respect. This led me to investigate the matter, with the
following curious results.

If we call / the flexure for any given thickness t, and /' the flexure

f f^
for any other thickness t\ then -p = j^tor any given load or weight

approximately. But as the weight increases directly as the
thickness, the flexure of the discs due to their own weight, which

/ ^.

is what we want to know, may be expressed as ^ = -,

Let us now consider the effect of this flexure on the image. In
any lens bent by its own weight, whatever part of its surface is
made more or less convex or concave by the bending, has a corres-
ponding part bent in the opposite direction on the other surface, which
tends to correct the error produced by the first surface. This is
one reason why reflectors which have not this second correcting sur-
face are so much more liable to show strain than refractors. If
the lens were infinitely thin, moderate flexure would have no effect
on the image. The effect increases directly as the thickness.
If then the flexure, as I have shown, decreases directly as the thick-
ness, and the effect of that flexure increases directly as the thickness,
it is clear that the effect of flexure of any lens due to its own weight
will be the same for all thicknesses ; in other words, no advantage is
gained by additional thickness.

This has reference, of course, only to flexure of the lens in its
cell after it has been duly perfected, and has nothing to do with the
extra difficulty of supporting a thin lens during the grinding and
polishing processes.

1886.] on Telescopic Objectives and Mirrors. 421

Polishing.

The polishing process can be, and is often, conducted precisely
in the same manner as the grinding, except that the abrading powders
used (oxide of iron, rouge, an oxide of tin putty-powder) is of a finer
and softer descrijDtion, and the surface of the polishing tool is made
of a softer material than the metallic grinder.

Very nearly all my polishing is done on the machine I shall pre-
sently describe ; but before doing so, I will, with your permission,
say a few words on the general principles of the polishing process.
Various substances are used for the face of the polisher — fine cloth,
satin or paper, and pitch. Pitch possesses two important qualities
which render it peculiarly suitable for this work, and it is a curious
fact that we owe its application for this purpose to the extraordinary
perspicuity of Sir Isaac Newton, who we may fairly say was the first to
produce an optically perfect surface, and that that material is not
only still used for the purpose, but is as far as I know the only sub-
stance which possesses the peculiar qualifications necessary to fulfil
the required conditions. "With skill and care, moderately good sur-
faces can be obtained from cloth polishers ; but it is easy to see why
they can never be perfect. There is a certain amount of elasticity in
cloth and in its " nap," and there is consequently a tendency to
round off the surfaces of the pits left by the grinding powder, and to
polish the bottom or floor of these pits at the same time as the upper
surface. It is easy to show mathematically that any process which
abrades the floors of the pits at the same time as general surfaces even in
a very much less degree, can never produce more than an approximation
to a perfect surface, and practice agrees with the theory. Paper is said
to be much used by the French opticians. I can say nothing about it.
I have tried it and failed to produce a perfect surface with it, nor
indeed should I expect it. It is of course open to the same objection
as cloth. Pitch possesses, as I said, two most important qualities
which render it suitable for the work ; the first, in its almost perfect
inelasticity ; the second, a curious quality of subsidence, which we
utilise in the process.

If we watch with a microscope, or even a magnifier, the character
of two surfaces during the process of polishing, the one with cloth,
and the other with pitch, the difference is very striking. With the
cloth polisher, the polish appears much quicker, and it would at
first sight appear as if the same polishing powder abraded more
quickly on the cloth than on the pitch polisher, but I do not believe
that such is the case, for if we look at the surface with a magnifier
we shall find that while all the surface has assumed a polished appear-
ance, the surface itself has retained some of the form of the original
pitted character with the edges rounded off ; while in the pitch half-
polished surfaces, the floors of the pits are as grey as ever, and the
edges are sharp and decisive. In pitch polishing, too, a decided

422 Mr. Hoimrd Gruhh [April 2,

amount of polish appears very quickly, and tlien for many hours there
appears to be little or no further effect. Suddenly, however, the
remaining greyness disappear^, and the surface is polished. The
reason of this is very obvious. The polisher being very inelastic,
polishes first only the tops of the hills, and has to abrade away all
the material of which these hills are composed before it reaches the
valleys or floors of the pits. When it does reach them, the proper
polish quickly appears. The second quality of pitch, that of sub-
sidence, is also most valuable.

Pitch can be rendered very hard by continued boiling. By pitch
I mean the natural bituminous deposit which comes to us from
Archangel, not gas-tar pitch. It can be made so hard that it is
impossible to make any impression on it with the finger-nail without
splitting it into pieces ; and yet even in this hard condition if laid on
an uneven surface it will in a few days, weeks, or months subside
and take the form of whatever it is resting upon. The cohesion of
its particles is not sufficient to enable it to retain its form under
the action of gravity ; and as this condition is that which science tells
us marks the difference between solids and liquids, we must, paradoxical
though it may appear, class even the hardest pitch among liquid instead
of solid substances.

Now how do we utilise this peculiar quality.

The polishing tool is made by overlaying a metal or wooden disc
formed to nearly the required curves by a set of squares of pitch, and
while these are still warm pressing them against the glass, the form of
which they immediately take.

In the grinding process, I showed you that the regulation of the
abrasion was managed partly by the character of the stroke given, and
partly by the local touches given to the tool by the stoning process.

In polishing we still retain the same facilities for modifying the
stroke, and the same rules I gave apply generally to the polishing
process as well as the grinding ; but we have not got any process
equivalent to that of the local stoning, and even if we had it would
be useless, for this very quality of subsidence of the pitch would in
a few minutes cause any part of its surface which had been
reduced to come into good contact again ; we must therefore look
for some other means for producing more or less abrasion whenever
we require it. This we effect by modifying the size of the squares of
pitch in the various zones. Practically it is done in this way by a
knife and mallet. Whenever the squares are reduced, the abrasion
will be less.

This is a well-known method of regulation ; but the rationale is, I
think, not generally understood. It is generally explained that there
is less abrasion because there is less abrading surface. I do not think
this is the true, or at least the entire, explanation. In order to under-
stand the action, you must conceive the pitch to be constantly in a
state of subsidence, the amount of that subsidence depending of course
on the pressure placed upon it. Now if wo reduce the size of the

1886.] on Telescopic Objectives and Mirrors. 423

squares in any zone while retaining the same distance from centre
to centre of squares, we increase at first the pressure per unit of area
on the pitch squares in that zone, and consequently the subsidence will
be greater, and the action will not be so tight or severe on that zone.
I know of no substance but pitch and a few of the resins which
possess this peculiar quality except perhaps ice, and it is curious to
think that the same quality which in ice allows of that gradual creep-
ing and subsidence and consequent formation of glaciers with their
characteristic moraines, &c., will in pitch help us to produce
accui-ate optical surfaces.

Polishing Machines.

The two best-known polishing machines are those of the late
Earl of Rosse and the late Mr. Lassell, the general forms of which are
shown in these diagrams. Time will not permit me to enter into a
minute description, of their working, nor is it necessary, as both have
been often described.

A few words, however, as to the different character of the strokes
given by these machines may be interesting. The stroke of Lord
Rosse's machine may be imitated in hand-work by the operator travers-
ing the polisher or mirror in a series of nearly straight strokes, of
about one-thii'd the diameter of the glass, to and from himself, at the
same time that he keeps walking slowly round the post, and instead of
allowing the centre of polisher to pass directly over the centre of
mirror, each stroke that he gives he slides a little (about one-tenth
diameter) to one side and then a little to the other.

Mr. Lassell's stroke may be imitated by causing the polisher to
describe a series of nearly circular strokes a little out of the centre,
walking round the post at the same time ; thus the centre of polisher
will describe a series of epicycloidal or hypocycloidal curves on the
speculum.

Many years ago my father devised a machine, figured and
described in Nichols' ' Physical Science,' by which either of these
motions could be obtained. He appeared to have got better results
with Mr. Lassell's strokes, for he afterwards devised a machine which
gave the same character of stroke, but over which the operator had
greater control, and this machine has been used for many years
with great success. Like all machines, however, which give a
series of strokes constantly recurring of the same amplitude, it is
apt to polish in rings. It is impossible to obtain absolute homo-
geneity in the pitch patches, and if any one square be a shade harder
than the general number, and that square ends its journey at each
stroke at the same distance from the centre of speculum or glass,
there will almost surely be a change of curvature in that zone. To
avoid this I have made a slight modification in the machine, which has
increased its efficiency to a great extent. I will now place in the
lantern a model of this machine, and first draw you a few curves with
the machine in its old state, and afterwards in its improved state.

424 Mr. Howard Gruhh [April 2,

In order to convey some idea of the relative quantities of material
removed by the various processes, I have placed upon the walls a
diagram which will illustrate this point in two distinct ways.

The diagram itself represents a section of a lens of about 8 inches
aperture andl inch thick, magnified 100 times, and shows the relative
thickness of material abraded by the four processes.

The quantity removed by the rough grinding process is repre-
sented on this diagram by a band 25 inches wide, the line grinding
by one -^^ inch wide, the polishing by a line -^q inch wide, while the
quantity removed by the figuring process cannot be shown even on
this scale as it would be represented by a line only x^oo i^^^
thick.

I have also marked on this diagram the approximate cost of
abrasion of a gramme of material by each of the four processes,
viz : —

£ s.

d.

Eough grinding, about 0 0

1 per gramme.

Fine grinding, „ 0 0

n ,.

Polishing, „ 0 10

0

Figuring, „ 48 0

0

Figuring and Testing.

By the figuring process, I mean the process of correcting local errors
in the surfaces, and the bringing of the surfaces to that form, what-
ever it may be, which will cause the rays falling on any part to be
refracted in the right direction. When an objective has undergone
all the processes I have described, and many more which are not so
important, and with which I have not had time to deal, and when the
objective is centered and placed in its cell, it is, to look at, as perfect
as it will ever be, but to look through and use as an objective it may
be useless. The fact is that when an objective has gone through all
the processes described, and is in appearance a finished instrument, I
look upon it as about one-fourth finished. Three-fourths of the work
has probably to be done yet. True, sometimes this is by no means
the case, and I have had instances of objectives w^hich were perfect on
the first trial ; but this is, I am sorry to say, the exception and not the
rule.

This part of the process naturally divides itself into two distinct
heads : —

1. The detection and localisation of faults — what may, in fact, be
termed the diagnosis of the objective.

2. The altering of the figures of the difi'erent surfaces to cure
these faults. This may be called the remedial part.

It may be well here to try to convey some idea of the quantities we
have to deal with, otherwise I may be misunderstood in talking of
great and small errors.

1886.] on Telescojjic Objectives and Mirrors. 425

I have before mentioned that it is possible to measure with the
spherometer quantities not exceeding 5-77^0 o ^f an inch, or with special
precaution much less even than that ; but useful as this instrument is
for giving us information as to the general curves of the surface, it is
utterly useless in the figuring process, that is, an error which would be
beyond the po\ver of the spherometer to detect, would make all the
difference between a good and a bad objective.

Take actual numbers and this will be evident. Take the case of
a 27-inch objective of 34 feet focus ; say there is an error in centre of
one surface of about 6 inches diameter, which causes the focus of that
part to be -^^ of an inch shorter than the rest.

For simplicity sake, say that its surface is generally flat ; the
centre 6 inches of the surface therefore, instaad of being flat, must be
convex and of over 1,000,000 inches radius, about 17 miles. The versed
sine of this curve, as measured by spherometer, would be only about
2'5'uowo^ 4 millionths of an inch, a quantity mechanically unmeasu-
rable, in my opinion.

If that error was spread over 3 inches only instead of 6 inches,
the versed sine would only be about iooooott- Probably the effect on
the image of this 3-inch portion of -^q inch shorter focus would not
be appreciable on account of the slight vergency of the rays, but a
similar error near edge of objective certainly would be appreciable.
Until therefore some means be devised of measuring with certainty
quantities of 1 millionth of an inch and less, it is useless to hope
for any help from mechanical measurement in this part of the process.

If then no known mechanical arrangement be delicate enough to
measure these quantities, how, it may be asked, are these errors
detected ?

The answer to this is, that certain optical arrangements enable us
to carry our investigations far beyond the limits of mechanical
accuracy. Trials of the objective or mirror as a telescope are really
the crucial test, but there are various devices by which defects are
detected and localised.

The best object to employ is generally a star of the third or fourth
magnitude, when such is available, but as it frequently occurs that no
such object is visible, recourse is had to artificial objects. The
minute image of the sun reflected from little polished balls of
speculum metal, or even a thermometer bulb is a very good object ;
polished balls of black glass are also used with good effect ; but as
the sun also is of somewhat fickle disposition in this country, we have
frequently to have recourse to artificial light. Small electric lamps,
such as this, with their light condensed, and thrown on a polished ball
are very useful. In fact, I am never without one of them in working
order.

For the detection and localisation of errors it is very useful to be
provided with sets of diaphrams which leave exposed various zones
of the surface, the foci of which can then be separately measured, but
a really experienced eye does not need them.

426 Mr. Howard Gruhh [April 2,

For concave surfaces, Foucault's test is useful. I shall not tres-
pass on your time to explain this in detail, as it is described very fully
in many works, in none better than in Dr. Draper's account of the
working of his own reflecting telescope. This diagram will give an
idea of the principle of the system, which is really the same as what
I have described as useful for detecting want of homogeneity in the
substance of the glass.

This system is extremely useful for concave spherical surfaces, but
is not available for convex surfaces, and only partially available for
concave parabolic surfaces.

The really crucial test is, as I said before, the performance of the
objective when used as a telescope ; and the appearance of the image
not only at the focus, but on each side of it, conveys to the practised
eye all the information required for the detection of the errors.

If an objective have but one single fault, its detection is easy ; but
it generally happens that there are many faults superposed, so to
speak. There may be faults of achromatism, and faults of figure in
one or all the surfaces ; faults of adjustment, and perhaps want of
symmetry from some strain or flexure; and the skill of the artist is often
severely taxed to distinguish one fault from the rest and localise it
properly, particularly if, as is generally the case, there be also dis-
turbances in the atmosphere itself, which mask the faults in the
objective, and permit of their detection only by long and weary
watching for favourable moments of observation.

It would be impossible in one or a dozen of such lectures as this
to enumerate all the various devices that are practised for the locali-
sation of errors, but a few may be mentioned, some of which have
never before been made public.

For detection of faults of symmetry, it is usual to revolve one
lens on another, and watch the image. In this way it can generally
be ascertained whether it is in the flint or crown lens.

With some kinds of glass the curves necessary for satisfying the
conditions of achromatism and spherical aberration are such that the
crown becomes an equi-convex and the flint a nearly plano-concave of
same radius on inside curve as either side of the crown. This form is
a most convenient one for the localisation of surface errors in this
manner.

The lenses are first placed in juxtaposition and tested. Certain
faults of figure are detected. Now calling the sui-faces A B C D in
the order in which the rays pass through them, place them again
together with Canada balsam or castor-oil between the surfaces
B and C, forming what is called a cemented objective. If the fault
be in either A or D surface, no improvement is seen ; if in B or C the
fault will be much reduced or modified. Now reverse the crown
lens cementing surfaces A and C together. If same fault still shows,
it must be in either B or D. If it does not show, it will be in either
A or C. From these two experiments the fault can be localised.

It often happens that a slight error is suspected, but its amount is

1886.] on Telescopic Objectives and Mirrors. 427

so slight that it appears problematical whether an alteration would
really improve matters or not. Or, the observer may not be able to
make up his mind as to the exact position of the zone he suspects
to be too high or too low, and he fears to go to work and perhaps do
harm to an objective on which he has spent months of labour, and
which is almost perfect. In many such cases I have wished for some
means by which I could temporarily alter the surface and see it so
altered before actually proceeding to abrade and perhaps spoil it.

During my trials with the great objective of Vienna, I thought of
a very simple expedient, which efifects this without any chance at all
of injuring the surface. If I suspect a certain zone of an objective
is too low, and that the surface might be improved by lowering
the rest of it, I simply pass my hand, which is always warmer than
the glass, some six or eight times round that particular zone. The
effect of this in raising the surface is immediately apparent, and is
generally too much at first, but the observer at eye end can then
quietly watch the image as the effect goes off, and very often most
useful information is thus obtained. The reverse operation, that of
lowering any required part of the surface, is equally simple. I take
a bottle of sulphuric ether and a camel's-hair brush, and pass the
brush two or three times round the part to be lowered, blowing on it
slightly at the same time ; the effect is immediately perceived, and can
always be overdone if required.

So far then for the diagnosis. Now for the remedy. When the
fault has been localised, the lens is again put upon the machine and
the polisher applied as before, the stroke of the machine and the
size of the pitch patches being so arranged as to produce, or tend to
produce, a slightly greater action on those parts that have been found
to be too high (as before described while treating of the polishing

The regulation of the stroke, excentricity, speed, and general action
of the machine, as well as the size and proportion of the pitch
squares, and the duration of the period during which the action is to
be continued, are all matters the correct determination of which
depends upon the skill and experience of the operator, and con-
cerning which it would be impossible to formulate any very definite
rules. All thanks are due to the late Lord Eosse and Mr. Lassell,
and also to Dr. de la Eue, for having published all particulars of the
process which they found capable of communication ; but it is a
notable fact that, as far as it is possible to ascertain, every one who
has succeeded in this line has done so, not by following written
or communicated instructions, but by striking out a new line for
himself; and I think I am correct in saying that there is hardly
to be found any case of a person attaining notable success in the art
of figuring optical surfaces by rigidly following directions or instruc-
tions given or bequeathed by others.

There is one process of figuring which is said to be used with
success among Continental workers. I refer to the method called the

428 Mr. Hotvard Gruhh [April 2,

process of local toucli. In this process those parts, and those parts
only, which are found to be high are acted upon by a small polisher.

This action is of course much more severe ; and if only it were
possible to know exactly what was required, it ought to be much
quicker ; but I have found it a very dangerous j)rocess. I have some-
times succeeded in removing a large lump or ring in this way (by
large I mean 3 or 4 millionths of an inch), but I have also and
much oftener succeeded in spoiling a surface by its use. I look
upon the method of local touch as useful in removing gross quantities,
but for the final perfecting of the surface I would not think of
employing it.

In small-sized objectives the remedial process is the most trouble-
some, but in large-sized objectives the diagnosis becomes much the
more difficult, j)artly on account of the rare occurrence of a suffi-
ciently steady atmosphere. In working at the Vienna objective
it often happened when the figure was nearly perfect that it was
dangerous to carry on the polishing process for more than ten minutes
between each trial, and we had then sometimes a week to wait before
the atmosphere was steady enough to allow of an observation suffi-
ciently critical to determine whether that ten minutes' working had
done harm or good. It must not be supposed either that the process
is one in which improvement follows improvement step by step till
all is finished. On the contrary, sometimes everything goes well for
two or three weeks, and then from some unknown cause, a hard patch
of pitch perhaps, or sudden change of temperature, everything goes
wrong. At each step, instead of improvement there is disimprove-
ment, and in a few days the work of weeks or months perhaps is all
undone. Truly any one who attempts to figure an objective requires
to have the gift of patience highly developed.

In view of the extraordinary difficulty in the diagnostic part of
the process with large objectives, it is my intention to make pro-
vision which I hope may reduce the trouble in the working of the
new 28-inch objective for the Royal Observatory, Greenwich.

Two of the greatest difficulties we have to contend with are:
Istly, the want of homogeneity in the atmosphere, through which we
have to look in trials of the objective, due to varying hygrometric and
thermornetric states of various portions ; and 2ndly, sudden changes
of temperature in the polishing room. The polisher must always be
made of a hardness corresponding to the existing temperature. It
lakes about a day to form a polisher of large size, and if before the
next day the temperature changes 10^ or 15°, as it often does, that
polisher is useless, and a new one has to be made, and perhaps before
it is completed another change of temperature occurs. To grapple
with these two difficulties I propose to have the polishing chamber
underground, and leading from it a long tunnel formed of highly
glazed sewer-pipes about 350 feet long, at the end of which is placed
an artificial star illuminated by electric light ; on the other side of the
polishing chamber is a shorter tunnel, forming the tube of the telescope,

1886.] on Telescopic Objectives and Mirrors. 429

terminating in a small chamber for eye-pieces and observer. About
half-way in the long tunnel there will be a branch pipe connected
to the air shaft of the fan, which is used regularly for blowing the
blacksmith's fire, and through this when desired a current of air
can be sent to " wash it out " and mix up all currents of varying
temperature and density. It may be found necessary even to keep
this going during observations.

By this arrangement I hope to be able to have trials whenever
required, instead of having to wait hours and days for a favourable
moment.

Figuring of Plane Mirrors.

There is a general idea that the working of a plane mirror or
one of very long radius is a more difficult operation than those of
more ordinary radii. This is not exactly the case. There is no
greater difficulty in figuring a low curve than a deep one, but the
difficulty in the case of absolutely plane mirrors consists simply in the
fact that in their figuring there is one additional condition to be
fulfilled, viz. that the general radius of curvature must be made
accurate within very narrow limits. In figuring a plane mirror to
use, for instance, in front of even a small objective, say 4-iuch aperture,
an error in radius which would cause a difference of focus of ywo
of an inch would seriously injure the performance. This would be
about equivalent to saying that the radius of curvature of the mirror
was about 8 miles, the versed sine of which with the 6 -inch
spherometer would be about -50-^0^ of an inch. Now what I mean
to convey is this ; that it would be just as difficult to figure a convex
or concave lens of moderate curvature as a flat lens of tho same size
if it were necessary to keep the radius accurate to that same limit,
i. e. one-tenth of a division of this spherometer.

Lick Observatory.

For the final testing of large objectives or mirrors, it is necessary
to have them properly mounted, and in such a manner that they can
be directed conveniently on any celestial object, and kept so directed
by clockwork to enable the observer to devote his whole attention
to the testing. I had not intended touching at all on the subject
of the mounting of telescopes, but I have been asked to call your
attention to this model of a proposed observatory for Mount Hamilton,
California, as it embraces some novel features, but I shall do so in
only a very few words.

Most here are probably aware that a monster observatory is in
course of erection in California, a large sum of money having been
left for the purpose by a Mr. Lick. The observatory is already
partly complete, and contains some excellent instruments of moderate
size, the work already done with which warrants us to hope that the
great 3 6 -inch refractive about to be erected will be placed under

430 Mr, Howard Gruhh [April 2,

more favourable conditions for work than any other large telescope
in the world.

The 36-inch objective is at present in process of construction by
the Messrs. Clark of America, but the mounting has not yet been
contracted for.

Some years since, in a paper published in the Transactions of the
Royal Dublin Society, I shadowed forth a principle which I con-
sidered should be adopted in great telescopes of the future. The
trustees of the Lick observatory having invited me to design an
instrument for the 36-inch objective, I have put into practical form what
I had before given but general principles of, and the design which this
model illustrates is the result.

Whether this design will ever be carried out or not I cannot tell,
but even as a proposal I trust it may be interesting enough to excuse
my introducing it (somewhat irrelevantly perhaps) to your notice
to-night.

The design includes the equatorial itself, with its observatory,
dome, and provision for enabling the observer to reach the eye end
conveniently.

The conditions I laid down for myself in designing this observa-
tory were that it would be possible for the observer single-handed to
enter the equatorial room at any time, and that, without using more
physical exertion than is necessary for working the smallest-sized
telescope, or even a table microscope, he should be able to open the
70-foot dome, turn it round backwards and forwards, point the equa-
torial to any part of the heavens, revolving it in right ascension and
declination to any extent, and finally (the most difficult of all) to
bring his own person into a convenient position for observing. I say
this last is the most difficult of all, for I think any who have worked
with larger instruments will allow that there is generally far more
trouble in moving the observatory chair (so called) and placing it in
proper position than in pointing the instrument itself. In this
instrument the " chair " would require to be 25 feet high, and with
its movable platform, ladder, balance-weight, &c., would weigh
probably some tons. Even if very perfect arrangements were made
for the working of this chair, the mere fact that the observer while
attempting to make the most delicate observations is perched upon a
small and very unprotected platform 25 feet above the floor and in
perfect darkness, tends to reduce his value as an observer to an extent
only to be appreciated by those who have tried it.

No matter how enthusiastic a man may be at his work, I would not
put a high value on his determinations if made while in a position
which calls for constant anxiety for his own personal safety. I would
go even further still, and say that even personal comforts or discomforts
have much to do with tho value of observations.

I propose, therefore, that all the various motions should be effected
by water power. There are water engines of various forms now
made, some of which have no dead point, and having little vis

1886.] on Telescoinc Objectives and Mirrors, 431

inertia, are easily stopped and started, and are consequently well
adapted for this work.

I propose to use four of them : one for the right ascension motion
of the instrument, and one for the declination ; one for revolving the
dome, and one for raising and lowering the observer himself; but
instead of having anything of the nature of a 25-foot chair or scaffold,
I propose to make the 70-foot floor of the observatory movable. It
is balanced by counterjDoise weights, and raised and lowered at will
by the observer. Then the observer can without any effort raise and
lower the whole floor, carrying himself and twenty jpeople if desired,
to whatever height is most convenient for observation ; and wherever
he is observing, he is conscious that he has a 70-foot floor to walk
about on, which even in perfect darkness he can do in safety.

The valves and reversing gear of the water engines are actuated
by a piece of mechanism, the motive power of which may be a heavy
weight raised into position some time during the previous day by man
or water power. By means of a simple electrical contrivance, this
piece of machinery itself is under the complete control of the observer,
in whatever part of the room he may be, and he carries with him a
commutator of a compact and convenient form, with eight keys in
four pairs, each pair giving forward and backward movements respec-
tively to

A. Telescope movement in right ascension ;

B. Telescope movement in declination ;

C. Eevolution of dome ;

D. Raising of floor.

The remaining operation, opening of shutter, is easily effected
without any additional complication.

It is only necessary to anchor the shutter (which moves back
horizontally) to a hook in the wall and move the dome in the opposite
direction by motion C ; the shutter must of course be opened by this
motion.

It is very possible that there may be some here who have found
what I have had to say on the subject of the figuring of objectives very
unsatisfactory. They may have expected, naturally enough, that
instead of treating of generalities to such a large extent as I have
done, I should have given precise directions, by the following of
which rigidly any person could make a telescopic objective.

To those, however, who have followed me in my remarks, the
answer to this will probably have already suggested itself. It is the
same answer which I give to those who visit my works and ask what
the secrets of the process are, or if I am not afraid that visitors will
pick up my secrets. All the various processes which I have described
up to that of the figuring are I consider purely mechanical processes,
the various details of which can be communicated or described as any
mechanical process can be ; but in the last final and most important
process of all there is something more than this. A person might
spend a year or two in optical works where large objectives are made,

Vol. XI. (No. 80.) 2 f

432 Mr. H. Grubh on Telescopic Objectives and Mirrors. [April 2,

and miglit watch narrowly every action tliat was taken, see every part
of tlie process, take notes, and so forth, and yet he could no more
expect to figure an objective himself, than a person could expect to be
able to paint a jDicture because he had been sitting in an artist's
studio for the same time watching him at his work. Experience
and experience only can teach any one the art, and even then it is only
some persons who seem to possess the power of acquiring it.

A well-known and experienced amateur in this work declared his
conviction that no one could learn the process under nine years' hard
work, and I am inclined to think his estimate was not an exaggerated
one.

True, it may be said that large objectives can be and are generally
turned out by machinery, but what kind of an objective would any
machine turn out if left to guide itself, or left to inexperienced
hands ?

At the risk of being accused of working by what is generally
called the rule of thumb, I confess that conditions often arise, to meet
which I seem to know intuitively what ought to be done, what crank
to lengthen, what tempering is required of the pitch squares ; and yet if
I were asked I should find it very hard to give a reason for my so
doing which would even satisfy myself.

I may safely say that I have never finished any objective over
10 inches diameter, in the working of which I did not meet with some
new exj)erience, some new set of conditions which I had not met with
before, and which had then to be met by special and newly devised
arrangements.

A well-known English astronomer once told me that he con-
sidered a large objective, when finished, as much a work of art as a
fine painting.

I have myself always looked upon it less as a mechanical opera-
tion than a work of art. It is, moreover, an art most difficult to
communicate. It is only to be acquired by some persons, and that
after years of toilsome effort, and even the most experienced find it
impossible to reduce their method to any fixed rules or formulae.

[H. G.]

188G.] General Montlihj Meeting. 433

GENERAL MONTHLY MEETING,

Monday, April 5, 1886.

The Duke of Northumberland, K.G. D.C.L. LL.D. President,

in the Chair.

John Wolfe Barry, Esq M. Inst. C.E.

Sir Thomas Brassey, K.C.B. M.P.

Arthur Carpmael, Esq.

Ernest Carpmael, Esq.

Allan Harvey Drnmmond, Esq.

Edmund Macrory, Esq.

William Hugh Spottiswoode, Esq.

were elected Members of the Royal Institution.

The following Lecture Arrangements were announced : —

. Professor Arthur Gamgee, M.D. F.R.S, Fullerian Professor of Physiology,
R.I. — Six Lectures ou The Function of Circulation; on Tuesdays, May 4 to
June 8.

Professor Dewar, M.A. F.R.S. M.R.I. Fullerian Professor of Chemistry,
R.I. — Three Lectures on The Alkaloids ; on Thursdays, May 6 to 20.

Professor Alexander Macalister, M.D. M.A. F.R.S. — Three Lectures on
Habit as a Factor in Human Morphology ; on TJiursdays, INIay 27 to June 10.

Professor Ernst Pauer — Three Lectures on How to form a Judgment on
Musical Works (with Musical Illustrations) : on Saturdays, May 8 to 22.

Professor George Gabriel Stokes, M.A. D.C.L. LL.D. Pees. R.S.— Three
Lectures on Light, with Special Reference to Effects resulting from its
Action on various Substances ; on Saturdays, May 29 to June 12.

The Pkesents received since the last Meeting were laid on the
table, and the thanks of the Members returned for the same, viz. : —

The Governor-General of JwtZm— Geological Survey of India. Records, Vol. XIX.
Part 1. 8vo. 1885.
Palseontologia Indica ; Memoirs, Series X. Vol. III. Parts 7 and 8. fol. 1886.
The Lords of the Admiralty — Diurnal Change in the Magnitude and Direction of

the Magnetic Forces in the Horizontal Plane, 1841-76. 4to. 1885.
Accademia dei Lincei, Beale, Roma — Atti, Serie Quarta ; Rendiconti. Vol. 11.

Fasc. 2-6. 8vo. 1886.
American Academy of Arts and Sciences — Memoirs, Vol. XI. Part 3, Nos. 2, 3.
4to. 1885.
Proceedings, Vol. XXI. Part 1. 8vo. 1885.
American Philosophical Society— Troceedm^B, No. 121. 8vo. 1886.

2 F 2

434 General Monthly Meeting. [April 5,

Antiquaries, Society of~Proceedmga,Yol. X. "No. 5. 8vo. 1885.

Asiatic Society, Royal (Bombay Branch)— J onvrnd, Vol. XVI. No. 43, 8vo. 1885.

Astronomical Society, Boyal — Monthly Notices, Vol. XL VI. No. 4. 8vo, 1886.

Ateneo Veneto — Revista Mensile. 8vo, 1883-5.

Balfour, The Relations of the late F. M. (the Autlwr) — Works. Memorial Edition.

4 vol. 4to. 1885.
Bankers, Institute o/— Journal, Vol. VII. Part 3. 8vo. 1886.
British Architects, Royal Institute of — Proceedings, 1885-6, No. 9-12. 4to.
British Museum (Natural History)— Catdlogue of Fossil Mammalia. By R.
Lydekker. Part 2. 8vo. 1885.
Catalogue of Palaeozoic Plants. By R. Kidston. 8vo. 1886.
Cambridge Philosophical Society — Proceedings, Vol. V. Part 5. 8vo. 1886.
Chemical Society — Catalogue of the Library. 8vo. 1886.

Journal for March, 1886. 8vo.
Chief Signal Officer, U.S. Army— Be^ort, 1884. 8vo.
Report of the International Polar Expedition to Point Barrow, Alaska. 4to.
1885.
Civil Engineers' Institution — Minutes of Proceedings, Vol. LXXXIII. 8vo.

1885-6.
Comptroller of the Currency, U.S. — Annual Report, 1885. 8vo.
Editors — Amateur Photographer for March, 1886. 4to.
American Journal of Science for March, 1886. 8vo.
Analyst for March, 1886. 8vo.
Athenaeum for March, 1886. 4to.
Chemical News for March, 1886. 4to.
Engineer for March, 1886. fol.
Horological Journal for March, 1886. 8vo.
Iron for March, 1886. 4to.
Nature for March, 1886. 4to.
Revue Scientifique for March, 1886. 4to.
Telegraphic Journal for March, 1886. 8vo.
Zoophilist for March, 1886. 4to.
Fleming, S. (the ^wf/ior)— Universal or Cosmic Time. 8vo. 1885.
Franklin Institute— J omnol. No. 723. 8vo. 1886.
Geographical Society, Royal — Proceedings, New Series, Vol. VIII. Nos. 3, 4.

8vo. 1886.
Horticidtural Society, i?o?/aZ— Journal, Vol. VII. No. 1. 8vo. 1886.
Johns Hopkins University — Studies in Historical and Political Science, Fourth
Series, Nos. 2, 3. 8vo. 1886.
American Journal of Philology, No. 24. 8vo. 1886.
University Circular, No. 47. 4to. 1886.
American Chemical Journal, Vol. VII. No. 6. 8vo. 1886.
Kendal and Dent, Messrs. (the Authors)— Time Chart of the World. 1886.
Lisbon, Sociedade de Geographic — Boletim, 5* Serie, Nos. 7, 8. 8vo. 1885.
Madden, T. More, M.D. (the Author) — Recent Progress of Obstetric and Gynaeco-
logical Medicine. 8vo. 1886.
Manchester Geological Society — Transactions, Vol. XVIII. Parts 14, 15, 16. 8vo.

1886.
Marks, W. D. Esq. (the Author) — Law of Condensation of Steam in Cylinders.

And Development of Dynamic Electricity. 8vo. 1886.
Meteorological O^ce— Monthly Weather Report for Sept. Oct. Nov. 1885. 4to.

Hourly Readings, 1883. Part 3. 4to.
Meteorological Society, Royal — Quarterly Journal, No. 57. 8vo. 1886.

Meteorological Record, No. 19. 8vo. 1885.
Numismatic Society — Chronicle and Journal, 1885, Part 4. 8vo.
Odontological Society of Great Britain — Transactions, Vol. XVIII. Nos. 2 3, 5.

New Series. 8vo. 1885-6.
Parker-Rhodes, C. E. Esq. (the Author) — Universal Reading of Time. 12mo.
1885.

1886.] General Monthly Meeting. 435

Fharmaceutical Society of Great Britain — Journal, March, 1886. 8vo.

Photographic Society— J omnal, New Series, Vol. X. No. 5. 8vo. 1886.

Bodcl, Major J. R. M.B.I. — Feda, with other Poems. By Rennell Kodd. 12mo.

1886.
Royal Society of London — Proceedings, No. 241. 8vo. 1885.
Saxon Society of Sciences, Royal — Mathematische-Physische Classe : Berichte,

1885. No. 3. 8vo. 1886.
Society of Arts — Journal, March, 1886. 8vo.

St. Petershourg, Academic des Sciences — Bulletins, Tome XXX. No. 3. 4to. 1886.
United States Geological Survey— BuUet'ma, Nos. 7-14. 8vo. 1884-5.

Mineral Resources of the United States, 1883-4. By A. Williams. 8vo. 1885.
Vereins zur Beforderung des Geiverbfleisses in Preussen — Verhandlungen, 1886 :

Heft 2. 4to.
Vienna — Naturhistorischen Hofmuseums — Annalen. Band I. No. 1. 4to. VVien

1886.
Wild, Dr. H. (the .DeVec^or)— Annalen der Physikalischen Central-Observa-

toriums, 1884. Thiol 2. 4to. 1885.
Zoological Society— Tiansixotions, Vol. XI. Part 11; Vol. XII. Part 1. 4to.

1885-6.

436 Mr. Anderson [April 9,

WEEKLY EVENING MEETING,

Friday, April 9, 1886.

Sir William Bowman, Bart. LL.D. F.R.S. Vice-President,
in the Chair.

William Anderson, Esq. M. Inst. C.E. 3LB.L

On New Applications of the Meclianical Properties of Cork to the Arts.

It would seem difficult to discover any new properties in a substance
so familiar as cork, and yet it jDossesses qualities which distinguish it
from all other solid or liquid bodies, namely, its power of altering
its volume in a very marked degree in consequence of change of
pressure. All liquids and solids are capable of cubical compression, or
extension, but to a very small extent ; thus water is reduced in volume
by only one two-thousandth part by the pressure of one atmosphere.
Liquid carbonic acid yields to pressure much more than any other
fluid, but still the rate is very small. Solid substances, with the
exception of cork, offer equally obstinate resistance to change of bulk,
even indiarubber, which most people would suj^pose capable of very
considerable change of volume, we shall find is really very rigid.

I have here an apparatus for applying pressure by means of a
lever. I place a piece of solid indiarubber under the plate
and you see that I can compress it considerably by a very light
pressure of my finger. I slip this same piece of indiarubber into a
brass tube, which it fits closely, and now you see that I am unable to
compress it by any force which I can bring to bear, I even hammer
the lever with a mallet and the blow falls as it would on a stone.
Tlie reason of this phenomenon is, that, in the first place, with the
indiarubber free, it spread out laterally while being compressed
longitudinally, and consequently the volume was hardly altered at all ;
in the second case, the strong brass tube prevented all lateral exten-
sion, and because indiarubber is incapable of appreciable cubical com-
pression, its length only could not be sensibly altered by pressure.

Extension, in like manner, does not alter the volume of indiarubber.
In this glass tube is a piece of solid round rubber which nearly fills
the bore. The lower end of the rubber is fixed in the bottom of the
tube and the upper end is connected by a fine cord to a small wind-
lass, by turning which I can stretch the rubber. I fill the tube to
the brim with water and throw an image of it on to the screen. If
stretching the rubber either increases or diminishes its volume, the
water in the tube will either overflow or shrink in it. I now stretch
the rubber to about 3 inches, or one-third of its original length, but
you cannot see any ai^preciable movement in the water-level, hence
the volume of the rubber has not changed.

1886.] on New Applications of the Mechanical Properties of CorJc. 437

Metals wlien subjected to pressures wliicli exceed their elastic
limits, so that they are permanently deformed, as in forging or wire-
drawing, remain j)ractically unchanged in volume per unit of weight.

I have here a pair of common scales. To the under sides of the
2)ans I can hang the various specimens that I wish to examine ; under-
neath these are small beakers of water which I can raise or lower by
means of a rack and pinion. Substances immersed in water lose in
weight by the weight of their own volume of water ; hence if two
substances of equal volume balance each other in air, they will also
balance when immersed in water, but if their volumes are not the
same, then the substance having the smaller volume will sink, because
the weight of water it displaces is less than that displaced by the
substance with the larger volume. To the scale on your left hand is
suspended a short cylinder of ordinary iron, and to the right hand
scale a cylinder of ordinary copper. They balance exactly. I now
raise the beakers and immerse the two cylinders in water, you see the
copper cylinder sinks at once, and I know by that, that copper has a
smaller volume per pound than iron, or, as we should commonly say,
it is heavier than iron. I now detach the copper cylinder and in its
j)lace hang on this iron one, which is made of the same bar as its
fellow cylinder, but forced, while red hot, into a mould by a pressure
of sixty tons per square inch and allowed to cool under that pressure.
The two cylinders balance, as you see. Has the volume of the iron
in the comj)ressed cylinder been altered by the rough treatment it
has received ? I raise the beakers, immerse the cylinders, the balance
is not destroyed, hence we conclude that although the form has
been changed the volume has remained the same. I substitute for
the hot compressed cylinder one pressed into a mould while cold, and
held there for some time, with a load of sixty tons per square inch ;
the balance is not destroyed by immersion, hence the volume has not
been altered. I can repeat the experiments with these copper cylinders
and the result will be found the same. Extension also is incapable of
appreciably altering the density of metals. I attach to the scales
two specimens of iron taken from a bar which had been torn asunder
by a steady pull. One specimen is cut from the portion where it had
not been strained, and the other from the very point where it had been
gradually drawn out and fractured. The specimens balance, I
immerse them, you see the balance is not destroyed ; hence the
volume of the iron has not been changed appreciably by extension.

But cork behaves in a very different manner. I place this
cylinder of cork into just such a brass tube as served to restrain the
indiarubber and apply pressure to it in the same way : you see I can
readily compress the cork, and when I release it it expands back to its
original volume : the action is a little sluggish on account of the
friction of the cork against the sides of the tube. In this case,
therefore, a very great change in the volume of the material has been
easily effected.

But although solids evidently do not change sensibly in bulk,

438 Mr. Anderson [April 9,

after having been released from pressures high enough to distort
them permanently, yet, while actually under pressure, the volumes
may have been considerably altered. As far as I am aware, this
point has not been determined experimentally for metals, but it is
very easy to show that indiarubber does not change.

I have here some of this substance which is so very slightly
lighter than water, that, as you see, it only just floats in cold water
but sinks in hot. If I could put it under considerable pressure while
afloat in cold water, then, if its volume became sensibly less, it ought
to sink. In the same way if I load a piece of cork and a piece of
wood so that they barely float, if their volumes alter, they ought to
sink.

In this strong upright glass tube, I have, at the top, a piece of
indiarubber, immediately below it a piece of wood, and below that a
cork, the wood and the cork are loaded with metal sinkers to reduce
their buoyancy. The tube is full of water and is connected to a
force-pump by means of which I can impose a pressure of over
1000 lbs. per square inch. The image of the tube is now thrown on
the screen and the pressure is being applied. You see at once the
cork is beginning to shrink in all directions, and now its volume is
so reduced that it is incapable of floating and sinks down to the
bottom of the tube. The indiarubber is absolutely unaffected, the wood
does contract a little, but not sufficiently to be visible to you or to cause
it to sink. I open a stop-cock and relieve the pressure, you see that
the cork instantly expands, its buoyancy is restored and it floats again.
By alternately applying and taking off the pressure I can produce
the familiar effect, so well known in the toy called " the bottle imps."
It is this singular pro2)erty which gives to cork its value as a means
of closing the mouths of bottles. Its elasticity has not only a very
considerable range, but it is very persistent. Thus in the better
kind of corks used in bottling cham^^agne and other effervescing
wines, you are all familiar with the extent to which the corks expand
the instant they escape from the bottles. I have measured this
expansion, and find it to amount to an increase /)f volume of
75 per cent, even after the corks have been kept in a state of com-
pression in the bottles for ten years. If the cork be steeped in hot
water, the volume continues to increase till it attains nearly three
times that which it occupied in the neck of the bottle.

When cork is subjected to pressure, cither in one direction, as in
this lever press, or from every direction, as when immersed in water
under pressure, a certain amount of permanent deformation or
" permanent set " takes place very quickly. This property is common
to all solid elastic substances when strained beyond their elastic limits,
but with cork the limits are comparatively low. You have, no doubt,
noticed in chemists' and other shoi)s, that when a cork is too large
to fit a bottle, the shop-keeper gives the cork a few sharp bites, or, if
he be more refined, he uses a pair of specially contrived j^incers, in
either case he squeezes the cork beyond its clastic limits and so makes

1886.] OH New Applications of the Mechanical Properties of Cork. 439

it permanently smaller. Besides the permanent set, there is a
cei'tain amount of what I venture to call sluggish elasticity, that is,
cork on being released from pressure, springs back a certain amount
at once, but the complete recovery takes an appreciable time.

While I have been speaking, a piece of fresh cork, loaded so as
barely to float, has been inserted into the vertical glass pressure-
tube. I apply a slight pressure, you see the cork sinks. I release
the pressure, and it rises briskly enough. I now apply a much higher
l^ressure for a moment or two, I release it, and the cork will either
not rise at all, or will do so very slowly ; its volume has been
permanently altered ; it has taken a permanent set.

In considering the properties of most substances, our search for the
cause of these properties is baffled by our imperfect powers and the
feeble instruments we possess for investigating molecular structure.
With cork, happily, this is not the case ; an examination of its
structure is easy, and perfectly explains the cause of its peculiar and
valuable properties.

All plants are built up of minute cells of various forms and
dimensions. Their walls or sides are composed chiefly of a substance
called cellulose, frequently associated with lignine, or woody matter,
and with cork, which last is a nitrogenous substance found in many
portions of plants, but is especially developed in the outer bark of
exogenous trees, that is, trees belonging to an order, by far the
most common in these latitudes, the stems of which grow by
the addition of layers of fresh cellulose tissue outside the woody
part and inside the bark. Between the bark and the wood is inter-
posed a thin fibrous layer, which, in some trees, such as the lime, is
very much developed, and supplies the bass matting with which all are
familiar. The corky part of the bark, which is outside, is composed
of closed cells exclusively, Figs. 1 and 2, so built together that no
connection of a tubular nature runs up and down the tree, although
horizontal passages radiating towards the woody part of the tree are
niunerous. In the woody part of the tree, on the contrary, and
in the inner bark, vertical passages or tubes exist, while a con-
nection is kept up with the pith of the tree by means of medullary
rays. In one species of tree, known as the cork oak, the corky part
of the bark is very strongly developed. I project on the screen
the magnified image of a horizontal section of the bark of the cork
oak ; you see nine or ten bands running parallel to each other,
these are the layers of cellulose matter that have been deposited in
successive years. I turn the specimen, and you now see the vertical
section with the radiating passages clearly marked.

The difference between the ai'rangement of the cells or tissue forming
the woody part of the tree and the bark is easily shown. I have here
three metal sockets, supported over a shallow wooden tray. Into
them are fitted, first, a cork cut out of the bark in a vertical
direction, next, a cork cut in a radial direction, and, lastly, a piece of
common yellow pine. By means of my force-pump, I apply a couj)le

440

Mr, Anderson

[April 9,

of atmospheres of hydraulic pressure. I jDrojcct an image of the
apparatus on the screen, and you see the water has made its way
through the wood and through the cork cut in the radial direction,
while the cork cut in the vertical direction is impervious.

Fig. 1.

Vertical Section.
Fig. 2.

Horizontal Section.
Magnified about 300 diameters.

riie cork tree, a species of evergreen oak, is indigenous in Tortugal
and along both shores of the Mediterranean. The diagram on the
wall has been painted from a sketch obligiugly sent to me by Mr.

1886.] on New Applications of the Mechanical Properties of Cork. 441

C. A. Friend, the Resident Engineer of the Seville Waterworks, to
whom I am also indebted for this branch of a cork tree, these acorns,
this axe used in getting the cork, and for a description of the habits
of the tree, its cultivation, and the mode of gathering the harvest.

The cork oak attains a height of thirty to forty feet ; it is not
cultivated in any way, but grows like trees in a park. The first crop
is not gathered till the tree is thirty years old, the next nine or ten
years later ; — both these crops yield inferior cork, but at the third
crop, gathered when the tree is fifty years old, the bark has attained
full maturity, and after that will yield the highest quality of cork
every nine or ten years. In the autumn of the year, when the bark
is in a fit state, that is, for small trees, from three-quarters of an inch
to one inch thick, and for larger ones up to one and a half inch, a
horizontal cut is made, by means of a light axe like the one I hold in
my hand, through the bark a few inches above the ground ; succeeding
cuts are made at distances of about a yard, up to the branches, and
even along some of the large ones, then two or more vertical cuts,
according to the size of the tree, and the bark is ripped off by inserting
the v>'-edge-shaped end of the axe-handle. In making the cuts great
care is taken to avoid wounding the inner bark, upon the integrity of
which the health of the tree depends ; but where this precaution is
taken, the gathering of the cork does not in any way injure the tree.

After stripjDing, the cork is immersed for about an hour in hot
water, it is dressed with a kind of spokeshave, then laid out flat and
weighted in order to take out the curvature ; it is then stacked in the
open air, without protection of any kind, for cork does not appear to
be susceptible of receiving injury from the weather.

The minute structure of the bark is very remarkable. First, I
project on the screen a microscopic section of the wood of the cork
tree. It is taken in a horizontal plane, and I ask you to notice the
diversity of the structure, and especially the presence of large tubes
or pipes. I next exhibit a section taken in the same plane of the corky
portion of the bark, Fig. 2. You see the whole substance is made up
of minute many-sided cells about -j-^o ^^^^ ^^ diameter and about
twice as long, the long way of the cells being disposed radially to
the trunk. The walls of the cells are extremely thin, and yet they
are wonderfully impervious to liquids. Looked at by reflected light,
if the specimen be turned, bands of silvery light alternate with bands
of comparative darkness, showing that the cells are built on end to
end in regular order. The vertical section next exhibited, Fig. 1, shows
a cross-section of the cells looking like a minute honey-comb. In some
specimens large numbers of crystals are found. These could not be
distinguished from the detached elementary spindle-shaped cells, of
which woody fibre is made up, were it not for the powerful means of
analysis we have in polarized light. I need hardly explain to an
audience in this Institution that light passed through a Nicol prism
becomes polarized, that is to say, tl^ vibrations of the luminiferous
ether are all reduced to vibrations in one i^lane, and, consequently, if

442 Mr. Anderson [April 9,

a second prism be interposed and placed at right angles to the first,
the light will be unable to get through ; but if we introduce between
the crossed Nicols a substance capable of turning the plane of vibra-
tion again, then a certain portion of the light will pass. I have now
projected on the screen the feeble light emerging from the crossed
Nicols. I introduce the microscopic preparation of cork cells between
them, and you see the crystals glowing with many-coloured lights on
a dark ground.

Minute though these crystals are, they are very numerous and
hard, and it is partly to them that is due the extraordinary rapidity
with which cork blunts the cutting instruments used in shaping it.
Cork-cutters always have beside them a sharpening stone, on which
they are obliged to restore the edges of their knives after a very few
cuts.

The cells of the cork are filled with gaseous matter, which is
very easily extracted, and which has been analysed for me by Mr.
G. H. Ogston, and proved to be common air. I have here
a glass tube in which are some pieces of cork which have been
cut into slices so as to facilitate the escape of the air. I
connect the tube with an exhausted receiver and project the image on
the screen ; you see rising from the cork bubbles of air as numerous,
but much more minute than the bubbles which rise from sparkling
wines ; much more minute, because the bubbles you see are expanded
to seven or eight times their volume at atmospheric pressure, on
account of the vacuum existing in the tube. The air will continue
to come off for an hour or more, and from measurements made by
Mr. Ogston I find that the air occluded in the cork amounts to
about 53 per cent, of its volume. The facility with which the air
escaj^es, compared with the impermeability of cork to liquids, is very
remarkable.

I throw on the screen the image of a section cut from a cork which
was kept under a vacuum of about 26 inches for five days and nights ;
aniline dye was then injected, and yet you see that the colour has
not more than permeated the outermost fringe of cells, those, in fact,
which had been broken open by the operation of cutting the cork.
By keeping cork for a very long time in an almost perfect vacuum,
and then injecting dye, a slight darkening of the general colour of a
section of the cork may be noticed, but it is very slight indeed. How,
then, does the air escape so readily when the cork is placed in vacuo ?

The answer is, that gases possess the property of diffusion, that is,
of passing through porous media of inconceivable fineness. When
two gases, such as hydrogen and air, are separated by a porous medium,
they immediately begin to pass into each other, and the lighter gas
passes through more quickly than the heavier.

I have here a glass tube, the upper end of which is closed by a
thin slice of cork, the lower end dips into a basin of water. Some
hours ago the tube Avas filled with hydrogen, which you know is about
fourteen and a half times lighter than air, conse(j[uently, according to

1886.J on NeiD Applications of the Mechanical Properties of Cork. 443

the law of diffusion, it will get out of the tube through the cork
quicker than the air can get in by the same means, and the result must
be that a partial vacuum will be formed in the tube, and a column of
water will be drawn up. You see that such has been the case, and
we have thus proved that the cells of cork are eminently pervious to
gases. The pores in the cell-walls appear, however, to be too minute
to permit the passage of liquids.

I closed the end of a glass tube 11 mm. diameter, with a" disc of
cork 1*75 mm. thick, cut at right angles to the axis of the tree, I
placed a solution of blue litmus inside the tube, and suspended it in
a weak solution of sulphuric acid. Had diffusion taken place, both
liquids would have assumed a red colour, but after sixteen hours no
change whatever could be detected. A like inertness was exhibited
when the tube was filled with a solution of copper sulphate and sus-
pended in a weak solution of ammonia ; a deep blue colour would
have appeared had any intermixture taken place, and the same tube
is before you immersed in ammonia and filled with red litmus solu-
tion. It has been in this condition since the 28th of February, but
no diffusion has taken place. A disc of wood 6 mm. thick under
the same circumstances showed, after a couple of hours, by the liquids
turning blue, that diffusion was going on actively. It is this property
of allowing gases to permeate while completely barring liquids that
enables cork to be kept in compression under water or in contact with
various liquids without the air-cells becoming water-logged, and that
makes cork so admirable an article for waterproof wear, such as boot
soles and hats, for, unlike indiarubber, it allows ventilation to go on
while it keeps out the wet. The cell-walls are so strong, notwith-
standing their extreme thinness, that they appear, when empty, to be
able to resist the atmospheric pressure, for the volume of the cork
does not sensibly diminish, even when all the air has been extracted.
Viewed under very high power, cross-stays or struts of fibrous matter
may be distinguished traversing the cells : these, no doubt, add to the
strength and resistance of the structure.

From what you have seen you will have no difficulty in arriving
at the conclusion that cork consists, practically, of an aggregation of
minute air-vessels, having very thin, very water-tight, and very strong
walls, and hence, if compressed, we may expect the resistance to com-
pression to rise in a manner more like the resistance of gases than
the resistance of an elastic solid such as a spring. In a spring the
pressure increases in proportion to the distance to which the spring
is compressed, but with gases, the pressure increases in a much more
rapid manner, that is, inversely as the volume which the gas is made
to occupy. Bat from the permeability of cork to air, it is evident
that if subjected to pressure in one direction only, it will gradually
part with its occluded air by effusion, that is by its passage through
the porous walls of the cells in which it is contained. This fact can
be readily demonstrated by the lever press which I have used, for if
the brass cylinder containing the cork be filled with soap and water

444

Mr. Anderson

[April 9,

and pressure be then applied, minute bubbles will be found to collect
on the surface, and their formation will go on for many hours.

On the other hand, if cork be subjected to pressure from all sides,
such as operates when it is immersed in water under pressure, then
the cells are supported in all directions, the air in them is reduced in
volume, and there is no tendency to escape in one direction more than
another. An indiarubber bag, such as this, distended by air, bursts,
as you see, if pressed between two surfaces, but if an indiarubber cell
be placed in a glass tube and subjected to hydraulic pressure, it is
merely shrivelled up, the strain on its walls is actually reduced.

To take advantage of the peculiar properties of cork in mechanical
applications, it is necessary to determine accurately the law of its
resistance to compression, and for this purpose I instituted a series of
experiments of this kind. Into a strong iron vessel of 5J gallons
capacity I introduced a quantity of cork, and filled the interstices full
of water, carefully getting out all the air. I then proceeded to
pump in water, until definite pressures up to 1000 pounds per square
inch had been reached, and, at every 100 pounds, the weight of water

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pumpecl in was determined. In this way, after many repetitions, I
obtained the decrease of volume, due to any given increase of pressure.
The observations have been plotted into the form of a curve. Fig. 3,
which you see on the diagram on the wall. The base-line reiDresents a
cylinder containing one cubic foot of cork divided by the vertical
lines into ten parts ; the black horizontal lines according to the scale
on the loft hand represent the pressures in pounds per square inch

1886.] on New Applications of the Mechanical Properties of Cork. 445

which were necessary to compress the cork to the corresjDonding
volume. Thus to reduce the volume to one-half, required a pressure
of 250 pounds per square inch. At 1000 pounds per square inch the
volume was reduced to 44 per cent., the yielding then became very
little, showing that the solid parts of the cells had nearly come
together, and this corroborates Mr. Ogston's determination, that the
gaseous part of cork constitutes 53 per cent, of its bulk. The
engineer, in dealing with a compressible substance, requires to know
not only the pressure which a given change of volume produces, but
also the work which has to be expended in producing the change of
volume. The work is calculated by multiplying the decrease of
volume by the mean pressure per unit of area which produced it.
The ordinates of the dotted curve on the diagram with the corre-
sponding scale of foot pounds on the right-hand side are drawn equal
to the work done in compressing a cubic foot of cork to the several
volumes marked on the base line. I have not been able to find
an equation to the pressure curve, it seems to be quite irregular, and
hence the only way of calculating the effects of any given change of
volume is to measure the ordinates of the curve constructed by actual
experiment. As may be supposed the pressures indicated by ex-
periment are not nearly so regular and steady as corresponding
experiments in a gas would be, and the actual form of the curves
will depend on the quality of the cork experimented on.

The last point of importance in this inquiry relates to the
permanence of elasticity in cork.

So far as preservation of elasticity during years of compression
is concerned, we have the evidence of wine corks to show that a
considerable range of elasticity is retained for a very long time.
With respect to cork subjected to repeated compression and exten-
sion, I have very little evidence to offer beyond this, that cork which
had been compressed and released in water many thousand times,
had not changed its molecular structure in the least, and had con-
tinued perfectly serviceable. Cork which has been kept under a
pressure of three atmospheres for many weeks appears to have shrunk
to from 80 to 85 per cent, of its original volume.

I will conclude this lecture by bringing under your notice two
novel applications of cork to the arts.

Before the lecture-table stands a water-raising apparatus called
a hydraulic ram. The structure of the machine is shown by a diagram
on the wall, Eig. 4. The ram consists of an inclined pipe A, which
leads the water from a reservoir into a chamber B, which terminates in
a valve C, opening inwards. Branching up from the chamber is a
passage leading to a valve D, opening outwards and communicating
with a regulating vessel E, which is usually filled with air, but which
I prefer to fill with cork and water. Immediately beyond the inner
valve, is inserted a delivery pipe F, which is laid to the spot to which
the water has to be pumped, in this case to the fountain jet in the
middle of this pan.

446

Mr. Anderson

[April 9,

The action of the ram is as follows : — The outer valve C which
opens inwards, is, in the first instance, held open, and a flow of water
is allowed to take place through it down the pipe and chamber. The
valve is then released, and is instantly shut by the current of water
which is thus suddenly stopped, and, in consequence, delivers a blow

Fig. 4,

similar to that produced by the fall of a hammer on an anvil, and
just as the hammer jumps back from the anvil, so does the water
recoil back to a small extent along the pipe.

During this action, first, a certain portion of water is forced by
virtue of the blow through the inner valve D, opening outwards, into
the cork vessel, and so to the delivery pipe, and, instantly afterwards
the recoil causes a partial vacuum to form in the body of the ram and
permits the atmospheric pressure to open the outer valve C and re-
establish a rush of water as soon as the recoil has expended itself.
In the little ram before you, this action, which it has taken so long
to describe, is repeated 140 times in a minute.

The ram is now working, you hear the regular pulses of the
valve, and you see a jet of water rising some 10 feet into the air. I
throw the electric light on the water, and I ask you to notice the
regularity of the flow. You can, indeed, detect the pulses of the
ram in the fountain, but that is because I am only using a regulating
vessel of the same capacity as that generally used for air, and you
will recollect that 44 per cent, of the substance of cork is solid and
inelastic. By closing a cock, I can cut off the cork vessel from the

1886.] on New Applications of the Mechanical Properties of Cork. 447

ram, you see the regularity of tlie jet has disappeared, it now
goes in leaps and bounds. This demonstrates that the elasticity of
cork is competent to regulate the flow of water. When air is
used for this purpose, the air-vessel has to be filled, and, with
most kinds of water, the supply has to be kept up while the ram
is working, because water under jDressure absorbs air. For this
purpose a " sniff-valve," G, is a necessary part of all rams. It is
a minute valve opening inwards, placed just below the inner
valve ; at each recoil, a small bubble of air is drawn in and
passed into the air-vessel. This "sniff-valve" is a fruitful source
of trouble. Its minuteness renders it liable to get stopped up by
dirt ; it must not, of course, be submerged, and, if too large, it
seriously affects the duty performed by the ram. The use of cork
gets rid of all these difficulties, no sniff- valve is needed, the ram will
work deeply submerged, and there is no fear of the cork vessel ever
getting empty. The duty which even the little ram before you has
done is 65 per cent., and larger ones have reached 80 per cent.

The second novel application of cork is, for the purpose of storing
a portion of the energy of the recoil of cannon, for the purpose of
expending it afterwards in running them out.

The result of the explosion of gunpowder in a gun is to drive the
shot out in one direction, and to cause the gun to recoil with equal
energy the opposite way. To restrain the motion of the gun, " com-
pressors" of various kinds are used, and in this country, for modern
guns, they are generally hydraulic, that is to say, the force of recoil
is expended in causing the gun to mount an inclined plane, and, at
the same time, in driving a j)iston into a cylinder full of water, the
latter being allowed to squeeze past the piston through apertures,
the areas of which are either fixed, or capable of being automatically
varied as the gun recedes ; or else the water is driven out of the
cylinder through loaded valves. As a rule, the gun is moved out
again into its firi^ position by its weight, causing it to run down
the inclined plane, up which it had previously recoiled. For naval
purposes, however, this plan is inconvenient, because the gun will
not run out to windward if the vessel is heeling over, on account of
the inclined plane becoming more horizontal, or even inclined in
the reverse direction, and should the ship take a permanent list,
from a compartment getting full of water, the inconvenience might
be very considerable.

In land service guns, when mounted in barbette, the rising of the
gun exposes it and the loading detachment more to the enemy's fire,
and in both cases, when placed in ports or embrasures, the ports must
be higher than if the gun recoiled horizontally, and will therefore
offer a better mark to the enemy's fire, especially that of machine
guns, while the sudden rise of the gun in recoiling imposes a severe
downward pressure on the deck or on the platform.

To obviate these disadvantages I have contrived the gun-carriage, a
model of which is before you on the table, and a diagram of which, Fig. 5,

Vol. XI. (No. 80.) 2 g

448

Mr, Anderson

[April 9,

on the wall illustrates tlie internal construction. The gun is mounted
on a carriage composed of two hydraulic cylinders A, united so as to
form one piece. This carriage slides on a pair of hollow ways B, and
also on to a pair of fixed rams C, the rear ends of which are attached to
the piece D forming the rear of the mounting. There are water passages
down the axes of the rams, and these communicate through an

Fig. 5.

.^^r..^^

^^^^^^v^\N\\\\\\\\\:\\\\\\\\\\\N\\x\\^^

automatic recoil valve E, opening from the cylinders, with the two
hollow slides B. There is a second communication, between the
cylinders and slides by means of a cock F, which can be opened or shut
at pleasure. The hollow slides are packed full of cork and water,
the latter also completely filling the cylinders, rams, and various
connecting passages.

By means of a small force-pump enough water can be injected to
give the cork so much initial compression as will suffice to run the
gun out when the slides are inclined under any angle which may bo
found convenient.

When the gun is fired, the cylinders A are driven on to the rams C
and the water in the cylinders is forced through the hollow rams into
the cork and water vessels formed by the slides B, and the cork is
compressed still farther. When the recoil is over, the automatic
recoil-valve E closes, and the gun remains in its rearward position
ready for loading.

As soon as loaded, the running-out cock F is opened, the expansion
of the cork drives the water from around it into the cylinders, and so
forces the gun out.

If it be desired to let the gun run out automatically immediately
after recoil, it is only necessary to leave the running-out cock F open,
and then the water forced among the cork by recoil returns instantly
to the cylinders, and runs the gun out quicker than the eye can follow
the motion,

I will now load the model and fire a shot into this strong steel
cylinder, at the bottom of which is a thick layer of soft wood. I will
close the running-out valve, so that the gun shall remain in the recoiled
position. Sir Frederick Abel has kindly arranged some of his electric

1886.] on New Applications of the Mechanical Projjerties of Cork. 449

fuses si3ecially to fit tins minute ordnance, and I can fire the gun by
means of a small electro-magnetic battery. The gun has now recoiled,
and remains in its rear position. I load again, open the running-out
cock, the gun runs out, and I fire without closing the cock. You see
the gun has recoiled and run out instantly again.

The arrangement I have adopted may he made by using air instead
of cork, but air is a troublesome substance to deal with ; it leaks out
very easily and without showing any signs of having done so, which
might readily lead to serious consequences. A special pump is
required to make up loss by leakage.

The merit of cork is its extreme simplicity and trustworthiness.
By mixing a certain proportion of glycerine with the water it will
not freeze in any ordinary cold weather.

[W. A.]

2 G 2

450 Professor Sir Henry E. Eoscoe [April 16,

WEEKLY EVENING MEETING,

Friday, April IG, 1886.

Sir William Bowman, Bart. LL.D. F.R.S. Vice-President, in the

Chair.

Professor Sir Henry E. Eoscoe, M.P. LL.D. F.R.S.

On Recent Progress in the Coal-tar Industry.

Those who have read Goethe's episodes from his life, known as
' Wahrheit und Dichtung,' will remember his description of his visit
in 1741 to the burning hill near Dutweiler, a village in the Palatinate.
Here he met old Stauf, a coal philosopher, 'pliiloso^phus per ignem,
whose peculiar appearance and more peculiar mode of life, Goethe
remarks upon. He was engaged in an unsavoury process of collecting
the oils, resin, and tar, obtained in the destructive distillation of
coal carried on in a rude form of coke oven. Nor were his labours
crowned with pecuniary success, for he comj)lained that he wished
to turn the oil and resin into account, and save the soot, on which
Goethe adds that in attempting to do too much, the enterprise alto-
gether failed. We can scarcely imagine, however, what Goethe's feel-
ings would have been could he have foreseen the beautiful and useful
products which the development of the science of a century and a half
has been able to extract from Stauf 's evil smelling oils. With what
wonder would he have regarded the synthetic power of modern
chemistry, if he could have learnt that not only the brightest, the
most varied colours of every tone and shade can be obtained from
this coal tar, but that some of the finest perfumes can, by the skill of
the chemist, be extracted from it. Nay, that from these apparently
useless oils, medicines which vie in potency with the rare vegeto-
alkaloids can be obtained, and lastly, perhaps most remarkable of
all, that the same raw material may be made to yield an innocuous
principle, termed saccharine, possessed of far greater sweetness than
sugar itself. The attainment of such results might well be regarded
as savouring of the chimerical dreams of the alchemist, rather than
expressions of sober truth, and the modern chemist may ask a riddle
more paradoxical than that of Samson, "Out of the burning came
forth coolness, and out of the strong came forth sweetness " ; and by
no one could the answer be given who had not ploughed with the
heifer of science, " What smells stronger than tar and what tastes
sweeter than saccharine ? " That these are matters of fact we may
assure ourselves by the most convincing of all proofs — their money
value, and we learn that the annual value of the products now ex-
tracted from an unsightly and apparently worthless material, amounts

1886.] on Becent Progress in the Coal-tar Industry. 451

to several millions sterling, whilst tlic industries based upon these
results give employment to thousands of men.

Sources of the Coal-tar products. — In 'order to obtain these products,
whether colours, perfumes, antipyretic medicines, or sweet principle, a
certain class of raw material is needed, for it is as impossible to get
nutriment from a stone as to procure these products from wrong
sources. All organic compounds can be traced back to certain hydro-
carbons, which may be said to form the skeletons of the compounds,
and these hydrocarbons are divisible into two great classes : (1) the
paraffinoid, and (2) the benzenoid hydrocarbons. The chemical dif-
ferences both in properties and constitution between these two series
are well marked. One is the foundation of the fats, whilst the other
class gives rise to the essences or aromatic bodies. Now all the
colours, finer perfumes, and antipyretic medicines referred to, are
members of the latter of these two classes. Hence if we wish to
construct these complicated structures, we must employ building
materials which are capable of being cemented into a coherent edifice,
and therefore we must start with hydrocarbons belonging to the
benzenoid series, as any attemjDt to build up the colours directly
from paraffin compounds would prove impracticable. Of all the
sources of hydrocarbons, by far the largest is the natural petroleum
oils. But these consist almost entirely of paraffins, and hence
this source is commercially inapplicable for the production of
colours. We have, however, in coal itself, a raw material which by
suitable treatment may be made to yield oils of a valuable character.
Of these treatments, that followed out in the process of gas-making is
the most important, for in addition to illuminating gas in abundant
supply, tar is produced which contains principally that benzenoid
class of substances already referred to, and which, to use the words
of Hofmann, " is one of the most wonderful productions in the whole
range of chemistry." The production of these latter as distinguished
from the paraffinoid group appears to dejDcnd upon a high temperature
being employed, to effect the necessary decomposition.

The quantity of coal made into coke for use in the blast furnace
is larger than that distilled for gas-making, no less than between eleven
and twelve million tons of coal being annually consumed in the blast
furnaces of this country in the form of coke, and capable of yielding
two million tons of volatile products. Uy) to recent times, however, the
whole of these volatile products has been burnt and lost in the coke
ovens. But lately, various processes have been devised for preventing
this loss, and for obtaining the oils, which might be made available
as colour-producing materials. It is, moreover, a somewhat remark-
able fact that only in one or two cases have the conditions been
complied with which render it possible to obtain the necessary
benzenoid substances. In the ordinary coking ovens, as well as in
the blast furnaces, although the temperature ultimately reached is far
in excess of that needed to form the colour-giving hydrocarbons, yet
the heating process is carried on so gradually that the volatile pro-

452 Professor Sir Henry E. Boscoe [April 16,

ducts from tlie coal are obtained in the form of paraffinoid bodies
mainly, and hence are useless for colour-making purposes. Amongst
the few coking processes in which the heat is suddenly applied, and
consequently a yield of colour-giving hydrocarbons is obtained, may
be mentioned the patented process of Simon-Carves, the use of which
is now spreading in England and abroad. The tar obtained in this
process is almost identical in composition with the average gas-works
tar, whilst the coke also appears to be equal for iron-smelting purposes
to that derived from other coke-ovens. A third source of these oils
yet remains to be mentioned, viz. those obtained as a by-product in
blast furnaces fed with coal.

Another condition has, in addition, to be considered in thisindustry,
and that is the nature of the coal employed for distillation. It is a
well-known fact that if Lancashire cannel be exclusively employed in
gas-making a highly luminous gas is obtained, but the tar is too rich
in paraffins to be a source of profit to the tar-distiller, whilst, on the
other hand, coal of a more anthracitic character, like that from New-
castle or Staffordshire, yields a tar too rich in one constituent, viz.
naphthalene, and too poor in another, viz. benzene. It is also known
to those engaged in carbonising coal principally for the sake of the
tar that the coal from diflferent measures, even in the same pit, yields
tars of very different constitution. That under these varying con-
ditions products of varying composition are obtained is a result that
will surprise no one who considers the complicated chemical changes
brought about in the jDrocess of the destructive distillation of coal.

History of Benzene and its derivatives. — Having thus sketched the
principles upon which the formation of these valuable tar colours
depends, we should do wrong to pass over the history of the discovery
of benzene (CqHq), which contributed so much to the unlocking of
the coal-tar treasury.

Faraday in 1825 discovered two new hydrocarbons in the oils
obtained from portable gas. One of these was found to be butylene
(C4H8) ; to the other Faraday gave the name of bicarburet of hydrogen,
as he ascertained its empirical formula to be C2H (C = 6). By ex-
ploding its vapour with oxygen, he observed that one volume contains
36 parts by weight of carbon to 3 parts by weight of hydrogen, and
its specific gravity compared with hydrogen is therefore 39.*

Mitscherlich, in 1834, obtained the same hydrocarbon by distilla-
tion of benzoic acid, C7II6O2, with slaked lime, and termed it benzin.
He assumed that it is formed from benzoic acid simply by removal of
carbon dioxide. Liebig denied this, adding the following editorial
liOte to Mitscherlich's memoir: — " We have changed the name of the
body obtained by Professor Mitscherlich by the dry distillation of
benzoic acid and lime, and termed by him benzin, into benzol,
because the termination ' in ' ajipears to denote an analogy between
strychnine, quinine, &c., bodies to which it does not bear the slightest

* i p

Phil. Trans.; 1825, p. 440.

1886.] on Becent Progress in the Coal-tar Industry. 453

resemblance, whilst the ending in ' ol ' corresponds better to its pro-
perties and mode of production. It wonld have been perhaps better
if the name which the discoverer, Faraday, had given to this body-
had been retained, as its relation to benzoic acid and benzoyl com-
pounds is not any closer than it is to that of the tar or coal from
which it is obtained."

Almost at the same time Peligot found that the same hydrocarbon
occui's, together with benzene, C13H10O (diphenylketone CO(CoH5)^),
in the products of the dry distillation of calcium benzoate.

The different results obtained by Mitscherlich and Peligot arc
represented by the following formula : —

C-HgO. + CaO = CgHe + CaCOg.
(C;H.d2)2Ca = CisHioO + CaCOg.

Peligot obtained benzene only as a by-product, exactly as in the
preparation of acetone (dimethylketone) from calcium acetate, a
certain quantity of marsh gas is always formed.

It is not clear how Liebig became acquainted with the fact that
benzene is formed by the dry distillation of coal, as his pupil Hof-
mann, who obtained it in 1845 from coal-tar, observes: "It is
frequently stated in memoirs and text-books that coal-tar oil contains
benzene. I am, however, unacquainted with any research in which
this question has been investigated." It is, however, worthy of
remark that about the year 1834, at the time when Mitscherlich had
converted benzene into nitrobenzene, the distillation of coal-tar was
carried out on a large scale in the neighbourhood of Manchester ; the
naphtha which was obtained was employed for the purpose of dissolving
the residual pitch, and thus obtaining black varnish. Attempts were
made to supplant the naphtha obtained from wood-tar, which at that
time was much used in the hat factories at Gorton, near Manchester,
for the preparation of " lacquer," by coal-tar naphtha. The substitute,
however, did not answer, as the impure naphtha left, on evaporation,
so unpleasant a smell, that the workmen refused to employ it. It
was also known about the year 1838, that wood-naphtha contained
oxygen, whilst that from coal-tar did not, and hence Mr. John Dale
attempted to convert the latter into the former, or into some similar
substance. By the action of sulphuric acid and potassium nitrate, he
obtained a liquid possessing a smell resembling that of bitter almond
oil, the properties of which he did not further investigate. This was,
however, done in 1842 by Mr. John Leigh, w^ho exhibited considerable
quantities of benzene, nitrobenzene, and dinitrobenzene, to the
Chemical Section of the British Association meeting that year in
Manchester. His communication is, however, so printed in the
Report, that it is not possible from the description to identify the
bodies in question.

Large quantities of benzene were prepared in 1848, under Hof-
mann's direction, by Mansfield, who proved that the naphtha in coal-
tar contains homologues of benzenes, which may be separated from it

454 Professor Sir Henry E. Roscoe [April 16,

by fractional distillation. On the ITth of February, 1856, Mansfield
was occupied with the distillation of this hydrocarbon, which he
foresaw would find further aj^plications, for the Paris Exhibition, in
a still. The liquid in the retort boiled over and took fire, burning
Mansfield so severely that he died in a few days.

The next step in the production of colours from benzene and
toluene is the manufactui'e of nitrobenzene, CgHsNOa and nitrotoluene,
C7H7NO2. The former compound, discovered in 1834 by Mitscherlich,
was first introduced as a technical product by Collas under the name
of artificial oil of bitter almonds, and Mansfield in 1847 patented a
process for its manufacture. It is now used for perfuming soap, but
mainly for the manufacture of aniline (CgHgNlIa) for aniline blue
and aniline black and for magenta. It is made on a very large scale
by allowing a mixture of well-cooled fuming nitric acid and strong
sulphuric acid to run into benzene contained in cast-iron vessels pro-
vided with stirrers.

To prepare aniline from nitrobenzene, this compound is acted
upon with a mixture of iron turnings and hydrochloric acid in a
cast-iron vessel. Commercial aniline is a mixture of this compound
with toluidine obtained from toluene contained in commercial benzene.
Some idea of the magnitude of this industry may be gained from the
fact that in one aniline works near Manchester no less than 500 tons
of this material are manufactured annually. From the year 1857,
after Perkin's celebrated discovery * of the aniline colours, up to the
present day, the history of the chemistry of the tar products has been
that of a continued series of victories, each one more remarkable than
the last.

Coal-tar Colours. — To even enumerate the difierent chemical com-
pounds which have been prepared during the last thirty years from
coal-tar would be a serious task, whilst to explain their constitution and
to exhibit the endless variety of their coloured derivatives which are
now manufactured would occupy far more time than is placed at my
disposal. Of the industrial importance of these discoveries, the
speaker reminded his audience of the wonderful potency of chemical
research, as shown by the fact that the greasy material which in 1869
was burnt in the furnaces or sold as a cheap waggon grease at the rate
of a few shillings a ton, received two years afterwards, when pressed
into cakes, a price of no less than one shilling per pound, and this
revolution was caused by Grabe and Liebermann's synthesis of
alizarin, the colouring matter of madder,| which is now manufactured

* See Lectures by Professor Hofmann, F.E.S., 'On Mauve and Magenta,'
April 11, 1862, and W. H. Perkin, F.R.S., 'On the Newest Colouring Matters,'
May 14, 1869, Proc. Roy. Inst. ; also President's Address (Dr. Perkin, F.R.S.),
' Journal of Society of Chemical Industry,' Vol. IV., July 1884, on Coal Tar
Colours.

t ' On the Artificial Production of Alizarine, the Colouring Matter of
Madder,' by Prof. H. E. Roscoe, Proc. Roy. Inst., April 1, 1870 ; also Dr. Peildn,
F.R.S., ' On the History of Alizarine,' Journal Society of Arts, May 30, 1879.

1886.] on Recent Progress in the Coal-tar Industry. 455

from anthracene at a rate of more tlian two millions sterling per
annum ; and it is stated that an offer was once made, in the earlier
stages of its history, by a manufacturer of anthracene to the Paris
authorities to take up the asphalt used in the streets for the purpose
of distilling it, in order to recover the crude anthracene.

Again, we have in the azo-scarlets derived from naphthalene a
second remarkable instance of the replacement of a natural colouring
matter, that of the cochineal insect, by artificial tar-products, and the
naphthol-yellows are gradually driving out the dyes obtained from
wood extracts and berries. It is, how^ever, true that some of the natural
dye-stuffs appear to withstand the action of light better than their arti-
ficial substitutes, and our soldiers' red coats are still dyed with cochineal.

The introduction of these artificial scarlets has, it is interesting
to note, greatly diminished the cultivation of cochineal in the Canaries,
where, in its place, tobacco and sugar are now being largely grown.

Let us next turn to inquire as to the quantities of these various
products obtainable by the distillation of one ton of coal in a gas-
retort. The six most important materials found in gas-tar from which
coloui's can be prepared, are : —

1. Benzene. 4. Metaxylene (from solvent naphtha).

2. Toluene. 5. Naphthalene.

3. Phenol. 6. Anthracene.

The average quantity of each of these six raw materials obtainable
by the destructive distillation of one ton of Lancashire coal is seen
in Table I. Moreover, this table show^s the average amount of certain
colours which each of these raw materials yields, viz. :— -

2:K-ta 0-623 lb. ^ V^S.' 'scL^i^ • U lbs.
3. Aurin 1-2 lb. 6. Alizarin 2-25 lbs. (20%).

Further it shows the dyeing power of the above quantities of
each of these colours, all obtained from one ton of coal, viz. : — •

1 and 2. Magenta, 500 yards of flannel.

3. Aurin, 120 yards of flannel 27 in. wide.

K* > Vermilline scarlet, 2560 yards of flannel.

6. Alizarin, 255 yards Turkey red cloth.

Lastly, to point out still more clearly these relationships, the
dyeing-power of one pound of coal is seen in the lowest horizontal
column, and here we have a particoloured flag, which exhibits the exact
amount of colour obtainable from one pound of Lancashire coal.

Let us moreover remember, in this context, that no less than
ten million tons of coal are used for gas- making every year in
this country, and then let us form a notion of the vast colouring
power which this quantity of coal represents.

456

Professor Sir Henry E. Boscoe

[April 16,

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1886.] on Hecent Progress in the Coal-tar Industry. 457

The several colours here chosen as examples are only a few
amongst a very numerous list of varied colour derivatives of each
groujD. Thus we are at present acquainted wdth ahout sixteen distinct
yellow colours ; about twelve orange ; more than thirty red colours ;
about fifteen blues, seven greens, and nine violets; also a number
of browns and blacks, not to speak of mixtures of these several
chemical compounds, giving rise to an almost infinite number of
shades and tones of colour. These colours are capable of a rough
arrangement according as they are originally derived from one or
other of the hydrocarbons contained in the coal-tar. The fifty
specimens of different colours exhibited may thus be classified, but
in this Table, for the sake of brevity, only the commercial names and
not the chemical formulso of these compounds is given.

Azo-colours. — Amongst the most important of the artificial colour-
ing matters may be classed the so-called azo-colours. These colours
are chiefly bright scarlets, oranges, reds, and yellows, with a few
blues and violets. They ow^e their existence to the discovery by
Griess, in 1860, of the fact that the so-called azo-group — N = N —
can replace hydrogen in phenols and amido compounds. But it is
to Dr. 0. N. Witt that is due the honour of having given the first
start in a practical direction to the chrysoidine class of azo-colours
by the discovery of chrysoidine, and perhaps still more so by the
suggestions contained in a paper read before the Chemical Society.
Dr. Caro, of Mannheim, was also acquainted with several compounds
which belong to this class at the time Witt published his results, but
it does not appear that he made practical use of them until Witt
introduced the chrysoidines and tropeolines. To Koussin, of the
firm of Poirrier of Paris, is due the credit of having first brought
into the market some of the beautiful azo-derivatives of naphthol.
Griess, therefore, as the original discoverer of the typical compounds
and reactions by which the azo-colours are obtained, may be considered
as the grandfather, whilst Eoussin and Witt are really the fathers, of
the azo-colour industry. Nor must it be forgotten that it is to
Perkin we owe the recognition of the value of the sulpho group in
relation to azo-colours, a discovery patented in 1863. Moreover it is
interesting to note that changes in colour from yellow to red and
claret are eftected by the increase in the molecular weights of the
radicals introduced as well as by the relative positions occupied by
these groups.

Indophenol. — Witt is also the discoverer of a new blue dye-stuff
termed indophenol, which has been used as a substitute for indigo.
Certain difficulties, however, have arisen in the adoption of this colour
on the large scale. The most important use indojohenol is at present
put to is for producing dark blues on reds dyed with azo-colours,
both on wool and cotton. The piece goods are dyed a uniform red
first, and then printed with indophenol white ; for like indigo itself
indophenol yields a colourless body on reduction, and this being a
very powerful reducing agent destroys the azo-coloui', being itself
transformed into indophenol blue. The process works with surprising

458 Professor Sir Henry E. Boscoe [April 16,

w

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sjiojpj^ sucnojg; sdduvuQ '^P^^l SQjqg spjot^i sud^u^)

1886.] on Becent Progress in the Coal-tar Industry, 459

nicety and is very cheap. The blue is formed and the red discharged
with such precision that patterns can be produced in which the blue
discharge covers a great deal more space than the original red. This
new printing process was devised by Mr. H. Koechlin, of Lorrach.
The reds used for the purpose are in the case of wool, the usual
azo-scarlets, for cotton congo-red.

Artificial Indigo. — About five years ago the speaker had the
honour of bringing before this audience * the remarkable discovery
made by Baeyer of the artificial production from coal-tar products of
indigo blue. Since that time but little progress has been made in
this manufacture, as the cost of the process, unlike the case of alizarin,
has as yet proved too serious to enable the artificial to compete suc-
cessfully in the market with the natural indigo.

Through the kindness of a number of eminent colour manu-
facturers in this country and on the Continent, the speaker was
enabled to illustrate his subject by a most complete series of speci-
mens both of the colours themselves and of their application to the
dyeing and printing of fabrics of all kinds. His thanks are especially
due to his friend, Mr. Ivan Levinstein, of Manchester, for the
interesting series of samples of cloth dyed with known quantities of
fifty difierent coal-tar colours, each having a different chemical com-
position ; also to the same gentleman, and to Messrs. Burt, Boulton,
and Haywood, of London, for the interesting and unique series of
specimens indicating the absolute quantities of products obtainable
from one ton of coal, as well as for much assistance on the part of
Mr. Levinstein in the preparation of the experimental illustrations
for this discourse. To Dr. Martins of Berlin for a valuable series of
colours, especially the well-known Congo red, made by his firm,
including samples of wool dyed therewith, he is also much indebted.
For the interesting details concerning indophenol and its applica-
tions the speaker owes his thanks to Dr. Witt and M. Koechlin.

Cocd-tar Antipijretic Medicines. — Next in importance to the colour
industry comes the still more novel discovery of the synthetical
production of antipyretic medicines.

Up to this time quinine has held undisputed sway as a febrifuge
and antiperiodic, but the artificial production of this substance has as
yet eluded the grasp of the chemist. Three coal-tar products have,
however, been recently prepared which have been found to possess
strong febrifuge qualities, which if still in some respects inferior to
the natural alkaloids, yet possess most valuable qualities, and are now
manufactured in Germany at Hochst and at Ludwigshafen in large
quantity. And here it is well to call to mind that the first tar
colouring-matter discovered by Perkin (mauve) was obtained in 1856
during the prosecution of a research which had for its object the
artificial production of quinine.

' On Indigo and its Artificial Production,' Proc. Koy. Inst., May 27th, 1881,

460 Professor Sir Henry E. Boscoe [April IG,

In considering the historical development of this portion of- his
subject, the speaker added that it is interesting to remember that the
initiative in the production of artificial febrifuges was given by-
Professor Dewar's discovery in 1881 that quinoline, the basis of these
antipyretic medicines, is an aromatic compound, as from it he
obtained aniline. Moreover, that Dewar and McKendrick were the
first to observe that certain pyridine salts act as febrifuges. So that
these gentlemen may be said to be the fathers of the antipyretic
medicines, as Witt and Eoussin are of the azo-colour industry.

Kairine, the first of these, was discovered by Prof. O. Fischer, of
Munich, in the year 1881, whilst engaged on his investigations of the
oxyquinolines. The febrifuge properties of this substance were first
noticed by Prof. Filehne, of Erlangen. Kairine is manufactured from
quinoline, a basic product derived from aniline by heating it with
glycerin and nitrobenzene by the following process. When treated
with sulphuric acid, SO4H2, it forms quinoline sulphonic acid, and
this when fused with caustic soda yields oxi/quinoline, which is then
reduced by tin and hydrochloric acid into tetrahydroxyquinoline, and
this again on treatment with OaHgBr yields ethyl-tetraoxyquinoline
or kairine. The lowering of the temperature of the body by this com-
pound is most remarkable, though, unfortunately, the action is of
much shorter duration than that effected by quinine itself ; but on the
other hand, with the exception of its burning taste, it exerts no
evil effects such as are often observed after administration of large
doses of quinine. The commercial article is the hydrochloride,
the price is 85s. per lb., and the quantity manufactured has lately
diminished owing to the discovery of the second artificial febrifuge,
antipyrine.

The following graphical formula shows the constitution of
kairine : —

C^HjCOH) < N(CH3)CH,

A

HCl

Antipyrine, the second of these febrifuges, was discovered in 1883
by Dr. L. Knorr in Erlangen, and its physiological properties were
investigated by Prof. Filehne of Erlangen. The materials used in
the manufacture of antipyrine are aniline and aceto-acetic ether. The
aniline is first converted into phenylhydrazine, a body discovered by
Emil Fischer in 1876. This body combines directly with aceto-acetic
ether, with separation of water and alcohol, to form a body called
pyrazol (C10H10N2O). The methyl derivative of pyrazol derived by
treating it with iodide of methyl, is antipyrine, its composition being
C11H12N2O. As a febrifuge, antipyrine is superior in many respects
to kairine and even to quinine itself. It equals kairine in the certainty
of its action whilst in its duration it resembles quinine. It is almost
tasteless and odourless, is easily soluble in cold water, and takes the
form of a white crystalline powder. Its use as a medicine is accom-

1886.] on Becent Progress in the Goal-tar Industry. 461

panied by no drawbacks. It occurs in commerce in the free state.
The production of antipyrine, in spite of these valuable qualities, is as
yet small, its chief employment being in Germany, where it has been
successfully used in cases of typhoid epidemic. The price is 6s. per
pound.

The following equations explain the formation and constitution of
this interesting body. The foregoing febrifuges are manufactured at
Hochst under the superintendence of Dr. Pauli, to whose kindness the
speaker is indebted for an interesting series of specimens illustrative
of the manufacture of antipyrine.

CH3.CO.CH2.CO2C2H. + CeHj.NH.NH.

Acetoacetic ether Phenylhydrazine

= H2O + C0H5.OH + Cio H10N2O

Tyrazol

CioH.oN^O + ICH3 = IH.CioH,(CH3)N20

Antipyrine-liydriodide

Dr. Knorr formulates pyrazol thus :

CgH^ C CII3

CO CH2

And antipyrine is

N N CH,

./ V

co-

The antipyretic effect of this compound is strikingly shown in the
following temperature readings in a case of typhoid kindly com-
municated to the speaker by his friend Dr. Dreschfeld of Manchester.
Each of the second set of readings was made two hours after a dose
of 30 grains of antipyrine had been administered.

I. II. Diff.

lOo-O

103-0

2?0

103-5

100-2

3-2

103-8

100-8

30

105-2

101-4

3-8

104-4

100-6

3-8

Tlialline. — The third of the artificial febrifuges is thalUney which is
offered as the tartrate and sulphate. It is manufactured by the Badische
Company. Thalline is said to be used as an antidote for yellow
fever. Its scientific name is tetrahydroparaquinanisol, and it was first

462 Professor Sir Henry E. Boscoe [April 16,

prepared by Skraiip by tlie action of methyl iodide and potash on
paroxyquinoline.

We must, however, bear in mind that none of these synthetical
febrifuges are antiperiodics, and therefore cannot be employed instead
of the natural alkaloid quinine in cases of ague or intermittent fevers.

Coal-tar Aro^natic Perfumes. — A third group of no less interest
comprises the artificial aromatic essences, and of these may here be
mentioned, in the first place, cimarin, CgHgOa, the crystalline solid
found in the sweet woodruff, in Tonka bean, and in certain sweet-
scented grasses. This is now artificially prepared by acting upon
sodium salicyl aldehyde with acetic anhydride by the reaction which
is associated with the name of Dr. Perkin, and is used in the manu-
facture of the perfume known as " extract of new-mown hay."

A second interesting case of a production of a naturally occurring
flavour, is the artificial production of vanillin, the crystalline prin-
cipal of vanilla. Vanilla is the stalk of the Vanilla planifolia,
which incloses in its tissues prisms of crystalline vanillin, to which
substance it owes its fragrance. Tiemann and Harrmann showed that
vanillin is the aldehyde of methyl protocatechuic acid

C,H3 (OH) (OCH3) CHO, [CHO : OCH3 : OH :^ 1 : 3 : 4].

The chief seats of the vanilla productions are on the slopes of
the Cordilleras north-west of Vera Cruz in Mexico, also the island
of Eeunion, and in the Mauritius. Since the discovery of the arti-
ficial production of vanillin, the growth of the vanilla has been very
much restricted.

A variety of vanilla, termed vanillon, obtained in the East Indies,
has long been used in perfumery for preparing " essence of helio-
trope." This contains vanillin together with an oil, which is probably
oil of bitter almonds. The essence of white heliotrope is now entirely
prepared by synthetical operations. It is manufactured by adding a
small quantity of artificial oil of bitter almonds to a solution of
artificial vanillin ; when these substances are allowed to remain for
some time in contact, the mixture assumes an odour closely resembling
that of natural heliotrope. Through the kindness of Mr. Rimmel
the speaker was able to render the fragrance of this coal-tar perfume
perceptible to his audience. Nor must we forget to mention the so-
called essence of mirbane (nitrobenzene), of which about 150 tons
per annum are used for perfuming soap ; and artificial oil of bitter
almonds, employed as a flavour in place of the natural oil.

Coal-tar Saccharine. — Of all the marvellous products of the coal-
tar industry, the most remarkable is perhaps the production of a
sweet principle surpassing sugar in its sweetness two hundred and
tiventy times. This substance is not a sugar, it contains carbon,
hydrogen, sulphur, oxygen, and nitrogen. Its formula is

C«^^^<SO,>N"'

1886.] on Becent Progress in the Coal-tar Industry. 463

and its chemical name is benzoyl sulphonic imicle, or for common
use, saccharine. It does not act as a nutriment, but is non-poisonous,
and passes out of the body unchanged. The following is a concise
statement of its properties, and mode of production from the toluene
of coal-tar. It should, however, be first mentioned that the compound
benzoyl sulphonic imide (saccharine) was first discovered by
Constantin Fahlberg and Eemsen, in America. But no patent was
taken out for a commercial process till recently, and it is now
patented in this country.

Step I. — Toluene is treated with fuming sulphuric acid in the
cold, or it is heated with ordinary sulphuric acid of 168^° Twaddell
on the water-bath, or not above 100° C. The latter method is the
better. The acid is best caused to act upon the toluene iu closed
vessels rotating on horizontal axles.

CeH,CH3 + SO,U, = CoH, {go^ OH + H,0.

Toluene. Toluene sulphonic acids

(ortbo and para).

Step II. — After all toluene (which as toluene is insoluble iu the
acid) has disappeared, the contents of the agitating vessel are run
into wooden tanks iu part filled with cold water, and the whole liquid
is stirred up with chalk to neutralise the excess of sulj)huric acid used
and to obtain the two isomeric toluene sulphonic acids as calcium
salts.

K^«^^ !sa . oh) + ^^^^2 + 2(CaC03) =

Toluene, ortho- and
para- sulphonic acids

(c«Hi^^^A^C.^ + CfiSO, + 2CO2 + 2H2O.

Calcium toluene ortho-
and para-sulphonates

The neutralised mass is filtered through a filter-press to separate
therefrom the precipitate of gypsum, which is washed with hot
water, and the washings added to the filtrate.

Step III. — The calcium salts are now treated with carbonate of
sodium, to obtain the sodium salts, with precipitation of carbonate
of calcium. The precipitate is removed by means of a filter-
press from the solution containing the sodium ortho- and para-
sulphonates.

(c.H,{CH3),Ca + NaXO, = CaCO, + 20,H,{2^^ ^^^

The sodium toluene sulphonates

Step IV. — The solution of the sodium salts from III. is evapo-
rated either in an open- or in a vacuum-pan so far that a portion taken
out will solidify on cooling. The contents of the pan are then run

Vol. XI. (No. 80.) 2 h

464 Professor Sir Henry E. Eoseoe [April 16,

into moulds of wood or iron, and allowed to cool and solidify. The
lumps are at length taken from the moulds, broken up small, and dried
in a drying-room, and subsequently in a drying apparatus heated
with steam, until quite desiccated.

Step V. — The sodium sulphonate salts are now converted into
their corresponding sulphonic chlorides. This is effected as follows: —
The dried sulphonates are thoroughly mixed with phosphorus tri-
chloride, itself as dry as possible. The mixture is then placed in
lead-lined iron vessels, and a current of chlorine is passed over the
mixture till the reaction is ended. The temperature generated by
the reaction must be properly regulated by cooling the apparatus
with water. The phosphorus oxychloride resulting from the decom-
position is driven off, collected, and utilised for developing chlorine
from bleaching powder for the chlorinating process, phosphate of
lime being precipitated, which can be used in manures. For this
purpose the oxychloride is treated with water, and the mixture, now
containing hydrochloric and phosphoric acids, is brought into contact
with the chloride of lime.

The reaction by which the ortho- and para-toluene sulphonic
chlorides are produced is indicated by the following equation : —

^^^^SOaNa + (^^^^ + 2^^) = ^«^^ {sO.Cl + ^^^^3 + NaCl

Toluene sulphonic chlorides

The two sulphonic chlorides remaining in the apparatus are
allowed to cool slowly, when the solid one (the para compound) is
deposited in large crystals, so that the liquid one can bo easily
removed by the aid of a centrifugal machine. The crystalline residue
is freed from all the liquid sulphonic chloride by washing with cold
water. Only the liquid orthotoluene sulphonic chloride is capable of
yielding saccharine, and the liquid product above separated is cooled
with ice to crystallise out the last traces of the crystalline compound.
The solid parasulphonic chloride obtained as by-product, is decom-
posed into toluene, hydrochloric, and sulphurous acids by mixing it
with carbon, moistening the mixture, and subjecting it under pressure
to the action of superheated steam. The total change proceeds in two
stages : —

1- ^^H^oh + I^^« = C.H,{^^3^jj + HCl.

2. 2 (CeH,|^'o,bH) + C = 2 (C„H,.CH3) + CO^ + SO^.

The toluene is then used again in Stej^ I., and the hydrochloric and
sulphurous acids in Step VII.

Step YI. — The liquid orthotoluene sulphonic chloride is now
converted into the orthotoluene sulphonic amide by treating the former
with solid ammonium carbonate in the required proj^ortious, and sub-
jecting the resulting thick pulpy mixture to the action of steam.

1886.] on Recent Progress in the Coal-tar Industry. 465

Carbonic acid is set free, and a mixture of ortliotoluene sulphonic
amide and ammonium chloride remains.

^^^^SO/CI + (NHJ,C03 = CeH, [2'^; ^^^ + NH.Cl + H,0 + CO^.

Toluene sulphonic chloride Toluene sulphonic amide

As the mixture is very liable to solidify on cooling, cold water is at
once added to prevent this, and to dissolve out the ammonium chloride,
the amide remaining in the solid state. The liquid is separated by
centrifugating.

Step VII. — The orthotoluene sulphonic amide is now oxidised,
preferably by means of potassium permanganate. The result of this
will be, precipitated manganese dioxide, free alkali and alkaline
carbonate, and an alkaline orthosulphamido-benzoate. The alkaline
liquid requires careful neutralisation during the oxidising jDrocess,
and especially before evaporating, with a mineral acid, or else the
sulphamido-benzoate formed would be again split up into ortho-
sulphonic benzoate and free ammonia, thus : —

^.H^ga-Tn, + NaOH = C.H,{C0.0Na^ ^ ^^^
The oxidation process itself is thus represented : —

C«H.{gg=.NH, + 30 + NaOH = C,H.{CO-p^ + 2H,0.

Sodium orthotoluene
sulphamido-benzoate

By precipitation with dilute mineral acids, such as hydrochloric or
sulphurous acids, the pure benzoyl sulphonic imide is at once pre-
cipitated : —

C.H.{^§;.^^"^ + HOI = KaCl + H,0 + C.H.{CO Jnh.

" Saccharine," or benzoyl
sulphonic imide

Saccharine possesses a far sweeter taste than cane sugar, and has a
faint and delicate flavour of bitter almonds. It is said to be 220
times sweeter than cane sugar, and to possess considerable antiseptic
properties. On this account, and because of its great sweetness, it is
possible that it may be useful in producing fruit preserves or jams,
consisting of almost the pure fruit alone ; the small percentage of
saccharine necessary for sweetening these preserves being probably
sufficient to prevent mouldiness. Saccharine has been proved by
Stutzer, of Bonn, to be quite uninjurious when administered in con-
siderable doses to dogs, the equivalent as regards sweetness in sugar
administered, being comparable to over a pound of sugar each day.
Stutzer found, moreover, that saccharine does not nourish as sugar
does, but that it passes off in the urine unchanged. It is proposed
thus to use it for many medical purposes, where cane sugar is excluded
from the diet of certain patients, as in cases of " diabetes mellitus,"

2 H 2

466 Pro/. Sir Henry E. Boscoe on the Coal-tar Industry, [April 16,

and in this respect it may prove a great boon to suffering humanity,
although we must remember that, as certain of the aromatic compounds
if administered for a length of time are known to exert a physiological
effect, especially on the liver, it will be desirable to use caution in
the regular use of saccharine until its harmless action on the human
body has been ascertained beyond doubt.

Saccharine is with difficulty soluble in cold water, from hot
aqueous solutions it is easily crystallised. Alcohol and ether easily
dissolve it. Hence from a mixture of sugar and saccharine, ether
would easily separate the saccharine by solution, leaving the sugar.
It melts at about 200° C. with partial decomposition.

The taste is a very pure sweet one, and in comparison with cane
sugar it may be said that the sensation of sweetness is much more
rapidly communicated to the palate, on contact with saccharine, than
on contact with sugar. The speaker expressed his thanks to the dis-
coverer of saccharine, Dr. Fahlberg, of Leipzic, for a complete and
interesting series of preparations illustrating the domestic and
medicinal uses of this remarkable compound, and also to his friend
Mr. Watson Smith for the kind aid afforded him in the experimental
illustration of his discourse.

[H. E. E.]

1886.]

Annual Meeting.

467

ANNUAL MEETING,

Saturday, May 1, 1886.

Sir Frederick Bramwell, F.R.S. Honorary Secretary and Vice-
President, in the Chair.

The Annual Eeport of the Committee of Visitors for the year
1885, testifying to the continued prosperity and efficient management
of the Institution, was read and adopted. The Real and Funded
Property now amounts to above 85,0007. entirely derived from the
Contributions and Donations of the Members.

Twenty-six new Members paid their Admission Fees in 1885.

Sixty-three Lectures and Nineteen Evening Discourses were
delivered in 1885.

The Books and Pamphlets presented in 1885 amounted to about
354 volumes, making, with 464 volumes (including Periodicals bound)
purchased by the Managers, a total of 818 volumes added to the
Library in the year.

Thanks were voted to the President, Treasurer, and the Honorary
Secretary, to the Committees of Managers and Visitors, and to the
Professors, for their valuable services to the Institution during the
past year.

The following Gentlemen were unanimously elected as Officers
for the ensuing year :

President— The Duke of Northumberland, E.G. D.C.L. LL.D.
Treasurer — Henry Pollock, Esq.
Secretary — Sir Frederick Bramwell, F.R.S.

Managers.

Sir Frederick Abel, C.B. D.C.L. F.R.S.

Sir William Bowman, Bart. LL.D. F.R.S.

Joseph Brown, Esq. Q.C.

Sir James Crichton Browne, M.D. LL.D. F.R.S.

William Crookes, Esq. F.R.S.

Henry Doulton, Esq.

Sir William Withey Gull, Bart. M.D. D.C.L. F.R.S.

Ricrht Hon. The Lord Halsbury.

WfUiam Huggins, Esq. D.C.L. LL.D. F.R.S.

Alfred Bray Kempe, Esq. M.A. F.R.S.

Sir John Lubbock, Bart. M.P. D.C.L. LL.D. F.R.S.

Hugo W. Miiller, Esq. Ph.D. F.R.S.

Sii- Frederick Pollock, Bart. M.A.

John Rae, M.D. LL.D. F.R.S.

Lord Arthur Russell.

Visitors.

Shelford Bidwell, Esq. M.A.

Stephen Busk, Esq.

Michael Carteighe, Esq. F.C.S.

Arthur Herbert Church, Esq. M.A. F.C.S.

Vicat Cole, Esq. R.A.

William Henry Domville, Esq.

James Edmunds, M.D. F.C.S.

Charles Hawksley, Esq. M.LC.E.

Alfred Gutteres Henriques, Esq. F.G.S.

David Edward Hughes, Esq. F.R.S.

George Matthey, Esq. F.R.S.

John W. Miers, Esq,

Lachlan Mackintosh Rate, Esq. M.A.

William Chandler Roberts-Austen, Esq. F.R.S.

Alexander Siemens, Esq.

468 General Monthly Meeting. [May 3,

GENERAL MONTHLY MEETING,

Monday, May 3, 1886.

William Huggins, Esq. D.C.L. LL.D. F.R.S. Manager, in the Chair,

William Henry Allen, Esq.

Mrs. George Baden Crawley,

William James Farrer, Esq.

Alexander Gray, Esq.

John Kudd Leeson, M.D. F.G.S.

George John Eomanes, Esq. M.A. LL.D. F.R.S.

Arthur William Eiicker, Esq. M.A. F.R.S.

Lewis Richard Shorter, Esq.

were elected Members of the Royal Institution.

John Tyndall, Esq. D.C.L. LL.D. F.R.S. was re-elected Pro-
fessor of Natural Philosophy.

The Managers reported that they received the following letter
from Mr. George Busk, the late Treasurer of the Royal Institution : —

"32, Harley Street,

" February 2Uh, 1886.

" Dear Sir Frederick,

" I much regret that I shall not be able to attend the Committee this
" afternoon, and as 1 fear from the state of my healtli that I shall very probably
*' not be equal to attending any meetings at the Koyal Institution in future, I
" should be obliged if you would be good enough to lay my resignation of the
" Office of Treasurer, with which I have been honoured for so many years, before
" the meeting of Managers on Monday next. I have further to beg that you will
" assure the Managers' that I do this with tlie greatest regret and from the fullest
"conviction that it is for the best interests of the Royal Institution.

" Believe me, yours truly,

*<Geo. Busk.
" Sir Frederick Bramwell, F.R.S."

The Managers further reported that at their meeting on April 5th
last it was Resolved, " That Mr. Busk be informed that the Com-
mittee of Managers desire to express their very sincere regret that
the state of his health should have rendered it necessary for him to
resign an office which he has filled for so many years with advantage
to the Institution and at a considerable sacrifice of time and labour
to himself, and that they cannot accept his resignation without
exi)ressing their sense of the value of his past services and support
to the Institution, aud their very sincere hope that he may experience
improved health in the future."

1886.] General Montlily Meeting. 469

Besolved, « That this Meeting cordially adopt the Resolution of
tlie Managers passed at their Meeting on the 5th of April in relation
to the resignation of Mr. George Busk from the office of Treasurer
of the Royal Institution."

The Special Thanks of the Members were returned for the
following donation to the Fund for the Promotion of Experimental
Research : —

Lachlan Mackintosh Rate, Esq. £50.

The Presents received since the last Meeting were laid on the
table, and the thanks of the Members returned for the same, viz. : —

The Governor-General of India — Geological Survey of India. Palaeontologia

Indica ; Memoirs, Series XIII. Vol. I. Part 5. fol. 1886.
Ministry of Public WorJcs, i?ome— Giornale del Genio Civile, Serie Quarta,

Vol. VI. Nos. 1, 2. 8vo. And Disegni. fol. 1886.
Accademia dei Lincei, Reale, Roma — Atti, Serie Quarta : Rendiconti. Vol II.

Fasc. 7. 8vo. 1886.
Asiatic Society of Bengal — Journal, Vol. LIV. Part 1, Nos. 3, 4 ; Part 2, No. 3
8vo. 1885.
Proceedings, 1885, Nos. 9,.10. Svo.
Astronomical Society, Royal — Monthly Notices, Vol. XL VI. No. 5. Svo. 1886.
Bankers, Institute o/— Journal, Vol. VII. Part 4. Svo. 1886.
Bavarian Academy of Sciences — Abhandlungen, Band XV. 2te Abtheilung.
4to. 1885.
Sitzungsberichte, 1884, H«ft 4, 1885. Svo.
British Architects, Royal Institute of — Proceedings, 1885-6, Nos. 13, 14. 4to.
Dax : Socie'te' de Borda — Bulletin, Onzieme A nne'e. 1^ Trimestre. Svo. 1886.
Chemical Society — Journal for April, 1886. Svo.
Crisp, Frank, Esq. LL.B. F.L.S. &c. M.R.I, (the Editor)— Jomnal of the Royal

Microscopical Society, Series II. Vol. VI. Part 2. Svo. 1886.
Editors— AuieYicsin Journal of Science for April, 1886. Svo.
Analyst for April, 1886. Svo.
Athenaeum for April, 1886. 4to.
Chemical News for April, 1886. 4to.
Engineer for April, 1886. fol.
Horological Journal for April, 1886. Svo.
Iron for April, 1886. 4to.
Nature for April, 1885. 4to.
Revue Scientifique for April, 1886.
Telegraphic Journal for April, 1886. Svo.
Franklin Institute — Journal, No. 724. Svo. 1886.
Geological Institute, Imperial, Vienna — Jahrbuch : Band XXXVI. Heft 1. Svo.

1886.
Horticultural Society, Bo ?/aZ— Journal, Vols. V. VI, VII. No. 1. Svo. 1877-86,
Johns- Hopkins University — Studies in Historical and Political Science, Fourth
Series, No. 4. Svo. 1886.
American Chemical Journal, Vol. VIII. No. 1. Svo. 1SS6.
Lettsom, W. G. Esq. M.R.I. — Elements of Electricity and Electro-Chemistry. By

G. J. Singer. Svo. 1814.
Linnean Society — Journal, Nos. 113, 142. Svo. 1886.
Mechanical Engineers' Institidion—Froceedmgs, 1886, No. 1. Svo.
Medical and Chirurgical Society, Royal — Proceedings, No. 12. Svo. 1886.
Catalogue of Library, 1885, Supplement IV. Svo. 1886.

470 General Monthly Meeting. [May 3,

Meteorological 0/^ce— Meteorological Observations at Stations of the Second

Order for 1881. 4to. 1886.
MiUer, W. J. C. Esq. (the Reg istrar)— The Medical Register, 1886. 8vo.

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Vol. XXXV. Part 2. 8vo. 1886.
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Series. Svo. 1886.
Pernj, Rev. 8. J. F.R.S.and Prof. B. Stewart, F.R.S. (the ^wf/tors)— Fluctuations

of Declination at Kew and Stonyhurst, 1883-4. (Proc. Royal Society, 1885.)
Pharmaceutical Society of Great Britain— J omr\?il, April, 1886. Svo.
Photographic Societt/— J ouvunl, New Scries, Vol. X, No. 6. Svo. 1886.
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Royal Society of London— Proceedings, No. 242. Svo. 1886.
Saxon Society of Sciences, Royal — Philologisch-Historische Classe: Berichte, 1885.

No. 4. Svo. 1886.
Second Geological Survey of Pennsylvania--Gxa.w(\. Alias : Div. I. County Geo-
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Div. III. Petroleum and Bituminous Coal Fields, Part 1 ; Div. IV. South

Mountain and Great Valley Topographical Maps ; Div. V. Central and

S.E. Pennsylvania, Part 1. 1884-5.
Snell, H. Saxon, Esq. M.R.I, (the Author)— Circular Hospital Wards. (Trans.

Sanitary Inst.) 1885.
Hull Royal Infirmary. Svo. 1885.
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1886.
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Surgeon-General's Office, U.S. ^rw?/— Index-Catalogue of the Library, Vols. 1-6.

4to. 1880-5.
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Heft 3. 4to.
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Wise, Thomas A. M.D. (the Author)— Hhiory of Paganism in Caledonia. 4to.

1884.
Zoological /S'oc/e/?/— Transactions, Vol. XII. Part 2. 4to. 1886.
Proceedings, 1885, Part 4. Svo.

1886.] Mt\ F. Siemens on Dissociation Temj>eratures^ dc. 471

WEEKLY EVENING MEETING,

Friday, May 7, 1886.

William Huggins, Esq. D.C.L. LL.D. F.R.S. Vicc-Prcsidout,
in the Chair.

Frederick Siemens, Esq.

On Dissociation Temperatures with special reference to Pyrotechnical

questions.

In bringing the subject of dissociation before the Royal Institution of
Great Britain, I wish it to be understood that I propose to confine
myself to its influence on combustion and heating, that is to say, to
its effects on combustible gases and the products of combustion, and
on furnace work generally. My researches have been made for the
most part in connection with large gas furnaces constructed according
to my new system of working with radiated heat, or what may be
otherwise called free development of flame. In perfecting this system
of furnace the principle of which is in many respects the reverse of
that generally accepted, both as regards construction and working,
I had to examine into the accuracy of certain scientific theories which
could not be brought into harmony with the actual results I obtained.

In order that I may be clearly understood it is necessary to
describe shortly my system of furnaces before entering upon the
theory which alone appears to explain satisfactorily the practical re-
sults obtained by its means. These furnaces have of late been largely
introduced and are now extensively applied. I first described them
in a paper read at tlie Meeting of the Iron and Steel Institute held
at Chester in September 1884; their main peculiarity consists in the
arrangements by which the heat is abstracted in two different ways,
and at two different periods. In the first, or active, stage of com-
bustion the flame passes through a large combustion chamber (all
contact with its surfaces being avoided), and parts with its heat by
radiation only ; while in its second stage the products of combustion
are brought into direct contact with the surfaces and materials to be
heated, by which means the remainder of its heat is abstracted. This,
in a few words, is a description of the method of heating with free
development of flame, and it now only remains to explain how to
construct fireplaces and furnaces on this principle.

As regards its principal application hitherto, namely, to regene-
rative gas furnaces, the two successive stages of heating are, by
radiation in the furnace chamber, and by contact in the regenerators.
The flame during active combustion heats the furnace chamber and
material placed therein by radiation only, and as soon as this stage is
completed the fully burnt gases enter the regenerative chambers and
deposit their remaining heat by coming into contact with the loose

472 Mr. Frederick Siemens [May 7,

brickwork filling them. As it is essential that the flame during its
first stage, while still in chemical action, should give up heat by
radiation only, it is found absolutely necessary that it should not
touch the sides or walls of the furnace chamber, or any material con-
tained in the furnace. The sides and arches of the furnace and the
flues leading into it must therefore be so arranged i\i?ii the flame does
not touch anything, and its length must be sufficient to allow time for
complete combustion before the flame leaves it. When regenerative
furnaces are arranged so as to fulfil these conditions the heat de-
veloped by the flame is much more intense than otherwise, while
notwithstanding the higher temperature and increased working power
attained, their durability is largely augmented.

Intensity of temperature and durability are two advantages of the
greatest importance which were formerly seldom found combined in
furnaces. The manner in which these advantages are insured in
the radiation furnace may be thus explained : —

Adopting the generally accepted theory of combustion, according
to which a flame consists of a chemically excited mixture of gases,
whose particles are in violent motion, either oscillating to and from each
other or rotating around one another, it follows that any solid substance
brought into contact with gases, thus agitated, must necessarily have
an impeding effect on their motion. Motion being the primary
condition of combustion, the latter will be more or less interfered with,
according to the greater or less extent of the surfaces which impede
the action of the particles forming the flame; in the immediate
neighbourhood of such surfaces the combustion of the gases will
cease altogether, because the attractive influence of the surfaces will
entirely prevent their motion ; further off, their combustion will be
partial, and only at a comparatively great distance the particles of gas
will be free to continue unimpeded the motion required to maintain
combustion. On the other hand, the surfaces themselves must suffer
from the motion of the particles of gas producing the flame, for
however small these particles may be, they produce, while in such
violent motion, an amount of energy wlaich acting constantly will in
time destroy the surfaces opposed to them, just as "continual
dropping wears away stone." This circumstance fully accounts for
the fact that the inner sides of furnaces, and the materials they con-
tain, are soon destroyed, not by heat, but by the mechanical, and
perhaps also by the chemical action of the flame. It would seem
strange that the heating power of a large volume of flame should be
so much interfered with by the contact of its outer parts only with
the inner sides of a large furnace chamber, if there was not another
cause besides imperfect combustion to reduce the heating effect of a
flame, which touches the surfaces to be heated. A flame when in
the state of combustion radiates heat not only from its outer surface,
but also from its interior by allowing the heat to radiate through its
mass. In this manner every particle of flame sends its rays in all
directions, but if the flame itself touches anywhere combustion ceases

1886.J on Dissociation Temperatures, dc. 473

there, free carbon is liberated and produces smoke which envelopes
that part and prevents the rays of heat of the other portions of the
flame from reaching it.

Eadiation plays a much greater part in all heating operations
than has been hitherto acknowledged, consequently any cause which
tends to lessen the radiating power of flame, or to screen its rays,
reduces also the amount of heat which can be thus utilized.

If the flame is not allowed to come into contact with bodies to be
heated, combustion is improved, while full advantage is also gained
of its heat-radiating power, which would otherwise be diminished
more or less, as already explained. The ordinary mode of applying
flame, by allowing it to impinge directly upon the surfaces to bo
heated, causes imperfect combustion, prevents the rays of heat from
reaching them, and also destroys, or tends to destroy them ; this is
particularly the case when hydrocarbons and carbonic oxide are used.
These statements are fully borne out by the results which I have ob-
tained in practice with the new and old form of regenerative furnace
respectively, and they also fully agree with the theoretical explanation
I have suggested ; that theory, however, is still incomplete, as it does
not deal with the subject of dissociation, a subject to which for various
reasons I have avoided referring until recently, although it has been
brought forward by several writers, and used as an argument against
my new system of furnace ; as according to these writers it would
appear to be impossible to produce such exceedingly high tempera-
tures as I claim to reach. I have long held the opinion that appear-
ances of dissociation not being observable in furnaces heated by
radiation, but occurring in furnaces in which the flame is allowed
to come into contact with surfaces, must be due to the action on the
flame of those surfaces at high temperature. I was led to this con-
clusion partly from my own observations, and partly from descriptions
of dissociation observed by others, amongst whom was my brother,
the late Sir William Siemens, who described a case of dissociation
(see lecture delivered March 3rd, 1879, at the Royal United Service
Institution, entitled " On the production of Steel and its application
to military purposes ") which occurred in a regenerative gas furnace
constructed according to our old views of combustion and heating.
The conclusion at lohich I have arrived is, that solid surfaces, besides
ohstructing active combustion, must cdso at high temperatures have a dis-
sociating influence on combustible gases and on the products of combustion.

In order to obtain information on this subject I examined the laws
and theory of dissociation, and endeavoured to bring the various
results obtained by scientific authorities into agreement with one
another, and with my own experience, but failed entirely in doing so.
The temperatm-es of dissociation of carbonic acid and steam, the two
principal gases forming the products of combustion when ordinary
fuel is used, vary very much according to these observers, and the
results I have obtained in practice are different from most of them.
1 hope to prove that the temperature at which dissociation sots in, is,

474 Mr. Frederick Siemens [May 7,

in most cases, much higher than generally admitted ; and that the
authorities I am about to refer to have omitted in almost all the
experiments they have made to take into proper consideration one
element which is liable to alter materially the results obtained by
them. This element is the surface, form^ and material of the apparatus
used for those experiments.

In considering the question of dissociation, I propose to com-
mence with Deville, who first discovered and called attention to
the dissociation of gases at high temperatures. He made numerous
experiments with various gases, dissociating steam, carbonic acid,
and also carbonic oxide (in the latter case producing carbonic
acid and carbon), and fixed certain temperatures at which he found
that either complete or partial dissociation took place. Without
going into details I may mention that Deville required to use vessels
and tubes of definite dimensions, material, and structure, in order
to obtain the results stated. One experiment had to be made with a
porous tube, another required the use of a vessel with rough interior
surfaces, or containing some rough or smooth material. In this way
Deville arrived at a great variety of results, and although he does not
state that the rough surfaces, or porous tubes, or the solid material
placed inside the vessels which he employed, had any particular
influence on the temperature at which dissociation took place, yet
it would appear that he could not obtain his results without having
recourse to those means. Deville's results depended very much upon
the various kinds of surfaces he used in his experiments, if they were
not entirely brought about by them ; these experiments, moreover,
were of a very comjDlicated nature, so I propose to pass on to more
modern authorities whose experiments are of simpler character, and
less open to objection.

The most important experiments, which modify those of Deville,
are due to Bunsen. Bunsen observed the dissociation of steam and
carbonic acid by employing small tubes filled with an explosive mix-
ture of these gases, to which suitable pressure gauges were attached.
On igniting the gaseous mixture explosion took place, and a high
momentary pressure was produced within the tube ; from the pressure
developed Bunsen calculated the temperature at which the explosion
took place, and found that it varied with the mixtures cmi)loyed.
He records the circumstance that only about one-third of the com-
bustible gases took part in the explosion, from which circumstance
he concluded that the temperature attained was the limit at which
combustion occurred. To prove this, Bunsen allowed the gases suf-
ficient time to cool, after which a second explosion was produced, and
oven a third explosion when time was allowed for the gases to cool
down again. Bunsen's theory seems very plausible, besides which
he obtains much higher temperatures for his limits of dissociation
than other physicists, so that I might have accepted the figures at
which ho arrives ; these arc for steam about 2100° C, and for car-
bonic acid about 3000' C. These temperatures arc i)robably higher

6

xIBi/

o p

(5

1886.] on Dissociation Temyeratures, dx. 475

than are reached in the arts, as materials used in furnace-building
would not withstand such temperatures for any length of time ; but
still I must call attention to the circumstance that if the influence of
the inner surfaces of the tubes on the combustion of the gases therein
could be removed, the dissociation temperatures arrived at would be
found still higher. I cannot admit that Bunsen's explanation of the
cause of the second and third explosions is quite satisfactory, as it
is not the cooling of the gases alone which renders the subsequent
explosions possible, but also the thorough re-mixture of the gases by
diffusion after each explosion. This I will illustrate by means of
the diagrams exhibited, Figs. 1 to 6, which represent: —

1. A tube filled with an explosive gas mixture which is shown white.

2. The same tube immediately after an explosion has taken place,
the white margin indicating the unexploded mixture close to the
sides, and the deep-red, towards the middle of the tube, the exploded
gases. The white is shown as merging into deep-red by degrees,
because close up to the sides the surfaces prevent explosion or
combustion altogether; nearer the middle partial combustion takes
place, whilst only in the middle of the tube the gases find sufficient
space for complete combination.

3. The same tube after the burnt and unburnt gases have mixed
by means of diffusion, which is coloured light-red.

4. The same tube immediately after the second explosion, coloured
light-red at the sides, turning into deep-red by degrees towards the
middle.

5. The same tube after diffusion has done its work a second time,
coloured a deeper shade of red.

6. The same tube after the third explosion, coloured nearly
deep-red throughout, but still a lighter shade on the sides.

In Bunsen's mode of determining dissociation at high tem-
peratures we have only to deal with the obstruction which surfaces
offer to combustion, leaving out their dissociating influence at high
temperatures which affect most of Deville's results. For that reason
Bunsen arrives at much higher dissociation temperatures than Deville,
and his mode of experimenting possesses the advantage that it may
lead to a proper settlement of the question of temperatures at which
dissociation would set in when taking place in a space unencumbered
by surfaces.

I should wish some one more experienced than I am with purely
physical investigation to make the following experiment : —

Take a narrow tube of about the same size as Bunsen used for his
experiments, and a hollow sphere of the same capacity, in both of
which Bunsen's experiment should be repeated. The sphere offering
less surface than the tube in proportion to the quantity of gas it
contains, the dissociation temperature should be found higher in the
former than in the latter, if my views are correct. The results that
would, in my opinion, be obtained are shown approximately by the
red and white coloured surfaces in the diagram (Figs. 7 to 10).

476 Mr. Frederick Siemens [May 7,

From the temperatures tliiis obtained, in each case, the real
dissociation temperature, if no surfaces were present to influence the
result, might be approximately calculated.

Bunsen's method of experimenting, according to my view of the
matter, should form the foundation of further research to determine the
dissociation temperatures of products of combustion. Even if means
were found for'eliminating the influence of surfaces, no known material
at our disposal could withstand the very high temperature to which
the vessels or tubes would be subjected if experiments were carried
out according to Deville's method.

That the surfaces of highly heated vessels or tubes either pro-
duce, or tend to produce, dissociation, has been corroborated lately by
two Eussian experimentalists, Menschutkin and Kronowalow. These
gentlemen found that dissociation of carbonic acid and other gases
was much facilitated when the vessels used for the experiments were
filled with material offering rough surfaces, such as asbestos or broken
glass.

My view of the theory of dissociation caused or influenced by
surfaces, may be given as follows : — Increase of temperature producing
expansion of gases will reduce the attractive tendency of the atoms
towards one another, or, in other words, diminish their chemical
affinity. In the same ratio as the temperature is increased the
repelling tendency of the atoms must increase also, until at last
decomposition, or what is called dissociation, takes place. This being
admitted, it will follow that the adhesive or condensing influence of
surfaces on the atoms of the gas, which action will increase at high
temperatures, will assist this decomposition by increasing the repel-
ling tendency of the atoms.

Victor Meyer, who at first disjrated the accuracy of the results
obtained by the two physicists I have mentioned, ultimately accepted
them. This circumstance I was very j)leased to learn as their experi-
ments confirmed the results I arrived at in practical work with
furnaces. Thus the question may be considered nearly settled, the
more so as Meyer is himself a great authority in questions of dis-
sociation, having carried out many interesting experiments. Meyer,
for instance, proved dissociation by dropping melted platinum into
water, and finds that oxygen and hydrogen are evolved from the steam
produced. There can be no doubt on this point, but the question
arises whether heat is the sole agent that brings about the dissocia-
tion of steam in this case. In the first place the dissociating influence
of the highly heated surfaces of platinum on steam has to be taken
into consideration, and secondly the chemical affinity which platinum
has for oxygen, and still more for hydrogen. The same remarks
apply to Meyer's experiment of passing steam or carbonic acid through
heated platinum tubes, in which case he obtains only traces of dis-
sociation, the temjDerature beiug much lower. Other experiments
might bo mentioned; but none lead to a difibrcnt conception of the
question.

1886.] on Dissociation Temperatures, &c. ^11

There is one other circumstance connected with dissociation, proved
by experiment, which however, requires explanation. It is considered
as a sure sign that dissociation is going on when a flame whose tem-
perature is raised becomes longer ; this it is said can only be
accounted for by dissociation taking place. I agree with this con-
clusion, but the experiments by which it has been proved have been
made, like others referred to, in narrow tubes or passages in which
the dissociating action of the heated surfaces must come into play.
It is not alone the heat to which the gases are raised that in these
cases causes dissociation and increases the length of the flame, but
also the influence of the heated surfaces in contact with the com-
bustible gases, more especially if these gases contain hydrocarbons.
The extension of the flame is also partly due to the obstruction which
the surfaces ofi'er to the recombustion of the dissociated gases through
want of space. If the same flame be allowed free development in a
space unencumbered by surfaces, as in my radiation furnace, no such
extension of its length would be observed; but, on the contrary, it
would get shorter with increase of temperature. This action can be
best observed in a regenerative gas-burner whose flame is shorter the
greater the intensity of the temperature, and therefore of the light
produced. On the other hand, flame may be extended almost to any
length if conducted through narrow passages ; this may be seen in
regenerative furnaces which will send the flame to the top of the
chimney if the reversing valves are so arranged that the flame, instead
of passing through the furnace chamber, is made to burn directly
down into the regenerators. No proper combustion can then take
place in the brick checkerwork of the regenerative chambers, and the
flame will consequently continue to extend until cooled down below a
red heat, being ultimately converted into dark smoke ; thus in this
case, the extensive surfaces offered by regenerators will act both ways,
by preventing combustion, and by assisting dissociation.

It will now be understood that regenerative furnaces themselves
offer special opportunities for making experiments, most questions
being best settled by the results obtained in actual work. If dissocia-
tion sets in we see the consequences in want of heat, reduced output,
and in destruction of furnace and material. If the causes of dissocia-
tion are removed we immediately become aware of the circumstance
by a rise in temperature, increased output, longer furnace life, and
saving of material.

Similar results may be obtained' with other furnaces, but the
beneficial action will not be so great as in the case of the regene-
rative furnace, because the intensity of heat obtainable in them is
much lower.

In applying the principle of heating by radiation, or free develop-
ment of flame, to boilers, it is necessary to prevent the flame in its
active stage of combustion from touching either the sides of the boiler
or its brickwork setting. The flame is allowed free space to burn in,
and thus good combustion is obtained, after which the jjroducts of

478 Mr, Frederick Siemens [May 7,

combustion are broiiglit into intimate contact with the surfaces to be
heated. While combustion is going on in the open space heat is
transmitted by radiation only, but after active combustion is com-
pleted it is transmitted by contact, and it is in this manner that flame
must be applied to boilers, and may be applied equally well to
nearly all other heating operations.

In heating a boiler the intensity of heat produced is not very
great, because the relatively cold surfaces abstract heat from the flame
very eagerly, thus preventing its temperature from rising above a
certain point which is below that of dissociation. But although no
dissociation of the products of combustion can take place in boiler
firing, the detrimental effect on combustion of the surfaces of the
boiler is nevertheless very great, perhaps, indeed, greater than in any
other application of firing and heating. The cold surface of the
boiler has the power of extinguishing flame altogether, especially if
brought into actual contact with it, because, besides the peculiar in-
fluence of surfaces on combustion, the cooling in this case is so great that
the necessary temperature for combustion cannot be maintained. Thus
it seems clear that heating by radiation must be most advantageous for
firing boilers, but particular care should be taken that the products of
combustion, as distinguished from the flame, are brought as much as
possible into contact with their surfaces. Galloway tubes are pre-
ferable to bafflers for this purpose, but it will be necessary to be
careful that combustion is complete before the products of com-
bustion are allowed to come into contact with these tubes or bafflers,
as otherwise they would interfere with combustion at that point.

In the paper I read before the Iron and Steel Institute, to which
I have already referred, I described a boiler heated on the radiation
principle, fired with the producer gas used in our regenerative gas
furnaces, and with that boiler no smoke is produced. I will now
describe a boiler worked on the same principle, fired with common
coal, by the use of which great saving of fuel is effected, and very
little or no smoke is produced. In this boiler one end of the internal
flue is lined with brickwork, and contains an ordinary fire-grate,
while the longer part is furnished with rings of cast iron or fire-clay,
which prevent the flame from striking on the inner boiler surface.
The products of combustion, after leaving the inner flue, where
the flame has not come into contact with the boiler plates, are con-
ducted underneath and at the sides of the boiler, and in these channels
they may be directed by means of bafflers against the boiler sides and
bottom. If the internal flue of the boiler is so long that the flame
ceases before reaching its extremity, bafflers, in the form of cones, may
also be placed at its far end for the purpose of ca..sing the products
of combustion to strike against its sides. Instead of cones, cross
tubes of the Galloway type may be used with advantage, but it is
absolutely necessary that active combustion should have ceased before
the products of combustion come into contact with cither bafflers or
tubes. In a boiler so arranged and constructed that the flame heats

1886.] on Dissociation Temperatures, dec. 479

mostly by radiation in its first, and by contact in its second stage, a
great saving of fuel is effected, and almost no smoke produced. To
avoid altogether the production of smoke in this boiler, the fuel
should be charged on the grate in a uniform manner. It is quite
impossible to avoid producing smoke and waste if fuel is charged
unequally on the grate and at irregular intervals, however well the
boiler may have been arranged and constructed. Various kinds of
automatic and mechanical coal-feeding arrangements have been sug-
gested, and some have been aj)plied, but none have given full satis-
faction. At the London Smoke Abatement Exhibition numerous
apparatus of this kind were to be seen, and apparently worked
successfully, but when tested at other places, and under different
conditions, they have been found wanting, owing to the faulty manner
in which the flame and products of combustion were dealt with.
These clever appliances would, in my opinion, have worked more
satisfactorily if firing and heating had been carried out in them in
two successive stages.

There is a very simple way of firing, which I have employed,
that may possibly not be quite new, but answers very well, and does
not require complicated constructions and appliances, always more
or less objectionable. It depends upon the following considerations.
When fresh coal is charged upon incandescent fuel, as is the case in
the usual mode of firing boilers, the volatile gases of the fresh fuel
are rapidly evolved, filling the fire-box to such an extent as to prevent
the ingress of air through the grate, and this occurs at the very time
the air-supply should be considerably increased. The result is
imperfect combustion and consequent waste of the very best com-
bustible gases, viz. the hydro-carbons, which cannot burn for want of
air to combine with ; free carbon is thus liberated from these gases,
and smoke is produced. In order to avoid smoke, and consequent
loss of fuel, any sudden production of volatile gases, either during or
after firing, must be prevented ; and sufficient air should always be
introduced, and so distributed, as to burn those gases as quickly as
the}' are produced. This can be done in the following manner : —

Before putting on fresh coal the burning fuel should be pushed back
from the front part of the grate and distributed on the incandescent
fuel behind, care being taken that this portion of the grate is entirely
free from hot fuel. When the front part of the grate has become
comparatively cool owing to cold air passing through it, fresh coal
is distributed thereon. The freshly charged fuel lying on the cool
grate with cold air passing through it will be heated by radiation
only, partly from the incandescent fuel behind, partly by the flame
from its own gases, and partly by the surrounding hot brickwork. The
volatile gases will consequently be liberated at a comparatively slow
rate, and will combine with the air which entering through the inter-
stices in the fuel on the cool part of the grate will be evenly dis-
tributed over its surface. Gas and air will thus be supplied in nearly
the proper proportions for complete combustion of the fuel, and as

Vol. XI. (No. 80.) 2 i

480 Mr. Frederick Siemens [May 7,

the production of volatile gases diminislies, the air passing through
the front part of the grate, will enter into combustion with the fuel
thereon which has been deprived of nearly all its volatile constituents.
By means of this simple arrangement the sudden production of a large
volume of volatile gases is avoided, and air in a well divided state is
always present to consume the gases liberated ; thus smokeless com-
bustion and saving of fuel are realised. Care must be taken that the
fresh fuel is charged at regular intervals of time and in equal
quantities. It still remains to be considered in what manner the
clinkers and ashes may be most easily removed, but by the use of a
movable pocket at the far end of the grate to collect them in, and
a hooked bar to draw it forward at intervals, good practical results
would be obtained.

Having dealt so fully with the subject of heating furnaces by radia-
tion, I wish to be allowed to bring before your notice an apparatus
for warming rooms by the same means, which I have found to be
both satisfactory and economical, and England, I believe, is the
country in which it is likely to be fully appreciated, as heating by
radiation is almost exclusively used for domestic purposes here.

It must be borne in mind that the regenerative flame radiates
much more heat than an ordinary fire or gas flame, because most of
the heat which passes away from ordinary flames is in this case
employed to increase the temperature, or to accumulate heat, the
intensity of the flame, and consequently its radiating power, are thus
much increased, or in other words, the heat ordinarily passing away
from the flame with the products of combustion is converted into
radiant heat.

The apparatus to which I refer is a stove provided with a
regenerative hiirner, supplied with ordinary illuminating or retort gas,
and is intended to warm apartments mainly by the radiated heat of
the intensely hot flame produced ; it was fully described by me in a
paper read at the meeting of the Gas Institute held in Manchester
last year. We find in nature that direct heating is eftected by
radiation exclusively ; every organism, as well as all mankind, owe
their existence and development to the radiated heat from the sun,
and we should try to imitate nature in our methods of obtaining
artificial heat. The wind which produces that change of air we
require for our well being is another result of the action of the sun.
Both heating and ventilation I have endeavoured to supply by means
of this stove. Although there is only a small amount of heat passing
away from the flame after having heated the air required for com-
bustion it is entirely utilised for the sake of economy ; but in cases
where economy is not the primary object, but hygienic considerations
are paramount, the regenerative gas flame is phaced at the foot of
the chimney in front of the grate in place of the ordinary coal fire.
The background of the stove is of china or other white material, to
act as a reflector, by which means the heat, otherwise lost by being
radiated backwards or sideways, is recovered to assist in w^arming

12

1886.] on Dissociation Temperatures, &c. 481

the room. Owing to the high temperature of the regenerative gas
flame and the employment of a reflector, which would be quite impos-
sible with an ordinary fire, the economy of fuel attained by the use
of this stove, and in a less degree by the use of the chimney fire, is
considerable. The maximum consumption of gas in the stove exhi-
bited is about 12 cubic feet per hour. Considering that the gas
need not burn constantly, or may be lowered as required, its daily
consumption may be set down at 50 to 150 cubic feet of gas for an
ordinary room of about 4000 to 5000 cubic feet capacity.

There is still one very important point which remains to be
mentioned in connection with a regenerative gas flame of high
intensity, provided with a reflecting background ; that is, the better
distribution of the radiated heat. I find that a room warmed by
means of a stove or open fire, such as described, is of a more uniform
temperature than when warmed by an ordinary fire or by a gas and
coke fire," such as my brother was engaged in introducing into this
country shortly before his death.

This, in my opinion, is mainly due to the fact that a source of
radiant heat of low intensity but of large surface, sending out its
rays at various angles, heats an object in its vicinity very much more
than is the case with a smaller source of radiant heat of greater
intensity, whose rays strike the object from one direction only, not-
withstanding that both sources radiate the same quantity of heat.
This action is illustrated by means of the two diagrams exhibited,
Figs. 11 and 12, which represent two rooms, the one, Fig. 12,
heated by a small flame of high intensity, and the other. Fig. 11,
by a large flame of low intensity, both radiating the same
quantity of heat. In each room two objects, globes or spheres,
are represented, the one close to, and the other at a distance from
the source of heat. The object in the one room near to the source
having the large heating surface is almost enveloped in rays, while
that in the second receives rays only in one direction, the former there-
fore being much more heated than the latter. This difference does not
occur when the two globes at a distance from the two sources of heat
are compared. The law that the rays of heat are diminished in the
inverse ratio of the square of the distance is only correct as regards
small but intense sources of heat, whilst the decrease of radiant heat
takes place in a much higher proportion, in the case of large sources
of heat of low intensity. This clearly proves that for the purpose of
warming rooms by means of radiation, it is important that the heat
should be concentrated in an intensely hot focus, as is the case in
nature, our earth being warmed in this way by the radiant action of
the sun.

From various considerations I am led to believe that the question
of sanitary and economical warming is one which commands a great
deal of attention in this country. Not many years ago I had to report
to my own Government on the Smoke Abatement Exhibition, held in
this city, and I understand that a Smoke Abatement Institution has

2 I 2

482 Mr. F, Siemens on Dissociation Temperatures, &c. [May 7,

since been inaugurated. There seems to be a general feeling tbat
something will before long have to be used instead of the present
fireplace with its smoky chimney, especially now that people are
massed together in enormous cities in which cleanliness and pure air
are of the greatest importance. Under these circumstances I would
venture to draw the attention of authorities in sanitary science to the
method of warming dwellings to which I have shortly referred, as
resting on a scientific basis, being cleanly and easy of application,
demanding little or no attention, and fulfilling all sanitary and
economical requirements, and finally as being entirely free from all
dissociating influences owing to the free development of the flame.

[F. S.]

1886.] Sir William Thomson on Caj>illary Attraction. 483

WEEKLY EVENING MEETING,

Friday, January 29, 1886.

William Huggins, Esq. D.C.L. LL.D. F.E.S. Vice-President, in the

Chair.

Sir William Thomson, D.C.L. LL.D. F.E.S. M.B.I.

Capillary Attraction.

The heaviness of matter had been known for as many thousand years
as men and philosophers had lived on the earth, but none had
susiDOcted or imagined, before Newton's discovery of universal gravi-
tation, that heaviness is due to action at a distance between two
portions of matter. Electrical attractions and repulsions, and mac'-
netic attractions and repulsions, had been familiar to naturalists and
philosophers for two or three thousand years. Gilbert, by showing
that the earth, acting as a great magnet, is the efficient cause of the
compass needle's pointing to the north, had enlarged people's ideas
regarding the distances at which magnets can exert sensible action.
But neither he nor any one else had suggested that heaviness is the
resultant of mutual attractions between all parts of the heavy body
and all parts of the earth, and it had not entered the imagination of
man to conceive that different portions of matter at the earth's
surface, or even the more dignified masses called the heavenly
bodies, mutually attract one another. Newton did not himself give
any observational or experimental proof of the mutual attraction
between any two bodies, of which both are smaller than the moon.
The smallest case of gravitational action which w^as included in the
observational foundation of his theory, was that of the moon on the
waters of the ocean, by which the tides are produced; but his
inductive conclusion that the heaviness of a piece of matter at the
earth's surface, is the resultant of attractions from all parts of the
earth acting in inverse proportion to squares of distances, made it
highly probable that pieces of matter within a few feet or a few inches
apart attract one another according to the same law of distance and
Cavendish's splendid experiment verified this conclusion. But now
for our question of this evening. Does this attraction between any
particle of matter in one body and any particle of matter in another
continue to vary inversely as the square of the distance, when the
distance between the nearest points of the two bodies is diminished to
an inch (Cavendish's experiment does not demonstrate this, but makes
it very probable), or to a centimetre, or to the hundi-ed-thousandth
of a centimetre, or to the hundred-millionth of a centimetre ?
Now I dip my finger into this basin of water; you see proved

484 Sir William Thomson [Jan. 29,

a force of attraction between the finger and the drop hanging from
it, and between the matter on the two sides of any horizontal plane
you like to imagine through the hanging water. These forces are
millions of times greater than what you would calculate from the
Newtonian law, on the supposition that water is perfectly homo-
geneous. Hence either these forces of attraction must, at very small
distances, increase enormously more rapidly than according to the
Newtonian law, or the substance of water is not homogeneous. We
now all know that it is not homogeneous. The Newtonian theory of
gravitation is not surer to us now than is the atomic or molecular
theory in chemistry and physics ; so far, at all events, as its assertion
of heterogeneousness in the minute structure of matter apparently
homogeneous to our senses and to our most delicate direct instru-
mental tests. Hence, unless we find heterogeneousness and the
Newtonian law of attraction incapable of explaining cohesion and
capillary attraction, we are not forced to seek the explanation in a
deviation from Newton's law of gravitational force. In a little
communication to the Eoyal Society of Edinburgh twenty-four years
ago,* I showed that heterogeneousness does suffi.ce to account for any
force of cohesion, how^ever great, provided only we give sufficiently
great density to the molecules in the heterogeneous structure.

Nothing satisfactory, however, or very interesting mechanically,
seems attainable by any attempt to work out this theory without
taking into account the molecular motions which we know to be
inherent in matter, and to constitute its heat. But so far as the main
phenomena of capillary attraction are concerned, it is satisfactory to
know that the complete molecular theory could not but lead to the
same resultant action in the aggregate as if water and the solids
touching it were each utterly homogeneous to infinite minuteness, and
were acted on by mutual forces of attraction sufficiently strong
between portions of matter which are exceedingly near one another,
but utterly insensible between portions of matter at sensible
distances. This idea of attraction insensible at sensible distances
(whatever molecular view we may learn, or peo23le not now born may
learn after us, to account for the innate nature of the action), is indeed
the key to the theory of capillary attraction, and it is to Hawksbee f
that we owe it. Laj)lace took it up and thoroughly worked it out
mathematically in a very admirable manner. One part of the theory
which he left defective — the action of a solid upon a liquid, and the
mutual action between two liquids — was made dynamically perfect
by Gauss, and the finishing touch to the mathematical theory was
given by Neumann in stating for liquids the rule corresponding to
Gauss's rule for angles of contact between liquids and solids.

Gauss, expressing enthusiastic appreciation of Laplace's work,
adopts the same fundamental assumption of attraction sensible only

* Proceedings of the Royal Society of Edinburgh, April 21, 1862 (vol, iv.).
t Royal Society Transactions, 1709-13.

1886.] on Capillary Attraction. 485

at insensible distances, and, while projoosing as chief object to
complete the part of the theory not worked out by his predecessor,
treats the dynamical problem afresh in a remarkably improved
manner, by founding it wholly upon the principle of what we now
call potential energy. Thus, though the formulas in which he
expresses mathematically his ideas are scarcely less alarming in
appearance than those of Laplace, it is very easy to translate them
into words by which the whole theory will be made perfectly
intelligible to jDcrsons who imagine themselves incapable of under-
standing sextuple integrals. Let us place ourselves conveniently at
the centre of the earth so as not to be disturbed by gravity. Take
now two portions of water, and let them be shaped over a certain
area of each, call it A for the one, and B for the other, so that when
put together they will fit perfectly throughout these areas. To save
all trouble in manipulating the supposed pieces of water, let them
become for a time perfectly rigid, without, however, any change in
their mutual attraction. Bring them now together till the two
surfaces A and B come to be within the one-hundred-thousandth of
an inch apart, that is, the forty-thousandth of a centimetre, or
250 micro-millimetres (about half the wave-length of green light).
At so great a distance the attraction is quite insensible : we may feel
very confident that it differs, by but a small percentage, from the
exceedingly small force of attraction which we should calculate for it
according to the Newtonian law, on the supposition of perfect
uniformity of density in each of the attracting bodies. Well-known
phenomena of bubbles, and of watery films wetting solids, make it
quite certain that the molecular attraction does not become sensible
until the distance is much less than 250 micro-millimetres. From
the consideration of such phenomena Quincke (Pogg. Ann., 1869)
came to the conclusion that the molecular attraction does become
sensible at distances of about 50 micro-millimetres. His conclusion
is strikingly confirmed by the very important discovery of Eeinold
and Eiicker* that the black film, always formed before an undisturbed
soap bubble breaks, has a uniform or nearly uniform thickness of
about 11 or 12 micro-millimetres. The abrupt commencement, and
the permanent stability, of the black film demonstrate a proposition of
fundamental importance in the molecular theory : — The tension of the
film, which is sensibly constant when the thickness exceeds 50 micro-
millimetres, diminishes to a minimum, and begins to increase again
when the thickness is diminished to 10 micro-millimetres. It seems
not possible to explain this fact by any imaginable law of force
between the different portions of the film supposed homogeneous, and
we are forced to the conclusion that it depends upon molecular
heterogeneousness. When the homogeneous molar theory is thus
disproved by observation, and its assumption of a law of attraction
augmenting more rapidly than according to the Newtonian law when

* Proc. Eoy. Soc, June 21, 1877 ; Trans. Koy. Soc, April 19, 1883.

486 Sir William Thomson [Jan. 29,

the distance becomes less than 50 micro-millimetres is proved to be
insufficient, may we not go farther and say that it is unnecessary to
assume any deviation from the Newtonian law of force varying
inversely as the square of the distance continuously from the
millionth of a micro-millimetre to the distance of the remotest star or
remotest piece of matter in the universe ; and, until we see how
gravity itself is to be explained, as Newton and Faraday thought it
must be explained, by some continuous action of intervening or sur-
rounding matter, may we not be temporarily satisfied to explain
capillary attraction merely as Newtonian attraction intensified in
virtue of intensely dense molecules movable among one another,
of which the aggregate constitutes a mass of liquid or solid.

But now for the present, and for the rest of this evening, let us
dismiss all idea of molecular theory, and think of the molar theory
pure and simple, of Laplace and Gauss. Eeturning to our two pieces
of rigidified water left at a distance of 250 micro-millimetres from
one another. Holding them in my two hands, I let them come
nearer and nearer until they touch all along the surfaces A and B.
They begin to attract one another with a force which may be scarcely
sensible to my hands when their distance apart is 50 micro-
millimetres, or even as little as 10 micro-millimetres ; but which
certainly becomes sensible when the distance becomes one micro-
millimetre, or the fraction of a micro-millimetre ; and enormous,
hundreds or thousands of kilogrammes' weight, before they come
into absolute contact. I am supposing the area of each of the
opposed surfaces to be a few square centimetres. To fix the ideas,
I shall suppose it to be exactly thirty square centimetres. If my
sense of force were sufficiently metrical I should find that the work
done by the attraction of the rigidified pieces of water in pulling my
two hands together was just about 4^ centimetre-grammes. The
force to do this work, if it had been uniform throughout the space of
50 micro-millimetres (five-millionths of a centimetre) must have been
900,000 grammes weight, that is to say, nine-tenths of a ton. But
in reality it is done by a force increasing from something very small
at the distance of 50 micro-millimetres to some unknown greatest
amount. It may reach a maximum before absolute contact, and then
begin to diminish, or it may increase and increase up to contact, we
cannot tell which. Whatever may be the law of variation of the
force, it is certain that throughout a small part of the distance it is
considerably more than one ton. It is possible that it is enormously
more than one ton, to make up the ascertained amount of work of 4J
centimetre-grammes performed in a si^ace of 50 micro-millimetres.

But now let us vary the circumstances a little. I take the two
pieces of rigidified water, and bring them to touch at a pair of
corresponding points in the borders of the two surfaces A and B,
keeping the rest of the surfaces wide asunder (see Fig. 1). The
work done on my hands in this proceeding is infinitesimal. Now,
without at i>ll altering the law of attractive force, lot a minute film

1886.1

on Capillary Attraction.

487

of tlie rigidified water become fluid all over each of the surfaces
A and B ; you see exactly what takes place. The pieces of matter
I hold in my hands are not the supposed pieces of rigidified water.
They are glass, with the surfaces A and B thoroughly cleaned and
wetted all over each with a thin film of water. What you now see
taking place is the same as what would take place if things were
exactly according to our ideal suj^position. Imagine, therefore, that
these are really two ineces of water, all rigid, except the thin film
on each of the surfaces A and B, which are to be put together,
Eemember also that the Royal Institution, in which we are met, has

Fig. 1.

been, for the occasion, transported to the centre of the earth so that
we are not troubled in any w^ay by gravit}^ You see we are not
troubled by any trickling down of these liquid films — but I must
not say down, we have no up and down here. You see the liquid
film does not trickle along these surfaces towards the table, at least
you must imagine that it does not do so. I now turn one or both of
these pieces of matter till they are so nearly in contact all over the

488 Sir William Thomson [Jan. 29,

surfaces A and B, that the whole interstice becomes filled with water.
My metrical sense of touch tells me that exactly 4J centimetre-
grammes of work has again been done ; this time, however, not by a
very great force, through a space of less than 50 micro-millimetres,
but by a very gentle force acting throughout the large space of the
turning or folding-together motion which you have seen, and now
see again. We know, in fact, by the elementary principle of work
done in a conservative system, that the work done in the first case
of letting the two bodies come together directly, and in the second
case of letting them come together by first bringing two points into
contact and then folding them together, must be the same, and my
metrical sense of touch has merely told me in this particular
sense what we all know theoretically must be true in every case
of j)roceeding by different ways to the same end from the same
beginning.

Now in this second way we have, in performing the folding
motion, allowed the water surface to become less by 60 square
centimetres. It is easily seen that, provided the radius of curvature
in every part of the surface exceeds one or two hundred times the
extent of distance to which the molecular attraction is sensible, or, as
we may say practically, provided the radius of curvature is every-
where greater than 5000 micro-millimetres (that is, the two-hundredth
of a millimetre), we should have obtained this amount of work with
the same diminution of water-surface, however performed. Hence
our result is that we have found 4-5/60 (or 3/40) of a centimetre-
gramme of work per square centimetre of diminution of surface.
This is precisely the result we should have had if the water had been
absolutely deprived of the attractive force between water and water,
and its whole surface had been coated over with an infinitely thin
contractile film possessing a uniform contractile force of 3/40 of a
gramme weight, or 75 milligrammes, per lineal centimetre.

It is now convenient to keep to our ideal film, and give up
thinking of what, according to our present capacity for imagining
molecular action, is the more real thing — namely, the mutual
attraction between the different portions of the liquid. But do not, I
entreat you, fall into the paradoxical habit of thinking of the surface
film as other than an ideal way of stating the resultant effect of
mutual attraction between the different portions of the fluid. Look,
now, at one of the pieces of water ideally rigidified, or, if you please,
at the two pieces put together to make one. Eemember we are at
the centre of the earth. What will take place if this piece of matter
resting in the air before you suddenly ceases to be rigid ? Imagine
it, as I have said, to be enclosed in a film everywhere tending to
contract with a force equal to 3/40 of a gramme or 75 milligrammes
weight per lineal centimetre. This contractile film will clearly
press most where the convexity is greatest. A very elementary piece
of mathematics tells us that on the rigid convex surface which you
Bee, the amount of its pressure per square centimetre will be found

1886.] on Capillary Attraction. 489

by multiplying tlie sum * of the curvatures in two mutually-perpen-
dicular normal sections, by the amount of the force per lineal centi-
metre. In any place where the surface is concave the effect of the
surface tension is to suck outwards — that is to say, in mathematical
language, to exert negative pressure inwards. Now, suppose in an
instant the rigidity to be annulled, and the piece of glass which you
see, still undisturbed by gravity, to become water. The instantaneous
effect of these unequal pressures over its surface will be to set it
in motion. If it were a perfect fluid it would go on vibrating for
ever with wildly-irregular vibrations, starting from so rude an initial
shape as this which I hold in my hand. Water, as any other liquid,
is in reality viscous, and therefore the vibrations will gradually
subside, and the piece of matter will come to rest in a spherical
figure, slightly warmed as the result of the work done by the forces
of mutual attraction by which it was set in motion from the initial
shape. The work done by these forces during the change of the
body from any one shape to any other is in simple proportion to the
diminution of the whole surface area ; and the configuration of
equilibrium, when there is no disturbance from gravity, or from
any other solid or liquid body, is the figure in which the surface
area is the smallest possible that can enclose the given bulk of
matter.

I have calculated the period of vibration of a sphere of water "f
(a dew-drop !) and find it to be I a^, where a is the radius measured
in centimetres : thus —

1

i

2-54

I

4

2

16

16

36

36

07

„ 13,200

The dynamics of the subject, so far as a single liquid is concerned,
is absolutely comprised in the mathematics without symbols which I
have put before you. Twenty pages covered with sextuple integrals
could tell us no more.

Hitherto we have only considered mutual attraction between the
parts of two portions of one and the same liquid — water for instance.
Consider, now, two different kinds of liquid : for instance, water and
carbon disulphide (which, for brevity, I shall call sulphide). Deal
with them exactly as we dealt with the two pieces of water. I need

* This sum for brevity I henceforth call simply " the curvature of the surface "
at any point.

t See paper by Lord Kayleigh in Proceedings of the Koyal Society, No. 196,
May 5, 1879.

490 Sir William Thomson [Jan. 29,

not go tlirongli the whole process again ; the result is obvious.
Thirty times the excess of the sum of the surface-tensions of the two
liquids separately, above the tension of the interface between them,
is equal to the work done in letting the two bodies come together
directly over the supposed area of thirty square centimetres. Hence
the interfacial tension per unit area of the interface is equal to the
excess of the sum of the surface-tensions of the two liquids separately^
above the worh done in letting the tioo bodies come together directly so as
to meet in a unit area of each. In the particular case of two similar
bodies coming together into perfect contact, the interfacial tension
must be zero, and therefore the work done in letting them come
together over a unit area must be exactly equal to twice the surface-
tension ; which is the case we first considered.

If the work done between two different liquids in letting them
come together over a small area, exceeds the sum of the surface-
tensions, the interfacial tension is negative. The result is an
instantaneous puckering of the interface, as the commencement of
diffusion and the well-known process of continued inter-diffusion
follows.

Consider next the mutual attraction between a solid and a liquid.
Choose any particular area of the solid, and let a portion of the sur-
face of the liquid be preliminarily shaped to fit it. Let now the
liquid, kept for the moment rigid, be allowed to come into contact
over this area with the solid. The amount by which the work done
per unit area of contact falls short of the surface-tension of the liquid
is equal to the interfacial tension of the liquid. If the work done per
unit area is exactly equal to the free-surface tension of the liquid, the
interfacial tension is zero. In this case the surface of the liquid when
in equilibrium at the place of meeting of liquid and solid is at right
angles to the surface of the solid. The angle between the free sur-
faces of liquid and solid is acute or obtuse according as the interfacial
tension is positive or negative ; its cosine being equal to the inter-
facial tension divided by the free-surface tension. The greatest
possible value the interfacial tension can have is clearly the free-
surface tension, and it reaches this limiting value only in the, not
purely static, case of a liquid resting on a solid of high thermal con-
ductivity, kept at a temperature greatly above the boiling-point of
the liquid ; as in the well-known phenomena to which attention has
been called by Leidenfrost and Boutigny. There is no such limit to
the absolute value of the interfacial tension when negative, but its
absolute value must be less than that of the free-surface tension to
admit of equilibrium at a line of separation between liquid and solid.
If minus the interfacial tension is exactly equal to the free-surface
tension, the angle between the free surfaces at the line of separation
is exactly 180'^. If minus the interfacial tension exceeds the free-
surfiice tension, the liquid runs all over the solid, as, for instance,
water over a glass plate which has been very perfectly cleansed. If

1886.] on Capillary Attraction. 491

for a moment we leave the centre of the earth, and suppose ourselves
anywhere else in or on the earth, we find the liquid running up,
against gravity, in a thin film over the upper part of the containing
vessel, and leaving the interface at an angle of 180^ between the free
surface of the liquid, and the surface of the film adhering to the solid
above the bounding line of the free liquid surface. This is the case
of water contained in a glass vessel, or in contact with a piece of glass
of any shape, provided the surface of the glass be very perfectly
cleansed.

When two liquids which do not mingle, that is to say, two liquids
of which the interfacial tension is positive, are placed in contact and
left to themselves undisturbed by gravity (in our favourite Laboratory
in the centre of the earth suppose), after performing vibrations sub-
siding in virtue of viscosity, the compound mass will come to rest, in
a configuration consisting of two intersecting segments of spherical
surfaces constituting the outer boundary of the two portions of liquid,
and a third segment of spherical surface through their intersection
constituting the interface between the two liquids. These three
spherical surfaces meet at the same angles as three balancing forces
in a plane whose magnitudes are respectively the surface tensions of
the outer surfaces of the two liquids and the tension of their interface.
Figs. 2 to 5 (pp. 492, 493) illustrate these configurations in the case of
bisulphide of carbon and water for several different proportions of
the volumes of the two liquids. (In the figures the dark shading
represents water in each case.) When the volume of each liquid is
given, and the angles of meeting of the three surfaces are known,
the problem of describing the three sj)herical surfaces is clearly
determinate. It is an interesting enough geometrical problem.

If we now for a moment leave our gravitationless laboratory, and,
returning to the Theatre of the Eoyal Institution, bring our two
masses of liquid into contact, as I now do in this glass bottle, we have
the one liquid floating upon the other, and the form assumed by the
floating liquid may be learned, for several different cases, from the
phenomena exhibited in these bottles and glass beakers, and shown on
an enlarged scale in these two diagrams (Figs. 6 to 8, p. 494) ; which
represent bisulphide of carbon floating on the surface of sulphate of
zinc, and in this case (Fig. 8) the bisulphide of carbon drop is of
nearly the maximum size capable of floating. Here is the bottle
whose contents are represented in Fig. 8, and we shall find that a
very slight vertical disturbance serves to submerge the mass of bi-
sulphide of carbon. There now it has sunk, and wo shall find when
its vibrations have ceased that the bisulphide of carbon has taken the
form of a large sphere supported within the sulphate of zinc. Now,
remembering that we are again at the centre of the earth, and that
gravity does not hinder us, suppose the glass matter of the bottle
suddenly to become liquid sulphate of zinc, this mass would become
a compound sphere like the one shown on that diagram (Fig. 3), and

492

Sir William Thomson

Fig. 2.

[Jan. 29,

Fig. 3.

1886.]

on Capillary Attraction.
Fig. 4.

493

Fig. 5.

494

Sir William Thomson

[Jan. 29,

would have a radius of about 8 centimetres. If it were sulphate of
zinc alone, and of this magnitude, its period of vibration would be
about 5J seconds.

Fig. 6.

Fig. 7.

Fig. 8.

Fig. 9 shows a drop of sulphate of zinc floating on a wine-glassful
of bisulphide of carbon.

In observing the phenomena of two liquids in contact, I have found
it very convenient to use sulphate of zinc (which I find, by experi-
ment, has the same free-surface tension as water) and bisulphide of
carbon ; as these liquids do not mix when brought together, and, for
a short time at least, there is no chemical interaction between them.
Also, sulphate of zinc riiay be made to have a density less than, or
equal to, or greater than, that of the bisul2)hide, and the bisulphide
may be coloured to a more or less deep purple tint by iodine, and this
enables us easily to observe drops of any one of these liquids on the

1886.]

on Capillary Attraction.

495

other. In the three bottles now before you the clear liquid is sul-
phate of zinc — in one bottle it has a density less than, in another
equal to, and in the third greater than, the density of the suljihide
— and you see how, by means of the coloured sulj)liide, all the phe-
nomena of drops resting uj^on or floating within a liquid int i which
they do not diiiiise may be observed, and, under suitable arrangements,
quantitatively estimated.

When a liquid under the influence of gravity is supported by
a solid, it takes a configuration in which the difference of curvature
of the free surface at different levels is equal to the difference

Fig. 9.

of levels divided by the surface tension reckoned in terms of weight
of unit bulk of the liquid as unity ; and the free surface of the liquid
leaves the free surface of the solid at the angle whose cosine
is, as stated above, equal to the interfacial tension divided by the free-
surface tension, or at an angle of 180" in any case in which minus the
interfacial tension exceeds the free-surface tension. The surface
equation of equilibrium and the boundary conditions thus stated
in words, suf&ce fully to determine the configuration when the volume
Vol. XI. (No. 80.) 2 k

496 Sir William Thomson [Jan. 29,

of the liquid and the shape and dimensions of the solid are given.
When I say determine, I do not mean unambiguously. There
may of course be a multiplicity of solutions of the problem ; as,
for instance, when the solid presents several hollows in which,
or projections hanging from which, portions of the liquid, or in
or hanging from any one of which the whole liquid, may rest.

When the solid is symmetrical round a vertical axis, the figure
assumed by the liquid is that of a figure of revolution, and its form is
determined by the equation given above in words. A general
solution of this problem by the methods of the differential and
integral calculus transcends the powers of mathematical analysis,
but the following simple graphical method of working out what
constitutes mathematically a complete solution, occurred to me a great
many years ago.

Draw a line to represent the axis of the surface of revolution.
This line is vertical in the realisation now to be given, and it or any
line parallel to it will be called vertical in the drawing, and any line
perpendicular to it will be called horizontal. The distance between
any two horizontal lines in the drawing will be called difference
of levels.

Through any point, N, of the axis draw a line, N P, cutting it at
any angle. With any point, 0, as centre on the line N P, describe a
very small circular arc through P P', and let N' be the point in which
the line of 0 P' cuts the axis. Measure N P, N' P', and the difference
of levels between P and P'. Denoting this last by 8, and taking a as
a linear parameter, calculate the value of

Va^^OP NP N'PV

Take this length on the compasses, and putting the pencil point
at P', place the other point at 0' on the line P'N', and with
0' as centre, describe a small arc, P'P". Continue the process
according to the same rule, and the successive very small arcs
so drawn will constitute a curved line, which is the generating
line of the surface of revolution inclosing the liquid, according
to the conditions of the special case treated.

This method of solving the capillary equation for surfaces of revo-
lution remained unused for fifteen or twenty years, until in
1874 I placed it in the hands of Mr. John Perry (now Professor
of Mechanics at the City and Guilds Institute), who was tiien
attending the Natural Philosophy Laboratory of Glasgow University.
He worked out the problem with great perseverance and ability,
and the result of his labours was a scries of skilfully executed
drawings representing a large variety of cases of the capillary
surfaces of revolution. These drawings, which are most instructive
and valuable, I have not yet been able to prej^arc for publication, but
the most characteristic of them have been reproduced on an enlarged

1886.]

on Capillary Attraction.

497

scale, and are now on the screen before you.* Three of these diagrams,
those to which I am now pointing (Figs. 10, 11, and 12), illustrate
strictly theoretical solutions — that is to say, the curves there shown

Fig. 10.

* The diagrams here referred to are now published in Figs. 10 to 21 of the
present report of the lecture at the Eoyal Institution. These figures are accurate
copies of Mr. Perry's original drawings, and I desire to acknowledge the great
care and attention which Mr. Cooper, engraver to Nature^ has given to the work.

2 K 2

498

Sir William Thomson
Fig. U.

[Jan. 29,

1886.]

Capillary Attraction.

499

do not represent real capillary surfaces — but these mathematical
extensions of the problem, while most interesting and instructive, are
such as cannot be adequately treated in the time now at my disposal.
In these other diagrams, however (Figs. 13 to 28), we have
certain portions of the curves taken to represent real capillary
surfaces shown in section. In Fig. 13 a solid sphere is shown in
four different positions in contact with a mercury surface ; and again,
in Fig. 14 we have a section of the form assumed by mercury resting

Fig. 13.

Mercury in contact with solid spheres (say of glass).

Fig. 14.

Sectional view of circular V-groove containin

g mercury.

in a circular V-groove. Figs. 15 to 28 (pp. 500-502) show water-
surfaces under different conditions as to capillarity ; the scale of the
drawings for each set of figures is shown by a line the length of
which represents 1 centimetre ; the dotted horizontal lines indicate
the positions of the free water-level. The drawings are sufficiently
explicit to require no further reference here save the remark that
water is represented by the lighter shading, and solid by the darker.

We have been thinking of our pieces of rigidified water as be-
coming suddenly liquefied, and conceiving them inclosed within ideal
contractile films ; I have here an arrangement by which I can exhibit
on an enlarged scale a pendant drop, inclosed not in an ideal film,
but in a real film of thin sheet indiarubber. The apparatus which
you see here suspended from the roof is a stout metal ring of 60
centimetres diameter, with its a2)erture closed by a sheet of india-

500

Sir William Thomson

[Jan. 29,

Fig. 15.

Fig. 16.

Fig. 17.

Fig. 18.

^Bfrl- m Fig. 19.

m Fig. 20.

Fig. 21.

Fig. 22.

Water in glass tubes, the internal diameter of which may be found from Fig. 22,
which represents a length of one centimetre.

Fig. 23.

Water resting in the space between a solid cylinder and a concentric hollow cylinder.

1886.]

on Capillary Attraction.

501

602

Sir William Thomson

[Jan. 29,

rubber tied to it all round, stretched uniformly in all directions, and
as tightly as could be done without special apparatus for stretching
it and binding it to the ring when stretched.

Fig. 27.

Section of the air-bubble in a level ti;be filled with water, and bent so that its axis
is part of a circle of large radius ; scale is represented in Fig. 28.

Fig. 28.

Represents a length of one centimetre for Figs. 24-27.

I now pour in water, and we find the flexible bottom assuming
very much the same shape as the drop which you saw hanging from
my finger after it had been dipped into and removed from the vessel
of water (see Fig. 16). I continue to pour in more water, and the
form changes gradually and slowly, preserving meanwhile the general
form of a droj) such as is shown in Fig. 15, until, when a certain
quantity of water has been poured in, a sudden change takes place.
The sudden change corresponds to the breaking away of a real drop
of water from, for example, the mouth of a tea-urn, when the stop-
cock is so nearly closed that a very slow dropping takes place. The
drop in the indiarubber bag, however, docs not fall away, because
the tension of the indiarubber increases enormously when the india-
rubber is stretched. The tension of the real film at the surface of
a drop of water remains constant, however much the surface is
stretched, and therefore the drop breaks away instantly when enough
of water has been supplied from above to feed the drop to the
greatest volume that can hang from the particular size of tube which
is used.

1886.]

Capillary Attraction,

503

I now put this siphon into action, gradually drawing off some of
the water, and we find the drop gradually diminishes until a sudden
change again occurs and it assumes the form we observed (Fig. 16)
when I first poured in the water. I instantly stop the action of the
siphon, and we now find that the great drop has two possible forms
of stable equilibrium, with an unstable form intermediate between
them. Here is an experimental proof of this statement. With the
drop in its higher stable form I cause it to vibrate so as alternately
to decrease and increase the axial length, and you see that when the
vibrations are such as to cause the increase of length to reach a
certain limit there is a sudden change to the lower stable form, and
we may now leave the mass performing small vibrations about that
lower form. I now increase these small vibrations, and we see that,
whenever, in one of the upward (increasing) vibrations, the contrac-
tion of axial length reaches the limit already referred to, there is
again a sudden change, which I promote by gently lifting with my
hands, and the mass assumes the higher stable form, and we have it
again performing small vibrations about this form.

The two positions of stable equilibrium, and the one of unstable
intermediate between them, is a curious peculiarity of the hydrostatic
problem presented by the water supported by indiarubber in the
manner of the experiment.

Fig. 29.

I have here a simple arrangement of apparatus (Figs. 29 and 30)
by which, with proper optical aids, such as a cathetometcr and a

604

Sir William Thomson

[Jan. 29,

microscope, we can make the necessary measurements on real drops
of water or other liquid, for the purpose of determining the values
of the capillary constants. For stability the drop hanging from the
open tube should be just less than a hemisphere, but for convenience
it is shown, as in the enlarged drawing of the nozzle (Fig. 30),

Fig. 30.

exactly hemispherical. By means of the siphon the difference of
levels, h, between the free level surface of the water in the vessel to
which the nozzle is attached, and the lowest point in the drop
hanging from the nozzle, may be varied, and corresponding measure-
ments taken of Ji and of r, the radius of curvature of the droj) at its
lowest point. This measurement of the curvature of the drop is
easily made with somewhat close accuracy, by known microscopic
methods. The surface-tension T of the liquid is calculated from the
radius, r, and the observed difference of levels, Ji, as follows : —

2T

= h

for example, if the liquid taken be water, with a free-surface tension
of 75 milligrammes per centimetre, and r = "05 cm., h is equal to
3 centimetres.

Many experiments may be devised to illustrate the effects of
surface-tension when two liquids, of which the surface-tensions are
widely different, are brought into contact with each other. Thus wo
may place on the surface of a thin layer of water, wetting uniformly
the surface of a glass plate or tray, a drop of alcohol or ether, and
so cause the surface-tension of the liquid layer to become smaller in
the region covered by the alcohol or ether. On the other hand, from
a surface-layer of alcohol largely diluted with water we may arrange
to withdraw part of the alcohol at one particular place by promoting
its rapid evaporation, and thereby increase the surface-tension of the

1886.] on Capillary Attraction. 505

liquid layer in that region by diminishing the percentage of alcohol
which it contains.

In this shallow tray, the bottom of which is of ground glass
resting on white paper, so as to make the phenomena to be exhibited
more easily visible, there is a thin layer of water coloured deep blue
with aniline ; now, when I place on the water-surface a small
quantity of alcohol from this fine pipette, observe the effect of
bringing the alcohol-surface, with a surface-tension of only 25*5
dynes per lineal centimetre, into contact with the water-surface,
which has a tension of 75 dynes per lineal centimetre. See how the
water pulls back, as it were, all round the alcohol, forming a circular
ridge surrounding a hollow, or small crater, which gradually widens
and deepens until the glass plate is actually laid bare in the centre,
and the liquid is heaped up in a circular ridge around it. Similarly,
when I paint with a brush a streak of alcohol across the tray, we
find the water drawing back on each side from the portion of the tray
touched with the brush. Now, when I incline the glass tray, it is
most interesting to observe how the coloured water with its slight
admixture of alcohol flows down the incline — first in isolated drops,
afterwards joining together into narrow continuous streams.

These and other well-known phenomena, including that interesting
one, " tears of strong wine," were described and explained in a
paper " On Certain Curious Motions Observable on the Surfaces
of Wine and other Alcoholic Liquors," by my brother, Prof. James
Thomson, read before Section A of the British Association at the
Glasgow meeting of 1855.

I find that a solution containing about 25 per cent, of alcohol
shows the " tears " readily and well, but that they cannot at all be
produced if the percentage of alcohol is considerably smaller or
considerably greater than 25. In two of those bottles the coloured
solution contains respectively 1 per cent, and 90 per cent, of alcohol,
and in them you see it is impossible to produce the " tears " ; but
when I take this third bottle, in which the coloured liquid contains
25 per cent, of alcohol, and operate upon it, you see — there — the
" tears " begin to form at once. I first incline and rotate the bottle
so as to wet its inner surface with the liquid, and then, leaving it
quite still, I remove the stopper, and withdraw by means of this
paper tube the mixture of air and alcoholic vapour from the bottle
and allow fresh air to take its place. In this way I promote the
evaporation of alcohol from all liquid surfaces within the bottle, and
where the liquid is in the form of a thin film it very speedily loses
a great part of its alcohol. Hence the surface-tension of the thin film
of liquid on the interior wall of the bottle comes to have a greater and
greater value than the surface-tension of the mass of liquid in the
bottom, and where these two liquid surfaces, having different surface-
tensions, come together we have the phenomena of " tears." There,
as I hasten the evaporation, you see the horizontal ring rising up the
side of the bottle, and afterwards collecting into drops which slip

506 Sir William Thcmison [Jan. 29,

down the side and give a fringe-like appearance to the space through
which the rising ring has passed.

These phenomena may also be observed by using, instead of
alcohol, ether, which has a surface-tension equal to about three-
fourths of that of alcohol. In using ether, however, this very curious
effect may be seen.* I dip the brush into the ether, and hold it
near to but not touching the water-surface. Now I see a hollow
formed, which becomes more or less deep according as the brush is
nearer to or farther from the normal water surface, and it follows the
brush about as I move it so.

Here is an experiment showing the effect of heat on surface-
tension. Over a portion of this tin plate there is a thin layer of
resin. I lay the tin plate on this hot copper cylinder, and we at once
see the fluid resin drawing back from the portion of the tin plate
directly over the end of the heated copper cylinder, and leaving a
circular space on the surface of the tin plate almost clear of resin,
showing how very much the surface-tension of hot resin is less than
that of cold resin.

Note of January 30, 1886. — The equations (8) and (9) on p. 59
of Clerk-Maxwell's article on " Capillary Attraction " in the ninth
edition of the " Encyclopaedia Britannica " do not contain terms
depending on the mutual action between the two liquids, and the
concluding expression (10), and the last small print paragrajDh of the
page are wholly vitiated by this omission. The paragraph immedi-
ately following equation (10) is as follows : —

" If this quantity is positive, the surface of contact will tend to
contract, and the liquids will remain distinct. If, however, it
were negative, the displacement of the liquids which tends to enlarge
the surface of contact would be aided by the molecular forces, so that
the liquids, if not kept separate by gravity, would become thoroughly
mixed. No instance, however, of a phenomenon of this kind has been
discovered, for those liquids which mix of themselves do so by
the process of diffusion, which is a molecular motion, and not by the
6j)ontaneous puckering and replication of the boundary surface
as would be the case if T were negative."

It seems to me that this view is not correct ; but that on the
contrary there is this " puckering " as the very beginning of diffusion.
What I have given in the lecture as reported in the text above seems
to me the right view of the case as regards diffusion in relation
to interfacial tension.

It may also be remarked that Clerk-Maxwell, in the large print
paragraph of p. 59, preceding equation (1), and in his application of
the term potential energy to E in the small print, designated by
energy what is in reality exhaustion of energy or negative energy ;

* See Clerk-Maxwell's article (p. 65) on " Capillary Attraction " C Encyclo-
pscdia Britannica,' 9tli edition).

1886.] on Capillary Attraction. 507

and the same inadvertence renders the small print paragraph on p. 60
very obscure. The curious and interest 'ng statement at the top of
the second column of p. 63, regarding a drop of carbon disulphide in
contact with a drop of water in a capillary tube would constitute a
perpetual motion if it were true for a tuba not first wetted with water
through part of its bore — " ... if a drop of water and a drop of
bisulphide of carbon be placed in contact in a horizontal capillary
tube, the bisulphide of carbon will chase the water along the tube."

Additional Note of June 5, 1886. — I have carefully tried the
experiment referred to in the preceding sentence, and have not found
the alleged motion.

[W. T.]

508 Professor Thomson [May 14,

WEEKLY EVENING MEETING,

Friday, May 14, 1886.

Henry Pollock, Esq. Treasurer and Vice-President, in the Chair.

Professor John Millar Thomson, F.C.S.

Suspended Crystallisation,

The phenomena attending the ordinary solution of metallic salts
in water have been so often and ably brought before the considera-
tion of this audience, that I have determined to confine myself this
evening to certain considerations relating to the formation of and de-
position from so-called supersaturated solutions of these salts. At the
same time it is necessary for me to remind you of one or two points
connected with the ordinary solution of a salt in water, which I may
enumerate as follows.

The solubility of a salt in water depends :

(a) On the mass of salt presented to the water for solution, and
the state of aggregation in which that mass may be at the time of
solution.

(6) The temperature at which the solution of the salt is carried
out ; rise in temperature generally producing an increase in the
solubility of the salt, although there are certain exceptions to this
rule.

(c) Each salt has its own definite rate or amount of solubility ;
some being extremely soluble, as calcium chloride or sodium acetate ;
others having a very low amount of solubility, as calcium sulphate.

{d) On the cooling of a hot solution containing large quantities
of salt, a deposition of the salt takes place, which deposition is known
under the term " crystallisation."

Certain salts, however, which generally present abnormal pheno-
mena in their solution show no tendency to be deposited from their
solutions on cooling, provided such solutions are kept covered from
the access of the outside air. Such solutions are said to have become
supersaturated.

This branch of the subject is the one which will engage our
attention.

It may be divided into two classes. (1) That which occurs in
the presence of the undissolved salt ; and (2) That which occurs in
the absence of the undissolved salt ; this latter class being the one
we shall examine.

Glauber's salt (sulphate of soda) affords a very good example of this.
If the crystallised sulphate be added to boiling water in a flask, as long

1886.] on Suspended Crystallisation. 509

as it is dissolved the water will take up nearly twice its weight of
salt. If this solution be now allowed to cool in an open vessel an
abundant deposition of crystals will take place, as the water when
cold will only dissolve about one-third of its weight of crystallised
sulphate. But if the flask be tightly corked or stoppered with cotton
wool whilst the solution is boiling, it may be kept for several days
without crystallising, although moved about from place to place. On
withdrawing the plug, however, the air on entering the flask will pro-
duce a slight disturbance of the surface of the fluid, and from that
point beautiful prismatic crystals shoot through the solution until the
whole has become perfectly solid.

It is not necessary in preparing such solutions that the flask be
closed completely with a stopper, as we find that plugging the neck
with cotton wool exercises the same eflfect in preserving the solution,
and that the air which enters the flask during the cooling becomes
thoroughly deprived of its crystallising influence, evidently under-
going a filtering process. A very good instance of the inability of
filtered air to start crystallisation is afforded by a solution of alum
saturated at 194"^ F., and allowed to cool in a flask stoppered with
cotton wool in the manner previously described. On withdrawing
the plug of cotton wool the crystallisation, which in this case takes a
much longer time to commence than with the sulphate of soda, will
be seen beginning at various points on the surface of the liquid, and
will spread slowly from these, octahedral crystals of alum half an inch
or more in length being built up in a few seconds.

It is evident from these two experiments that the cause of this
sudden crystallisation is to be sought for in the peculiar action of the
air when it comes in contact with the solution ; but that it is not due
to the action of the air alone is shown by the fact that the air in the
flask plugged with cotton wool must enter during the cooling, and
that therefore the action of the cotton by filtering the air in some
way deprives it of its active property.

But it will be found that there are other means of destroying this
activity without filtering the air through cotton wool. Thus, if the
solution of sodium sulphate containing two-thirds of its weight of
crystallised salt be allowed to cool in a flask closed by a cork, fur-
nished with two tubes plugged with cotton wool ; on removal of the
cotton plugs air may be blown from the lungs through the longer
tube without causing the crystallisation, apparently from the fact that
the air has been deprived of the nucleus which induces the crystallisation
by passage through the lungs. On blowing air, however, from a
bellows, after a few strokes the solution will be found to solidify
almost instantaneously.

The earliest ideas concerning this sudden solidification were
naturally those which supposed that the mere entrance of air into the
flask upon opening it started the crystallisation. The late Dr. Graham,
and Professor Thomas Thomson, held this view ; and the former of
these chemists carried out a considerable series of investigations on the

510 Professor Thomson [May 14,

action of different gases in determining tbe crystallisation. These
ideas were followed by the statement of Ziz, that not only air but
also solids were capable of acting as nuclei when dry, but that
when wet, or boiled with the solution, or placed in it when hot
and allowed to cool at the same time with it, they lost their effect.
The activity of air, however, as in itself a nucleus, has been sub-
sequently shown by Lowel to be incorrect ; but at the same time
he admits that solid bodies after exposure to air become active.

In 1851 two chemists, Selmi and Goskynski, introduced the
explanation that dry air is active by virtue of its getting rid of the
water at the surface, thus producing small crystals which continue
the action. This seems to be a repetition of the theory propounded
by Gay Lussac, who held that the air absorbed at the surface
precipitated a portion of the salt in the same way that one salt
precipitates another, and that this deposition continued the crystal-
lising action. By an elaborate series of investigations, conducted
in 1866, and also during later years, the French savants, MM.
Gernez and Violette, came to the conclusion that there is only
one nucleus for a supersaturated solution, and that is a crystal
of the body itself; also indicating in certain experiments that
substances which possess the same crystalline form and chemical
structure may be found active to supersaturated solutions of each
other. They have conclusively shown at the same time that
heated or washed air, or bodies of different constitution but chemi-
cally clean, remain perfectly inactive as regards their supersaturated
solutions.

That disruption of the solution may take place without causing
crystallisation when the body added is perfectly clean may be
easily shown by carefully removing the cotton plug from a solution
of sodium sulphate containing only two-thirds its weight of crystals.
On introducing a perfectly clean platinum wire no crystallisation is
induced, but on removing the wire and touching it with a substance
which has not previously been rendered chemically clean, and on
again introducing it in the flask, the moment it touches the liquid
crystallisation is at once induced.

This question of the nuclear action of substances upon these
solutions has received considerable attention from English chemists,
most notably from Mr. Tomlinson, Professor Liversidge, and
Professor Grenfell, all of whom have conducted elaborate researches
on the subject, leading, however, to different conclusions with each
investigator. The arguments held by Tomlinson are strongly in
suj)port of some physical cause for the phenomenon, and that the
result may be brought about by the action of substances possessing
no chemical relations to the solutions experimented on. Professor
Liversidge, on the other hand, has tried the action of several sub-
stances with the most careful precautions, that their addition to the
solutions should be effected without contamination from, or access of,
the external air to the flask during the experiments. The result of

1886.] on Suspended Crystallisation. 511

his inquiries, so far as the substances he has experimented with are
concerned, confirms those of Gernez, and limits the number of bodies
capable of acting as nuclei within very narrow limits. In fact, he
concludes that the only body capable of causing the crystallisation of
such solutions is a crystal of the substance itself, of exactly the same
composition as it possesses when in a state of supersaturation. Thus
Glauber's salt, which exists in a supersaturated solution, combined
with 10 parts of water, will only crystallise by the addition of a
crystal of the substance also containing 10 parts of water, and is
perfectly inactive to crystals of the same salt which contain 7 pro-
portions of water, or those which are anhydrous.

As it is almost impossible to conceive that our atmosphere is
laden with minute particles of the many different metallic salts
which we are acquainted with, some hesitation in accepting such a
limited explanation may be excusable ; but when we consider that it
has been shown by Dr. Angus Smith and others that the aii*, especially
in the vicinity of large manufacturing towns, is filled with small
particles, more especially of Glauber's salt, we are not surprised that
solutions of this body at least crystallise at once on the removal of
the filtering medium. And the probability of the explanation may be
further strengthened by the fact that these solutions when opened
in the still air of country places may retain their liquid condition for
considerable lengths of time.

At the same time the limit fixed by Professor Liversidge may
appear a somewhat narrow one, and experiments made some time ago
and published in the ' Journal of the Chemical Society of London '
(May 1879, and September 1882), have confirmed a few experiments
first indicated by Gernez, and go a considerable length in showing
that bodies possessing not only the same crystalline form but an
identical chemical structure are active nuclei in causing the
crystallisation of supersaturated solutions.

In these experiments two methods for the addition of the nuclei
intended to excite crystallisation were adopted. The first of the^e
consisted of a flask and bulb tube, the supersaturated solution of the
salt to be experimented on being placed in the flask, whilst the small
bulb was filled with a solution of the body intended to act as nucleus.
The solution in the bulb having been thoroughly boiled, the tube is
stoppered with cotton wool and then introduced through the centre
of a second cotton plug into the neck of the flask. The contents of
the flask are now heated, the contents of the bulb receiving a second
warming from the steam rising from the solution in the flask. The
flasks so 23repared are then allowed to stand till perfectly cold before
performing an experiment. When it was desired to perform an
experiment the solution of the body intended as nucleus contained
in the bulb tube is first crystallised by touching with a platinum
wire, or preferably by introducing a crystal of the salt contained
in the bulb. Crystallisation having thus taken place in the bulb,
and the crystal added having become enclosed in the fresh deposit.

Vol. XI. (No. 80.) 2 l

612

Professor Thomson

[May 14,

the bulb is lowered into the liquid contained in the flask and allowed
to remain there for some time to show that the disturbance produced
by its introduction into the fluid does not excite crystallisation. The
bulb is finally lightly brokeu under the fluid and the result observed.
Bulbs also containing water, pieces of washed glass, &c., may be
broken under the supersaturated solutions, to show that the dis-
ruption produced on breaking does not excite crystallisation.

A second method which may be employed for the introduction
of nuclei is that introduced by Professor Liversidge.* This consists
of a siphon tube, in which crystallisation is induced in the first
limb and allowed gradually to pass over the bend and down to the
point of the second limb.

The following table gives the results of many experiments on
the action of isomorphous and also of dissimilar substances on
supersaturated solutions of each other.

IsoMORPHors Sulphates on Magnesium Sulphate.

Substance in solution.

Substance added.

Result.

Remarks.

MgS04.7H.,0 .. ..

ZnSO^.THoO
NiSO,.7H20

Active ..

5> ••

( Crystallisation induced at
\ once, the crystals form-
1 ing long needles.
( Crystallisation indnced af-

CoSO,.7H„0

»>

J ter some time, the crvs-

,,

FeSO^.THoO

5>

J tals forming attached to
\ the nucleus.

,,

MgSO^.TH^O ..

?J

[ Crystallisation induced af-

..

NiSO^-GH^O

»» • •

ter some time, the crys-

reSO,.a-H„0

< tals attached to the nu-

,,

CoSO^-xH^O

5?

cleus generally being
I truncated needles.

Dissimilar Bodies on Magnesium Sulphate.

MgSO,.7H20

MgK.(SO,).,.6H..O
Na.,SO..10HoO ..
Na:S,03.5H;0 ..

NaCr

Glass

Inactive.

Isomorphous Salts on Sodium Sulphate.

Na2SO,.10II.O

Na.,SeO4.10H.,O ..
NaJCrO^.lOH^O ..

Active ..

Crystallisation immediate.

* Proc. Hoy. Soc, xx. 497.

188G.J on Suspended Crystallisation.

Dissimilar Bodies on Sodium Sulphate.

5i;

Substance in solution.

NaaSO^.lOHoO

Substance added.

MgS0,.7IL0
NaoSeO, .." .. .
Na^S.Oa.oH.O .
Na.HP0^.ldH20
KC'l .. ..
NaCl .. ..

KCIO3

Nal.lH^O ..
Glass

Result.

Inactive.

Remarks.

Chrome Alum and Iron Alum on Common Alu3I.

AlK(SO,)2.12HoO..

CrK(S0,\.12H.,0
FeK(SOj2-12H20

The chrome alum solution
was prepared by satu-
rating at 70°, and then
allowing it to crystallise
in the bulb tube.

Bodies of the same form or belonging to the same system, but not
similarly constituted on Alum.

A1K(S0,)2.12H20

NaCl (cubes)
FeSg (cubes)
Fe304 (octahedra)

Inactive.

Hydro-disodic Phosphate and Hydro-disodic Arsenate.

Na2HPO,.12H20

Na2HAsO,.12H20

Crystullication immediate
and very rapid.

When two salts which are not isomorphous are in a suj)ersaturated
solution together a separation of one or other of the salts may be
effected within certain limits. Thus in a mixture of sodium sul-
phate and nickel sulphate, the former may be crystallised by
touching with a crystal of the salt, and in allowing the mixture to
remain at rest for a few minutes the liquor containing the nickel
sulphate may be entirely poured off from the crystals of sodium
sulphate.

A similar phenomenon may be seen by preparing in a long glass
cylinder two supersaturated solutions one above the other, the lower
one being sodium thiosulj)hate dissolved in its water of crystallisa-
tion, the upper one sodium acetate dissolved in a quarter its weight

2 L 2

614

Professor Thomson

[May 14,

of water. When the whole has cooled down under a stopper of
cotton wool a crystal of sodium thiosulphate may be introduced ; this
will pass through the acetate solution without solidifying it, but
will cause the immediate solidification of the thiosulphate solution.

The following phenomena may be seen in experiments carried
out on mixtures of dissimilar salts.

A. When the mixture consists of two salts which are not iso-
morj^hous.

(1) Sudden crystallisation may take place, gradually spreading
through the solution on the addition of a nucleus, causing a deposi-
tion of the body belonging to the nucleus only.

(2) That when sudden crystallisation takes place, causing the
deposition of both salts, there is a prej)onderance of the salt of the
same nature as the nucleus.

(3) That the nucleus may remain growing slowly in the solution,
becoming increased by a deposition of the salt of the same nature as
the nucleus.

B. When the mixture consists of two isomorphous salts.

(1) Sudden crystallisation may occur, giving a deposition of both
salts, apparently in the proportions in which they exist in solution.

(2) That when slow crystallisation takes place, the nucleus
increases by a deposition of the least soluble salt, showing that in
mixed supersaturated solutions a gradation of phenomena may be
experienced, passing from those shown in the crystallisation of a true
supersaturated solution to those shown in the crystallisation of an
ordinary saturated solution.

Passing from the action of nuclei on supersaturated solutions of
mixtures of dissimilar salts, it is interesting to examine the action of
the different constituents on supersaturated solutions of double salts.
The following table gives the results of certain experiments with
such double salts : —

Substance in solution.

Nucleus added.

Result.

HgCl2(NH,Cl)2,8H20
HgBr2(NH"Br)2,3H"2b

HgI,(KI),

A1K(S0,)2,12H20 ..
NaNH,HAs04.4H20

HgClj (prismatic)

HgClz (depositeil from hot
solution).

NH.Cl

HgBr^ (deposited iu the
cold).

HgBrj (deposited from hot
solution^.

(NHJBr

Hglj (needle-shnped crys-
tals).

KI

AU(SO,),18H20 .. ..

K2SO4

NaoHAsO.,12HoO .. ..

(NH,)JIAsO„Aq2 .. ..

Active.

Both active and in-
active.
Inactive.
Active.

Both active and in-
active.
Inactive.
Active.

Inactive.

1886.] on Suspended Crystallisation. 515

From these experiments it will be seen that in the case of the
double salts formed by the halogen acids, certain of the component
salts are capable of inducing crystallisation, but in the case of the
salts formed from acids of higher basicity the component salts are
incapable of causing that particular disruption of the solution.

Having now treated this question experimentally, it may be
of advantage to examine it shortly from a theoretical point of view to
see if any explanation may be offered at least with our present
knowledge of these sudden changes from liquid to solid.

At the present time it would be rash to attempt a comj)lete answer
to the questions —

(a) What fully takes place when a salt dissolves ?

(6) Why some salts always separate out when their hot solutions
are cooled : and conversely why certain ones remain dissolved under
the same conditions ?

In order that a salt may dissolve in water we must suppose some
attraction between the molecules of the salt undergoing solution, and
the molecules of the water. With most salts, the power of the water
to dissolve them is increased with rise of tem^ierature, and this rise
in temperature means increase in the active movement of the water
and the salt molecules, and therefore greater facility for them to
come near enough to one another for their mutual attractions to be
exerted.

Then why do not all salts dissolve more in hot than in cold
water? all do not do so, as you have seen in my diagram during
lecture. This leads us to following up the completion of this
attraction ; namely, the combination of the water and the salt molecules
which I have alluded to in my lecture under the term hydration.

We must suppose that some hydrates exist at a higher temperature
than others, and this is borne out by exj)eriment. In the case of salts
whose hydrates exist only at the lower temperatures, the effect of
raising the temperature would be merely to increase the vibratory
movements and so shake asunder the water and salt molecules, the
dehydrated salt naturally separating out, and therefore we could not
expect more to go into solution by merely heating the liquid.

With regard to the second point. We must remember that there
exists a strong attraction between the individual molecules which
compose the salt. Taking then the case of a salt-like potassium
chlorate, which in the solid state contains no water attached to it.
We dissolve it in hot water, and on cooling, much of the salt sepa-
rates out. We can suppose that the attraction of the water for the
salt and the active movement produced by the rise in temperature
overcome this attraction of salt molecule for salt molecule, but as the
solution cools, this exercises its full force, and crystallisation ensues.

Now, taking the instances where the salt remains in solution
even after cooling, but in much larger quantities than can be obtained
by treating the solid salt with water at that temperature ; this bein»
what I have called " suspended crystallisation."

616 Professor Thomson on Suspended Crystillisation. [May 14,

Let us consider the case of sodium sulphate as perhaps the most
familiar instance. You have seen a large volume of that salt
suddenly solidify on the introduction of the proper nucleus. Now
why did not that salt behave like the potassium chlorate instead
of remaining in solution in the liquid after cooling ?

It has been suggested that this szfper-saturated solution is merely
a saturated solution of the anhydrous salt. That may or may not
be so. If it be the case, we can suppose that the molecules of the
salt and water are prevented from arranging themselves in their
normal order and proportions, and so there is a kind of strain
throughout the liquid. This can only be overcome by something
which will disturb the molecules sufficiently to bring about the neces-
sary rearrangement.

Taking the instance of the susj)ended solidification of water cooled
below its freezing point ; we know that only the disruptive effect of
shaking is required ; but witli sodium sulphate in water and many
others, no amount of shaking, as we have seen, is sufficient. Some
stronger force is required ; this stronger force is found so far as we
know at present only in the attraction for the salt of the body itself,
or of some substance having the same crystalline form and a similar
chemical composition, as has been already shown.

I say advisedly at j)resent, because in my opinion it has not yet
oeen conclusively proved, that no form of what we should call simply
mechanical disturbance may not bring about sudden crystallisation in
these so-called supersaturated solutions. Indeed, there is an interest-
ing experiment which seems to foreshadow such a possibility. By
dropping a single carefully washed crystal of alum into a super-
saturated solution of that salt, we notice a very interesting phenomenon.
The whole surface of the solution is covered with small crystals
separated by definite and considerable intervals, and it appears
as if the mere mechanical disturbance produced by the first crystal
attracting to itself similar molecules, had caused the union of
other molecules to form crystals in the remoter parts of the liquid.
This is, I think, a very interesting case, which if studied with other
similar instances may throw additional light on the causes of such
crystallisation. If we suj)i)ose that the salt exists in solution as a
hydrate, that is, in actual combination with water, we can imagine that
each individual molecule of the hydrate attracts each other one, and
is attracted by it equally ; so if one molecule were to move towards
another, it would be restrained by its neiglibour, and that in its turn
by those near it, and so a state of equilibrium would come about.
However, whatever may be the condition of the salt in solution, the
same cause, namely, the attraction of similar molecules, aj^pears
always to render the equilibrium unstable.

[J. M. T.]

1886.] Sir John Liibhock on the Forms of Seedlings. 517

WEEKLY EVENING MEETING,

Friday, May 21, 1886.

The Duke of Northumberland, K.G. D.C.L. LL.D. President, in

the Chair.

Sir John Lubbock, Bart. M.P. D.C.L. LL.D. F.R.S. M.B.L
The Forms of Seedlings : the causes to which they are due.

Sir John Lubbock commenced, the lecture with some general remarks
on the innumerable types of foliage among mature plants and the
causes to which we might refer their various forms, the breadth of
some and narrowness of others, the differences of position, the dif-
ferences of length in conifers, &c. He said that these considerations
had led him to study the cotyledons or first leaves of seedlings.
Cotyledons do not present such extreme differences as leaves ; never-
theless, they afford a very wide range. Some are broad, some narrow,
some are long, some short, some are stalked, some sessile, some
lobed, some even bifid or trifid. At first sight, these differences seem
interminable, and it might appear hopeless to attempt to explain them.
Sir John Lubbock, however, pointed out, as regards many species,
taking especially the commonest plants, such as the familiar mustard,
and cress, the beech, sycamore, pink, chickweed, &c., the conditions
of their formation and growth, and it is beautiful to see the various
reasons to which the differences are due, gradually unfolding them-
selves ; the same result being sometimes brought about by very
different circumstances, emargination of the cotyledons, for instance,
being due to at least six different causes. He mentioned one curious
peculiarity in the seedling of a species allied to our common mistletoe.
It is a parasitic species, and its fruit, like that of the mistletoe, is
somewhat viscid, so that it adheres to any plant on which it falls.
But, even if it reaches the plant on which it grows, it may light on
an unsuitable position — say, for instance, a leaf. What then happens ?
The radicle elongates for about an inch and then developes on its tip
a flattened disc, which applies itself to the plant. If the situation be
suitable, there it grows ; if not, the radicle straightens itself, tears the
berry from the spot where it is lying, curves itself, and then brings
the berry down on to a new spot. The radicle then detaches itself,
curves in its turn, and thus finds a new point of attachment. We
are assured that this has been seen to happen several times in succes-
sion, and that the young plant thus seems' enabled to select a suitable
situation.

The form of the cotyledons, or scedleayes, depends greatly on that

518 Sir John Luhhock [May 21,

of the seeds, long narrow seeds naturally in most instances producing
embryos with narrow cotyledons. The cases, however, which can be
so simply accounted for are comparatively few. Many plants with
narrow cotyledons have flattened and orbicular seeds. In such
species, however, the cotyledons lie transversely to the seed. An
interesting case is afforded by the pink family, where the jpink itself
has broad cotyledons, while the chickweed has narrow ones. In both
cases the seeds are flattened and orbicular, but in the pink the seed is
dorsally compressed, and the cotyledons lie in the broad axis of the
seed ; while in the chickweed seed is laterally flattened, and the coty-
ledons lie transversely to the seed.

Another very interesting case which he gave is that of the genus
Galium, to which the common " cleavers " of our hedges belongs.
Here also we find some species with narrow, some with broad coty-
ledons ; but the contrast seems to be due to a very different cause.
Galium aparine has broad, Galium saccharatum narrow, cotyledons.
So far as the form of the seed is concerned there is no reason why the
cotyledons should not be much broader than they are. The explana-
tion may perhaps be found in the structure of the pericarp, which is
thick, tough, and corky. It is very impervious to water, and may be
advantageous to the embryo by resisting the attacks of drought and
of insects, and perhaps even if the seed be swallowed by a bird, by
protecting it from being digested. It does not split open and is too
tough to be torn by the embryo. The cotyledons therefore, if they
had widened as they might otherwise have done, would have found it
impossible to emerge from the seed. They evade the difliculty, how-
ever, by remaining narrow. On the other hand, in Galium aparine
the pericarp is much thinner and the embryo is able to tear it open.
In this case therefore the cotyledons can safely widen without endan-
gering their exit from the seed. The thick corky covering of Galium
saccharatum is doubtless much more impervious to water than the
comparatively thin test of Galium aparine. The latter species is a
native of our own Isles, while Galium saccharatum inhabits Algiers,
the hotter parts of France, &c. May not then perhaps, he suggested,
the thick corky envelope be adapted to enable it to withstand the
heat and drought. In this genus, as in many other plants, the
embryo occupies only a part of the seed, being surrounded by a store
of food or " perisperm." In many cases the embryo occupies the
whole seed, and the cotyledons must, therefore, in large seeds, either
be thrown into various folds, as in the beech, or be thick and fleshy
as in the bean or oak. The reasons for their numerous differences
open up an inexhaustible variety of interesting questions. Sir John
gave a great number of examples, which were rendered clearer by
means of numerous diagrams of seeds and seedlings.

In conclusion, he said it might be asked whether the embryo con-
formed to the seed, or the seed to the embryo, and showed that, at
least as regards certain species, the former was the case ; while the
shape of the seed, again, might be shown to be influenced by consi-

1886.] on the Forms of Seedlings. 519

derations connected with the construction of the fruit. In reply to
this, he compared the seedlings of the sycamore and of the oak. In
the sycamore, the seed is more or less an oblate spheroid, and
the cotyledons, which are long and ribbon-like, being rolled up
into a ball fit it closely, the inner cotyledon being generally
somewhat shorter than the others. On the other hand, the nuts
of the beech are triangular. An arrangement like that of the
sycamore would therefore be utterly unsuitable, as it would neces-
sarily leave great gaps. The cotyledons, however, are folded up
somewhat like a fan, but with more comj^lication, and in such a
manner that they fit beautifully into the triangular nut. Can we
however, he said, carry the argument one stage further ? Why should
the seed of the sycamore be globular, and that of the beech triangular ?
Is it clear that the cotyledons are constituted so as to suit the seed ?
May it not be that it is the seed which is adapted to the cotyledons ?
In answer to this, we must examine the fruit, and we shall find that
in both cases the cavity of the fruit is approximately spherical. That
of the sycamore, however, is comparatively small, and contains one
seed, which more or less exactly conforms to the cavity in which it
lies. In the beech, on the contrary, the fruit is at least twice the
diameter, and contains from two to four nuts, which consequently, in
order to occupy the space, are compelled (to give a familiar illustra-
tion, like the pips of an orange) to take a more or less triangular
form. Thus then, he said in conclusion, in these cases, starting with
the form of the fruit, we see that it governs that of the seed, and that
the seed again determines that of the cotyledons. But, though the
cotyledons often follow the form of the seed, this is not invariably the
case. Other circumstances, as I have attempted to show, must also
be taken into consideration, and we can throw much light on the
varied forms which seedlings assume.

I fear you may consider that I have occupied your time by a
multiplicity of details, and I wish I could hope to have made those
little plants half as interesting to you as they have made themselves
to me ; but, at any rate, I may plead that without minute, careful, and
loving study, we cannot hope in science to arrive at a safe and satis-
factory generalisation.

The lecture was accompanied not only by numerous diagrams, but
by specimens, kindly lent by the authorities of Kew, and by some
practical illustrations.

620 Professor Lodge [May 28,

WEEKLY EVENING MEETING,

Friday, May 28, 1886.

Sir Frederick Pollock, Bart. M.A. Vice-President, in the Chair.

Professor Oliver Lodge, D.Sc.

The Electrical Deposition of Dust and SmoJce, with special reference to
the collection of metallic fume, and to a possible purification of
the atmosphere.

The research of which I have the honour to speak in this theatre to-
night, takes its origin in an observation made by Dr. Tyndall,
frequently shown by him in this place, and of which he has published
an account in your ' Proceedings' for 1870.

The phenomenon discovered by Dr. Tyndall was a dark or dust-free
space formed over a hot body when held in strongly illuminated dusty
air. A ilame or hot poker held beneath the concentrated beam of an
electric lantern shows it perfectly, and the appearance is as of wreaths
of black smoke. [Experiment.]

That it is not smoke, but anti-smoke, is perhaps rendered most
evident by observing the utterly diiferent appearance of smouldering
brown paper held in the same place. [Experiment.] In fact it is
manifest that what we see in a sunbeam is not the beam itself but the
dust illumined by it. It is somewhat misleading, though customary,
to speak of the motes as rendering a sunbeam visible ; it is really the
beam which renders visible the motes. And the more motes there
are, the more there is to see, naturally ; hence smoke in the beam
greatly increases its luminosity, while anything which removes or
expels the dust-particles destroys its luminosity, leaving a clear dark
channel.

Now what is the cause of this dust-free space ? The first idea
was that the dust is burned and destroyed by the flame. But this
explanation is negatived by using a moderately warm body, say a hot
kettle, and noticing that above this also the dark space is perfectly
distinct, though narrow.

Dr. Frankland next suggested that much of visible dust consisted
of moisture, and that it was dried and rendered invisible by warmth.
Both explanations can be at once disproved by replacing common
miscellaneous dust of unknown origin by a carefully chosen smoke,
say that of burnt magnesium, which is certainly neither volatile nor
combustible.

Finally Dr. Tyndall suggested an ingenious mechanical explana-
tion, that the air was dragged up in convection currents faster than
its supported dust, which consequently got left behind ; and with this
ho was content.

1886.] on the Electrical Deposition of Dust and Smoke. 521

So the matter rested until 1881, when Lord Eaylcigh re-examined
the phenomenon, " not feeling satisfied with the explanation given by
the discoverer," and conclusively established the inefSciency not only
of all ready-made hypotheses concerning it, but also of those which
occurred to himself. A most interesting reversal of the experiment
was made by Lord Eayleigh, for, instead of holding a warm body
under the beam, he held a cold body above it, and witnessed the for-
mation of a down-streaming dark plane of great sharpness, bordered
by bright fringes of extra dusty air, which he attributed to the dew-
l^oint being passed and the consequent condensation of moisture uj)on
dust-nuclei.

Three years ago I took up the subject at Liverpool, and, with
the active co-operation of the late Mr. J. W. Clark, then acting as
Demonstrator, repeated all known experiments with minute care, in
order to find out the cause of the singular phenomenon.

The results of this research are numerous ; I can do no more than
summarise a few of them to-night, though I believe that some of them,
if followed up, would lead to results of considerable interest. The
first thing we observed was that the ascending dark plane was the
extension and upstreaming of a dust-free coat which invested the
surface of the warm body, and which was really the essential part of
phenomenon, the dark plane being merely an uj^streaming extension
of it. From gently warm bodies the upstreaming dark plane, being
made by the uniting of two coats, one from either side of the body, is
easier to see than the coats themselves, but they are usually quite
distinct, and on the average may be taken as about the hundredth of
an inch thick.

[Appearance of coat and plane shown by diagram.]

Round red-hot bodies the coat is obtrusively evident. We first
observed the coat on the concave side of a hemi-cylinder of sheet
copper. We tried this shape in order to disprove Lord Eayleigh's
suggested explanation that the dust-freeness might be due to the
curvature of the stream-lines and centrifugal force. This idea it
does disprove most effectively, for the curvature being negative on
the inside of the cylinder, dust ought to be thrown towards the body,
instead of being kept well away from it, as in fact it is.

[Lantern slide of planes.]

It is not easy to project the actual dark coat and plane on to a
screen, because the light from the dust particles is but feeble ; but it
is possible to send a beam along the rod, instead of across, and to
show that the dust-free space is more transparent than the sur-
rounding smoky air. In this way a projection of a thick coat and
plane, in light, upon the screen, is easily made.

[Experiment. A platinum wire a few inches long is stretched
across a glass box, and arranged to be pulled straight at all tem-
peratures. A parallel beam is sent exactly along the wire, and
through a lens, the box is filled with brown paper smoke, and a few
Grove cells applied.]

522 Professor Lodge [May 28,

In trying this experiment one often finds a copy of the appearance
imprinted upon the glass wall of the box in smoke, and this dust-
graph also serves to illustrate the phenomenon.

[Projection on screen of dust-graph formed on a vertical glass
plate, where the end of a hot rod is held against it in still dusty
air.]

It may be convenient here to state, at least roughly, the line of
explanation to which we have ultimately been impelled. We regard
it as quite certain that the facts serve as another illustration of the
kinetic theory of gases, of the same kind as Mr. Crookes's radiometer.
The dust particles are kept out of contact with the warm body by
means of a differential molecular bombardment on their surfaces.
True, the thickness of the coat is far larger than the mean free path
of a molecule at the corresponding pressure ; and accordingly no body
as big as a radiometer vane could at that distance be acted upon ; but
Prof. Osborne Eeynolds has shown that very minute bodies are sus-
ceptible to a bombardment at much greater distances ; and it is, I
think, in accord with his theory that dust particles should be repelled
from hot bodies over a measurable distance even at ordinary atmo-
spheric pressure, although radiometer vanes would only be acted upon
at a pressure of a thousandth, or something approaching a millionth,
of an atmosphere. I do not say that this explanation is yet complete,
and I am not aware that any one has adopted it. It is, however,
pretty clear that there will be an outward pressure from the surface
of a hot body,* so long as the air near it is getting warmer : and if
convection currents are allowed, the air near a hot body is continually
in the state of getting warmer.

The main facts which we assured ourselves of may be thus briefly
summarised.

1. The dark plane becomes visible over a cylindrical thermometer
bulb indicating a temperature only half a degree warmer than the air.

2. The dark coat becomes just visible round a body one degree
hotter than the air ; at two degrees it is distinct ; and at five degrees it
is fairly thick.

3. The coat enlarges with diminished pressure, and narrows when
the pressure is increased.

4. In hydrogen the coat is thicker, and in carbonic acid thinner,
than in air,

5. If volatile smoke like volatilised camphor is used, the coats
become thicker, though less sharply defined.

6. Eound a rod of camphor in ordinary smoke the dust-free
coat is extra thick, owing to the extra bombardment of evaporation.

7. liound cold bodies the coat is practically absent, esjiecially on
the top of the body ; and if the cold is too great no descending dark
plane is formed : only a bright one.

* See for instance some experiments of Mr. Crookcs ou rcpulaion by hot
surfaces, described in ' Nature,' vol. xv. page 301.

1886.] on the Electrical Deposition of Dust and SmoJce. 523

8. Liquids containing solid powder in suspension (e. g. dried
ferric oxide in water) form a very narrow dark plane over a
moderately warm cylinder. But the thickness of the plane is so
slight that it is difficult to observe, and it gets thinner with increase
of temperature, instead of thicker as in the case of gases ; hence the
experimental rod in a liquid must be only gently warmed.

The formation of a descending dark plane in dusty air below a
moderately cool body is singular, for it would not naturally have been
expected on the bombardment hypothesis. The dust particles must
be driven towards, instead of away from, a cold body ; and this fact is
obtrusively evident, from the fact that such a body becomes quickly
covered with soot in an atmosphere of MgO or other smoke, while a
warm body remains clear.

It is easy to illustrate this fact by two black conical flasks, one full
of hot water, the other of cold, both put under a bell-jar of thick white
smoke. In about live minutes, if they be taken out, it will be found
that the hot oue is nearly free from soot, the cold one covered as
with hoar-frost.

[Experiment. Either because they were left too long, or for
some other reason which I proceed to investigate, this experiment
in this particular instance completely failed.]

Mr. Aitken, of Edinburgh, has also observed this fact, and has
pointed out that it explains the deposition of soot in chimneys, and
of lampblack on cold glass, Mr. Aitken's paper in the 'Transactions
of the Eoyal Society of Edinburgh ' for 1884, is a most comprehensive
and lucid account of all this part of the subject. His work was
concurrent with ours, as related in the ' Philosophical Magazine ' for
1884, and it is better described.

Bodies colder than the air in contact with them have the dust in
it bombarded on to them ; as is well seen on a wall above hot-water
pipes, or on a ceiling above a gas-jet. Smoking of the gas-jet will of
course provide more material to be deposited, but the dust and smoke
naturally (or unnaturally) in the air are usually ample to effect a
sufficient blackening, over even a perfectly clear flame. An incan-
descent electric lamp hung a foot or so under a white ceiling will
similarly cause a small black patch.

In rooms warmed by radiation (open fire or sunlight) objects
are warmer than the air and keep much dust off themselves ; though
the bombardment may not be sufficiently vigorous to overcome the
gravitation of the larger dust particles, especially over a flat hori-
zontal surface, where convection is sluggish.

In stove-heated rooms things are liable to be colder than the air,
and thus get exceedingly dusty.

The cause of the clearing of smoky air inside a bell-jar by the in-
troduction of a hot platinum wire, or other hot body, as observed by
Tyndall, who called it calcining of the dust, is now manifest : the
dust is bombarded on to the sides and floor of the vessel by the
warmed air. The self-formed picture of dark coat and plane formed

524 Professor Lodge [May 28,

on a glass surface when tbe end of a hot cylinder is held against it
is similarly completely explicable.

But, it may be asked, if dust gets driven towards cold bodies
instead of away from them, how is it that any dark or dust-free
plane forms beneath them ? At very low temperatures I believe it
does not, but rather a bright or dusty layer forms instead. From a
rod a few degrees below the air a fine dark plane is visible, however,
edged by two bright ones. I do not know what Lord Eayleigh's view
of this descending plane is, but it may be due to the gravitative
settling of the dust through the air immediately beneath the cold
body: a thing which is shown to occur by the existence of a thin
dark half-coat formed underneath, but not above, such a rod, and by
the deposit of dust on its upper surface. The rod shelters the
air immediately beneath it from the shower, and so a layer of clear
air forms and streams downward continuously. If the downward
convection currents are too rapid the settling has not time to occur,
and no dark plane is visible.

The original plan of experiment included a series of measurements
of the thickness of the dark-coat at different temperatures (both
excess and absolute), at different pressures, and in different kinds of
gas. This research Mr. Clark had indeed begun to arrange for, but
his untimely death last year cut short this jjart of the investigation.
Another very necessary thing is to see how it varies with size of
dust particles. Meanwhile I had devoted myself to developing a
branch of the subject which we had accidentally hit upon in the
course of testing one hypothesis which had at an early stage occurred
to us as perhaps a clue to the cause of the phenomenon of the dust-
free plane. We thought it possible that air in streaming over
the surface of the solid might get electrified, and that, from air so
electrified, dust might somehow be expelled. To test this hyjDothesis,
we purposely electrified the rod, positively and negatively, to see what
happened. A hundred volts or two produced a barely noticeable
effect ; positive electrification causing a slight widening, negative
electrification, a slight narrowing, of the dust- free coat. But as soon
as the potential rose to a few thousand volts, and brush discharge
began to be possible, a very violent and remarkable effect was
noticed : the dark coat widened enormously and tumultuously, and
the whole box was rapidly cleared of smoke.

To specially observe this new phenomenon is very easy. Fill a
bell-jar with any kind of smoke : tobacco, camj^hor, turpentine, mag-
nesia, amnionic chloride, ammonic sulphite, brown paper, steam,
phosphoric oxide, lead fume, zinc fume, no matter what, and then
discharge electricity into it from a point connected with a Voss or
Wimshurst machine, or even with a common frictional machine, the
other pole of which is connected with the ground or with the base of
the bell-jar.

In a second or two, aggregation of the smoke particles sets in,
they form in masses or flakes along the lines of force, and in another

1886.] on the Electrical Deposition of Dust and Smolce. 625

instant the jar is clear of smoke : it has all been condensed on the
sides and floor of the vessel.

[Experiment.] *

The kind of smoke used is quite immaterial, it is all acted ujion
in the same way, but to make the effect visible to an audience, it is
better to use something which does not dirty or render opaque the
glass. Burning magnesium ribbon makes a very good and clean smoke.
For exi)eriments on a large scale a cheap smoke is obtained by burning
sulphur in the neighbourhood of a pan of ammonia. Whether
positive or negative electricity be used seems to make no difference.

Instead of a single point, a double set of points may be used, each
connected with one pole of the machine. A round knob will act
instead of a point, but not so quickly. Brush discharge, or anything
that electrifies the air itself, is the most effectual. When a knob
or pair of knobs is used, the lines of force are interestingly mapped
out by the dust-flakes.

The cause of the phenomenon is manifest enough. The electri-
fied or polarised particles attract each other, and are attracted by the
opposite poles, just as iron filings are influenced near a magnet. In
thinking over what manifestations of this aggregating power of elec-
tricity were already known, the beautiful observations of Lord
Rayleigh on water-jets occurred to me ; though the cause in this case
is not so clear. The experiment is not so well known as it should be,
and, being an extremely simple one, I venture now to show it. A
vertical water-jet two feet high, from an opening ^V i^^h in diameter,
scatters into drops and falls as a shower like rain ; but hold a piece of
rubbed sealing wax a yard or so distant from the place where the
jet breaks into drops, and they at once cease to scatter : they fall in
large blobs as a thunder-shower.

[Experiment. The rain may be allowed to patter on to paper,
when the difference in sound is very distinct. The air should be free
from electricity beforehand, as the jet is extremely sensitive. |

Clouds can probably be caused to rain by discharging electricity
into them ; at any rate, a cloud of steam in a bell-jar rapidly turns
into Scotch mist or fine rain, and so disappears.

[Experiment. Insulation in this case is a slight difficulty, but it
is easily managed.]

To make a thick mist or fog it is sufficient to introduce a scrap of
burning sulj)hur under the bell-jar ; instantly the country mist becomes
more lilvc a town fog, but this also is rapidly dispersed by electricity.

[Experiment.]

I have ventured to think it possible that the coagulation or com-
bination of oppositely charged dust particles is a gross imitation of

* Note added July 1886, My attention has just been drawn to a paragraph
in 'The Mechanics' Magazine' for November 1850, wherein it appears that this
phenomenon was at that time observed by a Mr. C, F. Guitard ; a fact of which
I had been quite ignorant.

526

Professor Lodge

[May 28

the cohering of oppositely charged atoms in a chemical compound.
When nitrogen and hydrogen are subjected to sparks they unite gra-
dually into ammonia. When a brush discharge passes into oxygen
it aggregates into ozone, as is well known from the smell near an
electrical machine in action. Such actions (especially the latter) do
seem to me of the same nature as the aggregation of charged smoke
particles, though far more refined. The size of a smoke particle is
not great, but it is enormous compared with an atom. Each granule
of a lycopodium cloud may be taken as containing pretty exactly one
trillion molecules. A smoke particle is a good deal smaller than a
lycopodium granule, but not incomparably smaller. It is because of
the minuteness and the interleaved arrangement of oppositely charged
atoms in a compound, that its electrical cajDacity is so enormous ; so
that ten billion units of each kind of electricity can be stowed away
among the atoms of a milligram of water, without raising the poten-
tial of each above a volt or two.*

r

!'!!!!lfi!iii'':''^:'!!!!!!i'll!!iiii''ii

Two bell-jars as used for smoke and fog condensation in lecture
experiments. The one with the point let in at top is for any dry smoke ;
the other is for any damp or acid smoke. Insulation is in this latter
case quite outside the chamber, and the rod, swathed in glass or gutta-
percha, enters through a wide hole in the base-board. The little
flask is only to catch drip. The ivory ball is to be illuminated by
a beam of light, and to shine through the fog as it clears.

* In connexion with this part of the subject, see B.A. Report for 1885
(Aberdeen), page 744, where an electrostatic tlieory of chemistry is discussed.

1886.] on the Electrical Deposition of Dust and Smoke. 527

Application of the Coagulating Power of Electricity to practical

purposes.

In many industries the presence of fine dust or fume suspended
in the atmosphere is highly objectionable, sometimes because of the
poisonous or dangerous nature of the dust, sometimes because it is
valuable and apt to escape and be wasted.

In flour-mills and coal-mines, the fine dust is dangerously explo-
sive. In lead, copper, and arsenic works it is both poisonous and
valuable.

Mr. Alfred Walker, of Walker, Parker & Co., first informed me
of the difficulty which lead-smelters labour under in condensing
the fume which escapes along with the smoke from red-lead smelting
furnaces, and he wished to put an electrical process of condensation
to the test on a large scale.

The devices which are in use at difterent works to collect or
condense this fume are very numerous, and some of them very
cumbersome. Prof. Eoberts- Austen has been kind enough to lend me
diagrams illustrating several of these contrivances.

At Bagillt the method used is a large flue two miles long, coiled
up in the side of a hill between the furnace and the chimney ;
much is retained in this flue, but still a visible cloud of white lead
fume continually escapes from the top of the chimney.

The only difficulty in the way of depositing fume in the flue
by means of a sufficient discharge of electricity, is the violent
draught which is liable to exist there, and which would blow away
mechanically any deposited dust. In some ways the blast may be
helpful, for instance, by keeping the electrical points clear and pre-
venting local clogging, but a large chamber must be provided
somewhere for the coagulated flakes of dust to settle and remain in
calm.

The plan I suggest at present is to line a certain portion of the
interior of a flue with spikes, and then to hang in the middle of it
wire netting, well insulated and studded all over with ragged edges
and points. It may be suspended lengthways in the flue. If the
chamber be very large, it may be well to have a number of long prickly
nets arranged parallel to each other, and kept alternately positive and
negative.

The insulation of the suspended conductor, whatever its shape, has
of course most carefully to be arranged : everything depends upon that.

[Experiment showing the action of an electrical point held above
a model chimney emitting smoke. Its first efioct is to destroy or
reverse the draught : but if the chimney be itself provided with
points at the top, and an electrified cap be held over it, e. g. a small
Bheet of prickly wire gauze, the draught is assisted, and the smoke is
mainly condensed.]

I do not regard this as a good method of dealing with smoky
chimneys : the right way to deal with them is to abolish them, i. e. to
make combustion so perfect that no unburnt matter escapes.

Vol. XI. (No. 80.) 2 m

528 Professor Lodge [May 28,

The experiment illustrates, however, that smoke can be caught and
deposited on the wing.

[Special apparatus for producing and condensing quantities of
smoke was next shown in action. It could be kept electrified by a
splendid machine kindly lent by Mr. Wimshurst, but a small Voss
machine was amply sufficient for the purpose. After the lecture I
had an opportunity of trying Mr. Wimshurst's 8 -plate machine on
the smoke-chamber, and the rapidity with which it was cleared was
surprising. Eoughly speaking it might be called instantaneous.]

When such a machine as this of Mr. Wimshurst's comes to be
used, one may hope to make an impression on fume produced on a
manufacturing scale. But further data in this direction are desirable.

Leaving these sublunary and industrial applications, let us ask
finally if there may not perhaps be some possible mode of artificially
affecting atmospheric conditions by means of electricity. It certainly
seems to me rather probable ; and I should much like to have the
means of discharging a large quantity of high-pressure electricity
into the air, either for the purpose of acting on a fog, or in the hope
of perhaps affecting the weather.

This much I regard as certain, that if a kite or a captive balloon
(a kite for windy days, a balloon for calm ones) be flown into a
cloud, and made to give off electricity for some time, that cloud will
begin to rain.

It is just possible, though hardly probable, that by the automatic
coalescence of drops into larger ones, the potential of the charge so
given could become high enough to cause an artificial thunderstorm.
The amount of electricity in a thunderstorm is not very great
(Faraday reckoned it as less than the amount in a thimble-full of water,
and he was quite right) ; its potential is enormous, but there is
certainly some automatic regenerative action going on in the atmo-
sphere, which is able to raise the potential of a given charge higher
and higher until a flash occurs.

It is well known, from observations made with Sir W. Thomson's
atmospheric recorder, that variations in the electrical condition of the
air precede a change of weather, but it is not known which is cause
and which is effect in this case.

With a very large voltaic battery such as that constructed by Dr.
de la Rue, or perhaps even a bigger one, of sufficient E.M.F. to give
a constant brush discharge from points, a tremendous quantity
of electricity could be poured into the atmosphere, and its electrical
condition could be certainly disturbed.

Whether this disturbance would be beneficial or not, is, I know,
another matter. I do not see how one is to tell without trying the
experiment.

Perhaps usually the weather is best left alone ; but there are times
when any change feels as if it must be for the better.

Very little is known at present concerning the causes operating in
the formation and dissipation of those Cyclones which act so powerfully

1886.] on the Electrical Deposition of Dust and Smohe. 529

on our climatic conditions as to be now the main object of study with
meteorologists, since Mr. Buchan proved to us their existence and
showed us how to study them. Some of them are gigantic, but some
are small and almost local whirls. A long way we are at present
from even entertaining the idea of artificially controlling them ; but
we have learnt to control a great number of natural agents — torrents,
cataracts, fire, electricity ; and the main effect of a thunderstorm on a
civilised town is now merely to clear its air and stir up its lightning
conductors. Storms, earthquakes, and volcanoes we have not yet
learnt to control, perhaps we never shall. Perhaps also we may
always remain unable to exert any effect even on ordinary winds,
clouds, and rain ; but the interests involved at certain seasons of the
year in the presence or absence of a succession of rain-compelling
cyclones, or of frost- and sun-transmitting anti-cyclones, are so
prodigious, that even the barest glimpse of the possibility of exerting
any kind of effect upon these great agents is worth attention, and it
is a subject eminently suited for experiment. The experiments,
however, must be on a large scale, and must be costly ; were it not
so, I for one should not hesitate to make some preliminary attempts
in the direction indicated.

Beferences to the Literature of the Subject.

Proc. Roy. Inst. vi. p. 1 (1870), Tyndall (Discovery of dust-free space).

Proc. Eoy. Soc. xxv. p. 542, Frankland (Brief).

" Floating Matter of the Air," Tyndall, p. 5.

Proc. Eoy. Soc. December 1882, or Nature, xviii. p. 139, Lord

Rayleigh (Dark plane).
Nature, 26th July, 1883, xxviii. p. 297, Lodge (Preliminary Letter).
Nature, 31st January, 1884, Aitken (Abstract).
Phil. Mag. March, 1884, or Proc. Phys. Soc. February 1884, Lodge and

Clark (Main paper, with plate).
Trans.R. S. Edin. xxxii. p. 239 (1884), Aitken (Main paper, with plate).
Minor Papers :

Nature, 24th April, 1884, Lodge (Lecture to Eoyal Dublin Society,
on Dust- free spaces).

Nature, 22nd January, 1885, Lodge (Lecture to Brit. Assoc.
Montreal, on Dust).

Nature, xxix. p. 417, Lodge and Clark (Abstract).

Engineering, 5th June, 1885, Walker.

Engineering, 21st May, 1886, Wimshurst.

La Nature, or Electrician, 21st May, 1886, Tissandier.
Nature, xv. p. 302 (1877), Crookes (Eepulsion by hot Surface).
Phil. Trans. 1879, ii. p. 727, Osborne Reynolds (Dimensional

Properties of Gases).
Proc. Eoy. Soc. March and May, 1879, and June 1882, Lord

Eayleigh (Liquid jets).
Brit. Assoc. Eeport, 1885, pp. 744 et seq. Lodge (Electrostatic view

of Chemical Action). [O. L.]

2 M 2

530 Mr. Walter H. Gaskell [June 4,

WEEKLY EVENING MEETING,

Friday, June 4, 1886.

John Rae, M.D. LL.D. F.R.S. Manager, in the Chair.

Walter H. Gaskell, M.D. M.A. F.R.S.

The Sympathetic Nervous System.

The lecturer commenced by giving a short sketch of Bichat's views
of the division of life into organic and animal life, and pointed out
Low that division naturally led to the conception of two separate
central nervous systems, the one, the sympathetic, to which all the
organic functions are to be referred, the other, the cerebro-spinal,
regulating the animal functions. He then pointed out how Remak's
discovery of a special kind of nerve-fibre, — the non-meduUated nerves
— associated only with the ganglia of the sympathetic system, tended
strongly to confirm Bichat's teaching of the existence of two separate
central nervous systems in the human body, each of which com-
municated with the other by means of its own special kind of nerve-
fibres; the cerebro-sj)inal supplying the sympathetic system with
white meduUated fibres, and the sympathetic supplying the cerebro-
spinal with grey or gelatinous non-meduUated fibres. He then con-
tinued as follows : —

Even at the present day the teaching of Bichat still very largely
holds its ground. It is true that the tendency of modern physiology
is to increase the number of centres of action for the organic nerves,
which exist in the cerebro-sj)inal central axis, and therefore to do
away with the necessity for a separate independent symj)athetic
nervous system, yet the automatic actions of isolated organs such
as the heart, and the existence of special nerve-fibres in connection
with this system still induce the neurologists of the present day to
place the sympathetic nervous system on an equality with the brain
or spinal cord. In this lecture to-night I hope to give the death-blow
to Bichat's teaching, and to prove to you that the whole sympathetic
system is nothing more than an outflow of visceral nerves from certain
nerve-centres in the cerebro-spinal system, the ganglia of which are
not confined to one fixed position as is the case with the ganglia of
the posterior roots, but have travelled further away from the central
axis.

I do not propose to-night to deal with the argument for the inde-
pendence of the symj^athctic nervous system, which is based upon the
automatism of such isolated organs as the heart ; I have already in
various papers given the reasons and arguments why I look upon
such automatic movements as due to the automatism of the cardiac

1886.] on the Sympathetic Nervous System. 531

muscular tissue rather than to any action of nerve-cells comparable
to the nerve-centres of the spinal cord ; I shall deal entirely with the
anatomical argument and show you step by step how the nerve-iibres
which constitute the symj^athetic system can be traced to their origin
in the central cerebro-spinal axis.

Evidently, in endeavouring to determine by anatomical means
whether the sympathetic and cerebro-spinal systems are in reality
independent of one another, our attention must necessarily be
especially concentrated upon the nature of the connecting link be-
tween the two systems, i. e. upon the nature of the rami communi-
cantes. Largely owing to the preconceived notions of anatomists,
you will find that the rami communicantes are arranged symmetrically
in connection with all the spinal nerves of the body. In reality this
is far from being the case, the rami communicantes of the thoracic
nerves differ from those above them, i. e. of the cervical nerves, and
from those below them, i. e. of the lumbar nerves, in two important
particulars : in the first place the corresponding sympathetic ganglion
is connected with each thoracic nerve by two rami communicantes ;
and secondly, these two rami differ in colour, one being grey, i. e.
composed almost entirely of non-medullated nerves, and the other
white, i. e. composed essentially of medullated nerve-fibres.

This double nature of the ramus communicans is confined to the
region lying between the two large plexuses which supply the anterior
and posterior extremities, viz. the brachial, lumbar, and sciatic
plexuses; the rami communicantes to the lower cervical and first
thoracic nerves, as well as those to the nerves forming the anterior
crural and the sciatic, are, on the other hand, single, and are composed
only of grey rami. In other words, the sympathetic chain is con-
nected with the central nervous system by means of white rami com-
municantes only between the second thoracic and second lumbar
nerves.

Further, I have been able to trace both the white and grey rami
in their journey to the spinal cord by means of consecutive sections
of osmic acid preparations, and have found that the grey rami pass
out of the sympathetic ganglion as a single nerve, and then ramify in
the connective tissue about the vertebral foramina, a portion only
reaching the spinal nerve-trunk ; the grey fibres of this portion pass
mainly along the nerve peripherally, the few which pass centrally
never reach the spinal cord, but pass out with the connective tissue
which lies in between the medullated nerve-fibres of the anterior and
posterior roots, to ramify over and to supply the blood-vessels of the
various membranes which inclose the spinal cord.

In fact the grey rami communicantes are peripheral nerves, which
partly supply the vertebrae and the membranes of the cord, and partly
pass to their destination in the same direction as the efferent fibres
of the spinal nerve itself.

So far then I come to these conclusions :

1. The sympathetic does not send non-medullated fibres into the

632 Mr. Walter H. Gaskell [June 4,

cerebro-spinal system, because these fibres all pass out of the nerve-
roots before they reach the spinal cord.

2. White or medullated nerve-fibres constitute the only link
between the sympathetic and cerebro-spinal systems, constituting the
white rami communicantes.

3. Consequently the connection between these two nervous
systems is limited to the region of white rami communicantes, i. e. to
the region between the second thoracic and second lumbar nerves.

Fui'ther, these conclusions are borne out when we attempt to
follow the white rami communicantes into the central spinal axis by
means of their structural peculiarities ; sections of osmic preparations
show that each white ramus is composed chiefly of very small
medullated nerve fibres, varying in size from 1*8 /x to 3*6 ya, very
much smaller, therefore, than the large medullated nerves which form
the bulk of the anterior roots of the spinal nerves, these latter varying
between 14 ^ to 20 /x or even larger. Clearly then the fibres of the
white ramus communicans ought to show very conspicuously among
the large fibres of the anterior roots whenever they are present in those
roots. I have cut sections of the anterior roots of all the spinal nerves
in the dog, and have found, as I show you on this screen, that these very
fine medullated nerve-fibres make their appearance for the first time
in the anterior roots of the second thoracic nerve ; they are found in
large quantities in all the anterior roots between the second thoracic
and second lumbar, and then again the anterior roots immediately
below the second lumbar are free from such groups of very fine fibres.
We see then that exactly corresponding to the presence of white rami
communicantes in the thoracic region we find groups of characteristic
fine medullated fibres existing in the anterior roots, fibres which
clearly form part of the white ramus communicans, and confirm by
their presence the conclusion already arrived at, viz. that the nerves
which pass from the spinal cord into the sympathetic system are
limited to the thoracic region of the cord.

We can now go a step further and argue in the reverse direction
that the presence of groups of these very fine medullated fibres in
the anterior roots of any nerve implies the existence of nerve-fibres
belonging to the same system as the white rami communicantes or
rami viscerales as we may now call them. Examination shows how
just is this argument, for I find that the same groups of fine nerve-
fibres suddenly appear again in the anterior roots of the second and
third sacral nerves, and can be traced into that well-known nerve
which passes from the second and third sacral nerves into the hypo-
gastric plexus to supply the rectum, bladder, and reproductive organs ;
a nerve, therefore, which may be looked upon as the white ramus
communicans of the sympathetic ganglia which form the hypogastric
plexus.

Again, in the cervical region, although such groups of fine fibres
are absent from the anterior roots of all the cervical nerves, yet they
form a conspicuous part of the upper roots of the spinal accessory

1886.] on the SympatJietic Nervous System. 533

nerve, and upon tracing them outwards I find that they separate
entirely from the large fibres of the accessory which form its external
branch, to pass as the internal branch into the ganglion trunci vagi
(see Fig. 2, p. 536). Here, then, we see in the upper cervical region
that the internal branch of the spinal accessory nerve is formed on the
same plan as a white ramus communicans, the ganglion belonging to
which is the ganglion trunci vagi.

Among the cranial nerves we find, especially in the vagus, glosso-
pharyngeal, and chorda tympani, groups of fine nerve-fibres belonging
to the same system. We can therefore say that the communication
between the so-called sympathetic and cerebro-spinal systems is not
symmetrical throughout, but consists of three distinct outflows of
characteristic visceral nerves, viz. : 1, cervico-cranial ; 2, thoracic ;
3, sacral, the break of continuity corresponding to the exit of the
nerve plexuses which supply the upj^er and lower extremities.

These medullated visceral nerves then pass out from the central
nervous system into the various ganglia of the sympathetic, and it is
possible that these latter ganglia bear the same kind of relation to
them as the ganglia on the posterior roots bear to the sensory nerves.
Before, however, we can accept this view it is absolutely necessary to
account for the non-medullated nerves which arise from the sympa-
thetic ganglia. Now it is hopeless to follow, by anatomical means,
any special nerve-fibre through the confusion of a ganglion. What
we cannot effect by anatomical methods we can by physiological. If
we find two nerves, one of which enters a ganglion and the other
leaves it, and we find their function absolutely the same on both sides
of the ganglion, we have a perfect right to conclude that we are
dealing with the same nerve in different parts of its course. Thus,
in the case of the posterior root ganglion, the same sensory nerves
are found on each side of the ganglion, although they are in connec-
tion with nerve-cells of the ganglion itself.

So also with the sympathetic ganglia ; we know, for instance,
that the nerves which increase the rate and strength of the heart's
beat, pass to the ganglion stellatum along the rami communicantes of
the second and following thoracic nerves, and we know also that the
same nerves pass to the heart from the ganglion stellatum, from the
annulus of Vieussens, and from the inferior cervical ganglion. Now
seeing that these nerves are known to pass out of the cord in anterior
roots, and from thence into the white rami communicantes of the
upper thoracic nerves it follows that they are medullated in this part
of their course, and are to be found among the bundles of very fine
medullated nerves which we have seen are characteristic of the
anterior roots of this region and of the white rami communicantes.

We can then say with certainty that the accelerator nerves enter
the ganglia stellata as fine white medullated nerves. I am also able
to say with absolute certainty that the accelerator nerves in that
part of their course which lies between the chain of sympathetic
ganglia and the heart are entirely composed of non-medullated fibres.

534 Mr. Walter H. Gaskell [June 4,

I know no other bundle of nerve-fibres wliicTi is so absolutely free
from meduUated nerves : in other words, nerve-fibres of the same
function enter a sympathetic ganglion as white medullated fibres
and leave it in increased numbers as grey non-meduUated nerves.

Throughout we find the same fact, all the vasomotor nerves behave
in exactly the same manner as the accelerators of the heart. In all
cases the non-medullated fibres of the sympathetic are simply the fine
medullated visceral nerves which have passed from the spinal cord in
one or other of the three visceral outflows and lost their medullary
Bheath in their passage through the ganglia of the sympathetic system ;
together with that loss of medulla they have increased in number by
division.

Seeing then that the non-medullated (so-called sympathetic)
nerve-fibres are throughout modified medullated (so-called cerebro-
spinal) fibres, and do not, therefore, arise in the sympathetic ganglia,
we may fairly look upon the sympathetic ganglia as bearing the same
kind of relation to the visceral nerves that the ganglia of the posterior
roots bear to the ordinary sensory nerves. This conception is re-
markably confirmed by the observations of Onodi, who has shown that
the ganglia of the sympathetic are developed in close connection with
the posterior root ganglia, and travel further away from the central
axis as the animal grows.

Finally, the meaning of the sympathetic as a simple outflow of
ganglionated visceral nerves from certain portions of the spinal cord
and medulla oblongata is to my mind conclusively settled by the
intimate relationship which exists between the structure of the spinal
cord and the presence or absence of rami viscerales. In the grey
matter of the spinal cord we find, as shown in the accompanying dia-
gram, certain well-defined groups of nerve-cells, viz. a, a group of
large nerve-cells in the anterior horn (4 in Fig.) ; these are known to
be the origin of ordinary motor-fibres (4) ; h, a group of nerve-cells
(3) split off from this and forming the lateral horn ; c, a group (2)
known as Clarke's column; and d and e, two sets of nerve-cells
(4 and 5) in the posterior horn connected with sensory nerves. All
these groups of nerve-cells are found along the whole length of the
spinal cord, except those of Clarke's column. Their connection with
nerve-fibres of different functions is known, except those of Clarke's
column. Thus both sets in the anterior horn are connected with
ordinary motor nerves ; both sets in the posterior horn with ordinary
sensory nerves. Now Clarke's column is limited to certain definite
regions of the cord, being conspicuous : firstly, between the second
thoracic and second lumbar nerves ; secondly, at the top of the cervical
region and extending into the cranial region ; and thirdly, an isolated
patch in the sacral region. In other words, its cells correspond
exactly in position to the distribution of tlie white rami communi-
cantes, so that, corresponding to the variation of this cell-group we
find variations of the number of very fine medullated fibres in the
anterior roots, and we find corresponding variations in the white rami

1886.]

on the Sympathetic Nervous System.

535

communicantes, which latter, as I have told you, are the only true
connections of the cerebro-spinal nerve-centre with the sympathetic.
In other words, we have driven home to their origin these visceral
nerve-fibres, and we find that they do not arise from any nerve-cells
outside the brain and spinal cord, but from a definite nerve-group
within the spinal cord.

Fig. 1.

Fig. 1. — Diagram of section of spinal cord to show the various groups of
nerve-cells in the grey matter, and the formation of a spinal nerve with its
sympathetic ganglion.

1. Cells of posterior horn and somatic sensory nerves.

2. Cells of Clarke's column and ganglionated splanchnic nerves.

3. Cells of lateral horn and non-ganglionated splanchnic nerves.

4. Cells of anterior horn and somatic motor nerves.

5. Solitary cells of posterior horn and splanchnic sensory nerves.

We can, I think, go further than this, and say, with Bichat,
that two nerve-systems do exist, the one for organic, and the other
for animal life. These two, however, are not separate and distinct,
but form parts of the same central nervous system. Looking
at this diagram of the upper cervical region of the cord, we see
that the voluntary striped muscles may be divided into two groups,
according to their nerve supply, viz. a group supplied by the
anterior (4), and one by the lateral horn of nerve-cells (3), and we
know also that these two groups of nerve-cells separate from one
another more and more as we pass into the brain region. So that we
find for the muscles of the face a distinct separation of two groups,
viz. 1, those which move the eyes and the tongue — these are supplied
by nerves which arise from the continuation of the anterior horns ; and,
2, the muscles of expression and mastication, the nerves of which arise
from the continuation of the lateral horn ; and remembering how the
smile, the laugh, and the snarl, as well as the action of swallowing, are
at the bottom only modified respiratory movements, we see that Charles
Bell was not so far wrong when he inserted a lateral or respiratory
system of nerves in between the anterior and posterior roots. This
insertion is actually to be seen at the upper part of the cervical cord

536

Mr. Walter H. Gaskell

[June 4,

(see Fig. 2), where a separate nerve is formed by elements whicli arise
laterally, known as the spinal accessory, and what is most striking is
this fact, that in this region the fine medullated fibres (2 in Fig.) are
found only in connection with these lateral motor nerves, and not with

Fig. 2.

Gangl. Ininn.

bil.ltrannh

the anterior motor, so that not only do these lateral or respiratory tracts
supply special muscles with motor nerves, but these motor nerves
have a closer relationship to the visceral nerves than other motor
nerves. What is true of the upper cervical region is true also of the
medulla oblongata. Here again, the visceral fine medullated nerves

1886.] on the Sympathetic Nervous System. 537

are closely connected with the motor fibres which arise from the
lateral horn, e. g. the chorda tympani and the facial. Undoubtedly
this particular group of muscles has some closer relationship to the
viscera than other trunk muscles, and that relationship is explained
immediately if we can accept and extend van Wijhe's investigations,
viz. that in the cranial region the muscles which are supplied by the
third, fourth, sixth, and twelfth cranial nerves are derived from the
myotomes, while the muscles supplied by the seventh and fifth
cranial nerves are derived from the lateral plates of mesoblast.

In fact, we may look upon the body as composed of two parts —
an outside or somatic part, and an inside or splanchnic part. Each
part has its own system of voluntary muscles ; each part is supplied
by nerves arranged on the same plan, viz. a ganglionated and non-
ganglionated portion ; and each part has its own individual centres of
action, the inside portion of the grey matter of the spinal cord con-
taining the centres for the splanchnic roots (2, 3, 5, in Fig.), i. e. the
centres of organic life ; the outlying horns the centres for the somatic
roots (1 and 4), i. e. centres for the animal life. It is a strange and
suggestive fact that these two sets of centres are not arranged sym-
metrically along the spinal axis, but that two great breaks occur in
which the centres of organic life fall into the background in com-
parison to those of animal life. These two great breaks correspond
to the origin of the nerves for the legs and arms, and suggest that
the formation of the limbs in the originally symmetrical ancestor of
the vertebrata — i. e. the large outgrowth of somatic elements in two
definite portions of the body, caused of necessity a corresponding
increase in the centres for animal life, while there was no necessity
for a corresponding increase in the centres for organic life. The
oldest part of us is undoubtedly the vital part ; those organs and
their nervous system by which the mere act of existence is carried on.
With these two there may have been originally a symmetrical seg-
mental arrangement of locomotor organs. Such symmetry, however,
went for good when it was found more convenient to concentrate the
locomotor machinery into the anterior and posterior extremities and
with the asymmetrical arrangement of the locomotor organs disap-
peared also the symmetry of the central nervous system. This cor-
respondence between the plan of the central nervous system and the
development of the extremities is to my mind strongly in favour of
the view which I have put before you to-night. In conclusion, I
thank you for the kindness with which you have listened to me, and
hope that I have succeeded in convincing you that Bichat's teaching
of an independent sympathetic system is finally dead.

[W. H. G.]

538 General Monthly Meeting. [June 7,

GENERAL MONTHLY MEETING,

Monday, June 7, 1886.

Sir Fbederick Abel, C.B. D.O.L. F.R.S. Vice-President, in
the Chair.

The following Vice-Presidents for the ensuing year were
announced : —

Sir Frederick Abel, C.B. D.C.L. F.R.S.

Sir William Bowman, Bart. LL.D. F.E.S.

Eight Hon. The Lord Halsbury.

William Huggins, Esq. D.C.L. LL.D. F.R.S.

Sir John Lubbock, Bart. M.P. D.C.L. LL.D. F.R.S.

Sir Frederick Pollock, Bart. M.A.

Henry Pollock, Esq. Treasurer.

Sir Frederick Bramwell, F.R.S. Honorary Secretary.

Sir Nathaniel Barnaby, K.C.B.
Charles Selby Bigge, Esq. J.P.

were elected Members of the Royal Institution.

The Presents received since the last Meeting were laid on the
table, and the thanks of the Members returned for the same, viz. : —

FEOM

The Governor- General of India — Geological Survey of India. Records, Vol. XIX.

Part 2. 8vo. 1886.
Ministry of Public Worhs, i?ome— Giornale del Genio Civile, Serie Quarta,

Vol. VI. No. 3. 8vo. And Disegni. fol. 1886.
Accademia dei Lincei, Beale, Roma — Atti, Serie Quarta : Rendiconti. Vol. II.

Fasc. 8, 9. 8vo. 1886.
Academy of Natural Sciences, Philadelphia — Proceedings, 1885, Part 3. Svo. 1886.
Agricultural Society of England, Royal — Journal, Second Series, Vol. XXII.

Part 1. 8vo. 1886.
Aahhurner, C. A. Esq. (the Author)— Geology of Natural Gas in Pennsylvania.

Svo. 1885.
Product and Exhaustion of the Oil Regions of Pennsylvania and New York.

8vo. 1885.
Asiatic Society, i?o?/aZ— Journal, Vol. XVIII. Part 2. Svo. 1886.
Astronomical Society, Royal — Monthly Notices, Vol. XL VI. No. 6. Svo. 1886.
Bankers, Institute o/— Journal, Vol. VII. Part 5. Svo. 1886.
Bell, Sir Loivthian, Bart. F.R.S. M.R.I (the Author)— Iron Trade of the United

Kingdom. Svo. 1886.
Birt, W. Esq.— KoVidny Notes in East Anglia. 12mo. 1886.
British Architects, Royal Institute of — Proceedings, 1885-6, No. 16. 4to.

1886.] General Monthly Meeting. 539

Chemical Society — Journal for May, 1886. 8vo.

Domville, Wm. H. Esq. M.B.I. — Natural History Journal of the Hungarian

National Museum, 1882. 8vo. 188.S.
East India Association— Journal, Vol. XVIII. Nos. 2, 3. 8vo. 1886.
Editors — Amateur Photographer for May, 1886. 4to.

American Journal of Science for May, 1886. 8vo.

Analyst for May, 1886. 8vo.

Athenseum for May, 1886. 4to.

Chemical News for May, 1886. 4to.

Engineer for May, 1886. fol.

Horological Journal for May, 1886. 8vo.

Industries, Part 1. fol. 1886.

Iron for May, 1886. 4to.

Nature for May, 1886. 4to.

Eevue Scientifique for May, 1886. 4to.

Telegraphic Journal for May, 1886. 8vo.

Zoophilist for May, 1886. 4to.
Franklin Institute — Journal, No. 725. 8vo. 1886.
Geographical Society, Boyal — Proceedings, New Series, Vol. VIII. No. 5. 8vo.

1886.
Geological Society — Quarterly Journal, No. 166. 8vo. 1886.
Gordon, Surgeon-General C. A. M.D. C.B. M.B.I, (the Author-) — New Theory and

Old Practice in Medicine, &c. 8vo. 1886.
Hamhleton, G. W. Esq. (the Author)— What is Consumption ? 8vo. 1886.
Harlem Societe' Eollandaise des Sciences — Archives Ne'erlandaises, Tome XX.

Liv. 4. 8vo. 1886.
Historical Society, Boyal — Transactions, New Series, Vol. III. Part 2. 8vo.

1886.
Johns Hopkins University — Studies in Historical and Political Science, Fourth
Series, No. 5. 8vo. 1886.

University Circular, No. 48. 4to. 1886.

American Chemical Journal, Vol. VIII. No. 2. 8vo. 1886.
Laivrence-Hamilton, J. Esq. M.B.I. — Allgemeines Handbuch der Freimaurerei.
3 vol. 8vo. 1863-7.

Francma(;onnerie. Par J. M. Eagon. 6 vol. 8vo.

CEuvres Ma^onniques de N. C. Des Etangs. Par F. D. Pillot. 8vo. 1848.

Manuel Ma^onniques. 8vo. 1820.

Cours Oral de Franc-Ma^onnerie Symbolique. Par H. Cauchois. 8vo. 1863.

Collection des Cahiers des Grades Symboliques. 4to. 1858.

Explication des Douze Ecussons. Par F. Bouilly. 4to. 1838.

Etudes Historiques et Symboliques sur la Franc-Ma9onnerie. Par F. Vaillant.
12mo. 1860.

Eecueil Precieux de la Maconnerie. 16mo. 1786.

Le Secret de la Socie'te des Mopses. 16mo. 1745.

Katechismen der Freimaurerei. Von E. Fischer. 3 vol. 12mo. 1873-5.

Masonic Eitual and Monitor. By M. C. Duncan. 12mo. 1866.

Manual of Freemasonry. By E. Carlile. 12mo.

Freemason's Monitor. By T. S. Webb. 12mo. 1868.

Les Eituels Ma9onniqucs avec Commentaires. Par J. Lawrence-Hamilton.
8vo. 1873.

Catalogue of Books on Freemasonry, &c. 8vo. 1870.
Linnean Society — Journal, Nos. 143-4, 150. 8vo. 1886.
Madden, T. More, Esq. (the Author) — Memorials of Dr. E. E. Madden. 8vo.

1886.
Manchester Geological iSoczeit/— Transactions, Vol. XVIH. Parts 17, 18. 8vo.

1886.
Meteorological Office — Monthly Weather Eeport for Dec. 1885 and Jan. 1886. 4to.
Meteorological Society, Boyal — Quarterly Journal, No. 58. 8vo. 1886.

Meteorological Eecord, No. 20. 8vo. 1886.

540 General Monthly Meeting. [June 7,

National Association for Social Science — Conference on Temperance Legislation,

London, 1886. 8vo.
National Life-boat Institution, Eoyal — Annual Keport, 1886. 8vo.
Odontological Society of Great Britain — Transactions, Vol. XVIII. No. 7. New

Series. 8vo. 1886.
Pharmaceutical Society of Great Britain — Journal, May, 1886. 8vo.
Photographic Society — Journal, New Series, Vol. X. No. 7. 8vo. 1886.
Eohins, E. C. Esq. {the Author)— The Site of the new Admiralty and War OflBces.

8vo. 1886.
Saxon Society of Sciences, Royal — Mathematische-Physische Classe :

Abhandlungen, Band XIII. No. 5. 8vo. 1886.
Second Geological Survey of Pennsylvania — Reports A A and Atlas, C 5 and T 3.

8vo. 1885.
Smith, Basil Woocld, Esq. iJf.E.I.— Middlesex County Records. Vol. I. Edited

by J. C. Jeaffreson. 8vo. 1886.
Society o/^rfe— Journal, May, 1886. 8vo.
St. Pe'tershourg, Acade'mie des Sciences — Bulletins, Tome XXXI. No. 1. 4to.

1886.
Tasmania Royal Society — Proceedings for 1885. 8vo. 1886.
United States Geological Survey — Bulletins, Nos. 15-23. 8vo. 1885.
Vereins zur Beforderung des Gewerhfleisses in Preussen — Verhandlungen, 1 886 :

Heft 4. 4to.
Victoria Institute— J omnal, No. 77. 8vo. 1886.

1886.] Prof. Dewar on Becent Besearches on Meteorites. 641

WEEKLY EVENING MEETING,

Friday, June 11, 1886.

Henry Pollock, Esq. Treasurer and Vice-President, in the Chair.

Professor Dewar, M.A. F.R.S. M.B.I.

Becent Besearches on Meteorites.

Professor Dewar explained that Mr. Gerrard Ansdell and himself
had been engaged in an examination into the gaseous constituents of
meteorites, and he proposed this evening to abstract the results of the
investigation, which had been laid before the Eoyal Society.

The nature of the occluded gases which are present to a greater or
less extent in all meteorites, whether belonging to the iron, stony, or
carbonaceous classes, has engaged the attention of but few chemists.
It is, nevertheless, an especially interesting and important subject,
owing to the uncertainty which still exists as to the origin of these
celestial bodies.

Graham (Proc. Eoy. Soc. vol. xv. (1867) p. 502) was the first
who made any experiments in this direction, when he determined the
gases occluded in the Lenarto meteoric iron, which yielded 2 • 85 times
its volume of gas, 86 per cent, of which was hydrogen, and 4*5 per
cent, carbonic oxide. He was followed in 1872 by Wohler (Pogg.
Ann. vol. cxlvi. p. 297) and Berthelot (Compt. Eend. vol. Ixxiv.
pp. 48, 119), who estimated approximately the gases contained in the
Greenland Ovifak iron. These gases consisted of about equal parts
of carbonic acid and carbonic oxide ; the celestial origin of this iron
is, however, very doubtful.

In the same year (1872) the American chemist. Mallet (Proc.
Roy. Soc. vol. XX. p. 365), made a very complete determination of
the gases occluded by the Augusta Co., Virginia, meteoric iron,
which, however, differed very considerably from Graham's results.
He obtained an amount of gas equal to 3' 17 times the volume of the
iron, made up of 85 • 83 per cent, of hydrogen, 38 • 33 per cent, carbonic
oxide, 9 * 75 per cent, of carbonic acid, and 16*09 per cent, of nitrogen.

Wright and Lawrence Smith followed Mallet, and our present
knowledge of this interesting subject is principally due to these
American chemists. They have taken advantage of the numerous
meteoric masses which have fallen from time to time throughout
America, and which can easily be obtained in sufficient quantity for
complete and accurate observations on their gaseous constituents.

Wright contributed several papers to the ' American Journal ' in
1875 and 1876, and, according to his analyses, the total volume of
gas occluded and the composition of the same differs considerably in
the two principal classes of meteorites. He found the total volume

542 Professor Dewar [June 11,

of gas extracted was mucli greater in tlie case of the stony meteorites
than in the iron ones, the principal characteristics of these gases
being, that in the former the carbonic acid greatly predominated,
accompanied by a comparatively small amount of carbonic oxide and
hydrogen, whereas in the latter the carbonic acid never exceeded
20 per cent., the carbonic oxide being, as a rule, considerably more
than this, and the hydrogen sometimes reaching as high as 80 per
cent.

It is impossible, however, to arrive at anything more than general
conclusions as to the total amount of gas given off by any special
meteorite, or its composition, for, as shown by Wright and confirmed
by Mr. Ansdell and the lecturer, both the total quantity and com-
position of the gases vary very considerably according to the tem-
perature at which they are drawn off.

Wright found a notable quantity of marsh-gas in all the stony
meteorites which he examined, though not a trace in any of the iron
ones; this seemed to be a distinctive difference between the two
classes of meteorites, but subsequently Dr. Flight, of the British
Museum (Phil. Trans, vol. clxxiii. (1882) p. 885), found marsh-gas
in a specimen of the Cranbourne siderite, so that it is evident certain
of the iron meteorites also contain this gas.

Lawrence Smith (Amer. Journ. 1876) confined himself princi-
pally to an examination of the graphite nodules which are frequently
found imbedded in the iron meteorites, and to the nature of the carbon
in the so-called carbonaceous meteorites. He extracted the organic
or hydrocarbon-like bodies by means of ether, but did not determine
the gases given off on heating. Previous to this, Eoscoe (Pro. Phil.
Soc. Man. 1862) had obtained the same hydrocarbon-like body by
exhausting the Alais meteorite with ether, but the quantity he had to
work upon was so small that he could not make a very complete
examination.

These are some of the principal points that have been made out
with regard to the gases occluded by meteorites. The results,
however, are so comparatively few, that it was thought worth while to
take the opportunity which presented itself, of having several good
specimens of meteorites to confirm these results, and, if possible, add
something to our present knowledge of the subject.

The investigation may be divided into five parts, having the
following objects in view : firstly, the confirmation of previous
results by the examination of some well-known meteorite ; secondly,
the analysis of several whole meteoric stones, whose interior had
never been exposed to the effects of the atmosphere, by reason of the
characteristic coating of glaze ; thirdly, the examination of a celestial
graphite nodule, taken from the interior of an iron meteorite;
fourthly, the comparison of some meteorite of the carbonaceous class
with the above ; and fifthly, the examination of different terrestrial
graphites.

The method employed for the abstraction of the gases was exactly

1886.] on Recent Researches on Meteorites. 543

the same in every case, so that a short description will suffice for all.
The temperature was kept as nearly as possible the same in every
experiment, but no doubt differences of many degrees occurred in
some of the experiments, which was unavoidable in using an ordinary
combustion furnace.

The meteorite or graphite, as the case might be, was broken up
into a coarse powder, introduced into a convenient length of
combustion tubing, and connected up with a Sprengel pump, a small
bulb-tube immersed in a freezing mixture intervening, so as to retain
any moisture or condensable volatile products that might come off.
The tube was first thoroughly exhausted and then heated in an
ordinary gas combustion furnace to a low red heat. The gases, during
the heating, were gradually drawn off by the Sprengel pump, and
when the tube had remained for several minutes at a low red heat it
was completely exhausted. The total quantity of gas collected was
in every case used for the analysis.

The " Dhurmsala" specimen was an ordinary fragment of a much
larger original mass, but in the case of the Pultusk and Mocs
meteorites, comj)lete stones were fortunately obtained, weighing
respectively 57 and 103 grams, having the characteristic black glaze
on their surfaces.

Such a large quantity of water was condensed in the bulb tube in
heating the Dhurmsala meteorite, it being the first one examined,
that it was thought it might be principally due to the great absorptive
power of these porous bodies, and that therefore the moisture might
have been condensed in the pores of the meteorite from the surround-
ing air. The Pultusk and Mocs specimens appeared to be especially
adapted for ascertaining whether this was the case, as the complete
covering of black glaze would probably prevent the moisture from
penetrating to the interior of the stones. The fragments of these
stones were therefore transferred as quickly as possible to the
combustion tube after they had been broken up. Notwithstanding
these precautions, fully as much water was condensed from them as
from the Dhurmsala specimen, which seems to suggest that the w^ater
is really combined in some form in the stone and not obtained directly
from the surrounding atmosphere, although it must be admitted that
the glaze on both the stones was not of a very glossy character, and
did not have the appearance of being absolutely impervious to
moisture.

The pumice-stone was examined merely with a view to comparing
the gases occluded by a porous body of volcanic origin with those
contained in meteorites. The sample taken was a fresh piece of
stone, which had not been dried or purified in any way.

It is evident that it differs considerably from the meteoric stones,
the total occluded gas being very small, only about half its volume,
the carbonic acid at the same time being much less, with a propor-
tionate increase in the carbonic oxide.

The general method of analysis was as follows, and the accuracy

(Vol. XI. No. 80.) 2 n

544

Professor Dewar

[June 11,

of the results was confirmed by varying in some cases the method of
separating the gases. The carbonic acid was first removed from the
mixture by caustic potash, the carbonic oxide being then absorbed by
subchloride of copper, and the remainder of the gases exploded with
excess of oxygen. The carbonic acid formed was again removed by
caustic potash, and the excess of oxygen by alkaline pyrogallate, the
residue being taken as nitrogen. The relative quantities of marsh-gas
and hydrogen were calculated from the total diminution after explo-
sion, and the amount of carbonic acid formed : —

Sp. Gr.

Occluded

Gases in

vols, of the

Meteorite.

Percentage CompoEition.

CO2.

CO. H.

CH4.

N.

Dhurrasala ..
Pultusk .. ..

Mocs

Pumice-stone . .

3-175
3-718
3-67
2-50

2-51
3-54
1-94
0-55

63-15
66-12
64-50
39-50

1-31 ^ 28-48
5-40 ; 18-14
3-90 22-94
18-50 25-4

3-9

7-65

4-41

1-31

2-69

3-67

16-60

It will be seen that the above numbers are quite confirmatory of
Wright's results, the carbonic acid in the three meteorites examined
being by far the largest constituent, while marsh-gas in considerable
quantity was found in all. The percentage of this latter gas is some-
what higher than that found by Wright in the stony meteorites he
examined, but this is probably due to the fact that a rather higher
temperature was employed by the lecturer to drive off the gases.
This supposition seems to be confirmed on considering the analysis
of the Pultusk meteorite ; for whereas Wright's abstracted gas only
reached 1 • 75 times the volume of the stone, the total quantity of gas
obtained by the lecturer was twice as much or equal to 3 • 54 times
its volume.

It is therefore unquestionable that marsh-gas is given off on heating
these meteoric stones, but whether it exists as such occluded in the
material, or whether it is formed by some chemical decomposition of
some organic constituent of the mass, is by no means clear.

Wright came to the conclusion " that the marsh-gas really existed
as such in the stony meteorites, as the temperature at which it was
driven off would be too low for its formation," at the same time he
thinks it quite possible that " at very much higher temperatures, in
the reaction by which the carbonic acid is broken up by the iron, a
portion of the carbon might combine with the hydrogen present to
form marsh-gas."

Knowing the great absorptive power for gases possessed by porous
bodies generally, it was thought advisable to determine directly what
this absorptive power was in the case of these stony meteorites,
which are of such an eminently porous nature.

1886.]

on Becent Researches on Meteorites »

545

For this purpose the powdered Dhiirmsala meteorite, from which
the gases had been removed, vvas left in moist air under a bell-glass,
for different periods of time as tabulated below, the gases being drawn
off at a low red heat after each period : —

After 24 hours . .
After 6 days more
After 8 days more

Occluded
Gas in vols.

of the
Meteorite.

0-61
2-47
0-63

COq

CO.

540
47-0
96 1

5-0
2-0

42-4

47-0

1-5

3-6
l-Q

The absorption of water and gases evidently went on tolerably
rapidly for the first seven days, but after the second heating of the
meteorite, its porosity seems to have been affected in some way, for
after a further period of eight days, it was found to take up only about
a fourth of the quantity of gas which it had absorbed in the previous
six days.

The actual amount of water given off after this exposure to a moist
atmosphere was considerably less than what was obtained in the
original heating of the meteorite, and from this it was inferred that the
water is chemically combined in the stone. It would be difficult to
explain, otherwise than by chemical combination, the power by which
the water is retained by these meteorites, as it is not given off until a
very high temj)erature is reached. In any case it is clear that the
hydrogen must come from the action of water on the iron-nickel
alloy, or finely disseminated carbon. Greville Williams has pointed
out that the large amount of hydrogen obtained from heating finely
divided zinc-dust is not due to free hydrogen, but to the action of the
zinc on the hydrated oxide of zinc.

To pass on to the consideration of the various graphites ex-
amined. The celestial graphite was a perfect oblong nodule weighing
30 grams, which had been taken from the interior of a mass of the
Toluca meteoric iron. It had a uniform dull-black colour, except at
one end where there was a slight incrustation of sulphide of iron. Its
fracture showed a uniform dull-black, compact mass; it was easily
pounded up in a porcelain mortar, and formed a fine granular powder
without any lustre.

On extracting the gases from this specimen a considerable quantity
of marsh-gas was obtained, so that it appeared most important to
compare it with some samples of terrestrial graphites, more espe-
cially as the occluded gases had never, as far as the lecturer was
aware, been determined in these bodies.

For this purpose four samples of native graphites were obtained.
The Cumberland graphite was a magnificent specimen of the original
Borrodale, and had been in a private cabinet for over fifteen years. It
had the characteristic dense homogeneous structure and brilliant

2 N 2

646

Professor Dewar

[June 11,

external lustre of the graphites coming from this district. The
Siberian example was from the Alexandref Mine ; its structure was
columnar and striated, with little external lustre ; it was rather more
easily broken up than the Borrodale, but formed the same dull black
powder. The specimen from Ceylon was of -^ the type usual to that
island : highly lustrous and flaky, breaking up very easily, and
forming small shining plates when ground up. The last sample,
which was from the same cabinet as the others, but whose origin
was unfortunately unknown, had a dull external surface, was exceed-
ingly porous, and much more brittle than any of the previous ones,
grinding up very easily into a dull black powder. It had more the
appearance of the celestial graphites, which was heightened by having
slight incrustations of sulphide of iron on its surface. Its low specific
gravity also shows it to be some exceptional variety.

It seemed most important in connection with this subject to
examine some matrix with which the graphites are usually found
associated. These rocks are very variable, but consist principally of a
kind of decomposed trap or gneiss. A good specimen was obtained
of semi-decomposed gneiss from Canada with a considerable quantity
of graphite disseminated throughout the mass, and also several
samples of Ceylon graphite imbedded in its matrix, which in this
case consisted of felspar and quartz.

The results, as tabulated below, confirm Wright's analyses of
several trap rocks, in which he found principally carbonic acid and
hydrogen. The small quantity of marsh-gas no doubt comes from
the disseminated graphite, but the presence of the hydrogen is more
difficult to explain and requires further investigation.

Occluded

Sp. Gr.

Gases ia
vols, of the
Graphite.

CO2.

CO.

H.

CH4.

N.

Celestial graphite . .

2-26

7-25

91-81

2-50

5-40

0-1

Borrodale

2-86

2-60

36-40

7-77

22-2

26-11

6-66

Siberian

2-05

2-55

57'4l

6-16

10-25

20-83

4-16

Ceylon

2-25

0-22

66-60

14-80

7-40

3-70

4-50

Unknown

1-64

7-26

50-79

3-16

2-50

39-53

3-49

Gneiss

>»

2-45

5-32

82-38

2-38

13-61

0-47

1-20

Felspar ..

..

2-59

1-27

94-72

0-81

2-21

0-61

1-40

On comparing these samples of graphite, it will be seen that the
Borrodale and the Siberian give off about the same total volume of
gas, that the celestial and the unknown graphites closely approximate
each other in this respect, yielding more than double the volume of
the others, and that the Ceylon sample stands alone in yielding a very
minute quantity. All the terrestrial samples, except that from Ceylon,
are alike in giving off a very considerable quantity of marsh-gas,
though they differ somewhat in the actual quantity, and it is evident

1886.]

on Becent Besearches on Meteorites.

647

that although the celestial graphite contains a considerable amount,
it is very much less than that yielded by the terrestrial samples.

A few tentative experiments were made to ascertain the absorbing
power for gases of this celestial graphite. For this purpose dry car-
bonic acid, marsh-gas, and hydrogen were respectively drawn through
the tube containing the previously exhausted graphite for twelve
hours in the cold, the gases being pumped out at a low red heat after
each treatment with the dry gas. After the carbonic acid treatment
the volume of gas collected was only 1 • 1 times that of the graphite,
containing 98*4 per cent, of carbonic acid ; after the marsh-gas the
volume of the gas was only 0*9 that of the graphite, containing 94*1
per cent, carbonic acid ; and after the hydrogen the volume of the gas
collected was only 0* 17 times that of the graphite, containing 95 -0 per
cent, of carbonic acid. It is therefore evident that the large quantity
of gas occluded in celestial graphites cannot be explained by any
special absorptive power of this variety of carbon. In view of the
large and varying percentages of marsh-gas in the gaseous products
of all these graphites, it appeared of especial interest to ascertain
whether the quantity of marsh-gas extracted coincided in any way
with the hydrogen obtained by their combustion. All the samples
were therefore submitted to ultimate analysis, with the following
results : —

Percentage Composition.

Hydrogen.

Carbon.

Ash.

Celestial graphite

Borrodale „

Siberian „

^eylon „

Unknown „

0-11

0-11

0-17

0-017

0-246

76-10
94-76
79-07
90-90
78-51

23-50
4-85

20-00
9-08

21-26

These analyses do not seem to point to any very definite conclusion
as to the origin of the marsh-gas. The unknown graphite, which
contains the largest percentage of marsh-gas, certainly comes out far
the highest in hydrogen, and the hydrogen in the Ceylon graphite
also bears a certain relation to the small quantity of marsh-gas it
contains, but the first three samples are very similar to each other in
the amount of hydrogen they contain.

In order to get some further insight into the origin of this marsh-
gas in the celestial graphite, about 2 grams of the original nodule
were very finely ground up and digested for several hours with
strong nitric acid. After being thoroughly washed from every trace
of nitric acid and dried at 110° C, it was again submitted to analysis,
with the result that the amount of hydrogen remained exactly the
same as before, proving that it existed in the form of some very
stable compound in the graphite.

548

Professor Dewar

[June 11,

To clear up this matter still further, about 10 grams of the original
nodule were digested with pure ether in the way described by
Lawrence Smith for extracting the hydrocarbon-like bodies. It was
allowed to stand for twenty-four hours with excess of ether, and then
filtered, and washed with more ether. The graphite thus treated was
dried at 110° C, and the gases extracted from it.

For the purpose of comparing one of the terrestrial graphites
with the above in regard to its behaviour with ether, the specimen
of unknown origin was selected, as yielding the largest quantity of
marsh-gas. The residue, after digestion with ether, was dried, and
the gases pumped out as before.

It will be seen that by this treatment with ether the volume of gas
given off by the celestial graphite, and also the marsh-gas, have bee a
reduced to rather more than one-half, while with regard to the un-
known graphite, although the total volume of gas remains about the
same (probably due to a rather higher temperature being employed),
the marsh-gas has also been reduced to rather less than one-third
the original amount, and the hydrogen has correspondingly increased.

Occluded

Gases in

vols, of the

Graphite.

CO2.

CO.

H.

CH4.

N.

Celestial graphite beforej

treatment with ether . . J
Celestial graphite after treat-"!

ment with ether . . . . /
Unknown graphite before"!

treatment with ether .. /
Unknown graphite after"!

treatment with ether . . j

7-25
3-50
7-26
715

91-81
81-50
50-79
64-86

10-63
3-16
5-67

2-50
1-41

2-50
14-37

5-40

2-12

39-53

12-96

0-1

0-74
3-49
2-00

These experiments prove that either the ether did not dissolve out
all the actual carbonaceous compounds present, or that the marsh-gas
was subsequently formed during the heating of the graphite.

As Dr. de la Eue had kindly placed at Professor Dewar's disposal
a splendid specimen of the Orgueil meteorite, the opportunity was
taken of comparing the gases occluded by this typical specimen of
the carbonaceous class with those obtained from the stony meteorites
and the graphites. This meteorite has been so thoroughly examined
by Cloez and Pisani (Compt. Kend. vol. lix. (1864) pp. 37, 132)
with regard to its chemical inorganic constituents, that nothing need
be said as to its general composition. The investigation was there-
fore confined to the gases given off on heating which had not pre-
viously been determined.

During the heating of the meteorite a large quantity of water, on
which floated numerous small pieces of sulphur, collected in the bulb
tube immersed in the freezing mixture. This water was strongly acid,

1886.]

on "Recent Researches on Meteorites,

549

and indeed smelt strongly of sulphurous acid. On evaporating it to
dryness with a drop of hydrochloric acid, abundance of ammoniacal
salts were found in the residue. In the cool anterior part of the
comhustion-tube a considerable sublimate had collected, which proved
to be principally sulphate of ammonium with traces of sulphides and
sulphites, and a large quantity of free sulphur. A very large quan-
tity of gas was given off, having the following composition : —

Sp. gr.

Occluded

Gases in

vols, of the

Meteorite.

Percentage Composition.

CO2.

CO.

CH4.

N.

SO2.

Orgueil meteorite ..

2-567

57-87

12-77

1-96

1-50

0-56

83-00

Sulphurous acid is evidently the main constituent of the gases given
off ; but if this gas, which has been formed from the decomposition
of the sulphate of iron, be- eliminated, the meteorite yields 9 • 8 times
its volume of gas, having very much the same composition as that
from some of the stony meteorites, viz. : —

CO2, 76-05; CO, 11-67; CH4, 8-93; N, 3-33.

Cloez found the organic matter in this meteorite to be composed of
carbon 63 • 45, hydrogen 6 • 98, oxygen 30 • 57, which is nearly in the
proportions of a terrestrial humus substance. It is known that such
substances break up by the action of heat into gases of the nature
found above, at the same time, however, a quantity of the carbonic acid
undoubtedly comes from the presence of the carbonates of magnesium
and iron. The operation by which terrestrial carbon has been
changed into graphite is by no means clear. As a rule the transition
of one kind of carbon into another necessitates the action of a very
high temperature. If, therefore, a really high temperature is in all
cases necessary, it is difficult to explain how compounds of carbon
came to resist decomposition, and should come to be found associated
with all natural graphites.

It may be assumed that the graphite resulted from the action of
water, gases and other agents, on the carbides of the metals, and that
during the chemical interactions which took place, a portion of the
carbon became transformed into organic compounds.

In either case it points to the conclusion that the method of for-
mation of the meteoric and terrestrial graphites was similar, and it is
perfectly possible they may after all have come from a common
source.

It is proposed to continue this investigation, and in order to
acquire further information, to examine the gases given off from
meteorites at definite temperatures, and especially the gases from such
as can be found coated with an impervious glaze, and to examine

650 Professor Dewar [June 11,

more particularly iuto the presence of water in such bodies, and the
source of the nitrogen found in the same.

Since the above analyses of different graphites were made, a
sample of the artificial graphite which results from the action of
oxidising agents on the cyanogen compounds present in crude caustic
soda has been examined. The following analysis shows that this
artificial variety of graphite is characterised by giving a very large
yield of marsh-gas.

CO2 45-42

CO 39-88

CH- 4-43

H 8-31

N 2-00

Occluded gases in volumes of the graphite = 53-13.

Meteorites, no doubt, have an exceedingly low temperature before
they enter the earth's atmosphere, and the question had been raised
as to what chemical reactions could take place under such conditions.
It resulted from Professor Dewar's investigations that at a tem-
perature of about — 130° C. liquid oxygen had no chemical action
upon hydrogen, potassium, sodium, phosphorus, hydriodic acid, or
sulphydric acid. It would appear, therefore, that as the absolute
zero is approached even the strongest chemical affinities are inactive.

The lecturer exhibited at work the apparatus by which he had
recently succeeded in solidifying oxygen. The apparatus is illustrated
in the accompanying diagram,* where a copper tube is seen passing
through a vessel kept constantly full of ether and solid carbonic acid ;
ethylene is sent through this tube, and is liquefied by the intense
cold ; it is then conveyed by the tube, through an indiarubber stopper,
into the interior lower vessel ; the outer one is filled with ether and
solid carbonic acid. A continuous copper tube, about 45 feet long,
conveying oxygen, passes first through the outer vessel, and then
through that containing the liquid ethylene ; the latter evaporates
through the space between the two vessels, and thus intense cold is
produced, whereby oxygen is liquefied in the tube to the extent occa-
sionally of 22 cubic centimetres at one time. The temperature at
which this is effected is about — 180° C, at a pressure of 75 atmo-
spheres, but less pressure will suffice. When the oxygen is known to
be liquid, by means of a gauge near the oxygen inlet, the valve A is
opened, and the liquid oxygen rushes into a vacuum in the central
glass tube below ; some liquid ethylene at the bottom of the next
tube outwards is also caused to evaporate into a vacuum at the same
moment, and iustantly some of the liquid oxygen in the central tube
becomes solid, owing to the intense cold of the double evaporation.

♦ This illustration appeared in 'Industries' of July IG, 1886, and is kindly
lent by the proprietors.

I ETHYLENE CAS

Apparatus fob Solidiftiko Oxtqen.

1886.] on Becent Besearches on Meteorites. 551

The outer glass vessel serves to keep moisture from settling on the
sides of the etliylene tube. By means of the electric lantern and a
lens, an image of this part of the apparatus was projected upon the
screen, this being the first time that the experiment had been shown
on a large scale in public.

Performing the experiment, the temperature reached was a little
below 200^ C, that is only 50° to 70'^ above the absolute zero of tem-
perature, and in the experiment about 5 lbs. of liquid ethylene were
employed.

With reference to the main subject, the lecturer said that meteorites
came from regions of intense cold into our atmosphere ; most of them
weigh but a few ounces or pounds, but exceptional meteorites weigh
several hundredweight. A spherical body 3 feet in diameter, moving
at the rate of 18 miles a second at the height of 23 miles, where the
barometric pressure is only two-tenths of an inch, produces locally a
compression pressure 5600 times greater than that of the surround-
ing air. Descending vertically, it would pass through the whole
atmosphere in 15 seconds. The velocity stated in these data is
relatively low as compared with that of planetary bodies. Meteorites
travel at the rate of about 36 miles in a second. The velocity of a
shot from a 100-ton gun is about half a mile per second.

Meteorites reach the earth covered with a thin and very remarkable
glaze, due to the fusion of their external surface during their brief
passage through the atmosphere. A velocity of 145 feet per second
in air gives an increase of 10° temperature, and the rate continues
as the square of the velocity. The surface temperature of a body
moving at the rate of 39 miles per second would reach 2,000,000°.

The lecturer placed a piece of iron against a rotating emery
wheel, the friction of which caused showers of sparks to be thrown
out. These were so hot that some of the little globules of iron
composing them were fused into a plate of glass placed to catch
them. Great similarities exist between the flight of these globules
and the flight of meteorites, the heat and light in both cases being
partly due to friction and partly to chemical action. That chemical
action has an influence, he proved by applying oxygen gas to
the sparks, thereby causing them to burn more brilliantly, and by
applying carbonic acid to them, thus reducing their brilliancy.
When a piece of meteorite was applied to the emery wheel in place
of the piece of iron, the sparks were far less abundant, and of a dull
red colour. The glaze of meteorites can be imitated to some extent
by cooling a piece of meteorite to 20.0° C, and then dropping it for
a moment into the electric furnace; the temperature explains the
glazing of a meteorite, and that it has a motion of rotation must also
be considered in estimating the amount of friction, and therefore of
heat, to which it is subjected in its passage through the atmosphere of
the earth. An enormous amount of its energy, however, is expended
in heating the air, and aerial vibrations thus set up explain the noises
made by the passage of meteorites.

552 Prof. Dewar on Becent Researches on Meteorites. [June 11,

What is the origin of the gases in meteorites? Their presence
agrees with the discovery of Dr. Huggins, that comets give a hydro-
carbon spectrum. The origin of terrestrial graphite is far from
being agreed upon by geologists ; in some places it is evidently
transformed coal, in other cases they cannot say whether it comes
from vegetable or primitive sources. Whatever the origin of the
graphite in meteorites, it contains similar impurities to those in
terrestrial graphite ; the nodules in celestial graphite are similar to
those of terrestrial graphite, and might as well have come from
some body like the earth as from any other source. Another con-
clusion is that the marsh-gas is not occluded in meteorites, but is a
product of distillation by heat, just as the gas might be distilled from
shales. The graphite of meteorites has no power of occluding marsh-
gas, therefore the inference is that the marsh-gas and hydrogen in
them are the result of the decomposition of organic bodies. In the
spectrum of one of the comets. Dr. Huggins once photographed a
peculiar band in the ultra-violet, which band indicated the presence
of cyanogen. One meteorite on the table contained chloride of
ammonium, therefore it contained a compound of nitrogen, and such
would account for the production of cyanogen.

[J. D.]

1886.] Professor Tyndall on Thomas Young. 553

WEEKLY EVENING MEETING,

Friday, January 22, 1886.

Sir William Bowman, Bart. LL.D. F.R.S. Vice-President,

in the Chair.

Professor Tyndall, D.C.L. LL.D. F.R.S. M.B.L

Thomas Young.

Early Lite and Studies.

Four great names are indissolubly associated with the establishment
in which we are now assembled. Its founder, Benjamin Thompson,
better known as Count Eumford ; its Chemical Professor, Humphry
Davy ; its Professor of Natural Philosophy, Thomas Young ; and,
finally, the man whom so many of us have the privilege to remember,
Michael Faraday. Of the character and achievements of the third of
the great men here named, less seems to be publicly known than
ought to be known. Even a portion of this audience may possibly
have some addition made to its knowledge by reference to the labours
of a man who served the Institution in the opening of the present
century. I therefore thought that such a brief account of him as I
could compress into an hour might not be without interest and
instruction at the present time and place.

Thomas Young was born at Milverton, in Somersetshire, on the
13th of June, 1773. His parents were members of the Society of
Friends. Nearly seven years of his childhood were spent with his
maternal grandfather. He soon evinced a precocity which might have
been expected to run to seed and die rapidly out. When two years
old he was able to read with considerable fluency, and before he had
attained the age of four years, he had read the Bible twice through.
At the age of six he learnt by heart the whole of Goldsmith's
'Deserted Village.' His first formal teachers were not successful,
and his aunt in those early days appears to have been more useful
to him than anybody else. When not quite seveu years of age, he
was placed at what he calls a miserable boarding school at Stapleton
near Bristol. But he soon became his own tutor, distancing in his
studies those who were meant to teach him.

In March 1782, he was sent to the school of Mr. Thompson,
at Compton, in Dorsetshire, of whose liberality and largeness of
mind Young spoke afterwards with affectionate recognition. Here
he worked at Greek and Latin, and read a great many books in both
languages. He also studied mathematics and book-keeping. Of preg-
nant influence on his future life was the reading of Martin's ' Lectures
on Natural Philosophy,' v^nd Ryland's ' Introduction to the Newtonian

554 Professor Tyndall [Jan. 22,

Philosophy.' He read with particular delight the optical portions of
Martin's work. An usher of the school, named Jeffrey, taught him
how to make telescopes, and to bind books. Here the early years of
Young and Faraday inosculate, the one, however, pursuing book-
binding as an amusement, and the other as a profession. Young
borrowed a quadrant from an intelligent saddler named Atkins, and
with it determined the principal heights in his neighbourhood. He
took to botany for a time, but was more and more drawn towards
optics. He constructed a microscope. The disentangling of difficult
problems was his delight. Seeing some fluxional symbols in Martin's
work, he attacked the study of fluxions. Priestley on Air fascinated
him. The Italian language was mastered by the aid of one of his
schoolfellows named Fox.

After leaving Compton, he devoted himself to the study of Hebrew.
Mr. Toulmin, of whom Young speaks with affection, lent him
grammars of the Hebrew, Chaldee, Syriac, and Samaritan languages,
all of which he studied with diligence and delight. Mr. Toulmin
also lent him the Lord's Prayer in more than a hundred languages,
the examination of which, Young declares, gave him extraordinary
pleasure. Through one of those accidents which enter so largely
into the tissue of human life, Young found himself at Youngsbury,
near Ware in Hertfordshire. It was a strong testimony to his talent
and character, that Mr. Barclay here accepted him as the preceptor of
his grandson, Mr. Hudson Gurney, although Young was then little more
than fourteen, and his pupil only a year and a half younger than
himself. Thus began a life-long friendship between him and Hudson
Gurney. Young spent five years at Youngsbury, which he deemed
the most profitable years of his life. He spent the winter months in
London, visiting booksellers' shops and hearing occasional lectures.
He kept a journal in Hertfordshire, the first entry of which informs
us that he had written out specimens of the Bible in thirteen different
languages. It is recorded of Young that, when requested by an
acquaintance, who presumed somewhat upon his youthful appearance,
to exhibit a specimen of his handwriting, he very delicately rebuked
the inquiry by writing a sentence in his best style in fourteen different
languages.

Although the catalogue of Young's books might give the impression
that he was a great reader, his reading was comiDaratively limited ;
but whatever he read, he completely mastered. Fichte comj)ared the
reading of reviews to the smoking of tobacco, affirming that the two
occuj)ations were equally pleasant, and equally profitable. Young,
in this sense, was not a smoker. Whatever study he began, he never
abandoned ,* and it was, says Dean Peacock in his ' Life of Young,'
to his steadily keeping to the principle of doing nothing by halves,
that he was wont in after life to attribute a great part of his success
as a scholar and a man of science.

Young's mother was the niece of Dr. Brocklesby, and this eminent
London physician appears to have taken the greatest interest in the

1886.] on Thomas Young. 655

development of his youtliful relative. He, nevertheless, occasion ally-
gives Young a rap over the knuckles for what he calls his " prudery."
We all know the strenuous and honourable opposition that has been
always offered to negro slavery by the Society of Friends. In carrying
out their principles, they at one time totally abstained from sugar,
lest by using it they should countenance the West Indian planters.
Young here imitated the conduct of his sect, which Dr. Brocklesby
stigmatised as " prudery." " My late excellent friend Mr. Day," says
the Doctor, " the author of ' Sandford and Merton,' abhorred the base
traffic in human lives as much as you can do ; and even Mr. Granville
Sharp, one of the earliest writers on the subject, has not done half as
much service as Mr. Day in the above work. And jet Mr. Day
devoured daily as much sugar as I do. Keformation," adds the
Doctor, " must take its rise elsewhere, if ever there is a general mass
of public virtue sufficient to resist such private interests."

Over and above his classical reading, from 1790 to 1792, Young
read Simpson's Fluxions, the Principia and Optics of Newton, and
many of the works of other famous authors, including Bacon, Linnasus,
Boerliaave, Lavoisier, Higgins, and Black. He seems to have confined
himself to works of the highest stamp. He mastered Corneille and
Racine, read Shakespeare, Milton, Blackstone, and Burke. But he
was, adds his biographer, " contented to rest in almost entire ignorance
of the popular literature of the day."

I must, however, hasten over the early years and acquirements of
this extraordinary personality. During his youth, he had none of the
assistance which is usually within the reach of persons of position in
England. All that I have here mentioned, and a vast deal more, he
had acquired without having ever entered a public school, or touched
a University. As a classic, he was, we are assured, both precise and
profound. As a mathematician, he was many-sided, original, and power-
ful. : Such an education, however, though well calculated to develop
the strength of the individual, was not, in Peacock's opinion, the best
calculated to put Young into sympathy with the mind of his age.
" He was, throughout life, destitute of that intellectual fellow-feeling
(if the phrase may be used), which is so necessary to form a success-
ful teacher or lecturer, or a luminous and successful writer."

Young was intended for the medical profession, and his medical
studies began in 1792. He came to London, and attended the lectures
of Dr. Baily, Mr. Cruikshanks, and John Hunter. He made the
acquaintance of Burke, Windham, Frederick North, Sir Joshua
Reynolds, and Dr. Lawrence. By the advice of Burke he studied
the philosophical works of Cicero. The bent of Young's moral
character may be inferred from the quotations which he habitually
entered in his commonplace book. Here is one of them : — " For my
part," says Cicero, " I think the man who possessed that strength of
mind, that constitutional tendency to temperance and virtue, which
would lead him to avoid all enervating indulgences, and to complete

556 Professor Tyndall [Jan. 22,

the whole career of life in the midst of labours of the body and efforts
of the mind ; whom neither tranquillity nor relaxation, nor the flat-
tering attentions of his equals in age and station, nor public games
nor banquets would delight; who would regard nothing in life as
desirable which was not united with dignity and virtue ; — such a man
I regard as being, in my judgment, furnished and adorned with some
special gifts of the gods."

His medical studies were pursued with the same thoroughness
which marked everything Young took in hand. He was an assiduous
attendant at the best lectures. His delight in optics naturally drew
him to investigate the anatomical structure of the eye. In regard to
this structure most of you will remember that in front is the cornea,
holding behind it the aqueous humour ; then comes the iris, surround-
ing the aperture called the pupil, at the back of which we have the
beautiful crystalline lens. Behind this, again, is the vitreous humour
which constitutes the great mass of the eye. Thus, optically con-
sidered, the eye is a compound lens of great complexity and beauty.
Behind the vitreous humour is spread the screen of the retina, woven
of fine nerve-fibres. On this screen, when any object looked at is
distinctly seen, a sharply defined image of the object is formed.
Definition of the image is necessary to the distinctness of the vision.
Were the optical arrangements of the eye rigid, distinct vision would
be possible only at one definite distance. But the eye can see dis-
tinctly at different distances. It has what the Germans call an
Accommodations Vermogen — a power of adjustment — which liberates
it from the thrall of rigidity. By what mechanical arrangement is
the eye enabled to adjust itself both for near and distant objects ?
Young replied, " By the alteration of the curvature of the crystalline
lens." His memoir on this subject was considered so meritorious,
that it was printed in the ' Transactions of the Royal Society ' ; and in
the year following, at the age of twenty-one, he was elected a Fellow
of the Society.

Young's memoir evoked sharp discussion, both as regards the
priority and the truth of the discovery. It was claimed by John
Hunter, while its accuracy was denied by Hunter's brother-in-law,
Sir Everard Home, who, jointly with Mr. Ramsden, affirmed that the
adjustment of the eye depended on the changed curvature of the
cornea. A couched eye, that is to say, an eye from which the crystal-
line lens had been removed, they affirmed to be capable of adjust-
ment. In the face of such authorities, Young, with the candour of
a true man of science, abandoned the views he had enunciated. But
it was only for a time. He soon resumed his inquiries, and proved to
demonstration that couched eyes had no trace of the power ascribed
to them. Before the time of Young, moreover, weighty authorities
leaned to the view that the adjustment of the eye depended on the
variation of the distance between the cornea and the retina. When
near objects were viewed, it was thought that the axis was lengthened,
the retina or screen being thereby thrown further back. In distant

1886.] on Thomas Young. 557

vision the reverse took place. But Young proved beyond a doubt that
no sucli variation in the length of the axis of the eye occurs ; and this
has been verified in our own day by Helmholtz. The change in the
curvature of the crystalline lens has been also verified by the most
exact experiments. When we pass, for instance, from distant to
near vision, the image of a candle flame reflected from the front
surface of the lens becomes smaller, proving the lens to be then more
sharply curved. When we pass from near to distant vision, the
image becomes larger, proving the curvature of the lens to have
diminished. The radius of curvature of the lens under these cir-
cumstances has been shown to vary from six to ten millimetres.
The theory of Young, therefore, with regard to the adjustment of
the eye, has been completely vei-ified. But it is still a moot point as
to what the mechanism is by which the change of curvature is pro-
duced. Young thought that it was effected by the muscularity of
the lens itself. The muscles, however, would require nerves to
excite them, and it would be hardly possible, in the transparent
humours of the eye, for such nerves to escape detection. They,
however, have never been detected.

While passing through Bath in 1794, Young, at the instance of
Dr. Brocklesby, called upon the Duke of Eichmond. The impression
made by Young at this time may be gathered from a note addressed
by the Duke to the Doctor, in these terms : — " But I must tell you how
pleased we all are with Mr. Young. I really never saw a young man
more pleasing and engaging. He seems to have already acquired
much knowledge in most branches, and to be studious of obtaining
more. It comes out without affectation on all subjects he talks upon.
He is very cheerful and easy, without assuming anything ; and even
on the peculiarity of his dress and Quakerism, he talked so reasonably,
that one cannot wish him to alter himself in any one particular. In
short, I end, as I began, by assuring you that the Duchess and I are
quite charmed with him." The Duke, then Master of the Ordnance,
was a very competent man. He was well acquainted with the
instruments used in the great Trigonometrical Survey under his
control. He offered to Young the post of private secretary. Young's
acceptance would have brought within his reach both honour and
emolument. But, to his credit be it recorded, he refused the post,
because its acceptance would have rendered necessary the abandon-
ment of his costume as a member of the Society of Friends. Soon
afterwards, he paid a visit to a celebrated cattle-breeder near Ash-
bourne, and describes with vivid interest what Mr. Bickwell had
accomplished by the process of artificial selection. Facts like these
it was which, presented afterwards to the pondering mind of Darwin,
caused the great naturalist to pass from artificial to natural selection.
Young visited Darwin's grandfather, and criticized his ' Zoonomia.'
The inspection of Dr. Darwin's cameos, minerals, and plants, gave
him great delight, the supreme pleasure being derived from the

568 Professor Tyndall [Jan. 22,

cameos. Dr. Darwin stated that he had borrowed much of the
imagery of his poetry from the graceful expression and vigorous
conception which these cameos breathe. His opinion of his visitor is
pithily expressed in a letter of introduction to a friend in Edinburgh :
" He unites the scholar with the philosopher, and the cultivation
of modern arts with the simplicity of ancient manners."

Young went to Edinburgh to pursue his medical studies. His
reputation had gone before him, and he was welcomed in the best
society of the northern capital. Here he met Bostock, Bancroft,
Turner, Gibbs, Gregory, Duncan, Black, and Munroe. He dwells
specially upon the lectures of John Bell, whose demonstrations in
anatomy appeared to him to be of first-rate excellence.

There is nothing that I have met in Dean Peacock's 'Life of
Young,' to denote that he was fervently religious. The Ciceronian
"virtue," rather than religious emotion, seemed to belong to his
character. The hold which mere habit long exercised over him,
and which his loyalty had caused him to maintain at a period
of temptation, became more and more relaxed. He gradually
gave up the formal practices of Quakerism, in regard to dress
and other matters. He took lessons in dancing, and appeared to
delight in that graceful art. I remember the late Mr. Babbage
telling me that once, upon a Londoji stage, by the untimely raising
of a drop-scene. Young was revealed in the attitude of a dancer. He
assiduously attended the theatre. So, it may be remarked, did the
profoundly religious Faraday. On leaving Edinburgh he paid a
farewell visit to his friend Cruikshanks, who took him aside, and after
much preamble, " told me," says Young, " that he had heard that I
had been at the play, and hoped that I should be able to contradict
it. I told him that 1 had been several times, and that I thought
it right to go. I know," he added, " you are determined to discourage
my dancing and singing, and I am determined to pay no regard
whatever to what you say."

After completing his studies at Edinburgh, Young went to the
Highlands, and the houses in which he was received show the con-
sideration in which he was held. He visited the chief seats of learn-
ing, and the principal libraries, as a matter of course; but he had
also occasion to enjoy and admire "the good sense, frankness,
cordiality of manners, personal beauty, and accomplishments " of the
Scottish aristocracy. So greatly was he delighted with his visit to
Gordon Castle, that before quitting it, he wrote thus : " I could
almost have wished to break or dislocate a limb by chance, that I
might be detained against my will. I do not recollect that I have
ever passed my time more agreeably, or with a party whom I thought
more congenial to my own disposition." He visited Stafia, but
appears to have taken more pleasure in Pennant's plates and descrip-
tions, than in Fingal's Cave, or the scenery of the island. From the
Duchess of Gordon he carried a letter of introduction to the Duke of
Argyll, and spent some time at Inverary. In riding out he was given

1886.] on Thomas Young. 559

his choice whether to proceed leisurely with tlie Duke, or to ride with
the ladies and be galloped over. His reply was, that of all things,
he liked to be galloped over, and made his choice accordingly. He
compares the two daughters of the Duke to Venus and Minerva, both
being goddesses. He visited the Cumberland lakes. But here it may
be said, once for all, that Young was somewhat stunted in his taste
for natural scenery. He was a man of the town, fond of social inter-
course, and of intellectual collision. He could not understand the
possibility of any man choosing to live in the country if the chance of
living in London was open to him. At Liverpool he dined with
Roscoe, proceeding afterwards to Coalbrookdale and its ironworks.
As previously at Carron, he was greatly impressed by the glare of
the furnaces. Mr. W. Eeynolds, who appeared to interest himself in
physical experiments on a large scale, told him that he had the inten-
tion of making a flute 150 feet long and 2 J feet in diameter, to be
blown by a steam engine and played upon by barrels. From Young's
letters, it is evident that he then saw the value and necessity of what
we now call technical education.

In October 1795, he went to Germany to pursue his medical studies
at the University of Gottingen. He gives an account of his diurnal
occupations, embracing attendance at lectures on history, on materia
medica, on acute diseases, and on natural history. He is careful to
note that he had also lessons twice a week from Blessmen, the
academical dancing-master, and the same number of lessons on the
clavichord from Forkel. Young's pursuit of " personal accomplish-
ments " is considered by his biographer to be somewhat excessive.
At Gottingen he had, on Sundays, tea dances or supper dances. The
mothers of handsome daughters appear to have been somewhat wary
of the students, having reason " to fear a traitor in every young man."

He made at Gottingen the acquaintance of many famous professors

of Heyne, Lichtenberg, Blumenbach, and others. He records a joke
practised on the professor of geology which had serious consequences.
The students were rather bored by the professor's compelling them
to go with him to collect " petrifactions ; " and the young roo^ues,
says Young, "in revenge, spent a whole winter in counterfeiting
specimens and buried them in a hill which the good man meant to
explore, and imposed them upon him as the most wonderful lusus
naturse." Peacock adds the remark that the unhappy victim of this
" roguery " died of mortification when the imposition was made known
to him.

Before taking his degree, it is customary for the student in
German Universities to hand in a dissertation written by himself.
This is circulated among the professors, and is followed by a public
disputation. On the 16th of July, Young did battle in the Auditorium,
the subject chosen for discussion being the human voice. He ac-
quitted himself creditably, was complimented by those present, and
received his degree as doctor of physic, surgery, and midwifery. lu

Vol. XL (No. 80.) 2 o

660 Professor Tyndall [Jan. 22,

the thesis chosen for discussion, Young broke ground on those studies
on sound which, for intrinsic merit, and suggesting as they did, his
subsequent studies on light, will remain for ever famous in the history
of science. During a pause in the lectures he visited the Hartz
mountains, making himself acquainted with the scene of Gothe's
Walpurgisnacht on the summit of the Brocken. Wedgwood and
Leslie accompanied him on this tour. The curious fossils dug up by
the young men in the Unicorn's Cave at Schv^arzfeld, excited curiosity
and wonder, but nothing more. Their significance at that time had
not been revealed. Hearing Kant so much spoken of in Germany,
Young naturally attacked the ' Critique of Pure Eeason,' but his
other studies prevented him from devoting much time to the critical
philosophy. To the portion of it which he read he attached no high
value. He admitted Kant's penetration, but dwelt upon his confusion
of ideas. The language of the Critique he thought unpardonably
obscure.

He visited Brunswick, where, clothed in the proper costume, he
was presented at court. After the reception came a supper, about
twenty ladies sitting on one side of a table, and twenty gentlemen
on the other. He endeavoured to converse with his neighbour, but
found him either sulky or stupid. The dowager duchess, whom he
likened to a spectre, made her appearance, and began to converse
pleasantly. When told that Young had studied at Gottingen, and
that he was a doctor of medicine she asked him whether he could feel
a pulse, and whether the English or the Germans had the best pulses.
Young replied that he had felt but one pulse in Germany, the pulse
of a young lady — and that it was a very good pulse. Gottingen
was then the foremost school of horsemanship in Europe. Young
was passionately fond of this exercise, and there were no feats of
horsemanship, however daring or difficult, which he did not attempt
or accomplish. His muscular power had been always remarkable,
and he could clear a five-bar gate without touching it. He was better
known among the students for his vaulting on a wooden horse than
for writing Greek, regarding which they had neither knowledge nor
respect. At a court masquerade he appeared in the character of
harlequin, which gave him an excellent opportunity of exhibiting
his personal activity. Notwithstanding all this, he did not quite
like his life in Gottingen. The professors of the University were
worked too hard to leave much time for the receptions and social
gatherings in which Young delighted. So he quitted Gottingen on
the 28th of August, " with as little regret as a man can leave any
place where he has resided nine months."

From Gottingen he walked to Cassel, and thence by Gotha,
Erfurt, Weimar, and Jena, to Leipzig. He saw everything which to
him was worth seeing, and as he carried letters of introduction from
the most eminent men of the age, he was welcomed everywhere. Most
of the professors were absent on their holiday, but at Weimar he
conversed with Herder, who, though well versed in the English poets,

1886.] on Thomas Young, 561

cared notMng, it is said, about rhyme. At Jena he found Biitmer,
who, at the age of eighty- three, was about to begin the publication of
a general dictionary of all existing languages. He visited Dresden,
the Saxon Switzerland, and the mines of Freiberg. Here he made
the acquaintance of the celebrated Werner. From Freiberg he went
to Berlin, where he dined twice with the English Ambassador, Lord
Elgin, and once with Dr. Brown, a Welsh physician, in great favour
with the King. Over the monotonous sandy flat that lies between the
two cities, he journeyed from Berlin to Hamburg. Detained here for
a time by adverse winds, he was treated with great hospitality.

One word in conclusion regarding the German schools of learning.
Germany is now united and strong, her sons are learned, and her
prowess is proved. But the units from which her blended vigour has
sprung ought not to be forgotten. These were the little principalities
and powers of which she was formerly composed. Each of them
asserted its individuality and independence by the establishment of a
local University, and all over Germany, in consequence, such institu-
tions are sown broadcast. In these nurseries of mind and body, not
only Bismarck and von Moltke, but numbers of the rank and file of the
German army found nutriment and discipline ; so that though, as long
as her principalities remained separate, Germany as a whole was weak,
the individual action of those small states so educated German men
as to make them what we now find them to be.

Two epochs of Young's career as a medical student have been
now referred to — his residence in Edinburgh, and his residence at
Gottingen. Immediately after his return to England he became a
fellow-commoner of Emanuel College, Cambridge. When the master
of the college introduced him to those who were to be his tutors, he
jocularly said, " I have brought you a pupil qualified to read lectures
to his tutors." On one occasion, in the Combination Eoom, Dr. Parr
made some dogmatic observation on a point of scholarship. " Bentley,
sir," said Young promptly and firmly, " was of a different opinion."
" A smart young man that," said Parr when Young quitted tlie room.
His lack of humour, and want of knowledge of popular literature,
sometimes made him a butt at the dinner-table, but he bore the
banter with perfect good humour. The materials for Young's life at
Cambridge are very scanty; but there is one brisk and energetic
letter, published by Dean Peacock, written by a man who was by no
means partial to Young. " Young," he said, " was beforehand with
the world in perceiving the defects of English mathematicians. He
looked down upon the science, and would not cultivate the acquaint-
ance of any of our philosophers. He seemed never to have heard the
names of the poets and literary characters of the last century, and
hardly ever spoke of English literature." According to Peacock's
correspondent, there was about Young no pretence or assumption of
superiority. " He spoke upon the most difficult subjects as if he took
it for granted that all understood the matter as well as himself. But

2 0 2

562 Professor Tijndall [Jan. 22,

he never spoke in praise of any of the writers of the day, and could
not be persuaded to discuss their merits. He would speak of know-
ledge in itself — of what was known or what might be known, but
never of himself or of any one else, as having discovered anything, or
as likely to do so. His language was correct, his utterance rapid,
but his words were not those in familiar use, and he was therefore
worse calculated than any man I ever knew for the communication of
knowledge." This writer heard Young lecture at the Eoyal Institution,
but thought that nothing could show less judgment than the method
he adopted. " It was difficult to say how he employed himself at
Cambridge. He read little ; * there were no books piled on his floor,
no papers scattered on his table. His room had all the appearance
of belonging to an idle man. He seldom gave an opinion, and never
volunteered one ; never laid down the law, like other learned doctors,
or uttered sayings to be remembered. He did not think abstractedly.
A philosophical fact, a difficult calculation, an ingenious instrument,
or a new invention, would engage his attention ; but he never spoke
of morals, or metaphysics, or religion. Of the last, I never heard him
say a word. Nothing in favour of any sect or in opposition to any
doctrine."

The impression made upon Young by Cambridge was, from first
to last, entirely favourable. In those days, six years' study were
indispensable before the degree of Bachelor of Medicine could be
taken. Young graduated in 1803, when he was thirty years of age,
and five years more had to elapse before he could take the degree of
M.D. Meanwhile he had begun the practice of medicine. Dr.
Brocklesby died, in 1797, on the night of a day when he had
entertained his nephew and some other friends at dinner. During
dinner he seemed perfectly well, but he expired a few minutes
after he went to bed. He left Young his house and furniture in
Norfolk Street, Park Lane, his library, his j^rints, a collection of
pictures chiefly selected by Sir Joshua Reynolds, and about 10,000/.
in money.

The Wave Theory.

On the IGth of January, 1800, Young communicated to the Royal
Society his memoir entitled " Outlines and Experiments respecting
Sound and Light." In this paper he treated of the interference of
sound, and his researches on this subject led him on to the discovery
of the interference of light — " Which has proved," says Sir John
Herschel, " the key to all the more abstruse and puzzling i)roperties
of light, and which would alone have sufficed to place its author in
the highest rank of scientific immortality, even were his other almost
innumerable claims to such a distinction disregarded." Newton con-
sidered the sensation of light to be aroused by the darting into the

* Critics aud commentators must be f^ircat readers ; but creators in scionoe
and philosoi^hy do not always belong to this cntegory.

1886.] on Thomas Young. 563

eye, and the impinging against the retina, of particles inconceivably
minute. Huyghens, on the contrary, supposed the sensation of light
to be aroused by the impact of minute waves against the retina.
Young favoured the theory of undulation, and by his researches on
sound he was specially equipped for its thorough examination. Before
he formally attacked the subject, he gave, in a paj^er dealing with other
matters, his reasons for espousing the wave theory. The velocity of
light, for instance, in the same medium is constant. All refractions
are attended with partial reflection. The dispersion of light is no
more incompatible with this than with any other theory. Reflection
and refraction are equally explicable on both suppositions. Huyghens,
indeed, had proved this, and much more. Inflection may be better
explained by the wave theory than by its rival. The colours of thin
plates, which are perfectly unintelligible on the common hypothesis,
admit of complete explanation by the wave theory. In dealiuf^ with
the colours of thin films, of w-hich the soap-bubble offers a familiar
example. Young first proved his mastery over the undulatory theory.
In the pursuit of this great task, he was able to convert Newton's
Theory of Fits into the Theory of Waves, and to determine the
lengths of the undulations corresponding to the different colours of
the spectrum.

We now approach a phase of Young's career which more specially
concerns us. The Royal Institution, as already stated, was founded
by Count Rumford, supported by many of the foremost men in
England. The King was its patron, the Earl of Winchilsea its
first president, while Lord Morton, Lord Egremont, and Sir
Joseph Banks were its vice-presidents. On the 13th of January,
1800, the Royal Seal was attached to the charter of the Royal
Institution. Dr. Thomas Garnet was appointed Professor of Natural
Philosophy and Chemistry. During his previous residence in
Bavaria, Rumford had ruled with beneficent but despotic sway, and
the habit of mind thus engendered, may have made itself felt in his
behaviour to Dr. Garnet. At all events, they did not get on well
together. On the 16th February, 1801, Davy was appointed
Assistant Lecturer in Chemistry, Director of the Chemical Labora-
tory, and Assistant Editor of the Journals of the Institution.
The post of Professor of Natural Philosophy was offered to Young,
and he accepted it. The salary was to be SOOl. a year. On
the 3rd of August, 1801, the following resolution was passed : —
" Resolved, that the Managers ajDprove of the measures taken by Count
Rumford, and that the appointment of Dr. Young be confirmed."
Young, it is said, was not successful as a lecturer in the Institution,
and this Dr. Peacock ascribes to his early education, which gave him
no opportunity of entering into the intellectual habits of other men.
More probably, the defect was due to a mental constitution, not
plastic, like that of Davy or Faraday, in regard to exposition. Young
now fairly fronted the undulatory theory of light. Before you is

564 Professor Tyndall [Jan. 22,

some of the apparatus he employed. I hold in my hand an ancient
tract upon this subject by the illustrious Huyghens. It was picked up
on a bookstall, and presented to me some years ago by my friend
Professor Dewar. In this tract, Huyghens deals with refraction and
reflection, giving a complete explanation of both ; and here, also, he
enunciated a principle which now bears his name, and which forms
one of the foundation stones of the undulatory theory.

The most formidable obstacle to Young's advance, and one which
he never entirely surmounted, was an objection raised by Newton to
the assumption of a fluid medium as the vehicle of light. Looking
at the waves of water impinging on an isolated rock, Newton observed
that the rock did not intercept the wave motion. The waves, on the
contrary, bent round the rock, and set in motion the water at the back
of it. Basing himself on this and similar observations, he says, " Are
not all hypotheses erroneous in which light is supposed to consist of a
pression or motion propagated through a fluid medium ? If it consisted
in pression or motion, it would bend into the shadow." He instances
the case of the sound of a bell being heard behind a hill which conceals
the bell ; of the turning of corners by sound ; and then, with con-
clusive force he points to the case of a planet coming between a fixed
star and the eye, when the star is completely blotted out by the
interposition of the opaque body. This, Newton urged, could not
possibly occur if light were propagated by waves through a fluid
medium, for such waves would infallibly stir the fluid behind the
planet, and thus obliterate the shadow.

Young was firmly persuaded of the truth of the undulatory
theory. The number of riddles that, by means of it he had solved,
the number of secrets he had unlocked, the number of difficulties he
had crushed, rendered him steadfast in his belief; still, he never fairly
got over this objection of Newton's ; and it was first set aside by one
of the most illustrious men that ever adorned the history of science.
A young French officer of engineers, Augustin Fresnel, first really
grappled with the difficulty and overthrew it. The principle of
Huyghens, to which I have already referred, is, that every particle,
in every wave, acts as if it alone were a centre of wave motion. When
you throw a stone into the Serpentine, circular waves or ripples are
formed which follow each other in succession, retreating further and
further from the point of disturbance.* Fix your attention on one of

* '* I prove it thus, take heed now
By experience, for if that thou
Threw in water now a stone
Well west thou it will make anoue,
A little rouudell as a cercle,
Peraventure as broad as a couercle,
And right anone thou shalt see wele,
That whele cercle wil cause another whole.
And that a third and so forth brother,
Every cercle causing other."

Chaucer'' s ' House of Fame*

1886.] on Thomas Young. 565

these circular waves. The form of the wave moves forward, but
the motion of its individual particles, at any moment, is simply a
vibration up and down. Now each oscillating particle of every
moving wave, if left to itself, would produce a series of waves,
not so high, but in other respects exactly similar to those produced
by the stone. The coalescence of all these small waves produces
another wave of exactly the same kind as that which started them.
The princij^le that every particle of a wave acts independently of all
other particles, while the waves produced by all the particles after-
wards combine, is, as I have said, the great principle of Huyghens.
Taken in conjunction with the interference of light, first established
by Thomas Young, which proved that when waves coalesce or combine,
they may either support each other, or neutralise each other, the
neutralisation being either total or partial, according as the opposition
of the combining waves is complete or partial; taking, I say, the
principle of interference in conjunction with that of Huyghens,
Fresnel proved that although light does diverge behind an opaque
body, as Newton supposed that it would diverge, these divergent
waves completely efface each other, producing the shadow due to the
tranquillity of the medium which propagates the light.

By reference to the waves of water, Young illustrates, in the most
lucid manner, the interference of the waves of light. He pictures
two series of waves generated at two points near each other in a
lake, and reaching a channel issuing from the lake. If the waves
arrive at the same moment, neither series will destroy the other. If
the elevations of both series coincide, they will, by their joint action,
produce in the channel a series with higher elevations. But if the
ridges of one series correspond to the depressions of the other, the
ridges will exactly fill the depressions, smooth water in the channel
being the result. " At least," says Young, " I can discover no alter-
native, either from theory or from experiment. Now," he continues
— gathering confidence as he reasons, " I maintain that similar effects
take place whenever two portions of light are thus mixed, and this I
call the genei*al law of the interference of light."

The physical meaning of all the terms applied to light was soon
fixed. Intensity depended upon the amplitudes of the waves. Colour
depended on the lengths of the waves. Two series of waves coalesced
and helped each other when one was any number of complete un-
dulations or, in other words, any even number of half-undulations,
behind the other. Two series of waves extinguished each other when
the one series was any odd number of semi-undulations behind the
other. But inasmuch as white light is made up of innumerable
waves of different lengths, such waves cannot all interfere at the
same time. Some interfere totally, and destroy each other ; some
partially ; while some add themselves together and enhance the effect.
Thus, by interference, a portion only of the white light is withdrawn,
and the remaining portion is, as a general rule, coloured. Indeed
the most glowing and brilliant effects of coloration are thus pro-

566 Professor Tyndall [Jan. 22,

duced. Young applied the theory successfully to explain the colours
of striated surfaces which, in the hands of Mr. Eutherfurd and others,
have been made to produce such splendid effects. The iridescences
on the polished surfaces of mother-of-pearl are due to the striae
produced by the edges of the shell-layers, which are of infinitesimal
thickness ; the fine lines drawn by Coventry, Wollaston, and Barton
upon glass also showed these colours. Barton afterwards succeeded
in transferring the lines to steel and brass. Most of you are ac-
quainted with the iridescence of Barton's buttons. A descendant of
Mr. Barton has, I believe, succeeded in reproducing the instrument
wherewith his grandfather produced his brilliant effects.

But the greatest triumph of Young in this field was the explana-
tion of the beautiful phenomenon known as Newton's rings. The
colours of thin plates were profusely illustrated by the experiments of
Hooke and Boyle, but Newton longed for more than illustrations. He
desired quantitative measurement. The colour of the film was known
to depend upon its thickness. Can this thickness be measured ? Here
the unparalled penetration of Newton came into play. He took a
lens consisting of a slice of a sphere of a diameter so large that the
curved surface of the lens approximated to a plane surface. Upon
this slightly convex surface he placed a plate of glass whose surface
was accurately plane. Squeezing them together, and allowing light
to fall upon them, he observed those beautiful iris-circles with which
his name will be for ever identified. The iris-colours were obtained
when he employed white light. When monochromatic light was
used he had simply successive circles of light and darkness. Here
then, from the central point where the two glasses touched each other,
Newton obtained a film of air which gradually increased in thickness
as he retreated from the point of contact. Whence this wonderful
recurrence of light and darkness ? The very constitution of light
itself must be involved in the answer. His desire was now to
ascertain the thickness of the film of air corresponding to the
respective rings. Knowing the curvature of his lens, this was a
matter of easy calculation. He measured the diameter of the fifth
ring of the series. This might be accurately done with a pair of fine
compasses, for the diameter was over the fifth of an inch in length.
But it was the interval between the glasses corresponding to this
distance that Newton required to know, and this he found by calcula-
tion to be 1-37, 000th of an inch. This, be it remembered, is the
distance corresponding to the fifth ring. The interval corresponding
to the first ring would be only a fifth of this, or, in other words, about
l-180,000th of an inch. Such are the magnitudes with which we have
to deal before the question " What is Light ? " can be scientifically
answered.

Newton's explanation of the rings, which he was the first to
discover, though artificial in the highest degree, is marked by his
profound sagacity. He was hampered by the notion of the " cor-
poreity" of light. He could not get over the objection raised by

1886.] on Thomas Young. 5C7

himself as to the existence of shadows in a fluid medium. He
held therefore that light was due to the darting forth of minute
particles in straight lines; and he threw out the idea that colour
might be due to the difference of bigness in the particles. He endowed
these particles with what he called Jits of easy transmission and
reflection. The dark rings, in his immortal experiment, were produced
where the light-particles were in their transmissive " fit." They went
through both surfaces of the film of air, and were not thrown back to
the eye. The bright rings occurred where the light-particles were
in their reflective fit, and where, on reaching the second surface of
the film, they were thrown back to the eye. The cardinal point
here is, that Newton regarded the recurrence of light and darkness
as due to an action confined to the second surface of the film. And
here it was that Young came into irreconcilable collision with him,
proving to demonstration that the dark rings occurred where the
portions of light reflected from both sides of the film extinguished
each other by interference, while the bright rings occurred where
the light reflected from the two surfaces coalesced to enhance the
intensity.

Young next applied the wave theory to account for the diffraction
or inflection of light, that is to say, the effects produced by its bending
round the edges of bodies. When a cone of rays issuing from a very
minute point impinges on an oj^aque body, so as to embrace it wholly,
the shadow of the body, if received upon a screen, exhibits fringes of
colour. They follow so closely the contour of the opaque body, that
Sir John Herschel compared them to the lines along the sea-coast in
a map. If a very thin slip of card, or a hair, be placed within such a
cone, it is noticed that besides the fringes outside the shadow, bands of
colour occur within it ; the central, or brightest band, being always
white when white light is employed. It is a singular and somewhat
startling fact, that by the interposition of an opaque body, say a small
circle of tinfoil, the point on which we should expect the centre of the
shadow to fall, is, by the joint action of diffraction and interference,
illuminated in precisely the same degree as it is when the opaque
circle is withdrawn.* In reference to the interior fringes. Young made
the observation, which is of primary importance, that, if you intercept
the light passing by one of the edges of the strip of card or of the
hair, the fringes disappear. It requires the inflection of the waves
round both edges of the object, and their consequent interference, to
produce the fringes.

Young's attempt to explain the phenomena of diffraction was a
distinct advance on the extremely artificial hypothesis of Newton.
Still his attempt was not so successful as his explanation of the
colours of striated surfaces and of thin, thick, and mixed plates.
Here the young officer of engineers to whom I have already referred,

* A similar diffraction has been proved by Lord Kayleigh to occur in the case
of sound.

568 Professor Tyndall [Jan. 22,

Fresnel, entered the field. He presented in 1815, to the French
Institute, a memoir on Diffraction, which marks an epoch in the
history of the wave theory. It is usual, when such a paper is pre-
sented, to refer it to a " Commission " who consider it and report upon
its merits. The commissionaires in this instance were Arago and
Prony.

Arago had read the memoirs of Young in the ' Philosophical
Transactions,' but had not understood their full significance. The
study of Fresnel's memoir caused the full truth to flash upon him
that his young countryman had been anticipated thirteen years pre-
viously by Dr. Young, Fresnel had re-discovered the principle of
interference independently, and had applied it, with profound insight
and unrivalled experimental skill, to the phenomena of diffraction.
It was no light thing to Fresnel to find himself, as regards the
principle of interference, suddenly shorn of his glory. He, however,
bore the shock with resignation. He might have readily made claims
which would have found favour with his countrymen and with the
world at large. But he did nothing of the kind. The history of
science, indeed, furnishes no brighter example of honourable fairness
than that exhibited throughout his too short life by the illustrious
young Frenchman. Once assured that he had been anticipated — what-
ever might have been the extent of his own labours, however in-
dependently he might have arrived at his results, he unreservedly
withdrew all claim to the discovery. There is, I repeat, no fairer
example of scientific honour than that manifested by Augustin
Fresnel.

Fresnel was a powerful mathematician, and well versed in the
best mathematical methods of his day. With enormous labour he
calculated the positions where the phenomena of interference must
display themselves in a definite way. He was, moreover, a most
refined experimentalist, and having made his calculations, he devised
instrumental means of the most exquisite delicacy, with the view of
verifying his results. In this way he swept the field of diffraction
practically clear of difficulty, solving its problems where even Young
had failed.

Truly, these were minds possessing gifts not purchasable with
money ! and round about the central labours of both of them, minor
achievements of genius are to be found, which would be a fortune
to less opulent men. I hardly know a finer example of Young's
penetration than his account of the spurious or supernumerary
bows, observed within the true primary rainbow. These interior
bows are produced by interference. It is not difficult, by artificial
means, to form these bows in great number and beauty. This is
a subject on which, as you are aware, I worked a couple of years ago
myself. And often, when looking at these bows, the words of Young
seemed to me like the words of proiDhecy. The bows were the
physical transcript of what Young stated must occur ; a transcript,
moreover, which, when compared with his words, was far more com-

1886.] on Thomas Young. 669

plete and impressive than any ever exhibited by the rainbow in nature.
Many of you are acquainted with the beautiful rings of colour ob-
served when a point of light is looked at through the seeds of lycopo-
dium shaken over a piece of glass, or shaken in the air so as to form a
cloud whose particles are all of the same size. The iridescence of
clouds that I have once or twice seen in great splendour in the Isle
of Wight, but more frequently in the Alps, is due to this equality
in the size of the cloud-particles. Now the smaller the particles, the
wider are the coloured rings, and Young devised an instrument called
the Eriometer, which enabled him, from the measurement of the rings,
to infer the size of the particles. Again, Bitter had discovered the ultra-
violet rays of the spectrum, while Wollaston had noticed the darken-
ing effect produced by these rays when permitted to fall on paper or
leather which had been dipped in a solution of muriate of silver.
Employing these invisible rays to produce invisible Newton's rings,
Young projected an image of the rings upon the chemically prepared
paper. He thus obtained a distinct photographic image of the rings.
This was one of the earliest experiments wherein a true photographic
picture was successfully obtained. Young had little notion at the
time of the vast expansions which the art of photography was sub-
sequently to undergo.

But Young was not permitted to pursue his great researches in
peace. The ' Edinburgh Eeview ' had at that time among its chief
contributors a young man of vast energy of brain and vast power of
sarcasm, without the commensurate sense of responsibility which
might have checked and guided his powers. His intellect was not
for a moment to be measured with that of Young ; but as a writer
appealing to a large class of the public, he was, at that time, an
athlete without a rival. He afterwards became Lord Chancellor
of England. Young, it may be admitted, had given him some
annoyance, but his retaliation, if such it were, was out of all pro-
portion to Young's offence. Besides, whatever his personal feelings
were, it was not Young that he assailed so much as those sublime
natural truths of which Young at the time was the foremost exponent.
Through the undulatory theory he attacked Young without scruple or
remorse. He sneered at his position in the Koyal Institution, and tried
hard to have his papers excluded from the ' Philosophical Transac-
tions.' " Has the Eoyal Society," he says, " degraded its publications
into bulletins of new and fashionable theories for the ladies of the
Eoyal Institution ? Let the Professor continue to amuse his audience
with an endless variety of such harmless trifles, but in the name of
science let them not find admittance into that venerable repository which
contains the works of Newton and Boyle and Cavendish and Maskelyne
and Herschel." The profound, complicated and novel researches on
which Young was then engaged, rendered an occasional change of
view necessary. How does the reviewer interpret this praiseworthy
loyalty to truth ? " It is difficult," he says, " to deal with an author

570 Professor Tyndall [Jan. 22,

filled with a medium of so fickle and vibratory a nature. Were we to
take the trouble of refuting him lie might tell us, ' my opinion is changed,
and I have abandoned that hypothesis. But here is another for you.'
We demand if the world of science which Newton once illuminated is
to be as changeable in its modes as the world of fashion, which is

directed by the nod of a silly woman or a pampered fop ? We

have a right to demand that the hypothesis shall be so consistent with
itself as not to require perpetual mending and patching ; that the
child we stoop to play with shall be tolerably healthy, and not of the
puny and sickly nature of Dr. Young's productions, which have
scarcely stamina to subsist until the fruitful parent has furnished us
with a new litter, to make way for which he knocks on the head,
or more barbarously exposes, the first." He taunts Young with
claiming the inheritance of Newton's queries, " vainly imagining that
he fulfils this destination by ringing changes on these hypotheses,
arguing from them, as if they were experiments or demonstrations,
twisting them into a partial coincidence with the clumsy imaginations
of his own brain, and pompously parading what Newton left as hints,
in a series of propositions, with all the affectation of system."

To Brougham's coarse invective Young replied in a masterly and
exhaustive letter. A single copy, and one only, was sold by its pub-
lisher. There were at that time in the ranks of science no minds
competent to understand the controversy. The poison worked with-
out an antidote, and, for thirteen years, Young and his researches on
light had no place in public thought. His discoveries remained ab-
solutely unnoticed until their re-discovery by Fresnel lifted the pall
which for so many years had been thrown over this splendid genius.

Young lectured for two years at the Eoyal Institution, and he
afterwards threw the lectures into a permanent form in a quarto volume
of 750 pages with 40 plates, and nearly 600 figures and maps. He also
produced at the same time a second volume of the same magnitude,
embracing his optical and other memoirs, and a most elaborate classed
catalogue of works and papers, accompanied by notes, extracts, and
calculations. For this colossal work Young was to receive lOOOZ.
His publisher, however, became bankrupt, and he never touched the
money. His lectures constitute a monument of Young's power almost
equal to that of his original memoirs. They are replete with profound
reflections and suggestions. In his eighth lecture, on "Collision,"
the term energy, now in such constant use, is first introduced and
defined. By it he was able to avoid, and enable us to avoid, the con-
fusion which had crept into scientific literature by the incautious em-
ployment of the word force. The theory now known as the Young-
Helmholtz theory, which refers all the sensations of colour to three
primary sensations — red, green, and violet — was clearly enunciated by
Young in his thirty-seventh lecture, on " Physical Optics." His views
of the nature of heat were original and correct. He regarded the
generation of heat by friction as an unanswerable confutation of the

1886.] on Thomas Young. ^71

whole doctrine of material caloric. He gives appropriate illustrations
of the manner in which he supposed the molecules of bodies to be
shaken asunder by heat. " All these analogies," he says, " are cer-
tainly favourable to the opinion of the vibratory nature of heat, which
has been sufficiently sanctioned by the authority of the greatest
philosophers of past times and by the most sober reasoners of the
present." In anticipation of Dr. Wells, Young had observed and
recorded the fact, that a cloud passing over a clear sky sometimes
causes the almost instantaneous rise of a thermometer placed upon the
ground. The cloud he assumed acted as a vesture which threw back
the heat of the earth. Eadiant heat and light are here placed in the
same catagory. William Herschel had already shown their kinship,
by proving that the most powerful rays of the sun were entirely non-
luminous. Subsequent to this, the polarization of heat, by Principal
James Forbes, rendered yeoman's service in the propagation of the
true faith.

The passage in which Young introduces and defines the term
energy is so remarkable, that I venture to reproduce it here.

" The term energy may be applied, with great propriety, to the
product of the mass or weight of a body into the square of the number
expressing its velocity. Thus, if a weight of one ounce moves with a
velocity of a foot in a second, we may call its energy 1 ; if a second
body of two ounces have a velocity of three feet in a second, its
energy will be twice the square of three, or 18. This product has
been denominated the living or ascending force, since the height of
the body's vertical ascent is in proportion to it ; and some have con-
sidered it as the true measure of the quantity of motion ; but although
this opinion has been very universally rejected, yet the force thus
estimated well deserves a distinct denomination. After the con-
siderations and demonstrations which have been premised on the
subject of forces, there can be no reasonable doubt with respect to
the true measure of motion ; nor can there be much hesitation in
allowing at once that since the same force, continued for a double
time, is known to produce a double velocity, a double force must also
produce a double velocity in the same time. Notwithstanding the
simplicity of this view of the subject, Leibnitz, Smeaton, and many
others, have chosen to estimate the force of a moving body, by the
product of its mass into the square of its velocity ; and though we
cannot admit that this estimation of force is just, yet it may be allowed
that many of the sensible effects of motion, and even the advantage
of any mechanical power, however it may be employed, are usually
proportional to this product, or to the weight of the moving body,
multiplied by the height from which it must have fallen, in order to
acquire the given velocity. Thus, a bullet moving with a double
velocity, will penetrate to a quadruple depth in clay or tallow; a
ball of equal size, but of one-fourth of the weight, moving with a
double velocity, will penetrate to an equal depth ; and, with a smaller
quantity of motion, will make an equal excavation in a shorter time.

672 Professor Tyndall [Jan. 22,

This appears at first sight somewhat paradoxical ; but, on the other
hand, we are to consider the resistance of the clay or tallow as a
uniformly retarding force, and it will be obvious, that the motion,
which it can destroy in a short time, must be less than that which
requires a longer time for its destruction. Thus also when the
resistance, opposed by any body to a force tending to break it, is to
be overcome, the space through which it may be bent before it breaks
being given, as well as the force exerted at every point of that space,
the power of any body to break it is proportional to the energy of its
motion, or to its weight multiplied by the square of its velocity."

Young's essay on the Cohesion of Fluids, is to be ranked amongst
the most important and difficult of his labours. It embraced his
views and treatment of the subject of capillary attraction. But as
this topic is to be treated here next week by a spirit kindred to that
of Young himself, * I may be excused for saying nothing more about
it. The essay drew Young into a controversy with the illustrious
La Place, in which the Englishman exhibited that scimitar-like
sharpness of pen which more than once had drawn him into con-
troversy.

Young resigned his post at the Eoyal Institution because of the
conviction that his devotion to work alien to his profession would be
sure to injure his prospects as a physician. In the summer of 1802
he visited Paris, and at one of the meetings of the Academy was intro-
duced to the First Consul. In March 1803, he became M.B. of Cam-
bridge— six years after entering the University — while five years more
had to elapse before he was able to take the degree of M.D. In June
1804, he married Miss Eliza Maxwell, the daughter of J. P. Maxwell,
Esq., of Trippendence, near Farnborough, in Kent.

As regards medical practice. Young was probably too cool and
cautious in the examination of his data, and trusted too little to the
lancet and the calomel invoked in the vigorous practice of his time, to
be a popular physician. After a somewhat strenuous contest he was
appointed Physician to St. George's Hospital, and the appointment
was a strong proof of the esteem in which he was held. His lectures,
however, were not so well attended as those of his colleagues, for he
lacked the warmth and pliancy which usually commend a lecturer
to young men. Young's medical works, embodying the results of
great labour and research, were received with high consideration and
esteem.

By the force of his sarcasm and the glamour of his rhetoric,
Brougham had succeeded in inflicting a serious, if not irreparable
wound, on the science of his country. After Young's crushing reply,
which produced no effect whatever upon the public, the author of that
reply was practically forgotten as a factor in the advancement of
physical optics. But Science has always before her the stimulus

* Sir WiUiam Tliomsou.

1886.] on Thomas Young. 573

of natural problems demanding solution, and after a temporary lull
the desire to know more of the nature of light grew in force. New
stars arose in France, while the strenuous industry and experimental
discoveries of Brewster did much to hold us in equipoise with the
Continent. In Paris, La Place, Malus, Biot, and Arago were all
actively engaged. The three first proceeded strictly on the New-
tonian lines, and by the memoir of La Place, on Double Kefraction,
all antagonism to the theory of emission was considered to be for ever
overthrown. In the ' Quarterly Eeview,' Young criticised this memoir
with sagacity and power, and his criticism remains valid to the present
time. In accordance with the principles of the wave theory, Huyghens
had given a solution of the problem of double refraction in Iceland spar.
The solution was oj)posed to that of La Place. Dr. Wollaston, a man
of the highest scientific culture and the most delicate experimental
skill, subjected the theory of Huyghens to the severest metrical tests,
and his results proved entirely favourable to that theory. Wollaston,
however, lacked the boldness which would have made him a com-
mander in those days of scientific strife. He saw opposed to him the
names of Newton and La Place, and in the face of such authority he
shrank from closing with the conclusions to which his own experi-
ments so distinctly pointed.

We now come to a critical point in the fortunes of the wave
theory. I need not again refer to the difference between the motion
of a wave and the motions of the particles which constitute a wave.
A wave of sound, for instance, passing through the air of this room
would have a velocity of about 1100 feet a second, while the particles
which constitute the wave, and propagate it at any moment, may only
move through inconceivably small spaces to and fro. Now, in the case
of sound, this to-and-fro motion occurs in the direction in which the
sound is propagated, and a little reflection will make it clear that no
matter how a ray of sound, if we may use the term, is received upon
a reflecting surface, it would be echoed equally all round as long as
the angle inclosed between the reflecting surface and the ray remains
unchanged. In other words, the sound ray has no sides and no
preferences, as regards reflection. Now, Malus discovered that in
certain conditions a beam of light shows such preferences. When
caused to impinge upon a plane glass mirror, placed in a certain
position, it may be wholly reflected; whereas when the mirror is
placed in the rectangular position it may not be reflected at all.

Up to the hour when this discovery was made by Malus, light
had been supposed to be propagated through ether exactly as sound
is propagated through air. In other words, the direction in which the
particles of ether were supposed to vibrate to and fro coincided with
that of the ray of light. Those who had previously held the undu-
latory theory were utterly staggered by this new revelation, and their
perplexity was shared by Young. He was for a time unable to conceive
of a medium capable of propagating the impulses of light in a way
different from the propagation of the impulses of sound. To ascribe

574 Professor Tijndall [Jan. 22,

qualities to the light-medium which would enable it to diflfer in its
mechanical action from the sound-medium was an idea too bold —
I might indeed say too repulsive — to the scientific mind to be seriously
entertained. Yet, deeply pondering the question, Young ww,s at
length forced to the conclusion that the vibrations concerned in the
propagation of light were executed at right angles to the direction of
the ray. By this assumption of transverse vibrations, which removed
all difficulty, Young also removed the ether from the class of aeriform
bodies, and endowed it with the properties of a semi-solid.

Fresnel's memoir on Diffraction, upon which, as already stated,
Arago had reported, initiated a lasting friendship between the two
illustrious Frenchmen. They subsequently worked together. Fresnel,
the more adventurous and powerful spirit of the two, came indepen-
dently to the same conclusion that Young had previously enunciated.
But so daring did the idea of transverse vibrations appear to Arago —
so inconsistent with every mechanical quality which he could venture
to assign to the ether — that he refused to allow his name to appear
in conjunction with that of Fresnel on the title-page of the memoir
in which this heretical doctrine was broached. Still, the heresy has
held its ground, and the theory of transverse vibrations as applied to
the ether is now universally entertained.

Fresnel died in the fortieth year of his age.

Allow me to wind up this section of our labours by reference to
a German estimate of Young's genius. " His mind," says Helmholtz,
" was one of the most profound that the world has ever produced ;
but he had the misfortune of being too much in advance of his age.
He excited the wonder of his contemporaries who, however, were
unable to rise to the heights at which his daring intellect was accus-
tomed to soar. His most important ideas lay, therefore, buried and
forgotten in the folios of the Eoyal Society, until a new generation
gradiially and painfully made the same discoveries, and proved the
truth of his assertions and the exactness of his demonstrations."

HiEEOGLTPHICAL EeSEAKCHES.

Young's capacity and acquirements in regard to languages have
been already glanced at. As a classical scholar his reputation was
very high, and his Greek calligraphy was held to vie in elegance
with that of Person. A man so rounded in his culture could hardly
be said to have an intellectual bent ; but if he had one, the examina-
tion and elucidation of ancient manuscripts must have fallen in with
it. It is quite possible, however, that, had he not been disheartened
by the apparent success of Brougham, he would have clung more
steadfastly to physical science. However this may be, we now find
him in a new field. In October 1752 the first rolls of the papyri of
Hercnlaneum, wearing the asjiect of blackened roots, were discovered

1886.1 on Thomaa Young. 575

in what appeared to be the library of a palace near Portici. They
had been covered to a depth of 120 feet with the mixed ashes, sand,
and lava of Vesuvius. The inscriptions were for the most part
written in Greek, but some of them were in Latin. The leaves were
carbonised and hard, being glued together by heat to an almost
homogeneous mass.

Learned Italians — Father Antonio, a writer of the Vatican, in
particular — had devoted great labour and ingenuity to the separating
of the leaves and the deciphering of the inscriptions. To the credit
of the Prince of Wales, afterwards George IV., let it be recorded
that he manifested from the first an enlightened, a liberal, and truly
practical interest in these researches. He wrote to the Neapolitan
Government, offering to defray all the expenses of unrolling and
deciphering the papyri ; and he sent out Mr. Hayter, a classical
scholar of repute, to act as co-director with Eossini in the super-
intendence of the work. Mr. Hayter appears to have been unequal to
the task committed to him. His translations were defective ; his
lacunse serious and numerous, and he finally abandoned the manu-
scripts when he fled from Naples, with the Eoyal family, on the
French invasion in 1806. Some of the rolls, which had been pre-
sented to the Prince of Wales, were committed to the care of the
Eoyal Society, and placed by the Society in the hands of Dr. Young.
He spent many months in devising and applying means for the
opening of the leaves ; and, though only partially successful in this
respect,* he was able to correct many important errors, and to fill
many serious gaps in the work of his predecessors.

The ' Quarterly Eeview ' was established in 1809, and Young was
intimate with its leading contributors. One of these, George Ellis,
" a man of ardent affections," had resented, almost as personal to
himself, the attacks on Young in the ' Edinburgh Eeview,' and
Young's pen was soon invoked to enrich and adorn the pages of its
rival. A great work, the Herculanensia, had been published, contain-
ing learned dissertations by the Eev. Eobert Walpole, Sir William
Drummond, and others, on the ancient condition of Herculaneum and
its neighbourhood. The review of this work was committed to
Young, and his article upon it, embodying his own views and
researches, was published in 1810. " The appearance of the article,"
says Peacock, " equally remarkable for its critical acuteness and
vigorous writing, at once placed its author, in the estimation of the
public, in the first class of the scholars of the age." Gifford, the
editor of the ' Quarterly,' described the article as " certainly beyond
all praise." Ellis, at the same time, wrote thus to Young : — " It is a
consolation to know that Brougham, who took advantage of the growing
circulation of the ' Edinburgh Eeview ' to disseminate his vile abuse
of you, and Jefirey, who permitted him to do so, should be condemned
to hear your praises upon all sides." The tide had clearly turned in

* Davy afterwards tried his hand upon the rolls, with imperfect success.
Vol. XL (No. 80.) 2 p

676 Professor Tyndall [Jan. 22,

Young's favour, even prior to his final and triumphant vindication by
Fresnel.

From this time forward inscriptions of all kinds were sent to
Young for discussion or interpretation. They were found in numbers
among his papers after his death.*

It was a mind thus endowed and thus disciplined that now turned
to the task of deciphering the hieroglyphics of Egypt. The more
immediate cause of his grappling with this formidable but fascinating
subject was the finding by Sir W. Kouse Boughton, in a mummy-case at
Thebes, of a papyrus in Egyptian running hand, fragments of which,
after serious injury to the manuscript, fell into the hands of Young.
To Sir W. Boughton's communication to the Antiquarian Society,
Young appended a short notice, the chief significance of which is the
relation in which it stands to his subsequent researches. An adum-
bration of these, which must, under the circumstances, be weak and
faint, I will endeavour to bring before you.

The famous Kosetta stone was discovered by the French in Egypt
in 1799. It bore three inscriptions : the first, hieroglyphical or
sacred ; the second Enchorial f — a name given by Young to the
common language employed by the Egyptians in the time of the
Ptolemies ; and the third Greek. At the end are given the following
directions : — " What is here decreed shall be engraved on a block of
hard stone, in sacred, in native, and in Greek characters, and placed

* " In the 19th volume of the ' Archaeologia,' " says Young's biographer, " we
find an interesting notice of a fragment of a very ancient papyrus, as well as
several curious but somewhat barbarous sepulchral inscriptions of a late age from
Nubia, which were submitted to him by Lord Mountnorris. In the Appendix to
Captain's Light's Travels in Egypt, Nubia, Palestine, and Cyprus, he furnished
translations and restorations of several Greek inscriptions ; and when Barrow
gave an account in the • Quarterly Keview ' of recent researches in Egypt, more
especially those of Caviglia on the Great Sphinx, it was from Young that he ob-
tained the restoration of the inscription on the second digit of the great paw."
In the 3rd volume of Young's Works, this inscription, taken from the 19th volume
of the ' Quarterly Keview,' is given, with translations into modern Greek, Latin,
and English. The last-mentioned runs thus : —

" Thy form stupendous here the gods have placed.

Sparing each spot of harvest-bearing land;
And with this mighty work of art have graced

A rocky isle, encumber'd once with sand ;

And near the Pyramids have bid thee stand :
Not that fierce Sphinx that Thebes erewhile laid waste,

But great Latona's servant mild and bland ;
Watching that prince beloved who fills the tlirone
Of Egypt's plains, and calls the Nile his own.
That heavenly monarch [who his foes defies],
Like Vulcan powerful [and like Pallas wisej."

t Called in the Greek "Enchoria grammata," or letters of the country.
Young deprecates the introduction, afterwards, by Champollion, of the term
" Demotic," or popular.

1886.] on Thomas Young. 577

in each temple of the first and second and third gods." . All three in-
scriptions were more or less mutilated and efiaced when the stone was
discovered. Porson and Heyne had, however, succeeded in almost
completely restoring the Greek one.

It had been a custom with Young to pay an annual visit to
"Worthing, and to pursue there for a portion of the year his practice
as a physician. The Society of Antiquaries had caused copies of
the three inscriptions of the Eosetta stone to be made and published,
and in the summer of 1814, Young took all of them to Worthing,
where he subjected them to a severe comparative examination. Baron
Sylvestre de Sacy, an eminent orientalist, had discovered in the
native Egyptian, certain groups of characters answering to proper
names, while Akerblad, a profound Coptic scholar, had not only
added to the number, but attempted to establish an alphabet answer-
ing to the native Egyptian inscription. Young took up the re-
searches of these distinguished men as far as they could be relied on.
Assuming all three inscriptions to express the same decree, one of
them being in a language known to scholars, it was inferred by
Young that a strict comparison of line with line, word with word, and
character with character, would lead him by the sure method of
science from the known to the unknown. He rapidly passed his pre-
decessors. De Sacy had determined three proper names in the
Egyptian ; Akerblad nine others, and five or six Coptic words ; while
Young soon after detected the rudiments of fifty or sixty Coptic
words, which, however, formed but a very small fraction of the whole
inscription. And here an unexpected stumbling-block was en-
countered. The effort of Akerblad to reduce the whole Enchorial
inscription to Coptic had failed,* and it soon became evident to
Young that every such attempt must of necessity fail. His conviction
and its grounds are first mentioned in a letter to Mr. Gurney, written
in August 1814. "I doubt," he writes, " if it will be ever possible
to reduce much more of it to Coptic, especially as I have fully ascer-
tained that some of the characters are hieroglyphics y As bearing
upon the derivative origin of the Enchorial inscription, the discovery
here announced is of the highest importance. Young continues:
" I have, however, made out the sense of the whole sufficiently for
my purpose, and by means of variations from the Greek, I have been
able to effect a comparison with the hieroglyphics which it would have
been impossible to do satisfactorily without this intermediate step."
In a letter to the Archduke John of Austria, dated 2nd August, 1816,
Young announced that he had " now fully demonstrated the hiero-
glyphical origin " of the Enchorial inscription.f

* " Notwithstanding this failure, his name," says Peacock, " should ever be
held in honour as one of the founders of our knowledge of Egyptian literature,
to the investigation of which he brought no small amount of patient labour and
philological learning."

t "The same discovery," says the editor of the third volume of Young's
Works, " was announced by M. ChampoUion, as his own, in his memoir ' De

2 P 2

578 Professor Tyndall [Jan. 22,

" I had thought it necessary," says Young, in an essay written to
clear the air on this and various other points some years afterwards,
" to make myself in some measure familiar with the remains of the
old Egyptian language as they are preserved in the Coptic and
Thebaic versions of the Scriptures ; and I had hoped, with the assist-
ance of this knowledge, to be able to find an alphabet which would
enable me to read the Enchorial inscription, at least into a kindred
dialect. But in the progress of the investigation I had gradually
been compelled to abandon this expectation, and to admit the con-
viction that no such alphabet would ever be discovered, because it
had never been in existence.

" I was led to this conclusion, not only by the untractable nature
of the inscription itself, which might have depended on my own want
of information and address, but still more decidedly by the manifest
occurrence of a multitude of characters which were obviously imper-
fect imitations of the more intelligible pictures that were observable
among the distinct hieroglyphics of the first inscription, such as a
Priest, a Statue, a Mattock, or Plough, which were evidently, in their
primitive state, delineations of the objects intended to be denoted by
them, and which were, as evidently, introduced among the Enchorial
characters."

Young, as we have seen, had begun his labours on the Rosetta
stone in May 1814, and in the month of August he was able to
announce to Mr. Gurney his discovery that some of the Enchorial
characters were hieroglyphics. Prior to Young, no human being had
dreamt of the transfer of the characters of the first inscription to the
second. The first was pictural and symbolic; the second, to all
appearance, a purely alphabetical running hand. It had always been
regarded in this light. By means of the funeral papyri Young still
further established the relationship between the first and second
inscriptions. In 1816 he obtained from Mr. William Hamilton a
loan of the noble work entitled ' Description de I'Egypte,' in which
were carefully published several of the papyrus manuscripts. Many
of the inscriptions dealt with the same text, and by comparing them
one with another Young was able to trace the gradual departure from
the original hieroglyphic characters. Probably with a view to more
rapid writing, these had passed through various phases of degradation,

I'Ecriture Hieratique des Anciens Egyptiens,' published at Grenoble in 1821.
.... This memoir contained several plates in which the hieroglyphic and
hieratic characters are compared, on the same plan as Dr. Young's specimens in
the ' Encyclopedia Britannica,' published in 1819. He sent a copy of them to
Dr. Young, but withheld the letterpress. Dr. Young accordingly remained for
several years under the impression that tliis work had been published at a much
earlier period." Writing to Sir William Gell in 1827, in reference to this point.
Young remarks, " I never knew till now how much later his publication was, for
he gave it to me without the text." The publication was Cliampollion's
' Comparative Table of Hieroglyphics,' " containing," says Young, •* what I had
published in 1816," five years earlier.

1886.] on Thomas Young. 579

until they reached the stage corresponding to the Enchorial inscription
of the Eosetta stone, " which," says Young, " resembled in its general
appearance the most unpicturesque of these manuscripts." Long
before the time of Young, learned men had tried their hands on the
Eosetta characters, but no relationship like that here indicated had
ever been discerned.

Pre-eminent among the Egyptologists of that time was the cele-
brated Champollion, librarian at Grenoble. In his very first reference
to Champollion, Dean Peacock speaks thus of the illustrious French-
man : — " He had made the history, the toj)ography, and antiquities of
Egypt, as well as the Coptic language and its kindred dialects, the
study of his life, and he started therefore upon this inquiry with
advantages that probably no other person possessed ; and no one who
is acquainted with his later writings can call in doubt his extraor-
dinary sagacity in bringing to bear upon every subject connected with
it, not merely the most apposite, but also the most remote, and some-
times the most unexpected, illustrations." Thus equipped, however,
Champollion made next to no progress before the advent of Young.
" With the exception," says Peacock, " of the identification of a few
additional Coptic words, very ingeniously elicited from the Egyptian
text, he made no imjDortant advance on what had already been done
by Akerblad. Like him, also, he abandoned the task of identifying
the hieroglyphical inscription, or portions of it, with those cor-
responding to them in the Egyptian or Greek text, as altogether
hopeless, in consequence of the very extensive mutilations which it
had undergone."

Young, however, had determined about 90 or 100 characters of
the mutilated hieroglyphic inscription (the funeral papyri enabled
him afterwards to more than double the number), and these suflSced
to prove, " first, that many simple objects were represented by their
actual delineations ; secondly, that many other objects, represented
graphically, were used in a figurative sense only, while a great
number of the symbols, in frequent use, could be considered as the
pictures of no existing objects whatever; thirdly, that a dual was
denoted by a repetition of the character, but that three characters of
the same kind following each other implied an indefinite plurality,
more compendiously represented by three lines or bars attached to a
single character; fourthly, that definite numbers were expressed by
dashes for units, and arches, either round or square, for tens ; fifthly,
that all hieroglyphic inscriptions were read from front to rear, as
the objects naturally follow each other ; sixthly, that proper names
were included by the oval ring, or border, or cartouche ; * and
seventhly, that the name of Ptolemy alone existed on this pillar,
having only been completely identified by help of the analysis of the
Enchorial inscription. And," adds Young, " as far as I have ever

* Young's editor adds here, *' The discovery was long afterwards made by
Champollion that the cartouches were confined to the names of royal personages."

580 Professor Tyndall [Jan. 22,

heard or read, not one of these particulars had ever been established
and placed on record by any other person, dead or alive."

No man was a better judge of intellectual labour than Dean Pea-
cock. The whole of Young's writings, preparatory and otherwise,
were before him when he wrote ; and he states emphatically, that it is
impossible to estimate either the vast extent to which Dr. Young had
carried his hieroglyphical investigations or the progress which he had
made in them, without an inspection of these manuscripts. In re-
ference to an article entitled "Egypt," written by Young in 1818,
and published in the ' Encyclopaedia Britannica ' for 1819, a writer in
the 'Edinburgh Eeview' for 1826 delivers the following weighty
opinion : " We do not hesitate to pronounce this article the greatest
effort of scholarship and ingenuity of which modern literature can
boast." Even to an outsider it offers proof of astonishing learning
and research. Still, Peacock assures us that this publication of 1819
could hardly be considered more than a popular and superficial sketch
of the vast mass of materials on which it was founded.

Young was limited to what Peacock here calls "a popular and
superficial sketch," by the fact that the article in the ' Encyclopaedia
Britannica ' was written for ordinary readers rather than for critics or
learned men. In this article, however, we are allowed a glimpse of
Young's mode of collating and comparing the different inscriptions.
He looks at the Enchorial inscription, and notices certain recurrent
groups of characters; he looks at the Greek inscription, and finds
there words with the same, or approximately the same, periods of
recurrence. Thus, " a small group of characters occurring very often,
in almost every line, might be either some termination or some very
common particle ; it must therefore be reserved till it is found in
some decisive situation, after some other words have been identified,
and it will then easily be shown to mean and. The next remarkable
collection of characters is repeated twenty-nine or thirty times in the
Enchorial inscription ; and we find nothing that occurs so often in
the Greek except the word Mng. ... A fourth assemblage of cha-
racters is found fourteen times in the Enchorial inscription, agreeing
sufficiently well in frequency with the name of Ptolemy. ... By a
similar comparison, the name of Egypt is identified. . . . Having
thus," says Young, " obtained a sufficient number of common points
of subdivision, we next proceed to write the Greek text over the
Enchorial in such a manner that the j)assages ascertained may all
coincide as nearly as possible ; and it is obvious that the intermediate
parts of each inscription will then stand very near to the cor-
responding passages of the other. . . . By pursuing the comparison
of the inscriptions thus arranged, we ultimately discover the signifi-
cation of the greater part of the individual Enchorial words."

Having thus compared the Greek text with the Enchorial, Young
next proceeded to compare the Enchorial with the hieroglyphical.
About half the lines of the latter were obliterated, and the rest were

1886.] on Thomas Young. 581

considerably defaced. Towards the ends, however, both inscriptions
were fairly well preserved ; and these were the portions subjecte 1 to
the scrutiny of Young. Making allowance for the differences of space
occupied by the two inscriptions, and measuring from the final words of
the inscriptions, proportional distances, determined by the Enchorial
characters for God, King, Priest, and Shrine, the meaning of which
had been well established, Young sought at the places indicated by
these measurements for the corresponding hieroglyphics. He soon
found that shrine and priest were denoted by pictures of the things
themselves. The other terms, God and King, were still more easily
ascertained, from their situation near the name of Ptolemy. Having
thus fixed his points of orientation, Young placed them side by side,
and subjected the characters lying between them to a searching com-
parison. He offers in his article of 1819, the last line of the sacred
characters, with the corresponding parts of the other inscriptions, as
a "fair specimen of the result that has been attained from these
operations."

Up to the time of which we now speak, although profoundly learned
men had attempted to decipher the funeral papyri of Egypt, if we
omit the labours of Young, very little progress had been made even
in this direction ; while in regard to the decipherment of the hiero-
glyphics nothing had been done. To Young '* belongs the honour of
having within a short space of time, discovered that the Enchorial
writings contained symbolic as well as phonetic signs, and that the
hieroglyphic inscriptions possessed not only a symbolic but a phonetic
element. The latter discovery was based chiefly upon his analysis of
the names of Ptolemy and Berenice."

A vast extension of our knowledge of Egyptian writing is to be
ascribed to a circumstance which might almost be called miraculous.
An Italian named Cassati, had brought to Paris several manuscripts
from Upper Egypt. One was written exactly in the Enchorial character
of the second inscription on the Kosetta stone. Ifc was a deed of sale,
and on the back of the manuscript was an endorsement in Greek.
When in Paris, Young had received from Champollion a tracing of
the Enchorial deed, but not of the Greek endorsement. About the
same time, Mr. Grey, an English traveller, brought to England a
n amber of manuscripts, which he placed in the hands of Dr. Young.
One of them was written entirely in Greek, and Young immediately
perceived that it was a perfect copy of the Enchorial deed of sale.
He wrote immediately to Champollion, informing him of the fact, and
begging him to send a copy of the Greek endorsement which he had
omitted. This he did not do ; but his countryman Eaoul Eochette
courteously and promptly responded to Young's request, and sent
him a correct copy of the whole Cassati manuscript.

The possession of the Greek translation was of course an immense
help to Young in his efforts to decipher the Enchorial deed, on which
he was at this very time engaged. " I could not," he says, " but

582 Professor Tyndall [Jan. 22,

conclude that a most extraordinary chance had brought into my
possession a document which was not very likely, in the first place,
ever to have existed, still less to have been preserved uninjured for
my information through a period of near two thousand years. But that
this very extraordinary translation should have been brought safely
to Europe, to England, and to me, at the very moment when it was
most of all desirable to me to possess it, as the illustration of an
original which I was then studying, but without any reasonable hope
of being able to fully comprehend it, — this combination would in
other times have been considered as affording evidence of my having
become an Egyptian sorcerer."

Grey's manuscript related not to a sale of a house or field, but to
portions of the collections and offerings made from time to time for
the benefit of a certain number of mummies. The persons of whom
the mummies were the remains were described at length in bad Greek,
but though bad, a comparison between it and the Enchorial writing,
gave the most important information regarding the orthography of
ancient Egypt. Mr. Grey's collection contained three other similar
deeds, all written in the Enchorial character of the Eosetta stone, and
endorsed with the Greek registry. The dates of these documents
closely corresponded with that of the Cassati manuscript which was
146 years before Christ. They refer to the sale of land, the
boundaries of which were very clearly defined.* In those days, as wo
know, the Egyptians were the best land surveyors in the world. The
comparison of these documents formed, as might be expected, an epoch
in the history of Egyptian literature.

We now approach a period of stormy discussion regarding the
claims of different discoverers. And as the tempest raged chiefly round
Young and Champollion, it is desirable to fix with precision, if that
be possible, the position of the learned Frenchman before he came
into contact with Young. This, a work published by Champollion

* And the persons concerned equally well defined. In this respect the
Egyptians might vie with the writers of Continental passports. The following is
a translation of the famous papyrus of Anastasy, recording a deed of sale : —
" There was sold by Pamonthes, aged about forty-five, of middle size, dark com-
plexion, and handsome figure, bald, round faced, and straight nosed ; by
Snachomneus, aged about twenty, of middle size, sallow complexion, likewise
round faced and straight nosed ; and by Semmuthis Persinei", aged about twenty-
two, of middle size, sallow complexion, round faced, flat nosed, and of quiet
demeanour ; and by Tathlyt Persinei, aged about thirty, of middle size, sallow
complexion, round face, and straight nose, with their principal Pamonthes, a
party in the sale; the four being of the children of Petepsais of the leather
cutters of the Memnonia ; out of the piece of level ground which belongs to them
in the southern part of the Memnonia, eight thousand cubits of open field. ... It
was bought by Nechutes the less, the son of Asos, aged about forty, of middle
size, sallow complexion, cheerful countenance, long face, and straight nose, with
a scar upon the middle of his forehead, for 601 pieces of brass, the sellers standing
as brokers, and as securities for the validity of the sale. It was accepted by
Nechutes the purchaser."

1886.] on Thomas Young. 583

at Grenoble, in 1821, enables us to do. After speaking of the notions
previously entertained regarding the hieroglyphical and epistolo-
graphic characters of the Egyptians, and of the opinion, universally
diffused, that the Egyptian manuscripts, like those of to-day, are
alphabetical, the author states his case thus : — " Une longue etude, et
surtout une comparaison attentive des textes hieroglyphiques avec
ceux de la seconde espece, regardes comme alphabetiques, nous ont
conduit a une conclusion contraire.

II resulte, en effet, de nos rapprochements : —

1° Que I'ecriture des manuscrits Egyptiens de la seconde espece
(I'hieratique) n'est point alphabetique ;

2° Que ce second systeme n'est qu'une simple modification du sys-
teme hieroglyphique, et n'en differe uniquement que par la forme
des signes ;

3° Que cette seconde espece d'ecriture est I'hieratique des auteurs
Grecs, et doit etre regardee comme une tachygraphie hieroglyphique ;

4° Enfin, que les caracteres hieratiques sont des signes de choses,

ET NON DES SIGNES DE SONS."

There is no mention here of the name of Young, though he had,
many years previously, made known to the world, as the result of his
own researches, the first, second, and third of these propositions. With
regard to the fourth, it incontestibly proves, as maintained by both
Klaproth and the Dean of Ely, " that at this epoch, Champollion had
either formed no conception of the existence of phonetic hieroglyphics,
or had given it up as altogether untenable, if he had once entertained
it." Immediately after the publication of this work in 1821, Cham-
pollion became acquainted with the " popular and superficial sketch. "
— ^in reality the transcendently able article of Young — published in
the ' Encyclopaedia Britannica ' for 1819.

Peacock's analysis of what next occurred is not agreeable reading.
ChampoUion's memoir of 1821 was rapidly suppressed, and soon be-
came so scarce that it has been passed over by almost every author
v^ho has written on the subject. In the following year Champollion
addressed a letter to M. Dacier, in which, to use the language of
Peacock, we suddenly find him pushed forward into the inmost recesses
of the sanctuary, reached by Young five years before. The plates,
moreover, of the suppressed memoir were circulated, without dates and
without letterpress. A copy of these plates was given by Cham-
pollion to Young, who was left in entire ignorance of the date of
publication. " The suppression of a work," writes Peacock, in strong
reproof, " expressing opinions which its author has subsequently found
reason to abandon, may sometimes be excused, but rarely altogether
justified; hut under no circumstances can such a justification he pleaded,
when the suppression is either designed or calculated to compromise the
claims of other persons with reference to our own. The memoir in
question very clearly showed that so late as the year 1821, Cham-
pollion had made no real progress in removing the mysterious veil
which had so long enveloped the ancient literature of Egypt. The

584 Professor Tyndall [Jan. 22,

article " Egypt," written by Young, had meantime confessedly come
under his observation. He saw the errors of his views and sup-
pressed them, without giving due credit to the man who had first
struck into the true path." In reference to an account given by
Champollion of the labours of Young, Peacock remarks, " It would
be difficult to point out in the history of literature a more flagrant
example of the disingenuous suppression of the real facts bearing upon
an important discovery."

And yet the Dean of Ely is by no means stingy in his praise
of Champollion. It would be unjust, he says, to refuse to Cham-
pollion the honour due to his rare skill and sagacity, not merely
in the application of a principle already known, but in its rapid
extension to a multitude of other cases, so as not merely to point out
its character and use, but also to determine the principal elements of
a phonetic alphabet. His long-continued studies, Peacock remarks,
had fitted him more than any other living man, Young himself
hardly excepted, to deal with this subject, " and the rapidity of his
progress, when once fully started on his career of discovery, was
worthy of the highest admiration." Peacock, moreover, describes his
work as ever memorable in the history of hieroglyphical research,
not only from the vast range of knowledge which it displays, but
from the clear and lucid order in which it is arranged. " It was," he
continues, " singularly unfortunate that one who possessed so much
of his own, should have been so much wanting in a proper sense of
justice to those who had preceded him in these investigations, as
materially to lessen his claims to the respect and reverence which
would otherwise have been most willingly conceded to him."

With regard to the lack of literary candour, thus so strongly
commented on, it is of interest to note the views concerning
Champollion held by one of his own countrymen. Soon after the
researches of Young had begun, an extremely interesting corre-
spondence was established between him and De Sacy. As early as
October 1814, Young was able to submit to his correspondent a
" conjectural translation " into Latin of the Egyptian Eosetta inscrip-
tion. He subsequently sent him an English translation, the receipt
of which is acknowledged by De Sacy in a letter dated Paris, 20th
July, 1815. The opening paragraph of this letter contains an
allusion of considerable historic importance : — " Outre la traduction
latine de I'inscription egyptienne, que vous m'avez communiquee, j'ai
reQU posterieurement une autre traduction anglaise imprimee, que
je n'ai pas en ce moment sous les yeux, Vayant prete a M. Champollion
8ur la demande, que son frere m'en a faite d'aprcs une lettre qu'il
rna dit avoir re^u de vous.'' In view of the statement of Champollion
in a Freds of his researches published in 1824, that he had arrived
at results similar to those obtained by Dr. Young, without having any
knowledge of Young's opinions, the foregoing extract is significant.
De Sacy goes on to recognise formally the progress which had been
made by Young at the date of the foregoing letter. He asks some

1886.] on Thomas Young. 585

questions regarding Young's method, whicli in certain cases appeared
to him enigmatical. The requisite explanations were promptly-
given by Young. In a labour of the kind here under consideration,
that force of genius which we vaguely term intuition must come con-
spicuously into play ; and it is not always easy for him to whom the
exercise of this force is habitual to make plain to others the nature
and results of its action.

De Sacy embodies in the letter above quoted some personal
remarks which, were it not that their omission would involve a virtual
injustice to Young, one would willingly pass over. " Si j'ai un conseil
a vous donner," writes the Baron, " c'est de ne pas trop communiquer
vos decouvertes a M. Champollion. II se pourrait faire qu'il pre-
tendat ensuite a la priorite. II cherche en plusieurs endroits de son
ouvrage a faire croire qu'il a decouvert beaucoup des mots de
I'inscription egyptienne de Eosette. J'ai bien peur que ce ne soit
la que du charlatanisme : j'ajoute memo que j'ai de fortes raisons de
le penser." The work of Champollion here referred to was entitled
*L'Egypte sous les Pharaons, ou recherches sur la geographic, la
religion, la langue, les ecritures, et I'histoire de I'Egypte avant
I'invasion de Cambyses.' Two volumes of the work were published
in 1814, but it was never completed.

In a letter written towards the end of 1816 Young passes the
following judgment upon this book in regard to its relation to the
Eosetta inscriptions : —

" I have only spent literally five minutes in looking over Cham-
pollion, turning, by means of the index, to the parts where he has
quoted the inscription of Eosetta. He follows Akerblad blindly,
with scarcely any acknowledgment. But he certainly has picked
out the sense of a few passages in the inscription by means of Aker-
blad's investigations — although in four or five Coptic words which he
pretends to have found in it, he is wrong in all but one — and that is
a very short and a very obvious one. 3Ij/ translation is printed ; it
is anonymous, and must for some time remain so ; hut everybody whose
approbation is worth having will know the author."

Our neighbours, the French, have been always fond, perhaps
rightly fond, of national glory, not only in military matters, but
also in science and literature. They rallied round Champollion.
Even De Sacy. who had previously warned Young against him,
eventually joined in the general paean. Arago also, who, in regard
to the optical discoveries of Young had behaved so honourably,
delivered an Eloge of Young, founded, according to Peacock, on
the most imperfect and narrow views of the case. In fact, patriot-
ism came into play, where cosmopolitanism ought to have been
supreme. Arago seeks to make out that Young stands in the same
relation to Champollion as Hooke, in regard to the doctrine of inter-
ferences, stands to Young. This is certainly a bold comparison. If,
as observed by Young's editor, Arago had gone as far back as Zoega,

586 Professor Tyndall [Jan. 22,

the comparison might have been just. Arago himself gives his
reasons for entering the controversy, and they are these : — " que
I'interpretation cles hieroglyphes egyptiens est Tune des plus belles
decouvertes de notre siecle ; que Young a lui-meme mele mon nom
aux discussions dont elle a ete I'objet ; qu'examiner enfin, si la France
pent pretendre a ce nouveau tifcre de gloire, c'est agrandir la mission que
je remplis en ce moment, c'est faire acte de bon citoyen. Je sais
d'avance tout ce qu'on trouvera d'etroit dans ces sentimens ; je
n'ignore pas que le cosmopolitisme a son beau cote ; mais en verite, de
quel nom ne pourrais-je pas le stigmatiser si lorsque toutes les
nations voisines enumerent avec bonheur les decouvertes de leurs
enfans, il m'etait interdit de chercher dans cette enceinte memo
parmi des confreres dont je ne me permettrai pas de blesser la modeste,
la preuve que la France n'est pas degeneree, quelle aussi apporte
chaque annee son glorieux contingent dans le vaste depot des con-
naissances humaines."

The Copley medal of the Eoyal Society of London had been
awarded to Arago in 1825, and on the 30th of November of that
year, on handing over the medal to the gentleman deputed to receive
it, Sir Humphry Davy, then President of the Society, had used the
following words : — " Fortunately science, like that nature to which it
belongs, is neither limited by time nor by space. It belongs to the
world, and is of no country and no age." I do not hesitate to say
that I prefer the sentiment of Davy to that of Arago.

Still, even in France, Young did not lack defenders. M. de
Paravey, Inspecteur de I'Ecole Eoyale Polytechnique, for example,
speaking of himself in the third person, makes the following remarks
in a letter dated February 1835, six years after Young's death : —
" II y admira la science avec laquelle M. le Docteur Young avait
retabli la chronologic des Eois d'Egypte, ne commen9ant leur serie
qu'a la XVIII dynastie de Manethon, en regardant les series ante-
rieures comme inadmissibles ; resultats auxquels des travaux tout
differents avoient egalement conduit M. de Paravey : et, en outre, il
jugea, et il juge encore, que le premier il entroit d'une maniere
plausible et sure dans I'interpretation des hieroglyphes, fournissant
ainsi a M. Champollion lejeune une clef sans laquelle ce dernier n'auroit
jamais pu arriver aux resultats importants et curieux que dejpuis il a
ohtenu"

In the same sense, and almost in the same words, writes Sir Gard-
ner Wilkinson, an ardent admirer of Champollion, and his chivalrous
defender against the assaults made upon him after his death. After
speaking of him as the kindler into a flame of the spark obtained by
Young, he continues thus : — " Had Champollion been disposed to
give more credit to the value and originality of Dr. Young's re-
seiirches, and to admit that the real discovery of the hey to the hiero-
glyphics, which in his dexterous hand proved so useful in unlocking
those treasures, was the result of his [Young's] labours, he would un-

1886.] on Thomas Young. 687

questionably have increased his own reputation, without making any
sacrifice." In another place, Wilkinson remarks, in regard to the
reading of the hieroglyphics, " that Dr. Young gave the first idea
and proof of their alphabetic force, which was even for some time
after doubted by Champollion."

Peacock speaks with wondering admiration of the modesty and
forbearance which he invariably showed in regard to Champollion. He
complained a little, but he throws no doubt or insinuation upon the
Frenchman's honour. He confines himself exclusively to his published
writings, and makes no reference to the loads of labour which lay
upon his shelves unpublished. Peacock complains, and justly complains,
of the unfairness of comparing the Champollion of 182*4 with the Young
of 1816. Young was the initiatory genius. He gave Champollion the
key, which he used subsequently with that masterly skill and sagacity
which have rendered his name illustrious. But Peacock emphatically
affirms that, while Champollion passed over Young's special researches
in connection with the papyri of Grey and Cassati, he affirms with
equal emphasis that whatever principle of discovery had been per-
ceived and established or made known, is appropriated without
acknowledgment, and the dates which would have proved the unques-
tionable priority of Dr. Young are carefully suppressed. No oppor-
tunity is lost of bringing prominently before the reader whatever
error he may have committed, with a view of showing not only his
(Champollion's) own superiority, but his entire independence and
originality.

The Dean of Ely obviously felt very sore in regard to the treat-
ment of Dr. Young. " It is not our object," he says, " to underrate
the merits of the great contributions which were made by Cham-
pollion to our knowledge of hieroglyphical literature, but to protest
against the persevering injustice with which he treated the labours of
Dr. Young ; and we feel more especially called upon to do so in
consequence of finding that an author like Bunsen, occupying so
high a position among men of letters, should have supported with
the weight of his authority some of the grossest of his misrepresenta-
tions." Peacock acknowledges his own obligations to the valuable
labours of his friend Mr. Leitch ; but he also claims to have pursued
an independent course by consulting the unpublished documents in
his possession, which were unknown even to himself, until he was
compelled to study them in connection with the publications which
had been founded upon them. " It was only," he says, " after this
perusal that I became fully aware how imperfectly the published
writings of Dr. Yonng represented either the extent or the character
of his researches ; or the real progress he had made in the discovery
of phonetic hieroglyphics many years before Champollion had made
his appearance in the field."

588 Professor Tyndall on Thomas Young. [Jan. 22,

The following Inscription, written by Mr. Hudson Gurney, was
placed on a slab beneath the medallion by Sir Francis Chantrey in
Westminster Abbey. The same inscription, somewhat modified, was
placed on a marble slab in the village church of Farnborough, near
Bromley, Kent, where the remains of Dr. Young were deposited in
the vault of his wife's family : —

SACRED TO THE MEMOEY OF

THOi¥AS YOUNG, M.D.,

FELLOW AND FOREIGN SECRETAEY OF THE EOYAL SOCIETY,

MEMBEE OF THE NATIONAL INSTITUTE OF FRANCE ;

A MAN ALIKE EMINENT

IN ALMOST EVEEY DEPAETMENT OF HUMAN LEAENING.

PATIENT OF UNINTEEMITTED LABOUR,

ENDOWED WITH THE FACULTY OF INTUITIVE PERCEPTION,

WHO, BRINGING AN EQUAL MASTERY

TO THE MOST ABSTRUSE INVESTIGATIONS

OF LETTERS AND OF SCIENCE,

FIRST ESTABLISHED THE UNDULATOEY THEOEY OF LIGHT,

AND FIEST PENETEATED THE OBSCUEITY

WHICH HAD VEILED FOE AGES

THE HIEROGLYPHICS OF EGYPT.

ENDEARED TO HIS FEIENDS BY HIS DOMESTIC VIETUES,
HONOUEED BY THE WOELD FOE HIS UNRIVALLED ACQUIREMENTS,
HE DIED IN THE HOPES OF THE EESUEEECTION OF THE JUST.

BORN AT MILVEKTON, IN SOMEESETSHIEE, JUNE 13tH, 1773,

DIED IN PAEK SQUAEE, LONDON, MAY IOtH, 1829,

IN THE 56th YEAE OF HIS AGE.

1886.] General Monthly Meeting. 589

GENERAL MONTHLY MEETING,

Monday, July 5, 1886.

William Huggins, Esq. D.C.L. LL.D. F.R.S. Vice-President, in the

Chair.

George A. Crawley, Esq.

The Eight Hon. W. H. Smith, M.P.

were elected Members of the Royal Institution.

The Managers reported that they had re-appointed Professor
James Dewar, M.A. F.R.S. as Fullerian Professor of Chemistry.

The Presents received since the last Meeting were laid on the
table, and the thanks of the Members returned for the same, viz. : —

The French Government — Documents Inedits sur I'histoire de France : Melano-es

Historiques. Tome V. 4to. 1886.
Negociations Diplomatiques de la France avec la Toscane. Tome VI. 4to.

1886.
Accademia dei Lincei, Reale, Roma — Atti, Serie Quarta ; Kendiconti. Vol. H

Fasc. 10, 11. 8vo. 1886.
American Philosophical Society — Proceedings, No. 122. 8vo. 1886.
Antiquaries, Society o/^Archseologia, Vol. XLIX. Part 2. 4to. 1886.
Astronomical Society, Royal — Montlily Notices, Vol. XL VI. No. 7. 8vo. 1886.
Bankers, Institute of — Journal, Vol. VII. Part 6. 8vo. 1886.
Bell, Robert, 3LD. LL.D. (the Author)— The Forests of Canada. 8vo. 1886.

Mineral Resources of the Hudson's Bay Territories. 8vo. 1886.
Bernays, Albert J. Ph.D. F.C.S. M.R.L (the Author)— ^otes on Analytical

Chemistry. 2nd Edition. 12mo. 1886.
British Architects, Royal Institute of — Proceedings, 1885-6, Nos. 17, 18. 4to.
British Museum (Natural B/sfori/)— Catalogue of Birds. Vol. XI. 8vo. 1886.
Illustrations of Lepidoptera Heterocera. Part VI. 4to. 1886.
Catalogue of Fossil Mammalia. Part III. 8vo. 1886.
Introduction to the Study of Meteorites. 8vo. 1886.
Brymner, Douglas, Esq. (the Archivist) — Report on Canadian Archives, 1885.

8vo. 1886.
Chemical Society— J ourndl for June, 1886. 8vo.
Civil Engineers' Institution — Minutes of Proceedings, Vol. LXXXIV. 8vo.

1885-6.
Cornwall Polytechnic Society Royal — Fiftv-third Annual Report. 8vo. 1885.
Crisp, Frank, Esq. LL.B. F.L.S. &c. M.R.I, (the Editor)— Journal of the Royal

Microscopical Society, Series II. Vol. VI. Part 3. 8vo. 1886.
East India Association — journal, Vol. XVIII. No. 4. 8vo. 1886,
Eury^ Lord (the Author) — The Laity and Church Reform. 8vo. 1886.

590 General Montldy Meeting. [July 5,

Editors — Amateur Photographer for June, ] 88G. 4to.

American Journal of Science for June, 1886. 8vo.

Analyst for June, 1886. 8vo.

Athenaeum for June, 1886. 4to.

Chemical News for June, 1886. 4to.

Engineer for June, 1886. fol.

Engineering for June, 1886. fol.

Horological Journal for June, 1886. 8vo.

Iron for June, 1886. 4to.

Nature for June, 1886. 4to.

Kevue Scientifique for June, 1886. 4to.

Telegraphic Journal for June, 1886. 8vo.

Zoophilist for June, 1886. 4to.
Franklin Institute— Journal, No. 726. 8vo. 1886.

General Medical Council— Second Eeport of Statistical Committee. 8vo. 1886.
Geographical Society, Boyal—Froceedings, New Series, Vol. VIII. No. 6. 8vo.

1S86.
Georgofili Beale Accademia — Atti, Quarta Serie. Vol. VIII. Disp. 4. Vol. IX.

Disp. 1. 8vo. 1885-6.
Harlem, Societe' Hollandaise des Sciences— Avchives Neerlandaises, Tome XX,
Liv. 5. 8vo. 1886.

Liste Alphabetique de la Correspondance de Huygens. 4to. 1886.
Johns Hopkins University — Studies in Historical and Political Science, Fourth
Series, No. 6. 8vo. 1886.

American Journal of Philology, No. 25. 8vo. 1886.

University Circular, Nos. 49, 50. 1886,
Ministry of Public Worhs, Eome— Giornale del Genio Civile, Serie Quarta,

Vol. VI. No. 4. 8vo. And Disegni. fol. 1886.
Numismatic Society — Chronicle and Journal, 1886, Part 1. 8vo.
Pharmaceutical Society of Great Britain — Journal, June, 1886. 8vo.
Photographic Society — Journal, New Series, Vol. X. No. 8. 8vo. 1886,
Roberts- Austen, W. Chandler, Esq. F.B.S. M.R.I. — Annual Reports of the Deputy

Master of the Mint, 1880-5. 8vo.
Royal Dublin ^Soc/e^— Transactions, Vol. III. Nos. 7-10. 4to. 1885.

Proceedings, Vol. IV. Parts 7-9 ; Vol. V. Parts 1, 2. 8vo. 1885-6.
Royal Society of London — Proceedings, No. 243. 8vo. 1886.
Smithsonian Institution, Washington— A.nn\XQ\ Report for 1884, 8vo. 1885.
Society of ^r^s— Journal, June, 1886. 8vo.
Telegraph Engineers, Society o/— Journal, No. 61, 8vo. 1886.
United Service Institution, ii'o^/aZ— Journal, No. 134. 8vo. 1886.
Vereins zur Beforderung des Gewerbfleisses in Preussen — Verhandlungen, 1886 :

Heft 5. 4to.
Vernon-Harcourt, L. F. Esq. M.A. (the Author) — Blasting Operations at Hell

Gate, New York. (Inst. Civil Engrs. Proc. LXXXV.) 8vo. 1886.
Yienna — Naturhistorischen Hofmuseums — Annalen, Band I. No. 2. 4to. Wien 5,

1886.
Zoological Society — Proceedings, 1886, Part 1, 8vo.

1886.J General Monthly Meeting. 591

GENERAL MONTHLY MEETING,

Monday, November 1, 1886.
Henry Pollock, Esq. Treasurer and Vice-President, in the Chair.

Charles Witham Herbert, Esq.
Arthur Lasenby Liberty, Esq.

were elected Members of the Royal Institution.

The Presents received since the last Meeting were laid on the
table, and the thanks of the Members returned for the same, viz. : —

The Governor-General of India — Geological Survey of India. Records, Vol. XIX.
Part 3.
Memoirs : Palseontologia Indica. Ser. X. Vol. IV. Part 1. ; Ser. XIV. Vol. I
Part 3, Fasc. 6. 4to. 1886.
The Secretary of State for India — Great Trigonometrical Survey of India.

Synoptical, Vol. XIII. A. 4to. 1886.
The Lords of the Admiralty — Greenwich Observations for 1884. 4to. 1886.
Greenwich Spectroscopic and Photographic Eesults, 1884. 4to. 1886.
Observations of the Great Comet, 1882, II. 4to, 1886.
Cape Meridian Observations, 1879-1881. 8vo.
Ministry of Public Works, Rome — Giornale del Geuio Civile. Serie Quarta.

Vol. VI. Nos. 5-6. 8vo. And Disegni. fol. 1886.
Accademia dei Lincei, Reale, Roma — Atti, Serie Quarta : Rendiconti. Vol. II.
Fasc. 12, 13, 14 ; Vol. II. 2^ Semestre, Fasc. 1, 2, 3, 4, 5, 6. 8vo. 1886.
Memorie della Classe di Scienze Morali, Stt.riche e Filologiche. Serie 3*^,

Vol. XII. 4to. 1884.
Memorie della Classe di Scienze Fisiche, Matematiche e Naturali. Serie 3a
Vols. XVIII. XIX. ; Serie 4% Vol. II. 4to. 1884-5.
Academy of Natural Sciences, Philadelphia — Proceedings, 1886, Part 1. 8vo. 1886.
Amsterdam Royal Society of Zoology — Bijdragen tot de Dierkunde, Afl. 13. 4to,

1886.
Antiquaries, Society ©/—Proceedings, Vol. XI. Nos. 1, 2. 8vo. 1886.
Armagh Observatory — Second Armagh Catalogue of 3300 Stars for 1875. 8vo.

1886.
Asiatic Society of Bengal — Journal, Vol. LV. Part 1, Nos. 1, 2; Part 2, Nos. 1, 2.
8vo. 1886.
Proceedings, 1886, Nos. 1-7. 8vo.
Asiatic Society, Royal— Journal, Vol. XVIII. Parts 3, 4. 8vo. 1886.
Astronomical Society, Royal— Monthly Notices, Vol. XL VI. Nos. 8, 9. 8vo. 1886.
Australian Museum, Sydney — Catalogue of Echinodermata, Part 1. 8vo. 1885.
Bankers, Institute o/— Journal, Vol. VII. Part 7. 8vo. 1886.
Basel Naturforschende Gesellschaft — Verhandlungen, 8te Theil, Heft 1. 8vo.

1886.
Behnke, Emil, Esq. {the J.M<7ior)— Physician and Voice Trainer. 8vo. 1886.
British Architects^ Royal Institute o/— Proceedings, 1885-6, No. 19 ; 1886-7, No. 1.
4to.
Transactions, Vol. II. 4to. 1886.
Kalendar, 1886. 8vo.
Vol. XL (No. 80.) 2 q

592 General Monthly Meeting. [Nov. 1,

British Association for the Advancement of Science — Eeport of Meeting at Aber-
deen, 1885. 8vo. 1886.

Canadian Economics. 8vo. 1885.
British Museum {Natural History) — Catalogue of the Blastoidea. 4to. 1886.

Guide to Galleries of Geology and Palaeontology. 8vo. 1886.
Chemical Society — Journal for July-Oct. 1886. 8vo.
Chile, Officina Central Meteorolojica — Annuario, 1886. 8vo. Nos. 1, 2.
Civil Engineers^ Institution — Minutes of Proceedings, Vols. LXXXV. LXXXVI.

8vo. 1885-6.
Clinical Society — Transactions, Vol. XIX. 8vo. 1886.
Cobden Clah—G. "W. Medley. Keciprocity Craze. 12mo. 1881.

Hon. G. C. Brodrick. Keform of English Land System. 12mo. 1883. *

W. E" Baxter. Our Land Laws of the Past. 12mo. 1885.

Sir L. Mallet. National Income and Taxation. 12mo. 1885.

E. R. Pearce-Edgcumbe. Popular Fallacies regarding Trade and Foreign
Duties. 12mo. 1885.

Sir R. Torrens. Transfer of Land by Registration. 12mo. 1885.
A. Mongredien. Trade Depression. 12mo. 1885.

Free Trade and English Commerce. 12mo. 1885.

Western Farmer of America. l2mo. 1886.

W. Birkmyre. The India Council. 12mo. 1885.

Secretary of State for India in Council. 12mo. 1886.

J. E. T. Rogers. Local Taxation. 12mo. 1886.

F. C. Montague. Old Poor Law and New Socialism. 12mo. 1886.
C. S. Salvin. The Crown Colonies of Great Britain. 12mo. 1886.
R. Gowing. Richard Cobden. 12mo. 1886.

Collins, Louis, Esq, (the Author) — The Advertisers' Guardian, No. 3. 8vo. 1886.
Crisp, Frdnk, Esq. LL.B. F.L.S. &c. M.E.I. (the Editor)— J omnsil of the Royal

Microscopical Society, Series II. Vol. VI. Parts 4, 5. 8vo. 1886.
Dax : Societe de Borda — Bulletins, 2« Serie, Onzieme Anne'e, 2« and 3® Trimestre.

8vo. 1886.
Devonshire Association for the Advancement of Science, Literature, and Art—
Report and Transactions, Vol. XVIII. 8vo. 1886.

The Devonshire Domesday, Part 3. 8vo. 1886.
East India Association — Journal, Vol. XVIII. Nos. 5, 6. Svo. 1886.
Edinburgh, Royal Observatory — Astronomical Observations, 1877-1886, Vol. XV.
4to. 1886.

Editors — American Journal of Science for July-Oct. 1886. Svo.

Analyst for July-Oct. 1886. 8vo.

Athenseum for July-Oct. 1886. 4to.

Chemical News for July-Oct. 1886. 4to.

Chemist and Druggist for July-Oct. 1886. 8vo.

Engineer for July-Oct. 1886. fol.

Engineering for July-Oct. 1886. fol.

Horological Journal for July-Oct. 1886. Svo.

Industries for July-Oct. 1886. fol.

Iron for July-Oct. 1886. 4to.

Nature for July-Oct. 1886. 4to.

Revue Scientifique for July-Oct. 1886. 4to.

Telegraphic Journal for July-Oct. 1886. Svo,

Zoophilist for July-Oct. 188*6. 4to.
Ellis, William, Esq. F.R.A.S. {the Author)— Bx'iei Historical Account of the

Barometer. (Journ. of Meteorological Society, XII.) Svo. 1886.
Florence, Biblioteca Nazionale Centrale — Bulletino, Num. 1 to 15. Svo. 1886.
Franklin Institute— J ournsd, Nos. 727, 728, 729. Svo. 1S86.
Geographical Society, Royal — Proceedings, New Series, Vol. VIII. Nos. 7-10.

Svo. 1886.
Geological Society — Quarterly Journal, No. 167. Svo. 1886.
Geological Society of Ireland, Royal — Journal, Vol, XVII. Part 1. Svo. 1886.

1886.] General Monthly Meeting. 593

Glasgow Philosophical Society — Proceedings, Vol. XVII. 8vo. 1886.
Hamilton Association — Journal and Proceedings, Vol. I. Part 2. 8vo. 1885.
Harlem Societe Hollandaise des Sciences — Archives Ne'erlandaises, Tome XXI.

Liv. 1. 8vo. 1886.
Iron and Steel Institute — Journal, 1886, No. 1. 8vo.

JablonowsM sche Gesellschaft, Leipzig, Furstliche — Preisschrift, No. 26. 8vo. 1886.
Johns Hopliins University — Studies ia Historical and Political Science, Fourth

Series, Nos. 7, 8, 9. 8vo. 1886.
University Circular, No. 51. 4to. 1886.
American Chemical Journal, Vol. VIII. No. 4. 8vo. 1886.
Linnean Society— J onmsil, Nos. 114, 115, 116, 145, 146, 147, 151. 8vo. 1886.
Transactions, 2nd Series : Zoology, Vol. II. Parts 12, 15, 16, 17 ; Vol. III. Part 4.

4to. 1885-6.
Liversidge, Professor A. F.R.S. (the Author) — Address to Eoyal Society of New

South Wales. 8vo. 1886.
Madrid Eoyal Academy of Sciences — Eevista : Tome XXI. Nos. 7, 8, 9 ; Tome

XXII. No. 1. 8vo. 1886.
Manchester Steam Users'" Association — Boiler Explosions Act, 1882. Board of

Trade Eeports, Nos. 87-129. fol. 1886.
Manila : Universidad de Sto Tomas — Discurso por M. L. Hernando. 4to. 1886.
Mechanical Engineers' Institution — Proceedings, 1886, No. 2. 8vo.
Medical and Chirurgical Society, Royal — Proceedings, New Series, No. 13. 8vo.

1886.
Transactions, Vol. LXIX. 8vo. 1886.
Meteorological O^ce— Monthly Weather Keport for Feb. 1886. 4to.

Observations of the International Polar Expeditions, 18S2-3. Fort Eae. 4to.

1886.
Meteorological Society, Royal — Quarterly Journal, No. 59. 8vo. 1886.

Meteorological Eecord, No. 21. 8vo. 1886.
Middlesex Hospital— Be^oits for 1884. 8vo. 1886.
North of England Institute of Mining and Mechanical Engineers — Transactions,

Vol. XXXV. Part 3. 8vo. 1886.
Numismatic Society — Chronicle and Journal, 1886, Part 2. 8vo.
Odontological Society of Great Britain — Transactions, Vol. XVIII. No. 8. New

Series. 8vo. 1886.
Perry, Rev. S. J. F.R.S. (the Author) — Eesults of Meteorological and Magnetical

Observations, 1885. 12mo. 1886.
Pharmaceutical Society of Great Britain — Journal, July-Oct. 1886. 8vo.
Phipson, Dr. T. L. (the Author) — Outlines of a New Atomic Theory. (British

Association.) 4to. 1886.
Photographic Society — Journal, New Series, Vol. X. No. 9; Vol. XL No. 1. 8vo.

1886.
Physical Society of London — Proceedings, Vol. VIII. Part 1. 8vo. 1886.
Popoff, Constantine, Esq. (the Translator) — What I Believe. By Leon Tolstoi.

8vo. 1885.
Preussische Akademie der Wissenschaften — Sitzungberichte, I.-XXXIX. 8vo.

1886.
Radcliffe Observatory— B.adcliSe Observations for 1883. 8vo. 1886.
Richardson, B. W. M.D. F.R.S. (the Author)— The Asclepiad, Vol. III. Nos. 11, 12.

8vo. 1886.
Royal College of Surgeons of Englaiid—Calendai, 1886. 8vo.
Royal Society of London — Philosophical Transactions, Vol. CLXXVI. Part 2.

4to. 1886.
Proceedmgs, Nos. 244, 245, 246. 8vo. 1886.
Saurheck, A. Esq. (the Author) — Prices of Commodities and the Precious Metals.

(Joum. of Statistical Society.) 8vo. 1886.
Saxon Society of Sciences, Royal— Ph\\o\ogi&<ih-E\s\ioxiche Classe: Berichte, 1886,

No. 1. 8vo.
Mathematische-Physische Classe : Berichte, 1886. 8vo.

594 General Monthly Meeting. [Dec. 6,

Seismological Society of Japan — Transactions, Vol. IX. Part 2. 8vo. 1886.

Society of Arts — Journal, July-Oct. 1886. 8vo.

Statistical Society— J ouiiml. Vol. XLIX. Parts 2, 3. Svo. 1886.

Catalogue of the Library. Index. 4to. 1886.
St. Petersbourg, Academie des Sciences — Memoires, Tome XXXIII. Nos. 6, 7, 8 ;

Tome XXXIV. Nos. 1-4. 4to. 1886.
Telegraph Engineers, Society of — Journal, Nos. 62, 63. 8vo. 1886.
ToMo University — Calender der Medicinischen Fakultat, 1883-4. 8vo. 1885.
United Service Institution, Boyal — Journal, No. 135. 8vo. 1886.
United States Geological Survey — Bulletins, Nos. 24-26. Svo. 1885.

Monograph IX. 4to. 1885.

Fifth Annual Report, 1883-4. 4to. 1885.
Upsal University — Bulletin Mensuel de I'Observatoire, Vol. XVII. 4to. 1885.

Nova Acta, Ser. III. Vol. XIII. Fasc. 1. 4to. 1886.
Vereins zur Beforderung des Gewerhfieisses in Preussen — Verhandlungen, 1886:

Heft 6, 7. 4to.
Victoria Institute — Journal, No. 78. 8vo. 1886.

Victoria Royal Commissioners — Illustrated Handbook of Victoria. 4to. 1886.
Yorkshire Archxological and Topographical Association — Journal, Part 36. Svo.

1886.
Zoological Society — Proceedings, 1886, Parts 2, 3. Svo.

Transactions, Vol. XII. Part 3. 4to. 1886.

GENEEAL MONTHLY MEETING,

Monday, December 6, 1886.

Henry Pollock, Esq. Treasurer and Vice-President, in the Chair.

Mrs. Lauder Brunton,

Thomas Buzzard, M D. F.R.C.P.

The Right Hon. Lord Thurlow, F.R.S.

Mrs. Annie S. Tweedie,

were elected Members of the Royal Institution.

With reference to the report of the Managers read at the previous
meeting, a Resolution was unanimously passed authorizing the Sale
of a part of the New Three per Cent. Consols or Consols belonging to
and standing in the name of the Royal Institution of Great Britain,
sufficient to raise a sum of not exceeding £2000 cash.

The Special Thanks of the Members were returned to John P.
Fearfield, Esq. MM.I. for his valuable present of a Turning Lathe.

1886.] General Monthly Meeting. 595

The following Lecture Arrangements were announced :

Professor Dewar,- M.A. F.R.S. M.B.I. Six Lectures (adapted to a Juvenile
Auditory) on The Chemistry op Light and Photography. On Dec. 28
{Tuesday), Dec. 30, 1886; Jan. 1, 4, 6, 8, 1887.

Professor Arthur Gamgee, M.D. F.R.S. Eleven Lectures on The Function
OF Respiration. On Tuesdays, Jan. 18 to March 29.

Professor A. W. Rucker, M.A. F.R.S. M.R.I. Five Lectures on Molecular
Forces. On Thursdays, Jan. 20, 27, Feb. 3, 10, 17.

Edmund Gosse, Esq. M.A. Three Lectures on The Critics of the Age of
Anne. Ou Thursdays, Feb. 24, March 3, 10.

Professor F. Max Muller, M.A. LL.D. Three Lectures on The Science
of Thought. On Thursdays, March 17, 24, 31,

Carl Armbruster, Esq. Five Lectures on Modern Composers of Classical
Song. On Saturdays, Jan. 22, 29, Feb. 5, 12, 19.

The Right Hon. Lord Rayleigh, M.A. D.C.L. LL.D. F.R.S. M.E.I Six

Lectures on Sound. On Saturdays, Feb. 26, March, 5, 12, 19, 26.

The Presents received since the last Meeting were laid on the
table, and the thanks of the Members returned for the same, viz. : —

The Governor- General of India — Geological Survey of India. Records, Vol. XIX.
Part 4. 8vo. 1886.

Memoirs : Palseontologia Indica. Ser. X. Vol. IV. Part 2. 4to. 1886.
The Coriooration of the City of london — Descriptive Account of the Guildhall of

the City of London. By J. E. Price, fol. 1886.
Agricultural Society of England, Royal — Journal, Second Series, Vol. XXII.

Part 2. 8vo. 1886.
Banhers, Institute o/— Journal, Vol. VII. Part 8. 8vo.. 1886.
Birmingham Philosophical Society — Proceedings, Vol. V. Part 1. 8vo. 1886.
British Architects, Royal Institute o/— Proceedings, 1886-7, Nos. 2, 3. 4to.
Chemical Society — Journal for Nov. 1886. 8vo.
Ebstein, Professor W. {the Author) — La Goutte: sa Nature et son Traitement.

Traduction du E. Chambard. 8vo. Paris, 1886.
Editors — American Journal of Science for Nov. 1886. 8vo.

Analyst for Nov. 1886. 8vo.

Athengeum for Nov. 1886. 4to.

Chemical News for Nov. 1886. 4to.

Chemist and Druggist for Nov. 1886. 4to.

Chemists' and Druggists' Diary for 1887. 4to.

Engineer for Nov. 1886. fol.

Engineering for Nov. 1886. fol.

Horological Journal for Nov. 1886. 8vo.

Industries for Nov. 1886. fol.

Iron for Nov. 1886. 4to.

Nature for Nov. 1886. 4to.

Revue Scientifique for Nov. 1886. 4to.

Telegraphic Journal for Nov. 1886. 8vo.

Zoophilist for Nov. 1886. 4to.
Franklin Institute— J oinnal. No. 731. 8vo. 1886.

Geographical Society, i?o?/aZ— Proceedings, New Series, Vol. VIII. No. 11. 8vo.
1886.

Supplementai-y Papers, Vol. I. Part 3. 8vo. 1886.

596 General Monthly Meeting. [Dec. 6, 1886.

Geological Society — Quarterly Journal, No. 168. 8vo. 1886.

GeorgofiU Reale Accademia — Atti, Quarta Serie. Vol. IX. Disp. 2, 3. 8vo. 1886.

Johns Hopkins University — Studies in Historical and Political Science, Fourth

Series, No. 10. 8vo. 1886.
University Circular, No. 52. 4to. 1886.
American Chemical Journal, Vol. VIII. No. 5. 8vo. 1886.
Lee, Henry, Esq. M.R.I, (the Author) — Tapetum Lucidum. (Medico-Chir.

Trans. LXIX.) 8vo. 1886.
Linnean Society — Journal, No. 126. 8vo. 1886.

Maryland Medical and Chirurgical Faculty — Transactions, 1886. 8vo.
Mauritius Royal Society of Arts and Sciences — Transactions, Vols. XI. to XVIII.

8vo. 1888-6.
Meteorological Office — Quarterly Weather Keport, 1878, Part 1. 4to. 1886.
Monthly Weather Keport for June 1886. 4to. 1886.
Weekly Weather Report, Vol. III. Nos. 34 to 41. 4to. 1886.
Meteorological Society, Royal — Quarterly Journal, No. 60. 8vo. 1886.

Meteorological Kecord, No. 22. 8vo. 1886.
Ministry of Public Works, jRome— Giornale del Genio Civile, Serie Quarta,

Vol, VI. Nos. 7, 8. 8vo. And Disegni. fol. 1886.
New South Wales Department of Mines — Annual Eeport for 1885. fol. 1886.
North of England Institute of Mining and Mechanical Engineers — Transactions,

Vol. XXXV. Part 4. 8vo. 1886.
Odontological Society of Great Britain — Transactions, Vol. XIX. No. 1. New

Series. 8vo. 1886.
Pharmaceutical Society of Great Britain — Journal, Nov. 1886. 8vo.
Physical Society of London — Proceedings, Vol. VIII. Part 2. 8vo. 1886.
Saxon Society of Sciences, i?o?/aZ— Mathematisch-pliysische Classe : Abhandlungen,

Band XIII. Nos. 6, 7. 8vo. 1886.
Society of Arts — Journal, Nov. 1886. 8vo.
St. Petersbourg, Academic des Sciences — Bulletin, Tome XXXI. No. 2. 4to.

1886.
Teyler Museum— ArclnYes, Ser. II. Vol. II. 4^ Partie. 4to. 1886.

Catalogue de la Bibliotheque, 3% 4% Liv. 4to. 1886.
United Service Institution, Roijal — Journal, No. 136. 8vo. 1886.
Vereins zur Beforderung des Gewerbjleisses in Preussen — Verhandlungen, 1886.

Heft 8. 4to.

INDEX TO VOLUME XI.

Abel, Sir Frederick, Accidental Ex-
plosions by Non-explosive Liquids ,
219.

Alps, Building of the, 53.

Anatomical and Medical Knowledge
of Ancient Egypt, 378.

Anderson, W., New Applications of the
Mechanical Properties of Cork, 436.

Animal Magnetism, 25.

Annual Meetings (1884)84, (1885)283,
(1886) 467.

Ansdell, Gerrard, Eesearches on Mete-
orites, 541.

Antipyrine, 460.

Arago's Discovery in Induction, 123.

Arnold, Matthew, Emerson (no
abstract), 43.

Benzene and its Derivatives, 452.

Besant, Walter, Art of Fiction, 70.

Bichat's View of the Nervous System,
530.

Biblical Cities of Egypt, 384.

Bicycles, 13.

Bolometer, 273.

Bonney, Professor T. G., Building of
the Alps, 53.

Boys, C. Vernon, Bicycles and Tri-
cycles, 13.

Braid, Dr., and Mesmerism, 26, 35.

Bunsen's experiments on Dissociation,
474.

Busk, George, resigns Treasurership,
468.

Cailletet Apparatus, 148.

Capillary Attraction, 483.

Carruthers, W., British Fossil Cycads,
and their relation to Living Forms
(no abstract), 283.

Chladni's Theory of Meteorites, 332.

Cholera : its Cause and Prevention, 288.

Christie, W. H. M., Universal Time, 387.

Coal Tar Industry, 450 ; Sources of
Products, 451; Colours, 454; Anti-
pyretic Medicines, 459 ; Aromatic
Perfumes, 462 ; Saccharine, 462.

Cold: its Production, and Efiects on
Microphytes, 305.

Coleman, J. J., Mechanical Production
of Cold, 305.

Colours, 107.

Common, A. A., Photography as an
Aid to Astronomy, 367.

Cork, 437 ; Applications of its Mecha-
nical Properties, 444.

Corona, Solar, 202 ; Photographed, 204.

Cotyledons, 517.

Critical Temperatures and Pressures of
various Substances, 151.

Crystallisation, 508.

Darwinian Theory of Instinct, 131.
Devi lie's Experiments on Dissociation,

474.
Dewar, Professor, Liquefied Gases, 148.
Liquid Air and the Zero of

Absolute Temperature (no abstract),

318.

The Story of a Meteorite, 328.

Eesearches on Meteorites, 541.

" Dhurmsala " Meteorite, 328 ; 543.
Dilatancy, 354.

Dissociation Temperatures, 471.
" Doterel " Explosion, 227.
Dust and Smoke, 520.

" EcoNOMiSEE " for Grates, 342.
Egypt : Anatomy and Medicine, 378.
Egypt Exploration Fund, 384.
Electrical Deposition of Dubt and

Smoke, 520.
Energy defined, 571.
Explosions by Non-explosive Liquids,

218.

Faraday's Eesearches on Induction,

119.
Fauna of the Seashore, 168.
Fiction, Art of, 70.
Films, 243.

Fireplace Construction, 338.
Fixed Stars, Distances of, 91.
Fleming, Sandford, Scheme for

Universal Time, 390.
Flower, Professor W. H., The Wings

of Birds, 364.
Fluids and Solid Metals, 395.
Frozen Meat, 308.

Garrick as an Actor, 304.
Gas Furnaces, 471.

598

INDEX.

Gases, Liquefied, 148 ; Solidified, 550.
Gaskell, Dr. W. H., Sympathetic

Nervous System, 530.
Gill, David, Distances of the Fixed

Stars, 91.
Glass Manufacture, il3.
Granular Material, Properties of, 354.
Graphites, 545.
Grubb, Howard, Telescopic Objectives

and Mirrors, 413.

Henderson's Observations, 95.
Hieroglyphical Researches, 574.
Horsley, Victor. Motor Centres of the

Brain, and the Mechanism of the

Will, 250.
Hugi^ins, Dr. W., Solar Corona, 202.
Hughes, Professor D. E., Theory of

Magnetism, 1.
Hypnotism, 26.

Indigo, Artificial, 459.
Indophenol, 457.
Induction, 119.

Inhibition of Nerve Centre, 31.
Instinct, Tiieory of, 131.

Joule's Explanation of the Heating of

Meteorites, 333.
Judd, Professor J. W., Krakatoa, 85.

Kairine, 460.

Koch's, Dr., Cholera Investigation, 300.

Krakatoa, 85.

Lamp Explosions, 230.

Langley, J. N., Physiological Aspect
of Mesmerism, 25.

S. P., Sunlight and the Earth's

Atmosphere, 265.

Lankester, Professor Ray, Marine Bio-
logical Laboratory, 215.

Leaves, Forms of, 197.

Lick Observatory, 429.

Light in relation to Plants, 113.

Liquid Films, 243.

Living Contagia, 161.

Lodge, Professor Oliver, Electrical
Deposition of Dust and Smoke, 520.

Lubbock, Sir John, Forms of Leaves,
197.

Forms of Seedlings, 517.

Macalister, Professor A., Anatomical
and Medical Knowledge of Ancient
Egypt, 378.

McKendrick, J. G., Effects of Cold
upon Microphytes, 305.

Magnetism, Theory of, 1.
Magneto- Electric Induction, 119.
Marine Biological Laboratory, 215.
Mascart, Mons. E., Sur les Couleurs,

107.
Mechanism of the Will, 250.
Mesmerism, Physiological Aspect, 25.
Metals, 395.
Meteorites, 328.
Meyer's Experiments on Dissociation,

476.
Mirrors, Figuring of Plane, 429.
Mohammedan Mahdis, 147.
Monthly Meetings : —

(1884) March, 11 : April, 68; May,
88; June, 116; July, 153 ; Novem-
ber, 155 ; December, 159.

(1885) February, 175 ; March, 216 ;
April, 263 ; Mav, 285 ; June, 317 ;
July, 319; November, 321;
December, 325.

(1886) Februarv, 335 ; March, 376 ;
April, 433 ; May, 468 ; June, 538 ;
July, 589 ; November, 591 ; Decem-
ber, 594.

Moseley, Professor H. N., Fauna of

the Seashore, 168.
Motion, 178 ; of Water, 44.
Motor Centres of the Brain, 250.

Naville's Discoveries in Egypt, 384.

Nervous Systems, 530.

Newton, Charles T., German Dis-
coveries at Pergamus (no abstract),
211.

Objectives, 413 ; Calculation of Curves,
415 ; Measurement of Curves, 418 ;
Flexure, 419 ; polishing, 421 ; Figur-
ing and Testing, 424.

Odling, Professor W., Dissolved
Oxygen of Water (no abstract), 90.

Optical Glass Testing, 413.

Otto Bicycle, 23.

Oxygen Liquefied, 148; Solidified, 550.

Parallaxes of Stars, 96.

Pasteur's Researches, 161.

Pauer, Professor Ernst, Works of
Living Composers for the Piano-
forte, 171.

Petroleum, 234 ; Explosions, 222.

Pianoforte Music, 171.

Photography applied to Astronomy,
104, 367.

Plateau's Researches on Films, 243.

Pollock, W. H., Garrick as an Actor,
304.

INDEX.

599

Poole, R. S., Discovery of the Biblical
Cities of Egypt, 384.

Rayleigh, Lord, Water Jets and Water
Drops (rto abstract), 284.

Reflex Action from tiie Cerebral Cor-
tex, 29.

Regenerative Furnaces, 471.

Reynolds, Osborne, Two Manners of
Motion of Water, 44.

Experiments showing Dilatancy,

354.

Roberts-Austen, Professor W. Chand-
ler, Properties common to Fluids and
Solid Metals, 395.

Romanes, G. J., Darwinian Theory of
Instinct, 131.

Roscoe. Sir Henry E., Recent Progress
in the Coal Tar Industry, 450.

Rucker, Professor A. W., Liquid
Films, 243.

Rumford's Researches on Fuel and
Heat, 338 ; Principles of Fireplace
Construction, 344.

Saccharine, 462.

Sanderson, Dr. J. Burdon, Cholera : its
Cause and Prevention, 288.

Seedlings, 517.

Sidereal Astronomy, Future Problems,
91.

Siemens, Frederick, Dissociation Tem-
peratures, 471.

Smith, W. Robertson, Mohammedan
Mahdis, 147.

Willoughby, Volta-Electric and

Magneto - Electric Induction, 119.

Solar Corona, 202.

Energy, 279.

Spring's Researches on Metals, 405.

Stoney, G. Johnstone, How Thought
presents itself in Nature, 178.

Sun, Colour of the, 265.

Sunlight and the Earth's Atmosphere,

265.
Sympathetic Nervous System, 530.

Teale, T. Pridgin, Principles of

Domestic Fireplace Construction,

338.
Telescopic Objectives and Mirrors, 413.
Temperatures, 148, 471, 550.
Thalline, 460.
Thomson, J. Millar, Suspended

Crystallisation, 508.
Sir William, Capillary Attraction,

483.
Thought in Nature, 178.
Time-reckoning 387.
Tricycles, 13.
Tyndall, Professor, on Living Contagia,

161.
on Thomas Young, 553.

Universal Time, 387.

Volcano of Krakatoa, 85.
Volta-Electric Induction, 119.

Water, Motion of, 44.

Wave Theory. 562.

Weldon, W. F. R., Adaptation to sur-
roundings as a Factor in Animal
Development (iio abstract), 287.

Wheels moving round a Curve, 19.

Whitney, Mount, 275.

Wings of Birds, 364.

Wright's Researches on Meteorites, 541 .

Young, Thomas, Early Life and
Studies, 553 ; the Wave Theory, 562 ;
Hieroglyphical Researches, 574.

END OF VOL. XI.

Vol. XI. ^No. Si).)

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