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THE 


LONDON, EDINBURGH, anv DUBLIN 


PHILOSOPHICAL MAGAZINE 


AND 


JOURNAL OF SCIENCE. 


CONDUCTED BY 
SIR ROBERT KANE, LL.D. F.R.S. M.R.LA. F.C.S. 
AUGUSTUS MATTHIESSEN, Pu.D. F.RS. F.CS. 
AND 


WILLIAM FRANCIS, Pu.D. F.LS. F.B.A.S. F.C.S. 


“Nec aranearum sane textus ideo melior quia ex se fila gignunt, nec noster 
vilior quia ex alienis libamus ut apes.” Just. Lips. Polit. lib. i. cap. 1. Not. 


VOL. XXXVIII—FOURTH SERIES. ~ | 
AY JULY—DECEMBER, 1869. 4risst} 


LONDON. 


TAYLOR AND FRANCIS, RED LION COURT, FLEET STREET, 
Printers and Publishers to the University of London ; 


SOLD BY LONGMANS, GREEN, READER, AND DYER; SIMPKIN, MARSHALL AND CO.; 
WHITTAKER AND CO.; AND KENT AND CO., LONDON:—BY ADAM AND 
CHARLES BLACK, AND THOMAS CLARK, EDINBURGH ; 

SMITH AND SON, GLASGOW; HODGES AND 
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NEW YORK. 


“Meditationis est perscrutari occulta; contemplationis est admirari 
perspicua..... Admiratio generat questionem, queestio investigationem, 
investigatio inventionem.”’—Hugo de S. Victore. 


—“ Cur spirent venti, cur terra dehiscat, 

Cur mare turgescat, pelago cur tantus amaror, 
Cur caput obscura Phcebus ferrugine condat, 
Quid toties diros cogat flagrare cometas ; 

Quid pariat nubes, veniant cur fulmina ccelo, 
Quo micet igne Iris, superos quis conciat orbes 


Tam vario motu.” 
J. B. Pinelli ad Mazonium. 


CONTENTS OF VOL. XXXVIITI. 


(FOURTH SERIES.) 


NUMBER CCLII.—JULY 1869. 


Page 
The Hon. J. W. Strutt on some Electromagnetic Phenomena 
considered in connexion with the Dynamical Theory ...... 1 
Dr. W. H. Broadbent on the Function of the Blood in Muscular 
MTN Pie) irc ce el. 4d. 9 sess ae aie’ HAR deepsea 15 
Mr. T. R. Edmonds on Vital Force according to Age, and the 
Spemes ese eb apie y | s:sjr4: sac bls we o ait js dleitle a ee og 'd eres 18 
Prof. W. A. Norton on the Fundamental Principles of Molecular 
Piysics. siteply to Professor Bayma, |: i¢s-< ses saws + 34 
Prof. Challis’s Note on the Hydrodynamical Theory of Mag- 
“NEEIGTS —. - 9 005 SARS Rn oY ree ee eee 42 
Mr. W. C. Roberts’s Note on the Experimental Illustration of 
the Expansion of Palladium attending the Formation of its 
Seon ELV GTOO CMIUDA 564 nica false dts oeaiac@ em» aro ote eovier = « 51 
Prof. Haidinger on the Polarization of Light by Air mixed with 
nO prictier Sh. Linie wvajnawrs O49 Jur ba bary es eke 54 
Dr. A. H. Gallatin on Ammonium ee and on Nascent- i 
drogen Tests .... 57 
Proceedings of the Royal Society : — 
Mr. G. Gore on a momentary Molecular Change in Iron 
Pome Hs Gasioriiee iy Te cunt re hls ae ow ph 59 
Mr. G. Gore on the Development of Electric Currents by 
iaemetismpamd Eleaf jg) i ald acalt feerseceeud’ sede mth 64 
Messrs. E. Frankland and J. N. Lockyer’s Preliminary Re- 
searches on Gaseous Spectra in relation to the Physical 
Ponahitutiontof the Sums: i4s\-< 212 stan shedtinllt «f) ~ eh 66 
Mr. W. Huggins on a Method of viewing the Solar Promi- 
meuces without an Hehipse, 2/16 i? Tawa ese els 3s oe 68 
Wie, Fugeins onthe Heat of the Stars 3..........- 69 
Sir W. Thomson on the Fracture of Brittle and Viscous 
Solds by) <: SMeATIM Gyan. Ase ede atin: © a) Garey sini ¢ 71 


Proceedings of the Geological Society :— 
' Mr. G. M. Browne on Floods in the Island of Bequia .. 73 


lv CONTENTS OF VOL. XXXVIII.—FOURTH SERIES. 


Page 

Capt. F. W. Hutton’s Description of Nga Tutura, an Ex- 5 
tinct Volcano in New Zealand 
Mr.:J. W. Mason on Dakosourus 3.2.05. 2... 1-2 eee 74 . 
Mr. P. M. Duncan onthe Anatomy of the test of Amphi- 
detus (Echinocardium) Vi ee Forbes; and on the 


genus Breynia .... 74 
Mr. H. Bauerman’s Notes wee a Geological Reeonmaicenee 
in Arabia iPetrea,. chi)... ee ee eee 75 


On the Heat consumed in Internal Work when a Gas dilates 
under the Pressure of the Atmosphere, by M. J. Moutier .. 76 
Investigations on obscure Calorific Spectra, by M. Desains.... 78 


NUMBER CCLIII.—AUGUST. 


M. G. Quincke on the Constants of Capillarity of Molten 
Bodies 
Canon Moseley on the Descent ofa Solid Body on an Inclined 
Plane when subjected to alternations of Temperature ...... he) 
Mr. R. Moon on the Structure of the Human Ear, and on the 
Mode in which it administers to the Perception of Sound .. 118 
Captain F. W. Hutton on the Mechanical eee involved 
in the Sailing Flight of the Albatros. ..... Ar te) 
Mr. J. Parnell on a new Fluorescent Substance. siols jn leeatn 136 
Dr. E. Warburg on the Heating produced in Solid Bodies 
when they are Sounded 
Proceedings of the Royal Institution :— 
Mr.J. N. Lockyer on Recent Discoveries in Solar gee 
made by means of the Spectroscope.......... 142 
Proceedings of the Royal Society :— 
Dr. Tyndall on the Formation and Phenomena of Clouds. 156 
Dr. A. Dupré and Mr. F. J. M. Page on the Specific Heat 
and other physical properties of ey Mixtures and 
Solutions ... ole bias De LAD eae ae 
Proceedings of the Geological Society : — 
Mr. H. Bauerman on the occurrence of Celestine in the 
Tertiary Rocks of Hgypt' 2272. 2. Se eee 162 
Dr. P.M. Duncan on the Echinodermata, Bivalve Mollusca, 
and some other Fossils from the Cretaceous Rocks of 


imal Sea . 163 
M. C.-Martins on the Existence during the Quaternary 
Period of a Glacier of the Second Order Be 5 8 i 163 
On the Compressibility of Liquids, by MM. Amaury and Des- 
camps. 164 
Measur ement of the Electrical ‘Conductivity a ‘Liquids ‘hitherto 
supposed to be Insulators, by M. Said-Effendi .... 165 
On the Heat developed in Discontinuous Currents, by MM. Ja- 
min and Roger 2202 00). Gl 02 Re Ae certo eee 


CONTENTS OF VOL. XXXVIII.—FOUKTH SERIES, 


NUMBER CCLIV.—SEPTEMBER. 


Prof. E. Edlund on the Construction of the Galvanometer used 
in Electrical Discharges, and on the Path of the Extra Cur- 
rents through the Electric Sparkie 25" eee ensers v5 whe ee. 

Prof. J. LeConte on some Phenomena of Bmocuias Vision. . 

Mr. C. Tomlinson on the Formation of Bubbles of Gas and of 
Vapour in Liquids. . : : 

Dr. T. Fritzsche on the Production of a » Columnar Structure 
mm Metallic Tin ..... 

Prof. W. A. Norton on the Fundamental Principles of Mole- 
cular Physics. Reply to Professor Bayma .............. 

Mr. C. Tomlinson on a Remarkable Structural Appearance in 
-.) SLICE: aS Sie eee oe ne ean heer ina ines 

Mr. C. Tomlinson on the Supposed Action of Light on Com- 


TEE TE cc ce ote eae aE atta ti i el ee a 2 


Mr. J. Croll on the Opinion that the Southern Hemisphere 
loses by Radiation more Heat than the Northern, and the 
supposed Influence that this has on Climate ............ 


Prof. G. C. Foster on some Lecture-experiments in Electricity. 2 


Proceedings of the Geological Society :— 

Prof. W. King and Dr. ‘I. H. Rowney on the so-called 
SeUsOCalaMCOCK a's isc sees coe she wos he es 

Mr. T. W. Kingsmill on the Geology of China ........ 

prot. D. Hi. Huxley on Hyperodapedon : 

Mr. W. Whitaker on the Locality of a new Specimen of 
Hyperodapedon on the South Coast of Devon? ........ 

Mr.W. H. Baily on Graptolites and allied Fossils occurring 
in Ireland, and on Plant-remains from beds interstratified 
with the Basalt in the County of Antrim. 

Mr. G. T. Clark on the Basalt rile of the Mainland of 


dices oe ee 
Dr. Sutherland on . Wate gual Meee in iseache eter 
Africa, . : Wen, Wed 
Note on Electrolytic Polarization, ‘by Professor Tait cwlocuot ee 


On the Spectrum of the Aurora Borealis, by J. A. Angstrom. ‘ 
On the Thermal Energy of Molecular Vortices, by W. J. Mac- 
quorn Rankine, C.E., LL.D., F.R.SS. Lond. & Edinb. &c... 


NUMBER CCLV.—OCTOBER. 


Dr. W. M. Watts on the Spectra of Carbon. (Witha Plate.) 

Prof. E. Edlund on the Cause of the Phenomena of Voltaic 
Cooling and Heating discovered by Peltier............... 

Prof. Challis’s Comparison of a Theory of the Dispersion of Light 


Page 
169 
79 
204 
207 


208 


249 


V1 CONTENTS OF VOL. XXXVIII.—FOURTH SERIES. 


Page 
on the Hypothesis of Undulations with Ditscheiner’s determi- ’ 
nations of Wave-lengths and corresponding refractive Indices 268 

Prof. E. C. Pickering’s Observations of the Corona during the 
Total Eclipse, AUS ISt s7tbe WS GOS 5 cate emia tera ic te : 281 

Dr. H. Herwig’s Investigations on the Conformity of Vapours 

to Mariotte and Gay-Lussac’ s Law. (Witha Plate.) . 284 

Mr. J..S. Aldis on the Nebular Hypothesis... .20..> ¢ 9 oemier 308 

M. P. A. Favre’s Thermal Researches on the Battery........ 310 

Proceedings of the Royal Society :— 

The Earl of Rosse on the Radiation of Heat from the Moon. 314 

Proceedings of the Geological Society :— 

Mr. E. Hull on the Evidence of a ridge of Lower Carboni- 
ferous Rocks crossing the Plain of Cheshire beneath the 
DIVAS. +5 «soflny ib “hats “anecciche de sPeades laced os Bue iS ence 321 

The Rev. T. Wiltshire on the Red Chalk of Hunstanton,. 321 

On the Expansion of Gases, by M. A. Cazin, .....,......-. 322 

On the Employment of the Spectroscope in order to distinguish 
a feeble Light in a stronger one, by M. J. M. Seguin . 020 

On the Mean Velocity of the Motion of Translation of the Mo- 
lecules in Imperfect Gases, by M. P. Blaserna .......... 326 

NUMBER CCLVI.—NOVEMBER. 

Dr. Marcet’s Observations on the Temperature of the Human 
Body at various Altitudes, in connexion with the act of As- 
cendingycis, 329 

Licut. J. “Herschel on that portion ae the Report of ‘the ‘Astro- 
nomer to the Madras Government on the Eclipse of August 
1868 which recounts his Spectroscopic Observations. ...... 308 

MM. C. Borgen and R. Copeland’s Short Account of the Win- 
terings in the Arctic Regions during the last fifty years.... 340 

M. F. Zéllner on a New Spectroscope, together with contribu- 
tions to the Spectral Analysis of the Stars. ....-......... 300 

Mr. R. Moon on the Structure of the Human Ear, and on the 

_ Mode in which it administers to the Perception of Sound .. 369 

Mr: W. K. Brideman’s'Pheory of ‘the Voltaic Pile 255.4 377 

Proceedings of the Royal Society :— 

Prof, A.W; (ChurchvonW@uracine). 43). 2). eee 383 

Mr. W. Crookes ona Se ie of Binocular a 
trum-Microscope ... .. 383 

Mr. W. Crookes on some - Optical Phenomena of Opals .. 388 

Sir W. Thomson on a new Astronomical Clock, and a Pen- 
dulum-governor, for Uniform Miotion.., <<. uae ee 393 

Dr. W.A. Miller on a Self-registering Thermometer adapted 
to Deep-sea Soundings... cei eee oe ee 

Proceedings of the Geological Society :— 

Mr. W. B. Dawkins on the British Postglacial Mammalia. 399 


CONTENTS OF VOL. XXXVIII.—FOURTH SERIES. Vil 


Page 
Mr. J. W. Judd on the Origin of the Northampton Sand. 400 
Prof. H. Coquand on the Cretaceous Strata of England and 


the North of France ..... AO | 
Mr. W. Carruthers on the Saueture ‘ahd Affinities ‘ee ist 
gillaria and allied genera .... 402 


Dr. H. A. Nicholson on the British Species of the Genera 
Climacograpsus, Diplogr ar Dicranograpsus, and Di- 


dymograpsus ...... . 402 
Mr. F. O. Adams on the ‘Coal- mines at Kaianoma .... .. 402 
Mr. M. Morgans on a peculiarity of the Brendon-Hills 
Spathose Ore- WEIMeh FASS OR IY SO oe 403 
On the Emission and Absorption of Heat radiated at Low Tem- 
Perecese my G. Magnus: 2. <2 is. i ek eee es eee 403 
On the limits of the Magnetization of Iron and Steel, by Prof. 
Pent warmdoren eels aie ee uD LO oe aa OU 404 
On the Reflection of Heat from the surface of Fluor-spar and 
Monemadres: by G, Magnus!) 0.2). 0.0.0 5 072 tte. 405 


On the Luminous Effects produced by Electrostatic Induction in 
Rarefied Gases.—Leyden Jar with Gaseous Coatings, by M. 
©. TP Lui JEG UTSIE [Cec bet iP dea Pr 407 


NUMBER CCLVII.—DECEMBER. 


Mr. C. Tomlinson on the Motions of Camphor on the Surface of 


es Ne 2 hee owas Wot a toad GRAY & oes eee 409 
Prof. A. Kenngott’s Microscopical Investigation of thin polished 

Laminz of the Knyahynia Meteorite. (With a Plate.) .... 424 
Mr. W. H. Preece on the Parallelogram of Forces .......... 428 


Prof. F. Kohlrausch on the Determination of the Specific Heat 
of Air under constant Volume by means of the Metallic Ba- 
NOME PM Me a OE ren, ocvera cS ctole! etd efetechatio dt cheaty ern ot, & 430 
M. Abich on Fulgurites in the Andesite of the Lesser Ararat, and 
on the Influence of Local Agents on the Production of Thun- 


derstorms ..... ee 436 
M. Abich on Hailstorms i in Russian Georgia. “(With : a Plate. ) 440 
Mr. T. T. P. B. Warren on Electrification JRL SBE Jeepers 441 


Prof. J. Plateau’s Experimental and Theoretical Researches 
into the Figures of Equilibrium of a Liquid Mass without 
Ptetedtee—— Meth, Series 5.0. oe) a deere we i dale le ee 445 

Dr. W. Odling ona Theory of @ondened Ntmmon Compounds. 455 

Notices respecting New Books :— 

M.J. G. Fitch’s Methods of teaching Arithmetic.—Dr. J. 
Cornwell and Mr. J. G. Fitch’s School Arithmetic, and 
BUCS CICNCe Of ATICMMECHIC. jaueeeets 6s bs 5 se. 457 

Proceedings of the Royal Society :— 

Mich oranamron, Lydropentums.s | F. 2st. ced lk es 459 


Vlil CONTENTS OF VOL. XXXVIII.—FOURTH SERIES. 


Page 
Proceedings of the Geological Society :— ‘ 
M. F. Ruschhaupe on the Salt-mines of St. Domingo .. 465 
Messrs. 8S. Wood, Jun., and F. W. Harmer on a peculiar 
instance of Intraglacial Erosion near Norwich...... -. 466 
Mr. E. J. Beor on the Lignite-mines of Podnernuovo.... 466 
Mr. T. C. Wallbridge on the Geology and Mineralog ey of 


Hastings County, Canada West .... s{s'e ee “0G 
Mr. J. W. Flower on the distribution of Flint Implements 
inthe Davitics: 24 <8 eh. eo). oct eee ae eee 467 


On the Extension of Liquids upon each other, by R. Ludtge.. 468 
On the Measurement of the Electrical Conductivity of Liquids 
hitherto supposed to be Insulators, by Thomas T. P. Bruce 


NWianrenie. cise o ote mds eid: ee Cae 470 
On the Freezing-point of Water ‘containing dissolved Gases, 
and on the Regelation of Water, by C. Schultz iti eee 471 


Disturbances of Respiration, Circulation, and of the Production 
of Heat at great heights on Mont Blanc, by M. Lortet .... 472 


Emde: sreiersi «aM aieseie ol Sis 5S Bis Oe Se eee 


PLATES. 


I. Tllustrative of Dr. H. M. Watts’s Paper on the Spectra of Carbon. 


II. Illustrative of Dr. H. Herwig’s Investigations on the Conformity of 
Vapours to Mariotte and Gay-Lussac’s Law. 


III. Illustrative of Prof. A. Kenngott’s Microscopical Investigation of thin 
polished Lamine of the Knyahynia Meteorite, and M. Abich’s 
Paper on Hailstorms in Russian Georgia. 


THE 
LONDON, EDINBURGH, ann DUBLIN 


PHILOSOPHICAL MAGAZINE 


AND 


JOURNAL OF SCIENCE. 


[FOURTH SERIES.] 


J OL, VO 1869) 


I. On some Electromagnetic Phenomena considered in connexion 
with the Dynamical Theory. By The Hon. J. W. Srrurt, 
Fellow of Trinity College, Cambridge*. 


ia is now some time since general equations applicable to the 

conditions of most electrical problems have been given, and 
attempts, more or less complete, have been made to establish an 
analogy between electrical phenomena and those of ordinary 
mechanics. In particular, Maxwell has given a general dyna- 
mical theory of the electromagnetic field+, according to which 
he shows the mutual interdependence of the various branches cf 
the science, and lays down equations sufficient for the theoretical 
solution of any electrical problem. He has also in scattered 
papers illustrated the solution of special problems by reference 
to those which correspond with them (at least in their mathe- 
matical conditions) in ordinary mechanics. There can be no 
doubt, I think, of the value of such illustrations, both as help- 
ing the mind to a more vivid conception of what takes place, 
and to a rough quantitative result which is often of more value 
in a physical point of view, than the most elaborate mathemati- 
cal analysis. It is because the dynamical theory seems to be 
far less generally understood than its importance requires that I 
have thought that some more examples of electrical problems 
illustrated by a comparison with their mechanical analogues 
might not be superfluous. 

As a simple case, let us consider an experiment first made b 
De la Rive, in which a battery (such as a single Daniell cell) 

* Communicated by the Author. 
t Philosophical Transactions for 1865. 
Phil. Mag. 8. 4. Vol. 38. No. 252. July 1869. B 


2 The Hon. J. W. Strutt on some Electromagnetic Phenomena 


whose electromotive force is insufficient to decompose water, be- 
comes competent to do so by the intervention of a coil or elec- 
tromagnet. Thus, let the primary wire of a Ruhmkorff coil be 
connected in the usual manner with the battery, and the elec- 
trodes of the voltameter (which may consist of a test-tube con- 
taining dilute sulphuric acid into which dip platinum wires) 
with the points where in the ordinary use of the instru-- 
ment the contact is made and broken. There will thus be 
always a complete conducting circuit through the voltameter ; 
but when the contact is made the voltameter will be shunted, and 
the poles of the battery joined by metal. Now when the shunt 
is open the battery is unable to send a steady current through 
the voltameter, because, as has been shown by Thomson, the 
mechanical value of the chemical action in the battery corre- 
sponding to the passage of any quantity of electricity is less 
than that required for the decomposition of the water in the 
voltameter. When, however, the shunt is closed, a current es- 
tablishes itself gradually in the coil, where there is no permanent 
opposing electromotive force, and after the lapse of a fraction of a 
second reaches its full value as given hy Ohm’s law. Ifthe con- 
tact be now broken, there is a momentary current through the vol- 
tameter, which causes bubbles of gas to appear on the electrodes, 
and which is often (but not, I think, well) called the extra cur- 
rent. Allowing the rheotome to act freely we get a steady 
evolution of gas. 

To this electrical apparatus Montgolfier’s hydraulic ram is 
closely analogous. The latter, it will be remembered, is a ma- 
chine in which the power of a considerable quantity of water 
falling a small height is used to raise a portion of the water to a 
height twenty or thirty times as great. The body of water from 
the reservoir flows down a closed channel to the place of discharge, 
which can be suddenly closed with a valve. When this takes 
place, the moving mass by its momentum is able for a time to 
overcome a pressure many times greater than that to which it 
owes its own motion, and so to force a portion of itself to a con- 
siderable height through a suitably placed pipe. Just as the 
electromotive force of the battery is unable directly to overcome 
the opposing polarization in the voltameter, so of course the 
small pressure due to the fall cannot lift a valve pressed down 
by a greater. But when an independent passage is opened, the 
water (or electricity) begins to flow with a motion which con- 
tinues to accelerate until the moving force is balanced by fric- 
tion (resistance), and then remains steady. At the moment the 
discharge-valve is closed (or, in the electrical problem, the shunt- 
contact is broken), the water, by its inertia, tends to continue 
moving, and thus the pressure instantly rises to the value re- 


considered in connexion with the Dynamical Theory. 3 


quired to overcome the weight of the great column of water. 
The second valve is accordingly opened, and a portion of the 
water is forced up. Now the electrical current, in virtue of 
self-induction, can no more be suddenly stopped than the cur- 
rent of water ; and so in the above experiment the polarization of 
the voltameter is instantly overcome, and a quantity of electricity 
passes. 

If no second means of escape were provided for the water in 
the hydraulic ram, the pipe would in all probability be unable 
to withstand the shock, and in any case could only do so by 
yielding within the limits of its elasticity, soas gradually, though 
of course very quickly, to stop the flow of water. The bursting 
of the pipe may properly be compared to the passage of a spark 
at the place where a conductor carrying an electric current is 
opened. Just as the natural elasticity of the pipe or the com- 
pressibility of the air in a purposely connected air-vessel greatly 
diminishes the strain, so the electrical spark may be stopped by 
connecting the breaking-points with the plates of a condenser, 
as was done by Fizeau in the induction-coil. Contrary to what 
might at first sight have been expected, the fall of the pri- 
mary current is thus rendered more sudden, and the power of 
the instrument for many purposes increased. Of course the 
spark is equally prevented when the breaking-points are con- 
nected by a short conducting circuit, as in our experiment by 
the voltameter. In fact the energy of the actual motion which 
exists the moment before contact is broken is im the one case 
transformed into that of the sound and heat of the spark, and in 
the other has its equivalent partly in the potential energy of the 
decomposed water, partly in the heat generated by the passage 
of the momentary current in the voltameter branch. 

The experiment will be varied in an instructive manner if we 
replace the voltameter by a coil (with or without soft iron), ac- 
cording to the resistance and self-induction of the latter. In 
order to know the result, we must examine closely what takes 
place at the moment when contact is broken. The original cur- 
rent, on account of its self-induction or inertia, tends to conti- 
nue. At the same time the inertia in the branch circuit tends 
to prevent the sudden rise of a current there. A force is thus 
produced at the breaking-points exactly analogous to the pres- 
sure between two bodies, which we will suppose inelastic, one 
of which impinges on the other at rest. The pressure or elec- 
trical tension continues to vary until the velocities or currents 
become equal. All this time the motion of each body or cur- 
rent is opposed by a force of the nature of friction proportional 
to the velocity or current. Whether this resistance will affect 
the common value of the currents (or velocities) at the moment 


4 The Hon. J. W. Strutt on some Electromagnetic Phenomena 


they become equal, will depend on its magnitude as compared 
with the other data of the problem. 

There is for every conducting circuit a certain time-constant 
which determines the rapidity of the rise or fall of currents, and 
which is proportional to the self-induction and conductivity of 
the circuit. Thus, to use Maxwell’s notation, if L and R be re- 
spectively the coefficient of self-induction and the resistance, the 
time-constant is Boa If the current c exist at any moment 
in the circuit and fall undisturbed by external electromotive 

t 
force, the value at any time ¢ afterwards is given by z=c.e 7. 
Any action which takes place in a time much smaller than 7 will 
be sensibly unaffected by resistance. 

We see, then, that we may neglect the effects of resistance 
during the time of equalization of the currents, provided that 
the operation is completed in a time much smaller than the time- 
constants of either circuit. And this I shall suppose to be the 
case. The value of the common current or velocity at the mo- 
ment the impact is over will of course be given by the condition 
that the momentum, electromagnetic or ordinary, is unchanged. 
If Land N be the coefficients of self-induction for the main and 
branch circuits respectively, 2 and X the original and required 
currents, the analytical expression of the above condition is 


(L4+N)X=Lz, 
or 
L 
X= LiN Le 


It is here supposed that there is no sensible mutual induction 
between the two circuits. 

The spark is the result of the excess of the one current over 
the other, and lasts until its cause is removed. Its mechanical 
value is the difference between that of the original current in 
the main circuit and that of the initial current in the combined 
circuit, and is expressed by 


4La®—3(L-+N)3?; 
or if the value of X be substituted, 
L 


~ L+N 


Exactly the same expression holds good for the heat produced 
during the collision of the inelastic bodies, which is necessarily 
equal to the loss of ordinary actual energy, at least if the per- 


1 2 
tha 


considered in connexion with the Dynamical Theory. 5 


manent change of their molecular state may be neglected. From 
the value X the current gradually increases or diminishes to that 
determined according to Ohm’s law, by the resistance of the 
combined circuit. It may be scen from the expression just found 
that the resistance of the branch may be varied without affect- 
ing the spark, provided always that it is not so great in relation 
to the self-induction as to make the time- constant compa- 
rable in magnitude with the duration of the spark. The spark 
depends only on the comparative self-induction of the branch 
circuit, being small when this is small, and when this is great 
approximating to its full value ¢La’. 

These results are easily illustrated experimentally. I have 
two coils of thick wire belonging to an electromagnet, which for 
convenience I will call A and B. Each consists of two wires of 
equal length, which are coiled together. These may be called 
aeoee) bo. When A, A, are “joined consecutively, so that 
the direction of the current is the same in the two wires, we have 
a circuit whose self-induction is four times that of either wire 
taken singly. But if, on the contrary, the current flows oppo- 
site ways in the two wires, the self-induction of the circuit be- 
comes quite insensible. 

The main circuit may be composed of the wire A, (A, remain- 
ing open) into which the current from a single Daniell cell is 
led, and which can be opened or closed at a mercury cup. One 
end of the branch circuit dips into the mercury while the other 
communicates with the wire whose entrance or withdrawal from 
the cup closes or opens the main circuit. In this way the coils 
of the branch may be said to be thrown in at the break. 

If the branch is open, we obtain at break the full spark, 
whose value is $Lz?. If the wire B, be thrown in, the spark 
is still ponsiderable, having approximately the value +L? for 
N=L. And if B, B, are thrown in, so that the currents are 
parallel, the spark 1 . still greater and is measured by $La? x 4. 
But if the currents are opposed, the spark disappears, Bdeause 
now N=O; so that the addition of the wire B,, whereby the 
resistance of the branch is doubled, diminishes the spark. It 
is true that to this last case our calculation is not properly 
applicable, masmuch as the time-constant of the branch is so 
exceedingly small. But it is not difficult to see that in such a 
case (where the self-induction of the branch may be neglected) 
the tension at the breaking-points, or more accurately the dif- 
ference of potential between them, cannot exceed that of the 
battery more than in the proportion of the resistances of the 
branch and main circuits, so that it could not here give rise to 
any sensible spark. Soft iron wires may be introduced into the 
coils in order to exalt the effects; but solid iron cores would 


6 The Hon. J. W. Strutt on some Electromagnetic Phenomena 


allow induced currents to circulate which might interfere with 
the result. | 

In this form of the experiment there was no sensible mutual 
induction between the coils A and B. Should there be such, 
the result may be considerably modified. For instance, let the 
wire A, be thrown at the break into the cireuit of A, and the bat- 
tery. This may happen in two ways. If the connexions are so 
made that the currents are parallel in A, Aj, there will be no 
sensible spark ; but if the directions of the currents are opposed, 
the spark appears equal to the full spark $La”. 

And this is in accordance with theory. The current X is 
given by the same condition as before, which leads to the 
equation 


Le +Ma=(L+2M+4+N)X, 


M being the coefficient of mutual induction between the two 
circuits. The spark is therefore 
x? L—M 
tLa2?—} (L+2M+N) =o Sore as N=L. 
Now in the first-mentioned connexion M=L very nearly, and in 
the second M=—L; so that the observed sparks are just what 
theory requires. 

With regard to those electrical phenomena which depend on 
the mutual induction of two circuits, it may be remarked that it 
is not easy to find exact analogues in ordinary mechanics which 
are sufficiently familiar to be of much use as aids to conception. 
A rough idea of the reaction of neighbourmg currents may be 
had from the consideration of the motion of a heavy bar to 
whose ends forces may be applied. If when the bar is at rest 
one end is suddenly pushed forwards in a transverse direction, 
the inertia of the material gives the centre of gravity in some 
degree the properties of a fulcrum, and so the other end begins 
to move backwards. This corresponds to the inverse wave in- 
duced by the rise of a current in a neighbouring wire. If the 
motion be supposed infinitely small, so that the body never turns 
through a sensible angle, the kinetic energy is proportional to 

3 (a? + KA) a? + 2 (DP + k*)y? + (ab—K)ay, 
where a and 0 are the distances of the driving-points (whose velo- 
cities are z and 7) from the centre of gravity, k? the radius of gyra- 
tion about the latter pomt. This corresponds to the expression 
for the energy of the electromagnetic field due to two currents, 
tLz?-+ May+4Ny?; 

and if we imagine the motion of the driving-points to be re- 
sisted by a frictional force proportional to the velocity, we get a 
very tolerable representation of the electrical conditions. 


considered in connexion with the Dynamical Theory. 7 


Or we may take an illustration, which is in many respects to be 
preferred, from the disturbance of a perfect fluid, by the motion 
of solid bodies in its interior. Thus if in an infinite fluid two 
spheres move parallel to each other and perpendicularly to the 
line joining them, and with such small velocities that their rela- 
tive position does not sensibly change, the kinetic energy may 
as usual be expressed by 

$Lz?+ May+4Ny?, 

x,y denoting the velocities of the two spheres, and L,M, N being 
approximately constants*. When the spheres move in the same 
direction, the reaction of the fluid tends to press them together ; 
but if the motions are opposed, the force changes to a repulsion. 
We see here the analogues of the phenomena of attraction and 
repulsion discovered by Ampére. If when all is at rest a given 
velocity is impulsively impressed on one sphere, the other im- 
mediately starts backwards, and, as Thomson + has shown, with 
uch velocity that the energy of the whole motion is the least 
possible under the given condition. 

This theorem is general, and leads directly to the solution of 
a large class of electrical problems connected with indaction ; 
for whenever a current is suddenly generated in one of the 
circuits of a system, the initial currents im all the others are 
to be determined so as to make the energy of the field a mini- 
mum. These initial currents are formed unmodified by resist- 
ance whenever the electromotive impulses to which they owe 
their existence last only for a time which may be regarded as va- 
nishingly small compared with the time-constants of the circuits. 
The sudden fall of a current when a circuit is opened generates 
the same currents, except as to sign, in neighbouring circuits as 
those due to a rise of the first current, and the condition as to 
sufficient suddenness is more generally fulfilled ; at the same time 
it is more convenient in explaining the theory to take the case of 
the establishment of the primary current. 

Suppose, then, that in the wire A, of our coil a current 2 is 
suddenly generated, while the ends of A, are joined by a short 
wire. ‘The condition of minimum energy 1s obviously fulfilled 
if there arise in A, a current represented by—z; for then the 
energy of the field is approximately zero. But if the self-induc- 
tion of the wire joining the ends of A, be sensible, the annihi- 
lation of the energy can no longer be perfect. Thus, let the 
circuit of A, be completed by B, B,, then the general expression 
for the energy of two currents becomes in this case 


+ Lx? + Lay + sly? x (5 or 1, 


* Thomson and Tait’s ‘Natural Philosophy, pp. 262, 264. 
+ Thomson and Tait, p. 225, 


8 The Hon. J. W. Strutt on some Electromagnetic Phenomena 


according to the connexions) ; and the value of y for which this 
is a minimum is —2(1 or1). In the first case, the exterior 
part of the induced circuit having uo sensible self-induction, 
takes away nothing from the initial current; but in the second 
there is a reduction to one-fifth. On the other hand, it makes 


; *k 
no difference to the total current (- =*) , as measured by the 


deflection of the galvanometer-needle, which way the connexion 
is made; for the smaller initial current, in virtue of its greater 
inertia, sustains itself proportionally longer against the damping 
action of resistance, which is the same in the two cases. The 
heating-power and the effect on the electrodynamometer, which 
depend on the integral of the square of the current while it lasts 
[2 

oS x ), will be different ; but the easiest proof of the diver- 
sity of the currents is to be had by comparing their powers of 
magnetizing steel. 

Thus, if we include in the induced circuit a magnetizing spiral 
in which is placed a new sewing-needle, we shall find an im- 
mense difference in the magnetization produced by a break-in- 
duced current, according as its direction is the same or otherwise 
in the wires B, B,. Inthe actual experiment the diluted current 
was unable, even after several repetitions, to give the needle any 
considerable magnetization (the vibrations were only about three 
per minute), while after one condensed current the needle gave 
sixteen, raised by repetition to nmeteent. A new needle submit- 
ted to the action of several condensed currents also gave nineteen 
per minute. The magnetic moments, which are as the squares 
of these numbers, show a still greater disproportion. 

The truth seems to be that the time required for the perma- 
nent magnetization of steel is so small as compared even with 
the duration of our induced currents, that the amount of acquired 
magnetism depends essentially on the imitial or maximum cur- 
rent without regard to the time for which it lasts. 

The increased heating-effect when the two parts of the current 
in B are opposed in direction is, of course, at the expense of the 
spark in the mercury-cup. The mechanical value of the spark 
is the difference between the values of the currents which exist 
at the moments before and after the breaking of the contact, and 


LL a?—1LNy? =}2°(L- 7) =}0*(L—) neatly. 


* R, S are the resistances of the primary and secondary circuits respec- 
tively. 
+ These were complete vibrations. 


considered in connexion with the Dynamical Theory. 9 


Now, according to the connexions, N=L or 5L; and so in the 
first case the spark disappears, while in the second it falls short 
of the full spark by only one-fifth. 

While considering the dynamics of the field of two currents, 
I noticed that the initial induced current due to a sudden fall of 
a given current in the primary wire is theoretically greater the 
smaller the number of terms of which the secondary consists ; 
for in calculating the energy of the field, it makes no difference 
whether we have a current of any magnitude in a doubled 
circuit, or twice that current in a single circuit. The same 
conclusion may be arrived at by the consideration of the ana- 
lytical expression for the initial induced current 


M 
JOR Ns 


for if the secondary circuit consists essentially of a single coil of 
n terms, we have, ceteris paribus, M « n, while N a n?, so that 


1 
Yo%>. The whole induced current if ydt c Mon. Interme- 
2 


diate to these is the heating-effect Jf yrdt, which a wy> and is 


therefore independent of n. Thus it was evident that neither the 
galvanometer nor electrodynamometer were available for the veri- 
fication of this rather paradoxical deduction from theory, at 
least without commutators capable of separating one part of the 
induced current from the rest. On the other hand, it appeared 
probable that the smaller total current, in virtue of its greater 
maximum, might be the most powerful in its magnetizing action 
on steel. 

With the view of putting this idea to the test of experiment, 
I bound three wires of ‘001 inch diameter, and about 20 feet 
long, together into a coil whose opening was sufficient to allow 
it to pass over the coil A. The ends of the wires were free, so 
that they could be joined up in any order into one circuit, which 
was also to contain the magnetizing spiral. It is evident that 
if the currents are paralle] in the three wires (an arrangement 


which I will call a), then 
M=3M,, N=9No 


M, N, being the values of the induction-coefficients for one wire ; 
while if in the two wires the current flows one way round and in 
the third the opposite (6), we shall have M=M,, N=N . Inas- 
muchas the self-induction of the magnetizing spiral was relatively 
very small, these may be regarded as the induction-coefficients 
for the secondary circuit as a whole. This arrangement was 
adopted in order that there might be no change in the resistance 


10 The Hon. J. W. Strutt on some Electromagnetic Phenomena 


in passing from one case to the other. The primary current was 
excited by a Daniell cell in the two wires of A arranged collate- 
rally, and was interrupted at a mercury-cup. The needle was 
submitted to the break induction-currents only—although the 
make currents had no perceptible magnetizing-power, on ac- 
count of the relatively large time-constant of the primary cir- 
cuit, and the consequent slow rise of its current to the maximum. 

On actually submitting a new needle to the current a, I 
obtained after one discharge 12 vibrations (complete) per 
minute, a number raised after several discharges to 15. On 
the other hand, a new needle after one discharge b gave 
only 5 per minute, and was not much affected by repetition. 
The last needle being now submitted to discharge a gave 83, 
and after several 12. Other trials having confirmed these 
results, there seemed to be no doubt that the current a was 
the most efficient magnetizer. There remained, however, some 
uncertainty as to whether the time-constant, especially in 8, 
was sufficiently large relatively to the time for which the spark 
at the mercury cup lasted to allow of the initial current being 
formed undiminished by resistance. In order to make the fall 
of the primary current more sudden, I connected the breaking- 
points with the plates of a condenser belonging te a Ruhmkorff 
coil, and now found but little difference between the magneti- 
zing-powers of a and b. Seeing that the theoretical condi- 
tion had not been properly fulfilled, 1 prepared another triple 
coil of much thicker wire, and, for greater convenience, arranged 
a mercury-cup commutator, by means of which it was possible 
to pass at once from the one mode of connexion to the other. 
The magnetizing spiral was still of fine wire coiled, without any 
tube, closely over the needle, and its ends were soldered to the 
thicker wire of the triple coil. 

The experiment was now completely successful. Out of the 
large number of results obtained, the following are selected as 
an example. A new needle was submitted to the break dis- 
charge of arrangement 0, and gave, 


After 1 discharge, 19 per minute. 
3) 3 3) 23 PB) 
3) 6 PP) 24, 3) 


Another needle was now taken and magnetized by discharge a. 
It gave, 
After 1 discharge, 11 per minute. ° 
3) 3 3) 12 oY 
3) 10 3) 125 PP) 


On submitting this needle, which had received all the mag- 


considered in connexion with the Dynamical Theory. ue 


netism that a could give it, to current b, I obtained, 


After 1 discharge, 21 per minute. 
33 3 3) 4 


PP) 


In fact it was the general result of the experiments that 
more magnetism is always given to the needle by arrangement 
6 than by a. In order, however, that the difference may be 
striking, it is advisable not to approach too nearly the point of 
magnetic saturation. The numbers quoted were obtained with 
the condenser, which was still necessary, in order to make the 
break sufficiently sudden. I have no doubt, however, that it 
might have been dispensed with had the triple coil consisted 
of a larger number of turns. 

The circumstances of this experiment are in some degree 
represented by supposing, in the hydrodynamical analogue, one 
of the balls to vary in size. When a given motion is suddenly 
impressed on the other ball, the corresponding velocity gene- 
rated in the first would vary inversely with its magnitude; for 
the larger the ball the greater hold, as it were, would it have 
on the fiuid. 

It is interesting also to examine the influence of neighbour- 
ing soft iron on the character of the induced current. This in- 
fluence is of two sorts; but I refer here to the modifications 
produced by the magnetic character of iron. The circulation 
of induced currents in its mass may generally be prevented 
from exercising any injurious influence on the result by using 
ouly wires, or fragments of small size. The proximity of soft 
iron always increases the coefficient of self-imduction N, while 
M may be either increased or diminished. The latter state- 
ment is true also for the initial current y, which is propor- 


tional to a For the two wires of the coil A, however, it is 


easy to see that M and N are approximately equal, whether 
there be soft iron in their neighbourhood or not. Thus, if A, 
be connected with a Daniell cell while the circuit of A, is com- 
pleted by the magnetizing spiral, the magnetism acquired by 
the needle, after a break-induced current, is not much altered, 
even if a considerable number of iron wires are placed in the 
coil. The total current is increased fifteen times or more; but 
this is because the current lasts longer, the maximum or initial 
value being no greater than before. This experiment strikingly 
illustrates the comparative independence of the magnetizing 
effect of a current on its duration. It seems probable a priori, 
and is partly confirmed by some of my experiments, that this is 
more especially true if we take the limiting magnetism which 


12 The Hon. J. W. Strutt on some Electromagnetic Phenomena 


an induced current can produce, after repetition, as the measure 
of its magnetizing powers. 

The same kind of reasoning may be applied to more compli- 
cated problems. As an example, we may recur to a former 
combination, in which the primary current is excited in the 
wire A,, while the secondary circuit includes A,, B,, and the 
magnetizing spiral. The initial current y, on which, as we 
have seen, the magnetizing power mainly depends, will be greatly 
increased if the ends of the wire B, are joined so as to make a 
tertiary circuit; for a current in B, is developed, which, being 
equal and contrary to that in B,, neutralizes its action on the 
magnetic field, and so allows the energy, immediately after the 
sudden rise of the current x in A,, to be vanishingly small, 
exactly as when the secondary circuit consisted of A, alone. 
The effect of closing B, is therefore to increase the current yp 
from —3 az to —z, and at the same time to produce a new cur- 
rent denoted by +2 in B, itself. The following were some of 
the experimental results :— 

A new needle, 
B, open After 1 break-discharge, gave 74 per minute. 
3) 8 3) 33 3) 
On closing B, we had, with the same needle, 


After 1 discharge, 15 per minute. 
3) 8 33 17 3) 
A new needle gave, 
After 1 discharge, 17 per minute. 
9) 8 3) 19 39 


Another new needle in the tertiary circuit gave, 


After 1 discharge, 16 per minute. 
3) 4 33 19 3) 
3) 8 93 195 39 

The magnetizing spiral was here removed from the secondary 
to the tertiary circuit; and although its resistance was by no 
means relatively small, the results are none the less compara- 
ble; for in this experiment resistances (within limits) are of 
no account, and the self-induction of the spiral was quite in- 
sensible. 

Had there been twentycolsA BCD...... similar to A B, 
with the wires B, C,, C, D,, &c. connected, as im the experi- 
ment just described, the magnetizing power of the current in 
the last would not, I imagine, be much less than im the first ; 
for the condition of mmimum energy would still be fulfilled by 
currents in the series of coils all equal in numerical value, and 
alternately opposite m algebraic sign. On this subject much 


considered in connexion with the Dynamical Theory. 13 


confusion seems to have prevailed, as shown by the numerous 
inquiries into the direction of the induced currents of high 
orders. The currents, as a whole, at least after the first, can- 
not properly be said to have any direction at all, as they in- 
volve, when complete, no transfer of electricity im any direc- 
tion. Nevertheless the positive and negative parts are not si- 
milar ; and if they were, one must necessarily precede the other ; 
so that in this way directional effects may be produced. The 
magnetizing power, for instance, depends essentially on the initial 
maximum magnitude of the induced current, and is probably 
but little affected by the character of the diluted but compara- 
tively long-continued remaining parts. This being understood, 
the alternately opposite magnetizations observed by Henry in a 
series of induced currents of high order, is an immediate con- 
sequence of the dynamical theory. 

The circuits being denoted by the numbers 1, 2, 3,..., let 
the coefficient of mutual induction between 2 and 3 be denoted 
by (2 3), and of self-induction of 2 by (22), and so on. The 
result is only generally true when there is no mutual induction 
except between immediate neighbours in the series ; and it will 
therefore be supposed that 


Gye A) p01 (i) verbo QkA)i 


vanish, as indeed they practically would in the ordinary arrange- 
ment of the experiment. The energy of the field is given by 


BH=4(1 1)a?+3(2 2)a2+3(8 3)a2+... 
+ (1 2)a,7.4+ (2 3)rqor34+ (8 4)aga,+ ... 
Here a, is the given current in the first circuit, and 2, z5,... 
are to be determined so as to make KE a minimum. Now, HE 
being homogeneous in 2, %,..., we have identically 


di di 
ott ees Te rey 606 


And since, when EF is a minimum, 


ap at ... all vanish, 
dz, dx, 
we see that 
QE (min.) =2, 4" = (1 1)z2+ (1 2)ar,29 


lp 

1 
But if x,, #3,... had been all zero, 2K would have been equal 
to(11)#?. It is clear therefore that (1 2)2, 2, is negative ; 
or, as (1 2) is taken positive, the sign of x, is the opposite of 
that of z,. 


14 The Hon. J. W. Strutt on some Electromagnetic Phenomena. 


Again, supposing z, z, both given, we must have, when EH is 
a minimum, 


dB de, 
dats dx, ) Py IR! ) 
and thus 


2K (min.) =z, [(1 l)z,+ (1 2)aq] 
+aq[(1 2)a, + (2 2) a+ (2 3)ars] 
= [1 1)2?+2(1 2)x, ryt (2 2)u?2 + (2 8) rons. 
As before, 2E might have been 
(1 Va? +21 2)a, a, + (2 2)a2; 


and therefore the mimimum value is necessarily less than this, 
and accordingly the signs of 2, and #, are opposite. This process 
may be continued, and shows that, however long the series, the 
initial induced currents are alternately opposite in sign. In any 
definite example, the actual values of the initial currents are to 
be found from the solution of the linear equations 


dk CAD 


ipo ae 


==) re 
but the sign of the result does not appear at once from the form 
of the expression so obtained. In order to exhibit it, it is ne- 
cessary to introduce a number of relations which exist between 
the induction-coefficients, and which are the analytical expres- 
sion of the fact that the energy is always positive, whatever may 
fethe valuesi0t 27, gaa-ee 

It has been assumed throughout that the time of rise or fall 
of the current in the primary wire 1s very small as compared with 
the time-constants of the other circuits. In the case of coils, 
such as are generally used in induction-experiments, and which 
are not clogged by great external resistances, this condition is 
abundantly fulfilled at the break of the voltaic current*. The time 
of rise depends more on the nature of the circuit, but may be 
made as small as we please by sufficiently increasing the resist- 
ance in proportion to the self-induction ; of course, in order to 
get an equally strong current, a higher electromotive force must 
be employed. In this way the rise may be made sufficiently 
sudden to fulfil the condition. Indeed, with a battery intense 
enough the rise of the current at make may become more sudden 


* A rough measurement by Maxwell’s method (Phil. Trans. 1865) gave 
for the time-constant of the circuit composed of the two wires of coil A 
0023". The time-constant is the same whether the wires are collateral or 
consecutive, the greater self-induction of the latter arrangement being 
balanced by its greater resistance. For one wire only, the time-constant 
would be half the above. 


On the Function of the Blood in Muscular Work. 15 


than the fall when contact is broken. In some of Henry’s ex- 
periments this seems actually to have cccurred. Thus, with 
a single cell as electromotor, he found the shock at make 
barely perceptible ; but when the battery was increased to thirty 
cells, the shock became more powerful at make than at break. 
And here [ must bring this rather disjointed paper to a close. 


Terling Place, Witham, 
June l. 


II. On the Function of the Bloodin Muscular Work. By W. H. 
BroapBent, M.D., Lecturer on Physiology at St. Mary’s 
Hospital Medical School*. 


‘ the Philosophical Magazine for May 1867 there is a paper 

under the title given above by Mr. C. W. Heaton, Professor 
of Chemistry at Charing-Cross Hospital, the purport of which is 
to show that the oxidation which yields the force exerted by the 
muscles is intravascular, or that muscular force is generated en- 
tirely from the blood and within the blood-vessels. As this 
communication is considered by some eminent physiologists to 
have established the hypothesis that the blood itself 1s both the 
source and the seat of all the chemical change by which force is 
developed in the animal organism, it is desirable to examine 
whether the considerations on which it is based are really so con- 
clusive. 

The point in question is whether the oxidation which evolves 
muscular force is intravascular or extravascular. The arguments 
employed by Professor Heaton are as follows :— 

1. “If the oxidation of muscle is effected in the tissue itself, 
it is clearly necessary to suppose either that the oxygen, upon 
the stimulus of the motor nerves, leaves its combination in the 
corpuscle, traverses the walls of the capillary in company with 
the outgoing stream of nutrient fluid, and only enters into new 
combinations when it has passed to some comparatively dis- 
tant muscle-fibre, or else that the corpuscle itself liquefies and 
passes out bodily through the thin membrane with its loosely 
combined oxygen..... Any oxygen which passes. out into the 
tissues must obviously pass in solution in the exudate.” 

2. The lymph collected from the tissues and again poured into 
the blood may be taken as the measure of the exudate which 
passes out of the capillaries into the structures; and it is shown 
by careful calculation, exaggerating both the amount of exudate 
and the proportion of oxygen dissolvable in it, that the quantity 
of oxygen which could thus be carried to the tissue is utterly 


* Communicated by the Author. 


16 Dr. W. H. Broadbent on the Function of 


inadequate to effect the oxidation required for the evolution of 
the force actually exerted by the muscles. 

The entire question thus turns on the assumption that oxygen 
can leave the capillaries only by passing through the thi mem- 
brane of which they consist, in solution in a fluid exudate. The 
necessity for a current of fluid to convey the oxygen is supposed 
to arise from the fact that the oxygen, being in solution in the 
blood, carries with it its solvent in passing through the capillary 
wall—yjust as in dialysis the saline matter is accompanied by the 
water in which it is dissolved. But this view of the process 
leaves entirely out of consideration the fact that if oxygen 
leaves the capillaries, the products of oxidation (carbonic anhy- 
dride &c.) must enter them; and when two diffusible substances 
are in solution on opposite sides of a thin membrane, the ad- 
verse currents of the common solvent more or less neutralize each 
other, and there is interchange of the dissolved matters with 
comparatively little movement of fluid. 

If oxygen can leave the blood only in solution in a current of 
fluid, how, it may be asked, does it enter the blood in the lungs ? 
It would seem that there ought to be a stream of fluid setting in 
from the air-cells into the pulmonary capillaries ; and this would 
be required were it not that, as the oxygen enters the blood, car- 
bonic anhydride leaves it. On the hypothesis that oxidation is 
extravascular, the exchange of oxygen for carbonic anhydride 1s 
effected very similarly in the pulmonic and systemic capillaries. 
In the lungs the oxygen is dissolved in the moisture of the walls 
of the air-sacs; there is thus outside the capillary membrane 
fluid containing oxygen, while in its interior is moving the blood 
charged with CO?; interchange of the two gases consequently 
takes place. In the systemic capillaries the blood is oxygenated, 
while outside the capillaries is the interstitial fluid of the textures 
containing the CO*® which has resulted from oxidation. The 
conditions under which interchange will occur are here again 
realized; the capillary wall stands between two fluids, one charged 
with O, the other with CO?. Here, however, the O is in the 
blood, instead of CO? as in the lungs. It is not the affinity of 
a distant fibre for oxygen which overcomes the weak “ molecular 
combination ” of this gas with the blood-corpuscles, but the pre- 
sence of CO? in the surrounding fluid; and the affinity of O and 
CO? for hematoglobin is so nearly balanced, that they mutually 
displace each other according as one or the other predominates. 

It is thus evident that, supposing the oxidation to take place 
outside the capillaries, the oxygen does not require a stream of 
fluid to convey it to the tissues; and this being the case, the 
calculation by which it is shown that the exudate is insufficient 
for the purpose has no bearing whatever on the question whether 


the Blood in Muscular Work. 7 


the oxidation is intra- or extravascular. This consequently has 
to be decided on other grounds; and the evidence in favour of 
the view that the oxidation takes place outside the capillaries 
preponderates greatly. In muscle, besides the proper muscular 
fibre with its connective tissue and the capillaries, there is an in- 
terstitial fluid (the “muscular juice”), which Claude Bernard 
calls the ‘ mzliew”’ of the fibre, and which may be regarded as 
a medium common to the fibre and the vessel. On the one 
hand, it is by the reaction between the fibre and this fluid 
which surrounds and saturates it that the chemical change takes 
place (oxidation or its equivalent) by which the force is evolved ; 
on the other hand, this fluid being separated from the blood only 
by the thin capillar y wall, the most perfect equalization of their 
diffusible constituents must take place by osmosis, oxygen pass- 
ing from the blood into the interstitial fluid, and products of 
oxidation from this fluid into the blood ; so far, then, as the sup- 
ply of oxygen is concerned, the muscular juice is equivalent to the 
blood. Were intravascular oxidation the source of muscular 
force, the evolution of the force must cease absolutely on the 
supply of blood being cut off. We find, on the contrary, that a 
muscle continues to contract for some time after its removal from 
the body, showing that force (or, in other words, oxygen and 
oxidizable material) is stored up in the muscle; and it is further 
found that after frequent and sustained contraction the muscular 
juice is changed in composition. We find, again, that muscular 
contractility survives removal longest in cold-blooded animals, 
whose blood contains a minimum of oxygen; and when a 
warm-blooded animal is brought into a state analogous to that 
of reptiles, its blood being rendered venous and its tempera- 
ture greatly lowered, its muscles also retain their contractility, 
as has been shown by Claude Bernard’s “lapin a sang froid,” in 
which the above conditions are induced by section of the cervical 
spinal cord. Itis perhaps scarcely necessary to notice a difficulty 
in the hypothesis of Professor Heaton; but it might fairly be 
asked how force evolved within the capillary is transmitted to 
the “comparatively distant fibre” by which it is manifested. 
Oxidation has been spoken of in this discussion as the source 
of muscular work without any qualification; but it should be 
understood that there is an essential difference between the mode 
of oxidation which yields the animal heat, and that which affords 
mechanical work or nerve-force. While heat is evolved continu- 
ously and uniformly, nervo-muscular action takes place inter- 
mittently, abruptly, and with varying intensity on the application 
of a “stimulus,” 7. e. the oxygen and oxidizable matter being in 
presence, the combination only occurs when some impulse 1S 
given. It is thus not a simple case of combination of oxygen 


Phil. Mag. 8. 4. Vol. 88. No. 252. July 1869. C 


18 Mr. T. R. Edmonds on Vital Force according 


with a combustible, but the rearrangement of the elementary 
constituents of a complex molecule in a state which, for want of 
a better term, I have called elsewhere* “ chemical tension.” In 
the communication alluded to the evolution of nerve-force only 
was considered, and the conclusion here stated was reached de- 
ductively, but experimental confirmation is afforded by Hermann’s 
researches on the chemical changes attending muscular action. 


III. On Vital Force according to Age, and the “English Life Table.” 
By Tuomas Rows Epmonns, B.A. Cantab.t 


BSERVATIONS on the vital force of man at different ages 
from birth are all of modern date. The idea of the exist- 
ence in every population of a law of vital force according to age 
was not entertained by mankind until near the end of the seven- 
teenth century. The embodiment of this idea in a “Table of 
Mortality ” was first made about the year 1693, by our country- 
man, Dr. Halley. The form of the Table of mortality adopted 
about the year 1738, and continued in use to the present time, 
may be described as follows :—Such Table consists of three co- 
lumns. The heading of the first column is ‘ Age,” of the se- 
cond column “ Living,” and of the third column “ Dying.” The 
numbers in the first column denote completed years of age from 
birth-time, beginning at age O and ending, say, at 99 years. 
The numbers in the second column denote the living or suryi- 
vors at any completed year of age out of a given number born or 
livmg at the age 0. Lastly, the numbers in the ¢hird column 
denote the numbers dying during the year of age next following 
the completed year marked, i the same horizontal line, in the 
first column. 

In a Table of mortality, if the numbers in the column of 
“Living” be represented by the letter P, the numbers in the 
column of “Dying”? will be represented by AP, for a unit of 
time or age taken to be one year. If the time or age be reckoned 


from birth, we shall have at any age ¢ the quantity atl re- 
t 


present the ratio of the numbers dying during the (¢+1)th year 
of age to the numbers living at the beginning of the same year 
of age. If the intervals of age, instead of being each one year, 
be diminished indefinitely, we shall have to substitute the differ- 
ential of P; or d. P, for AP? in the above ratio. We shall then 


P, 


P, 


obtain d 


, or d. log, P; for the expression of the ratio of the 


* Proceedings of the Royal Society, June 1868. 
ft Communeated by the Author. 


to Age, and the “English Life Table.” 19 


dying to the living, during an infinitely small given time df, at 
the precise age ¢ years, ¢ being either a whole number or frac- 
tional. Ifa simple function of the variable ¢ can be discovered 
which will represent d.log, P; at all ages, then by integration 
the value of log, P;, and consequently of P;, may be determined 
for all ages. It may be useful here to state that the ratio of 
the dying tothe living for an indefinitely small given time df, 
at the exact age 7, represents the force of mortality at that age— 
also that the vital force at any age ¢ 1s represented by the reci- 
procal of the force of mortality at the same precise point of age. 
A Table of mortality for a particular population is a mode of 
exhibiting the ratio of the dying to the living in that population 
for every year of age from birth-time to the end of life. The 
knowledge of this series of annual ratios (which is the founda- 
tion of every true Table of mortality) can be obtained only by 
observations of the contemporary numbers living and dying at 
every interval of age. In the making of such observations, the 
intervals of age ought to be quinquennial at all ages above five 
years, biennial at ages above one and less than five years, quar- 
terly in the first year of age, and monthly in the first quarter 
of year from birth. No observation of the kind now described 
was known to the public until near the end of the eighteenth 
century, when the Sweden Table of mortality constructed by 
Dr. Richard Price was published. Dr. Halley’s Table for 
Breslau, as well as all other Tables of mortality for specific 
populations, which had been constructed previously, were defec- 
tive and not to be relied upon through not being founded on 
the requisite data mentioned above. These defective Tables had 
been deduced from observations made only on the registered 
number of deaths at different ages belonging to the several 
populations, without any observation or enumeration of the 
contemporary numbers living at the same ages. The defects 
inseparable from such Tables were partially remedied in various 
ways. Populations were selected for observation in which the 
numbers living at all ages were nearly stationary, and in which 
the annual births had been nearly equal to the annual deaths for 
along period of time. Then the supposition was made that the 
living population at each interval of age was constant and not 
increased or diminished by migration. Lastly, corrections were 
introduced to rectify manifest deviations from the assumed con- 
dition of a stationary population at every interval of age. 
Observations made correctly, and in the proper form for de- 
termining the vital force of man at different ages, are very few 
im number. In the first rank are the observations of the living 
and dying, according to age, of the population of Sweden, 
commencing about the year 1750 and continued to the present 


C2 


20 Mr. T. R. Edmonds on Vital Force according 


time. In these observations the ages and numbers of the con- 
temporary living and dying are given for quinquennial intervals 
at all ages above five years of age, and for biennial and annual 
intervals below that age. Next in time and very high in rank 
comes the observation of the living and dying, according to age, 
of the population of Carlisle, made for the nine years ending with 
the year 1787. This observation was made spontaneously by a 
private individual, Dr. Heysham, without aid in money or labour 
from the public. This observation, on the vital force, according 
to age, of the population of a town of no great magnitude, is 
in accuracy and form of so high a character, that it is equal in 
value to any ordinary observation of the same kind made on a 
population a hundred times as great in extent. Last in time 
comes the observation on the living and dying, according to age, 
of the population of England for the seventeen years 1838-1854. 
This observation was published in the year 1864, by authority 
of the Registrar-General for England, and was accompanied by 
the “ English Life Table” deduced therefrom by Dr. William 
Farr. 

In the earlier part of the English observation, made for the 
seven years ending with 1844, and published in 1849, the num- 
bers of the living and dying, according to age, were given for 
quinguennial intervals at all ages above 15 years. But in the 
observation for the total period of seventeen years ending with 
1854 the numbers living and dying, according to age, are given 
for decennial intervals only at ages above 15 years. Ne reason 
has been assigned for thus withholding mformation which 1s very 
valuable as an index of the truth, or want of truth, in the re- 
ported ages and numbers of the living and dying on which the 
“English Life Table” is founded. On the present occasion, 
however, this defect in the English observation for the entire pe- 
riod of seventeen years has been remedied, as may be seen on 
reference to Tables IV. and V. hereunto annexed. The rates 
of mortality for decennial intervals of age have been given for 
the period of seven years and for the period of seventeen years, 
whilst the rates for quinquennial intervals of age have been given 
also for the seven years ending with 1844. From these data 
the quinquennial rates for the seventeen years ending with 1854: 
have been determined as nearly as can be desired for any useful 
purpose. 

All Tables of mortality, especially those founded on good ob- 
servations, agree with one another in exhibiting one uniform 
progressive rate of increase of vital force according to age during 
childhood, and another uniform progressive rate of decrease accord- 
ing to age during manhood, reckoning from puberty to the latest 
age of life. The true law according to which the vital force uni- 


to Age, and the “English Life Table.” 21 


formly increases during childhood, as well as the true law ac- 
cording to which the vital force uniformly decreases during 
manhood, were first communicated to the public through the 
Philosophical Magazine of January 1866, in a paper written by 
me. I had previously, in the year 1832, given to the public a 
triple series of “ Life Tables,” all founded upon an empirical law 
which yields results nearly ponte dene with the results of the true 
law published in1866. For practical purposes, in the construction 
of Tables of mortality, it is not easy to determine whether the 
true law of 1866 ought to be preferred to the empirical law of 
1832. In either case the law of variation of vital force from 
birth to the end of life is expressible in very simple terms, the 
result in either case being a differential of the logarithm of the 
living (d.log,P) of great simplicity. But when the two differ- 
entials are integrated, the resulting formula for the living (or 
survivors) at any specified age ¢ or a+¢ is found to be more 
simple when the empirical law is adopted than when the true 
law is adopted as the basis of calculation. 

In the Philosophical Magazine for January 1866 (No. 206, 
page 9), it has been shown, according to the true law, that the 
force of mortality at any age, either in the period of childhood 
or in the period of manhood, is known when the force of mor- 
tality at any other age in the same period is known, from the for- 


mula following, 
1 


(45) 
ao at+t 


wherein ¢ is the difference of age; ais a constant representing 
distance (in time or age) from a fixed point, which is one of the 
two zeros of life; a 1s a given or observed force of mortality at 
a known absolute age a; a, 1s the force of mortality to be de- 


termined for any other absolute age (a+7); and wherein 2 is 


| k 
the hyperbolic logarithm of 10, and equal to 2302585. 

There are two zeros of vital forcee—one belonging to the period 
of childhood, and the other to the period of manhood. The zero 
of childhood is at the age 21 years before birth, or at the age 14 
year before conception. The zero of the period of manhood is 
at the age 102 years after birth-time. The length of the period of 
childhood (which terminates at 9 years after birth-time) is 
244+9=114 years. The length of the period of manhood is 
102—12=90 years. The length of the period of manhood is 
just eight times the length of the period of childhood. The in- 
crease of vital force during each year in childhood is just eight 
times as great as the decrease of vital force during each year in © 
the period of manhood. There is an intermediate period, from 


« 


22 Mr. T. R. Edmonds on Vital Force according 


the age of 9 to the age of 12 years, during which the rate of 
mortality is constant and at a minimum. It may be well to ob- 
serve that the zero of life m the period of childhood may be real 
and mark the commencement of animal organization. Also it 
may be useful to observe that, if the law of mortality is conti- 
nuous above and below 84 years of age as well as above and 
below birth-time, it will ensue that the rate of mortality at the 
age 90 years is equal to the rate of mortality immediately after 
the time of conception, and the rate of mortality at the age 96 
years 1s equal to the rate of extinction of germs existing at the 
age of 9 months, measured from the day of commencement of 
organization. 

The differential of the hyperbolic logarithm of the living or 
surviving at any age a@+7 is known when the force of mortality 
a at the absolute age a measured from one of the two zeros of 
vital force is known, and is of the form Ue — 


log Bie (+ a) Eat 


The above equation yields on integration (after assuming P 
to be equal to unity when ¢=0) the following equation, corre- 
sponding to any absolute age a+47, 


com. log Py= — “ats 1 = ( ibe = ay", 


i mee 
wherein n= i —]1=1:'302585, and wherein ais the decrement 
i , 


in a unit of time on a unit of life, at the absolute age a whence 
¢ is measured, the infinitesimal rate of decrement for the same 
precise age being adf. 

The above formula for the surviving population from a given 
age a to any other age a+¢ is similar to the formula which re- 
presents the ratio of increase of the expansive force of water 
(with its steam envelope) from a given temperature a to any 
other temperature a+¢, measured from the zero of heat, which 
is at 276° C. (or 496°'8 F.) below the temperature of melting 
ice. That is to say, the law of surviving population accord- 
ing to age is the same as the law of expansive force of water 
according to ¢emperature. Both laws are expressed by similar 
functions of the variables, whether in time or in temperature. 
The expansion by heat of the force of water (or of steam in- 
cumbent on water) is the chief instrument employed by man 
in producing motion for mechanical purposes. In mterest and 
importance to man, the law of vital force is at least equal to 
_ the law of steam force. The knowledge of either of these two 
laws is as valuable as the knowledge of any other law which 
concerns mankind, 


to Age, and the “ English Life Table.” 23 


In the case both of surviving population and of steam force, 
dlog.P is of the same form though of different signs, whether P 
represents population or pressure per square foot of steam of 
maximum density. The differential of log, P represents decre- 
ment in one case and increment in the other case. Surviving 
population is always diminishing as age increases ;_ whilst steam 
force is always increasing as temperature increases. 


In the case of population, d. log’ P, or a represents rate of 


decrement of life or force of mortality at the absolute age a+t. 
In the case of steam force, d.log,P stands for rate of incre- 
ment of force, to which no specific name is attached We 


; ; ip Samy 
know, however, something of the chief factor ( 1+ 5 * con- 


tained in the expression d.log,P applicable to the pressure 
of steam of maximum density; for if steam were a perfectly 
elastic gas and did not increase in density according as the 
temperature of the subjacent water increased, in that case the 
increment per degree of the expansive force of such steam atany 


=I 
temperature a+¢ would be represented by 2(1 == -) > lf @ re- 


presented the increase of expansive force per degree at the tem- 
perature a. That is to say, the factor which represents incre- 
ment of force per degree in the two cases is the same, with this 
difference, however, that the exponent of the factor in one case 
is unity and in the other case 7 = 2802585. The law just 
mentioned as expressing the increment per degree of expansive 
force of a perfect gas according to temperature, was discovered 
eighty years ago, by Dalton in England, and by Gay-Lussac in 
France. The quantity a measuring degrees from the zero of 
heat is the same in the case of air as in the case of steam of 
maximum density. The value of a is 276° C., being the dis- 
tance of the zero of heat below the temperature of melting ice. 

Recurring to the formula for the force of mortality already 
given, we have, in the period of childhood, for the force of mor- 
tality at any age ¢ measured from birth-time, where a, is given 
by observation and @=2°25 years, 


I 5) 
a T. \—-= 
=o 5 )= ent eS Ey (a+t) %- 


= is, the force of mortality at any age ¢ varies inversely as 


Ri, if R be taken equal to (a+t) and be made to represent dis- 
tance in time or age from a fixed point which is the zero of 


24, Mr. T. R. Edmonds on Vital Force according 


vital foree. The chief of physical forces is that of gravity, which, 
according to distance from a fixed point in space, varies inversely 
as R*. ‘That is to say, the law of variation of the force of mor- 
tality measured from a central point, differs from the law of va- 
riation of the force of gravity similarly measured, only in the 
exponent of the radial distance. The exponent is two in the 
case of the force of gravity, and the exponent is = or 2°302585 
in the case of the force of mortality. 

The empirical formula published in 1832 was founded on the 
supposition that the mortality according to age decreases or in- 
creases in a constant geometrical ratio im each of three definite 
periods of human life. The com. logs. of the three constant 
ratios are —‘17, +°0128, and +°0333; the corresponding 
numbers being ‘6761, 1:0299, and 10797. The first period 
begins at birth, and ends near 9 years of age. The second 
period begins at 12 and ends near 55 years of age. Andthe 
third period begins near 55 years of age, and continues until 
the end of life. There is probably an intermediate fourth pe- 
riod, from the age of 9 to the age of 12 years, during which 
the rate of mortality is constant and at a minimum. 

From the above law of geometric increase or decrease of mor- 
tality according to age, was obtained for each of the three periods 
the differential equation following, viz. 

0 Ogee = — apt ; 
and afterwards by integration, assuming P=1 when ¢=0, 
kre aes t 
com. log P;= vi (l—p*) or P,=107  ??. 

The quantity « in the empirical formula of 1832 represents 
the annual rate of mortality at the precise age a whence ¢1s mea- 
sured, that is when ¢=0. ‘The actual or infinitesimal rate of 
mortality at the time or age when ¢=0 is edt. The actual or 
infinitesimal rate at any other point of time, say ¢ years or frac- 
tions of years, is ep’dt. The quantity « thus used to indicate 
the rate of mortality at a particular point of age was not known 
to the public until the year 1832. In my book of “ Life Tables,” 
published in that year, the above quantity was first described and 
made the subject of a special Table, of which the following is the 
title:-—“Table A 27, showing at quinquennial intervals of age the 
force of mortality, or the number of deaths which would occur 
in one year, upon 100 constantly living.” Without the quantity 
a, as first described by me, any formula similar to that of 

ke 


com. log P;= ue: (1—p‘) is of no use except for the imterpola- 


to Age, and the “ English Life Table.” 25 


tion of new values of P between two or more values of P; ex- 
tracted from any Table of mortality not regulated by any definite 
law of decrement of life according to age. 

In facilities afforded for the rapid construction of Tables of 
mortality, the formula of 1832 has the advantage over the for- 
mula of 1866, chiefly through yielding successive values of 
log A log P; differing from one another by a constant quantity 
which is the common logarithm of the annual ratio of increase 
of the mortality according to age. The formula of 1882 yields 
the equation following, i 


log A log P;,, — log A log P;== — log p. 
The formula of 1866 yields 
1 
log A log P;,, — log A log P; = — Fae nearly. 

In the former case the numbers in the column containing 
log A log P are obtained with exactitude by successive additions 
of a constant which is log». In the latter case the numbers in 
the same column are obtained nearly by successive additions of 


the variable => The smaller the intervals of age adopted, 
a 


the nearer will be the approach to exactitude in the latter case. 
For practical purposes, the results from both formule, obtained 
as above, will be equally valuable when the intervals of age are 
yearly. Nevertheless the above short method of constructing 
Tables according to the formula of 1866 is not likely to find 
favour with calculators; for they will generally prefer the 
direct use of the formula yielding accurate results, to the indi- 
rect and short course attended with errors however insignificant. 

The vital force relative to age is probably the same im all indi- 
viduals, the rate of increase of such force during childhood and 
the rate of decrease during manhood being the same for all. 
But the absolute vital forces at the same ages may vary greatly 
when individuals are compared with individuals and classes with 
classes. One of the earliest fruits of the study of the law of 
human mortality was the discovery of the fact that the rates of 
mortality, at all ages, of the populations of large towns were 
much greater than the rates, at the same ages, prevailing in the 
populations of the small towns and villages of the same nation. 
The general rule appeared to be, that the absolute rates of mor- 
tality at every age increased according as the magnitude and 
density of these town populations increased. The earlier writers 
on human mortality considered large cities to perform the func- 
tion of graves, in swallowing up all excess of births over deaths, 
and thus preventing the populations of long settled countries 
from increasing. 

In the year 1832 the present writer gave to the public three 


26 Mr. T. R. Edmonds on Vital Force according 


series of theoretical Life Tables—one representing “ Village Mor- 
tality,” another “ Mean Mortality,” and the third “ City Mor- 
taly,”? the principal series being that of Mean Mortality. At 
any given age the rates of mortality in the three Tables are to 
one another in the proportion of the numbers 5, 6, and 74 respec- 
tively. The same three numbers were intended to represent for 
the fixed age of ten years the annual mortality per thousand 
living according to the same three several Tables. The above 
three Tables were deduced from the same formula, 

se Bee 2 pt 
com. log P;= 7 (l—p’), 


with the three different values of a above mentioned. These 
Tables were the first ever published in which the rate of morta- 
lity at any age was connected by a continuous and definite law 
of increase or decrease with the rate of mortality exhibited for 
every other age. The first of these theoretical Tables, desig- 
nated as “ Village Mortality,” is almost in exact coincidence at 
every age with Heysham and Milne’s Table for Carlisle (pub- 
lished in 1815), as may be seen on inspection of Tables I. and 
VI. hereunto annexed. 

In the ‘ Lancet’ of the 9th and 16th of March, 1850, there ap- 
peared a paper in which I compared the results of the * Village,” 
“ Mean,” and “ City” Tables of mortality with the observed 
rates of mortality, according to age, of various parts of the po- 
pulation of England during the seven years 1838-1844, these 
observed rates having been published by authority of the 
Registrar-General in the year 1849. Extracts from these com- 
pared results will be found in Table III. hereunto annexed. 
On inspection of this Table it will be seen that the mortality, 
according to age, of the total male population of the four heal- 
thiest of the eleven Registrar’s districts into which England has 
been divided is sufficiently well represented by the theoretical 
Table of “ Village Mortality.” Also it will be seen that the 
theoretical Table of ‘‘ City Mortality” 1s a good representation 
of the mortality, according to age, of the male population of the 
chief towns of Kngland. Taking four classes of such towns, ar- 
ranged according to intensity of mortality, it will be seen that 
the mortality according to the “ City ” Table, at the various in- 
tervals of age, agrees nearly with the mean mortality observed 
in these four classes of chief towns. 

It is worthy of remark that, although the “ City ” Table is a 
good representation of the mortality of the population of English 
cities at ages under 10 years and at ages above 30 years, it is 
not so for the intermediate period of age. One of the remark- 
able results of the English observation is, that the mortality 
of the populations of great towns between the ages of 10 and 30 


to Age, and the “ English Life Table.” 27 


years is shown to differ very little from that of the general po- 
pulation at the same interval of age. If the fact is in accord- 
ance with the observation, the result may be ascribed to the free 
interchange of town and country population at this interval of 
age. ‘There commonly occurs at this interval of age a great in- 
flux of population into the large towns from the surrounding 
country. <A portion of these immigrants become a part of the 
permanent population of these large towns; another portion re- 
turns and again form part of the country population. The 
greater the competition and the greater the freedom of in- 
terchange of the country with the town population, the more 
will the mortality of the two classes of population, between the 
ages of 10 and 30 years, approach to equality. 

The English Life Table for males, which was published in 
1864, coincides nearly at all ages with my theoretical Table of 
“Mean Mortality,” published in 1882, and with the Table de- 
duced from my formula of 1866. This will be seen on inspec- 
tion of Table II. hereunto annexed, in which is exhibited for 
quinquennial intervals of age, according to the three Tables, the 
numbers surviving and the numbers dying relative to 1000 sur- 
vivors at the age 12 years. The differences between the English 
Life Table and the two theoretical Tables are small; and these 
differences are of no importance, because they are equalled, if not 
exceeded, by the errors of observation and errors of calculation 
involved in the English Life Table. 

In Table IV. (hereunto annexed) a comparison is made for 
decennial intervals of age, from the age 15 to the age 95 years, 
of the observed rates of mortality of the total male population 
of England for the seventeen years 1838-1854, with the corre- 
sponding rates exhibited by the English Life Table. In three 
out of the eight decennial intervals “of age compared, there is a 
considerable “discrepancy between the rates observed and the 
rates exhibited by the English Life Table. The three errors of 
calculation are all in the same direction, and are in diminution 
of the rates of mortality observed. ‘The error at the decennial 
interval of age 15 to 25 is 8°5 per cent., at the interval from 
795 to 85 it is 7°4 per cent., and at the mites val from 85 to 95 
years it is 13°1 per cent. 

In Table V. (hereunto annexed) a comparison is made for 
quinquenmial intervals of age, from the age 25 to the age 75 
years, of the observed rates of mortality of the total male popu- 
lation ef England for the seventeen years 1838-1854, with the 
corresponding rates exhibited at the same ages by the English 
life Table. In these ten quinquennial intervals of age the 
proportional errors of observation vary from 6 per cent. to 12 
per cent., and are alternately positive and negative. The mean 
quinquennial error of observation is 9 per cent., either positive 


28 Mr. T. R. Edmonds on Vital Force according 


or negative. In the construction of the English Life Table it 
has been assumed that the errors of any two consecutive quin- 
quennial rates observed are in opposite directions and balance 
one another. This is the most favourable mode of estimating 
the amount of error existing—one observed rate being supposed 
to be 9 per cent. above the true rate, and the next observed rate 
being supposed to be 9 per cent. below the true rate. The least 
favourable mode of estimating the amount of error existing is 
by supposing that the errors in two consecutive quinquennial 
rates are not im opposite directions, and that the errors in 
such observed rates are united or concentrated on one only of 
the two observed rates, so that the proportional errors are al- 
ternately 18 per cent. and nothing. 

In observations of rates of mortality according to age, no 
lower estimate than 5 per cent. can be admitted as the probable 
amount of errors of observation. This amount or rate of error 
of observation is fifty times as great as the rate of error of obser- 
vation made on the force of steam according to temperature. 
The formula for steam-force according to temperature is the 
same as the formula for surviving population according to age, 
with difference of sign only. Hither formula is 

| kaa iNet 
com. loo iP, =a: at _ (1+ ‘) +5 
In the case of steam-force, the formula gives results which seldom 
differ from the results of observation so much as one in a thou- 
sand at any temperature from 30° to 230° C., or from 86° to 
446° F. The observations on steam-force alluded to are those 
of M. Regnault, published in 1847, and contained in the twenty- 
first volume of the Mémoires de l Academie de l’ Institut de 
France, p. 624. This insignificant amount of error of observa- 
tion is applicable not only to the quantity P representing pres- 
sure in pounds to the square foot, but also to the rate of incre- 


ment - for any degree of temperature throughout the above 


range of 200° C. The comparison between the observed rates 
and the theoretical rates for steam-force may be seen at pages 
185 & 186 of the Philosophical Magazine for March 1865. 

In Table VI. (hereunto annexed) is presented a comparison of 
the results of the two principal observations which have been made 
in England on the mortality according to age of children below 12 
years of age, with the results at the same intervals of age as indi- 
cated by two different theoretical Tables. It will be seen that, with 
exception of the first month from birth, the Carlisle Table of Heys- 
ham and Milne is in close agreement with my Table of “ Village 
Mortality ” (and with the empirical formula of 1832 on which it 
1s founded) at each of nine intervals of age comprehended between 
birth and 12 years of age. Also it will be seen that, with a 


to Age, and the “English Life Table.” 29 


similar exception, the English Life Table for males is in close 
agreement, at the same nine intervals of age, with the Table 
constructed according to the true law and formula of 1866. In 
the two excepted cases the apparent defects are the same, and 
consist in the observed rates of mortality in the first month from 
birth being just three times as great as they ought to be accord- 
ing to either of the two theoretical Tables. This apparent defect 
will vanish if it be assumed, as is probably true, that two out 
of three of the deaths in the first month after birth would have 
been uterine deaths, in the eighth and ninth months of pregnancy, 
if approaching death had not induced premature birth. 

The errors of construction in the “ English Life Table” at ages 
above 75 years (as exhibited in Table LV. hereunto annexed) have 
their origin in a novel principle adopted for the determination of 
the annual rates of mortality at the precise ages 20, 30, .. . 80, 
and 90 years. The constructor of that Table (Dr. Farr) has made 
the gratuitous assumption that the above annual rates are identical 
with the annual ratios of the dying to the living according to 
observation for the decennial intervals of age, 15-25, 25-35, . 
75-85, and 85-95 respectively. This assumption, unsupported 
by any evidence, although near the truth at ages under 55 years, 
is probably more or less erroneous at every age. At ages above 
75 years there is no appearance of truth in the above assumption, 
as may be seen on inspection of any ordinary Table of mortality. 
For example, according to my Table of “ Mean Mortality,” the 
annual ratio of the dying to the living for the decennial interval 
from 75 to 85 years of age is identical with the annual rate of 
mortality at the precise age 79°] years instead of 80 years. Also 
the annual ratio of the dying to the living in the decennial in- 
terval from 85 to 95 years of age is identical with the annual 
rate of mortality at the precise age 87:9 years, instead of 90 
years, as assumed by Dr. Farr. These differences in age corre- 
spond to errors of 7 per cent. and 13 per cent. in understate- 
ment of the rates of mortality observed and truly belonging to 
the ages 80 and 90 years respectively. . 

The constructor of the English Life Table does not proceed 
directly to the interpolation of the values of m at annual inter- 
vals from the erroneous values of m at decennial intervals assumed 
as above, but commences by deducing for each of the decennial 
values of m the corresponding value ‘of the peelbelnine of living 


one year by the use of my formula com. log P= ** (l—p‘), 


and making ¢ = unity. The probabilities of living one year at 
the precise ages 20, 30,... . 80, and 90 years having been thus 
erroneously obtained, the corresponding probabilities of living 
one year for all inter mediate years of age have been interpolated 
by the method of finite differences. 


30 Mr. T. R. Edmonds on Vital Force according 


In applying my formula to the determination of the probability 
of living one year at the precise ages 20, 30,.... 80, and 90 
years, Dr. Farr substitutes the ambiguous quantity m for the @ 
of my formula, at the same time* describing m as equal to the 
annual rates of mortality at the “precise ages”? 20, 30,... 80, 
and 90 years. According to this definition, the m of Dr. Farr’s 
formula is identical with the « of my formula as described by me 
in 1832. But this definition is immediately followed by the 
inconsistent and contradictory statement that m at the age 20 
years is represented by the mortality “ruling” from the age 194 
to 204 years. This statement is elsewhere confirmed by Dr. 
Farr, and made to extend to quinquennial and to decennial inter- 
vals of age. ‘The erroneous principle adopted in the construc- 
tion of the English Life Table is, that the annual rate of mortality 
at the middle point of any interval of age is identical with the 
annual ratio of the dying to the hving during that interval, 
whether such interval is one year, five years, or ten years. This 
erroneous principle may otherwise be described as resting on the 
erroneous and gratuitous assumption, that the area of the curve 
of surviving opuleticny or \ Pat, between limits ¢ and ¢+1 (in 


age) is always represented by the ordinate (multiplied by unity) 
corresponding to the abscissa ¢-+ 4, whatever be the unit of age, 
whether one year, five years, or ten years. 

In its second and principal signification, as adopted by Dr. 
Farr, the apparently simple quantity m, which has been substi- 
tuted for the constant quantity « of my formula, is in reality a 
variable quantity of great complexity, and more unknown than 
the quantity P, which is to be expressed in terms of m. For m, 
which represents the “ mean mortality”? at any or the (¢-+1)th 
interval of age, is of the form following : 

Bria le 

\ Pat 


The numerator of the above fraction, expressed in terms of the 
variable ¢ and constants, 1s 


ka 
10%" 
whilst the denominator for integration between limits ¢ and/+ 1 is 


n= 


_pt+1 ka. (yt 
Pp SSN Ons (l—p") 


\ ore mar 


If the above fraction could be expressed in finite terms, there 
would be no ground for supposing that the value of m for the 
first interval of age, if multiplied by p’, would represent the 
value of m for the (¢+ 1)th interval of age. No more is there 
any ground for supposing that the differential of log,P is equal 


* See Introduction to ‘ English Life Table,’ pp. xxiii & xxiv. 


to Age, and the “ English Life Table.” 31 


to —mp‘dt, as isalleged by Dr. Farr. Even if this had been the 

true differential, the integral thereof could not have been at all 

similar to my formula (of 1832), which is derived from the dif- 

ferential —ap‘di ; for mis a function of f, whilst « is a constant. 

Tasxie [.—Proportional numbers Living or Surviving at decennial inter- 
vals of age, according to three theoretical Tables of Mortality, compared 
with similar numbers exhibited by three well-known Tables of Mortality 
not supposed to be regulated by any definable law according to age. 


Age in Heysham |Edmonds’s}| Milne’s |Edmonds’s Halley’s Edmonds’s 


and Milne. | ‘* Village |} Sweden. ““Mean Bree ** City 

AERES: Carlisle |Mortality’’|| Males to |Mortality’’ a Steel Oui ortality’’ 
(1815). (1832). 1795. | (1832). (1093). (1832). 
0 1562 1514 1642 1465 1916 161] 
5 1062 10638 1089 1064 1133 1080 
10 1009 1010 || 1015 10a: |. L028 1016 
12 1000 1000 1000 1000 1000 1000 
15 984 983 981 980 972 975 
25 919 21) «| 906 904 888 881 
35 838 840 810 | 811 759 770 
45 739 744 | 702 701 615 641 
55 636 632 | 566 576 452 502 
65 472 476 390 410 297 328 
75 262 259 174 197 136 132 
85 70 70 34 41 23 13 
90 22 22 10 10 2 3 

95 5 4 2 ] 


Tas ie IJ.—Comparison of the numbers Surviving at successive quin- 
quennial intervals of age, according to the ‘‘ English Life Table”? for 
Males, with similar numbers from two theoretical Tables; the common 
basis adopted being 1000 Living or Surviving at the age 12 years. 


Edmonds’s ‘‘ Mean | English Life Table. Edmonds’s formula 
Mortality ?? (1832). Males (1864). of 1866. 
ANB | penne RE Bs oe | eee 
Living. | Pymgin || Living, | Dying in Living. | Dying in 
; || 5 years. 5 years. 5 years. 
0 1465 AOI 1465 405 1427 372 
7) 1064 51 1060 49 1055 44 
10 1013 33 10]1 25 1011 28 
15 980 36 986 3l 983 3l 
20 944 AO 955 A) 952 34 
25 904 44 915 43 918 38 
30 860 49 872 45 880 43 
35 8il 53 827 48 837 48 
40 798 57 779 53 739 55 
45 701 61 726 58 734 61 
50 640 64 668 68 673 70 
a) 576 74 600 78 603 79 
60 502 92 922 90 924 88 
65 410 105 432 105 436 97 
70 305 108 327 110 339 103 
79 197 93 217 Doe 236 101 
80 104 63 118 70 135 83 
$5 4] 31 48 34 02 44 
90 10 9 14 12 8 8 
95 1 1 | 2 2 | 0 0 


32 


TaBLE II[.—Annual Mortality per cent., according to age, during the 
seven years 1838-44, of the Male Population of the chief Towns of En- 
gland, and of the four healthiest Registrar’s Divisions of England, com- 
pared with the theoretical Tables of ‘City Mortality”? and “ Village 


Mr. T. R. Edmonds on Vital Force according 


Mortality,” published in 1832, 


(From the ‘ Lancet,’ vol. 1. (1850) p. 330.) 


Tuterval Regier 5 Edmonds’s| Twelve Hight |Edmonds’s Liverpool 
; Sg | eoWallage large larger ** City London. | and Man- 
DEAE ae “Mortality.” towns. towns. /|Mortality.” chester. 
— —- a —. os 
0-5 5:57 7°45 8:46 10°51 8:47 9°31 14-01 
5-10 85 1:02 114 1:24 1:24 1-24 1:58 
10-15 18 04 00 57 82 48 “60 
15-25 “31 67 86 “89 1-01 76 ‘96 
23-35 95 “90 1:08 1:12 1°35 1:07 1-28 
35-45 1:07 1-2] 1:43 1-62 1-81 179 2°07 
45-55 1:45 1:62 2-06 2°42 2°43 2°73 3°20 
59-65 2°65 2:78 3°99 4:26 4:14 4°81 9°27 
65-75 5°83 5°87 7:06 8:47 8:64 9:18 10°39 
75-85 13:22%) 12-11 15°58 16:99 17:50 18:47 20°24 
85-95 28°92 Zar D dl cee eer Mil eae eel 04:10 32°00 
Meee aa eS 257 125i see 274 | 351 
ae ee ee aa ——ee ef 
Population 
in thou- fo mists 256 ZS > ecscke 913 202 
sands ... 


TaBLeE LV.—Annual Mortality per cent., according to age, of the total 
Male Population of England during the 17 years "1838- 54, according to 
observation, and according to the “ English ‘Life Table ” intended to re- 


present the result of such “obs 


ervation. 


Edmonds’s| Observed 


| 
Observed | English 


Interval “* Mean rate, 
of age. |Mortality’’} 7 years 
(1832). | (1838-44). 
0- 5 6:70 707 
5-10 we) 93 
10-15 ‘69 ‘00 
15-25 ‘S1 80 
25-35 1-08 AY 
30-45 1:45 1:25 
45-55 1-95 1:78 
55-65 3°33 3:14 
659-75 6-99 6:61 
79-85 14:31 14:39 
85-95 28°17 29°65 
All ages...| 255 | 297 | 


rate, Life ‘Table 
17 years for 17 
(1838-54). years. 
7°25 701 
292 96 
52 30 
82 79 
1-00 1:00 
1:28 1:29 
1:85 1:90 
3°18 324 
6°69 6:58 
14:76 13°74 
30°14 26:20 
2°33 2°50 


Difference _Propor- 
or error. itional error 
per cent. 
= 007 8-5 
— 1:02 74 
—3-94 | 13°] 
ror iY aa eae | 


to Age, and the “ English Life Table.” 33 


TaBLEe V.—Showing for quinquennial intervals of age, above 15 years, for 
the total Male Population of England, the discrepancies between the 
rates of mortality observed and the rates exhibited by the ‘‘ English Life 
Table,” published in 1864. 


Sweden, |Edmonds’s} Observed} Probable : 
nest Males. ee ean. rate, ane feel Difference ae 
ry ae, cea | DASE | FER | formate: | 7% [Der cent 
percent. | percent. | percent. | percent. | percent. 
15-20 68 795 71 73 ‘63 — ‘10 13:7 
20-25 ‘90 87 “92 “94 87 — 07 74 
25-30 1:06 1:00 98 1-01 96 — ‘05 5:0 
30-35 1:17 1:16 97 1:00 1:06 + :06 6:0 
35-40 1:26 1°35 1:26 1:29 1:20 — 09 7:0 
40-45 1:60 1:56 1:25 1:28 1-40 + :-]2 9:4 
45-50 1:92 181 1-73 1:80 1-68 — 12 67 
50-55 2°40 2:10 1:84 1:91 2:14 + °23 12:0 
55-60 3°00 2-74 2:97 3°01 2°77 — ‘24 8:0 
60-65 4:39 4-02 3°32 3°36 3°78 + 42 12°5 
65-70 6°63 9°88 5:97 6:05 5°47 — 58 9-6 
70-75 9:28 8:58 741 7°49 8:12 + ‘63 8:4 
75-80 13:25 12°50 12°71 12°87 12:00 — $7 6:8 
80-85 18°64 18°16 17-53 17-75 17:34 — Al 2:3 
85-90 24:67 26°23 28:33 28°55 24:46 — 4:09 14:3 
4:7 


90-95 33°52 37°61 35°51 35°79 33°67 | —2-12 


TasuLe VI.—Proportional numbers Dying at each of nine intervals of age 
below 12 years, relatively to 1000 Survivors to that age, according to 
the Carlisle Table of Heysham and Milne, according to the ‘‘ English 
Life Table,” and according to each of two theoretical Tables of Mor- 
tality. 


Heysham Edmonds’s English Life | Edmonds’s 


Interval of age. and Milne. "Village Table. Males} formula of 


st as ii fas (1864). 1866. 
0 to 1 month. 83 20 FTf 25 
1 ,, 3 months. 38 37 46 44 
ery Gilt 5 40 50 46 53 
Gipea Fb 80 $2 71 73 
1 ,, 2 years 107 114 78 84 
re A 122 118 67 74 
Ate Gt 1: 50 50 34 33 
Ge | ek 58 29 28 29 24 
OE BE oc ll 15 17 17 

Total deaths under 

MARVEAES) ncccees oe } ae oe aD acd 


Phil. Mag. 8. 4. Vol. 88. No, 252. July 1869, D 


[sieat “ 


IV. Fundamental Principles of Molecular Physics. Reply to 
Professor Bayma. By Professor W. A. Norton. 


To the Editors of the Philosophical Magazine and Journal. 
GENTLEMEN, 


HE paper by Professor Bayma, entitled “ Fundamental 
Principles of Molecular Physics,’ published in recent 
Numbers of the Philosophical Magazine, is obviously of a cha- 
racter to demand some answer at my hands. In replying to it 
I do not propose to take up in detail, and in the order in which 
they occur, all the points made by the learned author, nor strive 
to make good all the positions before taken in my reply to his eri- 
ticisms on my ‘ Memoir on Molecular Physics.’ My aim will 
be to present the important points on which we are at issue in 
what appears to me to be their true attitude, im such order as 
may best conduce toa clear understanding of the whole subject, 
alluding occasionally to such side issues as may demand atten- 
tion. The cause of truth will apparently be best subserved in 
this way ; and this is of far more importance than that my ac- 
curacy and consistency should be formally justified by defend- 
ing anew every position I have taken. Whether any important 
position, either taken in my original paper or in my reply to 
Professor Bayma’s criticisms, has been effectually assailed or 
not, there will be a fair opportunity of judging when the whole 
ground shall have been gone over. 

By way of introduction to a general view of the case, I will 
first remark that I did not mean to convey the idea, in what 
Professor Bayma calls my first proposition, that molecular 
science is ‘‘ without established principles,” is a “pure heap of 
hypotheses.” I had no thought of implying that I did not re- 
gard the existence of matter, with its fundamental properties of 
inertia, &c., the operation of forces of attraction and repulsion 
in nature, and other kindred principles, as established truths ; 
and it is surprising that such an intimation should have been 
thrown out by my critic, who, with all his unquestionable acute- 
ness, is, | doubt not, animated by a sincere desire to deal justly 
and with entire fairness. I meant, and could reasonably be 
supposed to mean, no more than that every new theory of mole- 
cular physics must of necessity znvolve one or more hypotheses 
that “ have been rendered more or less probable, either by in- 
duction from observations or @ prior? reasonings,” and to be 
tested by a comparison of the deductions from the theory with 
facts, and therefore that its foundation is essentially hypotheti- 
cal—just as it is affirmed that the strength of a structure is the 
strength of its weakest part. The doctrine is, in other words, 
that a new theory of molecular physics must, when first pro- 


Prof. W. A. Norton on Molecular Physics. 35 


pounded, occupy precisely the same hypothetical position that 
all former physical theories have at first done—as that of uni- 
versal gravitation, the undulatory theory of light, &c. It is by 
triumphantly withstanding all possible tests that these and other 
theories have come to be admitted among the established truths 
of physical science. It is in this way alone that physical science 
has hitherto made all its great advances. In no instance has a 
physical theory sprung into existence, Minerva-like, in full 
armed panoply, the complete full-grown impersonation of wis- 
dom and truth. 

It does not follow, then, as our author intimates, because 
such theories have had, and as I conceive must continue in 
each new instance to have, more or less of a hypothetical foun- 
dation, that no physical theory can lead to established truths. 
The deductions from it have, it is true, no higher certainty, as 
mere deductions, than the fundamental induction from which 
they are derived; but every legitimate deduction that accords 
with known facts, furnishes thereby a new confirmation of the 
essential truth of the theory. It gains assurance of strength by 
its victories, and, when crowned with years of triumph, is worthy 
of all honour, despite its humble origin. 

Professor Bayma conceives that the time has arrived when a 
theory of molecular physics can be securely erected upon a few 
philosophical principles which may be regarded as established 
truths, and that the legitimate deductions from the theory will 
have the same character of certainty. If this claim could be 
admitted, I should be far from desirmg to put a single straw in 
the way of his success, and would gladly recognize the “ eternal 
verities ” evolved from his philosophy. Nor would there be of 
necessity any conflict between us; for in proportion to the 
strength of my confidence in the essential truth of my own 
theory of the modes of evolution of phenomena, would be the 
. strength of my conviction that his theory must embrace my own 
generalizations within its comprehensive grasp, though placing 
them in a new attitude and on a deeper foundation. But I can- 
not but entertain a decided conviction that our author’s claim, 
that his legitimate theoretical deductions are positive certain- 
ties, rests on fallacious grounds. It implies that his fundamental 
principles, whether formally expressed or implied, are all either 
universally admitted truths, or truths which he has himself de- 
monstrated. Now certain of these principles do not, in the na- 
ture of things, admit of positive proof. They cannot have any 
other foundation than certain conceptions with regard to matter 
or active powers which can only be regarded as mere assump- 
tions. For example, it is laid down as a fundamental principle 
that matter in its ultimate analysis is made up of absolute 


D2 


36 Prof. W. A. Norton on the Fundamental 


points separated by finite distances, every one of which acts 
upon every other pomt, and hence that there cau be no such thing 
in Nature as an atom that has continuous extension. Now 
this principle is no inevitable deduction from recognized facts ; 
for the only certain knowledge furnished by the entire range 
of physical science with regard to the so-called atoms, is that 
they have certain properties and active powers. ‘The essential 
origin and mode of evolution of these properties and powers must 
for ever remain an impenetrable mystery. It may be confidently 
asserted that few links of the mystic chain that binds each 
ultimate atom to the throne of the Creator will ever be certainly 
discerned. We may indeed recognize that the so-called “ che- 
mical atoms” are really complex in their constitution, and 
should accordingly be termed “primitive molecules,” as both 
Professor Bayma and myself maintain, and frame hypotheses as 
to the nature of their physical constitution and the immediate 
origin of the forces they exert, suggested by physical phenomena, 
and to be tested by comparing the deductions from them with 
facts ; but the elements, or primary atoms, of which they are 
composed, what are they? Are these of necessity mere points, 
mere mathematical centres of force? Is it not absurd to sup- 
pose that when we can know nothing of the essential nature 
and origin of the primary powers, or activities, of these atoms, 
anything can be predicated with certaimty with regard to their 
size and the question of their continuity or non-continuity, and 
to claim that a certain conception formed of their geometrical 
character is not an assumption, not an hypothesis, but an absolute 
verity. Our author’s ‘ demonstration,” that an atom having 
continuous extension is an impossibility, rests upon the assump- 
tion that if an atom be conceived to be continuous, each point 
of it must act upon every other point in the same manner and 
in the same degree at equal distances. Now in our absolute 
ignorance of the manner in which force and matter are linked 
together, how can we be sure that this is an imevitable conclu- 
sion. It is im fact a mere inference from the assumption that 
force may be evolved from a mathematical point, and take effect 
upon another mathematical point which is the centre of a similar 
activity. If this be a truth, the knowledge of it can be gained 
from inspiration alone. 

Let us examine it a little from a philosophical point of view, 
somewhat different from that which our author occupies. The 
principle of activity cannot subsist in a mere mathematical point, 
for activity implies a something to act, and a mathematical pomt 
is nothing but position. Also a mathematical point cannot be 
acted upon, for an activity exerted implies something having 
receptivity, and a mathematical point can have no such pro- 


Principles of Molecular Physics. 37 


perty, since it is nothing but position. If it be urged in reply 
that the points supposed are not mere mathematical points, but 
also centres of force, the answer is, if the possibility of mere cen- 
tres of emanation of force be admitted, still to suppose that one 
centre of force acts upon another is to suppose that one force 
acts directly upon another force, or that the principle of acti- 
vity acts upon itself. Again, mobility cannot be predicated of a 
point, since a force cannot impart motion to nothing, nor to an- 
other force or collection of forces ina point. This reasoning 
may not be deemed conclusive ; but the real question here is, not 
whether it is conclusive or not, but whether it is not as much 
entitled to be called so as the “demonstration” we find on 
page 28 of the ‘ Molecular Mechanics,’ that ‘the hypothesis 
that bodies are made up of particles materially continuous leads 
to an absolute impossibility of communication of motion,” or as 
the demonstration on page 30, that ‘matter cannot be conti- 
nuous.” 

If it should be urged that we cannot conceive of an atom of 
which every point does not possess the same activity as every 
other point, or that the entire space occupied by an atom should 
alone determine the definite power which it exerts outwardly and 
receives, it is equally impossible to conceive of mere points en- 
dued with all the essential properties and powers that belong to 
matter (these powers differimg in intensity and kind, although 
belonging to mere points), resisting change of place with vary- 
ing degrees of inertia, and retaining the same activities as they 
shift their position from one point of space to another. We may 
as well frankly admit that in all such attempts to reach true 
conceptions we are vainly striving to sound the fathomless depths 
of the unknown. 

Another of Professor Bayma’s fundamental principles is, that 
simple elements act at all distances according to the inverse ratio 
of the squares of the distance. This principle may be admitted 
as the law of elementary action if we regard such action as a pro- 
pagated emanation ; and it may be adopted as an hypothesis if 
we conceive, with Professor Bayma, that such action is instanta- 
neous at all distances; but he undertakes to demonstrate its 
truth by both ‘‘ metaphysical and mathematical reasoning.” The 
demonstration, whatever may be said of the metaphysics, is open 
to this fatal objection—that it involves the conception that gra- 
vitation and molecular attraction are but the same elementary forces 
operating at different distances. To show that this cannot be true, 
let us suppose a primitive molecule posited at the distance (d) 
from a certain point of the earth’s surface, at which the attrac- 
tion of adhesion becomes sensible; and let us conceive the 
earth’s surface to be perfectly smooth and spherical. Now New- 


38 Prof. W. A. Norton on the Fundamental 


ton has shown that if the law of elementary action be that of the 
inverse squares, the attraction of such a homogeneous sphere for 
an element exterior to it is the same as if the whole mass were 
concentrated at the centre, The demonstration involves the 
supposition that equal portions, however small, of each spherical 
layer are occupied by equal quantities of matter. The principle 
demonstrated holds good for every distance of the element at- 
tracted from the surface—except that at very minute distances, 
not many times greater than the distance between two contiguous 
molecules of the earth’s mass, it may happen that two lines di- 
verging from the element in question under a small angle will 
not actually contain within them any matter on the immediately 
contiguous portion of the earth’s surface, and as a consequence 
the entire attraction of the first spherical layer would be repre- 
sented by that of its mass concentrated at a pomt slightly more 
remote than the centre. The result would then be that, in the 
case supposed, the entire attraction exerted by the earth would 
be slightly less than the Newtonian deduction. It follows, 
therefore, that if the element at the supposed minute distance 
(d) from the earth’s surface were to approach the surface, the 
entire attraction it would experience would not be sensibly 
greater, would in fact be less than at the distance (d); whereas 
the attraction of adhesion that would actually come into play is 
immensely greater than the simple force of gravity near the sur- 
face. We thus demonstrate that the attraction of gravitation can- 
not be the force of molecular attraction operating at greater dis- 
tances, either as a whole or in its elements; and accordingly 
show that the law of inverse squares proved for gravitation can- 
aot be extended inferentially, or by any process of reasoning, to 
the force of elementary attraction at minute distances. 

The same important conclusion may be reached more directly 
in another way. ‘The enormous excess of the attraction of adhe- 
sion or of cohesion at distances a little greater than the distance 
between contiguous molecules, over the force of gravity at the 
distance (d) above specified, can only be attributed, from Pro- 
fessor Bayma’s point of view, to a greatly increased attraction of 
the molecules lying at or near the earth’s surface. Now the 
number of separate lines that can be drawn from the element 
attracted through attractive elements so situated is incalculably 
small, we may say insensibly small, in comparison with the num- 
ber that can be drawn through more remote elements which by 
their united action determine the force of gravity ; and hence the 
attraction of adhesion should be incaleulably small in comparison 
with the force of gravity. 

It may here be incidentally remarked that, unless the position 
just taken can be proved to be untenable, it must be admitted 


Principles of Molecular Physics. 39 


that Professor Bayma’s theory not only fails to include the known 
force of gravitation, but actually excludes it as something alto- 
gether impossible—since his supposed or “ proved” molecular 
actions are all that possibly exist in accordance with his funda- 
mental principles, and these, as we have just seen, do not include 
the actual force of gravity, but have, as their necessary concomi- 
tant, an attractive action at considerable distances vastly greater 
than the actual attraction. Or, if he prefers the other horn of 
the dilemma and admits the actual force of gravitation, we are 
then conducted to the inevitable inference that his theory makes 
no adequate provision for the known molecular attraction, since 
the molecular attraction deduced from the force of gravity 1s of an 
exceedingly smail intensity in comparison with the attractive 
action known to exist. 

The same inference may be extended to the force molecular 
repulsion, since the actual repulsion is in equilibrium with the 
attraction at ordinary molecular distances; and hence the theo- 
retical repulsion must have an intensity correspondent to that of 
the theoretical attraction, and therefore be exceedingly small as 
compared with the actual repulsion. In fact, if I mistake not, 
the objection here urged saps the foundation of the whole theory 
developed and maintained with such signal ability by Professor 
Bayma in his ‘ Molecular Mechanics.’ ‘To comprehend the full 
force of this objection, it should be borne in mind that our 
author maintains that all material elements are mere points, and 
are either attractive under all circumstances or repulsive under all 
circumstances,—that the action of each element takes effect upon 
all other elements according to the law of the inverse squares, and 
without the least interception by intervening elements,—and 
that these direct actions of the two classes of elements, attractive 
and repulsive, are the sole determining’ cause of all material phe- 
nomena. It should be added that each “ primitive molecule” 
is conceived to consist of a central attractive portion, and an ex- 
terior repulsive envelope (each of these being composed of ele- 
ments separated by finite distances)—and that the “ molecular 
radi” are regarded as “infinitesimal quantities,” in comparison 
with the distance between contiguous molecules at which their 
effective attraction manifests itself. 

We find in the ‘ Molecular Mechanics’ the following funda- 
mental propositions: ‘one and the same element A cannot 
attract the element B and repel another element C when B and 
C are equally distant from A ;” and “ one and the same element 
of matter cannot be attractive for one distance and repulsive for 
another.” These are not direct inferences from physical facts, 
since we recognize among molecular actions precisely the differ- 
ences which it is here stated cannot have place in the activities 


40 Prof. W. A. Norton on the Fundamental 


exerted by the ultimate elements. But the attempt is made to 
establish them by metaphysical reasoning, of which it may be 
said that it involves certain conceptions of the “ principle of ac-~ 
tivity,” “nature,” and “ determinations ” of elements, designated 
as “substance,” though they are nothing but mathematical 
points, which are neither self-evident truths nor have any cha- 
racter of certainty, but are mere shadows dimly discerned in that 
metaphysical region which the finite mind strives in vain to enter. 
The most that can be conceded is that they have a certain air of 
probability, and may reasonably be adopted by our author as hy- 
potheses to be ultimately substantiated or overthrown by the 
appeal to facts. 

It will be apparent from what has been stated that an impor- 
tant difference obtains in the nature of the foundations on which 
Professor Bayma’s theory and my own have heen erected, in the 
methods of construction employed, and in the claims asserted 
with reference to the true character of the results achieved. The. 
theory developed in my memoir on Molecular Physics rests upon 
the most comprehensive generalizations and principles to which 
the progress of physical science has conducted, and in no degree 
upon metaphysical conceptions or reasonings with respect to the 
nature of matter, the size of atoms, the possibilities or impossibili- 
ties of certain inherent material actions, &c. On the other hand, 
in the groundwork of Professor Bayma’s theory are included, as 
we have seen, certain conceptions and reasonings of this character 
which I maintain are fundamentally hypothetical. Professor 
Bayma has proceeded on the philosophical and what he deems 
the strictly scientific plan of construction, while I have restricted 
myself to the simple deduction of molecular forces and pheno- 
mena. He claims that his fundamental principles are either 
universally admitted or demonstrated truths, and that his legiti- 
mate deductions are to be received as established truths. I do 
not venture to prefer any higher claim than that the fundamental 
principles I have adopted are universally admitted (with the 
sngle exception of the hypothesis of an electric fluid or ether ; 
an this is the only distinct fundamental conception which the 
vrocess of inductive research has evolved from electric pheno- 
mena), and that the recognized molecular forces and the various 
classes of physical phenomena can be legitimately deduced from 
the few fundamental postulates laid down without the aid of new 
hypotheses. In this I claim to have pursued the ordinary me- 
thod of physical speculation, and the only one which has hitherto 
achieved any substantial success. Professor Bayma virtually 
admits (Phil. Mag. March 1869, p. 183) that his method 1s ra- 
dically different from the methods of research hitherto employed 
by physicists. This, which he esteems its most excellent feature, 


Principles of Molecular Physics. 41 


and as constituting an especial claim to favourable regard, will 
be likely to prove its sufficient condemnation. 

The entirely different stand-point occupied by Professor Bayma 
from that which I have taken, and the consequent liability he 
has incurred of misunderstanding my views, is the occasion of 
much of the criticism he has indulged in. Thus he assails from 
all points, and in a variety of modes, what he regards as one of 
my strongholds, viz. that a primary atom has continuous exten- 
sion and is spherical in form. Now, as a matter of fact, in fra- 
ming my theory I took scarcely any thought of the question of 
the continuity of matter in a primary atom. Conceiving the real 
constitution of the atom to be incapable of detection, I simply 
adopted the ordinary conception of it, recognizing in it the em- 
bodiment of three essential truths, viz. (1) that the ultimate 
element, called,an atom, is incapable of division by either me- 
chanical or chemical means, (2) that it acts with equal energy in 
all directions, (3) that its surface opposes a repulsive resistance 
to any other atoms that may be urged toward it by the attraction 
of the whole atom. ‘These three features cannot be conceived to 
belong to a single point, but may either to a continuous material 
sphere, or to a spherical collection of material points. It mat- 
ters not, from my theoretical stand-point, which of these two 
views be taken. 

But I have since been led (see my answer to Professor Bayma’s 
criticisms in the Philosophical Magazine, February 1869, p. 106) 
to adopt the fundamental conception that the effective attraction 
of a primary atom of ordinary matter for the luminiferous ether 
probably consists in a diminished repulsion. Upon this view 
the question of the size and constitution of primary atoms can 
have no value in physical science, and may be left for the enter- 
tainment of those who have a predilection for metaphysical spe- 
culations. 

Before taking up briefly some of the specific points discussed 
in Professor Bayma’s paper, it may be well to say a word in reply 
to his affirmation that ‘‘ hypothesis begins only where real science 
ends.” I would ask our learned author if real science had come 
to an end when Newton conceived the hypothesis of universal 
gravitation and followed it out to its legitimate consequences— 
or when Huyghens imagined the existence of luminiferous ether 
waves, and so laid the foundation of the undulatory theory of 
light. 

Yale College, U.S., 


June 1, 1869. 
[To be continued. | 


Pude> | 


V. Note on the Hydrodynamical Theory of Magnetism. 
By Professor Cuatuis, M.A., F.R.S., F.R.A.S.* 


the Numbers of the Philosophical Magazine for January 

and February 1861 I proposed a theory of magnetism 
founded on hydrodynamical principles, which is also reproduced, 
with modifications and additions, in my work ‘ On the Principles 
of Mathematics and Physics,’ recently published. It has since 
occurred to me that an objection might be raised against the 
theory because it does not account for the variation of magnetic 
action according to the law of the inverse square, which seems to 
be established by Gauss’s process for determining the absolute 
measure of the intensity of terrestrial magnetism. The purpose 
of this Note is to meet this objection. 

Whatever may be thought of Gauss’s fundamental hypotheses 
of two fluids acting attractively and repulsively under certain 
conditions according to the law of the inverse square, and of the 
dependence of sensible magnetic action on the “separation” of 
_ these fluids, it is certain from the numerical results he has ob- 
tained that his investigations must have a real physical basis, 
A true theory of magnetism ought to be capable of indicating 
what that basis 1s, and how far the hypotheses are expressions of 
facts, or are simply empirical. I proceed to try the hydrodyna- 
mical theory by this test. 

It will be necessary, first, to state the leading principles of 
this theory. All visible and tangible substances are supposed 
to consist of inert spherical atoms of constant form and magni- 
tude, retained in positions of equilibrium by the resultant actions 
of the forces which I have named atomic repulsion and mole- 
cular attraction. The laws of these forces admit of being ma- 
thematically deduced from the hypothesis of a universal and con- 
tinuous ether, supposed to press proportionally to its density, 
and from the combination of its action with the reaction of the 
atoms due to their constancy of form. The space occupied by 
atoms is assumed to be very small compared to the intervening 
spaces, even for substances of yreat density. This assumption 
1s justified by an inference from the undulatory theory of light, 
as is shown in page 410 of the above-mentioned work. 

These hypotheses being understood, we may next consider 
what will take place when a steady stream of the ether enters 
into a substance atomically constituted in the manner above 
stated. For the sake of precision it will be supposed that the 
body has the form of a cylinder the diameter of which is small 
compared to the length of the axis, and that the direction of the 
axis coincides with that of the stream. Then from the hydro- 


* Communicated by the Author. 


On the Hydrodynamical Theory of Magnetism. 43 


dynamics of steady motion it follows that the fluid will have 
ereater velocity and less density within the cylinder than with- 
out, simply because of the contraction of channel by the occupa- 
tion of space by the atoms. There will be confluence of the 
lines of motion towards the extremity at which the stream enters, 
and equal divergence of the lines of motion from the extremity 
out of which it issues. These lines, as well as the velocity and 
density along them, will be symmetrically disposed about the 
axis of the cylinder prolonged in both directions, and also with 
respect to a plane transverse to the axis through its middle 
point. Under these circumstances there is no acceleration of 
the mean current, the quantity of fluid which crosses any unli- 
mited plane transverse to the axis being the same as if the stream 
had not been interrupted by the cylinder. 

The above description of the courses of the lines of motion 
applies to any solid cylinder whether or not it be magnetic. If 
it is not magnetized, but susceptible of magnetism, the modifi- 
cation which the original stream undergoes by passage through 
the cylinder is proper for magnetizingit. For it is evident that, 
by reason of the variation of the density of the ether from point 
to point, the atoms of the cylinder, especially those at and near 
its extremities, will be caused to vibrate; and it appears from 
experiment that the magnetizing of a substance 1s effected when- 
ever a magnetic stream traverses it while its particles are in a 
state of vibration. This is remarkably indicated by the well- 
known experiment in which a plate of iron, placed with its faces 
in the direction of magnetic dip, is magnetized by being repeat- 
edly struck with a hammer. Possibly the permanent magnetism 
of the loadstone may have been gradually induced by the etherial 
streams which relatively pass through it in consequence of the 
earth’s motion in space. 

Supposing that the cylinder, either by the process above men- 
tioned, or by some other, has been magnetized, let us inquire 
what influence this circumstance will have on the stream which 
traverses it. But it is first necessary to define the magnetized 
state. According to the theory of magnetism I long since pro- 
posed, this state depends solely on a small and regular increment 
of atomic density from one end to the other of the cylinder, the 
equilibrium of the atoms being maintained by the equality, at 
each point, of the atomic repulsion towards the rarer part, and 
the molecular attraction towards the denser part. Conceive now 
the ztherial stream to traverse the cylinder in any direction. At 
exit and entrance there will be the same cause of disturbance of 
the lines of motion as in the previous case of a cylinder of uni- 
form density ; and, besides, the gradation of density will have 
the effect of generating new streams, which for distinction I shall 


44 Prof. Challis on the Hydrodynamical 


call secondary streams. The particular mode of generation of 
these streams is next to be considered. 

The incident stream being supposed to have originally the 
same velocity and density at all points of any section transverse 
to its direction, it follows, by the laws of steady motion, that 
after entrance into the cylinder its resulting mean velocity will 
be greater and mean density less, the greater the atomic density. 
This is an immediate consequence of the contraction of channel 
by the atoms. Hence the fluid will be impressed at all points in 
the interior of the cylinder by a constant accelerative force acting 
in the direction from the rarer towards the denser end. The 
consequent effective accelerative force will, by reason of the 
inertia of the fiuid, accelerate a given particle towards a trans- 
verse plane through the middle point of the cylinder, and equally 
retard it after it has passed that plane. Thus there will be a 
maximum of velocity at the points where the plane is cut trans- 
versely by the lines of motion. Also as there can be no transfer 
of the whole fluid mass, supposed to be of unlimited extent, by 
means of an accelerative force impressed on a limited portion of 
it, there will necessarily be return currents at different distances 
from the cylinder, such that the lines of motion of these secon- 
dary currents will be reentermg. The courses of these lines will 
be symmetrical with respect to the axis and the above-mentioned 
transverse plane, and will cross this plane outside the cylinder at 
right angles. Such is the general character of the secondary 
streams to which the theory attributes-the phenomena of the 
magnet. 

It will be seen that the intensity of the secondary stream is the 
same whatever be the direction of the primary, so long as the 
latter is of given intensity. Also it must be admitted that the 
secondary stream, as generated by the interior gradation of den- 
sity of a magnetized body, is dynamically far more effective than 
that modification of the primary stream which was above de- 
scribed as being produced whether or not the body be magne- 
tized; for otherwise magnetic streams would be perceptible in 
the case of a non-magnetized body. The great intensity of the 
secondary streams is to be attributed to the efficacy of the im- 
pressed accelerative forces by which they are generated, the 
equation p=a*p showing that, on account of the great magni- 
tude of a, the extremely small variation of p due to the grada- 
tion of density may cause a large change of p. In the subse- 
quent reasoning the above-mentioned small modification of the 
primary stream is left out of account. ni 

It may be supposed that the whole mass of the fluid in which 
the secondary streams are generated partakes of the primary 
motion. In that case, if the primary velocity were impressed in 


Theory of Magnetism. 45 


the opposite direction both on the fluid and the cylinder, the 
secondary streams would be unaffected, the fluid would be re- 
duced to rest, and the cylinder would be made to move in it in a 
given direction with a given velocity. This is the case of nature, 
a magnetized body being carried through space by the earth’s 
motion, and its magnetism being the result of the generation of 
secondary streams by the relative motion of the ether and by 
the interior gradation of density. It is, however, to be observed 
that the motion which the earth has in common with the solar 
system, the motion in its orbit, and the rotation about its axis, 
produce independent magnetic effects, and that the total magne- 
tism is the swm of the magnetisms which these motions would 
produce separately. The reasons for this statement are that the 
resultant of these motions is not a uniform motion in a fixed di- 
rection, and, as there will be occasion to show subsequently, the 
secondary motions which they would generate singly are such 
steady motions as can coezist. 

Reverting now to the case of the magnetic streams of the cy- 
lindrical magnet, which may be conceived to have a fixed position 
im space, let C be the middle point of the axis, and let the den- 
sity increase from the end A to the end B, so that the course of 
the secondary streain is in the direction from A towards B. Ac- 
cording to hydrodynamical principles, there can be, on the whole, 
no transfer of fluid across any plane perpendicular to the direc- 
tion of the axis, the motions of the fluid within and outside the 
cylinder being both taken into account. In calculating the ve- 
locity of the fluid at any point, the effect of the occupation of 
space by the atoms will be considered only so far as it produces 
secondary streams by the gradation of density. 

To show how the above-mentioned condition is fulfilled is the 
object of the following argument. Conceive the axis to be cut 
perpendicularly by a plane at the distance x from C in the direc- 
tion towards B, and draw any straight line from C intersecting 
the plane in P. Let CP=r, the angle PCB=90, and, y being 
an unknown function of x, let y?+2?=R?. Since the motion 
of the fluid is wholly in planes passing through the axis, the 
velocity at P may be resolved into U along CP and W perpen- 
dicular to this line. It will now be assumed that for any point 
in the transverse plane, beyond the distance y from the axis, 


VRP VR 
ee cos?, W=— 5,3 


The forms of these expressions have been adopted from a consi- 
deration of the circumstances of the motion when the fluid is 
impelled by a moving sphere, in which case, as is known, both V 
and KR are constant, and the expressions apply to all points of 


sin 0. 


ye 


46 Prof. Challis on the Hydrodynamical 


the fluid. We have next to calculate the quantity of fluid which, 
according to these values of U and W, passes at any instant a given 
transverse plane. 


These velocities, resolved parallel to CB, are respectively 


R3 Vina 
3 cos? @ and — 9,8 sin? @, so that the whole resolved velocity 


in that direction is 


3 
(8 cos*0—1). 


Hence the quantity of fluid which passes the part of the plane 
exterior to the circle of radius y in the small time 6¢ is 
3 


8t | Qarr sin 6. ee cos? 9—1)d.rsin 0, 


the integral being taken from 7 = R to r = infinity. Since 
r cos 0=z, this integral is equal to 


Q 
nvresr | & = a1) 
fie is 


which taken between the above limits is 


x? 
—nVR*(1— $5) 6 

If the plane intersect the axisof the cylinder produced, at any point 
beyond either A or B, we must suppose that y=0, or that R?=2*. 
Since in this case the integral vanishes, there is no permanent 
transfer of fluid across such planes, with respect to which, there- 
fore, the required condition is fulfilled. Thus the assumed ex- 
pressions for U and W are so far justified. 

In other cases, by putting for R? the value y?+ 2°, the integral 
becomes —7Vy*. Now let f(z) be the mean velocity with which 
the fluid within the distance y crosses the same transverse plane 
in the direction from A towards B, then the whole quantity 
that passes that plane in the time 6¢ is 


uf (x) y?st—7Vy70t. 
Since by the principle already enunciated this quantity is zero, 
it follows that f(x) =V. 

Hence, by having regard to the above signification of f(z), and 
to the circumstance that the lines of motion converge towards 
the parts about A and diverge from those about B, it is clear 
that the velocity V diminishes with the distance from C accord- 
ing to some unknown law. In default of an exact a priori in- 
vestigation of this law, I shall now make the provisional suppo- 
sition that V varies inversely as R%, or that VR® is equal to a 


Theory of Magnetism. A7 


constant ~. Then we shall have, at any point exterior to the 
circle of radius y, 


Wie = cos 0, W=— 53 sin 0. 


Consequently, at points for which 6=0 and @=z, W=0 and 
U= 5 reckoned in the direction from A towards B; and at 
points in the plane through C transverse to the axis, U=0 and 
Ww=— so Hence at the same distance r, the backward motion 


across that plane parallel to the axis is half the forward motion 
along the axis; and each of these velocities varies as the cube of 
the distance from C. 

Since y is an unknown disposable quantity, the above suppo- 
sition that VR°, or V(y?+ 2?) 2 is equal to a constant, is not ille- 
gitimate. The function that y is of will depend on the form 
of the magnet. In the case of a cylindrical magnet y will not 
generally differ much from the radius. It is also to be remarked 
that the above value of U for a point on the axis, and that of W 
for a point in the transverse plane, are to be considered as ap- 
proximative functions of 7, The more complete values would pro- 


bably be of the form 


Oe Os =- 44( -*) 
= 5(1 =) W= 973 i pele 


The motion in these magnetic streams is an instance of steady 
motion for which udx+vdy+wdz may be assumed to be an 
exact differential. This may be maintained on the principle that, 
after the impulse is given to the fluid within the magnet in the 
direction of its axis, the consequent curved courses of the lines 
of motion are determined solely by the mutual action of the parts 
of the fluid. Also there may be reason to conclude that for flud 
of unlimited extent that expression is an exact differential in any 
case in which the lines of motion may be cut by surfaces of con- 
tinuous curvature—that is, whenever the motion is proper to a 
fluid, and ‘not such as a fluid is capable of when it may be con- 
ceived to consist of parts that are solid. Leaving, however, this 
point for future consideration, I shall now assume, for the rea- 
son given above, that udv+vdy+wdz is an exact differential 
for magnetic streams. In that case, as is known, the relation 
between the density p, and velocity V, for the streams of a given 
magnet is expressed by the equation 


Mat 
Pi =Poe 2; 


48 Prof. Challis on the Hydrodynamical 


Po being the density where the fluid is undisturbed. So for an- 


other set of streams 
Vo2 


P2= Poe 2”. 


But the steady motions to which these formule apply may coewist. 
(This proposition I have proved in the Philosophical Magazine 
for February 1861, and in the ‘ Principles of Mathematics,’ 
p- 242.) Consequently the differential 
(uy +Ug) da + (v, +0,)dy + (w, + w,) dz 
applies to the steady motion compounded of the two sets, and is 
plainly an exact differential. Hence if p! be the resulting den- 
sity and V! the resulting velocity, we have 
v2 

p'= poe 2. 

Having determined the character of the magnetic streams of a 
cylindrical magnet, and the laws of the composition of such 
streams, we are prepared to investigate the mechanical action of 
one cylindrical magnet on another. I shall confine myself to the 
two instances of the disturbance of a moveable magnet by a fixed 
one, relative to which Gauss has obtained numerical determina- 
tions. (See Gauss’s ‘ Absolute Measure of the Intensity of Ter- 
restrial Magnetism,’ Gottingen, 1833; andthe Annales de Chimie 
et de Physique, vol. lv. pp.56 & 57.) In these experiments the 
magnets were about a foot long, and the different distances be- 
tween their middle points varied from four feet to thirteen feet. 
In both sets the moveable needle when undisturbed was in the 
plane of the magnetic meridian, the end I have called A being 
northward, and the end B southward. Also both needles were 
horizontal with their axes in the same plane. 

In the jirst set of experiments the axis of the fixed needle was 
perpendicular to the plane of the magnetic meridian, and pointed 
to the middle of the moveable needle. Let us take the case of 
the experiments made when the fixed needle was on the east side 
of the moveable one, and its end B (from which the current 
flows) was turned towards the latter. There were three other 
cases of relative positions of the magnets; but this one will suf- 
fice for my purpose. We have next to determine the action of 
the composite streams on the individual atoms of the moveable 
needle, so far as such action tends to move the needle as a whole 
about a vertical axis. ‘The diameter of each needle is supposed 
to be small compared with its length. 

At the position of any atom of the moveable needle let the 
velocity of the fluid due to the fixed needle be resolved into uw, 
parallel to the axis of the former, v, perpendicular to this axis, 
and w, in the vertical direction; and let 22, vo, We be the analo- 


Theory of Magnetism. 49 


gous resolved velocities due to the moveable needle. Then, p’ 
and V' being the density and velocity at that position, by what 


is shown above 
v2 


_va yi 
pP'=Ppoe 27 = po( 1 _ =) nearly, 


and 


/ 
DE =F (uy tug)? + (0, +05)? + (wy + w,)?}- 
Po 2a 
Now the velocity and density being functions of space only, it 
is easy to see that the accelerative action on any atom must have 
a constant ratio to the acceleration of the fluid where the atom 
is situated. I have found that this ratio is dependent of the 
magnitude of the atom (Principles of Mathematics, p.315). As 
the moveable needle is capable of motion only about a vertical 
. axis through its middle point, we are concerned exclusively with 


QT! 
a force proportional to — y being the distance from the 


Poly 
axis. The stream of the fixed needle is symmetrical with respect 
to a vertical plane through its axis, and flows nearly perpendi- 
cularly to the axis of the moveable needle, so that wv, is very small 
at the positions of all its atoms. A little consideration of the 
courses of the streams will suffice for perceiving that neither the 
forces proportional to (w, + uv) os -- 7) nor those proportional 
to (w,+ we) ae ia ; produce any momentum of rotation of 


the needle. Consequently the motion of rotation wholly depends 
on the forces proportional to 


dv, | 
(v, + U9) dy ok dy . 


Now the forces 0», evidently produce equal and opposite 


nomenta on the north and south arms of the needle; the same 
is the case with the forces yee because the values of v, are 
equal with opposite signs at equal distances on the opposite sides 
of the centre of motion. Also the forces v, = are mutually de- 


structive, because v, at any distance from the centre of motion 
has equal positive and negative values on the opposite sides of 
the axis. There remains, therefore, only the momentum due to 


the forces v, ie These will clearly tend to produce rotation, 


Phil. Mag. 8. 4. Vol. 38. No. 252. July 1869. 1D) 


20 On the Hydrodynamical Theory of Magnetism. 


because, while v, retains the same sign, v, has equal values with 
opposite signs for the two arms. 

According to the before-supposed positions of the magnets, 
the stream from the fixed one will oppose the transverse part of 
the stream from the moveable one on the east side of the north 
arm, and conspire with it on the west side, so that the pressure, 
being greater as the composite velocity is less, will be im excess 
on the east side. For like reasons the pressures on the atoms 
of the south arm will be in excess on their west sides. Hence 
the movement of the needle will be the same as if the pole B of 
the fixed needle repelled the pole B of the moveable needle and 
attracted its pole A. 

By this reasoning it is shown that the momentum of rotation 
of the moveable magnet is proportional to the velocity v,; and 
from the foregoing mathematical theory it appears that v is in- 
versely proportional to D?, D being the distance between the 
centres of the magnets, or, presumably, that 


be h? 
= D3 (i a i) 


In the second set of experiments the fixed needle was placed 
either to the north or to the south of the moveable one,so that ° 
the latter pointed to its centre, and the direction of its axis was 
still perpendicular to the plane of the meridian. In these posi- 
tions the stream of the fixed needle will cut at right angles the 
axis of the moveable one, and its action on the latter will be very 
nearly the same in kind as in the former set of experiments, but 
will differ in the circumstance that the velocity at the distance 
D is half the velocity in the other case at the same distance. 
The more exact proportion of the momenta of rotation in the 
two cases for the same value of D is presumed to be 


1 ie 
~ 7/2 pela alie) 
ae yee or 2(1 — Meet 3) nearly. 
ea? 


These results agree with Gauss’s numerical determinations both 
as regards the law of the inverse cube and the ratio of the mo- 
menta of rotation. This ratio is shown by the experiments to 
be nearly equal to 2, and to be less than this value by a greater 
quantity as the distance D is less; which accords with the above 
expression, if 4? be greater than h’?. 

The hydrodynamical theory of magnetism has thus given intel- 
ligible reasons for the facts of these experiments. The provisional 
assumption that VR?= a constant, for the approximate truth of 
which an antecedent reason was assigned, seems by these results 


Mr. W. C. Roberts on the Expansion of Palladium. 51 


to be proved to be the expression of an actual law. In Gauss’s 
theory analogous results are obtained on the hypothesis of two 
magnetic fluids, which are assumed to be capable of separation, 
and to be such that, when separated, like fluids mutually repel, 
and unlike mutually attract, according to the law of the inverse 
square. But what are we to understand by the separation of 
dissimilar fluids, and the dependence of mutual attractions and 
repulsions on this condition? It is as hard to conceive of rea- 
sons for these hypotheses as to account for the magnetic facts 
proposed to be explained by them. The present theory tends to 
show that there is no physical foundation for such hypotheses, 
the facts admitting of explanation on the supposition that a single 
fluid (the zther) acts in a manner conformable to hydrodynamical 
principles. The argument contained in this communication I am 
entitled, I think, to regard as confirmatory of the hydrodyna- 
mical theory of magnetism. 


Cambridge, May 22, 1869. 


VI. Note on the Experimental Illustration of the Expansion of 
Palladium attending the Formation of its Alloy with Hydroge- 
num. By W. CHanpiter Roserts, F.C.S., F.G.S.* 


— has recently been directed to the experimental 
demonstration of the absorption of hydrogen by palladium+. 

As the present writer has had the pnivilege of being con- 
nected with Mr. Graham’s recent researches, he ventures to 
offer a description of the special arrangements that, from some 
experience, appear to him best suited to the purpose of illus- 
tration. 

It will be remembered that Mr. Graham finds palladium, by 
the occlusion of 936 volumes of hydrogen, to sustain an increase 
in its linear dimensions of 1-605 on the 100; or assuming the 
expansion to be equal in all directions, the cubic expansion will 
be 4-908 on the 100, equal to sixteen times the dilatation of pal- 
ladium when heated from 0° C. to 100° C. A simple illustra- 
tion, well adapted for lecture-experiments, consists in arranging 
two fine palladium wires on the same plane, but slightly inclined 
towards each other; these are placed in a cell filled with acidu- 
lated water, which may be illuminated by an electric or other 
lamp, and the image of the wires thrown upon a screen. The 
wires are to be connected with either element of a small battery, 
a commutator intervening. 

* Communicated by the Author. 

+ James Dewar, F.R.S.E.,“ On the Motion of a Palladium Plate during 


the Formation of Graham’s Hydrogenium ;” and Poggendorff, “On the 
Voltaic Deportment of Palladium :” Phil. Mag. No. 251, pp. 424 and 474. 
E2 


ow 


02 Mr. W. C. Roberts on the Experimental Illustration 


On completion of the circuit the following facts will be ob- 
served: from the positive wire, gas (oxygen) is freely evolved, 
while the negative wire is perfectly quiescent, the hydrogen 
being for some time entirely absorbed by the metal. When the 
hydrogen makes its appearance it rises from the end nearest to 
the positive electrode. 

On reversing the direction of the current, evolution of gas 
ceases from both wires, the hydrogen being occluded by the one, 
and the oxygen being consumed by the previously absorbed hy- 
drogen in the other*. Attention should also be directed to the 
flexure produced by the unequal absorption of gas on different 
sides of the wire. 

To obtain a direct demonstration of the expansion, the writer 
availed himself of the deportment of a compound riband of pal- 
ladium and platinum when made to form the negative electrode 
of a battery decomposing acidulated water. The riband con- 
sists of two strips, one of palladium, the other of platinum-foil, 
300 millims. long, 3 millims. wide; these are soldered together 
and coiled into a circle, the palladium being inside. If, in the 
first instance, the coil be connected with the zine end of the 
battery, hydrogen will be thrown on the surface of the palla- 
dium, which absorbs the gas, and, by the consequent expansion 
of that metal only, opens the coil, the motion being rendered vi- 
sible by a light moving index. 

On reversing the direction of the current, oxygen will be 
thrown on the compound riband, and by its combination with 
the previously absorbed hydrogen, will relax the spiral and 
cause the index to move rapidly back to zero. 

But the employment of an index to magnify the motion is 
scarcely necessary with so rapid an angular velocity at command. 
The simplest form, and at the same time the most efficient, consists 
in placing as the electrodes two strips of palladium-foil varnished 
on one side and coiled into spirals (each 300 millims. by 5 to 7 
millims.) as indicated in the figuret. When one of the strips is 


* This experiment was skown at the Meeting of the British Association 
at Norwich, August 1868. 
+ As the varnish soon becomes cracked and detached from the foil, it is 


of the Expansion of Palladium. 53 


uncoiling, the other rolls up on itself. These effects are com- 
paratively slow at first; but as the molecular state of the strips 
is gradually altered, the evolutions are performed through a 
large sweep with singular rapidity. 

The most strikimg experiment of all is afforded by the fact 
that an electrodeposited film of extreme tenuity is capable of oc- 
eluding hydrogen, and at the same time possesses sufficient 
tenacity to produce by its expansion a very considerable amount 
of motion. 

A thin strip of platinum-foil, 200 millims. long by 4 millims. 
wide, was coiled into a circle (like a watch-spring), the external 
periphery being varnished. Upon the exposed surface a thin 
film of palladium was deposited by a small battery (3 litre Bun- 
sen) from a solution of about 1°6 per cent. of the chloride of 
palladium, the time of exposure being six minutes. The posi- 
tive pole was represented by a fine platinum wire, a very small 
portion of which was immersed. A grey coherent film was thus 
obtained. ‘The strip was then placed in acidulated water and 
connected with the zinc end of a small battery. 

In consequence of its absorption, there was no evolution of 
gas from its surface; but the metal instantly uncoiled itself, the 
unattached end passing through an arc of 65°. 

On reversing the direction of the current, the strip as rapidly 
returned to its normal position. The tenacity of the film soon 
becomes impaired. 

In order to give an estimate of the thickness of the film, a 
sheet of platinum-foil, 20 millims. x 20 millims., having there- 
fore on both sides a surface of 800 square millims., was accu- 
rately weighed on a delicate assay-balance at the Mint and ex- 
posed for six minutes, as in the case of the strip, to the chloride- 
of-palladium solution. The foil, after washing in distilled water 
and drying 7m vacuo, showed an increase in weight of 0:0009 grm. 

The following calculation gives the thickness of the film ca- 
pable of producing so remarkable a result. 


; grm. 
Weight of the palladium 0:0009 —0-0000762 cub. centim., 


Sp. gr. assumed tobe . 11°8 
or ‘0762 cubic millimetre. 
‘0762 —0-000095 ofa millim. thick 
CIA: 62 a cucaeh 16500 |... HCl, 


OY yohae Of a millimetre. 
For the sake of comparison | 

gold leaf =57q554 inch= 7545, millimetre. 
better (before varnishing) to cover one side of the palladium strip with a 


thin layer of solder, although the simplicity of the arrangement is to some 
extent sacrificed. 


[weal 


VII. On the Polarization of Light by Air mixed with Aqueous 
Vapour. By Professor HarpincEer*, 


To Professor Tyndall, F_R.S. 
Dormbach near Vienna, 
My pear Sir, June 13, 1869. 
ae late experiments and reports on the polarization of 
light by cloudy matter (Proceedings of the Royal Society, 
No. 108, vol. xii. pp. 223 &e., Jan. 14, 1869) have made a deep 
impression on my mind. 

Permit me to advert to an ancient observation of mine relating 
to a subject of the kind, but under circumstances widely different, 
which nevertheless I now very much should wish you may think 
worthy of a glance in the development of your further inquiries. 

I have observed the polarization of ight by air mixed with 
watery vapour. I gave an account of it in Poggendorff’s An- 
nalen for 1846, vol. xvi. pp. 738-87 (77). Abbé Moigno, hke- 
wise, from Poggendorff, gave a report of it in the fourth volume 
of his Répertoire d’Optique Moderne, 1850, pp. 1838 & 13839. 
Both were accompanied with diagrams. In the vapour-bath, of 
course, I had no optical apparatus with me; but having shortly 
before been struck with the appearance of the brushes of polarized 
light, or of polarization (Polarisations-biischel), I was well pre- 
pared to test or to recognize polarized hght under certain circum- 
stances with the naked eye, by trying whether I could not see 
these brushes. 

It is perhaps hardly discreet of me to demand you should be 
at the trouble of searching out old volumes; so I beg you will 
permit me just to translate that portion of one of my old papers 
which refers to the subject. 

“ Brushes of polarization observed in watery vapour. 

“White bows or nebulous arches (Vebelbogen) have been ob- 
served in fogs or mists, having nearly the apparent diameter of 
rainbows. The light of the rainbow has been found to be pola- 
rized by Biot and Sir David Brewster, conformably to the well- 
known explanation by single reflection of the light of the sun for 
the interior rainbow, and by double reflection for the exterior 
rainbow. 

‘“T had an opportunity to observe the white vapour-bows or 
arches in the vapour-baths of the ‘ Sorbienbad,’ a most merito- 
rious establishment, conducted by M. Marawetz in the suburb 
Landstrasse in Vienna. Since my observation a new building 
has been raised on the east side, so that it 1s no longer possible 
there to repeat the observation. 

“The sun shone bright at 7 o’clock in the morning, under a 


* Communicated by Professor Tyndall. 


Prof. Haidinger on the Polarization of Light by Vapour. 55 


small elevation through the window into the vapour. A beau- 
tiful cireular arch presented itself to the eye, the centre of which 
was the shadow of the head. I endeavoured to represent it in 
the diagram fig. 1, A B C D being the projection of the window 
upon the wall on the opposite side of Fig. 1. 
the room. ———— 
“The colour of the arch fisapale = 
bluish white. It is slightly frmged on 
both sides with a pale orange or brown- 


oN 


E_ 
ish yellow, not over bright. The ey = 
space e without and the space gy within SY 2 a= 
the arch is inferior in light, andofa E@@ux—<2 Se 
grey, rather reddish colour. Opposite ES "Sos = c= 
to the eye, the sun just grazing the eye, Wa <5 § 7 = 
there appears a brighter circular spot a, WN aS 
fringed at 6 with the slight yellowish = SC? == 


or reddish tint. Beginning from4, the light is distinetly polarized. 
The brushes of polarization are quite visible if the eye from one 
place or direction is quickly directed to another. The brushes 
have a direction corresponding to the radius in the whitish arch, 
and a tangential direction in the spaces within and without it. 
The light of the arch appears, then, to be polarized by reflection 
from the surface of the particles of vapour or water. The spaces 
without and within the arch appear, therefore, to be polarized by 
transmission perpendicularly to the polarization of the arch. The 
bluish-white and the reddish tints may be faint mixtures of the 
bluish or reddish fringes of diffraction, combined with the direct 
refiection from the watery particles floating in the air. 

“Tt is well known that a real rainbow may be produced on a 
small scale by taking some water in the mouth and then forcibly 
spouting or puffing it out reduced to the finest watery dust or 
powder. I availed myself of this method to ascertain, at least 
approximately, the diameter of the nebulous arch, being without 
any other apparatus in a vapour-bath. The nebulous arch still 
continued visible, as in fig. 2; but the first or interior rainbow 
now became visible, and was situ- 
ated pretty much in the central line 
of the nebulous arch; the exterior 
rainbow, visible only in faint traces, 
appeared beyond the nebulous arch. } 
The angular values of the semidia- {y= 
meters being for the red of the m- WW) 
terior rainbow 42° 2’, for its breadth 
1°45', for the red of the outer rain- 
bow 50° 58’, and its breadth 3° 10', for the distance of the two 
rainbows 8° 15/, the breadth of the nebulous arch is consequently 


Bigs 2: 


Wy 
>, 


‘ 
‘ 
\ 
Nw 


56 Prof. Haidinger on the Polarization of Light by Vapour. 


equal to about 12°, its central line being nearly at the angular 
distance of 41° from the centre. But I must claim for these 
angular values only the character of approximations, as I could 
only note the data from memory, and did not succeed in getting 
another sight of the phenomenon. 

“In the situation fig. 38, looking at the column of air loaded 
with vapour and obliquely Fig. 3. 
illuminated by the sun en- 
tering through a small win- 
dow, the transverse brushes 
of polarization produced by 
transmission were distinctly 
visible at a, while from the 
wet boards of the floor at b 
the polarization of reflection 
was as distinctly visible in 
the longitudinal brushes. 

“Ina manner somewhat 
analogous to the preceding 
observations, the tangential 
or transverse brushes of po- 
larization may be observed 
near the sun in vapoury air, 
while the sun itself is screened from the eye of the observer by 
intervening objects.” 

You see, my dear Sir, I have reported only the bare observa- 
tion, and that only for the sake of following up the “ brushes of 
polarization.” But I have not found myself either sufficiently 
prepared nor prompted by circumstances to follow up the 
study of the subject itself in the manner it well deserves. You 
are now in the course of the most interesting inquiries; and I 
should be happy to find that you would give some kind glance 
at my own long ago brought forward and now nearly antiquated 
endeavours. 

I still retam the most lively recollection of your friendly visit 
at my house in Vienna in 1856, when [ still was laid up in my 
bed from the cold I had caught the first day of the opening of 
our scientific association. And greatly interested I was at so 
many of your investigations, several of which I had the good 
luck to quote in confirmation of my humble contributions. Per- 
haps I should have written this letter in German, so completely 
are you master of my own language, but I thought this mode of 
writing would be more in agreement with your daily general 
practice and intercourse. 

Believe me ever, my dear Sir, 
Yours very truly, 
W. HarpineGeEr. 


[ 587 J 


VIII. On Ammonium Alloys, and on Nascent-Hydrogen Tests. 
By Avsert H. Gauiarin, M.D., of New York*. 


(oad and De Pontin in 1808, using the voltaic cur- 
rent as Davy had done, endeavoured to do as much for the 
ammoniacal compounds as he had done for those of the fixed 
alkalies. They made what is known as the ammoniacal amal- 
gam. That ammonium exists in this body has never been de- 
monstrated, notwithstanding that its constituents in their proper 
proportions were always found escaping from the amalgam: that 
does not prove that they were united; on the contrary, 2 vols. 
of NH? and 1 vol. of H are the products. Moreover, if it were 
ammonium, it had never been made to unite with any other 
metal than mercury. I have endeavoured to overcome both of 
these objections. 


1. On the Existence of Ammonium in the Ammoniacal Amalgam, 
and on a new Test for the presence of Nascent Hydrogen. 


If the hydrogen escaping from the mercury together with the 
ammonia can be shown to be in the nascent state, it would be 
evidence that it had just been in chemical combination with the 
ammonia, in other words, that metallic ammonium (NH*) ex- 
isted in the amalgam. Some pellets of sodium were placed in 
contact with some particles of the transparent variety of phos- 
phorus, wrapped in bibulous paper and plunged beneath the sur- 
face of water. A red glow was seen; and as the nascent hydro- 
gen from the decomposing water came into contact with’ the 
phosphorus, bubbles of phosphide of hydrogen were formed. 
Occasionally one would inflame as it came into contact with the 
atmosphere, placing the nature of the reaction beyond doubt. 
As phosphide of hydrogen cannot be formed by direct synthesis 
if ordinary free hydrogen be employed, this becomes a test for 
the presence of that gas in its nascent state. The hydrogen 
escaping from the ammoniacal amalgam was now tested by this 
process. A sodium-amalgam dipped beneath a solution of chlo- 
ride of ammonium was employed; and it became necessary to 
wait until the scdium was exhausted, that results might not be 
vitiated by the nascent hydrogen escaping from the water. At 
the proper time the decomposing amalgam was covered with 
fragments of transparent phosphorus, when many bubbles of 
inflammable phosphide were obtained. The hydrogen must 
then have been in the nascent state and just escaping from the 
ammonium. 


* Communicated by the Author. 


58 Dr. A. H. Gallatin on Ammonium Alloys. 


2. On the Existence of an Alloy of Ammonium and Bismuth, and 
on another new Test for the presence of Nascent Hydrogen. 


Ammonium had never yet been seen united with any other 
metal than mercury. Mercury being the only metal fluid at 
ordinary temperatures, should another alloy be formed it would 
be a solid. Some bismuth was melted in a porcelain dish and 
alloyed with sodium by dropping a piece of that metal on the 
clear surface of the fluid bismuth. Chloride of ammonium was 
then dusted on the fluid alloy, and then water added in a fine 
quick stream. The bismuth swells, appears pasty and porous, 
and then congeals. Abundance of hydrogen escapes from the 
water, and the ammoniacal odour is set free. This body must 
now be dried. If it be placed near the ear a distinct crackling 
noise will be heard, a phenomenon which endures for some days. 
To ascertain if this be ammonium escaping from the bismuth, the 
body was placed beneath the surface of water, when bubbles of 
hydrogen escaped, easily to be collected and recognized ; the 
ammonia, if any, must have been absorbed by the water. To 
test for this red litmus-paper was placed in the hquid. Wherever 
the currents from the bismuth struck it a blue spot became vi- 
sible. On dissolving sulphate of copper in distilled water and 
placing the well-dried bismuth therein, the characteristic flocculi 
of ammonio-sulphate of copper appeared at once. 

It remains to show that the hydrogen escaping is in the nas- 
cent state. There was not enough of it to test with phosphorus. 
The bismuth compound, when placed in a solution of sulphate of 
copper, becomes rapidly coated with metallic copper. Now bis- 
muth unalloyed will not precipitate copper fromits sulphate. To 
test if the precipitation of the metallic copper was due to the 
presence of nascent hydrogen, an alloy of bismuth and sodium 
was made and dipped in a solution of sulphate of copper. It 
instantly became coated with that metal, owing to the nascent 
hydrogen escaping from the water. The hydrogen was there- 
fore escaping in the nascent state from the bismuth and am- 
monia, and therefore it was a true alloy of bismuth and ammo- 
nium. If the temperature of this alloy be raised, it will rapidly 
decompose with a crackling noise. On one occasion it exploded, 
sharply scattering the metal. The loud crackling noise produced 
by this substance may be heard for many days after it is made. 
That there is no mere surface-action in the case of the mercurial 
and bismuth alloys of ammonium, is shown by the pores which 
are formed by the escaping gases in both cases. In the amalgam 
these pores may be seen produced by the escaping ammonium 
long after the water has exhausted the sodium. In the mercu- 
rial body the pores are evanescent ; in the case of bismuth they 


Royal Society. 59 


remain, and may be examined at leisure. These are different 
phenomena from those displayed by spongy platinum when it 
forces hydrogen and oxygen to combine. 


Appendix.—Continuation of the investigation at the laboratory 
of the Royal Mint, London, by the kind permission of Mr. 
Roberts :— 

The alloy was dried in vacuo over sulphuric acid. It was then 
heated im vacuo by means of a Sprengel pump, when it decom- 
posed, and the resulting gas was collected over mercury. It was 
found to have twenty-seven times the volume of the original 
solid. Analysis of the gas proved it to contain nitrogen and 
hydrogen. The results of a further examination will shortly be 
given. 

June 23, 1869. 


IX. Proceedings of Learned Societies. 


ROYAL SOCIETY. 


[Continued from vol. xxxvii. p. 474.] 


Jan. 28, 1869.—John Peter Gassiot, Esq., Vice-President, in the 
| Chair. 


fae following communications were read :— 
“On a momentary Molecular Change in Iron Wire.” By G. 
Gore, F.R.S. 

Whilst making some experiments of heating a strained iron wire 
to redness by means of a current of voltaic electricity, I observed that, 
on disconnecting the battery and allowing the wire to cool, during 
the process of cooling the wire suddenly elongated, and then gra- 
dually shortened until it became quite cold. 

On attempting, some little time afterwards, to repeat this expe- 
riment, although a careful record of the conditions of the experiment 
had been kept, it was with some difficulty, and after numerous trials, 
that I succeeded in obtaining the same result. Having again ob- 
tained it, I next examined and determined the successful conditions 
of the experiment, and devised the following arrangement of appa- 
ratus. 

A A (fig. 1) is a wooden base 61 centimetres long and 15:5 cen- 
timetres wide. B and C are binding-screws ; they are provided with 
small brass mercury-cups fixed in the heads of the screws for attach- 
ment of the wires of a voltaic battery. Dis a binding-screw for 
holding fast the sliding wire hook EK. F is a cylindrical binding- 
screw, fixed to the sliding wire G, which is held fast by the binding- 
screw B. H is the iron or other wire (or ribbon) to be heated: one 
end of this wire passes through the screw F and is tightly secured by 
it, whilst the other end is held fast by the cylindrical binding-screw I; 
the binding-screw I has a small projecting bent piece of copper wire 


¢ 
SEES LERAEY SRA SYA 
pe - a 


» #077998 
z 


Tha 


Gore on a momentary 


G. 


:—Mr. 


= 
‘= 
S 
R 
La) 
8 
>> 
=) 
a} 


Molecular Change in Iron Wire. 61 


secured to it, which dips into a little shallow dish or cup of mercury, 
J; and the mercury in this cup is connected by a screw and strip 
of brass to the binding-screw C. Kis a stretched band of vulcanized 
india-rubber, attached at one end to the hook of the wire EK, and 
at the other end to the hook L (see fig. 2). The cylindrical binding- 
screw I has a hook by which it is attached to the loop M (fig. 2). 
N is an axis suspended delicately upon centres, and carrying a very 
light index pointer O. The hook L and loop M are separate pieces of 
metal, and move freely upon an axis, P (fig. 2). The distance from 
the centre of the axis N to that of P is 12°72 millimetres (=0°5 
inch), and to the top of the index pointer 25°45 centimetres (=10-0 
inches) ; every movement horizontally, therefore, of the loop M is 
attended by a movement, twenty times the amount, of the top of the 
pointer. Q is a screw for supporting the axis N. I have found it 
convenient to put the zero-figure of the index towards the left-hand 
side of the index-plate. R is a separate piece of wood fitting into a 
rectangular hole in the base-board ; it carries a graduated rule, S, for 
measuring the length of the wire to be heated, andis easily removed, 
so that the wire may, if necessary, be heated by means of a row of 
Bunsen’s burners. The rule T is used when measuring the amount 
of strain. U is a vertical stud or pin of brass (of which there are 
two) for limiting the range of movement of the pointer O. 

In using this apparatus, a straight wire or ribbon, H, of a suitable 
length and thickness was inserted, the index pointer brought to 0 by 
adjustment of the sliding wire G, and a suitable amount of strain 
(varying from less than two ounces to upwards of twenty) put upon 
the wire by adjusting the sliding hooked wire E. One pole of a vol- 
taic battery, generally consisting of six Grove’s elements, was con- 
nected with the binding-screw C, and the other pole then inserted in 
the mereury-cup of B. As soonas the needle O attained a maximum 
or stationary amount of deflection, the battery-wire was suddenly re- 
moved from 8B, and the wire allowed to cool. The movement of the 
needle O was carefully watched both during its movement to the 
right hand and also during its return, to see if any irregularity of 
motion occurred. 

Wires of the following metals and alloys were employed :—palla- 
dium, platinum, gold, silver, copper, iron, lead, tin, cadmium, zine, 
brass, german-silver, aluminium, and magnesium ; metallic ribbon was 
also employed in certain cases. | 

In these experiments the thickness and length of the conducting- 
wire or ribbon had to be carefully proportioned to the quantity and 
electromotive power of the current, so as to produce in the first ex- 
periments with each metal only a very moderate amount of heat ; 
thinner (and sometimes also shorter) wires were then successively 
used, so as ultimately to develope sufficient heat to make the metal 
closely approach its softening or fusion-point. The battery employed 
consisted in each case of six Grove’s cells, each cell containing two 
zinc plates 32 inches wide, and a platinum plate 3 inches wide, each 
immersed about 5 inches in their respective liquids. The amount 
of tension imparted by the elastic band required to be carefully ad- 


62 Royal Sociely :—Mr. G. Gore on a momentary 


justed to the cohesive power of each metal ; if the stretching power 
was too weak, the phenomenon sought for was not clearly deve- 
loped; and if too great, the wire was overstretched or broken when 
it approached the softening-point. The amount of strain imparted 
was approximately measured by temporarily substituting the body 
of a small spring balance for the hooked wire F. The heated wire 
must be protected from currents of cold air. 

With wires of iron 0°65 millimetre thick (size “ No. 23”) and 
21°5 centimetres long, strained to the extent of 10 ounces or more, 
and heated to full redness, the phenomenon was clearly developed. 
As an example, the needle of the instrument went with regularity to 
18-5 of index-plate; the current was then stopped; the needle in- 
stantly retreated to 17°75, then as quickly advanced to 19°75, and 
then went slowly and regularly back, but not to zero. If the tempe- 
rature of the wire was not sufficiently high, or the strain upon the 
wire not enough, the needle went directly back without exhibiting the 
momentary forward movement. The temperature and strain required 
to be sufficient to actually stretch the wire somewhat at the higher 
temperature. A higher temperature with a less degree of strain, 
or a greater degree of strain with a somewhat lower temperature, 
did not develope the phenomenon ; the wire was found to be per- 
manently elongated on cooling. The amount of elongation of the 
wire during the momentary molecular change was usually about 545 
part of the length of the heated part of the wire; but it varied in 
different experiments ; it was greatest in amount when the maximum 
degrees of strain were applied. The molecular change evidently 
includes a diminution of cohesion at a particular temperature during 
the process of cooling ; and it is interesting to notice that at the 
same temperature during the heating-process no such loss of cohe- 
sion (nor any increase of cohesion) takes place; a certain tempera- 
ture and strain are therefore not alone sufficient to produce it ; the 
condition of cooling must also be included. The phenomena which 
occur during cooling are not the exact converse of those which take 
place during heating. 

The phenomenon of elongation of iron wire during the process of 
cooling evidently lies within very narrow limits; it could only be 
obtained (with the particular battery employed) with wires about 
21°5 centimetres (=8;4 inch) long, and about 0°65 millimetre 
(=Nos. 22 & 23 of ordinary wire-gauge) thick, having a strain 
upon them of 10 ounces or upwards; with a weaker battery the 
phenomenon could only be obtained by employing a shorter and 
thinner wire. 

The experiment may easily be verified in a simpler manner by 
stretching an iron wire about 1:0 millimetre diameter between two 
fixed supports, keeping it in a sufficient and proper degree of ten- 
sion by means of an elastic band, then heating it to full redness by 
means of a row of Bunsen’s burners, and, as soon as it has stretched 
somewhat, suddenly cutting off the source of heat. In some experi- 
ments of this kind, with a row (42 centimetres long) of 21 burners 
and a row (76 centimetres long) of 43 burners, and the wire attached 


Molecular Change in Tron Wire. 63 


to a needle with index-plate, as in the figure, conspicuous effects 
were obtained; but the momentary elongation was relatively much 
less (in one instance 4, of the length of the heated part) than 
when a battery was employed, apparently in consequence of the wire 
being less intensely heated. 

A large number of experiments were made with wires of palla- 
dium, platinum, gold, silver, copper, lead, tin, cadmium, zinc, brass, 
german-silver, aluminium, and magnesium (wire and ribbon), dimi- 
nishing the length and thickness of the wire in each case, and ad- 
justing the tension until suitable temperature and strain were obtained ; 
but in no instance could a similar molecular change to that observed 
in iron be detected. Palladium and platinum wires of different 
lengths, thickness, and degrees of strain were examined at various 
temperatures, up to that of a white heat; but no irregularity of co- 
hesion, except that of gradual softening at the higher temperatures, 
was observed; they instantly contracted with regular action on stop- 
ping the current. Several gold wires were similarly examined at dif- 
ferent temperatures up to that of a full red heat; no irregularity 
occurred either during heating or cooling; but little tension (about 
4 ounces) was applied, on account of the weak cohesion of this metal. 
Wires of silver similarly examined would only bear a strain of about 
2 ounces, and a temperature of feeble red heat visible in daylight ; 
no irregularity of elongation or contraction occurred during heating 
and cooling. By employing exactly the proper temperature and 
strain, a very interesting phenomenon was observed: the wire melted 
distinctly on its surface without fusing in its interior, although the 
surface was most exposed to the cooling influence of the air ; this oc- 
curred without the wire breaking, as it would have done if its interior 
portion had melted: the phenomenon indicates the passage of the 
electricity by the surface of the wire in preference to passing by its 
interior. Wires of copper expanded regularly until they became red- 
hot; they then contracted slightly (notwithstanding the strain ap- 
plied to them), probably in consequence of a cooling effect of in- 
creased radiation produced by the oxidized surface, as a similar effect 
occurred with brass and german-silver*. On stopping the current 
the wire contracted without manifest irregularity. Wires of lead and 
tin were difficult to examine by this method, on account of their ex- 
tremely feeble*cohesion and the low temperature at which they soft- 
ened: wires about 1°63 millimetre diameter, 25°5 centimetres long 
(with a strain upon them of about one ounce), were employed; no 
irregularity was detected. Wires of cadmium from 1°255 millimetre 
to 1°525 millimetre thick, and 24-2 centimetres long (with a strain 
of two ounces), exhibited a slight irregularity of expansion at the 
lower temperatures ; they elongated, and also cooled, with extreme 
slowness, more slowly than those of any other metal. Wires of zinc 
exhibited a slight irregularity of expansion, like those of cadmium ; 
the most suitable ones were about 25 centimetres long and 1:2 mil- 
limetre in diameter, with a strain of 10 ounces. Wires of brass and 


* This supposition does not agree with the results obtained with iron wire, 
which also oxidizes freely. 


64 Royal Society :—Mr. G. Gore on the Development of 


german-silver, when heated to redness, behaved like those of copper 
in expanding regularly until a maximum was attained, and then con- 
tracting slightly to a definite point whilst the battery remained con- 
nected ; on stopping the current they contracted without irregularity. 
When examined at lower temperatures, with a greater degree of 
strain, no irregularity was observed. Various wires of aluminium 
were examined; the most suitable was one 0°88 millimetre thick, 
20°4 centimetres long, with a strain of 12 ounces; no irregularity 
was observed at any temperature below redness ; aluminium expanded 
and cooled very slowly, but less so than cadmium. Various wires and 
ribbon of magnesium were also examined below a red heat, but no 
irregularity of cohesion, except that due to gradual softening by heat, 
was detected. 

All the metals examined exhibited gradual loss of cohesion at the 
higher temperatures if a suitable strain was applied to develope it. It 
is probable that if the fractions of time occupied by the needle in 
passing over each division of the index were noted, and the wire 
perfectly protected from currents of air, small irregularities of mo- 
lecular or cohesive change might be detected by this method; cad- 
mium and zine offer a prospect of this kind. 

This molecular change would probably be found to exist in large 
masses of wrought iron as well as in the small specimens of wire 
which I have examined, and would come into operation in various 
cases where those masses are subjected to the conjoint influence of 
heat and strain, as in various engineering operations, the destruction 
of buildings by fire, and other cases. 


“On the Development of Electric Currents by Magnetism and 
Heat.’ By G. Gore, F.R.S. 

I have devised the following apparatus for demonstrating a rela- 
tion of current electricity to magnetism and heat. 

A A, fig. 3, is a wooden base, upon which is supported, by four 
brass clamps (two, B, B, on each side), a coil of wire, C ; the coil is 6 
inches long, 13 inch in external diameter, and 2 of an inch internal 
diameter, lined with a thin glass tube ; it consists of 18 layers, or 
about 3000 turns of insulated copper wire of 0°415 millim. diameter 
(or size No. 26 of ordinary wire-gauge) ; D isa permanent bar-mag- 
net held in its place by the screws E, E, and having upon its poles two 
flat armatures of soft iron, F,F, placed edgewise. Within the axis of 
the coil is a straight wire of soft iron, G, one end of which is held 
fast by the pillar-screw H, and the other by the cylindrical binding- 
screw 1; the latter screw has a hook, to which is attached a vul- 
canized india-rubber band, J, which is stretched and held secure 
by the hooked brass rod K and the pillar-screw L. The screw H is 
surmounted by a small mercury-cup for making connexions with one 
pole of a voltaic battery, the other pole of the battery being secured 
to the pillar-screw M, which is also surmounted by a small mercury- 
cup, and is connected with the cylindrical binding-screw I by a cop- 
per wire with a middle flattened portion O to impart to it flexibility. 
The two ends of the fine wire coil are soldered to two small binding- 


Electric Currents by Magnetism and Heat. 65 


screws at the back; those screws are but partly shown in the sketch, 
and are for the purpose of connexion with a suitable galvanometer. 
The armatures F, F’, are grooved on their upper edges, and the iron 
wire lies in these grooves in contact with them ; and to prevent the 
electric current passing through the magnet, a "small piece of paper 
or other thin non-conductor is inserted between the magnet and one 
of the armatures. The battery employed consisted of six Grove’s ele- 
ments (arranged in one series), with the immersed portion of platinum 
plates about 5 inches by 3 inches ; it was sufficiently strong to heat 
an iron wire of 1:03 millim. diameter and 20°5 centims. long to a low 
red heat. 

By making the contacts of the battery in unison with the move- 
ments of the galvanometer-needies, a swing of about 12 degrees of 
the needles each way was obtained. The galvanometer was not a very 
Sensitive one; it contained 192 turns of wire. Similar results were 
obtained with a coil § inches long and 1} inch in diameter contain- 
ing 16 layers, or about 3776 a: of wire of 0°415 millim. diame- 
ter (or No. 26 of ordinary wire-gauge), and a permanent magnet 10 
inches long. Less effects were obtained with a 6-inck coil consisting 
of 40 layers, or about 10,000 turns of wire 0°10 millim. in diameter, 
also with several other coils. The maximum effect, of 12 degrees 
each way, with six Grove’s cells in one series was obtained when the 
wire became visibly red-hot, and this occurred with an iron wire of 1:03 
millim. diameter (or No. 19 of ordinary wire-gauge) ; but when em- 
ploying ten such cells as a double series of five, the maximum effect 
was then obtained with an iron wire of 1:28 to 1°58 millim. diameter 
(size Nos. 17 and 18), the deflection being 16 degrees each way. By 
employing a still thicker wire and a battery of greater heating-power 
still greater effects were obtained. 

The galvanometer was placed about 8 (and in some instances 12) 
feet distant from the coil. A reversal of the direction of the battery- 
current did not reverse or perceptibly affect the current induced in 
the coil; but by reversing the poles of the magnet, the direction of 
the mduced current was reversed. On disconnecting the battery, 
and thereby cooling the iron wire, a reversed direction of induced cur- 
rent was produced. By substituting a wire of pure nickel 24:5 cen- 
tims. long and 2°1 millims. in diameter, induced currents were obtained 
as with the iron, but they were more feeble. No induced current 
occurred by heating the iron wire if the magnet was absent; nor was 
any induced current obtained if the magnet was present and wires 
of palladium, platinum, gold, silver, copper, brass, or german-silver 
were heated to redness instead of iron wire, nor with a rod of bis- 
muth of 3°63 millims. diameter enclosed in a glass tube and heated 
nearly to fusion ; it is evident, therefore, that the axial wire must be 
composed of a magnetic metal. 

No continuous current (or only a very feeble one) was produced in 
the coil by continuously heating the iron wire. In several experi- 
ments, by employing twelve similar Grove’s elements as a double series 
of six intensity, an iron wire of 1°56 millim. diameter was made bright. 
red-hot ; and by keeping the current continuous until the galvano- 
meter-needles settled nearly at zero, and then suddenly disconnecting 


Phil, Mag. 8.4. Vol, 38. No, 252, July 1869. Ii 


66 Royal Society :—Frankland and Lockyer on Gaseous Spectra 


the battery, the needles remained nearly stationary during several 
seconds, and then went rapidly to about 10: this slow decline of the 
current during the first few seconds of cooling was probably connected 
with the ‘“‘ momentary molecular change of iron wire”’ during cooling 
which I have described in the preceding paper. The irregularity of 
movement of the needles did not occur unless the wire was bright red- 
hot, a condition which was also necessary for obtaining the molecular 
change. 

The direction of the current induced by heating the iron wire was 
found by experiment to be the same as that which was produced by 
removing the magnet from the coil; therefore the heat acted simply 
by diminishing the magnetism, and the results were in accordance 
with, and afford a further confirmation of, the general law, that where- 
ever there is increasing or decreasing magnetism, there is a tendency 
to an electric current in a conductor at right angles to it. 


February 11.—Dr. W. B. Carpenter, Vice-President, in the Chair. 


The followmg communication was read :— 

“‘ Preliminary Note of Researches on Gaseous Spectra in relation 
to the Physical Constitution of the Sun.’’ By Edward Frankland, 
F.R.S., and J. Norman Lockyer, F.R.A.S. 

1. For some time past we have been engaged in a careful exami- 
nation of the spectra of several gases and vapours uuder varying con- 
ditions of pressure and temperature, with a view to throw light upon 
the discoveries recently made bearing upon the physical constitution 
of the sun. 

Although the imvestigations are by no means yet completed, we 
consider it desirable to lay at once before the Royal Society several 
broad conclusions at which we have already arrived. 

It will be recollected that one of us in a recent communication to 
the Royal Society pointed out the following facts :— 

i. That there is a continuous envelope round the sun, and that in 
the spectrum of this envelope (which has been named for accuracy of 
description the “‘chromosphere”’) the hydrogen line in the green 
corresponding with Fraunhofer’s line F takes the form of an arrow- 
head, and widens from the upper to the lower surface of the chromo- 
sphere. 

il. ‘That ordinarily in a prominence the F line is nearly of the same 
thickness as the C line. 

i. That sometimes in a prominence the F line is exceedingly 
brilliant, and widens out so as to present a bulbous appearance above 
the chromosphere. 

iv. That the F line in the chromosphere, and also the C line, extend 
on to the spectrum of the subjacent regions and re-reverse the Fraun- 
hofer lines. 

v. That there is a line near D visible in the spectrum of the chro- 
mosphere to which there is no corresponding Fraunhofer line. 

vi. That are many bright lines visible im the ordinary solar spec- 
trum near the sun’s edge. 

vil. That a new line sometimes makes its appearance in the chro- 
mosphere. 


in relation to the Physical Constitution of the Sun. 67 


2. It became obviously, then, of primary importance— 

i. To study the hydrogen spectrum very carefully under varying 
conditions, with the view of detecting whether or not there existed a 
line in the orange, and 

ii. To determine the cause to which the thickening of the F line 
is due. 

We have altogether failed to detect any line in the hydrogen 
spectrum in the place indicated, 7.e. near the line D; but we 
have not yet completed all the experiments we had proposed to 
ourselves, 

With regard to the thickening of the F line, we may remark that, 
in the paper by MM. Pliicker and Hittorf, to which reference was 
made in the communication before alluded to, the phenomena of the 
expansion of the spectral lines of hydrogen are fully stated, but the 
cause of the phenomena is left undetermined. 

We have convinced ourselves that this widening out is due to 
pressure, and not appreciably, if at all, to temperature per se. 

3. Having determined, then, that the phenomena presented by the 
F line were phenomena depending upon and indicating varying pres- 
sures, we were in a position to determine the atmospheric pressure 
operating in a prominence, in which the red and green lines are 
nearly of equal width, and in the chromosphere, through which the 
green line gradually expands as the sun is approached*. 

With regard to the higher prominences, we liave ample evidence 
that the gaseous medium of which they are composed exists in a con- 
dition of excessive tenuity, and that at the lower surface of the chro- 
mosphere itself the pressure is very far below the pressure of the 
earth’s atmosphere. 

The bulbous appearance of the F line before referred to may be 
taken to indicate violent convective currents or local generations of 
heat, the condition of the chromosphere being doubtless one of the 
most intense action. 

4. We will now return for one moment to the hydrogen spectrum. 
We have already stated that certain proposed experiments have not 
been carried out. We have postponed them in consequence of a 
further consideration of the fact that the bright line near D has ap- 
parently no representative among the Fraunhofer lines. This fact 
implies that, assuming the line to be a hydrogen line, the selective 
absorption of the chromosphere is insufficient to reverse the spec- 
trum. 

It is to be remembered that the stratum of incandescent gas which 
is pierced by the line of sight along the sun’s limb, the radiation from 
which stratum gives us the spectrum of the chromosphere, is very 
great compared. with the radial thickness of the chromosphere itself ; 
it would amount to something under 200,000 miles close to the 
limb. 

Although there is another possible explanation of the non-reversal 
of the D line, we reserve our remarks on the subject (with which the 
visibility of the prominences on the sun’s disk is connected) until 
further experiments and observations have been made. 

* Will not this enable us ultimately to determine the temperature ? 


68 Royal Society :— 


5. We believe that the determination of the above-mentioned facts 
leads us necessarily to several important modifications of the received 
theory of the physical constitution of our central lumimary—the 
theory we owe to Kirchhoff, who based it upon his examination of 
the solar spectrum. According to this hypothesis, the photosphere 
itself is either solid or liquid, and it is surrounded by an atmosphere 
composed of gases and the vapours of the substances incandescent in 
the photosphere. 

We find, however, instead of this compound atmosphere, one 
which gives us nearly, or at all events mainly the spectrum of hy- 
drogen ; (it is not, however, composed necessarily of hydrogen alone ; 
and this point is engaging our special attention ;) and the tenuity of 
this incandescent atmosphere is such that it is extremely improbable 
that any considerable atmosphere, such as the corona has been ima- 
gined to indicate, lies outside it,—a view strengthened by the fact 
that the chromosphere bright lines present no appearance of absorp- 
tion, and that its physical conditions are not statical. 

With regard to the photosphere itself, so far from being either a 
solid surface or a liquid ocean, that it is cloudy or gaseous or both 
follows both from our observations and experiments. The separate 
prior observations of both of us have shown :— 

i. That a gaseous condition of the photosphere is quite consistent 
with its continuous spectrum. The possibility of this condition has 
also been suggested by Messrs. De La Rue, Stewart, and Loewy. 

ii. That the spectrum of the photosphere contains bright lines 
when the limb is observed, these bright lines indicating probably an 
outer shell of the photosphere of a gaseous nature. 

i. That a sun-spot is a region of greater absorption. 

iv. That occasionally photospheric matter appears to be injected 
into the chromosphere. 

May not these facts indicate that the absorption to which the re- 
versal of the spectrum and the Fraunhofer lines are due takes place 
in the photosphere itself or extremely near to it, instead of in an ex- 
tensive outer absorbing atmosphere? And is not this conclusion 
strengthened by the consideration that otherwise the newly disco- 
vered bright lines in the solar spectrum itself should be themselves 
reversed on Kirchhoff’s theory ? this, however, is not the case. We 
do not forget that the selective radiation of the chromosphere does 
not necessarily indicate the whole of its possible selective absorption ; 
but our experiments lead us to believe that, were any considerable 
quantity of metallic vapours present, their bright spectra would not 
be entirely invisible in all strata of the chromosphere. 


February 18.—Lieut.-General Sabine, President, in the Chair. 


The following communication was read :— 

“Note on a Method of viewing the Solar Prominences without an 
Eclipse.’ By William Huggins, F.R.S. 

Last Saturday, February 13, I succeeded in seeing a solar promi- 
nence so as to distinguish its form. A spectroscope was used; a 
narrow slit was inserted after the train of prisms before the object- 
glass of the little telescope. This slit limited the light entering the 


Mr. Huggins on the Heat of the Stars. 69 


telescope to that of the refrangibility of the part of the spectrum 
immediately about the bright line coincident with C. 

The slit of the spectroscope was then widened sufficiently to admit 
the form of the prominence to be seen. The spectrum then be- 
came so impure that the prominence could not be distinguished. 

A great part of the light of the refrangibilities removed far from 
that of C was then absorbed by a piece of deep ruby glass. The 
prominence was then distinctly perceived, something of this form. 


A more detailed account is not now given, as I think I shall be 
able to modify the method so asto make the outline of these objects 
more easily visible. 


February 25.—Captain Richards, R.N., Vice-President, in the Chair. 

The following communications were read :— 

“Note on the Heat of the Stars.’ By Wilham Huggins, F.R.S. 

In the summer of 1866 it occurred to me that the heat received 
on the earth from the stars might possibly be more easily detected 
than the solar heat reflected from the moon. Mr. Becker (of Messrs. 
Elliott Brothers) prepared for me several thermopiles, and a very 
sensitive galvanometer. Towards the close of that year, and during 
the early part of 1867, I made numerous observations on the moon, 
and on three or four fixed stars. I succeeded in obtaining trust- 
worthy indications of stellar heat in the case of the stars Sirius, 
Pollux, and Regulus, though I was not able to make any quantita- 
tive estimate of their calorific power. 

I had the intention of making these observations more complete, 
and of extending them to other stars. I have refrained hitherto 
from making them known; I find, however, that I cannot hope to 
take up these researches again for some months, and therefore ven- 
ture to submit the observations in their present incomplete form. ~~ 

An astatic galvanometer was used, over the upper needle of which 
a small concave mirror was fixed, by which the image of the flame of 
a lamp could be thrown upon a scale piaced at some distance. Usu- 
ally, however, I preferred to observe the needle directly by means of 
a lens so placed that the divisions on the card were magnified, and 
could be read by the observer when at a little distance from the in- 
strument. ‘The sensitiveness of the instrument was made as great as 
possible by a very careful adjustment from time to time of the mag- 
netic power of the needles. ‘The extreme delicacy of the instrument 
was found to be more permanently preserved when the needles were 
placed at right angles to the magnetic meridian during the time that 
the instrument was not in use. The great sensitiveness of this in- 


70 Royal Society:— 


strument was shown by the needles turning through 90° when two 
pieces of wire of different kinds of copper were held between the finger 
and thumb. For the stars, the images of which in the telescope are 
points of light, the thermopiles consisted of one or of two pairs of 
elements; a large pile, containing twenty-four pairs of elements, was 
also used for the moon. A few of the later observations were made 
with a pile of which the elements consist of alloys of bismuth and 
antimony. 

The thermopile was attached to a refractor of eight inches aperture. 
I considered that though some of the heat-rays would not be trans- 
mitted by the glass, yet the more uniform temperature of the air 
within the telescope, and some other circumstances, would make the 
difficulty of preserving the pile from extraneous influences less for- 
midable than if a reflector were used. 


The pile a was placed within a tube of cardboard, 6; this was en- 
closed in a much larger tube formed of sheets of brown paper pasted 
over each other, c. The space between the two tubes was filled with 
cotton-wool. At about 5 inches in front of the surface of the pile, 
a glass plate (e) was placed for the purpose of intercepting any heat 
that might be radiated from the inside of the telescope. This glass 
plate was protected by a double tube of cardboard, the inner one of 
which (d) was about half an inch in diameter. The back of the pile 
was protected in a similar way by a glass plate (7). The small inner 
tube (h) beyond the plate was kept plugged with cotton-wool; this 
plug was removed when it was required to warm the back of the pile, 
which was done by allowing the heat radiated from a candle-flame to 
pass through the tube to the pile. The apparatus was kept at a 
distance of about 2 inches from the brass tube by which it was 
attached to the telescope by three pieces of wood (2), for the pur- 
pose of cutting off as much as possible any connexion by conduction 
with the tube of the telescope. 

The wires connecting the pile with the galvanometer, which had 
to be placed at some distance to preserve it from the influence of the 
ironwork of the telescope, were covered with gutta percha, over 
which cotton-wool was placed, and the whole wrapped round with 
strips of brown paper. ‘The binding-screws of the galvanometer 
were enclosed in a small cylinder of sheet gutta percha, and filled 
with cotton-wool. These precautions were necessary, as the ap- 
proach of the hand to one of the binding-screws, or even the impact 
upon it of the cooler air entering the observatory, was sufficient to 


Mr. Huggins on the Heat of the Stars. 71 


produce a deviation of the needle greater than was to be expected 
from the stars. 

The apparatus was fixed to the telescope so that the surface of the 
thermopile would be at the focal point of the object-glass. The 
apparatus was allowed to remain attached to the telescope for hours, 
or sometimes for days, the wires being in connexion with the galvano- 
meter, until the heat had become uniformly distributed within the 
apparatus containing the pile, and the needle remained at zero, or 
was steadily deflected to the extent of a degree or two from zero. 

When observations were to be made, the shutter of the dome was 
opened, and the telescope, by means of the finder, was directed to a 
part of the sky near the star to be examined where there were no 
bright stars. In this state of things the needle was watched, and 
if in four or five minutes no deviation of the needle had taken place, 
then by means of the finder the telescope was moved the small dis- 
tance necessary to bring the image of the star exactly upon the face 
of the pile, which could be ascertained by the position of the star as 
seen in the finder. The image of the star was kept upon the small 
pile by means of the clock-motion attached to the telescope. The 
needle was then watched during five minutes or longer; almost always 
the needle began to move as soon as the image of the star fell upon 
it. The telescope was then moved, so as to direct it again to the sky 
near the star. Generally in one or two minutes the needle began 
to return towards its original position. 

In a similar manner twelve to twenty observations of the same star 
were made. These observations were repeated on other nights. 

The mean of a number of observations of Sirius, which did not 
differ greatly from each other, gives a deflection of the needle of 2°. 

The observations of Pollux 13°. 

No effect was produced on the needle by Castor. 

Regulus gave a deflection of 3°. 

In one observation Arcturus deflected the needle 3° in 15 minutes. 

The observations of the full moon were not accordant. On one 
night a sensible effect was shown by the needle; but at another time 
the indications of heat were excessively small, and not sufficiently 
uniform to be trustworthy. 

It should be stated that several times anomalous indications were 
observed, which were not traced to the disturbing cause. 

The results are not strictly comparable, as it is not certain that 
the sensitiveness of the galvanometer was exactly the same in al] the 
observations, still it was probably not greatly different. 

Observations of the heat of the stars, if strictly comparable, might 
be of value, in connexion with the spectra of their light, to help us 
to determine the condition of the matter from which the light was 
emitted in different stars. 

I hope at a future time to resume this inquiry with a larger tele- 
scope, and to obtain some approximate value of the quantity of heat 
received at the earth from the brighter stars. 


“On the Fracture of Brittle and Viscous Solids by ‘ Shearing.”’’ 
By Sir William Thomson, F.RS. 


On recently visiting Mr. Kirkaldy’s testing works, the Grove, 


72 Royal Society. 


Southwark, I was much struck with the appearances presented by 
some specimens of iron and steel round bars which had been broken 
by torsion. Some of them were broken right across, as nearly as 
may be in a plane perpendicular to the axis of the bar. On examin- 
ing these I perceived that they had all yielded through a great de- 
gree to distortion before having broken. I therefore looked for bars 
of hardened steel which had been tested similarly, and found many 
beautiful specimens in Mr. Kirkaldy’s museum. ‘These, without 
exception, showed complicated surfaces of fracture, which were such 
as to demonstrate, as part of the whole effect in each case, a spiral 
fissure round the circumference of the cylinder at an angle of about 
45° to the length. This is just what is to be expected when we 
consider that if A BDC (fig. 1) represent an infinitesimal square 
on the surface of a round bar with its sides A C and B D parallel to 
the axis of the cylinder, before torsion, and ABD’O! the figure 
into which this square becomes distorted just before rupture, the 
diagonal A D has become elongated to the length A D’, and the dia- 
gonal B C has become contracted to the length BC’, and that there- 


Fig, 1. 
CC’ Dp C 


A B 


fore there must be maximum tension everywhere, across the spiral 
of which BC’ is an infinitely short portion. But the specimens are 
remarkable as showing in softer or more viscous solids a tendency to 
break parallel to the surfaces of “‘shearing’”? AB, CD, rather than 
in surfaces inclined to these at an angle of 45°. Through the kind- 
ness of Mr. Kirkaldy, his specimens of both kinds are now exhibited 
to the Royal Society. Ona smaller scale | have made experiments on 
round bars of brittle sealing-wax, hardened steel, similar steel tem- 
pered to various degrees of softness, brass, copper, lead. 

Sealing-wax and hard steel bars exhibited the spiral fracture. All 
the other bars, without exception, broke as Mr. Kirkaldy’s soft steel 
bars, right across, in a plane perpendicular to the axis of the bar. 
These experiments were conducted by Mr. Walter Deed and Mr. 
Adam Logan in the Physical Laboratory of the University of Glas- 
gow; and specimens of the bars exhibiting the two kinds of fracture 
are sent to the Royal Society along with this statement. I also 
send photographs exhibiting the spiral fracture of a hard steel cylin- 
der, and the “shearing” fracture of a lead cylinder by torsion. 

These experiments demonstrate that continued “ shearing ”’ pa- 
rallel to one of planes, of a viscous solid, developes in it a ten- 
dency to break more easily parallel to these planes than in other di- 
rections, or that a viscous solid, at first isotropic, acquires “‘ cleavage- 


planes” parallel to the planes of shearing. Thus, if CD and AB 


Geological Society. 73 


(fig. 2) represent in section two sides of a cube of a viscous solid, and 
if, by “shearing”’ parallel to these planes, C D be brought to the 
position C! D’, relatively to A B supposed to remain at rest, and if this 
process be continued until the material breaks, it breaks parallel to 
AB and C'D’. 

The appearances presented by the specimens in Mr. Kirkaldy’s 
museum attracted my attention by their bearing on an old contro- 
versy regarding Forbes’s theory of glaciers. Forbes had main- 
tained that the continued shearing motion which his observations 
had proved in glaciers, must tend to tear them by fissures parallel 
to the surfaces of “shearing.” ‘The correctness of this view for a 
viscous solid mass, such as snow becoming kneaded into a glacier, 
or the substance of a formed glacier as it works its way down a 
valley, ora mass of débris of glacier-ice, reforming as a glacier: after 
disintegration by an obstacle, seems strongly confirmed by the ex- 
periments on the softer metals described above. Hopkins had argued 
against this view, that, according to the theory of elastic solids, as 
stated above, and represented by the first diagram, the fracture 
ought to be at an angle of 45° to the surfaces of “‘shearing.” There 
can be no doubt of the truth of Hopkins’s principle for an isotropic 
elastic solid, so brittle as to break by shearing before it has become 
distorted through more than a very small angle; and it is illus- 
trated in the experiments on brittle sealing-wax and hardened steel 
which I have described. The various specimens of fractured elastic 
solids now exhibited to the Society may be looked upon with some 
interest, if only as illustrating the correctness of each of the two 
seemingly discrepant propositions of those two distinguished men. 


GEOLOGICAL SOCIETY. 
[Continued from vol. xxxvul. p. 311.] 


Nov. 25th, 1868.—Prof. T. H. Huxley, LL.D., F.R.S., 
President, in the Chair. 


The following communications were read :— 

1. “On Floods in the Island of Bequia.” By G. M. Browne, 
Esq. Communicated by the Secretary of State for Foreign Affairs. 

On the 17th of March, at 8 o’clock p.m.,a steady strong wave was 
seen bearing down upon Admiralty Bay; it had no perceptible 
erest, and was three feet in height; it encroached upon the land to 
distances varying from 70 to 350 feet. A second, smaller wave 
followed. No shock of an earthquake was felt. 

2. * Description of Nga Tutura, an Extinct Volcano in New 
Zealand.” By Capt. F. W. Hutton, F.G.S. 

This volcano is situated on the west coast of the North Island of 
New Zealand, between Raglan and the mouth of the River Waikato. 

A section of 15 miles is exposed along the coast, which trends 
in a north-west and south-east direction, showing beds of Me- 
sozoic age forming a synclinal trough between the south head of 
Waikato and Otehe Point, and descending below the sea-level at Wai- 
kawau. Upon them lie Tertiary strata, following the same synclinal 


74 Geological Society :— 


curve as the older rocks, and broken through, nearly in the centre 
of the curve, by the basaltic cone of Nga Tutura. This volcano is 
about 600 feet high, and is chiefly composed of basaltic lava-streams, 
with but little tuff. The eruption is considered by the author to 
have been submarine. 

Capt. Hutton then stated his conviction that the fluid matter 
which escaped was not connected with a central molten interior of 
the earth, but was derived from rocks not much more than 1000 
feet in depth, and that the synclinal in question was caused by a 
subsidence into the cavity thus formed. 


3. “On Dakosaurus.”” By J. Wood Mason, Esq., F.G.S. 

The Kimmeridge Clay of Shotover Hill has yielded five specimens 
of the teeth of this reptile, now for the first time represented as a 
British genus. After noticing the bibliography of the subject, and 
the presence of specimens in various museums, the author proceeded 
to describe the characters of the teeth. They are large, conical, 
incurved, and slightly recurved, having two sharp, prominent, cre- 
nulated, ‘longitudinal ridges, which are situated mudi a between 
the convex and concave curvatur es. 

This reptile was regarded by the author as foreshadowing the 
form of dentition that characterizes the existing group of Varanide. 
If the materials were at hand for a complete definition of its com- 
parative osteology, Dakosaurus would probably exhibit a combina- 
tion of Lacertilian and Crocodilian characters, but with the croco- 
dilian elements predominant. 


The PrestpEnt differed from the author as to the conclusions he 
drew from the structure of the teeth. The teeth of existing Croco- 
dilia had been but imperfectly described, and he thought he could 
point out among existing Crocodiles teeth bearing the character 
which the author regarded as Lacertilian. He agreed with Prof. 
Owen in regarding Dakosaurus as Crocodilian rather than Dinosau- 
rian or Lacertilian. 


4, “On the Anatomy of the test of Amphidetus (Echinocardium) 
Virginianus, Forbes; and on the genus Breynia.” By P. Martin 
Duncan, M.B., F.R.S., Sec. G.S., &e. 

After a careful examination of the Miocene Amphidetus from the 
Virginian Tertiaries, the recent species of the genus from the Ku- 
ropean and Australian seas were stated to form a group of yery 
closely allied forms. The Crag specimen of A. cordatus described 
by Forbes could not be found; but the examination of a series of 
recent specimens decided that they were not specifically different 
from the Miocene form. 

The unusual form of the ambulacral spaces, the nature of the 
fasciole crossing them, and the resulting absence (more or less) of 
pores within the fasciole, were asserted to be of a third-rate cha- 
racter as regards structural importance; and the author did not 
consider that the genera chinocardium, Breynia, Lovenia, &e. 
had a common origin or that there was a close genetic relationship 
between them because they had this fasciolar structure. He con- 


Notes of a Geological Reconnaissance in Arabia Petrea. 75. 


sidered the fasciole to be an appendage to several generic groups 
which were distinctly separated by other structural distinctions, 
The result of an examination of the Nummulitic Breynie in the 
Society’s collection satisfied Dr. Duncan that there were only race 
characters separating them from Breynia Australiensis—a recent 
Kchinoderm. The persistence of these species, widely distributed 
and of great geological age, was very remarkable. 


December 9th, 1868.—Prof. T. H. Huxley, LL.D., F.R.S., 
President, in the Chair. 


The following communication was read :— s 

“ Notes of a Geological Reconnaissance in Arabia Petrea.” By 
H. Bauerman, Esq., F.G.S. 

The district to which this paper referred is that between Suez 
and the lower part of Wady Ferran in the peninsula of Arabia 
Petrea, and includes the copper and turquoise mines worked by the 
ancient Egyptians. The rocks within this area were classified as 
follows :— 

1. Gneiss and granites, forming the central chain of Sinai and the base of all 
the stratified deposits. 

. Red Sandstone series. 

. Cretaceous rocks. . 

White limestones, with flints, salt, and bitumen. Eocene. 
. Flint conglomerate, with coralline limestone. Miocene. 
Gypseous marls of Wady Taragi. 

- Reconstructed gypseous sands and conglomerates. 

. Raised beaches, coralline and miliolitic limestones. 

. Alluyium and desert drift. 

The Red Sandstone series consists of three members, a thin bed 
of limestone being the central and containing remains of Encrinites 
referred by Mr. Etheridge to the Muschelkalk form Encrinites moni- 
hformis. Iron, manganese, and copper ores are found near Nasb 
and Serabib el Khadem. ‘The turquoise mines of Wady Maghara, 
which were referred to the same horizon, are among the most ancient 
monuments of the world. The author considered that the tools 
employed were flint chisels or flakes, and hammers made from pieces 
of a neighbouring doleritic lava. he flakes were supposed to have 
been mounted on wooden blocks. 

The Cretaceous rocks, which rest unconformably on the Triassic 
sandstones, consist chiefly of green sand, with alternations of thin 
argillaceous limestones, containing Echinoderms which prove them 
to be of the age of the Upper Greensand. Above them comes the 
Hippurite-limestone series. The fossils were described by Dr. Dun- 
can, F.R.S., in a subsequent communication. 

The white limestone, with flints, the next group of rocks in 
ascending order, strongly resembles the European chalk with flints ; 
but, according to the author, it must be regarded as representing the 
nummulitic limestone of Egypt, as several species of Nummulites 
have been detected in it near the shores of the Red Sea, below 
Wady Gharandel. The Miocene flint conglomerate series is a mass 
of coarse flint shingle alternating with these coralline limestones. 
The author considered that a great physical break ensued between 


CO 00 ST S> OUD 09 DO 


76 Intelligence and Miscellaneous Articles. 


the Eocene and Miocene period, while a gradual transition occurred 
between the Cretaceous and Eocene rocks. 

In the gypseous series which overlies the flint conglomerate 
several peculiar effects were noted, owing to the easy manner in 
which tumbled and broken masses of gypsum are reconstructed by 
partial solution and recrystallization when they have been removed 
from their original position by the slipping of the underlying shales. 

The alluvial gravels of the Sinaitic valleys are generally similar 
in containing a coarser and a finer material; the latter is the elder, 
and has apparently been deposited by comparatively slow-flowing 
streams. In conclusion, the author called attention to the evidence 
of lakes, marshes, and streams having formerly occupied what are 
now dry barren valleys. 


X. Intelligence and Miscellaneous Articles. 


ON THE HEAT CONSUMED IN INTERNAL WORK WHEN A GAS DI- 
LATES UNDER THE PRESSURE OF THE ATMOSPHERE. BYM.J. 
MOUTIER. 

M CLAUSIUS has shown that the quantity of heat necessary to 
He heata body consists in general of three distinct parts: the first 

represents the increase of the quantity of heat actually existing in the 

interior of the body; the second has for its equivalent the external 
work, and the third the internal work. When a gas dilates under the 
pressure of the atmosphere, the external work is easily estimated. If 
we call 6 the density of the gas compared with the air, and @ the coef- 
ficient of dilatation of the gas under the pressure of the atmosphere, 
the increase of volume experienced by 1 kilogramme of gas in passing 
from zero to]° is, in cubic metres, __® | Moreover the atmo- 
1:29382x6 

spheric pressure upon one square metre is equal to 10333 kilogs. ; 

consequently when 1 kilog. of gas dilates from zero to 1° under 

the constant pressure of the atmosphere, the external work is equal 
10333 x a 

a 

1°2932 x0 

by dividing this number by the mechanical equivalent of heat, 425. 

If we represent by C the specific heat of the gas under the pressure 

of the atmosphere, by K the absolute specific heat independent of 

the physical condition of the body according to M. Clausius, and by 

y the heat consumed in internal work, we have, when 1 kilog. of 

gas dilates by 1° under the pressure of the atmosphere, 

@xe Ka buy 10888 2a ae 
425 1:29382xd 

This equation contains two unknown quantities, K and y. 
Messrs. William Thomson and Joule have succeeded in demon- 
strating the existence of internal work in a gas which expands 
without effecting any external work. ‘The diminution of tempera- 
ture which accompanies the flow of the gas allowed the calculation 
of the proportion of the internal to the external work when the gas 


and the heat consumed in external work is obtained 


Intelligence and Miscellaneous Articles. 77 


dilates with displacement of the point of application of an external 
pressure ; this proportion, which is insensible in the case of hydrogen, 
is perfectly appreciable with air, and much greater in the case of 
carbonic acid. 

M. Hirn has assumed the internal work to be negligible in hy- 
drogen. He has deduced from the preceding equation the absolute 
specific heat of that gas; and by applying the law of Dulong and 
Petit to the absolute specific heats, he has been able to obtain under 
this hypothesis the values of y with respect to various gases. By 
combining the equation (1) with the law of absolute specific heats, 
Wwe may compare the values of y for various gases without the as- 
sumption of any hypothesis with regard to hydrogen. 

Air and Hydrogen.—According to the experiments of M. Reg- 
nault, we have, for hydrogen, C=3'409 between zero and 200°, 
a=0°003661 between zero and 180°, and 6=0°06926. The equa- 
tion (1) gives for this gas 

K=29°41523—y. . . « hid may 2) 

The experiments of M. Regnault give for air, C’ =0°23751 be- 
tween zero and 200°, «’=0° 00367 eeween zero and 100°. The 
equation (1) applied to this gas gives 

We Ome EBay, Lunt LS Same eae Ce) 

Now 100 parts by weight of air contain 77 parts of nitrogen and 
23 parts of oxygen; if we apply, with M. Clausius, the law of abso- 
lute specific heats to air considered as a compound body, designating 
by K, and K, the absolute specific heats of nitrogen and oxygen, 

100K'=77K,+23K,. 

But if we apply the same law to nitrogen, to oxygen, and to hy- 
drogen, the atomic weights of which are to each other as the num- 
bers 14, 16, and 1, 

K=14K,, K=16K,. 
By transferring these values of K, and K, into the preceding 
equation, 
K’=0°069375K ; 
and by replacing K and K’ in this last equation by the values de- 
duced from the equations (2) and (3), we have, finally, 
y' =0°069375y+0°000956. 

Carbonic Acid and Hydrogen.—The data furnished by M. Reg- 
nault’s experiments for carbonic acid are, C’’=0°21692 between 10° 
and 210°, «’=0:003710 between zero and 100°, @’=0°52901. The 
equation (1) gives for this gas 

Brea GEES027 v1. atita 4 Midian Aa) 

If we represent by 3 the atomic weight of iednaaen, the mean 
atomic weight of carbonic acid is 22, ‘and according to the law of 
absolute specific heats, 


1K = 22K", 
Replacing K and K" in this equation by the values deduced from 
the equations (2) and (4), we have 
y' =0'06818ly+0-006628. 


78 Intelligence and Miscellaneous Articles. 


In these calculations the specific heats are taken between zero and 
200°, and the coefficients of dilatation are in relation to the interval 
from zero to 100°; it is probable that between 100° and 200° the 
coefficients of dilatation of air and hydrogen retain sensibly the 
same value, and that the coefficient of dilatation of carbonic acid 
tends to diminish, so that the value calculated for y” is a little too 
small. 

Conclusion.—If for each of these three gases (hydrogen, air, and 
carbonic acid) we take the proportion of the heat consumed in in- 
ternal work to the specific heat under a constant pressure, we find the 


tl 


: Ye OG YE 
following values for a? a Gi? 
Fydropent. 163.0%, Teuoae 0°297 
Aare iat SOR Se owed ss 0°297 40008 
Carbonic*acials se aie we 0°317+0:035 


We see, therefore, that the heat consumed in internal work, when 
the gas dilates under the constant pressure of the atmosphere be- 
tween zero and 20U°, isa fraction of the specific heat under constant 
pressure, which goes on increasing from hydrogen to air and from 
air to carbonic acid. 

We may likewise compare the quantities of heat expended in in- 
ternal work under the same circumstances by considering the three 
gases under the same volume at the temperature of melting ice. If 
we take as the common volume the volume occupied by 1 kilog. of 
hydrogen, the weight of equal volumes of air and carbonic acid are 
respectively 

1 kilog. eu 1 kilog. 

0°06926 0°06926 
and the quantities of heat consumed in internal work are respectively 
for these three gases, considered under the same volume, 


* 1°529; 


Say! OE ln: _1:529 
706996 = 06996" 
or Hydrogen.. hh ceed ey 
Ire Wo ee eri b. anen UgleOOl ae sabes 
Carbonic acid ......... 1:505y+0°146. 


These quantities of heat likewise increase from hydrogen to air 
and from air to carbonic acid. 

The law of Dulong and Petit applied to absolute specific heats, 
therefore, leads us to arrange hydrogen, air, and carbonic acid, with 
regard to internal work, in the order which the experiments of 
Messrs. W. Thomson and Joule assign to these very gases.— 
—Comptes Rendus, January 11, 1869, vol. Ixviii. pp. 95-98. 


INVESTIGATIONS ON OBSCURE CALORIFIC SPECTRA. 
BY M. DESAINS. 
I have the honour to lay before the Academy the results of new 
investigations on obscure calorific spectra. The questions I have 
deavoured to solve are the following :— 
(1) Given, in a spectrum formed by a prism of definite nature and 


Intelligence and Miscellaneous Articles. 79 


angle, a group of rays of almost the same refrangibilities, and forming 
a band of feeble but constant magnitude, to investigate how the ca- 
lorific action of this band varies with its mean refrangibility on the 
one hand, and with the nature of the source of heat on the other. 

(2) To investigate further how the transmissibility of such rays 
through a screen of given thickness changes when either their mean 
refrangibility is varied, or else the nature of the source or that of 
the absorbent is altered. 

The difficulties experienced in these researches are those always 
met with in attempting to form, with rays other than the solar rays, 
pure spectra of an intensity sufficient for calorimetric experiments. 
I do not dare to affirm that I have completely solved these difficul- 
ties; but, at any rate, I think I have succeeded in finding the condi- 
tions in which the mixture of the rays is so feeble as not to exert an 
appreciable influence on the result of my experiments. 

. To produce these spectra I concentrated the rays from the source 

of heat on a narrow slit. A lens with a focus of about 16 centims. 
was placed about 30 centims. from the slit, and formed a defined 
image of it in the conjugate focus. The prism placed behind this 
lens deflected the rays, and transformed the colourless image into one 
whose luminous part extended over from 0'015 to 0°025 metre, ac- 
cording to the nature of the prisms used. The thermoscopic pile 
was linear and very narrow, its aperture being scarcely broader than 
0-001 metre. 

Under these circumstances the purity of the spectra, and therefore 
the certainty of the results furnished by analysis, must obviously 
depend on the breadth of the slit which served as the source of heat. 

The ideal case would be that in which this slit was infinitely nar- 
row. ‘This cannot be realized; but in all the experiments whose 
results I am about to indicate, I found that I could vary the breadth 
of the slit from 0°0005 to 0°0015 metre (that is, in the proportion 
of 1 : 3) without at all changing the conclusions to which I was led 
concerning the distribution of heat in the various parts of the spec- 
trum, or regarding the absorptions which the consecutive parts of 
these layers experience in different media. I think I am thence 
justified in assuming that in my experiments any injurious influence 
of the mixture of the rays was eliminated. 

I worked with four different sources :— 

(1) A thick platinum wire kept at a red heat in the flame of a 
Bunsen’s burner. 

(2) A bat’s-wing burner with the section turned towards the slit . 

(3) An ordinary moderator lamp. 

(4) A Bourbouze lamp. The flame cf this lamp is a kind of 
thimble of very close platinum-wire gauze, kept at a red heat by 
means of a gas-flame fed by compressed air. 

With the first two sources I used lenses and prisms of rock-salt ; 
with the two others glass lenses, and prisms of flint glass or of rock- 
salt. In the experiments in which Bourbouze’s lamp was used, I 
modified the radiation by making it pass through a glass trough full 
of water interposed between the source and the slit. 

It would be impossible to detail all the results of my experiments ; 


80 Intelligence and Miscellaneous Articles. 


but I will give a comparative view of the results obtained with a 
beautiful prism of rock-salt, using as a source of heat either the gas- 
lamp or Bourbouze’s lamp. 

All the arrangements were the same in the two sets of experiments; ; 
in both cases the prism was in the position relative to the minimum 
deviation of the red, which for the extreme red was 40° 18’. Under 
these circumstances, working with the Bourbouze lamp, and taking 
as the unit of effect that obtained in the extreme red, that obtained 
at half a degree from this position is 2°2, at 1 degree 0°3 only, and at 
1° 25' itis zero. At the same time the rays of the first three layers 
are transmitted through a fluor-spar trough containing a layer of 
water 2 millims. in thickness, in the proportionsof 0:90,0°60,and 0°75. 

On the other hand, with a bat’s-wing burner, taking as unit the 
effect produced in the extreme red, that obtained at half a degree 
from this position becomes 4 instead of 2°2, at 1 degree it is 5 in- 
stead of 0°3, and at 2 degrees it is still very appreciable. The spec- 
trum thus extends much further into the obscure region. But it is 
far less transmissible through water. For the band at half a degree 
from the obscure red the transmission is scarcely 0°14 instead of 
0:60, and for that at a distance of 1 degree from the red it becomes 
insignificant. 

Other differences are met with between the spectra furnished by 
these two sources. With the gas-burner, under the conditions of my 
experiments, no heat is found either in the yellow or the green, and 
still less in the extreme white of the spectrum. With Bourbouze’s 
lamp I easily found some in the green, although the intensity of the 
maximum was not different in the two cases. 

I may also be permitted to adduce the following results. 

Working with Bourbouze’s lamp, the transmissibility of rays of 
the maximum through water seemed a little less than that of the rays 
which precede or succeed them in the order of refrangibility. 

A similar effect is observed in the solar rays; I have also observed 
a similar maximum in investigating the action of a trough full of 
chloroform on the rays from a gas-burner. 

Iodized chloride of carbon allows all the obscure part of the radia- 
tion from this source to pass in abundance; in other words, the 
transmission through it of the extreme red rays is very little different 
from that of the other obscure rays ; if there be any difference, it is in 
favour of the transmissibility of the least-refrangible rays. The lu- 
minous part of the spectrum is reduced by the action of this absorbent 
-to two beautiful bands, one red and the other violet, separated by a 
well-defined dark space. 

The transmissibility through ether diminishes with the refrangibi- 
lity when a moderator-lamp is used as source of heat; but it is very 
appreciable for rays of the maximum. 

All these experiments agree with those I had the honour of pre- 
senting to the Academy the 9th of last August, to prove that if, in 
pure spectra, we isolate the pencils formed of rays whose deviations 
by the same prism are almost identical, these pencils may be very 
unequally transmissible through the same absorbent if they arise 
from different sources. —Comptes Rendus, Noy. 30, 1868, 


THE 
LONDON, EDINBURGH, ann DUBLIN 


PHILOSOPHICAL MAGAZINE 


AND 


JOURNAL OF SCIENCE. 


(FOURTH SERIES.] 


UG Us  Veog, 


XI. On the Constants of Capillarity of Molten Bodies. 
By G. Quincxy*, 


1. J POINTED out ina previous communicationt that the con- 

stants of capillarity of different fluids might be compared 
at temperatures in the immediate neighbourhood of their solidi- 
fication- or melting-points. [have now thought it proper to ex- 
tend the determinations given elsewhere to a greater number 
of chemical elements and compounds, as the forces which the 
particles of any given fluid exert upon each other certainly de- 
pend on circumstances less complicated than those between par- 
ticles of heterogeneous substances, and we may hope accordingly 
to obtain some clearer ideas in this way of the nature of the 
perplexing molecular forces, which act (almost always) only at 
exceedingly small distances. 

The following inquiry rests on two principles, previously 
established by Dr. Thomas Young, which, however, I may, for 
the sake of connexion, demonstrate 1 this place. 

2. A mass of fluid, m, at the point P of the free surface (2. e. 
bounded by vacuum) of a fluid is attracted by another particle 
A of the surface-layer (fig. 1), from which its distance 1s d, with 


* Communicated in abstract to the Royal Academy of Sciences, Berlin, 
May 28,1868. ‘Translated by Professor Jack, Owens College, Manchester. 

+ Berliner Monatsbericht, Feb. 27, 1868, p. 132. Poge. Ann. vol.cxxxiv. 
p. 356. 

Phil. Mag. 8. 4. Vol. 38. No. 253. Aug. 1869. G 


82 Prof. G. Quincke on the Constants of 


the force mm'd(d). The direction of this Fig. 1. 
force is the line joming the particles. The 
function of the distance depends on the re- 
sultant of attracting and repelling forces, and 
disappears when d is larger than the radius 
of their sphere of action, which is a barely sen- Q 
sible magnitude. The plane through A and 
the normal at P to the fluid surface, cuts the = 
latter in a curve which, near P, coincides d, 
with a circle whose radius is p. A rp 

A second particle, m,, symmetrically situ- 
ated at B on the other side, exerts the same force as A. The 
components of these two forces perpendicular to the normal de- 
stroy one another; the sum of the components parallel to the 
normal, which is the resultant of the two forces, is 


2mm, (a) cos (7, d) =mm,d(d) a 


We obtain the action of all the molecules of the normal section 
on the particle m situated at P by sunming up these expressions 
from d=0 to d= a certain value exceeding the indefinitely small 
radius of the sphere of molecular action. Neglecting the con- 
stant, we have for this sum 

Simm!) = - 

Calling p, the radius of curvature of a second normal section 
which is perpendicular to the former, similar considerations give 
a similar result, and the whole action of the particles in two 
normal sections perpendicular to each other on a particle at the 
point P is | ay 

A+ u¢ -. =), 

Pics rudeat 

where & is the attraction which the particles of two normal sec- 

tions perpendicular to each other exert on an element of the 

plane surface of the size of the unit surface. The well-known 
principle of Euler gives 

ein od 1 

Bolieh a By 

where R is the greatest and R, the least radius of curvature on 

the surface. The entire action of the mass of fluid on P, or the 

capillary pressure (p) at the poimt P of the fluid-surface, is 


therefore l l 
or, introducing two new constants for these summations, 


r=K+5(qtE) ot 


= constant, 


Capillarity of Molten Bodies. 83 


This pressure is normal to the surface. K is the pressure at a 
point on the plane fluid-surface, H is the difference of pressures 
which would be exerted on the unit of a plane fluid-surface and on 
the unit surface of a sphere with unit radius. The right-hand term 
of (1) may become negative if the two radii of curvature lie out- 
side the fluid, or when the surface is concave. Both H and K 
depend only on the nature of the fluid; both stand for the con- 
stants which Laplace* denoted by the same letters. The constants 
f and & are proportional to the masses which exert influence. 
If the density of the fluid be the same inside and on the surface 
and be called «, & and / (and therefore also K and H) must be 
proportional to e* for the same values of } and the same values 
of the radius of the sphere of activity. Accordingly, assuming 
an increasing temperature and taking ¢ as constant, the capillary 
pressure must decrease proportionally to the square of the density. 

Experiment teaches that (1) is true for points in the free sur- 
face not only in presence of vacuum, but also when that surface 
is bounded by any gas or by atmospheric air. 

3. If z be the elevation of a point P ina capillary surface above 
the level or horizontal part of the surface, we deduce from (1), 
and from the hydrostatical principle that there must be the same 
pressure throughout a horizontal plane within the fluid, 


Myz= = (+ +e) aie kes 


in which M is the mass of a unit volume of a fluid, and g the 
accelerating force of gravity. For surfaces of rotation and points 
at distance xz from the axis of rotation we have, therefore, 


dz 
Ticatlarsitt athe 5 
ey e ° ° ® ( ) 
da? 


If a hollow cylinder, the radius of which is 7, be immersed in 
a fluid with a level surface, and if the axis of z be its axis, the 
volume between the two cylinders which have z for their height 
above the level, and # andz+dz for the radu, will bez. 27x da; 
and the entire weight W of the fluid which is raised above the 


level 1 ‘ : 
0 


or, substituting the value of z given in (8), 


Pd bane 2 
atte 2 ate (BY 
Meets) (+ aa) J 


* CEuvres de Laplace, vol. iv. p. 407 (1845). 
G2 


84: Prof. G. Quincke on the Constants of 


If we call w the angle which the last element of the fluid sur- 
face, where it meets the solid, makes with the vertical solid 
bounding wall, 


dz 
=| Ee t dx B 
& ae rk ( FEO = COS ; 
1+ 7 a 
dx? 


and equation (4) becomes 
NY pad 
ap = g 608. ~- » te ecb te) a re 

The weight of the fluid per unit of length of the circumference 

of the cylinder which is lifted above the horizontal level is 


> cos @; 7. e. it is independent of the radius of the cylinder, and 


depends only on the nature of the fluid and of the enclosing solid 
wall. The equation is also true for cylinders not hollow; and 
every vertical wall may be considered approximately a part of 
such a holiow or solid cylinder. 

In fluids which wet the solids (7. e. where the last element of 
the fluid layer is vertical) w is 0, and 

iis FEE Or i a 
aan ae 
The weight of afluid sustained per unit of length of the line of con- 
tact (which is the line of intersection of the vertical wall and the 
capillary surface) 2s a constant quantity, and measures the mutual 
attraction of the particles of the given fluid—that is, is its cohe- 
sion- or capilarity-constant. 

Since Poisson’s time, the quantity 

9 
a es eee 

g Mg 

is frequently called the constant of capillarity. The advantage 
is, that when it is divided by the inner radius it gives the mean 
elevation above the horizontal level to which a fluid which wets 
the solid ascends. The elevation of a fluid which wets a plane 
vertical wall, or the rise of the highest point of the curved fluid 

surface over the horizontal level, is «. 

4, Equation (7) is true also for drops which are formed at 
the mouth of a vertical pipe, on the assumption that, in con- 
sequence of the gradual accession of new fluid, the same pres- 
sure 1s found in the interior fluid, at the mouth of the pipe, as in 
a level fluid surface. The drop goes on increasing till o=0, or 
till the highest element of the fluid is vertical, and then it falls off. 
If the radius of the cylinder on which the drop is formed be very 
small, the weight of the portion of fluid which remains hanging 


Capillarity of Molten Bodies. 85 


may be neglected, and the weight of the portion of the drop 
which falls may be treated as the W in equation (7). 

We may equally neglect the fact that new fluid comes down 
at the time when the drop is separating, which tends to make 
the drop too large. When this access of fluid is too great, 
on the other hand, there is a thin jet of fluid which may readily 
be resolved into smaller drops by taps from the outside. This 
is the explanation of the fact that, in the case of many fluids, the 
drops attain a maximum for a determined velocity in the supply 
of the issuing fluid *. 

Although it thus appears that the process of the formation of 
drops 1s exceedingly complicated, the application of equation (7) 
would give us approximate values of the capillarity-constants « ; 
and this method has at least the recommendation that there is 
no better, or none which is not complicated by too many expe- 
rimental difficulties. 

5. The experiment is simplest for gold and silver. Vertical 
threads of these metals were held by pincers and brought down 
into a small gas-flame the dimensions of which were not greater 
than 3 millims. diameter and 8 millims. height, so that the metal, 
as soon as it was melted, formed in a drop at the lower end of the 
thread. The drop increased in this way, and rose on the solid 
thread, which was gradually lowered to the flame. When it 
was too large it fell into a vessel filled with water, and was 
immediately solidified, and afterwards dried and weighed. After 
a little practice it became easy to avoid any shaking of the 
threads, by which the drops were apt to be too soon detached. 

The molten metal was colder above than below; and at the 
upper part the temperature was only a little above that of the 
melting-point of the substance. The weight of the drop in mil- 
ligrammes, divided by the circumference of the wire in milli- 
metres, gives us accordingly the constant of capiliarity « for that 
melting-point. 

The shorter the distance between the drop and the pincers 
holding the wire, the larger the drops seemed to be. This was 
due probably to the lower temperature of the drop, in conse- 
quence of the abstraction of heat by the wire and pincers. 

Further, the drops from a gold wire melted over a common 
gas-flame and over one fed with oxygen weighed nearly the same ; 
so that the influence of temperature in these experiments may 
be neglected. 

The diameter of the wires was measured by a microscope and 
an eyepiece-micrometer which gave one hundred divisions. Hach 
single division (and tenths of a division could easily be esti- 
mated) corresponded, therefore, according to the magnifying- 
power used, to from ‘007 millim. to-02 millim. 

* Compare Pogg, Ann. vol. exxxi. p. 130, 


86 Prof. G. Quincke on the Constants of 


The silver was stated to be chemically pure; the gold was 
slightly alloyed with silver, chiefly to facilitate the process of 
wire-drawing. 

Glass threads, drawn out before the lamp from a thicker piece 
of glass, were also treated like wires. The determinations, how- 
ever, were less trustworthy, because glass becomes soft before 
melting, and accordingly, through a commencing drop-formation 
above the fluid drop, the glass cylinder from which the drop falls 
off is really widened. A series of determinations was made for each 
wire, and the mean of them taken. The results collected below 
prove that the weight of the drops really increases (as it ought to 
do according to theory) in proportion to the diameter of the wires. 


_ Silver. | Gold. 


2r. W. ae 2r. W. a. 2r. 


millim./grm. |mgrms,|/millim./grm. |mgrms.|millim./grm. |mgrms. 
0:4971| 0:0733| 47-14 || 0°2566 0-080 | 99-24 06709) 0-0422; 20-02 
0-2318)| 0:0299| 41-13 || 02009 0-075 |103. - || 0-5232/ 0:0273) 16-62 
(:0993) 0:0130) 41°66 || 0-0695| 0:0215| 98-42 || 0:2441) 0-0134| 17-48 
O077FS0 O10) AT OO Cee tere al eee) | ieecee er 0:2006; 00115) 18°24 


Mean | 42°75 || ...... Mean |100-22 || ...... Mean | 18:09 


6. The measurements for platinum and palladium wires were 
made in the same way as those for gold and silver. Oxygen, 
however, was conducted into the gas-flame through a platinum 
nozzle. Palladium was volatilized with such remarkable rapi- 
dity in the oxyhydrogen flame, that I might compare the palla- 
dium drops in this respect to ether drops at the ordinary tem- 
perature. The melting- and boiling-points appear to be very 
near each other, since | was unable with an ordinary blow- 
pipe-flame (the ‘pointed flame of the glass-blowers) to melt the 
metal; the drop lost more by volatilization, as soon as it had 
attained a certain size, than it gamed by fusion of new wire, 
Accordingly I found the values of a always too small in my nu- 
merous experiments, and that which I give below makes no pre- 
tence to accuracy. When palladium solidifies, there are formed 
on the smooth drop-surface needle-shaped excrescences, which 
give the mass a peculiar appearance. 


Platinum. Palladium. 
2r. We ah. 2r. Wie ah. 
millim. jgrm. mgrms. |/millim. erm. merms. 
05675 | 02912 | 163 || 0-6829 | 01300 | 163-4 


0-3689 | 0:2055 177-4 || 
071921 | 0:0996 L651 1) 
0:0998 | 0:0580 169°8 
0:0767 | 0-0410 169°9 


Mean | 169-041] » | 


Capillarity of Molten Bodies. 87 


7, To obtain drops of éim and selenium, these substances were 
molten in glass tubes, the lower part of which was funnel-shaped, 
ending in a thin vertical pipe. The part of this pipette-shaped 
pipe which was cut off by the glass-knife was used to determine 
the inner or outer diameter by means of microscope and eyeplece- 
micrometer. Figs. 2 and 3 show the drop attached to the cuter 
and inner circumference. Determinations in which the drops 
had formed partly on the inside, partly on the outside (fig. 4), 


Figs 2, Fig. 3. Fig. 4. 


or where the outer glass wall was wetted 
by the drops (fig. 5), were rejected. The 
drops fell into a flat porcelain saucer filled 
with water, or which was simply kept 
cold. I took great pains to see that the 
drops were formed as slowly as possible. 
They followed each other usually so much 
the more slowly the more the cooling 
down progressed. The last drop which 
fell before complete solidification was 
heavier than that preceding, which was 
again heavier than that before it, and so 
on; so that the capillarity-constant in- 
creases with diminishing temperature. 
The difference, however, is insignificant, 
and in some cases I have given means 
collected from these last drops. Strictly 
speaking, the last drop determines the 
eapillarity-constant in the neighbourhood 
of the melting-pomt. From the upper 
part of the pipette-shaped vessel a piece of india-rubber tubing 
went to the mouth, which made it easy to regulate the speed 
of the issuing fluid. 

The determinations for zinc were made in the same way; but, 
in consequence of the higher melting-point, it was found more 


88 Prof. G. Quincke on the Constants of 


convenient to use the glass-blower’s flame instead of that of an 
ordinary Bunsen. 


Selenium. | atime Zine. 


Pa eo ilo Ln eee. 


miilim./grm. See aen grm. |mgrms.|/millim.jgrm. |mgrms, 
0-9670) 0°0214| 7-045 | 0-665 | 0-1200) 57-41 || 0-8368) 02122) 80-74 
0°7164| 0-:0158) 7-021 || 0-642 | 0:1245) €1-69 || 0-7285) 0-1920| 83-90 
0°6688) 0°0155| 7°377 || 0-549 | 0-0976| 56°52 || 0-7020) 0:1847| 83°75 
0°6125| 0:0140, 7:276 0-470 | 0:0800| 54-25 
0:437 | 9-090 | 65°39 

| 0-395 | 0-072 | 58:08 

| 0'311| 0-064 | 65°62 


a ee ee 


Mean | 7-180 


ieee Mean | 59°85 |) ..... Mean | 82:79 


8. In the case of bodies which, like phosphorus, cadmium, lead, 
antimony, bismuth, ‘oxidize easily, 1t was necessary to produce 
the drops in an atmosphere of carbonic acid. In the case of 
zine also, where oxidation might have been suspected in the open 
air, several of the experiments were performed in an atmosphere 
of carbonic acid, which demonstrated that the capillarity-con- 
stants are little, if at all, dependent on the nature of the sur- 
rounding gas when the surface is not altered by oxidation. 

The phosphorus was melted in a test-tube under water, a ball 
of india-rubber fastened on the glass tube which had been drawn 
out into the shape of a pipette, and the molten phosphorus 
sucked up by pressure on this ball. The glass pipe was care- 
fully dried on the outside with blotting-paper. In these ex- 
periments it often happens that the phosphorus remains in a 
fluid state far below its melting-pomt, and that we find the 
weight of the drop or the capillarity-constant too large. Pos- 
sibly the abnormal result given by Dupré*, who found a =8°407 
milligrammes for 46° C., a number about twice as large as that 
which is deduced from my experiments, isto be explained in this 
way. ‘The drops taken up under water remain also fluid for a 
considerable time ; and it happens frequently, when they follow 
each other quickly, that several gather themselves into one, 
which then itself continues fluid for a considerable time. In 
the determination of the constant of capillarity it is natural in 
this case to take account of the number of drops which have 
been collected into one. 

Zine and antimony were molten in the flame of the glass- 
blower’s lamp, cadmium and lead in that of a Bunsen’s burner. 

The carbonic acid was obtained from marble and hydrochloric 
acid, led through a washing-bottle with a solution of carbonate 
of soda and a series of Babo’s bulb-tubes, which were also 


* Ann, de Chim. et de Phys. vol. ix. (1866) pp. 330 & 384. 


Capillarity of Molten Bodies. 89 


wet with this solution, so as to remove the last traces of hydro- 
chloric acid which might be taken over along with it. A black 
caoutchouc tube and a vertical glass pipe conducted the carbonic 
acid to the bottom of a beaker filled with water to the height 
of several centimetres, over the edge of which the gas then 
escaped. The lower opening of the pipette tubes was brought 
into this atmosphere of carbonic acid; and care was taken, by 
moving them about, that the different solidified drops in the 
beaker-glass should fall at different places on the bottom. 

In the cases of cadmium and phosphorus, which are very rea- 
dily oxidized, this arrangement was frequently unsatisfactory. 
The carbonic acid was in this case led into the lower end of a 
glass tube, A B, of 120 millims. height and 20 millims. dia- 
meter, which dipped into a saucer of porcelain filled 15 millims. 
high with water. The narrow glass tube was completely filled 
with pure carbonic acid; a slow current of gas prevented its 
being mixed by diffusion with atmospheric air. Care was taken, 
by shifting the porcelain saucer under the fixed glass tube in the 
middle of which the drops formed, tbat the single drop should 
solidify at different places. 

The formation of drops in the different substances takes place 
in different, and frequently in highly characteristic ways. A 
mere glance at the solidified drop is sufficient to decide from 
which of the metals it has been formed. 

Cadmium exhibits a remarkable phenomenon when the car- 
bonic-acid atmosphere contains traces of air. <A long jet of 
molten metal then falls out of the opening of the glass tube, and 
speedily becomes tarnished at different points. These spots show 
clear thin cracks parallel to the axis of the cylindrical jet. This 
swells regularly out at certain places, where a formation of drops 
takes place, while the metal surface appears as if oxidized. 


Zine (in CO2). | Lead (in CO2). 
2r. WwW. | ZT | WE a. 
millim. /grm. imgrms. | millim. ‘arm. imgrms. 
09949 0:2550 | 81:58 || 0579 | 0-0840 | 46:17 
0°8756 | 0-2620 | 95°23 0-543 | 00754 | 44:20 
0:7668 | 0:2225 | 92:37 || 0:288 | 0:0422 | 46°61 
0°7534 | 0-1930 | 81:56 | 
Meang sh) 84:68. il! 1... Mean 45°66 
Phosphorus (in CO”). Antimony (in CO?). 


| 08882 | 0-0127 | 4559 | 1308 | O-1040 | 25-80 
08497 | 0-:0123 | 4-610 | 0-9224 | 0-0724 | 24-99 
0-8024 | 0-0115 | 4:562 || 0:6357 | 0-0480 | 24-48 
0:5325 | 00092 | 3-471 | 
0:5066 | 0-0060 | 3-770 

Mean | 4-194 Mean| 24-92 


90 Prof. G. Quincke on the Constants of 


Bismuth (in CO?). 


2r. Ne a. 
millim. grm. mgrms. 
0°8650 01150 42°31 
0.5265 0.0598 36°16 
0-4238 0:0500 37°97 
03609 00450 39°69 
Mean 38°93 


9. The same process as was applied in the case of phosphorus 
was extended to sodium and potassium, with this difference, 
that the water was replaced by petroleum, in which the drops 
were received, and that the carbonic acid, after its treatment 
with carbonate of soda, was thoroughly dried in a wash-bottle 
and Babo’s bulb-tubes by means of hydrated sulphuric acid. 
The determinations present great difficulties in the case of these 
metals, since, whenever the carbonic acid is not quite pure or 
the temperature is a little high, we have oxidation of the surface 
and phenomena like those with cadmium. It may even happen 
in the latter case that the metal kindles in the carbonic acid. I 
have accordingly not been able for potassium to make deter- 
minations free from error, since a slight oxidation of the sur- 
face seems to take place even under favourable circumstances. 
The mouth of the glass tube is readily lined with a border of 
solid potash, the diameter 27 becomes greater than the mea- 
surement gave it, and the constant of capillarity found is too 
great. Accordingly I give the numbers for potassium subject 
to these reserves. The potassium-drops are readily distin- 
guished from all others by their great volume. 


| 


Sodium (in CO”). || Potassium (in CO?). 

2r. W. a. 2r. Ww: a. 
millim. | grm. mgrms. |} millim. | grm. merms. 
1-384 0:1166 | 26°83 || 1:195 01552 | 41°35 
0:9426 | 0:07580 | 26:34 1105 01444 | 41°55 


0:9224 | 0:0785 27°10 0:9629 | 0:1095 | 36-21 
0:395 0:0665 23°60 0:38295 | 0:0889 | 34:12 
0°597 0:0465 24°85 0:7756 | 0-0840 | 34-47 
0:6766 | 00790 | 37:17 
0°2218 | 0:0242 | 34:73 


Mean PAY Fi Wed et iar ens Mean| 37:09 


Or 


10. For a series of salts, beads of the substances on a hori- 
zontal platinum wire of measured diameter were molten in a 
small gas-flame or in the blowpipe-flame of the glass-blowers. 
More of the salt could be added or taken away, as was required, 


Capillarity of Molten Bodies. 91 


by a second platinum wire. By trial, the quantity of salt was 
determined which was just carried by the lower end of the ver- 
tical wire, or which just fell off when it was a little too heavy 
or when the temperature was too high. A horizontal wire 
carries a larger drop than a vertical one in the same circum- 
stances, in consequence of the longer line of contact. 

In many cases, the bead ascends on the vertical wire, because 
it cools from the top downwards ; and the meniscus always tends 
towards the position where the capillarity-constant « of the molten 
salt has its greatest value. 

The beads of salts which fell off were taken up on a piece of 
platinum-foil and weighed, in the case of hygroscopic salts, be- 
tween two watch-glasses. The measurements given below are 
the means of the drops of the salt which fell off, and of those 
which still adhered to the platinum wire. 


| 
Boracic acid. Borax. Phosphorus-salt. 
2r; NG a. W. a. W. ue 

millim. |grm, mgrms. |igrm. mgrms. |/grm. mgrms. 
05569 | 0:01982| 10-16 || 0:03653| 20:88 || 0:0367 20:98 
0°3974 | 0:0132 10°56 || 0°:0285 22°33 || 0:02472; 19:8] 
0-1808 | 0:00577| 11433 || 001198; 21:08 || 0:01188| 20°91 
Mean | 10°69 Mean| 21:60 Mean | 20°57 


Carbonate of Chloride of 


Carbonate of soda. 


potash. calcium. 
0:5569 | 0:0278 16°38 || 00341 19-49 || 0:02686| 15°36 
0-3974 | 0:02097| 16°79 || 0-:02888, 23:14 || 0:01843) 14:77 
0:1808 | 0:0093 15°39 || 0-0115 20:25 || 000898; 15°81 
Mean | 16:33 Mean} 20:96 Mean | 15°31 
Chloride of Chloride of Chloride of 
potassinm. sodium. lithium. 
05569 | O-01611 | 9208 || 0:0196 11-20 || 0021387 | 12:22 
0:3974 | 001203} 9-636 || 0-01892| 11-15 || 001523; 12-20 
O-1308 | 000551 | 9-703 | 000712) 12-04 0.0067 1180 
Mean | 9516 | Mean) 11°63 | Mean| 12-07 
Nitrate of potash. Chloride of silver. 
Tr. W. a. Pay We th. 
millim. |grm. mgrms. ||millim. |grm. mgrms. 
0:5569 | 0-:0170 9°716 || 05380 | 0:0315 | 18-92 
):3974 | 0:0130 | 10-41 0726905) 50.0159 19a 
01805  0:00553 9-763 | 
Mean | Doge Na as, Mean | 19-01 


92 Prof. G. Quincke on the Constants of 


11. If we treat bromine with pure hydrated sulphuric acid in 
order to have it perfectly free from water, and if we then allow 
it to drop in the way described above, the numbers which we 
obtain in this way for the constants of cap:llarity nearly agree 
with those determined by Beéde*, who found a?=2°51 square 
millims. to 2°81 square millims. for 6°8 C. 


Bromine (¢=3']8). 


2a 

2r. W.. ae er Co. 
millim. rm. mgrms. _{sq. millims. 

0°8407 0:0088 3°335 2:097 

0:6998 0:00744 3385 2:128 

0:4934 0:0053 3°420 2°15] 


Temp. =138° C. 


The observation of the elevation / in capillary tubes of radius 
r for the same substance gave 


Bromine. 
27. h. | ahr. 
— 

millim. Sine millims. 
0°4635 11:7 2°712 
0:2079 28:3 2°943 

Temp.=13° C 


These numbers agree, all of them, very closely with the deter- 
minations by Béde. 

I suspected, however, that the capillarity-constants of bro- 
mine altered rapidly with the temperature, and I attempted ac- 
cordingly to make a determination in the neighbourhood of the 
freezing-poimt. A rather wide test-tube, which contained bro- 
mine and a glass tube divided into millimetres, of ‘208 millim. 
diameter, was set obliquely in a mixture of salt and snow, so 
that the bromine solidified. The glass tube was then brought 
out of the freezing-mixture into the usual temperature and set 
vertical. When the bromine was thawed, it showed an elevation 
of 37°5 millims., from which we deduce 


a? =3°895 sq. millims., «=6°328 milligrms. 
for the melting-point of bromine. 
Determinations of this sort are made much more easily in 
winter. 


* Mém. Cour. et des Savants etrangers del Académie de Belgique, vol. xxx. 
(1860) p. 163. 


Capillarity of Molten Bodies. 93 


12. I was interested to note the values of the constants of ca- 
pillarity for water and mercury by this method of drops, as I had 
made numerous determinations of them at the usual tempera- 
tures by other methods. As the following Tables show, the re- 
sults gave very different values (especially for water) for the con- 
stants, according to the speed with which the drops were formed. 

The numbers obtained for mercury are usually smaller than 
those resulting from my own previous determinations *|(from 55:21 
to 58°79 milligrammes); but they differ from the results of other 
observers, which were obtained by much more accurate methods 
(elevations in tubes, and drops on a horizontal surface) by incon- 
siderasle amounts. According as the measurements were made 
immediately after the formation of the surfaces or at a later time, 
the results for « ranged for mercury between 40 and 50 milli- 
gramines. 


Mercury. 
Slow. : Quick. 
2r. Ws ae W. Ce 
millims. grm. mgrms. grm. mgrms, 
1:029 0:1307 40:42 0°1359 42°06 
0:308 0:0422 43°62 0:0522 97:06 
Water. 
2°478 0:0422 5°428 0:0450 5781 
0°493 0:0097 6:259 ,0-0170 10:96 


13. By observation of the capillary elevations, the following 
results were found for water :— 
Gay ussag te «pay 1 = 7565 
Magen at ebeey a; di yb ==7' 508 
By weighing the capillary-raised meniscus, 
WilhelmiyQar 2. ise =7°945 
I had myself determined the capillarity-constant for water 
ten years ago, when I observed the elevation on the inner wall 
of a thin-walled glass cylinder of about 50 millims. diameter. 
Distilled water was boiled in a glass vessel with vertical walls 
till about two-thirds of the fluid was left. While the water 
was still boiling the vessel was corked, and a glass rod with 
* Pogg. Ann. vol. ev. p. 33 (1858). 
T Poisson, Nouvelle Théorie de P Action Capillaire, p. 113 (1831). 


t Abh. d. Berl. Akad. 1845, p. 34. 
§ Poge. Ann. vol. cxix. p. 186 (1863). 


94 Prof. G. Quincke on the Constants of 


a fine point was inserted air-tight in the cork. When the bottle 
was inverted, after the water had cooled down with the access of 
the external air shut off, this point lay in the water immediately 
below the lowest part of the upper surface of the fluid. The 
meniscus was formed on a part of the glass wall which had 
previously remained wet, and was observed with the microscope 
of the cathetometer which I previously described*. One or two 
seconds after the formation of the meniscus, the cross threads of 
the microscope were directed upon its upper limiting surface. 
This surface, lighted up from behind by a paper half white, half 
black, so that the horizontal limit of the black and white lay at the 
same height with it, appeared as a well-defined dark line. The 
point lying in the water was mirrored in the water-surface 
bounded by the space free from air. The cross threads were 
set in the middle between the point and its image, and so the 
position of the horizontal part of the fluid surface was determined. 
The point seen through the water distinctly in the microscope 
appeared in the middle of the bottle, while the wall of the me- 
niscus was first seen distinctly sideways from the middle of the 
bottle ; between the two determinations the microscope had there- 
fore to be shifted on the plate of the cathetometer, which was 
made accurately horizontal by a spirit-level. 

Previously to this boiling, the bottles as they came from ‘the 
elass-blower were purified partly with water and alcohol, partly 
with hot concentrated sulphuric acid, and were then filled with 
distilled water and allowed to stand aside for some hours. The 
water used for the experiments was put in a little before the 
boiling. 'The measurements were made as soon after the turning 
upside down of the bottle as possible, as the elevation diminishes, 
at first rapidly and then gradually, immediately after the formation 
of the capillary meniscus. 

I may give here a series of determinations for different bottles 
the diameters of which are denoted by D, from which we may 
infer the accuracy which it is possible to secure in such deter- 
minations. it ie Ill. IV. 


millims. millims. millims. millims. 
D=52°7 52:05 50°3 50'3 

Tenage) UPd) Osyth 5 Lag (7) 

millims. millims. millims. millims. 

4015 4:072 Ar O04: 40207 

4°176 4-015 4105 Ar 164, 

4-110 3'9938 4180 4-110 

4°155 3°900 4160 4166 

Mean. 4114 3'995 4119 4161 


* Poge. Ann. vol. cv. p. 12 (1858). 


Capillarity of Molten Bodies. 95 


ht VI. VII. VIII. 
millims. millims. millims. millims. 
D=50°3 50:3 50°3 
(1 .% ?) 19°-44: 19°8 
millims. millims. millims. millims. 


40345 4033 4-016 4°04:7 
4°232 4-024: 4-036 4048 
Ae 284: 4-040 4-QOO0 Ae O47 


Mean . 4°287 4-032 4-013 A: O47 

Between the series VII. and VIII. of these experiments the 
water, which had been previously purged of air, was shaken about 
and mixed with it, so that, within the limits of observation-error, 
water void of air andordinary water seem to have the same con- 
stant of capillarity. 

In the case of water which had stood in the bottles for several 
weeks shut off from the air, we had :— 


LX: X. XI. 
millims. millims. millims. 
= 53-7 50°3 50°38 
Temp. 13°1 17°°48 18°05 
millims. millims. millims. 
3°922 3°910 4075 
3°900 3°868 4025 
3°899 3°824 4.007 
Mean . 3:907 3°867 4036 


If the water is left some time in the same glass vessel, the 
elevation or constant of capillarity of the water appears, accord- 
ing to these experiments, to dimmish. I imagine that this has 
its explanation partly in the solution of the glass wall im the 
distilled water. 

If we neglect the curvature of the walls, the elevation is pre- 
cisely the constant a which was determined by Poisson. Assu- 
ming the increase of the capillarity-constant given by Brunner* 
for a diminution of temperature, we have thus for water, at 0°, 

a=4°193 millims., a?=17°58 sq. millims., e=8°79 milligrms. 

The values of the constants are greater than those found by other 
observers, because they allowed a longer interval to elapse be- 
tween the formation and the measurement of the meniscus. 

14, The different values of the constant « are collected in the 
following Table, and the substances are arranged according to 
its magnitude. It must be understood that, except where I have 
expressly mentioned the fact, all the substances were as pure as | 
could obtain in commerce. 


* Poge. Ann. vol. Ixx. p. 515 (1847). 


96 Prof. G. Quincke on the Constants of 


The constant for sulphur is calculated from the experiments 
of Frankenheim+, and that for wax from those of Wertheimt. 


Besides the constant a, the Table gives a?= = and a, where 


o is the specific gravity of the fluid. I have determined the 
specific gravity o for the temperature 0°, with the exception 
of those cases which are marked *; and I have calculated o for 
the melting-poimt. The values of o which are given in these 
cases are more or less unreliable, on account of our ignorance of 
the expansion-coefficients, the precise melting-points, and the 
expansion or contraction which takes place during the process 
of melting. 


TaBLeE I, 


Capillarity-constants of Molten Bodies. 


Melting- 


Substances. point. a o 3 a’, a 
Ss mgrms. | sq. mill. |millims. 
ey Platinum)... cca (2000) | 20-083 |18:915| 169:04 | 17:86 | 4-227 
2. Palladian \s.wawseniicnn (1950) | 11-4 10°83 |(136-4) | 25:26 | 5-026 
SL CTO) (ol bhi rss saat 1200 | 18-002 |17:099 | 100-22 | 11-71 | 3-423 
ae Zinc) (in C02) eae 360 7119 ; 6:900.) 87-68 | 25:42) oa2 
Beene (Mealy) eee eete 360 7-119 | 6:°900} 82:79 | 24 4°899 
6. Cadmium (in CO?)...} 320 8:627 | 8394) 70-65 | 16°84 | 4-103 
ee aN ee ing ook: et 230 7°267 | 7°144| 59°85 | 16:75 | 4094 
SoMencuny Sos. uke - 40) 1) 139506") enn 98°79 8°646 | 2°94] 
Oe head (an CO?) snc-...2 331 | 11-266 |10°952| 45-66 8:339 | 2-887 
MOMS ile etna mceceenae ce 1000 | 10-621 |10:002| 42°75 8549 | 2-923 
11. Bismuth (in CO?) ....) 265 9819 | 9:709| 35-93 8°019 | 2°831 
12. Potassium (in CO”)... oh (UtelOedl nedece (37:09) | 85°74 | 8-768 
13. Sodium (in CO?)..... 90 O27 Lees. 25:75.) || 52:97) Ge geanes 
14. Antimony (in CO’)... 482 6620 | 6:528| 24:92 7°635 | 2°764 
Nays Byes tga aeaerper Raman (1000) | 26 | 25 21°60 | 17:28 | 4-254 
16. Carbonate of soda....) (1000) | 2:509+| 2-45 20-96 L7-lt 4-136 
i7= Niverocosmyc) Salt... -|) owen: 2-502 | 2-45 20:57 | 16:79 | 4:098 
18; 1Chloride of-silver, 3.0.) « ase 5:59 ¥| 9°95 19-01 6-911 | 2°629 
PO NGL ASS oe. 08s bbe sae | (1100) | 2-452 | 2-380] 18:09 | 15:21 | 3-899 
20. Carbonate of potash..| 1200 2°300 | 2:2 16°33 | 14:82 | 3-846 
21. Chlorideofcalcium....} ...... dar NS) ifs) 15°31 14:24 | 3:774 
22. Chlorideoflithium....} ...... eee oa onan 12:07 | 12:10 | 3-478 
23. Chlorideof sodium....| ...... 2°092 | 2:04 1163 | 13:40 | 3377 
24.) Boracie acid (.aee.-. (1300) | 1°83 x) 1-75 10°69 | 12:22 | 8495 
25. Nitrate of potash......| 339 2:059 | 2°04 9°954| 9°759 | 3-124 
26. Chloride of potassium.| ...... 1:932 | 1:870 9516} 10°18 | 3:19 
iis Water (cm, hetmonpaeeree 0 Dy Speplieeeas: 8:79 | 17:58 | 4:193 
BOs SCLOMMUM ie cteenen ae 217 4-3 +| 4:2 7'180| 38-419 | 1-849 
POM IDTOMINC ees seereee nee —2] 3187 | 3:25 6:328| 3:895 | 1-973 
OOF Nulpliur Pes. seceeeees 111 2:033 | 1-966 4:207| 4:280 | 2-068 
31. Phosphorus (in CO”). 43 1:986*| 1:833 A194) 4-575 | 2:140 
ee MNVAX. ical oxen kereee sean 68 0:963. | eee. 340 7061 | 2-657 


t+ Pogg. Ann. vol. Ixxu. p. 193 (1847). 
{ Comptes Rendus, 1857, vol. xliv. p. 1024. 


Capillarity of Molten Bodies. OG 


From the foregoing Table the remarkable result follows, that 
the values of the constant a* arrange themselves for the metals, and 
partly also for the other substances, in groups in which they are 
nearly equal, and which are separated from each other by the fact 
that it is a different whole multiple of 4°3 in each. 


Tasie II. 
ie ite III. 
a°= 4:3, ==a-G- a®?=12°9, 
Selenium ..... . 3:42 | Mercury ...... SOG: . crecancc wecsee seuss 11°71 | 
Bromine ’.:.... 9°90 | Lead ......... 8:34 | Chloride of lithium ... 12°10 | 
Sulphur ...... 4:28 | Silver ......... 8:55 | Chloride of sodium ... 11:40 | 
Phosphorus ... 4°58 | Bismuth ...... 8-02 | Boracic acid ............ 12-22 | 
Antimony ... 763 | | 
Wax 2s 7-06 | | 
| EV: VI. GE XX. | 
Hang oe a?=25°8. a —Ul-6; a’=86. | 
| DiMA, 628s oo, 17°86 | Palladium. 25°26 |Sodium. 52-97 |Potassium 85°74 
CAMMOIUMT ..:...00e-.. 16°84 | Zinc ..... 23°41 
nea ale 16°75 
OS ee 17:28 


Carbonate of soda... 17°11] | 
Microcosmic salt ... 16°79 
RESTS rds wcrc cca ssc 15°51 | 
Carbonate of potash 14:82 
Chloride of calcium. 14°24 
| Water ..........--... 17°58 


In the foregoing tabular comparison all the substances of the 
first Table appear except chloride of potassium, nitrate of potash, 
and chloride of silver, which perhaps ought to be reckoned in 
group II.,—-since these salts, like the other chlorides, have un- 
dergone decomposition in melting; and the amount of carbonate 
may have produced an alteration in the value of a’, as the sur- 
face-layer, which determines the magnitude of the drop, must 
be the first which is altered. More accurate determinations on 
the point require more experimental facilities and more compli- 
cated apparatus than I at present possess. 

Since the volume of the drops which fall from a tube of 2 mil- 
lims. circumference is a?, the following law would result from 
the Tables :—‘“‘ The volumes of drops of different substances in a 
state of fusion, at a temperature near that of fusion, falling from 
tubes of the same diameter, stand to one another in the propor- 
tions of 1, 2, 3, &c.” 

This law is, as might be expected, only approximate, like 
many physical laws. If we reflect, however, what are the diffi- 

Pit. Mag. 8S. 4. Vol. 38. No. 253. Aug. 1869. i 


98 On the Constants of Capillarity of Molten Bodies. 


culties and sources of error in these observations, that the velo- 
city of the formation of the drop is left out of account, that for 
a substance such as water, the values of a® given by different 
experienced observers vary between 13°5 and 17°58 sq. millims., 
we see that the deviations from the law may very possibly be 
due to errors of observation*. No relation such as has been sus- 
pected to exist} between these constants of capillarity and other 
physical or chemical properties of the substances can be deduced 
from these Tables. 

15. According to equation (7), the constant ais the weight in 
milligrammes of the mass of fluid which can be carried by 1 mil- 
lim. of the contact-line of the fluid meniscus, and which is half of 
the constant which Laplace calls H. The magnitude « measures, 
therefore, the difference of the forces of pressure which are ex- 
erted on the unit of a plane fluid surface, and on the unit of 
a spherical surface, of diameter 1, in the direction of the nor- 
mals. We may say, therefore, that a measures the attraction 
which the particles within the fluid exert for a given form of 
the surface on a volume of the surface-layer, the base of which 
is the unit of surface. 

If the surface-layer of fluid had the same density in all points 
with the fluid inside at a finite distance from the surface, the 


quantity = or half the quantity a?, would measure the attraction 


which is exerted on the unit mass of the surface by the particles 
within the fluid, and the attractive functions for different sub- 
stances would be complete multiples of the same magnitude. 
The assumption that in the surface there is the same density 
as in the inside of the fluid appears, however, not to be admis- 
sible. If we conceive the fluid divided into three (partial) layers 
parallel to the fluid surface, each of these (partial) layers will 
be attracted by the molecular forces inward, and with a force 
so much the less the nearer it lies to the centre of the fluid. 
But the layers overlying each individual layer press upon it, so 
that the capillary pressure increases up to a certain value, if we 
proceed inwards from the first external layer. Since the fluid 
is not incompressible, the density in each separate layer will be 
different on account of the difference of pressure, and within the 
fluid it will be different from what it is on the outside. The 
* The constants a? are determined for a series of simple fluids, e. g. 
ether (5 sq. millims.), alcohol (5'861 sq. millims.), and oil of turpentine 
(6°708 sq. millims.), for the usual temperature, which is much higher than 
that of fusion of the fluid. It appears to me, therefore, very probable 
that these fluids belong to group II., and that, could we determine their 


capillarity-constants in “the neighbourhood of the points of fusion, we should 
have a?=8'6 sq. millims. 


t Conf. Dupré, Ann. der Chem. (4) vol. ix. p. 330 et seqq. 


On the Descent of a Solid Body on an Inclined Plane. 99 


density in the single (partial) layers of the entire surface-layer is 
therefore not constant at all points, and we cannot assign to 
a the meaning given above. ‘The following appears to me to 
represent most accurately the present state of knowledge on the 
subject. 

Taking the radius of the sphere of action as equal for all sub- 
stances, which makes the volume V of the inside fluid particles 


. c a 
which work on the particles at the surface the same, — measures 
om 


the force which the mass 1, uniformly distributed over the vo- 
lume V, exercises on the surface-layer of the fluid. In other 


» 9 
5 wh 
words, the half of Poisson’s constant a*= — measures the attrac- 
o 


tion which is exerted on a portion of the surface-layer of the 
fluid, the base of which is unity, by a mass | inside the fluid, 
and it may be called specific capillary attraction or specific cohesion. 

From the preceding Tables it follows that the specific cohe- 
sion of the metals and many other substances in a molten condition, 
at temperatures little above their meltiny-points, is nearly as the 
numbers 1, 2, 3, &c. 

The law expressed in the preceding statement as to the spe- 
cific cohesion of the fluids becomes intelligible if we assume that 
the molecular function is the same for all bodies, and that in 
the surface-layer, the density of which is not the same in all its 
parts, masses are enclosed which, in different substances, bear to 
each other the proportions of the series of the natural numbers. 


Berlin, October 1868. 


XII. On the Descent of a Solid Body on an Inclined Plane when 
subjected to alternations of Temperature. By Henry Mose.ey, 
M.A., Canon of bristol, F.RS., Instit. Imp. Sc. Paris, Cor- 
resp.* 


KT A B(fig.1) be an elementary plate of the solid, andconceive 

it to be divided into an infinite number of equal elements 

by planes perpendicular to its length. Let X bea point so taken 
in it that, if it were divided in X, the thrust necessary to push 
the part X A up the plane would equal that necessary to push 
XB down it. Let the element at X be imagined to have its 
temperature so raised as just to equal this thrust; and let the 
temperatures of all the elements in X A, beginning from X, be 
equally raised in succession. Hach will thus be dilated more 
than the one before it, because its dilatation will be opposed by 


* Communicated by the Author. 


Hl 2 


100 Canon Moseley on the Descent of a Solid Body on an 


a less resistance; and the displacement of the extremity upwards 
will equal the sum of these several dilatations. In like manner, 


tie, 


Fig. 2. 


oe abe 
Bi 
if the same temperature be added to the elements of XB in 
succession, beginning from X, each will be dilated more than the 
one before it, and the displacement BB, of the extremity B 
downwards will equal the sum of these several dilatations. The 
pomt X will obviously be nearer to A than to B, because the 
same thrust: of dilatation of the element at X would not be able 
to push so great a length of the bar up the plane as it would 
down it. 

In this state of the temperature of the plate, let a point X, 
be taken such that, if it were divided there, the strain necessary 
to pull the part X, A, down the plane would just equal that ne- 
cessary to pull X, B, up it. Let the temperature of the element 
at X, be so diminished as by its contraction just to produce this 
strain, and let the temperatures of all the elements from X, 
to A, in succession be equally reduced. Hach will contract 
more than the one before it, because a less resistance will be 
offered to its contraction ; and the displacement A, A, of A, down 
the plane will equal the sum of these separate contractions. In 
the same way the displacement B, B, of B, up the plane will 
equal the sum of the separate contractions of the elements of 
X,B,. The point X, will be further from A, than B,, because 
the same strain of contraction of an element at X, would pull a 
greater length of the bar down the plane than up it. It is by 


Inclined Plane when subjected to alternations of Temperature. 101 


the dilatation of the greater length of the plate X B favoured by 
its weight that the extremity Bis displaced down the plane when 
the temperature is raised; whilst it is by the contraction of the 
less length X,B against its weight that it is displaced up the 
plane when the temperature is lowered. The extremity B 1s 
therefore more displaced down the plane by a given raising of 
the temperature than it is displaced up it by a corresponding 
lowering. On the whole, therefore, the extremity B is made to 
descend the plane by a given alternation of temperature. It is 
by the dilatation of the tess length X A that the extremity A is 
displaced up the plane, and by the contraction of the greater 
length X, A, that it is displaced down the plane. It is there- 
fore less displaced up by dilatation than it is down by contrac- 
tion, and on the whole it descends by a given alternation of tem- 
perature. Both the extremities A and B of the plate are there- 
fore made to descend when it is subjected to a given elevation 
and then to a corresponding depression of its temperature ; that 
is, the whole plate is made to descend. 

It is the object of the following paper to discuss the mathe- 
matical conditions of this descent with a view to its application to 
the theory of the descent of glaciers. Formula (22) is the ma- 
thematical expression of the result. 

Two principal cases arise in this discussion. An increase 
of temperature has been supposed to be communicated to an 
element at X such as would be sufficient, if the plate were di- 
vided at that point, to push X A up the plane and X B down. 
This determines the increment of temperature with reference to 
the length of the plate; and so of the corresponding decre- 
ment, which must be sufficient to pull X, A, down and X, B, up. 
The first case is that in which the alternation of temperature to 
which the plate is subjected is equal to, or greater than, this. 
In this case the plate descends. The second case is that in 
which the alternation of temperature is less than this. The 
thrust of dilatation produced by the given increment of tempe- 
rature of an element at X which is sufficient to push X A up 
not being sufficient to push X B down, let x B (fig. 2) be a part 
of the plate which it would be just sufficient to push down, and 
let the whole plate receive this increment of temperature. The 
parts X A and 2B will then be dilated to A, and B,, but Xz 
will remain undilated. Let now X, be a point in the plate at 
which, if an element experience a corresponding decrease of tem- 
perature, the strain of its contraction would be sufficient to pull 
X A, down but not X, B, up; and let x, B, be the part of the 
plate that it would just pullup. If, then, the whole plate expe- 
rience this decrement of temperature, X, A, will be contracted 
to X, Ao, and x, B, to x, B,, but X, x, will remain uncontracted., 


102 Canon Moseley on the Descent of a Solid Body on an 


The part X,# will thus have remained unmoved either by the 
increment or the decrement of the temperature, and the plate 
will not descend. ‘The strain will be greatest on the points X, 
and xv, when the plate suffers a diminution of temperature; and 
it is a possible case that the tensile strength may not be suffi- 
cient to bear this stram. The plate will then be torn asunder 
at those points. Although the plate was before too long to be 
made to descend by the given alternation of temperature, yet the 
parts into which it is thus separated may not. The points X 
and x are those which sustain the greatest thrust when the tem- 
perature is raised; they are therefore those at which there is the 
greatest tendency tocrush. The distances X A,a B, X,A,, 2, B, 
are independent of the length of the plate. 

If the plate adhere to the plane, so that, besides the resistance 
of friction to its descent, there is that of its shearmg upon it, and 
if in any new position into which it is sheared the adhesion be 
supposed to be reestablished as perfectly as it was in the position 
Jrom which it was sheared, and if, lastly, the thrust and strain of 
expansion and contraction due to an alternation of temperature be 
sufficient to overcome the resistance to shearmg of the surfaces in 
contact, then for a given weight of the plate and inclination of the 
plane the resistance to shearing will be the same as it would be 
if a given addition were made to the resistance of friction; and 
taking for the coefficient of friction one equal to the sum of the 
actual coefficients of friction and the coefficient of this equivalent 
imaginary friction, the cases of friction and adherence may be 
treated as one of friction only. 

Let the plate be rectangular and of uniform thickness, and let 
it rest lengthwise upon the plane. 

Let its dimensions and weight, and the conditions of its dila- 
tation and contraction, be represented as follows :— 

a = length in feet at the given temperature T° Fahr. 

K = transverse section in square inches. 

H*=' modulus of elasticity. 

»X = dilatation or contraction per foot for every variation of 

1° F. in the temperature of the plate or bar. 
1, =1+At,= length to which each foot in the length of the 
bar is dilated when (dilating freely) it is heated from 
the temperature T° by 7,° F. 

l,=1—Xt,= length to which each linear foot of the bar is 
shortened, when from the temperature T° it is cooled by 
t.°, contracting freely. 

* The modulus of elasticity is here assumed to be that weight in pounds 
which, if applied as a tension to a bar of the metal 1 square inch im section 
and 1 foot long, would lengthen it by one foot, or which, if apphed as a 


thrust, would (if the same law obtained, however great was the compression) 
compress it by one foot. . 


Inclined Plane when subjected to alternations of Temperature. 103 


w= weight in pounds of a portion of the bar 1 foot long and 
1 square inch in section. 
u = inclination of the plane. 
o*= limiting angle of resistance between the surface of the bar 
- and the surface of the plane. 
_ sin (69 
‘hoe db 
necessary to push it down the plane. 
__ sin (b +4) 
er db 
necessary to push it up the plane. 
w= distance in feet of any point P in the bar from the fixed 
end of it. 


= thrust per pound of the weight of the bar 


= thrust per pound of the weight of the bar 


( a,= what x becomes when T° becomes (T° +7,). 
p= poe, a 5B) oe) 2) 
oe) y99, 1% » 9 os to) - 
Ag 3) a 3) 3) +) dd 


&,= value of # in respect to the point where the 
dilatation of the bar begins. 


end of the bar is fixed 
and the lower end free. 
en Ne 


&,= value of x in respect to the point where the 
contraction of the bar begins. 


l 
ee 

=. 
© $ ( X,= what x becomes when T° becomes (T° +7,). 
x — Ai= , @ ” ey) 9 
oe ear 5 fe) 
ms = X= 9 « & 9 » (T —t,). 

iP) 
es | Aj= » (& ” 23 ey) 2 

S 
= 5 | B,= value of a in respect to the point where the di- 
Ss latation of the bar begins. 
ss 
aS E,= value of x in respect to the point where the 


Case1I.—When the lower Case 1.— When the upper 


contraction of the bar begins. 


* In the case in which there is a resistance of shear of the surfaces 
as well as of friction; let w represent the unit of shear corresponding to a 
unit of surface of 1 foot by 1 inch, and let o be the area of the surfaces of 
contact measured in the same units; then yo is the resistance of shearing 
to the descent of the plate. Let also f be the cvefficient of friction, then 1s 
fwe cose the resistance of friction. If, therefore, tan ¢ be the coefficient of 
a friction equivalent to the actual resistance of friction and the resistance to 
shearing, then 

wo tan fd cost=po+fwe cos., 


ee ee a) 


_ The value of @ bemg determined by this equation, the following diseus- 
sio includes the case of adherence together with friction, and the resulting 
formule are applicable to that case alse. 


Ae (ano o= 


104 Canon Moseley on the Descent of a Solid Body on an 


r; 
Casr I.—When the upper end of the plate is fixed. 


Tet Az be a finite increment of # at the temperature T. 

When T became T+7,, Av would become /,Azw if nothing 
were opposed to its dilatation. ‘To dilate, it must, however, 
thrust the portion P B of the plate (fig. 1) down the plane; and 
the resistance to this displacement is represented by 


Kw(a—2)\f." 


Suppose Aw first to have dilated freely, so as to have become 
,Az, and then to have sustained a thrust equal to the above- 
mentioned resistance, and thereby to have been brought back to 
the dimensions it would have had if it had experienced the re- 
sistance from the first. 

Let 6(/,Az) represent the compression of the element caused 
by this thrust. Per foot of the length of the plate this compres- 
sion is represented by 

6(J,Az) 
l,. Ae 


But if the same law which holds in respect to small compressions 
held in respect to all, however great, K lbs. per square inch of 
section applied as a thrust would, per foot of the length of the 
plate, produce a compression of one foot ; therefore 

E6(/,Az) 


l,. Aw 


will produce a compression of 


§(1,A2) 


per foot of length, per square inch of section. But the resistance 
Kwla—z)f, 
Kk 


produces also this compression ; 


Ko(,Av) — Kw(a—2)f, 
ee a K 


Oa) — iti (a—x) Az. 


But 
Agr, =1,Az—6(/,Aa) ; 


Inclined Plane when subjected to alternations of Temperature. 10 


*, Av, =lAr— _ (a—x) Az, 


or =, Hh —w). ae ee (1) 


Similarly, if the temperature T be reduced by ¢, and if the drag 
upon the element Az (in the act of contracting) of the portion of 
the bar below it be applied as a strain after Aw has contracted 
to l,Az, then this drag being represented, per square inch of 
section, by (a—-«)wf, we have, as before, 
Ed ((,Az) 
Ga 
Av = LAr é(ljeAa) ; 


gy Aa —iAg-- iE (a—x)Aa, 


d L, | 
a2 =l,+ wh Gas hh ae 2) 
Case I1.—When the lower end of the plate ts fixed and the rest free. 
Reasoning as before, 
oe =wfa(a—2), 


E6(/,Az) 
l, Aw re 2): 


== \(G—= 2 if, 


AX, =,Ar—8(1,A2), 
AX, =/,Axr+8(i,A2), 


AX, =],Ac— Hae (a—x)Aa, 


AX,=/,Aa+ oe (a— x) Aa, 


aX wl 

aah ea, 2. 8) 

dX wi 

Fe i ee egy 
I. 


General solution of Cases 1. and II., a part of the plate being 
supposed neither to dilate nor contract. 
Integrating equations (1), (2), (3), and (4), and observing 
that &,, &, 5, So represent the values of x at the points where 
dilatation and contraction respectively begin, 


106 Canon Moseley on the Descent of a Solid Body on an 
Wa (0 ie ; 
m—B=h{ (1 )e— 8) +o ey |, 


w f, AY 
me —=hy (1+ )@—8) + Meera |, 


Reducing, 


ee ah, 41- a (2a ~a—£) b@w—), 


X,-2,=] fiw s(2a—0-B,) ba eh) 
K,-8,=4414 % fi @a—a—B.)  (e— 
Substituting for /,, 1,, f,, f, their respective values, 
#-B=(1+ta) {1 “Sa! a—a—£) Fle-8), 
,—6= (1 1p) {1+ Pa EE (ea—2—f) be-8), 


ees Osa {1- sa Canis J (2a—w—E,) }(e-B), 


2K cos 
te ae OUISVa (GE) Gro aes t _ 
X,— = (1—7t,A) {1 = has $ (2a—xv—E.) -(a#—.,)- 


When « becomes a, 7, z,, X,, X, become @,, G5, 2 eaonee 
spectively. Therefore 


4—8= (149) {1- SG aie | 
| 


a —£= (It) 1+ PEP (ag, | (a8), 


is _ wsin eheat ie —5,) | (een 


ee eral sean —!) -2,) | oy) | 
A,-E,=(1-1)) {14 Mead (1) fo). 


\| 
D 
a 
i 
eS 

Se 


A —F, 


Inclined Plane when subjected to alternations of Temperature. 107 


Subtracting (a—&), (a—&,), (a—H,), (a—H,) from these 
equations respectively, 


tay i ateg ee pee | 


a—a= | — Dt, + ETM SNOT) a_g) ba§), 


: (6) 
A-a=f ,— wt eM) lO +) Gz.) | eB), | 


2H cos p 


A an{ — a, + MOSSE a5) ba) 


Now the values of x represented by &,, &,, 5, &, are those for 
which Avy=Az,=Az,=AX,=AX,. Therefore, by equations 
(1), (2); (3), (4); 


wl 
1=i,— “wi a—£), 


Substituting the values of /,, Z,, f,, f,, and transposing, 


Enz, cos 


rh w(1+Azt,) sin (6—¢) dowd 
Hit, cos h 
an bar w(1—At,) sin (b+ 0) 
ao EAzt, cos b ieee 
O31 = Ty (L4ad,) sin (b+). 
ite ie HAL, cos b 


~~ w(1—At,) sin (b— 2) J 


Eliminating* (a—£,), (a—&,), (a—H,), (a—#a), between 
equations (6) and (7), 


* It is easily seen from this elimination that the dilatation of the whole 
plate is equal to one half what that of the part of it which dilates would 
have been if that part had dilated freely. And so of the contraction. 


108 Canon Moseley on the Descent of a Solid Body on an 


joe En2Z} cos b | 

/ 2w(1+Azé,) sin spe ’ | 

2 ee EX2/3 cos f 4d 
2w(l— —Xi,) ) sin ( (p+) 

Mais Eni} cos b [ 

2w(1+é,) sin (6 +4)” | 

Agee E245 cos = Es 


2w(1—AzZ,) sin ( 


When the plate is first heated (t,°) and then Men (to). 

Let a, be its length after such heating and subsequent cool- 
ing when fixed at the top, and ,A, when fixed at the bottom. 
Then, since a, becomes ,a., and A, becomes ,A, by a diminution 
of temperature ¢,, we have by the second and fourth of equa- 
tions (8), 

En23 cos 
2w(1—Az,) sin (fb + ¢) 

EA2#: cos b : 
2w(l— At.) sm (6—2) 


Adding these equations respectively to the first and third of equa- 
tions (8), 


1497 4h = | 


A,—-A\=— 


1 


EX? cos a 
er Rome © 


ao Us rare (esrarces ee 


t} 
oF +Az,) sin(d+0) Te sin (h — ate 
When it is cooled back to its first temperature, ¢;=t,=¢; 
EA70? cos p (sinecosp+Atsingecost) | 


ve 14g — a= w(1 —r21?) sin (p+0) sin (¢—1) | 6 
Ajet 7 — —- cos. d ( sim 6 COS ) + sin d cos t) a ( 
io w(1 —n2?) sin (fb +4) sin (b—2) J 


When the plate is fixed at the top, it 1s lengthened, therefore, 
by being beated and cooled back to the same temperature ; and 
when it is fixed at the bottom, it is as much shortened. 


Inclined Plane when subjected to alternations of Temperature. 109 


Til. 


General solution of Cases I. and II., every part of the plate 
being supposed to dilate or contract. 

In this case equations (1), (2), (3), (4) must be integrated 
between the limits z and O instead of between the limits # and 
E,, &, By, Se, the results of which integrations may be obtained 
by making the latter quantities zero in equations (5). 

We thus get 


2K cos 
= (wy, 41 ct ee apeti be 
oer obese boot 
Aj=(1—\,) i+ ee iba. 
Or, sine sy is an exceedingly small quantity, 
a,—-a= 4 tho eae y® 
@—a=— { ir— aa ) | (12) 
aan fo nees}e [ 
dete fanpiele 


When the plate (every part of which dilates or contracts) 1s heated 
t,° and then cooled t,°. 

By the heating the length a becomes a, or Aj, according as 
the fixed point is at the top or the bottom; and by the cooling 


these lengths become ,a, and ,A,. ‘Therefore by the second and 
fourth of equations (11), 


w sin (p+e 
125 = (1—Azt,) ) {14 Tica ow 


w sin ( 
Ae=(1—A4) 4 1+ me a, LA, 


Eliminating a, and A, between these equations and the first 


110 Canon Moseley on the Descent of a Solid Body on an 


and the third of equations (11), and observing that because of 
the small difference of a, from a, and the exceeding smallness 
of the factors 
w sin (6+) w sin (p—t) 
2K cosh ang 2K cosh 


we may consider 
w sin (p+) ei w sin (b+) r 
2Zheosd 7=  2hicasa 7 


w sin (p— 8) Wolas ¥ w sin (6—t) 
2K cos b 2Kcosh 


we have 


if wad w sin (d +2) 
,=(14aeyl ni)4 1+ Seed : ab 


{1 w sin (p—4) | ? 


Aj=(1 +4)(1-A4)4 1 in ae 


JS, _. wsin ($+0) } iti 
i 2K cos g ae 


whence, by reduction, 


dp a(1+tA)\(1—ta) 


{(1+ wa sin a) us (2 ea cos ‘yt | a 


pA,=a(1+4,r)1— Ws 


| 1 weet) — wa tan d cos e\2 
+h 2E ( 2K ee 


or, approximately, 


iig=a(1-+>., (I=) (14 224), 
Ap=e(1 +a) (1— —ni)(1— ao 


ry: 
Case I11.—-When no point in the plate is mechanically fixed. 


Since X (fig. 1) is a point so taken that if the plate were cut 
asunder ¢here, the resistance of the part X A to being thrust 


Inclined Plane when subjected to alternations of Temperature. 111 


upwards would equal that of XB to being thrust downwards 
when the temperature is raised, an element at X will dilate 
equally upwards and downwards, and the point X itself (sup- 
posed the centre of the element) will remain fixed. 

In the same way, since X, is a point so taken that the resist- 
ance to X,A being pulled downwards is equal to that to X,B 
being pulled upwards if the temperature is lowered, an élement 
at a will contract equally upwards and downwards, and the 
centre X, of that element will remain fixed. 

To determine the positions of X and X,. 


Pressure necessary to thrust XA upwards = Kwf,XA, 
re Fe » XB downwards = Kwf,(a—XA), 
a to pull X,A downwards = Kwf,X,A, 
i a » %,Bupwards =Kuwf,(a—X,A); 
. Kwf,XA=Kwf,(a—XA), 
Kwf,X A =Kwf,(a—X,A). 


Whence we obtain, substituting for f, and f2 their values, 


sin ( ea tan 6 
ei! sles dost sin = cost 2 a4 tan tan b a, 
yas sim (P+s) _ Se lay tan 4 
ee aeat 2 sin ne COS L ie tan d (19) 
n (d+e) yo} tan t 
esd Ha 
ag had sind cost Ae tan d mee) 


a (p— 


tans ) 


=yaq1— neh. ay 


X and X, are therefore symmetrically placed in the bar. 

It is evident that while the plate is in the act of dilatation, the 
point X may be considered mechanically fixed, and whilst it is 
in the act of contraction, the point X,. 

_ The equal and opposite resistances at X and X, may, first, equal 
or be less than the thrust of dilatation, im either of which cases 
the whole plate will suffer dilatation or contraction ; or, secondly, 
the equal and opposite resistances at X and X, may be greater 
than the thrust of dilatation, in which case a portion only will 
dilate or contract. 

Now the ¢hrust with which the plate tends to dilate under an 


sin } cos oho 


112 Canon Moseley on the Descent of a Solid Body on an 
increase of temperature of ¢,° is represented by 

sey 

1+tr 


And similarly the s¢rain with which it tends to contract under 
a diminution of temperature f, is 


KEt) + 
1] ae t,» ! 
Whence it follows that the opposite resistances at X and X, are 


respectively greater than the elasticity of the plate, so that a por- 
tion only dilates and contracts, when 


pia KELX 
XAf,Kw > I ime 
1 
and 
KEt,x 
X, Bf, Kw => ie 
or, since 
Ta ly poi, es 
] 7" cosesin d 
and 
sin (pb +2) 
i, cosh . * 
when 


3 KEt,~ 

Une sin(@—e) sin(P+e)” 1+dAt, 

? cosesind cosp _ KEZA 
1a 


* Tf ro resistance were opposed to the dilatation of the element Az, it 
would become, by an increase of temperature ¢,, (1+¢,A)Av. To bring it 
back, therefore, to the length from which it has dilated, each foot must be 


tAAv : : ay ge 
compressed Dy aa gauAe Since, therefore, its section is K, the thrust 


necessary to compress it is represented by (mua orby 747 
: 1 


+ If R represents the resistance to crushing per square inch of section, 
and S similarly represents the tensile strength, the bar will crush at X if 


and will tear asunder at X, if 


IRE 32 
aw >KS. 


Inclined Plane when subjected to alternations of Temperature. 118 
or generally when 


_1i ka sin 2 $ cost 
w (L4éA) sin(f+e) sm (b—s)" 


In the case in which this condition is nof satisfied, or when the 
whole plate, having no point mechanically fixed, dilates or contracts 
by the supposed variation in its temperature, let A, B, (fig. 2) be 
what A B becomes when heated by ¢,. Then, since X A dilates 
as it would doif fixed at the bottom, and X B as it would do if 
fixed at the top, substituting the values (14) and (15) of XA 
and XB in the third and first of equations (11), 


al tr ee (6—t) {1- wa sin (6+ ¢)sin ae 


(18) 


sin Cos & AK cos } sin ¢ cos t 
eis sin raat _ wasin (6 +4) mea \ 
ees tM) sin d cos & Tmeribteas dh sin Cost i 


- ee! wasin (6+) sin (P— , 
*. AB = a(1+Az,) {1- BR sine 008 4 pe 8) 


Similarly, 
wa sin (d+) sin (d@—e 
A.B,=a(1—At,) 41 oa QE sin2écos. Bee rg (2))) 


If the plate be first subjected to an increase of temperature, 
becoming A, B,, and then to a diminution, becoming A, B,, the 
value of "A, B, from the former of the above equations must be 
substituted ae a in the latter. 

We shall then have approximately, 


an wa*sin?(d +2)sin*(d— S , 
Ae a1 ++ rz,)(1 —ni,) 41 oF AK? sin2 20 cos? t ° (21) 


By every such heating and equal cooling the bar will therefore 
experience an exceedingly small diminution of its entire length. 


V. 


The descent of the plate when subjected to an increase and then 
to a decrease of temperature, supposing the whole to dilate and 
contract. 


Observing that X B (fig. 2) dilates as it would do if X were 
fixed, and substituting for a, in the first of equations (12), the 
value of XB (equation (15), ~ 


B= _. sin sin (6+) fin— w sin (p+e)sin(p—4) | 
=F 


sin Cos 6 2H sin 2d cost 
Phil. Mag. 8. 4. Vol. 88. No. 258. Aug. 1869. I 


114 Canon Moseley on the Descent of a Solid Body on an 


Observing also that X,B, contracts as it would do if X, were 
fixed, and that in estimating its contraction by substituting X,B 
instead of X,B, for a in the second of equations (12), an error 
will arise only in respect to terms of two dimensions in A and 


1 
— we obtain as before 


KH’ 
sin (6—1) fy we sin (b+) sin (b—2) 
sin @ cose | ” 2H sin 2¢6 cose } ; 


Bjb.= 


a 


bole 


Subtracting this equation from the last, 


i a : ] i 
BBa= sa paar sin (p+) — fy sin ia 


wa sin (b+) sin (d—e) tane, 
ak 3 


2K sin d 
or, by reduction, 
_ atans { | a ae 
BB. 2 tan d (> Gensel) tan ¢ | (22) 
__ wasn (b+4) sn (6—0) } [ 
E sin 2¢ cos ¢ 


by which equation is determined the descent of the plate after 
having been heated by ¢, and then cooled by é, supposing the 
whole of it to dilate and contract. 

If ¢t;=t.=¢, or if the plate, having been heated by ¢° above 
T°, is then cooled down to the temperature T° again, 


tan t _ wa sin (p+2) sin (6—2) , 
BBLS tGad | BE sn 26 cosy 


The bar descends if 


wa sin (p+e) sin(d—e) : 
{> ~ QEAsin2d cose — e e e ° ° e e ° (24) 


Vi. 


When part only of the plate dilates or contracts by the assumed 
variation of temperature, no point init being mechamecally fixed, to 
determine the length. 

Substituting the values of XB and X;B for a in the first 
and second of equations (8), and XA and X A in the third 
and fourth, 


Inclined Plane when subjected to alternations of Temperature. 115 


XB 1,50 (b +1) EA2 Zi cos b ‘eo 
1 2"sin @ cost | 2w(1+Az,)sin (6—0) | 
X Bargin (=) ____EN& cos $ 
2 2"sind@cose  2w(1—dé,) sin (b+) Qs 
XA —1, 50 (p—1) En2¢; cos ( ma 
1 2"sin cose 2w(1+A¢#,) sm (b+0) ° | 
XA —1, 50 (b+.) En2é5 cos b | 
= a a 


sing@ cose 2w(l—Ad,) sn (P—1) J 


Adding the first and third of the above equations and the 
second and fourth, and reducing, 
EA2Z; sin 2¢ cos ¢ 
2w(1 +Az,) sin (+0) sin (6—s) (26) 
____ EBA*4 sin 2¢ cost 
2w(1—rz,) sin (+2) sin (b—) 
To determine the length of the plate when having been first 


heated by t, it is cooled by t,, the value A,B, from the first of 
the above equations must be substituted for a in the second, 


iB, ED? sin 2¢ cose ‘(ea e iB \ 
i ae=4T dy sin (b+4) sin (P— elena sity ee. ; 


A\By=a+ 


A,B,=a— 


or 

ean EN? (E, +2) (41: —t —Atyt,) sin 2¢ cost 
ae 2w(1+rt,)1 —ré,) sin (b+ 4) sin(d—s)* 

The bar will be lengthened if 


(£—t,)>Alyty, ov if (-- =) aN, 
to 


(27) 


Vil. 


When the plate is heated (t,°), to determine what part is not di- 
lated ; and when it 1s cooled (t,°), what part is not contracted. 

2X (fig. 2) is the part which, when the plate is heated 
(,°), 1s not dilated; and z, X, is the part which, when the 
bar is cooled (¢,°), is not contracted. In the two cases the 
points X and X, respectively may be considered pomts mechani- 
cally fixed. Therefore taking XB to be represented by a in the 
first of equations (7), and observing that a—&,=XB—Xwv=Bz, 


HAt, cos @ 
hace w(1+A4,) sin( (f6—c) 
Similarly, taking 2A to be represen ted by a in the third of equa- 


tions (7), and observing that a— 2, =2A—«X=AX, 
12 


116 Canon Moseley on the Descent of a Solid Body on an 
— Enz, cos b 


eae Che.) eee) 
Yn like manner, 
Et, cos b 
Hee w(l—A”é,) sin (6+ 1) 
Eni, cos h 
Rte w(1—At,) sin(p—v) 
whence 
Enz, sin 2¢ cos ¢ 
Ta Me en 7y case 1 3 
ae w(1+Az,) sin (6 +2) sn (h—2z) 
X» HAZ, sin 2¢ cos t 


2, =a— w(1—At,) sin (b+ 4) sin C= 


If these expressions vanish or become negative, there is no 
part} of the plate which does not dilate by the assumed increase, 
and contract by the assumed decrease of temperature. 

The fact of the descent of a solid body upon an inclined plane 
when subjected to alternations of temperature was first observed 
in the descent of the lead on the southern side of the roof of the 
choir of Bristol Cathedral, and was communicated to the Royal 
Society { in April 1855. I have since verified it by the fol- 
lowing experiment. I fixed a deal board 9 feet long and 5 inches 
broad to the southern wall of my house so as to form an inclined 
plane, and upon it [ placed a sheet of lead, turning its edges 
down over the side edges of the board, and taking care that it 
should not bind upon them, but be free to move with no other 
obstruction than that which arose from its friction. The ineli- 
nation of the board was 18° 82!, the thickness of the lead 1} 
of an inch, its length 9 feet, ‘and its weight 28 lbs. The lower 
end of the board was brought opposite to a window, and a ver- 
nier was constructed which could be read from within, and by 
which the position of the lead upon the board could be deter- 
mined te the 100th of an inch. I began to measure the descent 
of the lead on the 16th of February, 1858, and recorded it every 
morning between 7 and 8 o’clock, and every evening between 6 
and 7 o’clock until the 28th of June. 


* If a sheet of lead rest on a plane of oak inclined at 223°, 
Xx#=a—30°63t,, Xi7,=a—30°63 t,, 

where the length is measured in feet, and the temperature in degrees of 
Fahrenheit, and the modulus of elasticity of lead is assumed to be 720,000, 
its coefficient of expansion 7534555, and the limiting angle of resistance be- 
tween it and oak 222°, 

t This agrees with inequality (18). 

{ Proceedings of the Royal Society, vol. vii. p. 341. 


Inclined Plane when subjected to alternations of Temperature. 117 


The following were the measurements observed during the 
month of May :— 


Distance of the lower 

end of the lead from 
Date, | zero of the vernier, in | Descent in| Descent in| Descent in 
1858. inches. the day. | the night. | 24 hours. 


Morning. | Evening. 


May 1. | 10-95 W310 | -15 
( |The lead, overlapping the end of the board 


3. by nearly a foot, was this evening drawn 
1 back to 0-77 

4 0:78 1:06 28 03 3l 

5 1-09 1:21 12 03 15 

6 1:24 1:44 "20 10 30 

7 154 1-65 ‘ll G2 13 

8. 1-67 1:88 21 00 21 

9 1:88 1:93 05 07 12 
10 2:00 2:19 19 00 19 
1] 2°19 2°25 06 05 11 
12 2:30 2°33 03 03 06 
13 2°36 2°40 04 09 13 
14 2:49 2°55 06 00 06 
15 2:55 2°68 13 06 19 
16 2-74 2:90 16 01 17 
7 2°91 2:92 0] 03 04 
18 2°95 3°08 13 08 21 
19 3:16 3°50 34 10 44 
20 3°69 377 17 10 27 
21 o87 3°87 00 03 03 
22 3°90 4-12 22 03 25 
23 Al5 4-54 a 04 A3 
24 4°58 4-64 06 00 06 
25 4°64 5°16 52 04 56 
26 5°20 5°41 21 09 30 
27 5°50 5°84 34 01 35 
28 5°85 6:05 20 02 22 
29 6:07 6°37 30 03 do 
30 6:40 6:55 15 08 23 
3] 6°63 6°80 17 


The daily observations were given up on the 31st of May ; but 
the positions of the lead were registered on the 19th, 22nd, 2drd, 
24th, and 26th of the following month. The average daily de- 
scents 1n successive months, measured in inches, were— 


February. March. April. May. | June. 


wm i eee 


-1000 -13806 16133 21500 | 21888 


To compare the actual descent on any day with that com- 
puted by formula (22), it would be necessary to know, not the 
extreme temperatures only of the lead on that day, but every 
oscillation of temperature between those extremes; for every 


118 Mr. R. Moon on the Structure of the Human Ear, and on 


such oscillation of the temperature up and down in the course 
of the day and night contributed to the daily descent; and it is 
the effect of these oscillations, however numerous and however 
separately small, which that descent totalizes. I accordingly 
remarked that it was on days when the thermometer in the sun 
varied its height rapidly and much (as on bright days with cold 
winds, or when clouds were driven over. the sun) that the de- 
scent was greatest. So remarkably indeed was this the case, 
that every cloud which shut off the sun for atime from the lead, 
and every cold gust of wind which blew upon it in the sunshine, 
seemed to bring it a step down. On the contrary, when the sky 
was open and clear, and the heat advanced and receded uniformly, 
the descent was less, although the difference of the extreme tem- 
peratures of the day might be greater. It was least of all on 
days when there was continuous rain. During the night it 
was often imperceptible—especially in the earlier months of the 
year, when it was dark from the time of the evening observation 
to that of the morning. In April and May this interval included 
a period of sunlight in the early morning, to which the descent 
registered as having taken place in the night was no doubt due. 


XIII. On the Structure of the Human Ear, and on the Mode in 
wiich it administers to the Perception of Sound. By R. Moon, 
M.A., Honorary Fellow of Queen’s College, Cambridge*. 


| STATED in a former papert that the human ear is so con- 

structed as to suppress vibrations arising from waves of 
condensation which become incident upon it, at the same time 
that it transmits to the sensorium vibrations arising from waves 
of rarefaction. JI now propose to exhibit the grounds upon 
which I rest this assertion. 

The view of the constitution and functions cf the organ of 
hearing which I have just expressed, incredible as it may at first 
sight appear, will be found, if I mistake not, to dissipate the 
mystery which has hitherto characterized that most complicated 
anatomical problem. ‘The circumstances by which this view of 
the subject was first suggested to me require some words of ex- 
planation. 

I have elsewhere shown} that if the problem of the propaga- 
tion of sound through air be pursued by a strict analysis, we 
shall be led to a conclusion with regard to the velocity of pro- 


* Communicated by the Author. 

+ “On the Theory of Sound.” See Phil, Mag. for March last. 

{ See the paper last referred to, and an earlier one, ‘On the Theory of 
Pressure in Fiuids,” in the Phil. Mag. for August 1868. 


the Mode in which it administers to the Perception of Sound. 119 


pagation materially different from that to which a provisional 
and imperfect theory would conduct us. 

I have shown that the velocity with which a small disturbance 
is propagated through air of a given density is not, as the exist- 
ing theory would teach us, invariably the same whatever the 
character of the disturbance,—that, on the contrary, the disturb- 
ances capable of such transmission are divisible into two classes, 
viz. waves of condensation, in which the density is throughout 
greater, and waves of rarefaction, in which the density is through- 
out less than the original density of the air through which the 
propagation takes place*—in waves of the first kind the velocity 
of propagation being somewhat less, while in waves of the second 
kind it is somewhat greater than the calculated velocity given by 
the existing theory}. 

In arriving at these conclusions I was confronted by this great 
difficulty, viz. that in a great variety of instances sounding 
bodies give rise to waves of condensation and waves of rarefac- 
tion simultaneously ; so that in such instances we should have a 
double sound whenever the distance of the sounding body from 
the ear is considerable, unless the ear were so constructed as to 
suppress one of the two classes of waves. 

So incredible did this latter conclusion appear to me, that 
nothing but the conviction which reiterated examination had 
wrought in me of the certainty of the results at which I had 
arrived would have induced me so much as to examine into the 
evidence upon the subject. 

But, however perfect might be the parallelism which I was 
disposed @ priorz to attribute to waves of condensation and waves 
of rarefaction as agents for the transmission of sound, the slight- 
est examination of the auditory apparatus was sufficient to show 
that no such parallelism exists in their modes of action upon 
the organ of hearing, or in the contrivances by which the latter 
is adapted to their reception. 

The shghtest examination was sufficient to show, as I propose 
by and by to point out, that some of the most striking and 
characteristic features of the auditory mechanism are specially 
calculated to transmit the action of rarefied waves, are essential 
to such transmission, and can exercise no function in the trans- 
mission of condensed waves. Nevertheless a long-cherished 


* Although waves of condensation and waves of rarefaction are very 
commonly called into play simultaneously, it may be shown, even upon 
the principles of the existing theory, that waves of either kind are capable 
of transmission when no waves of the other kind are present. 

+ I must be understood to refer here to the theoretical velocity of pro- 
pagation apart from Laplace’s correction, which correction, for the reasons 
stated in the paper of March last before referred to, 1 cannot regard as 
otherwise than untenable. 


120 Mr. R. Moon on the Structure of the Human Ear, and on 


though erroneous mode of viewing the subject had its natural 
influence—a false theory leading to false assumptions as to mat- 
ters of fact—and for a long time prevented my recognition of 
the truth of which I was in search, and which I now proceed 
forthwith to establish, viz. that waves of condensation may be left 
out of account in considering the phenomena of aéreally transmitted 
sound. 

The structure of the human ear is described by anatomists 
with a lucidity and precision than which nothing can be more 
admirable; but when we turn from the accounts of the structure 
to the accounts of the functions of the different parts of the organ, 
all is confused and contradictory*. The subject is undoubtedly 
beset by great difficulties, two of which have been very generally 
felt and recognized :— (1) that arising from the supposed double 
transmission of motion from the tympanal membrane to the la- 
byrinth, viz. through the bones of the ear and by means of the 
air in the tympanal cavity—ain other words, through the fenestra 
ovalis and through the fenestra rotunda; (2) that due to the 
fact that very considerable power of hearing, even articulate 
sounds, often remains after the tympanal membrane has been 
removed, and the chain of bones hangs loose in, or is absent 
from the cavity. 

Nevertheless I cannot but think that the great difficulty has 
consisted in the unaccountable and unfortunate propensity+ 
which, so far as [ am aware, has characterized every writer on 
the subject, of considering the effect upon the ear of condensed 
waves alone—the efforts of each investigator being thus confined 
to examining the effect of a particular kind of wave upon an 
organ which, as I hope to show, has been expressly contrived so 
that waves of that kind shall produce upon it no effect whatever. 


* Take, for example, the testimony of Sir John Herschel, delivered so 
far back as the year 1830, but the justice of which at the present time, I 
apprehend, few will be inclined to dispute. 

‘* Of all our organs, perhaps the ear is one of the least understood.... 
In the ear everything is.... obscure. It is not with it as with the eye, 
where the known properties of light afford a complete elucidation of the 
whole mechanism of vision, and the use of every part of the visual ap- 
paratus.” | 

‘Tn the cavity behind the tympanum is placed a mysterious and com- 
plicated apparatus” [the bones of the ear]. See Ency. Met. Art. Sound, 
Nos. 319, 320. | 

+ This propensity is the more surprising when we remember that no one 
has ever supposed waves of rarefaction to be without their mfluence in the 
production of sound, that the least consideration suffices to show that 
either kind of wave may be propagated without the other, and that in a 
great number of instances, as for example the sounds produced froma 
kettledrum, where both kinds of waves occur, rarefied waves head the 
column. 


the Mode in which it administers to the Perception of Sound. 121 


The human ear may be divided into three principal regions, viz. 

(1) The external ear, of which the only portion which here 
concerns us is the meatus externus terminating in the tympanal 
membrane. 

(2) The tympanal cavity, which in the normal state is kept 
filled with air through the intervention of the Eustachian tube 
communicating with the throat; which tube is considered to be 
ordinarily closed, and from time to time opened, during the act 
of deglutition. 

(3) The internal ear or labyrinth, consisting of a chamber or 
system of mutually communicating chambers enclosed in the solid 
bone of the skull. 

Omitting details unnecessary for our present purpose, the la- 
byrinth may be described as filled with a liquid in which are 
immersed the nerves through whose agitation the sensation of 
hearing is produced. 

The fluid in the labyrinth is everywhere surrounded by the 
solid bone, with the following exceptions :— 

(a) Two small apertures, denominated respectively fenestra 
ovalis and fenestra rotunda, where in place of the bone as a boun- 
dary are substituted membranes, by which the labyrinth is sepa- 
rated from the tympanal cavity, and by which the liquid in the 
former is prevented from flowing into the latter. 

() Certain foramina or (so-called) aqueducts, through which 
the nerves with their attendant blood-vessels which supply the 
labyrinth communicate with the general nervous and circulating 
systems. 

The sensation of hearing may be occasioned by means of vi- 
brations transmitted through the bone of the skull to the laby- 
rinth ; but all articulate sounds, and in general all sounds which 
are conveyed by the air, are transmitted to the labyrinth through 
the two fenestree (ovalis and rotunda) above spoken of. 

When the ear is in its normal state (that is, when the tympa- 
num is perfect), all aéreally conveyed sounds become incident on 
the tympanal membrane in the first mstance, and are thence 
transmitted to one or both of the tympanal fenestrae by a machi- 
nery or agency which will be described hereafter. But the agi- 
tation of the tympanal membrane is a sine qud non as regards the 
transmission to the sensitive system of articulate or other aéreally 
conveyed sounds. 

And here it may be observed that if the human tympanum 
were, as its name implies, a drum (that is, a stretched flat mem- 
brane whose movements are restrained solely by the circular 
frame upon which it is fixed), no such simultaneous transmission 
of waves of rarefaction and suppression of waves of condensation 
as has above been spoken of could possibly take place. 


122 Mr. R. Moon on the Structure of the Human Ear, and on 


For under such circumstances, if a wave of rarefaction, for in- 
stance, were incident upon the tympanum, the pressure of the 
air without the tympanal membrane being less than the mean 
pressure, while the air within the tympanal membrane has the 
mean pressure, a motion of the tympanal membrane—which (if 
any) would necessarily be a motion outwards—could only take 
place by reason of the membrane being stretched. ‘The occur- 
rence of such a motion outwards would afford decisive proof that 
the membrane was capable of being stretched; and, being so 
capable, it would follow, when a wave of condensation was inci- 
dent upon it (the external being in this case greater than the in- 
ternal pressure), that motion of the tympanal membrane would 
again occur, though in this case taking place in a direction con- 
trary to that in which it occurred in the former. 

But the tympanal membrane is neither flat, nor are its move- 
ments confined simply by the quasi-circular tympanal bone to 
which it is affixed. 

The membrane is concave outwards, convex inwards; from 
which it results, as will immediately be shown, that the action 
upon it of rarefied waves and of condensed waves must be radi- 
cally different. 

When ararefied wave is incident on the membrane, the motion 
will take place outwards ; and the membrane being concave out- 
wards, all that is requisite for this is a simple flexure, a simple 
change of form of the membrane without any stretching, and 
which may be effected whether the membrane be elastic, or ca- 
pable of beimg stretched, or not. 

When a condensed wave is incident upon the membrane, on 
the other hand, the circumstances are altogether different. The 
motion in this case (if any) must take place inwards; and the 
membrane, being convex inwards, will be incapable of motion 
unless it be capable of being stretched. Nor would a mere ca- 
pacity for being stretched be sufficient to allow of continuous 
action of the ear for auditory purposes. The membrane must 
possess the power of speedily returning to its original status ; 2. e. 
it must be highly elastic. 

When the ear is in its normal state, therefore, it clearly ap- 
pears that, in order to the transmission to the sensorium of the 
vibrations of a rarefied wave, flexibility of the tympanal mem- 
brane without elasticity is sufficient; while for the like trans- 
mission of the vibrations of condensed waves elasticity of the 
membrane is essential. 

What, then, is the character as regards elasticity of the tym- 
panal membrane ? The membrane is thus described by the late 
Mr. Toynbee :— 

“Looked at from without inwards, the membrana tympani 


the Mode in which it administers to the Perception of Sound. 128 


may be described as consisting of the following layers :—(1) the 
epidermis; (2) the dermis ; (3) the fibrous layer, composed of 
(a) the lamina of radiating fibres, (b) the lamina of circular 
fibres; (4) the mucous membrane*. 

It thus appears that the tympanum is a compound membrane 
consisting of five layers which are mutually adherent, two of the 
layers partaking ofthe character of fibrous membrane. 

Dr. Brennan} has furnished a Table of the principal organic 
tissues in the order of their elasticity, which I give complete as 
follows :— 

(1) Yellow fibrous tissue, (2) cartilage, (3) fibro-cartilage, 
(4) skin, (5) cellular membrane, (6) muscle, (7) bone, (8) mu- 
cous membrane, (9) serous membrane, (10) nervous matter, 
(11) fibrous membrane. 

It thus appears that the tympanal membrane, instead of being 
highly elastic, as it has been shown that it ought to be in order 
to admit of the motion produced by waves of condensation being 
transmitted through the tympanum, involves in its composition, 
and has its elasticity measured by that of fibrous membrane, 
which is the least elastic and the most unyielding of all the or- 
ganic tissues, as to which Dr. Brennan observes that it ‘ 1s re- 
markable for its low degree of elasticity.” And that we may 
be certain that the particular membrane of the tympanum is no 
exception to the rule with regard to fibrous membrane in general, 
we have the following testimony of Mr. Toynbee :— 

“ Neither do the component fibres of the laminz appear to 
evince more than an extremely slight degree of elasticity.” 
(Diseases of the Ear, p. 1841.) 

Other arguments in favour of the position which I have been 
seeking to establish will hereafter be adduced; and in particular 
I shall endeavour to show that the auditory apparatus deprived 
of the tympanal membrane, equally with the apparatus in its 
normal state, is calculated to transmit waves of rarefaction and to 
suppress waves of condensation ; but in the mean time I would 
ask whether, if it had been the design of nature to secure such 
transmission and suppression respectively in the perfect ear, any 
construction of the tympanal membrane could have been devised 
better calculated to accomplish those objects than that which ac- 
tually occurs—the concavity of the membrane combined with its 
flexibility ensuring the transmission of rarefied waves, whilst the 
same concavity combined with inelasticity forbids the transmis- 
sion of condensed waves. 


* Diseases of the Har, with Supplement, by Hinton. London, 1868. 

+ Todd’s ‘ Cyclopedia of Anatomy and Physiology,’ vol. i. p. 60. 

t “On n’y trouve point de fibres Clastiques.”—Traité d’ Anatomie de- 
scriptive, par Cruveilhier. Paris, 1868, vol. 11. p. 674. 


124 Mr. R. Moon on the Structure of the Human Ear, and on 


The argument is not limited, however, to a bare demonstra- 
tion that the ear is open to the action of one class of waves 
while it suppresses the action of the other. It may be shown 
that some of the most remarkable and characteristic portions of 
the auditory apparatus are expressly contrived with a view to fa- 
cilitate and regulate the admission and transmission of waves of 
rarefaction, and have no intelligible function as applying to the 
transmission of condensed waves. 

If the tympanal membrane were capable of being stretched 
when a condensed wave becomes incident upon it, it is quite 
certain that its elasticity, 2. e. its tendency to recover its original 
form, would be sufficient to bring it back to its original position 
and status. 

But when, through the incidence upon it of a rarefaction, 
the membrana tympani is pushed outwards, what is to bring it 
back to its original position? There is no property of the 
membrane itself capable of producing this effect. A distinct 
machinery is requisite for the purpose; and this machinery we 
have in the muscles acting upon the bones of the ear. 

To make this clear, it will be necessary to view more in detail 
the structure of the organ. 

The tympanal membrane is connected with the fenestra ovalis 
by a chain of small bones, variously estimated as three and four 
in number, but which for our present purpose may be regarded 
with sufficient accuracy as consisting of three, stretching across 
the tympanal cavity, and respectively denominated :—(1) the 
malleus, next to the membrana tympani; (2) the incus; (3) 
the stapes, or stirrup bone, whose name describes its shape, 
the base of which is attached to the membrane of the fenestra 
ovalis. 

The three bones or ossicles are articulated upon one another 
in the order in which they have been named. The body of the 
malleus and the body of the incus, which are in juxtaposition, 
are much more massive than the other portions of the ossicu- 
lar system. The former puts out a comparatively slender arm 
called the handle of the malleus, which extends from the side of 
the tympanal cavity to about the centre of the membrana tympani. 
At the centre of the membrane, and nearly along the entire 
length of the handle of the malleus, the latter is attached to the 
membrane and moves with its motion. 

The incus sends out a slender process on the other side to 
the apex of the stirrup, to which it is attached. 

The base of the stapes is described by Sir W. Wilde as fitting 
into the fenestra ovalis “somewhat like a stopper or the piston 
of acylinder, and is attached to its circumference by a ligamento- 
fibrous membrane.” 


the Mode in which it administers to the Perception of Sound. 125 


When the membrana tympani moves outwards, as it will do 
when a rarefied wave is incident upon it, it carries along with it 
the handle of the malleus, and the tendency will be to pull out 
the base of the stirrup-bone, a tendency which, no doubt, will 
be in some degree yielded to*. And we may thus see how the 
incidence of a rarefied wave may give rise to motion of the fluid 
in the labyrinth, and consequently to such an excitation of the 
auditory nerve as will occasion the perception of sound. 

It has been already observed that when the membrana tym- 
pani has moved outwards, it has no property by which it can 
restore itself to its original position. 

This function is performed by another and most important 
part of the auditory apparatus—to wit, the muscles of the ear, 
which are thus described by Mr. Wharton Jones. 

“‘ Some anatomists admit four muscles—three attached to the 
malleus, and one to the stapes. Of the three attached to the 
malleus, two are described as having for their action the relaxa- 
tion of the membrana tympani; but these so-called laxatores 
tympani are merely ligaments..... Two muscles only can be 
strictly demonstrated, and these two are both tensors of the 
tympanum.” (Cyclop. Anat. and Physiology, vol. u. p. 547.) 

Of these two muscles, the principal (tensor tympani) is at- 
tached to the anterior surface of the handle of the malleus; and 
by its action “ the handle of the malleus is drawn inwards and 
forwards, whilst the head is moved in the opposite direction... 
The result of this movement of the bone is that the membrana 
tympani....is also drawn inwards and stretched.” In addi- 
tion to which, “‘ the base of the stapes is forced against the ves- 
tibular fenestra, in consequence of the movement communicated 
by the head of the malleus to the incus, which tends to press 
inwards the long extremity of the latter.” (Ibid. p. 549.) 

The second and smaller of the muscles (stapedius) is “ in- 
serted into the posterior and upper part of the head of the 
stapes.” 

“The first effect of the action of this muscle will be to press 
the posterior part of the base of the stapes against the vestibular 
fenestra. At the same time the long branch of the incus will 
be drawn backwards and inwards, and the head of the malleus 
being by this movement of the incus pressed forwards and out- 
wards its handle will be carried inwards, and the membrana 
tympani thus put upon the stretch.” (Ibid. p. 549.) 

It thus appears that it is the effect of both muscles :— 


* The action which takes place along the chain of bones is exactly that 
which occurs along the bell-wires when a chamber-bell is rung. Of the 
degree in which the stapes will yield to the tendency to pull it out more will 
be said hereafter. 


126 Mr. R. Moon on the Structure of the Human Ear, and on 


(1) To draw backwardsand stretch the membrana tympani ; 
(2) To force inwards the stapes*; 

that is, the effect of the muscles combined with the bones of the 
ear is to produce in the stapes and membrana tympani a motion 
opposite to that produced in them by rarefied waves of air. 

Hence, since in order that the auditory apparatus shall con- 
tinue in the exercise of its proper functions it is essential that 
it shall possess in itself the means of restoration to its normal 
state after disturbance—since, as has been seen, the combined 
bones and muscles of the ear are adequate to perform this func- 
tion as regards rarefied waves—since no other mode of perform- 
ing it is apparent—and since no other intelligible function has 
ever been ascribed to this combination of bones and musclest, 
we are justified in concluding that that most remarkable and 
characteristic portion of the auditory mechanism (the muscles of 
the ear) has been provided solely with reference to the action 
upon the organ of rarefied waves. 

It has been already stated that when the membrana tym- 
pani moves outwards, its tendency to pull out the stapes will be 
in some degree yielded to. The whole scheme of the contrivance 


* The late Mr. Toynbee (Diseases of the Ear, p. 177) appears to have 
entertained the opinion that the two muscles have opposite functions. 

I think we may conclude with certainty that such cannot be the ease; 
for otherwise, the muscles heing of the voluntary class (Wilde’s ‘ Practical 
Observations on Aural Surgery,’ 1853, p. 314), a person in the midst of 
the most absolute silence might by a mere exercise of volition produce all 
the effects occasioned by actual sounds. 

When the stapes is drawn home (that is, is forced as far as possible into 
the vestibule), there can be no doubt that if the tendon of the stapedius 
were pulled, the effect would be slightly to pull out the stapes, and at the 
same time slightly to relax the membrana tympani. But, apart from 
the question as to how far the muscle would act when the bone was 
in this position, it is evident that if instead of being driven inwards the 
stapes had been forced outwards, as it would be by the action of rarefied 
waves, any action of the stapedius muscle consequent thereupon would be 
to draw the stapes inwards and to stretch the membrana tympani. 

A careful consideration of the passages above cited from Mr. Wharton 
Jones will show that when the tensor tympani is exercised, the effect, 
amongst other things, is to produce a pressure on the anterior extremity of 
the vestibular fenestra and a slight rotation upon it, to counteract which is, 
in the perfect ear, the special function of the muscle of the stapes. 

+ Mr. Toynbee considered, and others have concurred with him in this 
opinion, “‘ that the function of the tensor tympani muscle is to protect the 
membrana tympani and the labyrinth from injury by loud sounds.” 
(Diseases of the Kar, p. 179.) Since the action of the tensor tympani takes 
place in the same direction as the action (if any) of condensed waves, it 
is not easy to see how the tensor tympani could diminish the effect of the 
latter on the membrana tympani and labyrinth. On the other hand, 
since the action of rarefied waves on the tympanum is opposite to that 
of the tensor tympani, we can comprehend how, when rarefied waves are 
incident, the tensor tympani might operate to mitigate their effect. 


the Mode in which it administers to the Perception of Sound. 127 


requires that such should be the case; but the mode in which 
this effect occurs demands very careful consideration. 

If there were no round aperture, it is clear, either that such 
effect could not occur at all, or could occur only to an extent 
almost, if not absolutely imperceptible, and certainly very much 
less than the structure of the stapes with the membrane at- 
tached to it is calculated to admit of. For in such case the 
labyrinth would be a closed vessel filled with liquid, and in all 
parts rigid except at the oval aperture. Consequently the va- 
cuum which the motion outward of the stapes would tend to 
produce must be filled up by the liquid contents of the laby- 
rinth, a result which could only occur (1) through an expan- 
sion of the liquid in the labyrinth, or (2) through a contraction 
in the space occupied by that liquid by reason of the expansion of 
the walls and solid contents of the labyrinth. It may well be 
doubted whether the expansion of the liquid in the labyrinth, or 
the contraction in the space occupied by that liquid through the 
agency just referred to, would be traceable by the aid of the 
finest instruments, whereas the extent to which the stapes may 
vibrate is perceptible, | apprehend, to the naked eye. We may 
conclude, therefore, that the existence of the fenestra rotunda is 
essential to the production in the stapes of that degree of motion 
of which it is susceptible. 

The mode in which the fenestra rotunda operates for that 
purpose may be gathered from the following passage from Sir 
W. Wilde. 

«That the membrane [of the fenestra rotunda] vibrates is 
proved by experiment; and one use of it may be to allow the 
fluid contained within the vestibule, when pressed upon by the 
base of the stapes (covering like a lid the fenestra ovalis), to 
bulge a little into the cavity of the tympanum.” (Practical Ob- 
vations &c., p. 312%.) 

Assuming that such is the case when the organ isin its normal 
state, the membrana tympani being drawn inwards+, the stapes 


* J take the following still more decisive testimony from one of an in- 
teresting series of papers in the ‘ Lancet’ by Dr. Allen. ‘ The tensor 
tympani influences principally and chiefly the drumhead by pulling in- 
wards the handle of the malleus and the membrane in which it is im- 
bedded; and in the second, but not less important, place, it stretches the 
membrane of the round cochlear opening by pressing the base of the stapes 
into the oval vestibular opening, and driving the liquor Cotunnii (or laby- 
rinth fluid) through the scale against the inner surface of the membrane 

of the round aperture] and causing it to bulge outwards.” (See ‘ Lancet’ 
for May 1, 1869.) 

7 According to Politzer (cited by Mr. Hinton), the act of swallowing 
will produce this effect by diminishing the pressure of the air in the tym- 
panal cavity. (Diseases of the Har, p. 443.) 


128 Mr. R. Moon on the Structure of the Human Ear, and on 


pressed home, and the membrane of the fenestra rotunda bulging 
out into the tympanal cavity, it is evident that when a rare- 
fied wave becomes incident upon the membrana tympani, the 
latter will move outwards, drawing the stapes from the labyrinth, 
the fluid in the latter following the stapes by reason of the 
pressure of the air in the cavity of the tympanum on the mem- 
brane of the cochlear fenestra, which would thus be driven 
inwards. 

I think that the foregoing remarks will have made evident 
what are the true relative functions of the two apertures from 
the tympanal cavity into the labyrinth. So long as disturbance 
was supposed to be transmitted along the chain of bones exactly 
in the same manner as if they had constituted a rigid bar, with- 
out producing in any degree that opening or shutting of the 
labyrinth which the whole scheme of the mechanism proves is 
possible, and was intended to be produced, the supposition that 
a like transmission took place through the air in the tympanal 
cavity was a perfectly natural and proper one. But if it be ad- 
mitted that the stapes is so fitted to the vestibular aperture as 
to admit of being pushed inwards and outwards—if the action of 
a rarefied wave on the membrana tympani is to pull it out- 
wards, while the action of the muscles of the ear is to pull it in- 
wards—and if, as we have seen, none of these capacities or ten- 
dencies can be carried into effect unless the action of the cochlear 
membrane be such as we have described it, it is clear that the 
action of the two fenestree must be opposite to each other—the 
one tending to move in as the other tends to move out, and 
vice versd, the two thus combining to produce that one effect 
(to wit, the agitation of the fluid in the labyrinth) which is essen- 
tial to the perception of sound. 

But although I consider the explanation above offered suffi- 
cient, so far as relates to the action of the perfect ear, it is 
evident that when the membrana tympani is destroyed, or, 
being perfect, the ossicular connexion between it and the laby- 
rinth is broken, the above reasoning ceases to be applicable ; 
and yet in these latter cases a very considerable amount of audi- 
tory power is frequently retained. 

I think, from what has preceded, we are entitled to assume 
that it is the function of the muscles of the ear to restore the 
auditory apparatus to its normal position of equilibrium*; 
whence it will follow, even where the membrana tympani is 


* In confirmation of this view, I cite the following passages from 
Cruveilhier. 

“La base de Vétrier, est une plaque mince... dont la configura- 
tion est exactement adaptée a celle de la fenétre ovale, qu’elle remplit par- 
faitement, ef dont on ne la retire quavec un léger effort ; en sorte que 


the Mode in which it administers to the Perception of Sound. 129 


absent, or its connexion with the labyrinth is destroyed, that 
the membrane of the round aperture, when in its normal post- 
tion, will bulge out into the tympanic cavity,—such bulging out 
resulting, in the first of the cases now spoken of, it may be, ‘from 
the united action of both the muscles of the tympanum, while 
in the latter it must be due to the operation of the stapedius 
alone. 

Such being the case, a condensed wave which became inci- 
dent upon the ear under such circumstances would be stopped 
by the membrana tympani, if that membrane were perfect ; 
or if it were absent, the condensed air pressing upon the stapes 
could have no operation to force it further into the labyrinth, 
that bone, through the operation of the stapedius muscle, being 
supposed to have been already driven as far into the labyrinth 
as the shape of the aperture, or the liquid in the labyrinth, 
would allow. 

The manner of the suppression of condensed waves, when 
the tympanal membrane is destroyed, thus readily appears. The 
mode of operation of rarefied waves under similar circumstances, 
or when, the membrana tympani being present, there is dis- 
connexion in the chain of bones, is a matter of greater de- 
licacy. 

In this case, to produce that combined action of the stapes 
and cochlear membrane which in the perfect ear has been 
shown to be essential in order to occasion the perception of 
sound, we must have, when a rarefied wave is incident, a va- 
riation in the external pressure on the two fenestre. Such a 
variation of pressure I conceive would necessarily arise from the 
different positions which the two apertures into the labyrinth 
occupy with respect to the meatus externus, the base of the 
stapes being nearly centrically opposite, and in a plane parallel 
to the position which would be occupied by the tympanal mem- 
brane if the latter were present*, while the cochlear membrane 


Vétrier a plus de tendance a tomber dans le vestibule que dans la caisse du 
tympan ”’ (vol. i. p. 680). 

“La paroi externe de la cavité du vestibule... présente Vorifice de la 
fenétre ovale ; mais cet orifice est si parfaitement comble par la base de 
Pétrier, que cette circonstance ne trouble Vaspect lisse et égal de cette 
paroi”’ (vol. ii. p. 691). See also Henle’s Handbuch gc. vol. i. p. 758. 

* For the foregomg statement I rely on the general tenor of the ac- 
counts I have read upon the subject, and on observation of preparations 
of the part in the dry bone which I have had an opportunity of examining 
in the Museum of the Royal College of Surgeons in London. As confir- 
matory, so far as they go, I would refer to the plates in Cruveilhier, vol. i. 
pp- 669 and 693 (given also in Dr. Henle’s Handbuch der systema- 
tischen Anatomie des Menschen, vol. ii. pp- 731, 760), and to that in Dr. 
Allen’s paper in the ‘ Lancet ’ for January 16, 1869. 


Phil. Mag. 8. 4. Vol. 88, No, 253. dug. 1869. K 


130 Captain F. W. Hutton on the Mechanical Principles 


is oblique to the latter—the vestibular aperture being opposed 
directly to the full stream of the wave, while the cochlear aper- 
ture is exposed to it obliquely, and, as I apprehend, though I 
speak less confidently as to this point, laterally with respect to 
the main stream of the incident wave*. 

The difference of pressure thus cccurring at the opposite ex- 
tremities of the labyrinth will necessarily cause a motion of the 
stapes outwards, to counteract which the muscle of the stapes 
will be called into play, so as to produce eventually a motion in 
the opposite direction—the same action in the labyrinth being 
thus occasioned which it has already been shown occurs when 
the ear is in its normal state, and which, I would submit, the whole 
scheme of the apparatus shows to be essential in order to cause 
in the human subject the sensation of hearing. 

The question here naturally arises—If, the tympanal mem- 
brane being absent and the malleus, incus, and Eustachian tube 
being deprived of all intelligible function, the ear is so compe- 
tent an instrument for the perception of sound, what can have 
led to the adoption of the complicated apparatus, the items of 
which have just been enumerated ? 

The consideration of this question, as of other points of the 
greatest interest connected with the subject, I must reserve to 
some future occasion. 


6 New Square, Lincoln’s Inn. 
June 22, 1869. 


XIV. On the Mechanical Principles involved in the Sailing Flight 
of the Albatros. By Captaim F. W. Huron, F.G.8.+ 


is TIL lately no subject in ornithology had been less suc- 

cessfully treated than that of flight, notwithstanding its 
great interest. This, no doubt, is owing to the great difficulty of 
the problem; for not only has the mechanism of the organs of 
flight to be perfectly understood, but the complicated question 
of the resistance of the air to differently shaped surfaces moving 
with variable velocities must also be more or less completely 
solved. The first part (i. e. the mechanism of the organs of 


* The assumption that the obliquity of the cochlear fenestra will affect 
the pressure upon its membrane implies, of course, a variation of pressure mm 
the incident wave according to the direction m which it is estimated. In 
the March paper above referred to I have shown that when a pulse is pro- 
pagated along a tube, the vibration being parallel to the axis, a diminution 
in the pressure exerted on a plane perpendicular to the axis will be due to 
the velocity. I see no reason to suppose that under the same circumstances 
any change will occur in the pressure on a plane parallel to the axis. 

+ Communicated by Alfred Newton, M.A., F.L.S. &c. 


involved in the Sailing Flight of the Albatros. 131 


flight) has recently been very ably and fully discussed by the 
Duke of Argyll in ‘The Reign of Law,’ and by Dr. Pettigrew in 
the Transactions of the Linnean Society, vol. xxvi.; the second, 
however, as far as know, has never been attempted; and I propose 
therefore to make a few remarks on the “sailing” flight of the 
Albatros (Diomedea exulans, L.), and try to determine approxi- 
mately the probable resistance of the air in order to allow it to 
sail for half an hour without moving its wings. Before com- 
mencing, however, it may be necessary to remark that the velo- 
cities spoken of are velocities of the bird through the air, and not 
over the water; for the latter will be very different when a wind 
is blowing. 

I estimate the under surface of the wings, body, and tail of 
the Albatros to be about 8 square feet (see fig. 1) ; and if we take 


Fig. 1. 


an 


OTOL 


the weight of the bird to be 16 lbs., we find that it would take a 
pressure of 2 lbs. per square foot to support it in theair. This 
pressure would be given by an upward current of air having a 
velocity of 31 feet a second if the surface acted upon were flat: 
but the wings of the bird when sailing are bent downwards (see 
fig. 2), which would increase the resistance ; on the other hand, 


Fig. 2. 


Ea i 


the body of the bird is convex, and the wings are inclined at an 
angle to the horizon, both of which would decrease the resist- 
ance, while the surface of the wings is about three times as large 
as the surface of the body and tail. Balancing one against the 
other, we perhaps shall not underestimate it if we take an up- 
ward current of air with a velocity of 30 feet per second as sutfii- 
cient to support it. This, in other words, means that on a per- 
fectly still day an Albatros with its wings outstretched, but with 
no forward movement, would fall downwards at a constantly in- 
creasing rate until it had attained a velocity of 30 feet per second, 


K 2 


132 Captain F. W. Hutton on the Mechanical Principles 


which velocity it would maintain until it fell ito the sea. This 
is called its “ terminal velocity.” 


Let AB represent the axis of the body of the bird flying in 
Fig. 3. 


the direction B A and at an angle AEH with the horizon. Let 
C D represent the wings of the bird making an angle CEH with 
the horizon. Take the lme HE to represent the velocity at 
which the bird is flying, or the number of feet it passes through 
the air in one second. From H draw the perpendicular H A; 
this line will represent the distance which the bird will rise (omit- 
ting for the present the force of gravity) by means of the angle 
at which he is flying to the horizon. But the force of the wind 
HE acting upon the inciined wings C D will be resolved into 
two forces, one of which, H K, will be parallel to the wings and 
so have no effect on them, while the other, KE, will be at 
right angles to them. This force will be again resolved into two 
others at right angles to one another—one, K L, opposing the 
forward movement of the bird, and the other, LE, causing it to 
rise ; so that the total amount that the bird will rise per second 
will be LE+HA feet. But we have previously seen that it will 
fall by the action of gravity 30 feet a second; so that in order 
that it may fly horizontally, without either rising or falling, 
LE+HA must equal 30; and we want to find what must be 
the length of HE, or, in other words, the velocity of the bird to 
do this. 

Now KE=HEsin CEH, because CHH is equal to EHK, 
and LE is equal to KE cos CEH, because KEL is also equal to 
CEH. Therefore 


LE=HE sin CEH cos CEH, and AH equals HE tan AEH ; 
“. HE tan AEH + HE sm CEH cos CHH =80, 
HE (tan AEH + sin CEH cos CEH) =80; 
ETB ep 
tan AHH + sin CHH . cos CHH 


If, now, we take AEH =0 and CEH=15>°, we shall find that 
ITE equals 115. If we take AHH =7° and CEH =22°, we find 


involved in the Sailing Flight of the Albatros. 138 


that HE equals 64. So that if an Albatros starts with a velocity 
of 115 feet a second, it could maintain a constant height above 
the sea until its velocity was reduced to 64 feet a second by 
merely increasing the angle to the horizon at which it was flying 
from 0° to 7°. 

The velocity of the air in a “ fresh sailing-breeze” is about 
30 feet a second, in a “ moderate gale” 60 feet a second, ina 
“strong gale” 90 feet a second, and in a “great storm” 120 
feet a seeond. Now an Albatros can often be seen sailing, 
though slowly, directly against a strong gale; his velocity must 
therefore often be more than 90 feet a second; he is, however, 
most at home in a strong breeze or moderate gale, when the ve- 
locity of the wind is 50 or 60 feet a second, and consequently 
when his velocity would have to be 70 or 80 feet a second to 
enable him to fly easily against it. In a calm or light air, when 
the wind has a velocity of only 10 feet a second, the Albatros 
rarely sails for so long as a minute at a time—the reason for 
this being that as, in order to sustain himself in the air, he must 
move through it with a velocity not less than 64: feet a second, 
he would, even when flying against the wind, have to travel over 
the sea at the rate of not less than 54 feet per second, or 36 
miles an hour, and so could not reach it properly for good, nor 
stop himself quick enough when he saw anything; so that the 
velocity and manner of flight observed in the Albatros correspond 
closely enough with those calculated as necessary from theore- 
tical considerations. 

We will now proceed to see what the resistance of the air to 
his forward progress ought to be to enable him to start with a 
velocity of 115 feet a second and sail for half an hour without 
flapping his wings, and at the end of that time to have reduced 
his velocity to 64 feet per second. 

If a body starts with a velocity V, and after moving for ¢ 
seconds the resistance of the air reduces its velocity to v, it can 


be shown that Te fal __ Aght 


arene "Ww? o ° e r e ° ° (1) 


where W represents the weight of the bird in pounds, A the area 
of its front surface in square feet, g the force of gravity, and k a 
constant quantity depending on the form of the surface exposed 
to the air, and probably on the velocity at which the body moves ; 
so that, in order to find this cree Be the Albatros, we have 


1 

Pee (-5 7) oi 
Aye ony 
moe Geel 


34 Captain F. W. Hutton on the Mechanical Principles 


If we take A, in the case of the Albatros, to represent one 
square foot, and put the other values into the equation, we get 
uy 16x51 
~ 115 x 64x 82 x 1800 x 1 
= 0:000002 ; 


so that the formula for the resistance of the air to the Albatros 
ought to be 


k 


R=0:000002 22. 
The formula given by Poncelet for the resistance to round shot is 
R=0-0006 Av’. 


If, therefore, these calculations are tolerably correct, the resist- 
ance offered to the Albatros must be =4,, of that offered to round 
shot. This at first sight seems to be impossible; but I must 
remark, first, that the terminal velocity of the bird may be less, 
and the angle at which it flies to the horizon greater than those 
that I have taken, either or both of which would reduce the ve- 
locity at which it was compelled to sail in order to support itself 
in the air; secondly, that the resistance of the air to the flight of 
elongated projectiles seems to be very much less than that to 
round shot; but I have seen no experiments on the subject ; 
and as the shape of the Albatros is perhaps the best that could 
be devised for penetrating the air (see fig. 1), the resistance it 
had to overcome would undoubtedly be considerably less than _ 
that offered to the best-shaped projectile ; and thirdly, that the 
formula, as obtained by experiment, for round shot does not pre- 
tend to absolute correctness, and applies to projectiles starting 
with an initial velocity of 1200 feet a second; and it is highly 
probable that the law that the resistance decreases as the square 
of the velocity does not hold good for small velocities such as 
those we are now considermg. For example, the range of the 
larger mortar-shells, which start with an initial velocity of 300 
to 400 feet per second; is‘ much more truly calculated by the pa- 
rabolic theory, which omits the resistance of the air altogether, 
than by allowing for it by means of the formula R=0-0006 Av”. 
Still the resistance to the Albatros seems very small, and it 
would be interesting to try to obtain it experimentally. From 
formula (1) we obtain 

ie W(V—v) 
ENG ag, Weg 


by which we see that weight is necessary for a bird to be able to 
sail, and that the greater the weight the longer it can continue to 
sail; but J cannot agree with the Duke of Argyll (Reign of Law, 


involved in the Sailing Flight of the Albatros. 135 


p. 152) and Dr. Pettigrew (Trans. Linn. Soe. vol. xxvi. p. 218) 
that weight is absolutely essential for ordinary flight. The fact 
of many birds diving and catching fish under water is a sufficient 
refutation of this view, as diving is only flying in water, or in 
a medium of greater specific gravity than the body of the bird ; 
for all birds, even the Penguin, are lighter than water and float 
upon it when shot; but, as Dr. Pettigrew has said (p. 214), 
the wings must in this case act differently, as they have to over- 
come an upward force of gravity instead of a downward one. 
As the resistance of the air decreases as the square of the ve- 
locity, it is evident that low velocities are favourable for long- 
continued sailing, although practically these velocities must be 
regulated by the velocity of the wind that is necessary to sail 
against. Now low forward velocities depend upon the bird having 
a small terminal velocity, which in its turn depends to a great 
extent upon a large under surface for the air to act upon, so that 
it may be said that the sailing-powers of a bird depend upon its 
weight and the expanse of its wing in proportion to its weight,— 
weight enabling, indeed compelling, it to fly, and expanse of 
wing enabling it to sail for along time. For these reasons | 
cannot agree with the Duke of Argyll (p. 157 et seg.) and Dr. 
Pettigrew (pp. 216 & 257) that long narrow wings are essential 
for sailing, and I appeal to the Condor, the Vulture, and the 
Great Bustard to bear me out. In India I have often lain on 
my back and watched through a telescope the vultures sailing 
high up in the sky, and have never seen the slightest movement 
of a wing; and in the Crimea, on the plains of the Alma, I have 
been astonished at the sailing-powers possessed by the Great 
Bustard (Otis tarda), having once seen it wheeling round in 
large circles for several minutes without moving its wings. 
Long and pointed wings, however, are necessary for turning 
quickly ; and the Albatros could not top the waves so neatly as he 
does if his wings were shaped like those of the Condor, which, 
soaring high in the air, has no necessity for sharp turns, and 
consequently for sharp-pointed wings. I may here remark that 
it is quite easy to understand, on these principles, that a bird 
having a very large expanse of wing in proportion to its weight, 
might sail for a very long time on a calm, or nearly calm day, 
when there was no wind to carry it away, and when consequently 
its velocity might be very slow. If, now, for the sake of compa- 
rison, we take the Cape-pigeon (Procellaria capensis) and assume 
the area of its under surface to be 2°5 square feet, and the area 
of its front surface to be 0:25 square foot, its weight beimg, from 
my own observations, 14 oz. or 0°88 lb., we find that it would 
have a terminal velocity of 13 feet per second, which, when fly- 
ing at the same angles as we have taken for the Albatros, will 


136 Mr. J. Parnell on a new Fluorescent Substance. 


give velocities of 52 and 29 feet per second respectively. There- 
fore 
te 0°88 x 23 
~ 52 x 29 x 82 x 0:000002 x 0°25" 


{= 843 seconds or 14 minutes ; 


so that the Cape-pigeon could sail half as long as the Albatros, 
the resistance of the air being supposed to be proportionately 
the same in both cases. This is more than we should expect, 
considering the great difference of weight of the birds, but is 
owing to the small terminal velocity of the Cape-pigeon. It 
must, however, be observed that although it seems that under 
favourable circumstances a Cape-pigeon could sail for 14 mi- 
nutes, the velocity of 29 feet a second is so smail that, in order 
to make headway against the wind, it would have to stop sailing 
and use its wings long before it had reached its least possible 
velocity ; so that it could not sail for long without being carried 
away by the wind, neither could it sail at all in a strong gale, 
except when sheltered by the waves; and this answers very well 
to what we observe; for in a gentle air the Cape-pigeon sails 
longer than the Albatros, but hardly ever in a gale. Once du- 
ring a fresh gale, the air moving probably 70 or 80 feet a second, 
when standing at the stern of the ship, a Cape-pigeon was blown 
into my hands and I caught it. 

In the foregomg brief remarks I do not pretend to have done 
more than indicate the principles involved in the flight of the 
Albatros when sailing along without moving its wings. The 
problem still remains to be solved ; but until some experiments 
have been made on the resistance offered to the air by the front 
and lower surfaces of birds, a tolerably accurate solution is not 
possible; and I hope that some person with the necessary oppor- 
tunities and means may be induced to take up this highly inter- 
esting subject. 


XV. Note on a new Fluorescent Substance. 
By Joun Parne wn, M.A., F.R.AS 


HEN aniline is heated with mercuric chloride, besides the 
ordinary formation of aniline-red, a substance is pro- 

duced in no inconsiderable quantities which possesses such a re- 
markable fluorescence that the author, not having been able to 
find any notice of it hitherto published, cannot but think it 
must up to the present time have escaped observation. The 


* Communicated by the Author. 


Mr. J. Parnell on a new Fluorescent Substance. 137 


crude mass obtained by the process above mentioned, when 
pounded, mixed with water, and washed with ether, gives an 
ethereal solution which in a concentrated state exhibits a fluo- 
rescence which it is believed has never been surpassed by any 
known body*. By this means, however, the powdered mass is 
apt to cake together, so that it is difficult to extract all the sub- 
stance in question, which, to avoid periphrasis, it is proposed tem- 
porarily to call Fluoraniline. A better method appears to be to 
dissolve the crude mass in dilute hydrochloric acid, to add am- 
monia in excess, and then to wash out with ether. The ethereal 
solution thus obtained must be repeatedly washed with water 
until the washings cease to acquire a pink colour. Thus purified it 
has a greenish-yellow colour and exhibits a green fluorescence. 
When evaporated to dryness spontaneously, the residue consists of 
two amorphous substances, one red and the other orange, the fluo- 
rescence being due apparently to the latter. The author has not 
succeeded at present in perfectly eliminating the red substance, 
although it may be got rid of to a great extent by washing the 
ethereal solution with dilute hydrochloric acid (which will extract 
the whole of the crude fluoraniline), reducing with zine, adding 
ammonia in excess, extracting with ether, and, if necessary, re- 
peating the process. From a specimen of aniline-red prepared by 
Messrs. Maule and Nicholson, but by what process the author has 
been unable to learn, as much as 10 per cent. of crude fluoraniline 
has been extracted. When an ethereal solution of fluoraniline 
is evaporated spontaneously till all the ether has gone, and then 
heated on a water-bath to drive off the small quantity of residual 
water, a strong smell of peppermint is evolved. As the heat is 
increased, a substance is volatilized which condenses as a dark 
brown matter insoluble in ether, and as still further heat is ap- 
plied hydrocyanic acid is evolved. 

Fluoraniline is almost insoluble in water when cold, but 
shghtly soluble in hot water, being precipitated as the water 
cools. It is soluble in dilute hydrochloric, nitric (thus distin- 
guishing it from chrysaniline), sulphuric, and acetic acids, giving 
fluorescent solutions, is not affected by sulphide of ammonium, 
and but slightly by hypochlorite of calcium. ‘The alcoholic so- 
lution is of a much darker colour than the ethereal, and not so 
fluorescent ; but alcohol added to a solution of fluoraniline in hy- 
drochloric acid increases its fluorescence ; it was, indeed, by add- 
ing that acid to an alcoholic solution of anilime-red that atten- 
tion was first drawn to this subject. The fluorescence of this 
substance is most remarkable. When a beam of sunlight made 


* The author has not had an opportunity of examiming a new substance 
exhibiting a green fluorescence, which has recently been obtamed by M. 
Wurtz by a totally different process. ; 


138 Dr. E. Warburg on the Heating produced in 


conical by a quartz lens is projected upon a concentrated ethereal 
solution, all the rays capable of developing fluorescence are ab- 
sorbed at the surface, so that no cone of light is visible in the 
solution; but with a dilute solution a brilliant green cone is pro- 
duced. The colours of the ethereal solution and its fluorescence 
bear a remarkable resemblance to those of uranium-glass, but 
with this difference, that when the fluorescent light is examined 
in the spectroscope, while the fluorescent spectrum of uranium- 
glass is, as is well known, discontinuous, that of fluoraniline is 
continuous. , 

As the investigation of this subject cannot be continued for 
some time to come, it has been thought desirable to publish the 
above imperfect note, that other experimenters may have the be- 
nefit of the results hitherto obtained. 


Hadham House, Upper Clapton, 
July 19, 1869. 


Postscript, July 21.—Since the above paper was written, the 
author has discovered, in the aniline-red made from stannic 
chloride, another fluorescent substance associated with fluorani- 
line. The fluorescent spectrum consists of red, a very bright 
green band, and some blue only. To the unassisted eye the fluo- 
rescence has a cold blue tint. 


XVI. On the Heating produced in Solid Bodies when they are 
Sounded. By Dr. K. Warsure*. 


Ls the twenty-fourth volume of Poggendorff’s Annalen, Wil- 

liam Weber mentions that his attention was excited by the 
difference which bodies exhibit in the rapidity with which their 
sound fades away. He shows that the resistance of the air, which 
must diminish the amplitude the more rapidly the smaller the 
mass of the body upon which it acts, is madequate to explain 
this phenomenon, and he arrives at the conclusion that it must 
have its origin in the special nature of the substance. 

As a matter of fact, the sound of lead fades away more rapidly 
than that of steel, while the density of lead is far greater than 
that of steel. 

From these considerations, part of the vis viva of the vibrations 
must be consumed im the interior of the sounding body; and the 
conclusion is obvious that it is here ‘changed into heat. ‘This 
portion will be greater in the case of those bodies in which, as 
in lead, the sound rapidly fades away—that is, only impart a 
small amount of the motion to the surrounding medium. 


* Translated from the Berliner Monatsbericht for February 1869. 


Solid Bodies when they are Sounded. 1389 


The phenomenon of deadening produced when bodies are con- 
nected with other sounding bodies gives rise to similar considera- 
tions. Ifa leaden tube (even a thin one) be so fitted to a glass tube 
as to form its prolongation, it is found that the longitudinal tone 
of the glass tube is very considerably deadened. This is the case 
even if the leaden tube is as long as half a wave-length, in which 
case the deadening is least. A steel or brass rod produces under 
these circumstances scarcely any perceptible deadening. These 
phenomena lead to the assumption that part of the ws viva of the 
vibrations in the interior of the body is consumed—and therefore 
also to the assumption that by sounding there is a production of 
heat, and a greater one in‘lead than in steel. 

The author proposed to himself the task of investigating the 
production of heat by sound from this point of view*. He 
placed the soldering of a thermopile, in the circuit of which was 
inserted an astatic galvanometer, against the part to be examined 
after a body had been made to sound. Before each experiment, 
he proved that placing the soldering against the body produced 
no deflection on the galvanometers. 


Longitudinal Tones. 


He first succeeded in demonstrating the heating produced by 
sound by means of a bar of wax, the sound of which rapidly fades 
away. A rod of wax was fixed to a thick glass tube in such a 
manner that it formed its prolongation; its length amounted 
to half a wave-length of the note (calculated from the velocity 
of the propagation of sound in wax, which the author has ascer- 
tained, and the detail of which will appear in Poggendorff’s 
Annalen). When the soldering of the thermo-element was placed 
against a node, a deflection of 800 divisions im the direction of 
heat was produced, while in the loops there was only a deflection 
of fifty divisions in the same direction. 

A leaden tube of 9 millims. external diameter fastened to the 
glass rod instead of wax, and also as long as half a wave-length, 
exhibited a heating of 800 to 400 divisions at a node, and 
-of 40 divisions in a loop. <A thinner lead tube (4 millims. ex- 
ternal diameter) of the same length, connected with the same 
glass tube, became more strongly heated: a deflection of 600 di- 
‘visions was obtained when the thermo-element was placed against 
the node after sounding the tube. The two leaden tubes were 
then placed end to end at the same end of the glass tube: in 
this case there was the same heating virtually in both. It is 


* It has not hitherto been proved experimentally that heat is produced in 
solids by sounding; for Sullivan’s experiments (Phil. Mag. S. 3. vol. xxvii. 
p- 261) and Le Roux’s (Comptes Rendus, vol. 1. p. 656) cannot be regarded 
_as a. proof of this. 


140 Dr. E. Warburg on the Heating produced in 


thence to be concluded that a thinner and thicker tube, the am- 
plitude of whose vibrations is the same, develope equal amounts 
of heat in the unit of section, that in the above experiments the 
thinner tube was only heated more strongly because the ampli- 
tude of the oscillations was greater in it; the latter is also seen 
in the circumstance that the note of the system is distinctly 
louder when the thinner is replaced by the thicker tube. 

The investigation of self-sounding lead tubes led to the same 
result. Of three tubes of the same thickness of tubing and 
length, 2 


A tube of 16 millims. external diameter after brisk rubbing 
gave no deflection at the node. 

A tube ‘of Q-millims. «2° a 2 eet OO ine 

A tube of 4-muillims; Ue 3s pee oe mOUNe es 


The intensity of the deflection decreased the greater the distance 
from the node, and in the loops there was virtually no heating 
at all. There can be no doubt that here the stronger heating of 
the thinner tubes is simply explained by the fact that when the 
same amount of force is used to excite the tone, the amplitudes 
of vibration in the narrow tubes must be greater than in wider 
ones; for with wider ones a greater mass is set in motion than 
with narrower ones. 

After it had been thus established what arrangement of the 
experiment produced the greatest increase of temperature by 
sounding, it was easy to demonstrate such a heating also in other 
bodies. The only plan, however, was to connect the metals in 
the form of thin wire with the sounding body, and then to put 
this into powerful vibrations. <A brass wire 14 to 2 millims. in 
diameter, the length of which was half the wave-length of the 
tone of the glass tube, indicated heat in the node corresponding 
to 100 divisions. If by shortening the wire the strength of the 
resonance was increased, 300 divisions were obtained. Then 
come, in decreasing order of intensity of temperature observed, 
copper, iron, steel, wood. 

A body very remarkable for its deadening properties is caout- 
chouc; and hence it is not surprising that on a short piece of 
caoutchouc tubing being fastened to the sounding glass tube 
a heating of more than 1000 divisions was obtained. A ther- 
mometer which, laid on before the experiment, showed 19°, rose, 
after the sounding, to 21°; the actual increase in temperature 
amounted therefore to 2°. 

While in tubes of other materials when several nodes are formed 
the increase of temperature on the various nodes is much the 
same, in the case of caoutchouc this is only perceptible at a small” 
distance from the place where it is fastened on the glass tube. 


Solid Bodies when they are Sounded. 141 


This is probably due to the sound becoming so enfeebled by its 
passage through the caoutchouc that its intensity 1s soon too 
small to produce an appreciable increase. 

The only substance on which I did not succeed in obtaining 
an increase of temperature by heat was glass. Thin glass tubes 
put in strong vibration by resonance invariably cracked; and 
with thick bars I could not observe a development of heat, pro- 
bably because they could not be put in sufficiently powerful vi- 
brations. 


Transversal Tones. 


From what has been said, alternate condensations and rare- 
factions which occur in longitudinal tones are an essential con- 
dition for heating to be produced by sound. Since condensations 
and rarefactions are connected with the bendings which occur in 
the case of transverse vibrations, an increase in temperature was 
to be expected in transverse vibrations. This was indeed ob- 
served; yet there was a far more complicated distribution of the 
heat than in the case of longitudinal tones. In producing the 
tones it is best to use a tuning-fork, and to connect with one leg 
the body to be investigated in the form.of wire or thin tubes, in 
such a manner that it constitutes the prolongation of the leg in 
question. It was thus possible to demonstrate an increase of 
temperature after sounding in the case of caoutchouc, lead, brass, 
copper, iron, and steel; and the intensity in the various materials 
corresponded to the values obtained by longitudinal vibrations. 
Yet in the loops in transverse vibrations there is, after sounding, 
in general as great an elevation of temperature as on the nodes ; 
in the case of caoutchouc it was certainly ascertained to be greater ; 
only at the free end it was in all cases null. The latter circum- 
stance leads to an explanation of the phenomena. In transverse 
vibrations the positions of greatest bending are those which nearly 
coincide with the loops, and they are also places where most heat 
is developed—just as in longitudinal vibrations the places where 
there is the greatest change in density, which coincide with the 
nodes, have also been seen to be places where most heat is deve- 
loped. In like manner, in accordance with Kundt’s experiments*, 
the action of sounding bars on transmitted polarized light dimi- 
nishes in the case of longitudinal vibrations towards the loops, 
and in the case of transverse vibrations towards the nodes and 
the free ends. 

Hence we may sum up the result of this investigation by say- 
ing that every solid becomes perceptibly heated by being sounded, 
provided that sufficiently powerful condensations and ravefactions 


* Poggendorff’s Annalen, vol. exxii. 


142 Royal Institution :-— 


are produced, and that the amount of heat very rapidly increases 
with the intensity of these condensations and rarefactions. 

It has further been established that various bodies exhibit a 
greater increase in temperature after being sounded the more ra- 
pidly their sound fades away, or, what.is the same, the more they 
deaden the sound of other bodies; the greatness of the differ- 
ence in the increase of temperature observed justifies the state- 
ment that the larger increments of temperature do not depend 
upon a smaller specific heat of the bodies in question, but on the 
fact that a greater quantity of heat is produced when they are 
sounded. 

In comparing the various bodies as regards the quantity of 
heat produced by sounding, it is remarked that the production 
of heat in bodies is greater the smaller the velocity of sound in 
them ; it is greatest in caoutchouc, in which sound scarcely tra- 
vels 40 metres in asecond. ‘This is connected with the fact that 
the wave-length diminishes with the velocity of sound, and that, 
if bodies are sounded with the same force, the condensations and 
rarefactions must be greater in the shorter than in the longer 
waves. 

It is also possible that specific differences in substance may 
contribute their share to the difference in the production of heat 
in various bodies. 


XVII. Proceedings of Learned Societies. 
ROYAL INSTITUTION OF GREAT BRITAIN. 


May 28, QO’ Recent Discoveries in Solar Physics made by means 
1869. of the Spectroscope. By J. Norman Lockyer, F.R.S. 
In the year 1865 two very important memoirs dealing with all the 
telescopic and photographic observations accumulated up to that 
time on the subject of solar physics were given to the world. One 
of them was privately printed in this country; the other appeared in | 
the Comptes Rendus of the Paris Academy of Sciences. 

I shall not detain you with a lengthened notice of these remark- 
able papers. I shall merely refer to the explanation given in both 
of them of the reason that a sun-spot appears dark—the very key- 
stone of any hypothesis dealing with the physical constitution of 
the sun. 

English science, represented by Messrs. De La Rue, Stewart, and 
Loewy, said that a spot is dark because the solar light is absorbed 
by a cool, non-luminous, absorbing atmosphere, pouring down there 
on to the visible surface of the sun, in other words, on to the photo- 
sphere. 

French science, represented by M. Faye, said that a spot is dark 
because it isa hole in the photosphere, and the feebly luminous and, 
therefore, radiating interior gases of the sun are there alone visible. 


Mr. J. N. Lockyer on Recent Discoveries in Solar Physics. 143 


Now most of you will see ina moment that here was a clear 
issue, which probably the spectroscope, and possibly nothing else, 
could solve; for the spectroscope is an instrument whose special 
métier it is to deal with radiation and absorption. It tells us that 
the light radiated from different bodies gives us spectra of different 
kinds according to the nature of the radiating body—continuous 
spectra without bright lines in the case of solids and liquids, and 
bright lines, with or without continuous spectra, in the case of gases 
and vapours. It tells us also that absorption dims the spectrum 
throughout its length when the absorption is general, and dims it 
here and there only when the absorption is selective, the well-known 
Fraunhofer lines being, as you will readily see, an instance of the 
latter kind. So that we have general and selective radiation, and 
general and selective absorption. 

Now, then, with regard to the English theory, if there were more 
absorption in a spot than elsewhere, we might expect evidences of 
absorption ; that is, the whole solar spectrum would be visible in the 
spectrum of a spot, but it would be dimmed, either throughout the 
length of the spectrum or in places only. 

With regard to the French theory, only radiating gaseous matter 
to deal with, we should, according to the then generally received 
idea, get bright lines only in the spot-spectrum. 

Here then was a tempting opportunity, and one which I consi- 
dered myself free to use; for, although the spectroscope had then 
been employed (and you all know how nobly employed) for four 
years in culling secrets from stars and nebule, there was not, so far 
as I know, either published or unpublished observation on the sun, 
the nearest star to us. The field was therefore open for me, and I was 
not entering into another man’s labour, when, on the 4th of March, 
1866, I attached a small spectroscope to my telescope in order to 
put the rival theories toa test, and thus bring another power to bear 
on a question which had remained a puzzle since it was first started 
by Galileo some two and a half centuries ago. 

What I saw I will describe more fully by and by. It is suffi- 
cient here to mention that it was in favour of the English theory. 
There was abundant evidence of absorption in the spots, and there 
was not any indication of gaseous radiation. 


Having then thus spectroscopically broken ground on the sun, a 
very natural inquiry was how next to employ this extension of a 
method of research, the discovery of which Newton had called, nearly 
two hundred years before, “‘ the oddest, if not the most considerable, 
detection which hath hitherto been made in the operations of nature.” 

There seemed one question which the spectroscope should now 
put to the sun above all others, and it was this :— 

*‘Assuming this absorbing atmosphere to encircle the sun, in ac- 
cordance with the general idea and Kirchhoff’s hypothesis, what are 
those strange red flames seen apparently in it at total eclipses, jut- 
ting here and there from beyond the sun’s hidden periphery, and 
here again hanging cloudlike?”’ 


144. Royal Institution :— 


The tremendous atmosphere, which apparently the spectroscope 
had now proved to be a cool absorbing one, was supposed to be 
indicated during eclipses by a halo of light called the “‘ Corona,” in 
which corona the red flames are visible. Now as the red flames are 
always observed to give out more light than the corona, they were 
probably hotter than it; and reasoning thus on the matter with my 
friend Dr. Balfour Stewart one day, we came to the conclusion that 
they were most probably masses of glowing gas. 

Now this being so, the spectroscope could help us, and in this way. 

The light from solid or liquid bodies, as you all I am sure know, 
is scattered broadcast, so to speak, by the prism into a long band of 
light, called a continuous spectrum, because from one end of it to 
the other the light is persistent. 

The light from gaseous and vaporous bodies, on the contrary, is 
most brilliant in a few channels; it is husbanded, and, instead of 
being scattered broadcast over a long band, is limited to a few lines 
in the band—in some cases to a very few lines. 

Hence, if we have two bodies, one solid or liquid and the other 
gaseous or vaporous, which give out exactly equal amounts of light, 
then the bright lines of the latter will be brighter than those parts 
of the spectrum of the other to which they correspond in colour or 
refrangibility. 

Again, if the gaseous or vaporous substance gives out but few lines, 
then, although the light which emanates from it may be much less 
brilliant than that radiated by a solid or liquid, the light may be so 
localized, and therefore inténsified, in one case, and so spread out, 
and therefore diluted, in the other, that the bright lines from the 
feeble-light source may in the spectroscope appear much brighter 
than the corresponding parts of the spectrum of the more lustrous 
solid body. Now here comes a very important point: supposing 
the continuous spectrum of a solid or liquid to be mixed with the 
discontinuous spectrum of a gas, we can, by increasing the number 
of prisms in a spectroscope, dilute the continuous spectrum of the 
solid or liquid body very much indeed, and the dispersion will not 
seemingly reduce the brilliancy of the lines given out by the gas; 
as a consequence, the more dispersion we employ the brighter re- 
latively will the lines of the gaseous spectrum appear. 

The reason why we do not see the prominences every day in our 
telescopes is that they are put out by the tremendous brightness of 
our atmosphere near the sun, a brightness due to the fact that the 
particles in the atmosphere reflect to us the continuous solar spec- 
trum. There is, as it were, a battle between the light proceeding 
from the prominences and the light reflected by the atmosphere, and, 
except in eclipses, the victory always remains with the atmosphere. 

You will see, however, in a moment, after what I have said, that 
there was a possibility that if we could bring a spectroscope on the 
field we might turn the tide of battle altogether, assuming the 
prominences to be gaseous, as the reflected continuous spectrum 
might be dispersed almost into invisibility, the brilliancy of the pro- 
minence-lines scarcely suffering any diminution by the process. 


Mr. J. N. Lockyer on Recent Discoveries in Solar Physics, 145 


The first attempt was made in 1866, a Herschel-Browning spec- 
troscope being attached to my telescope ; and the first and many suc- 
ceeding attempts failed: there was not dispersion enough to dilute 
the spectrum of the regions near to the sun sufficiently, and as a 
consequence the tell-tale lines still remained veiled and invisible. 
Nature’s secrets were not to be wrested from her by a coup de main. 


The year 1868 brought us to the now famous eclipse, to see which 
scientific men hastened from all civilized Europe to India. To this 
eclipse and its results I need only refer, as they have already been 
dwelt on at some length in this theatre; suffice it to say that in the 
eclipse the spectroscope did its duty, and that the gaseous nature of 
the prominences was put beyond all question. 

But there was a magnificent pendant to the eclipse, to which I 
must request your special attention. One of the observers, M. 
Janssen—a spectroscopist second to none—the representative, in that 
peaceful contest, of the Académie des Sciences and of the Bureau des 
Longitudes, was so struck with the brightness of the prominences 
rendered visible by the eclipse that, as the sun again lit up the scene, 
and the prominences disappeared, he exclaimed, “Je reverrai ces 
lignes-la!”’ and being prevented by clouds from putting his design 
into execution that same day, he rose next morning long before the 
sun, and as soon as our great luminary had risen from a bank of 
vapours, he succeeded in obtaining spectroscopic evidence of the pro- 
tuberances he had seen surrounding the eclipsed sun the day before. 
During the eclipse M. Janssen had been uncertain even as to the 
number of lines he had observed; but he now by this new method 
at his leisure determined that the prominences were built up of 
hydrogen, this fact being indicated by the presence of two bright 
lines corresponding to the dark lines C and F in the ordinary solar 
spectrum. 

Let me show you how this result was accomplished, by throwing 
an enlarged photograph of my telescope and spectroscope on the 
screen. We have first the object-glass of the telescope to collect the 
sun’s rays and to form an image of the sun itself on a screen. In 
this screen is an excessively narrow slit, through which alone light 
can reach the spectroscope. ‘This entering beam is grasped by an- 
other little object-glass and transformed into a cylinder* of light con- 
taining rays ofall colours, which is now ready for its journey through 
the prisms. In its passage through them it is torn by each succeed- 
ing prism more out of its path, till at last, on emerging, it crosses 
the path it took on entering, and enters the little telescope you see, 
thoroughly dismembered but not disorganized. 

Instead now of a cylinder of light containing rays cf all colours, 
we have a cylinder of each ray, which the little telescope compels to 
paint an image of the slit, Where rays are wanting, the image of 
the slit remains unpainted—we get a black line; and when the tele- 
scope is directed to the sun, so that the narrow slit is entirely within 
the image of the sun, we get in the field of view of the little tele- 
scope a glorious coloured band with these dark lines crossing it. 


* Cylindrical, that is, in the case of each pencil. 


Phil. Mag. 8. 4, Vol. 38. No. 253. Aug. 1869. y 


146 Royal Institution :— 


Of course it is necessary for our purpose to allow only the edge of 
the sun to fall on the slit, leaving apparently a large portion of the 
latter unoccupied. What is seen, therefore, is a very narrow band in 
the field of view of the little telescope and a large space nearly dark, 
as the dispersion of the instrument is so great that the atmospheric 
light is almost entirely got rid of, for a reason you are already ac- 
quainted with. . 

Mr. Ladd will now show you on the screen what is seen when the 
slit reaches a prominence. First a line in the red, very obvious and 
brilliant, next a more delicate line in the yellow, then another in the 
green, and two others in the violet; all these lines, with the excep- 
tion of the yellow line, are in the positions occupied by known 
lines of hydrogen. 

As the height of these bright lines must vary with the height of 
the prominences, and as the lines will only be visible where there is 
any hydrogen to depict, it is obvious that the form of the prominences 
may be determined by confining the attention to one line, and slowly 
sweeping the slit over it. 

The first fruits then of this new method of working with an un- 
eclipsed sun was to tell us the actual composition of the prominences, 
and to enable us to determine their shapes and dimensions. 


For the next steps you must permit me to refer more particularly 
to my own observations. 

When I was first able to obtain results in this country similar to 
those previously obtained by M. Janssen, though unknown to us, my 
instrument was incomplete ; when other adjustments had been added 
by Mr. Browning, I found that at whatever part of the sun’s edge I 
looked I could not get rid of the newly discovered lines. ‘They were 
not so long as I had seen them previously; but there they were, not 
to be extinguished, showing that for some 5000 miles in height all 
round the sun there was an envelope of which the prominences were 
but the higher waves. This envelope | named the ‘‘ Chromosphere,” 
as it is the region in which all the variously coloured effects are seen 
in total eclipses, and because I considered it of importance to distin- 
guish between its discontinuous spectrum and the continuous one 
of the photosphere. And now another fact came out. The bright 
line F took the form of an arrow-head, the dark Fraunhofer line in 
the ordinary spectrum forming the shaft, the corresponding chromo- 
spheric line forming the head; it was broad close to the sun’s edge, 
and tapered off to a fine point, an appearance not observed in the 
other lines. 

Nature is always full of surprises, and here was a surprise and a 
magnificent help to further inquiry lurking in this line of hydrogen! 
MM. Plicker and Hittorf had already recorded that, under certain 
conditions, the green line of hydrogen widened out; and it at once 
struck me that the “arrow-head”’ was nothing but an indication of 
this widening out as the sun was approached. 

I will now, then, for one moment leave the observatory work to 
say a word on some results recently obtained by Dr. Frankland and 
myself, in the researches on the radiation and absorption of hydrogen 


Mr. J. N. Lockyer on Recent Discoveries in Solar Physics. 147 


and other gases and vapours, upon which we have for some time 
been engaged. 


First, as to hydrogen, what could laboratory work tell us about 
the chromosphere and the prominences? 

It was obviously of primary importance— 

(1) To determine the cause to which the widening of the F line 
was due. 

(2) To study the hydrogen-spectrum very carefully under varying 
conditions, with a view of detecting whether or not there existed a 
line in the orange. 

We soon came to the conclusion that the principal, if not the only, 
cause of the widening of the F line was pressure. 

Having determined, then, that the phenomena presented by the F 
line were phenomena depending upon and indicating varying pres- 
sures, we were in a position to determine the atmospheric pressure 
operating in a prominence, in which the red and green lines are 
nearly of equal width, and in the chromosphere, through which the 
green line gradually expands as the sun is approached. 

With regard to the higher prominences, we have obtained evidence 
that the gaseous medium of which they are composed exists in a con- 
dition of excessive tenuity, and that even at the lower surface of the 
chromosphere (that is, on the sun itseif, in common parlance) the 
pressure is very iar below the pressure of the earth’s atmosphere. 

Now I need hardly point out to you that the determination of the 
above-mentioned facts leads us necessarily to several important mo- 
difications of the received theory of the physical constitution of our 
central luminary—the theory which we owe to Kirchhoff, who based 
it upon his examination of the solar spectrum. According to his 
hypothesis, the photosphere itself is either solid or liquid, and it is 
surrounded by an extensive cool and non-luminous atmosphere com- 
posed of gases and the vapours of the substances incandescent inthe 
photosphere. 

We find, however, instead of this compound cool and non-luminous 
atmosphere outside the photosphere, one which is in a state of in- 
candescence, is therefore luminous, and which gives us merely, or at 
all events mainly, the spectrum of hydrogen; and the tenuity of this 
incandescent atmosphere is such that it is extremely improbable that 
any considerable atmosphere, such as the corona has been imagined 
to indicate, exists outside it. 

Here already, then, we find the ‘‘ cool absorbing atmosphere”’ of 
the theorists terribly reduced in height, and apparently much more 
simple in its composition than had been imagined by Kirchhoff and 
others. Dr. Frankland and myself have shown separately :— 

(1) That a gaseous condition of the photosphere is quite consist- 
ent with its continuous spectrum, whether we regard the spectrum 
of the general surface or of spots. The possibility of this condition 
has also been suggested by Messrs. De La Rue, Stewart, and Loewy. 

(2) That a sun-spot is a region of greater absorption. 

(3) That when photospheric matter is injected into the chromo- 
sphere we see bright lines. 

2 


148 Royal Institution :— 


(4) That there are bright lines in the solar spectrum itself. 

All these are facts which indicate that the absorption to which the 
reversal of the spectrum and the Fraunhofer lines are due takes place | 
in the photosphere itself or extremely near to it, instead of in an 
extensive outer absorbing atmosphere. And this conclusion is 
strengthened by the consideration that otherwise the newly disco- 
vered bright lines of hydrogen should themselves show traces of ab- 
sorption on Kirchhoff’s theory ; but I shall show you presently that, 
so far from this being the case, they appear bright actually in the very 
centre of the disk; and, moreover, the vapours of sodium, iron, mag- 
nesium, and barium are often bright in the chromosphere, showing 
that they would always be bright there 7f the vapours were always 
present, as they should be on Kirchhoff’s hypothesis; so that we 
may say that the photosphere plus the chromosphere is the real at- 
mosphere of the sun, and that the sun itself is in such a state of 
fervid heat that the actual outer boundary of its atmosphere (7. e. the 
chromosphere) is in a state of incandescence. 

With regard to the line in the orange I have nothing yet to tell. 
Dr. Frankland and myself are at the present moment working upon it. 


I have next to take you a stage lower into the bowels, not of the 
earth, but of the sun. 

As arule, the chromosphere rests conformably, as geclogists would 
say, on the photosphere; but the atmosphere (as I have just defined 
it) is tremendously riddled by convection-currents ; and where these 
are most powerfully at work, the upper layers of the photosphere are 
injected into the chromosphere. ‘Thus I have observed the lines due 
to the vapour of sodium, magnesium, barium, and iron in the spec- 
trum of the chromosphere, appearing there as very short and very 
thin fines, generally much thinner than the black lines due to their 
absorption in the solar spectrum. 

These injections are nearly always accompanied by the strangest 
contortions of the hydrogen-lines, of which more presently. Some- 
times during their occurrence the chromosphere seems full of lines, 
those due to the hydrogen towering above the rest. 

At the same time we have tremendous changes in the prominences 
themselves, which I have recently been able to see in all their beauty. 
I have attempted to accomplish this in the first instance by means 
of an oscillating slit; but hearing that Mr. Huggins had succeeded 
in doing the same thing by means of absorptive media, using an open 
slit, it struck me at once that an open slit was quite sufficient; and 
this I find to be the case. By this method the smallest details of the 
prominences and of the chromosphere itself are rendered perfectly 
visivle and easy of observation, and for the following reason. As you 
already know, the hydrogen Fraunhofer lines (like all the others) ap- 
pear dark, because the light which would otherwise paint an image of 
the slit in the place they occupy is absorbed; but when we have a pro- 
minence on the slit, there is light to paint the slit; and as, in the case 
of any one of the hydrogen-lines, we are working with light of one 
refrangibility only, on which the prisms have no dispersive power, 
we may consider the prisms abolished. Further, as we have the 


Mr. J. N. Lockyer on Recent Discoveries in Solar Physics. 149 


prominence-image coincident with the slit, we shall see it as we sce 
the slit, and the wider we open the slit the more of the prominence 
shall we see. We may use either the red, or yellow, or green light 
of hydrogen for the purpose of thus seeing the shape and details of 
the prominences; how far the slit may be opened depends upon the 
purity ofthe sky atthe time. I have been perfectly enchanted with 
the sight which my spectroscope has revealed to me. The solar and 
atmospheric spectra being hidden, and the image of the wide slit and 
the part of the prominence under observation alone being visible, the 
telescope or slit is moved slowly, and the strange shadow-forms flit 
past and are seen as they are seenin eclipses. Here one is reminded, 
by the fleecy, infinitely delicate cloud-films, of an English hedge-row 
with luxuriant elms; here of a densely intertwined tropical forest, 
the intimately interwoven branches threading in all directions, the 
prominences generally expanding as they mount upwards, and chan- 
ging slowly, indeed almost imperceptibly. 

It does not at all follow that the largest prominences are those in 
which the intensest action or the most rapid change is going on—the 
action as visible to us being generally confined to the regions just in 
or above the chromosphere, the changes arising from violent uprush 
or rapid dissipation, the uprush and dissipation representing the birth 
and death of aprominence. As arule, the attachment to the chromo- 
sphere is narrow and is not often single ; higher up, the stems, so to 
speak, intertwine, and the prominence expands and soars upward 
until it is lost in delicate filaments, which are carried away in float- 
ing masses. 

Since last October, up to the time of trying the method of using 
the open slit, I had obtained evidence of considerable changes in the 
prominences from day to day. With the open slit it is at once evi- 
dent that changes on the small scale are continually going on; but 
it was only on the 14th of March that I observed any change at all 
comparable in magnitude and rapidity to those already recorded by 
M. Janssen. 

About 9° 45™ on that day, with the slit lying nearly along the 
sun’s edge instead of across it as usual, I observed a fine dense pro- 
minence near the sun’s equator, on the eastern limb, with signs of 
intense action going on. At 10° 50™, when the action was slacken- 
ing, I opened the slit and saw at once that the dense appearance had 
all disappeared and cloud-like filaments had taken its place. The 
first sketch, now exhibited, embracing an irregular prominence with 
a long perfectly straight one, was finished at 11° 5", the height of 
the prominence being 1! 5", or about 27,000 miles. If left the ob- 
servatory for a few minutes, and on returning at 11> 15™ I was 
astonished to find that the straight part of the prominence had en- 
tirely disappeared; not even the slightest rack appeared in its 
place. Whether it was entirely dissipated, or whether parts of it had 
been wafted towards the other part, I do not know, although I 
think the latter explanation the more probable one, as the other part 
had increased. 

So much, then, for the chromosphere and the prominences, which 


150 Royal Institution :-— 


I think the recent work has shown to be the last layer of the true 
atmosphere of the sun. I shall now invite your attention to spots. 

Now, as a rule, precisely those lines which are injected into the 
photosphere by convection-currents are most thickened in the spec- 
trum of a spot, and the thickening increases with the depth of the 
spot; so that I no longer regard a spot simply as a cavity, but as a 
place in which principally the vapours of sodium, barium, iron, and 
magnesium occupy a lower level than they do ordinarily in the 
atmosphere. . 

I have told you before, that when these lines are observed in the 
chromosphere, they usually are thinner than their usual Fraunhofer 
lines. 

I will now show a photograph of a spot-spectrum on the screen. 
You will see a black band running across the ordinary spectrum ; 
that black band indicates the general absorption which takes place 
in a sun-spot. Now mark the behaviour of the Fraunhofer lines ; 
see how they widen as they cross the spot, putting on a sudden 
blackness and width in the case of a spot with steep sides, expanding 
gradually in a shelving one. The behaviour of these lines is due to 
selective absorption. 

We have, then, the following facts: mark them well :— 

(1) The lines of sodium, magnesium, and barium, when observed 
in the chromosphere, are among those which are thinner than their 
usual Fraunhofer lines. 

(2) The lines of sodium, magnesium, and barium, when observed 
in a spot, are among those which are thicker than their usual Fraun- 
hofer lines. 

They show, I think, that a spot is the seat of a downrush or 
downsinking. 

Messrs. De La Rue, Stewart, and Loewy, who brought forward 
the theory of a downrush before my observations of an actual down- 
rush were made in 1865, at once suggested as one advantage of this 
explanation that all the gradations of darkness, from the faculee to 
the central umbra, may be supposed to be due to the same cause, 
namely, the presence to a greater or less extent of a relatively cooler 
absorbing atmosphere—thus suggesting as one cause of the darken- 
ing of a spot 

(1) The general absorption of the atmosphere, thicker here than 
elsewhere, as the spot is a cavity. 

To which the spectroscope added in 1866, as you know, 

(2) Greater selective absorption. 

J have Dr. Frankland’s permission to exhibit an experiment con- 
nected with our researches on absorption which will show you that 
this increased selective absorption can be fairly grappled with in our 
laboratories. I will show you on the screen the absorption-line due 
to sodium-vapour, in one part as thin as it is in the ordinary solar 
spectrum, in another almost if not quite as thick as it appears in a 
spot; and I accomplish this result in the following way :—Here I 
have an electric lamp, and by means of this slit I only permit a fine 
line of ight to emerge from it; here the beam passes through a bi- 


Mr. J. N. Lockyer on Recent Discoveries in Solar Physics. 151 


sulphide-of-carbon prism, and there you see on the screen the glo- 
rious spectrum due to the dismemberment of the fine line of poly- 
chromatic light. Mr. Pedler will now place a glass tube containing 
metallic sodium, sealed up with hydrogen, in front of the slit, and 
will heat it with a spirit-lamp. 

As the sodium-vapour rises you see the dark line of absorption 
make its appearance as an extremely fine line, and finally you see 
that the light which traverses the upper layer of the sodium scarcely 
suffers any absorption—the line is thin; while, on the contrary, the 
light which has traversed the lower, denser layers has suffered tre- 
mendous absorption: the line is jnordinately thick, such as we see 
it in the spectrum of a spot. 

So much, then, for the selective absorption. My recent observa- 
tions, to which I will shortly draw attention, show, I think, that it 
is of great importance, especially in connexion with the fact that the 
passage from the penumbra to the umbra is generally less gradual 
than that from the photosphere to the penumbra. You see now how 
much is included in the assertion that the photosphere is gaseous. 


You are all, I know, familiar with that grand generalization of 
Kirchhoft’s, by which he accounted for the Fraunhofer lines. 

If we have a gas or a vapour less luminous than another light- 
source, and view that light-source through the gas or vapour, then 
we shall observe absorption of those particular rays which the ga- 
seous vapour would emit if incandescent. 

Let us confine our attention to the hydrogen Fraunhofer lines. 

When I observe the chromosphere on the sun’s limb, with no 
brighter light-source behind it, I observe its characteristic lines 
bright. But when 1 observe them on the sun itself (that is, when 
the brighter sun is on the other side of the hydrogen envelope), then, 
as a rule, its function is reduced—is toned down; the envelope acts 
as an absorber, the lines are observed black. 

Now what must we conclude when I tell you that at the present 
time it is almost impossible to observe the sun for an hour without 
observing the hydrogen-lines, every now and then, bright upon the. 
sun itself ? 

Not oniy are the lines observed bright, but it would appear that 
the strongly luminous hydrogen is carried up by the tremendous 
convection-currents at different pressures ; and under these circum- 
stances the bright line is seen to be expanded on both sides of its 
normal position. Moreover at times there is a dim light on both 
sides of the black line, and the line itselfis thinned out, showing that, 
although there is an uprush of strongly luminous material, the co- 
lumn is still surmounted by some less luminous hydrogen, possibly 
separated from the other portion, which still performs the functions of 
an absorber. This seems established by another fact, namely that 
at times the lines, still black, expand on both sides, as if, in fact, in 
these regions there was a depression in the chromosphere; you 
already know that the pressure is greater at the base of the chromo- 
sphere than at the summit. 

For this reason it is best to observe these phenomena by means of 


152 Royal Institution :— 


the green line, which expands in a more decided manner by pressure 
than does the red. 


J now come to a new field of discovery opened out by these in- 
vestigations, a branch of the inquiry which I fear you will consider 
more startling than all the rest—a branch, however, which I have 
had many opportunities of studying, and which has required me to 
move with the utmost caution. I allude to the movements of the 
hydrogen envelope and prominences at which I have before hinted. 

Any one who has observed the sun with a powerful telescope, 
especially in a London fog (all too,great a rarity unfortunately for 
such work), will have been struck with the tremendous changes ob- 
served in spots. Now, change means movement; and as spot-phe- 
nomena occur immediately below the level of the chromosphere, we 
may easily imagine that the chromosphere and its higher waves (the 
prominences) will also partake of the movements, be they up- or 
downrushes, cyclones, or merely lateral motions. I have thrown on 
the screen a photograph of a drawing of a sun-spot observed under 
the ciear sky of Rome by Father Secchi—a drawing I regard as a 
most faithful counterpart of nature. 

You see how the photosphere is being driven about and contorted— 
how here it seems to be torn to ribbons by the action of some tre- 
mendous force, how here it is dragged down and shivered to atoms. 

The spectroscope enables us to determine the velocities of these 
movements with a considerable approach to accuracy; and at times 
they are so great that | am almost afraid to mention them to you. 


Let me first endeavour to give you an idea how this result is 
arrived at; and I must here beg your indulgence for a gross illustra- 
tion of one of the most supremely delicate of nature’s operations. 

Imagine a barrack out of which is constantly issuing with mea- 
sured tread and military precision an infinite number of soldiers in 
single or Indian file, and suppose yourself in a street seeing these 
soldiers pass. You standstill and take out your watch and find that 
so many pass you in a second or minute, and that the number of 
soldiers as well as the interval between them is always the same. 

You now move slowly towards the barrack, still noting what hap- 
pens. You find that more soldiers pass you than before in the same 
time, and, reckoned in time, the interval between each soldier is less. 

You now move still slowly from the barrack, 2. e. with the soldiers. 
You find that fewer soldiers now pass you, and that the interval be- 
tween each is longer. 

Now suppose yourself at rest, and suppose the barrack to have a 
motion now towards you, now from you. 

In the first case the men will be paid out, so to speak, more 
rapidly. The motion of the barrack-gate towards you will plant 
each soldier nearer the preceding one than he would have been if 
the barrack had remained at rest. The soldiers will really be nearer 
together. 

In the second case it is obvious that the interval will be greater, 
and the soldiers will really be further apart. 


Mr. J. N. Lockyer on Recent Discoveriesin Solar Physics. 153 


So that, generally, representing the interval between each soldier 
by an elastic cord, if the barrack and the eye approach each other by 
the motion of either, the cord will contract ; in the case of recession, 
the cord will stretch. 

Now let the barrack represent the hydrogen on the sun perpetu- 
ally paying out waves of light, and let the elastic cord represent one 
of these waves; its length will be changed if the hydrogen and the 
eye approach each other by the motion of either. 

Particular wave-lengths with the normal velocity of light are re- 
presented to us by different colours. 

The long waves are red. 

The short waves are violet. 

Now let us fix our attention on the green wave, the refrangibility 
of which is indicated by the F line of hydrogen. If any change of 
wave-length is observed in this line, and not in the adjacent ones, itis 
clear that it is not to the motion of the earth or sun, but to that of 
the hydrogen itself and alone that the change must be ascribed. 

If the hydrogen on the sun is approaching us, the waves will be 
crushed together; they will therefore be shortened, and the light will 
incline towards the violet—that is, towards the light with the short- 
est waves; and if the waves are shortened only by the +p>py'yy 70 
of a millimetre we can detect the motion. 

If the hydrogen on the sun is receding from us, the waves will be 
drawn out ; they will therefore be longer, and the green ray will in- 
cline towards the red. 


I must next point out that there are two different circumstances 
under which the hydrogen may approach or recede from the eye. 

I have here a globe, which we will take as representing the sun. 
Fix your attention on the centre of this globe: it is evident that an 
uprush or a downrush is necessary to cause any alteration of wave- 
length. A cyclone or lateral movement of any kind is powerless ; 
there will be no motion to or from the eye, but only at right angles 
to the line of sight. 

Next fix your attention on the edge of the globe—the limb, in 
astronomical language; here it is evident that an upward or down- 
ward movement is as powerless to alter the wave-length as a la- 
teral movement was in the other case, but that, should any lateral or 
cyclonic movement occur here of sufficient velocity, it might be de- 
tected. 

So that we have the centre of the disk for studying upward and 
downward movements, and the limb for studying lateral or cyclonic 
movements, if they exist. 

If the hydrogen-lines were invariably observed to broaden out on 
both sides, the idea of movement would require to be received with 
great caution ; we might be in presence of phenomena due to greater 
pressure, either when the lines observed are bright or black upon the 
sun; but when they widen out, sometimes on one side, sometimes 
on the other, and sometimes on both, this explanation appears to be 
untenable, as Dr. Frankland and myself in our researches at the Col- 
lege of Chemistry have never failed to observe a widening out, equally 


154 Royal Institution :— 


or nearly so, on both sides of the F line when the pressure of the 
gas has been increased. 


You see now on the screen a diagram showing the strange con- 
tortions which the F hydrogen line undergoes at the centre of the 
sun’s disk. Not only have we the line bright, as I have before told 
you, but the dark one is twisted in places, generally inclining towards 
the red; and often when this happens we have a bright line on the 
violet side. Yousee it sometimes stopping short of one of the small 
sun-spots, swelling out prior to disappearance, invisible in a facula 
between two small spots, changed into a bright line and widened 
out on both sides two or three times in the very small spots, beco- 
ming bright near a spot and expanding over it on both sides—very 
many times widened out near a spot, sometimes considerably, on the 
less refrangible side, and, finally, extended as a bright line without 
any thickening over a small spot. 

Now the other Fraunhofer lines on the diagram may be looked 
upon as so many milestones telling us with what rapidity the uprush 
and downrush take place; for these twistings are nothing more nor 
less than alterations of wave-length, and, thanks to Angstrom’s map, 
we can map out distances along the spectrum from Fin zppp/ppa0ths 
of a millimetre from the centre of that line; and we know that an 
alteration of that line z5gq5gn7 millim. towards the violet means 
a velocity of 38 miles a second towards the eye (2. e. an uprush), and 
that a similar alteration towards the red means a similar velocity 
from the eye (7.e.adownrush). The fact that the black line inclines 
to the red shows that the less bright hydrogen descends; the fact 
that the bright line (where both are visible side by side) inclines to 
the violet shows that the more vivid hydrogen ascends; and the alte- 
ration of wave-length is such that 20 miles a second is very common. 

Now, observations of the lateral motions at the limb are of course 
made by the chromospheric bright lines seen beyond the limb. Here 
the velocities are very much more startling—not velocities of uprush 
and downrush, as you now know, but swinging and cyclonic motions 
of the hydrogen. 

I will first show you a cyclone observed on the 14th of March ; 
but before I do so Jet me make one remark. Although the slit used 
is as narrow as I can make it, let us say =3, (I have not measured 
it) of an inch, a strip of this breadth, of the sun’s image, is some- 
thing considerable, as the glorious sun himself is painted by my 
object-glass only about ‘94 inch in diameter, so that after all the slit 
lets in to be analyzed a strip some 1800 miles wide. 

Now, suppose we have a cyclone of incandescent hydrogen some 
1500 miles wide tearing along with a very rapid rotatory motion, it 
is clear that all this cyclone could fall within the slit, and that, if the 
rotatory motion were sufficiently rapid, the spectroscope should sepa- 
rate the waves which are carried towards us from those which are rece- 
ding. It does this: as you see, we have an alteration of wave-length 
both towards the red and violet, amounting to something like 40 miles 
a second. Now it should be clear to you that, by moving the slit 
first one way and then the other, we may be able to bring it in turn 


Mr. J. N. Lockyer on Recent Discoveries in Solar Physics. 155 


to such positions that only the light proceeding from either side of 
the cyclone can enter it. Then we shall have changes of wave- 
length in one direction only ; in each case precisely as you see was 
observed. 

Now let us suppose that instead of a cyclone we have a motion of 
some portions of the prominence towards the eye, and that, more- 
over, the rate of motion varies excessively in some portions. What 
we shall see will be this. The portion of the prominence at rest will 
give us no alteration of wave-length; its bright line will be in a line 
with the corresponding black one in the spectrum. The portion 
moving towards the eye, however, will give us an alteration of wave- 
length towards the violet. You are now in a position to grasp the 
phenomena revealed to me by my spectroscope on the 12th instant, 
when at times the F line was triple! the extreme alteration of wave- 
length being such that the motion of that part of the prominence 
giving the most extreme alteration of wave-length must have ex- 
ceeded 120 miles per second, if we are to explain these phenomena 
by the only known possible cause which is open to us. 

By moving the slit it was possible to see in which part of the pro- 
minence these great motions arose, and to follow the change of 
wave-length to its extremest limit. 


By the kindness of Dr. Balfour Stewart I am able to exhibit to 
you some of the Kew sun-pictures, which show you how these spec- 
troscopic changes are sometimes connected with telescopic ones. 

On the 21st of April there was a spot very near the limb which I 
was enabled to observe continuously for some time. At 7.30 a.m. 
there was a prominence visible in the field of view, in which tremen- 
dous action was evidently going on, for the C, D, and F lines were 
magnificently bright in the ordinary spectrum itself; and as the spot- 
spectrum was also visible, it was seen that the prominence was in 
advance ofthe spot. The injection mto the chromosphere surpassed 
anything I had seen before, for there was a magnesium cloud quite 
separated from the limb, and high up in the prominence itself. 

By 8.30 the action had quieted down; but at 9.30 another throb 
was observed, and the new prominence was moving away with tre- 
mendous velocity. While this was going on, the hydrogen-lines 
suddenly became bright on the other side (the earth’s side) of the 
spot, and widened out considerably—indeed to such an extent that 
I attributed their action to a cyclone, although, as you know, this 
was a doubtful case. 

Now, what said the photographic record? The sun was photo- 
graphed at 10° 55™ a.m., and I hope you will be able to see on the 
screen how the sun’s surface was disturbed near the spot. A sub- 
sequent photograph, at 4" 1™ p.m. on the same day, shows the limb 
to be actually broken in that particular place; the photosphere seems 
to have been absolutely torn away behind the spot, exactly when the 
spectroscope had afforded me possible evidence of a cyclone! 


In connexion with the last branches of the research I have brought 
to your notice, | may remark that we have two very carefully pre- 


156 Royal Society:— 


pared recent maps of the solar spectrum, one by Kirchhoff, the other 


by Angstrom, made a few years apart and at different epochs with 
regard to the sun-spot period. If you look at these maps you will 
see a vast difference in the relative thicknesses of the C and F lines, 
and great differences in the relative darkness and position of the 
lines; and if I had time I could show you that we now may be sup- 
plied with a barometer, so to speak, to measure the varying pres- 
sures in the solar and stellar chromospheres; for, depend upon it, 
every star has, has had, or will have a chromosphere, and there are 
no such things as ‘‘ worlds without hydrogen,” any more than there 
are stars without photospheres. I suggested in 1866 that possibly 
a spectroscopic examination of the sun’s limb might teach us some- 
what of the outburst of the star in Corona; and already we see that 
all that is necessary to get just such an outburst in our own sunis to 
increase the power of his convection-currents, which we know to be 
ever at work. Here, then, is one cataclysm the less in astronomy 
—one less ‘‘ world on fire,” and possibly also a bright light thrown 
on the past history of our own planet. 

I might show you further that we now are beginning to have a 
better hold on the strange phenomena presented by variable stars, 
and that an application of the facts I have brought to your notice 
this evening, taken in connexion with the various types of stars 
which have been indicated by Father Secchi with admirable philo- 
sophy, opens out generalizations of the highest interest and import- 
ance, and that, having at length fairly grappled with some of the 
phenomena of the nearest star, we may soon hope for more certain 
knowledge of the distant ones. 

At present, however, we may well leave speculation for those who 
prefer it to acquiring facts; let us rather, emboldened by the work 
which this new method of research has enabled us to accomplish in 
this country, under the worst atmospheric conditions, in seven short 
months, go on quietly deciphering one by one the letters of this 
strange hieroglyphic language which the spectroscope has revealed 
to us—a language written in fire on that grand orb which to us 
earth-dwellers is the fountain of hght and heat, and even of Iife 
itself. 


ROYAL SOCIETY. 
[Continued from p. 73.] 
March 4, 1869.—Lieut.-General Sabine, President, in the Chair. 


The following communication was read :— 

“Note on the Formation and Phenomena of Clouds.’’ By John 
Tyndall, LL.D., #.R.S. 

It is well known that when a receiver filled with ordinary undried 
air is exhausted, a cloudiness, due to the precipitation of the aqueous 
vapour diffused in the air, is produced by the first few strokes of the 
pump. It is, as might be expected, possible to produce clouds in 
this way with the vapours of other liquids than water. 

In the course of the experiments on the chemical action of light 


Dr. Tyndall on the Formation and Phenomena of Clouds. 157 


which have been already communicated in abstract to the Royal 
Society, I had frequent occasion to observe the precipitation of such 
clouds in the experimental tubes employed; indeed several days at a 
time have been devoted solely to the generation and examination of 
clouds formed by the sudden dilatation of the air in the experimental 
tubes. 

The clouds were generated in two ways: one mode consisted in 
opening the passage between the filled experimental tube and the 
air-pump, and then simply dilating the air by working the pump. 
In the other, the experimental tube was connected with a vessel of 
suitable size, the passage between which and the experimental tube 
could be closed by a stopcock. This vessel was first exhausted ; on 
turning the cock the air rushed from the experimental tube into the 
vessel, the precipitation of a cloud within the tube being a conse- 
quence of the transfer. Instead of a special vessel, the cylinders of 
the air-pump itself were usually employed for this purpose. 

It was found possible, by shutting off the residue of air and vapour 
after each act of precipitation, and again exhausting the cylinders of 
the pump, to obtain with some substances, and without refilling the 
experimental tube, fifteen or twenty clouds in succession. 

The clouds thus precipitated differed from each other in luminous 
energy, some shedding forth a mild white light, others flashing out 
with sudden and surprising brilliancy. This difference of action is, 
of course, to be referred to the different reflective energies of the par- 
ticles of the clouds, which were produced by substances of very dif- 
ferent refractive indices. 

Different clouds, moreover, possess very different degrees of sta- 
bility ; some melt away rapidly, while others linger for minutes in 
the experimental tube, resting upon its bottom as they dissolve like 
a heap of snow. ‘The particles of other clouds are trailed through 
the experimental tube as if they were moving through a viscous 
medium. 

Nothing can exceed the splendour of the diffraction-phenomena 
exhibited by some of these clouds; the colours are best seen by 
looking along the experimental tube from a point above it, the face 
being turned towards the source of illumination. The differential 
motions introduced by friction against the interior surface of the 
tube often cause the colours to arrange themselves in distinct layers. 

The difference in texture exhibited by different clouds caused me 
to look a little more closely than I had previously done into the 
mechanism of cloud-formation. A certain expansion is necessary to 
bring down the cloud; the moment before precipitation the mass of 
cooling air and vapour may be regarded as divided into a number of 
polyhedra, the particles along the bounding surfaces of which move in 
opposite directions when precipitation actually setsin. Every cloud- 
particle has consumed a polyhedron of vapour in its formation; and 
it is manifest that the size of the particle must depend, not only on 
the size of the vapour polyhedron, but also on the relation of the 
density of the vapour to that of its liquid. If the vapour were 
light, and the liquid heavy, other things being equal, the cloud- 


158 Royal Society :—Messrs. Dupré and Page on the Physical 


particle would be smaller than if the vapour were heavy and the 
liquid light. There would evidently be more shrinkage in the one 
case than in the other: these considerations were found valid through- 
out the experiments. The case of toluol may be taken as representa- 
tive of a great number of others. The specific gravity of this liquid 
is 0°85, that of water being unity; the specific gravity of its vapour 
is 3°26, that of aqueous vapour being 0°6. Now, as the size of the 
cloud-particle is directly proportional to the specific gravity ef the 
vapour, and inversely proportional to the specific gravity of the 
liquid, an easy calculation proves that, assuming the size of the va- 
pour polyhedra in both cases to be the same, the size of the particle 
of toluol cloud must be more than six times that of the particle of 
aqueous cloud. It is probably impossible to test this question with 
numerical accuracy ; but the comparative coarseness of the toluol 
cloud is strikingly manifest to the naked eye. The case is, as I have 
said, representative. 

In fact, aqueous vapour is without a parallel in these particulars ; 
it is not only the lightest of all vapours, in the common acceptation 
of that term, but the lightest of all gases except hydrogen and am- 
monia. ‘To this circumstance the soft and tender beauty of the clouds 
of our atmosphere is mainly to be ascribed. 

The sphericity of the cloud-particles may be immediately inferred 
from their deportment under the luminous beams. The light which 
they shed when spherical is conéinuous: but clouds may also be pre- 
cipitated in solid flakes ; and then the incessant sparkling of the cloud 
shows that its particles are plates, and not spheres. Some portions of 
the same cloud may be composed of spherical particles, others of 
flakes, the difference beg at once manifested through the calmness 
of the one portion of the cloud, and the uneasiness of the other. 
The sparkling of such flakes reminded me of the plates of mica in 
the river Rhone at its entrance into the Lake of Geneva, when shone 
upon by a strong sun. 


March 11.—Lieut.-General Sabine, President, in the Chair. 


The following communication was read :— 
“On the Specific Heat and other physical properties of Aqueous 
Mixtures and Solutions.” By A. Dupré, Ph.D., and F. J. M. Page. 


Part I. 
Mixtures of Hthylice Alcohol and Water. 
Section 1. Specific Heat. 


For the methods employed in estimating the specific heat of these 
mixtures, see a former abstract, ‘ Proceedings of the Royal Society,’ 
vol. xvi. p. 336 (Phil. Mag. 8. 4. vol. xxxv. p. 464). 

- the present paper the authors give the specific heat of an ad- 
ditional number of mixtures, so as to complete the series for every 
10 per cent. from water to absolute alcohol. 

The following Table gives the mean of the results obtained in all 
experiments, details of seventy-four of which are given :— 


Properties of Aqueous Mixtures and Solutions. 159 


Percentage of Specific heat Specific heat . 

alcohol, by eit ‘ found. EaagSe Dilenaing: 
5 Tey toy a ne. ee Soe er ee 

10 103°576 96043 7 533 

20 104°362 92086 12°276 

30 102'602 38°129 14°473 

40 96°805 : 84°172 12°633 

45 94/192 82°193 11°999 

50 90°633 80°215 10°418 

60 34.°3 32 76258 8°074. 

70 78°445 72°301 6144 

80 71°690 68°344. 3°346 

go 65°764 64°387 1°377 

100 60°4.30 So PETA PaNOURS Mame: So Dey! 


Section 2. Heat produced by the mixing of Alcohol and Water. 

This was estimated as follows:—The liquid which formed the 
smallest portion of the mixture was sealed up in a thin glass bulb ; 
this was then introduced into the calorimeter, the glass bulb was 
broken, the mixture formed, and the rise in the temperature of the 
calorimeter observed. 

The units of heat evolved in the formation of 5 grms. of each 
mixture were thus calculated, and found to be— 
10 per cent. spirit .... 26°6850 | 50 per cent. spirit .... 35°5850 
20 


= i ee 435°9545"+ 60 ps ss Be earl iy.) 
30 » ie ene 1479500, ) 70 % Fe ete 1Os8200 
40 t. Pan 5s 144-3630; % SO Pe > dal! D247 7 5 
45 ”? 99 ~ 38°8095 90 ” 99 es eee 7°7025 


Section 3. Bozling-points. 

A smail flask was taken ; into this 100 cub. centims. of the mixture 
was introduced, and the mouth of the flask closed by a doubly perfo- 
rated cork. Into one of these perforations a thermometer was intro- 
duced, into the other a bent tube, dipping beneath the surface of the 
liquid in the flask, and connected at its other extremity with a Liebig 
condenser. This tube had a lateral opening (inside the flask) just 
beneath the cork; by means of this the vapour escaped to the con- 
denser, and trickled back into the flask after being condensed. Thus 


Percentage of Boiling-point Boiling-point 


alcohol, by weight. observed. calculated *. Difference. 
° BO A ee eee alh | eewieet saree AC Orly) She cperataay ae 
10 90°98 97°25 — 6:27 
20 86°50 95°10 — 8°60 
30 84°01 92°95 — 894 
40 32°52 go"go — 3°38 
45 81°99 89°72 HY s 
50 31°33 88°60 —7'27 
60 80°47 86°50 — 6°03 
79 79°61 84°35 —4°74 
80 73°34. 32°20 —3°36 
90 73°01 80°05 —2°04 
100 FARGO Pah MIS) Ne els Bieta 8 Kas 3 


* Calculated on the assumption that the alcohol and water in a mixture have 
an influence on the boiling-point of the mixture proportional to their respective 
weights. 


160 Royal Society :—Messrs. Dupré and Page on the Physical 


the composition of the mixture was retained as uniform as possible. 
Thus estimated, the barometer standing at 744°4 millims., the boil- 
ing-points are given in the preceding Table. 


Section 4. Capillary Attraction. 


This was estimated by carefully observing the heights to which 
the several mixtures rose ina capillary tube 0°584 millim. in diameter. 

These heights were measured by means of a telescope and a mil- 
limetre-scale etched on a glass rod. This glass rod was fixed to the 
capillary tube, and terminated at its lower extremity in a point, 
which was made just to touch the surface of the liquid. 

Several precautions were necessary to render the measurements ac- 
curate. 

The results are contained in the following Table :— 


Percentage io . ine : 
ge | Height, assuming Relative molecular 


of alcohol, by water eta Aha Height caleulated.| Difference. 
weight. = 100 millims. 

re) I00°0O Io0o°o0o TOO%0O% = ba eee ete e itt ° 
10 69°17 68°07 93°11 —25°04 
20 56°43 54°33 86°22 — 31°39 
30 48°19 46°15 79°34 — 33°19 
40 45°30 42°56 72°45 —29°89 
45 43°74 40°64, 69°00 — 28°36 
50 42°93 39°43 65°56 —26°13 
60 42°30 37°89 58°68 —20°79 
70 41°76 36°42 51°79 5537 
80 41°29 35°03 44°90 ST 
go 40°54 33°35 38°02 — ae 

100 39°21 31°13 31°13 an sip eee 


The third column gives the length of a column of water equal in 
weight to the thread of alcoholic mixture contained in the second 
column, and gives, therefore, a measure of the relative strength of 
the molecular attraction in the various mixtures. 

The experiments were made at a temperature of 16° C. 

Section 5. Rate of Expansion. 

This was determined by estimating the specific gravity of the dif- 
ferent mixtures at the temperatures 10°C., 15°°5 C., 20°C. 

The specific-gravity bottle has two necks ; into one was fitted a ther- 
mometer with a long bulb, whilst the other ended in a capillary tube. 

This bottle was placed in a water-bath, whose temperature was 
under perfect control, and thus the specific gravity could be accu- 
rately estimated at the above-named temperatures. 


Section 6. Compressibility. 


This property was estimated by an apparatus similar to the one em- 
ployed by Regnault and Grassi, but of simpler construction. 

The piezometer was of glass; pressure was applied to the inside 
and outside by forcing air into the apparatus by means of a small 
pump ; 0°000002 was always added as a correction for the compres- 
sibility of the piezometer. 

The two following Tables give the results obtained in Sections 5 
and 6, 


Properties of Aqueous Mixtures and Solutions. 161 


Percentage ° ° 
Volume at | Volume at 20° C.,| Volume at 20°C., : 
pF steohol, by 10° C. found. calculated, IDRIS EG 
weight. 
fe) 100 TOO"I 54. 100154. pieeehietd 
fe) 100 100°2 12 100°272 —o6o0 
20 100 100°405 100°386 +019 
30 100 100°632 100°498 +°134 
40 100 100°733 100°601 +°182 
45 100 100°827 100°652 +175 
50 100 100°868 100°700 +'168 
59°77 100 100°914, 100°789 +°125 
69°73 100 100°980 100'3874 +°106 
79°81 100 TOI'O20 1009 54. +'066 
89°89 100 IOI"O52 IO1°034. +:o18 
100°00 100 101088 TODOS Ss buyer ine aaleteey ae 
Percentage | Compressibility | Compressibility for 
of alcohol, by for one one atmosphere, Difference. 
weight. _jatmosphere, found. calculated. 
fe) 0°00004774. GiOGCOAT IAAL MAGE POLC et seres 
fe) 0°000043 51 0°00005387 0°00001036 
20 0°00003g911 0700005998 0'00002087 
30 0°00003902 0°00006 534. 0°00002682 
40 0°00004.347 0°00007118 0°00002771 
45 0700004608 0°00007366 0°00002758 
50 0°00004878 0°00007600 0°00002722 
59°77 0°0000 5620 0°00008029 0°00002409 
69°73 0°00006159 0°00008426 0°00002267 
73°31 0°00006942 0°00008775 0°00001833 
89°89 0*000079 50 0°00009140 O*0O0001 190 
100°00 0°00009349 0°00009 349 


Weight of water contained in the piezometer 114°9727 germs. 
In conclusion the authors confine themselves to pointing out cer- 
tain relations which connect the various physical properties examined. 


These properties may be divided into two classes, according as 


they reach a maximum deviation from the theoretical mean a 30 


per cent, or 40 per cent.; each of these is divided into two sub- 
classes, one containing those properties in which the numbers found 


are above those calculated, and the other containing those in which 


they are below. 
Class I 


Subclass a. 


Specific heat. 


Heat produced by mixing. 
oe 6. Boiling-point. 
Capillary attraction. 
Class IT. 
Subclass c. Rate of expansion. 
d. Compressibility. 

Other characters, examined by previous investigators, are :— 
1. Vapour-tension: this falls under Class I. Subclass 6. 
2. Specific Gravity. 

3. Index y refraction. 
Phil. Mag. 8.4. Vol. 38. No. 258. Aug. 1869. M 


162 Geological Society :— 


The two latter form a new class, coming to a maximum deviation 
from their theoretical value at 45 per cent. 

In subclass a, specific heat—by reference to the Tables given, it 
will be seen that the first addition of alcohol to water (though 
alcohol has a specific heat much lower than that of water) produces 
mixtures which have a higher specific heat than water, and that a 
mixture containing between 30 and 40 per cent. alcohol has the 
same specific heat as water. 

Similarly alcohol, though much more compressible than water, 
yet, when added to it, forms mixtures less compressible than water ; 
so that a mixture containing between 45 and 50 per cent. alcohol 
has the same compressibility as water. 

The rate of expansion is remarkable, as, starting from water, it at 
first 1s below the theoretical value, then rises; at 17 to 18 per cent. 
the rate of expansion is identical with the calculated expansion ; for 
all mixtures stronger than this, the rate of expansion is constantly 
above that calculated. 

The whole of the physical characters of mixtures of alcohol and 
water come to a maximum deviation from their theoretical values 
somewhere between 30 per cent. and 45 per cent. alcohol by weight. 
The 30 per cent. nearly corresponds to the formula C, H,O+6 OH, 
(=29-87 per cent.) ; the 45 per cent. has approximately the formula 
C, H, 0+3 0 H, (=46 per cent.). 

Some of the physical properties examined seem to be especially 
connected with each other; these are :— 


1. Specific heat and heat produced by mixing; for by dividing 
the number of units of heat evolved by 5 grammes of any 
mixture by 3°411, the elevation of the specific heat of such 
mixture above the theoretical specific heat is obtained. 

2. Boiling-point and capillary attraction ; by dividing the depres- 
sion of the capillary attraction by 3°6, the depression of the 
boiling-point is obtained. 

Deville & Hoek have shown the specific gravity and index of re- 
fraction to be connected with each other (Ann. de Chim. et de Phy- 
sique, 3rd ser. vol. v. Pogg. Ann. vol. cxii.). 

Whether the relations thus established between the various phy- 
sical properties of alcoholic mixtures hold good with other similar 
substances, or whether these mixtures ferm a singular exception, 
must be decided by further research. 


GEOLOGICAL SOCIETY. 
[Continued from p. 376. ] 

December 9th, 1868.—Prof. T. H. Huxley, LL.D., F.R.S., 
President, in the Chair. 

The following communications were read :— 

2. “On the occurrence of Celestine in the Tertiary rocks of 
Egypt,” By H. Bauerman, Esq., F.C.S., and C. Le Neve Foster, 
D:8e,,.8:G.8. 

This communication referred to the presence of celestine at two 
different horizons in the Tertiary escarpment of Mokattam. The 
beds forming the escarpment may be divided into two parts, namely;— 


Dr. P. M. Duncan on Echinodermata, &¢. of Sinai. 168 


the upper beds, which are brown, sandy, cellular limestones with 
numerous oyster-beds; and the lower, or white Nummulitic lime- 
stone proper. A bed of marl with fibrous gypsum generally occurs 
at the junction of the two groups of strata. 

In the upper or brown beds celestine occurs with gypsum, some- 
times in isolated crystals, but more generally in stellar or spheroidal 
nodular aggregates, the points of the crystals being turned outwards. 
About thirty feet lower down in the white limestone, rough irregular 
erystals of the same mineral are found in open hollows or druses. 
They are often large, but much decomposed, and apparently crusted 
with Nummulites, Bryozoa, &c., which are in reality included in 
the crystals, and have become exposed by erosion. The erosion 
and alteration of the crystals commences by the roughening of the 
faces of the prism, owing to the formation of numerous fine stria- 
tions parallel to the basal planes, and goes on frequently until the 
entire disappearance of the crystals. The ultimate product is a 
hollow cast of the crystal, which may then be filled with limestone, 
forming a pseudomorph by total replacement. This, however, ap- 
pears to be rare. More generally the dissolved celestine has been 
redeposited upon the altered crystals, forming macled groups. The 
secondary crystals are compact, brilliant, and well formed, without 
included foreign bodies. These phenomena were attributed by the 
authors to the solubility of sulphate of strontia in chloride of sodium. 


3. “Note on the Echinodermata, Bivalve Mollusca, and some 
other Fossils from the Cretaceous Rocks of Sinai.” By Dr. P. Martin 
Duncan, F.R.S., Sec. G.S., &e. 

The author identified the fossils brought by Mr. Bauerman from 
Sinai as belonging to the Upper-Greensand and Hippuritic-Chalk 
horizons, and correlated them with those of Algeria and South- 
eastern Arabia. He determined the following species :— 


Heterodiadema Libycum, 4g. & Desor, | Neithia tricostata, Bayle. 
we Exogyra plicata, Goldfuss. 
Discoidea subucula, Klein. Ostrea Auressensis, H. Coq. 
Forguemolli, H. Coq. , var. major, Dune. 
Epiaster distinctus, Agass. Mermeti, H. Cog. 
tumidus, Desor. Exogyra Overwegi, von Buch. 
Periaster oblongus, D’ Orb. Ostrea Delattrei, H. Cog. 


Hemiaster Cenomanensis, Cotteau. 
Phymosoma Delmarrei, Desor. 
Pseudodiadema variolare, Brongn. 


eurvirostris, lVi/ss. 
Caprotina Toucasiana, D’ Ord. 
subequalis, D’ Ord. 


Pedinopsis, sp. —— Archiacianus, D’ Ord, 
Plicatula Fourneli, H. Cog. Radiolites, sp. 
Pecten asper, Lam. Clavagella, sp. 


Neithia alpina, D’ Orb. 


4, “On the Existence during the Quaternary Period of a Glacier 
of the Second Order, occupying the ‘ cirque’ of the valley of Palheres 
in the western part of the granitic ‘massif’ of the Lozére.” By M. 
C. Martins, For. Corr. G.S. 

After mentioning that no one had satisfactorily proved the former 
existence of glaciers in the Puys of Auvergne, the Cevennes moun- 
tains, or the massif of the Lozere, the author stated that, from study- 
ing the Government map, it occurred to him that traces of a glacier 
ought to be found in the eastern part of the granitic massif of the 


M 2 


164 Intelligence and Miscellaneous Articles. 


Lozére, at the upper portion of the Valley of Palheres, which opens 
near Villefort. An examination of the district in question proved 
the former existence of a glacier which was limited to the cirque 
which enclosed it, and did not descend into the valley. A lateral 
and a terminal moraine were found, and roches perchées were ob- 
served on the sides of the valley. No striz or polished surfaces 
were seen, owing to the schistose rocks being easily decomposed. 


XVIIL. Intelligence and Miscellaneous. Articles. 


ON THE COMPRESSIBILITY OF LIQUIDS. 
BY MM. AMAURY AND DESCAMPS. 

N June 1868, in conjunction with M. Jamin, we laid before the 
Academy a method for measuring the compressibility of liquids ; 
since then M. Jamin has intrusted to us the task of continuing this 
research. We have made a great number of determinations, the 
results of which we have the honour to lay before the Academy. 
The following Table gives the coefficients of compressibility for one 


atmosphere :-— 35 
Distilled. water athe ols Chara. mae 0:0000457 
INOUE aoa) fu tones ore G@UAODODS 3a 
Wilicolt@his. cert tens 15 sees th. « nO OO0OS IE 
Hehenmea hea ects Otis intern Se 0:000109 
ther. sey ase la Jeeteis wes -, pOVOOOI 
Sulphide vongcanbony Iisa ore cea 0:0000635 
MCKCUTY tact eee One te eee 0:00000187 
Solution of chloride of potassium,— 

Containing in 1000 of water 50 of KCl...... 0:0000419 
6 ys LOOips totes Baton 0:0000388 
$5 i 15) OF rere nren ots 5 « 0°0000556 
sy 35 2OOs 1555 Ties Cae 0°0000332 
6 ¥5 oO 8 comet tee ener 0:0000318 
A sis 300 4; .. «tue 00000306 

Wiater:%y. waiiiek. sts otters omar te. Ua Meer eee 0:0000457 


These coefficients have been deduced from experiments in which 
the pressure varied from 1 to 10 atmospheres. 

We may observe that the coefficient 0°00000187 found for mer- 
cury varies considerably from the coefficient 0:00000295 which 
Grassi obtained by the use of M. Regnault’s method, while with the 
more compressible liquids the agreement between our numbers and 
those of M. Grassi is perfect. ‘This difference arises from the cir- 
cumstance that, as the compressibility of mercury is very small, the 
least error in the measurement of the correction due to the change 
of volume in the piezometer has a considerable influence on the true 
coefficient, whereas with the more compressible liquids this source 
of error is less apparent. 

The expansion of liquids, as is well known, gradually increases 
with the temperature, and, when they reach the boiling-point, is vir- 
tually equal to that of gases. We imagined it would be the same 
with their coefficient of compressibility, and we made very accurate 
experiments with water, alcohol, and ether from this point of view. 
We measured the coefficient of compressibility under very feeble 


Intelligence and Miscellaneous Articles. 165 


pressures (only about a centimetre higher than the maximum ten- 
sion of these liquids), but we were unable to recognize any change in 
the value of the coefficients of compressibility.—Comptes Rendus, 
June 28, 1869. — 


MEASUREMENT OF THE ELECTRICAL CONDUCTIVITY OF LIQUIDS 
HITHERTO SUPPOSED TO BE INSULATORS. BY M. SAID-EFFENDI. 
M. Jamin has desired me to execute a method which he devised 
for electrolyzing liquids of small conducting-power. The experi- 
ments were made in the laboratory of the Sorbonne under his direc- 
tion. The method is as follows :— 

The quantity of electricity which passes through a conductor is 
proportional to its conductivity and its section, but is inversely as its 
length. If the length be diminished and the section increased, a 
current may be passed even through substances supposed to be insu- 
lators. In the case of liquids this is effected by superposing two 
large plates of platinum, kept apart by flannel or silk or glass, and 
coiling them round a tube; then, after being connected with the poles 
of a battery, they are immersed in a voltameter. ‘They thus repre- 
sent a conductor, the length 7 of which is the thickness of the ma- 
terial which separates the plates, and the section is twice their surface 
2s. In the present experiments / was about a millimetre, and 2s 
amounted to 195,000 square millimetres. When the roll was im- 
mersed in a liquid the conductibility of which was c, the resistance 

ich tan 
Mecteqian ta) —, OF tO ——— = 

2s ¢ 195000 c 
had become about two hundred thousand times as great. 

By this means even the worst-conducting liquids are readily tra- 
versed by the current. The following are the principal facts which 
have been observed :— 

(1) Distilled water disengages with four Bunsen’s elements as 
much gas as acidulated water in an ordinary voltameter. It is there- 
fore an electrolyte. Butit becomes heated ; for a portion of the gases 
recombines on the surface of the platinum. ‘The volume of gas is 
thus less with this pure water than with a voltameter containing 
acidulated water placed in the circuit. As the intensity diminishes 
the difference increases, and when the current is very weak there is 
no apparent decomposition in the apparatus. 

(2) It is only when subjected to the action of powerful batteries 
that alcohol has hitherto afforded signs of decomposition, which might 
be attributed to the presence of foreign substances. With our appa- 
ratus four elements disengage considerable quantities of hydrogen, 
mixed with a small quantity of oxygen. 

(3) Oil of turpentine conducts far worse; eight Bunsen’s ele- 
ments are necessary to produce a distinct decomposition. 

(4) Rectified oil cf petroleum is decomposed with great ease. 
The gas collected is inflammable, and during its combustion it de- 
posits carbon upon the sides of the belljar in which it is contained. 
This deposit may be due to the presence of petroleum-vapour in the 
liberated gas. 

Further researches will give us the composition of the products 
disengaged during these experiments. I have been especially en- 
gaged in measuring the conductivity of these various liquids. 


It was as if the conductivity 


166 Intelligence and Miscellaneous Articles. 


I passed the current through the apparatus and through a tan- 
gent-compass, which at the first moment indicated an intensityz. The 
apparatus was then removed and replaced by coils of known resist- 
ance, and by a rheostat the length of which could be varied so as to 
reproduce the intensity 2. The resistance of the liquid was equal to 
that of the coils and of the rheostat. 

The numbers obtained are the following; they are inversely as 
the conducting-power of the liquid :— 


Liquids. Turns of rheostat. Conductivity. 
Water ys ci ate e me eens 55 1000 
Petroleuta ng si a ame anos 72 
Sulphide of carbon ...... 1000 55 
ACOH ON is pa ere Steusteuan 1130 49 
LOLELO SH Mon Ve app AOR OR iE Ug iN 1375 40 
Oil of turpentine........ 2380 23 
Benzolesa.. s. : .. 3480 16 


—Comptes Rendus, June 28, 1869. 
ON THE HEAT DEVELOPED IN DISCONTINUOUS CURRENTS. 
BY MM. JAMIN AND ROGER. 


Pouillet has shown that when a current of the intensity I is passed 
into a short rectilinear circuit which developes no phenomena of 
induction, and which is broken at very short and regular intervals 
by a vibrating apparatus, the tangent-compass exhibits an apparent 
intensity I,. This intensity is equal to I diminished in the ratio 
of the time a, during which the current passes, to the duration I of 
one vibration of the break, so that we have 

li=Te. 
We may infer from this result that the broken current is made up 
of successive fragments of currents which last during the time a, 
and which have a real intensity I, and that there is no change either 
at the moment of making or of breaking each. 

On the other hand, we know that, according to Joule, the amount 
of heat, C, disengaged in the unit of time in each resistance 7, by a 
current having the intensity I, is proportional to this resistance r and 
to the square I? of this intensity; it is equal to KrI’, K being a con- 
stant. ‘This law has been found to hold good for continuous cur- 
rents ; we have investigated whether it holds in the case of broken 
currents. 

For this purpose we passed these currents through a thermorheo- 
meter, an instrument which one of us devised, and which was laid 
before the Academy on the 6th of July 1868. It consists essen- 
tially of a fine platinum wire, the length of which may be varied, 
and which is immersed in the reservoir of a thermometer in the 
middle of an isolating liquid. ‘The heat developed by the current 
is transmitted to this liquid, and is measured by the expansion ob- 
served. Operating in this manner, we have ascertained that broken 
currents always develope more heat than continuous currents of the 
same apparent intensity, I. 

This fact does not contradict Joule’s law; we shall, on the con- 
trary, see that, when generalized, it justifies the ideas of Pouillet. For 


Intelligence and Miscellaneous Articles. 167 


according to this physicist, each section of the current, having a real 
intensity I and a duration a, must disengage during a vibration a 
quantity of heat equal to KrI’a. If the real intensity I is replaced 
KrI, 


1 ° 
a 
it will bea minimum whena=1, that is, when the current is con- 
tinuous; it will increase when @ diminishes, that is, when the du- 
ration of each fragment of a current decreases. 

To verify this theoretical formula we used an ordinary Froment’s 
break. A platinum point fitted to a vibrating spring, on sinking, 
dipped into a mercury-cup and transmitted the current ; 1t emerged 
from it as it rose, and broke the current. The duration of each 
fragment was prolonged by raising the level of the mercury, and was 
diminished by lowering it; the value of « (that is, the duration of the 
immersion) was easily measured. 

The following Table shows :—(1) that I,, the apparent intensity of 
the broken current, may be calculated by Ohm and Pouillet’s law, 


by its value a the heat should be Other things being equal, 
a 


A 
and that it is equal to owe A being the electromotive force, and 


R-+r the total resistance of the circuit; (2) that the quantity of heat 
2 
developed in the resistance r, divided by “1 is a constant quantity 
a 


equal to K (K=0°19), whether the current is broken or whether it 
is continuous. 


TasiE I.—Values of K and of I, without Coil. 
(A=410°8, R=3°65.) 


Intensity I,. a=1. a—0°06. 
Resist- 
Ob- Galcus (Ke Ca K= La 
served. | lated. C. 714?" oe ala 


14-40 14:20 25°30 1080 0:20 1620 0:18 
15°45 15°10 23°62 1160 0-20 1716 0:18 
16°55 16°63 21:04 1150 0:20 183 0°19 
18:90 19-40 18:°}2 1120 | 0-20 2118 0:19 
21:43 21-23 15°70 1470 0-20 2120 0-19 
24°16 24:25 13°25 1640 0-21 2520 0°19 
28°72 28 82 10-66 1800 0:20 3820 0:20 
35°60 39°39 7:97 2150 0-21 3510 0:20 
44:70 


45°29 5°42 2490 0:23 4150 0-20 


Means..c) O20. oseced. 0°19 


It is known that matters are not so simple when there is placed 
in the circuit a coil containing soft iron; the apparent intensity 
of the discontinuous current is not given by the formula I, =Ia; it 
is far smaller, and follows new laws now well known and investi- 
gated by several physicists. Let us denote it by I’; it is obvious that 
then each fragment of the current is very complicated—enfeebled at 
the outset by the counter-current, and increased when it is broken by 
the final shock (the extra current). It was probable that Joule’s 
law would be modified in a thermorheometer placed in the circuit. 


168 Intelligence and Miscellaneous Articles. 


This was not so; the quantity of heat disengaged in this thermo- 
rheometer was always represented by the formula Krl’,’, at least 
when the breaks were rapid enough, just as if each section of the cur- 

! 


rent had a real constant intensity = ; I’, was determined by the special 


action of the coil according to new laws, which are not those of Ohm. 
This is shown by the following Table, obtained as the result of 
experiments where a coil was interposed in the circuit. 


Taste II1.—Values of K with a Coil in the Circuit. 


a=. a—0'5. 
Inten- | Resist- 
Sity ise ance. 05) Toe Pee | Cu 
C. rl',? I’, 
9 25°46 440 0-20 647 0:19 
9:25 23°88 350 0:17 755 0-17 
9-92 21:04 376 0:18 845 0-21 
11-00 18:44 381 0:17 1039 (23 
12:52 15°78 466 0:18 915 0:18 
13:90 13°15 426 0-18 997 0-21 
15°65 10°57 427 0-16 970 0-718 
18:70 7°36 476 0-17 1014 0:19 
22°50 5:29 467 0:16 965 0:17 
23°83 3:37 289 0-15 791 0:20 
25:95 1-81 265 0-21 611 0°25 
Means:.2)*. O18 tT 0:19 


But if there is no change in that portion of the circuit which is made 
up of the thermorheometer (that is, in the portion where there is no 
induction), all is modified in the coil; and if its resistance is R, the 
heat there produced is far more than that calculated by the formula 
KRI'” 

a 
of a current upon itself in that portion of the circuit where this in- 
duction takes place; but it is only changed in this portion. We 
shall, before long, investigate this change. 

We may be permitted to advert to a claim of priority which 
M. Le Roux has made. 

M. Le Roux published in 1857 some purely theoretical ideas, ac- 
cording to which a fragment of a current would meet in every por- 
tion of the conductor a resistance greater than the statical resistance 
which Ohm’s laws assign to this conductor; and in our prece- 
ding experiments he has seen a confirmation of his ideas. 

Weare the more at a loss to understand this reclamation because 
our formule are in entire disagreement with those of M. Le Roux, 
and because, far from having justified his theory, we think we have 
proved that it has no foundation. 

In this investigation we prove that the basis of his reasoning is 
inexact, and that a broken current acts in a rectilinear circuit like 
a continuous current. ‘True, things are far more complex in a coil; 
but that is a case of pure induction, as Helmholtz has proved. 
— Comptes Rendus, March 22, 1869. 


The law has' therefore been changed during the induction 


THE 
LONDON, EDINBURGH, ann DUBLIN 


PHILOSOPHICAL MAGAZINE 


AND 


JOURNAL OF SCIENCE. 


[FOURTH SERIES.] 


SEPTEMBER 1869. 


XIX. On the Construction of the Galvanometer used in Electrical 
Discharges, and on the Path of the Extra Currents through the 
Electric Spark. By EH. Eptunp*. 


I. 
VELEN an electric discharge is passed through a galva- 


nometer in which the individual coils are well insu- 
lated, it frequently happens that the position of equilibrium of 
the needle is altered, and that this alteration lasts even after the 
discharge. This disadvantage may be greater or less, according 
to the construction of the galvanometer and the distance from 
the coils to the moveable parts of the instrument, while the 
quantity and density of the discharged electricity moreover exert 
great influence in this respect. If the electrical discharges are 
very powerful, it may happen that the galvanometer becomes 
quite spoiled for accurate determinations of the discharge. 

There are several causes for this imperfection of the instru- 
ment in question. Itis well known that strong discharges can 
bring about a change in the distribution of magnetism in the 
magnet. The electrical shock can make the magnetic distribu- 
tion stronger or weaker, or even invert the poles, or change the 
line of connexion between them. If the galvanometer has an 
astatic system, the electrical shock may easily alter the ratio of 
the strength of the magnetisms in the two needles, by which the 
delicacy is altered, and sometimes a change ensues in the post- 
tion of equilibrium of the system of needles. Hence a galvano- 


* Translated from Poggendorff’s Annalen, No. 3, 1869. 
Phil. Mag. 8. 4. Vol. 88. No. 254. Sept. 1869. N 


170 Prof. E. Edlund on the Construction of 


meter for electrical discharges cannot well be provided with an 
astatic system: a single needle must be used; and to make it 
more delicate, either a portion of the directive force of the earth’s 
magnetism must be compensated by external magnets, or, what is 
better, a mirror with telescope and scale may be used. Ifin using 
a single needle the suspending thread had no tendency to tor- 
sion, the delicacy of the instrument would be independent of the 
strength of the magnetism in the needle; for the directive force 
of the needle in this case would increase or decrease in the same 
ratio as the action of the current upon it. The position of equi- 
librium of the needle would also be independent of the strength 
of the magnet, provided the position of the magnetic axis im the 
needle were unchanged. The position of equilibrium is also un- 
changed if the strength is increased or diminished, provided the 
force of torsion of the thread only tends to bring the needle into 
the magnetic meridian. Hence, in order that the instrument 
may retain as far as possible its delicacy, and moreover not have 
its position of equilibrium altered by changes in the strength of 
the magnetism which powerful electrical discharges may cause, the 
directive force which the suspending thread exerts on the needle 
in virtue of its torsion must be small as compared with the action 
of the earth’s magnetism, and the position of equilibrium caused 
by torsion must coincide with the magnetic meridian. Accord- 
ing to Professor Riess*, the magnetism of the needle is greatly 
protected if between it and the coils there is a thick copper 
sheath, which at the same time acts as a damper in bringing the 
oscillating needle quickly to rest. 

But it is easy to see that the action of the electricity on the 
magnet is not the sole or even the principal cause of the change in 
the position of equilibrium which results from the passage of the 
electrical discharge through the coils of the galvanometer. The 
galvanometer which I used in my former experiments on the 
electromotive force of the electrical spark had a single needle, 
which was firmly connected with a mirror, by the aid of which 
the deflections were read off by the telescope and scale in the 
ordinary manner. The mirror consisted of glass, and the back 
was covered with a thin metal disk. The galvanometer-wire, 
which consisted of copper, was 1 millim. in diameter, and was 
surrounded by a coating of gutta percha 2 millims. thick. Hence 
the entire thickness of the wire, including the insulating coating, 
was 5 millims. This wire was wound in forty coils round a ma- 
hogany frame. The aperture in the frame, in which the magnetic 
needle was suspended by a cocoon-thread, was 50 millims. in 
length by 30 in height. The length of the needle was 42 mil- 


* Abhandlung: “Zu der Lehre von der Reibungs-Electricitat,” Berlin, 
1867, p. 314. 


the Galvanometer used in Electrical Discharges. 171 


lims. The mirror was above the frame which was surrounded 
by the wire ; and the whole was protected by a bell-jar. When 
the magnetic needle was removed and replaced by a brass needle 
of the same size, and the mirror with its affixed needle was sus- 
pended by two cocoon-threads, by which the moveable system 
obtained a definite position of equilibrium, it was observed that 
this position of equilibrium was altered when a strong discharge 
was passed through the galvanometer-wire. The alteration in 
the position of equilibrium could not be due to a change in the 
magnetism of the needle ; for there was no magnetic needle in the 
apparatus. When the glass globe was carefully removed and the 
mirror investigated, it was found to be electrical. This alteration 
in the position of equilibrium was thus due to the fact that in 
the discharge electrical induction was produced in the moveable 
parts of the instrument, which acted electroscopically on the 
fixed parts and produced an altered position of equilibrium. 

Hence the moveable parts had to be constructed in such a 
manner that the electrical action between them and the fixed 
parts should be unable to turn the moveable system about its 
own axis. It is clear that if the moveable body suspended by a 
cocoon-thread were bounded by a surface of rotation the axis of 
which were the prolongation of the cocoon-thread, and if the sur- 
face were made of a conducting material, the electroscopic action 
between this body and the fixed parts of the instrument could 
not effect any rotation about the axis in question. If electricity 
of either kind has collected upon any place (for instance on the 
gutta-percha-covered wire), this induces electricity in the body 
in question: the electricity of the opposite kind collects in 
the point nearest to the fixed attracting point, and the other elec- 
tricity is driven to the furthest. But if the body is bounded 
by a surface of the kind mentioned, it is readily seen that the 
line of junction between the fixed point of action and the two 
corresponding points upon the moveable body will go through 
the axis of rotation, and there can thus be no rotation. All 
that could possibly happen is, that the system would be attracted 
a little on one side, so that the axis of rotation would no longer 
be vertical; but no rotation can be thereby produced, provided 
the centre of gravity of the system lies in the axis. But since 
a plane mirror is necessary for reading off, the moveable system 
cannot have the form in question. I have accordingly endea- 
voured to obtain this object in the following manner :— 

The glass mirror which I previously used was exchanged for a 
round plane-polished silver mirror, the diameter of which was 
30 millims. The object of this was to remove the non-conduct- 
ing glass. Both above and below this mirror, and in direct con- 
tact with it, a horizontal circular disk of thin metal foil was placed. 


N 2 


172 Prof. E. Edlund on the Construction of 


Both disks were of the same size (that is, 50 millims. in diame- 
ter); and the axis of rotation of the system, when suspended by 
the cocoon-thread, went through the centre of each. The mag- 
netic needle was let into a cireular copper disk in such a manner 
that the upper sides of the needle and of the disk lay in the same 
plane, and their centres coincided. The disk and the needle 
were soldered together so as to produce perfect conduction be- 
tween them. The centre of this disk was 
now made to coincide with the axis of ro- 
tation, so that it became horizontal; the 
adjacent figure renders this arrangement 
more intelligible. s is the silver mirror, 
ab the round metal rod which constitutes 
the axis of rotation, and c, d,and e are the 
circular disks, in the latter of which the 
magnetic needle is inserted. The coils 
of the galvanometer surround the disk e 
and pass between d and e, so that the 
disks d and cand the muror are at the top. 
If, now, in the discharge electricity re- 
mains upon any point, for instance at /, 
in the coils, it is clear that it can produce no rotation in con- 
sequence of its influence on the disks ¢, d, or e. Of the electri- 
city which is produced in the mirror s in consequence of induc- 
tion, one part is repelled to the disk c, and the other attracted 
to the disk d, and both thereby become innocuous. 

On testing, it was evident that this arrangement has a de- 
cided advantage over that previously employed. In my former 
experiments, a Leyden jar charged to saturation could not be dis- 
charged through the galvanometer without producing a material 
change in the position of equilibrium. When one of the galva- 
nometer-wires was directly connected with one of the combs of 
a Holtz’s induction-machine, and the other ended with a knob in 
the vicinity of the other comb, so that while the machine was at 
work sparks sprang across, in my previous experiments a consi- 
derable alteration was produced in the position of equilibrium 
after the action of the machine had ceased. Hence to avoid this 
a shunt was used between the conducting-wires, so that only a 
small portion of the shock traversed the galvanometer. 

In the new arrangement of the moveable part of the galvano- 
meter this bridge was quite superfluous, and the entire discharge 
could pass through the galvanometer. There was indeed an 
alteration in the position of equilibrium if the discharges were 
particularly strong; but it was not so great as to act injuriously 
on the accuracy of the measurements, and still less to render 
them impossible. When one galvanometer-wire was connected 


the Galvanometer used in Electrical Discharges. 173 


with one comb of the induction-machine and the other was free 
and insulated, so that the galvanometer-wire became saturated 
with electricity while the machine was at work, there was a ma- 
terial alteration in the position of equilibrium. But this altera- 
tion disappeared immediately one of the wires was put in con- 
nexion with the earth. These preliminary experiments were 
made partly when the metallic disk on which was the magnetic 
needle was firmly screwed to the axis of rotation, and partly 
when this metal disk was removed and instead of it another 
metal disk of equal size, but without a magnet, was fixed to the 
axis, in which latter case the system attained its position of equi- 
librium by a bifilar suspension from two cocoon-threads.» As the 
experiments gave the same result in both cases, the alteration 
in the position of equilibrium must have been due to some elec- 
troscopic cause. When the two round disks ¢ and d were re- 
moved, experiment showed that the changes in the position of 
equilibrium becaine considerably greater; hence the disks per- 
formed their expected service. That the galvanometer with the 
new arrangement of the moveable parts was not quite unaffected 
by very strong discharges was doubtless due to the moveable 
system being somewhat obliquely attracted by the electrical ac- 
tion; so that the axis of rotation cannot have hung quite ver- 
tically. If in this case everything is not accurately centred, so 
that the centre of gravity lies in the axis of rotation (which is very 
difficult, if not impossible), it is clear that a change in the posi- 
tion of equilibrium must ensue. Seeing that electroscopic phe- 
nomena may under certain circumstances so closely resemble 
magnetic ones that a confusion between them is possible, before 
a galvanometer is used for actual measurements we must satisfy 
ourselves that under the present circumstances no electroscopic 
actions occur. 


IT. 


When a closed conducting-wire is in the vicinity of the circuit 
of an electrical battery, an electric current is produced in the 
former when the battery is discharged through the latter. This 
secondary current in the conducting-wire is stronger the longer 
the portions of the wires which act upon each other. Hence, in 
order to obtain strong inductive actions, the wire and the circuit 
must be coiled spirally near to one another. ‘These currents 
were discovered almost simultaneously by Henry, Marianini, and 
Riess. A similar inductive action is also produced if the circuit 
at one part consists of two branches, one of which is long and 
coiled as a spiral. In the discharge of the battery, which 
in this case partially traverses both branches, an induction-cur- 
rent is formed in the spiral, which discharges itself through the 
other branch. Baron Wrede has shown from theoretical consi- 


174 Prof. E. Edlund on the Path of the 


derations that, like those resulting from voltaic induction, these 
currents are formed of two currents equal in quantity, one of 
which has the same and the other the opposite direction to that 
of the primary current*. As these currents are equal in quan- 
tity, and in opposite directions, they cannot deflect the magnetic 
needle; but they can disengage heat, and, as their intensities 
may be unequal, can also produce magnetic induction in har- 
dened steel needles. This view as to the nature of the induction- 
currents in question, which rests upon theoretical considerations, 
has been confirmed since the discovery of the electrical valve has 
furnished an unfailing means of distinguishing between the two 
opposed currents. The electrical valve consists of a hollow glass 
cylinder in which air is rarefied at pleasure. One end of this is 
closed air-tight by a glass disk; and at the other end is a brass 
cap with a stopcock, by which it can be connected with an air- 
pump. Through the glass disk passes a platinum wire, of 
which one end is level with the inner surface of the glass disk, 
and the outer end can be connected with a conducting-wire. 
Inside the cylinder a brass rod extends from the brass cap; the 
rod terminates in a brass disk, which is parallel with, and at a 
short distance from, the glass disk. When the air is adequately 
exhausted, and the platinum wire connected with one and the 
brass cap with the other end of the induction-spiral, it is proved 
that only one of the two mduction-currents can traverse the 
valve; for Riess found that when a galvanometer is placed in 
the circuit, the magnetic needle gives a deflection in a direction 
which differs according as one or the other end of the induction- 
spiral is connected with the platinum wire fF. 

In my investigation on the electromotive force in the electrical 
spark, there was no other spiral in the circuits than those which 
were formed by the forty coils of the galvanometer{. In this 
spiral induction-currents were of course formed when the elec- 
trical discharge traversed them; but it is readily seen, from the 
manner in which the experiments were arranged, that these in- 
duction-currents could have no influence upon the deflection of 
the magnetic needle. In the adjacent figure, A B represents the 
rotating induction-disk, and ab the two combs. An insulated 
copper wire, ac, was directly connected with a, whereas the insu- 
lated wire de terminated in a brass knob d in the neighbourhood 
of 6. From ¢ and e insulated conducting-wires passed to the 
knobs f and g. Two other conducting-wires went from the 
points c and e to the galvanometer G. Atma rheostat was in- 
serted, consisting of an insulated thin German-silver wire. Be- 


* Berzelius, Jahresbericht, vol. xx. p. 119. 
+ Pogg. Ann. vol. exx. p. 513. 
{ Ibid. vol. exxxiv. p. 337. Phil. Mag.S. 4. vol. xxxvu. p. 41. 


Extra Currents through the Electric Spark. 175 


tween the points 2 and & was a bridge 

of German-silver wire; andthe pomt A B 
k& was moreover connected by the 
conducting-wire/ with the water- 
pipe in the house, and was thus placed 
in conducting communication with 
the earth. When the disk AB was 
rotated, sparks passed between J and 
d as well as between f and g, and the 
needle made a deflection. The re- 
sistance in the wire / was infinitely 
small, compared with that of the rheo- 
stat » and in the spark between f 
and g. Hence the induction-currents 
formed in the coils of the galvanome- 
ter passed almost exclusively through 
the bridge 4; and as they were equal 
in quantity while opposite in direc- 
tion, their action upon the needle 
was of course imperceptible. This 
would not have been the case if the 
bridge / had not existed, and the currents had had to pass through 
the spark between f and g; for this, as will afterwards be shown, 
acts like an electrical valyve—that is, transmits one current but 
stops the other. Polarization-experiments showed, moreover, that 
the current obtained arose from the spark between fand g, and not 
from the induction of the discharge-current in the galvanometer- 
coils; for in these experiments the galvanometer was removed, 
and there was no other spiral in the conductions; so that there 
could be no induction. After the galvanometer, as previously 
shown, had been so much improved that the bridge h could be 
removed without disadvantage, I investigated more closely the 
phenomena in question ; and as the results obtained seem to offer 
some interest, I will give them here. 

At the time the galvanometer was made I also had a coil con- 
structed for making induction-experiments, which in all respects 
was like the coil of the galvanometer. The wooden frame had 
the same dimensions ; the wire covered with gutta percha was of 
the same kind ; and the number of windings in both coils was 
the same, namely forty. Hence under the same circumstances 
both coils must exert the same inductive actions. If the vol- 
taic resistance in the rheostat m was called 100, it was found 
that the resistance in each of the coils was 4°5, and the resist- 
ance in the two conducting-wires from the Points c and e to 
the galvanometer amounted to about as much. The following 
experiments were made with this coil, which in the sequel will 


be called R :— 


176 Prof. E. Edlund on the Path of the 


Experiment I.—The bridge 4 was removed, so that the entire 
discharge traversed the galvanometer :— 
52°5 
50:5 
49-0 


——_ 


Mean= 730. . -a0zz, 


The coil R, was thereupon interposed between e and m, and the 
deflections obtained were 

30:1 
27°38 
27° 
27°6 
Meany A) entre sie 

When R was placed towards n on the opposite side, there was 
obtained 93-3 
28°1 
27°9 
Mean ie) caco 


The coil R was then removed, and, in order to ascertain if there 
had been any change in the induction-machine, the first experi- 
ments were repeated. The following deflections were observed :— 

51:2 

50:2 

46:2 

Mean . . 49:2 

The mean of the first and last experiments is 50:0, and that of 
the middle ones 28:1. Hence the induction-currents in the 
coil R had diminished the deflection of the magnetic needle by 
21-9 divisions. Of these induction-currents, one had the oppo- 
site and the other the same direction as that of the discharge. 
The first may be designated as A, and the latter as B. Hence 
in these experiments the currents A traversed the spark between 
f and g more easily than the currents B. The spark accordingly 
acts in this case like an electrical valve. 

Experiment 11.—This experiment was made in order to in- 
vestigate the action of induction-currents upon the deflection when 
R. was interposed between g and e. ‘The currents now traversed 
R in the opposite direction to the former one. When no coil 
was interposed in the conduction the following deflections were 
observed :— 


40°5 
42-0 
Mean. - 41:3 


Extra Currents through the Electric Spark. 177 


R was inserted between g and e, by which there was obtained 
27°38 
27°38 
Miran? 7. (27°73 


After removing R there was once more observed 
40°3 
41-3 
Mean... .. 40:3 


In this case also the deflection was diminished by the induc- 
tion-currents. It is easily ascertained that it was the currents 
B which traversed the spark between f and g with greater facility. 
By introducing the coil R into the circuit the resistance was a 
little increased. To convince myself that this was not the cause 
of the diminution in the deflection of the magnetic needle, a few 
experiments were made in which the resistance of the rheostat 
when R was interposed was so much diminished that the total 
resistance was a little less than when R was removed. But 
these experiments gave just the same results as the above. The 
small alteration in the resistance had therefore no perceptible 
influence upon the result obtained. The experiments were made 
in such a manner that the place where the spark was formed 
was removed from the position indicated by the figure, a little 
towards n, while the rheostat took its place between c ande. But 
in this case also the deflection was lessened in the same manner 
as before by the induction-currents. 

It may at first sight appear unexpected that in one case the 
currents A, but in the other the currents B, should be able more 
easily to traverse the spark. Yet closer consideration shows that, 
in one view, A in the first and B in the second experiment have 
a common character, upon which some stress must here be laid. 
In the first case it is the current A which traverses the spark in 
the same direction as the electrical discharge, while in the second 
it is the current B. It follows hence, that of the induction-cur- 
rents formed by electro-induction, those which endeavour to tra- 
verse the spark in the same direction as the discharge also penetrate 
it most readily. 

That the induction-currents which are formed in the coil of 
the galvanometer itself also diminish the deflection of the needle, 
necessarily follows from what has preceded, and scarcely needs 
any proof. Yet it was very easy to demonstrate this experi- 
mentally in the following manner. In front of the galvano- 
meter a German-silver wire was iiserted between the points z 
and k, the resistance of which was thrice that of the resistance 
in the coil of the galvanometer. Hence, of the currents which 


178 = On the Extra Currents through the Electric Spark. 


arose in the electric spark, only three-quarters traversed the 
galvanometer. If there is a bridge between 7 and 4, the re- 
sistance of which is small as compared with the resistance in the 
spark and in the rheostat m, the greatest part of the induction 
produced in the galvanometer passes through the bridge; and as 
they are equal in quantity and opposite in direction, their action 
on the magnetic needle is eliminated. But if the bridge is re- 
moved, the induction-currents act upon the magnetic needle. 

If, now, this action is in the opposite direction to that which is 
caused by the spark, the deflection on inserting the bridge must 
be more than three-fourths of that which ensues when the bridge 
is removed. 

The following experiments show that the first deflection is even 
considerably greater than the latter. 

Experiment I11.—The bridge inserted between the points 2 
andk. There were thus obtained the following deflections when 
the machine was at work :— 

Divisions. 
24:0 
26:0 
25:5 


Mean . . 25°2 
Without the bridge the deflections were 
13°3 
12:3 
13°3 
12°8 
Nieange. a e-9 


The bridge was again introduced, upon which the deflections 
became 
26:2 
23°2 
23°7 
20°7 
Mean.) .\5. 2338 


If the mean be taken of the first and third means, the number 
24°35 is obtained, which is double as much as when the bridge 
was removed. A few other experiments, which it is superfluous 
to publish here, showed that the amount of diminution in the 
deflection of the magnetic needle which the induction-currents 
produce was, by far, not proportional to the number of turns of 
the induction-spiral, but increased much more slowly. 


pois] 


XX. On some Phenomena of Binocular Vision. By Josnru 
LeConte, Professor of Chemistry and Geology in the Univer- 
sity of South Carolina*. 

(Continued from vol. xxxvii. p. 140.] 


II. Rotation of the Eye on the Optic Ais. 
a all the experiments described in this paper had 


already been made and the results obtained, when my 
attention was called to Helmholtz’s Croonian Lecture “ On the 
Normal Motions of the Eye in relation to Binocular Vision’’+. 
From this lecture I received some useful hints as to the best 
method of experimenting on this subject, which have been of 
great service to me, and have made my results much more satis- 
factory, without, however, materially modifying them. As these 
results differ very greatly and fundamentally from those of 
Helmholtz, I repeated the experiments daily for many weeks, 
modifying them in every conceivable way to avoid the possibility 
of error. I am perfectly sure, therefore, that the results are 
true for my own eyes; and as far as I have been able to have 
them verified, they are true also for most other normal eyes. 
Unfortunately, however, the difficulty of verification for other 
eyes is very great. Many of these experiments, which I find 
perfectly easy, are almost impossible for most persons. 
Helmholtz’s lecture, I suppose, is the most authoritative state- 
ment which we have of the present condition of science on the 
subjects of the motions of the eye and of the horopter. It 
seems to be an abstract of more extended researches which I have 
not seen. Qn this account it is obscure in some parts; yet I 
think I cannot be mistaken in his general results. In order to 
make myself clear, whether in discussing Helmholtz’s results or 
in describing my own experiments, I find it necessary to detine 
the terms I shall most frequently use. The position of the eye 
when the optic axes are parallel and at right angles to the 
vertical line of the face, as when with head erect we look ata 
point on a distant horizon, is called by Helmholtz the primary 
direction of the eye, and the visual line in this case 1s the primary 
direction of the visual line. All other directions are called 
secondary directions. A plane which passes through the visual 
line is called a meridian plane of the eye, and the intersec- 
tion of such a plane with the retina we will call a meridian of the 
eye. The vertical line of demarcatian is that meridian of the eye 
upon which the image of an apparently vertical line falls when 
we look directly at the line, and which therefore divides the 
retina into two equal halves containing corresponding points 


* From Silliman’s American Journal for March 1869. 
t+ Proc. Roy. Soc. April 1864, vol. xi. p. 186. 


180 Prof. J. LeConte on some Phenomena 


in the two eyes. The horizontal line of demarcation is that me- 
ridian of the eye upon which, under similar circumstances, the 
image of an apparently horizontal line falls. The plane which 
passes through the two visual lines we will call the visual plane, 
and that visual plane which is at right angles to the line of the 
face the primary visual plane. The line joining the root of the 
nose and the point of sight, and which therefore bisects the angle 
of optic convergence, we will call the median line of sight. 

Now Helmholtz gives as the law controlling all the move- 
ments of the eye the following, viz. that when the eye turns 
from its primary to any secondary position, zt turns “on a fixed 
axis which is normal both to the primary and to the secondary 
visual line.’ In other words, the eye may turn on any axis at 
right angles to the optic axis, but does not rotate about the optic 
axis. Again, he states that “vertical and horizontal lines keep 
their vertical or horizontal position in the field of vision when 
the eye is moved from its primary direction vertically or hori- 
zontally.” This law had been previously stated by Listing, but 
without proof; Helmholtz claims to have established it by ex- 
periment. His method is very ingenious. It is well known 
that if we look for some time at a bright object, and then turn 
the eye upon a comparatively obscure field, a spectrum having 
the form of the object will be seen. As such spectra are the 
result of a temporary modification of the retina itself, they must 
follow the motions of the eye with the greatest exactness. If 
therefore the bright object be a dine, then if there be any rota- 
tion of the eye on the optic axis, in turning the eye in various 
directions the linear spectrum ought to incline to one side or the 
other. Suppose, then, the object be a bright-red vertical line 
on a grey wall at the exact height of the eye: Helmholtz finds 
that on gazing at the bright line with one eye, taking care that 
the eye shall have its primary direction, and then turning the 
eye in a horizontal plane to the night or left, the spectrum retains 
perfectly its verticality. ‘1 found,” he says, “the results of 
these experiments in complete agreement with the law of List- 
ing.’ For the ingenious device of Helmholtz for getting the 
primary position of the eye we must refer the reader to his lec- 
ture. I have tried Helmholtz’s experiments with similar results. 
Nevertheless I believe it may be demonstrated that though rota- 
tion of the eye does not take place under the circumstances of 
these experimeuts, yet it does so under other circumstances not 
touched by them, and that ina manner which deeply affects the 
question of the horopter. The law of Listing 1s doubtless true, 
or nearly true, when the eyes move together parallel to each 
other, but is far from being true in strong convergence. ‘The 
experiments which follow prove beyond a doubt that in my own 


of Binocular Vision. 18] 


case, and in most other cases tried, the eyes in convergence rotate 
on the optic axes outward, and that the amount of rotation in- 
creases with the degree of convergence. Meissner* has attempted 
to determine experimentally the position of the horopter, and 
from the position thus determined he infers the rotation of the 
eyes: my experiments prove directly the rotation of the eyes; 
and from this, as well as from direct experiment, I hope to esta- 
blish the position of the horopter. 

Helmholtz, it is true, admits some degree of rotation of the 
eye on the optic axis, particularly when the eye makes wide ex- 
cursions in the field of view; but that he does not regard this 
as sufficient to interfere seriously with the law of Listing is evi- 
dent from the form of the horopter which he deduces. More- 
over, according to Helmholtz, these slight rotations are con- 
trolled by the law of Donders, viz. ‘ that the eye returns always 
into the same position when the visual line is brought into the same 
direction.” He regards this law as rigorously exact. ‘ Every 
position of the visual line,” he says, “is connected with a deter- 
mined and constant degree of rotation.” But the experiments 
about to be described prove that under certain circumstances the 
law of Donders, too, is far from being true. 

We have already stated (p. 186) that when the squares of the 
ruled diagram (fig. 5) are combined by converging the optic 


Fig. 5. 


axes, if the amount of convergence be great, the horizontal lines 
of the two images are distinctly observed to cross each other at a 
small angle. After my attention was once directed to this fact, 
I could see slight crossing of the horizontals for every degree of 
convergence ; but the verticals seemed to coalesce perfectly. By 
placing, however, both the diagram and the head perfectly 


* Bib. Un. Archiv. des Scien. II. vol. ii. p. 160. 


182 Prof. J. LeConte on some Phenomena 


perpendicular, looking straight forward at a point exactly at 
the same height as the eyes, the visual plane therefore in the 
primary position, and then slowly increasing or decreasing the 
convergence of the optic axes so that the vertical lines of the two 
images passed slowly over one another, it was plainly seen that 
the verticals of the two images were not parallel, but crossed 
each other at a small angle. 

This, my original diagram, however, is not well adapted to 
experiments on this subject, for two reasons: (1) it is difficult to 
distinguish the image of one eye from that of the other; (2) it 
is difficult to control perfectly the convergence of the eyes. When 
the vertical lines approach each other, they, as it were, leap and 
cling together as a single line, even though they really cross at 
a considerable angle; the really crossing lines, by a well-known 
law of stereoscopic combination, being seen as a single line in- 
clined to the visual plane. I therefore constructed a similar 
diagram, one-half of which consisted of black lines on a white 
ground, and the other half of white lines on a black ground. It 
is convenient also to have two small circles, one on each half and 
similarly situated (fig. 6). IfI place such a diagram perfectly 


Fig. 6. 


perpendicularly before me, Lith the head perfectly erect and the 
eyes at precisely the same height as the small circles, and then 
stereoscopically combine the circles by crossing the eyes, I dis- 
tinctly see the white and black lines, both vertical and hori- 
zontal, crossing one another at small angle, as if the images 
of both eyes had rotated on the visual line in opposite direc- 
tions. This angle of crossing increases as the plane of the 
diagram is brought nearer, and decreases as the diagram is 
carried further from the eyes. Or these different angles of cross- 
ing may be obtained without moving the diagram or the head, 
by converging the eyes more and more and causing the white 


of Binocular Vision. 183 


and black vertical lines to pass successively over each other. This 
is more easily done if there are several small circles on each half, 
similarly situated but at different distances from each other. In 
this diagram, the lines being of different colours do not stereo- 
scopically combine easily—they do not cling together as in the 
other case. Their approach toward, or recession from, one an- 
other, and the angle which they make with one another, may be 
marked with the utmost exactness. Nor is there any danger of 
confounding the two images; for since the eyes are crossed, we 
know that the white lines belong to the right eye and the black 
lines to the left eye; we can therefore determine the direction in 
which each image rotates. I find always that the black lines or 


the image of the left eye rotates to the right #—, and the white 
lines or the image of the right eye rotates to the left ~-«. Now, 


as the image always moves in a direction contrary to the motion 
of the eye (differing in this respect from spectra), this indicates 


a rotation of both eyes on the optic axes outward .-« *-, 


To test this question still further, I constructed another dia- 
gram, with the horizontal lines continuous across, but the verticals 
not perfectly vertical, the upper ends of those of the right half 
inclining to the left, and those of the left half to the right, by 
about 1° 20! (fig. 7). On bringing the circles together I found 
that at a certain distance of the diagram (but only at a certain 


Fig. 7. 


SSS SS SSS SS 


distance, depending upon the interval between the circles) the ver- 
ticals coalesced perfectly ; the horizontals, however, as might have 
been expected, still crossed at a small angle, and in the same direc- 
tion as before ; viz. the whites or right-eye image thus ——_ , 
and the blacks or left-eye image thus ~~~_, indicating in this 
case also rotation of each eye outward. Beyond the proper dis- 


184 Prof. J. LeConte on some Phenomena 


tance the verticals approach but do not attain parallelism ; 
within the proper distance they cross in a direction contrary to 
that in the diagram. When the circles are ten inches apart, the 
proper distance is nearly three feet, and the image therefore 
about seven inches from the eyes. 

Helmholtz has a diagram similar in all respects to my own, 
except turned upside down, in which, he states, both verticals 
and horizontals coincide perfectly when the circles are combined. 
Our own figure (fig. 7) turned upside down will answer for Pro- 
fessor Helmholtz’s. We quote his own words :—“ The horizontal 
lines are parts of the same straight line; the vertical lines are 
not perfectly vertical. The upper end of those of the right 
figure are inclined to the right, and those of the left figure to the 
left, by about 13°.” But his experience differs from our own in 
a most unaccountable manner. He says: “Now combine the 
two sides stereoscopically, either by squinting or by a stereoscope, 
and you will see that the white lines of the one coincide with the 
black lines of the other as soon as the centres of both figures 
coincide, although the vertical lines of the two figures are not 
parallel to each other.’ He accounts for this, not by rotation 
of the eyes, but by ¢he principle of the difference between real and 
apparent verticality. The ignorance of this principle he believes 
has vitiated the results of all previous observers. He illustrates 
this principle thus: “ When you draw on paper a horizontal 
line, and another line crossing it exactly at right angles, the 
right superior angle will appear to your right eye too great and 
to your left eye too small; the other angles show corresponding 
deviations. ‘Tl'o have an apparently right angle, you must make 
the vertical line incline by an angle of about 11° for it to appear 
really vertical. We must distinguish, therefore, between the 
really vertical lines and the apparently vertical lines in the field 
OlVIEW. . ca: Now look alternately with the right and the left 
eye at these figures (fig. 7 turned upside down). You will find 
that the angles of the right figure appear to the right eye equal 
to right angles, and those of the left figure so appear to the left 
eye; but the angles of the left figure appear to the right eye to 
deviate much from a right angle, as also do those of the right 
figure to the left eye.’ Professor Helmholtz therefore believes 
that the perfect stereoscopic coincidence of the vertical lines of 
his diagram is the result of this principle. ‘ Therefore,” he 
says, “not the really vertical meridians of the two fields corre- 
spond as has been hitherto supposed, but the apparently vertical 
meridians. On the contrary, the horizontal meridians really cor- 
respond, at least for normal eyes which are not fatigued.” 

On this principle Professor Helmholtz builds his whole theory 
of the horopter. But that this principle cannot account for the 


of Binocular Vision. 185 


phenomena he observes, I think can be proved. In the first 
place, I find that if there be any distinction between real and 
apparent verticality for my eyes, the difference is too small to be 
detected by the simple observation of lines drawn at right angles 
with each other. For my own eyes really vertical lines are also 
apparently vertical, and lines inclined 11° from verticality are not 
at all apparently vertical. I have tried several other normal 
eyes with the same result. But, leaving this aside, in the 
second place, it is by no means indifferent whether the two 
halves be combined by a “ stereoscope or by squinting.” If they 
are combined by a stereoscope as stereoscopes are usually con- 
structed, the right half is looked at by the right eye and the left 
half by the left eye, so that the point of sight and the plane of 
combination is beyond the diagram; coincidence in this case, 
therefore, would be a true illustration of Professor Helmholtz’s 
principle. But if they are combined by squinting, the eyes are 
crossed, and therefore the right eye is looking at the left half and 
the left eye at the right half of the diagram, and therefore, in 
Professor Helmholtz’s own words, the verticals should ‘ deviate 
much froma right angle,” viz. 24°. I have tried many eyes 
and I have yet found none in which the coincidence of the verti- 
cals of Professor Helmholtz’s diagram was perfect when com- 
bimed by means of a stereoscope, 7. e. beyond the diagram ; but 
I have found one person to whom the coincidence seemed to be 
perfect when the combination was made by squinting. 

Tt is evident, then, that Professor Helmholtz’s principle can- 
not explain the stereoscopic coincidence by squinting in his own 
experiment. I myself believe that if the coincidence takes place 
only by squinting (as in the case mentioned above), it can only 
be explained by rotation of the eyes inward. It is true that in 
this case the horizontals ought to cross also ; but Professor Helm- 
holtz himself admits that such is sometimes the fact, but attri- 
butes it to fatigue. ‘“ After keeping the eyes,” he says, “a long 
time looking at a near object, as in reading or writing, I have 
found that the horizontal lines cross each other; but they became 
parallel again when | had looked for some time at a distant object.” 

On reading Professor Helmholtz’s lecture and finding his re- 
sults so different from my own, I immediately tried his figure 
by squinting, but found the verticals cross one another at an in- 
clination much greater than in the diagram itself, while the ho- 
rizontals also crossed but at a less angle. On turning the figure 
upside down, however, the verticals coincided perfectly when the 
proper distance was obtained, though the horizontals crossed as 
before. All these phenomena are easily explained by rotation of 
the eyes outward. To test the question still more thoroughly, I 
then constructed other diagrams in which both verticals and 

Phil. Mag. 8. 4. Vol. 38. No. 254. Sept. 1869. O 


186 Prof. J. LeConte on sume Phenomena 


horizontals were inclined so as to make an angle of 1}° with 
the true vertical and the true horizontal (fig. 8), and therefore 
perfect squares with one another. At the proper distance, when 
the small circles were brought together, the coincidence of both ver- 
ticals and horizontals seemed to be perfect. When the plane of the 
diagram was too near or too far, all the lines crossed, in the one 
case 1u one direction and in theother case in the other direction. 
I then constructed still other diagrams, in which the inclination 
of the lines with the true vertical and the true horizontal were 
40 minutes, 24 degrees, and 5 degrees. Im all cases I brought 
the lines into coincidence, but of course by different degrees of con- 
vergence. In the last the optic convergence necessary was ex- 
treme, and the strain on the eyes considerable ; but in the other 
cases there was not the slightest difficulty or strain. Recollect- 
ing, however, that Professor Helmholtz supposed that the change 
of position of the horizontals might be the result of fatigue, I tried 
repeatedly after long rest, but always the phenomena were pre- 
cisely the same. In the diagram in which the inclination of the - 
lines was 5 degrees I observed, however, that a greater degree of 


convergence was necessary to bring the horizontals into coincidence 
than to bring the verticals into coincidence. The difference in the 
distance of the diagram in the two cases was about two inches, 
and the difference in the distance of the point of sight was about 
half an inch. I cannot explain this except by supposing that 
the form of the optic globe was changed by the excessive action 
of the muscles. 

I can conceive of no possible source of fallacy in these experi- 
ments. From long practice they have become almost as easy to 
me as any ordinary act of vision. ‘They do not now fatigue my 
eyes in the slightest degree. I see the lines of the two images, 


of Binocular Vision. 187 


which I bring together just as plainly as if they were black and 
white threads. While watching them [control their motions almost 
as perfectly as if I was sliding with my hands two frames with 
white and black threads stretched across them. There is not the 
shadow of a doubt, therefore, that in my own case the eyes in con- 
vergence rotate slightly outward, and that the amount of rota- 
tion increases with the degree of convergence. 

I next proceeded to determine the amount of rotation for dif- 
ferent distances of the point of sight. In the diagram in which the 
inclination of the lines was 5 degrees, the distance of the image 
was only 2 to 24 inches; for the lines inclined 24 degrees, the 
distance of the image was 4 inches; for lines inclined 14 degree 
the distance was 7 inches; and for 40 minutes the distance was 
about 12 to 14 inches. I am able by great strain to obliterate, 
or nearly obliterate, the common field of view of the two eyes. In 
this case, of course, the eyes both look at the root of the nose. 
In this extreme convergence I find that limes coincide which 
make with each other an angle of 22°, or 11° with the vertical. 
This would seem, therefore, the extreme rotation for my eyes. 
The distance of the image in this case is nearly at the root of 
the nose. 

If, however, in extreme convergence rotation on the optic axes 
takes place to the extent of 11°, this rotation ought to be de- 
tectable by means of ocular spectra, or even by direct observa- 
tion of the eye itself. I determined to try these also. My 
method of experimenting with ocular spectra is as follows :— 
Standing in a somewhat obscure room, I gaze with the left eye 
(the other being shut) at a vertical crevice in a closed window 
until a distinct spectrum is obtained. Placing myself now op- 
posite a vertical line on the wall of the room, with my right side 
toward the wall, I turn my head until my left eye II (fig. 9), look- 


Fig. 9. 


2 Of Cc 
aol : 
a 
¢< 


ing across the root of my nose, n, can see the vertical line. I 
now gaze at a point very near the vertical line, and, by inclining 
my head to one side or the other, bring the spectrum exactly 
parallel to the vertical line. In this position, if the wall be at 


02 


188 Prof. J. LeConte on some Phenomena 


some distance from the observer, the axes of the eyes may be re- 
garded as nearly parallelas 1c, 16. Inow by a voluntary effort 
bring the point of sight along the line IIc nearer and nearer, 
until it reaches a near the root of the nose. In doing so the 


spectrum is always seen to incline to the left, thus \ . On re- 


laxing the convergence and looking again at the wall, the spec- 
trum retains its inclined position for an appreciable time and 
then gradually recovers its original verticality. In similar ex- 
periments with the right eye the spectrum is always seen to in- 


cline to the right, thus / 


I next tried direct observation of the eye itself. As I could 
not find ony one with the necessary control over the eyes, I 
was compelled to make myself the subject of this observation. 
While, therefore, with the right eye shut I gaze with the left eye 
across the root of the nose on vacancy, or on a distant object as 
in the figure (fig. 9), an observer, conveniently placed near the 
visual line, carefully examines the iris of my eye so as to recog- 
nize the position of the radiating lines. When now, without 
changing the position of the visual line of the left eye, I turn the 
right eye inward as in the previous experiment, until the point 
of sight is at a, the globe of the left eye is distinctly seen to ro- 
tate outward. I got four different persons to make this obser- 
vation upon my eye, and the testimony of all was the same. 

I had proceeded thus far in my experiments when I was led 
to reflect further upon the phenomena presented by the diagram 
in which the lines were highly inclined. In this diagram, it will 
be remembered, the verticals were combined with more facility 
than the horizontals. I now repeated all my experiments with 
more care and with especial reference to this point. As I ex- 
pected, I found the same true for all the diagrams; but the dif- 
ference was so small that it had escaped detection. This led me 
to suspect that there might be some truth in Professor Helm- 
holtz’s principle of real and apparent vertical. I therefore con- 
structed many other diagrams to test this point. I constructed 
first a diagram exactly like fig. 6, except that the circles were the 
same distance apart as my eyes, viz. 25 inches. On placing this 
diagram before me and gazing on vacancy, the eyes therefore in 
their primary position, the circles were brought together. In 
this experiment the verticals came together parallel. 1 sometimes 
thought there was a scarcely perceptible inclination in the diree- 


tion required by Helmholtz’s principle, viz. thus /\. If any 


such inclination really existed, it could not have been more than 


of Binocular Vision. 189 


10! for each line with the vertical, or 20! with one another ; for 
this angle I can distinctly detect under these circumstances. [ 
next constructed a diagram like Professor Helmholtz’s, except 
that the outward inclination of the verticals was only 40! in- 
stead of 11°. On combining the two halves of this diagram by 
means of a stereoscope, there really seemed to be perfect coin- 
cidence of both verticals and horizontals ; but I soon found, by 
trying several, that stereoscopes differ much in this respect. I 
therefore discarded them as unreliable. On combining the same 
diagram with the naked eye in the manner of a stereoscope, 2. e. 
beyond the plane of the diagram, the verticals coincided per- 
fectly when the point of sight was about twelve inches distant, 
but the horizontals very perceptibly crossed, though certainly, I 
think, at an angle less than 40! (it seemed about 20'). On com- 
bining the two halves by squinting (of course turning the dia- 
gram upside down), I found the result precisely the same when 
the point of sight was at the same distance, viz. 12 inches. In 
the next diagram which I constructed the verticals inclined 11° 
and the horizontals 50', the difference being therefore 25’. In 
this case both seemed to combine perfectly when the point of 
sight was distant 74 inches. The next diagram tried had the 
verticals inclined 5° and the horizontals 3° 45/, the difference 
being 11°. In this case both verticals and horizontals combined 
perfectly at the distance of 2°2 inches. I then tried one in 
which the verticals inclined 10°. In this case I could not make 
perfect coincidence of both verticals and horizontals until the dif- 
ference of inclination was made as great as 5°. The diagram 
used is shown reduced in the figure (fig. 10). The point of 


Fig. 10. 


sight in this experiment was only 11 inch from the line joining 


—— ae ess ASS 


eee 


eee 


190 Prof. J. LeConte on some Phenomena 


the optic centres, or about a quarter of an inch from the root of 
the nose. 

I attribute these phenomena to a slight distortion of the 
ocular globe under the action of the oblique muscles—a distor- 
tion which increases with the degree of optic convergence. We 
will refer to this again. 

In all the experiments described above, the greatest care was 
taken that the visual plane should be in the primary direction, 
2. e. at right angles to the line of the face, and especially that 
the median line of sight should be at right angles to the 
plane of the diagram. I now wished to try the effect of turn- 
ing the visual plane upward and downward. Meissner, from 
his experiments on the position of the horopter, had arrived 
at the conclusion that the rotation of the eye was zero, what- 
ever the degree of convergence, when the visual plane was in- 
clined downward 45° from its primary position, and that the 
rotation increased as the plane was elevated toward the eye- 
brows. I was anxious to test this result. The plane of the 
diagram still remaining vertical, I now turned the face upward 
(taking care, however, that the eyes should still be on an exact 
level with the circles of the diagram) until the eyes looked in 
the direction of the point of the nose. In this position, on ste- 
reoscopically combining the small circles, the lines, both vertical 
and horizontal, in all cases maintained their true position: i. e. 
in the diagram with parallel lines (fig. 6), the coincidence of all 
the lines was perfect; in the diagram with inclined verticals 
(fig. 7), the horizontals coalesced perfectly and the verticals 
crossed at their true angle of inclination; while in the diagram 
with the verticals and horizontals both inclined (fig. 8), both 
the verticals and horizontals crossed at their true angle of in- 
clination. JI tried the same experiment for various distances, 
and therefore various degrees of optic convergence, but always 
with the same result. There is, therefore, no rotation of my 
eyes when the plane of vision is inclined 45° downward. In con- 
tinuing the inclination still further downward, I observed a de- 
cided rotation of the eyes in the contrary direction, i. e. in- 
ward. As the eyes are raised from the position 45° downward, 
the rotation increases until the visual plane is again in its pri- 
mary direction. When the visual plane is raised above this, 
however, I do not find the rotation to increase as stated by 
Meissner, except in cases of extreme convergence, but rather to 
decrease again, although it does not again become zero*. In 


* More recent experiments, just concluded, have convinced me that in 
my own eyes, if the convergence is very slight, the outward rotation does 
reach zero and may even be converted into an inward rotation. The reason 


of Binocular Vision. 191 


strong convergence, however (as, for instance, when the point 
of sight is less than seven inches distant), the rotation continues 
to increase as stated by Meissner. 

In all these experiments, in order to detect the true rotation, 
it is absolutely necessary that the median line of sight should be 
exactly at right angles with the plane of the diagram. The least 
error in this respect will cause perspective convergence of the pa- 
rallel verticals, or increase or decrease of the angle of inclination 
of the inclined verticals. With the diagram three feet distant, if 
my eyes look one inch above or below their true level, on combi- 
ning the two halves of the diagram I can detect the perspective 
convergence, upward or downward, with the greatest ease. In’ 
all cases also, but particularly when the convergence is very 
strong, it is necessary to fix the attention on that horizontal 
which passes through the small circle ; for those above and below 
converge by perspective. 

In these experiments the size of the diagrams is of little 1m- 
portance. I have used them of every size from 5 by 10 inches 
to 15 by 30 inches. 

My next desire was to determine how far these results were 
general for normal eyes. The great difficulty was to find any 
one who was able to repeat the experiments. Nevertheless I have 
found four young persons with normal eyes who, with some 
practice, have succeeded in all except the most difficult of them. 
Their results agreed perfectly with my own. In a fifth case, how- 
ever, in which great difficulty was experienced and the results 
were uncertain, I was led to believe that the eyes in convergence 
rotated inward. It is not improbable, therefore, that normal 
eyes differ in this respect. 

We believe, therefore, that we are justified in the conclusion 
that when the eye is in its primary position and therefore pas- 
sive, the vertical line of demarcation coincides with the vertical 
meridian, and the horizontal line of demarcation with the hori- 
zontal meridian of the eye, and therefore these two lines of de- 
marcation are at right angles to each other. But as soon as the 
eyes begin to converge, the oblique muscles (particularly the 
inferior oblique) begin to act, rotating the eye on the optic axis 
and slightly distorting its form; so that the vertical line of de- 
marcation is now not only no longer coincident with the vertical 
meridian, but also no longer at right angles to the horizontal 


is, that when my eyes are parallel or nearly so, elevation of the visual plane 
causes inward rotation. In some other eyes, however, I have found that 
elevation of the visual plane when the eyes are parallel causes outward 
rotation as stated by Meissner. In these cases, therefore, Meissner’s 
results on this point are entirely true. 


192 Prof. J. LeConte on some Phenomena 


line of demarcation. Both the rotation and the change in the 
relation of the two lines of demarcation increases with the degree 
of optic convergence. It is possible that the frequent action of 
the muscles distorting the globe of the eye may leave some per- 
manent impress upon the form of the globe, so that even in a 
passive state the vertical line of demarcation does not coincide 
perfectly with the vertical meridian. If so, then to that extent 
Helmholtz’s principle of real and apparent vertical in the primary 
position of the eye will be true. Or, to express it differently, 
we have seen that the inclination of the vertical upon the hori- 
zontal line of demarcation decreases as the point of sight recedes ; 
at 17 inch it is 5°, at 2:2 inches it is 11°, at 7:5 inches it is 25/, 
andat 12 inches 20/. It is possible that even when the point of 
sight recedes to infinite distance, and the horizontal line of de- 
marcation becomes coincident with the horizontal meridian, the 
vertical line of demarcation may still make a small angle with 
the vertical meridian. Ifso, this angle is the difference between 
the real and apparent vertical spoken of by Professor Helmholtz. 
We do not yet admit this as probable, however; for the natural 
position in which all lines at all distances combine when the 
visual plane is inclined 45° downward seems inconsistent with 
this idea. 

The decrease of the rotation of the eye when the visual plane 
is inclined downward, and its increase when the visual plane is 
inclined upward, seem to be the result of the relative power of 
the two oblique muscles. Ordinarily the inferior oblique is the 
stronger, and the rotation is therefore outward ; but as the visual 
plane is inclined downward, the action of the two become more 
and more nearly equal, until at 45° they balance each other and 
there is no rotation. Below 45° the action of the superior 
oblique predominates, and the eye therefore rotates inward. In 
turning the visual plane upward and converging strongly, the 
action of the inferior oblique predominates more and more. 

It will be observed that the rotation of the eye which we have 
demonstrated necessitates, in optic convergence, a difference be- 
tween the real and apparent vertical ; but our views differ entirely 
from those of Professor Helmholtz in the following respects :— 
(1) Professor Helmholtz admits only a difference between real 
and apparent vertical; we have shown a difference between the 
real and apparent horizontal as well as the real and apparent 
vertical. (2) Professor Helmholtz’s difference is a constant one, 
viz. 14°; ours varies from 11° to 20', and probably to zero. 
(3) According to Professor Helmholtz, the relation of the appa- 
rent vertical to the apparent horizontal is a constant one, viz. an 
angle of about 883°; our experiments prove that this relation 
varies to the extent of 5°. 


of Binocular Vision. 193 


It is certain, therefore, that the law of Listing is far from 
being true in strong convergence. Evidently the reason is, that 
in convergence muscles are used which are not used in simply 
turning the eyes from side to side, as in the experiments used by 
Helmholtz to prove this law (p. 180). That different muscles 
are used in strong convergence is easily shown as follows :—It is 
easy to turn either eye inward until it looks in the direction of 
the root of the nose, provided the other eye moves parallel with 
it, 2. e. outward; but it is almost impossible to turn both eyes 
at the same time so as to look at this point. Great strain is 
experienced in producing convergence even much short of this. 
The eyes are turned from side to side, parallel to each other, by 
means of the interior and exterior recti muscles, while in con- 
vergence the oblique muscles are also used. For this reason 
Professor Helmholtz’s experiments on spectra do not apply to 
convergence. 

The law of Donders is equally untrue for strong convergence. 
This law asserts that the position of the eye is rigorously con- 
stant for every position of the visual line. But in the experi- 
ment represented by fig. 9, the eye II, although the direction of 
its visual line ts unchanged, rotates on its axis when the visual 
line of the other eye is turned from the direction Id to the di- 
rection La. 

The reason is, that as I turns toward a the oblique muscles 
in both eyes begin to act. It is probable that the action of the 
oblique muscles, and therefore the rotation of the eye, is consen- 
sual with the two adjustments and with the contraction of the 
pupil; and it is well known that, under the circumstances repre- 
sented by the figure, the pupil of the eye II would contract also, 
although the direction of the visual line is unchanged. 


III. The Horopter. 


If we look intently at any point, the visual lines converge and 
meet at that point. Its image is therefore impressed on exactly 
corresponding points of the two retinz, viz. on the central spot 
of each. A small object at this point is therefore seen single. 
We have called this point the poznt of saght. Allobjects beyond 
or on this side of the point of sight are seen double, for their 
images do not fall on corresponding points of the two retine. 
But objects above or below, or to one side or the other of the 
point of sight, may possibly be seen single also. The sum of all 
the points which are seen single, while the point of sight remains 
unchanged, is called the horopter. Or it may be expressed dif- 
ferently thus: each eye projects its retinal images outward into 
space, and therefore has its own field of view crowded with its 


194. Prof. J. LeConte on some Phenomena 


own images. When we look at any object, we bring the two 
external images of that object mto coincidence at the point of 
sight. Now the point of sight, together with all other corre- 
sponding points of the two fields of view which coalesce at that 
moment, constitute the horopter. Of course the images of all 
points lying in the horopter fall on corresponding points of the 
retina. 

Is the horopter a surface or is it a line? In either case what 
is its form and position? These questions have tasked the inge- 
nuity of physicists, mathematicians, and physiologists. If the 
position of identical points of the retine under all circumstances 
were known, then the question of the form of the horopter would 
become a purely mathematical one. But the position of identical 
points evidently depends upon the laws of ocular motion. It is 
evident, therefore, that it is only on an experimental basis that a 
true theory of the horopter can be constructed; and yet the ex- 
perimental investigation as usually conducted is very unsatisfac- 
tory, on account of the indistinctness of vision when the object 
is at any considerable distance from the point of sight in any 
direction. 

The most diverse views have, therefore, been held as to the 
nature and form of the horopter. Aguilonius, the inventor of 
the name, believed it to be a plane passing through the point of 
sight and perpendicular to the median line of sight. Others 
have believed it to be the surface of a sphere passing through the 
point of sight and the optic centres; others, a torus formed by 
the revolution of a circle passing through the point of sight and 
the optic centres on a line joining the optic centres. The sub- 
ject has been investigated with great acuteness by P. Prévost, A. 
Prévost, J. Miller, G. Meissner, E. Claparéde*, and, lastly, by 
Helmholtz+. A. Prévost determines in it, as he supposes, a circle 
passing through the optic centres and the point of sight, which 
he calls the “ horopteric circle,’ anda straight line passing 
through the point of sight at right angles to the visual plane, 
which he calls the “ horopterie vertical.” 

Until the investigations of Meissner, almost all attempts to 
determine the form of the horopter have been by mathematical 
calculations, based upon the doctrine of identical points, and 
assuming the law of Listing. Meissner attempts the same ques- 
tion experimentally. We condense the following account of his 
admirable investigations from Claparéde’s memoir on this sub- 
ject t already referred to. 


* Bib. Un. Archiv. des Scien. I. vol. ii. pp. 1388 & 225. 
t Proce. Roy. Soc. April 1864. 
t Bib. Un. Arch. des Scien. II. vol. iu. p. 138. 


of Binocular Vision. 195 


Let R (fig. 11) be an observer and I, II his two eyes, A the 
point of sight, B an 
object beyond and Bi Fig. 11. 
an object nearer than 
the point of sight, but 
all in the same line, 
joining the root of the 
nose and the point of 
sight. Of course both 
B and B! will be seen 
double. If,now, while 
the sight is still fixed 
uponA, B be elevated, 
its two images, ac- 
cording to Meissner, 
will approach until at some point, W, they coalesce. If, on the 
contrary, B be depressed, its images separate more and more. If, 
now, B! be elevated, its images separate; but if it be depressed, 
its images approach and coalesce at O. The line WAO is, 
therefore, the horopter or line of single vision. It is not at 
right angles, but inclined to the plane of vision. Again, accord- 
ing to Meissner, if instead of pots we have vertical lines like 
threads, W B and OB) (fig. 11), then O B! will double at B’, 
the images being crossed, and they will approach one another and 

\ IBF 


meet at O, in other words, will appear thus, ; while BW will 
O 


also double at B but not cross (2. e. each image will have the 
same name as the eye), and will be seen to converge and meet 


WwW 
at W thus, / \ Lastly, if the vertical line pass through the 


point of sight A, the images will cross one another like an X. 
Meissner accounts for these phenomena by supposing that, in 
converging the optic axis, the eyes rotate on the optic axis out- 
ward, so that the vertical lines of demarcation C D (fig. 12) no 
longer coincide perfectly with the vertical meridians A B, as 
they do when the eyes Fig. 12. 
are in the primary direc- 
tion (the axis parallel), 
but cross them at a small 
angle. In the primary 
direction of the eye the 
image of a vertical line, 
according to Meissner, 
falls on the vertical line 
of demarcation C D in both eyes (for these lines then coincide 


-— SS — —— ‘ 
oS SS 


196 Prof. J. LeConte on some Phenomena 


with the vertical meridian) and is therefore seen single. But if 
the eyes rotate on the optic axes outward, then the image of a 
vertical line still fallimg on the vertical meridian must cross the 
line of demarcation in opposite directions in the two eyes, and 
therefore cannot be seen single except at the point of sight, the 
image of which corresponds to the central point O of the retina 
of each eye. In order that the image of a line shall fall on the 
line of demarcation in both eyes and thus be seen single, it must 
be inclined at a certain angle with the vertical, the lower end 
being nearer and the upper end further away. It is moreover 
evident, upon a little reflection, that when the eye rotates, the 
horopter cannot be a plane or a surface of any kind; for objects 
right and left of the horopteric line must all be doubled by dis- 
placement of the horizontal line of demarcation GH (fig. 12), 
which therefore no longer coincides with the horizontal meri- 
dian, EF. 

From various experiments made at different distances and 
with different degrees of inclination of the visual plane upward 
and downward, Meissner concludes :—(1) That, looking straight 
forward at an infinite distance, the horopter is a plane at right 
angles to the visual lines. (2) That for all other distances, the 
visual plane remaining the same, the horopter is a straight line 
passing through the point of sight and increasing 1n inclination 
to the visual plane as the convergence of the optic axes increases. 
(3) That in turning the visual plane downward, the inclination 
of the horopteric line with that plane becomes less and less, 
until at 45° downward it becomes perpendicular, and therefore 
the horopter again expands into a plane at right angles to the 
median line of sight. (4) That in raising the visual plane up- 
ward toward the eyebrows, the inclination of the horopter to the 
visual plane increases. 

We have given Meissner’s investigations more in detail, be- 
cause by entirely different methods we have confirmed almost all 
of them. 

Claparéde by similar experiments fails to confirm the conelu- 
sions of Meissner, and therefore rejects them. He concludes, 
partly from his own experiments and partly from calculation, 
that ‘‘ the horopter is a surface of such a form that it contains 
a straight line perpendicular to the plane of vision and passing 
through the point of sight, and that every plane passing through 
the optic centres makes, by intersection of this surface, the 
circumference of a circle.” In other words, he believes that 
the horopter is a surface which contains the horopteric vertical 
BAB! (fig. 13) and the horopteric circle OAO of Prévost, 
and that in addition the surface is further characterized by the 
fact that, while the point of sight remains at A, the intersection 


of Binocular Vision. 197 


with it of every plane passing 
through the optic centres O, O! 
upward or downward as O B O! 
and O B’O'is also a circle. It 
is evident that as these circles 
would increase in size upward 
and downward, the horopter, 
according to Claparéde, must 
be a surface of singular and 
complex form. 

Finally, Helmholtz arrives at 
results entirely different from 
those of all previous observers. R 
He sums up his conclusions as 
follows :— 

“When the point of conver- 
gence is situated in the middle 
[vertical] plane of the head, 
the horopter is composed of a 
straight line drawn through the 
point of convergence [direction 
not stated, but evidently not at 
right angles to the visual plane, 
for see below the sentence marked 4], and a conic section passing 
through the optic centres and intersecting the straight line.” 

“When the point of convergence is in the plane which con- 
tains the primary visual lines [primary visual plane], the horop- 
ter is a circle going through that point and the optic centres 
| Prévost’s horopteric circle] and a straight line intersecting the 
circle [ where and in what direction not stated | ee 

‘When the point of convergence is situated as well in the 
middle plane of the head asin the primary visual plane, the ho- 
ropter is the circle just described [ Prévost’s horopteric circle] 
and a straight line going through that point [direction not 
stated |.” 

“There is but one case in which the horopter is really a plane, 
viz. when the point of convergence is in the middle plane of the 
head and at an infinite distance. Then the horopter is a plane 
parallel to the visual plane and beneath it, at a certain distance 
which depends upon the angle between the really and apparently 
vertical meridians, but which is nearly as great as the distance 
of the feet of the observer from his eyes when he is standing. 
Therefore, when we look at a point on the horizon, the horopter 
as the ground on which we stand. *When we look at the ground 
on which we stand at any point equally distant from both eyes, 


the horopter is not a plane; but the straight line which is one of 


198 Prof. J. LeConte on some Phenomena 


its parts coincides completely with the horizontal plane on which 
we stand.” 

These conclusions of Helmholtz are the result of refined ma- 
thematical calculations based entirely upon the supposed constant 
difference between the real and apparent vertical. If this principle 
be true for all normal eyes, then it is probable that Helmholtz’s 
conclusions in regard to the form and position of the horopter 
are also true for those cases in which the point of sight is at a 
considerable distance, and in which, therefore, the rotation of 
the eye is very small. JI am not able to test all of Professor 
Helmkoltz’s conclusions by calculations based upon this prin- 
ciple, but I easily see that the position of the horopter lying 
along the ground is the necessary consequence of a difference of 
11° between the real and apparent vertical when the eyes are in 
their primary direction. For if a line be drawn from each pupil 
downward, making an angle of 24° with each other or of 11° 
with the vertical, they will intersect each other at the distance 
of about five feet below the eyes or about the feet of the observer 


standing erect. Now if these two lines be placed thus \ i be- 


fore the observer whose eyes are in the primary direction, it is 
plain that their stereoscopic combination would be a line lying 
along the ground to infinite distance. if the difference between 
the real and apparent vertical be less than 11°, then the distance 
below the eyes of the horopteric plane will be greater. We 
have already shown that if there be any such difference in our 
own eyes, it cannot be more than 10'; in this case the horopteric 
plane will be at least 35 to 40 feet below the eyes. But Pro- 
fessor Helmholtz takes no account of rotation of the eyes on the 
optic axes, which greatly affects the form and position of the ho- 
ropter when the point of sight is near; and we believe that it is 
only when the point of sight is near that the form and position 
of the horopter is of any practical importance in vision, for it is 
only then that the doubling of images lying out of the horopter 
is perceptible. 

It has been with much hesitation that I have ventured to eri- 
ticise the conclusions of so distinguished a physicist. My ability 
to do so, if well founded, I attribute entirely to a facility in the 
use of the eyes such as I have never seen equalled in the case of 
any other person. 

Although I believe Meissner has arrived at truer results than 
any one who has yet written on this subject, yet [ think his me- 
thod very unsatisfactory. I have wondered at the skill and 
patience which could attain such true results by such imperfect 
methods. I have tried Meissner’s experiments without any sa- 
tisfactory results, and [ confess I commenced these experiments 


of Binocular Vision. 199 


with the conviction that his theory was untenable; but, contrary 
to my expectations, his views have been in a great measure con- 
firmed. The difficulty with Meissner’s method, and, in fact, with 
all previous experimental methods, as already stated, is the in- 
distinctness of objects at any considerable distance from the 
point of sight in any direction. In Meissner’s experiment with 
the three points B’, A, and B (fig. 11), in lowering B! or eleva- 
ting B the indistinctness was so great that I could not tell with 
certainty whether the images approached each other or not ; and 
in his second experiment with the thread, the obstinate disposi- 
tion on the part of the eye to see single by stereoscopic combi- 
nation, even when the images cross, interferes seriously with the 
certainty of the result. But in my experiments, by virtue of 
the complete dissociation of the axial and focal adjustments, the 
lines are seen perfectly clearly ; and by making them pass each 
other slowly, their relation to each other may be observed with 
great exactness. 

I will now state my own results in regard to the horopter. 

It is evident that if, in convergence, the eyes rotate on the 
optic axes, as my experiments prove, then in this state of the 
eyes the horopter cannot be a surface, but a line; and this line 
cannot be vertical, but inclined to the visual plane. Perhaps 
this requires further explanation. If the eyes in a state of con- 
vergence be fixed on a vertical line, then if the eyes rotate the 
line must be doubled except at the point of sight. This doubling 
is the result of horizontal displacement of the two images in op- 
posite directions ; and therefore the two images may be brought 
together by bringing the doubled portion of the vertical line 
nearer or carrying it further away. This is done in inclining 
the line as in fig. 11. But all points to the right and left of the 
horopteric line are also doubled by rotation; but this doubling 
is the result of vertical displacement of the images: now vertical 
displacement cannot be remedied by increasing or decreasing the 
distance, because the eyes are separated horizontally. Therefore 
no form of surface can satisfy the conditions of single vision 
right and left of the horopteric line. The restriction of the 
horopter to a straight line and the inclination of that line to 
the visual plane are therefore necessary results of rotation on 
the optic axes. But I have also proved this by direct experi- 
ment: 

If two lines, one white on black and the other black on white 
(fig. 14), be drawn at an angle of 11° with the vertical, and 
therefore 24° with each other, then by bringing my eyes so 
near to them at any point aa (taking care that the median 
line of sight shall be perpendicular to the plane of the lines) 
that the visual lines without crossing shall meet beyond the 


200 Prof. J. LeConte on some Phenomena 


diagram at the distance of seven inches from 
the eyes, the two lines are brought into per- 
fect coincidence. If, on the contrary, the 
same figure be turned upside down and the 
eyes be placed a little further than seven 
inches, so that the two points a,a are brought 
together by crossing the optic axes at the 
distance of seven inches, then also the lines 
are brought into perfect coincidence. The 
accompanying figure (fig. 15),in which O, O! 
are the eyes, A the point of sight, aH, a H, 
and a! H’, a’ H’ are the lines in the two po- 
sitions, will explain how the stereoscopic 
combination takes place in each case. ‘The 
lime H'A H is the horopter. This experi- 
ment is difficult to perform satisfactorily. 
When the lines come together it is difficult 
to determine whether there is real coinci- 
dence or not. I have observed, however, 
that when the coincidence is not perfect the 
white and black lines seem to run spirally 
round each other. The best plan is to observe them at the mo- 
ment of coming together or of separating. I feel quite confident 
of the reliability of the conclusions reached. 


Fig. 15. 


I made many calculations, based upon these experiments and 
on the previous experiments on the rotation of the eye, to deter- 
mine the inclination of the horopteric line for different degrees 
of convergence, 2. e. for different distances of the point of sight. 
The results of these calculations were not entirely satisfactory. 
I had expected from Meissner’s results that there would be found 
a progressive increase as the distance decreased. But I could 
not be sure from my calculations of any increase or decrease 
with distance. For all distances the inclination seemed to come 


of Binocular Vision. 201 
i AO) 


out about 7°—in some a little less, in some a little more. 
Beyond 3 inches there seems to be a slight progressive increase 
rather than decrease ; within 3 inches the action of the eyes was 
irregular. 

I then adopted another method. I used the diagram of pa- 
rallel lines (fig. 6) and inclined it at an angle of exactly 7° from 
the perpendicular in the supposed direction of the horopter and 
at the distance of 3 feet. In this position the verticals, of course, 
all converge by perspective. I then brought together sueces- 
sively the lines 3 inches apart, then those 6 inches apart, then 
those 9 inches, 12 inches, 15 inches, 18 inches, and so on even 
to the last, which were 30 inches apart: in each case the lines 
seemed to come together parallel; or at least the divergence, if any, 
was so small that I could not be sure about it. Now in this 
experiment the point of sight varied from 164 inches to only 
2°8 inches in distance, and yet the inclination of the horopterie 
line seemed to be nearly the same for all, viz. 7°. If there was 
any difference at all, it seemed to be in favour of greater inclina- 
tion at greater distance. ‘This result (which I arrived at, though 
doubtfully, by experiment alone) would be the necessary result of 
any residual difference between the real and apparent vertical, 
or, in other words, any residual inclination of the vertical upon 
the horizontal line of demarcation of the eye in its primary po- 
sition, such as Helmholtz maintains and as I have supposed 
possible. Still it by no means proves the existence of this resi- 
dual difference. 

It must not be supposed, however, because the lines 3 inches, 
6 inches, 9 inches, 12 inches, &c. apart are all brought into 
coincidence at the same or nearly the same inclination, that 
therefore the amount of rotation of the eye is the same for all. 
The perspective convergence of the lines, of course, increases 
with their distance apart, and therefore the rotation of the eye 
necessary to bring them successively into coincidence increases 
also. It is quite possible that the rotation should increase with 
the optic convergence, and yet the inclination of the horopteric 
line remain constant or even decrease with the convergence. 
Whether the inclination of the horopteric line increases or de- 
creases with distance would depend upon the law of increase of 
rotation with increasing convergence. If it increases with dis- 
tance, then it is possible that when we look at the ground before 
us the horopter may be a line lying along the ground, as main- 
tained by Helmholtz. 

I next tried the same experiments with the eyes inclined 
downward 45°. The lines do not change at all their natural per- 
spective convergence. In all the experiments made with eyes in 
this position the inclination of the lines in the image was the 


Phil. Mag. 8. 4. Vol. 38. No. 254, Sept. 1869. P 


202 Prof. J. LeConte on some Phenomena 


same as in the object. I conclude, therefore, that in this posi- 
tion of the eyes the horopter is at right angles to the plane of 
vision; and since there is no rotation of the eye, the horopter 
in this position expands into a surface. Below this inclination 
the horopter again becomes a line, but inclined now the other way, 
1. e. the upper end towards the observer. In turning the eyes 
upward toward the eyebrows, I have found the rotation, except 
in cases of strong convergence, less than looking straight for- 
ward. I conclude, therefore, that in this position the horopteric 
line inclines less to the visual plane than it does when the visual 
plane is in its primary direction*. 

The points in which my experiments do not confirm Meissner 
ave (1) the increasing inclination of the horopterie line with m- 
creasing convergence, (2) the increasing rotation of the eye as 
well as inehination of the horopteric line under all circumstances 
in turning the eye upward. Again, I believe that Meissner is 
also wrong in supposing that the horopter i is a plane when the 
eyes are depressed 45°. In this position it is a surface, but not 
a plane. It is clear that the images of points situated to the 
right and left of the point of sight and in the same plane with it 
cannot fall on corresponding points of the two retine. As to 
the form of this surface, I feel myself unequal to the task of its 
mathematical investigation; and its experimental investigation 
presents, I believe, insuperable difficulties. 

We have seen that the eye in convergence rotates on the optic 
axis. ‘The question naturally occurs, Is this rotation to be re- 
garded in the light of an imperfection of the instrument (of 
which there are several examples in the structure and mechanism 
of the eye), and should the law of Listing be regarded as the 
ideal of ocular motion, though an ideal seldom or never realized 
in nature? or does the rotation of the eye subserve some useful 
purpose in vision? I believe there is no doubt that the latter 
view is the correct one; for there seem to be special muscles 
which are adapted for this rotation, and the action of these 
muscles is consensual with the adjustments of the eye and the 
contraction of the pupil. This purpose I explain as follows. A 
general view of objects in an extended field is absolutely ne- 
cessary to animal life in its highest phases, but an equal distinct- 
ness of all objects in this field would only distract the attention ; 


* As stated in note on p. 190, eyes certainly differ in this respect. In 
my own, if convergence be small, the outward rotation decreases with the 
elevation of the visual plane, becomes zero, and is even converted into an 
mward rotation; the inclination of the horopter, therefore, decreases, 
becomes perpendicular, and even inclines the other way. In some other 
eyes the outward rotation increases whatever be the convergence; in this 
ae of course, the inclination of the horopter increases as stated by 

eissner. 


of Binocular Vision. 2038 


therefore the eye is so constructed and moved as to restrict as 
much as possible both distinct vision and single vision. Thus as 
in monocular vision the more elaborate structure of the central 
spot of the retina restricts distinct vision to the visual line, and 
the focal adjustment still further restricts it to a single point in 
that line, so also in binocular vision, axial adjustment restricts 
single vision to the horopter, while rotation restricts the horop- 
ter toa single line. 
Conclusions. 


The most important conclusions arrived at in this paper may 
be briefly summed up as follows :-— 

(1) The axial and focal adjustments of the eye are not so in- 
sepatably associated as is generally supposed; but, on the con- 
trary, when distinctness of vision requires it they may be com- 
pletely dissociated*, 

(2) In this dissociation the contraction of the pupil associates 
itself with the focal in preference to the axial adjustment. 

(3) In optic convergence there is a rotation of both eyes on 
the optic axes outward, and this rotation increases with the degree 
of convergence. 

(4) In inclining the visual plane downward, the rotation of 
the eyes for the same degree of convergence decreases until, when 
the visual plane is inclined 45° downward, the rotation becomes 
zero for all degrees of convergence. Below the inclination of 
45° the rotation is inward. In turning the eyes upward, except 
in cases of strong convergence, the rotation also decreases 
shghtly but does not reach zeroy+; in strong convergence it in- 
creases as stated by Meissner. 

(5) Besides the rotation produced by optic convergence, there 
is also a decided inclination of the vertical line of demarcation 
upon the horizontal line of demarcation, which increases with 
the degree of convergence. ‘This change in the relation of these 
two lines is probably the result of distortion of the ocular globe. 

(6) As a necessary consequence of the rotation of the eyes, 
for all degrees of convergence in the primary visual plane the 
horopter is a dine inclined to the visual plane, the lower end 
nearer the observer; but whether the inclination increases or 
decreases with distance I have not been able to determine with 
certainty. It probably increases with distance. 

(7) In inclining the visual plane below the primary position, 
the inclination of the horopteric line becomes less and less until, 


* While these pages were passing through the press, I discovered that 
in this conclusion I had been anticipated by Donders and others. All 
previous experiments, however, were made by means of glasses. Mine 
were made with the naked eye. 

T See this statement modified in note on p. 190. 


P2 


204: Mr. C. Tomlinson on the Formation of 


when the visual line is lowered 45°, the horopteric line becomes 
perpendicular to that plane and at the same time expands into a 
surface. Below 45° the horopter again becomes a line, but now 
inclined in the contrary direction, 7. e. the upper end nearer the 
observer. 

(8) In inclining the visual plane upward or toward the brows, 
if the optic convergence be strong the inclination of the horop- 
teric line increases ; but if the optic convergence be small it de- 
creases, but does not reach zero or become perpendicular*. 

(9) In looking downward 45°, for all distances the horopter 
is a surface passing through the point of sight and perpendicular 
to the median line of sight; but the form of the surface I have 
not attempted to determine. In looking straight forward at in- 
finite distance, the horopter is also a surface passing through the 
point of sight ; but the inclination of this surface I am unable to 
determine. 

(10) It is possible that in some eyes which would be consi- 
dered normal there is, in convergence, a rotation of the eyes 
inward, probably from greater power in the superior oblique. In 
such cases the position of the horopter would be different. 


Columbia, 8.C., 
November 16, 1868. 


XXI. On the Formation of Bubbles of Gas and of Vapour in In- 
quids. By Cuartus Tomutinson, #.R.S., F.C.S.7 


io the fifth Number of Poggendorff’s Annalen for the present 

year, dated May 31, and published, I suppose, early in 
June, is a paper by Herr Schréder on the conditions under 
which bubbles of gas and of steam are formed in liquids{. The 
paper is dated “ Mannheim im December 1868,” and a conti- 
nuation is promised for a future Number. In paragraph 4, 
which is devoted to the history of the subject, the author does 
me the honour of referring to two papers of mine which appeared 
in the Philosophical Magazine just two years ago§, although he 
says he was not aware of the existence of my papers nor of those 
of M. Gernez||, until he had completed the greater part of his 
researches on this subject. Still he: does not think it super- 
fluous to publish his paper, since he believes it will add new re- 
sults to those obtained by M. Gernez and myself. 

* See this statement modified in note on p. 202. 

+ Communicated by the Author. 

* “Untersuchungen tiber die Bedingungen, von welchen die Entwick- 


lung von Gasblasen und Dampfblasen abhiingig ist, und uber die bei ihrer 
Bildung wirksamen Krafte,” p. 76. 

Si. On the so-ealled iiaciee Condition of Solids,” Phil. Mag. for Au- 
eust and September 1867. 

|| Comptes Rendus for 1866 and 1867. 


Bubbles of Gas and of Vapour in Liquids. 205 


I am not aware whether Herr Schréder has seen my subse- 
quent papers on the subject of which he treats* ; but as he uses 
the same authorities, and no other, it is probable that he has. 
It cost me a considerable amount of research to find out the 
various memoirs of Ctrsted, Schénbein, Liebig, and Gernez on 
the hberation of gases from solution under the influence of nu- 
clei—of Watt and Southern, Achard, Gay-Lussac, Rudberg, 
Marcet, Bostock, Magnus, Donny, Grove, and Dufour on the 
phenomena of boiling liquids; and yet all these authorities, and 
no other, are made use of by Herr Schroder. 

It is equally remarkable that Herr Schréder should use the 
terms “clean” and “unclean” in precisely the same sense that 
I do, in distinguishing between a body that is “inactive” in 
liberating gas or vapour from liquids and one that is “active” 
in doing so—and that he should describe an inactive body as 
being made active by drawing it through the “finger and thumb” 
(I say “the hand ”’), when it becomes contaminated with greasy 
or fatty matter which renders it active. It is also remarkable 
that Herr Schroder should have hit upon the same explanation 
of the action of flame, sulphuric acid, alkaline solutions, alcohol, 
&e. in rendering dirty bodies chemically clean, and therefore in- 
active as nuclei in gaseous and vaporous solutions. 

I should have been quite content to leave all these matters 
unnoticed, seeing that priority of publication is in my favour, 
were it not that Herr Schroder claims for his distinguished coun- 
tryman Schonbein the merit of first distinguishing in 1837 be- 
tween an “inactive” and an “unclean” body in liberating gas. 

Now-in Schénbein’s short paper} there is not the slightest 
evidence that the author had any idea whatever of the difference 
between clean and unclean bodies in liberating gas from solution. 
His theory was that solids acted by carrying down air, into which 
the gas in solution expanded and so got liberated. He expressly 
says that metals from whose surface the adhering film of air has 
been removed by dipping them into boiling water, do not disen- 
gage bubbles of steam from boiling liquids. Herr Schroder also 
makes Schonbein refer to the action of porous bodies as nuclei, 
whereas Schénbein does not even mention permanently porous 
bedies, such as charcoal, pumice, &c. He states, as Bostock 
had done twelve years before, that bits of wood are particularly 


* <On jsome Effects of a Chemically Clean Surface,” Phil. Mag. for 
October 1868. 

“On the Action of Solid Nuclei in liberating Vapour from Boilmg Li- 
quids,” Proceedings of the Royal Society for January 1869. 

“Historical Notes on some Phenomena connected with the Boiling of 
Liquids,” Phil. Mag. for March 1869. 

“On Catharism, or the lifluence of Chemically Clean Surfaces,” Jour- 
nal of the Chemical Society for April 1869. 

7 Pogg. Ann, vol. xl. p. 391. 


206 On the Formation of Bubbles of Gas and of Vapour in Liquids. 


active so long as their pores are full of air, but when, by long 
boiling or steeping, the air is expelled they become quite inert *. 

Schonbein was by no means satisfied with the theory which 
attributed the action of solids in liberating gases or vapours from 
liquids to their carrying down air, a film of which was supposed 
to adhere to all bodies exposed to it; and he expressed his opi- 
nion that any one would perform an important service both to 
physics and to chemistry who could satisfactorily account for the 
varied phenomena connected with the subject of nuclei. 

Although Herr Schréder had not seen the papers either of 
M. Gernez or myself, yet his own theory is a sort of compromise 
between the two. M. Gernez says that solids act as nuclei by 
carrying down air into which the gas in solution expands. I say 
that such solids act by a kind of differential force depending on 
the amount of adhesion between gas and an unclean body, and 
between water and an unclean body. The gas will adhere; the 
water,as arule, will not ; but when it does so, itis with diminished 
force. Herr Schréder says it is true that unclean bodies act 
because they are covered, more or less, with a film of fatty or- 
ganic matter; but it is this film which enables the air to adhere 
to the solid, which adhering air, according to him and Gernez, 
is the efficient cause in liberating gas and vapour from liguids. 

With respect to imactive or chemically clean solids made so 
by the action of flame, sulphuric acid, &c., I say that the super- 
saturated solution, whether of gas, of salt, or of steam or vapour, 
adheres to such solids as a whole (that is, there is the same 
force of adhesion between the gas, salt, or vapour and the solid, 
as between the liquid and the solid), and hence there is no sepa- 
ration, Herr Schréder says that the action of flame, sulphuric 
acid, &c. is to prevent the air from adhering to the solid, so 
that when inserted into the liquid there is no separation, because 
no air has been carried down into which the gas can expand. 

It is not necessary for me to refer to any of the numerous 
experiments by which I justify my views on this interesting 
branch of inquiry. I do not ask Herr Schréder, or any one else, 
to adopt my theory or my experiments; they must go at their 
market price in the mart of science; but I do ask that when 
an observer takes up a subject which has been already handled, 
he should make himself acquainted with recent papers which, I 
suppose, are to be found in every public library ; and when ma- 
king use of scientific papers, whether old or new, that he acknow- 
ledge them and quote them fairly. 

Highgate, N., 
August 11, 1869. 
* Schonbein says, “Ganz besonders stark wirkt Holz so lange dessen 


> ee . > Nee . = = 
Poren noch mit Luft angefiillt sind, aber gar nicht mehr, wenn diese aus- 
getrieben ist.” 


i; 2070. 


XXII. On the Production of a Columnar Structure in Metallic 
Tin. By Dr. T. Frirzscun of St. Petersburg*. 
HE occurrence of a curious structural change in block tin 
from Banca was observed by Dr. Fritzsche. The metal 
became crystalline, and fell into small pieces having a columnar 
form. This change was attributed to the intense cold prevailing 
in St. Petersburg at the commencement of the year 1868. 

Dr. Fritzsche thus describes the experiments instituted to 
confirm his view :—‘“‘ Although I was persuaded that this phe- 
nomenon was produced by the intense cold that we had at the 
beginning of 1868, I wished to prove it by experiments. These 
experiments I have lately completed. I exposed some fragments 
cut from a block of Banca tin in an alcohol-bath reduced to the 
temperature of —32°-35° R. They underwent a change exactly 
similar to that in the blocks in question. 

“It is necessary for a like cold to be sustained for some hours 
to induce the commencement of the crystallization, which showed 
itself by the appearance of button-like prominences of a steel-grey 
colour rising from the surface of the tin. Hach prominence re- 
presents acentre from which the crystallization proceeds, if the 
cold be sustained. Gradually the meeting of the acicular erys- 
tals produces fissures at the points of contact, and the fragment, 
the volume of which is much augmented, falls in pieces, which 
are very friable and crumble between the fingers. 

“A remarkable fact is that elevation of temperature causes 
the steel-grey colour to disappear. This may be shown by 
plunging the steel-grey tin (enclosed in a sealed glass tube) into 
hot water, when the natural white colour reappears but without 
the former metallic lustre. This change of colour is not attended 
by a loss of weight; neither is the transition of cast tin into 
the crystalline modification, in the presence of air or in alcohol, 
attended with any loss of weight. Ihave met with cavities in the 
altered blocks, one of which had a capacity of -80 cub. centim. ; 
I do not believe that such large cavities were formed during the 
cooling of the blocks. I attribute their formation to the act of 
crystallization ; but on cutting these blocks I found that the 
change was only superficial, the centre being in the natural con- 
dition. I have there found similar cavities; and it is beyond 
doubt that they existed before the commencement of the change. 
As yet English tin has resisted the crystallization ; but Banca tin 
also undergoes the change even after being melted. 

“J shall continue my researches, as it 1s necessary to compare 
specific weights and to make analyses. I will communicate the 
ultimate results if they are of sufficient importance.” 


* Fyom a letter to Mr. Graham, dated June 18, 1869. Communicated 
by Mr. Graham. 


|. 208° 4 


XXII. Fundamental Principles of Molecular Physics. Reply to 
Professor Bayma. By Professor W. A. Norton. 


[Continued from p. 41.] 
A FTER replying to the general remarks in the first part of 


my paper, Professor Bayma proceeds to the consideration 
of my answer to his criticisms of my original paper on ‘ Mole- 
cular Physics,’ and ends by reaffirming his objections. I pro- 
pose to examine briefly the more salient points in this portion 
of his elaborate reply. 

Three Forms of Matter.—On this point we shall most readily 
eet at the true state of the case by quoting the postulates im my 
original memoir bearing upon it. They are the following :— 

‘All bodies of matter consist of separate indivisible parts, 
called atoms, each of which is conceived to be spherical in form.” 

“‘ Matter exists in three essentially different forms. These 
are (1) ordinary or gross matter, of which all bodies of matter 
directly detected by our senses either wholly or chiefly consist ; 
(2) a subtile fluid or ether associated with ordinary matter, by 
the intervention of which all electrical phenomena originate or 
are produced. This electric ether, as it may be termed, is 
attracted by ordinary matter, while its individual atoms repel 
each other. (3) A still more subtile form of zether which per- 
vades all space and the interstices between the atoms of bodies. 
This is the medium by which light is propagated, and is called 
the luminiferous ether, or the universal eather. The atoms or 
‘atomettes’ of this ether mutually repel each other; and it is 
attracted by ordinary matter, and is consequently more dense in 
the interior of bodies than in free space.” 

In what sense the term form is here used would seem to be 
abundantly manifest. It is plain that the “ three different forms” 
of matter are regarded as differing from each other in certain 
attributes which determine the precise office each fills im the 
scheme of Nature—and that the idea of a difference of geome- 
trical form could not have been entertained, since it 1s distinetly 
asserted that all atoms are conceived to be spherical in form. In 
the next paragraph of my memoir I consider the question of the 
probable constitution of a single primitive molecule, and remark 
as follows :—‘“ We are thus led to conceive of a molecule as con- 
sisting of an atom of ordinary matter surrounded with two atmo- 
spheres, ethereal and electric, the former being the more attenu- 
ated and pervading the other.” ‘The three “ forms of matter,” so 
called, are then the central atoms of molecules and the atoms of 
the two ethers. Each of these three general classes of atoms has 
certain characteristic attributes, in consequence of which their po- 


Prof. W. A. Norton on Molecular Physics. 209 


sition and office in nature are different. Professor Bayma also 
recognized, in his ‘ Molecular Mechanics,’ three distinct portions 
or general varieties of matter differimg in certain attributes, viz. 
the attractive nucleus or “nuclei” of a primitive molecule,a repul- 
sive “envelope” surrounding the nuclei,‘and the ether of space. 
In my reply to his criticisms, I stated that we agree in admitting 
the existence of two kinds of matter and three forms of matter. 
Thus, according to my view, ordinary or gross matter, 7. e. ordi- 
nary material atoms or elements, constitutes one kind of matter, 
and ethereal matter another kind. The latter has the same fun- 
damental properties, inertia, &c. as the former, but differs from 
it in some special property or attribute. Thus the atoms of or- 
dinary matter were regarded as mutually attractive, and those of 
ethereal matter as mutually repulsive. It was also conceived 
that the active forces of the atoms of ordinary matter might be 
much less intense than those of ethereal matter—although the 
enormous difference between the elastic forces of the ether of 
space and of the electric ether and those in operation within 
bodies of ordinary matter might be wholly due to the fact that 
the latter forces are the reciprocal effective actions of molecules, 
which are differential, being the resultant of antagonistic actions. 
I will here take occasion to remark that the notion that the 
atoms of ordinary matter are mutually attractive, at first adopted, 
does not seem to be a necessary one; for if we regard them as 
mutually repulsive, it is conceivable that the attraction of gra- 
vitation might consist in a feeble excess in the attraction of the 
central atom of each molecule for the atmosphere of every other 
over and above the repulsion subsisting between the atmospheres 
of the two molecules, together with the corresponding excess in 
the attraction of the electric atmosphere of the first molecule for 
the central atom of every other over the repulsion subsisting be- 
tween the central atoms of the two molecules. In fact the ex- 
istence of the former excess is one of the theoretical deductions 
of my ‘Molecular Physics.2 Upon the view now taken, an 
atom of ordinary matter may differ from an eether-atom only in 
exerting a less energetic repulsion (in accordance with the theory 
propounded in my former answer to Professor Bayma), and in 
exerting a direct attractive action upon the atoms of the electric 
ether. The two ethers, which differ only in subtilety, and ordi- 
nary matter, as it has been defined, constitute the “ three forms 
of matter.” 

With Professor Bayma the distinction between two kinds of 
matter lies wholly in the kind of activity manifested. The one 
kind is essentially attractive for all other elements, and the other 
essentially repulsive. He recognizes two varieties or forms of 
attractive matter—the molecular nuclei and the luminiferous 


210 Prof. W. A. Norton on the Fundamental 


eether,—and one form of repulsive matter, viz. the molecular 
envelope. 

If, after the explanation I have now given of my meaning in 
the phraseology used and of the conceptions actually formed, our 
author is still disposed to renew the question “ on what evidence 
are we to grant that matter exists in three forms essentially dif- 
ferent from each other,” 7. e. one attractive in the mutual action 
of its elements, and two repulsive in the same sense, or all re- 
pulsive in this sense, but exerting different intensities at repul- 
sion, I will reply by asking him ‘the same question, “on what 
cqidente are we to grant that matter exists in three forms,” viz. 
one repulsive and two attractive. If he should refer me to his 
‘Molecular Mechanics’ for the evidence, I should respond by re- 
ferring him to my ‘ Molecular Physics’ for the evidence. 

There is no occasion to add anything more on the question of 
the three forms of matter, except to remark that Professor 
Bayma’s apparent success in exposing the “fallacy of my argu- 
ment” about “ gross matter” is attributable to the fact that he 
represents me as holding that gross matter is made up of mole- 
cules, whereas, as I have already shown in my conception and 
characterization of the three forms of matter, the gross or ordi- 
nary matter is simply the central atoms of the molecules. It 
may be as well to remark, also, that the term ‘ gross matter” 
was adopted in conformity with common usage, m ‘designation of 
what is universally called matter, without “intending to imply 
that the atoms of necessity « differed from the ethereal atoms, 
except in the intensity of their active forces as compared with 
the quantities of matter in the atoms. 

Two Atthers.—It is asked, ‘‘ Why two ethereal fluids when 
one might suffice.’ The “clear and positive answer” I have to 
give 1s this :—for the simple reason that, as I have endeavoured 
to show in my ‘ Molecular Physics,’ from the conception of two 
ethers, the recognized molecular forces and the different classes 
of molecular phenomena in their diverse mutual relations and 
interdependence may be evolved, while all attempts to accom- 
plish this result by means of the hypothesis of a single ether 
have signally failed. If our author or any other physicist will 
give us any substantial reason to believe that the notion of a 
single ether may really suffice to explain electric phenomena, 
we shall be ready to admit that his query throws a shadow of 
doubt on the hypothesis of two ethers. But we certainly can- 
not make the same admission in deference to his mere assertion 
that “one ether might suffice.” 

The proof, or, rather, strong evidence (which is all that the case 
admits of), that two eethers, both repulsive, exist in nature, 1s that 
optical and electric phenomena have given direct indications of 


Principles of Molecular Physics. all 


their existence, and the entire range of molecular phenomena 
can be shown to be deducible from their fundamental properties 
and relations to ordinary matter. 

Electric Aither.—My critic still cherishes the illusion that a dis- 
crepancy or fallacy exists in my conception of the electric ether. 
It is true that in my original memoir 1 hinted that the effective 
mutual repulsion of the electric atoms might have its origin in 
a repulsion between ethereal atmospheres condensed around 
them by an attraction; but in my reply to Professor Bayma it 
was distinctly averred that I did not advocate this doctrine, and 
was only disposed to admit the possibility of its truth. If my 
pertinacious critic is still disposed to run a tilt, against it under 
the hallucination that it is one side of my citadel, I can only look 
upon his adventure with the same sort of interest with which we 
contemplate the exploits of a knight-errant in a romance. 

I will take occasion in this connexion to remark that the con- 
viction entertained by our author and other eminent physicists, 
that the supposed electric fluid or ether is not to be regarded as 
a vera causa in nature, appears to have its origin in certain mis- 
conceptions or groundless assumptions. 

(1) It is deemed more philosophical to seek for the true origin 
of electric and kindred phenomena in some mode of motion of 
the ultimate parts of bodies, notwithstanding that the existence 
of an ether (the luminiferous) having the same character of sub- 
tilety and enormous energy of elastic force as the supposed elec- 
tric wether is distinctly recognized. This is as much as if, after 
Cavendish had discovered the properties of hydrogen gas, and 
the phenomena exhibited by oxygen had been carefully studied, 
it had been insisted that chemists must seek to explain these 
phenomena by some imagined modification of the mechanical 
condition of hydrogen, instead of attributing them to a new gas 
having certain specific differences of property from oxygen. Why 
should the hypothesis of a new ether similar to the luminiferous 
be regarded as inherently less probable than several hypothetical 
motions of the atoms or molecules of ordinary matter. 

(2) It is imagined to be a simpler conception to refer electric 
phenomena to some mode or modes of motion of the atoms or 
elements of bodies than te a new ether. Atoms may be con- 
ceived to have any one of three different motions, viz. a vibra- 
tory motion, a motion of rotation, or a motion of revolution. 
Now let any one of these motions be hypothetically taken, and 
the attempt made to obtain some glimpse of the manner in which 
the phenomena might possibly evolve themselves. In the first 
place, there must be two different motions answering to the posi- 
tive and negative electric states. In the next place, these mo- 
tions must be capable of propagation from molecule to molecule 


212 Prof. W. A. Norton on the Fundamental 


without changing their character, to represent a current of free 
electricity. Again, they must be capable of propagation from 
molecule to molecule with a continued reversion of their cha- 
racter, to explain the phenomena of induction. Still, again, 
these atomic or molecular motions must take place simultane- 
ously with some other mode of motion, answering to heat, and 
another, representative of the magnetic or diamagnetic condition ; 
and these different modes of motion must be convertible each 
into every other, &c. So far from being led into a region of 
attractive simplicity, the complexity of the scene that presents 
itself to the mind’s eye would scem to be enough to appal the 
most determined explorer in the field of speculative science. 

(3) It is conjectured by some physicists that the luminiferous 
eecther may be equal to the duty assigned to the electric. But 
no approximation to a successful attempt has yet been made to 
realize this idea. It is a mere conjecture, and therefore un- 
worthy of serious regard. 

My own position on the question of the existence of an electric 
eether was not, as intimated by Professor Bayma, that it is an 
established truth, at least with the same degree of certainty that 
the existence of a luminiferous ether is, but an hypothesis (and 
the only definite hypothesis hitherto suggested by electric phe- 
nomena) which had been shown to be in accordance with the en- 
tire range of such phenomena, and thus come to be generally 
received. If it be true, as I maintain, that the molecular forces 
and molecular phenomena generally, in all their interdependence 
and mutual convertibility, can be derived from this hypothesis, 
when this shall come to be acknowledged it will then be admitted 
that full confirmation of the principle reached by induction has 
been furnished by the deductive test. The existence of an elec- 
tric ether will then become an established truth in the most po- 
sitive sense in which this can be affirmed of any principle m 
physics. 

Origin of Heat.—In expressing the strong conviction that 
heat does not originate in the vibrations of gross molecules, re- 
ference was had to vibrations of the molecules as a whole, to the 
one side and the other of the positions of equilibrium. What is 
meant by “ vibrativity 7” I do not fully comprehend. If we are 
to understand by it an alternate contraction and expansion of the 
repulsive envelope of a molecule, then Professor Bayma’s theory 
of heat bears a certain analogy to my own, and may, for all that 
appears to the contrary, be free from the objections that may be 
urged against the doctrine that heat consists in a true vibration 
of atoms or molecules. 

Luminiferous Aéther.—There need be no hesitation as to the 
proper answer to be made to our author’s argument to show that 


Principles of Molecular Physics. 213 


the discovery made by Encke, that the comet which bears his 
name affords decisive evidence of the existence of a resisting me- 
dium in the fields of space, is really no discovery at all. In the 
first place, the attraction of unknown bodies would in all proba- 
bility produce effects not recognized in the disturbed motions of 
Kincke’s comet—for example, would alter the position of the 
plane of the orbit. In the second place, Professor Bayma’s me- 
chanics is at fault; for though the direct tendency of the resist- 
ance of the supposed medium is to diminish the orbital velocity, 
a resulting effect is that the orbit is contracted, and the return 
of the comet to its perihelion expedited. This is Encke’s view 
of the matter, and it has hitherto met with general acceptance. 
The words that issue from the filmy trumpet of this unwearied 
celestial traveller on each successive return have, then, quite a 
different meaning from those attributed to them by our author, 
and proclaim the insufficiency of the foundation on which his doc- 
trine of an attractive ether has been erected. . 

As to Professor Bayma’s comments on the objections urged 
against this doctrine, I think it must be admitted by the candid 
reader that the evidence in favour of my view of the constitution 
of a primitive molecule has been in no degree impaired by his 
criticisms. His idea that ‘‘no possible production of heat and 
electric currents affords a sufficient ground for assuming a re- 
duction of resistance and retardation” is altogether fallacious ; 
for if the impmging atoms of the ether of space take effect 
directly upon dense electric or ethereal atmospheres enveloping 
the atoms of gross matter, they may give rise to waves and cur- 
rents in those atmospheres, propagated thence to other molecular 
atmospheres, and the energy conveyed by them eventually ra- 
diated in waves of heat through the interstitial ether and into 
free space from all sides of the atoms, and with no less tensity 
from the further sides than from those in advance. A similar 
principle to this is admitted in the theory of overshot water- 
wheels, when it is assumed that the mechanical effect due to the 
water received into the cell is lost—not communicated to the 
wheels—being expended primarily in imparting agitations on 
waves and currents to the water already in the cell, and eventu- 
ally passing off in the form of heat. The state of the case then 
is this: the resistance of an ethereal medium in space will 
not of necessity retard the motions of the planets, if their atoms 
be surrounded by dense ethereal atmospheres, as I have been 
led to conceive them to be, on quite different grounds. 

We come now to consider the answer given to my objection 
to Professor Bayma’s doctrine of an attractive medium, viz. that 
it really involved the operation of an energetic resistance. I 
freely admit the sufficiency of his answer, if it follows from his 


214 Prof. W. A. Norton on Molecular Physics. 


views that the repulsive envelope of each molecule must “ beat 
back” the ether of space which it encounters before it comes 
within the range of the attraction of the central “ nuclei.” But 
does he not, in thus escaping one difficulty, encounter another 
equally great? This “beating back” of the ether implies that 
the molecules of the earth’s mass in the advance are, by reason 
of the earth’s motion, at such a diminished distance from the 
ethereal atoms immediately contiguous to them that a repulsive 
action of the molecular envelopes upon these atoms comes into 
play superior to that due to the condition of equilibrium that 
would obtain if the earth were at rest. If this be admitted, 
it must then at the same time be admitted that the molecules on 
the following side of the earth are at a corresponding increased 
distance from the ethereal atoms immediately behind them. If, 
then, the atoms of the ether are attractive, as our author main- 
tains, since they are in closer proximity to the envelopes of the 
molecules of the earth on its preceding than on its following side, 
the attraction exerted by the ether upon the molecules must be 
more energetic on the former than on the latter side of the earth, 
and hence the earth should be accelerated in its motion through 
space by the operation of the attractive ether supposed. J must 
therefore conclude that the logical necessity still exists of “ abo- 
lishing the ether of space altogether.” 

“A Molecule.’—The position called in question under this 
head had a phenomenal bearing only, as is sufliciently evident 
from the expression “in all outward relations,” and the subse- 
quent allusion to the production of phenomena. I was well 
aware that his “ molecule” was, in the details of its constitution, 
quite different from my own—and in another connexion alluded 
to the multiplicity of assumptions made by the learned author of 
the ‘ Molecular Mechanics’ in fashioning so complex and artifi- 
cial a structure, and urged the objection that if we admit his 
conception of matter and of the several material activities, we 
still require the miraculous interposition of the Creator in the 
construction of every individual molecule in the universe. The 
eround taken was that in the evolution of phenomena, the nu- 
cleus or “nuclei” and envelope must each play, to all intents 
and purposes, the parts I had assigned to the central atom and 
electric atmosphere of my own molecule. If Professor Bayma is 
not disposed to admit this, I shall await with curiosity the fur- 
ther development of his theory, when I shall be in a position to 
decide with certainty how far | may have been in error in taking 
the ground just mentioned. 


[To be continued. ] 


XXIV. Ona Remarkable Structural Appearance in Phosphorus. 
By Cuarves Tomuinson, F.R.S., F.C.S* 


HE following remarkable appearance in phosphorus was 
described to me some months ago by Mr. James John 
Field, F.C.S., who requested me, if possible, to account for it. 

About four years ago Mr. Field placed half a dozen sticks 
of phosphorus in a cylindrical jar containing water which rose 
about half an inch above the ends of the sticks, and the jar 
was closed with a bung. This jar was placed in a cellar, where 
it remained undisturbed for about three years. The cellar is 
flagged with stone, is surrounded by damp w alls, and almost en- 
tirely protected from light and currents of air. The maximum 
temperature probably does not exceed 50° or 55° F. 

After this long repose the jar was taken into the laboratory, 
when it was found that the level of the water had sunk to about 
one-third of its original height, and the liquid left in the jar had 
become as dense and thick as the strongest syrup; it consisted 
of a solution of PO? and PO. 

The portions of phosphorus that rose some inches above the 
liquid, instead of being cylindrical as before, were conical from 
a sharp point to the full diameter, and each cone had a double 
spiral running down it from left to right, as if two flat tapering 
bands of the substance had been made to cohere at right angles 
lengthwise, and then twisted into a pointed Cee just as if 
the sticks had been mounted in a screw- -cutting lathe, geared to 
cut a coarse tapering double spiral. The sticks had also y changed 
from the creamy opaque surface to a translucent barley-sugar 
appearance from the surface of the liquid up to the points. 

In attempting to explam the appearances described, we must 
consider, fist, the wasting away of the sticks and their conical 
form, and, secondly, the twisted structure. 

First. The wasting away of the sticks and their conical form 
are clearly effects of ‘slow combustion, diminishing in intensity 
downwards. The continued combustion and also the evapora- 
tion of the water must have been due to a badly fitting cork 
which, during a falling barometer, allowed a portion of the moist 
air to escape from the j jar, and during a rising barometer allowed 
a portion of comparatively dry air to stream in. Had the jar 
been subject to considerable variations in atmospheric tempera- 
ture, the effects would have been more rapid; but as the tempera- 
ture of the cellar was pretty constant, there is nothing to detain 
us here. Going back, then, to variations in atmospheric pres- 
sure, the level of the water in the j jar would be gradually lowered 


* Communicated by the Author, haying been read at the British Asso- 
ciation at Exeter, August 19, 1869. 


216 Ona Remarkable Structural Appearance in Phosphorus. 


during the oscillations of the barometer, until at length the tops 
of the sticks of phosphorus became exposed. Slow combustion 
would then set in, the resulting acid would go into solution, and 
small quantities of fresh air would stream in to supply the par- 
tial vacuum, and so continue the action. During a falling ba- 
rometer nitrogen and moisture would stream out “of the j jar, the 
level of the water would be again slightly lowered, and a fresh 
portion of phosphorus be exposed to the attacks of the next 
portion of oxygen drawn in. In this way by very slow degrees 
the liquid would be lowered and fresh portions of phosphorus 
exposed. Those already out of the water would be attacked by 
every ingress of air, and thus being acted on not only more ener- 
getically, but also for a longer time than the lower portions, 
they would necessarily have a conical shape. Moreover the air 
that streamed into the jar would gradually lose its oxygen in 
descending, so that the lower portions would be acted on less 
strongly than the upper. The phosphoric acids as generated 
would also pass into solution with a certain rise of temperature 
and a certain expansion of the nitrogen left in the jar. As this 
cooled down, a little more air would be drawn in, and combus- 
tion and solution would go on as before. But the most ener- 
getic action would take place when under a falling barometer a 
quantity of moist nitrogen streamed out of the jar, and duringa 
rising barometer a fresh supply of atmospheric air streamed in, as 
already explained. 

Secondly, as to the spiral markings. ‘These cannot have been 
formed by any action that took place in the jar; but they show, 
I think, the new and interesting fact that the curves which the 
theory “of hydraulics assigns to liquids flowing from an ori- 
fice, and producing the vena contracta, actually form part of the 
structure of a body suddenly arrested in its flow by being made 
solid. 

It is well known that in the ordinary mannfacture phosphorus 
is formed into sticks by being made to flow from a fead or re- 
servoir of the molten element along a short pipe or qoutage 
into cold water ; or, rather, as soon as the stick of phosphorus 
begins to emerge from the warm ajoutage and shows itself in 
the cold bath, it is seized by hand and cut off at intervals, or 
drawn out by machinery into a continuous length, so that from 
15 to 20 lbs. and upwards of phosphorus can be moulded in less 
than a quarter of an hour. 

Now, of course, in the flow of the molten phosphorus Torri- 
celli’s theorem applies; viz. that particles of fluid on escaping 
from an orifice possess the same velocity as if they had fallen 
freely in vacuo from a height equal to that of the fluid-surface 
above the centre of the orifice. If the head of phosphorus were 


On the Supposed Action of Light on Combustion. 21% 


not too deep, there would be seen immediately over the orifice a 
hollow depression which increases until it becomes a cone or funnel 
the centre or lowest point of which is in the orifice, and the liquid 
flows in lines directed towards the centre. In this condition of 
the liquid a rotatory motion is necessarily imparted to it; and 
this rapidly increases, because all the particles are approaching 
. the centre, and by virtue of their inertia they tend to maintain 
the same velocity which they had ima larger circle, so that their 
angular velocity (or the number of revolutions in a given 
time) is constantly being increased. As the particles approach 
the orifice they converge to a point beyend it, so that the liquid 
in escaping is narrower or more contracted at the point to which 
it converges than it is either before it arrives at that point, or 
after it has passed it. But as this point in the phosphorus to 
which the rotating lines converge, though fixed in or uear the 
tube, is being constantly shifted in the phosphorus by being 
drawn out and moulded in the tube, the converging lines are 
also drawn out, and thus give the appearance of a double spiral. 
Of course some of the lines are obliterated by the moulding 
action of the tube, and are probably of a different texture as to 
hardness as compared with the drawn-out lines. These flattened 
or moulded portions first yield to the action of slow combustion, 
and leave the harder drawn-out lines in relief. 
Highgate, N., 
July 31, 1869. : 


XXV. On the Supposed Action of Light on Combustion. 
By Cuaries Tomuinson, F.R.S., F.CS.* 


aoe popular idea that “light puts out the fire”’ is so fixed, 

that probably no conclusions drawn from actual experi- 
ment are likely to disturb it, especially if they be adverse to the 
notion. It is a matter of daily experience, people say, that if the 
fire is nearly out and you put a screen before it, or draw down 
the blind, or close the window-shutters, it will immediately 
begin to revive. It is generally forgotten that a fire which looks 
dull or “‘out” in a well-lighted room will appear to be in tole- 
rable condition in the same room when darkened. It only re- 
quires to be “ put together”? to make it burn up, and it might 
have done so just as well in the light. 

Experiments on this subject are not easy to make, on account 
of the many disturbing causes. In an old volume of the ‘Annals 
of Philosophy’ is an account of some experiments by Dr. 
M‘Keever, who took two portions of green wax taper, each 

* Communicated by the Author, having been read at the British Asso- 
ciation at Exeter, August 20, 1869. 


Phil. Mag. 8. 4. Vol. 38. No. 254, Sept. 1869. Q 


218 Mr. C. Tomlinson on the Supposed Action 


weighing ten grains, and ignited both at the same moment. 
One piece was placed in a dark room at 67° F., the other was 
exposed to broad sunshine at 78° F. In five minutes 


The taper in sunshine lost 8} grains. 
The taper in the darkened room lost 91 grains. 


The taper, divided into inches, was also burnt in the coloured 
portions of the solar spectrum, when it was found that the time 
required to burn two inches of taper varied as follows :— 


Inthe redmay it toolo tae. Gao 
In the ‘green’vay it tooki: “9. S720 
Tnothe violet ‘ray 1b tooks 2) 2192 NSho9 
At the verge ofthe violet it took 8 57 


The conclusion is that the solar rays, in proportion to their 
intensity, have the power of retarding to a considerable extent 
the process of combustion ; and it is supposed that the chemical 
rays act in some way on the portion of oxygen about to combine 
with the fuel so as to delay, if not prevent, combination. 

Supposing in these experiments the taper was so uniform that 
one inch contained precisely the same quantity of matter as an- 
other inch, the time occupied in burning was too short to justify 
so important a conclusion as Dr. M‘Keever arrived at, whether 
the results were taken by measure or by weight. 

Every one engaged in photometrical observations must be 
aware of the difficulty of getting rid of disturbing causes and 
perplexing results. In comparing candles of the same make, 
the light is affected both in quantity and economy by a number 
of small circumstances, such asthe warmth of the room, the ex- 
istence of shght currents of air, the extent to which the wick 
curls over when burning, and so on. In testing the quality of 
gas, the standard candle defined by Act of Parliament is a sperm 
candle of six to the pound, burning at the rate of 120 grains per 
hour. From such a standard we get the terms “12-candle gas,” 
“]4-candle gas,’ &e. Mr. Sugg, in his ‘Gas Manipulation,’ 
has pointed out some of the difficulties in obtaining a uniform 
standard candle. The wick does not always contain the same 
number of strands; they are not all twisted to the same degree 
of hardness ; the so-called sperm may vary in composition, one 
candle containing a little more wax than another, or variable 
quantities of stearime, or of paraffine ; the candle may have been 
kept in store a long or a short time; the temperature of the 
store-room may have varied considerably, and the temperature 
of the room in which it was burnt may have been high or low. 
All these circumstances affect the rate of combustion and the 
illuminating-power of candles, irrespective of the action of light, 
if such action really exist. 


of Light on Combustion. 219 


I have lately had a good opportunity of testing this action at 
the works of Price’s Patent: Candle Company at Battersen: Under 
the direction of Mr. Hatcher, the accomplished chemist of the 
Company, the greatest possible care is taken to ensure identity 
of composition and illuminating-power in candles of the same 
name. ‘There has lately been an extensive series of experiments 
on the photometrical value of sperm candles, during which, at 
my request, Mr. Hatcher was good enough to note the rate of 
combustion of such candles in a darkened room, and also in broad 
daylight and even in sunshine. 

In the first observation, three hard and three soft candles 
were burned each for four hours in a dark closet. A similar 
set of candles taken from one and the same filling were burned 
during the same time in open daylight, partly in sunlight. The 
average consumption per hour of each candle was as follows :— 


Sperm mathe dark .° . . ., 134 grains. 
meoememin tne leht’. ’. . °. V4 
No. 2 Composites in thedark. 1383 ,, 

»  Compositesinthelight. 140 ,, 


d3 


It must be noticed that the temperature in the light was 72°, 
and in the dark 71°. Moreover in the light there was a much 
greater motion of the air than in the dark closet. Both these 
circumstances would operate in producing a larger consumption 
of candle. 

Im a second trial with No. 2 composites the results were :— 


In the dark . . . 140 grains each candle. 
imtiedicht .. ... 4, 134 3 i 


In a third, also with No. 2 composites, the results were :— 


Mi the dark +. 3. Pl. prams. 
iitthGnevheht as 3 xe L208, 


In these two trials the flames were protected as far as possible 
from currents of air, and in the third trial the temperature both 
in the light and in the dark was nearly equal. 

The fourth trial was made ona bright sunshiny day with hard 
sperm candles, which are less affected by variations of tempera- 
ture than the composites. The results were— 

In the dark (temp. 81°) . . 544 grains, 
or 136 grains per hour. 

In the light (temp. 84°) . . 567 grains, 
or 142 grains per hour nearly. 

It is evident that in this case the inerease of temperature 
eaused by the bright sunshine led to an increased consumption 
of material. 4 

a2 


220 =Mr. J. Croll on the supposed greater Loss of Heat 


Tt will be seen that in the first and fourth trials there is a 
ereater consumption of material in the light than in the dark, 
and in the second and third trials the consumption is greater in 
the dark than in the light; but im any case the difference 1 1s SO 
small, amounting only to from 2 to 7 grains per hour, that it 
may fairly be referred to accidental cireumstances, such as differ- 
ences in temperature, in currents of air, and in the composition 
and make of the candles, the final conclusion to which I am led 
being that the direct light of the sun or the diffused light of day 
has no action on the rate of burning, or in retarding the com- 
bustion of an ordinary candle. 

Highgate, N., 

July 1869. 


XXVI. On the Opinion that the Southern Hemisphere loses by 
Radiation more Heat than the Northern, and the supposed Influ- 
ence that this has on Climate. By James Crottu, of the Geo- 
logical Survey of Scotland. 


HE total amount of heat received from the sun between 
the two equinoxes is the same in both halves of the year, 
whatever the eccentricity of the earth’s orbit may be. For ex- 
ample, whatever extra heat the southern hemisphere may at pre- 
sent receive from the sun during its summer months owing to 
greater proximity to the sun, is exactly compensated by a cor- 
responding loss arising from the shortness of the season; and, 
on the other hand, whatever deficiency of heat we in the northern 
hemisphere may at present have during our summer half year 
in consequence of the earth’s distance “from the sun, 1s also ex- 
actly compensated by a corresponding length of season. 

But the surface-temperature of our globe depends as much 
upon the amount of heat radiated into space as upon the amount 
derived from the sun, and it has been thought by some that this 
compensating principle holds only true in regard to the heat 
directly received from the sun. In the case of the heat lost by 
radiation the reverse is supposed to take place. ‘The southern 
hemisphere, it is asserted, has not only a colder winter than 
the northern in consequence of the sun’s greater distance, but 
it has also a longer winter; and this extra loss of heat from 
radiation is not compensated by its nearness to the sun du- 
ring summer months, for it gains no additional heat from its 
proximity. And on the same principle our winter im the north- 
ern hemisphere, owing to the less distance of the sun, is not only 
warmer than that of the southern hemisphere, but is also at 


* Communicated by the Author. 


by the Southern than by the Northern Hemisphere. 221 


the same time shorter. Consequently it is concluded our hemi- 
sphere is not cooled to such an extent as the southern, and thus 
the mean temperature of the winter half year, as well as the in- 
tensity of the sun’s heat, is affected by a change in the sun’s 
distance. 

This circumstance was, so far as I am aware, first noticed by 
Humboldt in his memoir “ On Isothermal Lines and the Distri- 
bution of Heat over the Globe”*. Upon it M. Adhémar has 
founded a theory of change of climate, and attributes the great 
extension of the ice around the south pole to this extra amount 
of heat lost by radiation in consequence of the seven or eight days 
of excess in the length of the southern winter over the northern. 
“The south pole,” says Adhémar, “loses in one year more heat 
than it receives, because the total duration of its nights surpasses 
that of the days by 168 hours; and the contrary takes place 
for the north pole. If, for example, we take for unity the mean 
quantity of heat which the sun sends off in one hour, the heat 
accumulated at the end of the year at the north pole will be ex- 
pressed by 168, while the heat lost by the south pole will be 
equal to 168 times what the radiation lessens it by in one hour, so 
that at the end of the year the difference in thé heat of the two 
hemispheres will be represented by 336 times what the earth re- 
ceives from the sun or loses in an hour by radiation” fF. 

Adhémar supposes that about 10,000 years hence, when 
our northern winter will occur in aphelion and the southern in 
perihelion, the climatical conditions of the two hemispheres 
will be reversed; the ice will melt at the south pole, and the 
northern hemisphere will become enveloped in one continuous 
mass of ice, leagues in thickness, extending down to temperate 
regions, 

Although I always regarded this cause of Humboldt’s to be 
utterly madequate to produce such effects as those attributed 
to it by Adhémar, still in former papers { I stated 1t to be a vera 
causa which ought to produce some sensible effect on climate. 
On a more careful consideration of the whole subject, I now feel 
inclined to suspect that the circumstance in question can, accord- 
ing to theory, produce little or no effect on the climatic condition 
of our globe. 

The rate at which the earth radiates into space the heat re- 
ceived from the sun depends upon the temperature of its surface ; 
and the temperature of its surface (other things being equal) 
depends upon the rate at which the heat is received. The greater 
the rate at which the earth receives heat from the sun, the greate 


* Edinb. Phil. Journ. vol. iv. p. 262 (1821). 


+ Révolutions de la Mer, p. 37 (second edition). 
{ Phil. Mag. S. 4. vol. xxvin. p.131. Reader, December 2, 1865. 


222 Mr. J. Croll on the supposed greater Loss of Heat 


will therefore be the rate at which it will lose that heat by radia- 
tion. The total quantity of heat received during winter by the 
southern hemisphere is exactly equal to that received during 
winter by the northern. But as the southern winter is longer 
than the northern, the rate at which the heat is received during 
that season must be less on the southern hemisphere than on 
the northern. Now this less rate, were it not for a circum- 
stance presently to be noticed, ought exactly to compensate 
for the longer winter. The southern hemisphere loses heat 
during a longer period than the northern; but then it does not 
lose it so rapidly. Therefore the total quantity of heat lost, were 
it not for the circumstance alluded to, would be the same on both 
hemispheres. The same mode of reasoning is equally applicable 
to the summers of the two hemispheres. The southern sammer 
is shorter than the northern; but the heat is more intense, and 
the surface of the ground kept at a higher temperature; conse- 
quently the rate of radiation into space 1s greater. 

When the rate at which a body receives heat is increased, the 
temperature of the body rises till the rate of radiation equals the 
rate of absorption, after which equilibrium is restored; and when 
the rate of absorption is diminished, the temperature falls till 
the rate of radiation is brought to equal that of absorption. 

But notwithstanding all this, owing to the slow conductivity 
of the ground for heat, more heat will pass into it during the 
longer summer of aphelion than during the shorter one of peri- 
helion; for the amount of heat which passes into the ground 
depends on the length of time during which the earth 1s receiving 
heat, as well as upon the amount received. Also in hke manner 
during the longer winter in.aphelion, more heat will pass out of 
the ground than during the shorter onein perihelion. Suppose 
the length of the days on the one hemisphere (say the northern) 
to be 23 hours, and the length of the nights, say, 1 hour; while 
on the other hemisphere the days are 1 hour and the nights 23 
hours. Suppose also that the quantity of heat received from the 
sun by the southern hemisphere during the day of 1 hour to be 
equal to that received by the northern hemisphere during the 
day of 23 hours. It is evident that although the surface of the 
ground on the southern hemisphere would receive as much heat 
from the sun during the short day of 1 hour as the surface of 
the northern hemisphere during the long day of 23 hours, yet, 
owing to the slow conductivity of the surface for heat, the amount 
absorbed by the ground would not be nearly so much on the south- 
ern hemisphere as on the northern. The temperature of the 
surface during the day, it is true, would be far higher on the 
southern hemisphere than on the northern, and consequently 
the rate at which the heat would pass into the ground would be 


by the Southern than by the Northern Hemisphere. 223 


greater on that hemisphere than on the northern; but notwith- 
standing the greater rate of absorption resulting from the high 
temperature of the surface it would not compensate for the short- 
ness of the day. On the other hand, the surface of the ground 
on the southern hemisphere would be colder during the long 
night of 23 hours than it would be on the northern during the 
short night of only 1 hour; and the low temperature of the 
ground would tend to lessen the rate of radiation into space. 
But the decrease in the rate of radiation would not compensate 
fully for the great length of the night. The general and com- 
bined result of all those causes would be that a slight accumula- 
tion of heat would take place on the northern hemisphere and a 
slight loss on the southern. But this loss of heat on the one 
hemisphere and gain on the other would not go on accumula- 
ting at a uniform rate year by year, as Adhémar supposes. 

Of course we are at present simply considering the earth as 
an absorber and radiator of heat, without taking into account the 
effects of distribution of sea and land and other modifying causes, 
and are assuming that everything is-the same in both hemi- 
spheres, with the exception that the winter of the one hemi- 
sphere is longer than that of the other. 

What, then, isthe amount of heat stored up by the one hemi- 
sphere and lost by the other? Is it such an amount as to sen- 
sibly affect climate ? 

The experiments and observations which have been made on 
underground temperature afford us a means of making at least 
a rough estimate of the amount. And from these it will be seen 
that the influence of an excess of seven or eight days in the 
length of the southern winter over the northern could hardly 
produce an effect that would be sensible. 

Observations were made at Edinburgh by Professor J. D. 
Forbes on three different substances, viz. Sandstone, Sand, and 
Trap-rock. By calculation, we find from the data afforded by 
those observations that the total quantity of heat accumulated 
in the ground during the summer above the mean temperature 
was as follows :—In the sandstone-rock the quantity accumu- 
lated was sufficient to raise the temperature of the rock 1° C. 
to a depth of 85 feet 6 inches. In the sand the quantity 
was sufficient to raise the temperature 1° C. to a depth of 72 feet 
6 inches. And in the trap-rock the quantity stored up would 
only suffice to raise the temperature 1° C. to a depth of 61 feet 
6 inches. 

Taking the specific heat of the sandstone per unit volume as 
determined by Regnault, at -4623, and that of sand at -3006, 
and trap at ‘5283, and reducing all the results to one standard, 
viz. that of water, we find that the quantity of heat stored up 


924 Mr. J. Croll on the supposed greater Loss of Heat 


in the sandstone would, if apphed to water, raise the tempera- 
ture of the water 1° C. to a depth of 39 feet 6 inches; that 
stored up in the sand would raise the temperature of the water 
1° C. to a depth of 21 feet 8 inches, and that stored up in the 
irap would raise the water 1° C. to the depth of 32 feet 6 inches. 
We may take the mean of these three results as representing 
pretty accurately the quantity stored up in the general surface 
of the country, This would be equal to 31 feet 3 mches depth 
of water raised 1° C. The quantity of heat lost by radiation 
during winter below the mean was found to be about equal to 
that stored up during summer. 

The total quantity of heat per square foot of surface received 
by the equator from sunrise till sunset at the time of the equi- 
noxes, allowing 22 per cent. for the amount cut off in passing 
through the atmosphere, is 1,780,474 foot-pounds. In the 
latitude of Edinburgh about 938,460 foot-pounds per square 
foot of surface is received, assuming that not more than 22 per 
cent. is cut off by the atmosphere. At this rate a quantity of 
heat would be received from the sun in two days ten hours (say, 
three days) sufficient to raise the temperature of the water 1° C. 
to the required depth of 31 feet 3 inches. Consequently the 
total quantity of heat stored up during summer in the latitude 
of Edinburgh is only equal to what we receive from the sun 
during three days at the time of the equmoxes. Three days’ 
sunshine during the middle of March or September, if applied 
to raise the temperature of the ground, would restore all the 
heat lost during the entire winter; and another three days’ 
sunshine would confer on the ground as much heat as is stored 
up during the entire summer. But it must be observed that 
the total duration of sunshine in winter to that of summer in 
the latitude of Edinburgh is only about as 4 to 7. Here is a 
difference of two months. But this is not all; the quantity of 
heat received during winter is scarcely one-third of that received 
during summer; yet notwithstanding this enormous difference 
between summer and winter, the ground during winter loses 
only about six days’ sun-heat below the maximum amount pos- 
sessed by it in summer. 

But if what has already been stated is correct, this loss of heat 
sustained by the earth during winter is not chiefly owing to the 
fact of the longer absence of the sun durmg winter, but to the 
decrease in the quantity of heat received in consequence of 
his longer absence combined with the cbliquity of his rays 
during that season. But in the case of the two hemispheres, 
although the southern winter is longer than the northern, the 
quantity of heat received by each is the same. But suppo- 
sing it held true, which it does not, that the loss of heat sus- 


by the Southern than by the Northern Hemisphere. 225 


tained by the earth in winter is as much owing to the excess 
in the length of the winter nights over those of the summer as to 
the deficiency of heat rceccived in winter from that received in 
summer, three days’ heat would then in this case be the amount 
lost by radiation im consequence of this excess in the length of 
the winter nights. The total length of the winter nights to 
those of the summer is, as we have seen, about as 7 to4. This 
is a difference of nearly 1200 hours. But the excess of the 
south polar winter over the north amounts to only about 184 
hours. Now if 1200 hours give a loss of three days’ sun-heat, 184. 
hours will give a loss of scarcely 54 hours. 

It is no doubt true that the two cases are not exactly analo- 
gous; but it is obvious that any error which can possibly arise 
from regarding them as such cannot materially alter the con- 
clusion to which we have arrived. Supposing the effect were 
deuble, or even quadruple, what we have concluded it to be, still 
it would not amount to a loss of two days’ heat, which could 
certainly have little or no influence on climate. 

But even assuming all the preceding reasoning to be incor- 
rect, and that the southern hemisphere, in consequence of its 
longer winter, loses heat to the extravagant extent of 168 hours, 
supposed by Adhémar, still this could not materially affect cli- 
mate. The climate is influenced by the mere temperature of the 
surface of the ground, and not by the quantity of heat or cold 
that may be stored up under the surface. The climate is deter- 
mined, so far as the ground is concerned, by the temperature 
of the surface, and is wholly independent of the temperature 
which may exist under the surface. Underground temperature 
can only affect climate through the surface. If the surface 
could, for example, be kept covered with perpetual snow, we 
should have a cold and sterile climate, although the tempera- 
ture of the ground under the snow was actually at the boiling- 
point. Let the ground to a depth of, say, 40 or 50 feet be de- 
prived of an amount of heat equal to that received from the sun 
in 168 hours. This could produce little or no sensible effect on 
climate ; for, owing to the slow conductivity of the ground for 
heat, this loss would not sensibly affect the temperature of the 
surface, as 1t would take several months for the sun’s heat to 
penetrate to that depth and restore the lost heat. The cold, if 
I may be allowed to use the expression, would come so slowly 
out to the surface that its effect in lowering the temperature of 
the surface would scarcely be sensible. And, again, if we sup- 
pose the 168 hours’ heat to be lost by the mere surface of the 
ground, the effect would certainly be sensible, but it would only 
be so fora few days. We might in this case have a week’s 
frozen soil, but this would be all. Before the air had time to 


226 Mr. J. Croll on the supposed greater Loss of Heat 


become very sensibly affected by the low temperature of the sur- 
face the frozen soil would be thawed. 

The stormg up of heat or cold in the ground has in reality 
very little to do with climate. Some physicists explain, for ex- 
ample, why the month of July is warmer than June by referring | 
it to the fact that by the month of July the ground has become 
possessed of a larger accumulation of heat than it possessed in 
June. This explanation is evidently erroneous. The ground in 
July certainly possesses a greater store of heat than it did in 
June; but this is not the reason why the former month is hotter 
than the latter. July is hotter than June because the air (not 
the ground) has become possessed of a larger store of heat than 
it had in June. And why the air is warmer in July than in 
June is this: it is with extreme difficulty that the air can be- 
come heated by the direct rays of the sun; itis by means of 
contact with the hot surface of the ground and by radiation 
from the earth that the air becomes slowly heated. Conse- 
quently, although the sun’s heat is greater in June than it is in 
July, it is near the middle of July before the air becomes pos- 
sessed of its maximum store of heat. We therefore say that 
July is hotter than June because the air is hotter in the former 
month than in the latter, and consequently the temperature in 
the shade is greater in the former month than in the latter. 

If the distribution of sea and land were the same in both 
hemispheres, it follows, according to theory, that, owing to the 
excess of 184 hours in the length of the southern polar winter 
over the northern, there would be a very slight loss of heat 
on the southern hemisphere and a very slight gain of heat on 
the northern. But owing to the present distribution of sea and 
land, the very reverse in reality takes place. At present the 
northern hemisphere loses by radiation far more heat than the 
southern. The reason of this is obvious. The greater part of 
the southern hemisphere is occupied by sea. Water is a much 
worse radiator than land. There are a great many reasons for 
this, afew of which may be enumerated :—(1) The temperature of 
the surface of the water does not rise so high under the direct rays 
of the sun as that of the surface of the ground. (2) The heat-rays 
from the sun penetrate the water to a considerable depth, and in 
this case it is only a part of the heat that is received by the surface 
of the water, whereas in regard to land all the heat is received 
by the surface. The temperature of the surface of the land is 
thus raised enormously, and the heat rapidly thrown back into 
stellar space; this effect is also increased by the fact that the 
specific heat of the land is not one-half that of water. (3) The 
ground can only store up heat by the very slow process of con- 
duction, whereas water, by the mobility of its particles and 


by the Southern than by the Northern Hemisphere, 227 


transparency for heat-rays, especially those from the sun, be- 
comes heated to a considerable depth rapidly. The quantity of 
heat stored up in the ground is comparatively small; the quan- 
tity stored up in the ocean is great. (4) The aqueous vapour of 
the air acts asa screen to prevent the loss by radiation from 
water, while it allows radiation from the ground to pass more 
readily into space. (5) The air is heated more rapidly by con- 
tact with the hot surface of the ground than it is by contact 
with the surface of the ocean. Consequently the heat which 
is carried up into the higher regions of the atmosphere and 
thrown off into stellar space chiefly comes from the land. 

But it may be asked, If the southern hemisphere absorbs far 
more heat than the northern, why, then, is its mean tempera- 
ture so much below that of the northern? The lower tempera- 
ture of the southern hemisphere is evidently due, not to the 
loss of heat by radiation as supposed by Adhémar and others, 
but to a cause which has been completely overlooxed, viz. to the 
normous amount of heat transferred from that hemisphere to 
the northern by means of ocean-currents. 

The great ocean-currents of the globe take their rise in 
three immense streams from the Southern Ocean, which, on 
reaching the tropical regions, become deflected in a westerly 
direction and flow along the southern side.of the equator for 
thousands of miles. A considerable portion of these currents 
returns into the Southern Ocean without ever crossing the 
equator, but the greater portion of them crosses over to the 
northern hemisphere. Since there is then a constant flow of 
water from the southern hemisphere to the northern in the form 
of surface-currents, it must be compensated by undercurrents of 
equal magnitude from the northern hemisphere to the southern. 
The currents, however, which cross the equator are far higher 
in temperature than their compensating undercurrents; conse- 
quently there is a constant transference of heat from the south- 
ern hemisphere to the northern. Any currents taking their 
rise in the northern hemisphere and flowing across into the 
southern are comparatively trifling, and the amount of heat 
transferred by them is also trifling. There are one or two cur- 
rents of considerable size, such as the Brazilian branch of the 
great equatorial current of the Atlantic, and a part of the South 
Equatorial Drift-current of the Pacific, which cross the equator 
from north to south: but these cannot be regarded as northern 
currents ; they are simply southern currents deflected back after 
crossing over to the northern hemisphere. The heat which 
these currents possess is chiefly obtained on the southern he- 
misphere before crossing over to the northern; and although 
the northern hemisphere may not gain any temperature by 


228 On the Loss of Heat by the Southern Hemisphere. 


means of them, it, on the other hand, does not lose much ; for 
the heat which they give out in their progress along the southern 
hemisphere does not belong to the northern hemisphere. 

But after making the fullest allowance for the amount of heat 
carried across the equator from the northern hemisphere to the 
southern, we shall find, if we compare the mean temperature of 
the currents from the southern hemisphere to the northern with 
the mean temperature of the great compensating undercurrent 
and the one or two small surface-currents, that the mean tempe- 
rature of the water crossing from the southern hemisphere to the 
northern 1s very much higher than the mean temperature of the 
water crossing from the northern to the southern. The mean 
temperature of the water crossing the equator from south to north 
is probably not under 65° F., while the mean temperature of 
the undercurrent is probably not over 39°F. But we must add 
to them the surface-currents from north to south. And let us 
assume that this will raise the mean temperature of the entire 
mass of water flowing from north to south to, say, 45° F. Here 
we have a difference of 20° F. Hach cubic foot of water which 
crosses the equator will in this case transfer about 1250 units of 
heat from the southern hemisphere to the northern. If we had 
any means of ascertaining the volume of those great currents 
crossing the equator, we should then be able to make a rough 
estimate of the total amount of heat transferred from the southern 
hemisphere to the northern; but as yet no accurate estimate has 
been made on this point. Let us assume, what is probably much 
below the truth, that the total amount of water crossing the 
equator is at least double that of the Gulf-stream as it passes 
through the Strait of Florida, which amount we have already 
found to be equal to 133,816,320,000,000 cubic feet daily*. 
Taking the quantity of heat conveyed by each cubic foot of water 
of the Gulf-stream at 1500 thermal units, it is found that an 
amount of heat is conveyed by the current equal to all the heat 
that falls within 63 miles on each side of the equatort. Then, 
if each cubic foot of water crossing the equator transfers 1250 
thermal units, and the quantity of water is double that of the 
Gulf-stream, it follows that the amount of heat transferred from 
the southern hemisphere to the northern is equal to all the heat 
falling within 105 miles on each side of the equator, or equal to 
all the heat falling on the southern hemisphere within 210 miles 
of the equator. This quantity taken from the southern hemi- 
sphere and added to the northern will therefore make a differ- 
ence in the amount of heat possessed by the two hemispheres 
equal to all the heat which falls on the southern hemisphere 

* Phil. Mag. for June 1867, p. 433. Geol. Mag. for April 1869. 
tT Ibid, p. 434, 


Prof.G. C. Foster on some Lecture-experiments in Electricity. 229 


within somewhat more than 420 miles of the equator, supposing 
the sun to be vertical over the whole area. 

This enormous difference is quite sufficient to account for the 
lower mean temperature of the southern hemisphere. 

But it may be noticed that although the return currents at the 
equator are colder than the direct currents, yet they are not so 
in the polar regions. The water which leaves the polar seas is 
much colder than the water which replaces it from the tropical 
regions. 

The general tendency of the great system of ocean-currents is 
to cool the equatorial region of the globe and to warm the tem- 
perate and polar regions. Also, owing to the present distribu- 
tion of sea and land, and partly to the effects on the trade-winds 
resulting from the eccentricity of the earth’s orbit**, small as that 
eccentricity is at present, there is a constant transference of heat 
by means of currents from the southern hemisphere to the 
northern. Ocean-currents tend to reduce the enormous differ- 
ence of temperature which, according to theory, ought other- 
wise to exist between the equator and the polest. 

On a former occasion it was shown that aérial currents at the 
equator only tend to cool the equator; they do not carry heat 
to higher latitudes. But aérial currents in temperate and polar 
regions diffuse over the land the heat carried by ocean-currents. 
It is the ocean and not the air that conveys the heat from the 
tropics to the temperate and polar regions {, 


XXVIII. Description of some Lecture-experiments in Electricity. 
By Professor G. C. Fostrer, F.R.S.§ 


mpeue object of this communication is simply to point out 

methods, differing somewhat from those commonly de- 
scribed in the books, of demonstrating two or three familiar 
truths of electricity. The experiments [ am about to describe 
may probably be well known under one form or another, espe- 
cially to practical electricians, who often have opportunities of 
using apparatus and witnessing phenomena which do not fall to 
the lot of mere scientific students. Idonot claim for them any 
novelty, unless it be as lecture-room illustrations, _ 

1. Haperiments with the Hlectrophorus.—So far as Iam aware, 
the experiments by which the accepted explanation of the action 
of the electrophorus is supported refer exclusively to the statical 
conditions of the instrument, or, in other words, to the states of 

* Phil. Mag. 8S. 4. vol. xxvii. p. 135; vol. xxxu. p. 122. 

+ Ibid. vol. xxx. p. 435; vol. xxxiv. p. 128. 

{ Ibid. vol. xxxii. pp. 127-130. Geological Magazine for April 1869, 

§ Communicated by the Author, 


230 Prof. G. C. Foster’s Description of some 


electrical equilibrium which it exhibits. The dynamical pro- 
cesses by which these statical conditions are brought about are 
no doubt, in their main features, very easily traced, and are per- 
fectly well known; but, until quite recently, it has been a rare 
exception for clectricians to be in possession of the instrumental 
means requisite for making them the subject of direct investi- 
gation. Now, however, the form of reflecting galvanometer de- 
vised by Professor Sir William Thomson is in the hands of a 
great many experimenters; and it accordingly seemed to me 
that, with the view of calling attention to the ease with which 
the transient electric currents accompanying the production and 
disappearance of electrostatical charge in various familiar cases 
can be observed, and even measured, by means of this instrument, 
it might be worth while to describe the following experiments. 

An insulating table was made by laying a thin board across 
two insulated cylindrical conductors, such as are to be found in 
every collection of electrical apparatus. On this was placed a 
piece of sheet zinc, to serve as the lower plate of an electropho- 
rus, the “cake” of which consisted of a circular piece of vulca- 
nized india-rubber, about 15 inches in diameter and 4 inch 
thick, and the “cover” of a circular brass plate 12 inches in 
diameter, with a glass handle. The lower metal plate was con- 
nected, by means of an insulated wire, with one terminal of a 
Thomson’s astatic galvanometer having copper-wire coils of up- 
wards of 6900 B.A. units resistance, the other terminal of which 
was connected with a gas-pipe in the laboratory, so as to make 
a good earth-contact. On rubbing the india- rubber with the 
hand, the cover having been removed, the galvanometer showed 
a deflection which, as soon as it had become steady enough to 
be read, amounted to 35 divisions of the scale on the side indi- 
cating the passage of a positive current from the earth into the 
electrophorus- plate. This deflection gradually diminished while 
the rubbing was continued, the spot of light finally returning to 
zero. The earth-wire was now removed from the galvanometer 
and replaced by a wire connected with the cover: on laying the 
cover upon the india-rubber, the galvanometer gave a deflection 
of 250 divisions on the opposite side to that observed during 
the rubbing. On lifting the cover again, there was a deflection 
of 230 divisions in the original direction, followed by a deflection 
of 200 to the other side on replacing it. On repeatedly lifting 
and replacing the cover, deflections were obtaimed every time, 
though gradually diminishing in amplitude in consequence of 
the imperfect insulation of the india-rubber. 

In a second similar experiment, the maximum deflection during 
the rubbing was 40 divisions ; the deflection on putting on the 
cover, 260 divisions; on removing it, 240. 


Lecture-experiments in Llectricity. 231 


These results show very plainly the nature and importance of 
the electrical changes which take place in the lower plate of the 
electrophorus while the apparatus is being used. Their mean- 
ing is too obvious to require further comment. 

Equally decisive results are obtained if the lower plate is left 
constantly in connexion with the earth through the galvano- 
meter, and the cover is repeatedly put on, touched, raised, dis- 
charged, and replaced, as in the common way of taking a series 
of charges from the electrophorus. On putting on the insu- 
lated cover, the galvanometer is not affected; but on afterwards 
touching the cover, a strong deflection is obtained in the direc- 
tion indicating a downward positive current (that is, a current 
through the galvanometer into the ground). When the cover is 
raised, there is a deflection to the opposite side, indicating an 
upward positive current, which is again inverted if the cover be 
replaced without having been discharged; but, if it be touched be- 
fore being replaced, no deflection is caused on putting it on again. 

The importance of free electrical communication between the 
lower plate of the electrophorus and the earth is still further 
illustrated by the following experiments. First, the lower plate 
was insulated, both during the rubbing and afterwards, and the 
cover was connected through the galvanometer with the earth- 
wire : On now putting the cover on or taking it off by means of 
the glass handle, a deflection of from 5 to 10 divisions was ob- 
tained alternately on the two sides of zero. Next, the expert- 
ment was repeated, the india-rubber being rubbed the same 
number of times, in the same manner as before, but during the 
rubbing the lower plate was uninsulated ; this time the deflec- 
tion caused by putting on the cover amounted to 180 divisions, 
and on taking it off to 127. 

A Thomson’s galvanometer also serves very conveniently 
for proving the movement of electricity which takes place when 
a conducter is charged by statical induction. For example, one 
terminal of the galvanometer being connected to earth and the 
other with an insulated brass cylinder 2 inches in diameter and 
17-5 inches long, a deflection of 10 or 12 divisions was obtained 
on bringing the slightly charged cover of the electrophorus near 
to the cylinder, and an equal deflection on the opposite side on 
removing it. These deflections, which might easily have been 
increased by using a body more strongly electrified, could be 
reproduced an indefinite number of times by simply moving the 
electrophorus-cover towards or away from the brass cylinder. 

2. Comparative Measurement of the Electrical Capacity of Con- 
ductors.—The quantity Q of electricity which passes into or out 
of any insulated conductor, when put into electrical communi- 
cation with any source of constant electrical potential, is pro- 


232 Prof. G. C. Foster’s Description of some 


portional to the difference of potential EK between the insulated 
conductor and the source, and to a coefficient S called the elec- 
tric capacity of the conductor and depending on the extent and 
disposition of its surface, and its position relatively to other con- 
ductors. This relation is very easily proved by means of a 
Thomson’s galvanometer connected with a Leyden battery and 
a galvanic battery in the way shown in the figure. 


= galvanometer. 
B=galvanic battery. 
C=Leyden battery. 
K=key. 
E=earth-contact. 


E 


For example, a Leyden battery of six jars, each jar having a 
diameter of 18 centims. and being coated to a height of 24 cen- 
tims. from the bottom, was charged and discharged through the 
galvanometer by four Grove’s cells arranged in series. The sum 
of the deflections on both sides of zero, due to the charge and 
discharge, was (as the mean of several experiments) 88°8, the 
highest reading being 90, the lowest 88. When three of the jars 
were removed, so as to leave a battery of only half the previous 
capacity, the mean reading of several experiments was 45:1, the 
maximum being 45°5 and “the minimum 44:5. 

3. Comparative Measurement of Electromotive Force.—Pre- 
cisely the same arrangement of apparatus and mode of experi- 
menting that serves for comparing the capacities of conductors, 
also serves for comparing the electromotive forces of batteries ; 
but, in order to make the comparison more accurate, it is ad- 
visable to substitute a conductor of greater capacity for the Ley- 
den battery mentioned in the last paragraph, unless the electro- 
motive forces to be compared are rather considerable. In the 
following experiments the condenser of a medium-sized Ladd’s 
induction-coil was used. 

When the condenser was charged and discharged through the 
galvanometer by one Grove’s cell, the sum of the readings on 


Se 


ane 


a 


\ 


Lecture-experiments in Electricity. 233 
the two sides of zero was 
252 divisions ; 
with two Grove’s cells, the sum of the readings was 


507 divisions. 


Divisions. 
With one Daniell’s cell, the sum of the readings was 152 
fvismeanother Daniell’s cell, itwas; .. 2 . . » 155 


ol 90) alee eee a aS 307 


With the two Daniell’s cells connected in series, the sum of the 
opposite deflections was 307 divisions. 

These numbers give, as the mean ratio of the electromotive 
force of one Grove’s cell to that of one Daniell’s cell, 


J07 2007 —1-Go = 1. 


According to Poggendorff, the ratio, as determined by his me- 
thod of compensation, is 1°68 : 1. 

The mode of comparison by means of the galvanometer and 
condenser may be rendered more accurate by increasing the ¢a- 
pacity of the latter, so as to get larger readings and so diminish 
the relative importance of the errors of observation. The above 
numbers, however, which are of course given merely for the sake 
of illustration, do not represent the limit of accuracy attainable 
with the apparatus I employed: by simply altering the position 
of the adjusting magnet of the galvanometer, so as to render the 


suspended magnets more perfectly astatic, a deflection of 355 


was obtained instead of 307. For proving to a class the way in 
which the electromotive force of a galvanic battery depends upon 
the mode in which the cells composing it are connected together, 
and other fundamental facts of a like nature, this method can 
easily be made abundantly accurate, and is probably as conve- 
nient and rapid as any of the methods in common use. 

4, Method of demonstrating the existence of the Inverse and 
Direct Extra-currents.—The only method of rendering distinctly 
evident the retardation in the establishment of electric currents 
in coiled conductors, or Faraday’s extra-current on making bat- 
tery-contact, which I have found described in any of the ordinary 
text-books of physics, is one due to Edlund, and requires the use 
of a differential galvanometer. By an arrangement of apparatus, 
which may be regarded as a modification of that employed by 
Edlund, it is easy to show the extra-current both on making 
and breaking the circuit upon an ordinary galvanometer. This 
arrangement will be understood by reference to the figure, where 


Phil. Mag. 8, 4. Vol. 38. No. 254. Sept. 1869. R 


234 Description of some Lecture-eaperiments in Electricity. 


B represents a galvanic battery of one 
or two cells, K a key for making and 
breaking the battery circuit, G the gal- 
vanometer, C and C! two coiled conduc- 
tors, with or without iron cores, and R 
and Ri two zigzag or uncoiled conduc- 
tors, of which the resistances are so ad- 
justed relatively to the resistances of C 
and C! that, when the battery-contact 
is permanently maintained, no current 
passes through the galvanometer. Then, 
on completing the circuit, there is a 
temporary deflection of the galvanome- 
ter due to the inverse extra-current, 
and on breaking it there is an opposite 
deflection due to the direct extra-cur- 
rent. The reason of this is easily seen. 
Supposing p to be the positive and n 
the negative pole of the battery, when 
the key K is pressed down the current 
is immediately established in the circuit 
BRadR'B, causing a corresponding deflection of the galvano- 
meter ; after a very short interval, however, the current is also 
established in the circuit BCdaC'B, and brings the galvano- 
meter-needle to rest. On raising the key the current ceases in- 
stantaneously in the uncoiled conductors R and R,, but continues 
for a short time in the coiled conductors C and C’, traversing 
the galvanometer from 6 to a and causing a momentary deflec- 
tion in the opposite direction to that produced on making the 
battery-circuit. Using for the conductors C and C! the primary 
wire of a medium-sized Ladd’s mduction-coil and the wire of a 
straight electromagnet, and uncoiled German-silver wires for 
the conductors R and R/, I obtained with one cell of Grove’s bat- 
tery a swing of from 50° to 60° on a large astatic galvanometer 
with heavy needles 8 inches long on completing the battery-cir- 
cuit, and an equal swing in the opposite direction on breaking 
contact after the needles had come to rest. ‘The directions of 
the swings were such as to indicate that the current both com- 
menced and ceased more suddenly in the uncoiled than in the 
coiled conductors. 

The only special precaution that need be pointed out in order 
to ensure the success of this experiment, is that the resistances 
of the several conductors shall be so small, and their mass so 
great, that they may‘not become sensibly heated and so have 
their relative resistances changed during the passage of the 
current. 


Geological Society. 239 


It will be seen that the combination of conductors that has 
been described is essentially the same as that constituting Wheat- 
stone’s “ electrical balance ;” in fact the whole experiment con- 
sists in purposely exaggerating an effect which, in comparing 
electrical resistances by means of that arrangement, it is neces- 
sary to get rid of by a well-known artifice in the mode of making 
contact. 


XXVIII. Proceedings of Learned Societies. 
GEOLOGICAL SOCIETY. 
[Continued from p. 164.] 


December 23rd, 1868.—Prof. T. H. Huxley, LL.D., F.R.S., 
President, in the Chair. 


VHE following communications were read :— 

1. “ On the so-called ‘ Kozoonal’ Rock.” By Prof. W. King and 
Dr. T. H. Rowney. Communicated by Sir R. I. Murchison, Bart., 
OCB: B.RS., V.P.G:S. 

The authors noticed that, since the reading of their former commu- 
nication in 1866, further descriptions of Hozoon have been published 
by Hochstetter, Giimbel, Carpenter, Dawson, and Logan ; and aftera 
few words on those by the first two, they proceeded to criticise the 
others more fully, intimating that the English and Canadian observers 
have by no means mastered all the difficulties of the subject, nor 
answered the objections brought forward by them. In the course of 
these remarks, Messrs. King and Rowney, objecting to the specimen 
from Tudor, of which they have seen the photograph, and which was 
described and figured in 1867 (Q. J. G.S. No. 91), suggested that 
it is nothing more than the result of infiltration of carbonate of 
lime, with entangled impurities, between two layers of the sandy 
limestone. They also stated their belief that the term ‘“ Hozoonal”’ 
is applicable to any of the ophites they describe, inasmuch as, it was 
contended, the structure of the latter is similar to that of the Cana- 
dian rock containing the so-called Hozoon. 

The authors then proceeded to treat of the supposed foranunferal 
characters of “ Eozoon.” First, as to the “ cell-wall” or “ nummu- 
line layer,” they advanced repeated evidence of the value of their 
former proofs that the typical form is due to aciculate serpentine 
(or modified chrysotile) of inorganic origin, having examined, be- 
sides others, a Canadian specimen presented by Dr. Carpenter. 
Secondly, nothing new was adduced with regard to the mineral 
structure of the so-called “intermediate skeleton.” ‘Thirdly, in proof 
that the “chamber-casts” are not of organic origin, the authors 
referred to their former work, and stated that chondrodite and pyral- 
lolite may be added to the list of minerals that occur, as such, disse- 
minated in limestones. They thought it strange that a carbonate, as 
well as a silicate, should not have been found filling the so-called 


R2 


236 Geological Society :—Messrs. Rowney and King on the 


chambers; and they decidedly refused to accept the Tudor spe- 
cimen having some tubuli filled with calcite, to which they suppose 
Dawson refers when speaking of chambers filled with calcite, as 
a case in point; they were unacquainted with any published in- 
stances of this mineral being an infilling. Fourthly, reiterating 
their observations on the so-called “ canal-system,” they suggested 
that the globoso-vermicular bodies noticed by Dawson and Giimbel 
may be metaxite; and they insisted on the difficulty of explaining 
the presence of isolated unbroken tube-casts in patches of pure 
limestone. The Madoc specimen, described by Dawson as having its 
“canals” and “ chambers” filled with calcite, was next referred to ; 
and it was argued that the so-called calcite, both in this and in 
another specimen, described by Carpenter, is doubtful and not 
proved; for they had not been able to confirm the accuracy of the 
observations in these cases, having examined a Canadian specimen, 
presented by Dr. Carpenter as an example of the kind, which had in 
it ‘“ homogeneous and structureless forms of the canal-system” that 
were not dissolved in the decalcification. Fifthly, the organic nature 
of the so-called ‘‘ stolons” was regarded as quite disproved. .Minera- 
logical considerations of Kozoonal rocks were next entered upon ; 
and from the study of Canadian specimens, and of others from Con- 
nemara and Neybiggen (?), described in full, the authors concluded 
that they fully prove the “ canal-system,” ‘‘ chamber-casts,” and 
“ nummuline layer” to be structural and inorganic modifications of 
serpentine—that the whole have originated from the change or waste 
of granules, plates, &c. of serpentine; and they incline to the belief 
that the calcite of the “intermediate skeleton ” is pseudomorphic 
after one or other form of serpentine by infiltration and replacement. 
The rounded form of the granular masses of chondrodite, cocco- 
lite, &c. in some limestones was also referred by the authors to the 
gradual removal of their surfaces by deep-seated hydrothermal 
agency. 

It was then argued that the organic nature of Hozoon cannot be 
supported by the cumulative evidence afforded by the combination 
of foraminiferal features ; for these features, combined and due to 
purely mineral paragenesis, had occurred to the authors in certain 
ophites, though some are wanting in other ophites, just as they 
are not always present in the Eozoonal rock of Canada. 

Serpentine has been described as having been deposited in the 
cavities of Hozoon, and having taken the place of its sareode; but 
the authors criticised all the quoted analogies of such a precipitation 
of any siliceo-magnesian substance, disbelieved them, and put aside 
glauconitic infiltration as beside the question. 

Considered geologically, with reference to its occurrence in a 
metamorphic rock, the authors regarded the Hozoon as an organic 
impossibility ; and they asked why it should never be found in any- 
thing but crystalline or semicrystalline rocks—in ophites or ophi- 
calcites of widely different ages. Particularly they found eozoonal 
structure in the Liassic ophite of Skye; and this they described in full. 
They criticised Sterry Hunt’s change of opinion, who used to think 


so-called § Eozoonal Rocks.’ 237 


that the serpentinous rocks of Canada were once earthy amorphous 
silicates, and afterwards metamorphosed, but who now supposes they 
were deposited in a crystalline state; and they asked why, if so, may 
not all the Laurentian rocks have been so deposited? In conclusion, 
they totally denied that Eozoonal structure has anything to do with 
any organism ; and repeated that, like all analogous conditions of 
serpentine, chondrodite, &c., it is of purely mineral origin. 


Dr. Carpenter need not repeat the grounds on which he regarded 
this as an organic structure. He objected to criticisms unless founded 
on examination of actual specimens. Sir Wm. Logan had been first 
led to regard the Hozoon as organic by finding alternations of cal- 
careous and siliceous layers in various minerals. A specimen which 
Sir William had brought from Canada contained much iron, and had 
the canal system wonderfully preserved ; and it presented this cha- 
racter—that the larger branches were infiltrated with serpentine, 
and the middle branches with sulphide of iron, while the smallest 
branches were filled with carbonate of lime, of the same nature as 
the matrix. It was only under a favourable light that these smaller 
tubes were visible, as the calcite in them was of the same crystalline 
character as the surrounding network. ‘This was conclusive evidence 
of the structure not arising from the mere infiltration of one chemical 
substance into another. Moreover this foreign matter could not 
penetrate the cleavage-planes. 

When cut, some specimens had given out a strong odour of musk, 
which they to some extent still retained. This, again, seemed to be 
evidence of organic origin. He regretted that Prof. King had not 
examined the large collection of specimens in his (Dr. Carpenter’s) 
collection. Recent Foraminifera, when decalcified, exhibited pre- 
cisely the same asbestiform layer round the chamber-cast as the 
fossil Hozoon. Different genera of Foraminifera in recent seas were 
infiltrated by different minerals, which presented some analogy with 
the condition of the fossil under consideration. In the great seas 
of the present day, at various depths and temperatures, was a large 
extension of sarcodic substance, and in this there were Rhizopods 
with and without shells, but of similar low structure; and such 
forms might have continued in existence through any length of time, 
so that the occurrence of Hozoon'so far down as Jurassic times could 
afford no matter for surprise. He would not be astonished even if 
such a structure as Hozoon were found in deep-sea dredgings of the 
present day. 

The Prestpent mentioned the Bathybius, which he has found 
with coccoliths and other forms in deep-sea soundings. In some 
newer specimens of Atlantic mud given him by Dr. Carpenter he 
had found Bathybius forming a sort of network, somewhat similar 
to the plasmodia of botanists. He could not call it either plant or 
animal. It was, however, a living substance, susceptible of appa- 
rently indefinite growth. This removed one of the difficulties in 
believing in the wide extension of the Hozoon. The Hydrographer 
had since sent him the soundings taken by Captain Shortland in 
‘The Hydra,’ In soundings from 2800 fathoms in the Arabian 


238 Geological Society :— 


Gulf Bathybius was plentiful; and over an area 7000 miles long the 
same organism occurred in abundance. He agreed in thinking it 
possible that such organisms might have gone on living from the 
earliest geological times. 

In answer to Prof. Ramsay, the Presiprnt stated that the sound- 
ings in which the Bathybius occurs alone, as analyzed by Dr. Frank- 
land, contained 14 per cent. of nitrogenous organic matter. 


2. “Notes on the Geology of China, with more especial refer- 
ence to the provinces of the Lower Yungtsi.” By Thomas W,. Kings- 
mill, Esq. 

The sedimentary deposits of the south of China were described as 
commencing at the base with a series of coarse grits and sandstones, 
having a thickness of about 12,000 feet, and overlain conformably 
by limestones and shales (with coal in the lower part), attaining a 
thickness of between 6000 and 8000 feet. The whole of these 
rocks were described by the author as the ‘“ Tung-ting Series.” 
In the Nanking district this formation is succeeded by sandstones, 
erits, and conglomerates, which the author has grouped together 
under the name of the ‘“‘Chung-shan Series.” Its uppermost member 
contains beds of coal, and possesses an unknown thickness; but the 
remaining beds are together about 2400 feet thick. Mr. Kingsmill 
described in detail the geological relations and geographical extension 
-of these rock-masses; he then gaye a sketch of the superficial 
deposits, which occupy an important position in the geology of 
China, and from the older of which Mammalian bones and teeth 
have been obtained ; and he concluded by stating that he had been 
uniformly unsuccessful in his frequent searches for traces of glacial 
action. 


January 13th, 1869.—Prof. T. H. Huxley, LL.D., F.R.S., President, 
in the Chair. 

The following communications were read :— 

1. On Hyperodapedon.” By Prof. T. H. Huxley, LL.D., F.R.S., 
Pres. G.S. 

The author described the characters of the genus Hyperodapedon, 
dwelling especially upon those presented by the head and dentition. 
The head presents indications of a bone forming a second zygomatic 
arch on each side; the upper jaw is produced and bent downwards, 
forming a strong beak; and the lower jaw is produced on each side 
of the symphysis into a pointed process, between which the decurved 
beak of the upper jaw is received. The maxillary and palatine teeth 
are arranged in rows, and present some resemblance to the large nails 
in the sole of a boot; they are inserted on each side of the upper jaw 
upon the sloping sides of a deep groove, and are worn down and 
polished by the action of the mandibular teeth, which form a con- 
tinuous and very close single series along the upper edge of the 
mandible. The author remarked upon this peculiarity of arrangement, 
which, he said, enables the teeth of Hyperodapedon to be recog- 
nized wherever they may occur. The vertebrae have their centra 
slightly concave at each extremity. The other known parts of the 


Prof. Huxley on Hyperodapedon. 239 


skeleton described by the author were the ribs, scapula, coracoid, 
and part of the humerus, the pelvis, femur, and proximal ends of 
the tibia and fibula, and the abdominal false ribs, which are largely 
developed in this Reptile. 

The author declared the affinities of Hyperodapedon to be de- 
cidedly Lacertilian. Its nearest fossil ally is the Triassic genus 
Rhynchosaurus, and in the present day its type of structure is 
most closely reproduced by the singular genus Sphenodon (= Hat- 
teria) of New Zealand. In its habits Hyperodapedon was probably 
terrestrial, or perhaps fluviatile; in Warwickshire and India it is 
associated with Labyrinthodonts. The remains hitherto met with 
do not justify the formation of more than one species, Hyperoda- 
pedon Gordoni; and the genus ranges from Britain to Central India, 
indicating a great extent of dry land during the period to which it 
belongs. 

Specimens of Hyperodapedon from the Trias of Warwickshire, 
collected many years ago by Dr. Lloyd, were exhibited; but 
in discussing the question whether Hyperodapedon is to be re- 
garded as determining the Triassic age of any rock in which it may 
be found, the author referred to the fact that Crocodiles bridge over 
the whole interval between the Mesozoic and existing conditions, 
and Bery« in like manner connects the Cretaceous with our present 
fish-fauna. As Hyperodapedon is at least as nearly allied to the 
existing genus Sphenodon (= Hatteria) as it is to the Triassic hyn- 
chosaurus, the author inquires why may it not have inhabited the 
dry land of the Permian, Carboniferous, or Devonian period? Car- 
rying the idea thus raised still further, he indicates, from certain rela- 
tions between the Reptilian faune of Kurope, 8. Africa, and India at 
the period when Hyperodapedon lived in the first and third of these 
localities, not only that there must then have been a vast extent of 
continental land, but that this may have persisted with but little 
change in the nature of its inhabitants, while the fauna of the 
neighbouring seas underwent great alterations. He remarked that 
our geological chronology rested too much upon a marine founda- 
tion, and that such a persistence of dry land as was now suggested 
by him was not only possible, but, in the present case, probable. 
He suggested the use of Conybeare’s term ‘“ Poikilitic” for the 
series of deposits containing the remains of terrestrial and fluviatile 
plants and animals and corresponding with the marine beds deno- 
minated Permian and Triassic, Finally, the author remarked upon 
the important light thrown upon the question of the geographical 
distribution of animals as affected by the discovery of these Reptiles 
and other recently detected fossils, and upon the interest attaching to 
them from their high grade of development. The five great classes of 
Vertebrata were represented during the “ poikilitic” epoch by 
species so high in the scale that we can hardly doubt their having 
been preceded by other forms, so that some of us may hope to sce 
the fossil remains of a Siluriam mammal. 

Sir R. I. Murcutson argued in favour of the overwhelming im- 
portance of paleontological evidence, and maintained that /Hypero- 


Oi 


240 Geological Society:— 


dapedon was Triassic. He objected to the use of the term “ poiki- 
litic,” which was merely indicative of the spotted character of the 
beds, and protested against the mingling of the Permian and Triassic 
series. 


2. “On the Locality of a new Specimen of Hyperodapedon onthe 
South Coast of Devon.” By W. Whitaker, Esq., F.G.S. 

The author described the section presented by the South Devon 
coast westward from the great landslip at Dowlands. The cliffs here 
show Rheetic beds passing down into Red Marls of Upper Triassic 
age, which have greenish layers among them, favouring the view that 
the Rheetic beds might as well be classed with the Trias as with . 
the Lias. Below these beds are Red Marls and Sandstones; and at 
Budleigh Salterton a bed of quartzite pebbles occurs. West of the 
Exe the cliffs are of sandstone with layers of breccia; and beyond 
Dawlish the breccia gradually predominates, until towards Teign- 
mouth the cliffs are almost wholly formed of it. This breccia forms 
the base of the New Red of Devonshire. The thickness of the whole 
series is several thousand feet; Mr. Pengelly estimates that 1t may 
be four miles or more. The jaw of Hyperodapedon referred to by 
Professor Huxley was found in the sandstone on the left bank of 
the Otter, immediately above the Budleigh-Salterton pebble-bed, in 
the lower part of the uppermost bed of sandstone, which, with the 
other sandstones and marl-beds, the author regarded as belonging 
to the Keuper. He referred to the opinions of Mr. Pengelly and Mr. 
Ormerod, and suggested that the breccias might possibly be of Per- 
mian age. 


Sir Cuaruus Lyett, referring to the occurrence of Hyperodapedon 
with Stagonolepis and Telerpeton in the uppermost sandstones of 
Elgin, remarked that he came to the conclusion in 1859 that these 
beds were Triassic, and that Mr. Symonds had in that year stated 
them to be the equivalents of the Rhynchosawrus-sandstones of 
Shropshire. 

Professor Ramsay regarded the Red Marls and Sandstones de- 
scribed by Mr. Whitaker as Keuper, and the lower members of his 
section as of Permian age. He confirmed Prof. Huxley’s views as 
to the existence of a great extent of continental land at the epoch 
when Hyperodapedon and the Reptiles associated with it were in 
existence, and remarked that these Reptiles inhabited the shores of 
the great salt lakes of the Triassic land. He objected to the use of 
the term ‘“ poikilitic,” and remarked that if the idea embodied by 
Prof. Huxley under it were to be accepted, it would have to be 
extended to all terrestrial deposits from the Silurian period to the 
present day. 

Dr. Ginrner referred to his description of Sphenodon (=Hat- 
teria), and remarked that in that genus there are uncinate processes 
on the ribs, asin Birds, which do not exist in Hyperodapedon. He 
remarked upon the resemblance of the beak in the latter to that of 
the Tortoises, especially Trionya, and suggested that the jaws might 
have had a horny covering, 


Mr. W. H. Baily on Graptolites and allied Fossils in Ireland. 241 


Dr. Mrryon inquired as to the implantation of the teeth in the 
jaws of Hyperodapedon, and suggested that the position and direc- 
tion of the orbits were not accordant with terrestrial habits, and 
also that the absence of processes on the ribs indicated a flexibility 
of the body consistent with a fluviatile mode of life. 

Prof. Huxtey showed that no conclusion could be drawn from the 
want of processes on the ribs or the position of the orbits as to the 
habits of the animal, and remarked that the processes in Sphenodon 
were not anchylosed to the ribs; he considered it possible, but not 
probable, that the jaws had a horny covering. He stated that in 
using the term “ poikilitic,’ he was desirous of indicating that, 
while several marine formations with changing forms of life suc- 
ceeded each other, the terrestrial fauna may, in certain cases, have 
been continuous. He believed that terrestrial forms were at least 
as persistent as marine. 

Dr. CarrutHErs remarked that the Permian vegetation showed 
mesozoic affinities, and in fact that the commencement of the Meso- 
zoic flora was to be sought in the Permian. 


January 27th, 1869.—J. Gwyn Jeffreys, Esq., F.R.S., Treasurer, 
in the Chair. 

The following communications were read :— 

1. “ Notes on Graptolites and allied Fossils occurring in Ireland.” 
By W. H. Baily, F.G.S. [First Paper. | 

After remarking that the Graptolites are now generally regarded 
as belonging to the class Hydrozoa, the author detailed the various 
localities in the south of Ireland in which they had been found, and 
indicated the species occurring in each place. The localities are 
situated in the counties of Waterford, Wexford, Clare, and Tipperary ; 
and the species are as follows :— 


Didymograpsus sextans, Hall. Cladograpsus gracilis, Hall, 
elegans, Carr. (=D. flaccidus, | Diplograpsus pristis, Hs. 
Hall?, Nich.). mucronatus. 
caduceus, Salt. -—— teretiusculus. 


— -- Forchhammeri. dentatus, Brongn. 
Graptolithus (sagittarius) Hisin- | Climacograpsus bicornis, Had/. 
geri, Carr. Dicranograpsus ramosus, Hail. 
Sedgwicki. Cyrtograpsus gracilis, Hal/. 
tenuis. 


hamatus, Bavly. 


priodon. 


The most widely distributed of allis Diplograpsus pristis, to which 
the author thinks D. mucronatus and dentatus probably belong. ‘The 
fossils described by the author as T’heca cometoides may probably be 
the gonothecee of D. pristis, as had been suggested by Mr. Carruthers. 


2. “ Notice of Plant-remains from beds interstratified with the 
Basalt in the county of Antrim.” By W. H. Baily, Esq., F.G.S. 

The deposit referred to by the author was discovered by the late 
M.G. V. Du Noyer in cuttings of the Northern Railway of Ireland 
near Antrim ; it consists of a layer from 4 to 8 inches in thickness, 
separated by a conglomerate bed of 10 or 12 feet from the under- 
lying basalt, and by earthy beds of about equal thickness from the 


242 Geological Society. 


superficial basaltic layer. The remains are imbedded in a Red Clay, 
and associated with heematitic iron ore. 

The author regarded a large cone as that of a true Pimus, and 
branches of another coniferous tree as belonging to a Sequoia nearly 
allied to S. Sternbergi, Heer; of this a smali imbricated cone might 
possibly be the fruit. Other fragments of Coniferee seem to belong 
to Cupressites or Tuaites. The fossils consist chiefly of leaves of 
true Dicotyledonous plants. The author identified some of these 
with species of Fthamnites, Olea, Fagus, and Quercus. Leaves of 
endogenous plants, such as Sedges and Grasses, occur not unfre- 
quently. A large mass of fossil wood of dicotyledonous structure 
was obtained from the hematitic conglomerate. Carpolithes are also 
found. The vegetable remains are accompanied by a few elytra of 
Beetles. 

The author remarked that these remains seem to differ as a group 
from those of the island of Mull. Their alliance appears to be with 
Mid-European forms, and they are certainly of Upper-Tertiary age, 
probably Miocene. 


3. Remarks upon the Basalt Dykes of the Mainland of India 
opposite to the Islands of Bombay and Salsette.” By G. T. Clark, 
Esq., F.G.S. 

The author described the general features of the country referred 
to, and stated that the dykes which traverse it vary from | or 2 to 
100 or 150 feet in width, and often extend many miles. ‘They are 
all basaltic, with a tendency to prismatic structure, but neyer co- 
lumnar. The adjacent Trap is but little modified, only somewhat 
hardened, so as to resist weathering; by this means long, narrow 
ridges, more or less deeply furrowed aboye by the weathering of the 
basalt dyke itself, are produced. ‘The general direction of the dykes 
is parallel to the lines of volcanic vents; those near the main axis of 
the Concan lying N. and 8., and those near the subordinate axis in 
the Malseji valley, about E.N.E. and W.S.W. They run nearly 
straight, and have their faces usually parallel, but sometimes swell out 
or contract, or include a rider. The author considered that these 
dykes were formed probably during the latest periods of volcanic 
action in Western India. They probably belong, in his opinion, to 
two periods, as dykes of different grain frequently intersect each 
other. The dykes running N.E. and 8.W. often traverse and slightly 
dislocate those lying more N. and §., and are probably of later date. 


4, “ On Auriferous Rocks in South-eastern Africa.’ By Dr. 
Sutherland, 

Fourteen years ago the author expressed the opinion that gold 
would be found in the metamorphic rocks of Natal. A few months 
since Mr. Parsons found this metal by washing the iron-sand of 
some of the southern rivers of the colony. The gold is in micro- 
scopic rounded grains. Dr. Sutherland considers that the gold is 
diffused as minute particles in the granite and gneiss underlying the 
Silurian rocks of South Africa. 

These old gneissic rocks are yery much contorted, include ex- 


Intelligence and Miscellaneous Articles. 243 


tensive veins and lenticular masses of quartz, and are traversed by 
basalts. The Silurian strata, resting unconformably on the gneiss, 
haye been invaded byjgneous matter (which is never granitic), and, 
though generally horizontal, are frequently flexuous, and in some 
places greatly faulted, to the extent of even 1000 feet, together 
with the gneissic rocks beneath. These latter have been deeply 
eroded by the rivers, frequently to the depth of 500-1000 feet, and 
even of 3000 feet in some valleys; and in the alluvia of these 
valleys the gold occurs. The valleys have sometimes evidently com- 
menced in great displacements, forming “ valleys of elevation,” on 
which the denuding agency has been operating ever since. 

In certain mountains in the basin of the St. John’s River, 
Natal, dioritic rock traverses the secondary strata; and along the 
line of contact it contains copper-ores with 100 grains of gold to 
the ton. 


Mr. Davip Forzns was glad to find that Dr. Sutherland corrobo- 
rated his views as to the occurrence of gold in two ways :-— 

1. In auriferous granite, as in Wicklow and elsewhere. 

2. In eruptive diorite, a basic rock without free quartz, and cer- 
tainly of postoolitic date, almost always accompanied by copper 
veins. Most Californian alluvial deposits of gold were derived from 
this class of rocks. 

In constructing some of the railways of South America the granite 
was found to be so soft, from decomposition, that 1t could be cut with 
the pick and spade; and this softened granite, when washed, pro- 
duced gold. 

Prof. T. Rupert Jones considered that, by means of Dr. Suther- 
land’s communication, the Laurentian and Silurian rocks were now, 
for the first time, to be recognized as existing beneath the Dicy- 
nodon-rocks of the Natal ridge. 


XXIX. Intelligence and Miscellaneous Articles. 
NOTE ON ELECTROLYTIC POLARIZATION. BY PROFESSOR TAIT. 


| HAD just obtained one of Sir W. Thomson’s most recent forms 

of quadrant electrometer, and it occurred to me that ¢his must be 
the proper instrument for determining polarization, as its indications 
are not affected by electric resistance, and give directly (that is, 
without assuming the truth of Ohm’s law for reverse electromotive 
forces, and the consequent necessary determinations of resistance) 
the quantities required. The method employed by Wheatstone, 
Poggendorff, Buff, and others assumes that the whole electromotive 
force in the circuit is the algebraic sum of those of the decomposing 
battery and of the electrodes—an assumption whose truth some may 
consider to require proof, and which it is certainly useful to verify 
by an independent process. Again, after the decomposing action 
has ceased, the resistance of the films (of gas or oxide) which are 
deposited on the electrodes may change in value, ‘That neither of 


, 
‘ 
| 
‘ 


24.4 Intelligence and Miscellaneous Articles. 


these circumstances produces any marked effect is, however, amply 
proved by the numbers which follow, which, though given only as 
first approximations, are within the limits of difference of the results 
given (from galvanometric determinations) by former experimenters. 

As the polarization in most cases diminishes with very great rapi- 
dity from the instant of breaking contact with the decomposing 
battery, and as (for this and other reasons) the mode of measurement 
by the first swing of the index-needle of the electrometer is not de- 
serving of much confidence, it was necessary to devise a process by 
which the electrometer could be charged at leisure up to any desired 
potential, and then, for an instant only, placed in connexion with 
the electrodes. ‘The apparatus I employed bears a certain analogy 
to the Wippe of Poggendorff, but differs from it in some essential 
particulars, both of construction and mode of working. 

In aplate of vulcanite, or other good insulator, ten holes are cut 
as below, and filled with mercury. ‘Those marked E are connected 


with pairs of opposite quadrants of the electrometer, P with the 
electrodes, B, with the decomposing battery, and B, with the auxi- 
liary (or charging) battery. Also metallic connexion, as indicated 
in the sketch, is permanently established between the two central 
holes and the holes connected with the electrometer. 

The rocker consists of four wires, supported on an insulating bar 
of vulcanite, the two outermost having three points, the middle one 
longer than the others, and the two inner being similar, but wanting 
one of the extremities. When the four middle stems dip vertically 
into the four central mercury-cups, the other stems do not reach the 
mercury in any of the other six cups. If the instrument be inclined 
to the right the four prongs enter the holes to the right, thus simul- 
taneously connecting the electrodes with the decomposing battery, 
and the electrometer with the charging battery. When the instrument 
inclines to the left, the electrodes are shunted from the decomposing 
battery on to the electrometer, the latter having just before, by the 
same action, been cut off from the charging battery, and thus left 
charged. 

The modus operandi is simply this :—Leave the rocker leaning to 
the right by its own gravity, decomposition and polarization going 
on; adjust the wires B, to different points ina wet string (or a nar- 
row canal of water) closing the circuit of the charging battery; 


Intelligence and Miscellaneous Articles. 245 


work the rocker quickly to the left, and allow it instantly to fall 
back again-—a process which need not occupy more than a small 
fraction of a second, yet which must not be performed too quickly, 
on account of the inertia (small as it is) of the needle and mirror of 
the electrometer. If the deflection of the electrometer be suddenly 
increased or diminished by this action, slide one of the wires B, 
along the wet string, a little further from or nearer to the other, 
and rock again,—continuing this process till a charge is found which 
leaves the electrometer at rest when the rocking to and fro is per- 
formed. Reverse a commutator attached to the wires E, and repeat 
the operation. The difference of the scale-readings in these two 
cases gives a number proportional to the electromotive force of the 
polarized plates—(I say difference, because the scales commonly 
used with Sir W. Thomson’s instruments are, to avoid confusion, 
graduated from one end to the other, as they ought to be, instead 
of being graduated opposite ways from the middle). ‘To enable this 
measure to be reduced to absolute units, a normal Daniell’s cell was 
applied at intervals, during each day’s work, directly to the elec- 
trodes of the electrometer, then reversed; and the difference of the 
readings was tabulated as representing its electromotive force. 

In the other experiments I used a plate of gutta percha in which 
the ten holes were bored, but for a time discontinued its use on sus- 
pecting that it sometimes led to irregular working of the apparatus 
by imperfect insulation. ‘The cups were then separately mounted 
on insulators 3 inches high; but this was not found to be an im- 
provement of any consequence, and the holes are now made ina 
small, but thick, plate of vulcanite. 

In this note the numbers presented must be looked upon only as 
first approximations; but the apparatus has now been carefully con- 
structed by an instrument-maker, and Mr. Dewar has begun an 
elaborate series of experiments with it, from which valuable results 
may soon be expected. In the trials which have as yet been made 
we employed a temporary apparatus, rudely built up of wires, seal- 
ing-wax, and gutta percha. We have rather been endeavouring to 
determine whether the process, complicated as it is by the inertia of 
the moveable part of the electrometer, the quickness with which the 
rocking can be conducted, and the rate at which the polarization 
begins to diminish as soon as the polarized plates are detached from 
the decomposing battery, is capable of being made to give good re- 
sults, than in actually attempting to getsuch. So far as I can yet 
see, the first of these complications is alone likely to cause any 
serious embarrassment; and should such be the case, which I do not 
anticipate, a form of experiment a little more laborious than that 
above described, and which I have already once or twice tried, seems 
to be well adapted to meet it. 

The following are, for the most part, means of a great number of 
determinations. ‘The electrolyte was usually dilute commercial sul- 
phuric acid, 1 part acid to 10 of water; and to the lead and other 
impurities it was found to contain we may ascribe the fact that the 
results were not very accordant from day to day, so that it was not 


SSS mes 


246 Intelligence und Miscellaneous Articles. 


easy to decide how to take the means.. Mr. Dewar is now working 
with substances chemically pure, and obtains much more constant 
results. 

The unit employed is the electromotive force of an ordinary Da- 
niell’s cell. The Grove’s cells used in the electrolysis had (very 
constantly) an electromotive force about 1°74 as great. 


I. Freshly-burned Platinum Plates. 


eS of Grove’s cells in \ 1 9 3 4 9 
ecomposing battery 
Resulting polarization .. 1°64 gs 2°01 2°12 2°30 
II. Platinum +, Palladium —. 
Gelisoleatemeh, Aneeadk l 2 4° 
Polarization \saG, <1. «2 1750 1°82 1°85 
Ill. Palladium +, Platinum —. 
Cells INTE nha Metnd 2 4 
Polarizavom 0. fo: 1°60 92 “Sane 
lV. With Three Cells. 
Platinum +, Iron —. Platinum —, [ron +. Iron plates. 
Polarization... 2°16 0-0 0:0 
V. Aluminium Plates. 
Celis is nie 9 1 2 3 4 6 


Polarization . 1:09 Daley, 2°44(?) 4:01 5°20 

The last results are very remarkable, showing, as they do, from 
aluminium electrodes a reverse electromotive force of more than five 
Daniell’s when six Grove’s are in circuit. The polarization alters 
so rapidly during the electrolysis (in the case of aluminium) that I 
cannot be certain that the numbers above given represent fully the 
maximum effect. Various other combinations have been tried, but 
are being repeated by Mr. Dewar.—irom the Proceedings of the 
Royal Society of Hdinburgh, Session 1868-69. 


SPECTRUM OF THE AURORA BOREALIS. 
fo) 


BY J. A. ANGSTROM. 

From the time when Franklin made his remarkable experiments 
on lightning, to the present time, a complete parallelism has been 
shown tc exist between the actions of the forces of nature and those 
of frictional electricity ; and hence it might have been expected 
that the spectrum of lightning would be like the spectrum produced 
by the ordinary electrical discharge. This has also been fully proved 
by M. Kundt’s observations. As, moreover, the aurora borealis and 
terrestrial magnetism are so intimately connected that the occurrence 
of the former phenomenon is always connected with disturbing ac- 
tions on the magnetic needle, it might be assumed that the northern 
light is nothing more than an electrical luminosity, such as is pro- 
duced in the electrical egg in rarefied air. 

This, however, is not the case. In the winter of 1868-69 I was 
several times able to observe the spectrum of the luminous are which 
surrounds the dark segment, and is never wanting in faint aurore. 


Intelligence and Miscellaneous Articles. 247 


The light was almost monochromatic, and consisted of a single bright 
line, which was on the left of the well-known group of lines of cal- 
cium. By measuring its distance from this group I determined the 
wave-length of the line, and found it 

A\=5567. 

Besides this line, the intensity of which is relatively very great, I 
observed, after the slit had been widened, traces of three very faint 
bands which extended nearly as far as F. Only once, when the lu- 
minous are was much agitated, owing to undulations which altered 
its shape, did I see the regions in question momentarily illuminated 
by some faint spectrum-lines; yet, from the feeble intensity of these 
rays, we may still say that the light of the luminous arc is almost 
monochromatic. 

One circumstance imparts to this observation of the spectrum of 
the aurora borealis a far greater, | may almost say cosmical, interest. 
In March of 1867 I observed for a whole week the same line in the 
zodiacal light, which at that time displayed an extraordinary in- 
tensity. Finally, on a starlight night, when the whole sky was in 
some degree phosphorescent, I found traces even in the faint light 
which proceeded from all parts of the heavens. 

It is a remarkable fact that the line in question does not coincide 
with any of the known lines in the spectra of simple or of compound 
gases—at any rate, as far as I have investigated them. 

From what has just been said it follows that an intense northern 
light, such as can be observed within the polar circle, will probably 
give a more complex spectrum than that which Ihave observed. If 
this be the case, we may also hope that in the future we shall be able 
to explain more easily the origin of the lines found and the nature of 
the phenomenon itself. But since I cannot at present give this ex- 
planation | intend to revert to it on a future occasion.—Poggendorff’s 
Annalen, May 1869. 


ON THE THERMAL ENERGY OF MOLECULAR VORTICES. BY W. J. 
MACQUORN RANKINE, C.E., LL.D., F.R.SS. LOND. & EDINB. ETC.* 


In a previous paper, presented to the Royal Society of Edinburgh 
in December 1849, and read on the Sth of February 1850 (Transac- 
tions, vol. xx.), the author deduced the principles of thermodynamics, 
and various properties of elastic fluids, from the hypothesis of mole- 
cular vortices, under certain special suppositions as to the figure and 
arrangement of the vortices, and as to the properties of the matter 
which moves in them. In subsequent papers he showed how the 
hypothesis might be simplified by dispensing with some of the special 
suppositions. In the present paper he makes further progress in the 
same direction, and shows how the general equation of thermody- 
namics and other propositions are deduced from the hypothesis of 
molecular vortices when freed from all special suppositions as to the 
figure and arrangement of the vortices, and the properties of the 
matter that moves in them, and reduced simply to the following 
form—that thermometric heat consists in a motion of the particles of 


* Communicated by the Author, having been read before the Royal 
Society of Edinburgh, May 31, 1869. 


. 


248 Intelligence and Miscellaneous Articles. 


bodies in circulating streams with a velocity either constant or fluctua- 
ting periodically. ‘This, of course, implies that the forces acting 
amongst those particles are capable of transmitting that motion. 

The principal conclusions arrived at are the following :— 

(1) In asubstance in which the action of the vortices is isotropic, 
the inteusity of the centrifugal pressure per unit of area is two-thirds 
of the energy due to the steady circulation in a unit of volume. 
The centrifugal pressure is the pressure exerted by the substance in 
the perfectly gaseous state. 

(2*) If there be substances in which the action of the vortices is 
not isotropic, then in such substances the proportion already stated 
applies to the mean of the intensities of the centrifugal pressures in 
any three orthogonal directions. 

(3*) The proportion which the whole energy of the vortices, in- 
cluding that of the periodic disturbances, bears to the energy of the 
steady circulation alone may be constant or variable. 

(4) Absolute temperature is proportional to the energy of the 
steady circulation in unity of mass, and to the specific volume in the 
perfectly gaseous state. 

(5) In substances which are nearly in the perfectly gaseous state, 
experiment shows the proportion in which the whole energy exceeds 
that of the steady circulation to be sensibly constant; and its value 
may be found by computing in what proportion the dynamical value 
of the specific heat at constant volume exceeds once and a half the 
quotient found by dividing the product of the pressure and volume by 
the absolute temperature. *The following are examples :—air, 1°634; 
nitrogen, 1°630; oxygen, 1'667; hydrogen, 1°614; steam-gas,2°242, 

(6) The known general equation of thermodynamics is deduced 
from the hypothesis of molecular vortices*, freed from the special 
suppositions made in the paper of 1849-50. 


The new conclusions obtained in the present paper are marked *, 
Those not so marked were arrived at in the paper of 1849-50. 


[The general equation of thermodynamics is here stated for con- 
venience :—Let dQ be the thermal energy which must be given to 
unity of mass of a given substance in order to produce a given inde- 
finitely small change in its temperature and dimensions; then 


dQ=7d.¢; 
in which 7 is the absolute temperature, and ¢ the thermodynamic 
function. ‘The value of that function is 
dU 
dr’ 
Jc being the dynamical value of the real specific heat, U the potential 
energy of the elasticity of the body at constant temperature, and 
x(7) a function of the absolute temperature, which is null or inap- 
preciable in a substance capable, at that temperature, of approxi- 
mating indefinitely to the perfectly gaseous state, and is included in 
the formula in order to provide for the possibility, suggested by 
Clausius, that there may be substances which have not that property 
at all temperatures. ] 


¢=Jchyp. log r+y(7)+ 


| 
; 


THE 


LONDON, EDINBURGH, ann DUBLIN 


PHILOSOPHICAL MAGAZINE 


AND 


JOURNAL OF SCIENCE 


[FOURTH SERIES.] 


OCTOBER 1869. 


XXX. On the Spectra of Carbon. By W.M. Watts, D.Sc., 
_ Physical-Science Master in the Manchester Grammar School*. 


[ With a Plate.] 
Lepeapiiadads considerable progress has been made in spec- 


trum-analysis since its first principles were enunciated by 
Bunsen and Kirchhoff, we still seem to be in considerable un- 
certainty as to the changes in the spectrum of an element which 
it is possible to bring about by altering the conditions under 
which itis produced. The interesting investigations of Pliicker 
and Hittorf and of Willner have shown that it is possible for 
an element to have more than one spectrum; and these totally 
different spectra have been supposed to belong to different allo- 
tropic modifications, apparently on the supposition that changes 
of temperature produce changes in the spectrum consisting 
merely in the addition of new lines. The following observa- 
tions, in which four different spectra are described as belonging 
to the element carbon, are offered as contributions to our know- 
ledge of this subject. 

The principal previous investigations on the spectra of the 
carbon-compounds, to some of which reference is afterwards 
made, are comprised in the following list :— 

Swan, Edinb. Phil. Trans. vol. xxi. p. 411 (1856). 

Attfield, Phil. Trans. 1862, p. 221. 

Plicker, Pogg. Ann. vol. evil. p. 497. 

Dibbits, Pogg. Ann. vol. exxii. p. 499, and De Spectraal 
Analyse. 

* Communicated by the Author. 
Phil. Mag. 8. 4. Vol. 38. No. 255. Oct, 1869. S 


MPF a 


250 Dr. W. M. Watts on the Spectra of Carbon. 


Pliicker and Hittorf, Phil. Trans. 1865, p. 1. 

Morren, Ann. de Chim. et de Phys. 1865, vol. iv. p. 805. 

Lielegg, Phil. Mag. S. 4. vol. xxxiv. p. 302; vol. xxxvil. p. 208. 

Deville, Lecons sur la Dissociation, and Phil. Mag. S, 4. vol. 
KRW. LI. 

Willner, Phil. Mag. S. 4. vol. xxxvu. p. 405. 

Frankland, Proc. Roy. Soc. vol. xvi. p. 419. 

I select as the typical form of the first carbon-spectrum that 
obtained when olefiant gas and oxygen are burnt together in an 
oxyhydrogen blowpipe-jet. The flame thus obtained exhibits a 
central cone of intense green, which, examined by the spectro- 
scope, gives the spectrum first obtained by Swan, and ascribed 
by Attfield to the vapour of carbon. The spectrum which is 
drawn, Plate I. fig. 1a, is one of the most beautiful which ean be 
imagined, and consists of five groups of lines—e in the red, yin 
the greenish yellow, 6 brilliant emerald-green, ¢in the blue, and 
f violet. 

Group «* contains five lines, of which the third 1s the bright- 
est. ry contains seven, of which the least refracted is the brightest, 
and each succeeding line is less brilliant than the one before; so 
that the group rises sharply out of darkness on the left, and 
fades gradually away on the right. The group 6, which con- 
tains four lines, presents the same gradation of intensity : €con- 
tains four lines of nearly equal intensity, the fourth being double; 
and f consists of a broad band, then a fine bright line, and then 
a band fading away on the most refracted side. When the spec- 
trum is obtained very brightly, there may be observed in addition 
six very fine bright lines of equal intensity, which gave the 
readings 86, 87:5, 89, 91, 98, 95. The band 128-133 is also 
seen to be shaded by a large number of nearly equidistant fine 
dark lines; and the least refrangible band of the group f (121- 
126) is resolved into lines. 

This spectrum may be obtained from the flame of any hydro- 
earbon, though in many cases, owing to the faintness of the 
spectrum, only some of the groups can be recognized. In the 
flame of an ordinary Bunsen burner 6 and ¢ are easily seen, y and 
f are much fainter, and the red group cannot be detected. 

This spectrum is proved to be that of carbon, inasmuch as it 
can be obtained alike from compounds of carbon with hydrogen, 
with nitrogen, with oxygen, with sulphur, and with chlorine. 
I have obtained it, namely, from each of the following com- 

* This is the group described as new by Professor Lielegg, Phil. Mag. 
March 1869. It is true, as he notes, that Dibbits strangely omits it, and 
that Plucker and Hittorf give only three lines; but the group of five lines 
is given by Morren, and they are distinctly figured in the drawing to my 
paper on the Bessemer-spectrum in the Philosophical Magazine for De- 
cember 1867. 


OO 


Dr. W. M. Watts on the Spectra of Carbon. 251 


pounds :—olefiaut gas, cyanogen, carbonic oxide, naphthalin, car- 
bonice disulphide, carbonic tetrachloride, amylic alcohol, and 
marsh-gas. 

It may be obtained from olefiant gas either by burning the gas 
with oxygen, as already described, or by taking the spark of an 
induction-coil in the gas at the ordinary pressure. In the lat- 
ter case, however, carbon is rapidly set free and the spectrum 
becomes continuous. The electric discharge in olefiant gas under 
diminished pressure gives a different spectrum, which will be 
afterwards described. 

The spectrum obtained from cyanogen varies with the mode 
of production. The flame of cyanogen in oxygen exhibits y, 6, 
ande. ‘The red group is replaced by a series of bands which 
show an opposite character to the rest of the spectrum, inasmuch 
as each band is brightest at the most refracted edge. If cyano- 
gen be burnt in air instead of in oxygen these bands are more 
numerous, extending nearly to 6, and replacing y, which is 
then not to be seen*. Instead of the group f we have two very 
brilliant groups of lines—&, which includes seven lines (105-113), 
and @, which is composed of six lines (186-142). Fig. le isa 
reduction of Dibbits’s drawing of the spectrum of cyanogen burn- 
ing in air (De Spectraal Analyse), and agrees well with my own 
observations. 

If the cyanogen, instead of being burnt, be rendered incan- 
descent by the discharge of an induction-coil in the gas at the 
ordinary pressure, a spectrum is obtained which contains y, 6, ¢, 
€, and 0, but which does not exhibit f. The red group e may 
be obtained precisely the same as from the olefiant-gas flame; 
but when the intensity of the spark is increased a different aspect 
comes out, which is represented in the Plate, fig. ld. 

Precisely the same spectrum is obtained from a Geissler’s tube 
enclosing cyanogen of a few millimetres pressure. The spectrum 
consists of a, y, 6, €, & and @. 

When a Leyden jar is included in the circuit, the relative in- 
tensity of the lines is altered, but the spectrum is essentially the 
same, with the addition of the nitrogen-lines obtained from the 
spark in air. 

The flame of carbenic oxide gives only a continuous spectrum ; 
but if the induced spark be taken in the gas at the atmospheric 
pressure, we obtain again the carbon-spectrum, comprising 
sometimes y, 6, e, and f, and sometimes y, 6, ¢, ¢, and 8. The 
red end is too faint to determine. The replacement of the 
group f by € and @ is very curious, but I have been unable to 


* These bands are thus obtained more completely developed at the lower 
temperature of the flame in air, and are doubtless due to the compound 
cyanogen itself, 


a 
S2 


252 Dr. W. M. Watts on the Spectra of Carbon. 


determine the conditions on which the presence of one or the 
other of these groups depends. A touch of the contact-breaker 
will sometimes cause f to disappear and be immediately replaced 
by the other two groups. The change of temperature (if it be 
so) thus caused is not attended, then, simply by the addition of 
new lines, but causes the disappear ance of one group and its re- 
placement by two other quite different groups of lines. When 
a Leyden jar is included in the secondary circuit, no trace of the 

carbon-lines is obtained if the jar be large enough, but instead a 
brilliant spectrum, which is described afterwards as the fourth 
carbon-spectrum and is represented in fig. 4a.- I have employed, 
instead of a Leyden jar, a graduating condenser consisting of two 
opposed disks of metal, the distance between which could be 
varied at pleasure. When the plates are separated, the conden- 
sation is so feeble that the spark in carbonic oxide shows the 
carbon-spectrum only; but as the plates are gradually approxi- 
mated, the fourth carbon-spectrum appears gradually replacing 
the old spectrum and finally completely extinguishing it. The 
blue band / is the first to disappear, and is replaced by “the group 
123-1383 of fig. 4, and the conspicuous line 76 of fig. 4: appears 
nearly bisecting the interval between the first and second lines 
of the group 6. 

When the density of the carbonic oxide is increased while the 
spark (without condenser) passes through it, the gas is more 
rapidly decomposed, the spark becomes more luminous, and the 
spectrum more nearly continuous. At two atmospheres’ pres- 
sure the spectrum obtained is the carbon-spectrum, consisting 
of ry, 6, €, € and @ (the red end probably contains «), e, & and @ 
being very brilliant. Increase of pressure up to about ten atmo- 
spheres only produces the effect of filling up the intermediate 
spaces with white light. 

The spectrum, including the groups € and @, is also obtainable 
from compounds of carbon with hydrogen. A Geissler’s tube 
enclosing naphthalin gives a splendid carbon-spectrum, in which 
the groups € and @ are especially brilliant. They are therefore 
abundantly proved to be produced by carbon itself. 

By passing the spark through the vapour of carbonie disul- 
phide, there can be obtained at will either Pliicker’s sulphur- 
spectrum of the second order or the carbon-spectrum on a 
background of continuous light due to the separation of sul- 
phur. 

The spark in the vapour of carbonic tetrachloride gives either 
the carbon-spectrum or the chlorine-spectrum, according to cir- 
cumstances. 

A Geissler’s tube enclosing amylie alcohol gives the carbon- 
spectrum, consisting of a, y, 6, ¢, and f. 


Dr. W. M. Watts on the Spectra of Carbon. 253 


A Geissler’s tube enclosing marsh-gas gives y, 6, ¢, and @, 
but the group ¢ is not observed. This spectrum contains also 
a line at 74, which may belong to the second carbon-spectrum. 

Carbonic oxide has been stated to yield the ordinary carbon- 
spectrum when the induced spark is taken in the gas at the or- 
dinary pressure. The discharge through a Geissler’s tube, 
however, exhibits an entirely new spectrum which contains none 
of the ordinary carbon-lines. That this new spectrum is also 
due to carbon itself is shown by the fact that it is obtained either 
from a vacuum-tube enclosing carbonic oxide, or from one enclo- 
sing olefiant gas*; and it becomes a question of much interest 
to determine upon what conditions the production of one or the 
other of these forms of the carbon-spectrum depends. Olefiant 
gas is capable of yielding either spectrum. When the discharge 
is passed through a tube containing olefiant gas of only a few 
millimetres pressure, the spectrum drawn (fig. 2e) is obtained, 
but the gas at the ordinary pressure yields the first form. In 
order te determine at what pressure the second spectrum dis- 
placed the first, a tube provided with platinum wires was con- 
nected with the air-pump so that it could be exhausted, and by 
means of a tap with a source of olefiant gas. It was also pro- 
vided with a gauge-tube, by means of which the pressure could 
be measured. When the pressure is about 12 millims., the 
spark is violet and gives the carbon-spectrum of fig. 2; when 
the pressure of the gas was gradually increased the spark became 
blue; and ata pressure of about 100 millims. the spectrum 
changed to that of the first form. When still more gas was ad- 
mitted the spark became white, and carbon was rapidly sepa- 
rated. 

Plucker} has observed these lines of the second carbon-spec- 
trum. In his earlier paper he describes them as lines belonging 
to the compound carbonic acid; but in the paper published in 1865 
he represents them as belonging to carbon itself. Fig. 2,a& 6, 
shows the observations of Pliicker, reduced from the drawing to 
his paper in the Philosophical Transactions to the scale employed 
throughout this paper. Fig. 2a shows the spectrum obtained 
from spectral tubes enclosing carbonic oxide of 82 millims. pres- 
sure. A comparison of this spectrum with that of carbonic oxide 
(fig. 2c) and with that of olefiant gas (fig. 2 e), shows that Plucker 
did not succeed in completely separating the two spectra. I 
have, however, repeatedly obtained the second spectrum alone, 
consisting of the bands A, 7, k, 1, m, n, and o, and exhibiting no 

* This curious difference in the spectra obtained from different carbon- 
compounds was first noted by Dr. Roscoe, in a lecture delivered before the 


Royal Institution in May 1864. 
f Poge. Ann. vol. evil. (1859). Phil, Trans. 1866, 


204 Dr. W. M. Watts on the Spectra of Carbon, 


trace of a,y, 6, ¢. Fig. 2, ¢ and d, shows the result of a direct 
comparison of the carbonic-oxide vacuum-spectrum with that of 
the olefiant-gas flame when the two are seen simultaneously in 
the spectroscope. 

The carbonic-oxide vacuum-spectrum shows the lines A, 7, k, 
l,m,n,andoe. A spectrum-tube enclosing olefiant gas (or coal- 
gas, or a mixture of equal volumes of olefiant gas and hydrogen) 
gives h, 7, k, l, m,n, and o, and sometimes the group @ of the 
first carbon-spectrum; occasionally 6 is also faintly visible. 
Pliicker* has obtained from a vacuum-tube containing carbonic 
disulphide, carbon fh, 7, k, J, m, and n. 

I believe that we have a third form of the carbon-spectrum in 
that obtained from the Bessemer-flame, which I described in a 
paper published in this Magazine for December 1867. Professor 
Lielegg+ regards the Bessemer-spectrum as that of carbonic 
oxide. It is, however, impossible to obtain it either from the 
flame of carbonic oxide or from the gas rendered incandescent by 
electricity: in the first case a continuous spectrum only is ob- 
tained ; and in the latter either the spectrum of carbon (fig. 1) or 
that obtained also from carbonic anhydride (fig. 4) 1s produced. 
I have always looked upon this spectrum as that of carbon 
itself, and have sought to obtain it from compounds of carbon 
with nitrogen or with hydrogen, but without success. It appears 
to be produced only under conditions very nearly the same as 
those of the Bessemer-flame itself. Thus I have observed it in 
one or two furnace-flames in which a very high temperature is pro- 
duced. The flame of carbonic oxide in an ordinary melting-cupola 
gives a very brilliant continuous spectrum, but exhibits only the 
sodium-line. In the working of a blast-furnace it is usual, after 
the iron has been run, to turn on the blast so as to help the iron 
out. This produces a large white flame from under the tymp, 
which exhibits a very bright continuous spectrum with the so- 
dium- and lithium-lines brilliant, together with a faint Bessemer- 
spectrum. I have observed the lines of the Bessemer-spectrum 
also in the flame of a small furnace, used on the works at Crewe 
for loosening the tyres of wheels, in which coke is burnt by a 
blast of air; and the Bessemer-spectrum is always obtained in 
the combustion of coke alone in the convertor. The spectrum 
of the coke-flame exhibits the Bessemer-lines faintly, and the 
lines of sodium and lithium: the introduction of the charge of 
molten pig iron seems to cool down the flame, so that for two or 
three minutes after the commencement of the blow a continuous 
spectrum only is seen. As the temperature rises the sodium- 


* Pogg. Ann. vol. evii. p. 538. 


Tt Phil, Mag. 8.4, yol, ysxiv. p. 302. 


. Dr. W. M. Watts on the Spectra of Carbon. 255 


line first becomes visible ; then the lithium-line is added, and 
gradually the lines of the Bessemer-spectrum, increasing in bril- 
lianey to the end of the. blow. 

The spiegel-spectrum, as I have pointed out, is only the Bes- 
semer-spectrum in which some of the lines are still further in- 
creased in brilliancy, and is doubtless due to the highest tempe- 
rature of all ; for we have the hot carbon of the molten spiegeleisen 
burnt by the intensely heated oxygen absorbed by the liquid 
steel. The spiegel-spectrum 1s occasionally identical with the 
ordinary Bessemer-spectrum, when, namely (as shown by the 
spectroscope and by the analysis of the steel), the blast has been 
stopped somewhat short of the proper point. The effect of an 
increase of temperature is thus to split up the Bessemer-spectrum 
into groups of lines, in each of which the brightest line is the 
most refrangible—an aspect which is exactly the reverse of that 
so noticeable in the ordinary carbon-spectrum, where each group 
has its strongest line on the left hand. 

A fourth spectrum, also probably due to incandescent carbon, 
is obtained from the induced spark in either carbonic oxide or 
carbonic anhydride when a Leyden jar is included in the circuit, 
and is represented in fig. 4. It is one of the spectra termed 
by Plicker “spectra of the second order,’ consisting, not of 
bands, but of sharply defined lines, frequently in pairs. It 
has been already stated that the induction-spark (without con- 
denser) gives in carbonic oxide the carbon-spectrum No. 1, and 
in carbonic anhydride a continuous spectrum. With a suffi- 
ciently large condenser the spectrum obtained from carbonic 
oxide is identical with that obtained from carbonic anhydride, as 
will be seen on comparing fig. 4.a@ (spectrum of carbonic oxide) 
with fig. 45 (spectrum of carbonic anhydride). The carbonic 
oxide was prepared from potassium ferrocyanide and well washed 
with caustic potash. ‘The spectrum obtained from air under 
similar conditions is es for the sake of comparison. The 


carbon double band 1565 6-5 


double band in the air-spectrum. If, however, while the spark 
continues to pass, the carbonic anhydride be blown out of the 
discharge-tube and replaced by air, it is distinctly seen that the 
two are not coincident. The left-hand nitrogen-line is slightly 
more refrangible than the left-hand carbon-line; the right-hand 
members are (with one prism) apparently coincident. 

The continuous spectrum obtained by the discharge of an in- 
duction-coil in carbonic anhydride may be converted into this 
fourth carbon-spectrum, either by increasing the electric conden- 
sation as described above, or by increasing the density of the gas. 
Carbonic anhydride in the compression-apparatus which [ have 


is at first sight identical with the 


i 
| 
| 


2. Se ae 


a Pf ae BE 


256 Dr. W. M. Watts on the Spectra of Carbon. 


used for experiments on gases under pressure, shows at the or- 
dinary pressure only a faint continuous spectrum ; at two atmo- 
spheres’ pressure the spectrum is much brighter but still conti- 
nuous ; andat pressures between seven and ten atmospheres’ the 
spark passes with difficulty, and the spectrum shows a number 
of bright bands which agree in position with the lines 76, 99, 
108, and 106 of fig. 46. They differ in character, however, 
being bands instead of fine lines, thus bearing the same relation 
to the fine lines obtained from carbonic anhydride at the ordinary 
pressure as the expanded lines of hydrogen do to the fine lines 
obtained from a hydrogen vacuum-tube. These bands are ob- 
tained also in the spectrum of the condensed spark in the vapour 
of amylic alcohol, 

The spectrum of the direct discharge in a tube containing 
hydrogen of a few millimetres tension only and a trace of methyl- 
oxalic ether is faint, but contains the lines k, /, m of the second 
carbon-spectrum ; but when by warming the tube the ether is 
volatilized, the spark passes only in brilliant flashes, and the 
spectrum then contains lines 34, 75, 85-90, 99, 103, 106, 120, 
125, and 140 of the fourth carbon-spectrum again as bands. 

This fourth spectrum, obtained from carbonic oxide and car- 
bonic anhydride, may either be due to carbon, or to carbonic 
oxide, or to carbonic anhydride. It is, of course, not the spec- 
trum of oxygen. I believe it to be due to carbon; but I have 
not been able to obtain such complete evidence as is afforded for 
the spectra Nos, 1 and 2 in their production from different car- 
bon-compounds. Thus I have not been able to obtain this fourth 
spectrum from a compound of carbon with hydrogen alone; the 
condensed spark in cyanogen at the ordimary pressure gives, 
however, together with the carbon-spectrum No. 1] and the ni- 
trogen-spectrum of the second order, the lines 34, 56, 76, and 
103 of the carbon-spectrum No. 4. This conclusion (that the 
spectrum is really due to carbon itself) seems to be supported by 
the fact that, when this spectrum is obtained from either carbonic 
oxide or carbonic anhydride, there is always a perceptible deposit 
of carbon ; since if it were due to carbonic oxide we should not ex- 
pect to have carbon deposited in either case ; and if it were due to 
carbonic anhydride, though carbon would be set free from the car- 
bonic oxide, there would be none from carbonic anhydride itself, 
It would appear that carbonic oxide is more easily decomposed 
than carbonic anhydride, either ito carbon and carbonic anhy- 
dride, or into carbon and oxygen ; so that at the low temperature 
of the direct discharge carbonic oxide is decomposed and gives 
the carbon-spectrum No. 1, while carbonic anhydride resists de- 
composition. Ifthe temperature of the spark be increased either 
by the intercalation of a Leyden jar or by increasing the density 


Dr. W. M. Watts on the Spectra of Carbon. 257 


of the gas, the carbonic anhydride is decomposed and the new 
earbon-spectrum becomes visible. 

If we attempt to define the conditions under which these dif- 
ferent forms of the carbon-spectrum are produced, we are met 
by very considerable difficulties. The knowledge we possess of 
the temperature of gases ignited by the electric discharge is so 
small, that we cannot with any certainty compare the spectra 
produced in this way with those obtained from the flames of car- 
bon-compounds. Indeed it seems by no means certain that 
we are right in attributing the differences obtained in electric 
spectra simply to the different temperature to which the gas is 
heated. 

In comparing the spectra of fig. 1, we notice that the changes 
take place at the ends of the spectra, the central groups y¥, 6, ¢ 
remain substantially the same. If we pass from the spectrum 
of the olefiant-gas flame to that of the cyanogen-flame, we find 
the change at the blue end of the spectrum consisting in the dis- 
appearance of the group f and its replacement by the groups € 
and @. The group fis not absolutely proved to belong to car- 
bon (that is, it may be caused by carbonic oxide or carbonic 
anhydride) ; but the groups € and @, since they are common to 
carbonic oxide, cyanogen, and naphthalin, must be due to car- 
bon, and their presence may with much probability be attributed 
to the higher temperature of the cyanogen-flame. 

The temperatures of flames, calculated on the assumption that 
the total heat of combustion is expended _in heating up the pro- 
ducts of combustion, have been shown by Deville to be immensely 
too high. Thus, for example, the temperature of the oxyhydrogen- 
flame, which calculation fixes at 6880° C., is determined experi- 
mentally by Deville* to be not higher than 2500° C., and by 
Bunsen not higher than 2800° C. The following are the cal- 
culated temperatures of some flames, with which are compared 
the recent experimental results of Bunsen +:— 


Calculated. Experimental. 


Fliyaroxen Imalr’ .1) 1 2738.0. | 202410. 


Hydrogen inoxygen. . . 6880 2844 
Carbonic oxide inair. . . 2996 1997 
Carbonic oxide in oxygen . 7067 3033 
Cyanczentinlar? 00s |e BdolD 3297 


Cyanogen in oxygen. . . 10557 
Olefiant gasinair . . , 2619 
Olefiant gas in oxygen . . 8626 


* Legons sur la Dissociation, p. 281. 
Tt Pogg. Ann. vol. cxxxi. p. 161. 


258 Dr. W. M. Watts on the Spectra of Carbon. 


- There is another element of uncertainty which must not be 
forgotten. The calculated temperatures and those obtamed ex- 
perimentally by Bunsen are the mean temperatures of the flames, 
and it is quite possible for one part of a flame to be 1000° C. 
hotter or 1000° C. colder than the temperature given as the 
temperature of the flame. ‘The blue cone of a Bunsen gas- 
flame, from which the carbon-spectrum is obtained, is certainly 

such colder than the exterior cone of the flame at the same 
point. 

I have made several attempts te reduce the temperature of the 
olefiant-gas flame, but have not succeeded in altering the spec- 
trum at all. Olefiant gas, burnt by means of oxygen in an 
atmosphere of hydrogen, gives the carbon-spectrum brilliantly 
with all the fine limes previously described; and a mixture of 
olefiant gas and steam burns with a colourless flame which ex- 
hibits the same spectrum. 

A mixture of 2 vols. carbonic anhydride and 1 vol. olefiant 
gas burns with a barely luminous flame, the blue part of which 
gives the groups y, 6, e, and f of the carbon-spectrum. ‘The 
calculated temperature of such a flame is 2016° C.; but in all 
probability the temperature is much less, as no allowance 1s made 
in the calculation for any refrigerating effect produced by the 
decomposition of the carbonic anhydride. 

The fusing-point of gold is given by Deville* as 1300° C., 
and of platinum as 2000° C. The interior blue cone of a Bun- 
sen-flame about 10 millims. above the jet, which is the part 
which yields the carbon-spectrum most plainly, 1s capable of 
melting gold, but does not melt platinum. It is incapable of 
fusing steel, which 1s fused by the outer cone at the same point ; 
and platinum resists the flame at any pointy. We may therefore 
probably assign to the inner blue cone a temperature of about 
1500° C. 

The temperature of the flame of olefiant gas and oxygen has 
not been determined by experiment; but it can hardly be above 
2500° C., and we may therefore conclude that the groups y, 6, ¢ 
are produced by incandescent carbon between the temperatures 
of about 1500° C. and 2500° C.+ 

In order to determine the inferior limit of the groups and @, 
a mixture of equal volumes of carbonic anhydride and cyanogen 
was made; it burnt with a violet flame of small intensity, yield- 
ing the carbon-spectrum, including the group @ and the bands 

* Lecons sur la Dissociation, p. 284. 

+ A fine platinum wire, which could not be fused in any part of a Bun- 
sen-flame, was easily fused at one point in an ordinary bat-wing gas-burner. 

{ The groups y, 6, € are those observe ¢by Huggins in the spectrum of 
Winnecke’s comet. 


Dr. W. M. Watts on the Spectra of Carbon. 259 


of cyanogen. As the temperature calculated for the cyanogen- 
flame agrees closely with the experimental result, we are probably 
justified j in accepting the calculated temperature in this case also 
as not very far from the truth, and may therefore conclude that 
0 begins to be visible about 2200° C. Platinum and steel are 
easily fused in the flame of cyanogen burning in air. 

The temperature of a gas ignited by the electric discharge de- 
pends upon the resistance and upon the quantity of electricity 
transmitted in each spark ; and this may be increased either by 


increasing the condensing surface, or by increasing the tension of 


the electricity at discharge. This tension depends upon the 
nature of the gas: thus the spark passes with great ease through 
hydrogen, with more resistance through carbonic oxide, carbonic 
anhydride or oxygen, and with extreme difficulty through cya- 
nogen. But for one and the same gas the tension at discharge 
and resistance experienced are increased by increasing the den- 
sity ; and the heat produced thus increasing more rapidly than 
the quantity of matter to be heated, the temperature rises*. 
Hence we understand why the groups ¢ and @ are added to the 
spectrum of the spark in carbonic oxide when the density of the 


gas is increased, and why the spark in the gas cyanogen, which. 


offers 80 great resistance ,always gives a spectr um contaiming ¢ and 
@. We have also the explanation of the fact that a vacuum-tube 

containing either the dense vapour of naphthalin, or the badly 
conducting gas cyanogen, gives always the spectrum of carbon 
belonging t to the high temperature, although the pressure of the 
gasis only a few millimetres. 

It is impossible to assign any temperature as the superior 
limit of this first form of the carbon-spectrum which shall have 
any meaning, or to guess with any probability at the temperature 
of the condensed spark. It cannot be less than 10,000° C.; but 
the temperature calculated for the flame of cyanogen in oxyg “en 
(without doubt the hottest flame known) can hardly be trusted. 
The carbon-spectrum No. 4 may then roughly be said to be due 
to incandescent carbon above 10,000° C. 

It has been shown that carbon -at 1500° C. gives the first form 
of carbon-spectrum, and that the same spectrum is given by the 


electric spark in either carbonic oxide or olefiant gas at the ordi- 


* I have repeatedly observed this increase of resistance in the experi- 
ment on condensed gases. The spark which passed with ease in carbonic 


anhydride at the ordinary pressure could hardly be got through the gas at’ 


7 atmospheres’ pressure, while there was no perceptible increase in the re- 
sistance afforded by hydrogen when the pressure was increased to 9 atmo- 
spheres; and the spark which passed with ease through 7 millims. in 
hydrogen at 9 atmospheres’ pressure would hardly pass through 5 millims. 
in cyanogen at the ordinary pressure, and through only a fraction of a mil- 
limetre in cyanogen at 4 atmospheres’ pressure. 


I 


260 Dr. W. M: Watts on the Spectra of Carbon. 


nary pressure, but that when the pressure of the gas is increased 
the temperature of the spark rises. When, then, we find that 
on gradually diminishing the pressure the same spectrum is 
given until the pressure falls to about 100 millims., and then 
suddenly changes to the third form, we can hardly resist the 
conclusion that this third form of carbon-spectrum is due to 
carbon rendered luminous below 1500° C. The result that 
the temperature of the discharge in a vacuum-tube may be 
below 1500° C. is certainly unexpected, but it can hardly be 
rejected* unless we give up the attempt to account for the dif- 
ferences in the spectra of the same element by differences in the 
temperature of ignition. We may, of course, suppose the exist- 
ence of allotropic modifications of carbon-vapour, but we have no 
proof of the existence of such. 

The explanation of the Bessemer-flame is extremely difficult. 
I have endeavoured to obtain some approximation to the tempe- 
rature of the flame both by calculation and by experiment. The 
calculation is based upon the composition of the gas issuing from 
the convertor. A sample of the gas collected from the converter 
at the Steel-works at Crewe was analyzed by Mr. C. R.A. Wright, 
B.Sc., and gave the following result :— 


Carbonic anhydride . . . 3878 
Carbonicoxide) ac 4% gee aie 6:20 
Oxyeen php ana earits ane Od 
Nitropenigsrovell a, ne Nsanpmi sad Orick 


99°99 


The temperature is calculated on the assumption that the 
oxygen of the air is used up in burning the carbon of the cast 
iron to carbonic oxide and carbonic anhydride, and in burning 
the iron to ferroso-ferric oxide. 


litres. Ts. ors. 
3°78 carbonic anhydride weigh 7:43 and contain 2:03 carbon. 
16°20 carbonic oxide a 20°27 iS 8°69 
0°57 oxygen 53 0°82 
79°44 nitrogen 3s 99°92 


33 


The total volume of oxygen contained in the gaseous products 
of combustion is 


* Willner (Pogg. Ann. Dec. 1868) regards the temperature in a hydro- 
gen vacuum-tube as at a maximum when the tension is about 30 millims., 
being lessened either by increase or diminution of the pressure. 


Dr. W. M. Watts on the Spectra of Carbon. 261 


litres. litres. 
3°78 in 3°78 carbonic anhydride. 
8:10 in 16°20 carbonic oxide. | 
0°57 | 
12°45 


But 79°44 litres of nitrogen are mixed in air with 21 litres of 
oxygen. Hence 21—12:45=8°55 litres of oxygen have com- i 
bined with iron. 

The heat produced by the combustion is as follows :— — : 


Thermal units. 


ers. | 
2°03 carbon burning to CO? ialve™® 2-03 x 8080= 16402 i 
8:69 y » 869x2474= 21499 ‘ 
82°08 iron __,, Fe? Of ,, 82°08x1582= 50778 } 
88679 | 
The products of combustion and their specific heats are as i 
follows :— i 
es 
FA3 CO” © X'0:216- =" 1-60 i 
20°27 CO x0:248 = 5:03 " 
44°26 Fe? O* x0°152*= 6°73 ! 
99:92 N x 0°244 = 24°38 
0:82 O x 02138" = 018 
37°92 
and the temperature of the flame is therefore 
88679 
—~ =23389° C. 
37-99 =e oes Onl 


The result of this calculation is, of course, open to the same 
objection as all calculated flame- temperatures, that no allowance 
can be made for dissociation. It is too high also for another 
reason—that a very considerable part of the heat produced is 
expended in heating up the molten metal itself, which is im- 
mensely hotter at the end of the blow than it is at the beginning. | 
If we assume that, together with the quantities given above, we | 
have 300 girs. iron heated up from 1000° C. to the temperature 


» 3X644+4x4 _ 9. 159. 
at. wt. Fe? O* | 
T This calculation represents 10 grs. carbon burnt for 32 grs. iron. As- i 
suming the pig-iron to contain 3 per cent. carbon, this would give a loss of 
32 iron for Ae X 10=333 pig iron, or about 10 per cent. The average | 


loss from all causes is reckoned, I believe, at about 15 per cent. 


262 Dr. W. M. Watts on the Spectra of Carbon. 


of the flame (which is, of course, not really the case), we obtain 
as the temperature of the flame 1700° C. instead of 2339° C. 

Mr. Ramsbottom has kindly placed at my disposal the result 
of an experiment made at Crewe to determine the ‘heat of the 
Bessemer-flame, in which it was found that on exposing a bar of 
cast iron (quality not stated), 1} inch in diameter, to the action 
of the flame at a distance of about 12 inches from the mouth of 
the vessel, it began to melt mm about 54 minutes, the iron drop- 
ping off in small globules at the rate of about 380 or 40 per 
minute. <A bar of wrought iron exposed im a similar manner for 
about six minutes at the end of the blow did not melt.” 

We may therefore conclude that the temperature of the Bes- 
semer-flame lies between 1000° C. and 1500° C. It is worthy 
of remark (since it throws light on the question whether the 
carbon-spectra are to be regarded as produced by carbon in the 
gaseous state or not) that the Bessemer-spectrum contains the 
lines of iron. There is probably as much difficulty in suppo- 
sing the existence of iron-vapour below 1500° C. as in supposing 
the. existence of carbon-vapour at the same temperature. 

The Bessemer-spectrum is either due to carbon or to carbonic 
oxide. If it be produced by carbon, we are compelled to admit 
the existence of two spectra produced by carbon at the same 
temperature ; for the Bessemer-flame les between 1000° C. and 
1500° C., and the gas of the vacuum-tube is below 1500° C. 
If we assume that the Bessemer-spectrum is due to carbonic 
oxide, we have to explain why in the Bessemer-flame carbonic 
oxide gives a spectrum consisting of bright lines, and in the 
carbonic-oxide flame a continuous Spectr um. Deville* has shown 
that the carbonic-oxide flame varies in temperature from about 
1000° C. at the top of the flame to a temperature considerably 
above the fusing-point of platinum, or probably 2500° C, at the 
blue cone 10 millims. from the jet; so that we have then to 
admit the existence of two spectra of carbonic oxide within 
the same range of temperature. It may be objected that the 
determination of temperature is very uncertain, and that if car- 
bonie oxide were more intensely heated it would give out the 
Bessemer-spectrum; and indeed at the highest temperature 
obtainable from carbonic oxide and oxygen burnt together at 
the oxyhydrogen jet a faint spectrum does become visible from 
the blue cone, which Deville has shown to possess the highest 
temperature; but it is identical with the carbon-spectrum 
No. 1. The probability is that the compound carbonic oxide, 
like the compound carbonic anhydride, always gives a conti- 
nuous spectrum—but that at the extremely high temperature 
obtained in the experiment mentioned above the carbonic oxide 

* Lecons sur la Dissociatiom, p. 302. 


On the Cause of the Phenomena of Voltaic Cooling and Heating. 263 


becomes dissociated, and the carbon set free then gives off the 
ordinary carbon-spectrum. 

In conclusion, my best thanks are due to Professor Roscoe 
for valuable advice and assistance rendered me in this investi- 
gation. 


XXXI. On the Cause of the Phenomena of Voltaic Cooling and 
Heating discovered by Peltier. By EK. Kytunp*. 


| oe a voltaic current passes through a metal conductor, heat is 

developed, and its quantity is proportional to the resistance 
and the square of the intensity. An exception to this rule, how- 
ever, 1s formed by the place of junction of two heterogeneous 
metals. Peltier showed, so long ago as 1834+, that the solder- 
ings between two different metals become either colder or warmer 
than the other parts of the conductor, according to the direction 
in which the current traverses the places of contact. Peltier 
found that the strongest action was that between bismuth and 
antimony. If the current passed through the junction from the 
bismuth to the antimony there was a fall of temperature, while 
in the opposite case there was an increase. These experiments 
were confirmed by Moser{. Lenz subsequently$ gave this 
experiment an attractive form by showing that at the place of 
contact between bismuth and antimony water can be made to 
freeze if a feeble current passes from the former to the latter 
metal and both have been previously cooled in a mixture of ice 
and water. 

Peltier was led by his experiments to the view that these phe- 
nomena of cooling and heating are closely connected with the 
electrical conductivity of the metals. When the current passes 
from a worse to a better conductor, in his opinion the tempera- 
ture at the soldering is higher than when the current goes in 
the opposite direction. EK. Becquerel, however, has shown || 
that this is not always the case, and that therefore the voltaic 
resistance is of no importance from this point of view. He 
made special experiments to ascertain whether at the point of 
contact the voltaic resistance was in any manner dependent on 
the direction of the current, so that in one case it should be 
ereater and in another smaller than in the other parts of the 
circuit. But the experiments gave a negative result; the ob- 
served differences in the resistance, according to the direction of 


* Translated from Poggendorff’s Annalen, having been read before the 
Swedish Academy of Sciences at Stockholm, April 14, 1869. 

+ Ann. de Chim. et de Phys. vol. lvi. p. 371. 

t Repertorium der Physik, vol. 1. p. 349. 

§ Poge. Ann. vol. xliv. p. 342. 

|| Ann. de Chim. et de Phys. S. 3. vol. xx. p. 53, 


264 Prof. E. Edlund on the Cause of the Phenomena 


the current, were not more than might be assumed to arise 
from the differences in temperature at the points of contact. 
The experiments thus did not at all prove that the cooling 
and heating observed by Peltier had anything to do with the 
voltaic conducting-power. It is also clear that if the voltaic re- 
sistance were indeed different with the direction in which the 
current traversed the point of contact, it would certainly follow 
that the degree of heating might vary with the direction of the 
current, but in no case could there be a cooling or real absorp- 
tion of heat. Becquerel was of opinion, however, that these 
experiments indicated another connexion between the pheno- 
mena in question and previously well-known voltaic phenomena ; 
for he found that when the voltaic current which traverses the 
place of contact has the same direction as the thermoelectric 
‘current which would be formed by heating the junction, 
the temperature diminishes at the place of contact, but that 
when the current is in the opposite direction there is a rise in 
temperature. The phenomena in question would thus have a 
connexion with the thermoelectric properties of bodies. How 
far this conclusion is right or not under all circumstances can 
only be definitely settled when a larger number of metals and 
alloys have been investigated with this view. 

G. v. Quintus Icilius has made careful examination of the 
quantitative relations of these phenomena, from which it resulted 
that the difference in temperature produced by the current at 
the junctions of a thermoelectric pile of bismuth and antimony 
was proportional to the intensity of the current. Hence these 
phenomena follow a totally different law from that of the ordi- 
nary thermal action of the voltaic current ; for while the former 
are simply proportional to the intensity,the latter thermal action 
is proportional to the square of the intensity. The accuracy of 
this result has been confirmed by Frankenheim’s investigation*, 
which was made in a manner totally different from the above. 
Hence it may be regarded as demonstrated that the variations in 
temperature in question are proportional to the intensity of the 
current by which they are caused. 

It is in itself a very remarkable fact that under certain cir- 
cumstances the voltaic current can produce an absorption of heat ; 
for its ordimary action is to produce heat. Hence I have thought 
that an account of the cause of this deportment might have 
some interest; for, as will afterwards be shown, Peltier’s phe- 
nomena of cooling and heating may be easily deduced from the 
idea of electromotive force; their existence may be proved to 
be absolutely necessary; so that they might have been disco- 
vered @ priori if their existence had not previously been demon- 

* Poge. Ann. vol. xci. p. 161. 


of Voltaic Cooling and Heating. 265 


strated. The proof rests upon the general principles which 
have been introduced into science by the mechanical theory of 
heat. 

An electromotive force, like any other natural force, cannot pro- 
duce mechanical work out of nothing. The well-known principle, 
ex nihilo nihil fit, finds everywhere a confirmation. Hlectromotive 
forces are only “transforming forces,” which change one kind of 
motion into another, and always in such a manner that the kind of 
motion which is changed has the same mechanical value as that 
into which it is changed; they are mechanically equivalent to 
each other. Ifaclosed conducting-wire is brought uear a voltaic 
current or is removed from it, induction-currents are formed in 
the conducting-wire; and a certain amount of work is required 
to effect this approximation or removal. By the force of induc- 
tion this work is changed into electricity, which in turn pro- 
duces a quantity of heat, which, as I have elsewhere* shown, 
constitutes the mechanical equivalent of the work used. If one 
soldering of a closed ring consisting of two metals be heated, a 
thermoelectric current is formed which produces heat in the 
conductors which it traverses. But this heat cannot be pro- 
duced from nothing. The mechanical theory of heat requires 
that just as much heat shall disappear at the heated junction, 
or, to speak more correctly, be changed into electricity. When 
the temperature has become the same at both junctions and the 
thermoelectric current has ceased to circulate, as much heat will 
haye been developed in the circuit as has been changed into 
electricity at the point of contact. Hence work has neither 
been produced nor destroyed by the thermoelectric current. 
If we join by a metallic wire the poles of an electromotor, for 
instance a voltaic battery, in which chemical combinations result 
from the action of the current, an amount of heat is produced 
which is proportional to the square of the intensity, and to the 
entire resistance in the battery and in the interpolar. Now, from 
the mechanical theory of heat, as much heat must disappear in 
the electromotor or be changed into electricity. If the heat re- 
sulting from the chemical combinations be designated by a, that 
produced in the electromotor by the action of the current by 4, 
and that produced in like manner in the interpolar conductor by 
e, the quantity of heat produced in the electromotor will be 
equal to (a+b)—(b+c)=a—c. Hence the entire quantity of 
heat obtained in the electromotor and the interpolar conductor 
will be equal to that which would have been formed from the 
same chemical action without any current having been formed. 
The current, therefore, has neither produced nor consumed heat ; 
the heat necessary for the production of the current was just as 

* Pogg. Ann. vol. exxil. p. 193. 


Phil. Mag. 8. 4. Vol. 88. No. 255. Oct. 1869. Ak 


266 Prof. E. Edlund on the Cause of the Phenomena 


ereat as that which it produced by its passage through the cir- 
cuit. Hence it has only transferred the heat from the elec- 
tromotor to the interpolar conductor without any loss or gain of 
heat. That this conclusion is quite correct has been experimen- 
tally proved by Favre*. This distinguished physicist has proved 
that the amount of heat liberated by a voltaic element whose 
poles are connected by a conducting-wire of greater or less re- 
sistance agrees quite accurately with the amount of heat which 
the operations which have taken place in the battery would have 
furnished if no current had been formed. The heat obtained in 
the interpolar conductor, together with that which appears in the 
battery itself, form a total amount of heat which is equal to 
that produced by the chemical action. The current has neither 
increased nor diminished this quantity of heat. Hence, as was 
remarked above, in a thermoelectric pile which is unaccompanied 
by any chemical action, the total amount of heat produced must 
be null. I will now apply these principles to the phenomena of 
cooling and heating discovered by Peltier. 

2. Assuming we have an electromotor of any quality, the poles 
of which are connected with each other by a conductor, if the elec- 
tromotive force is e, and the entire resistance in the electromotor 
together with that in the conductor is equal to /, the total quantity 

2 
heat evolved by the current is _ ie > or, if s is the intensity, 
=ces. But, from what has been said, as much heat must disappear 
in the electromotor or be converted into electricity. Hence 
there must be an absorption of heat whichis proportional to the 
electromotive force multiplied by the intensity of the current. 
If there are two electromotors whose electromotive forces are 
e+e', and these both act in the same direction, the entire quan- 
she 
tity of heat developed by the current is oe = (e+e')s,, if s, 
1 

and /, denote respectively the intensity and the resistance. Hence 
this quantity of heat must be absorbed in the two electromotors 
together. It follows thence that in each electromotor there 
must be an absorption of heat which is proportional to the com- 
mon intensity multiplied by the electromotive force. The result 
will, of course, be the same if there is a larger number of electro- 
motors, provided only they act in the same direction. 

If the electromotive forces act in opposite directions and e is 
greater than e,, a current is obtained in the direction of the first 
force; the total quantity of heat developed by the current is 
= (e—e,)s, when the intensity is s,; and just this quantity of 
heat must disappear in the two electromotors. But in the first the 


* Ann, de Chim. et de Phys, S. 3. vol. xl. p. 293. 


of Voltaic Cooling and Heating. 267 


quantity of heat es,, will be absorbed, which is greater than that 
produced by the current. The difference between the two, or e's, 
must therefore be produced in the other clectromotor, so that the 
algebraic sum of that which is produced and of that which dis- 
appears may be equal to zero. It therefore follows that if a 
current traverses an electromotor in the opposite direction to the 
current which is produced by it, heat is developed in this elec- 
tromotor proportional to the product of the electromotive force 
into the intensity. Hence is obtained the final result :—If a 
voltaic current traverses an electromotor in the same direction as 
the current which is produced by the electromotor, absorption of 
heat ensues ; if the current is in the opposite direction, heat is pro- 
duced ; the quantity of heat which is absorbed in the first case and 
produced in the latter is proportional to the intensity of the current 
multiplied by the electromotive force at the place where the change 
of heat ensues. 

If two heterogeneous metals are brought into contact with one 
another, an electromotive force ensues at the point of contact. 
If a voltaic current traverses the place of contact, there must 
either be absorption or production of heat. Here, then, we have 
the cause of Peltier’s phenomena. The quantities of heat ab- 
sorbed in the one and produced in the other case are propor- 
tional to the product of the intensity into the electromotive 
force. Hence, if with different intensities experiments are made 
with the same two metals, the differences in temperature must 
be proportional to the intensities, as has already been experi- 
mentally shown. But if, retaining the same intensity of the 
current, experiments are made with different metals, the quanti- 
ties of heat must be proportional to the electromotive forces. 
Hence by measuring the quantities of heat we should be na 
posit:on to arrange the metals in the actual electromotive series. 
But this series must be quite different from that obtained when 
the metals are arranged according to the observed differences in 
temperature; for these differences, besides depending on the 
quantities of heat absorbed and produced, depend also on the 
thermal capacities of the metals, on the greater or less degree of 
cooling during the experiment, and so forth. All experimenters 
who have worked at this subject have found the difference in 
temperature to be greatest at the contact of bismuth and anti- 
mony; but this by no means proves that the contact between these 
metals produces the greatest electromotive force. The difference 
in temperature must, as has been said, depend essentially on the 
capacity for heat. Comparing the thermal capacities for equal 
volumes of the metals with which Peltier’s experiments were 
made, it is found that bismuth has the least capacity of all me- 
tals, and next to itantimony. Hence, when the current passes, 


A 


268 Prof. Challis on a Theory of the Dispersion of Light. 


the contact between these two metals must show relatively great 
variations in temperature, without these indicating any consider- 
able electromotive force between them. 

If the metals are arranged according to the quantities of heat 
which are absorbed or produced in case a voltaic current traverse 
the place of contact, it does not seem to me that it is a priort 
certain that we should obtain the same series as that formed 
when they are arranged according to their electrical tension on 
contact. It seems conceivable that the magnitude of the cur- 
rent which a contact can produce does not depend simply on the 
tension which. the electricity can attain when the insulated 
metals are placed in contact, but also on the time necessary 
for the production of this state. Though this time is certainly 
very short, it may doubtless be comparable with the time for 
the passage of the current from one pole to the other. If it 
is indeed so, the ordinary electrical series for the case in which 
a real current is produced cannot without further proof be re- 
garded as the right one. What is the real state of the case must 
be decided by trustworthy measurements of the heat absorbed 
and produced. Peltier’s phenomena obtain thus an unexpected 
interest. If time and circumstances permit, I hope before long 
to make an experimental determination of the quantities of heat 
In question. 


——— 


XXXII. Comparison of a Theory of the Dispersion of Light on the 
Hypothesis of Undulations with Ditscheiner’s determinations of 
Wave-lengths and corresponding refractive Indices. By Pro- 
fessor Cuanuis, M.A., F.R.S.,; F.R.A.S* 


Te Theory of the Dispersion of Light which I proposed in 

this Journal in 1864 is, I believe, the only one which may 
be strictly said to rest on the hypothesis of undulations. It was 
commenced in the Number for June of that year; and in the 
Supplementary Number for December it 1s compared with the 
refractive mdices of two substances for seven principal rays, 
Fraunhofer’s values of the wave-lengths of the rays being adopted. 
At the end of an article on the Undulatory Theory of Light in 
the Philosophical Magazine for May 1865 the same comparison 


is made by means of Angstrdém’s values of 2 for the same rays. 
The theory is reproduced in my work ‘On the Principles of Ma- 
thematics and Physics ’—at first, just as 1t was originally pro- 
posed; but subsequently, while the work was in the press, it 
occurred to me that a course of reasoning somewhat different in 
principle would be more exact, and, accordingly, by another in- 


* Communicated by the Author. 


Prof. Challis on a Theory of the Dispersion of Light. 269 


vestigation (in pages 421-426) I obtained a new formula for 
dispersion. The numerical results from the two investigations 
(exhibited in page 427) show that the second formula accords 
with the experiments in a slight degree better than the first. 
Since the publication of that volume I have become acquainted 
with Ditscheiner’s measures of a large number of wave-lengths 
for dark rays of the solar spectrum, and of corresponding refrac- 
tive indices ; and my present object is to compare these data with 
the theory modified as above stated, Ditscheiner’s measures, 
accompanied by investigations of appropriate formule, are given 
in a memoir in the Sztzungsberichte of the Mathematico-physical 
Class of the Imperial Academy of Sciences at Vienna (vol. 1. 
part 2 (1864), p. 296). The values of X% were determined, 
according to Fraunhofer’s method, by the diffraction-spectrum. 
The mean interval between the lines of the grating, in default 
of means of measuring it directly, was, at first, inferred, by ob- 
servation and calculation combined, from Fraunhofer’s determi- 
nation of the value of for that component of the double Ime D 
which is nearest the violet end of the spectrum; and the wave- 
lengths obtained for the other lines were thus made dependent 


on that determination. Subsequently, having learnt that Ang- 
stro6m had employed a value of the interval between the lines of 
his grating obtained by direct mechanical means, Ditscheiner 
succeeded in effecting a like determination with respect to his 
own grating, and was thus enabled to calculate independent 
values of all the wave-lengths. The results of this calculation, 
which differ but little from those previously obtained, are given 
in the above-cited publication (vol. li. part 2 (1865), p. 289). 
Those of these values to which there are corresponding determi- 
nations of refractive indices, the number of which is seventy- 
three, are used in the subjoined comparison with theory. 

Before entering upon this comparison, I propose to give some 
account of the principles of the theory, and of the above-men- 
tioned modification of it. The diminished rate of propagation 
of waves in transparent substances is ascribed to the obstacle to 
the free motions of the particles of the ether caused by reflec- 
tions due to the incidence of the waves upon the atoms. These 
reflections are supposed to take place as if the fluid were incom- 
pressible ; and as they would thus be transmitted instantane- 
ously, the mean effect, at a given position, of the simultancous 
reflections from a vast number of atoms may be conceived to 
bear a finite ratio to the incident velocity, even though the space 
occupied by atoms should be extremely small compared to the 
intervening space. It is presumed that that ratio may be the 
same at different parts of the same wave, and, consequently, that 
the retarding force due to the atoms has a constant ratio to the 


270 Prof, Challis on a Theory of the Dispersion of Light. 


effective accelerative force of the ether. Hence putting «'a?f 
for the latter force, Kx'?a*f for the retarding force, and «?a?f for 
the accelerative force of the ether due to the actual variations 
of density, we have 


wa? f= K2a®f—Kr?af, or K?(14+ K)=k?. 


Putting, therefore, w for the ratio of « to x’, which is the ratio 
of the rate of propagation outside the medium to the rate within, 
it follows that 1+ K=,p?. Hence, since the retardation must 
vary ceteris paribus as the number of atoms in a given space 
(that is, as the density of the medium), if we put 6 for the den- 
sity, and H6 for K, we getu?=1+H6. The constant K, being 
by hypothesis the same for different parts of the same wave, will 
also be the same for waves of different breadths. 

In this reasoning the atoms are regarded as fixed. Supposing, 
as must be the case, that they are moveable about their mean 
positions of equilibrium, the retardation due to the reflections 
from each atom will be altered in the ratio of the velocity of the 
eether relative to the atom to the actual velocity of the ether. 
That is, @ being the distance at the time ¢ of the centre of the 
atom from a fixed plane perpendicular to the direction of the 
propagation of the waves, and V the velocity of the ethereal par- 
ticles at that distance, we shall have 


we—l= Hai 


_ we 
Vat) 


the medium being supposed at present to be a simple one. In 
order, therefore, to obtain a formula for yw it is necessary to cal- 


culate a 
dt Vie 
Now the velocity or of the vibrating atom may be considered 


to result from three different actions :—(1) the distribution about 
the surface of the atom of the condensation and pressure due to 
the incidence of a given series of ethereal waves, which, in fact, 
is the primary cause of its movement; (2) the resistance of the 
sether to the motion of the atom; (8) the action of the proper 
molecular forces of the medium called into play by the displace- 
ment of the atom. In my original researches I supposed that 
the first of these actions depended on the relative motion of the 
atom and the ether; but afterwards it occurred to me to reason 
as follows. The atom being supposed to have a vibratory mo- 
tion from any cause, conceive to be impressed upon it and upon 
the whole of the fluid at each instant this motion in the opposite 
direction. The atom will thus be brought to rest; and as the 
motion and propagation of the wayes will in no manner be 


Prof. Challis on a Theory of the Dispersion of Liyht. 271 


affected by a motion common to all the parts of the fluid, they 
will be incident on the atom just as before, excepting that by 
reason of this common motion a given condensation will reach a 
given point of space a little earlier or a little later than it other- 
wise would. As the effect of this inequality, as far as regards 
the action on the atom, is a quantity of the second order, it may 
be neglected in this investigation. Consequently the distribution 
of condensation about the surface of the atom is to be determined 
just as if the atom were fixed. 

The problem for the case of the fixed atom is discussed in the 
Number of the Philosophical Magazine for May 1866 (pp. 353- 
360), and in ‘The Principles of Mathematics’ (pp. 279-287 & 
441-446) ; and the expression obtained for the accelerative ac- 
tion on the atom, insignificant terms being omitted, 1s 


3H, dV 

EE wucaitia 
A being the ratio of the density of the atom to that of the ether, 
and H, a certain constant factor depending in an unknown man- 
near on the breadth of the undulations. 

The resistance of the ether to the motion of the atom may be 
at once inferred from the solution of the well-known problem of 
the resistance of the air to the motion of a ball-pendulum; and 
accordingly the part of the accelerative action due to this cause 

1 dx 

Bek at’ 
The molecular force of the medium called into action by the 
relative displacement of its atoms will, when the condition of 
transparency 1s satisfied, have a fixed ratio to the actual accelera- 
tion of the atom. I have therefore given it the expression 

etn. nara 
a? dt?” 
elasticity of the medium. 

From these considerations it follows that 

Gave Olle ON oly Oey, Ce ew 


Bet ON da 2A de Tat dP 


18 


the constant e? depending on the proper molecular 


: dx i ane: 
Hence, supposing V and a to vanish at the same time, which is 
di 

another necessary condition of transparency, we have by inte- 
grating, 

da OH x'?a? 

Vdt ~~ (1+2A)«'?a? — 2Ae? 

It appears from reasoning contained in the discussions above 

mentioned, that the constant H, is equal to unity for an incom- 


272 Prof. Challis on a Theory of the Dispersion of Light. 


pressible fluid, and that for a compressible fluid it is different for 
different values of X. According to the adopted hydrodynamical 
principles, this quantity becomes a function of only in conse- 
quence of the effect produced on the distribution of condensation 
about the surface of the atom by lateral spreading due to trans- 
verse vibrations, these vibrations being brought into action by 
the disturbance of the waves caused by their incidence on the 
atom. I have not succeeded in obtaining by a priori investiga- 
tion an exact expression for the condensation thus modified ; 
but from the general expression for the condensation in trans- 
verse vibrations I have inferred that the distribution of conden- 


peas Feu 1 : 
sation in this case must be a function of ' being the effec- 


i /2? 
tive breadth of the waves. (See Phil. Mag. (Supplement) for 
December 1864, p. 500, and ‘Principles of Mathematics,’ p.370.) 

Accordingly it has been assumed that, to a first approximation, 


k! 
H,=s(1— <3) 


k and k’ being unknown physical constants. Consequently, 
since N=pA! and c=px', the formula for dispersion in a simple 
Ea da 


medium becomes 
ERO: 
Bah -- nes ) 
a 


Hoo Vai > Sea 2A) Soe 


The same form of expression applies to a compound medium, as 
is shown in ‘ The Principles of Physics,’ pp. 429 & 430. In the 
existing state of physics it does not appear possible to obtain, 
either by theoretical calculation or by experiment, the values of 
the constants H, 4, 4’, A, and e?. But since the equation may 
be put under the form 3 


the values of A’, B’, and C! may be found by means of three sets 
of corresponding values of « and 2X given by observation. The 
formula may then be employed to calculate values of > from 
other given values of w; and a comparison of the results with 
the corresponding observed values of » will, in proportion to the 
degree of accordance, be evidence of the truth of the theory. 
Having gone through such calculations by making use of the 
before-mentioned values of 4 and X obtained by Ditscheiner, I 
have collected the results in the annexed Table, in which also 
Kirchhoff’s measures are inserted for the sake of identification 
of the lines. Instead of calculating the constants A’, B’, C 


Prof. Challis on a Theory of the Dispersion of Light. 273 


from the values of w and A for Fraunhofer’s lines B, E, H, which 
would probably be the most favourable for obtaining results in 
accordance with observation, in order to put the theory to a 
severer test I have calculated, first, with the data for the lines 
B, E, G, and then with those for C, F, H. As the comparisons 
in the two cases would necessarily be affected by errors in the 
data, and as I had no reason to prefer one set of data to the 
other, I have considered the mean between the values of » given 
by the two calculations to be a more correct expression of the 
theoretical result than either value taken separately. 

By the preliminary calculations the constants A’, B!, C’ were 
determined as follows :— 


By 1, log A'=1:0708283, log B’=0°30138700, C’=7-161816. 
By 2, log A'=1:0604669, log B'=0°2746509, Cl=7:057775. 


Excess of calculated wave- 


Designa-| 5. hoff? Ditschei- | Ditschei- Henge 
tion of IPCHAOH'Siner’s refrac-|ner’s wave- 
ray. measure. | tive index.| length. | By first |Bysecond 
calcula- | caleula- | Mean. 
tion. tion. 
Bers s: 593:0 1:61358 68833 0 +1317 + 58 
CIV hare. 694-0 1-61537 65711 — 80 0 — 40 
877°0 1-61824 61470 —106 — 66 — 86 
1D ey aise 1004:8 1-62020 59021 —100 — 78 — 89 
1135:0 1:62166 57193 + 92 +104 + 98 
1207°5 1:62274 56240 — 70 — 64 — 67 
1280-9 1:62363 55368 — 64 — 64 — 64 
1324°8 1:62415 54854 — 37 — 39 — 50 
1351°3 1:62448 54549 — 34 — 37 — 35 
1389-6 1:62494 54132 — 28 — 33 — $l 
1421°6 1:62530 53792 — 3 = {Y) = § 
Be ac 1523°5 1:62650 52783 0 — I] = & 
15775 1:62705 52349 — 7 — 19 = 1183 
1634:0 1-62760 51912 + 2 — 12 = & 
1648°8 1:62775 51809 — 10 — 24 — 7 
1655°6 1°62782 51754 — 8 — DY — 15 
1693°8 1:62817 515038 — 21 — 36 = Wo) 
1750-4 1-62872 51068 + 9 = § fo 
17774 1:62897 50879 el 0 JL 
1834:0 1:62953 50493 =O = 1183 A 
1885°8 1:63003 50145 a2 — iil = @& 
1920-0 1°63038 49914 en — 1% eo he 
1961°0 1:63075 49653 eels = & fe 
1989-5 1:63113 49412 + 7 — 13 = § 
2005:0 163133 49269 + 2] 0 + 10 
2041-4 163177 48990 + 19 = & He 
2067-0 1:63205 48791 + 42 + 20 + 31 
its Beane 2080°1 1:63225 48687 = 22 0 =e 
21198 1:63269 48317 +122 +100 +111 
2187-1 1:63390 47717 + 7 — 17 — § 


| | Excess of calculated wave- 
aaa Kirchhoff’s Ditschei- Ditschei- | = 
ion of | easure, (Bers refrac-\ner’s wave- ) 
ray. * | tive index.| length. | By first |Bysecond 
calcula- | caleula- | Mean. 
| tion. tion. 
2233°7 163446 47271 + 33 | + 9 |4 21 
2264-3 163492 47106 | + 42 |4+ 17 | + 30 
2309-0 1-63560 | 46742 | + 35 | + 10 | + 22 
2416-0 163718 46097 | —1438 | —169 | —156 
2436°5 1-63743 45901 — 7d — 99 — 86 
2467-4 1-63789 | 45606 |— 7 | — 32 | — 20 
2489-4 1-63818 45409 | + 49 | + 23 | 4+ 36 
2537-1 1-63886 45089 | + 42 |4+ 17 | + 30 
2566-3 1-63928 44880 | + 54 | + 28 | + 41 
2606-0 1-63986 44633 | + 33 | + 7 | + 20 
2627-0 1-64013 44498 | + 45 | + 20 | + 32 
2638-6 1:64031 44418 | + 44 |} + 18 | + 3] 
2670-0 1-64080 419392 | 4-22 |— 42 es 
2636-6 1-64101 44121 |} +30 |4+ 5 |4+ 9 
2721-6 1-64150 43908 |} +30 |;+ 5 |+ 18 
2734-9 1-64168 43813 | + 48 | +33 |4 —@ 
27756 164224 43600 | + 23 |— 2 | 
2797-0 1-64251 43466 | + 44 | + 20 | + 32 
| 2822-8 1-64287 43314 | + 48 | + 23 | + 36 
SG eacds 2854-7 164334 43170 0 |=—- 24 | — Bb 
2869-7 1-64352 43070 + 27 + 3 + 15 
a Niewcsd) | wakbliccss 1-64369 42953 | + 76 | + 52 | + 64 
, foe ae eee 1-6442] 42789 | + 34 |+ 10 | + 2 
ers 164448 42668 | + 50 | + 26 | + 38 
DB Wibecs| chien 1-64476 42555 | + 54 | + 31 | + 4 
aoe ee ee 164511 42425 + 50 + 27 + 38 
ee a 1-64536 49325 | +55 | +32 |4+4 
a en a 1-64569 42938 |} +18 |— 5 |+ 7 
ee ee ean 1-64606 42069 | + 49 | = a7 |= S85 
oe pe ee 1-64630 | 41871 | +159 | +136 | +148 
ee ee ee 164687 | 41792 | +31 |+ 9 |+2 
a er 1-64742 41626 | + 1 |— 22 | — 11 
BP Cbcssall | nsdn 164771 41498 |} + 27 | + 5 | + 16 
Po deses| © hhc: 1-64819 41392 |— 35 | — 56 | — 45 
ee oe a 1-64893 41077 |} + 27 | te FTF 1+ 
B Sod! adhe 16494] 40876 | + 67 | 4+ 47 | 4+ 57 
= one ee. 1-64966 40829 + 31 + il + 21 
oi) 165009 | 40685 | + 34 | + 14 | + 2 
Me css 1-65064 40506 | + 385 | + 16 | + 25 
Be cessed. mitectcnanc 165113 40392 — 7 — 26 — 17 
a ene ee ee 1-65194 40117 | + 15 |;— 8 /+ 6 
a? See ee 165317 39742 +17 | 0 |;+ 8 
ED scecwa) | Bc 1-65435 39405 | + 8 |— 8 0 


Table (continued). 


Prof. Challis on a Theory of the Dispersion of Light. 


In the foregoing Table Fraunhofer’s principal rays are indi- 
cated, as usual, by the letters B,C, D, E, F, G, H. The other 
letters were employed by Ditscheiner to designate lines for which 
there were no measures by Kirchhoff. The numbers opposite to 


Prof. Challis on a Theory of the Dispersion of Light. 275 


the double line D apply to the mean position between the com- 
ponents. ‘The refractive index corresponding to the measure 
1989-5 has been altered conjecturally, the given value (1-63133) 
having been the same as that corresponding tothe measure 2005:0. 

Respecting the numbers in the last four columns, it is to be 
stated that they express actual lengths in millimetres multiplied 
by 10°. It will hence be seen that the differences between the 
calculated and observed values of X are generally very small. The 
larger differences occur so exceptionally that they must plainly be 
referred to errors of the data from observation. This is especially 
the case with respect to the rays whose measures by Kirchhoff 
are 1135-0, 2119-8, 2416-0, and 2436°5, and the ray designated 
by the letter «. Leaving out of account the discordant results 
for the ray 1135-0, there seems to be a systematic variation be- 
tween the calculated and observed wave-lengths in the part of 
the spectrum from B to E, but not nearly in the same degree in 
any other part. Also it is to be noticed that there is a close 
agreement between the results from the two calculations, the 
difference in no case exceeding 26, excepting in the first three 
comparisons, for which the differences are respectively 117, 80, 
and 40. This circumstance might be supposed to indicate a 
discrepancy in the data for the rays B and C. 

Tn order to clear up this point, 1 went through for the seven 
principal rays the same calculations as those by which the Table 
above was constructed, only using, instead of Ditscheiner’s values 


of X, those given by Angstrom in his Recherches sur le Spectre 
solaire, pp. 81 & 32. The results in the two preliminary calcu- 
lations of the constants A’, B’, C’ were 


log A'=1°0870469, log B'=0°3399332, C'’=7:343192; 
log A'=1:0576341, log B/=0°2657302, C’=7-028368. 


The excesses of the calculated values of X resulted as follows :— 


| l 


i 
| A Angstrom’s Excess of calculated wave-length. | 
_ Former 
Ray. Wave- | 
| length. | By first | By second | M ee | 
} . 3 . Mean. 
| calculation. calculation. 
| Bijis.- | 68671 | Oo | +191 | +95 | +658 
See | 65621 | —I31 | 0 |. —65 .| . —40 
Dy sseee: | 58921 | —108 | — 67 | iden (ellie 
Bit. | 52691 | 0 Ae aig miceigs !ijy venus 
a | 48607 | + 13 Sane 1G dpe 
Bees... _ 45073 Pes | ke 12 
= ode | 39681 | - 52 | eet 16 + 8 


276 Prof. Challis on a Theory of the Dispersion of Light. 


nearly the same law as in the former comparison, and that the 
differences between the results of the first and second calcula- 
tions are, for these three rays, even greater than before. These 
inferences make it probable that the discrepancies are not due to 
error in Ditscheiner’s wave-lengths for the rays B and C. 

I next performed the same calculations with Fraunhofer’s 
values of w for flint-glass No. 13 and Ditscheiner’s values of X, 
and obtained the following results :— 

By first calculation, 


log A'=1-1982448, log B/=0-5816970, C!’=8-687700; 
by second calculation, 
log A'=1°1255825, log B'=0°4350178, C!’=7-746712. 


Excess of calculated wave-length. 


Ray. | Value of pw.) Value of 2. 
By first | By second Mean 
calculation.| calculation. ; 
1B} dgagoe 162775 68833 0 + 32 + 16 
(ipl eas: 162968 65711 +7 0 + 4 
Ro! 59053 —88 —147 —117 
IBY césoed 163504 58989 Gey oly 95 _ 53 
1B) o5 386 164202 52783 0 — 65 — 32 
BF accee 164826 48687 +47 0 + 23 
Go en ee 1-66029 43170 0 + 10 + 5 
HM S48 1:67106 39742 —69 0 — 35 


In this case there is not the same discrepancy between the 
comparisons for the rays B and C as in the two former calcula- 
tions, and the law of the mean excesses is in some degree altered. 
It must not, however, be concluded that the previous discord- 
ances arose from inaccuracy in either or both of Ditscheiner’s 
values of yu for those rays, because it is possible that differences 
in the character of the results may be due to differences in the 
qualities of the glasses employed, and that the dispersion-formula, 
which can only be regarded as approximate, may apply more 
accurately in proportion as the refractive and dispersive powers 
are larger. This point will be adverted to again presently. 

It being uncertain to which of the two lines D Fraunhofer’s 
determination of mw applies, I have compared the calculated 
value of X with the observed value for each line. ‘The excesses, 
given above within brackets, show that the more refrangible line 
is considerably more in accordance with the theory than the other. 

The calculations were then repeated with the same values of 


pw and with Angstrom’s values of © already cited, and the wave- 
length obtained for D was compared, as above, with the observed 


Prof. Challis on a Theory of the Dispersion of Light. 277 


wave-lengths of both lines, viz. 58951 and 58891, the mean be- 
tween which was used in the previous comparison. The results 
from the two sets of data were as follows :— 


log A’=1-2351358, log B'=0-6461311, C!=9-229205 ; 
log A'=1°1215922, log B/=0:4245740, C'=7-699899. 


Excess of calculated wave-length. 


Ray. 
By first By second 

Wire iion. Ne iG Mean. 
Beast . 255.5: « )) +106 + 53 
Oe Geen -43 0 = 4) 
D j —94 —135 —I114 
Se ae i) | —34 Ypy 75 ae 54 
Big tet seis. 0 — 58 — 29 
te a +37 0 + 18 
(Cri a 0 + 30 + 19 
PME ees cetecs —118 0 — 59 


Here again the mean excesses for B and C are more accord- 
ant than those deduced by the former calculation from Ditschei- 
ner’s values of uw and the same values of A. Also the law of the 
mean excesses agrees generally with that of the means obtained 
by the next preceding calculation, although their amounts are 
somewhat larger. As the more refrangible of the lines D again 
gives more consistent results than the other, the theory, I think, 
may be considered to have decided that this line was bisected by 
Fraunhofer. In future calculations I shall assume that this was 
the case. 

It remains to discuss more particularly the consequences of 
applying the dispersion-formula to substances of different densi- 
ties and different refractive powers. With this object in view I 
begin with comparing Ditscheiner’s values of » for the seven 
principal rays (that for D being 58989), with values calculated 
by the formula from Fraunhofer’s refractive indices for flint-glass 
No. 23 (prism of 60°) and flint-glass No. 8. The specific gravi- 
ties of the two substances are respectively 3°724 and 3°512 (that 
of No. 13 is 3°723). In these two instances the calculation of 
A', B', C' was made from one set of data, viz. the observed values 
of w and X for the rays B, KH, G. The following results were 
obtamed, C.—O, signifying the excess of the calculated above 
the observed value of %:— 

For No. 23, 

log A’=1:0667953, log B'=0°2920263, C'=7-095094; 
for No. 3, 


log A'=1:0581414, log B!=0°2846254, C’=7-061636. 


278 Prof. Challis on a Theory of the Dispersion of Light. 


Flint-glass Flint-glass 
Ray. No. 23. Ca—O,. No. 3. Cva—O,. 
Value of z. Value of pu. 
SL Baccaoe 1:62660 0 160204 0 
Gcpaoe 162847 6 1:60380 —128 
LD pendehaes 1:63367 —36 1-60849 —131 
Bees es 164050 0 1°614538 0 
Hat ce sc 1-64676 + 6 162004 + 48 
Gee 1:65885 0 163077 0 
EL oes 1-66969 +23 1:64037 — 28 


Here it is observable that the values of C,—O, for No. 23, 
like those for the similar substance No. 13, are very small, and 
considerably less than the values for No. 3. The law of the 
excesses of calculation for the latter substance is nearly the same 
as that of the excesses deduced with the same values of X from 
Ditscheiner’s values of w, but they are of larger amount, at the 
same time that the refractive indices are less. It seems, therefore, 
that the dispersion-formula becomes inexact in proportion as the 
refractive power of the substance is less than that of No. 13 or 
No. 23. I found, in fact, on applying it, just as in the last two 
instances, to Fraunhofer’s crown-glass No. 138, the specific gra- 
vity of which is 2°535, and the refractive and dispersive powers 
very low, that it altogether failed. Yet, since the results of the 
other calculations seemed to indicate generally a systematic de- 
viation of the calculated from the observed vaiues cf X, there 
was a probability that the deviations were such as might be cor- 
rected by a more approximate formula, and that the failure in 
the instance of the crown-glass might be due to inadequate ap- 
proximation, and not to error in the principles on which the 
formula was founded. In order to obtain a nearer approxima- 
tion I reasoned as follows. 

Ii the principles of the theoretical investigation be true, the 
variations of «* for a given substance depend wholly on varia- 


: ; é 1 
tions of 503 that is, “2 is a function of 52 and constants. We 


may therefore assume that 


Uo ay gu 
what SESE 


To ascertain the degree of approximation attainable by this series, 
I first applied it in the instance of the crown-glass No. 13, 
taking only the first three terms. The values of Ag, Aj, Ao, cal- 
culated from the subjoined values of « and A for the rays B, H, H, 
were found to be 


A =2'254474, A,=[0-4926929], —A,=[1:2120022]. 


+ —* + &e. 


Prof. Challis on a Theory of the Dispersion of Light. 279 


Hence the following results were obtained, C,—O, signifying 
the excess of the calculated above the observed value of p:— 


Ray. [en Ye GAO. 
iz) oadeeaae 152431 68833 0:00000 
feeb). 152530 65711 — (00288 
te 1-52798 5:8989 —0-00142 
Pt ca. : 1-53137 52783 0:00000 
1.1 iin ea 153434 4:8687 | -10-00080 
Gee a 1-53991 43170 | +0-00100 
Hine. 2S. 154468 39742 0:00000 


The values of C,—O, forthe rays C, D, F, G, inasmuch as they 
correspond to large values of C,—QO,, show that it is necessary 
to take into account a greater number of terms of the series. It 
was, in fact, to be expected, from what was said above, that an 
approximation could not be obtained by determining only three 
constants. 

The above data for the rays B, D, F, H having been employed 
for calculating the constants of four terms of the series, the 
results were 


A =2'290885, A,=[0-2260364], —A,=[0-8234811], 
Ag= [1°7942593)]. 


Hence on calculating the values of w for the rays C, E, G by 
means of these constants and the above values of X for the same 
rays, the excesses C,,—O,, to five places of decimals were found 
to be respectively + 0-00001, 0-00000, —0-00006. These re- 
sults prove that the relation between mw and X for this substance 
is very closely expressed by taking account of only four terms of 
the series. 

Lastly, I employed the same series to four terms to calculate 
C,—O,, for the rays C, EH, G for water, the means (to five places 
of decimals) of two determinations of the refractive indices by 
Fraunhofer being adopted, viz. 


Bu=1:33096, Cu=1:33171, Dw=1:33358, Ew=1-33585, 
Fu=1:33780, Gu=1:34128, Hu=1°34417. 
Calculations made with the data for B, D, F, and H gave 
Ape 7438267, 7A = (010493790) A, — [(0:9854382" 
Aa— (l-8i7 2302) ; 


and the values of C,—O, found for the rays C, EH, G were re- 
spectively —0:00002, +0°00002, —0-00005. These differences, 


280 = Prof. Challis on a Theory of the Dispersion of Light. 


which are of the same order as those between the different expe- 
rimental determinations of yw, sufficiently attest the accuracy of 
the formula. 7 

I take occasion to advert here to a memoir by the Astronomer 
Royal in the Philosophical Transactions for 1868 (part 1, p. 29), 
the object of which is to calculate the wave-lengths correspond- 
ing to Kirchhoff’s scale-measures of lines of the spectrum, in 
order to increase the scientific value of these measures. The 
calculations for this purpose are based upon Ditscheiner’s deter- 
minations of the wave-lengths for the lines B, C, D, H, F, G. 
Kirchhoff’s measure is expressed as a function of the correspond- 
ing wave-length by a simple algebraical formula of interpolation 
containing six constants, the values of which are found by means 
of the scale-measures and wave-lengths of the above six lines. 
Mr. Airy chose this method because he did “ not know any phy- 
sical reason for adopting one formula in preference to another.” 
The method appears not to have been successful, several of the 
differences between the computed and observed wave-lengths in 
the part of the spectrum between F and G ranging between 800 
and 900, and in some cases exceeding the latter number. In 
the Table given in this communication, the greatest difference 
between the calculated and observed values of X in the case in 
which the calculations were founded on the values of w and X 
for only the three lines B, BH, G is 106, a few larger (evidently 
affected by errors of observation) being excepted. The superior 
accuracy of the results thus obtained is not to be attributed to 
my calculations having been made with refractive indices instead 
of Kirchhoff’s measures, because these are data of the same kind as 
the others and equally trustworthy. My better success is rather to 
be accounted for by the advantage I have taken of the indications 
of the Undulatory Theory of Light, and may, I think, be justly 
regarded as some evidence of the truth of the proposed theory of 
Dispersion. Since Kirchhoff’s scale-measure is a function of p, 
the results of the foregoing calculations made by assuming for 

2 Ne cod: rag ae ei oni 

#" a series proceeding according to powers of <3, would seem to 
prove that, by the intervention of a like series for the scale- 
measure, it would be possible to calculate the corresponding 
wave-length with great accuracy, 


Cambridge, August 20, 1869. 


fe 2S la} 


XXXIII. Observations of the Corona during the Total Eclipse, 
August 7th, 1869. By Professor Epwarp C. Pickrrine*. 


AMONG other expeditions to observe the recent eclipse was 

one under the direction of Professor Henry Morton, sent 
by the Nautical-Almanac Office to photograph the sun. I was 
attached to this party to make general and physical observations, 
and from our station at Mount Pleasant, Iowa, arrived at the 
following results. 

It is commonly supposed that the light of the corona is polar- 
ized in planes passing through the sun’s centre, and that it shines 
by reflected light. Wishing to verify this observation, I pre- 
pared an Arago’s polariscope (in which the objects are viewed 
through a plate of quartz), and a double-image prism of Iceland 
spar. The two images appear of complementary colours when 
the light is polarized, the tint changing with the plane of polar- 
ization. I therefore expected to see two coloured coronas, the 
tint of each portion being complementary to that of the part at 
right angles to it, and the colour revolving with the polariscope. 
In reality the two images were pure white without any traces of 
colour; but the sky adjoining one was blue, adjoining the other 
yellow. As the instrument is of considerable delicacy, we must 
conclude that little or no polarized light is emitted by the co- 
rona. The sky adjoining it, however, is polarized in a plane in- 
dependent of the position of the sun, since its colour (as seen in 
the polariscope) is the same whether above, below, or on one 
side of it. The most probable explanation of this curious phe- 
nomenon is, that the earth beyond the limits of the shadow, being 
strongly illuminated, acts as a new source of light, and thus gives 
rise to a polarization in a plane perpendicular to the horizon. 

In hopes of determining the cause of discrepancy between 
this observation and those previously made, I have endeavoured 
to learn what form of polariscope has heretofore been used ; but, 
unfortunately, in most cases no description has been published. 
One observer used a Savart’s polariscope, and, holding it with 
its principal plane vertical, found strong traces of polarization in 
this plane. This observation, however, agrees with mine if we 
suppose that the polarization of the sky was taken for that of 
the corona, a natural mistake with this form of instrument. 
Another observer, who used a single plate of tourmaline, saw no 
evidence of polarization, that of the sky being too feeble to be 
perceived in this way. I verified my results with a simple prism 
of Iceland-spar, with which two images of the corona were seen 
precisely alike and showing no signs of polarization. We can- 
not infer from this that the corona is self-luminous, since polar- 


* Communicated by the Author. 
Phil. Mag. 8. 4. Vol. 38. No. 255. Oct. 1869. U 


282 Prof. E. C. Pickering’s Observations of 


ization is produced only by specular and not by diffuse re- 
flection. 

The spectrum of the corona was observed in the following 
manner. A common chemical spectroscope was used; but in- 
stead of attaching it to a telescope, it was merely pointed in the 
proper direction a short time before totality. As its field of 
view was 7 or 8 degrees in diameter, the sun remained in it for 
a considerable time, and the spectrum obtained was that due to 
the corona, protuberances, and sky near the sun. Qn looking 
through the instrument during totality, a continuous spectrum 
was seen free from dark lines, but containing two or three bright 
ones—one near H, anda second near C. At the time, I supposed 
that these were due to the protuberances; but Professor Young, 
with a large spectroscope of five prisms, found a line near HE 
which remained visible even when the image of the protuberance 
‘was moved off the slit, and therefore inferred that it was due 
to the corona. He also found the continuous spectrum free 
from dark lines—and that one, perhaps three of the bright 
lines coincide with those of the aurora borealis. These results 
would lead to the belief that the corona is self-luminous, the 
bright lines rendering its gaseous nature probable. If it isa 
part of the sun, even the remoter portions are one hundred times 
as near as the earth, and would receive ten thousand times as 
much heat, which would be sufficient to raise any known. sub- 
stance to incandescence. 

Other observations, however, point to quite a different con- 
clusion. A thermometer with blackened bulb was exposed to 
the sun’s rays and the temperature recorded every five minutes. 
I found that it began to rise some time before contact, descend- 
ing again as soon as the moon’s limb became visible. It did 
not reach its former temperature until about a quarter of an hour 
after the eclipse began, or until a seventh of the sun’s disk was 
obscured. The approach of the moon, therefore, appeared to 
cause an increase in the sun’s heat. The amount of the change 
was only about 1°°3 C., the total difference between this ther- 
mometer and one in the shade being about 18° C., or in the 
ratio of 1 to 14. This fraction is but one-half of that given 
above, owing perhaps to the diminution of heat on the borders of 
the sun. During totality the difference between the two ther- 
mometers was almost nothing. In examining the photographs 
taken by the party, it was noticed that, while the light dimi- 
nished near the edge of the sun, the moon’s limb was very di- 
stinct, and that there was a marked increase in the light of the 
parts nearest it. It was suggested that this might be a subjec- 
tive effect ; but an examination of the photographs is sufficient to 
convince any one that the appearance is areal one. The glass 


the Corona duriny the Total Eclipse, August 7, 1869. 283 


positives especially show that this effect extends over a large part 
of the sun’s disk. The exposure was rendered instantaneous by 
passing a diaphragm with a slit in it in front of the camera, the 
rapidity of motion being regulated by a series of springs. Any 
irregularity in the motion would cause variations in shade in the 
photographs; but these would form bands parallel to the slit, 
while the shade mentioned above was not parallel to it and was 
curved so as to follow the moon’s edge. Since, then, there is an 
increase both of the actinic power and of the heat, it would seem 
that these effects are real, since the methods of observing them 
are so totally different that no error in one could be introduced 
into the other. The only explanation of the phenomenon that 
seems possible is to assume the presence of a lunar atmosphere. 
The corona would then be caused by refraction, light reaching 
the observer from parts of the sun already eclipsed. Although 
for various reasons this hypothesis is unsatisfactory, yet it is 
strengthened by other observations. The protuberances have 
often seemed to indent the moon’s edge, an appearance usually 
ascribed to irradiation. Several of the photographs, however, 
show this same effect ; and in some of them the exposure was so 
short and the edges of the protuberances are so well defined that 
it cannot be caused by the intensity of their light, but must have 
its origin outside of the eye of the observer. It is noticeable on 
all sides of the moon, sometimes in half a dozen protuberances 
in a single photograph. An atmosphere of rapidly increasing 
density might produce this effect by reflection, and of course 
would not influence the corona if it was caused by refraction. On 
this supposition reliance could not be placed on measurements 
of the moon’s diameter by occultations, or by contacts during 
eclipses, and would account for the uncertainty of this constant. 

The principal reason for supposing the corona a portion of the 
sun is, that during totality it does not appear to move with the 
moon, but remains concentric with the sun, or, more properly, 
is brightest where the sun’s edge is nearest. Many of the pho- 
tographs show this very well, the difference on the two opposite 
sides of the moon being very marked. Now this effect would 
be explamed equally well by supposing the corona caused by 
refraction. For the centres of the sun and moon never differ 
during totality by more than half a digit, while the breadth of 
the corona is sometimes several times as much ; so that merely 
covering a small portion of it would not produce a greater di- 
minution of light than would be caused by a slight change in 
the direction of the sun’s rays shining through a lunar atmo- 
sphere. On the other hand, it is difficult to conceive of an at- 
mosphere dense enough to produce these effects, and yet so 
transparent that the edges of the full moon are perfectly di- 

U2 


284 Dr. H. Herwig’s Investigations on the Conformity 


stinct, and that the light of the sun during an eclipse should be 
increased rather than diminished. Again, we should expect 
that such variations would be produced by changes of tempera- 
ture that they could scarcely fail to be detected. 

We then conclude that the polariscope gives only negative re- 
sults, and cannot be regarded as proving that the light is reflected. 
The evidence of the spectroscope needs confirmation, since the 
dark lines may have been invisible owing to the feeble light of 
the corona. but if the observations with it are correct, the self- 
luminous character of the corona is established. The thermo- 
metric and actinic experiments point towards a lunar atmosphere 
as the cause of the corona. 

In the above I have endeavoured to give the evidence in favour 
of each view, unbiased by any theory, leaving to those best able 
to judge to determine whether either explains all the facts ob- 
served. The absence of a lunar atmosphere is so generally ad- 
mitted, that its existence is suggested only with reluctance, and 
merely as the most natural explanation of the observations. 

Boston, U.S., Sept. 1, 1869. 


XXXIV. Investigations on the Conformity of Vapours to Mariotte 
and Gay-Lussac’s Law. By Dr. Hermann Herwie*, 
[With a Plate. ] 


oni 

HE relation which, according to the twofold law of Mariotte 
and Gay-Lussac, in the case of an elastic fluid connects 
the three quantities the pressure P, the volume V, and the ab- 
solute temperature a+¢, cannot, after the experiments of Reg- 
nault, be considered strictly valid for permanent gases. Many 
important deviations from this law may be acounted for by the 
vapours being near their point of condensation. Very few direct 
experiments have been made as to the actual relation holding in 
the case of vapours between the quantities P, V, and (a+/¢). 
More frequently has half this problem been attacked, by assuming 
the constancy of one of these three quantities and deducing the 

reciprocal dependence of the other two. 

The first more nearly exact numbers were given almost simul- 
taneously by Bineau and Cahours. Bineaut+ found the vapour- 
densities of aceticacid, of formic acid, andof sulphuric acid too high; 
whereupon Cahours pointed out the influence of the selection 
of too low temperatures by Bineau; for he showed for several 
bodies under a constant pressure (of one atmosphere) the mutual 

* Communicated by the Author, having been read before the Nieder- 
rheimische Gesellschaft fir Natur- und Heilkunde, August and November 
1868. Translated by H. R. Greer, Esq., B.A. 

t Comptes Rendus, vol. xix. p. 767. 


of Vapours to Mariotte and Gay-Lussac’s Law. 285 


dependence of temperature and density, 7. e. of temperature 
and volume. Cahours’s investigations do not justify a wider 
conclusion than the general one that these bodies exhibit a 
vapour-density more widely different from the theoretical one the 
nearer they are to their condensation. Bineau then furnished a 
few numbers concerning the relation between all three quantities, 
P, V, and a+¢, for the three above-named acids. However, 
these few numbers demonstrate only the absolute fact of a de- 
parture of vapours from the laws of the ideal gaseous condition. 

Regnault showed later* for aqueous vapour, that at low tem- 
peratures (from 30° to 55°) it does not conform to the laws of 
gases until the tension amounts to about ‘8 of the maximum 
tension corresponding to the particular temperature. 

More detailed investigations respecting the same vapour were 
instituted by Fairbairn and Tate+. These physicists determined 
the specific volume of perfectly saturated vapour for temperatures 
from 136° to 199° and from 243° to 288° Fahr., and, further, 
deduced the coefficient of dilatation for vapour heated some de- 
grees above the latter temperature. Their method consists in 
heating different quantities of water to the same degree in two 
communicating globes; a change in the levels of the mercury 
enclosed in them indicates the moment when the smaller mass 
of water is changed entirely into vapour, and so a less ten- 
sion commences to be exerted. But in this mode of operating 
there lurk many sources of error. My own experiments have 
above all things assured me of this, that it is by no means at the 
same instant when the temperature that has been reached requires 
theoretically a certain density that the vapour will indicate the 
corresponding pressure, but a certain time is requisite for the 
manifestation of this condition. I have found generally that the 
vapour does not pass instantaneously even from a superheated 
state into another degree of superheating as soon as the external 
circumstances are produced. Much more slowly will the forma- 
tion of stable conditions proceed at the limit of the saturated 
State. 

Besides this incorrectness in the method of Fairbairn and 
Tate, it appears also, from the arrangement of their bath, to be 
scarcely possible that the temperatures prevailing im the globes 
should be sharply defined. 

Hirn also has investigated the case of aqueous vapourt. He 
has calculated the volume of the (superheated) vapour under 
pressures of 1, 3°5, 4, and 5 atmospheres, and at a few different 
temperatures for each. Thus the degree of the dilatation of super- 
heated aqueous vapour is maintained under different circum- 

* Mém. Acad. Scien. vol. xxvi. p. 700. 


+ Phil. Mag. S. 4. 186], vol. xm. p. 230. 
{t Théorte Mécanique de la Chaleur, 


286 Dr. H. Herwig’s Investigations on the Conformity 
stances. Unfortunately these experiments are not very numerous 
(in all about twenty). 

Quite recently Horstman has published* experiments on the 
interdependence of the pressure, volume, and temperature of the 
vapours of bisulphide of carbon and of ether; but these he does 
not consider sufficiently trustworthy to warrant the deduction of 
a law from them. More correct are his experiments on the inter- 
dependence of temperature and vapour-density, under a pressure 
of one atmosphere, for ether, water, and acetic acid, which lead 
to the same result as the experiments of Cahours. 

The survey of these incomplete observations shows that many 
experiments are still necessary in order that the problem so 
peculiarly interesting for the mechanical theory of heat may 
meet with its solution. Even for one limit of all the conditions 
of vapour which come into question here, viz. the case of perfect 
saturation, a very imperfect support has been afforded by obser- 
vations to the theoretical speculations concerning the mecha- 
nical theory of heat. According to a method which I will pre- 
sently describe, I have attempted to furnish some contributions 
to the solution of this problem. 


§ 2. 

The apparatus, which is intended to render a simultaneous 
variation of pressure, volume, and density possible, was indicated 
to me by Professor Willner, to whom I return my best thanks 
for the friendliness with which he always allows my work to be 
carried on in his laboratory. 

The vapour was placed over mercury, in a divided carefully 
calibrated tube (ad, fig. 1, Plate II.), of 3-9 centims. diameter 
and 48 centims. length, which was firmly clamped, with its lower 
end open, by means of an india-rubber plug im an iron sheath. 
By means of a screw and a piece of caoutchouc this sheath was 
fastened in a cavity in a thick iron plate (7 s), 15 centims. long 
and 10 broad; in this plate was a second cavity, connected with 
the former by an interior canal, and in which a smaller iron 
sheath was similarly fastened. In this last sheath there was 
fastened, by means of an india-rubber plug, a tube 6°8 centims. 
wide, 2°6 centims. long, terminating above in a narrow tube (cd), 
which served as a reservoir for the mercury which would overflow 
from the calibrated tube when filled with vapour. The apparatus 
was placed in a copper bath, 64 centims. high, 25 long, and 16 
broad, in the two front sides of which were glass plates, so that 
both tubes were visible in their whole circumference during the 
observation. On the two other sides of the bath there were cases 
closed at the top and cut out of sheet iron; under these the heating 
gas-flames could be keptquite steady. The temperature of the bath 

* Liebig’s Annalen, Suppl. vol. yi. p. 51. 


of Vapours to Mariotte and Gay-Lussac’s Law. 287 


was indicated by fine Geissler normal thermometers graduated to 
the tenth part of a degree, which were controlled by comparison 
with other normal thermometers, and by repeatedly checking their 
fixed points. By means of a double stirrer, which could be rapidly 
moved up and down, a uniform temperature was preserved 
throughout the bath. Outside the bath a T-shaped glass tube, 
pomn, was now connected with the protruding end of the tube, 
ed, by an india-rubber tube and some luting-wax. The descend- 
ing branch (0 n) of this tube, which was provided with a perforated 
glass cock, was connected with an air-pump, while the other end, 
om, conducted into a chloride-of-calcium tube, ~, and thence 
into-a manometer, ef. The connexion between these last two 
ends was made by means of an india-rubber plug, which em- 
braced the narrow tube and was forced into the larger one. All 
the points of connexion were so tightly secured that the appara- 
tus, so long as it was in use, was perfectly air-tight, even under 
the highest ranges of the manometer. A barometer (9) of a 
very wide bore gave the atmospheric pressure, whilst a thermo- 
meter (¢') placed beside this and the manometer gave the corre- 
sponding temperature. 
The course of investigation was as follows :—As soon as the 
calibrated tube, being perfectly dry, was filled with warm, very 
pure and dry mercury, freed to the utmost from air, and when a 
bursting bulb containing a weighed quantity of fluid had been 
placed on this, it was closed by means of a small wooden 
disk, lied on one side with caoutchouc and provided with a 
knob on the other, and being then inverted was placed in the 
larger iron sheath. The latter operation was rendered possible 
by placing about the sheath a wooden case which, filled with 
mercury, afforded plenty of room for the purposes of manipula- 
tion. Into the smaller iron sheath the tube cd was introduced 
half filled with mercury. The remaining half of the same, being 
still free, served for the reception of the mercury that over- 
flowed from the calibrated tube in the course of the experiment, 
while the circumstance that the lower half already contained 
mercury facilitated the necessary compression. For compres- 
sions, the calibrated tube a 0, as well as the mdia-rubber collar 
embracing it, was secured firmly to the iron sheath by means of 
iron rods and a cross tie. ‘This portion of the apparatus being 
thus prepared was placed in the bath, and, with the principal 
.tube in a strictly vertical position, was united, after the fashion 
described above, to the other part, which was fastened to a strong 
fixed table on which the whole stood. Now, to measure the 
mass of air from which such a large tube could scarcely be kept 
entirely free, the air in the intermediate part of the apparatus 
(dp omue) was greatly rarefied by means of the air-pump while 
the bath was kept at a given temperature; and after closing the 


288 Dr. H. Herwig’s Investigations on the Conformity 


stopcock at n the apparatus was thus kept unchanged for some 
time. Hence the air collected itself over the mercury which 
lay deep in the tube ab; and when this had been effected, the 
tightness of all the communications of the apparatus could be 
simultaneously controlled. 

Then by varying the pressure of the air in the intermediate 
part of the apparatus, the volume of the air confined in the tube 
ab was made to vary, and that from the largest to the smallest 
possible volume, while the simultaneous states of pressure and 
volume were, naturally, measured with the bath at constant 
temperature. To determine the pressure there were six mercury- 
levels to be measured—besides those of the barometer and ma- 
nometer, those in the tubes ab and cd. A very excellent ca- 
thetometer with a corrected telescope, by Staudiger of Giessen, 
which admitted of reading off to the tenth part of a millimetre, 
was used for this purpose. From one set of determinations of 
the simultaneous pressure and volume of the enclosed air, the 
quantity itself was determined with perfect accuracy. They 
could also be applied to the purposes of direct calculation im 
afterwards measuring the total tension exerted in the tube ad; 
this, however, was never very great. 

Now the bulb filled with hquid was burst, and to obtain 
the solution of the real problem, viz. the determination of the 
volume, pressure, and density of vapour formed under differ- 
ent circumstances, we proceeded as follows. The relation be- 
tween pressure and volume, always at a constant temperature, 
was to be sought from the point of saturation of the vapour up 
to the point where, for this temperature, it follows Mariotte’s law ; 
and different temperatures would be investigated in this wise. For 
this purpose, first of all, a definite temperature of the bath was 
maintained with the greatest care, which could be effected very 
readily by reason of the large size of the bath (25 litres) and 
the mode of heating employed, which was scarcely disturbed by 
draughts. It was possible to maintain the temperature invariable 
within 0:1 of a degree for a series of hours, and during the time 
of measurement to keep it steady to :05 of a degree. The 
temperature being constant, then, as in the measurement of 
the air, as large a volume as possible of vapour was produced, 
and made to pass thence into a smaller volume by means of 
the gradual introduction of air into the intermediate part of the 
apparatus. However, before taking a measurement of the coex- 
isting pressure and volume, a considerable pause was made each 
time so as to allow the condition of the vapour to become sta- 
tionary. The commencement of the stationary condition could 
be recognized by the repeated measurements. 

We may remark that the converse process (of passing to a 
larger volume from the state of saturation of the vapour by 


of Vapours to Mariotte and Gay-Lussac’s Law. 289 


means of a gradual rarefaction of the air in the intermediate 
part of the apparatus) does not recommend itself. We should 
then run the risk of individual particles of fluid adhering to the 
glass, without evaporating, perhaps much longer than would 
correspond with the par ticular temperature and rarefaction of the 
air. However, before any measurement was taken, we kept the 
vapour for a long time dilated to such a volume that it obeyed 
Mariotte’s law a the defined temperature, and then allowed it 
to proceed to asmaller volume by the gradual introduction of the 
air, whereby a longer time was allowed for the acquisition of a con- 
stant condition before each measurement of the vapour, so that we 
had more confidence that we were observing circumstances which 
actually corresponded to the external pressure and temperature. 

The determination of the pressure by the measurement of the 
six mercury-levels could be made very accurately with the above- 
named cathetometer. The cathetometer itself, which stood on a 
strong fixed table, was daily corrected. 

Through the telescope of the cathetometer we could clearly 
read off the volume of the vapour found in the calibrated tube to 
the tenth part of a cubic centimetre. Having measured the 
volume and pressure coexisting at the given temperature, we 
then subtracted from the latter the pressure exercised under these 
circumstances by the air-bubble, which had been determined 
first of all. For each temperature, the volume v and the pres- 
sure p of the vapour were measured from the maximum of ten- 
sion, 2. e. from the saturation of the vapour, to such a distance 
from saturation that the vapour followed Mariotte’s law. The 
commencement of this latter was manifested by the constancy of 
the product pv, which up to this time had been always increasing. 


3. 

One word here as to the ioetbaey of the numbers thus arrived 
at. Neither the apparatus nor the method of investigation can 
admit of errors from any other source than the two usual ones, 
which cannot be quite avoided, viz. slight variations of tempera- 
ture in the bath, and slight irregularities in placing the catheto- 
meter on the six quicksilver-levels. As to the first, it has been 
already remarked that the variations of temperature arising du- 
ring the measurement did not amount to ‘05 of a degree. The 
error arising hence in the estimation of the tension (which was not 
necessarily in strict accordance with the same temperature, yet at 
most could vary from the specified temperature on either side to 
the extent of 0°5 of a degree) 1s greater or smaller as the variation 
of the tension with the temperature is greater or smaller. The 
extreme case must be that of the maximum tension. Taking the 
maximum tension of alcohol at 69° as 537°63, a variation of tem- 
perature of 0°°05 would correspond to about Lmillim. However, 
that the errors which actually occurred never reached these amounts 


290 Dr. H. Herwig’s Investigations on the Conformity 


is shown by a mutual comparison of the maximum tensions at dif- 
ferent temperatures. ‘l’o the sum of the errors in tension 1s still 
to be added the influence of the second of the above-named cir- 
cumstances, viz. the variation in the position of the cathetometer 
when placed successively on the six quicksilver-levels, which can- 
not have been of precisely similar form in all respects. But 
in general we found under the maximum tension a deviation of 
only O°5 of a millim. from the mean; the greatest deviation that 
occurred is *6 of a millim. in the case of aleohol at 62°-9, where 
the mean of eight measurements of maximum tension amounted 
to 96°83 millims., while the measurement in which the aberra- 
tion was greatest was 397°43. 

From a variation in adjusting the cathetometer on the mercury- 
level in the tube contaiming the vapour, and from placing the 
tube in a position not exactly vertical, a further error in taking 
the volume might be committed, to the amount, perhaps, of 0: 3 
of a cubic centimetre. In order to check the errors arising from 
this source, we had to see how much one of the products pv, 
which for any one temperature already obeyed Mariotte’s law and 
were constant, deviated from the mean of all these pv’s, and, 
moreover, how widely this mean deviated from the mean values 
holding for other temperatures, differently from what is required 
by Gay-Lussac’s law. We had also to take the mean of the 
vapour-densities for the different temperatures which are derived 
from the constant p v of each temperature, and calculate accord- 
ingly the true mean values of the constants pv for each tempe- 
rature,and then seek for the greatest deviation therefrom. Besides 
these errors in volume, the errors in tension already spoken of 
would also naturally come into consideration. But we invariably 
found much smaller deviations than the extreme deviation, which 
arises in the case of alcohol at 69°-9, where, with a volume of 98 
cubic centims. and a tension of 127:54 millims., the product 
11861 was calculated instead of the true mean value 11797. If 
we here assume an error of ‘3 cubic centim. in volume, the ad- 
ditional error in tension will only amount to 0:3 millim., which 
is far within the specified limits. Upon the whole it follows, 
then, that the greatest errors in tension are to be taken at most 
at O°6 millim., and of volume at °3 cubic centim., and that these 
limits were reached in very exceptional cases only. 

§ 4. Hxamination of the Vapour of Alcohol. 


The first numbers found, according to the method sketched out, 
were those given in the following Table for alcohol. They con- 
tain the values of the volume v (in cubic centims.) and of the 
tension p (in millimetres of mercury) corresponding to the eight 
temperatures examined. ‘There are also given the products pv. 
The cessation of saturation, as well as the occurrence of Ma- 
riotte’s law, is indicated on each occasion by the horizontal lines. 


291 


of Vapours to Mariotte and Gay-Lussac’s Law. 


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292 Dr. H. Herwig’s Investigations on the Conformity 


The size of the air-bubble which was present amounted to 
‘064 cubic centim. for 0° and a pressure of 0°760 millim. The 
weight of the alcohol examined was 0248 grm. Hence are cal- 
culated, for the following different temperatures, the final vapour- 
densities which correspond to the mean value of the constant pv 
for each temperature. 


23 


1550 


30°5 


See ee 


1:555 


36°4 


1°555 


41°9 


1:550 


47°8 


1°552 


Temperature .. 69:9 


1:548 


57°8 : 62:9 


1-351 1-552 


Vapour- density . 


That these eee are all too small is due simply to this— 
that the alcohol that was used was not entirely free from water, 
but had been allowed to stand in the air for a considerable time 
in a flask closed by only a cork. On this the first filling of the 
apparatus, it was my intention only to test its accuracy. How- 
ever, as it immediately proved itself to be reliable, I then carried 
on this first investigation to the end. But even as regards the 
object in view, it is of small consequence whether the alcohol 
were perfectly pure or contained some water; it 1s only necessary 
to keep in mind that the numbers obtained above refer to alcohol 
not entirely free from water. 

A comparison of the vapour-densities obtained at different 
temperatures shows clearly that the vapour-densities are con- 
stant. It therefore exhibits the simultaneous appearance of 
Gay-Lussac’s law and that of Mariotte; and, indeed, nothing 
different could have been expected a prior. At the same time 
it is shown experimentally that by means of the apparatus here 
employed the vapour-densities can be accurately determined even 
at low temperatures (much below the boiling-point of the bodies 
examined), which is worth noting, by reason of the difficulty 
encountered in the determination of the vapour-densities of 
several bodies when at a high temperature according to the 
usual methods. 

A further comparison of the figures entered in column pu, 
the particulars of which exhibit the magnitude of the deviation 
of the vapour from Mariotte’s law at different temperatures, 
shows us that at each approach to condensation the deviation 
increases with ascending temperatures. That it does so in the 
case of water, at least, Clausius tells us in his first memoir*. 

If the volume and density of perfectly saturated vapour, which 
thus has absorbed the last drop of liquid, be denoted by v, and 
pi, while V and P are the corresponding quantities for a condition 
of the vapour in which it already obeys Mariotte’s law at the 


specified temperature, then the quotient —— will increase with 
increasing temperatures. 171 
* The Mechanical Theory of Heat. London, 1867. Van Voorst. 


293 


Furthermore we may also see from the above numbers an in- 


of Vapours to Mariotte and Gay-Lussac’s Law. 


crease of the product p,v, with an increasing temperature. Put 

PV 

=a (¢) and p,v,=¢(¢); then we shall have f(t) and (2) 
1 


functions of the temperature ¢, and increasing with it. The 
product of these functions, f(t) .(¢), or PV, must be a function 
of the temperature such that PV=const. (a+2), if by (a+?) 
the absolute temperature is denoted. This relation, as well 
as the proportionate mode of increase of both the func- 
tions f(z) and @(¢) when taken at all possible magnitudes, led 
me to the conjecture that perhaps the assumption f(t) =c Va+t 
and o(t)=c, “a+t, where c and c¢, are constant, might fall in 
with the numbers found. In order to prove this, in the first 
place I selected some of the observed temperatures in which I 
had seen with tolerable precision the point of cessation of maxi- 
mum tension (2. ¢. I knew the value of v,), and calculated 
therefrom, as the value of c, c=:059487, on the assumption 
f(tj)=ceVa+t. With these values I then calculated the value 
of v, for the other temperatures, where I had not so accurately 
observed the limit of the maximum tension. The following 
Table contains the values of v,, as well as the two members of 
the calculation. 


TABLE I. a. 

Temperature ¢ ......... ZS LOO cra oOe4) | -Al-O)) Agos.|'57°:8) 620-9) 690-9 
eee 10191 | 10421 | 10625 | 10852 | 11038 | 11391 | 11554 | 11826 
Mean PV corrected 
for the mean vapour- +| 10183 | 10442 | 10644 | 10834 | 11038 | 11381 | 11554 | 11797 
density 1552 ...... 
ae 17-205 | 17-421 | 17-590! 17-745 | 17-911 | 18-188 | 18-328 | 18-518 
0:0595 Va+t= (— J 1-02347) 1-03632| 1-04638) 1-05560| 1-06547| 1-08195| 1-09028) 1-10158 

17] 
Py, calenlated from ]} 5) | ‘ x x 
this by the aid ofPV. | 9949 | 10076 | 10172 , 10263 | 10359 | 10519 | 10597 | 10709 
SS aaa 50-23 | 77-58 | 108-00 | 144-70 | 196:50 | 315-80 | 396-83 | 537-63 
», calculated from this.) 198-1 |129:9 | 94:2 | 709 | 52-7 | 333 | 267 | 19-9 


Since the accurate determination of v, can hardly be made 
in this way by experiment, because the tension recedes so slowly 
from the maximum that the differences of the tension in the 
neighbourhood of the real v, he within the errors of obser- 
vation, and since in the investigation of alcohol I had not so 
carefully noticed the cessation of the maximum tension, I give 
therefore, as follows, the extreme limits between which v, must 
always fall without directly contradicting the observations ; also 
I have calculated for these limits the values of ¢ in the formula 


f(t)=c Vatt. 


294 Dr, H. Herwig’s Investigations on the Conformity 


TaBLeE I. 0. 
pe i 23° | 30°-5 | 36°4 | 41°-9 | 47°-8 | 57°-8 | 62°-9 | 69°-9 
| | 
Tate of 197°8 125°9 89-6 69:9 52-5 on yy. 19-8 
se of 201-6 | 133 95 72 544 | 342 | 275 | 205 
‘Correspond- 0:05957,) 0: 06137, 0:06247) 0:0 F036) 0:05974' 0:06004' 0:06304' 0:05977 
ING, Cae «i. 0:05613! 0:05809 0:05898) 0:05860) 0: 05765, 0: 03793 0: 0577, 0.05773 


A consideration of these figures gives great Seba to the 
assumption that in ¢ we have a genuine constant; and compa- 
ring the v, calculated with c=:0595, as above, with the parti- 
culars of the tension in the neighbourhood of these volumes, as 
they may be seen in Table I., it would appear with the highest 
probability that these values are correct. Hence it appears to 


me that the relation ='0595 Va+t holds actually, at least 


joey 
for such temperatures of alechol-vapour as have been ex- 
amined, ‘Taking this relation as universally correct for alcohol, 
it follows hence that, for the particular temperature at which 
0595 /a+t=1, the product p,v,=PV,; 2. e. that at this tempe- 
rature the vapour of alcohol, so soon as it 1s separated from the 
fluid, already follows Mariotte’s law. As to the temperature at 
which this happens, it is calculated from the value c=:059487 
as £=9°'589 Celsius. The investigation, unfortunately, could 
not be carried on as far as this temperature in the warm weather 
of the season; ice thrown into the bath would not have given 
sufficiently steady temperatures. Moreover the deviation of the 
vapour from Mariotte’s law which exists at 23° is already so small, 
that it only slightly oversteps the possible errors of observation 
in the slight tension belonging to that temperature. Now, 


whether the relation PAG )="0595 Vatt holds good quite to 
the temperature of 9°°5 for vapour of alcohol, and whether at’ 
that and lower temperatures the vapour follows Mariotte’s law 
when free from fluidity, or whether a slight departure from 
Mariotte’s law takes place in the opposite direction (perhaps 
even according to the law f(é)=c Vatt t), just as Regnault 
found for hydrogen under a high pressure*, is a question which 
must be decided by further investigations, attended, of course, 
by greater difficulties; and these I intend to execute. 

With respect to the particulars of the products pv which lie 
between p,v, and PV, after many trials I have not been able to 
find any formula to which these products would conform as to an 
actual law. It is probable that the relation actually existing for 
these products is complicated, like the tension-curve of saturated 
vapours, the theoretical expression for which has hitherto been 
sought in vain. 

* Mém. del’ Acad. des Sciences, vol. xxi. p. 395. 


of Vapours to Mariotte and Gay-Lussac’s Law. 295 


§ 5. Examination of the Vapour of Chloroform. 


As the second fluid I took chloroform ; during the examination 
of this, in order to avoid the chemical influence of light, I 
covered the side of the bath which was turned towards the win- 
dow with a piece of yellow glass. For this preparation, as well 
as for the bisulphide of carbon, which will be discussed further 
on, both of them perfectly pure, I return my best thanks to Dr. 
Glaser. The following Table gives the numbers for chloroform, 
obtained in the same manner as those given for alcohol :— 


TaBLE IJ.—Chloroform. 


30°°4, 39°°8. 49°°8, 64°°8. 

v. D- pu. | v. Ps de| PVN Bs es hl ganas gS 2 Del Pye 
29-3 | 243-21 35°6 | 354:58 2192 51413, 

48-1 | 243°19 38 | 354:98 28-2 | 514-25 

55°7 | 242-92 48:4 | 354-76 35°6 | 514-14 27°4 | 843°75/23144 
61°3 | 243-19 57°5 | 854°67 42-1 | 513-76 34:4 | 687°31/23664 
70°7 | 243-24 60°5 |:354°86 —|———-—|——__}_ 40°5 | 588°72 23856 
74:7 | 243-08 - -| 45 | 504-74/22730) 40:8 | 584-78 23871 
83°5 | 242°78 63°4 | 382°73.21761} 51-7 | 443°84|22946) 47-4 | 505°42/23962 
87:2 | 242-99 70:6 | 314-08 22175} 58-9 | 390-70, 23016] 57 =| 421-49, 24025 
—— 77-~—(| 290°57|22372) 65-7 | 851-07|28065] 63 | 382°92/'24124 
91 | 238-56|21709) 83 | 269-94'22403} 74:2 | 311-77|23183) 70-7 | 841-58/24149 


92°7 | 234:55/21738} 91-6 | 244-96. 22434] 83-7 | 276°63/238151] 83:3 | 290:98)'24236 

98-9 | 220:09|21776] 98-6 | 227-66,22452} 91-4 | 253-75|23188) 92-7 | 261-69,24254 
104-8 | 208-10|21809/103-8 | 216:99,22524] 97-7 | 237-40|23193)100°8 | 240-94 24295 
112-4 | 194:53|21862|— 191-6 | 228-43)/23215}100°9 | 240-74 24304 
120 | 182-44,21899]109°5 | 206-14 22572)108-4 | 214-58/23260/11 1-2 | 218-69 24315 
——125'6 | 179°75|22572H117 =| 198-98)/238271j113-1 | 215-13/24827 
132°5 | 165-54 /21930}129-9 | 173-90 22589j; ——- 116 | 209°96 24347 
140-7 | 155°70/21908]1380 | 173-60,22567}118°6 | 196°44,23306)122 | 199-90)/243938 
(141°3 | 155:25/21931)141-2 | 160°33'22644}124 =| 188-05|23319 — - 
183°1 | 175-25)23321j128 | 190°95|24442 
145-4 | 160°29|23307/128'3 | 190°37|24423 
128-6 | 189-79 24407 
136°5 | 179-15)24447 
140°8 | 173°64, 24450 


The air-bubble amounted in this case to 0°31 cubic centim. 
at O° and under a pressure of 760 millims. The weight of the 
chloroform examined was ‘1406 grm. The final constant vapour- 
densities calculated therefrom are, for the different temperatures, 
the following, which agree sufficiently :— 


Temperature ......| 30°4 | 39°8 | 49°8 | 642-8 | 


| ee i 


Vapour-density ....../ 4190 | 4191 | 4-191 | 4-185 | 


These vapour-densities differ more from the theoretical one 
(4°138) than can be accounted for by small errors in weighing. 
Indeed I think I remarked for some hours (before the beginning 


96 Dr. H. Herwig’s Investigations on the Conformity 


of the measurements), when the chloroform was not yet protected 
by the yellow glass, that a small trace had been already decom- 
posed. This, however, could not make a greater difference in the 
weight than 1:5 milligrm. The examination of bisulphide of car- 
bon, which will be subsequently described, gave a similar result, 
where the traces of the sulphur which might be separated during 
the boiling out and sealing of the bursting bulb also could not 
have produced the difference of weight necessary in order to bring 
the vapour-densities actually found into accordance with the theo- 
retical ones. That in both these cases no error can lurk in the 
method which would induce the differences may be indubitably 
recognized from this, viz. that at each temperature the final 
vapour-densities for the most various volumes are, within the 
limits of errors of observation, exactly proportional to the final 
vapour-densities at all other temperatures. Besides, in general 
the experimental determinations of the vapour-densities do not 
rigorously lead to the theoretical densities. Even though many 
of the old determinations could not give any exact results because 
no attention was paid to the question whether the vapours were 
sufficiently far from their condensation, yet deviations from these 
causes must always give only an increase in the vapour-density 
over the theoretical values, while a converse course of determina- 
tions would furnish equally important smaller values. 

Now, as to the relation holding for vapour of chloroform cor- 


d 
responding to that found for alcohol, viz. eee Vatt, I 


11 
first of all conjectured that, even if the like holds here also, 
the constant ¢ might perhaps be different from that found to be 
valid for chloroform, in such sort that the temperature at which 
the perfectly saturated vapour follows Mariotte’s law might, 
for chloroform, lie as much under 9°°5 as the boiling-point of 
chloroform under atmospheric pressure lies under the boiling- 
point of alcohol. Meanwhile the first set of experiments showed 
decisively that this was not the case; on the other hand, the 
surprising result presented itself, that in the admittedly valid 


formula Lae Wa+t the constant ¢ had the same value as for 


1 
alcohol. in what follows I give the Table of v, calculated from 
the specified relation with c=-0595, and at the same time, as for 
alcohol, the extreme limits of v, and c, which are consistent with 
the observations. In this case I have sought to observe more 
accurately the exact point of retreat of the vapour from the state 
of maximum tension. I must remark that at the last tempera- 
ture (64°°8) the apparatus unfortunately did not sustain the 
compression which was necessary in order to arrive at the state 
of maximum tension. The only observations that I could make 


of Vapours to Mariotte and Gay-Lussac’s Law. 297 


with certainty at 64°°8 are those given in Table II. But by the 
help of one approximately estimated maximum tension, which is 
taken from the relation of the remaining maximum tensions to 
those of Regnault* (touching which I may remark that the 
difference between the two is greatly affected by the difference 
in the preparations), the probably correct value of v, may be 
caleulated, since with a small value of v, and a high value of p,a 
mistake in the latter to the amount of a few millimetres would 
alter the value of v, only very little. 


TasueE II. a. 


@ewmmperature 2.1 605 5....4.. 30°°4 39°°8 49°8 64°°8 
Mean of the observed PV...) 21923 22590 23313 24434 
Mean PV corrected for 
the mean vapour-den- 21928 22602 23313 24399 
STS) ts 
eos PV 
00595 Natt(=—) eee] 103614 1:05209 1:06881 109331 
) ves | . : 
Pv, calculated from this by 216 ; 
‘the aid of PV corrected ae ASE alle Se 
P,, mean of the observations.| 243-08 3894°77 514:07 870 nearly 
v, calculated from this ...... 87°] 60:6 42-4 25°7 


Table II. d. 


MeMpPErAtUrert, 2326..60).0.60 30°°4, 39°°8. 49°°S. 
Extreme limits i Wooe see ou ae rk 
pe orespomding ¢ in: the 0-05949 0-:05961 | 0-05997 
ratio 7 Se NGeEp (|| . 0.08858 0-05864 005871 

iar 


A survey of these Tables shows how closely the assumption 


pe, =0:0595 “a+¢ harmonizes with the observations. Hence 
1 

also for alcohol and chloroform the same temperature (9°°5) must 
exist at which the vapours of both fluids, so soon as they pass 
from a fluid state, follow Mariotte’s law; the point of maximum 
tension (very different at 9°5 5) appears to have no influence on 
the position of this temperature. 


§ 6. Examination of the Vapour of Bisulphide of Carbon. 


To prove perhaps the universal validity of this remarkable 
phenomenon, there was taken for the third body bisulphide of 
carbon, the maximum tension of which at 9°°5 is considerably 
greater than that of chloroform. This body, having been pre- 
pared so as to be quite pure, was protected from the hight during 
the investigation by a piece of yellow glass. The following Table 
gives the simultaneous v and p for five temperatures, and there- 
with the EUs products pv. 

* Mém. de l Acad. des Sciences, vol. xxvi. p. 403. 
Phil Mag. Ss. 4. Vol. 38. No: 255. Oct. 1369. xX 


H 
f 
i 


’s Investigations on the Conformity 


o 
5 


i 


Dr. H. Herw 


298 


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of Vapours to Mariotte and Gay-Lussac’s Law. 299 


The size of the air-bubble was °325 cubic centim. at 0° and 760 
millims. pressure; the weight of the bisulphide of carbon was 
‘0717 grm. The final vapour-densities calculated therefrom 
“oe with one another very well, as the following comparison 
shows :— 


Temperature ...... 8°°5 14°-2 20°] 32° 35°°9 


— 


Vapour-density ...| 2°686 2-683 2°682 2-680 2-680 


Their deviation from the theoretical vapour-densities has been 


mentioned above. The relation irae VY a+t is exhibited with 
1V) 


the same constant, c=:0595, in fact confirmed here also, as 
a comparison of the following Tables with the corresponding 
preceding one shows :-— 


TABELEPLILL. a: 


| PPEHIPELATUEC fsa... .0ss00e0s 8°°5 14°-2 20°°1 32° 35°°9 


Mean of the observed PV ...| 16175 16521 16867 17565 17792 
Mean PV corrected for 
the mean yapour-den- 16199 | 16528 | 16867 | 17552 | 17777 
Sivan GOL kcass:-5.....: 


0:0595 Na+e(= aA ee 1 1:00813 | 1:01842| 1:03888 | 1:04554 


Pir 
Pp v, calculated from this by : 
the aid of PV corrected. 16199 | 16385 | 16562 | 16895 | 17003 


P,, mean of the observations.| 183-09 | 234-45 | 294:12 | 461°54 | 531-59 
v, calculated from this ...... 88:5 69:9 96°3 36°6 32 


Tasxe III. 6. 


FEMIPErALUTE Eo. cec60- sce s 8°°5 14°-2 20°°1 32° 35°°9 
e . DQA- ° 
Extreme limits of v, ...... { ae Be eo Z fe 7 ite 


Corresponding ¢ in the ] | 9.9¢204| 0-06012| 0:05961 | 0-06204 | 0-06057 
ratio ~  _. Waae... [| 0:05949| 0-05943 | 0-05877| 0-05818 | 0-05852 
Pir) : 


The temperature 8°°5 was taken on a cold October day, yet 
could not be maintained without the help of some ice. This 
certainly influenced the degree of constancy in the temperature 
which existed in all other cases. The numbers obtained are less 
accurate; but they appear to show pretty clearly that for these 
temperatures the vapour already follows Mariotte’s law imme- 
diately on its declension from the point of maximum tension. 
The differences of the four products, given in Table ITI., are some- 
what irregular; but when we take into account the small fluc- 
tuations of temperature which certainly did exist, they may lie 
quite within the errors of observation. 


X2 


300 Dr. H. Herwig’s Investigations on the Conformity 


8 7 
V ai Thy 
Now we have the relation ° irae Yat+é true (at least within 


the limitof errors of Sannin) ear the vapours of the very differ- 
ent bodies treated above, viz. alcohol, chloroform, and bisulphide of 
carbon, the same value in all cases being assigned to the constant, 
VIZ. G=="0595. Simultancously with this there must hold the 


other necessary relation, viz. p,v,=c, ¥ /a+t, where c, means a 
constant depending only on the density of each vapour, namely 
) 
ie 05 : yi . Atthe same time it follows that the pressure 
095 (a+?) 

of perfectly saturated vapour is proportional to the square root 
of the absolute temperature. From the relation pv, =c Vatt, 
a more perfect understanding is afforded concerning the condi- 
tion of perfect saturation, 7. e. concerning one limiting condition 
of these superheated vapours, so soon as “the curve of maximum 
tension is known. That important curve in the mechanical 
theory of heat may then be constructed which exhibits the mu- 
tual connexion of the magnitudes denoted above by p, and », 
provided we know the relation existing between p, and f, 1. e. 
when the curve of tension is given. 

The values of v, given in Tables I.a, Il. a, III.a are taken 
from the mass of vapour used on each occasion. Dividing these 
values by the weight of the vapour in question, we shall obtain 
the specific volumes, so called in the mechanical theory of heat, 
of perfectly saturated vapour. Witha kilogramme as the unit of 
weight, we find the following specific volumes expressed in cubic 
centimetres : 


Tape IV. 


Alcohol. 

Temperature ...| 23° | 30°5 | 36°-4! 41°-9 | 47°°8| 57°8 62°-9| 69°-9 
Specific Polumes) 79879 9°2379) 3° 57084 2:°858¢ 89 212 13428 10766, 08024 
Chloroform. 

Temperature ...... 30°°4 ; 39°:8 49°°§ + lis otatedeena eed 
Specific volumes .. 6202 0-4310 03016 1898 


Bisulphide of Carbon. 


Temperature ...... 8°°5 | 14°-2 20°] | 32° 35°:9 


Bee ls 1-2343 | 0:9749 0:7852 | 0:5105 0:4463 


of Vapours to Mariotte and Gay-Lussac’s Law. 301 


The specific volumes of the three vapours examined are found, 
according to the principles of the mechanical theory of heat, laid 
down in Zeuner’s Grundziige, 1866, where the values of u given 
in Tables 3. b, 5. 6, and 7. 6, multiplied by the values of o given 
page 288, determine the specific volumes for each vapour. 
The values of u given there are calculated on the basis of Reg- 
nault’s formule for tension and the heats of evaporation com- 
municated by Regnault. In order to render possible a compa- 
rison of the specific volumes of perfectly saturated vapour thus 
obtained with those derived from the relation p,v,= const. /a+t, 
I have calculated these last from Regnault’s tensions, using the 
theoretical vapour-densities, and at the same time I have given 
the volumes which result according to the old view when the 
vapours are supposed to follow the laws of Mariotte and Gay- 
Lussac. The foundations for these last have thus been built upon 


Regnault’s tensions and the theoretical vapour-densities. 


Taste V.—Specific volumes of perfectly saturated vapour. 


Alcohol. 
a. b. Ge 
Temperature. | According to | Calculated from| On the old as- 
Zeuner. pwy=C1 Natt. sumption. 
10° 173294 15°7730 15°7859 
30 57316 50854 5-2142 
50 2°1345 18567 1:9851 
7 08822 0:7775 0:8566 
100 0:2863 02585 0:2970 
120 0°1538 0:1894 0:1643 
140 0:0902 0:0814 0:0984 
Chloroform. 

10 14698 1:4644 1°4656 
30 0°6413 0:°6150 0°6368 
50 031438 0:2938 0-314] 
70 01693 0:1554 0:1712 
100 0:0774 0:0696 0:0799 
120 0:0498 0:0442 0:0521 
140 00339 0:0296 0.0358 


Bisulphide of Carbon. 


10 11719 1°1660 1:1669 
30 05662 05508 0:5703 
50 0°3005 0:2884 0:3084 
70 0:1720 0:1641 0°1805 
100 0.0834 0:0799 0:0918 
120 0:0547 005380 0:0625 
140 0:0374 00368 — 0:0444 


3802 Dr. H. Herwig’s Investigations on the Conformity 


The difference between the figures entered in columns a@ and b 
is manifest. We may remark that it seems impossible that the 
volumes as calculated by Zeuner should be correct, as being 
larger than those entered under column c. Since, however, the 
figures in columns 0 and ¢ are derived from the theoretical va- 
pour-densities, possibly the preparations examined by Regnault 
may have possessed a somewhat different final vapour-density, 
which would account for the discrepancy. In the first figures 
the difference (in the case of alcohol) is, of course, too large to be 
accounted for by this explanation. Besides, we may suppose 
that the specific volumes calculated on the basis of the mechanical 
theory of heat are obtained in such a circumstantial way that 
such a variation in the fundamental data of observation (the 
maximum tension, the total amount of heat, and the heat of 
the fluid) as, according to Regnault’s investigations, would le 
within the errors of observation might evoke a proportionately 
important variation in the final result. For these reasons no very 
trustworthy conclusions can be drawn from the comparison given 


above in Table V. 
§ 8. 


As to the whole question of the superheated state of vapour, 
I have already remarked that as yet I have not been so fortunate 
as to derive a precise law from the course of the products pu which 
he between saturation and the gaseous condition. 

But some interesting conclusions may be obtained from the 
examination of the other limit, which separates the condition of 
vapour deviating from the laws of the ideal gas (which for short- 
ness I will designate exclusively as the superheated condition) 
from the gaseous condition. Of course the experiment of fixing 
these limits accurately has never been made with success, since 
the product pv varies too shghtly in the vicinity of its constant 
condition to allow of the differences falling without the errors of 
observation. Generally, from the occurrence of Mariotte’s law 
(z. e. from the constancy pv for each temperature), we can only 
infer that the eventual small differences of pv are not perceptible 
by our instrumental measurements. But, on the other hand, if 
the examination always shows an undoubted fluctuation beyond 
these limits, then a further determination can be instituted to at 
least some degree of approximation. And in the case before us 
the observations suffice to exhibit a very unexpected result. 

Considering now the particulars of V, (2. e. of the volumes for 
which the vapour first enters into the gaseous condition at dif- 
ferent temperatures), Table II. shows for chloroform, and, still 
more, Table III. for bisulphide of carbon, that these volumes do 
not constantly diminish with increasing temperatures, as one 
might have supposed, but from a certain point increase with the 


of Vapours to Mariotte and Gay-Lussac’s Law. 303 


temperature. Itis only necessary, by means of a comparison of 
the pv’s which stand in Tables II. and III. immediately over 
and under the last corresponding horizontal lines with the mean 
volumes of PV given in Tables II.a and III. a, to make sure of 
the correct position of the horizontal lines, and to inspect the 
values of the volumes v between which the horizontal lines lie. 
In the case of chloroform, at the temperatures examined, may be 
remarked first a decrease and then an increase of V,, while in 
the case of bisulphide of carbon there is a continual increase from 
the lowest temperature (8°°5). In the case of alcohol, nothing 
analogous can be seen at the temperatures examined. [For 
the clearer exhibition of these relations, a graphic construc- 
tion of V, may be contrived. It is usual in the plane coordinate 
system to take the absolute temperatures as the abscisse x, and 
as the ordinates y to take simultaneously the corresponding 
values of the specific volumes (marked v,) of perfectly saturated 
vapour, and also those of the volumes V, referred to the vapour- 
unit of weight (1 kilog.). Of the two curves so constructed, 
that of vy, must always drop as the abscisse increase, and run 
asymptotically into coincidence with a line parallel to the axis of 
abscissee. The volume characterized by this parallel is the least 
at which the unit weight of vapour can exist without assuming 
the fluid form. For the three vapours which have been dis- 
cussed, the curve of V, coincides with the curve of v, at the 
abscissa =a+9°5, and afterwards, with increasing values, as- 
sumes a course more removed from the axis of abscissze than the 
curve of v, ; indeed it appears from all the foregoing obscrva- 
tions, that the difference V,—v, constantly increases. Therefrom 
results the necessity of a minimum of the curve V,, provided 
there be an initial descent. For chloroform this minimum is 
actually proved from the observations. For bisulphide of carbon 
the same lies close to the neighbourhood of a temperature of 10°, 
and then the observed constant increase of V, along with the 
temperature commences. For alcohol, the temperature at which 
the minimum exists, according to this, would he higher than 
70°. At higher temperatures there would probably be found 
a constant but small increase of V,; at least such appears to 
be the most natural supposition, after the proof of a minimum 
of the curve V,. 

Since any volume of the unit of weight of vapour corresponds 
to any temperature of the superheated condition when it falls be- 
tween curves V, and v, in the representation by coordinates, and, 
on the other hand, corresponds to the gaseous condition when it 
has both curves between it and the axis of abscissze, the preceding 
considerations lead to the following result. We can draw a pa- 
rallel (MN, fig. 2) to the axis of abscisse from any point of the 


304 Dr. H. Herwig’s Investigations on the Conformity 


curve v, which will cut the curve V, twice; 7. e. the unit of 
weight of vapour being enclosed in an invariable volume, may at 
any temperature be perfectly saturated vapour; with an increasing 
temperature it will withdraw itself from the superheated and 
approach to the gaseous condition ; in this latter it continues for 
a time under a still rising temperature, and under a higher in- 
crease of temperature it again arrives at the superheated condi- 
tion, indeed probably approaches this the more nearly the higher 
the temperature is raised. Since, according to the mechanical 
theory of heat, the temperature represents “the measure of the 
vis viva of molecular motion, while the greater or less deviation 
of the vapour from the gaseous condition consists in a more or 
less marked influence which the interaction of the isolated mole- 
cules exerts on this motion, it must consequently be admitted 
that the unit weight of vapour, when occupying an invariable 
space, may, for a certain inertia of the molecular motion, display 
a considerable degree of the maintenance of the molecular interac- 
tion, which decreases as the motion becomes more active, entirely 
disappears, and then, with a greater intensity of movement, reap- 
pears and increases in energy the higher the molecular motion 
is raised. 

This conception is difficult, it cannot be denied ; but the ob- 
servations compel us thereto; nothing else can be deduced from 
the observations, even under the assumption of the widest pos- 
sible errors in them. Moreover this conception appears to me 
to be not at all inconsistent with the mechanical theory of heat. 
For since the influence which the interaction of the molecules 
exerts on their movement is measured by the quotient of the 
time during which a molecule taken at random is found within 
the sphere of action of other molecules, and of the time during 
which it moves free therefrom, and since this quotient is a func- 
tion, first, of the time elapsed during a single movement of two 
molecules within their sphere of mutual action, and, secondly, 
of the repetition of such meetings, therefore it 1s probable, con- 
sidering the utter uncertainty in which we find ourselves concern- 
ing the details of this occurrence, that at the commencement of 
the above-described process the first moment especially, and at 
the end the second moment come into account, while between 
them there lies a condition when both moments are of impercep- 
tible action. 

oo: 

Very similar results are obtained from the consideration of P, at 
different temperatures, 7. e. of the different tensions under which 
the vapour at each temperature first enters into the gaseous con- 
dition. Representing graphically the connexion of the tensions 
p, and P, with the temperature (fig. 3), the curve p, becomes 


of Vapours to Mariotte and Gay-Lussac’s Law. 305 


the well-known tension-curve, which constantly withdraws itself 
from the axis of abscissze as the temperature increases. At the 
abscissa a+9°5 the curve P, coincides with the curve p,, but 
afterwards at higher temperatures approaches nearer to the axis. 
And here the vapours of chloroform and of bisulphide of carbon 
show that the curve P; may have a maximum. Now, since we 
cannot assume that, beyond the maximum, P, constantly decreases 
with an increasing temperature, therefore the curve P, after the 
maximum must have a minimum, in order that it may withdraw 
itself more and more from the axis of abscissz, as is approxi- 
mately shown in fig. 3. 

Consequently we may draw a parallel to the axis of abscisse 
from a point on the curve p, which shall cut the curve P, three 
times ; 7. e. the same tension of the vapour may correspond to 
the superheated condition for lower temperatures and to the ga- 
seous for higher temperatures, then the vapour may enter again 
into the superheated, and finally into the gaseous state. This 
conclusion is connected with that drawn previously from the 
course of V,, since the product P,V, must increase proportion- 
ately to the absolute temperature (the abscissa in the diagram). 


§ 10. 


From what has been said in the last two paragraphs, a surpri- 
sing conclusion is arrived at concerning the behaviour of the co- 
efficients of dilatation of vapours of constant volume and under 
a constant pressure. 

Since the superheated condition shows a smaller product pv 
than there would be in the corresponding gaseous condition, it 
follows that whenever a constant volume v is taken, the pressure 
p must be smaller for superheated vapour than it is, under other- 
wise similar circumstances, for an ideal gas. Hence it follows 
that when the vapour under a constant volume and with a gra- 
dually increasing temperature passes gradually from the super- 
heated condition into the gaseous condition, it must exhibit a 
greater coefficient of dilatation for a constant volume than that of 
an ideal gas would be; and, conversely, in a gradual progress 
from the gaseous to the superheated condition with an increasing 
temperature the coefficient of dilatation of the vapour under a 
constant volume must be smaller than that of an ideal gas. All 
this holds good when the volume v is interchanged with the pres- 
sure p for the coefficient of dilatation under a constant pressure. 

From the particulars of the curve V,, as represented in fig. 2, it 
follows that the coefficient of dilatation can exhibit the behaviour 
of the vapour in its dependence on the temperature when under 
a constant volume, as is given in fig. 4, where the abscisse @ re- 
present the temperature, the ordinates y the coefficient of dila- 


3806 Dr. H. Herwig’s Investiyations on the Conformity 


tation, and the parallel to the axis of abscissze MN the coefficient 
of dilatation of an ideal gas. The curve, fig. 4, drops from a 
value which is larger than that for an ideal gas, down to this 
value, and in its further course arrives at still smaller values. 

In the same way, from the particulars of the curve P, (fig. 3), 
it follows that the coefficient of dilatation of a vapour under a 
constant pressure may depend on the temperature in the manner 
shown in fig. 5, which is arranged after the fashion of fig. 4. 
The curve (fig. 5) crosses the line which represents the coefficient 
of dilatation of an ideal gas, so that, starting from greater values, 
it meets this line, further on it arrives at a minimum lying 
under it, then rises to a maximum which lies over it, and finally, 
from a certain high temperature, runs into and along with it. 

Since the last part of the curve in fig. 4 lies always below the 
line of the coefficient of gas, while the last part of the curve in fig. 5 
coincides with this line, consequently, for such vapours as those of 
chloroform and sulphuret of carbon, the coefficient of dilatation 
at and from a certain high temperature is much smaller for a 
constant volume than for a constant pressure, a property which 
reminds us of Regnault’s experiments on the so-called permanent 
gases. 

On looking back, I find that some other observations besides 
those here communicated on the coefficient of dilatation under a 
constant pressure appear to point to such a behaviour of this 
coefficient as is represented in fig. 5. That thecurve has most 
probably the maximum lying in the neighbourhood of B (fig. 5) 
has been observed by Deville and Troost* in the case of vapour 
of hyponitric acid under a pressure of one atmosphere. Any way 
the want of any other explanation can no longer make it neces- 
sary to assume a dissociation of hyponitric acid. Of course in case 
such relations be assumed for hyponitric acid as I have found 
for chloroform and bisulpbide of carbon, and there also the 


validity of the relation rad =c Va+t be supposed, the constant 


v 
e must have a much lem value than °0595, since the den- 
sity found at 26°°7 of the vapour when all but saturated dif- 
fers considerably more from the final vapour-density than it 
would on the assumption of the constant c=*0595. I will not 
make any assertion respecting this case; I wish only to suggest 
the possibility of such an explanation of the results of Deville 
and Troost. 

On the other hand, we may perhaps deduce the existence of 
the minimum of the curve in fig. 5 which lies at A, from Hirn’s 
researches quoted in §1. Hirn gives, amongst other examples, 
the specitic volumes of superheated aqueous vapour under a 

* Comptes Rendus, vol. xiv. p. 237. 


of Vapours to Mariotte and Gay-Lussac’s Law. 307 


pressure of one atmosphere for several temperatures. Although, 
for the right determination of the coefficient of dilatation under 
1 


dt 
Big ] 
the correct knowledge of the relation existing between ¢ and v 
is indispensable, we may yet calculate approximately, by help of 
the not very large differences of the volumes here treated of, the 
mean coefficient of dilatation between each pair of temperatures 

Vo—v 
Vty—Vot 
Hirn’s statements the following values :— 


a constant pressure acccording to the formula «= 


by means of the formula «= Thereby we obtain from 


Temperature, Mean coefficients of 
Celsius. dilatation. 
ie) 
rae - 0:004181 
= 2, . 0:004212 
oa 0002902 
200 i 0:003059 
246-5} 0:003838 


These numbers naturally give only a very rough picture of the 
relations which hold; but perhaps their course is sufficiently de- 
terminate to point to some such minimum of the coefficient of 
dilatation as my own observations have given for chloroform 
and bisulphide of carbon, of course under a less pressure. 


§ 11. 


From the considerations set forth in the last paragraph, we 
may see that such a form of the equation of condition as Zeuner 
first gave, in the Zertschrift des Vereins deutscher Ingenieure, 1867, 


kl 
p- 49, for superheated aqueous vapour, puv=B(a+t)—Cp =, 
where B, C, and & are constant, cannot be employed with certainty 
for the vapours of chloroform and of bisulphide of carbon consist- 
ently with the observations here communicated, Indeed accord- 
ing to this equation a course of the curve P, similar to that de- 
scribed would not be possible. Suppose in the equation the pres- 
sure p constant, then it follows from B(a+?¢) —pv= const. that 
pv will correspond more closely with B(a +2), 1. e. will approach 
more nearly to a gascous condition, the larger that (a+) is. 
Therefore for a constant pressure with an increasing tempera- 
ture the vapour must, in conformity with this equation, be con- 
tinually approximating to it. 

Zeuner deduces the equation on the grounds of two assump- 
tions: (1) that the specific heat of aqueous vapour is constant 


—— 


308 Mr. J. S. Aldis on the Nebular Hypothesis. 


under a constant pressure c,; and (2) that on aqueous vapour’? 
=i 
as well as for the gases, the relation Gshtoyy ile holds at two 
at+to po ; 

points of the same unicursal curve, where the constant k has, of 
course, a different value from what it has in the case of gases. 
Zeuner holds, moreover, even a slight variation of the quantities 
c, and k to be not unlikely, wherefore the above equation would 
give the true relations approximately only. 

We may remark that the assumption of a constant ¢ for va- 
pours generally is not supported by Regnault’s experiments * in 
a conclusive manner ; and for bisulphide of carbon it appears even 
more decisively that a variation of c, must result from Regnault’s 
figures. 

I am engaged in a further prosecution of the observations 
here communicated, and will report them hereafter. 


Bonn, February 2, 1869. 


XXXV. On the Nebular Hypothesis. 
By J. 8. Avis, M.A., late Scholar of Trinity College, Cambridget. 


fl he test of theory is the deduction of numerical results. It 

is not very easy to obtain such results from the nebular 
hypothesis. Still the principle of the conservation of areas 
affords a few results hitherto, we believe, unnoticed. They are 
not, however, altogether free from objection. 

Every planet when detached from the central body, whether 
as a ring or (as appears to us more probable) as the stalk end of 
the pear-shaped central mass, must have rotated on its axis in 
its periodic time round the central body. Assuming, then, 
that the portions when detached did not differ much from a 
spherein shape, we calculate the densities of the different planets 
when first detached. They are as follows, that of the earth being 
unity :— 

Mercury )4 40 5.1, yee aOOMLS 
Venus oi. ey Sine a OUOZAIL 
Earth and Moon. . *0000128 
Mars is oe jayts 25700004. 
Jupiler s len wt sy oe  OOO0O0Z3 
Saturn + . » =. “0000000285 

These results are strikingly mm accordance with theory. Mer- 
cury, Venus, and Mars have their densities nearly inversely as 
the cubes of their distances, the others not. Whatever the law 


* Mém, de [ Acad. vol. xxvi. p. 163, 
+ Communicated by the Author. 


Mr. J. S. Aldis on the Nebular Hypothesis. 309 


of density in the central body, the exterior part would vary in 
density according to such a law, as that body contracted. 

Those that do not obey this law confirm the nebular hypo- 
thesis quite as well. They all have satellites, and have them 
because the detached body was not spherical but elongated, the 
stalk end of the pear-shaped mass being unusually long. The 
impossibility of homogeneity necessarily would develope a pear- 
shaped mass in the cooling down of the central body rather than 
the ellipsoidal or spheroidal. The density of the earth should 
be about seven or eight times what the above Table indicates, 
for it to vary between the inverse square and inverse cube (the 
law is nearly the inverse cube, but not quite); and to have that 
increased density with the same amount of angular momentum 
in the detached body, the latter should be some three or four 
times as long as broad, and hence in contracting, as it would 
in length be about double the distance of the earth from the 
moon, it would naturally separate into two bodies. The moon’s 
original day apparently was nearly half as long again as that of 
the earth. 

The densities of Jupiter and Saturn are far less than the law 
would give, and due to the same cause, since they abound with 
satellites, though the great ‘gap between Mars and Jupiter 
strongly sug sgesls ¢ ease nebulz where a central mass is sur- 
rounded by. a ring, on the outskirts of which hang smaller 
nebule. 

There is connected with this hypothesis a point in the struc- 
ture of the earth deserving attention. It has been remarked 
that there is a tendency in mountain-chaims to run north and 
south, and to present steep slopes to the west, gentle declivities 
to the east. This may arise from the contraction of the earth. 
If a portion of unsupported crust sink towards the centre, it 
will subside on to that which is moving east less rapidly than 
itself, and in consequence will, so to speak, fall over towards the 
east, the surface forming a gradual slope to the east, and the 
fractured western edge a precipitous descent to the west. 

In the moon, too, we see proofs of the contraction continued 
long after the stage in which we now find the earth. The 
spheroid of the moon has contracted since it assumed that shape, 
and, contracting less in the longer diameter, is now more sphe- 
roidal than it should be according to theory, whilst the thick- 
ened crust, no longer crushed down on the interior, has left cavi- 
ties in which the moon’s ocean and atmosphere are entombed for 
ever. 


Manchester Free Grammar School, 
September 16, 1269. 


[810 ] 


XXXVI. Thermal Researches on the Battery. 
By M. P. A. Favre*, 


I HAVE formerly insisted upon the utility of considering, in 

the investigation of voltaic currents, the absolute quantity 
of heat put in play in the whole circuit and in each of its parts. 
The investigations contained in this paper have principally for 
their object to ascertain the origin of the heat which is not found 
in the circuit, and which is confined to the couples. As in this 
abstract I cannot produce the numerous Tables referring to the 
various series of experiments, I shall restrict myself to indica- 
ting the tendency of the results and the conclusions which seem 
to follow from them. 

I. I repeated Pouillet’s experiments on the intensity of the 
current according as we work with a single couple or with a 
battery of any number of couples—the electromotive force and 
the internal resistance of each couple being equal, and the ex- 
ternal resistance R either equal to zero or varied by the mtro- 
duction of different lengths of wire. Working under these con- 
ditions, I restricted myself to investigating the distribution of 
heat corresponding to the resistances R and r of the circuit. 

I worked successively with one, two, three, four, and five 
couples+, and found that for the same amount of chemical action 
and the same finite value of R, the quantity of heat due to the 
internal resistance of the battery was greater than the quantity 
due to that of the couple. Thus the calorific effects in both cases 
are in the direction which Pouillet had remarked for the inten- 
sities. 

II. I repeated the same experiments a great number of times 
in succession, and without renewing the liquid, until at least half 
of the sulphuric acid was changed into sulphate of zinc. It was 
difficult to exceed this limit ; for when I made several couples 
work simultaneously, R being equal to O, the platinum of one or 
more couples became covered with so large a quantity of zine, 
that it could not dissolve with sufficient rapidity, rendering 
impossible any calorimetric determination. 

In each series of experiments R was made alternately =O 
and =250, 500, and up to 7000 millims. of my normal platinum 
wire, SO that I could calculate the internal resistance of the 
couple or the battery in each of the successive experiments. 

I give here the numbers furnished by the first and the last 
operation of one of the series of experiments made by means of 


* Translated from the Comptes Rendus, November 23, 1868. 
T The liquid was renewed each time. 


M. P. A. Favre’s Thermal Researches on the Battery. 311 


a battery of five elements. The acid was pure* in the first ope- 
ration, while, in the last, half of it had been replaced by sulphate 


of zinct. 
Heat confined to Heat expended in 
Maulucrot fr. the battery. 7000 millims. of wire. 
millims. units. units. 
eee, ee 70 1994, 17840 
(sy). "106 9282 10552 
whence 


Total heat of the 
circuit R-+-7r. 


Heat confined 
to the battery. 


units. units. 
ep tes bp ol pgOTs 1816 
Gee 10712 9122 


What is the origin of this quantity of heat which thus re- 
mains confined within the battery {? 

It seems to me that it can only be explained on the assump- 
tion that the following actions come into play either together or 
separately :—(1) the condensation of hydrogen upon the plati- 
num, which becomes an obstacle to the transmission of the cur- 
rent; (2) the local action due to the passage of the hydrogen 
from the nascent to the ordinary state; (8) the action, also 
local, due to the sulphatation of the zinc deposited on the pla- 
tinum plates—a deposit arising from the electrolysis of sulphate 
of zinc, as this salt continually increases in the liquid in which 
the couples are immersed. 

I will first remark that if the hydrogen offers a passive resist- 
ance to the passage of the current, this resistance 1s included in 
the internal resistance of the battery, the thermal constituent of 
which has already been calculated. Moreover I estimate that 
no considerable fraction of the quantity of heat indicated by the 
calorimeter in which is the battery (a quantity which increases 
with the number of anterior operations) can be attributed to 
the influence of the condensed hydrogen. 

III. I have confirmed a fact already stated by several phy- 
sicists, that the quantity of hydrogen condensed on the surface 
of the platinum is very small, and does not go on increasing in- 
definitely. Working with two of Smee’s elements joined to- 


* The sulphuric acid used, of a given degree of dilution, liberated 19,834 
thermal units in acting upon zinc. 

+ I may mention that in my couples the passive resistance which the 
sulphate of zinc presents to the current is sensibly equal to that presented 
by sulphuric acid. ” 

+t In my previous experiments I had found this quantity equal sometimes 
to 4000, sometimes to about 6000 units; the variation is much greater in 
the present experiments (from 1800 to 2000), but under well-defined con- 
ditions. 


312 M.P.A. Favre’s Thermal Researches on the Battery. 


gether, | measured the gases which they separately disengaged. 
One of these elements, having served for various operations before 
being used for the present experiment, was covered with all the 
hydrogen it could condense, while the other, working for the 
first time, had not been able to condense hydrogen on its surface. 

I then took a new couple, the platinum of which had been 
treated with boiling nitric acid, then heated to redness, and 1m- 
mersed in a considerable mass (about 2 litres) of my normal 
acid*, ‘The intensity of the current did not appreciably vary in 
the numerous successive experiments, and the quantity of heat 
indicated by the calorimeter containing a rheostat was virtually 
the same. Hence the hydrogen condensed on the surface of the 
platinum does not exercise any appreciable influence on the phe- 
nomenon in question, and the variations observed should be at- 
tributed to the differences of chemical composition which the 
liquid of the couple experiences under ordinary circumstances. 

Lastly, it is sufficient to renew the liquid of the couples of 
Smee’s battery which have worked for some time, in order to 
recover the original intensity and the corresponding thermal 
result. 

The influence of the other causes above mentioned has still to 
be investigated. 

I will first observe that in the first of the experiments II. the 
local phenomenon of the solution of the zine deposited on the 
platinum in the acid can only play a very small part in the 1816 
thermal units indicated by the calorimeter m which is the battery. 
In fact, at the beginning of the experiment there is no sulphate of 
zine in the liquid ; and the absolute quantity at the end is very 
small, while the sulphuric acid which remains free is in a relatively 
large proportion (only about 5 of the sulphuric acid has been 
changed into sulphate of zinc). Hence I have necessarily been led 
to attribute the heat which remains in the couples whenever the 
acid liquid is renewed, almost exclusively to the local phenomenon 
of the change of condition of the hydrogen. May we consider 
the number adduced of 1816 units as representing even approxi- 
mately the effect due to the change ef state of the hydrogen? I 
think not; for the quantity of heat corresponding to the che- 
mical action, which is not met with in the circuit R+7 and 
which is confined to the couples, is greater (other things being 
equal) the shorter the time in which the electrolysis of sulphuric 
acid is effected. 

IV. The following numbers justify this assertion ; they corre- 
spond to experiments in which the liquid of the battery was re- 
newed each time, and in which the length of the platinum wire 
in the external part of the circuit was successively reduced :— 

* The quantity of acid ordinarily employed is 90 cubic centims. 


M. P. A. Favre’s Thermal Researches on the Battery. 318 


Heat confined Heat corresponding 
Value of R. within the battery. to Retr. a 
millims. units. units. 

7000 1816 18018 
4000 2349 17485 
1000 3373 1846] 
500 A777 15057 
250 5410 14.424. 


V. Resuming my determinations of the electrolysis of sulphate 
of copper and sulphate of hydrogen*, and varying the conditions 
of the experiments, I obtained a number higher than those I 
have given, and which must be nearer the real number repre- 
senting the change of condition of hydrogen. This number, 
which is about 6000 thermal units, is but little different from 
that given in my previous memoir. 

In the present series of researches I have taken the precaution 
to collect and analyze the gases disengaged in the voltameter, 
and to allow for the formation of oxygenated water and for the 
water which is reformed. 

When, instead of working with pure and renewed acid, the pro- 
portion of sulphate of zinc is allowed to increase, the influence 
due to the electrolysis of the salt is soon evident. In conse- 
quence of it a deposit of zinc is formed on the surface of the pla- 
tinum. In dissolving, this produces a quantity of heat which is 
not transmissible to the circuit—a fact which explains the num- 
ber.9122 which expresses the quantity of heat which is not 
found in the circuit R+7, and which the causes previously in- 
vestigated would not have produced. 

VI. In fact, when we examine what takes place in a battery 
of several Smee’s elements, we see, when by successive operations 
the liquid has become charged with sulphate of zinc, that one or 
several of the couples scarcely disengage any gas-bubbles; then 
when the circuit is opened, the couples disengage more and 
more rapidly the complement of gas, forming for each element 
a total equal to that which had been disengaged by each couple 
working regularly to the moment of opening the circuit. 

The same phenomenon is produced with a single couple, and 
becomes markedly apparent; for the disengagement of gas is 
seen to continue for a certain time after the circuit is opened, and 
then suddenly to stopt. 

The quantity of sulphate of zinc thus decomposed, and the 
acid of which being liberated attacks the zine of the couple, 
always corresponds to an equivalent quantity of sulphuric acid 
which does not come into play in the reaction; so that for the 
same intensity there is always the same amount of zine attacked 

* Comptes Rendus, vol. lxvi. Feb. 10, 1868. 

fT I may remark that, the circuit being open, the zinc may remain ini- 
mersed for a whole week without any gas being liberated. 


Phil. Mag. 8S. 4. Vol. 38. No. 255. Oct. 1869. Ni 


314, Royal Society :— 


to the advantage of the current; but as the metalloid radical 
SO‘ which attacks the zinc is not solely taken from the sulphuric 
acid but comes partially from the dissolved sulphate of zine, it 
follows that the electromotive force, and therefore the power of 
the battery, diminishes proportionally to the quantity of heat 
necessary for the electrolysis of this latter salt. no 

To the electrolysis of zine, therefore, we must principally at- 
tribute the want of constancy in the intensity of the current 
furnished by a Smee’s couple*. 

VII. Substituting amalgamated cadmium for zinc in the for- 
mation of the couples, I observed perfectly similar results. 

VIII. Finally I introduced into the part of the circuit exterior 
to the calorimeter which contained the pile a rheostat, in some cases 
at the ordinary temperature, and in some heated to bright redness. 
In the latter case the resistance was almost doubled, and the 
quantity of heat furnished by the battery was that which would 
have been taken from it by a rheostat of double the length and 
kept at the ordinary temperature. I shall soon revert to this 
subject. 


XXXVII. Proceedings of Learned Societies. 
ROYAL SOCIETY. 


[Continued from p. 162.] 
May 27, 1869.—Lieut.-General Sabine, President, in the Chair. 


HE following communication was read :-— 
“On the Radiation of Heat from the Moon.” By the Earl 
of Rosse, F.R.S. 

The following experiments on Lunar Radiant Heat were under- 
taken with the view of ascertaining whether with more powerful and 
more suitable means than those previously employed by others, with 
little or no success, it would be possible to detect and estimate the 
amount of heat which reaches the earth’s surface from the moon. 

Professor Piazzi Smyth had conducted a series of experiments on 
the Peak of Teneriffe with a thermopile, but apparently without 
any means of concentrating the moon’s heat beyond the ordinary 
polished metal cone. 

Melloni had employed a glass lens of considerable diameter (I be- 
lieve about three feet); but as glass absorbs rays of low refrangibility, 
it was not so well adapted to concentrate heat as a metailic mirror. 

In the following experiments the point sought to be determined 
was, in what proportions the moon’s heat consists of :— 

(1) That coming from the interior of the moon, which will not 
vary with the phase :— 


* I preferred the use of Smee’s battery in my researches, because I was 
not concerned with the constancy of the current, and it is both rapid and 
easy to work with. 


The Earl of Rosse on the Radiation of Heat from the Moon. 315 


(2) That which falls from the sun on the moon’s surface, and 
is at once reflected regularly and irregularly. 

(3) That which, falling from the sun on the moon’s surface, is ab- 
sorbed, raises the temperature of the moon’s surface, and is after- 
wards radiated as heat of low refrangibility. 

The apparatus consisted of a thermopile of four elements, the faces 
half an inch square, on which all the moon’s heat which falls on 
the large speculum of the 3-foot telescope is concentrated, by means 
of a concave mirror of 3} inches aperture, 2°8 inches focal length. 

As it was found difficult to compensate the effects of unequal ra- 
diation on the anterior face of the pile, by exposing the posterior 
face also of the same pile to radiation from the sky, during the 
later experiments (beginning with March 23rd) two piles were used, 
and the following was the form of apparatus adopted. 


DE is the large mirror of the telescope; FG the two small 
concave mirrors of 33 inches aperture, and 2°8 inches focal length, 
fixed in the plane of the image formed by the large mirror DE. 
The two thermopiles are placed respectively in the foci of F and 
G, their anterior faces shielded from wind and other disturbing 
causes by polished brass cones, and their posterior faces kept at a 
nearly uniform temperature by means of brass caps filled with 
water. The thermopiles and accompanying mirrors are supported 
by a bar screwed temporarily on the mouth of the tube. Two wires 
are connected with the two poles of each pile; and the ends of the 
wires are connected, two and two, close to the galvanometer, in such 
a manner that a given amount of heat on the anterior face of one 
pile will produce a deviation equal in amount, and opposite in direc- 
tion, to that produced by an equal amount of heat on the anterior 
face of the other pile. Thomson’s Reflecting Galvanometer was the 
one used. 

This apparatus has not yet had a fair trial, as I was unable to 
obtain from Messrs. Elliot a pile ready made of similar dimensions 
to that which I already possessed. That which they sent had only 
one-fourth the required area of face. 

The following Table (p. 316) is a summary of the results. 

In column 3 is given the mean of the deviations of all the single 
differences from the mean difference of all the readings taken with 
the moon on and with the moon off the apparatus. 

In column 4 the arithmetic mean of all the observed deviations. 

In column 5 the calculated deviation for each night at midnight, 
on the assumption that the deviation corresponding to full moon 
=100, and that the moon is a smooth sphere. 


Ne 2 


316 Royal Society :— 


: | = ist 
ty (o) ' 2 2 3 ae ' 
2 ieee d | 2 [fa [Esle |3 
5 s a laces S Fe las |* 
= A u Ss ~~ oS i) BS ise 
ro) Q 2° e q & 6 2/2 fe) 
iS ° B 2 S) S gels 4 
q Ce © re) alae Weal eet) eo "3 o 
2 ° 3 eo | @A eS gi lola gis. 
a A S| 8 |AS8 Of sF Sie dias 
1868. a 
T-) Dec: 30)... 103-7 179417 110 19 
II i POus Gens | OOM MOOI! | FOO izo8 
1869. 
TT an, ol. 67°5 | 73:1 | 92-1 | 47 
IV Paige 34 41:9") 81:1 | 79 |... | ..2- |Occasional clouds: 
White frost. Mirrors became 
dewed; but the readings 
Mh » 26 83 96°7 | 85°8 | 15 | 56 taken after this took place 
| have been rejected. 
Vin Mar 230) 34a eo 67-7 | 84:2 | 57 | ... | 40 |Occasional nee 
Occasional ds, str 
Vi | ©) 27140 hs PeoG fis: 1 sels les | cts of ee ai 
VIII , 28.| 35 |113 96-1 |117 16 | 30 | 49 No note of cloud, very little 


breeze, generally calm. 

Moon low, sky covered with 
hazy clouds, through which 
the moon was seen with much 
diminished brilliancy. 

“Very clear and calm, but 
moon low; no perceptible 
ee imparted to the 
needle. 

Wind blowing strong into 
the mouth of the tube nearly 
the whole time. 

No note of cloud till just at 


NG Fares 19: 943 aloe) Ord. 1 OO 85.| 25 | 14 the end of these observa- 


Ps 


Morr AA | ee sts Sion Adee 123) 0225 4/5 4: 


Xe OTs, AS h| ALG Gu eo eeO: DrelAGs 


tions. 

j A sa little wind ; occasional 
clouds. 

Halo with hazy clouds; 
moon seen through them 
with much-diminished bril- 
liancy. 

Frequent passing clouds du- 
ring the latter part of these 
observations. 

No cloud visible, but haziness 
suspected, as it existed both 
at sunset and at sunrise. 


XO ee 20s 88D. a3 48:8 | 68 72 | 35 | 51 


DONG ee 7 | aickt Pe RAPIDS Taney | Goocce 239) || 550 kD 


————_} | —— | | | | | 


We have then Q (quantity of heat coming from the moon’s surface) 


si cos 0. cos (e—8) dé 
ail {r—e .cose-+ sin el®, 


* This formula is based on the assumption that the heat coming to the earth 


The Karl of Rosse on the Radiation of Heat fromthe Moon. 317 
where e=az—apparent distance between the centres of the sun and 


a When e=0 (full moon), Q= = a 


when e= 5 (half moon), Q= 9° 
when e=z (new moon), Q=0; 
‘. if full moon =100, Q in general 


=100(1—£cos e+ sine). lueeeiee.. | p.a'(2)) 


Tv 


In column 6 we have the deviation for full moon calculated from 
the observed mean deviation for each night. 

In column 7 the supplement of the apparent distance between the 
centres of the sun and moon. 

In column 8 the approximate mean altitude of the moon. 

In column 9 the number of times the telescope was put on or off 
the moon during the observations included in the mean result. _ 

In all these observations the deviations which have been measured 
are those due to the difference between the radiation from a circle of 
sky containing the moon’s disk, and that from a similar circle of 
sky close to it not containing the mcon’s disk. 

The annexed diagram will show approximately the rate at which 
the moon’s light increases and diminishes with its phases as deduced 
from formula (a); and the ringed dots with the accompanying Roman 
figures (for reference) give the quantity of the moon’s heat as deter- 
mined by observation on different nights. 

Although there is considerable discordance between some of the 
observed and calculated quantities of heat, the results suggest to us 
that the law of variation of the moon’s heat will probably be found 
not to differ much from that of the moon’s light. tt therefore follows 
that not more than a small part of the moon’s heat can come from 
the first of the three sources already mentioned. 

With the view of ascertaining what proportion of the sun’s heat 
does not leave the moon’s surface until after it has been absorbed, 
some readings of the galvanometer were taken on four different 
nights near the time of full moon, with a disk of thin plate glass in 
front of the face of each pile; and the deviation was about six or 
eight divisions. 

As the glass screens were examined with care for dew after re- 
moval on each night, and none was perceived except on one occasion, 
the probable percentage of the moon’s heat which passes through plate 
vlass is 8, or rather less. 

Few experiments appear to have been made on the absorptive power 
of glass for the sun’s rays; but, from the best data that I have been 
able to obtain, I find that probably about 80 per cent. pass through 

lass. 
: The greater part of the moon’s heat which reaches the earth ap- 
pears, therefore, to have been first absorbed by the lunar surface. 


from an element (OS) of the moon’s surface =K.0S.cos@.cos ¢, 6 and ¢ being 
respectively the inclinations of the lines to the sun and to the earth from the 
normal to that point of the moon’s surface, and K a constant. 


Royal Society : 


318 


€ 
ie 


OF OF 


09 


OOT rayay 
OGT OZI 
aye 3 “101, BIAVG 
| | | | | 
i: o08T o09T o0FI o0GI o00T 008 009 oP 006 rie) 006 o0P 009 008 o00T o0GT o0FI o09T oO8T 
“NOOW MAN UALAVAS LSVI “"NOOW TINA MALUVAOD LSuIa “NOON MAN 


The Earl of Rosse on the Radiation of Heat from the Moon. 319 


It now appeared desirable to verify this result, as far as possible, 
by determining by direct experiment the proportion which exists 
between the heat which reaches the earth from the sun and from the 
moon. 

If we start with the assumption that the sun’s heat is composed 
of two portions, 

the luminous rays, whose amount = L, 


and the non-luminous, as a a Oe 


also that the moon’s light consists of two corresponding portions, 
L’, O’7, the luminous not being absorbed, and the non-luminous being 
entirely absorbed in their passage through glass, then 


Se aap LIHO! 
L' =-08: L' L+0O 
L'+0' 
Substituting for <i its generally received value (800,000), we have 
L'+0' ] 


L+O — 80,000 

Owing to the extremely uncertain state of the weather, only one 
series of eighteen readings was obtained for the determination of the 
sun’s heat. A beam of sunlight was thrown, by means of a plane 
mirror, alternately on and off a plate of polished metal with a hole 
‘175 inch in diameter. At a short distance behind this the pile was 
placed. The deviation thus found was connected with that pre- 
viously found for full moon by using the deviation produced by a 
vessel of hot water as a term of comparison. 

The relative amount of solar and lunar radiation thus found was 

BUSIIgrMinmretne bar Shs boy, <(e) 
which is quite as near that given by (0) as we could expect when we 
consider the roughness of the data. 

As a further confirmation of the correctness of the two rough 
approximations to the value of the ratio existing between the sun’s 
and the moon’s radiant heat already given, the subject was investi- 
gated from a purely theoretical point of view. It was assumed 

(1) That the quantity of heat leaving the moon at any instant may 
without much error be considered the same as that falling on it at 
that instant. 

(2) That the absorptive power of our atmosphere is the same for 
lunar and solar heat. 

(3) That, as was already assumed in obtaining formula (a), the 
moon is a smooth sphere not capable of reflecting light regularly. 
Then the heat which leaves the moon in all directions = quantity 


which falls on the moon = of the quantity which falls on the 
earth from the sun 


or. Eh 
13°55 


=K. (“{@—0 .cose+ sine} sine.de= aoe 
eo 


320 Royal Soctety. 
The part which falls on the earth 
1 


—K Be cose+ sine} sine. de 
0 
Do COS (ls O91 Jean 
399°964 


= = 4 { —m .versin (1° 55')+ 3 sin (1° 56" } 


= s, E suppose ; 


therefore (if we may be allowed the expression) 


_~h $ 5 of; 
Suncneat | 18102 XS 79,000 (cna proxine) ens 


In the above, the proportion between the areas of surface pre- 
sented by the moon and earth to the sun is taken =13°95, and the 
angle subtended by the earth at the moon =1° 55’. 

The value of the readings of the galvanometer was determined by 
comparison with those obtained by using a vessel of hot water coated 
with shellac and lampblack varnish as a source of heat. The vessel 
was of tin, circular, and subtended the same angle at the small con- 
cave reflectors as the large mirror of the telescope. It was thus 
found that (the radiating power of the moon being supposed equal 
to that of the lampblack surface and the earth’s atmosphere not to 
influence the result) a deviation of 90 for full noon appears to in- 
dicate an elevation of temperature through 500° Fahr.* In deducing 
this result allowance has been made for the imperfect absorption 
of the sun’s rays by the lunar surface. 

In the present imperfect state of these observations it would be 
premature to discuss them at greater length; but as some months 
must elapse before any more complete series can be obtained, and 
the present results are sufficient to show conclusively that the mcon’s 
heat is capable of being detected with certainty by the thermopile, I 
have thought it best to send this account to the Royal Society ; and 
I shall be most happy to receive suggestions as to improvements in 
the method of working, and as to the direction in which it may be 
most desirable to carry on future experiments. 


GEOLOGICAL SOCIETY. 
(Continued from p. 243. ] 


February 10th, 1869.—Prof. T. H. Huxley, LL.D., F.R.S., 
President, in the Chair. 


The following papers were read :— 


* This may seem a very large rise of temperature; but it is quite in accordance 
with the views of Sir John Herschel on the subject (Outlines of Astronomy, 
section 432 and preceding sections), where he says that, in consequence of the long 
period of rotation of the moon on its axis, and still more the absence of an atmo- 
sphere, “‘ The climate of the moon must be most extraordinary, the alternation 
being that of unmitigated and burning sunshine, fiercer than that of an equatorial 
noon, and the keenest severity of frost, far exceeding that of our polar winters, 
for an equal time.” And again, “. ... the surface ot the full moon exposed to 
us must necessarily be very much heated, possibly to a degree much exceedirg 
that of boiling water.” 


Geological Society. 321 


1. “On the Evidence of a ridge of Lower Carboniferous Rocks 
crossing the Plain of Cheshire beneath the Trias, and forming the 
boundary between the Permian Rocks of the Lancashire type on the 
North and those of the Salopian type on the South.” By Edward 
Hull, Esq., M.A., F.R.S., F.G.S. 

In this paper the author proposed to account for the dissimilarity 
of mineral and stratigraphical characters of the Permian formation 
of Lancashire and the North of England as compared with that of 
the Midland Counties and Shropshire, on the ground that they had 
originally been deposited in separate basins, divided off from each 
other by a ridge of Lower Carboniferous rocks, stretching from west 
to east, under the central plain of Cheshire. 

The author showed that there was evidence of such a ridge on the 
east side of the plain of Cheshire, by the uprise of the Lower Car- 
boniferous rocks to the north of Congleton Hdge, in the valley of 
the River Dane, and that the date of this uprise and the denudation 
of the Upper Carboniferous beds along the axis of elevation was 
clearly determined to be antecedent to the Permian period by the 
outlier of Permian rocks at Rushton Spencer. 

On the west side of the plain there was evidence of a similar axis of 
upheaval to the south of the Flintshire Coal-field near Hope, where 
the Lower Carboniferous rocks (Yoredale and Millstone beds) are 
brought up to the surface at the margin of the New Red Sandstone. 

Mr. Hull regarded the uprise on each side of the plain as 
referable to the same Prepermian age, and as belonging to the East 
and West system of flexures into which the Carboniferous rocks 
were thrown at the close of the Carboniferous period over the north 
of England. Such an axis had its antetype in the concealed ridge 
which once occupied the valley of the Severn, and divided the Devo- 
nian rocks of Devonshire from those of South Wales; and the author 
suggested that a similar ridge, now concealed beneath the Triassic 
formation of Cheshire, offered the only satisfactory explanation of 
the dissimilarity in the two types of Permian beds—that of Lanca- 
shire, and that of Shropshire and the Midland Counties. 


2. “On the Red Chalk of Hunstanton.” By the Rey. T. Wilt- 
shire, M.A., F.L.S8., F.G.S. 

The author described the section exposed in Hunstanton Cliff as 
showing :—1. White Chalk with fragments of Inocerami. 2. White 
Chalk with Siphonia paradoxica, having its base undulated and 
the cavities filled up with a thin bright red, argillaceous layer, resting 
upon (3) the Red Chalk, which is divisible into three sections :—a, 
hard, containing Avicula grypheoides and Siphona paradowica, and 
with fragments of /nocerami at its base; 6, hard, rich in Belemnites ; 
c, incoherent at its base, rich in Terebratule. 4. Carstone, a yellow, 
coarse, sandy deposit, resting on a bed of clay, containing no fossils 
in its upper part, but with a band of nodules containing Ammonites 
Deshayesti and other species about 30 feet down, together with 
ironstone nodules like those of the Lower Greensand of the Isle of 
_ Wight, and bearing impressions of fossils which correlate the lower 
part of the Carstone with the base of the English Lower Greensand. 


322 Intelligence and Miscellaneous Articles. 


The author gave a list of these fossils, and also of those of the Red 
Chalk, the latter amounting to sixty-one, and presenting a mixture 
of forms belonging to the Lower Chalk, Upper Greensand, and 
Gault. On comparison with the Gault section at Folkestone, the 
author considered it evident that the Red Chalk of Hunstanton was 
equivalent to the upper part of that formation. He mentioned that 
ten miles south of Hunstanton, in artificial sections, blue gault has 
been found resting upon the Carstone, whilst rather nearer to 
Hunstanton the same place was occupied by a red clay, connecting 
the two dissimilar deposits, which, however, were shown by analysis 
to contain nearly equal quantities of iron. If the Upper Greensand 
be represented in the Hunstanton section, the author considered that 
its place must be in the band numbered 2, containing Siphonia para- 


ON THE EXPANSION OF GASES. 
NOTE BY M. A. CAZIN, PRESENTED BY M. LEVERRIER. 


{* 1862* I gave an experimental method for making known the re- 

lation that exists between the pressure and the specific weight of 
a gaseous mass when it expands without losing or receiving heat. 
At that time I had applied this method between limits of pressure 
only slightly differing from one another, not having the requisite ap- 
paratus. I have now been able to work upto a pressure of 9 atmo- 
spheres ; and it is the result of these new experiments that I have the 
honour to communicate to the Academy. 

The apparatus is set up ina hall of the observatory. I owea part 
of the materials of it to the Scientific Association of France, and to 
the generosity of M. Hugon. One of his gas-engines worked a 
compression-pump ; and I cannot praise too highly its excellent ser- 
vice. Let me be allowed here to thank MM. Leverrier and Hugon 
for their kind assistance. 

I will now sketch out the principle of my method. The gas is 
enclosed in two reservoirs, A and B, connected by a stopcock of 
large orifice (4 centims. diameter). This stopcock being closed, a 
pump withdraws the gas in the reservoir B and compresses it to the 
pressure p, in the reservoir A. Let us suppose that we open the stop- 
cock and close it again at the precise moment when there is an equa- 
lity of pressure on both sides of the orifice. During the flow there 
has been acooling in A; then, after closing, the sides have reco- 
vered their initial temperature. The final pressure p, is measured ; 
afterwards the stopcock is opened again, the equilibrium is allowed 
to be reestablished, and the pressure p, is measured. When the re- 
servoir B is sufficiently large, this pressure does not differ appreciably 
from the pressure acquired by the gas at the end of the expansion. 
I observed this fact in pursuing a method which I have explained 
in a preceding communication (March 9,1868). The gaseous mass, 
then, which remains in the reservoir A has passed rapidly from the 
pressure p, to the pressure p,, and its specific gravity has passed 

* Annales de Chimie et de Physique. 


Intelligence and Miscellaneous Articles. 323 


from the value p, to the value p,. The quantity p, is calculated from 
p,, and p, from p,. 

But it is necessary to determine whether the closing of the stop- 
cock has been instantaneously effected at a given moment; this is 
the essential point of the method. For this purpose a voltaic circuit 
is arranged, containing an electromagnet ; and the movement of the 
stopcock determines the closure of this circuit at the moment when 
the orifice is opened, and afterwards its rupture at the moment when 
the orificeis closed. ‘The electromagnet moves a pencil which leaves 
a trace upon a sheet of paper which moves at a known rate; from 
the length of this trace is deduced the duration T of the opening of 
the stopcock. A series of experiments comprises those in which we 
make T vary without changing either p, or p,. This series is re- 


presented by a line having for abscissz the values of T, and for ordi- 
Te 
f———*, 


nates the values o The ordinates vary according to a cer- 


tain law as long as‘ a below the duration @ which corresponds to 
the instant sought, and according to a different law when T is above 
that duration. The curve is then formed of two very different 
branches, the point of intersection of which is determined graphi- 
cally. ‘The abscissa and the ordinate of that point give the duration 
@ of the complete flow and the value of p, which we want. 

The lower branch was virtually aright line, nearly parallel to 
the axis of abscissee, which indicated a very slow heating-action on 
the partof the sides. Hence is deduced a correction giving the supe- 
rior limit of the value that p, would have assumed if the sides had 
been impervious to heat. ‘The feebleness of the thermal action of 
the sides is remarkable; we may attribute it to the formation of a 
gaseous sheath varnishing the sides. 

First mode of observation.—p,—p, is small; it is measured by 
means of an oil manometer, whose branches communicate respec- 
tively with the reservoir A (29 litres) and the reservoir B (520 
litres), and by an open-air manometer communicating with one of 
the reservoirs. Similarly p,—p, is measured. All necessary pre- 
cautions are taken so that the gas enclosed in the manometers 
may not by its motion disturb the expansion. In this way I 
found that the quantity 


pe IOs 

log p, —log p 
was constant for air and carbonic acid when p, varied from 1 to 5 
atmospheres. I did not raise the pressure higher, because the resist- 
ance of the sheet-iron reservoir B imposed this limit, Carbonic 

acid presented the oscillation that I described in 1862. 

I concluded from this that, if one of these gases expanded in a 
space impervious to heat without acquiring an appreciable velocity, 


the law of expansion would be represented by the known formula 


of Laplace and Poisson, p=Ap”, 


A and m being two constants for the same gas; m=1°41 for air, 
and 1:29 for carbonic acid. 
This result is interesting as regards the mechanical theory of heat, 


B24 Intelligence and Miscellaneous Articles. 


We know that this theory leads to this formula when we suppose 
the internal work due to the change undergone by the gas equal to 
zero. Lt would seem that this does not hold for carbonic acid, the 
internal work of which is considerable. M. Hirn has put forward a 
theory applicable to this case which leads to the same formula ; 
my experiments are consequently favourable to this theory; but 1 
ought to remark that this law represents an ideal expansion which 
cannot be realized, and it will be seen that real expansions comport 
themselves differently. 

Second mode of observation.—We keep p, constant and vary p,. It 
is thus that I have studied expansion from a pressure of 9 atmo- 
spheres to 5, 4, 8, .... atmospheres. The principal results of this 
investigation are given in the annexed Table. 

p,= 6576 millims. of mercury, p, =6°61302. 


The specific gravity p=1 under a pressure of 1000 millims. 


Air. 


eS 

4219|4728°0 | 29:4 |0°15 /0-00610 |4°74641 |4°74861 |4:82721 |0-07860 
2998/3685:0 | 50:9 0°23 |0°00590 |3°69553 |3°70043 |3°78846 |0-08803 
2173/2925°9 | 70-2 |0°40 |0:01080 |/2:93198 |2:94618 |3°00548 |0°05930 
1437/2156°5 | 91°0 |0°54 |0:01321 |2°15923 |2°18513 |2°24883 |0:06370 
769|1349°7 |117°4 |0°70 |0°02341 |1°35022 |1°38272 |1°44338 |0-06066 


| | 


Carbonic acid. 


3285 3838°9 | 13°4 {0°42 |0°0045 = |3°93501 |3°93947 |4:56492 |0°62545 
2073|2686°8 | 62°3 |0°64 0°0070 /2°72537 |2°74074 |3:46253 |0-72179 
811/1275:1 | 99°3 |1:12 /0°0061 = |1°27795 |1°31483 |1-94386 |0°62903 


The specific gravities have been calculated by the help of M. Reg- 
nault’s formulas for the compressibility of gases. 

At is the decrement of the temperature, calculated according to 
p, and p; by means of Gay-Lussac’s law. 

Ay is the diminution of the ordinate for the lower branch of the 
curve which represents each series, corresponding to an increment 
of the abscissa equal to one second. It is by means of these 
values that the correction relative to the sides has been made. 

p, 1s the observed specific weight without any correction. 

p is this weight corrected according to the thermic actionof the sides. 

o is this weight calculated from the formula of Laplace and 
Poisson with m=1°'41 for air and 1°291 for carbonic acid. 

If we calculate the differences p'’—p,, we find quantities which, 
according as p, diminishes, vary very little for air, but which for 
carbonic acid first increase, then decrease. The result shows that 
the real specific gravity at the end of the expansion is always smaller 
than if the gas followed the preceding law, and that the deviation 
cannot be solely due to the influence of the sides; for according as 


Intelligence and Miscellaneous Articles. 320 


p, diminishes, the decrement of the temperatnre Af increases consi- 
derably ; consequently the heating by the sides ought to increase 
the deviation more and more if no other cause intervened. We 
must also remark that this deviation is greater for carbonic acid 
than for air, although the thermic effect of the sides is less. 

I regard, then, the observed deviation as the result of two distinct 
causes ; one is the thermic action of the sides, the other is of a dif- 
ferent nature. 

We have the effect of this latter in the last column of the Table. 
-We see that for the two gases, p'’’—p’ begins by increasing when 
p, diminishes ; this difference reaches a maximum and then decreases. 
Now there is a mechanical effect which varies in the same manner. 

Let us consider the expansion from 9 atmospheres to 1 in two 
distinct cases :— 

(1) Without appreciable velocities : the law is that of Laplace and 
Poisson. 

(2) As takes place in our apparatus; the molecules situated near 
the orifice are animated with a certain velocity; there is in the re- 
servoir A less gas than in the first case; according as the pressure 
diminishes, the velocity increases; but soon it diminishes; conse- 
quently it passes through a maximum. According to the period at 
which the flow is stopped, the difference of the specific gravities 
which exist in A in the two cases ought to vary in the same manner. 

It is true that my experiments do not exactly realize the second 
case. Thus in the first series the expansion takes place from 9 to 
about 5 atmospheres, but the reservoir B is found also under a 
pressure of 5 atmospheres at the end of the flow; while in the last 
series the reservoir A is subjected to 5 atmospheres when the re- 
servoir B is found subjected to a less pressure. However, we can 
conceive that this circumstance does not influence the direction of 
the deviation. 

In fine, the formula of Laplace and Poisson can be applied to a 
reversible expansion ; but there must be another law in the case of 
an irreversible expansion. ‘The investigation of this law will be the 
object of a further study. 

I would also remark that, the difference p'’—p' being greater for 
carbonic acid than for air, the impulse of the gas in the irreversible 
expansion varies in the same direction as the internal work. We 
meet, in short, with an effect of the gaseous viscosity that M. Reg- 
nault speaks of in his memoir on the velocity of sound.—Comptes 
Rendus, August 9, 1869. 


ON THE EMPLOYMENT OF THE SPECTROSCOPE IN ORDER TO DIS- 
TINGUISH A FEEBLE LIGHT IN A STRONGER ONE. BY M. J.M. 
SEGUIN. 


To the two poles of a Ruhmkorff-coil of middle size there are 
attached two fine platinum wires which are kept im a horizontal 
position, their extremities being separated by an interval of about 
1 centim. The spark is produced with its usual characteristics, and 
we especially observe the shell of blue light which envelopes the end 
of the negative wire. We bring the positive wire gradually nearer 


326 Intelligence and Miscellaneous Articles. 


and nearer to the negative one. The latter begins to redden; 
at first the blue light continually grows fainter, then becomes in- 
visible; at least we cease to distinguish the shell that it forms 
around the wire ; andif any trace of it remains, it is only a bluish tint 
in the light due to the incandescence. Whien the wires are almost in 
contact, especially if the finger is presssd lightly on the hammer of 
the contact-breaker, the incandescence of the negative wire becomes 
dazzling, and then there is no more appearance of the blue light. 

I was curious to know if it had really disappeared, or if it was 
only concealed by the brilliancy of the wire when white-hot; and I 
thought that the now celebrated method by which we discover the 
trace of the solar protuberances amongst the intenser rays of his 
disk might be applied here. 

I made use of a vertical spectroscope by Duboscq. The slit 
is vertical, and can be moved from one wire to the other along the 
spark. ‘The characteristics of the spectrum change according as we 
view the brilliant point where the spark is detached from the posi- 
tive wire, or the blue shell which envelopes the extremity of the 
negative wire, or, finally, if that is incandescent, the red parts which 
lie beyond the blue shell. 

We keep the slit upon the blue shell while the spark is too long 
to admit of the wire becoming red. ‘The spectrum is characterized 
chiefly by a group of four green rays, a group of two rays placed be- 
tween the green and the blue, a group of three violet rays, beyond 
which we can see others of less brilliancy. 

As before, we gradually bring the positive wire nearer to the ne- 
gative wire, which latter begins to redden. One would expect to see 
a continuous spectrum; and this in fact is what actually happens, if 
we direct the slit towards the parts of the red wire which are 
beyond the blue electric glow. We have then a continuous spectrum 
which is worth noting, because we thus learn, without requiring 
to light up the micrometric scale, that the violet rays given by the 
blue light correspond nearly to the most refrangible extremity of this 
continuous spectrum. JBringing back the slit to the extreme end 
of the negative thread, we find again the streaked spectrum of 
the blue light. The red in it becomes more brilliant in propor- 
tion as the thread becomes more incandescent; but the green, blue, 
and violet rays still continue. But when the incandescence is very 
intense, the green rays disappear, then the blue, and the spectrum is 
continuous into the violet, but at the extremity of the violet we still 
perceive the group of three violet rays, which become less distinct, 
but mark their position until the thread begins to melt. The 
ultra-violet rays have ceased to be visible. Thus the spectroscope 
permits us in this case, as well as in the observation of the solar pro- 
tuberances, to ascertain the presence of a feeble glow in the midst of 
a light which to the direct vision is dazzling.—-Comptes Rendus, 
June 7, 1869. 


ON THE MEAN VELOCITY OF THE MOTION OF TRANSLATION OF 
THE MOLECULES IN IMPERFECT GASES. BY M. P. BLASERNA. 


We are often led to inquire whence arise the deviations from 


Intelligence and Miscellaneous Articles. 327 


Mariotte’s law that experiment reveals in the different gases. I 
do not think that we can accept the explanation that M. Dubrunfaut 
has lately offered*, an explanation which tends to ascribe these de- 
Viations to small quantities of aqueous vapour existing in even the 
most perfectly dried gases. When Plicker published his experiments 
on Geissler’s tubes, I succeeded in preparing tubes of nitrogen and 
of carbonic acid which contained no traces whatsoever of the three 
brilliant rays which belong to hydrogen and aqueous vapour. To 
accomplish this, I made use of agood common air-pump ; I exhausted 
the receiver thirty or forty times, and I dried the gases by the ordi- 
nary means, except only that the electrodes were of platinum in- 
stead of aluminium, which is very often employed. 

This is the method, pointed out by Rudberg, that M. Regnault 
and all experimenters have followed. If, nevertheless, a trace of water 
does remain, it seems to me impossible that it should produce the 
great deviations that we observe in the case of imperfect gases. 

I have also proved that for air and carbonic acid the molecular 
state cannot be considered to result solely from mutual attractions 
or repulsions, whatever may be the law of these actions; in short, a 
cold and expanded gas, being then heated and compressed to the 
same volume, ought to exhibit the same phenomena with regard to 
its compressibility, which is contrary to experience. And the re- 
searches of M. Amagat have lately proved the same thing for am- 
monia and sulphurousacid. ‘The mechanical theory of heat leads us, 
as a natural consequence, to regard heat as resulting from the mo- 
tions of the molecules, and to define a gas as a body whose molecules 
travel in all directions in space. But MM. Krénig and Clausius 
have shown that if we suppose these progressive motions in the gas 
to be rectilinear, we arrive at Mariotte’s law; and M. Clausius has 
even developed a formula which has enabled him to calculate the 
mean velocity of these motions for the better-known gases. 

The deviations from Mariotte’s law arise consequently from attrac- 
tions which still exist in the gases, and which are nothing but a par- 
ticular case of universal attraction: these attractions are more or less 
feeble according to the mass and the mean distances, greater or 
less, by which the gaseous molecules are mutually separated. This 
is the simplest explanation we can offer of the phenomenon; it is 
the one which I believe is most generally accepted. 

All this being granted, we may determine the actual velocities of 
the molecules in imperfect gases. 

Imagine a kilogramme of gas, at temperature zero, and under 
an initial pressure p, so slight that the volume v, shall be very 
great, so that we may disregard the attractions. Increasing the 


v 
pressure to p, the volume will be v’,, and we shall have stk = 1+A),, 
. San fee 
A, being the deviation from Mariotte’s law under the pressure p. 
Raising the temperature to ¢, the pressure being constant, the vo- 
v 


lume v', becomes v, and we have a =1l+a,t, %, being the coeffi- 


te) 


* Comptes Rendus, vol. lxviii. p. 1262. 


328 Intelligence and Miscellaneous Articles. 


cient of expansion under a constant pressure between 0 and ¢, and 
for the pressure p. 
Putting Po“o% — Rp, ae =a,, we have 
PEs, Ap 

puSRilartt)! oa io) 2 
a formula which combines the law of the compressibility and the 
law of the dilatation of imperfect gases, and in which R, and ap 
change with the pressure. Thus we have for R, the following 
values :— 


Ome-| 0°76 1 5 10 15 20 
De tre. | metre.} metre.|metres./metres.|/metres.| metres. 
AT Seas. cctoos ee R,= 29°222) 29°325) 29°347) 29°672) 30°007| 30°265) 30-446 
Carbonicacid.) Rp= 19329 19-388) 19°437| 20°417 21°907, 23°867 25°915 
; : u? 
But, according to M. Clausius, we have also ie) being the 
g 


acceleration due to gravity, andu the mean velocity of the progres- 
sive motion; then 

we VSR Gast), 7 eer 
a formula which differs from that given by M. Clausius for perfect 
gases in that R, and @, are not constant, but functions of the pres- 
sure or volume. It may serve to determine the mean velocity of the 
molecules in the different gases. In the case of air and of carbonic 
acid, for which we have the requisite experimental data, we thus 
obtain the following velocities, expressed in metres per second :— 


Pressure, Air. Carbonic acid. 


IM ME CHES; [ise ace es ol eee es ee a 
$= 40°85 = 10022 = 382-3 C100: 

0 485°1 566°9 393°3 459°7 

0°76 484°4 566°9 392-1 459°2 

1 484°8 566°9 391°3 459°0 


5 483°8 566°9 385:°0 456°4 
10 482°8 566°9 374°5 452°8 
15 482°0 566°9 362°9 449°4 


20 481-4 566°9 350°4 4462 


The velocities found for the pressure zero represent the ideal case 
of a gas infinitely rarefied (that is to say, perfect), the attractions being 
infinitely small. We see that the velocities diminish when the pres- 
sure increases—that is to say, when the volume becomes small and 
the attractions are more intense. For atmospheric air at 100° it is 
necessary to carry the calculation to the second decimal place in 
order to find the differences, which shows clearly the degree of 
perfection that this gas reaches at that temperature. It seems 
almost superfluous to remark that, in order that the numbers given 
for air may have a real significance, we must consider air, not as 
a mixture of two gases, but as a single ideal gas whose molecules 
possess the physical properties of nitrogen and of oxygen in known 
proportions.—Comptes Rendus, July 12, 1869. 


THE 


LONDON, EDINBURGH, ann DUBLIN 


PHILOSOPHICAL MAGAZINE 


AND 


JOURNAL OF SCIENCE. 


[FOURTH SERIES.] 


NOVEMBER 1869. 


XXXIX. Observations on the Temperature of the Human Body at 
various Altitudes, in connexion with the act of Ascending. By 
WitiraMm Marcer, M.D., F.R.S., Assistant Physician to the 
Hospital for Consumption and Diseases of the Chest, Brompton*. 


URING an excursion over the Mont-Blanc range I had an 

opportunity this summer of ascertaining the temperature 

of my body under various circumstances connected with the act 

of ascending. ‘The number of observations is, I must admit, 

much too small; still their individual results, when compared 

with each other, agree closely enough to allow of certain conclu- 
sions to be derived from them. 

I had with me a thermometer carefully made by Casella, and 
divided in fifths of degrees Centigrade, allowing of a tenth of a 
degree to be read off. The instrument could be accurately ob- 
served while its bulb was under my tongue, by means of a 
small mirror which, on being placed near the stem of the 
thermometer at a certain angle, reflected its image into my eyes, 
so that I could see the mercury rising or fallmg as plainly as 
if I was looking at it directly. It is useless to add that in 


* Communicated by the Author, haying been read to the “‘ Société de 
Physique et d’ Histoire Naturelle of Geneva” on the 3rd of September, 1869. 

+ On every occasion, I observed the height of the thermometer several 
times, and made sure of its being constant before noting the temperature, 
thus avoiding the fallacy which may easily arise from too short an exposure, 
as shown by Dr. Ch. Baeumler (Brit. Med. Journ. August 1869). Two ob- 
servations made in London in the sitting posture, at 11 a.m. (breakfast 
at 9), with a thermometer constructed for me since my return by Casella, 


Phil. Mag. S. 4. Vol. 38. No, 256, Nov. 1869. Zi 


330 Dr. Marcet on the Temperature of the Human Body at 


these experiments the greatest care was taken to keep the bulb 
of the thermometer as far back as possible beneath the tongue, 
while the margin of that organ was applied firmly against the 
lower jaw, the lips being kept closed, so that respiration was 
entirely effected through the nose. It was, consequently, im- 
possible that any of the air used for breathing could come into 
contact with the bulb of the thermometer while these observa- 
tions were carried on. 

The questions which offered themselves for investigation re- 
lated (1) to the influence of various degrees of altitude on animal 
heat, the body being in a state of rest; (2) to the imfluence of 
the act of ascending on animal heat observed at different heights ; 
and (3) to the influence of the act of descending on the tempe- 
rature of the body. I shall limit myself, on the present occasion, 
to the first two questions, leaving the influence of the act of 
descending on animal heat for future consideration. 

I soon ascertaimed the necessity of taking the temperatures 
while actually engaged in climbing; accordingly this was done. 
The instrument was withdrawn from its case and introduced 
under my tongue; the looking-glass was removed from the 
pocket, together with my watch ; and the height of the thermo- 
meter was observed while in the act of ascending, and taking 
every care to slacken my speed as little as possible. 

I began by noticing that frequently, while ascending, the 
thermometer after a sufficiently long exposure showed a tempera- 
- ture which, though steady at the time, commenced rising shortly 


as nearly as possible on the model of that which I had used, gave the fol- 


lowing results ; the bulb was kept under the tongue, and the degrees read 
off with a looking-glass :— 


Temperature. 
minutes. a 
Ty After ain" exposure ured sc eee ae 36°2 Centigrade. 

bs : DER PENA.» HR 36°5 

9 ” yiishe Sap. OLtan 36°7 

oP) 59 4 eeecC ee eer eee 36'8 

9 2 De) Pa RAE aaa 36°8 

$j 44 6 F-steady at nem. poo 

39 33 OOP OO OF OPO CY Ch OLS 36'°9 

” % OP Pasaeeeiae olies we 36°9 

I vAfter an exposure, of 20 i. sak en ee 36°4 
Next day under the | 5, js 

same circumstances, fe ae 36° 

” ” 3s Viexeduve op eas! ove) ave OU, 

oy) oy) ee aias dclekad sevnk 36'8 

ue x, 53 Steady at./i.. 869 

9 29 63 wiebe epecispevabedeuava 36°9 

5 9» Kasiacthiewe 369 


various Altitudes, in connexion with the act of Ascending. 331 


after (say a minute later), while I continued walking. The 
temperature, I conclude, was steady when first observed, as I 
could read it several times over without its altering; and the 
rising which took place a minute or two later was rapid, and 
would not have allowed of two similar readings being taken in 
succession. I explain this by assuming that, with the object of 
observing correctly the degrees of the thermometer, I was neces- 
sarily compelled to slacken my speed a little, thereby allowing 
heat to be formed afresh by the body to make up for that which 
had been used in excess in the act of climbing. 

I made a rule, with every observation, to note the time 
when food had been last taken, and observed that walking 
up hill fasting cools the body to a greater degree than it does 
after taking food, or while digestion is going on. Thus on arri- 
ving at the “ Pierre & l’échelle,”? 2060 metres, while in the act of 
ascending my temperature was 36°°5, and shortly after 36°°8. 
I made two excursions from Chamounix, with the object of 
determining the influence of food on the temperature of the body 
while going up hill. About an hour’s climbing on the Bre- 
vent takes the tourist to a hut called the “‘ Chalet des Cha- 
blettes.” I left Chamounix about an hour and a half after a 
plentiful breakfast and while digestion was still going on ; about 
a quarter of an hour before arriving at the chalet, and without 
slackening my speed, I ascertained my temperature under the 
tongue to be steady at 36°°5 after four minutes’ exposure; and 
on walking slower, after having noted this result, the temperature 
rose to 387°. On one of the following days, I left Chamounix 
for the Chalet des Chablettes early in the morning before break- 
fast, and consequently having taken no food whatever since the 
previous evening. About a quarter of an hour before arriving 
at the chalet, and while keeping up the speed of ascent, I ascer- 
tained my temperature to be 85°'3, the bulb of the thermometer 
having been kept for six minutes under my tongue. The heat of 
the body in this last experiment, or while ascending with an empty 
stomach, was therefore 1°-2 less than in the previous experiment, 
when food had been taken. After showing 35°3 in this last 
experiment, the thermometer rose rapidly, probably because I did 
not walk up quite so fast as I had done before reading the 
instrument; and on arriving at the chalet it was up to 36°4. 

I have thought it best to report my observations in the form 
of Tables, which are appended to this communication ; the results 
obtained are as follows. 

Result |.—That the temperature of the body, in the state of rest, 
does not, as a rule, appear to fall at increasing altitudes above 
the sea, and consequently a lessening of the atmospheric pressure 

9 


a 


332 Dr. Marcet on the Temperature of the Human Body at 


does not appear to have a marked influence on the temperature 
of man while at rest. Thus, 


Temperature of the body at Chamounix, 1050 metres, | 26.9 
betore-brealstastousien a4 wine it ates 


Same experiment another day . . abe oe 
At the “ Cabane des Grands Mulets, i 8050 arsliiace be- 3 
36'5 
fore breakfast. wee 
At the summit of the Col du Géant, eB 3362 metres, | gg. 
after eight minutes’ rest and fasting Seale 8 
At the Grand Plateau (Mont Blanc), “4000 metres, at Lag 
ws) 
rest-and fasting . . oe: 


On the highest «Bosse du Dromadaire? ? (Mont Blanc), 37°] 
4672 mehies about 24 40™ after breakfast, and at ae 


In twenty observations made while in the state of rest, at alti- 
tudes varying from 1050 to 4672 metres, and in various condi- 
tions as regards the food taken, the temperature of my body 
varied from 36° to 37°1, or 1°1 only; and it is remarkable 
that the highest temperature was found at the greatest altitude*. 

Although there exists a comparative degreee of uniformity be- 
tween the various temperatures observed when at rest, it is worth 
remarking that the highest can, as a rule, be connected with the 
circumstance that food had been taken not long previously, or 
with the fact that the thermometer had been observed while in 
the act of resting on the way down hill. The six highest readings 
of the thermometer, with but one exception, may be accounted 
for in that way; they are as follows :-— 


Temp. 
metres. 4 
1050 37°1 Chamounix, # of an hour after breakfast. 
3050 37'1 After arrival at the Grands Mulets about 23 hours after 


a full breakfast with meat. 

4672 37'1 Bosse du Dromadaire; breakfast with meat 2% hours 
before; then a steep and exciting ascent, but slow 
and without fatigue. 

1621 370 Fasting, but down ‘hill (Col du Géant), for four or five 
hours: 

1565 36°9 Chalet des Chablettes, 14 hour after full breakfast. 

3362 36°35) Summit of Col du Géant, breakfast with coffee three 
hours before ; temperature taken after eight minutes’ 
TeSb. 


This last observation, made at the summit of the Col du Géant, 
appears to be an exception to the rule: the temperature then 


* An observation at Planpraz, showing a temperature of 35°°5, is not 
here taken into account; it is exceptionally low, which must be owing to 
some extraordinary circumstance, such as excessive perspiration during the 
last part of the ascent. 


various Altitudes, in connexion with the act of Ascending. 3383 


noted was very high, considering that there could be at that 
time no food in the stomach, and the ascent had been uninter- 
rupted for the previous three hours. This was perhaps due to 
a reaction, the temperature having fallen very low (84°°5) during 
the ascent. 

Result 11.—That the temperature of the body during the act 
of ascending has invariably a tendency to fall, but that the degree 
of cooling depends mainly on a condition of fasting, or want of 
food, at the time. A rapid and steep ascent on an empty stomach, 
when the body is out of breath and perspiring freely, appears to 
be attended with the greatest reduction of heat. 

In twelve observations made while walking up hill the tempe- 
rature of the body varied from 34°'5 to 36°°5, the range being 
thus 2°-0. The greatest fall of temperature observed on four oc- 
casions was as follows :— 


At 4000 metres . . . . 84:5, fasting. 
PUG: ina wera sian/la eO45land35"; fasting! 
POCA sei ys .aeace 2 (O4sb fasting: 

EMM OO u tysier a: ox oh ade.) 80°05 fasting: 


The influence of walking up hill on the temperature of the 
body was well marked in the two following experiments :— 

f walked up from Chamounix to Planpraz (Brevent) soon after 
an excellent breakfast and during digestion. When halfway up 
(at the “ Chalet des Chablettes”), and after walking up hill for 
an hour, my digestion was hardly over, and I was free from the 
slightest sensation of fatigue ; my temperature under the tongue, 
while ascending, was then much the same as before leaving 
Chamounix, being first 86°°5, and a few minutes after 37°. I 
then contmued my way up to Planpraz, an hour’s walk above 
the previous station. Being in a hurry to attain this spot, I took 
short cuts, climbing the face of the mountain, which was rather 
steep, and I reached Planpraz much out of breath and perspiring 
freely ; the last few minutes before arriving, while walking, my 
temperature was 34°°5, and shortly afterwards 35°, say 1° lower 
than on reaching the ‘“ Chablettes.” It was very obvious that 
my morning meal was then no longer able to make up for the 
loss of heat from the climbing which it had done an hour before ; 
I had been moreover walking faster up a steeper hill than at 
first. 

In the second experiment, in order to make sure that during 
the act of climbing the process of cooling (to which the body 
was subjected) was really due to muscular exercise and not 
to a change of altitude, I took a mule at Courmayeur for a part 
of the distance to the “ Pavillon du Mont Fréty,” an altitude of 


‘ 


8334 Dr. Marcet on the Temperature of the Human Body at 


2197 metres. When about two-thirds of the way up, I ascertained 
my temperature under the tongue to be 86°4. Ithen got down 
and ascended on foot as quick as possible to the pavillon ; this 
lasted 82 minutes, when on nearing my destination I ascertained 
my temperature to be 35° (after about five minutes’ exposure), 
or 1°:4 lowerthan when leaving the mule. Shortly before start- 
ing from Courmayeur, an hour after dinner, the reading of the 
thermometer in my mouth was 36°38; at about 650 metres 
higher up, while ascending on the mule and keeping very quiet 
all the time, my temperature was 36°4; and after ascending 
about 328 metres higher up, walking fast, I had lost no less than 
1°-4, of heat, showing the influence of walking in excess of that 
which could possibly be due to increased altitude*. 

Taking 36°'6 as the average temperature at rest, according to 
my observations we have an average loss of heat of 1°3 due to 
the act of climbing. 

Result 111.—That the temperature of the body, after falling 
while walking up hill, rises afresh very rapidly on resting, or on 
merely lessening the speed of ascent. -Thus, afew minutes before 
arriving at the Pavillon du Mont Fréty, while in the act of as- 
cending, the temperature under my tongue was 35°; after half 
an hour’s rest at the pavillon it had risen to 36°°6, or 1°6. 
As I was on the point of reaching the Col du Géant, while still 
ascending, the thermometer with its bulb under my tongue 
showed 34°5; after remaining quiet for eight minutes on the 
summit of the pass, my temperature had risen to 86°°8, or 2°°3. 
Just before reaching the Chalet des Chablettes, while ascending, 
temperature after six minutes’ exposure 85°°3 ; immediately after 
recording this in my note-book, although actually without stop- 
ping, the mercury rose to 36°, and in about five minutes later to 
36°4, I had evidently recovered my lost temperature during 
the interruption of the rate of ascending, owing to the act of 
taking the note. 

The experiment at Planpraz was equally interesting. Just 
before arriving, while ascending rapidly and after four minutes’ 
exposure, the temperature was 34°'5, remaining steady for about 
oneminute ; then having lessened my speed, the thermometer rose 
rapidly to 35°. During the first three minutes’ rest at Planpraz 
the temperature increased again by 0°:8, and after about a quar- 
ter of an hour was steady at 35°°6. 

I cannot explain the increase of temperature which occurred 
in the following observations, unless by assuming it to have been 


* This experiment, however, should have been made by riding a mule 
up to a certain height, ascertaiming the body-heat, and repeating the same 
ascent on foot, when the temperature should have been again determined. 


various Altitudes, in connexion with the act of Ascending. 335 


due to the necessity of slackening my speed of ascent in order to 
record my observations. 

At about 1565 metres above the level of the sea, the thermo- 
meter in my mouth, and while I was ascending, showed 36%5, 
but rose to 37° during the next few minutes. In another expe- 
riment at the same place, although under different circumstances, 
the thermometer after five minutes’ exposure was up to 35°38, 
rising immediately after to 36°, and five minutes later to 36°3, 
although I had not stopped walking up hill. At a height of 
2060 metres, near “Pierre Pointue,” while ascending, the tem- 
perature under my tongue, after five minutes’ exposure, was 
35°°5, rismg during the subsequent few minutes’ climbing to 
36°38. At the “ Pierre & échelle,” near the glacier “ Des Bos- 
sons,” while ascending and after an exposure of six minutes, 
the temperature first observed was 36°5, and five minutes later 
36°°8, although I had not stopped. 

Result 1Y.—Finally, the sickness many people suffer from at 
ereat altitudes appears to be attended with a remarkable fall in 
the temperature of the body. 

I suffered from this affection, fora short time, at the Pavillon 
du Mont Fréty, on awaking early in the morning. Immediately 
after an attack of retching, my stomach being then quite empty, 
I took the temperature under my tongue: the reading of the 
thermometer was steady at 35°; and the mercury rose slowly 
during the following few minutes to 36°, during which time I 
recovered my health perfectly. On arriving at the summit 
of Mont Blanc the same kind of sickness returned. I then 
attempted to ascertain my temperature, but while so doing had 
the misfortune to break my thermometer. Professor Lortet 
of Lyons, with whom I had the pleasure of making the ascent, 
then kindly lent me a maximum-thermometer, which he read 
after its bulb had been under my tongue for a short time ; 
the instrument then showed a much lower temperature than I 
had ever yet observed; but the time of exposure was, I feel cer- 
tain, too short for an accurate observation ; still, after a similar 
exposure while in health, I believe the mercury would have 
risen higher. J can hardly think that in perfect health, and 
with no great degree of muscular exhaustion, the heat of the 
body at rest is much lower at the top of Mont Blanc than in 
the plain—and this for the reason that on the highest point of 
the “ Bosse du Dromadaire,” at an altitude of 4672 metres, and 
consequently only 138 metres below the very summit of Mont 
Blanc, my temperature when sitting down was 37°"1, which is cer- 
tainly not below the normal temperature of man in the plain. 
I then felt in no way indisposed, and not at all tired. 


336 Dr. Marcet on the Temperature of the Human Body at 


I cannot help thinking that mountain-sickness is due to 
want of power in the body of recovering the heat it loses under 
those physiological circumstances to which it is subjected on 
mountains. Ata certain height the body is altogether placed 
under cooling circumstances, such as cold weather and frequently 
insufficient clothing; at night there is often a deficiency of 
bed-clothes; and as a climber must be an early riser, he com- 
mences his day’s work (after a cold mght) precisely at the pe- 
riod in the twenty-four hours when, under ordinary circum- 
stances, his body is coldest ; food has often to be taken cold ; 
and to this may be added the cooling process from muscular 
exertion in the act of climbing. In order to resist this cooling 
action, the vital energy ought to be proportionally high ; it is 
so in many cases, but not always, either from exhaustion, or from 
a deficient supply of food, or from want of appetite to take 
it—insufficient food not only contributing to reduce the vital 
energy, but also depriving the body of the material on which 
this energy has to act in order to make heat. 

The result of my experience is that the circumstances which are 
known to be productive of animal heat are those best calculated 
to cure mountain-sickness. 

These may be considered—as, first, going down- instead of up- 
hill, which is known by many sufferers to cure the sickness. On 
going down hill there is little or no muscular exertion, and con- 
sequently, it may be anticipated, no great expenditure of animal 
heat. 

I suffered last year from mountain-sickness on Mont Blane 
from the “ grand plateau” to the top of the Mur de la Céte, 
but felt immediately relieved on going down, and was quite well 
shortly afterwards. On that occasion every circumstance under 
which I happened to be, combined to lower my temperature: I 
had started from the Cabane des Grands Mulets having taken 
little or no food; an intensely cold wind, many degrees below 
the freezing-point, was driving clouds of frozen snow into the 
face; hands and feet were benumbed ; and I had gone up by 
the corridor, where the well-known want of air must have assisted 
in lowering every vital phenomenon. 

Next, a violent attack of vomiting is often followed by imme- 
diate return of health. At first I could not possibly understand the 
reason of this remarkable fact, nothing being brought up from 
the stomach, which was mvariably empty, showing that the 
sickness could not be due to indigestion ; but on considering 
this circumstance I have come to the conclusion that, by increa- 
sing considerably the rate of the circulation, the retching caused 
arising of the heat of the body. 


various Altitudes, in connexion with the act of Ascending. 337 


Finally, if food can be taken on the sickness first coming on, 
it will be found very useful to arrest or relieve the illness. 

The best precaution to take against mountain-sickness is 
obviously to eat plenty of good substantial food, and to repeat 
the meals at short intervals. Should the appetite fail, I think it 
best to endeavour to take a little food as often as possible, 


Temperature of the Body at increasing Altitudes in the state of 


rest. 
Height in metres. Temp. under 
(I metre =3 feet 32 inches very nearly.) the tongue. 
1050. Chamounix, before breakfast ....eeseseee 36°2 
1050. Same experiment another day .......... 36°3 


1050. Chamounix, immediately after breakfast... 36°5 
1050. Chamounix, # of an hour after breakfast... 36°] 
1050. Chamounix, sitting on way down from Cha- 36-7 


GStiesp tastiaoeh iy acts tad etd silane wa ks 

1215. Courmayeur, before dinner ........++0. 36°60 

1215. Courmayeur, | hour after diner ........ 36°8 

About 1320. (Chamounix) Cascade de Blaiticre, about 23 } 365 
Bourspaiter luncheon 4)... 2.22 ..66* 06 

About 1565. Chalet des Chablettes, before breakfast ..  36°3 


a x after breakfast .... 36°9 

About 1621. Above Montanvert, afterrapiddescent, fasting 37:0 
About 1869. Ascent to Pavillon du Mont Fréty, riding.. 36°4 
2080. Planpraz, fasting (4 hours after breakfast). 35°6 

2197. 4 an hour after arrival at Pavillon du Mont 36-6 


WECiya Asta wae kis Pe eee ke ea he st 

2197. Mont Fréty, after sickness, fasting Gosh ie 36°0 

3050. Cabane des Grands Mulets, resting, and jee 
about 23 hours after meal ..........6: 

3050. Cabane des Grands Mulets, 2 a.m., before } 36:5 
WRC AAS 6 Sia robe wie hos Rade Owe. goa w aetareds 

3362. Summit, Col du Géant, after 8 minutes’ rest, 36-8 
ALT SETS OV Lhe a rian pane Winirenicihds coe nic 


4000. Grand Plateau, 43 hours afterlight breakfast. 36°3 

4672. Créte of the Bosse du Dromadaire, after 8 | 

minutes’ rest, last meal about 3 hows 371 
mbetoreron Grand: Plateant sn 2s scala a lets 


Meare 8; BP 0 BEG 


Twenty observations. 


Ext ee 
xiFemes ) 36:0 omitting the experiment at Planpraz. 


rl 


338 Lieut. J. Herschel on the Eclipse of August 1868. 


Temperature of the Body at increasing Altitudes during the act 


of ascending. 
Temp. under 
metres. the tongue. 
About 1350, Blaiticre Waterfall, about 5 hours after | 5-5 
breakfast .... (4 minutes’ exposure) { . 


About 1500. Fasting(Chablettes) (Gminutes’expesure) 35°3 
‘i Chablettes, after full breakfast... (4 mi- : 
> 36°5 
: nutes’ exposure) 
2060. Pierre Pointue, fasting.... (5 minutes’ | 35:5 
exposure) | 


2080. Planpraz, about 4 hours after prea 345 
fast. . (4 minutes’ exposure) 
About 2100. Under Pavillon ‘du Mont Fréty, fasting 35-0 
(about 5 minutes’ exposure) 
About 2260. Arriving at Pierre a échelle, in full di-?! 36:5 
gestloOn ...% 5% (6 minutes’ exposure) { 
3050. Arriving at “ Grands Mulets,” fasting... 395°8 
3362. Arriving at Col du Géant, fasting .. (over | 34:5 
5 minutes’ exposure) { 


3900. Arriving at Grand Plateau (Mont Blanc), [ 
about 100 metres below, fasting.. (60r} 35°6 
7 minutes’ exposure) | 
4000. Immediately on arrival at Grand Plateau, 
not walking, fasting (rose very rapidly > 34°5 
tOVAHNS) swe eavhoa we cee Belek 
4331. Déme du Gouter (Mont Blanc)...... 34°6 


MM carte’ Set eer 353 


Twelve observations. Lowest temperature 34°°5 


XL. On that portion of the Report of the Astronomer to the 
Madras Government on the Eelipse of August 1868 which 


recounts his Spectroscopic Observations. By J. Herscuen, 
Lieut. RB 


6 ies instrument used by Mr. Pogson for this portion of his 
observations was of the same pattern, it 1s believed, as 

that used by the present writer. In the annexed Table the 
positions of Mr. Pogson’s bright hnes are fixed with all the ac- 
curacy at present attainable, by comparison with data in the 
writer’s possession. 

The first column indicates Fraunhofer’s lines. 

The second shows readings taken im the early part of 1868 
with the Royal Society’s spectroscope referred to above. 

The third is deduced from the second by the empirical for- 


* Communicated by the Author. 


Lieut. J. Herschel on the Eclipse of August 1868. 339 


mula 86:°2H +1440, which refers the readings to another scale 
and zero. 

In the following column are shown Mr. Pogson’s readings of 
the solar lines, of which those in ztalics are bright-line measures*. 
The dark-line measures correspond with converted measures in 
the previous column; and the close agreement shows that the 
empirical formula is correct, and that the dispersions of the two 
instruments are commensurable throughout. Mr. Pogson’s dark 
solar lines are also unmistakably identifiable with B, C, D, 4, F, 
aud another, unnamed line, instead of those whose names he has 
assigned, 

In the fifth column, those in the fourth are converted by the 
empirical formula 4°40 P — 6207, which refers the readings to 
the scale and zero of that part of Kirchhoff’s map in which the 
bright lines must be placed. 

The sixth column is derived from the second by the formula 
440(86°2 H + 1440) —6207, or 379°311+129, and is merely 
a check on the identity of the lines supposed to have been mea- 
sured. 

The seventh column shows Kirchhoff’s measures. Compared 
with the two previous ones, it is evident that the empirical for- 
mulz by which they are obtained are only applicable strictly to a 
small portion of the spectrum—as was to be expected. 

The last columns show the positions on Kairchhoff’s scale of 
all the bright solar lines of which measures are available, with 
their (temporary) reference letters. 

Mr. Pogson’s data would be more valuable had the dark solar 
lines been measured zmmediately before and after the event ; but 
he assures the writer that there was little, if any, change of zero 
to be detected. He is also quite confident of the accuracy of the 
bright-line measures. 

It is very remarkable that the red lme Ha was quite unseen. 
Equally noteworthy is the evident preeminent brilliance of the 
green lines (measured) which he describes as very bright, 
although (owing perhaps to distressed eyesight) he was uncon- 
scious at the time of their absolute colour. 

No green lines have yet been seen here with an uneclipsed 
sun, although H y is frequently seen. Unless, therefore, greatly 
increased dispersion can be brought to bear, future eclipses must 
be depended on for the identification of these lines, whose exist- 
ence has been vouched for by four observers of the late memorable 
one. 


* [Sic in MS. The italics indicated are evidently the measures corre- 
sponding to P; and P, in column 9,—J. F. W. H.] 


340 MM. C. Borgen and R. Copeland’s Short Account of the 


Taste showing the identification of Mr. Pogson’s Solar Dark 
Lines, and calculated places of his Solar Bright Lines, and 
also the positions of the other known bright fines. 


ie DL aes: 4, 5. 6. 7 8. 9. 


aan Positions 
ene with Mr. Pog- of known 
hofer’s Sey ae Fd son’s [py — gt — erent Reference 
letters. spectro- 86'2 H |measures.} 4°40P | 379°3H KS ieee letters. 
scope +1440. 1 — 6207. “205 hoff’s 
1a fp scale. 
basen 0°86 1514 dors) aes aR 593 
655 ?? € 
Oa 1:25 1548 1547 ru 603 694 | 694 He 
Ds tee 2°30 1638 1639 1005 1001 1005 
1014-5 ) 
OOO: ideas sean: Amn Ae 1210 1207 
M743 | Ma Goeee eee 146222] P, 
SrA as ae eel rede a Meeerece 1464 1463 
Byers SOSA IE. cece RES Re APA sia See 1525 1523 
17633) 5508 | ee ee 155022] P, 
One. a 3°97 1782 | 1782; | 1634 1635 1634 
1784 f 
As Gig) wees Salle, Sens ies. ae 1893 1909 
4:79 cash all MRE oMTe Okamoto 1946 1961 
| teste 5:03 1873 Ike }7 Ae lipases 2037 2080 | 2080 Hp 
2596? 
710 2052 QOD a Riheen ce Hieewerhe 2721 
2796 
Gree LEDOTE ace snol lt. seeen Sexi Uae eesen alpen 2855 


1. The accordance between H! and P proves the commensu- 
rability of H and P throughout. 

2. The accordance between H" and K from D to b is a mea- 
sure of commensurability of H and K, and .*. of P and K within 
those limits. 

3. Therefore P! within those limits is equivalent to K. 


Bangalore, August 30, 1869. 


XLI. Short Account of the Winterings in the Arctic Regions 
during the last fifty years. By C. Boreun and R. Copenann, 
Astronomers and Physicists to the second German Polar Expe- 
dition*. 

pre cy the present moment, when it is intended to send out a 

second expedition to the arctic regions from Germany 
with the purpose of wintering there, it may not be uninteresting 
to give a short historical review of the winterings which have 


* Translated by W. S: Dallas, F.L.S., from Petermann’s Mittheilungen, 
1869, pp. 142-154, 


Winterings in the Arctic Regions during the last fifty years. 341 


been effected during the last fifty years. The precautions which 
were found useful in these, the number of deaths and accidents, 
the occupations and scientific operations will be particularly in- 
dicated, in order to show how unfounded is the opinion still fre- 
quently entertained by the general public that it is impossible 
for Europeans to endure the winter in those climates, and at the 
same time to lay down more accurately the scientific operations 
which may be carried out during the winter. 

The first wintering of an exploring expedition of which we 
have any knowledge is the unfortunate one of Sir Hugh Wil- 
loughby in the year 15538, who, being cast away by a storm, 
was frozen in upon the coast of Lapland, and perished by hunger 
and cold with his whole crew. 

This melancholy occurrence did not, however, deter other bold 
seamen from repeatedly making the attempt to discover a com- 
mercial route north of Kurope and Asia to the fabulous kingdom 
of Cathay ; and by these expeditions Spitzbergen, Nowaja Semla, 
&c. first became known to western Europeans. 

One of these expeditions sailed from Holland in the year 
1596; its conduct was entrusted to Jakob Heemskerk and his 
truly wonderful pilot,William Barents. Their ship was beset by 
the ice on the north-east coast of Nowaja Semla, and they them- 
selves compelled to pass the winter on that inhospitable shore. 
Of the crew, which consisted of seventeen persons, five died— 
two during the residence on Nowaja Semla, three during the 
return voyage, among whom was Barents; all of them suffered 
more or less from scurvy. Nevertheless this wintering must be 
regarded as a very successful one for that time; and even to the 
present day our entire knowledge of the north and north-east 
coasts of Nowaja Semla is founded upon this voyage, as no one, 
since Barents, has succeeded in reaching the “ Hishafen”’ where 
he wintered. 

Many attempts have subsequently been made to pass the win- 
ter in the arctic and otherwise uninhabited regions, upon Spitz- 
bergen, Jan Mayen, and in the Hudson’s Bay Territories, but 
of these unfortunately by far the greater part were failures. 
The causes of this in most cases were scurvy and the necessity, 
owing to the want of sufficient clothing, of keeping too carefully 
shut up inthe huts. We must, however, admire the courage and 
steadfastness of these people, who exposed themselves in such com- 
plete dependence upon good luck to the inclement climate, and at 
the same time, with the greatest perseverance, so long as the hand 
weakened by illness could barely guide the pen, continued to 
write in their journals, in which they described the course of the 
weather and the conditions of temperature. 


342 MM. C. Borgen and Rh. Copeland’s Short Account of the 


Successful wintering are, however, to be noted even among 
these, and indeed one in which this was hardly to be expected. 
In the year 1630, eight sailors belonging to an English whaler 
were separated from the ship and compelled to pass “the winter 
on Spitzbergen under 77° N. lat. Of course they had no pro- 
visions from the ship, aia we might therefore have anticipated 
that they would not live through ‘the winter. But this very cir- 
cumstance was their salvation; for in order to obtain nourish- 
ment they were obliged to go hunting, and were fortunate 
enough to kill a sufficient number of reindeers and bears to fur- 
nish them with fresh meat and warm clothing. The fresh meat, 
in conjunction with much moving about in the open air (the two 
conditions of health in this climate), kept them strong and 
healthy, and thus they were found and brought home in May of 
the following year by their former ship, without any of them 
having been “seriously ill during the winter. 

But unfortunately such a successful wintering as this was at 
that time an exception; and it 1s therefore no wonder that fifty 
years ago the opinion was still entertained that 1t was impossible 
for Europeans to pass the winter safely im the arcticregions. In 
the present day we may certainly say that at that time, and 
with the equipment in provisions and clothing then supplied, a 
wintering was attended with great danger to life; but that it 
is now no longer perilous has been sufficiently proved by the 
recent voyages. 

For more than two centuries the idea of a “ north-west pas- 
sage,” north of America from the Atlantic to the Pacific Ocean, 
as a commercial route to the Hast Indies and China, produced a 
series of English expeditions which led to the exploration of 
Hudson’s and Baffin’s Bays, to the discovery of Lancaster, 
Smith’s, and Jones’s Sounds, &c. But they showed at the 
same time that, if anorth-west passage really existed, 1t was not 
fitted for commercial purposes. Hence, after Cook, in his last 
voyage in 1779, had made an attempt to penetrate through 
Behring’s Straits, these voyages, which were commercially 
useless, were given up, and people contented themselves with 
working the rich fisheries found on the previous voyages of 
discovery. 

For nearly forty years voyages of discovery towards the north 
ceased, until in 1815 Kotzebue made a fresh attempt to force 
the north-west passage from Behring’s Straits. He got no 
further, however, than to the sound which is named after him. 
Now also a series of attempts was again made on the part of the 
English, to discover the north-west passage. But the object was 
now no longer to find a commercial route to China, but rather 


Winterings in the Arctic Regions during the last fifty years. 343 


to explore the wide unknown regions to the north of America, 
to determine how far the continent extended towards the pole, 
or whether islands lay off the coast, &c. 

As the first of these voyages, we must name that undertaken 
in 1818 by Sir John Ross. Properly speaking, he only repeated 
the voyage made two centuries previously by Baffin, but did not 
consider it advisable to penetrate any further than the latter, and 
returned to England in the autumn of the same year, after making 
the rich fisheries in Lancaster Sound and Pond Bay accessible. 
If, therefore, this voyage did not essentially advance discovery, 
it nevertheless cpened up a perfectly new region for the fishery 
in these waters. 

The next expedition which sailed from England, well equipped 
scientifically and indeed with the intention of wintermg, was 
sent out in the following year under Parry*, who had accom- 
panied the preceding expedition under Ross. As this is the 
first wintering of a scientific expedition that produced valuable 
results, and the leaders of all subsequent voyages having guided 
themselves by the observations collected in it by Parry, we may 
be allowed to consider it somewhat in detail. 

The expedition consisted of two ships, the ‘Hecla’ and 
‘Griper, the former of 375, the latter of 180 tons burthen ; 
the crews respectively of 51 and 386 men, officers and sailors 
together. On the 15th of May Parry left Yarmouth Roads, and 
on the 4th of September passed the 110th degree of longitude 
west of Greenwich, which had been appointed by the Admiralty 
for the gaining of a prize of £5000. He wintered in Melville 
Island, in the place named by him “ Winter Harbour,” under 
110° 48! 29"-2 W. long. and 74° 47! 19"-4, N. lat.; but in the 
summer of the following year by a land expedition he attained 
113° 48! W. long., halfway between Baffin’s Bay and Behring’s 
Straits. 

The expedition was equipped for two years, and especially 
well-furnished with the known antiscorbutic materials, such as 
dried vegetables, sauerkraut, pickles, vinegar (partly in a very 
concentrated state), lemon-juice with sugar &c., as also with 
preserved meat, all of the best quality and packed in air-tight 
vessels. Instead of bread a large stock of carefully dried flour 
was taken, so that fresh bread,. baked on board, could always 


be had. 


* Journal of a Voyage for the Discovery of a North-west Passage from 
the Atlantic to the Pacific, performed in the ears 1819-20 in H.M.SS., 
‘Hecla’ and ‘Griper’ under the orders of William Edward Parry, R.N., 
F.R.S.: London, 182]. And Supplement to the Appendix of Captain 
Parry’s Voyage for the Discovery of a North-west Passage in 1819-20, 
containing an account of the subjects of Natural History: London, 1824. 


344 MM. C. Borgen and R. Copeland’s Short Account of the 


These precautions proved to be extraordinarily beneficial to 
the health of the wintering party. The sick-list of the surgeon, 
Dr. Edwards, usually bore only one, or at the utmost two names 
of people who had slight attacks of scurvy ; and these were cured 
in a few weeks by the administration of an extra dose of lemon- 
juice with sugar. On one occasion, however, when a fire 
broke out m the observatory, a considerable number (sixteen) 
of the people suffered a good deal from frost, as in their ex- 
citement they had neglected the necessary precautions; and 
this led in some cases even to the amputation of fingers. 
The expedition had only one death to lament; and this was 
caused by disease of the lungs, which became combined with 
scurvy. The sanitary condition of this wintering was there- 
fore excellent, thanks to Parry’s indefatigable care and its ad- 
mirable equipment. 

The ships were laid up for wintering in the followmg man- 
ner; but itis to be observed that in subsequent winterings these 
arrangements were altered and improved in some few particulars, 
which will be noticed hereafter. ‘The moveable ropes and yards 
were taken down. The former were left lying in the open, where 
they froze quite hard, and in this state were completely protected 
from rotting, to which they would have been exposed in the 
moist air between decks. 

The entire deck was then provided with a high-pitched roof 
of oil-cloth, and served during the winter, in bad weather, as an 
exercise-ground and promenade for the officers and men. At 
first Parry had the water kept open around the ships, until he 
found that this would be too troublesome. Then he allowed the 
ships to be frozen in, and had snow shovelled up against their 
sides in order to keep in the heat; and this at the same time had 
the great advantage that the ice round the ship did not become 
so thick as where no snow covered it. 

The greatest evil that Parry had to contend against was the 
great amount of moisture in the cabins, which in some eases 
reached such a pitch that the beds were one half frozen, and one 
half completely wet through. At first the ice condensed on the 
walls was removed daily ; and once when this had been omitted 
for some weeks, no less than 5000 or 6000 pounds of ice were 
taken out of the cabins. Twice a day, when the crew were abroad, 
their quarters were examined by the commander and the surgeon ; 
and in general the actual observance of the precautions was most 
rigidly watched by the officers: thus, for example, the people 
were obliged every day to take the pr escribed quantity of lemon- 
juice and sugar in the presence of one of the officers. The damp- 
ness was very much increased by the circumstance that Parry 
was obliged to have all the clothes washed during winter dried 


Winterings in the Arctic Regions during the last fifty years. 345 
between decks. The fixed berths, which had been introduced 


into the ships quite against the ordinary practice of a man-of- 
war, had to be exchanged for hammocks, entirely on board the 
‘Griper,’ and partially on board the ‘ Hecla;’ and this (from the 
great amount of moisture) contributed greatly to the mainte- 
nance of good health; nay, one officer, whose life was consi- 
dered in some danger, was thereby completely restored in a few 
weeks. 

That the cabins could not be cleaned with water under such 
circumstances was a matter of course. Instead of this the floors 
were scrubbed with stones and hot sand which had stood all 
night upon the stove. 

All these precautions would not, however, have sufficed for the 
preservation of health if the people had not played and been ex- 
ercised in the open air for several hours daily. Hunting parties 
obtained a provision of 8766 pounds of fresh meat, which formed 
a welcome addition to the stock of provisions, leaving out of con- 
sideration the good effect of movement upon the health. To 
keep up their spirits, which might well evaporate even from the 
boldest heart during the long polar night, a weekly journal was 
edited by Captain Sabine (now General Sabine, and President of 
the Royal Society), which contained articles of a mixed, serious 
and lively character; and a theatre was set up on which some 
small piece was acted every fortnight; and this was carried on 
with so much zeal that even a temperature of —2° F. (—15° BR.) 
upon the stage did not deter the improvised actors from contri- 
buting to their own and their companions’ amusement. 

That the scientific objects of the expedition were not at the 
same time neglected is proved by the long series of observations 
and investigations which are appended to Parry’s report, and of 
which we shall shortly have to speak more in detail. 

As a precaution in case of fire, a hole was kept open in the 
ice near the ships; but this fortunately was never required ; 
for the observatory, in which a fire broke out, was at a distance 
of 2100 feet from the ships, and must therefore have been ex- 
tinguished in some other manner, during which operation, as 
already mentioned, sixteen of the people suffered a good deal 
from frost. 

As regards scientific results, we must mention in the first 
place the discovery of Barrow’s Strait, and the opening up of an 
extent of coast of 35° of longitude, which subsequently proved 
to be the south coast of a series of islands; and towards the 
south the existence of a broad strait (Prince-Regent Inlet) was 
ascertained, which was further investigated by Parry on a sub- 
sequent voyage. On the return voyage the whole east coast of 
Cockburn’s Land, extending for 8° of latitude, was surveyed. 


Phil. Mag. 8. 4. Vol. 38. No, 256. Nov. 1869. 2A 


346 MM. C. Borgen and R. Copeland’s Short Account of the 


Here Sabine commenced his pendulum-experiments for the 
determination of the figure of the earth, which have since been 
continued with so much success and completeness; he also de- 
termined the magnetic constants of various points by very ex- 
tensive observations. To the meteorology of the arctic regions 
the expedition devoted a series of observations continued unin- 
terruptedly for twelve months between the parallels of 74° and 
75° N. lat. The geographical position of Winter Harbour was 
established by the enormous number of 6862 moon-distances 
and 39 meridian altitudes. Tidal observations were regularly 
made; and, further, no fewer than fifteen chronometers, partly 
taken for the purpose of being tested, were examined as to the 
uniformity of their rates. Zoology and botany found in Dr. Ed- 
wards a zealous representative, who, with the assistance of Sabine, 
Parry,and James Ross, brought back a rich collection of specimens 
belonging to the animal and vegetable kingdoms, among which 
were several previously unknown species. At the same time he 
fulfilled his important duties as surgeon with the greatest zeal and 
care ; and to his exertions and ceaseless watching of the sanitary 
condition the small number of cases of illness and death during the 
winter is mainly to be ascribed. This voyage, which laid down the 
rules for all subsequent wintering expeditions, was also scienti- 
fically the richest of all in results. It was followed by two other 
voyages of Parry’s, one of them in the years 1821-238, in which 
two winters were passed in the arctic regions with equally fa- 
vourable results with regard to health as in the first case*. 
The two winterings were performed exactly in the same fashion 
as in the preceding voyage ; it would therefore lead only to un- 
necessary and tedious repetitions if we were to describe the ship 
in its winter harbour &c. In fact Parry himself says that we 
cannot easily imagine two things possessing more resemblance 
to each other than two winters in the higher latitudes of the 
arctic regions. } 

The first of the two winters was passed by Parry in Lyon’s Inlet. 
Heproved in it that Melville Peninsula is united to the mainland of 
North America, whereas it had previously been supposed that there 
was in this region a passage to Prince-Regent Inlet. Inter- 
course with the Eskimos during the winter furnished him with 
much important information as to the configuration of the land, 
and the existence of a great extent of open water in the north- 
west. Subsequent investigations showed the correctness of this 
and of many other geographical statements of the aborigines. In 


* Journal of a Second Voyage for the Discovery of a North-west Pas- 
sage, performed in the years 182], 1822, 1823 in H.M.SS. ‘Hecla’ and 
‘Fury,’ under the orders of W. E. Parry, R.N., ¥.R.S. London, 1824: 
Murray. 


Winterings in the Arctic Regions during the last fifty years. 347. 


the following year only a small advance towards the north was 
made, and the winter was passed in Iglulik, when the Fury and 
Hecla Straits were discovered and examined during the winter 
by Parry’s officers, who actually obtained a sight of the great 
sea of the Eskimos as a large surface covered with ice, which 
was afterwards known as the Gulf of Boothia. 

After this second successful wintering, Parry returned with his 
two ships in good condition to England, having furnished, by 
passing two consecutive winters in the arctic regions with very 
little loss of life, a proof that it was very possible for Europeans 
to dwell in winter in those latitudes. 

In the following year (1824) Parry sailed again for the 
discovery of the north-west passage, having set before him for 
this purpose the examination of the great passage, Prince-Re- 
gent Inlet, which had been observed on his first voyage. Being 
detained by the unfavourable condition of the ice in Baffin’s 
Bay, Parry was compelled to winter in Port Bowen, a small har- 
bour on the east coast of Prince-Regent Inlet. Here he had 
the misfortune of having one of his crew drowned. 

He examined by land the west coast of Cockburn’s Land, from 
his winter-harbour southwards to 72° N. lat., and northwards to 
Lancaster Sound. In the summer of the following year Parry 
went to the other side of Prince-Regent Inlet and investigated 
Creswell Bay, but lost his ship the ‘Fury.’ With his usual 
foresight Parry had the provisions and the extra stores of 
clothing brought on shore and enclosed in a wooden house built 
for this purpose. This depdt was of incalculable value to sub- 
sequent expeditions ; and the stores assisted the last Franklin- 
expedition under M‘Clintock, as much as thirty-three years after- 
wards, to complete their own equipment. 

The land and coast expeditions in the north of America, car- 
ried out before 1830 by Richardson, Franklin, and Beechey, 
were obliged to winter under very different conditions; and as 
we have here chiefly to show what has been attained by means 
of ships, and how the dangers of the arctic winter may be dimi- 
nished in naval expeditions, they need not be taken into consi- 
deration. It is sufficient to say that, with enormous toil and the 
loss of many men, they discovered and surveyed the north coast 
of North America from Cape Turnagain in 109° W. long. to 
Return Reef in 148°. 

The next great naval expedition was undertaken by Sir John 
Ross in 1829%. It was fitted out by Sir Felix Booth, a rich mer- 
chant ; and Ross desired by this voyage to reestablish his fame 


* Narrative ofa Second Voyage in search of a North-west Passage, and 
of a residence m the Arctic Regions during the years 1829, 1830, 1831, 
1832, 1833. by Sir John Ross, Captain in the Royal Navy. London, 1835. 

2A2 


348 MM. C. Borgen and R. Copeland’s Short Account of the 


as a discoverer, which since 1818 had been frequently and vio- 
lently attacked. in this he and his nephew, Sir James Clarke 
Ross, who has since become so famous by his antarctic voyages, 
most perfectly succeeded. 

The expedition sailed from London in a paddle-steamer (the 
‘ Victory’) of 150 tons, with a crew of twenty-three persons, 
officers and men. ‘The engine soon proved to be quite useless ; 
and after a stoker had unfortunately lost his arm by means of 
it, and some unsuccessful attempts to employ it had been made, 
it was given up and finally disembarked at Fury Point (where 
Parry lost his ship). The unfortunate stoker had been left be- 
hind on the coast of Scotland and replaced by another. 

Ross sailed through Lancaster Sound into Prince-Regent 
Inlet and wintered in Felix Harbour in 69° 58! 42" N. lat. and 
92° 1'7" W. long. On landing the engine, be took some pro- 
visions from the store left by Parry at Fury Point, so that at the 
beginning of the wimter he was completely provisioned for two 
years and ten months. In arranging the ship for the winter, 
Parry’s precautions and experiences served in general as a guide ; 
but Ross introduced the essential improvements of covering the 
whole deck with snow, and establishing condensers for the pur- 
pose of keeping the space between decks dry. The latter were 
large metallic vessels turned upside down over openings of several 
inches in diameter made in the ceilings of the cabins. They were 
covered with snow, and the moist vapours arising from the space 
below were condensed in these cold cupolas, so as to prevent all 
moisture below the deck; the ice collected in them was removed 
weekly, when it amounted on an average to 500 or 600 pounds. 

For the entertainment of his little crew a school was esta- 
blished, and otherwise the time was passed as in Parry’s expedi- 
tion. By frequent journeys in the summers of 1830 and 1831, 
James Clarke Ross investigated the two coasts of Boothia Felix, 
and ascertained that this land was connected with the American 
continent by the Isthmus of Boothia. On one of these journeys 
he reached the magnetic pole. Frequent intercourse with the 
Eskimos, who here again displayed great knowledge of their 
native country, gave him information of a large open water still 
further to the west (Victoria Strait)—just as Parry, when on the 
other side of the Melville peninsula, had heard much of the 
Gulf of Boothia, which was now cleared up by Ross. The na- 
tives even mentioned to him the subsequently discovered Bellot 
Strait which unites Prince-Regent Inlet with Franklin’s (Peel’s) 
Strait*; but when he examined the place described by them, the 
strait, which was concealed by several islands lying in front of 
it, escaped his observation, and he regarded the indentation of 

* Op. cit. pp. 299 & 338. 


Winterings in the Arctic Regions during the last fifty years. 349 


the coast as a bay (Brentford Bay). The second winter he was 
obliged to pass nearly in the same place where he had remained 
during the first winter ; and he then had to decide upon wintering 
for the third time quite close to his previous winter quarters, in 
Victoria Harbour. At the end of May 1882 he was obliged to 
quit his ship (the ‘ Victory’) and to endeavour to save himself 
by means of sledges, taking his boats with him. They reached 
Fury Beach and afterwards Batty Bay. In this retreat Parry’s 
precaution of bringing the,‘ Fury’s’ stores on shore saved the 
brave band from “ipPePiauite After pressing on to Batty Bay, 
Ross was surprised by the winter, and compelled, in order to 
save the lives of himself and his men, to return to Fury Beach. 
Here, in a house built of planks and coated with blocks of ice, 
they continued, by means of good stoves, to provide themselves 
with a comparatively warm and comfortable dwelling. 

In the following summer they at last succeeded in reaching 
Barrow’s Strait, and thence they sailed on in their boats and 
were taken up at the entrance of Lancaster Sound by the 
‘ Tsabella,’ which had been sent to their assistance. 

As regards the health of this expedition, we may say that in 
the first two winters it was very good. In the winter of 1829-30 
Ross lost only a single man, who had concealed a disease of the 
lungs which had previously brought him several times to the 
hospital. No scurvy made its appearance. The first case of 
this disease occurred on the 20th of November, 1831, conse- 
quently at the beginning of the third winter, and it carried off 
two men. 

When the expedition at last returned to England, after an 
absence of four years and a half, the crew was naturally in a very 
low state, and one of them died after the return to England in 
consequence of the hardships he had undergone ; but nevertheless 
it must be a matter of wonder that no more fatalities occurred 
during so long a sojourn. 

Again there was a period of twelve years during which all ex- 
peditions for the discovery of a north-west passage ceased. But, 
much as had been done in the exploration of the arctic regions 
of North America, there was still much to do before these regions 
could be regarded as even tolerably well known. ‘The question 
as to the theoretical or practical possibility of a north-west pas- 
sage was still unsolved; and the Government, finally yielding to 
the pressing instances of the Secretary to the Admiralty, Sir 
John Barrow, and to public opinion, ordered the ships ‘ Erebus’ 
and ‘ Terror,’ which had just returned from the antarctic expe- 
dition under Sir James Clarke Ross, upon a new voyage of dis- 
covery in the regions already so frequently visited, and conferred 
the command upon Sir John Franklin. 


350 MM. C. Borgen and R. Copeland’s Short Account of the 


The unfortunate termination of this expedition is well known. 
Although the history of the last desperate attempt to escape 
contains many doubtful and unexplained points, we may obtain 
much information upon the earlier part of the expedition from 
the short report which was left on King William’s Land by Cro- 
zier and Fitzjames, and discovered by Lieutenant Hobson, who 
accompanied the last searching expedition under M‘Clintock. 

The portion of this short report which is particularly interest- 
ing to us relates to the number of deaths, and runs as follows :— 

25 April, 1848..... Sir John Franklin died on the 11th 
of June 1847, and the total loss by deaths in the expedition has 
been to this date nine officers and fifteen men.” When the ex- 
pedition sailed in the summer of 1845 the entire crew consisted 
of 129 people, officers and men, deducting the few who were 
sent back from Baffin’s Bay on account of illness. The provi- 
sions were calculated for three years; but unfortunately a great 
part of them was supplied by the marine purveyor Goldner, who 
sought by the most shameful fraud to make a fortune, and filled 
the preserved-meat cases with completely useless offal instead of 
with eatable materials. By this means the provision was con- 
siderably diminished; but as Sir John Franklin wrote from 
Baffin’s Bay full of hope that, if necessary, he should be able 
to hold out for five or even seven years by renewing his stores 
from the produce of the chase, we may assume that, notwith- 
standing the loss of what was useless, the provision was sufficient 
for three years in case of need. 

The ships were abandoned in April 1848; and we may sup- 
pose that want had not then reached any very high degree. Up 
to this moment the expedition had hardly been in any worse po- 
sition than that under Ross, for example, after the same lapse of 
time; and the number of deaths reported up to this period, 
although doubtless considerable, is by no means very surprising, 
especially when we consider that three of them occurred as early 
as the first winter (1845-46), on Beechey Island. What became 
of the 105 who were still living after the abandonment of the 
ships, will probably always remain in obscurity. 

The apprehensions as to the fate of Franklin and his compa- 
nions gave rise to a long series of searching expeditions, which 
are known in the history of arctic voyages as the Franklin-expe- 
ditions. . To go through all the numerous expeditions singly 
would lead us too far. In M‘Dougal’s account of the voyage 
of the ‘ Resolute’ in the years 1852-54*, there is an account of 
the numbers of the crews who wintered and the deaths which 


* The eventful Voyage of H.M. Discovery Ship ‘ Resolute’ to the Arctic 
Regions in search of Sir John Franklin, by George F. M‘Dougall (London, 
1857), p. 498. 


Winterings in the Arctic Regions during the last fifty years. 351 
occurred during the winterings. The following are English ex- 
peditions :— 

Crews. Deaths. 


1848-49, Sir James Clarke Ross . 188 7 
1850-51, Captain Austin . . . 180 1* 
1850-51, Captain Penny. . . . = 46 
1849-50, Mr. Saunders. . . . 40 4. 
1850-54, Captain M‘Clure ... . 66 5+ 
1852-54, Sir E. Belcher. . . . 90 2 
1852-54, Captain Kellett . . . 90 At 


1852-54, Commander Pullen . . 40 


The great scientific results of these expeditions, and especially 
the enormous extent of coast which was explored by them, are 
well known. Inthe first place, towards the north, Smith Sound 
was investigated by Kane; and the coasts of Wellington Channel 
and the entire north coast of Parry Island were examined by 
Belcher. M‘Clure penetrated from Behring’s Strait through 
Investigator Sound, wintered three times in Banks’s Land, and 
once, when he was obliged to abandon his ship, on Melville 
Island with Kellett ; and he was the first who demonstrated the 
existence of a north-west passage by his actually tracing water- 
passages from Behring’s Strait to Baffin’s Bay, although these 
were in part impassable for ships. Kennedy and the French 
officer Bellot, who attached themselves to the expedition as vo- 
lunteers, discovered Bellot’s Strait, named after the latter, ex- 
plored Prince-of-Wales’s Land on the further side of Franklin’s 
(Peel’s) Strait, and returned northwards round North Somerset 
to their winter harbour in Batty Bay. 

This is the longest sledge-journey that has been undertaken 
during the arctic explorations; its entire length amounts to 1200 
nautical miles ; and it was performed without any depots for the 
return journey. Of his crew of eighteen men Kennedy did not 
lose one, and he had only a few quite unimportant cases of ill- 
ness. He succeeded in bringing his little vessel (892 tons) back 
to England in safety. 

M‘Clintock, in Austin’s expedition, gave a quite unprece- 
dented development to sledge-journeys; he improved the con- 
struction of the sledges and the mode in which the depots were 


* Sickly from the first, and died in consequence of hardships on sledge- 
journeys. 

+ All the deaths in the last year, from scurvy. 

{ One from disease of the heart, two from weakness in consequence of 
hardships, and one upon asledge-journey. 

It is unfortunately not stated, J. c., what the causes of death were; and 
only in the cases here cited in the notes are we able to give any account of 
them. 


352 MM. C. Borgen and R. Copeland’s Short Account of the 


thrown out; and it was only by means of these improvements 
that the important results were secured. 

The principal service done by this expedition was the enlarge- 
ment of our yeographical knowledge of these regions, which, 
indeed, was the necessary consequence of its object. Allits en- 
deavours were directed to one end, namely the discovery of 
Franklin or of his traces; and hence it follows, as a matter of 
course, that whatever was not connected with this must have been 
regarded as a subsidiary matter. 

Among the searching expeditions the two Grinnell expeditions 
were of scientific importance, and also very instructive in other 
respects; they were fitted out by a New York merchant named 
Grinnell, and accompanied by Dr. EK. K. Kane. 

The first of these expeditions* left New York on the 22nd of 
May, 1850. It consisted of the ships ‘ Advance’ and ‘ Rescue,’ 
and was under the orders of Lieutenant de Haven, who himself 
commanded the ‘ Advance,’ whilst the ‘ Rescue’ was commanded 
by Griffin. In the ‘Advance’ was the most important person 
of the company im a scientific point of view, Dr. Khsha Kent 
Kane. The crews of the ships, which were of 144 and 91 tons, 
consisted in all of 17 and 16 men. Their equipment was rather 
hastily performed ; and hence there was no superfluity, especially 
of antiscorbutic agents. Kane himself, who was stationed in the 
Gulf of Mexico, received the order to take part in the expedition 
only two days before its departure, and had only forty hours in 
New York to look after his personal equipments and procure 
some scientific instruments; the latter, however, unfortunately 
were not put on board. 

They reached Beechey Island in good time, and in conjunction 
with the English expeditions under Austin and Penny, which 
were there at the same time, undertook the investigation of 
Beechey Island, where the first certain traces of Franklin’s expe- 
dition were found; they then made their way into Wellington 
Channel and discovered Grinnell Island. When they were then, 
in accordance with their instructions, about to return to New 
York, they were beset by the ice, and carried with it through Lan- 
caster Sound and Baflin’s Bay into the Atlantic Ocean. During 
this process they had to undergo many dangers and hardships ; 
and the hasty and insufficient equipment now revenged itself 
upon them bitterly. It was only through the almost superhuman 
exertions of Kane, who, although himself ill, tended his compa- 
nions in suffering with a truly affecting solicitude, that there was 
no loss of life to be lamented. He not only cared for the medical 
treatment of his patients, but brought from his hunting expedi- 


* The United States Grinnell Expedition in search of Sir John Franklin, 
by E. K. Kane, M.D., U.S.N. London and New York, 1854. 


Winterings in the Arctic Regions during the last fifty years. 353 


tions much fresh meat into the ship, which did much good to 
the sick. But they had not only to suffer from scurvy; the cold 
also could not be sufficiently kept off. The ship was lifted so 
high upon the ice that it was impossible to heap the sides with 
snow or to adopt other customary precautions. It contributed 
not a little to heighten the difficulty of their position, that the 
‘Rescue’ got into so bad a situation that she had to be aban- 
doned for a time and her crew transferred to the ‘ Advance.’ 

Notwithstanding his heavy medical duties, Kane did not neg- 
lect to do whatever lay in his power for science. His report 
contains very many important notices upon the formation and 
movement of the arctic glaciers, with hints as to the deficiencies 
which still remain to be filled up in this field, and upon the pe- 
culiar ice-structures which occur here and there. 

He complains that the confined space and overloading of the 
ship did not allow him to be so regularly active as he desired in 
scientific matters. The observations of temperature are irregular, 
but still very numerous; and in connexion with them he calls 
attention to various points, to precautions which must be em 
ployed in order to obtain correct readings, and to many other 
things. The northern lights found in him a zealous observer; 
and here also it did not escape his acute mind how much still 
remains to be explained in the theory of these phenomena. 

The second voyage*, which was commanded by Kane himself, 
was fitted out by the two merchants, Grinnell of New York and 
Peabody of London, and its object likewise was to search for Sir 
John Franklin. The ‘Advance’ was again the abode of Kane 
and his little crew, seventeen in number, to whom a native (Hans 
Christian) was afterwards added. This vessel was a sailing brig 
of 140 tons, and had proved on the previous voyage to be a good 
ship for the ice. The equipment consisted of india-rubber 
tents, sledges of the newest construction, and provisions consist- 
ing of 2000 lbs. of pemmican, bread, flour, dried fruits, preserved 
vegetables, &c., and besides these a considerable quantity of 
salted meat, which had better have been left behind. As ascien- 
tific equipment, there were on board a large library and a yalu- 
able stock of instruments. 

Kane selected Smith Sound for his base of operations, as he 
had explained in a memoir read before the Geographical Society. 
From this he proposed to push towards the north. That he 
could find nothing there relating to Franklin’s expedition ap- 
peared clearly enough from the subsequent discoveries; but he 
penetrated far to the north, surveyed the shores of Smith Sound 


* Arctic Explorations.—The Second Grinnell Expedition in search of Sir 
John Franklin, 1853, 1854, 1855, by Elisha Kent Kane. 2 vols, Philadel- 
phia, 1856. 


354 MM. C. Borgen and R. Copeland’s Short Account of the 


and Kennedy’s Channel as far as 81° N. lat., and discovered the 
enormous Humboldt glacier, which extends more than a degree 
in width. He was oblised t@eeniaintin Rensselaer Bay, in 78° 37! 
N. lat. and 70° W. long., where he passed one winter, which 
threw many of his companions and himself upon a sick bed. 
Nearly all had scurvy; and the fatiguing sledge-journeys were 
by no means adapted to improve the health of the expedition. 
Upon one of these journeys, made by some of the crew in order 
to establish a depot of provisions, they were beset by the ice, 
and would have been destroyed if Kane had not relieved them ; 
he could not, however, prevent two of them from dying in con- 
sequence of the fearful hardships. Hunting did not furnish any 
very considerable results ; and feeling certain that they would be 
set free in the following summer so as to return home, they were 
not so economical in the use of what was procured by the chase 
as they might perhaps have been. But the summer brought 
them no release, and they were compelled to hunt for their pro- 
visions until the next winter, but, unfortunately, with small 
results. In one of their very distant hunting expeditions, which 
was led by Morton and the Greenlander Hans, they reached in 
81° N. lat. a coast which was washed by a sea perfectly free from 
ice and with long regular dunes. 

Dr. Hayes, who was making his first arctic voyage, discovered 
Grinnell Land, and, besides fulfilling his medical duties, which 
were in themselves great and heavy enough, made many journeys 
for the purpose of hunting and exploring, in which he was assisted 
by the astronomer, August Sonntag. 

The second winter was long and severe, and brought with it 
many hardships and much suffering; diseases, especially scurvy, 
combined with cold and hunger to put the courage and steadi- 
ness of the explorers to the hardest test. As the second spring 
again failed to set them free, they were forced to adopt the de- 
sperate expedient of seeking inhabited regions in small open 
boats. After infinite exertions, which cost one of them his life, 
they reached Upernavik, and were afterwards taken up in God- 
havn by the expedition under Hartstein, which had been sent to 
seek for them. 

Notwithstanding the many difficulties and hardships with 
which this expedition had to contend, its scientific results are 
by no means inconsiderable. Observations of temperature, to 
which Kane attached great importance, were made hourly during 
the voyage, but showed at the same time how careful it is ne- 
cessary to be in such cases in order to avoid the influence of the 
warm ship, which is observable at a distance of several hundred 
paces. They showed further the untrustworthiness of the spirit- 
thermometer at low temperatures; the eleven thermometers 


Winterings in the Arctic Regions during the last fifty years. 355 


which were constantly read differed at a temperature of —68° F. 
from the mean of all readings by no less than 12°; the difference 
increased from —20° F. downwards, at which temperature it 
varied between —1°°2 and +1°2 for the different thermometers. 

The mean temperatures, compared with those obtained in 
other parts of the arctic regions, furnish interesting data for the 
comparison of the climates, and show that the climate of Green- 
land, from being an insular climate in the south, approximates 
towards the north to the coast climate of the arctic archipelago 
in the west of Baffin’s Bay, the character of which is not far 
from that of a continental climate. We shall have to speak more 
in detail upon this point hereafter. Magnetic observations were 
made in great numbers by Sonntag; and during the winter of 
1854-55 six magnetic terms of 24 hours each were kept, the 
results of which are to be found in the appendix to the Report, 
which also contains a long list, with descriptions, of the plants 
and animals collected by leant upon the two expeditions. 

We have already mentioned Kane’s voyages as very instructive 
in every respect; and they are especially instructive negatively, 
inasmuch as they show the dangers to which arctic voyages are 
exposed when the greatest care is not- employed in their equip- 
ment. If instead of the salted meat he had had some 1000 pounds 
more pemmican, he would certainly not have had to undergo 
such terrible want and suffermg. He regarded the salt meat 
as so useless and so injurious to those who were ill of scurvy, that 
in sending out a company to bring in the provisions stored in a 
depot, he gave the strictest orders that all salted meat should 
be left behind, and this at a time when the expedition was in 
danger of dying with hunger. 

It was a modest desire to spare as much as possible the means 
of the high-spirited men who fitted out the expedition, and a 
certain expectation that he would be able to return after the first 
winter, that induced Kane not to provide himself with stores 
of better quality and for a longer time, although he had under- 
gone similar experiences on his first voyage. Far be it from us 
to wish to reproach him with this; his courage and perseverance, 
and his remarkable management and scientific activity, in which 
he far surpassed all previous arctic voyagers, place him in the 
first rank of travellers, and the smallness of the loss of human 
life which this expedition had to regret is to be ascribed solely 
to his medical skill and persevering care. The hardships of this 
second expedition threw the brave man, soon after his return, 
upon a sick bed, from which he was never again to rise. 

His reports upon the two journeys are full of hints upon 
the arrangements for wintering and for scientific observations, 


which will be of the greatest service to future travellers. In 


356 MM. C. Borgen and R. Copeland’s Short Account of the. 


connexion with the first, he introduced the improvement of 
carrying the cabin stairs not only down to the floor, but below 
this into the hold, and then bringing another stair from the 
latter up again into the antechamber of the cabin—an arrange- 
ment which was of extraordinary service in keeping up the 
temperature. 

We come now to the last of the so-called Franklin-expeditions*. 
It was the fourth of the expeditions fitted out by Lady Franklin ; 
and the command of it was entrusted to Captain M‘Clintock. 
He sailed on the Ist of July 1857, from Aberdeen, in the screw- 
steamer ‘ Fox,’ of 180 tons, with a crew in all of 25 men. The 
officers were Lieutenant Hobson of the Royal Navy as first, and 
the merchant-captain Allen Young as second officer. Besides 
these there were in the cabin a surgeon, Dr. Walker of Belfast, 
two engineers, and Petersen an interpreter. The stores con- 
sisted of 6000 pounds of pemmican and a large stock of pre- 
served vegetables, with the well-known antiscorbutic remedies 
lemon-juice and sugar), and was calculated for twenty-eight 
months. 

The voyage was prosperous as far as Melville Bay; but when 
M‘Clintock attempted to make his way into Lancaster Sound the 
ship got into pack-ice, became fixed, and drove with 1t down Baf- 
fin’s Bay for 242 days. The first winter, therefore, had to be 
passed in the pack-ice; but the ice was quiet, and they were ex- 
posed to none of the perils which so frequently occur under similar 
circumstances. No cases of illness occurred; but the second engi- 
neer died in consequence of a fall in the engme-room. As soon 
as the ship was again set free, they turned once more towards 
the north, and succeeded this time in passing through Lancaster 
Sound. An attempt to saildown Franklin’s (Peel’s) Strait was 
unsuccessful, as it was completely blocked with ice in the nar- 
row part. M‘Clintock then attempted to push through Prince- 
Regent Inlet and Bellot’s Strait into the southern part of Peel’s 
Strait and so to King William’s Land, but here also was pre- 
vented by ice from penetrating further. 

Nothing then remained but to allow themselves to be frozen 
up in a small harbour in Bellot’s Strait, and to do by sledge- 
journeys what could not be done with the ship. How far this 
was successful, how the greater part of the coasts of Peel’s, Ross, 
and Victoria Straits was surveyed by M‘Clintock, Hobson, and 
Young, and how Hobson found that important document which 
furnishes the only authentic intelligence of the condition of 
Franklin’s expedition up to April 1848, is too well known to 
render it necessary for us to dwell upon it here. 


* The Voyage of the ‘Fox’ in the Arctic Seas. London, 1859. And 
Petersen: Den sidste Franklin-Expedition med Fox, Capt. M‘Clintock. 


Winterings in the Arctic Regions during the last fifty years. 357 


During this second winter the first engineer and the steward 
died—the former by an apoplectic attack, and the latter of scurvy, 
because he obstinately rejected all precautions, lived almost ex- 
clusively upon salt meat, and was also somewhat addicted to the 
use of spirits. Nearly all the crew suffered more or less from 
scurvy; and Lieutenant Hobson especially was rather severely 
attacked by it. However, all soon recovered. On the sledge- 
journeys, as might be expected, they were a good deal affected 
by frost; but all evil consequences disappeared on their return 
on board the ship. On the 23rd of September 1859 the ship 
lay in good condition in the docks of London. 

The intelligence of the melancholy fate of Franklin’s expedition 
was followed by the exhaustion natural after such enormous ex- 
ertions. Since this period no arctic expedition has been sent out 
from England; but Dr. J. J. Hayes, the companion of Kane on 
his second voyage, procured the means of fitting out an expedi- 
tion to Smith Sound*, and started well equipped from Bos- 
ton, in July 1860, in the sailing schooner ‘ United States,’ of 
133 tons, with a company of fourteen men (among whom was 
the astronomer Sonntag, who had already accompanied Kane on 
his second voyage), to which were subsequently added three 
Europeans and three Eskimos, and, lastly, the Eskimo Hans with 
his family, already known by having accompanied Kane’s expe- 
dition. Huis object was to reach a harbour on the east coast of 
Grinnell Land before the commencement of winter, and thence 
if possible to pass through Kennedy’s Channel and penetrate 
into the polar sea seen by Morton. This object, however, he 
did not attain, but was obliged to remain in Port Foulke, 20! of 
latitude further south than Rensselaer Harbour, and situated at 
the entrance of Smith Sound—much to his regret, as that sound 
is always difficult to pass through. From this point, where he 
took up his quarters for the winter, he attempted in October of 
the same year to make a sledge-journey into the interior of the 
country, but was compelled to return by a cutting north wind 
against which it was impossible to contend for any length of 
time. Nevertheless this short journey into the interior furnished 
interesting information as to the glaciers of Greenland. 

Whilst the people specially fitted for them undertook scientific 
operations, such as meteorological, magnetic, and pendulum ob- 
servations, the others were sent upon the chase, and brought an 
extraordinary quantity of game into the kitchen. As they had 
no dogs, Hayes sent Sonntag with Hans to the Eskimos living 
further to the south in order to procure some. After an absence 
of a month Hans returned alone, and reported that Sonntag had 


* The Open Polar Sea, by Dr. J. J. Hayes. German edition by Coste- 
noble, Jena, 1868. 


358 MM. C. Borgen and R. Copeland’s Short Account of the . 


fallen through a fissure of the ice into the water, had then gone 
several miles in his wet clothes, and died in a hut which they 
reached. 

In the spring of the following year Hayes commenced one of 
the most toilsome sledge-journeys that has ever yet been made. 
Its object was to penetrate as far as possible upon the coast of 
Grinnell Land, and to reach the polar sea which had been seen by 
Morton. On the way he was obliged to leave behind him a por- 
tion of his party, and went forwards with only one young man of 
19 years old (Knorr) and one dog-sledge, until his further progress 
was prevented, under 81° 35! N. lat. and 70° 30’ W. long., by 
rotten ice and partially open water which extended as far as the 
eye could reach. He was compelled to abandon his desire of 
penetrating into this water with the ship, as Smith Sound was 
not free from ice this year; and so Hayes returned from his 
interesting voyage in the autumn of 1861, to Boston. The im- 
portant scientific results of this expedition have been published 
by the Smithsonian Institution. 


Conclusions. 


With this the series of marine expeditions which have wintered 
in the north is for the present closed. They furnish evidence 
that with a little care a residence in the arctic regions is by no 
means impossible. 

In the following Table the deaths which have occurred in these 
arctic expeditions, so far as we are able to find reliable statements, 
are summarized and their annual percentage for each expedition 
given, in calculating which the actual duration of the expedition 
has been taken into account, the duration of a voyage whieh ex- 
tendedover a single winter being reckoned as a year and one-third. 


| 


No. Commander and year. Ships. | Crews.|Deaths see 
he ence TET ine a iat Peel on bien aug 
2. | John Ross, 1829-33......... GOs. 23 4:1, (20g 
3. | Franklin, 1845-48. ...... 22... 2 ships.| 129 24 6:20 
4, | J. C. Ross, 1848-49 ......... 1 ship. | 188 7 3°80 
5. | Saunders, 1849-50 ......... 1 40 4 7:50 
G.- | Austin, 1850-5) 25. 5.Gae. 4 ships.| 180 ] 0:42 
Ze | Benny, USO Ho cone ce oc newer hss a) ear!) 0:00 
8. | De Haven (Kane), 1850-51. ei ne Tallnes 0:00 
9. | M‘Clure, 1850-54 ..,......... 1 ship.| 66 5 1:75 

10. | Belcher, 1852-54 ............ 2ships.| 90 2 0:95 

1]. | Kellett, 1852-54 ............ 25 90 4 1-91 

12. | Pullen, 1852-54 ....,....... 1 ship.| 40 0 0-00 

13. al Kane. Loon O0 non cuchcans 144 tons.| 18 3 714 

14. | M‘Clintock, 1857-59 ...... 1 SON To . 25 3 5:14 

15:-. (Hayes, 1860-6), 2.23.03. Lt, Jas ahy 18 1 4:17 

AVCTARC ancl a scscmeois) oriesvteae 2-92 


SS Ue A) ge a 


Winterings in the Arctic Regions during the last fifty years. 359 


Remarks. 


1. Died of lung disease. 

2. One of lung disease concealed on the voyage out; two of 
scurvy; one after return in consequence of hardships. 

3. According to the information found by M‘Clintock. 
Causes of death unknown; three died in the first winter (1845-46), 

4. In consequence of a sledge-journey of forty days with in- 
sufficient provisions. 

6. Sickly from the first; died in consequence of hardships 
on sledge-journeys. 

8. Suffered much from scurvy; equipment rather hasty. 

9. All the deathsin the last winter, from scurvy. 
™ 11. One of heart-disease ; two from weakness in consequence 
of hardships; one on a sledge-journey. 

13. Two died in consequence of a sledge-journey; one on 
the return voyage in consequence of a dislocation. 

14. One in consequence of a fall; one of apoplexy; one of 
scurvy. 

15. In consequence of a fall into the water. The Eskimos 
that Hayes had with him are omitted. 

From this review it appears, therefore, that the percentage of 
deaths is on the average very favourable when compared with 
the mortality upon voyages in the tropics. The result would 
have come out much more favourably if we could have taken in 
Collinson’s and some other winterings; but with regard to these 
reliable information was wanting. 

yen when compared with the ordinary mortality at the age 
of 30, which, according to Milne’s Carlisle Tables, amounts to 
1:19 per cent., the result may be called very satisfactory, espe- 
cially if we consider that most of the deaths occurred in conse- 
quence of great hardships upon sledge-journeys, or were pro- 
duced either by diseases the germs of which were previously in 
existence, or by accidents which could not be foreseen; the last 
are possible upon any journey, even when it is not directed 
towards the North. » 

We believe that in the preceding statements we have furnished 
a proof that a winter residence in the arctic regions is by no 
means dangerous for Kuropeans, always supposing thatthe neces- 
sary precautions are taken. ‘These precautions are as follows :— 

First, a thoroughly good equipment of the ship, rendering its 
sides as strong as possible—partly to resist the pressure of ice, 
and partly for the sake of warmth. How the ship is to be 
prepared for its winter quarters we have already described cir- 
cumstantially, and may therefore abstain frem its repetition. 

The second main point is good nourishing food, especially 
fresh meat and pemmican—salt meat bemeg not good even for 


360 M. F. Zollner on a New Spectroscope, together with 


the healthy, whilst for those affected with scurvy it is absolute 
poison. In order to keep off the latter disease, a certain and 
not too small quantity of lemon-juice and sugar must be taken 
daily, besides vegetables, the eating of which in abundance is of 
great benefit. Nowadays, when all these things can be so easily 
procured of good quality, there is not the least difficulty in pro- 
visioning a ship in the most suitable manner. 

The third thing upon which the vigour and welfare of a win- 
tering company depend is warm clothing, which should consist 
less of furs than of several layers of woollen stuffs one over the 
other. 


-— 


XLII. On a New Spectroscope, together with contributions to the 
Spectral Analysis of the Stars. By F. ZOLuNER*. 


N recent times the spectrum-analysis of the stars, apart from 
its disclosures as to the physical constitution of the celestial 
bodies, has begun to claim attention in another and not less 
interesting direction; for it affords a prospect of demonstrating 
and, under favourable circumstances, even of measuring the in- 
fluence which the component of the relative motion of the earth 
and of the star observed, acting along the line joining them, 
exerts upon the position of the lines of the spectrum in question. 

A simple consideration shows that actions which two separated 
bodies exert upon one another through periodical impulses of 
finite velocity of propagation, must be modified by a steady alte- 
ration in the distance of the two bodies. ‘To Doppler, in the year 
1841+, is due the merit of having first recognized this influence, 
though the conclusions which he deduced therefrom as to the 
colour of the stars must be admitted to be incorrect, owing to his 
having neglected the invisible part of the spectrum. 

The experiments of Ballot, Mach, and others have shown that, 
as regards sound, the influence in question is in accordance with 
the requirements of the theory. 

In the case of light, it has not hitherto been possible to con- 
firm by observations magnitudes of that influence which could 
with certainty be demonstrated; for even the cosmical motions, 
which are the greatest we can use for this purpose, are very 
small when compared with the velocity of the propagation of light. 

Yet the great improvements which, since the discovery of 


* Translated from Poggendorff’s Annalen, September 1869, having been 
read before the Royal Saxon Society of Sciences, February 6, 1869. 

+ “Ueber das farbige Licht der Doppelsterne und eimiger anderer 
Gestirne des Himmels,” Abhandlungen der Bohm. Ges, d. W. vol. i. 
(1841-42) pp. 465-482. 


contributions to the Spectral Analysis of the Stars. 361 


spectrum-analysis, have been made in the optical instruments for 
observing the spectrum, open out the prospect of demonstrating 
that influence on the spectra of the stars. Theory requires that 
this should consist of a small displacement of the spectrum-lines, 
which, for instance, for the mean velocity of the earth of 18:2 
miles in a second, amounts to the tenth part of the distance 
between the two sodium-lines. This magnitude, which is very 
easily deduced from the velocity of light and the length of oscilla- 
tion of the rays corresponding to the sodium-lines, has been 
quite recently again deduced by J. C. Maxwell in accordance 
with earlier calculations by F. Hisenlohr*. 

Yet the magnitude of the displacement appears to Maxwell to 
be so small, that he concludes his observations with reference to 
the spectrose»pes hitherto constructed and the method of deter- 
mining the position of the lines with the remark, “it cannot be 
determined by spectroscopic observations with our present instru- 
ments, and it need not be considered in the discussion of our 
observations” +. 

Huggins, nevertheless, in his most recent paper f{, of which the 
above-mentioned investigations of Maxwell form an integrant 
part, has attempted the solution of the problem in question by 
using a spectroscope with not less than five prisms, of which 
two are flint-glass Amici’s, and three crown-glass. 

The great enfeeblement of light produced by so great a num- 
ber of prisms permits the observation of only the brightest stars. 
Huggins even restricts himself to the communication of his 
results from observations on Sirius, and thought he had here 
found a slight displacement of the line F compared with a bright 
hydrogen-line produced by aGeissler’s tube. The direction and 
magnitude of the displacement would indicate an increase of the 
distance between the earth and Sirius with a velocity of 41°1 
English miles in a second. 

Eliminating the component of the earth’s motion, which at the 
time of observation amounted to twelve miles, the velocity with 
which Sun and Sirius move apart would be 29:4 miles in a 
second. 

Huggins himself considers this result as affected with great 
uncertainty—an uncertainty partly due to the enfeeblement of 
the light produced by numerous prisms, partly to the difficulty 
of comparing the coincidences of the bright lines of terrestrial 
luminous sources with the analogous dark ones of the star- 
spectra. The latter have at times a different appearance—are, 
for instance, indistinct at the edges and of variable breadth, as is 
just the case with this line F in the spectrum of Sirius. 

* Heidelberger Verh. d. phys. med. Ges. vol. iit. p. 190. 
T Phil. Trans. 1868, p. 532. t Ibid. p. 535. 
Phil. Mag. 8. 4. Vol. 38. No. 256, Nov. 1869. 2B 


362 M. F. Zéllner on a New Spectroscope, together with 


The most important of these difficulties which have heretofore 
hindered a definite solution of the problem in question, I think 
I have overcome by a new construction of the spectroscope, the 
first specimen of which I have the honour of laying before the 
Society. 

The arrangement is essentially as follows :—The line of hight 
produced by a slit or by a cylinder lens is in the focus of a lens 
which, as in all spectroscopes, first renders parallel the rays to 
be dispersed. The rays then pass through two Amici’s direct- 
vision prisms, which I obtained of superior excellence from the 
optical workshop of M. Merz in Munich. 

They are so fastened together that each of them transmits one- 
half of the rays emerging from the object-glass of the collimator, 
but so that the refracting edges are on opposite sides, and thus 
the total mass of rays is decomposed into two spectra of opposite 
directions. The object-glass of the observing-telescope, which 
again unites the rays to an image, is cut at right angles to the 
horizontal refracting edges of the prisms, as in the heliometer ; 
and each of the two halves may be moved micrometrically, both 
parallel to the line of section and also at right angles thereto. 
Thus not only can the lines of one spectrum be successively made 
to comeide with those of the other, but both spectra, instead of 
being superposed, may be placed closed beside each other (so 
that one is displaced in reference to the other like a nonius), or 
they may be partially superposed. By this construction, not 
only is the delicacy of the double image as a means for deter- 
mining any change in position of the spectrum- -lines utilized, but 
any such Pheri ts also doubled, inasmuch as its influence in 
the two spectra is exerted in opposite directions. 

The principle of the reversion of the spectra, fundamental to 
the instrument described (for which I therefore propose the 
name ‘‘ Reversion-Spectroscope”’), may be applied even without 
using Amici’s systems of prisms. It is only necessary to reverse, 
by reflection from a muror or from a prism, one part of the pen- 
cil of rays emerging from an ordinary prism, and then to observe 
the whole pencil as above by means of a telescope provided with 
a cut object-glass. This principle also dispenses with the simul- 
taneous introduction of artificial sources of ight for investigating 
small alterations of refrangibility, and enables those changes to 
be seen and measured by the alterations in position of perfectly 
homogeneous objects. 

The series of measurements which were made with the 
dark lines D of the solar spectrum, as well as with the bright 
sodium-lines of the flame of a taper impregnated with salt, 
and which I here adduce as a criterion of the capability of the 
instrument, justify the hope that by means of this spectroscope 


contributions to the Spectral Analysis of the Stars. 363 


we Shall succeed not only in detecting the influence of the earth’s 
motion, but in determining its amount with such accuracy as is 
desirable for a preliminary control of theoretical conclusions. 

The numbers adduced signify parts of the micrometer-screw, 
and refer to the distance of the two sodium-lines :— 


Sodium-fiame. Sun. 
49°5 49°5 
50°5 51:5 
53:0 48°] 
A9°5 48:9 


Mean . . 50°6+0°6 Meat 9 49. Gc00'o 


In the following series of observations the reversion-spectro- 
scope had been provided with another micrometer-screw with a 
somewhat coarser thread, and also two other systems of prisms, 
the dispersion of which in the vicinity of the sodium-line is 1°77 
as much as that of the system used for the above measurements. 
In this case, also, the former achromatic object-glasses of the col- 
limator and of the observing-telescope were replaced by non- 
achromatic ones, whereby not only was there no loss of sharpness, 
but, as was intended, by increasing the intensity of light, there 
was a gain in clearness and distinctness. 


Sun. 

Parts of the screw. Deviations from the mean. 
67°1 —0°8 
69°4: +1°5 
68:4: +0°5 
67°9 0:0 
66°6 —1°3 
66°1 —1°8 
68:2 +0°3 
68:0 +0°1 
69:°6 +1°7 


Mean’ 2° { 67:9-++-0'3 


Hence the distance of the two D lines would be determined 
with a probable error of 33, of its magnitude. From what has 
been said above, an alteration of the distance between the source 
of light and the spectroscope with a velocity of nineteen miles 
in a second produces a reciprocal displacement of the lines of the 
two spectra amounting to one-fifth of that distance—a magni- 
tude, therefore, forty times that above found as the probable 
error from the mean of nine readings. 

Hence if, in observing stellar spectra, a sufficient quantity of 
light can be used, it may be minicy decided by the way de- 

2B 2 


364 M. F. Zollner on a New Spectroscope, together with 


scribed whether the expected displacement of spectral lines occurs 
or not. In reference to the requisite intensity of light, I may 
be permitted to remark that I had a non-achromatic lens* of 
1 Paris foot diameter and 6 feet focal distance; the pencil was 
received a few inches in front of its focus on a suitable concave 
meniscus of flint glass, and, thus freed as far as possible from 
spherical and chromatic aberration, it impinged on the slit of the 
spectroscope. I think I must here more especially point out that, 
in the use of a slit, achromatism of the optical image is not ne- 
cessary for the observance of the spectrum, especially of indivi- 
dual parts of it, and that therefore the above construction may 
claim the advantage of being cheaper than when achromatic 
glasses of great luminous intensity have to beused. Of course 
in those cases in which the obiects to be observed require as 
sharp separation as possible, as in the case of the double stars, 
this advantage must be given up 

I may be permitted, in conclusion, to make a few observations 
on problems and methods which refer to spectrum-observations 
of the sun, and with which I am at present occupied. 

The sun possesses a velocity of rotation in virtue of which a 
point on its equator moves with a velocity of about a mile in a 
second. If, therefore, by means of a heliometer, or in any other 
way, a double i image of the sun be produced, and if by suitable 
adjustment two points of the edge of the equator be brought into 
contact, parts of the sun’s surface are bounded by the point of 
contact, of which one set move towards us and the other move 
from us with a velocity of the amount mentioned. There is 
thus produced a difference in the velocity of the parts touching 
of about two and a half miles. In accordance with what has 
been above said, such a magnitude of motion would produce an 
alteration in the position of the sodium-lines corresponding to 
the jth part of their distance. Hence if, by combining a suffi- 
cient number of prisms, such a magnitude can be perceived or 
measured, it is only necessary to bring the middle of the slit to 
the lime of the two centres of the sun’s pictures to see in the 
field of view of the spectroscope the two spectra of the sun’s 
edges close to one anotier, and thus observe the displacement in 
question under the most favourable circumstances. In this 
manner the position of the sun’s equator might be determined ; 
and, provided the measurements could be executed, the velocity 
of rotation in various heliographic latitudes might also be deter- 
mined, which would be of the greatest interest in reference to 
opinions recently expressed upon this subject. 

Apart, however, from a quantitative determination of the phe- 
nomenon in question, by evena qualitative proof a simple means 

* Constructed in the optical workshop of M. H.. Schroder in Hamburg. 


contributions to the Spectral Analysis of the Stars. 365 


would be found of separating all the lines which result from ab- 
sorption in the earth’s atmosphere from those which owe their 
origin to the sun’s atmosphere, masmuch as the displacement in 
question can only affect the latter. 

Another subject of investigation by spectrum-analysis of the 
sun are the protuberances. Lockyer and Janssen have, as 1s 
well known, succeeded in observing the spectrum of these ob- 
jects (consisting of three bright lines) independently of a total 
solar eclipse. 

At present attention is directed on all sides to finding out 
methods which shall enable not only those lines, but the entire 
figure of the protuberances to be simultaneously observed. 

The position of the bright limes corresponds to the magnitude 
of the dimension of the protuberance in question which falls in 
the direction of the sht. When the slit is brought successively 
into various directions so that it cuts the protuberance in just so 
many positions, we are in a position to construct the shape of 
the body observed, as Lockyer has already done. Janssen has 
proposed the construction of a rotating spectroscope, so that, with 
adequate velocity of rotation, by means of the duration of the 
impression of light the shape of the entire protuberance might 
be seen at once. 

Apart from the mechanical difficulties of such a rotating spec- 
troscope, in which one of the three bright protuberance-lines 
must be exactly in the axis of rotation, the object in view might 
be more simply and completely obtained by oscillating the slit 
at right angles to its direction. We should then be in a position 
to observe the same protuberance simultaneously in three differ- 
ently coloured images corresponding to the three different lines of 
its spectrum. Yet in these methods with a moveable slit, the 
difference in brightness, through which the protuberance stands 
out against the ground, is considerably enfeebled according to 
the distance traversed by the slit. With the rotating spectro- 
scope more especially, the brightness of the protuberance would 
be weakened from the centre of rotation towards the edge, and 
the observation of the natural relative brightness of the image 
would be prevented. 

For this reason I intend using another very simple means for 
attaining the object in question, of the practicability of which I 
have convinced myself by experiments (to be subsequently de- 
scribed) on terrestrial sources of hight. The principles upon 
which this method depends are the following :— 

(1) The apparent brightness (lustre, claritas visa*) of a protu- 
berance-band is independent of the breadth of the slit, provided 
that it always retains a perceptible breadth upon the retina. 

* Lambert, Photometria &e. §§ 36 & 37. 


366 M. fF. Zollner on a New Spectroscope, together with 


(2) The brightness of the superposed spectrum increases pro- 
portionally to the breadth of the slit. 

(3) With an oscillating or rotating slit the brightness of the 
superposed spectrum remains unaltered ; that of the image of 
the protuberance decreases according to a law which depends 
upon the number and duration of the impressions produced on 
the place of the retina in question im the unit of time, and on 
the refrangibility of the observed protuberance-band. 

Assuming, for simplicity’s sake, that the entire surface overwhich 
the slit moved in its rotation or oscillation were occupied by the 
protuberance, and assuming that the intensity of the after-image 
formed were inversely proportional to that surface (corresponding 
to a uniform distribution over that surface of the light passing 
through the stationary slit), then assuming the above three prin- 
ciples, the ratio of the intensity between ground and protube- 
rance would remain the same, whether, 

First, by oscillation of the slit the brightness of the image 
of the protuberance were diminished, and thus the brightness 
of the superposed spectrum or of the ground (according to (2)) 
were left unchanged, or whether, 

Secondly, the stationary slit was so far opened that its aper- 
ture just extended over the space over which in the first case the 
oscillation extended. Hereby, according to (1), the apparent 
brightness of the protuberance would remain unchanged, while 
that of the ground would be increased in the same ratio in which 
it was formerly weakened when the ground was unaltered. 

Hence, under the above suppositions, the intended object would 
be far more simply attamed in the second way, by taking care 
that, on account of dazzling, the intense direct light of the sun 
did not penetrate into the slit. 

The slit need then only be opened so far that the protuberance, 
or a part of it, appears inthe aperture. By polarizing or absorb- 
ing media, placed in front of the eyepiece, a suitable weakening 
of the entire field of view must be provided for, in order that 
the ratio between the intensities of the protuberance and su- 
perposed spectrum may be as striking as possible. 

Led by these considerations, I have attempted to realize by 
means of terrestrial sources of liglit the conditions under which 
the protuberances are visible, in order thus to test both methods 
and convince myself of their practicability. In order the better 
to understand the experiments described, the following remarks 
may be premised. 

The reason why, under ordinary circumstances, by deadening 
the intense solar image the protuberances are not visible at its 
edge, lies in the superposed strongly illuminated particles of our 
atmosphere. In a total solar eclipse this superposed light is so 


contributions to the Spectral Analysis of the Stars. 367 


considerably weakened, that then the intensely luminous protu- 
berances stand out from the illuminated parts of the corona 
of the darkened sun. We may form an idea of the magnitude 
of the necessary enfeeblement of the diffuse light of our atmo- 
sphere, if we assume that the mean luminosity of the atmosphere 
during a total solar eclipse is equal to that during an average full 
moon. From my photometrical measurements* this luminosity 
is 618,000 times less than that produced by the sun. Hence 
the selective absorption of coloured media must stand in a similar 
ratio to that of the homogeneous light of the protuberance, if, 
as is attempted on various sides, we wished to make the protu- 
berances visible without dispersion. 

On the other hand, the possibility of attaiming this object by 
the aid of the prism by dispersing the superposed atmospheric 
light depends essentially upon the circumstance that this hght 
consists of rays of all refrangibilities, while that of the protube- 
rances only consists of three homogeneous kinds of rays. 

I have in the following manner produced artificially the su- 
perposition of a non-homogeneous mass of light over a body 
shining with homogeneous light and bounded by sharp outlines. 

The wick of an alcohol-flame was impregnated with chloride 
of sodium and chloride of lithium. Ata distance of eighteen feet 
from this flame, a piece of plate glass was so placed at an angle 
of 45° to the direction of observation, that the reflected image of 
a petroleum-flame at the side covered the feebly luminous alcohol- 
flame, and by its considerably greater intensity rendered it quite 
invisible. About a foot in front of the reflecting glass plate was 
a small lens of 6 inches focus, which threw an image of the alco- 
hol-flame upon the slit of the spectroscope. The latter was 
fastened to the end of a spring about 10 inches long, by which, 
removed from its position of equilibrium and left to itself, it 
could for about five minutes be made to perform oscillations of 
sufficient amplitude. 

The breadth of the slit was first of all so far diminished, that 
when the slit was at rest the double line D, and m comparison 
feebly the lithium-line, appeared well defined in the field. 

When the slit was made to oscillate, these lines changed into 
sharp images of the alcohol-flame, of which the two soda images 
were about halfcovered. The apparent brightness of these three 
images was considerably smaller than that of the bright lines, 
and hence their prominence on the diffusely illuminated spec- 


trum-ground smaller m the same ratio than that of the lines when: 


the slit was at rest. 
When now I applied the second of the above proposed me- 
thods, and opened the stationary slit so far that the image of 
* Photometrische Untersuchungen &c. p. 105. Leipzig, 1860. 


368 M. F. Zollner on the Spectral Analysis of the Stars. 


the alcohol-flame was just bounded by the rectangular shit, I 
was surprised by the far greater beauty and distinctness with 
which the images of the flame stood out from the diffusely 
illuminated spectr um-ground. 

I may remark that I used in this experiment only one of the 
above-mentioned newer prisms; but it is clear that, with mcrea- 
sing dispersion, the enfeeblement of the superposed non-homo- 
geneous light may be enhanced at pleasure. 

In principle no difficulties prevent the application of this me- 
thod to the sun’s protuberances*. Yet practical success, with the 
given ratio of the intensities of homogeneous protuberance- and 
supe posed atmospheric light, is essentially dependent on whether 

a sufficiently strong dispersion for this ratio can be attained. If, 
inaeiel from the ‘intensity and distinctness with which the lines 
of the protuberances appear, especially the middle one (of which 
I have convinced myself by my own observation at the Berlin 
Observatory on the 24th of last December), it is allowable to 
infer a very considerable relative brightness of the protuberances, 
the means now at my disposal (four excellent systems of prisms) 
will probably be sufficient to solve satisfactorily, in the way here 
proposed, the problem of the visibility of protuberances. 


Leipzig, February 1869. 
Appendix. 


M. Faye, after giving an account to the Academy of Sciences, 
on September 20, of the above paper, proceeds as follows :— 

“MM. Zollner has subsequently applied his new method to the 
sun with the most complete success. He has been able to follow 
and map from minute to minute with surprising facility and ac- 
curacy the magnificent phenomena of the chromosphere ; he is 
even about to photograph them, utilizing the images due to the 
ray situated in the most photogenic part of the spectrum. 

“Some of the drawings above mentioned have been published 
by Zollner in a separate pamphlet. They show clearly that the 
protuberances are violent eruptions (Mr. Lockyer has already 
approximately determined their velocity), and not clouds sus- 
pended in an atmosphere. They might be said to consist of a 
gaseous mass projected vertically into an almost vacuous space, 
expanding almost immediately, and then falling more slowly, 
assuming the most capricious forms. Perhaps in this way we 
shall be able to group the new manifestations of the force which 
the sun exerts upon the very light material of comets,—a polar 
force, according to Bessel and Olbers, like electricity and mag- 
netism; a force merely repulsive according to another hypothesis, 


* Owing to my not having yet completely set up the necessary imstru- 
ments, I have been unable actually to test this method. 


a 


Mr. R. Moon on the Structure of the Human Ear. 369 


with which M. Roche’s beautiful researches are connected. In 
any case these drawings, which refer to four days, give the key 
to a very curious enigma presented by the eclipses observed in 
South America, in Chili, and in Brazil; I speak of the black 
protuberances. They seem to me to be due merely to the dark 
interval which exists for a few minutes either between two adja- 
cent eruptions the plumes of which join, or between the ascending 
column of an eruption and its plume falling on the side of it. 

“Thus to observe the protuberances with the spectroscope at 
any hour of the day, even when the sun is near the horizon, it is 
sufficient to open slightly the slit of the spectroscope. Perhaps 
M. Zollner will succeed in seeing them all together as in an 
eclipse, by using very large prisms and aslit curved as an arc of 
a circle.” 


XLII. On the Structure of the Human Ear, and on the Mode in 
which 1t administers to the Perception of Sound. By kh. Moon, 
M.A., Honorary Fellow of Queen’s College, Cambridge. 


[Continued from p. 130.] 
ie my last paper I endeavoured to show :— 


1. That the fact of the tympanal membrane being concave 
outwards, coupled with its flexibility, adapts it as an agent for 
the transmission to the sensorium of the motion arising from 
rarefied waves, while the same concavity, coupled with the in- 
elastic and unyielding character of the membrane, forbids the 
transmission of the motion arising from condensed waves. 

2. That if the ear yields to the impressions which rarefied 
waves tend to produce upon it, an apparatus will be required by 
means of which, after exposure to such waves, the membrana 
tympani may be brought back to its original position, and the 
organ generally be restored to its normal status; that the 
muscles acting upon the bones of the ear are calculated to per- 
form that office; and that no other adequate function has ever 
been assigned to them; whence we may conclude that that por- 
tion of the auditory apparatus has been contrived with exclusive 
reference to the action upon the ear of rarefied waves. 

3. That when either the tympanal membrane or the malleus 
or incus is wanting, or the latter of those bones is disconnected 
from the other or from the stapes, then, under the influence of 
rarefied waves, the oscillations between the vestibular and cochlear 
fenestre of the fluid in the labyrinth will still be maintained by 
the alternate action, on the one hand of a difference in the ex- 
ternal pressures upon the fenestra, and on the other of the sta- 
pedius muscle; and that in this way a considerable power of 


370 Mr. R. Moon on the Structure of the Human Ear, and on 


perception of sound may occur; at the same time, that when the 
ear 1s exposed to the action of condensed waves under the same 
circumstances no motion of the fluid in the labyrmth, and con- 
sequently no perception of sound can occur. 

The question here naturally presents itself, 1f, when the mem- 
brana tympani, malleus, and incus are wanting, and the Eusta- 
chian tube ceases to perform any recognizable function, hearmg 
occurs in a manner, mM some cases, not very much less perfect 
than when the ear is in its riorettral state, how comes it that a 
machine so much more extensive and complicated is ordinarily 
resorted to by nature for the accomplishment of that object ? 

To this it has been replied, that in the perfect ear the ma- 
chinery is much more efficiently protected from external injury, 
whether arising from foreign bodies which find their way into 
the meatus, or from cold*, than is the case with the mutilated 
organ. 

It may be added, moreover, that, on the view of the aachitions 
apparatus above set forth, the unyielding character of the tym- 
panal membrane must operate to protect the organ from injury 
arising from condensations of the atmosphere, while the opposite 
actions of the tensor muscle and of rarefactions of air must tend 
to mitigate the effect upon the organ of the latter. 

It may readily be conceived, too, in a general way, that the ear 
in 1ts normal state must be a more powerful, more refined, and 
more manageable instrument than that presented by the simple 
labyrinth with its contents and closures, aided by the stapedius 
muscle only. 

A more important consideration, however, still remains. 

If we regard the importance and delicacy of the functions per- 
formed in the perfect ear by the two muscles combined and in 
the imperfect ear by the stapedius alone, if we consider that 
these muscles are under the influence of nerves which are not 
involuntary but are subject to the action of the will, if we 
advert to the very slow and gradual manner in which the recog- 
nition of articulate sounds is developed in infancy, if we take 
account of the apparently boundless interval between the ca- 
pacity for appreciating sounds possessed by the obtuse rustic 
and by the finest musical genius—if we keep in view these 
various facts, I think it cannot but be evident that a long and 
most delicate process of education of the nerves and muscles must 
be passed through before that degree of proficiency is attained 
which is requisite for the comprehension of spoken language, 
and that one still more extended and refined must be undergone 


“ The inconvenience from this latter cause, when the membrana tym- 
pani is absent, is often very great. See papers by Sir Astley Cooper in the 
Philosophical Transactions for 1800 and 1801. 


the Mode in which it administers to the Perception of Sound. 371 


before reaching that degree of perfection with which many are 
capable of discriminating the most complicated harmonies. 

This process of education may be surmised to be greatly faci- 
litated by the possession of the complete and perfect instrument ; 
and it by no means follows that, because the education once ac- 
quired through its instrumentality can toa certain limited extent 
be turned to account by the imperfect organ, therefore the needful 
training could equally have been attained by the aid of the latter 
alone. 

The relation of the ear in its normal condition to the ear de- 
prived of the membrana tympani may be likened to that between 
a violin with the ordinary provision of four strings and the same 
instrument when three of its strings have been taken away: 
with regard to which it may be observed that, although in the 
latter case a musical prodigy has been known to elicit from it 
effects which, in the absence of actual experience, would have 
passed belief, it is at the same time clear that, without the skill 
and dexterity acquired upon the more perfect instrument, no 
such effects could have been producible. 

I now propose to advert to one or two miscellaneous points of 
interest connected with the subject. 

I. I would in the first place recall attention to the description 
of the muscles of the ear already cited from Mr. Wharton Jones 
(vide anté, p. 125), who informs us that the muscles attached to 
the malleus have been by some anatomists [herein following 
Sommerring] stated to be three in number, of which two are 
laxative and one a tensor of the tympanal membrane. Of 
these Mr. Jones declares that the last named only can be strictly 
demonstrated, and that the supposed laxatores tympani are 
simply ligaments. 

Now of these latter it isclear that, had they been attached to 
muscles which would have relaxed the tympanum, being of the 
nature of tendons and therefore fibrous and inextensible, they 
would operate to resist any further stretching of the membrana 
tympani; so that if the membrane had been elastic (which, as has 
been shown, and as is well known, it is not), and to that extent 
capable of being stretched by the action of condensed waves in- 
cident upon it, these so-called laxatores tympani would prevent 
any such effect taking place, and would thus, as it would appear, 
have been of themselves sufficient to obviate any action upon the 
sensorium of condensed waves—thus showing that the laxatores 
tympani ligaments tend to corroborate the effect resulting from 
the inelastic character of the membrane. 

II. The foregoing conclusion is of peculiar importance when 
we come to consider the auditory apparatus of birds, in which 
and in that of mammalia alone is to be found a true tympanum. 


3872 Mr. R. Moon on the Structure of the Human Ear, and on 


The apparatus among mammalia is essentially the same in 
character as inman. That of birds differs (so far as regards our 
present purpose) in two features :—first, that the bones are in 
part replaced by cartilage, and, as regards their mutual colloca- 
tion, are somewhat differently arranged; secondly, that the 
tympanal membrane is convex outwards, and not concave out- 
wards as in the case of mammalia. 

The apparatus in birds may be described as consisting of the 
labyrinth and of asingle true bone (which from the correspond- 
ence of its functions with those of the stapes im mammals may 
be designated as a stapedal bone), connected with the upper part 
of which and with the sides of the tympanal cavity is a cartila- 
ginous appendage to which the tympanal membrane is attached, 
and by which the membrane is supported in its convex (out- 
wards) position as upon a bent spring. 

A reference to the principles unfolded in my former paper will 
make it evident that the membrana tympani being convex out- 
wards, its want of elasticity (even if it were inelastic) would 
oppose no obstacle to the transmission to the sensorium of the 
action of condensed waves; so that, so far as this part of the ap- 
paratus is concerned (whatever may be the case in man and in 
mammals), birds might have perception of sound through the 
agency of waves of condensation—an instrument of conveyance 
which, as has been stated, is slower, and therefore less efficient 
than is offered by waves of rarefaction. 

Any such effect as that just described is obviated by means of 
a fibrous band stretching from the neighbourhood of the Eusta- 
chian tube, and attached at its other extremity to the cartilagi- 
nous appendage before spoken of ; which band, for the purpose 
we are now considering, may be regarded as replacing the laxa- 
tores tympani in man and n mammalia. Respecting this band, 
M. Breschet informs us that ‘ Lorsqu’on la tiraille, on opére 
la tension de la membrane du tympan”* ; that is, the effect of 
the band, if it were attached to a muscle (which it is not), would 
be, when the muscle was contracted, to draw the tympanal mem- 
brane outwards; and its effect in the (actual) absence of any 
muscle attached to it must be to resist any tendency to force the 
membrane inwards ; that is, its effect is to counteract the only 
effect capable of being exerted upon the membrane by a con- 
densed wave. 

III. Having shown the manner in which the auditory appa- 
ratus in birds is adapted to suppress the action upon it of con- 
densed waves, it may be proper to point out the mode in which 
rarefied waves operate upon it. 


* Recherches Anatomiques et Physiques sur ? Organe de l’ Audition chez 
les Oiseaux (Paris, 1836), p. 24. 


the Mode in which it administers to the Perception of Sound. 378 


The tympanum of birds is provided with a single muscle only, 
the effect of which, when contracted, is to relax the membrane, 
2. e. to draw it inwards (Breschet, pp. 24, 380). Hence the po- 
sition of equilibrium of the auditory apparatus of birds (2. e. the 
position which it assumes when not acted upon by any sound) 
may be defined to be that in which it is placed when the muscle 
or muscular fibres connected with the organ have produced their 
utmost effect, by drawing in the membrana tympani to the full 
extent which the fibrous band above mentioned will admit of; in 
which position, of course, the membrane will be incapable of 
being forced further inwards through the action of condensed 
waves. 

If a rarefied wave be incident upon the organ when im this 
position, the tendency would be of course to move the tympanal 
membrane outwards; and the membrane being convex outwards, 
in order that such motion outwards may occur one of two things 
must happen—namely, either the membrane must be elastic, or 
else it must, when in the position of equilibrium, be somewhat 
loosely stretched upon the cartilaginous spring of which we have 
spoken. 

I have nowhere found any statement as to the elasticity or 
inelasticity of the tympanal membrane of birds; but for the sake 
of perspicuity I shall assume, as seems most probable, that, like 
the tympanal membrane in mammalia, it is inelastic, and conse- 
quently that in the position of equilibrium the membrane rests 
loosely on the cartilaginous spring which supports it. 

When the general apparatus is in equilibrium, we may suppose 
that the cartilaginous spring which forms part of it will also be 
in equilibrium. But when through the action of a rarefied wave 
the membrane has been moved outwards, the elasticity of the 
spring will immediately come into play, and will tend to bring 
the membrane back to its original position—a contrast being pre- 
sented in this respect in the apparatus in birds and in mammalia : 
for whereas in the latter case, when the membrane has been 
moved outwards, the muscles of the tympanum are the essential 
and only means of bringing back the organ to its original status, 
there are in the former case two different and efficient agents for 
producing the same result—to wit, the elasticity of the cartila- 
ginous spring and the tympanal muscle. It may be observed, 
however, that although the elasticity of the spring would in the 
first instance tend to bring back the membrane in the manner 
above described, there can be no doubt that, when the membrane 
had reached the position in which its further motion inwards 
would be stopped by the fibrous band above spoken of, it would 
receive a sudden and complete check; and this occurring at a 
time when its velocity was a maximum, the membrane would 


374 Mr. R. Moon on the Structure of the Human Ear, and on 


rebound and again move outwards. A single atmospheric pulse 
might thus throw the auditory apparatus into a state of oscilla- 
tion for a considerable time—a circumstance which would mate- 
rially interfere with the distinct perception of articulate sound. 
To obviate such an effect is the special function of the tympanal 
muscle in birds. 

It is worthy of remark that, although in the auditory apparatus 
of birds recourse is had to the principle of elasticity to the extent 
above explained, the principle requires to be kept in check, and 
is kept in check in the manner above described. In the more 
perfect organ of man and of mammals, on the other hand, the 
uncertain and unmanageable principle of elasticity is through- 
out excluded, the tympanal membrane, the ligamento-fibrous 
membrane wrapped about the base of the stapes, and the mem- 
brane of the fenestra rotunda being alike inelastic and inex- 
tensible. 

IV. I would next remark that the success of the experiment 
of Valsalva (which, though in general only temporary in its effects, 
I apprehend to be of all known means for the diminution of 
deafness the most simple and the most universal of application) 
is confirmatory of the views with regard to the mode of action 
of the human ear which I have endeavoured to set forth. 

For if, as I have stated, the sensation of hearing is produced 
primarily by the tympanal membrane and the stapes being forced 
outwards, and the cochlear membrane being drawn inwards by 
the operation of rarefied waves, and secondarily by these parts of 
the apparatus being restored to their former status through the 
operation of the muscles of the ear, the first and most natural 
step to be taken in any case of defective hearing is obviously to 
strengthen the tendency to move outwards of the tympanal mem- 
brane and stapes when under the influence of rarefied waves ; 
and this will clearly be effected by Valsalva’s experiment*, by 
which the density of the air in the tympanal cavity 1s temporarily 
increased. The enhanced effect of the experiment, as performed 
under the improved method introduced by Politzer, is thus also 
strikingly accounted for. 

In the cases to which it is applicable (that is, when the tym- 
panal membrane is wholly or im part present, and the connexion 
between the ossicles is wholly or partially maintained) the effect 
of Valsalva’s experiment, upon the principles before explained, is 
precisely that of raising the voice in speaking to the patient. 

On the other hand, if hearing took place through the agency 
of condensed waves, the result of the experiment would be to 
diminish the difference of the pressures on the two sides of the 


* By this experiment, the nose and mouth being closed, air is forced 
through the Eustachian tube mto the tympanal cavity. 


the Mode in which it administers to the Perception of Sound. 375 


tympanal membrane. If this assumption were true, therefore, 
Valsalva’s experiment would occasion deafness rather than re- 
move it. 

V. As a particular instance under the last head, we may take 
the case where the tympanal membrane is relaxed. 

The deafness hence arising is known to be temporarily relieved 
by Valsalva’s experiment; and that it is so may be explained 
in this way :—When a rarefied wave is incident, its effect will be 
immediately to move the tympanal membrane outwards; but, on 
account of the relaxed state of the membrane, the effect will not 
be immediately to move out the stapes, the moving out of which 
is essential to produce the sensation of sound. Before this latter 
effect can be produced the membrane must be moved outwards 
until it becomes tightly stretched; and when it is so stretched, 
and not till then, the stapes will begin to move outwards. We 
may thus see how relaxation of the membrane diminishes the 
hearing-power. 

VJ. In contrast with the foregoing may be taken the following 
ease related by Meniére*:—‘ An old judge had been accus- 
tomed for at least sixteen years, by pressure of a blunt gold 
needle against the membrana tympani, to make himself, for an 
hour or so, a tolerably good hearing-power. Meniére examined 
the ear during this state of things, found the membrana tympani 
uninjured, and that the pressure was made upon the handle of 
the malleus, which was pressed somewhat inwards. He speaks of 
having seen several similar cases, and considers them cases of ner- 
vous deafness, which were improved to a certain degree by pressure 
upon the ossicula auditus, and through them on the labyrinth.” 

I think there can be no doubt that the explanation here sug- 
gested (if it can be called such) is erroneous. In elucidation of 
the case before us, I give the following passage from Dr. Bren- 
nan’s article on Elasticity, in the Cyclopedia of Anatomy and 
Surgery t :— 

“ When the disturbing force ....1is slowly applied, there ap- 
pears to exist some degree of elasticity, even in fibrous mem- 
branes; thus in hydrops articuli the structures about the joint 
are frequently much distended by the accumulation of fluid 
within, upon the absorption of which they slowly resume their 
proper condition.” 

The true explanation of the case in Meniére I take to be, that 
in the undisturbed state of the patient’s ear, before the applica- 
tion of the needle, the tympanal membrane was unnaturally tight- 


* The citation which follows im the text is taken from an American 
translation of Von Troltsch’s Lectures, Philadelphia, 1864. 

+ The passage here cited immediately follows the statement as to the in- 
elastic character of fibrous membrane quoted in my former paper. 


SS a SO 


a = 


—— oo 


——— 
—. — 5 4 


376 Mr. R. Moon on the Structure of the Human Ear. 


ened in such a manner as to draw out the stapes, whereby the 
auditory apparatus, before the sonorous impressions became inci- 
dent upon it, was placed in a state unfavourable for their reception. 
By the action of the needle the tympanal membrane would be- 
come stretched, thus allowing the stapes to assume its proper 
position ; and this effect would continue until, by the gradual 
but slow recovery by the membrane of its former status, in the 
manner described by Dr. Brennan, the original obstacle to the 
hearing of the patient would recur. 

VII. In conformity with the views which I have endeavoured 
to explain, loud sounds may be expected to produce deafness 
either (1) by rupture of the tympanal membrane, (2) by dis- 
connexion of the chain of ossicles either from one another or 
from the tympanal membrane, or (3) by sudden convulsive 
action of the muscles of the tympanum, through which the stapes 
becomes so firmly fixed in the fenestra ovalis as to be with diffi- 
culty withdrawn. 

I conceive that deafness might result, i the manner last men- 
tioned, even in cases where the sound which is the cause of it is 
not exceptionally loud, provided that it was so sudden and unex- 
pected as to cause alarm. 

Probably also there is a fourth mode in which, in the case of 
loud sounds, deafness might result, namely where a great con- 
cussion of the air occurs; in which case the tympanal membrane 
may become stretched by reason of the unusual pressure exerted 
upon it by the condensed wave, in the manner in which Dr. 
Brennan describes it as capable of being stretched by the conti- 
nued action of a more moderate pressure. The same cause 
which stretched the membrana tympani would force in the stapes, 
and thus tend to produce the same kind of deafness as No. 3 
just referred to. 

VIII. The mode in which deafness is sometimes relieved by 
means of a loud sound falling upon the ear is readily explicable 
upon the principles before set forth, if we suppose the deafness 
to have resulted from the stapes having become too firmly im- 
bedded in the fenestra ovalis, or from rigidity of the articula- 
tions of the ossicles. 

IX. In accordance with the same principles, nervous deafness 
may be expected to occur in either of two ways, viz. by paralysis 
or torpor (1) of the auditory nerve proper, (2) of the motor 
nerves connected with the muscles of the tympanum. 

I shall seek for another opportunity to point out the functions 
of the membranous labyrinth and the semicircular canals*. 


6 New Square, Lincoln’s Inn, 
October 1, 1869. 


* Jn connexion with the explanation given in my former paper of the 


pe ore 


XLIV. Theory of the Voltaie Pile. 
By W. Kencery Bripeman, L.D.S.* 


‘HXHERE are extant at the present time two theories of the 
voltaic pile, neither of which, however, can be said to be 
sufficiently satisfactory to set the matter altogether at rest. 

The conclusions arrived at by the late Professor Faraday were 
to the effect that the source of power in the battery was derived 
from “the chemical force alone” (Experimental Researches, 
2053) ; but as chemical force is not supposed to be able to ori- 
ginate itself, or to become developed otherwise than by generation 
from some antecedent force or forces, the disturbing cause, or 
initiating step whereby it becomes excited to action, still remains 
for elucidation. 

On the other hand, Professor Tyndall expresses his belief m 
“the contact electricity of Volta being a reality,” though it could 
produce no current, and goes on to observe that Sir Wilham Thom- 
son “and others now hold what may be called a contact theory, 
which, while it takes into account the action of the metals, also 
embraces the chemical phenomena of the circuit ” (Faraday asa 
discoverer, by John Tyndall, note, p. 66) ; but as Faraday has 
demonstrated in the clearest possible manner (Exp. Res. 879- 
883) that metallic contact is not requisite for the completion 
of the circuit and obtaining the current, it can scarcely be admis- 
sible to recognize contact of the metals as one of the conditions 
necessary to the action of the battery. 

In conducting the Experimental Researches relating to the 
action of the battery, Faraday starts with the assumption that 
“ when an amalgamated zinc plate is dipped into dilute sulphuric 
acid, the force of chemical affinity exerted between the metal and 


action of the auditory apparatus when the tympanal membrane is absent, I 
may mention that I am assured by an eminent aurist that when the mem- 
brane is absent the interposition of the promontory would prevent the ex- 
posure of the cochlear membrane to the direct action of a wave of sound 
which had traversed the meatus externus, and that the latter me & brane 
could only be reached by a reflected wave. 

I may observe that the statement (p. 126, note) as to the action of ¢ he sta- 
pedal muscle, so far as the tympanal membrane is concerned, is perhaps 
made too positively. Whatever that action may be, I apprehend that it must 
always be subordinate to the action of the tensor tympani; so that while 
the joint effect of the two muscles combined must necessarily be to draw 
in the membrana tympani, that of the smaller and weaker muscle may be 
to effect some minute adjustment of the form of the membrane. A similar 
remark would apply to the functions of the laxatores tympani muscles, if 
upon further examination it should appear that such muscles exist. 

* Communicated by the Author. 


Phil. Mag.S8. 4. Vol. 38. No. 256. Nov. 1869. ae 


f 
: 


378 Mr. W. K. Bridgman on the Theory of the Voltaic Pile. 


the fluid is not sufficiently powerful to cause sensible action at the 
surfaces in contact and occasion the decomposition of water by 
the oxidation of the metal’”’ (Exp. Res. 893). 

Again, in reference to a cylinder of amalgamated zine placed 
inside a double cylinder of copper, and the two then inserted 
within a jar of dilute sulphuric acid, it is asserted that ‘being 
thus arranged there was no chemical action whilst the plates 
were not connected” (957) ; and “a battery constructed with 
the zinc so prepared (that is, amalgamated), and charged with 
dilute sulphuric acid, is active only whilst the electrodes are con- 
nected, and ceases to act or be acted upon by the acid the instant 
the communication is broken” (1000). 

The very decided manner in which the assertion, that no che- 
mical action takes place unless the dissimilar metals of the battery 
be put into communication, is made, and the frequency with which 
the belief in it is reiterated in various forms, make it appear 
that this supposed fact was considered of some importance in 
connexion with the conclusions arrived at. If, however, it be put 
to the test of examination, it will be found to receive a direct 
negative from experimental evidence and shown to be altogether 
a fallacy. 

A rod of absolutely pure zinc, 3} mches long and weighing 
487 grains, after being thoroughly amalgamated and drained, 
was placed half its length in cold dilute sulphuric acid (one part 
pure acid to ten of water), and the other half exposed to the at- 
mosphere in the same position as the ordinary plates of a battery, 
In a very short time bubbles of hydrogen made their appear- 
ance over the whole of the surface exposed to the acid, and after 
forty-eight hours the zine was found to have lost upwards of two 
grains in weight. This loss, however, was by far the least im- 
portant part of the results obtained. The immersed portion of 
the metal had not been acted upon uniformly over its entire sur- 
face, but the action had been greatest at the surface of the liquid ; 
at the same time the exposed portion had become covered with 
patches of crystalline sulphate of zinc, high and dry upon the 
projecting part of the metal. In addition to the fact of chemical 
action having been exerted between the metal and the acid and 
the water decomposed, there is the further evidence of the metal 
having been polarized. 

In order to render the effect more apparent, the experiment 
was repeated with copper instead of amalgamated zinc, as the 
colour of the crystals and the colouring of the acid afford more 
conspicuous evidence of the results which are being produced. 

A piece of stout copper wire was then similarly placed in acid ; 
the latter very soon gave signs, by the colouring it received, 


Mr. W. K. Bridgman on the Theory of the Voltaic Pile. 379 


of the former commencing to undergo solution ; and after having 
been suffered to remain undisturbed for twenty days, it presented 
the appearance exhibited in the diagram, fig. 1. Fig. 1. 

The portion A which had been immersed in 
the acid was partially corroded into pits and 
furrows, gradually decreasing in extent down- 
wards. 

The upper end, B, exposed to the atmosphere 
had become coated with a layer of minute and 
beautiful crystals of sulphate of copper, extending 
from the top down to within about three-six- 
teenths of an inch of the lhquid. 

At the intermediate portion, C, a greater 
amount of chemical action had been induced—cor- 
roding the wire, as represented, about halfway 
through and forming a neck tapering upwards. 

The solution contaming the end A was only 
slightly tmged in proportion to the amount of 
copper dissolved, the crystallization having been 
derived almost wholly from the metal above the 
surface of the liquid. 

“It is at present generally admitted that, in the normal con- 
dition, the atmosphere is charged with positive electricity .... 
The terrestrial globe, on the contrary, is charged with negative 
electricity, as is proved by a variety of observations, direct and 
indirect ; it is, moreover, a consequence of the presence of posi- 
tive electricity in the atmosphere; for one of the electricities 
cannot manifest itself in the free state without the appearance of 
an equal quantity ofthe other kind’’*. 

It is a fair inference to assume that it is in obedience to this 
law that the exposed portion of the metal has been rendered 
electro-negative, as its behaviour indicates it to be, while that 
submitted to the acid has taken the opposite or electro-positive 
state. 

That the action which arises between the metal and the acid 
is due to polarization is evidenced by the following proceeding. 

A piece of copper wire wholly submerged in the acid so as to 
entirely exclude any portion of it from coming into contact with 
the air, has remained for many months without imparting the 
slightest tinge to the liquid. Another portion having a piece of 
platinum-foil connected with it has been attended with similar 
results. A piece of wunamalgamated zinc-foil has also been kept 
in dilute acetic acid in the same way with equal effect. 

But on suffering the lquid to evaporate so as to bring the 

* Phil. Mag. 8.4. vol. xxxiv. p. 322, “ Note on the Electrical Condi- 
tion of the Terrestrial Globe,” by arene Rive. 


380 Mr. W. K. Bridgman on the Theory of the Voltaic Pile. 


upper end of the metal near to its surface, the instant the slight- 
est portion becomes exposed chemical action immediately begins. 

The first perceptible indication of this polarization is in the 
partial dewing of the copper immediately above the surface of 
the liquid. ‘This gradually increases in extent until the whole 
exposed portion becomes wet with the solution, after which mi- 
nute crystals soon make their appearance and in time cover the 
exposed part, as shown in fig.1. The determination of fluids to the 
negative portion causes the acid to rise and spread itself over the 
surface of the metal; and this, becoming saturated in its ascent, 
furnishes the material from which the crystallization is derived. 

Two equal portions of wire were similarly placed in acid, only 
that one was fully exposed to the atmosphere in an open tube, 
while the other was placed in a phial, the acid occupying half 
its height, and was kept closely corked for several weeks—after 
which the fully exposed metal had lost in weight two-fifths more 
than the one which had been excluded from contact with fresh 
portions of air, showing that contact with the atmosphere in bulk 
is necessary to the fullest action. 


A piece of copper wire 3 inches long was immersed one-third — 


in dilute acetic acid and exposed to the atmosphere im an open 
tube. In avery short time a dull coating of amorphous acetate 
of copper had been formed on the surface as far as the vapour of 
the acid had reached; but by degrees this dry formation became 
moistened, and as this occurred it was at once converted into 
minute and beautiful dark-green crystals. 

In each of these instances it is thus indisputably shown that, 
in the position in which the plates of the battery are placed (that is, 
one portion immersed in the exciting liquid and the other exposed 
to the air), chemical action does invariably occur, and is in fact an 
inevitable consequence of such partial immersion; and taking place 
where there is no sufficient normal affinity existing between the 
metal and the acid to effect the decompo- Fig. 2. 
sition of water, but arising from the metal 
being first polarized by the atmosphere, 
there is hence an additional element in- 
troduced that assumes a very significant 
character when applied to the composition 
of the battery. 

Let A B, fig. 2, represent the zinc ele- 
ment of the battery immersed half its. 
length in the acid. The condition it im- 
mediately assumes will correspond to that 
shown in fig. 1—that is, the upper end 
negative, and the immersed end positive. 

It will now appear that there are two 


Mr. W. K. Bridgman on the Theory of the Voltaic Pile. 381 


pairs of poles, namely, the metal B and the air above, and the 
metal A and the acid below, or a voltaic series composed of one 
metal and two fluids. 

But as the air is a non-conductor, no current can yet be ob- 
tained. It is essential therefore to insert a conductor as its 
representative which shall retain the same relative condition of 
polarity, this polar condition being secured by its having a less 
affinity for oxygen than the zinc or primary metal. 

A secondary plate of platinum, as in fig. 3, being substituted 
for the acid and the air of fig. 2, gives 
an arrangement of two equally polarized 
plates with their alternate poles in oppo- 
sition ; and having their lower poles joined 
bya conducting medium, they require only 
to be connected by their upper poles or 
electrodes to complete the circuit. 

While separate, the chemical action is 
confined to the primary plate, and takes 
place in an upward direction ; but imme- 
diately the electrodes are put into commu- 
nication with each other, the action is di- 
verted to the negative opposed to it in the 
conducting acid, and is now spread uni- 
formly over the whole surface of the im- 
mersed metal. The polarization of the electrodes is thus shown 
to constitute an integral part of the battery itself; and these, by 
the addition of conducting-wires, are only made to undergo an 
extension of surface without alteration of electrical condition. 

It is now obvious that placing between the electrodes any con- 
ducting substance capable of being decomposed must effect a 
corresponding action to that which takes place in the exciting 
fluid, and that an equal amount of chemical action will be effected 
at either end of the metals. Metallic contact, however, will re- 
duce the two pairs of poles to one, as in the case of the horse- 
shoe magnet, and thus effect a concentrated action. 

In the first instance the secondary platinum plate only repre- 
sents the polarity of the acid and the atmosphere; but on im- 
mersing the primary plate, and on this becoming equally polarized 
and combining with the oxygen of the electrolyte, there is a de- 
finite amount of hydrogen liberated, which retains its combining 
force unbalanced, and which then augments the charge of the 
secondary plate in an equal degree, and thus imparts to it a 
feeble degree of tension additional to the first power of the com- 
bination. 

The chemical action occurring with the single metal chiefly at 
the surface of the fluid and but feebly within the acid lower 


382 Mr. W. K. Bridgman on the Theory of the Voltaic Pile. 


down, exerts only a trifling amount of force upon the secondary 
metal; but the instant the connexion is made through the elec- 
trodes, the whole of the electrolyte enclosed between the metal 
poles becomes electrolyzed and its ions separated, increasing the 
electromotive force in like proportion. 

The contact of two dissimilar metals in air does not represent 
the two dissimilar metals of the battery, but simply corresponds 
with the two electric states of the primary metal alone. Scarcely 
any two metals have an equal affinity for oxygen, and any two of 
these placed together at once become polar and determine the 
mixed gases of the atmosphere to their respective poles. The 
combination which then takes place between the more oxidizable 
metal and the oxygen evolves or induces a certain amount of elec- 
trical force by which the combined metals and the adjacent por- 
tions of air become charged respectively positive and negative. 

In the chemical action which takes place with the polarized 
primary alone, it was stated that the greatest amount of chemical 
action was found to oceur near to the surfaces of air and acid in 
contact. The determimation of oxygen from the atmosphere to 
the positive metal, combined with the electrolysis of the elec- 
trolyte, was here exhibited in the greater extent of oxidation 
and solution of the metal, and the less degree exhibited in the 
metal which had been partly excluded from the atmosphere. 

That no current can be obtained from the contact of two me- 
tals in air is due to the fact that the atmosphere 1s not an elec- 
trolyte. It was distinctly defined by Faraday that no current is 
obtainable from chemical action unless by the decomposition of 
an electrolyte, the cation from which being absolutely indispen- 
sable for creating the tension of the secondary metal. The 
oxygen of the air having no cation to part with, is therefore un- 
provided with the means of accomplishing it. 

The fact of this non-combination of the elements of the atmo- 
sphere constitutes the means of initiating the action of the bat- 
tery. The electrolyte of the battery being held together by a 
combining force, cannot of its own accord separate itself into its 
component elements, but requires the introduction of some anta- 
gonistic force equivalent to or counterbalancing its cohesion, so 
as to set its elements free—to repolarize them in fact; this is 
accomplished by the introduction of the polarized metal, which, 
rendering the force equal on all sides, electrolyzes the water and 
allows its elements to rearrange themselves according to the 
polar influences then presented to them. 

Were the atmosphere an electrolyte, it would then require 
some antecedent to effect its electrolysis, as the action must 
begin by a non-combination of elements, or a condition requiring 
no antecedent. 


Norwich, September 1869, 


BichS3y? | 


XLV. Proceedings of Learned Societies. 
ROYAL SOCIETY. 
[Continued from p. 320. ] 
May 27, 1869.—Lieut.-General Sabine, President, in the Chair. 


HE following communications were read :— 

‘Researches on Turacine, an Animal Pigment containing Cop- 
per.” By A. W. Church, M.A. Oxon., Professor of Chemistry in 
the Royal Agricultural College, Cirencester. 

From four species of Touraco, or Plantain-eater, the author has 
extracted a remarkable red pigment. It occurs in about fifteen of 
the primary and secondary pinion-feathers of the birds in question, 
and may be extracted by a dilute alkaline solution, and reprecipi- 
tated without change by an acid. It is distinguished from all other 
natural pigments yet isolated, by the presence of 5:9 per cent. of 
copper, which cannot be removed without the destruction of the 
colouring-matter itself. The author proposes the name turactine for 
this pigment. The spectrum of turacine shows two black absorption- 
bands, similar to those of scarlet cruorine ; turacine, however, dif- 
fers from cruorine in many particulars. It exhibits great constancy 
of composition, even when derived from different genera and species 
of Plantain-eater—as, for example, the Musophaga violacea, the Co- 
rythax albo-cristata, and the C. porphyreolopha. 


‘““On a New Arrangement of Binocular Spectrum-Microscope.”’ 
By William Crookes, F.R.S. &e. 

The spectrum-microscope, as usually made, possesses several dis- 
advantages: it is only adapted for one eye* ; the prisms having to be 
introduced over the eyepiece renders it necessary to remove the eye 
from the instrument, and alter the adjustment, before passing from 
the ordinary view of an object to that of its spectrum and vice versd ; 
the field of view is limited, and the dispersion comparatively small. 

I have devised, and for some time past have been working with, 
an instrument in which the above objections are obviated, although 
at the same time certain minor advantages possessed by the ordinary 
instrument, such as convenience of examining the light reflected from 
an object, and comparing its spectrum with a standard spectrum, are 
not so readily associated with the present form of arrangement. 

The new spectrum-apparatus consists of two parts, which are 
readily attached to an ordinary single or binocular microscope; and 
when attached they can be thrown in or out of adjustment by a touch 
of the finger, and may readily be used in conjunction with the po- 
lariscope or dichrooscope; object-glasses of high or low power can be 
uséd, although the appearances are more striking with a power of 


* Mr. Sorby in several of his papers (Proc. Roy. Soc. 1867, xv. p. 433; ‘How 
to Work with the Microscope,’ by L. Beale, F.R.S., 4th edition, p. 219) refers 
to a binocular spectrura-microscope ; but he gives no description of it, and in one 
part says that it is not suited for the examination of any substance less than +5 
of au inch in diameter, 


384 Royal Society :—Mr. W. Crookes on a New Arrangement 


‘inch focus or longer; and an object as small asa single corpuscle of 
blood can be examined and its spectrum observed. 

The two additions to the microscope consist of the substage with 
slit &c., and the prisms in their box. The substage is of the ordi- 
nary construction, with screw adjustment for centring, and rackwork 
for bringing it nearer to or withdrawing it from the stage. Its 
veneral appearance is shown in fig. 1, which represents it in position. 
A B is.a plate of brass, sliding in grooves attached to the lower part 


Bice wilh 


of the suvstage; it carries an adjustable slit, C, a circular aperture, 
D, 0 Ginch in diameter, and an aperture, O, 3 inch square. A spring 
tup euables either the slit or one of the a; ertures to ve brought into 
the ceutre of the field without moving the eye from the eyepiece. 
Screw adjustinents enable the slit to be widened or narrowed at will, 
aud also varied in length. At the upper part of the substage is a 


of Binocular Spectrum- Microscope. 385 


screw of the standard size, into which an object-glass of high power 
is fitted. E represents one in position. I generally prefer a }-inch 
power; but it may sometimes be found advisable to use other powers 
here. ‘The slit C and the object glass E are about 2 inches apart ; 
and if light is reflected by means of the mirror along the axis of 
the instrument, it is evident that the object-glass E will form a small 
image of the slit C, about 0°3 inch in front of it. The milled head 
F moves the whole substage up or down the axis of the microscope, 
whilst the screws G and H, at right angles to each other, will bring 
the image of the slit into any desired part of the field. If the slide 
A B is pushed in so as to bring the circular aperture D in the 
centre, the substage arrangement then becomes similar to the old 
form of achromatic condenser. Beneath the slit C is an arrangement 
for holding an object, in case its surface is too irregular, or substance 
too dense, to enable its spectrum to be properly viewed in the or- 
dinary way*. 

Supposing an object is on the upper stage of the microscope 
(shown in fig. 2) and viewed by light transmitted from the mirror 
through the large aperture D and the condenser EK, by pushing in 
the slide A B soas to bring the slit C into the field, and then turning 
the milled head F, it is evident that a luminous image of the slit C 
can be projected on to the object; and by proper adjustment of the 
focus, the object and the slit can be seen together equally sharp. 
Also, since the whole of the light which illuminated the object has 
been cut off, except that portion which passes through the slit, all 
that is now visible in the instrument is a narrow luminous line, in 
which is to be seen just so much of the object as falls within the 
space this line covers. By altering the slit-adjustments the length 
or width of the luminous line can be varied, whilst, by means of 
the rackwork attached to the upper stage, any part of the object may 
be superposed on the luminous line. The stage is supplied with a 
concentric movement, which permits the object to be rotated whilst 
in the field of view, so as to allow the image of the slit to fall on 
it inany direction. During this examination a touch with the finger 
will at any time bring the square aperture O, or the circular aperture 
D into the field, instead of the slit, so as to enable the observer to 
see the whole of the object; and in the same manner the slit can 
as easily be again brought into the field. 

The other essential part of this spectrum-microscope consists of 
the prisms. ‘These are enclosed in a box, shown at K (fig. 2). The 
prisms are of the direct-vision kind, consisting of three flint and two 
crown, and are altogether 1°6 inch long. The box screws into the 
end of the microscope-body at the place usually occupied by the 
object-glass ; and the object-glass is attached by a screw in front of the 
prism-box. It is shown in its place at L. The prism-box is suffi- 


* In carrying out the experiments which were necessary before this spectrum- 
microscope could be made in its present complete form, | have been greatly as- 
sisted by Mr.C. Collins, Philosophical-Instrument Maker, 77 Great Tichfield Street, 
to whom lL am also indebted for useful suggestions as to the most convenient ar- 
rangement of the different parts, so as to render them easily adapted to micro- 
scopes of ordinary construction. 


386 Royal Society :—Mr. W. Crookes on a New Arrangement 


ciently wide to admit of the prisms being pushed to the side when not 
wanted, so as to allow the light, after passing through the object- 
glass, to pass freely up the tube K. Apinat M enables the prisms 
to be thrown either in or out of action by a movement of the finger. 

As the prisms are close above the object-glass, the usual sliding 
box, carrying the binocular prism and the Nicol? s prism (shown at N), 
may be employed as usual, and the spectrum of any substance may 
thus be examined by both eyes simultaneously, either by ordinary 
light, or when it is under the influence of polarized light. The inser- 
tion of the prism-box between the object-glass and the bedy of the 
microscope does not interfere with the working of the instrument in 
the ordinary manner. ‘The length of the tube is increased | or 2 
inches, and a little additional rackwork may In some instruments be 
necessary when using object-glusses of low power. ‘The stereoscopic 
effect when the Wenham prism is put into action does not appear 
to be interfered with. 


For ordinary work both these additions may be kept attached to 
the microscope, the prisms being pushed to the side of the prism- 


of Binocular Spectrum-Microscope. 387 


box, and the large aperture D being brought into the centre of the 
substage. When it is desired to examine the spectrum of any por- 
tion of an object in the field of view, all that is necessary is to push 
the slit into adjustment with one hand, and the prisms with the 
other. The spectrum of any object which is superposed on the image 
of the slit is then seen. 

The small square aperture at O (fig. 1) is for the examination of 
dichroic substances. When this is pushed into the field, by placing 
a double-image prism P between A B and EK, two images of the aper- 
ture are seen in juxtaposition, oppositely polarized ; and if a dichroic 
substance is on the stage, the differences of colour are easily seen. 

When the spectrum of any substance is in the field and the double- 
image prism P is introduced, two spectra are seen, one above the other, 
oppositely polarized, and the variations in the absorption-lines, such 
as are shown by didymium, jargonium, &c., are at once seen. 

A Nicol’s prism, Q, as polarizer, is also arranged to slip into the 
same position as the double-image prism, and another, R, as analyzer, 
above the prism-box. The spectra of the brilliant colours exhibited 
by certain crystalline bodies, when seen by polarized light, can then 
be examined. Many curious effects are then produced, a description 
of which I propose to make the subject of another paper. Both the 
prisms P and Q are capable of rotation. 

If the substance under examination is dark coloured, or the illumi- 
nation is not brilliant, it is best not to divide the light by means of 
the Wenham prism at N, but to let the whole of it pass up the tube 
to one eye. If, however, the light is good, a very great advantage 
is gained by throwing the Wenham prism into adjustment and using 
both eyes. The appearance of the spectrum, and the power of grasp- 
ing faint lines, are incomparably superior when both eyes are used ; 
whilst the stereoscopic effect it confers on some absorption and in- 
terference spectra (especially those of opals) seems to throw entirely 
new light on the phenomena. No one who has worked with a ste- 
reoscopic spectrum-apparatus would willingly return to the old mo- 
nocular spectroscope*. 

If the illumination in this instrument is taken from a white cloud 
or the sky, Fraunhofer’s lines are beautifully visible ; and when using 
direct sunlight they are seen with a perfection which leaves little to 
be desired. The dispersion is sufficient to cause the spectrum to fill 
the whole field of the microscope, instead of, as in the ordinary in- 
strument, forming a small portion of it, the dispersion being four or 
five times as great ; whilst, owing to the very perfect achromatism 
of the optical part of the microscope, all the lines from B to G are 
practically in the same focus. 

As the only portion of the object examined is that part on which 
the image of the slit falls, and as this is very minute (varying from 

* Jt is not difficult to convert an ordinary spectroscope into a binocular instru- 
ment. The rays after leaving the object-glass of the telescope are divided into 
two separate bundles and received on two eyepieces properly mounted. Asitis - 


immaterial whether the spectrum be stereoscopic or pseudoscopic, a simpler form 
of prism than Mr. Wenham’s arrangement can be used. 


388 Royal Soctety:— 


0:01 to 0:001 inch, according to the actual width of the slit), it is 
evident that the spectrum of the smallest objects can be examined. 
If some blood is in the field, it is easy to reduce the size of the image 
of the slit to dimensions covered by one blood-disk, and then, by 
pushing in the prisms, to obtain its spectrum. 

If the object under examination will not transmit a fair image 
of the slit (@f it be a rough crystal of jargoon for instance), it must 
be fixed in the universal holder beneath the siit and the light con- 
centrated on it before it reaches the slit. If the spectra of opaque 
objects are required, they can also be obtained in the same way, the 
light being concentrated on them either by a parabolic reflector or by 
other appropriate means. 

By replacing the illuminating lamp by a spirit-lamp burning with a 
soda-flame, and pushing in the spectrum-apparatus, the yellow sodium- 
line is seen beautifully sharp; and by narrowing the slit sufficiently 
it may even be doubled. Upon introducing lithium- or thallium-com- 
pounds into the flame, the characteristic crimson or green line is 
obtained ; in fact so readily does this form of instrument adapt 
itself to the examination of flame-spectra, that for general work I 
have almost. ceased to use a spectroscope of the ordinary form. The 
only disadvantage I find is an occasional deficiency of light; but by 
an improved arrangement of condensers I hope soon to overcome this 
difficulty. 


“On some Optical Phenomena of Opals.” By William Crookes, 
F.R.S. &e. 

When a good fiery opal is examined in day-, sun-, or artificial 
light, it appears to emit vivid flashes of crimson, green, or blue light, 
according to the angle at which the incident light falls, and the rela- 
tive position of the opal and the observer; for the direction of the 
path of the emitted beam bears no uniform proportion to the angle 
of the incident light. Examined more closely, the flashes of light 
are seen to proceed from planes or surfaces of irregular dimensions 
inside the stone, at different depths from the surface and at all angles 
to each other. Occasionally a plane emitting light of one colour 
overlaps a plane emitting light of another colour, the two colours 
- becoming alternately visible upon slight variations of the angle of the 
stone; and sometimes a plane will be observed which emits crimson 
light at one end, changing to orange, yellow, green, &c., until the 
other end of the plane shines with a blue light, the whole forming 
a wonderfully beautiful solar spectrum in miniature. I need scarcely 
say that the colours are not due to the presence of any pigment, 
but are interference colours caused by minute strize or fissures lying 
in different planes. By turning the opal round and observing it 
from different directions, it is generally possible to get a position in 
which it shows no colour whatever. Viewed by transmitted light, 
opals appear more or less deficient in transparency and have a slight 
greenish yellow or reddish tinge. 

In order to better adapt them to the purposes of the jeweller, opals 
are almost always polished with rounded surfaces, back and front ; 


Mr. W. Crookes on some Optical Phenomena of Opals. 589 


but the flashes of coloured light are better seen and examined when 
the top and bottom of the gems are ground and polished flat and 
parallel. 

A good opal is not injured by moderate heating in water, soaking 
in turpentine, or heating strongly in Canada balsam and mounting 
as a microscopic slide. 

By the kindness of Mr. W. Chapman, of Frith Street, Soho, and 
other friends, I have been enabled to submit some thousands of opals 
to optical examination ; and from these I have selected about a dozen 
which appeared worthy of further study. 

If an opal which emits a fine broad crimson light is held in front 
of the slit of a spectroscope or spectrum-microscope, at the proper 
angle, the light is generally seen to be purely homogeneous, and all 
the spectrum that is visible is a brilliant luminous line or band, 
varying somewhat in width and more or less irregular in outline, but 
very sharp, and shining brightly on a perfectly black ground. If, 
now, the source of light is moved, so as to shine into the spectrum- 
apparatus through the opal, the above appearance is reversed, and 
we have a luminous spectrum with a jet-black band in the red, iden- 
tical in position, form of outline, and sharpness with the luminous 
band previously observed. If instead of moving the first source of 
light (the one which gave the reflected luminous line in the red) an- 
other source of light be used for obtaining the spectrum, the two ap- 
pearances, of a coloured line on a black ground, and a black line on 
a coloured ground, may be obtained simultaneously, and they will be 
seen to fit accurately. 

Those parts of the opal which emit red light are therefore seen to be 
opaque to light of the same refrangibility as that which they emit ; 
and upon examining in the same mamner other opals which shine 
with green, yellow, or blue light, the same appearances are observed, 
showing that this rule holds good in these cases also. It is doubtless 
a general law, following of necessity the mode of production of the 
flashes of colour. 

Having once satisfied myself that the above law held good in all 
the instances which came under my notice, I confined myself chiefly 
to the examination of the transmitted spectra, although the following 
descriptions will apply equally well, mutates mutandis, to the re- 
flected spectra. The examinations were made by means of the spec- 
trum-microscope, which instrument is peculiarly adapted to exami- 
nations of this sort, both on account of the small size of the object 
which can be examined in it, and also as it permits the use of both 
eyes In viewing the spectrum. 

The following is a brief description of some of the most curious 
transmission spectra shown by these opals. The accompanying 
figures, drawn with the camera lucida, convey as good an idea as pos- 
sible of the different appearances. The exact description will of 
course only hold good for one portion of the opal; but the general 
character of each individual stone is well marked. 

No. 1 shows a single black band in the red. When properly in 
focus this has a spiral structure. Examined with both eyes it appears 


390 Royal Society : — 


in decided relief, and the arrangement of light and shade is such as 
to produce a striking resemblance to a twisted column. 

No 2. gives an irregular line in the orange. Viewed binocularly, 
this exhibits the spiral structure in a marked manner, the different 
depths and distances standing well out; upon turning the milled 
head of the stage-adjustment, so as to carry the opal slowly from left 
to right, the spiral line is seen to revolve and roll over, altering its 
shape and position in the spectrum. It is not easy to retain the 
conviction that one is looking merely at a band of deficient light in 
the spectrum, and not at a solid body, possessing dimensions and in 
actual motion. 

No. 3 has a line between the yellow and green, vanishing toa point 
at the top, and near the bottom having a loop, in the centre of which 
the green appears. Higher up, in the green, is a broad green band, 
indistinct on one side and branching out in different parts. 

No. 4 has a broad, indistinet, and sloping band in the blue, and 
another, still more indistinct, in the violet. 

No. 5 has a band in the yellow, not very sharp on one side, and 
somewhat sloping. Upon moving the opal sideways, it moves about 
from one part of the yellow field to another. In one position it 
covers the line D, and is opaque to the sodium-flame of a spirit- 
lamp. 

No. 6 shows a curiously shaped band in the red, very sharp and 
black, and terminating in one part at the line D. In the yellow 
there is a black dot. The spectrum of this opal showed by reflected 
light intensely bright red bands, of the shape of the transmission 
bands. On examining this opal with a power of 1 inch, in the or- 
dinary manner, the portion giving this spectrum appeared to glow 
with intense red light, and was bounded with a tolerably definite 
outline. Without altermg any other part of the microscope, the 
prisms were then pushed in so as to look at the whole surface of 
the opal through the prisms, but without the slit. The shape and 
appearance of the red patch were almost unaltered; and here and 
there over other parts of the opal were seen little patches of homo- 
geneous light, which, not having been fanned out by the prisms, 
retained their original shape and appearance. 

No. 7 shows a black patch in the red, only extending a little dis- 
tance, and a line in the yellow. On moving the opal the line in the 
red vanishes, and the other line changes its position and form. 

No. 8 shows the most striking example of a spiral rotating line 
which I have yet met with. On moving the opal sideways the line 
is seem to start from the red and roll over, like an irregularly shaped 
and somewhat hazy corkscrew, into the middle of the yellow. The 
drawing shows the appearance of this band in two positions. 

No. 9 is one of the most curious. A broad black and sharp 
band stretches diagonally across the green, touching the blue at the 
top and the yellow at the bottom. 

No. 10 gives a diagonal band, wide, but straight, and tolerably 
sharp across the green. By rotating these opals, 9 and 10, in azi- 
muth, whilst in the field of the instrument, the lines cau be made to 


Mr. W. Crookes on some Optical Phenomena of Opals. 


391 


aa | 


392 Royal Society :-— 


alter in inclination until they are seen to slope in the opposite di- 
rection. 

No. 11 gives another illustration of a diagonal line, across the yel- 
low and green, not extending quite to the,top. 

No. 12 is one of the best examples I have met with of a narrow, 
straight, and sharply cut line. It is in the green, and might easily 
be mistaken for an absorption-band caused by an unknown chemical 
element. 

Other opals are exhibited, which show a dark band travelling along 
the spectrum, almost from one end to the other, as the opal is 
moved sideways. 

It is scarcely necessary to say that the colour of the moving lumi- 
nous line varies with the part of the spectrum to which it belongs. 
The appearance of a luminous line, slowly moving across the black 
field of the instrument, and assuming in turn all the colours of the 
spectrum, is very beautiful. 

All these black bands can be reversed, and changed into luminous 
bands, by illuminating the opal with reflected hight. They are, how- 
ever, more difficult to see; for the coloured light is only emitted at a 
particular angle, whilst the special opacity to the ray of the same 
refrangibility as the emitted ray holds good for all angles. 

The explanation of the phenomena is probably as follows :—In the 
case of the moving line, the light-emitting plane in the opal is some- 
what broad, and has the property of giving out at one end, along its 
whole height and for a width equal to the breadth of the band, say, 
red light; this merges gradually into a space emitting orange, and 
so on throughout the entire length of the spectrum, or through that 
portion of it which is traversed by the moving line in the instrument, 
the successive pencils (or rather ribbons) of emitted light passing 
through all degrees of refrangibility. It is evident that if this opal 
is slowly passed across the slit of the spectrum-microscope, the slit 
will be successively illuminated with light of gradually increasing 
refrangibility, and the appearance of a moving luminous line will be 
produced ; and if transmitted light is used for illumination, the re- 
versal of the phenomena will cause the production of a black line 
moving along a coloured field. A diagonal line will be produced if an 
opal of this character is examined in a sloping position. 

The phenomenon of a spiral line in relief, rolling along as the 
opal is moved, is doubtless caused by modifying planes at different 
depths and connected by cross planes ; I can form a mental picture 
of a structure which would produce this effect, but not clear enough 
to enable me to describe it in words. 

It is probable that similar phenomena may be seen in many, if not 
all, bodies which reflect coloured light after the manner of opals. A 
magnificent specimen of Lumacelli, or Fiery Limestone, from Italy, 
kindly presented to me by my friend David Forbes, shows two sharp 
narrow and parallel bands in the red. I have also observed similar 
appearances in mother-of-pearl. The effects can be imitated to a 
certain extent by examining ‘‘ Newton’s rings,”’ formed between two 
plates of glass, in the spectrum-instrument. 


Sir W. Thomson on a new Astronomical Clock. 893 


June 10.—Lieut.-General Sabine, President, in the Chair. 


The following communications were read :— 

“On a new Astronomical Clock, and a Pendulum-governor for 
Uniform Motion.’ By Sir William Thomson, LL.D., F.R.S. 

It seems strange that the dead-beat escapement should still hold 
its place in the astronomical clock, when its geometrical transforma- 
tion, the cylinder escapement of the same inventor, Graham, only 
survives in Geneva watches of the cheaper class. or better portable 
time-keepers, it has been altered (through the rack-and-pinion move- 
ment) into the detached lever, which has proved much more accurate. 
If it is possible to make astronomical clocks go better than at present 
by merely giving them a better escapement, it is quite certain that 
one on the same principle as the detached lever, or as the ship-chro- 
nometer escapement, would improve their time-keeping. 

But the inaccuracies hitherto tolerated in astronomical clocks may 
be due more to the faultiness of the mercury compensation pendulum, 
and of the mode in which it is hung, and of the instability of the sup- 
porting clock-case or framework, than to imperfection of the escape- 
ment and the greatness of the are of vibration which it requires ; 
therefore it would be wrong to expect confidently much improvement 
in the time-keeping merely from improvement of the escapement. I 
have therefore endeavoured to improve both the compensation for 
change of temperature in the pendulum, and the mode of its support, 
in a clock which I have recently made with an escapement on a new 
principle, in which the simplicity of the dead-beat escapement of 
Graham is retained, while its great defect, the stopping of the whole 
train of wheels by pressure of a tooth upon a surface moving with 
the pendulum, is remedied. 

Imagine the escapement-wheel of a common dead-beat clock to be 
mounted on a collar fitting easily upon a shaft, instead of being rigidly 
attached to it. Let friction be properly applied between the shaft 
and the collar, so that the wheel shall be carried round by the shaft un- 
less resisted by a force exceeding some small definite amount, and let a 
governor giving uniform motion be applied to the train of wheel-work 
connected with this shaft, and so adjusted that, when the escapement- 
wheel is unresisted, it will move faster by a small percentage than it 
ought to move when the clock is keeping time properly. Now let 
the escapement-wheel, thus mounted and carried round, act upon 
the escapement, just as it does in the ordinary clock. It will keep 
the pendulum vibrating, and will, just as in the ordinary clock, be 
held back every time it touches the escapement during the interval 
required to set it right again from having gone too fast during the 
preceding interval of motion. But in the ordinary clock the interval 
of rest is considerable, generally greater than the interval of motion. 
In the new clock it is equal to a small fraction of the interval of mo- 
tion: 54, in the clock as now working, but to be reduced probably 
to something much smaller yet. The simplest appliance to count 
the turns of this escapement-wheel (a worm, for instance, working 
upon a wheel with thirty teeth, carrying a hand round, which will 


Phil. Mag. 8.4. Vol. 38. No. 256, Nov. 1869. 2D 


394. ~ Royal Society :— 


correspond to the seconds’ hand of the clock) completes the instru- 
ment ; for minute- and hour-hands are a superfluity in an astrono- 
mical clock. 

In various trials which I have made since the year 1865, when 
this plan of escapement first occurred to me, I have used several 
different forms, all answering to the preceding description, although 
differing widely in their geometrical and mechanical characters. In 
all of them the escapement-wheel is reduced to a single tooth or arm, 
to diminish as much as possible the moment of inertia of the mass 
stopped by the pendulum. ‘This arm revolves in the period of the 
pendulum (two seconds for one second’s pendulum), or some multiple 
of it. Thus the pendulum may execute one or more complete pe- 
riods of vibration without being touched by the escapement. 

I look forward to carrying the principle of the governed motion 
for the escapement-shaft much further than hitherto, and adjusting 
it to gain only ;{,5 per cent. on the pendulum ; and then [ shali 
probably arrange that each pallet of the escapement be touched only 
‘once a minute (and the counter may be dispensed with). The only 
other point of detail which I need mention at present is that the pal- 
lets have been, in all my trials, attached to the bottom of the pen- 
dulum, projecting below it, in order that satisfactory action with a 
very small are of vibration (not more on each side than ;4,5 of the 
radius, or 1 centimetre for the second’s pendulum) may be secured. 

My trials were rendered practically abortive from 1865 until a 
few months ago by the difficulty of obtaining a satisfactory governor 
for the uniform motion of the escapement-shaft; this difficulty is - 
quite overcome in the pendulum-governor, which I now proceed to 
describe. 

Imagine a pendulum with single-tooth escapement mounted on a 
collar loose on the escapement-shaft just as described above—the 
shaft, however, being vertical in this case. A. square-threaded screw is 
cut on the upper quarter of the length of the shaft, this being the part 
of it on which the collar works, and a pin fixed to the collar projects 
inwards to the furrow of the screw, so that, if the collar is turned 
relatively to the shaft, it will be carried along, as the nut of a screw, 
but with less friction than an ordinary nut. The main escapement- 
shaft just described is mounted vertically. The lower screw and 
long nut collar, three-quarters of the length of the escapement-shaft, 
are surrounded by a tube which, by wheelwork, is carried round 
about five per cent. faster than the central shaft. This outer shaft, 
by means of friction produced by the pressure of proper springs, 
carries the nut collar round along with it, except when the escape- 
ment-tooth is stopped by either of the pallets attached to the pen- 
dulum. A stiff cross piece (like the head of a T), projecting each 
way from the top of the tubular shaft, carries, hanging down from 
it, the governing masses of a centrifugal friction governor. These 
masses are drawn towards the axis by springs, the inner ends of 
which are acted on by the nut collar, so that the higher or the lower 
the latter is in its range, the springs pull the masses inwards with 
less or more force. A. fixed metal ring coaxial with the main shaft 


Dr. W. A. Miller on a Self-registering Thermometer. 395 


holds the governing masses in when their centrifugal forces exceed 
the forces of the springs, and resists the motion by forces of friction 
increasing approximately in simple proportion to the excess of the 
speed above that which just balances the forces of the springs. As 
long as the escapement-tooth is unresisted, the nut collar is carried 
round with the quicker motion of the outer tubular shaft, and so it 
screws upwards, diminishing the force of the springs. Once every 
semiperiod of the pendulum it is held back by either pallet, and the 
nut collar screws down as much asit rose during the preceding inter- 
val of freedom when the action is regular; and the central or main 
escapement-shaft turns in the same period as the tooth, being the 
period of the pendulum. If through increase or diminution of 
the driving-power, or diminution or increase of the coefficient of 
friction between the governing masses and the ring on which they 
press, the shaft tends to turn faster or slower, the nut collar works 
its way down or up the screw, until the governor is again regulated, 
and gives the same speed in the altered circumstances. It is easy 
to arrange that a large amount of regulating power shall be implied 
in a single turn of the nut collar relatively to the central shaft, and 
yet that the periodic application and removal of about 3; of this 
amount in the half period of the pendulum shall cause but a very 
smail periodic variation in the speed. The latter important condi- 
tion is secured by the great moment of inertia of the governing masses 
themselves round the main shaft. I hope, after a few months’ trial, 
to be able to present a satisfactory report of the performance of 
the clock now completed according to the principles explained 
above. As many of the details of execution may become modified 
after practical trial, it is unnecessasy that I should describe them 
minutely at present. Its general appearance, and the arrangement 
of its characteristic parts, may be understood from the photograph 
now laid before the Society. 


June 17.—Lieut.-General Sabine, President, in the Chair. 
The following communication was read :— 


“‘ Note upon a Self-registermg Thermometer adapted to Deep-sea 
Soundings.’ By W. A. Miller, M.D., Treas. and V.P.R.S. 

The Fellows of the Royal Society are already aware that the Ad- 
miralty, at the request of the Council of the Society, have placed a 
surveying-vessel at the disposal of Dr. Carpenter and his coadjutors 
for some weeks during the present summer, to enable them to insti- 
tute certain scientific inquiries in the North Sea. Among the objects 
which the expedition has in view is the determination of deep-sea 
temperatures. 

Now it is well known that self-registering thermometers of the 
ordinary construction are liable to error when sunk to considerable 
depths in water, in consequence of the diminution produced for the 
time in the capacity of the bulb under the increased pressure to which 
it is subjected. The index, from this cause, is carried forward beyond 


2D2 


396 Royal Society :—Dr. W. A. Miller on a Self-registering 


the point due to the effect of mere temperature, and the records fur- 
nished by the instrument rise too high*. 

A simple expedient occurred to me as being likely to remove the 
difficulty ; and as upon trial it was found to be perfectly successful, 
I have thought that a notice of the plan pursued might not be 
unacceptable to future observers. 

The form of self-registermg thermometer which it was decided to 
employ is one constructed upon Six’s plan. Much care is requisite 
in adjusting the strength of index-spring, and the size of the pin, 
so as to allow it to move with sufficient freedom when pressed by 
the mercury, without running any risk of displacement in the ordi- 
nary use of the instrument while raising or 
lowering it into the water. Several of these 
thermometers have been prepared for the 
purpose with unusua. care by Mr. Casella, 
who hasdetermined the conditions of strength 
in the spring and diameter of tube most fa- 
vourable to accuracy. He has also himself 
had an hydraulic press constructed expressly 
with the view of testing these instruments. 
By means of this press the experiments 
hereafter to be described were made. 

The expedient adopted for protecting the 
thermometers from the effects of pressure 
consisted simply in enclosing the bulb of 
such a Six’s thermometer in a second or 
outer glass tube, which was fused upon the 
stem of the instrument in the manner shown 
in the accompanying figure. This outer tube 
was nearly filled with alcohol, leaving a little 
space to allow of variation in bulk due to 
expansion. The spirit was heated to dis- 
place part of the air by means of its vapour, 
and the outer tube and its contents were 
sealed hermetically. 

In this way, variations in external pres- 
sure are prevented from affecting the bulb 
of the thermometer within, whilst changes of 
temperature in the surrounding medium are 
speedily transmitted through the thin stra- 
tum of interposed alcohol. ‘The thermo- 
meter is protected from external injury by 
enclosing it in a suitably constructed copper 
case, open at top and bottom, for the free 
passage of the water. 

In order to test the efficacy of this plan, 
the instruments to be tried were enclosed 


* In sea-water of sp. gr. 1-027, the pressure in descending increases at. the 
rate of 280 Ibs. upon the square inch for every 100 fathoms, or exactly one ton 
for every 800 fathoms. 


Thermometer adapted to Deep-sea Soundings. 397 


in a strong wrought-iron cylinder filled with water, and submitted 
to hydraulic pressure, which could be raised gradually till it reached 
three tons upon the square inch; and the amount of pressure could 
be read as the experiment proceeded, upon a gauge attached to the 
apparatus. 

Some preliminary trials made upon the 5th of May showed that 
the press would work satisfactorily, and that the form of thermo- 
meter proposed would answer the purpose. 

These preliminary trials showed that, even in the thermometers 
with protected bulbs, a forward movement of the index of from 0°°5 
to 1° F. occurred during each experiment. This, however, I be- 
lieved was caused, not by any compression of the bulb, but by a real 
rise of temperature, due to the heat developed by the compression of 
the water in the cavity of the press. 

This surmise was shown to be correct by some additional experi- 
ments made last week to determine the point. On this occasion 
the following thermometers were employed :— 

No. 9645. A mercurial maximum thermometer, on Prof. Phillips’s 
plan, enclosed in a strong outer tube containing a little spirit of wine, 
and hermetically sealed. 

No. 2. A Six’s thermometer, with the bulb protected, as proposed 
by myself, with an outer tube. 

No. 5. A Six’s thermometer, with a long recurved cylindrical bulb, 
also protected in a similar manner. 

No. 1. Six’s thermometer, with cylindrical bulb of extra thickness, 
noé protected. 

No. 3. Six’s thermometer, with spherical bulb, extra thick glass, 
not protected. 

No. 6. Admiralty instrument, Six’s thermometer, ebonite scale, 
bulb not protected. 

No. 9651. An ordinary Phillips’s maximum mercurial thermo- 
meter, spherical bulb, not protected. 

The hydraulic press was exposed in an open yard, and had been 
filled with water several hours before. A maximum thermometer, 
introduced into a wrought-iron, tube filled with water, open at one 
end to the outer air, closed at the other, where it passed into the 
water contained in the press, registered 46°°7 at the commencement, 
and 47° at the end of the experiment. Temperature of the external 
air 49° F. 

In commencing the experiment, the seven thermometers under trial 
were introduced into the water in the cavity of the press, and after 
a lapse of ten minutes the indices of each were set, carefully read, 
and each instrument was immediately replaced in the press, which 
was then closed, and by working the pump the pressure was gra- 
dually raised to 23 tons upon the inch. It was maintained at this 
point for forty minutes, in order to allow time for the slight elevation 
of temperature caused by the compression of the water to equalize 
itself with that of the body of the apparatus. At the end of the forty 
minutes the pressure was rapidly relaxed. A corresponding depres- 
sion of temperature was thus occasioned, the press was opened im- 


398 Royal Society. 


mediately, and the position of the indices of each thermometer was 
again read carefully ; and the water was found to be at a temperature 
sensibly lower than before the experiment began, by about 0°6 F. 
By this means it was proved that the forward movement of the index 
in the protected thermometers, amounting to 0°°9, was really due 
to temperature, and not to any temporary change in the capacity of 
the bulb produced by pressure. 

This will be rendered evident by an examination of the subjoined 
Table of observed temperatures :— 


First Series: Pressure 24 tons per square inch. 


Nuiiber oe Minimum index. || Maximum index. ees 
Thermometer. Before. | After. || Before. | After. After. | 
Jeimoegisebn.§ SIO) || oat gadh Ie Lcegdee 47-0 | 47-7 
‘ pe BN ATO 46°5 46-7 47-6 46°5 
% tipo 20 46'3 46°5 47-6 46:0 
Meare ccc se  Iperree, oiler eeen: 47-6 
Unprotected. 1)| 46-7 46°4 46°5 54:0 46 
i} 3| 47-0 46°5 46°5 56°5 46 
; 56] 47:0 46:0 47-0 55°5 46 
i, SOLS) ae Me See Ao | ALSio 
Mean <.-:-: 46°9 46:3 46-7 | seen 46:1 
Temperature of external air...... 49 49 


Temperature of thermometer ’ 
ATL MOLES pe se seat ee sect once | 0 2s 


In the Phillips’s maximum thermometer, with unprotected sphe- 
rical bulb, No. 9651, the bulb had experienced so great a degree of 
compression as to drive the index almost to the top of the tube. In 
all the other unprotected instruments, which had been made with 
bulbs of unusual thickness, the index had been driven beyond its 
proper position from 6°°4 to 8°9 F.; and it is obvious that the 
amount of this error must vary in each instrument with the varying 
thickness of the bulb and its power of resisting compression. 

Notwithstanding the great pressure to which these instruments had 
been subjected, all of them, without exception, recovered their ori- 
ginal scale-readings as soon as the pressure was removed. 

It will be seen that the mean rise of temperature indicated by the 
three protected instruments was 0°-9 F., whilst the mean depression 
registered on removing the pressure amounted upon all the instru- 
ments which admitted of its measurement to 0°°6, an agreement as 
close as was to be expected from the conditions of the experiment. 

A second set of experiments was made upon the same set of instru- 
ments, with the exception of 9651; but the pressure was now raised 
to 3 tons upon the inch; this was maintained for ten minutes. When 


Geological Society. 399 


it had risen to 22 tons a slight report was heard in the press, indi- 
cating the fracture of one of the thermometers. On examining the 
contents of the press afterwards it was found that No. 2 was broken ; 
the others were uninjured. The broken thermometer was the earliest 
constructed upon the plan now proposed, and it was consequently not 
quite so well finished as subsequent practice has secured for those of 
later construction. The results of the trial under the higher pres- 
sures showed an increase in the amount of compression experienced 
bythe unprotected instruments rising in one instance to as much as 
11°-5 F. With the protected instruments the rise did not exceed 1°°5, 
due, as before, to the heat evolved from the water by its compression. 
A pressure of 3 tons, it may be observed, would be equal to that 
of 448 atmospheres of 15 lb. upon the square inch; and if it be as- 
sumed that the diminution in bulk of water under compression con- 
tinues uniformity at the rate of 47 millionths of its bulk for each ad- 
ditional atmosphere, the reduction in bulk of water under a pressure 
of 3 tons upon the square inch will amount to about ;4 of its ori- 
ginal volume. This probably is too high an estimate, as the rate 
of diminution would most likely decrease as the pressure increases. 


GEOLOGICAL SOCIETY. 
[Continued from p. 322. ] 


February 24th, 1869,—Prof. T. H. Huxley, LL.D,, F.R.S., 
President, in the Chair. 


The following communication was read :— 

«On the British Postglacial Mammalia.” By W. Boyd Daw- 
kins, Esq., M.A., F.R.S., F.G.S. 

The author stated that the Postglacial or Quaternary Mammalia 
of Englard and Wales amounted to 47. Of these only 15 are found 
in Cayes and not in River deposits, whilst out of 31 found in the 
latter, only 1 does not occur in caves; hence the author inferred 
that the Cave and River deposits are palzontologically synchronous. 
In Scotland, remains of Mammalia have occurred only in five places, 
and in Ireland only in two places, in beds of Postglacial age. The 
author ascribed this unequal distribution to the long continuance of 
subaérial glaciation in Ireland, Scotland, and North Wales. 

The author then compared the Postglacial with the Preglacial 
Mammalia. The British species of the latter are :— 


Ursus arvernensis. Bos primigenius. 

—— speleus?. Hippopotamus major. 

Sorex. Equus fossilis. 

Mygale moschata. Rhinoceros megarhinus. 

Talpa europea. Htruscus. 

Cervus megaceros ¢ Elephas antiquus. 
capreolus. meridionalis. 

—— elaphus. Arvicola amphibia. 
Sedgwickii. Castor fiber. 

—— Ardeus. Trogontherium Cuvieri. 


400 Geological Society :— 


Of these 19 species inhabiting Britain before the deposition of the 
Boulder-clay, 13 survived into Postglacial times*. 

Passing from Postglacial to Prehistoric time, the Sheep, Goat, Bos 
longifrons, and Dog make their appearance, while the great Pachy- 
dermata, the Cave Mammals, and nearly all the northern forms dis- 
appear. The characteristic postglacial mommals were defined by 
the author to be 


Paleolithic man. Ovibos moschata. 

Gulo luscus, Rhinoceros tichorhinus. 

Ursus speleus ? Elephas primigenius. 
ferox, Lemmus. 

Felis leo. Spermophilus citillus, 
pardus. erythrogenoides. 

Hyena spelea. 


The author finally discussed the question of the age of the Lower 
Brick-earths of the Thames valley and Clacton, and indicated the 
difficulty of proving, from Paleontological evidence, whether they 
are pre- or postglacial. He supposed that durihg the glacial sub- 
mergence, the valley of the Lower Thames roughly marked the 
coast-line of the icy sea, with a climate too cold to allow the con- 
tinued residence of the Preglacial mammals, but which might still 
occasionally be visited by their surviving descendants, the remains 
of which would thus be mingled with those of Arctic immigrants. 


March 10th, 1869.—Prof. T. H. Huxley, LL.D., F.R.S., 
President, in the Chair. 

The folowing communications were read :— 

1. “On the Origin of the Northampton Sand.” By John W. 
Judd, Hsq., F.G.S., of the Geological Survey of England. 

This paper was an attempt to base on the study of a rock, both 
in the field and the laboratory, a complete and consistent theory of 
the conditions of its original deposition, and of the sequence and 
causes of its varlous metamorphoses. 

The Northampton Sand was described as consisting of various 
strata, usually of an arenaceous character, which frequently pass, 
both vertically and horizontally, into a ferruginous rock, the well- 
known Northamptonshire ore. 

The different features presented by the formation in various 
localities were then indicated; and the lithological, microscopical, 
and chemical characters of its constituent rocks described at length. 

These characters were shown to point to the conclusion that the 
beds were accumulated in a delta of one or more great rivers. 

Arguments were then adduced in opposition to the theory of the 
formation of ironstones by direct deposition, and in favour of the 
hypothesis that the Northamptonshire ore consisted of beds of sand 
altered by the percolation through them of water containing carbo- 
nate of iron. 

The cause of the redistribution of the iron in the rock was then 
discussed ; and, in opposition to the views of Mr. Maw, who has 


* The names of these are printed in italic. 


Prof. Coquand on the Cretaceous Strataof England and France. 401 


referred the phenomena in question to “ segregation,” they were all 
shown to be easily capable of explanation on well-known chemical 
principles, and to be due to the action of atmospheric water finding 
access to the rock by its joints and fissures. 

The paper concluded with a sketch of what was inferred to be the 
history of the rock from its accumulation to the present time, and 
some remarks on the varied and important effects of water when 
acting under different conditions on rocks. 


2. “On the Occurrence of Remains of Pterygotus and EHurypterus 
in the Upper Silurian Rocks in Herefordshire.” By the Rev. P. B. 
Brodie, M.A., F.G.S. 

In this paper the author described the occurrence of numerous 
specimens of Crustacea, chiefly belonging to the genera Huwrypterus 
and Pterygotus, in beds of Upper Silurian age, probably the “ passage 
beds,” in the Woolhope district and near Ludlow. 


March 24th, 1869.—Sir Philip de M. Grey Egerton, Bart., M.P., 
F.R.S., in the Chair. 


The following communications were read :— 

1. “ On the Cretaceous Strata of England and the North of France, 
compared with those of the West, South-west, and South of France, 
and the North of Africa.” By Professor Henri Coquand, of Mar- 
seilles. 

In this paper the author indicated that the agreement between the 
Cretaceous strata of England and the North of France, as far as the 
Basin of Paris, is such that the same classification may be applied to 
the whole, but that in advancing to the west and south new beds 
make their appearance. This is also the case in Algeria, the pale- 
ontological differences between the Cretaceous rocks of that country 
and those of the Anglo-Parisian basin being so great as to lead at 
first sight to the impression that they belong to two different 
formations. The author arrived at the following classification and 
nomenclature of the divisions of the Cretaceous rocks, the paleonto- 
logical characters and geographical range of which were described 
in the paper :— 


I. Upper CRETACEOUS. 


A. Red Lancustrine Sandstone of Vitrolles (=Garumnien of Leymerie). 
B. Dordonien. 
C. Campanien (= Upper Chalk). 
D. Santonien (=Superior Lower Chalk). 
E. Coniacien (Sandstone). 
IT. Mipprz Cretaceots. 
F. Provencien. 
G. Mornasien. 
H. Angoumien. 
I. Ligérian (=Inferior Lower Chalk). 
J. Carentonien. 
K. Gardonien. 
L. Rothomagien (=Upper Greensand and Chalk-marl). 


M. Gault. 


402 Geological Society. 


III. Lower Creracrovs. 
N. Aptien. 
1, Upper. 
2. Middle 
3. Lower 
O. Neocomien. 
P. Valengien. | 

2. “On the Structure and Affinities of Sigillavia and allied 
genera.” By W. Carruthers, Esq., F.L.S., F.G.8. 

The author indicated the characters of the medullary rays of dico- 
tylcdonous stems, and stated that these stems have a vascular hori- 
zontal system connected with the axial organs, in which respect the 
dicotyledonous and acrogenous stems agree. ‘The woody columns of 
Stigmaria and Sigillaria are destitute of medullary rays, the struc- 
tures previously described as such being the vascular bundles run- 
ning to the rootlets and leaves. Hence the author concluded that 
Sigillaria is a true cryptogam—a position supported by the charac- 
ters of the organs of reproduction as described by Goldenberg. The 
paper concluded with an enumeration of the forms of fruits belong- 
ing to Stgillaria and its allied-genera, with indications of the exist- 
ing forms to which they most nearly approach. 


3. “On the British Species of the Genera Climacograpsus, Diplo- 
grapsus, Dicranograpsus, and Didymograpsus.” By H, Alleyne Nichol- 
son, D.Sc., M.B., F.G.S. 

The author stated that all the genera referred to in this paper 
appear to be exclusively of Lower Silurian age,—Clhmacograpsus and 
Diplograpsus occurring almost throughout the Lower Silurian;series, 
whilst the other two genera belong chiefly to the Llandeilo series of 
rocks, or to strata of corresponding position out of Britain. 

The British species of the above genera admitted by the author 
are :— 

Climacograpsus teretiusculus (His.). Diplograpsus tamariscus, Nich. 


bicornis (Hall). putillus (Hai/). 
tuberculatus, Nich., sp. n. nodosus, Harkn. 


} = Lower Greensand. 


Diplograpsus pristis (/Zs.). —— pinnatus, Harkn. 

— mucronatus (Hall). , Sp. 

— Whitfieldii (Hall). Dicranograpsus ramosus (Hail). 
Harknessii, Nich. D'dymograpsus Murchisoni (Bech). 


affinis, Vich., sp. n. 
—— cometa, Gein. divaricatus (Hall). 
palmeus, Barr. anceps, Vick. 
—— acuminatus, Nich. —— flaccidus (Hal?). 
vesiculosus, Nich. — sextans (Hall). 
—— pristiniformis (Hall). 
The paper included descriptions of the supposed embryonic states 
of several of the species. 


April 14th, 1869.—Prof. Huxley, LL.D., F.R.S., President, 
in the Chair. 
The following communication, were read :— 
1. “On the Coal-mines at Kaianoma, in the Island of Yezo.” By 
F. O. Adams, Esq., Hon. Secretary of Legation in Japan. 
The writer states that the works at Kaianoma have made con- 


confertus, Nich. 


Intelligence and Miscellaneous Articles. 403 


siderable progress since they were reported upon by Mr. Mitford 
last year*. There are four seams of coal, each about 7 feet thick, 
from 50 to 100 feet apart. A tunnel has been driven through one 
of the seams for a distance of between 150 and 250 feet, and at an 
elevation of 430 feet above the sea. From this the coal obtained is 
carried down to the shore on the backs of men, mules, and ponies. 
The writer adds that there is abundance of coal “of the canrel 
description.” 


2. “On a peculiarity of the Brendon-Hills Spathose Ore-veins.” 
By M. Morgans, Esq. 

The author described the Brendon Hills as consisting of a Devo- 
nian slate dipping 8. by HE. and N. by W. on the two sides of the 
axis of elevation. The cleavage-lamine dip 8. by W. at an angle 
of 80°; and the cleavage-strike forms only a slight angle with that 
of the beds, which, however, is sometimes irregular. Veins of 
spathose iron-ore, very rich in manganese, occur in the slate; and 
the ~eneral dip of these appears to coincide with that of the cleavage- 
planes. The veins consist of thin “tracks” of softened clay-slate 
and quartz, with larger or smaller pockets of productive ore. These 
metalliferous portions do not descend parallel to the line of their 
dip, but slope more or less, usually to the west. The author stated 
that the veins have been segregated from the adjoming clay-slate, 
the unproductive portions of them occurring where the conterminous 
strata were not impregnated with sufficient ferruginous matter to 
produce a lode of iron-ore ; the slope of each productive part, called 
“‘end-slant” by the author, is determined by the line of inter- 
section of the plane of the vein with the boundaries of the ferru- 
ginous portions of the beds. 


XLVI. Intelligence and Miscellaneous Articles. 


ON THE EMISSION AND ABSORPTION OF HEAT RADIATED AT Low | 
TEMPERATURES. BY G. MAGNUS. 


ie IFFERENT substances, when heated to 150° C., emit dif- 
ferent kinds of heat. 

9. There are bodies which emit only one kind of heat, and others 
which emit several. 

3. To the first class belongs rock-salt when it is quite pure. Just 
as the ignited vapour of this substance, or of one of its constituents 
(sodium), only emits one colour, so, too, it only radiates one kind of 
heat. It is monothermal,as its vapour is monochromatic. 

4, Rock-salt absorbs the heat radiated by rock-salt in larger quan- 
tity, and more energetically, than that of sylvine (chloride of potas- 
sium) and other kinds of heat. Hence, contrary to what Melloni 


* See Quart. Journ. Geol. Soc. vol. xxiv. p. 511. 


404 Intelligence and Miscellaneous Articles. 


and Knoblauch allege, it does not transmit all kinds of heat equally 
well. 

5. Absorption by rock-salt increases with the thickness of the ab- 
sorbing plate. 

6. The great diathermancy of rock-salt does not depend upon a 
small absorbing-power for different kinds of heat, but upon the cir- 
cumstance that it only emits one kind of heat and only absorbs 
this one, and that almost all other bodies at a temperature of 150° C, 
emit heat which only contains a small portion, or none at all, of the 
rays which rock-salt emits. 

7. Sylvine behaves like rock-salt, but is not monothermal to the 
same extent. In this case also we have an analogy with its ignited 
vapours or those of potassium, which is known to give an almost con- 
tinuous spectrum. 

8. Fluor-spar absorbs the pure heat from rock-salt almost com- 
pletely. It would thence be expected that the heat which it emits is 
also strongly absorbed by rock-salt ; yet 70 per cent. passes through 
a rock-salt plate 20 millims. thick. ‘Taking into consideration the 
sum of the heat which fluor-spar emits, which is more than thrice as 
much as that of rock-salt, this phenomenon might be explained; but 
it needs further investigation. 

9. If it were possible to construct a spectrum of the heat radiated 
at 150° C., and if rock-salt were the substance, the spectrum would 
contain only ove band. If sylvine were used for radiation the spec- 
trum would be more extended, but would only occupy a small por- 
tion of that which would result from the heat radiated by lampblack. 
— Berliner Monatsbericht, June 1869. 


ON THE LIMITS OF THE MAGNETIZATION OF TRON AND STEEL. 
BY PROF. A. WALTENHOFEN. 

The author has subjected to exhaustive calculations the whole of 
the present materials of observation on the connexion between elec- 
tromagnetism and current-intensity, and has thus arrived at the fol- 
lowing result. 

The limiting value of the magnetic momentum of the unit of weight 
corresponding to the condition of magnetic saturation of iron is an 
absolute constant (that is, independent of the shape and magnitude 
of the electromagnet) whose numerical value amounts to very nearly 
2100 absolute units per milligramme. 

{t follows from this that the theoretically possible temporary 
magnetization of iron is more than five times as much as the perma- 
nent which has been attained by the best steel magnets, if, with M. 
Weber, we take the latter as 400 absolute units per milligramme. 

The author considers it remarkable that just this degree of satu- 
ration is also that required by the law which he discovered in 1863, 
in reference to the temporary magnetization of steel bars by means 
of the electrical current ; while, in the case of iron, Lenz and Jacobi's 
law of proportionality, as the author shows, only holds up to a degree 
of saturation of (on the average) 800 absolute units per milligramm 


Intelligence and Miscellaneous Articles. 405 


The author regards the absolute limiting value of the magnetic 
momentum of the unit of length as a physical constant characteristic 
of iron, and comparable with the constants of elasticity, solidity, 
&e.; and he holds that its existence is quite in accord with the 
theory of rotatory molecular magnets, of the probability of which he 
thinks a striking proof has been afforded by his discovery of abnormal 
magnetization and the phenomena connected therewith. 

The author finally points out that the result of his calculation, 
contained in the above law, also justifies the conclusion that the pro- 
portionality indicated by Muller between the coefficient B of his 
formula and the length of the bar, but considered inaccurate and 
imperfectly established, must have general validity. At the same 
time the circumstances are mentioned to which it must be ascribed 
that both Muller and the author were led to doubt, from existing 
data, the applicability and universality of this formula. 

The author refers to a research by Oberbeck which has recently 
appeared, of which he only heard after his investigation was finished : 
in it the question of the existence of an independent limiting value of 
the magnetic momentum of the unit of valumeis discussed. But the 
author remarks that this research involves no change or completion 
of the results above adduced; for the amount of the limiting value is 
neither ascertained nor adduced, and the results of the experiments 
show too irregular a course to permit a numerical deduction of such 
a limiting value, although the existence of such a one seems to follow 
from two of the series of them.—Sitzungsberichte der Kaiserlichen 
Akademie in Wien, 1869, No .12. 


—— 


ON THE REFLECTION OF HEAT FROM THE SURFACE OF FLUOR- 
SPAR AND OTHER BODIES. BY G. MAGNUS. 


After succeeding in freeing the heat from various substances 
raised to 150° C. from the rays of the heating-flame and of other 
heating-bodies, it was possible to show, in the research laid 
before the Academy on June 9, that there are some bodies which 
only radiate one or at most a few wave-lengths, others which emit a 
greater number. Hence it seemed interesting to answer the question, 
what is the reflecting-power of these bodies? whether tke same dif- 
ferences which are observed in reference to the absorption and trans- 
mission of heat by bodies that are identical as regards the action of 
light also occur in the reflection of heat. 

Differences in reflecting-power can only definitely occur when 
rays are reflected which only contain one or a few wave-lengths. 
Such rays have been already obtained by using individual parts of 
a spectrum produced by a rock-salt prism, or by allowing the rays 
of a source of heat which radiates many wave-lengths (those of a 
lamp for instance) to pass through substances which only absorb a 
certain number. But there are very few substances which transmit 
rays of only one or of a few wayve-lengths ; and these are, moreover, 
of small intensity. 


4.06 Intelligence and Miscellaneous Articles. 


In spite of this difficulty, MM. La Provostaye and Desains showed 
in 1849* that, according as heat from a Locatelli’s lamp has passed 
through glass or through rock-salt, various quantities are reflected by 
speculum-metal, silver, and platinum; and in the case of all re- 
flecting surfaces, less was reflected of that which had passed through 
glass than of that through rock-salt. 

The same inquirers have subsequently published a comprehensive 
series of experiments made with the heat of a lamp decomposed by 
means of a glass prism, in which it was shown that heat from the 
different parts of the spectrum is variously reflected. But they 
restricted their experiments to reflection from metallic surfaces, 
doubtless on account of the feeble intensity of the incident heat. Now 
that we possess in rock-salt a substance which only emits one or a 
few wave-lengths, and we also know other bodies which at the tem- 
perature of 150° C. radiate a limited number of wave-lengths, it is 
possible to make experiments on the reflection of non-metallic sur- 
faces. It has thus been found that from these the different kinds of 
heat or wave-lengths are reflected in very different quantity. Only 
one of the most surprising examples shall be here mentioned. It 
refers to the reflecting-power of fluor-spar. 

Of heat which very different substances radiate, there are reflected 
at an angle of 45° quantities which are indeed not equal, but which 
do not differ much from each other. 


Silver, between .... 83 and 90 per cent. 
Glass hs G1 Ae a 
Rock-salt i... pais a vt 
Fluor-spar_,, (opis esate) 


Of the heat from rock-salt, fluor-spar reflects 28 to 30 per cent., 
while silver, glass, and rock-salt do not reflect larger proportions of 
this than of the other kinds of heat. 

Here, as in the experiments on the transmission of heat, it has 
been confirmed that sylvine emits a large quantity of rock-salt heat, 
but at the same time emits other kinds of heat. And fluor-spar 
reflects 15-17 per cent. of sylvine-heat, consequently less than 
it reflects of rock-salt heat, and more than it does of that from the 
other radiating bodies. 

If our eyes had the power of distinguishing the various wave-lengths 
of heat as well as the colours of light, fluor-spar would appear brighter 
than all other substances when the rays of rock-salt fell upon them. 
If the rays came from sylvine, fluor-spar would also appear brighter 
than all other bodies, but not so bright as with the radiation from 
rock-salt. 

Melloni has taught us that various substances transmit very dif- 
ferent quantities of heat, and that the source from which it origimates 
has great influence on its transmission. But the sources of heat 
were only distinguished as to their degree of heat, and we knew that 
with increasing temperature the diversity of the radiation increased. 


* Comptes Rendus, vol. xxvil. p. 501. 


Intelligence and Miscellaneous Articles. 407 


It has now been found thateven at one and the same temperature, and 
that a temperature (150° C.) which is very far from a red heat, dif- 
ferent substances emit very different kinds of heat, and that thus, in 
any space whatever, an extraordinarily large number of different wave- 
lengths are continually crossing each other. This manifold crossing 
is especially increased by the selective absorption which is met with 
at different surfaces. 

Hence an eye which could discriminate the various wave-lengths 
of heat like the colours of light, would see all objects in the most 
different colours, evenif they were not specially warmed.—Poggen- 
dorff’s Annalen, September 1869. 


ON THE LUMINOUS EFFECTS PRODUCED BY ELECTROSTATIC IN- 
DUCTION IN RAREFIED GASES.—LEYDEN JAR WITH GASEOUS 
COATINGS. NOTE BY M. F. P. LE ROUX. 


I, In a previous communication I described a certain number of 
experiments which render evident the induction that takes place in 
the body of rarefied gases, in vessels formed of a continuous insula- 
ting material, and devoid of all metallic communication with the ex- 
terior. ‘These effects are manifested by true currents which illumi- 
nate the gaseous masses in the body of which they are propagated. 

The facts here treated of have interesting consequences in the way 
of explaining certain meteorological phenomena. ‘They must play 
an important part in the luminous manifestations of the electricity of 
the globe to which is given the name of polar auroras; and the dif- 
fused part of the glows which constitute them, it seems to me, should 
be attributed to an electrostatical induction seated in the higher 
strata of the atmosphere, under the influence of the discharges of the 
aurora. 

This same induction, operating in the rarefied strata of the atmo- 
sphere, seems to me to furnish the explanation of a remarkable cir- 
cumstance which often accompanies the lustre of the lightning-dis- 
charge. When the lightning strikes, it produces an illumination 
which surrounds the perfectly serene regions of the sky, when there 
are any; the circumstances of this phenomenon do not appear to 
me to be capable of explanation by a phosphorescence of the atmo- 
sphere properly so called. Itseems to me that we must rather per- 
ceive in it the manifestation of the return shock which must take 
place in the higher regions of the atmosphere at the moment when, 
through the effect of the discharge which constitutes the lightning, 
the clouds revert to their neutral condition. 

As to the heat-lightning, so called, which is observed in a clear 
sky at a certain height above the horizon, there is no doubt that 
itis due to the same cause. 

II. The electrostatical induction of rarefied gaseous masses ap- 
pears to operate instantaneously across insulating envelopes; at 
least this is what seems to me to result from the working of the 
apparatus that I have constructed, in which the illumination is pro- 


408 Intelligence and Miscellaneous Articles. 


duced under the influence of a toothed disk of india-rubber previ- 
ously electrified. We remark, in short, that the flash of the illumi- 
nation increases with the velocity of the disk. This circumstance 
is but little favourable to the hypothesis according to which the in- 
fluence would be exercised across dielectrics by a polarization of 
successive layers ; it would be necessary in that case that the polar- 
ization should be instantaneous, and we cannot see in what the 
difference between insulating bodies and conductors would consist. 

III. Tubes filled with rarefied gases and provided with metallic 
wires sealed at the ends like Geissler’s tubes, but terminated ex- 
ternally by knobs to prevent the wires from acting like points, may 
be applied with advantage to demonstrate the movements of electricity 
to which the influence gives rise, especially those of the return shock. 
I have executed these experiments; but the credit of them is due to 
M. G. Govi, of Turin, who has very ingeniously employed this means 
of demonstration in the place of metallic conductors armed with 
pendulums, of the electroscopic frog, and of the other contrivances 
usually employed in this part of the study of electricity *. These 
luminous conductors have also been made use of by him to exhibit 
the phenomena of induction of different orders by interposing them 
in long metallic circuits. 

IV. In the course of the experiments which I have had occasion 
to make with rarefied gases, [ have remarked that the glass was 
charged by the intervention of gaseous conductors with the same 
facility as by means of metallic conductors. I have thus been led 
to construct a Leyden jar in which the metallic coatings are replaced 
by rarefied gas: itis composed of a closed primary tube enveloped by 
a second, to which it is fused; each of the tubes is provided with a 
platinum wire ; a vacuum is created in them to the extent of about 3 
millims. Such a system is charged with a Leyden jar of the same 
dimensions ; the residues init seem to be less abundant than in ordi- 
nary jars; but this question, in order to be fully solved, requires 
more numerous experiments. 

In fine, rarefied gases behave precisely as metallic conductors. It 
is to be remarked that such a medium formed into a point acts just 
like a metal of the same shape, and manifests the same effects of 
tension, to such an extent that, in the glass vessels intended to con- 
tain gases with a view to the experiments here treated of, it is neces- 
sary to avoid all such tapering of the tubes as would give to the 
interior surface the form of an acute point. If this circumstance 
does happen, and the interior gas is strongly electrified, we often see 
the electricity strike out for itself a passage through the glass at that 
place; and if the glass be too thick, the electricity, in place of 
opening a direct path for itself, cracks off the little button of melted 
glass which generally terminates the tapering ends closed by the 
blowpipe.—Comptes Rendus, May 31, 1869. 


* Gazette officielledu Royaume d’Italie, No. 49, 1865. 


NOV. 13, 1438 


THE 


LONDON, EDINBURGH, ann DUBLIN 


PHILOSOPHICAL MAGAZINE 


AND 


JOURNAL OF SCIENCE. 


[FOURTH SERIES.] 


DECEMBER 1869. 


XLVII. On the Motions of Camphor on the Surface of Water. 
By Cuartes Tomurnson, F.R.S.* 


Is Wop phenomena presented by the motions of camphor on 

water form a kind of scientific waif, which has at va- 
rious times been claimed by certain scientific lords of the manor, 
quarrelled over, and then thrown aside. At one time it has 
wandered over the outer boundaries of science, occupying a sort 
of no-man’s-land; at another it has been admitted into the best 
society, which latter position it may be said to occupy at the 
present time. 

2. During the current year a remarkable memoir! has been 
couronné by the Royal Academy of Sciences of Belgium, and 
favourably reported on to the Academy” by that distinguished 
Belgian physicist M. Plateau. As the author has done me the 
honour of frequently referring to my labours, and was so 
good as to forward to me a copy of his memoir, I trust an 
account of it will not be considered out of place in the Philoso- 
phical Magazine. 

3. But first it may be of advantage to give an account of the 
phenomena in question as briefly as is consistent with clearness. 
Some years ago I took considerable pains to read up all that had 


* Communicated by the Author. 

1 Sur la Tension superficielle des Liquides considérée au point de vue de 
certains mouvements observés a leur surface, par G. Van der Mensbrugghe, 
Répétiteur a l Université de Gand. | 

2 Bull. de V Acad. Roy. des Sciences de Belgique, 10th July, 1869. 
Phil. Mag. 8. 4. Vol. 88. No. 257. Dec. 1869. 2 i 


410 Mr. C. Tomlinson on the Motions of Camphor 


been published on the subject ; and it is chiefly from the account 
then given? that the following details are condensed. 

4. In 1686 Dr. Heyde* noticed that when fragments of cam- 
phor placed on olive-oil are viewed under the microscope certain 
currents are observed, particles setting out, as it were, from a 
centre and returning to the same point. 

5. In 1748 Romieu* first described the rapid. gyrations of 
camphor on the surface of water: the motions are favoured by 
heat, and their cause is referred to electricity. 

6. In 1773 Dr. Franklin®, in his account of the effects of oil 
in stillmg the waves, states that being about to show the expe- 
riment to Smeaton the engineer, on a small pond near his house, 
he was informed by Mr. Jessop, a pupil of Smeaton’s, that in 
cleaning an oily cup in which some flies had been drowned, he 
threw the flies upon water, when they began to spin round very 
rapidly as if they were vigorously alive. ‘To show that this 
was not any effect of life renewed by the flies,” says Franklin, 
““T imitated it by little bits of oiled chips and paper cut in the 
form of a comma of the size of a common fly, when the stream 
of repelling particles issuing from the point made the comma 
turn round the contrary way.” 

7. In 1785 Lichtenberg’ notices that the camphor experiment 
succeeds best on warm water, or when the roomis not very cold. . 
On plunging a thermometer into water at 130° the motions sud- 
denly ceased, in consequence of some alteration in the surface ; 
or, as he says, the thermometer may not have been quite clean, 
so that the water became covered with a thin film. He refers 
the motions of the camphor to the varying attractions consequent 
on the constant change in form of the fragments brought about 
by solution and evaporation. He disproves the electrical theory 
of Romieu (5). 

8. In 1787 Volta® examined the experiment with great care. 
He refers the motions to an effluvium which escapes from the 
camphor explosively after the manner of a firework, and pro- 
duces motion by the force of reaction. Similar motions are pro- 
duced by benzoic acid, salt of amber (succinic acid), and volatile 
concrete alkali (carbonate of ammonia). Salt of amber is parti- 
cularly recommended, as it makes manifest to the eye the cause 
of the motions; for the fragment is evidently driven back from 

* Experimental Essays, published in Weale’s series, 1863. Essay I. On 
the Motions of Camphor on Water. 

4 Centuria Observationum Medicarum. Amsterdam, 1686. Obs. LYVII. 

° Hist. de V Acad. Roy. des Sciences de Paris, 1762. 

® Letter to Dr. Brownrigg, November 7, 1773. Posthumous Writings 
of Dr. B. Franklin,:F.R.S. &c. London, 1819. Part IV. p. 268. 


7 Delectus Opusculorum Medicorum, edited by Frank. Ticini, 1787. 
© Tbid: 


on the Surface of Water. 411 


the point where the effluvium is discharged most abundantly, 
covering the water and suffusing it with colour. It is further 
shown that when the water becomes impregnated with the cam- 
phor &c. the motions cease, that warm water and fine weather 
are favourable to the phenomena, that the purity of the water 
and of the containing vessel are necessary to success (indeed the 
success or failure of the experiment is a sort of indication of the 
purity of the water), that agitation of the water assists the expe- 
riment, and, lastly, that the gyrations take place on wine but 
not on spirits of wine, and not very well cn olive-oil. 

9. About the year 1794 Carradori? began to publish a number 
of papers and memoirs, sull’ attrazione di superficie, in which he 
shows, by a great variety: of ingenious experiments, that the 
surface of water exerts a remarkable attractive force on various 
bodies ; and in 1800, referring to the motions of camphor, he 
says!°, “I prove that on this surface-attraction, and on no other 
cause, the motions of camphor depend.” And again, “ The me- 
chanical force of the elastic vapour against the water has nothing 
to do with the phenomenon; it depends entirely on surface- 
attraction ;” and in order to show that a non-volatile body will 
rotate, he repeats Franklin’s experiment (6) on the gyration 
of bits of paper smeared with a fixed oil and thrown on the sur- 
face of water. 

10. Several of Carradori’s papers are in answer to the theory 
of B. Prevost!', which attributes the motion of camphor and 
other volatile bodies to the formation of an atmosphere of elastic 
fluid round them, and to the impact of such fluid on the air. 
According to Prevost, a fragment of camphor of the size of a pea 
on a metallic disk four or five lines in diameter, and so placed 
on water, rotates. 

11. Fourcroy”, in reporting Prevosi’s paper, expressed his own 
opinion that these motions are due to the attraction of odorous 
matter both for air and for water, and their solution in one or both. 

12. In 1797 Venturi!®? showed that a column of camphor 
fixed vertically in water wastes away chiefly at the junction of 
the air and the water. The oily matter of the camphor covers 
the surface and evaporates; and this explaims the motion of 
camphor when free to move. This motion is the mechanical 
reaction which the oily substance, in spreading on the water, 
exerts on the camphor itself. 


9 Opus. scelti di Milano, vol. xx. Giornale Fisico di Brugnatell, vol. 
vil. &e. 
© Giornale di Fisica &c. Pavia, vol. i. p.97. See also vo's. iii., iv., 
Vill., 1X., and x. 
% Annales de Chimie, vol. xxi. p. 254; vol. xxiv. p. 31. 
eon 13 bid. vol'xxi, p..262, 
2H 2 


412 Mr. C. Tomlinson on the Motions of Camphor 


13. In 1800 Carradori!* approves of this explanation and 
claims it as his own. The camphor owes its motion to the ex- 
pansion of an oil drawn from it by the surface-attraction of the 
water. He combat’s Prevost’s theory (10), and denies that the 
camphor on a bit of cork or other substance floating on water 
has any motion. He insists on the energetic surface-attraction of 
water. Oils, whether fixed or volatile, have a strong adhesion 
or surface-attraction for water, but no cohesion or affinity of 
ageregation forit. White wax and hard suet, which have no odour 
and contain an oil that is not volatile, rotate on water. Oils, 
whether fixed or volatile, are more strongly attracted by the sur- 
face of the water than camphor 1s, and hence they arrest its mo- 
tion. And not only so, but star ch and other vegetable products 
and the juice of milky plants arrest the motions on account of 
the strong surface-attraction. Many odorous bodies that do not 
give out an oil to the surface of water have no motion. 

14. In 1801 Prevost!® denies Carradori’s position (13), and 
further supports his own case by stating that minute fragments 
of camphor, benzoic acid, and dry musk rotate on clean dry mer- 
cury, and indeed on any clean dry surface. He has seen under 
the microscope minute fragments of camphor, too small for the 
unassisted eye, rotate on various kinds of support. Camphor 
will even rotate on small disks of mica placed on mercury. 

15. In 1801 Biot!® confirms some of Prevost’s leading re- 
sults, and gives the following experiment in support of his 
theory :—If a very small pointed cone of camphor be presented 
without contact to a thin film of water on a clean glass plate, it 
will repel the water and ieave a dry space round it. Hence he 
concludes that camphor acts on water at a distance, and that its 
movements on water are due to the mechanical reaction produced 
on itself by the resistance which its vapour experiences in dart- 
ing against the liquor which surrounds it, and that this emis- 
sion of vapour is most abundant in the horizontal plane where 
the air and the water meet. The camphor-cone will also repel 
fragments of gold leaf floating in water without touching it or 
ther! 

16. In 1808 Carradori!” replied to precaee It is curious to 
note the common feature of this and other scientific controversies, 
that one man cannot follow the reasoning or even repeat the ex- 
periments of his antagonist, so difficult does observation become 
when another man’s results are looked at through the spectacles 
of one’s own theory. ‘Thus Carradori denies that a capsule of 


4 Annales de Chimie, vol. xxxvii. p. 38. 15 Thid. vole pee. 
6 Bulletin des Sciences par la Société Philomatique, No. 54, p. 42. 
" Annales de Chimie, vol. xlviii. p. 197. 


on the Surface of Water. 413 


ether suspended over water containing bits of gold leaf repels 
them by its vapour acting at a distance. He denies that cam- 
phor on a raft floating on water rotates; while Prevost, on his 
part, knows nothing “of surface-attraction, or of the oil that is 
said to issue from camphor in contact with water, and which is 
said to produce rotation by its reaction on the fragment. He 
has looked in vain for such oil, and believes it exists only in the 
imagination of the Italian physicist. Carradori replies, “ What 
wonder is it that camphor should cover the water with an oily 
film, since camphor is itself a very volatile concrete oil?” He 
insists on surface-attraction, and cites this ingenious experl- 
ment :—A bottle 2 inches in diameter with a neck only 3 lines 
im diameter was filled with water; fragments of camphor thrown 
into the narrow neck did not rotate for want ofa sufficient expanse 
of surface-attraction. Hnough water was drawn out by means 
of a straw so as to lower the surface to the wide part of the bottle, 

when the camphor rotated briskly on the larger surface. Here, 

again, the two observers are at variance; lon Prevost, in nis 
former paper (14), says that camphor will move in capillary tubes 
previously cleaned by drawing threads through them, and that 
lively motions may be seen in them with the aid of a magnifying- 
glass. 

17. In 1812 we meet with Carradori again!®. He describes 
some experiments, based on an observation by Accum, that phos- 
phorus rotates on the surface of mercury. He gives this as a 
further illustration of the attraction of surface, the phosphorus 
covering the mercury with a subtle varnish ‘which gradually 
arrests the motion; but it may be renewed by filtering the mer- 
cury. Phosphorus was also found to rotate on the surface of 
tepid water. 

18. In 1820 Serullas!9 describes the motions of alloys of po- 
tassium, sodium, &c. ona shallow surface of water 1 or 2 lines 
deep resting on mercury. Small fragments of the alloy of po- 
tassium and antimony rotated, disengaging hydrogen, especially 
from one point: each fragment described a circular path in the 
opposite direction to the point of greatest liberation of the gas. 
An alloy of potassium and bismuth rotates on the surface of 
mercury. An alloy of potassium with lead or tin does the same ; 
but if water be added the motions are morerapid. The smaller 
the fragments the more rapid the motions: ‘on les voit voltiger 
avec une étonnante vivacité: on dirait des mouchons retenus 
dans les piéges, faisant des efforts pour s’en délivrer’*®. Alloys 


8 Giornale di Fisica &c. di Bignell vol. il. pp. 261, 373; vol. iv. 
297: 
es , Journal de Physique, vol. xci. p. 172. 
° Prevost also says of the motions of camphor on mercury, “ on ett dit 
les y voir voltiger,” for they scarcely touched the mercury. 


414 Mr. C. Tomlinson on the Motions of Camphor 


of sodium with most of the metals also rotate on mercury, or on 
a thin plate of water on mercury. 

19. In 1825 the brothers Weber®!, in noticing Franklin’s ex- 
periment (6), reiterate the fact that a downy feather smeared 
with oil rotates on water, and express their opinion that the mo- 
tions of camphor and of various other bodies on water still remain 
to be accounted for by a satisfactory theory. 

20. In 1833 Matteucci? states that raspings of cork steeped 
in ether rotate on the surface of water, and continue to do so as 
long as the surface is supplied with ether, as by conducting a 
thread from the ether bottle to the surface. His conclusion 
is that it is to the currents of volatile substances that the mo- 
tions are due. 

21. In. 1841 Dutrochet®? described the following experi- 
ment :—If cork be steeped in a solution of caustic alkali and 
dried and then be placed on water, the solution is projected 
strongly from the cork, and this moves in the opposite direction. 
“This motion of the cork is evidently the effect of recoil produced 
by the repulsion which the solid alkali contained in the cork exerts 
on its own solution. It is very probable that this repulsion is elec- 
trical, and arises from the fact that the solid body dissolved has a 
Grniler electricity to that of the solution. However this may be, 
the fact of the reciprocal repulsion of the soluble body and of the 
aqueous solution is certain, and it is to this repulsion that we 
may attribute the motion that takes place at the surface of water 
of all floating bodies that dissolve in it. This occurs not only 
in the case of alkalies, acids, and salts, but in gum resins, such 
as opium, aloes, &c. 224. 


22. In 1841 Messrs. alg and Boisgiraud?? bring before the 


1 Wellenlehre. Leipzig, 1825. 
Ann. de Chim. et de Phys. vol. liu. p. 216. 
Comptes Rendus, vol. xu. p. 2. 

“4 This experiment is evidently. based on Prevost’s experiments (note "), 
intended to show that almost all liquids are each susceptible of repelling 
all others or of being repelled by them; that is, ifa liquid be made to cover 
a glass plate, and a drop of another liquid properly selected be placed on 
the film, the latter will be driven away and the second will occupy its place. 

Thus 


5 bb bt 
to 


nN 
wo 


Ether repels Alcohol. 

Alcohol » Essential oil of peppermint. 
Oil of peppermint ,, Oil of bergamot. 

Oil of bergamot >, Oil of origanum. 

Oilof origanum ,, Oil of savory. 

Oil of savory 5) Fixed-oils. 

So also pure water repels many solutions of salts. A solution of alum 
repels one of vitriol; this repels sodic sulphate; this potassic nitrate; this 
sodie chloride, and so on. 

*> Comptes Rendus for 1841, p. 690, which contains a Report on the 


Memoir. 
\ 


on the Surface of Water. 415 


Academy of Sciences a memoir which clashes a good deal with 
Dutrochet’s (21) ; and the noise is heard at intervals during this 
and the first half of the following year. The authors do not 
seem to have added much to the subject in hand. They found 
that thin slices of cloves, pepper, orange-peel, &c. rotated on 
water, and that naphthalin, though motionless on the surface of 
water, rotated briskly on that of mercury. The advantage of 
working with mercury is that it renders visible effects which are 
not seen on the surface of water. 

23. Although Dutrochet’s researches. (21) occupy nearly 
seventy pages of the Comptes Rendus between the 4th of January 
and the 5th of April, 1841, he felt that he had published them 
with too much precipitation, and accordingly retired for awhile 
in order to reconsider the whole subject. This led to the pub- 
lication of a separate work, in two parts®, in which not only 
the motions of camphor, but a vast number of other interesting 
facts are traced to the influence of a force residing on the surface 
of liquids, and hence named epipolic (ému7roAn,, surface). He does 
not admit, and probably did not see, that this is nothing more 
than another name for Carradori’s attraction of surface (9), (138), 
(16), (17); for he does not seem to have been master of the 
Italian language, in which Carradori’s earlier memoirs are printed, 
and that at a time when the noise of conquest would scarcely 
allow the voice of science to extend so far as from Italy to Frauce, 
unless it were unusually loud, as when Galvani and Volta spoke 
for her. In the early part of his work Dutrochet says that “ when 
a bit of camphor is placed on the surface of water, there forms 
around it a portion of camphorated water, which immediately 
becomes endowed with a rapid centrifugal extension due to the 
development of the epipolic force. The morsel of camphor, sur- 
rounded by camphorated water incessantly renewed and inces- 
santly projected circularly on the surface of the surrounding 
water by a kind of intermittent explosion, must necessarily par- 
take by reaction of the motions of the liquid which surrounds it, 
and receives from it those motions of progression which we see it 
execute on the surface of the water. Such is, in short, the cause 
of this phenomenon”?’. In the second part of his treatise he 
says :— The motion of camphor on water is an effect of reaction 
produced by heat-repelling epipolic currents, which are formed 
near the small fragment of this volatile substance, especially near 
its points or angular parts” (part u. p. 159). “ Everything 
concurs to prove that these epipolic currents, produced on water 
by a morsel of camphor placed on the surface of that liquid, are 
due to the local heat developed on such surface by the vapour of 

26 Recherches Physiques sur la Force Epipolique, part i. 1842; part i. 
March 1843. 7 Thid. part i. p. 74. 


416 Mr. C. Tomlinson on the Motions of Camphor 


the morsel of camphor, and probably also by its immediate 
contact ”*8. 

24. In 1861-62 I was led by the phenomena of cohesion- 
figures to pay some attention to the motions of camphor &c. on 
water”, It was evident that Carradori’s attraction of surface 
exerted a powerful influence on the phenomena, since a globule 
of creosote, carbolic acid, &c. on the surface would sail about and 
exhibit the most lively motions and even be torn to pieces and 
disappear in the course of some seconds, while below the surface a 
drop would remain asa globule unchanged for hours or even days. 
So also a drop of a solution of camphor in benzole &c. would move 
over the surface, darting out waving tongues and so disappearing. 
But phenomena of this kind seemed to be simple effects of ad- 
hesion of surface, tending to overcome the cohesion of the drop 
by spreading it out into the form of a film; and the various 
amounts of resistance offered by different liquids led to such dif- 
ferent resultant phenomenaas those of cohesion-figures, and the 
various motions of camphor and other bodies. But in the case 
of camphor and other solid bodies, not only was a film detached 
from its surface by the adhesion of the water, but the reaction 
of this film on the fragment seemed to be a sufficient force to 
account for its gyrations. It is true that in the case of camphor 
the film is not visible, but im many other cases this objection 
does not apply. Oil of aniseed, for example, solidified by cold, 
gyrates like camphor, only more slowly, with the advantage of 
leaving a filmy trail on the surface. A fragment of this oil on 
water, apparently performing the whole of its work under the 
eye of the observer, seemed to give irresistible proof of the truth 
of the theory, viz. that the adhesion of the water detaches a film 
from the solid, which film in the act of spreading on the surface, 
produces motion by reaction. If the film remain on the surface 
the motion ceases ; but if it be rapidly disposed of by evaporation 
and solution, the motion may continue so long as the fragment 
lasts. If proper arrangements be made, motions which admi- 
rably represent the phenomena may be kept up for days together. 
For example, if a three- or four-sided stick of camphor held in 
forceps be made to dip just below the surface of clean water pre- 
viously dusted with a very thin coating of lycopodium-powder, a 
film is detached from each side of the camphor the moment it 
touches the water; there is instant repulsion of the powder as 
by a flash ; then a momentary pause, during which the film is 
disposed of by evaporation and solution ; another film is detached 
in like manner, and the solution of camphor from each film, cor- 
responding with each side of the stick, travelling on, or rather 

a8 Recherches ep a sur la Force Epipolique, part ii. p. 160. 


29 See note ? 


on the Surface of Water. 417 


being propelled on by successive films to the curved surface of 
the glass, divides and curls round in two opposite directions, 
thus producing a pair of wheels for each face of the camphor, 
which the lycopodium renders distinetly visible. I have allowed 
this action to go on during sixty hours with no other interrup- 
tion than having to lower the stick two or three times when a 
portion had been cut off by the sawing action of the surface- 
water. 

Now this process, like a machine in motion which goes on so 
long as it 1s wound up, fails unless free course be given to the eva- 
poration of the camphor-film. The experiment cannot be con- 
ducted in a large bottle. The camphor has been made to dip 
into the water contained in a clean bottle: at first there were 
faint indications of a current; but these soon ceased. After 
many hours some of the water was poured from the bottle mto 
an open vessel ; and the moment the camphor was lowered into it, 
the currents set in with much of their accustomed vigour. The 
experiment also fails if the lycopodium dust be laid on too thickly; 
a very faint shower from a muslin bag is sufficient for the pur- 
pose. The motions are more vigorous on a bright clear day 
‘than on a dull cloudy one, more active in summer than in 
winter. 

25. That this experiment depended on the constant formation 
and evaporation of a film of camphor seemed to be evident from 
the perfect way in which it could be imitated by means of ether. 
At the end of a narrow tube a bit of sponge was tied, and the 
tube filled with ether was supported vertically about an inch 
above the surface of water previously dusted with lycopodium ; 
a very perfect, sharply cut, well-defined disk of ether is formed 
on the surface of the water by the condensation of the vapour 
pouring down from the sponge. The disk does not increase in 
diameter, but the excess of ether pours off from it and proceeds 
radially to the surface of the glass, where each branch curls round 
in two opposite directions, throwing the powder into pairs of 
wheels precisely as in the case of the camphor current (24). 

26. Another phenomenon, which I named “ camphor pulsa- 
tions,’ seemed also to illustrate the view I had taken of these 
motions. A stick of camphor with a square base is lowered so 
as to touch the bottom of a shallow glass vessel 6 or 7 inches in 
diameter, containing a little water, not more than about two 
ounces. As soon as the camphor touches the water the whole 
surface becomes agitated with rapid pulsations, at least 250 per 
minute. As the water soon becomes saturated, the pulsations 
gradually diminish to 60 or 80 per minute, and they may even 
sink down to8 or 10 per minute. 

According to my explanation, as soon as the camphor is low- 


418 Mr. C. Tomlinson on the Metions of Camphor 


ered to the bottom of the vessel, the water rises by capillary 
attraction some way up the stick and detaches a portion of 
its substance, which is then spread out as a film by suriace ad- 
hesion and disposed of by solution and evaporation. As the film 
is being detached, it repels the water from the camphor and pro- 
duces a depression of surface all round the stick; the water 
recovers itself, capillarity again comes into play, another film is 
detached, and matters proceed as before—the result being a series 
of pulsations or waves which rise up so that at length their crest 
may be one, two, or three tenths of an inch above the general 
surface of the water. The variations in height are marked by a 
series of curved grooves or ripple-lines on the sides of the cam- 
phor, which gradually exchanges its dull translucent appearance 
for a bright transparent one, showing that the water has pene- 
trated it. In the meantime an incision is made in the camphor, 
which goes on increasing as successive films are detached, until 
the stick is cut through and the submerged portion rises to the 
surface and commences a series of gyrations on its own account. 
27. As, in the case of small fragments of camphor rotating on 
the surface of water, the motions are stopped if the surface be 
touched with a fatty oil, so these pulsations are immediately 
arrested if the water be touched with a drop of any substance 
which forms a film and arrests evaporation. The point of a pin 
dipped into olive-oil and brought into contact with the water at 
once stopped the lycopodium currents (25); a second contact 
stopped the pulsations (26). So also if a body be added to the 
water that satisfies its adhesion so as to stop the solution of the 
camphor, the pulsations are arrested. Thus a drop of oil of 
camphor stops the pulsations by depriving the water of the 
power of dissolving camphor ; a drop of olive-oil stops the pul- 
sations by preventing evaporation; but a drop of oil of bitter 
almonds, which speedily evaporates, allows the pulsations to go 
on after a slight interruption. Turpentine and bodies that 
leave a permanent film stop the pulsations; but ether, alcohol, 
benzole, bisulphide of carbon, caustic potash, and sal-ammoniac 
allow them to go on. A bit of sponge tied to the end of a glass 
rod, dipped into ether and held near the camphor, will hold up 
the wave of water against the camphor for some time. A drop 
of benzole does not stop the pulsations; but it makes them less 
rapid. The pulsations go on in a solution of caustic potash and 
in one of sal-ammoniac. The pulsations and rotations of camphor 
are not arrested by the addition of acids to the water, including 
butyric acid. _Camphor even rotates on the surface of acetic acid. 
28. In 1863 I obtained a result®° which seemed to place the es- 
sential oils in a new light with respect to the surface of water. It 


30 Phil. Mag. September 1863. 


on the Surface of Water. 419 


was shown in my original essay that. essential oils did not per- 
manently arrest the motions of camphor, but only so long as they 
remained in the form of films on its surface. When these had 
evaporated without leaving any residue or oxidized deposit, the 
motions set in as before. But I now found that if the oils were 
freed from oxidized products by being distilled in contact with a 
bit of sodium or caustic potash, they did not arrest the motions 
of the camphor at all. The fragments skated through them and 
cut them up in all directions. “The oils had so far ‘improved in 
cohesive force that they no longer formed films, but lenticular 
masses with rounded edges. From ten to twenty drops of an 
oil might thus be deposited on the water without interfering in 
any way with the gyrations. Fragments of benzoic acid, ob- 
tained by exposing oil of bitter almonds, or of Laurus cerasi, to 
the air for some time, were singularly active below, in, and 
among the oil. This showed that there was little or no adhe- 
sion of the oils to the surface of the water; so that the frag- 
ments were as free to move as if the oil were not present. 

29. It was not until after reading Professor Van der Mens- 
brugghe’s memoir (note ') that I attempted to repeat the expe- 
riment of camphor on a raft on the surface of water (10). It 
was evident to me that if this were a true result, it would be 
fatal to the reaction theory—although Prevost (14) ‘and Biot (15) 
insist on the force of the experiment, and explain it on the prin- 
ciple of reaction on the air, while Carradori (13) is equally 
energetic in denying the possibility of the experiment unless 
there is reaction on the surface of the water. I placed camphor 
on a tinfoil raft and also on cork, and never obtained any motion 
unless the water wetted the camphor, or had some direct com- 
munication with it. Professor Mensbrugghe suggests that my 
rafts and their cargo of camphor were too heavy. I now see 
that this was the case, and that the cork, from being too thick, 
was too high out of the water. I formed a raft of a small square 
of mica, placed on it a bit of camphor about thesize of a small pea, 
took up the raft on the point of a penknife, and so launched it 
upon the surface cf 6 ounces of water contained in a very clean 
cohesion-figure glass 34 inches in diameter. Before the raft had 
touched the water, a visible shudder passed over its surface, 
showing the action of camphor at a distance, as in Biot’s expe- 
riment (15). No sooner was the raft fairly launched than it 
began to sail about, and continued to do so with gradually 
slackening effort during a whole week. The advantage of using 
mica is that its suriied valunceiny fleur d@eau, and it Soils about 
without allowing the camphor to be disturbed or to become 
wet. 

30. The principle upon which the new theory is based is that 


420 Mr. C. Tomlinson on the Motions of Camphor 


of the surface tension of liquids. The researches of Segner®! in 
1751, and of Dr. Thomas Young** im 1806, rendered it very 
probable that there existed a contractile force or tension at the 
surface of liquids. The labours of Henry®?, Lamarle**, Dupré 
de Rennes®, Van der Mensbrugghe*’, and others have con- 
verted this probability into a certainty ; so that the existence of 
such a force (which is a more perfect definition of Carradori’s 
attraction of surface (9), and of Dutrochet’s epipolic force (28)) 
is not only capable of proof, but can also be expressed numeri- 
cally for different hquids at a given temperature. As this force 
cannot be said to be yet recognized in our Manuals of Physics, 
perhaps i may be excused for quoting the following lines from 
one of the few books, imtended for the use of the student, in 
which it 1s noticed :— 

“‘ very liquid possesses a certain amount of fenacity or direct 
cohesion, whereby its parts resist separation by being directly torn 
asunder. ‘This cohesion has been proved to be the result, in 
whole or in part, of an attractive force between the particles of the 
liquid, which acts at appreciable though exceedingly small dis- 
tances; in consequence of which there exists at the external 
surface of every liquid mass a layer or film of liquid of unknown 
but exceedingly small thickness, which is of somewhat less den- 
sity than the internal mass of liquid, and consequently in a state 
of tension. ‘This superficial tension is the force which sustains 
a hanging drop; and its amount may be computed from the 
weight and dimensions of the largest drop of the liquid which 
can hang. It causes the surface of every isolated mass of hquid 
(such as a falling drop), or cavity i a mass of liquid (such as 
an air-bubble), to contract to the smallest possible dimensions, 
and consequently to assume the figure of a sphere. It also 
causes the surface of every isolated jet of lquid to tend to as- 
sume a form of circular section, or to oscillate about sucha form. 
It modifies the form of the surface of every mass of liquid by 
rounding more or less the corners, which would otherwise be an- 
gular. Cohesion also exists to a greater or less degree between 
liquids and solids; and the combined effects of this force and of 
the superficial tension due to the cohesion of the liquids them- 
selves, constitute what are known as phenomena of capillary at- 
traction. It is by reason of this tendency of the external film 
of a liquid mass to assume a definite figure, viz. the sphere, that, 
in defining the word ‘liquid,’ non-resistance to change of figure 

31 De Figuris Superficierum fludarum comment. Gotting. 1751. 

® Phil. Trans. 1805. Essay on the Cohesion of Fluids, p. 65. 

33 Phil. Mag. 1845. 

3 Mém. de P Acad. Roy. de Belgique, 1864. 


35 Ann. de Chim. et de Phys. Ser. 4, vols. vi.., 1x., &e. 
Bull. de ? Acad. Roy. de Belgique, vols, XXU., XXIl. 


on the Surface of Water. 4.21 


has been predicated of the interior parts of a liquid body only 
and not of the whole mass”’®7. 

31. In order to produce distinct experimental results on sur- 
face-tension, Professor Van der Mensbrugghe had to devise a 
method by which one portion of a tensile liquid surface could be 
separated from another portion of the same surface, so as to show 
" variations in tension between the two portions. For this purpose 
filaments of a silkworm’s cocoon were cut into lengths of about 
12 centimetres, and, ten or fifteen of these being laid parallel, were 
tied at the two extremities. The bundle thus formed was bent 
into an irregular circle, washed in alcohol and then in distilled 
water, and flattened between the leaves of a book. The bundle 
was now taken up by means of a clean glass rod, and placed on 
the surface of water im such a way as to be exactly in contact 
with it without being below the level. | 

32. Let the two liquids be distilled water (whose surface-ten- 
sion is equal to 7°3) and ether (of which the tension is 1:88). The 
water is contained in a large capsule, and a drop of ether is held 
above that portion of the surface limited by the coil of fila- 
ments; this immediately undergoes lively trepidations, and 
tends to assume the circular form, evidently because the vapour 
of ether diminishes the tension of the subjacent portion of sur- 
face within the silken boundary, and this, in its turn, yields to 
the superior traction of the portion external to it. The moment 
the drop of ether touches the surface within the flexible contour, 
the silk expands into a circular form; but it as quickly con- 
tracts, since the evaporation of the ether cools the surface and 
so restores its contractile force. When, on the other hand, the 
ether is deposited outside the silken boundary, this immedi- 
ately becomes reduced in size, but expands again as the cold 
produced by evaporation augments the contractile force of the 
exterior portion. 

33. In this way may be explained the observation of Prevost 
(14), that ifa bit of camphor be held near the surface of water 
that has been dusted with lycopodium, the powder is repelled 
towards the edge of the vessel; or, as in Biot’s experiment (15), 
if camphor be brought near a thin layer of water, this opens 
and leaves a dry space on the support just under the camphor. 
In such cases the water locally dissolves a small quantity of the 
vapour of camphor, and thereby has its tension locally reduced, 
while the contractile force of the other parts of the surface is free 
to act. 

34. The rotations of camphor on the surface of a liquid, and 
similar phenomena, are included in the following general propo- 


37 Nichols’s ‘ Cyclopedia of the Physical Sciences,’ 2nd edit. 1860. Art. 
* Liquid.” 


4.22 Mr. C. Tomlinson on the Motions of Camphor 


sition :—When on the surface of a liquid, A, we deposit a small 
fragment of a solid, B, which is more or less soluble in A, or 
detaches from its surface matter that is so, the equilibrium of 
the superficial layer of A is disturbed. Ifthe solution take place 
equally all round the fragment, this does not move; if unequally 
in different azimuths, the fragment displays sudden movements 
of translation and rotation. 

85. In order to show the action of camphor in diminishing 
the surface-tension of water, flexibte filaments were taken, 30 or 
40 centims. inlength. On scraping a few fragments of camphor 
upon the space defined by the filaments, these were quickly 
thrown into the form ofa perfect circle. The camphor produced 
great diminution in the contractile force of the water, reducing 
it to 4°5; and as this diminution takes place unequally round 
each fragment, this must necessarily rotate. Ifthe camphor be 
placed outside the ring, the filaments immediately contract. 

36. By repeatedly adding fragments of camphor to the water, 
this became reduced in tension to 4°5, and the camphor no 
longer rotated. Or if the surface be touched with the finger, 
the tension is reduced to 4°75 im consequence of a greasy film 
being transferred to the water. A similar effect 1s produced by 
an unclean vessel, or the presence of smoke, or of the vapours of 
essential oils &c. in the air of the room. 

37. The various bedies that rotate on water act like camphor 
in locally diminishing its surface-tension. The reason why the 
motions are not in general observed on the surface of oils, spirit, 
&c. is, that their surface-tension is feeble, although their adhe- 
sion to the camphor &c. 1s sufficiently energetic to dissolve 1t. 

38. There are many circumstances which render this theory more 
acceptable than the recoil theory, which has so long found favourin 
accounting for these motions. For example, in one of the experi- 
ments described in my essay (note °), a well-shaped lens of water 
with a well-defined rounded edge was formed on a glass plate, and 
also on the surface of clean, pure mercury, and on this lens mi- 
nute fragments of camphor were set spinning. I observed that 
the fragments would often pass over the edge and rotate in a nearly 
vertical tangent plane, and then go back again to the upper sur- 
face of the lens. A similar effect was also noticed with phos- 
phorus on the surface of mercury. I could not understand by 
what influence the fragments recovered their position from a 
nearly vertical to a horizontal plane. The surface-tension theory 
makes it clear. Another difficulty was that the rotations of bits 
of paper smeared with oil are very rapid on the surface of water, 
notwithstanding the friction ; flakes of camphor, formed by ex- 
posing oil of camphor to the air, or flakes of benzoic acid, formed 
by a similar exposure of oil of bitter almonds, move with even 


_on the Surface of Water. 423 


ereater rapidity; indeed their gyrations are sometimes so rapid 
as to make the fragment appear hazy. This also occurs when 
the ether-sponge is held over the rotating camphor. Flakes of 
solid acetic acid are amazingly active on water ; while the needles 
of solid. carbolic acid have a peculiar rapid jerking kind of 
motion, not consistent with the reaction of the solution on the 
fragment. Then, again, the sharply defined character of the 
perfectly circular disk of ether formed by holding the ether- 
sponge over the surface of the water (25) seemed to point to 
the action of a force acting equally around and exterior to the 
disk. 

39. With respect to the rotations on the surface of mercury 
in which the camphor &c. are not soluble, the theory is not quite 
so clear. But I gather from the memoir that the rotations are 
due to variations in surface-tension consequent on the adhesion 
of the camphor. This must be very slight; for Prevost says 
(note 7°) the fragments seemed scarcely to touch the surface. 
I also do not see how Prevost’s experiment (14) on the motions 
of camphor on solid plane surfaces is to be accounted for on 
this theory. It is very desirable to repeat this experiment; and 
I hope some of our microscopists will do so. I also do not see 
how the case of pure or recently distilled essential oils, occu- 
pying the surface of the water without interfering with the mo- 
tions of the camphor (28), is met by the theory, unless it can be 
said that the oil is bound up, as it were, by its own surface-ten- 
sion, so as not to interfere with the surface-tension of the water. 
If this condition be admitted, the fragments are as free to move 
as if the oil were not present. Although the fragments pass 
through and cut up the oil, the latter does not lose its lenti- 
cular form, so that its tension is probably not diminished by 
the presence of the camphor. 

40. There are a large number of facts contained in, or sug- 
gested by this memoir (such as those relating to the action of 
vapours and films on the surface of water), which may perhaps 
ceail for a separate notice. Butas far as the motions of camphor 
&e. on the surface of water are concerned, I am bound to admit 
(notwithstanding 39) that this curious and suggestive problem, 
which has occupied so many scientific minds during nearly two 
centuries, has at length received a satisfactory solution. And 
this, like every true scientific work, has absorbed a vast number 
of phenomena which apparently had little or no mutual con- 
nexion. During these two centuries many labourers have been 
working in the same field, tilling a difficult soil, which to the 
most diligent culture never yields a harvest, but only now and 
then a few grains, for which, it may be, the proper granary is 
not known, until at length the master comes and collects the 


424 Prof. A. Kenngott’?s Microscopical Investigation of 


grain from the various labourers into the proper storehouse 
which Nature herself condescends to point out to him. Such 
I believe to have been done by the Belgian whose work I have 
surveyed with so much pleasure and profit. All honour to him! 


Highgate, N., Nov. 13, 1869. 


XLVI. Microscopical Investigation of thin polished Lamineof the 
Knyahynia Meteorite. By Professor A. Kenneort, of Zurich*. 


[ With a Plate. | 
P | ‘HE general tint of these lamine is grey, spotted with yellow; 


they are semitransparent, with the exception of some opaque 
or dark-yellow spots. Incident light shows not unfrequently 
minute spots of metallic lustre. The whole appears fine-grained 
to the unassisted eye, and spheroidally grained (“oolitic,” to 
use a somewhat imadequate term) under a magnifyig-power 
of two to four. The granules are grey, some of them more 
or less angular; the yellow tints appear only in irregular 
spots, not ‘being proper to any distinct component. Opaque 
substances are irregularly interspersed, in some cases mark- 
ing the outlines of isolated granules. The spherical granules 
pass gradually into angular forms with rounded edges; and 
some of them lose their rounded form under strone magni- 
fying-powers. Rounded and distinct sections appear scarce 
under a thirtyfold magnifying-power, which has proved the best 
for examining the structure in its totality. 

Besides the metallic and opaque particles, two crystalline mi- 
neral species are discernible; one of them is colourless and trans- 
parent, the other grey and translucent ; both are bi-refractive, 
and show various polarization colours, not separated from each 
other by distinct limits. Some spherules consist essentially 
of one or the other of these minerals; in others their outlines 
have become indistinct. The opaque substances are subordinate, 
nor have they any influence on the structure, being merely in- 
terposed among the rounded or angular granules. 

The structure of the Knyahynia meteorite (the relative size 
being left out of consideration) reminds one of the globular diorite 
of Corsica, and may therefore be supposed to be rather the result 
of a process of crystallization within its own substance than an 
ageregation of separately formed corpuscles. The opaque com- 
ponents are light-grey metallic iron, greyish-yellow magnetic 
iron-pyrites (Haidinger’s “troilite’”’), and a black substance. 

* From a letter to Chevalier W. de Haidinger, read to the Imperial 


Academy of Vienna, May 13, 1869. Translated and communicated by 
Count Marschall, F.C.G.S. &e. 


thin polished Lamine of the Knyahynia Meteorite. 425 


These three components may be best discerned by the microsco- 
pical examination of the lamine under zncidené light. Ifthe light 
from above is stopped, they all appear black by transmitted 
light. Iflight from above is admitted, only the black substance 
seems to be opaque, the iron appearing dark-grey and translucent, 
and the pyrites blackish yellow and faintly diaphanous by the 
effect of reflected light. This optical illusion could not be left 
unnoticed; as, besides the frequent grey and translucent minerals, 
another dark-yellow faintly diaphanous substance is visible at 
two places of the lamina. 

The grey and the uncoloured silicates are differently affected 
by hydrochloric acid; and it may be inferred from this differ- 
ent action, and from the crystalline structure, that the first is 
pyroxemc (probably enstatite), and the other peridotic. The 
erey silicate, if polished, shows stripes, indicative of lamellar 
structure; the hyaline one shows merely fissures. Both appear 
in angular and rounded granules. 

Plate III. fig. 1 shows the section of a granule nearly every- 
where surrounded by irregular angular granules of the black 
opaque mineral. Its diameter is 0:48 to 0°64 millim. ; it is im- 
perfectly round, and is surrounded by transparent particles, ex- 
cept at four places, where it is in contact with small particles of 
the black mineral. It shows distinct stripes, also appearing in 
the small granule on the right, the other three showing merely 
irregular minute stripes. An extremely delicate transparent sub- 
stance interposed between the grey, partly parallel, partly diver- 
gent stripes, makes them perceptible. Some few isolated black 
points lie within the round granule. Further to the right (at e) is 
metallic iron, with a black opaque substance around it ; and a yel- 
lowish tint, equally affecting the grey and the hyaline silicate (ind1- 
cated by the outline and the letter y), extends into the rounded 
granule. The tinging substance is oxyhydrate of iron. The black 
particles lying isolated within the granule and around it have 
undoubtedly been expelled outward by the progress of crystalli- 
zation. ‘The structure just described becomes more and more 
indistinct as the magnifying-power is increased, and resolves 
itself into a mere aggregation of grey and hyaline particles 
when the power is =900. 

Fig. 2 represents another object, 0°5 to 0°6 millim. in dia- 
meter, of which (perhaps rather fortuitously) the greater half 
offers the form of a hexagon. ‘This granule is essentially com- 
posed of the grey mineral, showing linear formation only in its 
lower portion—its upper half showing irregular, light-coloured, 
rounded spots with darker margins, reminding one of granular 
texture. The whole is framed in by a light-coloured border with 
isolated fissures, which is distinctly limited by an aggregation of 

Phil. Mag. S.4. Vol. 38. No. 257. Dec, 1869. 2 F 


426 Prof. A. Kenngott’s Microscopical Investigation of 


the black opaque substance in minute granules. On the right 
(at e) is metallic iron bordered with black, and on the left, above, 
another minute particle of iron. The dark granular substance 
outside and above the figure is granular magnetic pyrites (froz- 
lite) connected and framed by black opaque substance. 'The di- 
stinctly linear portion of the granule touches a small portion of 
striped grey substance below, which separates it from the iron (e), 
and from a diaphanous fissured granule. A number of particles 
of the black opaque substance become visible in the interior of 
the granule under a magnifying-power of 120 to 330. 

The third object (fig. 3) is a round granule of the grey mi- 

neral, 0°7 millim. in diameter, nearly circular, rather distinctly 
limited by a double row of minute opaque black granules accu- 
mulated laterally into two black spots. The whole surface ap- 
pears made up of white aud grey under a magnifying-power of 
75 to 120, and spotted or speckled under a higher power. Some 
large fissures run irregularly through the whole. The double 
border of black granules is worthy of particular notice. A mag- 
nifying-power of 450 and more shows the whole to be inter- 
spersed with extremely minute yellow granules, quite different 
from the irregular yellow tints of some single places more or 
less spread over the whole polished surface. 
. The grey mineral constitutes essentially the round or rounded 
granules figured in figs. 1, 2, and 3, besides many others, larger 
and smaller, and more or less varied. All of them prove this 
mineral to possess a certain degree of crystalline structure, as it 
is observable in enstatite and diallage, and manifested by linear 
stripes on the sections under certain aspects. An oblong round 
granule of 0°8 to 1:2 millim. shows several groups of parallel 
stripes, one near the other, as would an aggregation of a number 
of individuals. Another granule, 0°6 millim. in diameter, pre- 
sents very dark stripes together with lighter ones. The black 
opaque granules along or near the margin are rarely wanting. 

Other granules consist of a compound of a transparent and 
of a translucent mineral substance. Fig. 4 is a large round 
granule 1°5 millim. in diameter, showing a crystalline granular 
aggregation of the transparent silicate, with irregularly angular 
or rounded granules cemented together by the dark-grey silicate. 
Some few black granules appear locally, accumulated here and 
there along the margin of the outline. A small portion of me- 
tallic iron, bordered with a black substance, appears at e ; and at 
another place is a dark spot of magnetic pyrites, smaller than 
that im fig. 2, and likewise bordered with black substance. 
Another granule, 0°8 millim. in diameter, shows within a light- 
coloured border (about 0:08 millim. in breadth) an aggregation 
similar to that in fig. 4, only the transparent granules are reia- 


thin polished Lamine of the Knyahynia Meteorite. 427 


tively larger, and the grey substance is of somewhat lighter tint. 
The margin is exclusively formed by the transparent fissured 
mineral. The somewhat sinuated outline of the whole granule (or 
rather of its section) is marked in some places by black granules. 
A rounded section, 0°6 millim. in diameter, is merely a crystalline 
granular aggregation of transparent silicate, with many black 
Opaque granules more approximated towards the margin than in 
the central region. Wherever the rounded granules appear less 
distinctly, the granular aggregations of the transparent silicate 
are irregularly associated with the grey one, whose stripes are then 
no longer perceptible. Where the grey silicate prevails (as in 
the portion, 1 millim. in breadth, shown in fig. 5), the stripes 
become more distinct and appear either parallel or divergent. 

The specimens hitherto described prove both silicates to have 
crystallized stmultaneously—one or the other of them, according 
to circumstances, having accumulated around certain centres in 
a spherical form, thus imparting to the meteorite, as a whole, a 
somewhat oolitic aspect. An alternation of substances within 
one and the same granule, as it occurs in globular diorite, is seen 
in the section of a granule 15 millim. in diameter. In its 
interior the grey mineral with irregular fine stripes is associated 
and partly framed with the black opaque substance (see fig. 6). 
Around this central portion is a granular aggregation of the 
transparent fissured silicate, locally interspersed with granules 
of the black opaque substance and of metallic iron. The outer 
border is marked by irregular particles of iron bordered with 
black substance. Small yellow granules of magnetic pyrites, 
associated with black substance (as in fig. 2), appear on the left 
side. 

The grey mineral is likewise the essential component of an- 
other rounded granule, 0°36 millim. in diameter, some few 
linear individuals appearing more conspicuously. A broad mar- 
ginal zone includes some black granules. The whole granule is 
surrounded with portions of the three opaque minerals, compa- 
ratively more extensive than those in fig. 6, and themselves parts 
of a more extensive zone of granular erystalloids of the trans- 
parent mineral, whose intervals are filled up with amorphous par- 
ticles of the grey mineral. This zone gradually vanishes into 
the general aggregation. 

A third granule, 1 millim. in diameter, shows likewise a grey 
nucleus and a surrounding transparent zone, both including abun- 
dant particles of black substance and magnetic pyrites. 


Fig. 8 is a portion of the transparent mineral, 1 millim. in 


length and 2 millims. in breadth, whose appearance and optical 

condition are those of one single individual, interwoven with an- 

other dark greenish brown, faintly pellucid mineral, and itself ex- 
282 


| 


428 Mr. W. H. Preece on the Parallelegram of Forces. 


hibiting a great number of fissures in nearly equal directions. A 
similar but by far smaller portion appears in a rounded section, 
0-6 millim. in breadth, occupying one-half of the whole diameter, 
and bordered on both sides by granular aggregations of the 
transparent mineral. 

The metallic iron, like the two other opaque minerals, generally 
appears interspersed in proportionally minute particles. In some 
few cases (see fig. 7) particles of iron, of 0°6 to 0:8 millim., in- 
clude granules of the transparent silicate, with some few black 
granules in its interior, and others at the external margin of the 
central granule and of the iron. 

Small fragments acted on by the blowpipe-flame are locally 
covered with a black glossy enamel. The grey powder of the 
meteorite, brought into contact with curcuma-paper moistened by 
distilled water, offers a distinct and sometimes intense alkaline 
reaction ; it is partly soluble in hydrochloric acid, emitting sul- 
phuretted hydrogen and leaving gelatinous silica. 


XLIX. The Parallelogram of Forces. 
By Witt1am Henry Preece, Assoc. Inst. CE. &c.* 


if is said that there are twenty-seven known proofs of the pa- 

rallelogram of forces. Any attempt to add to this number 
appears to be a needless undertaking; but the proofs usually 
inserted in elementary works are generally so laboured, that 
beginners rarely succeed in mastering them fullyin their first jour- 
ney through statics. Indeed it appears to me that the proof that 
the resultant is represented in magnitude as well as in direction 
by the diagonal, as usually given, is defective; for we are required 
to draw a line equal to an unknown quantity, and then to show 
that another line is equal to this lme without obtaming the un- 
known quantity. 

I have therefore ventured to arrange another proof based 
upon the principle of couples, which not only attempts to re- 
move this defect, but to free the usual proofs from the necessity 
of subdividing the proposition into the two cases of commensu- 
rable and incommensurable forces—a veritable pons asinorum to 
all students. 

Definitions. 

(1) A couple is a system of two equal forces acting in dissi- 
milar directions in parallel lines. 

(2) The arm of a couple is the perpendicular distance between 
the lines of direction of the two forces. 


*“ Communieated by the Author. 


Mr. W. H. Preece on the Parallelogram of Forces. 429 


(3) The moment of a couple is the proauc of the magnitude 
of either force into the arm of the couple, (It is the numerical 
measure of its Importance.) 


Axioms. 


(1) Any system of forces may be replaced by their resultant. 

(2) Two equal and opposite forces acting on different points 
of a rigid body, so as to balance each other, are upon the same 
straight line. 

(3) Two equal and opposite couples acting at the same point 
of the same rigid body, balance each other. 

(This is a Cor. to Definition 3; for the two couples have the 
same moments, but of different signs.) 

1. Let the two forces P,Q act upon the point A; it ts required 
to find the direction of their resultant. 
Take A C, A D respectively equal 
in magnitude and direction to the 
forces P,Q. Through C draw C B 
parallel to AD, and through D 
draw DB parallel to A C, meeting 
CBinB. JomAB. Then ACBD 
is a parallelogram, and A B is its 

diagonal. 

At B, rigidly connected with A, apply a force P, equal and 
opposite to P, and also a force Q, equal and opposite to Q. 

The system is in equilibrium ; for at the pomts A, B we have 
the couple (P, P,) acting in one direction, and also the couple 
(Q, Q,) acting in the other direction; and these couples are 
equal, for the moment of (P, P,) is B D x Cc, and the moment of 
(Q, Q,) is ADxDd; and these two products are evidently 
equal, for they are each equal to the area of the parallelogram 
ADBC. Hence they balance each other, and the system is in 
equilibrium. 

Now the forces P and Q have a resultant which acts between 
them ; we may therefore replace them by their resultant without 
disturbing the equilibrium: call it R. 

The forces P, and Q, have also a resultant which acts between 
them; we may also replace them by their resultant, which we 
will call R.,. 

But these two systems of forces are equal and opposite; and 
since they balance each other, their resultants must be equal and 
opposite and also balance each other ; and therefore, by axiom 2, 
the resultants must be in the same straight line. / 

Hence the resultant of the forces P and Q acting at A must 
be along the diagonal A B of the parallelogram ACBD whose 
sides are equivalent to the forces P and Q. 


4.30 Prof. F. Kohlrauseh on the Deternunation of 


2. The diagonal A B also represents the magnitude of the result- 
ant of the forces P and: Q at A. Fig. 2. 

For if the diagonal A B does 
not represent the resultant of 
P and Qin magnitude, it must 
either be greater or less than 
this resultant. Let it be 
‘greater, and take AG less 
than A B to represent the re- 
sultant in magnitude. © Draw 
DE parallel to BA. Produce 
CA tomeet DEin E. Draw 
GF parallel to BD or CE meeting DE in F, and join AF. 
Then A EF G is a parallelogram, A F is its diagonal, and. A K 
=A C, for both equal BD by construction. 

Apply a force R at A along A E equal and opposite to P, and 
therefore represented in magnitude and direction by A E. 

Suppose the three forces P, Q, and R acting at A. We may 
replace P and Q by their resultant AG. Hence the forces AG 
and R acting at A must have a resultant acting in the direction 
of A i. 

Therefore P and Q and R at A produce the same effect as a 
resultant force acting along AF’. Now if we remove P and R, 
which we can do as they are equal and opposite, we have left Q 
acting along A F as wellas along A D, which is absurd. 

Hence the resultant cannot be less than AB. In the same 
way it may be proved that it cannot be greater; and therefore 
A F must coincide with AD, and the point G with the point B. 
Therefore the diagonal A B represents the magnitude as well 
as the direction of the resultant of P and Q. 


i yh Deie mination re He a: Heat t of Air oe constant 
Volume by means of the Metallic Barometer. By ¥. Kout- 
RAUSCH*, 


HE value universally assumed for the specific heat of air 
under constant volume has been calculated from the velo- 
city of sound. There has hitherto been no exact direct determi- 
nation; for the observations made by Clément and Désormes, 
as alk as by Gay-Lussac and Welter}, can only be regarded 
as approximations by which the proof has been furnished that 
* From Poggendorff’s Annalen, No. 4, 1869. 
t+ Clément and Désormes, Journal de Physique, &c., vol. Ixxxix. pp. 321, 
428 (1819) ; Gay-Lussac and Welter in Laplace’s Mécanique Celeste, vol. v. 
p. 125. In the first paper all details are wanting which would render pos- 
sible an opinion as to the accuracy of the experiments. Only one experi- 
ment is given in full; of all the others only the mean of the results is given. 


the Specific Heat of Air under constant Volume. 431 


the magnitude in question is not far removed from that calcu- 
lated by Laplace. The observers mentioned, as is well known, 
subjected an enclosed volume of air to a sudden change of den- 
sity by connecting it for a very short time with a large reservoir 
of air under a known pressure (mostly that of the atmosphere), 
and then measured the change in temperature. But as even the 
most delicate thermometer is too slow to follow rapid alterations 
of temperature, the enclosed air was itself used as a thermometer 
by observing the change in pressure which it experienced when 
the original temperature was restored. As the change in pres- 
sure was small, it was measured by a column of water instead of 
by one of mercury. 

Nothing can be urged against the principle of this method. 
The doubts which might arise from the evaporating water would 
be removed by the use of sulphuric acid. The question is 
whether the two assumptions can in practice be simultaneously 
realized—first, that the duration of the communication with 
the atmosphere is sufficiently short to justify the neglect of 
the equalization of temperature which takes place during this 
time, and, secondly, that after so short a communication the 
pressure in the receiver is at first exactly equal to the atmospheric 
pressure. Doubts asto the simultaneous fulfilment of these two 
conditions will arise at the outset; an empirical proof has not 
been afforded by the observers. To remove this objection, a 
knowledge cf the condition immediately after the change in pres- 
sure must be sought in some other way; and this is afforded 
by not merely remarking the total change in pressure from the 
moment of rarefaction or condensation of the mass of air to the 
final restoration of the original temperature, but commencing the 
observation very soon after the primary change in pressure. 
From the course observed, the law of the equalization of tempe- 
rature will be ascertained by which the condition corresponding 
to the time zero is to be calculated. The duration of the com- 
munication between the receiver and reservoir may be as small as 
the mechanism of the apparatus permits. Indeed when once this 
duration is known it can be readily allowed for in the calculation. 

Such a method was not applicable so long asthe pressure was 
to be measured by a column of liquid; for in order to diminish 
capillary actions a tolerably wide tube must be used, and there- 
fore, owing to the initial oscillations of the column of liquid, 
the most important time for observation is lost. 

The metallic barometer now constructed in great perfection fur- 


By arather arbitrary correction this mean value was brought into accordance 
with that which followed from the then known velocity of sound. The 
experiments of Gay-Lussac and Weiter, of which Laplace gives an example, 
do not appear to have been published. Compare also Dulong, Poggen- 
dorff’s Annalen, vol. xvi. p. 404. 


4.32 Prof. F. Kohlrausch on the Determination of 


nishes a very delicate means of measuring pressure. From the 
smallness of the mass put in motion in the action of this instru- 
ment, the initial oscillations are of very short duration. The 
moment of inertia of a manometer which 1s specially intended for 
such experiments, may be materially diminished as compared with 
that of the commercial instruments, in which little attention is 
ordinarily paid to this element of delicacy. 

I will here communicate a few observations which I made at 
the instigation of Professor Weber, which cannot indeed serve 
for more than a preliminary trial of the method, and should in- 
cite to a more accurate repetition with more perfect means. 

The instrument used was a Paris barometer graduated in milli- 
metres. It was placed on the plate of an air-pump under a re- 
ceiver of about 6 litres capacity. The air under the receiver was 
dried by means of chloride of calcium. Bya rapid stroke of the 
piston, the air in the receiver was rarefied and immediately shut 
off by a stopcock. ‘The index of the barometer at first moved ra- 
pidly towards the smaller numbers, and then retrograded, at first 
rapidly, and then more slowly through a number of divisions. 
During this time one observer gave a signal as often as he noted 
that the index passed over a whole division ; a second noticed the 
corresponding time. When the motion of the index had become 
slower, parts of a division were noted. After a lapse of sixty 
seconds a motion could no longer be perceived; that is, the mass 
of air had assumed the temperature of the surrounding atmosphere. 

With the aid of Dr. Nippoldt the six following series of ex- 
periments -were made, from which a mean may be easily de- 
duced. ‘The diminution in pressure of the air, which before the 
experiment was under atmospheric pressure, was nearly equal in 
all experiments ; after the original temperature had been restored, 
the maximum was 38°5 millims. and the minimum 34 millims. 
As the individual series are proportional, they can all be reduced 
to the mean alteration in pressure, 37 millims. The observations 
thus corrected are contained m the following Table, in which ¢ 
represents the time in seconds which elapses from the beginning 
of the stroke of the piston, y the distance in millimetres of the 
index at the time / from its ultimate position. 


™~ 
© 
™~ 
S 
~“™ 
S& 
“ 


Ye t. Ye t. y. 


seconds.|millims.fseconds.|millims.{seconds.|millims.{seconds.|millims.'seconds, millims.{seconds. millims. 


| 
20 | 71 1 20] 80,] 2:0 |. 82 | 21 | 7-4.) 2:0 1 7-55 1 aes 
40 | 52] 38 | 59°] '36 | 62 [3:8] °5:5-| 39. | o:Go 1) amen 
51 | 42 1°60 | 37 | "51 | 43 1.60 1°36) 62 || ayo eee 
83 19-2180 12-6 1 et 19 Se -08) ae |e eee 82 | 26 
120 | 1:3. ]103 | 15 [711-0] 14/110] 16 | 101 | 1-75]108 | 16 
21-0 | 03 | 200 | 0-4 119-4 | 0-4 | 18:2 | 07 | 202 | 0351183 | 06 
40 | O1]40 | 02 [40 | 005]-40 | O1 ]35 | O15]40 | O91 


the Specitic Heat of Air under constant Volume. 433 


The calculation of a mean from these individual series is faci- 
litated by the circumstance that the first observation was in each 
case made about the same time (two seconds) after the com- 
mencement of the stroke, and that thenceforward the intervals 
of time were almost equal. Hence it is sufficient if we take the 
arithmetical means both of the almost equal times ¢ and of the 
corresponding values of y. 


Thus we find 


y. 
t. TES os a |) Ditterences 
Observed. Calculated. 
seconds. millims. millims. millim. 
2°07 7°62 774A —()-12 
3°87 5°66 5°52 +()°14 
5°75 3°85 3°88 —0:03 
8:12 2:46 2°49 —0:03 
10°87 1-52 1:48 +0:04 
19-52 0:46 0:29 +017 
39-2 0-12 0:07 +0:05 


The calculated values are obtained thus. Putting the quan- 
tity of heat added to the mass of air in each minute proportional 
to the difference in temperature from the surrounding medium, 
or, what is the same thing, the alteration in pressure propor- 
tional to the difference y of the momentary from the final pres- 
sure, we have 


dy 

dt 
We introduce in the calculation for A and C, 

C=11°41, A=0:1877: 


=—Ay, lognaty=log nat C—At. 


The calculated values, as we see, agree well with observation. 
The expression is valid only from the moment at which the 
stopcock was closed, which was the case at 0°75 second. We 
get for this time from the formula y=9°912. 

In order to calculate accurately the amount cf heat absorbed 
from the beginning of the stroke to that time, it would be neces- 
sary to have an exact knowledge of the course of the piston; 
but the correction may be approximately calculated in the fol- 
lowing manner :—At the time 0°75 we get the change in pres- 
sure due to change in temperature 


yeas os 
= 71800. 


At the time 0 it was =O. Hence as the mean from 0 to 0°75 


434, Prof. F. Kohlrausch on the Determination of 


we may assume 
dy : 
ag —0°930 ; 

from which the change of pressure till then, due to change in 


temperature, will be 
—0°75 x 0:939 = —0°698 millim. 


This number must be added to the value y=9-912 calculated 
for 0°75 second, from which the diminution in pressure due to 
lowering of temperature when the air is rarefied 1s 


Yo=10°610 millims. 


From this we get the ratio of the specific heat under constant 
pressure c to that under constant density c, in the following 
manner. If the mass of air unity, at the temperature @, is rare- 
fied from d to d, without the access of heat from without, it un- 
dergoes a diminution in temperature of 


1+2a0 d—d, c-—e, 
a a Cy 


if « is the coefficient of expansion of gases with the temperature. 

If the residual pressure after rarefaction, but after restoration 
of the original temperature, be called p,, the above lowering of 
temperature produces a diminution of Len c: 


d—d, ¢— 
VORP dl ve =, 
or, if p is the pressure before rarefaction, 
Dp Cae 
NOP amet aa 


D C 

whence 
ae =i sO ie 
Cy P-Pi hh 


Now in the experiments there was obtained 


g=/o2 millims,, = 705.0) 7,— ole 
hence 
ro = 
Cube ai ABs epee age) 
Ci By ia 15 
I have repeated the observations under various conditions 

—namely with greater and less change of density, with com- 
pression of the above mass of air instead of rarefaction, with 
shorter duration of communication (by rapidly opening and clo- 
sing the stopcock), finally with three different barometers, one 


the Specific Heat of Air under constant Volume. 435 


of which was a small and extremely good English one; and within 
the limits of accuracy attainable by a single observer I have 
always obtained the same value. I see no reason why the result 
should not deserve at any rate the same confidence as the older 
experiments with the water manometer. 

Yet the value found above (=1:302) would be in disaccord 
with the observed velocity of sound and with the number assumed 
for the mechanical equivalent of heat; for it would lead to 
319°4 metres for the velocity of sound, taking 0:00129384 as the 
density of dry air at 0° and 756 millims. pressure. Taking, 
with Regnault, the specific heat of air under constant pressure 
as 0°2377, the mechanical equivalent of heat would be 582, 
taking Delaroche and Bérard’s number (0°2669) it would be 
equal to 473 kilogrammetres. The most recent experiments of 
Regnault have given 330°3 metres for the velocity of sound, 


from which = =1:392, and the mechanical equivalent of heat 


1 

(putting c=0°2377) would be equal to 437 kilogrammetres. In 
our experiments ¥ would have to be = 14°5 millims., mstead 
of 10°61, to agree with this result. 

It would be difficult to discover a source of error to this 
amount in the above measurements. It is, however, advisable 
to repeat the experiments with improved instrumental means. 
In the Jatter we should include first of all a method of pro- 
ducing the change of density in a time much shorter, but 
capable of accurate measurement. Both the motion of the 
cocks and the observation itself would be best effected by mecha- 
nism. Moreover a metallic manometer of as small moment of 
inertia as possible should be constructed. Doubtless, too, by 
using a larger receiver with badly conducting sides, the equali- 
zation of temperature might be considerably retarded. | 

I doubt not that if these conditions be fulfilled a trust- 
worthy direct determination may be made by the above method 


of the ratio < (and thus an important gap in physics be filled), 


not merely for atmospheric air, but also (with no greater difficulty) 
for other gases, which is of especial interest. Apart from this, 
the indication of this simple method of quantitatively determin- 
ing with approximate accuracy the heating produced by com- 
pression in gas may be welcome to many a lecturer. 


Gottingen, January 1869. 


[ 436 ] 


LI. On Fulgurites in the Andesite of the Lesser, Ararat and on 
the Influence of Local Agents on the Production of Thunder- 
storms. By M, Axpicu*, 


nae influence of the geographical distribution of mountain- 

masses on the limit-lines between the eastern over-heated 
(and therefore over-dried) steppe-atmosphere of the continent of 
Asia, and the mozst and cooler masses of air brought by north- 
west atmospherical currents, is nowhere so conspicuous as within 
the region of the Great and Lesser Ararat group, where it finds 
its highest expression in the beginning of the eestival half of the 
year, under the form of frequent and sudden thunderstorms in 
the summit-region. These phenomena stand in close relation 
with the orographical constitution of the mountain-group. The 
first clouds and the first electrical discharges within them begin 
generally on the north-west side of the group, where its most 
powerful massif reaches furthest into the region of the Araxes 
valley, conspicuously spreading in breadth. The thunderstorm, 
in its rapid development, soon envelopes in a south-east direction 
the whole top region of the mountain, remaining stationary 
within the space between the Great and the Lesser Ararat, the 
north-west high portion, called “ Kippgolil,”’ standing at the 
same time in full sunlight. After a shorter or a longer space of 
time the flumderstorm: dies away on the Lesser Ararat, or it 
descends with gradually dimimishing energy into the plain 
towards Nachitshevan and Dzaulze. These well-characterized 
and regular thunderstorms begin in April (old style), reach 
their maximum in May, and have considerably diminished in 
the course of June. Although rare in July and August, they 
may possibly break out suddenly during this period, and be thus 
an obstacle to ascending Ararat. The journal of a meteorolo- 
gical station at Erivan, established by M. Abich and continued 
during more than fourteen months, registers for April 10, for 
May 14, and for June 6 several thunderstorms in this Ararat re- 
gion, not mentioning those which had broken out in the inter- 
vals of the hours (six every day) fixed for the observation of the 
instruments. 

M. Abich, having repeatedly ascended the Lesser Ararat, has 
been enabled to ascertain some physico-lithological facts demon- 
strating the frequence of thunderstorms in these lofty regions,and 
of the mutual action of atmospherical and terrestrial electricity. 
The chief rock of the Lesser Ararat is a fine-grained amphibolic 
andesite, risimg im cliffs above the slopes covered with decom- 


* From a letter to Chevalier W. de Haidinger, dated Tiflis, June 25, 1869. 
Communicated and translated by Count Marschall, F.C.G.S. &e. 


M. Abich on Fulgurites in the Andesite of the Lesser Ararat. 437 


posed andesite, or in obtuse pyramidal massifs, on the margin of 
a fault across the mountain, thus constituting its extreme top, 
12,106 feet above the sea-level, according to the measurements 
taken by M. Abich in 1844. When ascending the moun- 
tain from its easier, north-west side, M. Abich saw on the 
upper slope some dark stripes on the light-brown rock, whose 
vitrified aspect was evidently due to the action of lightning. 
The path of the electrical discharge was constantly traced in the 
form of a narrow tube,in the form of a thick goose-quill, traversing 
the rock, and lined on its inside with a dark green vitreous slag. 
These tubes increase in number towards the top, and have 
modified a portion of the top itself into a variety of andesite, 
which may properly be called “fulguritic.’? The originally 
compact rock of microcrystalline texture, traversed in every di- 
rection by vermiform fulgurites bearing evident marks of igneous 
fusion, has taken a cavernous aspect not unlike wood completely 
disaggregated by the borings of Teredines. The depth to which 
the rock had been attacked by lightning could not be sufficiently 
ascertained. M. Abich’s laborious examinations of the top of 
the Great Ararat could not discover there any traces of fulgurites, 
either on the cliffs of black trachytic porphyry on the steep 
south-east slope of the upper cone, reaching an absolute altitude 
of 13,000 to 14,000 Paris feet, or on the reddish-brown scori- 
aceous rocks rising above the snow on the margins of the flattened 
top. An investigation of the north-west side of the Ararat, be- 
tween the Kipp-Goll and Professor Parrot’s encampment, 12,954 
Paris feet above the sea-level, led to the same negative result. 
The investigation of the upper region of the south slope proved 
more satisfactory. The first fulgurites were observed on the 
massive trachyte cliffs at the mouth of a deep-cut glacier-ravine, 
the only real valley on the south side of the Ararat, exactly co- 
inciding in longitudinal direction with the Valley of St. Jacob on 
the north-west side. The slight depression of the top line of 
Ararat, as its projection appears when seen from the north, would 
coincide with the defile between these two valleys running in 
opposite directions. The absolute altitude of the glacier’s termi- 
nation in the first-mentioned ravine is 11,200 feet according to 
M. Abich’s statements, based on corresponding barometrical 
observations made at Hrivan and Nachitshevan. 

Another trace of fulgurites has been noticed in the Goéll-Dag, 
as the Jessidian Kurds call a conspicuous conical eminence visible 
from Bajazid, on the same apparent level as the south-west side 
of the Ararat. This eminence isabout 14 hour’s march distant 
from the flatly vaulted plateau of the Kipp-Goll (10,648 Paris 
feet above the sea-level). The Goell-Dag is the highest point 
of a rocky ridge diverging from the main mass of Ararat nearly 


438 M. Abich on Fulgurites in the Andesite of the Lesser Ararat. 


on the horizon of permanent snow, and stretching downward in a 
N.35° E. direction. Its component rock is a light-coloured pho- 
nolite-like, fine-grained trachyte, separating into sonorous lamine, 
quite different from the dark-coloured doleritic lava covering 
the mountain-slopes. A similar ridge, at. some distance from 
the first, and somewhat diverging from it, runs from the top 
ridge of the Ararat down to the lower region. These ridges are 
undoubtedly the upheaved margins of the powerful fissures tra- 
versing the foundations of the Ararat mass, probably coeval with 
its last great upheaval, and antecedent to the great effusion of 
lava attending it. ‘The whole structure of the Ararat slope con- 
firms this view. From the Goélldag (11,340 Paris feet above 
the sea-level) the eye looks down into the broad, valley-like space 
between the tworocky ridges, which converge upwards and at a 
short distance towards a third ridge. In this place the dolerite 
is covered by glacier-detritus; anda large current of lava, de- 
scending in a south-west direction, having advanced in the 
form of a wall on the plain of Bajazid, had evidently found here 
a fissure or excavated bed. Another current of lava, reaching 
the plain in the direction towards Bajazid, seems to have also 
broken out alongside of this second rocky ridge. The only traces 
left by lightning in these regions are isolated traces of fusion 
and perforations of trachyte plates. No such traces had been 
ascertained on the north side of the Ararat. 3 

Isolated fulgurites occur on the Parlydag (‘‘ Mountain of 
Lightning” in the Tartar language), an extensive trachyto- 
porphyritic system, dominating the plateau of Sinak, on the 
nitrachytic top of the Magaz*, and on the highest top of the 
Sahand near Tawris (Adherbeidjan) at an altitude of 11,600 
Paris feet. The light-coloured vitreous and lithoid rhyolites, 
forming the prominent tops of the Agdag and Boosdag moun- 
tain-systems (11,168 and 10,726 Paris feet above the sea-level), 
offered no traces of fulgurites; nor did the crater-margin of the 
great eruptive trachytic system of the Ischichlydag (9740 feet), 
or the T'ardourek, a flatly vaulted cone south-west of the Ararat 
behind Bajazid. 

All these details are necessary for demonstrating the frequence 
of thunderstorms in the region of the Lesser Ararat, and the 
very frequent and intense action of lightning perceptible on its 
summit, to be facts depending not only on general physico- 
geographical circumstances, but still more on the situation of 
this mountain-system relative to the plain of the Araxes and to 
the Great Ararat. 


* Altitudes measured by M. Abich :—plateau of the Sinak, 7582 Paris 
feet ; uppermost peak of Parlydag, 6887 feet. Uppermost peak of the Magaz 
(Imperial Russian Staff-Corps), 12,610 Paris feet. 


Influence of Local Agents in the Production of Thunderstorms. 439 


If we suppose the Pontic atmosphere, coming from W.N.W. 
at considerable altitudes, to pass over the Taurian Highlands, 
radiating heat in consequence of protracted insolation, it must 
become saturated nearly to its maximum with aqueous vapour 
and receive a notable amount of negative electricity. Whenever 
this atmosphere meets with the colossal prominence of Ararat, 
the electricity of the clouds, accumulated in the aqueous vapour, 
is suddenly increased ; and, of course, electrical compensation 
begins first on the north-west side of the Great Ararat. The 
elliptical form and the situation of summit and ridge of Ararat 
force the accumulated atmospheric current coming towards its 
side to the broad elevated valley between the two Ararats, and to 
its opening into the region where the atmosphere arising from 
the hot south portion of the Araxes-plain has reached its maxi- 
mum of heat and dryness. 

The greater half of the Lesser Ararat, whose base is notably 
inclined east-north-eastward, and which rises to more than 9000 
feet above the plain of the Araxes*, is almost to its summit 
under the action of this pure and non-electric atmosphere, moving 
constantly south-eastwards, and counteracted by a cold north- 
west current descending from the depression between the two 
mountain-groups (altitude 8274 feet). The notable energy of this 
counter-current is a necessary consequence of the local thermal 
contrast between the summit-region and the neighbouring heated 
plain. The uncommonly rapid decline of temperature observed on 
the higher horizons of this valley is indicative of an accelerated 
fall of the higher strata of clouds, containing (as M. Vogel sup- 
poses) aqueous vapour of a temperature far below the point of 
congelation, and the presence of which causes the violent falls of 
hail, attending in most cases the thunderstorms breaking out in 
the lower half of the valley. The clouds, highly charged with elec- 
tricity, coming rapidly from the Great Ararat and turning round 
the mountain, discharge each other on the north and east side of 
the Lesser Ararat, as the difference between the temperature and 
the point of degelation of the air in those regions increases with 
the distance from the mountain towards the plain. At the same 
time the increased permanent electro-negative tension of the 
summit of the Lesser Ararat discharges the latent electricity of 
the vapours, and provokes a continued intense compensation 
with the electrically charged clouds constantly coming from the 
Great Ararat. At all events, the degree of freedom from vapour 
of the atmosphere above the Nachitshevan half of the Araxes 
plain, as resulting from preceding meteorological conditions, 
and consequently its degree of electrical conductibility, must 


* Absolute altitude of the Araxes plain in the meridian of the Great 
Ararat, about 2400 feet, 


44.0 M. Abich on Hailstorms in Russian Georgia. 


cause the thunderstorm rising in the Ararat region either to 
exhaust itself in the Lesser Ararat, or to pass it rapidly and to 
spread over the whole opposite plain. The facts and observa- 
tions above mentioned seem to confirm MM. Peltier and La- 
mont’s views on the origin of thunderstorms and of atmospheric 
electricity. : 


LII. Hailstorms in Russian Georgia. By M. Astcu*, 


[With a Plate. | 


HE first of these storms took place May 27, 1869, at 
3 p.M., the other June 6, at 6 P.m., both within a limited 
region of the Trialat Mountains near Beloi Kliutsch, about forty 
wersts (263 Engl. miles) from Tiflis. The hailstones, although 
different in form in both cases, were of uncommon size, and 
deserve some attention. In the first case they presented a 
quite regular flattened spheroidal form, somewhat like the so- 
called “‘mandarin-oranges,” and a series of varieties almost re- 
minding one of organic evolution. The second case was a com- 
plete ‘ shower of ice erystals’”—not of fragments of ice of indi- 
stinctly crystalline outlines, but of spheroidal crystalloid solids, 
densely but irregularly beset, on the surfaces corresponding to 
their longitudinal diameter, with limpid regular crystals showing 
various combinations of forms belonging to the tri- and mono- 
axial systems—a peculiarity which, it seems, has not yet been 
observed, or at least published. The forms characteristic of 
calcareous spar and of specular oxide of iron prevailed, especially 
the scalenohedron, combined with rhombic planes, in crystals 
15 to 20 millims. in length. Other crystals exhibit the prism, 
combined with obtuse rhombohedra, and with the terminal plane 
perpendicular to the principal axis. Some specimens that fell 
soon after the beginning of the storm were aggregations of 
tabular crystals, 30 to 40 millims. in diameter, resembling the 
rosette-like aggregations of specular oxide of iron from Mount 
SG otthardt. 

Both these storms caused enormous devastations; strong 
branches were struck down as if cut with some sharp implement. 
The specimens gathered immediately after the fall presented 
perfectly sharp edges and somewhat convex surfaces, like some 
crystals of diamond—except the scalenohedral surfaces, which 
were completely flat. MM. Abich made drawings from ten of the 
most remarkable and best preserved specimens, intending to pub- 
lish in extenso his observations on the phenomena in question. 
These hailstorms have a close connexion with the abnormal me- 


* From a letter to Chevalier W. de Haidinger, dated Tiflis, June 25, 
1869. Communicated and translated by Count Marschall, F.C,G.S8, &e. 


ol 


Mr. T. T. P. B. Warren on Electrification. 441 


teorological conditions observed in Georgia during June 1869, 
and characterized by uncommonly intense frequent rains and 
thunderstorms. On June 20, a hailstorm, still more violent than 
those of May 27 and June 6, caused horrible devastations in the 
valley of Manglis, 18 wersts from Tiflis, and progressed, in the form 
of rain and electrical discharges, as far as into the valley of Algat. 

PI.III. figs.9 and10 are intended to represent the outlines of two 
of the most remarkable varieties of hailstones as true to nature as 
possible, without any pretence to elegant execution. In the two 
cases under notice, personal observation sets more or less at de- 
fiance any theory of the formation of hail hitherto established. 
How could indeed the formation of such crystalline aggregations, 
as regular as those of the calcareous spars of Andreasberg, be 
possible in the midst of the tumult generally supposed to 
be necessarily connected with the formation of hail? These 
ageregations may have had a long stay within a medium of 
highly refrigerated aqueous vapour before they fell to the ground. 
It must be remarked, to fully understand the drawings, that the 
shaded portion of the flattened spheroidal fundamental form 
of the groups is not always opaque in the original. Only the 
circle round the centre has a milky aspect, due to the air-bubbles 
enclosed in it, as also the nucleus of the greater number; in 
other specimens the nucleus is transparent, especially when re- 
duced by melting away into disks of ? to 1 inch in diameter, 
sometimes affecting the form of a perfect regular hexagon. In 
this case the milky circle around the centre appeared distinctly 
as an intricate tissue of minute lengthened pores and of capillary 
fissures filled with air. The shadow next to the margin of the 
larger peripherical circle is only intended to indicate the rounded 
and flattened spheroidal form of the chief body, on whose broader 
margin the crystals themselves adhere parasitically, or are in- 
serted, as in an alveole, made visible by the commencement of 
fusion (see a in fig.9). All the specimens presented lengthened 
vermiform and pyriform pores filled with air, extending radially 
from the centre to the circumference. The drawing shows these 
pores of-approximately natural size. 


LUI. On Electrification. 
By Tuomas T. P. Bruce Warren*. 


\ V HEN an insulated wire or cable is connected to a battery, 
and the deflection noted on a galvanometer, the first 
rush of current into the cable is due to the electrostatic capacity 
* Communicated by the Author, having been read at the Exeter Meet- 
ing of the British Asaociation, in Section A, August 1869. 


Phil, Mag. 8. 4. Vol. 38. No. 257, Dec. 1869. 2G 


442 Mr, T. T. P. B. Warren on Electrification. 


of the insulator. Battery-contact being still maintained, the 
deflection falls very rapidly at first, and gradually becomes reduced 
for some time after. 

The shorter the length of cable and the lower the degree of in- 
sulation, the less defined will be the differences in the deflections 
after a few minutes’ contact. 

Great care must be taken, when making these experiments, 
that the cable has not been previously charged ; should the cable 
have been charged, it must be connected to earth for some hours 
before testing. The battery must be in very good condition, and 
unsteady deflections totally discarded. 

The ratio between the deflections for equal periods of contact 
is independent of the length, and is greater or less according to 
the specific resistance of the dielectric. 

The ratio is unaltered under different electromotive forces so 
long as constancy is maintained during the time of observation 
and the deflection itself the same with the different electromotors 
at the end of the first period of contact ; but when, with different 
electromotive forces, the deflections at the end of the first period 
of contact are not the same, we may obtain the deflections which 
should be given on prolonged contact if we know the deflection 
for a corresponding period by any electromotive force, since the 
deflections for the first period of contact will have to one another 
the same ratio which the deflections at any other period of con- 
tact have: thus if with a given electromotive force we obtain at 
the end of the first minute’s contact a deflection of 84, which at 
the end of the second minute is reduced to 76, and with a dif- 
ferent electromotive force we have a deflection of 70 at the end of 
the first minute’s contact, the deflection at the end of the second 
minute will have the same ratio to 76 which 70 has to 84. 

Under different temperatures the resistances corresponding to 
one, two, three, &c. minutes’ contact follow the same law of varia- 
tion. Thus if R=r x constant; represent the resistance after 
one minute’s contact, then 


R’ =,’ x constant; = resistance after 2nd minute. 


Hie SAll 
a ae ” ” » ord ” 
R™ =r 2» » ” 4th ” 
[oe yp ” » ” Sth ” 
RY =r" »” » ” nth ” 


ro, r!!, rl, rl", o ave the resistances determined after 1, 2, 3, 4, 
5, n minutes’ contact respectively, and R, R/, R’, Rl, Rl", R* the 
required resistances for the same differences of temperature ¢, and 
at the end of 1, 2, 3, 4, 5, n minutes’ contact. 

If at any temperature T we obtain a deflection G after one 
minute’s contact, which at the end of the second minute falls to 


Mr. T, T. P. B. Warren on Electrification. 443 


g, we may calculate what the deflection should be at the end of 
the second minute for any other temperature by knowing only 
the deflection after the first minute at this temperature. 

Let G and g be the deflections after one and two minutes’ 
contact respectively at a given temperature, and G! the deflection 
at the end of the first minute at any other temperature, then 
G:G'::g9:4'; g' will be the deflection at the end of the second 
minute at this temperature. 

By calculating in this way the value of g', and comparing it 
with the actual reading, much more reliance can be placed on the 
value of a test than can be done by correcting for temperature in 
the usual way. We are thus quite independent of temperature 
for knowing whether a cable or core has received the slightest 
injury in manufacture. 

G and g may readily be obtained by testing a core at a fixed 
temperature, as 75° F., which is now done. 

Coils having the same dimensions have rarely the same ratio 
in their resistances on prolonged contact with a battery; but 
when several coils are joined together, the ratio between the de- 
flections for any two successive durations of contact may be ob- 
tained from the reciprocals of the deflections of the several coils. 

In reducing tests of insulation by discharge to measures of 
resistance, it is impossible to obtain but approximations in the 
ordinary way of making the tests. The best way is to charge 
the cable or core for one minute and then note the discharge, 
recharge the core, and take the instantaneous discharge. By 


this method we know exactly the amount of electrification which | 


has been given to a core; but by taking the instantaneous dis- 
charge first, even although contact with the battery is made for 
one minute, we cannot say how much electrification is retained 
in the core. 

When a core is thus connected to a battery for one minute and 
afterwards removed, electrification still takes place, but, of course, 
not precisely as if connected to a battery; for the insulator, in- 
stead of being acted upon by a constant charge, is affected by 
the variable charge consequent upon leakage ; but when the core 
is held free for one minute, it is very easy to ascertain how much 
effect the electrification has had in reducing the loss. 

The amount of electrification retained at any given interval is 
proportional to the quantity of charge remaining at that time. 
‘The longer battery-contact is maintained, the slower will a core 
or cable lose its charge, and conversely. 

In a cable which has been charged by contact with a battery 
for one minute and afterwards held free for one minute, the elec- 
trification will be the same as if, instead of being held free, it had 
been left connected to a battery having the last tension, thus :— 

2G2 


AAA) Mr. T. T. P. B. Warren on Electrification. 


If the discharge after one minute’s contact and one minute’s 
insulation be 180, and the immediate discharge 200, the dura- 
tion of contact being also one minute, the total effect for electri- 
fication at the end of the minute’s insulation will be 95 per cent. 
of what it would have been if connected to the same battery for 
two minutes. 

By taking these considerations into account, the formula of Pro- 


fessor Fleeming Jenkin, R= (-——) x 10°, may be rendered 


K log. = 


strictly applicable for deducing from the loss of static charge in 
time ¢ the resistance for the same period of contact in absolute 
measure, or in terms of that system which makes R and K func- 
tions of each other; and we may expect that the capacity K can 
be eliminated from this formula when R is known, if we can 
determine the constant for electrification for the interval of time 
during which the core is held free. 

In this formula, if the test is performed in the manner here 
indicated, ¢ will be 60, and the value obtained for R will be the 


C 
resistance at the end of the second minute more nearly as 7 aP- 


proaches 1. This resistance has then to be divided by a number 
which expresses the ratio between the first and second minute’s 
contact ; approximately, and on short lengths of core, this may 
be obtained as follows :—Recharge the core, after being kept to 
earth for some hours, maintainig contact with the battery for 
two minutes before noting the loss; then by dividing the per- 
centage of loss in the first experiment by the percentage of loss 
given in the second experiment, we shall obtain a number by 
which, if R be divided, the resistance corresponding to one mi- 
nute’s contact may be found. 

The following ratio expresses the rate of crease in resistance 
on prolonged contact :—Let D be the deflection at the end of the 
first period of contact, and d the deflection at the end of the nth 
period, then D:d::d: deflection at the end of n* minutes; or 
the deflection after the first period of contact is to the deflection 
for any other period of contact as this deflection is to the deflec- 
tion at the period of contact corresponding to the square of the 
intervals. 

I have to acknowledge my obligation to Mr. Hooper for pla- 
cing at my disposal the necessary instruments and cores for the 
subject of this paper. 


[ 445 ] 


LIV. Experimental and Theoretical Researches into the Figures 
of Equilibrium of a Liquid Mass without Weight.—Vighth 
Series. By Professor J. Puateau*, 


Researches into the causes upon which the easy development and 
the persistence of liquid films deyend.—On the superficial ten- 
sion of Liquids.—On a new principle relating to the surfaces of 
liquids. 

N the last series of these researches, while discussing the 

various processes of producing liquid films, I tried to make 
it clearly understood that the production of such films always 
depends upon the cohesion and viscosity of the liquid—the former 
property opposing the rupture, and the second impeding the re- 

lative motion of the molecules when the liquid has reached a 

certain degree of thinness, and thus rendering any further atte- 

nuation of it more slow. I concluded, in consequence, that the 
property of undergoing extension into thin films must belong to 
all liquids, and I tried to show that this is really the case. 

But if all liguids are capable of beimg spread out into thin 
films, they nevertheless present important differences in the 
degree of facility with which the films are formed, and in their 
permanence when produced. Tor example, it is easy to blow 
large bubbles at the end of a pipe with soap and water, but no 
one would think of trying to do so with pure water. The easy ex- 
tensibility of solution of soap and of some other liquids into thin 
films of great size 1s generally ascribed to their viscosity ; but I 
find that viscosity, at least as commonly understood, plays only 
a quite subordinate part in this facility of extension. In fact 
experiments, which will be spoken of further on, show that the 
viscosity of a solution of 1 part of Marseilles soap in 40 parts 
of water, a solution with which bubbles can be blown more than 
25 centims. in diameter at the mouth of a common tobacco-pipe, 
is scarcely greater than that of pure water; moreover one part 
of the same soap in 500 parts of water is sufficient to give bub- 
bles a centimetre in diameter ; and, lastly, the fat-oils, glycerine, 
whether pure or mixed with water, treacle under the same con- 
ditions, and solutions of gum-arabic of various degrees of con- 
centration, liquids which are all of them more viscous than solu- 
tion of soap, are absolutely incapable of being blown into bubbles 
at the mouth of a pipe. We must consequently look elsewhere 
for the cause of the phenomenon: this 1s what I do in the pre- 


* Translated from the Annales de Chimie et de Physique, S. 4. vol. xvii. 
p- 260. For abstracts of the previous series see Taylor’s Scientific Me- 
moirs, vol. iv. p. 16, vol. v. p. 584; and Phil. Mag. (S. 4.) vol. xiv. p. 1, 
vol. xvi. p. 23, vol. xxi. p. 286, vol, xxiv. p. 128, and vol. xxxiu. p. 39, 


4.4.6 Prof. J. Plateau on the Figures of Equilibrium 


sent series; and it will be seen that the cause in question seems 
to reside in the most mysterious properties of liquids. 

I begin by the study of an element the influence of which 
must be regarded as self-evident—namely, the tension of liquid 
surfaces, a curious property whose existence has long remained 
a mere hypothesis. In order to place this matter in a clear 
light, I first of all give an historical sketch of this hypothesis, 
passing in review the researches of Segner, Leidenfrost, Young, 
Hough, MM. Henry, Hagen, Lamarle, Dupré, Van der Mens- 
brugghe, and Quincke; I also recall my general principle in re- 
lation to systems of films, and from the whole I draw the fol- 
lowing conclusions :— 

Ist, tension really exists in every liquid surface, and conse- 
quently in every liquid film; 2nd, this tension is independent of 
the curvature of the surface or of the film ; it is the same through- 
out the whole extent of the same surface, or of the same film, and 
at each point it is the same in all tangential directions; 3rd, it 
is independent of the thickness of the film, at least so long as 
this thickness is not less than twice the radius of the molecular 
attraction; 4th, it varies with the nature of the liquid; 5th, in 
the same liquid it varies in the opposite direction to the tempe- 
rature, but at ordinary temperatures it undergoes only small 
alterations; 6th, we possess a great number of processes for mea- 
suring this tension. 

The tension continually tends to break the films; but, accord- 
ing to the third conclusion above, this tendency is no stronger in 
a very thin film than in one that is comparatively thick. Con- 
sequently, if very thin films break im reality more easily than 
thicker ones, it is no doubt because they offer less resistance to 
external causes of rupture, such as movements of the air, slight 
shakings, &c. 

In the case of most liquids, films that are at all large burst as 
soon as they are formed. In order to be able to make observa- - 
tions on films of a great number of liquids, I have therefore been 
obliged to confine myself to films of small size; and I have 
chosen for the purpose of examination the hemispherical bub- 
bles formed at the surface of liquids by the ascent of air, study- 
ing those only the diameter of whose base was between 10 and 
12 milims. When the liquids under examination were more or 
less volatile, hke water, aqueous solutions, alcohol, &c., the obser- 
vations were made in an atmosphere saturated with its vapour ; 
and when, on the contrary, they had a tendency to absorb mois- 
ture, like glycerine, sulphuric acid, &c., they were made in a 
dried atmosphere. 

These experiments have led me to divide liquids, in relation 
to their formation of films, into three principal categories. The 


of a Liquid Mass without Weight. 447 


general characters of the first are the formation of little or no 
froth when shaken, the incapability of being blown into bubbles, 
the absence of colours on the hemispheric bubbles, or a tardy 
and only incipient coloration, showing only the red and green of 
the last orders. Among the numerous liquids which belong to 
this category, I may mention water, glycerine, sulphuric and 
nitric acids, ammonia, saturated solutions of tartaric acid, nitrate 
of potassium, carbonate of sodium, and chloride of calcium. 

The liquids of the second category are distinguished from the 
preceding by the prompt and decided coloration of their films, 
showing tints of all the orders. These liquids are the fat 
oils, lactic acid, glacial acetic acid, oil of turpentine, alcohol, 
benzine, Dutch liquid, chloroform, sulphuric ether, sulphide of 
carbon*, and no doubt many more. 

The liquids which belong to the third category are covered 
over, when shaken, with an abundant and very persistent froth ; 
they can be easily blown into bubbles at the end of a pipe; the 
hemispherical bubbles which they form last much longer than 
those formed by the liquids of the two preceding categories, usu- 
ally for several hours, and sometimes even for several days. They 
have generally at first a well-marked colourless phase, the dura- 
tion of which differs much in different liquids; they then become 
gradually coloured, but in a way which varies somewhat with 
the nature of the liquid. 

This category is not numerous: if we take away some sub- 
stances which are only liquid when hot, such as glass, it is re- 
duced essentially, I think, to the solutions of different kinds of 
soap, of saponine, and albumen, to which may be added solution 
of sesquiacetate of iron. 

In order not to make this abstract too long, I omit aseries of 
curious facts that have been met with in the course of the expe- 
riments, and an account of which will be found in the memoir. 
I pass on to the deductions which have an immediate bearing 
upon the question [ am discussing. 

We have seen that films of the second category assume, im- 
mediately on their formation or very soon afterwards, bright 
colours belonging to all the orders; whence we must conclude 
that they get thinner with extreme rapidity. 

We have seen also that there is never an immediate or nearly 
immediate coloration in the films of the first category : the very 
great majority remain colourless till they break; in the very 
rare cases in which such films do become coloured, this does 


* At ordinary temperatures, the hemispherical bubbles of sulphide of 
carbon, which last only a fraction ofa second, do not exhibit colours; but 
at a few degrees below zero a bright coloration may be observed on some 


of them. 


4.48 Prof. J. Plateau on the Figures of Equilbrium 


not happen till after several seconds, sometimes not till after 
two minutes. It evidently follows from this that in this cate- 
gory, on the contrary, the diminution of thickness is very slow. 

Again, we have seen that the films of the third category have 
generally a long colouriess phase, and that the coloration that 
appears afterwards never changes quickly. It follows from this 
that in the third category, as im the first, the diminution of 
thickness takes place very slowly. 

This great difference in the rapidity with which films of the 
second category diminish in thickness as compared with those of 
the other two, cannot be attributed to ordinary viscosity ; for 
the fat oils and lactic acid, for instance, which belong to the 
second category, are much more viscous than most of the liquids 
belonging to the first and second; oil of turpentine, again, 
which belongs to the second category, is more viscous than 
water, which belongs to the first, &c. Now the distinguishing 
character of a film is the great extent cf its surfaces in proportion 
to its volume ; we are consequently forced to recognize here an 
effect depending on the faces of the film, and to look for the 
cause of the great difference in question in a viscosity peculiar 
to the superficial layers, and independent, or nearly so, of the 
internal viscosity, and which is very weak in the liquids of the 
second category, but, on the contrary, is very strong in those of 
the first and third. 

This principle being admitted, let us apply it to the pheno- 
mena. ‘Take a hemispherical bubble at the moment of its for- 
mation, and let us fix our attention upon one of the two faces 
of the film, on the convex face, for example, and let us imagine 
it divided into horizontal molecular rings from the summit to 
the base. All these rings descend, and consequently each of 
them goes on always increasing in diameter; this implies that 
its molecules separate further from each other, and that other 
molecules belonging to the subjacent layer come and place them- 
selves in the intervals, so as to reestablish a uniform arrange- 
ment. This must evidently apply also to the concave face. Let. 
us now consider one of these molecular rings at the moment of 
its departure from the summit; it is clear that for any small 
space traversed there is a great increase of the distances between 
the molecules of this ring ; and it will be easily admitted be- 
sides that these movements are not performed with mathematical 
regularity, and hence that in the same ring the intervals between 
the molecules are not all absolutely equal. This being admitted, 
let us suppose that from some cause or other an obstacle inter- 
feres with the free arrival of the subjacent molecules into the 
intervals ; one or other of these will in this case soon become so 
great that the attraction of the molecules which it separates 


of a Liquid Mass without Weight. 449 


is no longer able to counterbalance the tension ; these mole- 
cules will then easily drag after them their inside neighbours, 
which will thus be separated in their turn also; the sepa- 
ration will gradually get deeper and deeper, and the film will 
break at this point. Now in hemispherical bubbles of the first 
category the superficial layers have, according to my principle, a 
very great viscosity, so that molecular movements take place 
with difficulty ; hence it is intelligible that very near to the 
summits of either of the faces an increased molecular interval 
may not have time to be filled up before the tension, if at all 
energetic, causes rupture as above. Such is, in my opinion, the 
explanation, of the breaking of nearly all the bubbles of the first 
category before any coloration is visible upon them. 

It will now be seen why it is impossible to blow bubbles with 
films of this category—namely, because the film cannot extend 
im consequence of the blowing, unless the molecules of its two 
faces get continually further apart, thus making room in the 
intervals between them for molecules nearer the inside of the 
film, and giving numerous opportunities for the film to break. 

In the films of the second category the rupture must be in- 
comparably more rare. In this case, according to my principle, 
the molecular mobility of the superficial layers is very great, 
and consequently there is little hindrance to the movement of 
the interior molecules into the widened intervals between those 
at the outside; hence films of this category become im a very 
short time extremely thin. This rapid attenuation teaches us 
why we cannot succeed in blowing bubbles with these liquids 
any more than with those of the preceding category. When we 
have taken up a plane film at the end of the pipe, the suction 
due to the small quantity of liquid which adheres to the circum- 
ference of the pipe-bowl, and the descent of the liquid due to 
the mouth of the pipe not being held perfectly horizontal, make 
a film of this kind almost instantaneously so thin that it often 
bursts by the unavoidable movements of the hand before it is 
possible to put the pipe to one’s mouth ; and when this does not 
happen, the bulging of the film produced by blowing and the 
descent of the liquid towards the lowest point soon bring about 
the same result. 

We now come to the third and most important category, that 
of the liquids which admit of being blown into bubbles. Here, 
as in the first category, the superficial layers have but little mo- 
lecular mobility, so that such films become thinner only slowly ; 
but they seldom break, because, notwithstanding the descent of 
the liquid and the effect of the blowing, the films subsist and 
are capable of undergoing great extension. Ifthe ideas above 
explained be admitted, we must conclude that in liquids of the 


450 Prof, J. Plateau on the Figures of Equilibrium 


present category the tension is insufficient to cause rupture; 
and this is supported by a comparison of the respective tensions 
of water and of our solution of Marseilles soap: the tension of 
a film of water at the common temperature is 14°6, and that of 
a film formed by a solution containing one part of Marseilles 
soap to forty of water is only 5°64°, or between one-half and 
one-third of the former. 

Nevertheless, in order that a liquid may be capable of exten- 
sion into bubbles, it is not indispensable that the tension should 
be absolutely weak, if only it is so in comparison with the vis- 
cosity of the superficial layers, or, in other words, if the ratio 
of the superficial viscosity to the tension be sufficitntly great. 
For instance, while the tension of a film of soap-water, as we have 
just seen, is only 5°64, that of a film of a solution of albumen, 
made by adding a tenth of its volume of water to white of egg, 
is 11°42, or twice as great ; but in hemispherical bubbles of soap 
the colourless phase is at most twenty seconds, while in those of 
albumen it lasts several hours. Thus when we pass from the 
first of these liquids to the second, the tension, or the force tend- 
ing to break the films, becomes double; but the resistance to rup- 
ture increases at the same time, in consequence of the greater 
viscosity of the superficial layers, and thus solution of albumen 
stretches out into bubbles like soap, but to a less degree. 

Such is the theory which I propose as a solution of the 
principal question treated of in the present series of these re- 
searches. In order that a liquid may be capable of forming 
large and persistent films, and may consequently admit of bemg 
blown into bubbles, it is necessary, in the first place, that the 
viscosity proper to the superficial layers of its films should be 
great, in order that the diminution of thickness may take place 
slowly ; it is also needful that the tension should be relatively 
small, in order that it may not overpower the resistance opposed 
by the above viscosity to the rupture of the film, when, in con- 
sequence of superficial movements, a more than ordinary sepa- 
ration of the molecules occurs. I have shown, however, by rea- 
soning which is too long to be dwelt upon here, that the ratio 
between superficial viscosity and tension, which makes the for- 
mation of bubbles possible, must be greater in proportion as the 
superficial viscosity 1s greater. 

I next pass to a series of facts in support of this theory. I 
have tried, in the first place, to prove by direct experiments the 
existence of a viscosity peculiar to the superficial layers, and the 
variations which it presents in different liquids. The following 
is, in substance, the method of experimenting that I adopted, 
and which I found perfectly successful. 

* These tensions are expressed in milligrammes per millimetre of length. 


of a Liquid Mass without Weight. | 451] 


A pivot, 25 millims. high, carrying a magnetized needle 10 
centims. long, was fixed at the centre of a cylindrical glass dish, 
11 centims. in internal diameter and 6 centims. deep. In making 
an experiment, the liquid to be examined was poured into the 
dish until it just came up to the lower face of the needle ; next, by 
means of a bar-magnet, the needle was turned through 90° from 
the magnetic meridian, and kept in that position until the surface 
of the liquid had again become motionless ; then the bar-magnet 
was suddenly removed and the time observed that the needle 
took in traversing a given angle: in my experiments this angle 
was 85°. When this time had been observed, more liquid of 
the same kind was added until the needle was covered to a depth 
of about 2 centims., the interior of the cap of the needle was 
freed from the small quantity of air which it contained, and 
under these new conditions the time occupied by the needle in 
traversing the angle of 85° was determined as before. 

Experiments of this kind were made with five liquids of the 
first category, namely, water, glycerine, and saturated solutions 
of carbonate of sodium, nitrate of potassium, and chloride of 
calcium. Now, although it would seem that the needle must 
experience about twice as little resistance at the surface of the 
liquid as it does in the interior, nevertheless for each of the 
above liquids its velocity was much less in the former case than 
it was in the second. With water, for instance, in one series of 
observations the mean time occupied in traversing 85° at the 
surface was 4°59 seconds, while in the interior it was only 2°37 
seconds. Consequently it is evidently necessary to assume that 
the surface of these liquids opposes a special resistance to the 
movement of the needle, or, in other words, that the superficial 
layer possesses a viscosity proper to itself and much greater 
than the interior viscosity. We may add that if, while the 
needle is kept at the surface at an angle of 90° from the mag- 
netic meridian, any very small light body, such as the smallest 
fragment of gold leaf, is laid on the surface of the liquid in 
the meridian, on setting the needle free, this small body is seen 
to be displaced and to move in the same direction as the needle, 
whence it follows that the whole surface of the liquid turns to- 
gether with the needle. 

Five liquids of the second category, namely, alcohol, oil of 
turpentine, olive-oil, sulphuric ether, and sulphide of carbon, 
were tried in the same way; and for each of these the velocity 
was, on the contrary, greater at the surface than in the interior, 
With alcohol, for example, the average time occupied by the 
needle in traversing 85° was 1°48 second at the surface, and 
3°30 in the interior. Moreover, in the case of these liquids, a 
small body floating on the surface in the magnetic meridian 


452 Prof. J. Plateau on the Figures of Equilibrium 


was in no way disturbed by the movement of the needle, which 
simply came and struck against it. It follows from this that in 
liquids of the second catecor y the superficial layer has not any 
ereater viscosity than the interior; but I have shown that in reality 
it has less. I will confine myself here to citing a single fact 
bearing on this point. If the experiment of a small floating 
body is made with a mixture of equal volumes of water and 
alcohol, the body is simply struck by the needle; thus the ex- 
cess of superficial viscosity possessed by the water is completely 
destroyed by the presence of the alcohol. It therefore follows 
that the superficial layer of the latter must be less viscous than 
the interior, or, if | may so express myself, that 1t possesses a 
negative excess of viscosity which neutralizes the positive excess 
belonging to the water. 

Lastly, five liquids of the third category were tried, namely, 
solutions of Marseilles soap, soft household soap, resin soap, 
saponine, and albumen, and showed, like those of the first ca- 
tegory, a superficial viscosity much greater than the interior 
viscosity. One of them (solution of saponine) yielded in this 
respect extraordinary results; its superficial viscosity is ex- 
tremely strong: the necdle placed at 90° from the magnetic 
meridian and then left free remains in this position, as if the liquid 
were covered with a solid pellicle; but yet it is impossible to 
detect by any means the presence of such a pellicle. Solution of 
albumen shows a similar behaviour, but in a less degree. 

Thus the results obtained by means of the magnetic needle in 
regard to the fifteen liquids that | have submitted to this kind 
of trial, fully confirm the consequences drawn from the experi- 
ments on the hemispherical films; we may therefore, I think, 
look upon the following principle as fully established :— 

The superficial layer of liquids has a proper viscosity, indepen- 
dent of the viscosity of the interior of the mass. In some liquids 


this superficial viscosity is greater than the internal viscosity, and | 


often much greater, as in water and, especially, in solution of sapo- 
nine ; in other liquids, on the contrary, it 1s less than the internal 
viscosity, and often much less, as in oil of turpentine, alcohol, &c. 

The idea of a viscosity proper to the superficial layer of liquids 
had already been put forward by M. Hagen; but he seems to 
consider that this viscosity is greater in all liquids than the 
internal viscosity. 

In order to be able to form a definite estimate of the relations 
between superficial viscosity and tension, we should require to 
have some accurate means of determining the numerical values 
of the first of these elements, in the same way as those of the 
second are determined. I have tried without success to find an 
accurate method for this purpose; but I have shown that, in the 


ee 


of a Liquid Mass without Weight. 453 


case of those liquids of the first and third categories in which 
the superficial viscosity does not greatly exceed that of water, 
we may adopt as approximate relative values the ratios between 
the times occupied by the movement of the magnetic needle at 
the surface and in the interior; a small correction, however, 
must be applied to this ratio in the case of liquids like glycerine, 
in which the internal viscosity is very great. I have therefore 
calculated these ratios; then representing the superficial visco- 
sity of water by 100, I have expressed those of the other liquids 
in the same units; and, lastly, I have divided the numbers so 
obtained by the respective tensions of the films, and have thus 
formed the two Tables which follow :— 


First Category. 


: : Ratio of superfi- 
Liquids. Beene) alee cal viscosity 
o tension. 
Wi diisiee cere nccccctonescs-se-80e 100-00 14-60 6°85 
Prieé’s glycerine «:............. 60°42 8:00 7°95 
Carbonate of sodium (saturated, 91-14 8-56 10-65 
SURGE WRI) ese cac ta caesesncus 
Nitrate of potassium (saturated 96°35 11-22 $59 
SLE TI) BeOS RRA Oe ener | 
Chloride of calcium (saturated, 90-62 11-06 8-19 
uD) - ¢ ict SAREE BROCE SET eee | 
= NX 
Third Category. 
Solution of Marseilles soap,1:40 94:79 5°64 16°81 
,», -soft household soap,1 : 30 96:95 6°44 14:96 
», potash resin-soap ......... §4°89 7°68 11-05 
Not determined, Not determined, 
», Saponine 1:100 ...... but extremely 8:74 but extremely 
great. great. 
PMD DUUTHCT I a. do o0 a. «a0. 65 «ocho Idem. 11-42 Idem. 


It will be seen, on looking at these Tables, that the ratios of 
superficial viscosity to tension are all greater for the liquids of 
the third category (that is to say, for those which yield bubbles 
and a copious froth) than for those of the first category, and 
moreover that, with a single exception, the difference is con- 
siderable. 

In the second place, of the liquids in the first Table, that one 
for which the ratio of these two elements has the highest value 
(namely solution of carbonate of sodium) is precisely the one 
which, when shaken in a flask, yields the most perceptible froth ; 
we may therefore suppose that if a saturated solution of carbonate 
of sodium is incapable of forming bubbles, it is not so far from 
having that property as the four other liquids. : 


454 On Figures of Equilibrium of a Liquid Mass without Weight, 


In the third place, among the liquids of the second Table, 
the one which shows the smallest ratio is solution of resin-soap, 
and this is also the liquid in which bubbles attain the smallest size. 

The small difference will no doubt be observed between the 
ratios 10°65 and 11-05, belonging respectively to solution of car- 
bonate of sodium, which does not admit of being blown into 
bubbles, and to solution of resin-soap which does yield bubbles 
up to a certain diameter. But this, again, is a consequence of 
our theory; in fact, according to our Tables, the superficial vis- 
cosity is smaller in the second of these liquids than in the first, 
and, as I have stated above, the ratio at which the formation of 
bubbles first becomes possible is higher the greater the super- 
ficial viscosity. Itis therefore intelligible that, if the ratio 11-05 
for resin-soap allows of the formation of bubbles of moderate 
size, this same ratio (and still less the somewhat smaller ratio 
10°65) will not allow of the formation of bubbles in solution of 
carbonate of sodium. 

Lastly, my theory leads me to a complete explanation of the 
long persistence of bubbles blown with the glycerine-solution, 
as well as of the singular property possessed by the film which 
forms them of not diminishing in thickness beyond a certain 
degree, and then increasing in thickness again. In the first 
place, I endeavour to find the approximate value of the superficial 
viscosity of the liquid in question, and I find it equal to 80°25, 
whence it will be seen that it is distinctly less than that of water ; 
the tension of the films is the same as for solution of soap, 
namely 5°64; hence for the ratio of these two elements in the 
elycerine-solution we have the number 14°22, Bearing in mind 
the comparatively low value of the superficial viscosity of the 
glycerine-solution, this ratio may be looked upon as high, and 
is much greater than is needful for the formation of bubbles; 
accordingly the glycerine-solution yields very large bubbles. 

But this liquid absorbs moisture from the air, and consequently, 
when a bubble has been blown with it, the film is subject to two 
opposite influences—namely, that of weight which tends to make 
it thinner, and that of absorption, which tends to thicken it, 
The former predominatesat first, and the film gets thinner; but 
the descent of the liquid becomes slower through two causes— 
first, the diminution of the mass, and, secondly, the gradual ab- 
sorption of moisture, which renders the liquid more aqueous and 
thus approximates its viscosity to that of water, It follows that 
soon the descent of the liquid becomes so slow that the augmen- 
tation of thickness due to absorption predominates. As regards 
the tension, M. Dupré has found that in solution of soap it 
varies extremely little with the proportion of water; and this 
probably holds good for the glycerine-solution also. 


Dr. Odling on a Theory of Condensed Ammonia Compounds. 455 


Thus, on the one hand, in consequence of the continual ab- 
sorption of aqueous vapour, the film can never at any phase of 
its existence become very thin ; and, on the other hand, the ratio 
between superficial viscosity and tension remains great enough 
to render the rupture of the film difficult, until the proportion 
of water assimilated by it has become very great. 

I conclude by showing that in relation to the ready develop- 
ment of large films and the persistence of them, the part played 
by cohesion is subsidiary to that played by internal viscosity. In 
fact, for different liquids, the cohesion is known to vary in the 
same direction as the coefficient of the sum of the curvatures in 
the expression for the capillary pressure—a coefficient which, 
according to the researches of M. Hagen and M. Dupré,is nothing 
else than the tension; and since this latter is much weaker in 
soap-water than in pure water, the same is necessarily true for 
the cohesion also; but, notwithstanding, solution of soap yields 
enormous bubbles, while water does not yield any. 


LV. Note on a Theory of Condensed Ammonia Compounds. 
By Wit11aM Opuiine, M.B., F.RS* 


HE unit of ammonia, N H?, has the well-known property 

of combining with the unit of hydrochloric acid, HCl, to 

form a unit of the more complex body sal-ammoniac, HCI,NH?. 

Hypothetical methylene being regarded as the analogue of 

ammonia, chloride of methyle will be the hydrochloride of me- 

thylene, corresponding to sal-ammoniac or hydrochloride of am- 
monia, 


HCILCH2, HCl,NH®. 


But this chloride of methyle or hydrochloride of methylene is 
known to be the first term of a series of compounds, the earlier 
terms of which are formulated below. In a parallel column are 
written the formule of what, if they existed, would form a similar 
series of sal-ammoniac compounds :— 


Chloride of methyle HCl,C H? HCl, N H® 
rh ethyle HCl, C? H? Hel Ne 6 
3 propyle HCl, C°H® HCl, N? H9 
bs butyle HCl, C*H® HCl, N+ H?? 
ne aunyle; PELCL C> Et? HCl, N° H' 
&e. &e. 


Substituting an equivalent of metallic chloride for chloride of 
hydrogen in the sal-ammoniac series, we have the following 


* Communicated by the Author, 


456 Dr. Odling on a Theory of Condensed Ammonia Compounds. 


compounds, all of which, and many like them, are fairly well 
known :— 


Z : 
Cl, N Ty? 
AgCl, N? H®, 
“Cl, N39, 
“ Ol, NAH. 
Chemists who express the composition of the chlorides of 
ethyle and butyle as underneath, may express the composition 


of the ammoniated chlorides of silver and calcium in a similar 
fashion ; thus— 


Cl, C H? Cl, C H? Cl, N H3 Cl, N H3 
| | | 

H, CH? CH Ag, NH N He 
| | 

C H? N H? 
| Cael 

H, CH CoN HS 


The polyammoniated salts are all more or less unstable. It 
is observable, however, that the diammonia compounds are 
habitually less unstable than their more highly ammoniated 
congeners, and coincidently that in the diammonia compounds 
alone is it possible for each unit of ammonia to be combined 
directly with a constituent of the hydrochloric acid or of its re- 
presentative metallic chloride. 

The superior solubility of diammonia compounds is especially 
recognizable in the case of the best-characterized metal-ammonia 
bases, such as platinamine and platosamine. In the salts which 
these and such like bases form with hydrochloric acid, a portion 
of the hydrogen of the ammonia, instead of the hydrogen of the 
hydrochloric acid, would appear to be replaced by its equivalent 
of metal. 

Still employing the equivalent method of notation, hydrochlo- 
ride of platosamine (the yellow salt) would be represented thus: 


HCl, NH? 


This salt very readily absorbs another unit of ammonia, and 
thereby forms the hydrochloride of diplatosamine, 


H, NH? 
| 
Cl, NH? » 


HCl, N?H®=t, or 


Notices respecting New Books. 457 


from which, as is well known, ammoniais not liberable by treat- 
ment of the salt with potash, or by its desiccation at upwards of 
100°. The base N? H®*!, 
state, as upon the above view of the cause of its stability it 
scarcely should be, is yet transferable from one salt to another 
by double decomposition with almost as much facility as am- 
monia itself, 

What I conceive to be the constitution of the different plati- 
nous and platinic ammonia compounds in relation to each other, 
is indicated in the last chapter of my ‘ Outlines of Chemistry,’ 
just published. 

It is observable that in no stable metallicized ammonia hydro- 
chloride is the number of nitrogen atoms more than double the 
number of chlorine atoms in the salt. Thus the empirical for- 
mul of the purpuro-cobaltic and luteo-cobaltic chlorides are 
Co? CI®, LJONH®, and Co? Cl®, 12 NH® respectively. These ex- 
pressions are of course easily translatable into forms harmoni- 
zing with the above suggested view of the constitution of con- 
densed ammonia compounds. 


though not procurable in the free 


— 


LVI. Notices respecting New Books. 


Methods of teaching Arithmetic. A Lecture addressed to the London 
Association of Schoolmistresses. By J. G,. Fircu, M.A. Pp. 81. 
London, 1869. 

The School Arithmetic. By J. Cornnwett, Ph.D., and J. G. Fircu, 
M.A. Pp. 144. Tenth edition. London, 1869. 

The Science of Arithmetic. By J. Cornnwett, Ph.D., and J. G. Frrcn, 
M.A. Twelfth edition. Pp.372. London, 1868. 


WE have put these books together at the head of a short notice 

on account of their common authorship, and of their being 
more or less supplementary to each other. The first of them (the 
lecture on methods of teaching arithmetic) contains many hints and 
remarks likely to be useful to the audience to which it was addressed. 
The point most dwelt on is the need of making learners understand 
the ultimate reasons of the rules for performing the elementary ope- 
rations of arithmetic, such as the rules for multiplication and division 
of integers. We doubt whether the importance of this point is not 
somewhat exaggerated. Any ordinary child of nine or ten years 
can be brought to divide, for instance, 5382 by 23 correctly, and be 
made to understand what is meant by the answer, viz. that if 5382 
marbles were divided equally between 23 boys, each boy would get 
234 marbles. But to make the child understand each separate step 
of the process of the division is quite another matter. And though 
much can be done by a good teacher by means of a discussion of 
particular examples, yet we question whether any but a few ex- 


Phil. Mag.S8. 4. Vol. 88. No. 257. Dec. 1869. 2H 


458 Notices respecting New Books. 


ceptional children of the above age could be brought to know much 
more about long division than that it is a process leading to a certain 
result. Nor does this to any serious extent diminish the value of the 
intellectual training which a child goes through in the study of 
arithmetic. ‘That training is undergone by means of particular ex- 
amples. Thus, let the question proposed be this :—‘‘ A watch gains 
uniformly 13 seconds a day. It is 2 minutes 10 seconds slow on a 
certain day, by how much will it be fast at the end of three weeks ?” 
The reasoning by which a child arrives at the answer is quite inde- 
pendent of his knowledge of the ultimate reasons of the processes 
of multiplication &c. that he employs. 

We suppose that in reality Mr. Fitch’s opinion is not very differ- 
ent from ours; for we find that in the book for children, of which he 
is the joint author (the ‘School Arithmetic’), no more is attempted 
than the statement and illustration of rules. The method of the 
book is this :—In each section a typical example is given and its so- 
lution reasoned out step by step; then follow a general rule, 
another example worked out by the rule, and finally many examples 
of the rule are given for practice. Of the examples some are such as 
can be worked mentally, others, involving larger numbers, are to be 
worked on slate or paper. This classification of the examples seems 
to us a very valuable feature of the book; and the work altogether 
seems a very good school arithmetic. If we were to hint a fault, 
it would be that, to secure cheapness, a paper and type are used 
likely to prove hurtful to young eyes. 

The third work on the list (the ‘Science of Arithmetic’) is one of 
more pretensions. It aims at imparting a systematic acquaintance 
with the principles as well as the rules of arithmetic. The authors 
have evidently bestowed much labour and thought upon the work, 
and have produced a book from which a teacher of arithmetic would 
doubtless learn much. The characteristic defect of the book is a 
want of precision of statement, which sometimes contrasts quite 
curiously with the air of laborious and systematic accuracy which 
pervades the book: e. g. the authors mark out nineteen arithmetical 
facts as axioms. Now, if we are justified in demanding precision in 
any statement, it is In an axiom; yet here is one, Axiom XV. 
p. 85 :—‘‘ If the dividend and divisor be either both increased or both 
diminished the same number of times, the quotient remains un- 
altered.” What the authors intend is pretty plain ; but if they were 
held to what they say, it would follow that the quotient of 12 divided 
by 6 might be the same as that of 9 divided by 38. In short, num- 
bers may be increased or diminished in other ways than by taking 
equimultiples of both or dividing both by a common factor, which is 
what they mean by increasing or diminishing the dividend and divisor 
a certain number of times. ‘This is by no means a solitary instance 
of an inexactness which seriously diminishes the value of a book in 
many respects well executed. 


[ 459 | 


LVIL. Proceedings of Learned Societies. 
ROYAL SOCIETY. 
[Continued from p. 399.] 
June 17, 1869.—Lieut.-General Sabine, President, in the Chair. 


(THE following communication was read :— 
“ Additional Observations on Hydrogenium.” By Thomas 
Graham, F.R.S., Master of the Mint. 

From the elongation of a palladium wire, caused by the occlu- 
sion of hydrogen, the density of hydrogenium was inferred to be a 
little under 2. But it is now to be remarked that another number 
of half that amount may be deduced with equal probability from 
the same experimental data. This double result is a consequence of 
the singular permanent shortening of the palladium wire observed 
after the expulsion of hydrogen. Ina particular observation formerly 
described, for instance, a wire of 609-14 millims. increased in length 
to 618°92 millims. when charged with hydrogen, and fell to 599°44 
millims. when the hydrogen was extracted. The elongation was 
9°78 millims., and the absolute shortening or retraction 9°7 millims., 
making the extreme difference in length 19°48 millims. The elon- 
gation and retraction would appear, indeed, to be equal in amount. 
Now it is by no means impossible that the volume added to the 
wire by the hydrogenium is represented by the elongation and re- 
traction taken together, and not by the elongation alone, as hitherto 
assumed. It is only necessary to suppose that the retraction of the 
palladium molecules takes place the moment the hydrogen is first 
absorbed, instead of being deferred till the latter is expelled; for 
the righting of the particles of the palladium wire (which are in 
a state of excessive tension in the direction of the length of the 
wire) may as well take place in the act of the absorption of the 
hydrogen as in the expulsion of that element. It may indeed 
appear most probable in the abstract that the mobility of the pal- 
Jadium particle is determined by the first entrance of the hydrogen, 
The hydrogenium will then be assumed to occupy double the space 
previously allotted to it, and the density of the metal will be reduced 
to one half of the former estimate. In the experiment referred 
to, the volume of hydrogenium in the alloy will rise from 4°68 per 
cent. to 9°36 per cent., and the density of hydrogenivm will fall 
from 1°708 to 0°854, according to the new calculation. In a series 
of four observations upon the same wire, previously recorded, the 
whole retractions rather exceeded the whole elongations, the first 
amounting to 23°99 millims., and the last to 21°38 millims. Their 
united amount would justify a still greater reduction in the density 
of hydrogenium, namely to 0°8051. 

The first experiment, however, in hydrogenating any palladium 
wire appears to be the most uniform in its results. The expulsion 
of the hydrogen afterwards by heat always injures the structure of 
the wire more or less, and probably affects the regularity of the ex- 
pansion afterwards in different directions. The equality of the ex- 
pansion and the retraction in a first experiment appears also to be 


2H 2 


4.60 Royal Society:— 


a matter of certainty. This is a curious molecular fact, of which 
we are unable as yet to see the full import. In illustration, another 
experiment upon a pure palladium wire may be detailed. This 
wire, which was new, took up a full charge of hydrogen, namely 
956°3 volumes, and increased in length from 609°585 to 619:354 
millims. The elongation was therefore 9'769 millims. With the 
expulsion of the hydrogen afterwards, the wire was permanently 
shortened to 600°115 millims. It thus fell 9°470 millims. below its 
normal or first length. The elongation and retraction are here within 
0-3 millim. of equality. The two changes taken together amount to 
19°239 millims., and their sum represents the increase of the wire 
in length due to the addition of hydrogenium. It represents a 
linear expansion of 3°205 on 100, with a cubic expansion of 9°827 
on 100. The composition of the wire comes to be represented as 
being, 


In volume. 
Palladiomas feet ant. et Ee 100:000 or 90°895 
Eby diogeminn asl. e045 etek e 9°827 or 9°105 


109°827 or 100:000 

The specific gravity of the palladium was 12°3, the weight of the 
wire 1°554 grm., and its volume 0°126 cub. centim. The occluded 
hydrogen measured 120°5 cub. centims. The weight of the same 
would be 0:0108 grm., and the volume of the hydrogenium 0°012382 
cub. centim. (100: 9°827:: 0°126:0°01238). The, density of the 
hydrogenium is therefore 

0:0108 

0°01238 


This is a near approach to the preceding result, 0°854. Calculated 
on the old method, the last experiment would give a density of 1:708. 

It was incidentally observed on a former occasion that palladium 
alloyed with silver continues to occlude hydrogen. This property 
is now found to belong generally to palladium alloys when the second 
metal does not much exceed one half of the mixture. These alloys 
are all enlarged in dimensions when they acquire hydrogenium. It 
was interesting to perceive that the expansion was greater than 
happens to pure palladium (about twice as much), and that, on after- 
wards expelling the hydrogen by heat, the fixed alloy returned to 
its original length without any further shortening of the wire. The 
embarrassing retraction of the palladium has, in fact, disappeared. 

The fusion of the alloys employed was kindly effected for me by 
Messrs. Matthey and Sellon—when the proportion of palladium was 
considerable, by the mstrumentality of M. Deville’s gas-furnace (in 
which coal-gas is burned with pure oxygen), or by means of a coke- 
furnace when the metals yielded to a moderate temperature. The 
alloy was always drawn out into wire if possible; but if not suffi- 
ciently ductile, it was extended by rolling into the form of a thin 
ribbon. The elongation caused by the addition of hydrogenium was 
ascertained by measuring the wire or ribbon stretched over a gra- 
duated scale, as in the former experiments. 

1. Palladium, Platinum, and Hydrogenium.—Palladium was fused 


=0°872. 


Mr. T. Graham on Hydrogenium. 461 


with platinum, a metal of its own class, and gave an alloy consisting, 
according to analysis, of 76°03 parts of the former and 23°97 parts 
of the latter. This alloy was very malleable and ductile; its specific 
gravity was 12°64. Like pure palladium, it absorbed hydrogen, 
evolved on its surface in the acid fluid of the galvanometer, with 
great avidity. 

A wire 601°845 millims. in length (23°69 inches) was increased 
to 618°288 millims., on occluding 701°9 volumes of hydrogen gas 
measured at 0° C. and 0°760 barom. This is a linear elongation of 
16°443 millims. (0°6472 inch), or 2°732 on a length of 100. It 
corresponds with a cubic expansion of 8°423 volumes on 100 vo- 
lumes ; and the product may be represented— 


In volume. 
ixcoemetals.. 66 Jose0 cee ..- 100°000 or 92°225 
PemnOcenmuna, Oy. .l cet ye.) oO  B423'or” °7°7 79 


108423 or 100-000 


The elements for the calculation of the density of hydrogenium 
are the following, the assumption being made as formerly, that 
the metals are united without condensation :— 


Original weight of the wire 4°722 grms. 

Original volume of the wire 0°373 cub. centim. 

Volume of the hydrogen extracted 264°5 cub. centims. 

Weight of the hydrogen extracted, by calculation, 0:0237 grm. 


The volume of the hydrogenium will be to the volume of the 
wire (0°373 cub. centim.) as 100 is to 8°423—that is, 0°03141 
cub. centim. Finally, dividing the weight of the hydrogenium by 
its bulk, 0°0237 by 0:03141, the density of hydrogenium is found 
to be 0°7545. 

On expelling all hydrogen from the wire at a red heat, the 
latter returned to its first dimensions as exactly as could be mea- 
sured. ‘The platinum present appears to sustain the palladium, so 
that uo retraction of that metal is allowed to take place. This alloy 
therefore displays the true increase of volume following the acqui- 
sition of hydrogentum, without the singular complication of the 
retraction of the fixed metal. It now appears clear that the retrac- 
tion of pure palladium must occur on the first entrance of hydrogen 
into the metal; the elongation of the wire due to the hydrogenium 
is negatived thereby to the extent of about one half, and the ap- 
parent bulk of the hydrogenium is reduced to the same extent; 
hydrogenium came in consequence to be represented of double its 
true density. 

The compound alloy returns to its original density (12°64) upon 
the expulsion of the hydrogen, showing that hydrogen leaves with- 
out producing porosity in the metal. No absorptive power for 
vapours, like that of charcoal, was acquired. 

A wire of the present alloy, and another of pure palladium, were 
charged with hydrogen, and the diameters of both measured by a 
micrometer. ‘The wire of alloy increased sensibly more in thickness 
than the pure palladium, about twice as much; the reason is, that 


4.62 Royal Society :— 


the latter while expanding retracts in length at the same time. The 
expansion of both wires may be familiarly compared to the enlarge- 
ment of the body of a leech on absorbing blood. The enlargement is 
uniform in all dimensions with the palladium-platinum alloy ; the 
leech becomes larger, but remains symmetrical. But the retraction 
in the pure palladium wire has its analogy in a muscular contraction 
of the leech, by which its body becomes shorter but thicker in a 
corresponding measure. 

The same wire of palladium and platinum, charged a second time 
with hydrogen, underwent an increase in length from 601°845 to 
618°2, or sensibly the same as before. The gas measured 258-0 
cub. centims., or 619°6 times the volume of the wire. The product 
may be represented as consisting of 


By volume. 


ixed metals s,s. c. s\2\5, 2 of a se ceoleielot a mea 
PEM GRO SCM ncaa bs 2 Sune.es ware ome ors | eS 
100-000 


The density of hydrogenium deducible from this experiment is 
0°7401. The mean of the two experiments is 0'7473. 

2. Palladium, Gold, and Hydrogenium.—Palladium fused with 
gold formed a malleable alloy, consisting of 75:21 parts of the former 
and 24°79 parts of the latter, of a white colour, which could be 
drawn into wire. Its specific gravity was 13:1. Of this wire 601°85 
millims. occluded 464°2 volumes of hydrogen with an increase in 
length of 11°5 millims. This is a linear elongation of 1:91 on 100, 
and a cubic expansion of 5°84 on 100. The resulting composition 
was therefore as follows :— 


In volume. 
Alloy of palladium and gold .... 100 or 94:48 
Piydnocenium ese. Wie ee nee 5°84 or 5ah2 


105°84 100-00 

The weight of the wire was 5°334 grms. 

The volume of the wire was 0°4071 cub. centim. 

The volume of hydrogen extracted, 189-0 cub. centims. 

The weight of the hydrogen, 0°01693 grm. 

The volume of the hydrogenium, 0°02378 cub. centim. 

Consequently the density of the hydrogenium is 0°711. 

The wire returned to its original length after the extraction of 
the hydrogen, and there was no retraction. 

The results of a second experiment on the same wire were almost 
identical with the preceding. 

The elongation on 601°85 millims. of wire was 11°45 millims., 
with the occlusion of 463°7 volumes of hydrogen. This is a linear 
expansion of 1:902 on 100, and a cubic expansion of 5°81 on 100. 
The volume of hydrogen gas extracted was 188°8 cub. centims., of 
which the weight is 0°016916 grm. The volume of the hydrogenium 
was 0°02365 cub. centim., that of the palladium-gold alloy being 
0°4071 cub. centim. Hence the density of the hydrogenium is 0°715. 

In a third experiment made on a shorter length of the sanie 
wire, namely 241-2 millims., the amount of gas occluded was very 


Mr. 'T’. Graham on Hydrogenium. 463 


similar, namely 468 volumes, and was not increased by protracting 
the exposure of the wire for the long period of twenty hours. There 
can be little doubt, then, of the uniformity of the hydrogenium com- 
bination, the volumes of gas occluded in the three experiments being 
464°2, 463-7, and 468 volumes. The linear expansion was 1°9 on 
100 in the third experiment, and therefore similar also to the prece- 
ding experiments. 

The hydrogenium may be supposed to be in direct combination 
with the palladium only, as gold by itself shows no attraction for the 
former element. In the first experiment the hydrogenium is in the 
proportion of 0:3151 to 100 palladium and gold together. This 
gives 03939 hydrogenium to 100 palladium ; while a whole equiva- 
lent of hydrogenium is 0°939 to 100 palladium*. The hydrogenium 
found is by calculation 0°4195 equivalent, or 1 equivalent hydroge- 
nium to 2°383 equivalents palladium, which comes nearer to 2 equi- 
valents of the former with 5 of the latter than to any other proportion. 

To ascertain the smallest proportion of gold which prevents retrac- 
tion, an alloy was made by fusing 7 parts of that metal with 93 parts 
of palladium, which had a specific gravity of 13°05. The button 
was rolled into a thin strip and charged with hydrogen by the wet 
method. An occlusion of 585°44 volumes of gas took place, with a 
lmear expansion of 1:7 on 100. A retraction followed to nearly 
the same extent on afterwards expelling the hydrogen by heat. 

With another alloy, produced by fusing 10 of gold with 90 of pal- 
ladium, the occlusion of gas was 475 volumes, the linear expansion 
165 on 100. The retraction on expelling the gas afterwards was 
extremely:slight. To nullify the retraction of the palladium, about 
10 per cent. of gold appears therefore to be required in the alloy. 

Another alloy of palladium of sp. gr. 13:1, and containing 24°79 
per cent. of gold, underwent no retraction on losing hydrogen, as 
already stated. 

The presence of so much gold in the alloy as half its weight did 
not materially reduce the occluding power of the palladium. Such 
an alloy was capable of holding 459-9 times its volume of hydrogen, 
with a linear expansion of 1°67 per cent. 

3. Palladium, Silver, and Hydrogenium.—The occluding power 
of palladium appeared to be entirely lost when that metal was alloyed 
with much more than its own weight of any fixed metal. Palladium 
alloys containing 80, 75, and 70 per cent. of silver occluded no hy- 
drogen whatever. . 

With about 50 per cent. of silver, pailadium rolled into a thin 
strip occluded 4U0°6 volumes of hydrogen. It expanded 1°64 part 
in 100 in length, and returned to its original dimensions without 
retraction upon the expulsion of the gas. The specific gravity of 
this silver-palladium alloy was 11°8 ; the density of the hydrogenium 
()°727. 

An alloy which was formed of 66 parts of palladium and 34 parts 
of silver had the specific gravity 11°45. It was drawn into wire 
and found to absorb 511°37 volumes of hydrogen. The length of 
the wire increased from 609-601 to 619°532 millims. This is a linear 

7% Fe — | Pd— 1060. 


464. Royal Society. 


elongation of 1°629 on 100, or cubic expansion of 4°97 on 100. 
The weight of the wire was 3°483 grms., its volume 0°3041 cub. 
centim. The absolute volume of occluded hydrogen was 125°1 cub. 
centims., of which the weight is 0:01120896. The volume of the 
hydrogenium was 0°015105 cub. centim. The resulting density of 
hydrogenium is 0°742. 

In a repetition of the experiment upon another portion of the 
same wire, 407°7 volumes of hydrogen were occluded, and the wire 
increased in length from 609°601 millims. to 619°44 millims. This 
is a linear expansion of 1'614 part on 100, and a cubic expansion of 
4-92 on 100. The absolute volume of hydrogen gas occluded was 
124-0 cub. centims., and its calculated weight 001111 grm. The 
volume of the hydrogenium being 0°1496 cub. centim., the density 
of hydrogenium indicated is 0°741. The two experiments are indeed 
almost identical. ‘The wire returned in both experiments to its ori- 
ginal length exactly, after the extraction of the gas. 

4, Palladium, Nickel, and Hydrogenium.—The alloy, consisting 
of equal parts of palladium and nickel, was white, hard, and readily 
extensible. Its specific gravity was 11:22. This alloy occluded 
69°76 volumes of hydrogen, with a linear expansion of 0°2 per cent. 
It suffered no retraction below its normal length on the expulsion of 
the gas by heat. 

An alloy of equal parts of dismuth and palladium was a brittle mass 
that did not admit of being rolled. It occluded no hydrogen, after 
exposure to that gas as the negative electrode in an acid fluid for a 
period of 18 hours. It seems probable that malleability and the 
colloid character, which are wanting in this bismuth alloy, are essen- 
tial to the occlusion of hydrogen by a palladium alloy. 

An alloy of 1 part of copper and 6 parts of pailadium proved mo- 
derately extensible, but absorbed no sensible amount of hydrogen. 
The metallic laminze which remain on digesting this alloy in hy- 
drochlorie acid, and which were found by M. Debray to be a defi- 
nite alloy of palladium and copper (Pd Cu), exhibited no sensible 
occluding power. 

The conclusions suggested as to the density of hydrogenium, by 
the compound with palladium alone and by the compounds with 
palladium alloys, are as follows :— 


Density of 
Hydrogenium observed. 
When unitedwith palladinm ieee bee i eee 0°854 to 0°872 
When united with palladium and platnum .... 0°7401 to 0°7545 
When united with palladium and gold ........ 0-71) “toste7is 
When united with palladium and silver........ 0°727 to 0°742 


The results, it will be observed, are most uniform with the com- 
pound alloys, in which retraction is avoided; and they lie between 
0°711 and 0°7545. It may be argued that hydrogenium is likely 
to be condensed somewhat in combination, and that consequently 
the smallest number (0°711) is likely to be the nearest to the truth. 
But the mean of the two extreme numbers will probably be admitted 
as a more legitimate deduction from the experiments on the com- 


Geological Society. 4.65 


pound alloys, and 0°733 be accepted provisionally as the approxi- 
mate density of hydrogenium. 

I have the pleasure to repeat my acknowledgments to Mr. W. C. 
Roberts for his valuable assistance in this inquiry. 

Could the density of hydrogenium be more exactly determined, it 
would be interesting to compare its atomic volume with the atomic 
volumes of other metals. With the imperfect information we pos- 
sess, one or two points may be still worthy of notice. It will be 
observed that palladium is 16°78 times as dense as hydrogenium 
taken as 0°733, and 17°3 times as dense as hydrogenium taken as 
0-711. Hence, as the equivalent of palladium is 106°5, the atomic 
volume of palladium is 6°342 times as great as the atomic volume of 
hydrogenium having the first density mentioned, and 6°156 as great 
with the second density. To give an atomic volume to palladium 
exactly six times that of hydrogenium, the latter element would 
require to have the density 0°693. 

Taking the density of hydrogenium at 0°7, and its atomic volume 
equal to 1, then the following results may be deduced by calculation. 
The atomic volume of lithium is found to be 0°826; or it is less even 
than that of hydrogenium (1). The atomic volume of iron is 5°026, 
of magnesium 4°827, of copper 4°976, of manganese 4°81, and of 
nickel 4°67. Of these five metals, the atomic volume is nearly 5 times 
that of hydrogenium. Palladium has already appeared to be nearly 
6 times. The atomic volume of aluminium on the same scale is 7°39, 
of sodium 16°56, and of potassium 31°63. 


GEOLOGICAL SOCIETY. 
[Continued from p. 403. | 


April 14th, 1869.—Prof. Huxley, LL.D., F.R.S., President, 
in the Chair. 


The following communications were read :— 

3. “On the Salt-mines of St. Domingo.” By F. Ruschhaupe. 
Communicated by Sir R. I. Murchison, Bart., F.P.G.S. 

The author described the Cerro de Sal, or Salt Mountain of St. 
Domingo. It extends about 3 leagues in length, and consists, ac- 
cording to the author, of rocks “ of the Red Sandstone class ”—which, 
where the chief visible deposits of salt occur, are principally gypsum 
schists, sometimes very argillaceous. The salt is generally surrounded 
by an ash-like mass consisting of gypsum and clay. The author 
compared the gypsum beds with those of the Keuper. The beds are 
thrown into a perpendicular position, and the same change is ob- 
servable for miles in the Savannas. Animmense body of salt, 250— 
300 feet broad, is exposed upon the north side of the mountain. 
The salt is very white and pure, and might easily be conveyed to the 
port of Barahona, about 18 miles distant. 

4, « A description of the ‘ Broads’ of East Norfolk, showing their 
origin, position, and formation in the Valleys of the Rivers Bure, 


Yare, and Wayeney.” By B. B. Grantham, Ksq., C.E., F.G.S8. 


4.66 Geological Society :— 


The author described the general characters of the “ Broads,” or 
shallow lakes of East Norfolk, and indicated their connexion with 
the river-valleys. He regarded them as the last traces of great es- 
tuaries, now cut off from the influence of the sea by upheaval. 

5. “Ona peculiar instance of Intraglacial Erosion near Norwich.” 
By Searles Wood, Jun., Esq., F.G.8., and F. W. Harmer, Esq. 

The authors described the general structure of the valley of the 
Yare near Norwich, in which the fundamental chalk-rock is covered 
by the following drift-beds:—1, the Chillesford sand and clay; 2, 
pebbly sands and pebble-beds; 3, the equivalent of the contorted 
Drift of Cromer; 4, the middle glacial sand; and 5, the Boulder- 
clay. The valley is hollowed out in these beds. Sewer-shafts sunk 
in the bottom of the valley near Norwich have shown the existence 
of an abrupt hole or narrow trough in the chalk, having one of its 
sides apparently perpendicular. This is filled up in part by a de- 
posit of dark-blue clay, full of chalk debris, exactly resembling the 
Boulder-clay at a distance from Norwich, but quite different in 
character from that occurring in the vicinity (No. 5); and this is 
overlain in part by a bed of the middle glacial sand (No. 4), and in 
part by a postglacial gravel. ‘The authors believed that this peculiar 
hole or trough was excavated by glacial action after the deposition 
of the bed No. 3, and that it belongs to the earliest part of the 
middle glacial period. At Sommerleyton Brick-kiln, near Lowestoft, 
a perfectly similar bed occurs between the drift and sand (Nos. 3 
and 4. 

6. “On the Lignite-mines of Podnernuoyo, near Volterra.” By 
K. J. Beor, Esq., F.G.S. 

The author states that the deposit of Lignite at Podnernuovo, 
near Volterra, is of lacustrine origin, and consists of two parallel 
strata of compact coal about 24 metres (=8 feet 4 in.) in thickness, 
separated by a thin stratum of marl, with marl-shells, The lower 
coal-bed lies on a bed of marl with marsh-shells, and the upper bed 
is covered by a marine formation belonging to the Upper Miocene. 
The lignite comes to the surface near the Alberese, where it extends 
for a considerable distance. Some shifts occur, bringing the upper 
bed down nearly to the level of the lower one; the inclination of the 
beds diminishes gradually ; and the intervening stratum of marl de- 
creases in thickness, and probably at last thins out altogether. ‘The 
coal in the upper bed is better than that in the lower one. The 
author remarks that this lignite deposit differs from those of the 
neighbouring valleys in being purely of marsh origin, while they are 
estuarine. 

April 28th, 1869.—Prof. T. H. Huxley, LL.D., F.B.S., 
President, in the Chair. 
The following communications were read :— 


1. “On the Geology and Mineralogy of Hastings County, Canada 
West.” By T. C. Wallbridge, Esq. 

Before describing the gold and iron-ores of Hastings, which formed 
the main subject of this paper, the author introduced a general 
sketch of the geology of the county. After noticing certain local 


Mr. Wallbridge on the Geology of Hastings County, Canada. 467 


deposits of recent origin, he described the extensive accumulations 
of drift-gravels and boulder-clay. A single boulder near the Shan- 
nonville railway-station was said to cover an area of about 5 acres, 
and to have a thickness of 100 feet. The evidences of glacial action 
over the whole country were referred to, and the direction of ice- 
marks cited from several localities. Below the posttertiary deposits 
the rocks consist, in the southern townships, of Lower Silurian lime- 
stones referred for the most part to the Trenton group, and, in the 
northern townships, of a large series of metamorphic rocks, supposed 
to be of Lower Laurentian age. Bosses of syenite and gneiss pene- 
trate the Silurian beds to the south of the main Laurentian mass; 
and several outliers of Trenton limestone point to the former ex- 
tension of the Silurian rocks northwards. All the minerals of eco- 
nomic value are confined to the Laurentian area. 

Gold was first discovered in the county of Hastings in 1866. The 
author described in detail the singular occurrence of the metal at 
the Richardson Mine in Madoc, where it was found in two pockets 
associated with a peculiar black carbonaceous substance, a ferru- 
ginous dolomite, and ochre-brown iron-ore. Assays of the sur- 
rounding rocks showed the existence of gold even at a considerable 
distance from the mine. Mention was also made of several other 
gold mines, in Madoc, Marmora, and Elzevir, from which specimens 
were exhibited, and analyses of ore quoted. 

The iron-ores of Hastings occur partly as magnetic oxide and 
partly as hematite. In addition to the well-known “ Big Ore- 
bed” and the “Seymour bed,” the writer called attention to some 
new localities of magnetic ore in Madoc. ‘The deposit of hematite 
called the ‘‘ Kane Ore-bed” was discovered by the author some 
years back; and from ancient workings in this bed (apparently 
those of the Indians, who may have used the ochre as war-paint) 
he has obtained bone needles and other objects of human workman- 
ship. Attention was then directed to a large deposit of specular 
iron-ore in Hungerford, hitherto undescribed, and to the pyrrhotine 
or magnetic pyrites of Madoc. 

The paper concluded with a notice of the galena and other less 
important minerals of the county. 

2. “On the distribution of Flint Implements in the Drift, with 
reference to some recent discoveries in Norfolk and Suffolk.” By 
J. W. Flower, Esq., F.G.S. 

The author noticed some recently discovered localities in the 
valley of the Little Ouse which have yielded Flint Implements, 
viz.:—at Broomhill, about 350 feet from and 5 or 6 feet above the 
level of the river ; at Gravel Hill, about 1 mile from and 10 feet above 
the river; at Shrub Hill, about 1 mile from and only a foot or two 
above the river ; and at Lakenheath, nearly 3 miles from the river, 
and 60 feetaboveit. In the first three of these localities the worked 
flints are in coarse gravel, resting immediately on the Cretaceous 
beds (chalk in the first and second, gault in the third), and overlain 
by regular deposits of gravel and sand. The implements resemble 
those of Acheul, Thetford, and Salisbury, but present some pecu- 
hiarities, from which the author inferred that each place had its own 


468 Intelligence and Miscellaneous Articles. 


workmen, and that the different forms were intended to answer dif- 
ferent purposes. At Brandon, implements formed of quartzite were 
found in a bed consisting of rounded quartzite pebbles mixed with 
about one-fourth of flints. Flint implements occurred beneath this 
bed. 

The author indicated the geographical characters of the district 
and the peculiarities in the distribution of the flint implements, which 
he regarded as in accordance with the phenomena presented by the 
valley of the Somme ; and he argued from the consideration of all the 
facts that the implements were not transported to their present 
situation by the agency of the rivers in whose valleys they occur, 
but that they were made upon the spot, exposed upon the surface 
with the gravels in which they are found and from which they were 
made, and finally covered up by the river-gravels and sandy beds 
which now overlie them. 


LVIII. Pareipenre and Misvelanevis Articles. 


ON THE EXTENSION OF LIQUIDS UPON EACH OTHER. 
BY R. LUDTGE. 


HEN a drop of liquid is placed on the surface of another liquid 

with which it does not mix, either the drop may retain the shape 

of a lens floating on this liquid, or it may spread out and form a very 

thin layer. The first case is that of a drop of water placed upon oil, 

or of a drop of oil upon alcohol; the second that of oil upon water, 
or of alcohol on glycerine. 

It is readily ascertained that the thickness of the liquid on which 
is placed the drop of the second substance has an influence on the 
extension of this drop on its surface. If this thickness is adequate 
(at least 1 centim.), the drop readily expands, forming a very thin 
layer, too thin indeed to produce the phenomenon of coloured rings. 
When it is very small (1 to 5 millims. and even less), the drop in 
extending hollows in its centre the liquid surface, to such an extent 
sometimes as to moisten the bottom of the vessel in which the surface 
was contained, by driving away at this point the liquid which origi- 
nally covered it. ‘The nature of the material of which the vessel is 
made has no influence on the relative positions which the two liquids 
assume under these circumstances; it does not seem to depend on 
any difference in the force with which the two liquids adhere to the 
bottom. 

M. Ludtge brings this out more clearly by the following experiment, 
in which he quite gets rid of the vessel, so that adhesion cannot 
come into play. On a lamina of oil produced in a circular iron wire 
frame, he places a drop of soap-water ; there is thus formed a circular 
lamina of soap-water which gradually extends into the interior of the 
lamina of oil until it fills the entire ring, while the oil is repelled in 
the form of smail droplets which adhere to the iron wire. A lamina 
of water may also first be produced in the ring; this may be driven 
away by a drop of oil delicately placed upon it, which spreads 
over the frame in its place; and this lamina of oil may finally be re- 
placed by another of soap-water, as we have seen. We might obvi- 


Intelligence and Miscellaneous Articles. 469 


ously work in this way with all substances which are capable of 
spreading over each other, were it not that there are some which 
cannot be made to form a thin plate on a framework. In the case 
of these liquids, the experiment is made by replacing the free Jamina 
by one almost as thin and as stretched, which is formed by letting 
the liquid extend on a carefully cleaned glass plate. 

One of the two substances may be extended as a thin lamina on 
another liquid, and the lamina thus produced may be worked with like 
a free one. ‘These two latter methods have this advantage over the 
use of a skeleton, that the surface of contact between the two liquids 
is smaller, and that they mix or combine less easily; thus the expe- 
riment is in many cases greatly facilitated. 

The author has investigated a great number of substances from this 
point of view. He has found it to be an extremely general fact, 
and that there is probably no liquid, excepting perhaps mercury, 
which has not the property of spreading as a thin lamina on a great 
number of liquids, and in regard to which other substances do not 
enjoy the same property. The following are the principal results to 
which this investigation has led. 

1. When one liquid can extend in a thin lamina upon the surface 
of another liquid, the second can never extend in the same way over 
the first. 

2. Two liquids whose reciprocal adhesion is greater than the co- 
hesion of that one of them in which this property is smallest, have 
always the property that a drop of the one with the smaller cohesion 
extends upon the other. 

3. A drop of the latter retains its shape when placed on the surface 
of the former, and becomes coated with a thin layer of the first 
liquid. 

4. All liquids which satisfy the above conditions as to the magni- 
tude of adhesion, may be arranged in a series in which each antece- 
dent liquid spreads on the surface of a succeeding one, and never 
conversely. 

5. This series is the same as that obtained when the same liquids 
are arranged in the order of their capillarity-constants 


(<% = H ey g=T=a), 
2r7r 2 2 


the smallest constant being first. 

6. The rapidity with which this extension takes place is almost 
proportional to the interval which separates them in the Table. 

7. The phenomenon is the more distinct the less the miscibility 
of two liquids and the greater the difference of their cohesions. 

8. The extension of a liquid on its own surface may be effected by 
placing a drop at a high temperature upon the surface of the liquid 
at a lower temperature. 

9. The greater the cohesion of a liquid the more difficult is it to 
obtain a clean surface. ‘This is the case with water for instance, on 
which almost all liquids can extend. 

The substances on which the author has worked are the following, 


ATO Intelligence and Miscellaneous Articles. 


arranged in such an order that each can extend a thin lamina on a 
following one; it will be seen by the numbers that the order is the 
same as that for the capillarity, the authority for which is given :— 


Hither 4 ecgk ieee see 6s 1789 | 

cee ether ecek ee eo 

PlCoMON ve eeee ess a ee 2°49 >Frankenheim. 
BenZOle 2 cece te ese ck) gO 

Essence of turpentine .. 2°78 

UAD-WaleL oss... .a. 62 02 O Melatcat 
ACCHIE ACIG : ae k tas 6 2°884 Bede. 

Oil of poppies... 202 bc ks 3°05 : 
Bisulphide of Carbon, 22+. “ool } Gash 
Solution of potash ...... 

Glyceniie Ota aay ea + Plateau. 
INMCMIO'ACIG fs rae st 6°026 

Sulphuric agids | sce e504 6°623 } Frankenheim. 
Eiydrochloric acid (5); - 7°026 

FANIVOOMIA See ce et cee 2 

Sulphate of copper ...... 

Water th tele as ens 8 7°58 Frankenheim. 


Chloride of ammonium 
Solution of chloride of iron. 


—Poggendorff’s Annalen, No. 7, 1869; Bibliotheque Universelle de 
Geneve, September 15, 1869. 


MEASUREMENT OF THE ELECTRICAL CONDUCTIVITY OF LIQUIDS 
HITHERTO SUPPOSED TO BE INSULATORS. 


To the Kditors of the Philosophical Magazine and Journal. 
Tamworth House, Mitcham Common, §., 
GENTLEMEN, September 22, 1869. 

You have given in the August Number of this Magazine an ex- 
tract from the Comptes Rendus for June, on the ‘“‘ Measurement of 
the Electrical Conductivity of Liquids hitherto supposed to be In- 
sulators.” Ina paper read in the Chemical Section of the British 
Association at Dundee, 1867, I gave the resistances, in B.A. units, of 
a definite length and thickness of oils, and pointed out in some in- 
stances the electrolysis resulting from the tests. This paper appeared 
inthe Report of the British Association for 1867, the Chemical 
News, October 1867, and in the Proceedings of the British Pharma- 
ceutical Conference, as well as in the Pharmaceutical Journal for 
October 1867. 

Some of the oils operated upon gave much higher resistances than 
any of the liquids tested by M. Said-Effendi. In the case of oil of 
turpentine, I found by continued contact with the battery that its 
resistance became considerably reduced in consequence of electrc- 
lysis, and pointed out the importance of this fact to the detection of 
oil of turpentine when employed as an adulterant to volatile oils. 

Yours obediently, . 
Tuomas I, P. Bruce Warren, 


Intelligence and Miscellaneous Articles. 471 


ON THE FREEZING-POINT OF WATER CONTAINING DISSOLVED 
GASES, AND ON THE REGELATION OF WATER. BY C. SCHULTZ. 


Gases, like solids or liquids, dissolved in water lower its freezing- 
point. ‘This is well known in the case of hydrochloric acid and of 
ammonia, which, from the exception they present to the law of the 
absorption of gases, are not considered to form mere solutions in water. 
The same effect is very distinct in the case of sulphurous and car- 
bonic acids; and by adopting certain precautions it may also be ob- 
served in the case of the permanent gases oxygen, hydrogen, and 
nitrogen. 

The following experiment shows that pure water solidifies at a 
temperature at which water containing dissolved air remains liquid. 
In a glass bulb provided with a U-tube, water, freed from air by 
boiling for a sufficient length of time, was introduced, and was shut 
off from communication with the atmosphere by mercury in the 
bend. ‘This vessel was surrounded by melting ice obtained from 
distilled water. Over this melting ice a current of air washed with 
water was passed. The water in the bulb had, by strong cooling, 
been made tc freeze, and the ice formed melted, except a very small 
piece. Ifthe vessel is then surrounded by the mixture of aérated 
water and ice, large crystals of ice are gradually formed on it. 

Helmholtz has given an experiment the method of which has 
been applied in the foregoing one. In a vacuous vessel containing 
water, ice is formed when it is surrounded with ice melting in the 
air. This experiment is designed to show that ice melting in the 
air has, owing to the external pressure, a lower melting-point than 
that which has been freed from this pressure. But it has been shown 
above that ice melting in the air has a lower melting-point than 
that which melts under the same pressure without contact with air. 

By comparison with the known lowering of the melting-point of 
pure water produced by pressure, we are in a condition to determine 
the small value cf the depression of the melting-point produced by 
absorbed air. If the open end of the U-tube in the above apparatus 
be connected with a column of mercury under an excess of pressure 
of two atmospheres, the renewed formation of ice almost ceases; and 
with an excess of pressure of 834 atmospheres the ice in the vessel 
gradually melts. According to Thomson, the lowering of the melt- 
ing-point of pure water by a pressure of 3 atmospheres amounts to 
0°-02; so that ice in contact with water which is saturated with air 
under the pressure of 1 atmosphere, melts at about this much lower 
temperature than it does under the same pressure, air being excluded. 
If we define the temperature 0° as that of the melting-point of pure 
water under a pressure of 760 millims. mercury, the zero-point of the 
thermometer may, on the ordinary determination in melting ice, lie 
between 0 and —=,°. 

The alteration in the melting-point of water by absorbed hydrogen 
is far smaller. Water which is saturated with hydrogen under the 
ordinary atmospheric pressure freezes in a mixture of ice and water 
saturated with air. 


472 Intelligence and Miscellaneous Articles. 


To investigate the influence of the quantity of the absorbed gases 
on the magnitude of the change in the melting-point, the tempera- 
ture of a mixture of ice and water which was saturated under 1, 2, 
3 atmospheres was examined, and was found to be —0°'13, 25, 
and —0°'35. Thealteration in the melting-point seems proportional 
to the amount of dissolved gas. 

The remarkable property which ice has of regelation has been 
variously interpreted. Faraday has explained it by assuming that 
the particles in the interior of a mass of ice have a higher melt- 
ing-point than those on the surface*. Forbest and others assume 
that ice on melting assumes an intermediate condition of softness, 
and that in this condition pieces adhere together, like those of weld- 
able metals. ‘Thomson { and, subsequently, Helmholtz explain the 
phenomenon by an alteration in the melting-point of ice by 
pressure. ‘There must always be an increase in pressure on inti- 
mate contact of the pieces of ice; under this pressure a portion of 
the ice must meit at the surface of contact, the water formed must 
run off, and, in virtue of its lower temperature, partially freeze again 
in places where it is liberated from pressure. 

If in regelation a fresh formation of ice from water be as- 
sumed, the action of the air on the melting-point must influence the 
process of regelation. Pure ice can only retain a temperature of 0° 
in pure water; when it slowly thaws in air, or in water containing 
air, its temperature is lower; a layer of pure water, or of water which 
is not saturated with air, can therefore freeze between two pieces of 
such ice. ‘This condition mustin many cases be considered to exist. 

Hence in an atmosphere of carbonic acid the phenomenon of 
regelation must be more decided than in common air; the experi- 
ment, in fact, frequently succeeds. Yet the rapidity with which 
water becomes saturated with carbonic acid seems to exert a disturb- 
ing influence; for probably the water between the surfaces in con- 
tact is also quickly saturated with carbonic; acid.—Poggendorff’s 
Annalen, No. 6, 1869. 


DISTURBANCES OF RESPIRATION, CIRCULATION, AND OF THE 
PRODUCTION OF HEAT AT GREAT HEIGHTS ON MONT BLANC. 
BY M. LORTET. 


On the 17th and 26th of August, 1869, I made two ascents of the 
highest peak of Mont Blanc. In the interval I twice passed the Col 
du Géant; and before returning to Lyons I traversed other high 
passes, and ascended several secondary summits in order to verify 
the results I had obtained in reference to the disturbance which re- 
maining or moving at great heights may produce in various physio- 
logical functions. ‘The instruments which I used for estimating these 
are the anapnograph of Bergeon and Kastus, Marey’s sphygmograph, 


* Proc. Roy. Soc. vol. x. p. 440. 
+ Phil. Mag. 8. 4. vol. xvi. p. 544. 
% Proc. Roy. Soc. yolux.sp. 14ke 


Intelligence and Miscellaneous Articles. 473 


and maximum thermometers with an air-bubble and index specially 
constructed by Baudin and which readily indicate the hundredth of 
a degree. 

In proportion as we ascend from a low to a considerable altitude, 
the disturbance of the physiological functions becomes greater and 
greater. While it is scarcely perceptible in going from Lyons to 
Chamounix (that is, from a height of 656 feet to one of 3444 feet), 
it is very appreciable from Chamounix to the Grands-Mulets (8444 
to 10,000 feet), more perceptible still from the Grands-Mulets to 
the Grand-Plateau of Mont Blanc (from 10,000 to 12,897 feet) ; 
lastly this disturbance becomes very appreciable from the Grand- 
Plateau to the Bosses-du-Dromadaire (14,944 feet) and at the summit 
of the Calotte of Mont Blanc (15,776 feet). We shall pass in re- 
view the variations which the respiration, the circulation, and the 
internal temperature of the body undergo at the different heights, 
either during actual walking or after a suitable time of rest. 

Respiration.—From Chamounix to the Grand-Plateau (from 3444 
to 12,897 feet) the disturbances of the respiration are little marked 
in those who are accustomed to the ascent of high mountains, who 
hold the head down to diminish the orifice of the respiratory organs, 
who merely breathe through the nasal orifice, and keep the mouth 
shut, taking care to suck an inert body, such asastone. From Cha- 
mounix to the Grand-Plateau the number of respiratory motions is 
scarcely altered ; we found twenty-four ina minute, as at Lyons and 
Chamounix. But from the Grand-Plateau to theBosses and thence 
to the top we observed thirty-six in a minute. The respiration is 
short and obstructed; it seems as if the pectoral muscles became 
rigid, and the sides squeezed in a vice. At the top, after two hours’ 
rest, these inconveniences gradually disappear. ‘The respiration 
_ sinks to twenty-five a minute; but it remains obstructed, and the 
anapnograph shows that the quantity of air inspired and expired is 
much less than on the plain. ‘he air being under a very low pres- 
sure, the quantity of oxygen brought in a given time into contact 
with the blood is necessarily very small. 

Circulation—During the ascent, although the pace was extremely 
slow, the circulation was enormously accelerated. At Lyons, ina 
state of rest and while fasting, the mean number of the pulsations 
was 64 inaminute. In the ascent from Chamounix to the top of 
Mont Blanc this number gradually increases, according to theheights, 
to 80, 108, 116, 128, 136, and finally, in ascending the last ridge, 
which leads from the Bosses to the top, to 160 and more in a minute. 
These ridges are, it is true, extremely difficult; they have an inclina- 
tion of from 45° to 50°; but the pace was very slow, never more 
than 32 paces in a minute, and frequently less. The pulse is 
feverish, rapid and weak. The artery is felt to be almost empty. 
Thus the least pressure stops the current of blood in the vessel. 
The blood must pass with great rapidity into the lungs, a rapidity 
which aggravates the bad oxygenation it already undergoes owing 
to the rarefaction of the air. From 14,760 feet the veins of the hands, 
the forearms, and the temples swell; and every one, including the 


Phil. Mag. 8. 4. Vol. 38. No. 257. Dec. 1869. 21 


474: Intelligence and Miscellaneous Articles. 


guides, feels a heaviness of the head and a somnolence which are 
frequently very painful, evidently due to a venous stagnation and 
imperfect oxygenation of the blood. Even after two hours’ com. 
plete rest and while still fasting, the pulse always remains between 
90 and 108. ‘The sphygmograph applied to the wrist after an hour’s 
rest indicates an extremely feeble tension, and a most pronounced 
dicrotism. According to M. Marey, this defect of tension must be 
due to the fact that, owing to muscular motion, the blood flows more 
rapidly through the small vessels. When the sphygmograph is ap- 
plied to persons suffering from mountain-sickness, curves are ob- 
tained which exactly resemble those obtained in cases of algidity. 
The pulse is so weak that the spring of the instrument is scarcely 
raised. This alone would indicate a general cooling of the body. 

Internal Temperature of the Body.—This was always taken with 
great care at different heights, the thermometer being placed in the 
mouth underneath the tongue; the mouth itself was closed, and 
breathing was effected through the nose. The thermometer was a 
Walferdin’s maximum with index, on which, from 30° to 40°, the hun- 
dredths of a degree could be read off. ‘The index facilitated the 
reading, and prevented any errors. ‘The instrument was always left 
for at least fifteen minutes in the mouth, a time which was far more 
than sufficient for it to reach the maximum. 

While fasting and exactly in the same conditions, during the ascent, 
the decrease of the internal temperature of the body is very remark- 
able, and zs proportional to the altitude reached. ‘This is easily seen 
by an inspection of the following Table, which condenses the ob- 
servations made upon myself during my two ascents of Mont Blanc. 


Temperature taken under the Tongue. 


Ascent on | Ascent on Temperature 
E Aug. 17, 1869. | Aug. 26, 1869.| of the air. 
: Height 

Names of the stations. |. 2... ——— = ar See Se 

Miele In mo Inmo-| Aug. | Aug 

At rest. tion. Atrest, tion. ike 26. 

ne ie) io) 1) fe) 1) 

TIYOMS sancteescooteees earseeee G56" 4S5 45 Stee aie eee ae Bp | 3 
Chamounixes.4..06 A 3,444| 36:55 | 363] 87-0 | 35:3 |+101|412-4 
Cascade-du-Dard ......... 4,920| 36-4 | 35:7] 363 | 34:3 |+11:2/+124 
Chalet-de-la-Para, ccusse.s2 5,264| 366 | 34:8 | 363 | 34:2 |+-11:38/41386 
Pierre-pointue ........... 6,721| 36:5 | 33:3 | 36:4 | 33°4 |-+-13°2)4141 
Grands-Mulets ............ 10,002| 86°5 | 33:1] 36:3] 33:3 |— O3/— 15 
Grand-Plateau ............ 12,897 | 36.3 | 32:8 | 36:7 | 325 |— 82\— 64 
Bosses-du-Dromadaire ...|14,944| 386°4 | 82:2] 35:7 | 32:3 |—10°3/— 42 
Top of Mont Blanc ...... 15,777| 363 | 32:0] 366 | 31°85 |— 91 )— 34 


It is thus seen that, during the muscular efforts of the ascent, the 
internal temperature of the body may be lowered in ascending from 
3444 to 15,777 feet by from 4° to 6°—an enormous diminution for 
mammals. If we remain stationary for a few seconds, the tempera- 
ture rapidly rises to very nearly its normal maximum; at the top of 


, 
; 
. 


Intelligence and Miscellaneous Articles. 475 


Mont Blanc, however, where every one feels a little uneasiness, 
more than half an hour elapsed before the thermometer attained 
its normal height. ‘These data cease to be true during digestion. 
Then, in spite of the efforts which the ascent necessitates, the tem- 
perature is maintained at about 36° or 37°, and even exceeds 37°'3. 
The influence of the food does not last long; scarcely half an hour 
after having eaten, the body is again cooled. 

Whence arises this diminution of temperature? In a state of rest 
and while fasting man burns the materials of his blood, and the heat 
developed is altogether employed in keeping his temperature constant 
during the variations of the atmosphere. On a plain, and by mecha- 
nical efforts, the intensity of the respiratory combustions, as Gavarret 
has shown, increases proportionally to the expenditure of force. 
Heat is transformed into mechanical force; but from the density of 
the air and the quantity of oxygen inspired, enough heat is formed 
to compensate this expenditure. On a mountain, on the contrary, 
especially at great heights and on very steep snowy ascents, where the 
mechanical labour of the ascent is very great, an enormous quantity 
of heat must be transformed into muscular force. This expenditure 
of force consumes more heat than the organism can furnish; hence 
the body is cooled, and frequent halts must be made in order to 
reheat it. Although the body be burning and ina state of perspira- 
tion, it becomes cooler in ascending, because it consumes too much 
heat, and the respiratory combustion cannot furnish a sufficient quan- 
tity, owing to the small density of the air. It is this rarefaction 
that causes less oxygen to enter the lungs at an elevated place than 
on theplain. ‘The rapidity of the circulation is also a cause of cool- 
ing, the blood not having sufficient time to become properly charged 
with oxygen. At a great height, as Gavarret has remarked, the 
respiratory and circulatory motions are accelerated, not only in order 
to render possible the absorption of a suitable quantity of oxygen, 
but also to remove from the blood the dissolved carbonic acid. But 
this gaseous exhalation, though very active, is no longer sufficient 
to keep up the normal composition of the blood, which remains super- 
saturated with carbonic acid; hence the headache, sickness, sleepi- 
ness which sometimes is almost irresistible, and the still greater cool- 
ing which affects both travellers and guides, on reaching a height 
of 13,000 or 14,000 feet. ‘The mountain-sickness, which attacked 
two of my companions very severely, is especially due to this con- 
siderable cooling, and probably also to the blood being vitiated by 
carbonic acid. During digestion the cooling becomes almost zero ; 
hence the usage of the guides to eat about every two hours. Unfor- 
tunately at great heights the want of appetite becomes usually so 
ereat that it is impossible to swallow any food. 

The secretions exhibited nothing remarkable. The urine contained 
neither sugar nor albumen; but it was considerably diminished.— 
Comptes Rendus, September 20, 1869. 


476 


INDEX to VOL. XXXVIII. 


ABIcH (M.) on fulgurites m the 
andesite of Lesser Ararat, and on 
the influence of local agents in the 
production of thunderstorms, 436 ; 
on hailstorms in Russian Georgia, 
440. 

Air, determination of the specific heat 
of, under constant volume by the 
metallic barometer, 430. 

Albatros, on the mechanical princi- 
ples involved in the sailing flight of 
the, 130. 

Aldis (J. 8.) on the nebular hypo- 
thesis, 508. 

Amaury (M.) on the compressibility 
of liquids, 164. 

Ammonia compounds, on a theory of 
condensed, 455. 

Ammonium alloys, on, 57. 

Angstrom (J. A.) on the spectrum of 
the aurora borealis, 246. 

Arctic regions, on the winterings in 
the, during the last fifty years, 340. 

Aurora borealis, on the spectrum of 
the, 246. 

Baily (W. H.) on Inish graptolites, 
and on plant-remains from beds in- 
terstratified with the basalt in An- 
trim, 241. 


Battery, thermalresearchesonthe,310. ° 


Bauerman (H.) on the geology of 
Arabia Petreea, 75; on the occur- 
rence of celestine in the tertiary 
rocks of Egypt, 162. 

Beor (KE. J.) on the lignite-mines near 
Volterra, 466. 

Bessemer-flame, on the spectrum of 
the, 254. 


Bismuth, on the existence of an alloy 
of ammonium and, 58. 

Blaserna (P.) on the mean velocity of 
the motion of translation of the mo- 
lecules mm imperfect-gases, 326. 

Blood, on the function of the, in mus- 
cular work, 195. 

Books, new:— Fitch’s Methods of 
teaching Arithmetic, 457; Cornwell 
and Fitch’s School Arithmetic and 
Science of Arithmetic, zbid. 

Borgen (C.) on the wintermgs in the 
polar regions during the last fifty 
years, 340. 

Bridgman (W. K.) on the theory of 
the voltaic pile, 377. 

Broadbent (Dr. W. H.) on the fune- 
tion of the bloodin muscularwork, 15. 

Browne (G. M.) on floods in the Island 
of Bequia, 73. 

Camphor, on the motions of, on the 
surface of water, 409. 

Capillarity of molten bodies, on the 
constants of, 81. 

Carbon, on the spectra of, 249. 

Carruthers (W.) on the structure and 
affinities of Sigillaria, 402. 

Cazin (A.) on the expansion of gases, 
322) 

Challis (Prof.) on the hydrodynamical 
theory of magnetism, 42; on a 
theory of the dispersion oflight, 269. 

Church (Prof. A. W.) on turacine, 383. 

Climate, on, 220. 

Clock, on a new astronomical, 393. 

Clouds, on the formation and pheno- 
mena of, 156. 


u i acure= 
Conductors, comparative measure 


INDEX. 


a of the electrical capacity of, 

3l. 

Combustion, on the supposed action 
of light on, 217. 

Copeland (R.) on winterimgs in the 
polar regions during the last fifty 
years, 340. 

Coquand (Prof. H.) on the cretacesus 
strata of England and the North of 
France, 401. 

Corona, observations of the, during 
the total eclipse, August 7, 1869, 
281. 

Croli (J.) on the supposed greater loss 
of heat by the southern than by the 
northern hemisphere, 220. 

Crookes (W.)on a binocular spectrum- 
microscope, 383; on some optical 
phenomena of opals, 388. 

Dawkins (W. B.) on the British post- 
glacial mammalia, 399. 

Desains (M.) on obscure calorific 
spectra, 78. 

Deschamps(M.)on the compressibility 
of liquids, 164. 

Duncan (Dr. P. M.) on the anatomy 
of the test of Amphidetus Virgi- 
nianus, 74; on fossils from the cre- 
taceous rocks of Sinai, 163. 

Dupré (Dr. A.) on the specific heat 
and other physical properties of 
aqueous mixtures and sclutions, 
158. 

Dynamical theory of the electromag- 
netic field, on the, 1. 

Ear, on the structure of the human, 
118, 369. 

Eclipse of August 1868, observations 
on the, 338. 

Edlund (E.) on the construction of the 
galvanometer used in electrical dis- 

~ charges, and on the path of the 
extra-currents through the electric 
spark, 169; on the cause of the 
phenomena of voltaic cooling and 
heating, 263. 

Edmonds (T. R.) on vital force ac- 
cording to age, and the ‘ English 
Life Table,” 18. 

Electric currents, on the development 
of, by magnetism and heat, 64. 

spark, on the path of the extra- 
currents through the, 169. 

Electrical conductivity of liquids sup- 
posed to be msulators, on the mea- 
surement of the, 165, 470. 


477 


Electricity, on some lecture-experi- 
ments in, 229, 

Electrification, observations on, 441. 

Electrolytic polarization, on, 243. 

Electromagnetic phenomena, 
some, l. 

Electromotive force, comparative mea- 
surement of, 232. 

Electrophorus, experiments with the, 
LEN 

Electrostatic imduction in rarefied 
gases, on the luminous effects pro- 
duced by, 407. 

Equilibrium of a liquid mass with- 
out weight, researches into the 
figures of, 445. 

Ethyhe alcohol and water, on the spe- 
cific heat and other physical pro- 
perties of mixtures of, 158. 

Extra-currents, method of demonstra- 
ting the existence of the inverse 
and direct, 233. 

Favre (P. A.), thermal researches on 
the battery by, 310. 

Flight of birds, on the mechanical 
principles mvolved in the, 130. 

Flower (J. W.) on the distribution of 
flint implements in the drift, 467. 

Fluorescent substance, on a new, 136. 

Fluor-spar, on the reflection of heat 
from the surface of, 405. 

Forces, on the parallelogram of, 428. 

Foster (Prof. G. C.) on some lecture- 
experiments in electricity, 229. 

Frankland (Prof. E.) on gaseous spec- 
tra in relation to the physical con- 
stitution of the sun, 66. 

Fritzsche (Dr. T.) on the production 
of a columnar structure in metallic 
tame 2O7e 

Fulgurites in the andesite of the 
Lesser Ararat, on, 436. 

Gallatm (Dr. A. H.) on ammonium 
alloys, and on tests for nascent hy- 
drogen, 57. 

Galvanometer, on the construction of 
the, used in electrical discharges, 
169. 

Gases, on the expansion of, 322; on 
the mean velocity of the motion of 
translation of the molecules in 1m- 
perfect, 326; on the luminous ef- 
fects produced by electrostatic in- 
duction in rarefied, 407. 

Geological Society, proceedings of 
the, 73, 162, 235, 320, 399, 465. 


478 


Gore (G.) on a momentary molecular 
change in iron wire, 59 ; on the de- 
velopment of electric currents by 
magnetism and heat, 64, 

Graham (T.) on hydrogenium, 459. 

Haidinger (Prof.) on the polarization 
ot light by air mixed with aqueous 
vapour, 54. 

Hailstorms, on remarkable, 440. 

Heat, on the development of electric 
currents by, 64; of the stars, on 
the, 69; consumed in internal work 
when a gas dilates under the pres- 
sure of the atmosphere, on the, 76; 
produced in solid bodies when 
sounded, on the, 138; developed 
in discontinuous currents, on the, 
166; on the supposed greater loss 
of, by the southern than by the 
northern hemisphere, 220; on 
the radiation of, from the moon, 
314; on the emission and absorp- 
tion of, radiated at low tempera- 
tures, 403; on the reflection of, 
from the surface of fluor-spar, 405. 

Herschel (Lieut. J.) on spectroscopic 
observations of the eclipse of Au- 
gust 1868, 338. 

Herwig (Dr. H.) on the conformity 
of vapours to Mariotte and Gay- 
Lussac’s law, 284. 

Horopter, on the, 193. 

Huggins (W.) on a method of view- 
ing the solar prominences without 
an eclipse, 68; on the heat of the 
stars, 69. 

Hull (E.) on a ridge of lower carboni- 
ferous rocks crossing the plain of 
Cheshire beneath the trias, 321. 

Hutton (Capt. F. W.) on Nga Tutura, 
an extinct voleano in New Zealand, 
73; on the mechanical principles 
involved in the sailing-flight of the 
Albatros, 130. 

Huxley (Prof. T. H.) on Hyperoda- 
pedon, 258. 

Hydrogen, on tests for nascent, 57. 

Hydrogenium, on the alloy of palla- 
dium and, 51; further researches 
on, 459. 

Iron, on the hmits of the magnetiza- 
tion of, 404. 

wire, on a momentary molecu- 
lar change in, 59. 

Jamin (M.) on the heat developed in 
discontinuous currents, 166. 


INDEX. 


Judd (J. W.) on the origin of the 
Northampton sand, 400. 

Kenngott (Prof. A.) on the microsco- 
pic structure of the Knyahynia 
meteorite, 424. 

King (Prof. W.) on the so-called eo- 
zoonal rock, 235. 

Kingsmill (T. W.) on the geology of 
China, 238. 

Kohlrausch (F.) on the specific heat 
of air under constant volume, 430. 

LeConte (Prof. J.) on some pheno- 
mena of binocular vision, 179. 

Le Neve Foster (C.) on the ocecur- 
rence of celestine in the tertiary 
rocks of Egypt, 162. 

Le Roux (F. P.) on the luminous 
effects produced by electrostatic 
induction in rarefied gases, 407. 

Light, on the polarization of, by air 
mixed with aqueous vapour, 54; 
on the supposed action of, on com- 
bustion, 2]7/; on a theory of the 
dispersion of, 269. 

Liquids, on the compressibility of, 
164; on the electrical conducti- 
vity of, 165,470; on the formation 
of bubbles of gas and of vapour in, 
204; on the superficial tension of, 
445; on the extension of, upon 
each other, 468. 

Lockyer (J. N.) on gaseous spectra, 
66; on recent discoveries in solar 
physies, 142. 

Lortet (M.) on disturbances of respi- 
ration, circulation, and of the 
production of heat on ascending 
great heights, 472. 

Ludtge (R.) on the extension of li- 
quids upon each other, 468. 

Lunar atmosphere, on the existence 
of a, 281. 

Magnetism, on the hydrodynamical 
theory of, 42; on the development 
of electric currents by, 64, 

Magnetization of iron and steel, on 
the limits of the, 404. 

Magnus (Prof. G.) on the emission 
and absorption of heat radiated at 
low temperatures, 403; on the re- 
flection of heat from the surface of 
fluor-spar and other bodies, 405. 

Marcet (Dr. W.) on the temperature 
of the human body at various alti- 
tudes, in connexion with the act of 
ascending, 329. 


INDEX. 


Mason (J. W.) on Dakosaurus, 74. 

Mensbrugghe (G. Van der) on the 
Superficial tension of liquids with 
regard to certain movements ob- 
served on their surface, 409. 

Meteorite, microscopical investigation 
of the Knyahynia, 424. 

Miller (Dr. W. A.) on a self-register- 
ing thermometer for deep-sea 
soundings, 305. 

Molecular physics, on the fundamen- 
tal principles of, 34, 208. 

—— vortices, on the thermal energy 
of, 247. 

Moon, on the radiation of heat from 
the, 314. 

Moon (R.) on the structure of the 
human ear, and on the mode in 
which it administers to the percep- 
tion of sound, 118, 369. 

Moseley (Canon) on the descent of a 
solid body on an inclined plane 
when subjected to alternations of 
temperature, 99. 

Moutier (J.) on the heat consumed in 
internal work when a gas dilates 
under the pressure of the atmo- 
sphere, 76. 

Nebular hypothesis, on the, 308. 

Norton (Prof. W. A.) on the funda- 
mental principles of molecular phy- 
sies, 34, 208. 

Odling (Prof. W.) on a theory of con- 
densed ammonia compounds, 455. 
Opals, on some optical phenomena of, 

388. 

Page (F. J. M.) on the specific heat 
and other physical properties of 
aqueous mixtures and solutions, 
158. 

Palladium, on the expansion of, at- 
tending the formation of its alloy 
with hydrogenium, ol. 

Parnell (J.) on a new fluorescent sub- 
stance, 136. 

Phosphorus, on a remarkable struc- 
tural appearance in, 215. 

Pickering (Prof. E. C.), observations 
on the corona during ‘the total 
eclipse, August 7, 1869, by, 281. 

Plateau (Prof. J.) on the figures of 
equilibrium of a liquid mass with- 
out weight, 4405. 

Pogson (Mr.) on spectroscopic obser- 
vations of the eclipse of August 
1868, 338. 


479 


Preece (W. H.) on the parallelogram 
of forces, 428. 

Quincke (G.) on the constants of 
capillarity of molten bodies, 81. 

Rankine (W. J. M.) on the thermal 
energy of molecular vortices, 247. 

Roberts (W. C.) on the expansion of 
palladium attending the formation 
of its alloy with hydrogenium, 51. 

Roger (M.) on the heat developed 
in discontinuous currents, 166. 

Rosse (Earl of) on the radiation of 
heat from the moon, 314. 

Rowney (Dr. T. H.) on the so-called 
eozoonal rock, 235. 

Royal Institution, proceedings of the, 
142. 

Royal Society, proceedings of the, 
59, 156, 314, 383, 459. 

Ruschhaupe (F.) on the salt-mines of 
Saint Domingo, 465. 

Said-Effendi (M.) on themeasurement 
of the electrical conductivity of 
liquids hitherto supposed to be in- 
sulators, 165. 

Schultz (C.) on the freezing-point of 
water containing dissolved gases, 
and on the regelation of water, 
471. | 

Seguin (J. M.) on the employment of 
the spectroscope to distinguish a 
feeble light inja stronger one, 325. 

Shearmg, on the fracture of brittle 
and viscous solids by, 71. 

Solar prominences, on a method of 
viewing the, without an eclipse, 68. 

Sound, on the structure of the ear, 
and on the mode in which it ad- 
ministers to the perception of, 118, 
369. 

Spectra, on gaseous, 66; on obscure 
calorific, 78; of carbon, on the, 
249. 

Spectroscope, on recent discoveries in 
solar physics made by means of the, 
142; on the employment of the, 
to distinguish a feeble hght m a 
stronger one, 324; description ofa 
new, 360. 

Spectrum-microscope, on a new ar- 
rangement of binocular, 383. 

Stars, on the heat of the, 69; on the 
spectral analysis of the, 360. 

Steel, on the limits of the magnetiza- 
tion of, 404. 

Strutt (The Hon. J. W.) on some 


480 


electromagnetic phenomena cons!- 
dered in connexion with the dyna- 
mical theory, lL. 

Sun, on the physical constitution of 
the, 66, 142; on the nature of the 
protuberances of the, 368. 

Sutherland (Dr.) on auriferous rocks 
in South-eastern Africa, 242. 

Tait (Prof.) on electrolytic polariza- 
tion, 243. 

Temperature, on the descent of a solid 
body on an inclined plane when 
subjected to alternations of, 99; of 
the human bodyat various altitudes, 
on the, 329, 472. 

Thermometer, on a self-registering, for 
deep-sea soundings, 395. 

Thomson (Sir W.) on the fracture of 
brittle and viscous solids by shear- 
ing, 71; on a new astronomical 
clock, and a pendulum-governor for 
uniform motion, 393. 

Thunderstorms, on the influence of 
local agents in the production of, 
436. 

Tin, on the production of a columnar 
structure in metallic, 207. 

Tomlinson (C.) on the formation of 
bubbles of gas and of vapour im 
liquids, 204; on aremarkable struc- 
tural appearance in phosphorus, 
215; on the supposed action of hight 
on combustion, 217; on the mo- 
tions of camphor on the surface of 
water, 409. 

Turacine, researches on, 383. 


INDEX. 


Tyndall (Prof. J.) on the formation 
and phenomena of clouds, 156. 

Vapours, on the conformity of, to Ma- 
riotte and Gay-Lussac’s law, 284. 

Vision, on some phenomena of bi- 
nocular, 179. 

Vital foree according to age, and the 
“Enelish Life Table,” on, 18. 

Voltaic cooling and heating, on the 
cause of the phenomena of, 263. 

—-— pile, on a theory of the, 377. 

Wallbridge (T. C.) on the geology 
and mineralogy of Hastings County, 
Canada West, 467. 

Waltenhofen (Prof. A.) on the limits 
of the magnetization of iron and 
steel, 404. 

Warburg (Dr. E.) on the heating pro- 
duced in solid bodies when they are 
sounded, 138. 

Warren (T. T.P.B.) onelectrification, 
441; on the measurement of the 
electrical conductivity of liquids 
supposed to be insulators, 470. 

Water, on the freezing-point of, con- 
taining dissolved gases, and on the 
regelation of, 471. 

Watts (Dr. W. M.) on the spectra of 
carbon, 249. 

Whitaker (W.) on Hyperodapedon, 
240. 

Wiltshire (Rev. T.) on the red chalk 
of Hunstanton, 321. 

Zollner (F.) on a new spectroscope, 
with contributions to the spectral 
analysis of the stars, 360, 


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_ GEOGRAPHERS, TOURISTS, and EMIGRANTS derive additional 
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me  Talxr 1 TRAD eh 


CONTENTS oF N° 252.—Fourth Series. 


I. On some Electromagnetic Phenomena considered in connexion 
with the Dynamical Theory. By The Hon. J. W. Srrurtrt, Fellow of 
Trinity College, Cambridge... 55 sul wena ov ta sO) See page 

II. On the Function of the Blood in Muscular Work. By W. H 
Broavsent, M.D., Lecturer on Physiology at St. Mary’s Hospital 
Medical School . 2... cco c ee ck tose bo ss 2 ne ee 

III. On Vital Force according to Age, and the ‘English Life Table.” 
By Tuomas Rowe Epmonps, B.A. Cantab. .. 2.50.5. eeee eevee 

IV. Fundamental Principles of Molecular Physics. Reply to Pro- 
fessor Baymia. By Professor W. A. NorTON .........0 0-05 5e om ore 

V. Note on the Hydrodynamical Theory of Magnetism. By Pro- 
fessor Coatuis, M.A., F-R.S., F.RoAsSvceec. eect cee cee 

VI. Note on the Experimental Illustration of the Expansion of Pal- 
ladium attending the Formation of its Alloy with Hydrogenium. By 
W.. Coanvier Roserts, F.0.8.;, FG Sie cece cewerd Oe ce Peewre oe 

VII. On the Polarization of Light by Air mixed with Ages Va- 
pour. By Professor Harprnerr ....)5.0.055 0... ee 

VIII. On Ammonium Alloys, and on Nascent-Hydrogen Tests. By 
Auzsrert H. Gatiatin; M.D, of New York.) .2 2 052 ee : 

IX. Proceedings of Learned Societies :— 

Royat Socrsty:—Mr. G. Gore on a momentary Molecular 
Change in Iron Wire, and on the Development of Electric Cur- 
rents by Magnetism and Heat; Messrs. E, Franxuanp and J. 
N. Locxyenr’s Researches on Gaseous Spectra in relation to the 
Physical Constitution of the Sun; Mr. W. Hueerns on a Me- 


thod of viewing the Solar Prominences without an Eclipse, and 


on the Heat of the Stars; Sir W. Tuomson on the Fracture of 


54 


57 


Brittle and Viscous Solids by “Shearing” ...... tare viete 59-73 
Gonogrean Soctery 5. Ae ee ro ae os oe es 


X. Intelligence and Miscellaneous atin —_ 
On the Heat consumed in Internal Work when a Gas dilates under 
the Pressure of the Atmosphere, by M. J. Moutier....... ‘oes 
Investigations on obscure Calorific Spectra, by M. Desains...... 


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1. 38. AUGUST 1869. No. 253. 


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THE 
LONDON, EDINBURGH, anno DUBLIN 


PHILOSOPHICAL MAGAZINE, 


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JOURNAL OF SCIENCE. 


Being a Continuation of Tilloch’s ‘ Philosophical Magazine, 
Nicholson’s ‘Journal,’ and Thomson’s ‘ Annals of Philosophy? 


CONDUCTED RY 


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AND 4 


WILLIAM FRANCIS, Px.D. F.LS. F.R.AS. FCS. 


FOURTH SERIES. 


Ne 253.—AUGUST 1869. 


LONDON: 


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BRITISH ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE. 


The NEXT ANNUAL MEETING of this Association will be held at EXETER, 
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President Elect. 

GEORGE G. STOKES, D.C.L., Sec. R.S., 

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ADVERTISEMENTS continued on 3rd page of Cover. 


1 | GEOGRAPHERS, TOURISTS, and EMIGRANTS derive additional 
pleasure from their rambles by being acquainted with Minrrats, Rocks, and Fossits. 
igMr. TENNANT, Geologist, 149 Strand, London, gives PRACTICAL INSTRUCTION 
min MINERALOGY and GEOLOGY to Ladies and Gentlemen; and from his extensive 
collection, comprising many thousand specimens, persons are enabled in a dozen or 
wenty lessons to acquire sufficient knowledge to identify all the ordinary components 
| lof crystalline and volcanic rocks, and most of the minerals and metals used in the Arts. 


TO GEOLOGISTS AND MINERALOGISTS. For Sale. 

' Two handsome Cabinets, measuring 9 feet 3 inches long, 2 feet 4 inches wide, and 3 feet 

0 inches high; each containing 45 drawers, with a Glass Case on the top of each Cabinet, 
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Minerals, the other with Fossils. 
_ Any person wishing to become practically acquainted with the interesting and important 
study of Mineralogy or Geology, or both, will find this a good opportunity to obtain an 
instructive and valuable Museum. 

The Collection contains upwards of three thousand specimens, many very select. The first 
Gold Nugget received from Australia, which was exhibited in the Exhibition of 1851, is in 
the Collection, and cost £37; it contains about 8 ounces of gold ; also a fine series of 
Coloured Diamonds, illustrating crystalline form and colour. The specimens have been fre- 
quently used to illustrate the Lectures on Mineralogy and Geology at King’s College, and 
at the Royal Military Academy, Woolwich*. Price 

THREE THOUSAND GUINEAS. 
Mr. TENNANT has other Collections, at one thousand, five hundred, one hundred, down to 
J Students’ Collections at fifty, twenty, ten, five, and two guineas each. ; 


Mf wich for seventeen years ; the Lectures were discontinued in December 1867, Lectures on 
@ Military History being substituted. 


® * Mr. Tennant held the appointment of Lecturer on Geology and Mineralogy at Wool- 


Mr. TENNANT is commissioned to sell several highly interesting Collections, viz. 
A CABINET OF PEARLS AND PRECIOUS STONES, 
_ WITH DESCRIPTIVE CATALOGUE, 
and the extensive Collection of 
MINERALS, ROCKS, AND FOSSILS, 
Collected by the late Lord Farnham. 
Particulars can be had at 149 Strand, W.C. August 1869. 


SOPWITH’S GEOLOGICAL MODELS IN WOOD. 
Sold in Case, bound and lettered to resemble a large folio volume. 
Twelve Models, 4 inches square............ £5 0 


A Catalogue of 2000 of the most common Fossils found in the British Isles, being a list 
of those in the private collection of J. TENNANT, F.G.S. Price 2s. 

A descriptive List of Fuint ImpLeMENTs found at St. Mary Bourne ; with Illustrations of 
the principal types. By Josep Stevens, Memb. Roy. Coll. Physicians, Lond. &c. Price 2s. 

All the recent Works relating to Mineralogy, Geology, Conchology, and Chemistry ; also 
Geological Maps, Models, Diagrams, Hammers, Blowpipes, Magnifying Glasses, Platina 
Spoons, Electrometer and Magnetic Needle, Glass-top Boxes, Microscopic Objects, Brass 
and Steel Forceps, Acid Bottles, &c., can be supplied to the Student in these interesting 
and important branches of Science. 


Size of the Gold Nugget. found, April 1869, 
at Kildonan, Sutherland. It contains two oz. 
of gold. A gilt Model can be had, price 2s. 6d,, 
of J. Tennant, 149 Strand, London, W.C. 


i of the firsts GOLD NUGGET received from Australia in 1851. The 
YA original is in the possession of J. Tennant, Mineralogist to Her Majesty, 
and contains about Eight Ounces of Gold. Price of the Model 3s. 6d., with glass- 
topped box to hold it, 1s. 6d.,—together, ds. 

Model of the “ Welcome” Gold Nugget, being the largest brought to England 
from Australia : it contained Gold to the value of £8,376. Price of the Model £3 3s. 


JAMES TENNANT, Mineralogist to Her Majesty, 149 Strand, W.C. 


CONTENTS or N° 253.—Fourth Series. 


XI. On the Constants of Capillarity of Molten Bodies. By G. 
QUINCKE foie dee ee he ee os Pie ee ote oe pee “page 81 


XII. On the Descent of a Solid Body on an Inclined Plane when 
subjected to alternations of Temperature. By Henry Moseg.ey, 
M.A., Canon of Bristol, F.R.S., Instit. Imp. Sc. Paris, Corresp..... 99 


XIII. On the Structure of the Human Ear, and on the Mode in 
which it administers to the Perception of Sound. By R. Moon, M.A., 
Honorary Fellow of Queen’s College, Cambridge ................ 118 


XIV. On the Mechanical Principles involved in the Sailing Flight 
of the Albatros. By Captain F.W. Hurron, F.G.S. ............ 1380 


XV. Note on a new Fluorescent Substance. By JoHn ParneELu, 
M.A.; FSRAASS 2) ojos oe eee elects es aoe ee Owe 136 


XVI. On the Heating produced in Solid Bodies when they are 
Sounded. By Dr. E. Warsur@ 3.0.5.0 0201 54.5.) 


XVII. Proceedings of Learned Societies :— 
Royat Institution :—Mr.J.N.Locxyer on Recent Discoveries 
in Solar Physics made by means of the Spectroscope........ 142 
Royat Socrety:—Dr. Tynpaut on the Formation and Pheno- 
mena of Clouds; Dr. A. Dupré and Mr. F. J. M. Pace on 
the Specific Heat and other physical properties of Aqueous 
Mixtures and Solutions: 2000/5 (0220202 156-162 
GHOLOGICAL Society 22.20) eee es ae o. sia op einai 162 


XVIII. Intelligence and Miscellaneous Articles :— 
On the Compressibility of Liquids, by wee Amaury and Des- 
CANIPS S05), saat sete aici . 164 
Measurement of ihe Electrical Goalies of riguite hitherto 
supposed to be Insulators, by M. Said-Effendi............ 165 
On the Heat developed in Discontinuous Currents, by MM. Jamin 
and Roger...... sien ects winds vse e sss 4 0 eor Ob eee 166 


*..* It is requested that all Communications for this Work may be addressed, 
post-paid, to the Care of Messrs. Taylor and Francis, Printing Office, Red 
Lion Court, Fleet Street, London. 


Published the First Day of every Month.—Price 2s. 6d. 


THE 
LONDON, EDINBURGH, ano DUBLIN 


PHILOSOPHICAL MAGAZINE, 
AND 
JOURNAL OF SCIENCE. 


Being a Continuation of Tilloch’s ‘ Philosophical Magazine,’ 
Nieholson’s ‘Journal,’ and Thomson’s ‘ Annals of Philosophy.’ 


CONDUCTED BY 


SIR ROBERT KANE, LL.D. F.R.S. M.R.LA. F.C.S. 
AUGUSTUS MATTHIESSEN, Pu.D. F.RB.S. F.C.S. 
AND 


WILLIAM FRANCIS, Pu.D. F.LS. F.R.AS. FC.S. 


FOURTH SERIES. 


N° 254.—SEPTEMBER 1869. 


LONDON: 


PRINTED BY TAYLOR AND FRANCIS, RED LION COURT, FLEET STREET, 
Printers and Publishers to the University of Lgndon. 
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CONTENTS or N° 254.—Fourth Series. 


XIX. On the Construction of the Galvanometer used in Electrical 
Discharges, and on the Path of the Extra Currents through the Elec- 
tric Spark. 5. By H. Hprenp 220074. gs a ee eee as vee page 

XX. On some Phenomena of Binocular Vision. By Joszpx 
LeConte, Professor of Chemistry and Geology in the University of 
South Carolia: 7.2. ena. 5 


XXI. On the Formation of Bubbles of Gas and of Vapour in Li- 
quids. By Craruus Tomuinson, F.R.S., F.C.S....0.....-.:+008 


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Tin. By Dr. T. Fairzscuz of St. Petersburg ....... 


XXIII. Fundamental Principles of Molecular Physics. Reply to 
Professor Bayma. By Professor W. A. NorTon ...............: 


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By Caarzres Tomiinson, PRS.) ECS. 200 ee Raa Ss 


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Cuares Tomuinson, F.R.S., F.C.S. 


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Radiation more Heat than the Northern, and the supposed Influence 


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vey of Scotlands ))202. 0... eT NONI inc 


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GEOLOGICAL Soctedy oy SU Sea era ac aeeaeomas 


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On the Spectrum of the Aurora Borealis, by J. A. Angstrom .. 
On the Thermal Energy of Molecular Vortices, by W. J. Mac- 
guorn Rankine, C.E., LL.D., F.R.SS. Lond. & Edinb. &c... 


169 


eee 


204 


215: 


a 


220: 


229: 


235: 


243) 
246 


247 


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PROFESSOR TENNANT, F.G.S., will deliver a Course of Lectures on MINERALOGY 
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and valuable Museum. 

The Collection contains six thousand specimens, many very select. The first Gold 
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at the Royal Military Academy, Woolwich*. Price 

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wich for seventeen years; the Lectures were discontinued in December 1867, Lectures on 
Military History being substituted. 


Mr. TENNANT is commissioned to sell several highly interesting Collections, viz. 


A CABINET OF PEARLS AND PRECIOUS STONES, 
WITH DESCRIPTIVE CATALOGUE, 
and the extensive Collection of- 


MINERALS, ROCKS, AND FOSSILS, 
Collected by the late Lord Farnham. 
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The Original Specimens are in the British Museum. Price 25s., published at £2 10s. 


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of those in the private collection of J. TENNANT, F.G.S. Price 2s. 

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All the recent Works relating to Mineralogy, Geology, Cunchology, and Chemistry ; also 
Geological Maps, Models, Diagrams, Hammers, Blowpipes, Magnifying Glasses, Platina 
Spoons, Electrometer and Magnetic Needle, Glass-top Boxes, Microscopic Objects, Brass 
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original is in the possession of J. Tunnant, Mineralogist to Her Majesty, 
and contains about Hight Ounces of Gold. Price of the Model 8s. 6d., with glass- 
topped box to hold it, 1s. Gd.,—together, 5s. 
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from Australia : it contained Gold to the value of £8,376. Price of the Model £3 3s. 
A gilt Model can be had price 2s. 6d., of the Gold Nugget found, April 1869, at 
Kildonan, Sutherland. It contains Two Ounces of gold. 


eee DLE TENNANT. Winer alozist to Her Majesty, 149 Strand, W.C. 


CONTENTS or N° 255.—Fourth Series. 


XXX. On the Spectra of Carbon. By W. M. Warts, D.Sc., 
Physical-Science Master in the Manchester Grammar School. (With 


a Plate.) ovine wicca vis Sew So kG Unive wea’ C RUR S gh eT Cee ee page 
XXXI. On the Cause of the Phenomena of Voltaic Cooling and -~ 
Heating discovered by Peltier. By E. Epzunp ...... one cee. om 


XXXII. Comparison of a Theory of the Dispersion of Light on the 
Hypothesis of Undulations with Ditscheiner’s determinations of Wave- 
lengths and corresponding refractive Indices. By Professor Cuatzis, 
M.A.) PuRiS., ER ALS. ac in as cue cee seen rr 


XXXII. Observations of the Corona during the Total Eclipse, 
August 7th, 1869. By Professor Epwarp C. PICKERING ........ 


XXXIV. Investigations on the Conformity of Vapours to Mariotte 
and Gay-Lussac’s Law. By Dr. Hermann Herwic. (With a Plate.) 


XXXV. On the Nebular Hypothesis. By J. S. Atnis, M.A., late 
Scholar of Trinity College, Cambridge .2 300... ace eee 


XXXVI. Thermal Researches on the Battery. By M. P. A. Favre. 


XXXVII. Proceedings of Learned Societies :— 
Royat Socrzery:—The Eart or Rosse on the Radiation of 
Heat from the Moon’, 20...) o hep i) ee 
Gxotoeican Socrnry :—Mr. Huut on the Evidence of a ridge 
of Lower Carboniferous Rocks crossing the Plain of Cheshire 
beneath the Trias; The Rev. T. Wittsuire on the Red Chalk 


of ‘Hunstanton $3.0 oo ee ee 


XXXVIII. Intelligence and Miscellaneous Articles :— 
On the Expansion of Gases, by M. A. Cazin .....2...0.00. 
On the Employment of the Spectroscope in order to distinguish 
a feeble Light in a stronger one, by M. J. M. Seguin ...... 
On the Mean Velocity of the Motion of Translation of the Mo- 
lecules in Imperfect Gases, by M. P. Blaserna............ 


263 


268 


281 


284 


308 


310 


314 


322 


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Lion Court, Fleet Street, London. 


ol. 38. NOVEMBER 1869. No. 256. 


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LONDON, EDINBURGH, ann DUBLIN 


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Nicholson’s ‘Journal, and Thomson’s ‘ Annals of Philosophy.’ 


CONDUCTED RY me ae 5 ae 
S22 Be 
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AUGUSTUS MATTHIESSEN, Pu.D. F.R.S. F.C.S. 


AND 


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: : 


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N° 256.—NOVEMBER 1869. 


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[ADVERTISEMENTS continued on 3rd page of Cover. 


_ PROFESSOR TENNANT, F.G.S., will deliver a Course of Lectures on MINERALOGY 
_ applied to GEOLOGY and the ARTS, at King’s College, London, on Wednesday and Friday 
! poe at 9 o'clock, during October, November, and December, commencing October 8. 
| Fee £2 2s. 

A Course of Lectures on MINERALOGY and GEOLOGY will also be delivered on 
Thursday evenings at 8 o’clock. These begin October 14, and will be continued to Easter, 
1870. Fee £1 lls. 6d. 

Professor TENNANT gives PRIVATE INSTRUCTION in Mineralogy and Geology, illus- 
_ trated by a large number of Specimens, at his residence, 149 Strand, W.C. 

Oct. 1, 1869. 


TO GEOLOGISTS AND MINERALOGISTS. For Sale. 

Two handsome Cabinets, measuring 9 feet 3 inches long, 2 feet 4 inches wide, and 3 feet 
10 inches high; each containing 45 drawers, with a Glass Case on the top of each Cabinet, 
4 feet 11 inches high, and 15 inches from back to front. One Cabinet is filled with 
2600 Minerals, the other with 3400 Fossils. 

Any person wishing to become practically acquainted with the interesting and important 
study of Mineralogy and Geology will find this a good opportunity to obtain an instructive 
and valuable Museum. 

The Collection contains six thousand specimens, many very select. The first Gold 
Nugget received from Australia, which was exhibited in the Exhibition of 1851, is in 
the Collection, and cost £37; it contains about 8 ounces of gold; also a fine series of 
Diamonds, illustrating crystalline form and colour. The specimens have been frequently 
used to illustrate the Lectures on Mineralogy and Geology at King’s College, London, and 
at the Royal Military Academy, Woolwich*. Price 

THREE THOUSAND GUINEAS, 

Mr. TennanrT has other Collections, at one thousand, five hundred, one hundred, down to 
Students’ Collections at fifty, twenty, ten, five, and two guineas each. 

* Mr. Tennant held the appointment of Lecturer on Geology and Mineralogy at Wool- 
wich for seventeen years; the Lectures were discontinued in December 1867, Lectures on 
Military History being substituted. 


Mr. TENNANT is commissioned to sell several highly interesting Collections. 


A CABINET OF PEARLS AND PRECIOUS STONES, 
WITH DESCRIPTIVE CATALOGUE, 
and the extensive Collection of 
MINERALS, ROCKS, AND FOSSILS, 
Collected by the late Lord Farnham. 


Particulars can be had at 149 Strand, W.C. October 1869. 
SOPWITH’S GEOLOGICAL MODELS IN WOOD. 


Sold in Case, bound and lettered to resemble a large folio volume. 
Twelve Models, 4 inches square............ £5 0 


DIAGRAMS TO ILLUSTRATE LECTURES ON GHOLOGY. 
A Coloured Lithographic Print (size 34 by 28 inches) of B. WaTEernovuse Hawxins’s, 
F.L.S.,&c., Restoration of the Extinct Animats of the Drirr- and CavzE-pPEriop. Price 12s, 
Six Diacrams or GENERIC ForMS oF FoRAMINIFERA. Size, three feet by two feet. 
Price 18s. for the Six Diagrams, either on paper or linen. They contain Highty-two Figures. 
Mr. Toomas Hawktns’s “ Great Sea-Dracons.” Containing 30 folio Plates (which 
form good school diagrams) of the Remains of Ichthyosaurus and Plesiosaurus from the Lias. 
The Original Specimens are in the British Museum. Price 25s., published at £2 10s. 
A Catalogue of 2000 of the most common Fossils found in the British Isles, being a list 
of those in the private collection of J. Tennant, F.G.S. Price 2s. 
A descriptive List of Ftint ImpLemeEnts found at St. Mary Bourne; with Illustrations of 
the principal types. By JosepH StEvENS, Memb. Roy. Coll. Physicians, Lond. &c. Price 2s. 
All the recent Works relating to Mineralogy, Geology, Cunchology, and Chemistry ; also 
Geological Maps, Models, Diagrams, Hammers, Blowpipes, Magnifying Glasses, Platina 
Spoons, Electrometer and Magnetic Needle, Glass-top Boxes, Microscopic Objects, Brass 
and Steel Forceps, Acid Bottles, &c., can be supplied to the Student in these interesting 
and important branches of Science. 


ODEL of the firsts GOLD NUGGET received from Australia in 1851. The 

original is in the possession of J. Tennant, Mineralogist to Her Majesty, 

and contains about Hight Ounces of Gold. Price of the Model 8s. 6d., with glass- 

topped box to hold it, 1s. 6d.,—together, 5s. 

Model of the “ Welcome” G'old Nugget, being the largest brought to England 

from Australia : it contained Gold to the value of £8,376. Price of the Model £3 3s. 

A gilt Model can be had price 2s. 6d., of the Gold Nugget found, April 1869, at 
Kildonan, Sutherland. The original contains Two Ounces of gold. 


JAMES TENNANT, Mineralogist to Her Majesty,149 Strand, W.C. 


CONTENTS oF N° 256.— fourth Series. 


XXXIX. Observations on the Temperature of the Human Body at 
various Altitudes, in connexion with the act of Ascending. By Wi1- 
LiAM Marcert, M.D., F.R.8., Assistant Physician to the Hospital for 
Consumption and Diseases of the Chest, Brompton .......... page 

XL. On that portion of the Report of the Astronomer to ‘the Ma- 
dras Government on the Eclipse of August 1868 which recounts his 
Spectroscopic Observations. By J. Herscuex, Lieut. R.E. ...... 

XLI. Short Account of the Winterings in the Arctic Regions 
during the last fifty years. By C. Borezn and R. Corrnanp, Astro- 
nomers and Physicists to the second German Polar Expedition .... 


XLII. On a New Spectroscope, together with contributions to the 


Spectral Analysis of the Stars. By F. Zéuungr ...... 

XLIII. On the Structure of the Human Ear, and on as Mode j in 
which it administers to the Perception of Sound. By R. Moony, 
M.A., Honorary Fellow of Queen’s College, Cambridge...... 


XLIV. Theory of the Voltaic Pile. By W. Kunczty Bripeman, 
LDS.) Goes ok 2 OYE Oe Ee REAL oS ee 


XLV. Proceedings of Learned Societies :— 

Rovat Society:—FProf. A. W. Cuaurcu on Turacine; Mr. W 
Crooxkgs on a NewArrangement of Binocular Spectrum-Micro- 
scope, and on some Optical Phenomena of Opals; Sir W. 
THomson on anew Astronomical Clock, and a Pendulum-go- 
vernor for Uniform Motion; Dr. W. A. Miuusr on a Self- 


registering Thermometer adapted to Deep-sea Soundings. 383— 


GrotoeicaL Socrery:—Mr. W. B. Dawkins on the British 
Postglacial Mammalia; Mr. J. W. Jupp on the Origin of the 
Northampton Sand; Prof. H. Coauanp on the Cretaceous 
Strata of England and the North of France; Mr. W. Carru- 
THERS on the Structure and Affinities of Sigi//aria and allied 
genera; Dr. H. A. Nicuozson on the British Species of the 
Genera Climacograpsus, Diplograpsus, Dicranograpsus, and 
Didymograpsus ; Mr. F. O. Apams on the Coal-mines at 
Kaianoma; Mr. M. Moreans ona peculiarity of the Bren- 
don-Hills Spathose Qre-vemsih, fesk Sie eee i Ree 399- 


XLVI. Intelligence and Miscellaneous Articles :— 
On the Emission and Absorption of Heat radiated at Low Tem- 
peratures; by G. Mapnust ii. 0). 2st ee 
On the limits of the Magnetization of Iron and Steel, by Prof. 
Ax Waltenhioten! oso-0e UN On i toe 20 ener ee, er 
On the Reflection of Heat from the surface of Fluor-spar and 
other Bodies; .by;G.. Magnus 3.) 42/2) oles ok ee 
On the Luminous Effects produced by Electrostatic Induction in 
Rarefied Gases.—Leyden Jar with Gaseous Coatings, by M 
BRS ee Roux ris 2 ee nee Sols nee ee 


329 


338 


340 


. 360 


. 369 


377 


399 


403 


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ol. 38. DECEMBER 1869. No. 257. 


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CONTENTS or N° 257.—Fourth Series. 


XLVII. On the Motions of Camphr on the Surface of Water. By 
Cuares Tomurnson, F.R.S.. sh cteluliens 5 . page 409° 


XLVIII. Microscopical Tasestipation of thin polished Lae of 
the Knyahynia Meteorite. By Professor A. Kennecott, of Zurich. 4 
CoV ith a Plates) eo hue Nee eee gece cigs 3 eee 12. 4244 


XLIX. The Parallelogram of Forces. By Witu1am Henry PREECE, 
Assoc. Inst. C.B. &e. 000: od She is os tin ee 428 © 


L. A Determination of the Specific Heat of Air under constant 
Volume by means of the Metallic Barometer. By F. Koutrauscy .. 430 


LI. On Fulgurites in the Andesite of the Lesser Ararat, and on the 
Influence of Local Agents on the Production of Thunderstorms. By 
WME ARICH 022 eS OS Oe tee ee 436 


Plate.) ic ea eo A AE NU de 440 
LIII. On Electrification. By Tuomas T. P. Bruce Warren.... 441 


LIV. Experimental and Theoretical Researches into the Figures 
of Equilibrium of a Liquid Mass without Weight.—Highth Series. 
By Professor J: PLATHAU j 2.) cake ius ote ie aes) 445 - 


LV. Note on a Theory of Condensed Ammonia Compounds. By 
WitLiam Oprine, M: Be RoRiSy one. ee ee 455. 


LVI. Notices respecting New Books :—Methods of teaching Arith- 
metic. By J. G. Frrcu, M.A.—The School Arithmetic, and the 
Science ofArithmetic. By J.Cornwett, Ph.D.,andJ.G.Fircu, M.A... 457 


LVII. Proceedings of Learned Societies :— 

Royat Society :—Mr. T. Grauam on Hydrogenium.. 459 

Geotocican Socrery:—M. F. RuscHHavuPrE on the Salt- 
Mines of St. Domingo; Messrs. S. Woop and F. W. Harmer 
on a peculiar instance of Intraglacial Erosion near Norwich ; 
Mr. E. J. Beor on the Lignite-mines of Podnernuovo, near 
Volterra; Mr. T. C. Watisripcs on the Geology and Mine- 
ralogy of Hastings County, Canada West; Mr. J. W. Frowzr 
on the distribution of Flint Implements in the Drift . 465-468 


LVIII. Intelligence and Miscellaneous Articles :— 
On the Extension of Liquids upon each other, by R. Ludtge.... 468 
Measurement of the Electrical Conductivity of Liquids hitherto 
supposed to be Insulators, by Thomas T. P. Bruce Warren .. 470 
On the Freezing-point of Water containing Dissolved Gases, and 
on the Regelation of Water, by C..Schuliz”. nc. ee 471 
On disturbances of Respiration, Circulation, and on the production 
of Heat at great Heights on Mont Blane, by M. Lortet .... 472 


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