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THE 
LONDON, EDINBURGH, and DUBLIN 

PHILOSOPHICAL MAQAZINE 

AND 

JOURNAL OF SCIENCE. 



CONDUCTED BY 

SIR DAVID BREWSTER, K.H. LL.D. P.R.SX. & E. &r. 
SIR ROBERT KANE, M.D. P.R.S. M.R.I.A. 
WILLIAM FRANCIS, Ph.D. P.L.S. F.R.A.S. P.C.S. 



" Nee araneanim sane textus ideo melior quia ex se fila gignunt, nee noster 
vilior quia ex alienis libamus at apes." Just. Lips. PoUi. lib. i. cap. 1. Not. 



VOL. XXVIII.—FOtJRTH SERIES. 
JULY— DECEMBER, 1864. 



LONDON. 

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

SOLD BT LONGMAir, GBEE5, LONGMAN, ROBKRTS, AND GREEN ; SIMPKIN, MARSHALL 

AND CO. ; WHITTAKBE AND CO. ; AND PIPER AND CO., LONDON : — 

BT ADAM AND CHARLES BLACK, AND THOMAS CLARK, 

EDINBURGH ; SMITH AND BON, GLASGOW; HODGES 

AND SMITH, DUBLIN ; AND PUTNAM, 

NEW YORK. 



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] ' 

I.. ' 

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" Meditationis est perscrutari occulta; contemplationiii est admirari 

penpicua Admiratio generat questionem, qusestio investigationein, 

investigatio inyentionem." — Hugo de S, Victore, 



— " Cur Spirent venti^ cur terra dehiscat^ 
Cur mare turgescat, pelago cur tantus amaror. 
Cur caput obscura Phoebus ferrugine condat, 
Quid toties diros cogat flagrare cometas; 
Quid pariat nubes, yeniant cur fulmina coelo^ 
Quo micet igne Iris, superos quis conciat orbes 
Tarn vario motu." 

/. jB. PinelU ad Matonium, 



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CONTENTS OF VOL. XXVIII. 

(FOURTH SERIES.) 



NUMBER CLXXXVL— JULY 1864. 

Page 
Prof. J. C. PoggendorfF on the Extra Current of the Induction- 
Current , 1 

Mr. C. Packe on the Discrepance between the English and 
French Barometer Scales ; and on the Corrections necessary 

in reducing the Readings to the Freezing-point 8 

Mr. T. K. Abbott on the Probability of Testimony and Argu- 
ments » 12 

Prof. Tyndall's Notes on Scientific History 25 

M. P. Tch^bychef on a Modification of Watt's Parallelogram. . 51 
Mr. P. E. Chase on the Barometer as an Indicator of the Earth's 

Rotation and the Sun's Distance 55 

Notices respecting New Books : — Dr. Apjohn's Manual of the 

Metalloids 59 

Proceedings of the Royal Society : — 

Mr. 6. G. Stokes on the supposed Identity of Biliyerdine 
with Chlorophyll, with remarks on the Constitution of 

Chlorophyll 63 

Drs. PlUcker and Hittorf on the Spectra of Ignited Gases 

and Vapours 64 

Mr. B. Stewart on Sun Spots 68 

Mr. J. P. Gassiot on a Train of Eleven Sulphide-of-carbon 

Prisms arranged for Spectrum Analysis 69 

Proceedings of the Geological Society : — 

Mr. J. W. Salter on some New Fossils from the Lingula- 

flags of Wales 72 

Messrs. Hull and Green on the Millstone-grit of North 
Stafibrdshire, and the adjoining parts of Derbyshire, 

Cheshire, and Lancashire 72 

Mr. W. P. Blake on the Geology and Mines of the Nevada 

Territory 72 

Mr. H. Seeley on the Red Rock in the Section at Hun- 
stanton 73 

The Rev. D. Honeyman on the Geology of Arisaig, Nova 

Scotia 74 

Mr. J. W. Kirkby on some Remains of Fishes from the 

"Upper Limestone " of the Permian Series of Durham. 74 
Mr. P. M. Duncan on the Fossil Corals of the West Indian 
Islands 74 



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IV CONTENTS OP VOL. XXVIII. — FOURTH SERIES. 

Page 
Remarks on the Distillation of Substances of different Volatili- 
ties, by M. Carey Lea 75 

Note on the Residual Charge of Electrical Condensers, by M. 

J. M. Graugain 76 

On the Boiling of Water, and on the Explosion of Steam-boilers, 
by M. L. Dufour of Lausanne 78 



NUMBER CLXXXVIL— AUGUST. 

Prof. Tyndall on the Absorption and Radiation of Heat by 

Graseous and Liquid Matter.— Fourth Memoir 81 

Dr. Woods on the Relative Amounts of Heat produced by the 

Chemical Combination of Ordinary and Ozonized Oxygen . . 106 
Mr. W. F. Barrett on a Physical Analysis of the Human 

Breath 108 

Mr. J. CroU on the Physical Cause of the Change of Climate 

during Geological Epochs 121 

Prof. Stefan on the Dispersion of Light by Quartz, owing to the 

Rotation of the Plane of Polarization 137 

Father Secchi on Earth Currents, and their relation to Electrical 

and Magnetic Phenomena 140 

Pof. Maskelyne and Dr. Lang's Mineralogical Notes (With a 

Plate.) 145 

Dr. Joule on the History of the Dynamical Theory of Heat . . 150 
Proceedings of the Royal Society : — 

Mr. W. Hugginsand Dr. A. Miller on the Spectra of some 

of the Fixed Stars 152 

Mr. P. E. Chase on Aerial Tides 154 

Mr. H. C. Sorby on the Microscopical Structure of Me- 
teorites 157 

Proceedings of the Geological Society : — 

Mr. T. Codrington on a Section with Mammalian Remains 

near Thame 159 

Mr. E. Witchell on a Deposit at Stroud containing Flint 

Implements, Land and Freshwater Shells, &c 159 

Mr. A. Lennox on the White Limestone of Jamaica, and 

its associated intrusive rocks 159 

Fort-Major T. Austin on the Earthquake which occurred 

in England on the 6th of October, 1863 160 

Apjohn's ' Manual of the Metalloids ' 160 

On the Measurement of the Chemical Brightness of various por- 
tions of the Sun's Disk, by Thomas Woods, M.D 166 

On the Colouring-Matter of Emeralds, by MM. Wohler and 

G. Rose 167 

Researches on the Respiration of Flowers, by M. Cahours ... 167 
On the Spectral Ray of Thallium, by M. J. Nickl^s 168 



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CONTENTS OF VOL. XXVIII. — FOURTH SERIES. V 

NUMBER CLXXXVIIL— SEPTEMBER. 

Page 
Prof. Mitscherlich on the Spectra of Compounds and of Simple 

Substances. (With Two Plates.) 169 

Prof. Breithaupt on the Quartz from Euba, and on the Biaxial 

character of P3rramidal and Rhombohedral Crystals 190 

Prof. Norton on Molecular Physics 192 

The Hon. Chief Justice Cockle on the Operating Symbol of 

Differential Covariants 205 

Prof. Plateau on the Conditions of Stability of thin Films of 

Liquids 206 

Mr. G. F. Rodwell on some Effects produced by a Fluid in 

Motion.— No. II. On the Trompe. (With a Plate.) 209 

Dr. Atkinson's Chemical Notices from Foreign Journals .... 225 
Proceedings of the Royal Society ; — 

Dr. T. B. Robinson on a New Mercurial Gasometer and 

Air-pump 235 

Proceedings of the Geological Society : — 

Captain Godwin-Austen on the Geology of part of the 

North-western Himalayas 241 

Prof. Huxley on the Cetacean Fossils termed Zipkius by 
Cuvier, with a notice of a new species (Belemnoziphius 

compressus) from the Red Crag 241 

Mr. W. B. Dawkins on the Rhaetic Beds and White Lias of 
Western and Central Somerset, and on the Discovery 
of a new Fossil Mammal in the Grey Marlstones beneath 

the Bone-bed 242 

Dr. HoU on the Geological Structure of the Malvern Hills 

and adjacent District 243 

On the Rotatory Power of Active Liquids and of their Vapours, 

by M. D. Gernez 243 

Inversion of the Absorption Bands in the Spectrum of Didymium, 

by R. Bunsen 246 

On a New Polarizing Prism, by Prof. H. W. Dove 247 

On the Optical Properties of Carthamine, by Prof. H.W. Dove. 247 



NUMBER CLXXXIX.-^OCTOBER. 

Dr. H. Draper on the Photographic Use of a Silvered- Glass 

Reflecting Telescope 249 

Prof. Tyndall on the Conformation of the Alps 255 

Prof. Potter on the Law of the Expansion of the Gases by in- 
crease of Temperature * 271 

Prof. Norton on Molecular Physics ; 276 

Dr. Rankine on the Properties of certain Stream-Lines 282 

Mr. P. G. Tait on the History of Thermo-dynamics 288 



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VI CONTENTS OF VOL. XXVIII. — FOURTH 8BBIB8. 

Pace 

Mr. A. G. Ramsay on the Erosion of Valleys and Lakes ; a 
Reply to Sir Roderick Murchison's Anniversary Address to 

the Geographical Society 293 

Prof. Bohn's Historic Notes on the Conservation of Energy . . 311 
Proceedings of the Royal Society : — 

Mr. T. Graham on the Properties of Silicic Acid and other 

analogous Colloidal Substances 314 

Proceedings of the Geological Society : — 

Mr. J. Powrie on the Fossiliferous Rocks of Forfeurshire 

and their contents 321 

Prof. R. Harkness on the Reptiliferous Rocks and Foot- 
print Strata of the North-east of Scotland 321 

Mr. J. Evans on some Bone- and Cave-deposits of the 

Reindeer-period in the South of France 321 

Prof. J. Helmersen on the Carboniferous Rocks of the 

Donetz and the Granite- gravel of St. Petersburg. . 322 

Mr. G. Maw on a supposed Deposit of Boulder- clay in 

North Devon 322 

Dr. Young on the former existence of Glaciers in the High 

Grounds of the South of Scotland 323 

Mr. T. Belt on the Formation and Preservation of Lakes 

by Ice-action 323 

Mr. S. H. Wintle on the Geological Features of Hobart, 

Tasmania 323 

On the Ebullition of Water, and on the Explosion of Steam- 
boilers, by M. L. Dufour 324 

On the Application of Zeiodelite, by R. Bottger 326 

On the Determinations of Temperature in the depth of some Ba- 
varian Mountain Lakes, by Prof. Jolly 326 

On the Meteorite of Albareto in the Modenese, by Dr. W. 
Haidinger 327 



NUMBER CXC— NOVEMBER. 

Prof. Tyndall on Luminous and Obscure Radiation 329 

Mr. D, Forbes on Evansite, a new Mineral Species 341 

M. £. Jochmann on Induction in a Rotating Conductor .... 347 
Mr. J. Bishop on the Influence of the Pitch of the Tuning- 

Fork on the Mechanism of the Human Voice 349 

Mr. C. Tomlinson on the Cohesion-Figures of Liquids. (With 

Two Plates.) 354 

Mr. E. J. Mills on a Defect in the Theory of Saturation .... 864 

Mr. J. Gill on the Dynamical Theory of Heat 367 

Father Secchi on Shooting- Stars 377 

Prof. Norton on Molecular Physics 382 

Notices respecting New Books : — Prof. Church's Laboratory 

Guide for Students of Agricultural Chemistry ! 390 



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CONTENTS OF VOL. XXVIII. — FOURTH SERIES, Vll 

Page 
Proceedings of the Royal Society : — 

Prof. Stokes on the Redaction and Oxidation of the Co- 
louring Matter of the Blood 391 

Influence of Heat-force on Vegetable Life, by George Bentham, 

F.R.S., President of the Linnaean Society 400 

Analysis of Langite, a new Mineral from Cornwall, by M. Pisani. 403 
On the History of Energetics, by Prof. Rankine, LL.D.,F.R.S. 404 
On the Temperature of Sea-water, by M. Charles Martins. . . . 405 

On the Ancient Aqueduct of Alatrl, by Father Secchi 406 

Phenomena observed in the Spectra produced by the Light of 
Induction-Currents in traversing Rarefied Gases, by M. J. 
Chautard 408 



NUMBER CXCI.-DECEMBER. 

Prof. Lorenz on the Theory of Light. — Second Memoir 409 

Prof. Norton on Molecular Physics 425 

M. G. Vander Mensbrugghe on some curious Effects of the 

Molecular Forces of Liquids 434 

Prof. Tyndall's Contributions to Molecular Physics. Being the 

Fifth Memoir of Researches on Radiant Heat 438 

Prof. Donkin on certain statements in Elementary Works con- 
cerning the Specific Heat of Gases 458 

Mr. C. J. Monro on the Nomenclature of the Physical Sciences. 461 
Prof. Church on Tasmanite, a new Mineral of Organic Origin. 465 

Dr. C. K. Akin on the History of Force 470 

Proceedings of the Royal Society ; — 

Comparison of Mr. W. De la Rue's and Padre Secchi's 

Eclipse Photographs, by Warren De la Rue, F.R.S. . . 477 

A Letter from John Davy, M.D., F.R.S., to the Editors of the 

Philosophical Magazine in reply to certain charges made by 

C. Babbage, Esq., F.R.S. , &c., against the late Sir Humphry 

Davy, when President of the Royal Society 480 

On the Comparison between the English and Metrical Readings 

in Double-scale Barometers, by W. Mathews, Jun 484 

On the Spectrum of Jupiter, by Father Secchi 486 



NUMBER CXCII.— SUPPLEMENT. 

Prof. Challis on the Dispersion of Light 489 

Prof. Maskelyne and Dr. Lang's Mineralogical Notes. (With a 

Plate.) 502 

Prof. Tyndall's Contributions to Molecular Physics. Being the 

Fifth Memoir of Researches on Radiant Heat 508 

MM. Pelouze and Maurey on Gun-cotton, with reference to the 

New Methods of General Baron von Lenk for preparing and 

employing this Substance • • 535 



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Vni CONTENTS OF VOL. XXVIII. — FOURTH SERIES. 

Page 
M. F. M. Raoult on the Thennal Phenomena of Voltameten, 
and Measurement of the quantities of Heat absorbed in Electro- 
chemical Decompositions 551 

Dr. C. K. Akin on Ray-Transmutation 554 

Notices respecting New Books : — ^Mr. W. A. Darby's Astrono- 
mical Observer. A Handbook to the Observatory and the 

common Telescope 561 

Proceedings of the Geological Society : — 

Messrs. P. M. Duncan and G. P. Wall on the Geology of 
Jamaica; with Descriptions of new Species of Cretaceous, 

Eocene, and Miocene Conds 562 

Mr. H. Tate on the Correlation of the Irish Cretaceous 

Strata 562 

On the Verification of the Law of Electrolysis when external 

work is performed by the Galvanic Current, by M. J. L. Soret. 563 
Index 564 



PLATES. 

I. & JI. Dlustrative of Prof. Mitscberlich's Paper on the Spectra of 
Compounds and of Simple Substances. 

IIL Illustrative of Dr. Viktor von Lang's Paper on the Crystalline forms 
of Gadolinite. 

TV*. Illustrative of Mr. G. F. Rodwell's Paper on the Trompe. 

V. & VI. Illustrative of Mr. C. Tomlinson's Paper on the Cohesion-figures 
of Liquids. 

VII. Illustrative of Dr. Viktor von Lang's Paper on some Cr3r8talline forms 
of Malachite, Gismondine, and Herschelite. 



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THE 
LONDON, EDINBURGH, and DUBLIN 

PHILOSOPHICAL MAGAZINE 

AlTD 

JOURNAL OP SCIENCE. 



[FOURTH SERIES.] 



JULY 1864. 



I. On the Extra Current of the Induction Current. 

By J. C. POGGENDOBFF*. 

IN my latest investigation laid before the Royal Academy in 
August last^ on the thermal action of electrical sparks^ in 
order to test the view propounded by Reitlinger^ that this action 
is proportional to the intensity of the current, I had interposed 
very long wires^ in the form of coils, in the path of an induction 
current. I thereby observed that the sparks, notwithstanding 
the considerable enfeeblement in intensity produced by this in- 
terposition, lost scarcely any of their heat^ just as they have long 
been known to become thereby more fully luminous, but to lose 
little or none of their striking-distance. 

I observed on this occasion that when the circuit of the in- 
ductorium is completely metallic through such accessory coils, 
the current, in spite of this metallic circuit, and in spite of the 
great enfeeblement which it experiences through the resistance 
of a very long and thin wire, possesses such tension that ex- 
tremely piercing sparks are obtained if the wires are merely 
touched in one point with the hand. 

I further found that the free electricity at the end of the ac- 
eessory coil turned towards i\it positive pole of the inductorium 
lApoiitive^ and negative at the other end; and that if two such 
accessory coils are placed end to end, the wire joining them ex- 
hibits far less tension than the t\vo wires leading from the coils 
to the inductorium, from which I concluded that in the long 
metallic circuit there must be a zero point of tension. Finally, 
I convinced myself, by individual interruptions of the voltaic ex- 

* Translated from the Monatsbericht der Berliner Akademie, November 
\S63, by Dr. E. Atkinson. 
PhU. Mag. S. 4. Vol. 28. No. 186. July 1864. B 



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2 Prof. J. C. Poggendorff an the Extra Current 

citing current^ that the tension observed only belongs to the 
current when it is opened. 

These phenomena are certainly surprising when it is considered 
that the poles of l^e inductoriam lose their tenaioo oompletebr 
when they are joined by a simple^ by no means short, \hiac 
metallic wire. It is indeed stated that they retain even then a 
trace of tension; bat with my apparatus! could not observe it, 
either by the gold-leaf electrometer or with the tongue. Even 
when I had approached the poles of a powerful apparatus till 
they produced sparks abundantly, I could, by means of 100 feet 
of a platinum wire O'l millim. in diameter, which was bait back- 
wards and forwards in the air, and was equal in resistance at 
least to 1000 feet of the induction wire, entirely take away not 
merely the sparks, but every perceptible trace of tension at the 
poles, when I connected them with the two ends of this wire. 
But these phenomena of tension were at once distinctly observed, 
though in a less degree, even with a oopper wire of 0*66 millim. 
in thickness and not more than 400 feet long which was rolled 
in the form of coil. 

Non-metallic, relatively bad conductors alone exhibited a dif- 
ferent deportment in this respect. A hemp string, for instance, 
moistened with feebly acid water, showed not merely tension in 
the electrometer, but gave just as delicate sparks as a large coil 
of wire, even when its length was only an inch or less. 

It differed remarkably from metallic wires (in which, as is well 
known, only veiy feeble heating is perceptible) by the fact that 
it became considerably heated — so much so, that a thermometer 
round whose cylinder it was coiled once, rose in a minute from 
40^ to 50°, that it smoked visibly^ gradually dried, then car- 
bonized, and finally disappeared with sparks. 

Although it was not impossible that even straight wires of 
great thickness and length, simply in virtue of their resistance, 
might exhibit a certain tension when united with the poles of 
the inductorium, I was yet convinced that the phenomena 
mentioned were not phenomena of resistance, but arose from an 
induction which might indeed occur in a feeble degree in straight 
wires, and I designated it even then as the result of such a 
process, without expressing an opinion as to the particular manner. 

Continued occupation with the subject has confirmed me in 
the original view, and leads me to consider it as not doubtful 
that the tension observed proceeds from an induction current, 
which the current of the inductorium, the current of opening, 
produces in the spires of the accessory coU in the opposite direction 
to its own. 

As it is usual to designate the current of induction, which die 
voltaio current can produce in its own wire on opening and 



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cfthe Induction Current, Z 

ekMing, as an extra current^ I do not hesitate to designate the 
current in question as i)ie extra current of the mduction current. 

To test this view more aceurately^ it appeared best to invesr 
tigate the deportment of various induction apparatus to each 
other. 

I firit combined two apparatus of this kind^ as similar as pos-* 
sible^ in opposite directions^ by joining in a corresponding manner 
the two external divisions of an inductorium with three divisions, 
by bright oopper wires of small length. Although each of these 
divisions only contained 1200 feet of copper wire of 0*26 millim. 
in thickness, and, both united in the same direction, exhibited no 
{perceptible trace of tension, yet when united in opposite direc- 
tions their junction wires gave painful sparks. 

There was no current in this ; for an electrical egg interposed 
in one of the joining wires showed no luminous phenomena. 

Thereupon I combined this inductorium as a whole, in which 
it contained about 8800 feet of wire, in an opposite direction 
with another large apparatus whose induction coil consisted of 
23,000 feet of wire .fth of a millim. in thickness, in which I 
passed one and the same voltaic current through the inducing 
coils of both, and interrupted them by one and the same hammer. 

I began by testing the induction coils singly, by causing 
one to give sparks at the micrometer while the other was closea 
by metal. As was to be presupposed, the larger apparatus was 
the more powerful ; the striking-distance of its sparks was more 
than double that of the sparks of the smaller. 

When they were now combined in an opposite direction (that 
is^ the similar poles of both coils united) by bright copper wires 
of no great length, a current moved in the direction of the 
stronger apparatus accompanied by a tension upon the joining 
wires, which yielded even more piercing sparks than those in the 
former case*. 

Both these results serve doubtless as a support of my view, in 
so far as they show that when, in a closed circuit of wire, two 
induction currents (whether equally or unequally strong is quite 
immaterial) act in opposite directions to each other, free elec- 
tricity occurs. 

It was now necessary to furnish a proof that in the original 
experiment the current of the inductoi:ium evoked an opposite 
current [Oegenetroni^ in the accessory wire. This was effected in 
two ways. 

* I will not omit to mention that even when both apparatus were ioined 
in the same direction, a tension was indeed observed on the wires, though 
somewhat feeble. This, however, I can only consider as abnormal, arising 
firom some not yet explained drcumstance. For^ if it were normal, it must 
Occur in each individual inductorium, as that may always be supposed to 
consist of two unequal instruments acting in the same direction. 

B2 



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I Mi CMflMcd «f tik m d 

m ttubuymatm ksrisr 10,000 1 

(Oismn^r ewnsfty to tkai the 
iH^^mA ^ytrmiEt and 
lurf ptMbcnl so vnnk. 

Bjr flwaM of this vmigeBciit, and vitlioat iraa vkc u the 
MQMwrf ml, I obtained a ddkcboo of dboni SO^intk gal- 
waJMmfter, and the wdMaMMrn huninositT in the tgg. When 
tbe ma wm interposed in the eoil, the dcAectioB sank at kaat 
to half iuamoont, and the light in the cg^ dnappeared afanoat 
^oaqdetdr, being c e d necd to a tew iiresnlar spades. 

Hcnee the strengthening of the opipadbt cuiCBt^ and Uiere- 
tote its enstenee, eannot be aafageet to any donhi. 

In what mannor soft iron straigthens the opposite eoirent 
does not eome into eonsidefation. I vill, however^ rennrk that 
an induction emrrentmagnetiard the iron in the same direction as 
that in which it defleets a magnetic needle, that it gives therefore 
to Ampere's mofecolar coiraits the same direction as its own; 
while in an adjacent wire, aeeorduEig to the observations of Henry 
and others, it prodaees an indoetion corrent of the second <»der in 
an opposite direction^. By its magn^intion the inm reacts on 
the magnetising induction wire, and as it prodoees in it an op* 
posite current, I conclude that this current is the prodoct of the 
commencing magnetism, and the disappeaiii^ aets little, or not at 
all. If in the momentary magnetisation which the soft iron 
experiences by the induction current, resulting frmn the opening 
of the voltaic current, both elements, the increase and decrease 
of the magnetism, were of equal influence upon that current, it 
could not be perceptibly^ affected. 

A closed coil inserted in the accessory coil acts differently, 
that is, enfeebles the opposite current, and therewith the tension ; 

'*' It is clear that an induction cmrent, since in its transitoiy career it in- 
creases and decreases, must induce two currents as well in its own as in an 
adjacent wire, one of opposite and one of the same direction. But ac- 
cording to all observations the first is« in ffslvanic induction, the stronger; 
hence I have only spoken of it, and (»lled it opposite current. 



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of the hiduction Current. 5 

for the inducing induction current produces in it a current of 
the same direction as the opposite current which reacts upon this. 
But I had no coil of a sufficient number of windings^ which I 
might have inserted in the accessory coil^ so as in this way com- 
pletely to destroy the opposite current. 

The inductorium itself gives the second proof of the existence 
of the supposed opposite current. For to produce the often 
mentioned phenomena of tension it is unnecessary to 'use an 
accessory coil ; the inductorium itself is quite sufficient. 

-Nothing more is necessary than that^ after the poles of the 
instrum^at at work have been united with one another by a 
short wire, the inducing coil together with its iron core be par- 
tially withdrawn. On commencing^ free electricity appears in 
the junction wire, and it increases until about two-thirds or 
three-fourths of the coil are withdrawn from the induction coil. 
It is true that in this case the empty part of the induction coil 
represents the position of the accessory coils in the earlier expe- 
riments, and so far this result is not surprising. 

If now the inducing coil is slowly reinserted, free electricity 
begins to decrease, and continues to entire disappearance when the 
coil has been restored to its original position. This also is 
natural. 

But, it may be asked, what happens in this second process 7 
Obviously nothing else than that, in the coils of the empty part 
of the induction coil, the original induction, partly or entirely 
removed, is reproduced. This induction destroys the earlier 
condition. But what destroys an induction can be only an in- 
duction, and one of opposite direction; hence by this experi- 
ment the existence of the opposite current is proved. I do not 
suppose that anything well founded can be urged against these 
simple conclusions. 

I will only add that the phenomenon of tension in question, 
if purely one of reustance, could never entirely disappear, but 
rather, even with the very best conduction between the poles of 
the instrument, must occur in full force ; for each partial current 
which is induced in an individual spire of the induction coil has 
to traverse the sum of all the other spires of the coil, and hence 
to overcome a resistance which would be quite sufficient to cause 
free electricity to appear if this were merely evoked by resistance. 

From all this I consider the origin of free electricity in the 
circuit of a metallic closed inductorium to be sufficiently esta- 
bUshed, and hence I think myself justified in passing over other 
experiments which I have undertaken in this direction. 

Tet I cannot help discussing an objection which seems to 
follow from the statement that the striking-distance of the in- 
duction spark uudergoes no enfeeblement from a wire circuit 



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Prof. J. G. Poggendorff an the Extra Current 

introduced into the path of the ourrent. The ttriking-ditttnee 
stands obyionalyin a direet ratio to the electromotiyerofce; and 
when this latter is enfeebled by an opposite corrent, it can scwoely 
be otherwise than that the strilong-distanoe should also be 
diminished. Althoagh my earlier investigations seem to speak 
against this^ I beliere that such a diminution actually occurs 
whenever the interposed wire is used in the form of coil, and 
that it is only on the one hand the indefinitenessof the striking* 
distance^ and on the other the weakness of the partial current, 
which may have prevented this diminution from being perceived. 
It does not here depend so much on the absolute length of the 
coil added, as upon its ratio to the length of the wire of the in« 
ductorium. With a certain ratio, the opposite current, or its en- 
feebling influence upon the inducing current, is most strongly 
developed, and then the diminution also naturally follows. 
Some experiments which I made in this respect were favourable 
to this view, although a repetition of them with greater means 
than those at my command would not have been superfluous. 
For straight wires, the above statement, though not perhaps with 
the utmost rigidity, applies with tolerable approximation. 

In the foregoing 1 have only spoken of the developments of 
the opposite current in free air; its occurrence is extremely 
striking when part of the circuit is in a rarefied space. 

If under the receiver of an extra plate of an air-pump which 
is provided with the necessary insulated conductors, a bright 
copper wire is stretched, and the air is adequately exhausted^ 
and if the arrangement is placed in the circuit of an inducto* 
rium provided with its accessory coil, as soon as the instrument 
is set to work the wire is seen to become brightly luminous, and 
to send bright rays towards the bell. The phenomenon is im- 
proved by clothing the bell externally with a strip of tinfoil 
corresponding to the wire, which is placed in connexion with 
the ground; and still more by bringing a small piece of phos« 
phorus under the bell. 

In general the wire does not become continuously, but partially 
luminous ; these luminous parts are in continual motion, nm 
backwards and forwards on the wire, and send ghmmering raya 
towards the tinfoil, which also becomes luminous <m the inside^ 
so that the whole, since at the same time the dark parts, by' 
contrast, appear to emit dark rays, has an appearance like that 
of the aurora borealis. 

I could see nothing of a stratification in this luminous phe« 
nomenon, although I had first with this view allowed phospho*' 
rus to evaporate under the bell ; the formation of stratifioation 
is probably suppressed or concealed by the great mobiUty of the 
light. Nor could I perceive any matenal difierence in ihe appear «^ 



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ofikelnAietianOurreni. 3 

macB and oolour of the light when the reoei?er was alternately 
tonohed on the positiTe and on the negative aide of the apparatus. 
Its colour is whitish throughout. 

!niis side light ^ as I will call it^ as it is obviously analogous to 
the lateral emissioDS which have long been known in powerful 
ideetric discharges in free air^ was most intense when the induc« 
torium was made to give sparks in the air, and at the same time 
the air surrounding part 6i the joining partiaUy exhausted. The 
further apart the poles are moved, the more intense is the light, 
«nd of course the tension upon the wires* It is, on the o&er 
lia&d, relatively feeble if the poles of the apparatus are con- 
nected with the armatures of a Ley den jar, in which, as is known, 
recurrent currents are formed, and the tension upon the wires is 
fcebler. 

The side light is a useful indicator of the degree of free elee« 
tfieity on the wires. 

If, for example, an induction coil is placed in metallic connexion 
with a larger one, and an induction current is alternately pro- 
duced in the first and in the second, while the other is used 
empty as an accessory coil, even the sensation of feeling shows 
that the tension in the wire is stronger when the current is in- 
duced tn the smaller coil, although the current is feebler in that 
Case than in the other; but this is shown much more convin- 
cingly by the side light. The strengthening action produced by 
introducing a bundle of iron wire into the accessory coil cannot 
be more surprisingly shown than by the side light. 

I must in conclusion mention that in 1859, Eoosen*, on the 
occasion of another investigation, made observations which are 
closely allied to mine, but do not quite coincide with them. He 
observes the phenomenon in a form in which it is essentially a 
phenomenon of partial currents. He offers, that is, two paths for 
the induction current, one through air and one through metal, 
by letting the poles of the instrument give sparks, and joining 
them at the same time by a very long wire, in which he finds 
that the striking-distance of the sparks, in spite of this metallic 
lateral circuit, is either not at all or not perceptibly diminished. 
The free electricity in the wire has not indeed escaped him ; but 
since he only states that the wire has a certain temion which can 
be shown by the gold-leaf electrometer, while he does not mention 
the sparks and their piercing action, he has probably not seen 
the pnenomenon in its full development, perhaps because he 
nsed'COvered and varnished wires^ perhaps because he only studied 
it at one branch of the current. Finally, he does not dwell 
iipon the cause of the phenomenon. Although he has in all pro- 
balnlity' used the wire in the form of coil, yet he does not say 
* ?ogj?. ilfiw. voLdvii. p.2n. 



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8 Mr. C. Packe en the Seales of the 

80^ but always speaks of the length and resistance of the wire. 
So that I do not consider the publication of my ezpenments to 
be superfluous. 

I have^ moreover^ repeated the observations in the manner 
described by Koosen^ and found them confirmed in the main 
point, as was to be expected; yet I have also observed that it 
depends on the relation between the length of wire in the aoeesaory 
coil and in the inductorium. An accessory coil of 10,000 feet 
took away completely the sparks of an inductorium of 23,000 
feet, while it left untouched those of a small instrument of 8000 
feet. The phenomenon is best seen as one of partial currents and 
of resistance when a hemp thread 5 or 6 feet in length, moist- 
ened with spring-water, which is fixed insulated in the air, once 
backwards and forwards, and connected with the poles of the 
spark micrometer. By moving a wire bridge laid across, it can 
be shortened at pleasure for the current, and it may be observed 
that the first action upon the sparks consists in an attenuation 
of them. 



II. On the Discrepance between the English and French Baro* 
meter-Scales; and on the Corrections necessary in reducing the 
Readings to the Freezing-point, By Charles Packe, Esq. 

To the Editors of the Philosophical Magazine and Journal. 

Gentlemen, 

HAVING brought out with me a barometer graduated with 
a double scale, reading millimetres on one side and inches 
on the other, I have been at some pains to investigate the slight 
apparent anomaly existing between the French and English 
scales as compared with the boiling-point, which I think may 
be satisfactorily accounted for in the following manner : — 

Boiling- Barometer, 

point, f in. mm. 

212° F., J 29-905 or 759-58, 

or = *] as given by the Kew 
100 C. I Committee of the British 
^ Association. 



fin. ,, mm. 

29-922 or 760, 
— '^ as given by Regnault in 
I his Tables of the Elastt- 
^ city of Vapour. 

The larger portion of this discrepance arises from the diflFer- 
ence of the standard temperature of the scales of the English 
and French barometers ; the remainder is accounted for by the 
difference of latitude producing a variation of gravity. 

First as to the discrepance arising from the standard tempe- 
ratures. That of the English barometer being 30° F. higher 
than that of the French scde, when the mercurial column is re- 



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Enfflish and French Barometers, 9 

dniced to the freesing-point^ the scale of the French barometer 
is also reduced to the freezing-point, but the scale of the English 
one is only reduced to the temperature of 62^ F* 

The consequence is that the French barometer^ when reduced, 
will always read higher than the English barometer. 
Let A be the height of the barometer observed ; 

B the linear expansion of brass for P F. =:*0000104344, . 
as given by Laplace and Lavoisier, or '000018782 for 
PC. 

The French barometer^ when reduced, will, on account of the 
difference of standard temperatures, read higher than the English 
barometer by an amount =30 AB ; e, g,, 

Let the height of the barometer be s= the boiling-point 212% 
i. e. 29-905 inches. 

B=: -0000104844= log 5-018467 

A=29-905 = log 1-475748 

80 = log 1-477121 

3-971331 ss -009361 inch excess of 
the French reading. 

By changing A it will be evident that we get the excess for any 
height of the barometer, but for the average height at the sea- 
level it may be taken as '009 inch* 

For exact observation, therefore, it is useless to have a baro- 
meter ma:rked with a double scale, — the French and English : 
they cannot be made to coincide ; e,ff. 

Let the barometer read 29 inches = 736-59 millims. (temp. 
62oF.=16°-67C.). In the English scale at 62° (the temperature 
of the standard) no correction is made for the brass scale. The 
only correction is for the expansion of the mercury —•087, 

in. 

29 
- -087 
reduced 28*913=734-38 millims. 

But in the French scale, the temperature of the standard being 
82° F., the correction to be made is for the expansion of the 
mercury — the expansion of the scale : 

mm. 

Expansion of mercury for 16°-67 C. = 2-212 
Expansion of brass scale for „ g— -231 



1-981 



736-59 
- 1-981 



reduced 734-61=28*9^24 inches. 

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10 Mr. CPadte on the 8eMb$ of ike 

' To reAieo the bthnneier to Hie freeniig^poiiit^ we haire the i 
folliywtBg fenniilB 2— I 

Let M = the cubic expanuon of meroury far the munber of 
degrees Centigrade or fthrenheit, by which the 
. obterred temperature differt from the freeiiiig-poiiit 
B = the linear expaneion of the brass scale for the num* 
ber of degrees by which the observed temperature 
difim from the standard. 
Hss the observed height of the barometer in inches or 
millimetres. 
The formula for the reduction of the English barometer will be 

Above 62° F, .... -.(M-^B)xH 
Below 62^ above 82^ . -(M^.B)xH 
Below 82° +(M-B)xH 

For the reduction of the French barometer^ 

Above the freezing-point • ^ (M — B) X H 
Below the freezing-point . -|-(M— B) x H 

By the difference in the standard temperatures we can thus 
acconnt for -00986 inch out of the 017 by which the Kew 

Suivaknt to the boiling-point differs from that of Bj^piault. 
le remainder is almost exactly accounted for by the difference 
of gravitation. 

The increase of gravitation^, i. «• gravity as diminished by the 
centrifugal forcOi is from the equator to the poles sst*0052005| 
or '00260 to the 45th degree of latitude. 

Adopting the law that it increases as the square of the sine of 
the latitude, we find that in 51° 301^ the latitude of London^ the 
increase of gravity is ss -0081852; in latitude 49% that of Parisi 
the increase of gravity 0029621. 

Let D be the difference of these two gravities ='0002281 ; 
B' the height of the mercurial column at London^ equiva- 
lent to a given pressdre ; 
B the corresponding height of the mercurial column at 
Paris, 
B will be equal (B'+ WSX) .e.g. 

Gravity in lat. 5P 80':ii-008185a 
Gravi^ itt ht. 49** = 0029621 

Differenee =^K)002381«e log 4*848805 «t:D 
29-905 = log 1-475744=B' 

8-824049 =-006688=80). 

To compare, therefore, the barometric column at London i 
with that representing a oorresp^iding pressure at Paris, we a 



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EmgUih amd French Baramaten. 1 1 

HiU9t add two oorraotionft-H>ne for the difference of the tempe- 
rature of stEDdard, and a second for the decceate of gravity. 
The corrections will be as follows : — 

Barometer at London observed and"n Ai>.Q^R 
reduced to freezing-point j '^'^^ 

Correction for temperature of standard + '009861 
Correction for decrease of gravity . + '006688 

* 29-921049 equivalent 
pressure at Paris. 

This is very close to the equivalent pressure which Begnault 
gives in his Tables, 760 millims. =329*922 inches*. 

Of course in a lower latitude the accurate correction for gravity 
will be greater; but practically all Tables are made to corre- 
•pond with that of London or Paris; or else the barometer is 
supposed to be reduced to the mean gravity of lat. 45^=: :0026008«. 
I am somewhat astonished to find that in all the Tables given for 
the reduction of the barometer to the freezing-point, the only 
elements taken into consideration in computing the dilatation 
of the mercurial column are the linear expansion of the brass 
scales, and the cubic expansion of mercury. Surely for real 
accuracy the superficial expansion of the glass tube (i. «. increase 
of its capacity) should also be allowed for, as was done by Mr« 
Stewart in his experiment to determine the melting-point of 
mercury (see Phil. Trans, vol. cliii. p. 480). 

Let the expansion in volume of mercury (i. e. cubic) be, as 
determined bv Segnault, s= -00018153 for each degree Centi- 
grade above the freezing-point, and the coefficient of linear ex- 
pansion of the glass tube he = *0000086130, as determined by 
Dulong and Petit; then the coefficient of the superficial ex- 
pansion (t. e. capacity)^ of the glass tube will be =s '00001 7226. 

Take M for the cubic expansion of the mercury, and Q for the 

* I h«fe taken the iacrssse el gravily adopted by Giiyet in His Tsblss. 
aeO*005fi(KN8, which ssstimeii the elliptictty of the earthy- 

If we take the ellipticity of the earth as given by the British Ordnance 
Survey^ ^ (see Phil. Mag. vol. xziv. p. 413), we shall get the increase of 

S-avity from tha equator to the pole a. -00^919, and ibis will gite the. 
fference between that of Paris and London 

=•00023642 = log 4-373684 
29-905 = log 1-475743 

3*849427 a 'OO707O, the amount to be added 
for gravity. 



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12 Mr. T. K. Abbott an the ProbabOUy of 

superficial expansion of the glass tube, for the nnmber of degrees 
observed above or below the freesing-point. 

The dilatation of the mercnrial column will be ssM— G^ or 

•00018153 
-■000017226 

s= 000164304 for each degree Centigrade^ 
=*000091280 for each degree Fahrenheit. 

The Tables, French and English, give as the correction, 

' -0001614 for 1° Centigrade;= -00008967 for V Fahrenheit ; 

but they all take Dulong and Fetit's coefficient for the cubic 
expansion of mercury, which is lower than that of Segnault, 
being only -000180180. 

When the column is thus reduced for the expansion of the 
mercury, the additional correction for that of the scale has to 
be applied. 

I am, Grentlemen, 

Yours faithfully, 
Gavarnie, Hautes Pyr^n^s, Chables Facke. 

April 22, 1864. 



III. On the Probability of Testimony and Arguments. ByT.K. 
Abbott, M^., Fellow and Tutor of Trinity College, Dublin*. 

THERE are certain questions respecting the probability of 
testimony and argument which, although of considerable 
practical importance, have been either neglected or erroneously 
treated by writers on the subject. It is the purpose of the pre- 
sent paper to consider briefly a few of these, keeping in view not 
so much theoretical generality or completeness, as the corre- 
spondence of the conditions assumed with those which occur in 
ordinary experience. 

The case of testimony is represented in the ordinary treatises 
as follows : — Suppose a witness. A, affirms that a certain event 
has occurred, the antecedent probability of which was/?, and let 
the witness's credibility be a. Then, it is said, there are only 
two possible cases. Either he is right, the chance of which is 

and the event has occurred, the chance of which is] 

/. the chance of this coincidence is 

* Communicated by the Author. 



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Teiiimony and Atgumenia. .18 

Or he is wrong, 

and the event has not occurred, 

i-Pi 

/• the chance of this coincidence is 

The sum of these gives the common denominator ; and hence 
the resulting probability, F, that the event has actually hap* 
pened is 

qti + l— al— |i 

Now let there be two or more witnesses who agree in the same 
assertion, their respective credibility being a., a,, &c. Then 
either they are together right, and the event has occurred, the 
chance of which is 

or they are together wrong, and the event has not occurred, the 
chance of which is 

1— fl, 1— fl£...l— fl^ 1—p. 
Hence the resulting probability of the event is 



P= 



From the first formula it follows that, i(as=^,Vssp ; that is to 
say, if this witness attests an event, of the diances of which we 
know nothing, his affirmation is enough to make the odds on it 
even ; but if we have any other means of estimating the chances, 
his testimony goes for nothing. This is certainly not practically 
true. But the second formula leads to a result more obviously 
absurd. Suppose 01=^2= • * • =^«>=i^ ^^^^ ^^ ^^^^ ^^ again 
f^p; that is to say, if any number of witnesses, supposed 
to be wholly independent, give coincident testimony, it adds 
nothing to the probability of the event, unless each separately is 
sufficiently credible to turn the odds in its favour. If the odds 
are against the truth of each witness separately, then the greater 
their number the less credit is due to their testimony. The 
weight usually attributed to the coincidence of independent wit- 
nesses is inconsistent with the formula, according to which 
agreement in truth is just as unlikely as agreement in falsehood. 
A calculation which yields such results as these must be erro- 
neous, or imply .conditions very different from those of ordinary 



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14 M. T. K. Abbott m tke ProbMUty of 

experience. In fact we have taken no account of the datum 
that error is manifold^ while truth ia one. 

Laplace analyzes the case of single witneaaea ai follows. His 
method generally is^ having stated the chances of every possible 
case^ to multiply each by the chances of the hypothesis in that par- 
ticular case. Ihusi suppose an urn contains 100 baSs numbered 
consecutively, and one is drawn. The witness A^ who knowa 
how many bdls there are, a£Srms that the ball drawn was No. 25. 
Let us suppose His general credibility to be | ; we have the fol* 
lowing cases: — 

Hypothesis. — ^A affirms No. 25. 

Either he is right = §, and it was drawn as ^^. In this 
case the hypothesis is certain, therefore the chances of this 
supposition =tTixF=Tk- 

Or he is wrong :^i, and No, 26 was not drawn, ^^^ ; bat 
this must now be miutiplied by the chance of the hypotnesis ixi 
this case, t. e. the chance that when A is wrong, his false testi* 
mony will be borne to No. 25. There being 99 balls not drawn, 
any of which might be asserted iUsely, this chance is therefore ^, 
and the total chances of this last supposition ^^^^^^Af^^ 

The chances of the two suppositions respectively are Uieiemre 
j^ and ^^; and as these exhaust all possible cases, the total 

probability of the event affirmed is ^ ^ ^ ^ • = ^, t, e. it i$ 

TzTTy.Fotr " 
the same as the witness's general credibility. The erroneous 

formula first quoted would have given as the resulting proba- 
biUty ^^ ^ — 



place, it 



Laplace, it will be seen, has taken account of the diversity of 
error ; yet his conditions do not correspond perfectly with those 
of actuu experience. In fact the resulting probability in the 
case supposed was found to depend solely on the credibility of 
the witness, not at all on the antecedent probability of theevent» 
This is a consequence of the supposition that the witness knows 
the number of balls in the urn ; so that the number of possible 
errors is 99, and the odds against any particular ball are also 
99 to I. In fact the chance of any ball being named at random 
is the same as the chance of its being drawn. But there is a 
further condition implied in the mode of stating the problem. 
Let it be supposed that there are 2 white balls, 8 yellowi 
5 red, in all 10. The witness asserts that white is drawn, his. 
credibility being still supposed =f . The chances in favour of 
his assertion are 

If he ia wrong, either yellow was drawn or red. The chancea 



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litHmony and Jrgyme9it8. 16 

oi the fonncr are ^; and as there are 7 balli not of this 
colour^ of which 2 are white, and the witness knows this, the 
ehanees of white being fidsely n^med in this case »^ f '** A* 
Similariy^ the chances of a false assertion of white wiien red is 
drawn =y^ ^ = ^. Total false assertions of white m^, to bis 
mvltqdied by the ehanoe that A speaks fidseljr m^. 
Hence, finally, the probability of A's assertion la 

_i 7. 

In gen^, on th» rapDOtttion, if tb«re are n OMes whose 
probabilities are />„ pp &c., the sum of these being "S,, the chances 
of a false assertion ofjp, are 






Call the quantity within the brackets C ; then if the credibility 
of the witness be a, and he asserts the event Pi, the probability 
that be is right is 

a 
a+(l— a)c' 

If we suppose that the witness knows the colours of the balls, 
but not the number of each colour, the case is different. Sup- 
pose, with the same numbers, be affirms white. Either he is 
rights and it is drawn 

Or he is wrong, and selects white from the two colours not drawn, 
Aesnlting probability id white 

In general, if there be n cases jpi, p^, &c. as above, and the wit- 
ness, knowing only the number of possible cases, asserts the 
event p^ the probability that be is right is 

{n^l)api 

(n-l)api+I-.a(2-/>i) 

Thus it is clear that on either hypothesis the case assumed by 
Laplace is not general. The condition involved in it, stated 
generally, will be seen to be, that, if the antecedent probability 
of the event named be J9, the chances of its being falsely namea 
when it has not occurred are 

JL.. 



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16 Mr. T. K. Abbotfc an ike Probability of 

Now let 118 see how Lapkoe treats the case of a witness attest- 
ing a fact of given antecedent probability. 

Suppose there are 100 balls^ of which one is iHiite and the 
rest black. The witness whose credibility is f asserts that the 
ball drawn was white. The cases are : — 

Hypothem, — ^A affirms white. Either he is right 3s|, and 
white was drawn =xi7y ; 

chances in favour of this supposition ss ^^. 
Or he is wrong = ^, and black was drawn = ^^; 
chances in &vour of this supposition = ^^. 

For on this supposition the hypothesis is certain, inasmuch as A, 
if he is wrong, must bear witness to white. Hence the total 
probability of white is 

6 5 

5+99"* 104' 

tn general if the whole number of balls be n, of which one only 
is white, the rest being black, and the witness whose credibility 
is a asserts that white was drawn, the probability of this event 
is evidently 



a+(l-fl)(n-l) 

The probability that the assertion is not true is 

(n-l)(l-a) . 
a + (n— 1)(1 — a) 

If n is very large, this will not di£Eer much from unity, t. e. 
certainty, if we suppose even a slight chance of mistake or decep- 
tion on the part of the witness. Now this is the case of an extra- 
ordinaiy event ; and the result, adds Laplace, confirms the judg- 
ment of common sense, that such an event requires far stronger 
evidence to prove it than an ordinary one. 

On the same conditions, if several (say r) witnesses join in 
attesting the drawing of white, then if their credibility is the 
same, the resulting probability is 

a^ ^ 

a''+(l-a)'-(n-l)' 

This corresponds with the formula quoted at the beginning of 
this paper, and the same consideration shows that it is not appli- 
cable to such cases as are met with in ordinary experience. Sup- 
pose, for instance, the number of balls is 10, and three indepen- 
dent witnesses testify that white was drawn. If the credibility 
of each is f (t. «., it is 3 to 1 that his unsupported testimony 



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Teiimony and Arguments. 17 

is true)^ then the three together do not make it an even chance 
that white was drawn. The odds are still 9 to 8 against it; and, 
as before noticed, if the testimony of these is supported by a 
number of independent witnesses whose average credibility is 
. only ^, it does not become a whit more probable. Common 
sense shows that this is to allow too much to the extraordinary 
character of the event, and that some condition must be involved 
in the calculation which does nojb apply to the events of ordi- 
nary life. 

One such condition was introduced by the assumption 
that when the witness is mistaken or deceived, there is no 
diversity of error possible. There are only two colours, and he 
knows this ; therefore if black is drawn and he is wrong, it can 
only be by testifying to white. In order to apply such a for- 
mula to the evidence for an extraordinary event in general, we 
must assume that, supposing it not to have occurred, any error 
on the part of the witnesses must have led to its being reported. 
Of course whenever this can be shown, the circumstance detracts 
immensely from the weight of the testimony; but it is very far 
indeed from being generally the case. Before examining the 

!>robIem more generally, it is worth while to show that Laplace's 
brmula applies only to the particular case which he has selected; 
lind that the extension of it by subsequent writers, who substitute 

p (the antecedent probability) for -, is fallacious, even when we 

frame our conditions in perfect analogy with, those of Laplace. 
Thus suppose, besides the 99 black and one white ball, we put 
into the urn 99 blue and one yellow, 99 red and one green. The 
drawing of white is exactly as extraordinary as before, and the 
chances against it greater, viz. M^. Nevertheless when it is 
affirmed its probability becomes (the witness's credibility being §) 

5 25 



5 + ^SL 824 

or more than half as much again as in the former case. We 
must therefore investigate the problem under more general con- 
ditions. 

Suppose then that the witness A does not know anything 
about the colours or number of the balls in the urn ; his affir- 
mations, th^efore, may range over all possible colours, say 
m. Now if he states that the ball drawn was white, we have the 
following cases : — 

Hypothesis. — A. affirms white. Either he is right and white 
18 drawuj n 

n' 

PUl. Mag. 8. 4. Vol. 28« No. 186. July 1864. C 

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16 Mr. T. K. Abbott on the ProbabaUy of 

or be is wrong and black is diamij 

a-.)(=il> 

on which supposition the probabiKty of the hypotheait, t. e. 
the chance that he affirms white oat of the m— 1 colours which 
are not drawn^ ia 

1 

The chances in fiivour of this supposition therefore are 

^ — n-1 1 
n m— 1 

Hence the probability of the event affirmed 

(m^l)tf 
"(m-l)ii+(l-«)(n-l)* 

If there are several (r) independent witnesses who give thf 
same evidence^ then^ supposing their credibility to be ths samci 
the probability of the event is 

(m-l)V 



(in-l)V+(l-fl)>-l) 

In the example above given of 10 balls and 8 witnesses each 
of credibility §^ if we suppose only four colours capable of being 
mentioned^ this formula gives as the probability of the event 
f^; that iS| the odds in favour of the event are 24 to 1 instead 
of being only 8 to 9. 

If now we return to the case put by Laplacci it may be asked, 
is it possible that the circumstance of the witness knowing or not 
knowing that there are only two colours in the urn can make 
such an enormous difference in the credibility of his testi- 
mony? I answer no; and for this reason, that a does not 
represent the same quantity in both cases. This will be at once 
obvious from the following consideration. When there are 100 
numbered balls, a man whose announcements are made altogether 
at random will be right only once in a hundred times ; but a man 
whose credibility is J-, t. e, who is right fifty times in a hundredi 
is a good witness. Two such witnesses agreeing would be equi- 
valent to one whose credibility is ^^. But u there are fifty 
black and fifty white balls, so that there are only two pos- 
sibilities to choose from, and the chances of these are equal, the 
random speaker will be right fifty times in a hundred. In this 
case, therefore, the credibility represented by ^ is no credibility 



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Tutmofiy and Arffumenii, 19 

at all^ and two saeh witnesses are accordingly of no more value 
than one ; so that the same degree of credibility is represented 
in the one case by yj^, and in tne other by J. The credibility, 
therefore, which was represented by ^ in the first case ought to 
be represented by a greater fraction m the second; the witness 
has not lost all his credibility because the event itself has become 
more probable. It is clear, then, that a represents not the 
antecedent credibility of the witness, but the chances of his 
announcement being right under the particular conditions sup- 



To consider the matter practically : — the chances of the witness 
being mistaken in the colour of a black ball are the sum of the 
chances of his taking it for white, for yellow, for red, and the rest 
of the m colours. Now if it is known that there are only two 
colours in the urn, he is excluded from m— 2 of the m— 1 possible 
mistakes, but we have no reason to suppose that when he is dis- 
posed to mistake blaek for red for example, he has no choice 
but to affirm white if he knows that red is not present. If we 
know nothing further about the case, we must suppose that ill 
all such instances (t. e. where he mistakes black or white for a 
colour known not to be present) he has no reason for choosing 
either black or white, and therefore divides his assertions equally 
between them. We have then the following cases ; — 

Hypothesis. — He affirms white, the probability of which isp, 
and his credibility a. 

Case 1. He believes that white is drawn, and it is so ; 

chances in favour of this supposition = ap» 

Case 2. White is drawn, and he mistakes it for some colour 
known to be absent ; 

chances as o & (I— ft)» 

In half of these instanoes he ttfflrms black, and the other half 
white; hence 

chances that he aifirms white on this supposition « (1 ^ a)p' ^^ . 
Case 8. Black is drawn, and he mistakes it for white ; 

chances = (1 — a) (1 — p) — ;;^- 

Case 4. Black is drawn, and he mistakes it for an absent 
colour, 

C2 

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20 Mr. T, K« AbbotC on the ProbMUttf of 

in half of which instances he affirms white; henoe 

chances that white is affirmed on this supposition 

On the whole, therefore, he affirms white in 

w— 2 
of which he is right in ap + (1 — «)j» ^ ^^ cases. Hence the 

probability that white was drawn is 

, ., . w— 2 

^+^i-«)^2;r:2 



^>^ + (l"«)^2^+(l-«)(l-')^ 



m— 2 
or puttuig a+ (1— a) ^ ^o ^^' ^* ^ 



orp 



His credibility in these particular circumstances, therefore, is 

not a, but «. When m is considerable, u nearly =s-^— ; t. e. 

the odds in his favour, instead of a to 1— a, are now 1+a to 
1 —a, or more than double. 

The result will be the same if we introduce the supposition 
that the witness intends to deceive, since the motives which 
usually affect his veracity cannot be supposed to operate uni- 
formly in favour of the assertion of white when the remaining 
colours are excluded. Indeed we ought rather to suppose that 
^n the absence of these colours a proportionate number of the 
motives to deception disappears ; so that if his veracity be v 

and his judgment r, he now affirms white truly in ^^{l — v) — — = 

cases, in which, if the other colours were present, he would be 
induced to affirm some one of them falsely. 

But it is useless to pursue this hypothesis any further. 
Enough has been said to show that it is altogether unfit to 
furnish a general formula. It would be quite as reasonable to 
neglect the probability of the event, and limit ourselves to that 
of its assertion, as to neglect the latter probability altogether. 
The general formula already given is independent of any hy- 
pothesis with respect to the knowledge of the witness, or the 



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TesHmmf and Arffuments. SI 

proportion between extraordinary and ordinary events in general. 
It maybe stated somewhat differently thus: — A witness whose 
credibility is a, announces an events the antecedent probability 
of which is p, and the chance of its being announced without 
reason r; then the resultant probability is 

op{l-r) 
ap(l-r) + (l-fl)(l-/>)r 

If complete generality is desired^ we must introduce separately 
the chances of the witness being mistaken k, and of his intending 
to deceive/, and also the chances of the event being invented if 
or being erroneously supposed to have happened $. It may be 
worth while to exhibit the formula in this shape. It is obvious 
that when the event has actually happened, it may or may not 
be that the causes which would lead to its being either invented 
or falsely believed have also existed, i. e. pi sudps are possible 
cases. This consideration simplifies the formula, which will be 
found to give for the resulting probability of the event announced 

p\{i-f){i-k)+fki\ 

p{(l-/)(l-*)+/K} +(l_^){(l_/)fe+/»} * 
When r=j9, the probability just given is reduced to a, and 
accordingly it frequently happens that, although the event 
announced is extraordinary, the chances of fiction or mistake 
may be proportionately smaU, and in such cases we are satisfied 
witn orcUnary testimony. 

Mr. J. S. Mill has some useful observations on Laplace's for- 
mula in the chapter on the '^ Grounds of Disbelief in his 
' System of Logic' He draws attention to the absolute identity 
supposed by hypothesis to exist between the 99 black balls, 
which renders the case unlike that of real events. I have not 
referred to this,, because in fact it results from the nature of the 
problem to be solved, in which we compare events of different 
degrees of antecedent probability; the 99 black balls are not in- 
tended to represent 99 similar events, but one and the same 
event. For the purposes of calculation, the chances in favour 
of an event must be treated as representing so many cases of its 
Occurrence. When we say that the chances are 9 to 1 in favour 
of a certain horse A beating another horse B, there are only two 
events conceivable, and only two sets of motives, &;c. possible : 
we do not conceive A as made up of 9 parts, each having an 
equal chance of victory with B. We may speak, indeed, of 10 
trials in which A will win 9 times ; but in each trial both horses 
and both sets of motives are equally present. To express degrees 
of probability, then, the most convenient method is to suppose 
a proportionate number of identical events, as Laplace has done. 



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22 Mr. T. K« Abbott on the ProbOnliiy of 

It is important, howeverj to consider that testimonji tme or 
falsei is not given without motives ; and therefore it may seem 
more proper that the formula should represent the operation of 
these. Let the probability of the event be ji; the probability 
that its occurrence would move the witness to announce it truly 
=^. The probability of the event not happening is l—p; let 
the chances that its non-occurrence would move the witness to 
deny it truly ^d. This may not be the same as L 

Now let the chances that a motive to lie exists be m, and the 
chances of A's yielding to it be ^, t. e. the chances of his lying 
^tufisBv, Then, supposing that A announces the event p, whidi 
is one of the possibilities : 

Either the event occurs and moves him to speak the trath| 
the motives to Ijring or to mistake not operating fspt{l'^v). 

Or the event does not occur, which non-occurrence has no effect 
on the witness, the motives to lying operating as (1 -^p) {l^d)v; 
but this must be multiplied by ti^e chances of the hypothesis, 
i, e. of A fixing on this particular event, on this supposition, 

namely — . This gives 



171 



(l-j,)(X-rf)^. 



Besulting probability that the event annoanoed ba« oocorred 



pt{\^v)+{\-p){\-d)^ 



If there are r witnesses, and the quantities /, i^ v the same for 
allj we have 

pr{i-vy 



m< 



In this formula t may represent, for example, the interest 
which the witness would have in truly reporting the event if it 
happened^ and ij[his interest in truly reporting its non-occurrence. 

The case of arguments conspiring or opposed is somewhat 
different from that of testimony; since an argument may be 
^lacious, and yet the conclusion true. In the case of argu- 
ments establishing the same conclusion with the probability a,bt 
&c. respectively, the resulting probability is clearly 

If two arguments are opposed, we have these cases : 



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TggHnumy and ArjfumenUf 28 

the argament a is invalid, b invalid ssa(l — -d) ; 

a invalid, d valid =ft{l— a); 

neither is valid =(1— a)(l— ft); 

Sum • • ssl **!!&• 
Hence the probability of the oondnsion to which a leads 

" 1-flft 

Now the case of arguments suggests an important question. 
It often happens that when a proposition has been established 
on probable evidence, it is found to lead to a further inference 
which admits of being tested directly to some extent. Thus the 
proposition A may assert that a certain narrative is the work of 
a credible witness, and B that a particular circumstance contained 
in it is true. Our hypothesis is. If A is true, 6 is true; and 
from this we infer conversely, If B is false, A is false. Logically 
these two propositions are convertible ; yet there lurks a great 
faUacy in the inference when we have to do, not with certain, but 
with probable propositions. For example, if the truth of B does 
not follow with certainty from that of A, wc have the foUowing 
.cases possible :-*• 

A true and B true; let the probability of this be X, 
A true and B fidse ; „ „ = fi^ 

AfUseandB true; „ „ ^ y, 

A false and B false; • „ „ ss p^ 

where 

Then if A is true, the probability that B is true is 

__ X 

If B is false, the probability that A is false is 

The former expression represents the probabihty of the state- 
ment, If A is true, B is true : the latter that of the converse. If 
B is false, A is false ; and it appears at once that these are really 
independent. Suppose it to be known that the third case is 
impossible, or nearlv so, i. e. v=:0; then, in order to determine 
the probability of the second inference, we must know besides 
that of the first, the absolute probabihty of A (or B). Let the 
pKobability of A be t}(ssX+/c^) ; then the probabihty of the in- 



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24 On the ProbahOUy of Tuiimamf mid Argumaiti. 
ference of the truth of B £rom that of A 

X 

and that of the conTene 

Let us analyze the problem more in detail. Suppose the pro* 
bability of A as proved directly 

the probability of the inference by which B is deduced firom A 

and the probability of the disproof of BsXj where, if ar^ Xp 
&c, be separate arguments against B, 

X=l-(l-«)(l-ara).... 

Then calling the inference C, we have the following cases : — 

1. A^ B, and C all true; probability t0y(l— X). 

2. A true, B and C false ,, tf;(l— y)X. 

8. A and B true, C false „ tt;(l— y)(l— X), 

4 A false, B and C true „ (1— tt;)y(l— X). 

5. A and B false, C true „ (1— ti;)yX, 

6. A and C false, B true „ (l-ic;)(l— y)(l— X). 
7. All three false „ (1— m;)(1— y)X, 

Sum = 1— uyX, 

the only supposition which is necessarily impossible being, that 
A and C are true, and B false. Hence on the whole the pro- 
bability of A 



of the inference C 
ofB 



l-X 



1— tt;yX 

The odds in favour of A are w— toyX to 1— ti; ; that is, they are 
diminished in proportion to the sti^ength of y and X combined ; 
the odds in favour of B are 1— X to X— iryX; these, therefore, 
are increased similarly. We deduce the important consequence 
that, as regards the evidence of A, it is precisely the same thing> 



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Prof. Tyndall's Notei on Scimt^e History. 25 

whether we strengthen the aigiunents or objections against B^ 
or strengthen the force of the inference of B firom A. If it be 
held that this inference is certain^ t. e. that y^l, then the odds 
in favour of Aareu;(l— X) to 1— u;^ and every argument against 
B tells with equal force against A. Let us ti^e a numerical 
iUustration. 

Let fv=:^, y=J, and X=^; then wyX-^^, and the 
probability of A is {^%, t. e. the odds in its favour are less than 
55 : 1. With this value of y, the probability of A cannot be 
reduced below -^A-, its value when X=], the odds being then 
49 J to 1, But if ys=^, then wyXs=^^lA-, and the cSds in 
favour of A are reduced to 1881 to 100, less than 19 to 1. "What- 
ever be the value of ti;, if ^=1 and X^^^, then the common 
denominator is <1— iti;, and uie odds in favour of A are less 
than |ti; to l^w. Thus if y=f ^ and X^^, the odds are only 
Jw to 1— te>. 



IV. Notes on Scientific History. By John Tyndall, F.R.S.^ 

1. 
1. npWO years ago, in a Friday evening discourse at the Royal 
-!• Institution t^ I drew attention to the scientific labours 
of Dr. Julius Robert Mayer, and since that time the knowledge 
of his writings has been widely diffused by the publication in 
English of four of the five memoirs which he completed before 
his health gave way. A translation of Mayer's first paper (date 
1842) will be found in the Philosophical Magazine, S. 4. vol. xxiv. 
p. 371. A risum6oi this paper, written by myself, appears in the 
Philosophical Magazine, S.4. vol. xxv. p. 878. A translation of his 
third paper (date 1848) will be found in the Philosophical Maga- 
zine, S. 4. vol. XXV. pp. 241, 387, 417. A translation of his 
fourth paper (date 1851) in the Magazine, S.4. vol. xxv. p. 493. 
No translation of his second paper (date 1845) has yet been 
published. Circumstances have recently compelled me to refer 
to this Essay ; and pending its full translation, I would ask per* 
mission to make such a r6sum6 of its contents as will give the 
readers of this journal some notion of its merits. The extracts 
will show the relationship of its author to other writers with whom 
he has been recently compared. From the works of these writers, 
moreover, I shall extract the portions on which their claims 
mainly rest, and thus the public will be enabled to form an in- 
dependent estimate of this passage in scientific history. 

* Communicated by the Author. 

t Proceedingsof the Royal Listitation^ June 1862. PhiL Mag. vol xxiv. 
p. 57. 



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26 Tfrot. Tyi^dali'i Notes on Scientific Hutcry\ 

2. Mayer was led from the contemplation of organio natute to 
tbe publication of his first paper '' On the Forces of Inorganic 
Nature/' An observation made in ISJOj on the blood of a 
patient in a tropical climate^ was tbe origin of bis scientific 
writings. It led him to tbe consideration of those physical 
forces on which the phenomena of vitality depend. This« if the 
laws of life were ever to become amenable to scientific investi- 
gatiouj he Imew must be his starting-point. The paper now 
under consideration may be broadly divided into two parts^ in 
the first of which he deals with the law of the conservation <^ 
energy* as it manifests itself in inorganic nature^ and in the 
second of which he applies the law to the phenomena of life. 

8. At the outset of this paper he announces^ as he had pre* 
viously done in that of 18429 the indestructibility of force, its 
convertibility, and its quantitative constancy. Chemistry, he 
says, teaches the qualitative changes which matter undergoes 
under different circumstances, the form of the matter and not 
its amount being changed. What chemistry does for matter, 
physics must do for force; the force is as unalterable as the 
matter, and the function of physics is to study force in its forms, 
and to ascertain the conditions of its metamorphoses. This is 
the sole problem with which natural philosophy has any concern ; 
for as to the creation or annihilation of force, either act lies as 
much beyond the range of human thought as of human power. 

4. For thousands of years men have employed the powers of 
inorganic nature to obtain mechanical effects. But to the forces 
of moving air and of falling water a new force has been added 
in modem timefr*<-<the force of heat, which may be converted 
into mechanical effect. Supposing that to a train weighing 
100,000 lbs. a velocity of 80 feet a second is to be imparted; 
this may be done by the expenditure of ordinary mechanical 
force^^by permitting, for example, the train to roll down an 
incline until the required velocity has been obtained. Trains, 
however, in general move without this exercise of gravitating 
force, and, despite the friction of their parts, they are kept in 
motion. Let this friction be supposed equivalent to a rise of 1 
in 150, then with a velocity of 80 feet a second the weight of 
the train will be lifted 720 feet in an hour, which corresponds 
to the work of about forty<flve horses. This large quantity of ge- 
nerated motion implies the expenditure of an equal amount of 
force. The force expended in the case of the locomotive is hM,t. 

The quantity of heat taken up by the steam employed to 
work the engine is greater than that which can be obtained from 
the recondensation of the steam. The difference between both 

* Rankine's temunology. 



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Prof. Tyndall'i Noiea on ScienHfie Htstary. 27 

is the heat naefiilly applied ; that is to bslj, this difference ex- 
presses the heat which has been converted into mechanical effect. 
The more perfect the machine^ the less will be the amount of 
heat obtainable from the condensation of the steam. The best 
engines give a difference of about 5 per cent. ; that is to say, 
100 lbs. of coalj burnt in such a machine^ give no more heat 
than 95 lbs. which are burnt without doing any work. 

(Considering the sort of criticism to which he has been re- 
peatedly subjected*, the manner in which Mayer establishes the 
leault last mentioned is worthy of particular attenticm. It 
will be observed that he deliberately chooses a substance which 
experiment proves to be suited to his purpo8&"**a substance, 
that is, in which tAe whole of the heat rendered latent is consumed 
in exterior work.) 

5. To prove this important proposition, we must mvestigate 
the relationship of elastic fluids to heat and to mechanical work. 
Ga^-Lussac has proved by experiment, that when an elastic 
fluid passes from one vessel into a second one of the same sise, 
but. exhausted, the vessel from which the elastic fluid issues is 
cooled, while that into which it enters is warmed by exactly the 
same number of degrees. This experiment, which is distin- 
guished for its simphcity, shows that a given weight and volume 
of an elastic fluid may expand to double, quadruple, &c« of its 
previous volume without experiencing any change of temperature^ 
or, in other words, that for the simple expansion of the gas 
no expenditure of heat is necessary. 

6. Let a cubic inch of air at Of aqcL under a pressure of 28 
inches of mercury, be heated to 374*^, and let the quantity of heat 
required to warm the air be w. When it streams into another 
exhausted recipient of the same volume, the air will retain its 
temperature of 274°; the medium surrounding the vessels will 
undergo no change of temperature. Again, let a cubic inch of 
air, not .at constant volume but under a constant pressure of 28 
inches <rf mercury, be heated from 0° to 274°, a greater quantity 
of heat is now needed than before; let the quantit^jr be sa+y* 
If the air be permitted to cool in the two cases, it will eive back 
the heat communicated to it. The air which is not foUowed by 
a pressure will^ on cooling from 274° to 0°, give out the heat x; 
that which cools under a constant pressure will yield the heat 

7. Steam in the engine, where it expands under the piston, 

* As an example, see ' Good Words/ October 1862> p. 604, note x — 
''Mayer's statements imply its indiscriminate application to all bodies in 
nature, whether gaseous* liquids or solid." Not what Mayer's words 
''imply/' but what they are is stated in the text. 

t All through his pspen Blaysr uses Ceatigrada dsgfees, 



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28 Prof. Tyndall^B Notes on Scientific History. 

behaves Kke the air under eonstant pressure. The heat neces- 
sary to the expansion of the steam is X+Y. When the steam 
is cooled, the pressure of the piston is absent, or it is exercised 
in a greatly oiminished degree : hence, in cooling, the heat 
given out will be X. With every stroke of the piston, there- 
fore, there is the loss of heat Y ; that is to say, with the action 
of the engine a consumption of heat is inseparably connected. 

8. From the quantity of fuel consumed in an engine, the 
total expenditure of heat may be calculated. The loss by radia- 
tion, transmission, and convection being subtracted, the re- 
mainder is the usefully applied heat. As, however, by far the 
greater part of the unused heat can be but roughly estimated, 
only an approximate result can be thus obtained. More sharply 
and more simply the problem may be solved by calculating the 
quantity of heat rendered latent when a gas expands under pres- 
sure. Let the amount required to heat a gas at constant volume 
1° be ^ j to produce the same elevation of temperature under 
constant pressure the heat necessary will be x-i-y. Let the 
weight raised in the latter case be F, and the height to which it 
is raised h ; then we have 

y=PxA. 

A cubic centimetre of atmospheric air at QP and 76 millims. 
barometric pressure weighs O'OOIS of a gramme; warmed 1° 
under constant pressure^ it expands ^f^th of its volume, and 
lifts a mercury column 76 centimetres long and of a square cen- 
timetre basis to a height of ^^t^ of a centimetre. 

The weight of this column is 1033 grammes; the specific 
heat of air, according to De la Roche and Berard, is 0*267 ; 
hence the heat communicated to our cubic centimetre of air in 
order to raise its temperature 1^ is equal to that which would 
raise the temperature of 00018 x 0-267 =0-000847 of a gramme 
of water 1°. 

According to Dulong, the specific heat at constant pressure is 
to that at constant volume as 1*421 : 1 ; therefore the quantity 
required to raise the temperature of our cubic centimetre of air 
at constant volume 1^ would be sufficient to heat 

0*000847 ^ ^^^^^ ^ ^ 
-j;^' =0000244 

of a gramme of water 1^. 

Hence the difiference (a?+y)— ^, or 

y=0-000847-0000244=0000103 

thermal units, by which a weight F=:1033 grammes is raised to 



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Frof . Tyndall's NoteB an ScierUific Hhhny. 29 

a height =^^^th of a centimetre. Sedacing these numberi^ 
we find 

1 thermal miit (1 gramme of water heated 1^ C)=l gramme 

• J A 1. • 1.A *i" 867 metres 
msed to a height of^ugo p„ f^^ 

This is Mayer's calcolation of the mechanical equivalent of 
heat. Be first published the result in 1842, making use of the 
specific heat of air as determined by De la Boche and Berard. 
Substituting for it the subsequent and more accurate determina- 
tion of M. Begnault^ and changing in no particular the method 
of calculation^ Mayer^s equivalent, instead of 367, becomes 426 
kilogrammetres; Joule's equivalent is 425. 

II. 

It has been man^ times affirmed that, In the calculation of 
the mechanical eqmvalent of heat, M. Seguin had anticipated 
Dr. Mayer by three years — that be had, in fact, pursued the 
same method and published the " same result.^' M. Seguin's 
book is in but few hands ; I shall therefore give, in his own 
language, the details of his calculation*. 

9. " Supposons done qu6 Pon ait renferm^ dans un cylindre 
ABCD, ayant un metre de section, un metre cube de vapeur 
k 100^, et que cette vapeur soit contenue par un piston CD, dont 
le poids equivaut k un kilogramme par centimetre carr^, et 
derriere lequel on a fait le vide ; ce qui repr^sente, k pen de 
chose pres, une pression egale k celle que ^atmosphere exerce sur 
tons les corps au niveau de la mer. L'appareil, d'ailleurs, etant 
dispose de telle sorte qu'il ne puisse ni ceder ni recevoir du 
dehors aucune portion de calorique. 

10. '^ Si Pon augmente la charge du piston CD, en y ajoutant 
successivement des poids pour comprimer la vapeur, jusqu'iL ce 
que sa temperature se soit elevee de 20^, son ressort fera alors 
^uilibre k une pression de 2 kil. par centimetre carre ; et, con* 
sid^rant que son volume augmente de 0*00375 de ce qu'il ^tait 
k 100** par chaque degr^ de temperature, Pespace ABFE qu'elle 
occupera sera exprime par 

1 + 1x20x000375 ^^^^^ 
5 =0*5375. 

On pourra done considererPefietcommesensiblement represent^ 
par la moyenne de toutes les preissions exercdes par la vapeur 
depuis DC jusqu'en EF multipiiee par Pespace parcouru DE. 

11. ''La pression ^tant de 1 kil. en DC et de 2 kil. en EF, 

* Sur rinJU»enee des Chemns de Fer (Paris, 1839), pp. 385-389 indosive. 

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80 Ptol.Tyni$ll*uNotmam8d0U^Bi$Uiy. 

et eroinant en progrenion gfom^triqae, en (Mrignant per 8 le 
Bomme des termes, par n le nombre des termes, le dernier^ a k 
premicTi et 9 la raison, P la preaaion moyenne ; faiaant im 100, 
ee qui soffit poor obtenir une valeur de P aaaes approcb^, et 
observant que la valeur de / ou la preaaion de la vapeor en EF, 
est ^gale It 2 kil. par eentim^tre carr^, et eelle de a qui ae rap- 
porta It CD, ^ale It 1 kil.^ nooa aurons pour determiner q 

l^af^\ j=*aJ^=1-007, 

a(y>^l) _ l(l>007^oo-.l) ^ 

^- n{q^l) " 100(1007-1) ^ 

Multipliant cette valeur par Pespace DE parcouru par le pistoui 
dgal It AD -AB=l-0-5375= 0-4625 et par 10,000 qui repr^- 
sente le nombre de centimetres carr^s contenus dans un metre 
carr^, on obtient 

1-43 X 0-4625 X 10,000= 6618 ka. 5 

ee qui nous indique que I'effet th&>rique obtenu par la dftenta 
d'un mitre cube de vapear comprim^e par un poida de 3 kiL 
par centimetre carr^, qu'on laisse r^pandre dans un eapace qui 
r^pond It une pression de 1 kiL et & un abaissement de tempera^ 
tuTe de 20^, est repr^sent^ par un poids de 6**618 kil. flev^ It 
un mitre, ou par O'^'OIS. 

12. '' En faisant un calcul analogue pour connidtre lea eapaeea 
qu'oceupe la vapeur, lorsqu'on augmente sa preaaion de maniira 
It faire elever aa temperature de 20 en 20 degr^s, on trouvera 

" 1. Que pour 140** la pression en GH =58"i*61, 

GE=0-587-0-819-0°"218j P=2Wi-83; 
et poor l'e£fet total, 

3-88 X 0-218 X 10,000=6170 kil. 
"2. Pour 160° la pression en IK 6^316, 
^^^l+lxfflxO-00876^ 

IG=0-319-0-199=0«-120, P=4^-82; 

et pour Peffet total, 

4-82 X 0*128 X 10,000« 5780 kil. 

"8. Enfin, pour 180° la pression LMaO^il-QS, 



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rrotTjnialV^ Notes on Sdeniifie History. SI 

LIssO-lSQ-O-lSl^On^OeS, P=s8Wi-00i 
et pour PeflFet totals 

8*00 X (H)68X 10,000 s6440 kil. 

13. ''Si nous fiupposons ensuite que lorsque la vapeurpousse 
le piston devant elle, et que la chaudi^re est en communication 
avec le cylindre, sa temperature s'abaisse d^une quantity propor* 
tionnelle k Peffet dynamique produit, nous trouverons que la 
vapeur s^introduisant dans le cylindre k 100°^ et perdant 20^ 
pendant le mouvement du piston^ la temperature^ k la fin de la 
course, sera de 80?^ et la pression de 0^*485. La presvion 
moyenne tf^'727. Soit pour Feffet total, 

. 0-727 xlx 10,000=7270 kU.> 

valeur qui se trouve k pen pr^s classic suivant la mftme loi que 
les autres quantit^s auxquelles nous sommes parvenus, en const- 
d^rant Peffet produit par la vapeur k des temperatures et k des 
pressionsplus eievees. 

14. ''En reunissant tons ces r^sultats, et en les comparant k 
Peieration de temperature qui leur correspond, nous formerons 
le tableau suivant : — 



PradMufn 
kflognmmes. 


Tenu^ntnm 


Eflet fpfochut 
1 mitre. 


BiiMraooM. 


eorreipon- 

duitetkreflbt 

ptodnit. 


Difftetiiew. 


0-48 
1 
2 
8-61 

9dd 


80 
100 
120 
140 
180 
180 


7270 
8818 
8170 
5780 
5540 


443 

390 
240 


p 

20 

18-20 
18-87 
15-90 
15-24 


1-80 
1-28 
1-07 
0-86" 



15. We have now the means of comparing S^uin's alleged cal< 
eulation of the mechanical equivalent of heat with that of Mayer* 
With reference to the foregoing Table^ Mr. Joule writes thus (Phil* 
Mag. August 1862):— "In page 389 he [M. S^uin] gives ft 
Table of the quantity of mechanical efifect produced corresponding 
to the loss of temperature of steam on expanding. From this ii 
appears that 1^ Gent, corresponds with 368 kilogrammes raised 

to the height of 1 metre Mayer discourses to the same 

effect as Segpiin, but at greater length, with greater perspicuity, 
and more copious illustration . He adopts the same hypothesis 
as the latter philosopher, viz. that the heat evolved on compress^ 
ing an elastic fluid is exactly the equivalent of the compressing 
force, and thus arrives at the same equivalent, viz. 865 Idlo- 
grammes per 1® Cent/' 



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82 Prof. Tyndall's Notes on Scieniific History. 

16. In the Philosophical Magazine for April 1863, Prof. 
Waliam Thomson of Glasgow, and Prof. Tait of Edinburgh, 
express themselves thus: — ^^'Does Prof. Tyndall know that 
Mayer's paper has no claims to novelty or correctness at all, 
saving this, that by a lucky chance he got an approximation to a 
true result from an utterly false analogy, and that even on this 
point he had been anticipated by Seguin, who, three years before 
the appearance of MayePs paper, had obtained and published the 
same result from the same hypothesis.^' I have nowhere in this 
paper introduced italics into quotations; wherever they occur 
they are in the original. 

17. And in reference to the same subject, a more recent 
anonymous northern writer* expresses himself thus: — ^'Of 
Segum and Mayer, it seems not very difficult to estimate the 
claims, so far as the true theory or the mechanical equivalent of 
heat is concerned. Seguin in 1889, and Mayer in 1842, gave 
as values of the mechanical equivalent : the first 863 kilogram- 
metres, or, in terms of the ordinary British units, 660 foot- 
pounds ; the second the almost identical number 865 or 663. 
It is curious also to observe that the methods employed are 
almost identical.'' 

18. Did the reputation of Dr. Mayer depend on his calculation 
of the mechanical equivalent of heat, and were the statements here 
quoted correct, his right to the recognition which I have thought 
his due might fairly be questioned. But let us inquire whether 
this is really the case. The Table on which the claim for M. 
Seguin is founded is now before the reader ; and on referring to it, 
two columns will be seen, the one headed ''Effet produit en kilo- 
grammes eleves k 1 metre," and the other headed *' Temperatures 
correspondantes k I'efifet produit." The first number in the first of 
these columns is 7270 kilogrammetres, and the ''temperature cor- 
respondante" is 20 degrees. Hence, dividing 7270 by 20, we have 
the quotient 363 as the number of kilogrammetres corresponding 
to a single degree. And so of the other pairs of numbers, which 
give 363, or thereabouts, as the mechanical effect due to a single 
degree. All this seems very plain; and did no text accompany 
the Table, and had not M. S^uin in that text explicitly defined 
his own terms, we might be justified in assuming that he meant 
the number 363 to stand for the mechanical equivalent of heat, 
in the same sense as Dr. Mayer meant the number 365 to stand 
for it. It is only necessary, however, to read the foregoing pages 
to see that Mayer and Seguin are peaking of two totally different 
things ; that the degrees of the one are not the degrees of the other / 
that the " temperatures correspondantes " of the latter , which refer 

* Not my Edinburgh reviewer, who, while he writes as a critic, knows how 
to preserve the style of a gentleman. 



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Prof. Tyndall's Noies on Scientific Hisiori/' 68 

to his compressed steam, are not thermal units at all, and that there 
is no determination whatever of the mechanical equivalent of heat 
in the above Table. 

19. The number 863 has been found for M. Seguin, not by 
him : he never made the division which results in this quotient. 
In 1847j for the first time, and without giving any description of 
his method *, M. S^guin gives his results '' reduced to the type 
of 1 gramme elevated 1 metre, and corrected with reference to 
the specific heat of water and vapour/' His equivalent there 
given varies from 895 to 529 kilogrammetres {Comptes Rendus, 
vol. XXV. p. 420). The data, moreover, on which M. S^uin 
founded this last calculation were subsequently declared erro- 
neous by himself: the experiments of M. Begnault, he states, 
'defeated the'calculations '* {Cosmos, vol. vi. p. 684) ; and Mr. 
Grove has shown that when the correct specific heat of steam, as 
determined by Begnanlt, is introduced into the calculations, M. 
S^gnin's equivalent becomes 1666 kilogrammetres instead of 363 
(Proceedings of the Royal Institution, vol. ii. p. 155). We have 
already seen that in Mayer's case, when the correct specific heat 
of air is employed, his result is almost identical with that derived 
from the mean of all the best experiments of Mr. Joule* The 
one is 426, the other is 425 f* 

III. 

20. After going formally through the calculation of the me- 
chanical equivalent of heat, Mayer proceeds to determine the 
useful efiect in steam-engines, and finds it to be about 5 per 
cent, of the consumed fuel. He then determines the useful 

* Such a description would be a desirable addition to our knowledge. 

t I have already drawn attention to these facts (Phil. Mag. vol. xxv. 
p. 385), but have been met, not by explanation, but by iteration. This, I 
trust, will now cease. It is no compliment to the scientific pubhc to think 
that mere hardihood of assertion can decide this question. 

To illustrate the difficulty of satisfying rival claimants, I may remark 
that in 1862 1 withdrew the name of Dr. Mayer from the list of candidates 
for the Copley medal, out of deference to an eminent man — not Mr. Joule — 
who thought his own claims prior to those of Mayer. What I have had 
to endure at the hands of two northern critics for my supposed depre- 
ciation and suppression of the claims of Mr. Joule is at least partially 
known to the scientific public. Afaan, a writer in M. Seffuin's periodical, 
Le Cosmos, while declaring that "Nh. Joule must be entirely put aside, the 
question of priority resting solely between S^guin and Mayer, charges me 
with haying manifested a wholly insufficient appreciation of M. S^guin. 
I should be a mere intellectual quicksand if I allowed myself to be swayed 
bj such criticisms. I have, judging from the facts, steered through these 
nyal claims with the best light uiat I possess, and not one of my censors 
appears to have gone to one-tenth of the trouble that I have incurred to 
morm myself of the rights of the question. 

Phil. Mag. S. 4. Vol. 28. No. 186. July 1864. D 



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84 Prof. Tyndall's Noie$ on Scientifie HUtary. 

effect in the case of gonpowderi and finds in ci»rtain oaaes thai 
9 per cent, of the force of the consamed charcoal is expended on 
the projectile. He gives various illostrationsof the genemticui 
of heat by mei^anical power, and describes some observi^tions of 
bis own, made in a paper-miU, in whiob were foiur pulping 
machines, each contaimng about 801bs« ctf paper and 1200 lb9» 
of water. The surrounding temperature bong 15° C, the pulp 
rose in thirty-two minutes fK)m 14'' to 16^, The highest observed 
temperature, which remained uniform for several hours, was 30^« 
Assuming that in one minute a horse can raise 27,000 lbs# a foot 
high, the heating of 1280 lbs. of water I degree in sixteen minutes 
(not taking into account the heat communicated to the apparatuv) 
is equivalent to 3*16-horse power. The estimate in the factory 
was, that the pulping machmes were worked with 5-horse power* 
Does the mechanical action of the five horses become nothing in 
the machine ? Fact replies, it becomes heat. 

21. He then goes on to show the relationship of mechaniesil 
work to electricity and magnetism, and passes to the eoii'* 
sideration of chemical processes as eompaied with mechanied 
operations. A weight at such a distance from the earth thut 
the attraction is insensible, he regards as in a state oitMchanioal 
separation ; the falling of the weight to the earth as a case of 
mechanical combination. Such a weight would reach the earth's 
surface with a velocity of 34,440 feet a second, and the heat 
generated by its collision would raise the temperature of an 
equal weight of water 17,856^. Chemical combination is in 
principle the same. The chemical combination of 1 gramme ti 
carbon and 2*6 grammes of oxygen is equivalent to the meehani* 
cal combination of a weight of ^ a gramme with the earth. The 
chemical combination of 1 gramme of hydrogen with 8 grammes 
of oxygen is equivalent to the mechanical combination of a weight 
of 2 grammes with the earth. The heat here developed is equal 
to 3^700 thermal units*. 

* In 1843 Mr. Joule wrote the following remarksUe pssasge s — '' I had 
before endeavoured to prove that when two atoms comlnne together, tiif 
heat evolved is exactly that which would have been evolved by uie eWetfis 
current due to the chemical action taking place, and is therdTors proper* 
tional to the chemical force causing them to combine. I now venturo to 
state more explicitly that it is not precisely the attraction of affiain^/bnt 
rather the mechanical force ex|iended by the atoms in falling towards out 
another, which determines the intensity of the cunent, and consequently 
the heat evolved'' (Phil. Mag. 1843, vol. xxiii. p. 442). I cite this as oaf 
of the points of osculation between these two remarkable neo. Tbey 
thus touched each other repeatedly. Joule being in advaaee sometimes, 
and Mayer sometimes. But their main achievements lie in distinct fields ) 
and these are, in my opinion, so balanced as to render them a kind of 
j ** double star, the light of eadi being, in a ceitain sense, eomplemeBtsfy 
i to that of the other .^' (Phil. Mag. 8. 4. vol. axn. p. 67.) 



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Prof. TyndaU's Naies on Scientific History. 85 

The manner in which Mayer expands his conceptions from 
the union of atoms to the union of worlds is a remarkable illus- 
tration of his generaliring power. After discoursing thus^ he 
goes on to say : — 

22. ''The earth moves in its orbit with a mean velocity of 
98,70(y. To produce this motion by the combustion of coal, 
fiffaeen times the earth's weight of coal would have to be 
consumed^ and the heat produced would be competent to raise 
the temperature of a quantity of water equal to the earth in 
weight 128,000^. A small portion therefore of the force with 
which the earth moves in its orbit would suffice to dissolve all 
mechanical connexion among its parts. Supposing a mass equal 
to the earth in weight to lie at rest on the surface of the sun, 
to raise that mass, place it at the earth's distance from the sun 
(215 times the sun's radius), and to impart to it there the velo- 
city of 93,70(y, would require 429 times the above quantity of coal, 
or a quantity 6486 times the weight of the earth." 
. 28. (In a letter published in the Philosophical Magazine for 
August 1862 Mr. Joule writes as follows : — " In 1847, in a popular 
lecture published in the ^ Manchester Courier,' I explained the 
phenomena of shooting- stars, and also stated that the effect of 
the earth falling into the sun would be to increase the tempera- 
ture of that luminary." The foregoing passage, giving the 
amount of the heat that would result from the falling of the 
earth into the sun, was published by Mayer in 1845 *.) 

24. Mayer next briefly considers the case of the voltaic battery 
and the gas battery. He then draws out a scheme of the five 
principal forms of energy which he has been examining, and 
under five-and-^twenty separate heads he states their relations and 
mutual conversions. " Preconceived notions," he says, " sanc- 
tioned by time and diffusion, and not the phenomena of Nature^ 
are opposed to the propositions here laid down. While," he 
adds, "we ascribe substantiality to motion^ we must entirely 
deny materiality to heat and electricity. I know quite well 
that we hare against us here the most deeply rooted convic- 
tions — hypotheses canonized by the greatest authorities. With 
the theory of imponderables we banish from science the last 
remains of the mythology of Greece j but we know that Nature 
in her simple truth transcends in glory the devices of the human 
phantasy, as much as she excels the operations of the human 
hand." 

* It has been said that in the application of the djniamical theory of 
heat to sbooting-stars, ''and some other points of celestial dynamics," 
Mr. Joule had "at least one year's priority/' (Phil. Mae. vol. xxv. p. 431.) 
The " some other points " shrink, ii I mistake not, to the point referred to 
in the text, and the year's priority is, in reality, two years' posteriority, 
Mr. Joule's remarks on shooting-stars shall be quoted further on. 

D2 



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86 Prof. Tyndall's Notes m SdmtifU History. 

IV. 

Having cleared his way throagb the powers of inorganic 
nature, he turns to vital phenomena, and at once fixes the 
attention of his readers upon t£ie sun. 

25. Measured by human standards, the sun is an inexhaust* 
ible source of physical energy. This is the continually wound- 
up spring which is the source of all terrestrial activity. The vast 
amount of force sent by the earth into space in the form of wave 
motion would soon bring its surface to the temperature of death. 
But the light of the sun is an incessant compensation. It is the 
sun's light, converted into heat, which sets our atmosphere in 
motion, which raises the water into clouds, and thus causes the 
rivers to flow*. The heat developed by friction in the wheels of 
our wind- and water-mills was sent from the sun to the earth in 
the form of vibratory motion. 

(The reader cannot fail to remark the insight implied in this 
last utterance. But a still higher order of thought immediately 
reveals itself.) 

26. Nature has proposed to herself the task of storing up the 
light which streams earthward from the sun — of converting the 
most volatile of all powers into a rigid form, and thus preserving 
it for her purposes. To this end she has overspread the earth 
with organisms, which, living, take into them the solar light, 
Mid by the consumption of its energy generate incessantly che- 
mical forces. 

27. These organisms are plants. The vegetable world con- 
stitutes the reservoir in which the fugitive solar rays are fixed, 
suitably deposited, and rendered ready for useful application. 
With this prevision the existence of the human race is also inse- 
parably connected. The reducing action of the sun's rays on 
inorganic and organic substances is well known ; this reduction 
takes place most copiously in full sunlight, less copiously in the 
shade, and is entirely absent in darkness, and even in candle- 
light. The reduction is a conversion of one form of force into 
another — of mechanical eflfectinto chemical tension. 

28. The time does not lie far behind us when it was a sub- 
ject of contention whether, during life, plants did not possess 
the power of changing the chemical elements, and indeed 
of creating them. Facts and experiments seemed to favour the 
notion, but a more accurate examination has proved the con- 
trary^ We now know that the sum of the materials employed 
and excreted is equal to the total quantity of matter taken 

* This, and much more, was stated by Sir John Herschel in 1833 (Out- 
lines of Astronomy), but Mayer was the first to show the relation of all 
these actions to the law of the conservation of energy. 



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Prof. TyndalPs Notes on SdenHfie History. 87 

up by the plant. The tree, for example, which weighs several 
thousand pounds, has taken every grain of its substance from 
its neighbourhood. In plants a conversion only, and not a 
generation of matter, takes place. 

29. Plants consume the force of light, and produce in its 
place chemical tensions. Since the time of Saussure, the action 
of light has been known to be necessary to the reduction. In 
the first place we must inquire whether the light which falls 
upon living plants finds a different application from that which 
falls upon dead matter ; that is to say, whether, e<Bteris paribus, 
plants are less warmed by solar light than other bodies equally 
dark-coloured. The results of the observations hitherto made on 
a small scale seem to lie within the limits of possible error. On 
the other hand, every-day experience teaches us that the heating 
action of the sun's rays on large areas of land is moderated by 
nothing more powerfully than by a rich vegetation, althougn 
plants, on account of the darkness of their leaves, must be able 
to absorb a greater quantity of heat than the bare earth. If, to 
account for this cooling action, the evaporation from the plants 
be not sufficient, then the question above proposed must be 
answered in the affirmative. 

30. The second question refers to the cause of the chemical ten- 
sion produced in the plant. This tension is a physical force. It is 
equivalent to the heat obtained from the combustion of the plant. 
Does this force, then, come from the vital processes, and without 
the expenditure of some other form of force ? The creation of 
a physical force, of itself hardly thinkable, seems all the more 
paradoxical when we consider that it is only by the help of the 
sun's rays that plants can perform their work. By the assump- 
tion of such a hypothetical action of the " vital force '' all further 
investigation is cut off, and the application of the methods of 
exact science to the phenomena of vitality is rendered impos- 
sible. Those who hold a notion so opposed to the spirit of 
science would be thereby carried into the chaos of unbridled 
phantasy. I therefore hope that I may reckon on the reader's 
assent when I state, as an axiomatic truth, that during vital pro^ 
cesses only a conversion of matter, as weU as of force, occurs, arul 
that a creation of either the one or the other never takes place. 

(To the philosophy of vegetable life here so firmly sketched, 
nothing to my knowledge has been added since. It will be 
immediately seen that Mayer's power does not relax when he 
treats of animal life and energy.) 

V. 

81. The physical force collected by plants becomes the pro- 
party of another class of creatures—- of animals. The living 

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88 Prof. Tyndall's Notes on Scientifie ISstonf; 

animal eonaumes combuatibla aubatanoea belongmg to the vega^ 
table worlds and cauaea them to reunite with the oxygen of the 
atmoaphere. Parallel to thia prooeaa runs the work done by 
animals. This work is the end and aim of animal existence. 
Plants certainly produce mechanical effects^ but it is evident 
that for equal masses and timea the sum of the effects produced 
by a plant is fanishingly small, compared with those produced 
by an animal. While^ then^ in the plant the production of 
mechanical effects plays quite a subordinate part, the converaion 
of chemical tensions into useful mechanical effect is the charac- 
teriatic sign of animal life. 

32. In the animal body chemical foroea are perpetually 
expended. Ternary and quaternary compounds undergo during 
the life of the animal the most important changea, and are^ for 
the most part, given off in the form of binary compounds--^aa 
burnt substances. The magnitude of theae forces, with re* 
ference to the heat developed in these proceaaea, ia by no means 
determined with sufficient accuracy; but here, where our object 
ia simply the establishment of a principle, it will be sufficient to 
take into account the heat of combustion of the pure carbon. 
When additional data have been obtained, it will be eaay to 
modify our numerical calculations so as to render them accordant 
with the new facts. 

33. The heat of combustion of carbon I assume with Dulong 
to be 8550^ The m'echanical work which correqwnda to the 
combustion of one unit of weight of coal correaponda to the 
raising of 9,670,000 units to a height of 1 foot. 

If we express by a weight of carbon the quantity of chemical 
force which a horse must expend to perform the above amount 
of work, we find that the animal in one day must apply 1*34 lb. ; 
in an hour 0*167 lb. ; and in a minute 0*0028 lb. of carbon to 
the production of mechanical effect. 

According to current estimates, the work of a strong labourer 
is f th of that of a horse. A man who in one day lifts l,850,0001bs. 
to a height of a foot muat conaume in the work 0*19 lb. of 
carbon. This for an hour (the day reckoned at eight hours) 
amounts to 0*024 lb. ; for a minute it amounta to 0*0004 lb. 98*2 
grains of carbon. A bowler who throws an 8-lb. ball with a 
velocity of 30^ consumes in this effort r^^^th of a grain of carbon. 
A man who lifts his own weight (150 Ids.) 8 feet high, conaumes 
in the act 1 grain of carbon. In climbing a mountain 10,000 
feet high, the consumption (not taking into account the heat 
generated by the inelastic shock of the feet against the earth) 
is 0*155 lb. =2 ozs. 4drs. 50grs. of carbon. 

34. If the animal organism applied the disposable dam- 
bustible material solely to the performance of wcvk, thm qaaDn 



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Prof. Tjnd^U's Noiet on Seientifie Hutmy. 89 

titiei of onbon juBt calculated woiild suffice for the times men- 
tioned. In reality^ however^ besides the production of mecha^- 
liical effects, there is in the animal body a continuoas genera* 
tion of heat. The chemical force contained in the food and 
inspired oxygen is therefore the source of two other forms of 
poirerj namely, mechanical motion and heat ; and the sum of 
these physical forces produced by an animal is the equivalent of 
the contemporaneous chemical process. Let the quantity of 
mechanical work performed by an animal in a given time be col- 
lected, and converted by friction or some other means into 
heat ; add to this the heat generated immediately in the animal 
body in the same time, we have then the exact quantity of 
heat corresponding to the chemical processes that have taken 
phce. 

35. In the active animal, continues Mayer, the chemical 
dianges are much greater than in the resting one. Let the 
amount of the chemical processes accomplished in a certain time 
in tiie resting animal be x, and in the active one d?+y< If 
during activity the same quantity of heat were generated as 
during rest, the additional chemical force y would correspond to 
the work performed. In general, however, more heat is produced 
in the active organism than in the resting one. During work, 
therefore, we shall have x plus a portion of y for heat, the residue 
of y being converted into mechanical effect. 

dO. I must now prove that the extra quantity of combustible 
matter consumed by the working animal contains the necessary 
force for the performance of the work. A strong horse, not 
working, is amply nourished on 15 lbs. of hay and 5 lbs. of oats 
a day. If the animal performed daily the work of lifting a weight 
of 12,960,000 lbs. 1 foot high, it could not exist on the same nu- 
triment. To keep it in good condition we must add 11 lbs. of 
oats. The SO lbs. of nutriment first mentioned is the quantity 
whieb we have named x, and contains, according to Boussingault, 
8H)741bs. of carbon. The additional 11 lbs. of oats, our quan- 
tity y, contains, according to the same authority, 4*734. 

Aceoriing to Boussingault, also, the carbon introduced is to 
that eicreted in a combustible form as 8938 : 1864*4. Calcu- 
lating from these data, we find x, or the quantity of carbon burnt 
by the resting animal, 5*2766 lbs., and j^ss 8*094 lbs. The quan- 
tity consumed in meehanicid effect is 1*84 lb., which we will 

87. We have therefore the following relations: — 1. The 
fDechanioal effect is to the total consumption as g : ^+]y=s0*16. 
2. The mechanical effect is to the surplus consumption of the 
working animal as g ! ynO'48. 3. The generation of heat at rest 
Ml to the generation of heat while working as a t x+y^g:siO*76. 



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40 Ptof . Tyndall^s Noiei m SdmUific But&rff. 

88. In the same way Mayer^ taking the data fbrniabed hjr 
Liebig regarding the prisoners and soldiers at Oiessen, deter- 
mines the following relations for a man. 1. The mechanical 
effect is to the total consumption as 95*7 : 5408=0*177. 2. The 
mechanical effect is to the surplus consumption of the man at work 
as 957 : 285sO*386. 8. The generation of heat in the restinj^ 
man to that in the working man as 255 : 540— -95*7=:0*57* 

39. In these calculations, he continues, I have confined my- 
self to the consumed carbon. If the heat of combustion be aet 
equal to the carbon + the hydrogen, the additional heat ol the 
hydrogen may be regarded as nearly=:^th of that of the carbon. 
According to the individual constitution and habits of life, the 
labour and the consumption must be liable to considerable va- 
riations. The above results, however, serve to demonstrate the 
following propositions : — 

(1.) The surplus nutriment consumed in the working or- 
ganism completely suffices to account for the work done. 

(2.) The maximum mechanical effect produced by a working 
mammal hardly amounts to ^ th of die force derivable from the 
total quantity of carbon consumed. The remainbg fths axe 
devoted to the generation of heat. 

VI. 

40. In order to enable them to convert chemical force into 
mechanical work, animals are provided with specific organs^ 
which are altogether wanting in plants. These are the muscles. 

41. To the activity of a muscle two things are necessary r — 
1. The influence of the motor nerves as the determining condi- 
tion ; and 2. the material changes as the cause of the mecha- 
nical effect. 

42. Like the whole organism, the organ itself, the muscle, has 
its psychical and its physical side. Under the former we include 
the nervous influence, under the latter the chemical processes. 

43. The motions of the steamship are performed in obedience 
to the will of the steersman and engineer. The spiritual influence, 
however, without which the ship could not be set in motion, or, 
wanting which, would go to pieces on the nearest reef, guides, 
but moves not. For the progress of the vessel we need physical 
force — ^the force of coal ; in its absence the ship, however strong 
the volition of its navigator, remains dead. 

yii. 

Thus does this remarkable man, at a time when the writings 
of the most celebrated scientific professors were beset with 
mysticism as regards the operations of the vital force, pour light 
upon the darkness, wd bring the processes of the animal body 



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Prof. Tyndall's Notes an Sdenti^ HUiary. 41 

into hannony with the great law of conservation^ wbich he 
himself, alone and unaided^ had thought out. 

44. Here follow a few of Mayer's remarks on muscular motion. 

In the first part of this memoir^ the part played by combus- 
tion in inorganic apparatus in the steam-engine^ for instance 
was, in its main characters, explained. Our present problem is 
to consider the phenomena of vitality in connexion with their 
physical causes, and thus give to the propositions of physiology 
the basis of exact science. 

45. It has been already stated that an active working man 
converts in a day 0*19 lb. of carbon into mechanical effect. 
The weight of the whole muscles of such a man, who weighs 
150 lbs., is 64 lbs. ; and, subtracting 77 per cent, of water, 15 lbs. 
of dry combustible material remains. Let it be assumed (though 
not granted) that the heat-giving pqwer of this mass (with 
40 per cent, of nitrogen and oxygen) is equal to that of an 
equal mass of pure carbon ; then, if the work were done at the 
expense of the muscles themselves, the whole of the muscles 
must be oxidized and consumed in mechanical effect in eighty 
days. 

46. This arithmetical deduction becomes still more evident 
if we confine our attention to the work performed by a single 
muscle — ^the heart. I assume, mth Valentin, the quantity of 
blood in the left ventricle to be at every systole on an average 
150 cubic centimetres. The hydrostatic pressure of the blood 
in the arteries is, according to Poiseuille, equal to the pressure 
of a column of mercury 16 centimetres in height. The me- 
chanical work done by the left ventricle during a systole may be 
calculated from these data. It is equal to the raising of a 
column of mercury 16 centimetres long, and with a base of a 
square centimetre to a height of 150 centimetres. The weight 
of the mercury amounts to 21 7 grammes. The mechanical effect 
of a systole therefore is 

{825*6 grammes raised 1 metre, 
2 lbs. „ 1 foot, 

which is equivalent to 0*887 of a thermal unit, or equivalent to 
the combustion of 0*0001037 of a gramme of carbon. Taking 
for a minute 70 strokes, and for a day 100800 strokes of the 
pulse, the work done by the left ventricle in a day is equivalent 
to the raising of 202000 lbs. to a height of one foot. This is 
equal to 89^8 thermal units, which is equal to the combustion 

®^ 1 168*8 tm^^ r^^ carbon. According to Valentin, the 
work done by the right ventricle is half that done by the left. 
The work of both chambers in a single day is therefore equal to 



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42 Prof. TyndfllpB Noieg on ScimU^ BUtory. 

the rttiiiHg of 808000 lbs. 1 foot high se 184148 thermal units 

47. AMuming the weight of the whole heart to be 500 
grammes^ and deducting from this 77 per cent, of water, we 
have remaining 115 grammes of dry combustible material. 
Assuming this material to be equal to that of pure carbon, it 
would follow that the entire organ, if it had to furnish the 
matter necessary to its action, would be oxidized in eight days* 
Taking the weight of the two ventricles alone as 202 grammes, 
under the same conditions the complete combustion of this 
musoular tissue would be effected in 8^ days. 

VIII. 

48. This partial rimm^i of half of Mayer's second memoir is 
now ended. It embraces only the first 56 pages of an essay whkh 
contains 112 pages. Mayer began, as has been stated, with the 
question of vital dynamics. The observation which led to his 
scientific labours was made on a patient at Java in 1840, and 
in 1842 he published his first paper. He informs us that he 
had put it briefly together to secure himself against casual- 
ties*; and having done this, he oontinued his inquiries, and in 
1846 published the memoir from which the foregoing extracts 
are taken. He did this in the intervals of a laborious profession, 
'^ ohne Hussere Ermunterung,'' as he himself touchingly observes. 
The full translation of the essay can alone give an adequate ides 
of the research which it implies. Mayer probably had not the 
means of making experiments himself, but he ransacked the 
records of experimental science for his data, and thus conferred 
upon his writings a strength which mere speculation can never 
possess. From the extracts which I have given, the reader may 
infer his strong desire for quantitative aoouracy, the clearness of 
his insight, and the firmness of his grasp. Regarding the redog<* 
nition which will be ultimately accorded to Dr. Mayer, a shade 
of trouble or of doubt has never crossed my mind. Individuals 
may seek to pull him down, but their efforts wiU be unavailing 
as long as such evidence of his genius exists, and as long as the 
generd mind of humanity is influenced by considerations ^f 
justice and of truth f- 

♦ Phil. Ma^. vol. XXV. p. 601. 

t The paucity of fscts in Mayer's time has been ufsed as if it Wers s 
reproach to him, but it ought to be remembered that the qusntity of fact 
necessary to a gemeralisfttion ia different for Afferent minds. " A word td 
the wise is sufficient for them/' and a single fact in 8om6 minds bears fruit 
that a hundred cannot produce in others. Mayer's data trei^ compatft- 
tivsly sssaty^ bat his genius went far to supply us husk of ssqieftaienty by 



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Prof: Tyndall's Ni4n an ScienH/la History. 48 

IX, 

49. There are a few points remaining, whicb^ to preserve the 
events of scientific history in their true relationship, ought to be 
referred to here. It has been asserted mildly (as is his wont) 
by Mr, Jonle^ less mildly (as is their wont) by his northern sup- 
porters, that, as regards vital dynamics, he anticipated Mayer 
Dj two years. In a letter published in the Philosophical Maga- 
»ne for August 1862, Mr. Joule writes thus : — '^ Permit me to 
remark, that I applied the dynamical theory of heat to vital pro- 
cesses in 1843.'^ Let all justice be done to Mr. Joule regaraing 
his application of the theory. In a postscript to a paper in the 
December Number of the Philosophical Ililagazine for 1848 he 
writes thus : — 

60. " On conversing a few days ago with my friend Mr. John 
Daviea, he told me that he had himself a tew years ago at- 
tempted to account for that part of animal heat which Craw- 
ford's theory had left unexplained, by the friction of the blood 
in the veins and arteries, but that, finding a similar hypothesis 
in Haller's ^ Physiology,' he had not pursued the subject further. 
It is unquestionable that heat is produced by such friction, but 
it must be understood that the mechanical force expended in 
the friction is a part of the force of affinity, which causes the 
venous blood to unite with the oxygen, so that the whole heat 
of the system must still be referred to the chemical changes. 
But if the animal were engaged in tiu^iing a piece of machinery, 
or in ascending a mountam, I apprehend that, in proportion to 
the muscular effort put forth for the purpose, a diminution of 
the heat evolved in the system by a given chemical action would 
be experienced.'' 

This citation embraces, I believe, every word that was written 
on " vital dynamics " by Mr. Joule, before the appearance of 
Mayer's paper on organic motion. It consists of a conjecture, the 
sagacity of which is in accordance with the insight always mani- 
fested by Mr. Jo^le. Let the reader compare it with se<Aion8 
4 to 7 of this rimmi, and make the deductions which he deems 
right from bis estimate of Mayer's work. 

61, In 1852 Prof. Wm. Thomson wrote on the subject of ^^ vital 
dynamics," and it will be instructive to compare what he has 
done with what bad been done by Mayer seven years earlier. 

enabhiig him to tee clearly the bearing of sueh ftets as he posseaaed. 
They enabled him to think out the law of conservation, and his ooncludons 
received the stamp of certainty from the subsequent experimental labours 
of Mr. Joule. In reference to their comparative merits, I would say that, 
as Seer and GteneraHser, Mayer, in my opinion, stands first^^^as Expwi- 
■Ma1»l Pfailesopher, Joule. 



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44 Prof. Tyndall's Notes ah ScienHfie Hisiary. 

The whole paper of Prof. Thomson^ published in the Philoso- 
phical Magazine for 1852, vol. iv., may be compared with the 
writings of Dr. Mayer now before the reader. 1, however, will 
limit myself here to the section *' On the Power of Animated 
Creatures over Matter'' (p. 258). 

''A principal object of the present communication is to 
point out the relation of this theory [that of animal heat and 
motion] to the dynamical theory of heat. It is remarked, in the 
first place, that both animal heat and weights raised or resistance 
overcome, are mechanical effects of the chemical forces which act 
during the combination of food with oxygen. The former is a 
dynamical mechanical effect, being thermal motions excited; 
the latter is a mechanical effect of the statical kind. The whole 
mechanical value of these effects, which are produced by means 
of the animal mechanism in any time, must be equal to the me- 
chanical value of the work done by the chemical forces. Hence, 
when an animal is going up-hill or working against resisting 
force, there is less heat generated than the amount due to the 
oxidation of the food, by the thermal equivalent of the mecha- 
nical effect produced. From an estimate made by Mr. Joule 
[in 1846, Phil. Mag. vol. xxviii. p. 454], it appears that from 
^ to ^ of the mechanical equivalent of the complete oxidation of 
all the food consumed by a horse may be produced from day to 
day as weights raised [Mayer published the same result a year 
previous to Mr. Joule, see 39] . The oxidation of the whole 
food consumed being, in reality, far from complete [see Mayer, 
86 to 89], it follows that a less proportion than |, perhaps 
even less than | of the heat due to the whole chemical action 
that actually goes on in the body of the animal, is given out 
as heat. An estimate, according to the same principle, upon 
very imperfect data, however, is made by the author, regarding 
the relation between the thermal and the non-thermal mecha- 
nical effects produced by a man at work [Mayer made the same 
estimate, see 88] ; by which it appears that probably as much 
as ^ of the whole work of the chemical forces arising from 
the oxidation of his food during the twenty-four hours may 
be directed to raising his own weight, by a man walking up-hill 
for eight hours a day; and perhaps even as much as ^ of the 
work of the chemical forces may be directed to the overcoming 
of external resistances by a man exerting himself for six hours 
a day in such operations as pumping. In the former case there 
would not be more than f , and in the latter not more than } 
of the thermal equivalent of the chemical action emitted as 
animal heat, on the whole, during twenty-four hours, and the 
quantity of heat emitted during the time of working would bear 
much smaller proportions respectively than these to the thermal 



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Prof. Tjradiill's Notes on Scientific History. 4S 

equivalents of the chemical forces actually operating during 
those times ^^ *. 

Comparing the foregoing remarks with what Mayer had 
written seven years earlier^ the reader will draw his own eondu* 
sions as to their comparative completeness. In his writings 
upon vital dynamics Prof. Thomson never once mentions the 
name of Mayer ; he is not^ I presume^ to be blamed for this 
omission; for when he wrote in 1852 he knew nothing about 
Mayer's most important labours. I state this because the 
opposite supposition is too unpleasant to be entertained. But 
in 1862 I gave him the titles of Mayer's memoirs, and requested 
him and others to refer to them, and correct me if I had erro* 
neously estimated the merits of their author. To my great 
regret, Prof. Thomson, without giving himself the trouble of 
consulting the documents to which I had referred him, sanctions 
the publication of the statement, that, as far back as 1851, he had 
g^ven to Mayer '^ the full credit which his scientific claims can 
possibly be admitted to deserve " f- 

52. In the paper from which I have just quoted, Prof. Wm. 
Thomson also refers to the deozidation of carbon and hydrogen 
from carbonic acid and water, effected by the action of solar 
light upon the green leaves of plants, as a mechanical effect of 
radiant heat. This action, he says, was pointed out by Helm- 
holtz in 1847. 

53. The words of Helmholtz are as follows (Erhaltung der 
Kraft, p. 69 J) : — '' There remains to us of known natural pro- 
cesses those of organic beings. In plants the processes are 
iprincipally chemical, and besides this, in some of them, at least, 
a slight generation of heat takes place. Of foremost importance 
is the fact, that in them a great quantity of chemical forces is 
deposited, the equivalent of which we obtain as heat on the com- 
bustion of the plant. The only vis viva which, according to our 
present knowlec^e, is absorbed during the growth of the plant, 
consists of the chemical rays of the sun. Results are, however, 
still wanting to enable us to make a sure and strict comparison 
of the forces which here disappear and appear. For animals we 
have, however, some grounds of comparison. They take in the 
complicated oxidizable compounds which are produced by plants 
and oxygen, and return them for the most part burnt as carbonic 
acid and water ; partly, however, they are excreted, reduced to sim- 

* On first reading this passage I thought it might be an abstract of a 
faller statement, but I have been unable to find anything more complete. 

t Phil. Mag. vol. xxv. p. 264. 

X This excellent essay was translated by myself many years ago, and 
published in the last volume of the Scientific Memoirs. (Taylor and 
Francis, Red Lion Court, Fleet Street.) 



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46 Prof* TyBdall't Notes on Seieni^ BkUny. 

pier cdmbinations. They therefore consume a quantitjr of ehoni* 
cal forces^ and generate in their place heat and mechanical forces* 
As the last represent a comparatively small amount of work in 
comparison with the amount of heat, the question of the eon* 
servation of force reduces itself to this : — ^Do the combustion and 
the change of materials in the nutriment generate an equal 
quantity of heat to that yielded up by the animal ? According 
to the experiments of Dulong and Desprets^ this question can^ at 
least approximately, be answered in the affirmative/' 

64. Helmholtz made this statement independently of Mayer^ 
for when he wrote he did not know what had been published two 
years before at Heilbronn * ; and clearly as the above paragraph 
illustrates his insight on this momentous point, it could not bt 
accepted as an adequate abstract of Mayer's previous writings 
on the same subject. In a lecture of varied excellence, trans** 
lated by myself, and published in the Philosophical Magasinei 
1856, voL ii., Helmholtz expresses in clear and beautiful Ian* 
guage the relation of animals to vegetables, and of both to ths 
sun. The lectnjre was given at Konigsberg on the 7th of Fe- 
bruary 1854; and if the reader vashes to resize fully the extent 
to which Mayer had occupied this field, and the scantiness of 
the additions made to our knowledge of vital dynamics during 
the nine years following the publication of MayePs essay, he may 
compare pp. 509, 510, and 511 of Uelmholtz's lecture with see* 
tions 4, 5, Q, and 7 of this rf^siumi^ 

66. One word more on this subject, which shall have as slight 
a personal tinge as I can under the circumstances impart to it 
In a religious periodical, which we are informed numbers 120,000 
readers. Prof. Thomson undertook to give an accurate account of 
the discovery, nature, and development of the law of the conservao 
tion of energy, professedly with the view of correcting the errors 
which he beUeved me to be disseminating regarding Mayer. In 
that article he charged me with depreciation and suppression, 
and these bad words rest unretracted in the pages of ' Good 
Words' to this hour. After dealing with various questions 
relating to the " conservation of enei^," Prof. Thomson comes 
at length to the ^^ grandest question of all,'' and states it 
thus ; — "Whence do we derive the stores of potential energy 
which we employ as fuel and foodf What produces the 
potential energy of a loaf or a beefsteak ? What supplies the 
coal and the water power, without which our factories would 
stop ? " And the answer to this question is " the sun." Prof. 
Thomson can now name the man who answered this question 
seventeen years before he called it the grandest of all — the man 

* " I myself, without being acquainted with either Mayer or Colding/' 
&c. — Phil. Mag. S. 4. vol. ii. p. 409. 



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Frof. TjrndaU's Notes m Scientific BUtary. 47 

wImm name^ to my deep regret^ he has never yet named in ecm-. 
nexion with this question^ though Mayer's relation to it has been 
BOW for two years known to him. But this is not all. In public 
and ill private — ^in articles which are so far manly as to bear 
their author's namesj and in an article which bears no narne^ but 
which has been recently mentioned with commendation in the 
pages of this Magasine-^I have been attacked for my support of 
I)r. Mayer in language which I would not stoop to characterise. 
While here^ from the pen of the man who^ in equal ignorance 
both of me and of the facts, instituted this ungentle crusade 
against me, I extract testimony to the greatness of Maker's 
work, stronger than I have ever uttered in attempting to vmdi^ 
cate hia claims. 

X. 

56. Sir W. Herschel had called the maintenance of solar heat 
^'TheGreat Secret/' Mayer endeavoured to solve it^ and published 
his essay on Celestial Dynamics in 1848. It will be seen, however, 
in a foregoing page that the idea of a meteoric source of solar 
heat wm at his hand in 1845. Hia calculation of the quantity 
of heat which would be generated by the mechanical combination 
of the earth and sun proves this (see 22ij. But in 1848 he pub- 
lished a complete development of his theory, and his essay is now 
readily accessible since its translation by Dr. Debus for the Philo- 
sophical Magazine ^» There could scarcely be a closer coincidence 
between two independent scientific memoirs than that subsisting 
between the essay of Dr. Mayer and the paper of Prof. Thomson, 
published six years subsequently f. Thomson considers and 
rejects the assumption that the sun is a heated body, losing 
heat; Mayer did the same. Thomson considers and rejects the 
assumption that the heat of the sun is due to chemical action j 
so did Mayer. Thomson considers and embraces the theory 
that meteors falling into the sun give rise to his heat ; so did 
Mayer. Thomson arrives at the conclusion that the main souree 
of solar light and heat is the zodiacal light. This was also 
Mayer's conclusion. Their calculations run parallel, and their 
deductions from them are the same. As an instance of eoinci<* 
deuce in detail the following is worthy of notice:— "A dark 
body," writes Prof. Thomson in 1854, " of dimensions such as the 
sun, in any part of space, might, by entering a cloud of meteors, 
become incandescent as intensely in a few seconds, as it could 
in years of continuance of the same meteoric circumstances, and 
again getting to a position in space comparatively free from 
meteors, it might almost as suddenly become dark again. It is 
far from improbable that this is the explanation of the appear- 

• Vol. XXV. pp. 241, 387, 417. 
t Phil. Mag. voL viii. p. 409. 



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48 Prof. Tyndall'g Notes on Scientific History. 

anee and disappearance of bright stars^ and the strange variations 
of brilliancy of others which have caused so much astonishment.^' 
(Phil. Mag. vol. viii. p. 415). Three years previous to the 
publication of the above paragraph Dr. Mayer wrote thus : — " It 
18 more than probable that the earth has come into existence in 
some such way^ and that in consequence of this process our sun, 
as seen from the distance of the fixed stars^ exhibited at that 
epoch a transient burst of light. But what took place in our 
solar system perhaps millions of years ago, still goes on at the 
present time here and there among the fixed stars; and the 
transient appearance of certain stars, which in some cases, Uke 
the celebrated star Tycho, have at first an extraordinary degree 
of brilliance, may be satisfactorily explained by assuming the 
falling together of previously invisible double stars.'' (Bemer- 
kungen ii. d. mech. Aequiv. d. Warme, p. 66 ; Phil. Mag. vol. xxv. 
p. 521.) 

57. At the commencement of his paper ''On the Mechanical 
Energies of the Solar System," Prof Thomson states that this 
theory was never brought forward in any definite form, so far 
as he was aware, " until Mr. Waterston communicated to the 
British Association at Hull a remarkable speculation on cosmical 
dynamics {Dynamik dee Himmels), in which he proposed the 
theory that solar heat is produced by the impact of meteors." 
Mayer is here definitely ignored; and I assume the reason to 
be the same that I have assigned for Prof. Thomson's silence 
regarding Mayer's writings on vital dynamics. But he was not 
left without information ; in my lecture in June 1862 1 referred to 
those writings in the following words : — " In 1853 Mr. Waterston 
proposed independently the meteoric theory of the sun's heat, 
and in 1854 Prof. Wm. Thomson applied his admirable mathe- 
matical powers to the development of the theory ; but six years 
previously the subject had been handled in a masterly manner 
by Mayer, and all that I have said on this question has been 
derived from him." I do not see how I could have stated the truth 
in more considerate terms. Instead, however, of making him- 
self acquainted with the essay of Mayer and nobly bidding him 
welcome, Prof. Thomson permits himself to sanction the following 
language towards me. ^' Prof. Tyndall is most unfortunate in the 
possession of a mental bias, which often prevents him (as, for 
instance, in the case of Rendu and glacier-motion)* from recog- 
nizing the fact that the claims of individuals whom he supposes 

* I have asked Prof. Thomson to point out the passages in my writings 
which Justify this language^ bat he has not done so. The readiness of 
Prof. Thomson to make such statements and to neglect their proof has 
excited attention in other quarters, and will assuredly furnish him with its 
harvest of results. 



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Prof. TyndalPs Notes onSci^tific History. 49 

to have been wronged, have, before lis intervention, been folly 
yentilated^ discussed, and settled by the general award 6i 
scientific men^'' Such rashness is rare in a man occupjring s6 
Tesponsible a position. The fact really is that if it could be 
riiown that Prof. Thomson had, '' before my intervention,'* been 
aware of what Mayer had done, he would at the present moment 
be in as unenviable a position as could possibly be occupied by 
a scientific man. I may add that he has never yet rendered' to 
Dr. Mayer the credit which belongs to him. 

58. How far Mr. Joule's lecture on shooting-stars (23) afiects 
the essay of Dr. Mayer on Cosmical Dynamics the reader must 
himself determine. Here is the extract from the ' Manchester 
Courier' {12th May 1847) referred to by Mr. Joule and printed 
in the Philosophical Magazine. '^ You have no doubt frequently 
observed what are called shooting-stars, as they appear to emerge 
from the dark sky at night, pursue a short and rapid course, 
burst, and are dissipated in shining fragments. From the 
Telocity with which these bodies travel there can be little doubt 
that they are small planets, which in the course of their revo- 
lation round the sun are attracted and drawn to the earth. 
Reflect for a moment on the consequences which would ensue 
if a hard meteoric stone were to strike the room in which you 
are assembled with a velocity sixty times as great as a cannon- 
ball.' The dire effects of such a collision are effectually prevented 
by the atmosphere surrounding our globe, by which the velocity 
of the tneteoric stone is checked, and its living force converted 
into heat, which at last becomes so intense as to melt the body 
and dissipate it in fragments, too small probably to be noticed in 
their fall to the ground. Hence it is that, though multitudes 
of shooting-stars appear every night, few meteoric stones have 
been found, those few corroborating the truth of our hypothesis 
by the marks of intense heat they bear on their surfaces." 
Those who have read Mayer's essay will never forget it, and will 
be able to judge how far its character could be affected by th6 
above extract ; even had it been under the eyes of Mayer from the 
moment of its publication. Those who have not read Mayer, 
will find him translated in the Phil. Mag. vol. xxv. pp. 241, 387, 
417. In my book on Heat I have given Mr. Joule due credit 
for the above hypothesis^. 

59. More than a year ago I addressed a letter to Prof. W. Thom- 
son which gave me great pain to write. I wrote it partly in de-» 
fence of Dr. Mayer, partly in defence of my own character. It was, 
I am told, vigorously expressed, but it has never been intimated 

* The hypothesis of the cosmical origin of meteorolites is due to 
Chladni, the protective power of the atmosphere and its sufficiency to dis- 
sipate meteors being the point brought forward by Mr. Joule. 

Phil. Mag. S. 4. Vol. 28. No. 186. July 1864. E 



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60 Vtii!.TjT^i9Xl'uNia09amScimUifi€lBitmrfi. 

to me that it ocmtauied a aiflgle ungoatleiiiaQly torm, It biqi^ 
me expr^oua of approval and sympathy from som^ of tb^ most 
epunfmt men in Europe j apd I was io cpntept mih thili that t 
wiUingly-^some tboughtj tiMndy^et the cUaooaaion drop, It waf 
quite natural that my atyle and matter abould be tbQ Tayeiraa tf 
agreeably to Prof, Tbomaon j audi at might be expect^4i b^ ^? 

freaiedbimselftQ this effect. Hecomplamedoftbelibertieawbiob 
bad taken with bia name; of the jibiirtiaa I bad taken with 
other names. In short, he oopaider^ my whole tone ^^ wpra^ 
pedented in aoientifiq diacuaaion/^ and be decUued baying «py- 
ibing to do with me. On Qn§ technical queation, moiwverj bf 
made a complamtj to whicbj aa it invplyes a point of personal 
courteayi I am anxioua to reply. He complained that I bad 
printed my letter in the Philosophical Magazmc without aending 
him the original. I am informed by good authority that tbs 
courae I pursued was the usual and proper one- Had it been 
cuatomary to send the original in aucb a caaej I should oertainb 
not have failed in this act of courtesy to Prof. Tbomaon, Had I 
even known bis personal yiewson the matter^ I abould bav§ leat 
him the priginalj regardless of the general practice* Nor lidiould 
I have allowed myself to.be in any degree influenced by the fart 
that Prof. Thomson bad inserted in ^ Good Worda' ^proaaiom 
injurious to my characterj which circulated unknown to mo amoiw 
the 120j000 readers of that periodicalj until tbcir accidental 
discovery by my assistant gave me au opportunity of demonstra* 
ting their baselessness, I would at the same time romind bim 
that, though there is a dignity in silence when exercised at th^ 
proper time and in the proper way, it is wt dignity^ nop &fm 
manlinesa aa defined iu England, that permits a map to mak9 
an unwarranted accusation, and prevents him from retracting it 
after ita injustice has been exposed. 

It is with great reluctance that I refer tp tbeae toincaj and 
were I alone concerned, I should give the world no further 
opportunity to animadvert on the dissensiona of those among 
whom, in the interest of their common vocation, brotherly kin£ 
ness ought to reign. But ailence is scarry becoming on my 
part when I aee the reputation of a man, in whom the fineii 
mtellectual qualities are associated with the moat abnnkiog 
modesty of character, made the target of anonymous reviewWi 
I never bad^an interest iu this controversy apart from the deai]*^ 
to do him justice. To me Dr, Mayer is personally uuknowRi 
and mjr own scientific labours, unlike those of my chief cenaori 
are entirely unaffected by anything that he baa dojoie, I may 
add that all that I had seen or known of Mr. Joule, previous to 
this discussiouj bad served to inspire me with respect and attaebit 
ment for bim- Personal liking and what baa bee& caUad -* p«« 



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holism '* ftdded tbemaalve^ to the exalted value which I attached 
to his researches. I held^ and still hold^ him to be one of the 
l#bk6t w^mi (tf Ma age; and my estimate of bis laboovs is 
Wt a phade Iciweredby tbia other conviction, that be must^ in tha 
Wattwy <rf ^eicnc6> aocept Dr, Mayer aa Wa seientifie brother,— 
that the Thinker and Generaliaer is fit to atand, and will be canaed 
to stand, beside the Experimental Philosopher, To permit Dr. 
Mayer to remain in the position in which I found bim> would be 
to &sten on myself the guiJt of that neglect of which the plea 
of ignorance alone acquita his cpntempcnrariea. In eveiy aen* 
tenoe that I have written in hia favour I have felt that strength 
which perfect single-mindedneas can alone impartj, and, fearleaa 
alike of his fate and of my own, I now commit bla reputatioUf 
and my conduct concerning it, to the impartial judgment of 
mankind* 

Sojal Institution, June 1864, 



t i | i i.l if ...'.t 4 it 



y^ Ona Modi/kation 0/ Wattes ParaUehgpram* 
By P, Tch6bychbf*, 

THB mechanism known as Watt's parallelogram furnishes a 
solution of the following practically important problem 1 
To producCy to a sufficient d^ee of approaoimation, rectilineal 
motion hy a combination of circular motions. 

The degree of precisioU attainable by contrivances of this kind 
depends obviously upon the number of its disposable elements, 
and in this point of view the parallelogram of Watt is far from 
being satisfactory. In its structure, for instance, two rods more 
are employed than in the mechanism a ftiau, and yet the mo- 
tion produced is the same. In attempting to produce approxi^ ' 
mate rectilineal motion by means of either of these two eontri» 
vances, the motion really attained is an oval one, which has at 
most five elements in common with the desired rectilineal motion. 
Now this degree of approximation is unquestionably small when 
we take into consideration the degree of complication presented 
by Watt's parallelogram. The latter, as is well known, pos* 
sesses four disposable elements, each of which, as therein em- 
ployed, furnishes two arbitrary parameters — its length and its 
directioa. Seeing, therefore, that, on the whole, eight parame- 
ters are involved, we are justified in seeking a contrivance of the 
same degree of complexity as Watt's parallelogram, but capable 
of furnishing a much more rectilineal motion — one, in fact, 

* From the Bulletin de r4Qa4, Imp, de$ Soieiuies de St. P^tersbourg, ^ 
voL iv. p. 433, 

E3 



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52 M^V.Teh4hyche{ on a Madificathn of WBtVf^ParMUebgram^ 

which has with the desired motion eighty instead of five common 
elements. 

We have done this, and found that the approximation in 
question may be attained by articnhting, witn each other and 
with the beamj the four rods of Watt's parallelogram in thefoU 
lowing manner. In this figure AB 
represents the semi-beam upon which 
it is required to construct a mechanism 
•capable of producing approximately 
rectilineal motion along the vertical 
line V V, passing through the extre- 
mity B of the beam when the latter 
has a horizontal position. B C, D E, 
C F^ F G are the four rods composing 
this mechanism ; C is the point whose 
motion is to be considered ; and F G, 
turning around a fixed axis G, repre- 
sents the counter-beam^ as in Watt's 

parallelogram. These rods are articulated with each other and 
with the beam in the same manner as in Watt's parallelogram, 
with the sole diflFerence that the rods D E and F C, instead of 
being connected with each other, are articulated with the counter-^' 
beam FG at two different points E and F. The lengths and 
distances adopted are the following: — 




^va^ ^5 + 1 



CF=FG 



4 



AB, 



^vn-^ ^5-1 



BD=EG 



AB. 



Consequently BD is a mean proportional between AB and AD, 
and EF is the half of AD. The rods BG and DE have the 
same length; and provided the latter do not sensibly exceed the 
semi-path of the point C, it may be arbitrarily chosen. The 
centre of oscillation G of the counter-beam FG is chosen so that, 
when the beam is horizontal, the rods BC and DE may be 



vertical, and at the same time the rods 
CF and FG may have the same hori- 
zontal position, as seen in fig. 2. 

Such is the composition of the me- 
chanism which, with the same number 
of rods as Watt employed, will give a 
motion having eight elements in com« 
men with the desired rectilineal one. 
This fact may be very easily verified by 
determining, as a function of the incli- 
nation of the beam, the variable distance 



Fig. 2. 



v 



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H. F* Tehebychef m a Modifiaaion 0/ Watt's PanraUdogram. 58 

of the point C from the yertical line YY' (fig. 1)*. It will 
then be at once seen that the vertical V V is a tangent, at 
the point corresponding to the horizontal position of the beam, to 
the curve described by C ; further, that in the neighbourhood of 
this point the curve has seven elements in common with its 
tangent, aud, lastly, that it cuts the same at a distance from G 
less than BG ; so that, within the space described by G, the curve 
and the vertical have necessarily an eighth common element. 

We see from this with what extreme rapidity the deviations of 
the point G from the vertical hne V V (fig. 1) increase with the 
amplitude of the oscillations of the beam, the distances being of 
the seventh order with respect to the inclination of the beam. In 
ordinary practical cases, where the inclination is never great, the 
working of this mechanism would, as far as precision is con- 
cerned, be greatly superior to that of Watt. Take, as an ex- 
ample, the case treated by Frony in his well-known '' Note sur le 
parallelogramme du balancier dela machine k feu ^'f, where the 
length of the semi-beam AB is 2*515 metres, that of the rod 
B C being 0*762 of a metre, and the greatest inclination of the 
beam 17^ 35' 30". With the improved mechanism the devia- 
tions from the vertical would be less than 0*05 of a millimetre, 
whereas, according to Frony, the deviations with Watt's paral- 
lelogram would amount to 2 millimetres, — a quantity forty times 
the above, and far from being insignificant in the working of a 
machine of this description. 

Hitherto, in seeking to approach as closely as possible to a 

* This variable distance is expressed by the formula 

^5!!^^.AB(cosV^--co8i^), 

wherein the angles ^ and ^ are functions of the inclination « of the beam 
which satisfy the two equations 

A 3-V6 V6-1 ^V 

(l.ea.-+^eos<^-^cos^y 

The anproximate expresuon for the distance in question is consequently 
given Dv the series 

7-3V6 AB^7, V5-2AB; 

32 BC *^+ "16^ BC** + '•' 



t Afmales des Mines, vol. xii. 



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64 M«P.Tch%eherimaiirMi#left<iono/WateiPAr«^^ 

teifticid motion, we have only consider^ bow inamf elements 
were common to the vertical and to the curve described by th^ 
point 1 the degree of approximation of the two^ howevor^ 
depends also very esaentially upon the position of these elements. 
We have already examined this question in the first part of a 
memoir entitled '* Th^rie des m^canismes counus sous le nom 
des parall^logrammes'^*^ and therein proposed methods for 
rendering such an approximation as perfect as possible. By 
applying these ihethods to the case under consideration^ we 
shomd be led to introduce certain small changes in the values 
of the several parameters^ in order to render the tnechanism as 
perfect as possible. By means of these corrections^ the devia- 
tions of the point G would be reduced in the proportion of about 
1 to 2^ (see § 5 of thd memoir cited). But since^ in practical 
cases^ these deviations^ as we have seen, are themselves ^mf 
small — amounting at most to some hundredths of a millimetre, 
— ^it is evident that by the application of the above oorrecti^ms 
the theoretical precision of the apparatus might be carried to a 
limit unattainable by the mechanician. Fof ordinary praetiM 
purposes, therefore, there is no inducement to seek a mecha- 
nism capable of giving rectilineal motion with greater aceufacy. 
This impitoved mechanism is the more worthy of atteutionj shicei 
as we have shown, the utmost desirable pilecision is attailldd by 
employing the same number of pieces as in Watt's paftiUek* 
gram, whose practical defects are often experienced^ 

We may observe, lastly, that the adjoining tiew i&ttA of the 
mechanism is obtained by changing the signs of the radicals in 
the foregoing values of the elementsi 

In this new form, where Kg. 3. 

CF=FG= ^^-^AB, ^ 

4 

BD=BG=^^^^AB, 

the degree of working precision is 
theoretically the same as before] its 
construction, however, would neces- 
sitate the prolongation of the beam, 
and thus be attended with great dis- 
advaUtagesi 

* M4mmn$ de SavtuUa Btrnkgergi vol. tiii 




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Vt. On the Barometer' as an Tmiieator t>f thd Satth^s Rotaiidn 
md the Sun'i Distance. By Pliny EAttLB Chasu*. 

THE existence of daily barometric tides lias been known for 
more than a hundred and fifty years, but their cause is 
still a matter of dispute. It is evident that they cannot be 
accounted for by variations of temperature^ for (1) their regul&^ 
rity is hot perdeived until all the knotun effects of temperature 
have been eliminated; (2] they occur in all climates, and at all 
seasons; (3) opposite, effects are produced at different times, 
under the same average temperature. Thus at St. Helena the 
mean Of three ftstn' hourly observation gives the foUowitig 
average barometric heights : — 

h h im h h iiii 

From Otold S8-3801 From 18 to 6 28-S8&8 
From IS to $282861 From 6 to 18 28-2784 
The tipper lines evidently embrace the coolest parts of the day^ 
and the lower lines the warmest. Dividing the day in the first 
method, the barometer is highest when the thermometei* is 
highest ) but in the second division the high barometer prevails 
duktlg the coolest half of the day. 

On account of the combined effects of the eai^h's rotation and 
devolution, ^ach particle of air has a velocity in the direction of 
ita orbit, vairying at the eqtlator from about 65,000 miles per 
hotil- at liobn, to 6?',000 tniles per hour at midnight. The force 
of rotation may be readily compared with that of gravity by 
observitig the effects produced by each in twenty-four hours, the 
intenral that felapses between two successive returns of any point 
to the satoe relative position with the sun. The force of rota- 
tion producing a daily mdtion of 24,895 miles, and the force of 
terrestrial gravity a motion of 22,738,900 miles, the ratio of the 
former to trie latter is a^y^gVcfoo^ ^^ *00l09. This ratio repre- 
sents the proportionate elevation or depression of the barometer 
abote of below its mean height that should be caused by the 
earth's rotation, and it corresponds v6ry il^ariy With the actual 
disturbance at stations near the ^uator. 

From 0^ to 6^ the air has a fdrward motion greater than that 
of the earth, so that it tends to fly aWay ; its pressure is there- 
fore diminished^ and the mercury falls. From 6^ to 12^ the 
earth's motion ib greatest j it therefore presses against the lag- 
ging air> and the barometer risfeSi From 12^ to 18*^ the earSi 
moves away from the air, and the barometer falls ; while from 
18^ to 24^ the increasing velocity of the air urges it against the 
earth, and the barometer rises. 

If the force of rotation at each instant be resolved into two 
components, one in the direction of the radius vector, and the 
* From SilHman's American Journal for Mav 1864. 



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66 



Mr. F« E. Chase on the Barometeir 



other parallel to the earth's orbit^ it will be readily perceived that 
whenever the latter tends to increase the aerial pressurej the 
former tends to diminish it^ and vice versd. Let B= the height 
of the barometer at any given instant; M= the mean height 
at the place of observation; 0—90°= the hour-angle; G= the 
earth's circumference at the equator; ^=24 hours; ^= the 
terrestrial gravity ; /= the latitude : and a simple integration 
^ves the theoretical formula 

Ti -niT /i sin cos cos/ 2C\* 
B=M(^l+ jp .^), 

This formula gives a maximum height at 9^ and 21^ and a 
minimum at 3^ and 15^. The St. Helena observations place the 
maximum at 10^ and 22^ and the minimum at 4^ and 16^, an 
hour later in each instance than the theoretical time. This is 
the precise amount of retardation caused by the inertia of the 
^ercury^ as indicated by the comparisons with the water baro- 
meter of the Royal Society of London. 

Aerial currents^ variations of temperature^ moisture, and cen* 
trifugal force^ solar and lunar attraction^ the obliquity of the 
ecliptic, and various other disturbing causes, produce, as might 
be naturally expected, great differences between the results of 
theory and observation. But by taking the grand mean of a 
series of observations, sufficiently extended to balance and elimi- 
nate the principal opposing inequalities, the two results present 
a wonderful coincidence. 

According to our formula, the differences of altitude at 1, 2, 
and 3 hours from the mean, should be in the respective ratios of 
*5, *866, and 1. The actual differences, according to the meaa 
of the St Helena observations, are as follows : — 



Differencea of Barometer. 


Batioi. 


Difference of time 
Before Ih 


Ih. 

•0166 

*0159 

•0122 

•0135 

•0136 

•0131 

•0161 

•0150 


2h. 

•0298 

•0266 

•0202 

•0239 

•0248 

•0215 

•0287 

•0265 


3h. 

•0365 

•0298 

•0243 

•0297 

•0284 

•0227 

•0348 

•0286 


Ih. 
•455 
•534 
•502 
•455 
•479 
•577 
•463 
•524 


2h. 
•816 
•893 
•831 
*805 
•873 
•947 
•825 
•927 


Sh. 


After Ih 


Before 7h 


After 7h 


Before 13h 


After 13h 

Before 19h 


After 19h 




Mean 


•0145 


•0252 


•0293 


•495 


•860 


1 





^ represents the effective ratio of an entire day» But there is in 
each day a half day of acceleration, and a half day of retardation, and the 
ratio for each half day is o "^ 4 ^ o?* 



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OB an Indicator of the Earth's Rotation, ifc. 57 

The mean of the above difFerences varies from the theoretical 
mean less than ^(jf^^ of an inch. If we take the mean of the 
ratios instead of the ratios of the means of the observed difier- 
ences^ the coincidence is still more striking. 

Difference of time I h. 2h. 3h. 

Means of observed ratios -498625 *864625 1*000000 

Theoretical means -500000 -800025 1000000 

The calculated time for the above-observed means differs less 
than 2(f' from the actual time. 

.Observed means -498625 -864625 1-000000 

Theoretical difference of time. SO' 48"^ 119' 40" 180' 

Observed difference of time... 60 120 180 

The varying centrifugal force to which the earth is subjected 
by the ellipticitv of its orbit^ must in like manner produce 
annual tides. The disturbing elements render it impossible to 
determine the average monthly height of the barometer with 
any degree of accuracy^ from any observations that have hitherto 
been made. We may^ however^ make an interesting approxima- 
tion to the annual range^ still using the St. Helena records^ which 
are the most complete that have yet been published for any sta-> 
tion near the equator. Comparing the mean daily range as de- 
termined by the average of the observations at each hour^ with 
the mean yearly range as determined by the monthly averages, 
we obtain the following results : — 

Amnroximtte 
Tear. I)ail]r range. Annual range* Ratio. solar distance. 

1844 •%>2 -1650 2*4553 137,070,000 

1845 -0646 *1214 1*8793 80,300,000 

1846 -0670 -1214 1-8120 74,660,000 

d)-1988 3)'4078 3)61466 

"■^0663 -1369 2-0489 95.446,000 

Mean 0663 '1290 1-9457 86,056,000 

2)1326 2)-2649 2)39946 

*0663 -1324 1-9973 90,702,000 

The approximate estimates of the solar distance are based on 
the following hypothesis : — 

Let e = eflfective ratio of daily rotation to gravity* 

a = arc described by force of rotation in a given time /. 
r =^ radius of relative sphere of attraction^ or distance 
through which a body would fall by gravity during 
the disturbance of its equilibrium by rotation. 
A= area described by radius vector in time /» 



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M On ike Satometet a» on Indkntor of the BartV$ Rotation, 

tm ^3 0^3 ff, A! )^pi!e86ht eohieipoiidDig eUmetili of the mmfil 
l^eVolatiotli Then 

A : A' : : or : a' r* : c c* : «'*. 



But the forces of rotation and 
that m iiSets but alightly from of. 



revolution are bo conneeted 






very neariy. 



It tiiay be interesting to obsetVe how nearly r (22,^38,900 

miles) corresponds with Kirkwood^s value of ^ (24,932,000 

iniles). A more thorough comprehension of all the Various effects 
of gravity and rotation on the atmosphere, would probably lead 
to modincations of our formulse that would show a still closer 
correspondence. 

There is a great discrepancy between the determinations of 
the solar distance that are based on the records of 1^44! and 1846; 
but it is no greater than we nlight reasonably have anticipated. 
On the other hand, it could hardly have been expected that any 
comparisons based on the observations of so short a period as 
three years^ would have furnished so near an approximation to 
the most lucent and most accurate determination of the earth^a 
mean radius vector. In order to obtain that approximation, it 
will be seen that I took, 1st, the mean of the ranges and ratios 
fol? thfee Successive years; 2nd, the fatiges ftnaMtios bt the 
metth faults of the tnl*ee years; 8M, the grahd inean dt these 
tW() bribiary meanst t could thihk of no othei^ method which 
would be so likely to destroy the effects of changing seasons, 
and other accidental disturbances. 

The following Table exhibits the. effects of latitude on the 
R^toh^fib tides. The differences between the theoretical and 
observed ranges may be owing partly to the equ^torial-polar 
cilff^atSj imd partly td insufficient dbservationit 



station. 


Latitude. 


Mean 
height. 


Mean 


Ratio. 


theoretical 
hitioi 


Ardtic Oc^an •...»« 
Girard Coll<ige ... 

Wishiti^oll 

BitHel($nai..tj.... 


dd5a 

15 57 



iti. . 
29-73» 
29-938 
800^0 
2^-282 
30709 


In. 
012 

•082 


•000404 
•002004 
K)02065 
'002S44 
•002670 


•000527 
•002046 
'0020?9 
•002567 
•002670 



The theoretical ratios are determined by multiplying the equa- 



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(oriai ratios by -^g-. The formula p== -^ • --3 (p indicating 
the ratio of the mean range to the mean height) gives — 







Theoivtical 


ObMmd 




. d 


ratio. 


ntio; 


Lfttitade .. 


•002190 


•002670 


Latitade .. 


.. 78 37 


•000432 


•000404 



showing that the ratio is less bear the pole lind greater neat the 
equator than our theory indicates, a natural consequence of the 
ceUtrifugal force at the equator and the Cold surface curr^ts 
that produce the trade-winds. 

The revolution of the sun around the great Central Sun must 
also cause barometric fluctuations that may possibly be measured 
by delicate instruments and long and patient observation. The 
Torricellian feolumu may thus become a valuable auxiliary in veri- 
fying or rectifying our estimates of the distances and masses of 
l^e principal heavenly bodies. 

VII* Notices respecting New Booksk 

Btmiuit of the Metalloids. By James ApjodN, M,D,, P.R.S., 
M.R.I,A„ Professor of Chemistry in the University of Dublin, 
LondDn: Longmans, 1864, pp. viii and 59^. 
^PHIS work foi^s one of the series of Scieiitific Manuals issued 
-^ Undeir the auspices 6f t'rofledsurs Galbraith and Haughton of 
Triiilty College, Dublin. With tegard to its intended scope and aim/ 
the cLuthor says, " lii pr^p^ing it my wish has been to produce a 
cotideiised, but Ht the sam^ time tolerably coMprehensive treatise, 
in which no topic of itnpottanc^ shoiild be otnitted, while all would 
be discussed With as much brevity as is tiOilisi^teht With clearness. 
It is intended as a Handbook in Chemistry for Students in Medicine 
and Engineering, :, a" 

In books intended for the Use t)f sttidetits, dbmpleteh^ss in relation 
to matters of detail is unattainable, and is hot eveU to be desired ; 
bat it is veiy important that such books should be ah free as possible 
from errorni and that the knowledge gained by the study bf them — 
thotigh neeessaHly limited iil extent-^should be ibcciurftt^, tiud liiiould 
serve as a firm foundation fdr fUifthef afeqUisitibtist Ih lltich Works, 
even slight mistakes i»ften amount to serious faUlls ; ahd they Art 
the less ^eusbble, since the author^ not being Called Upou to eUtei* 
apou the more abstruse patti of the sdenoei may genehdly ensure 
accuracy, upon the subjects of which it is desirable that he should 
treat, by exercising a moderate degree of eillre. Ifi the present 
volume, errors in regard to the simplest matters of fadt are, unfor- 
tunately, by no means i'ar^, nor are they aU of small importance. 
It would be tedious to the reader wero we Id quote all the passages 
upon which this asseltiOn is founded 1 the following mUst suffice as 
specimens of many more that might be given. 



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60 Notices refpeeting New Boots. 

At page 68 we read« *' The compoand, for example, generally 
known under the name of Dutch liquor, €,, H^ CI,, reacta upon water 
in the following manner : — 

€, H,C1, + H, 0= 2C1H + €,H,0. 
Now, Viewing this latter substance, Q^^ H^ O, as a derivative of water, 
it is clear that O, H^, now called ethylene, has replaced two atoms of 
hydrogen, and is therefore a binatomic body." What a capital pro- 
cess this is for preparing oxide of ethylene — ^upon paper, and what a 
pity that it does not answer equally well in sealed tubes ! 

On page 232 we are told that " the compounds of nitrogen with 
hydrogen are three in number, viz. amidogen, ammonia, and ammo- 
nium, and have their composition represented by the following for- 
mulae : — 

Amidogen NH, 

Ammonia NH, 

Ammonium • NH^.** 

A more misleading statement than this could not easily be put 
before the student ; for not only are the first and last of the three 
substances named completely unknown, but the whole analogy of 
the ascertained combining properties of nitrogen is against even the 
possibility of their existence, the most characteristic of all these 
properties being that, with elements of the hydrogen-class^ nitrogen 
unites in only one proportion, that namely of which ammonia is an 
example. But our author habitually pays little regard to fine-drawn 
distinctions between substances which fire well known as having a 
material existence, and those which are at best the convenient fic- 
tions of past or present theoretical systems. For instance (p. 256), 
he tells us that ** There are seven known oxides of sulphur, all of 
which possess the properties of acids. The name and atomic compo- 
sition of each is given in the subjoined Table :— 

Sulphurous acid ^ SO^ 

Sulphuric acid SO3 

Hyposulphurous acid S^ O^ 

Didiionic acid (Hyposulphuric) S^ O, 

Trithionic acid S3 O5 

Tetrathionic acid S^ Oj 

Pentathionic acid ^s O5. 

The hyposulphurous and pentathionic acids are instances of poly- 
meric bodies, or of such as have the same percentage composition, 
but different atomic weights." At page 478 occurs another example 
of the same kind : we there read, " The oxides of carbon are six in 
number, and of these all but the first are possessed of acid characters. 
They are — 

Carbonic oxide CO 

Carbonic acid CO^ 

Oxalicacid HO, C, O, -|- 2iH0 

Rhodizonic acid 3H0, C^ O^ 

Croconic acid HO, C, O^ 

Mellitic acid HO, C^ O3." 



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Notices respecting New Boohs. 61 

From these instances it will be seen that Dr. Apjohn^s lists of 
'^known compounds" include many substances with which other 
chemists are by no means well acquainted : hence it is natural that 
he should require to make room for them by ignoring substances 
which often receive a considerable share of attention. Thus 
(p. 502) the usual list of hydrocarbons is very much curtailed : we 
are told that " The number of compounds of carbon and hydrogen 
is very great. Those at present known are reducible to three 
groups : — ^Those whose general formula is Cn Hn, those represented 
by Cn Hn+i, and those by Cn Hn+2t n being always an even number." 
Again (pp. 463, 464), " The only known compounds of boron with 
the metalloids are the teroxide, tersulphide, terchloride, and ter« 
fluoride." Surely Dr. Apjohn has heard of nitride of boron. No 
ttmilarly distinct assertion is made of the non-existence of hydride 
of silicon and of the whole series of compounds corresponding with 
an oxide containing half as much oxygen as silica, discovered a few 
years ago by Wohler ; but, from the absence of the slightest allusion 
to any of these interesting substances, we must suppose that their 
existence is not yet recognized by our author. 

If, from the enumeration of the compounds of the various elements, 
we turn to the detailed description of their properties and reactions, 
we find no greater accuracy. We will quote but one passage in 
illustration of this remark. It occurs on pages 561 and 562, and 
refers to the volumetric process for estimating cyanogen, in presence 
of excess of potash, by means of a standard solution of nitrate of 
silver. "The free potash will develop oxide of silver? but this is 
immediately taken up by the cyanide of potassium, with a view [sic"] 
to the formation of Uie double cyanide ; so that, as long as there is 
uneombined cyanide of potassium, there will be no permanent pre* 
cipitate. But when the cyanide of potassium is altogether con* 
verted into the double cyanide of potassium and silver, if any addi- 
tional quantity of the nitrate be added, the oxide of silver separated 
from it by the potash will appear as a permanent precipitate." It is 
difficult to suppose that the writer of this passage has ever performed 
the operation he professes to describe, otherwise he could hardly 
have failed to notice that in reality it is the white cyanide of 
silver, and not the brown-grey oxide which " appears as a perma- 
nent precipitate." 

But the most remarkable portions of Dr. Apjohn's work are those 
in which he has occasion to refer to the past history of the science, 
or to record his opinion of the works of his contemporaries. At 
page 124, for instance, the relation of Lavoisier to the antiphlogistic 
system of chemistry is placed in a new light. *• Stahl conceived that 
combustible bodies, such as carbon, sulphur, phosphorus, and iron, 
included a fiery principle, which he called phlogiston ; and that, 
when they underwent combustion, the fiery principle is evolved. 
This phlogistic theory is at the present day only interesting in con« 
nexion with the history of chemistry. It held, however, its ground 
for a long time, and was only abandoned when it was shown by 
Ray and Mayow that bodies in burning, instead of becoming lighter, 
augment in weight. 



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OS Notwe$ revetting New Books. 

*' I^voiaier put forward on this tubjeet a very plausible ibrary, 
which was founded oa the well-kuown fact that, if a gas be com« 
pressed* beat will be developed/' This passage not only oontam 
a totally ipadequatei aiid therefore erroneous statement of {lay^iaier^f 
" plausibto ^eory/' but implies what is direcUy opntrary to (fij^ 
well known to all who have paid any attention to the bist()ry gf 
chenustry-wtnamely, that the phlogiitic theoiy held its ground long 
after it had been discovered that combustible bodies incr^an^ in 
weight when burned, and that this observation first came to ba 
regarded as a serious objection to the theory when it was shown by 
liavpisier ^o be connected with the disappearance of part of the atmor 
spbere in which combustion takes place. 

Every one knows that the discovery of the composition of water 
is attributed by some authorities to Cavendish, and by others t^ Janwi 
Watt ; according to Dr. Apjohn, similar rival claimii have be^n put 
forward to the discovery of hydrogen itself. He says (p, 13Q)t 
"Hydrogen t , • , . was first distinguished by Cavendish in 1766, 
and to Urn the credit of its discovery is usually giveni tbongh IQ 
modem times it has been claimed for Watt." 

Further on (p. 47 1^ we are told that Lavoisier and De Morv^au 
burned the diamond in oxygen (discovered by Priestley in Augusf 
1774) about the year 1764. On page 212, the " di$culty of prfh 
curing absolute nitric acid, NO,, now cdled nitric anhydride," i| 
stated to have "been recently overcome by Naeterer/' a chemi4i 
whose name we do not remember to have met with before, wbila 
nothing is said about M. H. Sainte-Claire D^ville as haying had any* 
thing to do with the matter. 

After these specimens of Professor Apjohn's historical accuracy, 
the reader will not be surprised at slight peculiarities of spelling in 
the names of foreign chemists, such as Schonbein for Schonbein, 
Schrotter for Schrotter, or Lassaign for Lassaigne ; but unless be 19 
very well acquainted with the Professor's style, he may be a little at 
a loss on reading Bertholon (p. 255, and repeated in the index) in* 
stead of Berthelot, or on being told (p. 407) that Lavoisier, instead of 
Le Verrier, investigated oxide of phosphorus (or at least a sub^tancs 
so called). 

We draw attention to these matters, not because the exact spelling 
of a chemist's name is of much importance to a student who is be« 
ginning the study of chemistry, but because they illustrate the inac- 
curacy and carelessness which pervade the whole book and give it 
throughout a slovenly air* Scrupulous accuracy in thq statement of 
scientific facts and theories need not be expected from an author who 
thus wrongly names his authorities, or allows such examples of 
English composition as the following to go forth under his name ;«^ 

Page 183. " We now come to consider the relative proportions of 
the oxygen and nitrogen of which the atmosphere is chiefly composed, 
This is always done by condensing the oxygen of a known voluma 
of atmospherical air, and measuring the nitrogen which is left." 

Page 248, ** Sqhlossing has ascertained that distillation by heat 
is not necessary ; and that a solution of ammoniacal salt, to which 
a little hydrate of potash has been added, if placed for twenty«fQn( 



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boiira imder a n^law bell with a cup of dilute sulphuric aoid> paa^e^ 
completely from the alkaline to the acid liquid." 

Pftge 417, "T*»joi>jp» i^Tf PsQgpppRus, PI,5=i285.-^Thif is oU 
taiQed wben iuto a thin test-tube, or email flask, contaiuiug pb<Mk 
phorue, aixd from which the m bes been displaced by dry parbouic 
i^cid, twdve times its weight of iodine is introduced," 

Page 397, '* Such a result indeed is always obtaiued when the 
laitric acid is pouccBtrated, aud that the bottle or flask (it should be 
a strong one) is immediately elosed by the pressure qr the tiiumb 
after the aeid has been iutroduced." 

lu oopqIusIpu, we pan couscientiously say, after a careful eiawina*- 
tion of tbp book before us, that we have been unable to discover any 
Qpe respect iw whiph it is superior to the average of elementary works 
on chemiatryi while, as we have pointed out, it frequency falls below 
the average, If such a work was to be published at all. it is tp be 
regretted that it was issued as one of a series of educational works 
whieh have already apquired a certain reputation for general e^^eel- 
lence, and are "rpcommpuded by the Committpe o| Council oft 
Education-," 



VIII. Pr&eeedmg% of Learned Societiee. 

iaOTAL SOCIETY, 

[Continued from vol x»vii, p. W80 
Febraaiy 85« 1864.'-«-MaJor-6eaeral Sabine, President, IntheOhaiv, 

I^HE following communication was read :-^ 
"On the supposed Identity of Biliverdin with CbloropbyU, 
^tb remarks on the Constitution of Chlprophyll." By G. G. Stokes, 
M.A., Sec.R,S. , , 

I have latelv been enabled to examine a specin^eU;! prepared by 
Professor Harley, of the green substance obtained from the bile, 
which has been named biliverdin, and which was supposed by Ber- 
zelius to be identical with chlorophyll. The latter substance yields 
with alcohol, ether, chloroform, &c., solutions which are characterized 
by a peculiar and highly disUnctive system of bands of absorption, and 
by a strong fluorescence of a blood-red colour. In solutions of bili^ 
verdin these characters are wholly wanting. There is, indeed, a 
vagu^ minimum of transparency in the red ; but it is totally unlike 
the intensely sharp absorption- band of ehlorophyU, nor are the other 
bands of chlorophyll seen in biliverdin. In feet, no one who is in 
the habit of using a prism could suppose for a moment that the two 
were identical ; for an observation which can be made in a few seconds, 
which re<)uires no apparatus beyond a small prism, to be used with the 
naked eye, and which as a matter of course would be made by any 
chf^mist working at the subject, had the use of the prism made its 
way faito the chemical world, is sufficient to show that chlorophyll 
a»d biHverdin are quite distinct. 

I may take this opportunity of mentioning th^t I have been for a 



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64 Royal Society : — 

good while engaged at interrals with an optico-cbemical ezammati(m 
of chlorophyll. I find the chlorophyll of land-plants to be a mix- 
ture of four substances, two green and two yellow, all posserame 
highly distinctire optiosl properties. The green substances yield 
solutions exhibiting a strong red fluorescence; the yellow substances 
do not. The four substances are soluble in the same solvents, and 
three of them are extremely easily decomposed by acids or even acid 
salts, such as binoxalate of potash ; but by proper treatment each 
may be obtained in a state of very approximate isolation, so far at 
least as coloured substances are concerned. The phylloeyanine of 
Fremy* is mainly the product of decomposition by acids of one of 
the green bodies, and is naturally a substance of a nearly neutral 
tint, showing howerer extremely sharp bands of absorption in its 
neutral solutions; but dissolres in certiun acids and acid solutions 
with a green or blue colour. Fren^s phyUoxanthine differs accord- 
ing to the mode of preparation, when prepared by removing the 
green bodies by hydrate of alumina and a little water, it is mainly 
one of the yeUow bodies ; but when prepared by hydrochloric acid 
and ether, it is mainly a mixture of the same yellow body (partly, 
it may be, decomposed) with the product of decomposition by acids of 
the second green body. As the mode of preparation ofphyUoxan- 
theine is rather hinted at than describea, I can only conjecture 
what the substance is ; but I suppose it to be a mixture of the second 
yellow substance with the products of decomposition of the other 
three bodies. Green seaweeds (Chloroepermea) agree with land- 
plants, except as to the relative proportion of the substances pre* 
sent ; but in olive-coloured sea-weeds (Melanospermeai) the second 
green substance is replaced by a third green substance, and the first 
yellow substance by a third yellow substance, to the presence of 
which the dull colour of those plants is due. The red colouring- 
matter of the red sea-weeds (Rhodo9perme€e)t which the plants con- 
tain in addition to chlorophyll, is altogether different in its nature 
from chlorophyll, as is already known, and would appear to be an albu- 
minous substance. I hope, before long, to present to the Royal 
Society the details of these researches. 

March 3. — Major-General Sabine, President, in the Chair. 

The following communication was read : — 

" On the Spectra of Ignited Gases and Vapours, with especial 
regard to the different Spectra of the same elementary gaseous sub- 
stance." By Dr. Julius Plucker, of Bonn, For. Memb. R.S., and 
Dr. S. W. Hittorf, of Munster. 

In order to obtain the spectra of the elementary bodies, we may 
employ either flame or the electric current. The former is the more 
easily managed, but its temperature is for the most part too low to 
volatilize the body to be examined, or, if it be volatilized or already in 
the state of gas, to exhibit its characteristic lines. In most cases it 
is only the electric current that is fitted to produce these lines ; and 

^ Comptes BenduB, torn. 1. p. 405. 

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Drs. Pliicker and Hittoff on the Spectra of Ignited Gases. 68 

the enrrent ftindshed by a powerful induction coil was what the 
juithors ^enerallj employed. 

In the application of the current, different cases may arise. The 
body to be examined may be either in the state of gas, or capable 
of being volatilised at a moderate temperature, such as gkss wiU b^ir 
without softening, or its volatilization may require a temperature still 
higher. 

In the first two eases the body is enclosed in a blown-glass vessel 
consisting of two bulbs, with platinum wires for electrodes, connected 
by a capillary tube. In the case of a gas, the vessel is exhausted by 
means of Geissler's exhauster, and filled with the gas at a suitable 
tension. In the case of a solid easily volatilized, a portion is intro- 
duced into the vessel, which is then exhausted as highly as possible, 
and the substance is heated by a lamp at the time of the observa- 
tion. In the third case the electric current is employed at the same 
time for volatilizing the body and rendering its vapour luminous. 
If the body be a conductor, the electrodes are formed of it ; but the 
spectrum observed exhibits not only the lines due to the body to be 
examined, but also those which depend on the interposed gas. This 
inconvenience is partly remedied by using hydrogen for the interposed 
gas, as its spectrum under these circumstances approaches to a con- 
tinuous one. If the body to be examined be a non-conductor, the 
metallic electrodes are covered with it. In this case the spectrum 
observed contains the lines due to the metal of which the electrodes are 
ffffmedi and to the interposed gas, as well as those due to the sub- 
stance to be examined. 

Among the substances examined, the authors commence with 
nitrogen, which first revealed to them the existence of two spectra 
belonging to the same substance. The phenomena" presented by 
nitrogen are described in detail, which permits a shorter description 
to siidfice for the other bodies examined. 

On sending through a capillary tube containing nitrogen, at a pres- 
sure of from 40 to 80 millimetres, the direct discharge of a powerful 
Bnhmkorff's coil, a spectrum is obtained consisting, both in its more 
uid in its less refrangible part, of a series of bright shaded bands : 
the middle part of tlM spectrum is usually less marked. In each of 
the two parts referred to, the bands are formed on the same type ; 
but the type in the less refrangible part of the spectrum is quite 
different from that in the more refrangible. In the latter case the 
bands have a channeled appearance, an effect which is produced by 
a shading, the intensity oi which decreases from the more to the less 
refracted part of each band. In a sufficiently pure and magnified 
spectrum, a small bright line is observed between the neighbouring 
cmannels, and the shading is resolved into dark lines, which are nearly 
equidistant, while their darkness decreases towards Uie least refracted 
limit of each band. With a similar power the bands in the less 
refran^ble part of the spectrum are also seen to be traversed by fine 
dark lines, the arrangement of which, however, while similar for 
the different bands, is quite different from that observed in the chan- 
neled spaces belonging to tlie more refrangible region. 

PhU. Mag. S. 4. Vol. 28. No. 186. My 1864. F 



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66 Royal Society ;— 

If, instead of sending tbe direct discharge of the indaction coil 
through the capillary tube containing nitrogen, a Leyden jar be 
interposed in the secondary circuit in the usual way, the spectrtun 
obtained is totally different. Instead of shaded bands, we hare now 
a spectrum consisting of brilliant lines havine no apparent relation 
whatsoever to the buids before observed. If the nitrogen employed 
contains a slight admixture of oxygen, the bright lines due to oxygen 
are seen as well as those due to nitrogen, whereas in the former 
spectrum a slight admixture of oxysen produced no apparent effect. 

The different appearance of the banas in the more and in the less 
refracted portion of the spectrum first mentioned 8Ugfl;ested to the 
authors that it was really composed of two spectra, which possibly 
might admit of being separated. This the authors succeeded in effect- 
ing by using a somewhat wider tube. Sent through this tube, the 
direct discharge gave a golden-coloured light, which was resolved by 
the prism into the shaded bands belonging to the less refrangible part 
of the spectrum, whereas with a smaU jar interposed the light was 
blue, ana was resolved by the prism into the channeled spaces belongs 
ing to the more refrangible part. 

By increasing the density of the gas and at the same time tbe 
power of the current, or else, in case the gas be less dense, by inter- 
posing in the secondary circuit at the same time a Leyden jar and 
a stratum of air, the authors obtained lines of dazzling brilliancy 
which were no longer well defined, but had become of appreciable 
breadth, while at the same time other lines, previously too faint to 
be seen, made their appearance. The number of these lines, how-, 
ever, is not unlimited. By the expansion of some of the lines, espe- 
dally the brighter ones, the spectrum tended to become continuous. 

l^ose spectra which are composed of rather broad bands, which 
show different appearances according as they are differently shaded 
by fine dark lines, the authors generally call spectra of the fint 
order y while those spectra which show brilliant coloured lines on a 
more or less dark ground they call spectra of the second order. 

Incandescent nitrogen accordingly exhibits two spectra of the first, 
and one of the second order. The temperature produced by the pas- 
sage of an electric current increases with the quantity of electricity 
which passes, and for a given quantity with the suddenness of the 
passage. When the temperature produced by the discharge is com* 
paratively low, incandescent nitrogen emits a golden-coloured light, 
which is resolved by the prism into shaded bands occupying chiefly 
the less refrangible part of the spectrum. At a higher temperature 
the light is blue, and is resolved bv the prism into channeled bands 
filling the more refrangible part of the spectrum. At a still higher 
temperature the spectrum consists mainly of bright lines, which 
at the highest attainable temperature begin to expand, so that the 
spectrum tends to become continuous. 

The authors think it probable that the three different spectra 
of the emitted light depend upon three allotropic states which 
nitrogen assumes at different temperatures. 

By similar methods the authors obtained two different spectra 



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Drs. Plucker and Hittorf on tke Spetdra of Ignited Gases, 67 

a£ sulpliai, one of the first and one of the second order. The spec- 
tcum of the first order exhibited channeled spaces, like one of the 
two spectra of that order of nitrogen ; but the direction in which 
the depth of shading increased was the rererse of what was obsenred 
with nitrogen, the darker side of each channelecl space being in the 
case of sulphur directed towards the red end of the spectrum. 

Selenium, like sulphur, shows two spectra, one of the first and one 
of the second order. 

Incandescent carbon, even in a state of the finest division, gives a 
continuous spectrum. Among the gases which by their decomposi- 
tion, whether in flame or in the electric current, give the spectrum of 
carbon, the authors describe particularly the spectra of cyanogen and 
olefiant gas when burnt with oxygen or with air, and of carbonic oxide, 
carbonic acid, marsh-gas, olefiant gas, and methyle rendered incan- 
descent by the electric discharge ; they likewise describe the spec- 
trum of the electric discharge between electrodes of carbon in an 
atmosphere of hydrogen, llie spectrum of carbon examined under 
these yariotts conditions showed great varieties, but all the different 
types observed were represented, more or less completely, in the 
spectrum of cyanogen fed with oxygen. The authors think it pos- 
sible that certain bands, not due to nitrogen, seen in the flame 6f 
cyanogen, and not in any other compoutid of carbon, may have been 
due to the undecomposed gas. 

The spectrum of hydrogen, as obtained by a small RuhmkoHTs 
coil, exhibited chiefly three bright lines. With the large coil em- 
ployed by the authors, the lines slightly and unequally expanded. 
On interposing the Leyden jar, and using gas of a somewhat higher 
pressure, the spectrum was transformed into a continuous one, with 
a red line at one extremity, while at a still higher pressure this red 
line expanded into a band. 

The authors also observed a new hydrogen spectrum, correspond- 
ing to a lower temperature, hut having no resemblance at all to the 
w^tctrti of the first order of nitrogen, sulphur, &c. 

Oxygen gave only a spectrum of the second order, the different 
Knes of which, however, expanded under certain circumstances .into 
narrow bands, but very differently in different parts of the spectrum. 

Phosphorus, when treated like sulphur, gave only a spectrum of 
the second order. 

Chlorine bromine, and iodine, when examined by the electric dis- 
charge, gave only spectra of the second order, in which no two of the 
numerous spectral fines belonging to the three substances were coin- 
cident. The authors were desirous of examining whether iodine 
would give a spectrum of the first order the reverse of the absorption- 
spectrum at ordinary temperatures. The vapour of iodine in an 
ozvhydrogen jet gave, indeed, a spectrum of the first order, but it 
did not agree with what theory might have led us to expect. 

In the electric discharge, arsenic and mercury gave only spectra 
of the second order. The metals of the alkalies sodium, potassium, 
lithium, thallium show, evra at the lower temperature of Bunsen's 
lamp, spectra of the second order. 

F2 



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68 Royal Society : — 

Barium^ gtrontiiiiii^ caldnm in the flame of Bunaen't lamp ahow 
banda like spectra of the first order« and in each case a weUniefined 
line»like spectra of the second order. On introducing chloride of 
barium intoanozjhydro^jet, die shading of the bands was resolved 
into fine dark lines, proTuig that the band spectrum of barium is in 
every respect a spectrum of the first order. 

Spectra of the first order were observed in the case of only a few 
of the heavy metals, among which may be particularly mentioned lea4 
which, when its chloride, bromide, iodid^ or oxide was introduced 
into an oxyhydrogen jet» gave a spectrum with bands which had a 
channeled appearance in consequence of a shading by fine dark 
lines. 

Chloride, bromide, and iodide of copper gave in a Bunsen^s lamp, 
or the oanrhydrogen jet, spectra with buids, and berides a few bright 
lines. Tiie bands in the three cases were not quite the same, but 
differed from one another by additional bands. Manganese showed 
a curious spectrum of the first order. When an induction discharge 
passed between electrodes of copper or of manganese, pure spectra of 
these metals, of the second order, were obtained. 

March 17. — Major-Gene^ Sabine, President, in the Chair. 

The following communication was read :-* 

'' Remarks on Sun Spots.'' By Balfour Stewart, M.A., F.B.S., 
Superintendent of the Rew Observatory. 

^n the volume on Sun Snots which Carrington has recently pubj 
lished, we are furnished with a curve denoting the relative frequency 
of these phenomena firom 1760 to the present time. This curve 
exhibits a maximum corresponding to 1788*6. A^un, in Dalton's 
' Meteorolo^ ' we have a list of aurorse observed at Kendal and Kes» 
wick from May 1786 to May 1793. 

The observations at Kendal were made b^ Dalton himself, and 
those at Keswick by Crosthwaite. This list gives— 

For the year 1787 .... 27auror8B, I For the year 1790. . . . 36auror«i 
1788. ...53 „ 1791. ...37 „ 

1789.. ..45 „ I 1792.. ..23 „ 

showing a maximum about the middle, or near the end of 1788. 
This corresponds veiy nearly with 1788*6, which we have seen is 
one of Carrington's dates of maximum sun spots. 

The following observation is unconnected with the aurora borealis. 
In examining the sun pictures taken with the Kew Heliograph undtf 
the superintendence of Mr.De la Rue, it appears to be a nearly um- 
versal law that the faculae belonging to a spot appear to the left of 
that spot, the motion due to the sun's rotation being across the pie* 
ture from left to right. 

These pictures comprise a few taken in 1858, more in 1859, a few in 
1861, and many more in 1862 and 1863, and they have been care* 
fVilly examined by Mr. Beckley, of Kew Observatory, and myself 
The following Table expresses the result obtained s«- 



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Mr. Gassiot on a TVain of Eleven Sutphide-of^carhon Prisms. 69 

No. of cases of No. of cases of No. of oases of No, of cases of fa- 
Year, fncola to left facula to right facuU equally on cqIsb mostly be- ■ 
of spot. of spot. both sides of spot, tween two spots. 

1858 2 

1859.... 18 3 

1861 9 1 3 

1862.... 64 4 7 3 

1863.... 47 9 2 

1864.... 18 1 2 1 

April 7. — ^Major-General Sabine^ President^ in the Cb^ir. 

Tbe following communication was read : — 

•'Description of a train of Eleven Sulphide-of-Carbon Prisma 
arranged for Spectrum Analysis." By J. P. Gassiot, F.R.S. 

Tbe principles which should regulate the construction of a bat- 
tery of prisms have been alluded to in the description of the large 
spectroscope now at Kew Observatory, which has a train of nine 
dense glass prisms with refracting angles of 45^*. 

While for purposes of exactitude, such as mapping out the solar 
spectrum, flint glass stands unrivalled ; yet when the greatest amount 
<n dispersion is the desideratum, prisms filled wi& bisulphide of 
carbon present obvious advantages, on account of the enormous dis- 
pendve power of that liquid — the difference of its indices of refrac* 
tion for extreme rays being, according to Sir David. Brewsteri as 
0-077 against 0-026 for flint glass. * 

In the fluid prisms of the ordinary construction, the sides are ce« 
mented on with a mixture of glue and honey. This cement, on har- 
dening, warps the sides, and con^sion of the spectral lines is the 
consequent result. To obviate this source of error, it has been pro* 
posed to attach an additional pair of parallel sides to such prisms, a 
thin film of castor-oil being interposea between the surfaces. The 
outer plates are then secured by means of sealing-wax, or some 
cement, at the comers. In the battery of prisms now about to be 
described, Mr. Browning has dispensed with this attachment at the 
corners, which is likely to prove prejudicial, and has secured 4he 
second sides in their proper position by extremely light metal frames 
which clasp the plates only on their edges. 

Thus arranged, the frames exert no pressure on the surfaces of 
the plates, and are quite out of the field of view, and they can be 
handled without any fear of derangement. 

On account of the lower refractive power of bisulphide of carbon^ 
as compared with flint glass, a refractive angle of 50^ waa given to the 
fluid prisms. Eight such prisms would cause a ray of light to travel 
more than a circle, and would be the greatest number that could be 
employed had the ordinary arrangement been adopted. 

In place, however, of giving to the fluid prisms two pairs of 

pandlel sides, Mr. Browning, taking advantage of the difference 

between the refractive and dispersive properties of crown glass and 

bisulphide of carbon, has substituted a pnsm of crown gla^ having 

* Phil. Mag., voL zxtiL p. 143. 



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70 



Royal Society : — 



a refraciiDg angle of 6^ for one of the outer plates of each prism— 
the base of this crown-^lass prism being brought to correspond with 
the apex of the fluid pnsm, thus :— 

Crown>gUss prism. 




By this means the angle of minimum deTiation of the prisms is so 
much decreased, that eleven of them thus constructed can be used 
in a circle instead of eight. An increase of dispersive power, due to 
refracting aneles of 150^ of the bisulphide of carbon, is thus gained, 
minus only the small amount of dispersion counteracted owing to 
the dispersive power of the crown-glass prisms being employed in 
the contrary direction. 

From the well-known low dispersive power of this medium, however, 
this loss is inconsiderable, amounting to scarcely more than a fifteenth 
of the power gained. Owing to the minimum angle of deviation being 
lowered, the further advantage is also secured of a larger field of view 
being presented to the telescope by the first and last prism of the train. 

Each prism, in addition to the 
light metal frame referred to, has 
a separate stand, furnished with 
screws for adjusting the prisms, 
and securing them at the angle 
of minimum deviation for any 
particular ray. The prism stands 
within a stirrup furnished vrith a 
welled head. By this arrangement 
the prisms can be removed and 
replaced without touching their 
sides — a matter of some import- 
ance, as all fluid prisms show dif- 
ferent results with every change 
of temperature. 

For the sake of simplicity, the 

* Direction of ray as it would pass throagh two pair of parallel sides, 
t Direction of ray as altered by interposing the crown-glass prisnt. 




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Mr. Gassiot on a Tram of Eleven SulpHde-of-carhon Primi. 71 

metal framing of the prisms, and the Tarions adjustmg-screws, have 
been omitted in the last sketch. 

The very unfavourable state of the weather prevented any observa- 
tions bebg made on the solar spectrum with these pnsms until 
Saturday the 12th inst. The results then obtamed may probably 
not be considered devoid of interest. They are as follows : 

The prisms were arranged so as to enable that portion of the speo- 
trum to be observed in which the well-defined D line of Fraunhofer 
IS situated. This h'ne, long since resolved as double, presented an 
angular separation of 3' 6", measured from the centre of one to that 
of the other principal line, this measurement being made by Mr. 
Balfour Stewart by means of the micrometer attached to *the tele- 
scope ; the value of the divisions of the micrometer he had previously 
determined relatively to the divided circle of the spectroscope. A 
centre line (clearly defined and figured in Kirchhoflf and Bunsen's 
map) was distinctly visible, and nearly equidistant from the centre 
towards the violet ; five clearly defined lines were perceptible, as also 
two faint lines on each side of the principal lines, between the centre 
line of Kirchhofif towards the red. Several faint liiies were also per- 
ceptible. 



The lines as represented in the diagram were drawn by Mr. 
Whipple, one of the assistants in the Observatory, as they were 
observed by him about 3.45 f.m Some of these may possibly be 
due to the earth's atmosphere, but the five most refrangible lines 
were observed at an earlier period of the day by Mr. Stewart, Mr. 
Browning, and myself. 

The great angular separation of the double D line to 3' 6'' is a 
proof of the power of this arrangement of the sulphide-of-carbon 
prisms, and offers the means of mapping out the entire solar spectrum 
on a scale not hitherto attained. 

Note. — Since the preceding observations were recorded, an inspec- 
tion has been made of the region of the spectrum towards the refran- 
gible side of double D ; and, from the comparisons made with a map 
of lines obtained by means of the battery of glass prisms with that 
given by thpse of the sulphide-of-carbou prisms, many new lines are 
produced in addition to those observable by the former, while the 
oattery of glass prisms itself eives a number of additional lines to 
those that are depicted in Kirchhoff's map. 



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72 Geological Society :^ 

GEOLOGICAL 80CIBTT. 

[Continued from toL xz?iL p. 646.] 
March 28, 1864.— W. J. Hamilton, Bsq., Preeident, in the Chair, 

The following communications were read : — 

1. ** On some new Fossils from the Lingula-flags of Wales." By 
J, W. Salter, Esq., F.G.S., A.L.S. 

Since the author's paper last session, on the discovery of Para- 
doxides in Britain, the researches of Mr. Hicks have hrought to light 
80 many new memhers of the hitherto scanty feiuna of the Primordial 
zone, that Mr. Salter was now enabled to describe two new genera 
of Trilobites and a new genus of Sponges, and to complete the de- 
scription of Paradoxides Davidis. He also remarked that the fia.una 
of the Lingula-flags shows an approximation, in some of its genera, 
to Lower Silurian forms, and some (the Shdh and a Cystidean) are 
of genera common to both formations ; but the Crustacea, which are 
the surest indices of the age of Palaeozoic rocks, are of entirely dis- 
tinct genera ; and their evidence quite outweighs that of the other 
fossils. The Primordial zone is moreover in Britain, separated from 
the Caradoc and liandeilo beds by the whole of the Tremadoc group, 
at least 2000 feet thick. 

2. "On the Millstone-grit of North Staffordshire, and the ad- 
joining parts of Derbyshire, Cheshire, and Lancashire." By £. 
Hull, Esq., B. A., F.G.S., and A. H. Green, Esq.. M.A., F.G.S. 

In this paper the Millstone-grit series was described, from the 
eastern edge of the Lancashire Coal-field southwards to the Coal- 
fields of North Staffordshire. 

After giving a general sketch of the Geology of the district, and 
defining the upper and lower limits of the Millstone-grit, the authors 
explained a series of sections, running from east to west, at intervals, 
across the country. In the most northerly of these the group con- 
sists of five thick gritstone-beds, separated by seams of shale, and 
attains a thickness of more than 2000 feet ; while on the extreme 
south all but two of these beds have thinned away, and the whole 
thickness is there not more than 300 or 400 feet. 

Between the base of the MiUstone-grit and the Carboniferous 
Limestone lies a group of shales' and sandstones, with thin earthy 
limestones towards the bottom, which seem to hold the place of the 
Yoredale Rocks of Yorkshire. The mineral character of these beds 
was described, and their place noted on the sections. 

A short notice was also given of two small inliers of Carboniferous 
Limestoae, namely, at Moxon, east of Leek, and at Astbury, near 
Congleton, 

April 18. — ^W. J. Hamilton, Esq., President, in the Chair. 

The following communications were read : — 
1. "On the Geology and Mines of the Nevada Territory." By 
W. Pbipps make, Esq. 

In describing the physical features of the country, the author 



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Mr. H. Seeley an the Red Rock m the Section at Hunstanton. 78 

observed tliat it is an elevated semi-deaert region, composed of a 
succession of longitudinal mountain-ranges with intermediate valleys 
and plains, the most abundant rocks being Metamorphio and 
Igneous; but Tertiary strata and Carboniferous Limestone also 
occur. 

The author then described the hot springs, which are extended 
along a line of fissure in a granitic rock* and parallel to the moun- 
tains, and which deposit silica in an amorphous and a granular 
state, sulphur being also seen in the cracks and cavities of the sili- 
oeous deposit. He considered these phenomena to illustrate the 
formation of a quartz-vein in a fissure. 

Mr. Blake then gave an account of certain mineral veins in por- 
phyry, which yield sulphurets of silver (including crystals of Ste- 
phanite, but very little ruby silver) and a little gold ; also galena, 
copper pyrites, iron pyrites, and a little native silver, the veinstone 
being a friable quartz. The prevailing direction of the veins was 
stated to be nearly north and south ; and the author remarked that 
they were richer in gold near the surface than at greater depths. 

2. «0n the Red Rock in the Section at Hunstanton." By 
Harry Seeley, Bsq., F.6.S., of the Woodwardian Museum, Gam- 
bridge. 

l%e physical structure of the rock was first considered, and it was 
shown to be divisible into three beds, the uppermost of which is of a 
much lighter colour than the rest, the middle being concretionary in 
structure, and the lower sandy. These three beds, with the over- 
lying white sponge-bed, were considered to belong to one formation, 
and were treated of in this paper as the Hunstanton Rock; but the 
thin band of red chalk some distance above was considered, though 
of similar colour, to be quite distinct, as also was the Carstone 
below. 

Mr. Seeley then showed that near Cambridge the Shanklin Sands 
and the Graijdt have both become very thin, so that there is a great 
probability of the latter being unconformable to the beds above as 
well as to those below. He considered the lower part of the Car- 
stone to be of the age of the Shanklin sands ; and as the Chalk is 
not unconformable to the Hunstanton Rock, he concluded that the 
latter could not be the Gault, but must be the Upper Oreensand.— 
a conclusion which he afterwards showed was supported by the 
evidence of the fossils, and the occurrence of phosphate of lime. 

The seam of soapy clay which separates the Hunstanton Rock 
from the Chalk was supposed to have resulted from the disintegra- 
tion of a portion of the former, the red colour of .which the author 
endeavoured to show was due to Glauconite. 

The upper part of the red rock of Speeton was thought to be 
possibly newer than that of Hunstanton, and perhaps to represent 
the time which elapsed between the formation of the latter and that 
of the band of red chalk. 

In conclusion, Mr. Seeley remarked that as the phosphate of lime 
is confined to Bed No. 2, and as many individuals of Grault species 
occur in Bed No. ^, while others of a Chalk character are met with 



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74 Oeolqgical Soeiety. 

in Bed No. 1« it is very probable that the Hunstanton Rock is a 
more typical example of the Upper Oreensand than is seen at Cam- 
bridge, and may represent also those periods which separate that 
fonnation from other divisions of the Cretaceous system. 

April 27. — ^W. J. Hamilton, Esq., President, in the Chair. 

The following communications were read : — 

1. " On the Greology of Arisaig, Nova Scotia." By the Bey. D. 
Honeyman, F.O.S. 

A careful examination of the country in the neighbourhood of 
Arisaig enabled the author to construct three sections and a map 
showing the geological constitution of the district. Two of these 
sections were nearly parallel to one another, running from N. to S., 
and taken some distance apart, while the third was nearly at right 
angles to the other two; thus a tolerably accurate idea of the 
geology of the country could be obtained. The author described 
each of these sections in detail, giving lists of the fossils found iu the 
different beds, which proved them to be of Upper Silurian age ; and 
he further considered that they justified the adoption for the sub- 
divisions of these Nova-Scotian Silurians of the terms May-hill, 
Lower Ludlow, Aymestry, and Tilestones, the first and third of 
which had been used for them previously by Mr. Salter. Besides 
Silurian rocks, there occurs in the western part of this district a 
conglomerate of Lower Carboniferous age, while trap-rocks occur on 
the north and south. 

2. " On some Remains of Fishes from the * Upper Limestone ' of 
the Permian Series of Durham." By J. W. Kirkby, Esq. 

The object of this paper was to record the discovery of Fish- 
remains in the upper Magnesian Limestone of the Permian forma- 
tion, which is higher in that series than any vertebrate remains had 
been previously known to occur, llie strata exposed in the quarries 
were described in detail, especially the bed from which most of the 
Fishes were obtained, and which is known as the "flexible limestone." 

The author stated that at least nine- tenths of the specimens 
belong to Palaoniscus varians, the remainder belonging to two or 
three species of the same genus, and to a species of Acrolepis. 
Detailed descriptions of the different species of Fishes were given, as 
also were short notices of the species of Plants sometimes found 
associated with them, one of which he believed to be Catamites 
arenaceus, a Triassic species. The occurrence of Palaonisci with 
smooth scales was stated to be antagonistic to Agassiz's conclusion 
that the Permian species of that genus have striated, and the Coal- 
measure species smooth scales. In conclusion Mr. Kirkby re- 
marked that the fauna of the period appeared to have an Estuarine 
facies, and he expressed his opinion that the Fishes were imbedded 
suddenly, as a result of some general catastrophe. 

3. •* On the Fossil Corals of the West Indian Islands. — Part 3. 
Mineral Condition." By P. Martin Duncan, M.B. Lond., Sec. G.S. 

The results of the process of fossilization, as seen in the West 
Indian fossil Corals, being very remarkable, and having much ob- 



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Intelligence and Miscellaneaus Articles. 76 

scured their specific characters, thus rendering their determination 
extremely difficult, Dr. Duncan found it necessary to thoroughly 
examine their different varieties of mineralization, and to compare 
their present condition with the different stages in the decay and 
fossilization of recent Conds as now seen in progpress. Thus the 
author was enahled to show the connexion between the destruction 
of the minuter structures of the Coral by membrane decomposing 
and certain forms of fossilization in which those structures are im- 
perfectly preserved ; and he likewise stated that the filling-up of the 
interspaces by granular carbonate of lime and other substances, as 
well as the induration of certain species, during a " prefossil " and 
"post-mortem'' period, gave rise to certain varieties of fossilization, 
and that the results of those operations were perpetuated in a fossil 
state. 

The forms of mineralization described by Dr. Duncan are— 
(1) Calcareous; (2) Siliceous; (3) Siliceous and Crystalline; (4) 
Siliceous and Destructive; (5) Siliceous Casts; (6) Calcareo- 
siHceous; (7) Calcareo-sUiceous and Destructive ;. (8) Calcareo^ 
siliceous Casts. 

In describing these forms, especial reference was made to those in 
which the structures were more or less destroyed during the re- 
placement (by silica) of the carbonate of lime which filled the inter- 
spaces, and during that of the ordinary hard parts of the Coral. 

In explaining the nature and mode of formation of the large casts 
of calices from Antigua^ the author drew attention to the fact that 
the silicification is more intense on the surface and in the centre of 
the coraUum than in the intermediate region ; and, when examined 
microscopically, it could be seen that the replacement of the carbo- 
nate of lime began by the silica appearing as minute points in the 
centre of the interspaces and of the sclerenchyma, and not on their 
surface. In conclusion, the relation of hydrated silica to destruc- 
tive forms of fossilization was discussed, together with the influence 
of all the forms enumerated above in the preservation of organisms^ 
and as one cause of the incompleteness of the geological record. 



IX. Intelligence and Miscellaneom Articles, 

REMARKS ON THE DISTILLATION OF SUBSTANCES OF DIFFERENT 
VOLATILITIES. BY M. CAREY LEA. 

SOME experiments which have been recently published by M. 
Berthelot recall to me a similar and remarkable case which 
attracted my attention several years ago. 

M. Berthelot distilled 92 parts of alcohol and 8 of water, and 
found that the distiUate at the beginning, middle, and end of the 
operation contained equal quantities of water and of alcohol. 

He distilled also a mixture containing a large quantity of sulphide 
of carbon and a small quantity of alcohol, and found that the least 
volatile body, the alcohol, passed over with the first portions of the 



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76 InteUigenee and Mitcdkmemu Articles. 

dkitUlnte, 8o that toward the end of the operatbn the retort ocm^ 
teined sulphide of carbon almost pure. 

To these &ct8» which tend to cast the greatest doubt on all the 
results obtained by the laborious process of fractional distillation, I 
now add the following. 

When a mixture containing the chlorides of ethylamine, diethyU 
amine, and triethylamine is Stilled with caustic alkali, we should, 
according to received ideas, expect to find the ethylamine, which is 
a gas at ordkuury temperatuies, distil over first. Trietiiylamme. 
wUoh is at ordinary temperatures and pressures a liquid, separates 
as such when a strong solution of its chloride is treated with caustic 
alkali, and, floating on the Btafaoe, as I have before pointed out, we 
would naturally expect to find it principally in the latter stages of 
the distillation. The contrary is, however, the case when the less 
substituted ammonias predominate in quantity. Almost the whole 
of the triethylamine passes over in the first portions of the distillate, 
and subsequent ones, though rich in ethylamine and diethylamine, 
scarcely contain a trace of triethylamine.— SiUiman's AmenctmJmar» 
nal. May 1864, 



NOTE ON THB RESIDUAL CHARGE OF ELECTRICAL CONDENSERS. 
BT M. J. M. GAUGAIN. 

When after having discharged a Leyden jar it is left to itself 
and after some time a new metallic connexion is established between 
its armatures, we all know that a second spark is obtained, less 
strong than the first This fact, generally known as the secondarf 
discharge, has been designated by Mr. Faraday the residmU charge. 
I have adopted this latter name, slightly modifying the sense, to 
designate, not the quantity of electricity which passes in a second 
discharge, but all that remains after the original discharge, a quan- 
tity which may give rise to a multitude of successive secondary 
discharges. 

The existence of the residual charge is generally explained by 
saying that part of the electricity of the armatures penetrates slowly 
into the interior of the dielectric when the condenser is charged, 
and that this portion, slowly absorbed, is restored with equal slow- 
ness. But this explanation can certainly not apply to the experi- 
ments of which I am about to speak ; for these experiments have 
been made in such conditions that the electricity of the armatures 
could not communicate itself to the dielectric, and yet the residual 
charge formed in certain cases more than three-quarters of the total 
charge. 

I worked, as in my former researches, on small fulminating 
panes, with moveable armatures : in certain cases the armatures were 
applied directly to the dielectric ; in other cases they were separated 
by small layers of air of uniform thickness, llie general results 
were the same in either case. 

In a first series of researches I proposed to ascertain according to 
what law the residual charge varies when the duration of the charge 



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IfiieUigenee and Mitcettaneous Articles. 77 

varies — ^that is^ the time during which the condenser is in connexion 
with the electrical source. I suppose the tension of this source to 
be invariable, as is the duration of the discharge. This was always 
a fraction of a second, the same in all the experiments* The ob- 
servations were made in the following manner. 

The lower armature of the fulminating pane on which I worked 
being in connexion with the ground, I connect for a definite time 
the upper armature with a source of constant tension ; the con- 
denser once charged, I detach the upper armature, and measure its 
total charge by the method which I have called gauging. 

Secondly, after this first operation, and when the dielectric has 
reverted to the neutral state, I charge the condenser again for the 
same time as at fiirst, then I discharge it immediately by connecting 
for an instant thjs armatures ; that done, I remove the higher arma- 
ture, and gauge the quantity of electricity which it retains ; this 
qnanrity represents the residual charge according to the definition 
given above. 

When this double series of operations is performed on the same 
condenser, giving successively different values to the duration of the 
^schaige, tibis very simple result is attained — that the difference be- 
tween ti^e total and the residual charge is constant. This difference^ 
which represents the quantity of electricity which has disappeared 
in an instantaneous discharge, is precisely equal to the total instan- 
taneous charge. I denote in this manner the quantity of electricity 
which the influencing armature would receive if the condenser, com- 
pletely discharged, were put in connexion with the source of elec- 
tricity during a small interval of time equal to that taken for the 
diMharge. This law was verified by a great number of experiments, 
and on very different dielectrics. I worked successively on disks of 
shellac, of stearic acid, and of gutta percha, and on a cake made of 
fioor of sulphur moistened by salad oil. I give the results obtained 
by a series of experiments made with the latter substance : — 

Duration of Total Residual Differ- 

the charge. charge. charge. ence. 

Fraction of a second 26 . . 26 

2 minutes 44 18 26 

4 minutes... 49 23 26 

8 minutes 55 28 27 

16 minutes 59 33 26 

The difference between the total and the residual discharge was 
sensibly the same for all durations of the charge, and equal to 26, 
a number which exactly represents the total instantaneous charge.' 

Although observation alone would have enabled me to ascertain 
this relation, it is easy to see d priori that it must exist if the bodies 
called insulating are generally formed, as I have been led to admit, 
of many elements of very different conductibilities. 

In the experiments I have just cited, the condenser was charged 
for a more or less long time, but always discharged immediately 
after being separated from the electric source. In another series of 



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7S IntMigence m$kd MuedkmtouM ArtideB. 

researches the condenser was always charged for the same tim, 
aad discharged daring the same fraction of a second ; but the dis- 
charge was separated from the charge by longer or shorter interralfl. 
This kind of observation appeared to me very soitable for pntUog 
in evidence the true origin of the residual charge. 

I shall cite the results of a series of experiments in whidi the 
duration of the charge was limited, like that of the <jBsciiarge, to a 
fraction of a second ; the dielectric was a disk of shellae 6 miUims. 
in thickness. 

1. The condenser was charged and gauged immediately after: 
the total charge was 45. 

2. The condenser, after being charged, was left to itself for 15 
minutes, and gauged at the end of this time : the total charge was 
again 45. 

3. The condenser was discharged immediately after being charged: 
the residual charge was zero. 

4. Lastly, the condenser was discharged 15 minutes after the 
charge : the residual charge was 27. 

Experiments 1 and 2 prove clearly that in the interval of 15 
minutes the armature gauged loses nothing of its charge, and that 
therefore no appreciable absorption is exerted by the shellac ; and 
yet it follows, from experiments 3 and 4, that in this time of 15 
minutes the residual charge rose from zero to 27. This increase of 
residual charge can only depend on a different arrangement of elec- 
tricity in the interior of the dielectric. When the charge has only 
been maintained for an instant, the parts of the dielectric which 
possess a great conductibility alone participate in the transmission 
of the influence ; and as an instant is sufficient to polarize them, 
an instant is sufficient to restore them to the neutral state. If, on 
the contrary, the apparatus has been charged for a sufficiently long 
time, the elements endowed with a feeble conductibility come into 
play ; and as they cannot be restored to the neutral state in a ver)' 
short time, they retain after the discharge almost all the electricity 
they had before. This electricity retains a portion of the electricity 
of opposite kind which is accumulated on the armature. 

The residual charge is thus seen not to depend on a property of 
absorption specially belonging to insulating bodies; it depends 
simply on electrical movements which take place in tie interior of 
these bodies in virtue of their conductibility. — Comptes Rendus, 
May 2, 1864. 



ON THE BOILING OF WATEE, AND ON TKfB EXPLOSION OF STEAM- 
BOILERS. BY M. L. DUFOITR OF LAUSANNE. 

In the experiments which I have had the honour of commuoi'* 
eating to the Academy, I have shown that the boiling-point of 
water and of other liquids may experience considerable retardation 
when these liquids are heated in the body of another liquid of the 
same density and without touching the sides of the vessels. In this 
mode of heating the liquids, it cannot be said that their boiling is 



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InieBigenee and Mmellaneoui Articles. 79 

produced at a fixed pomt; the change of state becomes plossifole 
when the temperatare can give to the vapour an elastic force equal 
to the external pressure; but this change takes place only very 
rarely at the exact point at which its possibility commences. 

With a view to llie study of ebullition, I have undertaken a great 
number of experiments ; and among others, I have endeavomred to 
study ebullition by arriving at this phenomenon rather by a change 
of pressure, which the liquid undergoes, than by an increase of 
its temperature. The apparatus resembles, with certain modifica- 
tions, that which M. Regnault used in studying the elastic force 
of aqueous vapour. A sheet-iron vessel communicates, by suit- 
able tubes, (1) with an air-pump, (2) with a mercury manometer, 
(3) with a glass retort. In this retort were placed the liquids expe- 
rimented upon, and a thermometer with a small reservoir plunged in 
the interior. By means of stopcocks, suitably arranged, the various 
parts of the apparatus could be connected. An observation of the 
manometer and of an external barometer obviously g^ve, at any 
moment, the external pressure of the apparatus. 

Studied under these circumstances, the boiling of water presents 
some characters worthy of attention. In the case of distilled water, 
it is soon seen that after a first heating to 100^, boiling obtained 
by diminution of pressure is only produced at the temperature 
which the known law requires. Water remains liquid sdthough 
the pressure is far below the tension of aqueous vapour for the 
temperature in question. When boiling commences, it is produced 
with tremulous violence, and usually part of the liquid is carried into 
the tubes with the first burst of vapour. These retardations are 
then more pronounced the more frequently water has been raised to 
a high temperature. They are more considerable when the water 
has been alternately heated to 110° and then cooled in the apparatus 
a certain number of times before being submitted to the test of dimi- 
nution of pressure. The following are some examples in which are 
noted in three successive columns, (1) the temperature of the 
liquid when boiling commences ; (2) the pressure at this time ; 
(3) the temperature at which normal ebullition would take place 
for this pressure : — 

™™* o 

71 175 64 

57 75 46 

66 108 53*5 

90-5 335 78-7 

53 37 33 

Retardations of 7^ IT, 11'''8, 20^ &c. are thus seen; that 
is, far more considerable than those observed for water in glass 
Teasels when ebullition is attained by reheating. 

Taking ordinary water, not distilled, and even tolerably calcareous, 
the same facts are observed ; but it is necessary that the water should 
have been two or three times heated to boiling, then cooled in the 
vessel, or submitted to a very prolonged ebullition before being sub- 
mitted to diminutions of pressure. Normal ebullition is less rare 



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80 IntelUgenee and MiseeUaneous Artielei. 

than with distilled water; but nevertheless very freqnent retarda- 
tions of 10^ 15^, and more are seen, as in preceding experiments. 

The presence of platinum, and in general of metallic substances, 
is known to have the reputation of hindering retardations oi ebul- 
lition in glass vessels; and for a long time platinum wires have 
been used in concentrating liquids to prevent them from jumping 
over. Platinum wires plac^ in distilled water hinder, in fact, these 
retardations from being produced when, after having been heated 
once or twice to 100°, water is subjected to a diminution of 
pressure. But if the liquid containing platinum wire is heated to 
boiling for several times, and then allowed to cool — ^if especially 
platinum is for some days in contact with water at the bottom of 
the vessel, it is soon seen that the metal has become inactive, and 
then delays are observed as considerable as if water alone were in the 
retort. If ordinary water is taken abundantly carbonated, if along 
with it various solid bodies are introduced, facts are observed ana* 
logons to that which has been mentioned in the case of platinum. 
I have tried pieces of iron, lead, tin, zinc, copper, &c. ; fragments 
of chalk, of wood, of quartz, paper, &c. In the first reheating, the 
presence of these bodies prevents any retardation, and ebullition 
takes place at the exact point at which the temperature of the liquid 
imparts to the vapour an elastic force equal to the superficial prei* 
sure. But if they are left for some time in contact with water, 
heated four or five times to ebullition, the contact of all these bodies 
appears to have become indifferent, and the liquid furnishes then 
very frequent examples of the retardation of ebullition. The fol« 
lowing are some examples in which the retort contained ordinary 
water, with fragments of iron, platinum, lead, chalk, and wood : — 

mm. o 

74 217 68-5 

85 171 63-2 

67 71 45 

72 87 49. 

These correspond to retardations of 5°-5, 21°-8, 22° 23°. Ebul- 
lition then commenced, sometimes spontaneously, sometimes by 
a blow given to the vessel; it was always very tumultuous and 
violent, almost explosive. 

These facts and others relative to other liquids, show that the 
ordinary law regarding the boiling-point of a liquid in reference to 
its pressure can only apply when ebullition is arrived at by a change 
in pressure rather than by a variation of temperature. These facta 
show, moreover, that water is susceptible of presenting great re- 
tardation in its ebullition, even when in contact with any metals 
and solid substances. Glass and porcelain vessels form by no means 
an exception. Lastly, it is seen that the contact of solids is some- 
times active and sometimes indifierent ; and by analyzing the expe- 
riments of which I have given extracts, it is soon seen that the very 
probable cause of this change of influence is the presence or absence 
round these solids of a more or less condensed gaseous atmosphere. 
— Compter Rendus, May 30, 1864. 



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THE 
LONDON, EDINBURGH, and DUBLIN 

PHILOSOPHICAL MAGAZINE 

AND 

JOURNAL OF SCIENCE. 



[FOURTH SERIES.] 



AUGUST 1864. 



X. On the Absorption and Radiation of Heat by Gaseous and 
Liquid Matter. — Fourth Memoir. By John Tyndall, 
F.R.8., 6fc.* 

THE Royal Society has already done me the honour of pub- 
lishing in the Philosophical Transactions three memoirs 
on the relations of radiant heat to the gaseous form of matter. 
In the first of these memoirsf it was shown that for heat ema- 
nating from the blackened surface of a cube filled with boiling 
water^ a^class of bodies which had been previously regarded as 
equally, and indeed^ as far as laboratory experiments went, per- 
fectly diathermic, exhibited vast differences both as regards radia- 
tion and absorption. At the common tension of one atmosphere 
the absorptive energy of olefiant gas, for example, was found to 
be 290 times that of air, while when lower pressures were em- 
ployed the ratio was still greater. The reciprocity of absorption 
and radiation on the part of gases was also experimentally esta- 
blished in this first investigation. 

In the second inquiry! I employed a different and more 
powerful source of heat, my desire being to bring out with still 
greater decision the differences which revealed themselves in the 
first investigation. By carefully purifying the transparent ele- 
mentary gases, and thus reducing the action upon radiant heat, 
the difference between them and the more strongly acting com- 
pound gases was greatly augmented. In this second inquiry, 
for example, olefiant gas at a pressure of one atmosphere was 

* From the Philosophical Transactions^ Part II. 1864^ having been read 
at the Royal Society June 18, 1863. 

t Phil. Trans. February 1861 ; and Phil. Mag. September 1861. 

t Phil. Trans. January 1862; and Phil Mag. October 1862. 
Pha. Mag. S. 4. Vol. 28. No. 187. Aug. 1864. G 



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8^ Prof. Tyndall an the Absorption and Radiation 

shown to possess 970 times the absorptive energy of atmospheric 
air^ while it was shown to be probable that^ when pressures of 
y\jth of an atmosphere were compared^ the absorption of olefiant 
gMi was nearly 8000 times that of air. A column of ammoniacal 
gas^ moreover^ 3 feef long^ was found sensibly impervious to the 
heat employed in the inquiry, while the vapours of many of the 
volatile liquids were proved to be still more opake to radiant heat 
than evQ^ tho most powerfully acting. permanent gases. In this 
second investigation, the discovery of dynamic radiation and 
absorption is also announced and Ulustrated, and the action of 
odours and of ozone on radiant heat is made the subject of expe- 
riment. 

The third paper* of the series to which I have referred was 
devoted to the examination of one particular vapour, which, on 
account of its universal diffusion, possesses an interest of its own 
— I mean of course the vapour of water. In this paper I con- 
sidered all the objections which had been urged against my 
i*esults up to the time when the paper was written; I replied to 
each of them by definite experiments, removing them one by 
one, and finally placing, as I believe, beyond the pale of reason- 
able doubt the action of the aqueous vapour of our atmosphere. 
In this third paper, moreover, the facts established by experi- 
ment are applied to the explanation of various atmospheric phe- 
nomena. 

I have now the honour to lay before the Boyal Society a fourth 
memoir, containing an account of further researches. Hitherto 
I have confined myself to experiments on radiation through gases 
and vapours which were introduced in succession into the same 
experimental tube, the heat being thus permitted to pass through 
the same thickness of different gases. A portion of the present 
inquiry is devoted to the examination of the transmission of 
radiant heat through different thicknesses of the same gaseous 
body. The brass tube with which my former experiments were 
conducted is composed of several pieces, whicn are screwed 
together when the tube is to be used as a whole ; but the pieces 
may be dismounted and used separately, a series of lengths 
being thus attainable, varying from 2*8 inches to 4&*4 inches. 
I wished, however, to operate upon gaseous strata much thinner 
than the thinnest of these ; and for this purpose a special appa- 
ratus was devised, and with much time and trouble rendered 
at length practically effective. 

The apparatus is sketched in fig. 1. G is the source of heat, 

which consists of a plate of copper against the back of which a 

steady sheet of flame is caused to play. The plate of copper 

forms one end of the chamber F (the "front chamber '^ of my 

• PhU. Trans. December 1862; and Phil. Mag. July 1863. 



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of Heat by Gaseous and Liquid Matter, 



83 



former memoirs). This chamber^ as in my previoas investiga- 
tions^ passes through the vessd Y^ through which cold water 




continually circulates, entering at the bottom and escaping at 
the top. The heat is thus prevented from passing by conduction 
from the source C to the first plate of rock-salt S. This plate 
forms the end of the hollow cylinder AB, dividing it from the 

G2 



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Si Prof. Tjrndall on the Absorption andRadtation 

front chamber F^ with which the cylinder AB is connected by 
suitable screws and washers. Within the cylinder A B moyes a 
second one^ 1 1^ as an ur-tight piston^ and the bottom of the 
second cylinder is stopped by the plate of rock-salt S'. This 
plate projects a little beyond the end of the cylinder, and thus 
can be brought into flat contact with the plate S. Fixed firmly 
to A B is a graduated strip of brass, while fixed to the piston is 
a second strip^ the two strips forming a yemier, vv. By means 
of the pinion B, which works in a rack^ the two plates of salt may 
be separated, their exact distance apart being given by the ver- 
nier. P is the thermo -electric pile with its two conical reflectors ; 
C is the compensating cube, employed to neutralize the radiation 
from the source G. H is an adjusting screen, by the motion of 
which the neutralization may be rendered perfect, and the needle 
brought to zero under the influence of the two opposing radia-> 
tions. The graduation of the vernier was so arranged as to 
permit of the employment of plates of gas varying from 0*01 to 
2*8 inches in thickness. They were afterwards continued with 
the pieces of the experimental tube, already referred to, and in 
this way layers of gas were examined which varied in thickness 
in the ratio of 1 : 4900. 

In my former experiments the chamber F was always kept 
exhausted, so that the rays of heat passed immediately from the 
source through a vacuum ; but in the present instance I feared 
the strain upon the plate S, and I also feared the possible intru- 
sion of a small quantity of the gas under examination into the 
front chamber F, if the latter were kept exhausted. Having 
established the fact that a length of 8 inches of dry air exerts no 
sensible action on the rays of heat, I had no scruple in filling 
the chamber F with dry air. Its absorption was nil, and it merely 
had the effect of lowering in an infinitesimal degree the tempe- 
rature of the source. The two stopcocks c and c' stand exactly 
opposite the junction of the two plates of salt S, SI when they 
are in contact, and when they are drawn apart these cocks are in 
communication with the space between the plates. 

After many trials, the following mode of experiment was 
adopted: — The gas-holder containing the gas to.be examined 
was connected by an india-rubber tube with the cock cf, the other 
cock c being at the same time left open. The piston was then 
moved by the screw B until the requisite distance between the 
plates was obtained. This space being filled with dry air, the 
radiations on the two faces of the pile were equalized, and the 
needle brought to zero. The gas-holder was now opened, and 
by gentle pressure the gas from the holder was forced first 
through a drying apparatus, and then into the space between 
the plates of salt. The air was quickly displaced, and a plate of 



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of Heat by Oaaeous and Liquid Matter. 



86 



the gas substituted for it. If the layer of gas possessed any 
sensible absorbing power, the equilibrium of the two sources of 
beat would be destroyed; the source C would triumph, and 
from the deflection due to its preponderance the exact amount 
of heat intercepted by the gas could be calculated. 

When oxygen, hydrogen, or nitrogen was substituted for 
atmospheric air, no change in the position of the galvanometeiv 
needle occurred ; but when any one of the compound gases was 
allowed to occupy the space between the plates, a measurable 
deflection ensued. The plates of rock-salt were not so smooth, 
nor was their parallelism so perfect as entirely to exclude the 
gas when they were in contact. The contact was but partial, 
and hence a stratum of gas sufficient to effect a sensible absorp- 
tion could find its way betlreen the plates even when they touched 
each other. On this account the first thickness in the following 
Tables was really a little more than 0*01 of an inch. The first 
colamn in each contains the thickness of the gaseous layer, while 
the second column contains the absorption expressed in hun- 
dredths of the total radiation. The first layer of carbonic oxide, 
for example, absorbed 0'3, and the second kyer 0*5 per cent, of 
the entire heat. 



Table I. — Carbonic Oxide. 



ThickDeMof 

0-01 of an inch 

002 

008 

004 

006 

01 

0-8 



Absorption in 

hundredths of 

the total 

radiation. 

02 

0-5 

0-7 

0-9 

1-4 

1-6 

80 



Absorption in 
Thickness of hundredths 
gas. of the total 

radiation. 
0*4 of an inch 8'5 



0-5 
0-6 
]0 
1-5 
20 



8-8 
40 
51 
6-1 
6-8 



Table II. — Carbonic Acid. 



0-01 of an inch 0-86 

002 „ 1-2 

008 „ 1-5 

004 „ 1-9 

005 „ 2-1 
0-06 „ 2-8 
0-1 „ 8-8 
0-2 „ 41 
0-8 „ 4-8 



0*4 of an inch 

0-5 „ 

0-6 „ 

0-7 „ 

0-8 „ 

0-9 „ 

1-0 „ 

1-5 „ 
20 



5-3 
5-7 
5-9 
60 
61 
6-2 
6-3 
7-0 
7-6 



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86 



Prof. Tyndall on the JhunjOwn atdlUdiatum 



Tabu III.— Nitrous Oxide. 



Tbicknenof 

0*01 of an inch 
002 „ 
008 

004 „ 
0-05 

01 
0-2 

0*01 of an inch 
0-02 „ 

005 „ 
01 



hunoredtht 

of the total 

radiation. 

1-48 

2-88 

8-80 

400 

4-20 

600 

7-77 



Thickneaa of 

gas, 

0-4 of an inch 

0-5 „ 

0-6 „ 

0-8 „ 

1-0 „ 

1-5 „ 

20 „ 



Table IY.— Olefiant Oaa. 



1-80 
808 
5-87 
914 



0*5 of an inch 
10 „ 
20 



himdfedths 
of the total 
radiatioii. 
10-2O 
llOO 
11-70 
1217 
12-80 
14-20 
15-7 



28-30 
26-33 
82-80 



We here find that a layer of olefiant gas only 2 inches in thick- 
ness intercepts nearly 33 per cent, of the radiation from our 
source. Supposing our globe to be encircled by a shell of olefiant 
gas only 2 inches in thickness^ this shell would ofier a scarcely 
sensible obstacle to the passage of the solar rays earthward, but 
it would cut off at least 83 per cent, of the terrestrial radiation 
and in great part return it. Under such a canopy, trifiing as it 
may appear^ the surface of the earth would be kept at a stifling 
temperature. The possible influence of an atmospheric envelope 
on the temperature of a planet is here forcibly illustrated. 

The only vapour which I have examined with the piston appa- 
ratus is that of sulphuric ether. Glass fragments were placed 
in a U tube and wetted with the ether. Through this tube dry 
air was gently forced, whence it passed, vapour-laden, into the 
space between the rock-salt plates S S'. The following Table 
contains the results. 



Table V. — Air saturated with the Vapour of Sulphuric Ether. 

Absorption in 
Thickness of huntvedths 
vapour. of the total 

radiation. 
0-8 of an inch 21-0 
15 „ 84-6 

20 „ 35-1 



Thickness of 
vapour. 



0'05 of an inch 

01 

0-2 

0-4 

Comparing these results with 
we find for thicknesses of 0*05 
ively the following absorptions : 



Ahsorption in 
hun^edths 
of the total 
radiation. 
207 
4-6 
8-7 
14-3 



those obtained with olefiant gas^ 
of an inch and 2. inches respect- 



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of Beat by Ocgeoni and Liquid Matter. 67 

Oleflant gas* Snlphuric ether. 

Thickness of 005 . . 5*37 Thickness of 0*05 . . 2*07 
Thickness of 2 inches . 82*80 Thickness of 2 inches. 85*1 

Sulphuric ether vapour^ therefore^ commences with an absorp- 
tion much lower than that of olefiant gas^ and ends with a higher 
absorption. This is quite in accordance with the result esta- 
blished in my second memoir*, that in a short tube the absorp- 
tion effected by the sparsely scattered molecules of a vapour may 
be less than that of a gas at a tension of an atmosphere, while in 
a long tube the gas may be exceeded by the vapour. The deport- 
ment of sulphuric ether indicates what mighty changes of climate 
might be brought about by the introduction into the earth^s at- 
mosphere of an almost infinitesimal amount of a powerful vapour. 
And if aqueous vapour can be shown to be thus powerful, the effect 
of its withdrawal from our atmosphere may be inferred. 

§ 2. The experiments with the piston apparatus being com- 
pleted, greater thicknesses of gas were obtained by means of the 
composite brass experimental tube already referred to. The 
arrangement adopted, however, was peculiar, being expressly 
intended to check the experiments, which. were for the most part 
made by my assistants. The source of heat and the front cham- 
ber remained as usual, a plate of rock-salt dividing, as in my 
previous investigations, the front chamber from the experimental 
tube. The distant end of the tube was also stopped by a plate 
of salt ; but instead of permitting the tube to remain continuous 
from beginning to end, it was divided, by a third plate of rock- 
salt, into two air-tight compartments. Thus the rays of heat 
from the source had to pass through three distinct chambers, 
and through three plates of salt. The first chamber was always 
kept filled with perfectly dry. air, while either or both of the 
other chambers could be filled at pleasure with the gas or vapour 
to be examined. For the sake of convenience I will call the 
compartment of the tube nearest to the front chamber the first 
chamber, the compartment nearest to the pile the ^econrf chamber, 
the term ' front chamber * being, as before, restricted to that near- 
est to the source. The arrangement is sketched in outline in fig. 2. 

The entire length of the tube was 49*4 inches, and this was 
maintained throughout the whole of the experiments. The only 
change consisted in the shifting of the plate of salt S' which 
formed the partition between the first and second chambers. 
Commencing with a first chamber of 2*8 inches long, and a 
second chamber 46*4 inches long, the former was gradually aug- 
mented, and the latter equally diminished. The experiments 
were executed in the following manner : — The first and second 
(Shambers were thoroughly cleansed and exhausted, and the needle 
* Phil. Trans, part 1, 1862 ; and Phil. Mag. vol. xxiv« p. 343« 



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88 Prof. Tyndall an the Jimnptum andRaiiatum 

brought to sero by the equalkation of the radiations ftlling upon 
the opposite faces of the pile. Into the first chamber the gas or 







»a 







vapour to be examined was introduced, and its absorption detcF- 
mined. The first chamber was then cleansed, and the gas or 



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of Heat by Gaseous and Liquid Matter. 89 

vapour was introduced into the second chamber^ its absorption 
there being also determined. iPinally the absorption exerted by 
the two chambers acting together was determined^ both of them 
being occupied by the gas or vapour. 

The combination here described enabled me to check the expe- 
riments, and also to trace the influence of the first chamber on 
the quality of the radiation. In it the heat was more or less 
siftedj and it entered the second chamber deprived of certain con- 
stituents which it possessed on its entrance into the first. On 
this account the quantity absorbed in the second chamber when 
the first chamber is full of gas, must always be less than it would 
be if the rays had entered without first traversing the gas of the 
first chamber. From this it follows that the sum of the absorp- 
tions of the two chambers, taken separately, must always exceed 
the absorption of the tube taken as a whole. This may be briefly 
and conveniently expressed by saying that the sum of the absorp- 
tions exceeds the absorption of the sum. 

Table VI. — Carbonic Oxide. 



Length. 




Absorption per 


100. 


' irt 


2nd 


' Irt 


2nd 


Both 


dunnber. 


dumber. 


chamber 


dutmber. 


diambenu 


2-8 


46-6 


6-8 


12-9 


12-9 


80 


41-4 


9-6 


12-2 


12-9 


12-2 


87-2 


10-7 


12-2 


12-9 


15-4 


840 


10-9 


12-2 


18-4 


17-8 


81-6 


111 


120 


18-8 


86-8 


181 


12-6 


10-8 


18-4 




Table Vllt — Carbonic Acid. 




2-8 


46-6 


8-6 


13-8 


18-8 


80 


41-4 


9-9 


12-7 


13-0 


12-2 


87-2 


110 


11-4 


130 


15-4 


840 


11-8 


121 


13-9 


28-8 


25-6 


11-7 


11-4 


131 


28'8 


25-6 


11-2 


11-2 


12-6 


23-8 


25-6 


10-4 


10-5 


120 


86-3 


181 


11-6 


10-0 


12-8 



Various causes have rendered these experiments exceedingly 
laborious. Could I have procured a sufficiently large quantity 
of gas in a single holder for an entire series of experiments it 
would not have been difficult to obtain concurrent results, but 
the slight variations in quality of the same gas generated at dif- 
ferent times tell upon the results and render perfect uniformity 
extremely difficult to obtain. The approximate constancy of the 
numbers i^ the third column is, however, a guarantee that the 



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00 Prof. Tyadall on theAk$orpium and Radiation 

detennmations are not very wide of the troth. Irregularities^ 
however^ are revealed. Some remarkable ones occur in the case 
of carbonic acid, with the chambers 23*8 and 25*6, — ^the absorp* 
tions in the first chamber varying in this instance from 11*7 to 
10*4, and in the second chamber from 11*4 to L0*6| and in both 
chambers from 13*1 to 12*0. The gas which gave the largest 
of these results was generated from marble and hydrochloric 
acid ; the next was obtained from chalk and sulphuric acid, and 
the gas which gave the smallest result was obtained from bicar^ 
bonate of soda and sulphuric acid. The slight differences aocom«> 
panying these different modes of generation made themselves 
felt in the manner recorded in the Table. 

Table VIII.— Nitrous Oxide. 



Length. 




Absorption per 


100. 


' It 


2nd 


'l.t 


2nd 


Both 


chamber. 


chamber. 


chamber 


chamber. 


chambers. 


2-8 


46-6 


161 


82-9 


33-9 


12-2 


87'2 


23-1 


300 


320 


15-4 


340 


23-6 


29-6 


320 


17-8 


31-6 


26-2 


29-6 


82-7 



The differences arising from different modes of generation are 
most strikingly illustrated by the powerful gases. My friend 
Dr. Frankland^ for example^ was kind enough to superintend for 
me the formation of a large holder of olefiant gas by the so-called 
" continuous process,'' in which the vapour of alcohol is led 
through sulphuric acid diluted with its own volume of water ; 
the following results were obtained :•«-«• 

Table IX.— Olefiant Gas. 



Length. 




Absorption per 


100. 


Ut 


2nd 


Ist 


2Dd 


Both 


chamber. 


chamber. 


chamber. 


chamber. 


chambers. 


2*8 


46-6 


34-6 


661 


67-7 


80 


41-4 


44-2 


65-3 


67-5 


15-4 


840 


53-6 


62-3 


67-0 



Considering the difficulty of the experiments, the agreement 
of the absorption of both chamb^s^ the sum of which was the 
constant quantity of 49*4 inches,, must be regarded as satisfac^ 
tory. This is the general character of the results as long as we 
adhere to the same gas. Olefiant gas generated by mixing the 
Rquid alcohol with sulphuric acid and applying heat to the mix- 
ture, gave the results recorded in the followiug Tables — 



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afHeai by Gaseous and Liquid Matter. 91 

Table X.— Olefiant Gas. 



Length. 




Abaorption per 


100. 


t 
Ut 


> 
2nd 


'1st 


2nd 


Both 


chamber. 




chamber 


chamber. 


chambers. 


12-2 


37-2 


54-8 


700 


76-3 


15-4 


340 


691 


72-7 


771 


19-8 


29-6 


67-8 


70-4 


770 


23-8 


25-6 


69-2 


70-2 


77-6 


36-3 


131 . 


72-8 


60-3 


78-8 



The absorptions of both chambers in this Table are almost 
exactly 10 per cent, higher than those found with the gas gene- 
rated under Dr. Frankland's superintendence. 

A few remarks on these results may be introduced here. In 
the case of carbonic oxide (Table YL), we see that while a length 
of 2*8 inches of gas is competent^ when acting alone^ to intercept 
6*8 per cent, of the radiant heat^ the cutting off of this length 
from a tube 49*4 inches long^ or^ what is the same^ the addition 
of this length to a tube 46*6 inches long^ makes no sensible 
change in its absorption. The second chamber absorbs as much 
as both. The same remark applies to carbonic acid^ and it is 
also true within the limits of error for nitrous oxide and olefiant 
gas. Indeed it is only when 8 inches or more of the column 
have been cut away that the difference begins to make itself felt. 
Thus^ in carbonic oxide^ the absorption of a length of 41*4 being 
12*2, that of a chamber 49*4, or 8 inches longer, is only 12*9, 
making a difference of only 0*7 per cent., while the same 8 inches 
acting singly on the gas produces an absorption of 9*6 per cent. 
So also with regard to carbonic acid; a tube 41*4 absorbing 
12*7 per cent.^ a tube 49*4 absorbs only 13*0 per cent., making 
a difference of only 0*3 per cent. As regards olefiant gas (Table 
IX.), while a distance of 8 inches acting singly effects an absorp- 
tion of 44 per cent., the addition of 8 inches to a tube already 
41*4 inches in length raises the absorption only from 65*3 to 
67*5, or 2*2 per cent. The reason is plain. In a length of 
41*4 the rays capable of being absorbed by the gas are so much 
diminished, so few in fact remain to be attacked, that an addi- 
tional 8 inches of gas produces a scarcely sensible effect. Simi- 
lar considerations explain the fact that, while by augmenting the 
length of the first chamber from 2*8 inches to 15*4 inches we 
increase the absorption of olefiant gas nearly 20 per cent., the 
shortening of the second chamber by precisely the same amount 
effects a diminution of barely 4 per cent, of the absorption. All 
these results conspire to prove the heterogeneous character of the 
radiation from a source heated to about 250° C. 

The sum. of the absorptions placed side by side with the 



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92 Prof. Tyadall on tke AkMrpium mul RaHatian 

absorption of the sum exhibits the influence of sifting in an in- 
stnictiye manner. Tables YL, VII.^ YIII., IX.^ and X., thus 
treated^ give the following comparative nambers : — 





Tabu XI.— Carbonic Oxide. 




Length of cfaamben 


Smn of •baorptiou. Abwwption of (om. 


2-8 


46-6 




19-7 


12-9 


8-0 


411 




21-8 


12-9 


12-2 


87-2 




22-9 


12-9 


15-4 


840 




23-1 


18-4 


17-8 


81-6 




28-1 


13-8 


86-8 


181 




22-9 


18-4 






Means 


22-3 


13-1 




Tablb XII. — Carbonic Acid. 




2-8 


46-6 




22-4 


13-3 


80 


41-4 




22-6 


130 


12-2 


87-2 




22-4 


18-0 


15-4 


84-0 




23-9 


18-9 


23-8 


25-6 




231 


131 


86-8 


181 




21-6 


12-8 






Means 


22-6 


18-1 




Tablb XIII.— 


•Nitrous Oxide. 




2-8 


46-6 




490 


83-9 


12-2 


87-2 • 




531 


82-0 


16-4 


840 




53-2 


82-0 


17-8 


81-6 




55-8 


82-7 






Means 


52-8 


82-7 




Tabm XIV.— 


•Olefiant Gas. 




2-8 


46-6 




100-7 


67-7 


80 


41-4 




109-5 


67-5 


12-2 


87-2 




109-4 


65-0 


15-4 


84-0 




115-9 


67-0 






Means 


108-9 


66-8 




Table XY.— Olefiant Gas. 




12-2 


87-2 




124-8 


76-8 


15-4 


84K) 




131-8 


77-1 


19-8 


29-6 




138-2 


77-0 


23-8 


25-6 




139-4 


77-6 


86-8 


181 




183-1 


78-8 



Means 138-4 77-3 



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of Heat by Gaseous and Liquid Matter. 08 

The conclusion that the sum of the absorptions is greater than 
the absorption of the sum is here amply verified. The Tables 
also show that the ratio of the sum of the absorptions to the 
absorption of the sum is practically constant for dl the gases. 
Dividing the first mean by the second in the respective cases^ we 
have the following quotients : — 

Carbonic oxide' 1'70 

Carbonic add 1*72 

Nitrous oxide 1*61 

Olefiant gas (mean of both) • • 1*68 

The sum of the absorptions ought to be a maximum when 
the two chambers are of equal length. Supposing them to be 
unequal^ one being in excess of half the length of the tube^ let 
OS consider the action of this excess singly. Placed after the 
half-lengthy it receives the rays which have already traversed 
that half j placed after the shorter lengthy it receives the rays 
which have traversed the shorter length. In the former case^ 
therefore^ the excess will absorb less than in the latter^ because 
the rays in the former case have been more thoroughly sifted 
before the heat reaches the excess. From this it is clear that, 
as regards absorption, more is gained by attaching the excess to 
the short length of the tube than to the half-length ; in other 
wordsj the sum of the absorptions, when the tube is divided into 
two equal parts^ is a maximum. This reasoning is approximately 
verified by the experiments. Supposing^ moreover, one of the 
lengths constantly to diminish, we thus constantly approach the 
limit when the sum of the absorptions and the absorption of the 
sum are equal to each other, the former being then a minimum. 
The effect of proximity to this limit is exhibited in the first expe- 
riment in each of the series; here the lengths of the compart- 
ments are very unequal, and the sum of the absorptions is, in 
general, a minimum. 

After the absorption by the permanent gases had been in this 
way examined, I passed on to the examination of vapours. They 
were all used at a common pressure of 0*5 of an inch of mer- 
cury, or about ^\jth of an atmosphere. The liquid which yielded 
the vapour was enclosed in the flasks described in my previous 
memoirs, and the pure vapour was allowed to enter the respec- 
tive compartments of the experimental tube without the slightest 
ebullition. The following series of Tables contains the results 
thus obtained. 



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94 Prof. Tyndall on the Absorption and Radiation 

Tablb XVI. — ^Bisulphide of Carbon. Pressure 0*5 of an inch. 



Lenctb. 




Absorption per 


100. 


lit 2iid 


Ut 


2nd 


Both 


chamber. chamber. 


chanber. ebambcr. 


chamben. 


• 2-8 46-6 


8-6 


7-6 


7-6 


8'0. 41-4 


4-4 


7-3 


7-6 


15-4 840 


6-7 


6-0 


7-5 


17-8 81-6 


5-8 


6-4 


7-5 


23-8 26-6 . 


6-7 


60 


7-8 


Table XVII.— Chlorofortn. Pressure 0*5 of 


an inch. 


2-8 46-6 


5-5 


15-9 


16-3 


80 41-4 


9-2 


15-6 


16-8 


12-2 87-2 


10-5 


14-8 


171 


15-4 840 


11-6 


141 


16-9 


23-8 25-6 


15*0 


140 


18-4 


86-3 131 


15-6 


10-9 


17-2 


Table XVIII. — ^Benzole. Pressure 0*6 of an inch. 


2-8 46-6 


40 


200 


20-6 


8-0 41-4 


8-4 


17-3 


20-4 


12-2 37-2 


9-8 


16-5 


19-0 


17-8 31-6 


11-9 


15-7 


201 


23'8 25-6 


14-3 


151 


210 


["able XIX.— Iodide of Ethyle. 


Pressure 0*5 of an inch. 


2-8 46-6 


7-1 


23-6 


25*4 


80 41-4 


91 


21-1 


23-3 


12-2 37-2 


12-8 


20-5 


25-2 


16-4 340 


14-6 


20-8 


25-2 


17-8 31-6 


16-8 


200 


25-5 


Table XX.— Alcohol. 


Pressure 0*5 of an 


inch. 


2-8 46-6 


11-7 


461 


46tl 


8-0 41-4 


18 5 


43-6 


47-0 


12-2 37-2 


260 


441 


47-5 


15-4 840 


32'1 


41-1 


47-0 


17-8 81-6 


32-4 


40-0 


47-6 


Table XXI.— Alcohol 


. Pressure 0*1 of ar 


I inch. 


8-0 41-4 


80 


22-2 


24*9 


15-4 340 


121 


200 


24-7 


17-8 31-6 


131 


19-7 


25-7 


23-8 25-6 


14-8 


18-4 


25-2 


36-3 131 


191 


13-8 


251 



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qfHmii by Gatecm and Liquid Mutter. 96 

Table XXII. — Sulphuric Ether. Pressure 0*5 of an inch. 



Length. 




Absorption per 100. 


' Ist 2nd ' 


l«t 


2nd 


Both 


chamber. chamber. 




chamber. 


chamber*. 


2-8 46-6 


14-8 


BOO 


51-6- 


80 41-4 


23-9 


51-0 


53-9 


12-2 37-2 


30-9 


48-8 


53-6 


15-4 340 


840 


47-8 


531 


Table XXIII.— Acetic Ether. 1 


Pressure 0*5 of 


an inch. 


2-8 46-6 


170 


*60-2 


62-9 


80 41-4 


30-7 


581 


64-6 


12-2 37-2 


41*6 


561 


64-2 


15-4 340 


44-4 


55-5 


62-4 


23-8 25-6 


50-9 


52-7 


64-7 


36-3 131 


581 


42-6 


64-8 


Table XXiV.— Formic Ether. 


Pressure 0-5 of 


an inch. 


2-8 46-6 


17-4 


680 


64-4 


80 41-4 


33-3 


59-1 


63-4 


17-8 SI'S 


40-0 


48-4 


60-3 


23-8 25-6 


45-6 


472 


60-2 



I have already compared the sum of the absorptions for gases 
with the absorption of the sum ; in the following Tables the same 
comparison is made for the vapours. 

Bisulphide of Carbon^ 0*5 inch. 



Table XXV. I 


Length of chambers. 


2-8 


46-6 


80 


41-4 


1 5*4 


840 


17-8 


81-6 


23-8 


25-6 


Table XXV 


2-8 


46-6 


80 


41-4 


12-2 


37-2 


15-4 


340 


28'8 


25-6 


86-3 


131 



Sum of absorptions. 


Absorption of sum 




11-2 




7-6 




11-7 




7-6 




11-7 




7-5 




12-2 




7-5 




12-7 




7-8 


Means 


11-9 




7-6 


[. — Chloroform, 


0*5 inch. 




21-4 




16-8 




24-8 




16-8 




25-3 




17-1 




25-2 




16-9 




290 




18-4 




26-5 




17-2 


Means 


25-36 




171 



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96 Prof. Tyndall on the AbiorpHan and Radiation 

Table XXVIL— Benzole, 0-5 inch. 



Length of chamber*. Stun 

2-8 46-6 

8-0 41-4 
12-2 87-2 
17-8 81-6 
28*8 26-6 


ofabMwptkms. 
240 
25-7 
26-8 
27-6 
29-4 


AbMvptioncrfnim. 
20-6 
20-4 
190 
201 
210 






Means 


26-6 


. 


20-2 


Tablb XXVIII 


.—Iodide of Ethyle, 


0*5 inch. 


2-8 

80 

12-2 

15-4 

17-8 


46-6 
41-4 
37-2 
340 
81-6 




30-6 
80-2 
83-8 
85-4 
35-8 




25-4 
23-3 
25-2 
25-2 
25-2 






Means 


831 




24-9 


Table XXIX.—. 


ilcohol, 0*5 inch. 




2-8 

80 

12-2 

15-4 

17-8 


46-6 
41*4 
37-2 
340 
31-6 




57-8 
62-1 
701 
73-2 
72-4 




461 
470 
47-5 
470 
47-6 






Means 


671 




47-0 


Table XXX.— Alcohol, O'l inch. 




80 
15-4 
17-8 
23-8 
36-3 


41-4 
340 
31-6 
25-6 
13-1 




30-2 
321 
32-8 
33-2 
32-9 




24-9 
24-7 
25-7 
25-2 
25-1 






Means 


32-2 




251 


Table XXXI 


— Sulphuric Ether, 0-5 inch. 


2-8 

80 

12-2 

15-4 


46-6 
41-4 
37-2 
34-0 




64-8 
74-9 
79-7 
81-8 




51-6 
53-9 
53-6 
531 






Means 


75-3 




5305 



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of Heat by Qauom and Liquid Matter. 97 

Tablb XXXII.— Formic Ether, 0*5 inch. 

Sum of Absorption 

Length oi chamben. absorptions. of sum. 

2-8 46-6 80-4 644 

80 41-4 82-4 63-4 

17-8 81-6 88-4 603 

28-8 25-6 92-8 60-2 





Means 


860 


62-07 


Table XXXIII. 


— Acetic Ether, 


0-5 inch. 


2-8 46-6 




77-2 


62-9 


80 41-4 




88-8 


64-6 


12-2 87-2 




96-7 


64-2 


15-4 340 




99-9 


62-4 


23-8 26-6 




103-6 


64-7 


86-3 131 




100-7 


64-8 



Means 945 63*9 

An inspection of the foregoing Tables discloses the fact that, 
in the case of vapoars, the difference between the sum of the 
absorptions and the absorption of the sum is, in general, less 
than in the case of gases. This resolves itself into the prpposi- 
tion that for equal lengths, within the limits of these experi- 
ments, the sifting power of the gas is greater than that of the 
vapour. The reason of this is that the vapours are examined in 
a state of tenuity which is only ^\jth of that possessed by the 
gases. Thus, no matter how powerful the individual molecules 
may be, their distance asunder renders a thin layer of them a 
comparatively open screen. 

§ «L The entrance of a gas into an exhausted vessel is accompanied 
by the generation of heat ; and the gas thus warmed, if a radia- 
tor, will emit the heat generated. Conversely, on exhausting a 
vessel containing any gas, the gas is chilled, and thus an exter- 
iial body, which prior to the act of exhaustion possessed the same 
temperature as the gas within the vessel, becomes, on the first 
stroke of the pump, a warm body with reference to the gas 
remaining in the vessel; and if the external body be separated 
from the cooled gas by a diathermic partition, it will radiate into 
the gas and become chilled by this radiation. It was shown in 
my second memoir* that this mode of warming and of chilling 
a gas or vapour furnished a practical means of determining, 
without any source of heat external to the gaseous body itself, 
both its radiative and absorptive energy. For the sake of con- 

• Phil. Trans, part 1, 1862 j and Phil. Mag. vol. xxiv. p. 337. 
Phil. Mag. S. 4. Vol. 28. No. 187. Aug. 1864. H 



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98 Prof. Tyndall on the Abwrption andRaHaium 

▼enience I have called the radiation and absorption of a gas or 
▼apour thus dynamically heated and cooled^ dynamic radiation 
and dynamic absorption. 

In illustration of the manner in which dynamic radiation may 
be applied in researches on radiant heat^ I have had made^ 
during the last half-year, a considerable number of experiments^ 
■ome of which I will here describe. In the first place, the expe- 
rimental tube was divided iato two compartments, as in the 
experiments described in the foregoing section. The source of 
heat was abolished, and one end of the experimental tube was 
stopped by a plate of polished metal ; the other end was stopped 
by a transparent plate of rock-salt, while the space between the 
ends was divided into two compartments by a second plate of 
rock-salt. The thermo-electric pile occupied its usual position 
at the end of the tube, the compensating cube, however, being 
abandoned. For the sake of convenient reference, I will call the 
compartment of the tube most distant from the pile the first 
chamber, and that adjacent to the pile the second chamber. 
An outline sketch of the arrangement is given in fig. 3. 




Fig. 3. 



& 



2^d, Chconb* 



Ist^Chamh 



j± 



:^ 



Z^ 



The experiments were conducted in the following manner:— 
Both compartments being exhausted and the needle at zero, the 
gas was allowed to enter the first chamber through a gauge- 
cock which made its time of entry 40 seconds. The second 
chamber was preserved a vacuum ; the gas on entering the first 
chamber was dynamically heated, and radiated its heat to the 
pile through the vacuous second chamber ; the needle moved^ 
and the limit of its excursion was noted. The first chamber 
was then exhausted and carefully cleansed with dry air. The 
second chamber, was filled with the same gas, not with a view to 
determine its dynamic radiation, but to examine its effect upon 
the heat radiated from the first chamber. The needle being at 



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of Heat hy Gaseous and Liquid Matter. 99 

ierOf the gas was again permitted to enter the first chamber 
exatctly as in the first experiment^ — the only difference between 
the two experiments beings that in the first the heat passed 
through a vacuum to the pile, while in the second it had to pass 
through a column of the same kind of gas as that from which it 
emanated. In this way the absorption exerted by any gas upon 
heat radiated from the same gas, or from any other gas, may 
be accurately determined. Finally, the apparatus being cleansed 
and the needle at zero, the gas was permitted to enter the second 
chamber, and its dynamic radiation from this chamber was deter- 
mined. The intermediate plate of salt S' was shifted, as in the 
former experiments, so as to alter the lengths of the two cham- 
bers, but the sura of both lengths remained constant as before. 

In the following Tables the three columns bracketed under 
the head of " Deflection,'' contain the arcs through which the 
needle moved in the three cases mentioned; (1) when the radia- 
tion from the gas in the first chamber passed through the empty 
second chamber; (2) when the radiation from the first chamber 
passed through the occupied second chamber; and (3) when the 
radiation proceeded from the second chamber. 

Dynamic Radiation of Gases. 
Table XXXIV.— Carbonic Oxide. 





Leiigth. 




Deflection. 

A 








' By 1st 
chamber, 
2nd chamber 
empty. 


By 1st 
chamber, 
gas in 2nd 
chamber. 


1 

By2ttd 
chamber. 




' 1st 
chamber 


2nd 
chamber. 




2-8 
15-4 
36-3 


46-6 
34-0 
131 


o 

10 

3-8 

13-7 


do 

21 
6-3 


280 
24-4 
16-6 






Table XXXV.— Carbonic Aoid. 






2-8 
15-4 
36-3 


46-6 
840 
13-1 


10 

3-7 

16-8 


00 

1-25 

6-6 


33-6 
23-3 
17-5 






Table XXXVI.— Nitrous Oxide. 






2-8 
15-4 
86-8 


46-6 
340 
13-1 


10 

4-3 

19-5 


0-2 
1-2 
62 


44-5 
31-7 
220 






Table XXXVII.— Olefiant Gas. 






15-4 
28-8 
86-3 


340 
25-6 
131 


11-9 
22-8 
590 


10 

30 

10-4 

H2 


68-0 
650 





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100 Prof. Tyndall an the Ahwrpiion and RaHaium 

The gases, it will be observed, exhibit a gradually increwmg 
power of dynamic radiation from carbonic oxide up to olefiant 
gas. This is most clearly illustrated by reference to the resulta 
obtained in the respective cases with the first length of the 
second chamber. They are as follows : — 

o 

Carbonic oxide 28*0 

Carbonic acid • 88*6 

Nitrous oxide 44*5 

Olefiantgas 680 

Its proximity to the pile, and the fact of its having to cross 
but one plate of salt, makes the action of the second chamber 
much greater than that of the first. 

Each of the Tables exhibits the fact that as the length af the 
chamber increases the dynamic radiation of the gas contained in 
it increases,aQd as the length diminishes the radiation diminishes. 
We also see how powerfully the gas in the second chamber acts 
upon the radiation from the first. With carbonic oxide, the pre- 
sence of the gas in the second chamber reduces the deflection 
from 13°*7 to 6°*3 ; with carbonic acid it is reduced from 16*8 
to 6*6 ; with nitrous oxide it is reduced from 19*5 to 6*2* Now 
this residual deflection, 6°*2, is not entirely due to the transpa- 
rency of the gas, to heat emitted by the gas. No matter how well 
polished the experimental tube may be, there is always a certain 
radiation from its interior surface when the gas enters it. "With 
perfectly dry air this radiation amounts to 8 or 9 degrees. Thus 
the radiation is composite, in part emanating from the mole- 
cules in the first chamber, and in part emanating from the sur- 
face of the tube. To these latter, the gas in the second cham- 
ber would be much more permeable than to the former ; and to 
these latter, I believe, the residual deflection of 6 degrees^ or 
thereabouts, is mainly due. That this number turns up so 
often, although the radiations from the various gases differ con- 
siderably, is in harmony with the supposition just made. In 
the case of carbonic oxide, for example, the deflection is reduced 
from 13^*7 to 6°-3, while in the case of nitrous oxide it is reduced 
from 19°* 5 to 6^*2 ; in the case of olefiant gas it is reduced from 
59° to 10°*4, while in other experiments (not here recorded) the 
deflection by olefiant gas was reduced fi*om 44*^ to 6°. 

As may be expected, this radiation from the interior sur&oe 
augments with the tarnish of the surface, but the extent to which 
it may be increased is hardly sufficiently known. . Indeed the 
gravest errors are possible in experiments of this nature if the 
influence of the interior be overlooked or misunderstood. An 
experiment or two will illustrate this more forcibly than any 
words of mine. 



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efHeai by Oaaeoua and Liquid Matter. 101 

A brass tube 3 feet long, and very slightly tarnished within, 
was used for dynamic radiation. Dry air on entering the tube 
produced a deflection of 12 degrees. The tube was then polished- 
within, and the experiment repeated; the action of dry air was 
instantly reduced to 7*5 degrees. 

The rock-salt plate at the end of the tube was then removed, 
and a lining of black paper 2 feet long was introduced within it. 
The tube was again closed, and the experiment of allowing dry 
air to enter it repeated. The deflections observed in three suc- 
cessive experiments were 

80°, 81°, 80°. 

This result might be obtained as long as the lining continued 
within the tube. 

The plate of rock-salt was again removed, and the length of 
the Uning was reduced to a foot ; the dynamic radiation on the 
entrance of dry air in three successive experiments gave the 
deflections 

76°, 74°, 75°. 

The plate was again removed and the lining reduced to 3 
inches ; the deflections obtained in two successive experiments 
were 

66°, 65°. 

Finally the lining was reduced to a ring only 1^ inch in width ; 
the dynamic radiation from this small surface gave in two suc- 
cessive trials the deflections 

56°, 56°-5. 

The lining was then entirely removed, and the deflection 
mstantly fell to 

7^-5. 

A coating of lampblack within the tube produced the same 
effect as the paper lining; common writing-paper was almost 
equally effective; a coating of varnish also produced large 
deflections, and the mere oxidation of the interior surface of the 
tube is alsQ very effective. 

In the above experiments the lining was first heated, and it 
then radiated its heat through a thick plate of rock-salt against 
the pile. The effect of the heat was enfeebled by distance, by 
reflexion from the surfaces of the salt, and by partial absorption. 
Still we see that the radiation thus weakened was competent to 
drive the needle almost^ through the quadrant of a circle. If, 
instead of being thus separated from the lining, the face of the 
pik itself h^d formed part of the interior surface of the tube, 
receiving there the direct impact of the particles of air, of course 
the deflections would be far greater than the highest of those 



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102 Prof. Tyndall on the Abtcrptian ani Radiation 

above recorded. Indeed I do not doubt my ability to cause the 
needle of my galvanometer to whirls by the dynamic heating of 
the surface of my pile^ through an arc of 1000 degrees. As- 
suredly an arrangement subject to disturbances of this character 
cannot be suitable in experiments in which the greatest delicacy 
is necessary. 

Experiments on dynamic radiation, similar to those executed 
with gases, were made with vapours. The tube was divided 
into two compartments as before. Both compartments being 
exhausted, vapour was permitted to enter the first chamber. 
Dry air was afterwards permitted to enter the same chamber; 
the air was heated, it warmed the vapour^ and the vapour 
radiated its heat against the pile. The heat passed in the first 
experiment through a vacuous second chamber, and in the 
second experiment through the same chamber when it contained 
0*5 of an inch of the same vapour as that from which the rays 
issued. A third experiment was made to determine the dynamic 
radiation from the second chamber. The following Tables con- 
tain the results : — 

Dynamic Radiation of Vapours. 
Table XXXVIII.— Bisulphide of Carbon, 0-5 inch. 

Length. Deflection. 

. '\ , . ^ . 



By Ut By 1st 

Ist 2ud chamber^ chamber. By 2Dd 

chamber, chamber. 2nd chamber Vapour in chamber, 
empty. 2nd chamber. 

15-4 340 2-4 i-6 142 

36-3 131 975 5-5 90 

Table XXXIX. — Benzole, 0*5 inch, 

16-4 340 30 11 340 

86-3 131 21-6 11-9 151 

Table XL. — Iodide of Etbyle, 0-5 inch. 

15-4 340 3-4 " 2-7 38-8 

36-3 131 25-4 13-8 190 

Table XLI. — Chloroform, 0*5 inch. 

15-4 340 ' 45 21 410 

36-3 13-1 .22-3 100 190 

Table XLII. — Alcohol, 0*5 inch. 

15-4 340 4-9 20 58-8 

86-8 131 83-8 169 34-9 



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of Heat by Gaseous and Liquid Matter. 103 

Table XLIII.— Alcohol, O'l inch. 
Length. Deflection. 

, .r^ , , '^ , 

By Ut By Ist 

1st 2nd chamber^ chamber. By 2nd 

chamber, chamber. 2nd chamber vapour in chamber, 

empty. 2nd chamber. 

15-4 340 20 1-3 35-7 

86-3 131 21-8 16-2 115 

Table XLIV. — Boracic Ether, 0*1 inch. 

15-4 340 6-3 21 610 

36-3 131 291 15-7 316 

Table XLV.— Formic Ether, 05 inch. 

15-4 840 6-3 2-5 680 

86-3 131 460 28-8 410 

Table XLVI.— Sulphuric Ether, 0*5 inch. 

154 340 5-6 2-5 680 

868 131 45-3 22-4 36-5 

Table XLVIL— Acetic Ether, 0*5 inch. 

15-4 34-0 5-7 10 73-9 

36-3 131 49-1 220 410 

Collecting the radiations from the second chamber for the 
lengths 34 inches and 13*1 inches together in a single Table, we 
see at a glance how the radiation is affected by varying the length. 

Table XLVIII. 

Dynamic radiation of Tarions 
vapours at 0*5 inch pressure 
and a common thickness of 

t ^ •' s 

34 inches. 13*1 inches. 

o o 

Bisulphide of carhon . . . 14*2 9*0 

Benzole 34*0 15'1 

Iodide of ethyle 38*8 19-0 

Chloroform 410 19*0 

Alcohol 53*8 34*9 

Sulphuric ether 680 36'5 

Formic ether 680 41-0 

Acetic ether • 73-9 41-0 

At a pressure of 0*1 of an inch. 

Alcohol 35-7 . 11-5 

Boracic ether 610 31-6 



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Z04 Prof. Tyndall <m ths Ahiorptim and Radiatian 

The extraordinary energy of boraeie ether as a radiant may 
be inferred from tne last experiment. Although attenuated 
to y^th of an atmosphere^ its thinly scattered molecules are able 
to urge the needle through an arc of 61 degrees, and this merely 
by the warmth generated on the entrance of dry air into a 
vacuum. 

Arranging the gases in the same manner, we have the follow- 
ing results : — 

Tablc XLIX. 

Dynamic radiation of gases 
at 1 atm. pressure and a 
common tliickness of 
, A 

34 inches. 13*1 inches. 

o o 

Carbonic oxide 24*4 16*6 

Carbonic acid 28*3 17*5 

Nitrous oxide 31*7 220 

Olefiantgas 680 65*0 

The influence of tenuity which renders the vapour at 0*5 of 
an inch a more open screen than the gas at 30 inches is here 
exhibited. In the case of the vapour, a greater length is avail- 
able for radiation than in the case of the gas, because the radia- 
tion from the hinder portion of the column of vapour is less 
interfered with by the molecules in front of it than is the case 
with the gas. By shortening the column we therefore do more 
injury to the vapour than to the gas; by lengthening it we pro- 
mote the radiation from the vapour more than that from thegpas. 
Thus while a shortening of the gaseous column from 34 inches 
to 13*1 causes a fall in the case of carbonic oxide only from 23^*3 
to 17^*5, the same amount of shortening causes benzole vapour 
to fall from S4P to 15*^*1, — a much greater diminution. So also 
as regards olefiant gas, a shortening of the radiating column 
from 34 inches to 13*1 inches causes a fall in the deflection only 
from 68^ to 65^ ; the same diminution produces with sulphuric 
ether a fall from 68^ to 36°*5 ; and with acetic ether from 73''-9 
to 41^. In the long column acetic ether vapour beats olefiant gas^ 
but in the short column the gas beats the vapour. 

One of the earliest series of experiments of this nature which 
were executed last autumn, though not free from irregularities^ 
is nevertheless worth recording. The experiments were made 
with a brass tube, slightly tarnished within, the tube being 49*4 
inches long, and divided into two equal compartments, each 24*7 
inches in length, by a partition of rock-salt placed at the centre 
of the tube. 



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of Heal by Oaseaw and Liquid Matter. 105 

Table L. — ^Dynamic radiation of Vapours. 

Deflection. 

. ^ , 

B}' Ist chamber. By Ist chamber, 

2nd chamber vapour in 2nd By 2nd 

empty. chamber. chamber. 

Bisulphide of carbon . 8*2 5*8 21*2 

200 12-4 45-9 

24-3 10-9 55-2 

27-5 14-7 55-8 

42-7 22-3 69-0 

46-3 21-7 80-5 

47-5 19-8 79-5 

49-8 25-0 82-8 

53-3 300 82-1 



Benzole 
Chloroform • 
Iodide of ethyle 
Alcohol • . 
Sulphuric ether 
Pormic ether . 
Propionate of ethyle 
Acetic ether • . 



To ascertain whether the absorption by the vapours bears any 
significant relation to the absorption by the liquids from whicn 
these vapours were derived^ the transmission of radiant heat 
through those liquids was examined. The open flame of an oil- 
lamp was used^ and the liquids were enclosed in rock-salt cells. 
Thus the total radiation from the lamp, with the exception of 
the minute fraction absorbed by the rock-salt^ was brought to 
bear upon the liquid. 

In the following Table the liquids are arranged in the order 
of their powers of transmission. 

Tabu LI. 

Traiumiasion in 
Name of liquid. hundredths of 

the radiation. 

Bisulphide of carbon 83 

Bisulphide of carbon saturated with sulphur . • 82 
Bisulphide of carbon saturated with iodine . • 81 

Bromine 77 

Chloroform ... 73 

. Iodide of methyie . ' 69 

Benzole 60 

Iodide of ethyle 57 

Amylene 50 

Sulphuric ether 41 

Acetic ether • 84 

Formic ether 83 

Alcohol 30 

Water aaturated with rock-salt 26 

These results are but approximate^ but they are not very far 

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106 Dr. Woods an the Relative Amounts of Heat produced by 

from the truth ; and it is impossible to regard them without 
feeling how purely the act of absorption is a molecular act, and 
that when a liquid is a powerful absorber the vapour of that 
liquid is sure also to be a powerful absorber. 

To experiment with water, it was necessary to saturate it with 
the salt of which the cell was formed, but the absorptive energy 
is due solely to the water. We might infer from this alone^ were 
no experiments made on the aqueous vapour of the atmosphere^ 
that that vapour must exert a powerful action upon terrestrial 
radiation. In fact, in all the statements that I have hitherto 
made I have underrated its action. 

The deportment of the elements sulphur and iodine, dissolved 
in bisulphide of carbon, is in striking harmony with all that we 
have hitherto discovered regarding the action of elementary 
bodies. The saturation of the bisulphide by sulphur scarcely 
affects the transmission, while a quantity of iodine sufficient to 
convert the liquid from one of perfect transparency to one of 
almost perfect opacity to light, produces a diminution of only 
two per cent, of the radiation. This shows that the heat really 
used in these experiments consists almost wholly of the obacore 
rays of the lamp. It is worth remarking that the obscure rays 
of a luminous source have a much greater power of penetration 
in the case of the liquids here examined than the rays from an 
obscure source, however close to incandescence. The deport- 
ment of bromine is also very instructive. The liquid is very 
dense, and so opake as to cut off the luminous rays of the lamp ; 
still it transmits 77 per cent, of the total radiation. It stands in 
point of diathermancy above every compound^liquid in the list, 
except bisulphide of carbon. This latter substance is the rock- 
salt of liquids. 

Before a strict comparison can be made between vapours and 
liquids, they must be examined by heat of the same quality, and 
I have already made arrangements with which I hope to obtain 
more complete and accurate results than those above recorded. 



XI. On the relative Amounts of Heat produced by the Chemiedl 
Combination of Ordinary and Ozonized Oxygen. By Thomas 
Woods, M.D.* 

THE difference between the physical conditions of ordinary 
oxygen and oxygen in its more active state, or ozone^ does 
not seem to be known. Clausius considers the atoms of the 
former to be grouped in a binary arrangement, and those of the 
latter to be either isolated, or so joined to the molecules of ordi- 

* Cominuiiicated by the Author. 



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the Chemical Combination of Plain and Ozonized Oxygen. 107 

nary oxygen as not to occupy any volume of their own ; whilst 
Von Babo and others think an exactly opposite disposition of 
the atoms is the true one. 

The interest that attaches itself to ozone^ both from its pecu- 
liar actions and the extraordinary constitution it must possess^ 
as shown by the researches of Andrews and Tait^ make it most 
desirable that more should be known about it. I have endea- 
voured to do something towards fixing a knowledge of its consti- 
tution. I have tried to find which opinion, Clausius^s or Von 
Babo's, is the correct one ; that is, whether ozone is composed of 
combined or isolated atoms. 

The manner in which I have endeavoured to solve the pro- 
blem is founded on the principle I proved in this Magazine in 
October 1851, and now universally admitted, viz. that the de- 
composition of compounds absorbs heat. I thought that, sup- 
posing ozone to differ from oxygen in the arrangement of its 
atoms, less heat should be produced by it than by oxygen from 
union with another body if the atoms were in a combined state, 
because a certain amount of the heat of combination would be 
absorbed by the decomposition or disuniting of the compound 
molecule, — and that an opposite result might be expected from a 
difiFerent arrangement. I therefore determined to cause both 
ordinary and active oxygen to unite with a like body under 
similar circumstances, to find which, if either, produced the 
greater amount of heat. I accordingly mixed a measured quan- 
tity of ozonized air over water with a known volume of deut- 
oxide of nitrogen; and with the same quantity of ordinary 
air I mixed a like volume of the deutoxide as in the first experi- 
meDt, and marked the rise of temperature with a thermometer in 
both instances. I took every possible precaution to ensure uni- 
formity of circumstance in the two series of trials, and I repeated 
them frequently, but I found that no difference in the rise of 
temperature produced was apparent. The increase of tempera- 
ture in both amounted to 9° F. 

The ozonized air was obtained by putting a mixture of sulphuric 
acid and permanganate of potash, according to Bottger's plan, 
under an inverted funnel, the narrow end of which entered a bottle, 
80 as to keep any ozonized air that was produced. After twelve 
hours the starch- and iodide-of-potassium papers were turned 
blue. I made ozone also by leaving phosphorus partly covered 
with water in a large bottle. I could not, however, compare the 
air thus ozonized with common air, because the former contained 
a variable quantity of oxygen. After twenty-four hours^ partial 
immersion of the phosphorus in water nearly all the oxygen was 
removed, having formed phosphoric acid; the quantity that 
remained was not known, and therefore could not be compared 
with ordinary air. 



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108 Mr. W. F. Barrett an a Physical 

I also compared ozonized oxygen (not mixed with nitrogen as 
in the air) with ordinary oxygen as to its power of producing 
heat by combining with deutoxide of nitrogen. I mixed, as in 
the previous experiments, a measured volume of each with a 
similar quantity of the deutoxide over water, but no difference 
in amount of increase of temperature resulted. The ozonized 
oxygen was obtained by transmitting a current from a DanielPa 
battery (ten in series) through water acidulated with sulphuric 
and chromic acids. 

It would only be occupying space unnecessarily, to give more 
fully the details of the experiments, as the results were entirely 
negative, no difference whatever in the amount of heat produced by 
the combination in equal volumes of plain and ozonized oxygen was 
found. If, therefore, any arrangement of particles exist in one 
oxygen which does not in the other, these different states of 
a^regation do not at all events require any force to trans- 
mute them. 

Parsonstown, July 1864. 



XII. On a Physical Analysis of the Human Breath, By W. P. 
Bareett, Assistant in the Physical Laboratory of the Royal 
Institution*. 

IN a memoir by Professor Tyndall, read before the Royal 
Societv on the 17th of March 1864, it was shown that 
when a carbonic oxide flame is used as a source of heat, the 
absorption by carbonic acid is extremely large, even exceeding 
that by olefiant gas, which with other sources is by far the most 
powerful absorbent. Thus, of the radiation from heated lamp- 
black, olefiant gas absorbs six times as much as carbonic acid ; 
whilst of the heat emitted by a carbonic oxide flame, the absorp- 
tion by carbonic acid at small tensions is more than twice that 
effected by olefiant gas at the same pressure. 

This very large absorption of heat by carbonic acid, suggested . 
to me the possibility of this method of experiment being applied 
to the determination of that gas in certain cases where it existed 
in small quantities. By the desire and under the direction of 
Professor Tyndall I have made, with this view, several experi- 
ments upon air and upon the human breath. As Professor 
Tyndall is now in Switzerland, I publish the results at his 
request, but without his supervision, and upon my own respon- 
sibility. 

The apparatus used in this investigation consisted of the same 
instruments (with the exception of the source of heat and " front 



^ Communieaied by the Author. 

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Analysis of the Human Breath, 1 09 

chamber "), and was arranged in the same manner as that figured 
iu the Philosophical Magazine for September 1861^ and described 
by Professor Tyndall in his memoirs ^^ On the Absorption and 
Sadiation of Heat by Graseous Matter/' The source of heat was 
a small flame of carbonic oxide. It is well known in what a 
capridons and unstable manner carbonic oxide bums in the open 
air^ as it is extremely difficult to keep a small flame of this gas 
from being extinguished when unguarded from the currents of 
air present in a room. The first consideration was therefore to 
provide a means of protecting the source^ so as to bring it under 
control and render it at once steady and uniform. The follow- 
ing method was finally adopted and adhered to throughput the 
investigation. 

A glass globe 4 inches in diameter had its upper part drawn 
into a short chimney^ and its lower into a neck which fitted 
tightly into a brass gallery^ this being held at right angles by a 
brass stem. At a short distance from the gallery the stem was 
bent perpendicularly downwards, and then passed into a suitable 
stand in which it could be raised or lowered at pleasure, thus 
enabling the lamp to be fixed at any desired elevation. The 
globe was pierced by a third opening midway between the chim- 
ney and the neck. Through this aperture, which formed a tubu- 
lure 1*1 inch in diameter, the radiation from the source passed 
unchanged in quality into the experimental tube. Part of the 
interior surface of the globe opposite the central opening was 
thickly coated with silver-leaf, which by reflexion increased the 
total radiation without sensibly altering its character. Through 
the neck of the lamp passed a brass tube terminating in a small 
jet, by means of which any gas could be conveyed and burnt in 
the centre of the globe. 

Carbonic oxide gas, contained in a large air-holder, was then 
forced by gentle pressure through a regulator, and finally caused 
to issue from the burner fixed in the lamp. The gas burnt with 
a small blue flame about half an inch in length, which could be 
adjusted by means of stopcocks or by slightly altering the regu- 
lator. And thus a source of heat nearly constant from day to day, 
and extremely steady, was obtained. In front of the lamp was 
mounted the brass experimental tube, 49*4 inches long and 2*4 
inches in diameter, its ends Being stopped by polished plates of 
rock-salt. As the diameter of the tube was greater than that of 
the opening in the lamp, a diaphragm was made of double 
polished brass having a central aperture of the same size as the 
opening. When fitted to the end of the tube next the source, 
the stop completely suppressed all radiation from the heated 
sides of the glass globe. 

The radiation from the flame^ after passing through the expe- 
rimental tube, fell on the anterior face of a thermo-electric pile, 



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110 Mr. W. P. Barrett on a Physical 

and produced a certain deflection in a delicate galvanometer ; 
this deflection was neutralized by a compensating cube contain- 
ing water heated by steam and placed before the opposite face of 
the pile. The needle of the galvanometer was brought precisely 
to zero by the adjustment of a double metal screen placed between 
the cube and the pile. Another double screen of plated metal 
was now introduced between the tube and the source ; a deflec- 
tion of the needle took place indicating the amount of heat fall- 
ing on the posterior face of the pile ; and as this amount exactly 
neutralized the radiation from the flame, it corresponded to that 
radiation^ and consequently gave the total heat emitted by the 
source. This deflection was carefully noted; the double silvered 
screen was now removed ; the needle then descended to zero, 
and everything was ready for the first experiment. 

After taking the total heat in the above manner^ the brass 
adjusting screen before the compensating cube was left untouched, 
the slight variations which occurred throughout the day being 
remedied by altering, within small limits, the size or distance of 
the source. 

The experimental tube having been exhausted, and the needle 
of the galvanometer standing at zero, air from the laboratory was 
drawn first over a U-tube filled with marble moistened with a 
solution of potash, and then over sulphuric acid into the experi- 
mental tube. Whilst the air was passing into the tube the needle 
was closely watched through a telescope, and it was found that 
the only efiect of 30 inches of this pure air was slightly to aug- 
ment the amount of heat passing through the tube, this action 
being due to the feeble dynamic radiation of the air. After the 
tube had been exhausted, air direct from the laboratory, and 
retaining therefore its carbonic acid and aqueous vapour, was 
allowed to enter ; the needle instantly moved in the direction of 
absorption, and when the tube was filled, a deflection of 9^*3 
was observed ; this deflection corresponds to an absorption of 
15 per cent, of the total radiation. The tube was again ex- 
hausted, and air was drawn into it after passing over sulphuric 
acid ; this dry air gave a deflection of 8°-7, or 13*8 per cent, 
absorption. The small amount of carbonic acid present in. the 
air could in this case have been the only agent whicL intercepted 
nearly 14 per cent, of the whole radiation. 

Tol)e assured of this remarkable result, fragments of solid 
potash were placed in a glass tube about 4 inches long, and com- 
mon air passed over the potash alone into the tube, when a de- 
flection of only 4P, or an absorption of 6*4 was obtained. This 
seems to establish the fact that, with a source such as a carbonic 
oxide flame, where the chief radiating body is heated carbonic 
acid^ the absorption by the minute amount of carbonic acid in 



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Arudt/sis of the Human Breath, 111 

our atmosphere was easily measurable^ and far exceeded the 
absorption by the aqueous vapour. The quantity of this latter 
gas is about 35 times the quantity of carbonic acid^ and yet 
the generally feeble carbonic acid intercepts nearly 8 per cent, 
more of the radiation from a carbonic oxide flame. Taking 
the average state of our atmosphere as containing by volume 
4 parts of carbonic acid and 140 parts of aqueous vapour in 
every 10,000 parts of air, and estimating the quantities of 
these gases present in the laboratory at the time of experiment 
at double this amount, the absplute quantities contained in the 
experimental tube and producing the above absorptions are found 
to be •IS cubic inch of carbonic acid and 6*3 cubic inches of 
aqueous vapour, the capacity of the tube itself being 225 cubic 
inches. 

In the memoir by Professor Tyudall referred to at the com- 
mencement, it was stated that the degree of accord between the 
oscillating periods of the molecules of a source of heat and those of 
a body placed in the path of its rays, determines the amount of ab- 
sorption which those rays will undergo in passing through the in- 
terposed substance. This statement is illustrated in the foregoing 
experiments, whilst it was confirmed by substituting for the flame 
of carbonic oxide a small flame of hydrogen. Here^ as before, air 
passed over potash and sulphuric acid showed only slight dynamic 
radiation ; common air sent direct from the laboratory into the 
tube gave a deflection of 6°, or an absorption of 10 per cent. 
In the next experiment the air was dried by passing over sul- 
phuric acid ; the needle in this case showed no absorption what- 
ever, the same amount of heat reaching the pile when the tube 
was filled with dry air as when the tube was exhausted. To 
complete the comparison, air was drawn into the tube after 
being deprived of its carbonic acid ; here a deflection of 2*^*5 was 
found, or 4*4 per cent, absorption. 
The following Table shows these results placed side by side : — 

Table I. 

Source : 



r 
Carbonic oxide flame, 

Deflec- Absorp- 
tion, tion, 



Hydrogen flame. 

Deflec- Absorp- 
tion, tion. 

do 0-0 

60 100 
00 00 
2-5 4-4 

The day on which these measurements were made was remark- 



Air passed over potash and"! « 

sulphuric acid ... . J^'" ^'^ 

Air direct into tube . . . 9*3 15 

Air minus aqueous vapour . 8-7 13*8 

Air minus carbonic acid . * 4*0 6*4 



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112 Mx. W. F. Bwrett MaPkgtkat 

ably fine and dry^ so that the abaorptiona are eertainly beknr 
those that might be expected under other circamstancea. 

On different days the absorption of the heat from a carbcmic 
oxide flame by common air was found to be aa follows : — 

Table U. — Source : small carbonic oxide flame. 



CommoD air. 


AbMrptkmpvlOO. 


On March 5 


. . . 18-7 


On April 18 . 


... 16-0 


On April 28 . 
On May 8 . 


. . . 181 


. . . 19-8 



It is here evident that the variations in the amount of carbonic 
acid in the atmosphere can be detected by this mode of experi- 
ment : such a variation was strikingly shown by comparing air 
obtained from Brighton Downs with air taken from the labora- 
tory. In both cases the air was dried, and the determinations 
made without altering the position of the source or experimental 
tube. The results are : — 

Absorption per 100. 
Air from Brighton Downs • . 13*5 
Air from the laboratory • . . 17*8 

The foregoing experiments led me to examine the abaorption 
by the carbonic acid contained in our breath. 

An india-rubber bag fitted with a stopcock was filled with air 
from the lungs. The experimental tube was exhausted and the 
needle brought to zero, where it steadily remained. Breath from 
the bag was now passed over sulphuric acid and into the tube; 
the needle moved quickly on the side of cold, and finally showed 
an absorption of 80°-8, or 50 per cent Half the entire radia- 
tion from the carbonic oxide flame was thus cut off by the car- 
bonic acid mixed with the air from the lungs. 

Smaller pressures of breath from the same bag were next 
allowed to enter the tube, the absorptions found are given in the 
following Table : — 

Table III. — Source : Carbonic oxide flame. 

Tension, in Deflection. Absorption 

inches. ^ per lOO. 

1 72 120 

3 150 250 

5 200 88-8 

30 30-8 500 

The bag used as a reservoir was put to a direct test, and found 
to have no influence on the absorption. 



Carbonic aci4 of breath < 



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Analysis of the Human Breath. 118 

A platinum spiral, heated to whiteness by a voltaic cnrrent^ 
was substituted for the carbonic oxide flame^ — ^the object of this 
being to compare the relative absorption^ by air and breath, of 
the heat emitted from the incandescent spiral and from the flame. 
With the spiral as source, 30 inches of common air absorbed 5 
per cent, of the total radiation, while an equal quantity of dried 
air from the lungs gave almost exactly the same absorption. 

On April 26, experiments with the carbonic oxide flame were 
renewed, for the purpose of making numerous measurements of 
the absorption by air from the lungs taken at different periods^ 
and also to determine the amount of pure carbonic acid neces- 
sary to produce the same absorption. The percentage of carbo- 
nic acid in breath could then be calculated; and the amount 
found by this means, compared with an accurate chemical analy- 
sis, would show the reliability and advantages of this novel mode 
of experiment. 

The experiments were conducted in precisely the same manner 
as that already described. 

Two large vulcanized india-rubber bags, provided with suitable 
stopcocks and connexions, were thoroughly cleansed, by dry air, 
from any possible impurity. These bags were taken home, and 
No. I. filled with air from the lungs about half an hour after 
rising, and No. XL filled from the lungs of the same person 
about 10 minutes after breakfast. A third and smaller bag was 
also filled with air from the lungs after a brisk walk. 

Dr. Frankland very kindly undertook to analyze these differ- 
ent specimens of breath, — ^the amount of carbonic acid in each 
being determined by him with that precision which his own deli- 
cate apparatus and high experimental skill enabled him to com- 
mand. 

The same day on which the chemical analyses were made, the 
absorption by the breath contained in each bag was ascertained^ 
and is given in the next Table. 

Table IV. — Carbonic oxide flame. 

Tension, in Absorption 

inches. per 100. 

10-2 
Bag No. I. . . ^ 15 47-2 

50-6 



L . . J 15 
L30 

3. n. . i 15 
Lso 

0. III. • i 15 
[30 



10-75 
Bag No. 

52-8 

11-8 
Bag No. III. • ^ 15 48-7 

' " 53-7 

Pha. Mag. S. 4. Vol. 28. No. 187. Aug, 1864. 

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114 liJjr. W. ¥. Barrett on a Physical 

. The defiectionB are not given in this Table, because the absorp- 
tions are the mean of two or more experimenta« The first bag 
was now emptied of the remaining breath it contained and deanaed 
with dry air ; it was then filled from the lungs by Dr. Franklandj 
after he had undergone considerable exertion. The absorptiop 
by this breath is given in the fifth column of Table Y., a cbemi* 
cal analysis of it being also made by Dr. Frankland. In the 
next Table the absorptions by air from the four bags are col- 
lected together and can be seen at a glance. 

Table V. 



- Teiuioii,in 










inches. 


Bag No. I. 


No. II. 


No. III. 


No. IV. 


1 . . 


. 10-2 


10-7 


11-8 


121 


16 . . 


. 47-2 


a • 


48-7 


50-0 


80 . . 


. 50-6 


52-8 


53-7 


54-0 



The analysis made by Dr. Frankland gave the following results 
as the percentage amount of carbonic acid contained in the seve- 
ral bags : — 

Table VI. 

Air ttovCL the lungs 
Carbonic acid per cent, in taken 

Bag No. I. . • 4'311 before breakfast. 

yy II. . • 4*656 after breakfast. 

y, III. • . 4*061 after walking. 

„ IV. . . 5*212 after severe exertion. 

By comparing in each case the absorption given in Table V. 
with the analysis in Table VI., relative correctness is evident 
-with one exception, namely that of bag No. III. An error 
from some cause must have arisen here, as an inspection of the 
two Tables shows that, whereas in all the other cases increase in 
absorption accompanies increase in the amount of carbonic acid, 
this bag is found to have a medium absorption, but, according ta 
Dr. Frankland, contained the least amount of carbonic acid. The 
error may have been caused by the substance of the bag itself, 
which was different from, and newer than, the other two that 
were used. This bag was therefore rejected to avoid in future 
any chance of error, and in subsequent experiments the two other 
bags, which had been repeatedly tested, were adhered to. 

A series of experiments was now commenced with a view of 
making quantitative measurements of the carbonic acid in breath. 

This was thought to be easily accomplished by admitting into 
the exhausted tube a known quantity of pure carbonic acid until 
a deflection was obtained corresponding to that produced by the 



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Analysis of the Human Breath. 116 

breath. As the absorptions in the two cases were eqnal^ the 
percentage of carbonic acid in the breath could be readily found. 
The following Table shows how far experiment corroborated 
theory : — 

Table VII. — Source : Carbonic oxide flame. 

Pure carbonic acid gas. Absorptioii per 100. 

2*5 inches 54*5 

4*0 inches 57*7 

30-0 inches 700 

Referring to Table Y.^ we see that 80 inches of breath from 
bag No. IV. absorbed 54 per cent, of the whole radiation. The 
nearest approach to this absorption is the first in the above 
Table^ and from this we may roughly assume that about 2*4 
inches of pure carbonic acid gives about the same absorption as 
30 inches of dried breath. The following proportion should then 
give the fimount of carbonic acid in the breath'from bag No. IV., 

80:100:: 2-4:8, 

from which it appears that the breath in bag No. IV. contained 
8 per cent, of carbonic acid. Chemical analysis shows us that 
there is but 5*2 per cent, of carbonic acid in this specimen of 
breath. Here is at once a formidable difficulty. It would be 
impossible to doubt the correctness of Dr. Franluand's analysis, 
for 8 per cent, is far beyond the average amount of carbonic acid 
found in expired air, yet at the same time the absorption was 
most accurately determined and confirmed by repeated experi- 
ments. Could any of the conditions of experiment in the two cases 
have been different f It was just possible that the burner in the 
lamp might have been moved ; and if raised, the radiation from 
the heated iet would probably come into play and thus slightly 
alter the character of the source. The burner was therefore 
lowered a quarter of an inch, and in this position the following 
obsenrations were made : — 

Table VIII. — ^Pure carbonic acid gas. 



Tension, in 




per UK). 


inches. 


Deflection. 


10 . . 


. . 28-2 


45-5 


1-5 . . 


. . 81-5 


60-8 


20 . . 


. . 830 


581 


2-5 . . 


. . 84-5 


55-6 


80 . , 


. . 85-5 


57-2 


Total heat 


. . 450 


1000 



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116 Mr. W. F. Barrett on a Phyiical 

We have here raised the absorption by the pure gas, but the 
calculated percentage is still very wide of the mark. Theoreti* 
cally^ nearly 1*6 inch of the pure carbonic acid should give the 
same absorption as 30 inches of breath from bag No. IV. The 
discrepancy was evidently not owing to any external cause; and 
the only difference was, that in the case of breath the carbonic 
acid was mixed with air, whilst with the pure gas no such medium 
was present. Possibly the air might have had an effect upon 
the carbonic acid somewhat similar to that which it is known 
to have upon aqueous vapour, by preventing any partial conden- 
sation of the gas. The following is the result of an experiment 
made to decide this question : — 

Table IX. — Pure carbonic acid gas and dry air. 

Tension^ in Deflection. Ahsorption 

inches. o per 100. 

10 29-8 44-4 

1-3 320 47-7 

Tube now filled with dry air . 342 53*8 

Total heat 46-1 1000 

Here carbonic acid at 1*3 inch tension absorbed nearly 47'7 
per cent, of the heat from the carbonic oxide flame ; but when 
28 inches of dry air, perfectly inert when alone, were added to 
the gas in the tube, the absorption was raised to 53*8, or more 
than 6 per cent. This singular effect is most probably owing to 
the cause above mentioned, namely, that carbonic acid at small 
tensions is partially condensed on the polished surface of the 
interior of the tube : the entrance of dry air removes the film, 
and consequently throws a larger amount of gas in the path of 
the rays from the source. Many experiments were made to put 
this result beyond doubt, and to determine with certainty the 
absorption by carbonic acid at different tensions when it was 
mixed with dry air. It was found to be the best mode of experi- 
ment to admit into the tube a certain quantity, say 20 inches, of 
dry air first, observing its absorption, if any, and when the 
needle was at zero, adding a definite amount of pure carbonic 
acid to the air in the tube. The quantity of gas admitted was 
accurately found by observing, through a magnifying lens, the 
depression of the barometer-gauge attached to the air-pump, 
and which was in communication with the experimental tube. 
The following Table contains some of the results : — 



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Analysis of the Human Breathe 



117 



Table X. — ^Dry air and carbonic acid gas. 



20 inches of dry air^ admitted^ 

first, gave J 

1*2 inch of carbonic acid 

1-5 

2-0 

Total heat 



7> 





Abaori >tion 
perlDO. 


Deflection. 


do 


00 


34-5 


510 


85-5 


53-4 


370 


57-3 


47-5 


100-0 


00 


00 


31-5 


48-4 


321 


49-4 


32-7 


50-7 


33-2 


520 


33-6 


52-9 


33-9 


53-5 


35 


561 


37-8 


640 


46-0 


1000 



20 inches of dry air 
1 inch of carbonic acid 

11 „ ,, 

1*4 

*- ^ 3> }> 

2*0 inches „ 

50 

Total heat . • • • 

I next tried to determine the. absprption by carbonic acid at 
lower pressures than one inch^ but found that when the gas was 
added to the air in the tube^ it required to obtain a certain ten- 
sion before absorption became manifest. Although one-tenth of 
an inch of gas can be easily measured when added to one or two 
inches of carbonic acid already in the.tube> yet one, two, or 
even three tenths, when admitted into an e^^hausted tube, show 
scarcely an appreciable absoi*ption. 

Table XL — Dry air and carbonic acid gas. 

Deflection; Absorption 



21 inches of dry air first 
O'l inch of carbonic acid 
0-2 
0-3 
0-5 
10 

1'2 ,> yj 

1*3 „ „ 

1** » » 

1-7 » „ 

2*0 inches „ 



O-O 

0-5 

05 

0-5 

21-5 

32-3 

33-2 

33-4 

33-8 

360 

35-9 

Bemaining 7 inches of dry air 36*0 

Total heat 46-6 



per 100. 

0-0 

0-7 

0-7 

0-7 

821 

48-2 

50-4 

50-9 

51-8 

54-5 

56-8 

570 

1000 



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118 Mr. W. F. Barrett on a Pkfrieal 

It will be aeen in the above Table that the absorption suddenly 
rises at five-tenths of an ineh : it will also be observed that the 
effect of filling the tube with 7 inches of dry air adds scarcely 
anything to the previous absorption. 

These results, with a few others not before recorded, are placed 
together in the following Table, in which the first column shows 
the absorption by carbonic acid alone, and the second the absorp- 
tion by the same amounts of carbonic acid added to about 20 
inches of dry air, the absorption by the latter being nil : — 









TIblb XII. 






. c 


Absorption per 


100 by 


Tension, in 


'Srbonic add 


Dry air and 


inehes. 


gas alone. 


caibonic acid, 


05 . . . 


• ••• 


821 


10 








450 


48-4 


10 








44-8 


48-2 


11 








••• 


49-4 


1-2 








••■ 


510 


1-2 








••• 


50-7 


1-2 








••• 


60-4 


1-8 








47-7 


520 


1-4 








• •• 


52-9 


1-4 








• •• 


61-8 


1-5 








50-8 


58-4 


1-5 








• •• 


58-5 


1-7 








51-2 


54-5 


20 








581 


57-3 


20 








580 


56-8 


20 








580 


561 


2-5 








54-9 


• •• 


2-5 








. 541 


• •• 



The slight discrepancy between some of the repeated observa- 
tions is probably the result of a small chemical difference in the 
carbonic acid prepared at different periods. 

This Table gives us the power of calculating the percentage of 
carbonic acid in the different samples of breath ; to obtain greater 
accuracyi omissions in Table XII.,'and the intervals between the 
tenths of an inch, are calculated and given with the mean expe- 
rimental results in the annexed Table. 



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Antdffiis of the Human Breath. 119 

Table XIII. 

Tension of gas, in Absorption per 100 by 

parts of an inch: carbonic acid and dry air. 

0-5 321 

10 48-8 

1-05 48-8* 

11 49-4 

115 500* 

1-2 50-7 

1-25 51-3* . 

1-3 520 

1-35 52-3* 

1-4 52-6 

1-45 ..... 530* 

1-5 53-4 

1-55 63-7* 

1-6 ..... 540 

1-65 54-3* 

1-7 54-5 

1-76 ..... 54-9* 

1-8 55-2* 

1-9 55-9* 

20 56-5 

Referring to the absorption by 30 inches of breath in bag 
No. 11. given in Table V. and found to be 52*8 per cent., we next 
compare this absorption with the nearest approach to it seen in 
the above Table; this is at 1*4 of an inch tension; this amount 
of carbonic acid, when mixed with 20 inches of dry air, absorbs 
52*6 per cent, of the entire radiation from a carbonic oxide flame. 
We may therefore conclude that the absorption by 30 inches of 
breath in this case is approximately the same as by 1*4 inch of 
carbonic acid ; from which we obtain 4*66 as the percentage of 
carbonic acid in the breath of bag No. II. Let us now turn to 
the analysis made by Dr. FranUand of the same breath. In 
Table VI. we find he states this expired air to contain 4*656 of 
carbonic acid. Our determination is therefore a remarkably 
close approximation, considering the novelty of this analysis by 
physical means, and the difficulties attending these first experi- 
ments. 

A number of other specimens of breath taken at difierent 
periods were examined ; their absorption and the percentage of 
carbonic acid are given in the following Table. Dr. Frankland 

* llie absorptiona: t^ua. marked have been intercalated. 

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120 On a Pkyncal Analysis of the Human Breath. 

having analyzed only the first foar^ the other determinations 
remained unchecked. 







Table XIV. 






Abwwptioii 

By 30 inchet 
of breath. 


per 100 

By pare car- 
bonic add 
and dry air. 


Tension of CO*, 

in parts of an 

inch. 


Percentage of caibonie 
add found 


Bag 
No. 


By absorp. By chemical 
tion. analysis. 


I. 


. 50-6 


50-7 


1-2 


400 4-311 


II. 


. 52-8 


52-6 


1-4 


4-66 4-556 


III. 


. 53-7 


53-7 


1-55 


5-16 4061 


ly. 


. 540 


540 


1-6 


5-33 5-212 


V. 


. 500 


500 


115 


3-83 


VI. 


. 52-7 


52-6 


1-4 


4-66 


VII. 


. 500 


500 


115 


3-83 


VIII. 


. 52-1 


520 


1-3 


4-33 



The percentage of carbonic acid foand in bags No. II. and IV. 
only vary 0*1 from the chemical analysis ; even this small dif- 
ference will disappear in extended and repeated experiments. 
In bag No. I. the difference amounts to 0*3 per cent. : this 
would be considerable in a chemical analysis; but bearing in 
mind the small data upon which the physical determinations are 
made^ it is sufficiently near to prove the correctness of the prin- 
ciple and the general accuracy of the observations. Bag No. III. 
shows a difference of upwards of 1 per cent, between the physical 
and chemical analyses. This anomaly has already been referred 
to^ and may be accounted for by supposing that the material 
of which the bag is conoiposed had imparted to the breath con- 
tained in it an impurity which could not be detected by chemical 
analysis^ but which strongly influenced the more deUcate mode 
of experiment. 

In order to make these preliminary experiments complete^ and 
to imitate as nearly as possible the condition of the breath as it 
entered the experimental tube^ the following experiment was 
made. 

A glass bolt-head^ having rather a larger capacity than the 
brass tube^ was fitted vrith a cap and stopcock and well exhausted. 
It was connected with the gauge of the air-pump^ and also with 
drying-tubes, leading to a gas-holder containing carbonic acid. 
A stopcock was now carefully opened^ and 1*4 inch of dry car* 
bonic acid allowed to enter the bolt-head. The stopcodc was 
then promptly closed^ the drying-tubes and gas-holder removed, 
and pure dry air caused to fill the glass vessel. Thus a mixture 
was obtained containing 1*4 part of carbonic acid, and 28*6 
parts of pure air, this being about the average composition of 



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On the^Change of Climate during Geological Epochs, \%\ 

bieath. The bolt-head was next counected with the experi- 
mental tube^ and the latter thoroughly exhausted^ the source of 
heat and the tube remaining the same as in previous experi- 
ments* Communication between the bolt-head and tube was 
then made, and closed when the barometer-gauge had sunk 15 
inches. The needle showed a deflection of 28^*1, or an absorp- 
tion of 43*3 per cent. When the whole contents of the bolt- 
head were allowed to diffuse themselves between the vessel and 
the tube, it was found that the mercury of the gauge had sunk 
nearly 17 inches. The absorption found in the last observation 
was therefore due to rather less than half the quantity of gas 
admitted into the bolt-head. 

After the tube had been cleansed and exhausted, 0*7 inch of 
carbonic acid was allowed to enter : this quantity of gas gave an 
absorption of 347 per cent. ; but when 14-3 inches of dry air 
were added to the gas in the tube, the absorption rose to 43*6 
per cent. The absorption of the mixture from the bolt-head, 
containing rather less than 0*7 inch of carbonic acid, was found 
to be 43*3 per cent. Thus no difference exists between the ab- 
sorption when carbonic acid and dry air are admitted into the 
tube together, or when they are allowed to enter successively. 

In the first section of this paper some experiments are recorded 
which determine the absorption by the carbonic acid in the atmo- 
sphere. The amount of carbonic acid producing this absorption is 
so extremely small, that it is impossible to measure anything like 
its quantity with the barometer attached to the air-pump. A 
tension of only '012 of an inch of the pure gas should theoreti- 
cally be equal to 30 inches of common air. As yet, therefore, 
this estimation cannot be made; though possibly it might 
he accomplished by making use of the rectangular barometer 
invented by Cassini and Bernoulli, and also by admitting the 
carbonic acid after it has been mixed with air in a large receiver. 

Royal Instttution, 
Jidy 1864. 



XIII. On the Physical Cause of the Change of Climate during Geo- 
logical Epochs. By James Croll*. 

NO fact in geological science is better established than that 
in former periods of our earth's history great changes 
of climate, in so far at least as the northern portions are con- 
cerned, must have taken place. But although there is universal 
agreement among geologists in regard to the fact of those changes 
having taken place, yet there is the greatest diversity of opinion 

* Commuiiicated by the Aathor. 



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1 22 Mr. J. Croll on the Phyrieal Cau8e of the 

regarding their cause and origin. The great dirersity aad ei« 
treme character of those changes^ as indicated by the remains of 
ancient ./Zorie ejid fauna, are such as to render it difficult to find 
anypossible cause adequate for the effect. 

The point regarding which the greatest difficulty has been 
felt^ is in accounting for the extreme cold of the glacial epochs 
and the warm and tropical character of the carboniferous. 

Before entering on the consideration of a cause which appears 
in a great measure to have been overlooked by geologists^ we 
shall briefly refer to a few of the more prominent theories which 
have been advanced to account for those changes. 

The warm character of the climate during the Silurian^ Car- 
boniferous and other periods of the Palaeozoic age^ was at one 
time generally referred by geologists to the influence of the 
earth's internal heat. But it has been proved by Professor 
William Thomson* that the general climate of our globe coold 
not have been sensibly affected by internal heat at any time 
more than 10^000 years after the commencement of the solidi- 
fication of the surface. And Mr. Hopkins has concluded t that the 
present effect of internal heat is only about ^th of a degree on 
the mean superficial temperature. Professor W. Thomson^ from 
calculations based upon more correct data, has lately found that it 
only amounts to about^jth of adegree ]:. Professor Phillips, how- 
ever, is still of opinion that the warm climates of ancient epochs 
may have been due to the influence of internal heat. He does not 
question the correctness of the calculations made by Thomson^ 
Fourier, Poisson, and others, but thinks that they have over- 
looked the fact that the condition of the earth^s atmosphere, as 
regards its power of conducting heat, might have been different 
in former ages from what it is at present. " The state of the 
atmospheric mantle/' he says, ''which envelopes the terraqueous 
globe, mitigates solar heat and stellar radiation, and, like the 
clothing of a steam cylinder, prevents excessive waste of the 
warmth treasured within ''§. It is quite true, ^as Professor 
Phillips suggests, that a diminution in the conductivity or in 
the diathermancy of the earth's atmosphere, and an increase in 
its height, would increase the influence of internal heat on the 
climate. But when we reflect that under the present condition 
of the atmosphere the internal heat could not even sensibly 
affect the climate after the short period of 10,000 years from 
the commencement of solidification of the earth's surface, it 
appears very improbable that our atmosphere could have ever 

♦ Phil. Mag. for January 1863. 

t Journal of the Geological Society, vol. viii. 

X Proceedings of the Royal Society of Edinburgh for March 21, 1864. 

§ Life on the Earth, p. 163. 



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Change of Climate during Geological Epochs. 123 

been so far different from what it is at present^ that by 
means of it the internal heat conld have produced and main- 
tained that high temperature of climate which is supposed by 
some to have prevailed during the long Palaeozoic ages of the 
earth^s history. And besides^ the important fact is overlooked 
that any change in the condition of the atmosphere which 
would prevent the dissipation of the earth's internal heat into 
lurrounding space^ such as .an increase in the quantity of 
aqueous vapour contained in the atmosphere^ would at the same 
time tend to lower the temperature of the earth's surface by 
diminishing the quantity of radiant heat reaching the surface 
from without. Such a state of things would no doubt equalize^ 
to a certain extent, the extremes of summer and winter tem- 
perature, but would not very sensibly increase the mean, annual 
temperature of the climate. In fact it would rather have an op- 
posite tendency. 

Some have attempted to account for the change of climate 
by assuming that the earth's axis of rotation may have shifted 
its position in consequence of the uprising of large mountain 
masses on some part of the earth's surface between the equator 
and the poles. But it has been shown by Professor Airy* and 
others, that the earth's equatorial protuberance is such, that no 
geological change on its surface could ever possibly alter the 
position of the axis of rotation to an extent which could at all 
sensibly affect the climate. 

Others, again, have tried to explain the change of climate by 
supposing, with Poisson, that the earth during its past geological 
history may have passed through hotter and colder parts of 
space. This, to say the least of it, is not a very satisfactory hy- 
pothesis. There is no doubt a difference in the quantity of 
force in the form of heat passing through different parts of space ; 
but space itself is not a substance which can possibly be either 
cold or hot. If we adopt this hypothesis, we must therefore 
assume that the earth during the hot periods must have been in 
the vicinity of some other great source of heat and light besides 
the sun. But the proximity of a mass of such magnitude as 
would be sufficient to affect to any great extent the earth's cli- 
mate would, by its gravity, seriously disarrange the mechanism 
of our solar system. Consequently if our solar system had ever 
during any former period of its history really come into the vi- 
cinity of such a mass, the orbits of the planets ought at the 
present day. to afford some evidence of it. But again, in order 
to account for a cold period, such as the glacial epoch, we have to 
assume that the earth must have come into the vicinity of a 

* Athenaeum for September 22, I860. 

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12i Mr. J. Croll on the Physical Cause of the 

cold body. ABtronomical science affords not the sliglitest evi- 
dence in favour of such an hypothesis *. 

A theory has lately been propounded by Prof. Franklandfj 
wherein the changes of climate experienced by our earth during 

East epochs is referred to a difference in the influence of internal 
eat on the sea and on land. He concludes that the cooling of the 
floor of the ocean would not proceed so rapidly as if it had been 
freely exposed to the air. And hence it would continue at a 
comparatively high temperature long after the surface of the 
dry land had reached its present mean temperature. And as 
heat is transmitted from the bottom to the surface of the ocean^ 
not by conduction^ but by convection, viz. by the warm stratum 
of water in contact with the bottom rising to the surface, the 
temperature of the ocean would consequently be higher than 
the mean temperature of the earth^s surface. He concludes 
that this state of things satisfactorily accounts for the glacial 
epoch. " The sole cause of the phenomena of the glacial epoch/^ 
he says, ^^was a higher temperature of the ocean than that 
which obtains at present." 

The high temperature of the ocean, he believes, would give 
rise to augmented atmospheric precipitation. This would pro- 
duce such an accumulation of snow during winter months as 
would defy the heat of summer to melt. The overcast sky 
during summer, caused by the great amount of evaporation, 
would intercept the sun^s re^ys/md thus reduce the summer's 
temperature. 

While admitting the general correctness of Prof. Frankland's 
theory, we, however, fear that it does not altogether harmonize 
with the facts of geology. There is no evidence to support the 
conclusion that the ocean was warmer duriug the glacial epoch 
than at present; but, on the contrary, we have geological 
evidence to conclude that it must have been much colder than 
at present. For example, on examining the fauna of the marine 
drift of that period, we find that it is decidedly of an arctic cha- 
racter, indicating the low temperature of the seas during that 
epoch. These beds show, for example, that our British seas 
during that period contained in abundance numerous species of 
shells which are now only to be found in more northern lati- 
tudes X' Ii^ the glacial drift of Scotland alone there have been 
found the following species of an arctic character, and which are 

* See Mr. Hopkins's remarks on this theory. Journal of the Geological 
Society, vol. viii. 

t Phil. Mag. for May 1864. 

X This important fact was first noticed by Mr. Smith of Jordan Hill, 
and communicated to the Wernerian Society in the early part of 1839. 
See his Collected Papers published by John Gray, Glasgow. 



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Change of Climate during Geological Epochs. 125 

novf extinct in our British seas^ viz. Mya Uddevallensis, Saxicava 
rugosa, Tellina proxima, Thracia myopsis, Astarte arctica, Leda 
minuta, Leda truncata, Leda oblonga, Pecten Gromlandicus, 
Pecien Islandicus, Margarita cinerea, Turritella erosay Scalaria 
Groerdandica, Natica clama, Velutina undata, Buccinum ciliatumy 
Fusus carinatus, Cylichna alba. Other arctic shells^ such as 
the Panopaa Norvegica, Puncturella Noachina, Nucula tenuis, 
Trophon clathratus, Trophon scalariformis, Natica pusilla, Natica 
helicoides, Trichotropis borealis, Saxicava arctica, Hypothyris 
psittacea, Margarita undulata, Margarita helicina, Buccinum 
Humphreysianum, Cyprina Islandica, existed during the glacial 
epoch in great abundance in our British seas^ but are now fast 
dying out in the deep and cold recesses of the ocean where they 
have retreated in order to find a temperature more congenial to 
their nature*. 

We freely admit that a warmer sea and a colder land would 
tend to produce an accumulation of snow and ice such as pre- 
Tailed during the glacial period. And did the facts of geology 
and the principles of physical science favour the idea that the 
sea during that period was warmer than at present^ we should 
assuredly admit the warm sea to be at least one of the causes 
of the glacial epoch. But when the very same result may be 
conceived to follow upon the contrary supposition, which agrees 
better with the evidence of geology — ^that the sea was actually 
colder during the glacial period than at present — we feel incUned 
to refer the cold of that period to some other cause than to a 
warm sea. That a reduction of the mean temperature of both 
land and sea in our latitude would produce the same effect, will 
be obvious to all who will but reflect that at the present day 
there exists in places where the mean annual temperature is not 
much above the zero of the Fahrenheit scale, glaciers in magni- 
tude equal to, if not greater than any which covered our valleys 
dnring the glacial epoch. At the present day there are glaciers 
upwards of 50 miles in breadth, and 2000 feet in depth, 
merging into the cold and frozen seas around the north of 
Greenland f- Greenland at the present day is probably a re- 
presentation of what our island was during the glacial period. 

Of late, evidence of the most conclusive character has been 
adduced by Prof. Ramsay and others of the existence of a 
glacial epoch in this country during the far back Palaeozoic age. 

♦ See a valuable paper " On the Glacial Drift of Scotland," by 
Archibald Geikie, F.R.S.E., F.G.S. John Gray, Glasgow, 1 863. See also 
a paper by Prof. E. Forbes " On the Connexion between the Distribution 
of the existing Fauna and Flora of the British Isles, and the Geological 
Changes which have affected their area during the period of the Northern 
Drift" (Memoirs of the Geological Survey, vol. i.). 

t See Dr» Kane's 'Second Expedition/ voL i. chap, xviii. 



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126 Mn J. Cfoll on the Physical Cauie of the 

But the existence of glacien in such an early age ia certainly iii* 
consistent with Prof. Frankland's theory, and in fact with every 
possible theory based upon the principle of internal heat. 

Prof. Frankland accounts for the glaciers of the Fennian 
period as follows : — 

^^I have already argued/' he says, ''that perpetual snow 
would first tip the mountain peaks, and then slowly and gra- 
dually descend to the sea-level. But it must be borne in mind 
that during the whole of the pre-glacial period the atmo* 
spheric precipitation was even greater than during that period, 
and consequently wherever the land rose well above the snow- 
line, glaciers, on a scale far surpassing any of the present time, 
would be the inevitable consequence " *. 

But glaciers on the sides of elevated mountains will not ex- 
plain the facts of the Permian breccia. These breccias afford 
conclusive evidence that in that early age our British mT)untaiii8 
were not only covered with perpetual snow, but must have had 
glaciers stretching into the sea, and breaking up and floating 
away as icebergs in a manner similar to what we find occurring 
in Greenland at the present day. We cannot do better than 
state the matter in Prof. Ramsay's own words. 

'' These breccias are chiefly formed of the moraine-matter of 
glaciers, drifted and scattered in the Permian sea by the agency 
of icebergs . . . They were therefore deposited in water with 
considerable regularity, and, as we have seen, over a large area* 
It is altogether unlikely that the stones were poured into the 
sea by rivers in the manner in which some conglomerates are 
formed on steep coasts where mountain-ridges nearly approach 
the shore, 1st, because the fragments, being derived almost 
exclusively from the Longmynd country, if the sea then washed 
its old shores, no river-currents passing out to sea could carry 
such large fragments from thirty to fifty miles beyond their 
mouths and scatter them promiscuously along an ordinary sea- 
bottom ; and, 2ndly, if the rivers merely passed from the Long- 
mynd across a lower land to the sea, transporting stones and 
blocks of various size, these would have been waterwom on 
their passage seaward after the manner of all far-transported 
river-gravels, whereas many of the stones are somewhat flat, like 
slabs, and most of them have their edgea but little rounded ''t« 

If we adopt the theory that the climate of our globe has been 
gradually becoming colder during all past ages, in consequence 
of the gradual diminution of the influence of internal heat, how 
are we to account for the glaciers and icebergs of the Permian 

* Phil. Mag. for May 1864. 

t JoumaL of the Geological Society, vol ad. p. 198. 



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Change ofChmate during Geological Epochs. 127 

periods following as they really do immediately after ^the warm 
coal-period ? 

Passing beyond the coal-period to the earlier age of the Old 
Bed Sandstone, we again meet with the evidence of glacial ac- 
tion*. 

It was long ago suggested by Agassiz^ that the ancient climate 
was subject to alternate depressions and risings of temperature, 
coinciding with great destruction and renewal of life. Modem 
geological investigation seems to favour this conjecture. '^ Thus, 
looking/^ says Mr. Page, "at the Cambrian strata of the 
northern hemisphere— their angular grits and conglomerates, 
their extreme paucity of fossil forms, and other features — we 
are at once reminded of the action of ice and the presence of 
ungenial conditions. This is followed over the same areas by 
the more genial and exuberant period of Siluria; which is in 
torn succeeded by the Old Red Sandstone, whose grits and 
bouldery conglomerates, as well as paucity of vegetable forms, 
once more suggest the recurrence of colder influences. Follow- 
ing the Old Red, we have the exuberant flora and fauna of the 
cosd-period, again to be succeeded by the scanty life-forms and 
grits and conglomerates of Permia. Again the trias and oolite 
of the northern hemisphere are characterized by life-forms that 
betoken warm and genial conditions ; while the chalk that suc- 
ceeds imbeds water^wom blocks of granite and lignite, which 
would seem to imply the presence of ice-drift and deposit in 
seas that were open to boreal influences. Next the early terti- 
aries occur over the same areas, marked by plants and animals 
that indicate a warm and genial climate ; and this in turn gives 
place to the well-known glacial or boulder-drift epoch, once 
more to be succeeded by the milder influences of the post-ter- 
tiary or current era '^ t- 

The principal cause why geologists have been so slow in ad* 
mitting the existence of cold epochs during the earUer ages of 
our earth's history, is the idea still entertained by some, that, 
owing to the influence of internal heat, the climate of our globe 
was then very much warmer than at present, and that, ever since, 
it has been gradually growing colder and colder in consequence 
of the decrease of internal heat. But, as we have already seen, 
the notion is quite erroneous. If the climate in former ages was 
wanner than at present, the cause must be sought for elsewhere. 
* Some have referred the change of chmate to a difierence in 
the distribution of land and sea. It has been supposed by some, 

* See * The Past and Present Life of the Globe.' By David Page, 
F.G.S., p. 91 ; and 'Advanced Text-Book,' p. 132. 
t The Past and Present Life of the Globe, p. 190. 



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128 Mr. J. Croll on the Phtfsical Came of the 

for example^ that the cold of the glacial epoch might result 
from the absence of the Gulf-stream during that period. 

Mr. Hopkins calculates that the absence of the Gulf-stream 
would lower the mean temperature of January 24® F. in the 
north of Scotland^ but could have no sensible influence on the 
July temperature of London, or places in western Europe further 
to the south*. 

Mean annual temperature due to the Gulf-stream. 

Iceland 18 F. 

North of Scotland . • • 12-25 

Snowdon 7*5 

Alps 3 

Were the indications of ancient glaciers confined to the 
western parts of Europe, the absence of the Gulf-stream might 
to a considerable extent account for the phenomena of the glacial 
period. But we know that the glaciation extended over the 
greater part of northern Europe and northern America. It is 
perfectly evident that the absence of the Gulf-stream in our seas 
could not, for example, greatly lower the temperature of the 
climate of North America. Neither would a decrease of 3° F. 
in the mean annual temperature of the Alps, account for the 
enormous glaciers which we know existed there during that 
period. 

Sir Charles Lyell supposes that, were the land all collected 
round the poles while the equatorial zones were occupied by the 
ocean, the temperature of the climate would be lowered to an 
extent that would account for the glacial epoch. And on the 
other hand, were the land all collected along the equator, while 
the poles were covered with sea, a temperature such as existed 
during the coal-period might be produced. Professor Phillips 
admits that if the land were all collected round the poles, the 
temperature of the globe would be lowered ; but he remarks, 
truly, that this supposition does not agree with the observed 
facts regarding the glacial deposits, for these require deep sea 
over much of what is now in circumpolar zones. Professor 
Phillips appears to doubt very much whether the collecting of 
the land along the equator would sensibly increase the tempera- 
ture of the globe; but suggests that the rise of temperature 
might result from the land being divided into low islands scat- 
tered over the area of the globe, amidst large breadths of water. 
But he brings forward no geological evidence in favour of such 
a state of distribution of land and sea during the warm epochs. 
It is perfectly evident that if the great changes of climate 

* Journal of the Geological Society, vol. viii. 



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Change of Climate during Geological Epochs. 129 

whieh have been experienced by our globe are to be attributed 
to. differences in the distribution of sea and land^ changes oa 
the earth's surface of the most extravagant and unlikely character 
mudt be assumed to have taken place. Another objection which 
we have to all these hypotheses which have come under our con- 
sideration is^ that every one of them is irreconcileable with the 
idea of a regular succession of colder and warmer cycles. 

The recurrence of colder and warmer periods evidently points 
to some greats fixed^ and continuously operating cosmical law. 

We have already referred to the hypotheses of our system 
passing through colder and hotter parts of space^ and of the 
shifting of the earth's axis of rotation^ and have shown that they 
receive no support whatever from the known facts and principles 
of physical science. The true cosmical cause must be sought 
for in the relations of our earth to the sun. 

There are two causes affecting the position of the earth in rela- 
tion to the sun, which must, to a very large extent, influence the 
earth's climate; viz., the precession of the equinoxes and the 
change in the excentricity of the earth's orbit. If we duly examine 
the combined influence of these two causes, we shall find that the 
northern and southern portions of the globe are subject to an 
excessively slow secular change of climate, consisting in a slow 
periodic change of alternate warmer and colder cycles. 

In a paper read before the Geological Society in 1830 *, Sir 
John Uersdiel directed attention to the probable influence of 
the change in the excentricity of the earth's orbit as a cause of 
the change of climate during geological eras. But as no trust- 
worthy calculations had then been made regarding the superior 
limit of excentricity, he was unable to arrive at any positive re* 
suits on the subject. It is true that Lagrange had investigated 
the subject, and had arrived at results which were afterwards 
found to be almost correct ; but as this geometer had assigned 
very erroneous values to the masses of. the smaller planets, not 
much confidence could be placed in his results. 

Owing to his not having taken fully into consideration certain 
conditions which greatly affect climate. Sir John Herschel seems 
to have been of opinion that the general climate of our globe 
cannot be much affected by the change in the excentricity of its 
orbit, and this perhaps is the reason which has led geologists in 
general to take for granted that the changes in ancient chmate 
cannot be attributed to this cause. 

Both the superior and the inferior limit of excentricity have 
now been determined by M. Leverrier, and it may be well to 
examine to what extent climatic changes may be referable to 
this cause. 

* Tramnctioos of the Geological Society, 2nd series, vol. iii. p. 295. 
PhU. Mag. S. 4, Vol. 28. No. 187. Aug. 1864. K 



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180 Mr, J. Croll on the Pkytieal Cause of the 

According to the calculations of Leverrier^ the superior limit 
-•of the earth's ezcentricity is '07775, and the inferior limit 
-008814. The excentrici^ is at present diminishing, and will 
eontinue to do so during 28,980 years from the year ISOO'i^. 

The change in the excentricity of the earth's orbit may affect 
the climate in two different ways ; viz., it may affect the climate 
by either increasing or diminishing the mean annual amount of 
heat received from the sun, or it may affect it by either increas- 
ing or diminishing the difference between summer and winter 
temperature. 

Let us consider the former case first. The total quantity of 
beat received from the sun during one revolution is inversely 
proportional to the minor axis. 

The difference of the minor axis of the orbit when at its 
maximum and its minimum state of excentricity is as 997 to 
1000. This small amount of difference cannot therefore sensibly 
affect the climate. Hence we must seek for our cause in the 
second case under consideration. 

When the excentricity is at a maximum, the distance of the 
sun from the earth, when the latter is in the aphelion of its 
orbit, is no less than 102,256,878 miles ; and when in the 
perihelion it is only 87,503,039 miles. The earth is therefore 
14,753,834 miles further from the sun in the former positioi^ 
than in the latter. The direct heat of the sun being inversely 
as the square of the distance, it follows that the amount of heat 
received by the earth when in these two positions will be as 
19 to 26. According to the determinations of Hansen le* 
garding the present excentricity of the earth's orbit, the earth 
during winter, when nearest to the sun, is 93,286,707 miles 
distant. Suppose now that, according to the precession of the 
equinoxes, winter in our northern hemisphere should happen 
when the earth is in the aphelion of its orbit, at the time when 
the orbit is at its greatest excentricity \ the earth would then be 
8,970,166 miles further from the sun in winter than at present 
The direct heat of the sun would therefore be one-fifth less 
during that season than at present; and in summer one-fifth 
more than at present. The difference between the heat of 
summer and winter in this case would be two-fifths greater than 
at present. This enormous difference would affect the chmate to 
a very great extent. But if winter under these circumatanoes 
should happen when the earth is in the perihelion of its orbit> 
the earth would then be 14,753,834 miles nearer the sun in 
winter than in summer. In this case the difference between 
¥dnter and summer in the latitude of this country would be 
almost annihilated. But as the winter in the one hemispkefe 
* CcmMKUsance det Tempi for 1843 (Additions). 



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Change of Climate during Geological Epochs. ISl 

corresponds with the summer in the other^ it follows that while 
the one hemisphere would be enduring the greatest extremes of 
summer heat and winter cold^ the other would be enjoying a 
perpetual spring. 

It is quite true that whatever may be the excentricity of the 
earth's orbit, the two hemispheres must receive equal quantities 
of heat per annum ; for proximity to the sun is exactly com- 
pensated by the effect of swifter motion. The total amount of 
heat received from the sun between the vernal and autumnal 
equinoxes is the same in both halves of the year, whatever the 
excentricity of the orbit may be. For example, whatever extra 
heat the southern hemisphere may at present receive from the 
sun during its summer months in consequence of greater 
proximity to the sun, is exactly compensated by a corresponding 
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, is exactly 
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. It will be observed, however, 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 takes place. The southern hemi- 
sphere, for example, has not only a colder winter than the 
northern, in consequence of greater distance from the sun, but 
it has also a longer winter. And this extra loss of heat from 
radiation is not compensated by its nearness to the sun during 
summer months ; for, as we have already seen, it gains nothing 
in consequence of proximity. And on the same principle our 
winter in the northern hemisphere, in consequence of our 
proximity to the sun, is not only warmer than that of the 
southern hemisphere, but is also at the same time shorter. 
Consequently our hemisphere is not cooled to such an extent as 
the southern. It follows therefore, other things being equal, that 
the mean temperature of the winter half year, as well as the 
intensity of the sun's heat, must be inversely as the square of 
the sun's distance. But it is not on this change in the mean 
winter temperature, as we shall presently see, that the change of 
climate chiefly depends. 

The Climate of the Carboniferous Epoch. 
It is the generally received opinion among both geologists 
and botanists that the^ora of the coal-period does not indicate 
the existence of a tropical, but a moist, equable, and temperate 

K2 



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132 Mr. J. Croll on the Physical Cause of the 

eliinate. '^ It seems to have become/^ says Sir Charles Lyell, 
" a more and more received opinion that the coal-plants do not, 
on the whole, indicate a climate resembling that now enjoyed in 
the equatorial zone. Tree-ferns range as far south as the 
southern parts of New Zealand, and Araucarian pines occur in 
Norfolk Island. A great preponderance of ferns and lyco- 
podiums indicates moisture, equability of temperature, and 
freedom from frost, rather than intense heat'**. 

Mr. Robert Brown considers that the rapid and great growth 
of many of the coal-plants showed that they grew in swamps 
and shallow water of equable and genial temperature. 

'^ Generally speaking," says Mr. Page, *' we find them resem- 
bling equisetums, marsh -grasses^ reeds, club-mosses, tree-ferns, 
and coniferous trees ; and these in existing nature attain their 
maximum development in warm, temperate, and subtropical, 
rather than in equatorial regions. The Wellingtonias of Cali- 
fornia and the pines of Norfolk Island are more gigantic than the 
largest coniferous tree yet discovered in the coal-measures '*t* 

The coal-period was not only characterized by a great pre- 
ponderance over the present in the quantity of ferns growing, 
but also in the number of different species. Our island pos- 
sesses only about 50 species, while no fewer than 140 species 
have been enumerated as having inhabited those few isolated 
places in England over which the coal has been worked. And 
Humboldt has shown that it is not in the hot, but in the 
mountainous, humid, and shady parts of the equatorial regions 
that the family of ferns produces the greatest number of species. 

^^Dn Hooker thinks that a climate warmer than ours now is 
would probably be indicated by the presence of an increased 
number of flowering plants, which would doubtless have been 
fossilized with the ferns ; whilst a lower temperature, egtud to the 
mean of the seasons now prevailing, would assimilate our climate 
to that of such cooler countries as are characterized by a 
disproportionate amount of ferns *' J. 

The enormous quantity of the carboniferous flora shows also 
that the climate under which it grew could not have been of a 
tropical character, or it must have been decomposed by the heat. 
Peat, so abundant in temperate regions, is not to be found in 
the tropics. 

The condition most favourable to the preservation of vegetable 
remains, at least under the form of peat, is a cool, moist, and 
equable climate, such as prevails in the Falkland Islands at the 
present day. '^In these islands," says Mr. Darwin, '^almost 

* Elementary Geology, p. 399. 

+ The Past and Present Life of the Globe, p. 102. 

X Memoirs of the Geological Survey, vol. ii. part 2. p. 404. 

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Change oj Climate during Geological Epochs, 138 

every kind of plants even the coarse grass which covers the whole 
surface of the land, becomes converted into this substance''*. 

From the evidence of geology we may reasonably infer that 
were the difference between our summer and winter temperature 
nearly annihilated^ and were we to enjoy an equable climate 
equal to, or perhaps a little above the present mean annual 
temperature of our island, we should then have a climate similar 
to what prevailed during the Carboniferous epoch. 

But we have already seen that such must have been the cha- 
racter of our climate at the time that the excentricity of the 
earth's orbit was at a maximum, and winter occurred when the 
earth was in the perihelion of its orbit. For, as we have already 
shown, the earth would in such a case be 14,753,834 miles 
nearer to the sun in winter than in summer. This enormous 
difference would almost extinguish the difference between sum- 
mer and winter temperature. The almost if not entire absence 
of ice and snow, resulting from this condition of things, would 
probably tend to raise the mean annual temperature of the 
climate higher than it is at present. 

The Climate of the Glacial and other Cold Epochs, 
In this country the greater portion of the moisture of the air 
is precipitated in the form of rain, and what happens to fall 
during winter as snow disappears in the course of a few weeks 
at most. But were the winter temperature very much reduced, 
it is obvious that what now falls during that season as rain, 
would then fall as snow. Under such circumstances it would 
be very doubtful whether the heat of summer would be sufficient 
to melt the snow of winter. Whether this would be the case or 
not would depend upon the character of the summer. Under a 
cloudless sky, the direct rays of the summer-sun would, in our 
latitude, be more than sufficient to remove the winter's accu- 
mulatiou of ice and snow. But if from thick fogs or an overcast 
sky the direct rays of the sun were prevented from penetrating 
to the earth, the heat of summer would not in such a case be 
sufficient to remove the snow and ice; and the formation of 
glaciers would be the inevitable result. Some may at first sight 
suppose that the rain of summer would be sufficient of itself to 
melt the snow of winter, but such would not be the case ; for 
it takes nearly eight tons of water at 50° F. to melt one ton of 
snow, even when the latter is already in a thawing condition. 
It is therefore perfectly evident that all the rain of summer 
would not be sufficient to melt more than one-eighth part of the 
snow of winter t. Prof. Forbes found that not more than onc- 

''' Journal of Researches, chap. xiii. 
t Phil. Mag. for May 1864. 



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134 . Mr. J. CroU an the Physical Cause of the 

fiftieth part of the mow of Norway is liquefied by the rain of 
summer. 

The conditions necessary to the formation of glaciers would 
be secured by a state of things the reverse of what produced the 
elimate of the coal-period^ viz.^ by winter occurring when the 
earth was in the aphelion of its orbit, at the time of greatest 
excentricity. 

We have already seen that the direct heat during winter 
would, under these conditions, be nearly one-fifth less than at 
present. This would no doubt bring our mean winter tempe- 
rature below the freezing-point. The low temperature of the 
winter would not only prevent the melting of the ice and snow, 
but would cause the entire moisture of the air to be precipitated, 
not in the form of rain as at present, but as snow. It is also 
more than probable that a diminution of one-fifth in the total 
quantity of heat received from the sun during the winter months, 
would lower the tempeftiture to such an extent as would freeae 
our British seas. It is quite true that the direct heat of the son 
during the summer would be one-fifth greater than at present. 
But it is questionable whether the summers would on this ac- 
count be warmer than they are at present. The temperature of 
the summer is not always proportionate to the quantity of heat 
directly received from the sun. In the Straits of Magellan, in 
68® S. lat., where the direct heat of the sun ought to be as great 
as in the centre of England, MM. Churruca and Galeano have 
seen snow fall in the middle of summer ; and though the day was 
eighteen hours long, the thermometer seldom rose above 42*^ or 
44® F., and never above 51°*. 

The great strength of the sun's rays during summer, due to 
its nearness at that season, would, in the first place, tend to pro- 
duce an increased amount of evaporation. But the presence of 
snow-clad mountains and an icy sea would chill the atmosphere 
and condense the vapour into thick fogs. The thick fogs and 
cloudy sky would effectually prevent the sun's rays from reaching 
the earth, and the consequence would be that the snow would 
remain unmelted during the entire summer. In fact we have 
this very condition of things exemplified in some of the islands 
of the southern ocean at the present day. Sandwich Land, 
which is in the same parallel of latitude as the north of Scot- 
land, is covered with ice and snow the entire summer. And in 
the island of South Georgia, which is in the same parallel as the 
centre of England, the perpetual snow descends to the very sea- 
beach. The following is Capt. Cook's description of this dismal 
place: — ^''We thought it very extraordinary,'* he says, "that 
an island between the lat. of 54° and 55° should, in the very 
* Edinburgh Philosopliieftl Journal, vol. iv. p. 266. 



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Change of ClimaU during Geological Epochs. 185 

height of summer^ be almost wholly covered with fi^OEen snow, 
in some places many fathoms deep. . . . The head of the bay was 
terminated by iee-clifts of considerable height ; pieces of which 
were eontinually Jbreaking off^ which made a noise like a cannon. 
Nor were the interior parts of the country less horrible. The 
savage rocks raised their lofty summits till lost in the clouds^ 
and ralleys were covered with seemingly perpetual snow. Not 
a tree nor a shrub of any size were to be seen. The only signs 
of vegetation were a strong-bladed grass^ growing in tufts, wild 
bumet^ and a plant-like moss, seen on the rocks. . . . We are 
inclined to think that the interior parts^ on account of their ele- 
vation, never enjoy heat enough to melt the snow in such quan- 
tities as to produce a river, nor did we find even a stream of 
fresh water on the whole coast''*. 

This rigorous climate chiefly results from the rays of the sun 
being intercepted by the dense fogs which envelope the island 
during the entire summer; and the fogs, again, are due to the 
air being chilled by the presence of the snow-dad mountains, 
and the immense masses of floating ice which come from the 
antarctic seas. A reduction of one-fifth in the amount of heat 
received from the sun during winter would, in this country, 
produce a state of things as bad as, if not worse than that which 
at present exists in South Oeoi^ia. 

Some may be apt to suppose that the presence of the Oulf- 
stream would under such a condition still prevent our British 
seas from freezing during winter. We may, however, remark 
that it is not necessary for us to assume that our seas were frozen 
daring the glacial epoch. We know that the seas around Sand- 
wich Land, and the island of South Georgia, are never frozen, 
and yet the perpetual snow descends to a lower level than it does 
in Greenland or in Spitzbergen. All that seems necessary would 
be the presence of immense masses of floating ice during summer 
months, and this we should then no doubt certainly have^ not- 
withstanding the presence of the Gulf-stream. 

But if we examine the matter fully, we shall find that the 
Gulf-stream as well as the climate is affected by the change in 
the excentricity of the earth's orbit. 

It is now generally admitted that the cause of the great oceanic 
currents is the constant impulse of the trade-winds on the sur- 
face of the ocean. The trade-winds, on the other hand, owe their 
existence to the difference of temperature between the equatorial 
and polar regions of the globe. Now any cause which tends to 
increase or diminish this difference will, other things being 
equal, tend also to increase or diminish the strength of these 
aerial currents. The general tendency of the under currents of 
* Capt. Cook's Second Voyage, vol. ii. pp. 232, 235. 



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1 36 On the Change of Climate during Geological Epochs. 

the atmosphere is to pass from the polar to the equatorial regions. 
We have already seen that, as the excentricity of the earth's orbit 
increases^ the severity of the winter in the one hemisphere is 
augmented, while that in the other hemisphere is diminished. 
The glacial epochs as we have already founds probably occurred 
in Europe at the time when the winters in the northern hemi- 
sphere were at their severest, and those in the southern hemi- 
sphere at their mildest condition. The great accumulation of ice 
and snow in the northern regions, arising from the severity of 
the seasons, and its comparative absence in the southern hemi- 
sphere^ would tend to keep the air in the northern regions of the 
globe much colder than the air in the southern hemisphere, and 
the consequence would be that the aerial currents from the north 
would be stronger than those from the south. The general 
eflFect of this state of things would be to diminish the Gulf- 
stream^ as we shall presently see. 

According to Captain Duperrey, the constant ocean currents, 
of which the Gulf-stream is one, sbem all to take their rise from 
three great currents of cold water from the south pole. We 
have first the great equatorial current of the Pacific^ taking its 
rise in a cold current from the south pole. A portion of this 
equatorial current passes through the Asiatic archipelago and 
joins a second cold stream flowing into the Indian Ocean from 
the south. The cuiTent then flows westward, passes round the 
Cape of Good Hope, where it joins the third southern current, 
which passes along the western coast of Africa, and then takes a 
westerly direction, forming what is called the equatorial current 
of the Atlantic. On approaching Cape St. Boque, this current 
divides itself into two portions ; the principal portion flowing 
into the Gulf of Mexico, and forming what is known as the 
Gulf-stream, the other portion directing its course to the south 
along the coast of Brazil. 

The diminution of the aerial currents in the southeni hemi- 
sphere would tend in the first place to reduce the great currents 
of cold water from the south pole which feed the equatorial cur- 
rents j and this in turn would diminish the equatorial current 
of the Atlantic, the feeder of the Gulf-stream. The equatorial 
current being reduced, the Gulf-stream would also be reduced. 
But there is another way in which the Gulf-stream is affected 
by this state of things. At present the S.E. trades of the At* 
lantic blow with greater force than the N.E. trades, and the 
consequence is that the S.E. trades sometimes extend to 10^ or 
15° N. lat., whereas the N.E. trades seldom blow south of the 
equator. But during the glacial epoch the very reverse must 
have occurred. Hence the great equatorial current of the Atlantic 
must during that period have been driven considerably to the 



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Prof; Ste&a on the Duperiion of Light by Quartz. 137 

south of its pres^Qit position. And in this case, the configuration 
of the land being supposed to have been similar to what it is at 
present^ a greater proportion of the current would be turned into 
the southern branch along the Brazilian coast^ and of course a 
correspondingly smaller proportion would flow into the Gulf of 
Mexico. The Gulf-stream would consequently be greatly di- 
minished^ if not altogether stopped. 

If a relation could be properly established between geological 
epochs and changes of climate^ due to the change in the excen- 
tricity of the earth's orbit, we might then have some hope of being 
able to arrive, at least approximately, at a knowledge of the posi- 
tive ages of the various strata composing the earth^s crust. The 
total age of the crust itself, as we have already noticed, can be 
determined bv other means. Taking the temperature of melting 
rock at 7000^ F., Prof. William Thomson has calculated, from 
principles of cooling established by Fourier, the probable age of 
the earth's crust to be about 98,000,000 years*. The entire 
geological history of our globe must therefore be comprehended 
within this period. 

As yet no calculations have been made regarding the time 
-when the excentricity was at a maximum, or of the time required 
to pass from the maximum to the minimum state of excentricity. 
In the Annates of the Paris Observatory, vol. ii. p. 29, there 
is a Table giving •0473 for the excentricity at 100,000 years 
before the year 1800, and 0189 for the excentricity 100,000 
years after 1800. There are subordinate maxima and minima 
in that interval of 200,000 years; but the principal maximum 
I have been informed does not fall within that period. We 
may therefore safely conclude that it is considerably more than 
100,000 years since the glacial epoch. 



XIV. On the Dispersion of Light by Quartz, owing to the Rota- 
tion of the Plane of Polarization. By Prof. Stefan f. 

THERE are only two possible forms of dispersion ; to each 
colour in white light may be assigned either a particular 
velocity of propagation or a particular direction of vibration . The 
first kind of colour- dispersion occurs in refraction and diffraction ; 
the second kind when light passes through a substance which 
turns its plane of polarization, inasmuch as the rotation has a 
different magnitude for each colour. 

A spectrum resulting from the alteration of the plane of po- 

* Phil. Mag. 'or January 1863. 

t Trandated by Prof. Wanklyn from the papers issued hy the Kaiser- 
licfae Akademie der Wissenschanen in Wien, 1864, No. 15. 



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138 Prof. Stefan an the Dispersion of Light bif Qwarts, 

lariiation may be exhibited in the following manner : — ^Polansed 
light is passed through the rotating medium^ made to fall upon 
a conical mirror^ which serves as an analyzer^ and projected upon 
a screen placed perpendicular to the axis of the mirror^ The 
white light falling upon the cone appears spread out into a 
coloured fan* Or a plate of calcareous spar is introduced into a 
polarizing apparatus^ so that the ring-like figures appear small 
and near the centre of the fields whilst the black cross is spread 
over the whole field. If the pencil of rays, where it consists of 
parallel rays^ be passed through a plate of quartz cut perpen- 
dicular to the axis^ then the black cross just mentioned will be 
transformed into a coloured fan. 

The occurrence of dispersion through refraction^ or through 
alteration of the plane of polarization^ leads to the conclusion 
that in the one case the refractive index, and in the other the 
angle of rotation is a function of the length of the undulations 
of a colour. Each colour is determined by the length of the 
undulations, also by the refractive index, or by the angle of rota- 
tion in a given substance. There must therefore be a connexion 
between the two last-named quantities. This connexion may 
be disclosed by a prismatic analysis of the light as it leaves the 
polarizing apparatus. 

The rotation of the plane of polarization is proportional to 
the thickness of the plate of quartz. When the latter is con- 
siderable, then the amount of rotation for the different colours 
is equal to several complete revolutions. When the polarizer 
and analyzer are placed parallel, the latter removes from the 
light coming through the quartz all coloured rays which have 
undergone rotations which are odd multiples of 90^. In the 
places of these colours, dark bands appear in the spectrum. 
In order to arrive at the number of the bands, the thickness of 
the plate in millimetres should be multiplied by ^ and | ; the 
number of odd integers between the two products is the number 
of bands. 

For the purpose of getting the bands as sharply defined as 
possible, the following rule may be given : — Place the prism so 
that it gives with a mean ray a minimum of deviation, and the 
quartz plate so that the bands in the fixed spectrum have the 
maximum deviation. The latter is the sign that the rays pass 
through the quartz parallel to the optic axis 

On making the analyzer rotate, the bands pass from the red 
towards the violet end, or the reverse, according as the analyzer 
moves in the sense of the rotation of the plane of polarization 
or the contrary. Thereby the number of bands may be eheired 
by a unit. 

The relative position of the- bands is dependent upon the 



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owing to the Rotation of the Plane of Polarization. 13d 

AiUire of the substanee forming the prism, and upon the thick- 
need of the rotating plate. For a prism made of crown glass the 
fallowing propositions may be deduced from the measurements:--* 

1. The dark bands of the spectrum are equidistant. 

2. The distance between two contiguous bands is inversely 
proportional to the thickness of the quartz plate employed. 

8. The bands move regularly and correspondingly on turning 
the analyzer. 

Since the dark bands answer to colours of which the angles 
of rotation differ by a constant quantity^ it follows that the 
distances of the colours in the spectrum are proportional to the 
differences of their angles of rotation. 

By the refractions in the prism^ the directions of propagation 
rf the coloured rays, and by rotation in the quartz, their direc- 
tions of vibration are spread out so as to form a fan. The ar- 
rangement of the colours follows the same law in both fans. 

On calculating the refractive indices of the individual dark 
bands, the following law is arrived at : — ^Equal differences of re- 
fractive index correspond to equal differences of rotation. Angle > 
of rotation and refractive index are therefore in linear con- J 
nexion ; consequently both are similar functions* of the length of 
the undulations. 

Making the reciprocal squares of the lengths of the undula- 
tions abscissae and the indices of refraction ordinates, then, ac- 
cording to Cauchy^s law of dispersion, the terminal points of the 
latter will lie in a straight line. The dispersion through rota- 
tion in quartz follows therefore the same law. Biotas law, that 
the angle of rotation is inversely proportional to the square of 
the length of the undulations, cannot be maintained. The line 
drawn for the angles of rotation cuts the axis of ordinates, 
not at the origin, but on the negative side. If this line is also 
correct for the ultra-red rays, then for rays of a certain length of 
undulation, a right-rotating quartz may become left-rotating, 
and vice versd. 

The investigation of the spectrum of flint glass led to the same 
laws. For the spectra of water and quartz, it was found that 
the dark bands lay nearer to one another towards the violet end. 
A corresponding departure of the refraction produced by this 
tobstance from Gauchy^s law was therefore inferred, and found 
to be supported by direct observation. 

Moreover a direct way was devised for finding the depen- 
dence of the angle of refraction upon the length of the undula- 

* If by " similar functions " be meant functions differing merely by a 
eonstaiit multiplier, as the reasoning in the next paragraph seems to unply, 
the itatemeat is clearly wrong. The author seems to have forgotten the 
neeessity of introducing an arbitrarv^Bonstant after integration. The ex- 
perimental results stated are in perroct harmony with Biot's law.— G. 0. S. 



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140 M. Seochi on Earth-Currenis, and their 

tions. The light proceeding from the analyser was sent through 
a fine grating {Gitter) insteaa of through a prism ; the dark bands 
appeared in the spectra produced by diffraction. The bands are 
not equidistant^ but approach one another quite dose at the 
yiolet end. If the reciprocal squares of the sines of the devim* 
tions of the bands be taken, they will be found to be in arith- 
metical progression. The former hiw is thereby afresh supported. 

This opportunity was also taken to measure the lengths of 
nndulation of the following Fraunhofer's lines, viz., A, a, B^ C^ 
D, E, b, F, 6 ; and the following values in millionths of a milli- 
metre were found: 7598, 7178, 6872, 6558, 5894, 5253, 
518-7, 484-3, 4302. 

For the angles of rotation of the lines B, C, D, £, F^ 6, H, 
these values were obtained: 1555, 17-22, 2167, 2746, 3269, 
42*37, 50*98 degrees. The constant part in the dispersion- 
formula^iB— 1*697*, the part divided by the square of the length 
of unduktion is +81088. 

The foregoing phenomena are well adapted for exhibition by 
projection. The following arrangement answers : — Heliostat, slit 
in window-shutter, polarizing prism, quartz column, analyzing 
Nicol, lens of 1 ^ metre focus, prism in minimum deviation, or 
grating directly against the lens, distance of the latter from the 
slit 3 metres, screen where the image is distinct. 



XV. On Earth Currents, and their relation to Electrical and 
Magnetic Phenomena. By Father SECCHif. 

A RECENT communication by M. Matteucci on Earth Car- 
rents, in which he mentions my researches on the same 
subject, affords me an opportunity of presenting the results 
which I have obtained by comparing observations of magnetized 
bars and of the atmospheric electricity. The limits of this Note 

trevent my entering upon the details of these observations, and 
shall confine myself to the principal results. 
But before presenting tliese comparative results, I think it 
well to resolve some difficulties on the origin of these currents. 
M. Matteucci's investigation has proved directly that they are 
not the effect of the chemical action of the terminal plates. I 
have arrived at the same conclusion in an indirect manner by 
changing the terminal plates, and finding that the current of the 
plates, which is strong enough for short circuits, becomes very 
feeble for the resistance of conductors when the circuit is long 
enough, and that in other cases the direction is often opposite to 
that of the electromotive force of the plates. My researches, 
moreover, were not directed towards the absolute value of these 

* There must be some mistake. The constant term ought assuredly to 
be positive. — G. G. S. 
t Comptei Rendus, June 27, 1864. 



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relation to Ekctrical and Magnetic Phenomena. 141 

currents^ but simply to their variations ; so that a constant cur- 
rent of any origin would have no influence on the results. 

But in these researches there is a source of error which could 
not be neglected; that is^ the influence of temperature on the 
line-wires. This may be regarded from a twofold point of 
view: (1) the current itself may be considered to be thermo- 
electric in virtue of the solar action on the wire; (2) a variation 
of resistance in these wires^ due to the temperature^ may make a 
constant current appear periodical. Thus the current from 
Rome to Anzio^ although constant^ might appear variable. 

To resolve this difficulty^ it seemed to me that the use of two 
wires at right angles^ one in the meridian and the other in the 
parallel^ would give sufficient elements; for, these two wires 
being subjected to almost the same thermal variations, the 
resulting difierence ought to have the same phases. Only 
having at my disposal the meridional wire, I requested M . Jaco- 
bini. Inspector of Telegraphs, to be good enough to use his 
leisure and the intervals of inactivity of a line directed towards 
the east, and to compare it simultaneously with another directed 
in the meridian to see if they presented notable differences. 

M. Jacobini commenced then a series of observations between 
Rome and Arsoli, a station to the east of Borne, 50 kilometres 
distant, in the Apennines, and which is at right angles to the 
magnetic meridian. Observations were simultaneously made 
on the line from Rome to Anzio, 52 kilometres in length and 
on the magnetic meridian, the same line as is used for the Obser- 
vatory. After several preliminary trials, a regular system of 
observations was arranged towards the end of May ; I give here 
the results of the first half of June from the 1st to the 16th, 
excluding, however, the days 7, 8, 9, and 10 ; for on these days 
there was a strong magnetic disturbance, and currents in all 
directions traversed the wire in a very abnormal manner, to 
which I shall afterwards revert. 

Currents observed on the Telegraphic Wire from Rome to 
Arsoli and to Anzio. 





6 a.m. 


7. 


8. 9. 


10. 


11. 


Mid- 
day. 


1P.M. 


2. 


3. 


Arsoli, E... 
Anzio, S... 


170 
200 


2/0 
180 


260 
20-5 


21-0 


16-2 
220 


140 
22-4 


l!6 
88-0 


140 
20-5 


l^o 

20-3 


19-5 
180 




4 

P.M. 


5. 


6. 


7. 


8. j 9. 


10. 


11. 


Mid. 
night. 


Anoli, E... 
Anzio, S.... 


]§0 

17-5 


lS-0 
170 


190 
18-0 


160 
200 


1 

iSo iSo 

190 190 

t 


^•0 
JKM) 


190 
20*5 


230 
20-5 



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142 M. Secohi on Earth Owrmttt, and thmr 

The conclusions to be drawn from this Table are obnomly 

the following : — 

(1) The flactoation of the current in the direction of the Ter- 
tical (or equatorial) is greater than in the direction of the men*' 
dian. 

(2) The maximum of the one corresponds to the minimam 
of the other^ so that the two periods are almost complementary! 
thus the maximum of the equatorial is about 8 o'clock, and 
the minimum of the meridian is at 7 o'clock, or 7.30 ; the eqiuu- 
torial minimum is midday, and the meridional maximum between 
11 o'clock and midday. I say between these limits, because as 
the observations were not always made exactly at the hour, in the 
mean these fractions of an hour were reduced to the nearest 
entire hour, which is adequate in this matter. 

(3) Besides the principal maxima and minima, there are^ 
after midday, other but more feeble secondary maxima and 
minima, in which the same law of complement prevails si 
that observed in the morning. 

(4) During night the current is almost constant, but higher. 
From the nature of these results, it appeared impossible to 

attribute these currents to thermal actions, from whatever point 
of view they are regarded. But these results give a valuable 
clue to the discovery of the source of these variations, and shov 
that it is sufficient to compare the period of the current in one 
direction to obtain that of the other ; and thus our researches may 
be utilized although made solely in the direction of the meri*- 
dian. 

The three following Tables condense the observations made 
during one year in 'the meridional terrestrial current from Rome 
to Anzio, and I compare it with those of the bifilar and of atmo* 
spheric electricity. I do not add the periods of the declino- 
meter and of the vertical, because they are simpler and better 
known. The minimum of the vertical is between 11 o'clock 
and midday ; that of the declinometer according to well-known 
laws. The maxima of the vertical are the morning and the 
evening, after which there is a feeble nocturnal minimum. 
What most affects the bifilar is that its period changes with 
the season, so that in winter the minimum after midday dis- 
appears. 



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relation to Electrical and Magnetic Phenomena. 14S 

Table I. — Mean Values of the Terrestrial Currents observed 
between Rome and Anzio at the College Bomain. 







Time. 


Date. 






7 a.m. 


9. 


10.30. 


Mid- 
day. 


1.30 > , 
P.M. 1 «• 


5. 


7. 


9. 


10. 


1863. 




















May 25 to 28 


463 


6-0 


75 


6-20 


5-53 3-85 


4-3 


413 


4-33 


4-70 


Aug, 10 to 31 


7-31 


912 


9-91 


8-90 


716 6-98 


6-58 


700 


7-37 


7-86 


Sept. 1 to 30 


6-90 


7-80 


9-9 


8-3 


6-78 6-43 


6-92 


6-6; 


676 


711 


Oct. 1 to 18 


81 


8-42 


9-26 


817 


7-74 6-28 


625 


610 


6-27 




Nov. 6 to 30115-62 


14-15 


13-77 


13-87 


9-31 14-52 


1513 


11-31 


11-8 


15 80 


Dee. ltol7 


13-84 


11-3 


11-93 


12-15 


11-45 1157 


1015 


11-48 


11-86 




1864. 




















Jan. 1 to 31 


8-79 


8-95 


8-85 


8-97 


8-42 7-78 


815 


8-56 


8-65 




Feb. 1 to 29 


7-66 


8-2 


8-67 


8-81 


7-98 7-21 


7-20 


673 


7-35 




Mar. lto31 


6*87 


8-93 


10-5 


9-55 


6-65 6-21 


6-72 


7-75 


7-95 




Apr. 1 to 24 


5-42 


8-6 


8-;5 


7-21 


5-55j 5 34 


4-46 


6-34 


6-52 





By this long series of observations^ the diurnal period with its 
principal minimum in the morning between 7 and 9 o^ clocks 
and the maximum near midday^ is seen to be confirmed ; but 
the influence of seasons tells, for there is anticipation in sum- 
mer, and retardation in winter. 

Although the absolute value of the current does not enter 
into our discussion, the enormous increase which is attained 
during the last quarter of 1863, and especially in the month of 
November, must not be overlooked. 

It is interesting to compare these variations with those of the 
hmeontal force. 

Table II. — Indications of the Bifilar. 



Date. 



Time. 



Therm. 



7a.m, 



1863. 
May 
Aug. 
Sept. 
Oct. 
Not. 
Dec 
1864. 
Jan. 
Feb. 
Mar. 
Apr. 



134-4 
125-4 
127-2 
1390 
149-9 
160-7 

96-6 
96-8 
87-5 
85-7 



9. 



133-7 
1230 
124-7 
135-9 
147-3 
155-7 

94-2 
941 
84-9 
82-4 



10.30. 



136-9 
124-6 
126-5 
134-7 
146-9 
167-9 

93-9 
92-2 
83-6 
83-7 



Mid. 
day. 



136-0 
1269 
127-9 
135*7 
146-3 
157-2 

92-2 
91-7 
83-9 
86-7 



1.30. 

P.M. 



137*4 
127-9 
120-9 
136-9 
144-4 
156-2 

93-3 
92-9 
84-8 
870 



135-4 
127-4 
128-2 
135-7 
144-3 
155-4 

92-6 
92-4 

84-4 
85-9 



5. 



136-5 
127-5 
1245 
137-7 
1448 
1561 

929 
92-4 
856 
85-6 



9. 



135 4 137-4 
1281 128-7 
128-9; 129-3 
137 31 138-7 
145*9i 147-4 
1571 157-3 



93-3 
93-3 



93-7 
94-2 



85-6 85-8 
86-9 87-4 



10.30. 



136-7 
129-7 
128-4 



Fahrei- 

heit. 



148-8J 
158-6 



86-5 



i$6-95 
79-30 
7642 
69-63 
62-92 
53-12 

4767* 
49-47 
55-84 
53-99 



* The acale changea at the beginning of the year. 



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144 



M. Seoeki en Earth CurretiU. 



Here the last column contains the mean temperature of eaeh 
month, and a pr6portiohal correction of 0*9 must be applied for 
each degree of tbermometric variation. But even after this cor- 
rection the months of November and December are signalized 
by an enormous increase in the absolute value of the horisontsl 
component, which I can also verify in the observations of Lisbon, 
and which I think general^ and which has obliged us to change 
the scale. 

As regards the diurnal variation, the minimum is seen to 
correspond to the maximum of the equatorial current, and in 
the summer season the two instruments exhibit after midday 
a secondary oscillation which disappears in winter. 

Lastly, I shall adduce the results of the atmospheric electri- 
city obtained with the moveable conductor in the same period of 
observations. I must first remark that for their absolute value 
the numbers must be referred to the unit of measure in the last 
column, dividing them by this number. M. Volpicelli, in a Note 
printed in the Comptes Rendus, has said that our apparatus con- 
tains a long wire covered with gutta percha, which being agi- 
tated might falsify the indication. That is not correct ; for the 
communication between the conductor and the electrometer is 
effected by a veiy short wire, not more than a metre, and which 
is naked, having only been varnished long after it was ascertained 
that that had no appreciable influence. 

Table III. — Mean Monthly Values of the Atmospheric Statical 

Electricity. 



Date. 


Time. 


Unit. 


7 a.m. 


9 


10 


Mid- 
day. 


1-35 


3 


6 


7 


9 


10.30 




1863. 








1 














May 


6-41 
612 


7-63 

7-44 




4-89 
5*62 


467 
4-49 


4-81 
472 


4-60 
4-32 


6-24 
615 


703 

810 


6*91 
7-69 


709 
6-96 


August 


September ... 


472 


5-31 




473 


417 


4-00 


500 


5-81 


6-22 


4-44 


500 


October 


3-97 


3-81 




505 


415 


3-98 


5-65 


6-29 


3*98 


■•.... 


615 


November ... 


4-46 


3*85 




472 


5-68 


4-48 


877 


7-85 


4-61 


670 


5-20 


December ... 


4-37 


7-00 




813 


6-75 


6-69 


876 


879 


7-09 


610 


5-29 


1864. 
























January 


3-66 


6-82 


6-00 


713 


6-96 


676 


6-32 


8-30 


579 




4-87 


February 


276 


3-81 


4-42 


3*89 


2-97 


2-56 


274 


519 


3*64 




4-25 


March 


388 


3-86 


3-63 


3-32 


312 


272 


318 


617 


5*69 




4-46 


April 


4*13 3'35J 


3-49 2-641 


2-69 


278 


3-46 


4-64 


403 




4*50 






1 




1 







It is seen by this Table that in general the electricity has a 
double maximum and minimum, especially in summer. The 
first maximum corresponds in the morning to 1 o'clock, the time 
of the maximum of the current; and it is the same; with the 



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^Prof. Maskelyne and Dr. Lang's Mineraloffical Notes. 146 

maximum of the eyenrng. But there is this difference^ that 
while the maximum of the morning is the principal in the cur- 
rent, it is only the secondary in statical electricity. 

Tlie generu conclusion to be drawn from all this is, that the 
variations in the currents of magnetized bars and of atmospheric 
electricity may be derived from the same principle in motion ; that 
this action cannot be confounded with that of solar heating ; and 
that rather a kind of diurnal electrical flux and reflux must be 
assumed allied to the solar action, but whose energy in this 
transformation is manifested in a different manner to that of 
direct heat and light. The opinion already enunciated by M. 
De la Bive, that the different variations of magnetized bars may 
be derived from the atmospheric electricity, appears thus to ac- 
quire great probability. 

I shall conclude with a word on the extraordinary magnetic 
variations. Observations made during the 7th, 8th, 9th, and 
lOth of June, when there was a great magnetic disturbance, have 
once more shown that these motions of the bars are connected 
with motions of the currents ; bat a profound discussion cannot 
find a place here. I may, however, simply remark that the 
existence of irregular earth currents in telegraphic wires has 
become to M. Jacobini a vei*y marked sign of approaching bad 
weather and surrounding storms; and I think this might be 
utilized in other telegraphic lines for predicting the weather. 
This is also a new and unsought-for confirmation of the con- 
nexion between storms and magnetic variations. 

XVI. Mineralogical Notes. By Professor N. S. Maskeltne 
and Dr. Viktor von Lano, of the British Museum^ 

[With a Plate.] 

[Continued from vol. xxvi. p. 139.] 

On some Combinations of Gadolinite. By Viktor von Lang. 

THE researches of A. B. Nordenskjold* and Th. Scheererf 
have shown that the crystals of Gadolinite belong to the 
prismatic system. To the same conclusion I was led by the 
examination of the specimens of Gadolinite in the mineralogical 
collection of the British Museum, although several of the crystals 
i examined were of a decidedly oblique habit. But as we find 
that on such apparently oblique crystals sometimes the longer, 
sometimes the shorter diagonal of the prism comes to simulate 
the axis of symmetry, we are justified in considering that fact 
only another proof of the prismatic character of these crystals. 

♦ dfe€r8%fft,afKmghVetenshapAhademiemFfh'handl%ngar,\^b9,l^^ 
p. 287. 

t Neites Jahrhuchfur Min, &c. 1861, p. 134. 

Phil. Mag. S. 4. Vol. 28. No. 187. Avg. 1864. L 



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146 Prof. Maskelyne and Dr. Lang's Mineralogies Netei. 

The planes hitherto known on Oadolinite are^ 

100, 001, 110, 101, 102, 111, 112. 

In addition to these I have foand the new planes 

210, 014, 211, 322, 428,— 

fig. 9, Plate III. representing the poles of all these planes. 

From the angles measured by Nordenskjold with only th« 
hand-goniometer, we deduce the elementsf 

a: i:c=l:0-6249: 1-3780. 

They represent also my measurements (which on the crystals of 
Gadolinite can never be made with great accuracy) sufficiently 
well, and with them are calculated the angles of the fdlowing 
Table:- 





100. 


010. 


001. 


110. 


110 
210 


68 i) 
38 40 


3^ b 
51 20 


90 O' 
90 


6 6 
19 20 


201 
101 
102 


19 57 
36 58 
55 26 


90 
90 
90 


70 3 
54 2 
34 34 


60 7 
64 36 
72 30 


014 


90 


61 8 


28 62 


66 60 


111 
112 
211 
322 
423 


60 21 
65 10 
41 18 
49 31 
44 3 


37 41 
47 46 
46 10 

53 3 

54 64 


68 68 
62 26 
74 11 
71 42 
66 59 


21 2 
37 34 
24 47 
21 20 
29 43 



The following observed combinations are represented in 
Plate III. 

Pig. 1.— 001, 110, 101, 102, 111, 112. 

Fig. 8.— 10 0, 001, 110, 210, 101, 210, 211. 

Fig. 4.— 100, 010, 110, 210, 101, 102, 111. 

* In the ' Handbook of Mineralogy ' by Brooke and Miller, a plane, e, 
parallel to the axis b is given with an angle ee^^33^ 34', so that the symbol 
of that plane would become nearly (0 1 4). Bat as the crystal measured 
by Miller is the same as that investigated by Phillips, a comparison of the 
two measurements shows that the above angle is very probably to be taken 
as the inclination c, 1 0. As the calculated angle 102. 100 = 34** 34' 
comes near to the former angle, the symbol of the plane e is certainly (102). 

t The elements which I had deduced from my measurements before I 
became acquainted with Nordenskj old's memoirs are 

a:6:c = l: 0-6289: 1-3746. 



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Vrot. MMkelyne oJMf Dr. Lang?! MineralogUd Nate6. 147 

These forms were observed on large crystals from^Ytterby^ 
Sweden. The crystals are of an opake green material^ which is 
traversed by white veins : they may perhaps be only pseadomor- 
phoas> after the forms of real Oadolimte. The pluies are here 
end there bnlliant. 

I found on the crystals figs. 1 and 4^ 



110.010 = 


:3i 15 


32 Ocalc. 




210. 


110si21 appr. 


19 20 „ 




102.001 = 


:34 28 


34 84 „ 




102. 


.101 = 


= 19 10 


19 28 „ 




110. 


,102 = 


= 72 81 


72 80 „ 




110. 


,llls21 25 


21 2 „ 




111. 


112 = 


: 17 appr. 


16 32 „ 




The crystal fig 


;. 3, the 


: right half of which only was developed. 


x>uld only be measared with the hand-goniometer, 


and gave 




101, 


101=74 


7l 66 oak. 






110. 


211=25 


24 47,, 





211 being in the zone [110, 1 1]. 

Fig. 2.-100, 001, 110, 201, 101, 102. 

A large black crystal engaged in reddish felspar from Ytterby. 
I found with the hand-goniometer, 

001.102 = 34 34 84calc. 
102.101 = 19i 19 68 „ 
101.201 = 16 16 1 „ 

Pig. 5.— 001, 110, 210, 102, 111, 112, 014, 822. 
A detached black crystal, of which fig. 6 gives a vertical pro- 

{'ection. The symbols of the new planes 014 and 322, the 
atter in the zone [110, 1 02], aire deduced from the following 
approximate measurements : — 



0T4 001 = 29 


28 52 calc. 


110 822 = 22 


21.20 „ 


1 1 2 1 = 20i 


19 20 „ 



Fig. 7.— 001, 110, 210, 101, 102, 111, 428, 
The half of a smaller black crystal, which in fig. 8 is repre- 
aeoted in vertical projection. The faces reflect the light very 
badly. The following angles are therefore only very rough ap- 
proximations : — 

110.210 = 17-18 21 20 calc. 
111.423= 16 18 1 „ 

493 being in the zone [1 1 1, 1 lO]. 

L2 



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148 Pfof, MMkdyne md Dr. Lang^s Mmer^fkgical Nalm. 

NoHcei ofAHroKtet. By Neyil Story Maskelyne. 

KuiiaKf Kumaan. 

A Mnall but very interesting fragment of M aerolite waa 
sent to me a few weeks since by my friend Dr. Oldham^ the . 
Director of the Oeoloffical Sanrey of India« It weighs 63 grains. 
It was accompanied py the following statement from Dr. 01d» 
ham : — 

*^ Small fragment of meteorite that fell close to Kusiali vil- 
lage, in the district of British Gurhwal (say 30^ N. lat., 79^ E. 
long.). There are stated to have been eight or ten explosions 
nearly half an hour before the stone fdl, to have been a strong 
light like burning gunpowder in the track of the stone^ whi<£ 
came (apparently to observers) from the north-north*weat to 
south-fiouth-east* 

'^The mass is described to have fallen on an open surface of. 
hard gneiss-rock^ and to have been shattered into fragments, 
none of which were larger than the piece I send, most of them 
much smaller.^' 

The fall took place a few minutes before 5 o'clock A.U., on 
the 16th of June 1860. 

Dr. Oldham adds that there was only one other specimen 
preserved^ and that it has unfortunately been lost. The rest of 
the fragments were eagerly seized by the natives^ who attribute 
to these sky-stones healing properties^ that recall to our minds 
superstitions that have raised minerals into talismans, from the 
remotest time down to our own days. It may not be impossible, 
however, that the iron that is present in these bodies in a state 
of such minute division may nave been found to act medici- 
nally as a tonic. 

The strange statement that the fall of the aerolite was pre* 
ceded, by so long a period as half an hour, by a series of explo- 
sions, is one so irreconcilable with any intelligible explanation 
that should connect the two phenomena, that we may fairly hold 
ourselves relieved from the attempt to supply such an explana- 
tion. 

The Kusiali stone is a chondrite, but it belongs to the group 
of this class which is least charged with spherules. 

It is very full of the opake white flocculence which is so 
abundant in some aerolites and entirely absent from others; 
and in the interstices of this confused aggregate of mineral are 
seen crystalline granules that are sometimes complete eryatala,. 
but oftener without any geometrical form that can be traced* 
These generally seem to be olivine, but they are also sometimes in 
bars, and have occasionally the divergent structure, features which 
I take to be, in these as in similar cases, characteristic of the au-: 



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Trof. Maskelyne and Dn Lang^i Mmerai^fieal Notet. 149 

^tie and felqmthic iagredients of the aerolile. The Labndorite 
crystals in some Melaphyrs, and especially in a specimen from 
Darmstadt (among sevend that M. Keaselmeyer was so good aa 
to forward to me)^ present a remarkable similarity to some of 
these bacillary aerditic minerals^ and are simikrly associated 
with a white nearly opake body. 

The section of the Kusiali meteorite is sprinkled with small 
iron-particles^ and by Troilite in a somewhat smaller amount. 

Kaee, Oude, 

Aimmg the recent acquisitions made to the Collection of 
Meteorites in: die British Museum is a stone presented by Tho* 
mas Macl^r, Esq., Astronomer Royal at the Cape of Good Hope, 

This uniq|tte little aerolite was accompanied by a document in 
Persian, which was '' a copy of the original in the intelligence 
department of the district of Sandee in the Elakar or country 
of Aga Mirsa (in the kingdom of Oude), dated 2nd of Zeekad, 
1253 hisree, correspondmg with January 29, 1838.'' 

The stone, and the record of its fall, were sent by the King 
of Oade to Col. Caulfield, Acting Resident at the Oude Court, 
to be forwarded to the Resident, Col. Low, C.B. Col. Low 
gave them to the Astronomer Royal at the Cape, to whose libe-^ 
xalitythe British Museum has been indebted for them, as on 
previous occasions it had been for specimens of the Cold Bok* 
keveldt Meteorite. 

The certified translation of the Persian document runs as 
follows : — " To-day, after sunset, though there were no clouds, 
thmider was heard, and the men were astonished ! It was 
afterwards ascertained that in the village of Kaee, held in nakar 
(rent-free) by Hidayut Allee, the Taalookdar of the village of 
Kagtalee, ftc., a stone fell from the sky. The aforesaid 
Taalookdar sent that stone to the reporter of intelligence ; its 
colour is black, and it weighs 17 tollahs and 6 massahs.'' 

This ^' sky-stone,^' as it is called in the Persian superscription^ 
u a small complete aerolite, presenting the well-known appear- 
ance of an irregular solid, bounded by planes comparatively flat 
with their edges rounded. The crust had been broken away 
doDg two of the edges, and one of these has been worked so as 
to exhibit a considerable polished surface, in which the characters 
of the stone may be seen. The weight of the stone is 
7 01. 160 grs. In external appearance the Kaee stone much 
wsembles the aerolites of Doroninsk, Ohaba, and Griinberg, 
And is, Uke them, a member of the large Chondritic class of Rose, 
Thev present on their polished faces much meteoric iron, in 
unall but thickly sown and pretty equably disseminated grains, 
i^Ather showing a tendency to agglutination or to being stnin|; 



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160 BrV Jonle on the HMcry of the ^ 

tbgeihef. Spherales remarkably rounds and^ in section^ yer^ 
daric and brilliant, are plentifully distribnted through the mass 
of the stone, and are associated with others of a lighter hire. 
The aerolite is very compact and takes a good poUsh. Its spe* 
cific gravity is 3*63. It contains Troilite in about an equal 
proportion in bulk to the iron, and it is similarly disseminated. In 
the microscope some of the spherules are seen to consist of the 
grey mineral, with a fan-like structure radiating from an edge or a 
point external to the spherule, apparently belonging to one of 
the oblique systems. Th^re are also the usual kinds of spherule, 
in which the clear olivine-like mineral is seen forming a- sort of 
breccia, and engaged in a flocculent aggregate of confusedly 
crystalline matter, from which a ray of polarized light emerges 
without any definite plane of polarization. Similar ingredients 
fill the interspherular space, and the aspect of the aerolite in the 
microscope is that of a pretty uniform mixture of this flocculent 
aggregate and fragmentary but clear crystals. There arc like- 
wise a few crystals or broad clear bars of crystal, unlike the 
ordinary olivine in their habit, but with their plane of polarization 

Iiarallel or perpendicular to the direction of the bar. It is not 
ikely to be augite seen in a section parallel to the plane 100 
{and perpendicular to the axis of symmetry) ; and it is difficult 
to resist suggesting the probability of its being enstatite, cut pro* 
bably nearly parallel to one of its planes of cleavage. It is not 
a rare ingredient of aerolites. 

XVII. Note on the History of the Dynamical Theory of Heat, 
By James P. Joule, LL.D., F.R.S. 

To the Editors of the Philosophical Magazine and Journal. 
Gentlemen^ 

SOME observations in Professor TyndalPs " Notes on Scien- 
tific History " call for an early notice on my part. After 
the perusal of thitf article, I freely admit that I erroneously took 
the degrees in the fifth column of S^guin's Table for thermal 
units in kilogrammes. I regret this oversight the more particu- 
larly, as it seems to have misled others who have since written on 
the subject. But I must still express my conviction that in the 
statement of his hypothesis S^guin anticipated Mayer. To 
prove this, I will give the following extracts from the Chemins 
deFer:— 

*' il me parait plus naturel de supposer qu'une certaine 

quantity decalorique disparait dans Pacte m£mede la production 
de la force ou puissance mecanique, et reciproquement ; et- que 
les deux ph^nom^nes sont li^s entre eux par des conditions qui 
leur oBsignent des relations invariables. II resulterait, comme 



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Dynamictd Theory of Heat. 151 

oon86}aeiice de cette maniere d^envisager les faits^ que Bi Ton 
fait passer directement de la vapeur d^eau^ de la chaudiere qui la 
produit k travers une masse d^eau dans laquelle elle se condense^ 
cette vapeur elevera plus la temperature de Teau que si on la 
faisait servir prealablement k mettre en jeu une machine k vapeur^ 
dans laquelle elle perdrait une partie de son ressort/^ (p. £^2.) 

^^ L^abaissement de temperature qui accompagne Fexpanaion 
de tout fluide aeriforme dans un espace plus grand que celui qui 
repond au degre de tension ou il etait d'abord^ et le ph^nomene 
oppose, ou la production de chaleur qui est toujours la suite de 
sa compression, me paraisseot deux circonstances qui viennent 
k Pappui de cette assertion." (p. 383.) 

'' Je vais done raisonuer dans Fhypothese que I'abaissement 
de temperature de la vapeur, lorsqu^elle se dilate, represente 
exactement la quantite de puissance qui apparait alors." (p. 384.) 

"Enfin Pabaissement subit de temperature de la vapeur 
lorsqu'elle s^echappe dans Fair, circonstance mise k profit de nos 
jours pour utiliser son ressort et sa puissance, montre que, dans 
ce cas, I'efiFort qu'elle exerce en recul contre les appareils qui la 
laissent ^chapper, ou la vitesse qu^elle communique k Pair am- 
biant^ forment un Equivalent de la perte de chaleur qu^elle 
dprouve." (p. 394.) 

S^guin gives data from which the mechanical equivalent of heat 
may be readily deduced on his hypothesis, the result being too 
great in consequence of the thermal eflfect of the compression of 
vapour being understated. Neither inSeguin'swritingofl839,nor 
in Mayer's paper of 1842, were there such proofs of the hypothesis 
advanced as were sufficient to cause it to be admitted into science 
without further inquiry. I believe that the experiment attributed 
to Gay-Lussac was not referred to by Mayer previously to the year 
1845. Mayer appears to have hastened to publish his views for 
the express purpose of securing priority. He did not wait until 
he had the opportunity of supporting them by facts. My course, 
on the contrary, was to publish only such theories as I had esta- 
blished by experiments calculated to commend them to the scien« 
tific public, being well convinced of the truth of Sir J. HerschePs 
remark, that ^' hasty generalization is the bane of science." 

I applied the dynamical theory to steam-engines, to electro- 
magnetic engines, to vital processes, and to chemistry in 1843. 
In the postscript alluded to in § 50 of Mr. TyndalFs article, I 
intended the word " apprehend " to express the meaning applied 
to it in Johnson's Dictionary, viz. '^to conceive by the mind,^' 
not '^to conjecture* ". My popular lecture will show that the 
outlines of cosmical and other applications of the theory were so 

♦ fWith respect to this passage, we had. before receiving Dr. Joule's 
eommuBicatioii, been requested by Prof. Tyndall, in a letter dated Pontre- 
sina, July 18, to substitute the word "statement" for "conjecture".— W. F.] 



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152 Royal Society t— 

familiar to my mind^ and such obvious deductioDS from what h 
had established^ that I did not deem them of sufficient novelty 
to present them to oar own local scientific Society. 

1 believe that no one who has the advantage of acquaintance 
with Prof. Thomson will for a moment doubt his eagerness to 
give due credit to M. Mayer^s just claims. But has justice 
been done to Thomson himself^ who has done far more than any 
other individual towards the application, development, and pro- 
mulgation of the dynamical theory of heat ? I fear not. 
1 am, (Gentlemen, 

Yours very respectfully, 

James P. Joule 

XVIII. Proceedings of Learned Societies. 

ROTAL SOCIETY. 

[Continned from p. 71*] 

May 26, 1864.— Major-General Sabine, President, in the Chair. 

I^HE following communication was read : — 
" On the Spectra of some of the Fixed Stars." By W. Huggins, 
F.R.A.S., and William A. Miller, M.D., LL.D. 

After a few introductory remarks, the authors describe the appa- 
ratus which they employ, and their general method of observing the 
spectra of the fixed stars and planets. The spectroscope contrived 
for these inquiries was attached to the eye end of a refracting tele- 
scope of 10 feet focal length, with an 8-inch achromatic object-glass, 
the whole mounted equatorially and carried by a clock-movement. 
In the construction of the spectroscope, a plano-convex cyUndrical 
lens, of 14 inches focal length, was employed to convert the image 
of the star into a narrow line of light, which was made to fall upon 
a very fine slit, behind which wa^ placed an achromatic coUimating 
lens. The dispersing portion of the arrangement consisted of two 
dense flint-glass prisms ; and the spectrum was viewed through a 
small achromatic telescope with a magnifying power of between 5 and 
6 diameters. Angular measures of the difiPerent parts of the spec- 
trum were obtained by means of a micrometric screw, by which the 
position of the small telescope was regulated. A reflecting prism 
was placed over one half of the slit of the spectroscope, and by 
means of a mirror, suitably adjusted, the spectra of comparison were 
viewed simultaneously with the stellar spectra. This light was usually 
obtained from the induction spark taken between electrodes of diffe- 
rent metals. The dispersive power of the apparatus was sufficient to 
enable the observer to see the line Ni of Kirchhoff between the two 
solar lines D ; and the three constituents of the magnesium group 
at b are divided still more evidently'*'. Minute details of the methods 
adopted for testing the exact coincidence of the corresponding metallic 

* Each unit of the scale adopted wa« about equal to t^^ ^^ ^^ distanpe 
})etween A and H in the solar spectrum. The measures on oiiferent occasions of 
the same line rarely differed by one of these units, and were often identical. 



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On the Spectra of some qfthe Fixed Stare. 158 

Hoes witb those of the solar and lunar spectram, are given, and the 
authors then proceed to give the results of their observations. 

Careful examination of the spectrum of the light obtained from 
yarious points of the moon's surface failed to show any lines resem- 
bling those due to the earth's atmosphere. The planets Venus, Mars, 
Jupiter, and Saturn were also examined for atmospheric lines, but 
none such could be discovered, though the charactenstic aspect of the 
solar spectrum was recognized in each case ; and several of the prin- 
cipal hues were measured, and found to be exactly coincident with 
the solar lines. 

Between forty and fifty of the fixed stars have been more or less 
completely examined ; and tables of the measures of about 90 lines 
in Aldebaran, nearly 80 in a Orionis, and 15 in /3 Peeasi are given, 
with diagrams of the lines in the two stars first named. These dia- 
grams include the results of the comparison of the spectra of various 
terrestrial elements with those of the star. In the spectrum of 
Aldebaran coincidence with nine of the elementary bodies were ob- 
served, Tiz. sodium, maenesium, hydrogen, calcium, iron, bismuth, 
tellurium, antimony, and mercury ; in seven other cases no coinci- 
dence was found to occur. 

In the spectrum of a Orionis five cases of coincidence were found, 
viz. sodium, magnesium, calcium, iron, and bismuth, whilst in the 
case of ten other metals no coincidence with the lines of this stellar 
spectrum was found. 

/3 Pegasi furnished a spectrum closely resembling that of a Orionis 
in appearance, but mucn weaker : only a few of the lines admitted 
of accurate measurement, for want of light ; but the coincidence of 
sodium and magnesium was ascertained ; that of barium, iron, and 
manganese was doubtful. Four other elements were found not to be 
coincident. In particular, it was noticed that the lines C and F, 
corresponding to hydrogen, which are present in nearly all the stars, 
are wanting in a Orionis and (i Pegasi. 

The investigation of the stars which follow is less complete, and 
no details of measurement are given, though several points of much 
interest have been ascertained. 

Siriue gave a spectrum containing five strong lines, and numerous 
finer lines. The occurrence of sodium, magnesium, hydrogen, and 
probably of iron, was shown by coincidence of certain lines in the 
spectra of these metals with those in the star. In a Lyra the 
occurrence of sodium, magnesium, and hydrogen was also shown by 
the same means. In Capella sodium was shown, and about twenty 
of the lines in the star were measured. In Jreturus the authors 
have measured about thirty lines, and have observed the coincidence 
of the sodium line with a double line in the star- spectrum. In Pol* 
lux they obtained evidence of the presence of sodium, ma^esium, 
and probably of iron. The presence of sodium was also indicated in 
Procyon and a Cygni, 

In no single instance have the authors ever observed a star-spec- 
trum in which lines were not discernible, if the light were sufficiently 
intense, and the atmosphere favourable. Rigel, for instance, which some 
authors state to be free from lines, is filled with a multitude of fine lines. 



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154 MUy^S^ddg:— 

Fhotogniilttof Uiei|MCtnof SiriBsaiidCiqpdkw^ taken apon 
coDodkm ; but thoo^ toknblj ikaip, tbe appantus employed was 
not fluifideDtlj perfect to afford wmj indicatioD of lines in the photo- 
gimph. 

In the condoding porti<Hi of their papor, the authors apply the 
£Kt8 obaeired to an explanation of the e(4onn of the stars. They 
consider that the difference of ooloar is to be sought in the difference 
of the cmiBtitatioB of the inTesting stdlar atmoqiheres, which act 
bj abaorbing partirnlar portions of the light emitted by the incan- 
descent solid or Hqoid photosphere, the %ht of which in each case 
they suppose to be the same in quality originally, as it seems to be 
independent of the diemical nature of its constituents, so far as ob- 
servation of the Tarioos solid and liqcnd elementary bodies, when 
rendered incandescent by terrestrial means, appears to indicate* 

June 16. — ^Mijor-General Sabine, President, in the Chair. 

The following communications were read: — 

"Aerial Tides.*' By Pliny Earie Chase, A.M., S.P.A.S. 

The remarkable coinGidence which I haye pointed out* between 
the theoretical effects of rotation and the results of barometrical 
observations, has led me to extend my researches with a view of 
defining more precisely some of the most important effects of lunar 
action on the atmosphere. The popular belief in the influence of the 
moon on the weather, which antedates all historical records, has 
receiyed at various times a certain degree of philosophical sanction. 
Herschel and others have attempted partially to formulate that influ- 
ence by empirical laws, but the actual character of the lunar wave 
that is daily rolled over our heads, appears never to have been inves- 
tigated. 

Major-Greneral Sabine has shown that the moon produces a diurnal 
Tariation of the barometer, amounting to about *006 of an inch at 
St. Helena, which is nearly equivalent to -^ of the average daily yaria- 
tion (Phil. Trans. 1847, Art. V.). This would indicate a tidal wave 
of rather more than 1 ft. for each mile that we ascend above the 
earth's surface, or from 3 to 6 ft. near the summits of the principal 
mountain-chains. It is easy to believe that the rolling of such a wave 
over the broken surface of the earth may exert a very important 
influence on the atmospheric and magnetic currents, the deposition of 
moisture, and other meteorological phenomena. As the height of the 
wave varies with the changing phases of the moonf, its effects must 
likewise vary in accordance with mathematical laws, the proper study 
of which must evidently form an important branch of meteorological 
science. 

Besides this daily wave, there appears to be a much larger, but 
hitherto undetected, weekly wave. M. Flangerguesits <ui astronomer 
at Viriers in France, extended his researches through a whole lunar 
cycle, from Oct. 19, 1808 to Oct. 18, 1827, and he inferred from his 
observations — 

* See Proceedings of Amer. Philos. Soc. voL ix. p. 283. 

t The height at St. Helena appears to fluctuate between about '9 and 1*6 ft.' 

t Bib. Umv., Dec. 1827. 



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Mr. F. £. Chase m Atrial Tides. 



15S 



1. That in a synodical reyqlution (^ the moon, the harometer rises 
regularly from the second octant, when it is the lowest, to the second 
quadrature, when it is the highest, and then descends to the second 
octant. 

2. That the Tarying declination of the moon modifies her influence^ 
the barometer being higher in the northern lunistice than in the 
southern. 

The more recent and more complete observations at St. Helena 
give somewhat different results, which serve to confirm the natural ^ 
priori conviction that there are two maxima and two minima in each 
month. The means of three years' hourly observations, indicate the 
existence of waves which produce in the first quarter a barometric 
effect of +'004 in., in the second quarter of —'016 in., in the third 
quarter of +-01 8 in., and in the fourth quarter of —'006 in. — 
results which appear to be precisely accordant, in their general 
features, with those which would be naturally anticipated from the 
combination of the cumulative action of the moon's attraction, with 
the daily wave of rotation, and the resistance of the aether. 

One peculiarity of the lunar-aerial wave deserves attention, for the 
indirect confirmation that it lends to the rotation theory of the aero- 
baric tides, and the evidence it furnishes of opposite tidal effects^ 
which require consideration in all investigations of this character. 
When the daily lunar tides are highest, their pressure is greatest, 
the lunar influence accumulating the air directly under the meridian, 
BO as to more than compensate for the diminished weight consequent 
upon its ''lift." But in the general aerial fluctuations, as we have 
seen heretofore, and also in the weekly tides which we are now con- 
sidering, a high wave is shown by a low barometer, and vice versd. 
The daily blending of heavy and light waves produces oscillations 
which are indicated by the alternate rise and fall of the barometer 
and thermometer at intervals of two or three days. 

M. Flangergues's observations at perigee and apogee seem to show 
that a portion of the movement of the air by the moon is a true lift» 
which, like the lift of rotation, must probably exert an influence 
on the barometer. On comparing the daily averages at each of the 
quadratures and syzygies, I found the diflerence of temperature too 
slight to' warrant any satisfactory inference, but a similar comparison 
of the hourly averages, at hours when the sun is below the horizon, 
gave such results as I anticipated ; as will be seen by a reference to 
the following 

Table of Barometric and Thermometric Means at the Moon^s Changes* 



Moon's Phase. 


Average 
Height of 
Barometer, 
in inches. 


Height of 
Lunar 

Weekly 
Tide*. 


Height of 
Lunar 
Daily 
Tides. 


Daily 
Height of 
Thermo- 
meter. 


Thermo- 
meter at 

IS F.M. 


Thermo- 
meter at 

4 A.M. 


Full 


28-270 
28-289 
28-282 
28-286 


in. 
-•0115 
+ •0065 
+H)005 
+•0044 


in. 

•0054 
•0087 
-0064 
•0047 


67-67 
61-68 
61-65 
61-63 


60-22 
60-41 
60-31 
60-37 


59-787 
59'824 
69-716 
59-823 


Third Quarter 


rifBt Quarter 



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186 BopalSaeidf:'^ 

In obtaimng the aboTe avenges, I was obliced to mteirpolate for 
audi ehangea as took place on Simdajs or holidays, when no obser^ 
vations were taken. The interpolation, however, does not change the 
general result, and on some accounts the Table is more satisfactory 
than if the observations had been made with special reference to the 
determination of the lunar influences, accompanied, as such a refer* 
ence would very likely have been, by a bias to some particular theory* 

The thermometric and barometric averages show a general corre* 
spoHdence in the times of the monthly maxima and muiima, — ^the 
correspondence being most marked and uniform at midnight, when 
the air is most removed from the direct heat of the sun, and we 
m^ht therefore reasonably expect to find the strongest evidences of 
the relations of temperature to lunar attraction. 

By taking the difference between the successive weekly tides, we 
readily obtam the amount of barometric effect in each (|uarter. The 
average effect is more than three times as great in the third and fourth 
quarters as in the remaining half-month, — ^a fact which suggests inte- 
resting inquiries as to the amount of influence attributable to varying 
centrifugal force, solar conjunction or opposition, temperature, &c. 

Although, as in the ocean tides, there are two simultaneous cor- 
responding waves on opposite sides of the earth, those waves are not of 
equal magnitude, the barometer being uniformly higher when the 
moon is on the inferior meridian, and its attraction is therefore 
exerted in the same direction as the earth's, than when it is on the 
superior meridian, and the two attractions are mutually opposed. 
Some of the views of those who are not fully satisfied with the prevail- 
ing theory of the ocean-tides, derivea partial confirmation fromthis fact. 

I find, therefore, marked evidences of the same lunar action on 
the atmosphere as on the ocean, the combination of its attraction 
with that of the sun producing both in the air and water, spring 
tides at the syzygies, and neap tides at the quadratures ; and I believe 
that the most important normal atmospheric changes may be explained 
by the following theory : — 

The attraction- and rotation-waves, as will be readily seen, have 
generally opposite values, the luni-solar wave being 

Descending, from 0° to 90*^* and from 180^ to 270^ 
Ascending, from 90^ to 180** and from 270^ to 0®; 
while the rotation-wave is 

Ascending, from 330^ to 60^ and from 150^ to 240°, 
Descending, from 60"^ to 150"^ and from 240° to 330°« 
' From 60° to 90° and from 240° to 270°, both waves are descend* 
ing, while from 150° to 180° and from 330° to 360° both are 
ascending. In consequence of this chanse of values, besides the 
principal maxima and minima at the syzygies and quadratures, there 
should be secondary maxima and mimmaf at about 60° in advance 
of those points. 

• CountiDg 9 from either sjrzygy. 

t The lecondary maximt tnd minima shoald corretpcmd with the daSty mtoL^ 
imt and minuna, which occur at St. Helena at about 4^ and 10^ a.m. and p.m., 
giying 0=60^ a maximum, and 0>b150^ a minimum. 



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Ifr. Sorby cm the Miemsopkd Sirudwre oj Maearitu. 197 

The eonfirmatioii. of these theoretical inferenoes bj the 8t» Hdeiui 
obsenratbna eppwa to me to be quite as remarki^ as that of mj 
primary hjpotnesis* If we arrange those obserratioiis in acoonlaiiee 
with the moon's jMNdtimi, and take the average daily height of the 
barometer^ we obtain the following 

Tiible of the Lunar Barometric Tides. 





Hetti Daily Height of the Bvometer «t St. Helena* 


Moon's 
Poiitioiu 


28 inches + the numbers in the Table. 


1844. 


1845. 


1846. 


1844-6. 
Average. 


o 




•2621 


•3020 


•2701 


•2781 


15 


•2650 


•3058 


•2693 


•2800 


30 


•2707 


•3153 


•2707 


•2856 


45 


•2691 


•3165 


•2688 


-2848 


60 


•2625 


•3077 


•2688 


•2797 


75 


•2682 


•3093 


•2783 


•2853 


90 


•2667 


•3184 


•2800 


•2884 


105 


•2593 


•3170 


•2721 


•2828 


120 


•2595 


•3124 


•2686 


•2802 


135 


•2677 


•3099 


•2691 


•2822 


150 


•2712 


•3118 


•2715 


•2848 


165 


•2710 


•3104 


•2735 


•2850 


180 


•2621* 


•3020 


•2701 


•2781 



This Table shows — 

1. That the ayerage of the three years corresponds pr^me/y with 
the theory, except in the secondary maximum, which is one day late* 

2. That the primary maximum occurred at the quadratiures ia 
1845 and 1846, and one day earlier in 1844. 

3. That the primary minimum occurred at the ffyzygies in 1 844 
and 1845, and one day later in 1846. 

4. That 1 846 was a disturbed year ; and if it were omitted from the 
Table, each of the remaining years, as well as the average, would 
exhibit an entire correspondence with theory, except in the priuMtiy 
maximum of 1844. 

.5. That 1845 was a normal year, the primary and secondary 
maxima and minima all oorrespondmg with theory, both in position 
and relative value. 

" On the Microscopical Structure of Meteorites.'' By H. C. Sorby, 
F.R.S., &c. 

For some time past I have endeavoured to apnly to the study of 
meteorites the principles I have made use of in the investigation of 
terrestrial rocks, as described in my various papers, and especially 
in that on the microscopical structure of crystals (Quart. Joum* 
Geol. Soc. 1858, vol. xiv. p. 453). I therem showed that the pre- 
sence in crystals of '* fluid-, glass-, stone-, or ffas-cavities" enables uiT 
to determine in a very satisfactory manner under what conditions the 
crystals were formed. There are also other methods of inquiry still 
requiring much investigation, and a number of experiments must 

* Sinee the tabnlar numbers represent the temuueei of the barometric curre, 
and not the dmple ardmatu, the vtfuea for 0^ and 180'' are the same. 



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158 Beyal80eUt!h 

be niaSeWkieli w31 ooeupy mudi time; yet, notwiihiiig to posfcpene 
tli^ ptibMoBtioa of oeitam facts, I purpose now to give a short ieeoont 
oi them, to be extended and oompleted en a sabseqnent occasion^ . 

In the first place it is important to remark that the <^Tine of me* 
teorites contains most excellent " glass-eaTities," similar to those in 
the olivine of lavas, thus proving that the material was at one time 
in a state of igneous fusion. The olivine also co nt ai n s '' gas-^cavities," 
like those so common in volcanic minerals, thus indicating the pre- 
sence of some gas or vapour (Aussun, Pamallee). To see these 
cavities distinctly, a carefully prepared thin section and a magnifying 
power of severed hundreds are required. The vitreous substance 
found in the cavities is also met with outside and amongst the cnrs- 
Btals, in such a manner as to show that it is the uncrystidline residue 
of the material in which they were formed (Mezo-Madaras, Par- 
nalke). It is of a claret or brownish colour, and possesses the cha- 
racteristic structure and optieal properties of artificial glasses. Some 
isolated portions of meteorites have also a structure very similar to 
that of stony lavas, where the shape and mutual relations of the 
crystals to each other prove that they were formed in situ, on solidi* 
fication. Possibly some entire meteorites should be considered to 
possess this peculiarity (Stannem, New Concord), but the evidence 
is by no means conclusive, and what crystallization has taken place 
in situ may have been a secondary result ; whilst in others the con- 
stituent particles have all the|characters of broken fragments (L' Aigle). 
This sometimes gives rise to a structure remarkably like that of con- 
solidated volcanic ashes, so much, indeed, that I have specimens 
which, at first sight, might readily be mistaken for sections of meteor- 
ites. It would therefore appear that, after the material of the me- 
teorites was melted, a considerable portion was broken up into small 
fragments, subsequently collected together, and more or less consoli- 
dated by mechanical and chemical actions, amongst which must be 
classed a segregation of iron, either in the metallic state or in com- 
bination with other substances. Apparently this breaking up oc- 
curred in some cases when the melted matter had become crystal- 
Une, but in others the forms of the particles lead me to conclude 
that it was broken up into detached globules whilst still melted 
(Mezd-Madaras, Pamallee). This seems to have been the origin of 
some of the round grains met with in meteorites ; for they occasion- 
ally still contain a considerable amount of glass, and the crystals 
which have been formed in it are arranged in groups, radiating from 
one or more points on the external surface, in such a manner as to 
indicate that they were developed after the fragments had acquired 
their present spheroidal shape (Aussun, &c.). In this they differ 
most characteristically from the general type of concretionary globules 
found in terrestrial rocks, in which they radiate from the centre ; 
the only case that I know at all analogous being that o{ certain 
oohtic grains in the Kelloways rock at Scarborough, which have 
undergone a secondary crystallization. These . facts are all quite 
independent ot the fused black crust. 

* The names given thus (Stannern) indicate what mete<Nrite8 I more particu- 
larly refer to in proof of the various fiiots previously stated. 

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Geologieal Society, 159 

. Same df the mmenis in meteorites^ luiiallj cooeider^ to be tbe 
none as tkose in volcanic ro^u, have yet very chajracteristic differ- 
ences in stracture (Stamiern), whidi I shall describe at greater length 
on a fixtore occasion. I will then also give a full acconnt of the mi- 
croscopioal stracture of meteoric iron as compared with that produced 
by varioQis artificial processes, showing that under certain conditionH 
the ktter may be <4ytained so as to resemble very closely some varies 
ties of meteoric origin (Newstead, &c.). 

Th^re are thus certain pecuharities in physical stracture which 
connect meteorites with volcanic rocks, and at the same time others 
in whidL they differ most charai^eristically, — ^£Bcts which I think 
must be borne in mind, not only in forming a conclusion as to the 
origin of meteorites, but also in attempting to explain volcanic action 
in general. The discusrion of such questions, however, should, I 
think, be^deferred until a more complete account can be given of all 
the data on which these conclusions are founded. 



GEOIiOOIOAL SOCIETY. 

[Continued from p. 7^0 
May 11, 1864. — W. J. Hamilton, Esq., President, in the Chair. 
The following communications were read : — 

1. *' On a Section with Mammalian Remains near Thame." By 
T. Codrington, Esq., F.G.S. 

A railway- cutting through a hill between Oxford and Thame 
having exposed a section of certain gravel-beds, from which many 
Mammalian remains were collected, the author now gave a short 
description of the section and a list of the bones he had obtained 
from it. The hill is nearly surrounded by the Thame and two small 
tributaries, and consists of Kimmeridge clay capped by a bed of 
coarse gravel overlain by sandy clay. The gravel consists of 
chalk -flints, pebbles derived from the Lower Greensand, and frag- 
ments of mica- schist, &c., indicating a northern-drift origin ; it con- 
tained many bones of Elephant, Rhinoceros, Horse, Ox, and Deer, 
and a single phalanx of a small carnivore, but no flint implements 
were discovered. 

2. " On a Deposit at Stroud containing Flint Implements, Land 
and Freshwater Shells, &c." By E. Witchell, Esq., F.G.S. 

In the construction of a reservoir near the summit of the hill 
above tiie town of Stroud, the author observed, about two feet from 
the surface, a deposit of tufa containing Land- shells, with a few 
freshwater Bivalves ; in it he subsequently discovered several flint- 
flakes of a primitive type, and in the overlying earth a few pieces cf 
rude pottery, 

8. "On the White Limestone of Jamaica, and its associated in- 
trusive rocks." By A. Lennox, Esq., F.G.S., late of the Geolo- 
gical Survey of Jamaica. 

The White Limestone of Jamaica was described as including a 
basement series of sandstones and shales, a hard white limestone, a 
yellowish limestone, and an uppermost member consisting of dark- 
red marl; it was estimated to be at least 2600 feet thick; and the 



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100 hidUgmce and MiieMmmui Artielm. 

nnthor stated tfaat» at the jimotioii^of the cakerecnu rock widi the 
gmute» the former wee often more or lese altered ; and this appeared 
to be the best proof of the Tertiary age of the latter. 

Mr. Lennox then adverted to a diagram-eection of the rock- 
fannationB of Jamaica by the late Mr. Barrett (Quart. Jonm. Qtd, 
Soc. Tol. xix. p. 515), which he coneidered erroneone on the follow- 
ing groonds :---(l) he knows no section in Jamaica in which the 
relation of the White Limestone to the Hippurite-limestone is seen ; 
^2) the White Limestone he belieyes to be of Miocene age ; and 
(3) the shaly and sandy beds represented in the section as oyerlying 
the White Limestone he considers to be undoubtedly in infia- 
position. 

The author then discussed the question of the age of the White 
Limestone, first on physical grounds, and afterwards pal»ontolo- 
gically, inferring that it was decidedly of Miocene date ; and in 
conclusion he remarked that the White Limestone had probably 
been deposited slowly in a tranquil sea. and discussed its relation to 
the Tertiary beds of the other West Indian Islands. 

4. " Facts and Observations connected with the Earthquake which 
occurred in England on the morning of the 6th of October* 1863." 
By Fort-Major T. Austin, F.G.S. 

Earthquakes in the British Isles attract usually but little notice, 
owing probably to the mild form in which they generally occur ; but 
the one treated of in this paper, owing to its greater violence, 
aroused attention to the subject. The disturbance was said to ex- 
tend from a point in St. George's Channel forty or fifty miles to 
the north-west of Pembrokeshire to Yorkshire, and the focus of the 
disturbance to be situated near the former spot. The author 
brought forward a number of facts for the purpose of proving the 
intensity of the shock, the time at which it occurred, the number of 
vibrations, their direction (which was considered to be from W.N. W. 
to E.S.E.), and the occurrence of incidental phenomena, and con- 
cluded by passing in review the natural causes competent to produce 
these and other characteristics of earthquakes. 



XIX. Intelligence and Miscellaneous Articles. 

APJOHN^S 'manual OF THE METALLOIDS.' 

To the Editors of the Philosophical Magazine and Journals 
Gbntlbmbn, 

HAVING been many years since an occasional, though, I fear, a 
not very valuable contributor to the pages of the Philosophical 
Magazine, or rather of its predecessor, the Annals of Philosophy, I 
trust you will permit me to make a few remarks on the review of my 
volume on the Metalloids which has appeared in the last Number of 
your Journal. In these remarks you will, I hope not, find anything 
uncandid, or exceeding the just limits of scientiiBc discussion. I am 
quite aware how unreasonable it would be to occupy your pages 
with a lengthened paper on questions chiefly relating to myselfi, and 
shall therefore make my notice of the review as brief as possible. 



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hi^igence and Mk&eUaneout Artideg. ' ]f6l~ 

. In page 68 of my. book, with a view to a brief explanation for the 
Tyro \n chemistry of what is meant by abinatomic body, a brief 
statement is made which is certainly not correct. In point of fact 
the reaction described between Dutch liquor and water has not been- 
observed ; but, assuming it to take place, we have a simple expla*. 
nation of what is meant by a triatomic organic radical ; and what 
was in my mind when writing this passage was, to speak hypotheti- 
cally of the reaction, though this I find has not been done. I can 
assure the reviewer that I was not ignorant of the series of processes 
by which biniodide of ethylene is convertible into glycol, and the 
latter into the biniodide of ethylene ; but the description of these 
would have been quite unintelligible to the junior student, and, at 
the same time, altogether unsuited to my introductory chapter* 

In pages 561'and 562 I give an explanation of Liebig's well-known 
method for the estimation of hydrocyanic acid, in relation to which 
the reviewer has the following passage : — " It is difficult to suppose 
that the writer of this passage has ever performed the operation he 
professes to describe, otherwise he could hardly have failed to notice 
that in reality it is the white cyanide of silver, and not the brown- 
grey oxide which appears as a permanent precipitate." In reply to 
this commentary, I beg to state that the inference suggested would 
be quite erroneous. The experiment in question is one which, as a 
teacher of chemistry, I am obliged repeatedly to perform ; and I may 
add that, in doing so, I have not failed to observe the white precipi- 
tate of which he makes mention. This, however, or rather the por- 
tion of it which first falls, is not cyanide, as alleged in the review, but 
ehloride of silver, arising from the alkaline chlorides invariably pre- 
sent in the ordinary solutions of soda and potash. If the solution 
of caustic potash was absolutely pure, it appeared to me a probable 
conclusion that the precipitate would be oxide of silver, and hence 
it has been described as such ; but I am now by actual experiment 
aware that this is not the case, and that, after the whole of the 
hydrocyanic acid has been converted into the soluble double cyanide* 
it may be thrown down as insoluble cyanide of silver by adding just 
as many measures (chloride being supposed absent) of the volume- 
tric solution of nitrate of silver as have been already employed* 
The ignorance on this latter point, which I freely avow, the reviewer 
no doubt considers as quite unpardonable ; but I am not without 
hope that the candid critic will feel himself at liberty to pronounce 
a more lenient judgment, the more especially as a knowledge of 
the nature of the permanent precipitate which appears in this volu- 
metric process is not necessary with a view to the accuracy of the 
experiment. Chemical reactions cannot be always predicted with 
certainty ; and the charge against me simply amounts to this, that, 
not having made the trial, I did not know that the cyanide of potas- 
aiiun of the double cyanide would be precipitated by nitrate of silver. 

The next charge preferred against me is one of rather a paradoxical 
nature, being actually that I have stated the compounds of nitrogen 
with hydrogen to be three in number, viz. amidogen, ammonia, and 
ammonium, — of which he says that " a more misleading statement 
could not easily be put before the student/' As a further illustra- 

Phil. Mag. S, 4. Vol. 28. No. 187. Aug. 1864. M 



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102 InieUiffence end MiiceUtm&m» Arlide$, 

tkm of my tnmgreflsioiis in this dLrectioii, the offence i» imputed to 
me of enumerating eeren oxides of salphur, and six of carbon. Ob 
these pcnntB I decline to enter upon any defence, further than to say 
that, in the best works on chemistry recently published, ];HPecisely the 
same enumeration of these compounds has been made. If I have 
nnned against scientific accuracy, of which I must aay I am quite 
unconscious, precisely the same offence has been committed by 
modem chemists of great eminence, such as Pelouze and Fremy, 
Regnault, Miller, and sereral others ; and I am at a loss to under- 
stand why so humble an individual as myself should be singled out 
for especial censure, while my distinguished contemporaries are per« 
Biitted to pass unscathed. Many of the atomic groups here referred 
to have certainly not as yet been insulated, and are therefore to a 
Certain extent hypothetic ; but this does not appear to me to consti- 
tute any sufficient reason why their constitution and properties, as 
Us as these can be deduced from the known compounds in which they 
occur, should not be considered and discussed. 

Of a somewhat similar character are the remarks upon my mode 
of dealing with the compounds of carbon and hydrogen. In page 
502 I state that these numerous bodies form properly a part (rf 
oi^nie chemistry, but that there are a few of ^em, in particular 
C^ H^ and C2 H^, to which the student should pay an early attention. 
Notwithstanding this distinct announcement of the plan which I in- 
tended to pursue, and the fact that in all almost all treatises on 
themistry olefiant gas and marsh-gas alone are discussed in con- 
nexion with carbon, the reviewer does not hesitate to use the loUow- 
ing language: — "From these instances it will be seen that Dr^ 
Apjohn's lists of known compounds include mtiny substances with 
which other chemists are by no means well acquainted : hence it is 
natural he should require to make room for tbem by ignoring sub- 
vtanoes which often receive a considerable share of attentioB. Thus 
^page 502) the usual list of hydrocarbons is much curtailed.** Of 
the tone of this extract, and there are several other passages in th« 
review on a level with it, i do not oomplain. Some persons thizdc 
that in every kind of controversy a sarcasm or a sneer constitutes 
the most effective weapon, and therefore naturally resort to them* 
I would suggest, however^ that there is no sufficient excuse for the 
misstatement or distortion of facts exemplified in the passage which 
1 have just quoted. 

In the remainder of the review there is a good deal of criticism of 
a hostile nature, npon the details oi which it is not my intention to 
tenter. I am quite prepared to admit that in my book there are some 
omissions, and that in particular the interesting compounds of silicon 
with hydrogen and with oxygen, discovered by Wohler and Buff, 
have not been noticed. This was not an intentional omission ; fitf 
<the manuscript was prepared^ but, through some accident, not fop- 
warded to the printer. There are also other errors which I have no 
disposition to deny or justify. It is, for example, quite true l^at 
the rival claims of Watt and Cavendish had reference, not to the 
discovery of hy<kogen, but to a kindred question — the discovery of 
the composition of water \ and that the combustion of the diamond 



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kj Lavrisier and Morveau was effeoted« not seventy^ but about eighty 
jeafs after tiie analogous experiment oi the Florentine academician. 
X am also quite aware that the spelling of the names of foreign che- 
j&ists is sometimes erroneous, and tliat in a few instances, as a con- 
sequence of the omission of oertain words, the composition has been 
^rendered faulty. These errors, however, are, I believe, of small con- 
eequence ; nor is their number unusually great, considering that the 
yokune extenda to about dOO pages, and that, from much preoccu- 
pation of time by other duties, I was unfortunately unable to pay 
.sufficient attention to the correcting of the press. Such as they are» 
they> or at least the majority of them (some will no doubt escape 
detection), have beetf carefully noted by myself and others (I have 
had, for example, for a considerable time on my list of errata all those, 
with a single exception, animadverted on by ^e reviewer, to which I 
attach any importance) ; and ^om the next edition, which will, I 
presume, shortly appear, as the book is very nearly out of print, 
they will of course be excluded. 

Though very unwilling to add to the length of thia c<»nmunica- 
tion, I must not omit adverting briefly to the criticism which has 
been passed on the few remarks tnade by me in page 124 on the 
origin of the heat and light attendant on combustion. These remark^ 
are pronounced by the reviewer to contain not only " a totally inade- 
quate and therefore erroneous statement" of Lavmsier's views, bnt 
to imply '* what is directly contrary to facts well known to all who 
' have paid any attention to the history of chemistry — ^namely, that the 
phlogistic theory held its ground long after it had been discovered 
that combustil^ bodies increase in weight when bumea, and that 
this obs«-vBtion first came to be regarded as an objection to the 
theory when it was shown by Lavoisier to be coaneoted with die disap- 
pearance of part of the ataoosphere in which combustion takes place." 

In r^ly to this, I beg to say that the experiments of Ray and 
Mayow constituted in my mind a full refutation of the Stahlian 
the(»ry ; for, after their publicaticHi, it became impossible to maintain 
it except upon the absurd assumption that a principle existed in 
inflammable bodies which conferred upon them levity instead of 
weight. The abandonment indeed of a prevalent theory is, I am 
aware, a alow process ; and it is quite possible diat, notwithstanding 
its obvious absurdity, the phlogistic hypothesis continued to be em- 
ployed by some chemists until oxygen, and the part which it plays 
in all ordinary cases of combustion, were discovered by Lavoisier. 
It should, however, be recollected that I did not contemplate any- 
thing like a complete discussion of the theories of combustion. 
This is a topic merely glanced at incidentally in my ' Manual ;' and 
my method of handling it may possibly be, with justice, described 
as *• inadequate." I deny that it is -erroneous." I also allege 
that my statement of Lavoisier's views is substantially accurate; 
but, instead of bandying contradictions with my anonymous adver- 
sary, I would solicit the attention of the reader to the following 
extract from vol. i. p. 184, of the eighth edition of Turner's 
* Chemistry,' brought out und^ the supervision of Liebig and 
Gregory; — 

M2 



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IM hiieKgenee and MiseeUaneaui Artida. 

** To aeeount for the production of heat and light during com- 
bustion, Layoisier had recourse to Black's theory of latent heat. 
Heat is always eyolved when a substance, without change of form, 
passes from a rarer into a denser state, and also when a gas be- 
comes liquid or solid, or a liquid solidifies, because a quantity of heat 
previously combined or latent within it is then set free. Now this 
is precisely what happens in many instances of combustion. Thus 
water ib formed by the burning of hydrogen, in which case two 
gases give rise to a liquid ; and in forming phosphoric acid with 
•phosphorus, or in oxidizing metals, oxygen is condensed into a solid. 
When the product of the combustion is gaseous, as in the burning 
of charcoal, the evolution of heat is ascribed to the circumstance 
that the oxidized body contains a smaller quantity of combined heat, 
or has a smaller specific heat than the substance by which it is 
produced." 

This passage, combined with that which immediately succeeds it, 
and which I abstain from quoting merely because of its length, 
enunciates very distinctly the views which I have ascribed to La- 
voisier in relation to the origin of heat and light which accompany 
combustion. If they are mistaken views, I have, at all events, the 
consolation of having fallen into error in good company. 
' I may, in conclusion, observe that I fear I have suffered much in 
the estimation of the reviewer by continuing to employ the Amp- 
litlic * methods of explanation, and the atomic weights long in use 
among chemists, instead of those of the unitary system, of which, I 
make no doubt, he is a zealous advocate. In my introductory chapter 
I have explained my motives for adhering, at least for the present, 
to the equivalents and the language of Berzelius and Davy, and I 
regret that before entering on the details of the work, he did not, as 
it were, lay the axe to the root, and point out the errors I may have 
committed in such fundamental discussion. If convicted of any 
inaccuracies, either of statement or inference, in relation to the 
system of the illustrious Gerhardt, I trust I have given sufficient 
proof that I would be prepared to admit them, and, as far as pos- 
sible, atone for them. 

Jambs Apjohw, M.D., F.R.S., M.R.I.A., 
Professor of Chemistry in the University of Dublin. 



Out of deference to Professor Apjohn's wishes, we have adopted 
the somewhat unusual course of publishing his reply to the criticisms 
on his work entitled ' A Manual of the Metalloids/ Wiich appeared 
in the last Number of this Journal. Upon this reply, the reviewer 
claims the right of adding the few following remarks : — 

Professor Apjohn's work is intended for the use of junior students 
in chemistry, and comes before them, not only with the prestige 
conferred upon it by the distinguished position of its author, but 
with the additional advantage of being published as one of a series 

* This phrase is at present sometimes used as one of reproach by gen- 
tlemen who have studied chemistry in a German school, and who are quite 
satisfied with the fictions of the unitary system. 



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InteUiffence and Miseettmeam Artieki. ]6$ 

of educational manuals which* as we have already stated, Enjoys the 
recommendation of the Committee of Council on Education. On 
examining the book, we found that it fell very far short of what an 
introductory text-book of Chemistry ought, in our judgment, to be ; 
and we felt it needful to express our opinion of it all the more em* 
phatically, since we thought it probable that the circumstances of its 
publication would secure for it a considerable circulation, quite in* 
dependently of its intrinsic merits. Dr. Apjohn's statement that the 
first edition is already nearly out of print, confirms us in this sup« 
position. We did not, however, condemn the work in vague and 
general terms. We stated as clearly as we were able the grounds of 
our objection to it, quoting literally several passages in support of 
our charges, and accompanying the quotations with precise references 
to the pages where they might be found in the original. But not-^ 
withstanding all our care and our anxiety to quote fairly and cor- 
rectly. Professor Apjohn brings against us the charge of *' misstate- • 
ment or distortion of facts." This charge is made with reference 
to what is said (p. 61 of the review) respecting Dr. Apjohn's treat- 
ment of the compounds of carbon and hydrogen. In the review it is 
stated that " the usual list of hydrocarbons is very much curtailed " 
by our author ; and this passage is followed by a quotation from the 
book under review, which we conceive fully bears out our assertion. 
Professor Apjohn now states that, in writing that passage, he had 
in view only those compounds of carbon and hydrogen which are 
usually treated of among inorganic compounds. In answer to this, 
we can only say that, whatever the author's intention may have 
been, nothing of this kind is apparent in the book itself: the pas- 
sage we have quoted is the opening passage of the section devoted 
to these compounds, and is immediately preceded by the heading 
CABBO-HYDROGENS iu Small Capitals. The following is the whole 
of the first paragraph of this section, and we leave the reader to 
judge whether a charge of " misstatement or distortion " in connexion 
with it is most applicable to Professor Apjohn or to ourselves : — 

** The number of compounds of carbon and hydrogen is very 
great. Those at present known are reducible to three groups : — 
Those whose general formula is C^ Hn> those represented by Cn Hn+i, 
and those by C^ Hn+i, n being always an even number. The sub- 
ject of these hydrocarbons belongs properly to organic chemistry, 
but there are a few of them to which the student must direct an early 
attention. Those which will be considered here are only two in 
number, and belong, one to the first, the other to the third group. 
The former is called olefiant, the latter marsh-gas." 

Professor Apjohn also takes exception to what we have said in 
reference to the history of the antiphlogistic theory of combustion. 
In reply, we have only to state that we were concerned, not with 
what he regards as '* a full refutation of the Stahlian theory," but 
with what was regarded as such a refutation by the contemporaries 
of Ray and Mayow and of Lavoisier ; and that we objected to his 
statement of Lavoisier's theory of combustion, not because we con- 
ceived that he has wrongly represented Lavoisier's views with re- 
spect to the production of light and heat, but because it seems to 



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166 MelSffenM mid MiktJkimom Ar^^ 

Hft to be Implied in the pasaftge that we quoted tiiat this theory et* 
tended to the explanation of the light and heat of combustioa only* 
We do not think it needfol to add an3rthing in defence or expUi» 
nation of our other criticisnis, since Dr. Apphn himself admits their 
justice; but with regard to his statement that he had deteoted 
several of the faults which we have pointed out, and that they will 
be corrected in a new edition, we may renund him that, had this 
statement accompanied the copy of his book sent for review, we 
should probably have contented ourselves with laying it before 
our readers and recommending any who intended purchasing tbe 
work to wait for the second edition. And since we now understand 
that a new edition is likely soon to appear, we may farther remind 
him that his having had on his list of errata all the errors, " with a 
single exception," pointed out in our review, is no proof of the oom« 
pleteneeB of his revision, for we made no attempt to enumerate all 
the faults we had detected : our quotations were, as we have already 
Maid, intended merely as specimens to prove that our criticisms were 
not made without good reason ; and in case of need we are quite pre* 
|)ared to produce at least as many more of very similar quality. 



ON TETft MEAStTREMEIlT OP THE CHEMICAL BRIGHTNESS OF 
TARTOtTS PORTIONS OP THE SXTN^S DISK. BY THOMAS 
WOODS, M.D. 

Professor Roscoe's paper " On the Measurement of various por- 
tions of the Sun*8 Disk," read to the Royal Society, an abstract of 
which appears in the May Number of this Magazine^ is extremely 
interesting. The chemicsJly active rays decrease in intensity from 
the centre to the circumference, which the Professor found by expo- 
sing a prepared paper in a camera to the action of the sun's picture, 
and comparing the shade of tint produced thereby at the centre and 
at the circumference with a certain standard. I would, however, 
suggest the plan I described in this Magazine in July 1854.. It 
consists in exposing the prepared paper to the sun's picture in the 
camera for a period so short that the centre or most active rays only 
have time to act on it ; then for the next impression to leave the 
paper exposed for a somewhat longer time, so that a somewhat larger 
picture is obtained ; and so on until the entire picture is given. For 
instance, suppose the sun's picture is divided into zones by concen- 
tric circles thus, and suppose the centre rays could 
affect the preptured paper in one second, the second 
zone in two seconds, the third in three seconds, and 
the circumference in four ; then by exposing the 
paper for these periods of tim^e a corresponding 
amount of the disk would be obtained; the- size of 
the impression produced would be in proportion to the time of expo- 
sure ; and the intensity of the rays from any part of the disk would 
be more accurately fixed by onc6 getting the time required for their 
action, and more permanently, I fancy, than by the use of the stand- 
ard tints. This was the plan I adopted in 1854 to show the identity 




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Intelligence and MifcellanetmS' Artidet. 167 

of the swa's action on a photographic surface irith that of flame, the 
centre rays of the latter being also more intense in chemical acticm 
tiian those at the circumference. 
Parsonstown, July 1864. 



ON THE COLOURIN6-MATTEB OF EMERALDS. 
BY MM. WOHLEB AND G. ROSE. 

Vauquelin, after having discovered oxide of chrome in the eme- 
rald, attributed to this oxide the green colour of the stone. In 1858 
M. Lewy published very interesting researches on the deposit, the 
formation, and the composition of the emeralds of Muso in New 
Granada. His conclusion is that the colour is due to an organic 
substance, the existence of which he proved by very accurate expe- 
riments. Thus he says that the green colour disappears when the 
emeralds are heated to redness. As we were unable to verify this 
assertion in the blowpipe experiments to which we subjected the 
emerald, M.Rose andmyself exposed a piece of Muso emerald, weigh- 
ing 7 grammes and of a deep green colour, for an hour to the tem« 
perature of melting copper. The colour did not disappear ; the spe- 
dmen simply became opake. Yet it had lost 1*62 per cent, of its 
weight, which agrees closely with the numbers given by M. Lewy^ 
On analysis the above specimen gave 1*186 per cent, of its weight 
of oxide of chrome. M. Lewy thinks that such a small quantity of 
oxide is insufficient to communicate so pronounced a tint to eme- 
rald. 

To settle this question, we melted 7 grammes of colourless glass 
with 13 miiligrammes of oxide of chrome. We thus obtained a trans- 
parent homogeneous glass of a green colour, identical with that of 
the emerald analyzed. Hence it seemed proved that 1-3 parts of 
oxide of chrome are sufficient to communicate a very deep green 
colour to 7000 parts of a silicate, and we do not hesitate to assume 
tliat die colour of emerald is due to oxide of chrome, without, how- 
ever, contesting the existence of an organic substance in this mineral. 
— Comptes Rendus, June 27, 1864. 



RESEARCHES ON THE RESPIRATION OF FLOWERS. 
BY M. CAHOURS. 

The author gives the following summary of the results arrived at 
in the course of his researches :— 

1. Every flower left in a confined space of normal atmospheric air 
consumes oxygen and produces carbonic acid in variable proportions, 
^nrhether the flower has odour or not. 

2. The circumstances in which this takes place being the same, 
the proportion of carbonic acid increases as the temperature rises. 

3« That generally for flowers gathered on the same plant, and 
-whose weights are virtually equal, the quantity of carbonic acid jaro^ 
duced is somewhat more considerable when the apparatus in which 
the experiment is made is exposed to light, than when placed in 



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168 InteJUgence and Miseettaneous Articles. 

complete darkness ; that nevertheless in certain cases the proportion 
is virtually the same under the two conditions. 

4. When normal air is replaced by pure oxygen, the differenceer 
observed become much more marked. 

5. That the flovirer whose development is commenciug, disengages 
a little more carbonic acid than that which has attained its complete 
development, which may be explained by a more powerful vital action. 

6. Every flower left in an inert gas disengages small quantities of 
carbonic acid. 

7. We see, in conclusion, that, of the various elements constituting 
the flower, the pistil and the stamina, in which the greatest vitality 
resides, are those which consume the greatest quantity of oxygen, and 
produce the largest proportion of carbonic acid. — Comptes Rendus^ 
June 27, 1864. 



ON THE SPIICTRAL RAY OF THALLIUM. BY M. J. NICKLES. 

I have found that there are compounds of thallium which do not 
possess the property of colouring the flame green, and of developing 
the . characteristic spectral ray ; these are compounds with sodium, 
and especially with chloride of sodium. By its flame and its yellow 
frays this chloride, completely hides the green ray. 

Although chloride of thallium is insoluble in cold water, it is not 
so in water saturated with chloride of sodium. Thus, on potuing a 
solution of the latter into acetate of thallium, a precipitate of chloride 
of thallium is indeed formed, but the mother-liquors retain a consi- 
derable quantity of the latter without colouring the flame green. If,* 
then, among the rays of the solar spectrum that characteristic of 
thallium has not been found, nothing proves that this metal does 
not exist in the sun ; for if it has not been found, sodium has, the 
paralyzing action of which, when present in a certain proportion, I 
announce in this Note. 

This incompatibility between the ray of sodium and that of thal- 
lium ought to be taken into account in toxicological or medico-legal 
researches directed upon thallium ; for when it is present in animal 
tissues or liquids, it may be accompanied by sodium-compounds in suf- 
ficient quantity to annul its action on the flame, and thus lead to 
the supposition that this poisonous metal is absent. 

Thus, also, if thallium is to be sought in mineral waters or mother- 
liquors, and generally in saline waters containing excess of chloride 
of sodium, it must first be disengaged from the sodium compounds, 
either by displacing it by means of pure zinc, or by means of the 
battery, or by precipitation by hydrosulphate of ammonia or iodide 
of potassium. 

In regard to the latter, I have assured myself that liquids containing 
chloride or bromide of thallium in solution are precipitated by iodide 
of potassium, which gives rise to an iodide of thallium of a beautifid 
yellow colour, insoluble in the precipitating iodide but fairly so in 
distilled water.— Cwnp^e* Rendus, Jan. U, 1864. 



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Fig z. 





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THE 
LONDON, EDINBURGH, and DUBLIN 

PHILOSOPHICAL MAGAZINE 

AND 

JOURNAL OF SCIENCE. 

[FOURTH SERIES.] 



SEPTEMBER 1864. 



XX. On the Spectra of Compounds and of Simple Substances. 

By Albxandbr Mitscherlich*. 

[With Two Platet.] 

IN a previous paper I have shown that compounds of the 
metals have other speetra than the metals themselves. 
This fact appeared to me of great importance, because by the 
observation of the spectra a new method is found of recognizing 
the internal structure of the hitherto unknown elements^ and of 
chemical compounds. Hence I have investigated the spectra of 
all the metals which I could procure, and of many of their com- 
pounds, and have found that compounds of the first order, in so 
far as they are volatile and remain undecomposed when ade- 
quately heated, always exhibit spectra which completely differ 
from those of the metals. The observations which I have re« 
oently made in this respect are communicated- in the following 
research. 

In the spectra of the compounds of the metals, to which I 
shall subsequently recur in detail, a regularity is most observed 
in the arrangement of the bright and obscure parts ; thus^ for 
example, in the spectrum of chloride, bromide, and iodide of 
copper. (See the delineations of the spectra.) 

£1 these spectra, lines occur, or appear under special circum- 
stances, which do not seem to me to belong to the spectra, 
because they contravene their regularity ; such lines occur, for 
instance, in the spectra of copper- and of bismuth-compounds. 
It was obvious to suppose that these lines' belonged to previously 
unknown metals ; for the spectra produced by the introduction 
of compounds of oxide of copper or bismuth into the flame, and 

' • Translated from PoggendorTs Annakn, No. 3, 1864, by Dr. E. At- 
Vinson. 
PAtf. Mag. S. 4. Vol. 28. No. 188. Sept. 1864. N 

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170 Frof. Mitoeheilich on tkf 8peetra cfCompaundi 

those wUdij mmppottiig » d»ertmeiit aiia]oe0«». to the alks- 
fies, must belong to the metals, exhibit a regular shading by 
nthMvoAomist only the speetra oi the eovpoiuiAi aie chwa^ 
terised. Bilt Ae lanfiiber of these t w tpp ese d mm mMk mwHii 
soon haTe reached that of those at present kno?m. The diseo- 
Tery of soch metals appeared easiest in bismuth eompounds. 
Tm> line^oednfrec^^^nB which ^omi sooik astfettodurd to be that 
of the abeacfy known thallium, and a second near the division 
77 of the sc»le. By precip i t a tio n s, subUmations, reductions, 
and oxidations conducted in the most carefiil manner, I could 
not separate from bismuth the metal belonging to the line 77* 
Subsequent investigations showed that, according to the manner 
in which the spectrum was prepared, this line in the speetra of 
bismuth compounds occurred or disappeared^ it always ooenrred 
when deoxidiidng giuses came in contact with the metal at a high 
temperature, and disappeared with oxidizing gases. The Ime 
in question can be obtained quite pure when metallie bismuth 
is volatilized in hydrogen and I9re latter is ignited. From 
these observations it foUows that tins line belongs to bismuth as 
setaL 

i liave snveatagaAed most bodies and emnpoonds in which m 
iqpectram mo^t beeupposed, and b^ difibrent metboda, in ocder 
t^ avoid the chance «f ohtaiwng nused or enoneoms speetnt by 
fbreign xnflumsees* Aa a source of Ugfat, I used ibma aaud the 
dedmid daschstsge* I will briefly adduce the OMilhods which I 
used for staining the Sffictra^ and des^ate tbaiaby wunfaevi 
ibar aoixvenssnee of anbeeqnesii v^Smeott^ 

1^ A itnelfluMi vrittch I hairo described itt ithf memoir aaeor- 
tioaedabo^e. AromatufaedbMedat ihet(9Mid'P»»ndedm& 
ft very smldl apertne at ils lower bent en«^ a soltttioiL eontiam* 
OQsly lows, by mtoaiHiof a wick ef very &m platiwim ivire, into 
a flame of coal-gas, or of hydrogen ; the gas emerges &eim ft 
naittow aperfeare. Hbe liquid ia qoestiofi brought by the wick 
tfqiidly evapoaatas in ihe flame. Carboa does not s^acate ia 
the 4mi'»gaa;; it ia pssvented from 'doing ao hf the prescBee of 
watei, bf Which hydxiigen and dsf bonis oxide are formed. 

2. The BubstanCaa are boongbt into a «9al*gas flame iwhkda 
bu«8 in joxjisf^* iAn m^vydrogen hnraw is use4> £^w^ whoae . 
sfiddie aperture soalHgaa, and fi»sim whose external ring Q^fSfmk 
issues^ VAAuBt by vegubtiag the eqrgen lOc the position <if tike 
substances, ithey oan be natrodueed into a iiednciBg or oridiriM 
flaioe. Vhe spectram of carbon which waulid hoie be foiftacd 
disappeara almost enfcirely^ in consequence xif the fcHnastioa ^ 
oarbwic okide> which again^ in riitue of tike feeble intensky o£ 
ita light, does not lessen the purity of the pheiM)mena wbea a 
substance to be volatilized is brought into the flame. 



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tmd 4^Smph Sift^^m^. If I 

noe uNit^ q( <fffei^ mi l^dioogm m^^sA of pQ^d-g^ m tb? 
bmiM^, Tbf^ spi^t^nm wi^kik migjij; b^ fwined l;^y the iww?^ ioif 
tb«0^ b^^ is top iM>l« tp b^ ofmry^i wly la viery fp^h 
ImgjSLtmm in the gr^ 19 perc^tible. 

4. BroEiine or iodine is evaporated in hycUpgen, ^nd ^s i^ 
bxHrnt in ji^r pr i|Ei oxygm> wd th^ suh^tainc^ yplntiU^^d in th^m. 

6. If tbe sub^^cea to b^ imrq^tig^tied are x^ombpi^t jibl^ gi^se«»» 
tb?J are aUow^ to emergie ioul; of tbe middle aperture of tb4^ 
qsj^yidrpgen Wiioer instep^ of (K>al-ga9j md cm thus be bum^^d 
uii4r Q^ iA g^yge^ j if tbsy a^ not combustible^ they i^re n^is^ed 
with a combustible gas such as carbonic oxide or hvdrpgep, 
Tb^ light p^uoed by the combif^tion of x^arbopic (We and of 
bydrogim i» ^ feebjie that it may be quite diar^gi^rded ia CQnr 
sidi^isg the fermaliop of other spectra by its meau9« 

(5. The AoUd substancf&s are introduced inio a tube, ow end of 
vhii^ m OQun^et^d with a Rose's hydrogen^apparatus, or with a 
gasrbcJd^r filled with ^rbomie ojcide, By heating, the suh^tanop 
is vojatilisfwl ia the gases, and kindled at the othepr epd of tbQ 
tube. If the substauoes ar^ volatile, a small bulb is blown iifi 
the tube, mt^ which tiiie substaQ^ is brpughtt 

In the abpvQ w jaixeithods the light is produced by a flame, while 
ift the two foUow^g thiB substance to be investigated is volatir 
liy^d by th^ discWge of ^ apM Stphrier's induction-apparatus, 

7. Im a ^S9(4 Reused by % cask, 1 caused the el^tncal sp$u^]c 
t^ paip9 «ith^ betwof^ t]V9 WVW of the metal investigi^ted^ o^ 
b^tweei:^ ^alts fastened on the e^ds of wires. T^e vessel was 
prQvid^ wth two glass tubes, by which it could be fiUed with 
a»y ^vw gas aftd eJwed# or by which a wrrwt of gas pp^ld he 
ftimd dwr^ th^ diaeharg^. 

8. In order to be able to use. liquids 
a» wi^iii^^Udf fc)r deptrodw, two tu.b^s^ 
b(^t m ahiwA iv^ tiip an»ex^ figure, 
W0re fxed i» th^ fork of thjS vessel and 
fiUed wiith liquid tiU this reached itihe 
low^ apertui^ Two thin plati^am 
wiiv^ ift 0QW<Bi(iQ» with the inductiouT 

. q^pamtos wore brought in both tubes 
t^ »efur the apcyrtwre. The spark thw 
passes from liquid to liquid . By means 
of W)#f fysfiA in the ^vessel, as ui th^ 
other m^thpd^ the e^piqrime^t m^y be 
niade in dififewrf gaaas. It is obs^ed 
that if Ae 9|^k only passea from liquid 
tgt4iq»idi.th^ gaaes in the v^selare with" 
oi^ mtkm 1^999' >th# apeptruwi mi thait 

N2 



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172 Prof. MiUcherlich on the Spectra ofCan^maub 

therefore the temperature of the discharge is so lowered by the 
liquid electrodes that the gases are uot ignited sufficiently to 
produce luminous phenomena. The latter mode of experiment 
is important^ because spectra of the metals and of their com- 
pounds can thus be produced free from any admixture with 
spectra of the gases. 

The spectra produced by the methods described are mostly 
depicted in Plates I. and II. ; the luminous parts are expressed 
in as accurate shading as is possible by printing-ink. The 
lines produced by method 8 (liquid electrodes) are designated 
by e in the Plates. As regards the investigations themselves I 
remark as follows. 

The spectra of the compounds of copper and of bismuth can 
be very conveniently obtained pure. Chloride^ bromide, and 
iodide of copper^ and salts of oxide of copper^ such as the acetate 
and nitrate^ were investigated by method 6 (volatilization in the 
glass tube). The spectra of chloride^ bromide^ or iodide of cop- 
per are obtained perfectly pure and very distinct by methods 3 
(CI and H) and 4 (Br^ or I, and H), using even any salts of cop- 
per. The spectrum of fluoride of copper is best obtained by 
method 2 (H, or coal-gas, and 0), using fluoride of copper and 
fluoride of ammonium. If in the latter method but little oxygen 
is admitted to the burning gases, a new line is formed in the same 
place in all spectra of the copper compounds. If the tempe- 
rature is increased by copious addition of oxygen, the spectra 
disappear almost entirely, and instead of it the above line 
appears very bright with a few other feebler ones. This line 
might perhaps be due to a degree of oxidation of the copper, 
were it not that it is formed, as I shall subsequently state, when 
oxygen is completely excluded; hence it must belong to copper 
as metal. 

It follows therefrom that the spectrum which is only obtained 
from the oxides of copper, and which I formerly considered to 
be that of the metal, belongs to an oxide of copper. There 
occur, therefore, in this, as in other copper compounds, at high 
temperatures the lines of metallic, copper. Hence at a very 
high temperature of ignition all copper compounds are decom- 
posed into their constituents, whereas these compounds remain 
undecomposed at a lower temperature — that, for example, of the 
hydrogen flame. 

The spectrum of metallic copper produced by electricity con- 
tains, besides the lines obtained by the flames, other lines of dif- 
ferent luminous intensity. This is also the case with other 
metals, with the sole difference that the additional lines in these 
are of less luminosity. I cannot decide how these new lines are 
formed, since the greater intensity of the light of the electrical 



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I 



4md of Simple Substances* 1 78 

apectram could only explain the occurrence of the feebler of 
them. 

The compouuds investigated by method 8 (liquid electrodes) 
were more or less decomposed according to the magnitude of 
the affinity of their constituents at this temperature^ — ^which is 
evident from the spectra ; the spectrum of chloride of copper is 
seen very distinctly, while the spectra of bromide and of iodide of 
copper are more aifficult to recognize. 

MetalUc copper investigated by method 7 (solid electrodes), in 
chlorine, bromine, iodine, oxygen, and nitrogen, and in othe^ 
gases, always gives the spectrum of copper very distinctly, and, 
further, that of the kind of gas, and in chlorine the spectrum of 
chloride of copper very feebly. 

Hence the temperature produced by the passage of the spark 
between solid electrodes is much higher than that between 
liquids, because, in the first, iodide and bromide of copper remain 
partially undecomposed, which in the latter are completely 
decomposed. 

New lines occur in these spectra which neither belong to the 
metal nor to the gas, and whose formation and origin I &ve not 
yet investigated ; for the lines are mostly so obscure that a cer- 
tain result could not be deduced from them. Sulphate and 
nitrate of copper, and iodide, bromide, and chloride of copper, 
examined in the different gases as solid salts by method 7, behave 
like metallic copper. 

Bismuth in the formation of its spectrum exhibits almost 
entirely the same phenomena as copper, excepting that the com- 
pounds are much more easily decomposed, when the spectrum of 
the metal appears. The spectra of chloride, bromide, and iodide 
of bismuth are obtained by method 6 (volatilization in the glass 
•tube). But if the tube is strongly heated, the compounds are 
partially decomposed, even at this temperature, in the manner 
described. The spectrum of an oxide of bismuth readily occurs 
along with that' of the haloid salt when water is present in the 
latter or is formed in appreciable quantity. 

The spectrum of the metal is best obtained if any bismuth 
compound or the metal itself is brought into the reducing flame 
in method 3 (hydrogen, or coal-gas, and 0) ; that of the oxide, 
if in the same method bismuth is held in the strongly oxidizing 
flame. 

In whatever way the spectrum of metallic bismuth is obtained, 
whether by electricity or by flame, it is under all circumstances 
the same. 

The compounds of calcium, of strontium, and of barium give 
almost as many spectra as do those of copper and bismuth. But 
to obtain them pure is more difficult than with the above metals. 
The spectra of barium and of strontium by the flame, I could 



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V/4 Prof. Mitadieriieti M tkf! SpMfB iff Compounds 

tfnYy cA>tam^ free from tboisci of theii totn^nnin, in meting 
2 (H, or coal-gas, and 0), by using a very small quantity of 
fluoride of barium or fluoride of strontium. The spectrtnli of 
^kium I could nevisr obtdin by the flame quite free from tbose 
<>f tbe oxide or of tbe haloid salt. By method 7 (solid electrodes) 
tiie latter is obtained free from admixtures by the tlsd of hydrogen 
ttnd metal ; but at this high temperature there occur, along with 
the lines which are produced in tbe flame, a great nttmber of 
-ilioi^ feebly lumitious lines. T!hti lines which could only be 
^iHialned by this method are not depicted in the spectra given. 

In the case of barium, I could free the spectrum of the miAe 
frdte that of the metal in the same way as with bt^muth i I evth 
succeeded, when I investigated nitrate of baryta or iodide trf 
barium by method 1 (wick of platinum wire), in producing the 
apectrum of baryta in individual parts of the flame. In order 
to obtain the spectra of the oxides of the other alkaline tnetal^, 
which indeed can usually only be obtamed simultaneously with 
the spectra of their metals, 1 have used in method 1 a miktute 
of nitrate of Ammonia with the nitrates or a solution of the 
iodides ; the latter ar^ decomposed at high temperatures, and 
give the spectra of tbe oxides very beautiftilly. In thes^ three 
m^tak I succeeded in obtaining the spectra of the haloid safts 
ttte from the spectra of the oxides, and but seldom mixed with 
those of the metals. The chlorine compounds have been investi- 
gated by method 1 (wick of platinum wire), and by method B 
(H and Gl). It is to be observed that in the hydrochloric flame 
itself they give no light at all, not even if the compound rolAti- 
lized by uie hydrogen burning iii air enters the flame. Hits c^h 
wAj be ^plained bv assuming that tbe temperature ;[)i^ueed 
by the tinioti of bydrogfen and cMoritie is not high enough to 
wing tblorine compounds to himiijosity. The specti*a of fhe»e 
l»d»mpounds are obtained pure if there id nIOfe hydrogen tbah Is 
necessary for union with chlorine, which free hydrogeft bttrn&g 
in the rir produces a higher tompertotuire. 

The spectra of bromine eompoutids Were pi*epai*ed bj^ to€*bt^ 
4 (Brand H)^ using th^ bromides in solutions, Whicli w«W in- 
fi^>^ueed into the flume by method 1. 

The iodine compounds are decomposed, ad stated ; the iodide- 
-Of-barium ^ectrum is only obtaitied if the iodine compound is 
volatilized in a hydrogen flame which contains much iodine 
Vapour,— although truly it is then not free from that of the 
tdtide, 80 that the fedbler lines of the iodidc'-ftf-barium spectrum 
cannot be recognized; but the lines depicted occur with all their 
sharpnessw 

I'luoriwe compounds were intestignted by method 2 (H, or 
-dtikl^pi^, and Oh using a mik^ri^e df the oxide #ith flUoriiAe i6f 
"Mttmotiium ih ttbuttdafttSfe. 



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it it not poniUe to oktam t&e q>eDtmm «f tke ralpbiur cool* 
ponnds of Uiese in«faki> wkidi » also the case with these 4f 
copper and bisnnitl^ as aU sulphur tsomponnda appear to be 
€OBi]defeIy noB^voiatile. I made the experiment by briagiog the 
metallie sul^de into hydrogen saturated with Muphide of car- 
bon, or into sulphuretted hydrogen^ which burned in an oxygoi 
atmosphere (mediod 5). In the latter eoEperiment no spectrum 
was seen; in the former fireqfuently a spectrum wUek was pv^ 
by the deeonipasitMoi «f the sulphur oompoundsb Nor did I 
sooceed in obtaiping die spectra of oyanogen eompomids ; if 
the saits €f the above metak are brought into biuaung oymogOB, 
spectra are fecmed as in OM^sry flame. 

As regards the eampoundsof kad^ goid^ iroa^ and manganese^ 
I could only obtain spectra in a very fbw caaoBb Chloride of 
lead by method 6 (volatilieation in the' glass tube)^ eraastate of 
lead by nwduNl 2 in the oaidicingpart of ibe flame^ ahntys give 
Ae speetrum at the oxide. By chloride of lead or aostatie of 
kad^ heated according to method 2 <H attd O) in the Todmcing 
part of the ikmc, the apectrum of the natal eonld nerer he 
obtained free from that o^ oxide of lead. 

^ metibod SJliquid eketrodfls) it is obtained free from that 
of the oxides. The lines which are seen in this method are de- 
noted by the letter e in the spectra given ; it is probable that 
tiiey ase also eootakied in the qwdriim of lead whiehis obttHiied 
by ^e fisme, and that they are only obacured by the brightness 
ef die oadde spectrum. By method 3 (H and Cl)^ the eUorid^ 
of load speetnutt is formed even with the most varied lead com- 
pounds^ but aoraewhat obscurely. Iodide o£ lead^ bromide of 
kffd and fluoride of lead, exanraaed by method € (volatiliiaCion 
m the glasa tube)^ gmre idways only the oxide^ot^ked speetrum, 
fanaed by the burning of lead to oxide of lead at this higjh 
temperature. 

iDfaloride of fold, i^ method 6 (vohtilisaitMm m the glass tfcib^j^ 
gores the spectrum <» this compound. In so other way could T 
ditaiv a apeotrmn of a gcdd oompound^ ueitfaer by using hypo- 
aulphke of pretoxide of gold and sods, nor potassio^iodide of 
cold or potassJD'-c^aiiide of gdd. The spectrum of gold itself 
m fvepared v^th cUoride of gold by asethod ft (liquid eleetrodes). 

Of nroQ leoaldonlyobtaintheapectrumof an>0xideand that 
of tbe metaL The former is produced if the chloride or iodide 
flw used by aocjthod 6 (vdatiliaation in the glass tube), and very 
distinctly with sesquichloride of iron. By method 2 ^H, or eoid* 
gaa^ and O}^ aoeordmg as the volatile iron salt is brought into the 
reducing or ooidiamg flame^ this is^eetriun is obtmned simnl* 
taneousfy with Ihsit ef iron or without it By method 8 (hcluid 
eieetcodio^, using oonoentrated solution of sesquidilocide of imin. 



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176 Prof. Mitseherlieh on ihe Spectra iif Compounds 

the ftpeetnim of the metid is obtained alitioet quite fiee £ft>m 
that of the oxide ; it is only obtained perfectly so by method 7 
(solid electrodes)^ using iron and iron compoands. 

Chloride of manganese^ investigated by method 6 (yolatilisatioii 
in the glass tube), gives the spectrum of the oxygen compound 
pure ; it is obtained much more beautifully simultaneously with 
the spectrum of the metal by method 2 (H and O). By the 
beauty of its colours and the sharpness of its lines^ this spectrum 
is about the most beautiful of all. By this method I could only 
detect one line which belonged to the metal, probably because 
the bright parts of the spectrum of the oxygen compounds 
obscure that of the metal ; investigated hj method 8 (liquid 
electrodes), the manganese compounds give moreover a. few 
bright find several feebly luminous lines, of which the bright 
are depicted. 

The spectrum of an oxide of tin, obtained by method 2 (H,or 
coal-gas, and O), using oxide of tin, and that of an oxygen or 
chlorine compound of chromium, using chloride of chromium, by 
method 8, 1 have not drawn, as both were too obscure. The 
spectra of metallic tin and chromium were prepared by method 
2 (H, or coal-gas, and 0) and by method' 8 (liquid electrodes). 



From the investigations adduced, it follows, as I have already 
expressed in an earlier paper, that every compound of the first 
order which is not decomposed, and is heated to a temperature 
adequate for the production of light , exhibits a spectrum peculiar 
to this compound, and independent of other circumstances. 

The decomposition of compounds may be caused by the gases 
of flame, or even by the high temperature alone, independent of 
thje gases : thus, for instance, chloride of bismuth, if its solution 
is used instead of the electrodes in the electrical discharge in: 
chlorine, is decomposed by the high temperature of the electrical 
discharge alone. Individual compounds resist even this tem- 
perature — as, for instance, bromide of copper and iodide of copper^ 
and others, which show the spectrum of the metal tc^ther 
with that of the compound. But if, instead of the solutions 
which produce a diminution of temperature by their rapid 
evaporation, the salts themselves are used as solid electrodes, at 
the then higher temperature most salts are decomposed (as, for 
instance, these copper salts), and but few compounds remain 
undecomposed. 

With a great number of metals such a decomposition takes 
plaice even under the temperature at which a luminous appearance 
is observed ; hence in this case it has as yet been impossible tp 
observe a direct spectrum of the compounds ; and therefore a 



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wd af Stn^k 8ubil4mces. 177 

Mmpfflisoa of the spectra of aU oompoimds has hitherto been 
impossible. ] 

The metals whose compounds are decomposed at such a low 
temp^atnre^ and hence only give, the spectrum of the metal 
itself^are potassium^ sodium^ lithium^ magnesium^ zinc^ cadmium, 
silver^ and mercury. Potassium, sodium*, lithium, as metal, 
qranides or chlorides, investigated by method 6 (voli^tilization 
in the glass tube) or by method 2 (H and 0), give, especially 
in the spectra produced by the first method, several lines in addi- 
tion to those depicted by other observers. 

By method 2 (H and 0) there are further obtained the spectra 
of magnesium, zinc, cadmium, silver, mercury — by the use of 
chloride of magnesium and chloride of ammonium, of chloride 
of zinc, of carbonate of cadmium, of cyanide of silver, and of 
cyanide of mercury. By the use of other mercury compounds, 
sach as chloride and sulphate of mercury, no lines can- be 
obtained by this method. In burning magnesium, the same 
spectrum is obtained as in the methods adduced. 

By method 8 (liquid electrodes) these spectra can also be 
more or less well obtained with the use of various solutions. 
In the spectra obtained by this method other lines occur, which^ 
however, are for the mQst part more feebly luminous than those 
formed by the flame. If zinc is burned m iodine, a brightness 
only is observed in the spectrum, doubtless produced by ignited 
particles of iodide of zinc. 

That in the case of sodium compounds the metal actually 
giyes the spectrum, I have shown in the paper already mentioned. 
I have found the same when I obtained this spectrum with 
the use of the metal by method 7 (solid electrodes), excluding 
oxygen. That the spectrum found with the use of the com^ 
pounds of magnesium, zinc, cadmium, silver, and mercury is in 
each case the spectrum of the metal itself, I proved in the 
same manner f* 

From the fact that in sodium compounds the metal gives 
the spectrum, I thought myself justified, in the above paper, in 
expressing the opinion that in the oxygen compounds of ba- 
rium, strontium, and calcium the spectrum is also produced by 
the metal itself. This opinion, as I have already stated, has not 

* Brightness without any shading, as formed in the sodium and potassium 
speetra, and which I could only ascribe to the ignited solid particles in 
tne flame, I have omitted in the spectra depicted. 

t The objection urged against me in an English paper (' The Photo- 
graphic News ') after the publication of mv former paper, that spectra 
produced by the volatilization of carbonate of soda, chloride of sodium, &c. 
which are brought into heated tubes could not have been formed, because 
the temperature is too low for the volatilization of theae salts, does not 
hold; for I have myself observed the vapours* 



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Md good, ioumudi mi mA d! tbo qMOtnt it 0Din|KMBd «f tke 
■pectrum of the metal and that of the oxide. 

In the flame paper, by tke experineiit in wfaidi whes ddbnde of 
potaasiiim is bnmglit into a mme with nradi chloride ef amm^ 
nium no ftpeetnm is peraeived, I have ahown that mder eertain 
enreatnstaneea metalfio eonpounda of the fint order, even when 
foktile, mar gife no spectra. Thia ia eonfiraaedby the fiust that 
6fen thieyeHow ookrar of the ao^tiwa flame ahnoat diaap^>eazB if a 
flame containing aodium ia brought orer strongly Tolatibsmg aal- 
ammoniac, — and farther by the fad that if any aodiaan, lithium, 
or potasainm compound m iima a ti g a ted by method 8 (H and 
CI), not even a colenred flame, and atSl leaa a apeetnm, ia 
fimned. The reank is sknilar if coBi p oiinda of the alkabea are 
TOlatiliaed in burning aulphuvetted h y drogen; it can be dia- 
tinetly observed that die interiot core retaina ita coloar per- 
fectly if these compoiHids are volatilised in it, bvt tiiat in Ae 
outer core, where the Bi:^ph«ir ia already baraed, a fisebk oob>or 
is formed. Under certain circumstanoea, metalB, even vhoi 
volatQising in the flame, may show no speetrum — ihtn, for in- 
stance, in the case of any of the compounda of mercnay, e»- 
eepting the cyanide, and exoepting mercury itaeif, by aaetiiod 1 
(wick of phtinum wire), 3 (H, or coaUgaSj, aoid O), or fay method 6 
(volatiKzation in the glass lube) . If the merevDry ooupottuda aoDS 
heated higher, for instance by tht ^eetrical spark, or if the qr- 
anide is investigated by method 2 (H, or cou^^aa, and O), the 
ape ctr mn is observed very distinctly. 

Nickel, cobak, «id aluminium, investigated m the moat 
varied compounds by method 3 (H and O) and method 6 
(evaporation in the glass tube), gave no perceptible apeotrum; 
this was also the case with the eompounda of titaninm, tungaten^ 
vanadium, molybdenum, uranium, platinum, aud palladitim in- 
vestigated by method 6 (vdatilization in the glass tube) and other 
methods. When aluminium was burned in bromine, a oontip 
nuous brightness only could be induced, as was the caae with 
l9ie combustion of zinc in iodine. Arsenie and antimony, exa* 
mined as chlorides by method 8 (H and CI) and by mothod € 
(vohttiiisation in the glass tube), in the form cS other compounds 
and aa metal, dMwA a luminosity without bri^ter or darker 
lanes in the spectrum. Only by method 7 (solid electrodes) 
todd lines be found in the methods adduced^ which I thus 
investigated. I have not inveatigated the still rarer metals and 
their compounds. 

From the decompositions which, according to these invesfiga- 
^>0>M, take placein the flame, It would follow that if, for instance, 
P^^!^*''^ wppat ia heated with «emiaon salt, the chlorine which 
IS liberated at a high temperature by the deeomposition of the 



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iMlt >c(iiited tnth dopper find fonns a ebbridti-of^K^pp^r ipeetrtun, 
ttBce <;liloride of coj^r is not de6otii|K)Md at Hiu temp^rtittiNL 
-'^^^ttd ftitth^f^ that if oicid^ of co|yper i» mi»id untk chloride « 
iM>dkitn^ the free dylorine would aifto partiidly eombine with eop* 
^tj ^^ «dptie Bftfts kivestiealed by m^od 8 {H and €1) give 
^le chldrid^'-of-iiopper erpeetfum. These deeotnpoaitioiia do in 
^K$t talked plaee. If, for imtattoe^ ehtoride of sodium is fhiied 
«poti a pm^hed copper plate at a high temperature^ the bright 
ti&pptr is attacked ; ai^ if it ia tttOM i^ro&gly heated^ ehlotide of 
tf9pp^ is ti^ttdiljr dbeterred ift the flatue by the speetrntti^pparatas, 

Chewieal pr^^teSiea at high tempifrataiea ttiay be atttdied by 
llkletttis ef the spectta. The nlost beautiful ttiathod is by the 
Mxdight. For Cdtnpoutids wfaieh give a more cobtmnotts spec* 
fi^ttu^ sudh a study would be more diffidult^ but v^ 6ftsy for 
l^e haloid compOtttK^ of bariutti^ strotttittm^ and caMum. I 
(hitik c^ shortly making such a set of eiperfmefits. 

As I aupposed te ai^y foraofer mcteoir^ we aMty by these deeom^ 
ffOsHiotis compafe^ \sl an interesting niantter> the tesapemtuics 
which give rise to dev^ptnents of light of various kinds-«-thus^ 
fbr instance, the temperacufe of electrioil discharges with the 
tenrperatute of light ptodaced by oombustion^ or with that of 
1;fae solar light* It follows ftom the e^tperiraent^ adduced^ espe- 
dally frotn those with copper cottipoands^ that the deetrical 
iparks have a lower temperature when they eome ttom liquid 
^Itectrodes, that this tomperature is about that of the oxyhydro^ 
^e^ Mowpipe^ bat that the tetoftperature resuHmg from the pas- 
tiage of sparks between solid eleot^odes is much h%ber than that 
df any lli^e. 

The ^p^VA of the metalltrids and of their compounds with one 
)ttie^er are not very numeroMi 

Tbe ispetlt^ of hydmgen, «ttygen> n^M^en^ and chlorine only 
ttsanlt from the electrical sparit \ they are kno«m> jiist as sre 
^Adse of iodine and bromine^ which can be |M<epared by the dee- 
trical spark or by the lA^rption of wfcifte light* 

H ie^e is ^ittmmed by method 6 (vohkl^iisatkm in the glass 
tube)^ the fTpectrum ^piicted is obtained) bcft if very much 
io^ne is vdhitili^ed, the absorption spectrum is produced. I 
tfiftH recur to these phenomena subsoqa«ntiy>r I have vtck sue^ 
receded in obtaining a spectrum of chlorine or of bromine in a 
similar manner, not even with b«>mine l^en hydMgen, in which 
Inromine vapours were volatilised, burnt in otygen $ a contimious 
t)ri^tness was all that could be perceived. 

The spectrum «f sulphur was pt^paned by method 7 (aelid 
^ectrodeii), those of selenium imd tdhirium by method 6 {w\t!&!^ 
ifesMiott in the glasil tube). 



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180 Prof. Mitiieberlich on the Spectra qfCompaunde 

The speetram.of pho9ph<Nii8 obtaitied by method 6 (fertili- 
sation in the glass tube) is only visible if very much hydrogen is 
burned with traces of phosphoras ; if more phosphorus is used^ 
much phosphoric acid is formed^ which separates as ignited 
solid substance and^ like all such substances, gives a continuous 
spectrum, which by its brightness conceals the spectrum of phos* 
phorus. This experiment gives a clue to the affinity at high 
temperatures of hydrogen to oxygen as compared with that dT 
phosphorus to the same substance ; for phosphorus first bums 
with a green flame, probably to phosphorous acid ; subsequently 
hydrogen bums to water, and phosphorous to phosphoric acid. 

Carbon compounds, examined by methods 5 (combustion of 
gases) and 6 (volatilization in the glass tube), give different spec- 
tra according to the nature of the body combined with carbon. 
Hydrocarbons and chlorides of carbon always show the well- 
known spectrum of coal-gas flame, which arises from the carbon 
as such ; by method 7 (solid electrodes) the spectmm of hydro- 
gen is simultaneously seen, and for the most part a separation 
of carbon. But if the carbon is combined with oxygen or sul- 
phur, as in carbonic oxide and sulphide of carbon, a continuous 
brightness is observed on burnings in which I did not succeed 
in discovering dark or bright lines. The metalloid which is 
united with carbon (for instance chlorine, bromine, iodine, and 
sulphur) can never, with very few exceptions, be recognized by 
the flame when investigated by methods 1 to 6. With nitrogen 
this is not the case ; if the compound is not very rich in oxygen, 
it can be recognized by the formation of a spectrum of ammonia. 

I obtained the spectra of silicon and fluorine by effecting the 
electrical discharge in silioofluoride of hydrogen and in hydro- 
fluoric acid. The spectmm of fluorine which I obtained with 
that of hydrogen alone, was deducted from that of fluoride of 
silicon, and thus the latter recognized. Both spectra consist of 
individual lines. These spectra, like the rest which are only 
formed by the passage of the sparks from dry electrodes, I have 
not depicted. Silicon and fluorine, investigated by method 5 
(combustion of gases), using fluoride of silicon with hydrogen, 
give only luminosities in which no shadings are perceptible. 

The spectrum of boron was prepared with the use of boracic 
acid by methods 6 (evaporation in the glass tube) and 8 (liquid 
electrodes), and with fluoride of boron by method 7 ; in both 
cases I obtained the same spectmm. 

Spectra of the compounds of the metalloids with one another 
I could only observe in small number. Most compounds give a 
spectrum which, from the small intensity of its light, cannot be 
investigated — ^thus, for instance, hydrogen and hydrochloric 
acid; others give a continuous one, as, for instance, sulphu- 



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' and of Sifi^te Substances. iSi 

ifettecl hydrogen, sulphide of carbon, sulphide of nitrogen> car- 
bonic oxide. I never succeeded in recognizing dark or bright 
lines in the spectra of these compounds. Of the compounds of 
the metalloids with one another, I could only recognize the spectra 
of cyanogen and ammonia : the first is already kpown, but not 
in a state of purity; the lines of the carbon spectrum which 
result from the decomposition of cyanogen when burnt in hydro- 
gen haife been assigned to the cyanogen spectrum ; the spec- 
trum of ammonia has recently, during my research, been depicted 
by M. Dibbits. It is interesting to recognize again in the 
spectra of both compounds the properties of the simple sub- 
stances resembling them. While ammonia always appears with 
more or less intensity in the spectra of its compounas and thus 
behaves like the metals, cyanogen, like iodine, bromine, &c., 
loses in its compounds the property of producing a spectrum; 
thus hydrocyanic acid, sulphocyanogen, cyanic acid, &c. give no 
j^ecognizable spectrum. 

The spectrum of ammonia can best be depicted by method 5 
(combustion of gases), by the use of oxygen; it is obtained of 
feebler luminosity by method 6 (evaporation in the glass tube), 
from ammonia compounds, or best by urea. 

The decomposition and formation of cyanogen at high tempe- 
ratures, which can easily be followed by the spectra, is interesting. 
for if the electrical discharge passes in cyanogen, the gas is 
decomposed, very dense carbon being deposited in characteristic 
curves, but if much carbonic oxide is added it remains unde- 
composed ; but if the electrical spark be allowed to strike for a 
short time through air which contains a hydrocarbon, cyanogen 
is formed. Hence at the same temperature the compound is 
formed and decomposed. 

If hydrogen is brought to burning cyanogen, a change of colour 
is speedily observed in the flame, and the formation of ammfonia 
is readily shown by the spectrum. If carbonic oxide is admitted 
to cyanogen, no change, as already observed, is produced. Hence 
at this high temperature hydrogen has a greater affinity for 
nitrogen than carbon. 

Of the compounds of the metalloids, I further examined by 
method 6 (volatilization in the glass tube), or method 5 (com- 
bustion of gases), protoxide of nitrogen, binoxide of nitrogen, 
nitrous acid, nitric acid, chloride of sulphur, oxychloride of phos- 
phorus, and, further, sulphuretted hydrogen and sulphide of 
carbon mixed with chlorine; in all cases I only obtained lumi- 
nosities without shadings. By a decomposition of the com- 
pounds, selenious and selenic acids give the selenium spectrum, 
and chloride of iodine the iodine spectrum. 



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18» Prof. Mit8Qbedich0iM^%dyv«^CScm^^ 
If the. vedm am fKnnpii:<4 mth om wf£ber, ii jwl9wAtiitt 

of tkfiir iX>IIII]Oai>ds inth tkft nru3Aa.llni<lfl / flBMS ftn trng IIm* hlfc l4 ^ flilttt 

of csalciujny stcoRtiniOf md biirimn, wliow 4|^«QtiiL coomife^ w4i«r 
vidu«l liDe») are coiapoaed of Woad lummoaitiM witb ttMmv 
dark lioea whicb i^w at dafinit^ i»ben«}s. 

By meam of tluit propart^j tbai apectia of the iMiioid ifoi»^ 
poonda^ calciu»i atrpQiHm^ mi banum Ma ispaddjr ofti»yaiw4 
with each other j ^nd it ia at ouee ohai^rvad that wdifidwil 
characteriatic liaaa x^owc in th9 spectra of one md t^e aaiw 
metal, which, according to the halegeoai aise wore «ir leaa ^ataet 
from oue aoother^ by which meana the «ietalia eaaily t&9ogm»i 
m. the q^ecibra of ita co«»ppui»da. The ftaorid^ Ipto aa ^^q^.* 
tioatotUi^ 

If thia pheoion^ium is inveatigated ia the <ca«i of the hadma 
compounda bf the apectra de^iicted^ iit ia fow»d that the diatwow 
of the two prominent lines in the various apeetrii ai^a to eadi^ 
other as the atomic weights of these cwipounds. Thia relation 
givfia ijse to fiirther interesting conclusions* Th^s fvom «a obr 
served dista^ice of such linetb the diataoce gS the cori?esp(w^diii|; 
lines in the spectra of other hacmm coi»|^kOM»ds imy h» i^sim^ 
hied;, further, from the distance and oue known •faamic weight 
that of the other cftBapowds may tie deterouned. 

If we start from the chloride*o£4HU9uin lines, wbkh are .moat 
easily procured^ and if we forn^ frow- th^ afami^ weightaiof tbfe 
componnds and tiie ^hsttoice of the chief lines of the cUende-ref-^ 
baamn spectrum, which is e);pressed by 3*9 degrees of the sei^ 
the equation for the distance of these lines m the i^odldeHofi*^ 
barium spectrum, we obtawj taking the ate^ni^ w^ht. i^ iodide 

of barium at 195*5, that of chloride of barium at 104, — ^ tskHc* 

J;VvO 

fiiem whicb 4p^7*«S : the draimng ghrea 7*8. 

fmt as these eqnatiQBS anay be Mated lar the Mam of Mdide 
of bsrium from those of eUoride eC harimHi^ so in like mamier 
we grt &r broRiide /af bAriwos, iriieee atooiie weight is 148*6, 

8*9 104 
the equation — ^Tzgi^j* 6^^ which ^=i5'5i according to 

tiie drawing it is S*2« 

Of coarse liie atomic w^bts of the Ibarium coD^^eiuiidB men* 
tioned may be -calenlated fima the spectra, as well as the apGC^mt 
from the sitomic wai|^ts, OAer equsitions may also beobtaised 
wUch express the vehtiom of biomide of barknn to iodide «f 
barium. 

The Crebkr Ikes of the ehleride- and bronride-of-berittm 
spectra may also be compared like tiie stpoiig lines^; but inr the 
case of iodide of barium &ey 4)euld not be drawn, and in bro- 



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> Md cUoride of baiiiw tk^ had not tbe pseciwxiand dis* 
tinctoess necessary for making <»dculationB from them. ■ 

In the spectra of those haloid salts of barium whose light con- 
siats of more stronglj refracted mjSj the distances of Uie indi* 
vidoal linea from each other are less than in the spectrum of •each 
haloid salt whose corresponding lines are produced bylSght of 
greater wave-Ieogth* for thia relation I hare also smveeded in 
finding an expression. 

The distance of the more strongly refracted bright line of the 
chloride of barium Irom a definite point of the scale, is to the: 
£stajice of the other bright line from this same point na tbft 
cliatanee&from the same starting-point of the coixesponding linea 
of the eiuectra of iodide aad bromide of barium. In order to find 
the starting-point, whose distance from th»t of the most ^onglj 
refracted Ime of the chloride-of-barium spectrum is expressed by 
y, I formed from the spectra of chloride of barium and bromide 
of barium the following equation, in which the unit is a degree 
of the scale : — 

Distance of the first chloride-of-bariam Sne y 



Bifstance of the second chlevide^f-bariuin line y -f- 3^ 
^ Distance of the first bromide-^eif-barium line y+ft 
Distance of the second bromide-of-barium tine y-f-8'IB' 



whick yaB9^. 

Fromijie apectta of chloride 4^ bariom wd iodide of bariwi 
the equation is obtained^ 

From tiiose tif hromide of barinxn tmd to£de oif 'barinm, 

Item the above equafious we obtain for the position of the com- 
mon starting-point 96-1 —y, that is,96-l—9*7=8e-4 degrees*. 

From these and the preceding equations, it follows tJiat if two 
spectra of the chloride, hromide, or iodide of barium ape known 
ly the first equations, the distances from each other of the prin- 
cipal lines in the spectrum of the third compound maj be cal- 
Gcdated from them. From the latter equations, which have 
given the starting-point, ttie position of fiiese lines may be cal- 
cnlated. 

•^ I iMPf^ Mtffmi/td the «tartiiv OiiMS in thMpectra of tfaeimetslafay tka 
lettera. 



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164 Prof. Mitseherlich on the Spedira ofCompoundi 

These relatidns cannot be established in the case of fluoride 
of barium. 

Comparing the spectra of the haloid compounds of calcium^ 
which mostly consist of three lines^ two ver^ near each Other, 
the third somewhat distant, with the atomic weights of these 
compounds, it is found that the distances from each other of corre^ 
sponding lines are inversely proportional to the atomic weights. 

Taking for the atomic weight of iodide of calcium 147, of 
bromide of calcium 100, and of iodide of calcium 55*5, we obtain 
the -following equation for calculating the distance of the most 
divergent lines of bromide of calcium (which I denote by a?), from 
the distance of the chloride of calcium lines, which, according to 
calculation is 6*5 for the latter compound : — 

From the drawing of the bromide-of-calcium spectrum the same 
result is obtained, a? =3*6. 

From the observed position of the lines of both compounds, 
the equation for the starting-point of the spectra of the calcium 
compounds is the following, in which y is the distance of the 
least refracted lines of the chloride-of-calcium spectrum from the 
starting-point, which in this case is opposite to the starting.-, 
point found in the spectra of the barium compounds : — 

Distance of the first chloride-of-calcium line y 
Distance of the second chloride-of-calcium line y +6'5 
^ Distance of the first bromide-of-calcium line y— 'I'g 
Distance of the second bromide-of-calcium line y+2r2' 
from which y=2'6. 

The starting-point lies near 129*8 of the division. 

In iodide of calcium I have not succeeded in observing a spec- 
trum ; I shall calculate this from the distance of the chief lines 
of chloride of calcium and from the atomic weights, taking the 
starting-point found as a basis. In accordance with ' this, the 
equation for the two lines of iodide of calcium which have the 
greatest difference is 

srz = T7»9 from which a?=2'5, ^ 
6*5 147 

The equation for the position of the lines of iodide of calcium is 
as follows, if the distance of the line nearest^ the starting-point 
from the starting-point is 9=y :*- 



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and of Simple Subatanees. 185 

Distance of the first chloride-of-caleium line from the 
starting-point 2*5 

Distance of the first iodide^f-calciam line from the y 
starting-point 

Distance of the second chloride-of •calcium line from 

_ the starting-point • 9 

^ Distance of the second iodide-of-calcium line from the y+2*5* 
starting-point 

from which y=l. 
Hence the distance of the first iodide-of-calcium line would be 
near the division 128*8, and the other near 126*3. The position 
of the third line close to 128*8 might be directly determined 
from the position of the line corresponding to it in the chloride- 
of-calcium spectrum; it must be near 128*6. 

The observations of the fiuoride-of-calcium spectrum do not 
agree with the calculations. . By calculation from the same equa- 
tions as in the case of iodide of calcium, the distance, for instance, 
of the two extreme lines of the fluoride of calcium would amount 
to 9 degrees, while from observation it is 22 degrees. From 
calculation from other equations these lines must be about 117 
and 126; in the spectrum observed they are, on the contrary, 
at 102 and 124. 

In the spectra of the haloid salts of strontium there is the 
same behaviour as in those of calcium. 

Calculating from the distance of the extreme sharp lines of 
bromide of strontium those of the corresponding lines of chloride 
of strontium, taking the atomic weights of chloride of strontium 
at 79*6, of bromide of strontium 123*8, the distance of these 
bromide-of-strontium lines from one another being 6*5, the equa- 
tion obtains 6*5 79*6 

T" ^ 123^' ^^^ "^^^^^ a;=10*l. 
Prom the drawing x also = 10. 

Proceeding as with calcium, the starting-point calculated from 
both spectra gives the following equation : — 

Distance of the first chloride-of-strontium line from 

the starting-point y+0*5 

Distance of the first bromide-of-strontium line from y 

the starting-point 
Distance of the second chloride-of-strontium line from 

^ the starting-point y+ 10*5 

"" Distance of the second bromide-of-strontium line from y + 6*5 
the starting-point 

from which y=0-9. 
Hence the starting-point lies near the division 138*4. 
PhU. Mag. S. 4. Vol. 28. No. 188. SepL 1864. O 



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186 Prof. Mitscherlich an the Bpetira of Compounds 

If^ as ID the case of the calciiun oompoundsy the distance of 
the lines in the spectram of fluoride of strontium is calculated 
from that of bromide of strontium, we obtain the equation 

From observation ^= 18. Hence^ as in the case of fluoride of 
calcium and fluoride of barium, this does not agree with calcu- 
lation. 

The iodide-of- strontium, like the iodide-of-barium spectrum, 
I could not observe. According to the following equations, 
which are formed as in the case of barium, it has been calcu- 
lated : — 

X 123-8 . , . , ,^ 

6^=170^'^°^^*""^^=^'- 

From the distances and from the position of the starting-point, 
we obtain the following equation for the position of the lines for 
iodide of strontium : — 

Distance of the first bromide-of-strontium line 

from the starting-point 1 

Distance of the first iodide-of-strontium line y 
from the starting-point 

Distance of the second bromide-of-strontium line 

from the starting-point 7 

~ Distanceof the secondiodide-of-strontiumline from y+4'y 
the starting-point 

from which y=0'67. 

Hence the first line of iodide of strontium is at the division 
137*3, and the other at 132'6. The position of the other bright 
lines of the iodide of strontium which lie between the two has 
been calculated in the same way. 

Hence for the haloid compounds of barium, excepting fluoride 
of barium, it follows that the distances of corresponding lines in 
their spectra are directly proportional to the atomic weight, and 
that for the haloid compounds of calcium and strontium, except- 
ing the fluorides, these are inversely proportional to the atomic 
weights. Further, that the relation of the line nearest the 
starting-point to the same, to the distance of the furthest line, 
is the same for the same metal in the case of the haloid com- 
pounds of barium, strontium, and calcium. Here also the fluo- 
rides are to be excepted. 

I hope I shall hereafter succeed in finding the reason for this 
abnormal relation of the fluorides. 

The fact appears important to the significance of the starting 



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and of Sinqde Suistanees. 187 

point on the barium spectrum^ that I could observe a distinct 
line in the spectrum of this metal. This line only becomes 
visible by methods 6 and 7 (electricity), or by bringing barium 
compounds into the fliame of cyanogen burning ih oxygen. 

Such a relation, as in the case of calcium, strontium, and 
barium compounds, could not be discovered in the other mietals. 
Similarity in the spectra of the compounds of a metal is easily 
seen in the case of copper — for instance, in the violet part of the 
bromide- and chloride-of-copper spectrum, and in the green part 
of the chloride-, bromide-, and iodide-of-copper spectrum ; but no 
relation could be established between these spectra and the other 
properties of the compounds. 

As there are resemblances in the spectra between individual 
compounds of a metal, so there are such between compounds of 
different metals with oxygen. Most striking is the resemblance 
between the spectra of lime and of strontia ; the individual parts 
correspond to each other, but the lime spectrum is more extended 
than that of strontia. 

The spectra of baryta and oxide of lead are also very similat 
in certain respects. This similarity is difficult to express in the 
drawings, while it is very striking to the sight. 

Relations between these spectra and the atomic weights I have 
not as yet been able to establish, but it may be expected that 
sach exist. 

I have not been able to find properties of the spectra of the 
metals which enable a connexion of the metals with one another 
to be recognized : similarity of individual spectra together with 
similar properties of the metals seems to point at such a con- 
nexion; thus, for instance, the spectrum of zinc is very like 
that of cadmium. 



The metalloids show the same spectra, provided with regular 
shading, as the metallic oxides ; and if, for instance, the spectrum 
of the oxygen compounds of bismuth is compared with the spec^ 
tram of iodine obtained by method 6 (volatilization in the glass 
tabe), a resemblance is observed corresponding to that which I 
have noticed as existing between the spectrum of oxide of lead 
and of baryta. The oxides of both these metals are decomposed 
by high temperatures, and show individual lines as spectra. 
Iodine also, when investigated by method 7 at a high tempera- 
ture, exhibits an entirely different spectrum, consisting of indivi- 
dual lines like the spectra produced at high temperatures from 
these metallic oxides; and from the phenomenon that iodine 
shows two spectra, from their similarity with the spectra of the 
metallic oxides and those of the metals, and from its ana- 

02 



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188 Prof. Mitselierlich tm the Spectra of Compounds 

logous deportment with the first at high temperatures, the 
opinion might be expressed that ordinary iodine is a compound 
body. 

From this it would follow that iodine at ordinary temperatures, 
and iodine at the temperature of hydrogen flame, must be con- 
ceived as two different compounds, because the spectrum of 
iodine formed at ordinary temperatures is different from that pro- 
duced by the hydrogen flame. A compound of hydrogen with 
iodine in this flame cannot be the cause of it, because the same 
spectrum is obtained when iodine is in a carbonic-oxide flame ; 
•from the ready decomposability of oxygen compounds of iodine, 
the presence of one of these cannot well be the cause. 

Spectra resembling those of iodine I could not detect by the 
flame in the case of chlorine and bromine. If the preceding 
supposition is correct, bromine must be regai'ded as a compound 
body ; as it has two spectra, one formed by absorption, and the 
other by the electrical spark. 

If we compare with the flame spectrum of iodine the spectra 
of the metalloids as formed by the flame of selenium, tellurium, 
phosphorus, and those of sulphur and nitrogen, resulting from 
feeble electrical charges, it is found that all these metalloids have, 
in their spectra, the character of this iodine spectrum, and 
would thus, if the above-expressed supposition be confirmed, be 
compound bodies. 

In comparing these spectra, several peculiarities are observed : 
thus in the distinctly marked part of the sulphur and sdenium 
spectra, the number of luminosities appears to be inversely as the 
atomic weights ; a similar relation appears to obtain to that which 
exists between the spectra of the haloid compounds of barium. 
I must, however, add here that the spectrum of sulphur, like 
that of tellurium, could not by the methods which I have hitherto 
used be obtained with the distinctiveness which the spectra of 
other bodies exhibited. 

These communications on the connexion of the spectra with 
one another and with the atomic weights can only be regarded 
as precursory. I shall continue the investigations with more 
accurate apparatus, and in due time make further communications. 

Appendix. 

In conclusion I will adduce some observations which refer to 
the flames giving spectra. 

The flames giving spectra are in most cases produced by the 
luminous gases of the volatilized bodies, — thus, for instance, in 
burning cyanogen, and in the metals and metallic compounds 
which are brought into the flame. 



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and of Simple Substances, 189 

. If the bodies are contained in the. flame in such large quan- 
tity that they cannot volatilise completely^ or if they are not at 
all volatile^ they become white-hot and give the spectra of all 
ignited bodies, that is^ a perfectly continuous one, without dark 
or bright lines. The former is the case if phosphorus is inves- 
tigated by method 6 (volatilization in the glass tube, and this 
somewhat strongly warmed) ; for the latter, the carbon separated 
from hydrocarbons is the best example. 

If such a body, which is brought in excess into the flame and 
hence does not evaporate sufficiently, has only few lines in the 
spectrum (so that an absorption spectrum of it is otherwii^e easily 
obtained, since in the middle there is a brightly luminous body, 
and round about the vapours of this body), its absorption spec- 
trum is obtained. This is the case if sodium is burned, or much 
sodium volatilized in a hydrogen flame. This phenomenon can 
best be investigated if more or less iodine is brought into the 
hydrogen flame. If there is only little iodine, the new spectrum 
which I have found is obtained ; but if there is much iodine, the 
absorption spectrum is obtained. The middle of the flame is 
white-hot; the white light must pass through iodine vapours 
and these absorb a part, as is the case if a candle Jight is viewed 
through iodine vapours. 

It is not eveiy volatile body which, introduced into the flame, 
gives a spectrum. For particular bodies, a very high tempera- 
ture is necessary to heat them so strongly that they disengage 
light. This is best seen with mercury ; for mercuiy salts, ex- 
cepting cyanide of mercury, investigated by methods 1 (wick of 
platinum wire), 2 (H, or coal-gas, and 0), and 6 (volatilization in 
the glass tube), hence at a lower temperature, give no spectrum ; 
while, when heated by methods 7 (solid electrodes) and 8 (liquid 
electrodes), they produce a very bright spectrum. This is fur- 
ther observed in the case of oxygen, nitrogen, and other gases, 
which only by the electrical discharge are sufficiently heated to 
jgive a spectrum. 

To investigate whether solid bodies did not also produce 
spectra, I caused white light to pass through a gold-leaf trans- 
parent with blue light, or through gold which was precipitated 
in extremely dilute solution, but I could not observe either dark 
or bright lines in either experiment. 

Berlhi> February 1864. 



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C 190 ] 

XXI. Upon the Quartz from Euba, and on the Biaxial character 
of Pyramidal and Rhombohedral Crystals. By Professor A. 
Bbeithavpt*. 

IN volume czx. of PoggendorflPs Annalen Prince Salm- 
Horstmar alludes to a quartz from Euba^ near Chemnitz in 
Saxony, and makes mention of its inferior hardness and low spe- 
cific gravity^ and observes also that it is optically biaxial. I 
conceive that it is I who may claim to have been the first to 
discover these peculiarities, for there was assuredly no one who, 
prior to my doing so, had called attention to them. 

What first of all interested me was the felspar that is associ- 
ated with this quartz^ of which, under the name of Paradoxite^ 
I shall shortly publish a description. I accidentally found, on 
separating the two, that this quartz is of less hardness than is 
usually attributed to this mineral, and I was thence led to address 
myself to M. Steeg to prepare me some slices thereof for optical 
purposes. He on that wrote me to say that he too, when cutting 
slices at right angles to the principal axis, found this quartz to 
be only of the hardness of adularia. On scratching it I find, 
however, that it is somewhat, but very little, harder than adu- 
laria. According to my scale, its hardness is from 8 to 8^ ; at 
the free summits of the crystals it even attains a hardness of 8^, 
taking that of the Zinnewald smoky quartz, or the transparent 
quartz of St. Gk)tthard, or from Oraubiindten, as equal to 9. 

Not knowing whether anyone besides myself has determined 
its specific gravity, I may state that it fluctuates between 2*578 
and 2*682, and that it so far goes hand in hand with the hard- 
ness, that fragments of the crystals on the ends where they 
were seated are of the lowest specific gravity, while fragments 
of the free ends were of the highest, yet never attaining that of 
other varieties of quartz that I have examined. 

In the optical sections prepared [for me by M. Steeg, I dis- 
covered at once the very distinct biaxial character of the mineral. 
The hyperbolas are not, however, black, but appear bluish. M. 
Jenzsch, the Councillor of Mines, has met with both left-handed 
and right-handed individuals. 

Although it is stated in the notice referred to that this quartz 
is cloudy, this is only partially the case, for some of the crystals 
met with are quite transparent. 

This quartz possesses also another peculiarity, being more 
liable to be weathered than any other with which I am acquainted. 
I cannot say how many thousand times I have noticed quartz 
lying on the surface of the ground, but I have never met with 

* Communicated by W. G. Lettsom, Esq. From Poggendorff't ^nnaim 
der Physik, vol. czn. p. 326. 



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f 



Biaxial character ofPyramddl and Rhombohedral Oryatab. 191 

any that is as mach weathered as this Eaba quartz now aUd then 
is. It may be assumed for a fact that it is more liable to become 
so than is its neighbour the paradoxite. 

My friend M. Reich^ the Superior Councillor of Mines^ had 
the kindness to examine this quartz chemically for me^ and 
found therein nothing but silica^ with traces of oxide of iron 
amounting to \ per cent. Professor Wohler has been so good 
as to say he will prepare some sihcon from it and submit it to 
a further examination. 

This quartz occurs at Euba in veins^ which are four in numbef 
in all. Three of them do not exceed 1 inch or 2 inches in widths 
but the fourth is above 2 feet thick. In the former^ quartz and 
paradoxite alone occur; but in the latter^ fragments of porphyry 
are met with^ as also fluor in considerable quantity, and some 
calcite and mica* 

As I was famiUar with paradoxite elsewhere only in connexion 
with tin-iveins, and as the blue fluor, as it occurs here, is specially 
associated with veins of that kind, I caused large fragments of 
the general mass of the veins to be broken up, stamped, and 
washed, when, lo, tin-ore was obtained by washing, from which 
beautiful metallic tin was got before the blowpipe with oxalate 
of potash upon charcoal. The tin-vein formation, therefore, 
which hitherto has been held to be one of the oldest, is a very 
recent one, for the veins in question occur in the lower new red 
sandstone. 

There are also other varieties that may be held to belong to 
this quartz, especially, for instance, the so-called ^^ar-gvor^xr from 
the vicinity of Bautzen in Saxony, and from the neighbourhood 
of Hohenelbe in Bohemia. These are of the hardness of adu«« 
laria. They consist of wedge-shaped, bacillary, aggregated pieces 
radiating in a stellar form; they are, however, quite cloudy, 
and for the most part somewhat weathered. The Euba quarts 
assumes partially the same structure ; but it is rarely stellar, it 
is commonly fascicular. I am acquainted also with another 
star-quartz from the Hill of Molignon in the Tyrol. 



As I have for the last four years occupied myself to my utmost 
with optical studies, I will here mention, quite in a preliminary 
way, and as concisely as I can, some of the principal results at 
which I have arrived. 

lie grossular garnet from Siberia is in one tetragonal axis uni- 
axial, as is the case with essonite and almandine. The garnets 
whose specific gravity is the highest, namely the manganese gar- 
nets, are optically isotropic. 

In the pyramidal syitem, I have found that all transparent 



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192 Prof. Norton an Mokcular Phfsies. 

minerals to which I have had access are, with one single excep- 
tion^ optically hiaanaL The species that exhibit this character 
the most clearly are Cromfordite (muriocarbonate of lead) , SeheeU 
ites of various localities^ hyacinth-zircon from, the neighbour- 
hood of Schandau in Saxony, different Wulfenites, and mellite. 
The biaxial character is exhibited strongest in a meionitefrom 
Monte Somma (in others it is comparatively very weak), and in 
the yellowish zircon from Ceylon. That apophylhtes are opti- 
cally biaxial was established by Sir David Brewster more than 
twenty years ago. The observations upon mellite were made by 
M. Reich, Superior Councillor of Mines, and by M. Jenzsch, 
Councillor of Mines, quite iudependently of each other. 

The one single exception is Matlockite, which is optically uni- 
axial. There is also a green uranite, which is so feebly biaxial 
that many an observer might take it for uniaxial. 

In the rhombohedral system pretty much the same holds 
good. Tamarite (copper mica), dioptase, the majority of cal- 
cites, Smithsonite, most apatites, nepheline, most quartzes (pro- 
bably all), beryl, phenakite, spartalite, Greenockite, and so forth, 
are optically biaxial. Mimetite from Johanugeorgenstadt is as 
clearly and strongly so as many a biaxial mica is (Muscovite). 
• That biaxial quai*tzes are met with was already known, and 
the same is the case with respect to beryl. 

As far as I have proceeded as yet in the determination of the 
angles of the crystals, not only in the optically uniaxial crystals 
of the cubic system, but also in the optically biaxial crystals of 
the pyramidal and rhombohedral systems, those deficiencies of 
symmetry may be shown to occur to which attention was directed 
by me some years ago. 

When in the course of last year M. de Kokscharow witnessed 
in so marked a manner, while with me, the biaxial character of 
various idocrases, he, of his own accord, observed that he would 
repeat his measures of that class of crystals. The manganesian 
idocrase from St. Marcel in Piedmont is optically the most 
remarkable. 

.Freiburg, January 1864. 



XXII. On Molecular Physics. By Prof. W. A. Norton*. 

IT is proposed in the present paper to give a general exposi- 
tion of a Physical Theory of Molecular phenomena, based 
upon the highest generalizations, and the most reliable physical 
conceptions to which the progress of science has hitherto con- 

1* From Silliman'« American Journal for July 1864. 



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Prof. Nortou an Molecular Physics. 198 

ducted 'I'* A theory so comprehensive in its scope can be com* 
pletely substantiated only by undertaking a thorough discussion 
of the minute details of special phenomena in the several depart- 
ments of physical science^ and subjecting it at all practicable 
points to the rigid test of numerical calculation. But before any 
detailed discussions can be entered upon^ we must deduce from 
the fundamental conceptions adopted the general principles of 
molecular action^ or the laws of the molecular forces^ note the 
characteristic features of the different provinces into which the 
entire field of research is naturally divided^ and trace out the 
general relations which they bear to each other^ or^ in other 
words, recognize the mutual dependence and essential correlation 
of special physical forces. 

The established truths and generally received ideas which 
form the basis of the theory are as follows : — 

1. All the phenomena of material nature result from the action 
of force upon matter. 

2. All the forces in operation in nature are traceable to two 
primary forces, viz. attraction and repulsion. 

3. All bodies of matter consist of separate indivisible parts, 
called atoms, each of which is conceived to be spherical in form. 

4. Matter exists in three different forms, essentially different 
from each other. 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 sether, asso- 
ciated with ordinary matter, by the intervention of which all 
electrical phenomena originate or are produced. This electric 
mtkeri as it may be termed, is attracted by ordinary matter, while 
its individual atoms repel each other. . (3) A still more subtile 
form of sether, which pervades all space and the interstices be- 
tween the atoms of bodies. This is the medium by which light 
is propagated, and is called the lurmniferous aiher, or the universal 
atker. The atoms, or '' atomettes,^' of this sether mutually repel 
each other ; and it is attracted by ordinary matter, and is conse- 
quently more dense in the interior of bodies than in free space. 

5. Heat, in all its recognized actions upon matter, manifests 
itself as a force of repulsion. 

The comer stone of a physical theory of molecular phenomena 
must consist in the conception that is formed of the essential 
constitution of a single molecule — understanding by a molecule 
an atom of ordinary matter endued with the properties and in- 
vested with the arrangements which enable it to exert forces of 

* The principal features of the general theory here propounded have» 
with few exceptions, been advocatea by the author before the Connecticut 
Academy of Arts and Sciences, at various meetings of the Academy during 
the last six years. 



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Id4 Rrof. Norton on Molecular Phyma. 

attraction and repulsion npon other molecules. In seeking for 
this^ the most philosophicial course that can be pursued is to 
follow out to their legitimate conclusions the general principles 
already laid down. We have admitted the existence of a subtile 
aether^ attracted by all bodies^ and pervading their interstices ; 
now if bodies attract this sther^ the atoms of which they are 
composed must exert an attractive action upon it. Every atom 
must therefore be surrounded with an mthereal atmosphere, con- 
densed upon its surface^ and extending indefinitely outward. 
Again, it is conceded that the electric aether or fluid, if it exists, 
must be attracted by ordinary matter; but if this attraction 
subsists it must be exerted by the individual atoms, and there- 
fore every atom must also be surrounded with an atmosphere of 
electric aether — an electric atmosphere, as it may be termed. We 
must suppose that the interstices between the atoms of this elec- 
tric atmosphere will be pervaded by the more subtile asthereal 
atmosphere. We are thus led to conceive of a molecule as con- 
sisting of an atom surrounded with two atmospheres, aethereal 
and electric — ^the former being the more attenuated, and perva- 
ding the other. We may suppose either that these two aethers 
exercise no direct action upon each other, or, what is more pro- 
bable, that the electric atoms attract the aethereal, and are there- 
fore surrounded, like the central atoms of the molecules, with 
aethereal atmospheres. To this supposed fact we may attribute 
the mutual repulsion subsisting between the electric atoms, and 
thus restrict the fundamental property of repulsion to the atoms 
of the universal aether. 

The conception here formed of a molecule involves the idea 
of the operation of the two forces of attraction and repulsion : a 
force of attraction is exerted by the atom npon each of the two 
atmospheres surrounding it, and a force of mutual repulsion 
between the atoms of each atmosphere. These we regard as the 
primary forces of nature, from which all known forces are derived. 
They determine primarily the physical relations of the atom to 
its atmospheres. In seeking for the molecular actions that may 
result from their operation, there are two different routes that 
may be taken. We may conceive that the atmospheres sur- 
rounding each atom are naturally in a condition of statical equi- 
Ubrium, and that the primary forces with which the molecule is 
invested take effect at all distances, without the intervention of 
any medium, and unobstructedly through all intervening matter ; 
or we may conceive the natural equilibrium of the molecukr 
atmospheres to be a dynamical one, and that, as a necessary 
consequence, recurring impulses, both attractive and repulsive, 
are propagated outward by the surrounding aether from each 
molecule, and take effect upon other molecules. Here, as before. 



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Prof. Norton on Molecular Phyriai. 195 

we shall follow the indications of existing science^ which, as will be 
generally conceded, point to a dynamical origin of the molecular 
forces. The .ideas we have thus been led to form with regard 
to the real nature and mode of action of these forces are as 
follows. 

The molecular forces consist of — 

1. A repulsive action of the electric atmosphere of a molecule 
exerted primarily upon the electric aether immediately exterior 
to it. This force of repulsion is made up of recurring impulses, 
which are propagated in waves through the circumambient elec- 
tric sether. These impulses fall upon the electric atmospheres 
of contiguous molecules, and are thence propagated down to the 
surfaces of the central atoms, and take effect upon these as a force 
of repulsion. 

2. An attractive action exerted by the central atom of the 
molecule upon the electric aether surrounding it ; originating a 
series of successive contractions of this atmosphere, and thus of 
inward-acting impulses, which are propagated outward and form 
a set of attractive waves. These are received, like the repulsive 
impulses, upon the surfaces of contiguous electric atmospheres, 
and propagated to the central atoms, upon which they take effect 
as an attractive force. The recurring contractions of the atmo- 
sphere here supposed do not necessarily imply that the force 
which produces them acts by impulses, for every such contrac- 
tion must develope a resistance^ which will occasion a subsequent 
expansion ; and, at the same time, recurring expansions should 
result from the similar impulses propagated from surrounding 
molecules. The electric atmospheres that envelope the atoms of 
bodies may accordingly be in a perpetual dynamical condition 
of alternating contractions and expansions, or of alternating 
inward and outward movements of their atoms, although the 
primary forces acting upon these atoms should be continuous in 
their action. 

But if we confine our attention to the action of a single atom 
upon its electric atmosphere, it will be seen that the expansions, 
which of necessity follow the contractions, must be of less extent 
than the contractions; for a part of the contractile force is ex- 
pended in impelling a portion of the universal sether compressed 
upon the surfece of the central atom normally outward from this 
surface. To the extent that this takes place will the contraction 
of the atmosphere exceed the expansion which immediately fol- 
lows it, and an effective attractive force be propagated through 
the surrounding electric sether. We are thus led to recognize 
the existence of a third molecular force, viz. a force of repulsion 
originating in the attractive action exerted by the atom of the 
moleoule upon its electric atmosphere. 



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196 Prof. Norton &n Mokeubtr Phytks. 

3. A third molecnlar foree, then^ consists of a series of repul- 
sive or outward-acting impulses imparted to the universal sether 
at the surface of the atom of a molecule by the contractile force 
exerted by the atom upon its electric atmosphere. This repul- 
sion is equals at its origin^ to the attraction which developes it. 
It is propagated in waves which, unlike the waves conveying the 
other molecular forces, proceed through the universal aether. 
These waves, if each contraction of the atmosphere were not fol- 
lowed by a partial expansion, would be of the character of ^^ waves 
of translation,^' and would convey only outward-acting impulses; 
they are, in fact, oscillatory waves, in which the outward predo- 
minate over the inward acting-impulses. 

The force thus originating may be regarded as the primary 
force of heaty and may be termed heat repulsion. The other two 
molecular forces may be designated as the forces oi electric attrac- 
tion and electric repulsion. But they should not be confounded 
with the special electric forces that come into play whenever the 
natural quantity of electric sether associated with atoms, or 
present on different sides of atoms, experiences any material 
increase or diminution — which will be considered in another 
connexion. 

The molecular forces that have now been specified might be 
otherwise characterized as follows: (1) A repulsion of the one 
electric atmosphere for the other, operating through the inter- 
vention of the electric sether posited between the two. (2) An 
attraction of the gross atom of the one molecule for the electric 
atmosphere of the other, also taking effect by means of the in- 
tervening electric wther. (3) A repulsion exerted by the atom 
of the one molecule upon that of the other, through the inter- 
vening universal aether, and originating in the attraction just 
mentioned. These forces consist of recurring impulses propa- 
gated in waves through the sethereal media, which take effect 
ultimately as attractive or repulsive impulses upon the central 
atoms of molecules. The law of diminution of the propagated 
forces is that of the inverse squares. 

If the {Ethereal as well as the electric atmospheres of particles 
be conceived to be in a state of dynamical equilibrium, their 
alternate contractions and expansions should originate oscilla- 
tory waves that would be propagated indefinitely onward through 
the aether of space. If we admit, with Professor Challis^ that 
such purely oscillatory waves, when they fall upon particles^ 
will give rise to an attraction or a repulsion, according to the 
breadth of the waves in comparison with the diameter of the 
particles, and that the force of gravitation may be conveyed by 
such waves, we have in the supposed dynamical condition of 
aethereal atmospheres of particles a possible origm of waves of 



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Prof. Norton on Molecular Physics. 197 

grantfttion, which cannot be founds primarily^ in any supposed 
motion of gross atoms in an isolated condition. It should be 
observed, too, that the dynamical condition of atmospheres here 
considered is really a necessary consequence of the first opera- 
tion of the force of attraction of atoms upon the surrounding 
sether, if the elasticity of the aether be perfect. 

A di£ferent view of the possible nature and origin of the mole- 
cular forces from that which has been given, may be obtained 
by changii^g our stand-point. 

We may conceive the same three forces, viz. one of attrac- 
tion, and two of repulsion, to be in operation, but we may re- 
place the forces of electric attraction and repulsion by equivalent 
forces propagated through the universal aether. This may be 
realized as a physical conception by regarding the atoms of the 
molecules and those of the surrounding electric aether, each en- 
compassed by its aethereal atmosphere, as being, or rather their 
atmospheres, in the dynamical condition of alternate contraction 
and expansion, and thus as being centres from which proceed 
oscillatorv waves, and that, as the result, in accordance with the 
general theory so ably advocated by Professor Challis, the elec- 
tric atoms of two atmospheres may repel each other, and the 
central atoms which they surround may also repel each other ; 
the general result being that similar atoms repel, and dissimilar 
attract. Upon this view the forces wx have deduced from the 
dynamical state of the electric atmospheres, which must still be 
in operation, must be overshadowed by those now considered. 
Upon the former idea it is the forces now derived from the dyna- 
mical state of the eethereal atmospheres that must be oversha- 
dowed by the others. A discussion of phenomena can alone de- 
cide which of these two general views should be adopted. In 
the present memoir we shall chiefly occupy the ground first taken. 
Among the physicists of the present day there seems to'be a 
growing inclination to discard the notion of an electric fluid as 
distinct from the aether of space, and attempts have been made 
by Challis, Tyndall, and others, to frame a consistent dynamical 
theory of molecular forces and phenomena based upon the sup- 
posed existence of only two forms of matter, viz. gross matter, 
smd the aether of space. The fundamental position taken by 
these distinguished physicists is that the molecular forces, inclu- 
ding heat, are conveyed by purely oscillatory waves, and origi- 
nate in a vibratory motion of the ultimate particles of bodies. 
Against this idea, however plausible it may seem, and however 
admirable may be the ingenuity and skill with which it has been 
sustained, many serious objections may be urged. One or two 
of these may be briefly stated. 
l*..Na possible mode of explaining the phenomena of electri- 



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198 Prof. Norton an Molecular PkyricB. 

city and magnetism has yet been indicated by the advocates of 
this theory. The electric fluid is erpelled by them from the vast 
field it has hitherto occupied^ but all attempts to supply its place 
have proved futile. 

2. Another obvious objection is^ that vibratory motions of gross 
atoms are supposed to originate the forces by which such atoms 
are primarily aggregated into masses^ whereas it is essential to 
the possibihty of such vibrations that contiguous atoms should 
exercise a mutual action upon one another — ^that is> be previously 
aggregated. We must suppose, then, the existence originally of 
other forces, to bring isolated atoms together and make the sup- 
posed forces due to vibratory motions of the atoms possible; 
that is, these latter forces become possible only when there is no 
longer any further occasion for them. We have seen that another 
possible origin may be ascribed to such oscillatory waves that 
does not involve the physical impossibility just referred to, from 
which those who seek for the key to all molecular phenomena 
in the motions of gross atoms can hardly escape. 

3. The notion advocated by Tyndall in his admirable work 
on ' Heat considered as a Mode of Motion,' that heat and light 
originate in a vibratory motion of ordinary atoms, involves the 
supposition that these atoms are capable of vibrating at the 
astonishing rate of six hundred trillion vibrations in a second, 
while the most rapid vibration of atoms, or of a collection of 
atoms, known to take place in the production of sound, does 
not exceed 24,000 per second. It may be conjectured that this 
immense chasm may be spanned by the idea that the ultimate 
particles of bodies are immeasurably smaller than any coUec- 
tion of atoms which may be simultaneously vibrating when 
bodies emit sound; and that since a musical string vibrates 
more rapidly in proportion as it is shorter, a single particle may 
vibrfte at an inconceivably rapid rate by reason of its exceeding 
minuteness. But the analogy here supposed does not exist aa 
a physical fact, and no such inference can be drawn from it ; for 
the rate of vibration of the string depends upon the distance 
between its two fixed points, but in no proper sense can it be 
said that two particles between which another is situated, are 
fixed, so as to be incapable of taking on the motion imparted ta 
the intermediate one. So far from this being the case, the dis- 
placed particle can only vibrate by reason of the reaction of the 
contiguous particles to the action which it exercises upon them ; 
and in receiving this action the motion must be transmitted. If^ 
to remove the difficulty, we conceive the particle to oscillate aa 
if it were wholly isolated, in union with an oscillatory vraye 
falling upon it, we then fall upon the second objection stated 
above^ and seek in vain through the universe for the vibratory 



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Prof. Norton m Mohadar Physics. 199 

motion of atoms of ordinary matter in which this wave convey- 
ing such wonderfully rapid vibrations can have originated. We 
at the same time remove the necessary foundation for the 
explanation of a variety of special facts and phenomena^ which 
require the assumption of special rates of vibration^ proper 
to the particles of different bodies — as the different colours of 
bodies^ &c* 

Again, if the rates of vibration of ultimate particles depend 
upon the mutual actions subsisting between the displaced par- 
ticle and those adjacent to it, the vibrations in which the heat- 
force is supposed to consist, should be propagated from par- 
ticle to particle, just as any mechanical force is; in other 
words, heat should be conducted after the same manner, es- 
sentially, and at the same rate, that sound is conducted by the 
same medium. 

By ascending to the reservoir of primary force, from which 
all the different streams of force flow, as has been attempted in 
this communication, we may avoid some of the difficulties at- 
tending the rejection of the idea of the existence of an electric 
sether; and in many portions of the field of physical science 
the part played by the electric sether is so similar to that which 
we may suppose would be performed by the universal sether 
under similar circumstances, that the suspicion at times arises 
that all the offices now attributed to the former will eventually 
be found to be discharged by the latter. If so, the processes of 
operation will not of necessity be changed, but only the agent 
or medfium. 

Admitting that the molecular forces consist of two forces of 
repulsion and one of attraction, as characterized on pp. 196-6, let 
us proceed to inquire into the variations that may occur in the 
effective action of two similar molecules, separated by various 
intervals of distance. Let a?= the distance between two mole- 
cular atmospheres ; r= the radius of either atmosphere ; m^the 
constant of electric repulsion, that is, the force of electric repul- 
sion exerted upon either atom when ^=1; and n= the con- 
stant of the electric attraction, which will also be the constant of 
the equal force of repulsion propagated from the surface of the 
atom through the universal sether. Also let u= the force of 
electric repulsion, and i?= the excess of the attractive force over 
the sethereal repulsion developed by the attraction, — all the forces 
being considered as taking effect upon the central atom. The 
effective action exerted by either molecule upon the other will 
be the difference between the values of u and v. Denote it by 
/; then /=i7— tt. When the calculated value of /is positive 
the action will be attractive ; when it is negative the action will 
be rqpulaive. We have for the force of attraction the general 



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200 



Prof. Norton on Moleeuhtr Pk^sici. 



expression . r^; for the ethereal repulsion the expression 



(2r+a?y 



;; and for the electric repulsion ■^. Then 



m 



f>= 



n{3r^±2rx) 



(r+a?)« (2r+^)« (r4-a?)«(2r+^)«' 



t<= 



m 



.«» 



(I) 



(2) 



_ n(3r«4-2r^) m 
/«„-«_ —-^^,-^_^^^,-- -5 (5; 

As the two forces of electric attraction and repulsion have an 
entirely different origin, we have no reason to suppose that 
n=m; nor have we any means of ascertaining, on a priori 
grounds, their comparative values. But we can assume that 
ti=t; for some supposed value of x, determine the ratio of n to 
m on this supposition, and calculate the values of /for various 
values of ar, both greater and less than that for which we have 
taken /=0. 

Table I. 



/==0 when | /=0 when 


f^ 


Owhen 


/-O when 


/-Owhen 


d7=20r. 


a?=10r. 




r=5r. 


ar=3r. 


ar=2r. 


n=12-410m. 


n=7-576»i. 


n = 


5-428W. 


n=4-938m. 


n=5l43m. 


s. 


/. 


X, 


/. 


X, 


/ 


or. 


/. 


X, 


/. 


0-5r 


-0-470 i 


0-5r 


-l-8450it 


0-5 r 


-2-4560 * 


2-Or 


-0-00996* 


l-8r 


-0-00881A 


0-6 


+0-2341 


0-7 


-0-4586 


10 


-02461 


25 


-000075 


1-9 


-000361 


0-7 


+0-5510 


0-9 


-00368 


1-5 


-001906 


27 


-0-00001 


1-95 


-0K)0164 


09 


+0-7275 


1-0 


+00522 


1-672 


0-00000 


2-8 


+0 00009 


2-0 


OOOOOO 


10 


+0-7236 


1-2 


+01310 


1-7 


+OH)0207 


2-9 


+0-00008 


2-1 


+0-00246 


1-3 


+0-6146 


1-3 


+0-1447 


2-0 


+0-01386 


30 


000000 


2-2 


+0-00408 


1-4 


+0-5709 


1-4 


+0-1497 


2-2 


+001576 


3-2 


-0-00034 


2-3 


+0-00508 


1-5 


+0-6360 


1-5 


+01492 


2-25 


+001585 


3-5 


-0-00102 


2-4 


+0-00663 


2-0 


+03533 


1-7 


+01398 


2-3 


+0-01584 


40 


-0-00215 


2-5 


+000586 


5-0 


+00514 


2-0 


+0-1183 


25 


+0-01506 


50 


-0-00360 


2-7 


+000668 


100 


+00064 


4-0 


+00301 


275 


+001322 


60 


-0-00416 


3-0 


+000460 


150 


+000109 


50 


+0-0158 


3-0 


+001102 


70 


-000421 


4-0 


+OK)0036 


20K) 


0-00000 


7-0 


+000444 


4-0 


+0-00384 


8-0 


-000404 


4-1 


+OK)0003 


250 


-0000265 


100 


000000 


50 


000000 


9-0 


-0-00377 


45 


-0-00109 


300 


-0-000317 


150 


-0-00107 


60 


-0-00181 


100 


-000349 


50 


-0-00211 


350 


-OH)00306 


200 


-0-00097 


70 


-0-00280 


150 


-000224 


70 


-0-0036 


40-0 


-0-000280 


300 


-0-00061 


80 


-0-00289 


20-0 


-000150 


8-0 


-0O036 


800 


-0-000110 


40-0 


-0-000413 


90 


-0-00292 


400 


-0000487 


lOO 


-OH)038 






80-0 


-0-000128 


100 
150 
200 
40 
800 


-000283 
-000202 
-000141 
-0-00047 
-0000136 


800 


-0-000138 


150 
200 
40-0 
800 


-0-00215 
-0O0146 
-0-000481 
-0000137 



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P^f . Norton im Moheular Physics. feOl 

Thfi pceceding Table contains the results of numerouBcalcnlai- 
tions made after this manner, in which k stands for -a. 

. From these results it appears that for values of ~ greater than 

4*988, or thereabouts, there are two alternations of the effective 
force { as the distance between the molecular atmospheres increases 
indefinitely from zero. The first is from a repulsion to an attrac- 
tion ; the second is from an attraction to a repulsion. The re«- 
pulsion which becomes effective beyond the limit of the attrac- 
tion at first increases, and then decreases, extending to an inde- 
finite distance. If the ratio — be less than about 4*988, the 

m ' 

effective action of the two molecules upon each other will be 

repulsive at all distances. It will be observed also that the 

range of distance within which an attractive force takes effect is 

n 
greater in proportion as the value of — is greater, and that this 

becomes reduced nearly to zero when this ratio is equal to 4*938 ; 
also that in all cases in which an effective attraction manifests 
itself at any distance whatever between the molecules (that is, in 
the qase of every known solid and liquid), the effective repulsion 
within the limit of the attraction obtains at less distances between 
the electric atmospheres of the molecules than about 3r, — that is^ 
than once and a half the diameter of either atmosphere. 

For the more accurate determination of the least value of tb^ 

ratio — , we have the following results of computation : — 

For/=0 when a?=3r, - =4*93827; for/=Owhen a?=2*9r, 

~ P=4*98449 : fDr/=0 when jr=2-8r, - =4-934409; for /=0 

^ n ^ n 

when a?=2*7r. — =4'93847. If then the ratio- be greater than 

m m ^ 

4*9344, the two alternations of effective molecular force above 
taientioned will have place ; if the ratio be less than 4*9344, the 
effective action of the one molecule upon the other will be repul- 
sive at all distances. ' 

It is assumed in the foregoing calculations that the surface of 
each molecular atmosphere which receives the impulses^ whether 
attractive or repulsive, propagated from the other through the 
intervening electric aether, may be regarded as the same as that 
from which the electric repulsion proceeds outward ; but it will 
be readily seen that they may be supposed to differ within cer- 
tain limits, without vitiating the result that for certain values of 

Phil. Mag. S. 4. Vol. 28. No. 188. Sept 1864. P 



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202 Prof. Norton ati Maleeular Phyties. 

- two alternations of the effective force will subsist. The forces 
m 

may also experience losses^ to a certain extent, in their propaga- 
tion, and tliis general principle still hold good. 

It should also be observed that when two particles are remote 
from each other, as ia the case of a particle of cometic matter 
repelled by the sun, we must suppose the intervening space to 
be occupied by the universal sether only. In such a case, then, 
both the attractive action and the electric repulsion will be want- 
ing, and the only force remaining will be the athereal or heaU 
repulsion ; which should operate at indefinite distances, accord- 
ing to the law of inverse squares. A discussion of the pheno- 
mena of evolution of cometary envelopes, and of the outstreaming 
of jets of nebulous matter from particular parts of the surface 
of the nucleus, must be had before we can decide how far the 
electric repulsion may be in operation in the processes of ejection 
of cometic matter from the nucleus*. 

The general law of the variations of the force of effective 
molecular action is graphically represented by the curve ram 
€ n in fig. 1, The abscissas represent the comparative distances 
between the electric atmospheres of the two molecules, and the 
ordinates the intensities of the effective force corresponding to 
these distances. When the ordinate lies above the axis of 
abscissas, the force is attractive ; when it lies below, the force is 
repulsive. The two axes are asymptotes to the curve. The 
curve has been constructed from the calculated results obtained 
on the supposition that/=0 when a?=5r. 

There are four points, marked a, 6, c, d, to be especially noted. 
a and c, where /=0, represent positions of equilibrium, a being 
a position of stable, and c of unstable equilibrium. When the 
atmospheres are separated by the distance O b the attraction has 
its maximum value, b m ; and when they are at the distance O d, 
the repulsion, beyond the outer limit of the attraction, has its 
maximum value, rfw. In order that two particles may unite 

* 111 the memoir by the author " On the Theoretical Determination[ of the 
Dimensions of Donati's Comet," published in No. 87, vol. xxix., and in No. 
94,vol. xxxii. of Silliman's American Journal^ the conclusion was reached, as 
one result of the computations, that " the repulsion exerted by the sun, 
and also by the nucleus (of the comet), is not a property belonging to all the 
particles of the mass, like the attraction of gravitation ; and is probably 
therefore a force emanating from the surface of the body, or from a portion 
only of its mass.** We now see that the existence of such a force is also a 
legitimate deduction from the theory of molecular forces under considera- 
tion, and that it consists in the force of sethereal repulsion^ which we have 
denominated heat^repulsion. Its impulses constitute the entire force of 
radiant heat given off by the body into free space, and vary in intensity or 
amount with the temperature. 



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Prof. Norton on MoUctdnr Physics. 



203 



when influenced by their own proper forces only, the distance 
between their atmospheres mast be less than Oc. But if they 

Fig. 1. 



are subject to an external pressure urging them toward each 
other, it suffices that this pressure should exceed the maximum 
repulsion dn^ at the greater distance Od, To separate the parti- 
cles/the force in operation must exceed in intensity the maximum 
molecular, attraction, bm^» ^ 

If heat be imparted to the two particles under consideration, 
it will obviously tend to depress the entire curve of molecular 
action, and diminish the range a c of the attractive force. If 
the amount be continually increased, the distances between the 
two positions of equilibrium, a and c, will eventually be reduced 
to zero, and the curve thrown entirely below the axis of abscissas, 
or the effective force become a mutual repulsion at all intervals 
of distance between the particles. This would be the neces- 
sary tendency of the introduction of new repulsive impulses 
into the system, even if the original forces continued in full 

* To guard against misapprehension, it may be well to observe here that 
the resisting force of cohesion which is brought into play when a body is 
ruptured by a pulling force is not necessarily proportional to the intensity 
of the maximum force of attraction between two of its particles. For it 
must depend, not only upon the intensity of this attraction, but also on the 
number, distance, and position of the other particles that oppose, by their 
attractive action, the separation of the two. Incidentally the displacement 
these particles may experience, from the action of the rupturing force, 
comes in as a modifying cause. 

P2 



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204 Prof. Norton ah Mofecular Pky9ic9. 

operation aa heiarei bat heat, by ei^anding tbe molecular 
atmospheres, should also tend to diminish the ratio of n to f9»« 
and therefore to modify in a similar manner the natural curve 
of molecular action. 

It is easy to see that a similar curve will also serve to repre-: 
sent the mutual actions of dissimilar molecules, which obtain 
when a chemical union is formed between two different sub- 
stances. But in this case a force of electric attraction not yet. 
considered may come into play. 

The general principle of two alternations of the effective action' 
of molecules, to which we have been theoretically conducted, is 
distinctly recognized as a physical fact in the three dijOTerent 
states of aggregation of matter — ^in the molecular fittraction 
and repulsion manifest in solids and liquids, an'd in the mutual 
repulsion subsisting between the same particles when widely 
separated in the vaporous condition. It will be seen hereafter 
that the law of molecular action, as portrayed in the curve 
shown in fig. 1, furnishes, in the probable vanations of the ratio. 

— , an adequate general cause for the varied results of this action 

exhibited in the different properties of substances ; and at the 
same time reveals the probable explanation of many physical 
and chemical phenomena occurring at surfaces of contact, and 
of the dependence of these phenomena upon temperature and 
other circumstances, as in oxidation, combustion, &c. 

From the stand-point now taken, new views open up to us on 
all sides. The more conspicuous of these we will proceed to 
sketch, in general outline, under the several heads of the Mole- 
eular Comtitution and Mechanical Properties of Bodies, Heat, 
Light, Electricity y Magnetism, and Chemical Action, The inti- 
mate relations subsisting between the phenomena occurring in 
these different departments of Nature, and between the specinl 
agents by which they are produced, or the ^^ correlation of the 
physical forces,^^ will be seen to be deducible from the funda* 
mental conceptions adopted. It will be observed that all these 
varied phenomena are but different results of the action of the 
primary forces, which consists in an attraction of atoms for their 
atmospheres, and in a mutual repulsion between the atoms of 
these atmospheres ; that they are, primarily, movements or dis- 
turbances produced in these subtile atmospheres, from which 
aethereal waves of impulses and motions of molecules and masses 
may result. 

[To be continued.l 



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[ 205 ] 

XXIIL On the Operating St/mbol of Differential Covariants. By 
The Honourable Chief Justice Cockle, President of the Phih- 
, sophical Society of Queensland*. 

CONSIDEBING the complete form of differential cubic, the 
Operating symbol A, of my paper " On Differential Cova- 
riants ** in the last March (1864) Number of this Journal, will 
become 

or ththet we ought to say 

A=8-[.^]-.[»i]-8[.|]. 

in order to mark the indissoluble nature of the bond which con- 
nects the elements, or constituents, of the constituents or ele- 
ments of the operator. Moreover a, b, c, /, and w being treated 
as independent, we have 



or^ more fully^ 



A- = — A 
dx dx ^ 

AK'=A^ = ^.AK. 
dx dx 



Illustration will probably serve all the purposes of a more 
laboured exposition, and the use of the brackets in giving clears 
ness and precision to the operations will appear from the follow- 
ing transformation : 

If AK vmislies, the commutative property of ^ and A enablaf 

us to perceive that AK' vanishes also. That AK', vanishes may 
be shown directly, thus : 

AK'j=A(2ftft'-a'c-c/fl + aA"-»fl") 

=0. 

If w6 employ differentials instead of differential coefficients^ 
the operator for 
. {a^hcjjdsd^fy 

'I' Communicatejl by the Author. . . 

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206 Prof. Plateau on the Conditions of 

In these laat expressions dr is to be treated as if it were an 
ordinary symbol of qnantityi and S is now defined by the equation 

Brisbane, QueenslaDd, Australiai 
May 30, 1864. 



XXIV. On the Conditions of Stability of thin Films of Liquids ; 
a Report hy Professor Plateau on a Memoir by Professor 
Lamarle ofGhent^. 

IN the Sixth Series of my researches *^0n the Fignres of 
Equilibrium of a Liquid. Mass without Weight "t^ I bave 
established^ in part experimentally and in part theoretically^ the 
laws which relate to films terminating in a common liquid edge^ 
and to liquid edges which meet at the same liquid point. From 
these laws I drew the conclusion^ which I. have tried to confirm 
by experiment^ that every equilibrated system of films in whicli 
they are not fulfilled is an unstable system^ and I ended thia 
series by saying :— 

** I will return once more to systems of films^ in order to con- 
sider the theory of them from a more general point of view. In 
fact, as I have already observed, the liquid films of which they 
are made up may be compared to stretched membranes, and 
hence it will be seen that each system will arrange itself so that 
the sum of the surfaces of all its films will be a minimum. Bnt 
I reserve this point for a futui^ Series.'^ 

In expressing myself thus, my intention simply was to take 
as examples certain particular systems of films, which from their 
simplicity are capable of being made the subjects of direct cal- 
culation, and to show that the sum of the surfaces of the films is 
a minimum relatively to some one mode of deformation ; but I 
had no intention of treating the problem in all its generality, for 
I did not consider it practicable to do so. I perceived that there 
must exist a necessary connexion between the principle of the 
minimum sum of the areas and my laws; but I could not seize 
the precise nature of this connexion, and it ceemed to me next 
to impossible to do so. All these difficulties, however, have been 

* Communicated by Professor Plateau, from the Bulletin de VAcad^mie 
oyale de Belgique, 2**8^. vol. xvii. No. 6. 
t Phil. Mag. S. 4. Vol. *xiv. p. 128. 



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Stability of tUn Films of Liquids. 207 

overcome with wonderful sagacity and rare good fortune by M. 
Lamarle. 

He begins by establishing; more definitely than I had done^ the 
above-mentioned principle of the minimum; and then, starting 
from this, he discusses the case of films meeting at the same 
liquid edge. He supposes any number of plane films starting 
from solid edges and all uniting in one common liquid edge, and 
imagines the whole cut by a plane perpendicular to this latter. 
The section consists of straight lines starting respectively from ' 
fixed points and all meeting at the same point ; and he shows 
first, by elementary geometrical considerations, that if the straight 
lines are three in number, their sum will be a minimum when 
they make equal angles with each other. If the straight lines 
are more numerous, he shows, by considerations equally simple, 
that, in order that their sum may be the smallest possible, the 
single point of junction must be replaced by several points con- 
nected together by additional straight lines in such a way that 
at each of these points there are only three straight lines making 
equal angles vrith each other. Lastly, the diminution in the sum 
of the straight lines beginning with the commencement of these 
modifications (that is to say, for exanlple, in the case of there 
being more than three straight lines, as soon as the point of 
junction divides so as to giv6 rise to new straight lines and 
points), .it follows that the demonstration applies equally to 
curved lines, for these may always be replaced by their tangents 
in the immediate neighbourhood of the point of junction. 
M. Lamarle th^i shows that all these results extend to the films 
themselves, all of which, whether plane or curved, are cut by the 
plane in question ; that is to say, the minimum of the sum of 
the »reas requires that these films should meet three by three 
under eqnal angles in each liquid edge. 

My first law — namely, that in every stable system of liquid 
films more than three films never meet in the same edge, and 
that these always make equal angles with each other — is thus 
completely demonstrated, and appears as a consequence of the 
principle of the minimum. 

M» Lamarle next considers the question of liquid edges meet- 
ing at the same liquid point. In dealing with it, he supposes a 
number of plane liquid films all meeting at the same point in the 
interior of the system, and he investigates the conditions which 
these films must satisfy in order that they may meet three by 
three, forming equal angles with each other> conformably with the 
iiKregoing law. He considers the point which is common to all the 
planes as the centre of a sphere, which is therefore cut by them 
along arcs of great circles; we have thus a number of hollow 
pyramids whose summits lie in the same point, and whose bases 



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20S On the CmdiHom qfStabiliiy qf thin FUm oflAq ids. 

are sphmcal polygons having angles of 120° exclasiTely* M« 
liamarle points out in the first place that these polygons can 
only be either triangles, four«8ided figures, or pentagons, and 
hence he derives one analytical relation between the respective 
numbers of these several kinds of polygons and the total number 
of films ; a second relation he finds in the fact that the sum of 
the surfaces of all the polygons must make up the whole surCaoe 
of the sphere ; lastly, these polygons must all be in simple juxta* 
position, without encroaching upon each other in some places 
and leaving empty spaces at other places. From these three 
conditions, M. Lamarle deduces that th^re are only seven posiii- 
ble combinations of films starting from the same point, and 
joined together three by three under equal angles. 

If, in each of these combinations, the sides of the spherical 
polygons are replaced by their chords, we have the edges of a 
complete polyhedron, and the seven polyhedrons thus formed 
are, — the regular tetrahedron ; the right triangular prism with 
equilateral base, the height being in a determinate ratio to the 
length of the side of thet)ase; the cube; the right pentagonal 
prism with regular base, the height being in a determinate ratio 
to the length of the side of the base ; two peculiar polyhedrons 
made up of four-sided figures and pentagons ; and, lastly, the 
regular dodecahedron. In these polyhedrons the numbers of 
liquid edges are 4, 6, 8, 10, 12, 16, and 20 respectively. 

Now M. Lamarle proves that for each of these systems of • 
films, except that of the regular tetrahedron, it is possible to 
conceive such a mode of displacement that, firom its commence* 
ment up to a certain limit, a diminution of the sum of the areas 
of the films will result from it : the system of the regular tetra- 
hedron, in which not more than four liquid edges meet at the 
same liquid point, and make equal angles with each other, is 
therefore the only one of these which can be stable. Hence, 
when the films are plane, the liquid edges which meet at any one 
liquid point are necessarily four in number and make equal 
angles with each other. Lastly, M, Lamarle shows that the same 
conclusion applies to curved films, and, by consequence, to curved 
edges; there is, in fact, no limit to the smaUness which the 
above-mentioned sphere may be conceived to have, and henee we 
are free to conceive of it as so minute that the portions of the 
films contained within it may be regarded as plane. 

My second law — namely, that in every stable system of liquid 
films the number of liquid edges meeting in any one liquid point 
is always four, and that they make equal angles with each other 
— is thus demonstrated by M. Lamarle as completely as the first^ 
and like it, is deduced from the principle of the minimum. 
/ It may be added that the modes of displacement si^qppoaed bgr 



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On 8(meEffeeti produced by a Fhiid in Motion. 209 

M. Lamarle^ and which^ by an ingenious way of treating them^ 
he is able to refer all to the same principle are exactly those 
which lead to the real results obtained — to those^ that is^ given 
by the experiments with the skeletons of iron wire. 

To sum up, M. Lamarle has solved questions which seemed 
extremely difficult, and his investigation is an important contri- 
bution towards a complete theory of liquid films. 

XXV. On some Effects produced by a Fluid in Motion. 
By George F. Rodwell, F.C.8.* 

[With a Plate.] 
No. II. On the TVompe. 

A STREAM of water falling through a tube may, under cer- 
tain conditions, be caused to carry down air with it, which 
air^ when removed from the direct influence of the stream, is able 
in virtue of its small specific gravity compared with water, to sepa- 
rate itself therefrom, and may be collected and employed for any of 
the purposes for which a blast of air is requisite. An arrange- 
ment for producing a blast by the above means has been in use 
for the last 200 years, and is known as a trompe. 

I. 

Baptista Porta is said to have invented a machine for pro- 
ducing wind by the flow of water; but among the numerous 
hydraulic machines which he figures in his work, entitled ' I tre 
Llbri de' Spiritali' (1606), I am unable to find one which bears 
the least resemblance to a trompe ; neither, so far as I am aware, 
is the trompe mentioned in the ' Mechanica Hydraulico-Pneuma- 
tica * of Caspar Schottus, nor in the ' Mundus Subterraneus ' of 
Athanasius Kircher, although the latter was well acquainted with 
the discovery. 

Grignont states that the trompe was discovered in Italy about 
, the year 1640, but he gives no authority for the assertion. The 
earliest account of the invention which I have been able to find 
is in a work by Father Jean Pran9oi8, published in 1655 J, in 
which there is a section entitled '' Du Meslange des Eaux avec 
PAir, et d'une invention pour exciter un vent impetueux/' In 
this section Pran9ois states that it had been recently discovered 
that water is capable not only of dragging along with it terres- 
trial bodies, but also air ; and that an arrangement for supply- 

* Communicated by the Author. 

t M^moitH d$ Physique sur Vart de fabriquer le fer, d^enfondre et 
forger dies canons d'artiUerie, &c. Paris, 1775. 

f Les Seimees des Bmu^, qwi esmUque en qtuttre parties leur formation, 
eotnsn iinic af ion, fnouoetnsnSf et fse s u t nges* 



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210 ;Mr. 0. F. Rodwell on the Effects 

ing furnaces with air by this means had been invented, and was 
extensively used. Although a new invention, it was at this time 
(1655) used in Germany and Italy, and in more than a hundned 
places in Dauphiny. 

The machine described by Fran9oi8 consisted of a channel or 
trough in which water was caused to flow in a horizontal direc- 
tion ; from the bottom of the trough two vertical tubes proceeded, 
and the lower extremity of each passed into a wooden tub fur- 
nished with an outlet for water, and a tube near its upper part 
for the exit of air : within each tub, and immediately beneath 
the lower extremity of the tube which entered it, a large convex 
stone was placed in order to break the fall of the water; the 
upper extremity of each tube near its juncture with the trough 
was enlarged and of a conical form, but in some forms of the 
machine the tubes had holes pierced in their circumference for 
the purpose of giving freer access to the air. Fran9ois mentions 
that Kircher assured him that he had seen more than forty of 
these machines with tubes in an inclined position. 

In the first volume of the Philosophical Transactions (1665) 
there is a short description*, accompanied by a figure of a 
water-blowing machine used in Italy. A stream of water is 
represented flowing through a large, vertical, rectangular tube, 
midway between the top and bottom of which there is a pipe 
for conveying the blast to a furnace; but the machine is evi- 
dently wrongly figured and described, for it is impossible that a 
current of air could be produced by such an arrangement. 

In the 43rd volume of the Philosophical Transactions there is 
a paper (read March 1744-45) by a Mr. James Stirling, 
entitled " A Description of a Machine to blow fire by the fall of 
Water.^^ This machine was a modified form of that described 
by Fran9ois ; it consisted of a large funnel 5 feet high, from 
the apex of which proceeded a tube from 14 to 16 feet long; 
the lower extremity of the tube passed into a vessel 5^ feet dia- 
meter, provided with a tube for the exit of the air carried down, 
and also with an outlet for water ; four orifices were made in the 
circumference of the tube just beneath its juncture with the 
funnel. 

From the fact of this paper having been read before the Royal 
Society, it would appear that the trompe was but little known 
in England even a hundred years after its invention ; but that 
this was the case is scarcely to be wondered at when we remem- 
ber that such a machine can only be used with advantage in 

* Extract of a letter lately written from Venice by the learned Doctor 
Walter Pope, to the Reverend Diean of Rippon, Doctor John Wilkins, con- 
cerning the Mines of Mercury in FriuU; and a way of producing wind by 
a fall of water. .n <. 



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prdduced by a FltUd in Motion. 21 1 

moimtamotts countries^ where small streams of water with aeon- 
considerable fall abound. The trompe described by Mr. Stirling 
was oaed in a Scottish lead mine. 

I am not aware when the water-blowing machine was first 
called a trompe ; in neither the account given by Fran9ois, nor 
in Dr. Pope^s letter is the word employed, and nearly a hundred 
years later Mr. Stirling gives no name to the machine ; but it 
was called a trompe in France long before his paper was pub- 
Ushed. 

Qrignon* writes as follows : *' Les trompes ont tire leurs noms 
de ces m^t^res qui portent le mSme nom, et dont il y a deux 
sort-es, Pune marine et Pautre terrestre : celle qui se forme sur 
mcr est une colonne d'eau immense, enlevee par la violence du 
vent; et celle que Ton voit sur terre est formee par une tour- 
billon de vent dont le mouvement est determine par les mon- 
tagnes; ee tourbillon enveloppe un nuage, le comprime et en 
finue nne colonne compost d'air et d'eau qui se pr^cipite sar 
hsni&oe de la terre ou se brise contre un rocher.*' 
; The Italian iromia, French trombe, signifies a pump, an ele- 
phant's trunk, and a trumpet, as well as a waterspout: tbe 
Spanish irompa signifies a trumpet, an elephant's trunk, and a 
krge top. Prof. Max Miiller informs me that trompe is the old 
French form of trombe^ and that Dicr, in his 'Lexicon Etymo- 
logicum,' derives trombe in the sense of trumpet from the Latin 
tuba, the insertion of the r being warranted by the analogy of 
tronar instead of tonar. 

( Landais, in his ' Dictionnaire des Dictionnaires,' derives trombe 
in the sense of waterspout from arpofilSo^. Now arp6fi/3o^ 
means a top, a spindle, a round shell, and is derived from 
irrpi^oD, to turn, twist, revolve. I will not pretend to decide 
whether (adopting Bier's derivation) a trumpet and a waterspout 
were called by the same word on accoiint of their being tubiform, 
or whether the trumpet was so named from the fact of its being 
the first musical instrum^t with a straight tubef, and the water- 
spout afterward snamed from its trumpet-shape; or whether 
(adopting Landais's derivation, and this seems to me the most 
plausible) the waterspout was first called a trombe (from 
arpi<f>ai) ; the trumpet and elephant's trunk from their being 
shaped like a waterspout; the top from its rotatory motion; and 
the pump from the fact of water being apparently drawn up in 
it, in the same way that it is drawn up in a waterspout. 
- I conceive the water-blowing machine received the same name 
as a waterspout, either because of the mixed column of air and 
water produeed in certain forms of the machine, or, more pro- 

♦ In the' work dted above. 

t Tuba meant originally a straight tube, as opposed to comu. 



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213 Mr. O. 9. Bodwell an the SffeeU 

bably, from the whirling motion of the water around a conical 
cavity^ which, as we shall see hereafter, is produced in the trough 
of machines similar to that mentioned by Fran9ois, and in all 
machines with inclined tubes : in both these respects there is a 
resemblance to a waterspout. 

Several modifications of the trompe have been constructed 
since its first invention, the main di£ference consisting in the 
way in which air is allowed to enter the tube : thus there is 
the trompe without orifices for the admission of air, as in that de- 
scribed by Fran9ois, and in the trompe mentioned by Mariotte 
(in his Traiti du Mauvemeni des Eauaf), in which latter modifi'* 
eation a blast is produced by a stream of water falling firom a 
height of 10 or 12 feet into a funnel which communicates by 
a vertical tube with a vessel for collecting the air carried down | 
or, again, there may be orifices in the tube, as in the trompe 
described by Mr. Stiriing, and in that now used ; or air may be 
admitted by two small tapering tubes which enter the trompe 
tube just below its juncture with the water-cistern, and pass 
upwards through the water therein till they reach the air : this 
latter arrangement was much used formerly. 

The modem trompe consists of a large cistern in which there 
is a constant depth of from 4 to 6 feet of water ; from the bot* 
torn of the cistern proceed two tubes from 20 to 80 feet long, 
the lower extremities of which pass into a wooden wind-chest 
furnished with an arrangement for keeping the water at a certain 
level, so that no air can escape except by a blast pipe in th^ 
upper part of the chest : beneath the lower extremity of each tube 
there is a flat iron plate to break the fall of the descending wat»« 
The upper part of each tube is contracted at the point where it 
joins the cistern, and immediately beneath the contracted pari 
four holes are made in the circumference of the tube. When 
water is allowed to flow from the cistern into the air^chest, a 
quantity of air is carried down with it, and a perfectly regular 
and constant current of air issues from the blast pipe. 

11. 

I have endeavoured in this paper to ascertain the most favour^ 
able conditions under which air is carried down by a stream ci 
water, and to arrive at a satisfactory explanation of the cause 
of the descent of air in the different modifications of the trompe^ 

In a former paper * I have given an account of some experi« 
ments made with a view of determining the quantity of air ear- 
ned down by a known amount of water ; but as the method there 
employed was scarcely so satisfactory as could be desired, I 

* " On some Effects produced by a Fluid in Motioa/' Niif. h^ Fhilo- 
soplucsl.-M«gftiiii6 for January 1804* 



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produces by a FMd in Mgtvm. 21S 

subsequently devised the apparatus of which the following is 
a description. 

A^ Plate IIL fig. 1^ is a conical glass vessel closed above 
and below by corks; through the upper cwk passes a glass 
tube B, 24 inches long and f^ths of an inch internal diameter ; 
8 inches of B are within the vessel A, and a scale of inches is 
attached to that part of B outside A ; a tube C^ i^ths of an inch 
diameter^ communicating with the interior of A^ is bent twice at 
right angles^ and passes into a circular glass vessel D^ which 
has a scale of inches attached to it^ and is provided with a stop- 
cock £• A tube F of small diameter communicates with the 
interior of A both above and below ; a scale is attached to it, 
and by it the absolute level of water in A is shown ; through 
the lower cork of A passes a stopcock 0. H is a glass tube 
communicating with the water*cistem by means of a caoutchouc 
tube, 1 1 1 ; a similar caoutchouc tube, K K, is connected with the 
stopcock G, and the two tubes are brought together and can be 
closed or opened simultaneously by the spring clip L. A half- 
litre flask, M, collects the air which is carried down by the 
descending stream. The dotted lines a, i, c, d, e show the dif- 
ferent levels at which water was caused to remain constant in A 
during separate experiments. 

The water-cistern was about 8 feet from the apparatus, and 
the water within it was kept at a constant level of 2 feet above 
the orifice of the delivery •tube H. The caoutchouc tube. III, 
was of such diameter that it delivered half a litre of water in 16 
seconds at the height of the tube H. 

In order to prepare the apparatus for an experiment, water 
is placed in the vessels A and D to the level required in each ; 
the flow from H is determined, and the orifice of H is then 
brought on a level with that of the tube B, and so placed that 
when water is flowing, it passes exactly down the axis of B> 
The efflux from H remaining constant, the efflux from A is 
made equal to it ; this is done by keeping the eye on the scale of 
F and turning the stopcock 6 until the water-column in F 
remains perfectly immoveable at the desired level; the caout- 
chouc tubes III and K K are then brought together at one 
point, and are closed by the spring clip L ; finally, the half-litre 
flask M is filled with water, and inverted over the orifice of th^ 
tube C. A watch, suspended behind a large lens, is placed in 
such a position that the eye can observe both it and the level of 
water in D with as little difficulty as possible. Immediately 
before an experiment, the spring clip L is removed from the two 
caoutchouc tubes, and they are kept closed by the thumb and 
forefinger of the left hand so as to be capable of instant and 
aimultuieouB release; the right hand is placed on the stopcock 



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214 Mr. G. F. Bodwell an the Effeets 

"E, and the eyes are fixed on the second hand of the wateh ; at 
a certain second the caoutchouc tubes are released at L, E is 
simultaneously turned^ and the level kept constant in D^during 
the experiment ; when the half-litre flask M is full of air^ the 
caoutchouc tubes are simultaneoasly closed and the exact second 
not^d. By repeating this several times^ we determine the time 
to a part of a second required by a stream of water flowing at a 
known rate to carry down half aliti*e of air under the conditions 
of the experiment. 

It is obviously necessary that the level in A should remain 
perfectly constant during an experiment — that is to say^ that the 
influx and efflux should be equal ; for if the efflujc fix>m A be 
greater than the influx^ less than the real amount of air carried 
down will make its appearance in M ; if, on the contrary, the 
influx be greater than the efflux, more than the real amount of 
air carried down will appear in M : it is also necessary to keep 
the level in D constant, otherwise the pi^ssure on the orifice of 
C, and consequently on the air in A, will vary. It is difficult 
to cause the descending current of water to pass exactly down 
the axis of the tube B, and a vei*y slight variation from that 
position greatly diminishes the amount of air carried down ; 
when perfectly in the axis, a peculiar roughness is added to the 
roaring sound produced ; but in order to remove any possible 
source of error from this cause, the amount of air carried down 
by the stream from each delivery-tube, under certain known 
conditions, when the stream passed absolutely down the axis of 
B was determined, and before each set of experiments, the same 
conditions were made to obtain, and the delivery-tube adjusted 
until the standard amount of air, previously found to be earried 
down under those conditions, was carried down, when (the stream 
being known to be in the exact axis of B) any other conditions, 
as to pressure &c., not involving the removal of the delivery- 
tube could be made to obtain. Great care was taken that the 
whole apparatus should be perfectly vertical before each set of 
experiments, and the whole was made as immoveable as possible. 

It may be considered unnecessaiy to give these details of ex- 
periment, but I am well aware that results are often doubted 
because their author has neglected to state the exact method by 
which he obtained them. 

Before giving the results obtained by the apparatus described 
above, it will be as well to consider some facts connected with a 
water-jet. 

A jet of water moving with considerable velocity from above 
downwards is observed to widen gradually as it gets further from 
a point just below the orifice from which it issues ; and at a cer- 
tain distance from the orifice the velocity of the particles becomes 



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projiuced b^ a Fluid in Motion. 215 

ao gteaily accderated by gravity, that the cohesion of two con- 
tigaous oroas sections of the jet is destroyed, and the jet, ceasing 
to be continuoas^ breaks up into separate masses of water. We 
observe^ moreover, that when the continuity begins to be broken, 
particles of water are thrown out from the centre stream and 
move downwards in a gradually diverging line inclined at a small 
angle to the main stream. Now when such a stream passes 
downwards through a long vertical tube, the area of the cross 
section of which is not many times as great as that of the 
orifice from which the stream issues, we find that at a certain dis- 
tance from the orifice the quantity of spray thrown off from the 
stream which reaches the sides of the tube is so great that, by 
the adhesion of the water-particles to the glass, the whole stream 
is. dragged to the sides of the tube; it is not, however, dragged 
to one side of the tube, as would be the case if the jet were not 
perfectly vertical, bat it is evenly and equally spread out in a 
dome shape, and for the rest of its course fiovvs as a tube of water. 
If the lower orifice of the tube through which it flows is perfectly 
free, the water as it passes out forms a long conical bag filled 
ivith air. 

Above the point where the jet is spread out by the adhesion 
of the glass there is a good deal of spray ; and although it is 
insufficient to drag the jet to the sides of the tube, it accuDiu- 
lates ; tlie tube is thus narrowed at certain points, and disks of 
water are formed which are pushed down by the stream above 
and force down air beneath them : at the moment of the forma- 
tion of a disk the conical bag of water at the end of the tube is 
expanded laterally by the air forced into it, and bursts, deliver- 
ing up its contents ; this bursting occurs with great rapidity 
under certain conditions. 

J The pressure ou the lower orifice of the vertical tube through 
which the stream passes also tends to the formation of disks, 
because the descending masses of water will have a tendency to 
be flattened out by the air beneath them ; the greater the pres- 
sure, the higher within certain limits will disks be formed ; but 
the quantity of air forced down will be less, because the chance 
of the rupture of the disks will be increased; and when this 
occurs, the air beneath them escapes upwards between the de- 
scending stream and the sides of the tube. The formation of 
disks can only happen below a certain point, because the stream 
above that point ceases to be sufficiently broad to allow of their 
being produced ; the point varies with the nature of the stream, 
the relative dimensions of the tube and of the orifice from which 
the stream flows, and with the pressure on the lower orifice of 
the tujbe. ... 
. If a stream is very small compared with the tube through 



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318 Mr. G. F. Rodwell cm tie Bffecii 

which it paaaea, or if there is sufficient preisuie on the confioe of 
the tube to support a column of water at a height in the tube 
above. that at which the stream is sufficiently broad to allow 
disks to be formed, the stream meets the water surface in direet 
collision^ and air is then undoubtedly carried down, for the reasm^ 
proposed by Prof. Magnus*. This physicist observed that small 
solid bodies, if allowed to fall into water, produce a cavity of 
greater or less depth, into which air enters ; and the water, if the 
particles at its surface possess any motion (which they must do 
from the disturbance caused by the falling body), unites over the 
cavity and thus air is enclosed. Magnus conceives that a waters 
jet falling into water acts in a precisely similar manner, the de« 
tached masses of water forming cavities like solid bodies. We 
have a frequent example of this action of detached fluid masses : 
if we wish to pour out beer so that it shall have no froth, we 
pour it down the side of the glass, the adhesioit of wliich flat- 
tens the stream into a ribbon, and it enters the fluid in the glass 
slowly : there is no falling of detached masses here, consequently 
no air is carried down ; on the other hand, if we wish to produce 
froth, we pour out the beer from as great a height as possible, 
and the masses detached by the accelerating force of gravity 
carve out channels in the liquid, into which air enters and is car- 
ried down, and afterwards rises to the surface in bubbles. 

Bichardf states that a M. Mercadier constructed artificial 
trompes in which sand, wheat, rye, millet, salt, mercury, and lead 
shot were severally caused to fall into water in place of a descend- 
ing stream of that liquid, and a considerable blast of air was 
obtained thereby. 

The quantity of air carried down by a solid body falling into 
water is very surprising. I took small lead shot about ^^th of 
an inch diameter, and weighing *072 gramme. apiece, and threw 
them one at a time from a height of about a foot and a half 
into a vessel containing water to a depth of 6 inches ; in order 
to collect the air, a wide-mouthed vessel was filled with watei^ 
inverted, and placed with its mouth near the water-surface in the 
vessel into which the shot was thrown. By throwing in a shot 
at an angle of about 60 degrees, and as near as possible to the 
edge of the inverted vessel, the air carried down could be coUectedi 
and I thus found that the lead shot caused no less than 190 
times its own bulk of air at 18^ C. to penetrate beneath the 
water. The same shot falling by its own weight from a height 
of 4 feet into 6 inches of water appeared to carry down quite as 
much air, but in this case it is obvious the amount could not be 
determined. 

• " On the Motion of Fluids," Phil. Mag. for January 1861, p. 8. 
t Etudes iur Vart d'extravre imm^diatment U Fer de m$ Mmsrm »am$ 
wmoetiir le mital enfonte. Paris, 1838. 



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produced by a Fluid in Motion. 217 

No one who has fired a gun into water can have failed to 
observe the numberless bubbles of air which rise to the surface 
for a few seconds after the penetration of the shot. Each shot 
jsloughs for itself a channel, into which air enters^ is enclosed by 
the water, and penetrates to a greater or less depth according as 
the velocity of the shot is considerable or otherwise. 

Let us now pass on to the experiments made with the appa- 
ratus described above. 

The number of seconds required by half a litre of water to 
flow from the delivery-tube H, and the number of seconds 
required bv that water to carry down half a litre of air, being 
determined in the manner stated above, the number of cubic 
centimetres of air carried down by half a litre of water could 
obviously be readily calculated. Each of the results given below 
is the mean of several determinations — generally of ten, except 
in those cases in which four or five consecutive determinations 
gave absolutely similar results. 

Circular delivery-tube (H, fig. 1) g'^ths of an inch internal 
diameter. (The comparative dimensions of the delivery-tube 
and the vertical tube B are shown full size at A, fig. 2.) 
Flow = half a litre of water in 24 seconds. 









Quantity of air 




Quantity of air 








carried down by 




carried down 




Depth of water 
mainlMned con- 




half a litre of 




when the orifice 


Level of water m«iii- 


Order of 


water when the 


Order of 


ofthe tube deli. 


tained cooatant in A 


atant in D during 


ezperi- 


orifice of the tube 


experi- 


Taring the air 




tiie experiment. 


menta. 


delivering the air 

(c, fig. 1) 

B^ths of an 

inch in diam. 


menta. 


B^th of an 
inch in diam. 


At 2 inches below 


1 










the orifice of B 


- 1 inch. 


1. 


615 cub. cent. 


16. 


136 cub. cent. 


(«,fig. 1) 












At 1 inch below 


: 










the orifice of B 


II 


2. 


615 „ 


17. 


136 „ 


(*,%!) 












At the orifice of B 
(c,fig.l) 


II 


3. 


545 „ 


18. 


137 „ 


At 1 inch above 


•1 










the orifice of B 


• II 


4. 


201 „ 


19. 


132 „ 


(rf.fig.l) 












At 2 inches above 


' 










the orifice of B 


II 


6. 


174 „ 


20. 


182 „ 


(^fifcl) 


inches. 


6. 


153 


21. 


123 „ 


At 0, fig. 1 


ft *f »» 


II 


7. 


153 „ 


22. 


122 „ 






8. 


167 


23. 


113 >f 


II •'» i» ••••••••. 

II ^1 II •••••.••• 


II 

II 


9. 


157 „ 


24. 


•78 „ 


II ^1 II ••••••••• 




10. 


125 


25. 


171 „ 


II ^1 II ...••.... 


5 inches. 


11. 


130 „ 


26. 


171 „ 


II *i II ••••••••• 


II 
II 
II 


12. 
13. 
U. 
15. 


130 ;; 

125 „ 
U3 „ 
118 „ 


27. 

2.S. 
29. 
30. 


171 „ 
171 „ 
166 „ 
165 „ 




" d " ****!'!!! 


g * "* 





PMl. Mag. S. 4. Vol. 28. No. 188. S^t. 1864 

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218 Mr. G. F. Bodwell (m the Effects 

In the first and second experiments^ in which the resistance 
was least, we see that half a litre of water carried down 615 
cubic oentims. of air, a quantity (with one exception) more than 
three times as great as that carried down in any of the other ex- 
periments given above. The air escaped from G with perfect regu- 
larity, and the results were very constant. In experiment 8 the 
orifice of the tube B (fig. 1) was caused to touch the water- sur- 
face in the vessel A, and we find a diminution of 70 cubic cen^ 
tims. in the amount of air carried down ; on further increasing 
the resistance by causing B to dip one inch under the water- 
surface (exp. 4), the quantity of air was at once diminished t6 
201 cubic centims. ; the air-disks were now formed higher ill 
the tube, and the air escaped from C irregularly, proving that 
the disks were constantly broken, and that the air beneath them 
escaped upwards; the highest of the disks formed at IS inches 
from the orifice of H ; the results were less constant than before. 
In experiment 5 the air came over still moie irregularly ; in 
other words, the disks were more frequently broken. In the 
6th and 7th experiments we have obviously the same amount of 
resistance as in exp. 5, but the orifice of B was free. In expe- 
riment 8 we have precisely the same conditions as in exp. 5, 
and nearly the same amount of air was carried down. In expe- 
riment 5 the resistance was = 3 inches of water, for B dipped 
2 inches under water, and there was 1 inch of water in D. 
So also in experiment 8 the resistance was = 3 inches, because 
there were 3 inches of water in D, and the orifice of B touched 
the water-surface. In experiment 9 there were 4 inches of water 
resistance, and in experiment 10, 5 inches. In experiments 11 
and 12 the resistance was obviously the same as in experiment 10, 
but the orifice of B was free. In experiment 13 we have pre* 
cisely the same conditions as in the 10th experiment, and the 
same amount of air was carried down. In experiments 14 and 
15 there was still greater resistance; the highest of the disks 
formed at 13 inches from the orifice of H. 

The conditions were now somewhat changed, the resistance to 
the descent of air into A being greatly increased in consequence 
of the air having to escape from an orifice one-eighth the sise of 
that used in the first fifteen experiments. In the 16th, 17th, 
18th, and 19th experiments the resistance, as judged of from 
the effects produced in the tube, was about equal to that in the 
11th experiment. In experiment 20 the pressure was sufficient 
to keep a column of water suspended in B at an unvarying height 
of 11 inches from the orifice of H, and a persistent collision be- 
tween the descending stream and the water-surface took place 
at that height : the air escaped from C in a perfectly regular 
manner, and the results were very concordant^ not the least 



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produced by a Fluid in Motion. 



»19 



yariation in ihe quantity of air carried down being observable in 
a number of consecutive experiments* In experiments %\, 22, 
and 23 the resistance was insufficient to keep a column of water 
suspended in B^ and the disk action returned, the air escaping 
from C .very irregularly. In experiment 24 there was persistent 
collision at about 11 inches from the orifice of H^ and we get 
nearly the same result a« in experiment 20. In experiments 
25, 26, 27, and 28 the collision was persistent at 10 inches from 
the orifice of H, in experiment 29 at 9 inches, and in experi- 
ment 30 at 8 inches. We see, therefore, that in the above 30 
experiments, air was carried down by disk action in 22 (viz. expe- 
riments 1 to 19, and 21 to 23) ; and by direct collision, accord- 
ing to the theory of Magnus, in 8 (viz. experiments 20 and 24 
to 30). 

The nearer the collision approached the orifice from which the 
jet issued, the less was the quantity of air carried down ; and 
when the water in B touched the orifice of H, air only entered 
at intervals, and was seen to force its way through the water 
into the line of the descending jet. This latter effect is due to the 
diminution of pressure in the Une of a moving fluid, — an effect 
which may be shown by introducing a small mercury gauge into 
the line of a current of liquid flowing in any direction ; or in a 
more striking manner if we allow a liquid to flow from a delivery- 
tube A (fig. 3), dipping beneath the surface of water in a vessel B, 
and place in the line of the current the lower orifice of a tube, C, 
open at both ends. Air will now be found to force its way into 
the current against the pressure of the column of water D £• 

Experiments with delivery-tubes of various shapes, a constant 
depth of 1 inch of water being maintained in the vessel D. 
Orifice of the tube delivering the air (C, fig. 1) = /^yths of an 
inch diameter. The comparative dimensions of the tube B 
(fig. 1) and the delivery-tubes employed are shown in fig. 2. 

I. Circular delivery- tube y-Z^ths of an inch in diameter (B, fig. 2). 
Flow = half a litre of water in 39 seconds. 



Leyd of water maintained constant 
in A during the experiment. 


Quantity of air carried down by 
half a litre of water. 


At ] inch helow the orifice of B 

At the orifice of B (c, fig. 1). 
At 1 inch above the orifice of B 


No air was carried down. 

211 cubic centims. 
147 „ 



No air was carried down in the first experiment, because there 
was not sufficient water in the stream to allow of the formation 

Q2 



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220 Mr. 6. F. Rodwell on the Effects 

of a conical bag at the bottom of the tube B, and the air oonse-* 
quently escaped upwards between the sides of the tube and the 
descending stream ; but immediately the orifice of B touched the 
water- surface^ B was virtually closed, and the air being unable 
to escape upwards was carried over into M. 

11. Rectangular delivery-tube /^ths by^^^thsof an inch (G^fig.2)» 
Flow = half a litre of water in 16 seconds. 



Level of water maintained constant 
in A during the experiment. 


Quantity of air carried down by 
lialf a litre of water. 


At 4, fig. 1. 
tt c, „ 
tt ^t tt 


615 cubic centims. 
500 „ „ 
246 „ „ 



III. Rectangular delivery-tube ^th by f^th of an inch (D, fig. 2). 
Flow = half a litre of water in 31*5 seconds. 



Level of water maintained constant 
in A during the experiment. 


Quantity of air carried down by 
half a litre of water. 


At b, fig. 1. 

n ^f tt 
i» ^t tt 


No air carried down. 
298 <mbic centims. 
140 „ 



IV. Square delivery-tube rs^xi^h^ ^^ *" ^^^^ ^^ ^^^ ^^^^ (E, fig. 2). 
Flow as half a litre of water in 16*25 seconds. 



Level of water maintained constant 
in A during the experiment. 


Quantity of air carried down by 
half a litre of water. 


At^fig. 1. 
i» ^f tt 
tt d, f, 


677 cubic centims. 



y. Triangular delivery -tube ith of an inch in the side (F, fig. 2). 
Flow = half a litre of water in 16*5 seconds. 



Level of water maintained constant 
in A during the experiment. 


Quantity of air carried down by 
half a litre of water. 


At b, fig. 1. 

tt c, y, 
tt d, „ 


733 cubic centims. 

*^* M tt 



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produced by a Fluid in Motion* 221 

III. 

When a fluid is flowing from, an orifice in the bottom of a 
vessel^ it sinks steadily until within a sbort distance of the bot- 
tom^ when the particles of water immediately over the orifice 
begin to move circularly around a centre, and a conical cavity is 
formed extending from the water-surface to a greater or less 
depth into the issuing stream. This cavity/ according to M. 
Laroque*, begins to be formed ^'quand la vitesse angulaire est 
devenue suffisamment grande pour que la force centrifuge qu'elle 
engendre puisse vaincre la pression hydrostatiique et la cohesion 
du liquide/' 

If water possesses rotatory motion at the time of its efflux 
from the bottom of a vessel, the conical cavity is formed much 
sooner than it otherwise would be, and extends to a far greater 
depth into the liquid. 

A stream of water entering water at right angles to its surface 
does not produce rotation ; but if it enters at an angle differing 
ever so little from a right angle, rotation in the direction in which 
the stream flows is at once communicated to the water into which 
it flows. 

A discharge-tube 2 inches long by i^th of an inch diameter 
was fitted into the bottom of a cylindrical vessel 10 inches high 
by 4| inches diameter ; water was placed in the vessel until it 
stood at a height of 9 inches from the upper orifice of the dis- 
charge-tube ; it was allowed to come to perfect rest, and the 
orifice was then opened : the water sank steadily till within ^th 
of an inch of the bottom, when a cavity formed over the orifice. 

The same experiment was repeated; but before the commence- 
ment of efflux, rotatory motion was given to the water in the 
vessel ; when efflux commenced, the conical cavity formed at 8 
inches from the orifice of the discharge-tube and extended into 
the issuing jet. When a discharge-tube of double diameter was 
substituted, the cavity appeared at half an inch from the orifice of 
the discharge- tube wnen the water was perfectly at rest prior to 
efflux. When rotatory motion was given to the water, the cavity 
appeared at 8 inches from the orifice and extended into the 
issuing stream ; air entered through the cavity and expanded 
the water as it issued from the vessel into an ellipsoid 3 inches in 
its longer diameter by 1 inch in its shorter. The rate of efflux 
was three times as slow as when no rotatory motion was given 
to the water. 

If when the conical cavity has extended to some distance into 
the issuing stream the latter is caused to enter water, the air 
which enters through the cavity is seen to penetrate but a very 

♦ Ann, de Ckim, et de Phys, March 1864, "Recherches Hydrauliques.'* 

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222 Mr. O. F. Rodwell on the Effects 

short distance into the water; but if we make such an arrange- 
ment that we have a vessel perpetually emptying itself by a long 
tube^ air enters by the conical cavity^ is detached from the apex 
of the cone^ and passes down the tube with the descending water. 

In order to determine the amount of air carried down by this 
means, I fitted a small funnel N, fig. 1, into the upper orifice of 
the tube B, and placed the delivery-tube H in such a position 
that the water which it delivered impinged against the side of 
the funnel. This being the case, a hollow cone of water possess- 
ing rapid rotatory motion was formed in the funnel, and air 
entered through its centre : the air and water on issuing from 
the funnel formed alternate disks in the tube B, and these rapidly 
descended into the vessel A. A mercury gauge communicating 
with the interior of A showed that the pressure remained per- 
fectly constant, and precisely the same amount of air came over 
during a number of successive experiments. 

The amount of air carried down was very large : when the 
circular delivery-tube ^^ths of an inch diameter (used in some 
of the previous experiments) was employed, no less than 1200 
cubic centims. of air were carried down by half a litre of water, 
the water-surface in A being 1 inch below the orifice of B (viz. 
at b, fig. 1). The flow from the delivery-tube was = half aUtre 
of water in 24 seconds. 

With the smaller circular delivery-tube, y^^^^^ ^^ ^^ ^^^ 
diameter, and delivering half a litre of water in 39 seconds, 1892 
cubic centims. of air were carried down by half a litre of water ; 
the water-surface in A being, as before, 1 inch below the orifice 
of B. Stated in other words, a little stream of water, about 
^th of an inch in diameter at the orifice from which it issues, 
with a head of water of 2 feet, carries down in one hour 128 
litres of air. By this method we see, therefore, that 1 part of 
water carries down more than 2| times its own bulk of air — 
the largest quantity which I have found under any circumstances 
to be carried down by water. 

The mouth of the funnel N was covered air-tight with a thick 
sheet of caoutchouc, and a small vibrating tongue, such as is used 
in Wheatstone's concertinas, was fitted into the caoutchouc ; the 
delivery-tube was then passed through the cover, and so placed 
that it delivered water, as before, against the side of the funnel : 
when water flowed, the tongue was readily vibrated by the enter- 
ing air. A second tongue was now added, and it was found that 
the flow from the delivery-tube might be diminished from half 
a litre of water in 24 seconds to the same quantity in 40 seconds, 
and yet the tongues were readily vibrated. 

A musical instrument might thus be constructed in which the 
air cottld be twice used before leaving the instrumeat; for the 



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produced by a Fluid in Motion. 228 

air rushing in to penetrate through the conical cavity, and that 
same air after having been carried down by the water and col- 
lected, might be employed separately to produce vibrations in 
vibrant bodies according to any of the usual methods. 

IV. 

There is one other way in which water passing through a tube 
may carry down air. 

Suppose a continuous vertical tube with water flowing through 
it. If now the water is caused to cease flowing, it will remain 
suspended in the tube by atmospheric pressure ; and such would 
of course be the case with any tube under 83 feet in length ; but 
let an orifice be made anywhere in the circumference of the tube, 
and the whole column beneath that orifice will instantly fall, 
because it has no longer the weight of the atmosphere on its 
lower end alone, but also at the orifice ; the influence of the 
atmosphere is consequently annulled below the orifice, and the 
eolumn falls by its own weight. 

If v^rater be flowing through such a tube, the column below 
the orifice will have greater velocity than that above it ; hence 
ruptute of the column will ensue at the orifice, and air will enter ; 
but as water is continually flowing, the orifice is quickly closed, 
and we thus obtain an intermittent entry of air. 

In order to see how much air might be carried down by this 
means, a short glass tube 0, fig. 1, ^^ths of an inch diameter. 
Was fitted into the upper orifice of the tube B by means of a 
cork ; a piece of caoutchouc tubing, P, was adapted to the tube 
0, and a circular delivery-tube H, ^ths of an inch diameter, 
was connected with the upper part of the caoutchouc tube. H 
delivered half a litre of water in 24 seconds. An orifice ^th 
of an inch diameter was made in the circumference of the caout- 
chouc tube midway between the orifices of H and O ; thus a 
perfectly continuous tube, with the exception of an orifice ^th 
of an inch diameter, intervened between the water-cistern and 
the vessel A. 

Matters being thus arranged, water was allowed to flow from 
H, and it was found that half a litre of water carried down 218 
cubic centims. of air. 

When a caoutchouc tube with four orifices in its circum- 
ference was substituted for that with one orifice, half a litre of 
water carried down 820 cubic centims. of air : in both instances 
the water-surface in A was 1 inch below the orifice of J3 (vix. at 
», fig. 1). 

V. 

We Me from the above that there are four modes by which 

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324 On the Effects produced by a Fluid in Motion. 

air can be carried down by a stream of water falling through 
a tube. 

1. If the area of the cross section of the tnbe through which 
the water falls be not much greater than that of the orifice from 
which the water flows, disks will be formed in the tube, and, 
being pushed down by the descending stream, will force down 
the air beneath them. 

2. If the area of the cross section of the tube through which 
the water falls be much greater than that of the orifice from 
which the water flows, so that disk action is prevented, or if the 
pressure on the lower end of the tube be competent to support a 
column of water in the tube at such a distance from the orifice 
from which the water flows that the descending stream has not 
widened sufficiently to allow of the formation of disks, air will 
be carried beneath the water-surface on account of the formation 
of cavities, according to the theory of Magnus. 

3. If there is not a great depth of water in the vessel which 
supplies the descending stream, or if (the depth not of necessity 
being small) rotatory motion is from any cause imparted to the 
water, air will enter through a cavity formed above the orifice 
from which the descending stream issues, and extending into the 
descending stream. 

4. If the area of the cross section of the orifice fmm which 
the water flows be as great, or nearly as great, as that of the 
tube through which the water falls, and if at the same time the 
orifices for the admission of air do not exceed a certain area 
compared with that of the orifice from which the water flows, 
air will enter at the rupture of the stream, produced at the 
orifices by the accelerated motion of the water below those 
orifices. 

The cause of the descent of air in the different modifications 
of the trompe is not due to any one action of a stream of water ; 
air is carried down by all four of the modes of action mentioned 
above. 

Generally only one mode obtains in one form of the machine ; 
but there may be two modes acting simultaneously, the parti- 
cular mode or modes being determined («) by the relation of the 
area of the cross section of the trompe-tube to that of the orifice 
from which the stream flows ; {b) by the head of water above 
the orifice from which the stream flows ; {c) by the fact of whether 
there are causes w hich induce rotatory motion in the water before 
it leaves the cistern ; {d) by the form of the orifice from which 
the streain fiows; {e) by the manner in which air is allowed 
access to the interior of the tube ; and lastly, (/) by the amount 
of pressure on the lower orifice of the tube. 

The first and fourth modes least seldom obtain ; the second 



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On the actum of Marsh and Olefiant Gases on Metallic Oxides. 225 

' obfcains in the generality of modem trompes ; and the third 
obtains in the trompe described by rran9ois, in trompes with 
very shallow cisterns, in trompes in which the water before 
leaving the cistern receives rotatory motion, either by the stream 
which supplies the cistern entering at im angle to the water- 
surface, or by some other cause, and in all trompes with in- 
clined tubes (of which, as stated above, Kircher had seen forty 
prior to the year 1655). 

I consider the most economical, and in every way the most 
efficient form of trompe to be the old form, in which there are 
no air-holes, and the air enters by a conical cavity in the water 
above the orifice from which the descending stream issues. It 
will be seen from the above experiments that by this method we 
obtain nearly double the amount ^f air obtainable by other 
means. The construction of such a trompe, moreover, is com- 
paratively easy; there is no need to have the tubes perfectly 
vertical, and less spray is carried into the furnace than by the 
form of trompe now in use. 

20 Great Marlborough Street, London, 
July 28, 1864. 



XXVI. Chemical Notices from Foreign Journals. 
By E. Atkinson, Ph.D., F.C.S. 
[Continued from vol. xxvii. p. 506.] 

MULLER* has investigated the action of marsh-gas on several 
metallic oxides at high temperatures. The marsh-gas was 
prepared by heating in a charcoal fire a mixture of acetate of soda^ 
potash, and lime in a coated retort, by which almost the theore- 
tical quantity of gas was obtained. 

Pure sesquioxide of iron, Fe* 0^ heated in a hard glass tube 
in a stream of the gas, soon became black, while a large quantity 
of water was formed. Subsequent investigation and quantita- 
tive analysis of the altered substance showed that it was proto- 
sesquioxide of iron, Fe® 0*. When sesquioxide of iron placed in 
a porcelain tube, through which passed a current of marsh-gas, 
was heated in a charcoal fire, protosesquioxide was obtained, which 
contained, however, a larger quantity of protoxide. 

Protosesquioxide of manganese was easily attacked by the 
gas and reduced to protoxide of manganese. 

The oxide of cobalt, Co^ 0^, by heating in a current of marsh- 
gas, was reduced to metallic cobalt with formation of water. 
Oxide of copper was likewise reduced to metallic copper, while 
oxide of tin and oxide of zinc remained unchanged. 

* Poggendorff's Annalen, May 1864. 

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226 Branner an the Action of Hydrogen on Metallic Solutions. 

Peroxide of lead, even when gently heated in a current of the * 
gas, was reduced with explosive violence to protoxide of lead. 
Oxide of bismuth was slowly, but at last completely reduced to 
the metallic state. 

The result of these experiments showed that the action of the 
gas was in all cases reducing ; in no case could any carbon be 
detected in the substances formed. And they further show that 
at a red heat the affinity of metals for carbon is inconsiderable. 
The author also subjected the above metallic oxides to the 
action of olefiant gas. When sesquioxide of iron was heated in 
this gas, at first a formation of water ensued, which gradually 
became smaller. The decrease in weight, as ascertained by seve« 
ral successive weighings, never amounted to 30 per cent., which 
would have been required by a reduction of the sesquioxide to 
metallic iron. The maximum decrease was about 20 per cent. ; 
while there was subsequently an increase of weight. Hence 
something more than reduction had taken place : either some 
oxygen was left with the iron, or for a portion of the disen- 
gaged oxygen some carbon had been substituted. That this 
latter was the case, was proved by subsequently heating the 
residue in hydrogen, when neither was any water formed nor 
was there any change in weight. When the black residue was 
treated with hydrochloric acid it dissolved with effervescence, 
and at the same time the characteristic odour perceived in the 
solution of cast iron was observed, while carbon was set free. 
Hence part of the carbon was combined and part in a state of 
mixture ; and the amount of the former appeared to be more 
considerable than the quantity present in cast iron. The author 
is of opinion that a partial reduction of the sesquioxide first 
takes place, and that then this lower oxide, losing some further 
oxygen, takes up carbon at the same time. 

Protosesquioxide of manganese is at first reduced to greenish 
protoxide, which afterwards increases in weight, doubtless owing 
to the separation of carbon. Oxide of copper, heated in a cur- 
rent of gas, is at first reduced to metallic copper ; and when this 
is complete, a separation of carbon takes place. 

Brunner* has examined the action of hydrogen on the solu- 
tions of certain metallic salts. When pure hydrogen was passed 
through moderately strong neutral solution of nitrate of sUvcr it 
became turbid, and on continuing the action for several hours a 
slight grey precipitate was formed, which under the microscope 
was seen to consist of metallic silver. But the quantity was very 
small, and did not seem to increase even with several weeks' 
action. 

* Poggandorff't Amuden, May 1864« 



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M. Kronig an the Theory of the Davy Lamp. 227 

' When hydrogen was passed through a nputral solution of 
bichloride of platinum it soon became turbid^ and partly a black 
pulverulent and partly a metallic lustrous precipitate was formed. 
At the same time the solution became clearer, and was finally 
free from platinum. On this deportment Brunner bases a method 
for separating platinum from its solutions, the details of which he 
describes ; and he indicates the possibility of a technical appli- 
cation of this method for separating platinum from its ores. 

Palladium is as readily reduced from its solutions as platinum ; 
while the reduction of chloride of iridium is quite insignificant, 
and chloride of gold' is unchanged. The same is the case with 
solutions of chloride of mercury if the hydrogen is under the 
ordinary pressure. But Brunner found, as Beketoff had also 
done,, that under a pressure of 100 atmospheres this substance 
is reduced and mercury deposited in distinct globules. 

Davy referred the action of his safety-lamp to the cooUng 
action of the wire gauze. Dissatisfied with the inadequacy of 
this, Kronig proposes* the following: — 
. ^^ Although experiment shows that a wire gauze can cool the 

Steous products of combustion present in a flame to a point 
ow the temperature at which they ignite, the question arises, 
on what does this action depend. Several things are possible. 
A cold wire gauze introduced into the flame can take away heat. 
But the cooling thus produced is less the higher the tempera- 
ture of the gauze rises ; and a continuous cooling of the flame 
by the wire gauze is only possible when the wire gauze loses on 
the outside the heat it receives from the flame. Such a loss can 
occur either by conduction or by radiation. If the flame is small, 
heat may be conducted from the middle parts of the heated wire 
gauze ; but this conduction must be less the greater the flame. 
Hence it is probable that the wire gauze loses heat more by 
radiation than by conduction. 

"The assumption that metal gauze radiates more heat than the 
gaseous flame is a matter of course, for we know that ignited 
solid bodies radiate more light than gaseous bodies at the same 
temperature.'' 

T^is opinion, says Kronig, has become a certainty since the 
publication of Magnus's interesting eicperiments in his paper 
" On the Constitution of the Sun^t- For not only does he show 
that the introduction of a disk of platinum into a non-luminous 
gas-flame causes it to radiate more heat, but also that this radia- 
tion experiences a further increase when the platinum is soaked in 
carbonate of soda. This observation appears completely to ex- 

• Poggendorff '8 Annaien, May 1864. 
t Plm.lfag. S. 4. vol. zxvii.p.d76. 



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228 M. Bachner on the Purification of Sulphuric Add. 

plain the statemeot of Graham*^ that the wire gauze of the safety 
lamp soaked with solution of alkali becomes mudi more rmper* 
vious to the flame. 

Buchner nine years ago gave a method for freeing sulphuric 
acid from arsenic^ which was based on the ready conversion of 
arsenious acid into the more volatile chloride of arsenic by means 
of hydrochloric acid^ and which simply consisted in passing a 
current of HCl through heated sulphuric acid. Bussy and 
Buignet^ and, independently of them, Bloxamf^ found that sul- 
phuric acid could not be purified in this way from arsenic. On 
going into the experiments of Bussy and Buignet, Buchner found 
the cause to be that the arsenic was present as arsenic, and not as 
arsenious acid. Now arsenic acid in solution is but imperfectly 
converted into chloride of arsenic. Souchay, under Freseuius's 
direction, has recently found that from a boiling mixture of 
arsenic and hydrochloric acids very little arsenic is volatilized ; 
and indeed it is on this fact that Fresenius and Babo's method 
for removing, by means of chlorate of potash and hydrochloric 
acid, organic matters from solutions containing arsenic is based. 

Buchner :[ accordingly proposes, as a modification of his method^ 
to convert any arsenic acid which may be present first into arse- 
nious acid. This is best effected by heating the acid to be 
purified with a few pieces of charcoal ; sulphurous acid is libe- 
rated, which in a few minutes reduces the arsenic acid so com- 
pletely to arsenious acid that every trace may be subsequently 
removed by passing a current of hydrochloric acid through. 

Delafontaine§ has determined the atomic weight of thorium^ 
and communicated some considerations on the formula of thoria. 
Berzelius, in 1829, had found a series of numbers for the atomic 
weight of thorium agreeing but imperfectly with each other, and 
the mean of which (calculated according to the modem atomic 
weights for sulphur, barium, and potassium ; for Berzelius^s de- 
termination was made with the sulphate of thoria and potash) is 
59*38. Delafontaine used for the preparation of thoria the 
minerals thorite and orangite ; and the method he used is that 
employed by Marignac for the treatment of cerite. The pow- 
dered mineral was moistened with water and made into a semifluid 
paste with sulphuric acid, by which so much heat was produced 
as to expel most of the excess of sulphuric acid. The residual 
mass was heated until all acid was driven off. The residue was then 
dissolved in cold water and filtered. The solution was^ next con- 

* Poggendorff 's AnnaUny vol. zxxvii. p. 367. 

t Journal of the Chemical Society, vol. xv. p. 52. 

X Liebig's Annalen, May 1864. 

§ Archives des ^Sciences Physiques et NutureUes, vol. xviii. p. 343. 



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M. Ddalbntaine on Thorium and its Oxide* 229 

oentrated and heated in the water-bath to 100^, by which a sul- 
phate of thona little soluble in hot water was deposited. This 
operation was repeated several times^ and the precipitate was 
Qonsidered to be pure when, on heating, it left a perfectly white 
residue. The mother-liquor from all these crystallizaticms, ou 
the addition of sulphate of potash, yielded the thoria in them in 
the form of double salt. 

The sulphate of thoria thus obtained is heavy, white, and 
caseous ; it consists of a large number of very small interlaced 
needles, which gave to it a porcelain-like appearance. In no 
case could distinct crystals be seen ; but when ou thi$ salt was 
poured a quantity of water insufficient for its solution, it became 
converted into clear colourless crystals in the form of 6 to 8-sided 
prisms with pointed ends. 

These two compounds differ in the quantity of water they 
contain. The water in them was determined by heating them 
from 400° to 450°, and the thoria by heating the salt to redness 
until the weight remained constant. To determine the sulphuric 
acid, the thoria was first precipitated as oxalate, and in the 
filtrate the sulphuric acid was precipitated by chloride of barium, 
hydrochloric acid having been previously added. 

The results of Delafontaine^s analysis show that if thoria is to 
be considered as a base, ThO, the salts must have respectively 
the improbable formula 4R0 SO^+QAq and 2 ThO S0«+9Aq. 
But some time ago* Nordenskiold and Chydenius showed that 
crystallized thoria prepared in the dry way had the same form 
and angles as stannic and titanic acids. This, then, seems to show 
that thoria, like zirconia, which it so much resembles, consists of 
one atom of metal and two of oxygen ; if, then, this is the case, 
the above salts have the formulae 

2Th02S0^+9Aq 
and 

Th02S08 + 9Aq. 

The objection that the water in the first salt is expressed by a 
fraction, it shares with the sulphates of uranium, cadmium, 
yttrium, and didymium. The atomic weight of thorium is then 
231-5. 

St.-Claire Deville and Troostf have made the following expe- 
riment, which shows that iron is permeable to hydrogen gas at 
a high temperature. A tube of cast steel was taken containing 
so little carbon that it could not be hardened, and so soft that it 
could be drawn out in the cold to a tube of 3 to 4 millimetres in 

* Phil. Mag. vol. xx. p. 375. 

t Comptes Rendus, vol Ivii. p. 966. Liebig's Annalen, May 1864. 

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280 M. Detrille on DiffutUm tkrwgh Iran Tubei. 

diameter. To the ends of this tube^ which wu thus eonstraeted 
without soldering, two thinner copper tubes were soldered^ and 
in these glass tubes were cemented. The whole tube was placed 
in a porcelain tube in a furnace, and one of the ends connected 
with a hydrogen-apparatus^ while the other was provided with a 
long vertical delivery-tube which dipped under mercury. While 
the tube was kept at a very high temperature, hydrogen was 
passed through until its action on the sides of the tube must 
have been terminated and all atmospheric air and moisture com-< 
pletely expelled. When now the hydrogen-tube was sealed^ the 
mercury rapidly ascended in the vertical tube at the rate of 3 to 
4 centimetres in a minute, and more rapidly according as the 
heat of the furnace was increased. Hence in the interior of the 
apparatus an almost vacuous space was formed in consequence 
of hydrogen passing through the tube in opposition to the ex- 
ternal atmospheric pressure. 

Deville has continued* on these thick tubes of iron the expe- 
riments which, in conjunction with Troostf, he had previously 
made on porous earthen tubes, and has .arrived at some unex- 
pected results. 

To the two ends of an iron tube about 3 miliims. in thickness 
were soldered two very fine copper tubes, by which it communi- 
cated on the one hand with a source of nitrogen, and on the 
other with a manometer. Two good stopcocks (immersed for 
safety^s sake in cold water) were cemented to the ends of these 
copper tubes ; by one of them a current of nitrogen could be 
introduced or stopped «t will, and by the other, which was a 
three-way stopcock, the interior of the tube could be connected 
either with a manometer or with a mercury or a water pneu- 
matic trough to collect the gases and analyze them. 

The iron tube was introduced into an impermeable porcelain 
tube very slightly longer than itself. This was closed at each 
end by a cork perforated so as to permit the copper tube to pass, 
and at each end a glass tube was fitted so as to allow a current 
of any gas to cuter the annular space between the porcelain 
and the iron tube. The middle of this apparatus was fastened 
firmly in a furnace fed by gas-coke, and by a ventilator which 
renders the operator entirely master of variations in the tempe- 
rature. 

In this manner there could be introduced into the iron tube, 
and into the annular space which surrounds it, two separate 
currents of gas isolated by a metallic disphragm several miHime* 
tres in thickness. 

At first pure nitrogen was passed into the iron tube and into 

* Comptes Rendus, July 18, 1864. f Phil. Mag. vol. xzii. p. 61. 

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M. Deville.ofi Dtjfitfton throuffh Iran Tube$. 281 

the annular space ; heat was applied^ and kept pretty constant. 
This is indicated by the manometer^ which ought not to vary 
appreciably when the stopcock, by which the nitrogen enters the 
iron tube^ is closed. At this moment (the nitrogen-stopcock 
being closed) a current of hydrogen was passed into the annular 
space. It was thus seen that, in proportion as hydrogen displaced 
nitrogen in the annular space^ the mercury ascended in the 
manometer and attained such a level as to indicate that the 
internal pressure had been more than doubled. This is pur6 
hydrogen^ which^ penetrating the sides of the iron tube, adds its 
pressure to that of the nitrogen, which does not escape in any 
appreciable quantity. 

After some. hours the pressure attains a maximum; the pres- 
sure could be calculated from the height of the mercury in the 
manometer; the three-way stopcock was then worked so as to 
allow the gas in the interior of the tube to be collected and ana- 
lyzed. Thus there were all the elements for obtaining the pressure 
of each gas in the inside of the iron tube. Throughout the ex- 
periments a constant current of hydrogen traversed the annular 
space. 

After this first experiment, one or more may be made by 
placing in its original position the three-way cock, which simply 
places the iron tube in communication with the manometer (the 
nitrogen stopcock is not touched, and thus new quantities of gas 
are not introduced). This second heating gives rise to a new 
maximum pressure, less, however, than the first. And in the 
same way a third and fc^rth experiment may be made. 

M. Deville then gives a tabular statement of his results, from 
which he draws the following conclusions. 

''Hydrogen passing into the annular space at the atmospheric 
pressure tends to enter the iron tube by traversing its pores. 
(1) At a temperature but little elevated, hydrogen has both in- 
side and outside the iron tube exactly the same pressure (that of 
the atmosphere) as if there were no nitrogen in the interior. 
Hence the law of the diffusion of gases, whether into liquid or into 
gases themselves, is verified. (2) If the temperature is very high, 
the pressure of hydrogen in the iron tube is much higher than 
the pressure in the exterior. These results are in complete 
contradiction with all facts known regarding the diffusion of 
gases. 

'* The only two circumstances which might serve for their ex- 
planation are as follows : — 

" 1 . In the inside of the tube a mixture of nitrogen and hydro- 
gen acts like a homogeneous substance, drawing to itself pure 
hydrogen from the outside as if part of the physical properties 
of the hydrogen were destroyed by the presence of the nitrogen. 



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282 M. Debray an tame CryiUJUzed PhosphaUs and Aneniaiei. 

Bat in the present state of science it would be difficult to admit 
this explanation. 

'^ 2. In the inside the gases are at rest ; outside, hydrogen is in 
motion. If it were to this difference alone that the phenomenon 
had to be attributedi I might draw important conclusions in 
support of the mechanical theory of heat, of the new ideas on 
the constitution of gases^ and of the hypothesis of Mr. Graham. 
But before this I desire to examine carefully the conditions of 
the experiment, which might have escaped me, and discuss them 
again in all their parts.^' 

M. Debray has made a communication on the production of 
some crystallized phosphates and arseniates*. The phosphates 
and arseniatcs obtained by precipitating metallic solutions by 
soluble phosphates are gelatinous, or at least amorphous ; but 
the precipitates formed in solutions of magnesia or cobalt by 
phosphate of ammonia are rapidly transformed into small crystals 
of definite composition. Debray finds now that this transforma- 
tion of phosphates is more general than had been supposed, and 
that there are few which do not finally pass, under favourable 
circumstances^ from the amorphous state into that of well- 
defined crystals. He explains this as follows.- The amorphous 
precipitates produced by soluble phosphates and metallic solu- 
tions are not quite insoluble in the saline, acid, or alkaline liquors 
in which they are formed. Hence if by any diminution of tem- 
perature their solubility diminishes, a portion crystallizes either 
on the sides of the glass or on the aEiorphous substance; an 
increase, on the contraiy, dissolves a part of the amorphous sub- 
stance, which is more readily soluble than the crystals ; so that 
by a series of changes in the solvent power of the liquid, as 
feeble as may be desired, but continuous, the amorphous sub- 
stance ought to be entirely changed into crystals. 

This transport of matter from the amorphous to the crystal- 
line state is analogous to the phenomena discovered by M. 
Devillet, in which amorphous oxides were converted into crystal- 
line oxides under the influence of a current of hydrochloric acid. 
Here the acid acting on the amorphous oxide gives a chloride and 
water, between which the inverse action takes place. But the 
oxide thus formed is crystalline, and much more difficult of 
attack than the amorphous, which is thus acted upon until it is 
entirely changed. 

M. Debray describes the production of a series of oxides be- 
longing to the magnesian group. At the ordinary temperature 
he obtains with an excess of phosphate, in two or three days, 

* Comptes Rendus, July 4, 1864. 
t Phil. Mag. vol. xxii. p. 515. 



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. Mic^D^bray on 8<me Crystallized PhosphaieB and Araeniaies. 283 

•and often sooner^ the following new salts in well-defined crys* 
tals : — . 

Phosphate of ammonia and nickel . 2NiO,NH*0,PO* + 12HO 
Phosphate of ammonia and zinc . • 2ZnO,NH*0,PO^+12HO 
Phosphateofammoniaaridmanganese 2MnO,NH*0,PO^+ 2H0 
Phosphate of ammonia and iion . . 2FeO,NH40,PO*+ 2H0 

At a temperature of about 80^ G. ammoniacal double salts are 
obtained with magnesia^ cobalt, nickel, manganese, and iron in 
nacreous crystals, which have the general formula 

2R0,NH40,P0s+2H0. 
Zinc forms an exception ; it produces an anhydrous phosphate. 
Chancel's phosphate of ammonia and cobalt, 
2CoO, NH^O, POH 12H0, 
when left in contact with a concentrated acid solution of phos- 
phate of ammonia for seven or eight days, is transformed into 
tolerably large rose-coloured crystals of a phosphate which is also 
insoluble, and which has the composition 

CoO,NH40, H0,P0H4H0. 

Phosphate of iron undergoes a similar change. 

In very acid liquids no precipitates are formed, but beautiful 
crystals are obtained on spontaneous evaporation. 

With phosphate of ammonia and magnesian salts in excess 
no ammoniacal phosphates are obtained, and the products vary 
with the temperature. Thus the salts of magnesia and of manga- 
nese give phosphates in the form of fine rhomboidal octahedra, of 
the following composition : 

2MnO,HO,POH6HO and2MgO,HO,PO*+6HO. 

At 100° C, manganese gives a tribasic phosphate, 
3MnO,P05+3HO, 

which has the form of Hureaulite, and may be considered as a 

variety of this mineral free from iron. 
Arseniate of ammonia gave precipitates which could not be 

transformed at the ordinary temperature ; but kept for several 

days at 100°, well-defined crystals were obtained. Those of zinc 

and of manganese are as follows : — 

2MnO, HO, AsO^+2HO ; 2ZnO; HO, AsOH2HO. 

With phosphate of soda in excess and salts of the magnesian 

group the products vary with the nature of the salt employed. 

The following are the principal ones obtained ;— 

' Phosphate of magnesia . . 2MgO, HO, P0« + 14H0 
Phosphate of zinc .' . . . 3ZnO,POS+4HO 
Phosphate of iron . . .. . 3FeO,PO^ + BHO 

Phil. Mag. S. 4. Vol. 28. No. 188. Sept. 1864. R 



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284 Damoiir on the Density and Refractive Index of same 2Srcons» 

The latter is Vhrianiie in small crystals quite like those of Com- 
mentry. It has never before been artificially prepared. 

Phosphate of nickel and soda, 2NiO, NaO, P0^+ 14H0 
Phosphate of cobalt and soda, SCoO, PO«-h2NaO, HO, PO* 

+ 8H0. 
The latter is in small crystals t>f a magnificent blue colour. 

M. Damour* has communicated a note on the density of 
zircon. In the course of his researches on the density of mineraU, 
he had been led to observe the great variations in the density of 
zircon, which oscillates between 4*04 and 4'67 ; and he set him- 
self to ascertain whether this arose from a difference in composi- 
tion, or was due to a special molecular state. He analyzed a 
specimen from Ceylon, of the specific gravity 4*183, and found 
that the analytical results corresponded with the formula of sir- 
con, ZrO^ SiO^. Results very closely agreeing with these were 
obtained by Berzelius for a zircon of Epailly which had the spe- 
cific gravity 4*667. 

The difference did not arise therefore from chemical composi- 
tion. Damour accordingly endeavoured to modify the molecular 
state. A zircon from Ceylon, whose density was 4*183, was 
heated to dull redness, without, however, producing any loss of 
weight or alteration in density. But heated to an incipient 
white heat its density rose to 4'534, there being little or no loss. 
The same experiment, repeated five times on different specimens, 
gave always the same result — an increase of ^^ to ^ in the 
density. 

A temperature of white redness produced by a turpentine 
flame fed by air is inadequate to melt zircon. By the oxyhydrogen 
blowpipe, however, the surface becomes fused and covered with 
a thin layer of white enamel. 

Damour compared the refractive indices of the specimens dif- 
fering in their density. Senarmont had found for a specimen 
from Ceylon, whose density was 4*636, the numbers 

For the ordinary ray . »= 1*921 ^ , 
For the extraordinary ray €=1*97/ ^^^ ^^ ^^' 

And Damour found for another specimen from Ceylon, whidi 
had the density 4*210, the numbers 

For the ordinary ray . «=! 1*851 - , 
For the extraordinary ray €= 1*86 J ^^^ ^^ "^y** 
Hence the refractive index increases with the density. 

It is doubtless to the allotropic state of zirconia that these 
different physical properties of zircon are due. Zirconia, aa ob<> 

* Comptes Rendus, January I8« 1864. 



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Royal Sockfy. 285 

tained in the form of hydrate, exhibits a brisk incandescesnee 
when exposed to a temperature of dull redness, and its physical 
properties are found to be greatly modified. Denoting these 
two conditions of the earth by Zr(fl) and Zr(i), it is easy to 
suppose that their mixture in varying proportions will produce 
numerous variations in the physical characters of the compound 
of which this substance forms part. 

. The author gives, finally, a list of the densities of a number of 
nroons. 

Lemoine* has found that when sulphur is combined with red 
phosphorus in excess, a new sulphide of phosphorus, P' S^ is 
obtained. When 1 equivalent of sulphur is mixed with 1 of 
red phosphorus and the mixture heated to 100% a violent action 
is set up accompanied by great evolution of heat. The residue 
consists of sesquisulphide of phosphorus mixed with excess of 
hposphorus. The two bodies are most readily separated by 
solution in bisulphide of carbon. Whatever excess of red phos* 
phorus is taken, the substance formed is the same ; but if the 
sulphur is in excess, tersulphide of phosphorus is obtained. 

Sesquisulphide of phosphorus crystallizes from sulphide of 
carbon or from chloride of phosphorus in right rhomboidal 
prisms. 

It melts at 142°, and distils between 300° and 400°. At 260° 
it volatilizes completely in a current of dry carbonic acid. The 
sublimate thus obtained does not colour polarized light, which 
circumstance, together with its aspect and the mode of its group- 
ing, place it in the regular system. It is therefore dimorphous. 
It is almost unalterable in the^air and in cold water. 

XXVII. Proceedings of Learned Societies, 

BOTAL SOCIETY. 

[Continued from p. 159.] 

June 16, 1864. — Major- General Sabine, President, in the Chair. 

^HE following communication was read : — 

-^ " Description of a New Mercurial Gasometer and Air-pump." 

By T* R. Robinson, D.D., LL.D., F.R.S., &c. 

In some experiments on the electric spectra of metal and ga^es, 
I felt the want of a mercurial gasometer for working with such of 
the latter as are absorbable by water. That of Pepys is on too large 
a scale for my requirements, and it seemed better to contrive one 
more easily manageable, which I saw could also be made to act as a 
mercurial air-pump. In this I have succeeded to my satisfaction ; 
and I hope that a description of it may be useful to those who are 
^gaged in similar researches. 

* Comptet Rendus, May 16, 1864. 
R2 



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2d6 Royal Society :— 

There have been several attempts made to exhaust by means of 
mercury, the chief of them with which I am acquainted being those 
of Close (Nicholson's Journal, 4to, iii. p. 264), Edelcrantz (Nicholson, 
8vo, vii. p. 188), Traill and Children (Nicholson, xxi. pp. 63 & 
161), and that of Geisler, which he uses in preparing the beautiful 
vacuum-tubes which bear his name. In all the principle is the 
same. A vessel is filled with mercury, which is made to descend 
from it, leaving in it a Torricellian vacuum; this vessel may be 
made to communicate with a receiver, and abstract from it a por- 
tion of the gas which fills it; and by repeating the process the- 
receiver can be exhausted as by successive strokes of an air-pump. 
In the two first instruments to which 1 have referred, the descent of 
the mercury is produced by lifting a plunger which fills one leg of 
an inverted siphon, the vacuum vessel being at the top of the other 
leg. On depressing the plunger, the mercury is again forced up to 
fill that vessel ; and of course both legs must be longer than the 
barometric column. In the two next, the receiver itself is filled with 
mercury, which, by opening a cock, falls through a tube of sufficient 
length into a cistern below. Here the stroke (so to call it) cannot 
be repeated. In Geisler* s the bend of the siphon is of vulcanized 
caoutchouc, so that one leg can be inclined down to a horizontal posi- 
tion, and thus allow the metal to fall from the other, or when raised 
to the vertical position fill it again. This I believe acts well, but it 
must be rather unwieldy ; and my practical acquaintance with the 
working of tubes of that material has made me suspicious of their 
tightness and permanence under such circumstances. 

As in all these cases the mercury is supported in the vacuum- 
vessel by atmospheric pressure, it is obvious that its descent will be 
produced by removing in any way that pressure ; and an effective 
means of doing this is supplied by the common air-pump ; more 
tedious certainly than the mechanical means above mentioned, but 
far more manageable ; and as any mercurial pump must be slow in its 
working, while it is only required for special purposes, this defect is 
not of much importance, and moreover is compensated by some 
special advantages. 

But besides bringing down the mercury, means must be provided 
for raising it again. My first plan was to do this by condensed air, 
the same syringe which made the exhaustion having its action 
i;eversed by a well-known arrangement. It worked extremely well, 
was lighter, and required less mercury than the contrivance which I 
finally adopted ; but it is less convenient for gasometric work, as the 
syringe must be worked while gas is delivered. The machine in its 
present form is shown in fig. 1 . Its base is a stout piece of maho- 
gany, 21 inches by 10*5, with a rim round it 0*6 deep to prevent 
the loss of any spilled mercury, and handles at the ends by which it 
can be transported. To this is firmly fixed the iron stand B, 3*5 
high, 4 in diameter above ; its upper surface is carefully trued to a 
flanch, in which is cemented the vacuum-bell A, so that when the 
touching surfaces are lightly smeared with a mixture of lard and wax 
and screwed together by the six screws (some of which appear in the 



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Dr. Eobinson on a New Mercurial Gasometer and Air-pump. 287 

figure), the joint is air-tight. The bell A is 2 inches in diameter and 
6*5 high; it has a tubulure at the top, in which is ground a glass 
cock C, whose construction is shown in fig. 2. The key of it is 
pierced from its bottom to a level with the bore, with which this 
perforation communicates occasionally by a lateral opening. In the 
position of the figure, it will be seen that the bell communicates 
with the branch a ; if the key be turned half round, it is connected 
with the branch r ; and in an intermediate position it is completely 
shut off. These glass cocks have this great advantage over those of 




metal, that it can always be ascertained if they are air-tight ; their 
transparency permits us to see if the key and shell are in optical con- 
tact; and the slightest air-way there is at once detected. They 
should not be lubricated with oil, which grips and mav perhaps 
find its way into the bell and soil its interior. I find the best mate- 
rial to be castor oil with rosin dissolved in it. A hole is drilled 
down the axis of B, which communicates by a tube (sunk in the 
wood and therefore not visible in the figure) with the cast-iron 
'^^liader D. This is 13 inches high and 3*2 in internal diameter; 



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288 Royal Society: — 

its top and bottom are secured to it air-tight by screws ; in it works 
a plunger of boxwood well varnished 10*4 high, and moving so loosely 
that mercury may pass it easily. The plunger is wrought by a rod 
passing through the collar of leather H. In the top of the cylinder 
IS a stopcock £, to which is fixed a tube of vulcanized caoutchouc 
(varnished with a solution of caoutchouc in benzidine), which is 
shown hanging down; it has a coupling to connect it with an 
ordinary air-pump. There is also in the top a screw S for admitting 
- air. One end of the bell's cock communicates with the atmosphere, 
the other with the receiver-plate B. This is of glass 2 inches in 
diameter, 0-75 thick, and is cemented on the top of the iron pillar P. 
Through it are drilled the passages shown in fig. 3 ; in ^ is ground 
the glf^s tube, shown in fig. 1 by T, the end of which is in contact 
with the cock, and their junction made air-tight by a tube of Para 
caoutchouc; in y and k are similarly ground the siphon-gauge G- 
and the glass cock K. These all communicate with the receiver by 
the passage v, and by removing the tubes can be easily dried or 
cleaned. The cock K is connected by elastic tube with the catch-jar 
N, which is supported in a small mercurial trough M. 

The operation of this machine as an air-pump is as follows : — ^The 
receiver being placed on R, open the screw S, press down the plunger 
nearly to the bottom of the cylinder, remove the key of the bell-cock, 
and pour through the opening which it leaves as much mercury as 
will fill the bell to the bore of the cock. In this one 10 lbs. are 
required. Raise the plunger to the top, and the metal will subside 
from the bell till only 0*3 of an inch remains on the top of B, filling 
the space left vacant in D by the rising of the plunger. The length 
of the plunger and the height of B must be adjusted to this condi- 
tion. Replace the key ; turn it to communicate with the atmosphere 
(which position I call (a)), and depress the plunger. The mercury 
will rise again in the bell, filling it, and expelling the air from it, till 
at last a little mercury will appear in the bore of the cock. To 
prevent this from being splashed about, a bit of bent tube v is ground 
on the end of the cock, which receives it, and when it has too 
much is removed and emptied into D through S. Secondly, turn 
the key to shut off the bell (position (o)) ; draw up the plunger, 
close S, open E, and couple it to an air-pump, with which exhaust D. 
This pump may be of the commonest description, for an exhaustion 
of one or two inches is quite sufficient. The mercury will sink in 
the bell, leaving above it a Torricellian vacuum. Close £, and 
turn the key to communicate with the receiver (position (r)) ; its air 
or gas will etpand into the bell. 

These three operations form the cycle of operation, and must be 
repeated till the required exhaustion be obtained, with one modifi- 
cation of the first one. In it, at the second and all subsequent strokes, 
the key is to be at (o) and S opened ; thus the atmospheric pressure 
will raise the mercuty and do much of the plunger's work ; that must 
then be depressed ami the key set at (a) ; the other two steps mt as 
at first. 
.. Wlk^n ibA jnrtnunent is to be used as 9, gas-bajdei; eiUisr the 



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Dr. Robinson an a New Mercurial Gasometer and Air-pump. 389; 

lecelyer must be in its place, or the opening of R must be closed by 
a piece of flat glass ; the bell must be filled by the plunger, and 
made, by (r) and by opening Jc, to communicate with the jar N. 
The mercury will rise in that to its neck, and sink in A ; fill A again, 
pass gas into N, and, by carefully working the key, draw it into A 
till that is full. As this gas will be mixed with the air of the yessels 
tnd passages, it must be expelled, and A refilled till its purity is cer- 
tain. If it be noxious, it must be conducted into some absorbent 
fluid by an elastic tube, slipped on the a end of the cock ; which will 
also convey the gas to any yessel. 

If it be required to fill a receiver for experiments in an atmo" 
sphere of gas either at common pressure or a less one, it may either 
be exhausted by an air-pump connected with K, and filled from A, 
or exhausted by A and filled from N. The former can only be done 
with gases which have no action on brass. 

These operations seem complicated when described with so much 
detail, but in practice they are very easy, and their result is good. 
Some precautions, however, are required to ensure it. The bottom 
of the bell-cock and of its key must be ground, so as to leave no 
shoulder or hollow in which air may be entangled when the bell is 
filled. Every part of the metal work must be air-tight ; this can 
only be secured by covering, not only its joints, but its whole surface 
with several coats of varnish-paint — best of white lead. When the 
first coat is applied, on exhausting the apparatus, every hole or pore 
is revealed by an opening in the paint (often almost microscopic)^ 
which must be filled up as it forms till all is tight. It is almost 
needless to mention that the whole must be perfectly dry. If the 
bell be filled a few times with undried air, enough of moisture will 
adhere to its walls to prevent an exhaustion of more than 0*1 inch. 
In such a case it must be dried by drawing air into it through sul- 
phuric acid, and this repeatedly. Moisture also occasionally finds 
its way into a part still more troublesome, into the passage which 
connects the bell and cylinder ; it is probably condensed there when 
the mercury is colder than the atmosphere. I remove this by connect* 
ing the tube of K with a desiccator ; setting G to (r), opening K and 
E, and by working the air-pump drawing a stream of dry air into D, 
which bubbles up through the mercury in the passage, and at last 
sweeps away all trace of water and its vapour. In this operation it is 
necessary to remove a portion of the mercury, as otherwise it would 
be sucked into the pump ; indeed this mischief might occur in ordi- 
nary work by some mistake in the manipulation — for instance, bj 
leaving E open with (a). To prevent the possibility of this, D is 
connected with the pump by a mercury trap, easily imagined, which 
intercepts any of that metal that might come over. And lastly, the 
Ulterior of the bell must be perfectly clean if the highest degree of 
i^xhaustion is required. This state is obtained by washing it with 
strong nitric acid, then with distilled water, and when quite dry wiping 
it with linen, from which all traces of soap or starch have been re-s 
moved by boiling it in rain-water. Thus we reduce to a minimum 
t^e film of air which adheres to the bell even when filled with iper- 



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240 Royal Society. 

cury, and lessens its vacuum. When all these precautions were taken,- 
I found that with a receiver containing 3*7 inches, the fifth opera- 
tion brought the gauge (which had been similarly cleaned and care^ 
y»% boiled) down to 0*01. The sixth brought it still lower, but my 
present means of measurement* are not sufficient to determine the 
precise amount. In this machine the old air-pump theorem ought 
to hold, and by it, with the fraction '^, I find that the fifth should 
give 0*007, and the sixth 0*0014 ; so that the presence of adhering 
air is still sensible, though very slight. So high a power, however, 
is not long maintained ; for by use, and especially with oxygen, which 
(probably from the presence of ozone) has a peculiar tendency to 
dirty mercury, the bell becomes soiled ; but it continues to give a 
vacuum of 0*02, which is quite sufficient for ordinary objects. At 
common pressure and temperature, the electric discharge through 
the receiver shows no evidence of the presence of mercurial vapour ; 
but at 0*02 it is otherwise ; the discharge is greenish white, and the 
Spectrum shows little except the lines of mercury. If the gauge were 
detached, perhaps this vapour might be absorbed by gold-leaf. 

The apparatus acts well as a mercurial gas-holder, and can deliver 
i8*5 inches. Like all other contrivances for confining gaseous matter 
by mercury, it is liable to have its contents contaminated with air 
by diffusion between the metal and the vessel which contains it ; but 
1 expected that in this arrangement the defect would be little felt. 
In order that it may take place, the air must pass a distance of 17*2 
inches, of which 14*6 is a tube only 0*125 in diameter, and the rest 
is in a vertical direction against the pressure of 2*6 inches of mer- 
cury. A single experiment will show how far this avails. The bell 
was filled with dry hydrogen, which was found to contain 0*901 of 
the pure gas ; it was left for ten days exposed to considerable changes 
of temperature, and was then found to have 0*854 ; it was there- 
fore contaminated at the rate of 0'005 per day. I am not aware of 
similar measures with ordinary mercurial apparatus; nor is this 
amount of error very important ; but it may I believe be corrected 
by a means long since announced by the late Professor Daniell which 
has been strangely neglected. He proposed it to prevent the infil- 
tration of air into barometers. If the liquid metal adhered to the 
surface which it touches, as water would, this action could not occur ; 
tiow it wets, if I may use the word, several metals, as copper or 
silver, but it also dissolves them, and becomes less fluid. Daniell, 
however, found that it does wet platinum without acting on it in 
any injurious degree ; and advised that a ring of platinum wire should 
be fused round the tube where it dips into its cistern. On inquiring 
of his friend and fellow-labourer. Dr. \V. A. Miller, I learn that it 
was completely successful, but was not taken up by the opticians, 
and passed out of memory. It is obvious that if a bit of platinum 
tube were cemented in the vertical passage below D, it would eflec- 
tually bar the diffusion. I do not like to undo the joint there, 
which is now perfectly tight ; but I will certainly, when the oppor- 
tunity offers, try the experiment. 
* A micrometer microscope put in the place of the telescope of my theodolite. 



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Geological Society. 241 

GEOLOGICAL SOCIETY. 

[Continued from p. 160.] 

May 25, 1864. — W. J. Hamilton, Esq., President, 
in the Chair. 

The following communications were read : — 
1. "On the Geology of part of the North-western Himalayas.*' 
By Capt. Godwin- Austen. With Notes on the Fossils, by T, 
Davidson, Esq., F.R.S., F.G.S., R. Etheridge, Esq., F.G.S., and 
S. P. Woodward, Esq., F.G.S. 

The geological formations occurring in these regions were stated to 
be (1) a fluvio-lacustrine series, (2) a Siwalik series, (3) Nummulitic 
limestone, (4) Jurassic rocks, and (5) a Palaeozoic series. In refer- 
ence to the fluvio-lacustrine strata, the author gave a rSsumS of the 
conclusions respecting their physical features and mode of formation 
at which he had arrived in a former paper, and in addition gave some 
details respecting their position and stratigraphical characters, espe- 
cially describing the mode of occurrence in them of some land and 
freshwater Shells, which were referred to in a Note by Mr. S. P. 
Woodward. The lakes in which the lacustrine deposits were formed 
were supposed by Capt. Godwin-Austen to have been produced in 
consequence of the mouths of valleys, into which rivers run, be- 
coming blocked up by means of glaciers and otherwise, as now often 
happens in the same region. Stratigraphical details of the other series 
of rocks were then given, the Jurassic formation being supposed to 
belong to the Middle division of the Oolites, and the Palaeozoic lime- 
stone being described as Carboniferous Limestone, both of which de- 
terminations were confirmed by Messrs. Etheridge and Davidson in 
Notes on the Fossils. The age of the clay-slate and mica-slate was 
stated to be very doubtful, and the author concluded by describing 
the localities in which granitic rocks occur, but chiefly as forming 
the axis of the North-western Himalayas. In Notes appended to 
the paper, Mr. Davidson described species of Brachiopoda from 
three deposits, one of Carboniferous age, one of Jurassic, and one of 
unknown date ; Mr. Etheridge described the remaining fossils from 
the Jurassic strata ; and Mr. Woodward noticed the Shells from the 
fluvio-lacustrine series. While the latter were stated to be nearly 
all recent British species, Mr. Etheridge remarked on the great 
affinity of the Jurassic fossils to those of the same age (Middle 
Oolite) in England, and Mr. Davidson observed that the fossili- 
ferous limestone of the Carboniferous series bore a great resem- 
blance, lithologically and in its fossils, to deposits of a similar age in 
Great Britain. 

2. '* On the Cetacean Fossils termed Ziphius by Cuvier, with a 
notice of a new species (Belemnoziphivs compressvs) from the Red 
Crag." By Prof. T. H. Huxley, F.R.S., F.G.S. 

llie genius Ziphius, as originally constituted by Cuvier, contained 
three species described by him, namely, Z, cavirostris, Z. plant* 



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242 Oeologicat Society. 

rostris, and Z, longirostris ; but it is probable that each of these really 
belongs to a distinct genus — the first to ZipKius, the second to Cho- 
neziphius, and the last to the author's genus Belemnoziphius , More 
recently M. Gervais has established a new species — Ziphius Becanii 
— from a specimen formerly considered to belong to Z, longirostris ; 
and this species, with that described in this paper, and Professor 
Owen's MS. species, were also considered referable to Belemno- 
giphius. 

Besides the foregoing conclusions respecting the affinities of the 
fossil Rhynchoceti, Professor Huxley discussed the relations of the 
recent genera and species belonging to the same group, including 
the cetacean of Aresquiers, which was considered by Gervais to 
belong to the genus Ziphius, He exhibited these relations in a 
tabular form, and concluded by stating that he had arrived at the 
following results : — 

1. Unless the cetacean of Aresquiers be identical with ZiphiuM 
cavirostris, all the Ziphii of Cuvier belong to Cetacea generally 
distinct from those now living. 

2. If the cetacean of Aresquiers be identical with Ziphius caviroS' 
tris, it is not certain that the latter is truly fossil ; nor, if it be so, 
have we any knowledge of its stratigraphical position. 

3. Of the certainly fossil Ziphii, the stratigraphical position of 
Belemnoziphius longirostris is unknown ; but all the other species of 
that genus, and Choneziphius planirostris, are derived from the 
English or Antwerp Crag, and are not known to occur out of it. 

4. So that at present we are justified in x^^fixdmg BeUmnoziphim 
and Choneziphius as true Crag Mammals. 

June 8, 1864. — ^W. J. Hamilton, Esq., President, 
in the Chair. 

The following communications were read : — 

1 . "On the Rhaetic Beds and White Lias of Western and Central 
Somerset, and on the Discovery of a new Fossil Mammal in the Grey 
Marlstones beneath the Bone-bed." By W. Boyd Dawkins, Esq., 
B.A., F.G.S. 

After describing the sections in the district, and showing the 
palaeontological relations of the White lias to the Avicula contorta 
series and the zone of Ammonites planorbis, the author enunciated 
the following conclusions : — (1) That the true position of the White 
Lias is immediately above the Avicula contorta zone of Dr. Wright, 
and at the base of the Lower Lias shales ; (2) that it is entirely 
distinct from the Rhaetic beds, lithologically and palseontologically ; 
and (3) ft'om the discovery of Rhsetic fossils in the Grey Marh 
below the Bone-bed, that the latter belong to the Rhaetic formation"^. 
He then proceeded to describe a two-fanged mammalian tooth, which 
he had found in the Grey Marlstones below the Bone-bed, and 
which he considered to be the analogue of the trenchant four* 
ridged premolar of Hypsiprymnus, of the section to which H. Hun- 
feri belongs. Until additional remains be found, its affioitiea to 



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• Intelligence and Miscellaneous Articles. 243 

.Mierolestes or to Plagia%lax cannot be determined ; Mr. Dawkins has 
therefore named it provisionally Hypsiprymnopsis Rhsticus. In con- 
clusion he traced the range of the Marsupials in space and time, 
showing that of the six families into which Van der Hoeven divides the 
existing Marsupials, two — the entomophagous and sarcophagous 
Dasyurina, and the phytophagous Macropoda— had been repre- 
sented in England during the interval between the deposition of 
the Purbedc beds and that of the Rhaetic Marlstones below the 
Bone-bed. 

2. " On the Geological Structure of the Malvern Hills and ad- 
jacent District." By Harvey B. Holl. M.D., F.G.S. 

The object, of this communication was threefold, namely (1) to 
discuss the structure and origin of the crystalline rocks of the Mal- 
vern Hills, (2) to give the results of an examination of the super- 
posed Palseozoic strata, (3) to state the chronological relationship 
of the several events in their geological history. 

The geological structure of these hills was described in detail^ 
and it was concluded that the rocks hitherto treated of as syenite, 
and supposed to form the axis of the range, are in reality of meta- 
morphic origin, consisting of gneiss (both micaceous and horn- 
blendic), mica-schist, hornblende-schist, &c., all invaded by vein of 
granite and trap-rocks. It was then shown that the Hollybush 
-Sandstone is the equivalent of the Middle Lingula-flags, and that 
the overlying black shales correspond with the Upper Lingula-beds, 
the whole being overlain, as in Wales, by Dictyonema-shales. These 
rocks, on the east of the Herefordshire Beacon, are altered by trap- 
dykes, which were shown to be of later date than those traversing 
the crystalline rocks before alluded to. Allusion was next made to 
the Upper Llandovery strata which overlie unconformably the primor- 
dial rocks just noticed, after which the several faults in the district 
were described in detail. 

Dr. Holl concluded with some remarks on the general relations of 
the rocks of the Malvern Hills with those of the surrounding dis- 
tricts, describing the successive physical changes supposed to havtf 
been consequent upon their deposition and their subsequent eleva- 
tions and depressions. 



XXVIII. Intelligence and Miscellaneotis Articles, 

OK THE ROTATORY POWER OP ACTIVE LIQUIDS AND OP THEIB 
VAPOURS. BY M. D. GEBNEZ. 

WHEN Biot, in 1815, was accidentally led to the discovery of ro- 
tatory polarization in liquids, he soon recognized in this re- 
jDc^arkable phenomenon all the characters of a property depending oh 
the individual form of the molecules. Among the experiments which 
he devised to exhibit this phenomenon, the best consisted in volati- 
lining an active liquid (oU of turpentine) and cmvsing a ray of pola- 



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244 



Intelligence and MisceUanetme Articles. 



rized light to traverse the vapour. After many fruitless attempts. 
Blot finally succeeded ia establishing the existence of the rotatory 
power of the vapour of the oil, when an explosion and a fire destroyed 
his apparatus. Either because this experiment presented too many 
dangers, or because its arrangement appeared too difficult, it has not 
been repeated since 1818. It remained, however, to inquire if the 
rotating power is the same in magnitude and in direction in the 
vapour and in the liquid which has produced it ; nor was it uninter- 
esting to determine the law of dispersion of the planes of polariza- 
tion of rays of various colours under these two different conditions. 
Such was the object of my researches, which doubtless 1 could not 
have executed without the kind encouragement of MM. Pasteur 
and Verdet, and the resources which the laboratory of the Ecole 
Normale Sup^rieure presented. 

Some preliminary experiments made with the vapours of essence 
of turpentine and of camphor, by means of a tube 15 metres in lengthy 
heated by a series of gas jets, showed that the rotatory power pre- 
vails in vapours in the same direction as in liquids. The magnitude 
of the rotation was sufficient to allow me to. reduce the length of 
the tube to 4 metres, and to arrange it so that the temperature was 
uniform from one end to the other. But working upon liquids of 
considerable rotatory power, I could see that the numbers represent- 
ing the molecular rotatory powers of the vapours were much less 
than those corresponding to liquids condensed at the ordinary tem- 
perature ; I was thus led to investigate whether the molecular rota- 
tory power of these essences did not vary with the temperature. 

These liquids were examined at various temperatures, with special 
apparatus, and by methods the description of which will be found 
elsewhere. I will merely remark that I decided to work on 
essences as homogeneous as possible ; and as liquids always slightly 
alter when kept for several hours at high temperatures, I commenced 
these determinations at lower temperatures. 

Representing by («) the molecular rotatory power at the tempe- 
rature /, the determinations made up to 160^ are contained in the 
following formulas : — 



Rays. 


Essence of orange yalues 

of(«). 


Essence of bigarade yalues 

of(«). 


Essence of turpentine 
values of («;. 


c 

D 
£ 
F 
G 


90-45-00893/-0 000054/^ 
115-91 -0-1237/- 0000016/2 
148-82-01585/-0000028/2 
180-67-0-1979/-0-000001/=^ 
2il-20-0 2331/-0!000181/» 


9^-79-0-1041 /- 0000106/« 
118-65-01175/-0-000216/2 
1 63-81 - 0-1 667/ - 0001 98/^ 
1 86-89 - 0-2 1 62/ - 00001 52/= 
249-33-0-2638/-0-000403/'' 


2%-29-0K)03187/ 
36-61-0-004437/ 
46-29-0006187/ 
5500-0-007000/ 
7101-0008437/ 



llie molecular rotatory power may thus be expressed as a function 
of the temperature by the parabolic formula a—bt — c/^ a being very 
small for the essences of orange and bigarade, and virtually zero for 
essence of turpentine. 

If the values of (a) are compared for the same temperature and'for 



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Intdligenee and Miscellaneous Articles. 



245 



Ae different rays of the spectrum, it is seen that the essences of 
orange and of bigarade diverge much more than essence of turpen- 
tine from the law of the inverse ratio of the square of the wave- 
length ; the product («)X^ varies in fact from the ray C to the ray 
G by about one- seventh of its value in the case of essences of orange 
and of bigarade, v^rhile the variation is only one-fifteenth in the case 
of essence of turpentine. 

The ratio of the rotatory powers for the same ray is taken at any 
two temperatures ; it is found to be the same whatever ray of the 
spectrum be considered ; it is thus easily deduced that the law of 
the dispersion of the planes of polarization of rays of different colours 
is the same for all temperatures. 

The preceding liquids, like camphor, were brought to the state 
of vapour in a tube 4 metres in length, surrounded by a jacket, 
which could be raised to any temperature by means of a series of 
gas-jets. I measured the rotations produced by this column of 
vapour, and I compared them with those that would be produced by 
a certain length of the liquid arising from the condensation of the 
vapour. The following Table refers to this series of experiments : — 



Rays. 


Essence of orange. 


Essence of bigarade. 


Essence of turpentine- 


Camphor. 


Va. 
pour. 


Li- 
quid. 


Ratio. 


Va- 
pour. 


Li. 1 
quid. |B»tio. 


Va- 
pour. 


Li- 
quid. 


Ratio. 


Va- 
pour. 


Li- 
quid. 


Ratio. 


c 

D 
E 
F 
G 


/ 

o 

12Y0 

14-39 
17-46 
23-44 


/ 



45-97 
69-57 
72 24 
97-19 


4-15 
414 
415 


/ 

:7°74 
9-83 
12-75 
15-37 
20-75 


/ 

36-08 
46-06 
59-54 
71-61 
96-63 


4-66 
4-69 
4-67 
4-66 
4-66 


\ 

436 
6-67 
709 
8-36 
10-96 


\ 

13-03 
16-59 
21-08 
24-96 
32-68 


2-99 
2-98 
2-97 
2-99 
2-98 


/ 

6-89 

9-44 

13-36 

17-7 

2811 


/ 

19-43 
26-71 
3782 
50-12 
79-62 


2-82 
2-83 
2-83 
2-82 
2-83 



The ratio of the rotations for the same ray in the two conditions 
is the same for all rays of the spectrum, the diffe;rence being less 
than the errors of observation ; hence it may be concluded that the 
law of dispersion is independent both of the temperature and of the 
condition of the body. 

. It remained to follow the variation of the molecular rotatory 
power after the change of condition. For this determination, which 
necessitates experimental precautions that I cannot here enumerate, 
I used the observation of the sensible tint, the use of which, is justi- 
fied by the preceding. The measurement being made when the 
tube was saturated with vapour at a known temperature and pres- 
sure, the vapour was expelled by a current of carbonic acid ; it was 
condensed, and the molecular rotatory power of the liquid deter- 
mined at various temperatures. For essence of turpentine and for 
camphor, the molecular rotatory power of the vapour is almost 
exactly the same as that of the liquid supposed to be at the same 
temperature ; for the essences of orange and of bigarade it is a little 



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240 JfUMgenee and MiicdloMouu Attida. 

less, and the curve which represents it continues to approfteh th'e 
axis of the temperatures in the part which corresponds to the state 
of vapour. 

In fine, the rotatory power of substances which I have studied for 
a definite ray of the spectrum is not a constant ; it varies regularly 
with the temperature, and changes neither direction, nor virtually 
intensity, when the liquid passes into the state of vapour. 

For rays of different colours, the law of the deviation of the planes 
of polarization is independent of the temperature and of the condi*' 
tion of the substance. 

Iff then, it be admitted that the rotatory power of active sub« 
stances depends on their molecular structure, it may be concluded 
from the preceding that the liquid molecules vaporize without any 
modification taking place in their form. — Comptes Rendus, June 13» 
1864. 



INVERSION OF THE ABSORPTION BANDS IN THE SPECTRUM OF 
DIDYMIUM. BY R. BUNSEN. 

By an experiment which I have made at the instance of Professor 
Kirchhoff, I have succeeded in changing the dark lines which the 
absorption spectrum of solutions of oxide of didymium shows into 
bright lines. If a small quantity of oxide of didymium is heated 
with microcosmic salt at a red heat until the mass is free from gas- 
bubbles and has become transparent, an amethyst-coloured glass is 
obtained on cooling, which, held between the slit of the spectrum- 
apparatus and the source of light, produces the characteristic ab- 
sorption spectrum of didymium compounds. As source of light, an 
ignited platinum wire as fine as a hair is used, the image of which, 
by means of a small lens of short focal distance, is made to fioll upon 
the slit in a suitable manner. If then the didymium glass melted in 
a platinum spiral is brought between the source of light and the lens, 
the stronger absorption lines of didymium, and more especially the 
chief band aDi near Fraunhofer's line D, are seen in the spectrum- 
apparatus with perfect distinctness. If the didymium glass in the 
spiral (which issustained by a holder) is gradually heated by a non- 
luminous fiame held below it, so long as a red heat has not been 
attained the band aDi is seen to become gradually broader. If the 
temperature is raised to a continually increasing red heat, the dark 
band diminishes more and more in darkness, and finally entirely dis* 
appears. If now the platinum wire which serves as hindermost 
source of light is removed, a spectrum of the fused ignited didymium 
glass appears, which has exactly, in the position of the dark band 
aOi in the absorption spectrum, a similarly shaped bright line on a 
dark ground. Indications of a similar inversion may also be perceived 
in the other absorption lines of the same spectrum. 

Professor Bahr in Upsala made two years ago the interesting 
observation that the salts of the metals occurring along with yttrium, 
and designated by Mosander erbium and terbium, give remarkable 
absorption spectra which are wanting in solutions of pure yttria. 



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JfUeUigence and Misioellamom Articles: 247 

Aoiong the lines of these spectra first ohserved by Bahr, and used 
as tests, there is one of great intensity, which is readily changed 
into a bright band in the manner described. — Liebig's Annalen, 
August 1864. 

ON A NEW FOLARIZINa FBISM. BT PROF. H. W. DOYB. 

This contrivance consists of an isosceles right-angled prism of calc- 
spar, one of whose equal sides is perpendicular and the other parallel 
to the optic axis of the crystal, and therefore the hypothenuse-side 
at an angle of 45^ with it. TKis rhombohedron-surface occupies 
the axis of the polarizing-apparatus previously constructed by the 
author, instead of the Nicol's prism which is otherwise placed there, 
so that the light of a lamp, concentrated by a condensing lens, arrives 
at the analyzing-apparatus after having suffered two refractions at 
the equal surfaces of the prism and one total reflexion at the hypo- 
thenuse-surface. The large quantity of light admitted by the appa- 
ratus renders practicable the employment of the most deeply coloured 
glasses, in order to obtain the perfectly definite separation of the 
various homogeneous systems of rings. It can also be used with 
advantage in the polarizing microscope, and for the production of 
the systems of rings on a white screen by means of solar or the elec- 
tric light. This prism, which acts like a Nicol, has been ground 
according to my directions by M. Langhoff, the optician. — Poggen- 
dorfTs Annalen, vol. cxxii. p. 18. 



ON THE OPTICAL PROPEBTIBS OF CABTHAMINE. 
BY PROF. H. W. DOVE. 

In the Proceedings of the Berlin Academy for 1857, page 209, I 
have described a method of combining the visual impressions made 
upon the two eyes simultaneously so as to produce the appearance of 
a vivid chromatic lustre in substances which, when illuminated in 
the u^ual way, show no trace of it. The method consists in holding a 
piece of differently coloured glass before each eye, and looking through 
both at a picture in which the colours of the two pieces of glass are 
so combined that a figure is executed in one colour upon a ground of 
the other colour. This reminded me that the so-called shot silks, in 
which the warp and weft are of different colours, as well as the 
wings of certain beetles, and, lastly, the dichroic platinum-compounds 
examined by Haidinger, especially those which are of a bright green 
by reflected light, and appear deep red by transmitted light, produce 
the impression of a lustre, which approaches very closely to that of a 
metal. In like manner a metallic lustre already possessed by a sur- 
face is distinctly heightened by combination with another colour, as 
is clearly shown when the surface becomes covered with a film of 
oxide, or is covered with a galvanic deposit thin enough to exhibit in- 
terference tints. To the same class of phenomena belong also the 
favourable changes in our impression of the colour of newly cast 
statues when they are allowed to stand exposed to the atmosphere. 
If these changes take place quickly, they soon lose in beauty through 



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248 InteUigence and Miscellaneous Articles. 

the darkening of the surface ; and hence we see that the colours must 
. cooperate in a definite ratio in order to excite the most favourable 
impression. 

It is well known that the imperfectly pure carthamine, which occurs 
in commerce in pink saucers, has a yellowish metallic lustre when 
allowed to dry in a saucer, and that in time it becomes greenish at 
the surface. Carthamine spread upon glass plates exhibits a bronze- 
like iridescence which afterwards disappears. Dr. Stahlschmidt 
very kindly prepared for me a series of glass plates upon which pure 
carthamine was spread with the greatest possible evenness. On look- 
ing through one of these, the whole plate appears of a deep red. On 
looking at a plate, coated on one side only, by reflected light, the 
coated side being below, the glass plate appears uniformly green. 
But if the plate is reversed, so that the daylight, to which the back 
of the plate is turned, is reflected by the layer of carthamine, the ob- 
server would fancy he was looking at a plate of polished brass. If 
carthamine is spread upon a plate of blue, yellow, red, or green glass, 
the green colour seen by reflexion in the first case disappears, but 
the metallic lustre seen in the second case remains unchanged. This 
latter therefore is produced by the combination of the reflected green 
light with the internally dispersed red light. 

The reflected green light appears with increased intensity if the 
plate, placed in such a position that the side coated with carthamine 
is below, is looked at through a Nicol's prism or through one of the 
polarizing prisms above described (p. 247) . This acts in the plane of 
reflexion like a Nicol's prism perpendicularly to the principal section. 
The cause of heightening of the colour thus occasioned is, that the 
light polarized in the plane of reflexion, by the outer surface of the 
glass, is got rid of. On the contrary, if the layer of carthamine is 
uppermost, the yellowish light gradually becomes more and more 
nearly green as the Nicol is turned round, Carthamine very slightly 
depolarizes transmitted polarized light, and, when the light is inci- 
dent at a very oblique angle, renders it elliptically polarized. 

I may take this opportunity of remarking that the polarizing prism 
described by me is especially well adapted for experiments with 
radiant heat. I have often exposed it to the concentrated heat of 
the sun until the cork into which it was fitted began to bum, with- 
out the prism itself being in any way injured. In using a Ni col's 
prism in sacchari metrical experiments, the prism is often injured, if 
a flame is brought very close to it, by the connecting layer of Canada- 
balsam becoming blistered. The same applies to experiments on the 
polarization of radiant heat. When employed as analyzing- appa- 
ratus, a Nicol's prism has the advantage that the object remains 
erect, while in mine the reflected image rotates. The latter, how- 
ever, possesses the recommendation for a polarizing-apparatus of 
ofl^ering a large field of view. It is preferable to Foucault's prism, 
since in this moisture is apt to be precipitated in the separating 
stratum and to render the surface dull, w^hereas in mine the surfaces 
can at all times be easily cleaned. — PoggendorfF's Annalen, vol. cxxii, 
p. 454, 



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FliiZ. Ma^. Ser. ^. Vol.28. KI. 



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THE 
LONDON, EDINBURGH, and DUBLIN 

PHILOSOPHICAL MAGAZINE 

AND 

JOURNAL OF SCIENCE. 



[FOURTH SERIES.] 



OCTOBER 186*. 



XXIX. On the Photographic Use of a Sihered-Glass Refteciing 
Telescope. By Henry Draper^ ilf.D., Professor of Natural 
Science in the University of New York*. 

SINCE the introduction of mirrors of silvered glass for astro- 
nomical uses by Foucault and Steinheil^ tliey have conti- 
nually increased in favour^ and have now assumed very consider- 
able importance. As a testimonial to their efficiency, I may state 
that one of 15^ inches aperture has furnished me the means of 
producing photographs of the moon 50 inches in diameter, well 
defined, and of good general effect. 

My attention was first directed to them in 1860, owing to 
some remarks made by Sir J. F. W. Herschel to my father. I 
had at that time a reflector of speculum-metal of 15 inches aper- 
ture and 12 feet focal length, mounted in an observatory which 
was described in a paper read at the Oxford Meeting of the 
British Association in 1860. Soon afterwards the speculum 
was replaced by a silvered-glass mirror of 15^ inches aperture 
and 12| feet focal length, which I had ground, polished, and 
silvered. Since then more than a hundred mirrors have been 
prepared in my workshop, in order to secure two of the highest 
perfection. The full account of these operations, illustrated by 
forty-seven woodcuts, has just been published by the Smithsonian 
Institution at Washington, in the * Contributions to Science/ 

In the past four years manjr opportunities have presented 
themselves for learning the qualities of these instruments, what 
their defects and advantages are, and the best means of con- 
structing them. When the eye has become experienced in 

* Comxnttnicqiied by the Author. 
Phil Mag. S. 4. Vol. 28. No. 189. Oct. 1864. S 



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250 Dr. H. Draper on the Photographic Use of 

judging of faults^ and the hand quick at correcting them, a 
short time suffices to bring the glass concave to a state of per- 
fection. If the rough grinding be completed, and the convex 
tool put into good condition, a single day should finish the 
surface. 

In the beginning of the experiments, one of the most serious 
difficulties encountered was that arising from the irregular dis- 
tribution of heat through the mass of the disk of glass. When, 
for instance, a mirror of 15 1^ inches is polished by a pitch tool 
of the same size, it is hard to avoid the production of rings of 
varying focal length, owing to the overplus of heating towards 
the middle. Where the tests are applied at the centre of cur- 
vature, and the operator does not have to depend on indications 
derived from telescopic observation, these and similar imperfec- 
tions are much more easily detected and avoided than where 
they have to be disentangled from atmospheric disturbances. 

Another obstacle, which proved to be formidable at first, was 
the unequal amount of compression that disks of glass and spe- 
culum-metal suffer when supported on different parts of their 
edges. In all the large disks examined, there has been a dia- 
meter of minimum compressibility, which ought to be kept 
always vertical. If set horizontjJly, the mirror immediately 
gives double images. 

As regards the best machine for producing parabolic surfaces, 
the experience of six years on several different ones, including 
those of Lord Rosse and Mr. Lassell, has brought me to the 
conclusion that the most satisfactory results are to be obtained 
only by employing polishers of much less diameter than the 
surface to be produced — a method of working first published by 
M. Foucault. A better mirror can be made by small locsl 
polishers moved by the hand, than by a full-sized polisher moved 
by any machine that I have tried. This is due to the complete 
control that the operator gains over the distribution of heat and 
moisture, and to the power of rubbing away only those parts 
which are necessary to be removed in order to extricate the 
parabolic surface below. The method resembles that of scra- 
ping used by mechanics to produce true planes. At the same 
time a thorough knowledge of the appearance of spherical, ellip- 
tical, parabolic, hyperbolic, and other surfaces at the centre of 
curvature must be gained. I have also polished several mirrors 
which could only bring oblique pencils to a sharp focus, and 
which were suitable for the Herschelian construction, the amount 
of the obliquity, 2° SCM, just carrying the image to the edge of 
the tube. Some of the best lunar photographs were taken when 
the diagonal mirror of the Newtonian was 6 inches out of cen- 
tre in the 16-inch tube. 



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a SUvereeUGlass Reflecting Telescope. 261 

Many different processes for silvering glass have been pro* 
posed^ some requiring the aid of heat, others doing as well cold. 
Those of M. Gimeg and Professor A. Martin have given the 
most satisfactory results. The reducing agents are respectively 
BocheUe salt and cane-sugar {intervertt). As the fortnulse may 
be of use to those interested in the matter, they are appended. 
For silvering a 15^-inch mirror, about 22 ounces of liquid are 
needed. In Cimeg's process, 800'grains of nitrate of silver must 
be dissolved in 4 ounces of water, and ammonia added until the 
precipitated oxide of silver is almost redissolved. In another 
vessel, 560 grains of tartrate of potash and soda are to be placed 
with 17 or 18 ounces of water. The concave surface of the 
glass must be thoroughly cleaned with nitric acid and water, and, 
when dry, coated with uniodized collodion, and the film polished 
off with cotton flannel. The liquids being mixed are then to be 
poured into a shallow vessel of hard india-rubber, and the glass 
immersed face downwards, the back standing out of the liquid 
and being freely exposed to daylight or sunlight. The same 
precautions are necessary to avoid streaks as in the case of a 
collodion negative. The silver, when polished, should be about 
200,000 ^f ^^ ^^^^ thick, and should show the sun by trans- 
mitted light as a light-blue disk. 

In Professor Martin's process only 100 grains of nitrate of 
silver are required. The formula is to dissolve the nitrate in 
water, add ammonia till the brown oxide redissolves completely, 
then pour in slowly 80 grains of caustic soda in solution. If 
this produces a precipitate, the quantity of ammonia must be 
increased. The reducing agent is procured by boiling 12^ parts 
of white sugar in 100 parts of water with 1 part of nitric acid, 
and adding water to make 500 parts with 50 parts of alcohol. 
Two ounces and a half of this liquid are to be mixed with the 
previous solution just before the glass is immersed. The draW'* 
back to this process, as compared with Cimeg's, is that there are 
often many minute holes in the silver, particularly if the solu- 
tions have been freshly prepared. They cannot be avoided by 
previous filtration. 

The durability of silver films under favourable circumstances 
is quite surprising. When not exposed to sulphuretted hydrogen, 
they do not show any disposition to tarnish, and, all thmgs con- 
sidered, are more lasting than the polished specula that are in 
the observatory. These latter are apt to accumulate a yellow 
film, which interferes as seriously with their photographic power 
as does the reddish colour so strongly seen in Gregorians and 
Newtonians when the copper and tin are incorrectly propor- 
tioned. The silvered surfaces however, are, occasionally liable 
to an accident which does not affect the others. A series of 

S2 



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252 Dr. H. Draper an the Photographic Use of 

minute fissures will spread all over tbem^ and the silver seem to 
lose its adhesion to the glass. This appears to arise from con- 
tinued exposure to dampness^ and may be obviated by covering 
the concave surface^ when not in use^ with a plate of flat glass^ 
the edge of the concave being ground flat. The diagonal mirror 
of my Newtonian is not subject to this difficulty^ owing to the 
free ventilation and greater warmth in its neighbourhood. The 
lower story of the observatory was contrived to keep the large 
metal speculum at a uniform temperature^ and is excavated out 
of the solid rock. Being cool^ it communicates to objects put 
in it a tendency to condense moisture from the warmer air that 
enters. It is obvious that an observatory for a silvered-glass 
instrument should "be altogether above ground, and not cooler 
than the adjacent air. 

The vapours which arise from fresh paint exercise a prejudicial 
effect, in depositing upon the surface a somewhat greasy film. 
After repainting the interior of the buildings, it became neces- 
sary to expose the large concave several times to the sun, and 
repolish it to keep it in working order. In the course of three 
months the trouble sensibly disappeared, the present mirror not 
having been taken off its air-sac since spring, nor will it require 
to be moved for a long time. 

The reflecting power of silver films varies considerably with 
the method of preparation. When deposited from alcoholic solu- 
tions in the manner recommended by M. Foucault, they have 
frequently a leaden appearance, while the two processes just 
described give surfaces of velvety blackness in oblique positions, 
and certain to show objects in their natural colours* This dulness 
results probably from the presence of foreign matters incorporated 
with the silver, as is shown by the fact that when such a film is 
dissolved offa piece of glass with nitric acid, an insoluble reddish 
powder is lefti 

For the purposes of celestial photography, a silvered-glass 
telescope offers, without doubt, the greatest advantages. Not 
only is ijb less difficult to manage than a speculum, but its higher 
reflecting power materially shortens the time of exposure of the 
sensitive plate. The superiority of any reflector to an achro- 
matic is of course too well known to require mention* I have 
no doubt that they will in future be constructed of much larger 
size than any speculum yet made, the intrinsic difficulties being 
much less. The glass need only weigh one-eighth as much as 
the metal. They are also more permanent ; for if by accideiit 
the silver should be injured, it is only a morning's work to dis- 
solve away the old film and replace it by a new one, which will 
copy the glass below with so much accuracy that the most refined 
tests (such as that with an eclipsing screen at the centre of cur- 



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a Silvered-Glass Reflecting Telescope. 253 

vature) will fail to indicate any change in figure. The glass 
covered by metal is even more durable than a lens. 

However, unless the astronomer can have access to a much 
steadier atmosphere than prevails at Hastings near New York, 
where my observatory is, there would be but slight inducement 
to build a very large instrument. In the nine months* interval 
between March and December 1863, only three really fine nights 
occurred, when the best lunar negatives could be taken. Up to 
the present date, September 1864«, there has not been a single 
occasion this year on which the results of the past one could be 
exceeded. The good nights have been during the absence of the 
moon. If the instrument could be transported to the Peruvian 
plateaus, 15,000 feet above the sea, or somewhere near the 
equator on the rainless west coast of South America, it could 
accomplish more. 

Notwithstanding these impediments, I have succeeded, as has 
already been stated, in making some photographs of the moon 
50 inches in diameter, and many of smaller sizes. In order to 
take advantage of a steady night when it does occur, it is neces- 
sary to get photographs whenever it is clear, so as to keep the 
chemicals and clock in the best order. For this reason about 
1500 original negatives were made in 1862 and 1863. A sin- 
gular cause has this summer led to the loss of a great deal of 
time. Owing to an excessive drought, the woods have been on 
fire in many places, and have communicated to the atmosphere 
the power of stopping the larger portion of the chemical rays. 
The moon of June 19 required an exposure of ten minutes to 
secure an impression, which was not more vigorous than one of 
that phase taken in ^^(jthof the time usually is. On the next 
night two seconds were sufficient. In the meantime there had 
been a heavy dew, but no rain. These smoky atmospheres give 
great prominence to the lines in the less refrangible parts of the 
spectrum about A. The diminution of the light on another 
occasion was so great that the eye could look without inconve- 
nience upon the meridian sun, which, as it declined to the west, 
was gradually extinguished, and this though there were no 
clouds. These phenomena are by no means confined to small 
areas, but extend over large tracts of country. When my regi- 
ment was stationed at Harper's Ferry in Virginia in 1862, a 
similar condition of atmosphere prevailed there and at the obser- 
vatory 200 miles distant. The yellowness was at that time attri- 
buted to dust in the air. 

In developing and enlarging photographs, care is necessary to 
preserve the proper relation of light and shade. In the case of 
the full moon, for instance, there is a tendency to flatness and 
an indistinct appearance. If^ however, the negative, instead of 



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264 Photogrfiphio Use of a Silvered^Glasa Reflecting Telescope. 

being developed with sulphate of iron^ is brought out with pyro* 
gallic acid, it assumes a much more brilUant aspect, the contrast 
of light and dark parts is greater, and the picture more lively. 
In enlarging such a photograph, by treating the reverse or posi- 
tive made from the original negative with iodide of mercury 
dissolved in iodide of potassium, the contrast can be increased 
at pleasure, the dark parts of the collodion film gaining more 
than their due proportion of strength. The eventual paper proof, 
instead of being fiat, is whiter in the high lights and darker in 
the deep shades than it should be. Such a result shows the 
uncertainty of any method of comparing the actinic force of 
various parts of the moon together, and attempting to deduce 
therefrom arguments as to their composition. The nature of 
the collodion and sensitizing compounds used makes also a ma- 
terial diflFerence. I have found that, as a rule, it is better to use 
sulphate of iron alone in those phases where the moon is about 
one-half illuminated, and graduate the strength of the solution 
so as to gain the most desirable result. The parts of the surface 
on which the sunlight is falling nearly perpendicularly, are only 
too prone to become overdark as compared with those on which 
the light strikes obliquely. The contrast requires restraint 
rather than encouragement. The negatives should present the 
appearance of overdone positives to enlarge well. Even with 
the best system of development, it is impossible to secure a good 
pictiure of the entire portion of the moon visible in the first and 
third quarters ; for either the larger portion must be overdeve- 
loped and overexposed to secure the extreme edge, or else the 
most obUquely illuminated part must be left undeveloped. It 
may be possible to overcome this difficulty in the future, by 
diaphragms so adjusted as to cut off the brighter light while the 
fainter parts continue to act. 

In any operation of forcing or intensifying, it is necessary to 
bear in mind that the deposit constituting the image is not a con- 
tinuous film, but is more or less granular. Most of the processes 
of redeveloping tend to increase the size of the silver grains, 
and, if practised injudiciously upon photographs that have sub- 
sequently to be magnified, may impair them seriously. Sulphate 
of iron employed alone for educing a picture seems to give the 
finest granulations, particularly if the sensitive plate, previous to 
exposure to light, has been washed in water so as to remove 
most of its free nitrate of silver. It requires, however, to be 
redipped in the nitrate-of-silver bath before being treated with 
the sulphate. The free nitrate of silver necessary to the reduc- 
tion cannot be advantageously supplied otherwise; and the sensi- 
tiveness would be decreased. 

No photograph that has to be magnified should be vamidied. 



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Prof. Tyndaii an i/w Canformatian of the Alps. 255 

Apart from the fact that it is entirely unnecessary^ it is sure to 
produce some markings or imperfections. Dust and little hairs 
adhere to the film while sticky^ and when dry it is certain to be 
either finely corrugated, or else dotted with little transparent 
elevations, which act like lenses toward the bright beam of light 
subsequently used. In order to be secure against accidents, I 
always keep two or three reverses of the finest negatives. These, 
being copied by contact in rays diverging from a point, are just 
as valuable as the original. 

With regard to] the means used for enlarging, they were at 
first single and compound achromatic combinations. But these 
present two defects. The visual and actinic foci are made to 
coincide, even approximately, with difficulty ; and when in addi<* 
tion a flat field, sometimes 5 feet in diameter, is required, such 
lenses as could be obtained failed entirely. It then occurred to 
me to supply their place by a concave mirror of suitable figure, 
and both difficulties have ih consequence been surmounted. 
The field is flat, as is shown by examination on ground glass, 
and in the produced photograph. As for the sharpness, I have 
made a picture of a scale of Lepisma saccharina under a power 
of 289, by taking a photograph magnified seventeen times, and 
then magnifying that. It shows the characteristic markings 
almost as well as a microscope. With this contrivance, the 
whole interior of the observatory, 27 feet long, can be used as a 
camera obscura. 

University, New York, 
September 1, 1864. 



XXX. On the Conformation of the Alps. 
By John Tyndall, F.R.S., ^c* 

TO the physical geologist the conformation of the Alps, and 
of mountain-regions generally, constitutes one of the most 
interesting problems of the present day. To account for this 
conformation, two hypotheses have been advanced, which may be 
respectively named the hypothesis of fracture and the h3rpothe8is 
of erosion. Those who adopt the former maintain that the 
forces by which the Alps were elevated produced fissures in the 
earth's crust, and that the valleys of the Alps are the tracks of 
of these fissures. Those who hold the latter hypothesis maintain 
that the valleys have been cut out by the action of ice and water, 
the mountains themselves being the residual forms of this grand 
sculpture. To the erosive action here indicated must be added 
that due to the atmosphere (the severance and detachment of 



* CpmmunicjEited by the Author. 



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256 Prof. Tyndall on the Cmformaiion of the Alps. 

rocks by rain and frost), as affecting the forms of the more 
exposed and elevated peaks. 

I had heard it stated that the Via Mak was a striking illus- 
, tration of the fissure theory — that the profound chasm thus 
named, and through which the Hinter-Rhein now flows, could 
be nothing else than a crack in the earth's crust. To the Via 
Mala this year I therefore went, to instruct myself by actual 
observation upon the point in question. The gorge commences 
about a quarter of an hour above the town of Tusis; and, on 
entering it, the conclusion which first gains credence is that it 
must be a fissure. This conclusion in my case was modified as 
I advanced. Some distance up the gorge I found upon the slopes 
to my right quantities of rolled stones, evidently rounded by 
water-action. Still further up, and just before reaching the first 
bridge which spans the chasm, I found more rolled stones asso- 
ciated with sand and gravel. Through this mass of detritus, for- 
tunately, a vertical cutting had been made, which exhibited a sec- 
tion showing perfect stratification. There was no agency in the 
place to roll these stones, and to deposit these alternating layers 
of sand and pebbles, but the river which now rushes some hun- 
dreds of feet below them . At one period of the Via Mala's history 
the river must have run at this high level. Other evidences of 
water-action soon revealed themselves. From the parapet of the 
first bridge I could see the solid rock 200 feet above the bed of 
the river scooped and eroded. It is stated in the guide books, 
that the river, which usually runs along the bottom of the 
gorge, has been known almost to fill it during violent thunder- 
storms ; and it may be urged that the marks of erosion which 
the sides of the chasm cfhibit are due to those occassional floods. 
In reply to this, it may be stated that even the existence of such 
floods is not well authenticated, and that, if the supposition were 
true, it would be an additional argument in favour of the cutting- 
P^wer of the river. For if floods operating at rare intervals 
could thus erode the rock, the same agency, acting without 
ceasmg upon the river's bed, must certainly be competent to 
excavate it. I proceeded upwards, and from a point near another 
bridge (which of them, I did not note) had a fine view of a por- 
tion of the gorge. The river here runs at the bottom of a cleft 
?f P'^^iound depth, but so narrow that it might be leaped across. 
That this cleft must be a crack is the impression first produced; 
but a brief inspection suffices to prove that it has been cut by 
the river. From top to bottom we have the unmistakeable marks 
of erosion. This cleft was best seen by looking downwards from 
anoint near the bridge; looking upwards from the bridge itself, 
the evidence of aqueous erosion was equally convincing. 
The character of the erosion depends upon the rock as well 



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Prof. Tyndall on the Conformation of the Alps. 257 

as upon the river. The action of water upon some rocks is almost 
purely mechanical; they are cut away^ sometimes in sensible 
masses. In other cases the action is chemical as well as mecha- 
nical. Water, in passing over limestone, charges itself with car- 
bonate of lime without damage to its transparency j the rock 
is dissolved in the water; and the gorges cut by water in such 
rocks often resemble those cut in the ice of glaciers by glacier 
streams. To the solubility of limestone is probably to be ascribed 
the fantastic forms which this rock usually assumes, and also the 
grottos and caverns which interpenetrate limestone formations. 
A rock capable of being thus dissolved will expose a smooth sur- 
face after the water has quitted it ; and in the case of the Via Mala 
it is the polish of the surfaces, and also the curved hollows 
scooped in the sides of the gorge, which assure us that the chasm 
has been the work of the river. 

About four miles from Tusis, and not far from the little village 
of Zillis, the Via Mala opens into a plain which is bounded by 
high terraces, evidently cut by water. It occurred to me the 
moment I saw it, that the plain had been the bed of an ancient 
lake ; and a farmer, who was my temporary companion, immedi- 
ately informed me that such was the tradition of the neighbour- 
hood. This man conversed with intelligence, and as I drew his 
attention to the rolled stones, which rest not only above the river 
but above the road, and inferred that the river must have been 
there to have rolled those stones, he saw the force of the evidence 
perfectly. In fact in former times, and subsequent to the retreat 
of the great glaciers, a rocky barrier crossed the valley at this 
place, damming the river which came from the residual glaciers 
higher up. A lake was thus formed which poured its waters 
over the barrier. Two actions were here at work, both tending 
to obliterate the lake — the raising of its bed by the deposition of 
detritus, and the cutting of its dam by the river. In process of 
time the cut deepened into the Via Mala ; the lake was drained^ 
and the river now flows in a definite channel through the plain 
which its waters once totally covered. 

From Tusis I crossed to Tiefenkasten by the Schien Pass, and 
thence over the Julier Pass to Pontresina. There are three or 
four ancient lake-beds between Tiefenkasten and the summit of 
the Julier. They are all of the same type — a more or less broad 
and level valley-bottom, with a barrier in front through which 
the river has cut a passage, the drainage of the lake being the con- 
sequence. These lakes were sometimes dammed by barriers of 
rock, sometimes by the moraines of ancient glaciers. An exam- 
ple of this latter kind occurs in the Rosegg valley, about twenty 
minutes below the end of the Rosegg glacier, and about an hour 
from Pontresina. The valley here is crossed by a pine-covered 



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258 Prof. Tyndall on the Conformation of the Alpe. 

moraine of the noblest dimensions : in the neighbourhood of 
London it might be called a mountain. That it is a moraine^ 
the inspection of it from a point on the Suriei slopes above 
it will convince any person possessing an educated eye. Where, 
moreover, the interior of the mound is exposed, it exhibits 
moraine-matter — detritus pulverized by the ice, with boulders 
entangled in it. It stretched quite across the valley, and at one 
time dammed the river up. But now the barrier is cut through, 
the stream leaving about one-fourth of the moraine to its right, 
and the remaining three-fourths to its left. Other moraines of 
a more resisting character hold their ground as barriers to the 
present day. In the Val di Campo, for example, about three- 
quarters of an hour from Fisciadello, there is a moraine com- 
posed of large boulders, which interrupt the course of a river 
and compel the water to fall over them in cascades. They have 
in great part resisted its action since the retreat of the ancient 
glacier which formed the moraine. Behind the moraine is a 
lake-bed, now converted into a meadow, which is quite level, and 
rests on a deep layer of mould. 

At Fontresina a very fine and instructive gorge is to be seen. 
The river from the Morteratsch glacier rushes through a deep and 
narrow chasm which is spanned at one place by a stone bridge. 
The rock is not of a character to preserve smooth polishing ; but 
the larger features of water-action are perfectly evident from top 
to bottom. Those features are in part visible from the bridge, 
but still better from a point a Uttle distance from the bridge in 
the direction of the upper village of Fontresina. The hollowing 
out of the rock by the eddies of the water is here quite manifest. 
A few minutes walk upwards brings us to the end of the gorge; 
and behind it we have the usual indications of an ancient Is^e, 
and terraces of distinct water origin. From this position the 
genesis of the gorge is clearly revealed. After the retreat of the 
ancient glacier which filled this valley, a transverse ridge of 
comparatively resisting material crossed the valley at this place. 
Over the lowest part of this ridge the river flowed, rushing 
steeply down to join at the bottom of the ridge the stream which 
issued from the Bosegg glacier. On this incline the water 
became a powerful eroding agent, and finally cut its channel to 
its present depth. Geological writers of reputation assume 
at this place the existence of a fissure, the " washing out ^' of 
which resulted in the formation of the gorge. Now no ex- 
amination of the bed of the river ever proved the existence of 
this fissure; and it is certain that water can cut a channel 
through unfissured rock — ^that cases of deep cutting can be 
pointed out where the clean bed of the stream is exposed, the 
rock which forms the floor of the river not exhibiting a 



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Prof. Tyndall (wi the Conformation of the Alps. 259 

trace of fissure. An example of this kind occurs near the 
Bemina Gasthaus, about two hours from Pontresina. A little 
way below the junction of the two streams from the ^Bemina 
Pass and the Heuthal the river flows through a channel cut 
by itself^ and 20 or 30 feet in depth. At some places the river- 
bed is covered with rolled stones ; at other places it is bare, but 
shows no trace of fissure. The abstract power of water (if I may 
use the term) to cut through rock is demonstrated by such in- 
stances. But if water is competent to form a gorge without the 
aid of a fissure, why assume the existence of such in cases like 
that at Pontresina ? It seems far more philosophical to accept 
the simple and impressive history written on the walls of those 
gorges by the agent which produced them. 

Numerous cases might be pointed out, varying in mag- 
nitude, but all identical in kind, of barriers which crossed 
valleys and formed lakes having been cut through by rivers, 
narrow gorges being the consequence. One of the most famous 
examples of this kind is the Pinsteraarschlucht in the Valley of 
Hasli. Here the ridge called the Kirchet seems split across, and 
the river Aar rushes through the fissure. Behind the barrier 
we have the meadows and pastures of Imhof resting on the sedi- 
ment of an ancient lake. Were this an isolated case, one might 
reasonably conclude that the Finsteraarschlucht was produced by 
an earthquake, as some suppose it to have been ; but when we 
find it to be a single sample of actions which are frequent in the 
Alps — when probably a hundred cases of the same kind, though 
different in magnitude, can be pointed out — it seems quite un- 
philosophical to assume that in each particular case an earthquake 
was at hand to form a channel for the river. As in the case of 
the barrier at Pontresina, the Kirchet, after the retreat of the 
Aar glacier, dammed the waters flowing from it, thus forming a 
lake, on the bed of which now stands the village of Imhof. Over 
this barrier the Aar tumbled towards Meyringen, cutting, as 
the centuries passed, its bed ever deeper, until finally it became 
deep enough to drain the lake, leaving in its place the alluvial 
plain through which the river now flows in a definite channel. 

But it may be urged that it is not necessary to assume the 
operation of a special earthquake to split each particular barrier. 
The broad view taken by the advocates of the fracture theory is 
that the valleys are the tracks of the fissures produced by the 
upheaval of the land, and the cracks across the barriers to which 
I have referred are in reaUty portions of the great cracks which 
formed the valleys. Such an argument, however, would virtu- 
ally concede the theory of erosion as applied to the valleys of the 
Alps. These narrow channels, often not more than 20 or 30 feet 
across, sometimes even narrower, frequently, occur at the bottom 



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260 Prof. Tyndall on the Conformation of the Alps. 

of broad valleys. Such a fissure might enter into the list of acci- 
dents which gave direction to the real erosive agents which scooped 
the valley out ; but the formation of the valley, as it now exists, 
could no more be ascribed to it than the motion of a railway train 
could be ascribed to the finger of the engineer which turns on 
the steam. 

' These deep gorges occur, I believe, for the most part in lime- 
stone strata; and the effects which the merest driblet of water 
can produce on such rocks are quite astonishing. It is not un- 
common to meet chasms of considerable depth produced by small 
streams the beds of which are dry for a large portion of the year. 
Bight and left of the larger gorges such secondary chasms are 
usually to be found. The idea of time must, I think, be more 
and more included in our reasonings on these phenomena. Hap- 
pily the marks which the rivers have, in most cases, left behind 
them, and which refer, geologically considered, to actions of 
yesterday, give us ground and courage to conceive what may be 
effected in geologic periods. Thus the modern portion of the Via 
Mala throws light upon the whole. Near Bergiin in the Valley 
of the Albula there is also a little Via Mala which is not less 
significant than the great one. The river flows here through a 
profound limestone gorge ; but to the very edges of the gorge we 
have the evidences of erosion. The most striking illustration of 
water-action upon limestone rock which I have ever witnessed is, 
I think, furnished by the gorge at Pfaffers. Here the traveller 
passes along the side of the chasm midway between top and 
bottom. Whichever way he looks, backwards or forwards, up- 
wards or downwards, towards the sky or towards the river, he 
meets evei-ywhere the irresistible and impressive evidence that 
this wonderful fissure has been sawn through the mountain by 
the waters of the Tamina. 

I have thus far confined myself to the consideration of the 
gorges formed by the cutting through of the rock barriers which 
frequently cross the valleys of the Alps ; as far as I have ex- 
amined them they are the work of erosion. But the larger ques- 
tion still remains. To what action are we to ascribe the formation 
of the valleys themselves ? This question includes that of the for- 
mation of the mountain ridges j for were the valleys wholly filled, 
the ridges would disappear. Possibly no answer can be given to 
this question which is not beset with more or less of difficulty. 
Special localities might be found which would seem to contradict 
every solution which refers the conformation of the Alps to the 
operation of a single cause. Still the Alps present features of a 
character sufficiently definite to bring the question of their origin 
within the sphere of close reasoning. That they were in 
whole or in part once beneath the sea will not be disputed. They 



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Prof. Tyndall on the Conformation of the Alps. 261 

are in great part composed of sedimentary rocks which must 
have required a sea to form them. Their present elevation above 
the sea is due to one of those local changes in the shape of the 
earth which have been of frequent occurrence throughout geo- 
logic time^ and which in some cases have depressed the land^ 
and in others caused the sea-bottom to protrude beyond its sur- 
face. Considering the inelastic character of its materials, the 
protuberance of the Alps could hardly have been pushed out 
without dislocation and fracture ; and this conclusion gains in 
probability when we consider the foldings, contoi*tions, and even 
reversals in position of the strata in many parts of the Alps; 
Such changes in the position of beds which were oncc.horizontal 
could not have been effected without dislocation. Fissures 
would be produced by these changes ; and such fissures, the ad- 
vocates of the fracture theory contend, mark the positions of the 
valleys of the Alps. 

Imagination is necessary to the man of science, and we could 
not reason on our present subject without the power of presenting 
mentally a picture of the earth's crust, cracked and fissured by 
the forces which produced its upheaval. Imagination, however, 
must be strictly checked by reason and by fact. That disloca- 
tions occurred cannot, I think, be doubted, but that the valleys of 
the Alps are thus formed is a conclusion not at all involved in 
the admission of dislocations. I never met with a precise state- 
ment of the manner in which the advocates of the fissure theory 
suppose the forces to have acted, — whether they assume a general 
elevation of the region, or a local elevation of distinct ridges ; or 
whether they assume local subsidences after a general elevation, 
or whether they would superpose upon the general upheaval minor 
and local upheavals. In the absence of any distinct statement, I 
will assume the elevation to be general — that a swelling out of the 
earth's crust occurred here, sufficient to place the most promi- 
nent portions of the protuberance three miles above the sea-level. 
To fix the ideas, let us consider a circular portion of the crust, say 
one hundred miles in diameter, and let us suppose, in the first 
instance, the circumference of this circle to remain fixed, and 
that the elevation was confined to the space within it. The up- 
heaval would throw the crust into a state of strain ; and if it 
were inflexible, the strain must be relieved by fracture. Cre- 
vasses would thus intersect the crust. Let us now inquire what 
proportion the area of these open fissures is likely to bear to the 
area of the unfissured crust. An approximate answer is all that is 
here required; for the problem is of such a character as to render 
minute precision unnecessary. No one, I think, would affirm that 
the area of the fissures would be yoo^^ ^^® ^^^^ ^^ *^® ^^^^* ^^*^ 
let us consider the strain upon a single line drawn over the sum- 



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262 Prof. Tyndall an the ConformaHan of the Alpg. 

mit of the protuberance from a point on its rim to a point oppo- 
site. Regarding the protuberance as a spherical swellings the 
length of the arc corresponding to a chord of 100 miles and a 
versed sine of 3 miles is 100*24 miles ; consequently the surface 
to reach its new position must stretch 0*24 of a mile^ or be broken. 
A jBsBure or a number of cracks with this total width would 
velieve the strain ; that is to say/ the sum of the widths c^ all 
the cracks over the length of 100 miles would be 420 yards. 
If^ instead of comparing the width of the fissures with the length 
of the lines of tension^ we compared their areas with the area 
of the unfissured land, we should of course find the proportion 
much less. These considerations will help the imagination to 
realize what a small ratio the area of the open fissures must 
bear to the unfissured crust. They enable us to say with cer- 
tainty, for example, that to assume the area of the fissures to be 
^th of the area of the land would be quite absiurd, while that the 
area of the fissures could be one-half or more than one-half 
that of the land would be in a proportionate degree unthink- 
able. If we suppose the elevation to be due to the shrinking or 
subsidence of the land all round our assumed circle, we arrive 
equally at the conclusion that the area of the open fissures 
would be altogether insignificant as compared with that of the 
unfissured crust. 

To those who have seen them from a commanding elevation, 
it is needless to say that the Alps themselves bear no sort of re- 
semblance to the picture which this theory presents to us. 
Instead of deep cracks with approximately vertical walls, we have 
ridges before us running into peaks, and gradually sloping to form 
valleys at angles which, I imagine, would average less than 40 
degrees, many of them certainly not reaching 30. Instead of a 
fissured crust we have a state of things closely resembling the 
surface of the ocean when agitated by a storm. The valleys, 
instead of being much narrower than the ridges, occupy the 
greater space. A plaster cast of the Alps turned upside down, 
so as to invert the elevations and depressions, would exhibit 
blunter and broader mountains, with narrower valleys between 
them, than the present ones. The valleys that exist cannot, I 
think, with any correctness of language be called fissures. It 
may be urged that they originated in fissures : but even this is 
unproved, and, were it proved, would still make the fissures play 
the subordinate part of giving direction to the agents which are 
to be regarded as the real sculptors of the Alps. 

The fracture theory, then, if it regards the elevation of the 
Alps as due to the operation of a force acting throughout the 
entire region, is, in my opinion, utterly ineompetent to account 
for the conformation of the country. If, on the other hand, we 



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Prof. Tyndall on the Conformation of the Alpg, 268 

are compelled to resort to local disturbaiices^ the manipulation 
of the earth's crust which will be necessary to obtain the valleys 
and the mountains will^ I imagine^ bring the difficulties of the 
theory into very strong relief. Indeed an examination of the 
region from many of the more accessible eminences — from 
the Galenstock^ the Orauhaupt^ the Pitz Languard^ the Monte 
Gonfinale — or^ better stilly from Mont Blanc^ Monte Bosa, 
the Jungfrau^ the Finsteraarhorn^ the Weisshom^ or the Mat- 
terhom, where local peculiarities are toned down^ and the ope- 
rations of the powers which really made this region what it is 
are alone brought into prominence, must^ I imagine, convince 
every physically minded man of the inability of any fracture 
theory to account for the present conformation of the Alps. A 
correct model of the mountains, with an imexaggerated vertical 
scale, produces the same effect upon the mind as the prospect 
from one of the highest peaks. We are apt to be influenced 
by local phenomena which, though insignificant in view of the 
general question of Alpine conformation, are, with reference to 
our customary standards, vast and impressive. In a true model 
those local peculiarities disappear ; for on the scale of a model they 
are too small to be visible ; while the essential facts and forms 
are presented to the undistracted attention. 

A minute analysis of the phenomena strengthens the conviction 
which the general aspect of the Alps fixes in the mind. We 
find, for example, numerous valleys which the most ardent plu- 
tonist would not think of ascribing to any other agency than 
erosion. That such is their genesis and history is as certain as 
that erosion produced the Chines in the Isle of Wight. From 
these indubitable cases of erosion — commencing, if necessary, 
with the small ravines which run down the flanks of the ridges, 
with their little working navigators at their bottoms — we can 
proceed, by almost insensible gradations, to the largest valleys 
of the Alps ; and it would perplex the plutonist to fix upon the 
point at which, in his opinion, fracture begins to play a mate- 
rial part. In ascending one of the larger valleys, we enter it 
where it is wide and where the eminences are gentle on either 
side. The flanking mountains become higher and more abrupt 
as we ascend, and at length we reach a place where the depth of 
the valley is a maximum. Continuing our walk upwards we 
find ourselves flanked by gentler slopes, and finally emerge from 
the valley and reach the summit of an open col, or depression in 
the chain of mountains. This is the common character of the 
large valleys. Crossing the col, we descend along the opposite 
slope of the chain, and through the same series of appearances in 
the reverse order. If the valleys on both sides of the col were 
produced by fissures, what prevents the fissure from prolonging 



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264 Prof. Tyndall an the Conformation of Use Alps. 

itself across the col ? The case here cited is representatiye ; and 
I am not acquainted with a single instance in the Alps where the 
chain has been cracked in the manner indicated. The cols are 
simply depressions ; and in the case of many of them the unfis- 
sured rock can be traced from side to side. 

The typical instance just sketched follows as a natural conse- 
quence from the theory of erosion. Before either ice or water 
can exert great power as an erosive agent^ it must collect in suf- 
ficient mass. On the higher slopes and plateaus — ^in the region 
of cols — the power is not fully developed; but lower down 
tributaries 'unite^ erosion is carried on with increased vigour^ 
and the excavation gradually reaches a maximum. Lower still 
the elevations diminish and the slopes become more gentle; the 
cutting-power gradually relaxes, until finally the eroding agent 
quits the mountains altogether, and the grand effects which it 
produced in the earlier portions of its coui*se entirely disappear. 

I have hitherto confined myself to the consideration of the 
broad question of the erosion theory as compared with the frac- 
ture theory ; and all that I have been able to observe and think 
with reference to the subject leads me to adopt the former. Under 
the term erosion I include the action of water, of ice, and of the 
atmosphere, including frost and rain. Water and ice, however, 
are the principal agents, and which of these two has produced 
the greatest effect it is perhaps impossible to say. Two years 
ago I wrote a brief note ^^ On the Conformation of the Alps *'*, 
in which I ascribed the paramount influence to glaciers. The 
facts on which that opinion was founded are, I think, unassail- 
able; but whether the opinion fairly follows from the facts may 
be regarded as an open question. The arguments which have 
been thus far urged against the opinion appear to me to be far 
from conclusive. Indeed the idea of glacier erosion appeared so 
daring that its boldness was deemed by many its sufficient refu- 
tation. It is, however, to be remembered that a precisely similar 
position was taken up by many respectable people when the 
extension of ancient glaciers was first mooted. The idea was 
considered too hardy to be entertained; and the evidences of 
glacial action were sought to be explained by reference to almost 
any process rather than the true one. Let those who so wisely 
took the side of ^' boldness '^ in that discussion beware lest they 
place themselves, with reference to the question of glacier erosion, 
in the position formerly occupied by their opponents. Looking at 
the little glaciers of the present day — mere pigmies as compared to 
the giants of the glacial epoch — ^we find that from every one of 
them issues a river more or less voluminous, charged with the 
matter which the ice has rubbed from the rocks. Where the 
* Phil. Mag. vol. xxiv. p. 169. 



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Prof. Tyndall on the Confurmation of the Alps, 265 

roeka areof a soft oharacterj the amount of this finely polverked 
matter suspended in the water is very great. The water, for 
^utrnpUj of the river which, flows from Santa Catarina to Bormio 
is thick with it The Rhine is charged with this matter, and by 
it has so silted up the Lake of Constance as to abolish it for a 
Isjrge fraction of its length. The Rhone is charged with it, and 
tens of thousands of acres of cultivable land are formed by it 
above the Lake of Geneva, In the case of every glacier we have 
two agents at work, — the ice exerting a crushing force on every 
point of its bed whiDh bears its weight, and either rasping away 
this point in powder or tearii^ it bodily fvom the rock to which 
it belongs ; ^diile the water which everywhere circulates upon 
the bed of the glacier continually washes the detritus away and 
leaves the rock clean for further abrasion. Confining the action 
of glaciers tp the simple rubbing away of the rocks, and allow- 
ing them sufficient time to a«t, it is not a matter of opinion, but 
a physical certainty, that they will scoop out valleys. But the 
glacier does more than abrade. Rocks are not homogeneous ; 
they are intersected by joints and places of weakness, which divide 
them into virtually detailed masses, A glacier is undoubtedly 
competent to root such masses bodily away. Indeed th^ a prim 
consideration of the subject proves the competence of a glaeier 
to deepen its bed. Taking the case of a glacier 1000 &et deep 
(and some of the older ones were probably three times thia dep&), 
and allowing* 40 feet of iee to an atmosphere, we find that on 
every square lAch of its bed sueh a gkeier presses with a weight 
of 375 lbs., and on every square yard of its bed with a weight 
of 486,000 lbs. With a vertical piessmre of this amount the 
glacier is urged down its valley by the pressure from behixkl. We 
ean hardly, I think, deny to such a tool the power to exi^avate.. 

While writing these i:«tmarks, I haitre refreshed mv memo^ 
by reference to the paper of Mr. John BaU« pnUisthsd in 
the 2&th volume of th& Phyosef>bieal Magasine (Feb. 1863)* 
Mr. Bairs great ^perienoe of the Alps is sure to render any* 
thing he writes regarding them interesting. I have read Us pap^ 
and att^ded to his su^estions, but I confess I do not see the 
0(^;racy of his arguments. An inspection of the map of Switzer- 
land, with reference to the direction of its vaUeys, suggests to my 
mind no objeotion to the theory of erosion. The perusal of the 
paper has assured me that Mr. Ball has paid attration to the for* 
mation of ancient lakes. He deems their beds a prominent feature 
of Alpine valleys; and he considers the barriers which dammed 
them up, and wnich were not removed by the ancient glaciers^ as ^^a 
formidable difficulty in the wayof Prof.Tyndaira bold hypothesis/' 
'' liooking at the operation as a whole,'' writes Mr. Ball, <^it ia 
to me quite inconceivable that a glacier should be competent tei 

Phil. Mag. S. 4. Vol. 28. No. 189. Oct. 1864. T 



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266 Prof. Tyndall on the Conformation of the Alps. 

scoop out valleys a mile or more in depths and yet be unable to 
remove the main inequalities from its own channel." Assuredly a 
glacier is competent to remove such barriers, and they probably 
have been ground down in some cases thousands of feet. But 
being of more resisting material than the adjacent rock, they are 
not ground down to the level of that rock. Were its bed uniform 
in the first instance, the glacier would, in my opinion, produce 
the inequalities which Mr. Ball thinks it ought to remove. I 
have recently had the pleasure of examining some* of these barriers 
in the company of Mr. Ball ; and to me they represented nothing 
more than the natural accidents of the locality. It would, I think, 
be far more wonderful to find the rocks of the Alps perfectly 
homogeneous, than to find them exhibiting such variations in 
point of resistance as are actually observed. 

The question of lake-basins is in competent hands ; and on 
its merits I will at present offer no opinion. But I cannot 
help remarking that the dams referred to by Mr. Ball furnish 
a conclusive reply to some of the arguments which have been 
urged against Prof. Ramsay's theory. These barriers have been 
crossed by the ice, and many of them present steeper gradients 
than Prof. Ramsay has to cope with in order to get his ice out 
of his lake-basins. An inspection of the barriers shows that 
they were incompetent to embay the ice : they are scarred and 
fluted from bottom to top. When it is urged against Prof, 
Ramsay that a glacier cannot drop into a hole 2000 feet deep 
and get out again, the distance ought to be stated over which 
these 2000 feet have to be distributed. A depression 2000 feet 
deep, if only of sufficient length, would constitute no material 
obstacle to the motion of a great glacier. With a suitable pres- 
sure from behind, the glacier would assuredly scrape along its • 
bed. The retardation of a glacier by its bed is often referred to 
as proving its incompetence as an erosive agent; but this very 
retardation is in some measure an expression of the magnitude of 
the erosive energy. Either the bed must give way, or the ice 
must slide over itself ; and to make ice slide over itself requires ' 
great power. We get some idea of the crushing pressure which 
the moving glacier exercises against its bed from the fact that 
resistance, and the effort to overcome it, are such as to make 
the upper layers of a glacier move bodily over the lower ones — a 
portion only of the total motion being due to the progress of the 
entire mass of the glacier down its valley. 

The sudden bend in the valley of the Rhone at Martigny 
has been regarded as conclusive evidence against the theory of 
erosion. Why, it has been asked, did not the glacier of the 
Rhone go straight forward instead of making this awkward bend ? 
But if the valley be a crack, why did the crack make this bend ? 



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Prof. Tyndall on the Conformation of the Alps. 267 

The crack, I submity had at least, as much reason to prolong 
itself in a straight line as the glacier had. A statement of Sir 
John Herschel with reference to aaother matter is perfectly ap- 
plicable here : — "A crack once produced has a tendency to run — 
for this plain reason^ that at its momentary limits at the point 
on which it has just arriyed^ the divellent force on the molecules 
there situated is counteracted only by half the cohesive force 
which acted when there was no cracky viz. the cohesion of the 
uncracked portion alone '' (Proc. Roy. Soq. vol. xii. p. 678). To 
account for the bend, the adherent of the fracture theory must 
assume the existence of some accident which turned the crack at 
right angles to itself; and he surely will permit the adherent of 
the erosion theory to make a. similar assumption. The influence 
of small accidents on the direction of rivers is beautifully illus- 
trated in glacier streams, which, on slopes of equal inclination, cut 
either straight or sinuous channels, the determining causes being 
apparently of the most trivial character. In his interesting paper 
'' On the Lakes of Switzerland,^' M. Studer refers to the bend of 
the Rhine at Sargans in proof that the river must there follow a 
pre-existing fissure. I made a special exfiedition to the place this 
year ; and though I felt that M. Studeir had good grounds for the 
selection of this spot, I was unable to arrive at his conclusion 
as to the necessity of a fissure. 

In the interesting volumie recently published by the Swiss 
Alpine Club, M. Desor informs us thai the Swiss naturalists 
who met last year at Samaden visited the end of the Morte- 
ratsch glacier, and there convinced themselves that a glacier had 
no tendency whatever to imbed itself in the soil. I scarcely 
think that the question of glacier erosion, as applied either to 
lakes or valleys, is to be disposed of so easily. My experience 
regarding the Morteratsch glacier shall now be recounted. I 
this year took with me a theodolite to Pontresina, and while 
there had to congratulate myself on the invaluable aid of my 
friend Mr. Hirst, who in 1857 did such good service upon the 
Mer de Glace and its tributaries. We set out three lines across 
the Morteratsch glacier, one of which crossed the ice-stream 
near the well-known hut of the painter Georgei, while the two 
others were staked out, the one above the hut and the other 
below it. Calling the highest line A, the line which crossed 
the glacier at the hut B, and the lowest line C, the following are 
the mean hourly motions of the three lines, deduced from obser- 
vations which extended over several days. On each line eleven 
stakes were fixed, which are designated by the figures 1, 2, 3^ 
&c« in the Tables. 



T2 

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288 Prof. Tjndall on the ConformaHm of the Alpt. 

MorUratteh Glacier, Line A. 

Na of (take. Howfy motioii. 

1 0-35 inch. 

2 049 „ 

8 0-53 „ 

4. 0-54 „ 

5 066 „ 

6 0-54 „ 

7 0-52 „ 

8 0-49 „ 

9 0-40 „ 

10. 0-29 „ 

11 0-20 „ 

As in allother measorements of this kind, the retarding infloence 
of the sides of the glacier is manifest : the centre moves with the 
greatest velocity. 

Merteratteh Cflaeier, Line B. 

No. of (take. Hourly motion. 

1 0-05 inch. 

2. 014 „ 

8 0-24 „ 

4 0-32 „ 

5 0-41 „ 

6. 0-44 „ 

7 0-44 „ 

8 0-45 ;^ 

9 0-43 „ 

10. 0-44 „ 

11 0-44 „ 

The first stake of this line was quite close, to the edge of the 
Racier, and the ice was thin at the ^lace, hence its slow motion. 
Crevasses prevented us from carrying the line sufficiently far 
across to render the rctardaticm of the further side of the glacier 
fully evident. 

Morteratich Glacier, Line C. 
Nq. of stake. Hourly motion. 

1 0-05 inch. 

2 0-09 „ 

3 0-18 „ 

4. 0-20 „ 

5 0-25 „ 

.6 0-27 „ 

' 7 0-27 „ 

8 0-30 „ 

» 0-21 „ 

10. . . . , . . 0-20 „ 

11. . . . •. -. . 016 „ 



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Prof, Tyndall on the Conformation of tie Afys. tW 

Comparing the tbtee lines together^ it will be observed that 
the velocity diminishes as ve descend the gkeier. In 100 hours 
the iiiaadmumiDOtionctf the tharee lines respettivdyis as follo«rB>^ 

Maximum Motion in 100 houri. 

Line A 56 inches. 

w B 45 „ 

>, C 80 „ 

This deportment eitplauors am appearance which must strike 
every observer who looks tipon this .glacier from the Pitz Lan- 
guard^ or from the new Bemina Boad. A medial moraine runs 
along the glacier, commencing as a narrow streak high up ; but 
towards the end the moraine extends in width, and finally 
quite covers the terminal portion of the glacier. The cause of 
this is revealed by the foregoing measurements, which prove that 
a stone on the moraine where it is crossed by the line A, ap- 
proaches a second stone on the moraine where it is crossed by 
the line C with a velocity of 26 mches in 100 hours. The 
moraine is in a state of longitudinal compressidn. Its materials 
are mo^e and more crowded together, and must consequently 
more laterally ^nd render the morldne at the terminal portion 
of the glacier wider than above. 

The motion of the Moiteratsoh glacier, then, diminishes as We 
descend. The masamum motion of the third line is 80 inches 
in 100 hoitfs, or 7 inches a day^-^a yery slow motion ; and had 
we run oar lines iiearer to (he end of the glacier, the motion 
WGKild have beeh sl<ywer stilL At the end itself it is nearly 
iBsensiUe. Now I submit that this is not due placci io seek flair 
the fittoopkig power of a glacien ¥he opinion appealt te be pve-. 
valent tbi^ it is tbe^mout of a glacier ihat Inust act die part 
of pkmgiMishiMj and it is certainly an erroneous ^inioiu The 
scooping fmrtt will exert ftself most Shells die wei^iit, and 'coii<> 
sequently, oftheir things bdtig equal, Ae taotaon is gr^tritest^ A 
glacier's snout often re^U upon ^natter whiek has been scodDed 
from the ^cier^s bed higher up. I tfaepcAm do not think snat 
the inspection of What the end of a glacier does or does not 
accompHsh can decide this question. 

The fifnovt of a glacier is pcrten^ %o reinov« anything against^ 
which k can fi^ly abut; and this imwa*^ notwithstmidiDg the 
slowness of the motion, manife^ itself at the end of the Mor* 
teratsch glacier. A hilfed^, bcttffing pine trees, was in 'front of 
tlie glacier wh^n Mt. Hirst and myself inspected its end ; and this 
hillock is beifng bodily removed by the thru»t of the ice^ Several 
of the treens are overturned ; and in a few years, if the glacier 
eofntinnes its related advance, the mound w^ certaiiily be 
plot^hed away* 



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270 Prof. Tyndall on the Conformation of the Alps. 

I will here add a few measurements executed on the Rosegg 
glacier: the line was staked out across the trunk formed by 
the junction of the Bosegg glacier proper with the Tschierva 
glacier, a short distance below the rocky promontory called 



Rosegg Glacier. . 

No. of stake. < . . c ^ourly motion. 

1 • . 001 inch. 

2 005 „ 

8 007 „ 

4. ..... . 0-10 „ 

5 Oil „ 

6 018 „ 

7 014 „ 

8 0-18 „ 

9 0-24 „ 

10 0-28 „ 

11 0-24 „ 

This is an extremely slowly moving glacier; the maximum 
here found hardly amounts to 7 inches a day. Crevasses pre- 
vented me from continuing the line quite across the glacier. 

To return to the question of Alpine conformation, — ^it stands, 
I think, thus : — We have, in the first place, great valleys, 
such as those of the Rhine and the Bhone, to which we might 
conveniently give the name of valleys of the Ist order. The 
mountains which flank these main valleys are also cut by lateral 
valleys which run into the main one, and which may be called 
valleys of the 2nd order. When these latter are examined, 
smaller valleys are found running into them, which may be called 
valleys of the 8rd order. Smaller ravines and depressions, again, 
join the latter, which may be called valleys of the 4th order, and 
so on until we reach streaks and cuttings so minute as not to 
merit the name of valleys at all. At the bottom of every valley 
we have a stream, diminishing in magnitude as the order of the 
valley ascends, carving eternally at the earth and carrying its 
materials to lower levels. We find moreover that the larger 
valleys have been filled for untold ages by glaciers of enormous 
dimensions, and that these glaciers were always moving, grinding 
down and tearing away the rocks over which they past. We 
have, moreover, on the plains which extend at the feet of the 
mountains, and in enormous quantities, the very matter derived 
from the sculpture of the mountains themselves. The plains of 
Italy and Switzerland are cumbered by the debris of the Alps. 
The lower, wider, and more level valleys are also filled to 
unknown depths vidth the materials derived from the higher 



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On the Expanmn of Gases by increase of Temperature. 271 

ones. In the vast quantities of moraine-matter which cum- 
ber many of the valleys we have also suggestions as to the 
magnitude of the erosion which has taken place. This moraine- 
matter^ moreover^ is only in part derived from the falling of 
irocks from the eminences upon the glacier \ it is also in great part 
derived from the grinding and the ploughing-out of the glacier 
itself. This accounts for the magnitude of many of these ancient 
moraines^ which date from a period when almost all the moun- 
tains were covered with ice and snow, and when consequently the 
quantity of moraine-matter derived from the naked crests cannot 
have been considerable. The erosion theory ascribes the forma- 
tion of Alpine valleys to the agencies here briefly referred to. It 
invokes nothing but true causes. The artificers by which its 
work is performed are still there, though, it may be, in dimi- 
nished strength ; and if they are granted sufficient time, it is 
demonstrable that they are competent to produce the effects 
ascribed to them. And what does the fracture theory offer in 
comparison ? From no possible application of this theory, pui:e 
and simple, can we obtain the slopes and forms of the moun- 
tains. Erosion must in the long run be invoked, and its power 
therefore conceded. The fracture theory infers from the dis- 
turbances of the Alps the existence of fissures; and this is a pro- 
bable inference. But that they were of a magnitude sufficient 
to determine the conformation of the Alps, and that they fol- 
lowed, as the Alpine valleys do, the lines of natural drainage of 
the country, are assumptions which do not appear to me to be 
justified either by reason or by observation. 
Roval Institution, 
September 1864. ^ 

P.S. — ^The foregoing paper was in the printer's hands before 
it was my privilege to read the last Anniversai^ Address to the 
Geographical Society by its President, Sir Roderick Murchison. 
I have since considered the arguments, and given, I trust, due 
weight to the authorities urged and cited in that excellent Address 
against the theory of erosion, as applied to the vaUeys of the 
Alps, fiut the effect on my mind is not such as to induce me 
to alter the opinions, based on observed facts, which I have ven- 
tured to express in these pages. 

XXXI. On the Law of the Expansion of the Gases by increase of 
Temperature. By Professor Potter, A.M.* 

IN the theory of heat, the law of the expansion of the gases 
by increase of temperature is a most important subject, not 
only on account of the air-thermometer having been taken as the 
* Communicated by the Author. 



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272 Prof. Potter an the Law of the Expanrian 

Btandard to wfaieh the liquid and solid thermometers irere torn* 
pared^ but also with respeet to the chemical hypothesk of equi- 
valent oombining-Tolvunes of gases. 

The laws of the expansion of the gases by eqtiid inerements, 
proposed by Oay-Lnssac^ and of uniform eitpansion^ proposed by 
Dalton, give results which differ very little between the points of 
the freezing and bmling of water^ but they diverge greatly at 
higher temperatures. Dalton's law^ esrpressed in the formula 
VssVq.c****, where V is the volume of a gas at /^ above the 
zero-point of the thermometric scale, and Vq the volume at die 
zero of the scale, had a greater primd facie claim to be considered 
a physical law than that of Gay-Lussac, of which the formula is 
y=VJl-f aO> because, the expansion for one degree in the 

V —V 
latter being --^ — - ^», obtained by putting f^l^, we do not 

see why any temperature for a gas may not be taken as reason- 
ably as the freezbg-point <tf water^ and that generally -e^ «<«££= 

constant : then integrating we obtain for Daltoii^s law Vst Vq.€*^ ; 
and expanding we have 

V^V^=:V„(l + -^+f5 + ^3+&c.). 

By stopping at the term with the first power of ^^iA-q on . 
Fahrenheit's scale nearly, we have Qay-Lussae*s law. Never* 
thetess I now think that Gay-^Lussac's law is a nearer approxi^ 
mation than Dalton's in ordinary temperatures, «md a very much 
nearer one for high temperatures. 

The important experiments of M. Regnautt show that the 
coefficient of expansion for air increases with Uie densi^, *or as 
the molecules are nearer together*. Carbonic acid gas exhibits the 
same property still morestvongly, -and sulphmrousadd gas -shows 
it in a still higher degree* The expansion or value of « for the 
interval betwe^i the freesing-and boiUng-p<Hnts of water at 
ordinary atmospheric pressure for carbonic aoid gas bei»g '&7099, 
it becomes *38455 at a pressure of rather more than three atmo* 
spheres; whilst hydrogen gas shows no reliable variation. 

Now as the atoms of a gas approach each other when the 
temperature is diminished, we have a right to expect the same 
result at lower temperatures at the same pressure : and 6ay- 
liUSdac's law gives such a result : for the constant increment 

V —V 
«=— ^— -fibears asmallerratioto the actual volumeV=VQ(l -huf) 

"o 
as the degrees f^ are increased, and a greater ratio as the degrees 
— /° are more below the freezing-point of water. 

♦ Relation des Bap&tences, &c., vol. i. p. 110, 



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iff the Gas^B hy increeae t>f Temperature. 



1878 



The idMhermometer beiiig tdkeu as thie i^tandftr^^ we ale not 
able to employ it toshoir its own-eirors, btit must have recourse 
to the liquefiable gases/'Wfaere the deviation Irom Gay-Lussae's 
law beeomes veiy great compared with that of aii*^ and will con- 
sequently be well ascertained by taking the air-thermometer as 
exact in the first instance, and afterwards attributing to air the 
same law, with different constants, as that found for the lique- 
fiable gas. In this manner we shall find that the air-thermo- 
meters must give place to a th^nlometer formed with hydrogen 
gas, or the mercurial thermometer accurately graduated for the 
law of uniform expansion, or otherwise for low temperatures the 
spirit-thermometer accurately graduated according to the law of 
the hyperbolic expansion of alcohol, wheti critically elEact tempe- 
ratures are required to be known. 

M. Regnault found'*' that a thermometer formed wi^ sulphu- 
rous acid gas, on being compared with an air-thermometer, gave 
the foUowing results for the mean value of a for Centigrade 
degrees ; — 

From 6 Centigrade to 98a2 C. the mean value of a =003825 1 
102-45 „ „ ±=0038225 

185-42 ^, „ =-0037999 

1267-17 „ „ =-0037923 

299-90 „ „ =-0037913 

310-31 „ „ =0037893 

In seeking lot the law 
which will mchide these 
results, we shall find that 
they conform to a hyper- 
bobc law of expansion; 
andOay-Lussac's law arises 
from taking at great dis- 
tanocB from the centre 
the asymptote of the hy^ 
perbola for the arc; and 
thus Gay-Luseac's law be- 
comes an exceedingly near 
approximation for hydrogen gas, and a very near one for oxygen, 
nitrogen, and atmospheric air. 

To apply the equation of lihe hyperbola to the results for sul- 
phurous acid, in the figure Jet Cd?, Cy be the axes of coordi- 
nates to the origin C as centre of the hyperbolic are PAP'; let 
C T, C T' be the asymptotes ; let be any origin from which 
the tempertCtttres are represented along the axis of 4?, whUst the 

♦ Relation des Experiences, &c., vol. i. pp. 188, 189, 



» 


}} 


V 


i) 


i> 


a 


ii 


n 




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274 Prof. Potter on the Law of the Expansion 

volumes of the gas are represented by the ordinates^ as P M=y 
when C M = 0?. Let C A = a = semi-major axis of the hyperbola^ 
CO=»i, and OM=a/ the temperatures f on the Centigrade 
scale^ so that xssm+af; then, the equation of the hyperbola 
being 

J* 
we have to find from three conditions the values of -^, m, and a^. 

Now, taking the volume of the gas at the freezing-point of 
water, and (represented in the figure hjpO =yo) as 100 measures, 
and OM^tai' being the Centigrade degrees, we have, if PM =y, 
j« 



and similarly 



y«=^((m+*')«-««). 



which by eliminating give 

y_ a^(y«-yo«)-j/(y'«-yo«) 

Calculating the volumes yj, y,, ys • • • ye from M. Begnault's 
values of a at the Centigrade temperatures x'„ af^ ^s • • • ^6> ^® 
have as follows : at 

»*,= 98-12 C. then y,=yoX 1-87532, 
«'j= 102-45 „ ya=yoX 1-39162, 



«'8= 185-42 



jp'4= 257-17 
a^6= 299-90 
a^6=810-31 



ya=J'oXl'''0458, 
y4=yoX 1-97527, 
y5=yoX 2-13701, 
ye=yoX2-17586. 



Taking x'^t/g, a/, y,, a^^y^ to determine the constants -^ m, and 
a% we find 

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of the Gaset by mereate of Temperature, 275 

T = -18918, and -=-8780, 

TO=277-464, 

fl«=5111-2, and a=71-492. 

Applying these to find the remaining values of y by the equation 
of the hyperbola, we have 

yo=100 
y,= 187-588, 
y,= 189-176, 
y8= 170-584, 
^4= 197-628, 
y5=218-700, 
ye=217-613, 

and we see that the ordinates of the hyperbola furnish volumes 
as near to M. Begnault's experimental results as can be expected. 

The value of- =-8780 is trig, tangent of the angle which 

the asymptote makes with the axis of x, and is the extreme 
value of «, which we see is not the same as for other gases, 
which M. Begnault expected* might be the case in the lifnit for 
very high temperatures, or in the state of extreme dilatation. 

By dSJSerentiating the equation of the hyperbola to the centre 
as origin, or 






f="-.{w*-a% 



we have 



and when *==+«, then ^ = infinity ; and this must be at the 

point of liquefaction of the gas^ which^ when known under a 
given pressure^ will give an important datum^ and probably much 
more accurate than can be found from the discussion of experi- 
ments like the preceding. When a?= infinity, we have ^ = -, 

which equals a in Gay-Lussac's law. The law of Amontons 
being expressed in the form j?«Acp(l4-a/°)> D^^st be received 
as the true law within the limits of accuracy which can be attri- 
buted to the laws of Boyle and Gay-Lussac^ of which it is com- 
pounded, but it is not an absolutely exact law for any gas. 

* Bjelatwn des Experiences, &c, vol. i. p. 120. 



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[ 276 ] 

XXXII. On MolenfUlar Physics. By Prot W. A. Nokton. 

[Continued from p; 204J| 

Molecular C<mstiMi(m and M^hanicai Properties of Bodies. 

Tj^ VERY body of matter consists of separate partidle&, or mok- 
JC^ cules in a state of equilibrium under the action of the forces 
proper to the particles^ or of these in connexion with extraneous 
forces taking effect upon the pstifticles. The interstices between 
the molecules we cfonceive to be pervaded by both the electric 
and the universal aether^ having probably different densities in 
different substances. The state of equilibrium in which each 
particle of the mass subsists^ implies that the effective forces 
acting upon it, from opposite sides, are equal and directly op- 
posed, or else that the effective fordes of each side are equal to 
zero. The different mechanical properties of different sub* 
stances may be ascribed,, primarily, to differences in the value 
of the ratio of the constants of electric attraction and repulsion 

f , in Table I. j; and to a certain extent also to differences in 

the size of the molecular atmospheres, upon which the value ot 

k in Table I. partly depends. In oonsequenee of these sup- 

n 
posed differences in the value of the ratio -, each substance 

should have its own special curve of molecular action. It is 
natural to suppose that the con^nt n ctf the force of attraction 
exerted by the atom upon its atmosphe^ would in general increase 
with the mass of the atom, and so that the force of cohesion would 
be greatest in those substances whose atomic weights are the 
greatest. But as we cannot affirm that the weight of an atom 
must necessarily be proportional to the force of attraction ex- 
erted by it upon its electric atmosphere, and as the constant m 
may also be subject to variations, substances of nearly equal 
atomic weights (^. g,, gold, platinum,, bismuth, and lead) may 
have different properties. 

The molecules of a substance in the solid state may be aggre- 
gated together as a homogeneous mass, or in groups more or less 
complex. The meehamicsd properties of the mass vary with the 
mode of aggregation. The form of aggregation assumed, in the 
process of solidification, depends upon the circumstances, with 
respect to cooling, pressure, fee, under which the solidification 
occurs. The effect of the same circumstances should vary with 
different substances, with their properties in relation to heat ; but 
these properties are primarily dependent upon the general fea* 
tures in the constitutioto ana condition of the molecules, upon 



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Prof. Norton on Molecular Phyrios. 977 

which the laws of effective moleeiUar action^, as shown by the 
proper curve^ depend. 

Contemplating from our present point of view the varying 
mechanical states and conditions which the same substance may 
assume under different circumstances^ we are led to recognize^ as 
an essential phyaical feature, upcm which such changes eithctr 
wholly or partiiUly depend, the fact that the mechanical condi- 
tion of the individual molecules is not filled and nnchangei^ble, 
but liable to material variations. We perceive their atmo-* 
spheres, expanding under the influence of be^t, and contracting, 
from the effect of eiiternal pressure, and that certain phenomena 
and permanent changes of property result from these atmospherics 
changes {e. ff. changes of propei-ty in passing from the solid 
to the liquid form, or vice ver^; permanent displacen^ent of 
particles produced by the temporary action of forces of a cej% 
tain intensity upon bodies). 

States of Aggfregation of Matier. — ^These are three essentially 
different states of equilibrium. In the solid form^ the particles 
immediately contiguous to each other are in a condition of equi- 
librium under the action of their own molecular forces j- if more, 
distant partides exercise any effective action, it is attractive, and 
neutralised bv a similar action on the other side of the particle. 
To be more definite, each molecule of the mass is surrounded 
by others at various orders of distance from it ; and each pair 
of molecules at the first order of distance from each other are in 
a condition of equilibrium by themselves^ which is equivalent to 
saying that their electric atmospheres are separated by the distance 
Oa, fig. 1 (p. 203). For the second order of distance the action 
should then be attractive; but it may very well be that when a 
permanent equilibrium of the mass has b^n reached^ th^ atmOr- 
spherea of two particles at this order of distance will be SQ exr 
panded by their attractive action^ on the line of their ceiktrea^. 

that, for the diminished value of - thus resulting, the distance 

tn 

between the atmospheres on this line will be the increased dis«^ 

lance Oa for the curve conesponding to this diminished value of 

\ Upon this supposition, each particle would be separately in 

equilibrium with every particle contiguous to it, both at the first 
and second order of distance. We shall have occasion to note 
hereafter that this state of things is probably more or less perfectly 
realized under different circumstances of solidification. As to 
the action of more distant molecules, it is first to be observed 
that, if two molecules are in equilibrium under their mutual 
actions^ the attractive and repulsive impulses exerted by each 
upon the central atom of the other miist be equalii and thei?efor^ 



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278 Prof. Norton an Molecular Phyrie9. 

that no effective action^ either attractiye or repulsive, can be 
transmitted to other more distant particles on the same line. 
Under these circumstances^ one molecule, in receiving the action 
of another, intercepts the action that would otherwise take effect 
upon other more distant molecules. This being admitted, it 
may be perceived, on examining Table I., that the attractive 
actions of particles which lie beyond the second order of distance 
from a given particle, will be in a great measure intercepted by 
intervening particles. . In what has now been stated with respect 
to the solid condition, we have had in mind a homogeneous mass 
of molecules only. We cannot here enter upon the considera- 
tion of the case in which the molecules are aggregated into groups. 
In the liquid state, the contiguous particles repel each other; 
and particles more chstant exert no sensible action, or a feeble 
attractive one. Here, as in the case of a solid, the sensible 
action is confined chiefly to particles that lie at the first and 
second orders of distance. These remarks apply to the general 
mass of the liquid. The molecular atmospheres are in an ex- 
panded condition from the effect of the heat of fluidity; and it 
is from this fact that the peculiar properties of the liquid state 
result. As we draw near the surface of the liquid, the atmo- 
spheres are in a condition of greater and greater expansion as 
the necessary result of the process of liquefaction, and therefore 
their proper attractive actions are less and less. From this 
cause it happens that each particle near the surface is more 
effectively attracted by those below it, beyond the first order of 
distance, than by those above it, and thus each layer of parti-^ 
cles is compressed upon that immediately below it ; also to a 
certain depth more particles will exert their attraction from below 
than from above. As a consequence, the density must increase 
from the surface to a certain small depth below it, and a force of 
compression be exerted throughout the whole liquid mass. This 
force determines, and is in equilibrium with, a mutual repulsion 
between the particles of the liquid. From the essential nature 
of a liquid, as we shall soon see, this increasing molecular repul- 
sion, from the surface downward, operates in all directions from 
each molecule, and so tends to neutralize the attractive actions 
between molecules separated by the second order of distance ; 
as the final result, therefore, at the depth at which the density 
ceases to increase, and all greater depths, the action between two 
such moleules should be either feeoly attractive, or altogether 
evanescent*. 

* The theory of the existence of a (ontractile force at the siufEtceof a 
liquid, as the result of molecular action, was advocated by Young and 
Poisson, and employed by them in explanation of the phenomena of capil- 
larity. It has also been ably sustained and illustrated by Professor Henry 
by many ingenious experiments. 



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Prof. Norton an Molecular Physics. 279 

The views which have now been presented enable us to form 
a definite conception of the probable arrangement of the mole- 
cules of a liquid. If the state of equilibrium be such as we have 
represented, we must conclude that a perfectly symmetrical ar- 
rangement of particles, similar to that which subsists in crystals, 
prevails throughout the whole mass. 

We conceive the fundamental distinction between a solid and 
a liquid, from the mechanical point of view, to be that the exter- 
nal impulses which fall upon the molecule of a solid, are propa- 
gated, either wholly or chiefly, in their original line of direction ; 
while those which fall upon the molecule of a liquid are radiated 
in every direction from it. The physical cause of this differ- 
ence in the mode of propagation of a force appears to be the 
simple fact that in the process of liquefaction the molecular 
atmospheres are forced by the heat of fluidity to a decidedly 
greater distance from the atoms which they surround; thus 
leaving below them a much larger volume of universal aether, to 
receive the impulses propagated down to it. If this difference 
between the mode of propagation of impulses by the molecules 
of a solid and liquid be admitted, it is not difficult to see that 
we have a sufficient cause for the different mechanical properties 
attendant upon these two states of aggregation, without having 
recourse to the prevalent idea of a permanent polarity of simple 
atoms. So far as any polarization of molecules comes into ope- 
ration, we shall have occasion to remark, in discussing briefly 
the topic of crystallization, that it is simply an induced, and for 
the most part a temporary condition of the molecular atmo- 
spheres, developed in the act of solidification. 

In the aeriform state the particles are so widely separated that 
each is repelled by all those which surround it, within the limit 
of effective action, and the equilibrium is determined by external 
pressure. The properties of gases and vapours, and the laws 
of their expansion and contraction, are deducible from equation 
(3), p. 200. The value of x that obtiEuns when a vapour formed 
at any temperature has its maximum tension, is the distance 
Od, fig. 1, answering to the maximum molecular repulsion dn ; 

and this varies for different temperatures, because the ratio - 

m 

decreases as the temperature rises. (See different values of 

maximum repulsion answering to different values of the ratio 

~ given in Table I., p. 200.) 

The process of transition from the solid to the liquid state 
occurs at the surface of the mass. As the heat is absorbed, the 
molecules near the surface recede from each other; and when 
this expansion has reached a certain point, the attractive forces 



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880 Prof. Norton m Molecular PHyries. 

of the particles at the different orders of distance come sneces- 
sively into action^ being less intercepted by intervening particles. 
At the same timei the individual molecul^ atmospheres expand,, 
or recede from their central atoms, under the action of the heat., 
pulses that penetrate to these atoms; and so the energy <^ the 
attractive force of each of these molecules declines, l^e sur« 
face particles will thus oontinue to recede at the same time that 
they are restrained by the attractions of those below them. 
This effect wiU extend from the surface downward; and as a 
final result, a certain number of layers are brought into the. 
liquid condition, in which, as we have seen (p. 278), the particles 
mutually repel eaek other, in consequence of the exertion of a 
compressing force at the surface. In the case of a liquid that 
emits vapour at the temperature of liquefaction, we must con- 
clude that the particles at the very surface become ultimately 
sul^ect to an effective repulsion from the united action of those 
below it, which is in eqiuUhrium with the tension of the vapour 
resting on the surface; and that this effective repulsion extends 
to all points above the surface. 

The heat of fluidity is consumed in forcing up the molecular 
atmospheres* A& a fijial result of the lique&ction,. these atmo* 
spheres remain in an expanded condition. The effect of this 
expansion is to diminish^the values of v given by equation (I) 
(see p. 2D0)^ and increase the distance Oa, fig« }. The actual 
distance between two eontiguous atmospheres is less tha^i the 
increased distance Off, by reason oi the compressing f<»roe that 
takes effect throughout the liquid mass. But the ultimate com»r 
pression imparted to the individual atmospheres will depencb 
in a ^reat degree upon the final value of the attractive action 
V between the molecules, wad may therefore still be less than 
tibat which obtdmed in the msiid state. In this diminished) viduc- 
of t^ we have, at the same tim^ the explanation of the 6imu. 
nished force of cohesion attendant upon the liquid state. The 
comparative densities of the liquid and solid also depend upon,' 
Vm For we have just seen that the distance between the eon-> 
t^guous atmospheres of two particles of the liquid is less than 
the increased value of Oa, but this distance may, according to 
the intensity of the attractive force v, be either greater or less 
than the originsl value of Do, which was the distance between^ 
the atmospheres of the same particles in the solid condition* 
Accordingly the liquid may be either more or less dense thaoi 
the solid from which it is derived. 

The passage from the liquid to the. solid state is essentially 
the inverse of that which has just been under consideration, and 
in the general survey we are now taking need not be consiaered 
in detaiU The mass of molecules and their indiyidusl atmp*. 



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Prof. Norton on Molecular Physics. 281 

spheres now contract instead of expanding; and in the final act 
of solidification the contiguous molecules assume the positions 
due to their own special forces. While all this is being accom- 
plished^ the molecular atmospheres contract, and heat is given 
out. 

The explanation of the process of evaporation will be readily 
inferred from what has already been stated with regard to the 
condition of the surface of a liquid (p. 280). The nice equipoise 
of the surface particles may be disturbed either by a slight ele- 
vation of temperature, or a diminution of the tension of the 
vapour resting upon them. The cooling effect of the evaporation 
is to be attributed to the expansion which the electric atmo- 
spheres experience on being freed from the compressing forces 
previously existing*. 

In the process of ebullition, the expansive action of the heat 
absorbed by the lower layers of the liquid increases nntil the 
superincumbent pressure, the cohesive attraction of the vessel 
for the liquid, and the effective attractions subsisting between 
the molecules of the liquid (represented by the ordinates be- 
tween a and i, fig. 1), are overcome. When this point is reached 
at any part of the liquid stratum, the separated particles will 
expand rapidly into bubbles of vapour, in opposition to the 
pressure of the atmosphere, and the attractions denoted by the 
decreasing ordinates between b and c, fig. 1. The expansion 
should continue until the distance between the atmospheres of 
two particles increases to the limit Od, at which the repulsion 
attains to its maximum value ; or rather to a limiting distance 
somewhat greater than Od, at which the repulsion due to the 
heat-pulses present in the molecules, plus the molecular repul- 
sion at that distance, is equal to the external pressure. 

It cannot proceed further than this without a direct expendi- 
ture of heat-force, which will raise the temperature of the vapour. 
The heat which becomes latent, as the phrase is, is expended in 
the act of expansion, and in forcing up the molecular atmo- 
spheres in opposition to the attractive action of the atoms and all 
compressing forces. The amount of work thus taken up by the 
atmospheres manifests itself also as work of expansion, since it 
is so much work of the atomic attraction and of the compressing 
forces, neutralized. When the heat-pulses are not wholly ex- 

♦ It is apparently not necessary to suppose, as has been done on p. 280, 
that the tension of the vapoiur resting on the surface of a liquid, when at 
its maximum, is in equilibrium with the outward repulsion experienced by 
the outer layer of liquid particles. The equilibrium may be a dynamical 
one, the vapour may be continually rising at certain points of the surface 
and continually passing back into the liquid condition at other points, 
the condensation compensating exactly for the evaporation. 

Phil. Mag. S. 4. Vol. 28. No. 189. Oct. 1864. U 



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Dr* Bankine on the Properties 

pended in this manner, a portion of them pass into the mole« 
cular atmospheres and elevate the temperature of the liquid. If 
the pressure upon the free surface of the liquid exceeds the 
pressure of the atmosphere, the molecular atmospheres are more 

compressed, the value of m becomes greater, and the ratio — 

diminishes in consequence ; from this cause the limit of the re- 
cess of the particles (Od, fig. 1) diminishes, and the maximum 
repulsion dn increases (see Table I.). The resulting vapour has^ 
therefore, at the same time a higher tension and a greater 
density. 

According to the theoretical views now advanced, the '^ inte- 
rior work " which Tyndall maintains is expended in the act of 
liquefaction, and also in that of vaporization, in *' moving the 
atoms into new positioos,'' or in conferring " potential energy '' 
upon them, is consumed in each instance in pressing up the 
electric atmospheres that surround the atoms of the substance ; 
and heat disappears in the process in proportion to the effect 
thus produced. 

[To be continued.] 



XXXIII. Summary of the Properties of certain Stream-IAnes. 
By W. J. Macquorn Rankinb, C.E., LL.D., F.R.88Jj.^E.* 

1. nr^HE investigation, of which the present paper is a sum- 
-i. mary, consists of three parts. It is a sequel to one of 
which an abstract was read at the Meeting of the British Asso- 
ciation in 1863, and which has since been printed in ftill in the 
Philosophical Transactionsf. It relates to the paths in which 
the particles of a liquid move past a solid body. In the previotis 
paper (which was confined to motion in two dimensions) those 
paths were called " Water-Lines,'' and were treated of with a view 
mainly to their use as figures for the horizontal or nearly hori- 
zontal water-lines of ships. In the present paper they are called 
" Stream-Lines,'' as being a more general term, and one less liable 
to be misunderstood when motion in three dimensions is con- 
sidered. 

The term "Neoid" (i^oe^S^?, ship-like) proposed in the pre- 
vious paper as a general name for water-line curves in two di- 
mensions, may be extended to all the stream-lines discussed in 
the present paper; for they are all applicable to certain lines on 
the surface of a ship. 

♦ Communicated by the Author, having been read at the British Asso- 
ciation Meeting, Bath, September 19, 1864. 

t An abstract of that previous investigation appeared in the PhiloiO- 
phical liagaxine for October 1863. 



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of certain Stream^lmes. 283 

Pakt I. — On some Exponential Stream-Lines in two 
Dimensions. 

2. It is well known that amongst the functions which satisfy 
the conditions of liquid motion in two dimensions^ are compre- 
hended all those of the form 

y+S.c*ycosaa?. 
Such functions as the above obviously represent curves ccmsist- 
ing of an endless series of repetitions of the same figure ; and 
many of those curves resemble the profiles of waves. 

8. The first part of the investigation consists of a discussion 
of the properties of the curves represented by the simplest of 
those exponential stream-line functions^ viz. 

J=y— e""*' cosa? (I.) 

By giving to d a set of values in arithmetical progression, this 
function is made to represent a set of stream-lines, dividing an 
indefinitely extended plane layer of liquid into a series of curved 
streams of equal flow. .Each of those stream-lines consists of an 
"endless series of repetitions of the same figure, the length parallel 
to X of each repetition being 27r ; and each repetition consists of 
a pair of symmetrical halves. 

4. The graphic construction of those stream-lines is very 
easy, by the aid of a general method of constructing curves first 
used by Professor Clerk Maxwell, and applied by the present 
author to stream-lines in the previous investigation already 
referred to. 

Draw a series of • straight lines parallel to x, and having for 
their equation 

— the values of m being in arithmetical progression, positive and 
negative, with a fraction for their common difference, which 
should be the smaller the more accurate the dratnng is to be. 
Then draw a series of curves of hyperbolic-logarithmic cosines, 
having for their equation 

e'"^C08a?=m', 

— ^the values of m', positive and negative, forming an arithmetical 
progression, and having the same common difference with those 
of m. The curves with positive values of m' lie between a?=0 

and a?= ^; those with negative values between a?= ^anda?^7r; 

and the straight line parallel to y, at ^r, is an asymptote to them 

all. One and the same mould serves to trace all those curves ; 
for they differ only in the maximum value of y, which is 

U2 



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984 Dr. Bankine on the Properties 

4:hyp. log n/. Then trace a series of curves diagonally through 
the intersections of the network already drawn^ in such a man- 
ner as to make m— »»'=J for each curve; these will be the 
required stream-lines. 

5. The ordinatcs for which a is an odd multiple of ±-^2Lre 

asymptotes to all the stream-lines at the negative side of the 
axis of w, and are also intersected by each stream-line at the 
point where y= J. 

6. Maximum values of y for all the stream-lines occur on the 
ordinates where x has the value 0, or any even multiple of Hhw. 

7. Minimum values of +y and — y occur on each ordinate 
where x is an odd multiple of + tt, but for those stream-lines 
only for which A>1. The stream-lines for which J<1 do not 
intersect those ordinates. 

8. The stream-line for which 6 = 1 consists of an endless 
series of equal and similar curves, each adjacent pair of which 
cut each other at right angles and the axis of x at angles of 45°, 
in the points where x is an odd multiple of ±7r. 

9. Each stream-line for which i<l consists of an endless 
series of equal and similar detached curves, having maximum 
and minimum values of x given by the equation 

cos^=: — e 

10. Each stream-Tihe for which i>l is made up as follows : — 
at the positive side of the axis of x, a continuous curve, present- 
ing an endless series of equal and similar waves ; at the negative 
side, an endless series of equal and similar detached curves. 

11. The wave-line curves thus formed, as they become more 
remote from the axis of x (that is, as b increases), approximate 
more and more nearly to the trochoidal form, which is known to 
be that of free waves in deep water ; and so rapid is that approxi- 
mation, that' though for A=l the diflFerence between the two 
kinds of wave- line is very great, it becomes almost imdistin- 
guishable for 4=1^. 

12. Quantities proportional to the component velocities of a 
particle and to the square of its resultant velocity, are derived 
from the stream-line function as follows : 



db 

= iH-e"ycosa?=l+v— ^. 

(11.) 



«=-7- =H-c~*cos«=l+y— d, 



db 

^y : .; 

tt«+»«=l +3c-» cos ar+c-*' 
=:l+2(y-6) +«-*'. 



J. . . (lU.) 



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of certain Streani'Lifies. 285 

At the point where the curves i==l cross the axis of a?, both 
the component velocities are nuU. The unit of velocity in each 
of those expressions is the velocity of a particle at an infinite 
distance in the positive direction from the axis of x, for which 
particle we have ws=l, t?=0. 

13. Suppose the plane of x and y to be vertical, and ^ to be 
positive downwards ; let the absolute value of the unit of mea- 
sure (that is, the radius of the circle whose circumference is a 
wave-length) be denoted by R; and let the heaviness (or weight 
of a unit of volume) of the liquid be W. Then the stream- 
lines for which b is not less than 1 may represent the profiles of 
a series of forced waves, capable of travelling with the absolute 
velocity 

c= >/^, (IV.) 

being the same with that of free waves of the same length ; and 
the absolute values of the velocities of any particle relatively to 
still water will be 



horizontal component, c(m— l)=-ce""ycosa?; 
vertical component, cr»=— ce'^sina?; 
resultant velocity, c>/|(m— l)*H-t?^| =c^"y. 



(V.) 



14. Those forced waves differ from free waves in the following 
respects. First, in free or trochoidal waves, each wave- surface 
is a surface of constant pressure, so that the upper surface of the 
liquid needs no pressure to be applied to it to compel the waves 
to travel ; whereas in the waves now in question the pressure at 
each wave-surface is not constant, being expressed by the fol- 
lowing formula, 

jp= constant +WJ — , • . . (VI.) 

of which the last term is variable ; and the upper surface requires 
a pressure varying according to this law to be applied to it, in 
order to compel the waves to travel. 

Secondly, free or trochoidal waves begin to break as they 
reach the cycloidal form, in which the surface near the crest is 
vertical, and the crest forms a cusp ; whereas in the waves now 
in question the steepest possible form, which cannot be passed 
without breaking, is that of the stream-line 6=1, whose crest is 
formed by two surfaces meeting each other at right angles, and 
sloping in opposite directions at 45°. Thirdly, the particles of 
water in free waves revolve in circles, and do not permanently 
advance ; whereas the orbit of each particle in the waves now in 
question is an endless coiled or looped curve, in which each revo- 
lution is accompanied by jan advance. The figure of that orbit 



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286 Dr. Bankine on the Properties 

is determined by the ratio which its radius of ciuTatare bears to 
the unit of measure B^ viz. 

The waves whose motion is investigated by Professor Stokes 
in the Cambridge Transactions are of a character intermediate 
between trochoidal waves and those here considered. . 

15. As waves are frequently observed whose figures present a 
general likeness to that now described, it is probable that a pres- 
sure approximating to the law expressed by equation (VI.) may 
be exerted upon them by the wind. 

16. It is evident that a pressure varving according to that law, 
or nearly so, will be exerted by the bottom of a ship upon the 
water, when the figures of the buttock-lines, or vertical longitu- 
dinal sections of her after-body, are exponential stream -lines, or 
trochoidal waves approximating to them, as in Mr. Scott Russell's 
system of shipbuilding. 

Fabt II. — On Lissoneoids in three Dimensions, 

17. The second part of the investigation relates to the mathe- 
matical properties of stream-lines of smoothest gliding in three 
dimensions. The properties of such lines in two dimensions 
were investigated, and the name "Lissoneoids'' proposed for 
them, in the previous paper already referred to. Tlieir essential 
mechanical properties are, to have fewer and less abrupt maxima 
and minima of the speed of gliding of the particles on them than 
on other stream-lines belonging to the same mathematical class, 
and to be the fullest lines of their class consistently with not 
raising moi^e waves than are unavoidable, when they are employed 
as the lines of a ship. 

18. The mathematical condition which such a stream-line ful- 
fils is, that at the midship*section or broadest part of the sohd 
to which the line belongs, two points of maximum and one of 
minimum speed of gliding coalesce into one point. 

19. The investigation shows that the before-mentioned con- 
dition is expressed mathematically as follows, for any stream-line 
which at its greatest breadth is parallel to the axis of a. Let u 
be the longitudinal component, and v and w the transverse com- 
ponents of the speed of gliding of a particle along the stream- 
line ; then at the point where that line crosses the midship sec- 
tion, supposing that we have- v=0, t£;=0, the following equation 
must be fulfilled : 



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Hf certain Stream-Linea., 287 

The oomsponding equation in two dimensions is formed by 
omitting the tem in g. 

Pabt III. — On some Stream^Lines of Revolution. 

20. The third part of the investigation relates to the stream- 
lines in which particles flow past certain totally immersed oval 
solids of revolution, bearing the same relation to a sphere that 
the oval neoids described in the previous paper bear to a circle. 
These lie upon.a series of surfaces of revolution, and are the 
sections of those surfaces by planes passing through the axis. 

21. Let the axis of figure be that of sc, and let there be two 
points in it, called foci, situated at the distances -j-a and —a 
from the origin. The distance a may be cs^lled the excentridty. 
Let the perpendicular distance of any particle from the axis be 
denoted by y; let /be a constant length, called the parameter i 
and let b be the radius of a cylinder which is an asymptote to a 
given stream-line surface. Then the equation of that surface is 
as follows : 

Or, in another form, let 6 and ff be the angles which two lines 
drawn from the given particle to the foci ( + «) and (—a) respect- 
ively make with the axis of -f ^ ; then 

i«=y«-/«(cos(9'-cos(9). .... (X.) 

22. For the primitive oval solid, J=0; and by giving J* a 
series of values increasing in arithmetical progression, a series of 
stream-line surfaces are formed, of gradually increasing width, 
which divide the liquid mass into a series of concentric tubular 
streams of equal discharge. 

23. The graphic construction of the stream-lines is as follows. 
From each of the foci draw a set of diverging straight lines, 
making angles with the axis whose cosines are in arithmetical 
progression, the common difference being a sufficiently small 
fraction. Through the network formed by these lines trace dia- 
gonally a series of curves traversing the two foci. (The equa- 
tion of each of those curves is cos^— cos^=w, and they are 
identical with the lines of force of a magnet having its poles at 
the foci.) Multiply the parameter (/) by the square roots of 
the terms of the arithmetical progression, and draw a series of 
straight lines parallel to the axis and at the distances from it so 
ifbund; these will be the asymptotes expressed by the equation 
6=/v^m. Then through the network formed by those parallel 
straight lines and the before-mentioned series of curves trace 



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28& Mr. P. G. Tait on the History of Thermo-dynamics. 

diagonally a new series of curves^ which will foe the stream-lines 
required. 

24. The stream-lines thus drawn closely resemble those in two 
dimensions, but are somewhat fuller. For those at a distance 
from the axis, the diflFerence of form is scarcely perceptible ; for 
those near the axis, and especially for the primitive oval, the 
greater fulness of form is conspicuous. 

25. The ratios of the component velocities of a particle on a 

stream-line surface of revolution to the velocity of a particle at 

an infinite distance from the disturbing solid are given by the 

expressions 

bdb bdb vvT \ 

tt=^i-: r= -J- (XI.) 

ydy' ydx ' 

26. By applying to those stream-lines of revolution the prin- 
ciples of the second part of the investigation, it is found that the 
radius (J) of the asymptotic cylinder of a lissoneoid surface of 
revolution bears the following relation to the greatest radius (^q) 
of the surface itself, and to the excentricity (a) of the set of sur- 
faces to which it belongs : 

6»=yo«-2(«H,„').^=g. . . (XII.) 

In order that this equation may be real, — must not be less 

/o /4V « 

than a/ _, nor greater than ( ^ ) . The corresponding para- 
meter is found by the general formula 

p^ (yp^-^^) ^a^ + Vo^ (XIII.) 

•* 2 2 
In the oval lissoneoid of revolution, fi*=0, -\ = -—= = 1*1547; 



«* 3 

September 1864. 



and ^-^=.r..^:M^ =0-644. 
«* 3 



XXXIV. On the History of ThermO'dyruimics. 
By P. G. Tait, M.A,, ^c. 

To the Editors of the Philosophical Magazine and Journal* 
Gentlemen, 

I WISH to make a few additional remarks on this subject : 
especially as it appears to me, after a careful perusal of all 
that Dr. Tyndall has written upon it, that he does not yet quite 
understand the points which Prof. Thomson and I wished to esta-^ 



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Mr. P. G. Tait on the History of Thermo-dynamics. 289 

blish when, in conseqnence of his lecture on " Force/' we wrote 
our article in ' Good Words ' nearly two years ago. 

We have all along held that the questions as to the nature of 
heat, and its equivalence to mechanical energy, were settled by 
Davy; and that Rumford experimentally obtained a very fair 
approximation to the equivalent. Also that, as Newton had 
completely enunciated the Conservation of Energy in ordinary 
mechanics, Davy's experiments brought heat under the same law; 
and that, therefore, in the beginning of the present century the 
Dynamical Theory of Heat was completely established, although 
not developed. The development has been since furnished by the 
experiments and reasonings of Joule on Electric Thermo-dyna- 
mics*, his experimental determinations of the mechanical equi- 
valent, his experiments and reasoning on the thermal effects of 
the condensation and rarefaction of airf ; and by the theoretical 
writings of Helmholtz, Clausius, Rankine, and Thomson; 

Hence, so far as regards the question of heat alone, Mayer 
has no title to the position Dr. Tyndall claims for him. He 
did no more than repeat what Davy and Rumford had done 
better ; and he has never, so far as even Dr. TyndalFs partisan- 
ship can show, attempted anything of the nature of either the 
theoretical or experimental developments which have advanced 
thermo-dynamic science during the present century. What, in 
point of fact, did Mayer do in thermo-dynamics ? In 1842 he 
published a paper, of which Prof. Thomson and I remarked as 
follows. "In this paper the results obtained by preceding 
naturalists are stated with precision — among them the funda- 
mental one of Davy — new experiments are suggested, and a 
method for finding the dynamical equivalent of heat is pro- 

* Of these the following are perhaps the most important : — 

" On the Production of Heat bv Voltaic Electricity " (Proc. Roy. Soc. 
Dec. 17, 1840). Printed in Phil. Mag. 1841, with the title " On the Heat 
evolved by Metallic Conductors of Electricity, and in the Cells of a Bat- 
tery during Electrolysis.'* 

" On the Electric Origin of the Heat of Combustion " (Phil. Mag. 1841). 
Extension of the same (Report of British Association, 1842). 

" On the Heat evolved during the Electrolysis of Water " (Lit. and 
Phil. Soc. of Manchester, Jan. 1843). 

" On the Calorific EflFects of Magneto-Electricitv, and the Mechanical 
Value of Heat " (Phil. Mag. 1843). 

"On the Heat disengaged in Chemical Combinations," sent to the 
French Academy in 1846^(Phil. Mag. 1852). 

" On the Mechanical powers of Electro-magnetism, Steam, and Horses," 
by Scoresby and Joule (Phil. Mag. 1846). 

" On the Economical Production of Mechanical Effect from Chemical 
Forces" (Manchester Memoirs, 1852, and Phil. Mag. 1853). 

t " On the Changes of Temperature produced by Rarefaction and Con- 
densation of Air," sent to the Royal Society, June 1844 (printed in Phil. 
Mag. 1845). 



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290 Mr. P. 6. Tait on the History of Themo-Jynames. 

pounded/' To this we added, in a note, at follows. ** Mayer^i 
method is founded on the supposition that diminution of the 
Tolume of a body implies an evolution or generation of heat ; 
and it involves essentially a false analogy between the natural 
fall of a body to the earth, and the condensation produced in an 
elastic fluid by the application of external force. The hypothesis 
on which he thus grounds a definite numerical estimate of the 
relation between the agencies here involved, is that the heat 
evolved when an elastic fluid is compressed and kept cool, is 
simply the dynamical equivalent of the work employed in com- 
pressing it. The experimental investigations of subsequent 
naturalists have shown that this hypothesis is altogether false, 
for the generality of fluids, especially liquids, and is at best only 
approwimately tme for air; whereas Mayer^s statements imply 
its indiscriminate application to all bodies in nature, whether 
gaseous, liquid, or solid, and show no reason for choosing air for 
the application of the supposed principle to calculation, but that 
at the time he wrote air was the only body for which the requi- 
site numerical data were known with any approximation to accu- 
racy.'' To every word of this, with the exception of the word 
''imply," which is not strong enough, I still adhere. Dr. Tyn- 
dall's mode of dealing with it is characteristic. He says — 
''not what Mayer's words 'imply,' but what they are" — ^and 
then quotes, not from the paper of 1843, to which alone we 
referred (as the only one which could have a chance of priority 
over either Joule or Colding), but from a pamphlet published 
in 1845. 

As to the question which might have arisen between S^guin 
and Mayer, supposing nothing to have been done in the matter 
by Davy and Rumford ; everything that was done by Mayer in 
1842 (I still confine myself to the question of Heat alone) was 
done by S^guin in 1839. Dr. Tyndall is correct in his remark 
that Seguin did not, as was originally supposed by Joule, give 
363 kilogrammetres as the dynamical equivalent. But to say, 
as Dr. lyndall does, that '' there is no determination whatever of 
the mechanical equivalent of heat in the above [t. e, S^guin's] Table/* 
is simply an error, for Seguin gives all the requisite data, though 
the thermal unit he employs is by no means convenient. Nothing 
can indeed be more distinct than his evaluation. An hypothesis 
expUcitly stated by him as to the heat of condensation of vapour, 
now known to be wrong and to give much less than the true ther- 
mal efiect, rendered the numbers in his Table largely in error. 
In S^guin's work we find the following passages : — 
" Ceci reviendrait h dire que la vapeur n'est que I'interm^diaire 
du calorique pour produire la force, et qu'il doit exister entre Ic 
mouvement et le calorique un rapport direct, ind^pendant de 



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Mr. P. 6. Tait on the History of ThermO'dynamics. 291 

Pinterm^diaire de la vapeur on de tout autre agent que Von pour- 
rait y substituer/' 

Compare this with Dr. Tyndall's quotation (Phil. Mag. Sept. 
1862). " The law/' says Mayer, " ' Heat = Mechanical EflFect ' 
is independent of the nature of an elastic fluid, which only serves 
as the apparatus, by means of which the one force is converted 
into the other/' 

Again, Seguin says, " La force m^canique qui apparaic pendant 
I'abaissement de temperature d'un gaz commc de tout autre corps 
qui se dilate, est la mesure et la representation de cette diminu- 
tion dechaleur;'' and further, in speaking of steam escaping 
into the air, ^' L'eflFort qu'elle exerce en recul contre les appareils 
qui la laissent ^chapper, ou la vitesse qu'elle communique h Pair 
ambiant, forme un equivalent de la perte de chaleur qu'elle 
eprouve/' Yet, according to Dr. Tyndall, it was Mayer ^' who 
first used the term ' equivalent * in the precise sense in which 
you'' (Joule, to whom the letter is addressed) ''have ap- 
plied it." 

But there is more than this in Seguin's very able work. He 
points out distinctly that steam which has done work in an 
engine ought not to heat the water in the condenser so much as 
if it had been led directly into it. He had made, he says, nu- 
merous experiments to test this, without however obtaining 
sufficiently decisive results. Again, he points out how very 
small a proportion of the heat of the steam is really employed 
in doing work. He says that the work obtained from a steam- 
engine, as ordinarily used, is represented by '^un abaissement 
de temperature d'environ 20°, qui iquivaut au tfentihne environ 
du calorique employe pour rSduire en vapeur Veau nScessaire a sa 
formation J^ That is, only ^th of the heat used, disappears as 
heat, and is given out as work. Thus we see that his 20° repre- 
sent ^th of the latent heat of steam, at 100° C. and at the 
atmospheric pressure : and his Table gives for the corresponding 
work done by a cubic metre of steam (in round numbers) about 
7000 kilogrammetres. Taking 640 as the latent heat, and 0*6 
kilogramme as the weight of a cubic metre, of steam, we have 

80x7000 
for the mechanical equivalent ^r^ — ^^ =650, about 50 per 

cent, too great. 

As to the Conservation of Energy. Dr. Tyndall, in a note to 
his last paper, ascribes the term, or terms, to Rankine. I cannot 
ascertain precisely when the term " Conservation " was intro- 
duced, but it must have been suggested at once to an English 
writer by the old term " Conservation of Vis Viva," of which the 
Conservation of Energy is only an extension. At all events Helm- 



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293 Mr. P. G. Tait on the History of Thermo-dyndrmcs. 

holtz's '^Erhaltung'^ is an identical word^ and was employed 
before Bankitie wrote on the subject. But the term Energy (as 
Dr. Tyndall surely is aware) is due to Young, who introduced it 
as a convenient English term synonymous with vk viva. Its exten- 
sion to. the two forms "static^' and "dynamic'' was made by 
Thomson. Rankine improved these to "potential'' and "actual;" 
and in ' Good Words ' Thomson and I have employed " kinetic " 
as less ambiguous and more suggestive than " actual," 

As to the discovery of the Conservation of Energy, I hold that 
to lay down, without experimental bases, such a maxim as " causa 
aquat effectum^' is entirely subversive of common sense and logic 
in an experimental science such as natural philosophy. The esta- 
blishment of the Conservation of Energy was utterly out of the 
sphere of the "Thinker;" and it would be absurd to give him 
more credit than is due to the promulgator of a clever specula- 
tion. Thousands of equally clever, but less lucky, though not 
more baseless, speculations are every day mercilessly extermi- 
nated by experiment. 

Celestial Dynamics forms no part of the Thermo-dynamic 
theory, though it affords exceedingly beautiful applications of it. 
The same must be said of Animal and Vegetable Physiology. 
Such applications, as is well illustrated by the famous little sen- 
tence of Joule's postscript of 1843, always attend careful work 
at a theory ; they are not discoveries, but inevitable consequences^ 
to the experimental or mathematical investigator. The word or 
two, required to complete the suggestions of Stephenson and 
Herschell, occurred to many minds, merely to be recorded in 
passing — as by Helmholtz in a popular lecture, and by Thomson 
in the proceedings of a society. 

I have written again to the Philosophical Magazine because I 
imagine that Dr. Tyndall still misunderstands the views which 
Prof. Thomson and I maintain on the history of the subject ; 
and that it is this which has led him to charge us with misrepre- 
isentations. His special charges against Prof. Thomson, which 
receive fresh development in every successive article, are so ob- 
viously unfounded that he can hardly be surprised that Prof. 
Thomson has not judged it necessary even to notice them. 

I am, Gentlemen, 

&c. &c., 

P. GuTHKiB Tait. 

6 Greenhill Gardens, Edinburgh, 
September 12, 1864. 



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[ 293 ] 

XXXV. On the Erosion of Valleys and Lakes; a Reply to Sir 
Roderick Murchison^s Anniversary Address to the Geogra^ 
phical Society. By A. C. Ramsay, F.R.S."^ 

AFTER, the publication of my memoir '^On the Glacial 
Origin of certain Lakes in the Ice-worn regions of Europe 
and North America," several eminent British and Continental 
geologists, and some other persons who have only a general 
literary acquaintance with physical geology, did me the honour, 
in special memoirs, or in letters in newspapers, to express opi- 
nions that my views were deserving of the strongest opposition.. 
To none of these opponents have I heretofore made any reply, 
and some of them, I found, were dealt with by men who met 
their arguments more ably perhaps than I could have done 
myself. Besides, I considered that if my theory, as I believe, 
be true, it would be sure in the long run to make its way just 
in the slow and steady manner it seems to me to be now doing. 
We all profess to appeal to nature, and " in nature there is no 
opinion ; there is truth in everything that is in nature ; and in 
man alone is error." To those who are not geologists in any 
practical sense it would never occur to me to reply. Physical 
geology, in the true meaning of the term, does not exist without 
a thorough practical acquaintance with, and experience of, rocks 
of all kinds on a large scale. The man who merely wanders 
about a country and looks curiously at rocks, without a long 
course of severe training, has no more scientific right to form a 
definite opinion as to the causes that brought about the external 
configuration of the land than the father of a family would have 
to decide questions in comparative anatomy, because for half 
his Ufe he had daily carved beef, mutton, pork, fowls, and fish. 

Of late, however, an exceedingly authoritative protest against 
my theory has been entered by Sir Roderick Murchison, in his 
Anniversary Address to the Geographical Society, — an address 
issued indeed to the geologists of Europe ; for the portion that 
bears upon icy phenomena has been printed separately for special 
distribution. It would almost be uncourteous on my part silently 
to pass over the remarks of one who in his own person has 
attained the highest honours in the Geological and the Geogra- 
phical Societies, and who is besides my oldest living geological 
friend. " As a geologist, with wide experience, the President of 
the geographers clearly states his conviction "t that my theory 
of the origin of certain lakes and other theories of denudation 
connected therewith, are so opposed to obvious facts, that, if 
his conviction be well founded, the wonder seems to me that 

* Communicated by the Author. 

t Geological Magazine, No. 3, p. 127. 



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294 Prof. A. G. Bamsay on the Erosion 

any man of weight and knowledge could be found to follow me 
at all. I may therefore be pardoned if in this instance I depart 
from the course of leaving the value of my theory to be worked 
out solely by time. 

I have said that Sir Roderick has entered an authoritative 
protest, because, as several persons have remarked to me, so much 
stress has been laid on the argumentum ad hominem, liberally as 
regards Continental geologists, and more sparingly with Ame- 
rican and English names. Indeed, in reading the Address, I 
was more than once reminded of the observation of one of my 
•opponents, who in the 'Reader* observed to this eflfect, "that 
Professor Desor entirely disagrees with Professor Ramsay — ^how 
can he do otherwise ? for Desor has lived among glaciers all his 
life,'* In like manner Studer and Escher von der Linth, " by 
numerous appeals to nature,'* Gastaldi, De Mortillet, and many 
more are all arrayed in opposition to the theory, the presumption 
being that the chances are therefore infinitely against it, and I 
must needs be wrong because they are so eminent, and some of 
them have lived so long among the Alps. For, differing from 
them, how is it likely that a man can be right who has only ex- 
plored the Alps five or six times with a special object, even though 
he may have spentjfive-and-twenty years on subjects allied to or 
identical with it ? Such is the general impression produced, not 
on myself alone, by many of Sir Roderick's remarks. I have no 
objection to this kind of argument ; it is so old in the history 
of science that its value is understood. To compare great things 
with our small matter, Copernicus and Galileo experienced it, 
Hutton and Playfair knew it well ; the most eminent geologists 
were for long deaf to the voice of William Smith, let him charm 
ever so wisely; and Agassiz himself, in glacial geology, had 
among his chief opponents distinguished seniors, some of whom 
even now only hesitatingly follow him. It is easy to " appeal to 
nature,'* but the language of her reply is not always to be 
understood merely by long poring on her face ; and it generally 
happens that many an abortive effort is made before some happy 
accident reveals the key. 

In my original memoir, when discussing the origin of the lake- 
basins, I found it necessary in some degree to treat of disturb- 
ances of rocks in general. Accordingly, Sir Roderick very pro- 
perly regard^ the question as one not merely of lakes, but as 
involving his belief "with the vast majority of practical geologists, 
that the irregularities of the surface of the Alps havebeen primarily 
caused by dislocations and denudations ;" and again, that " until 
lately geologists seemed so be generally agreed that most of the 
numerous deep openings and depressions which exist in all lofty 
mountains were primarily due to cracks which took place during 



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of ValhyB and Lakes. 895 

the various movements which each chain has undergone at various 
periods" &c» The meaning of this, I conceive to be, that moun- 
tain valleys lie in lines of curvature, dislocation, and fracture, 
and that the mountains on each side of them are mountains, far 
less because of denudation than b^ reason of operations of frac- 
ture and dislocation. Therefore important lakes that fill true 
rock-basins lie only in lines of fracture, or else, as in the myriad 
lak^s of North America, in hollows of wider dislocation somewhat 
aided by subsequent denudations. 

Every reasoning mind respects authority when it bears on 
questions that have been reduced to demonstration ; but this is 
precisely what has not been done with respect to the origin of 
fecial Alpine lakes and valleys by those whose main argument 
is disturbance of strata. Assertions and crude ideas in all kindB 
of books and papers are " as plenty as blackberries ) " but for 
clear demonstrations— none are given. Nor does Sir Roderick 
either attempt or point to any when he says that in the Alps he 
''long ago came to the conclusion that the chief cavities, vertical 
precipices, and subtending deep, narrow gorges, have been ori^ 
ginaUy determined by movements and openings of the crust, 
whether arranged in anticlinal or synclinal lines, or not less fre- 
quently modified by great transversal or lateral breaks, at right 
' angles to the longitudinal or main folds of elevation or depres* 
sion/' Now in my paper I gave six stratigraphical reasons to 
show why the lakes do not lie i"^ hollows of disturbance, and 
then pointed to ice as the only remaining agent by which they 
could be formed, thus attempting to reduce the matter as nearly 
as I could to a demonstration ; and what I want is an attempt 
at demonstration in return. But where is the proof beyond the 
general assertion and impression that craggy-sided mountains 
and valleys prove dislocations which gape. If they were mere 
close or nearly close fractures and denudation did the rest, the 
argument is equally in favour of my view ; for valleys which have 
been scooped out by denudation often necessarily coincide with 
lines of fracture, a proposition obvious to every geologist. But 
I want the proof that the Alpine valleys are dislocations. Let 
any one go into them and prove it in numerous cases, with his 
geological map in his hand, by the arrangement of the rocks on 
either side, and by the fracture or fault visible, or otherwise cer- 
tainly demonstrable in the bottom. Where are these valley faults, 
whose name ought to be legion, marked in the best geological 
maps of Switzerland ? If they exist, they remain yet to be indi- 
cated in definite lines; for indeed none know better than the 
many eminent geologists of Switzerland and the north of Italy, 
for whom and for whose work I have the highest respect, that 
the geological map of their country is as yet but an admirable 



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296 Prof. A. C. Ramsay on the Erosion 

sketch, and in all probability will remain so till their governments 
authorize more general and uniform painstaking surveys. When 
this is done, and when all the faults and curvatures possible are 
actually laid down, and when geological sections on a true scale 
have been run across the Alps, it will then be possible to reason 
with precision on the denudation of the mountains; and it 
will be found (what is well known now) that before the present 
surface of the valleys saw the light, vast piles of strata, as in 
Wales, have been removed by denudation, and the valleys were 
formed long after the latest important distm*bances of the strata 
took place. 

And now to prove that 1 also respect authority, let me quote 
from books of immortal repute ; and surely those who reverence 
authority most, will not disdain that of Hutton and Playfair. 
What say the father of physical geology and his great disciple ? 
'^ If,^' says Hutton, reasoning on this subject, " the valley was 
made for the rain by any other natural cause, either we should 
tell by what means this work had been performed, or all re.ason- 
ing on the subject is at end, and fancy substituted in its place. 
If, again, the river be considered as the means employed by 
nature in making this valley, then all the solid parts between 
the bounding mountains must have been removed.^' Again, 
reasoning on the weathering and erosion that originated the py- 
ramids on and around Mont Blanc, he observes, " It is trjue, 
indeed, that geologists have everywhere imagined to themselves 
great events, or powerful causes, by which these changes in the 
earth should be brought about in a short space of time ; but they 
are under a double deception ; first, with regard to time, which 
is unlimited*, whereas they want to explain appearances by a cause 
acting in a limited time; secondly, with regard to operation, 
their supposition of a great dSbdcle is altogether incompetent for 
the end required .^^ Again, arguing on the approximately hori- 
zontal gneissic strata of the neighbourhood of Monte Rosa, he 
shows that the great isolated peaks have been separated by " the 
greatest degradation, in being wasted by the hand of time. • . • 
Here,^' he says, " is nothing but a truth that may almost every- 
where be perceived " if we had only faculties to perceive it. 

Again, reasoning on strata that correspond on opposite sides 
of valleys, Playfair, in the Huttonian Illustrations, says, '^ there is 
no man, however little addicted to geological speculations, who 
does not immediately acknowledge that the mountain was once 
continued quite across the place in which the river now flows ; 
and, if he ventures to reason concerning the cause of so wonder- 
ful a change, he ascribes it [in the modern fashion] to some 
great convulsion of nature, which has torn the mountain asunder 
* In the original, " limited.". This is an evident misprint. 



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of Valleys and Lakes. 2^7 

and opened a passage for the waters. It is only the philo- 
sopher^ who has deeply meditated on the effects which' action 
long continued is able to produce^ and on the simplicity of the 
means which nature employs in all her operations^ who sees in 
this nothing but the gradual working of a stream^ that once 
flowed over the top of the ridge which it now so deeply inter- 
sects^ and has cut its course through the rock^ in the same way, 
and almost with the same instrument, by which the lapidary 
divides a block of marble or granite/' And in the Alps (p. 122) 
he shows that ^' the sharp peaks of the granite mountains .... 
but mark so many epochs in the progress of decay/' while the 
loftiness of the harder peaks is due not to mere upheaval but to 
the circumstance '^that the waste and detritus to which all 
things are subject will not allow soft and weak substances to 
remain long in an exposed and elevated situation.'' '^Thus, 
with Dr. Hutton (p^ 126), we shall be disposed to consider those 
great chains of mountains, which traverse the surface of the 
globe, as cut out of masses vastly greater, and more lofty than 
anything that now remains." I could multiply sentences of 
this kind from the writings of these great philosophers ; but 
enough has been said to recall to memory the fact that before 
the present race of " practical geologists " had written a line, 
men of rare knowledge, keen sagacity, and the highesit intel- 
. lectual powers, by appeals to nature aJready held- those views 
which some of their degenerate descendants have so readily repu- 
diated, but to which a younger school show strong symptoms of 
returning. I doubt also if some of the Swiss and Italian geolo- 
gists will be quite content to stand godfathers to the opinion that 
the Alpine valleys generally are apt to lie in lines of mere curva- 
ture or fracture, whether close or gaping ; but without further 
authority than that of personal conversation it would be impro- 
per to quote their names. 

Unless 1 were to write a special elementary treatise on denu- 
dation, enough has now been said to show that the theory of 
formation of great systems of valleys by erosion in which water 
and ice are main agents, is not a mere absurdity, and I do not 
therefore care minutely to analyze the assertions that many of 
the Alpine rivers " flow in fissures or deep chasms, . . . which 
water alone never could have opened out;" or again, that the 
Bhine and the Danube " never could have eroded those deep 
abrupt gorges through which they here and there flow, and 
which are manifestly due to original ruptures of the rocks." To 
vthe neglected and even half-forgotten school of Hutton and 
Playfair, and to many expert geologists of the present day whose 
Jives have been spent in practically analyzing the rocky struc- 
tures of countries, the manifest nature of such "origmal rup- 

Phil. Mag. S. 4. Vol. 28. No. 189. Oct. 1864. X 



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898 Frot. A. C^BMBmf an th^Eroiion 

txitm *^ 10 anytlttDg but evident; and I for one belieYe tbat tke 
'' niptHre9^' are only miinifest to those who accept aueh hypotheses 
'^ without iaqoiring ii^to what baa been the former state of thiags^ 
or what will be H^ foture '^ "S To this day there is no error so 
common, eye& among geologists, m that which vagnely atfcri- 
. butes the form and nature of the present surfiioe-oiidines ol die 
earth cbi^y to the operatkni <^ violent disturbance in Fsceat 
geological times, not clearly perceiving that the great a»d small 
outlines of mountain-i^ains, ^ valleys, of river-^gorges and of 
plains are the combined results of an immense number of op«»- 
tions, many of these going back to ezoeedmgly remote periods of 
geological antiquity, and a great proportion of their details being 
Ipst even to probable conjecture* 

These operations, howevi^, in the pisodijietion of scenery mainly 
resolve themselves into d)e following series, the parts of which, 
ever since land and water first existed^ may be arranged in any 
possible combination* 

a. OsinlkUion wik T€9peet to. the^ 8ea4wel afroek$ that have er 
kave not been contorted mdmetamorphoeedf aece^frg^0niedhypiau$es 
in osdUatum of greater or Use duration. 

h. Great pfaine of marine denudations 

c. ^mbaiBrial defwdatiane ef all kMe; u^earifif away qf eeo- 
. cQoets ; 0nd in the interior of the eountry, chemieal deeompo^itiom, 
frost, enouf, toe, tm4, rain, andriverai modified hy height^ land, 
a^nd tie vmous positioner kandness, and other characters of rocks. 

Contortion and metamorpbiftm seem to be essential accompa- 
niments of aU great mountain-chains. It may also possibly 
he proved that in intensely ewtorted r«^ns mountains-chains 
are high or low according to the rqlatiye antiquity of disturb- 
ance, while sometimes the irregular protuberances^ as in the 
Devonian and other rocks of the Bihine and MoseUei have bec^ 
planed away altogether. 

Plajns of marine d^udatiou are sure to be inolkied at a very 
low: angle if formed during slow depression of the land> 

Fu^ber, while the sea helps to make bays, the other agents ^f 
waste enumeiiated above eut out aU mountaiurpeaks not volcanic, 
all the minor valleys, in this term including such vidleys as those 
oi the Alps, the Highlands, Wales, ^., but not such a vaUey as 
the great one that Ues between the Alps and the Jura. 

Frsetures and volcanos, in die production of the great scenic 
futures of continental physical geography, are> as a rule, mere 
subordinate and subsidiary accidents, the first modifying the 
csffects pf denudation by juxtaposition of difierent kinds of rocks, 
and the seccmd (which seem to be connected with general ele- 
vations) forming atccidental mountains, hills, and hUly regions, 
* HiittoB» T(^ ii. p. 257. 



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of VaUetfs wl Lakes. 990 

which, as in the Andes, may form non-essential pi^s of moan«- 
lain^chains. 

I shall now make some remarks on what has been said in ^ 
Address respecting the action of ice in general, and its share in 
forming lakes that are trae rock-basina in particular, taking 
these in connexion with other points at issue. 

^ Before entering on the consideration of the new theory of 
the power of moving ice,'^ Sir Bodarick gives a brief review nf 
the recent progress of Alpine glacial geology, meaning by recent 
principally those t wenty^^five or thirty years that have elapaed sinee 
Agassiz began to insist not only on the enormous size of the old 
glaciers of the Alps, but on what is now generally recognized as 
the true glacial theory. '' Granting to the land glacialists their full 
demand ^' for the great size of the old glacier of the Rhone, it is 
stated by Sir Roderick, backed by the authority of Sir Charles 
Lyell, that there is nothing in that fact ^^ which supports the opi- 
nion that the deep cavity in which the lake [of Geneva] Ues was 
excavated by ice;'' for among other things it is ^' to be noticed 
in the case of the Lake of Geneva '^ diat it ^ trends from E. to 
W., whilst the detritus and blocks sait forth bv the old glacier 
of the Rhone have all proceeded to the N. and N.N.W., or in 
direct continuation of the line of march of the glacis which 
issued from the narrow gorge of the Rhone. By what momen- 
tum, then, was the glacier to be so deflected to the west that it 
could channel or scoop ont, on flat ground, the great hollow 
now occupied by the Lake odF Geneva ? And, after dSTeoting this 
wonderful operation, how was it to be propelled upwards fircnn 
this cavity on the ascent, to great heights on liie slopes of the 
Jura mountains f The same ailment it ia stated holds good 
of the Rhme glacier, which I have attonpted to show scooped 
X)ut the shallow hollow of the Lake of Constance. One would 
nippose these questions to be so conclusive, that the mere asking 
is enough, and any opposite views must be absurdities which no 
man of any sound knowledge could entertain ; and yet men are 
found who do entertain them in part or in whole, even authors of 
great authority on geological and physical subjects, not only in 
the three kingdoms, but on the continents of Europe and AmcK 
riea. Now with regard to the great old glacier of the Rhine, the 
sentence bearing on it is so worded that I am unable to make out 
whether it is implied that in the belief of Sir Roderick Murchi- 
son no great glacier issuing from the Upper Rhine valley ever 
overspread the region around the Lake of Constance, or whether 
he and M. Escher von der Linth simply at one time could not 
And signs of a glacier that so ^^pluqged into the flat regicm oi^ 
A^ east and north'' (of the Hohe Senlie) '^as to have scooped 
out the cavity in which the lake hes.'^ If the former^ then Sir 

X2 



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800 Prof. A. C. Ramsay on theErosion 

Roderick's opinion seems to have been formed a long time ago; 
for^ adopting M. Escher's authority^ anyone who consults bis 
map of the ancient extension of the Alpine glaciers, will see that 
he draws an enormous glacier^ which issuing firom the broad flat 
valley of the Rhine, tranquilly overspread the country on all sides 
of the lake, and without the necessity for any plunge, could only 
have been fed by smaller tributary streams of ice that, if such 
existed, descended on the northern slopes of the Hohe Sentis*. 

In like manner, Sir Roderick is of opinion that the basin of 
the Lake of Geneva was not scooped out by ice, because ''it 
trends from east to west,'' or at right angles to the main flow <^ 
the glacier — because ice, per se, neither has nor has had any 
excavating power" — because (p. 12) "in valleys with a very 
slight descent, .... no erosion whatever takes place, particularly 
as the bottom of the glacier is usually separated firom the sub- 
jacent rock or vegetable soil by water arising from the melting 
of the ice," and because even in gorges " whence the largest gla- 
ciers have advanced for ages, we meet with islands of solid rock 
and little bosses still standing out, even in the midst of the val- 
leys down which the icy stream has swept," and "there is no 
proof of wide erosion " — ^and, yet again, because (p. 15) " ice has 
80 much plasticity that it has always moulded itself upon the 
inequalities of the hard rocks over which it passed," and "has 
never excavated the lateral valleys, nor even cleared out their 
old alluvia," and furthermore, in general terms, because ice 
could not have been propelled up an inclination from the bottom 
of a lake, let the angle, I presume, be ever so small. 

Now the east and west course of the lake is here treated as if 
the glacier of the Rhone which overspread it were the only gla- 
cier which helped to cover the area; but if any one will take the 
trouble to refer to the map which accompanies my memoir, or, 
better still, to M. Escher's, he will see that the mass of ice must 
have been prodigiously swelled by the great tributary glacier of 
Chamouni, which, descending from Mont Blanc, filled a valley 
some fifty miles in length, and joined the Rhone glacier near the 
lower end of the Lake of Geneva. Neither does it require much 
reasoning to see that during the cold of the facial epoch all the 
higher region south of the lake must have maintained its glaciers 
and filled the valleys that run north ; for even now some of the 

* I have to apologize to my fiiend M. fischer von der Linth for not 
having used his map of the ancient elaciers as my chief authority when my 
Memoir on the Lakes was read. The first time I saw his map« which was 
sent me by Principal Forbes of St. Andrews^ was after the publication 
of my memoir. Had I seen it in time« I would certainly have availed my- 
self> m the construction of my sketch map, of the authonty of a geologist so 
lu^curate and distinguished as Escher von der Lmth, 



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of Valleys and Lakes, 801 

peaks are tipped with perpetual snow. The Bhone glacier had 
therefore no lack of tributaries to maintain its mass over all the 
area of the Lake of Geneva, though towards the west, where the 
glacier thinned away, that mass would be less than over the 
eastern half of the lake, where weight and grinding-power must, 
I believe, on that account have necessarily been greater. But 
the main flow of the ice, after escaping from the Rhone valley, 
was necessarily of a mixed nature, partly to the N.W., and also 
to a great extent to the N.E. and S,W., simply because the N.W, 
flace of the glacier abutted on the Jura. For it requires no pro- 
found knowledge of physics to perceive that any body, whether 
actually plastic like pitch, or of a modified plasticity that may be 
fractured and reunite like ^eZ/y*, or that by *^ fracture and regela- 
tion ^' behaves like a plastic body, — I say it requires no profound 
knowledge of physics to understand that such a body, constantly 
renewed and pressed on from behind, when opposed by a high 
impassable barrier (like the Jura), will spread itself out in the 
direction of least resistance, that direction in the case of the 
Rhone glacier having been at right angles to the general pres- 
sure, or N.E. and S.W., whence I believe the general form and 
trend of the Lake of Neuchatel. 

But, in the second place, is there indeed no proof that ice 
*' neither has nor has had any excavating power,^' whether in val- 
leys of large or of low inclination, narrow or broad ? Then why 
is it that all the rivers that flow from glaciers, great and small, 
me so muddy ? Surely no one will contend that all " the flour 
of rocks " that gives to the rivers a pipeclay colour has been 
washed in by streams from the surface. Alpine club men who 
drink (rarely) of the brooks that run on the surface of the ice 
will repudiate the idea; those who fancy they see in the Loess 
of the Rhine the old glacier-ground mud of the Alps will shrink 
from it ; and many, if not all the Alpine geologists versed in ice 
whom I have conversed with in Italy and Switzerland, will, I ven- 
ture to say, still hold that glaciers by erosion seriously aflfect 
their beds. What else is the meaning of the striation and deep 
grooving, the mammillation and the glassy polish, even of quartz, 
and of all the Alpine rocks, whether hard or soft ? The mud of 
the rivers is chiefly derived from this incessant ice-waste; and that 
is why it is so unearthy^ so clean, fresh, and impalpable. Were it 
merely or chiefly surface-wash, derived from the hills and Washed 
underneath and carried forward below the glaciers, the sediment 
in great part would be dirty, torrential, and coarse enough, espe^ 
cially if, as is stated, glaciers do not seriously grind along their 
rocky floors. So far from a glacier exercising only a trifling grind- 
ing-power, " because it is usually separated from the subjacent 
* I have obtained this comparison from the Master of the Mint, 



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802 Prof. A/C. RamMiy m the Erosion 

rock OT vegetable soil by water arising from the itteltitig of th^ 
ice/' the grinding power is so immense, that in nnweathered 
ground comparatively recently covered by a glacier, every foot 
of surface is often polished and striated. If, indeed, water Usually 
separates ice from the rock so that it does not press upon it^ 
a glacier, whether 80 or 8000 feet thick, would need to be 
treated in the main as a floating body; and it is well known 
that with floating ice there is some eight or teii times as much 
ice below as above the water. 

As for bosses ^ still standing out in the midst of the valleys'' 
proving that glaciers have no erosive power, the reader unlearned 
in theories of denudation will easily understand that the same 
kind of argument might be applied to the pillars of earth left 
for a time in the midst of a railway*cutting the actual exca- 
vation of which he had not seen; or because Goat Island still 
stands in the middle of the falls, the Niagara has not cut its 
gorge ; or because other low islands He higher up, the river has 
not worn out a channel on either side of them and will not 
destroy them ; or in marine denudation, that the chalk between 
Old Harry ami bis Wife and the mainland of Swanage Bay, and 
that between the Needles and the Isle of Wight, has not been 
washed away by the sea, because the islets still stand in the 
midst« If, however, it be said that the glacier-islets are the 
result of old subaerial denudations before the glacier began to 
flow, I might perhaps doubt it, but, for evident reasons, for the 
purpose of this argument, I will not quarrel with it. If they 
have not been left prominent either by streams or ice, then, 
according to the hypothesis which accounts for these valleys by 
disturbance, the bosses in the midst of the glaciers are the result 
of a process of dislocation of Which I should like to see the spe^ 
eial proof. 

The peculiarity and in part the amount of this wearing action 
of ice is indeed due to that very " plasticity '' which enables ice to 
mould " itsdf upon the inequalities of *the hard rock.'* And it is 
just therein that its excavating power difiers from that of water. 
Still water cannot excavate a large basin-shaped hollow, and in 
the depths of a lake water is still; but glacier-ice, having 
''moulded itself upon the inequalities of the hard rocks over 
which it passed," can even move right over a barrier of rock and 
grind it into roches moutormies. The very fact that a rocke mou^ 
tonnSe has, as stated by Sir Roderick, a "StosfhSeite,^* is indeed 
proof that with sufficient pressure behind, a glacier can to some 
extent pass uphill ; and those who remember the great size and 
height of many of these barriers in Switzerland, as, for instance, 
the Kirchet and the hill behind the Grimsel, will be prepared to 
follaw ike argumeats urged in my original pap^r-^and^ for dif- 



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ferait TCisons^ tho held hj De MoitiHet^vis. tiiat a glacier of 
sufficient thidcness could not only fill a lake^ bnt could flow up 
tke low angle of tke ascent towards t^e outflow and escape 
beyond its bounds*. 

If a glacier can round, polish, and cov» with striations die 
jrocks over which it passes — ^if, flowing from its caverns, it can 
dharge rivers thickly with the finest mud, then it can wear away 
its rocky floor and sides. Here indeed an appeal to nature may 
safely be made, and the answer will be easilv obtained ; for, 
standing on the surface of scores of glaciers, such as those of the 
Aar, and casting the eye upward, the whole mountain-sides are 
fnmUmmAf and parallel striations running along and down the 
valley are umversal ; and not there alone, but miles and miles 
below the end of the puny glacters <rf today iht sigm 4f( the 
same wearing actions of grander ice-streams are visible both in 
and thousands of feet above the present bottoms of the valley. 
It needs no subtle argmnent to prove it. Nature proclaims it ; 
we have but to open our even and look upon it to see that ice 
grinds, and has ground and planed away the surface of rodbf, as 
surdy us a planing machine cuts iron, and for much the same 
cause. ** What more,'' says Huttcm, writing of analogous waste, 
'^ what more is required f Nothing bui time. It is not any part 
of the process that wMl be disputedf ; but after allowing all the 
parts the whole will be denied; and (w whatf only because 
we are not disposed to idlow that quantity of time which the 
ablution of so much wasted mountain might requure." '' Timb,'' 
says Fbyfair, ^ per&nrms the office of integraiing the infinitesimal 
parts of which this progression is made up ;'' and though I have 
in this Magasine formerly M/txxvfXxA to show, for purely geolo« 
gical reasons, that the greater valleys in the Alps existed brfore tibe 
so-called glacial period, yet I know perfectly weli« not only that 
since that time glaciers have worn a vast quMstity of matter out- 
of them, but that, given sufficient time, a glacier of itself migfat 
scoop out a vaHey of any d^tb, just as tumihig water may do 
the same, or m surely as that, given sufficient time, the sea will 
wear away any island, soft or hard, large or smdl, that rises 
amidst its waves. 

In further proof of the assertion that gla<»er-ice can have no 
serious effect in wearing away its bottom, great stress is laid on 
the wdl-known fact that such short and steep glaciers as those 

* Unlets I am much mistaken, geolo^sts will some day be mueh snr* 
prised at the size and kind of hills tbiU; they will be obliged to allow that 
glaciers have travelled over. 

t Things, however, that he considered almost self-evident are now dis- 
puted every day, Tlie tendency of opinion be^^s to set in the opposite 
diMCfeion. 



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804i Prof. A. C. Bamaay an the Erosion 

of the Brenva and Miage ride over their inoraineB. I know the&e 
glaciers well, and the atatement that they do ride on their 
moraines is perfectly trne; but few geologists^ and probably no 
physical philosopher will rest his reputation on the assertion 
that, if thdse glaciers were to increase till they attained their 
ancient size, when as mere tributary sources they helped to swell 
the enormous mass that ploughed all down the Yal d^Aosta to 
beyond Ivrea, — ^will anyone, 1 say, rest his reputati6n on the 
belief that these moraine heaps would lie where they now do^ 
underneath a thousand or thousands of feet of ice, unmoved to 
all eternity, or at least till the complete decline of the glaciers 
permitted the loose material to be attacked by running water ? 
If so, again, whence the muddy glacier rivers, and whence the 
scratched stones that come Jrom under the glaciers 7 Tyndall will 
not believe in their immobility, nor Be Mortillet, nor Gbstaldi, 
nor Darwin, who was the first to show that the larger glaciers of 
Wales had ploughed the drift out of some of the greater valleys 
of the country ; and many other geologists of weight will equally 
shrink from the idea. Has ice no weight ? Do the huge glaciers 
of Victoria-land and of Greenland exert no pressure on the ground 
over which they flow ? and are there no stones and no powder of 
rocks beneath to help the grindihg-power 7 Rub iron with your 
finger often and long enough, and it will wear a channel in the 
metal ; for the skin, like the passing glacier, will be renewed, 
while the iron has no means of restoration. If yielding water 
Can wear out a channel, which few people will deny, far more, 
then, must the weight of a thick glacier exercise a prodigious 
abrading-power ; for surely no one on reflection will be so bold 
as to assert that 50 feet, or one, two, or three thousand vertical 
feet of ice with a specific gravity of nearly 0*92 will everywhere, 
or nearly everjrwhere, be separated from its floor by a stra- 
tum of water so complete that the glacier rarely touches the bot- 
tom. If Agassiz, Forbes, and Tyndall, backed by Studer, 
Escher, and Gastaldi, were to tell me so (and they would not 
dream of it), my reverence for authority (and it is great) could 
not persuade me to believe them. 

If, then, glaciers can waste rocks and deepen valleys, is it 
pos^ble that the great old gladers under favourable circum- 
stances have excavated lake-basins, when rocks of unequal hard- 
ness came in their course, or when from special causes the 
pressure of ice was unusually great on certain areas 7 Or were 
they apt to do so by a combination of these causes, when, ceas- 
ing to flow through valleys of great or of moderate inc ination, 
they descended into regions that are comparatively level 7 

I will not repeat what I have elsewhere printed about the 
effect of ice passing over rocks of unequal hardness, nor yet what 



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of Vatteyi and Lakes. 305 

I have said of the confluence of immense glaciers like- those that 
once united in the valley of the Lago Maggiore at what are now 
the Borromean Isles. But it seems to me that to any one who 
allows any excavating power to a glacier^ it will be evident that 
when the general inclination of a valley was comparatively steep, 
a glacier could have had no opportunity of cutting for itself any 
special basin-shaped hollows. Its course, with a difference, is 
like that of a torrent. But in a flat-bottomed part of a valley, 
or in a comparative plain that lies at the base of a mountain- 
range, the case is not the same. For instance, to take an ex- 
treme case, if a glacier tumble over a slope of 45^, no one would 
dream of the ice-flow producing any special effect, except that 
in the long run, the upper edge of the rock that forms the cata- 
riact being worn away, its average angle would be lowered. And 
so of minor slopes ; if the ice flowing fast (for a glacier) rendered 
the rocky surface underneath unequal, such inequalities could not 
become great and permanent ; for the rapidly flowing ice would 
attack the projecting parts with greater power and effect than the 
minor hollows, and so preserve an approximate uniformity, or an 
iBiverage angle of moderate inclination. But when a monstrous 
glacier descended into a comparative plain, or into a low, flat 
valley, the case was different. There, to use homely phrases, 
the ice had time to select soft places for excavation, and there, if, 
from the confluence of large glaciers, or for other reasons, the 
downward pressure of the ice was of extra amount, the excavating 
effect, I contend, must have been unusually great in special areas, 
atid have resulted in the formation of rock-bound hollows. And 
though the glacier of Ivrea has been constantly quoted as a case 
that completely proves the absurdity of my theory, this merely 
shows the unwariness of those who quote it ; for not only are 
there a great many rock-basins full of water above' Ivrea in 
atnong the vast roch^s moutannSes near the opening of the plain, 
but, where beyond this point the glacier spread out so wide on 
the Pliocene plain, it has scooped away so much material that 
parts of that plain are below the average level of the plains of 
Piedmont that lie outside the great moraine. Given sufficient 
time and extension of the glacier, and more matter still would 
have gone away. The same argument equally applies to the 
case on the Lake of Zurich, where glacier debris is said to lie on 
alluvial detritus. In reply to the question why in the actual 
viEilley of Aosta there are no lake-basins, I might with equal 
propriety say, Many contorted regions are much faulted, and 
there is often an evident connexion between contortion and faults ; 
but in some contorted regions there are few or no faults, and 
the reason of their absence remains to be accounted for. I have 
attempted to explain why the rock-basins are present, and not 



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306 Prof. A. C. Ramsay M the Erosion 

why they are absent. It may be that 4ome of 4;he alluTial flats 
of the valley are lake-hollows filled up. 

Bat another statement urged by Sir Roderick agaiHst my 
theory is^ that the soooping-ouit of such hcdlows by ice is im- 
possible, because ice cannot flow up an inclined plane, if so^ I 
repeat, what is the meaning of the " St^ss-Seite'* or upper skIo 
of a roche mouttmnSe that bars a wide glacier valley, through 
which barrier perhaps a mere narrow river goi^ paases-^^as, for 
instance, in the case of the Kirchet so well known to Alf»ne 
men, or, On a smaller scale, of the roches nundormiee near the 
slate-quarries in Nant Franoon f In both cases the barrier re- 
mained intact till the drainage of the glacier-formed Idces cut 
gorges thiough them — or, if Sir Roderick prefer it, till convul- 
sions made gorges. Its, tnoutonnie form will convince every 
accomplished glacialist that the ground was once covered by 
ice. The strike of the rocks will be enough for ordinary geokh- 
gists ; for no man can suppose who sees the corresponding forms 
of the roches mautonn^ on eithar side <tf the narrow gorge of 
the Aar, that that gorge existed before the period of the great 
glacier, and that die glacier flowed entirely between the walls i^ 
the narrow passage. If I am right in this, then the great old 
glacier of the Aar flowed right over the hill, from bottom to top, 
and away into regions far beycHkl, in the manner I have impeiv 
fecdy shown in my little book (m the old glaciers of Swita^land 
and North Wales, and equally so whether the gorge was foraied 
by sudden violence or by water. 

In the eiisteiicci, therefore, of " Stoss^Sekeh,'^ and in^ their 
upward striations, both in small and large roehes mo^otm^, 
there is proof that the belief that glaciers cannot flow over 
hillocks^ and even hills <^ considerable siz^ is a mare assertion 
founded on ptejudice : to fiie the wonder is, that imy one ean 
ever have believed it who has truly observed phenomaia in &e 
Alps, or who is familiar even with the ancient glaeiation of our 
own country. And if this be so, I see no difficulty in aeeepting 
the hypothesis that the length and kuclinatioii of the sk>pe 
which the bottom of a glacier may asCend depend simply on 
the thickness of the ice, and on the amount of the prOpellii^ 
power behind, that power being due to the weight and mass of 
the descendix^ ice, and the average angles of the valley bdiind 
the point whence the upward ascent begins*. 

Now, in dealing with this question, most of the gecdogista 
who have opposed me have treated the larger lake-hdlows much 
as they do Time^ Unconsciously they seem to me to be a&aid boA 
of it and of them. '^Look,'^ they seem to say, ''at these mountains^ 

'*' I think it ought be possible to make a very geed approxifliftte eakmb^ 
tion on thia pomtf and I hope it laay yet be doae. 



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of VaUeysmd Lakes. 807 

bow awfully bigh and ragged they are ; can a)iy amount of time, 
aided by weather, torrents, rivers^ and glaciers produce such 
e£fects? Old writers, like Hutton and Playfair, and a few 
modem observers (some of whom, both in America and Europe, 
have great familiarity with rocks), say they can; but we know that 
tending and fracture is the chief agent, and denudation is in com- 
parison quite a trifling affair. Look, again, at the hollows of the 
lakes, how awfully deep they are ! How is it possible for a glacier 
ever to have slid up a hill from a depth so profound ? '* In 
treating tke slopes as great, consists the viciousness of this sup- 
posed argument. Unconsciously, some of the arguers are draw- 
ing exaggerated diagrams in their minds. They foreshorten the 
slope, increase in their mind's eye its steepness, and forget 
their trigonometry altogether. But let me beg of them to try 
to reahse the real state of the case, and see how small by com- 
parison the depth really is, and how gentle the slope. Were 
the bottom of the Lago Maggiore not undulated (for I believe 
the islands to be mere roches tnoutonnSes), this slope from the 
deepest part of the lake (2600 feet) to its outflow would only 
be 2° 21' in a distance of about 12 miles, a slope so gentle that, 
were a man standing on it, by the eye he would barely be able 
to tell Whether he was on an inclinol plane or not*^. Again, 
take the Lake of (Geneva from the place where it is nearly a 
thousand feet deep to Geneva, the average slope is only about 
25', an angle so small that any geologist looking at it would be 
apt to consider the surface as horizontal. The question, then, 
as regards the lakes resolves itself into this : Is it possible that 
the ice of the great old glaciers could ever have travdled up 
these exceedingly small inclinations for a distance, saytyf 12 
miles in the one case and 20 to 25 miles in the other f 

And now, in connexion with this point, I could wish that Sir 
Roderick had expressed an opinion whether or not he agrees 
with the old geologists, that (p. 7) ^^the Lakes of Geneva and 
Neufehatel were so filled up with snow and ice that the advancing 
glaciers travelled on them as bridges of ice, the foundations of 
which occupied the cavities.'* If this were so, then, in other 
words, the lower strata of ice in the hollow of what is now a 
lake remained in a condition of static equilibrium, and over this 
ice the advancing part of the glacier slipped or was propelled. 
Strictly speaking, it is evident that this state of static equilibrium 
is impossible; for all the iee of a glacier a little below the sur- 
face being, even in winter, in a melting state, the lower strata 

* In my original paper on the glacial excavatkni of certain kkcs, I 
made an unfortunate error in calculation^ stating that the ansle is about 5^. 
In an able article in the ' Reader/ Professor Jiwejs eorrected the errot, and 
made the slope 2^. 



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SOS Prof. A. C. Ramsay on the Erosion 

above alluded to must have been destroyed and renewed over 
and over again ; and as glacier-iee is practically anything but a 
rigid body, I think it would be easy to show that, just as in Arc- 
tic regions in winter the more rapid flow of the lower strata of 
ice^ with a temperature of about S2°, shatters the more rigid 
and slowly-moving upper layers which have a temperature far 
below that point, so, for other reasons,' the motion of some 2000 
vertical feet of ice sliding over the basin, would be communicated 
to the lower strata ; for pressure in ice produces adhesion of parts* 
I for one cannot conceive a horizontal fracture of 40 miles in length 
over the area of the Lake of Geneva, clearly dividing two bodies 
of ice, the lower of which was, where thickest, nearly 1000 feet, 
and the upper and sliding stratum must have been nearly 8000 
feet thick. It is, in fact, a piece of mere elementary knowledge 
that any heavy body passing steadily across any other body, the 
parts of which are moveable, will communicate motion to the 
parts over which it passes, whether one or both of those bodies 
be viscid or plastic, or of some other compound character ; and 
when I wrote my original paper it never occurred to me that 
there was any need of mentioning a point so obvious. But in a 
glacier that fills a lake-basin, this is by no means the only, and 
perhaps n6t the principal, cause of motion. A glacier does not 
throughout all its course move on simply by virtue of gravity. 
Pressure from behind has a great deal to do with it ; as, for 
instance, in the case of the Rhone glacier, familiar to so many, 
and cited by Professor Merian and Dr. Tyndall. There, at the 
cataract, the ice fractures and slides down comparatively rapidly 
in masses, but at the base, where it moves slowly, pressure from 
behind causes the masses to touch and reunite, and the whole 
slides on, a re-formed mass, into the lower valley, the inclination of 
which is small. So, in the case of the lakes, tne depths of which 
seem so appalling, but the real angles of the beds of which are so 
small, there seems to me nothing either impossible or remarkable 
in the idea that the long and enormous onflowing inclined 
mass of the glacier of the Rhone pushed before it in the plain 
(for such it is) its own more sluggish continuation up a slope of 
25' for a distance of 20 or 25 miles. I believe that the same 
argument is equally applicable to the Lago Maggiore, where the 
already vast glacier, swelled by the mighty tributary of the Val 
d^Ossola, was thus enabled to push along the low average slope 
of 2^ 21' for a distance about half as great. The very islands in 
many a lake once filled with ice help to prove this ; for, as in 
the case of Loch Lomond, they are mere r aches moutonniesy and 
I for one cannot conceive that the mammillation ceases imme- 
diately below the surface of the water. 

Having got thus far, I will not repeat my arguments to show 



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of Valleys aad Lakes. 309 

that (as T attempted to prove in my original memoir) the Alpine 
and other ice-worn lakes known to me do not lie in areas of 
special subsidence, nor in gaping fractures , nor in simple synclinal 
basins, nor in hollows of watery erosion. If any one who reads 
this is curious about them^ he must refer to that memoir*^; but 
this at least I may be permitted to say : I used at all events 
arguments^ even somewhat elaborate^ and not mere statements, 
and whether these arguments are fated to be successful time 
alone will show. That they were at all events of some value^ the 
names of the distinguished geologists who have accepted my 
theory helps to show ; and I could add to these other names as 
high as the very highest of those on whose authority Sir Roderick 
so much depends^ did propriety permit me to quote from letters 
«nd commit men to opinions which they have not expressed in 
print. 

But before leaving the subject, let me say a little more about 
the possibility of these lakes lying in fractures. For this pur- 
pose let us take some of those that lie on the north side of the 
Alps, partly in the region of the Miocene strata. If they lie in 
lines of gaping fracture, nearly as wide as the present lakes, 
then on the hills, say between the Lake of Lucerne and Thun, 
and between Thun and the Lake of Zurich, the Miocene strata 
would be crumpled up in zigzag lines across the average line of 
strike, to an amount corresponding to the distance between the 
severed strata in the spaces now overlooking and occupied by the 
lakes. This is not the case. Again, if the fractures were mere 
narrow cracks, then the amount of denudation that took place 
so as to form the wide valleys has been enormous, and within a 
mere fraction of what I require, especially when we consider 
that the great denudation necessary to widen the fractures would 
have filled up the lake-basins. The theory of the chief forma- 
tion of Alpine valleys having been effected by weather, water, 
and ice, would therefore still hold good. 

I might continue these arguments, and discuss in detail what 
Sir Roderick has said about Scandinavia, North America, and 
other regions, and among other things show how unprecise is 
the knowledge that we actually possess respecting the details of 
the boulder-beds that overspread some of them, and how unsafe 
it is to conclude, because a country is not actually mountainous, 
and does not now lie high above the sea-level, that it was never 
covered by glacier-ice in motion, and mav not at one time 
have lain much higher. In spite of Agassiz^s memoirs, it is not 
long since all the lower Till of Scotland was considered not to 
be ordinary moraine-matter at all, but to have been formed 

* They are also given in 'The Physical Geology and Geography of 
Great Britam.' 



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810 On the Erdtion af Valleys and Lakes. 

solely in the sea by the transportiDg agency of icebergs* Let 
those who still belieye it refer for proof to the eentarary to Mr. 
Geikie^s admirable work ^ On the Fhe^Fiomena of the Glaeial Drift 
of Scotland/ I know enough of the superficial strata in North 
America to foresee that the erratic deposits there will some day 
also be divided into terrestrial and marine series^ and I am 
pretty sure that Sir William Logan will not deny the proba* 
bility. F<Hr the yast size of the ancient glaeiera of that con- 
tinent^ I wonld refer to Professor Dana'a admiraUe Manual of 
American Geology. It is a mistake to suppose that the stria- 
tions there merely run from north to souths for Sir William 
Logan, who has mapped them, proves that th^ often conform 
to the bends of the valleys. 

Aa regards the great lakes of that eontisent, ao far from bang 
^' cavities originally due to a combination of ruptures and denur 
diMiona of the rocks/^ it is impossible intimately to know the 
country and believe it. There the Silurian strata, amid which 
the lakes lie, are arranged so tranquilly and at angles so low, 
that the flattest chalk of Great Britain may be almost said to be 
tumultuous in comparison i and the forthcoming sections of Sir 
William I^ogan conclusively prove that around the lakes there 
is no trace of dislocation to help to form the hollows, nor yet do 
they lie in hollows of special subsidence. Only Lake Superior 
covers a faint synclinal curve; and Lake Ontario, so far from 
occupying an area of special depression, actually lies on a very 
low anticlinal bend of soft strata, the top of which has be^si 
denuded away. That Sir William, who has beai called the best 
stratigraphical geologist in America, believes that ice has some- 
thing to do with the scooping out of rock-basins, any one 
may see who refers to his late masterly report on the geology of 
Canada ; and Professor Newberry, wh(»n Sir Roderick knows as a 
jdiysical geologist and geographer, adheres strongly tothat opinion. 

As for the observation of my friend M. de Yemeuil, that the 
orographic hollows in Spain are precisely those that " a theorist *^ 
might ^^ attribute to excavation by ice,'^ I. decline to be judged 
by it, till I have seen them and declared that opinion. I object, 
both for myself and my supporters, that we should be judged in 
a manner so vague. And further, I think I appeal to Nature 
to some purpose when, neither for the first nor the second time, 
I ask philosophers to consider why it is that not only drift- and 
moraine-dammed lakes, but striated rock-basins of all sizes occur 
in such prodigious numbers in America, Scandinavia, the High- 
lands, and in all other rocky temperate regions, high or low, that 
have been glaciated, while in tropical and subtropical regions 
they are so rare as to be quite exceptional elsewhere than in 
inountain areas that now or once maintained their glacoera. 



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Beirenil other pointa nosed bv Sir Roderick in that part of hk 
Address that relates to i^ysical geology^ glaciers, and iceberg 
]:emaiii to be discussed. I have entered!, however^, on this ai^u- 
Qient wilnh great rductanoe, and, unless cireumstances again ooa* 
straia dm, I shall leave the remaining questions untoudied* 



XXXYI. Historic Notes on the Conservation of Energy. 
By Professor Bohn. 

To Professor TyndaU, Esq., F.R.8. 

I BEAD yotar " Notes on Scientific History^'* with great plea- 
sure and satisfaction. I agree perfectly with all yon say 
respecting Mayer's researches as compared with those of others ; 
in some respects, indeed, I am inclined to go further than you do. 
Seven years ago I studied the history of the principle of the 
Conservation of Energy, and arrived at the same conclusion, with 
respect to the modem dev^pment of this theorem, as the one 
for which you so ablv and warmly contend. Your recent disin^ 
terested advocacy of Mayer's daims, and my own conviction 
that historic truth is the sole object of your research, inspire the 
hope that the following remarks will be found worthy of atten*- 
tive perusal. 

Descartes, so far as 1 know> was the first to give expression to 
^dte thought that whatever is not material must necessarily be 
indestructible. This non-matmal something he called '' Force,^ 
a word which subsequently had, for a long pariod, divers and 
consequently vague meanings. ^ 

In Descartes's Principia Philosopkia (Pars II., § xxxvi.) we 
find the following : — '^ Deum esse primariam motus oausam et 
eandem semper motus quantitatem in universo ccmservare. 

''Mot4s naturA sic animadversft, oonsiderare oportet ejus 
eausam, eamque duplieem ; Primo scilicet univa^alem et pri- 
mariam, quae est causa generalis omnium motuum qui sunt in 
mundo j ac deinde particularem, h qu& fit, ut singulse materise 
partes motus, quos prius non habuerunt, acquirant. £t gene- 
ralem quod attinet, manifestum mihi videtur illam non aliam esse, 
quidn Deum ipsum, qui materiam simul cum motu et quiete in 
principio creavitf^ jamque per solum suum ooncursum ordinarium^ 
tantundem mot^s et quietis in eft tot& quantum tunc posuit 
eonservat. Nam quamvis ille motus nihil aliud sit in materiA 
mot& qukm ejus modus; certam tamen et determinatam habet 

* Phil. Mi^. S. 4. ToL xxviii. p. 26. 

t PhiLMag.S.d.vol.zzm.p.442(184d): Mr. Joule, '« That the grand 
agents of uAtore me 1^ the Creator's ^t iadestroetible." 



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812 Prof, Bohn an the Conservation ofEnerffj/. 

quantitatem, quam facile mtelligimus eandem seiiiper in totd 
rerum universitate esse posse^ quamvis in singulis ejus partibos 
mutetur. Ita scilicet ut putemus^ cum una pars materia dupl5 
celeriiis movetur^ qukm altera^ et bsec altera duplb major est 
qukm prior^ tantundem motiis esse in minore qukm in majore^ 
ac quanto motus unius partis lentior fit^ tanto motum alicujus 
alterius ipsi sequalis fieri celeriorem. Intelligimus etiam per- 
fectionem esse in Deo, non solum quod in ,se ipso sit immu- 
tabilis, sed etiam quod modo qu^m maxime constanti et iinmu- 
tabili operetur : Aded ut iis mutationibus exceptis, quas evidens 
experientia, vel divina revelatio certas reddit, quasque sine ull& 
in creatore mutatione fieri percipimus, aut Credimus, nullas alias 
in ejus operibus supponere debeamus, ne qua inde inconstantia 
in ipso arguatur. Unde sequitur qukm maxim^. rationi esse 
consentaneum, ut putemus ex hoc solo, quod Deus diversimode 
moverit partes materise, cum primum illas creavit, jamque totam 
istam materiam conservet, eodem plane modo, e&demque ratione . 
qxxk prius creavit, eum etiam tantundem motiis in ipsd semper 
conservare/' 

Descartes therefore, precisely like Colding, bases the proof of 
his theorem on a divine attribute. The unsatisfactory nature of 
fiuch a proof is manifest. Are we not equally justified in assert- 
ing that the assumption of a constant quantity of motion involves 
a limitation of divine power ? The almightiness of God must 
manifest itself by actual achievement, new motion must inces- 
santly be created ; therefore, assuming with Descartes the inde- 
structibility of that which exists, the quantity of motion must 
increase. 

Every attempt to deduce a natural law from an a priori con- 
<^eived attribute of God must inevitably be utterly fruitless. 

Leibnitz was the first to publish, in its proper form, the general 
theorem of the conservation of vis viva^ and to demonstrate 
the same by empirically ascertained and rationally established 
theorems. He at once opposes Descartes's views, and introduces 
the important conception of vis viva. All this will be found in 
his article in the Acta Eruditorumy Lips. 1686, entitled : " Brevis 
demonstratio erroris memorabilis Gartesii et aliorum circa legem 
naturse, secundum quam volunt a Deo eandem semper quantita- 
tem motus conservari^ qua et in re mechanica abutuntur/' 

In the warm discussion which arose, Leibnitz argued that the 
assumption of the incorrectness of his views involved the neces? 
$ity, or at least the possibility of a perpetual motion; which lat- 
ter he urged is manifestly absurd. Colding employs the same 
argument ; and Helmholtz, in 1847, in his well-known work ^ On 
the Conservation of Force,' attributes great importance to this 
theorem concerning the absurdity of perpetual motion^ ^ - 



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Prof, Sohii on the Conservation of Energy. 813 

John Bernoulli, however, gave the clearest exposition of the 
principle of the conservation of vis viva, as will be admitted after 
a perusal of his correspondence with Leibnitz ( Vivorum eel. G. 
C. Leibnitii et Joh, Bernoulli commercium phil, et math), of 
his "Discours sur les lois de la communication du mouvement '^ 
(Opera omnia, torn. iii. p, 1), and especially of his memoir entitled 
" De vera notione virium vivarum earumque usu in dynamicis '* 
{Opera omnia, tom. iii. p. 239). 

Allow me to draw your particular attention to the following 
two passages of the last-named memoir : — 

"§ III. Hinc patet vim vivam [quae aptius YOCSLvetixr facultas 
agendi, Gallice /^ />02{votr] esse aliquid reale et substantiate, quod 
per se subsistit, et quantum in se est, non dependet ab alio. Unde 
concludimus, quamlibet vim vivam habere suam determinatam 
quantitatem, de qua nihil perire potest, quod non in eiffectu 
edito reperiatur, Hinc sponte fluit, vim vivam semper conservari \ 
adeo ut quae ante actionem residebat in uno pluribusve corpo- 
ribus, nunc post actionem reperiatur necessario in alio, vcl aliis 
pluribus corporibus, nisi quid in prioribus remanserit. Atque 
hoc esty quod vocamus conservationem virium vivarum" 

One fact of peculiar interest is John Bernoulli's assertion that 
the vis viva which apparently disappears — that is to say, the vis 
viva which is not employed in external work such as the raising 
of a weight — may be consumed in molecular work. The follow- 
ing extract from § 9 of the above memoir will establish this 
point. 

"Si corpora non sunt perfecte elastica, aliqua pars virium 
vivarum, quae periisse videtur, consumitur in compressione cor- 
porum, quando perfecte se non restituunt ; a quo autem nunc 
abstrahimus, concipientes, compressionem illam esse similem 
compressioni elastri, quod post tensionem factam impediretur ab 
aliquo retinaculo, quo minus se rursus dilatare posset, et sic non 
redderet, sed in se retineret vim vivam, quam a corpore incur- 
rente accepisset j unde nihil virium periret, etsi periisse videretur.'* 
The conversion of vis viva into heat, or at least the possibility of 
such a conversion, was first asserted by Augustin Fresnel. The 
French translation of Thomson's ' Chemistry ' contains an ap- 
pendix "On Lighf from Fresnel's-pen, wherein he says: — 

" C'est un principe general du mouvement des fluides elas- 
tiques, que, de quelque fa9on que Tebranlement s'etende ou se 
subdivise, la somme totale des forces vives reste constante. Et 
voil^ principalement pourquoi la force vive doit Stre consideree 
comme la mesure de la lumifere, dont la quantity totale reste 
toujours k tres pen pres la m6me,tant qu'elle ne traverse du moins 
que des milieux tres transparens. Les corps noirs et roSme les 
surfaces metalliques les plus brillantes ne reflechissent pas h 

Phil. Mag. S, 4. Vol. 28. No, 189. Oct. 1864. Y 

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814 Royal Society : — 

beaucoup pres la totalite de la lumiere qui tombe sur leur surface ; 
lea corps imparfaitement transparens^ et meme les plus diaphanes^ 
quand ils sont assez epais^ absorbent aussi (pour me servir de 
Fexpression usitee) une quantite notable de la lumiere incidente ; 
mais il n^en faut pas conclure que le principe de la conservation 
des forces vives, n^est plus applicable k ces phfoomenes; il 
resulte au contraire de Tidee la plus probable qu'on puisse se 
faire sur la constitution mecanique des corps^ que la somme des 
forces vives doit toujours rester la mSme (tant que les forces 
acceleratrices qui tendent k ramener les molecules k leurs posi- 
tions d^equilibre n^ont pas change d^intensite)^ et que la quarUite 
de forces vives qui disparait comme lumiere est reproduite en 
chaleur*' 

Should you consider the contents of this letter suitable for 
the pages of the Philosophical Magazine, I should feel honoured 
by its publication in that journal. 
Giessen, August 14» 1864. 



XXXVII. Proceedings of Learned Societies, 

ROYAL SOCIETY. 

[Continued from p. 240.] 

June 16, 1864. — Major-General Sabine, President, in the Chair. 

THE following communication was read : — 
*' On the Properties of Silicic Acid and other analogous Col- 
loidal Substances." By Thomas Graham, F.R.S., Master of the 
Mint. 

The prevalent notions respecting solubiUty have been derived chiefly 
from observations on crystalline salts, and are very imperfectly appli- 
cable to the class of colloidal substances. Hydrated silicic acid, for 
instance, when in the soluble condition, is properly speaking a liquid 
body, like alcohol, raiscible with water in all proportions. We have 
no degrees of solubility to speak of with respect to silicic acid, like 
the degrees of solubility of a salt, unless it be with reference to silicic 
acid in the gelatinous condition, which is usually looked upon as des- 
titute of solubility. The jelly of silicic acid may be more or less 
rich in combined water, as it is first prepared, and it appears to be 
soluble in proportion to the extent of its hydration. A jelly containr 
ing 1 per cent, of silicic acid, gives with cold water a solution con- 
taining about 1 of silicic acid in 5000 water ; a jelly containing 5 
per cent, of silicic acid, gives a solution contaming about ] part of 
acid in 10,000 water. A less hydrated jelly than the last mentioned 
is still less soluble ; and finally, when the jelly is rendered anhydrous 
it gives gummy-looking white masses, which appear to be absolutely 
insoluble, like the light dusty silicic acid obtained by drying a jelly 
charged with salts, in the ordinary analysis of a silicate. 



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Prof. Graham on the Properties of Silicic AddSfC. 815 

The liquidity of silicic acid is only effected by a change which is per- 
manent (namely, coagulation or pectization), by which the acid is con- 
verted into the gelatinous or pectous form, and loses its miscibility 
with water. The liquidity is permanent in proportion to the degree 
of dilution of silicic acid, and appears to be favoured by a low tem- 
perature. It is opposed, on the contrary, by concentration, and by 
elevation of temperature. A liquid silicic acid of 10 or 12 per cent, 
pectizes spontaneously in a few hours at the ordinary temperature, and 
immediately when heated. A liquid of 5 per cent, may be preserved 
for five or six days ; a liquid of 2 per cent, for two or three months ; 
and a liquid of 1 per cent, has n9t pectized after two years. Dilute 
solutions of 0' 1 per cent, or less are no doubt practically unalter- 
able by time, and hence the possibility of soluble sihcic acid ex- 
isting in nature. I may add, however, that no solution, weak or 
strong, of silicic acid in water has shown any disposition to deposit 
crystals, but always appears on drying as a colloidal glassy hyalite. 
The formation of quartz crystals at a low temperature, of so frequent 
occurrence in nature, remains still a mystery. I can only imagine 
that such crystals are formed at an inconceivably slow rate, and nom 
solutions of silicic acid which are extremely dilute. Dilution no 
doubt weakens the colloidal character of substances, and may there- 
fore allow their crystalling tendency to gain ground and develope 
itself, particularly where the crystal once formed is completely inso- 
luble, as with quartz. 

The pectization of liquid silicic acid is expedited by contact with 
soUd matter in the form of powder. By contact with pounded gra- 
phite, which is chemically inactive, the pectization of a 5 per cent, 
silicic acid is brought about in an hour or two, and that of a 2 per 
cent, silicic acid in two days. A rise of temperature of l°'l C. was 
observed during the formation of the 5 per cent, jelly. 

The ultimate pectization of silicic acid is preceded by a gradual 
thickening in the liquid itself. The flow of liquid colloids through a 
capillary tube is always slow compared with the flow of crystalloid 
solutions, so that a liquid-transpiration-tube may be employed as a 
colloidoscope. With a colloidal liquid alterable in viscosity, such as 
silicic acid, the increased resistance to passage through the colloi- 
doscope is obvious from day to day. Just before gelatinizing, silicic 
acid flows like an oil. * 

A dominating quality of colloids is the tendency of their particles 
to adhere, aggregate, and contract. This idio-attraction is obvious in 
the gradual thickening of the liquid, and when it advances leads to 
pectization. In the jelly itself, the specific contraction in question, 
or symeresisy still proceeds, causing separation of water, with the divi- 
sion into a clot and serum ; and ending in the production of a 
hard stony mass, of vitreous structure, which may be anhydrous, or 
nearly so, when the water is allowed to escape by evaporation. The 
intense synseresis of isinglass dried in a glass dish over sulphuric 
acid in vacuo, enables the contracting gelatine to tear up the surface 
of the glass. Glass itself is a colloid, and the adhesion of colloid to 
colloid appears to be more powerful than that of colloid to crystalloid. 



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316 Royal Society: — 

The gelatine, when dried in the manner described upon plates of calc- 
spar and mica, did not adhere to the crystalline surface, but detached 
itself on drying. Polished plates of glass must not be left in con- 
tact, as is well known, owing to the risk of permanent adhesion 
between their surfaces. The adhesion of broken masses of glacial 
phosphoric acid to each other is an old illustration of colloidal 
synseresis. 

Bearing in mind that the colloidal phasis of matter is the result 
of a peculiar attraction and aggregation of molecules, properties 
never entirely absent from matter but greatly more developed in 
some substances than in others, it is not surprising that colloidal 
characters spread on both sides into the liquid and solid condi- 
tions. These characters appear in the viscidity of liquids, and 
in the softness and adhesiveness of certain crystalline substances. 
Metaphosphate of soda, after fusion by heat, is a true glass or col- 
loid ; but when thi? glass is maintained for a few minutes at a tem- 
perature some degrees under its point of fusion, the glass assumes 
a crystalline structure without losing its transparency. Notwith- 
standing this change, the low diffusibility of the salt is preserved, 
with other characters of a colloid. Water in the form of ice has 
already been represented as a similar intermediate form, both col- 
loid and crystalline, and in the first character adhesive and capable 
of reunion or " regelation." 

It is unnecessary to return here to the fact of the ready pectiza- 
tion of liquid silicic acid by alkaline salts, including some of very 
sparing solubility, such as carbonate of lime, beyond stating that the 
presence of carbonate of lime in water was observed to be incompa- 
tible with the coexistence of soluble silicic acid, till the proportion 
of the latter was reduced to nearly 1 in 10,000 water. 

Certain liquid substances differ from the salts in exercising little 
or no pectizing influence upon liquid silicic acid. But, on the other 
hand, none of the liquids now referred to appear to conduce to the 
preservation of the fluidity of the colloid, at least not more than the 
addition of water would do. Among these inactive diluents of silicic 
acid are found hydrochloric, nitric, acetic, and tartaric acids, syrup 
of sugar, glycerine, and alcohol. But all the liquid substances named, 
and many others, appear to possess an important relation to silicic 
acid, of a very different nature from the pectizing action of salts. 
They are capable of displacing the combined water of the silicic acid 
hydrate, whether that hydrate is in the liquid or gelatinous condition, 
and give new substitution-products. 

A liquid compound of alcohol and silicic acid is obtained by adding 
alcohol to aqueous silicic acid, and then employing proper means to 
withdraw the water from the mixture. For that purpose the mixture 
contained in a cup may be placed over dry carbonate of potash or 
quicklime, within the receiver of an air-pump. Or a dialyzing bag 
of parchment-paper containing the mixed alcohol and silicic acid 
may be suspended in a jar of alcohol : the water diffuses away, 
leaving in the bag a liquid composed of alcohol and silicic acid only. 
A point to be attended to is, that the silicic acid should never be 



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Trof. Graham on the Properties of Silicic Acid ^c. 317 

allowed to form more than 1 per cent, of the alcoholic solution, 
otherwise it may gelatinize during the experiment. If I may be 
allowed to distinguish the liquid and gelatinous hydrates of silicic 
acid by the irregularly formed terms of hydroaol and hydrogel of silicic 
acid, the two corresponding alcoholic bodies now introduced may be 
named the alcosol and alcogel of silicic acid. 

The alcosol of silicic acid, containing 1 per cent, of the latter, is a 
colourless liquid, not precipitated by water or salts, nor by contact 
with insoluble powders, probably from the small proportion of silicic 
acid present in solution. It may be boiled and evaporated without 
change, but is gelatinized by a slight concentration. The alcohol is 
Tetained less strongly in the alcosol of silicic acid than water is in the 
hydrosol, but with the same varying force, a small portion of the 
alcohol being held so strongly as to char when the resulting jelly is 
rapidly distilled at a high temperature. Not a trace of silicic ether 
is found in any compound of this class. The jelly burns readily in 
the air, leaving the whole silicic acid in the form of a white ash. 

The alcogely or solid compound, is readily prepared by placing 
masses of gelatinous silicic acid, containing 8 or 10 per cent, of the 
dry acid, in absolute alcohol, and changing the latter repeatedly till 
the water of the hydrogel is fully replaced by alcohol. The alcogel 
is generally slightly opalescent, and is similar in aspect to the hydrogel, 
preserving very nearly its original bulk. The following is the com- 
position of an alcogel carefully prepared from a hydrogel which con- 
tained 9*35 per cent, of silicic acid : — 

Alcohol 88-13 

Water 0*23 

Silicic acid .• 1 1 '64 

100-00 

Placed in water, the alcogel is gradually decomposed — alcohol diffu- 
sing out and water entering instead, so that a hydrogel is reproduced. 

Further, the alcogel may be made the starting-point in the forma- 
tion of a great variety of other substitution jellies of analogous con- 
stitution, the only condition required appearing to be that the new 
liquid and alcohol should be intermiscible, that is, interdiffhsible 
bodies. Compounds of ether, benzole, and bisulphide of carbon 
have thus been produced. Again, from etherogel another series of 
silicic acid jellies may be derived, containing fluids soluble in ether, 
€uch as the fixed oils. 

The preparation of the glycerine compound of silicic acid is faci- 
litated by the comparative fixity of that liquid. When hydrated 
silicic acid is first steeped in glycerine, and then boiled in the same 
liquid, water distils over, without any change in the appearance of 
the jelly, except that when formerly opalescent it becomes now entirely 
colourless, and ceases to be visible when covered by the liquid. But 
a portion of the silicic acid is dissolved, and a glycerosol is produced 
at the same time as the glycerine jelly. A glycerogel prepared from 
a hydrate containing 9*35 per cent, of silicic acid, was found by a 
combustion analysis to be composed of 



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818 Royal Society : — 

Glycerine 87*44 

Water 378 

Silicic acid 8-95 

100- 17 

The glycerogel has somewhat less bulk than the original hydrogel:. 
When a glycerine jelly is distilled by heat, it does not ftise, but the 
whole of me glycerine comes over, with a slight amount of decom- 
position towards the end of the process. 

The compound of sulphuric acid, sulphagel, is also interesting from 
the facility of its formation, and the complete manner in which the 
water of the original hydrogel is removed. A mass of hydrated 
silicic acid may be preserved unbroken if it is first placed in sulphu- 
ric acid diluted with two or three volumes of water, and then trans- 
ferred gradually to stronger acids, till at last it is placed in concen- 
trated oil of vitriol. The sulphagel sinks in the latter fluid, and may 
be distilled with an excess of it for hours without losing its transpa- 
rency or gelatinous character. It is always somewhat less in bulk 
than the primary hydrogel, but not more, to the eye, than one-fifth 
or one-sixth part of the original volume. This sulphagel is transparent 
and colourless. When a sulphagel is heated strongly in an open ves- 
sel, the last portions of the monohydrated sulphuric acid in combi- 
nation are found to require a higher temperature for their expulsion 
than the boiling-point of the acid. The whole silicic acid remains 
behind, forming a white, opaque, porous mass, like pumice. A sul- 
phagel placed in water is soon decomposed, and the original hydrogel 
reproduced. No permanent compound of sulphuric and silicic acids, 
of the nature of a salt, appears to be formed in any circumstances. 
A sulphagel placed in alcohol gives ultimately a pure alcogeL Similar 
jellies of silicic acid mav readily be formed with the monohydrates of 
nitric, acetic, and formic acids, and are all perfectly transparent. 

The production of the compounds of silicic acid now described 
indicates the possession of a wider range of affinity by a colloid than 
could well be anticipated. The organic colloids are no doubt in- 
vested with similar wide powers of combination, which may become 
of interest to the physiologist. The capacity of a mass of gelatinous 
silicic acid to assume alcohol, or even oleine, in the place of water of 
combination, without disintegration or alteration of form, may per- 
haps afford a clue to the penetration of the'albuminous matter of mem- 
brane by fatty and other insoluble bodies, which seems to occur in 
the digestion of food. Still more remarkable and suggestive are 
the fluid compounds of silicic acid. The fluid alcohol- compound 
favours the possibility of the existence of a compound of the colloid 
albumen with oleine, soluble also and capable of circulating with the 
blood. 

The feebleness of the force which holds together two substances 
belonging to different physical classes, one being a colloid and the 
other a crystalloid, is a subject deserving notice. When such a com- 
pound is placed in a fluid, the superior diflusive energy of the crystal- 
loid may cause its separation from the colloid. Thus, of hydrated 



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Prof. Graham on the Properties of Silicic Acid ^c, 819 

silicic acid, the combined water (a crystalloid) leares the acid (a col- 
loid) to dif^e into alcohol ; and if the alcohol be repeatedly 
changed, the entire water is thus removed, alcohol (another crystal- 
loid) at the same time taking the place of water in combination with 
the silicic acid. The liquid in excess (here the alcohol) eains entire 
possession of the silicic acid. The process is reversed if an alcogel 
be placed in a considerable volume of water. Then alcohol separates 
from combination, in consequence of the opportunity it possesses to 
diffuse into water; and water, which is now the liquid present in 
excess, recovers possession of the silicic acid. Such changes illust 
trate the predominating influence of mass. 

Even the compounds of silicic add with alkaUes yield to the decom- 
posing force of diffusion. The compound of silicic acid with 1 or 2 
per cent, of soda is a colloidal solution, and, when placed in a dialyzer 
over water in vacuo to exclude carbonic acid, suffers gradual decom- 
position. The soda diffuses off slowly in the caustic state, and gives 
the usual brown oxide of silver when tested with the nitrate of that 
base. 

The pectization of liquid silicic acid and many other liquid col- 
loids is effected by contact with minute quantities of salts m a way 
which is not understood. On the other hand, the gelatinous acid 
may again be liquefied and have its energy restored by contact with 
a very moderate amount of alkali. The latter change is gradual^ 1 
part of caustic soda, dissolved in 10,000 water, liquefying 200 parts 
of silicic acid (estimated dry) in 60 minutes at 100° C. Gelati- 
nous stannic acid also is easily liquefied by a small proportion of 
alkali, even at the ordinary temperature. The alkiQi, too, after 
liquefying the gelatinous colloid, may be separated again from it by 
diffusion into water upon a dialyzer. The solution of these colloids, 
in such circumstances, may be looked upon as analogous to the solu- 
tion of insoluble organic colloids witnessed in animal digestion, with 
the difference that the solvent fluid here is not acid but alkaline. 
Liquid silicic acid may be represented as the " peptone " of gelati- 
nous silicic acid ; and the liquefaction of the latter by a trace of alkali 
may be spoken of as the peptization of the jelly. The pure jellies of 
alumina, peroxide of iron, and titanic acid, prepared by dialysis, are 
assimilated more closely to albumen, being peptized by minute quan- 
tities of hydrochloric acid. 

Liquid Stannic and Metastannic Acids. — Liquid stannic acid is 
prepared by dialyzing the bichloride of tin with an addition of alkali, 
or by dialyzing the stannate of soda with an addition of hydrochloric 
acid. In both cases a jelly is first formed on the dialyzer ; but, as the 
salts diffuse away, the jelly is again peptized by the small proportion 
of free alkali remaining : the alkali itself may be removed bjr con- 
tinued diffusion, a drop or two of the tincture of iodine facihtating 
the separation. The liquid stannic acid is converted on heating it 
into liquid metastannic acid. Both liquid acids are remarkable for 
the facility with which they are p.ectized" by a minute addition of 
hydrochloric acid, as well as by salts. 

Liquid 7\tamc Acid la prepared by dissolving gelatinous titanic acid 



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^0 Royal Society. 

in a small quantity of hydrochloric acid, without heat, and placing 
the liquid upon a dialyzer for several days. The liquid must not 
contain more than 1 per cent, of titanic acid, otherwise it sponta- 
neously gelatinizes, hut it appears more stable when dilute. Both 
titanic and the two stannic acids afford the same classes of com- 
pounds with alcohol &c. as are obtained with silicic acid. 

Liquid Tungstic Acid, — The obscurity which has so long hung 
over tungstic acid is removed by a dialytic examination. It is in 
fact a remarkable colloid, of which the pectous form alone has 
hitherto been known. Liquid tungstic acid is prepared by adding 
dilute hydrochloric acidcarefully to ,a 5 per cent, solution of tung- 
state of soda, in sufficient proportion to neutralizeHhe alkali, and then 
placing the resulting liquid on a dialyser. In about three days the 
acid is found pure, with the loss of about 20 per cent., the salts 
having, diffused entirely away. It is remarkable that the purified 
acid is not pectized by acids or salts even at the boiling tempe- 
rature. Evaporated to dryness, it forms vitreous scales, like gum 
or gelatine, which sometimes adhere so strongly to the surface of 
the evaporating dish as to detach portions of it. It may be heated 
to 200° C. without losing its solubility or passing into the pectous 
state, but at a temperature near redness it undergoes a molecular 
change, losing at the same time 242 per cent, of water. When water 
is added to unchanged tungstic acid, it becomes pasty and adhesive 
like gum ; and it forms a liquid with about one-fourth its weight of 
water, which is so dense as to float glass. The solution effervesces 
with carbon«ate of soda, and tungstic acid is evidently associated 
with silicic and molybdic acids. The taste of tungstic acid dissolved 
in water is not metallic or acid, but rather bitter and astriilgent. 
Solutions of tungstic acid containing 5, 20, 50, Q^'^y and 79*8 per 
cent, of dry acid, possess the following densities at 19°, 1*0475, 
1-2168, 1*8001, 2-396, and 3-243. Evaporated in vacuo liquid 
tungstic acid is colourless, but becomes green in air from the deoxi- 
dating action of organic matter. Liquid silicic acid is protected 
from pectizing when mixed with tungstic acid, a circumstance pro- 
bably connected with the formation of the double compounds of these 
acids which M. Marignac has lately described. 

Molybdic Acid has hitherto been known (like tungstic acid) only 
in the insoluble form. Crystallized molybdate of soda dissolved in 
water is decomposed by the gradual addition of hydrochloric acid 
in excess without any immediate precipitation. The acid hquid thrown 
upon a dialyzer may gelatinize after a few hours, but again liquefies 
spontaneously, when the salts diffuse away. After a diffusion of 
three days, about 60 per cent, of the molybdic acid remains behind 
in a pure condition. The solution of pure molybdic acid is yellow, 
astringent to the taste, acid to test-paper, and possesses much stabi- 
lity. The acid may be dried at 100°, and then heated to 200° 
without losing its solubility. Soluble molybdic acid has the same 
gummy aspect as soluble tungstic acid, and deliquesces slightly when 
exposed to damp air. Both acids lose their colloidality when digested 
with soda for a short time, and give a variety of crystailizable salts. 



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Geological Society. 321 

GEOLOGICAL SOCIETY. 

[Continued from p. 243.] 

June 22, 1864.— W. J. Hamilton, Esq., President, 
in the Chair. 

1 . " On the Fossiliferous Rocks of Forfarshire and their contents," 
By James Powrie, Esq., F.G.S. 

Referring to his former paper for a detailed description of the 
lower members of the Forfarshire Old Red Sandstone, the author 
now gave a general sketch of the relations of the several beds, 
and then descriptions of the species of Crustacea and Fish oc- 
curring in them. The latter belong to five genera, two of which 
(Ischnacantkus and Euthacanthus) are new. After discussing the 
nature of Parka decipiens, and shortly noticing the genera of Crus- 
tacea that occur in the same rocks , Mr. Powrie concluded his paper 
with a short synopsis of the distribution of the members of the Old 
Red Sandstone in Fdrfarshire, and a discussion respecting the sub- 
division of that formation, in which he stated that Ptetygotu^, Parka 
decipiens, and Cephalaspis are always associated in the same beds, 
and extend through all the fossiliferous rocks of Forfarshire, instead 
of the latter characterizing a higher horizon than the others. 

2. " On the Reptiliferous Rocks and Foot-print Strata of the 
North-east of Scotland." By Prof. R. Harkness, F.R.SS. L. & E-, 
F.G.S. 

The author showed that the foot-print sandstones of Ross- shire 
constitute the upper portion of the Old Red Sandstone formation, 
and that the strata embraced in a line of section from the Nigg to 
Cambus Shandwick, from above the Gneiss to the foot-print sand- 
stones of Tarbet Ness inclusive, are conformable throughout, and 
are referable to each of the three divisions of the Old Red Sand** 
8tone,-*namely, the conglomerates and yellow sandstones (of a thick- 
ness of 1500 feet) belonging to the liower Old Red Sandstone; the 
grey flaggy sandstones and shales of Geanies — the equivalent of 
the Caithness flags — containing Osteolepis, Coccosteus, and Acan^ 
thodes, and thus referable to the Middle Old Red ; thirdly, conform- 
able strata, consisting of conglomerates and foot-bearing and other 
sandstones appertaining to the higher members of the system. 
The foot-bearing sandstones have a thickness of 400 feet, and re- 
present the reptiliferous sandstones of the Elgin area, though not 
overlain by Cornstones as in that district. 

The author, in conclusion, remarked that though Stagonolepis is 
decidedly • Teleosaurian in its afllinities, it does not consequently 
mark a Mesozoic group of rocks; for Mastodoniosauria:, which 
abound in the Trias, occur in the Coal-measures ; and stratigraphical 
evidence shows us that Teleosaurian crocodiles have a wider geo- 
logical range, since they are met with in the Old Red Sandstone. 

3. " On some Bone- and Cave-deposits of the Reindeer-period in 
the South of France." By John Evans, Esq., F.R.S., F.G.S. 

The deposits to which the author particularly called attention in 



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823 Geological Society : — 

this paper are those which have been, and are still being explored 
under the direction of MM. Lartet and Christy, and which were 
visited by him under the guidance of the latter gentleman and ac- 
companied by Mr. Hamilton, Aof. Rupert Jones, Capt. Galton, 
Mr. Lubbock, and Mr. Franks. 

Mr. Evans first gave -a detailed description of the physical features 
of the valley of the Vfe^re, and of the contents of the caverns of 
Badegoule, Le Moustier, La Madelaine, Laugerie- Haute, Laugerie- 
Basse, the Gorge d'Enfer, and Les Eyzies, giving a list of the 
animal-remains discovered, which are for the most part of the same 
species from all the caverns. 

The author then discussed the antiquity of the deposits according 
to four methods of inquiry, — namely, from geological considerations 
with regard to the character and position of the caves ; from the 
palaeontological evidence of the remains found in them ; from the 
archaeological character of the objects of human workmanship ; and 
from a comparison with similar deposits in neighbouring districts in 
France; and he came to the conclusion that they belonged to a 
period subsequent to that of the Elephas primigenius and Rhinoceros 
tichorhinus, but characterized by the presence of the Reindeer and 
some other animals now extinct in that part of Europe. 

4. " On the Carboniferous Rocks of the Donetz and the Granite- 
gravel of St. Petersburg." By Prof. J. Helmersen. (In a letter 
to Sir R. L Murchison, K.C.B., F.R.S., F.G.S., &c.) 

lliis letter relates (1) to the discovery in the Donetz Mountains 
of additional beds of coal and of iron-ore ; (2) to the proposed use 
of this coal for steam-purposes on the Volga; (3) to two geological 
expeditions to be sent out in 1864 for the purpose of surveying the 
Permian basin of Russia ; and lastly, to the successful completion 
of an Artesian boring at St. Petersburg. In this well the following 
beds were passed through : — Alluvium, 88 ft. ; Silurian clay, 300 ft, ; 
sandstone, 137 ft. ; bed of gravel, the result of the degradation of 
granite. 

5. *' On a supposed Deposit of Boulder-clay in North Devon." 
By George Maw, Esq., F.G.S.. F.L.S. 

A deposit of brown clay which occurs near Fremington, in North 
Devon, and has been worked for several years, was described by the 
author in this paper, and referred by him to the Boulder-clay forma- 
tion. The smallest amount of subsidence necessary for the deposi- 
tion of this clay at its present highest level would place a large area 
of Devonshire under water. 

Mr. Maw considered the raised beach at Croyd as being a much 
more recent deposit than the gravel just described; and in con- 
nexion with the question of the former submergence of Devonshire 
during the glacial period, he discussed the relation of the latter to a 
deposit of granite-drift gravel at Petrochstow, concluding that it 
could only have been transported thither during the submergence of 
the high ridges which intersect at right angles the country between 
tho two deposits. 



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Mr T. Belt an the Formation of Lakes by Ice-action, 828 

6. •* On the former existence of Glaciers in the High Grounds of 
the South of Scotland." By J. Young, M.D., F.R.S.E. 

The heights horderiog the counties of Peebles and Dumfries are 
stated by the author to contain well-preserved remains of a group of 
Glaciers belonging to a later period than the Boulder-clay, and 
some of which have been already alluded to by Mr. Geikie and Mr. 
Chambers. Dr. Young then describes the physical geography of 
the region, grouping the several hills into three ranges — the Broad 
Law Range, the White Coomb Range, and Hartfell — from which 
certain glaciers formerly descended into the valleys ; and he further 
divides the glaciers into two classes, which he terms respectively 
the " Social" and the " Solitary." The author then describes the 
form and extension of the masses of detritus which he considers to 
be glacial ddbris, contrasting their characters with those of the 
patches of Boulder- clay occurring in the neighbourhood. 

Many indications of glaciers are] shown to be much obscured by 
the prevalence of peat in the district ; but, in addition to the mo- 
raine matter, smoothed surfaces and r aches moutonnies are occa- 
sionally seen. 

7. "On the Formation and Preservation of Lakes by Ice-action." 
By Thomas Belt, Esq. 

During a residence of two years in the province of Nova Scotia, 
the author observed the remarkable number of lakes, great and 
small, occurring there, sometimes in connected chains and some- 
times on the sides and tops of hills. The lake-basins are stated to 
be chiefly in extremely hard quartzites and metamorphosed schists, 
irregularly studded with masses of Boulder-clay, beneath which are 
seen scratches, grooves, &c., that have been produced by ice-action. 
The author then describes all the phenomena in detail, and gives a 
resumS of the theory of their glacial origin, as propounded by Pro- 
fessor Ramsay, coming to the conclusion that in this way only can 
the facts be consistently explained. 

8. '* A Sketch of the Principal Geological Features of Hobart, 
Tasmania." By S. H. Wintle, Esq. 

The hills upon which Hobart is built, as well as those in the 
vicinity, are mostly composed of New (?) Red Sandstone, capped 
with Greenstone of variable composition and of great thickness in 
some places. 

The Carboniferous Limestone (?) is stated to be very extensively 
developed throughout the island, and to be very fossiliferous ; the 
author describes its lithological characters, as well as those of the 
Devonian rocks and the Silurian slates of Mount Wellington, which 
last have, as yet, proved unfossiliferous ; but he states that Mr. 
Gould has found a Calymene Blumenbachii in similar rocks in the 
interior. He then, after describing the Coal-formation of the island, 
and remarking upon the anthracitic nature of the coal, passes on to 
the " Boulder Drift (?)," which consists of immense boulders, prin- 
cipally of felspathic trap and greenstone, imbedded in stiff clay in 
some parts, and in loam in others. The boulders are also associated 



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834 Intelligence and Miscellaneous Articles* 

vlth fragments of New Red Sandstone and nodular masses of 
Dolomite. 

The author concludes by describing the mode of occurrences^ in 
the valley of the Derwent^ of a marine deposit which he considers of 
Postpliocene age, and which is found at an elevation of upwards of 
10()ft« above the sea- level, and at a distance of from 50 to 100 
yards from the water's edge — thus showing that the valley of the 
Derwent and the neighbouring country had been recently upheaved. 

XXXVIII. Intelligence and Miscellaneous Articles. . 

ON THE EBULLITION OF WATER, AND ON THE EXPLOSION OF 
STEAM-BOILEKS. BY M. L. DUFOUB. 

GASES, it is known, tend eminently to promote the vaporization 
of liquids with which they are in contact. But the superficial 
gaseous layer which adheres to solids, acting at first like gases 
themselves, is gradually removed by prolonged and successive heat- 
ing. When the solid surfaces are deprived of it, they no longer by 
their contact excite changes of condition, but become indifferent in 
the liquid. 

What confirms this view is the circumstance that, by maintain- 
ing or producing on the surface of bodies a gaseous layer, ebullition 
of a liquid is immediately produced if the temperature is suitable, 
and any retardation of ebullition is avoided. The following experi- 
ment realizes these conditions. Two platinum wires, communica- 
ting with the outside, pass through a cork in which a thermometer 
fits, and dip in water. They are connected with the two poles of a 
galvanic element, and a slight disengagement of gas, due to electro- 
lysis, takes i)lace on their surface. Under these circumstances, and 
so long as the current passes, it is impossible to obtain the least 
retardation of boiling. If these wires cease to be connected with a 
battery, after some successive heatings and by diminishing the super- 
ficial pressure, retardations are produced similar to those mentioned 
above. If the current is then made to pass, ebullition is imme- 
diately produced. If the retardation is considerable (from 15 to 20 
degrees), closing the circuit produces so abundant a production of 
vapour as to resemble a true explosion. The vapour appears to 
break away with an eflPbrt from the liquid mass, and the vessel exi>eri- 
ences concussions almost strong enough to break it. This experiment, 
which has frequently succeeded in my hands with ordinary water, is 
more striking in the case of slightly acidulated water, for then the 
retardations are more pronounced. 

It is therefore, I think, a property of water to tend in most cases 
to retain the liquid state, even when ebullition ought to take place, 
provided the boiling-point has been reached by a diminution of the 
superficial pressure after the liquid has been already heated, and after 
it has been in contact for some time with the solid substances of the 
vessel. This property is perhaps not without interest in its applica- 
tion to the explosions of steam-boilers. This formidable phenome- 
non is still enveloped in much obscurity. Various attempts have 



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Intelligence and Miscellaneotts Articles. 325 

been made to explain it ; among others, by saying that in a perfect 
calm, while the issue of vapour is suspended, everything being mo- 
tionless in the apparatus, and all the dissolved air expelled, the water 
may accidentally become heated beyond the point corresponding to 
its pressure, and then if ebullition sets in, it suddenly furnishes a 
mass of vapour which breaks the envelopes. But the embarrassing 
circumstance, and the one found in most cases, is that the accident 
takes place without the heating having been continued, while the 
workmen and the machine were at rest, and when, from cooling, the 
])ressure in the machine had diminished. These conditions, almost 
always mentioned with surprise in these accidents, exhibit an un- 
doubted analogy with the experiments which I have described. Is 
it not possible that at a moment of repose, and while the heating has 
been discontinued, the cooling which sets in at first diminishes the 
pressure of vapour existing in the boiler ? As water, in virtue of its 
great specific heat, cools very slowly, it retains for a longer time a 
temperature which ought to produce ebullition under this diminished 
pressure. This ebullition doubtless takes place most frequently in 
proportion as the diminution of pressure permits ; but it may happen 
that, under exceptional circumstances, a retardation similar to that 
described above is produced, and then after a longer or shorter delay 
ebullition sets in, either spontaneously, or in consequence of some 
foreign disturbance. This ebullition ought to manifest the charac- 
ters many times obsei*ved in my apparatus, where the concussions 
raised the heavy support to which the retort was fixed. From the 
large quantity of water contained in a boiler, these strokes might 
well cause a fracture of the sides, and the disastrous eflfects of this 
kind of accidents. 

The explanation which I attempt to give accounts, it is seen, for a 
1)oiler-explosion, even when heating has ceased, when all the machine 
is in a state of cooling, and the pressure has been diminished. Com- 
paring the details ordinarily noted in this kind of explosion with the 
conditions of the experiment above mentioned, it is impossible not 
to observe a striking analogy, if the hints above given are correct ; 
and it would remain to find out the means of preventing these de- 
plorable accidents. No solid body by its contact seemed to me to 
determine ebullition with certainty at the desired point ; and all of 
them at length and by repeated heating become inactive. Contact 
of gases, on the contrary, invariably provokes ebullition as soon as 
the temperature makes it possible. Hence, as M. Donny has already 
said, it is desirable permanently to produce gases in the interior of 
the boiler. Wires or platinum plates which dip in the water, and 
by which enters the current of even a feeble battery, would very 
probably be sufiicient to prevent retardations of ebullition. 

P.S. — Since writing'this Note, I have read (Cosmos, April 7, 1864) 
of a fact which agrees* very well with this proposed theory of the 
explosion of boilers. 

This is the explosion at Aberdare, where two boilers burst. The 
water supplied appeared to contain a little sulphuric acid. Some 
pieces of the sides presented by Mr. Fairbairn to the Manchester 



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326 Intelligence and Mucellaneoua Articles. 

Philosophical Societj were deeply corroded from chemioid action. 
The explosion has naturally been attributed to this attack of the 
sides by the acid, and doubtless an acidulated liquid ought to attack 
t)ie sides. 

Now we know that sulphuric acid, even in very small quantity, 
imparts to water the property of undergoing retardations of ebullition 
much more considerable and much more frequent than those of pure 
water. If, then, boiler explosions arise from a retardation in the 
ebullition of water when the pressure diminishes in the boiler, as I 
explain in my Note, it is seen that the two accidents in England are 
easily explained, inasmuch as the feeding water contained a little 
acid. — Comptes Rendus, June 6, 1864. 

APPLICATION OP ZEIODELITE. 

Zeiodelite is a mixture prepared by melting together 20 to 30 parts 
of roll sulphur with 24 parts of powdered glass or pumice, and which 
forms a mass as hard as stone, that resists the action of water and 
of the strongest acids. Prof. R. Bottger recommends it, therefore, 
for making water- and air-tight cells for galvanic batteries. — Pog- 
gendorfiF's Annalen, July 1864. 

DSTBBMINATIONS OF TEMPEBATUBB IN THE DEPTH OF SOME 
BAVARIAN MOUNTAIN LAKES. 

In the Sitzungsberichte of the Royal Bavarian Academy of 1862, 
Prof. Jolly describes a bathometer and aminimum thermometer of his 
invention, and gives some observations of the temperature at various 
depths in the Konigssee, the Obersee, and the Walchensee, \frhich 
may find a place here. 



Depth in 


Temperature 


Depth in 


Temperature 


metres. 


in degrees C. 


metres. 


in degrees C. 


Konigssee, 


1862, Aug. 


Obersee, 1 


1862, Sept. 





o o 

14-9-15-2 





16a 


22*6 


7-89 


271 


7-56 


26-8 


6-61 


31-4 


9*12 


37-8 


6-58 


62-3 


6-59 


67-2 


6-00 






95-5 
104-3 


5-83 
5-81 


Walcheniei 


J, 1862, Oct. 


153-3 


5-38 





150 


163-2 


5-50 


58-3 


6-76 


198-0 


5-44 


97-6 


6-07 


204*1 


5-52 


98-6 


6*12 


216-5 


5*34 


1070 


6-91 






248-8 


6*17 



Hence in these lakes (as in those of Switzerland) the temperature 
approaches, without actually attaining, that of the maximum density 
of water (from inadequate depth), and without following any regular 
progress in its decrease. — Poggendorflf's Annalen, August 1864. 



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Intelligence and Miscellaneous Articles. 827 

ON THE METEORITE OF ALBABETO IN THE MODENESE. 
BY DB. W. HAIDINGEB*. 

This meteorite, and the pamphlet by the Jesuit Dominico Troili 
describing it, have been mentioned by Chladni (1798 and 1819), by 
Ende (1804), and by Sir D. Brewster (Edinburgh Journal of Science, 
1819). Chladni, whose careful inquiries at Modena in 1819 could 
not make out any trace of this stone, thought it definitively lost. But 
lately a specimen of it was found to exist in the University Museum 
of Modena ; and of this, Dr. Homes, kindly assisted by Messrs. 
Greg, Senoner, Bianconi, and Bombici, obtained for th^ Imperial 
Museum of Vienna a fragment of 13*31 grammes in weight. It is 
tufaceous in aspect, dark grey, with numerous globular concretions — 
some greenish grey (as the Piddingtonite of Skalka, or the Chladnite 
of Bishopville), others dark grey or black, one of them conspicuous 
for its less density, yellowish-grey tint, dark- brown crust, and atoms 
of native iron disseminated through it. The particles of native and 
protosulphuretted iron irregularly distributed through the whole mass 
are sometimes discernible to the unaided eye ; in one place two 
brownish-black globules are united by metallic iron in such a way 
as to allow us to suppose the group to be a fragment of a larger 
piece of native iron including globules of silicates, like the Hima- 
layan iron. The globules are easily detached from the surrounding 
mass. The outer surface, offering the impressions common to all 
meteorites, is covered, on a surface of about 25 square lines, with a 
blackish-brown, nearly opake crust. In general aspect the Albareto 
meteorite stands next to those of Benares, Trenzano, and Weston. 
Its density, at 15° R., is 3*344. The sulphuretted iron of the me- 
teorites, generally passing under the denomination of magnetic iron- 
pyrites, is, according to Prof. Rammelsberg, a mechanical compound 
ofprotosulphurettediron(75'37 percent.), sulphuretted copper (0*71 
per cent,), chromate of iron (2'83 per cent.), and nickeliferous iron 
(19*83 per cent.), of 4' 7 87 density, yellowish brown, soluble in acids 
without residuous sulphur, and magnetic in consequence of the 
nickel contained in it. llie sulphuretted iron, in its state of purity, 
as it occurs in the Gamallee meteorite, in grains of the size of a pea, 
is, according to Prof. Wohler, a combination of 1 atom of iron with 
1 atom of sulphur (Fe S or iron 63*64, sulphur 36*36). For this 
sulphuret, hitherto not known to exist among the minerals compo- 
sing the terrestrial crust. Dr. Haidinger proposes the denomination 
of Troilite (commemorative of the first describer of the Albareto 
meteorite), and the following mineralogical characters : — amor- 
phous, in minute particles, disseminated through the lithoid sub- 
stance of meteorites, metallic brightness, bronze-brown, streak 
black, hardness 4, density 4*5-4*6; chemical formula, FeS. Ac- 
cording to Troili's pamphlet (Modena, 1766), the meteorite in ques- 
tion may have originally had a weight of about 25 lbs. It fell in 
the middle of July 1766, 5^ p.m., the sky being serene, but covered 
westward with heavy clouds, with frequent thunder and lightning. 
Witnesses assert its fall to have been preceded by a sound resem- 

* Communicated by Count MarachaU. 



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338 Intelligence and MiseeUaneoua Articles. 

bling a cannonade and the hissing of a cannon-ball through the air ; 
some describe it as having been in a state of incandescence, while 
others saw it dark and smoking. It penetrated into the ground to the 
depth of less than a " braccio " (about 2^ Vienna feet), and was dug 
out still hot; spreading a sulphurous smell, and covered with a crust. 
Troili, although quite uncertain as to the nature of the phenomenon, 
which he ascribes to a subterraneous commotion having thrown the 
stone into the air, whence it fell again to the ground, was evidently 
highly anxious to state its reality and every circumstance con- 
cerning it. This, at a time when the scepticism about these phe- 
nomena was such that anyone who asserted their reality could 
only expect incredulity and even ridicule, gave a most meritorious 
proof of moral courage. Supposing the Albareto meteorite to have 
fallen to the ground in a nearly vertical duection, and to have come 
from the west (as did the sounds preceding its fall), its point of de- 
parture may be traced to the constellation of Leo, well known to be 
the point from which the falling stars of the November epoch pro- 
ceed. Its trajectory may have been a segment of the elliptical 
orbit of a whole swarm of bodies moving within the sphere of terres- 
trial attraction on the branch of a hyperbolic orbit through cosmical 
space. Dr. Haidinger on this occasion recalled to mind his hypo- 
thesis on the cause of the high temperature in meteoric masses — pass- 
ing through the terrestrial atmosphere and generating heat by rapid 
compression, in the same way as in Prof. Mallet's experiment, suc- 
cessfully repeated befdre the Academy of Paris in 1803. Of late 
years (1840-57) the experimental researches of Messrs. Bianconi, 
Thomson, Joule, and Tyndall have shown that the temperature of a 
thin string of water rapidly forced through a narrow spiral tube 
rises from 1° F, to 4° F., that a solid body surrounded by a rapid 
airrcurrent was more heated than the ambient air, and that, if the 
rapidity of the air-current be brought to 1780 feet in a second, this 
difference of temperature may be raised to 137°. Even in an atmo- 
sphere rarefied to the utmost limits, any solid progressing within it at 
the rate of meteorites (6-30 miles a second) would come to a far higher 
temperature, still increased by the transformation of active forces 
(light, electricity, magnetism, &c.) into heat, in consequence of the 
resistance opposed to the rapid career of such a body. Prof. Bunsen, 
in a note on the Meteoric Iron of Atacama (Leonhard and Bronn's 
jahrhuch, 1857, p. 265), calculated the loss of active force during 
the fall of a solid coming into the terrestrial atmosphere with a pla- 
netary celerity to be sufficient to heat it to 1 ,000,000° C. Supposing 
" i^oV o" °^ ^^^^ ^^^^ ^° ^® 1°®^ i^ ^^6 ambient medium, such a body 
would still touch the ground with a temperature of 2000° C. 

What Dr. Haidinger has done for meteorites. Prof, Tyndall ha9 
ascertained for hailstones— the existence of a facial plane with inci- 
pient fusion in consequence of the condensation of the air, and of a dor- 
sal one, on which the rarefaction of the air has caused the congelation 
of atmospheric water. Similar circumstances have been observed by 
Prof. Goth, on hailstones fallen at Gratz in the summer of 1846 
(Wiener Naturwissenschaftliche Abhandlungen, published by Haidin- 
ger, vol. i. p. 91).— /mp. Acad. Sc. Vienna, March27, 1864. 



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THE 
LONDON, EDINBURGH, and DUBLIN 

PHILOSOPHICAL MAGAZINE 

AND 

JOURNAL OF SCIENCE. 



[FOURTH SERIES.] 



NOVEMBER 1864. 



XXXIX. On Luminous and Obscure Radiation. 
By John Tyndall, F.K8.y §•(?.* 

1. ^IR WILLIAM HERSCHEL discovered the obscure rays 
i^ of the sun, and proved that the position of maximum 
heat was beyond the red of the solar spectrum f. Forty yeare 
subsequently Sir John Herschel succeeded in obtaining a thermo- 
graph of the calorific spectrum, and in giving striking visible evi- 
dence of its extension beyond the red J. Melloni proved that an 
exceedingly large proportion of the emission from a fiame of oil, 
of alcohol, and from incandescent platinum heated by a flame of 
alcohol, is obscure §. Dr. Akin inferred from the paucity of lumi- 
nous rays evident to the eye, and a like paucity of extra-violet rays, 
as proved by the experiments of Dr. Miller, that the radiation 
from a flame of hydrogen must be mainly extra-red ; and he con- 
cluded from this that the glowing of a platinum wire in a hy- 
drogen-flame, as also the brightness of the Drummond light in 
the oxyh^drogen-flame, was produced by a change in the period 
of vibration ||. By a different mode of reasoning I arrived at the 
same conclusion myself, and published the conclusion subse- 
quentlylf. 

2. A direct experimental demonstration of the character of the 
radiation from a hydrogen-flame was, however, wanting, and this 
want I have sought to supply. I had constructed for me, by 
Mr. Becker, a complete rock-salt train of a size sufficient to 

* Communicated by the Author. 

t Phil. Trans. 1800. 

j Phil. Trans. 1840. I hope very soon to be able to turn my attention 
to the remarkable results described m Note III. of Sir J. Herschers paper. 

§ La Thermochrose, p. 304. ^ Phil. Trans, vol. cliv. p. 327. 

II Reports of the British Association^ 1863. 
PhU. Mag. S. 4. Vol. 28. No. 190. Nov. 1864. Z 



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330 Prof. Tyndall on Luminous and Obscure Radiation, 

permit of its being substituted for the ordinary glass train of a 
Duboscq's electric lamp. A double rock-salt lens placed in the 
camera rendered the rays parallel ; the parallel rays then passed 
through a slit^ and a second rock-salt lena placed without the 
camera produced, at an appropriate distance, an image of this 
slit. Behind this lens was placed a rock-salt prism, while late- 
rally stood a thermo-electric pile intended to examine the spec- 
trum produced by the prism. Within the camera of the electric 
lamp was placed a burner with a single aperture, so that the 
flame issuing from it occupied the position usually taken up by 
the coal points. This burner was connected with a T-piece, 
from which two pieces of india-rubber tubing were carried, the one 
to a large hydrogen-holder, the other to the gas-pipe of the labo- 
ratory. It was thus in my power to have, at will, either the gas- 
flame or the hydrogen-flame. When the former was employed, 
I had a visible spectrum, which enabled me to fix the thermo- 
electric pile in its proper position. To obtieiin the hydrogen- 
flame, it was only necessary to tarn on the hydrogen imtil it 
reached the gas-flame and was ignited ; then to turn off the ga^ 
and leave the hydrogen-flame behind. In this way, indeed, the 
one flame could be substituted for the other without opening the 
door of the camera, or producing any change in the positions of 
the source, the lenses, the prism, and the pile. 

3. The thermo-electric pUe employed is a beautiful instrument 
constructed by Ruhmkorff. It belongs to my friend Mr. Gassiot, 
and consists of a single row of elements properly mounted and 
attached to a double brass screen. It has in front two silvered 
edges, which, by means of a screw, can be caused to close upon 
the pile so as to render its face as narrow as desirable, reducing 
it to the width of the finest hair, or, indeed, shutting it off 
altogether. By means of a small handle and long screw, the 
plate of brass and the pile attached to it can be moved gently to 
and fro, and thus the vertical slit of the pile can be caused to 
traverse the entire spectrum, or to pass beyond it in both direc- 
tions. The width of the spectrum was in each case e^ual to the 
length of the face of the pile, which was connected with an ex- 
tremely delicate galvanometer. 

4. I began with a luminous gas-flame. The spectrum being 
cast upon the brass screen (which, to render the colours more 
visible, was covered with tinfoil), the pile was gradually moved 
in the direction from blue to red, until the deflection of the gal- 
vanometer became a maximum. To reach this it was necessary 
to pass entirely through the spectrum and a little way beyond 
the red ; the deflection then observed was 

80°. 
When the pile was moved in either direction from this position, 
the deflection diminished. 



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Frof. Tyndall an Luminous and Obscure Radiation. 331 

5. The hydrogen-flame was now substituted for the gas-flame ; 
the visible spectrum disappeared^ and the deflection fell to 

Hence^ as regards rays of this particular refrangibility, the emis- 
sion from the luminous gas-flame was two-and-a-half times that 
from the hydrogen-flame. 

6. The pile was now moved to and fro, and the movement in 
both directions was accompanied by a diminished deflection. 
Twelve degrees, therefore, was the maximum deflection for the 
hydrogen-flame ; and the position of the pile, determined pre- 
viously by means of the luminous flame, proves that this deflec- 
tion was produced by extra-red undulations. I moved the pile a 
little forwards, so as to reduce the deflection from 12° to 4 , and 
then, in order to ascertain the refrangibility of the rays which 
produced this small deflection, I relighted the gas. The recti- 
linear face of the pile was found invading the red. When the 
pile was caused to pass successively through positions correspond- 
ing to the various colours of the spectrum, and to its extra- violet 
rays, no measurable deflection was produced by the hydrogen- 
flame. 

7. I next placed the pile at some distance from the invisible 
spectrum of the flame of hydrogen, B.nd felt for the spectrum by 
moving the pile to and fro. Having found it, I without diffi- 
culty ascertained the place of maximum heating. Changing 
nothing else, I substituted the luminous flame for the non-lumi- 
nous one; the position of the pile when thus revealed, was 
beyond the red. 

8. It is thus proved that the radiation from a hydrogen-flame 
is sensibly extra-red. The other constituents of the radiation 
are so feeble as to be thermally insensible. Hence, when a body 
is raised to incandescence by a hydrogen-flame, the vibrating 
periods of its atoms must be shorter than those to which the 
radiation of the flame itself is due. 

9. The falling of the deflection from SOP to 12^ when the hy- 
drogen-flame was substituted for the gas-flame is doubtless due 
to the absence of all solid matter in the former. We may, how- 
ever, introduce such matter, and thus make the radiation origi- 
nating in the hydrogen-flame much greater than that of the gas- 
flame. A spiral of platinum wire plunged in the former gave a 
maximum deflection of 52^ 

at a timo when the maximum deflection of the gas-flame Was only 

38°. 

10. It is mainly by convection that the hydrogen-flame dis- 
perses its heat : though its temperature is higher, its sparsely- 
scattered molecules are not able to cope, in radiant energy, with 

Z2 



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332 Prof. Tyndall on Luminous and Obscure Radiation. 

the solid carbon of tlie luminous flame. The same is true for 
the flame of a Bunsen's burner; the moment the air (which 
destroys the solid carbon-particles) mingles with the gas-flame, 
the radiation falls considerably. Conversely^ a gush of radiant 
heat accompanies the shutting out of the air which deprives the 
gas-flame of its luminosity. When, therefore, we introduce a 
platinum wire into a hydrogen-flame, or carbon-particles into a 
Bunsen's flame, we obtain not only waves of a new period, but 
also convert a large portion of the heat of convection into the 
heat of radiation. 

11. The action was still very sensible when the distance of the 
pile from the red end of the spectrum on the one side was as 
great as that of the violet rays on the other, the heat-spectrum 
thus proving itself to be at least as long as the Ught-spectrum. 

12. Bunsen and Kirchhoff have proved that, for incandescent 
metallic vapours, the period of vibration is, within wide limits, 
independent of temperature. My own experiments with flames 
of hydrogen and carbonic oxide as sources, and with cold aqueous 
vapour and cold carbonic acid as absorbing media, point to the 
same conclusion*. But in solid metals augmented temperature 
introduces waves 6f shorter periods into the radiation. It may 
be asked, " What becomes of the long obscure periods when we 
heighten the temperature ? Are they broken up or changed into 
shorter ones, or do they maintain themselves side by side with 
the new vibrations ? '' The question is worth an experimental 
answer. 

13. A spiral of platinum wire suitably supported was placed 
within the camera of the electric lamp at the place usually occu- 
pied by the carbon points. This spiral was connected with a 
voltaic battery; and by varying the resistance to the current, it 
was possible to raise the spiral gradually from a state of darkness 
to an intense white heat. Raising it to a white heat in the first 
instance, the rock-salt train was placed in the path of its rays, 
and a brilliant spectrum was obtained. The pile was then moved 
into the region of obscure rays beyond the red of the spectrum. 
Altering nothing but the strength of the current, the spiral was 
reduced to darkness, and lowered in temperature till the deflec- 
tion of the galvanometer fell to 1°. Our question is, " What 
becomes of the waves which produce this deflection when new 
ones are introduced by augmenting the temperature of the 
spiral?'' 

14. Causing the spiral to pass from this state of darkness 
through various degrees of incandescence, the following deflec- 
tions were obtained : — 

* Phil. Trans, vol. cliv. p. 327. 



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Prof. Tyndall on Luminous and Obscure Radiation, 333 

Table I. 

Appearance of spiral. Deflection by obscure rays. 

6 
Dark 1 

Dark 6 

Faint red 10*4 

Dull red 125 

Red 180 

Full red 27*0 

Bright red 44*4 

Nearly white 54*3 

Full white 60-0 

15. The deflection of 60° here obtained is equivalent to 122 
of the first degrees of the galvanometer. Hence the intensity of 
the obscure rays in the case of the full white heat is 122 times 
that of the rays of the same refrangibility emitted by the dark 
spiral used at the commencement. Or^ as the intensity is pro- 
portional to the square of the amplitude, the height of the sethe- 
real waves which produced the last deflection was eleven times 
that of the waves which produced the first. The wave-length^ of 
course, remained the same throughout. 

16. The experimental answer, therefore, to the question above 
proposed is, that the amplitude of the old waves is augmented 
by the same accession of temperature that gives birth to the new 
ones. The case of the obscure rays is, in fact, that of the lumi- 
nous ones (of the red of the spectrum, for example), which 
glow with augmented intensity as the temperature of the radiant 
source is heightened. 

17. In my last memoir* I demonstrated the wonderful trans- 
parency of the element iodine to the extra-red undulations. A per- 
fectly opake solution of this substance was obtained by dissolving 
it in bisulphide of carbon, and it was shown in the memoir referred 
to that a quantity of iodine sufficient to quench the light of our 
most brilliant flames transmitted 99 per cent, of the radiation 
from a flame of hydrogen. 

18. Fifty experiments on the radiant heat of a hydrogen-flame, 
recently executed, make the transmission of its rays, through a 
quantity of iodine which is perfectly opake to light, 

100 per cent. 
To the radiation from a hydrogen-flame the dissolved iodine is 
therefore, according to these experiments, perfectly transparent. 

19. It is also sensibly transparent to the radiation from solid 
. bodies heated under incandescence. 

20. It is also sensibly transparent to the obscure rays emitted 
by luminous bodies. 

• Phil. Trans, vol. div. p. 327. [This memoir wUl appear in the Decem- 
ber Number of the Philosophical Magazine.] 



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834 Prof. Tyndall on Luminous and Obscure Radiation, 

21. To the mixed radiation which issues from solid bodies 
at a very high temperature^ the pure bisulphide of carbon is also 
eminently transparent. Hence^ as the bisulphide of carbon in- 
terferes but slightly with the obscure ray^ issuing from a highly 
luminous source^ and as the dissolved iodine seems not at all to 
interfere with them, we have in a combination of both substances 
a means of almost entirely detaching the purely thermal rays 
from the luminous ones. 

22, If vibrations of a long period, established when the radia- 
ting body is at a low temperature, maintain themselves, as 
indicated in paragraph 14, side by side with the new periods 
which augmented temperature introduces, it would follow that a 
body once pervious to the radiation from any source must always 
remain pervious to it. We cannot so alter the character of the 
radiation that a body once in any measure transparent to it 
shall become quite opake to it. We may, by augmenting the 
temperature, diminish the percentage of the total radiation trans- 
mitted by the body ; but inasmuch as the old vibrations have 
their amplitudes enlarged by the very accession of temperature 
which produces the new ones, the total quantity of heat of any 
given refrangibility transmitted by the body must increase with 
increase of temperature. 

28. This conclusion is thus experimentally illustrated. A cell 
with parallel sides of polished rock-salt was filled with the solu- 
tion of iodine, and placed in front of the camera within iidiich 
was the platinum spiral. Behind the rock-salt cell was placed 
an ordinary thermo-electric pile, to receive such rays as had 
passed through the solution. The roek-salt lens was in the 
camera in front, but a small sheaf only of the parallel beam 
emergent from the lamp was employed. Commencing at a very 
low dark heat, the temperature was gradually augmented to full 
incandescence with the foDowing results : — 

Table II. 
Appearance of spiral. Deflection, 

Dark ........ 1 

Dark but hotter .... 8 

Dark but still hotter . • • 5 
Dark but still hotter . . .10 

Feeble red 19 

Dull red 25 

Red 35 

Full red ,45 

Bright red 53 

Very bright red .... 68 

Nearly white 69 

White 76 

Intense white 80 



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Prof. Tyndall on Laminous and Obscure Radiaiion. dSS 

24. To the luminous rays from the intensely white spiral the 
solution was perfectly opake ; but though by the introduction 
of such rays the transmission^ as expressed in parts of the total 
radiation^ was diminished^ the quantity absolutely transmitted 
was enormously increased^ The value of the last deflection is 
440 times that of the first ; by raising therefore the platinum 
spiral from darkness to whiteness^ we augment the intensity of 
the obscure rays which it emits in the ratio of 1 : 440. 

25. A rock-salt cell filled with the transparent bisulphide of 
carbon was placed in front of the camera which contained the 
platinum spiral i*aised to a dazzling white heat. The trans- 
parent liquid was then drawn off and its place supplied by the 
solution of iodine. The deflections observed in the respective 
cases are as follows : — 

Radiation from White-hot Platinum. 
Through transparent CS^. Through opake solution. 

73-9 73-0 

73-8 . 72-9 

AU the luminous rays passed through the transparent bisulphide^ 
none of them passed through the solution of iodine. Still we 
see what a small difference is produced by their withdrawal. 
The actual proportion of luminous to obscure, as calculated from 
the above observations^ may be thus expressed : — 

26. Dividing the radiation from a platinum wire raised to a 
dazzling whiteness by an electric current into twenty-four equal 
parts f one of these parts is luminous and twenty-three obscure. 

27. A bright gas-flame was substituted for the platinum 
spiral, the top and bottom of the flame were shut off, and its 
most brilliant portion chosen as the source of rays. The result 
of forty experiments with this source may be thus expressed : — 

28. Dividing the radiation from the most brilliant portion of 
aflame of coal-gas into twenty ^five equal parts y one of those parts 
is luminous and twenty-four obscure, 

29. I next examined the ratio of obscure to luminous rays in 
the electric light. A battery of fifty cells was employed, and 
the rock-salt lens was used to render the rays from the coal 
points parallel. To prevent the deflection from reaching an 
inconvenient magnitude, the parallel rays were caused to issue 
from a circular aperture O'l of an inch in diameter, and were 
sent alternately through the transparent bisulphide and through 
the- opake solution. It is not easy to obtain perfect steadiness 
on the part of the electric light ; but three experiments carefully 
executed gave the following deflections : — 



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336 Prof. Tyndall an Luminous and Obscure Radiation^ 

Radiation from Electric Light. — Experiment No. I. 
Through transparent CS'. Through opake solution. 
72°0 70P'0 

Experiment No. 11. 
76^-5 75^0 

Experiment No. III. 
77^-5 76^-5 

Calculating from these measurements the proportion of lumi- 
nous to obscure heat, the result may be thus expressed : — 

30. Dividing the radiation from the electric liffht emitted by car- 
bon points, and excited by a Grove's battery of forty ceUs, into ten 
equal parts, one of those parts is luminous and nine obscure, 

31. The results may be thus presented in a tabular form : — 

Table III. — Radiation through dissolved Iodine. 

Source. Absorption. Transmission. 

Dark spiral 100 

Lampblack at 212Tahr. . 100 

Red-hot spiral • • . • 100 

Hydrogen-flame .... 100 

Oil-flame 3 97 

Gas-flame 4 96 

White-hot spiral .... 4*6 95-4 

Electric light 10 90 

Repeated experiments may slightly alter these results, but they 
are extremely near the truth. 

32. Having thus in the solution of iodine found a means of 
almost perfectly detaching the obscure from the luminous heat- 
rays of any source, we are able to operate at will upon the former. 
Here are some illustrations : — The rock-salt lens was so placed in 
the camera that the coal points themselves and their image 
beyond the lens were equally distant from the latter. A battery 
of forty cells being employed, the track of the cone of rays emer- 
gent from the lamp was plainly seen in the air, and their point 
of convergence therefore easily fixed. The cell containing the 
opake solution was now placed in front of the lamp. The lumi- 
nous cone was thereby entirely cut off*, but the intolerable tem- 
perature of the focus, when the hand was placed there, showed 
that the calorific rays were still transmitted. Thin plates of tin 
and zinc were placed successively in the dark focus and speedily 
fused ; matches were ignited, gun-cotton exploded, and brown 
paper set on fire. Employing the iodine solution and a battery 
of sixty of Grove's cells, all these results were readily obtained 



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Prof. Tyndall on Luminous and Obscure Radiation. 837 

with the ordinary glass lenses attached to Duboscq's electric 
lamp. They cannot^ I think^ fail to give pleasure to those who 
repeat the experiments. It is extremely interesting to ob- 
serve in the middle of the air of a perfectly dark room a piece 
of black paper suddenly pierced by the invisible rays^ and the 
burning ring expanding on all sides from the centre of ignition. 

33. On the 15th of this month I made a few experiments on 
solar light. The heavens were not free from clouds^ nor the 
London atmosphere from smoke^ and at best I obtained only a 
portion of the action which a clear day would have given me. 
I happened to possess a hollow lens^ which I filled with the con* 
centrated solution of iodine. Placed in the path of the solar 
rays^ a faint red ring was imprinted on a sheet of white paper 
held behind the lens^ the ring contracting to a faint red spot 
when the focus of the lens was reached. It was immediately 
found that this ring was produced by the light which had pene- 
trated the thin rim of the liquid lens. Pasting a zone of black 
paper round the rim^ the ring was entirely cut off and no visible 
trace of solar light crossed the lens. At the focus^ whatever light 
passed would be intensified nine hundredfold ; still even here no 
light was visible. 

34. Not so, however with the sun's obscure rays ; the focus 
was burning hot. A piece of black paper placed there was in- 
stantly pierced and set on fire; and by shifting the paper, 
aperture after aperture was formed in quick succession. Gun- 
powder was also exploded. In faqt we had in the focus of the 
sun's dark rays a heat decidedly more powerful than that of the 
electric light similarly condensed, and all the effects obtained 
with the former could be obtained in an increased degree with 
the latter. 

35. I introduced a plano-convex lens of glass, larger than 
the opake lens just referred to, into the path of the sun's rays. 
The focus on white paper was of dazzling brilliancy ; and in this 
focus the results already described were obtained. I then 
introduced a cell containing a solution of alum in front of the 
focus. The intensity of the li^ht at the focus was not sensibly 
changed ; still these almost intolerable visual rays, aided as they 
were by' a considerable quantity of invisible rays which had also 
passed through the alum, were incompetent to produce effects 
which were obtained with ease in the perfectly dark focus of the 
opake lens. 

36. Thinking that this reduction of power might be due to 
the withdrawal of heat by reflexion from the sides of the glass 
cell, I put in its place a rock-salt cell filled with the opake solu- 
tion. Behind this cell the rays manifested the power which they 
exhibited in the focus of the opake lens. 



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888 Prof. Tyndall on Luminous and Obscure Radiation. 

37« The rendering of metals incandescent by obscure rays 
has not yet been accomplished. This is a question on which 
Dr. Akin has been engaged for some years^ and it is not my 
intention to publish anything relating to it until the very pro* 
mising arrangements which he has devised have had a sufficient 
trial. 

38. Melloni's experiments led him to conclude that rock- 
salt transmits obscure and luminous rays equally well, and that 
a solution of alum of moderate thickness entirely intercepts the 
invisible rays^ while it allows all the luminous ones to pass. Hence 
the difference between the transmissions of rock-salt and alum 
ought to give the obscure radiation. In this way Melloni found 
that 10 per cent, only of the radiation from an oil-flame consists 
of luminous rays. The method above employed proves that 
the proportion of luminous heat to obscure, in the case of an 
oil-flame^ is probably not more than one-third of what Melloni 
made it 

89. In fact this distinguished man clearly saw the possible 
inaccuracy of the conclusion that none but luminous rays are 
transmitted by alum ; and the following experiments justify the 
clauses of limitation which he attached to his conclusion : — 

The solution of iodine was placed in front of the electric lamp, 
the luminous ravs being thereby intercepted. Behind the rock- 
salt cell containmg the opake solution was placed a glass cell, 
empty in the first instance. The deflection produced by the 
obscure rays which passed through both produced a deflec- 
tion of 

80P. 

The glass cell was now filled with a concentrated solution of alum ; 
the deflection produced by the obscure rays passing through both 
solutions was 

Calculating from the values of these deflections, it was found thai 
of the obscure heat emergent from the solution of iodine, and from 
the side of the glass cell, 20 per cent, was transmitted by the alum* 
40. A point of very considerable importance forces itself upon 
our attention here — namely the vast practical difference which may 
exist between the two phrases, "-obscure rays,'* and " rays from 
an obscure source.^' Many writers seem to regard these phrases 
as equivalent to each other, and are thus led into grave errors. 
A stratum of alum solution ^th of an inch in thickness is, ac- 
cording to Melloni, entirely opake to the radiation from all bodies 
heated under incandescence. In the foregoing experiments the 
layer of alum solution traversed by the obscure rays of our lumi- 
nous source was thirty times the thickness of the layer whidi 



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Prof. Tyndall on Luminoua and Obscure Radiation. i389 

Melloni fottnd sufficient to quench all rays emanating from ob- 
scure sources. 

41. There cannot be a doubt that the invisible rays which 
have shown themselves competent to traverse such a thick- 
ness of the most powerful adiathermic liquid yet discovered 
are also able to pass through the humours of the eye. The 
very careful and interesting experiments of M. Janssen *, prove 
that the humours of the eye absorb an amount of radiant 
heat exactly equal to that absorbed by a layer of water of the 
same thickness^ and in our solution the power of alum is added 
to that of water. Direct experiments on the vitreous humour 
of an ox lead me to conclude that one-fifth of the obscure rays 
emitted by an intense electric light reaches the retina ; and inas- 
much as in every ten equal parts of the radiation from an electric 
lamp nine consist of obscure rays, it follows that, in the case 
of the electric light, nearly two-thirds of the whole radiant 
energy which actually reaches the retina is incompetent to excite 
vision. With a white-hot platinum spiral as source, the mean 
of four good experiments gave a transmission of 11*7 per cent, 
of the obscure heat of the spiral through a layer of distilled 
water 1*2 inch in thickness. A larger proportion no doubt 
reaches the retinaf. 

43. Converging the beam from the electric lamp by a glass 
lens, I placed the opake solution of iodine before my open eye, 
and brought the eye into the focus of obscure rays ; the heat 
was immediately unbearable. But it seemed to me that the 
unpleasant effect was mainly due to the action of the obscure 
rays upon the eyelids and other opake parts round the eye. I 
therefore cut, in a card, an aperture somewhat larger than the 
pupil, and allowed the concentrated calorific beam to enter my 
eye through this aperture. The sense of heat entirely disap- 
peared. Not only were the rays thus received upon the retina 
incompetent to excite vision, but the optic nerve seemed un- 
conscious of their existence even as heat. What the consequences 
would have been had I permitted the luminous third of the 
condensed beam to enter my eye, I am not prepared to say, nor 
should I like to make the experiment. 

43. On a tolerably clear night a candle-flame can be readily 
seen at the distance of a mile.' The intensity of the electric 
light used by me is 650 times that of a good composite candle, 
and as the non-luminous radiation from the coal points which 
laches the retina is equal to twice the luminous, it follows that 
at a common distance of a foot, the energy of the invisible rays 

* Anwaies de Chimie et de Physique, torn. Ix. p. 7l« 
t M^ fpjxf. has sjboTm tj^ a portion of the lun's obscure rays reach the 
retina. ' . ' 



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840 Prof. Tyndall on Luminous and Obscure Radiation. 

of the electric light which reach the optic nerve^ but are incom- 
petent to provoke vision^ is 1300 times that of the light of a 
candle. But the intensity of the candle's light at the distance 
of a mile is less than one twenty-millionth of its intensity at 
the distance of a foot^ hence the energy which rendex*s the can- 
dle perfectly visible a mile oflF would have to be multiplied by 
1300 X 20^000^000, or by twenty-six thousand millions^ to bring 
it up to the intensity of that powerless radiation which the eye 
receives from the electric light at a foot distance. Nothings I 
thinks could more forcibly illustrate the special relationship 
which subsists between the optic nerve and the oscillating 
periods of luminous bodies. The nerve^ like a musical strings 
responds to the periods with which it is in accordance, while it 
refuses to be excited by others of vastly greater energy which 
are not in unison with its own. 

44. By means of the opake solution of iodine, I have already 
shown that the quantity of luminous heat emitted by a bright 
red platinum spiral is immeasurably small *. Here are some 
determinations since made with the same source of heat and a 
solution of iodine in iodide of ethyle, the strength and thickness 
of the solution being such as entirely to intercept the luminous 
rays. 

Radiation from Bed-hot Platinum Spiral. 
Through transparent liquid. Through opake solution. 

^•7 43°7 

437 43-7 

These experiments were made with exceeding care^ and all 
the conditions were favourable to the detection of the slightest 
difference in the amount of heat reaching the galvanometer ; still 
the quantity of heat transmitted by the opake solution was 
found to be the same as that transmitted by the transparent one. 
In other words, the luminous radiation intercepted by the former^' 
though competent to excite vividly the sense of vision, was, when 
expressed in terms of actual energy, absolutely immeasurable. 

45. And here we have the solution of various difSculties which 
from time to time have perplexed experimenters. When we see 
a vivid light incompetent to affect our most delicate thermo- 
scopic apparatus, the idea naturally presents itself that light and 
heat must be totally different things. The pure light emerging 
from a combination of water and green glass, even when rendered 
intense by concentration, has, according to Melloni, no sensible 
heating power f. The light of the moon is also a case in point. 
Concentrated by a polyzonal lens more than a yard in diameter 



♦ Phil. Trans, vol, cliv. p. 327. 

t Taylor's Scientific Memoirs, vol. L p. 392. 



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Mr. D. Forbes on Evansite, a new Mineral Species. 341 

upon the face of his pile^ it required all Melloni's acuteness to 
morse the calorific action up to a measurable quantity. Such 
experiments^ however^ demonstrate, not that the two agents are 
dissimilar, but that the sense of vision can be excited by an 
amount of force almost infinitely small. 

46. Here also we are able to offer a remark as to the appli- 
cability of radiant heat to fog-signalling. The proposition, in 
the abstract, is a philosophical one; for were our fogs of a 
physical character similar to that of the iodine held in solution 
by the bisulphide of carbon, or to that of iodine or bromine vapour, 
it would be possible to transmit through them powerful fluxes 
of radiant heat, even after the entire stoppage of the light from 
our signal lamps. But our fogs are not of this character* They 
are unfortunately so constituted as to act very destructively 
upon the purely calorific rays ; and this fact, taken in conjunc- ' 
tion with the marvellous sensitiveness of the eye, leads to the 
conclusion that long before the light of our signals ceases to be 
visible, their radiant heat has lost the power of affecting, in any 
sensible degree, the most delicate thermoscopic apparatus that 
we could apply to their detection. 

Royal Institution, October 1864. 



XL. On Evansite, a new Mineral Species. 
By David Forbes, F.R.8., ^c.^ 

THIS mineral was brought from Hungary in the year 1855 
by the late Mr. Brooke Evans of Birmingham t, and was 
then reported to be found in some abundance as an incrustation 
in drusic cavities which occurred in the brown iron ores. It 
was regarded as pertaining to the mineral species allophanej:, 
with which it agrees in many of its physical properties, as hard- 
ness, colour, specific gravity, &c., as well as in the percentage of 
loss sustained upon heating the mineral to redness. 

The specimen I received from Mr. Evans was labelled Allo- 
phane from Zsetcznik, Gomar Comitat, and was very beautiful 
in appearance, consisting of an agglomeration of small stalactites 
with reniform and globular excrescences on brown haematite, many 
of these excrescences much resembling artificial or natural pearls^ 
having both the figure and characteristic pearly lustre of such. 

I doubted the identity of the mineral with allophane; and a 

* Communicated by the Author. 

t After whom the species is now named. 

j A considerable number of specimens had been given by Mr. Evans to 
private collections in England all labelled " allophane," and I understand 
that many more had likewise been distributed in Germany under the same 
name. 



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842 Mr. D. Forbes on Evansite, a new Mineral Species. 

preliminary blowpipe examination immediately confirmed this 
opinion, by proving the absence of silica in any quantity^ and 
indicating the presence oi phosphoric acid ; and consequently I 
was more disposed to regard it as hydrargyllite or Gibbsite. I 
commenced^ however^ a systematic examination of the mineral^ 
but my sudden departure and prolonged absence in South Ame- 
rica has prevented my having had an opportunity of making the 
results public until my recent return. 

The physical characters of Evansite are as follows > — Amor* 
phous and without trace of crystallization ; reniform or botryoi- 
dal ; colourless or milk-white^ and sometimes faintly tinged with 
yellow or blue^ and occasionally presenting iridescent hues; streak 
white ; translucent to semi-opake. Lustre^ vitreous or resinous ; 
splendid and waxy internally ; very brittle. Fracture semicon- 
choidal and shining. 

Hardness 3*5 to 4^ scratching calc-spar with facility but not 
fluor-spar ; one fragment^ however^ was found to leave a faint mark 
on fluor-spar. 

Specific gravity. Several determinations were carefully made^ 
and precautions were taken to expel all air from between the 
laminse of the mineral by using boiling distilled water and allow- 
ing it to cool down to the temperature of 60° Fahr. ; the results 
were as follows : — 

1. Using 28*51 grains of the translucent colourless mineral 
in small fragments^ the loss in water was found to be 15*59 
grains^ and the consequent specific gravity 1*822. 

2. With 18*686 grains similar to last, the loss in water was 
7*31 grains^and the calculated specific gravity consequently 1*872. 

3. With 12*87 grains of faint-yellow-coloured mineral in frag- 
ments, the loss obtained was 6*13 gi's., and the consequent spe- 
cific gravity would be 2*099. 

4. When 18*793 grains of semiopake mineral in one piece 
was immersed under water, it lost 9*55 grains, and consequently 
had a specific gravity of 1*965. 

The mean of these four determinations will give 1*939 as the 
specific gravity of Evansite. 

The beTiaviour of this mineral before the blowpipe was found 
to be as follows : — 

In a closed tube it immediately evolved water, decr^itated^ 
and, on continued application of heat, gave off more water and 
remained behind in the form of a milk-white powder. On test- 
ing, the water evolved did not show any reaction^ with Brazil 
wood, red or blue litmus, or turmeric test papers. 

In an open tube the same reactions were observed. Heated 
between platinum points it very slightly swelled out, became of a 
milk-white colour, and presented, when viewed through the glasti 



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Mr. D. Forbes on Evanstte, a new Mineral Spedee. 848 

an innumerable series of minute cracks ; did not fuse in the 
strongest heat ; appeared to colour the outer flame bluish green^ 
but so feebly as to be all but indistinct. On moistening the 
mineral with sulphuric acid, this reaction was rendered rather 
more apparent. On charcoal it proved infusible and unaltered^ 
in both oxidizing and deoxidizing flames ; but when heated, after 
moistening it with a solution of nitrate of cobalt, an intense blue 
colour was communicated to the assay. It dissolved readily 
both in borax-glass and phosphateof soda* in the oxidating flame, 
forming colourless glasses, which remain colourless on cooling : 
some of the faint-vellow-coloured specimens give a very light- 
coloured yellow glass when hot, but, on cooling, become colour- 
less, a reaction due to the presence of iron. In the reducing- 
flame both these fluxes give the same reactions. In a few cases 
the glass formed by phosphate of soda shows a trace apparently 
of silica floating in the clear glass bead. 

A qualitative chemical examination showed the mineral to be 
completely soluble in sulphuric, nitric, and hydrochloric acids. 
The solution, when treated by a stream of sulphuretted Ivydrogen 
gas passing through it, gave no precipitate whatever. The acid 
solution gave a yellow precipitate, indicative of phosphoric acid, 
when treated with molybdate of ammonia ; and further, alumina 
and a trace of oxide of iron were found, but qo lime, glucina or 
zirconia, which were specially tested for. 

Fluorine was examined for by treating 12*10 grains in a pla- 
tinum crucible with sulphuric acid at a gentle heat, the crucible 
being at the same time covered with a glass plate waxed on the 
imder side and kept cold on the upper side ; some characters 
were traced through the wax with a line point ; no visible etch-i 
ing wis remarked after the operation. 

The mineral, therefore, consisted only of water, alumina, and 
phosphoric acid with an accidental trace of oxide of iron and 
silica. Its quantitative analysis was conducted as follows : — 

Determination of the Water, 

22'22 grs. of the transparent colourless mineral left, after 
heating to redness, 13'49 grs. residue ; also evolved 8*73 grs. grs. 
water, equivalent to 89*285 per cent, water in the mineral. 

15*38 grs., same quality, left under same treatment 8*98 
residue; also 6*45 grs. water, equivalent to 41*18 per cent. 

18*365 grs., translucent but of a faint yellow colour, left 8*105 
grs, residue; also 5*26 grs. water, which would make 39*87 
per cent. 

* Instead of, as commonly, using microcosmic salt (phosphate of soda 
and ammonia), I prefer employing the dried phosphate of soda prepared 
by heating strongly the above until all ammonia is driven off. It will be 
found much more convenient in practice, as it melts gently, and does not 
froth and spit ai the microooamie salt does. 



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344 Mr. D. Forbes on Evanrite, a new Mineral Species. 

24*877 grs.^ translacent and colourless, heated in a water- 
bath at 212^ Fahr. for twenty hours^ left 20*25 grs. residue, being 
4*627 grs. water^ or equal to 13-69 per cent, water given off at 
212° Fahr. ; on further heating to redness left 14*94 grs. residue, 
thus giving a total of 5*31 grs. water, or equivalent to 39*91 
per cent. 

The average of these four experiments affords 39*945 per cent, 
water. 

Determinaiion of the Insoluble Matter {Silica). 

18-07 grs. of the mineral were dissolved in hydrochloric 
acid with addition of a little nitric acid ; some flakes remained 
persistently insoluble, and were collected on a filter, washed, 
dried and incinerated, and weighed 0*250 gr., or equal to 1*39 
per cent. 

13*365 grs. of the translucent but yellow-coloured mineral, 
after having been previously ignited to determine the amount of 
water present, were now dissolved in nitrohydrochloric acid ; the 
insoluble residue collected on a filter, washed, and determined after 
incineration, weighed 0*46 gr., or equivalent to 3*44 per cent. 
I satisfied myself, however, that this result is quite erroneous 
and much too high, owing to a part of the phosphate of alumina 
in the mineral becoming itself insoluble, through the previous 
heating it had been submitted to in determining the percentage 
of water in it. 

Determination of the Phosphoric Acid* 

22*22 grs. of the white translucent mineral were dissolved 
in nitrohydrochloric acid, and to the solution an excess of a so- 
lution of molybdate of ammonia, previously rendered strongly 
acid by addition of nitric acid in large excess, was added until 
all phosphoric acid present was precipitated in the form of the 
yellow phosphomolybdate of ammonia. After filtration this pre- 
cipitate was dissolved in ammonia, and the solution then preci- 
pitated by adding a mixed solution of sulphate of magnesia, 
chloride of ammonium, and caustic ammonia. The precipitate 
of phosphate of ammonia and magnesia was allowed to stand for 
twelve hours, then filtered off, washed with ammonia-water, and 
determined on ignition, affording 6*40 grs. pyrophosphate of 
magnesia, equivdent to 4*09 grs. phosphoric acid, or 18*42 per 
cent, phosphoric acid in the mineral. 

Another estimation of the phosphoric acid in the mineral was 
made by Girard's modification of Reynoso's process, as follows : — 

15*38 grs, were dissolved in nitric acid, and 22 grs. of me- 
tallic tin then added to the solution and boiled until entirely 
oxidized ; the solution was then filtered off, and the insoluble 
oxi^e and phosphate of tin dissolved in excess of sulphide of 
ammonium by digestion ; the solution was filtered from some 



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Mr. D. Forbes on Evansite, a new Mineral Species. 845 

tittle insoluble residue^ and then precipitated by the addition of a 
previously mixed solution of sulphate of magnesia^ chloride of 
ammonium^ and ammonia in excess^ allowed to stand twelve hours, 
and the precipitated phosphate of ammonia and magnesia then 
filtered off and determined as in the last case ; the pyrophosphate 
of magnesia amounted to 4*605 grs., equivalent to 2*944 grs. 
phosphoric acid, or 19*01 per cent. 

A third determination of the phosphoric acid was now made 
upon 13*365 grs. dissolved in hydrochloric acid, some 50 
grs. crystallized tartaric acid added, and then ammonia in 
excess ; the solution remained clear, and was then precipitated by 
a mixed solution of sulphate of magnesia, chloride of ammonium, 
and liquid ammonia, and allowed to stand twelve hours. The 
supernatant solution was now carefully * decanted, and the pre- 
cipitate redissolved in hydrochloric acid, a little tartaric acid 
added, and then ammonia in excess : after standing twelve hours, 
the precipitated phosphate of ammonia and magnesia was col- 
lected and determined as usual ; the pyrophosphate of magnesia 
weighed 4*14 grs., equivalent to 2*63 grs.. phosphoric acid, or 
19*73 per cent, in the mineral. The mean of these three de- 
terminations of phosphoric acid will consequently amount to 
19*05 per cent. ..... 

Determination of the Alumina. 

22*22 grs. (the same as employed as before mentioned in deter- 
mining the phosphoric acid by the molybdate-of-ammonia me»- 
thod) were here made use of, and the solution, after separating 
the precipitate of phosphomolybdate of ammonia, was now sub- 
jected to the action of a stream of sulphuretted hydrogen gas 
until no more precipitate of sulphide of molybdenum fell ; it was 
then filtered from this precipitate, and the solution, after boiling 
to remove any excess of the gas, precipitated by ammonia, by 
which the alumina present was thrown down, which, being 
washed, dried, and incinerated, weighed 8*90 grains, or conse* 
quently 40*05 per cent, in the mineral. 

Another determination of the alumina was made on the 
quantity of mineral (15*38 grs.) used in determining the 
phosphoric acid according to the tin method. The matter 
insoluble in sulphide of ammonium was, as far as possible, 
dissolved in nitrohydrochloric acid, this solution .was added to 
the nitric-acid solution obtained in the first instance after filter- 
ing off the oxide and phosphate of tin, and the whole then pre- 
cipitated by ammonia and the alumina collected. ' Ftorn its ap- 
pearance, hovfever, it was suspected that it might contain tin ; it 
was redissolved in sulphuric acid and a stream of sulphuretted 
hydrogen passed through the solution, when a considerable 

Phil. Mag. S. 4 Vol. 28. No. 190. Nov. 1864. 2 A 



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846 Mr* D. Forbes on Evansite, a new Mineral Species. 

precipitate of the sulphides of lead aud tin* fell, which was filtered 
off, and the alumina determined as usual by precipitation by am- 
monia. After ignition it weighed 5*90 grs., or equivalent to 38*36 
per cent, in the mineral. 

The average of these two determinations of alumina will be 
39-20 per cent. 

From the results of the above determinations the analyses will 
now stand as follows : — 





a. 


b. 


e. 


Water . . . 


. 8-78 


6-45 


5-260 


Phosphoric acid 


. 409 


2-94 


2-680 


Alumina . . 


. 8-90 


5-90 


5-290t 


Insolable (silica) 


. 0-31 


009t 


0-185 


Loss in analysis 


. 019 
22-22 


15-88 






18-365 


id calculating the percentages 


derived from these results, — 




». 


b. 


e, Mem. 


Water .... 


89*29 


4118 


89-87 89-95 


Phosphoric add . 


18-42 


19-01 


19-78 19-05 


Alumina . . . 


4005 


88-86 


41-51t 89-81 


Insoluble (silica) . 


1-89 


l-45t 


1-39 1-41 


Loss 


0-85 




0-28 



10000 10000 10000 10000 
From the above analysis the formula 8Al«0^,PO*+18HO 
may^ I think, be safelv deduced. This formula will, on calcula- 
tion, represent the following percentage composition : — 
3AI«0«= 153-78 = 89-75 Alumina. 
6P05 » 71 00 ;= 18-86 Phosphoric add. 
18H0 = 162-00 = 41-89 Water. 

386-78 100-00 
For eomparison I annex a Table showing the chemical com- 
position of all the hydrated phosphates hitherto announced as 
having been found in the mineral kingdom. 



aAlS08,2P05+I2HO. 


aA1308,PO< 
+SHO. 


2AP03.P05 aAiaoa,PO«A1208,PO», 
+6H0. +8H0. +8H0. 


' WaveUite. Ktpridte. 


Kalaite. 


Peganite. Flacberite. Gibbute. ' 


Barnstaple. Hungaiy. 


Sileria. 


Striegii. Niwhna TngaL MaM.U.8. 


Phosphoric acid. 3498 3549 


30-90 


30-49 29-03 37*62 


Alumina . . . 37-18 39-69 


44-50 


44-49 38-47 2666 


Oxide of iron 


1-80 


2-20 1-20 .... 


Oxide of copper. «... .... 


3-70 


0-80 .... 


Gangue . • 


.... 


3-00 .... 


Water . . . 2800 2492 


1900 


22-82 27-50 35-72 


10016 10000 


99-90 


10000 100-00 10000 


Fnchs. St&deler. 


Zellner. 


xlCFlUlUUAa cLOTXQflUlQ* ^LflTIDJUEIB* 



* Doubtless the lead had been in the tin as an impurity, 
t Determined as loss. 



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[ 847 ] 
XLI« On Induction in a Rotating Conductor. 

By £. JOCHMANN*. 

THE equations (26) and (27) of my memoir ''On the Elec- 
tric Currents induced by a Magnet in a Rotating Gon« 
ductor'^t can be easily integrated^ by means of a development in 
series according to sphericsd functions^ in the special case of a 
conducting sphere rotating around one of its diameters. The 
results^ on account of their remarkable simplicity^ shall be 
here given. 

Let 

be the distance of an inducing pole from the centre of the sphere^ 
and X denote the angle between the directions of s and r, where 

then if p represent^ as before^ the distance of the point {xj y, z), 
within the conductor^ from tibe inducing pole^ so that 

p*3=r*+«*— 2r«cos\, 
we shall have 

\T o Lv r{cr^8z COS \) 
sp[p-{-8^rcos\) 

where the summation is to be extended to all the existing mag* 
netic poles. If, further, we put 

'^ p5(p + *— rcosX) 

the components of the current-density at the point (a?, y, z) 
will be 

Ox OZ 

dy ^ Ox 

From the form of these expressions it is manifest that the radial 
components of the current at each point within the sphere 
vanish, — ^in other words, that all the currents flow on concen- 

* From the Journal fur die reine und angewandte MathematiJc,roh xzxvi* 
p. 329. 
t PhiL Mag. S. 4. vol. zxvii. p. 522. 

2A2 



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348 M. E. Jochmann on Induction in a Rotating Conductor. 

trie spherical surfaces. It likewise follows therefrom that the 
results are also immediately applicable to the case of a shell 
hounded by two concentric spherical surfaces. In this case^ 
however, we must also assume a distribution of free electricity 
on the inner surface of the hollow sphere, of such a nature that, 
in virtue of its presence together with that of the electricity 
within the conductor and on its external surface, the potential 
V may acquire the above value. The form of the current- 
curves within the conductor is determined by the equations 

r= const., ^= const. 

The components of the action of the system of induced currents 
upon an external magnetic pole m are 

^Q m BQ 

^"^W '"^W """a?^ 

where f , rj, ^ are the coordinates of the pole, and 

Q= ^'^'^da^dy' dzf+ ^jV^«fe'rfy'rf/+ M'q^'lda^dy'dz', 

in which expression **' denotes what ^ becomes when x, y, z are 
changed into a/, y', z^, and, for brevity, we have put 

r«=(^-f)'+(y'-,)H(^'-?)«. 

The integration can easily be eflFected when it is required to 
calculate the reaction of the system of induced currents upon a 
single inducing pole, or when, after differentiation, ^, ^, ? are 
made equal to a, b, c respectively, and consequently Y to p. For 
then, putting for simplicity 6=0, we have in the case of a solid 
sphere of radius R, 

and in the case of a hollow sphere with internal and external 
radii equal to Rj, R^, respectively, 

^= 2^^L-?:::;^ -^-2^^'^-rrrir^^' 

whilst in both cases 

X=0, Z=0. 

The relation Between these results and those obtained in the 
former memoir for the case of a plane disk is manifest. 

The result takes a remarkably simple form under the hypo- 
thesis of a sphere rotating under the influence of a constant 
magnetic force, such as that of the earth. The coordinate plane 
y=0 may now be made to coincide with the plane of the axis of 
rotation and th^ direction of magnetic force, or, as we may call 



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Mr, J. Bishop on the Pitch of the Tuning-Fork. 849 

it, the plane of the magnetic meridian. This done^ we must put 
d=0, and afterwards allow 8 and /n to increase indefinitely in 

such a manner that the ratios - = sin 7 and ^ = T may preserve 

s s 

constant values. The quantity T will then represent the inten-. 
sity of the constant magnetic force, and 7 the angle between the 
direction of this force and the axis of rotation. In this case the 
current curves reduce themselves to the system of circles repre- 
sented by the equations 

r = const., y = const., 

all of which lie in planes parallel to that of the magnetic meri- 
dian. The constant current-density within each current-curve 
will be 

iniKTsiny.X, 
if [ 

be the radius of the current-circle. With respect to its external 
action, the current-system deports itself like a magnet whose 
axis coincides with that of y, or, in other words, is perpendicular 
to the plane of the magnetic meridian. Worthy of notice is the 
analogy which exists between this result and the one deduced by 
Poisson from his magnetic theory of rotation-magnetism in his 
memoir "Sur le Magn^tisme en mouvement'**, as well as the 
one found by Green f, in the case where a sphere of imperfect 
electric conductibility is supposed to rotate under the influence 
of a constant electrostatic force, or where a sphere consisting of a 
magnetizable substance endued with coercive force rotates under 
the influence of a constant magnetizing force. 
Berlin, March 1864. 



XLII. On the Influence of the Pitch of the Tuning-Fork on the 
Mechanism of the Human Voice. By John Bishop, F.ILS,X 

ALL those who have paid attention to acoustics know that 
what is denominated pitch in musical science refers to a 
certain definite number of vibrations or undulations of the air, 
and also that, for musical purposes, a tuning-fork has been con- 
structed to yield a note or sound termed C, which we may assume 
as the fundamental note in the diatonic scale, or gamut. 

Since, then, the pitch of the tuning-fork determines that of 
all the other notes, both in music, musical instruments, and 

* M^. de VAcad. des Sciences, vol. vi. p. 497. 

t Journal fur die reine und angewandte Mathematik, vol. xlvii. p. 18/. 

X Communicated by the Author. 



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850 Mr. J. Bishop on the Influence of the Pitch of the 

tones of tlie human voice in singings it is of the greatest import- 
ance^ not only that the pitch of the fork should be uniform^ but 
that it should be conformable to the structure and functions of 
the human organs of voice, to which all other instruments of 
sound ought to be subordinate. 

How widely this principle has been departed from, and how 
injurious these deviations have been to the vocal mechanism, it 
is the object of the following remarks to show. 

The pitch having once been disturbed, the Philharmonic 
Society adopted a particular one, the Opera another, and then 
almost every maker of musical instruments chose his own pitch, 
until at last it became difficult to get together performers on 
two or three instruments which were of the same pitch. The 
pitch of tuning-forks with " C Philharmonic '^ marked on them 
may be very different, and there seems no guarantee for the cor- 
rect pitch of many of these forks ; and where the pitch is so 
various, singers do not know whether or not the music they 
have been accustomed to sing is within the compass of their 
voice. 

In this state of uncertainty, the Society of Arts appointed a 
committee to investigate the subject, and to discover and report 
on the best means of remedying these difSculties. Upon this 
report being considered, 528 vibrations were recommended for 
adoption by the Society*. 

When the nature of sound was first investigated, the number 
of vibrations in the air which were necessary to constitute a sound 
of a given pitch was accurately ascertained. It was determined 
that any elastic body, such as a stretched cord or a spring, whose 
vibrations to and fro recurred every second, should be denomi- 
nated C, and that every power of the number two, expressing 
vibrations within the limits of the range of musical instruments, 
should constitute C in the diatonic scale of music. On this 
system was the tuning-fork constructed, being taken for conve- 
mence at the 10th power of 2, consisting of 1024 vibrations, 
which will be according to the German and the French system 
of notation, and 512 dovhle vibrations on the system of the 
English method of computation — this pitch, or some other of a 
less number, having obtained the sanction of all the musicians 
and mathematicians who had studied acoustics with reference to 
musical science. Among the latter may be noticed the names 
of Euler, I. and D. Bernouilli, Riccati, Poisson, Savart, Dr. 
Young, Weber, and Sir John Herschel. Among those who com- 
posed music nearly on this pitch of the fork are Handel, Mozart, 
Beethoven, and nearly all the great composers up to the begin- 
ning of the present century; and, moreover, musical-instrument 
* Journal of the Society of Arts, June 8, 1864. 



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Ihnmg-Fork on the Meehamsm of the Human Voice, 851 

makers had^ up to this period^ observed nearly the same funda- 
mental pitch for the tuning-fork. 

The following Table, with which I have been supplied by the 
kindness 6f my friend Mr. A. J. Ellis, will show the truth of the 
statement that the pitch of C'has been arbitrarily raised, in 
various degrees in different countries, since the time of Handel, 
and also that the Italian-Opera pitch is such as to render a great 
deal of vocal music impossible to be sung by any vocalists except 
those who possess an unusually extended compass; also that the 
scale of the Society of Arts is too high for general use, and has 
failed to produce that uniformity which was designed by its 
members; and the question resolves itself into whether the slight 
difference in the brilliancy of instrumental music is compensated 
for by the increase of difficulty and injury to the human organs 
of voice. We all know that the performance of the most favour- 
ite overture, executed by the most perfect of orchestras, faded 
into comparative insignificance when the tones of a Pasta, a 
Malibran, or a Jenny Lind reached the ear. 

Table of the Varieties of Pitch. 
When any note but G is the pitch note, the pitch of C is cal- 
culated from it according to the semitonic temperament of twelve 
equal semitones if not otherwise expressed, or according to the 
mesotonic temperament or system of perfect major thirds* 



No. 



Authority. 



Pitch notes. 




Dr. Smith, organ of Trinity College, Cambridgei 



1758; 



= d =262 (mesotonic).. 



Usual organ pitch 

Handel's tuning-fork, 1740 (mesotonic) 

Theoretical pitch, Hullah and Tomlinson, 1843. 

Philharmonic (1812-42) 

French normal diapason (1859) 

Stuttgardt Congress of Musicians (1834) 

Vienna Orchestra, 1834 (Schleibler) 

Berlin Orchestra, 1834 (Schleibler) 

Society of Arts, London (1860) 

Italian Opera, 1860 (Society of Arts' Report)... 



416 



433 

435 

440 

440-87 

441-625 



455 



283*42 

240-00 

247-35 

256 

257-47 

258-66 

261-63 

26214 

262-59 

264 

270-55 



N.B. — ^The pitch is here considered as the number of double 
vibrations in a second. In France and Germany the number of 
single vibrations is usually taken, and hence the preceding figures 
would be doubled. Thus the French normal diapason is called870. 



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852 Mr. J. Bishop on the Influence of the Pitch of the 

Shortly after the commencement of the present century there 
arrived in this country German performers on wind instruments 
whose pitch was much more acute than that of our standard. 
An opinion then prevailed that the tones of wind instruments 
were improved by this higher pitchy and under this impression 
the Philharmonic Society and the orchestral departments of 
the theatres acceded to this strange notion^ or what might rather 
be termed delusion. 

The effect of this alteration in the fundamental pitch of music 
has been very important. The pianoforte-makers have been 
obliged to shorten the strings of their instruments ; the organ- 
builders to shorten their pipes ; the flute-makers to cut off a por* 
tion of the length of their tubes ; and what is termed the opera 
pitch has transformed the C of the olden time into D ; and since 
Nature has made no corresponding change in the length of the 
cords of the vocal organs of the human race> it is manifest that 
some changes must be made^ either to adapt musical composi- 
tions to the changes in musical pitchy or to reduce the standard 
pitch conformably to the structure of the human organs^ in order 
to render their Execution possible. 

It has been already stated that the greater portion of our best 
music was composea at a period when the tuning-fork made 
about 512 vibrations for C. This is the case in the works of 
Handel^ Mozart^ Beethoven^ and in the old madrigals and masses. 
Let us suppose a person has a tenor voice whose limit on the 
old scale of pitch is A. He can no longer sing the same music 
when A is transformed into B. Take^ again^ the soprano or ulto, 
where^ with the new pitchy the music is rendered impossible of 
execution. We find accordingly that^ in order to diminish the 
evils which the present pitch has inflicted on the human voice, a 
large number of HandePs and Mozart's popular songs have been 
transposed by Callcott and others into lower keys, so as to bring 
them, for private nse, into a pitch as near as possible to that in 
use in the time of the composers. This is, however, only a partial 
remedy for the much greater evil, since it leaves the entire works 
of these great masters untouched as far as relates to their per- 
formance in public. Now, although this may be easily effected 
in short pieces of music, no one would think of changing the 
key for such a work as the Messiah, or a whole Mass ; and yet 
many singers can no longer join in the execution of these cele- 
brated productions. It must not be forgotten that in this age 
of vocal harmony, music was intended for assemblages of choral 
performers, and not merely for the few who possess such an 
extended range of voice as would enable them to disregard the 
change of pitch. 

We come now to the effects produced on the organs of voice 



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Tuning-Fork on the Mechanism of the Human Voice, 353 

by straining the vocal cords beyond their proper tension. A 
young lady, endowed with a fine soprano voice reaching to C in 
alt. or 1024 vibrations, by straining the vocal cords on that note 
raised to D, lost the power of exercising her voice for musical 
purposes during nearly three years. Even Madame Goldschmidt 
complains of the strain which the change of pitch has produced 
in her vocal organs ; and it is well known what an extended 
range of flute-like sounds this charming and accomplished singer 
possessed. Further, it is well known that the tones at the 
extreme limits of phonation are never so pure in quality, or so 
agreeable to listen to, as the notes within those limits; and 
moreover, when in order to execute a given note the vocal cords 
are stretched beyond their normal elastic length, they do not 
always so readily regain their tone of elasticity ; and if this be 
permanently impaired, the voice loses some of its range of notes, 
and will be unable to regain the power to execute the melody ^as 
before. The struggle to execute a pitch beyond the normal 
limits sometimes gives rise to spitting of blood, and has been 
known to produce apoplexy. These circumstances are surely 
sufficient to render the reduction of the pitch of C to its former 
limit of 512 vibrations imperatively necessary. 

The principle we wish to impress is, that the pitch of musical 
instruments intended to accompany the human voice should be 
made subordinate to the anatomical structure and mechanism of 
the human organs, instead of the latter being rendered subor- 
dinate to the former. Consequently the pitch of C should again 
be 512 vibrations ; and we advise all persons interested in the 
choice of pianos and other musical instruments intended for 
vocal accompaniments, to insist upon having them of that pitch. 

There appears to have been a general complaint against the 
present pitch of our musical instruments by almost all. the 
higher class of singers ; and on appealing to one of the most 
scientific of our pianoforte-makers for his opinion, he stated 
that the pitch had ruined many a fine voice, but, as long as the 
public demand for the higher pitch remains, it is not in the 
power of the instrument-maker to remedy the evil. We know 
how strongly Sir John Herschel protested against the decision 
.of the Committee of the Society of Arts, and all parties appear 
to have considered the decision at which they arrived as only 
a temporary measure; and its complete failure to produce uni- 
formity is a confirmation of his views, and shows the necessity 
for further investigation. 

These remarks have not been written as a mere theory, but in 
consequence of the numerous cases of injury to the human organs 
of voice from the above-mentioned causes which have been from 
time jbo tim;e submitted to the author^s opinion. 



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[ 864 ] 

XLIII. On the Cohesion-Figures of Liquids, 
By Charles Tomlinson, F.C.S.* 
[With Two Plates.] 

AT the Meeting of the British Association at Manchester in 
1861^ I had the honour of submitting to the Chemical 
Section a subject then new to science^ namely^ the cohesion- 
figures of liquids. In the memoir that was readt> I endeavoured 
to show that when a drop of an independent liquid (that is^ not 
a solution) is gently deposited from the end of a glass rod or 
from the point of a dropping-tube upon chemically clean water 
in a chemically clean glass^ the drop flashes out into a definite 
figure as it enters into solution or difibses over the surface. 
Each figure is characteristic of the liquid^ and is a function of 
the cohesive force and difiusibility of the liquid^ and the adhe- 
sion of the surface on which it is deposited. The figure may 
also probably be represented in other ways. It may be a function 
of the solubility and the difiusibility of the liquid in question^ 
or of the solubility, the density, ana the molecular attraction; 
while in the case of certain figures which are produced beneath 
the surface, and which I have named submersion figures, each 
figure seems to be a function of the solubility, the density, and 
the molecular attraction. 

In the production of cohesion-figures, water is the most con- 
venient adhesion surface. It must be contained in a glass that 
is kept chemically clean by occasional washing in sulphuric acid 
or in a solution of caustic potash, so that the water, which need 
not be distilled, may present a chemically clean surface. A 
shallow glass about 4 inches in diameter is adapted to these 
experiments. I have had a number of such glasses made for the 
purpose, and have placed a couple of them upon the table. The 
temperature best adapted for these experiments is that of an 
ordinary room, which in winter or summer may be taken at 
about 60^. I have not studied these figures by artificial light, 
but have been informed that they admit of being reflected in an 
enlarged form so as to be seen by an audience. I have published 
various precautions respecting these figures, both with respect to 
temperature and variations in the area of the adhesion surface. 
I have also shown how these figures may be applied to the de- 
tection of adulteration in liquids, and also how suggestive many 
of these figures might be to the pattern-designer, from the great 
beauty and novelty of form and the exquisite harmony of colours 
displayed in them j:. 

• Communicated by the Author, having been read before the British 
Association at Bath, September 15, 1864. 
t Phil. Mag. for October 1861. . . t Ibid. Mardi 18^. 



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Mr. C. Tomlinson on the Cohesion^Figures of Liquids, 865 

In order that the application of this subject to qualitative 
analysis might be brought more directly before the attention of 
persons who would value an easy and expeditious test^ I read a 
paper before the Pharmaceutical Society in February last, '^ On 
the Verification of Castor Oil and Balsam of Copaiba by means of 
their Cohesion-figures/^ These two liquids were selected to in- 
troduce the subject of cohesion-figures in general, and its appli- 
cation as a rough and ready test. The members were so much 
interested in the subject that they requested me to furnish their 
engraver with some figures for insertion in their journal, and 
also to state what variations took place in the figure of castor oil 
from various markets and of various growths. Accordingly I 
examined twelve specimens of castor oil collected from different 
sources, together with three or four specimens of balsam copaibse, 
and wrote a report on the same, which will be found in the 
Society^s Journal*. 

In order to invite attention to the commercial oils, I read a 
paper in March last before the Society of Arts, *^ On the Verifi- 
cation of Olive-oil by means of its Cohesion-figure.'' The sub- 
ject excited some interest and discussion f. 

In these communications I endeavoured to show that the co- 
hesion-figure of the same substance is liable to certain variations 
in different specimens, especially in the case of the oils, which 
may be more or less viscid, more or less acidified or resinified. 
1 do not here refer to the variations arising from adulteration 
and admixture; for this point is insisted on in all my papers. 
But I was not unmindful of the changes likely to be induced by 
age; for in my paper published in March 1862 (Fhilosophicd 
Magazine), I state that the cohesion-figure of the oil of lavender, 
for example, may vary in different specimens, since it varies in 
density from 0*87 to 0'94. The cohesion-figure of the oil of laven- 
der is so striking that I was induced to try a number of speci- 
mens in 1861, and in all of them I obtained the peculiar Carra- 
geen-moss pattern — unless, as was often the case, the specimen 
had been adulterated with turpentine, in which case there was 
no dijficulty in detecting the adulteration. I also found that an 
essential oil, entirely different from that of lavender in its pro- 
perties and cohesion-figure, and also of less density, might be 
made to give a somewhat similar cohesion-figure by dissolving a 
small portion of camphor in it under a gentle heat, so as to bring 
it to about the same density and texture as oil of lavender. I 
stated in my first paper, that if two independent liquids could be 
found of the same density dnd physical molecular constitution 
(that is, equally fluid or viscid, &c.), they would form the same 

* Pharmaceutical Journal for March and April 1864. 
t Society of Arts Journal for March 4, 1864. 



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366 Mr. C. Tomlinson on the Cohesion-Figures of Liquids* 

cohesion-figure on water, although of different chemical consti- 
tution. Dr. Gladstone has has been so kind as to send me a 
specimen of salicylate of methyle, €H^, G^ H^O^ which gives a 
figure somewhat resembling that of oil of lavender — arising, I 
have no doubt, from a similar physical constitution. Cases of 
this kind must be rare, and are not likely to interfere with the 
application of cohesion-figures as a test. A much more serious 
objection is the alteration which oils undergo by long keeping. 
The specimens of oil of lavender, for example, which in 1861 
gave the Carrigeen-moss-pattern figure, were so changed in 1864 
as to give only a plain film without any distinctive character. 
On redistilling these oils, however, so as to get rid of oxidized 
products, the distillate produced the lavender-oil pattern as it 
did in 1861. 

On the other hand, the method is occasionally so delicate as 
to excite the surprise of persons who have sought in vain for a 
method of detecting differences in oils &c. which they largely 
use in the course of their trade. For example, a manufacturer 
informed me that it would be a great thing for him to be able 
to detect the difference between beef-oleine and mutton-oleine. 
The respective cohesion-figures of these substances show the dif-» 
ference plainly. Again, balsam copaibse is often adulterated 
with castor oil, for the detection of which the usual tests are 
either troublesome or inadequate. The method of cohesion- 
figures detects the adulteration immediately. Again, olive oil 
is frequently mixed with poppy oil, or sesame-seed oil; not 
only may these mixtures be detected by means of their cohesion- 
figures, but also the relative proportions of the respective oils. 

Although for all practical purposes water would be used as 
the adhesion surface in the production of these figures, consider- 
able interest arises from noting changes undergone by the figures 
when other surfaces are used. In my first paper, in 1861, it 
was stated that wood-spirit on the surface of mercury gave a 
very different figure from what it did on the surface of water; 
and in my second paper (Phil. Mag. March 1862) I described 
the cohesion-figures of water, ether, and alcohol on the surface 
of sulphuric acid, and also those of one or two essential oils on the 
surface of acetic acid. I have lately obtained a large variety of 
figures by experimenting on such adhesion surfaces as those of 
cocoa-niit oil, castor oil, paraffin, spermaceti, white wax, olive 
oil, lard, and sulphur. Of course the substances, such as pa- 
raffin, wax, &c., which are solid at ordinary temperatures, were 
melted for the purpose of these experiments. Too high a tem- 
perature was found to be disadvantageous, on account of the ten- 
dency of the drop to assume the spheroidal state. Lard is ad- 
vantageous, on account of the length of time that it remains 



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Mr. C. Tomlinson on the Cohesion-Figures of Liquids, 357 

fluid after having been thoroughly melted. Castor oil was used 
at various temperatures, but some of the finest figures were ob- 
tained on its surface at the ordinary temperature of the air of 
the room. Fine figures were also obtained on the surface of 
cold olive oil. Some of these figures are represented in Plate VI. 

Cocoa-nut OiL — A drop of ether flattened into a very perfect 
disk about two-eighths of an inch in diameter : this was sur- 
rounded by a dentated ring, from which proceeded a multitude 
of rays, as shown in PI. V. fig. 4. The best-defined figure was 
obtained when the temperature of the surface was about 80°. 

Alcohol produced a disk about three-fourths of an inch in dia- 
meter, with a small boss in the centre surrounded by a number 
of concentric circles faintly tinted with iridescent colours, while 
the edge of the disk was delicately fringed with very short radial 
lines. The figure was first of the size shown in fig. 1, No. 1 ; 
it then expanded to No. 2, and disappeared by closing in upon 
its centre. The figure was quite sharp and distinct, giving the 
idea of a lid of a box turned in the lathe. The best result was 
obtained when the surface was at about 90°. 

Benzole gave a figure about 2 inches in diameter, consisting of 
a central depressed disk about three-eighths of an inch in diameter, 
with a slight conical projection in the centre and surrounded by 
a broad smooth flat ring terminating in a sharply-cut edge. Oil 
of turpentine gave a somewhat similar figure, only the outer 
edge was wavy. Paraffin oil and Persian naphtha also give 
figures of the same type. Oil of lavender gave a central disk, 
from which issued wavy processes which were torn away by the 
adhesion of the surface. 

Castor OiL — When the oil is at about 94° F., a drop of ether 
forms a large figure bounded by a well-defined circular edge, in 
the centre of which figure is a plain disk surrounded by a narrow 
plain line ; just outside the disk is the engine-turned pattern, 
and beyond this, as far as the boundary edge, the disk is quite 
smooth. The engine-turned pattern seems to be produced by; 
the revolution, or rather oscillation, of the central disk on the 
heated surface. On cold castor oil the ether figure consists of a 
central boss surrounded by rippled waves, very much like the 
rose-pattern of the turner. Fig. 3 represents these two figures. 

When the oil is at 94°, a drop of alcohol forms a central star 
in a large disk surrounded by iridescent rings. But a finer figure 
is produced on cold castor oil : the drop spreads out into a large 
disk with broad iridescent bands just within the sharp-cut edge ; 
having attained a diameter of about 3 inches, it retreats towards 
the centre, leaving a beautiful network of minute globules. A 
drop of camphorated spirit produces a still finer figure, an idea 
of the beauty of which can scarcely be conveyed in words. A. 



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858 Mr. C. Tomlinson mi ike Cohmor^Figures ofLiquidi, 

figure of a similar type is produced on the surface of olive oil 
(see PL V. fig. 6), and will be described further on. 

The bensole figure at 83^ consists of a small central disk sur* 
rounded by an engine-turned pattern, beyond which rippled 
waves extend to the circumference of a large figure. On the 
cold oil the engine-turned pattern is wanting (see fig. 11). Pa- 
raffin oil gives a somewhat similar figure. The turpentine figure 
consists of a central boss surrounded by a large flat ring. On 
the cold oil, a drop of oil of cajuput has a central depression sur- 
rounded by a large flat ring. 

Paraffin. — Solid paraffin was melted in an evaporating-dish, 
and after the heat had been removed and the surface had become 
tranquil, a drop of ether, allowed to fall on the surface at 180°, 
was at first spheroidal ; it then flattened down, and by its evapo- 
ration solidified a portion of the paraffin with which it was in 
contact ; the solidified portion rushed wildly about under the 
retroactive force of a little remaining ether, until it disappeared 
by solution in the liquid paraffin. 

Alcohol formed a disk which sailed about, shooting out flat 
disks resembling petals, so as to give the figure the appearance 
of a flower (see PI. V. fig. 5). 

Paraffin oil formed a disk which sailed about with much agi- 
tation, sending off waving lines. The oils of turpentine and 
cajuput, and some others, solidified a portion of the paraffin — ^in 
some cases permanently, while in others the solidified portions 
moved about over the surface. 

Olive oil and pure tallow oil assumed the spheroidal state on 
the surface at 180°, and then sank. 

Spermaceti. — On the surface of melted spermaceti a drop of 
ether becomes spheroidal, or, if the temperature be not too high, 
flattens down into a small raised disk which spins rapidly ; or it 
may solidify a portion of the spermaceti, when the solid portion 
darts about in wide sweeps rapidly over the surface until it is 
again taken up by the liquid. 

Alcohol, when the surface is at about 160^, forms a well-defined 
disk with a waving border and concentric rings, and a delicately 
fringed iridescent edge (see fig. 2) ; but at a lower temperature 
(about 116^) it solidifies a portion of the spermaceti into the 
form of a small coracle, which sails about carrying its small cargo 
of alcohol. Turpentine at 121° behaves in a similar manner, 
only the solidified portion breaks up and darts about. Oil of 
cajuput at 127° forms a large disk with a faint depressed centre. 
Benzole forms a large plain disk, in the centre of which is a 
small spinning disk with a raised conical projection in the centre. 
Camphorated spirit slightly chills the spermaceti, rotates in the 
form of a small lens or boss with an agitated kjjid of motion ; 



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Mr. C. Tomlinson on the CohesionrFigvares of Liquids, 859 

then settles down into a charming star-like figure surrounded 
by rings and iridescent colours, and a sharp boundary line. In 
one case the c^itral boss slipped off the figure^ leaving the disk 
with its iridescent rings^ &c. complete. 

White Wax. — ^With the surfece at 142°, ether solidified a por- 
tion which rushed wildly about. Alcohol solidified a portion in 
the form of a ring^ which immediately broke up and was dispersed 
in radial lines, while the alcohol settled down into a small 
sharply-defined disk. At a higher temperature, such as 170°, a 
drop of alcohol will solidify a cup-shaped cavity for its reception ; 
but if the drop be held for a short time over the surface so as to 
become warmed, it at once subsides into a sharp well-turned disk. 
Lard. — Good figures are formed on the surface of melted lard 
with ether, alcohol^ and the oils of turpentine, savin, paraffin, 
lavender, and some others. A drop of camphorated spirit 
formed a very beautiful figure, some idea of which may be 
gathered from fig. 7. The rippled concentric circles display 
several of the orders of Newton's, or rather of Nobili's rings. 

Olive Oil. — ^A fresh flask of the variety of this oil known as 
extra sublime, was opened for the purpose, and portions of it 
were poured into the ordinary 4-inch cohesion-figure glasses. It 
answers admirably as an adhesion surface at ordinary tempera- 
tures. A drop of ether produces a small beautiful figure, con- 
sisting of a disk surrounded by rays. Alcohol forms a disk about 
3 inches in diameter ; the drop diffuses well, and the disk is 
perfectly circular, with a central boss. Iridescent rings contain- 
ing the colours of four or five orders fringe the edge of the disk 
in broad bands, and outside this large disk is a fainter and more 
shadowy disk. When the figure is fully developed, it rapidly 
opens, and closes in upon the centre Uke a curtain being drawn 
in, and so vanishes, leaving no trace behind. Camphorated 
spirit (fig. 6) is even more beautiful and persistent than alcohol ; 
the iridescent rings are dentated, and this adds greatly to their 
beauty ; the film, which is of a very large size, retreats slowly 
inwards to the centre, leaving the camphor in the form of minute 
dots disposed in radial lines ; these lines in their turn retreat 
towards the centre, where the camphor collects in the form of a 
flat ring. 

Benzole forms a large plain disk with a cavity in the centre. 
Turpentine, cajuput, and lavender also form disks; but the 
most curious figure is given by a drop of pure wood-spirit. It 
flashes out into a disk about 1| inch in diameter, then retreats 
inwards with the elasticity of a spring, leaving a delicate fringe 
made up of innumerable small dots; the disk then becomes 
toothed at the edge so as to give it the appearance of a small 
circular saw ; the disk retreats inwards, and the point of each 



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860 Mir. C. Tomliiison on the Cohesion- Fiffures of Liquids. 

tooth projects a namber of globules^ the ultimate figure being si 
small disk in the centre with an immense number of dots radia- 
ting towards it. In fig. 9 an attempt is made to represent this 
effect^ first as the figure is expanding^ and secondly as it is retreat- 
ing. On cold castor oil a similar figure is produced^ only the dots 
are more numerous and finer ; and there is a very curious differ- 
ence in the figure of a drop of the wood-spirit of commerce as 
compared with that of the pure spirit. On cold olive oil and on 
lard at 120°^ or on cocoa-nut oil at a lower temperature^ the 
drop of impure spirit forms a small lens with ten or twelve short 
blunt arms projecting from it (see fig. 10), and each arm shoots 
put a multitude of globules ; and not doing so in equal times 
from each arm, there is a reactionary movement, which causes 
the disk to describe half a turn in olie direction and then half a 
turn in an opposite direction, the effect of which is to dispose 
the dots not in radial, but in curved lines, the curves often bend^ 
ing in opposite directions. The formation of the figure is suffi- 
ciently slow to allow it to be studied, and the effect is very curious. 
The difference between the two figures distinguishes the pure 
from the impure spirit in a very marked manner. It should be 
noticed that the surface of the oil soon becomes saturated, so 
that not more than two or three figures can be produced in suc- 
cession ; but by wiping the surface with a piece of filtering paper^ 
its adhesion is restored. 

Sulphur. — ^When sulphur is melted so as to be sufficiently 
liquid to pour easily, some good figures may be formed on its 
surface. A drop of ether at first assumes the spheroidal state ; 
it then forms a boss surrounded by two or three rings of the 
thinnest orders of colour, steel-blue prevailing, and the figure is 
bounded by an excentric ring some way off. Benzole forms a 
good figure, consisting of a boss, an irregular star from which 
small lenses are shot out, and these are circumscribed by a flat 
circle (PI. V. fig. 15). Oil of lavender forms a boss surrounded 
by iridescent rings in waving lines, then a large silvery space, 
and a narrow boundary ring of iridescent colours (see fig. 13) . The 
oils of rosemary, turpentine, and paraffin form each a boss sur- 
rounded by large wavy iridescent clouds of most brilliant metal- 
lic colours, paraffin oil being most brilliant of all. Creosote and 
carbolic acid form disks which flatten out into waving figures (see 
fig. 12). The figure formed by camphorated spirit is shown in 
fig. 8. Camphor moves about over the surface; water forms 
and occupies a cup-shaped cavity, sohdifying the sulphur as it 
evaporates. 

Submersion Figures. 
In the Philosophical Magazine for June 1864, 1 have described 
a new variety of the cohesion-figures of liquids, in which the 



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Mr. C. Tomlinson on the Cohmon-Figwres of Liquids. 861 

drop^ instead of diffasing over the surface of the adhesion liquid^ 
sinks into it and diffuses through it. For this purpose a column 
of liquid in a cylindrical glass is employed. When water is used^ 
a few drops of a strong solution of ammonia^ or of oxalate of 
ammonia^ or of alum are added^ for the purpose of throwing down 
the lime^ and also of assisting in the development of the figure. 
A strong solution of cochineal in water forms a figure which is 
typical of a number of cases of this kind of diffusion. A 
single drop on the surface sinks down^ opens into a ring^ which 
' becomes depressed at two opposite points^ and lets down lines 
with other rings attached to them; while each ring^ at 90^ 
from the point of attachment of each line, lets fall two other 
lines with a ring attached, which ring in like manner, from 
two points 90° distant from the line, lets fall other lines ; and 
in this way the figure is developed slowly and symmetrically. 
Oil of lavender in a column of spirits of wine behaves in a simi- 
lar manner, only the figure is much more complicated and 
crowded. A drop of fousel oil in a column of paraffin oil passes 
through some complicated changes resulting in a kind of pointed 
dome, the lower edge of which is cut into four symmetrical 
arches ; from the springing of each pair of arches a line is let 
down, and from the extremity of this proceeds four smaller 
domes similarly arched, and letting down four other lines and 
four other still smaller domes, forming a figure which lasts a 
considerable time, exciting surprise in all who have seen it by 
the kind of architectural symmetry produced. Figures of another 
type are formed in columns of benzole, of ether, &c. In some 
cases very perfect rolling rings are formed, for the details of 
which I must refer to my paper, my business today being to 
point out a variety of other forms of cohesion-figures by submer- 
sion; for which purpose cylindrical columns of cocoa-nut oil, 
castor oil, paraffin, spermaceti, white wax, lard, and olive oil 
were used as in the case of cohesion-figures on the surface. Heat 
must be employed when necessary; but the best results are 
obtained with the cold oils, or with only just a sufficient amount 
of heat to render the solid substances fluid. Indeed the figures 
vary considerably with considerable differences of temperature, 
not only with substances which require to be melted, but with 
oils which are fluid at ordinary temperatures. 

Cocoa-nut Oil, — When a column was at about 160®, a drop of 
patchouli oil flashed out into rings and festoons. Oil of cloves 
formed a wide ring, from which proceeded numerous festoons 
and small rings; oil of cinnamon two or three large rings and 
festoons. Oil of cummin descended as a riband with a globule 
attached, from which proceeded upwards a dome cut into arches 
with lines terminated by knobs at the springing of each pair of 

PhU. Mag. S. 4. Vol. 28. No. 190. Nov. 1864. 2 B 



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862 Mr. C. Tomlinson on the Coherion^FSgUrea ofLiquidt. 

arches. Balsam copaibse (when the oil was at 165^) desoeoded 
in the form of a single thick glassy ring of perfect stractore* 
Some of the fixed oils formed pretty figures in a column at llO^, 
Colza descended in the form of a cup with the edges turned over 
and inwards^ suspended by a line irpm the surface of the column 
to the centre of the cup. Linseed oil also forms a hemisphmcal 
cnp with the edges turned over^ but without the suspending line. 
Sesame a similar figure,^only instead of the suspending line there 
was an arched projection in the centre of the cup. Castor oil 
sank rapidly in the form of a cup with the edges turned over 
and inwards. Some of these figures are represented in Plate YI* 
and are marked a, b, c, d, e. 

Castor Oil, Olive Oil, — ^A column of each of these oils is well 
adapted for the exposition of sets of figures differing in many 
particulars^ but all distinguished by a btdb and a stem. Each 
figure may be compared to a thermometer with a small bulb 
and a long delicate stem. For example^ when a drop of oil of 
cloves is deposited on the surface of a column of cold castor oil^ 
6 or 7 inches in lengthy the greater portion sinks beneath the 
surface (see No. 1)^ while the remaining portion forms a disk 
on the surface^ attached to the submerged globule by means of a 
short neck (see No. 2). The weight of the globule drags upon 
the disk and forms it into a conical cavity^ containing a speck of 
air^ which, as the disk collapses by the weight of the descending 
globule, becomes enclosed and is drawn out with a portion of the 
oil of cloves into the form of a long narrow tube (No. 3) : the 
disk at the surface, now reduced to the diameter of the tube, 
remains attached to the surface, and, indeed, is so persistent in 
its character that, long after the bulb has spread over the bot- 
tom of the vessel, this tube or thread remains attached to its 
moorings at the surface, and even interferes with the proper 
development of a second figure in the same column if the latter 
be narrow. As the tube is drawn out by the descending globule, 
its material is supplied partly by the surface of the globule, and 
partly by the medium, namely the castor or olive oil. The lat^ 
ter, m passing over the surface of the oil^of-doves spheroid, 
detaches a portion of its substance^ and thus allows toe tube 
*to increase in length. In the meanwhile the original drop of 
oil of cloves, whidi near the surfieu^ was a sphere, flattens out 
into the form of a spheroid ; and when it has descended about 
one-third of the length of the column it appears to open, and the 
apparent opening is ornamented on either side by the weU-tumed 
volutes of an Ionic capital (see No. 4, and the figure further 
developed in No. 5). This effect appears to be due to the pene- 
tration of the spheroid at its lower surface by a portion of the 
medium itself, which enters and diffuses within the spheroid in 



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Mr. C. Tomlinson an the Cohemn^Flgwes of Liquids. 868 

the form of a very perfect ring. The volutes are the effects of 
an optical illusion arising from seeing through a number of the 
segments which compose the ring on either side, while at the 
front and back of the ring the edges only of the segments are 
seen. Figures of this type, with variations in detail^ which it 
would take too long to describe, are produced in cold castor oil 
by oil of cinnamon, creosote, carbolic acid, sulphuric acid, sul- 
pnate of indigo, and glycerine. 

In a column of olive oil a drop of creosote, of carbolic acid, 
of oil of cinnamon, or of eugenic acid is similarly penetratea 
from below. Other oils, however, in olive oil are penetrated 
from above. For example, a drop of croton oil descends at first 
as a bulb and stem, the stem, as before, being moored to the 
surface*. The bulb flattens out into the form of an oblate sphe- 
roid, and in attempting to flatten still more it gets turned over 
at the upper part into the form of a ring, but presenting the 
appearance shown in A ; the medium closes in upon the open- 
ing, which becomes deeper, as in B and C, until at length it 
penetrates to the bottom of the spheroid, forming a trumpet- 
riiaped mouth as in D. In doing so it unites with the stem, 
which thus appears to have penetrated to the very bottom of the 
spheroid ; while, to supply its length, the medium licks over the 
outer surface of the spheroid, as in the former case, Und thus 
allows the stem to accompany the altered spheroid to the bottom 
of the vessel. This series of processes, which it takes so long to 
describe, may be understood at a glance by a reference to the 
figures A to b. 

In some cases, instead of the voluted figure, the opening from 
below is pyriform, and as the spheroid descends the pear-shaped 
figure describes a circle within the spheroid, which gives it the 
appearance of rocking to and fro upon its stem (see figs, a*, a*, 
a*). Thus while in a column of olive oil a drop of cinnamon or 
of eugenic acid opens from below and forms a figure with volutes, 
a drop of oil of cloves, or of creosote, or of carbolic acid is pene- 
trated from below and a pear-shaped opening is formed within 
the spheroid. We use the word opening as we do the word 
volutes, to express the appearances presented. The openinp;, 
however, is a penetration of the spheroid by the medium m 
which it is subsiding. 

In a column of lard at about 170° and upwards, a drop of oil of 
cloves (and of some other oils) forms festoons and rings; but at 
lower temperatures, as from 140° down to 82° (at which point 
the lard used by me soUdified), figures of the bulb-and-stem 
type are formed. But in the case of castor oil there is some varia- 

* In the figures a portion only of the stem is shown. 
2B2 



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364 Mr. E. J. Mills on a Defect in the Theory of Saturation. 

tion : the drop of castor oil forms a bulb and stem : the bulb is 
penetrated from above^ separates from the stem^ and descends as 
a rolling ring (see figs. 6*, b^, Ifl, b^). Crotonoil also forms a 
beautifal large ring^ from which festoons descend^ and from the 
end of each festoon a ring separates and then commences rolling. 
A drop of balsam copaibae forms a bulb and stem ; the bulb en- 
larges^ expands upwards into a dome-shaped figure, from the 
lower edge of which festoons and rings are let down, which rings 
multiply and produce other festoons and rings. A drop of creo- 
sote forms rings and festoons when the lard is at about 130^ or 
140°; but at 110° it forms a bulb and stem, the bulb being 
penetrated from above. Carbolic acid at the lower temperature 
. forms a bulb and stem, the bulb being penetrated from above. 
A drop of oil of cloves forms rings and festoons in hot lard, but 
a bulb and stem with penetration from below at a lower tempe- 
rature. The same remark applies to oil of cinnamon : at about 
90° the spheroid is largely penetrated from below. 

It would occupy too much space and require too much picto- 
rial illustration to enter into further details respecting these 
submersion figures. They all admit of being grouped imder 
some four or five types : not that the figures of any one type are 
identical ; for whether they be rings and festoons, or bulb-and- 
stem figures, or dome-shaped, or cones or rolling rings, each 
liquid presents characters of its own, which are again subject to 
further variations in different media. 

King's College, London, 
September 1864. 



XLIV. On a Defect in the Theory of Saturation. 
By Edmund J. Mills, B.Sc."^ 

nnHE theory of atomicity— or, as it should be more correctly 
J- termed, the theory of saturation — may be justly con- 
sidered, according to Wurtz's suggestion f, as a development 
of the doctrine of multiple proportions. It expresses the result 
of an extensive induction, that there is a definite limit to the 
combination of one substance with another, and that this limit 
may be approached by successive stages. The atomicity or 
saturability of a given body is expressed ^by the number of unit 
weights of hydrogen which can be made to combine with a cer- 
tain standard weight of it. Thus > the radicals represented by 
the following formulae, 

♦ Communicated by the Author. 

t Lefons de PhUosophie Chimique, p. 221. 



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Mr. B. J. Mills on a Defect in the Theory of Saturation. 365 

C«, C«H, C«H«, C«H«, C«H*, C«H*, 

having the standard weights 

24, 25, 26, 27, 28, 29, 

are saturated respectively by 

6, 5, 4, 3, 2, 1 

unit weights of hydrogen. Complete saturation, with respect to 
either, is represented in the formula 

Owing, however, to the difficulty of always obtaining hydrogen- 
compounds, or to the absence of them, the following point has 
been allowed in practice — that a constant weight of any other 
element, equivalent to a unit weight of hydrogen, shall be ac- 
cepted in the place of the latter, and be considered, equally with 
it, a measure of the saturability of the given substance. This 
concession has been most frequently made in the case of chlo- 
rine-, bromine-, and iodine-compounds — an equivalent of either 
of the elements mentioned being supposed to function, with 
respect to saturation, in precisely the same manner as one part 
by weight of hydrogen. It is to this point that I wish briefly 
to direct attention. 

The question as to interchangeability of saturating function 
between any elements must depend not only on their being 
capable of transposition in terms of equivalent value, but also 
on their affinity for the substance to be saturated. For it would 
be impossible to attribute to the vicarious element (as, for ex- 
ample, chlorine used in the place of hydrogen) the power of satura- 
tion at all, unless it had an affinity for the substance employed ; 
nor could it conveniently be taken, if, as is sometimes the case, 
the affinity were variable in its nature. Furthermore this ex* 
change of function cannot be considered an equal one unless 
the two elements are precisely alike in their affinity for the third 
body. 

Let us suppose, for illustration's sake, a radical X' combined 
with chlorine, bromine, and iodine, the last two being successively 
weaker compounds. The measure of the full saturabiUty of X' 
will be the largest possible quantity (say, of one of these three 
elements) which has the greatest affinity for it. Hence it is 
obvious that X'Cl will only be fully saturated; X'Br and X'l 
will be deficient by some portion of a saturability, a positive 
number, which may be termed a? in the former, and (a+y) in 
the latter case. Each of these quantities might of course ap- 
proach or exceed unity if X were pbly-equivalentic ; and it is 
hardly necessary to say that these remarks apply to any radicals 



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866 Mr. E. J. Mills on a Defect in the Theory of Saturation. 

combined with X^ so long as they are interchangeable and of 
the same equivalency. 

Such a doctrine of residual saturability appears of very consi- 
derable interest. Based as it is on the well-known phenomena 
of difference in affinity^ it rests on a property of bodies still 
unsubmitted to numerical measurement^ but always received 
as a fact. The idea of unequal affinity rests chiefly on results 
derived from the decomposition of bodies — being thus comple- 
mentary to the current doctrine of saturation, which more ex- 
pressly leans on the facts of their synthesis. At the present 
moment especially it is desirable that the importance of connect- 
ing these should be taken into consider