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SIMlPORD-VNIVERSITy- HBlAm' 








V"- 



•^1 



PROCEEDINGS 



or THB 



ROYAL SOCIETY OF LONDON. 



From January 7, 1886, to June 10, 1886. 



• I 



VOL. XL. 



« » » . 



» • - 

I » f • ■ • * • I 



* » 



LONDON : 
HARRISON AND SONS, ST. MARTIN'S LANE, 

firinttu in 0rbia*rg ie jftt H^RJMtg. 
IfDCCCLXXXn , 



t * y 



( 



LOMDON : 
BABJtlROK IVD SONS, PBINTSH6 IX OBDIMIRT TO BBB MAJKSTV, 

ST. IflBTIX's LANB. 



« • 



1 1 2f>63 



• , » • 



CONTENTS. 



VOL. XL. 






No. 242.— /awMory 7, 1886. 

Experimental Beaearchea ou the Propagation of Heat by CJonduction in 
Muade, Liver, Kidney, Bone, and Brain. By J. S. Lombard, M.D., 
formerly Aaaistant Professor of Physiology in Harvard University 

Further Reeearchee into the Function of the Thyroid Gland and into the 
FMJiol^cal State produced by Removal of the same. By Professor 
Victor Horaley, RS., F.RC.S < 

Omtribations to the Anatomy of the Central Nervous System of Plagio- 
otomata. By Alfred Sanders, M.RC.S., F.LS K 



January 14, 1886. 

On the Action of Sunlight on Micro-organiamg, &c., with a Demonstra- 
tion of the Influence of Diffused Light. By Arthur Downes, M.D l'^ 

Notes upon the Straining of Ships caused by Rolling. By Francis Elgar, 
LLuD., F.RS.E., Professor of Naval Architecture and Marine Engi- 
neering in the University of Glasgow 2i 

Proteid Substances in Latex. By J. R. Green, B.Sc., B. A., Demonstrator 
of Physiology in the University of Cambridge 26 

The Coefficient of Viscosity of Air. By Herbert Tomliiison, B.A 4(j 



January 21, 1886. 

Family-likeness in Stature. By Francis Galton, F.RS. With an 
Appendix by J. D. Hamilton Dixon, Fellow and Tutor of St. Peter's 
College, Cambridge 42 

The Early Development of Julu8 terrestris. By F. G. Heathcote, M.A., 
Trin. Coll, Cam. 7.1 



^MdJMDt MMttar SpectroBoopy : Note on the Spectra of ErUa. liv 
muu Crvokee, FJ18. ^ ^ 



On 
Wniiam 



IV 

Pupe 

On the Clark Cell as a Standard of Electromotive Force. By the Lord 
Rayleigh, M.A., D.C.L., Sec. R.S 7ii 

Account of a new Volcanic Island in- the Pacific Ocean. By Wilfred 
Rowell, H.B.M. Consul in Samoa. In a letter to tlvB Hydrographer of 
the Admiralty « 81 

January 28, 188a 

On Local Magnetic Disturbance in Islands situated far from a Continent. 
By Staff-Commander E. W. Creak, RN., F.RS., of the Admiralty 
Compass Department ^ 83 

Description of some Remains of the Gigantic Land-Lizard (Megalama 
prisca, Owen) from Queensland, AustraSa, including^ Sacrum and Foot- 
Bones. Part IV. By Sir Richard Owen, KC.B., F.RS., &c. 93 

On the Development of the Cranial Nerves of the Newt. By Alice 
Johnson, Demonstrator of Biology, Newnham College, Cambricfge, and 
Lilian Sheldon, Bathurst Student, Newnham College, Cambridge 94 

List of Presents , 96 

On the Changes produced by Magnetisation in the Length of Rods of 
Iron, Steel, and Nickel. By Shelford Bidwell, M.A., LL.B 109 

No. 243.— February 4, 1886. 

On Intravascular Clotting. By L. C. Wooldridge, M.B., D.Sc, Demon- 
strator of Physiology in Guy's Hospital (from the Brown Institu- 
tion) 134 

A Further Enquiry into a Special Colour-relation between the Larva of 
Snierinthus oceUatus and its Food-plants. By Edward B. Poulton, 
M.A., of Jesus and Keble Colleges, Oxford 135 

On the Polarisation of Light by Reflection from the Surface of a Crystal 
of Iceland Spar. By Sir John Conroy, Bart., M.A., of Keble CoUege, 
Oxford 173 

February 11, 1886. 

On the Theory of Lubrication and its Application to Mr. Beauchamp 
Tower's Experiments, including an Experimental Determination of the 
Viscosity of Olive OiL By Professor Osborne Reynolds, LL.D., 
F.RS 191 

The Electrical Phenomena accompanying the Process of Secretion in the 
Salivary Glands of the Dog and Cat By W. Maddock Bayliss, B.Sc, 
and J. Rose Bradford, B.Sc, Senior Demonstrator of Anatomy in Uni- 
versity College, London (from the Physiological Laboratory of Univer- 
sity College) 20^ 

February 18, 1886. 

ObserratioDB on the Radiation of Light and Heat from Bright and 
Black Incandeacent Surfacea, By Mortimer I^vmib^ "M, loaX. C^., 
F.It.A.8. ^ '^'^^ 



Page 
On a Thermopile and a Galvanometer combined. By Professor George 
Forbes, M.A. 217 



February 25, 1886. 

On a Comparison between Apparent Inequalities of Short Period in Sun- 
spot Areas and in Diomal Declination-ranges at Toronto and at Prague., 
By Balfour Stewart, M.A., LL.D., F.RS., and William Lant Car- 
penter, RA., B.Sc. ^ 220 

On Radiant Matter Spectroscopy : Note on the Earth Yo. By William 
Crooke8,F.RS ^ 236 



March 4, 1886. 

list ol Candidates 237 

Thk Bakerian Lscturk. — Colour Photometry. By Captain Abney, 
RK, F.RS., and Major-General Festing, RE 238 

March 11, 1886. 

The Influence of Stress and Strain on the Physical Properties of Matter. 
Part I. Elasticity — continued. The Internal Friction of Metals. By 
Herbert Tomlinson, B.A. 240 

On Systems of Circles and Spheres. By R Lachlan, MA.,Fellow of 
Trinity College, Cambridge 242 

Effects of Stress and Magnetisation on the Thermoelectric Quality of Iron. 
By Professor J. A. Ewing, B.Sc, University College, Dundee 246 



March 18, 1886. 

The Relationship of the Activity of Vesuvius to certain Meteorological 
and Astronomical Phenomena. By Dr. H. J. Johnson-Lavis 248 

Od an Apparatus for connecting and disconnecting a Beceiver under 
Exhaustion by a Mercurial Pump. By J. T. Bottomley, M.A., 
F.R.S.K 249 

Comparative Effects of different parts of the Spectrum on Silver Salts. 
By Captain W. de W. Abney, RE., F.RS. 261 



March 25, 1886. 

Abstract of Paper upon the Minute Anatomy of the Brachial Plexus. By 
W. P. Herringham, M.B., MRC.P 255 

On the Changes produced by Magnetisation in the Length of Iron Wires 
• under Tension. By Shelford Bidwell, M.A., LL.B 257 

# £enark8 on the Cloaca and od the Copulatory Organs of the Ammota.. 
/ S^I^, Gadow <^i^i^ 

a 2i 



VI 

Electrolytic Conduction in Relation to Molecular Composition, Valency, 
and the nature of Chemical Change : being an Attempt t^ ^pplj a 
Theory of "Residual Affinity." By Henry E. Armstrong, Ph.D., 
F.RS., Professor of Chemistry, City and Guilds of London Central 
Institution « ^ 26 



No. 2U.—Apra 1, 1886. 

On the Correction to the Equilibrium Theory of Tides for the Continents. 
I. By G. H. Darwin, LL.D., F.RS., Fellow of Trinity College, and 
Plumian Professor in the University of Cambridge. II. By H. H. 
Turner, B.A., Fellow of Trinity College, Cambridge ^ 

Description of Fossil Remains of two Species of a Megalanian Genus 
(Metolaniay Ow.), from Lord Howe*s Island. By Sir Richard Owen, 
IL.C.B., F.RS. ,„ M........ —... .«. 2 

On the Luni-Solar Variations of Magnetic Declination and Horizontal 
Force at Bombay, and of Declination at Trevandrum. By Charles 
Chambers, F.RS 31 

On a New Form of Stereoscope. By A. Stroh 31 

Apnl 8, 1886. 

Croonian Lecture. — On the Coagulation of the Blood. By L. C. Wool- 
dridge, M.B., D.S., Demonstrator of Physiology in Guy's Hospital and 
Research Scholar to the Grocers' Company 3S 

April 15, 1886. 

Preliminary Notes on certain Zoological Observations made at Talisse 
Island, North Celebes. By Sydney J. Hickson, D.Sc, B.A 3! 

Dynamo-electric Machines. By John Hopkinson, D.Sc., F.RS., and 
Edward Hopkinson, D.Sc 3 

Mar/ 6, 1886. 

List of Candidates 3 

On an Effect produced by the Passage of an Electric Discharge through 
Pure Nitrogen. By J. J. Thomson, M.A., F.RS., Fellow of Trinity 
College, Cavendish Professor of Experimental Physics, Cambridge, and 
R Threlfall, B. A., Caius College, Cambridge, Professor of Experimental 
Physics in the University of Sydney 3 

Some Experiments on the Production of Ozone. By J. J. Thomson, M. A., 
F.RS., Fellow of Trinity College, and Cavendish Professor of Experi- 
mental Physics in the University of Cambridge, and R Threlfall, Caius 
College, Cambridge, and Professor of Experimental Physics in the 
University of Sydney 3 

The Influence of Stress and Strain on the Physical Properties of Matter. 

J^ari I. Elasticity — continued. The Effect of Change of Temperatiu-e 

on the Internal Friction and Torsional Elaatmty ol 'iilL^XaS^ ^>3 

Herbert Tomlinaon, B.A. 



Vll 



Page 



^ a New Means of converting Heat Energy into Electrical Energy. By 
Williard E. Case, of Auburn, New York, U.S.A 345 

Further Discussion of the Sun-spot Spectra Observations made at Ken- 
fflD^n. By J. Norman Lockyer, F.R.S * 347 



May 13, 1886. 

On the Structure of Mucous Salivary Glands. By J. N. Langley, M. A., 
F.R.S., Fellow and Lecturer of Trinity College, Cambridge ., 362 

On the Computation of the Harmonic Components, &c. By Lieut- 
General Strachey, RK, C.S.L, F.RS 367 

On the Sympathetic Vibrations of Jets. By Chichester A. Bell, M.B 368 

Intensity of Radiation through Turbid Media. By Captain Abney, RE., 
F.RS., and Ma jor-General Testing, RE 378 



May 20, 1886. 

Relation of * Transfer-Resistance ' to the Molecular Weight and Chemical 
Composition of Electrolytes. By G. Gore, LL.D., F.RS 380 

A Study of the Thermal Properties of Ethyl Oxide. By William Ram- 
say, PL D., and Sydney Young, D.Sc. 381 

On the Working of the Harmonic Analyser at the Meteorological Office. 
By Robert H. Scott, F.RS., and Richard H. Curtis, F.RMet. Soc. .... 382 

List of Presents 393 



No. 246.— i/a^ 27, 1886. 

Family-likeness in Eye-colour. By Francis Galton, F.RS 402 

A General Theorem in Electrostatic Induction, with Application of it 
to the Origin of Electrification by Friction. By John Buchanan, B.Sc, 
Demonstrator of Physics, University College, London 416 

^(AfSA on Alteration induced by Heat in certain Vitreous Rocks ; based 
on the Experiments of Douglas Herman, F.I.C., F.C.S., and G. F. 
Bodwell, late Science Master in Marlborough College. By Frank 
Ratley, F.G.S., Lecturer on Mineralogy in the Royal School of Mines . 430 

On the Relation between the Thickness and the Surface-tension of 
Liquid Films. By A, W. Reinold, M.A., F.RS., Professor of Physics 
in the Royal Naval College, Greenwich, and A. W. Rucker, M.A., 
F.R& 441 

Experiments with Pressure on Excitable Tissues. By George J. Romanes, 
KR& 446 

The Influence of Stress and Strain on the Physical Properties of Matter. 
Part I. Elasticity — coiUintied. The Effect of Magnetisation on tbft 
Ehisticitjr and the Internal Friction of Metals. By Herbert Tom^n- 
jtoa, KA. ^- 






TIU 

Beaearches in Stellar Fhotognf^j. 1. In its Belmtion to the Photometiy 
of the Stars ; 2. Its Af^cabilitj to Astronomical Measuronents df 
Great Precision. By the Kev. C. Pritchard, D.D., F.R&, Savilian 
Professor of Astronomy in Oxford.^ 449 

Besearcfaes upon the Self-induction of an Electric Current. By Pn^easor 
Contribution to the Study oi Intestinal Best and Movement. By J. « J 

•Aine 4, 1886. 
Election of Fellows «......,«. 471 

•/Hue 10, 188e. 

On the ]Nood-yeaBels of Mustelus cuUarctiau : a Contribution to the 
Morphology of the Vascular Sjrstem in the Yertebrata. By T. Jeffrey 
Parker, B.Sc., C.MZ.S., Professor of Biology in the University df 

A Minute Analysis (experimental) of the various Movements produced 
by stimukiting in the Monkey diffei'ent Begions of the Cortical Centre 
for the Upper Limb, as detined by Professor Ferrier. By Charles £. 
Beevor, M.D., MB.C.P., and Professor Victor Horsley, F.R.S., R&, 
FRCa 478^ 

On the Discrimination of Maxima and Minima Solutions in the Calculus 
of Variations. By E. P. CulverwelL «... 47fP 

On the Anatomy, Histology, and Physiology of the Intraocular Muscles 
of Mammals. By Walter H. Jessop, M.A., MB., Cantab., F.RCS., 
Demonstrator of Anatomy at St. Bartholomew's Hospital, London, &c. 479 

On the Place of Origin of Uric Acid in the Animal Body. By Alfred 
Baring Garrod, MD., F.RS 48#^ 

On the Lifting Power of Electromagnets and the Magnetisation of Iron. 
By Shelford Bidwell, MA,, LL.B 48^ 

On a New Scale for Tangent Galvanometers. By W. H. Preece, F.RS., 
and H. R Kempe 4^ 

On Fluted Craterless Carbons for Arc lighting. By Sir James N. 
Douglass 600 

On some new Elements in Cradolinite and Samarskite, detected spec- 
troscopically. By William Crookes, F.RS., V.P.Ca 50S 

The Distribution of Micro-oiganisms in Air. By Percy F. Frankland, 
Ph.D., B.Sc, F.C.S., F.LC, Assoc Boy. Sch. Mines 509 

On the Multiplication of Micro-organisms. By Percy F. Frankland, 
Ph.D., B.Sc, F.C.S., F.LC, Assoc Roy. Sch. Mines 526 

Observations on Pure Ice and Snow. By Thomas Andrews, F.RS,E, , 
F.C.S., Wortley Iron Works, near Sheffield 544 

On the Gaseous Constituents of Meteorites. By Gerrard Ansdell, F.C.S., 
and Prof. James Dewar, F.RS. 549 



IX 



reliminary Communication on the Structure and Presence in Sphenodon 
^nd other Ldzards of the Median Eye, described by von Graaf m AnguU 
fragilis. By W. Baldwin Spencer, RA., Demonstrator of Comparative 
Anatomy in University of Oxford, Fellow of Lincoln CoUeji^e 659 

^Ur Photography. The Effects of Lon? and Short Exposures on Star 
Magnitudes. By Isaac Roberts, F.RA-S 666 

An iBstrument for the Speedy Volumetric Determination of Carbonic 
Adi By W. Marcet, M.D., F.RS 666 

On the Practical Measurements of Temperatures ; Experiments made at 
the Cavendish Laboratory, Cambridge. By H. L. Callendar, B.A., 
Scholar of Trinity College, Cambridge 666 

The Det^raiination of Organic Matter in Air. By Professor T. Camelley 
and William Mackie 666 

The Carbonic Acid, Organic Matter, and Micro-organisms in Air, more 
especially of Dwellings and Schools. By Professor T. Camelley, J. S. 
Hahkne, and Dr. A. M. Anderson 666 

Miminary Report on the Pathology of Cholera Asiatica (as observed in 
^nin, 1885). By C. S. Roy, F.Ra, J. Graham Brown, M.D., &c, 
andC. a Sherrington, M.R 666 



liBte of Presents 



ibdex 



667 
576 



96ituary Notice : — 
Captain Sir Frederick J. O. Evans, RN., KC.B. 



PROCEEDINGS 



or 



THE ROYAL SOCIETY. 



-•s.-vvv- 



JantMry 7, 1886. 

Professor STOKES, D.C.L., President, in the Chair. 

The Presents received were laid on the table, and thanks ordered 
for them. 

The following Papers were read : — 



I. •* Experimental Researches on the Propagation of Heat by 
Conduction in Muscle, Liver, Kidney, Bone, and Brain." 
By J. S. Lombard, M.D., formerly Assistant Professor of 
Physiology in Harvard University. Communicated by 
Charles E. Brown-Sequard, M.D., LL.D., F.R.S. Received 
December 7, 1885. 

(Abstract.) 

The apparatus employed in the present investigations was the same 

thermo-electric one that was used in the experiments on conduction of 

heat in hone, brain-tissue, and skin, described in a former paper,* but 

the mode of application of the thermo-pile to the tissue was somewhat 

different. The tissue, whether hard or soft, was placed on a thin 

copper plate, which formed the floor of a square hole cat in the bottom 

of a small light wooden box. The pile, having been applied to the 

opper surface of the tissue, was held in place by means of a ]>aste- 

board collar, which was made fast with pins to the edges of the box. 

In the case of the soft tissue.^, light weights were affixed to the pile to 

regulate the pressure. With bone, in order to insure intimate contact 

between the pile and the tissue, and between the latter and the copper 

plate, a little marrow was used. The unoccupied space in the box 

was filled with finely chopped cotton-wool. The box had pasteboard 

nprights attached to it.s sides, by which it wna suspended from. t\ve> 



» u 



rOL. TU 



Proe. noj. 8oe./' vol 34, pp, 178, 193. 



2 Dr. J. S. Lombard. Conduction of Heai in [Jan. 7, 

sliding arm of a stand. The inferior surface of the copper plate was 
brooght in contact with water of a temperature lower than that of the 
air by fractions of a degree of centigrade, as in the former experiments 
referred to. 

Experimefits on Muscle, 

The muscles examined were those of the head, thigh, and leg of the 
sheep. 

It soon was noticed that the rate of transmission differed somewhat, 
according as the muscle was examined in the direction of its fibres or 
perpendicularly to them ; and this fact led to the division of the 
experiments into two classes, according as the line of conduction 
was parallel or at right angles to that of the fibres. 

Tables I and II give results obtained under these two conditions 
respectively. The results represent 104 observations on conduction 
panillel to tbe direction of the fibres, and 100 obeervations on condno- 
tion at right angles to this direction. 

Table I. — Conduction of Heat through 10 mm. of Sheep^s Muscle, 

parallel to the direction of the Fibres. 



Time. 


Percentages of heat transmitted. 


Arerages. 


Maxima. 


Minima. 


At the end of 4 minutes 

»» 6 „ 

>i 9 „ 

Permanent thermal condition . . . 


33 -985391 
51 -215703 
66-775211 
82 -730123 


58 -359600 
77 -219200 
93-108500 
99-500000 


19 -959500 
34 -712200 
48 133700 
63 -557000 



Table II. — Conduction of Heat through 10 mm. of Sheep's Muscle, 
perpendicular to the direction of the Fibres. 



Time. 


Percentages of heat transmitted. 


Ayerages. 


Maxima. 


Minima. 


At the end of 4 minutes 

II 6 „ 

»» 9 ,f 
Permanent thermal condition . . . 


27 038177 
40 -701253 
58 -174220 
76 -614920 


40-837000 
60-789900 
84-384200 
99-422300 


11-378300 
26-283600 
39-203600 
50 -911200 



-i^ will he seen that parallel conduction b\io^& t)aft "^oii^et ^t- 



1886.] 



MuscUy LiveTf Kidney^ Hone, and Brain. 



oentages — average, maximnm, and minimnm — at every period. The 
average percentages of superiority of parallel conduction over conduc- 
tion at right angles are as follows : — 



At the end of 
4 minutes. 

6 -947214 



At the end of 
6 minutes. 

10-51445 



At the end of 
9 minutes. 

8 -600991 



Permanent 

thermal 

condition. 

6 -115203 



The conductivity of muscle, unlike that of the other tissues 
examined, does not appear to depend, at least in any marked manner, 
upon the d^ree of freshness of the tissue. So long as the muscle is 
kept in a moist state, it seems to conduct equally well whether 
recently removed from the animal or after decay has commenced; 
and when the conductivity has been decidedly lowered by exposure 
to ihe air, it generally can be partially, and sometimes completely, 
restored, by moistening the tissue with water or fresh animal juices. 



Bxperinhenta on Liver, 

The liver examined was tha4; of the sheep, 
resalts of sixty experiments on this organ. 



Table III gives the 



Table 111. — Conduction of Heat through 1 mm. of Sheep's Liver. 


Time. 


Percentages of heat transmitted. 


Ayerages. 


Maxima. 


Minima. 


At the end of 4 minutes 

>» ^ ** 

w 9 ,} 

Pennanoit thermal condition -. . . 


45-628640 
64 -338080 
81-164906 
93-043060 


61-618700 
79-448900 
93 171900 
99-500000 


27 -367800 
48 -352500 
64 3S3H00 
78-004000 

1 



The conductivity of liver diminishes steadily and rapidly after 
de«th, and is not restored by moisture or fresh animal matter, 
tithough these latter seem to reduce the rate of loss. 

Experiments on Kidney. 

The observations were made on sheep's kidney. Tables IV and V 
give respectively the results of thirty experiments on the cortical 
nhetance, and of an equal number on the medullary tissue. 

The tables show that at every period of the observations, excepting 
the maximum for the ninth minute, which gives a slight baVaivce m 
faronrof the mednlJarjr tissue — the cortical tissue is the better coxl- 



rxKW- 



Dr. J. S. Lombard. Conduction of Heat in [Jan. 7, 



Table IV. — Oondnction of Heat throtigh 10 mm. of the Cortical 

Sabstance of Sheep's Kidney. 



Time. 


Pei-centages of heat transmitted. 


ATerages. 


Maxima. 


Minima. 


At the end of 4 minutes 

n 6 „ 

Permanent thermal condition . . . 


44 -512983 
64 -946250 
82 -431483 
97 -715600 


63-013900 
72-318700 
87 027000 
99-500000 


27 -725100 
59-696400 

78-138000 
93-466000 



Table V. — Oondnction of Heat throngh 10 mm. of the Medullary 

Snbstance of Sheep's Kidney. 



Time. 


Percentages of heat transmitted. 


Averages. 


Maxima. 


Minima. 


At the end of 4 minutes 

»i 6 „ 

n 9 it 

Permanent thermal condition . . . 


36 -541850 
56 -686350 
71 -536316 
91 -947716 


46-861700 , 
69 -645700 
87 121000 
98 -676300 


19-867800 
39-955000 
53-310900 
78-150400 



Both cortical and medullary substances behave like liver as regards 
the diminution of conductivity after death, and the effect of water 
and fresh animal matter on this loss. 



Experiments on Bone. 

The observations were made on the tibia and the ilium of the sheep. 
The experiments were divided into three classes, according as the tissue 
was compact, spongy or combined compact-spongy. Some 200 experi- 
ments were made, which were divided about equally between the three 
varieties of tissue. 

Tables VI, VII, and VIII give the results of these experiments. 
According to the tables, spongy tissue stands first in average, maxi- 
mum, and minimum conductivity, at every period, and the combined 
compact-spongy tissue comes next, also as regards all three valuations 
and every period of time. 



1*86.] 



MuscUy Liver, Kidney, Bone, and Brain. 



Table YI. — Conduction of Heat through 10 mm. of the Compact 

Tissue of the Head of Sheep's Tibia. 



Time. 


Percentages of heat transmitted. 


Ayerages. 


Maxima. 


Minima. 


At the end of 4 minutes 

» 6 f » 

1* ^ > 

PermftDent thermal condition . . . 


24-067400 
36 -305560 
47 -959167 
70 -770483 


30-377800 
40 -411400 
54-529600 
75 -717700 


16 106900 
30 -831300 
35 -357000 
66 179500 



Table VII. — Conduction of Heat through 10 mm. of the Spongy 
Tisfiue of the Head of Sheep's Tibia. 



Time. 

1 


Percentages of heat transmitted. 


Ayerages. 


Maxima. 


Minima. 


At the end of 4 minutes 

»» 6 „ 

Pennanent thermal condition .. . . 


35 -939917 
52 -274800 
70-911200 
89 -779800 


54 -671700 
74 -495300 
89 -498600 
97 -225600 


21-894200 
31-398500 
41 -547200 
62 -436700 



Table VIII. — Conduction of Heat through 10 mm. of Sheep*s Ilium. 

Compact and Spongy Tissues combined. 



Time. 


Percentages of heat transmitted. 


Ayerages. 


Maxima. 


! 
Minima. 


At the end of 4 minutes 

>i 6 »» 

»f 9 «» 

Pennanent thermal condition . . 


32 -736216 
48-374200 
61 - 197667 
74-741783 


45 -292000 
64-755300 
81 -495700 
95 -458500 


18-351600 
31-195800 
40 -602900 
59 -718700 



Both compact and spongy tissues lose their conducting power more 
or leM rapidly after removal from their natural surroundings ; spongy 
tissue much more quickly than compact. Spongy tissue may regain 
the greater part of the loss of its cond activity, after the app\\caXi\ou oi 
water or fresh &nim&l matter, but tbia is not the cane Yf'ilVi com^Wi\. 



6 Prof. Victor Horsley. [Jan. 7, 

tissue ; however, moistare seems to slightly reduce the rate of loss in 
the latter. With regard to the compound tissue — compact-spongj, 
the changes which its conductivity undergoes present simply a varying 
mean of those of its two components. After long exposure to the air, 
the bone being well dried, the conductivities of compact and of 
spongy tissue are found to closely approximate each other. 

Ih^eriments on Brain. 

The experiments on this tissue had reference only to the changes of 
its conductivity, due to exposure to the air, and to the effect of 
moisture and fresh animal liquids on these changes. 

Like liver and kidney, the tissue of brain quickly loses its power of 
oondaction after death, and neither moisture or fresh animal matter 
can restore this loss, although they may diminish its rate. 



II. "Further Researches into the Function of the Thyroid 
Gland and into the Pathological State produced by Removal 
of the s€tme." By Professor Victor Horsley, B.S., F.R.C.S. 
Communicated by Professor Michael Foster, M.D., Sec. R.S. 
Received December 10, 1885. 

In December, 1884, I showed that the thyroid gland was intimately 
connected with the process of mucin metabolism, that if the thjroid 
gland in monkeys was removed with antiseptic precautions (the same 
ensuring healing of the woand in three days) the conseqaences to the 
animal were — (1) symptoms of general nervous disturbance evidenced 
by tremors, paroxysmal convulsions, functional paralysis, mental hebe- 
tude, and finally complete imbecility ; (2) profound aneemia coupled 
with leucocytosis ; (3) all the symptoms of the disease discovered 
within the last decade and termed myxGedema; (4) that just as in the 
acute form of the disease just named there was found to be a great 
accumulation of mucin in the connective tissues through out the body 
(mucinoid degeneration), and in the blood, and as a consequence the 
same post-mortem appearances ; (5) that at the same time there was a 
great activity in the raucin-secreting glands, and, further, that the 
parotid gland under these abnormal circumstances secreted mucin in 
large quantity, the gland cells at the same time disintegrating. 

During the past year I have confirmed my previous observations, 

and greatly extended them, and have firm basis for my original 

opinion that the function of the thyroid gland is indispensable to the 

hi/^ber animala, and that it is duplex, since, in the first place, it 

reg-nlatea the formation of mucin in the body ; and, m VXi^ «i^^\i\ 



1886.] On the Function of the Thyroid Gland. 7 

place, it aids in the mannfactnre of blood-corpnscles. Mj researches 
daring the past year (1885) have been directed towards the investi- 
gation of (1) the circumstances which influence the course of the 
extensive disturbance of general nutrition which follows the loss of the 
gland; (2) the direct effect of the said fall in nutrition upon the 
nerve-centres ; and ^S) the haemapoietic function of the gland. 

(1.) 1 find that the determining factor jaar excellence of the value of 
the gland as regards its influence on the general metabolic processes of 
the animal is Age. The effect of removing the gland in the young 
animal is the rapid appearance x>f violent nerve symptoms and death 
in a few days ; in a rather older animal, i.e., a one-year old dog, the 
symptoms are less violent, later in their appearance, cind the animal 
survives perhaps for a. fortnight or three weeks ; in a very old animal 
the removal of the gland simply hastens the torpor of old age ; these 
observations refer to dogs and cats. In the higher animals, monkeys, 
the operation on a young individual produces the same result as in a 
young dog, but, as 1 showed last year, an older animal, if kept under 
ordinary circumstances^ will survive for six or seven weeks, dying at 
the end of that time o| myxosdema. On the whole, therefore, it 
appears that the thyroid gland is of extreme importance when tissue 
metabolism is most active, and that it diminishes as the senile state 
advances. Huschke has shown that the relative weight of the 
thyroid body to the body weight is greatest at birth, that it rapidly 
diminishes during the next few weeks, and that it steadily decreases 
as age advances. Finally, the structural degeneration of the gland in 
old age is well known. It is clear, therefore, that the gland plays an 
important and constant part in the metabolism of the body ; I desire 
here to draw special attention to the fact that the symptoms of old 
age, namely, wasting of the actively functional parenchymatous 
tissues, atrophy, and falling out of the hair, decay of the .teeth, dryness 
and harshness of the skin, tremors, S^., are exactly the most prominent 
features of the myxosdematous state, whether it occurs naturally in 
the human being, prematurely, as in cretinism, or artificially, as in 
my experiments on monkeys. It is, perhaps, well to remark here 
thai, as might have been foreseen, the previous state of nutrition of 
the body determines to a large extent the rapidity of onset and the 
course of the symptoms. 

The next circumstance of extreme importance which influences the 
course of the symptoms is the Temperature at which the animals are 
kept after the gland has been removed. I showed last year that one 
of the most obvious features of the fall of nutrition which follows the 
loss of the gland was a steady diminution of the body heat, this sug- 
gested to me a line of research which has yielded a striking resnlt. I 
have kept Another series of animaJs (on whom I have perloxm^'^^ 
tbjroideotomjr uader the conditions above stated) at a constanX. Wxa- 



6 Prof. Victor Horsley. [Jan. 7, 

tissue ; however, moisture seems to slightly reduce the rate of loss in 
the latter. With regard to the compound tissue — compact-spongy, 
the changes which its conductivity undergoes present simply a varying 
mean of those of its two components. After long exposure to the air, 
the bone being well dried, the conductivities of compact and of 
spongy tissue are found to closely approximate each other. 

Experiments on Brain, 

The experiments on this tissue had reference only to the changes of 
its conductivity, due to exposure to the air, and to the effect of 
moisture and fresh animal liquids on these changes. 

Like liver and kidney, the tissue of brain quickly loses its power of 
oondaction after death, and neither moisture or fresh animal matter 
can restore this loss, although they may diminish its rate. 



II. "Further Researches into the Function of the Thyroid 
Gland and into the Pathological State produced by Removal 
of the same." By Professor Victor Horsley, B.S., F.R.C.S. 
Communicated by Professor Michael Foster, M.D., Sec. R.S. 
Received December 10, 1885. 

In December, 1884, I showed that the thyroid gland was intimately 
connected with the process of mucin metabolism, that if the thyroid 
gland in monkeys was removed with antiseptic precautions (the same 
ensuring healing of the woand in three days) the consequences to the 
animal were — (1) symptoms of general nervous disturbance evidenced 
by tremors, paroxysmal convulsions, functional paralysis, mental hebe- 
tude, and finally complete imbecility ; (2) profound aneemia coupled 
with leucocytosis ; (3) all the symptoms of the disease discovered 
within the last decade and termed myxGedema; (4) that just as in the 
acute form of the disease just named there was found to be a great 
aocumulaiion of mucin in the connective tissues thronghout the body 
(mucinoid degeneration), and in the blood, and as a consequence the 
same post-mortem appearances ; (5) that at the same time there was a 
great activity in the raucin-secreting glands, and, further, that the 
parotid gland under these abnormal circumstances secreted mucin in 
large quantity, the gland cells at the same time disintegrating. 

During the past year I have confirmed my previous observations, 

and greatly extended them, and have firm basis for my original 

opinion that the function of the thyroid gland is indispensable to the 

hig'ber animals, and that it is duplex, smce, in t\iQ ^t%\) -^W^q^ \t> 

re'g'iilatea the forumtion of mucin in the body •, wvd, m VXi^ ^«^i^\A 



1886.] On (he Function of the Thyroid Gland. 7 

place, it aids in the manufacture of blood-corpnecles. Mj researches 
during the past year (1885) have been directed towards the investi- 
gation of (1) the circumstances which influence the course of the 
extensiTC disturbance of general nutrition which follows the loss of the 
gland ; (2) the direct effect of the said fall in nutrition upon the 
uerve-centres ; and J^S) the haemapoietic function of the gland. 

(1.) 1 find that the determining factor jaar excellence of the value of 
the gland as regards its influence on the general metabolic processes of 
the animal is Age, The effect of removing the gland in the young 
animal is tbe rapid appearance of violent nerve symptoms and death 
in a few days ; in a rather older animal, i.e., A one-year old dog, the 
symptoms are less violent, later in their appearance, and the animal 
survives perhaps for a fortnight or three weeks ; m a very old animal 
the removal of the gland simply hastens the torpor of old age ; these 
observations refer to dogs and cats. In the higher animals, monkeys, 
the operation on a young individual produces the same result as in a 
young dog, but, as 1 showed last yeart ^^ older animal, if kept under 
ordinary circumstances^ will survive for six or seven weeks, dying at 
the end of that time o| myxoddema. On the whole, therefore, it 
appears that the tbyroid gland is of extreme importance when tissue 
metabolism is most active, and that it diminishes as the senile state 
advances. Huschke has shown that the relative weight of the 
thyroid body to the body weight is greatest at birth, that it rapidly 
diminishes during the next few weeks, and that it steadily decreases 
as age advances. Finally, the structural degeneration of the gland in 
old age is well known. It is clear, therefore, that the gland plays an 
important and constant part in the metabolism of the body ; 1 desire 
here to draw special attention to the fact that the symptoms of old 
age, namely, wasting of the actively functional parenchymatous 
tissues, atrophy, and falling out of the hair, decay of the .teeth, dryness 
and harshness of the skin, tremors, &k:., are exactly the most prominent 
features of the myxoedematous state, whether it occurs naturally in 
the hunaan being, prematurely, as in cretinism, or artificially, as in 
my experiments on monkeys. It is, perhaps, well to remark here 
that, as might have been foreseen, the previous state of nutrition of 
the body determines to a large extent the rapidity of onset and the 
course of the symptoms. 

The next circumstance of extreme importance which influences the 
course of the symptoms is the Temperature at which the animals are 
kept after the gland has been removed. I showed last year that one 
of the most obvious features of the fall of nutrition which follows the 
loss of the gland was a steady diminution of the body heat, this sug- 
gested to me a line of research which has yielded a striking result. 1 
have kept another series o£ Animals (on whom 1 \iav© '^^Tiatvcv^ 
tbjroidectomjr under the oonditiona above stated) at a coiiaWiiX. Wca.- 



8 Prof. Victor Horsley. [Jan. 7, 

peratare of 90* P.,* and when they exhibited any nerve symptoms, t.e., 
tremors, &c., were placed in a hot-air bath at a temperature of 105^ F. 
The effect of this has been to lengthen the daratiou of life (in all hot 
very young animals) four or five times the extent of that observed in 
the first series. Instead of living four to seven weeks they now live 
as many months. At the same time several additional facts of im- 
portance are noted, and the symptoms before referred to are so modi- 
fied as to require the addition of a third stag^ to the two I described 
in 1884. (These observations refer solely to monkeys.) The animalsi 
kept under the extra high temperature above noted thus pasar tfaroug'h 
three stages — (1) neurotic, (2) mueinoid, (3) atrophic. I have said 
that the neurotic stage under these circumstances may be scarcely 
marked, or if the nerve symptoms occur, and the animal be put in the 
hot-air bath, they socm disappear. Next the animal lives through tbe 
mueinoid stage, i.e., myxoedematous condition, and arrives in the third 
stage — the atrophic. Now, the symptonw of the second stage aJ* 
just as much subdued as those of the first, therte is no excessive secre-^ 
tion of mucus, the parotid glands do not swell, and the post-mortem 
examination does not reveal the extensive mueinoid degeneration 
observed in the first series. Finally, the third, atrophic, stage into 
which the animal passes is evidenced by great euHtciation, functional 
paresis and paralysis, imbecility, falling blood pressure and tempera- 
ture, with death by coma. 

I am disposed to regard this fact of the animals passings throngli 
these neurotic, mueinoid stages^ and dying at ther end of the atrophic, 
as the key to the observation that cretins in whom the thyroid gland 
is very slowly destroyed^ and very chronic cases of myxcedema, do not 
exhibit much mueinoid degeneration. 

(2.) I will now briefly enumerate the direct effect of the fall of nutri- 
tion produced by the loss of the thyroid gland on the nerve-centres : 
(a) Effect on cortex. t The tetanus obtained by stimulating the cortex is 
remarkably changed (even as soon as one day after the thyroidectomy 
in a dog, who exhibited violent symptoms in twenty-four hours) by 
the fact of the fall (when the current was shtft off) being as sudden 
as that observed on stimulating the corona radiata. Next, that the 
tetanus in a more advanced case is soon exhausted^ the curve 
approaching the abscissa soon after the initiol rise ; at the same time 
the curve is foUowed by clonic epileptoid spasms, which, however, are 
soon exhausted. Stimulation of the corona radiata and spinal cord 
also gave the customary tetanus, which, like that of the cortex, was 
rapidly exhausted. These stimulations of the nervccentrea sup- 

* In my first experiments (1884) the animalw were kept at a temperature yarying 
/n?m 6(f to 70'* ¥, 
f OmphictiUy recorded aocordiDg to method deaoiibed b^ YtoI. ^c\\^«t wv»\ 
mjrgeJf C Froc. Boy. 8oc.," roi. 89, p. 404). 



1886.] On the Function of the Thyroid Gland. 9 

pressed the thyroid tremors jast as volnntarj movements do. Another 
evidence of the changes in the cortex is the frequency with which 
coiitinaons stimulation will evoke the appearance of clonic spasms on 
the original tetanic curve, the latter not being followed by epilepsy 
when the current is shut ofP. 

((.) Effect on the spinal cord. The tetanus obtained by stimulating 
the spinal cord like that of the cortex rises slowly to the highest point, 
and then steadily falls towards the abscissa although the stimulation 
is maintained^ and when the current is shut off the muscle completely 
relaxes, having absolutely lost its tone, and this tonic paralysis is not 
recovered from for ten to fifteen seconds. Stimulation of the spinal cord 
to ^Bkligue, after some time has elapsed so as to produce exhaustion of 
the preliminary tetanus, evokes a tremor of eight to ten per second. 

Tracings from an old animal (cat) which had survived the operation 
some months, and also from a dog, in which case the symptoms had 
been very severe for some days, exhibited only a very feeble tetanus 
in the former instance, and no reaction at all in the lattery this being 
the ultimate state of depression of function which the nerve-centres 
had arrived to. 

(3.) I have thonght it as well to add to the anatomical and physio- 
logical proofs I gave last year of the thyroid gland being a heema- 
poietic structure by counting the number of corpuscles in the blood 
of the thyroid artery and vein respectively. After discounting any 
possible alteration in the relative number of the corpuscles in the two 
vessels by changes in the fluid constituent of the blood which may 
have happened in the gland, the much greater number of corpuscles 
in the vein ( -I- 7 per cent.) confirms the deductions drawn from my 
previous observations. 

To sum up, the functions of the thyroid gland appears to me to be 
two-fold as already suggested, viz. : (I) Control of mucin metabolism, 
(2) Hsemapoiesisi The metabolic processes in the body may be 
regarded broadly as resulting in Construction and Destruction. The 
products of destruction are the waste products of tissue change, and 
being, as such, harmful to the organism, are cast out by the excretory 
oi^n. It appears to me that the thyroid gland aids in excretion of 
mucinoid substances or their precursors, not of course by excretion 
properly speaking, that is, casting them out from the body, but by 
metamorphosing them into some other form which is useful to the 
system. That this process, whatever it is, is of vital importance to 
the young mammal (seeing that interference with it causes death in a 
few days) is obvious, and such as it is the loss of it is distinctly con- 
nected with the appearances of the diseases known as myxoedema, 
cretinism, and senile degeneration. Finally, this defect in the circle 
of metabolism determines the appearance of 80-caV\e4 £\nic\AOi\a\ 
disorders of the nervous system. 



10 Mr. A. Sanders. On the Anatomy of the [Jan. 7, 



III. "Contributions to the Anatomy of the Central Nervous 
System of Plagiostomata." By Alfred Sanders, M.R.C.S., 
F.L.S. Communicated by Dr. Gunther, F.R.S. Received 
December 11, 1885. 

(Abstract.) 

After referring to the literature of the subject, the author gives a 
short account of the macroscopic appearance of the brains of the 
following species of Plagiostomata, viz^ Baja hatisj Bhina squatina^ 
Scyllium catulus, and Acanthias vulgaris. He thjen refers to the 
distribution of the cranial nerves, especially of the trifacial and 
vagus, pointing out the resemblance of the distribution of the last- 
mentioned nerve in Bhina to that described by Gegenbanr* in 
Hexanthus ; the difference lying in the fact that in the former the 
rami branchial es of this nerve, the number of which correspond to 
the number of the branchial arches, divide into two terminal branches 
only, the rami anteriores and posteriores, the third, the rami pharyngei, 
being absent. 

On the other hand, in Scyllium the rami branchiales do not divide, 
the terminal twigs, representing the rami pharyngei, onlj being 
present. 

The lobi olfactorii consist of two parts, the lobe proper and the 
peduncle. The lobe itself is more or less pear-shaped, broader at the 
anterior end where it abuts on to the olfactory organ, and narrower 
behind where it passes into the peduncle. It consists of three layers, 
counting from before backward, or from outside inward. The posterior, 
which is also the internal layer, occupies more than half of the lobe, 
and consists entirely of a mass of small cells embedded in a network 
of fibrilled and granular neuroglia. This network is of extreme 
tenuity, and the cells contained therein are oval, pear-shaped, or 
spherical in shape, and contain a nucleus and nucleolus ; they give off 
processes which join the network. In front .of these, and outside to 
a certain extent, is found a layer consisting of glomeruli olfactorii ; 
these are elongated or pear-shaped masses arranged with their Jong 
axes in the direction of the nerve fibres. They consist of a central 
core of closely intertwined fibrillee ; externally the fibrils are of rather 
larger size ; they run longitudinally in reference to the glomerulus ; 
in their course elongated cells are developed. 

The anterior or external layer consists of interlacing bundles of 
fibres which pass from the anterior ends of the glomeruli into the 
olfactory organ. The bundles themselves are flat, but the fibrillas of 
which they are composed are round. 

* " JenAisohe Zeitscbcift,'* Bd. 6, 1^11. 



1886.] Central Nervous System of Pfagiostomafa. 11 

The stmctnre of the peduncle resembles that of the olfactory lobe, 
and gradually passes into that of the cerebram at the posterior end. 
In Scyllinm, Bhina, and Acanthias it contains a passage which puts 
the ventricle of the olfactory lobe into communication with that of the 
oerebrum. In Raja, however, both the lobe and the pedancle are 
solid. 

The cerebmm contains two ventricles which posteriorly communi- 
cate with a single chamber, the foramen of Monro ; this is the case in 
ScylHum, Rhina, and Acanthias, but in Raja only a very small 
ventricle is present which represents the foramen of Monro, the 
remainder of the cerebrum being solid. Round the ei^temal surface 
of the cerebrum there is a layer of granular neuroglia with compara- 
tively few cells. The remainder of the parenchyma consists of a mass 
of cellB, larger ones, i3/i to 10/i in diameter, tKscupying the centre, 
and smaller ones predominating towards the internal surface. In 
Scyllium the cells are arranged in groaps of four or five, and in Raja 
also in groups of from nine to twenty-one, which make a meandering 
pattern through the parenchyma in some parts. At the base of the 
cerebrum there are four special groups of cells, two being placed in 
the outer walls and two in the inner walls; the outer groups are 
associated with the fibres of the anterior commissure, and the inner 
groups are associated with the fibres of the crura cerebri. 

The third ventricle is a gutter-shaped channel, long in Scyllium, 
but shorter in Raja, which leads from the cerebrum into the optic 
lobe ; above, it is closed in by processes of the pia mater which enter 
the ventricle and the foramen of Monro, forming a choroid plexus ; 
below, the third ventricle communicates by a passage, the infundi- 
bulum, with the ventricles of the hypoarium ; the parenchyma in this 
lobe contains numerous cells measuring from about 13/i by 7/i to 6u in 
diameter, which give off numerous processes to join a fine network 
which pervades the whole. The ventricle is lined by an endothelium 
which is continuous with a space in the hypophysis cerebri. There is 
a small tubercle in front of the optic lobe which corresponds to the 
tuberculum intermedium of Gottsche,* and from it a bundle of fibres 
can be traced passing towards the ventral surface of the medulla 
oblongata, which corresponds to the fibres of Meynert. 

The optic lobes which homologise with the anterior corpora 
qaadrigemina form a cover arching over the aqueduct of Sylvius, in 
the same position as in the Teleostei ; they are much thicker, but more 
simple in structure. Neither the tori longitudinales nor the tori 
semicirculares, those tuberosities which form prominences on the floor 
of the aqueduct in the Teleostei, are present in the Plagiostomata. 
Three layers may be distinguished in the optic lobe; the external 



# «' 



Mailer'8 Archly," 1835. 



12 Mr. A. Sanders. On the Anatomy of the [Jccn. 7, 

oocnpies about two- thirds of the thickness, and consists of longitudinal 
fibres which are derived from the optic tract, and numerous cells 
which attain their maximum number in this layer ; they are mostly 
spherical, but fusiform cells with their long axes placed radially are 
occasionally found. 

The second layer consists of bundles of transverse fibres partly 
derived from the lateral columns of the medulla oblongata, and partly 
from the commissura ansulata ; they correspond with the transverse 
fibres in the tectum lobi optici of the Teleostei. 

The third layer is characterised by large cells, which are rounded 
or sometimes pyriform ; they usually give off only one process which 
is directed outwards, and joins the above-mentioned transverse fibres. 
These cells differ in their arrangement in the different species, they 
are spread out in a flat layer in the optic lobe of the Scyllium and 
Raja. In Bbina and Acanthias they form a group in the central 
tuberosity that projects into* the aqueduct of Sylvius, resembling the 
arrangement in the Turtle. The .small cells which were described in 
the first layer extend in dinrinishing numbers into this third layer. 

The cerebellum in Scyllium, Bhina, and Acanthias presents a very 
large ventricle which in Raja is nearly obliterated ; the intimate 
structure resembles that of the Teleostei. There are the four layers, 
the molecular with Purkinje cells, the granular and the fibrous layers. 
The latter is connected by the crura cerebelli ad medullam through 
an inferior lobe with the restiform bodies of the medulla oblongata ; 
there is also an anterior cord passing longitudinally into the optic 
lobe which represents the crura cerebelli ad cerebrum (Quain). In 
the granular layer, in addition to the numerous cells forming that 
layer, there are little masses of fibrillao inextricably wound together 
resembling glomeruli on a small scale ; in other respects there is 
nothing peculiar in the structure of the cerebellum. 

The molecular and the granular layers are continued on the surface 
of the restiform bodies in all the species examined, and in Raja nearly 
as far as the posterior end of the fourth ventricle, but the absence of 
the Purkinje cells marks a difference of structure. 

In the spinal cord the grey substance of the ventral oomn contains 
numerous large cells arranged in an imbricated manner with their 
long axes directed obliquely from the ventral to the dorsal sur&oe. 
Their shape is generally elongated, and they give off several processes. 
In the cord the ventral comua are directed horizontally, but towards 
the posterior end of the medulla oblongata they are gradually depressed 
toward the ventral surface, and are finally lost in the grey substance 
on the floor of the fourth ventricle. The dorsal comua contain 
numerous nucleL There are four longitudinal columns in the spinal 
cvrd, the veDtrtd longitudinal columns \>eneatYi \Yi% cenXxiX ca.ta\^ tVv« 
iaiermJ coJamns mi the side^ and tbe doraA GoVumna i2bcit«. IftiJiNiyaL^x^ % 



1886t.] Central Nervous System of PlagioMtomata. 13 

fibres are not present in the Plagiostomata, the fibres of the ventral 
longitudinal oolamns varying very slightly in size ; bnt perhaps, it 
maj be mentioned here that large fibres, two in number, occupying 
positions corresponding to those of the Mauthner's fibres in Teleostei, 
occur in Ceratodus ; they have the peculiarity of possessing several 
axis cylinders inclosed in a single medullary sheath. 

The ventral columns form projecting longitudinal cords in the floor 
of the fourth ventricle. They can be traced into the ventral side of 
the posterior commissure which occupies the usual place at the pos* 
terior boundary of the third ventricle. 

The lateral columns on passing forward diminish greatly in number, 
the internal fibres are lost in the neighbourhood of the posterior 
conunissure ; those that are external seem to join the transverse fibres 
of the optic lobe, those between the two disappear in the region above 
the hypoarium, some crossing the crura cerebri which disappear in the 
same region. 

The optic nerves form a chiasma, the lower part of which is formed 
by the nerves of the two sides intersecting each other in bundles, but 
in the upper part the remainder cross each other en masse. The 
principal origin of this nerve is the optic lobe, where the outer two- 
thirds are occupied by its tract ; a few fibres, however, are derived 
from the hypoarium. 

The ocolo motorii are derived from two ganglia situated on the 
floor of the aqueduct of Sylvius ; they pass nearly straight down to 
the ventral surface of (the medulla oblongata. At this region there is 
a syst-em of transverse commissures connected with the second layer 
of the optic lobe, which corresponds to the commissura ansulata of 
Teleostei (Gottsche).* 

The ganglion of origin of the trochlearis was not found, bnt the 
fibres decussate at a part between the optic lobe and the cerebellum 
corresponding to the valve of Yieussens. 

The trifacial is derived from three roots, one of which comes for- 
ward from the posterior part of the medulla oblongata, where it can 
be traced into the lateral columns. The other comes backward 
through the tuberosity of the trifacial by the side of the medulla; 
these two cross each other at their entrance into the nerve, the third 
comes from a group of cells in the grey substance of the floor of the 
fourth ventricle. 

The abduceus can be traced from the ventral surface of the medulla 
oblongata at about its centre into the lower edge of the ventral 
longitudinal colunms. 

The facial can be traced into a small bundle of fibres which passes 
backward into the spinal cord in the substantia gelatinoaa ceiiiT«\vs^ 
jasi above the central canal. 

♦ Zor. eit,, p. 489. 



14 Dr. A. Downes. On the [Jan, 14,- 

Abont this region there is a system of arched oommissaral fibres, 
the fibrsd arcnatad. They seem to be connected with the cmra cere- 
belli and medullam. They occur not only through the external part 
of the ventral surface, bat also through the central portions. 

The acnsticus and glossopharyngeal arise from the grey substance 
on the floor of the fourth ventricle. 

The vagus arises from a series of rounded tuberosities situated on 
the side of the floor of the fourth ventricle ; each root arises from a 
separate tuberosity. 

The spinal nerves arise by dorsal and ventral root^s ; the latter from 
the ventral horn of grey substance. The former pass obliquely into 
the interior of the cord and there divide into two bundles ; one bundle 
from the anterior part of the root is directed backward, the other 
bundle from the posterior part of the root is directed forward. They 
pass over the next nerve both in front and behind, and join the 
lateral columns of the cord. This arrangement was first described by 
Stieda.* 



Jammrif 14, 1886\ 

Professor STOKES, D.C.L.^ President, in iih« Chair. 

The Presents received were laid on the table,, and thanks ordered 
for them. 

The following Papers were read ; — 

I. " On the Action of Sunlight on Micro-organisms, &<?., with 
a Demonstration of the Influence of Diffused Light." By 
Arthur Downes, M.D. Commimicated by Profeseor 
Marshall, F.R.S. Received December 9, 1885. 

Eight years ago, conjointly with my friend Mr. Blunt, I commu- 
nicated to the Broyal Society an account of an experimental inquiry 
into the action of sunlight on the micro-organisms of putrefaction 
and decay .f 

We adduced evidence, conclusive in our opinion, that the solar 
rays were very hostile to these lowly forms of life ; so much so that 
under favourable conditions bright sunlight, sufficiently prolonged, 
would altogether prevent their appearance in fluids which, under 

♦ "Zeitach. f. Wits. Zoologic," Bd. 2^,1W^. 
t " Froc. Roy. See.," vol. 26, p. 4aa, and -toY. 2%, ^. \^. 



1886.] Aetiofi of Sunliyht on Microorganisms, ^e. 15 

similar conditions of temperature and the like, bat screened from 
\ig;hty swarmed in a very few days with countless saprophytes. 

By means of suitable absorptive media, we learned that tbe most 
active rays were those of the more refrangible end of the spectrum. 

Seeking an explanation of the facts thus observed, we proceeded 
in the first instance by analogy. 

We found that light had an oxidising action on many organic sub- 
stances of comparatively simple composition, and we demonstrated 
that, in the presence of free oxygen, the molecule of oxalic acid might 
be speedily and entirely resolved into water and carbonic acid by the 
action of light, more especially bj those rays to which 1 have 
already referred. 

Proceeding to more complex substances, we applied the same method 
to one of those singular bodies, the so-called soluble or indirect 
ferments. 

In less than a month the properties, and, inferentially, the sub- 
stance, of the invertive diastascr of yeast were destroyed by light. 

Once more we foond that we had to deal with an oxidation. 
Finally, our inference that the action of sunlight on the organisms of 
our cultures would likewise prove to be an oxidation was confirmed 
by direct experiments, in which the effect varied in proportion to the 
amount of free oxygen present. 

As yet no one has repeated these investigations in their entirety, 
but sufficient confirmatory evidence has accumulated to justify me, 
I think, in briefly placing the case before the Society as it now stands, 
with one or two additional observations of my own, and to afford me 
an opportunity of replying to one or two points of criticism. 

The earliest corroboration of our work came out on the reading of 
our first memoir on this subject. 

Mr. Warington bad that same evening, in a paper to the Chemical 
Society, notified, but was unable to explain, the inhibitory action of 
light on the process of nitrification. Our experiments at once sug- 
gested to Dr. Gilbert the interpretation, since confirmed by several 
observers,* that light was inimical to the nitrifying ferment. 

Gladstone and Tribe ("Journ. Chem. Soc.," August, 1883) found 
that light was detrimental to the development of fungoid growths in 
solutions of cane-sugar exposed to atmospheric air.f Tyndall re- 

• Soyka, in " Zeit. f. Biol." 1878; Schloesing and Muntz, " Joum. of Chem. 
floe." (Ahfltr.), April, 1880. 

f It ifl right to state that yan Tieghem in his inyestigations on the organisms 
appearing in olive oil (" Bull. Soc. Bot.," xxTiii, p. 186), found that Fem'ciUium 
glamcum developed in oil at the most illiuninated spots. I have not been able to 
■ee the original paper, and am therefore not acquainted with the conditions of the 
experiment, egpedallj bb regarda the nature of the illumination, and l\ie «cce«6 qI 
Ave oxjgea. 



16 Dr. A. Downes. On the [Jan. 14, 

ported to the British Association ia 1881 the results which he had 
obtained in exposing flasks of animal and vegetable infusions to the 
influence of an Alpine sun. Corresponding flasks shaded from the 
light became turbid in twenty-four hours, " while thrice this time 
left the ex^)osed ones without sensible damage to their transparency/' 
He satisfied himself tbat this was not due to differences of tempe« 
rature. The. amount of insolation was insuflicient, however, to per- 
manently sterilise the cultures after removal to a warm kitchen. 

Confirmatory evidence aIso, invested with a special value by the 
author's great experience of saprophytic life, has more recently been 
adduced by Professor E. Duclaux.* With the usual precautions he 
introduced into a flat-bottomed Pasteur flask a drop of pure culture 
of the organism to be studied, and dried it under a desiccator. After 
the desired period of exposure to the sun, the flask was charged with 
sterilised nutrient liquid, of a kind specially suitable to the developmeitt 
of the 'particular organism^ and placed at a favourable temperature in 
an incubator. Corresponding flasks were kept in the dark. 

He finds that the general rule, that the spores oF these organisms 
resist adverse influences better than their vegetative forms, holds 
good in regard to the efi*ect8 of light. This accords with our own 
observations on the insolatioA of germs in water.f M. Duclaux, how- 
ever, reserves for a future memoir his conclusions on the insolation of 
the micrococci — among which the formation of spores is not certainly 
known. 

. The very hardy spores of the Bucillus^ to which he has given the 
name of Ttjrothrix filifnrmis.X were destroyed by thirty. five days' ex- 
posure to an autumnal sun. T, genxculatus was more resistant, but 
showed signs of commencing enfeeblement. T. scaher was only 
retarded in development by insolation during the month of August, 
1884, but a further exposure to the end of September — a not very 
fine month — sterilised two flasks out of four. 

Similar spores had survived for three years in the dark. Like 
Professor Tyndall, he was satisfied that these results were not 
effects of temperature ; his insolated flasks scarcely reached any point 
higher than their fellows kept in darkness in an incubator. 

He concluded, also, from further experiments, that the injurious 
influence of light here manifested was probably an affair of oxida- 
tion. 

M. Duclaux very rightly insists on the importance of careful adap- 
tation of the nutrient liquids to the organisms operated upon, ob- 
serving that, otherwise, spores might be regarded as dead which had 
only, perhaps, been enfeebled. " C'est \k Tobjection," he continues, 

• " Ann. de Chim. et de Phys." 6e ser., t. v, Mai, 1886. 
f "Proc. Roy, 8oc./' vol. 28, pp. 203-i. 
/ "^tudeg BUT la hit," "Ann. de Vlnstit. AgronomVcvue;' \«?^-«>. 



86*] Actiofi of Sunlight on Mxcro-organismB^ ^c. 17 

[a'on pent adresser aux ezp^rienoes tres bien oonduites, da reste, 
tres int^ressantes de M. A. Dowues." (" Proc. Boj. Soc.,*' yol. 26, 
488, 1877.) 

Ab regards the earlier of our memoirs, to which M. Duclaox refers, 
Is criticism is jast. At that date knowledge of revivification of 
rms in different media was neither so generally diffused nor so 
seise as it now is. This advance we owe not least to Professor 
idanx himself. Accordingly, in our first experiments we regarded 
Q-appearance of life in our insolated tnbes of Pasteur solution, or of 
ine, as proof of destruction of the organisms which thej had ori- 
lally contained. In our second and more complete memoir, how- 
er, we reserved our opinion on this point. 

Bat it was an essential principle of the method on which we worked, 
d the key to our success, that our nutrient fluids should be su£S« 
mtly resistant to bacterial growth to hinder the development of 
ganisms, through the night, or during cloudy days, from outrunning 
e inhibitory effects of insolation. It would probably, for example, 
i often be possible to secure in England the results which Tyndall 
•tained on the Alps with apparently considerable bulks of very 
Ltrescible materials. Pasteur solution and the like are at their best 
it limited media of nutrition ;* yet under special circumstances, as, 
r example, in the demonstration of the action of diffused daylight 
ven below, it is necessary to largely increase their resistance to 
^composition. 

Moreover, the question whether the germs in our solutions were or 
3re not actually dead, does not affect the truth oE our induction. I 
nnot put this more pithily than has Professor Duolaux himself, in 
very courteous communication with which he has favoured me. 
You have clearly shown," he says, '* that an insolated germ is a sick, 
metimcs very sick, germ ; death is but a step further."t 
It was an d pvtori probability that micro-organisms should vary 
rnsiderably in their powers of resistance to the oxidising influences 
light. In our previous papers, indeed, we gave examples of this 
the frequent survival over Bacteria of some less sensitive form of 
jccharomyces or Mucedo, 

I have lately met with an instance which may be worth recording, 
, it enabled me to isolate a Bacterium of which I can find no previous 
ascription. In each of a number of thickish glass tubes I had sealed 
) 3 c.c. of distilled water, together with a small bulb containing an 

* For prolonged insolation I have for another reason quite abandoned their use. 

lej are liable to take on a brown coloration in sunshine, and I hare had, in con- 

quence, to abandon a laborious series of experiments. 

t M. Duclaux teUa me that he has also confirmed our obfteTvatVoxi V\a\i \\v^ 

wfsM aiv deatrojred br Bunnght. He operated on the dia«ta«e pr^re^ \}tt» 

^ulaiing principle of rennet, 

OL. XL. 



18 Dr. A. Downes. On the [Jan. 14, 

eqnal qnantity of carefally sterilised peptone solntion (doable 
strength). Some of these tabes were insolated on an outside shelf 
facing soatb ; others were incased in laminated lead alongside. 

After the desired period of insolation, the balbs were broken by a 
jerk, and the tabes, now containing 6 c.c. of peptone solution of ordi- 
nary strength (2 per cent.), were removed to a warm capboard kept 
at about 20° C. By a week's exposare, May 29 — Jane 5, bacterial 
development was already retarded (sixty hoars as compared with 
twenty-foar). After insolation for nearly foar weeks, May 29 — 
Jane 24, ordioary bacterial development appeared in two incased 
tabes in thirty-six hoars. In two insolated tabes, at the same date, 
nothing was seen till the foarth day, when small flakes began to form, 
and by Aagast 3 had settled into a dirty-white collection, leaving 
the sapematant liqaid clear, presenting a notable contrast to the 
aniform tarbidity of the incased. 

These flakes were foand to consist of compact spherical or cylin- 
drical nodalated masses of zoogloea. They closely resembled in 
general appearance the Ascococcua BiUrothii or Ascohacteria of 
V. Tieghem, bat I was atterly anable to demonstrate the gelatinons 
envelopment from which those organisms take their name. 

On teasing oat a portion the colony was foand to consist of closely 
felted small rods, motile when freed from the mass, aboat 0*6^ dia- 
meter, and 2*0 — 3'0;4 long. 

On September 28, after foar months' exposare, the remaining tabes, 
three insolated and one incased, were taken in. Nine days elapsed 
before the latter became hazy with Bacteria. In eleven days one of 
the insolated contained flakes, sach as I have above described. In a 
day or two later similar flakes formed in another of these tabes. The 
third insolated tube subseqaently broke down with a scanty develop- 
ment of Bacteria^ not distingaishable from the kinds foand in the 
incased.* 

It is evident that the zooglo8a-lamp-forming Bacteriam was espe* 
dally resistant to sanlight, and so became isolated in almost pare 
caltares in foar-flf ths of the tabes insolated for a month and apwards. 

I wish now to direct attention to the fact that the tabes of the 
experiment which I have jast described, were exposed repeatedly to 
considerable elevations of temperatare. The meteorology of Green- 
wich may be taken as safficiently identical with that of Chelmsford, 

• This experiment — an insolation of germs in water only — ^might be regarded, and 
poesiblj rightly so, as confirmatory of what we have preyiously written on the 
resistance of germinal matter in a fluid devoid of nutrient material. But it should 
be remembered that the supply of free oxygen was necessarily limited in these 
sealed tubes, being rather less than 5 c.c. in each, and I am unable at present to tay 
whether this amount wouid be sufficient to oxidiae the g^Tm& oTdxottniL'^ "^t^msoXiV^ 
3 CO, of distilled water. 



1886.] Action of Sunlight on Micro-organisms^ ^c. 19 

where the inyestigaidon was made.* At the Royal Observatory the 
means of the maxima in the snn's rays were : — 

June 126r F. (523'* C). 

July 143-0 F. (61-6 C). 

August 129-2 F. (54-0 C). 

It cannot be doubted that these tubes were often exposed to a tem- 
perature of 140° F. (60"" C), and on at least one occasion (July 27) to 

160*F. (7r C). 

The incased tubes had for radianfc heat a somewhat greater 
absorptive power than the bare glass of the insolated. For tempera- 
tures below 100* F. (38® C.) this difference was comparatively slight ; 
at 100** F. it was 4-5° F. (2-5" C). 

It is certain, therefore, that any deleterious influence of heat should^ 
tell more on the incased than on the insolated. Yet at the end of 
four months Bacteria appeared, retarded in development, it is true, 
but still morphologically identical with the forms originally found in 
similar solutions. 

I lay stress on these facts, because an Australian observer has 
declaredf that we, and Professor Tyndall with us, have mistaken 
effects of heat for supposed effects of actinism.^ 

But Dr. Jamieson*s paper in abstract has gone the usual round of 
German year-books and periscopic notes of English journals, until ait 
impression has arisen that there is no satisfactory evidence of inju- 
rious influence of light on micro-organisms. I trust, therefore, to be 
permitted a few words in reply. 

Dr. Jamieson insolated Cohn*s solution in phials, and found that in 
a short space of time bacterial development might thereby be entirely 
prevented. But in some of his experiments he thought that he suc- 
ceeded better in hot weather than in cool, and he failed to produce 
any effect in diffused light. He asked himself, therefore, whether the 
results he had noted might not have been, after all, due to heat. 

This was a very legitimate question, but, instead of solving it by 
direct observation, he unfortunately recalled to mind experiments§ in 
which B. termo had apparently been killed by seven days' exposure to 
45° C. (113** F.), by fourteen hours at 47^ C. (116-6** F.), by three or 

• Greenwich Lat, 61*28 N. Long, 0*00. 

Chclmafoid „ 51*44 N. „ 0*28 E. 

t Boyal Society of Victoria. June, 1882. 

X We cannot dispense with some word such as this to connote energy not neces- 
sarily coincident with effects either of solar heat or luminosity. In using it above, 
I go a Utile further than Professor l^adall, who has not, I beliere, yet given any 
opinion as to the form of radiant energy, except that it is not heat^ which he found 
/o hinder bacteriBl development. 
§ "Eidam. Beit zur Biol, der PA/' Heft iii, p. 208. 



20 Dr. A. Downes. On the [Jan. 14, 

fonr hours at 60—52° C. (122— 125-6° F.), and by one hoar at 60* C. 
(140*^ F.). He argned that some of these temperatures were com- 
monlj attained in the sun's rays in Australia, and even in England ; 
he thought that 125* F. (51*6° C.) would occasionally be experienced 
for a few hours, and he concluded that his; our own, and Tyndall's 
results were all effects of temperature. 

The argument is fallacious. It is true that some organisms in 
certain stages of their development may be destroyed by lower degrees 
of heat than is commonly supposed. Duclaux has given an instance 
in which forfcy-eight hours at 38° C. (100*4° F.) was fatal to some very 
old yeast globules. 

But even of these it is true only in their vegetative forms ; theii* 
spores (and the spore-form is doubtless that in which the micro- 
organisms originally existed in our nutrient liquids) resist elevations 
of heat far surpassing anything noted above. Were it otherwise 
bacterial life would probably soon cease to be. It is obviously incor- 
rect to argue that, because some organisms in some phase of their 
existence are destroyed by moderate heafc, all organisms, in all phases 
and under all conditions, are so too, and any inference drawn from 
such reasoning must be rejected. 

Moreover, 1 have already shown that the laminated lead used in our 
experiments absorbed radiant heat in greater degree than the bare 
glass, and consequently that our incased tubes would be more affected 
by solar heat than our insolated. And I need only refer to our 
previous demonstration, that the greatest effect on micro-organisms 
is produced by those rays which occupy the cooler portion of the 
spectrum. 

Dr. Jamieson failed with diffused light. His failure was due to his 
method of experimenting.* 

I have already said that an essential element of success is to appor- 
tion the natural i^esistance of the cultivation liquids to the amount of 
light available. Bacterial development once started usually outruns 
even direct sunlight, both by increasing the opacity of the fluid, and 
by quickly reducing the amount of oxygen. Naturally diffused light 
would be far slower in action than the direct solar ray, and we must 
select either very cool weather for the experiment, or must choose 
solutions of considerable resistance. 

Keeping this principle in view, I have found, it eai^ to show that 
diffused light possesses properties differing only in degree from those 
which wo have demonstrated in regard to direct sunlight. I have 
made a number of experiments in which ordinary thin test-tubes 
plugged with cotton-wool were placed in a box (20*5 cm. cube) lined 

* Moreover, he Becms to have placed his bottles inside a window. The absorp- 

ii're power of glass has always prevented me from tuccoedxii^ Vo. %vLct\i cAxcxmsL* 
stances. 



1886.] Action of Sunlight on Microorganisms^ ^c. 21 

wiih white paper, having one side open, and tilted at snch an angle as 
to receive diffused light straight from the white clouds of the northern 
sky. By no possibility coald direct sunlight find an entrance. In 
the box were placed maximum and minimum thermometers, each 
pair with bulbs respectively incased or left bare. 

In September, 1883, using Cohn's solution five times the ordinaiy 
strengrthi in five days, four out of six incased tubes were noted as 
" turbid," and the other two as '* hazy," with bacteria. The exposed 
tubes were recorded " beautifully clear." At the end of two days 
more the latter were still clear, but in each were specks of mycelium. 
The survival of mycelial growth over bacterial has already been 
alluded to in the present paper, and is seen in Dr. Jamieson's own 
experiments^ 

But mycelial growth itself may be hindered by diffused light. 

In March, 1884, a slightly acid Cohn*s solution, two and a half times 
ordinary strength, being specially selected, I found that at the end of 
ten days -f of the incased tubes contained mycelial specks, the six 
exposed tubes being perfectly free. At the end of fifteen days my 
notes were : — '* Disks of mycelium plug |- of incased, \ of exposed ; 
small tufts of mycelium in the remaining incased tube, and in one of 
the exposed, three remaining exposed quite clear j The difierence in 
appearance of the two sets is remarkable." 

The means of the thermometrical readings during two periods 
were : — 

Encased. Exposed. 

On * ^9lM /^»^- ^^'^^ ^- (^''•S' C) ^^'^' ^- (17'8*C.). 

^ /Max. 560 F. (13-3 C.) 578 F. (14'3 C). 

uct. „ .. <^^^^ ^^.g J, ^ 2-0 c.) 36-8 F. ( 2-6 C). 

As the incased tubes were the better absorbers, so are they now seen 
to be the better radiators, and conditions of temperature were accord- 
ingly slightly more adverse to development of organisms in them as 
compared with the exposed. 

I now conclude this paper with a reference to the researches of 
Herr Pringsheim on chlorophyll.* I refer to them with especial 
gratification, as evidence of the truth of a generalisation which I had 
ventured to draw from our experiments. 

The micro-organisms of our solutions may be regarded as examples 
of protoplasm in its simplest forms, but there are no grounds for sup- 
posing that this " life-stuff " should be subject to hyperoxidation by 
light only when it exists in a Bacterium, or a mycelial thread. On the 
contrary we have probably to deal with a general law, and) without 
protective developments of cell wall, or of colouring ma^itet 's^\iisJDL 

* "M. B, Akad, Wis8.;' Berlin^ ISYO. 



22 Prof. F. Elgar. Ontlie [Jan. 14, 

sboold filter out injurious rays, Ac., living organisms oould hardly 
endure the solar light. 

Pringsheim operated on chlorophyll tissues. By means of a lens 
and a heliostat he concentrated upon them sunlight, from which hy 
suitahle media he had sifted out the heat rays. In a few minutes the 
green colouring matter was destroyed, the protoplasmic circulation 
arrested, the protoplasm disorganised, and the cell flaccid and inert. 
He found, as we had found, that the more refrangihle rays were the 
most powerful, and he, too, concluded that he was dealing with an 
oxidation, for in an atmosphere of hydrogen or of carbonic acid these 
destructiye results no longer ensued. 

The experiments of Siemens* and D^h^rainf also demonstrate both 
the destructive influence of the electric light on vegetation and the 
protective efEect of a glass screen. 

[Note. — According to an abstract in " Journal of Science," 8rd 
ser., vol. vii, p. 594, M. Duclaux has since published the results of his 
observations on six species of micrococci, apparently of pathogenic 
kind.{ 

Forty days of insolation (May 4 — June 13) proved sufficient to kill 
and less to attenuate these germs in the moist state. In a desiccated 
condition eight days (May 26 — June 3) proved fatal ; in July none 
resisted three days' exposure at a south window which received the 
sun only from nine to one o'clock each day, and where the tempera- 
ture did not exceed 102** F. (39** C). Fifteen days of July sun 
destroyed the micrococci in the moist state. He had not in these ex- 
periments eliminat'Cd any partial influence of temperature. January 
4, 1886.— A. H. D.] 

XL " Notes upon the Straining of Ships caused by Rolling." By 
Francis Elgar, LL.D., F.R.S.E., Professor of Naval Archi- 
tecture and Marine Engineering in the University of 
Glasgow. Commmijcated by Sir E. J. Reed, F.R.S. 
Received December 28, 1885. 

(Abstract.) 

It does not appear that any serious attempt has yet been made to 
investigate the amounts, or even the nature, of the principal straining 

• " Eep. Brit. Assoc," 1881. 

t ** Joum. Ohem. Soc.'* (Abst.), Jan., 1888. Considerations of time and space 

preyent me from noticing many other observations of interest in connexion with this 

subject; e.ff., of Engelmann on Pelomyxa (*'Arch. f. Phys.," xix, 1879) and on 

Jf. jfJko^omeiricttm ("J. Boy. Micr. Soc^* Abst., 1882-2), or of Stahl, "On the 

Amngement of Cbloropbyll Bodies in Plant-Cells" ("Bot. Zevt.^' \i^. 

/ "Comptes renduB," 1885. 



1886.] Straining of Sliips caused by Rolling. 28 

actions which the rolling of a ship brings into play, or of the efFect 
of those straining actions npon the material of which the hull is com- 
posed. Various writers, from Bongner in 1746, down to Professor 
Maoquome Rankine in 1866, and Sir E. J. Reed in 1871, have dis- 
enssed the straining actions that are caused by longitudinal racking 
and bending when a vessel is floating in statical equilibrium. Sir 
£. J. Beed elaborately investigated the subject in a paper contained 
in the *' Philosophical Transactions of the Royal Society" for 1871, 
and gave examples of the amounts and distribution of the stresses 
caused by such straining actions in several typical ships of Her 
Majesty's Navy. Mr. W. John supplemented this by a paper on the 
strength of iron ships, read before the Institution of Naval Architects 
in 1874, in which similar results were given for various classes of 
vessels in the mercantile marine. 

The later investigations of these longitudinal straining actions 
apply not only to the case of a ship floating in equilibrium in still 
water, but also to cases in which she is (1) in instantaneous statical 
equilibrium across the crest of a wave; and (2) in instantaneous 
statical equilibrium across the hollow of a wave — the wave-length 
being equal to the length of the ship. 

Cases frequently occur which show that the maximum stresses of 
the material of a ship's hull are not in proportion to the results 
obtained by the ordinary calculations; and that certain deductions 
that have been drawn from those results are by no means sound. 
For instance, it is said to follow from the analogy between the longi- 
tudinal bending action upon a ship afloat and that upon a loaded 
girder, that there is little or no stress exerted upon that portion of a 
ship's plating which is in the vicinity of the neutral axis for the 
upright position ; and the inference has been drawn that, subject to 
the consideration of the sides being occasionally bi*ought, in some 
degree, into the positions of flanges of a girder by large inclinations, 
the thickness of the material may be decreased with advantage near 
the neutral axis. Now it cannot be shown that the plating which 
is in the vicinity of the neutral axis when the ship is upright, is ever 
brought into such a position by the rolling of • vessel as to be much 
affected by mere longitudinal benduig. 

The reason commonly given for not decreasing considerably the 
thickness of side plating in the vicinity of the upright neutral axis, 
viz., that when a ship is in an inclined position, this plating may be 
so placed as to ofEer the greatest resistance to longitudinal bending 
is seen, if the matter be properly considered, to be obviously unsatis- 
factory. 

Other propositions respecting the relative distribution of stress 
in varioaa parts of the structure have been deduced iTom. «ya&\- 
derations and assumptions npon which the ordinary ca\cT3A2b\»\OTX& oil 



Prof. F. Elgar. On the 



[Jan. 14, 



24 

longitudinal stmngtb are based ; and mles have, in consequence, been 
proposed for re^nlating the etrength of the principal component parta 
of ships' halls. It IB only necessary here to say, that muiy of these 
deductions, like the one already noticed, are ansonnd, and are aoi 
oonaistent with the effects that may be observed of straining action 

A considerable experience at sea, where the writer has closely 
observed the effects of straining action oaased by twisting moments, 
and a farther experience in investigating the stroBses to which the 
varions portions of ships' hnlls are subjected according to the theories 
referred to, and in comparing the results so obtained with the visible 
evidences of straining action, hare convinced him that the stresses 
caused by twisting momenta are much greater than is genemlly sap- 
posed, and that no rules for regnlating the strength of ships can be 
.satisfactory if based npon hypotheses that exclude all practical con- 
sideration of twisting moments. 

The straining action which will be considered in this paper is that 
caused by the twisting moments which operate when a ship rolls 
from side to side; and which are cansed by differences in the longi- 
tudinal distribution of the momenta of the forces that cause rotation, 
and those which resist rotation. 




Let a unit of length included between two transverse vertical 
sections be taken at any point in a ship's length, and let 6g. 1 be the 
Bection of the ship at that point. The section may be taken as 
uniform over this short length. The energy of rotation of this unit 
of length will be ^tcl? ; where w is the angular velocity in the upright 



1886*] Straining of Ships caused hy Rolling* 25 

pofiitioxi, w is ihe weight of the unit of length and its contents, and 
^~Jfi 18 the moment of inertia of the nnit of length about the axis of 

ititatioii. 

In order to form an equation of energy and work, we require to 
assume an axis of rotation for the ship; and the assumption hero 
made is, that the axis of rotation is a principal longitudinal axis 
through the centre of gpravity G- of the whole ship and her contents. 
A ship's axis of rotation is not, in reality, fixed ; but that may for 
the present be disregarded. The important point in connexion with 
it is that, whatever position the instantaneous axis may occupy at 
any g^yen moment, it is the axis about which each unit of length of 
the ship is then rotating, with the same angular Telocity. This con- 
dition follows from the rigidity of the ship, or rather from the 
structure being so nearly rig^d that any motion of one part relatively 
to another, about the axis of rotation, is so small that it may be 
neglected. 

When the unit of length shown in section in fig. 1 is inclined to an 
angle from the upright, the principal forces which act upon it are — 
first, the weight w of every part of the ship and her contents that is 
contained in this length, acting vertically downwards through its 
centre of gravity g ; and, secondly, the weight of the volume of dis- 
placement d for the unit of length under consideration, acting ver- 
tically upwards in a line, dm, through its centre. These forces are 
equivalent to the couple dxgz, and a vertical force at g equal to 
ic — d. 

Let G be the point in which the axis of rotation through the 
centre of gravity of the ship intersects the section in fig. 1. Then 
the moment which resists the inclination of the section at any angle & 
will be the resultant of the two couples dxgs and —(w-'d)Ga, Let 
ir— cf =r. The work done in inclining the unit of length in fig. 1 to 

the angle of inclination 9 will be d\ gzd0—c\ GadO. If a curve be 

Jo Jo 

constructed with the length of the ship for an abscissa line, and the 

values of dl gzdO—Bi GadO for ordinafces — these values being set off 

Jo Jo 

at points in the length to which the sections for which they are cal- 
culated correspond — it will repi-esent the longitudinal distribution of 
the work done in opposition to the action of the righting moments. 
The base line in fig. 2 represents the length of the ship. Suppose 
the first ordinate to be at the plane of division for which the section 

of the ship is as shown at fig. 1, we then require to determine the 

Jo To 

gzdO—ci GaMf at this section, which may be readily 
Jo 

done. 



Prof. F. Elgar. On the 



[ Jao. 14, 



XM in Gg. 2 represents ^2 flasdfl— al Giu^, or the energy expended 
in taolming an onit of length at X against the resistance of the righting 
moment to the angle 6. If similar values be determined for onita of 
length at each of the other ordinates, and a cnrre MMM be drawn 
throngh the points so obtained, KMM will give the longitudinal dis- 
tribution of the work done against the resistance of the righting 
moments, or of what was called by Canon Moselef the dynamical 
stability. 

Let E£K in fig. 2 be a carve which shows in a similar manner the 
longitudinal dietribntton of the energy of rotation. XE will be the 

value of ^wJ^ for the unit of length at that ordinate ; and the other 

ordinates of the curve will be the values of — vsJfi at the oorrespond- 

ing pointx in the ship's length. 

The difference between the enei^y of rotation of any portion of the 
vessel's length AX and the work expended in inclining that portion, 
in opposition to the moments of the forces exerted by its weight and 
the fluid pressures upon it, is equal to the area M£A in fig. 2. This 
area measures the excess of energy of rotation in the volume between 
A and X, which is communicated throngh the hull of the ship to some 
other part of her length at which Uie energy of rotation per unit of 
length is less than the work required per unit of length to incline it to 
the angle 6. This excess of energy is transmitted, by means of a 
twisting moment npon the Hnll, to the part of the ship's length where 
it is ntilised in overcoming resistance. 

A graphical representation of the longitudinal distribation of the 
mean twisting moments which act npon the hull when the vessel is 
rolling to an angle 8 on each side of the upright position, may bo 
made by means of a curve bo that any ordinate of the curve will give 
the mean value of the twisting moment npon a section at the point for 
which the ordinate is drawn. 

The values thus obtained for the twisting moments will be mean 
ralaea oaly. The v&riatioa of twisting moment s.t in^ aacVian o^ Wn* 
oa// during a roU, and conaequently tie in8>xxmam tvn^ti^ mjumsnA., 




1886.] Straining of Shij^s caused hy Rolllnn. 27 

may be readilj determined ; and a method of doing this is described at 
kngth in ihe paper. 

I ^BWh vemlts given by the inyestigations described apply only to 
Ml^VoIIixig from side to side in still water, assuming that the water 
ililiii'iia TCsistanoe to rolling motion. It is obvions, however, that 
llillMNriiluig moments thus obtained must often be greatly exceeded 
• vOBol is rolling and pitching while lying or moving aoross a 
of long ocean waves. In these circamstances the bow or stem 
frequently has so little immersion that the righting moment acting 
upon a portion of one end is momentarily very small, and almost the 
whole of the energy of rotation is applied to the production of twisting 
moments. The resistance of the water wonld also often increase the 
twisting moments. 

It now remains to be seen what can be done in the way of deter- 
mining the stresses upon the hull which are caused by the twisting 
moments. We can learn something of the nature and distribution of 
those stresses; but, at present, their amounts cannot be calculated 
with any reliable approach to accuracy. Experiments are required 
upon the torsion of thin shells of various prismatic forms in order to 
furnish the requisite data for dealing with so complicated a case as 
that of a ship's hull. The difficulty of obtaining such data is very 
great ; but pending the time when it is to be hoped this want will be 
supplied, it may be useful to draw attention to some of the general 
considerations which affect the twisting moments and the distribution 
of the twisting strains and stresses over a ship's hull; and to the 
bearing which these have upon the important practical problems that 
relate to the structural strength of ships. 

The best data available for guidance in judging of the distribution 
of strain and stress due to twisting over the structure of a ship are 
to be found in M. de St. Yenant's investigations of the torsion of 
prisms.* These investigations assist us to form a general idea of the 
manner in which a ship's structure may be strained by twisting ; and 
they also indicate the nature of the experiments that are necessary to 
furnish data for more exact investigations. The mean amount of the 
twisting moment upon a ship's hull at any transverse plane of division, 
and also the maximum twisting moment, may be obtained by the 
method described in the present paper. The torsional strength of the 
hull at that section will depend (1) upon the thin iron or steel shell 
of which the structure consists, being stiffened internally so as to 
effectually resist change of form ; and (2) upon the ratio which the 
strength of a section of such form, when so stiffened, bears to that of a 

* "M^moires pr^sentds par diyen Sayants k TAcad^mio des Sciences de 
VJiuthut JmpSiial de France, " tome guatorzidme, 1856. ** M^moVre a\ic \&TQimow 



de PrismeB, Ac." Par M. de Saint-Venant," pp. 233-560. AAao T\iOix«oii vosS^ 
TMit's - Natural PbUosophy/* vol i. Part U, «ec8. 61 



28 ilr. J. R. Green. [Jan. 14, 

hollow circular cylinder of the same thickness and the same sectional 
area. Experiments npon the torsional strength of hollow prisms of 
various forms, having the same sectional area and thickness of shell, 
can alone determine the latter point; while, at the same time, sucli 
experiments would serve the further purpose of showing how the 
condition ahove referred to — that the shell shall be stiffened intemallj 
so as to effectually resist change of form — can best be complied 
with. 

The distribution of the torsional stresses over the transverse section 
of a ship's hull is obviously different from the distribution of the 
stresses due to longitudinal bending. The parts subjected to greatest 
stress by twisting are those which are near to the centre of gravity of 
the transverse section ; and they are the side plating near the neutral 
axis of longitudinal bending in the upright position and the middle 
portions of the plating of the decks. Those parts of the hull which 
are usually made the strongest, viz., the strakes of side and bottom 
plating that are farthest from the neutral axis, and the upper deck 
stringer plate, are those which are least affected by twisting. It in 
probably owing, in great measure, to the straining action caused by 
twisting, that experience has proved it to be necessary to make the out- 
side plating of a ship of nearly uniform thickness over the whole section ; 
and it cannot be because of the reason sometimes given, that the 
plating in the vicinity of the neutral axis when a ship is upright ia 
often brought by rolling into positions in which it is greatly strained 
by longitudinal bending. 

The importance of many of the structural arrangements of ships 
that are described in the present paper, which practical experience 
has shown to be necessary, may be understood from these considera- 
tions ; and it will also be seen that no rules for regulating the strength 
of ships are likely to be satisfactory if based, as is often done, upon 
the hypothesis that the straining actions caused by longitudinal 
bending are so much more important than all others that it is suffi- 
cient to regard them alone. 



III. " Proteid Substances in Latex." By J. R. Green, B.Sc^ 
B.A., Demonstrator of Physiology in the University of 
Cambridge. Communicated by W. T. Thiselton Dyer,. 
C.M.G., F.R.S., Director of Royal Gardens, Kew. Received 
January 4, 1886. 

In the study of the metabolism of plants, the natare of the pvow 
ducts resulting therefrom, and the different forms assumed by these 
bodies during the changes involved, attention has been chiefly 



1886.] Proteid Substances in Latex. 29 

directed to the seed. No doubt special facilities for investigation are 
afforded thereby, for the different bodies can be detected there by the 
aid of the microscope, and their behaviour under the action of 
different reagents watched. Hence valuable results have been 
arrived at, and our knowledge of vegetable metabolism has made 
oonsiderable advance. By the investigations of Hoppe-Seyler,* Wejl,t 
and Zoller,^ the similarity of vegetable proteids to those occurring in 
animals was pointed out, members of the globulin family at least 
being shown to e^ist. Later Vines, by an exhaustive examination, 
both macroscopic and microscopic, of a very large number of seeds, 
has added greatly to our knowledge of these bodies, proving that 
besideB globulins, a form of albumose, albuminates, and coagulated 
proteids are to be isolated, and showing the actual conditions and 
proportions in which these are present in the seeds. § 

It is evident, however, that our knowledge of the seed, even if made 
cxmiplete, will not give ns all the information we require concerning 
the nitrogenous metabolism of the plant. The condition of the 
proteid matter at a time antecedent to its appearance as reserve 
material must be considered as equal in importance and in interest. 
The round of changes g^ing on normally in the leaves and the soft 
tissues of the stem has hitherto remained unknown, nor had we any 
knowledge of the condition and characters of the proteid bodies circu- 
lating in the plant, and met with in the latex and in the soft green 
parts until recently, when Martin || published an account of his in- 
vestigations into the nature and action of the ferment present in the 
Papaw plant (Carica papaya) and has therein described certain pro- 
teids which he has found to be present in the dried milk of the fruit 
of the plant. These he says are four in number, two belonging to the 
group of the albumoses, a globulin and an albumin. To the albumoses, 
which are the most plentiful in amount, he gives the names of 
• and fi phytalbamose. 

During the summer of 1884 I was enabled, through the kindness of 
Mr. Thiselton Dyer, Assistant Director of the Royal Gardens, Kew, 
to make some investigations into the composition of the latex of 
several caoutchouc-yielding plants belonging to the nataral orders 
ApocijnecB and Sapotacece.% In most cases the latex was a very com- 
plex fluid, containiDg, besides proteids and carbohydrates, considerable 

• "Med.-Chem. Unt^rs./* 1807. 

t •* Zeitschr. f. Physiol. -Cliem.," i, 1877 j " Ber. d. deut. Chora. Oos.," xiii, 4, 1830. 

I *• Ber. d. dent. Chom. Ges./' xiii, 10, 1880. 

§ "Journal of Physiology," vol. iii, No. 2. 

I! Ibid., Tol. V, No. 4, and toI. vi, No. 6, p. 336. 

^ [These samples, thirty-four in number, were collected for Dr. Vines with very 
|rieat pains and trouble by Mr. D. F. A. Hervey, Besident Councillor, Malacca. — 
W. T. T. D.] 



30 Mr. J. R. Green. [Jan. 14, 

quantities of caontchonc, resinons matters, &c.y tlie latter being very 
variable in amount, and absent from some samples. The material was 
collected in the Malaj Peninsula from the plants, and a little alcohol 
having been added as a preservative, was sent to England in sealed 
bottles. On its arrival at the laboratory, some of the bottles had 
their contents hardly at all changed except that the large amount of 
caoutchouc contained in the fluid had undergone the process techni- 
cally known as coagulation, and was floating in a milky liquid. 
Others had become quite spoiled in transit, the latex having deposited 
a quantity of amorphous matter, which gave a xanthoproteic reac- 
tion, and seemed to be coagulated proteid. In the debris besides 
this, there appeared under the microscope, a number of small droplets 
of caoutchouc, a few sphsero-crystals, some spicular crystals, and some 
flat plates of rhomboidal form. 

Examination of these last as to proteids not being practicable, 
attention was given to the uninjured samples, which differed in no 
way from each other. The particular experiments, whose results are 
detailed below, were made upon the latex of a plant, the Malay name 
of which was given as " Gegrip puteh.*'* 

The mass of caoutchouc floating in the fluid was allowed to drain* 
dry, and was then with difiBculty cut up into small pieces and mace- 
rated some in water and some in salt solutions. Soaking for several 
days failed to extract anything of a proteid nature from it. Atten- 
tion, therefore, was directed to the liquid remaining after its separa- 
tion. This, as said above, was milky in appearance, of a faintly 
yellow colour, aromatic smell,[and neutral reaction. Under the micro- 
scope it was at once apparent that the milky appearance was due to 
minute droplets of caoutchouc which had not separated out with the 
bulk. There was nothing granular or amorphous visible, showing 
that the proteids had not been precipitated by the alcohol used. To 
free the latex from the caoutchouc, filtration under vacuum pressure 
through a porous pot was necessary, when the droplets formed a film 
round the earthenware, and as the liquid was gradually removed they 
fused together, giving rise to a thin sheet of india-rubber. The fluid 
passed through the pot clear and in a condition fit for examination. 

In this liquid so prepared a very curious proteid body was found 
to exist, diflering in important particulars from any hitherto described 
as occurring in plants.f Its presence was readily shown by the 

* [Yielded by an Apocynaoeoiu plant, Parameria glandvlifera. The selection of 
tliis particular sample, which happened to stand first in a series of thirtj-foor, was a 
little unfortunate, as it is not a very characteristic caoutchouc-yielding species. — 
W. T. T. D.] 

f In a communication made to the Cambridge Pliilosophical Society I have 
Bireadjr given a brief account of its properties and TeaetioiA (,*^ ^Syoc^. CvmiV&lAl, 
Sdc,, " vol r. Fart III, p. 183, October term, 1884). 



1886.] Proteid Substances in Latex. 31 

xaathoproteio reaction, the orange colour on the addition of the 
ammonia being very marked. On warming the liquid gradually to 
boiling point there was no coagulation or opalescence, and on adding 
nitric add there was no precipitate. Hence the body does not belong 
to the gpronps of albumins or globulins. On dropping the boiled 
liquid into large excess of alcohol, a precipitate was slowly formed, 
which after standing some hours settled to the bottom of the vesseL 
Theee reactions suggested a member of the class of peptones, and as 
these proteids, though thrown down from their watery solutions by 
alcohol, are not changed by contact with the spirit, the precipitate 
was allowed to remain as it settled for about three weeks. At the 
expiration of that time the alcohol was decanted off, and the precipi- 
tate dried. It was then found to be freely soluble in distilled water, 
and to give, as the original latex did, a well-marked xanthoproteic 
reaction. 

A further resemblance between this body and the group of peptones 
was revealed by its behaviour when submitted to dialysis. A quantity- 
of the solution of the precipitate that had been standing under alcohol 
was put into a dialyser and suspended in twice its volume of distilled 
water. After two days the fluid outside the dialyser was examined. 
It gave readily the xanthoproteic reaction, and on addition of a large 
volume of alcohol a marked opalescence appeared, which on standing 
became a precipitate. Hence this proteid body appeared to have 
considerable resemblance to the group of peptones, if not to be a 
member of it. 

Further examination, however, brought to light some points that 
indicated a relation to the albumoses also. Saturation of the solution 
of the alcohol precipitate by solid MgS04 gave a copious precipitate, 
which was redissolved on adding water. The liquid outside the 
dialyser in the last expei'iment behaved similarly. The precipitation 
took place with equal readiness whether the reaction of the solution 
were neutral or slightly either alkaline or acid. Till recently the 
precipitation of a proteid by saturation of its solution with a neutral 
salt was held to be a mark of a globulin, but this reaction cannot now 
be held to be sufficient of itself to prove this. Halliburton has shown* 
that it is possible to precipitate serum albumin by such a process, the 
salt necessary being the double sulphate of magnesium and sodium. 
Heynsius has statedf that peptone itself may be thrown down from 
its solution by anmionium sulphate in similar quantity ; a statement 
that is endorsed by Martin.^ Pollitzer§ denies this, as far as true 

• " Journal of Physiology," vol. r. No. 3, p. 182. 
t " Pflflger'a Archiv," Bd. 34, 8. 330. 
X Loc, eit., p. 848. 

§ "Ueberden NabrweHb einiger VeidftnuDgBproducte deB l^^e\BAe%r ^^"5^^^% 
Archiv/' Bd. xxxrii, H, 6 & 6, 1886, 



32 Mr. J. B. Gi\ en. [Jan. 14, 

peptone is concerned, and shows that by the process peptones and 
albnmoses may be separated. A recent paper by Kiihne* also dis- 
CQSses this question, and shows that true peptone remains in solation 
while the ammoninm sulphate throws down all the albnmoses. He 
further explains the results that Heynsius arrived at, by showing 
that the commercial specimens of peptones that the latter used and 
thought to be pure were largely mixed with albnmoses. Though 
peptone has not yet been precipitated by satmation of its solution 
with neutral salts, it seems to be almost the only form of proteid that 
has refused to behave so, and it seems to be rather a question of what 
salt vrill throw down a particular proteid, than that such precipitation 
is a mark of any particular group. 

The solution of the alcohol precipitate differed also from that of an 
animal peptone, in not giviog a pink colour on the addition of sodic 
hydrate and a drop of cupric sulphate (biuret reaction). It agreed 
with it, however, in not giving a precipitate with potassic ferro- 
cyanide and acetic acid. 

Careful investigation of this body disproved the idea that it might 
really consist of a mixture of an albumose and a peptone for the 
solution of the precipitate, whether prepared by saturation with 
neutral salt, or by treatment with excess of alcohol, uniformly 
answered all the tests applied as described above. The dialysate also 
behaved on all these points just as the solution before dialysis. 
There is no doubt, therefore, that the body was a single one and not a 
mixture. 

In examining the proteids found in other plants this body was again 
met with, and its reactions investigated at some length. It will be 
convenient therefore to postpone summarising them until later. 

A little later in the year Mr. Dyer kindly sent me a bottle of the 
latex of Mimusops glohosa^ Gssrtu (^Swpotacem),^ This differed very 
much from that of the East Indian latex-yielding trees, being a thick, 
almost pasty, liquid of white appearance and sour smell. It would 
not filter clear through paper and was therefore submitted to the 
action of the filter-pump used before. The diluted filtrate, and a 
watery extract of the dried residue, were taken for examination. 

The solution thus obtained proved on investigation to contain two 
proteid bodies, which could be separated from each other with 
tolerable ease. On heating the solution gradually, having first 
neutralised, a little opalescence appeared, but it did not become par- 
ticulate even at the boiling point. When the liquid was made either 

• "Albumen und Peptone," ** Verhand. d. Naturhist-Med. Ver.,*' Heidelberg, 
N. F., Bd. iu, n. 4, 1885, s. 286. 

t [The well-known source of the Gum Balata of British Guiima, from which the 
specimen waa obtained, TLe specimens were kindly pToouxed \>y 'Ux . Qc . ^ . ^ ctkeeas^^ 
Superintendent of the Botanic Gaiden, British QuVana.—\r.1.T.T>:\ 



1886.} Proteid^'^bstanees in Latex. 33 

acid or alkaline, however, it behaved differently. In a nitric acid 
solution an opalescence was noticeable when the temperature had 
Tiaen to 85 — ^90° C. This was not removed by the addition of more 
nitric acid. On keeping the vessel for some time at this temperature, 
the opalescence became a precipitate, which was soluble at ordinary 
temperatures in alkalis, slightly so in water, but not in nitric acid. 
The solutions gave the xanthoproteic reaction. A curious point about 
this body was the slowness with which the precipitate formed, it 
appearing not at all like the usual conversion into coagulated proteid 
on a rise of temperature, but more like a slow precipitation by the 
reagent at that particular point. This was confirmed by several ex- 
periments, one of which, often repeated, was the following. A 
quantity of the extract was made acid with nitric acid and warmed 
• to 76° C, a point considerably below that at which the precipitate was 
first observed to form. It was then allowed to cool, and as the tem- 
perature was gradually falling, the precipitate slowly separated out. 
The body seemed then to be' slowly precipitated by nitric acid, but 
not at the ordinary temperature. 

In an alkaline solution its behaviour was somewhat different. The 
opalescence set in at 79^ C, and a bulky precipitate settled out slowly 
at 85*" C. This was soluble to a large extent in nitric acid, and was 
reprecipitated when the liquid was made alkaline. A solution in 
caustic soda of the precipitate caused by nitric acid at 85° C. behaved 
similarly. The precipitation here also seemed to be caused by the 
reagent and not by the temperature, for the alkaline liquid deposited 
the proteid body on cooling just as the acid one did, and in about the 
same time as when the temperature was kept constant at 85° C. 
Both p]*ecipitates were unaltered in the separation; each went into 
solution readily in its appropriate medium, the solutions all giving 
the xanthoproteic reaction. 

This proteid gave no precipitate with acetic acid and potassic f erro- 
cyanide. 

After removal of this body by repeated boiling and filtration, the 
clear fluid gave a good xanthoproteic reaction. On applying some of 
the tests used in the case of the East Indian latex, the same peptone- 
like body was found to be present. It dialysed readily, and the 
solution in water gave a precipitate on saturation with solid MgSO^. 

Hence it appears that the latex of Mimusops globosa contains two 
proteids, one a member of the albumose group, precipitated under 
certain conditions by nitric acid or by potash, but not by boiling, and 
the other more nearly related to the peptones. 

In 1823, Boussingault and Mariano de Rivero* published some ob- 
servations on the latex of the cowtree of South America (Brosimum 

• "MSmoire Bur le L&it de I'Arbre de la, Vache (Palo de'Vac?^'),'* ^* ki\i«\c^ ^ 
Chimie et de Physique, " t. xziU, 1823, p, 219, 

VOL. XL. -. 



34 Mr. J. R. Oreen. [Jan« 14, 

gcUactodendion^ Don), one of the Artocarpem. They describe it as 
containing, among other conatitaents, a fibrous matter of animal 
natare, which was obtained by evaporating the latex down to dryness, 
washing the residue with essential oils to free it from waxy and 
resinous matters, and then getting rid of the essential oils by pressing 
dry and boiling with water. This treatment left them a brown mass 
which contained nitrogen. On heating this on hot iron they say it 
burned, giving off an odour similar to that coming from meat heated 
in the same way. This matter was not soluble in alcohol, and when 
obtained by repeated extraction with hot spirit, was left as a residue 
composed of white flexible threads. Thinking it possessed all the 
characteristics of animal fibrin they gave it the same name. 

Since the date of their paper no iuf ormation has been forthcoming 
as to the real nature of this vegetable fibrin. A quantity of the 
latex was obtained by Dr. Vines from Dr. Ernst of Caracas, and a 
bottle of it was, by his kindness, made available for the purposes of 
this investigation. The fluid had been mixed with a small amount of 
alcohol with a view to its preservation during its transit to England, 
and the treatment had been not quite so successful as that of the East 
Indian latex, some, but not much, of the proteid having been 
coagulated by the spirit. Still the fluid was of thick creamy con- 
sistency, and on digestion with water, and subsequent filtration, 
yielded a strongly proteid solution.* Extracts were made with water 
and with solutions of neutral salts, but the resulting liquid behaved in 
the same manner by whichever method it was prepared. 

This extract contained two proteids, one of which was of the natui'e 
of an albumin. When the solution made with distilled water was 
examined, it was found to contain no salts capable of holding a 
globulin in solution, the only ones present being a mere trace of 
phosphates. The solution, on being dialysed till free from salts 
altogether, did not deposit any precipitate. On being boiled there 
was a well-marked coagulum, and after filtration the now coagulated 
matter gave a strongly marked xanthopix)teic reaction. When the 
solution was gradually heated in the usual apparatusf the coagula- 
tion of the proteid took place at 68° C. The other tests for a proteid 
were fairly satisfactory, but were applied with more difficulty than 
with an animal albumin. With Millon's reagent there was a white 
precipitate, which went bi-ick-red on boiling ; with copper sulphate 
and sodic hydrate the violet colour was obtained, but not unless the 
soda solution was very strong. There was, however, no precipitate 
with acetic acid and potassic ferrocyanide. 

• The results of my examination of this latex, and a summary of the properties 
of the bodies found in this and other vegetable fluids described later, were commu- 
nJcBted to the Phjaiologic^l Society at its Cambridge meetmg, "NLvy ^,\^^- 
/ Oaingee's *' Fbjrsiological Chemistry," p. 15. 



1886.] Proteid Substances in Latex. 35 

This body 19 of great interest, as till lately no tme albumin has 
been described as occurring in plants. Bitthaasen's albumins, 
described by him in 1872,* as found in seeds, have been shown by 
later observers, notably by Vines, to be rather globulins held in 
solution by the neutral salts presoDt in the seeds. Even Ritthausen 
himself admits that the existence of a true albumin in seeds had not 
been established satisfactorily as lately as 1877.^ In Martin's paper 
already referred to, he describes a body which he has found to be 
present in Papaw juice, which has the properties of an albumin. It is 
coagulated on boiling, is not precipitated on dialysing an extract of the 
juice, nor on saturating the solution by solid neutral salt. The body 
just described as occurring in the latex of Brosimum seems to be 
identical with this. It is noteworthy that both in the case of 
Martin's albumin and that which has just been described, the albumin 
appears to be a form of the circulating and not of the reserve proteid. 
Boussingault's vegetable fibrin was probably this albumin coagulated 
by the action of the hot alcohol used in its extraction. There 
was no other body in the latex that would become coagulated 
proteid. 

The other proteid found in this latex remained in solution after 
boiling and filtering off the coagulated albumin. It was hence not 
changed by heating ; it dialysed easily through a membrane, was pre- 
cipitated bat not coagulated by alcohol, and was precipitated by 
saturation of its solution by solid MgSO^. It was therefore the same 
body as described above as a constituent of the East Indian latex. 
In the Brosimum latex there was a larger amount of it present, and 
its reactions wei'e therefore carefully confirmed. Besides those 
already mentioned, two more peculiarities were noticed. In dilute 
solution, a stream of COg passed through it for several hours caused 
a precipitate. On submitting it in concentrated or dilute solution to 
the action of artificial gastric juice, it underwent conversion into a 
true peptone, which gave a biuret reaction as readily as peptone pre- 
pared by the same method from fibrin or other animal proteid. 
There was not, however, during the digestion, any formation of acid 
albumin. 

To protect the result from a danger of error arising from peptone 
being present in the artificial gastric juice employed, the experiment 
was performed as follows : — 

A certain amount of the proteid was taken from under alcohol, dis- 
solved in water, and the solution decolorised by filtration through 
animal charcoal. A solution of pepsin in 0*4 per cent. HCl was 
made and filtered. To a quantity of the proteid solution an equal 

•i" Die Eiweiss-Korper der Getreidearten, &c." 1872. 
f J!x>c. ctV. 
$ " Faager'8 Aicbir," XT, 1877, p. 284. 



36 Mr. J. R. Green. [Jan. 14, 

bulk of this extract was added, and a similar quantity of the same 
was added, in another vessel, to as much water as the quantity of the 
proteid solution taken. The two were submitted to a temperature of 
40** C. for twenty-four hours. The biuret test was then applied to 
both, care being taken to have equal quantities taken, and the same 
amount of caustic soda and copper sulphate added to each. Peptone 
was shown to be present in both, but the colour was the deeper in the 
case of the proteid solution. Hence, though a trace of peptone was 
present in the juice employed, the experiment showed formation from 
the proteid in the latex. 

All the material investigated so far had been taken from the plant 
a considerable time before being examined ; also a certain but varying 
amount of alcohol had been mixed with it. There was consequently 
a double possibility of decomposition of some sort having taken place. 
In one case at least there was no doubt that a certain portion of the 
proteid had been coagulated. It seemed desirable therefore to in- 
vestigate certain plants that could be obtained in fair quantiiy in the 
fresh condition, and as laticiferous tissues were those in which most 
proteid matter would be found, choice was made of Manihot glaziovii 
Muell. Arg. (Euphorhincece)* and the common lettuce, Lactttca sdtiva^ 
L. {CovfvpositcB), A considerable number of the young plants of the 
former of these was kindly raised by Mr. Irwin Lynch, at the Botanic 
Garden, Cambridge, and on their attaining a height of about 10 feet 
they were cut down and examined. On wounding them a milky latex 
exuded, but it was impossible to get this to flow in sufficient quantity 
to work with, hence another method of extracting it proved necessary. 
The young plants were cut down, their stems taken and freed from 
leaves and branches, and the cortex scraped o£E by a blunt knife. The 
mass of tissue was then finely minced, pounded in a mortar, and put 
into a quantity of water just sufficient to cover the pulp. After 
standing for twenty-four hours the whole was strained in a press 
through a coarse cloth, yielding a filtrate, turbid, and full of small 
particles of dSbris, chlorophyll granules, &c. In quantity it was 
about twice the bulk of the water used ; this solution therefore was 
diluted latex, containing also any soluble matter originally present in 
the parenchymatous tissue of the cortex. Filtration, repeated many 
times, freed it ultimately from all colouring matters and debris 
arising from the preliminary treatment. Any soluble proteid existing 
temporarily or permanently in the tissue was hence in this extract. 

The proteids normally present in the sieve tubes of Manihot have 
not been determined, but it is fair to' assume that they do not materi- 
ally differ from those of Cucurhita. From these Zachariasf has found 
it possible to extract a proteid body which behaves like a globulin. 

* [The commercial source of Ceara rubber.— W.T.T.T>r\ 
f "Bot. Zeitg./* Februarj, 1884, p. 67. 



1886.] Proteid Substances in Latex. 37 

It is insoluble in distilled water or in snlphate of soda solution, but is 
soluble in weak acids or alkalis. Its precipitate in distilled water is 
changed by contact with alcohol into a white stringy mass. It gives 
the xanthoproteic reaction, and that with copper snlphate and potassic 
hydrate. Fischer* has observed also that the fluid contents of the 
sieve tubes in Cucurbita become coagulated on heating. 

The first investigation of the extract prepared as above, was not 
easy on account of the difficulty of getting rid of the soluble phos- 
phates, which were found to be present in considerable quantity. 
They were removed by warming with ammonia, but the last traces 
were very hard to throw down. The liquid finally, however, ceased 
to give a precipitate with ammonium molybdate. Besides the phos- 
phates the salts present were sulphates and chlorides, but both were 
much smaller in amount than the phosphates. 

Having freed the extract from phosphates, it was found to coagu- 
late on boiling, and the coagulum gave the xanthoproteic reaction. 
On heating it more slowly an opalescence was found to appear at 74— 
76** C, which was replaced by a precipitate at about 80** C. After 
filtering this precipitate off, no further opalescence took place up to 
boiling point. Dialysis for some time caused a precipitate, though 
not a very bulky one. Saturation of the neutralised liquid with 
MgS04 gave a precipitate, and a stream of COg through a weak 
solution did the same. These reactions, taken together, indicated the 
presence of a globulin, of pretty much the same character as that 
found in Cucurbita by Zacharias and Fischer. They were not, how- 
ever, quite conclusive, as several of the methods used would have 
thrown down, if it were present, the body described as occurring in 
latices examined before. This body was therefore looked for and 
found. After getting rid of the globulin by heating and filtering, the 
liquid gave the same reactions as those described before as belonging 
to that body. The dialysis especially was well marked, alcohol 
giving a proteid precipitate readily with the liquid outside the 
dialyser. The globulin was not so readily isolated, but it proved 
possible to get it by dialysis. It was not present in such large 
quantity as the other, and was more readily precipitated completely 
from its solution by saturation with solid MgSO^, for the fluid, when 
both were present, gave a xanthoproteic reaction after it had ceased 
to give a precipitate on boiling. It was also precipitated on very large 
dilation. 

Hence in the extract of Manihot are two proteids, one being 

globulin in nature and agreeing in its reactions with that of Zacharius 

and of Fischer ; being satisfactorily sepai*ated from the other without 

injury only by dialysis; both giving precipitates on saturation with 

solid MgSO^. A similar body to this globulin has \)eeii d^^criJoft^ V^ 

* "Berichte d. deutsch. bot. Gesdl.," yol. ii, 15To. 7 ,l«a^. 



38 Mr. J. R. Greeo. [Jan. 14, 

Martin* as being present in Papaw jnice. He speaks of it as being 
precipitated on boiling, the coagulating point being 70 — 74* C. ; pre- 
cipitated on dialysis ; by GO3 from dilate solution ; and by saturation 
of its neutral solution with MgSO^. The two appear to be identical. 

An extract of Lactuca saJtiva was prepared in a similar way to that 
described in the case of Manihot In this there was no globulin, but 
instead a proteid resembling Vines'sf hemialbumose. It was pre- 
cipitated on the addition of nitric acid, and the precipitate was largely 
soluble in excess. Addition of potassio ferrocyanide to this solution 
gave a precipitate. On filtering off the nitric acid precipitate it was 
found to be soluble in water and dilute alkalis, and the solution was 
not coagulated on boiling. The precipitate gave the xanthoproteic 
reaction. It differed from Yines's body in its solutions not giving 
the biuret reaction, but Agreed with it in not dialysing. After 
removal of this albumose the extract contained in solution a quantity 
of the dialysable proteid described as occurring in previous cases. 

Before leaving the investigation it seemed well to examine a plant 
which should belong to an order not specially laticiferous. The 
common cabbage (Brassica oleracea, L.), being succulent, was selected. 
Its examination was not particularly fruitful, bringing to light only 
the fact that the dialysable proteid was present there as well as in the 
other plants. It was not in this case examined very closely. No 
other proteid was found. 

My researches, so far, agree with those of Martin in not showing 
the presence of true peptone in plants. 

List of Proteids Found. 

1. Dialysable proteid, resembling peptone. 

This occurred in all plants examined. Its reactions may be sum- 
marised here : — 

a. Soluble in water. 

h. Not coagulated on boiling. 

c. Precipitated slowly by alcohol, but not coagulated by the 

reagent. 

d. Diffuses readily through membrane. 

e. Is not precipitated by nitric acid, nor by acetic acid and 

by potassic ferrocyanide. 
/. Is precipitated on saturation of its neutral or acid solution 

with solid MgSO^. 
g. Is precipitated slowly by a stream of CO3 through its dilute 

solution. 
h. Is converted into true peptone by the action of pepsin. 
#.' I?oes not give the biuret reaction. 

• Zroe. et'i, \ ioc. cit. 



1886.] Prateid Substances in Latex. 39 

The body most nearly resembling this which has hifcherto been 
deBcribed is that which is stated by Martin* to be produced by the 
ikction of papain on the proteids present in papain jnice. It differs 
from the one now described in that it gives the biuret reaction, and 
is precipitated by acetic acid and potassic ferrocyanide. He says 
nothing as to its power of dialysis. 

2. Hemialbumose (Laduca) — 

a. Soluble in distilled water. 
(. Not coagulated on boiling. 

e. Precipitated by nitric acid and by acetic acid and potassic 
ferrocyanide. 

This resembles very closely Yines's hemialbumose, and the body 
which Martin* has called a-phytalbamose. It differs in not giving 
the biuret reaction. 

3. Alhumose {Mimusops) — 

a. Soluble in distilled water. 

h. Not coagulated by boiling in neutral solution. 

c. Precipitated slowly by nitric acid at a temperature approach- 

ing 70** C. 

d. Not precipitated by acetic acid and potassic ferrocyanide. 

4. Albumin {Brosimum) — 

a. Soluble in distilled water. 

h. Coagulated at 68" C. 

c. Not precipitated by acetic acid and potassic ferrocyanide. 

5. Globulin (Manihot) — 

a. Precipitated by dialysis of its solution. 

b. Coagulated on heating to 74 — 76" C. 

c. Precipitated on saturation of neutral or acid solution with 

solid MgSO^. 

d. Precipitated on large dilution. 

e. Precipitated by a stream of COo through dilute solution. 

Both the albumin and the globulin seem to be the same bodies as 
described by Martin as occurring in Papaw juice. The probable 
identity of the former with Boussingault's vegetable fibrin has already 
been alluded to. 

• Loc. oit. 



f. 



40 Mr. H. TomlinBon. . [Jan. 14^ 



IV. "The CoeflScient of Viscosity of Air." By HERBERT 
ToMLiNSON, B.A. Communicated by Professor G. 6. 
Stokes, P.R.S. Received January 6, 1886. 

(Abstract.) 

The author has had occasion, whilst investigafcing the internal 
friction of metals, to determine the coefficient of viscosity of air. 
The viscosity of air has already engaged the attention of several dis- 
tinguished experimenters, amongst others, of G-. G. Stokes, Meyer, and 
Clerk Maxwell. The results obtained, however, differ so widely thai 
it was considered necessary to institute fresh researches into the same 
subject. 

The author employed the torsional vibrations of cylinders and 
spheres, suspended vertically from a horizontal cylindrical bar, and 
oscillating in a sufficiently unconfined space. The bar was suspended 
by a rather fine wire of copper or silver attached to its centre, which,, 
after having been previously subjected to a certain preliminary treat- 
ment with a view of reducing the internal molecular friction, was set 
in vibration. The vibrations were performed in a large box, which 
was rendered sufficiently air-tight to prevent currents of air from 
vitiating the results. The wire, which was about 97 cm. in length, 
was suspended in an air-chamber, the double walls of which enclosed 
between them a layer of water. This air-chamber was in turn 
surrounded by a second, also provided with double walls which con- 
tained sawdust in the space between them. The object of the two 
air-chambers was to protect the wire as much as possible from small 
ductuations of temperature, which last had been found to render the 
internal friction of the metal very uncertain. 

The coefficient of viscosity of air was obtained from observations of 
the diminution of the amplitude of vibiation, produced by the resis- 
tance of the air to the oscillating spheres or cylinders attached to the 
horizontal bar, arrangemente having been made so that the vibration- 
period of the wire should remain the same, whether the cylinders or 
spheres were hanging to the bar or not. In deducing the value of 
the coefficient of viscosity from the logarithmic decrement, the 
author has availed himself of the mathematical^ investigations of 
Profes.sor G. G. Stokes.* 

Five sets of experiments were made with hollow cylinders and 
wooden spheres, in the construction and measurement of which con- 
siderable care was taken. When the cylinders were used arrange- 

* See Professor Stokes's paper " On the Effect of t\ie liiteTn«2L'BTv:\AOTv o^ ^\>3^^% 
on ^e Motion of FendxdmnB," "Trans. Camb. Phil, aoc.,'* ^o\. \x, PmN. H A^'^s^. 



1886.] 



The Coefficient of Vtscoeity of Air. 



41 



ments were made to elimixiate the effect of the friction of the air on 
their ends. The following are the results : — 







Yibrstion- 
period in 


Temperature 
of the air in 


CoeflScient of 


Length in 


Diameter in 


viscoaitj of 


oentiinetTes. 


centimetres. 


depees 


the air in 






BVt^JUUO* 


centigrade. 


C.O.9. unite. 


1 
1 




CyUndere. 






60-876 


2*5686 


6-8873 


1202 


0-00018171 


60-885 


0-9636 


7 0590 


14-68 


0-00018122 


60-875 


2-5636 


3 -0198 


11-69 


0* 00018024 


1 63-175 

1 


2-5636 


2-9994 
Spheres, 


10-64 


00017845 




6-364 


2-8801 


9-35 


0-00017820 



Maxwell has proved* that the coefficient of viscosity of air is inde- 
pendent of the pressure and directly proportional to the absolute 
temperature. We can, therefore, calculate from the above data what 
would be the value of the coefficient of viscosity at 0° C. ; tod when 
this is done, in the case of each of the five sets of experiments, we 
obtain the following values : — 

Coefficient of 
Set of Tiflcosity of 

experiments. air at C. 

Ist 000017404 

2nd -00017201 

3rd 0-00017284 

4th 0-00017859 

5th 00017230 

The mean of these numbers is 0*00017296 with a probable error of 
only 0-14 per cent. The formula for finding /i/, the coefficient of 
viscosity of air at the temperature t^ C, is therefore — 

^,=0-00017296(1+^). 

The value of the coefficient of viscosity of air at 0^ C. given above, 
though much nearer to that obtained by Maxwell than any which 
has been got by other observers, nevertheless difiers from it by more 
than 8 per cent. Maxwell expenmented with dry air freed from 
carbonic acid, but it does not seem possible that the small amount of 
aqueous vapour and carbonic acid present in ordinary air can be 
credited with a dlminntion of 8 per cent, in the viacosvt^ \ tiot ^5»icw 

* ''FLU. Trans./' 1866, vol. 156, Part I. 



42 Mr. F. Galton. [Jan. 21, 

the author explain in any way the difference between his own resolt 
and that of Maxwell. 

[The method followed by Maxwell is liable to be vitiated to a very 
sensible degree by small errors of level of the movable disks, especially 
when they are closest to the fixed disks. The final adjustment is 
stated to have been that of the fixed disks, and no special precautions 
seem to have been taken to secure the exact horizontality of the 
movable disks, ^y a calculation founded on the equations of motion 
of a viscous fluid, I find that at the closest distance (about the one- 
sixth of an inch) at which the fixed and movable disks were set, an 
error of level of only l"* 8' would suffice to make the internal friction 
appear 8 per cent, too high. 

In Mr. Tomlinson's reductions no allowance has at present been 
made for the effect of the rotation of the spheres or cylinders about 
their own axes, which is not quite insensible, as it would be in the 
case of a ball pendulum. The introduction of a correction on this 
account would slightly diminish the values resulting from the experi- 
ments, especially in the case of the sphere, where it would come to 
about 4 per cent. — Q. G. S.] 



January 21, 1886. 

Professor STOKES, D.C.L., President, in the Chair. 

The presents received were laid on the table, and thanks ordered 
for them. 

The following Papers were read : — 

I. "Family Likeness in Stature." By FRANCIS Galton, 
F.R.S. With an Appendix by J. D. Bamilton Diokson, 
Fellow and Tutor of St. Peter's College, Cambridge. 
Received Januaiy 1, 1886. 

I propose to express by formulas the relation that subsists between 
the statures of specified men and those of their kinsmen in any given 
degpree, and to explain the processes through which family peculiarities 
of stature gradually diminish, until in every remote degree of kinship . 
the group of kinsmen becomes undistinguishable from a group 
.selected oat of the generai population at random. \ ok^XlL ^<e\«trc^^ 
^Ae constants in my formul© referring to kxnd:u.i^ -^n^^ «k xsaelfcoX. 



1886.] Family Likeness in Stature. 48 

degree of precision. These constants maj provisionallj and with 
some reservation be held applicable to other human peculiarities 
than statnre, while the formulsa themselves are, I presume, applicable 
to evexj one-dimensioned faculty that all men possess in some degree, 
bat that different men possess in different degrees. 

I selected stature for the subject of this inquiry, for reasons fully 
set forth in two recent publicationB,* which dealt with one small 
portion of the ground covered by the present memoir, and from 
which it will be convenient that I should maike as I proceed occa- 
sional short extracts, in order to complete the present argument and 
to save cross-reference. The reasons that combine to render stature 
an excellent subject for hereditary inquiry are, briefly, the ease and 
frequency of its measurement, its constancy during adult life, its 
inooiisiderable influence on the death-rate, its dependence on a mul- 
tqdioity of separate elements, and other points that I shall dwell on 
as I proceed, namely, the ease with which female statures are trans- 
mnted to their male equivalmts, and so enabled to be treated on 
equml terms with male statures, the tendency of the parental statares 
to blend in inheritance, and the disregard c£ stature in marriage 
selection. 

Sta^ure-schemes. — ^It is an axiom of statistics that large samples 
taken out of the same population at random are statistically similar, 
and in such inquiries as these which do not aim at minute accuracy, 
they may be considered identical. Thus the statures in every group, 
say of 1000 male adults, when distributed in order of their mag- 
nitudes at equal distances apart and in a row, will form almost 
identical figures ; it being only towards either end of the long row 
that irregularities will begin to show themselves. These are unim- 
portant in the present inquiry and I disregard them. The Diagram S, 
fig. 1, shows the outline of such a group of statares. It is drawn to 
SGEde, each of the statares being supposed to have been represented 
by a vertical line of proportionate length, standing on a horizontal 
base, the lines being at equal distances apart, and the whole system 
being compressed into the space between two termini, which may 
be set at any convenient distance asunder. The vertical lines in 
the figure do not indicate these statares, but they are divisions, 
ten in number, between each of which 100 stature lines are com- 
pressed. The first and last stature will not touch the termini, 
but will be removed from them by a half -interval. As it will 
be convenient to assign a name to this figure, I will call it a 

* (1.) " Prendential AddreM to the Anthropological Section of the British 
AifOcUtion in 1885." (2.) " Begrossion towards Mediocrity in Hereditary Stature." 
" Joum. Anthrop. Institute/' 1885, p. 246. The latter is a reprint of that ^rtiou 
of tlie former with which I am now concerned, together mth &otqq «A<^\\i\oxi'(i2L 
it contains tablea and diagrams, and should be referred to in ^telex^xwi©. 



[Jan. 21, 




"stature- scheme." The namerouB caaee near mediocritf that differ 
little from one ajiother, caase the middle portion of tbe upper 
bonndaiy of the statare-scheme to assnme a gentle slope, which 
increaaea rapidly towards either end, where the increasing rareness 
of more and more exceptional cases caoses that bonndarj line to slope 
upwards, as an asymptote to one of the termini, and downwards as 
an asymptote to the other. 

Now suppose that instead of compressing 1000 statnrea between 
the t«rmini, I compressed 1000 x 1000, or a million of them, the 
statnre-echeme wonld be nnaltered, except that anch small irregnlar- 
itiea as might have been previonsly seen wontd become amoothed. 
The height of the middlemost or median statnre-line would remain 
the same as before, and so wonld the heights of the lines standing at 
each qnarter, each tenth, and at every oiher proportionate distance 
between the termini. Or again, instead of arranging the lines in a 
single scheme, we might arrange them in a thousand schemes, whicb 
as wc have seen, wonld be practically identical in e^^^, mi4 -tj* tok^ 
p/aoff these echemea side by side, as is done m 'Zi,6g.\,iOTnaii%». 



6.] 



Family lAieness in Stature. 



45 

oadron " nambering 1000 atatores eacli w&y, the whole atandiug 
I a sqnare base. Oar Bqnadron may be considered a^ made np of 
» (parallel to the plane of £>) as in Z, or otfilei (parallel to the 
A of sy) aa in A. The ranks, as we have seen, are all similai* 
ire-schemea, the files are all rectangles which have the same 
dttu bat are of disaimilar heights. 

< i> now easy to give a general idea, to be developed as we proceed, 
tie way in which any large sample of a population gives rise to a 
ip of distant kinsmen in any given degree, who are statistically 
iH respects except nambers) ondistingnishable as regards their 
ma from themselves. I must suppose for convenience of ex- 
■tion, that tall, short, and mediocre men are equally fertilo 
ioh ia not, however, strictly the case, the tall being somewhat 
fartye than the short*), and then on referring to fig. 2, the 




incB of the distant descendants of two of the rectangnlar files of 
dron A will be seen ti-aced. 

1 the number of kinsmen, in any i-emotc degree we please to 
ify, of the men in each of the two files ia about the same ; I take 
■ of them in each case. Again, as the statu re- schemes of those 
men are identical with those of equal nnmbei-a of men taken at 
om, as samples of the general population, it follows that they 
"hldly enough, the tbortcst couple on nijr lis! Imv* the laTgesl f amW^ , nwwA^ 
t chiidrea, of whom fourteen were meastircii. 



46 Mr. F. Oalton. m [Jao. 21, 

will be identical with one another. Every other rectangular file 
being similarly represented, a complete sqnadron Z of the kinsmen 
is produced. It is obvious, then, that the squadrons A and Z are 
identical, and as the ranks of Z have proceeded from the files of A, 
the result is that the two squadrons will stand at right angles to one 
another. The upper surface of A was curved in rank, but was 
horizontal in file ; that of Z is curved in file, but is horizontal in 
rank. 

Kinsmen in near degrees are represented by squadrons of inter- 
mediate form. These will not have lost the whole of the curvature 
in rank of A, nor will they have acquired the whole of the curvature 
in file of Z. Consequently they will be curved moderately in both 
ways.* Also it will be found that the intersection of their surfaces by 
the horizontal plane of median height forms in each case an approxi- 
mately straight line that assumes difEerent and increasing inclinations, 
in the successive squadrons of intermediate shape between A and Z. 
These lines are indicated by straight lines on the squareB below the 
squadrons in fig. 4, which represent the square bases upon which the 
squadrons stand. 

I shall now show how these curves in rank and file should be 
treated. But before doing so, it is necessary to remark that female 
adult staturie (I speak throughout of adults) may be safely trans- 
muted to its male equivalent by multiplying it by a constant constant, 
which as regards my data is 1*08. After this has been done, the 
transmuted female statures may be treated on equal terms with the 
male statures, and the word " men " or other masculine term will 
include both sexes, unless otherwise stated distinctly. This procedure 
is adopted in the present memoir. 

It is now genei-ally recognised that the statures in every ordinary 

population are distributed in approximate conformity with what 

might have been inferred, if it were known that their variations were 

governed by such conditions as those upon which the exponential law 

of frequency of error is based. Therefore the upper boundary of the 

stature-scheme is approximately a curve (I call it an " ogive ") that 

admits of mathematical expi*ession. The abscissas of the normal ogive 

1 f' 
(fig. 3) are values of the probability integral —7=1 e'~^dt^ and the 

ordinates are the corresponding values of t. These are given in 
column A of Table I. Column B contains the same values divided 
by 0'4!77, by which means they are expressed in units of the probable 
eiTor. I find it convenient to call the oixiinates to an ogive (di'awn 

* A plaster model of one of these intermediate forms "was exhibited at the 
meeting hjr Mr. J. D. H. Dickson, who stated that his recent mathematical investi- 
gation of the properties of their surfaces, had sliovfTci t\Lat no «\.t\cVVj ft\.T«i^\.'NMi^ 
could be drawn upon them. — F. Ot, 



1886.] 



FcmUy Liietuut m Stature. 
rio. 3. 




from ita axis) by the name of " deviates," and to describe either of 
those two aymmetrical deviates of the normal ogive that stand at 
+ 25° by the name of " qoartile deviate," or, moi-o briefly, " quartile." 
I alao give this name to the mean length of the upper and lower 
qnartile, in those ogives which arc drawn from observed data, and 
which are not strictly symmetrical. The numerical valne of the 
quartile is identical with that of the well-known bat here inappro- 
priate term of " probable error." 

Cmuirueliou of Stature- Schemes and of Ogives from OhserBatioiis. — 
The method of drawing an ogive from observations of stfttnre is iis 
follows. The observations (see Tables III, IV, and V, and compare with 
VI and VII) are sorted into grades, snch a.s '' . . . cases of 60 inches 
andnnder 61," " . . . cases of 61 inches and under 62," &c. If we are 
constmcting a statn re- scheme, or desitc to obtain the median valne of 
the series, we have to consider theMi: viklues of inches, bat iu con- 
structing no more than an ogive, which is only the npper boundary of 
a stature-scheme, it suffices to consider them us successive gnidos 
of 1 inch each, and I reckon the fitst f^rade not as 0, but as 1 . 
This has been done in column A, Table VI, for the sake of 
treating different groups on a uniform plan. The nnnibei' of 
cs«es in these grades mb then sammed from the beginning, aud 
the mam, up to each gi-ado inclasivc, is written down, as sVu-kti 



48 Mr. F. Galton. [Jan. 21, 

in column B in Table YI. The percentage values of these, taking the 
total number of observations as 100, are written in column C. A series 
is there obtained which shows how many per cent, of the statures fall 
short of the parting value that separates each pair of adjacent grades. 
Thus if n per cent, of the statures fall within the first r grades, that 
is to say, are less than the value of the rth parting line, then 100 — n 
per cent, of them will exceed that value. Consequently, if the observa- 
tions are read off and recorded to the utmost nicety, r will be the value 
of the ordinate representing the stature which has to be erected on a 
base line at n per cent, of its length from one of its ends. In short, 
a base line of any convenient len^ h has to be divided into 100 parts, 
and an ordinate of a length proportionate to r erected at the division n. 
As observations are never read off and recorded with perfect accuracy, 
a correction has here to be applied according to the circumstances of 
the particular case, whenever we are drawing a stature-scheme, and 
not merely an ogive. If the records are kept to the nearest mth 
part of an inch, the phrase *' exceeding r inches " would really mean 
exceeding r— 1/m inches." This then is the true parting value corre- 
sponding to the nominal r. In drawing ogives, and not stature- 
schemes, this correction may of course be disregarded. Having 
erected prdinates corresponding to each value of r, their tops are 
connected by sti-aight lines forming a polygonal boundary that 
approximates to the curvature of an ogive, and would become one if 
it were corrected with a free hand, or otherwise smoothed. The 
centre of the ogive lies at the intersection of the curve with the 
ordinate drawn from the base at the fiftieth division, and the hori- 
zontal axis of the og^ve runs through that point of intersection (see 
fig. 3). 

A half-ogive, whose ordinates are the mean lengths of the symme- 
trically disposed ordinates of the complete ogive, is constructed od the 
same genei*al principles, but more simply, because the base from 
which it is plotted coincides with the axis of the ogive, and the 
graduations run alike, viz., from 0° to 50°. 

In Table VII, the entries in the first lines of each of the three 
groups it contains, are the lengths of the ordinates that have been 
measured from the bases of ogives constructed from the data in 
Table VI. The abscissae corresponding to the measured ordinates, 
are in every case the same fractional lengths of the bases. The 
entries in the second lines are the differences between these several 
ordinates and the median ordinate ; they are, therefore, the deviates. 
The entries in the third lines are the negative deviates written under 
the corresponding positive ones. The entries in the fourth lines are 
the means of the values of the positive and negative deviates, dis- 
regarding their signs. 

Comparison of Ogives, — The ogive being drawn according to the 



1886.] Family Likeness in Stature. 49 

observations, its axis is divided into 100 parts, the fiftieth division 
being reckoned as 0°, then the deviates standing at the + graduations 
of 10°, 20^ 25°, 30°, 40°, and 45° are measured. The mean of each 
pair of lengths, not regarding signs, has then to be divided by the 
mean lengths of the deviates at + 25°, that is by the quartile deviate, 
and so is made to yield a series that is directly comparable with 
column B in Table I. The closeness with which it conforms to that 
standard series is the test of the closeness with which the observations 
conform to the law of frequency of error. 

Table II effects this compari^^^n for all the series that I have to 
deal with in the present paper. ^ Ae values are entirely unsmoothed, 
except in two named instances, being taken from measurements made 
to the above-mentioned polygonal boundary. I thought it best to 
give these interpolated values in this, their rudest form, leaving it to 
be understood that with perfectly legitimate correction the accordance 
would become still closer. I do not carry the comparison beyond 45^, 
partly because my cases are not numerous enough to admit of a fair 
comparison being made, and chiefly because I am well aware that 
conformity is not to be expected towards the end of any series. I am 
content to deal with nine- tenths of the observations, namely, those 
between 0° and 45®, and to pay little heed to the remaining tenth, 
between 45** and 50**. It will be seen that the conformity of more 
than one half of each series is closer than to the first decimal place, 
and that in absolute measurement it is closer than to one-tenth of an 
inch. 

Arithmetic and Geometric Means. — I use throughout this inquiry the 
ordinary law of frequency of error, which being based on the assump- 
tion of entire ignorance of the conditions of variability, necessarily 
proceeds on the hypothesis that pltt^ and miniis deviations of equal 
amounts are equally probable. In the present subject of discussion our 
ignorance is not so complete ; there is good reason to suppose that 
plus and minus deviations, of which the probability is equal, are so 
connected together that the ratio between the lower observed measure- 
ment and the truth is equal to that between the truth and the upper 
observed measurement. My reasons for this were explained some 
years ago, and were accompanied by a memoir by Mr. Donald 
Macalister, showing how the law of frequency of en'or would be 
modified if based on the geometric, instead of on the arithmetic mean.* 
Though in the present instance the former process is undoubtedly the 
more correct of the two, the smallness of the error here introduced by 
using the well known law is so insignificant that it is not worth 
i-egarding. Thus the mean stature of the population is about 
68*3 inches, and the quartile of the stature-scheme (the probable 
error) is 1*7 inch, or only about one-fortieth of its amount, and the 

• "Proc. Roj. Soc.," Tol. 29 (1879), pp. 365, 367. 

VOL, XL, Y* 



50 Mr. F. Galton. [Jan. 21, 

diSerenoe between 40^/39 and 41 is that between about 41*025 and 
41*000, or only about 6 per thousand. 

Regression. — It is a universal rule that the unknown kinsman in 
any degree of any specified man, is probably more mediocre than he. 
Let the relationship be what it may, it is safe to wager that the 
unknown kinsman of a person whose stature is 68} + as inches, is of 
some height 68} + x inches, where x* is less than x. The reason of 
this can be shown to be due to the combined effect of two canses : 
(1) the statistical constancy during successive generations of the 
statures of the same population who live under, generally speaking, 
uniform conditions ; (2) to the reasonable presumption that a sample 
of the original population and a sample of their kinsmen in any 
specified degree are statistically similar in the distribution of tlieir 
statures. To fix the ideas, let us take an example, namely, that of 
the relation between men and their nephews : — (a.) A sample of men, 
and a sample of the nephews of those men, are presumed to be statis- 
tically alike in stature, that is to say, their mean heights and their 
quartile deviates of height will be of the same value. I will call the 
value of this quartile p. (h.) Each family of nephews affords a 
series of statures that are distributed above and below the common 
mean of them. They are deviations from a central family value, or, 
as we may phrase it, from a nepotal centre, and it will be found as 
we proceed (it results from what appears in Tables III, IV, and V) 
that these deviations are in conformity with the law of error, and 
that the quartile values (probable errors) of these systems of devia- 
tions, which we will call /, are practically unifonn, whatever the 
value of the central nepotal family stature may be. (c.) It will be 
found, as it is reasonable enough to anticipate, that the system of 
nepotal centres is distributed above and below the median stature of 
the population, in conformity with the law of frequency of error, and 
with a quartile valne that we will call d. It follows from (a) that we 
possess data for an equation between jp) /> and eZ, which, from a well- 
known property of the law of error, assumes the form (i'^-|-/'=2>*. 
Now the unknown nephew is more likely to be of the stature of his 
nepotal centre than any other stature that can be named. But the 
system of statures of nepotal centres is more concentrated than that 
of the general population (d^ is less than p°). That is to say, the 
unknown nephew is likely to be more mediocre than the known man 
of whom he is the nephew. What I shall have to show is expressed 
in fig. 4, where A and Z are side views of squadrons such as A and 
Z in fig. 2. [They are drawn shorter than the stature-schemes in 
fig. 1, and therefore out of scale, to save space, which is an unimpor- 
tant change, as it is only the variation in the ogives we are now 
concerned about.] Let m represent the level of mediocrity above the 
ground, m-^x and m— a; the heights of any two rectangular files in 



1886.J 



Family Likenen in Stature, 
Fio. 4. 




tl)e eqiiAdron of known mon. We hare seen that x becomes in 
remote d^^rees of kinship, and I shall ahow that in intermediate 
degrees the ralae of x'Jz is constant for all statures in the same 
degree of kinship. This fraction is what I call the ratio of regression, 
and I designate it by u>. Consequently tlie above formula becomes 
u^p^+f^=p\ which is uniTsrsally applicable to all degrees of kinship 
between man and man, so long as the statistics of height of the 
population remain nnchonged. 

Hence in the squadrons, the caivaturo in rank is an ogive with the 
quartile value of top, and in file with one having the qnai-tile valae of 
J, these two values being connected by the above formula. If the 
Hqoadron is i-csolved into its elements, and those elements are redis- 
tribnled into an ordinary stature-scheme, the quartile of the latter 
will be p. 

Another way of explaining the universal tendency to itigressioa may 
be followed by showing that this tendency necessarily exists in each of 
the three primary relationships, fraternal, filial, and parental, and there- 
fore in all derivative kinships. Fraternal regression may be ascribed 
to the compi'oniise of two conflicting tendencies on the part of the 
unknown bi-other, the one to resemble the given man, the other to 
resemble the mean of the race, in other wortle to be medioci-e. It will 
be seen that this comprumise insults in a probable fraternal stature that 
is expressed by the formulte (p^— fc^)/;"", in which li in a, constant as 
well as^, therefore the ratio of tialernal regression is also a constant. 
Filial regression is due (as I explained moi-e fully than 1 need do 
here, in the publications allnded to in the Hccood paragmpji) to the 
Goncnnence of atavism with the tendency to resemble the pareaL 
The remote ancestry in any mixed population resembles, as has bees 



52 Mr. F. Galton. [Jan. 21, 

already said, any sample taken at random out of that population, 
therefore their mean stature is mediocre ; consequently the parental 
peculiarities are transmitted in a diluted amount. Parental regres- 
sion is shown to be the necessary converse of filial regression by 
mathematical considerations, kindly investigated for me by Mr. Dick- 
son, in the Appendix to this memoir in Problem 1. It is easy in a 
general way to see that this would be the case, but I find it not easy 
otherwise to prove it. Still less would it be easy to prove the con- 
nexion between filial and mid-parental regression, which depend on 
oonsiderations tjiat are thoroughly investigated in the Appendix. 

Data. — I will now describe the data from which I obtain my 
oondusions. They consist of two sets of practically independent 
observations, though they do in some small degree overlap. 

(1.) Special observations. These concern variation in height 
among brothers. I circulated cards of inquiry among trusted cor- 
respondents, stating that I wanted records of the heights of brothers 
who are moi'e than 24 and less than 60 years of age ; not necessarily 
of all the brothers of the same family, but of as many of them as 
could be easily and accurately measured, the height of even twa 
brothers being acceptable. If more than one set of brothers were 
entered on the same card, the entries were of course to be kept 
separate. The back of the card was ruled vertically in three 
parallel columns : (a) family name of each set of brothers ; (h) order 
of birth in each set; (c) height, without shoes, in feet and inches. 
A place was reserved at the bottom for the name and address of the 
sender. The circle of inquiry widened, and I closed it when I had 
obtained returns of 295 families, containing in the aggregate 783 
brothers. 

I look upon these returns as quite as trustworthy as any such 
returns are likely to be. They bear every internal test that I can 
apply to them very satisfactorily. They are commonly recorded to 
quarter and half inches. 

(2.) R.F.F. data. By this abbreviation I refer to the Records of 

Family Faculties that I obtained in the summer of 1884, in reply to 

. an offer of prizes. I have been able to extract from these the heights 

of 205 couples of parents, with those of an aggregate of 930 adult 

children of both sexes. I have transmuted all the female heights to 

their male equivalents, and have treated them thus transmuted on 

equal terms with the measurement of males, except where otherwise 

expressed. These data have by no means the precision of the special 

observations. There is in many cases considerable doubt whether 

the measurements refer to the height with the shoes on or off; many 

entnieB are, I fear, only estimates, and the heights are commonly 

given only to the nearest inch. Still, speaking irom «>. 'k?iio'«\^^^ c^l 

lo&ny of the contiibntora, I am satiated t^t a iaii ^"^ajKWi oi V^[v»e& 



1886.] Family Likeness in Stature. 53 

returns are undoubtedly careful and thoroughly trustworthy, so that 
I have reason to place confidence in mean results. They bear those 
internal tests that I apply to them better than I should have expected, 
and when taken in connexion with and checked by the special data, 
and used with statistical caution, they have proved very valuable to 
ine. 

I have discussed these materials in a great variety of ways to gpwrd 
myself against rash conclusions, but I shall not present more than 
three primary tables, which contain suflEicient materials for determin- 
ing the constants of the formulsB to be used. 

The first of them (Table III) refers to the children of what I call 
^' mid-parents " of various statures. A mid-parent is the imaginary 
mean of the two parents, after the female measurements have been 
transmuted to their male equivalents, so that a mid-parent of 70 
inches in height refers to a couple whose mean stature under the above 
reservations is 70 inches. I have given data in the " Joum. Anthrop. 
Inst." (loe. cii.) to show that we need not regard differences in stature 
between the parents, inasmuch as the distribution of heights among 
the children proves to be statistically the same, so long as the mid- 
parentages are alike, whether the two parents are the same or of 
difEerent statures. This blending of paternal and maternal qualities 
in the stature of the offspring is one great advantage in selecting 
stature as a subject for the present inquiry. 

General Population, — (1.) Its variability. The value of the quartile 
deviate in the population ogive (that is to say, the probable error) 
may be deduced from the bottom lines of any one of the three Tables 
in, IV, and V. Those in III and IV refer to data that are in part 
but by no means wholly the same, that of V refers to almost totally 
distinct data. The work is shown in Tables VI and VII; in the 
former the ordinates are calculated whence the ogive is drawn, in the 
latter I have given the values of the measured ordinates at the same 
points along its axis as those to which the ordinates given in Table I 
refer. The values of the quartile that I obtain in this way from the 
three cases are 1*65, 1*7, and I'7. I should say that the more careful 
treatment that I originally adopted happened to make the first of 
these values also I'7, so I have no hesitation in accepting 1*7 as the 
proper value of p for all my data. 

(2.) Variability of system of mid-parents. I have published data in 
the memoir already alluded to, to show that marriage selection takes 
small account of stature, which is another great merit in stature as a 
subject for this inquiry. Some further proof of this may be got by 
comparing the variability of the system of mid-parents with that of 
the general population. If the married couples had paired together 
regardless of stature, their mean heights would be elements of a 
stat/seioaJ system identical with one in which the ]^\Ta YisA \3«wi 



54 Mr. F. Galton. [Jan. 21, 

selected at random. In this latter case the qnartile value of the 
system of mid-parents wonld be l/\/2 ,p=l'21 inch. Now, I find the 
qnartile of the series of the mid-parental system obtained from the 
two colmnns in Table III, that are headed respectively " Heights of 
the mid-parents'* and "Total number of mid-parents," to be 1*19 
inches,* which is an unexpectedly exact accordance. 

(3.) Median Stature. I obtain the values 68*2, 68'6^ 68*4, from the 
three series mentioned above, but the middle value, printed in itaUe$^ 
is a smoothed value. This is one of the only two smoothed values in 
the whole work, and has been justifiably corrected because the one 
ordinate that happens to accord closely with the median is out of 
harmony with all the rest of the curve. This fortuitous discrepancy 
amounts to more than 0*15 inch. It does not affect the quartile value, 
because neither the upper nor the lower quartile is touched, and, 
therefore, the half-intei'quartile remains unchanged. It must be 
recollected that the series in question refers to R.F.F. brothers, which 
are a somewhat conditioned selection from the general R.F.F. popula- 
tion, and could not be expected to afEord as regular an ogive as that 
made from observations of men selected from the population at 
hazard. It is undoubtedly in this group that the least accuracy was 
to have been expected. 

Mean Ratios of Regression in the Primary Degrees of Kinship. — (1.) 
From the stature of mid-parents of the same height, to the mean of 
the statures of all their children. I have already (he. cit.) published 
the conclusions to which I arrived about this, but it is necessary to 
enter here into detail. The data are contained in Table III, where 
each line exhibits the distribution of stature among the children of all 
the mid-parents in my list, who were of the stature that forms the 
arg^ument to that line. The median stature in each successive line 
is the mean stature of all the children, and is given at the side in the 
column headed " Medians." Their values are graphically represented 
in fig. 5. It will be there seen that these value are disposed about 
a straight line. If the median statures of the children had been the 
same as those of their mid-parents this line would have accorded with 
the line A6, which, from the construction of the table, is inclined at 
an angle of 45** to the line "Mean Stature of Population," which 
represents the level of mediocrity. However, it does not do this, but 
its position is inclined at a smaller angle, 0, such that 

tan : tan 45 : : 2 : 3. 

This gives us the ratio of regression {=to) in the present case ; and, 
therefore, in the notation I adopt u^^f. 

(2.) From the stature of men of the same height, to the mean of 
^^0 staenrea of all their children. We have ^uftt seen that when both 

la all my meaanrementB the second decimal is only iii^pTOTim«itd\3 wyrw*,. 



Family/ LikeneiB in Stature. 
FiOH. 5 «nd 6. 



parents have a deviate of +x, the mean of the deviates of all of their 
&milj centres will be +|x. It follows that if one parent only has 
that deviate ±z, and if the stature of the other parent is ankoown, 
and, therefore, on the avera^, mediocre, the mean of the statures of 
their children will be half the above amoiint, or ^. I cannot test this 
conclosioa very satisfactorily by direct observation, for my data are 
barely nnmerons enough to enable me to deal even with the mid- 
parentages. They are consequently insufficient to deal with a question 
involving the additional large nccertainty of the stature of one of the 
parents. I have, however, tabulated the data, but do not think it 
worth while to give them. They yield a ratio of regression of 0'40 
instead of 0'33 as above. I disregard it, and adopt the latter, namely, 

(3). From the stature of men of the same height to the mean of the 
statures of their mid-parents. By treating the vertical columns of 
Table MI in the same way as we have just dealt with the horizontal 
linos, we obtain results of the same general form as in the last para- 
graph but one, though of different values. 

Taking the height of a group of men of the same stature (viz., the 
" Adnlt Children ") as given in the line that forms the heading to 
the table, we find the median steture of all their mid-pareuts, whence 
I deduce in this case to^^. The apparent paradox that the same 
table should give results by no means converse in theii' values for 
converse deg^cs of kinship, will be more conveniently examined 
later on. 

(4.) From the statnre of men of the same height to the mean of 
the statures of all their brothere. In seeking for this I shall at first 
confine myself to the more accurate special data, reserving to the end 
a comparison bettreen their resulttt and those derived ttomtV©"B.SS. 
The eotrien in the column headed "medians" m TrM.6 X m» 



56 Mr. F. Galton. [Jan. 21, 

graphically represented in fig. 6, whence I deduce the value of 

VariahUity of Statures of " Go-kinsmen*^ about their common mean 
Value. — "Bj ** co-kinsmen " I desire to express the group distributed 
in any one line of Tables III, IV, V, or of other tables constructed 
on a like principle. They are the kinsmen in a specified degree, not 
of a single person, but of a group of like persons, who probably differ 
both in ancestry and nurture. For example, the persons to whom the 
entries opposite 68'5 in Table III refer are not brothers, but they are 
what I call " co-fratemals," or from another point of view, **co-filials," 
namely, the children of numerous mid-parentages, differing variously 
in their antecedents, and alike only in their personal statures. 

Co-filial Variability. — It appears from Table III that the mean of 
the quartiles derived fi*om the saccessive lines, and which I designate 
by /, is 1*5 inch ; also that the quartiles are of nearly the same value 
in all of the lines, allowance being made for statistical irregularities. 
A protraction on a large sheet of the individual observations in their 
several exact places, gave the result that the quartile was a trifle 
larger for the children of tall mid-parentages than for those of short 
ones. This justifies what was said some time back about the use of 
the geometric mean ; it also justifies the neglect here of the method 
founded upon it, on the ground that it would lead to only an insig- 
nificant improvement in the results. 

We have now obtained the values of the thi'ee constants in the 
general equation tu^p^+f-^p^, when it is used to express the relation 
between mid-parentages and cofilials. Thus the quartile of the popu- 
lation being p=zl'7, it was shown both by observation and by calcula- 
tion, that the quartile of the mid-pai*ental system was l/-v/2 .^j, or 1*21. 
It was also shown that the ratio of regression in that case was §, con- 
sequently the general equation becomes (|x l'2l)2-f-(l'5)2=(l'7)^ 
or 0*64-1- 2*25 =2*89, which is an exact accordance, satisfactorily 
crosis- testing the various independent estimates. 

Converse Ratios of Regression, — We are now sufficiently advanced 
to be able to examine more closely the apparent paradox that the 
ratio of regression from the stature of mid-parents of the same height 
to the mean of the statures of their sons should be f , while that of 
men of the same stature to the mean of the statures of their several 
mid-parents should be, not the numerical converse of this, but J. We 
may look upon the entries in Table III as the values of (vertical) 
ordinates in z to be erected upon it at the points where those entries 
lie, and which are specified by the arguments of " heights of mid- 
parents " written along the side, as values of ordinates in y, and of 
** heights of adult children " written along the top, as values of 
ordm&tea in a. The smoothed result would form a curved surface 
of frequency, I accordingly smoothed the table \>y -M^Titm^ «».\. ^«.^ 



1886.] Family Likeness in Stature. 57 

intersectioii of the lines that separated the vertical colamns with 
those that separated the horizontal lines, the sums of the four adja- 
cent entries. Then I drew lines with a free hand through all entries, 
or interpolations between entries, that were of the same value. These 
lines formed a concentric series of elliptical figures, passing through 
values of i that diminished, going outwards. Their common centre 
at which a was the greatest, and which therefore was the portion of 
maTimum frequency, lay at the point where both x and y were of the 
same value of 68^ inches, that is, of the value of the mean stature of 
the population. The line in which the major axes of the ellipses lay 
was inclined nearer to the axis of x than that of y. It was evident 
from the construction that the median value of the entries, whether 
in each line or in each column of the table, must lie at the point 
where that line or column was touched by the projection of one of these 
ellipses. It was easy also to believe that the equation to the surface 
of frequency and the lines of loci of the above-mentioned points of 
contact, admitted of mathematical expression. Also that the problem 
to be solved might be expressed in a form that had no reference to 
heredity. In such a form I submitted it to Mr. J. Hamilton Dickson, 
who very kindly undertook its solution, which appears as an Appendix 
to this paper, and which helps in various ways to test and confirm 
the appi'oximate and uncertain conclusions suggested by the statis- 
tical treatment of the observations themselves. I shall make frequent 
use of his mathematical res alts, both in respect to this problem and 
to another one (also given in the Appendix), in the course of my 
further remarks. 

As regards the present subject of the connexion between the regres- 
sion in direct and in converse kinships, it appears that it wholly 
depends on the relation between the quartiles of the two series of 
''arguments," and is expressed by the formula c^w^pho'. In this 
case c»=(l-21)*=l-46, and 2>'=2*89 ; also w;=f; therefore w'=^ 
nearly. 

It will be observed that in all cases of converse kinship, from man 
to man — as from man to brother, and conversely ; from man to nephew, 
and conversely ; from father to son, and conversely ; c=jp, therefore 
in these the ratio of regression is the same in the converse as in the 
direct kinship. 

Brotherly Variability, — The size of human families is much too 
small to admit of the quartile of brotherly variability being deter- 
mined in the same way as that of the population, namely, by finding 
the quartiles in single families, but there are four indirect ways of 
finding its value, which I will call h, 

(1.) A collection of differences (see Table VIII) between the statures 
of individual brothera, in familiea oi n brothers, and tliie Tnesiii oi ^V 
the n BtBtares in the same family, gives a quartile value, 'w\v\e\v\ '?i''0\ 



58 



Mr. F. GaltoD. 



[Jan. 21, 



call d, whence b may be dedaced aa followH: — Suppose an exceed- 
ingly large family (theoretically lufinitely large) of brothers; their 
qnartile would be b. Then if we select from it, at random, nnmeronn 
gronpB of n brothers in each, the means of the mid-deriates of 
the several gronps would form a series whose qnartils is l/v^nxb. 
Hence b is componnded of this valne and of d ; that is to say, 

62=,is+l/Bxfc« or fia=-^-,p. 

I treated in this way four gronps of families, in which the values of 
n were 4, 5, 6, and 7 respectively, as shown in Table YIII, whence 
I obtained for b the four valnes of I'Ol, I'Ol, 1'20, and I'OS, whose 
mean is 107, 

(2.) Let be the qnartile of a series of brotherly centres whose 
qnartile is unknown and has to be determined, and that the statnres 
of the individnal brothers diverge from their several family centres 
(7|Gi . . ., with a qoartUeb, the whole gronp of brothers thos forming a 
sample of the ordinaiy popniation ; conseqnently c^=j)'— 6*. Now in 
fig. 7, MS represents the deviate in statnre of a ^roap of like persons 




who are not brothers, and MG represeni« the mean of the mid-deviatea 
of their respective families of brothers. It can be shown (see Appendix, 
Problem 2) that if the position of c varies with respect to M with 
a qnartile = v^P*— t*, and if S varies with respect to e with a 
qnartile = b, then, when S only is observed, the most probable valne 
.CM, 



orb''=l^(l~m). 
Snbetitating 1-7 for p, and § for to, 

6=0-98 inch. 

(3.) It can also be shown (see Appendix, Problem 2) that the 

variability of particaUr mid-brotherly deviates, C|Cs . . ., abont C,the 



1886.] 



Family Likeness in Stature. 



59 



mean of all tbem, is snch tbat its quartile = -tt^ — r?-. ^ow ihe dis- 

tribation of Yalaes in each line of Table Y, whose quartile = /, is 
dne to the combination of two variables. The one is the variability 
of CiCi . . ., about C ; the other is the variability of the individual 
brothers in each family, about Gj, G^, &c., respectively. Therefore 

/^ ^ :5-rTQ+'**' Substituting for c* its value j?*—^^, we obtain 



c2 + 6» 



^=p(i>-y(l>2-/2)). 



The observed value of / in Table V is 1*24, whence we obtain 
6=110. 

(4.) Pairs of brothers may be taken at random, and the differences 
noted between their statures ; then under the following reservation, 
as regards the differences to be taken, we should expect the observed 
quartile of the difEerences to be = y/2 x h. The reservation is, that 
only as many difiEerences should be taken out of each family as are 
independent. A family of n brothers admits of n.n— 1/2 possible 
pairs, but no more than n— 1 of these are independent and only these 
should be taken. I did not appreciate this necessity at first, and 
selected pairs of brothers on an arbitrary system, which had at 
all events the merit of not taking more than four pairs of differences 
from any family, however numerous. It was faulty in taking thi-ee 
differences instead of only two from a family of three, and four 
differences instead of only three from a family of four, and therefore 
giving an increased weight to those families, but in other respects 
the system was hardly objectionable. On the whole the introduced 
error would be so slight as scarcely to make it worth while now to go 
over the work again. By the system adopted I found a quartile value 
of 1'55, which divided by v^2 gives &=110 inch. 

Thus far we have dealt with the special data only. The less trust- 
worthy R.F.F. give larger values of b. An epitome of all the results 
appears in the following table. 





Values of b obtained by 
different methods and 
from different data. 


Specials. 


R.F.F. 


(1.^ From families 


1-07 
0-98 
110 
110 


1-38 
1-31 
1-U 
1 35 


(2.) From w (Tables V and IV) .... 
(3.) From / (Tables V andl V) . . . . 
(4.) From pairs of brothers 

Mean 


1*00 





60 



Mr. F. Galton, 



[Jan. 21, 



The R.F.F. results refer to brothers only and not to transmuted 
sisters, except in method (2), where the paucity of the data com- 
pelled me to include them. I should point out that the data used in 
these foui' methods differ. In (1) I did not tise families under four. 
In (2) and (3) I did not use large families. In (4) the method of 
selection was as we have seen, again di£ferent. This makes the ac- 
cordance of the results still more gratifying. I gather from the 
above that we may securely consider the value of 6 to be less than 
1*10, and allowing for some want of precision in the special data, the 
very convenient value of 1*0 inch may reasonably be adopted. 

We are now able to deal completely with the distribution of 
statures in every degree of kinship of the kinsmen of those whose 
statures we know, but whose ancestral statures we are ignorant of or 
do not take into account. We are, in short, able to construct tables 
on the form of III, IV, and V, for every degree of kinship, and to 
reconstruct those tables in a way that shall be free from irregularities. 
The fraternal relation as distinguished from the co-fratemai has also 
been clearly explained. 

In constructing a table of the form of III, IV, and V, we first find 
the value of w for the degree of kinship in question, thence we deduce 
/ by means of the general equation tc^p^+f^^ji^ (p is supposed to be 
known, or for the general purpose of comparing the relative nearness 
of different degrees of kinship as tested by family likeness in stature, 
it may be taken as unity). The entries to be made in the several 
lines are then to be calculated from the ordinary tables of the " pro- 
bability integral." 

As an example of the first part of the process, suppose we are con- 
structing a table of men and their nephews. A nephew is the son 
of a brother, therefore in his case we have tr = ^ x f = ■} ; and 
/=2>v^(l-«;2),=l-66. 

Form of Data for calculating Tables of Distribution of Stature 

among Kinsmen. 



From any group of persons of the 
same height, to their kinsmen as 
below. 


Mean regression 

1C. 


Quartile of indiyidual 
Tariabilitj, 

/(=l>X-/(l-fP«). 


Mid-oarents 


2/3 

213 
1/3 
2/9 
1/9 


1-27 
1-27 
l-fiO 
1-66 

i-e9 


Brothers 


Fathers or sons 


Unclra or nephews 


Gh*andfatherB or erandsons 





Trtutworthiness of the Constants. — There is difficulty in correcting 
^Ae resnlia obtained soIeJy from the B..E.F. data, by help of the 
knowledge of their general inaccuracy ob coTo^gftaw^ "mV^ V5aa 



1886.] Family Likeness in Suuure. 61 

special data. The reason is tbat this inaccuracy cannot be ascribed 
to an nncertainty of eqnal + amonnt in every entry, such as might 
be dae to a doubt of '* shoes off" or *' shoes on." If it were so, the 
qnartile deviate of the II.F.F. would be greater than that of the 
specials, whereas it proves to be the same. It is likely that the in- 
accnracy is a result of the uncertainty above mentioned, which would 
increase the value of the quartile deviate, combined with a tendency 
on the part of my correspondents to record medium statures when 
they were in doubt, and which would reduce the quartile deviate. 
What the effect of all this might be on the value of w in Table IV, 
which is a datum of primary importauce, I am not prepared to say, 
except that it cannot be great. While sincerely desirous of obtaining 
a revised value of w from new and more accurate data, the provisional 
value I have adopted may be accepted as quite accurate enough for 
the present. 

Separate Contribution of each Ancestor to the Heritage of the Child. — 
I here insert a short extract from my paper in the " Joum. Anthrop. 
Inst.," with slight revision, as this memoir would be incomplete with- 
out it. 

When we say that the mid-parent contributes two-thirds of his 
peculiarity of height to the offspring, it is supposed that nothing is 
known about the previous ancestor. But though nothing is known, 
something is implied, and this must be eliminated before we can leaiii 
what the parental bequest, pure and simple, may amount to. Let 
the deviate of the mid-parent be x (including the sign), then the im-* 
plied deviate of the mid-grandparent will be ^a:, of the mid-ancestor 
in the next generation ^sp, and so on. Hence the sum of the deviates 
of all the mid-generations that contribute to the heritage of the off- 
spring is aj(l4- j4-|4-&c.)=ajf. 

Do they contribute on equal terms, or otherwise? I have not 
sufficient data to yield a direct reply, and must, therefore, try the 
effects of limiting suppositions. First, suppose the generations to 
contribute in proportion to the values of their respective mid-deviates; 
then as an accumulation of ancestral deviates whose sum amounts to 
x^, yields an effective heritage of only arf , it follows that each piece of 
heritable property must be reduced, as it were, by a succession tax, to 
J of its original amount, because f x ^=f . 

Another supposition is that of saccessive proportionate diminutions, 
the property being taxed afresh in each transmission to 1/r of its 
amount, so that the effective heritage would be — 



(-+3;3+3V+-)=*(3;3i) 



and this must, as before, be equal to arf, whence -= 



r U 



«2 Mr. F. Galton. [Jan. 21, 

A third possible supposition of the mid-ancestral deviate in any one 
remote generation contributing more than would be done by an equal 
mid-parental deviate, is notoriously incorrect. Thus the descendants 
of " pedigree wheat " in the (say) twentieth generation show no sign 
of the remarkable size of their mid-ancestors in that degree, but the 
offspring in the first generation do so unmistakably. 

The results of our only two valid limiting suppositions are therefore 
(1) that the mid-parental deviate, pure and simple, influences the 
offspring to |^ of its amount ; (2) that it influences it to the -^ of its 
amount. These values differ but slightly from ^, and their mean is 
closely ^, so we may fairly accept that result. Hence the influence, 
pure and simple, of the mid-parent may be taken as ^, of the mid- 
grandparent ^, of the mid-great-grandparent \, and so on. That of 
the individual parent would therefore be ^, of the individual grand- 
parent 1^, of an individual in the next generation -^^^ and so on. 

[I do not propose here to discuss the reason why the effective 
heritage of the child should be less than the accumulated deviates of 
his ancestors. It is obviously connected with considerations that 
bear on stability of type.] 

Pure breed, — In a perfectly pure breed, maintained during an in- 
definitely long penod by careful selection, w would become =0, and 
the value of h would be changed, but apparently only a little. Call its 
new value ft. It may be roughly estimated as follows. In mixed breeds 
the value of h includes the probable uncertainty of the implied value 
of the contributions inherited from tlie mid- grandparents, and from 
the mid-ancestry of each preceding generation. This can be but a 
trifle. Suppose the quartilo of the uncertainty in the implied stature 
of each grandparent to be even as much as 1*7 inch (we need not 
wait to discuss its precise value), then the qnartile of the uncertainty 
as regards the implied mid-grandparental stature would bel/\/4x 
that amount, or say 08. The proportion of this, which would on the 
avei*age be transmitted to the child, would be only ^ as much, or 0*2. 
From all the higher ancestry put together, the contribution would be 
much less than this, and we may disregard it. The result then is 
fc3=:/324.o-04. Taking 5=107, this gives /3=105 inch. 

Probable Stature of the Child when tJte Statures of several of his 
Kiusmen are knmon. — First we have to add their several contributions 
as assessed in the last paragraph but one, and to these we have to add 
whatever else may be implied. A just estimate of the latter requires 
the solution of a very complex problem. Thus : — a tall son has a 
short father; this piece of knowledge makes us suspect that the 
mother was tall, and we should do wrong to set down her unknown 
stature as mediocre. Our revised estimate would be further modified 
// we knew the atatare of one of her brotlaeTB, and so om. UloT^a^^t, 
the general equation tv^jp^+f^^p^ may cease to\io\d ^ood. TVi^^%. 



1886.] Family Likeness in Stature. 63 

sible problems are evidently very various and complicated, I do not 
propose to speak further about them now. It is some consolation to 
know that in the commoner questions of hereditary interest, the 
genealogy is fully known for two generations, and that the average 
influence of the preceding ones is small. 

In conclusion, it must be borne in mind that I have spoken through- 
out of heredity in respect to a quality that blends freely in inheri- 
tance. I reserve for a future inquiry (as yet incomplete) the 
inheritance of a quality that refuses to blend freely, namely, the 
colour of the eyes. These may be looked upon as extreme cases, 
between which all ordinary phenomena of heredity lie. 



Appendix. By J. D. Hamilton Dicksox. 

Problem 1. 

A point P is capable of moving along a straight line P'OP, making 
an angle tan~^-J with the axis of y, which is drawn through the 
mean position of P ; the probable eiTor of the projection of P on Oy 
is 1*22 inch : another point p, whose mean position at any time is P, 
is capable of movinpf from P parallel to the axis of x (rectangular 
co-ordinates) with a probable error of 1*50 inch. To discuss the 
" surface of frequency " oi }). 

1. Expressing the ** surface of frequency '* by an equation in a?, y, ^, 
the exponent, with its sign changed, of the exponential which appears 
in the value of z in the equation of the sui-face is, save as to a factor, 

^'' r,^^-^^' (1) 



(l-22)'^ • i)(l-50)=^ 

hence all sections of the " surface of frequency " by planes parallel to 
the plane of xy are ellipses, whose equations may be written in the 
form, 

(rfc+WW='^'''*^''''^'""* .... (2) 

2. Tangents to these ellipses parallel to the axis of y are found, by 
differentiating (2) and putting the coefficient of dy equal to zero, to 
meet the ellipses on the line, 

y ^ 3^-2// _^ ^ 
(1-22)2 -9(1-50)^ ' 

(3) 

that is '^=_JKi:M!_=_^ 

X 1 4 17-6 

(1-22)3^ 9(1-50)^ 

or, approximaMjr, on the line y=^x. Let this be tYie Wne OU. 



64 



Mr. J. D. Hamilton Dickson. 



[Jan. 21, 



From the nature of conjugate diameters, and beoanse P is tlie mean 
position of p, it is evident that tangents to these ellipses parallel io 
the axis of x meet them on the line d?=fy, vis., on OP. 

3. Sections of the '' surface of frequency " parallel to the plane of 
032;, are, from the nature of the question, evidentlj curves of frequency 
with a probable error 1*50, and the locus of their vertices lies in the 
plane 2OP. 

Sections of the same surface parallel to the plane of yz are got 
from the exponential factor (1) by making x constant. The result is 
simplified by taking the origin on the line OM. Thus putting x=Xi^ 
and y=y\'\-y\ where by (3) 



yi 



(1-22)2 ^-50)3 



the exponential takes the form 

4 



I a-2 



(1-22)2 9(i.50)« 



J^ Ul-22 



.+ 



f3aj,- 



(1-22)2 9(1.60) 



-2yi)n 

•60)8 / • 



. (4) 



whence, if e be the probable error of this section, 



+ : 



4 



^ (1-22)2 9(1-50)2 



or [on referring to (3)] e 



V 17( 



(5) 



that is, the probable error of sections parallel to the plane of y-? is 
nearly —y=. times that of those parallel to the plane of ajz, and the 

locus of their vertices lies in the plane rOM. 

It is important to notice that all sections parallel to the same co- 
ordinate plane have the same probable error. 

4. The ellipses (2) when referred to their principal axes become, 
after some arithmetical simplification, 



X 



'2 



— +-^ — :=constant (^^ 

20-68 5-92 ' ^^ 

the major axis being inclined to the axis of x at an angle whose 
tangent is 0*5014. [In the approximate case the ellipses are 

fll'2 i/'2 

— +^= const., and the major axis is inclined to the axis of x at an 
7 « 

angle tan""^|.] 

5. The question may be solved in general terms by putting 
YON=d, XOM=0, and replacing the probable errors 1*22 and 1*50 
hj a and h respectively : then the ellipses (2) are 



1886.] 



Famify lAktnet m Stature. 




t+ f'-y^'ty ^c (7) 

equation (3) becomee 

X 6*+a«tan*fl-' 

«nd (5) becomes U-.+^ .... (9) 

whence tan0 f 

tanff fcs ^'"^ 

If c be the probable on-or of the projection of p's whole motion on 
the plane of xi, then 

which is independent of the distance of p'B line of motion from the 
axis of ^. Hence also 



Problem 2. 
An index q mores andor some restraint np and down a bar AQB, 
ita mean position for any given position of the bai- being Q ; the bar, 
always carrying the index with it, moves nnder some restraint np 
and down a fixed frame YMY', the mean position of Q being M : the 
movements of the index relatively to the bar and of the bar relatively 
to the frame being qnitc independent. For any given observed posi- 
tion of q, required the most probable position of Q (which cannot be 
observed) ; it being known that the probable error of q rel&li.iel'j ia 



66 



Mr. J. D. Hamilton Dickson. 



[Jan. 31, 



Q in all positions is &, and that of Q relatively to M is c. The ordi- 
nary law of error is to be assamed. 

If in any one observation, MQ=fl!, Q9=t/, then the law of error 
requires 



c2"*"6« 



(12) 



to be a minimum, subject to the condition 

x+y=aj a constant. 
Hence we have at once, to determine the most probable values of 






X y a /'^Q^ 



and the most probable position of Q, measured from M, when g's ob- 
served distance from M is a, is 



ra. 



It also follows at once that the probable error v of Q (which may 
be obtained by substituting a^x for y in (12) ) is given by 

he 

(14) 



1 1^1 

v^ c» 5> v/^s-hc^ 



which, it is important to notice, is the same for all values of a. 

Throughout this discussion the technical term " probable error " has 
been used ; it may in every instance be replaced by Mr. Oalton's very 
apt'name *' quartile," in which case the results of these problems may 
be read in conjunction with Mr. G-alton's papers. 



1886.] 



Family Likeneta in Stature. 



67 



Table I. 
Ogive, or Normal Curve of Distribation of Error. 





Corresixmding ordinates (or deriateH) . 


AbeciiMD reckoned from 
, (fto ±5(f (ralue of the 
probability integral). 

f 


Value of the 

deyiate when 

modulus ■» 1, 

A. 


Value of deriate 
reduced propor- 
tionately to 
quartile = 1, 
B. 


! 10 
20 
Qiurtile 25 
30 
40 
46 


179 
0-871 
0-477 
0*595 
0-906 
1-163 


0-88 
0-78 
1-00 
1-26 
1-90 
2-44 



Table II. 
Comparison of observed Ogives witli the Normal. 



« 


Absciss® of the half-ogiye. 


Value 
of the 
unit in 
inches. 


Normal ogirc, from Table I. . . . 

j General population, B.F.F 

Population of brothers, B.F.F. . 

„ „ specials. 

Mid-parcntagee 


10. 


20. 


25. 


30. 


1 
40. 

1-90 
2 06 
1-95 
1-92 
2-12 
2 11 
1-88 


45. 


0-38 
0-33 
0-36 
0-38 
0-35 
0-47 
0-42 


0-78 
0-74 
0-78 
0-79 
0-79 
0-84 
0-78 


1-00 
1-00 
100 
1-00 
100 
100 
100 


1-26 
1*23 
1-41 
1-26 
1-28 
1-29 
1 25 


2-44 
2-62 
2 12 
2-46 
2-78 


1-00 

1-7 

1-7 

1-7 

1-2 


Brothers in random pairs, B.F.F. 
,, „ 8i)ecial8. 

i 


2-64 
2-44 


1-4 
1-4 



Note. — Tlic second decimal is only approximate. 



V I 



Mr. J, U. Hamilton Dioksoii. 



[Jan. 21. 





1 


ssssseess 








•5 

i 
1 


4 


-"sssssas— ' 


i 




•s 

1! 

SI 


H 


-SS8a2Sg8!i3 


i 




i 

1 
•s 

1 


1 


.vnmio ...... 


3 




k 




a 




z 




s 


s 


•al 

n 

§5 


— 


i-'-SSS :" : : 


s 


9 

s 


E 


:-S3Sa2'" : : 


s 


9 

8 


8 


i^-SSSSS-"- 


£ 


i 


SJS 


5 


:-"2SSS3:- :- 


S 




|! 


: :-"S3SE3"- 


s 


s 


S 


: :"-ESiS = -=" 


s 


£ 


is 


S 




s 




8" 


2 


::::3S3-"-|s 


£ 






u 


9= 


•s 


1 


:.•::::"»:-: 


" 




•5 




" 


J 


k 






■S-" 




1 




I 







1886.] 



Family IJikeaete in Stature. 



1 


ggissssse 




II 


2SS33SS|SSSS-" 


i 


1 

J 

■s 

1 


is 


•"■"»"-:-:-:::: 


= 


S 


":-"-"--::::;- 


s 


8 


""°a-"°- :--"- ;- 


s 


-"S'SSS"-'" : : 


s 


S 


f — m«»^^«i. »•#« .-H 


§ 


« 

S 


"""sgsssaa*' : : 


S 


s 


: - - = 3 S S S - • - : : - 


8 




-- :--»22s3-"-' :- 


s 


: : - - .- 2 > 3 a . - - : : 


J 


i 


- . -fisin -J !!»»■* — « , 


s 


s 


. .u-*fae>ni-f<s . . 


8 






2 


:::::::;:--::: 


" 


Is 




. 


ii 






... 


ri 


1 1 



70 



ilr. J. D. Hamilton Dickson. 



[Jan. 21, 



OS 

Q 



GQ 

1 



cB 

s 

2 



OQ 
0) 



§ 

n 

o 'O 

>s 

o S 

=1 

^ 08 

w « 

00 



o 

I 



;^ 



e 

e 

O 









'3 2 



o 

a 






Of 



5 



'^^c^aOfHOOeoAkOO'^Qeo 



S3 

00 






04 CO lO 



N 



^ 



CO 



coNoo'foo^eoi-H 



s 



g 



udooaoodO>u3co<Hi-i 



* 



CO 



^ iH 1-^ 1-^ 



s 



o 



pH 00 '^ CO ^^ 



CO 



00 
CD 



CO CO ^E O CO 



^r O CO CO 
^* R 00 CO ^ 



CO 
00 



00 *o ^ 



Ol 



kO 

CO 






CO 00 00 00 



\a 



yit^i-ioouiaoeoooO'^ 

fH r-l' eO yi CO ^ 



04 

uo 



to 
»o 

CO 



O) CO 00 X kO 00 00 
Ol CO fH 1H 



to 



fHOiiqaoOkooixco 



CO 



to 



»Hi-l"*C0C0»O|kO 



Ol 



-IS 



iM ^ 00 00 to lO 



CO 
Ol 









glOtOtOlOkOkOUOtOlOkOiO 



"^ CO ©1 ^ o 

t* t^ t^ t>. l> 



8 00 i<« CO kO 
^ CO CO CO 



SCO 00 
CO CD 




04 



kO 




























• 


r^ 


'f 


kO 


X 


s? 


lO 


CO 


o 


04 


M 


Ol 


^ 


^^ 


CO 








l-J 


lO 


00 


Ol 


rH 






• 


s 



: \. . \ 



1)}86.] 



FeanUy LUctnest in Stature. 



il 

3 = 

■£'-i 
■ . J 

! S S 
' 'Sf'S 

I i 

a 
1 1 



*s 


^1 




"-"-SSSSESSSSi ■ 


if 
P 


«asg||i||||i|| .. 


lit 


-d!SSSSS||||SSSS ; 


a 
1 


il 




""""-SligSSSSSgS 


1 


-"-8SSS|?|S2ig| 


■=1 


^-"ssisssssgiiass 


s 

1 
1 

1 


ii 




oo_,_2s?sasgsgs 


'4 


-"2S|si?i«giSli 




<"-SSSSS|S8S3S3 


s 


Hi, 


-i «■ «■ *■ « i ,i i i 6 ^ A A ■* ^ 



Family Likenett in Stature. [Jan. 21, 



■i 
i 

1 
•5 

1 

1 
1 


S 


i s s 


3 


S3 S 


5 


K?8 
S ' * 


^ 


3 ■* ■* 


■* 




3 

+ 


e s £ 


? 


!!S 


s 


3 8 8 


^ 


3 

+ 


s s s 


? 


1-! 


s 


" S S 


s 


+ 


!S! 


s 


3 2 E 


? 


B .I » 


! 


S 


B .• ^ 


! 


S ~ 5 


^ 


£!! 


s 


o 


s s s 

t- o o 


o 


?«8 

(O O O 


o 
b 


!i! 


b 


o 


S!88 

». o o 


I 


Is? 

r- o o 


SS8 

to o O 


? 

a 




3 

1 






S8 : 

8 •» 


K E ; 




1 


!! 


^ 


!! 


1 


s s 


!! 


9 

1 


£ ? 


1 


« « 


! 




ST 
fa 

! 


i 

■s 


! 

E 
•8 

J 



1886.] 



Early Development of Julus terrestris. 



73 



Table VIII. (Special Data.) 

Nninber of cases in which the Stature of individual Brothers was 
found to deviate to various amounts from the Mean Stature of 
their re8X)ective fiEunilies. 



Number of brotben in each fiimilj 


4 


5 


6 


7 




39 


23 


8 


6 




Amount of deriation. 


Number 
of cases. 


Number 
of cases. 


Number 
of cases. 


Number 
of cases. 


TJndftT 1 incb •tt»,T,trTTT...t,rTT 


88 
49 
15 

4 

* • 


62 

30 

17 

3 

3 


20 

18 

5 

2 


21 

14 

6 

1 

• • 


1 Mid under 2 


2 ^nd UndW 8 . t - - T T t T . . T . t T . t t - T 


3 and under 4 


4 and aboTo 





IL *' The Early Development of Julua terresirisJ** By F. G. 
Heathcote, M.A., Trin. Coll. Cam. Commmiicated by 
Professor M. Foster, Sec. R.S. Received January 6, 1886. 

The following are the principal results of my investigations on the 
early development of Julus terrestris since June, 1882. 

When laid the eggs are oval in shape, white, and covered with a 
thick chitinous chorion. The nucleus is situated in a mass of 
protoplasm in the centre of the ovum. This mass of protoplasm is of 
irregular shape, but its long axis corresponds with that of the ovum. 
From it, anastomosing processes radiate in all directions, forming a 
network throughout the egg. The yolk-spherules are contained 
within the meshes of this network. The nucleus is not a distinct 
vesicle but its position is marked by chromatin granules. There is no 
nucleolus. 

Early on the second day the nucleus and the central mass of 
protoplasm apparently divide into two parts. But this division is not 
complete, the two resulting masses with their nuclei remaining con- 
nected by a network of protoplasm. Each of these divides in the 
same incomplete manner, so that we now have four segments all 
connected together. This process is continued until there are a 
considerable number of segmentation masses present, and early on the 

* Mr. J. D. OibaoD Carmichael, F.L.8., has kindly ident\&ed t\ve «^cvft^ lot tcl^ ^a 
,/Mf/M^ /errar/rtj'. Leach, 1814. 



74 Mr. F. G. Heathcote. [Jan. 21, 

third day the first formation of the blastoderm begins. Early on the 
third day some of the segmentation masses make their appearance on 
the ontside of the ovnm at different parts, and there undergo rapid 
division, the resulting cells spreading out to form the blastoderm. 
At the close of the blastoderm formation, the ovum consists of an 
external layer of flat cells — the epiblaast — ^with deeply stained oval 
nuclei, these cells being continuous on the one hand with one another, 
and on the other with the cells in the yolk by means of fine processes 
of protoplasm. The cells in the interior of the yolk are the direct 
descendants of the first segmentation masses. They constitute the 
hypoblast. 

The fate of these hypoblast cells is various ; some of them are 
employed in the formation of the mesoblastic keel which I am about 
to describe, that is, in the formation of the splanchnic and somatic 
mesoblast. Another part gives rise to the hypoblastic lining of the 
mesenteron, while a third part remains in the yolk after the 
mesenteron is formed, and g^ves rise to mesoblast cells which are 
employed in the formation of various muscles and of the circulatory 
system. 

With regard to the retention of the primitive connexion of the 
cells of the ovum until this stage, nothing of the sort has, I believe, 
been described before except by Sedgwick in Peripatus. The most 
important part it seems to mc is not the connexion of cell to cell but 
of layer to layer by means of processes of the cells. 

About the middle of the fourth day several of the hypoblast cells 
approach the epiblast in the middle line of what will eventually be 
the ventral surface of the embryo. This is the first beginning of a 
mesoblastic keel such as Balfour has described for Agelena 
lahyrinthica. When a fair number of these cells are assembled in the 
middle line of the ventral surface a change takes place in the cells of 
the epiblast just outside them. They become more rounded, their 
nuclei become round ; in fact they come to resemble the cells which I 
have described as assembling immediately below them. 

The epiblast colls in the middle ventral line after altering their 
shape increase by division and take a considei^ble share in the formation 
of the keel. The hypoblast cells below them also increase, and on the 
fifth day the mesoblastic keel is complete. Both epiblast and 
hypoblast have taken part in the formation of this keel. 

At the end of the sixth day the keel is still present, but the cells of 
which it is composed are becoming elongated in the direction parallel 
to the surface. At the same time they continue to multiply and 
spread themselves out so as to form two definite layers within the 
epiblast. These are the splanchnic and somatic layers of the 
mesoblast. The cells of the splanchnic and ^omatio mesoblast are 
connected. 



1886.] Early Development of JuIur teiTestris. 75 

On the sevenih and eighth days the keel gradnallj difiappears, and 
the layers of mesoblast spread round a great part of the embryo, 
rather more than half way round. On the ventral snrface the 
epiblast cells assume a columnar form, thus giving rise to the ventral 
plate. 

The mesoblast now becomes thicker on each side of the middle 
ventral line. Both layers are concerned in this thickening, and at 
these points the two layers become indistinguishable. Outside the 
thickenings, that is further away from the middle ventral line, the 
two layers are closely applied to each other, and to the epiblast as 
before. The effect of these changes is that the greater part of the 
mesoblast is now arranged in two parallel longitudinal bands along 
the ventral surface of the embryo ; these bands being connected across 
the middle line by a thin portion consisting of a single layer. 

The two longitudinal bands now begin to be constricted off into the 
mesoblastic somites. The latter are formed from before backwards, 
and their position corresponds with that of the future segments of the 
body. The number of the somites is eight, corresponding with that 
of the eight segments with which the embryo is finally hatched. The 
somites are at first solid, afterwards a cavity appears in them. 

Early on the ninth day the stomodaram is formed as an invagination 
of the epiblast near one end of the ventral surface. Shortly after 
the first formation of the stomodaBum, the proctodsBum appears as a 
shallow somewhat wide invagination of the other end of the ventral 
sur&ce. 

The body-segments already established by the segmentation of the 
mesoblast now become more apparent, each being marked by a deep 
transverse farrow in the epiblast. The hypoblast cells are still 
present within the yolk, but are gradually becoming collected in the 
median line, just below the mesoblastic bands. The stomodaBum and 
proctodeum become more deeply invaginated, extending a considerable 
distance into the yolk, and at the same time the hypoblast cells 
begin to form the mesenteron, arranging themselves around a central 
lumen. 

On the tenth day the ventral flexure is formed by a deepening of 
the transverse furrow between the seventh and eighth segments. It 
is, therefore, first formed nearer the anal end of the embryo. As the 
furrow deepens and the embryo increases in size, the last segment 
grows in length. At the same time the embryo curves round towards 
the ventral surface. The effect of this is that the end segment is 
bent round against the head. The eighth segment is considerably 
longer than the others except the head, and the tissues there show a 
considerable difference. Even as late as the twelfth day, when the 
neryojis sjrstem is far developed in all other parts oi ttie )Qod"^>\a.^Vi^ 
eif^bth segment the tissues are imperfectly differentiBAi^^L^ \>Dkft Tv«r^^ 



76 Early Development of Julus terresfadfi. [Jan. 21, 

cords not showing anj ganglia, bnt lying on the epiblast and not 
quite separated from it. At a later period of development the anal 
segment is constricted off from this segment, while from its anterior 
part the fntare segments formed in the course of development are 
developed. 

Just before the appearance of the ventral flexure the embryo 
develops a caticnlar envelope over the whole snrface of the body. 
This is the so-called amnion of Newport. Jast before the formation 
of the ventral flexore the nervous system is formed. The first traces 
of this consist in a thickening of the epiblast on each side of the 
middle line. This is soon followed by the formation of a shallow 
furrow between the thickened parts ; this longitudinal furrow 
corresponds with that described by Metschnikoff in Strongylosoma. 
The bUobed cerebral ganglia are formed first, and the nerve cords are 
formed from before backwards, a pair of ganglia being present for 
each segment except the last. The posterior portion of the nerve 
cords is completed at a considerably later stage of development. 
The nerve cords are widely separated, but are connected by a thin 
median portion. In later embryonic life they are closely approached 
to one another, and almost form one cord. 

On the eleventh day the embryo has increased considerably in size. 
The ventral flexure is complete, and the animal lies with the long 
end segment folded closely against the rest of the body, the end of 
the tail being against the stomodsoum. The nervous system is now 
sompletely separated from the epiblast, and the epiblast has 
assumed the adult form. It now separates a second membrane like 
that which is formed on the tenth day. 

The splanchnic layer of mesoblast covers the mesenteron, the 
stomodsBum, and proctodsBum. 

Within the yolk, which is still present in great quantity in the body 
cavity, there are present a namber of hypoblast cells. These, as have 
already been mentioned, give rise to the circulatory system and to 
various muscles. They may, therefore, be now considered as 
mesoblastic cells which have been directly derived from the hypoblast. 

On the twelfth day the Malpighian tubes are formed as blind 
oatgrowths of the proctodasum, the nervous system is further 
developed, and the first rudiments of the appendages begin to appear. 
Late on this day the animal is hatched with only the rudiments of its 
appendages. I propose to reserve a full description of this stage for a 
future paper. 



1886.] 



On Radiant Matter Spectroscopy. 



77 



IIL ^Qn Radiant Matter Spectroscopy : Note on the Spectra of 
Erbia.** By William Crookes, P.R.S. Received Jan. 7, 1886. 

I liave recentl J succeeded in getting the earth erbia in a sufficiently 
poie state to allow me to examine its phosphorescent spectrom without 
the interference which might be produced by the presence of yttria, 
samaria, holmia, thulia, Y» or ytterbia. As in the case of yttria* 
the spectrum is best seen when erbic salphate is heated to redness and 
submitted to the electric discharge in a high vacuum. The addition 
of calcic sulphate interferes with the purity of the spectrum. In this 
respect erbia differs from samaria, as the latter earth seems to require 
the presence of some other metal to develop its phosphorescent 
properties. 

The phosphorescent spectrum of erbia consists of four green bands, 
of which the following measurements have been taken : — 



Scale of 


X 


1 


1 Bemorks. 


speotRMcope. 




X« 




9-750° 


5564 


3230 


Approximate centre of a \\-ide 


■ 






band, shading off at each side. 


9-650" 


5450 


3367 


Approximate centre of a band, 
narrower and somewhat fainter 
than the first band. 


9-525** 


5318 


3536 


Approximate centre of a narrow 
band, bright and moderately 
sharp on each side. 


9-40tf* 


5197 


3702 


Approximate centre of a band, 
similar in appearance to the 






• 


first band, but brighter. 



Fig. 1 shows the erbia phosphorescent spectrum drawn to the — 

X 

scale. 

These bands do not correspond in position to any in either the 
yttrium or samarium spectrum. The nearest approach to a coinci- 
dence is between the first erbia green and the samarium green, but 
when the two spectra are examined one over the other it is seen that 
the samarium band is less refrangible than the erbium band. 

The first green of Ya occurs midway between the first and second 
greens of erbia, and the second Y« green comes between the second 
and third erbia greens. 

Pure erbia is of a beautiful rose-pink colour.f When illuminated 

• " PhU. Trans.," vol. 174, p. 913, par. 71. 

f Koee-coloured erbia has already been obtained by Professor Cl^ve, who a year 
ago presented me with a Bpecimen of the earth as pure as the one 'w\v\c\i \^ >i)c!kft wJNi- 
jeet of this paper. 



78 On Sadiant Matter Sptctroteops. [Jan. 21, 



Fig. T. 




■H 


Tra. 2 


1 


'' 1 






UHMl^^H 


Fio.B 


'T ' ' 


II 


Fis. 1 




■■ 


Fio. r, 


■Hiiiiii 



by Biin or clectiic liglit and examined in the spectroscope it gives a 
Bpectmm of block lines and bands aa sharp and distinct aa the 
Fnanhofer lines. Fig. 2 shows the crbia spcctrnm bj reflection. 
It is strange that this moat characteristic property has bees recorded 
hj BO few observers. Indeed, the only notice of it I have come 
across is a passing remark of Profensor CK'vo's that "the light 
reflected by dry erbia shows absorption- bands." 

Pig. 8 shows the nbsorptioa spectnun given by a solntion of pare 
erbic chloride. It differs in some respects from tie drawings mapped 
from older observations, as the absorption lineH of holmia and thnlia 
lire absent. The fine group of lines in the green of the reflection 
flpoctmm is also absent in the absorption specti-am. 
The spectrum of bright lines enutted w\xei\ et\yiB, w TenS-weft. 
fncaDdeaceut m the blowpipe flame baa been ot\«no^»l6T^«au,^aTA\^l» 



188ti.] The Clark Cell a Standard of Electromotive Force. . 79 

lines in ihia oase are luminons on a fainter continuous background 
and are noi particularly sharp, whilst the reflection spectrum consists 
of Uaok lines sharply defined on a continuous spectrum. 

The ■peotmm emitted by incandescent erbia is shown in fi^. 4. 

Fig. 5 shows the characteristic lines in the spark spectrum of 
eAuun, taken from a concentrated acid solution of erbic chloride, 
with a Leyden jar in a shunt circuit. 

I haye thought it advisable to g^ve these five spectra of erbium, as 
they show how entirely different the phosphorescent spectrum is to 
any other spectrum given by this element. 



IV. " On the Clark Cell as a Standard of Electromotive Force." 
By the Lord Raylkigh, M.A., D.C.L., Sec. R.S. Received 
January 7, 1 886. 

(Abstract.) 

This paper, supplementary to that " On the Electrochemical Equi- 
valent of Silver, and on the Absolute Electromotive Force of Clark 
CeUs,"* gives the further history of the cells there spoken of, and 
disonsses the relative advantages of various modes of preparation. 
The greatest errors arise from the liquid failing to be saturated with 
zinc sulphate, in which case the electromotive force is too high. The 
opposite error of ^nper-saturation is met with in certain cases, 
especially when the cells have been heated during or after charging. 
Experiments are detailed describing how cells originally supersa- 
turated have been corrected, and how in others the electromotive 
force has been reduced by the occurrence of supersaturation conse- 
quent on heating. If these errors be avoided, as may easily be done ; 
if the mercury be pure (preferably distilled in vactio), and if either 
the paste be originally neuti*alised (with zinc carbonate), or a few 
weeks be allowed to elapse (during which the solution is supposed to 
neutralise itself), the electromotive force appeal's to be trustworthy 
to T^sV? pft^* This conclusion is founded upon the comparison of 
a large number of cells prepared by the author and by other physicists, 
including Dr. Alder Wright, Mr. M. Evans, Dr. Fleming, Professor 
Forbes, and Mr. Thi'elfall. 

As regards temperature coeflScient, no impoHant variation has been 
discovered in saturated cells, whether prepared by the author or by 
others. In all cases we may take with abundant accui^acy for ordinaiy 
applications — 

E=l-4:35{1- 0-00077(<-15°)}, 

the temperature being reckoned in centigrade degrees. For purposes 
of great delicacf it is advisable to protect the 8taTvdaTt3L& iTOixi \ax^^i 

* "Pbil. Trans.," vol. 175, 1884. 



• 



80 The Clark Cell a Standard of Electromotive Force. [Jan. 21, 

flaotnations of temperatiire. Under favonrable circmnBtances two 
cells will retain their relative valnes to -n^^ for weeks or months 
together. 

Unless carefallj sealed np, tbe cells lose liquid bj ezndation and 
evaporation, and then the electromotive force g^radnallj falls. Marine 
glue appears to afford a better protection than paraffine-waz, and 
there seems to be no reason why cells thus secured should not remain 
in good order for several years. 

In cells of the H-construction (§ 29 of former paper) the leg con- 
taining the amalgam (but not tbe one containing pure mercury) is 
liable to burst, apparently in consequence of a tendency to alloy with 
the platinum. Protection with cement of the part of the platinum 
next the glass has been tried, but no decisive judgment as to the 
adequacy of this plan can as yet be given. 

Recent cells, intended for solid zincs, have been made of a simplified 
pattern — nothing more, in fact, than a small tube with a platinum 
wire sealed through its closed end. The zincs are not recast, and the 
paste is prepared from (unwashed) mercurous sulphate rubbed up in 
a mortar with saturated solution of zinc sulphate and a little zinc 
carbonate. A stock of paste may be prepared and retained for use in 
a bottle. 

Experiments are described tending to prove that the irregularities 
observed during the first few weeks of the life of a cell prepared with 
acid materials, have their origin principally at the mercury electrode. 

Cells prepared with dilute solutions have a lower temperature 
coefficient (about 0*00038), but would be more difficult to use as 
standards whose value is to be inferred from the mode of preparation. 

Details are given of H-cells charged with amalgams of zinc and 
mercury in both legs, without mercurous sulphate. A very small 
proportion of zinc is sufficient to produce the maximum effect. Pure 
mercury, neither alloyed with zinc nor in contact with mercurous 
sulphate, has an uncertain electromotive value. 

Since the comparison of cells does not absolutely exclude a small 
general alteration of electromotive force with age, further determina- 
tions of the standard cell (No. 1) have been effected by means of the 
silver voltameter. The results — 

Table XVIU. 

E.M.F. of No. 1 at 15'* C. 
Date. in B.A. Tolts. 

October, 1883, to April, 1884 1 -4542 

November, 1884 1 4540 

August, 1885 1-4537 

are very satisfactoryf and indicate a conatancy sufi&cvencLt ioT almost all 
practical parposes. 



1886.] New Volcanic Island in the Pacific Ocean. 8 1 

Finallj, some comparisons are g^ven between Clark cells aod 
Daniells, with eqni-dense solations, both of Baonlt's pattern and uf 
that described recently by Dr. Fleming. 



V, " Account of a new Volcanic Island in the Pacific Ocean." 
By Wilfred Rowell, H.B.M. Consul in Samoa. In a 
letter to the Hydrographer of the Admiralty. Received 
January 17, 1886. 

JEydrographic Department^ Admiralty, 8. W., 
Sib, 16th January, 1886. 

I HAVE the honour to forward to you a photograph and a copy of 
a letter received from H.M. Consul at Samoa, relating to a volcanic 
island recently formed by a submarine volcano, in the vicinity of the 
Friendly Group in the Pacific Ocean, which I think may be of interest 
to the Royal Society. 

I also forward a chart of the locality showing the position of the 
new island. 

It is unfortunate that, as the hydrographical knowledge of the 
vicinity is very imperfect, no information exists as to the depths from 
which this island has pushed its way. 

(Signed) W. J. L. Wharton, 
The Secretary, Boyal Society. Hydrographer, 

(Enclosure.) 

H.B.M. Consulate, Samoa, 
Sib, November 2l8t, 1885. 

I HAVE the honour to report that whilst on a passage from the 
"Friendly" Islands to the "Navigators" Islands, on board the steam 
ship " Janet Nicoll,** we observed a newly-risen volcanic island. I was 
informed in "Tongatabu" that the eruption was first remarked from 
that island (a distance of over 40 miles) on Tuesday, 13th of October. 
We passed it on Sunday, the 8th of November, at a distance of alx)ut 
1^ miles. 

The following will be the approximate position by compass bear- 
ings : — 

Peak of "K[ao*' Island over centre of "Tefoa" Island, north by 
east. 

West end of '* Honga Tonga" Island, south by east. 

Centre of crater from ship west 1^ miles. 

The island appeared to he about two miles in lei\gt\vuoT\ik\i^ ^'?^\» 
snd south bf east, of about 200 feet in height, having a xee^ ox^ ^^^^ 

VOL. IL, O 



88 



New Voleanie Iiland in tht Pac^ Ocean. [Jan. 21, 
a extent, with one also to the sonth- 



norflum extremity of half a mQs ii 
ward of 1^ miles (approz.). 

I bare the honour to enclose a photograph which I took at the time 
the island bore west 1^ miles, and which although very inferior and 
taken under circamatanoeB of conaideiable difficnity, will give some 
idea of the appearance of the emptioD. 

(Signed) WiLraxD Bowell, 
To the Eydrographer of the E.B.M. Oontut, Sainoa. 

Admiralty, WhUehaU. 




1886.] On Local Magnetic Disturbance in lelande. 88 



January 28, 1886. 

Professor STOKES, D.C.L., President, in the Chair. 

The Presents received were laid on the table, and thanks ordered 
for them. 

The following Papers were read : — 

I. "On Local Magnetic Disturbance in Islands situated far 
froTn a Continent.** By Staff-Commander E. W. Creak, 
R.N., F.R.S., of the Admiralty Compass Department, 
Received January 11, 1886. 

[Platb 1.] 

It has been known for many years past that in the inlan'^s of 
St. Helena and Ascension observations of the three magnetic elements 
made at different stations gave remarkably divergent results, cansed 
by some xmdefined local magnetic attraction. 

Thus in the observations at St. Helena,* carried out under the 
auspices of the British Government in 1 840-46, it was found that the 
observed inclination and intensity differed considerably at the two 
stations of Longwood and Sister's Walk, 2^ mUes apart, and these 
again differed from those made on board ships in the anchorage. 

This question of local magnetic disturbance is one which has 
engaged the attention of observers on continents and islands adjacent 
to them, in making magnetic surveys, when sometimes large areas 
have been found affected, and in others but very small ones. In such 
cases the normal values of the three magnetic elements have been 
obtained either by calculation from observations made in supposed 
undisturbed districts, or by graphic methods. 

Thus in discussiner the results of the magnetic survey of Scotland, 
made by the late Mr. Welsh in 1857-58,t Professor Balfour Stewart 
obtained the values of the local disturbances in the islands of Skye 
and Mull by calculating the normal lines of equal values of the 
magnetic elements for the mainland of Scotland, and extending 
beyond the adjacent islands on the west coast. 

* See pp. 60, 61, toI. i of Obserrations made at the Magnetioal and Meteoro* 
logical Observatorj at St. Helena. Published under the Buperinteadenoe ot 
Lt.'Colonel Sabine, 1847. 
f Magnetic Surrey of ScoOtuid. See Eeport of British AfiftociaAioiv, \W>^ . 



84 Staff-Commander E. W. Creak. [Jan. 28, 

As an instance of nnnsaal local disturbance in that part of the 
British Islands, the Compass Hill in the island of Canna,* near Skje, 
may be mentioned. Here the disturbance was sufficient to render a 
compass useless, and every small movement of the observing instru- 
ments gave different results. 

For Ascension and St. Helena, and some other islands situated far 
from a continent, normal values of the magnetic elements have been 
obtained from observations at sea, and the object of this paper is to 
show how this may be done, and the resulting amount and nature of 
the disturbances in the islands visited. 

The following values of the three magnetic elements observed at 
eleven islands represent the data collected for this purpose. 

An inspection of them shows that they consist of a series of obser- 
vations made on land, and which when made at different stations on 
the same island g^ve divergent results caused by some local magnetic 
disturbance. 

In order to obtain undisturbed or normal values, observations made 
on board ships, in which the amount of magnetic disturbance is 
known, have been adopted. 

These normal values obtained on board ship are from observations 
made with the ship's head placed on eight or sixteen azimuths 
equally distributed round the horizon in the process called " swinging," 
all effects of the iron of the ship being eliminated by the methods set 
forth in the "Magnetical Instructions for H.M.S. * Challenger.' " 

It is important to note that these swingings took place in the neigh- 
bourhood of the island to be magnetically examined, and some small 
corrections had to be applied for differences of geographical position 
from the land stations. An example is given below of the method of 
deriving the normal values of the magnetic elements for a position on 
the green outside the Dockyard, Bermuda, f 

The observations have been divided into two sections — first, those 
made on islands situated north of the magnetic equator, and in which 
the local disturbances have been generally found to be due to an 
excess of blue^ magnetism above the normal ; secondly, those made on 
islands situated south of the magnetic equator, in which the disturb- 
ances are generally caused by an excess of red magnetism. 

Section L — Islands situated North of the Magnetic Equator, 

Bermuda Islands. 

The Bermuda group is that on which a more complete series of 

• Topographically and magnetically examined by the late Captain Evans, R.N. 
t This position has been selected as the declination is there almost undisturbed. 
It appears to be a toitable place for f atnie ofaeermtions. 

t In a freely suspended magnet the north-seeking end has red magnetism, the 
oiher end blue magDetUnL 



1886.] On Local Magnetic Disturbance in lelande* 



85 



observations has been made than in the other islands, and as the re- 
sults are remarkable they are the first to be discussed. 

Table I shows some valaes of the declination observed previously to 
the ** Challenger's " visit in 1873, but reduced to that epoch by allow- 
ing an annual change of 2* increasing. This annual change has been 
deduced from the best available observations at four stations. 



Table I. — Declination at Bermuda, 1873. 




Station. 


Declination. 


DiiferenoB 
from normal. 


Observer. 


Bastion C, Ireland Island 

i> n 

»» »» 

Fort Cunningham Flagstaff 

Hen Island Magazine 

(Near) lighthouse on G>ihbs' Hill . . 
In the dockyard 


8 00 „ 

6 26 „ 
5 00 „ 

7 64 „ 
3 56 „ 
7 30 „ 

9 00 „ 
7 12 „ 
7 13 „ 
7 19 „ 
7 18 „ 


+ 0* C 
+ 42 
-0 52 
-2 18 
+ 36 
-3 22 
•fO 12 
+ 1 42 
-0 06 
-0 05 
+ 01 
Normal 


Hill. 
Bamett. 
Bodie. 
Bamett. 

Bodie. 
Hill. 
Lefroy. 
Bodie. 

» 
" Challenger:' 


Mount Lanirton ...... t ......*. . 


Anchorage fH.M.S. "Boscawen" 

in Grassy < „ " Comwallis" 

Bay. L „ "Pembroke" 

Qreen outside dockyard 



In Table 11 are recorded the magnetical results of the *' Challenger" 
observed at Bermuda in 1873. 

In Tables I and III will be found the differences between the 
observed magnetical elements and the normal values at a station on 
the green outside the dockyard, deduced from the results of swinging 
in a position 15 miles south of it. 



Results of swinging at sea, 
corrected for effects of ship's 
iron. 


Correction for diff. 

of geographical 

position. 


Resulting nomtial 

values at green outside 

dockyard. 


Declination, n3' W 

iDcbnation, 65 18 N 


+ 5' 
+ 15' 
+ 0-03 


r IS' W. 

6S^ 33' N. 


Total force. 12 '22 





In the accompanying diagram No. 1 the difEerences of declination 
are shown at each station, and in diagram No. 2 the difEorences of 
inclination and vertical force. 

These results appear to point to the existence of a strong focus of 
blue magnetism situated above the position indicated by the dotted 



Staff-Commaacler E. W. Creak. 



[Jan. 28, 



■^1 



111 
III III 



3§l I 11 



^ 828 S8388 °SS2g 

U woo -JrHrtMO OOONtf 

I 11+ +1141 +(11 



1^ 



SSS 3 . .is 3 . 



. lis s.M i. 



s Jjs gsgsa s ■ 



gS9 SSSS2 



« 13-9 9 



.I3ihjl|lilii|;; 



; 53 g 



1886.] On Local Hagnetie Disturbance in Islands. 



87 



line of the diagram, the red ends of the declination and dipping 
needles being attracted towards this fooos with a force varying 
according to the place of observation. 

Thus in the case of the declination at all stations situated to the 
north-east of the focus, the westerly declinations are seen to be in 
excess, and those to the south-west in defect of the normal value. 

In the inclination and vertical force a great increase of value maj 
be seen in passing from the seaward side of the islands towards the 
area enclosed by the dotted line of the diagram. 

A portion of the disturbance just noticed may possibly be due to 
the ferruginous nature of the soil at Bermuda;* but this does not 
detract from the evidence just adduced of the existence of a strong 
focus of blue magnetism about the position assigned to it in the 
diagram. 

In' the eastern extremity of the group there are also evidences of 
local magnetic disturbance at the observing stations of Hen Island, 
Button Island, and Fort Cunningham. 

Madeira. 



1 


Declination. 


Inclination. 


Total force. 


ObserFor. 


Casa Branca. ••• 


16°49'W. 

17 8 

18 25 

19 35 

20 33 
20 33 


66** 14' N. 

56 12 

66 36 


8-784 

9-184 
9 '49 


H.M.S. 

** Challenger," 

1878. 




Cliff west of Loo Bock . 

»» i> 
Normal valuet 



The above observations of declination, made near Funchal, on the 
south side of the island, differ considerably (with one exception) from 
the normal, 3° 44' being the greatest difference. 

There is also much disturbance in the inclination. In one position 
visited by the oflScers of the " Challenger," and at 1 foot above the 
ground, a value of 48° 46' was observed, and at the usual height of 
the observing stand — ^\ feet — over the same spot, 56** 18'. At two 
other positions 20 yards apart, the inclination differed 40'. 

The greatest difference in the values of the total force is a decrease 
of 0-71 below the normal. 

These results point to the importance of adopting an uniform height 
for the observing stand if comparable results are to be obtained. 



* See *' Reniarks on the Chemical AnaljseB of Samples of Soil from Bermuda.*' 
By Genera] Sir J. H. Lefroj. Bermuda, 1873. 



88 



Staff-Commander E. W. Creak. 



[JaiuSS, 





Teneriffe. 


Canary Islands. 






Dedmation. 


Inclination. 


Total fbroe. 


Obserrer. 


Sta. Cmi 


21** 48' W. 
^ 00 


55* 18' N. 
52 42 


9-546 
9-230 


H.M.8. "Ohal- 
Iflnger," 1878. 


Normal valuu 



At this island observations were only made at one land station, but 
there is evidence of a strong development of blue magnetism at the 
observing Btation. 

Santa Cruz is on the east side of the island, and the westerly 
declination was foand to be in excess of the normal valne by If ^. The 
inclination was 2^**, and the force 0*3 in excess of their respedive 
normals. 

St. Vincent. Cape de Verde. 





Declination. 


Inclination. 


Total force. 


Obeerver. 


Porto Ghrande 

Normal values 


ir 8'W. 

18 52 

19 54 


43« 6'N. 
42 52 


8-577 
8''540 


H.M.S. "Chal- 
lenger," 1876. 



The observations were made on the west side of the island. Here 
the principal disturbance occurs in the westerly declination, which is 
nearly 3^ in defect of the normal value. This points to the presence 
of increased bine magnetism on the inland side of the observing 
station. 

The inclination and force are but little affected. 



St. Paul Rocks. (Atlantic Ocean.) 





Declination. 


Inclination. 


Total force. 


Observer. 


Land station 

Normal values 


ler 22' W. 
15 51 


22** 82' N. 
22 30 


7 00 
6-94 


H.M.S. "Chal- 
lenger," 1873. 



At these rocks the declination and total force are slightly disturbed, 
the inclination agreeing well with the normal. 



1886.] On Local Magnetic Disturbance in Islands. 



89 



SandwicH Islands. 





Declination. 


Inclination. 


Total force. 


Obserrer. 


Honolula • 


9** 84' E. 

8 47 


39*' 57' N. 
39 32 


8-612 
8-450 


H.M.S. "Ohal. 
lengep," 1875. 


Normal valmes 


Hilo, Cocoanat Island 
normal wduM 


r 29' B. 
8 16 


88^ 89' N. 
57 32 


8-698 
8-330 


Ditto 



At Honolala bine magnetism is predominant at the observing 
station, which is on the west side of the island, the easterly declina- 
tion being ^ in excess of the normal. The inclination and force are 
slightly increased. 

A marked difference is seen between the observed declinations at 
Honololn and Hilo. At the first-named place the easterly declination 
observed on the west coast is increased }^, whilst at the latter the 
easterly declination observed on the east coast is decreased }°. 

The large increase in the observed inclination and force at Hilo 
above the normal, conpled with the diminished declination, point to a 
strong development of bine magnetism in that portion of the island 
visited. 

This conclndes onr list of islands in which, with the exception of 
Madeira, bine magnetism appears to predominate. Madeira, however, 
requires a much more extended series of observations to be made on 
its shores before any conclnsions can be drawn as to the prevalence of 
either blue or red magnetism. 



Section II, — Islands situated South of the Magnetic Equator, 

Ascension. 





Declination. 


Inclination. 


Total force. 


Obserrer. 


Georgetown 

Oreen Mountain .... 
Normal values 


23^ 6' W. 
22 32 
22 41 


r 66' s. 
9 57 
7 37 


6-133 
6-217 
6-100 


H.M.S. "Chal- 
lenger," 1876. 



The observations at this island are complete at two stations. At 
Georgetown, on the coast, there is but little local disturbance, but at 
the Green Mountain Station the observed inclination exceeds the 
normal in value by 2^°, the force by 0*12 (nearly), thus pointing to 
an excess of red magnetism. 



90 



Staff-Commander K W. Creak. 



[Jan. 28, 



St. Hqlena. 





Declination. 


Inclination. 


Total force. 


Obeerrer. 


Longwood Magnetio 
Observatory 

Sister's Walk* 

Castle gardens 

At the anchorage .... 

Normal values 


22°48'W. 

• • 

19 88 
22 17 

22 63 


2r 2ir S. 

18 16 
20 8 

17 66 

18 37 


6 080 

6-287 

• • 

• • 

• • 

6 075 


Obserratoiy 
results. 

^er}l««- 
Boss, 1840. 
Dupetit Thou- 

ars,1889. 
Boss, 1840. 



At Longwood Magnetic Observatory the declination is apparently 
nndistnrbed, whilst in the Castle Gardens it differs 3^^ from the 
normal valne. The inclination at Longwood differs 2|^ from the 
normal, pointing to the presence of an excess of red magnetism in that 
locality. The total force is not mnch disturbed. 

At Sister's Walk the inclination at two stations, 50 yards apart, 
differs If ^, one being in excess of the normal by 1^° nearly, the other 
twenty minutes in defect ; the larger disturbance being due to red 
magnetism. The total force is increased as much as 0*2. , 

The result of the inclination by Dupetit Thenars, which is 42' 
below the value derived from Ross's observations, seems to indicate 
that a lower value might be accepted as the normal. 



Tristan d'Acunha. 





Declination. 


Inclination. 


Total force. 


Observer. 


Near Julia Point .... 
Normal values 


23** 5' W. 
21 15 


40^'40'S. 
41 42 


Not observed 
6-36 


H.M.S. "Chal- 
lenger," 1873. 



The observing station at this island was situated on the N.W. coast 
near some cliffs extending to the eastward. The westerly declination 
is increased about l^° above the normal, but as the inclination is 
slightly affected by blue magnetism, it is uncertain whether it is the 
red magnetism in the adjacent cliffs to the eastward repelling the red 
end of the compass needle, or the blue magnetism near it which causes 
the increase of the declination. 



* At Sister's Walk, Crozier's observing station was 60 yards S.S.E. of Boss' station. 
The dip circles were interchanged at the time to prove the difference observed was 
not due to instrumental error. 



1886.] On Local Magnetic Disturbance in Islands* 



91 



Kergnelen Island. 





Declination. 


Inclination. 


Total force. 


ObserFcr. 


Chrutmas Harbour . . 
Howe's Foreland .... 
formal wUuet 


33^*38' W. 
34 35 


70° 60' 8. 
72 
70 63 


11-032 
11003 


H.M.S. "Chal- 
lenger," 1874. 


Accessible Bay 

Sets J CoTo 


83° 34' W. 
34 
34 67 


71* 47' S. 
71 7 


11-422 
11-087 


HJi.8." Chal- 
lenger/* 1874. 


Normal vaUut 


Obseiratory Bay .... 
Swain's Haulo?er. . . . 
Thumb Peak 

Hoff Island • • • . 


36° 48' W. 

• • 

• • 

35 54 
35 20 


71° 66' 8. 
71 
71 7 

71 21 


11-143 1 
10-288 ^ 

•• J 
11-171 ' 


Perry, 1 Jan., 
1876. 

H.M.S. "Chal- 
lenger," 1874. 
1 Jan., 1876. 


Ifcrmal vcUuet 



The " Challenger " was not swnng in the neighbonrhood of Ker^ 
gnelen Island, and the normal values have therefore been derived from 
the results of single observations made at sea between the swinging, 
at the Cape of Good Hope, and that in lat. 63** 30' S., long. 90° 47' B. 
They are therefore less exact, but sufficiently so for the purpose of 
showing that the disturbances on the island proceed from red 
magnetism. 

Thus, at Christmas Harbour, Accessible Bay, and Betsy Cove, 
where there was high land to the westward of each observing station, 
the westerly declination is about 1^ less than the normal. At Howe's 
Foreland and Betsy Cove the inclination is increased, and at the latter 
place the total force is considerably above the normal. At Observatory 
Bay and the adjacent stations the disturbance is comparatively of a 
moderate amount, except in the total force at Swain's Haulover, 
which shows an unusually large diminution. 



Juan Fernandez. 





Declination. 


Inclination. 


Total force. 


Observer. 


Near Fort St. Juan 
Bautista 


16° '40' E. 


39° 40^ 8. 
S7 64 


8-138 

7-860 


H.M.S. 

"Challenger," 

1875. 


Normal values 



The sea observations from which the normal values have been 
deduced were made at two positions — one before, the other after the 
ship's arrival at Juan Fernandez. 



92 On Local Mafftietie Disturbance in Islands. [Jan. 28« 

The above observations, like those at St. Helena and Ascension, 
show the existence of an excess of red magnetism above the normal 
from the increased values of the inclination and total force. 

The general results of the observations just discussed is to show 
that in islands far from a continent and north of the magnetic 
equator, the local disturbances of the three magnetic elements are 
caused by an excess of blue magnetism above the normal values due to 
the position of the -islands on the earth considered as a magnet. 
South of the magnetic equator red magnetism is in like manner pre- 
dominant. 

Considering, however, that the observations were made with the 
instruments between 3 and 4 feet above the ground, the disturbances 
are not large. 

As an instance of large disturbance the results obtained at the 
bluff. Bluff Harbour, in the South Island, New Zealand, may be 
mentioned. In 1857, during the land survey by the local government 
officials, the following values of the declination were observed.* 

On the summit of the bluff 6^^ 54' E. 

30 feet north of the same position 9 36 W. 

„ west „ 5 04 E. 

„ east „ 46 44 E. 

Normal from sea observations /(? 20 'E. 

On the summit of the bluff there was thus shown to be a strong 
focus of red magnetism. 

During the survey of the South Island by the officers of H.M.S. 
"Acheron," it was found necessary to give up the use of compass- 
bearings at this place, and adopt the plan of observing nothing but 
true bearings. 

The evidences of local magnetic disturbance form a great difficulty 
in estimating the values of the secular change in these islands for 
past years. For example, Madeira may be mentioned, where it has 
been seen that a change in position of a few feet gave very different 
results of the inclination, and even at the same position the height at 
the observing instrument above the ground must be taken into con- 
sideration if comparable results are to be obtained. 

Before concluding this paper, I desire to draw attention to the 
following remarks on this subject of local magnetic disturbance. 

Firstly, reasons have been given for believing " that terrestrial 
magnetism is not produced in any important degree by magnetic 
forces external to the earth."t 

• " Transactions New Zealand Institute," 1878, vol. vi, p. 7. 
t See " Treatise on Magnetism,*' p. 100, par. 43, by Sir G, B. Airy, K.C.B., 
Ast. Bojal, 1870. 



Froc Jioy.Soc.Vol 40.F1.1. 




le>tJl<nnum.«.V.' 



1886.] Gigantic Land-Lizard (Megalania prisca, Owen). 93 

Secondly, '' that terrestrial magnetism does not reside in any im- 
portant degree on the earth's surface " " and therefore the 

source of magnetism mast lie deep."* 

In view of these reasons and the results obtained from the 
observations recorded in this paper, I draw the possible conclusion : 
That the increase of magnetic force observed in the islands under 
discussion proceeds from portions of those islands which have been 
raised to the earth's surface from the magnetised part of the earth, 
forming the source of its magnetism. 



TI. " Description of some Remains of the Gigantic Land-Lizard 
{Megalania prisca, Owen) from Queensland, Australia, 
including Sacrum and Foot-Bones. Part IV." By Sir 
Richard Owen, K.C.B., F.R.S., &c. Received January 13, 
1886. 

(Abstract.) 

The author, continuing to receive through the kindness of Dr. 
Bennett, F.L.S., of Sydney, New South Wales, and of Mr. George F. 
Bennett, Corr. M. Zoological Society, Toowoomba, Queensland, 
Australia, fossil remains of Megalania from a drift-bed of King's 
Creek, selected therefrom specimens contributing to the restoration 
of Meg. priscaj and which he had not obtained at the dates of com- 
munication of the papers to the Royal Society which have appeared 
in the " Phil. Trans.'' for the years 1864, 1880, and 1881. 

These specimens add to the characters of the sacrum, and give 
those of the terminal segment of one of the limbs of the extinct 
homed Saurian. 

The metapodial series are remarkable for the great breadth in pro- 
portion to the length of the bone ; that of one of the digits being as 
broad as long, and testifying to its character as a metatarsal by the 
distal trochlea for the articulation of a proximal phalanx. The digits 
were unguiculate, indicative of terrestrial life and locomotion. 

The subjects selected for description in the present paper are illus- 
trated by drawings of the natural size, which accompany the text. 



* See ufeffi, p. 101, par. 44. 



94 Misses A. Johnson and L. Sheldon. [Jan. 28, 

III. " On the Development of the Cranial Nerves of the Newt.** 
By Alice Johnson, Demonstrator of Biology, Newnham 
College, Cambridge, and Lilian Sheldon, Bathui-st Student, 
Newnham College, Cambridge. Commimicated by Pro- 
fessor M. Foster, Sec. R.S. Received January 14, 1886. 

The peripheral neryons system of the Newt does not begin to 
develop nntil the mednllary canal has become completely separate 
from the external epiblast. A nenral ridge appears on the dorsal 
surface of the medullary canal, and, at regular intervals, paired lateral 
prolongations of it grow out and form the spinal and cranial nerves. 
The former grow down between the mednllary canal and muscle- 
plates, the original outgrowth, in each case, becoming the dorsal root, 
while the ventral root is formed later. 

In the head, where there are no muscle-plates, the nerves are 
situated nearer to the surface. The 3rd, the 5th, the common rudi- 
ment of the 7th and 8th, the 9th, the 10th, and, probably, the olfac- 
tory nerves, all develop as outgrowths of the neural ridge. We have 
not traced the development of the 4th and 6th nerves. 

At first the cranial nerves are of necessity attached to the dorsal 
surface of the brain, since they arise from the neural ridge. The 
attachment next widens out, extending further down the side of the 
brain. Later, the dorsal part of the attachment is lost, the ventral 
part alone remaining as the permanent root. There is no secondaiy 
attachment entirely distinct from the first, and no part of the nerve 
is at any time situated dorsal to the root. This description applies 
specially to the 5th and 7th nerve-roots, but it is probably true for all 
the cranial nerves in which the shifting of the roots takes place. 

As soon as the cranial nerves become apparent, a series of thicken- 
ings of the inner layer of the epiblast appears on each side of the 
head. These thickenings, which are paired, are situated slightly 
above the level of the notochord, and correspond respectively to the 
5th, 7th, 9th, and probably also to the 10th nerves. They are destined 
to give rise to the mucous canals of the head. The olfactory organ 
and ear have similar relations to the 1st and 8th nerves, and may 
possibly belong to the same morphological category as these sense- 
organs ; but this point seems very doubtful. The mucous canals are 
at first confined to the head, but afterwards are present in the trunk 
also, and increase greatly in number. 

The nerves are directed outwards and downwards from the dorsal 
surface of the brain, each towards the sensory epiblastic thickening 
corresponding to it. After a short time, the two structures fuse 
together indistinguishably, so that a mass of cells is formed at this 
point, continuous, on the one hand, with the external epiblast, and, on 



1886.] On the Cranial Nerves of the Newt, 95 

the other, witH the nerre-root. The nerve-elements of this mass are 
probably derived from the nerves, and the sense-elements from the 
epiblast. This description holds for the 5th, 7th, and 9th nerves. We 
have not ascertained whether it is also tme of the 10th. The com- 
mon mdiment of the 7tb and 8th nerves fases with the sensory 
epiblast at two points — one behind the other. The posterior of these 
gives rise to the ear, the anterior to the sense-organ of the 7th nerve. 
Soon after the fusion has taken place, the common mdiment of the 
two nerves divides into two complete tronks, one innervating the ear, 
and the other the sense-organ of the 7th nerve. 

At the point where the 5th nerve is fused with the skin, the Ghis- 
serian ganglion is formed. Later, it begins to separate from the 
epiblast, retiring from the surface, but remaining still attached to it 
by a cord of cells, which constitutes the ophthalmic branch of the 5th 
nerve. At the same time, a main trunk grows out from the ganglion and 
soon divides into two branches — the inferior and superior maxillary. 

The 7th and 9th nerves develop similarly to each other, but in a 
somewhat different way from the 5th. In each the main trunk passes 
onwards from its point of fusion with the epiblast towards the cor- 
responding visceral cleft and fuses again with the epiblast of its dorsal 
wall, the 7th nerve, as usual, innervating the Ist cleft, and the 9th 
nerve the 2nd cleft. The clefts at this time are not perforated, but 
represented merely by lateral outgrowths of the fore-gut, which have 
fused with the epiblast at the points of contact. The ganglion which 
has been formed on the upper part of the trunk in connexion with 
the sensory epithelium next sinks inwards, remaining attached to the 
epiblast by a nerve-branch, as in the case of the 5th nerve. The 
lower part of the trunk becomes completely detached from its con- 
nexion with the epiblast, and gives off two branches, one behind, and 
one in front of the visceral cleft. Thus the first two clefts are each 
provided with a post-branchial and a prao- branchial branch, derived 
from the 7th and 9th nerves. 

We believe that all these branches of the cranial nerves are derived 
from the original outgrowths from the brain, none of them being split 
off from the external epiblast, as Mr. Beard has described in Elasmo- 
branchs, and Mr. Spencer in Amphibia. The fusion of some of the 
nerves with the skin seems to be comparable with what is known to 
occur in vertebrate embryos generally, in the nose and ear, where the 
nerve grows out from the brain to fuse with the sensory epithelium, 
and we take all such cases to be merely instances of the innervation 
of sense-organs. The innervation is generally completed very early 
in the nose and ear, and, in the Newt, it appears to take place rather 
earlier than usual in the mucous canals. Our observations seem to 
point distinctly to this conclusion rather than to the view that the 
nerves are, even partially, derived from the external epiblast. 



96 Presents. [Jan. 7, 



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1886.] iVtfMtte. 97 

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riWIililBl II !■ _B_JU -. •.w^TTT'tlZ.-, 



1886.] PreMenU. 99 

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Illustrated Science Monthly. Vol. IIL Noe. 7-9. Vol. IV. 

Nofl. 1-3. Roy. 8vo. London 1885. The Editor. 

Indian Antiquary. Vol. XIV. Parts 171-176. 4to. Bombay 

1885. The Editor. 

Journal of Science. July to December, 1885. 8yo. London. 

The Editor. 
Nature. July to December, 1885. 4to. London. The Editor. 

Notes and Queries. July, 1885, to December, 1885. The Editor. 
Observatory. July to December, 1885. 8vo. Lomlon. The Editor. 
Revue Politique et Litt^raire. July to December, 1885. 4to. Faris, 

The Director. 
Revue Scientifique. July to December, 1885. 4ito. Faria 1885. 

The Director. 
Symona' Monthly Meteorological Magazine. July, 1885, to Decem- 
ber, 1885. 8vo. London, Mr. Symons, F.R.S. 
Zeitschrift fur Biologie. Band XXI. Hefte 3-4. Band XXII. 
Hefte 1-2. 8vo. Miinchen 1885-86. The Editor. 



Baird (Major), F.R.S., and E. Roberts. Tide Tables for the Indian 
Ports for 1886. 12mo. London. The India Office. 

Fitzgerald (R. D.) Australian Orchids. Vol. II. Part 2. Folio. 
Sydney 1885. The Government, N.S.W. 

Hooker (Sir J. D.) The Flora of British India. Part XII. 8vo. 
London 1885. The India Office. 

Lephay (J.). Mission Scientifique du Cap Horn. 1882-83. Tome II. 
Meterologie. 4to. Faris 1885. Paris Academy. 

Marchesetti (Dr.) Di Alcune Antichit4 Scoperte a Vermo presso 
Pisino d'Istria. 8vo. Trieste 1883. La Necropoli di Vermo 
presso Pisino nell'Istria. 8vo. Trieste 1884. The Author. 

Roscoe (Sir H. E.), F.R.S. Spectrum Analysis. Fourth edition. 
Revised and enlarged by the author and by Arthur Schuster, 
r.R.S. 8vo. London 1885. The Author. 



1886.] JV#Mfito. 101 

Sars (G. O.) Norwegian North-Atlantio Expedition, 1876-78. 
Zoologj. Crastacea. Parts 1-2. Folio. Christiania 1885. 

Editorial Committee of the Expedition. 
Strove (Otto) Die Beschlusse der Washingtoner Meridianoonferenz. 
870. 8t. Petersbwrg 1885. Tabolas Qaantitatam BesBelianarom 
pro annis 1885 ad 1889 compatat». 8vo. Fetropdi 1885. 

The Author. 



Presents^ January 14, 1886. 
Transactions. 

Berlin: — K. P. Akademie der Wissenschaften. Politische corre- 
spondenz Friedrichs des Grossen. Band XIII. 4to. Berlin 
1885. The Academy. 

Brussels : — ^Mns^ Royal d'Histoire Natnrelle de Belgiqne. S^rie 
Paleontologique. Tome IX. Partie lY, avec un Atlas. Folio. 
Bruxellet 1885. Tome XI. Partie V, avec nn Atlas. Folio. 
Bruxelles 1885. The Mnsenm. 

Society G^logiqae de Belgiqne. Compte Rendu de la Reunion 
Extraordinaire. Verviers 1881 ; Li6ge 1883. 8vo. 1882, 1884. 

Professor Dewalque. 
London : — British Museum. Catalogue of the Lizards. By G. A. 
Boulenger. Vol. II. 8yo. London, 2nd edition, 1885. 

The Museum. 
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8vo. London 1885. The Society. 

Institution of Civil Engineers. Theory and Practice of Hydro- 
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Milan: — R. Instituto Lombardo. Memorie. Classe di Lettere e 
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matiche e Naturali. Yol. XY. Fasc. 2-3. 4to. Milano 1884. 
Rendiconti. Serie II. Yol. XYI-XYII. 8vo. Milano 1883- 
84. The Iii^t\W\ft« 



102 PreaentB. [Jan. U; 

Transactions (contin%ied)» 

Naples : — Society Italiana delle Scienze. Memorie di Maiematica 
e di Fisica. Serie III. Tom. V. 4to. Napoli 1885. 

The Society. 

Socieijt Italiana di Scienze Natnrali. Atti. Vol. XXYII. 

Fasc. 1-4. 8vo. Milano 1884-5. The Society. 

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83. 4 vols. 4to. Paris 1885. The Bnreau. 

Warwick : — Naturalists' and Archeeologists' Field Club. Proceed- 
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Observations and Reports. 

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Brisbane: — Colony of Queensland. Statistics, 1884. Folio. Bris- 
bane 1885. Vital Statistics, 1884. Folio. Brisbane 1885. 

The Registrar-General, 
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The Author. 

Survey of India Department. General Report, 1883-4. Folio. 

Calcutta 1885. The Government of India. 

Madison, Wisconsin : — ^Washburn Observatory. Publications. 

Vol. III. 8vo. Madison 1885. The Observatory. 

Madras: — Meteorological Office. Report to the Government of 

Madras, 1884-85. 8vo. Madras 1885. The Office. 

Melbourne: — Australasian Statistics, 1884. Folio. Melbourne 1885. 

The Government Statist. 

Mining Department. Mineral Statistics of Victoria for 1884. 

Folio. Melbourne 1885. Reports of the Mining Registrars, 



1886.] Pre$entt. 103 

Observations, &c. (caniimied). 

Quarter ended Marcb, 1885. Folio. Melhovirne, Keport, Mines 
and Water Supply, 1884. Folio. Melbourne 1885. 

The Minister of Mines. 

Office of the Government Statist. Statistical Begister of the 

Colony of Victoria for 1884. Parte 1-4. 8vo. Melbourne 1885. 

The Statist. 
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Beport of the Trustees for 1884. 8vo. Melbourne 1885. 

The Trustees. 

Rome: — Conference Sanitaire Internationale. Protocoles et Proc^s- 

Verbaux. Folio. Borne 1885. The Foreign Office. 

Sydney: — Department of Mines. Report, 1884. Folio. Sydney 

1885. The Department. 

Washington : — Coast and Geodetic Survey. Methods and Results. 

Appendices Nos. 8, 10, 15, 16. 4to. Washington 1885. 

The Survey. 
Naval Observatory. Astronomical and Meteorological Observa- 
tions, 1881. 4to. Washington 1885. The Observatory. 
Signal Service. Notes. Nos. 20, 22, 23. 8vo. Washington 1885. 
Professional Papers. Nos. 13, 15. 4to. Washington 1884. 

The Service. 



Attfield (John), F.R.S. Chemistry : General, Medical, and Pharma- 
ceutical. Eleventh edition. 8vo. London 1885. The Author. 

Chapman (Henry) Compound Locomotives. 4to. London 1885. 

The Author. 

Ellis (A. J.), F.R.S. On the Musical Scales of various Nations. 8vo. 
[London] 1885. The Author. 

Ewart (Joseph) A Few Words upon (I) The Lowest Forms of 
Living Things, (2) Physiology, (3) The Aryan and Aboriginal 
Races of India. 8vo. 1884. Forestry in India. 8vo. 1885. 

The Author. 

Haan (Dr. Bierens de) Bibliographie Neerlandaise. Sciences 
Math^matiques et Physiques. 4to. Borne 1883. Derde Rapport 
van de Huygens-Commissio. 8vo. Amsterdam 1885. Dr. Haan. 

Helmholtz (Hermann), For. Mem. R.S. On the Sensations of Tone. 
Second English edition. Translated by A. J. Ellis, F.R.S. 8vo. 
London 1885. Mr. Ellis, F.R.S. 

Moore (Joseph) The Queen*s Empire ; or Ind and Her Pearl. 8vo. 
Philadelphia 1886. The Author. 

Netto (Dr. L.) Conference faite an Museum National de Rio de 
Janeiro. 8vo. Bio de Janeiro 1885. The Author. 



i04 Pre$enii. [Jan. Si, 

Prestwioh (Joseph), F.R.S. Geology: Chemical^ Phjirical, and 
StratigraphiOal. Vol. I. Ohemical and Physical. 8vo. Oxford 
1886. Clarendon Press Delegates. 

Jones (T. Rupert), P.R.S., with others. Third Report of the Com- 
mittee on the Fossil Phyllopoda of the Palaeozoic Rocks. 8yo. 
London 1885. Notes on the Carhoniferons Ostraooda of the 
North-West of England. 8vo. Hertford 1885. Notes on the 
British Species of Ceratiocaris. 8yo. London 1885. 

Professor T. R. Jones, P.R.S. 

Reade (T. Mellard) The North Atlantic as a Geological Basin. 8vo. 
Liverpool 1885. The Author. 

Russell (W. J.), F.R.S. On London Rain. 4to. London 1884r-85. 

The Author. 



Presents, January 21, 1886. 
Transactions. 

Boston : — Society of Natural History. Proceedings. Vol. XXII. 

Part 4 ; Vol. XXIII. Part 1. 8 vo. 5o*ton 1884-85. Memoirs. 

Vol. III. No. 11. 4to. Boston 1885. The Society. 

Cambridge, Mass. : — American Academy of Arts and Sciences. 

Memoirs. Vol. X. No. 3; Vol. XL Part 2. No. 1. 4to. 

Cambridge, Mass. 1874, 1885. The Academy. 

Edinburgh : — Royal Society. Proceedings. Vols. XII-XIII. 

Nos. 114-120. 870. Edinburgh 1882-85. The Society. 

Geneva : — Soci^te de Physique. M^moires. Tome XXIX. Partie 1 . 

4to. Geneve 1884-85. The Society. 

Haarlem : — Mus6e Teyler. Archives. Ser. II. Vol. II. Partie 3. 

Large 8vo. Haarlem 1885. Catalogue de la Bibliotheque. 

Livr. 1-2. Large 8vo. Haarlem 1885. 
London : — Essex Field Club. Special Memoirs. Vol. I. Report on 

the East Anglian Earthquake, 18S4. 8vo. London 1885. 

The Club. 
Pharmaceutical Conference. Year Book of Pharmacy, 1885. 8vo. 

London 1885. The Editor. 

Royal Asiatic Society. JoamaL Vol. XVIII. Part 1. 8vo. 

London 1886. The Society. 

Louvain : — University Catholique. Annuaire. 1886. 12mo. 

Louvain. Theses S. Facultatis Theologic®, 1884-85. 8vo. 

Lovanii, De la Sensation et de la Pens6e. Theodore Fontaine. 

8vo. Louvain 1885. The University. 

Madrid: — Comisi6n del Mapa G«ol6gico de Espana. Memorias. 

1884. Large 8vo. Madrid 1884. Boletin. Tomo XII. 

Cuadermo 1. Large 8vo. Madrid 1885. The Commission. 



1886.] I¥Mnt3. 105 

TmoBftctioiui (eofUintiei). 

Kottdngham : — UniverBity College. Calendar, 1885-86. 870. Not* 

tingham. Prof. F. Clowes. 

Oxford: — Radoliffe Library. Catalogpae of Books added during 

1884. 8vo. Oxford 1885. The Libraiy. 
Paris : — £cole Normale Sap^rieure. Annales. S^r. III. Tome II. 

N06. ^10. 4to. Faria 1885. The School. 

Faculty des Sciences. Theses pr^sent^ pour obtenir le Ghrade 

de Dootenr ha Sciences Math^matiqnes. Five numbers; 

Sciences Natoralles. Fourteen numbers. Sdenoes Physiques. 

Six numbers. 4to and 8yo. Parts 1885. The Faculty. 

Perth : — Society of Natural History. Proceedings. Vol. I. Ptot V. 

Small 4to. Perth 1885. The Society. 

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Tokio : — Seismological Society of Japan. Transactions. Vol. III. 

1885. 8vo. ITokio.] The Society. 
Washington : — National Academy of Sciences. Proceedings. 

Vd. XI. Part 2. 870. Washington 1884. Memoirs. Vol. III. 
Part 1. 4to. Washington 1885. Eeports of the Academy, 
188a-84. 8vo. Washington lSS4rSb, The Academy. 

Yokohama : — Asiatic Society of Japan. Transactions, Vol. XIII. 
Part 2. 8vo. Yokohama 1885. The Society. 



Observations and Reports. 

Batavia: — Magnetical and Meteorological Observatory. Observtb- 
tions. Vol. VI. Parts 1-2. Folio. Batavia 1885. 

The Observatory. 
Dun Echt : — Observatory. Circulars. Nos. 99-109. 4to. 

The Earl of Crawford, F.R.S. 

Madrid : — Olbservatory. Resiimen de las ObservacioncH Meteoro- 

16gicas. Ano 1881. 8vo. Madrid 1885. The Observatory. 

Paris : — Dep6t des Cartes et Plans de la Marine. Annales Hydro- 

graphiques. S6r. 2. Semestre 2, 1885. 8vo. Paris 1885. 

The D6p6t. 
Turin : — Observatory. Bollettino. Anno XIX. 1884. Obi. 4to. 
Torino 1885^ Effemeridi del Sole, della Luna e dei principali 
Pianeti. Anno 188G. 8vo. TorirM 1885. Osservazioni 
dell'Ecclisse totale di Luna del 4-5 Ottobre, 1884. 8vo. 
Torino 1884. Sulla possibility che il valcano Krakatoa possa 
avere proiettato materie fuori deiratmosfera. 8vo. Torino 1884. 
Sulla freqnenza dei venti inferior! desunta dalle Osservazioni 
fatte dal 1866 al 1-884. 8vo. Tcrrino 1885. The Observatory. 



lt)ft B^eimiti, [Jati. 28; 

Brongniart (Charles) Les InsecteR FoBHiles des Terrains Piimaires. 

8vo. Bouen 1885. Ditto, translated by Mark Stirrup. Svo. 

Salford 1885. Analyse de deux travaux r^cents de MM. Scudder 

et Ch. Brongniart sur les Articul^s fossiles. Par A. P. de Borre. 

8vo. Oand 1885. 

M. Brong^art, through Sir John Lubbock, F.R.S. 
Oegenbaur (0.)., For. Mem. B.S. Lehrbach der Anatomie des Men- 

schen. Auflage 2. 8yo. Leipzig 1885. The Author. 

Haviland (Alfred) Gonsamption : Social and Geographical Causes 

eondnclng to its .Prevalence. Reprint. 8vo. Douglas 1885. A 

Lecture on the essential requisites of a Sea-side Health Resort. 

&c. 8yo. Douglas 1883. Sparborough as a Health Resort. 8yo. 

London 1883. The Author. 

Helmholtz (H. von), For. Mem. R.S. Handbuch der Physiologischen 

Optik. Auflage 2. Lief. 1. 8vo. Hamburg 1886. 

The Author 
Marcet (W.), F.R.S. Sur la Temp^ratare du Corps pendant TActe 

de TAscensipn, 8vo. Geneve 18S5. The Author. 

Plantamour (Ph.) Des Mouvements Periodiques du Sol. 8vo. 

Oeneve 1885. The Author. 

Pickering (W. H.) Coloured Media for the Photographic Dark 

Room. 8vo. [Fhiladelphia] 1885. The Author. 

Wodiczka (Franz) Die Sicherheita-Wetterfiihrung oder das System 

der Doppel-Wetterlosung fiir Bergbaue mit Entziindlichen 

Grubengasen znr Verhiitung der Schlagwetter-Explosionen. 

8vo. Leipzig 1885. The Author. 



Presents^ January 28, 1886. 
Transactions. 
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No. 3. 8vo. Alnwick 1885. The Club. 

Copenhagen : — Academic Royale. Bulletin. 1885. No. 2. 8vo. 
Coperiluigue, Memoirs. Sor. VI. Vol. III. No. 1 (two 
copies); No. 3 (two copies). 4to. Cop&nhague 1885. 

The Acadeipy. 
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The Union. 
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ceedings. Vol. XXI. 8vo. Melbourne 1885. The Society. 
Montreal : — McGill College and University. Calendar. 1885-86. 
8vo. Montreal 1885. The College. 



1886.] Presents. 10? 

Transactions (continued). 

Bojal Society of Oanada. Proceedings and Transactions. Vol. 11* 

1884. 4to. Montreal 1885. The Society. 

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castle 1885. The Institution. 

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actions. Vol. VI. Part 2. 8vo: New Haven 1885. 

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8vo. New York, 1883-84. The Academy. 

American Geographical Society. Bulletin. 1885. No. 1. 8yo. 

New York, The Society. 

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8vo. New York 1885. The Museum. 

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Fasc. 2. 8vo. Pisa 1885. Process! verbali. Vol. IV. 8vo. 

1885. The Society. 



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1885. The Observatory. 

Calcutta: — Geological Survey of India. Records. Vol. XVIII. 

Part 4. 8vo. Calcutta 1885. The Survey. 

Meteorological Observations at Six Stations in India. 1885. 

May — August. Meteorological Office, Calcutta. 

Dublin : — Science and Art Museum. Report of the Director. 8vo. 

Dublin 1885. The Museum. 

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8vo. Melbourne. The Observatory. 

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(three copies). Folio. Sydney 1885. The Museum. 

Victoria : — The Gold Fields of Victoria. Reports of the Mining 

Registrars, quarter ended September 30, 1885. Folio. Mel' 



108 



PreientB. 



Observations, &o, (continued), 

bourne. Statistical Registrar of the Colony of Victoria br 
1884. Parts V-VII. Folio. Melbourne 1884. 

The GoTemlneiit 8Mhk, 

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Folio. Wellington 1885. The BegistiaF-GenenL 



Journals. 
Astronomische Nachrichten. Bande 111-112. 4ito. Kid 1885. 

The Kiel Obsenratoiy. 
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1-3. 870. Cassel 1885-86. Mr. W. T. T. Dyer, P.RS. 

Bnllettino di Bibliografia e di Storia delle Scienze Matematiohe e 

Fisiche. Settembre, 1884, to Marzo, 1885. 4to. Boma, 

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The Editor. 

Mittheilnngen ans der Zoologischen Station zu Neapel. Band VI. 

Heft 3. 8vo. Berlin 1885. Zoologische Station. 

Year Book of Photography. 1886. 8vo. London. The Editor. 

Zoological Record. 1884. 8vo. Londim 1885, 

The Zoological Record Association. 



Changes produced by Magnetisation in the Length of Rods, 1 09 



♦* On the Changes produced by Magnetisation in the Length of . 
Rods of Iron, Steel, and Nickel." By Shelford Bidwkll, 
M.A., LL.B. Communicated by Professor Frederick 
Guthrie, F.R.S. Received April 1. Read April 23, 1885. 

The earliest systematio experiments on the effects prodaoed by 
inaipietisation upon the length of iron and steel rods were those of 
Joaley an account of which is published in the '* Phil. Mag." of 1847. 
The experiments were made wifch bars 36 inches long, which were 
|»laoed inside a solenoid 38 inches long ; and the variations in the 
length of the bars when currents of electricity were passed through 
the solenoid were measured by means of a delicate micrometer, each 
■division of which indicated a change of \ ' %^^^^ inch. 

Using bars of iron and soft steel, he found that their length was 
iaoreased by magnetisation, the elongation -varying up to a certain 
point as the square of the intensity of the magnetisation, temporary or 
permanent, of the bar, and he remarked that the elongation was, for 
the same magnetisation, greater in proportion to the softness of the 
metal. 

When the metal was hard steel it appeared that '' the bar was 
slightly increased in length every time that contact with the battery 
was broken." On passing the first current through the magnetising 
coil the length was unaffected, but when the circuit was broken after 
the passage of this current there occurred a small elongation 
equivalent to a fifth of a micrometer division, and each succeeding 
make and break of the current was accompanied by a further small 
elongation. 

These experiments were made with currents of gradually increasing 
strength ; Joule appears never to have tried what would be the effect 
of applying the same current twice in succession. Had he done so 
there is reason to believe, as will appear hereafter, that effeots of a 
somewhat different character would have been observed. He attri- 
buted the increase in length when the current was interrupted ** to 
the state of tension in the hardened steel," adding that he *' found 
that soft iron wire presented a similar phenomenon when tightly 
stretched." 

The phenomena were, however, not exactly identical in the two 
cases. From the account which he proceeds to give of his experi- 
ments with stretched wires, it appears that when the tension of the 
wire exceeded a certain limit, the effects produced by the current 
were exactly the opposite of those which occurred when the wire was 
unstretched ; magnetisation, instead of causing the wire to lengthen 
temporarily, caused it to shorten, while it resumed its original lea^th. 



110 Mr. S. Bid well. On the Changes produced by 

when the magnetising force ceased to act. Using a soft iron wire a 
quarter of an inch in diameter, Joule found that when it was loaded 
with a weight of 408 lbs. the efPects were the same in direction (though 
smaller in degree) as when the wire was unstretched ; its length 
increased when it was magnetised, and diminished to the same extent 
when it was demagnetised. When, however, the load was increased 
to 740 lbs. the effects were reversed, and maguetisation produced 
temporary retraction. After describing this experiment Joule 
expresses his belief that with a tension of about 600 lbs. (roughly 
the mean of 408 and 740), " the effect on the dimensions of the wire 
would cease altogether in the limits, of the electric currents 
employed," i.e., that currents which produced on his tangent galvano- 
meter deflections ranging from 6 to 58 degrees would neither increase 
•nor diminish the length of his quarter inch wire when stretched with 
a weight of 600 lbs. If he had actually made the experiment he 
would perhaps have found that the length of the wire was increased 
by a weak current, that a current of medium strength would have had 
no effect whatever, and that one of his stronger currents would have 
caused the wire to retract. 

Joule's experiments have many times been repeated, and his results 
generally confirmed. In particular Professor A. M. Mayer of the 
United States, carried out a series of very careful experiments with 
apparatus of elaborate construction and great delicacy.* The con- 
clusions at which he arrived were in accord with those of Joule so far 
as regards iron ; but in the case of steel there is apparently some 
discrepancy. Mayer found that (after the first magnetisation) the 
steel rods with which he worked, whether soft or bard, were invariably 
shortened when the circuit was made and lengthened when it was 
broken, the same current being used for the first and for the 
subsequent magnetisations. This result is, however, not necessarily 
inconsistent with Joule's, because the conditions of the experiment 
were not the same, the second current which Joale applied being 
stronger than the first, and the third stronger than the second. 
Again, while in the case of Joale's " soft steel " the movements were 
in the same direction as those observed with iron (though smaller in 
degree), Mayer's "soft steel " behaved in exactly the opposite manner, 
the movements (after the first magnetisation) being in the same 
direction as those which occurred when harder steel was employed. 
This difference may be accounted for, as Mayer himself suggests, by 
supposing that his so-called '* soft steel " was harder than Joule's. 
Possibly too there was a sufficient difference in the magnetising 
forces employed in the two cases to affect the results of the experi- 
ments. More will be said on this point further on. The effects 
resulting from the first action of the magnetising current are 

• "PhiL Mag.," vol. xlvi, p. 177. 



MagnetiBaiion in the Length of Metal Bods. Ill 

altogether distinct. The permanent magnetisation so prodnced was 
found by Mayer to impart a small permanent elongation to rods of 
soft and blue-tempered steel, and a small permanent retraction when 
the steel was tempered yellow. Mayer's paper also contains some 
new facts relating to details of minor importance. 

In 1882 Professor Barrett published an account in " Nature," 
vol. xxvi, p. 585, of some experiments which he had made not only 
on iron but also on bars of nickel and cobalt, with a view of 
ascertaining the effect of magnetisation on their length ; cobalt, he 
discovered, behaved like iron, but the elongations were smaller; 
nickel, however, retracted under the influence of magnetisation, the 
amount of its retraction being twice as great as the elongation of iron 
under similar circumstances. 

The knowledge on the subject up to the present time may be 
summarised as follows : — 

1. Magnetisation causes in iron bars an elongation, the amount of 
which varies up to a certain limit as the square of the magnetising 
force. When the '^ saturation point " is approached the elongation is 
less than this law would require. The effect is greater in proportion 
to the softness of the metal. 

2. When a rod or wire of iron is stretched by a weight, the 
elongating effect of magnetisation is diminished ; and if the ratio of 
the weight to the section of the wire exceeds a certain limit, magne- 
tisation causes retraction instead of elongation. 

3. Soft steel behaves like iron, but the elongation for a given 
magnetising force is smaller (Joule). Hard steel is slightly elongated 
both when the magnetising current is made and when it is interrapted, 
provided that the strength of the successive currents is gradually 
increased (Joule). The first application of the magnetising force 
causes elongation of a steel bar if it is tempered blue and retraction 
if it is tempered yellow ; subsequent applications of the same external 
magnetising force cause temporary retraction whether the temper of 
the steel be blue or yellow (Mayer). 

4. The length of a nickel bar is diminished by magnetisation, 
the maximum retraction being twice as great as the maximum 
elongation of iron (Barrett) . 

In order that the results obtained by Joule and Mayer might be 
comparable with those of my own experiments, I have made an 
attempt to estimate the magnetising forces with which they worked. 

In the first series of Joule's experiments — those in which he ob- 
served the elongation of iron and steel rods not under traction, he 
used a coilt)f the following dimensions : — 

Length of coil 38 in. = 96 "5 cm. 

Internal diameter .... 1 * 5 „ = 3 '8 

Length of Wire 110 yds. =10,058 



»» 
» 



1 12 Mr. S. BidwelL On the Changes produced by 

Each tarn would contain 3*8x cm. of wire (or rather more) =: 
12 cm. Therefore the number of turns would be 10,058/12=838. ]f 
there were more than one lajer of wire, the number of turns would be 
fewer* The magnetising force would be nearly-*- 

4x||c=1090. 

C being the current in C.G-.S. units. 

In Joule's experiments with stretched wires another coil was 
used. 

Length of coil 11 * 5 in. =s 28 '5 cm. 

Internal diameter .... 1 „ 

Length of wire. 33 yds. =1188 in. 

Thickness of wire • • . • *1 in. 

The number of turns of wire would therefore be about 1 188/1 'Isr 
=344, and the magnetising force about 

C being, as before, the current in C.G.S. units. 

Joule also describes his tangent galvanometer, and gives the deflec- 
tion which the magnetising current produced in every case. The 
galvanometer ** consisted of a circle of thick copper wire 1 foot in 
diameter, and a needle half an inch long furnished with an index." 
The radius, therefore, was 6 inches = 15*2 cm., and the constant, G, 
approximately 27r/16*2=0*41 .* The horizontal component of the earth's 
magnetic force was, at the date of Joule's paper, about 0'17; thus 
the factor by which the tangents of the angles of deflection should 
be multiplied to give the deflecting currents in C.G.S. units is 
017/0-41=0-41. 

The greatest deflection recorded in Joule's experiments with iron 
was 62'' 48\ the tangent of which is 1*95 ; the magnetising force was 
therefore 

1-95x0 -41x109=87. 

The greatest deflection in his experiments with steel was 70^30' 
= tan "■^2*824, the corresponding magnetising force being 126. 

The greatest galvanometer deflection in the experiments with 
stretched wires was 61° 25', the tangent of which is 1*835, the cor- 
responding current 075 C.G.S. units, and the magnetising force 114. 

Mayer used a coil 60*25 inches=153 cm. in length, the number of 

turns being 1919. The magnetising force at the centre of his coil 

1919 
wa3 thereiore about 4?r-^— --C=157'5C. 

loo 

• See Clerk Maxwell'a " Electricity," \o\, \\,^. ^^v>. 



Magnetisation in the I^ength of Metal Rode. 113 

It is less easy to estimate tbe strength of his current, since he gives 
no galvanometer readings, nor any .details as to the electromotive 
force and resistanoe of his battery. The resistanoe of his ooil he 
states to have been 0'75 ohm, and that of the rest of the circait 
(ezclnBive of the battery) about 0*25 ohm, making 1 ohm in all. He 
osed a battery of twenty-five Bansen cells, and, in his own words, 
'' the above interpolar resistance showed that the mazimnm effect of 
magnetisation would be given by connecting the twenty-five cells five 
in couple and five in series/' This implies that the resistance of the 
battery as thus arranged would be not far from 1 ohm, which, unless 
the cells were very small, is surprisingly high. Taking the electro- 
motive force of a Bunsen cell to be 1*9 volts, the electromotive force 
of Mayer's battery would be 9*5 volts, and the current 9*5/2=475 
amp^re8=0*475 G.G.S. xmit. The magnetising force would there- 
fore be about 157*5x0*475=75 nearly. But 1 ohm is probably too 
high an estimate for the resistance of the battery. Assuming the 
resistance of the battery, leading wires, and connexions to be 
0*5 ohm (which is the lowest reasonably probable estimate), the 
current would be 7'6 amperes=0*76 G.G-.S. unit, and the magnetising 
force 157*5x0*76=118 units. In point of fact the force was pro- 
bably something more than 75 and less than 118. 

In my own experiments both the magnetising coil and the rods of 
metal were much shorter than those used by Joule and Mayer. The 
length of the coil is 11*5 cm. ; it contains 876 turns of wire 1*22 mm. 
in diameter, wound in twelve layers on a brass tube with boxwood 
ends. The internal diameter of the tube is 1*5 cm., that of the coil is 
1'9 cm., and its external diameter is 5*2 cm. The mean length 
of the diagonals of the cylindrical layers of wire is 12 cm., and the 
field at the centre due to a current through the coil is approximately 

4*- 12 C~^1Q ^ when C is expressed in C.G.S. units, or 91*80 when 

C denotes the current in amperes. The strongest current which I 
have hitherto used was 3*27 amperes, and the greatest magnetising 
force was 3*27x91*8=300 units, Joule's maximum having been 126, 
and Mayer's, on the most favoui*able estimate, not gi*eater than 118. 

The apparatus for performing the experiment, which is of a very 
simple nature, is shown in fig. 1.* A mahogany table, TT, supported 
by three stout legs, the lower ends of which are let into a base board, 
G, carries a lever arrangement for causing the elongating or retract- 
ing rod under examination to deflect a mirror, M, which turns about 
its horizontal diameter upon knife edges. The lower end of the rod 
rests in a conical recess formed in a brass plate which is attached to a 
hinged board : the height of the plate can be adjusted by turniu:^ «i 
screw, 8s The rod passes through the coil, and also ttitow^ %. \v!C^<& 

* The diagram is not drawn to scale. 
VOL, XL, « 



114 Hr. S. Bidwell. On the Clumgn predueed b^ 




in the table, and its upper end, which is oh ittel -shaped, acts at B npon 
a brass lever, one end of which abate upon the knife edge. A, and the 
other upon a ehort arm, C, fixed to the back of the mirror. Shallow 
notches in the form of obtuse angles are cat in the lever (which is of 
square section) at the points where it bears upon the knife-edgt 
folcmm and the end of the i-od. The end of the lever remote from 
the fulcrum has the form of a chisel, the edge of which is tamed 
upwards and fits into a shallow groove cnt tranaveraely in the arm of 
the mirror. By means of a magic lantern, L, illuminated by a lime- 
light, the image of a horizontal wire is, after reflection from thf 
mirror, projected npon a distant vertical scale, E. A alight deflec- 
tion of the mirror caasea a couBiderabIc movement of the inoMre of the 
wire npon the scale. The actual dimensions aro as follows : — The dis- 
tance AB=10 mm., BC=170 mm., DC=7 mm., DE=3200 mm. 
(10 feet 6 inches). The maltiplying power of the arrangement, the 
beam of light being horizontal, is 3200x17x2/7=15,543 times.* 
The scale ia one of Elliott's ordinary galf-auometer scales, each divi- 
sion of which ia equal to a fortieth of au inch or 064 mm. There- 
fore a movement of the focuRsed wire tlirongh one scale division 
indicatea a difference in the length of the rod of 064/15,543= 
0'000041 mm. The length of magnetic metal in the rods used is 
100 mm., BO that a movement of one division shows a difference of 
0'00000041 in the length, equal to about a two and a half millionth 
part. 

For projecting the image of the wire npon the scale, a half-platv 
photographic portrait lens of high quality was used. When the best 
definition was secured, it was possible after a little practice to read 
the deflections to a quarter of a scale division with tolerable certainty. 

* The multiplior 2 ia used becauie tlic angle througli wliicli the leflerled b«am of 
ligfat ia deflected ii twice the ftDgle of dedeclion o[ the mirror. 



MagnetUaHan in the Length of Metal Rode, llj> 

In working with this apparatus, three possible sources of error were 
600B rerealed. The first was due to the expansion of the rod in con- 
sequence of the heating of the coil by the current. This effect could 
be distfaigiushed from the elongation resulting from magnetisation, by 
the £ut that tiie latter took place quite instantaneously, while the 
ezpHuion due to heat was gradual ; but it was likely to lead to un- 
oertuaiy in estimating the amount of permanent elongation accom- 
pu^ing the permanent or residual magnetism of the rod. This 
unoerteinty oould be reduced to a minimum by taking care to close 
the oiTouit only for a second or two when making an observation. 
The second possibility of error resulted from the gradual yielding of 
the magnetic rod, or, more probably, of some part of the base or 
frame of the apparatus, under the pressure, small though it was, of 
the brass lever. This may to a great extent be obviated by adjusting 
the apporatus and leaving it for half an hour before making an ob- 
servation ; but I am not quite sure that it ever entirely disappeared, 
for even though the image of the wire remained perfectly steady upon 
the scale so long as the apparatus was quite undisturbed, it is possible 
that the shocks produced by magnetising and demagnetising the rod 
might cause a sadden slight upward movement of the image, thus 
making the permanent elongation of the rod appear to be somewhat 
less than it in fact was. I think, however, that the error, after the 
apparatus has been at rest for a sufficient time, must be very small. 
In observing the purely temporary elongation resulting from so much 
of the magnetisation as is purely temporary, no uncertainty what- 
ever need arise from this cause, for the experiment can easily be re- 
|>eated as often as may be necessar}' to obtain uniform results ; but 
sin observation of the permanent extension cannot be repeated with- 
out dismantling the apparatus and demagnetising the rod, after which 
its condition will probably not bo exactly the same as before. 

Lastly, errors may arise from the electromagnetic attraction 
existing between the coil and the rod, which tends to draw a uniform 
rod into such a position that the middle point of its axis shall coincide 
with the centre of the coil. As at first constructed, the coil in my 
apparatus was attached by means of screws to the under side of the 
table, and the rod under examination passed freely through it, touching 
DOthing whatever except the brass plate at the bottom and the lever at 
the top. The length of the magnetic portion of the rod — that which 
Mras the subject of the experiment — was in every case, as already 
stated, exactly 10 cm., or 1*5 cm. less than the length of the coil. But 
the distance from the brass base plate to the lever was 21 cm., and in 
order to increase the experimental rods to this length, pieces of thick 
brass wire were screwed or soldered to their two ends ; thus the rodis 
when prepared for the experiment were of a compound form, con- 
sisting of iron, steel, or nickel in the middle, and brass at eaeh Qtid 



116 Mr. S. BidwelL On the Changes produced hy 

The relative lengths of the pieces of brass were so adjusted that when 
the compound rod was fixed in position, the centre of the magnetic 
portion of it coincided as nearly as possible with the centre of the 
coil. This arrangement was, however, found not to be entirely satis- 
factory. It was difficult to secure the required coincidence with 
perfect accuracy, and it was necessarily somewhat disturbed during 
the adjustment of the image of the wire upon the scale ; while, even 
supposing that the geometrical coincidence was perfect, it might well 
happen that owing to inequalities in the magnetic properties or 
physical condition of the rod, the source of error might still exist. 
A simple experiment showed conclusively the immense importance of 
guarding against any trace of this interaction between the rod and 
the coil. A compound rod of iron and brass was prepared, such that 
when it was placed with one end uppermost the centre of the iron 
was somewhat below that of the coil, and when the other end was 
uppermost the centre of the iron was about 5 mra. above that 
of the coil. A current was passed through the coil when the 
iron was in the first position and a certain elongation was 
indicated. The position of the rod was then reversed and the same 
current passed. It was expected that the apparent elongation would 
be diminished, but in point of fact an actual retraction equivalent to^ 
two or three scale divisions was indicated. The sucking action of th^ 
coil caused the lower end of the rod to press upon the base witl^ 
increased force ; the base yielded a few hundred thousandths of a. 
millimetre, and this was sufficient, in spite of the real elongation oP 
the rod, to cause the image of the wire upon the scale to move in the^ 
direction of retraction. 

It appeared that the only method of avoiding with certainty the 
misleading effects of this attraction between the coil and the rod 
would be to attach the two together. The pressure upon the base 
would then depend simply upon the joint weights of the coil and the 
rod, and would not be varied by any interaction between them. The 
coil was therefore detached from the table, and its ends were fitted 
with corks through which the experimental rod was passed, care 
being taken that it fitted tightly at both ends. The arrangement was 
then exactly as shown in fig. 1, the coil being supported solely by 
the rod ; and it was so used in all the experiments described in this 
paper. 

Before giving an account of the new effects which I have obtained, 
it may be well to state how far the maximum elongations and retrac- 
tions of iron and nickel bars, as indicated by mj apparatus, accord 
with those published by previous experimenters. This is done in the 
subjoined table. 



MapietiscUion in the Lengtii of Metal Rods. 



117 



Table I. 



Metal. 


Diameter in 
millimetres. 


Obsenrer. 


Mafn^etiRing 
force. 


Total 

elongation in 

fractions of 

the length. 


Soft iron .... 

Iron 

»» • • 

Nickii .*!!;!! 


6-85 
12-7 

25 4 

2-65 
3 65 

25 4 
9x0-75 


Joule 
Mayer 

Barrett ' 

BidweU 

ft 
Barrett 
BidweU 


64 

Between 

75 and 118 

" Maximum 

magnetisation" 

73 

Unknown 
800 


•00000562 
- -00000457 

[ -00000385 

•00000450 
•00000389 
•00000769 
•00001000 

• 



These fignres include tlie total elongation of the rods, i.e., that due 
to the permanent as well as to temporary magnetisation. 

The magnitnde of the effect nndoubtedlj varies considerably with 
the qaalitj of the iron employed ; that used in my own experiments 
was ordinary commercial iron wire annealed by being heated red hot 
and slowly cooled. The permanent elongation was, in both cases, 
rather more than one-third of the whole. For reasons already given, 
it was much easier to measure with certainty the temporary than the 
permanent effect. 

By using thinner rods and greater magnetising forces than those 
previously employed, I have arrived at the curious and interesting 
fact which it is the main purpose of this paper to describe. If the 
magnetisation be carried beyond a certain critical point, the conse- 
quent elongation, instead of remaining stationary at a maximum, 
becomes diminished, the diminution increasing approximately with 
the magnetising force. If the force be sufficiently increased a point 
is arrived at, varying according to the dimensions and quality of the 
iron, where the original length of the rod is totally unaffected 
by magnetisation. And if the magnetisation be carried beyond this 
point, the original length of the rod will be reduced. To take 
a concrete example: the maximum temporary elongation of my 
thinnest iron rod occurs when the external magnetising force is about 
45 ; an external force of about 212 has no effect whatever upon the 
length, which remains exactly the same as when the rod is unmagne- 
tised ; a force of about 300 causes the length of the rod to diminish, 
the amount of the retraction thus produced being about one-half that 
of the maximum elongation. Here I had exhausted the capability of 
my battery power — seven Orove cells — but so far 1 coTild. deW^Xt tlo 
indica^i^iz ibat a limit of retraction was being approached. 



118 Mr. S. Bidwell. 



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Magnetisation in the Length of Metal JRodB. 



i« 



I made a systematic conrae of observations witb three Iron rods of 
different thickneBses prepared ia the raanner described above. All 
were of ordinary commercial iron annealed in the usual manner. 
Their respective diameters were 265, 365, and 6'25 mm., and 
the len^h of each was 10(1 mm. The strength^ gf the fQCcessive 
magnetising currents in ampdres and the corresponding temporary 
elongations in scale divisions are given in Table II. The corrents 
can be approximately expressed as magnetising forces by moltiplying 
by 91*8, and the scale divisionB can be reduced to ten-milUonths of 
the length of the rod by moltiplying them by 4. 

The results are also shown graphically in the first three curves of 
fig. 2, in which the abscisse represent the magnetising currenta and 
the ordinatea the elongations. 




The elongations are those dne to temporary magnctiBation only. In 
oi'der to avoid the nncertainty attached to the elongating efiecta 
Iff permanent magnetism, I always at the beginning of an experiment, 
and before making an observation, passed through the coil the 
strongest current at my disposal, thus permanently magnetising the 
rod to sataratioQ. There appear to be two kinds of residnal mag- 
netism. When a strong current has been passed throngh the coil, 
tliB mngBetism which remaius after the current has ceaaei \iO %Qit Sa 
/or the moet part of a aafc-jsermanent nature. It t\ie tq4 w T)LTi.ftS&* 



120 Mr. S. Bidwell. On the Changes produced by 

turbed, the sab-permanent magnetism will remain wittioat material 
diminution for perhaps Half an hour, but in a short time it rapidly 
falls off. If, however, the rod is shaken, or even if it is remoYod 
from the coil with the greatest care, the magnetism which I have 
called sab-permanent instantly disappears. Bat, after the destraction 
of the sab-permanent magnetism, there still remains a small quantity 
of magnetism of a nature which may properly be called permanent, 
since it persists for days, or perhaps indefinitely, unless violent 
measures are resorted to for its removaL I find, by experiments 
which will be referred to hereafter, that when an iron rod has 
once been sub-permanently magnetised by a strong current, the 
intensity of the sub-permanent magnetisation is absolutely unaffected 
by the action of currents weaker, or not stronger, than the first. For 
a limited time (say half an hour) currents of varying strength may be 
passed through the coil, and the additional magnetism produced by 
their action is of a 'purely temporary nature, disappearing completely 
when the current ceases to flow, and leaving the sub-permanent 
magnetism exactly where it was before. The elongations referred to 
in my tables and curves are due to purely temporary magnetisation. 

The strength of the magnetising current was varied by means of a 
box of resistance coils, and was measured by a Helmholtz tangent 
galvanometer with four separate coils, of Elliott's manufacture. After 
the first two or three preliminary experiments, no attempt was made 
to read the galvanometer at the time when the observations of the 
elo.ngations were made : for, in order to do so, it was found necessary 
to keep the circuit closed for a period which was sufficiently long to 
cause the coil to become heated, and confusion was introduced owing 
to the heat expansion of the rod. A note was made of the resistances 
successively inserted, and the currents corresponding to the several 
resistances were afterwards leisurely and carefully determined. It 
was soon found that the action of the battery was so constant that 
several elongation experiments might be made on the assumption that 
the same currents accompanied the same resistances without any 
sensible error, except perhaps a slight one in the case of the strongest 
currents ; but the estimated currents were from time to time checked 
by reference to the galvanometer, and when any material variation 
was observed, a fresh series of galvanometer readings was made. 

An examination of the three iron curves discloses the following 
facts : — In every case the form of the curve for the first part of the 
ascent is sufficiently nearly parabolic in form to afford confirmation 
of Joule's law, that the elongation varies up to a certain point as the 
square of the magnetisation. After passing the maximum, the curve 
assumes a form which is apparently intended to be a straight line ; at 
all events, no single observation deviates irom. t\i© ^VwAi^i \vaa b-^ wi 
amount equivalent to more than hali a acal© divvsvoTi. Ai \>a\&\A^Q, 



Magnetisation in the Length of Metal Rods. ISl 

the retracidon after the mazimnin elongation increases with the 
external magnetising force. 

No oert&Ln indication of an approach to a limit of retraction is ob» 
s^rable in the carves. Stronger magnetising forces wonld of coarse 
show one, and I hope to be able to repeat the experiments with greater 
battery power. 

The maximum elongation is reached by the three rods with magne- 
tising currents which are the same in order of magnitude as the 
diameters of the rods. 

Lastly, it appears from the curves that the amount of maximum 
elongation is smaller when the diameter of the wire is greater. The 
successive maxima are 7, 6, and 4*25, and if an error of a quarter of 
a scale division be allowed, these maxima will be found to be in- 
versely proportional to the square roots of the diameters of the re- 
spective wires. 

7 X ^266=112 
6 X ^365=114 
4-25xy625=106» 

It seems to me difficult to account satisfactorily for this variation 
of the maximum elongation. It is of course easy to understand why 
a greater external magnetising force should be required to produce a 
^ven intensity of magnetisation in a thick rod than in a thin one. 
But it is not at first sight at all evident why, when the same mag- 
netisation is produced, the elongation should not be tHe same in both 
cases. Possibly my results may be due to a mere accident, such as a 
difference in the qualities of the three specimens of iron ; but their 
apparent regularity renders such an explanation somewhat improbable. 

It seemed extremely desirable that, if possible, a connexion should be 
established between the point of maximum elongation and some defi- 
nite phase of the magnetisation of the rod. Much time and labour 
were spent in endeavours to investigate the magnetisation by a method 
of induction ; but probably owing to the fact that the galvanometer 
used — one of Elliott's Thomson galvanometers, with the usual astatic 
system of magnets and an aluminium damping vane — was unsuited 
for the purpose, no results of any value were obtained. I was more 
successful in an attempt to measure by a deflection method the rela- 
tive values of the temporary moments which various magnetising 
currents prodaced in the three rods. The coil was placed in a 
horizontal position, and one of the rods inserted in the tube, where 
it was supported axially by means of corks at the two ends. A re- 
flecting galvanometer was placed at a suitable distance from it, as 
determined by preliminary trials, and the height and disposition of 
the galvanometer were so adjusted that its magnet woa on. «b\eN^ '^nJiJia. 

* If the last elongation bad been 4*5 the product wouVd h&^« V>©exv YVa. 



122 Mr. S. Bidwell. On the Changes produced by 

ihe axis of the coil, while the direction of the magnet bisected the 
axis of the coil at right angles. The galvanometer and the coil were 
connected in circuit with the box of resistance coils, the tangent 
galvanometer, and the battery, the connexions being so arranged that 
the electromagnetic actions of the magnetising coil and the galvano- 
meter coil nrged the galvanometer needle in opposite directions. The 
iron rod being temporarily removed from the coil, the galvanometer, 
which had a resistance of 1400 ohms, was shonted with a few centi- 
metres of German silver wire, and the length of the sbnnt was 
adjusted by trial until, when a strong current was passing, the action 
of the galvanometer coil upon the needle exactly balanced that of the 
maguetising coil and the connecting wires of the circuit, so that, on 
depressing the contact key, no movement of the needle occurred 
except (with the strongest currents) a slight momentary kick due to 
induction. 

The iron rod being replaced inside the coil, a strong current was 
caused to circulate round it for two or three seconds. The rod was 
thus sub-permanently magnetised as in the former experiments. The 
line of light was then brought to zero of the galvanometer scale by 
means of the controlling magnet. Great care was taken in setting 
up the scale to place it accurately at right angles to the magnetising 
coil, and in such a position that the perpendicular upon it from the 
middle of the galvanometer needle met it exactly at the zero point, a 
specially made T-square being used for the purpose. The magnetic 
Held in which* the galvanometer needle hung was the resultant of 
those due to the controlling magnet, the horizontal component of the 
earth's force, and the sub-permanent magnetism of the experimental 
rod. No attempt was made to determine its strength. 

Currents of gradually increasing strength were successively passed 
through the coil, and the deflections corresponding to the temporary 
moments of the rod were noted. When the circuit was opened, the spot 
of light returned in most cases accurately to zero, and the permanent 
deviations from zero never exceeded two or thi*ee divisions, equal to 
one-fortieth of an inch. The results are given in Table III, and shown 
graphically in the curves in fig. 3. In each separate experiment the 
galvanometer deflections are proportional to the temporary moments ; 
but these deflections and the ordinates of the curves are purely arbi- 
trary, and as regards the absolute values of the moments, they give 
no information, nor are the ordinates of one curve comparable with 
those of another. 

The relative changes in the values of the temporary moments with 

increasing magnetising forces are, however, clearly shown, and to 

ascertain the nature of these was the sole object of the experiment. 

7*l20 distance between the galvanometer magriet send tVia llax^^ rods 

was respectively 25 cm,, 36*5 cm., and 5S cm. 



Magnetiaation in tlie Length of Metal Rod». 



sipp^ipllip^ 



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124 Ht. S. Bidwell. On tht Change* prodne«d by 




The poiutH correspondiiig to the maximam elungation in the three 
carvBB ai-e marked with the letter £. At first sight the; seem to 
possess no particular distinguishing characteristic in common. In- 
deed the only points in the curves which appear to be marked hy any 
special property are those which are called by Chrystal (" Enc. Brit.") 
after Wiedemann, the "turning points." TJp to these points the 
temporary moments increase with the magnetising force, or even more 
rapidly ; after the points are passed, the rate of increase in the tem- 
porary moments is leas than that of the magnetising force. When the 
carve does not begin to ascend in a straight line, the turning points 
arc found by drawing tangents from the origin : they are indicated in 
Uie corves by the letter T,' but it is not easy to determine their posi- 
tions with perfect accuracy. 

From a careful examination of these curves it appears probable that 
a simple relation does exist between the turning points and the points 
of maximum elongation, the abscissa of the points of maximam elonga- 
tion being almost exactly equal to twice those of the turning points. 

• According to Bowland ("Phil. Mag.," 1878, vol. ii, p. 155), "the teraponuy 
mttgnoliam tncreuos continuaUj with ths current." Thii may be strictly true (up 
to the turning poiot) For rod* or riogB havtiig the di&meter of thoee uied hj 
BoffUnd. Thus the curre for m; tliichnt iron rod uwnda in a. perfectly itraiglit 
line/ but a ulight coavezity towuds the Bii< ot -c m&y be auspected in the mediuni 
one, and in the tbinaeM tttch cvnveiity i* i^iute en&ent. lt,\Kei«iTaoT«'Cai'^B&'v\ 
fJ" cam for » wire, 0'77mm. in dikmelor, given in&K. ^. 



Magnetisation in the Length of Metal Rode. 125 

re also made a great number of experiments with steel. The 
obtained appeared at first to be of the most inconsistent 
er, and it was with difficaltj that I finally succeeded in evolv- 
er out of them. The fact clearly is that the point of maximum 
Lon (when there is one) depends in a very remarkable manner 
le hardness or temper of the steel. Like Joule, I found that a 
dl rod which had been neither annealed nor tempered behaved 
' much the same manner as iron, though the effects were 
. There was a point of maximum elongation which was well 
, but I was not able by any current at my command to produce 
■etraction. A rod which was made exceedingly hard by being 
I into cold water when at a bright red heat, had no point of 
im elongation within the limits of my magnetising currents, 
nporary elongation continually increasing with increasing 
isation, and giving no evidence of an approach to a limit. 
Bn the same rod was let down to a yellow temper its behaviour 
together different. With a very small magnetising force it 
signs of retraction, and the retraction increased with strongei* 
ising currents, ultimately becoming very considerable. A rod 
)d blue also retracted when magnetised, bat the effect did not 
) appear until the magnetising force was much greater than 
pessary when the temper was yellow, and after the rod had 
ill further let down by heating, a measurable elongation 
i before the magnetising force was sufficient to cause retrac- 

Q, another piece of steel was hardened by raising it to a dull 
t and dropping it into cold water. It could easily be marked 
file, and was certainly softer than the last-mentioned rod before 
empered, though it appeared to be harder than the same rod 
allow condition. The new hard rod was slightly elongated by 
nagnetisation, and after passing a maximum retracted at about 
e rate as iron. 

iiese various results, which at first sight appeared to be discon- 
and inharmonious, point to the following conclusion : — The 
value of the magnetising force for a steel rod diminishes as the 
;s becomes greater up to a certain point corresponding to a 
temper, after which it increases, and, with very hard steel, 
3 very high. There is therefore a critical degree of hardness 
ch the value of the critical magnetising force is a minimum ; 
of a yellow temper the value of the critical magnetising force 
• than in steel which is either softer or harder. 
J careful experiments were made with the hard steel rod last 
i to. The results are contained in Table II, and the corre- 
\g curve in Gg. 2. As in the case of iron, t\vQ yo^ '^^ja ^-wK* 
'ntJj- magnetised by a current equal to the stxoiig;es\» SKjXi^^- 



126 Mr. S. Bidwell. On the Changes produced by 

qoently used. The relations of the magnetising force and temporary 
moment appear in Table III and in the last cnrve of fig. 3. In this 
experiment the distance between the steel rod and the galvanometer 
magnet was 15 cm. 

In the light of these experiments I have endeavonred to find an 
explanation of the anomalons results obtained by Joule and by Mayer 
with hard steel. It will be remembered that Jonle, using g^raduaUy 
increasing currents, found that (after the first current, which produced 
no efiect whatever while it circulated, but was followed by a small 
elongation when it had ceased) his hard steel bar was slightly 
elongated both when the current was made and when it was broken, 
the length of the bar being thus continuously increased. Though I 
have made many attempts, using steel rods in different conditions, to 
obtain Joule's results, I have never succeeded in finding a rod which 
behaved in the manner described by him. Below I give Joule's table, 
and also a diagpram in which I have plotted his results, the abscissas 
representing the magnetic intensity of the bar, and the ordinates the 
correspondiug elongations. Both are on an arbitrary scale : — 

Table IV (Joule's). 



Deflection of 
galvanometer. 


Magnetic 
intensity. 


Elongation 
of bar. 


39° 0' 


... Ill ... 








. . . 1 -se* . . . 


0-2 


52 35 


... 4-09 ... 


10 





. . . 2-85 ... 


1-3 


60 15 


... 5-10 ... 


1-8 





3-52 ... 


1-9 


69 45 


5-91 . . . 


2-5 





4-20 ... 


2 '7 



It clearly appears that the elongations due to permanent magne- 
tisation and to permanent + temporary (i.e., total) magnetisation lie 
upon separate curves. And, since the total cnrve is below the perma- 
nent curve, it follows that the temporary magnetisation has a nega- 
tive or retracting effect. Taking ordinates equal to the differences 
between those of the permanent and total curves, I have plotted the 
curve for temporary magnetisation, which, of course, lies on the 
negative side of the horizontal axis, and starts fi*om the point repre- 
senting a magnetic intensity of 1*11. Following the analogy of 
other experiments, I have continued the curve above the horizontal 
axis representing this part of it by a dotted line ; it is probable that 

* It is very extraordinarj that the '* magnetic intensity '* of the bar should be 
firroAter after the current had been cut off than it 'waa ^\ieii V\L<b c\xxt«(A. -sc^a ^hivi^%. 
'Joalc makes no reference to the fact. 



MagnetUation in the Length of Metal RoiU. 




anj elon^taon represented by the dntted portion wonld bo too small 
to bo measarable. 

The resnlts of this experiment of Joule's are thns shown to be 
■■«concilable with others, if we may make the assnmption that in this 
particnlar specimen of steel the elongations dne to temporary and 
permanent m^netiaation followed different laws, and that while the 
critical point of the former occurred at an nnusaally early stage, that 
of the latter was not reached within the limits of the experiment. It 
may be indeed that this is always the case, though under ordinary 
ci re nm stances the difference is too email to lead to the anomaloos 
result under discnssion. Having confined my attention almost 
entirely to the investigation of temporary effects, I have tittle experi- 
mental evidence to bring forward bearing upon the point.* 

Mayer's results may be mnch more easily accounted for. The fact 
that his steel rods were invariably shortened by magnetisation (after 
the first magnetisation, the effect of which varied in different specie 
mens) clearly indicates that his magnetising force exceeded the 
critical valne, which was smaller for the steel bars than for the iron 
which he bad previously used. He apparently never monetised bis 

• Were it not fur tlic pton'rbial accuracj of Joule's work, a simpler eiplanation 
of tlie anomaly would have Bugge«t«d itself. The lower of the two curves above 
the horiioatal hiib represeiitB the atot« of things uiAi7e a current it paniag, and the 
fact that this curve does not coincide with the upper one might, perhaps, be 
scoonnted for bj the " solenoidal suction " which would occur if the rod were not 
<|uitc Bymmetricall}' placed with respect to the coil, or even if it were not perfectly 
liomogeneous throughout. Thus, the apparent elongations when the circuit was 
braken would he really due to the cessation of the suction, while the elongationa 
indicated when the circuit was closed would be less than those which actually 
occurred. Each of the vertical diviaionB in the diagram represents only one 
thirteen -millionth part of the length of the rod : a very small variation in ttie 
preamtire ol the end of the rod upon its support would, tliewtoTei^ia^e n wnsft^ 
effect.— (Februarjr 23, 1886.) 



128 Mr. S. BidwelL On the Changes produced by 

steel with cnrrents of less tlian the maximum strength, and a smaller 
magnetising force would perhaps have produced elongation, unless 
indeed the permanent magnetisation induced by the first current 
equalled or exceeded the critical value. This was almost certainly 
the case with his yellow-tempered steel, which was permanently 
shortened by the first magnetisation, while all the other specimens 
were permanently elongated. These considerations are consistent 
with all the phenomena exhibited by Mayer's steel bars. 

In working with a rod of steel which had been neither annealed 
nor hardened, I obtained some very curious effects of which I am not 
at present prepared to ofier a complete explanation. I therefore 
describe the experiments exactly as they were performed, without 
attempting to account for the results. 

Experiment 1. — A current of 2 amperes was passed through the 
coil, whereupon the rod elongated 3 scale divisions. Without 
breaking the circuit, the current was reduced by inserting resistance 
to 0*6 ampere. The rod underwent a further elongation of 3 divi- 
sions, making the total elongation equal to 6 divisions. On breaking 
the circuit the rod retracted 6 divisions, returning to its original 
length ; but when the circuit was again closed, the resistance still 
being inserted and the current consequently 0*6 ampere, the resulting 
elongation was only 3 divisions. 

It appears therefore that a strong magnetising force subsequently 
diminished causes a greater temporary elongation than the diminished 
force is capable of producing if applied in the first place. 

Experiment 2. — A current of 2 amperes being passed through the 
coil, an elongation of 3 scale divisions was produced. The current 
was reduced to 0*26 ampere, when a further elongation of 1 division 
occurred. On breaking the current the rod returned to its original 
length. Once more a current of 0*26 ampere was passed through the 
coil, but no movement whatever occurred. 

From this it appears that the temporary elongation of a steel rod 
when once produced may be maintained by a magnetising force which 
is itself too small to cause any perceptible elongation whatever. 

Something of the same kind, though in a smaller degree, was 
observed by Mayer in rods of iron. 

Both these experiments were repeated many times, the results 
being invariably of the same character, and there is no doubt what- 
ever as to the reality of the effects described. 

On a small scale, I have repeated some of Joule's experiments with 
stretched wires, and found, as he did, that when a wire was loaded 
with a certain weight, the effect of magnetisation was not elongation 
but retraction. No measurements, however, were attempted, my 
apparatus not being well adapted for the purpose. 
Jt appeared, npon consideration, t\\at t\i^ xeauV^a oi V>caa ^^a.% 



Magnetisation in the LeTigth of Metal Rods, 



129 



of experimeats would be brought into perfect harmony with those 
already described, if it could be shown that the critical value of the 
magnetising force was lowered when the rod was stretched. There 
were reasons arising from the nature of my apparatus why I could 
not attempt to prove this directly ; but an indirect method affords 
strong evidence that this is the case. By the method of deflection 
already described, it could be easily ascertained whether the position 
of the '* turning point " was affected by stretching a wire. Now, in 
every case which I have hitherto investigated, it was found that the 
critical value of the magnetising force was very approximately equal 
to twice the magnetising force at the turning point. If therefore it 
should appear that the position of the turning point was affected by 
stretching, the presumption would be strong that the critical value 
would be altered to a corresponding extent. 

Four deflection experiments were therefore made: In the first the 
wire, which was of annealed iron 0*77 mm. in diameter, was supported 
in a horizontal position inside the coil by means of corks ; gradually 
increasing currents were passed through the coil and the galvano- 
meter deflections noted as in former cases. The wire was then 
removed, and after being demagnetised was replaced inside the coil, 
and a weight of 7 lbs. was attached to it by means of a cord passing 
over a pulley. Once more the deflections accompanying increasing 
currents were noted. 

The third and fourth experiments were similar to the first two, 
except for the fact that the wire was magnetised to saturation before 
any observations were made. The deflections recorded in the first 
and second experiments are due therefore to the sum of the permanent 



Table V. 



/ 





Magnetometer deflections for 


Magnetometer deflections for 




total magnetisation. 


temporary magnetisation. 


Currents. 








Unstretched. 


Stretched. 


Unstretched. 


Stretched. 


0012 


12 


IG 


4-5 


6-5 ' 


0-015 


16-5 


24 


6 


® 1 


023 


25 


35 


10 


15 ' 


027 


31 


40 


13 


18 


035 


38 


i7 


18 


23 


0042 


44 


51 


21-5 


27 


051 


51 


56 


27 


30-5 


061 


50 


59 


31 


34 


0-073 


62 


64 


30 


37 


o-ios 


71 


70 


44 


41-5 


0-185 J 
0-274 / 


80 


76' 


52 \ AH •\> 


88-5 1 


70 


55 


\ ^^ 



\ 



VOL. XL. 



130 Mr. S. Bidwell. On the Changn produced 6y 

&nil temporary inaguetdsationB, while those in the third and finrtii 
were produced bj the temporal^ magnetiafttioa only. The rendti 
are given in Table V and in the anhjoined cnrvea (Sg, 5). Bodi aeriea 




are inlerestiug as affording an tllustmtioD of the law which has been 
fully investigated by Sir William Thomson,* that the magnetisation 
of a wire is at first increased and afterwards diminished by stretch- 
ing; but the results of the second series only (in which the ordinates 
represent the temporary moments) are comparable with those of the 
former expcriments.t 

Befcrring to the carve of temporary magnetisation, it will be seen 
that the magnetising cuirent at the taming point is reduced by 
stretching with a weight of 7 lbs. from 0-051 to 0030 : presumably, 
therefore, the magnetising current for the critical point is at the 
same time reduced from about 0'10'2 to 0'060, and a current between 
these limits would be accompanied by elongation when the wiru was 
unstretched, and by retraction when it was stretched. 

For a few experiments made with nickel, a strip was used of the 
following dimensions : — Length 100 mm., breadth 9 mm., thickness 

• "Pliil. Trone.," 1876 and 1879. 

t It Bhou)d be noticed that tlia ordinate* are on a different Bcale In the two 
diagrams, as ttrj- bo seen bj compariai; tlio figures at tbe Bide. The distsnoe between 
IJie wire nad the centre of the galTanometer ma jnel t«« V^ irm- vn ii 'i« tn-^iTv- 



MagnetUation in Uie Length of Metal Rode, 131 

0'75 mm. Bmss wires wcro Bolderod to the onda in the nenal 



Tbo permanent magnetisation indnced by the strongest corrent 
appeal^ not to cause a permanent retraction of more than one scale 
diTision. The temporary retractions produced by increasing mag- 
netising forces are given in Table II and in fig. 6. The retractions 




arc of much greater extent than thu elongations of iron nndor similar 
circnmstftDcos, and thongh the cnrvo aSords evidence of an approach 
to a limit, it is nevertheless clear that a considerable farther retrac- 
tion would have occurred if the cnirent had been increased beyond 
the power of my battery. 

I also made a deficction experiment with the nickel, thinking it 
might possibly bo the case that it had no turning point., i.e., that the 
ratio of the temporary moments lo the magnetising forces docrcnscd 
ah initio. It appeared, however, that the taming point waa aanBunlly 
■well marked, occurring with a cnrrent of 0'042 amporo. The details 
are given in Table III and fig. 6. The experiment waa repeated two 
or three times with the same result, the nickel having been in each 
case previously magnetised with a strong current. The distance 
between the centre of the galvanometer needle and the nickel was 
15 cm. 

The bebavionr of a stretched nickel wire has, I believe, never 
hitherto been investigated. I therefore made the experiment with n 
nickel wire O'S mm. in dinmetcr, loaded with n wc\g\\\. ci^to^aXotA, ^o 
abont 2 lbs. The result of magnetisation was n ^crj coTiKv4«niNA% 



1 32 Mr. S. Bidwell. On the Changes produced by 

retraction, but for reasons already referred to I was unable to measure 
the amonnt. 

I have not for some weeks occupied myself with the investigation 
of the singular facts described in this paper withoat from time to 
time indulging in speculations as to their physical causes. It* is, 
however, evident enough that the investigation is incomplete, and 
many more experiments, some of them requiring additional apparatos 
of a special kind, remain to be tried. I hope to return to the subject 
on a future occasion, and in the meantime refrain from theorising as 
to the causes of the phenomena. 

SUMMABT. 

The experiments have not been sufficiently numerous to render 
generalisation in all cases perfectly safe ; but, so far as they go, they 
indicate the following laws : — • 

I. Iran. 

1. The length of an iron rod is increased by magnetisation up to 
a certain critical value of the magnetising force, when a maximum 
elongation is reached. 

2. If the critical value of the magnetising force is exceeded, tbe 
elongation is diminished*, until, with a sufficiently powerful force, the 
original length of the rod is unaffected, and if the magnetising force 
is still further increased the rod undergoes retraction. 

3. Shortly after the critical point is passed, the elongation 
diminishes in proportion as the magnetising force increases. The 
greatest actual retraction hitherto observed was equal to about half 
the greatest elongation ; but there was no indication of a limit, and 
a stronger magnetising force would have produced further retrac* 
tion. 

4. The value of the external magnetising force con*esponding to 
maximum elongation is nearly equal to twice its value at the " turning 
point.** 

Definition, — The turning point in the magnetisation of an iron bar 
is reached when the temporary moment begins to increase less rapidly 
than the external magnetising force. 

5. The external magnetising force corresponding to the point of 
maximum elongation is greater for thick rods than for thin rods. 

6. The amount of the maximum elongation varies inversely as the 
square root of the diameter of the rod. 

7. The turning point, and therefore presumably the point of maxi- 
mum elongation, occurs with a smaller magnetising force when the 
rod 18 stretched than when it is unstretcbed, 

♦ The elongationa and magnetisatlonB referred \» «t« ^lo^Twrj otX-j, 



Magneiisation in the Length of Metal Rods. 138 

II. Steel. 

The behaviour of steel varies gi*eatl7 with the hardness and temper 
of the metal. More experiments than I have hitherto made wonld be 
necessary to establish the general laws with certainty ; bnt my results 
are consistent with the following conclusions : — 

1. In soft steel magnetisation produces elongation, which increases 
np to a certain value of the magnetising force, and afterwards 
diminishes. The maximum elongation is less than in the case of iron, 
and the rate of diminution after the maximum is passed is also 
less. 

2. The critical value of the magnetising force for a steel bar 
diminishes with increasing hardness of the steel up to a certain point 
corresponding to a yellow temper, after which it again increases, and 
with very hard steel becomes very high. 

3. In soft steel a strong magnetising force subsequently diminished 
may cause a greater temporary elongation than the diminished force 
is capable of producing if applied in the first place. 

4. A temporary elongation when once produced in soft steel may 
be maintained by a magnetising force which is itself too small to 
originate any perceptible elongation. 

ni. NicTcel. 

1. Nickel continues to retract with magnetising forces far exceeding 
those which produce the maximum elongation of iron. The g^reatest 
retraction of nickel hitherto observed is more than three times as 
great as the maximum elongation of iron, and the limit has not yet 
been reached. 

2. A nickel wire stretched by a weight undergoes retraction when 
magnetised. 



VOL. XL. 



iSi On Intravascular Clotting. [Feb. 4^ 



February 4, 1886. 
Professor STOKES, D.C.L., President, in the Chair. 

The Presents received were laid on the table, and thanks ordered 
for them. 

The following Papers were read : — 

I. " On Intravascular Clotting." By L. C. Wooldridge, M.B., 
D.Sc, Demonstrator of Physiology in Gruy's Hospital (from 
the Brown Institution). Communicated by Professor 
BuRDON Sanderson, F.R.S. Received January 21, 1886. 

Notwithstanding all the work that has been done on the subject of 
the coagulation of the blood, the definite results which have been 
obtained as to intravascular clotting are extremely scsntj. 

I think most physiologists will agree witb me in the statement, that 
no method is known by which one can, at will, produce a complete 
fibrinous coagulation in the vessels of a living animal. I have found 
such a method, and one which appears to be infallible in its action. 

I have succeeded in obtaining from the testis and thymus gland of 
the calf, a substance presenting the characters of a proteid, the injcn*- 
tion of which in sufficient quantity into the veins of an animal, will 
cause instant death, owing to widespread intravascular clotting. 

In its preparation I proceed in the following manner : — The organ 
having been finely minced, is mixed with a large quantity of distilled 
water and aliowed to stand for some hours. The liquid is then 
strained off and subjected to the action of a centrifugal machine so 
long as any deposit is separated from it. The clear liquid is then 
made strongly acid with acetic acid, whereupon a bulky precipitate 
appears, which is collected by the centrifugal machine, and well 
washed with water acidified with acetic acid. 

If this precipitate is dissolved in alkaline salt solution and injected 
into the circulation, it produces intravascular clotting. If the quantity 
injected is considerable (1 to 2 grams), it causes instant death in a 
dog of moderate size with complete thrombosis of the vena porta and 
its branches. Clots are also found in the right side of the heart and 
in the pulmonary artery. In a rabbit I found that the injection of 
1 gram caused death before the injection was completed. Here there 
was thrombosis of the portal vein, iliac and renal veins, and of the 
vena cava and aorta, and clots in both sides of the heart. 

When death occurs, ^e blood which fLowE itoTii «*. c^\. ^xV^r^ \^^'q^ 



1886.] Larva of Smerinthus ocellatuB and its FoodrplanU. 135 

to coagulate, and when the qaantitj injected is insufficient to kill, the 
blood (drawn off after injection) may remain nncoagpilated for some 
days. In either case coagnli^tion of shed blood may be induced by 
the addition to it of the liquid which has been injected. It therefore 
appears that the agent which brings abont coagulation, intra vetuu, 
must disappear in the act of coagulation. The shed blood contains 
only a minute trace of fibrin ferment. 

The acetic acid precipitate is soluble* in 0*5 per cent. HGl solution. 
On digesting this solution at 37^, after the addition of pepsine, a part 
of it is converted into peptone, but a precipitate appears in the pro- 
cess which is permanent. When the digestive products (peptone 
and precipitate), having been rendered alkaline, are injected into the 
circulation, no effect is prodnced.f There is neither intravascular 
coagulation, nor is the blood deprived of its power of coag^ulation ; 
but if fresh acetic acid precipitate be added to the liquid, both effects 
follow injection. Consequently, the failure of effect when the pro- 
ducts of digestion are injected alone, is not due to presence of pepsine 
or peptone. I have ascertained that the acetic acid precipitate does 
not cause coagulation of dilute magnesium sulphate plasma, which 
coagulates readily on the addition of fibrin ferment. The agent, 
therefore, in producing intravascular coagulation cannot be identified 
with that body. 



II. " A Further Enquiry into a Special Colour-relation between 
the Larva of Smerinthus ocellatus and its Food-plants." 
By Edward B. Poulton, M.A., of Jesus and Keblo 
Colleges, Oxford. Communicated by Professor J. S. 
BuRDON Sanderson, F.R.S. Received January 26, 1886. 

CONTENTS. PAQB 

1. Introdactory 136 

2. EiperimenU upon the LarrsB of Smerinthus ocellatus during 1885 138 

3. The General Results of the Breeding Experiments 153 

4. ObserYStions in the Field upon LarvflB of Smerinthus oeeUatus during 1885 157 

5. Experiments upon Captured Larree 159 

6. Conclusions arrived at bj the Consideration of the Captured Lanrse : the 

Beconciliation of Conflicting Evidence 159 

7. The whole of the Evidence Summarised 165 

8. Conclusion 172 

1. Introductory, 

In my previous paper upon this subject (" Proc. Roy. Soc.,*' No. 237, 
1885, p. 209), *I gave an account of some breeding experiments under- 

* As casein is "Boluhle " in milk. 
t The total quantity of peptone is Tery «mttW. 

\k 2* 



136 Mr. E. B. Poulton. Colour^elation between the [Feb. i, 

taken in 1884 in which the larvao of Smerxnthus ocellatus were fed 
upon varions food-plants, and the resulting larval colonra were care- 
fnlly compared. I also described the colours of captured larvse of the 
same species, and mentioned the trees upon which they had been found. 
1 was extremely anxious to continue the investigation in the following, 
year (1885) in order chiefly to throw further light upon the two 
following points : — 

(1.) By means of experiments and observations I had been enabled 
to show that the colour of the larva was in most cases affected by the 
food-plant, but there remained a certain number of exceptions which 
had to be accounted for. I suggested that these might be explained 
by supposing that the tendencies towards certain colours which were 
produced by particular food-plants in one generation became inde- 
pendent larval tendencies in the next, which might modify or over- 
c< me the usual effects of the food-plants ; and that such transmitted 
infiuences augmented as the number of generations upon one food- 
plant (or others producing similar effects) increased. I was desirous 
of testing this theory by breeding from moths of which the history in 
the larval state was accurately known. 

(2.) In my last paper I also pointed out that there was considerable 
evidence for believing that the influence of the food upon the larval 
colour is not a comparatively simple phytophagic influence, but one 
which is exceedingly complex, being brought about by the colour of 
part of the leaf (the part which the larva resembles), acting as a 
stimulus to some larval sensory surface (presumably the ocelli) and so 
through the nervous system regulating the amounts and kinds of the 
vegetal pigments absorbed and made use of, and that of the larval 
pigments deposited. 

I wished to test this theory by feeding the larvae under such con- 
ditions that they could only be affected by the colour from one side 
of the leaves of their food- plant, and it seemed that the best way of 
achieving this object was by sewing the leaves together. In the sub- 
sequent experiments the edges of the leaves were at first pared with 
the scissors to make them correspond, but it was afterwards found 
better to double each single leaf longitudinal and sew together the 
opposite margins which were thus brought into contact. The inten- 
tion of the experiment was to compare the larvae which had been 
exposed to the colour of the under sides of the leaves only, with thoso 
which had been exposed to the upper sides only, and with those which 
had been fed upon the normal leaves. If the larval colours varied 
according to these three sets of conditions, it would be quite clear 
that the larvae were only influenced by the colour of the leaf-surface, 
because the leaf-substanoe eaten (from the edge through its whole 
thickness) must have been identical in all three cases. I also wished 
^ rsry the experiment by feeding some \arv» w^oiL\&v^«!^'^\ivs^\cai^ 



1886]. Larva of Smerinthtua ocellatus and its Food-plants. 137 

been given a dilEerent tint artificially by removing the " bloom " from 
the nnder surface, and to te^t whether the ocelli formed the impres- 
sionable part of the larvsB by investigating the efEect upon colonr of 
covering these organs with some innocaous opaque pigment. 

I also wished to further investigate the effect of certain food-plants, 
aboat which the evidence was conflicting, and to carefully watch for 
instances of individual variation among the larvso from the same batch 
of eggs and fed upon the same food, to look out for any indications 
which would throw light upon the red-spotted varieties, and also to 
further enquire into the periods during which, the larvas ai'e most 
susceptible to the influence of the food- plant. 

As far as these questions could be answered by work in the field, I 
was very successful, for the larvsB were even more abundant than in 
the summer of 1884, and I was able to extend my area of observation 
to Switzerland. I have also been exceedingly glad to be able to 
reconcile the conflicting evidence given in my last paper. But the 
breeding experiments did not yield adequate results, considering the 
immense amount of labour bestowed upon them. In the first place 
the moths emerged in an unfortunate order — a great many males, and 
later a great many females. Then of those which emerged together, 
there was great difficulty in obtaining such a system of pairing as I 
was desirous of instituting, the result being that I could get no larvae 
with a strong hereditary tendency towards the yellowish variety ; and 
these I was most anxious to obtain, because all ray bred larvsB in 
1884 tended very strongly in the opposite direction. The eggs I 
obtained in nearly all cases resulted from pairing the moths which 
came from these bred larvad (1884). Although disappointed in the 
pairing of the moths, it seemed likely that the experiments would 
yield sufficiently convincing results from the very comprehensive 
scale on which they were conducted, for in July, 1885, I had many 
hundreds of young larvsB belonging to five different families. After 
the great labour of bringing this large number through the most 
delicate period of their lives, and just before the results appeared, the 
larvae began to die off in hundreds, so that only seventy. five lived to 
an age at which trustworthy observations could be made. I can only 
suggest that this altogether exceptional mortality may have been due 
to the excessive heat and dryness which prevailed at the time. I do 
not think that it can have been due to the fact that both parents of 
the majority of the 1885 larvae resulted from larvad belonging to the 
same batch in 1884, because such interbreeding among moths does 
not produce injurious effects, at any rate until after it has been con- 
tinned for many generations. Besides, in one instance, the larvao 
^ere the offspring of parents which came from quite different 
loc&hties, and these did not ancceed any better iban ttie o\^iet^. ^xxfe 
altbongb a very email proportion of the larvae anrvived, VXie^ v5^t^ 



138 Mr. E. B. Poulton. Colour^elation between the [Feb. 4. 

still fairly nnmeroas, and formed a considerable body of evidence 
bearing npon the qnesidons alluded to above, and giving distinct 
answers to all of tbem, except the one which bears npon the time of 
life during which the larvso are most susceptible to the inflnenoes of 
the environment, and that which suggests the ocelli as the sensory 
surface which is influenced. 

Before describing the experiments in detail, I wish to express mj 
sincere thanks to my wife for her kind help in the labour of attending 
to so many larvao, and in the troublesome work of sewing the leaves 
together. Mr. O. C. Druce has also kindly supplied me with the 
branches of certain species of food-plant when I was away from home, 
and has rendered me invaluable assistance in naming the sallows. 
Mr. J. G. Baker, of Kew, also kindly named the Swiss sallows, of 
which specimens were sent to h*m by Mr. Druce. 

2. Experiments upon the Larvm of Smerinthus ocellatus during 1885. 

The following experiments are arranged in five different series, 
belonging respectively to five different batches of eggs. There is 
complete uncertainty as to the male parent (if any) in Series II, and 
consequently there is some doubt thrown over the male parent in 
Series III, because in these cases (alone) the same female laid two 
batches of eggs. The cause of the uncertainty is explained at the 
beginning of Series II. The series are arranged in a succession 
which corresponds to an advance in the (presumably) hereditary ten- 
dency from the whitish towards the yellowish variety. And so also 
in each series the different sets of experiments are arranged in an 
order which coiresponds to a similar advance in the tendencies known 
to be produced by the food-plants, i.e., beginning with apple and 
ending with ScUix rubra. 

But the order is merely provisional in the case of less definite 
tendencies, or of plants which are little known as food-plants. It 
must also be remembered that the difference between the hereditary 
tendencies of the various series is very small, because of the failure 
(except in one case in which very few larvso lived) to obtain any eggs 
from moths which came from yellowish larvsd. 

Series L 

Eggs were laid in June, 1885, by a female moth bred from a larva 
which had been fed during 1884, for the whole period of larval life 
upon ordinary apple, and which was a typically whitish-green variety 
(mentioned in "Proc. Roy. Soc.," No. 237, 1885, p. 300). The eggB 
were fertilised by a male moth bred from a larva which had been fed 
npon crab for the whole of its life, and was a similar whitish variety 
(also mentioned on p. 300). Hence the inherited tendencies must 
Aave been strong! jr towards the wViUeal vonaViy o^ V\^\%W^a, 



88R.] Lavjoa of Smerinthus oceUatufii and its Food^lants. 139 

Out of a large number of larvsB which hatched at the beginning of 
^nly, 1885, a very small proportion lived nntil they were old enough 
o be of use in the present investigation. A careful examination of 
he survivors was made on August 12th, with the following results: — 

1. PyrusMalus (wir. ctcerha), — Five larvfld (including one which was 
OQnd after escaping, and which almost certainly belonged to this lot) 
rere hatched on July 2nd, and now four were well in the last stage and 
mo was changing its last skin. All five were extreme whitish varieties. 
Sventually all these larvsB died, but their colour was unchanged, and 
hey were sufficiently advanced to warrant the conclusion that no 
'urther alteration would have taken place. 

2. PopulfM tremulay 8^c, — One larva, hatched July 2nd, was now 
^August 12th) changing its skin for the last time and seemed to be a 
whitish variety. By August 20th it was well in the last stage and an 
intermediate variety, and without further change on August 27th, 
when it was nearly full- fed (ceasing to feed in a day or two). After 
the first fortnight the larva was fed upon a somewhat similar species 
of poplar, which 1 have not yet been able to name with certainty. 

8. Sodix babyhnica, — One larva (hatched July 3rd) had now 
entered upon the last stage, and seemed to be well on the yellowish 
ude of an intermediate variety. This description especially applied 
to the back, but there was a blueness about the ventral surface and 
lower part of the sides which is never seen in a true yellowish variety. 
On August 20th the larva was still on the yellowish side of inter- 
mediate, but not to such an extent as that seen in larvso of Series 111, 
which had been fed upon the same plant. Later, the larva became 
less yellow, so that by August 27th it was distinctly intermediate, 
and remained without further change until September 3rd, when it 
ceased feeding. 

4. Salix amygdalina, July 4ith — ISth, S* triandra^ July \Zth — 14<^, 
and 8. rubra, July Uth, onwards. — One larva (hatched July 4th — 5th) 
was changing its last skin and apparently whitish. Another larva 
had died at the beginning of the last stage, and was also whitish. 
The former was dead by August 20th, so that no results were ob- 
tained from these larvad, except the fact that the tendencies of the 
food-plants (towards producing the yellowish varieties) had evi- 
dently been largely counteracted in these larvsB. This larva is after- 
wards described as if fed upon 8, rubray for the leaves were selected 
so as to be similar to those of this tree in their effects. 

The effects of hereditary influence are certainly seen in the larvsB of 
this series. The parent larvee were extreme white varieties, and 
belonged to a group which evidently inherited a very strong tendency 
in this direction, as was shown by the comparatively slight effect that 
followed the ztse of foods which most powerfully tmi^ \o ^^w^wwei 
fellow varieties. It is certain that more dependence^ e«ai/\>^ ^'dfi.^ 



140 Mr. E. B. Poolton. Colour^elation between tlie [Feb. 4, 

npon this proof of a larval tendency, than by trusting to the mazimnm 
resnlts obtained by the use of food-plants which tend to prodnce white 
varieties ; becanse the power of the latter is so g^at as to afford no 
means of discriminating between larv89 with different tendencies except 
when the latter are very exceptionally strong in the direction of yellow. 
(For the proof of the strong tendencies of the parent larvad, and an 
account of the effects of various foods upon them, see '' Proc. Roy. Soc," 
as above quoted, pp. 298 — 300.) The larval tendencies in this case were 
even stronger than in the parents, having been augmented by inheri- 
tance from the latter. Grab, which has no power in checking the 
tendency towards white (I cannot yet believe that it causes white itself) 
produced the most extreme white varieties in these larvsB as in their 
parents (No. 1). But 8<, rubra (with other similar foods unavoidably 
used during absence from home) evidently produced less effect than in 
the case of the parents. (No. 4), and the same is true of Salix bahylonica 
(No. 3) if we assume that this plant acts in the same manner as 
S, rubra. No conclusions can be drawn from the effects of Populus 
tremuUiy ho, (No. 2),. because this is, I believe, the only instance yet 
recorded of the larva feeding upon the food-plant in question. 

Series II. 

Eggs were laid by a female moth bred from a larva which had been 
fed during 1884 for the whole of its life upon Salix viminalis, and 
which became an intermediate variety with some tendency towards 
the whitish side. (The larva was one of those mentioned on p. 300 
of the paper already quoted.); In the case of this moth it seemed 
likely that no fertile eggs would be laid, for coitus did not take place 
when I placed a male in the same box with it. After this I put 
several males in the box, but I did not witness any act of coitus, 
although I watched the moths constantly, and the act lasts for several 
hours in all the cases which have come under my notice. In the 
meanwhile the moth kept laying eggs which I put in a box by them- 
selves and carefully labelled. The great majority of these eggs 
shrivelled up, but to my astonishment a few gave rise to larvae which 
are considered under these series. Subsequently to the laying of these 
mostly infertile eggs I succeeded in artificially inducing coitus, with 
the result that a large number of fertile eggs were laid, which were kept 
separate and are considered under the next series. Inasmuch as many 
males were present in the box with the female, it would be obviously 
impossible to maintain that the larvao of this series were partheno- 
genetically developed, but I may state in favour of such a view that 
in all other cases the coitus lasted long enough for me to witness it, 
sad that nearly all the eggs behaved like those which were laid by 
nCber female motha without coitus. 1 may ad^ ^^\. \ ^n^^^^ Mwwi- 
/aJIjr separated the eggs whicli were laid \)efoTG wi^ «A\»t ^CivH^i^^ ^xi^ 



1886.J Tjirva of Smerinthns ocellatus and its Food-plants, 141 

also tliat whon several males were together in the same box with a 
female, the former were distingQished from one another by small 
notches in the wings. 

The inherited tendency was probably towards the intermediate 
variety (argaing from the female parent only), because the parent 
larva was almost iatermediate after feeding on £f. viminalis for its 
whole life, although the gronp of larvee to which it belonged tended 
strongly towards white. 

The larv8B were examined on August 12th, with the folloyring 
results : — 

1. Salix viminalis, — Six larvee (hatched July 10th) of which four 
were nearly fall grown, and very similar, being good whitish varieties, 
though not so strong as those produced by apple. The two others 
are younger but apparently similar. By August 20th the four larger 
ones had all ceased feeding without any change of colour. The two 
smaller larvsB died. 

2. Salit Smithiana. — Two larvaB were well in the last stage and 
were greener than those just described — perhaps intermediate varie- 
ties. By August 16th one of these was decidedly intermediate, while 
on August 20th it was well on the yellowish side of intermediate and 
very nearly full grown. It ceased feeding without further change on 
August 27th. The other larva died soon after August 12th. These 
larvffi were fed for a considerable time upon the upper twigs (bearing 
large leaves) of the doubtful species of Salix mentioned in the note on 
p. 301 of the paper quoted above. Such leaves were indistinguishable 
from those of 8. Smithiana, 

These results are certainly perplexing, for the larvae upon S. vimi^ 
nalis (No. 1) were whiter than the parent larva which was fed upon 
tbe same plant (although the former probably represents the real 
tendency of the food-plant), while the one upon S, Smithiana (No. 2) 
was rather yellower than those which are generally produced by this 
plant, although the data are insufficient. On the other hand, there is 
nothing at all startling or violently opposed to the conclusions of 
the otber series in the above results, which in one case are those 
normal to the food-plant, and in the other differ but slightly from the 
normal result. It must also be remembered that there is complete 
uncertainty as to the male parent (if any) of these larvao. 

Series III, 

The eggs which produced the larvaa of this series were laid by the 
female moth described at the beginning of Series II. It was bred 
from a larva which had been fed upon Salix viminalis^ and which 
became an intermediate variety with some tendency toward* ibft 
whitish side. After laying the eggs which produced t^iQ \BLTVva o\ >i)cia 
Jasi series, coitus was artidcially indaced witli a male mo\»Vv, \i^vi ixoroi 



142 Mr. E. B. Poulton. Cohur-relatian bdween the [Feb. 4, 

a larva which had been fed for its whole life upon ordinary apple 
(mentioned at p. 300 of the paper quoted above), and which was a 
typical whitish variety. Hence the inherited tendencies were probably 
towards the white variety, somewhat modified in the direction of 
intermediate. Very many fertile eggs were laid after coitus, in June, 
1885, and were hatched about July 10th, and although a large nnmber 
died, a considerable mass of evidence was forthcoming from the 
fairly numerous larvsB which survived, and which were divided into 
nineteen sets of experiments. The results of the examination of these 
larvee on various dates are given below : — 

1. Ordinary Apple. — On August 12th two larv89 (hatched July 12 
— 16) were examined, and were in the fourth stage and very white, 
with a peculiar transparent appearance, which seems to be often 
caused by this food-plant. On August 20th they were both dead, 
but there could be no doubt of the tendency of the food-plant in thia 
case. 

2. Ordinary Apple. — On August 12th four larvaB (hatched July 10th) 
were examined: three were in the last stage and one in the fourth; 
all were very white. On August 20th all were dead except one, which 
died on Aug^t 27th. There was no doubt about the extreme 
tendency of the food; but apple seemed extraordinarily fatal in its 
effects during this last summer. 

3. Ordinary Apple {the leaves sewn so as to expose the under sides 
only). — One larva (hatched July lOtb) was examined August 12th, 
when it was at the end of the fourth stage and very white. On 
August 20th it had entered the last stage, and was unchanged in 
colour. On August 27th it was dead. There could be no doubt about 
the strong tendency of the food, but the unsewn apple leaves pro- 
duced such a maximum effect that thei*e was no room left for the 
sewn ones to do more. 

4. Ordinary Apple (the leaves sewn so as to expose the upper sides 
only). — Three larvsB (hatched July 10th) were examined August 12th, 
when they were young in the fourth stage and very white. By 
August 20th they were all dead, and so immature that it is impossible 
to draw any certain conclusions. It must also be noted that in the 
case of such broad leaves as apple, there is a constant tendency for 
the larv8B to expose considerable areas of the under surface by 
nibbling away part of one side of the leaf. 

5. Crab (Pyrus Malus, var. acerba). — Four larvsB (hatched July 
16th) were examined August 12th, when they were very small and 
apparently tending strongly towards the white variety. On August 16th 
one had died, and the others were only in the third stage. On 
August 20th they were still quite small and very white, and on 
August 27th they were all dead, except one which died soon after. 
As far as the observations went the larvae were typically white, but 



1886.] Larva of Smeiinthus ocellatuB and its Food-plants. 143 

they were very small. Neyertheless it is improbable that there would 
have been any change from this strongly marked tendency. 

6. SaUx viminalis, — One larva (hatched July 11th) was well in 
the last stage when it was examined on Angast 16th ; it was a 
whitish variety with tendencies towards intermediate. The larva was 
farther Examined on Angnst 20th and 27th, and on the last date was 
slightly on the white side of intermediate. This is the last note upon 
the larva, which must have been fnll fed by this time. 

7. SaUx viminalis, — Five larvfld (hatched July 10th) were examined 
on August 20th, when one had ceased feeding a few days before, 
three were nearly full fed, while one was small. All were slightly on 
the white side of intermediate. The larvso were again examined on 
August 27th, when only two were still feeding, but were practicaUy 
mature, and were very slightly on the white side of intermediate. The 
small one had died. The results are final as regards the other four larvff . 

8. Salix viminalis (the leaves sewn so as to expose the under sides 
only), — One larva (hatched July 10th) was examined on August 12th, 
when it was in the fourth stage, and veiy white. It was again 
examined on August 27th, when it had been fed for about a week on 
the ordinary nnsewn leaves of S. viminalis. It was well in the fourth 
stage and strongly white. The larva died shortly afterwards, but it is 
probable that the colour would not have changed. 

9. Salix alba. — Two larvao (hatched July 14 and 15) were examined 
on August 12th, when one was in the fourth stage and the other was 
well in the last stage. They were intermediate varieties, or perhaps 
rather on the yellowish side. On August 16th the younger one was 
dead without further change, and the older larva was examined on 
August 16th, 20th, and 27th, remaining on the yellowish side of inter- 
mediate until its death on the last of the above-mentioned dates. 

10. Salix Smithiana, — On August 12th four larvfld (hatched 
July 10th) in the last stage were examined, and were found to be 
on the white side of intermediate. By August 20th three were dead, 
and the remaining larva was examined then and on the 27th. On 
the last date the larva was well in the last stage and slightly on the 
white side of intermediate, this being the last note taken, and certainly 
representing the final effect of the food. These larvee were fed for a 
considerable time upon the upper twigs (bearing large leaves) of the 
doubtful species of Salix mentioned in the note on p. 301 of the 
paper quoted above. Such leaves were indistinguishable from those 
of £^. Smithiana, 

11. Salix cinerea, — Two larvso (hatched July 10th) were examined 
Angust 16th, when one was well in the last stage and one in the 
third. The former was intermediate, the latter too young for any 
certain results. On August 20th the younger larva was dead, the 
older one being still intermediate, while upon August 27th it waa 



144 Mr. E. B. Poulton. Colour^elatian lettoeen the [Feb. 4, 

nearly full fed, and slightly upon the yellowish side of intermediate, 
this being the last note, and giving the final result. 

12. Scdix cinerea. — Three larv» (hatched July 11th) were tolerably 
full fed when they were examined on August 16th. One was on the 
white side and one on the yellow side of intermediate, while the third 
was a yellowish variety (although not strongly yellowish). * It was 
extremely interesting to note that the latter — the only undoubtedly 
yellowish larva yet obtained in my breeding experiments in 1884 and 
1885 — ^possessed traces of the red spots that occur commonly on the 
yellowish varieties of S. oceUatus, On the first five abdominal 
segments there was a little local darkening of the green borders to 
the oblique stripes occupying the position of the upper row of red 
spots, and in the centre of each dark spot there was an extremely 
faint tinge of red. There was also a very slight tendency towards 
the sufEusion of the ground colour round the spiracles with a tinge 
of red. On August 20th the larvao were as they have been described 
(except that the whitish intermediate larva was now intermediate), 
and were practically full fed. The yellowest one was a bright yellow 
variety (although there was but little yellow on the under surface, so 
that the larva was not one of the strongest varieties). On August 22nd 
the yellow variety and the intermediate larva had ceased feeding, 
while the yellowish intermediate larva became adult about August 25th. 
There was no further change in the colour of any of the larvaB. 

13. Salix cinerea, — Three larvao (hatched July 12th) were well in 
the last stage when they were examined on August 16th. One was 
on the white side of intermediate, and two intermediate or slightly on 
the yellowish side. On August 20th and 27th the larvaa were again 
examined and had progressed in the direction of the yellowish variety, 
so that on the latter date — when two had ceased feeding, and the 
other, though still feeding, was mature — they were all on the yellowish 
side of intermediate, although only slightly so in one case. 

14. Populas nigra, — Five larvsB (hatched July 10th) were examined 
on August 12th, when four were in the last stage and one smaller. 
They were all whitish, but looked as though they were progressing in 
the direction of intermediate. On August 16th only two remained 
alive, one being well in the last stage and a whitish intermediate 
variety, while the other was whitish, being much smaller and not 
thriving. On August 27th the large larva was the only one alive and 
was advanced in the last stage, and a distinct intermediate variety 
without any tendency in either direction. This represents the final 
result, as the larva subsequently died without further change. 

15. Salix triandra, — Eleven larvad (hatched July 9 — 12th) — of 
which three were small, but eight were advanced in the last stage — 
were examined on August 12th, and were all intermediate varieties, 
as different as possible from those from the same batch of eggs which 



1886.] Larva of SmeiinthuB ooellatus and its Food-plants. 145 

were fed npon apple. On Angnst 16tli two of the eight large larva 
were quite clearly, though slightly, on the yellowish side of inter- 
mediate. On Angnst 18th fonr ceased feeding, and on Angnst 23rd 
three more without change of colour. The other larva and three 
small ones died. 

16. Salix triandra (wiihofU the whitish hloom upon the under side 
of the leaves), — The hloom was for the first part of the time mhhed 
off with the moistened fingers, hut aflerwards a tree was found near 
the Oxford University parks, of which all the leaves were without 
the hloom, and the larvso were fed upon this food for the later part of 
their lives. The following results afford a very interesting comparison 
with those given ahove, following the use of the ordinary leaves of 
8. triandra which presumably tend less towards the yellowish variety 
of larva than those supplied in the present instance. 

Ten larv89 (hatched Jnly 13 — 14th) were variously advanced in the 
last stage on August 18th, and on comparing them with those (see 
above) fed upon ordinary 8. triandra (most of which were rather 
older), it appeared that the former would be considerably yellower 
when they had reached an equal age. There were also other younger 
larv89 upon the same leaves, of which the tendency could be bett<T 
estimated at a later date. On Angnst 28rd one had ceased to feed, 
and was distinctly on the yellowish side of intermediate. On Angnst 
27th the small ones had died without any resnlts, while fonr of the 
older ones were full fed, and the others dead (although old enongh to 
indicate what their colour would have been). The results were very 
uniform, all being on the yellowish side of intermediate, while only a 
small proportion of those fed upon ordinary 8. triandra were at all 
beyond the intermediate form. 

17. 8atix babfflo7iica. — Four larv89 (hatched July 10 — llth) were well 
in the last stage on August 12th when they were examined. They had 
been fed on S. triandra for twenty-four hours (July 23rd — 24th) 
because I was travelling and con Id not get the proper food. On 
Angnst 12th they were all well on the yellow side of intermediate: 
they were again examined on August 20th and 27th, when two ceased 
feeding, one was practically mature, and one had died. The colour 
remained the same in all cases. 

When examining these larvsB at an earlier date (August 3rd), when 
they were more numerous, I noticed one which was in the fourth 
stage, and which possessed the upper row of rust-coloured spots which 
are often found on the yellow varieties of these larvsB. The spots were 
present on the second thoracic segment (very faintly), and upon the 
first five and the seventh abdominal segment. To my great surprise 
1 observed that the larva was distinctly whitish, and as I was most 
anxious to prove that such varities can bear the spots I changed its 
food from 8. habylonica to apple (August 3rd). The next day th<^ 



146 Mr. E. B. Poulton. Colour-'relatian between the [Feb. 4, 

larva ceased feeding before its last ecdjsis, and it died on August 20th 
when advanced in the last stage, and an intermediate variety. Thns 
it is qaite certain that the spots can appear on other than yellowish 
varieties. 

18. Salix rubra, — Three larvae (hatched Jnly 10th) were well in 
the last stage on August 12th, when they were examined. Like those 
upon 8, hcLbyUmica they had been fed for one day upon 8, triandra. 
One was decidedly on the yellow side of intermediate, one less 
markedly so, and one was intermediate. On August 20th the two 
former were decidedly on the yellowish side, and I have a note to the 
effect that I was sure that they were yellower than the larv89 fed upon 
this tree last year (1884), and of which an account is given in the 
paper already alluded to. At this time the two yellower larvae ceased 
feeding, while the third was still intermediate, and it ceased feeding 
about August 25th without further change. 

19. 8. rubra. — One larva (hatched July 10th) which had been fed 
for one day as above described upon 8. triandra was examined on 
August 16th, when it was in the last stage and apparently on the 
yellowish side of intermediate. On August 20th it was advanced in 
the last stage and unchanged in colour, and on August 27th it was 
about full fed and slightly on the yellowish side of intermediate, and 
there is no doubt that this result was final, for the larva could not 
have undergone further change when it was so mature, this being the 
last note I have about it. 

Reviewing these sets of experiments and comparing them with those 
of Series I and II, we find upon the whole considerable evidence for 
the existence of a hereditary force which influences the larval colour 
in this species. 

Ordinary apple (Nos. 1 and 2) produces a maximum effect, as might 
be expected from previous experiment and observation. It would 
probably do so even if there existed a strong hereditary tendency 
towards yellow, and in this case the transmitted influence deviated 
but little from the direction of the typical white variety (as indicated 
by the life histories of the present larvae). There is no doubt that a 
similar eflect would have been produced in the other two series if the 
larvas fed upon this food-plant had lived long enough to enable me to 
take reliable observations. (As this was not the case, such experi- 
ments were not alluded to in either series.) Since ordinary apple 
produced maximum effect, it was practically certain that the same 
result would follow the use of leaves which were sewn so as to show 
the white under sides only (No. 3). No. 4, in which the leaves of 
apple were sewn so as to show the upper sides only, did not terminate 
as I should have expected, as far as I could judge of the effects in the 
immature larvas. The process of sewing and paring causes injury to 
the leaves^ so that the larvae did not thrive upon them (being less 



1886.] Larva of Sinerinthus ocellatus and its FoodrplanU. 147 

healthy than they were npon the nnsewn leaves, although they were 
far from healthy upon the latter daring the past year). Nevertheless, 
I hope to succeed in the rearing the larvsB npon snch leaves in a more 
favonrahle season, and I helieve that some deviation from the extreme 
white variety will result (this conclasion heing warranted by the results 
of other experiments described in the present paper). Nos. 1 — 4 were 
not represented in the other two series. 

Crah (No. 5) produced white varieties, as far as could be ascertained, 
acting as it did on the present larv89 and in Series I (No. 1). It was 
qnite as fatal in its effects as ordinary apple, and the larvsB seem to 
grow more slowly when fed upon it than upon any other plant, as was 
also noticed in the case of the parent larvad. Considering the extreme 
effects following the use of this food in the other cases, it could hardly 
be expected that there would be any appreciable difference in the 
larv8B of this series. 

Salix viminalis (Nos. 6 and 7) produced exactly the same effects as 
in the parent larvsB, while the larvae of Series II (No 1) fed upon the 
same plant were fairly strong white varieties. This is a very strange 
contrast considering the parentage of the two series, but the un- 
certainty of the male parent in Series II prevents much importance 
from being attached to it. 

The effect of 8. viminalis^ sewn so as to show the under sides of 
the leaves (No. 8), affords a most interesting comparison with the 
results of Nos. 6 and 7, for the former produced a strong white 
variety (that is up to the time of its death). Here is a distinct proof 
of the effect of the colour of one leaf-surface as apart from the leaf- 
sabstance eaten by the larva. 

Salix alha (No. 9) cannot be compared with any previous experience 
of my own. I expected it to act like S. vimmalis^ but the larva was 
rather yellower than those which had fed upon the latter plant. The 
leaves of 8. alba vary much in whiteness, the young leaves being far 
more downy and white than the older ones, so that a different effect 
is probably produced by the two kinds. There is independent evidence 
(Mr. Bo8cher*s, which will be alluded to pi*esently) that this food- 
plant produces white larvsB. 

Salix 8mithtana (No. 10) produced a larva which when mature was 
on the whitish side of intermediate. This is probably the normal 
result of the food which in this case coincided with the hereditary 
influence. In Series II (No. 2), however, the larvae fed upon the same 
food-plant were rather yellower ; hence the effects of 8. 8m%thiana 
and 8. viminalis in the two series were the exact converse of each 
other — a very perplexing result. At the same time, as already 
pointed out, there was nothing at all unusual in the results of any of 
the individual sets of experiments. (See also the notes upon the 
parentage of the larvas of these two series.) 



148 Mr. E. B. Poulton. Colour^eleUion between the [Feb. 4, 

Salix cirierea (Nos. 11, 12, and 13) prodnced very interesting reenlts, 
varying from a good yellow variety to intermediate, nearly all being 
npon the yellowish side of the latter. Thus, there is a distinct, thongh 
slight, advance npon the effect of this food on the parents in the 
direction of yellow. 

The results obtained from the three larvsB of No. 12 are extremely 
interesting, showing that individual variation may sometimes play an 
important part in the colour produced, although tihe whole of the 
results of all observations and experiments conducted up to the present 
time certainly prove that such a factor is generally insignificant, and 
: rarely causes any effects that can be detected. By individual varia- 
tion I mean the development of a different colour than that which 
would be pi-odaced by the food-plant acting upon a larval tendency 
which is uniform for nearly all the larves from each bat<;h of ova, the 
latter tendency being probably explicable as the inherited results of 
previous food-plants for many generations. In other words, I mean 
breaches in the uniformity, however caused, of the larval tendency, 
and a study of this and the previous paper upon the same subject, 
will show that such irregularities are comparatively rare, and especially 
so when the food-plant itself is known to possess a strong infiuence in 
the direction of either extreme of coloration. 

Populus nigra (No. 14). — The results of this food -plant, inter- 
mediate as far as the evidence went, cannot be compared with any 
other experience, for this is, I believe, the only instance of the larvas 
having been known to eat this food-plant. From the green glabrous 
undersides of the leaves I should have anticipated a tendency towards 
yellow, which was only partially verified. 

ScUix triandra (No. 15). — I was especially anxious to gain abundant 
evidence as to the effect of this food-plant, because I believed that its 
tendency was towards yellow. Mr. Boscher described numerous 
instances of typical white larvae having besn found on it. I have, 
however, since ascertained that Mr. Boscher was mistaken in his 
identi6cation, and that the trees upon which he found the whitish 
larvfie were Salix alba, and such a result froru the latter food-plant is 
what I should have anticipated. At the same time, I should wish to 
point out that the identification of the various species of Salix is 
immensely difl&cult, and that I have only been saved from hopeless 
confusion by the skilled assistance of Mr. G. C. Druce, who has most 
kindly helped me, and, when necessary, has obtained other opinion?, 
throughout this investigation. During the past year (1885) I have 
proved by observation in the field (as will be seen) that the effect of 
8. triandra is to produce yellowish varieties, and the same thing is 
proved by these experiments, considering the hereditary influences. 
I have therefore verified the prediction npon which I ventured in my 
/ast paper (already quoted, p. 306), a\t\iong\i «b^ ^^ ^\h2l^ ^\v^\jl ^^ 



1886.] Larva of Smerinthus ocellatus and its Food-plants. 149 

paper was written, nearly all the evidence seemed to point the other 
way. The larvsB of this set were intermediate, inclining in some cases 
to the yellowish side. Hence the effects are the same as those pro- 
duced by leaves which are known to canse the yellowish varieties as a 
rule. These results can be compared with no previous experience, as 
the larva has never been bred upon this tree (as far as I am aware), 
and I can find no instance recorded of its being found in the field 
upon this food-plant, except the instances which occurred in 1885 (to 
be described). These agree with the breeding experiments, as does 
the result of an experiment given in my last paper (quoted above, 
p. 303), in which 8, triandra modified the colour of a whitish larva 
found upon S. ferrugtnea, 

Salix triandra (No. 16, without the whitish bloom on the under 
sides of the leaves). — These results compare in a very interesting 
manner with those of the last set, the infiuence in the direction of 
yellow being more strongly marked than in the case of the usual 
leaves of this plant. The numerous larv89 of these two sets were 
repeatedly placed side by side and compared in the most carefal 
manner, and there could be no doubt that there was a considerable 
difference in the predominance of yellow, while the larvea had been 
subject to exactly the same conditions, except in the one point men- 
tioned above. 

Salix habylonica (No. 17). — The larv89 were all well on the yellowish 
side of intermediate (except the one which was put upon another food 
when quite young), and this result compares favourably with that of 
the larvffi of Series I upon the same plaut (No. 3), where with the 
greater hereditary influence towards white the larva became an inter- 
mediate variety. In this case also the larvaa of the two series were 
examined side by side, so that there was no doubt about the difference. 
This result also compares favourably with the larvsD captured upon 
this food-plant during 1884. 

Salir rubra (Nos. 18 and 19). — These results also compare well 
with No. 4 of Series I. As far as it was possible to judge from the 
immature condition of the larvaD in the latter set, the effect was not so 
yellow as in Series III. The effect produced in the present case was 
stronger than in the larvsB from the same set as the parents, which 
were fed upon S. rubra. This was to be expected, because the 
tendency of the latter was very strongly towards the white variety, 
while in the present instance it was somewhat modified. 

Series IV, 

Eggs were laid by a female moth, bred from a larva, which had 

been fed in 1884 for the whole of its life upon Salix ctiierea^ atvd 

which became an intermediate variety. (The larva waa oii^ o^ Wicii^^ 

mentioned on p, 800 of the paper quoted.) The eggft Yrer© iet^-Civai^ 
roi^ XL. ^ 



150 Mr. E. B. Poulton. Colour-relation between the [Feb. 



k 



by a male moth bred from a larva which had been fed for its whole 
life upon Salix rubra (mentioned at p. 300), and which became a 
yellowish intermediate variety. The tendencies were thns presamablj 
towards intermediate, or slightly on the yellowish side. A large 
number of eggs were laid, and nearly all of them hatched snccessfnlly, 
yielding apparently healthy young larvsB, but the most extraordinarj 
mortality prevailed, so that no single larva arrived at maturity, or 
indeed at an age which would render any conclusions possible (except 
in the case of very marked colours which were not manifested). This 
is all the more to be regretted because I had reserved by far the 
greater part of this lot of larv89 for some experiments which would 
have conclosively decided some of the points in this difficult problem. 
A few larvae were fed upon some of the same food-plants as in the other 
instances, in order to gain further evidence as to their effect. Thus 
larvoe were fed upon Salix dnerea (in this case it would have been 
interesting to ascertain the effect of the food upon two generations of 
larvaB, although the female parent only had been so fed upon 8. cinerea) 
and upon S. Smithiana (the leaves sewn together so as to expose the 
under sides only). A few of the larvee were blinded before they had 
seen the food-plant, by carefully painting over the ocelli with lamp- 
black, a lens being used to make certain that all of the ocelli were 
covered. This was a task of considei-able delicacy and difficulty in 
the small and restless larva, but when once accomplished the larvae 
did not seem any the worse, and behaved in every way as the others 
which were not blinded. As the lamp-black only formed an opaque 
film over the transparent cuticular covering of the ocelli, and as the 
former is thrown ofiTat ecdysis, the pigment had to be renewed at the 
beginning of each fresh stage, and the greatest care was necessary to 
prevent the larvae from changing their skins at unexpected times, 
and thus having the opportunity of seeing the food-plant. Hence 
any larva which had ceased feeding before ecdysis was isolated and 
only put back upon the food after it had changed its skin and the 
pigment had been renewed. Larvae treated in this way were fed 
upon the two food-plants which tend most strongly in opposite 
directions — ordinary apple and Salix rubra, and at the same time 
large numbers of unblinded larvae from the same batch of eggs were 
fed upon the same plants. Had the larvae lived there must have been 
conclusive evidence as to one obvious theory of the origin of afferent 
impulses which determine the selection and the use of certain 
proportions of the mixed vegetal pigments, and the deposition of 
certain amounts and kinds of true larval pigments — the theory that 
such impulses are caused by the colour of one or both sides of the leaf 
acting as a .stimulus by means of the ocelli. I am indebted to Pro- 
/essor O. J. Romanes for the suggestion t\iat. ex^eTvav^xA^^* ^Vo\A<k \aft 
made upon blinded larvae, "wliile ProiesBOx ^. ^w^ Ijoii^^W^T ^^V^afe^ 



1886.] Larva of Smerinthus ocellatus and its Food-plants. 151 

me to use some harmless pigment instead of silver nitrate. The 
lamp-black mixed in the usual way with Mc. Guilp. acted in every way 
satisfactorily, drying very quickly and being perfectly innocuous, and 
completely opaque. The possibility of future success was shown by 
these experiments, for the death of the larvsB was certainly not dae to 
the conditions under which they were placed, as was shown by 
comparing them with the normal larveB. 

Further experiments were tried upon the larves from this batch of 
eggs, to ascertain if possible the exact periods of larval life which are 
most sensitive to the influence of the food-plant, as gauged by the 
persistence of effects after the change to another food-plant which 
tends in an opposite direction. Most of the larves were used in this 
series of experiments. A large number (forty or fifty) were fed upon 
)rdinary apple, and aboat an equal number upon Salix rubra. At 
:he end of the first stage a certain number (six) were shifted from 
ipple to 8. ruhray and an equal number from S, rubra to apple, and 
\o with each succeeding stage. Thus if the larvaB had lived there would 
lave been the following groups when they were full fed : — 

1 . Fed upon ordinary apple during stage 1, and 8. rvbra, stages 2-5. 

2. „ „ „ stages 1-2, „ „ 3-5. 

3- >» II >» >i l~"i >» » 2—5. 

4. „ „ „ „ 1-4, „ stage 6. 

0. „ ,, „ ,, 1-0. 

And again, 

1. Fed upon S. rubra during stage 1, and upon ordinary apple, stages 2-5. 

2. „ „ „ stages 1-2, „ „ „ 3-5. 

*'• »» M >> it '—"l >» »» >l ^^Om 

4. „ „ „ „ 1-4, „ „ stage 6. 

I think there is no doubt that a careful comparison of these ten 
p-oQps (which would in all cases have been kept separate as soon as 
their food was changed) would have very completely answered the 
question of which the solution was sought in this series of expe- 
riments. I have given an account of these experiments — although 
they yielded no results owing to the unfortunate and altogether 
exceptional season — because it is likely that future work on these 
lines will be successful in throwing some light on this difficult subject, 
and because it is to be hoped that others may be induced to assist 
in these investigations. 

Series V. 

Eggs were laid by a female moth bred from a larva which had 
been fed during 1884 for the whole period of larval \\£e u^oxl 8aV\» 
ruhrot and which was rather on the yellow side ot an Vuterxxi^^\^\» 
ranetf. (The larva was cue of those mentioned in t\\© i^apet c^oXfi^ 

11 ^ 



152 Mr. E. B. Potdton. Colour-relation between the 



[l'eb.V 



above, p. 300.) The eggs were fertilised hj a male moth bred from 
a yellowish larva found upon S. rubra on the River Cherwell 
Angast 7th, 1884, and mentioned on p. 301 of the paper quoted 
above, as the larva in the last stage without the brownish-red spots. 
The larva had been fed upon apple from August 10th — 18th, without 
causing any change of colour (see pp. 302 and 303). Thus the 
hereditary tendencies should be towards a rather strong yellowish 
variety, if they are due to a compromise between the tendencies of 
the two sexes. A large number of eggs were laid in June, 1885, 
which hatched at the beginning of July, but there was great mortality 
among the larvas in all stages, but especially when they were very 
young. A careful examination of the few surviving larvae was made 
on August 12th, all the others having died before the period at which 
it was possible to make any trustworthy observations of their colour. 

1. Salix viminalls {upper side). — One larva (hatched July 2nd) 
had been fed upon the leaves of S. viminalisj folded and sewn so that 
only the upper side was exposed. The larva died August 10th in the 
last stage, after failing for some time ; it was a very green inter- 
mediate variety, and although it had very little yellow about it, the 
contrast with larvee fed in a normal way npon the leaves of this 
food-plant was most interesting (although the different parentage 
must be taken into account). 

2. Salix cinerea. — Two adult larvee (hatched July 2nd) had been 
fed upon this plant for their whole life. One was decidedly but not 
strongly on the yellowish side of intermediate ; the other strictly 
intennodiate. By August 20th both had ceased feeding without 
fui'ther change. 

3. Populus nigra. — Two larvae (July 3rd) had not thriven at all. 
One was in the fourth and one in the third stage ; the former evi- 
dently tending towards the whitish variety, but they were too young 
for any certain conclusions, and by August 20th both were dead, 
without any further results. 

The review and comparison of these results is, on the whole, dis- 
appointing. 

Salix viminalts, upper side only (No. 1). — The result of this expe- 
riment was very interesting. The larva was frequently placed side 
by side with others upon ordinary 8. viminalis, and the difference 
was extremely marked. I do not think that too much weight mnst 
be attached to hereditary influence in producing this effect, because 
the other sets of experiments in this series do not prove the influence I 
to be as strong as I should have expected from the colour of the 
parent larvae. 

Salix cinerea (No. 2). — The effects compare unfavourably with 
those produced by this food-plant upon the larvae of Series III (Nos. 
2J, 12, 23), for the latter were rather more strongly influenced in the ! 



1886.] Larva of Smermthus ocellatus and its FoodrplanU. 153 

direction of yellow, while the hereditary tendency was presumably 
weaker. At the same time the effect was more marked than in the 
set of larvsB to which the parents belonged ; and there^was nothing at 
all nnnsnal in the results themselves. 

Populus nigra (No. 3). — There is little to be said'abovt this result. 
The larvffi were too young to warrant any conclusion, bmt they were 
whitish when they died. At the same time the larysB of Series III 
(No. 14), which were fed upon this food-plant were also whitish 
when youDg, while those that lived progressed in the direction of 
yellow ; so that the most mature was an intermediate variety at the 
time of its death. It is probable that the larvsB of Series Y may have 
also changed in the same direction if they had lived. 

It is noteworthy that the strong hereditary influence in the direc- 
tion of yellow, which we should suppose existed in Series V (because 
of the colour of the parent larvea), depends chiefly upon the male 
parent ; and how far this element asserts itself in (^position to the 
other sex is quite unknown in. this class of experiment. Indeed, a 
large number of data of thia kind. might be valuable in gauging the 
relative strengths of the sexes, in this form ol heredity, but the 
present data are far too limited to be regarded as a serious contri- 
bution to this aspect of the subject. . 

3. The General Results of the Breeding Experiments. 

It is now necessary to consider how far the questions suggested at 
the beginning of this paper have received answers from the experi- 
ments which have been detailed above. 

(1.) With regard to the first question, it is, I think, certain that 
the larval tendencies towards certain colours are transmitted, as was 
proved by the fact that the parent larvae had very strong tendencies 
towards the whitish variety, while in the next generation only a 
single yellowish form appeared out of seventy-five larvsB. On the 
other hand, there was conclusive evidence of the modified tendency 
towards white in the offspring following the change wrought in the 
parents by food-plants with strong tendencies. Thus, although food- 
plants such as S. rubra (tending strongly towards yellow) did not 
produce yellow varieties, yet the larves were, as a rule, yellower than 
in the case of the parents. There was no difference between the 
parents and offspring in the results of food-plants which tended 
strongly towards white, these being strong enough to overcome any 
ordinary hereditary tendencies. The results obtained by comparing 
the different series together are less conclusive, but it is unfortunate 
that a really satisfactory number of larvsB was only obtained in one 
case (Series III), the others being insufficient to afford any very con- 
vincing comparison. The comparison between Series I and III was 
certainly, as far as it went, in favour of a stronger tendency towards 



k 



154 Mr. E. B. Poulton. Colour^elaHon between the [Feb.V^ 

white in the former series, such as we should expect from the parentage. 
Scries II is the one about which there is so much obscurity, bnt its 
results wei*e rather irregular when compared together and with those 
of the other series. In Series V we should expect a greater pre- 
dominance of the yellowish tendency, if the male parent is of equal 
importance with the female in this respect, but the data were very 
insufficient. 

But it must be clearly understood that the question is really settled, 
because of the wonderfully uniform results of the comparison between 
parents and offspring as a whole, in which comparison we are dealing 
with strong and definite tendencies ; while in the case of the offspring 
we are considering delicate differences between such tendencies, 
which are obviously much more difficult to detect and need far larger 
data for their accurate determination. 

(2.) As to the second question, I think it may be said that con- 
clusive experimental proof has been afforded of the theory brought 
forward in my last paper — that the colour of the leaf, and not its 
substance when eaten, is the agent which influences the larval 
colours. It seems to me that this is proved by the breeding experi- 
ments in Series III, in which the larva9 from the same batch of eggs 
were whitish intermediate and white after being respectively fed upon 
S. viminalis and upon leaves of the same plant sewn so that only the 
under sides were visible (Nos. 6, 7, and 8). 

On the other hand an intermediate variety was produced by feeding 
a larva from another batch of eggs upon similar leaves sewn so as 
to expose the upper sides. (Series V, No. 1.) The same thing is 
proved by a comparison of two sets of larvae from the same batch 
of eggs, fed respectively upon 8. tnandra and upon the leaves of the 
same plant from the under sides of which the whitish bloom had been 
removed. 

Concerning the food-plants, about which the evidence was con- 
flicting, the experiments have in some cases helped to clear up the 
difficulties. The greatest of these difficulties concerned 8. viminalis 
and 8. triandra, but in the latter case there really was no confliction 
of evidence, as Mr. Boscher's white larvae were found upon the very 
similar but much whiter 8. alha. As to 8. viminalis, the difficulty 
does not at first sight appear to be cleared up by the breeding experi- 
ments, but I will defer its consideration until after detailing my 
experience with captured larvae, for what I believe to be the correct 
solution presented itself to me from the results of this part of the 
investigation. The experiments upon crab produced exactly the same 
results as in 1884 : this will «lso be considered later. With regard 
to other food-plants, the view I previously expressed that 8. 8mithmna 
tends to produce whitish intermediate varieties, is on the whole 
supported, and so also in the case of 8, bahylonica, which as I 



1886.] Larva of Smeiinthus ocellatuB and its Food-plants, 155 

saggested, is similar in its effects to 8, rubra. The effects of various 
plants hitherto untried have also been observed as a result of the 
experiments and work in the field. 

As to the occurrence of individual variation in larvsB from the same 
batch of eggs and fed upon the same food-plants, it is now quite 
certain that such variation may take place, but any considerable 
divergence is very exceptional. 

Thus in the twenty-three larvsB bred in 1884, there was practi- 
cally no individual variation, while in 1885 there were only eight 
instances out of seventy-five larvsB, and in none of these instances 
did the variation amount to more than a remove of one place from that 
which contained the largest number of larv89, and which therefore 
represented the normal result of the food-plant for each particular 
experiment In such a calculation the differences between the 
larval colours are arranged in five classes, i.e., white, whitish inter- 
mediate, intermediate, yellowish intermediate, and yellow. The 
difference between any two of these is very small, and hence it is 
seen how entirely insignificant was the amount of individual varia- 
tion even in the few cases in which it occurred. In one instance only 
was there a variation on both sides of the normal result, i.e., in 
Series III, Nos. 11, 12, 13, where seven larves fed upon S, cinerea 
became intermediate in one case, yellowish intermediate in five 
cases, and yellow in one case. Here there is a difference of two 
places between the extremes, but one larva only varied in each direc- 
tion, while five remained normal. Thus, although this is by far the 
most striking instance of individual variation met with in about a 
hundred bred larv89 in 1884 — 1885, it is by no means extreme, and 
cannot alone explain such excessive variations as have been met 
with in the field out of about an equal number of instances. I refer 
especially to the instance recorded in my last paper (p. 302), in which 
a bright yellowish variety was found upon apple, the divergence from 
the normal i*e9ult being as wide as possible (five places). Another 
almost equally striking instance was met with this year (as will be 
recorded) upon 8. cinerea in the field, one larva being whitish inter- 
mediate and four others yellowish. Here the divergence amounts to 
four places, and compares in an intei'esting way with the lesser 
divergence in the larger number of larvas bred upon the same plant. 
A divergence equal to that upon 8. cinerea was recorded in my last 
paper (p. 301) upon 8. ferruginea^ one larva being yellowish and three 
whitish intermediate. It is possible or even likely that considerable 
divergence is occasionally caused by individual variation, but that 
this is not the only or indeed the chief explanation of the few in- 
stances of extreme divergence recorded, is proved by the fact that 
Koch variation only occurs when the probabilities are greatly in 
&vonr of correspondingly different hereditary tendencies, and that 



156 Mr. E. B. Poulton. Colour^elaticn between the [Feb. ^ 

a much greater nniformity prevails when the larvsB are bred from 
the same batch of eggs. The former argument is euforced by the 
fact that the captured divergent larves are sometimes of different 
age (and therefore probably of different parentage) from the normal 
larvae upon the same tree. It must be clearly understood that in 
speaking of these extreme divergences in the field, I am not alluding to 
sach instances as Mr. Boscher^s eighteen yellow larv® upon 8, viminalis, 
or my own instances of yellow larvsB upon crab. I believe that these 
are to be interpreted in another way which will be explained laten 
There are altogether three factors which determine by their relative 
predominance the colour of these larvsB : (1) the tendency produced 
by the food-plant ; (2) the hereditary larval tendency ; (3) individual 
variation. (It does not signify for the present purpose whether the 
third factor is a definite and independent tendency, or merely a vari- 
able disturbance of a normal equilibrium between the first and second 
factors, or an irregular recurrence to the influences of earlier genera- 
tions.) Of these three factors the third has been shown to be com- 
paratively unimportant, while many extreme exceptions are explicable 
by the second. But I shall show later that the first factor may also 
produce variable results in the case of the same food-plant, and it is 
to such a cause that we must refer the interpretation of the conflicting 
testimony concerning the effects of S. viminalisj &c. At the outset it 
would be unlikely that the other two factors could have produced the 
exceptions (upon 8, viminalisj &c.), because of their number and 
uniformity upon certain varieties of the food- plant. (See Mr. Meldola's 
account of Mr. Boscher's captures, pages 241 and 306 of the English 
translation of Weismann*s ** Studies in the Theory of Descent," Part II.) 
I was very interested to find that two of the bred larvee possessed the 
red spot«. In my last paper I pointed out (p. 309) that the occur- 
rence of the spots upon the yellowish variety only was an '* argument 
against the conclusion that these effects are in any way due to the 
food-plants.*' It was, therefore, very satisfactory to find a spotted 
larva which did not advance beyond the intermediate variety, and 
which at an earlier stage was even whiter. (Series III, No. 17.) The 
other instance was in accordance with the observation (which was 
universal until the above recorded instance appeared) that the 
spots are always found upon yellow varieties, for out of about a 
hundred bred larvsD in 1884 and 1885, there was only one yellow 
variety, and this, with one exception, was the only red spotted larva. 
But if the spots were always necessarily connected with one variety, 
this would not prove that there could be no larval colour modifica- 
tions, depending on the colour of the food- plant (in fact nothing can 
do away with this conclusion now that it has so firm a basis of experi- 
mental proof). There are many reasons for thinking that the ancestral 
form of the larvtL was yellow, brig\it\y B^o\.\je^, %.\A oT\i».TCka\A*A 



1886.] Larva of Smerinthus ocellatus and its Food-plants, 157 

in other ways which are suggested in the larval ontogeny. (See 
•* Proc. Ent. Soc. London," 1885, Part II, August, pp. 290—296.) 
The newly hatched larvfe are always brightly yellowish even when fed 
upon apple. The particular form of protection now gained by the 
larva, by a resemblance to the foliage of its food-plant, has involved 
the laying aside of this ornamentation, but some of its features 
occasionally appear (by reversion), and when this is the case they are 
associated in nearly all cases with the ancestral ground-colour. It is 
possible that the differences of ground-coloar which are now de- 
pendent on the food-plant arose independently, and persisted for a 
long time as ordinary cases of dimorphism or polymorphism, and 
that their relation to the colour of the food-plant was determined by 
natural selection at a much later date. But although the diff ere aces 
may have commenced in this way, they did not probably reach any- 
thing like their present condition until they came to depend on the 
food-plant, for without such a relation the colours would often render 
the larva conspicuous instead of protecting it. 

4. Observations in the Field upon Larvoe of S. ocellatus during 1885. 

The larvae were very abundant last year and the results were more 
uniform than in 1884:. An account of all the captured larves is given 
below. 

August 2nd. — Upon Salix rubra in some fields by the River Cher- 
Trell, near Oxford, seven nearly full-grown larves and one small in 
the fourth stage, which was a bright yellowish variety. Of the 
former number four were bright yellowish varieties, and three were 
well on the yellow side of intermediate, almost good yellow varieties. 
Also upon 8, cinerea in the same locality, one nearly adult larva 
which was a good yellow variety. Also upon a small tree of 8, baby- 
lonica in a garden at Oxford (the same tree upon which seven larvffi 
were found in 1884 ; see " Proc. Roy. Soc," No. 237, 1885, pp. 301 
and 302), one nearly full-grown larva decidedly on the yellow side of 
an intermediate variety but not strongly yellowish. 

August drd, — Upon 8, viminalis on the River Cherwell, near Ox- 
ford, three larvffi in the last stage (upon the same tree) of which one 
was nearly adult and rather yellowish, but not more than an inter- 
mediate variety ; while the other two were much less advanced in the 
last stage, and were whitish varieties. 

August 4tth. — Upon 8, rubra by the Cherwell (as above, August 2), 
two nearly adult bright yellowish larvae. 

August 9th. — Upon 8. rubra by the Cherwell (as above), one nearly 
adult bright yellowish larva. Also upon 8. cinerea in the same 
locality, two almost full-fed larvae which were good yellow varieties. 
Also upon 8. linearis in the University Parks, one \arvai '«\i\Ci\i '^%Sk 
wrhaps slightly on the jrellow Bide of an interme^ate NOti^Vj . 



158 Mr. £. 6. Poulton. Cohur-reladm between the [FoIk 4, 

August \^th, — Upon 8, rubra by the Cherwell (as above), one nearly 
adult bright yellowish larva. Also upon 8. cinerea in the same 
locality two nearly adult larvsB (on the name bnsh), of which one was 
slightly on the whitish side of an intermediate variety, while the 
other was a rather bright yellowish variety. Also npon 8. triandra 
in the same locality one almost full-fed bright yellowish larva. 

August 28r^. — Upon 8. 8mithiana at Binsey upon the Isis, near 
Oxford, one nearly adult larva on the whitish side of an intermediate 
variety. Also upon 8. triandra in the same locality, one nearly adult 
bright yellowish variety. Also upon 8, triandra upon the lais at 
Medley Weir near Oxford, one bright yellowish larva which had just 
entered the last stage. 

August 25th, — Upon S. rubra (Cherwell) three small larves towards 
the end of the third stage, all strongly yellowish varieties, but differ- 
ing somewhat in intensity. 

August SOth. — Upon 8. triandra close to the bridge at Ferry 
Hincksey, near Oxford, one nearly adult larva which was a good 
yellowish variety, but rather whitish on the back. Also upon ordinary 
apple in a garden at Oxford one very white variety at the end of the 
fourth stage (changing its skin). 

8eptember 11th and 12th, — Upon a variety of *S^. alba with small 
narrow leaves, having smooth greenish under sides ; in a dry part of 
the bed of the river at Visp, Switzerland, two full-fed strong yellow 
varieties (although not the strongest because of the want of a distinct 
yellow tinge to the under surface). Both had the very sharply marked 
and distinct white stripes which are often found on larvae with this tint 
of ground-colour. Also September 12th, near the stream which flows 
through Brigue, Switzerland, three larvea upon different species of 
sallow. Upon a variety of 8. alba very similar to the above {? 8, 
vitellina)^ an adult intermediate variety rather strongly tending 
towards the yellowish form upon its dorsal sui'face, and having very 
distinct white stripes, such as were possessed by the larvea from Visp. 
Upon 8. incanaj a yellow variety of the larva, looking as though it 
would have been very yellow if it had been in a healthy condition. 
But the larva, which was well in the last stage, was much stunted and 
in very bad health, having been attacked probably by some parasite, 
and pierced in twenty-eight places. Also upon 8. alba (the leaves 
much like the common English form), a larva which was advanced in 
the last stage, and an exceedingly white variety — the palest I have 
ever seen. There was a little yellow on the under side, but it was 
not at all the tint of the yellowish varieties, and indicated no transition 
in that direction. The larva did not seem to be very healthy. It 
possessed in common with all very strong white varieties a distinct 
trace of the subdorsal line for its whole length, and there was a trace 
of the darkening for a border to a " nnvtVi atn?^^''^ xx^tv Vk^ ^vc\ 



1886.] Larva of Smerinthus ocellatus and its Food-plants. 159 

thoracic segment in front of and parallel with the more distinct and 
larger *' eighth stripe " upon the first abdominal segment. 

5. Experiments upon captured Larvae, 

Being engaged in the extenRive breeding experiments already 
described, I did not attempt much with the captnred larvad, especially 
as nearly all of the latter were fall-grown when fonnd. The strongly 
yellowish lanra in the fonrth stage, found August 2nd on Salix rvhra^ 
was put upon apple on August 3rd, when it was 24 mm. long. On 
August 27th it was 51 mm. long, and was much affected by the 
change of food, being an intermediate variety, or perhaps slightly on 
the yellowish side of intermediate. It was interesting to note that 
the change of colour afiected the shagreen dots, which became white, 
having been formerly yellow as in all strongly yellowish varieties. 

C. Conclusions arrived at hy the Consideration of the captured Larvos : 

The Beconciliation of conflicting Evidence, 

The colours of the captured larvas were wonderfully uniform for 
their respective food-plants. Salix rubra produced a large number 
of yellow larv8B, and others which were but little removed from 
yellow. The larva upon S. habylonica resembled these latter. 8, 
tnandra also produced yellow larv89, and so with S, cinerea (with one 
exception). There was but little confliction in the results of S. vimi" 
fialis, and S, Smithiava produced a normal larva, and the colours of 
the Swiss larvao (with the exception of that upon 8, incana) might 
have been almost exactly anticipated by investigating the colour of 
the under sides of the leaves. Thus there are fewer exceptions than in 
the larvsB captured in 1884, and yet among them was one instance 
which suggested to me the explanation of those conflicting results 
which have been the chief obstacle to the complete acceptance of my 
theory of the colour-relation between food-plant and larva ; I mean 
especially the immense difference between Mr. 6oscher*s experience 
(quoted by Mr. Meldola as above referred to) and my own with regard 
to 8. viminah's. The larva which suggested the interpretation was 
the yellowish intermediate variety found August 9th upon 8alix 
linearis. I had much wished to find a larva upon this foreign species 
of Salix, of which there are many fine specimens in the Oxford 
University Parks ; for I had noticed for over a year that the under 
sides of the leaves were more densely covered with down and whiter 
than any species of Salix I had ever seen, and even more so than 
apple. The upper sides of the leaves were dark-green and glossy, and 
the leaves were narrow, pointed, and very small, and extended at right 
angles to the twigs. The leaves resembled those of 8. viminah's, only 
they were much smaller and whiter underneath. I thon^Vit t\i%i\> ^tlvXsl 
a tree most produce the most extreme wh.ite vafvetiea, wA \ ^%ft 



160 Mr. E. B. Poulton. Colour-relation between the [Feb. 4, 

greatly astonished at the colour of the single larva foand npon it. 
Thinking oyer snch a result, I remembered that the one bright yellow 
variety which I had found upon 8. viminalis (on August 11, 1884; 
see p. 301 of the above-mentioned paper) wad upon a variety of the 
latter plant with very small leaves, while the white larvae were found 
upon the large-leaved variety which is the common one at Oxford. 
Shortly afterwards, through the kindness of Mr. Boscher and Mr. 
William White, 1 had the opportunity of looking at some twigs of 
the trees upon which the eighteen spotted yellow larves were found 
(see p. 304 of the former paper, <&c.). The trees were the small-leaved 
variety, and Mr. Boscher states that all the yellow larvsB were found 
upon such food-plants. Then again 1 remembered that in the case 
of the very bright yellow variety found upon crab {var, acerba) on 
August 14th, 1884 (see former paper p. 301), the latter tree had very 
small leaves. Finally, Salix incana at Brigue possessed leaves which 
were very white and downy underneath, but they were very small, 
and the larva found upon the tree was yellow. 

All this convergent evidence suggested the following explana- 
tion. The larv89 are only affected by that part of the environment 
which is so close to them as to be almost or quite in contact; 
the tint of mature life is (as far as it is caused by the colour of 
the food-plant) a resultant of the conflicting tints which have 
formed part of the immediate environment of the larva through- 
out its life, and the ultimate predominance of one larval tint is due 
to the relative proportion of the whole larval life during which that 
tint predominated in the environment. This conclusion in also 
supported by the breeding experiments and the experiments upon 
captured larvaa. Such being the case, the ultimate whiteness of a 
mature larva is largely due to the considerable proportion of its 
earlier life which is spent upon the white under sides of the leaves. 
(The young larv89 invariably take up this position.) During this 
period white is the only colour in its immediate environment, except 
when it is actually engaged in eating, and so may perhaps be affected 
to some extent by the colour of the upper sides. But when the larva 
reaches a certain size and weight, it must in nearly all cases quit this 
position and retire to the stem, because the leaf is not strong enough 
to bear it without being dragged into an unnatni^l position, or 
because it is too small to form a background for the larval body. 
Therefore the time at which it retires must chiefly depend upon the 
size and strength of the leaves. Having once quitted the small 
leaves the larva does not again rest upon them, because they can be 
entirely eaten from the stem, whereas the large leaves cannot be 
reached without venturing upon them, and therefore in the latter case, 
the chances are in favour of the larva being left upon a partially 
eaten Jaz^e leal during many of the peiioda oi t^«.^ «\^xi ^\» \s:c^ 



1886.J Larva of Smerinthua ocellatus and its Food-plants. 161 

advanced stage. When the larva is smaller and cats mnch less it 
remains on the same leaf for many days. But directly the larva rests 
on the stem the tints, of its immediate environment alter, for thej 
are then due to the colours of both sides of the leaves and of the stem 
itself. The relative predominance of the colours of the two sides of the 
leaves depends upon the position of the larva and the arrangement oi 
the leaves. Bat the position of the larva is uniform (except when it 
is wandering to a fresh twig), the head being always directed towards 
the apex of the stem. Hence in the case of food-plants whose large 
leaves regularly droop over from the vertical twigs, or are curved in 
the usual way with the concavity downwards, the tints of the under 
side still predominate after the larva has retired to the stem, and they 
will still form almost the only effective colour as was the case in 
earlier periods. When, however, the leaves hang irregularly or 
spread out horizontally from horizontal twigs, the colours of the two 
sides may be equally important, or may depend (in the latter case) 
upon the side of twig on which the larva rests. 

This explanation of course will apply but little to leaves of which 
the upper and under surfaces are approximately similar in colour, 
and accordingly there is very little conflicting testimony from such 
food-plants (Saltx rubra, S, bahylonicaf S. triandra), and such as there 
is, is mainly explicable by variations in the other two factors which 
go to influence larval colour. But even in these plants there is some 
difference between the colours of the two sides which would have an 
effect upon the larvae, as was proved by the experiment in which the 
bloom was rubbed off in the case of 8. triandra. But in the case of 
leaves with strongly white under sides such an explanation accounts for 
all the conflicting evidence met with in the field (due to this factor and 
recognised by the uniformity of results from trees with leaves of a 
particular size and arrangement). Thus when I expressed the opinion 
that Salix vimmalis produces white larvae I was thinking of our 
common long-leaved variety. The leaves of this variety often grow 
6 inches long near Oxford, and quite three-quarters of an inch 
wide. Such leaves would retain a larva until the end of the fourth 
stage, and often far into the last stage. Furthermore the long 
leaves droop over very regularly from the higher vertical twigs upon 
which the larvae are generally found, and so present their under 
sides to the stem and to a larva resting upon it. On the other hand, 
the leaves of the other variety are much smaller (from memory I 
should say that they are often about an inch and a-half long and three- 
eighths of an inch wide), and often hang in irregular wisps from the 
more vertical twigs, or droop vertically from the more horizontal 
branches. Thus such a variety of leaf would retain the larva for a 
compamtivelf short time, and after its retiremeiit \.o V\\^ ^^jetCL V5w^ 
colour of the immediate environment would be aalarg^Xy ^\xfe\.o\5M. 



162 Mr. E. B. Ponlton. Cohur^ekttion between the [Feb. 4, 

upper as tlie under side. Hence the effect of the narrow and small- 
leaved 8. viminalis in producing yellow larvsB, and the exceedingly 
white-leaved (under sides) Saltx linearii in producing a yellowish 
intermediate larva. The influence of 8. cinerea (in the direction 
of yellow) is probably in a great measure due to the same facts, 
for its small leaves are often downy underneath, and are always 
much whiter than those of S. ruhra^ &c. The mach stronger in- 
fluence of S, Smiihiana towards white is probably due to its much 
larger but very similar leaves. It is likely that some of the 
irregalar results referred to other factors may be explained in this 
way. Thus it was very obvious that the leaves of 8. ferruginea (?), 
upon which very differently coloured larves were found (p. 301 
of the former paper), varied very much in size, those on the lower 
branches looking like rather narrow leaves of 8. cinerea, the npper 
ones being exactly like those of 8, 8'nuthiana ; but in such an isolated 
ease it is not possible to determine certainly which of the factors 
caused the exception, or whether it was due to a combination of 
causes. I think it is unlikely that any great difference could be 
caused by a slight variation of habit in larvee, i.e., in the period at 
which different individuals would retire to the stem from leaves of the 
same size. It is probable that the habit is very uniform, and always 
leads the larvae to remain on the leaves as long as the size and 
strength of the latter will permit them to do so. In 8alix alba the 
question is complicated by the fact that after the larva retires (early 
in this case) to the stem, the whiteness of the environment will 
partially depend upon nearness to the apices of the twigs, for the 
upper sides of the young leaves are white as well as the under sides. 
The exceedingly strong influence of apple is readily explicable by the 
considerations advanced above ; for the leaves are large, broad, and 
strong, and will take the weight of a larva advanced in the last stage 
without bending. The single larva found upon apple in 1885 
(August 30th) was resting before changing its skin for the last time 
on the under side of the leaf, and I have often before found the large 
larv89 in the same position. After the larva retires to the stem the apple 
leaves form broad curved white surfaces, which everywhere environ 

' ft 

the (presumably) sentient part of its body, which is always directed 
during rest towards the apex of the twig. Upon all the varieties of 
food-plant, and especially upon apple, the larva tends to rests upon 
the young and vigorous twigs which stand out from the trees and 
bear fewer larger leaves at wider intervals, and with more regular 
arrangement than those upon the older wood below. Thus the larva 
gets the maximum effect from the under sides of the leaves after it 
has retired to the stem. This explanation also helps towards clearing 
np the difBcuUy about the irregular eftect oi eT%.\i. MWiow^Vi ^Xx^ 
under sides of the leaves are smootb and green, t\ie^ wj^ ^«i[i«t^^ ^1 \Sb 



1886.] Larva of Smerinthus ooellatus and its Food-plants. 163 

whitish-green, and I think that a white la^rva is better protected when 
resting on the under side of the leaf than a yellow larva would be, 
although this is often true in the case of trees which are known to 
produce yellow larrsB. Again the leaves are large as a rule, and so 
the larvsB are advanced when they rest on the stem, and even then the 
arrangement of the leaves and the position of the larva cause the under 
side to contribute most colour to the immediate environment. I have 
already mentioned that the bright yellow, red-spotted larva captured 
in 1884 upon crab, var. acerba^ was upon a tree with exceedingly 
small leaves. Fnrthermore, in this variety the leaves are extremely 
variable in size upon different parts of the tree. But although the 
conditions mentioned above may have conduced towards the fact that 
my bred larvad fed upon this plant became so white, I cannot but 
think that such a result was largely due to their strong hereditary 
tendency towards this colour, for the crab cannot compare with 
ordinary apple in the whiteness of the under sides of the leaves, nor 
is it in this respect equal to SaUx viminalis, Smithiana^ or even 
cinerea. I think that this food-plant more than any other requires 
further experimental work with larvaa of all varieties of hereditary 
tendency, but it is very unfortunate that the larvaa do not seem to 
thrive upon the plant, at any rate in confinement. 

Another great difficulty is, I think, completely explained by the 
above-mentioned consideration. I mean the fact that bred larvaa 
tending strongly towards white, became intermediate in 1884 and in 
many cases in 1885 when fed upon the large-leaved variety of Salix 
viminalis (for T have always fed my larvae upon this variety). In 
order to obtain the best leaves I have to walk to the Cherwell and 
take a boat ; and as this is not always convenient, I bring home and 
give to the larvae a great quantity. The leaves being very long and 
crowded in the glass cylinders in which the larvae are kept, their 
natural armngement is entirely altered, so that the upper sides are 
presented to the larvae to a much greaticr extent than happens on the 
tree. The result is to affect the environment of the larvae upon the 
leaves as well as those upon the stem, for in the former case the 
upper sides of other leaves must be often crowded close up to the 
under side of the one upon which a larva is resting. Furthermore, 
the leaves do not last so long without withering as upon the ti*ees in 
the open air, and therefore the larvae are frequently compelled to 
wander on to fresh leaves, and in so doing they must be affected 
by the colour of the upper as well as the under sides. In the future 
it would be well to breed some larvae in large cases which would hold 
the twigs without overcrowding, and would permit the leaves to tall 
naturally. In the case of apple the arrangement of the leaves has 
not been disturbed in the cyiinders, because I can gettVife W\%%V^ 
mj- garden, and becaaae the ieaves are of a more manfti^^^LXiV^ ^toj^^. 



164 Mr. E. B. Ponlton. ColoujMrelation between the [Feb. 4, 

It is possible that the same canses have helped to produce yellower 
results than are normal in the breeding experiments with Salia alba 
and 8. Smifhtana, for these leaves have been somewhat disturbed, 
although not nearly so much as in the case of 8, viminalis. I do not 
doubt the validity of this explanation for the latter plant, and the 
results of experiments are thus satisfactorily interpreted which have 
been sources of difficulty and uncertainty since the summer of 1884. 
This explanation also clears up what I felt to be a great difficulty in 
my former paper when I wrote the words (page 314) " it is only the 
part of the environment imitated which produces any effect, e.g., the 
under sides of the leaves in the case of 8. ocellatus, and yet the 
environment, of course, includes both surfaces." I have shown above 
that the effective part of the environment — the immediate environ- 
ment — does not in many eases include both surfaces, but either 
entirely or chiefly the under surface, i.e., that which is ipso facto 
imitated, and when it does include the other surface for a sufficiently 
long period, a different effect is produced (in the case of leaves with 
differently coloured sides). It is therefore obvious that when we speak 
of the tendency of a plant to produce a certain colour, we mean a 
tendency from the size and arrangement of the leaves to encourage a 
larval position in which the effective colour of the environment is 
only contributed by one leaf surface, or, on the other hand, a tendency 
to change the larval position into one in which both surfaces may 
become equally effective, or, again, into one in which either of them 
may predominate. In this explanation of what is meant by the 
tendency of a plant, I am, of course, especially referring to those 
with leaves having white under sides ; but it will probably apply to 
some extent in nearly all cases, for there is always some difference 
between the two sides of the leaves. 

There is one other comparison between the captured and bred 
larvBB which is a source of difficulty. The exceedingly unifonn 
results upon 8alix rubra in the field (I have found altogether twenty- 
two larvae, of which eighteen were yellow, three yellowish interme- 
diate, and one intermediate) render it more than probable that the 
plant has possessed^ an influence sufficiently powerful to reverse a 
larval tendency in the direction of white (for it is very unlikely that 
in all the eighteen instances of a maximum result the larva happened 
to tend in the same direction as the food-plant) ; and yet in the 
breeding experiments, out of nine larvae eight were yellowish interme- 
diate and one intermediate ; and thus in no case has the food-plant 
completely overcome a strong tendency (1884) or a somewhat modified 
tendency (1885) towards white. 

I have thought that part of this difference (also observable in the 
cases of S. babylonica and S. iriandira) may \>e due \iO Wve l^^it t\\«*.t tbe 
tops of the glass cylinders in which, the \ar7® wre \iTed, ^xe eo^^x^^ 



^1886.] Larva of Smerinthus ocellatus and its Food-plants. 165 

4)|nth white muslin, which prohably, therefore, prodnces some slight 
ppAbct on the lary». Again the larv» in the field are probably 
itdtected by the amount of light, and especially direct sunlight, 
whioh must brighten the ooloars of their environment. I have 
: commonly found them on 8, rubra (as in the other trees) upon 
L:'tiie higher younger branches standing out from the trees, and espe* 
' Dtally during the past summer upon twigs that have been allowed 
' to grow out from the tops of hedgerow sallows; and I have also 
■ noticed that they are better protected in these strong lights because 
of the brightness of their own colour than in the shadows of the 
• lower and more crowded leaves. The bred larv» have never been 
so freely exposed to light, and although the small leaves of the food- 
plant do not become much disarranged (probably hardly any effect 
would be produced if they were), yet the crowding certainly helps to 
■hade the leaves and to diminish the brightness of their colours. 
(During the past summer I have kept the larvaa under a north 
window to protect them as far as possible from the excessive heat.) 
It is very probable that some of the difference is to be explained in 
this way, but most of it is no doubt due to the hereditary tendencies 
of my bred larvaa, which were always towards white, while this ten- 
dency is probably less common than the other by the banks of streams 
(see former paper, p. 310). It will be very interesting in future 
experiments to breed the larvad under yellow and under white glass. 
Next year I hope to be able to make such experiments. 

7. The Whole of the Evidence Summarised, 

I have arranged all the results hitherto obtained in a table which is 
printed below. The only important omission is the hereditary tendency 
of the bred larvae, and this would have rendered the table too compli- 
cated, for there were four different series in 1885. It will, however, 
be remembered that all the larvae bred in 188-4 tended strongly towards 
white, while nearly all of them in 1885 possessed the same tendency in a 
slightly modified form. All the numbers without reference marks refer 
to my own observations or experiments conducted at Oxford ; while 
special marks call attention to the work of other observers, or to my 
own work in other localities. The 204 instances given below comprise 
all the cases in which the colour of the larva and the name of the 
food-plant have been noted, either in breeding or in field observations. 

Only in the case of the white varieties captured upon ordinary 
apple have I ventured to allude to the larvae under the vague term 
** very common,'* because such has been my experience and that of 
other observers, although no list of instances has been kept, and 
therefore no number can be quoted. Had I left the space blank it 
would have coDvejed an entirely wrong impreBsion oi ^'^wj ^•axv^T^ 
experience. It mast he anderstood that in the followAUg d^^eTv^\»\oii% 

rOL. XL. ^ 



166 Ur. E. B. Ponlton. Colour-relation betwen the [Feb. 4, 





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tptnAwU l^^J!fm h*>i ft&ally jpren t2*e bkrr& » {wver vhica » v^lik- 
Ur^ijjf ittfttkHinti^ (A hn Mt^oQ, ft f^>wer which ec^bies the orgmnisin 
fiM(if t/^ ftfMw^ mth cy>rnMfjr>iidint? coiciurs the ddfereoces which 
/ff/Atf* ^^^w^Kt^ ir» Tarvyoji food-planta. Arvi the ftctioQ difers no 
Phm( ff</m t^*^ nof^rrficiaillj irimilar caues o€ moeh more rwgkd. changes 
ir# tir*^ tifA/mt iA fAhtr t/r^hnixua (amphibia^ fish, Ac.) corresponding 
I// fi*i» t}UMrtf(ir»f( c^AoQrn of their enTironment, for in such organisms 
%h^, 4»f iirmftl colz/om »ct m a tttimnioA which, through a nerrons circle, 
tft^/fltf't^m ih^ Cffttdiium of existing pigments; while in the larva it 
m iU4} ar/ioonU arid kinds of vegetal pigments made nse of and 
Uf ral \ny^mhu\M (\tj\Hm\Un\ that are affected. The inflaenoe, in fact, 
mnkm itiMslf felt \fy affecting the absorption and production of 
\ny^mhuU^ rnihw than their modiGcation when formed; and such a 
ittt^\uA iff f(ai fling protection is, as far as we jet know, unique in the 
animal kirigfUmi. And such a power is not confined to the species in 
whif;h its exist^moe has been to some extent completelj proved. 
Thirro aro already proofs that many others can maintain a similar 
(foloijr-t'<)latiori Cseo my former paper, and the references given by 
Mr. MfiKlola in his translation to Weisinann's '^Studies in the Theory 
of lUmnwi/* i'art II), and I am sure that careful observation will 
reviNU nmfiy slight and protective differences among larvaa of the 
sainc) n\HH'um when found upon differently-coloured f(X)d-plants, and 
will prove that this power is not at all uncommon among the great 



1886.] On the Polarisation of Light by Iceland Spar. 173 

body of lepidopterons lary» which adopt the methods of protective 
resemblance. Furthermore, it is very probable, as suggested by 
Professor Meldola, that the colour of the environment will prove to 
act as one of the determining causes of the larval colours ultimately 
assumed by the individuals of dimorphic species (which are generally 
green and brown in lepidopterons larvaa). To show in what a light 
this colour-relation appears to Dr. August Weismann (whose essay 
upon ''The Markings of Caterpillars" first induced me to work at 
these organisms), I quote the following sentences from a letter I 
received from him after sending him my paper in the '' Entomological 
Society's Transactions," Part I, April, 1884, in which this subject is 
alluded to : — 

'* Dagegen verstehe ioh nicbt ganz, wie sie sich den ' phytophagio 
character of the ground-colour' entstanden denken. Ich habe 
augenblicklich mein Buch nicht zur Hand u. kann deshalb die Note 
Ton Meldola nicht nachsehen, erinnere mich auch derselben nicht. 
Sie scheinen zu glauben, dass die Nahrung der Baupe bis zu einem 
gewissen Grad ihre Farbe direJst hervorrufe. Ich ware sehr begierig, 
einen Beweis dafiir kennen zu lemen. Ich kann mir nicht denken, 
wie dies moglich sein, solle jedoch weiche ich den Thatsachen ! Ich bin 
begierig, zu erfahren, ob Sie solche inzwischen gefunden haben." 

I venture to hope that the facts spoken of by Professor Weismann 
are now satisfactorily demonstrated, not as proving the former theory 
to which he alludes, that the food itself causes the change of colour 
after it has been eaten by the larva, but as proving the existence of 
the more subtle form of influence described in the present and in my 
last paper. At the same time I must express my sense of the great 
extent to which I am indebted to Professor Meldola, to whom we owe 
the fornler theory, for without the most suggestive editorial notes to 
his translation of Weismann's work, and the experiments undertaken 
by Mr. Boscher at his request, it is most improbable that the present 
investigation would ever have been begun. 



III. " On the Polarisation of Light by Reflection from the 
Surface of a Crystal of Iceland Spar." By Sir John 
CONROY, Bart., M.A., of Keble College, Oxford. Communi- 
cated by Professor G. G. Stokes, P.R.S. Received 
January 27, 1886. 

(P1.ATB 2.) 

In the year 1819 Sir David Brewster communicated to the Royal 
Society ("Phil. Trans.," 1819, p. 145) an account of some experiments 
he had made on the polarisation of light by reflection from the surfsAQ 



174 Sir J. Conroy. On the Polarisation of [Feb. 4 

of double refracting sabstances, and showed that Mains* statement 
with regard to Iceland spar was incorrect. 

Mains said that Iceland spar behaves towards the light it reflects 
like a common transparent body, and that its polarising angle is about 
56** 30', and that whatever be the angle comprehended between the 
plane of incidence and the principal section of the crystal, the ray 
reflected by the first surface is always polarised in the same manner 
(" Th^rie de la Double Refraction," pp. 240, 241). 

Some years later Seebeck (" Pogg. Ann.,'* voL xxi, p. 290 ; vol. xxii, 
p. 196 ; vol. xzzviii, p. 276 ; vol. zl, p. 462) made a number of very 
accurate observations on the same subject, and in 1835 and 1837 
Neumann published in " Pogg. Ann.," vol. xl, 497, and voL xlii, p. 1, 
an account of further experiments that he had made on the reflection 
of light by Iceland spar. 

He begins his second paper by a brief summary of the results 
obtained by Brewster and Seebeck. *' Brewster found that the angle 
of complete polarisation for calcspar depends on the position of the 
reflecting surface relatively to the axis, and upon the position of its 
principal section to the plane of reflection; he also found that 
when the reflecting surface is covered with a liquid, the plane of 
polarisation of the completely polarised ray does not coincide with the 
plane of reflection, but makes a smaller, or greater, angle with this ; 
when a cleavage-face of calcspar is covered with oil of cassia this 
deviation may amount to 90°. The knowledge of these phenomena 
has only been further advanced in recent times. Dr. Seebeck has so 
followed out, by means of most accurate determinations, the influence 
of optically uniaxial crystals upon complete polarisation, that the 
angle of incidence at which this occurs can be determined as accu- 
rately beforehand as it can by Brewster's law in the case of uncrystal- 
lised bodies. Seebeck also discovered that the deviation of the plane 
of polarisation from the plane of reflection, which Brewster had 
observed, also occurs when the ray of light falls directly from air on 
to the surface of the crystal." 

Seebeck*s observations having been mainly directed to the deter- 
mination of the angle of polarisation, Neumann's object was to deter- 
mine the azimuth of the plane of polarisation of the reflected light. 
They both assumed, contrary to Fresnel's hypothesis, that the density 
of the ether in the two media was the same and the elasticity different, 
and therefore that the plane of vibration coincided with the plane of 
polarisation, and starting with this assumption succeeded in showing 
that the observed and calculated results were in close accordance. 

Seebeck and Neumann only repeated a portion of Brewster's experi- 
ments, and no one except Sir David Brewster appears to have made 
any determinations of the angles and azimuths of polarisation when 
the spar was in contact with media other than air. 



1886.] lAght by RefUetian from Iceland Spar. 175 

Professor Stokes very kindly called my atiention to these experi- 
ments of Sir David Brewster, and pointed out that as they had never 
been published in detail, and had not been repeated by anyone else, 
it was desirable that farther observations should be made on this 
subject. The experiments, the results of which I have the honour of 
submitting to the Royal Society, were undertaken at Professor Stokes' 
suggestion, and in carrying them out I had the benefit of his advice. 

The apparatus used was essentially the same as that employed by 
Seebeck ; the divided circle of the goniometer was, however, horizontal, 
and not vertical, as in Seebeck's instrument, and the arrangement for 
keeping the reflected ray constantly in the axis of the observing tube, 
whilst the angle of incidence was varied, differed from that employed 
by him ; the axes of the stage and of the observing tube were fitted 
with toothed wheels which geared into a double pinion, the diameters 
of the wheels being such that the angular velocity of the observing 
tube was double that of the stage. 

The goniometer had a vertical stage in addition to the ordinary 
horizontal one, which could be moved nearer to and further from 
the axis of the instrument, and this stage had four adjusting screws, so 
that the front surface could be placed parallel to the axis of rotation. 

A brass plate was clamped to this stage ; a short brass tube carrying 
an annular toothed wheel at one end, and a divided collar at the other, 
fitted into an aperture at the lower end of this plate, and could be 
rotated in the plane of the plate by turning a milled head fixed at the 
end of a rod, which carried a bevel pinion working into the annular 
wheel. 

A brass tube with a collar at one end could be fastened to the 
annular wheel by four screws passing through holes in the collar, the 
back of the collar and the inner surface of the wheel being portions of 
a spherical surface. 

The crystal whose reflective power was to be examined was fixed in 
the inner tube, which was then adjusted by means of the four screws 
so that the surface of the crystal was in the plane of rotation, and 
then, by altering the position of the vertical stage, the plane of rota- 
tion brought vertically over the axis of the goniometer. 

The crystal was cemented into the tube with plaster of Paris ; a 
little lard was rabbed on the edges of the face which was to be exposed, 
and it was placed on a plate of glass with this surface downwards, 
and the brass tube, the collar of which had also been greased, placed 
round it, and centred by means of a marked card placed under the 
glass, and plaster of Paris poured in. In one of the earlier experi- 
ments the crystal was found after a certain number of observations 
had been made to have become loose, owing to the plaster having 
shrank away from the tube ; three holes about 2 mm. in diameter were 
therefore drilled in the sides of the tube, and no further difficulty was 



176 SirJ. Conroy. On the Polarisation of [FeU 4, 

experienced from this cause, as the little projections of plaster which 
filled these holes effectuallj prevented any movement. 

In order to adjast the reflecting surface, a diaphragm with a small 
hole in it was fitted into the eye end of the observing tube, and a lamp 
with a flat wick so placed that its image was seen by reflection from 
the surface of the crystal, two of the adjusting screws of the tube 
being in the horizontal plane (i»e,y the plane of incidence). The 
tube was then turned through an angle of 180°, and the reflected 
image brought back half way into the centre of the field by altering 
the two screws of the tube which were in the plane of incidence, and 
the remainder of the distance by means of the screws of the stage, 
which, as well as the observing tube, remained clamped to the 
horizontal circle whilst this adjustment was being made. 

The tube was then turned back to its original position, and the 
adjustment repeated if necessary ; the tube was then turned through 
90**, and the second pair of screws altered till the reQected image 
remained in the centre of the field whilst the crystal was rotated. 
The adjustment was then examined by means of a simple form of 
diagonal eye-piece placed in the collimator tube of the goniometer, 
consisting of a brass tube with a diaphragm at either end, with a 
small aperture in each, and also in the side of the tube ; inside the 
tube, and opposite the aperture in the side, a piece of microscopical 
cover-glass was fixed at an angle of 45"* with the axis of the tube ; the 
lamp was placed opposite the aperture in the side of the tube, and 
the vertical stage rotat>ed until the light of the lamp reflected from 
the thin glass was reflected back by the crystal along the axis of the 
eye-piece to the observer ; the tube holding the crystal was then 
rotated, and if the spot of light remained visible whilst the tube made 
a complete rotation, the adjustment was considered to have been 
correctly made, and the position of the stage was then read on the 
horizontal circle of the goniometer, and this measurement taken as 
that of perpendicular incidence. 

Several such readings were made, and then the position of the tube 
and lamp altered, and several more readings made, and the mean of 
these, which usually were close together, taken as the zero for the 
angle of incidence. 

Two complete series of observations were made with cleavage- 
faces of Iceland spar in air, water, and tetrachloride of carbon, the 
water and tetrachloride of carbon being contained by a nearly cylin- 
drical thin glass vessel (a chemical beaker), which stood on the hori- 
zontal stage of the goniometer, the tetrachloride being prevented from 
evaporating by a layer of water floating on its surface. 

When the reflection took place in air, a paraffin lamp, with a flat 
burner placed edgew&jB (i.e., radially to the goniometer) was used as 
tjbe scarce of light; when the crysial waa m '^JBbWc or \»\?c«*^orA^ 



1886.] LiglU by Reflection from Iceland Spar. 177 

of carbon, its reflecting power was so muoh diminished that a moro 
intense source of light was ^ necessary, and a magic lantern (a 
** sciopticon '*) was used, a black card with a slit 3*5 mm. wide 
being placed in the slide-holder, and focassed on the sarface of the 
crystal, care being taken in both cases that the direction of the inci- 
dent light should coincide as nearly as possible with the axis of the 
collimator tube. 

The measurements were made by altering the angle of incidence 
and the azimuth of the observing Nicol until the light was reduced to 
a minimum, the position of the crystal remaining fixed. 

In order to obtain anything like accurate results with observations 
of this kind it is necessary to make a large number of determinations 
and take their mean : it was obvious that there were two ways in 
which any given number of observations might be grouped, either by 
making a good many separate determinations for a few positions of 
the crystal, or by making a few observations at a number of different 
azimuths ; the latter alternative being the one adopted, two readings 
were made at seventy-two different azimuths of the crystal. 

In the first series the observations started from one of the edges 
of the crystal, the tube containing it being turned through 10^ after 
each pair of readings ; after thirty-six pairs of readings the crystal 
was turned through 6° 20', and then thirty-six more double readings 
made at intervals of 10° from each other. 

In the second series the observations started from the principal 
section, and were also made at intervals of 10° ; the crystal was turned 
through 5° after thirty-six observations had been made, and then 
thirty-six more were made, also at intervals of 10°. 

It was thought that by working in this way the results would be 
more independent of each other, and therefore more trustworthy 
than if the readings had been made continuously round the whole 
circle. The position of the crystal was determined by placing a 
square on the horizontal stage of the goniometer, and rotating the 
tube carrying the ciystal until the edge of the crystal appeared to 
coincide with the vertical edge of the square, and noting the reading 
of the divided ring attached to the tube ; several such readings were 
made, and the tube and crystal turned through 180° and several moro 
observations made, and the mean of these taken as the position in 
which one of the sides of the crystal was vertical (i.e., perpendicular 
to the plane of incidence) ; the position of the principal section could 
then be readily determined as it bisects the obtuse angle, and there- 
fore, that angle being one of 101° 55', or nearly 102°, forms an angle 
of about 51° with the adjacent edges. 

The position of the crystal in which the principal section was in 
the plane of incidence and the obtuse summit neaTest \\\^ <^^^^^^ 
was cons/dored the zero poaition ; when the pr\nc\pa\ Eeci\.\oTv ^^>& vdl 



178 



Sir J. Conroy. On the PolaristxHon of [Feb. 4, 



the plane of incidence and the obtuse summit towards the side from 
which the light was incident npon it, was therefore asimnth 180°. 
The crystal was rotated clockwise, and the same direction of rotation 
was considered the positive direction for the Nicol. 

Table I gives the measurements made in this way with a cleavage- 
face of Iceland spar in air ; Tables II and III with the same face in 
water and carbon tetrachloride. Table IV contains the measurements 
made with another cleavage-face of the same crystal in water. 
Tables Y, YI, and YII, give the results with a cleavage-£ace of a 
second crystal in air, water, and carbon tetrachloride. 

Table I. 
Iceland Spar in Air. 



/ 



Azimntb 
of tbe 
principal sec- 
tion of the 
crystal. 


Aximnth 

of the 

plane of 

polarisation. 


Angle of 
polarisation. 


Aximnth 
of the 
prlndpal sec- 
tion of the 
crjstaL 


Ajdmnth 

of the 

plane of 

polarisation. 


Anffle of 
polaniwtion. 


DiflSeTence 
intbeTaloes 

of the 

polanslng 

angle at 9 

and 

»+18Cy>. 


o / 
+ 1 


/ 

+ 10 


67 20 


o / 
181 


o / 

+ 22 


o / 

67 06 


-J- 14 


7 20 


+ 35 


67 24 


187 20 


+ 47 


67 09 


+ 15 


11 


+ 30 


67 17 


191 


+ 1 10 


67 12 


+ 5 


17 20 


+ 40 


57 22 


197 20 


+ 1 60 


67 16 


+ 6 


21 


+ 25 


67 24 


201 


-1-2 05 


67 26 


- 1 


27 20 


+ 45 


68 


207 20 


+ 2 35 


57 29 


+ 31 


31 


+ 47 


67 50 


211 


+ 3 15 


67 69 


- 9 


37 20 


+ 37 


68 11 


217 20 


-1-3 25 


57 69 


+ 12 


41 


+ 40 


68 17 


221 


-1-3 30 


68 19 


- 2 


47 20 


+ 47 


68 39 


227 20 


+ 3 37 


68 31 


+ 8 


61 


+ 35 


68 34 


231 


-j-4 05 


68 34 





67 20 


+ 35 


69 02 


237 20 


+ 3 42 


68 52 


+ 10 


61 


-0 03 


68 48 


241 


-1-3 45 


69 03 


-15 


67 20 


-0 10 


69 18 


247 20 


-1-3 32 


69 12 


+ 6 


71 


+ 02 


69 13 


251 


+ S 37 


69 15 


- 2 


77 20 


-1 08 


69 32 


257 20 


-1-3 60 


69 42 


-10 


81 


-1 26 


69 24 


261 


-»-3 05 


59 32 


- 6 


87 20 


-1 43 


69 35 


267 20 


+ 3 10 


69 20 


+ 15 


91 


-1 33 


69 49 


271 


-f-2 46 


69 38 


+ 11 


97 20 


-2 30 


69 26 


277 20 


+ 2 12 


59 33 


- 7 


101 


-2 30 


59 38 


281 


+ 2 35 


69 45 


- 7 


107 20 


-2 33 


69 25 


287 20 


-»-l 15 


69 23 


+ 2 


HI 


-2 23 


69 11 


291 


+ 1 47 


69 20 


- 9 


117 20 


-2 48 


69 06 


297 20 


-1-0 62 


69 03 


+ 3 


121 


-2 58 


69 04 


301 


+ 65 


68 56 


+ 8 


127 20 


-3 13 


68 43 


307 20 


+ 30 


68 43 





131 


-3 05 


68 37 


311 


+ 05 


68 37 





137 20 


-3 


68 25 


317 20 


-0 20 


58 25 





141 


-2 55 


58 10 


321 





68 17 


- 7 


147 20 


-2 37 


57 47 


327 20 


-»-0 07 


58 06 


-19 


161 


-2 20 


57 54 


331 


-0 08 


67 48 


+ 6 


167 20 


-2 08 


67 26 


337 20 


-0 08 


67 64 


-28 


161 


-1 33 


67 43 


341 


-0 25 


67 30 


+ 13 


167 20 


-0 48 


67 22 


347 20 


-0 06 


67 22 





2T1 1 


-1 , 


57 28 


361 


, +0 0^ 


[ ^1 ^ 


I ^ ^ I 


177 20 I 


+ 012 1 


67 14 


367 20 


\ -0 1^ 


\ m ^1 


\-" 



.1886.] 



Light by Reflection from Iceland Spar. 



179 



Table H. 
Iceland Spar in Water. 



Azimnth 
of the 
principal sec- 
tion of the 
crystal. 


Azimnth 

of the 

plane of 

polarisation. 


Angle of 
polarisation. 


Azimnth 
of the 
principal sec- 
tion of the 
oystal. 


Azimnth 

of the 

plane of 

polarisation. 


Angle of 
polarisation. 


Difference 

in.theTaInes 

of the 

polarising 

angle at $ 

and 

•+180°. 


o / 

+ 1 


o / 
+ 12 


4& 19 


o / 
181 


O i 

- 03 


o / 
49 18 


/ 
+ 1 


7 20 


+ 40 


60 29 


187 20 


+ 20 


49 38 


+ 66 


11 


-t- 1 22 


49 42 


191 


+ 8 02 


49 11 


+ 81 


17 20 


+ 1 65 


49 59 


197 20 


+ 6 17 


49 26 


+ 88 


21 


+ 1 10 


60 10 


201 


+ 6 87 


49 64 


+ 16 


27 20 


+ 1 12 


51 15 


207 20 


+ 7 65 


51 07 


+ 8 


81 


+ 26 


50 30 


211 


+ 7 66 


50 06 


+ 24 


87 20 


+ 1 27 


51 30 


217 20 


+ 10 27 


60 44 


+ 46 


41 


+ 42 


51 33 


221 


+ 11 22 


61 14 


+ 19 


47 20 


+ 22 


52 30 


227 20 


+ 12 27 


52 28 


+ 2 


51 


- 23 


52 21 


231 


+ 13 07 


62 07 


+ 14 


67 20 


- 2 20 


53 37 


237 20 


+ 18 37 


68 24 


+ 18 


61 


- 2 48 


53 52 


241 


+ 18 42 


63 63 


- 1 


67 20 


- 3 03 


54 23 


247 20 


+ 13 47 


64 50 


-27 


71 


- 5 38 


64 49 


251 


+ 13 42 


64 52 


- 8 


77 20 


- 8 23 


65 66 


257 20 


+ 13 40 


55 14 


+ 42 


81 


- 7 35 


55 32 


261 


+ 12 62 


65 88 


- 6 


87 20 


- 8 40 


55 32 


267 20 


+ 12 10 


66 07 


-36 


91 


- 9 33 


65 87 


271 


+ 11 05 


66 11 


-34 


97 20 


-10 55 


66 05 


277 20 


+ 10 15 


65 47 


+ 18 


101 


-12 08 


66 08 


281 


+ 9 20 


65 49 


+ 19 


107 20 


-13 25 


65 34 


287 20 


+ 70 


65 41 


- 7 


111 


-12 38 


54 68 


291 


+ 7 10 


66 34 


+ 24 


117 20 


-14 03 


64 07 


297 20 


+ 4 57 


64 13 


- 6 


121 


-13 


64 18 


301 


+ 8 10 


68 23 


+ 55 


127 20 


-12 24 


62 41 


307 20 


+ 1 45 


68 44 


-68 


181 


-12 13 


53 04 


311 


+ 1 52 


63 42 


-38 


137 20 


-12 


53 02 


817 20 


- 10 


62 23 


+ 39 


141 


-11 


61 09 


321 


+ 1 05 


61 50 


-41 


147 20 


- 9 10 


51 04 


327 20 


+ 10 


61 42 


-38 


151 


- 8 58 


49 62 


331 


+ 37 


61 12 


-80 


157 20 


- 6 38 


49 42 


337 20 


+ 17 


60 39 


-67 


161 


- 6 10 


48 46 


341 


- 25 


49 53 


-67 


167 20 


- 4 13 


60 20 


347 20 


+ 27 


49 05 


+ 76 


171 


- 2 45 


49 18 


361 


+ 46 


49 65 


-37 


177 20 


- 1 65 


49 10 


357 20 


- 15 


49 25 


-15 



180 



Sir J. Conroy. On the Polaritation of [Feb. 4, 



Table Til. 
Iceland Spar in Tetrachloride of Carbon. 



Azimuth 
of the 
prindpel sec- 
tion of the 
crystal. 


Azimuth 

of the 

plane of 

polarisation. 


Anfcle of 
polarisation. 


Azimuth 
of the 
principal sec- 
tion of the 
crystal. 


Azimuth 

of the 

plane of 

polarisation. 


Anale of 
polarisation. 


Difference 

inUievaloen 

of the 

polarising 

ajigle at $ 

and 


o / 
+ 1 


o / 
+ 22 


o / 
44 34 


o / 
181 


o / 

- 43 


a / 

46 39 


-125 


7 20 


- 18 


46 35 


187 20 


+ 4 37 


46 15 


+ 80 


11 


+ 17 


45 46 


191 


+ 6 45 


44 20 


+ 86 


17 20 


•h 42 


45 40 


197 20 


+ 7 12 


46 19 


+ 21 


21 


+ 1 06 


46 22 


201 


+ 11 35 


46 18 


+ 64 


27 20 


+ 1 37 


47 43 


207 20 


+ 14 02 


46 55 


+ 48 


31 


+ 1 55 


47 


211 


+ 16 55 


47 39 


- 39 


37 20 


+ 07 


46 21 


217 20 


+ 19 15 


48 02 


+ 19 


41 


+ 07 


49 34 


221 


+ 22 40 


60 47 


- 73 


47 20 


- 2 38 


50 05 


227 20 


+ 24 50 


61 


- 55 


51 


- 38 


50 36 


231 


+ 26 30 


53 03 


-147 


57 20 


- 4 50 


63 87 


237 20 


+ 27 40 


63 51 


- 14 


61 


- 7 25 


55 39 


241 


+ 31 12 


57 48 


-129 


67 20 


- 8 48 


56 10 


247 20 


+ 31 22 


58 15 


-125 


71 


-16 50 


60 37 


251 


+ 33 47 


61 19 


- 42 


77 20 


-19 20 


59 41 


267 20 


+ 32 47 


62 35 


-174 


81 


-23 10 


61 27 


261 


+ 33 25 


64 59 


-212 


87 20 


-26 25 


62 40 


267 20 


+ 32 20 


64 43 


-123 


91 


-30 23 


64 47 


271 


+ 31 17 


64 11 


+ 36 


97 20 


-28 20 


60 60 


277 20 


+ 28 02 


64 16 


-206 


101 


-31 45 


64 09 


281 


+ 26 30 


64 49 


- 40 


107 20 


-32 15 


63 


287 20 


+ 20 57 


62 02 


+ 58 


111 


-32 30 


63 15 


291 


+ 21 37 


63 11 


+ 4 


117 20 


-28 38 


58 43 


297 20 


+ 15 02 


67 45 


+ 58 


121 


-32 


62 39 


301 


+ 13 52 


59 27 


+ 252 


127 20 


-27 45 


55 34 


307 20 


+ 10 40 


58 4S 


-194 


131 


-29 40 


58 34 


311 


+ 5 42 


55 47 


+ 167 


137 20 


-22 13 


56 23 


317 2i) 


+ 2 50 


60 25 


+ 298 


141 


-22 25 


52 12 


321 


+ 1 15 


52 31 


- 19 


147 20 


-20 35 


52 30 


327 20 


+ 1 25 


49 4L 


+ 169 


151 


-17 25 


51 06 


331 


+ 1 02 


49 49 


+ 77 


157 20 


-12 50 


44 49 


337 20 


- 10 


46 58 


-129 


161 


-13 35 


45 39 


341 


+ 30 


48 49 


-190 


167 20 


- 6 35 


45 04 


347 20 


- 15 


46 22 


- 78 


171 


- 5 30 


46 12 


351 


- 08 


47 31 


- 79 


177 20 


- 2 35 


44 08 


357 20 


- 53 


45 56 


-108 



1886.] 



Light by lUflecHon from Iceland Spar. 



181 



Table IV. 
Iceland Spar in Water. 















DifTerence 


Azimath 


AxinmUi 




Azhnttth 


Aximnth 




intheTaloee 


of the 

principal Mo- 

tionafUie 

CTjwtaL 


of the 

plane of 

poiarliatkm. 


Ani^e of 
polariiation. 


of the 

principal •(%;• 

tionof the 

cryital. 


of the 

plane of 

polariiation. 


Angle of 
polariiation. 


of the 

polariiinf: 

angle at f 

and 


o 
+ 1 


O i 

+ 1 22 


o / j 

48 42 


o 

181 


o / 

+ 37 


o / 
49 43 


-61 


11 


+ 50 


49 10 


191 


+ 4 02 


49 25 


-16 


21 


- 30 


18 43 


201 


+ 7 17 


49 52 


-69 


31 


+ 1 25 


50 11 


211 


+ 9 45 


50 35 


-24 


41 


- 18 


50 46 


221 


+ 11 36 


61 30 


+ 16 


61 


- 23 


52 19 


231 


+ 12 47 


52 69 


-40 


61 


- 2 43 


53 49 


241 


+ 13 07 


53 46 


+ 4 


71 


- 5 43 


54 48 


251 


+ 13 42 


56 11 


-23 


81 


- 8 


55 23 


261 


+ 11 60 


66 16 


+ 7 


91 


-10 28 


55 36 


271 


+ 11 01 


55 24 


+ 12 


101 


-12 30 


55 05 


281 


+ 8 25 


56 26 


-20 


111 


-14 40 


54 31 


291 


+ 5 22 


54 20 


+ 11 


121 


-12 40 


53 43 


301 


+ 3 20 


53 29 


+ 14 


131 


-12 23 


61 30 


311 


+ 20 


52 10 


-40 


141 


-12 


51 33 


321 


+ 1 37 


51 48 


-16 


151 


- 7 23 


50 15 


331 


- 1 


61 16 


-60 


161 


- 3 48 


49 35 


341 


- 48 


48 48 


+ 47 


171 


- 1 23 


49 19 


351 


+ 22 


49 11 


+ 8 



▼OL. XL, 



IS2 



Sir J. Conroy. On the Polarisation of [Feb. 4 



Table V. 
Iceland Spar in Air. 

















Azimuth 


Aximuth 




Aximuth 


Azimuth 




intheTaInc 


of the 
principal sec- 
tion of the 
crystal. 


of the 

plane of 

polarisation. 


Angle of 


of the 
principal sec- 
tion of the 
crjstal. 


of the 

plane of 

polarisation. 


An^leof 
polarisation. 


of the 

polarising 

angle at ( 

and 


o 

+ 


o / 
+ 32 


5^ 24 


180 


o / 
+ 87 


o / 

56 46 


-J- 38 


5 


+ 45 


56 56 


185 


+ 1 02 


56 22 


-1-34 


10 


+ 40 


57 29 


190 


+ 1 20 


66 52 


+ 37 


16 


+ 67 


56 67 


195 


+ 65 


66 39 


+ 18 


20 


+ 57 


67 34 


200 


+ 2 17 


67 10 


+ 24 


25 


+ 1 


57 11 


205 


+ 2 57 


66 47 


+ 24 


30 


+ 52 


57 54 


210 


+ 3 02 


57 36 


+ 18 


35 


+ 1 12 


57 37 


215 


+ 3 50 


57 11 


+ 26 


40 


+ 1 


58 11 


220 


+ 3 35 


67 56 


+ 15 


45 


+ 47 


58 03 


225 


+ 4 02 


57 51 


+ 12 


50 


+ 22 


58 50 


230 


+ 3 45 


58 10 


+ 40 


55 


+ 30 


58 28 


235 


+ 3 57 


58 06 


+ 22 


60 


+ 20 


59 19 


240 


+ 3 25 


68 36 


+ 43 


65 





58 59 


245 


+ 4 02 


59 19 


-20 


70 


-0 50 


59 33 


250 


+ 3 30 


69 19 


+ 14 


75 


-0 38 


69 04 


255 


+ 3 30 


58 52 


+ 12 


80 


-1 05 


59 49 


260 


+ 3 07 


59 15 


+ 31 


85 


-1 23 


59 22 


265 


+ 3 20 


59 03 


+ 19 


90 


-1 50 


60 07 


270 


+ 2 17 


59 39 


+ 28 


95 


-2 05 


59 24 


275 


+ 2 50 


59 


+ 24 


100 


-1 50 


59 43 


280 


-hi 42 


59 37 


+ 6 


105 


-2 53 


59 31 


285 


-hi 42 


58 50 


+ 41 


110 


-2 55 


59 36 


290 


+ 60 


59 23 


+ 13 


115 


-2 53 


58 56 


295 


+ 55 


58 50 


+ 6 


120 


-2 58 


59 04 


300 


+ 42 


58 34 


+ 30 


125 


-3 03 


58 47 


305 


-1-0 17 


58 27 


+ 20 


130 


-3 05 


58 22 


310 


+ 07 


58 47 


-25 


135 


-2 55 


58 27 


315 


+ 15 


58 01 


-34 


140 


-2 28 


57 59 i 


320 


-0 15 


58 06 


- 7 


145 


-2 23 


57 13 


325 


-0 05 


58 37 


-80 


150 


-2 55 


57 11 


330 


-0 25 


57 54 


-43 


155 


-1 35 


56 46 


335 


-0 03 


57 17 


-31 


160 


-1 20 


57 21 


340 


-0 25 


57 21 





165 


-0 43 


56 24 


345 


+ 02 


57 05 


-41 


170 


-0 28 


56 56 


350 





57 28 


-32 


175 


-hO 10 


56 22 


i 355 


+ 22 


66 58 


-36 



86.] 



lAghi by Reflection from Iceland Spar. 



188 



Table VI. 
Iceland Spar in Water. 



Azimntii 

of the 
indpal sec- 
ion of the 

crystal. 


Azimnth 

of the 

plane of 

polarisation. 


1 

1 

Angle of 
polarisation. 


Azimnth 
of the 
principal sec- 
tion of the 
crystal. 


A^»T*nth 

of the 

plane of 

polarisation. 


Angle of 
polansation. 


intheTaloea 

of the 
polarising 
angle at f 

and 
•+180«*. 


o 

+ 


o / 

- 08 


o / 

48 43 


180 


o / 

+ 35 


o / 

48 25 


+ 18 


5 


+ 17 


48 88 


186 


+ 1 32 


48 17 


+ 21 


10 


+ 32 


49 04 


190 


+ 80 


48 39 


+ 25 


15 


+ 1 45 


48 56 


196 


+ 5 85 


48 43 


+ 13 


20 


+ 50 


49 09 


200 


4. 6 47 


49 27 


-18 


25 


+ 1 15 


49 32 


205 


+ 7 47 


49 16 


+ 17 


do 


+ 47 


50 14 


210 


+ 9 07 


49 47 


+ 27 


35 


+ 55 


49 53 


215 


+ 9 27 


60 10 


-17 


40 


+ 12 


51 14 


220 


+ 9 40 


50 46 


+ 28 


45 


- 13 


51 14 


225 


+ 11 60 


50 67 


+ 17 


60 


- 20 


51 33 


230 


+ 12 50 


62 09 


-36 


65 


- 1 15 


51 52 


235 


+ 12 12 


52 19 


-27 


60 


- 2 15 


52 38 


240 


+ 13 


53 05 


-27 


65 


- 3 25 


53 43 : 


246 


+ 14 27 


63 23 


+ 20 


70 


- 4 38 


53 50 1 


250 


+ 13 16 


54 08 


-18 


75 


- 5 45 


54 32 1 


255 


+ 12 30 


54 28 


+ 4 


80 


- 7 50 


54 45 ' 


260 


+ 12 07 


65 08 


-23 


85 


- 7 13 


54 18 


265 


+ 10 67 


54 65 


-37 


90 


-10 23 


55 19 


270 


+ 10 32 


66 20 


- 1 


95 


- 9 55 


54 25 , 


275 


+ 9 30 


56 34 


-69 


100 


-10 58 


54 22 ; 


280 


+ 9 40 


56 40 


-78 


105 


-11 15 


53 35 


285 


+ 7 22 


64 45 


-70 


110 


-11 45 


54 15 


290 


+ 6 16 


54 07 


+ 8 


115 


-10 58 


53 35 


296 


+ 5 15 


54 12 


-37 


120 


-11 43 


53 05 


300 


+ 3 40 


52 39 


+ 26 


125 


-10 4.3 


52 15 


805 


+ 2 27 


52 45 


-30 


130 


-10 58 


51 23 


310 


+ 1 22 


52 05 


-42 


135 


-10 55 


51 25 


315 


+ 1 87 


62 16 


-61 


140 


-10 08 


61 07 i 


320 


- 30 


61 25 


-18 


145 


- 9 


49 54 


325 


- 33 


60 29 


-35 


150 


- 8 '18 


60 01 


830 


- 13 


50 07 


- 6 


155 


- 6 15 


49 36 


335 


+ 07 


49 55 


-19 


IGO 


- 5 13 


49 13 


340 


- 05 


49 26 


-13 


165 


- 3 48 


49 02 


845 


+ 10 


49 


+ 2 


170 


- 2 13 


48 38 


350 


+ 15 


48 59 


-21 


175 


- 1 


48 43 


855 


- 05 


48 30 


+ 13 



o^ 



184 



Sir J. Conroy. On the Polarisation of [Feb. 4, 







Table VII. 










Iceland Spar in 


Tetrachloride of Carbon. 




AzimnUi 
of the 
principal sec- 
tion of the 
ciyital. 


i^ximnth 

of the 

plane of 

polarisation. 


Ann^e of 
polarisation. 


Azimuth 
of the 
principal sec- 
tion of the 
crystal. 


Acimnth 

oftbe 

plane of 

polarisation. 


Angle of 
polarisatiea. 


Difference 
intbeTalnee 

of the 
polariainfr 
angle at 

and 
•+18(y». 


e 

+ 


o / 

- 10 


o / 

45 07 


+ 180 


o / 
+ 80 


o / 
44 44 


+ '23 


6 


+ 35 


45 28 


185 


+ 2 32 


45 05 


+ 23 


10 


+ 45 


45 55 


190 


+ 5 17 


45 47 


+ 8 


15 


+ 65 


46 52 


195 


+ 8 27 


45 41 


+ 71 


20 


+ 2 22 


46 36 


200 


+ 11 45 


46 30 


+ 6 


25 


+ 1 20 


47 06 


205 


+ 14 42 


47 26 


- 20 


30 


+ 17 


48 06 


210 


+ 15 57 


47 46 


+ 21 


35 


- 10 


48 38 


215 


+ 17 17 


48 13 


+ 25 


40 


- 23 


49 41 


220 


+ 21 57 


50 17 


- 36 


45 


- 2 


50 37 


225 


+ 24 52 


52 17 


-100 


50 


- 3 25 


52 14 


230 


+ 26 07 


53 19 


- 65 


55 


- 5 58 


53 41 


235 


+ 26 45 


54 12 


- 31 


60 


- 6 56 


54 30 


240 


+ 31 20 


57 26 


-176 


65 


-14 43 


58 23 


245 


+ 33 07 


58 32 


- 9 i 


70 


-15 45 


60 08 


250 


+ 30 45 


59 48 


-f- 20 


75 


-20 56 


60 18 


255 


+ 29 30 


59 31 


+ 47 , 


80 


-22 28 


60 43 


260 


+ 34 15 


65 43 


-300 


85 


-26 26 


62 13 


265 


+ 32 32 


63 24 


- 71 


90 


-25 28 


59 42 


270 


+ 29 05 


63 18 


-216 ; 


95 


-29 42 


61 05 


275 


+ 25 52 


61 52 


- 47 


100 


-31 10 


61 58 


280 


+ 26 47 


64 47 


-169 


105 


-32 13 


61 24 


285 


+ 22 07 


60 32 


+ 52 . 


110 


-28 13 


58 07 


290 


+ 17 15 


58 57 


- 50 


115 


-28 08 


56 47 


295 


+ 16 42 


58 07 


- 80 


120 


-30 50 


57 17 


300 


+ 10 32 


57 04 


+ 13 


125 


-27 50 


56 13 


305 


+ 9 47 


55 47 


+ 26 


130 


-22 53 


51 59 


310 


+ 7 05 


54 09 


-130 


135 


-21 30 


51 04 


315 


+ 3 32 


51 09 


- 6 


140 


-21 40 


49 23 


320 


+ 1 42 


50 38 ! 


- 75 i 


145 


-18 58 


49 15 


326 


+ 25 


48 40 


+ 35 


150 


-15 15 


47 08 


330 


- 05 


48 12 > 


- 64 


155 


-12 85 


47 30 


335 


- 1 03 


47 11 


+ 19 


160 


-10 43 


46 15 


340 


- 05 


47 25 


- 70 


165 


- 8 18 


46 12 


345 


- 10 


46 48 


+ 24 


170 


- 4 58 


45 16 


350 


+ 06 


46 02 


- 46 


175 


- 2 30 


45 11 


355 


+ 10 


45 06 


+ 5 



It had been intended to make similar measurements with artificial 
surfaces cut perpendicular and parallel to the axis of the crystal, and 
three pieces of Iceland spar cut respectively parallel to a natural face, 
and perpendicular and parallel to the axis, and all polished with 
" whiting " were obtained. 

Seebeck states ("Pogg. Ann.," vol. xxi, 290) that Iceland spar 
polished with rouge or putty powder differs in its optical properties 



1886.] 



Light by Reflection from Iceland Spar. 



185 



from the natural substance, but that an artificial surface polished 
with chalk behaves yerj nearlj, if not exactly, like a natural one. 

Seebeck's measurements were all made with the crystal in air, and 
as the changes in the azimuth of the plane of polarisation, and in 
the value of the polarising angle, for different azimuths of the crystal, 
when such is the case are small, it seemed desirable before making 
any measurements with the artificial surfaces cut perpendicular and 
parallel to the axis, to make some determinations with an artificial 
surface parallel to a natural face of the crystal when the crystal was 
immersed in water ; this was accordingly done. 

Contrary to the orders that had been given, the edges of the plate 
were cut away by the optician who polished it, and it was therefore 
impossible to determine the position of the principal section in the 
fiame manner as that previously employed with the other crystals. 
The results were therefore plotted, the divisions of the ring carrying 
the crystal being taken as abscisssB and the azimuths of the plane of 
polarisation of the reflected light as ordinates. It was assumed that 
the curve for the artificial face would be similar to that for the natural 
face, and the points at which the curve cut the x axis were taken 
as indicating the position of the principal section, and the azimuths 
of the crystal thus determined. Table VIII gives the results : — 



Table VIII. 
Artificial Surface of Iceland Spar in Water. 















Difference 


Aximath 


Azimuth 




Azimuth 


Azimuth 




intheTaluM 


of the 
principal sec- 
tion of the 
crystal. 


of the 

plane of 

polarisation. 


An^le of 
polarisation. 


of the 
principal sec- 
tion of the 
crystal. 


of the 

plane of 

polarisation. 


Ancle of 


of the 

polarising 

angle at 9 

and 

•+180°. 


5 


o / 

+ 32 


o / 

46 47 


185 


o / 

+ 57 


4^ 


/ 
-13 


15 


+ 1 37 


46 35 


195 


4 2 42 


46 40 


- 5 


25 


+ 2 12 


47 37 


205 


+ 4 55 


47 12 


+ 25 


35 


+ 3 05 


47 10 


215 


+ 6 40 


47 36 


-26 


45 


+ 3 


48 48 


225 


+ 7 25 


48 26 


+ 22 


55 


+ 3 02 


48 47 


235 


+ 8 45 


48 50 


- 3 


65 


+ 47 


50 13 


245 


+ 9 27 


49 59 


+ 14 


75 


+ 02 


50 11 


255 


+ 8 55 


50 06 


+ 6 


85 


-3 33 


51 37 


265 


+ 7 45 


51 06 


+ 31 


95 


-4 13 


50 38 


275 


+ 4 10 


50 46 


- 8 


105 


-6 38 


50 26 


285 


+ 2 17 


50 39 


-13 


115 


-7 20 


49 44 


295 


+ 1 22 


50 37 


-53 


125 


-8 


49 53 


305 


-0 35 


50 05 


-12 


135 


-7 10 


48 37 


315 


-1 28 


48 55 


-18 


145 


-7 15 


48 41 


325 


-2 58 


48 34 


+ 7 


155 


-4 38 


47 41 


335 


-2 08 


47 07 


+ 34 


165 


-3 38 


47 23 


345 


-1 35 


47 13 


+ 10 


175 


-1 30 


46 21 


355 


-0 08 


46 02 


+ 19 



IM SirJ.Comyf. Om Ae Fiimi^^im ^ [Fobu^ 



wisk % itftmJ &ee is mtcr (TaUcs II, IT, aad TI)l nd ift tfaereiote 
dad i«A tagyasr wortli winle to wiiVf snr Isrlfer f n wii f nt u with 
^mrintx^ jm it feeined eatuk tku tke icsaltB woald be 
twortij. 

Tfe differentfe Iwii w e ea tbe reaahs nhtiiwd wisk ^is artificial 
nvH^woe aowl witli & mtaral sarCMie of tke cryital ii too git. at to be 
eivfJwAed bf cvpfmring tbst the artificifti — r Cu ce ■ — not est aibsc^tely 
pumJli^ to the direction of the elesmge, and mast tkerefore be attri- 
bati!:d t// fome chaoge pfod a eed by tiie pcdidnng, poanblr due to the 
ynsmnm em^Ai^jed feonf. Seebeck, *^ Fogg- Ana ,^ toL xz, ISdO, 27). 

The irahiei of the azhnntka and angles of pofaoisation given in 
TaUea J, II, III, IT, Y, YI, YII, and Ym, were plotted on sectional 
paper; the azimoths of the principal section of tke crrstal being taken 
an absciase, and the aomnths of the Niool, and the angles of polarisa> 
lion — 4(r% MB the ordinates for the two sets of correa. 

In order to draw the smooth corres, a piece of plate-glass, rather 
smaller than the drawing paper, was moonted in a soft-wood frame, 
SO that one surface of the glass was flnsh with the wood, the sectional 
pi^r opon which the observations had been plotted was fixed to the 
wood with drawing pins, and a sheet of ordinary drawing paper 
placed over it, and fastened in the same manner. This glass drawing 
board was then placed in front of a lamp, and smooth cnrves drawn 
bj eye in the ordinary maimer. 

ProfessTir Stokes pointed out to me that the experimental resnlts 
which had been obtained were well suited for reduction by means of 
the harmonic analysis, and not only explained the method but himself 
reduced the first Het of observations made with a deavage-face in 
water. All the observations were accordingly reduced by this 
method ; the determinations made at azimuths 1°, 11°, <&c., and at 
7** 2(1', 17*' 20', Ac., in the one series, and at 0°, 10°, <fcc., and at 
5*, 1«5^, Ac, in the second series, being kept separate. 

Owing to the fact that the principal section of the crystal is a 
plane of symmetry, the periodic series for the development of the 
azimuths of tlie planes of polarisation can contain sines only, and 
that for the polarising angles cosines only, including the constant 
term ; therefore the coefficients of the cosines in the former case, and 
of the sines in the latter, were not calculated, except with the obser- 
vations made with the artificial surface ; it seemed possible that the 
process of polishing might occasion some want of symmetry, and 
that therefore it was desirable to calculate the values of the co- 
efficients for both sines and cosines. 

The observations in one set only having started at zero azimuth, in 
the other three there was a small correction to be made in the 
coefficients for the error thus produced; this was done by multiplying 



18860 ^^^ h H^fl^ction from Iceland Spar. 187 

the coefficients bj the secants of 1^, 2^, 3^ 4^, for the orders 1, 2, 3, 
and 4, in the first set; by the secants of 2*^ 40', S*' 20', 8% and lO"" 40^ 
in the second, and by the secants of 5^, 10*^, 15^, and 20^ in the 
fonrth set. This correction only exceeded 1' in sixteen cases, and 
attained its maximum valae in the second series of observations made 
in carbon tetrachloride, where in the case of the coefficients of sin 2^, 
sin 3^, and cos 20 it amounted to 9' and 8' respectivelj. 
Table IX gives the results and their means. 

Table IX. 

Iceland Spar in Air. Azimuths. 

Sbbus I. 

Obe. at 1% 10^ &c 23-2 Unne + l 47sin29 +4Bin4«. 

„ -2°40',r20',&o. 21-2 Usine + l 48 sin 20 + rain 3a -2 sin 49. 

Sbbies II. 

„ (f,l(f,Ao 20-2 02sine-l>l 6lBin2a •l>5Bin4a. 

„ 5%16%&c 31-2 12sine-i-l 62 sin 20 + 7' sin 3a -4 sin 40. 

Mean (A) 24-2 lOsina + l 49Bin2a + 2'sin8a + l8in4a. 

Iceland Spar in Air. Polarising Angles. 

Sbbibs I. 



o / / o / / / 



Obfl. at l^ 10^ &c 68 25- 2coea-l 12coB2a + lcoe3a + lcoe4a. 

„ -2^40^, 7^20^, &o. 68 25-l> 70000-1 10 000 20 + loos 30 -Icoe 40. 

Sbbibs II. 

„ 0», 10°, &c 58 21 + 14COS0-1 20 oos 20 + 1 oos 80 + 7 00s 40. 

^ 6^ 15^&c 67 56 + 18OOS0-1 20 000 20 -h 6 cos 30 + 1 oos 40. 

Mean (B) 58 17+ 8 oos 0-1 15 cos 20 + 2 oos 30 + 2 cos 40. 

Iceland Spar in Water. Azimuths. 

Sbbibs I. 

Obe. at r, l(f,&c 26-9 47 sin + 6 31 sin 20 + 4^ sin 30-14sin 40. 

„ -2^40^, 7''20', Ac. 23-9 428in0 + 5 48sin20 + 59sin30- lsin40. 

Sbbibs II. 

„ (f,l(f,&c 25-9 llsin0 + 5 I7sin20 + 55sin30- 8sin40. 

„ 6%15^&c 41-8 558in0 + 5 15sin20 + 38sin30- 4sin40. 

Sesibb in. 

„ V,lV,&c 28-9 39sin0 + 5 36 sin 20 + 41 sin 30 -22 sin 40. 

Mean (C) 27-9 27sin0 + 5 29 sin 20 + 47 sin 30 -10 sin 40. 

Iceland Spar in Water. Polarising Angles; 

Sbbibs I. 

Obs. at l^ IG^&o 52 21 + 16 oos 0-3 S» cos 20 + 3 cos 30 + 17 oos 40. 

„ - 2'' 40", r" 20^,^0. 62 34+ 9 oos 0-3 08cos 20-1 oos 30 + 10 cot 49. 



188 Sir J. Couroy. On Hie Polarisation of [Feb. 4, 

Sbbies II. 

Obs. at (f , 10% &o 5140+ ^cose-l lioo8 2a + 4oo8 8e-lVoos49. 

„ 5*', 15%&c 51 S2+ 7 cos e-3 12 cos 29-7 006 89 + 10 008 49. 

Sbbies III. 
„ r, ir, &c 52 05-110080-3 IGoos 29-5 008 39 + 13 000 49. 

Mean (D) 52 02- 5oo69-3 14 cos 29- looe 39 + 13 cos 49. 

Iceland Spar in Tetrachloride of Carbon. Azimuths. 

Sbbibs I. 

Obs. at 1% 11% &c 39-25 Odsin9 + ll 168in29 + l 28 sin 39 + 11 sin 49. 

,„ -2°40',r20',&c. 50-23 3l8in9 + 10 ll8in29 + 4 sin 39 -44 sin 49, 

Sbbibs n. 

„ OP, 10% Ac 56-23 26sin9 + 10 178in29 + 4 18 sin 39 -49 sin 49. 

„ 5%15%&c 28-23 07 sin9+ 9 55 sin 29 + 4 23 sin 39 -12 sin 49. 

Mean(£) 43-23 478in9 + 10 25sin29 + 4 17 sin 39 -24 sin 49. 

Iceland Spar in TetrachloHde of Carbon. Polarising Angles. 

Sebies I. 

Obs. at 1% 11% &e ^ 05-17 co89-9 40 cos 29 + 52 coa 39 + 1 18co849. 

„ -2"* 40', 7** 20', &c. 53 01 + 4 cos 9-8 45 cos 29 + 36 cos 39 + 59 cos 49. 

Sebies II. 

„ 0%10%&c 52 50 + 12cos9-8 41 cos 29 + 12 cos 39 + 1 23cos49. 

„ 5%15%&c 52 41- 3 cos 9-8 29 cos 29+ 7co839 + l 10cos49. 

Mean (F) 53 09- 1 cos 9-8 54 cos 29 + 27 cos 39 + 1 12 cos 49. 

Artificial Surface of Iceland Spar in Water. Azimuths. 

(O.).... 28'-3°52'8in9-9'co9 9 + 5° 11' sin 29 + 11' cos 29 + 33' sin 39 r 7' cos 39 

-21' sin 49 -4 cos 49. 

Artificial Surface of Iceland Spar in Water. Polarising Angles. 

(H.) 48°53'-l'8in9-l'cos9 + 4'sin29-2°09'co829+4'sin39-8' C0839 

4 1 cos 49. 

Brewster, in his paper in the "Phil. Trans." for 1819, p. 158, sajs, 
" in any given surface when A and A" are the maximum and minimum 
polarising angles, viz., in the azimuths of 0** and 90**, the polarising 
angle A' at any intermediate aximuth «, may be found by the formula 
A'=A + 8inVA"-A)." 

This expression is the same as that given by the harmonic reduc- 
tion of the observations set forth in the preceding pages, if we 
assume that the smaller terms are due to errors of observation, as in 
that case the expression for the polarising angle in air (B) becomes 
68"ir-r 15'co8 2^. 



1886.] Light by Reflection from Iceland Spar. 189 

Calling the coefficient of cos 20 x, and the minimum value of the 
polarising angle A, this is (A + a;) —a; cos 2^, which is identical with 
Bi^ewster's expression, since A"— A is the same as 2x, 

Brewster states that for a rhomboidal surface of calcareous spar 
A"— A 138', whereas the harmonic reduction gives the value as 150', 
which perhaps, considering the] nature of the determinations, is ais 
close an agreement as could be well expected. 

Brewster's formula also appears to hold good for the case of Ice- 
land spar in water, as the harmonic series for the value of the polar- 
ising angle (D) may be taken as 52° 02'— 3** 14'co8 2^. But with the 
spar in tetrachloride of carbon the agreement no longer holds, as the 
coefficient of cos 4^ becomes too large to be neglected, being 1° 12'. 
The determinations made in this strongly refracting liquid were less 
i^tisfactory than the others, as is shown by the figures in Tables lU 
and VII, but there is hai*dly sufficient ground for assuming that the 
valae of the coefficient of cos 4^ is merely due to en*ors of observation. 

The experiments of which an account had been given confirm the 
accuracy of Brewster's observations made with a surface of Iceland 
£par in contact with media other than air, and show moreover that, 
as Seebeck pointed out, the change in the value of the azimuth of the 
plane of polarisation of the reflected light also occurs, though to a 
far less extent, when the crystal is in air, and further, as the refractive 
index of the medium increases, the change in both these values is 
greatly augmented. 

The harmonic analysis affords a means of expressing, approximately 
At least, both these changes as functions of the azimuth of the principal 
section of the crystal, and further shows that when the crystal is 
in air or water, Brewster's formula for the angle of polarisation 
expresses the facts of the case. 

The constant term in the expression for the azimuth of the plane of 
polarisation of the reflected light being due partly to errors of 
observation and partly to the index error of the Nicol, and, for the 
reason stated by Professor Stokes in the note he has done me the 
honour of appending to this paper, the coefficients of the cosines of 
odd multiples of 6 in the expressions for the angles of polarisation 
being probably due to inaccuracies in the determination, it seems best 
t;o omit these terms (which at any rate are extremely small), so that 
%ve obtain as the final result the following approximate expressions in 
the several cases. 

Azimuths of the Plane of Polarisation of Light Polarised 

by Reflection. 

Cleavage surf, in air. - 2°10'8intf+ r 49^ sin 2tf + 0** 2'8in3« + 0'* r8in4«. 

Ditto, in water - 9° 27' sin «+ 5° 29' sin 26 + 0° 47' sin 30 - 0° 10' sin 40, 

Ditto, in CCI4 -23° 47' sin + 10" 25' sin 2$ ^ 4M7' sin 3tf-0° 24' sin 4S. 

Artificialsurf.inwater - 3''52'8in«+ 5** ll'sin2«+0° 83'8iiia6-0° 2\.'%W!l^. 



190 Light Polarised by Beflection from Iceland Spar. [Feb. 4» 

Polarising Angles. 

Cleayage Burface in air 5^ IT-V lb' coB^ + (f 2'co«4e. 

Ditto, in water 52° 2'-3** 14'ooa2« + (f 13'coB4e. 

Ditto,inCCl, 63** 9'-8*' 64'oo8 2« + n2'co8 4». 

Artificial surface in water 48'' 53' -2° 9'oos2e + 0'' roos49. 

From these expressions the values of the ordinates of the curves 
representing the phenomena were calculated, and Plates I and II 
give the carves as plotted from the values so obtained. 

These curves correspond very closely with the smooth curves 
drawn from the points given by the observations, the values of the 
ordinates for those portions of the curve corresponding to azimuths 
0—40®, and 320 — 360°, being rather greater than the values given by 
the smooth eye-drawn curve. The curves for the artificial surface in 
water (G and H) show clearly, when compared with the corresponding 
curves for the natural surface (G and D), how greatly these two sur- 
faces differed in their optical behaviour. 

In conclusion I must express my thanks to Professor Stokes for his 
advice and assistance, and for all the trouble he has taken with 
reference to the determinations of which an account is given in this 
paper. 



Note by Professor Stokes, P.R.S. 

On inspecting these numbers we may remark : — 

1. The coefficients of sin 4iO in the expressions for the azimuths are 
in all cases so small that they can hardly be said to emerge from 
errors of observation. Since, however, there is no i*eason to suppose 
that such a term does not exist, the coe^&cients may as well be 
retained, as being somewhat more probable than zero would be. 

2. Brewster found that the polarising angles were the same for any 
two azimuths differing by 180°, and MacCullagh afterwards deduced 
this result from theoretical considerations. If we assume this law as 
exact, the harmonic expression for the polarising angle will contain 
no terms involving cosines of odd multiples of 0, Now with one 
doubtful exception the coefficients in the above expressions are 
insensibly small. The single exception, where a coefficient has at 
first sight the appearance of being real though small, is that of the 
term involving cos 3^ for the observations in tetrachloride of carbon* 
The observations with this liquid were the most uncertain, probably 
from the feebleness of reflection arising from its high refractive index. 
If the differences of the polarising angles for azimuths of the principal 
plane differing by 180° be examined, it will be seen that a coefficient 
amounting in the mean to only 0° 27', and subject to a mean error 
from set to set of 17', can have little claim to be regarded as real. 



1886.] On the Theory of Lubrication. 19 

It seems best therefore in this, as well as other cases, to omit th 
^ terms inyolving cosines of odd multiples of 0. 

^ 3. As regards the observations with the artificial surface in watei 

4 the coefficients of the cosines in the expression for the azimuths an< 

of the sines in the expression for the polarising angles are insensibl; 

small, indicating no introduction of asymmetry with respect to thi 

principal plane arising from the process of polishing. The coefficient 

of the cosines of odd multiples of 6 in the second expression are al8< 

insensible. The constant term in the first expression, representin| 

I (on the assumption of symmetry with respect to the principal plane 

1 the index error of the circle carrying the Nicol, agrees almost exactly 

with those obtained for the cleayage surfaces in air and water. 

It would seem best then to omit those terms which we have reasoi 
to think are really ni/, and which the observations show to be at an; 
rate extremely small, and to exhibit the final result accordingly. 



February 11, 1886. 

Professor STOKES, D.C.L., President, in the Chair. 

The Presents received were laid on the table, and thanks ordere( 
for them. 

The following Papers were read : — 

I. "On the Theory of Lubrication and its Application t( 
Mr. Beauchamp Tower's Experiments, including an Expe 
rimental Determination of the Viscosity of Olive Oil." Bj 
Professor Osborne Reynolds, LL.D., F.R.S. Receivec 
December 29, 1885. 

(Abstract.) 

Lubrication, or the action of oils and other viscous fluids h 
diminish friction and wear between solid surfaces, does not appear t< 
have hitherto formed a subject for theoretical treatment. Sue] 
treatment may have been prevented by the obscurity of the physica 
actions involved, which belong to a class as yet but little known 
namely, the boundary or surface actions of fluids ; but the absence o 
such treatment has also been owing to the want of any general law 
revealed by experiment. 

The subject is of such fundamental importance in practica 
mechanics, and the opportunities of observation so frec^aeivt^ t^t ^ 



192 Prof. 0. Reynolds. [Feb. 11, 

may well be a matter of surprise that any general laws should baye 
for so long escaped detection. 

Besides the general experience obtained, the friction of lubricated 
sai*faces has been the subject of much experimental investigation by 
able and careful experimenters ; but although in many cases empirical 
laws have been propounded, these fail for the most part to agree with 
each other and with the more general experience. 

The most recent investigation is that of Mr. Tower, undertaken at 
the instance of the Institute of Mechanical Engineers. Mr. Tower *s 
first report was published in November, 1883, and his second in 1884 
(" Proc. Inst. Mechanical Engineers"). 

Ill these reports Mr. Tower, making no attempt to formulate, states 
the i*esults of experiments apparently conducted with extreme care, 
and under very various and well-chosen circumstances. Those of the 
results which were obtained under the ordinary conditions of lubrica- 
tion so far agree with the results of previous investigators as to show 
a want of any regularity. But one of the causes of this want of 
regularity, viz., irregularity in the supply of lubricant, appeal's to 
have occurred to Mr. Tower early in his investigation, and led him to 
include amongst his experiments the unusual circumstance of surfaces 
completely immersed in an oil-bath. This was very fortunate, for 
not only do the results so obtained sbow a great degree of regularity, 
but while making these experiments he was accidentally led to 
observe a phenomenon which, taken with the results of his experi- 
ments, amounts to a crucial proof that in these experiments with the 
oil-bath the surfaces were completely and continuously separated by a 
film of oil ; this film being maintained by the motion of the 
journal, although the pressure of the oil at the crown of the bearing 
was shown by actual measurement to be as much as 625 lbs. per 
-square inch above the pressure in the oil-bath. 

These results with the oil- bath are very important, notwithstanding 
that the condition is not common in practice. They show that with 
perfect lubrication a definite law of the variation of the friction with 
the pressui-e and the velocity holds for a particular journal and brass. 
This strongly implies that the irregularity previously found was due 
to imperfect lubrication. Mr. Tower has brought this out. Substi- 
tuting for the bath an oily pad of tow pressed against the free part 
of the journal, and making it so slightly greasy that it was barely 
perceptible to the touch, he again found considerable regularity in 
the results. These were, however, very different from those with 
the bath. Then with intermediate lubrication he obtained intermediate 
results, of which he says : " Indeed, the results, generally speaking, 
were so uncertain and irregular that they may be summed up in a 
few words. The friction depends on t\ie c\\x«Ai\A.Vj ^biiA. xraxioinaDL dia- 
tribntion of the oil, and may be anyt\i\ng Viet'we^n. >i^c^^ cin\-\i».V>CL t^wqNX& 



1886.] On the Theory of Lubrication. 193 

and seizing, according to the perfection or imperfection of tlie 
Inbrication." 

On reading Mr. Tower's first report, it occnrred to the anthor that 
in the case of the oil- bath the film of oil might be sufficiently thick 
for the unknown boundary actions to disappear, in which case the 
results would be dedncible from the equations of hydrodynamics. 

Mr. Tower appears to have considered this, for he remarks that, 
according to the theory of fluid friction the resistance would be as 
the square of the velocity, whereas in his results it does not increase 
according to this law. 

Considering how very general the law of resistance as the square of 
the speed is with fluids, there is nothing remarkable in it being 
assumed to hold in such a case. But the study of the behaviour of 
flnid in very narrow channels, and particularly the recent determina- 
tion by the author of the critical velocity at which the law changes 
from that of the square of the velocity to that of the simple mtio, 
shows that with such highly viscous fluids as oils, such small spaces 
as those existing between the journal and its bearing, and such limited 
velocities as that of the surface of the journal, the resistance would 
vary, cceteris paribus^ as the velocity. And further, the thickness of 
the oil film would not be uniform, and might be affected by tlio 
velocity, and as the resistance would vary, cceteris paribus, inversely 
as the thickness of the film, the velocity might exert in this way a 
secondary influence on the resistance ; and further still, the resistance 
-would depend on the viscosity (commonly called the body) of the oil, 
and this depends on the temperature. But as Mr. Tower had been 
careful to make all his experiments in the same series with something 
at a temperature of 90® F. (he does not state precisely what), it did 
not at first appear that there could be any considerable temperatui-e 
effect in his results. 

The application of hydrodynamical equations for viscous fluids to 
circumstances similar to those of a journal and a brass in an oil-bath, 
in so far as they are known, at once led to an equation* between the 
variation of pressure over the surface and the velocity, which appeared 
to explain the existence of the film of oil at high pressure. 

This equation was mentioned in a paper read before Section A 
at the British Association, at Montreal, 1884. It also appears from a 
paragraph in the Presidential Address (p. 14, Brit. Assoc. Rep., 1884) 

No. of equation 
in the paper. 

dx A' 

in which p ib the intensity of pressure, ft coefficient of viscosity, x the direction of 
motion, h the interval between the journal and the bTa8a,HY\iem%\.\\ft 's^xx'a ^VU 
for which the pressure is a maximum, U the surface velocity Va V\ife ^\r«i\Ka^ cH x. 



194 Prof: O. Reynolds. [Feb. 11, 

that Prof. BtolcM and Lord Bajleigk had simaltanetnuly arrived at ■ 
similar reaalt. At that tune the author had no idea of attempting 
the integration of thia eqnation. On Bufaeeqnent oonoideratum, how- 
erer, it appeared that ttie equation might he so transformed* at 




* If the journal and brau are both of CLrculor aection, as in flg. 1, and B u the 
radiuB of the journal, R -f a ladiiu of brnsi, J the centre of the journal, I the centre 
of the bnse, JI — ro, HO- the shorteit distance acroM the Blm, TO the line of loads 
through the middle of the bran, A. the eitremitj of the br»M on the o& side, B on 
the on tide, Pj the point of greatest pTcssure, 
Putting 01H-#o— -^ 

OIP,-fi 
OIP-« 

A-a{l + eMn(»-h)} 
i,=<.{lt,.Bin(#,-h)} 

the equation (31) beromei 

dp 6Ep^«nJ«-#^-sin(#,-^>[ 
da" a={'l+eW{8-ft,)}» 

Ibii equation, which is St once integrablo irhen e is imall, has hern 



(48) 



K 



large as 0-3. 



integrated i>j approximatioQ irhen c 
The friction is given by an equation 



ta.-h! ■ 



Thia it alto apptoiiraateij integnted up to e=0"S. 



1886.] On the Theory of Lubrication. 195 

to be approximately integrated by considering certain qaantities 
small, and the theoretical results thns definitely compared with the 
experimental. 

The result of this comparison was to show that with a particular 
journal and brass the mean thickness of the film would be sensibly 
constant for all but extreme values of load divided by the viscosiiy, 
and hence if the coefficient of viscosity were constant the resistance 
would increase approximately as the speed. 

As this was not in accordance with Mr. Tower's experiments, in 
which the resistance increased at a much slower rate, it appeared that 
either the boundary actions became sensible, or that there must be a 
rise in the temperature of the oil which had escaped the thermometer 
used to measure the temperature of the journal. 

That there would be some excess of temperature in the oil film on 
which all the work of overcoming friction is spent is certain, and 
after carefully considering the means of escape of this heat, it appeared 
probable that there would be a difference of several deg^rees between 
the oil-bath and the film of oil. 

This increase of temperature would be attended with a diminution 
of viscosity, so that as the resistance and temperature increased with 
the velocity there would be a diminution of viscosity, which would 
cause the increase of the resistance with the velocity to be less than 
the simple ratio. 

In order to obtain a quantitative estimate of these secondary effects, 
it was necessary to know the exact relation between the viscosity of 
the oil and the temperature. For this purpose an experimental deter- 
mination was made of the viscosity of olive oil at different tempera- 
tures as compared with the known viscosity of water. From the 
result of these experiments an empirical formula has been deduced 



^0 an<l 01 c^d c have to be determined from the conditions of equilibrium, which 



are 



y [pm9-fcone]dp^0 (44) 

f {pco8e+/eine}(/e-^ (45) 

t/'^-l <«> 

where 2^^ is the angle subtended bj the brass, L the load, and M the moment of 
friction. 

The solution of these equations may be accomplished when c is small and has been 
approximately accomplished for particular yalues of c up to 0*5, the boundary con- 
ditions ad regards p being 

whence suhatitnting the values of ^j, ^g* ^ '^ {^ ^^^ C^\ ^*>'^'^ \x\\A^gnXArL%^ ^l^QA 
vBluea of the friction and raluea of the pressure are obtamed. 



196 Pro£ 0. BeynoldEU [Feb. 11, 1 1 

for ihe yiscositj of oliye oil at all temperatares between 60^ 9ukM\ 
120** F* I, 

Besides the effect on fi the temperature might, owing to the diA^ I j 
rent expansion of brass and iron, produce a sensible effect on tiieli 
small difference a in the radii of the brass and journal, i.e., on thi I 
mean thickness of the film, E was taken for the coefficient of ihii I 
effect, and since, owing to the elasticity of the material, the radiui I 
would probably alter slightly with the load, m ^was taken as ft I 
coefficient for this effect, whence a is given by an equationf in tenm I 
of Oq, its value with no load and a temperature zero. I 

Substituting these values in the equations, the values of the prsB- I 
sure and friction deduced from the equations are functions of tlie I 
temperature, which may be then assumed, so as to bring the calcn- I 
lated results into accord with the experimental. I 

There was, however, another method of arriving, if not at tbe I 
actual temperatures, at a law connecting them with the frictions, | 
loads, and velocities. For the rise in temperature was caused by the 
work spent in overcoming friction, while the heat thus generated had 
to be carried or conducted away from the oil film. Consideration of 
this work and the means of escape gave another equation between the 
rise of temperature, the friction, and velocity. J 

The values of the constants in this equation can only be roughly 
surmised from these experiments, without determining them by 
substituting the experimental values of /, U, and T, as previously 
determined, but it was then found that the experiments with the 
lower loads gave remarkably consistent values for A, B, E, m, 
and Qq, which was also treated as arbitrary. In [proceeding to the 
higher loads for which the values of c were greater, the agreement 
between the calculated and experimental results was not so close, and 
the divergence increased as c increased. On careful examination, 
however, it appeared that this discordance would be removed if the 
experimental frictions were all reduced 20 per cent. This implied 
that 20 per cent, of the actual friction arose from sources which did 
not affect the pressure of the film of oil ; such a source would be the 
friction of the ends of the brass against flanges on the shaft commonly 

* An inch being unit of length, a pound unit of force, and a second unit of time, 
for oliye oil 

/i=0 00004787e-o^«iT (8) 

t a=(ao + »»L)eKT (117) 

J/-/^A + l\r + EATS (120) 

A •*- £T represents the rate at which the mechanical equiyalent of heat is carried 
away per unit rise of temperature ; B represents the rate at which^it ia conducted 
Aimy; 



1886.J On the Theory of Lvhrication. 197 

used to keep the brass in its place, or bj any irregularity in the longi- 
tudinal section of the journal or brass. Although no direct reference 
is made to such flanges in Mr. Tower's reports, it is such a common 
custom to neck the shaft to form the journal that there is great 
probability of the flanges being used. A coefficient n has therefore 
been introduced into the theory, which includes both the effect of 
neoking and of irregularity in longitudinal section. Giving n the 
value 1*25, the calculated results came into accordance with all 
Mr. Tower's results for olive oil, the diflerence being such as might 
well be attributed to experimental inaccuracy, and this both as regards 
the frictions measured with one brass. No. 1, and the distribution of 
the pressure round the journal with another. No. 2. 

Not only does the theory thus afford an explanation of the very 
novel phenomena of the pressure in the oil film, but it also shows, 
what does not appear in the experiments, how the various circum- 
stances under which the experiments have been made afiect the 
results. 

Two circumstances in particular which are brought out as principal 
circumstances by the theory seem to have hitherto entirely escaped 
notice, even that of Mr. Tower. 

One of these is a, the difference in the radii of the journal and of 
the brass or bearing. It is well known that the fitting between the 
journal and its bearing produces a great effect on the carrying power 
of the journal, but this fitting is supposed to be rather a matter of 
smoothness of surface than a degree of difference in radii. The 
radius of the bearing must always be as much larger than that of the 
journal as is necessary to secure an easy fit, but more than this does 
not seem to have been suggested. 

It now appears from this theory that if viscosity were constant the 
friction would be inversely proportional to the difference in the radii 
of thebeanng and journal, and this although the arc of contact is less 
than the semi-circumference ; and taking t^emperature into account 
it appears from the comparison of the theoretical frictions with the 
experiment on brass No. 1, that the difference in the radii at 70* F. 
was 

a= 0-00077 (inch), 

and comparing the theoretical pressures with those measured with 
brass No. 2, 

a =0-00084 (inch), 

or the difference was 9 per cent, greater in the case of brass No. 2. 

These two brasses were probably both bedded to the journal in the 
same way, and had neither been subjected to any gre&t ^.thot^t^X) ^V 
wear, so that there is nothing surprising in tlieir \>em^ ao lifewcVj VXjka 

VOL, XL, V 



198 Prof 0. Reynolds. [Feb. 11, 

saine fit. It would be extremely isterestiiig to find how iarwaim 
continnoxLS running prolonged wear tends to preserve this fii 
Mr. Tower's experiments afibrd only slight indication of this. It 
does appear, however, that the brass expanded with an increase of 
temperature, and that its radios increases as the load increases in a 
very definite manner. 

Another circumstance brought out by this theory, and remarked 
on both by Lord Bayleigh and the author at Montreal, but not before 
suspected is, that the point of nearest approach of the journal to the 
brass is not by any means in the line of load, and what is still 
more contrary to common supposition, it is on the qff^ side of this 
line. 

This point H moves as the ratio of load to velocity increases; 
when this ratio is zero, the point H coincides with 0, then as the 
load increases it moves away to the left, till it reaches a maximum 

distance ^^— 0b> being nearly — ~. The load is still small, smaller 

than anything in Mr. Tower's experiments, even with the highest 
velocities. For further increase of load, H retuj-ns towards 0, or 
^tr—</)o increases with the largest loads and smallest velocities to 
which the theory has been applied ; this angle is about 40°. With 
a fairly loaded journal well lubricated it would thus seem that the 
point of nearest approach of bi*ass to journal, i.e., the centre of wear, 
would be about the middle of the off side of the brass. 

This circumstance, the reason of which ia rendered perfectly clear bj 
the conditions of equilibrium, at once explains a singular phenomenon, 
incidentally pointed out by Mr. Tower, viz., that the journal having 
been run in one direction for some time, and carrying its load without 
heating, on being reversed began to heat again, and this after 
many repetitions always heating on reversal, although eventually 
this tendency nearly disappeared. Mr. Tower's suggested explanation 
appears to the author as too hypothetical to be satisfactory, even in 
default of any other ; and particularly as this is an effect which would 
necessarily follow in accordance with the theory, so long as there is 
wear. For the centre of wear, being on the off side of the line of lotids, 
this wear will tend to preserve or diminish the radius of the brass 
on the off side, and enlarge it on the on side, a change which will, if 
anything, improve the condition for producing oil pressure while 
running in this direction, but which will damage the condition on 
which the production of pressure in the film depends when the journal 
is reversed and the late off side becomes the new on side. That with 
a well-worn surface there should be sufl&cient wear to produce this 

• On and off sides are used by Mr. Tower to express respectively the sides of 
approach and recession, as B and A, fig. 1, p. 194^ the arrow indicating the direction 
of motion. 



1886.] On tlie Theory of Lubrication. 199 

remit, with snob slight ftmounts of using as those in Mr. Tower's 
'experiments before reversal, seems doubtfnl, but sapposing the brass 
new, and the surface more or less unequal, the wear for some time 
would be considerable, even after the initial tendency to heat had 
disappeared. Hence it is not surprising that the effect should have 
eventually seemed to disappear. 

The circumstances which determine the greatest load which a bear- 
ing will carry with complete lubrication, ».e., with the oil film con- 
tinuons between brass and journal throughout the entire arc, are defi- 
nitely shown in the theory, so long as the brass has a circular section. 

As the ratio of the load to velocity increases JI or c increases, and 
the point H approaches 0, when c reaches the value 0*5, which makes 
GH = a(l— c)=0*5a, the pressure of the oil in the film is every- 
where greater than at A and 6, the pressure in the bath, but for a 
further increase in the load the pressure falls near A on the off side, 
the fall will cause the pressure to become less than that of the atmo- 
sphere, or if sufficient to become absolutely negative, until discon- 
tinuity or rupture of the oil film occurs. The film will then only 
extend between brass and journal over a portion of the whole arc, 
and a smaller portion as the load 'ncreases or velocity diminishes, ».e., 
as c increases. Thus since the amount of negative pressure which 
the oil will bear depends on circumstances which are uncertain, the 
limit of the safe load for complete lubrication is that which causes 
the least separating distance to be half the difference in radii of the 
brass and journal. 

The rupture of the oil does not take place at the point of nearest 
approach, but on the q^side of this, and will only extend up to a point 
P, definitely shown in this theory, which is at the same distance on the 
off side of H as Pi is on the on side. Hence after this rupture the brass 
rcay still be in equilibrium, entirely separated from the journal, and 
the question as to whether it will carry a greater load without descend- 

ing on to the journal will depend on the relative values of — ; and on 

the smallness of the velocity. The condition then becomes the same 
as that for imperfect lubrication, and except in the case of a being 
very small, theory shows that the ultimate limit to the load will be the 
same with the oil-bath and with partial lubrication as Mr. Tower 
found it to be. 

This much may be inferred without effecting the integrations for 
imperfect labrications ; could these be effected, the theory would be as 
upplicable to partial lubrication as it has been to complete lubrication, 
i.e., a sufficient supply of oil. And as it is, sufficient may be seen to 
show that with any supply of oil, however insufficient for complete 
lubrication, the brass vrill still be complete\y ^ep^T^X^^ I^otdl Ni>Dft 
journal, although ^2ie supporting film of oil wii\ iio\. \«\ia\i ^'^^^^^s^ 



200 Prof. 0. Reynolds. [Feb. 11, 

except over a limited area, and it is sliown by general reasoning that 
in the one extreme, when the oil is very limited, the friction increases 
directly as the load, and is independent of the velocity, while in the 
other, where the oil is abundant, the circmngtances are those of the 
oil-bath. 

The effect of the limited length of bearings, and the escape of the 
oil at the ends, is also apparent in the equations. 

Although in the main the present investigation has been directed 
to the circumstances of Mr. Tower's experiments, namely, a cylin- 
drical journal revolving in a cylindrical brass, the main object has 
been to establish a general and complete theory baaed on the hydro- 
dynamical equations for viscous fluids. Hence it has been thought 
necessary to proceed from the general equations, and to deduce the 
equations of lubrication in a general form, from which the particular 
form for application has been obtained. It has been found necessary 
also to consider somewhat generally the characters of fluid friction 
and viscosity. 

The property of viscosity has been discussed in Section II of the 
paper, which section also contains the account of the experimental 
investigation as to the viscosity of olive oil. The general theory 
deduced from the hydrodynamical equations for viscous fluids with 
methods of application, including two cases besides the cylindrical 
journal in which the equations become completely integrable, viz., 
two plane surfaces of elliptical shape approaching, and one plane 
sliding over another not quite parallel plane surface, is given in 
Sections IV, V, VI, and VII. 

The physical considerations of the effect of the heat generated are 
discussed in Section VIII. 

As there are some circumstances which cannot be taken into account 
in the definite reasoning, particularly as regards incomplete lubrica- 
tion, besides which, as the definite reasoning tends to obscure the 
more immediate purpose of the investigation, a preliminary discussion 
of the problem presented by lubrication, illustrated by aid of graphic 
methods, has been introduced as Section III. 

Finally, the definite application to Mr. Tower's experiments is g^ven 
in Section IX, which concludes as follows : — 

The experiments to which the theory has been definitely applied 
may be taken to include all Mr. Tower's experiments with the 4-inch 
journal and oil-bath, in which the number of revolutions per minute 
was between 100 and 450, and the nominal loads in pounds per square 
inch between 100 and 415. The other experiments with the oil-bath 
were with loads from 415 till the journal seized at 520, 573, or 625, 
and a set of experiments with brass No. 2 at 20 revolutions per 
minate. All these experiments were under extreme conditions, for 
which by the theory c was so great aa to xeTsAer \\i>at\c»XAsycL wisisyai.- 



1886.] On the Tlieory of Lubrication. 201 

plete, and preclude the application of tlie iheorj without further 
integrations. 

The theory has, therefore, been tested by experiments throughout 
the extreme range of circumstances to which the particular integra- 
tions undertaken are applicable, and the results, which in many cases 
check one another, are consistent throughout. 

The agreement of the experimental results with the particular 
equations obtained on the assumption that the brass as well as 
the journal are truly circular, must be attributed to the same 
causes as the great regularity presented by the experimental results 
themselves. 

Fundamental amongst these causes is, as Mr. Tower has pointed 
out, the perfect supply of lubricant obtained with the oil-bath. But 
nearly as important must have been the truth with which the brasses 
were first fitted to the journal, the smallness of the subsequent wear 
and the variety of the conditions as to magnitude of load, speed, and 
direction of motion. 

That a brass in continuous use should preserve a circular section 
with a constant radius requires either that there should be no wear at 
edl, or that the wear at any point P should be proportional to 
sin (90°-POH). 

Experience shows that there is wear in ordinary practice, and even 
Ln Mr. Tower's experiments, there seems to have been some wear. In 
these experiments, however, there is every reason to suppose that the 
wear would have been approximately proportional to c sin (^—0) = 
t5sin(90**— POH), because this represents the approach of the brass 
to the journal within the mean distance a, for all points except those 
at which it is negative, at these there would be either no wear at all or 
a. slight positive wear. So long, then, as the journal ran in one direc- 
tion only, the wear would tend to preserve the radius and true circular 
Form of that portion of the arc from A to P (fig. I, note *), altering 
the radius at F, and enlarging it from F to B. On reversal, however, 
A. and F change sides, and hence alternate motion in both directions 
would preserve the radius constant all over the brass. 

The experience emphasised by Mr. Tower, that the journal, after 
running for some time in one direction, would not run at first in the 
9ther, strongly beai*8 out this conclusion. Hence it follows that had 
the journal been continuously run in one direction, the condition of 
lubrication, as shown by the distribution of oil pressure round the 
journal, would have been modified, the pressure falling between and 
B on the on side of the journal, a conclusion which is borne out by the 
Eact that in the experiments with brass No. 2, which was run for some 
^ime continuously in one direction, the pressure measured on the on 
side is Bomewhat below that calculated on the aas\xxn^\t\oTL o^ cso^'q^ax 
7rm, although the agreement ia close for t\ie otYifir ioTU "^SsiHa, 



202 On the Theory of Lubrication. [Feb. 11, 

When the surfaces are completely separated by oil it is diflScalt to 
see what can cause wear. But there is generally metallic contact at 
starting, and hence abrasions, which will introduce metallic partidea 
into the oil (blacken it), these particles will be more or less carried 
round and round with the journal, causing wear and increasing the 
number of metallic particles and the viscosity of the oil. Thus the 
rate of wear would depend on the metallic particles in the oil, the 

values of c, -, and the velocity of the journal, and hence would render 
a 

the greatest velocity of the jouruil at which the maximum load with 

a large value of c could be carried, small ; a conclusion which seems 

to be confirmed by Mr. Tower's experiments with brass No. 2 at 

twenty revolutions a minute. 

In cases such as engine bearings the wear causes the radius of cur- 
vature of the brass continually to increase, and hence a and c must 
continually increase with wear. But, in order to apply the theory to 
such cases, the change in the direction of the load (or the velocity of 
approach of the surfaces) would have to be taken into account. 

That the circumstances of Mr. Tower's experiments are not those of 
ordinary practice, and hence that the particular equations deduced in 
order to apply the theory definitely to these experiments do not 
apply to ordinary cases, does not show that the general theory as given 
in the general equation could not be applied to ordinary cases wei*e 
the conditions sufficiently known. 

These experiments of Mr. Tower have afforded the means of 
verifying the theory for a particular case, and hence have so far 
established its truth as applicable to all cases for which the integra- 
tions can be effected. 

The circumstances expressed by — 

A*7j g-ci0i,0, wiwc' AEB, 

which are shown by the theory to be, together with the supply of 
lubricant, the principal circumstances on which lubrication depends, 
although not the same in other cases, will still be the principal cir- 
cumstances, and indicate the conditions to be fulfilled in order to 
secure good lubrication. 

The verification of the equations for viscous fluids under such 
extreme circumstances affords a severe test of the truth and com- 
pleteness of the assumptions on which these equations are founded ; 
and the result of the whole research is to point to a conclusion 
(important to natural philosophy) that not only in cases of intentional 
lubrication, but wherever hard surfaces under pressure slide over each 
other without abrasion, they are separated by a film of some foreign 
matter, whether perceptible or not; and that the question as to 



1886.] Secretion in the SaUvary Glands of the Dog and Cat. 203 

whether the action can be continnons or not tnms on whether the 
motion tends to preserve the foreign matter between the surfaces at 
the points of pressure, as in the almost if not quite nniqne case of 
the revolving journal, or tends to remove it, and sweep it on one 
side, as is the action of all backward and forward rubbing with con- 
tinuous pressure. 

The fact that a little grease will enable any surfaces to slide for a 
time has tended doubtless to obscure the action of the revolving 
journal to maintain the oil between the surfaces at the point of 
pressure, and yet, although only now understood, it is this action that 
has alone rendered machinery or even carriages possible. The only 
other self-acting system of lubrication is that of reciprocating motion 
with intermittent pressure and separation of the surfaces to draw the 
oil back or to draw a fresh supply. This is important in certain 
machinery, as in the steam-engine, and is as fundamental to animal 
mechanism as is the continuous lubricating action of the journal to 
mechanical contrivances. 



II. '*The Electrical Phenomena accompanying the Process of 
Secretion in the Salivary Glands of the Dog and Cat." 
By W. Maddock Bayliss, B.Sc, and J. Rose Bradford, 
B.Sc, Senior Demonstrator of Anatomy in University 
College, London (from the Physiological Laboratory of 
University College). Communicated by E. A. SchaFER, 
F.R.S. Received Februaiy 4, 1886. 

(Abstract.) 

The glands examined were the submaxillary and parotid of the 
dog and cat, and in all of these we have determined that the process 
of secretion is accompanied by definite electrical changes ; as, how- 
ever, the submaxillary gland both in the dog and cat has been more 
thoroughly examined than.the parotid, the present communication is 
confined almost entirely to the former. 

The chorda tympani and sympathetic nerves were exposed in the 
usual manner, divided, and the peripheral ends arranged for stimula- 
tion, a canula being placed in Wharton's duct. The submaxillary 
gland having been exposed was led off in the following manner. 
One non-polarisable electrode was placed on the superficial or 
cutaneous aspect of the gland, and the second electrode so arranged 
in the wound as to touch the deep surface of the gland as close to the 
hilns as possible without pressing on the duct. 

A Thomson galvanometer of high resistance was used. 



204 Messrs. W. M. Bajliss and J. B. Bradford. [Feb. 11, 

Electrical Condition during Best, 

Dog, — The cntaneoas surface of the gland is in the great majoritj 
of cases negative to the hilos, both when examined as above de- 
scribed and also when the gland is removed from the animal and 
led off. 

In four experiments amongst twenty-four, the outer surface of the 
gland was positive. In two cases the outer surface was at first 
positive, but subsequently became negative, and in one case it was at 
first negative but subsequently became positive. 

The electromotive force of the current of rest varies very much 
both in different cases and in the same case at different times ; 
thus in the former case it may vary from -^ volt to 5-^ volt, but 
owing to a variety of structures (muscles, &c.) being unavoidably 
injured in the preparation, not much stress can be laid on this point. 

Cat. — Out of twenty experiments on the submaxillary gland, in 
fifbeen the surface of the gland was positive to the hilus, in three the 
surface of the gland was negative, in one the surface was at first 
negative and subsequently became positive, and in one the surface 
was at first positive and subsequently became negative to the hilus. 

Hence, although a corresponding amount of injury is inflicted on the 
tissues in the case of the cat as in the dog, yet on the whole the 
resting current is opposite in its sign in the two cases. 

Excitatory Changes. 

Dog. Chorda Tympo/ni. — On throwing an induction current into 
the chorda tympani, a very well-marked deflection of the galvano- 
meter is always observed of a sign indicating that the outer surface 
of the gland becomes negative to the hilus. Although in different 
dogs the amount of this deflection varies, yet never have we failed to 
obtain it. 

Frequently this variation is not the sole one observed, its course 
being interrupted by a second deflection showing the outer surface of 
the gland to become positive. This second variation, however, is by 
no means always observed, and more especially it is not seen if the 
first or main phase is very large, being then indicated only by a 
slight temporary arrest in the deflection caused by the first phase. 
The latent period of the variation is short, being about 0*37", as 
measured by the capillary electrometer. The deflection quickly 
reaches a maximum and begins to diminish before the cessation of the 
excitation, returning quickly towards zero, but as a rule leaving a 
slight after-effect. 

Atropine, in doses of 5 — 10 mgrms., abolishes the main phase of the 
chorda variation in from 2 — 3 minutes from its injection into the 
pleura. In those cases' in which this phase only had been observed, 



1886.] Secretion in the Salivarij Glands of the Do(j and Cat. 205 

frequently after such a dose of atropine the second phase (i.e., oater 
surface of gland positive to hilus) is seen on excitation of the chorda, 
although previously not detected, owing to the magnitude and 
rapidity of the deflection caused by the first or main phase. 

This second phase is more refractory towards atropine than the 
main phase, although ultimately abolished by it in large doses. 

Excitation of Sympathetic c&iiaes weU-marked changes of potential in 
the gland structures which are very different to those produced on 
excitation of the chorda ; the latter have a very short latent period, are 
readily abolished by atropine, and are of such a sign as to cause the 
outer surface of the gland to become negative, occasionally followed by 
the outer sur&ce becoming positive. 

Excitation of the sympathetic, however, produces after a very long 
latent period an electrical effect very refractory as regards the action 
of atropine on it, and of such a sign that the outer surface of the 
^land becomes positive to the hilus. 

Further, the course of the variation is very slow, and its amplitude 
is much less than that of the chorda variation. Thus in one case on 
excitation of the sympathetic a deflection of 62 was obtained, the 
chorda giving a deflection of 140 with j- shunt. 

Atropine in small doses has apparently no effect on the sympathetic 
variation, but in large doses, 40 — 100 mg^rms., it is not without e£Eect, 
at first producing great lengthening of the latent period, and then 
steadily diminishing the amplitude of the variation, although after 
even 100 mgrms. a slight variation, i.e., 10 — 15 divisions, is still per- 
ceptible. 

Gat, Chorda tympani. — In the cat, excitation of the chorda causes 
an electrical variation of such a sign that the outer surface of the 
gland becomes negative to the hilus, but whereas in the dog, a second 
phase was on the whole not observed in the majority of cases, in the 
cat a second phase is usually present, and very frequently is greater 
in amount than the first phase. Further, in a few cases, the first 
phase (i.e., outer surface of gland negative) was very small indeed, 
i.e.y less than 20 divisions, and in one case it was absent, the chorda 
giving a pure second phase. These varieties observed in the varia- 
tions are largely dependent on the nature of the accompanying 
secretion. 

In these cases in which the first phase was large, the secretion was 
very watery, and if the secretion obtained was viscid the electrical 
variation consisted of a small first phase and a large second phase. 

Atropine in doses of 2 — 20 mgrms. abolishes the first phase of the 
chorda variation, leaving the second phase, as in the dog, and this 
second phase requires a larger dose to abolish it, i.e., 20 — 40 mgrms. 

Excitation of the sympathetic in the cat produces an electrical 
effect resembling more the chorda effect of the cat than the sym^* 



206 On the Salivary Glands of the Dog and Cat. [Feb. 11^ 

tbetic effect of the dog. Thns the nsnal effect is a deflection aiinilar 
to the chorda effect of the cat, i.e., diphasic, but with this differencci 
that the first phase is usuallj larger than the second phase, and not as 
in chorda excitation, the second larger than the first. This yanatum 
is obtained if the accompanying secretion be watery in character, bat 
if, as occasionally happens, it be viscid, then the second phase is 
larger, and the first phase smaller in amonnt. 

Atropine in small doses abolishes the first phase, and in doses of 
10—40 mgrms. the second phase, thns showing a very great difference 
between its action on the sympathetic variation in the cat and dog 
respectively. 

Thns to snm up onr results : — 

In the submaxillary of the dog excitation of the chorda produces a 
copious slightly viscid secretion, and the electrical effect consists of a 
large first phase, the second phase being small, and although not 
always observed is probably always present. 

In the cat a similar excitation produces a copious viscid secretion, 
and the electrical effect is diphasic, the second phase being usually 
the larger. 

In the dog, excitation of the sympathetic produces a scanty viscid 
secretion, and the electrical effect consists of a pure second phase. 

In the cat, excitation of the sympathetic produces a very copious 
and but slightly viscid secretion, and the electrical effect is diphasic, 
the first phase being usually the larger. 

In the parotid the results obtained are similar to those in the sab- 
maxillary. 

In the dog excitation of the tympanic plexus causes the surface of 
the gland to become negative to the hilus, and the variation is readily 
abolished by atropine. Excitation of the sympathetic causes the 
surface of the gland to become positive to the hilus, and the variation 
is not readily abolished by atropine. 



1886.] On the Badiation of Light and Heat. 207 



February 18, 1886. 

Professor G. G. STOKES, D.C.L., President, in the Chair. 

The Presents received were laid on the table and thanks ordered for 
them. 

The following Papers were read : — 

I. '* Observations on the Radiation of Light and Heat from 
Bright and Black Incandescent Surfaces." By Mortimer 
Evans, M.In8t.C.E., F.R.A.S. Communicated by Lord 
Rayleigh, M.A., D.C.L., F.R.S. Received February 3, 
1886. 

In the course of an investigation into the nature of carbon filaments, 
such as are ordinarily used in the construction of incandescent lamps, 
my attention was arrested by certain variations in the amount of 
light emitted from filaments which were, to the best of my belief, of 
similar nature and composition, but which, when tested under pre- 
cisely similar conditions, gave the most anomalous results. I was 
also struck with changes which occurred to a greater or less degree in 
the light yielded by certain lamps when re-tested subsequent to a 
shock of over-incandescence, or long continued hard running at a high 
temperature ; the light yielded after this occurrence (indeed the light 
yielded by any lamps that had been much used) I found to be 
invariably lessened both in quantity and brightness, and to require a 
consideittble increase in the energy supplied to it to produce from 
the same filament the light it originally gave. After seeking vainly 
to account for these irregularities from structural differences in 
the carbon filaments themselves, and after testing and re-testing many 
carbons made in a variety of ways, both by myself and others, it 
occurred to me that the composition or structure of the carbon itself, 
of which the filaments were made, might have really little to do with 
the discrepancies and changes I had noticed. 

All the carbons I had tried gave in turn the most irregular results, 
and although some of these were porous, and some dense and com- 
pact, the light emitted from any one of them per unit of surface for 
each unit of electrical energy supplied to it was very varied and 
uncertain, and did not appear to follow any condition of the porosity 
or denseness of the filament itself. 

All the carbons in turn gave the same light per unit of aurfsAe- 



208 Mr. M. Evans. Observations on t/ie [Feb. 18, 

when raised to the same incandescence, bnt the energy reqoired to 
produce this light, or raise the filament to this incandescence, varied 
sometimes in a remarkable way. At times a filament was found 
which, with 2 watts or volt amperes passing through it, would yield 
the light of the standard candle. And again, with other filaments it 
sometimes occurred that no less than 5 volt amperes were required to 
produce this light. 

On collating a number of these observations, and comparing the 
filaments themselves with their various testings, I noticed, I thought, 
some difference in the outward appearance of those filaments which 
had tested well and those that had required any large amount of 
energy to give a satisfactory light, and, following up this idea, I soon 
became convinced that it was to this surface appearance or condition 
that the whole question of economical light giving or otherwise might 
be traced. All the filaments, it appeared, whose surfaces were of a 
dull black required the larger amounts of energy to yield the usual 
unit of light, while from those filaments with even moderately bright 
surfaces the light of the standard candle could be obtained for an 
expenditure of energy surprisingly less. To ascertain with greater 
certainty if this idea were correct, I prepared a number of carbons 
made from a vegetable fibre which, though yielding a somewhat 
poi*ou8 carbon, was strong and uniform in texture. 

Having selected two filaments as like each other as the eye could 
determine, and having ascertained by careful measurement that they 
were both of exactly the same length and diameter, and therefore of 
equal surface, I subjected each carbon in turn to the action of an 
electrical current in a hydrocarbon atmosphere, so regulating the 
current as to maintain the carbon filament at a white heat in the 
vapour until a sufficient deposit of carbon upon its surface was 
obtained. 

To provide for the deposit of carbon upon the one filament being os 
dull a black as possible, I used for the depositing medium an atmo* 
sphere of ordinary coal-gas drawn from a domestic burner, A large 
glass jar was filled with this, and a constant current of the cold gas 
kept circulating through it during the deposit, and the resulting 
surface was all that could be desired. It had all the appearance of 
being coated with lampblack, but the coating was quite permanent, 
and did not brush off, or even soil the fingers in handling. 

On the other of these two filaments I now deposited carbon of a 
bright silvery appearance in marked contrast with the dull black of 
that just described, and this deposit I found I could readily effect by 
.using as the depositing atmosphere the very hot vapour of almost any 
hydrocarbon having a high boiling point, though from the porous 
nature of the carbons I was using I did not get the surface as brilliant 
;as I subsequently obtained it from smoother carbons. 



1886.] Radiation of Light and Heat. 209 

This filament was then mounted on platinum electrodes, as the 
other had been, enclosed in a similar glass globe, and exhausted of 
air, the vacuum being carried to about the loo^ooo ^^ ^^ atmosphere. 

The remeasurement of these carbon filaments subsequent to the 
reduction of the carbon on their surfaces, showed no perceptible 
increase in their diameter, the deposit of carbon which had been 
added being in all likelihood less than the ten thousandth of an inch 
in thickness, and the surface areas of each filament still remained 
practically equal in all respects. 

Having now two carbon filaments with which a comparative test 
might be made, and in which the conditions were in all respect<8 
identical, except in that of surface condition or polish, the one being 
like soot and the other like silver, I passed a series of known electrical 
currents through each in turn, registering the light produced against 
a standard candle burning 120 grains per hour in a good photometer 
provided with a sliding screen. 

In Table No. I, Carbon A, are shown the testings of the blackened 
filament, and in Table II, Carbon B, those of the filament which was 
made bright. In diagram No. 1 maj be seen the plotting of these 
results and their relative curves. The dotted curve marked Carbon A 
shows the testings of the black filament, and the curve marked wifch a 
plain hard white line, Carbon B, gives the testings of the filament 
which was bright. The horizontal divisions in the diagram give the 
watts or volt amperes of energy passing through the filament, and 
the perpendiculars mark the corresponding candle powers. From 
these tests it may be noticed that with two carbon filaments identical 
in all respects but in that of sarface polish or brightness, the 
blackened filament required no less than 100 watts to keep its surface 
at an incandescence yielding 20 candles, whilst the filament with the 
bright surface was kept at the same incandescence, and gave an equal 
light with 74 watts only, also that each filament when consuming an 
energy of 4 watts per candle, that which was blackened required no 
less than 113 watts of energy to effect this (besides having its surface 
incandescence strained to yield 28 candles), while the bright filament 
with 71 watts only effected the same economy, viz., 4 watts only per 
candle, and had to give from its surface only 17 J candles. 

These results satisfied me that the condition of the carbon sui*face 
was wholly the cause of the large differences shown by these curves, 
and I determined therefore to carry out a more extended series of 
tests with carbons about which I knew nothing. 

For this purpose, therefore, I procured two cai'bons of foreign 
manufacture, but by whom made I did not know. The following 
were their chief characteristics. The carbons were very nearly 
square in section, and appeared before carbonising to have been 
sliced from some homogeneous material like parchment ^a^v. 



Mr. M. Evans. Obtervation* on the [Feb, 18, 





1 




1 










H 




H 




H 




H 




H 




ffl 




■ 




H 




1 




H 



Tbej* were both, I fooad from carefnl measurements, of preciael^ 
the same dimensions and sarface area, aad each presented the samt 
dull dead black surface ; the carbon itself appeared eiceedingt} 
dense and hard. Testing these filaments as I procured them, I placec 
them in balbs and exhausted as before. 



6] 



Sadiation of Light ixnd Heat, 



311 



Tables III and YI give the photometric tests of these carbons aa I 
procured them, and diagrams 2 and 3 show the plotting of these 
testa. I have narked these filaments C and D, the bhick dotted line 
in diagram 2 being the onrve for filament C, and the black dotted line 
in diagram 3 that for filament D. 

In theae two carves the extreme nniformity with which these car- 
bons tested is worthy of notioe, the one giving nineteen and a half 
candles and the other twenty for the eighty watts supplied to each. 




Mr. M. EvaiiM. Obgenations c 



[Feb. 1 




which not only well inside any error of oheervation, hnt is in nvst 
mensnre a snfiScient proof of the extreme equality of tie areaa of 
their radiatiDg surfaces. 



188H.] Radiation of Light and Heat. 213 

1 now dismoanted these filaments and subjected them to incande- 
scence in the hot hydrocarbon vapour as before with carbon B. 
The result was highly satisfactory, as they both took a surface much 
brighter than carbon B had done. Again remounting them and 
exhausting, they were placed in the photometer as before. The results 
are given in Tables lY and YII, and the curves from these tables are 
shown by the bright hard lines GC and DD, diagrams 2 and 3. 
These curves appear fully to bear out the assumption arrived at in 
the former tests. Tables I and II, and the improvement in light 
radiation per unit of energy is especially marked in the case of fila- 
ment C, where it may be noticed that at 2 watts of energy per candle 
of light the same filament in its black condition was strained to yield- 
iuff sixty candles nearly, while in its polished state it had only to yield 
thirty-seven, and still be as economical in its electrical energy as 
before. The same filament at 3 watts per candle, when black, had to 
give ofF 31 candles, equal to 270 candles per square inch of its sur- 
face, while in its polished state it required to give only 18 candles to 
eqnfj 3 watts per candle, and its surface was strained only to the 
extent of 155 candles per square inch. It is certain, therefore, that 
its lasting power with its surface bright would be many times greater 
at the foregoing expenditure of energy than in its black condition. 

As the filaments were still unbroken and appeared capable of yet 
another test, I resolved to attempt the reblackening of them, and to 
ascertain if possible if the test-curve under these conditions would 
again revert to its former position, but I had now to reblacken over 
the bright surface which could not be removed. The filaments were 
again successfully dismounted, and with some difficulty again re- 
blackened over their former polished surfaces. 

They were now tested, as is shown in Tables V and VIII, and the 
corresponding curves are given in diagrams 2 and 3, marked CCC, 
DDD. The recession of the curves was in both cases nearly com- 
plete, any difference being fully accounted for by the incomplete 
roblackening of the carbon surface. 

In carrying out these experiments I much regret not having made 
the necessary arrangements for simultaneously testing both the heat 
and . light emitted from each filament in its blackened and bright 
condition. I have little doubt the loss of efficiency when black was due 
to tiie energy supplied being radiated in large quantities as heat 
waves from the blackened surfaces, which these surfaces when bright 
would not permit. This radiation of heat, however, which had not 
been converted into light by emission from a bright surface was abun- 
dantly manifested in the handling of the lamps. The incandescent 
globe containing the bright filament could at all times be readily held 
in the hand even when giving its maximum of light, while the heat 
radiated from the filament when its surface was blackened was moat 

VOL. XL. ^ 



214 



Mr. M . Evans. ObiserooHona (m the [Feb. 18, 



intense, and not only cansed at times severe bums, bat occasionally 
would even char the little paper labels attached to the glass. 

I also regret not having dissipated bj a powerful current the black 
carbon deposited over the bright snr&oe in the last case, as an increase 
of economy in working and light-giving should have resulted, and this 
would have been the more interesting as ordinarily it is just the 
other way ; as soon as by overheating or long use the polished sur- 
faces of our best lamps are injured, so surely is there an increased 
waste of energy, and hence the extreme difficulty of preserving 
lamps made for use as standards for any long period. 

From these results it appears probable that the attainment of 
economical high E.M.F. lamps of oi-dinary sizes may be very diffi- 
cult, as what would be a high E.M.F. lamp with a black surface 
would be a low E.M.F. lamp were this black surface made bright; 
the energy required being less, both the E.M.F. and current would 
have to fall. The desire, therefore, for high E.M.F. lamps should be 
met not by a supply of black wasteful Blaments, but more properly by 
economical lamps of greatly increased size and candle power, or by 
lamps of a smaller candle power run two or more in series. 



DlAQBAM 1. 



Carbon A. 
Table I. 



Carbon B, 
Table II. 



1 

1 Candles. 


Volts. 


Amp. 


Watts. 


Volts. 


Amp. 


Watts. 


1 

4 


53-5 


1-12 


60 


38-5 


105 


40-4 


6 


56 


1-2 


67-2 


42 


118 


49*5 


8 


. . 


• . 


. . 


43 


1-23 


52-4 


10 


60-5 


1-32 


80 


45 


1-30 


58-5 


12 


« • 


• • 


. . 


46-5 


1-35 


62-5 


14 


63 


1-4 


88-2 


48 


1-41 


67-6 


16 


. . 


• . 


• • 


48-5 


1-43 


69-3 1 


18 


65 


1-46 


94-9 


49 


1-45 


710 ! 


20 


66*5 


1-52 


101 








22 


■ . 


. . 


. . 


50-5 


1-52 


76-7 


24 


67 


1-54 


103 








25 












. 


26 


. • 


• ■ 


« • 


52 


1-58 


82 1 ' 


28 


69 


1-62 


in -7 








80 


69 


1-65 


113-8 


53 


1-65 


87-7 


35 












1 


40 


74 


1-80 


133-2 


56 


1-78 


99-7 ' 


45 














50 


• . 


. • 


• • 


58-5 


1-9 


101 


65 


77 


1-95 


181 








/ eo 1 


• • 


• • 


• • 


62 


2 05 

\ 


127 

i 1 



1886.] 



JiatHatien of L^ht and Heat, 





DuoBAii 2. 






CarbmO. 




Curve 0. 


CO. 


C.CC. 


T»ble lit. 


T«bl« IT. 


Table V 



Candle*. 


Volt*. 


Amp. 


WttU. 


Volt.. 


Amp. 


Wittj. 


Volt.. 


A.P. 


Wstte. 


4 


45 


086 


38-7 


34 


0-96 


82-7 


39 


116 


45-2 


6 


62-5 


1-04 


54-6 


33 


1-02 


36-2 








Et 


64 


108 


58-3 


38 


1-08 


41 








10 


56 


112 


62-7 


39 


1-12 


43-7 


44-3 


1-38 


61-4 


n 


68 


117 


07-8 


40 


1-17 


47 3 








u 


69 


1'22 


71-9 


41 


1-30 


49-2 








16 


60 


1 23 


73 '8 


42 


1-22 


51-2 








18 


61 


1-27 


77-4 


43 


1 26 


64 








sio 


62 


1-38 


79-7 


44 


128 


5fi-8 


49-G 


1-63 


76-7 


n 


63 


IS 


81-9 


44-5 


1-33 


69 








24 


64 


1-32 


84-6 


46 


1-36 


60-7 








26 


65 


1-36 


88 '4 


46 


1-36 


62-6 








B8 


66 


1-38 


91-0 


46 8 


1-40 


6o-4 








30 


66-6 


1-40 


93 


47 


1-47 


67-2 








36 


68 


1-46 


99-2 














40 


69 


1-48 


102 


49 6 


1-64 


76-2 








4S 


70 6 


1-62 


107 


50 


1-60 


80-8 








60 


71 


1-54 


109 


62 


1-67 


86-8 








56 


72 


1-68 


113 


62-6 


1-70 


89-1 








60 


73-6 


1-62 


119 


63-8 


1-73 


91-3 









216 



Oh the Radiation of Light and Heat [Feb 



Curve D. 
Table VI. 



Diagram 3. 

Carbon D. 
D.D. 
Table VII. 



D.D.D. 
Table VII] 



Candles. 


VolU. 


Amp. 


Watte. 


Volte. 


Amp. 


Watte. 


Volts. 


Amp. 


V 


4 


46*5 


102 


47*4 


37-3 


1 


37*8 


34 


1*28 




6 


• • 


. • 


• • 


• • 


• • 


• • 


36 


1-4 




8 


51 


116 


69 1 


• • 


• • 


• • 


37 


1*45 




10 


52*5 


1*20 


63 


42 


1*13 


47*8 


38*5 


1-52 




12 


54*5 


1-27 


69-2 


• • 


• • 


. • 


40 


1-54 




14 


. • 


• . 


. . 


. . 


• • 


. a 


40-5 


1-62 




IG 


. • 


. . 


. . 


. • 


• • 


. . 


42 


1-72 




IH 


67 


1-84 


76-3 


47 


1-30 


61 1 


43 


1-75 




20 


68*3 


1-40 


82*1 


47-8 


1*32 


63 


43 


1-77 




22 




















24 


. . 


. . 


• • 


• • 


• • 


• • 


44-5 


1-84 


25 


61 


1*46 


89 












20 














" 




28 


. . 


• • 


. . 


• • 


• • 




46 


1-92 


30 


62 


1*50 


93 


50 


1-42 


71 


46-5 


1-94 




35 


• • 


. . 


• • 


. • 


• • 


• • 


47 


2 




40 


65 


1*62 


105 


52*5 


1-53 


80-3 


48 


206 




45 




















50 


68 


1*70 


115 


54*2 


1-60 


87-2 


50 


212 


1 


55 




















60 








57 


1*67 


95-2 


52 


2*3 


1 



1886.] Thermopile and Galvanometer combined. 217 



IL "On a Thermopile and Galvanometer combined" By 
Professor George Forbes, M.A. Communicated by Lord 
Rayleigh, M.A,, D.C.L., Sec. R.S. Received February 4, 
1886. 

The author has lately made ase of a special form of thermopile and 
galvanometer combined, which is very sensitive for the measurement 
of radiation. The apparatus is especially suitable for use as a lino- 
thermopile. 

The first experiments were made with two half tubes, one of anti- 
mony the other of bismuth, soldered together so as to make a short 
tube about 2 cm. external diameter, the walls being 2 nmi. thick, and 
the length of tube about 2 or 2^ cm. The sides of the tube where 
the junctions of the metals occur were then filed flat, so as to present 
a thin wall to receive the radiations and to enable it to rise in tempe- 
rature more rapidly, and also more uniformly throughoat the thick- 
ness of this wall. This tube was lamp-blacked. A Thomson's mirror 
and magnets (by J. White, of Glasgow), in its usaal brass cell, but 
with an insulated coating, was then inserted in the tube, and the 
whole apparatus mounted inside a brass cube with a brass cone at one 
side to throw the radiations upon one junction, and with a circular 
hole facing the mirror. This apparatus when properly adjusted with 
a lamp and scale was found to be very sensitive. It had been the 
intention of the author to use a telescope in place of a lamp, but the 
radiations of the lamp were found to give rise to no inconvenience. 

Let us compare the probable sensitiveness of this instrument, say, 
with a line-thermopile of the ordinary construction of 20 pairs, 
foiTning a line of the same length as the tube, the doable length of a 
pair of antimony and bismnth in the line-thermopile being equal to 
the circumference of the tube. Let E be the E.M.F. of one junction, 
and let R be the resistance of one pair in the line- thermopile, and let 
R' be the resistance of the galvanometer used with the line-thermopile. 
The total resistance of the line-thermopile is 20R, and that of the 

R 

tubular one is ^, and the currents in the line and tabular thermo- 

20Ei 20£i 

piles respectively are -- - — — and -^^— . If the galvanometer wei-e 

20ii-f-B R 

specially constructed to match the line-thermopile, R' would be mado 

E 
equal to 20R, and the current would be — , or one-fortieth of the cur- 

rent in the tubular thermopile and galvanometer combined. Thus it 
wonW require forty turns of wire in the low -resistance ^^N^AVtyccL^VKt^ 
if these coila occupied the same space as tlie meV«^ o\ vVe VoNyc^ax 



218 Prof. O. Forbes. On a [Feb.!!, 

thermopile, to equal the sensitiyeness of the latter, and a larger 
nnmber if it occupied a greater space. On the whole, it seemi i 
probable that bj specially designing a galvanometor to match tin 
line-thermopile the arrangement wonld be about as sensitiYe as the ' 
new instrument in the form hitherto described, but the simplicify and 
cheapness of construction of the latter commends it. 

The next apparatus was made according to the following instrno- 
tions : — 

Take a wedge whose distance from the apex to the base is about { 
6 cm., the base of the triangular section of the wedge being aboat 
3 cm., and the width of the wedge 6 cm. The wedg^ is half of 
antimony and half of bismuth, the diyision being made by the 
medial plane perpendicular to the three rectangular faces of the 
wedge cut off the apex of the wedge by a plane parallel to the base 
of the wedge, and exposing a surface of 1^ cm. width. This is the 
surface which receives the radiations, and it is lamp-blacked. A hole 
about 1 cm. diameter is now drilled (or it is better to file it out before 
the two metals are soldered together) through the two sides of the 
wedge, so as to leave only a thin wall along the junction of the 
metals at the surface which receives the radiations. A Thomson cell 
with suspended mirror and magnet is inserted in this hole and the 
instrument is complete, and ready to be placed inside the brass box 
with cone already described. 

The resistance of this cell is very low and its sensitivenesR thereby 
increased. Moreover this type has a great advantage in the fact that 
the mass of metal acts as a damper upon the vibrations of the magnet, 
and so we have a dead-beat instrument. 

The diameter of the cone to receive radiations at its mouth was 
5 cm. A candle at a distance of 30 cm. from the mouth of the cone 
gave a deflection of 52 divisions, a reading being easily made correct 
to one division. A duplex lamp burning para£&n oil at a distance of 
1^ metres gave a deflection of 60 divisions. 

The author takes this opportunity to describe a method of carrying 
the delicate Thomson cells without danger of breaking the silk tibre 
suspension. The cell consists externally of a brass tube. A horse- 
shoe magnet is obtained with the distance between its legs small 
compared with the diameter of the above-mentioned tube. The tube 
is placed so as to rest on the inner edges of the legs of the magnet, 
with the mirror over the poles of the magnet, the mirror magnets 
having their poles over poles of opposite name of the horse-shoe 
magnet, and with the silk fibre next to the magnet. The mutual 
magnetic attraction takes the tension off the silk fibre and holds the 
mirror fixed in position, and the fibre cannot be broken by a blow 
given to the apparatus. 

Fig'. 1 is a sketch of the first arrangement, m >i>aa \atm <5\ ^ 'cvs>Ji^, 



6.] Thermopile and Galvanometer combined. SI 



I- I 



i 





220 Prof. B. Stewart and Mr. W. L. Carpenter. [Feb. 25, 

Fig. 2 is a sketch of the low-resistance combination, showing the 
hole into which the Thomson cell is inserted. 

Fig. 3 shows the portable arrangement to prevent fractnre of the 
silk suspension. 



February 25, 1886. 
Professor STOKES, D.C.L., President, in the Chair. 

The Presents received were laid on the table, and thanks ordered 
for them. 

The following Papers were read : — 

I. '' On a Comparison between Apparent Inequalities of Short 
Period in Sun-spot Areas and in Diurnal Declination-ranges 
at Toronto and at Prague. By Balfour Stewart, M.A., 
LL.D., F.R.S., and William Lant Carpenter, B.A., B.Sc. 
Received Febniary 17. Read February 25, 1886. 

1. In a report to the Solar Physics Committee (" Proc. Roy. Soc," 
vol. 37, p. 290, 1884) we discussed the relations between certain 
apparent Inequalities of short periods in sun-spot areas on the one' 
hand and diurnal temperature-ranges at Toronto and at Kew of cor- 
responding periods on the other. 

In the present communication we proceed to discuss the connexion 
between the same solar Inequalities and the diurnal declination-ranges 
at Toronto and at Prague. 

For the Toronto declination-ranges we are indebted to the kindness 
of the Science and Art Department, South Kensington, and of Mr. 
Carpmael, Director of the Toronto Observatory, through whom we 
have received daily values (excluding Sundays) of the diurnal range of 
magnetic declination at Toronto extending from 1856 to 1879 inclu- 
sive, and thus forming a series of 24 years. 

Each number is the difference in scale-divisions of the declinometer 
between the greatest eastern and the greatest western deflection of 
the declination magnet on each day, as observed at the hours 6 a.m., 
8 A.M., 2 P.M., 4 P.M., 10 P.M., and midnight of Toronto mean time, one 
scale-division of the instrument being equal to 0''72 nearly. It is 
probable that such difEerences represent very nearly the true diurnal 

Disturb&ncea appear to be violent at ToToiAo^^^i^^^'^v^^'c^VscXfc^ 



1886.] Sun-spot Areas and Diurnal Declination-ranges. 221 

a few of the most disturbed observations, embracing those which 
denote ranges above forty scale-divisions, or 28''8. Although this 
rejection has been made, it must not be supposed that the remainder 
are entirely undisturbed, but only that they are freed from the 
excessive influence of the most violent disturbances. 

We have extracted the Prague ranges from the published records of 
that Observatory, and we have not found it necessary to exclude dis- 
turbances except in one or two very marked cases. The Prague 
ranges are derived from observations made at 6 a.m., 10 a.m., 2 p.m., 
and 10 P.M., hours which are common to the whole series, and there 
is reason to believe that the ranges thus deduced are not greatly 
different from those which would have been obtained from an hourly 
series of observations. 

2. The declination-ranges of the present paper have been reduced 
exactly in the same manner as the temperature-ranges of our previous 
report (" Proc. Roy. Soc," May 1, 1884, vol. 37, p. 290). It is there- 
fore unnecessary to discuss the method of reduction, this having been 
already done at considerable length. 

We proceed consequently at once to consider — 

Results of Comparison around 24 Bays. 

3. Comparison (w to Duration of Period. — This is given in the fol- 
lowing table, in which the sun-spot and Toronto temperature columns 
are transcribed from our former paper for the purpose of comparison. 
The sums in these columns are those of 36 years. The Prague decli- 
nation columns exhibit likewise suras of 36 years, while the Toronto 
declination columns exhibit sums of 24 years. As in our last paper, 
to save space we have divided each individual sum by 100 ; that is to 
say, we have dismissed the two right hand figures. 

We have inclosed in brackets the positions of all sufficiently well- 
defined maximum Inequalities of sun-spots, of Toronto temperature- 
ranges, and of Prague declination-ranges. But inasmuch as the 
Toronto declination-ranges only extend over 24 years, we have 
merely exhibited the numbers without brackets, believing these to be 
of inferior accuracy. 

Before the table is examined it may be well for the reader to be 
reminded that the sun-spot areas extend from 1882 to 1867 inclusive, 
thus embracing 36 years ; that the Toronto temperature and the 
Prague declination-ranges extend from 1844 to 1879 inclusive, thus 
embracing 36 years ; while the Toronto declination-ranges extend 
from 1856 to 1879 inclusive, thus embracing 24 years. It thus 
appears that the Toronto temperature and the Prague declination- 
TBJiges are for the same 36 years, 24 of wbicla. tiie'j Wn^ Va. ewYXiXSi^TL 
with the sun-spot series. On the other hand, the TlototAx^ ^^^vaaiOvina. 



1 



IS 



II ;S 



Si 

11 

if 



222 


Prof. B. Stewart and Mr. W. L. Carpenter. [Feb. 8S, 




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1 


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3SI!:8SSSSS$$S3!S2S;3«3SgS!:SS:gSSi!SS83i: 


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1886.J Sun-spot Areas and Diurnal DeclinaHonr-ranges. 223 

series of 24 years has its 24 years in common witH the Pra^e series, 
bat only 12 years in common with the sun-spot series. 

Confining onr comparisons in period to snn-spots, Toronto tempera- 
ture, and Prague declination-ranges, it will be seen that on the whole 
the positions of maximum appai*ent Inequality for sun-spots are near 
those for Toronto temperature and Prague declination. It may be 
desirable here to repeat the remark which we made in our previous 
communication, that while this likeness cannot be considered as 
conclasively proving a connexion, it is nevertheless the sort of 
similarity which might be expected to exist between phenomena 
physically connected, but which contain so many apparent Inequali- 
ties, and these so near together, that our series of observations is not 
sufficiently extensive to enable us to eliminate their influence upon 
each other, or to allow us to ascertain their true positions. 

We may likewise remark that in our opinion there is not a greater 
correspondence between sun-spots and declination -ranges than be- 
tween sun-spots and temperature-ranges. 

4. Comparison in Phase. — For this purpose we have treated the 
Toronto declination and the Prague declination Inequalities exactly 
in the way in which we treated the temperature-range Inequalities of 
our previous paper, so that the Inequalities of the following table 
(Table II) are quite comparable with those of our previous paper ; 
they are indeed virtually the same Inequalities. The only difference 
is that we have in Table II set for calculation in each case from the 
corresponding sun-spot minimum, which seems to be the most con- 
venient starting point when comparing together Inequalities such as 
those of this table, which as a rule have only one prominent maximum 
in their period. It thus appears that here the settings have been 
arranged by strictly celestial considerations. If, therefore, there is no 
connexion between these terrestrial and solar Inequalities, the declina- 
tion-range maxima should be distributed impartially up and down the 
table without any other than chance grouping together. Their 
behaviour is, however, very different from this — the maxima being 
comparatively closely grouped together about a position a couple of 
days after the corresponding sun-spot maximum. 

5. Constancy of Type in the various Inequalities. — There is a very 
considerable constancy of type in the declination Inequalities which, 
as already stated, have only one prominent maximum. Nevertheless, 
as will be seen both from Table II and from the diagram which 
accompanies this paper, there is a tendency to duplicity of phase in 
the terrestrial that is entirely wanting in the solar Inequalities. 



Prof. B.Stewart and Mr. W.L. Carpenter. [Feb. 85. 



1 






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886.] Sanspot Areas and Diurnal Declinafiim-rarigen, 225 



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22« Prof. B. Stewart and Mr. W. L. Carpenter. [Feb. 25, 

Eesulis of Comparison around 26 Day§. 

6. Comparison as to Duration of Period, — This is exhibited in 
Table III, which is precisely asalogons to Table I. The same remarks, 
too, are applicable to both tables, and it will be observed that here, 
as in the former table, the positions of maximum Inequality for son- 
spots, are, on the whole, near those for Toronto temperature and 
Prafipie declination. Nor is there, in our opinion, a greater corre- 
spondence between sun-spots and declination-ranges than between 
sun-spots and temperature- ranges. 

7. Comparison in Pha^e, — This comparison is exhibited in Table IV, 
which is precisely analogous to Table VI of our previous communica- 
tion, except that here we have introduced the Inequality — 52, which 
we had omitted from Table VI, because the Toronto Inequality 
was not sufficiently near the type. It will be noticed from Table IV, 
that at least as far as regards the Toronto declination, the constancy 
of phase is not so evident as for the Inequalities around 24 days. It 
will likewise be remarked, that while the chief Toronto declination 
maximum, like that for Inequalities around 24 days, follows a little 
after the sun-spot maximum, the chief Prague declination maximum 
decidedly precedes the other two. It thus appears that the similarity 
in time of maximum between the two declination stations which 
holds for Inequalities around 24 days (Table II) does not hold for 
Inequalities around 26 days. 

Broadly speaking, in both cases there are appearances of duplicity 
of phase, but in the case of Toronto the same maximum has remained 
the predominant one in both tables, while in the case of Prague the 
predominant maximum for the 24-day Inequalities has become the 
subsidiary maximum for those around 26 days. 

8. In attempted explanation of this we would in the first place 
desire to repeat the remark we made in our previous communication, 
namely, that there are two possible kinds of periodicity with regard 
to sun-spots, and that it is not necessary to regard the Inequali- 
ties around 24 days and those around 26 days as perfectly 
similar phenomena. Again, as regards the evidence we gave 
in a footnote to that communication, tending to show that the 
Inequalities around 26 days might denote the synodic periods with 
respect to the earth of those around 24 days, this evidence is, 
we find, borne out by the declination results. We prefer, however, 
to wait until we have accumulated more information before we venture 
to discuss this important subject. Meanwhile we shall content our- 
selves with remarking that the similarity between the two stations, 
Toronto and Pi'ague, for the one set of magnetic Inequalities, and 
their dissimilarity for the other, is at first sight in favour of the 
theory of a physical difEerence of some sort between the two. We 



ij.j Sun-tpot Areas and Diurnal DeeUnatwn-rangeK. 



it\- 



%H%i 






sss«ss^E!Ss=SES'-*:ii$sssR§ss 






S$^SSE9S3»S!iS,-:£S3 



ianS8g5sliil=ls5s*S£SEi2 



= E7iS25!SSS2SI5SSSS=S2SS8"SSS3 
8 S*Si3E3K5^S3SS="5!Sta8S3KsS 



228 . Prof. B. Stewart and Mr. W. L. Carpenter. [Feb. iS, 

have used the words ai first sight, because, apart altogether from the 
comparatively small number of the Inequalities discussed, there is t 
strictly terrestrial consideration which we must not lose sight of. 

It is well known to all magnelicians that we have not as yet arrived 
at any wholly satisfactory method of separating between the disturbed 
and the undisturbed magnetic observations, and the results now ezhi. 
bited have unquestionably been deduced from observations which 
include a good many disturbances. Now under these circumstanoee 
the effects of disturbances would only disappear from our results on 
the hypothesis that such effects have no reference whatever to the I 
periodicities of which we have been treating — that they are, in fact, 
non-periodic — so that they will become eliminated in a sufficiently 
extensive series of observations. But we have much reason to sup- 
pose that this is not the case, for the observations of Professor Loomis 
and of Mr. John Allan Broun would seem to indicate that short- 
period Inequalities of sun-spots occasion terrestrial magnetic dis- 
turbances, which follow closely on the celestial phenomena, so that a 
maximum of sun-spots is quickly followed by a maximum of dis- 
turbance. Now in the preceding tables we have discussed some of 
the most prominent solar Inequalities in connexion with their mag- 
netic effects, and doubtless the result we have obtained is a composite 
one, its components being an Inequality of solar diurnal declination- 
range (undisturbed), and an Inequality of disturbance declination- 
range. We may add that Toronto is a station whei^e the disturbance 
is great, and also that the sun-spot Inequalities around 26 days are 
greater than those around 24 days. 

Attempted Eliminatt07i of Disturbances, 

9. All these considerations point to the necessity of eliminating as 
much as possible the effect of disturbances before we venture to 
discuss our results. We have attempted to do this in the following 
manner : — 

First of all, we would remind the reader that the Inequalities 
around 24 and 26 days that we have been dealing with are most 
probably not all the Inequalities around these periods, but only the 
larger specimens of them. 

We remarked in our previous communication that observations 
founded on sun-spots might present the same variety of period, when 
treated as we have treated them, which they presented when 
treated in another way by Carrington, who found that the spots in one 
solar latitude had a different period of rotation from those in another. 
If there be any truth in this remark, we might expect that the few 
solar Inequalities which we have exhibited are only the most promi- 
nent members of a comparatively large series, packed, it may be, so 



1886.] Sun-spot Areas and Diurnal Declination-ranges. 221) 

closely together that we cannot disentangle them completely by our 
limited series of observations. Now it is probable that magnetic dis- 
turbances wonld limit themselves in great measnre to the especiallj 
large solar Inequalities, so that if we oonld find some method of 
treating not merely the larger but all the Inequalities, we might 
probably rid ourselves to a considerable extent of the influence of 
disturbance. But by our method we Have the means of doing this. 
We possess for each element, for each period altogether over 100 seriep^ 
representing Inequalities extending firom —52 to +52 of our 
notation. 

Furthermore, we have the same series of 24 years common to Toronto 
declination, Kew temperature, and Prague declination, and it is with 
this common series that we have made a compaxison as follows. The 
Kew tOTiperature Inequalities have virtually only one maximum and 
one minimum, and we have selected all those in which it is possible to 
ascertain accurately the position of the maximum, that is to say, all 
those which are according to type. Now let the Toronto and Pragae 
declination Inequalities be set in all cases so as to start from the 
maximum of the corresponding Kew temperature Inequality, using of 
course for this purpose not the whole 36 years of Prague observa* 
tdons, but only 24 of these. We are thus comparing 24 years of 
simultaneous declination records at Toronto and at Prague, the setting 
being in each case from the maximum of the corresponding Kew tem- 
perature record for the same 24 years. 

In this comparison all the Inequalities, great and small, may be 
imagined as made use of, and the influence of disturbance eliminated 
at least to a great extent. 

10. The results of this process are exhibited in the following table, 
and they may be at once compared with those given in Tables II and 
iV. For the purpose of this comparison we have transferred the 
starting points of the modified Inequalities to the solar minimum, so 
as to make them comparable with those of the previous tables. We 
can easily make the change from the knowledge derived from our 
previous paper that the Kew temperature maximum is about 2 days 
before the solar maximum. 

The Toronto declination Inequality for 24 days is not greatly 
altered by the modified process. 

In the Prague declination Inequality for 24 days the modification 
produced causes the two maxima to be more clearly separated from 
one another. 

In both of these Inequalities as modified, the great maximum is not 
lon^ after the solar maximum. 

If we turn next to the Inequalities around 26 days, we find that for 
Toronto the subsidiary maximum of Table IV becomes when modified 
the predominant one, and the prominent maximum of Table IV the 

VOL. XL. ^ 



230 



Prof. B. Stewart and Mr. W. L. Carpenter. [Feb. 25, 



subsidiary one, while there is no striking alteration in the Pragae 
Inequality. 

Table V. — ^Modified Values with Disturbances supposed to be 

Reduced. 



Toronto 


Prague 


Toronto 


Prague 


declination, 


declination, 


declination, 


declination, 


24 days. 


24 days. 


26 days. 


26 days. 


-31 


- 7 


+ 38 


+ 60 


-29 


- 9 


+ 37 


+ 64 


-22 


-11 


+ 39 


+ 63 


-12 


-12 


+ 37 


+ 71 


- 7 


- 9 


+ 36 


+ 61 


+ 1 


- 1 


■r23 


+ 60 


+ 9 


+ 3 


+ 5 


+ 30 


+ 17 


+ 5 


-10 


+ 28 


+ 29 


+ 6 


-19 


+ 32 


+ 36 


- 4 


-19 


+ 30 


+ 41 


- 9 


-26 


+ 16 


+ 44 


-12 


-31 


-15 


+ 40 


-13 


-43 


-40 


+ 37 


+ 1 


-41 


-59 


+ 29 


+ 17 


-29' 


-55 


+ 14 


+ 29 


-12 


-38 


- 1 


+ 36 


+ 3 


-16 


-17 


+ 33 


+ 7 


- 6 


-30 


+ 18 


+ 1 


- 8 


-32 


+ 1 


-17 


-36 


-31 


-12 


-29 


-67 


-27 


-20 


-24 


-98 


-27 


-18 


- 4 


-84 


-31 


-11 


+ 16 


-44 


• • 


• • 


+ 29 


+ 10 


• • 


• • 


+ 33 


+ 51 



Thus the result has been to do away with that want of similarity 
between the Toronto and Prague 26»day Inequalities which appeared 
in Table IV, and to substitute two series in which the predominant 
maximum of the one is near in position to that of the other, and the 
subsidiary maximum of the one near in position to that of the other. 

Nevertheless, the predominant maxima of the 24-day Inequalities 
sgree most nearly in position with the subsidiary maxima of the 
26-day Inequalities. In fine, the Inequalities around 26 days are dif- 
ferent from those around 24 days in much the same way for both 
stations. 

11. It appears to us that these results are in favour of there being 
some physical difference between the Inequalities around 24 days and 
those around 26 days, or at least we may use this as a working hypo- 
thesis. Professor Stokes has suggested that an outbreak of solar 



1886.] Sunrspot Areas and Diurnal DeclinaJtionrranges. 231 

octiyity wonld probably alter the quality as well as the quantity of 
the solar rays, so as to bring in a greater proportion of those which 
are absorbed in the upper regions of the atmosphere. We might pro- 
bably thus expect a set of terrestrial actions following promptly after 
the solar outbreak. This is similar to what we have more especially in 
the magnetic Inequalities around 24 days. 

On the other hand, if the Inequalities around 26 days are due to the 
earth's being placed in a favourable position for receiving the solar 
influence, we shall have a state of things physically different from that 
which we imagine to characterise the Inequalities around 24 days, and 
in our ignorance of the exact way in which the sun influences the 
m^netism of the earth, we cannot assert that the Inequality pro- 
duced in the o^e case will be necessarily the same as that produced in 
the other. 

Apparent Progress of Magnetic Weather. 

12. In order to prevent ambiguity, it is desirable to define what we 
mean by the apparent progress of magnetic weather. If a particular 
fitate of declination diurnal range — a maximum for instance — ^be 
found to occur at Prague four days after it occurs at Toronto, and if 
there is reason to believe that this difference in time depends upon the 
distance between the stations, we should characterise the phenomenon 
by termiug it an apparent progress of magnetic weather from west to 
cast. But this phrase must not be regarded as implying any theoreti- 
cal explanation of the observed fact, or as asserting that it is an actual 
progress of matter in the direction from west to east which gives rise 
to the phenomenon. 

It is obvious that if such a progression exists it will be most readily 
seen in the undisturbed observations, for it is one of the characteris- 
tics of a disturbance to occur simultaneously or nearly so at stations 
far apart, while it is another characteristic to exalt the daily range. 
Hence if disturbances possess periodicity, the maxima of their 
periods might be expected to occur simultaneously or nearly so at 
stations far apart. Magnetical weather is, however, something 
different from disturbances, and denotes, as we have used the term, a 
particular state or value of undisturbed diurnal magnetic range, just 
as a particular state or value of diurnal temperature-range may be said 
to denote a particular kind of meteorological weather. Again, in cer- 
tain preliminary investigations evidence has been given by one of us 
tending to show that there is possibly a progress of magnetic weather 
from west to east. But it is clear that in making a comparison of this 
nature not only must we get rid of disturbances as much as possible, 
but we must likewise limit our comparison to Inequalities of the same 
type or nearly so. Now both of these conditions are possessed by the 
eries of Table Y, for in the first place we may imagine that they are 



832 



Prof. B. Stewart and Mr. W. L. Carpenter. [Feb. 25^ 



nearly freed from distnrbanoey and in the next place the two aeries are 
very mnch alike in type. 

13. In order to compare the Inequalities of Table Y we may con. 
sider the Pragae series as stationary and the Toronto as morable, and 
take the algebraic addition of the two series in yarions relative posi- 
tions. For instance, Toronto pnlled backwards one or two diyisions 
(days) to the left; both together; Toronto poshed forward I9 2, 3^ 
4, 5, ACf diyisions to the right. The algebraic snm of the two will 
give the greatest range when the corresponding phases of the two- 
Ineqnalities are most nearly together. 

The following is the result obtained by this method of com- 
parison: — 

Table VI. 



24-daj Inequalities. 

Joint area 
of both. 

Toionto 2 to lef t 694 

1 „ 676 

Together 738 

Toronto 1 to right 776 



II 



II 
II 

ft 
ft 



ft 



tt 
II 

19 
II 



2 
3 
4 

5 

6 
7 
8 
9 
10 



II 
II 
II 

i> 
)i 
fi 
II 
II 
tt 



804"^ 

796 

794 

794 

792^ 

770 

742 

726 

694 



26-daj Inequalities. 

Joint 
of both 
Toronto 2 to left 1822 

,1 1 ,1 1448 

Together 1560 

Toronto 1 to right 162a 



II 

fi 
»> 
)i 
II 
II 



2 
3 
4 

5 
6 

7 



I) 
I* 
f) 
II 
it 
ft 



1658 
1670 
1642 
1574 
1532 
1500 



For the 24-day Inequalities the position of maximum area is some- 
what undecided, the numbers brsicketed being practically the same. 
On the whole we may consider that the middle point of this region^ 
which denotes " Toronto 4 to the right," expresses the nearest coin- 
cidence in phase. 

For the 26-day Inequalities the maximum is when Toronto is 
pushed three divisions to the right. We may therefore state that as 
far as this comparison is concerned, a given phase occurs at Toronta 
three or four days before it occurs at Pragae. In this preliminary in- 
vestigation no account has been taken of the difference in longitude 
between the two stations as affecting the strict simultaneity of the 
diurnal ranges. 

Comparison between Temperature-ranges a/nd Declination-ranges. 

14. The Toronto temperature-ranges and the Prague declination- 
ranges are for the same series of 36 years, and if we compare 
together the corresponding Inequalities of these ranges as given in 
Tables I and III, we obtain the following result by taking the 

Hi — 



1886.] Sunrspot Areas and Diunuxl Declinattan-ranges. 233 

Toronto Prague Toronto Pragne 

Temperature-range, Beelination-range, Temperature-range, Declination-range, 

24 days. 24 days. 26 days. 26 days. 

4735 4795 5293 6316 

We may conclnde from this comparison tliat, as treated by onr 
method, the declination-ranges and temperatnre-ranges exhibit 
Inequalities pretty much of the same magnitude. There is a slight 
excess of the declination over the temperatore for the 26-day In. 
equalities, but these, being larger, may possibly be influenced by the 
results of disturbance to a greater extent than those around 24 days. 
Disturbance would doubtless increase the range. 

Again, while both kinds of Inequalities are very much of the same 
size, the results of this and of our previous paper lead us to conclude 
that the one set of Inequalities does not exhibit a closer correspondence 
-with sun-spots than the other, so that as far as our experience goes 
there is no reason for saying that for short-period solar Inequalities 
the terrestrial result is more marked in magnetism than in me- 
teorology. 

15. It is perhaps worth while to exhibit the connexion between the 
temperatnre-range and the declination-range Inequalities in the fol- 
lowing manner (p. 234). 

We have already (Art. 9) mentioned how the Kew temperature- 
ranges were used by us for setting the Inequalities whose mean result 
is given in Table V. Now if there be no perceptible physical relation 
between temperature-range and declination-range, the declination- 
range Inequalities set by this method should have their corresponding 
phases distributed at random impartially up and down the paper. In 
Table VII we have exhibited the individual series representing 
Prague declination-ranges around 26 days that have been set by this 
method, only in order to save space we have grouped them into threes 
(with due regard to phase). It will, we think, be seen from this 
table that, with comparatively few exceptions, minus numbers are 
grouped together in the upper part of the table, and plus numbers in 
the lower. 

The result is thus, in our opinion, in favour of that hypothesis 
which asserts a physical relationship between the two Inequalities. 



Prof. B. Stewart and Mr. W, L. Carpeiiter. [Feb. 25 



1 

s 


isHiPlliipSijiJiijH^^^^ 


3 

S 

+ 


Si»538--5SS=S33«8EiSS5l«i!S 


SS"l!Ssl5||i5SS63jSSEs5B 


7, 


SiSSI=ss558jjsg54Ss3SiBSS» 


5 


J.i;=sj3IJS5SS5553SI85Sil!3i3 


2 
2 


++ 'Ill I+T++++1 1*^*+ 


usrfi'nKimnnnmiK 


-f 




? 


i;i5IS=iS=SSi:a'Sa5ii"SiiS!B5i= 


■; 


iPi!3SS7S5S=rssS3==3SSIS 






3 




^ 





On BadkaU Matter Sptetrotcopy. 



[Feb. 25, 



II. " On Radiant Matter 8pectroHoop7 : Note on tlie Earth T«." 
By WiLilAM C^OOKES, FJl.8. Beceived Febnuiy 18, 
1886. 
Among the samankite sarthfl whioli ooiioeiiti»t« towards the 
middle of the fiaodoaations there is one (or a gronp) which prefleott 
in the radiant matter tube a well marked pbosphoreaoent spectmm 
differing from thoae T have already described. 
The measarementa of the bands and lines are s^ven below : — 



BMleof 


X. 


1 
X' 


B«muki. 


10 MS" 


6M6 


M07 


•UM off on tho IsMt rafnn- 

gible dde. 
Somewhat iharp edge of the red 

band. 
Approiimate contro of a Teiy 

faint orange band. 








10-310 


MIS 


S430 


10 196 


6189 


2611 


10-130 


6094 


2693 


A sharp narrow orange-red line. 


10 060 


6970 


2806 


Approximate centre of a narrow 
bright orange band. (Between 
thi. Une and 2693 ia a faint«r 


9-840 


5676 


8104 


bright green band. 


9 790 


6613 


3174 


Approiimate centre of ft narrow 
green band, not quite so bright 
ae 3104. 


9-690 


B496 


3312 


Approiimate centre of a bright 
green band, widor than the 
other three green bands. 


g-610 


6406 


8122 


ApproiimaHi centre of a narrow 
bright green band. 









The accompanying figare gives the spectrum drawn to the -^ scale. 




The earth giving the above spectrnm, when sufficiently pnriGed, 

presents all the characteristics of the earth discovered by Marignac, 

and provisionally called by him Ya.* Through the kindness of M. de 

* "Comptei re&dus," xo, p. 899. 



1886.] 



Candidates for Election. 



287 



Marignac I have been enabled to compare a specimen of Ya of his 
own preparation with the earth described above. The two earths 
agree in their chemical characteristics, and their phosphorescent 
spectra are practically identical. 

No name has jet been given to this earth, as M. de Marignac appears 
to be in some doubt whether it is not identical with J. Lawrence 
Smith's earth mosandra.* A specimen of mosandra prepared by 
J. Lawrence Smith, and sent me by M. de Marignac, gave a phospho- 
rescent spectrum showing that it was compound, and that yttria was 
one of its constituents. 



March 4, 1886. 

Professor G. G. STOKES, D.C.L., President, in the Chair. 

The Presents received were laid on the table and thanks ordered for 
them. 

In pursuance of the Statutes, the names of the Candidates recom- 
mended for election into the Society were read from the Chair, as 
follows : — 



Atkinson, Prof. Edmund, Ph.D. 
Bidwell, Shelford, M.A. 
Bosanquet, Robert Halford Mac- 

dowall, M.A. 
Boys, Charles Vernon, A.B.S.M. 
Buchanan, John Young, M.A. 
Burdett, Henry Charles, F.S.S. 
Buzzard, Thomas, M.D. 
Cameron, Sir Charles Alexander, 

M.D. 
Cash, J. Theodore, M.D. 
Claudet, Frederic, F.C.S. 
Colenso, WiUiam, F.L.S. 
Corfield, Prof. William Henry, 

M.D. 
Curtis, Arthur Hill, D.Sc. 
Davis, James William, F.G.S. 
Denton, John Bailey, M.I.C.E. 
Dixon, Harold B., M.A. 
Douglass, Sir James Nicholas, 

M.LC.E. 
Ewart, Professor J. Cossar, M.D. 



Ewing, Professor J. A., B.Sc. 

Posting, Edward Robert, Major- 
General, R.E. 

Forbes, Professor George, M.A. 

Forsyth, Andrew Russell, M.A. 

Foster, Professor BalthazarWalter, 
F.R.C.P. 

Galloway, William. 

Gowers, William Richard, M.D. 

Green, Professor A. H., M.A. 

Hinde, George Jennings, Ph.D. 

Horsley, Prof. Victor, F.R.C.S. 

Latham, Peter Wallwork, M.D. 

Lewis, Timothy Richards, M.B., 
Surgeon-Major, A^M.D. 

MacGillivray, Paul Howard, 
M.A. 

Manson, Patrick, M.D. 

Meldola, Raphael, F.R.A.S. 

Milne, Professor John, F.G.S. 

Moxon, Walter, M.D. 

Ord, William Miller, M.D. 



Comptes rendus/' Ixxxvii, p. 145 j Ixxxrii, p. 831 *, bLxiix^ '^. 4^. 



238 



Captam Abnej and Major-General Festing. [Mar. 4r 



Palmer, Henry Spencer, Colonel 

R.E. 
Pickard-Cambridge, Brev. Octa- 

vins, M.A. 
Poynting, Prof. John Henry, 

B.Se. 
Pritchard, Urban, M.D. 
Pye-Smith, Philip H., M.D. 
Bamsay, Professor William, Ph.D. 
Ilodwell, George F., F.R.A.S. 
Bnssell, Henry Chamberlaine, 

B.A. 
Sanders, Alfred, P.L.S. 
Sedgwick, Adam, M.A. 
Snelus, George James, F.C.S. 
SoUas, Professor William Johnson, 

D.Sc. 



Stevenson, Thomas, M.D. 

Tate, Professor Ralph, P.G.S. 

Teale, Thomas Pridgin, F.R.C.S. 

Tenison- Woods, Bev. Julian E., 
M.A 

Tidy, Prof. Charles Meymotfc, M.B. 

. Tonge, Morris, M.D. 

Topley, William, F.G.S. 

Unwin, Prof. W. Cawthome, B.Sc. 

Warington, Bobert, F.C.S. 

Wharton, William James Lloyd, 
Captain B.N. 

Whitaker, William, B.A. 

White, William Henry. 

Wilde, Henry. 

Wright, Professor Edward Per- 
ceval, M.A. 



The Bakerian Lecture was then delivered as follows : — 



L The Bakerun Lecture. — "Colour Photometry." By 
Captain Abney, R.E., F.R.S., and Major-General Festikg, 

(Abstract.) 

One of the authors of this paper has already communicated to the 
Physical Society of London (" Phil. Mag.,'* 1885) a method by which 
a patch of monochromatic light could be thrown on a screen. This 
formed the starting point of the present investigation, which was to 
ascertain whether it was practicable to compare with each other the 
intensity of lights of different colours. 

The authors describe various plans they adopted to effect this 
purpose, and finally found that by placing a rod in front of the patch 
of monochromatic light, and of a candle by casting another shadow, the 
intensities of the two lights could be compared by what they term an 
oscillation method. It is known that on each side of the yellow of 
the spectrum the luminosity more or less rapidly decreases. By 
placing a candle at such a distance from the screen that the luminosity 
of the two shadows appears as approximately equal, it is easy to oscil- 
late the card carrying the slit through which the monochromatic rays 
of the spectrum pass. (The slit is in the focus of the lens which helps 
to form the spectrum.) The shadow of the rod cast by the candle can 
thus be made to appear alternately ** too light " or ** too dark " in com- 
parison with the shadow of the rod cast by the parts of the spectrum 
falling on the screen. By a rapid oscillation the position of equality 



1886.1 Colour Photomeiru. 239 

of tho two shadows can be distingnished with great exactness. The 
authors describe their method of fixing the position of the rajs employed 
and the source of light with which the spectrum is formed. Thej also 
enter into details as to the comparison light, the receiving screen, 
and the comparative value of the light as seen by them respectively. 
The curve of the intensity of the arc light spectrum, as seen by their 
eyes, which they call the normal curve, is then described. The 
question as to the effect of an alteration of the colour of the com- 
parison light is then discussed, as is the effect of the brightness of the 
spectrum. 

The next point touched upon is as to the value of mixed light as 
compared with its components. It is found that the following law 
holds good, viz. : fliat " ths sum of the intensities of two or more colours 
is equal to the intensity of the scmie rays when mixed^ This law is 
applied to Hering's theory of colour. 

The authors next state that with the majority of people the curve 
of luminosity of the spectrum is identical with the normal curve, but 
that in some cases slight differences may be observed, of which one 
example is given. Such slight deficiency does not constitute colour- 
blindness, since the want of appreciation of any colour is but very 
partial. They next describe observations made by four colour-blind 
persons, and show that there is a remarkable divergence in their 
curves from the normal. The deficiency curves are shown, irom 
which it appears that two of the observers are totally blind to red, 
whilst the other two are partially so. They then show that such 
observers would not give a true value for any light which is not of 
identically the same colour as the comparison light they might 
employ. It also appears that the intensity of illumination felt by 
a colour-blind is really less than that perceived by a normal-eyed 
person. 

Two examples of the normal curve for sunlight are then given, one 
taken on a day in July by the method of separating close lines by 
means of varying illumination, and the other in November, by the 
method adopted by the authors. Their results are compared with 
Vierordt's curve, obtained by extinguishing colour with white light. 

In order to ascertain the effect of the turbidity of a medium through 
which light passes (for instance sunlight), the authors compared the 
intensity of the spectrum after passing through clear water and turbid 
water, and found that the absorption agreed with Lord Kayleigh's 
theoretical deductions that I'=Iq6"'***'"*, where I' is the intensity after 
passing through a turbid medium, Iq the intensity after passing 
through clear water, x the thickness of the turbid layer, h a constant 
independent of X, \ being the wave length. 

The authors conclude their paper with a discussion of the intensity 
of incandescence of carbon electrically heated. 



240 Mr. H. Tomlinson. The Influence of [Mar. 11, 



March 11, 1886. 

Professor STOKES, D.G.L., President, in the Gbair. 

The Presents received were laid on the table, and thanks ordered 
ior them. 

The following Papers were read : — 

I. "The Influence of Stress and Strain on the Physical 
Properties of Matter. Part I. Elasticity — continued. The 
Internal Friction of Metals." By Herbert Tomlinson, B.A. 
Communicated by Professor W. Grylls Adams, M.A., 
F.R.S. Received February 18, 1886. 

(Abstract.) 

An abstract of a paper on this subject has been alreadjr published,* 
but the paper itself was withdrawn for the purpose of revision. The 
fresh experiments which have been for this purpose instituted during 
the last year were made with improved apparatus, and the coefficient 
of viscosity of air redetermined, with a view of enabling the author 
to make more accurate correction for the effect of the resistance of the 
air.f These more recent experiments on the loss of energy of a 
torsionally vibrating wire, Jjesides confirming the results of the older 
ones, as far as the latter have been published, have furnished, more or 
less in addition, the following facts relating to the internal molecular 
friction of metals : — 

The proportionate diminution of amplitude is independent of the 
amplitude, provided the deformations produced do not exceed a certain 
limit. This limit varies with the nature of the metal, and is for 
nickel very low. 

The logarithmic decrement of amplitude increases with the length 
of the vibration-period, but in a less proportion than the latter, and 
in a diminishing ratio. The amount of increase of the logarithmic 
decrement, attending on a given increase through a given range of 
the vibration-period, varies with the nature of the metal, and with 
those metals which possess comparatively small internal friction 
becomes almost insensible. It follows as a consequence that the 

• *' Proc. Roy. Soc," vol. 38, p. 42. 

t An abstracted account of this redetermination was read before the Royal 
Society, January 14, 1886. 



1886.] Stress and Strain on the Propertiee of Matter. 241 

internal friction of metals differs from the viscosity of fluids, for in 
cases of damping by the latter the logarithmic decrement is inveraehf 
as the length of the vibration-period. 

Permanent molecular strain resulting from loading not carried to 
a sufficient extent to produce sensible permanent extension, diminishes 
the internal friction, and increases the torsional elasticity. 

Considerable permanent longitudinal extension and permanent 
torsion produce increase of internal friction and diminution of tor- 
sional elasticity. The effect of torsion is much greater than that of 
extension, and the increase of internal friction is much greater than 
the decrease of torsional elasticity. As a consequence wire-drawing, 
where we have permanent extension and torsion combined, sometimes 
increases enormously the internal friction ; in fact in the case of six 
different metals, it was found that by careful annealing the internal 
friction was decreased from one-half to one-thirtieth of the original 
amount of friction of the metals in the hard-drawn condition. Almost 
equally remarkable is the effect of rapid fluctuations of temperature, 
even through ranges of only one or two degrees centigrade, in in* 
creasing the internal friction. 

The internal friction of a metal wire, whether in the hard-drawn 
or annealed condition, is temporarily decreased, and the torsional 
elasticity is temporarily increased by loading not carried beyond a 
certain limit, beyond this limit both the friction and the elasticity 
become independent of the load. 

The "fatigue of elasticity," discovered by Sir William Thomson 
in metal wires when vibrating torsionally, is not felt, provided the 
deformations produced do not exceed a certain limit, depending upon 
the nature of the metal. The above-mentioned limit is extraordi- 
narily low for nickel, so low, indeed, that it is difficult to avoid 
" elastic fatigue " with this metal. This last consideration, and others 
founded on the results of experiments on the effects of stress on the 
physical properties of nickel, tend to show that the molecules of this 
metal are comparatively easily rotated about their axes. 

The author agrees with Prof. Q. Wiedemann, that the loss of 
energy due to internal friction in a torsionally vibrating wire is mainly 
due to the to-and-fro rotation of the molecales about their axes ; any 
cause, therefore, which increases the molecular rotatory elasticity 
diminishes the internal friction, and conversely. The author has, by 
various means, succeeded in bringing down the internal friction to 
snob an extent that, in the case of one wire, it would have required 
upwards of 15,000 vibrations to diminish the amplitude to one-half 
of its initial value, provided the vibrations had been executed in 
vacuo. 

The molecules of a metal tend to creep into such positions as 
will ensure a maximum molecular rotatory elasticity, and they can bo 



842 Mr. B. Lachlan. [liar. 11, 

assisted in doing so bj agitations effected either by thermal or 
mechanical agency ; hence — 

Best after suspension, aided by oscillations at intervals, <1iTnintiJifly 
the internal friction of a wire which has been recently suspended, or 
which after a long suspension has been subjected to considerable 
molecular agitation by either mechanical or thermal agency. 

On the contrary, when a maximum molecular rotatory elasticily 
has been reached, molecular agitation, if carried beyond a certain 
limit, diminishes the elasticity ; hence the results of " &tigue of elas- 
ticity ;" and hence — 

Mechanical shocks and rapid fluctuations of temperature beyond 
certain limits may considerably increase the internal friction, and, 
though to a much less extent, diminish the torsional elasticity. 

The logarithmic decrement is independent of both the length and 
diameter of the wire. 



II. ** On Systems of Circles and Spheres." By E. Lachlan, 
B.A., Fellow of Trinity College, Cambridge. Communicated 
by Professor A. Cayley, F.E.S. Eeceived February 23, 1886. 

(Abstract.) 

This memoir is an attempt to develop the ideas contained in two 
papers to be found in the volume of Clifford's Mathematical Papers 
(Macmillau, 1882), viz., ** On Power Coordinates *' (pp. 546 — 555), 
and " On the Powers of Spheres " (pp. 332—336) ; the date of the 
former is stated to be 1866, and of the latter 1868, but the editor 
explains (see p. xxii, and note, p. 332) that though these papers 
probably contain the substance of a paper read to the London Mathe- 
matical Society, February 27, 1868, " On Circles and Spheres " (" Proc. 
L. M. S.," vol. ii, p. 61), they were probably not written out before 
1876. It is possible, therefore, that Clifford may be indebted to 
Darboux for the conception of the ^^ power of two circles," or spheres, 
as an extension of Stein er's use of the ^^ power of a point with respect 
to a circle. Darboux was the first to give the definition of the power 
of two circles, in a paper " Sui* les Belations entre les Groupes de 
Points, de Cercles, et de Spheres" ("Annales de Tficole Normale 
Superieure," vol. i, p. 323, 1872), in which some theorems analogous 
to the fundamental theorem of this memoir are proved. 

This memoir is divided into three Parts : Part I consists of the 
discussion of systems of circles in one plane ; Part II of systems of 
circles on the surface of a sphere ; and Part III of systems of spheres. 

The power of two circles is defined to be the squai*e of the distance 
between their centres less the sum of the squares of their radii. 



1886.] 



On Systems of Circles and Spheres. 



243 



Denoting the power of two circles (1, 2) by wi^^ it is proved that 
the power of any five cirdes (1, 2, 3, 4, 5) with respect to any other 
circles (6, 7, 8, 9, 10) are connected by the relation — 



'^4^ » ^^4.7 > ^4.8 



'^2.9 » ^2,10 
^Z,^ > *'8.10 

*'6,» > ^B.10 



= 



which may be conveniently written : — 



^Gb* ?! 8, i 10 



;)=o. 



This is the fundamental theorem of the paper ; it is shown that if 
the power of a straight line and a circle be defined as the perpen- 
dicidar from the centre of the circle on the stiuight line, and the 
power of two straight lines as the cosine of the angle between them : 
then the theorem is tme if any of the circles of either system be 
replaced by points, straight lines, or the line at infinity. 

Several special systems of circles are then discussed, the most 
remarkable perhaps being the case when the circles (1, 2, 3, 4) being 
given, the circles (5, 6, 7, 8) ai'e orthogonal to the former taken 
three at a time; then (x, y), denoting any other circles, the 
equation — 

T(;;i:J:?:J)=o 

becomes tt,,, = ^LlZVd + ^M_l_^2 ^ ^^.7 - ^y^ ^. ^'s - ^9A 



1.6 



2,6 



'8,7 



'4.8 



and as a particular case when the two circles {x, y) are replaced by 
the line at an infinity, we have 

J_+J-+J-+J-=0. 



'^LB '^S.e '^3,7 ^^4,8 

The general theorem is then applied to prove some properties of 
circles connected with three circles ; a formula is given for the radius 
of a circle which passes through three of the points of intersection of 
three given circles ; the eight circles which can be drawn to touch 
three circles are shown to be each touched by four of eight other 
circles, called Dr. Hart's circles, these arrange themselves in pairs ; 
if />, p' be the radii of a pair of Dr. Hart's circles, and B, B' the 
radii of the corresponding pair of the eight circles passing through 
the points of intersection of the given circles, it is shown that 



P p' U~B7 



SM MBLtLlmthhrn FKi^II, 







^i^ ^^^ 



1 t %r 



TiimatuLt uui % hs/abotpeutna ^^misas iMBriiii tmleA the 
fMS^ iLMfm die fiynirrrn of s&isr f=fii ^skect an ggwcr-cBBnffmtnt 

ffn^8P!MSQ» sb easT'iie:, Tahem h htmai^SgA %t t&e oaan£ziaaB cf tbe fine 

lUi sflkT "ht if*iM>.'<yi to <Kw of 



«^-rV-»'«'-ri«^=-> (A) 

Oe ftlwslaie bciBf x'-r f-^ ^^ mh=^Oi 

m a^'riy+£i'=:0 (B) 

«»+2/yx =0 (C) 

Ik simulate being s*-^/— 4nr=:0. 

TIm; dHf«r«Dt Carres are then discaaBed in detaO, there being nine 
i^M«ies m all, three in each group (A), (B), or (C). 

Part II ooDtaina merelj the extension of the results of Pari I to 
apfaerical geometrj ; the power of two circles on a sphere is defined to 
be the prrjduct of tan r, tan t\ cos tr, where r, /, are the radii, v tbeir 
angle dT interMction ; the power of a small circle radius r, and a great 
circle is, howeyer, defined as tan r cos tr ; and of two great circles as 

COS m. 

The fundamental theorem is as before 

connecting the powers of two systems of circles. 

Consequently the results obtained preyiouslj are extended with 
but slight modification. 

In Part III the method of Part I is applied to spheres ; it is proved 
at once that the powers of any systems of spheres must satisfy the 
relation 

^\f\ 8.' 0. lOk 11. u) =^> 

and any of the spheres may be replaced by planes, or the plane at 
mBmty, 
Several results obtained in Part 1 «kxe e^ja^Tl^ extonded, with one 



1886.] On Sy.items of Circles and K>jJieres, 245 

exoeption ; there are eight pairs of spheres which toach four given 
spheres, bat except in very special cases no spheres exist analogous 
to Dr. Hart's circles. 

The discussion of the equation of the first degree ia power-ooordi- 
nates is much the same as that in Part I. The reduction, however, 
of the general equation of the second degree is more complicated ; 
tiiere are four distinct forms to which the equation majr be reduced. 

aa^ + bi/^-{-cz^ + dto^+ev^=0 (a) 

the equation of the absolute being 

this is the general cjclide, of either the fourth or third order ; if (2 =s e, 
it has two cnic-nodes. and if 6 = c, d = e, it has four cnic-nodes ; bat 
in this case the sphere a; = must be imaginary. 

ax*^ht^'^ci^+duf=0 (/3) 

the equation of the absolute being 

This is the general case of a cyclide having one cnic-node, if 5 = c it 
Has three nodes ; the former ease is the inverse of a cenk^l quadric, 
the latter the inverse of a central quadric of revolution : the spheres 
^ y, z are real in this case. 

ax*'\'hy^'\'2hzw=0 (7) 

the equation of the absolute being 

This represents dr cyclide having two principal spheres and a binode ; 
if a or & = the node is a unode. 

ax'''\'2hijz + dw'=0 (0 

the equation of the absolute being 

This represents a cyclide having only one principal sphere ; and 
a cnic-node, which becomes a binode when a = 0, and a unode when 
A = 0. 

The different species of cyclides are then briefly discussed in 
detail. 



VOfj. XL. ^ 



216 Prof. J. A. Ewing. [Mjir. 11, 



III. *' Effects of Stress and Magnetisation on the Thermo- 
electric QuaKty of Iron." B7 Professor J. A. EwiNG, B.Sc., 
University College, Dundee. Oommnnicated by Sir 
William Thomson, F.R.S. Received February 24, 1886. 

(Abstract.) 

This paper con^prises a revised version of one snbmitted to the 
Bojal Society in 1881, under the title "Effects of Stress on the 
Thermoelectric Quality of Metals, Part I,"* along with much new 
matter. It deals principally with the cyclic changes of thermoelectric 
quality which an iron wire undergoes when exposed to cyclic variations 
of stress (described in the abstract of the former paper), and with 
the relations of these changes of thermoelectric quality to the changes 
of magnetism which also occur as an effect of stress. Stress was 
applied by exposing the wire to longitudinal pull by means of loads. 
The changes both of thermoelectric quality and of magnetism exhibit 
that tendency to lag behind the changes of stress to which in a 
previous paperf the author gave the name hysteresis, and the effects 
are sufficiently similar in regard to the two qualities to suggest that 
the changes of thermoelectric quality occur as secondary effects of 
changes of magnetism. To examine whether this is the case, simul- 
taneous measurements of the magnetic and thermoelectric effects of 
stress in an iron wire were made, and also independent observations of 
the thermoelectric effects of magnetisation, without change of stress. 
A companson of these made it clear that stress causes change in 
thermoelectric quality of iron directly, and not as a secondary effect 
of magnetisation. If the wire be completely demagnetised to begin 
with, and kept clear of all magnetisation during the application and 
removal of stress, the presence of liysteresis is not less marked than 
before. P]xperiments are given to show how the thermoelectric effects 
of stress are modified by the existence of more or less magnetisation 
in the wire ; and conversely, how the thermoelectric effects of mag- 
netism are modified by the existence of more or less constant stress. 
The influence of vibration in destroying the effects of hysteresis is 
investigated, and also the result of exposing the wire to the process of 
demagnetising by repeated rapid reversals of a continuously dimi- 
nishing magnetising force, and it is shown that this process acts in 
the same way as vibration in destroying the effects of hysteresis. 
Residual effects of hysteresis are studied, as, for example, the diffe- 
rence which presents itself when a wire is magnetised after having 

• Published in abstract in " Proo. Roy. Soc," No. 214^ 1881. 
t " Proc. Roy. Soc.," No. 216, 1881, p. 22. 



I886.J Effects of Strett and Moffnetiaation on Iron. 247 

been loaded Btrongly and then unloaded down to a certain conetant 
state of Btrees, and, on the other hand, when the same state of stresB 
has been prodnced by (limplj increasing the load ; and it is shown that 
these residaal effects are wiped oat by vibration or by demagnetising 
by reversals. With regard to the effect of stress on thermoelectric 
qnalily, it is shown that if a somewhat soft wire be more and more 
strongly magnetised, these effects become more and more similar to 
those which are found when the wire is hard drawn, bnt not magnet- 
ised. A few experiments were made with wires of silver, copper, 
lead, magnesinm, and German silver, bnt in none of these was 
hysteresis of thermoelectric quality with regard to load discovered. 

Special attention is directed to a peculiar featnre in the carves by 
means of which the experimental reeolts are exhibited. In cnrven 
showing the relation of thermoelectric electromotive force to load, it 
is shown that any reversal from loading to unloading, or vice versS, 
causes an inflection in the curve, the first effect of the new process 
being to continue the kind of change that was going on before. That 
this is not due to any mechanical disturbance which the loading or 
unloading produces, is shown by the fact that it occurs ia an equally 
marked way after the molecnles have been brought to a condition of 
stable equilibrium by vibratiug the wire before beginning to load or 
unload. It is suggested that the effects of hysteresis, described in the 
paper, have a possible relation to the properties which Professor 
. Oabome Reynolds has recently shown to be possessed by granular 
media. 

The experiments described in the paper are closely connected with 
those which were communicated in January, 1885, under the title 
"Experimental Researches in Magnetism," and are now being pub- 
lished by the Society, They were conducted in the Physical Labora- 
tory of the University of Tokio, in 1881-3, partly with the help of 
, one of the author's Japani.-se students, Mr. P. S. Satcai. The results 
I are given graphically, and ai-e for the most pai-t reduced to absolute 



248 TVuvttM and MeUarologieal PhenwmmL 




March 18, 1886. 

Professor O. G. STOKES, D.C.L., Pragideat, in the Chab. 

The Presents received were laid on tlie table, and thanks ordered 
for them. 

The following Papers were read : — 

I. " The Relationship of the Activity of Vesnvins to Certain 
Meteorological and Astronomical Phenomena." By Dr. H. J. 
Johnston-Lavis. Communicated by Professor Judd, F.R.S. 
Received February 26, 1886. 

(Abstract). 

The determination of the relations, if any snoh exist, between 
volcanic activity and certain astronomical or meteorological pheno- 
mena, cannot fail to throw much light apon the vexed question of the 
solid or liquid condition of the earth's interior. M. Perrey, as the 
result of his careful catalogue of earthquake phenomena, believed 
himself to have proved that these could be shown to have certain 
maxima and minima, which correspond with positions of the moon 
in relation to the earth and sun ; there are many considerations which 
point to the conclusion that great and sudden changes in barometric 
pressure may be followed by outbursts of volcanic violence; and, 
finally, if the eruptions of volcanoes, as many geolog^ts believe, are 
due to water percolating from the surface to a heated magma, rain- 
fall must have no inconsiderable influence in determining the periods 
of their occurrence. { 

The author of the paper has made use of the opportunity of ft 
residence in the neighbourhood of Vesuvius, to chronicle, according 
to a scale devised by himself, the varying quantities of vapour emitted 
from the crater during its usual quiet and continued (Strombolian) 
stage of eruption ; the period of every new outflow of lava, or of any 
increase in the flow of lava was also noted. These observations ^ 
having been carried on daily for a period of one year and nine months 
— from October, 1883, to June, 1885 — were recorded in tabular form 

Bide by side with the moon's quadratures and position in her orbit; 

with tbeae are also arranged t\ie dooY^ tq^^t^^ oil W^t^ height of the 



\' 



1886.] On eatmecHng and diaeanneeting a Rseeiver. 249 

barometer, and the amonnt of rainfall supplied to the antkor by 
Professor Brioschi of the Capodimonte Observatory. 

From the discussion of these tables, it is concluded by the author 
that there is a striking relationship between the curves which mark 
sudden changes in atmospheric pressure and those which indicate 
distinct variations in the volcanic activity. As regards the relation 
of changes in volcanic activity with the lunar positions, the author 
speaks with greater doubt, the period over which the observations 
have extended being insufficient to justify definite conclusions ; but 
he believes that his observations point to distinct tidal influences as 
affecting the liquid magma beneath the volcano. 



11. " On an Apparatus for connecting and disconnecting a 
Receiver under Exhaustion by a Mercurial Pump." By 
J. T. BOTTOMLEY, M.A., F.R.S.E. Communicated by Sir 
William Thomson, F.R.S. Received March 1, 1886. 

In experimental work with vacua, and especially with the high 
vacua given by the Sprengel pump, a connecting tap has often been 
much wished for which would enable the experimenter to remove 
a piece of apparatus from the pump for examination or preliminary 
experiment, and afterwards to reapply it to the pump without dis- 
charging the vacuum. So far as I am aware nothing satisfactory has 
hitherto been suggested. The ground glass stopcocks now made by 
some of the German and English glass workers are undoubtedly very 
highly finished ; but sooner or later, even with the best of them, the 
air begins to work its way round the grinding marks, in spite of lubri- 
cants, and, worse than this, when the apparatus under exhaustion 
has been removed from the pump and gauges, there is no way of 
knowing whether or not the air is leaking in round the interstices of 
the ground glass stopcock. 

To meet this difficulty, I have recently constructed a mercurial 
vacuum tap, which is certainly impervious to air, and which will, I 
think, be found to work easily and conveniently. In coustructing it 
I have taken advantage of a tap described by Mr. C. H. Gimingbam 
('* Proc. Roy. Soc," No. 176, 1876), by means of which a piece of appa- 
ratus may be disconnected from the pump without discharging the 
vacuum of the pump ; and thus by means of the complete tap, which 
I proceed to describe, the apparatus under experiment can be separated 
from the pump and replaced without either the pump or the appa- 
ratus being discharged. 

The tap consists of three parts. AB is a tube containing a glass 
float, of which the upper end is conical, and ground very carefully at 



850 On ecnneeting and dUeomieeting a Receiver. [Mftr. 18, 

aa to fit a conical opening to the npgoing spirit-bore tnbe AM ; and at 
M the apparatus which is to be exhausted woald be blown on^ At C 
there is an ordinary cup and stopper, ground to a very perfect fit, 



Vi 



D 



II 



and the joint at C is made perfectly air-tight in the usual way by 
pouring mercury into the cup. At the lower extremity of the part 
CD is a stopper closed at the bottom, but with a fine hole drilled atp; 
and in the tube of the cup EE there is a fine groove cut, which reaches 
half way up the ground part of the tube and stopper to jp; but above 
p there is a sufficient length of grinding to make a perfect joint.* 
When the hole p is tamed round to meet the groove, there is com- 
manwation through and throngh the tap, that is to say, from the 

• This cup and stopper form Mr. GVmvii^wii^\xi%wv\w»VK^» 



1886.] Effects of the Spectrum on Silver Salts. 251 

pnmp below F to the apparatus attached to M ; but when the opening 
p is turned away from the groove the pump is cut off. 

Suppose now that above p there is a vacuum, and that p is turned 
round so as to cut off the pump. Let the stopper at C be cautiously 
raised. Mercury flows from the cup C, and in the first place fills 
up the space below, and fresh mercury must be supplied to the cup 
and the supply kept up. The whole of the lower part of the space 
being filled, the mercury rises in the tube CB, lifts the glass float, and 
closes the opening aa with great pressure. To hold up the stopper at 
C during the flowing in of the mercury requires considerable force 
with an opening at C of an ordinary size ; but as soon as the whole 
space from da down to the bottom of D has been filled, the part of 
this force which is due to air pressure vanishes, and the stopper may 
be separated from C safely. The mercury in the tube AB does not 
drop out, as the orifice at e is very small ; and thus there is nothing 
to prevent the apparatus under exhaustion being handled in any way 
that may be desired. 

YHien the apparatus is to be reconnected with the pnmp, it is only 
necessary to replace the stopper in the cup C, and turn the hole p 
round to meet its groove. The mercary in the tube AB then drops 
into the pump. The float falls into its lowest position, and everything 
is once more as it was before the removal of the apparatus from the 
pump. 



III. *' Comparative Effects of different parts of the Spectrum on 
Silver Salts." By Captain W. de W. Abney, R.E., F.R.S. 
Received March 2, 1886. 

In 1881 I communicated to the Royal Society (" Proc. Roy. Soc.," 
vol. 33) the results of a research I had made on the comparative 
effects of different parts of the spectrum on the haloid salts of silver, 
and I pointed oat that a mixture of iodide and chloride, and iodide 
and bromide of silver gave rise to a very curious photographic 
spectrum, a minimum of action taking place at Q, the point where the 
iodide is mostly affected, two maxima consequently occurring. 1 
also gave some theoretical reasons why this should be. About a year 
afterwards Herr Schumann, of Leipzic, called in question this result, 
as applied to bromo-iodide of silver, when the two salts were formed 
simultaneously, i.e., when mixtures in water of soluble bromides and 
iodides were precipitated together by silver nitrate. He subse- 
quently found that a mixture of the two salts after separate precipi- 
tation did ^ive rise to a double maximum, ^ow Toy o^iv ^T;.^«tvcaKi3\«» 
showed that in either case such doable maxima ex\E\.^^ \ixsA» ^^^cW'^'s^ 



258 



Captaiu W. de W. Abney. Bfteit of [Mar. 18, 



thej were more marked when the Baits were precipitated aepaistelj, 
Thd only method at that time available to diBtinguish the nuudinit 
was b^ the appearance of a ne^tive photograph of the spectnun 
impreHBed upon it, and hence there was a liability to be deceived, 
sinco densities in deposit which are nearly alike are apt to be over 
looked. 

I Dtiltsed my method (" Phil. Ma^.," 1885) of obtaining patches nf 
monochromatic light from the spectrum, in examining afresh dif- 
ferent salts of silver aa regards sensitivenesB to different rajrs. The 
experiments were conducted in the folkiwing maimer : — A senst- 
tometer, designed by Mr. Sput^, was brought into use (" Photo- 
graphic Journal, " 1882, vol. vi). This consists of a series of small 
chambers, about 1 cm. square in section, and 2 om. deep. Below 
these chambers is a sheet of brass, punctured as shown in the 
tigare, each such poactore correspoadiug with the square chamber. 




Numbers are also punctured in the brass triangle, to correspond to 
the order of intensity in which the light is admitted to each chamber. 
Btlow this brass plate can be placed a sensitive plate to be tested. 
The tops of the chambers are also closed by a brass plate, in which 
hojes of different diameters are punctured. The area of each hole ia 
V2 that of the next, and the total number of chambers is 30. It 
will be thus seen that the difference in light from an equally illu- 
minated surface admitted to the first and last holes is immense. 

To obtain a surface equally illuminated two sheets of finely ground 
glass were used, one placed about one-eighth of an inch from the holes, 
anH tV"" other abont a centimetre away from the first. It was found 



1886.] Different Parts of the Spectrum on Silver Salts. 253 

that when the outside ground glass was illuminated hy a candle about 
3 feet awaj, the light shading every part of the bottom of each 
chamber was for all practical purposes uniform. A patch of mono- 
chromatic solar li^ht from one part of the spectrum was then thrown 
on the ground glass, and an exposure of 30 seconds given to a plate 
in contact with the brass punctured plate at the bottom of the cham- 
bers. Another portion of the spectrum was next thrown on a fresh 
sensitive surface, and a similar operation carried out, and so on till 
the whole of the range of the spectrum had been utilised. Tn each 
set of experiments it is scarcely needful to remark the same batch of 
plates was employed. All the plates were developed together for the 
same length of time, and the number of the chamber noted where no 
photographic action was visible. Thus if No. 8 showed a trace of 
photographic action, and No. 9 showed none. No. 9 was taken as a 
measure. All these numbers were then tabulated, and the admitted 
light calculated. 

Another series of experiments were then conducted precisely as 
before, the length of exposure being varied, and the numbers observed 
were again tabulated and compared with the first set. A third series 
was then taken, and a mean of the results taken. The plates were 
next fixed and the numbers read, and the light again calculated, with 
the result that the mean corresponded with the first mean. As a 
final dheck, each set of plates were printed on uniformly sensitised 
paper, and the gradations obtained by the method described in my 
Treatise on Photography (Longmans). The results obtained were 
almost identical with the first means. Various salts of silver and 
combinations of salts were tried, but I need only give one, which is 
that which has been disputed. The figure gives a graphic description 
of the results obtained. This series of plates was prepared with a 
mixture of 6 per cent, of iodide, and 94 per cent, of bromide of silver, 
and the two were precipitated together. It was somewhat difi&cult 
in a photograph of the spectrum, containing but little iodide, to be 
sure of this dip at G, owing to the occurrence of Fraunhofer lines. 
The method adopted brings the dip clearly into view. It might be 
thought that the strong band of lines near G produced it, but such 
is not the case, as pure bromide of silver without any admixture of 
iodide did not show it, and the one maximum of sensitiveness it 
had lay nearer G. 

In the mixed salt which was experimented upon we thus still get 
two maxima, though the percentage of iodide and bromide is but 
small. The same line of argument which was applied in the paper I 
have already referred to as to the cause of this dip near G, still 
therefore applies. 



254 



On Matter in the Gaeeaus and Liquid States. [Mar. 18, 



Table of Intensities. 



Scale No. 



Intensitj. 



26 
28 
30 
31 
82 
33 
34 
35 
36 
37 
38 
89 
40 
41 
42 
44 
46 



7 
14 
43 
75 
100 
95 
66 
43 
37 
25 
33 
28 
25 
20 
18 
12 
10 




3 




5 

5 

5 
5 



5 




I\^ **0n the Properties of Matter in the Gaseous and Liquid 
States under various conditions of Temperature and 
Pressure." By the late Thomas Andrews, M.I)., LL.D., 
F.R.8. Communicated by the President. Received 
February 7, 1886. 

(Abstract.) 

The followiDg are the general conclusions to which this inquiry ha** 
led:— . 

1. The law of gaseous mixtures, as enunciated by Dalton, is largely 
deviated from in the case of mixtures of nitrogen and carbonic acid 
at high pressures, and is probably only strictly true when applied to 
mixtures of gases in the so-called perfect state. 

2. The critical point of temperature is lowered by admixture with 
a permanent gas. 

3. When carbonic acid gas and nitrogen diffuse into each other at 
high pressures, the volume of the mixture is increased. 

4. In a mixture of liquid carbonic acid and nitrogen at temperatures 
not greatly below the critical point, the liquid surface loses its curva- 
ture, and is efiaced by the application of pressure alone, while at 
lower temperatures the nitrogen is absorbed in the ordinary way, and 
the curvature of the liquid surface is preserved so long as any portion 
oi the g&H is visible. 



«■ 



1886.] On the Minute Anatomy of the Brachial Plexus. 255 



March 25, 1886. 
Professor STOKIES, D.C.L., President, in the Chair. 

The presents received were laid on the table, and thanks ordered 
for them. 

The following Papers were read : — 

I. " Abstract of Paper upon the Minute Anatomy of the 
Brachial Plexus." By W. P. Herringham, M.B., M.R.C.P., 
Communicated by W. S. Savory, F.R.S. Received March 8, 
1886. 

The paper is based npon 55 dissections, 32 foetal and 23 adult. 

The posterior thoracic is formed by the 6th, 6th, and usually the 7th. 
The 5tb supplies the first two digitations, the 6th the next two, the 
6th and 7th the lower five, or if there is no 7th, the 5th may supply 
three, and join the 6th for the remainder. 

The suprascajpular is given off from the 5th, with or without a 
minute fibre from the 6th. 

The anterior thoradcs are formed usually by the 6th, the 7th, the 
8th, and the 9th. The 6th and 7th form the external, supplying the 
upper part of the pectoralis major, the 7th gives the communicating 
branch which supplies the middle, and the union of this with the 
internal from the 8th and 9th, supplies the lower part of the muscle. 
The minor is supplied bj the 7th, 8th, and 9th. 

The coraco brachialis is supplied bj the 7th. 

The rest of the musculo cutaneous is formed by the 5th and 6th. 
Both nerves enter the biceps and brachialis anticus. The cutaneous 
branch is mostly from the 6th, slightly also from the 5th. 

The median is formed by the 6th, 7th, 8th, and 9th. 

The 6th supplies the pronator teres, flexor carpi radialis, superficial 
thenar muscles, and radial finger, or fingers. 

The 7th supplies the flexor sublimis, occasionally the anterior 
interosseous, the palmar cutaneous, and the finger next the 6th. 

The 8th supplies the flexor sublimis, the anterior interosseous, and 
the fingers inside the 7th. 

The 9th supplies the anterior interosseous, and usually ends there. 

The ulnar is formed by the 8th and 9th ; the muscles in the forearm 
are supplied by both, those in the hand by the 8th. The 9th supplies 
the cutaneous branches in front, the 8th the dorsal braueibL^ 



256 On th$ Ktnidf Anaiamy qf ihe BraeHJ Pleaeus. [Max. t5» 

The internal and leaer intemal eiUaneout are nsaaUy supplied by the 
9ih, the former oocasionallj by the 8th as welL 

The posterior branches : — 

The nibscapidarU is supplied by branches from the 5th and 6th 
only ; the teres mc^or by the 6th, often with a twig from the 7th ; the 
latiBsimus dorti by the 7th, often with a twig from the 8th. 

The drcumflez is formed by the 5th and 6th. The latter is not 
traced to the teres minor. Both go to the deltoid. The oataneoas 
branch is formed by the 5th alone, or by both. 

The mueculospiral is formed by the 6th, ^^ and 8th ; sometimes 
the 5th, and rarely the 9th, send branches to it. 

The triceps is supplied by the 7th and 8th. The long head usually 
by the 8th, the inner head by the 7th and 8th, and the outer by the 
7th. The 6th sometimes nms to the outer head. 

The intemal cutaneous branch comes from the 8th. The short 
external cutaneous springs from the 6th, the long yaries round the 
7th. The brachialis anticus, supinator longus, and supinator brevis 
are supplied by the 6th. 

The extensor carpi radialis longer and brevier are supplied by the 
6th or 7th, usually the latter. 

The radial is supplied by the 6th alone, or by the 6th and 7th. 

The posterior interosseous is usually from the 7th alone, sometimes 
with aid from the 8th. 

The nerves, both sensory and motor, are shown to obey the follow- 
ing law : — 

I. Any given fibre may alter its position relative to the vertebral 

column^ hut iviU maintain its position relative to other fibres. 

An exceptional case is detailed in exemplifying this law. 

The muscles are classed in a table, according to their motor nerre 
supply. 

The system of the motor supply appears to be not according 
to use, but according to position, morphological not functional, and 
obeys the following law, composed of three rules : — 

II. A. Of two mMsdeSf or of two parts of a muscle, that which is nearer 

the head end of the body tends to be supplied by the higher, 
that which is nearer the tail end by the lower nerve, 

B. Of two fnuseles, that which is nearer ihe long axis of the body 

tends to be supplied by the higher, that which is nearer the 
periphery by the lower nerve. 

C. Of tv}o muscles, that which is nearer the sv/rface tends to be sup- 

plied by the higher, that which is further from it by the lower 
nerve. 



These rules are applied in detaiL 



188&] Magnetiaation and the Length of Iron Wires. 257 

The system of the sensory snpply is examined in detail. It is shown 
to follow a law composed of two rules : — 

III. A. Of two spots on the shin, that which is nearer the preaaial 
border tends to he supplied hy the higher nerve, 
B. Of two spots in the preaxial area, the lower tends to he supplied 
hy the lower nerve, and of two spots in the postasial area^ 
the lower tends to he supplied hy the higher nerve. 

It is shown that this is the case with all membranes stretched into 
a sheath by something pushing out into them, and the epiblastic layer 
of the epidermis is compared to such a membrane, pushed into a tubal 
sheath by the developing mesoblast. 

A note is added showing that other observers have reached similar 
results by other methods, and notably that Forgue has formulated 
laws for the motor nerves of the monkey, identical with those laid 
down in the present paper. 



IT. ** On the Changes produced by Magnetisation in the 
Length of Iron Wires under Tension." By Shelford 
BiDWELL, M.A., LL.B. Coramunicated by Professor F. 
Guthrie, F.R.S. Received March 10, 1886, 

In a paper communicated to the Royal Society about a year ago,* 
I discussed the results of certain experiments made by Joule in rela- 
tion to ** the Ef^ts of Magnetism upon the dimensions of Iron and 

Steel Bars."t 

It is well known that the length of an iron rod is in general slightly 
increased by magnetisation. Joule enunciated the law that the elonga- 
tion is proportional in a given bar to the square of the magnetic 
intensity, and that it ceases to increase after the iron is fully saturated.^ 
My own experiments, made with a greater range of magnetising forces 
and with thinner rods than those used by Joule, show that if the 
magnetising current is gradually increased after the so-called satura- 
tion point of the iron has been reached, the elongation, instead of 
remaining at a maximum, is diminished, until when the current has 
attained a certain strength, the original length of the rod is unaltered, 
and if this strength be exceeded, actual refraction is produced. 

Joule also found that when the experiment was performed upon an 
iron wire stretched by a weight, the magnetic extension was in all 

* " On the Changes produced by Magnetisation in the Length of Bods of Iron, 
Steel, and Kickel." *' Proc. Roy. Soc.," vol. 40, p. 109. 

t " Phil. Mag." [3], vol. xxx, pp. 76, 226, and the Phyt. Soc.'s Eeprint of 
Joule*B Scientific Pupen, p. 235, 

/ Beprint, pp, 245, 255. 



858 Mr. S. BidweU. On Chamges prod^md bj^ [Ibr. fil^ 



caaee cHm^niaKfldt ^^ ^ tihe weight were oenrndamUe^ 
caused retraction insteed of elongation. From theoefiKite lie appean 
to Iiaye formed the eondnsion that^ under a certain oritioal tenaiom, 
(difPering for different specimens of iron, but independent of the 
magnetising force) magnetisation would produce no effect whatever 
upon the dimensions of the wire. In one of his ezperiments* a ceN 
tain iron wire loaded with a weight of 408 lbs. was found to be 
slightly elongated when magnetised ; the weight waa then i ncroascd 
to 740 lbs. with the result that magnetisation was accompanied bj a 
slight retraction. In both cases the msgnetising onirents Taried over 
a considerable range, and the smaller ones were without any visible 
effect. Commenting upon these results, Joule conjectured tiiat ** with 
a tension of about 600 lbs. [which number I suppose is selected as 
being roughlj the mean of 408 and 740] the effect on the dimenaions 
of the wire would cease altogether in the limits of the electric currents 
employed in the above experiments, "f 

In reference to this surmise^ I ventured the following remark : — 
'^ If he had actuallj made the experiment, he would perhaps have 
found that the length of the wire was increased bj a weak current, 
that a current of medium strength would have had no effect whatever, 
and that one of his stronger currents would have caused the wire to 
retract." I had, in fact, reason to believe that the effect of tension 
was to diminish the "critical magnetising force" (which produces 
maximum elongation) so that the retraction which is found to occur 
in all iron rods when a sufficient magnetising force is employed, is 
observed with smaller magnetising currents when the rod is stretched 
than when it is free,§ bat want of suitable apparatus prevented me 
from submitting this idea to the test of direct experiment. 

I have lately modified the instrument, which is described in my 
former paper, in snch a manner that it can be used for observing the 
effects of magnetisation upon rods and wires under traction. The 
working part of it is shown in diagrammatic section in the annexed 
figure. The coil CC contains 876 turns of copper wire, 1*22 mm. in 
diameter, wound in 12 layers on a brass tube with boxwood ends. To 
the lower end A of the tube is fitted a brass plug or stopper, having 

* Beprint, p. 264. 

t These currents produced defleotionB ranging from 6° to 58° on his tang^'nt 
galvanometer, which *' consisted of a circle of thick copper wire one foot in diameter, 
and a needle half an inch long furnished with an index." 

X Joule's conjecture is sometimes quoted as if it were an experimental fact. See 
Chrystal's article on Magnetism, " Enc. Brit.," vol. xv, p. 269. 

§ My helief was principally founded upon the fact that while the critical mag- 
netising force appeared in all the cases which 1 had examined to he about twice that 
corresponding to the " turning-point " in the magnetisation curve, the tuminflr-point 
itself occurred at an earlier stage when the wire was stretched than when it was 
unstretched. 



1886.] MagnetUation in the Length of Iron Wint. 259 




nn axial hole drilled throngb it, whicli is tapped to receive & BCreivcd 
liraDS rod terminating in a etirrop S. The bottom of tbo stiirap is 
formed like a knife-edge with the edge uppermost, and beneath it iB 
fixed a hiM)k K, from which weights maj be aaspended. A Becond 
perforated stopper B is fitted to the upper end of the tube; the hole 
throngh this is left smooth and freely admits a brass rod, which is 
saspended by meFme of a pin at P from a thick brass plate attached to 
the mahogany table T. The height of P can be varied within small 
limits by means of a fine screw adjustment, not shown. The table T 
is attached to the base-board F of the instrament by three stout legs, 
only one of which, L, appears in the diagram. The wire under ex- 
)>criment, X, is clamped at its two ends between slits in the ends of the 
brass rods P and S, and tbas supports the coil in an upright position. 
Dy turning the screwed plug A the position of the wire X may be so 
adjusted that its middle point shall coincide with that of the axis of 
the coil.* The knife-edge of tbe stirrup acts upon the brass lever R, 
one end of which abuts upon a fixed fulcrum D, while the other 
* Exact coincidence 1* not eMentitl. 



260 Mr. S. BidwelL On Change9 produced by [liar. 2fi, 

actuates a siiort arm E attaohed to the back of a small oirciilar mizm 
M ; the mirror is capable of turning about its boriaontal diameter 
upon knife-edges, resting upon brass planes not shown in the figure. 
By means of a lantern illuminated by a lime-light^ the image of a 
horizontal wire is, after reflection from a mirror, prpjeeted upon a 
distant vertical scale ; a very slight deflection of the mirror causes a 
considerable movement of the image. The dimensions are as follows : — 
The distance SD =5 10 mm., SE == 170 mm., ME = 7 mm. ; the dis- 
tance from the mirror to the scale = 6400 mm., each scale division 
ssO'64 mra.y and the length of the experimental rod between the 
clamps = 100 mm. The movement of the focnssed image through one 
scale division therefore indicates a difference of about one five- 
millionth part* in the leng^ of the rod. The mirror is very ac- 
curately worked, and is silvered upon its outer surface ; the lens used 
for the projection is a compound achromatic of high quality, and it is 
easy to read with accuracy to a half or even a quarter of a scale 
division. 

The magnetising coil is 11*5 cm. long between the boxwood 
ends; its external diameter is 5*2 cm. and internal diameter 1*9 cm. 
A current of C amperes produces at its centre a field of about 92 C 
units. 

li will be seen from the above description that the wire under 
examination sustains the whole weight of the magnetising coil as well 
as that of the lever R. In order to ascertain the amount of the 
tension thus produced, the brass rod P was snspended from a hook 
beneath one pan of a large balance, and it was found that in order to 
maintain the lever B in a horizontal position it was necessary to 
place weights amounting to slightly more than 3 lbs. in the other 
scale pan. In all experiments with this apparatus, therefore, the 
iron wire is stretched by a minimum initial load of 3 lbs. For some 
reasons this is a disadvantage, and the arrangement in qaestion was 
not adopted until many experiments had made it evident that by po 
other method was it possible to avoid with certainty the source of 
error introduced by the electromagnetic action commonly known as 
solenoidal suction between the coil and the wire. When the coil is 
fixed independently of the wire, the smallest trace of this action 
produces upon the lever an effect which is enormously exaggerated in 
the deflection of the image upon the scale. The wire may be placed 
as accurately as it is possible to do so by measurement, with its 
middle point in the centre of the coil ; but a change in the stretching 
weight will at once displace it to a small but material extent; and 
even if the geometrical coincidence were perfect, a slight want of 
uniformity in the physical qualities of the wire would still render 
the objectionable action possible. Under ordinary circumstances the 

• More exaotly 0-00000020588. 



1886.} Moffnetiaation in tlie Length of Iron Wtrea, itil 

distnrbaiice thnB introduced would of conrae be altof^her insenaible ; 
bnt ia making iiMasnrementB in wbicb a hundred- thousand th of a 
nulUmetreisaoonBidemblequaiitity, itis fat- from negligible, as indeed 
was snfficieutlj proved by the inconBistency of the results obtained 
in Bome of my earlier experiments when the wire was free and the 
coil attached to the table T.* After the coil had been saspended 
npon the wire all such inconsistency at once disappeared, for no inter- 
action between the two coold then produce any external effect. 

Since the apparotns was not calcalated to bear any very heavy 
weight it was necessaiy to nse wires of small sectional area. Thin 
wires moreover possess an advantage in becoming more strongly 
magnetised by a given cnrrent than thick wires of the same length. 

The reBnlts of a series of experiments are presented in a synoptical 
form in the subjoined Table. Four specimens of iron were used. 
The first was a wire of commercial iron, 12 mm. in diameter, which 
had been softened by heating in a gas flame ; the second was a strip 
of annealed charcoal iron, 55 mm. wide and 055 mm. thick, its 
sectional area being about 3 mm. ; the third was a piece of bard 
unaunealed wire, 2'6 mm. in diameter ; and the last was a wire of 
very pure soft iron, 325 mm. in diameter, which had been carefully 
annealed. These were successively fixed in the apparatus, and 
loaded with weights varying from 3 lbs. — that of the coil and lever 
alone — to a total of 14 lbs. While under the influence of each load, 
four observations were made in the case of each wire : (1) A deter- 
mination was attempted of the smallest magnetising cnrrent which 
sensibly aSected the length of the wire in the direction of elongation 
or retraction. (2) The current producing maximum elongation (if 
any), and the extent of such maximum elongation were found. 
(3) A determination was mnde of the critical current which was 
without effect npon the original length of the wire, i.e., the current 
of snch strength that a weaker one would cause elongation and a 
stronger one retraction. (4) The retraction produced by a fixed 
current of 1'6 ampere was measured. 

The first operation, that of finding the smallest current which pro> 
daced a sensible deflection, was not easy to perform satisfactorily. 
Small differences in the disposition of the lever and mirror might 

* The Bsme aource of error troubled mo much in the experiments described in 
mj former paper until I adopted a aiiniUr method of avoiding it. The apparatui 
iiMd by Joule was far larger, more maaaive, and preeumablj lesa delioate than mine. 
In the inatrument employed in his strelchiag experiments the lerer alone without 
■DT additional weight produced a tenaion in the ■win at 80 Iba. Eirora ariaing 
from aolenoidal auction would therefore be less sensible, but it ia dilBcult la believe 
tbat some of his results were not affected bv them, especially in the case of the 
experiment (No. 8) on hard atcel described at p. 245 of the Bepriat, which I beliete 
no one has succeeded in repeating. 



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] 886.] Moffnetisation in the Length of Iron Wires. 263 

well cause variations in the readiness with which the arrangement 
woald respond to a movement equivalent to less than one-tenth of a 
8ca1e division. Nevertheless it is clear in spite of one or two dis- 
crepancies that a greater magpietising force is necessary to cause a 
sensible elongation when the load is gpreat than when it is small. In 
one case, that of the thin wire under a load of 14 lbs., there was no 
evidence of any elongation. It is probable, judging by analogy, that 
a maximum elongation, too small, however, for the instrument to 
detect, would occur with a current of about 0'12 ampere. Whether 
Rny load, however great, would render the preliminary elongation of 
the wire too small to be measured by an ideally perfect instrument is 
uncertain. 

The second determination could be made with far greater accuracy, 
liut the load had the effect of flattening the apex of the elongation 
L'urve in such a manner that the actual maximum was not so sharply 
defined as in the case of free rods. 

The third determination, that of the magnetising current under the 
influence of which the original length of the wire was unaltered, was 
susceptible of gpreat accuracy, and was the most important for the 
purpose of the present investigation. 

The measurement of the amount of retraction caused by a given 
strong current was also perfectly easy and certain. 

The figures recorded in the table disclose the following facts : — 

1. The effects produced by magnetisation upon the length of an 
iron wire stretched by a weight, are in general of the same character 
as those which have been shown in my former paper to occur in the 
case of a free iron rod. Under the influence of a gradually increasing 
magnetising force such a wire is at first elongated (unless the load 
be veiy great), then it returns to its original length, and finally it 
contracts. 

2. The maximum elongation diminishes as the load increases 
according to a law which seems to vary with difierent qualities of 
iron. If the ratio of the weight to the sectional area of the wire 
exceeds a certain limit, the maximum elongation (if any) is so small 
that the instrument fails to detect it. 

3. The retraction due to a given magnetising force is greater with 
heavy than with light loads. 

4. Both maximum elongation and neutrality (i.e., absence of both 
elongation and retraction) occur with smaller magnetising currents 
when the load is heavy than when it is light ; retraction, therefore, 
begins at an earlier stage. Thus the anticipation expressed in my 
former paper is justified. 

5. The effects both of elongation and of retraction are, as might be 
expected, greater for thin than for thick wires, and for soft than for 
hard iron. 

1" 



2M Vi.^.BiA^ma. Oaa»mgmproim)9dby [lfw.«S, 

Addition, AprQ 3rd, 1886. 

It would be difficult for aayone who lias not actoally seen the 
apparatus above described to appreoii^ its extreme delicacy, and the. 
accuracy with which it is capable of measuring such minute qoan- 
tities as would commonly be regarded as infinitesimal.* It has been 
suggested to me that greater yalue would be attached to the expe> 
rimental results contained in the present and former papers if the 
manner in which they were arrired at were describeid in greater 
detail, and a few of the actual scale readings given in full. 

In the case of the twelve series of observations to which the table 
given in this paper relates, my method of proceeding was as follows : — 
The iron wire having been placed in position and loaded with a 
weight, a short time was allowed for the apparatos to attain a nearly 
steady temperature. The reflected image of the indicating wire 
(which I will call the index) was then, by means of the fine screw 
adjustment, brought upon the upper half of the scale, the zero point 
of which was in the middle, and the index, which, owing to small 
variations of temperaturef, was rarely absolutely at rest, was watched 
until its upper edge nearly coincided with one of the scale divisions. 
The number of this division was noted and recorded from my dicta- 
tion, and at the instant when exact coincidence occurred, a contact 
key was depressed, which caused a current of 1*6 ampere to pass 
through the coil. The number of the scale division nearest to which 
the index was deflected was again noted and recorded as before ; and 
if the point which the index reached happened to be exactly midway 
between two divisions, the reading was recorded to half a scale divi- 
sion. When the deflections were small, the readings were taken to 
the nearest half scale division ; bat this, though easy enough, was in 
general considered to be a needless refinement. 

The next course was to find by a tentative method the strengths of 
the three currents which respectively produced — (1) the first sensible 
elongation ; (2) the maximum elongation ; (3) neither elongation 
nor retraction ; and in order to do this, the resistance in the circuit 
was varied by means of a large set of coils, and a succession of currents 
of different strengths (perhaps from twenty to fifty in number, or 
sometimes even more) were caused to pass through the apparatus.;^ 

* The inetrument was exhibited in action at the Soir^ of the Bojal Society, May, 

1885. 
t Taking the coefficient of expansion of iron to be 0'0000122 per degree C, the 

heat elongation due to a rise of temperature of one degree would produce a deflec- 
tion of sixtj-one scale dirisions ; but in addition to the iron there was a somewhat 
greater length of brass, and if this shared in the heat expansion, a total deflection of 
more than 160 scale dirisions per degree would be produced. 
^ It IB oi course understood that the circuit was actually dosed by the kej only 



1886.] Magnetiaaiion m the liength of Iran Wires. 



iii5 



These currents having been determined, the final step was to repeat 
the first observation of the .retraction produced by the fixed carrent 
of 1*6 ampere, and thas to check the accuracy of the experiment. 
The subtractions of the readings were then made, and if there had 
been a difference of more than one scale division between the pre- 



Retraction with Current of 1*6 Ampere.* 





Iron wire 1*2 mm. 


Prelimiuary readings . ■• 
Filial readings ' 


127/^ 
107/^ 


106/" 

K^llO 
118/*" 








t 


Iron strip. 


PreUminarj readings . • 
Final readings ' 




^}l^ 


96/18 


101 9ft 




Hard iron. Soft iron. 


Preliminary readings . « 
Final readiness ' 


901„ 
101/11 

103/" 


129 111 
140/** 

1351 11 
136/** 


70 lo 
78/® 


!?}ll 



liminary and the final result, it was mj intention to repeat, the series 
of observations. This, however, was not found necessary in a single 
instance. The actual figures as recorded in the note book are given 
above, the difierences being the numbers which appear in the last 
line of the table in the paper. The agreement between the pre* 
liminary and the final readings, when a number of experiments had 

at the moment of making an observation, and for a period of not more than half a 
Hxx>nd at a time. 

* In eighteen pairs of obserrations with iron there was exact agreement sixteen 
times and a difference of one scale diyision twice. With nickel the deQections were 
much larger, sometimes exceeding 100 divisions, and the agreement was not so close ; 
but the discrepancy did not eiceed two divisions. 



266 Dr.Gadow. Onihe [Mar. S5, 

intenrened between tbem, ia rerj remarkable, and oonld imly bave been 
attained, howeyer perfect the instrament, bj the method of obeerria- 
tion which has been deacribed, unless indeed the readings had been 
taken to fractions of a scale division. 

In the course of my erperience in working with the instmment, I 
hnre naturally become acquainted with a number of little devices, 
difficult to describe, which would give me an advantage over a novice 
in its use. But I believe that any competent manipulator would find 
it quite easy to obtain uniform and consistent results with it. 

The efficiency of the apparatus is due partly to the perfection of the 
optical arrangements and partly to the fact that in the moving parts 
unnecessary lightness has not been acquired at the expense of sufficient 
massiveness and rigidity. 



UL '^ Remarks on the Cloaca and on the Copnlatory Organs of 
the Amniota." By Dr. Gadow. Communicated by Pro- 
fessor M. Foster, Sec. R.S. Received March 11, 1886. 

(Abstract.) 

The sphincter muscles of the anus of Crocodilia are differentiatiouH 
of the postpelvic portion of the system of the m. rectus abdominis 
rather than of the true caudal muscles. 

The copulatory muscles of the CarinatsB are derived from the m. 
sphincter ani solely, whilst in tbe RatitsB they are also differentiations 
of muscles which are still attached to the pelvis, and are, therefore, 
skeleto-genital. 

The mammalian sphincter ani does not take a share in the muscle 
supply of the copulatory organ, and thus exhibits a difference from 
Birds and Lizards. 

Distinctly copulatory muscles in the Mammslia are derived from 
skeletal and from non-striped muscles. In this respect the Mammalia 
agree with Crocodilia and Chelonia. 

Then the author describes the nerve-supply of the cloacal region in 
Crocodilia. 

Third Chapter, — The modiBcations of the cloaca in the various chief 
groups of Amniota: Crocodilia, Lizards, Snakes, Hatteria, Birds, 
Tortoises, Mammals. 

Lizards and snakes together represent a special type. 

Hatteria comes nearest the Amphibia, or the embryonic condition of 
Sauropsida ; bears, however, resemblance to the Lizards. 

Chelonia represent a type somewhat intermediate between that of 
the RatitflB and Crocodilia and that of the Monotremata, at the same 
^*ne bearing slight resemblance to that of the Sauria. 



1886.] Cloaca and the Copulatory Organs of Amniota, 267 

Then the anal sacs or cloacal hladders of the Ghelonia are critically 
discnssed with reference to experiments on their being able to take in 
water. 

Then follows a discnsi^on of the peritoneal canals. 

The cloacal and copulatory organs of the Ghelonia lead with com- 
paratively slight modifications to the Monotremata, from which again 
a continuity of stages ap to the highest Placentalia can be traced. 

The whole cloaca of the Amniota consists originally, either per- 
manently or in the embryo only, of three successive chambers which 
may be distinguished as follows : — 

I. The ProctodaBura (termed thus by Professor Lankester). It 
is the outermost aual chamber of epiblastic origin. With 
its derivatives : (1) Bursa Fabricii in birds ; (2) various 
hedonic glands in most Amuiota ; (3) the copulatory 
organs, the at least partly epiblastic nature of which is 
indicated by the frequently developed homy armament of 
the glans, by the various sebaceous glands, and as shown in 
this paper by its development. 
II. The UrodsBum, from ovpov and Batov, Hypoblastic. This is 
the middle chamber or primitive cloaca, into which open 
the urinogenital ducts, and through which pass the feeces. 
With its dilPerentiations : (1) urinary bladder, ventral; 
(2) anal sacs in Tortoises, dorsal. 
III. The Coprodsdum, from Kovpoi and Batov, This is the inoermost 
cloacal chamber. 

The Urodsdum is the oldest portion of the whole cloaca, then 
follows the Proctodaeum, and, lastly, the Coprodaaum has 8econdai*i1y 
assumed cloacal functions. 

The various modifications of these three chambers, their function, 
and the gradual separation of feeces, urine, and genital products have 
been discussed in the third chapter, and are summarily explained in 
a table. 

A short note on the presence of Muellerian ducts in the males, and 
of Wolffian ducts in the females of young Crocodilia. 

Lastly, general conclusions regarding the phylogenetic development 
and the homologies of the copulatory organs of the Amniota. 



S68 PrclB.KArambKmg. £Sbo|yo%nfa [1CiK% 



lY. ** Electrolytic Cionduction in relation to Holecnlar Cumpoo- 
tion» Valency and the nature of Chemical Change : being 
an Attempt to apply a Theory of 'Beeidual Affinity."* 
By HsNBY E. Abmstrono, PhJD., F.B,S., Professor of 
Chemistry, Cify and Ouilds of London Central Institution* 
Received March 11, 188& 

In my recent address to the Chemical Section of the British 
Association at Aberdeen, I hare speoisUy oalled attention to ike 
^* afl&nity " of negoHve elements — chlorine, oxygen, sulphur, Ac — ^for 
negatiye elements ; and I have sought to show that the formation of 
so-called molecular oompaundt is hugely, if not entirely, an outcome 
of this peculiarity of negatire elements. I have also yentured to 
suggest " that in electrolysing solutions, the friction arising from the 
attraction of the ions for each other is perhaps diminished, not by 
the mere mechanical interposition of the neutral molecules of the 
solvent — in the manner suggested by F. Kohlrausch — but by the 
actual attraction exercised by these molecules upon the negative ion 
in yirtne of the affinities of the negative radicles.*' In this passage 
I but vaguely hinted at a modification of the current theory of 
electrolysis which had occurred to me ; as further consideration of 
the questioD, especially of Ostwald's electrochemical studies, has 
strengthened my views, I am led to think that it may be justifiable 
to submit them for discussion. 

It is usual to divide bodies into three classes according to the mode 
in which they are acted on by an electromotive force : metals forming 
one class, electrolytes a second, and dielectrics a third. In making 
this division, perhaps the fact is not sufficiently borne in mind that 
some compounds — silver chloride, for example — are per se electrolytes, 
while others — such as hydrogen chloride and water — are individually 
dielectrics, but behave as electrolytes when conjoined. On thia 
account, it appears to me desirable to distinguish between — 

(a) MetaU. 

(h) Simple electrolytes— compounds, like silver chloride, which in 
the pure state are electrolytes. 

(c) P^etido-dielectrics — compounds like water, hydrogen chloride 
and sulphuric acid, which behave as dielectrics when pure^ but as 
electrolytes when mixed with other members of their own class. 
Conducting mixtures of members of this class may conveniently be 
termed composite electrolytes, 

(d) Dielectrics. 






1886.] Conduction and Molecular Composition, ^-c. 269 

Simple Electrolytes. 

.^ It is nndoabtedly a fact that only a limited number of binary 

^ componnds are simple electrolytes ; and it is especially noteworthy 

tfaatv with the single donbtfnl exception of liqae6ed ammonia, no 
liydrogen compound — whether binary or of more complex com- 
^ » position — can be classed with the simple electrolytes. Indeed, all the 
: simple electrol3rte6 with which we are acquainted are either compounds 
I sacii as the metallic chlorides, or metallic salts — nitrates, sulphates, ^c. 
^i Including metallic chlorides and their congeners and the corre- 
al, t spending oxides and hydroxides among salts — regarding water as an 
^,- acid, in fact — and denying the title of salts — ^hydrogen salts — to the 
-:-; acids, Hittorf's proposition (" Wied. Ann.," 1878. 4, p. 374): " Electro- 
-. lyte sind Salze " may be safely upheld. But only some of the binary 
metallic salts are electrolytes : beryllium chloride, for example, belongs 
to the class of " pseudo-dielectrics ** (Nilson and Petterson, " Wied. 
•T Ann.," 1878, 4, p. 565; Humpidge, " Phil. Trans.," 1883, p. 604) ; and 
rfp in the case of those elements which readily form two classes of salts — 
so-called ous or j^ro^o-salts and ic or per-salts, the ous compounds alone 
appear to be electrolytes. 

It is highly remarkable that whereas fused silver chloride is easily 
decomposed on passage of a current of low electromotive force, 
hydrogen chloride is a "pseudo-dielectric** which forms when coupled 
with the " pseudo-dielectric** water a readily conducting "composite 
electrolyte ;" while mercuric chloride conducts with great difficulty — 
possibly not at all when pure — not only in the fused state, but even 
when coupled with water. No explanation of these facts seems to be 
afforded by thermochemical data.* 

The consideration of these and other similar cases, I think, can 

* The following numbers are given by Thomsen aa representing the amounts of 
hemt developed in the formation of the specified chlorides in the state of aggr<>ga- 
tion in which thej exist under ordinary conditions (2 x 35*4 grams of chlorine being 
in eftdi case used in the production of the chloride) :-^ 

Hjdrogen chloride. 44,000 units (gram ° C), 

Silver , 58,760 „ 

Hercnric „ 63,160 „ 

Stannic „ 63,625 „ 

Stannous „ S0,790 „ 

Lead m 82,770 „ 

Oflly three of the chlorides in this list are simple electrolytes. Ab much more 
hMit is developed in the formation of two of these three — stannous and lead 
chloridai — ^than in the case of any of the others, it would appear probable d priori 
that these would be the most stable ; obviously, therefore, the study of the heats of 
formation throws no light on differences in electrical behaviour such as are manifest 
between hydrogen, mercuric and stannic chlorides, on the one hand, and silver, 
Msanotts and \eaid chlorides on the other. 



4 



270 . Prof. H. E. ArmBtrong. EUctrolytic [Mar. 2S, 

but lead to one conolosion : that electroljBabilitj is conditioned both 
by the nature of the elements in the compound and its molecular 
structure. I haye put forward the hypothesis in my address — **^ that 
among metallic compounds, only those are electrolytes which contain 
more than a single atom of metal in their molecules/' The m0« 
presence of two or more associated atoms of metal in the molecule^ 
however, probably does not constitute a compound an electrolyte; 
and although the hypothesis may be applicable to the minority of 
simple electrolytes, it certainly does not appear to include aU the 
facts, and it does not serve to explain why certain salts are electro- 
lytes while others are not. 

The remarkable difference in the electrical behaviour of two com- 
pounds of the same element, such as stannous chloride, in which the 
ratio of tin to chlorine atoms is as 1 to 2, and stannic chloride, in 
which Sn : Gl = 1 : 4^the one being a simple electrolyte ; the other 
a pseudo-dielectric, if indeed it be not a dielectric — ^would appear 
almost to justify the conclusion that in the case of per-salts such as 
stannic chloride the metal is, as it were, enveloped in a non-conducting 
sheath of the negative radicle. But whether this be so or not. If — as 
appears to be the case — all simple electrolytes are metallic compounds, 
and if only proto-salts are electrolytes, may it not be that electric 
conduction in simple electrolytes is of the nature of ordinary metallic 
conduction, differing from it only in the circumstance that the com- 
pound is decomposed as a consequence of the passage of the current ? 

This would lead to the conception of an electrolyte as being a 
metallic compound of such elements, and so constituted, that electric 
conduction may take place through its mass in a manner similar to 
that in which it takes place through a mass of metal : in fact through 
the agency of its metallic atoms. On this view, it is essential that 
the metallic atoms in the molecules comprising a mass of an electro- 
lyte should be in proximity — as they probably are in proto-salts, but 
not in many per-salts. The conductivity of two-metal alloys is in 
many cases much less than that of either of the contained metals : 
for example, the conductivity of the alloy SnCui is about \i\i that 
of tin and about -j^jth that of copper. The specific conductivity of 
metals may, therefore, be much reduced by association with one 
another ; and this being the case, it appears probable that the specific 
conductivity of a metal would be still more reduced by association 
with a non-metal, and that if the metal were one of low specific 
conductivity, it might thus practically become altogether deprived of 
conducting power : perhaps the " exceptional" behaviour of mercuric 
and berylUum chlorides is to be explained by considerations such as 
these. 

To discuss such questions at all satisfactorily, however, we require 
to know much more of the electrical behaviour of pure fused salts ; 



1886.] Ctmduction and Molecular Composition^ Sfe* 271 

it is Barprising how little accurate knowledge we possess on this 
subject. 

Composite Electrolytes, 

I assnme it to be admitted that neither water nor liquid hydrogen 
chloride, for example, is an electrolyte, although an aqueous solution 
of hydrogen chloride conducts freely and is electrolysed by an 
electromotive force of but little more than a volt. 

The theory put forward by Clausius in 1857 in explanation of 
electrolysis is well stated in Clerk Maxwell's '' Elementary Treatise 
on Electricity " (p. 104), in the following words : — 

** According to the theory of molecular motion, every molecule of 
the fluid is moving in an exceedingly irregular manner, being driven 
first one way and then another by the impacts of other molecules 
which are also in a state of agitation. The encounters of the 
molecules take place with various degrees of violence, and it is 
probable that even at low temperatures some of the encounters are so 
violent that one or both of the compound molecules are split up into 
their constituents. Each of these constituent molecules then knocks 
about among the rest till it meets with another molecule of the 
opposite kind, and unites with it to form a new molecule of the com- 
pound. In every compound, therefore, a certain proportion of the 
molecules at any instant are broken up into their constituent atoms. 
Now, Clausius supposes that it is on the constituent molecules in 
their intervals of freedom that the electromotive force acts, deflecting 
them slightly from the paths they would otherwise have followed and 
causing the positive constituents to travel, on the whole, more in the 
positive than in the negative direction and the negative constituents 
more in the negative direction than in the positive. The electro- 
motive force, therefore, does not produce the disruptions and reunions 
of the molecules, but finding these disruptions and reunions -already 
going on, it influences the motions of the constituents during their 
intervals of freedom. The higher the temperature, the greater the 
molecular agitation, and the more numerous are the free constituents : 
hence the conductivity of electrolytes increases as the temperature 



• ,9 

rises. 



This theory has been widely accepted by physicists ; but it appears 
to me that, on careful consideration of the evidence, and especially of 
recent exact observations on conditions of chemical change, it must 
be admitted, as I have elsewhere contended (B. A. Address), that 
proof is altogether wanting of the existeuce of a condition such as is 
postulated by Clausius. Moreover, it has been shown by Hittorf that 
cuprous and silver sulphides, and by F. Kohlrausch that silver iodide, 
all nndergo electrolysis in the solid state; the partisans of the dis- 
aooiation hypothesis would, I presume, scarcely contend that it is 



Hi Prof. H. E. Armstxong. EkctrolyHe [Mar.X; 

easily applioable to snoh caaea as iliese. It also does Bot apysai fc 

afEord any explanation of the ahini^t change in condnotiyify 
occurs in solid silver iodide and sulphide as the temperatore is 
(see p. 280) ; nor of the pecaliar variation in condnctivil^ on dflniqg 
salpharic acid with water (see p. 282). 

Again, I venture to think that the conductivity of a miadmn d 
compounds which themselves have little or no conducting power ■ 
accounted for in but an unsatisfactory and insufficient manner hj ihi 
hypothesis put forward by P. Kohlrausch (" Pogg. Ann.," 1876, 159, 
p. 283) ; there appears to be far too grecU a difference in the behaviour of 
the pure compounds, water and liquid hydrogen chloride, for ezamph^ 
and of a mixture — no decomposition apparently of either compowii 
being effected by any electromotive force short of that which prodnoa 
disruptive discharge, although the mixture of the two will not with- 
stand an electromotive force of little more than a volt. InflueDced 
by these considerations, I am led to conclude that there is no satii- 
factory evidence that the constituents of the electrolyte are either 
free prior to the action of the electromotive force, or are primarily 
set free by the effect produced by the electromotive force upon either 
member separately of the composite electrolyte ; but that an additional 
influence comes into play, viz., that of the one member of the com- 
posite electrolyte upon the other while both are under the influence 
of the electromotive force. This influence, I imagine, is exerted by 
the negative I'adicle of the one member of the composite electrolyte 
upon the negative j-adicle of the other member. Assuming, for 
example, that in a solution of hydrogen chloride in water the oxygen 
atom of the water molecule is straining at the chlorine atom of the 
hydrogen chloride molecule, if when subjected to the influence of an 
electromotive force the molecules are caused to flow past each other 
— the phenomena of electric endosmoso may be held to afford evidence 
that in composite electrolytes the molecules are thus set in motion 
— it is conceivable that this influence, superadded to that of the elec- 
tromotive force upon the electrolyte, may bring about the disruption 
of the molecule and conduction : in short, that a state may be induced 
such as Clausius considers is the state prior to the action of the elec- 
tromotive force. 

A large amount of most valuable information on the connexion of 
dilution and electrical conduction in aqueous solutions has been 
recently published by Arrhenius, Bouty, F. Kohlrausch and Ostwald. 
In his most recent paper, Ostwald (" Journal fiir praktische Chemie," 
1885, 32, p. 300) has given the results of his determinations of the 
molecular conductivity vi* in the case of no less than about 120 different 

* m^ko, k being the Bpecific conductiyi^.y as onlinarily defined, and o the Tolume 
of the solution, i.e., the number of litres containing the formula weight in grams of 
the acid. Uis results are expressed in arbitrary units. 



1886.] Conduction and Molecular Cornposiilon, &-c. 



278 



acids : it appears to me that many — indeed all — of his observations afford 
Viost distinct evidence in favonr of the view I have expressed above. 
The .general resnlt of his investigation is that the molecular conduc- 
ttvity increases with dilation : in other words, that the dissolved sub- 
'Staiice exercises a greater specific effect, finally attaining a maximum ; 
it then diminishes, but he believes this to be due to impurities in the 
water, especially to neutralisation of l^e acid by traces of ammonium 
•oarbonate. The maximum, he appears to think, would be the same 
ior all acids if the dilution could only be pushed far enough : in the 
-ease of monobasic acids it is about 90 (arbitrary units) 4 it is twice 
Hue in the case of dibasic, thrice in the case of tribasic, and so on. 

I will quote first his results in the case of solutions of hydrogen 
ohloride, bromide, iodide, fluoride and silicon fluoride. 

Table T. 



r. 


Ha. 


HBr. 


HI, 


HF. 


HjjSiF^. 


2 


77-9 


80-4 


80*4 


• • 


47-81 


4 


80-9 


83-4 


83-2 


6*54 


57-29 


8 


88-6 


85 1 


84*9 


7-59 


62-20 


36 


85-4 


86-6 


86*4 


10 00 


67*08 


82 


87-0 


87-9 


87*6 


13 14 


71*52 


64 


88 1 


88-9 


88*7 


17-88 


75-61 


128 


88-7 


89*4 


89-4 


28 11 


79*22 


256 


89-2 


89-6 


89-7 


30-80 


83-89 


512 


89-6 


89-7 


89*7 


39*11 


91*62 


1024 


89-5 


89*5 


89-8 


49*49 


109-5 


2048 


89 5 


88*9 


8G'0 


59-56 


1440 


4096 


88*6 


87-6 


87-8 


69-42 


187 1 


8192 


• • 


• t 


• • 


• • 


226-6 


16S84 


• • 


• • 


• • 


• • 


258*6 


82768 


• • 


• • 


• « 


• • 


282-6 



It will be observed that hydrogen chloride, bromide and iodide 
practically behave alike ; the nambers for the chloride are, however, 
slightly lower than those for the bromide and iodide, and the maxi- 
mum is not reached quite so soon in the case of the chloride. Hydro- 
gen fluoride is altogether different: its molecular conductivity is 
exceedingly low to begin with, and is considerably below the maxi- 
mumi even when t7=4096. But I would call special attention to the 
nambers for hydrogen silicon fluoride, which is commonly regarded as 
a dibasic acid : at first, as Ostwald says, it behaves as a monobasic 
acid of moderate strength — iodic acid, for example ; bat the maxi- 
mum for monobasic acids being exceeded, the molecular conductivity 
increases more and more rapidly, ultimately exceeding the treble 
value, 270. It must be supposed that it undergoes decomposition in 
accordance with the equation — 

Hj,SiFa-f2H^O=SiOa+6HE. 






274 Prof. H. E. Armstrong. Eleeirolytie [Mar. 25, 

The notewortlij point is the large excess of water required to initkte 
tliis change: when t;=16 the solation contains less than 1 per oeni 
HiSiFe, and at this point, according to Ostwald, decomposition 
prohablj begins, bnt that it is far from complete even when a Teiy 
much larger excess is present is evident from the fact that the 
maximum when v = 32,768 is 282 and not above 400. 

Now it is well known that hydrogen chloride, bromide and iodide 
are, practically speaking, perfect gases under ordinary circnmstaneeB: 
in other words, masses of these gases would mainly consist of mole- 
cules such as are represented by the formulse HCl, HBr and HL It 
has been proved, however, by Mallet that hydrogen fluoride at tem- 
peratures near to its boiling point mainly consists of molecules of the 
formula H2F1. In the aqueous solution the molecules would be 
brought more closely together, and therefore it is probable that, even 
in the case of hydrogen chloride, bromide and iodide, a certain pro- 
portion of more complex molecules would result ; the relatively high 
boiling point of hydrogen fluoride (19*4**) renders it probable that in 
the liquid state this compound would at least partially consist of 
molecules more complex even than is represented by the formula 
H3F2. On the hypothesis put forward in this paper, the influence 
exoi^cised by the one member of the composite electrolyte upon the 
other member during electrolysis is at all events mainly exercised by 
their respective negative radicles, and the extent of the influence 
thus mutually exerted by these radicles would depend on the extent to 
which they are still possessed of "residual aflinity." If the hydrogen 
chloride, bromide and iodide are present chiefly as simple molecules, 
they should exert, ab initio^ almost the full effect which they are 
capable of exerting ; and the chief effect of dilution being to decom- 
pose the more complex molecules, conductivity should increase to but 
a slight extent if the extent to which simplification can take place be 
but small. On the other hand, if owing to the formation of molecular 
aggregates the residual affinity be more or less exhausted, the initial 
conductivity will be low, and it will increase on dilution only in pro- ■ 
portion as these aggregates become broken up. 

It appears to me that the behaviour of the four hydrides under 
discussion is absolutely in accordance with these requirements of the 
hypothesis. Even the difference between hydrogen chloride and 
hydrogen bromide and iodide is not without its bearing. The determi- 
nations of the density of chlorine at various temperatures by Ludwig, 
and of the density of bromine by Jahn (" Monatshef te fiir Chemie," 
1882, p. 176), have shown that it is necessary to raise the temperature 
considerably higher above the boiling point in order to reduce the 
density to the theoretical value in the case of chlorine than in the 
case of bromine : in other words, there is a greater tendency in 
chlorine to form aggregates more complex than those of the formula 



1886.] Conduction and Molecular Composition^ ^c. 



275 



C1« than there is in bromine to form aggregates more complex than 
those of the formula Br2. It is, therefore, not nnlikelj that the 
chlorine in HCl has more " residnal affinity " than the bromine in 
HBr,* and if so the aqneons solution of the former would have a lower 
initial conductivity than one of equivalent strength of hydrogen 
bromide, and the maximum would be obtained only on greater dilu- 
tion ; which is precisely the case. 

The evidence afforded by the oxy-acids derived from the halogens 
appears to me to be equally striking. The following are Ostwald*s 
numbers, including those for nitric acid. 



Table II. 





Nitric 


Chloric 


Pep- 
chloric 
acid. 


Bromic 


Iodic 


Periodic 


V, 


acid. 


acid. 


acid. 


acid. 


add. 


2 


77-9 


77-9 


79 1 


. . 


42-57 




4 


80-4 


80-2 


82-2 


• • 


50-56 


23-71 


8 


82-8 


82-3 


84-6 


• • 


59-00 


30*59 


16 


84-9 


84-0 


86-2 


. • 


66-3 


39-49 


82 


86-3 


83*3 


88-1 


79-4 


72-3 


49-23 


64 


87-4 


86*4 


89-2 


81-7 


76-9 


59-48 


128 


88-2 


87-9 


89-7 


841 


80-2 


69-06 


256 


88-4 


88-7 


89-9 


881 


81-8 


76-70 


512 


88-8 


88-7 . 


89-8 


87-4 


83 


82-59 


1024 


88-9 


88-6 


89-8 


88-4 


83 1 


85-38 


2048 


88-2 


87-3 


89-3 


89 


82-9 


87-95 


40% 


86-6 


85-7 


87-8 


88-8 


81-8 


86-62 



It will be observed that nitric, chloric and perchloric acids differ 
but little ; that bromic acid has a considerably lower initial conduc- 
tivity, and does not attain the maximum so soon; that iodic acid 
differs still more; and that the behaviour of periodic acid is 

* On other grounds also there is reason to helieve that hydrogen chloride differs 
more from hydrogen bromide or iodide than either of these differs from the other: 
thus less heat is developed on dissolving hydrogen chloride in water than on disso- 
lution of equivalent quantities of the bromide or iodide, the numbers given by 

Thomsen being — 

HCl. 4O0H2O- 17,300 units. 

HBr, 400HjO = 19,200 „ 

HI, 400H3O = 19,200 „ 

The solution of hydrogen chloride which distils unchanged at 112° at the ordinary 
preasnre has approximately the composition represented by the formula UCl'SHjO ; 
whereas the corresponding solutions of hydrogen bromide and iodide boil at 125^ 
and 127^, and their composition is approximately represented by the formuUs 
HBrSHgO and HI'5'5H;0. A solution of hydrogen fluoride approximately of the 
compodtion HF*2HsO distils unchanged at 120". 



276 



Prof. H. E. Armstrong. EkOrofyiie [lfar.19. 



altogeiher peonliftr— being that of a polybasio acid, it vmj be adUaS. 
Oatwald reg^ards it as most surprising — '* in kohem Orade hefrmnHUk ** 
— ^that periodic add sbonld be mnch weaker than iodic acid, and ifai 
the latter should be considerably inferior to iodhydnc acid. To nf 
mind, their behaviour is absolutely what might be expected of tibflw 
acids. Although the molecules in liquid nitric, chloric and perdUorie 
acids are probably not of the simple composition represented by the 
formulfls HNOi, HGlOs, and HGIO4 respectively, the chemical be- 
hayiour of these acids does not indicate any great difference between 
them ; owing, howeyer, to the accumulation of oxygen atoms, per- 
chloric acid may be expected to exercise a somewhat greater influence 
than chloric acid, as it actually does. Chemists are agreed that 
bromine has less affinity for oxygen than chlorine ; hence it may be 
inferred that the oxygen in bromic acid would have greater residual 
affinity than the oxygen in chloric acid, and that, therefore, bromic 
acid would form complex aggregates more readily than chloric acid, 
and consequently have less influence in electrolysis than chloric acid. 
This is true in a much greater degree of iodic, and still more of 
periodic acid :* it is well known that the former not only yields salts 
of the type M'lOs, but also acid salts such as KHI,Oc; and that 
periodic acid forms a series of very complex salts. 

The acids of phosphorus form another interesting series : — 



Table III. 



r. 


HgPO,. 


HsPOj. 


i 

HgP04. 


2 


30-89 


28-63 


14-22 


4 


87-91 


34-29 


17 00 


8 


45-81 


41 14 


21-26 


16 


54 IS 


4909 


27-09 


82 


62 10 


56-96 


84-41 


64 


69 06 


64-52 


43-05 1 


128 


74-05 


70-21 


53-11 


256 


77-84 


74-54 


61-8 


512 


79-92 


77-57 


69-9 


1024. 


61-00 


79-11 


75-4 


2046 


81-39 


79-76 


79-0 


4096 


80*48 


79 07 


79-8 



These numbers afibrd to my mind the clearest possible evidence 
that we are dealiug with complex molecules. It is especially note- 

* The existenoe of a stable oxide of the formula IjOg, aa well as thennocheznica] 
data, have been interpreted as eridence that iodine has a greater affinity for oxTgon 
than even chlorine. I am inclined to take the contrary view, however, and to regard 
the stability of the oxide IjO^ as due less to the high affinity of iodine for oxygen 
than to its low affinity for itself and the high affinity of oxygen for oxygen. 



1886.] Conduction and Molecular' Composition, <§'c, 277 

worthy that the TnaxiTmim never exceeds that of the monobasic acids* 
even in the case of phosphoric acid, which is universallj regarded as a 
tribasic acid, and that the monohasic hypophosphoms acid is the 
strongest and the tribasic phosphoric acid is the weakest. In very 
dilate solution phosphoric acid has less influence than even acetic 
acid, according to Kohlrausch. 

It may be well also to quote Ostwald's numbers for sulphnroaSy 
selenious, sulphuric and selenic acids. 



Table I\^ 



«• 


Sulphurous 


Selenious 


Sulphuric 


Selenic 


v. 


acid. 


acid. 


acid. 


acid. 


2 


• • 


7-63 


92-7 


97-3 


4 


19 19 


9-73 


96-4 


103-2 


8 


25-43 


12-70 


100-6 


109 9 


16 


32-79 


16-60 


107-4 


117-7 


32 


41-60 


21-73 


116-3 


127 


64 


50-1 


28-24 


127-3 


138-3 


128 


58-9 


36-15 


139-2 


148-7 


256 


66-5 


45 11 


150-6 


157-9 


512 


72-5 


54-27 


160-9 


164-4 


1024 


77 1 


62-79 


169-1 


169-7 


2048 


80-4 


69-40 


174-4 


173-4 


4096 


83-6 


73-58 


177-1 


174-4 


8192 


• • 


•« • 


176-9 


173-4 



It will be observed that sulphuric and selenic acids are nearly alike 
in behaviour, the latter being somewhat more active in concentrated 
solutions ; it is noteworthy that of all the polybasic acids studied by 
Ostwald, these are the only two containing a single negative radicle 
(S04,Se04) which exhibit a conductivity in excess of that which cha- 
racterises the monobasic acids.f 

The numbers obtained for sulphurous and selenious acids are 
deserving of study. Sulphur dioxide is far from being a perfect gas 
nnder ordinary conditions ; in the liquid state it is probably rich in 

* Ostwald appears to be of the opinion that if the dilution could be carried far 
enough, a maximum conductivitj^n '90 would eyentoally be attained in the case of 
ererj it-basic acid. It appears to me that neither do his numbers warrant this — and 
those here under discussion are an especiallj good illustration — nor is it Ukelj to be 
the case on my hypothesis. 

f Ostwald infers from the great increase in molecular conductivity that the 
manner in which the acid is electrolysed yaries with the strength of tlie solution ; 
he supposes that in more concentrated solutions sulphuric acid is resolved into H and 
HSO4, and that both atoms of hydrogen are spUt off only as the solution becomes 
more diluted. This appears to me to be altogether improbable. 

VOL. XL. \S 



278 Prof. H. E. Armstrong. Electrolytic [Mar. 25, 

aggregates of SOs molectiles, and these may be to a large extent con- 
served in concentrated aqueous solutions. But' the main explanation 
of the variation in conductivity on dilution must be looked for, I 
think, in the peculiar relation which sulphur dioxide manifests to 
water ; it is more than probable that the initial interaction involves 
the formation of a hydrate^ (SOa)jt(OHa)y, and that from this on dilu- 
tion is formed sulphurous acid, SO(OH)s, and perhaps also ^' sulphonic 
acid," H'SOjH. Taking into account the properties of selenious oxide, 
Ostwald's results appear to me in this case again to lead to but the 
one conclusion, that conductivity increases in consequence of the 
specific influence of the fundamental molecule of the compound 
making itself more and more felt as by dilution it becomes more 
and more disentangled from its fellows. 

The behaviour of solutions of neutral metallic salts on dilution is 
very similar to that of acids; abundant proof of this is afforded 
especially by F. Kohlrausch's refined measurements, of which an 
account has recently been published (" Wied. Ann.," 1886, 26, p. 162). 
1 venture to think that a similar explanation to that above given for 
oxides will apply to salts; and also that the low molecular con- 
ductivities of salts as compared with corresponding acids may be 
regarded as confirmatory of my hypothesis. I think we must admit 
that the metals generally have less aflGLnity than hydrogen for negative 
radicles ; if this be granted, we have at once an explanation of the 
fact that metallic salts are mostly fixed solids, few of which are more 
than moderately soluble in water while many are very difficultly 
soluble or insoluble, whereas the corresponding acids are mostly 
volatile and readily soluble in water, if not miscible with it in all 
proportions. The affinity of the negative radicles being less exhausted 
by union with metals than with hydrogen, the fundamental molecules 
of salts are more prone to unite together to form complex aggregates. 

Arrhenius, who has studied the electrical behaviour of solutions 
of a number of salts,* attribntes the change observed in molecular 
conductivity on dilution — as I have done — to molecular changes ; but 
his deductions are all based on the acceptance of the Williamson- 
Clausius hypothesis of dissociation. 

My hypothesis would also account for the increase in conductivity 

• " Bihang till Kongl. Sveneka Yetenskaps-Akademiens Handlingar." Attonde 
Bondet. Hafte 2. Stockholm, 1884. Arrhenius, S. : *' Recherches sur la Conduc- 
tibilit^ Ghilvanique des Electrolytes. I. La Conductibilite Galvanique des Solutions 
Aqueuses extr^mement dilute, determine au moyen des Depolarisateurs." 63 pp. 
II. " Th^orie Chimique des Electrolytes." 89 pp. Although aware of his work 
from Ostwald's reference to it, I was unable to study his memoir until after thi* 
paper had been elaborated. Ostwald's quotations, moreover, did not enable me to 
realise the importance which Arrhenius attaches to the occurrence of molecular 
simplification and changes in composition on dilution. 



1886.] Conduction and Molecular Composition^ S^e. 



279 



in composite elcfctrolytes with rise of temperatnre. It is true that as 
temperature rises the influence which individual molecules exert upon 
each other would be lessened ; but on the other hand, the complex 
aggregates would become more and more completely resolved into 
their fundamental molecules, the velocity of molecular motion would 
increase, and fche tendency of the constituent atoms to remain united 
would be lessened. From this point of view the determination of the 
coeflficient of change of conductivity with temperature in the case of 
substances whose molecular conductivity increases considerably on 
dilution in comparison with allied compounds which exhibit only a 
slight variation in molecular conductivity on dilution afEords an 
interesting subject for investigation. F. Koblrausch has already 
pointed out (" Pogg. Ann.,'' 1875, 154, p. 236) that in the case of all 
neutral salts, " der Einfluss der Temperatur anf das Leitungs- 
vermogen mit wachsender Yerdiinnung sich Anfangswerthen nahert, 
die zwischen engen Granzenliegen," and the experiments of F. Kobl- 
rausch and Nippoldt on solutions of sulphuric acid {ibid,^ 1869, 138, 
p. 286) show that the resistance diminishes to a much greater exten|; 
forequal increments of temperature in concentrated than in dilute 
solutions. Thus : — 

Table V. 







Percentage 


Percentage of 


Resistance 


increment of 


sulphuric acid. 


(Mercury =1.) 


conductivity 

for r 0. 


0-2 


465,100 


0-47 


8-3 


34,530 


0-653 


14*2 


18,946 


0-646 


20*2 


14,990 


0-799 


28 


13,133 


1 -317 


33-2 


13,132 


1-269 


41-5 


14,286 


1-410 


46 


15,762 


1-674 


50-4 


17,726 


1682 


55*2 


20,796 


1-417 


60-8 


25,574 


1-794 



As concentrated solutions would be richer in complex aggregates 
than dilute solutions, these results are in entire accordance with my 
hypothesis : it does not appear to me that they call be satisfactorily 
interpreted in terms of the dissociation hypothesis. 

In cases where the influence of the one member of the composite 
electrolyte upon the other is but slight, it may happen that the effect 
of temperature in diminishing this influence will outweigh that due to 



280 Prof. H. E. Annstrong. EUctrolytie |^(ar. SJ, 

molecular simplification, and that, in consequence, condnotiTily will 
diminiab with rise of temperatnre ; a miztnra of alcohol and ether 
would appear to famish an example of this kind; according to 
Pfeifier's recent observations (" Wied. Ann.," 1S86, 26, p. 226), snch a 
mixtore behaves as a metallic condnctor of very high resistance. 

The increase in conductivity of graphite and gas-retort carbon on 
heating, and the effect of light on the condnotiviiy of (P impnra) 
selenium and some other sabstances (Shelford Bidwell, " Ph3rB. Soc 
Proc.," 7, p. 129, 256), appear to me to be also explicable on the 
aseamptian that in all these oases we are dealing with composite 
electrolytes. 

If any farther proof be needed of an intimate connexion between 
molecular composition and electrolytic conduction, it is most oon- 
clusively afEorded, I think, by the observations of W. Elohlrausch on 
chloride, bromide and iodide of silver (" Wied. Ann.," 1882, 17, 
p. 642), which are exhibited in the accompanying corves. In the fused 




state, these componnds are better conductors than the moat highly- 
inducting mixture of sulphuric acid and water, which of all liquids 



1886.] Conduction and Molecular Compoaition, ^. 281 

is the best condactor at ordinary temperatnres. On reference to the 
cuTTea, it will be seen that the resistance of both ailver chloride and 
bromide snddenlf increases when the change from the fnsed to the 
solid state sets in ; bat that no such change takes place in the case of 
the iodide. Silver iodide fnses at 527° according to BodweU, bnt at 
abont; 540° according to K!ohlraasch ; its electrical resistance increases 
only gradnally after it has become solid, and remains almost a linear 
function of the temperature daring an interval of 400°, nnlil suddenly 
at near 150° it increases enormously, this change taking place at tiie 
moment whtn according to Rodwell (" Phil. Trans.," 1882, p. 1133) 
it passes from the transparent, plastic, amorphoas solid to theopaqne, 
brittle, crystalline state, the valnme increasing considerably as shown 
by the annexed carve. Kohlransch has proved most conclnsively that 




lbs wlid iodide may andergo electrolysiB. It wonld seem that almost 
imnediiitely after solidification in the case of silver chloride and 
faomide practically the whole mass consists of complex aggregates so 
oooBtitated as to be exceedingly had conductors, bnt that such aggre* 
gatM are formed mnch less readily by silver iodide. 

Metallic Conduction. 

I do not propose in any way to discnss metallic conduction, bnt 
merely to will attention to some of the analogies between it and 
electrolytic conduction. 

It ia conceivable, and it would appear probable ■ from the fairly 
regular manner in which the electrical resistance of most ^ut« xxt%^Bi.% 



282 Prof. H. E. ArmBtrong. EUctrofytic [Mar. 25, 

decreaaefi as the temperatore falis, the coefficients of change being 
practically very nearly the same in all cases, that the incieaae in 
resistance as temperature rises is mainly due k) the increase in mole- 
cnlar int«r-distancea. As a mle, resistaDce increases on the passage of 
a metal from the solid to the liquid state, but there are noteworthy 
exceptions from which it woald appear prohabls that even in pure 
metals conductivity to some extent depends on molecular compoflidon : 
thns the condnetivity of bismuth increases at the moment of fosioo 
from 0-43 to 073 of that of mercury at 21°, and that of antimony 
from 0-59 to 0-84 (L. de la Rive, " Compt. rend.," 1863, 57, p. 691) ; 
it is well known that bismuth contracts considerably on fusion, and 
this is probably also the case with antimony. Ag"-'", aooording to 
Bonty and Cailletet {ibid., 1885, 100, p. 1188), the rasistanoe of mei^ 
cury decreases at the point of solidification in the ratio 4*08 : 1 ; this 
is a remarkable increase in conductivity, and it is diffionlt to believe 
that it is wholly due to mere contraction of volume. 

That the behaviour of alloys is worthy of far more attention than 
it has hitherto received appears most clearly from the few data at 
disposal. As being the most instructive instance, I append the curve 




1886.] Co}u/wlion am/ Mokcidnr Compo^l/hii. <?•-■, 2^*;^ 

given by Profi/asor Lodge as representing the specitic cond activities of 
the copper-tin alloys ("Phys. Soc. Proc.," 1879-80, 3, p. 158). He 
examined five alloys, containing respectively SOS, 38'2, 31?, 12'6, 
and 9"7 per cent, by weight of tin, which wera prepared by Professor 
Chandler Roberts; the dotted carve represents the results obtained 
by Matthiessen, who did not examine any alloy between those con- 
taining 164 and 851 volnme per cent, of copper. The comparison of 
Professor Lodge's carve with that given by F. Kofalransch for mix- 
tares of salphnric acid and water — which 1 also append — appears to 



me to be in the highest degree snggestive. In the case of the latter, 
it will be observed that, starting from SO* on the one aide and H|0 on 
the other, minima oocnr at points on the cnrve corresponding to com- 
ponnds of the formula HjSOi and H,SO,'H,0 ; it is, however, well 
known that sach compoands are unobtainable at ordinary tempera- 
tures, and it is highly probable that if the pure componnds conld be 
examined, the minima would touch the base line, as in the case of 
water.* The point of maximnm condactivity does not correBpond 
to any known hydrate, bat as I have elsei^here remarked it is 
almost coincident with that of maximum heat evolution on mixing 
enlphnric acid aud wat«r, and it is therefore doubtless the point 
at which the maximnni chemical change occurs. On reference to the 
alloy corre, it is seen that the addition of quite a small amonnt 
of tin to copper prodnces a very marked effect just as does the addi- 
tion of a small sjuoont of water to aalphnric acid, the effect being, 
however, to diminish condactivity in the one case but to increase it 
in the other ; after the addition of only a moderato amonnt of tin, a 

* The ftdda rioher tban EiSO, in SO, hare been examined bj W. Eolilrau«ch 
(" Wied. Ann.," 1882, liii, p. 69) . It ia eapeciallj noteworthy, as I aaid trhen leading 
this paper, that the hydrate HtSjO; is a much wone oonduotor than either of the 
hydratM HgSO^ or H]80,'0H], and that the former of these conducts less readily 
than the latter, and in this connexion to remember that the compound H,8i07 is the 
most deOnite and easily obtained in a erjitalline shape, and that the hydrate 
EjSOt'OH, is the least definite of the three : the evidenos that oonduotiTitj dependt 
on absence of homt^eneity is OTonrhelming in this case. — [May 26, 1S86.^ 



284 Prof. H. E. Annsirong. Eleetrolytie [Mar. 85, 

prononnced TniTiiinqm is reached, correBponding to the pronoanoed 
maximiim attained on addition of a moderate amount of water to 
snlphnric acid, and at a point moreover corresponding to a definite 
oomponnd, SnCui ; a further slight addition of tin develops another 
minimnm less pronounced than the first, but also corresponding to a 
definite compound, SnCus ; the carve then falls slightly and exhibits 
a third minimum, its course being analogous to that of the sulphnzio 
acid and water curve near to sulphuric acid. If one or the other 
curve be inverted, the general similarity in form is especially striking. 
It is obviously important that alloys intermediate between those 
studied should be examined ; a comparison of Lodge's with Matthies- 
sen's curve shows how much may be missed ; this remark applies to 
alloys generally. Whatever may be the explanation,* it appears to 
me to be dear than in alloys as in composite electrolytes the con. 
stituent members of the system influence each other, and thus 
mutually contribute to the final result. The narked diminution in 
the conductivity of copper produced by veiy small quantities of 
oxygen, of phosphorus or of the metalloid arsenic is well known. 
It would appearprobable that this is in some way due to the occur- 
rence of an electrolytic change, which at least in part is opposed in 
direction to that taking place in the pui*e metal during conduction .f 

Valencif — Chemical Change, 

Notwithstanding the fierce controversy which has been waged 
between the advocates of the doctrine of fixed valency and the 
advocates of the doctrine of varying valency, our views on the 
subject are still in an unfortunate degree unsatisfactory and 
indefinite. Even those — and they probably form a large majority — 
who regard valency as a variable, dependent both upon the nature of 
the associated radicles and the conditions — especially as to tem- 
perature — ^under which these are placed, often hesitate to attribute a 
valency suflBciently high to account for every case of combination ; in 
fact both parties agp:eo in distinguishing " atomic " from " molecu- 
le " compounds, and differ only as to where the line shall be drawn. 



I 



4.- 



♦ It is veiy remarkable that not only do tho heat conductivity and the induction 
balance curres for the tin-copper alloys correspond (Chandler Roberts, " Phys. Soc. 
Proc.," 3, p. 156), but that the curres given by Thurston a« representing the strength 
of these alloys ('* Materials of Engineering,'' Part III, p. 412) also exhibit a marked 
similarity to the electrical conductivity curves. 

t The change produced in gold by a very small quantity of lead is most astonish- 
ing : its conductivity is reduced almost to that of lead and it becomes as brittle as 
g|a^. It is difficult to understand this change unless it be that opportunity is given 
for the gold itself to assume a different molecular state, owing to continuity becoming 
disturbed. The effect produced appears to be strictly comparable with that observed 
on lowering the temperature of ailveT io^de ixom «\kst« «^\)l\> \.^^ ^ «XLd in the 
jmsukge of liquid water at 0° into ice. 



1886.] Conduction and Molecular Composition^ 8^c. 285 

It is difficnlt to oyer-estimate the importance of the theory of 
Talency: its application has led to an enormous extension of our 
knowledge of carbon compounds especially, and it has furnished us 
with a simple and consistent system of classifying the mighty host) of 
these bodies ; but on the other hand, it may be questioned whether it 
has not led us away from the search into the nature of chemical 
change, and even if the introduction of the terms saturated and 
unsaturated has not had a directly pernicious efEect. The almost 
nniyersal disregard of molecular composition as an important factor in 
chemical change in the case of solids and liquids, and the popular 
tendency to overlook the fact that our formulad of such bodies are 
purely empirical expressions, has undoubtedly exercised a prejudicial 
influence. 

No known compounds are saturated — if any were, such would be 
incapable, I imagine, of directly taking part in any interaction, and in 
their case decomposition would necessarily be a precedent change. 
The paraffins are apparently of all bodies the most inert and the most 
nearly saturated, and next to them comes hydrogen — the unsaturated 
character of which is displayed in interactions such as occur at 
atmospheric temperatures between it and platinum and palladium, and 
when it displaces silver from silver nitrate or certain of the platinum 
metals from their salts. One of the most striking instances perhaps 
of popular error in this respect is water, which is always regarded as 
a saturated compound, although its entire behaviour and especially its 
physical properties characterise the molecule H2O, I think, as that of an 
eminently unsaturated compound : I fail to see how otherwise we are 
to explain the high surface tension and high specific heat of liquid 
water, its high heat of vaporisation, and its imperfectly gaseous beha- 
viour up to temperatures considerably above its boiling point, let alone 
its great solvent power and its tendency to form hydrates with a mul- 
titude of compounds — especially oxygenated compounds, be it added. 

The theory was brought most prominently under the notice of 
chemists by Helmholtz in the last Faraday lecture that electricity, 
like matter, is as it were atomic, and that each unit of affinity or 
valency in our compounds is associated with an equivalent of elec- 
tricity — positive or negative ; that the atoms cling to their electric 
charges and that these charges cling to each other. Thus barely 
stated, this theory does not appear to take into account the fact that 
the fundamental molecules even of so-called atomic compounds are 
never saturated, but more or less readily unite with other molecules to 
form molecular compounds — molecular aggregates; and unless the 
application of the theory to explain the existence of such compounds 
can be made clear, chemists must, I think, decline to accept it.* 

'^ leis notewoHhy that Clerk Maxwell (" Electricity MidTJlB^giie^Aam;' \^^,^^\> 
p. 313), when speaking of the theory of molecular chaTgw,ttBb^^/*T^sM^ >2!a»ar5 ^t 



286 Prof. H. E. Armgtroiig. Electrolytic [Mar. 25, 

* 

There is, however, a most significant passage in Helmholtz' paper, in 
which it is pointed out that (in a Daniell's cell) the phenomena are 
the same as if equivalents of positive and negative electricitj were 
attracted by different atoms, and perhaps also by the different values 
of affinity belonging to the same atom, with different force : are we to 
seek for an explanation in this direction ? The impression which the 
facts make npon the mind of the chemist certainly is, 1, that no 
two different atoms have equivalent affinities ; and, 2, that affinity is a 
variable depending on the nature of the associated elements : but 
owing to the recognised complexity of nearly all cases of chemical 
change, it is difficult to draw any very definite conclusion on this point. 
If, however, the nature and properties of so-called molecular 
compounds generally be considered, and if an attempt be made to 
form any conception of their constitution, one striking fact is 
noticeable, viz., that the nietaU in them apparently retain the 
properties which they exhibited in the parent atomic compounds. 
Every one knows the marked difference in properties of ferrous as 
contrasted with ferric salts : they differ not only in chemical 
behaviour, but also in their physical properties, and are readily 
distinguishable by their colour. The properties of the ferrous 
molecular compounds, however, are those of the simple ferrous 
compounds : ferrous potassium chloride, for example, FeaCl4'Cl2K2, is 
a green salt much like ferrous sulphate. Facts such as these have led 
me to suggest that in such cases the formation of the molecular 
compound is due to the attraction of the negative element of the one 
*' atomic " compound by the negative element of the other, the metal 
having no influence except that the amount of affinity of which the 
negative element is possessed depends on the nature of the metal with 
which it is associated. It would in fact appear that hydrogen and the 
metals generally may be regarded as the analogues of the CnH^+i 
and CnH2n-7 hydrocarbon radicles, and that their compounds with 
negative elements may be likened to unsaturated hydrocarbons of the 
form CnHan+i'CH'CHj. We know that whenever such a compound 
enters into combination, the CnB.2n+i radicle takes no part in the 
change, combination of whatever kind being effected by means of the 
unsaturated radicle CH'CHa with which it is associated. I do not 

molecular charges — he uses the expression molecular in the sense that the chemist 
uses the term atomic — maj serve as a method by "which we maj remember a good 
manj facts about electrolysis. It is extremely improbable that when we come to 
imderstand the true nature of electrolysis we shall retain in any form the theory of 
molecular chaises, for then we shall have obtained a secure basis on which to form a 
true theory of electric currents, and so ;become independent of these provisional 
theories." And later (p. 315) : "While electrolysis fully establishes the close rela- 
tionahip between electrical phenomena and those of chemical combination, the fact 
that eyery chemieaX compound is not an eVeetroY^V/e ^o^% \^'aXiO[^Tccv»«i2LQ)cycE^\x^^ 
is a process of a higher order of complexity tliaxi wry ^\3CMiV3 ^wiN;ris»SL^«o.ws«»ssii^' 



1886.] Conduction and Molecular Composition^ S^c. 287 

mean to contend that the metals are fallj neutralised in their 
compounds, but merely that as a rule they behave as though they were 
saturated just as do the CnH2tt_7 radicles derived from the benzenes. 
There can be little doubt that an absolute distinction must be drawn 
between hydrogen and the metals on the one hand, and the non- 
metals on the other. Regarding the facts in the light of our 
knowledge of carbon compounds, it is difficult to resist the conclusion 
that the differences observed are due to differences in structure of the 
stuffs of which the elements as we know them are composed, the 
which differences condition perhaps a different distribution of the 
electric charge or its equivalent, in the case of each element. 

In the earlier part of this paper I have ascribed the influence which 
the one set of molecules of the composite electrolyte exercise upon the 
other during electrolysis to the existence of "residual affinity." I 
believe this view also to apply to the explanation of the occurrence of 
chemical change. To quote the words of Arrhenius, " L'activit^ 
^lectrolytique se confonde avec Tactivit^ chimique." Several pregnant 
examples of this have already been given by Ostwald (" J. pr. Chem.," 
1884, 80, p. 93). 

The investigation of the nature of chemical change has assumed an 
altogether different aspect since the publication of Mr. H. B. Dixon's 
inquiry into the conditions of chemical change in gases ("Phil Trans.," 
1884, p. 617 ; see also " Chem. Soc. Trans.," 1886, p. 94). Mr. Dixon 
has clearly proved that it is impossible to explode a mixture of carbonic 
oxide and oxygen, and that the change 2C0 + Oa = 2CO2 is effected 
when sparks are passed across the tube containing the gaseous mixture 
only in the path of the discharge. If traces of water be present explo- 
sion takes place, the velocity of propagation of the explosive wave 
increasing with the amount of water up to a certain maximum. 
These results completely dispose of the popular explanation of such 
changes, viz., that the molecules in the path of the discharge undergo 
dissociation, that the dissimilar atoms thus liberated then combine 
together, and that as the heat developed in their union causes the 
dissociation of yet other molecules, change gradually extends through- 
out the mass.* Mr. Dixon's experiments have not only shown that 
the propagation of change is dependent on the presence of a third 
body, but that this third body must bear a certain relation to those 
with which it is associated ; CO2, CSj, CjNa, CCI4, SO2, and NjO were 
found by him to have no action, and only water — or bodies which 
formed water under the conditions of the experiment — were found 
capable of determining the explosion. There is an obvious difference 

* I am not to be understood to imply that dlBsociation does not take place in the 
path of the discharge ; on the contrary, for all the facts appeax tA txi^^ V^ Ssi^^a^iub 
thst conduction and electrolyais are inseparable p\ieiiOTXiQik& m \geAi&% «a\si\is^^^ 
(Comp. Schuster, "Proc. Rny. Soc," 1884, p. 317.) 



288 ftof. H. E. Armstrong. EUetrolytic [Hat.SS; 

in oonstitation between water and the bodies found inoapaUe of 
determining explosion : the former being a domponnd of a pontile 
with a negative element, the latter being all compounds of two nega* 
tive elements ; and if it be permissible to generalise from this singb 
instance, it may hence be stated, that in order that interaction duJl 
take place in cases snch as that under consideration, it is not only 
necessary that the elements of the ''catalyst" shall be dmaik^ 
between the interacting substances — the elements of COs are obviously 
as divisible between GO and Os as are those of HaO — but that the 
catalyst shall consist of a positive and a negative and not of two 
negative radicles. On this view, it is possible to understand that 
water itself may act as the catalyst in determining the formation dt 
water at high temperatures from hydrogen and oxygen.f 

In the case discussed (the oxidation of carbon monoxide), inter- 
action takes place at a very high temperature, and therefore— since 
high temperafcure may be regarded as the equivalent of high electro- 
motive force — under conditions under which the catalyst water is 
probably a simple electrolyte. The behaviour of sulphur dioxide 
in presence of oxygen and water is instructive as being a case of an 
analogous interaction occurring at a low temperature. From a most 
carefully conducted series of experiments by Mr. Dixon (" Joum. of 
Qas Lighting," 1881, 37, p. 704), it appears that not only does sulphur 
dioxide not undergo change in contact with dry oxygen, but that it 
even resists oxidation if water vapour be present and at a temperature 
of 100° ; as is well known, however, oxidation takes place — but only 
slowly — when an aqueous solution of sulphur dioxide is in contact 
with oxygen. In this case, in the gaseous mixture the water appa- 
rently is not under such conditions that it can act as a simple electro- 
lyte, or even form a composite electrolyte, and action only takes place 
when the conditions become such that a composite electrolyte can be 
formed ; Ostwald's observations may be held to prove, I imagine, that 
a very imperfect composite electrolyte results on dissolving sulphur 
dioxide in water, and in accoi*danGe with this is the fact that the 
aqueous solution is but slowly oxidised4 

* Mr. Dixon's experiments appear to prove that during the interaction of carbonic 
oxide and oxygen in presence of water an actual division of the elements of the water 
molecules takes place between the carbonic oxide and oxygen molecules, and hence 
that the water does not exercise a mere contact action. 

t When this question first came under discussion at the Chemical Society, 
I said that I looked forward to the time when probably it would be found that a 
mixture of pure hydrogen and oxygen was inexplosive, like one of pure carbonic 
oxide and oxygen. I was then still under the influence of current opinion and 
regarded water as a saturated compound, and had not yet realised the important 
function of " residual affinity '* in such clianges. 

J The behaviour here described of sulphur dioxide appears to me to furnish 
another argument adverse to the diaaociaitVoTi \iy^>i\i^«B» «a oiiftaSasstL \s^«^ -^^as^ 
under the conditionB least favourable to t^io occvflrencft ol ^Maocaa^x^ 



1886.] Conduction and Molecular Compontionj ^c, 289 

If a dear distinction can be drawn — as I suppose it can — ^between 
simple and composite electrolytes, the presence of a member of tbe 
latter class will probably be foand to be essential to tbe occurrence of 
many interactions taking place at moderate temperatures ; thus the 
oxidation of iron, which is generally supposed to take place only in 
moist air, is doubtless dependent, not merely on the presence of water^ 
bat of impure water — of water rendered conducting by association 
with foreign matt-ers ; similarly it may be expected that zinc will be 
found to have no action on water even when associated with a less 
positive metal, and it would doubtless have no action on sulphuric 
acid, if such a compound were obtainable in a pure state; but a 
mixture of sulphuric acid and water readily dissolves it, as the two 
together form a composite electrolyte of comparatively low resistance. 

It can scarcely be doubted that when our elements or compounds 
are resolved into their ultimate atoms, these atoms are capable of 
directly uniting, and that no catalyst is then required. But if this be 
the case, and if, as I suppose, the atoms rarely saturate each other, 
the direct union of compounds should also be possible in cases in 
which there is considerable residual affinity ; such union would not 
involve a separation from each other of the constituent elements of 
one or both of the interacting bodies such as takes place in the 
changes previously considered. Union of two molecules having 
taken place ; the elements of the interacting bodies having thus been 
brought into intimate association : it is very probable that in many 
eases intramolecular change will then supervene, resulting sometimes 
in mere atomic redistribution, at other times in the resolution of the 
complex molecule into simpler molecules. I am inclined to think that 
the majority of so-called double decompositions are thus brought 
about. 

The union of sulphuric anhydride with water to form sulphuric 
acid, and of sulphuric acid with water to form hydrates, are doubtless 
cases of this kind. The formation of the hydrate SOs'OHa must be 
supposed to be immediately followed by the occurrence of atomic 
redistribution if we accept the current view that sulphuric acid is a 
hydroxide of the formula S0t(0H)2 ; whether after the formation of 
the hydrate HjSOi'OHa has taken place atomic redistribution in like 
manner supervenes is a moot point; the large amount of heat de- 
veloped by the interaction of water and sulphuric acid is, however, 
specially noteworthy. 

Sodium hydroxide is universally regarded as the analogue of water : 
is its action on sulphuric acid analogous to that of water P I certainly 
am inclined to hold that it is, and that in the first instance an aggre- 
gate, NaHO'SOiHa, results, owing to the attraction of the oxygen of 
the hydroxide by the oxygenated radicle of tho ac\d •. ^A^otdag t^^\^Vtv.- 
bution tberenpon takes place, and either the moVecviXe \a t^^c\n^^\»^ 



290 Conduction and Molecular Composition^ ^e. [Mar. 25, 

two others, water and sodinm bydrogen Rnlpliate, or a new oomponnd 
is formed, whicli is easily resolvable into tbese latter. Moreover, I 
am inclined to attribute this change and the consequent displacement 
of the hydrogen in the acid by the sodium, not to the fact that 
sodium has a greater affinity than hydrogen has for SO4, but to the 
tendency of hydrogen to displace the sodium in sodium hydroxide and 
to form water. I do not contend that in such a case as that quoted 
direct interaction will take place between the substances as we know 
them in the solid state ; these may consist of oomparatively inert 
complex aggregates which require to be resolved into simpler molecules 
either by dissolution or by application of heat. In other words, the 
presence of water may be necessary, not because it is essential to have 
an electrolyte present, but because the occurrence of both molecular 
interaction and electrolytic conduction depends on identical molecular 
and intermolecular conditions. The chemical interaction takes place 
entirely independently of the water molecules, and these latter serve 
only to separate and keep apart the fundamental molecules of which 
the interacting bodies are composed. 

No final decision for or against the view here put forward can well 
be arrived at except by the study of the behaviour of gaseous bodies 
such as ammonia and hydrogen chloride, for example ; if proof can be 
given that these compounds are capable of directly uniting without the 
intervention of any third body, a most important step will have been 
made. 

Other cases deserving of study are the conversion of nitric oxide 
into nitric peroxide, oxidation by means of ozone, and the action of 
metals such as sodium on water. As the formation of nitric peroxide 
involves the prior separation of oxygen-atoms from oxygen-atoms, 
and not merely the combination of two molecules, it is not improbable 
that interaction between nitric oxide and oxygen molecules will only 
take place in the presence of a catalyst. But it is to be borne in mind 
that both nitric oxide and ozone are bodies which are capable of inter- 
acting with molecules of their own kind, and that considerable heat is 
thereby developed ; and it is conceivable that such bodies being pos- 
sessed of high residual affinity may directly enter into combination 
with others which have but little residual affinity. As regards the 
action of sodium on water, the difference in behaviour with dilate 
sulphuric acid between moderately pure zinc and very nearly pure 
zinc is so marked that the vigorous action between sodium and water 
cannot be held to prove much, as no special care is ever taken to pre- 
pare sodium pure; the question whether the aflBnity of the oxygen in 
water for sodium is sufficient to cause their direct association and 
consequent interaction is an interesting one for experimental inquiry-, 
although it would be very difficult to make the experiment properly. 

One other application of the theory dwelt on in this paper remains 



1886.] Presentf. 291 

to be mentioned. It is now well established that on exploding gaseouff 
mixtores within a closed chamber, the maximum theoretical tempera- 
tare is never reached ; and this has hitherto always been explained 
as dae to the occurrence of dissociation whereby the change is re- 
tarded. If in a mixture, say, of carbonic oxide, oxygen and water 
gases, the three kinds of molecales act together in the manner I have 
supposed, it is probable that the extent to which they mutually 
influence each other would vary with the temperature, and that it 
would tend to diminish above a certain temperature ; if such were 
the case, change would be retarded in the manner in which it appears 
to be in explosions within closed chambers. Dissociation undoubtedly 
does take place in many cases, but thei*e is now a considerable amount 
of evidence on record to show that the bounding surfaces exercise a 
most important influence ; this is usually not sufficiently taken into 
account. 



Presents, February 4i, 1886. 
Transactions. 

Bern: — Naturforschende Gesellschaft. Mittheilungen. 1884, 

Heft 3 ; 1885, Hefbe 1-2. 8vo. Bern. The Society. 

Budapest: — Kon. Ungar. Geolog. Anstalt. Mittheilungen. Bd. VII. 

Heft 2. 8vo. Budapest 1885 ; Foldtani Kozlony. K(5tet XIV. 

Fiizet 9-11. 8vo. Budapest lSS4i ; General-Index der TJngar. 

Geolog. Gesellschaft, 1852-1882. 8vo. Budapest 1884. 

The Society. 
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Tomo V. Entrega 2. 4to. Buenos Aires 1884. 

The Academy. 
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Nos. 1-2. 8vo. Calcutta 1885 ; Proceedings, Nos. 6-8. 8vo. 

Calcutta 1885. The Society. 

Catania : — Accademia Gioenia di Scienze Naturali. Atti. Serie 8. 

TomoXVIII. 4to. Ca^ama 1885. The Academy. 

Copenhagen: — Academic Royale. Bulletin. 1885. No. 2. 8vo. 

Copenhague. Sir J. Lubbock, Bart., F.R.S. 

Dresden: — ^Verein fur Erdkunde. Jahresbericht XXI. 8vo. 

Dresden 1885. The Association. 

Dublin : — Royal Geological Society of Ireland. Journal. Vol. XVI. 

Part 3. 8vo. Dublin 1886. The Society. 

Graz : — Naturwissenschaftlieher Verein fiir Steiermark. Mittheil- 
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Leeds: — Philosophical and Literary Society. Annual Report. 

1884-85. 8vo. Leeds 1885. The Society. 



298 iVeMitff. [FeL 4^ 

TiBiunctioxui (eanHnued), 

Leipsig : — ^Astronomiscbe G^sellschaf fc. YierteljabrBSohrift. Jaibg. 

XX. Heft 4. ftro. Leiptstg 1885. The Sodetj. 

London : — ^East India ABSociation. Jonmal. YoL XYIIL STo. 1. 

8vo. London 1886. The Aflsociaiion. 

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Medical Students. 8yo. London 1885. The CoonciL 

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XY. Livr. 1-3. 4to. Moacou 1884-85. The Society. 

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1885. 8vo. Palermo. The Ciroolo. 

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1862—1885. 8vo. Plymouth 1885. The Author. 

Rotterdam : — Bataafsch Genootschap. Nieuwe Yerbandelingen. 

Reeks 2. Deel III. Sfcuk 2. 4to. BoUerdam 1885. 

The Society. 
Switzerland: — Schweizereische Oesellschaft. Yerhandlungen, 1883 

-84. 8vo. Luzem 1884 ; Compte Rendu, 1883-84. 8vo. Geneve 

1883-84; NeueDenkschrif ten. Bd. XXIX. Abth. 1-2. 4to. 

Zurich 1884-85. The Society! 

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Toulovse, The Academy. 

Yienna : — Zoologisch-Botanische Gesellschaft. Yerhandlungen. 

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The Society. 



Observations and Reports. 

Cape of Good Hope : — Parliamentary Papers. Acts of Parliament, 
1885. Folio. Gape Town 1885; Yotes and Proceedings of 
Parliaments, 1885. Folio. Cape Town, Ditto, Appendix I. 
Yols. 1-2, and Appendix II. Folio. Cape Town 1885. 

The Cape Government. 

London : — ^Meteorological Ofl&ce. Contributions to our Knowledge 
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London 1885 ; Hourly Readings, 1883. Parts 1-2. 4to. London 
1885 ; Daily Weather Reports, Jan.-June, 1885. 4to. Ditto, 



1886.] Presents. 293 

Observations, Ac. (continued). 

Jane-December, 1885, in single sheets as published ; Weekly 

Weather Report., 1884, Vol. I. Appendix 2. Ditto, Vol. II. 

Nos. 10-46, with Appendices ; Monthly Weather Report, 1885, 

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8vo. London 1885. The Admiralty. 

Manchester : — Free Libraries. 33rd Annual Report, 1884-85. 8vo. 

Manchester,' The Committee. 

Philadelphia : — Second Geological Survey of Pennsylvania. Forty 

Volumes of Publications. 8vo. Harrisburg 1874-84. 

The Survey. 



Presents^ February 11, 1886. 
Transactions. 

Glasgow : — Faculty of Physicians and Surgeons. Catalogue of the 

Library. 4to. Glasgow 1885. The Faculty. 

London: — Physical Society. Proceedings. Vol. VII. Part 3. 

8vo. London 1886. The Society. 

Quekett Microscopical Club. Journal. Ser. IL Vol. II. No. 14. 

8vo. London 1886. The Club. 

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Vol. II. No. 1. 8vo. London 1885. The Society. 

Paris : — ficole Normale Superieure. Annales. Ser. III. Tome II. 

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1885. The Society. 

Prague : — Konigl. Bohm. Gesellschaft der Wissenschaften. Ab- 

handlungen. Folge VI. Band XII. 4to. Frag 1885 ; Jahres- 

bericht. 1882-85. 8vo. Praf/ 1882-85; Sitzungsberichte. Jahrg. 

1882-84. 8vo. Pra^ 1883-85 ; BerichtiiberdieMathematischeu 

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Frag 1884. The Society. 

Stockholm : — KoDgl. Vetenskaps Akademie. Of versigt. Arg. 42. 

No. 6. 8vo. Stockholm 1885. The Academy. 

VOL. XL. ^ 



204 PmmU. [Feb. ft, 

Transactions (corUinued), 

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Verslag 26. 8fo. Utrecht 1885. 
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AnderHon (Richard) Lightning Condactors, their Historj, Natara, 

and Mode of Application. Third edition. 870. London 1885. 

The Author. 
Bonaparte (Prince Boland) Note sur les r^nts Voyages du Dr. H. 

Cen Kate dans TAmerique dn Sad. 4to. Paris 1885. 

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Dupont sur le Poudingue de Weris. 8vo. Bruxelles 1885. 

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1885. 
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Orimsby 1886. The Author. 

Todd (D. P.) Preliminary Account of a Speculative and Practical 

Search for a Trans-Neptunian Planet. 8vo. Washington 1880 ; On 

Newcomb*8 and Levenner's Tables of Uranus and Neptnne. 4to. 

1883 ; Telescopic Search for the Trans-Neptunian Planet. 8vo. 

1885 ; The Lick Observatory, Mount Hamilton, California. 8vo. 

1885 ; Physical Training at Amherst. (Sheet.) 1885. 

The Author. 
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Molecnlaire. 8vo. Paris 1885. The Author. ^ 



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Florence : — 11. Comitato Geologico d*Italia. Bollettiuo. No. lie 

12. 8vo. Boma 1885. The Committee- 



1886-] PresmiB. 295 

Transactions {continued). 

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Budapest : — Ceiitral-Anstalt fiir Meteorologie und Erdmagnetis- 
mus. Jahrbucher. Bd. X-XIV. Jahrg. 1880-84. 4to. Buda- 
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London : — Standards Department. Account by the Cambridge In- 
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ternazionales. Anno XVI-XVIII. (imperfect). Obi. 4to. 
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im PreMenU. {9401^ 



Presents^ February 25, 1886. 
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Pesth :-:-K6n. Ung. Central-Anstalt fur Meteorologie und Erd- 
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The Meteorological Office. 

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4to. Washington 1885. The Survey. 

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The Indian Government. 



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Transactions. 
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Faac. 3e et 4e. 8vo. Bordeaux 1^^^. '^^V^ ^$««s«^^ 



188«.] Presents. 297 

rransactions (cmUinued). 

Breslaa : — Schlesische Gesellschaft fur vaterlandische Gnltnr. 
Jahres-Bericht fiir 1884. 8yo. Breslau 1885. 

The Society. 
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The University. 

Dijon : — Academie des Sciences, Arts et Belles-Lettres. Memoires. 

Ser. III. Tome 8. 8vo. Dijon 1885. The Academy. 

Loudon : — Royal College of Physicians. List of Fellows, Ac. 8vo. 

London 1886. The College. 

Marlborough : — College Natural History Society. Report. No. 34. 

8vo. Marlborough 1886. The Society. 

Pans : — ficole des Hautes £tudes. Sciences Philologiques et 

Historiques. Fasc. 63-4. 8vo. Paris 1885. The School. 

Soci^te Entomologique de France. Annales. S6r. 6. Tome IV. 

Trim. 1-4. 8vo. Paris 1884-5. The Society. 

Societe Geologique de France. Bulletin. S6r. III. Tonie XIII. 

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The Society. 

Watford : — Hei*tfordshire Natural History Society. Transactions. 

Vol.111. Part 7. 8vo. London 1885; Catalogue of the Society's 

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Milan : — R. Osservatorio Astronomico di Brera. Osservazioni 
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Milanu. The Observatory. 

Paris: — Mission Scientifique du Cap Hora, 1882-83. Tome II. 
Meteorologie, par J. Lephay. 4to. Paris 1885. 

Ministeres de Marine et de Tlnstruction Publique. 

Rome : — Osservatorio del Collegio Romano. Pontificia University 

continuazione del Bullettino Meteorologico. Vol. XXIII. 

Nos. 9-12. 4to. lioma 1884. The Observatory. 

Washington : — Bui*eau of Navigation. Astronomical Papers. Vol. 

II. Parts 3-4. 4to. Washingtoti 1885. The Bureau. 

Geological Survey. Bulletin. Nos. 7-14. 8vo. Washington 

1884-5. The Survey. 

Signal Service. Report of International Polar Expedition to 

Point Barrow, Alaska. 4to. Washington 1885. 

The Service. 
Bulletin of International Meteorological Obaeiry«fcvcya& fere "SS^fL 
nnd I f^fiS (imperfect). 4t(). Waaih\Tigtow •, lA.oxi>[)t\^ ^^s^^«« 

1.^ 



298 A^Mnte. [liifr|]» 

Obeervatioiui, Sbo. (eoniimted). 

Beview (General Weather Senrioe, 17.S.X 1888-84 (imparfsol) 
4iio. Woihingkm 1B8S^-S4i. The Meteorologioal QlBoa 

Treeamy Department. Animal Report of the Comptroller of Oib 
Cnrrenqy, 1885. 8yo. WatkingUm 1885. 

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TransactionB. 

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Zoological Society. TranHactions. Vol. XI. Part 2. Vol. JLiL 

Part 1. 4to. London 1885. The Society. 

Paris: — ^ficole Normale Sup^rienre. Annalcs. S6r. 3. Tome II. 

Supplement. 4to. Pa/ris 1885. The School. 

£cole Polytechniqne. Catalogue do la Biblioth^ne. 8vo. Paris 

1884. The School. 
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Sydney 1885. The Society. 

Vienna : — K. Akademie der Wisscnschaften. Denkschriften. Math.- 
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Phil.-Hist. Classe. Band XXXV. 4to. Wien ISSS. Sitznngs- 
berichte. Math.-Natarw. Classe. Abth. I. Band XC. Heft 
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Band XC. Heft 1-5. Band XCI. Heft 1-3. 8vo. Wien 1884- 
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berichte. Jahrgang 1885. 8vo. Wiirzburg. The Society. 

Journals. 

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1885. The Editor. 
Annales des Mines. S6r. VIII. Tome VIII. Livr. 5. 8vo. Paris 

1885. ^'WJvfc ^M&^^&XC^^^. 



1886.] Presents. 291) 

Journals {continued^, 

Aficlepiad (The) Vol. III. No. 9. 8vo. London 1886. 

Dr. B. W. Richardson, F.B.S. 
Bullettino di Bibliografia e di Storia delle Scieuze Matematlche e 
Fisiche. 1886. Aprile — Maggio. 4to. Boma, 

The Prince Boncompagni. 
Canadian Record of Science. Vol. II. No. 1. 8vo. Montreal 1886. 

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\ 1886.] On the Equilibrium Theory of Tides. 303 



April 1, 1886. 

Professor STOKES, D.C.L., President, in the Chair. 

Dr. John Francis Julias yon Haast (elected 1867) was admitted 
into the Society. 

The Presents received were laid on the table, and thanks ordered 
for them. 

The following Papers were read : — 

I. " On the Correction to the Equilibrium Theory of Tides for 
the Continents." I. By G. H. Darwin, LL.D., F.R.S., 
Fellow of Trinity College, and Plumian Professor in the 
University of Cambridge. II. By H. H. Turner, B.A., 
Fellow of Trinity College, Cambridge. Received March 12, 
1886. 

I. 

In the equilibrium theory of the tides, as worked out by Newton 
and Bemouilli, it is assumed that the figure of the ocean is at eacu 
instant one of equilibrium. 

But Sir William Thomson has pointed out that, when portions of 
the globe are occupied by land, the law of rise and fall of water ^ven 
in the usual solution cannot be satisfied by a constant volume of 
water.* 

In Part I of this paper Sir William Thomson's work is placed in a 
new li^ht, which renders the conclusions more easily intelligible, and 
Part II contains the numerical calculations necessary to apply the 
results to the case of the earth. 

If 7n, r, 2 be the moon*s mass, radius vector, and zenith 
distance ; g mean gravity ; p the earth*s mean density ; a the 
density of water ; a the earth's radius ; and ^ the height of tide ; 
then, considering only the lunar influence, the solution of the 
equilibrium theory for an ocean-covered globe is — 

\^^—J: (cos^z-i) . (1) 

• Thomson aad Tait's " Nat. PhiL," 188a, 1 8K». 
TOL, XL. X 



804 Prof, a H. Darwin. On the G>rrei^an to th0 [Apr.lJlJ 

This eqnilibrinin law would litill hold good when the ocean ii 
interrupted bj continents, if water were appiopriatelj supplied to or 
exhausted from the sea as the earth rotates. 

Since when water is supplied or exhausted the height of waiter wiD 
rise or fall eyerywhere to the same extent, it follows that the rise and 
fall of tide, aooording to the revised equilibrium theory, most be 
given by — 

l^^i4^/"*-«- • •■• « 

where s is a constant all over the earth for each position of the moot 
relatively to the earth, but varies for different positions. 

Let Q be the fraction of the earth's surface which is oooupied bj 
sea ; let X be the latitude and I the longitude of any point ; and lefc 
de stand for cos XdXdly an element of solid angle. Then we have — 






4irQ 



'i\^ 



integrated all over the oceanic area. 

The quantity of water which mnst be subtracted from the sea, so as to 
depress the sea level everywhere by a«, is iiTra^aQ ; and the quantity 

required to raise it by the variable height — — ^^ is the integral 

of this function, taken all over the ocean. But since the volume of 
water must be constant, continuity demands that — 



Sma 



^^(cosh-^)ds (3) 



integrated all over the ocean. 

On substituting this value of a in (2) we shall obtain the law of 
rise and fall. 

Now if X, Z be the latitude and W. longitude of the place of \ 
observation; h the Greenwich westward honr-angle of the moon at 
the time and place of observation ; and B the moon's declination, it is 
well known that — i 

oos'«— J-= J cos^ cos^^ cos 2(^— Z) + sin 2X sin i cos 5 cos (h—l) 

+|(i-sin2a)(i-sin8X) (4) 

We have next to introduce (4) under the double integral sign of (3), 
and integrate over the ocean. 

To express the result conveniently, let — 



1886.] Equilibrium llieorij of Tides for the Continents, 305 

-——I I cos^X cos 2Z (£5=008^X20082^3, -t—t\ lco82Xsin2ZcZ*=co82X2 8in2Z2, 

—I sin 2X cos Z€78=8in 2X^ cos Z^, -t—tA |8iii2XsiQZ(Z«=6m2X2siiiij, 

4w-QJJ wQJJ 

^jja 8iii2X-i)i.=|sm%-i (5) 

the integrals being taken over the oceanic area. 

These five integrals are called by Sir William Thomson 3U |t> ft» 
^y £, but bj introducing the five auxiliary latitudes and longitudes, 
^9 ^f ^i> hi \) ^^ shall find for the conclusions an easily intelligible 
physical interpretation. 

It may be well to observe that (5) necessarily give real values to 
the auxiliaries. For consider the first iotegral as a sample : — 

Every element of yycos^Xco8 2ZcZ« is, whether positive or negative, 
necessarily numerically less than the corresponding element of 43rQ, 
and therefore, even if all the elements of the former integral were 
taken with the same sign, (4irQ)"^j[/co82X cos 21 ds would be numerically 
less than unity, and a fortiori in the actual case it is numerically less 
than unity. 

Now using (5) in obtaining the value of /f(coa^Z'-^)d8, and 
substituting in (3), we have — 

fe-^ — -?!^— ^=icos2a[cos«Xcos2(A-Z)--cos2XjCOs2(A-y] 
a ' 2^(l-{<r//))r» 

+ sin 2^[8in X cos X cos (h—l) —sin X^ cos Xj cos (/'— Z^)] 

+ |-(J-sin2«)(sin2Xo-8in2x) (6) 

The first term of (6) gives the semi-diurnal tide, the second the 
diurnal, and the third the tide of long period. 

The meaning of the result is clear. The latitude and longitude 
Xj|, Z3 is a certain definite spot on the earth's sarface which has 
reference to the semi-diurnal tide. Similarly X], Z^ is another 
definite spot which has reference to the diurnal tide ; and Xq is a 
definite parallel of latitude which has reference to the tide of long 
period. 

From inspection we see that at the point X3, Z2 the semi- diurnal tide ' 
is evanescent, and that at the point X3, Z2 4>90** there is doubled tide, 
as compared with the uncorrected equilibrium theory. At the place 
X^, li the diurnal tide is evanescent, and at — X^, Z^ there is doubled 
diurnal tide. 

In the latitude X^ the long period tide is evBinQ&cei\.i^ %X!i^ >sjl 
latitude (Bometimes imaginary) arc sin-v/^^ — bxu^Xq^ ^;>DLfeT^ Sa ^oroW^ 
Jong period tide. 



306 Prof. O. H. Darwin. On Os CarrMiam to Oim [Ape 

Manj or all of these points maj hSi on contiiientfl, ao iShak 
evanescenoe or doabling maj onlj applj to the algebraioal ezpi» 
sions, wliicb are, unlike the sea, continaons over the whole glok 
But now let ns consider more precisely what the points axe. 

It is obvions that the latitude and longitude \ and 2^ iMqg 
derived from expressions for oos^co62Z| and 00Bh^8in2l^ xeal^ 
correspond with four points whose latitades and longitadea are — 

\. h\ -^1. kf ^s. ii+180^ -X^ ig+lSO'. 

Thus there are four points of evanescent semi-diurnal tide, aitoalel 
on a single great circle or meridian, in eqaal latitades N. and S., arf 
antipodal two and two. Corresponding to these fonr, there are hm 
points of doubled semi-diurnal tide, whose latitudes and longitndti 

^1, ^+90* ; -X^ Za+90*; X,, Za+270*; X,, «g4-270*, 

and these also are on a single great circle or meridian, at right anglei 
to the former great circle, and are in the same latitudes N. and S. u 
are the places of evanescence, and are antipodal two and two. 

Passing now to the case of the diurnal tide we see that Xj, \, 
being derived from expressions for sin 2\ cos ^ and sin 2X^ sin 2^, reailj 
correspond with foar points whose latitades and longitudes 



\.li\ -\, ^ + 180°; 90'-Xi, Zi; -90^+Xi, ^l + 180^ 

Thus there are four points of evanescent diurnal tide, situated on a 
single great circle' or meridian, two of them are in one quadrant in 
complemental latitudes, and antipodal to them are the two others. 
Corresponding to these four there are four points of doubled diurnal 
tide lying in the same great circle or meridian, and situated similarly 
with regard to the S. pole as are the points of evanescence with regard 
to the N. pole ; their latitudes and longitudes are — 

-Xi, Z^; Xi, Zi + lSO^ -90**+X^, Zi; 90**-Xi, Zl4-180^ 

r 

Lastly, in the case of the long period tide, it is obvions that the ] 
latitude Xg is either N. or S., and that there are two parallels of lati- 
tude of evanescent tide. In case sin^Xg is less than }, or X^ less than 
54° 44', there are two parallels of latitude of doubled tide of long 
period in latitude f arc sin \/{^— sin^Xg}. 

From a consideration of the integrals, it appears that as the con- 
tinents diminish towards vanishing, the four points of evanescent 
and the four points of doubled semi-diurnal tide close in to the pole, 
two of each going to the N. pole, and two going to the S. pole ; also 
one of the points of evanescent and one of doabled diurnal tide go 
to the N. pole, a second pair of points of evanescence and of doubling 
^^ j.^ 4^Ua g^ pole, a third paVc ol i^VhYa ol «^^3a»aR«w» %a^il ^ 



.886.] Equilihrium Theory of Tides for ike ContinenU. 307 

loabling coalesce on the equator, and a foarth pair coalesce at the 
•ntipodes of the third pair ; lastly, in the case of the tides of long 
leriod the circles of evanescent tide tend to coalesce with the circles 
»f doubled tide, in latitudes 35"* 16' N. and S. 

We are now in a position to state the results of Thomson's corrected 
lieory hj comparison with Bernouilli's theory. 

Consider i^e semi-diurnal tide on an ocean -covered globe, then at 
}he four points on a single meridian gpreat circle which correspond to 
;he points of evanescence on the partially covered globe, the tide has 
ihe same height ; aud at any point on the partially covered globe the 
lemi-diurnal tide is the excess (interpreted algebraically) of the tide 
it the corresponding point on the ocean-covered globe above that at 
the four points. 

A similar statement holds good for the diurnal and tides of long 
period. 

By laborious quadratures Mr. Turner has evaluated in Part II the 
five definite integrals on which the corrections to the equilibrium 
theory, as applied to the earth, depend. 

The values found show that the points of evanescent semi-diurnal 
tide are only distant about 9"" from the N. and S. poles ; and that of 
the four points of evanescent diurnal tide two are close to the equator, 
one close to the N. pole, and the other close to the S. pole ; lastly, 
that the latitudes of evanescent tide of long period are 34° N. and S., 
and are thus but little affected by the land. 

Thus in all cases the points of evanescence ara situated near the 

places where the tides vanish when there is no land. It follows, 

therefore, that the correction to the equilibrium theory for land is of 

no importance. 

G. H. D. 
II. 

For the evaluation of i^e five definite integrals, called by Sir 
William Thomson §i, |p, (t, Jp, €, and represented in the present paper 
by functions of the latitudes and longitudes X^, X.^, X^, and Z^, Zj, respec- 
tively similar in form to the functions of the " running " latitude and 
longitude to be integrated, it is necessary to assume some redistribu- 
tion of the land on the earth's surface, differing as little as possible 
from the real distribution, and yet with a coast line amenable to 
mathematical treatment. The integ^ls are to be taken over the 
whole ocean, but since the value of any of them taken over the whole 
sphere is zero, the part of any due to the sea is equal to the part due 
to the land with its sign changed ; and since there is less land than 
sea, it will be more convenient to integrate over the land, and then 

change the sign. 

Unless specially mentioned, we shall hereaiter Qj&^\iTXi& >[X^V» V^cl^ 
nt^^tion is taken over the land. 



808 



Mr. H. H. Turner. On the Cwrreetum to the [Apr. 1, 



The last of the integralB has already been evaluated faj Pr of ewo r 
Darwin,* with an approximate ooast Une, which follows parallela of 
latitude and longitude alternately. 

His distribution of land is given in the following table :— 



I 



N.lat. 



W. long. 



B. long. 



Lat. 8(f to 90° 
70 „ 80 
eo ,. 70 

60 ,, 60 



40 ,, 60 

80 „ 40 

20 „ ao 

10 „ao 



t» 



10 



S. lat. 



0°to lOP 

10 „ 20 

20 „ 80 

80 ,, 40 

40 ,, 50 

50 „ 60 

60 „ 70 

70 „ 80 

80 „ 90 



20'to60°. 
22^ to 66'' : 86"* to 116^ 
86"* to 62^ : 66'' to 80^ : 

9(f to 166^ 
(ftoef I 60Pto78° : 

90"tol8tf*. 
0* to 6** : 66* to 128*. 
0« to 8° : 78* to 120*. 
0* to 16* : 80P to 82* : 

97* to 110*. 
O*toir* : 87* to 96*. 

68*to78P. 



W. long. 



87* to 80" 
87 ,. 74 



45 
65 
65 
67 
66 






» 



}> 



»» 



71 
78 
78 
72 
65 



66* to 60* :90*toll0e. 
10*tol80P. 

10*tol40P t 166*tol60*. 

0* to 186*. 

(f to \2Xf : 186* to 188*. 

0* to 118*. 

0*to60* J 76*to86* : 

96'' to 108* : 122* to 125*. 
0*to48* : 98^tol06* : 

112* to iir. 



E. long. 



12* to 40* 
12* to 88* 

16* to 88* 
20* to 23* 
170* to 172*. 



110* to 18(f. 
45* to 60* : 

126* to 144*. 
115* to 161*. 
182* to 140*. 



120* to 180*. 
about 20^ of longitude. 
180* 



» 



>} 






N.B. — The Mediterranean^ being approximaiely a lake^ is treated as 
land. 

The limits of the 20* and 180^ of longitude between S. latitudes 
70^ and 90* are not specified. For the evaluation of the last integral 
this is not necessary, for restricting 



11 



(3sin»X-l)cosX(fX(2Z 

to a representative portion of the land bounded by parallels X^ and X^, 
^and ^, weget- JCZj-li) fsin X + sin 8x1 X ~ and similarly for Q ; 
80 that if ^2 fti^d ^2 he the number of degrees of longitude N. and S. 



• Thomson and TaitS •* "SaJt. ^\i^.r ^»». \ ^^^ 



1886.] Equilibrium Theory of Tides for the Continents. 



309 



of the equator respectively between latitudes X^ and \^ the last of the 
integ^ls becomes 

Si(^ + h) r«n X+ sin 3x1 

720-S(^+^jj)rsinx1 
But for {e,g,) 

I I cos'Xcos22cosX(2X(U 

=^r98inX+Bin3xl^r8in2z]'" 

the actual limits l^ and 7^ must be given, and not merelj their differ- 
ence. 

It is, however, obvious, on inspection of these integrals, that the 
land in high latitudes affects them bot little ; and we shall not lose 
much by neglecting entirely the Antarctic continent in their evalua- 
tiim. 

This evaluation is reduced by the above process to a eeries of multi- 
plications, and on performing them the following values of ^, |p, ft, |p, C, 
and Q are obtained on the two hypotheses. 

(1.) That there is as much Antarctic land as is given in the schedule, 
which is, however, only taken into account in the last integral C, and 
the common denominator AarQ of each. 

(2.) That there is no land between S. latitude 80** and the pole. 

The value of Q is given in terms of the whole surface, and repre- 
sents the fraction of that surface occupied by land ; it must be remem- 
bered that the Mediterranean Sea is treated as land. Professor 
Darwin quotes Bigaud's estimate* as 0-266 : — 





let hypothefliB. 


2nd hypothesis. 


% 


+ 008023 
+ 0-00539 
-0 -01976 
+ 0-02910 
-0-01620 
0-283 


+ 003008 
+ 00537 
-0 01966 
+ 0-02896 
-0-00486 
0-278 


c !.......! ! 


9 


Cr 

^ 


Q 


^.•. .••*... 



These results for (E and Q have already been given by Professor 
Darwin in '* Thomson and Tait's Natural Philosophy," and I have 
found them correct. 

• " Tmnf. Cam. PhiL 8oc.," vol. vL 



SIO 



'Mr, H. H. Tomer. On the Carreeikm to the [Apr. l,- 



We then find for the set of latitades snd longitudes of evaoeioeiit 
tide : — 



Katuxe of tide. 


* 




lit hypothetiB. 


2iid hypoUwrit. 


Loxur D6riod 


lat. Xo 


M^'Se'N. 


86*»4rN. 




Bimnal 




long, h 


r O'S. 
66 60 E. 


' r O'S. 

66 60 E. 


Sami-diorittl 


• * 

b 


lat X, 
long. 4 


6 8 W. 


W6e'N. 
6 4 W. 



The other points of evanesoeace are of oonrse easily derivable from 
these, as shown in the first part of this paper. 

As a slightly closer approximation to trath, I hare calcnlated these 
integrals on another supposition. There are cases Where lines satis- 
fying the equations 

Z= const, or X= const, 
diverge somewhat widely from the actual coast line, but a line 

+ oZ + &X= const. 



(where a and h are small integers) can 


be found following it more 


faithfully. An approximate coast line of the land on the earth is 


defined in the following schedule, west longitudes and north latitudes 


being considered positive. 


t 




Limits of 




Limits of 


longitade (I). 


Equation. 


latitude (X). 


-f 20'^to4- 10* ... 


. -X=Z-40 


.... +20^to+30" 


. • • 


1=10 


.... 4-30 „ +40 


+ 10 „ - 23 ... 


. -X=Z-60 


.. +40-,, +73 


- 23 „ +120 ... 


X=73 




• • • 


Z=120 


.... +73 „ +80 


+ 120 „ + 20 ... 


X=80 




• • • 


1=20 


.... +80 „ +70 


-f 20 „ + 6() ... 


. -3X=Z-230 


.... +70 „ +60 


-h 60 „ + 70 ... 


x=z+io 


.... +60 „ +80 


-h 70 „ -h 80 ... 


X=80 




-h 80 „ + 60 ... 


X=Z 


.... +80 „ +50 


-f 60 „ -h 90 ... 


. -2X=Z-160 


.... +60 „ +30 


+ 90 „ +100 ... 


X=30 




-flOO „ + 80 ... 


X=:Z-70 


.... +30 „ +10 


•f 80 „ + 70 ... 


X=10 




-h 70 „ -f 80 ... 


. 2X=Z-60 


.... +10 „ -10 


■f 50 „ -f 73 ... 


. -\=l-^ 


.... -\^ ,, -^-^ 


• . • 


l==7^ 


.... -^^ ,, — \^. 



*86.] EquiU&ritm Theory of Tid€$for &« Cmtinenta. 



limits of 




Limit! of 


longitude (0- 




UtitudB (X). 


+ 78-10+ 80' ... 


x.=2i-160 . . 


. -14-10 0- 


+ 80 „ +110 ... 


1=1-80 


„ +60 


+ 140 „ -150 ... 


X.=60 





-150 „ -100 . . . 


. -X=i+90 


. . +60 „ +10 


-100 „ - 90 . . . 


. +>.= l+110 .. 


. +10 „ +20 


- 90 „ - 80 ... 


. -X=l+70 


. . +20 „ +10 


- 80 „ - 65 . . 


\-i+90 


. +10 „ +25 


- 65 „ - 40 . . . 


. -\=i+40 


.. +25 „ 





l=-40 


„ -20 


- » „ - 20 . . . 


. -x=/+60 


. . -20 „ -40 


- 20 „ - 8} . . . 


1=41+40 


. -40 „ + 5 


- 8{„ + 12^... 


X=5 





+ 1%, + 20 .. 


X=2I-20 
^eto Qainea. 


.. + 5 „ +20 


-13010-150 .. 


2X=1+130 .. 


Olo-lO 


-160 „ -140 .. 


. ■ )i=-10 





-140 „ -l:i0 .. 


X=l+130 .. 
AuitraiM. 


. . -10 , 


-140 to -150 .. 


x=l+130 .. 


. . -10 to -20 





1=-150 


-20 „ -35 


-150 „ -115 .. 


X=-35 








1=-116 


. . -35 „ -22J 


-115 ., -140 .. 


. -2X=1+160 


.. -22J„ -10 



It will be Been that it in only ittrely necesaaiy to depart from the 
rmB of equation +\=I+ai and the two original forms X=conBt. l=s 
inat. to represent the coast line with considerable accnracy. There 
■B still left one or two outlying portions, of which mention will be 
ode later. 

Mow snpposiog we are to find the ralne of the first integral for the 
>rtion of land indicated by the shaded portion of the diagram, E, Q 
)iiig the eqnator : 




' eqaatJone to ita boand&rieB being WL-itt«a at ftie a.\4© ol e»^- 



312 Mr. H. H. Tomer. Onth$ GmwUom io ik§ [Aft-I*] 

We hsTe 1 

[[(M)8^JXooB2Zd2=JLrr9BmX+8m3x1^oo8 Udl | 

=1 p{9 am (1+0) +Bin3(Z+«)}ooe2{i« 
+ 1 (9 am c +8m So) cos 2{cS 

+ jJ-{9 Bin Kl+y)+gin Kt+y)} 008 2liL 

We maj thus simply travel roimd the bonndarj omitting tlis 
places where X= constant: being careful to go roond all the pieces o£ 
land in the same direction. If we suppose l=« to be the meridian of 
Greenwich, and the land to be in the northern hemisphere, ths 
direction indicated above is the wrong one for obtaining the value of 
the integrals, over the land, for the longitudes increase to the left; 
but by following this direction we shall obtain the values over the 
sea as is in reality required. 

The result of integration has, of course, a different form for each 
form of the relation between I and X representing the boundary. In 
computing the numerical values of the integrals, it is convenient to 
consider together all the parts of the boundary represented by similar 
equations. 

Below are given as representative the forms which the numerator 
of the first integral ^ assumes for different forms of the boundary, 
the quantities within square brackets being taken within limits. 

Form. Value of Integral. 

:f\=:l^x ±^[|co8 (6Z-|-3aj)-|-3co8(3?-h»)-hcos0 + 3jr) 

— 9cos(— Z-fa;)] 

X=aj .... -|-,>^(9sin»+sin3aj)[8in2Z] 

Z=a; .... Zero 

X=2Z-|-« — ^[icos(4Z+«)-9Zsinaj-|-^co8(8Z+3*) 

+ioos(4Z+3a5)] 

X=4iZ-|-« .... -Jt[ioos(6Z-H»)+f cos(2/+«)+A«>8(14^+3j;) 

^T\yCOs(10Z+3»)l 

4:2X=Z+« ±A[-Vcosi(5Z+aj)-6cosf(-3Z+«) 

+f cos Jc7Z+3a>)-2sini(-^+3aj)] 

-3\=Z+aj .... +^[VcosK7^+aj)-Jfcosi(-5Z+aj) 

+icos(3Z+»)— cos(— Z+»)] 



1886.] Equilibrium Theory of Tides for tJie Continents. 
Eyalaating these integrals on this supposition, we obtain 



313 





1st hjpothesia. 


2nd hypothesis. 


% 


+ 0-02119 
+ 0-00778 
-0 01890 
+ 0-03169 
-0-04364 
0*283 


+ 0-02110 
+ 00776 
-0-01882 
+ -03128 
-0*03319 
0-278 


<v 

« 


9 

c 


fi 


& 

^ 





V 



It will be noticed that the yalnes of Q are exactly the same as 
before. 

From these we dednce 



Nature of tide. 




1st hypothesis. 


2nd hypothesis. 


LoniF Deriod 


lat. Xq 


83° 29* N. 


83° 66' N. 




Diurnal 




lat. Xi 
long, li 


1° S'S. 
69 7 E. 


1° 3'S. 
68 68 £. 


Semi-diurnal 


lat. Xg 
long. ^ 


81° 22' N. 
10 6 W. 


81° 23' N. 
10 6 W. 



The agreement of these values of the quantities with the values 
calculated on the previous supposition is not quite so close as I anti- 
cipated, but it should be remarked that the numerators of the quan- 
tities ^ IP, (t, ^9 tt are the differences of positive and negative 
quantities of very much greater magnitude, as becomes obvious on 
proceeding to the numerical calculation; and thus a comparatively 
small change in one of the large compensating quantities, due to large 
tracts of land in different portions of the globe, affects the integrals 

a considerable extent. 

In this connexion I was led to investigate the effect of counting 
various small islands and promontories as sea, or small bays and 
straits as land. For instance, a portion of sea in the neighbour- 
hood of Behring's Straits is included as land, and a corresponding 
correction must be applied to the integrals. This correction I 
have estimated as follows: — The area of the sea is estimated in 
square degrees, by drawing lines on a large map corresponding to 
each degree of latitude and longitude and counting the squares 
covered by sea, fractions of a square to one decimal place being in- 
cluded, though the tenths have been neglected in the concluded sum. 
This area has then been multiplied by the value of (say) cos^X cos 21 



314 On the Eqailibrmm Theory of IMei. [Apr. 1, 

for the approximato centre of gravity of the portion, to find ui 
approximate valne of ibe iotegra! //coa'XcosSicosXiii over its sorface. 
By drawing the ftsanmed coastline on a map, it will become obvious 
that auch coiTectiona may be applied for the following portions, 
defined by the latitade and longitude of their centres of gravity; 
remarking that when there is a portion of land which may be fairly 
considered to compensate a portion of eea in the immediate neigh- 
bourhood, no correction has been applied. For instance, it would be 
seen that part of the £amschatkan Peninsula is excluded from the 
coast line, and part of the Sea of Okhotsk is included; bat these 
will pi-oduce nearly equal eSecta on the integrals in opposite dirtio- 
tiouu, and are thns left out of consideration. 



■quan: dogreea. 




Lmityde. 


+ 160 


+ 172° ... 


+ 6f 


+ 240 


+ 150 ... 


-. +71i 








+ 80 ... 


+ 60 


+ 52 


+ 68 ... 


+85 ... 


+ 9 


- 20 


+ 75 


+21 


- 69 


+ 55 


+ 4 


+ 43 


+ 34 


-11 


+ 22 


- 37 


-20 


- 18 


- 47 


-19 


+ 65 


- 53 


+ 18 


- 16 


-107 


+ 13 


- 31 


-102 


+ 2 


- 49 


-114 


+ 1 


- 27 


-123 


+ 12 


-11 


-118 


- 5 


- 4.3 


-138 


+36 


- 39 


-173 


-42 



N.B. — Land-areai are contidered potitive, tea negative. 

We then find the fallowing corrected valneB of the integrals :■' 



I 
f, 



l*t hypotheui. 2dA bjpotli 



02237 


* 02247 


Q 00230 


+ 0-00281 


01968 


-0 01961 


0- 02665 


rO 02676 


0- 01715 


-0 02810 


oam 


\ 0-H\ 



1886.] 



Fossil Remains of Meiolania, Ow. 



315 



and finally the following yalnes of the latitudes and longitudes of 
evanescent tides : — 



Nature of tide. 




Ist hTpothesis. 


2nd hypothesis. 


LonflT Deriod 


lat. Xq 


84** 33' N. 


34'' 7'N. 




Diurnal 


•{ 


lat. Xi 
long. ^ 


0' 57' S. 
63 47 E. 


O- 67' S. 
53 46 E. 


Semi-diurnal 




lat. X} 
long. 2, 


SV 23' N. 
2 56 W. 


81« 21' N. 
2 56 W. 



The estimation of corrections due to these supplementary portions 
has been checked in two cases by a detailed extension of the method 
of square blocks of land used previously for evaluation of the whole 
integrals; that is to say, two of these portions were separately 
divided into square degrees (instead of squares whose sides were 
each ten degrees), and the integral evaluated in a similar manner to 
that previously described. The agreement of the values so calcu- 
lated with those obtained by the above method of estimation was 
sufficiently exact to justify a certain confidence in the close agreement 
of the finally corrected values of the integrals with their theoretically 
perfect values. 

H. H. T. 



II. " Description of Fossil Remains of two Species of a Mega- 
lanian Genus (Meiolania, Ow.), from Lord Howe's Island." 
By Sir Richard Owen, K.C.B., P.R.S. Received March 15, 
1886. 

(Abstract.) 

In a scientific survey by the Department of Mines, New South 
Wales, of Lord Howe's Island, fossil remains were obtained which 
were transmitted to the British Museum of Natural History, and were 
confided to the author for determination and description. 

These fossils, referable to the extinct family of horned Saurians 
described in former volumes of the ** Philosophical Transactions "• 
under the generic name Megalania, form the subject of the present 
paper. They represent species smaller in size than Megalania prisca^ 
Ow., and with other differential characters on which an allied 
genus Meiolania is founded. Characters of an almost entire skull 
with part of the lower jaw-bone, of some vertebraB and parts of the 
scapula and pelvic arches, are assigned to the e^«<^\^^ Mefwc^laMMb 

♦ Vol 149, 1858, p. 43 ; ib., 1880, p. 10^7 •, <b.,\8SV,^.\^^n- 



816 Magneiie DeeUnaUon and Hanzcnial Farce. [Apr. 1, 

plaiycepi. Portions of a oraninm ftnd mandible are referred to a 
Meiolania mitior. Both Bpecies, as in Megalania^ are edentnloos unA, 
modifications of the month indicative of a homj beak, as in the 
Ohelonian order. The cranial and rertebral characters are, however, 
sanroid. Horn-cores in three pairs are present bnt shorter xelativelj, 
especially the first and third pairs, than in Megalania prisea. The 
indication of a seyenth more advanced and medial horn is feeble, and 
the anthor remarks that in the small existing lisard (MolocK) this 
horn has not an osseons support. The tail of MeiolarUa is long and 
stiff ; the yertebrsB being encased by an osseous sheath, developing, as 
in Mega^nia, tuberous processes in two pairs, corresponding with the 
vertebr» within : such defensive parts are less developed, relatively, 
than in Megalania prisea. 

The locality of these singular remains is an insular tract not 
exceeding 6 miles by 1 mile in extent ; situated mid- way between 
Sydney and Norfolk Island, in lat. 31'' 31' S., long. 159'' 9' E. 
The island is formed of three raised basaltic masses connected by 
low-lying grounds of blown coral-sand formation, consisting of 
rounded grains and fragments of corals and shells. In the parts of 
this formation converted into rock were found the petrified remains 
which are the subject of the present paper. It is accompanied by 
drawings of the most instructive fossils : these form the subjects of 
five plates illustrative of the text. 



III. "On the Luni-Solar Variations of Magnetic Declination and 
Horizontal Force at Bombay, and of Declination at Trevan- 
drum." By Charles Chambers, F.R.S., Superintendent of 
the Colaba Observatory, Bombay. Received March 24, 
1886. 

(Abstract.) 

The materials, described in this paper are twenty-five years of 
declination observations, and twenty-six and a half years of horizontal 
force observations, taken at the Colaba Observatory, Bombay, and 
some results of ten years declination observations taken at the 
Trevandrum Observatory. A consideration of the lunar diurnal 
variations derived from these observations for different seasons and 
phases of the moon, leads the author to form the hypothesis that 
these variations are, properly speaking, combinations of solar diurnal 
variations that run through a cycle of change in a lunation. The 
characteristics of the variations that give rise to the hypothesis are 
(1) that generally the great movements occur in them, as in the mean 
solar diurnal variations for full lunations, in the solar day hours^ 
whilst the night hours are relatively quiescent ; and (2) that they 



188(i.] On a Ntnc Form of Stereoscope. 317 

have generally the same character and range at intervals of half a 
Innation, and opposite characters at intervals of a quarter of a Inna- 
tion. An expression for the variation at any age of the moon that 
would satisfy these characteristics would take the form 

fciW cos2(^py f..,ih) sin 2(^«), 

where h is the honr of the solar day, P the mean period of a lunation, 
and i the age of the moon, and fe-zW^ fs-iW ^^ solar diurnal varia- 
tions that are constant for the same season of the year. It was found 
that although such a formula embraced the bulk of the phenomena, 
there remained minor characteristics of a systematic kind that found 
expression only in the extra terms of the formula when extended as 
follows ; — 

/,.i(A)co8(^«)+/.#)8ii.(^<)+/..5(ft)co8 2(2^if)+/..,Wsin2(^<) 

Not only does the hypothesis hold good in the different seasons oi 
the year and with respect both to the declination and horizontal force 
at Bombay, but the variations of the two elements are related to each 
other in a definite manner ; in the winter season the variations of decli- 
nation at one age of the moon are similar to those of the horizontal 
force at an age of the moon one-eighth of a lunation greater ; and 
conversely, in the summer and autumn the variations of horizontal 
force take precedence of those of the declination by one-eighth of a 
lunation. So far as the means of testing it are available, the hypo- 
thesis holds also in respect of magnetic variations at Trevandrum. 
£ach term of the formula is symbolical of a definite physical concep- 
tion, viz., that an otherwise constant variation swells and contracts 
with a wave-like motion, as the age of the moon increases, between 
the limits —f(h) and •j-f(h). The existence of luni-solar variations 
of the kind described is, so far as the author is aware, brought to 
light for the first time, by the long series of observations taken at 
Bombay, and their capability of expression in a compact form which 
has a definite physical significance cannot, the author thinks, fail to 
be helpful towards the discovery of the physical conditions that lie 
behind them. 



IV. " On a New Form of Stereoscope." By A. Stkoh. Commu- 
nicated by Lord Rayleigh, D.C.L., Sec. R-S. Received 
March 22, 1886. 

Although the late Sir Charles Wheatstone's beautiful invention, 
the stereoscope, gives the appearance of full relief or perfect solidity 
to photographs of objects seen by its aid, the photographs for the 



'818 HT.A.StToL [Apr. I, 

same most natnndlj be of limited dimenrionB ; and though Tiemd 
thiongb xnagnifjing lenses, the images of the objects are pnwm iad 
to the eye on a scale far below the size of their originals. 

It has therefore occurred to me, that if the magnified image of s 
photograph projected on a screen by the optical lantern could be madt 
stereoscopic, a still greater resemblance to the original might be 
obtained. 

With a view of producing snoh an effect, I have constmcted the 
apparatus I will now describe, which is, however, not intended to 
enable a large number of persons to see the projected pictures at the 
same time, as in the case of dissolving yiews, but is at present limited 
to the use of two persons simultaneously. It could, however, be 
easily constructed so as to be available for a greater number. 

The principle of the arrangement depends on the well-known 
effects of the persistence of vision ; revolving disks are employed for 
alternately obscuring two pictures, projected on a screen in the same 
place, and at the same time interfering with the view of the observer 
in such a manner that only one picture is seen by the observers* right 
eyes, and the other by the left eyes. 

Two optical lanterns are placed side by side, as for dissolving views. 
Two transparencies, photographed in the same manner, as if intended 
for an ordinary stereoscope, are placed one in each lantern, and pro- 
jected on a screen in such a position that they overlap each other as 
nearly as possible. The picture which is intended to be seen by the 
right eye may be placed in the right hand lantern, and the other in 
the left. 

Supported by suitable framework, and in the front of the two 
lenses of the lanterns, is a revolving disk, portions of which are cut 
away, so that during its revolutions it obscures the light of each 
lantern alternately, or in other words, so that only one picture at a 
time is thrown on the screen. A continuous change from one picture 
to the other is thus obtained. 

In the same framework, and in convenient positions for the observers, 
two pairs of eye-holes are provided, one pair on either side of the 
apparatus. Behind each pair is also a rotating disk, and these disks 
are connected by suitable wheel- work or driving bands with the one 
previously mentioned, in such a way that the three disks rotate 
together, and at the same rate. The two last-named disks are also so 
cut that they will obstruct the view through the right and the left 
eye-holes alternately. 

Finally the connexion between the three disks has to be so arranged 
that the time of obscuring the view of the observers' right eyes or 
left eyes shall coincide with the time when the light is shut off from 
the right or left lens of the lanterns respectively. 
It 18 obvious that by this airangemQiLt >i2ti^\^V\i ^^oa cs^ai. ^-^ %^^>(>^<^ 



1886.] On a New Form of Sterroscojie. 319 

pictnre projected from the left hand lantern, and the right eyes can 
only see that from the right hand lantern. 

The rotation of the disks must be of such a rate, that the alternate 
flashes of the right and left pictures on the corresponding eyes follow 
in such rapid succession that the impression made by one flash does 
not diminish sensibly before the next flash on the same eye is received. 
The number of flashes for each eye which is required to produce an 
apparently continuous view, without any flickering effect, is from 
thirty to forty per second. As the disks are so cut as to produce two 
flashes for the right eyes, and two for the left in one revolution, they 
must consequently be kept rotating at a rate of from fifteen to twenty 
revolutions per second. 

The rotation of the disks is effected by a driving-wheel and band, 
worked by a crank handle at the back of the apparatus. 

The perspective effect obtained by the above arrangement is very 
perfect, the image of each object standing out in solid relief. 

Considering that by this arrangement the two eyes never see at the 
same time, and that each eye views its picture after the other, it is 
interesting to find that the persistence of vision so completely bridges 
over the alternate interruptions to which it is subjected as to produce 
the effect of a continuous view. 

An unavoidable effect resulting from this arrangement is, that by 
the rotation of the disks one half of the light produced by each 
lantern is always cut off; the higher, therefore, the illuminating 
power used the better is the result. 

This defect is, however, I consider, counterbalanced by several 
advantages which this form of stereoscope possesses. Firstly, the 
pictures can be enlarged to such an extent as to appear equal, or even 
larger than the original objects from which they were taken ; and 
secondly, the eyes, in looking at the pictures, are not in any way 
subjected to strain by lenses, prisms, or reflectors, or by the difficulty 
which some persons experience in getting the two pictures to super- 
pose. For each eye views its corresponding picture in exactly the 
same position it would see it in if it were looking at the original, 
since the two pictures are practically in the same place, which is not 
the case in any other form of stereoscope. 

Although with the apparatus as here described only two persons 
can see the pictures at the same time, it would not be yerj difficult to 
construct it so as to be available for a greater number. The side disks 
above described only serve to control one pair of eye-holes each, but 
by making them a little larger they would serve for two pairs each, 
thus accommodating four observers. By increasing the number of 
disks, the number of observers might be increased proportiQi\aitAV|« 



{ 



^ 



VOL. XL. 






Dr. L. C. Wooldridge. [Apr. 8 



April 8, 18S6. 

ProfeSBor STOKES, D.C.L., President in the Chair. 

The Presents received were laid on the table, and thankB ordend 
for them. 

The Croonian Lecture was delirered : — 

I. Croonun Lkctobb.— « On the Coagulation of the Blood." 
By L. C. WOOLDRIDGE, M.B., D.Sc, Demonstrator of Phy- 
fiiologj in Guy's Hospital and Research Scholar to the 
Grocers' Company. Communicated by Professor M. FosTEB. 
Sec. R.S. Received April 6, l«8fi. 
(Abstract.) 

1. Aa to the relation of the corpascular eletnenta of the blood to 
ooagalation. - The plasma itself contains all Ibo elements necessary 
for coagnlatioa. 

The white blood corpasoles probably aid coagalation to a certain 
extent, but their inflnence is entirely secondary. 

The really imporfant factor in initiating coagulation is a substance 
dissolved in the plaama, discovered by the author, and called by htm 
A-fibrinogen. Lymph cells differ from white blood corpuscles ; they 
are very active in indncing coagulation. 

2. As to the chemical processes of coagulation, the author considers 
there are three congnlable bodies present in the plasma. These he 
names A-, B-, and C-fibrinogen.* They are closely allied to 
another, and are not separated by a sharp line from one another. 

C>fibriuogen is identical with the body which has hitherto been 
known as fibrinogen, but it is only present in minimal quantitiea in 
blood plasma; it is coagulable with fibrin ferment. The bulk of the 
coagnlable matter of the plasma is B-fibrinogen; it clots ou tiio 
addition of lecithin ; it does not clot with fibrin ferment ; it clots 
with leuoocytee from lymph glands. 

A-fibrinogen is separable from the plasma by cooling ; it separates 
as minute, regular, rounded granules ; it is not coagulable by fibrin 
ferment. 

A- and B-fibrinogen are componnds of proteid and lecithin. The 



1886.] 



(hi the Coagulation of the Blood, 



321 



essential point in tlie coagulation of the blood is a loss of lecithin on 
the part of A-fibrinogen, and a gain of lecithin on the part of 
B- fibrinogen. A-fibrinogen loses some of its lecithin to B-fibrinogen, 
and the resnlt is that in the place of the two fibrinogens we have 
fibrin. Previons authors have all regarded coagulation as essentially 
a fermentative process. 

The author regards the fibrin ferment as purely subsidiary, and 
considers that coagulation is nearly allied to crystallisation. 

3. In the fluid of lymph glands from which all the cellular elements 
have been removed, another form of fibrinogen exists closely allied to 
and probably the precursor of the A-fibrinogen of the blood. It 
differs from the latter in causing intravascular clotting,* whereas 
A-fibrinogen only causes under normal conditions clotting in shed 
blood. 

It is a proteid-lecithin compound, and its action can be shown to 
depend on the lecithin it contains. It has a wide distribution apart 
from lymph glands. 

In the fluid of serous cavities of certain animals, the only coagulable 
body present is C-fibrinogen, and since the blood of these animals 
contains both A- and B-fibrinogen, the vascular wall either only 
allows. C-fibrinogen to pass, or changes A- and B-fibrinogen into 
C-fibrinogen in their passage through. 

• Vide " Proc. Boy. Soc.," vol. 40, p. 184. 



J. t 



322 Dr. S. J. Hicksoa On certain [Apr. 15, 



ApHl 15, 1886. 

Professor STOKES, D.G.L., President, in the Chair. 

The Presents received were laid on the table, and thanks ordered 
for them. 

The following Papers were read : — 

I. " Preliminary Notes on certain Zoological Observations made 
at Talisse Island, North Celebes." By Sydney J. Hiokson, 
D.Sc, B.A. Communicated by Professor H. N. MOSELEY, 
F.R.S.* Received March 25, 1886. 

Notes upon an Alcyonarian (Clavnlaria viridis). 

In one of my earliest walks upon the coral reefs of Talisse, I came 
across a spot where Tnbipores and Comnlarias were more abundant 
than elsewhere. Quantities of the little crowds of brownish -green 
or pure brown polypes of these Alcyonarians, with occasionallj a 
crowd of the emerald-green polypes of a small species of Tubipora, 
were to be seen on every side. As I was wading along through the 
water on this spofc, my stick accidentally struck against a mass of 
what I thought was Tubipora ; but when the polypes had retracted I 
saw to my surprise that, instead of the usual bright red skeleton, 
there was a skeleton of a dirty green colour, the tnbes of which wei^e 
joined, not by platforms, but by tubes. Taking with me a large speci- 

• [Note hy Professor H. N. Moseley. — The Alcyonarian described here by 
Mr. Hickson is apparently identical with a specimen in the British Museum, 
collected by Mr. A. R. Wallace in the Aru Islands, and labelled Clatmlaria tfiridis. 
The existence of transverse communicating canals in Claytdaria, extending between 
the vertical tubes at successive heights above the stolon tubes, as in Syringopora, is 
apparently a new fact, and one of great interest. The genus Clavularia has received 
considerable attention from modern naturalists. G-. v. Koch has described the 
anatomy of Clavularia prolifera, and A. Kowalevsky and A. F. Marion the larval 
phases of Clavularia petricola ; but these forms, together with most others included 
in the genus, appear to have the vertical tubes united only at the level of the stolon, 
as is the case, according to Mr, Hickson, in the young state of the form he describes. 
Possibly his form will require to bo placed in a separate genus. The existence of 
rudimentary ampullsB in the coenosteum of Millcpora has been described by 
Mr. Q.ixelohf of the British Museum, but the actual gonads of the Milleporidie have 

hitherto remained undiacoveTed. TL\ie TioV«a \ia.-M«i Xi^ctv ^kyv\X«q. V3 '^^. \L\s^iM^w 

where he is of course unable to reteT to *c\exi\.i&.c\i\«T^^<>«ftvi 



1886.] Zoological Observations made in North Celebes, 323 

men of it in sea- water, I examined it carefully at my house, and the 
next morning I procured some more, and treated it in yarious ways 
for microscopic examination. 

There are one or two features in the anatomy of this Alcyonarian 
which throw a good deal of light not only upon the zoological position 
of Tubipora but also that of the extinct Syringopora. 

At present I have only found this form on the inside of the reef 
growing upon old and dead coral masses; in its neighbourhood are 
numerous specimens of Tubipora, some of them with unusually large 
tubes, two or three species of Comularia, a few Madreporas, and one 
or two AstrsBids. It clings to the rocks by a stolon of tubes, which 
nm in various directions and follow all the unevennesses of the sup- 
porting rock. It is very easy, however, to pull it away bodily, without 
injuring the stolon. 

The polype tubes spring perpendicularly from the stolon, and rise 
to a height of 2 or 3 inches. I have not found any tubes longer than 
that at present, in fact the average is rather below that. It may be, 
however, as is the case with Tubipora, that the masses grow much 
larger and the tubes much longer in more fikvourable localities. 
The tubes are united together, not by platforms, as in Tubipora, 
bat by simple tubes, as in Syringopora (fig. 1), and from these con- 
necting tubes new polype tubes spring. Each polype tube is marked 
by eight grooves, corresponding with the eight mesenteries, and these 
grooves, instead of running straight from the stolon to the mouth, 
turn to the left, and run up the tubes spirally, plainly showing that 
in the course of the growth of the polype from the stolon or connect- 
ing tube it is twisted from left to right. Examining a portion of the 
dried skeleton, I found that it is not purely calcareous, as is the 
skeleton of Tubipora, but consists of a few long spicules imbedded 
in a coriaceous substance, which is unaffected by strong hydrochloric 
acid. I should not like to say for certain of what chemical nature 
this substance is, but from its microscopic appearance I should expect 
elastin. The tubes are not perforated as in Tubipora, and I cannot at 
present discover any organic connexion between the mesoderm outside 
the tube and the mesoderm inside the tube. 

The polypes very closely resemble the polypes of Tubipora. They 
are of a rich brown colour, and contract but slowly when irritated. 
The tentacles have the usual Alcyonarian character, and are richly 
armed with nematocysts. 

At this season of the year this Alcyonarian does not seem to breed 
at all, as after examining a great many polypes I have found none 
Bcxnally mature. The young colonies, which are to be found in abun- 
dance on the reefs, closely resemble a species of GomalaanB.^ '^hk,\i >& 
fonnd here in abundance, consisting simply oi 'bTttm:^'^^ %\^QrD&^ Vc^t^ 
which the young poljpes spring. 



SSI Dr. 8. J. Hickaon. Oti eertetfi [Apr. 

Fw. 1^ 




Small portion of the Bkeleton ( k 2) aa it appesre when drj, ihowing the Ion; 
dinal grooTet irhicli coireapond with the meaenteriea ( J^), the connecting I 
(II), and ft jonng poljpe >pringing from b connecting tube (p). 



Histologically it does not eeem to differ in aoy important partic 
from Tnbipora, but I hope in a later and falter paper to be able 
give the rcBalts of a farther and better investigatioii. 

The importance and interest of this genns is two-fold. In the : 

place the structure of the stolon, the mode of connexion of the pol 

tnbes, and tbo fact that its akeleton is imperforate, show that i 

cloaely allied to the extinct gennB Syrvn^o^Mk, vjliick it resemble 

a// fiieee porticnlnrs. HotwithBlanivus; &« maaa c 



I Zoological OhservtUiona made in North Celebes. 825 

ea brought bj Moseley, Zittel, and otbera, to prove thai this 
geniiB is Alcyonarian, there are still some authors who main- 
lat it is Zoantharian. The pecnliar Htractore of the present 
;oes far to prove that the former opinion ia right, and the latter 

he second place the resemblance of the yonng colonies of this 
to the genns Comalario, and the resemblance of the adult 
is and polypes to those of Tubipora, jnstify the conclnsion I 
d at in a former paper, that Tabipora shonld be united with 
•rnularid» into a group, the Stolonifera ; this genns is, in fact, 
nnecting link between these genera which wsa formerly missing, 
we asenmed that Syringopora was undoubtedly Alcyonarian. 
ipe in a fntni« paper to be able to give some further particulars 
anatomy of this form, perhaps also some account of the eariy 
of its development, and some account of my researches upon 
ber Stoloniferons AJcyonaria, which are present here iu abnn- 



Note on Tuh^ora and on MUlepora. 
ve got the early stages of the development of Tnbipora. It is 
rly holoblaatic, and I think the gaatrala is formed by invagina- 

Finding, however, that it is very difficult to keep the embryos 
a this hot and dusty weather, I must wait until it becomes a 
ooler in December before I can get any very satisfactory results 
i latt«r point. 

generative products of Millepora are formed in little capsules 

walls of (be canaU, and I have found both male and female 
es in the same canals. The embryos, I believe from the evidence 

preparation only, reach a certain stage of development in 
:)us capsules in the canals, and they are then discharged into 
iter by the mouths of the gaetrozooids. 




Qeuerstive capsulea of Uillopi 



326 Dra. J. Hopkmflon and E. Hopkuuon. [Ap& U^ 



IL '* Dynamo-Electric Machines. — ^Preliminaiy Notice." Bjr 
John Hofkinson, D.Sc, F.B.S., and Edwabd Hopkinboii, 
D.Sc. Received April 3, 1886. 

Omitidng the indactive effdcts of the current in the armature itsd^ 
all the properties of a dynamo machine are most conTenlently de dn esd 
from a statement of the relation between the magnetic field and the 
magnetising force required to produce that field. This relatioiL 
given, ifc is easy to deduce what the result will be in all employmenls 
of the machine, also the result of varying the winding of the machjne 
in armature or magnets. The magnetic field may be expreawd 
algebraically as a function of the magnetising force, or more oonTO- 
niently by a curve (" Proceedings of the Institution of Meohanied 
Engineers," April, 1879, p. 246). Amongst the empirical formuk» 
which have been proposed to express the electromotive force of 
dynamo machines in terms of the currents around the magnets, we 

may mention that known as Frohlich's, where E = -- — r- , E being 

1+06 

the electromotive force of the machine at a given speed, c the exciting 
current, and a and b constants. For some machines this hyperbola is 
said to express observed results fairly accurately. In our experience 
it does not sufBciently approximate to a straight line in the part of 
the curve near the origin, and gives too high results for lai^ 
values of c. 

One purpose of the present investigation is to give an approximately 
complete construction of the characteristic curve of a dynamo of given 
form from the ordinary laws of electromagnetism and the known 
properties of iron. Let n be the number of convolutions on the 
magnets, c the current round the magnets, li the mean length of the 
lines of force in the iron of the armature, Ai the area of section of 
iron in the armature, 1% the distance from iron of armature to iron of 
pole pieces, A2 the area of the magnetic field in which the wires move 
corrected for its extension round the edg^ of the. pole pieces, ^3 the 
total length of the magnet cores. As the area of the magnet cores, I^ 
the mean length of lines of force in the yoke connecting the magnet 
limbs in machines of the type on which we have principally experi- 
mented, A4 the area of section of the yoke, h the mean length of the 
lines of force in each pole piece, A5 the mean area of section of pole 
piece, I the total induction through the armature, when no current 
passes in the armature, and vl the total induction in the magnet 
cores; and finally let the relation between the TxvQ.^QtlQ force («) 
and induction (a) (vide Thomson, ""EVecteroe^^^Ac^ wA ^^^s^gofeVassov;'' 



1886.] Dynamo-Electric Machines. 327 

p. 397, and Maxwell, "Treatise on Electricity and Magnetism/* 
vol. ii, p. 24) be represented by the equation a = /(a), then the 
cliaracteristic curve is — 



4nmc^ 



If the relation between a and a be given in the form of a curve, this 
formula indicates at once a perfectly simple gpraphical construction 
for the characteristic. Taking the curve of magnetisation determined 
bj one of us for wrought iron, and constructing a characteristio in 
this way, we have obtained a theoretical curve which agrees over a 
long range with the actual results of observation on a dynamo 
machine more closely than any empirical formula with which we are 
acquainted. 

To determine v, a wire was taken once round the middle of one 
magnet and connected to a ballistic galvanometer, a known current 
was then either suddenly passed round the magnets or short circuited, 
the elongation of the galvanometer being noted. A similar observa- 
tion was made with the same current, the galvanometer being con- 
nected to a single convolution of the armature in the plane of commu- 
tation. The ratio of the two elongations is the value of t^. 

The distribution of the t^aste field (v— 1) I was roughly ascertained 
in a similar manner. 

The currents in the fixed coils round the magnets are not the only 
magnetising forces applied in a dynamo machine. The currents in 
the moving coils of the armature have also their effect upon the 
resultant field. In well-constructed machines the effect of the latter 
is reduced to a minimum, but it can be by no means neglected. This 
introduces a second independent variable, viz., C, the current in the 
armature. The effect of the current in the armature depends upon 
the lead given to the brushes. Denote this by X, which we may also 
regard as an independent variable, as it is subject to arbitrary 
adjustment. 

If I=F(4jmc) be the characteristic curve when no current passes 
through the armature, then 

where tn is the number of convolutions in the armature. Here we 
omit the comparatively unimportant portion of the magnetic force in 
the core of the armature and the pole pieces. From this formula i|^ 
is not difficult to deduce a geometrical construction for the ol 
istio surface (i^ide "Practical Applications offi^ec^cnl^^^ 
delivered at the Institute of Civil Engineers, laft^S&^^^Wf' 



brmula i t -^ 
^hscsfiriMH 



328 Dynanto-Electric Maehineg. XAV^- **'' 

equation may be tlins expressed in words, if X bo each that the coils at- 
commutation ombraco the whole or nearly the whole induction. The 
effect of the current in the armatni-e upon the difference of potential 
between the bmsbca of any machine, ia the same as that of an 
addition to the resistance of the armature proportional to the lead of 
the brashes, and to the ratio of the waste field to the total field, 
combined with that of taking the main current — - times roand the 

magnet-s in a direction opposite to the current c Many conaeqaenceB 
can be deduced, of which we may notice the following :^ — In a serioa 
wound dynamo C is equal to c, and if c be increased beyond a certain 
point, I must attain a maximum and (hen diminish ; this has been 
frequently observed. We now Bee that it depends upon the eiiatence 
of a waste field. Secondly, let the coils of the magnets be entirely 
disconnected, and let \ be the negative : if the armature be short 
circuited through a skieI] reaiHtance and be run at a autficient speed, 
a large current may be jirodnced in the armature. This latter deduc- 
tion we have verified by direct experiment. 

The efficiency of the type of dynamo machine npon which the 
experiments before indicated have been made, has been accnrately 
determined by the device of coupling two similar machines, both 
mechauically and electrically, so that one Bhould act as a generator of 
electricity, driving the other electrically, whilst the latter acted 
as a motar driving the former mechanically ; the loss of power 
required to keep the whole combination in movement being determined 
by direct dynaraometric measurement, and the power passing electri- 
cally from the one machine to the other being measured by ordinary 
electrical appliances. 

The whole of the experiments were carried out at the works of 
Messrs. Mather and Flatt, to whom we are indebted for the ex- 
ceptional opportunities we have enjoyed of putting theoretical conclu- 
sions to the test of experiment on an engineering scale. 

The Society then adjourned over the Easter Recess to Thursday, 
May 6th. 



1886.] Passage of an Electric Discharge through Nitrogen. 329 



May 6, 1886. 
Lieut'.-General STRACHEY, R.E., Vice-President, in the Chair. 

« 

In pnrsuance of the Statutes the names of the Candidates recom- 
mended for election into the Society were read from the Chair as 
follows : — 



Bidwell, Shelford, M.A. 
Colenso, William, F.L.S. 
Dixon, Harold B., F.C.S. 
Festing, Edward Robert, Major- 

General R.E., 
Forsyth, Andrew Russell, M.A. 
Green, Professor A. H., M.A. 
Horsley, Professor Victor, F.R.C.S. 
Lewis, T. R., M.B. 
Meldola, Raphael, F.R.A.S. 



Pye-Smith, PhUip H., M.D. 
Rnssell, Henry Chamberlaine, 

B.A. 
Unwin, Professor W. Cawthome, 

B.Sc. 
Warington, Robert, F.C.S. 
Wharton, William James Lloyd, 

Captain R.N. 
Wilde, Henry. 



The following Papers were read : — 



L " On an Effect Produced by the Passage of an Electric 
Discharge through Pure Nitrogen." By J. J. THOMSON, 
M.A., F.R.S., Fellow of Trinity College, Cavendish 
Professor of Experimental Physics, Cambridge, and 
R. Threlfall, B.A., Caius College, Cambridge, Professor 
of Experimental Physics in the University of Sydney. 
Received April 13, 1886. 

In the course of some experiments which we have heen engaged 
with for some time past, on the temporary increase in the volume of 
a rarefied gas which takes place when an electric discharge passes 
through it (De la Rue and Miiller, " Phil. Trans.," 1880), we found 
that the passage of the spark always produced permanent as well as 
temporary effects when the gas was nitrogen and when the pressure 
was less than that due to 20 mm. of mercury. The experiments 
described below were undertaken to clear up this point, ajid from 
them we have drawn the following conclusions : — 

1. That when a succession of electric sparks of the proper kind is 
sent throngh a sealed discharge-tube coniaiimi^ mXiVi^et^ ^ ^^ssm 
pressure (less than 20 mm. of mercury^ a peTinaiii'erDX* ^Vm^Baian 



880 Profieu J. J. Thomfloii and B. ThrdfiilL [HajI^ 

the Tolome of the nitrogen takes place, wliioh reaches a mazmun^ 
after wliich the passage of sparks of the same kind pzodvoee no 
permanent effect upon the Yolnme. 

2. That for nitrogen at a pressure of 8 mm. of mercoiy, which is 
the pressure at which we have usually worked, the permanent disdnu- 
tion in Yolume is from 8 to 12 per cent, of the original Tolnme^ while 
at a pressure of 16 mm. of mercury the diminution is not more than 
from 2 to 3 per cent. ; thus, though there are twice arf many molecnles 
in the tube the effect is not so big. 

S. The diminution in volume takes a considerable time to reach its 
maximum value ; in our experiments, where the discharge-tubes are 
1 cm. in diameter and 25 cm. long, and the sparks were produced by 
an induction coil giving a spark about 4 inches long in air, it took 
about eight hours' sparking to produce the maximum diminution. 

4. That this diminution takes place equally well whether platinum 
or aluminium electrodes are used. 

5. That the ratio of the maximum diminution to the original 
volume is independent of the volume of the discharge-tube and of the 
extent of its surface. 

6. That if the tube be maintained at a temperature of over 100** C. 
for several hours, the gas regains its original volume. 

We attribute this diminution in the volume of the gas to the forma- 
tion of an alio tropic modification of nitrogen.* 

We now proceed to give a detailed description of the experiment 
and of the various parts of the apparatus. 

Discharge-tube and Gauge. 

We had a good deal of trouble in getting this part of the apparatus 
satisfactory; we found that discharge- tubes of the ordinary kind 
were very liable to leak round the electrodes after a series of sparks 
had been passed through them. The form of tube we finally adopted 
is represented in hg. 1. AB is a glass tube about 25 cm. in length 
and 1 cm. in diameter, into which the (J -piece E, F, Q, fused up at G, 
is fused, sulphuric acid or mercury is placed at the bend of this (J -tube, 
and serves as a gauge to measure alterations in the pressure of the 
gas in AB. The end B dips into a vessel containing mercury, the 
level of which is higher than that of the part of the tube through which 
the electrode passes ; a piece of glass tubing is placed over the top of 
the discharge-tube, and the interval between the tubes caulked with 
glass wool ; the cup thus formed is filled with mercury, which reaches 
above the entrance of the electrode into the tube. The electrodes are 

* Since tliis paper was sent to tbe Boyal Society we hare seen a book by Mr. 
StUUngBeet JohuBon, entitled ** Elementttry '^\\xo^«iir \xk^\vv^>^« tsss^^sKn^VosUm. 
» eome to horn pxuelj chemioaL TeaMna. 



1886.] Pataage of an Eketrie Ditcharge through Nitrogen. 331 
Fia. 1. 




then covered with mercary, which prevents any leakt^e between the 
electrode and the tnbe, which we found freqnentlj happened if this 
precaution was not taken. The tubes were cleaned before being nsed 
bj filling them (1) with aqna regia, which was boiled in the tnbe, (2) 
with caustic potash, (3) distilled water, (4) veiy pnre alcohol. After 
this they were carefully heated and dried. This was the treatment 
adopted for the greater part of the tnbes, some of them, however, 
were treated with boiling snlpharic acid in addition. 

The Bnlphnric acid in the gauge was boiled with sulphate of 
ammonia before being nsed ; when the sulphate was first added to the 
acid, the acid became dark, but it was boiled for about half a day 
nntil it was quite colourless, and its yolume aboat one-fourth of its 
original vslne. 

The levels of the liquid in the legs of the gHOge were read by a 
cathetometer ; when the liqaid was enlphuric acid the readings could 
be made accurately enough by placing a sheet of white paper behind 
the gauge and illuminating it by a gSB flame. When, however, the 
liquid in the gauge was mercury a different course was adopted. In 
the first place, the gauge-tube had to be much larger to prevent 
mistakes arising from the sticking of the mercury to the sides of the 
tube. The gauge naed for mercury was of the shape shown in fig. 2 ; 
the diameter of the tabe where the free surface of the mercury came 
into contact with it was abont 2 cm. A different method of reading 
the levels of the mercury in the lega ot ftio ^'■Il^b \i8A- ^iao ^ ^'o» 
adopted, because it tras found that when t^ie gu ftoiae "«»» "^ 



\ VK«*4 



332 Profs. J. J. Thomson and R. ThrellalL [May 6. 



r 




of the meronry different readings could be obtained by moving it 
about, the sarfnce of the mefcury waa therefore illnminated from 
behind by a parallel and horizontal beam of light which paswd 
through an alum cell to avoid aiij beating effect. 

The electrodes were either platinum or aluminium, generally pla- 
tinum ; in some of the tube.i these were fnned into small pieces of 
glass tubing, BO that only the tips of the olectpodes were exposed to 
the nitrogen. Before being sealed the tube was connected witli the 
pnmp and the gas supply in the way showa in fig. 3. After b«Dg 




cleaned and dried, and the gauge filled either with salphnric acid or 
mercory, the tnbe wag pnmped ont and filled with nitrogen, and this 
process waa repeated sevem] times ; when the preBsnre was very low 
the tube was heated to kb high & iempeTBitTictk %& ii Ntauld afand with- 
out Boiiening, in order to dri^e ofi. wkj ^a» ^w-^ m\s^\.\«. rai. "Casi 






1886.] Passage of an Electric Discliarge through Nitrogen. 333 

surface. Then a series of sparks from six very large Leyden jars 
charged with a Holtz machine were sent through the tube ; at first 
when the light produced by the sparks was examined by the spec- 
troscope the hydrogen lines were seen to be very bright, the hydrogen 
presumably coming out of the electrodes ; as the sparking and pump- 
ing continued the hydrogen lines diminished in brightness, and we 
went on sparking alternately with the Holtz and the induction coil 
until they had disappeared. We may mention in passing that the 
relative brightness of the hydrogen and nitrogen lines in a mixture 
of these gases is to a very large extent a question of pressure ; we 
found that after we had gone on sparking until there were no 
hydrogen lines visible at a pressure of 8 mm. of mercury, if we 
pumped out the gas until the pressure was reduced to 2 mm., the 
hydrogen lines immediately reappeared, and it required a great deal 
more sparking to get rid of them at this pressure. The lower the pres- 
sure the more prominent were the hydrogen lines. We went on spark- 
ing until there were no hydrogen lines visible at a pressure of 8 mm., 
when the sparks were produced either by the Holtz or the induction 
coil, and until there were no hydrogen lines visible at a pressure of 
2 mm., when the sparks were produced by the induction coil. We 
never, however, were able to satisfy ourselves that the hydrogen lines 
were absent when the large sparks from the Holtz were sent through 
the tube at this pressure, though if they were there they were oidy 
very faint. When we had reached this stage the hydrogen lines 
showed no tendency to reappear when fresh nitrogen was introduced 
into the tube, showing that the hydrogen came from the electrodes 
and not from damp in the nitrogen. We found more difficulty in 
getting the hydrogen out of aluminium terminals than out of platinum 
ones. When the tube had reached this stage fresh nitrogen was let 
in and pumped out until the pressure in the tube was the required 
value, generally 8 mm. of mercury ; the tubes g and fe, fig. 3, were then 
fused off, the gauges being watched all the time to see that there was 
no influx of air during this operation. When the tube had cooled the 
difference of level of the fluid in the (J -tube was read by the cathe- 
tometer. It was then generally left to stand over night, and another 
reading taken the next day ; except in the few cases when the tube 
had cracked, the readings were always found to be the same as those 
taken on the previous evening. The tube was then ready to be 
experimented on. 

TreparaJtion of the Nitrogen, 

The nitrogen was prepared by passing air over red-hot copper. 
A porcelain tube about 70 cm. long was placed on. ^ ^"^ l\ix\i^^^>*^ 
was GUed with copper turnings and copper gauzie \ daxivti^ oh^^^m^ ^^- 



384 Profs. J. J. Thomson and B. Tfaid&lL [Mmj 9, 

the ezperiments the g^nse was placed at ihe ends and tbe tomings h 
the middlei in the other half, half the tube iras filled with oof^ 
tnmings and the other half with ganse. The air was sacked throog^ 
a tabe containing pieces of pumice moistened with potash, and thzongh 
a bottle half filled with the same substance, the other end of the tube 
was stopped by an indiarubber cork coated with paraflBn, tlizoflgli 
which a glass tube passed which conducted the nitrogen to a series of 
bottles and tubes. These bottles and the porcelain tube ware made 
quite air-tight ; this was tested by putting the tube through which 
the air passed on its way to the copper in connexion with an air- 
pump, and exhausting down to a pressure of about 20 mm. of msrciuy, 
even with this exhaustion there was no appreciable leak through the 
whole arrangement of porcelain tube, drying-tubes and bottles, 
discharge-tubes and connexions. The porcelain tube was connected 
by a piece of thick- walled indiarubber tubing with a series of bottles 
and tubes containing purifying reagents. After leaving the copper 
the nitrogen passed through a potash solution in a bottle, then 
through two large tubes filled with carefully prepared pumice 
moistened with potash, it then babbled through sulphuric acid which 
had been boiled down with sulphate of ammonia to about one-fourth 
of its original volume, it then passed through two large ^ -tubes 
filled with phosphorous pentoxide divided up into a number of layers 
by asbestos plugs, it then went into a large bottle about one-fourth 
filled with phosphorous pentoxide. All the phosphorous pentoxide used 
was tested and found to be free from free phosphorus. The gas after 
leaving the phosphorous pentoxide bottle passed through thick-walled 
indiarubber tubing into the discharge-tube. The volume of the tubes 
and bottles was very large compared with that of the discharge-tube, 
and as our consumption of nitrogen was slow the gas we used had 
stood over the phosphorous pentoxide for several days at least and 
often much longer. On the other hand, the gas had only been in 
contact with indiarubber for a short time, for the indiarubber bungs 
in the bottles were all coated on the inside with paraffin, and the only 
long piece of tubing was that leading from the last drying bottle to 
the discharge-tube ; gas that had stood in this for more than a few 
minutes was always sucked out, and was never used for filling the 
discharge-tube. 

The oxide of copper formed in the tube was reduced from time to 
time, in most cases by passing hydrogen through the tube; the 
hydrogen was generally prepared by pouring sulphuric acid on zinc, 
but as we suspected that a trace of sulphur dioxide which we detected 
had its origin in this source, we endeavoured to reduce the copper 
oxide by electrolytically prepared hydrogen ; we could not, however, 
produce tbe hydrogen fast enou^\i m ^i^:^ ^^1^ ^^^ ^^ ^^ finally 
reduced the copper oxide \)y caTbou xnoTioxi^^ -^x^'^iwcfe^ ^x^tbl y^x^ 



1886.] Passage of an Electric Discharge through Nitrogen, 335 

formate of potassinm ; in this case the nitrogen showed no trace of 
snlphnr dioxide, there was, however, no alteration in its behavionr in 
the discharge-tube. 

We detected the trace of SO3 by the change produced by the gas in 
the colour of paper soaked in a mixture of ferric chloride and ferric 
cyanide, the amount of it, however, must have been very small, as the 
gas produced no colouration in a paper soaked in a solution of iodide 
of potassium and starch, which is a very delicate test for sulphur 
dioxide. The diminution in the volume of the nitrogen which we 
observed could not have been due to the trace of SO^, as it occurred 
when the copper oxide had been redaced by GO, and no trace of SO3 
was to be detected even by the ferric chloride and ferricyanide 
solution. 

Determination of the Quantity of Oxygen in the Oas. 

We were unable to detect any change of colour in a small quantity 
of a solution of pyrogallol and caustic potash when 50 c.c. of our gas 
was passed through into a eudiometer. It was thought desirable, how- 
ever, to have a more perfect testing arrangement, and the following is 
a description of the form ultimately adopted. 



FiG.4w 




The apparatus consists essentially of four tubes and a bottle whose 

volume is known ; by means of connexions of indiarubber tubing, 

taps, and clamps, each tube can be put in communication with the 

nitrogen supply and with the bottle separately. The iw^ bei'^^^T^ C> 

, and D being closed, and the tubing tempoTariYy "reTno^^^>C> Sa ^:^^^ V^ 

I about half way up the bulb with carefully boWed fto\xiX:\oTi o^ ^^v^s^:^s^ 

rOL, XL, % ^ 



886 Profk J. J. Thomson and B. ThrdfalL [Hay e^ 

potashy and D with a Bolation of pyrogallol, also well boiled. Tbe 
tube connexions are then replaced, and the bottle E, whoee Tolnme it 
large compared with that of the other parts of the apparatns, is tfaea 
exhausted as far as possible by means of a water-pamp. A stream of 
nitrogen is allowed to flow into the tabes, which are exhansted bj 
connecting them with the bottle. After exhausting and refilling 
several times the tabe C is left exhausted, and D in connexion with 
the nitrogen snpplj. The tap between C and D is then cautiously 
turned, as soon as this is down the contents of D flow over into C. 
As the potash solution is denser than the pyrogallol, a very perfect 
mixing of the fluids takes place automatically in C. As we never 
succeeded in getting the mixed solution colourless, it is necessary to 
preserve some of it as a standard for comparison. This is done by 
connecting B and with the nitrogen supply together, and opening 
the damp between them ; the liquid then flows into B till it stands at 
the same level there as in C. The capacities of the tubes are arranged 
so that there are sensibly the same quantities of liquid in B and G, 
this can be done by raising or lowering B. The clamp between B 
and C is now closed, C put in communication with the exhausted 
bottle, and D in communication with the gas supply.* The pressure 
of the gas in the exhausted bottle is observed : suppose it is p. The 
tap between G and D is then opened, so as to allow a slow stream of 
the gas to 2)ass from D up through G into the bottle ; as soon as a 
sufficient deepening of the colour has taken place in the liquid in G, 
the tap is turned off and the new pressure p' in the bottle noted. 
Knowing j? and jp' and the capacity of the bottle, we can calculate the 
quantity of gas which has flowed through the liquid in G. The stream 
of gas passes very slowly, and it is assumed that all the oxygen it 
contains has been absorbed by the liquid in G. We now require to 
know how much oxygen is required to produce the same change in 
colour, this is done by comparing the colour with that of the liquid in 
B. A is a pipette divided into cubic centimetres, and dipping below 
the surface of water contained in a beaker, the top of the pipette is 
connected with the delivery>tube sealed into and running down B. 
This tube is very fine inside B, and ends in a very fine point. In 
order to make the comparison of colour, the upper part of the tube is 
exhausted, and the clamp connecting it with the pipette slowly 
opened, a stream of air will pass up from the pipette into B. This 
process is stopped when the operator judges the colour of the liquid 
to be the same in B and G. The level of the water around the pipette 
is brought to the same level as that of the water inside, and the 
quantity of air taken is read off. From this we can calculate how 
much oxygen is required to prodace the same change of colour as that 



1886.] Passage of an Electric Discharge tlirough Nitrogefu 337 

produced hy the gas we are testing. We found in this way that onr 
gas certainly did not contain one part of oxygen in 500, and probably 
not one part in 1000. 

The Experiments, 

A tnbe caref ally prepared and sealed off in the way we lu^ve already 
described was taken, and after tbe catbetometer readings bad sbown 
tbat tbe pressure bad remained constant for several boars, it was 
sparked tbrougb, generally witb an induction coil. In order to get 
tbe effect we are describing, it is necessary to introduce a large resis- 
tance into tbe circuit, for tbis purpose we used a • piece of wetted 
string, tbis makes tbe discbarge tbrougb tbe tube mucb less intense 
and tbe beat produced comparatively small ; we were not able to get 
tbe effect wben tbe discbarge passed straigbt tbrougb tbe tube 
witbout any resistance beyond tbat of tbe tube and tbe connecting 
wires. Tbe fact tbat beat restores tbe gas to its original condition is . 
sufficient to account for tbis, for wben tbere is only a small resistance 
in tbe circuit, tbe beat developed in tbe tube is mucb greater and 
tbe tube becomes very bot. We noticed a similar tbing wben we 
nsed a Holtz macbine instead of a coil : if we cbarged up five large 
Leyden jars witb tbe Holtz and tben discbarged tbe jars tbrougb tbe 
tube, no permanent alteration in tbe pressure was observed ; if, bow- 
ever, we never allowed tbe jars to get fully cbarged, but sent a 
succession of small sparks tbrougb tbe tube, tben a permanent 
diminution in tbe volume of tbe gas took place. 

Wben tbe discbarge from tbe coil witb a piece of wet string in tbe 
circuit went tbrougb tbe tube, a slow diminution in tbe volume of tbe 
gas took place ; tbe rate of diminution diminished as tbe sparking went 
on and ultimately tbe permanent volume of the gas remained un- 
affected by tbe passage of tbe sparks. It took, however, a considerable 
time to reach this suite ; as a rule each tube was sparked through for 
between three and four hours on each of three consecutive days, tbe 
diminution in the volume at the end of the first day was about two- 
thirds of tbe maximum diminution, there was a diminution of about 
one- half of tbis on the following day, and no appreciable diminution on 
the third day. 

Tbe gauges of the tubes used at first were filled witb sulphuric acid, 
and after the discharge had passed tbrougb until the pressure bad 
become steady, it was always found that the sulphuric acid in tbe 
limb of tbe gauge next the tube had risen towards the tube, showing 
tbat tbe pressure exerted by the gas in tbe tube bad diminished. 
Tbe difference of level between tbe legs of the gauge increased in tbe 
case of five different tubes by from 4*5 to 7 mm. ; now the ^re^^wx^ vci. 
tbe tube was originally 8 mm. of mercury, or a\>o\]Lt %>% tmxi, o^^t^^ vt 
Mf that tbe diminution in the pressure exer^A. Vy \Xi^ ^:^\& tesrsa- 



388 Ptofk J. J. Thomson and B. ThrdfiilL [Ib^^ 

aibont 8 to 12 per cent. We thought at first that this dimmntion 
might be due to the combination of the nitrogen with the anlplnrie 
aoid Taponr. In order to test this we had a tabe made with a xtoercnrf 
gauge of the kind already described, the difference of level between 
the mercury in the two legs of the gauge was increased byO^ mm. of 
mercury by the sparking : 0*9 mm. of mercury are equivalent to aboni 
6*5 of sulphuric add, so that the magnitude cd the effect is praoticaOy 
the same whether the gnage be filled with mercury or sulphuric acid, 
and the effect therefore cannot be due to any combination of nitrogen 
with the vapour of sulphuric add. 

We then thought it might possibly be due to condensation of gas 
on the sides of the tube, though it seemed very improbable that tiiis 
cause could produce such a large efiEect upon the pressure. To test 
this, however, we had a discharge-tube made whose diameter was 
about 3^ times that of the tubes we had previously been using, 

. so that in this case the glass was much further away from the Une 
joining the electrodes, and in fact was so little affected by the glass 
that the heating was scarcely perceptible. In this case the final 
result was the same as for the smaller tabes, though it took longer to 
arrive at a state of equilibrium ; the difEerence between the levels of 
the sulphuric acid in the limbs of the gauge was increased by 4*8 mm. 
Another reason why the diminution in pressure can scarcely be due to 
this cause is that it depends very much upon the pressure of the gas. 
We sealed off a tube at a pressure of 16 mm. of mercury, and found 
that when the discharge had been sent through it until the pressure 
had reached a steady state, the pressure had diminished only by that 
due to 2*5 mm. of sulphuric acid ; so that the diminution is only about 
half the absolute value, and therefore only one-quarter of the relative 
value of that which takes place at a pressure of 8 mm. of mercury. It 
would seem to be difficult to explain this result by the hypothesis that 
it is due to an adhesion of gas to the surface of the glass. The 
experiment with the large tube shows that it cannot be due to an 
absorption of gas by the electrodes, for in this case the diminution in 
pressure would depend upon the ratio of the volume of the electrodes 
to the volume of the tube, so that if we increased the volume of the 
tube, keeping that of the electrodes the same, the effect ought to be 
diminished ; the experiment with the wide tube showed that it is not. 
We also found that the effect was not diminished by using a very long 
tube, about three times as long as the ordinary ones. 

We next tried whether the diminution in the pressure depended on 

the nature of the electrodes by having a tube made with aluminium 

electrodes, we got, however, with this tube, the same diminution as we 

had previously obtained with those furnished with platinum electrodes ; 

the tahe, however, was more trou\>\eBoxn^ \« ^"t«^'a!c^^^j^>3aa ^2^\oxs^tq. 

electrodes seemed to contain more Yiy^oo^eu >^tiBsa >5Jmi ^^LVjcaxoo. w«». 



1886.] Passage of an Electric Discharge through Nitrogen. 339 

This result shows that the decrease in pressure is not due to the 
formation of a compound of nitrogen and platinum, a conclusion which 
is confirmed by the fact that the decrease is independent of the ratio 
of the Tolume of the electrode to that of the tube. The diminution in 
the pressure is too large to be explained bj supposing that it is due to 
the formation of ammonia, which we know takes place when an 
electric spark passes through a mixture of nitrogen and hydrogen, for 
it would require at least 15 per cent, of hydrogen to be present to 
produce a diminution in the pressure of the gas of from 8 to 12 per 
cent., and we feel certain from the spectroscopic tests we have applied 
to the gas that the quantity of hydrogen or hydrocarbon present is 
extremely small, neither the hydrogen nor the hydrocarbon lines can 
be detected at the pressure at which we work. Again, the gas is 
restored to its original pressure by keeping it for some time at a 
temperature just above 100^ C, while ammonia is not decomposed 
except at a much higher temperature. 

The combination of nitrogen and oxygen which takes place when a 
spark passes through a mixture of the two gases is attended by a 
diminution in volume, but we have calculated a superior limit to the 
quantity of oxygen present, and find that it is very much too small to 
explain the effects which we have observed in our tubes. 

It seems to us that the effect is too big to be explained as the result 
of an impurity in the gas, and that the only hypothesis which agrees 
with the facts is that we have an allotropic modification of nitrogen 
produced by the passage of the sparks. The formation of this is 
quite analogous to that of ozone from oxygen, and we have found that 
jnst as ozone is destroyed by continuous heating, so the diminution in 
pressure which we have observed in nitrogen is permanently destroyed 
if the tabe be kept for some time at a temperature of 100® C. ; we 
have not observed any tendency for the diminution in pressure to 
disappear as long as the tube is kept at the temperature of the room, 
about 15® G. The diminution we have observed seems to depend even 
more than the formation of ozone on the kind of spark which passes 
through the gas, and we are disposed to attribute partly at any rate 
the great differences which we have observed at different pressures 
to this fact, at some pressures it seems impossible to get quite the 
right kind of spark. 

We have noticed that when the electrical discharge goes through 
nitrogen whose pressure has been diminished by previous sparking, it 
has a much greater tendency to produce a beautiful golden colour 
than when it passes through a new tube. Exactly (as far as we can 
judge) the same discharge which when it goes through a new tube will 
produce a bluish-pink colour, will, when it goes ihrou^\i ^t^ CkV^ ^taIH 
-which the preaaare has diminished, produce Ob i^e^xiXYdtT ^^qtry ^'^^ 
between that of cbamoia leather and gold. 



840 Fro£B. J. J. Thonuon and H Thzel£^ [Xkj6, 

We hare made no sttempta to aaoertun the ohemLcal properties of 
this modified gas, and there ate other pointa whi(A wb shonld have 
IDced to develop before publiahing an aooonnt of onr experimonta, but 
aa (me of tis is leaving Cambridge for Anstralia it aeemed advisable to 
pabliflh an account of the ezperimenta ■we faave been able to make 
together. 

We are indebted to Kr. Bobinaon for advioe on Bome chemieal 
pcnnts, and ire cannot oonolode irithont aoknowledging bow mncb we 
owe to tiae seal and ainlily ot Mr. Sinolair, the Assistant at the 
OaTendJah Laboratoiy, who has done mnoh the greater part of the 
large qnaatd^ of ghiss-blowing required tor this investigation. 



IL " Some Experimeuta on the Production of Ozone." 1^. J. ' 
J. Thomson, M.A., F.R.S.. Fellow of Trinity College^ nd 
Cavendiah Professor of Experimental FhyBics in tbe IKbi- 
versity of Cambridge, and R. ThBELFALL, Cains Colk^;e, 
Cambridge, and Professor of Experimental Physics in the 
University of Sydney. Received May 1, 1886. 

Tbe first experiment was made in order to see whether osone coold 
be formed hj placing oxygen in a very strong electric field, the field, 
hoicerer, being just not strong enough to caase sparks to pass through 
the gas. 

This experiment finally took the following form ; — ABC is a box 
made of flat pieces of glass abont ii^th of an inch thick, fastened 
together vitb paraffin ; into the box two glass tubes, G and H, are 
inserted, the air entering the box through O, and leaving it throngh 
H. Against one side of the box a glass bottle, D, with flat sides, is 
placed and filled with water containing a little sulphuric acid, this 
serves as one electrode ; the other electrode is a blEKskened tin plate, 
E, placed against the opposite side of the box, the distance between 
the electrodes being an inch and a half. The two electrodes are 
connected with the terminals of a Holtz machine. By altering the 
distance between the terminalB any difference of potential can be 
produced between the plates. When the terminals are close together 
all the sparks pass between them, but vrhen they are pulled far apart 
the sparks flash across the box, the discharge taking the form of a 
great nnmber of separate sparks from the inside of one plate to the 
inside of the opposite one ; the appearance of the box when the 
discharge passes is very pretty, it looks as if several hundred bright 
silver nails with broad heads were connecting the insides of the box. 

Tbe air entered the box througV ttie ^.^ii» G, \i»kto^ ■^T«vioualy 
paeeed tbiougii a series of tnbcB aivi \)ia\)[\«i ^fi\«,4. -wK^Rfiiijj^-^ -wiSo. 



1886.] ExpenmeniB on the Production of Ozone. 




phosphorons peotoxide, pumice moistened with Balptmric acid, and 
caostic potash; it was also treed from dnst by paseing throngh a 
tabe containing a plng of cotton-wool. Aiter paseing throngh the 
box it bubbled through a tcst-tnbe, F, containing an iodide of 
potassium and atarch eolntioo, pieces of filter-paper moistened with 
this Bolntiou were also fastened to the sides of the box. We deter- 
mined the most sensitive solution of potassium iodide and starch b^ 
adding a constant quantity of chlorine- water to various proportions 
of potassium iodide and starch ; vhen the most sensitive solution had 
been determined it was always made up of this strength. We fonnd 
that the papers were qaite as delicate a test of ozone as the test-tnbe 
full of the solution. 

When the observations were being made the whole arrangement 
was placed inside a large wooden bos, the sides of which wen 
blackened, the observer put his head thToug^i «> Via^e m Qt^% «V *^a% 



Experinteati on the Production of Ozone. [May 6, 

sides ot tho bos, and a black velvet cloth was then put ovei* the box 
■io that all straj light was excladed, and any spark trayeraiiig the box 
could easily be detected. The air was sacked through the box at tht 
rate of about a litre in ten minntea. Before trying the experiment 
air was sucked through for about half an hoar when the electrodes 
were at the same potential ; but not the slightest colonration of the 
potassium iodide solution in the test- tube or on the pieces of paper in 
ihe box could be detected. We thoa adjusted the distance between 
the terminals of the Holtz machine so that the sparks jaat did not 
pass across the Tesael, in this case the terminals of the Koltz were 
sbonl 4 inches ^wrt, m fliatflLe field was as intamsM it oi»ld )m 
withoat pTodooiii^ a discharge. Air was then sooked tiimagh for 
mtm ihan aa hoar, bat not the slightest txdoaiation could bs datwlad 
in either the test-tabe <nr the pieoee of paper, though the psMMga <4 * 
single flash was sniEoient to piodnoe a most distinct ddouttlMB. 
This expeiiment was repeated over and over again, bnt alwi^ iilft 
the same result ; we never foond any owns anleai we had prerowiil j 
seen a flash across the vessel, henoe wo oondnde ihat oiona is fldlj 
prodaoed when sparks pass through the oxygen. 

A special experiment was made is order to estimate tho delioaqy of 
the test for oione : to the same quantity of the solution of iodide of 
potassium as that through which the air babbled on its way out from 
the vessel, chlorine- wator was added until we conld detect a discolour- 
ation. The amount of chlorine in the quantity of chlorine-water 
added was then determined by finding the qoantity of iodine set free 
by 10 0.0. of it. This was done by means of some very carefully 
prepared solstion of sodium hyposalphite, kindly made np and 
standardised for ns by Mr. M. M. Pattison Muir, From the 
minimum quantity of chlorine required to produce a discolouration 
of the solution, we found that the amalleat quantity of ozone we 
oonld detect with certainty was 0'0381 mgram. But 6 litres of air, that 
is 1'5 litres of oxyi^n, had passed slowly through the apparatus and, 
since no discolooiatiou was prodaced, the amount of ozone formed 
most have been less than 0*0384 mgram., or less than 000016 of the 
whole quantity of oxygen which hod passed through the apparatus. 
In the second experiment we took an ozonizer made of two concentric 
tabes, and sealed up in it air free from ozone and a large quanti^ 
of phosphorous pentoxide, this was left for three months, so that at 
the end of the time the air was presumably diy; on causing the 
electric discharge to pass through it, however, osone was produced in 
large qnantities, so that ozone is produced when an electric spark 
passes through very carefully dried oxygen. 



86.] Stress and SUmn and the Properties of Matter. 843 



[. " The Influence of Stress and Strain on the Physical Pro- 
perties of Matter. Part I. Elasticity (continued). The 
EflFect of Change of Temperature on the Internal Friction 
and Torsional Elasticity of Metals." By Herbert 
TOMLINSON, B.A. Communicated by Professor W. Grylls 
Adams, M.A., F.R.S. Received April 13, 1886. 

(Abstract.) 

rhe author has recently had the honour of presenting to the 
siety a memoir relating to the internal friction of metals when 
)ratiog torsionally at temperatures ranging from 0^ C. to 25^ C. He 
w brings forward results which have been obtained in experiments 
the effect of change of temperature on the torsional elasticity and 
emal friction of metals. The apparatus used and the mode of 
perimenting are fully described in the paper, so that it will be 
£cient, perhaps, to state here that the vibration-period and the 
;arithmic decrement were very carefully determined at four 
Eerent temperatures between 0° C. and 100^ C, and that the 
mulee given below were worked out by the method of least squares ; 
»e formulas are to be found in Tables I and II. 
^ full account of the method adopted for eliminating the efEect of 
) resistance of the air has been given in the previous memoir above 
ided to. 

Table I. 



HetaL 


Formula for the torsional elasticity 
between 0° C. and 100° 0. 
r« and Tq represent the torsional elasti- 
city at the temperatures of f 0. and 
0° C. respectiyely. 


Percentage de- 
crease of tor- 
sional elasticity 
when the tem- 
perature is 
raised finom 
C'O. to 100^0. 


Silver 

Platinum 

Platinum* Bilyer 
Aluminium. . . . 
Tjino ........ . . 


r,«ro(l-00003769< -0-0000001690<«) 
r, - ro(l - • 00004456^ - •0000002987<2) 
r, = ro(l-0- 0003555^ +0 •0000005467^2) 
r,=ro(l-0-0005713^ -0* 0000000109^2) 
r,=ro(l-0-0010800< -0 0000049470<2) 
r, = ro(l-0- 0002267^ -0-0000003474^) 
r,=ro(l-0 0002442^ -0 0000002510/') 
r,=:ro(l-0 0002472^ -0' 0000004488^) 


3-938 
0-744 
3008 
6-724 
15 -747 
2-614 
2-693 
2-921 


Nickel 

Cron , . , 


Copper 



Before the experiments, of which the results are recorded in Tables 
.nd II, were made, the previously well annea\edV\"t^a'^«t^«^\^^\«^ 
» preliminarj' treatment extending over perioda Tan^"^^ ^oia. ^\s^ 



844 S^re9$ and Strain and the P^i)pertUi of Mailer, [lii^i 



Table 11. ' 



HeteL 



SilTer 

Platinum 

Flatinmn-flilTer 
AlniniTiiuTn. . . . 

Zino 

Niokd 

Iron 

Copper 



Fonnnla for tlie logarithmio decre- 
ment due to intemal firiotion be- 
tween (f 0. and 100° 0. 

Xf and Xq represent the logariUmiio 
deorements at f* 0. and 0^ C. xe- 
epeotiTelj. • 




-0 01244^+0 
1-0*01286^+0 
1 + 0-01410^ +0 
1-0*00806^ + 
1 + 001418^+0 
l + 0-00057<-0 
1-0-01699/+0 
l-0'0180U + 



0008016<*) 

OOOU 

•00010051 




0007122 
0000205 
000061 
•0006845; 




increaae of the 



Peroentage 
or 

logarithmic 
ment when tha tMB- 
peratnze ia xakad 
fitomO*0.tolOOrc. 
— ngnifin daeraaw 



•• 



+177*2 

- 19*6 
+ 141*6 
+ 588*8 
+858*5 

- 14*8 

- 78-4 
+454*4 



days to two months. This treatment consisted in repeatedly heating 
the wire to 100^ C, and then cooling it again nntil the torsioiial 
elasticity and the intemal friction both became constant at all the 
temperatures at which the wires were tested, and produced the 
following permanent effects :— 

(a.) Yerj appreciable increase of the torsional elasticity in the 
case of some metals and appreciable increase of the torsional elasticitj 
in all cases. 

(h.) Large diminution of the intemal molecular friction, the effect 
on the friction being considerably greater than the effect on the 
elasticity. 

(c.) Very appreciable increase of the limiting amplitude beyond 

which the logarithmic decrement ceases to be independent of the 

amplitude. 

From a consideration of Tables I and II it may be gathered 
that ^— 

(d.) The torsional elasticity of all metals is temporarily decreased 
by rise of temperature between the limits of 0^ C. and 100^ C, the 
amount of decrease per deg^e rise of temperature increasing with the 
temperature. To this may be added that the percentage decrease of 
torsional elasticity produced by a given rise of temperature is for most 
metals about twenty times the corresponding percentage increase of 
length. 

(e.) If we start with a sufficiently low temperature the internal 

friction of all annealed metals is first temporarily decreased by rise of 

temperature and afterwards increased. The temperature of minimum 

internal {notion is for most ttnneeXe^ m^^^^ V^i^een O*' G. and 



86-] On converting Heat Energy into Electrical Energy. 345 

0° C. ; for most hard drawn wire, however, the temperature of 
nimnm internal friction is below 0^ C. 

(/.) The temporary change, whether of the nature of increase or 
crease, wrought bj alteration of temperature in the internal friction 
metals, is in most cases enormously greater than the corresponding 
Eknge in the torsional elasticity. 



. " On a New Means of Converting Heat Energy into Eleo- 
trical Energy," By WiLLlARD E, Case, of Auburn, New 
York, U.S.A. Communicated by W. H. Preeoe, F,R.S. 
Received April 14, 1886. 

[t was shown by M. Henri Loewel (see " The Chemist,*' Part VHI, 
476) that the addition of a solution of chromous chloride to 
zinous chloride caused a precipitate of metallic tin, the reaction 
ming chromic chloride. 

On heating the solution to the boiling point, 212° F., it was found 
3 precipitated metal was in a great measure redissolved, forming 
3 original solution, chromous chloride and stannous chloride, with- 
t the liberation of hydrogen. 

On cooling this solution the tin was again precipitated, the action 
itinuing as often as the solution was heated and cooled. 
As chromous chloride has a great affinity for oxygen, it is necessary 
9 air should be excluded from the solution, otherwise the chromous 
Loride would be reduced to oxychloride of chrome, as Loewel states, 
d the reactions would cease to take place after a time, the stannous 
loride formed during each heating remaining in solution. 
I constructed, in the form of a simple galvanic cell, a small element 
th this solution, chromic chloride,* as the electrolyte, using tin as 
3 positive, and platinum as the negative metal. 
At 60° F. this element gives no electromotive force, although in 
is case, when the cell was first set up, it gave 0*0048 volt, owing 
obably to the presence of some foreign substance. 
On the elevation of its temperature by the application of heat, the 
tctromotive force rose and fell, as indicated in the diagram ; the 
rves A, B, C, D, E, represent its increase during the rising tempe- 
iure, and the curves F, G, H, I, J, its fall while cooling. 
The irregularity of the curves A, B, C, D, E, was probably due to 
equal heating. 

At the termination of the experiment, when the cell had cooled 
wn to 60° F., no electromotive force was observed, as indicated ou' 

^ The Bolution uaad waa made by combining chTomv\xTX\. \iTVQn\<\.^ V^^ \£)^i3»r 
7ric acid, and beating. 



846 On converting Beat Energy into Electrical Enei-^y. [May fi, 




the diAgram, of whioli the abscissn are proportional to the elootro- 
motiTe forces, the ordinateB to the temperatar^a Fahrenheit. 

The highest electromotive force was 02607 volt at 197" F., the 
highest degree to which the temperatnTe was raised. 

If the platiunm be replaced hy a negative electrode of carbon, the 

electromotiTe force will be higher. Ic may be of interest to mentioE 

that the action of this element daring heating is entirely different 

from that of the galranio bdtteiy dnring a similar elevation of it£ 

^ lAtaperatare. 



1886.] On the Sun-spot Spectra Ohservations at Kensington. 347 

W. H. Preece, Esq., F.R.S. (see " The Effects of Temperature on 
the Electromotive Force and Resistance of Batteries/' *' Proc. Boj. 
Soc.," vol. 36, p. 48), states "that changes of temporal are do not 
practically affect electromotive forces, hut that they materially affect 
the internal resistance of cells." 

When the temperature of this element was lowered to abont 145^ F., 
bhe leactions before mentioned took place. 

The tin taken np by the solution during heating commenced to 
precipitate, increasing as the temperature lowered, and the metal fell 
bo the bottom of the cell in a form to be again utilised in the genera- 
Lion of the current. 

The amount of local action or chemical corrosion which took place 
ibove 150° F. was excessive, but the metal taken up by the solution 
WBB Tery much less when the temperature of the electrolyte was not 
raised above the point of precipitation, 140^ F. 

The metal taken up below this point appears to be precipitated 
ander the same conditions as that taken up at higher temperature, and 
Beems to be precipitated whether the circuit be open or closed. 

It will be seen on the curves F, G, H, I, J, with falling temperature 
that the electromotive force increased between 150° F. and 140° F., 
this might have been due to the reactions which took place during the 
precipitation of the metal. 

Farther investigations to determine the efficiency of this element 
would be of interest. 



V. "Further Discussion of the Sun-spot Spectra Observations 
made at Kensington." By J. Norman Lookyer, F.R.S. 
Communicated to the Royal Society by the Solar PhysicB 
Committee. Received May 5, 1886. 

I have recently discussed, in a preliminary manner, the lines of 
several of the chemical elements most widened in the 700 spots 
observed at Kensington. 

The period of observation commences November, 1879, and extends 
\o August, 1885. It includes, therefore, the sun-spot curve from a 
minimum to a maximuifl and some distance beyond. 

It is perhaps desirable that I should here state the way in wliich 
the observations have been made. The work, which has been chiefly 
^one by Messi-s. Lawrance and Greening, simply consists of a sur\'ey 
>f the two regions F — h and h — D. 

The most widened line in each region — not the widest line, but the 
yt ost iculened, is first noted; its wave-length being given in the 
>l3servation books from Angstrom's map. Next, the \\uiis»k ^\i\^ 



348 Mr. J. N. Lockyer. On the [May 6. 

most nearly approach tte first one ia widening are recorded, and eo 
on till the positions of sis lines have been noted, the wave-lengths 
being given from Angstrom's map, for each region. 

It is to be observed that these observations are made withont any 
reference whatever to the origin of t!ie lines ; that ia to say, it is no 
part of the observer's work to see whether there are metallic coinci- 
dences or not; this point has only been enquired into in the present 
reductions, that is, seven months after the lost observations now dis- 
cussed were made. In this way perfect absence of all bias is 
secured. 

It may further be remarked that the nnmber of lines widened 
throughout a sun-spot period is about the same, so that the conditions 
of observation vary very little from month to month, and from year 
to year. 

It may be further remarked that the absolute uniformity of the 
resolte obUuned in the case of eaoli of the ohemioal elemeutB ia- 
Teetigated indicates, I think, that the observations have been 
thoTonghly well msde; and, as a matter of &ct, they are not 
difficult. 

I first give tables (A, B, C) abowing that for each of the chemical 
elements taken — iron, nickel, and titanium — the nnmber of lines seen 
in the aggregate in each handred observations is redaoed from 
minimnm to mazimnm, and that this result holds good for both 
r^ona of the apectmm. 

I next give another table (D) showing that during the observations 
the lines recorded as most widened near the maximum have not been 
recorded amongst metallic lines by either Angstrom or Thal^n, and 
that many of them are not among the mapped Fratmhofer lines, though 
some of them may exist as faint lines in the solar spectrum when the 
observing conditions are best 



Sun-»pot i^wtra Obaenationt at Kenaington. 






9- lt\1 

D-R19 
0-1E1S 

i-esw 

VSHM 

B-tK» 

Z-OTM 

e-test 

5.I»Bt 

g-«o» 

!:S 

S. liBt 













































— 























= 

















= 

















































~ 










































































— 








i 
fi 
if 

.5 

i 


i 

i 

Is 

il 
i 
t 


i 
q 

S3 

SI" 

!' 
1 


i 

!i 

1 


i" 

i! 
1 

1 


i 
I' 

is 

if 
1" 

i 


3 

1 

ll 

Is 
Si 

i 

1 



ib. 3. N. Lookjet. On At ]}Uy i, 

Tablj B.— Nickw.. 
last of most Widened Lines obeerTod a>t E^enringftoD. 





liiiiiliiiiiiiiiiiii 


ltd h(iudl«d liM 












Sndl»ii>di«dliDM 


















SrdbiudndlinM 














4U>liDndndliiMt 












etfalmndMdllDM 






6tli himdred line* 






JOi liiindnd linM 







Table C. — Titanium. 
List of most Widened Linos observed at 





iiiiiiiiiiiiiiiiiiiii 


let hundred line. 
















Sod Imndred linsa 


































3rd bundled linee 
























4tl> hundred lines 














eth hundred lines 












6tll hundrsd lines 






7lh liDndred lines 


Ho lines. 



1886.] Stm-^ot Spectra Observations at Kensington, 



351 



Table D. — ^Unknown Widened Lines observed at Kensington. 



4865 

4S85 

4888*3 

4891-8 

4910 

4944 

5017 -2 

5028-9 

5030 

5034-8 

5037 

5038-9 

5042 

5042*3 

5043 

5041*6 

5061 

5061*5 

5062 

5062-4 

5062-8 

5065 

5067 

5069-5 

5070-8 

5077 

5079-5 

5080 

5081-5 

5082 

5083 

5083-3 

5084 

5084-5 

6086 

5086-8 

5087 -7 

5088-1 

5088-6 

5089-0 

5101 

6103 -5 

5112 1 

5115-5 

5116 

5116-2 

5118 

5127 

5127*6 

5128-8 

5129-6 

5130 

5132 

5122-5 



TOL. XL, 



l8t 

Hundred. 



11 



4 



2nd 
Hundred. 



1 
1 
1 



1 
3 



1 
1 
1 



1 
1 



1 
1 
1 
1 



17 

• ■ 

14 



8rd 
Hundred. 



1 
3 

4 



8 



17 



22 

• • 
24 
7 
14 



19 
1 

21 
1 



4th 
Hundred. 



3 



4 



6th 
Hundred. 



6th 
Hundred. 



2 



2 
2 



1 
2 



7th 
Hundred. 






3 
2 
5 



i 



^^ 





Iti 


Snd 


Snl 


«tt 


«!, 


aih 


7tt 




HniMlTtd. 




UniKtrid. 


Handred. 


noDdnd, 


nuDdntiL 


HnMnd. 


6132-8 
















GlllS-fi 












'3 


17 


Gisa-e 




80 


47 






a 


27 


SIU 












41 


10 


nM-4 












19 




nsG 












30 


ii 


5I3S-G 




SS 


IB 






36 


20 


6135-8 






87 






2 




613S 












22 


37 


61311 6 
















6137 
















B187fi 












78 


22 


6137-8 




12 


85 






10 


s 


sisa 














8 


6139 














1 


Has -4 




'i 












6140-4 




2 












5148-2 


is 


4 












514S-8 




21 












5143 














20 


6148-2 
















6144-2 




'3 












6144-6 
















5146-6 












"1 




6146 
















6146 -X 
















GI48 














'i 


6148 -S 
















614a 


'2 


32 


31 








8S 


5149-2 
















6149-5 














29 


B149-B 




's 








"b 




6160 
















GlBl'S 
















6168 '8 
















61G4 














i 


6155 '4 












:: 




6156 




ia 


87 


74 




01 


96 


516G-6 
















51B7-2 
















6159 












ii 


41 


S159 ■& 


i 




31 






86 


67 


5160 












9 




G16D-4 




'i 










"4 


5162 












67 




61(ja-2 


"1 




23 






30 




5175 














'3 



The reductioQ of the latitadee of the spots is not jet completed. 

The result of these observ&tiooB may be thus briefly stated. As we 

pass from minimum to maximum, the lines of the chemical elements 

gmduMy disappear from among those most widened, their places 

being taken by lines ot -wHcV e.1 TjiTtBeTA -wft Vwi* -oa ^tsrcoalsrial 

■umtatires. Or, to put the -reBoit wmftise -ww^ — «*• "^^ "was 



1886.] Sun-spot Spectra Observations at Kensington, 353 

mnm period of snn-spots when we know the solar atmosphere is 
quietest and coolest, vapours containing the lines of some of onr 
terrestrial elements are present in sun-spots. The vapours, however, 
which produce the phenomena of sun-spots at the sun-spot maximum 
are entirely unfamiliar to us. 

The disappearance of the lines of iron, nickel, and titanium, and the 
appearance of unknown lines as the maximum is reached is shown by 
curves in fig. 1 given on the next page. 

The results, in my opinion, amply justify the working hypothesis 
as to the construction of the solar atmosphere which I published some 
years ago. (** Proc. Roy. Soc," vol. 34, p. 291.) In the region of the 
Bpectrum comprised between 4860 and 5160, I find in the ^^ase of 
iron, to take an instance, that sixty lines were distributed unequally 
among the spots in 1879 and 1880, many iron lines being visible in 
every spot. In the. last observations, about the maximum, only 
three iron lines in all are seen among the most widened lines. These 
three lines also have been visible in foar spots only out of the last 
hundred. The same thing happens with titanium and nickel, and 
with all the substances for which the redactions are finished. 

I am quite content, therefore, to believe that iron, titanium, nickel, 
and the other substances very nearly as complex as we know them 
here, descend to the sur&^e of the photosphere, in the downrush that 
forms a spot at the period of minimum, but that at the maximum, on 
the contrary, only their finest constituent atoms can reach it. It may 
also be remarked that these particles which survive the dissociating 
energies of the lower strata are not the same particles among the 
constituents of the chemical elements named which give the chromo- 
spheric lines recorded by Tacchini, Ricoo, and myself. 

Having thus found the working hypothesis to which I have referred 
stand the severe test which the sun-spot observations apply to it, I 
have gone further, and have endeavoured to extend it in two direc- 
tions. 

First. I found that the view to which the hypothesis directly leads, 
that the metallic prominences are produced by violent explosions dae 
to sudden expansions among the cooler matters brought down to form 
the spots, when they reach the higher temperature at and below the 
photosphere level, includes all the facts I know touching spot and 
prominence formation. Thus, for instance, the close connexion 
between metallic prominences and spots ; the entire absence of metallic 
prominences with rapid motion from any but the spot-zones ; the fact 
that the faculffi always follow the formation of a spot and never \ive- 
cede it; that the faealous matter lags beV\md t\i^ ^^o\. \\:"& ^ t\:\^\*v^^ 
existence of veiled spots and minor prommeTiceft m t^^v^ws «\Aa^»a 
tbe spot-zones; the general iniection oi uiikiio^NTv axxVi^^TLC^^ ^^^^» ^^^ 



Mr. J, N. Lockyer. On llif 

Xumbpr .,f B].p..aroju.,.H of Lnomi orul i.iil. 




•marred to at liBgtt „,, „„«,„ „^^„^_ „» im>W.»^^« <!».-45^ 
''d are nmply and aTiffidentty exp\«>.mcd.\i^ SN., 



1886.] Sun-spot Spectra Observations at Kensington. 355 

With regard to the extensions of volume to which I have referred, 
I find that if we assume tliat metallic iron can exist in any part of 
the sun's atmosphere, and that it falls to the photosphere to produce a 
spot, the vapour produced by the fall of one million tons will give us 
the following volumes : — 

Yolume in 
Temporature. Preflsore. cubic miles. 

2,000° C 380 mm 8 

10,000 760 „ 1-8 

20,000 Satmos 07 

60,000 760 mm 8*8 

60,000 190 36-2 

If we assume the molecule of iron to be dissociated ten times by 

SQOoessive halving, then the volume occupied will be 1024 times 

greater, and we shall have — 

Yolume in 
Temperature. Pressure. cubic miles. 

60,000^0 760mm 9,011 

60,000 190 „ 36,044 

In these higher figures we certainly do seem nearer the scale on 
whioh we know solar phenomena to take place; the tremendous 
rending of the photosphere, upward velocities of 250 miles a second, 
and even higher horizontal velocities according to Peters, are much 
more in harmony with the figures in the second table than the first. 

I may mention in connexion with this part of the subject, that 
the view of the great mobility of the photosphere which this hypo- 
thesis demands, so soon as we I'cgard metallic prominences as direct 
effects of the fall of spot material, is further justified by the fact that 
if we assume the solar atmosphere, that is the part of the sun outside 
the photosphere, to be about half a million miles high, which I 
regard as a moderate estimate, the real average density of the sun is 
very nearly equal to one-tenth that of water, instead of being slightly 
greater than that of water, as stated in the text-books.* 

We can then only regard the photosphere as a cloudy stratum exist- 
ing in a region of not very high pressure. It is spherical because it 
depends upon equal temperatures. 

The second direction in which I have attempted to develop the 
hypothesis has relation to the circulation in the 8un*s atmosphere. I 
have taken the facts of the solar atmosphere as a whole, as they are 
recorded for us in the various photographs taken during eclipses since 

• The densitj referred to water = 1*4 U and lo t\ie ea.T^i^l ^**25>^, ^jt^iot^^^^^^ 
Newcomb. 



Ur. J. N. Lookyw. Oh lie 



[M.y«, 



Fia. 2. HiHiinnc. 
Inwiiig of Neweomb'a obanratioii of 1S78, the brighter portioii ot a 
UddM b; ft «nNn. Show* the equtoiUl ai Umi an and oobm 




1871, and also in drawings made before that time, the drawings being 
read in the light afiorded by these photographs. 

1 find that the working hypothesia at once suggests to as that the 
snn-spot period is a direct effect of the atmospheric circnlation, and 
that the latitudes at which the spota commence to form at the mini> 
mam, which they occnpy chieflj at the mazimnm, and at whict they 
die oat at the end of one period in one hemisphere, probably at the 
moment they commence to form a second one in the other (as happened 
in 1878 — 9), are a direct result of the local heating prodnced by the 
fall of matter from above descending to the photosphere, and perhaps 
piercing it. The resalts of this piercing are, the liberation of heat 
from below, and varioas explosive effects dne to increase of votnme, 
which, acting along the line of least resistance, give, as a retam 
cnrrent, incandescent vapours ascending at a rate which may be 
taken as a maxim am at 250 TnWea w B«c«a&, * ■^€\wa't-^ wffiuassii^R 
'»rrp- tbem to yery considerable liB\^te. 



1886.] Sun-»pot Spectra ObterwHoiu at Kentingtw. 357 

Fta. 3. ilnmtjm, 
Tiaciiig of tJii retulta obteinad b; the eameiBs in 1878, showing inner portiou of 
equBtorial extension, and how Ibe lurfMra of it out the ooneentrio ktmo- 
(phera in l>t. S6 If . uid S., or thembonts. 






The view of the solar circnlataoQ at which I have arrived may be 
briefly stated as follows :— 

There are upper oatflows from the poles towards the equatorial 
re^oDB. In these outflows a particle constantly travels, so that its 
latitude decreases and its height increases, so that the tme solar 
atmosphere resembles the flattened globe in Plateaa's experiment 
(see photographs, 1876, and fig. 3). 

These cnrrents, as they exist in the higher r^ons of the atmo- 
sphere, carry and gather the condensing and condensed materials till 
it last they meet over the equator. 

There is evidence to show that thc^ probably extend aa solar 
meteoric masses far beyond the limits of the tme atmosphere, and 
'orm a ring, the section of which widens towards the san, and the 
lase of which ties well within the bonndary of the &imQ«^^«>t«(^%.^. 

If we aesnme aucb a ring under absolnteVy at8.\>\ft iioTi.4iv^\"aii&,'3(««* 
■ilJ be no disturbance, no fall of matenal, ttiOWiloTe fcKcft -w"^>»'n» 



«08 Ur. J: N. Locbyo-. OntJu 

tpoto, and therefore agun there irill be no praminences. Svoh «■■ I 
Uie atftte of things on ^e eontheora sarf&ce of the ring from Decern 
1877, to ApriJ, 1879, dnring wfaioh period there waa not ft maf^i 
obserred the umbra of whioh tma over 15-iiuUioittlis o( ttn ■ 
Tuible hemisphere. 

Aamin* a dutnliMioei Thia nay arise &om eotti _ 

OODiBOnaironldbsiaoallikaEf to happen among the part teles «A 
tlw antlaoe of the ring maeta tlo current from thv polos. In 
parlablaa frill £b11 towards the ann, thereby disturbing and utM 
the molioii of othar pwtiolea naaier the photosphere, ftnd finally tf 
.'wflldeaoendwitliataaahoBiothaphotosphero, from thai pointii. 
:the nAoa of tha ring enten the atmosphere, sumo distauvo fillAf^ 

The Anurioaii photogimpha in 187S supply us with ample 
thai tliia will be aomewlieTe abont latitude 30°, and hero 
du flni apoti be farmed Cor two reasons. 

(L) In the oentnl plane of the ring over the equator, the 
;ilill be more nnmerons, a r^td deecent, therefore, iu lbi«' 
']danewill be impoaaible, for the reaaon that the condeit^d 
hha to fall perhaps a million of miles through strata, 
(amparatnre ; there will, ^Lenfore, be no upots ; a; 
ipeeking, aa is known, there are no spots at the eqnatm 
Qun are many small apota wiUumt umbne between latitudes 9^ 
6° Hf. and S. 

Abore latitode 80°, as a role, we have no epote, bocaoac tlk:ere is ao 
ring, and further the atmosphere i» of lower elevation, so that then » 
not snfiBoient height of faJl to give the velocities required to bang 
down the material in the solid form. 

The lower corona where the coi'oiia ia high, and it is highest over 
the equator, acts as & shield or buH'er, volatilisation and dissociation 
take phu:e at higher levels. Where ihis occurs, spots are replaced 
by a gentle rain of fine particles slowly descending, instead of tlM 
fall of mighty masses and largo quantities of solid and liquid 
material. 

Yolatilisatiou will take place gradually during the descent, audit 
the utmost only a veiled spot will he produced. 

We know that when the solar foi'ces arc weak, such a descent ii 
biking place all over the son, becauMe at that time the spectrum of the 
corona, instead of being chiefly that of hydrogen, is one of a molt 
complex nature, so complex that before 1S82 it was regai>led by 
everybody ae a pure continuous spectrum, such as is given by the 
limelight. 

The moment the fall of spot material begins we get the letnin 
current in the shape of active metallic ^rominenceH, and the prodne- 
tion of coaea and lioms w^ucb igxcW^A-j i«^-K»if.iA VXie\aigQK&\. -AaitM of 



i6.] Sun-epot Spectra ObtervationB at Kmtington. 6&9 

mdeflcence over Targe araas and extending to great heights ; and, 
ides these, the production of streamers. See fig. i, 



Tncing of draving bj Lisia, ahowing "ooom." 




TO results follow : — 
Id consequence of the increased temperature of the lower 
jns, the Telocity of the lower currents towards the poles, and 
cftire of the upper cnrrcnta from the poles, is enormously increased. 

disturbance oE the ring will therefore be increased. 
Violent uprnsbes of tho heated photospheric gases, mounting 
I an initinl velocity of a million miles an hour, can also disturb 
ring directly. 

t this way the sudden rise to maximum in the sun-spot curve, and 
lowering of tlie latitude of the spots, follow as a matter of course. 
. the part of tho ring nearest the sun, its base, so to speak, is, it 
Id appear, thrown out of all shape, and we get falls over broad 
j of latitude N. and S. 

oes this hjpotheaiM explain then the slow dcBcent to minimnm and 
still decreasing latitude ? It does more, it demands it. For now 

atmosphere over those regions where the spots have hitherto 
I formed is so highly heated, and its height is so increased, that any 
irbed material descending through it will be volatilised before it 
reach the photosphere. 

le best chance that descending particles have lui'v ta isfn!\ «^V%, 
th ej^ fall from points in lower latiWdoe. 1\ia6iisi.^wwA,'*IoK«>- 



860 Hr. J. K. Looker. On On D^^ 

lore, of Qie nm-Bpot onrro most be restriotod to m -nrj larga mtmtt 
to Utitsdea ver7 near the eqaator, and this is the fiwjt alao, u u mil 

It will be aeon thftt on this riew, as the brightDess and therafint 
the temperature of the atmosphere as we know inoreues yerj ooi^ 
tUanUy from —*■**■"■ to maxtmum, the masses which cao Borvivs 
■' lUl itmptntax* mut fdl faom gTAdimlly^ incro&siiig heights. 

It waj be pointed ont^ liow perfectly this hypothesis explains tbe 
i'*l~"'l' Iwli obw r rad tad oaeociates them with those gathered ui 
<ftar fleldl of onqoi^. 

At tlia nril PTn '""! ihs risf is nearest the san, the subjacent atmo>' 
mfimt b loir nd TtSaiinij cogl. * 

Phitiolgt hS&ag Anm tlu ring t]ianfi>M,'aUhon{^ tih«r Mil 

.' aiullsf qn«ati<!r beamw tha diatnibuae U mnaSl, bat* A* WA 

«banaa of nwdung the -pbobotpkwn in tiie ■oms ooaditiui m tf^f 

1mt» ihs ring, Iwaoe »t &U tinio tbo iridoning in nunj fMnflkr Shi 

4f bon, niokal. titashim, Ao. 

The gndoal diaappeoranoe of these lines from the period of 
tninimnin to that of m&xlmam, is simply and s ufficimtiy enloinsd hj 
tlu view that the spot-forming materials fall through gradnalllif 
inoreaiing depths of an atmosphere whieh at the same time is Imvii^ 
its temperature as gradnally inoreaaed l^ tiie nanit of the action I 
, have before indicated, until flnalty when the maxiroam if r o ached, if 
we assume dissociation to take place at a higher level at the maximum, 
dissociation will take place before the Tapoura reach the photosphere, 
and the lines which we know in onr laboratories will cease to be visible. 

This is exactly what takes place, and this result can be connected 
as I have stated elsewhere, with another of a different kind. This 
hypothetical increasing height of fall demanded by the chemistry of 
the spots is accompanied by a known acceleration of spot movement 
over the sun's disk, as we lower the latitude — which can only be 
explained so for as I can see by a gradually increasing height of fall 
as the eqoator is approached, 

There are two other points. (1.) The stmspot cnrve teaches us that 
the slowiog down of the solar activities at the maximum is very 
gradual. We should expect therefore the chemical conditions at the 
maximum to be maintained for some time afterwards. As a matter 
of fact they have been maintained till March of the present year, and 
only now is a change taking place which shows us chemically that we 
are leaving the maximum conditions behind. (2.) The disappearance 
-of the lines of the metallic elements at maximum is so intimately 
connected with an enormous increase in the indications of the 
presence of hydrogen, that there is little doubt we are in the preoence of 
•oan se and effect. The hydrogen, I am now prepared to believe, is a 
uueoaence of the disaooiabion of the metallic elements. 



886.] Sun-spot Spectra ObservatioM at Kensington. 861 

It will be convenient to refer here to the facts which have been 
30orded during those eclipses which have been observed at the 
an-spot minimnm and maximum. 

At the minimum the corona is dim ; observations made during the 
Linimum of 1878 showed that it was only ^ as bright as the corona 
b the preceding maximum. There are no bright lines in its 
3ectrum, and both photographic and eye observations proved it to 
insist mainly of a ring round the equator, gp:^ually tapering towards 
8 outer edge, which some observations placed at a distance of twelve 
iameters of the sun from the sun's ceniare. 

The same extension was observed in the previous minimum in 1867, 
id the polar phenomena were observed to be identical in both 
slipses. At the poles there is an exquisite tracery curved in opposite 
Lrections, consisting of plumes or panaches, which bend gently and 
nnmetrically from the axis, getting more and more inclined to it, so 
lat those in latitudes 80° to 70^ start nearly at right angles to the 
OS, and their upper portions droop gp^acefully, and curve over into 
»wer latitudes. 

Although indications of the existence of this ring have not been 
)corded during eclipses which have happened at the period of 
lazimum, there was distinct evidence both in the eclipses in 1871 
id 1875 of the existence of what I regard as the indications of out- 
ard upper polar currents observed at minimum. 

The fact that the solar poles were closed at the maximum of 1882, 
hile they were open in 1871, is one of the arguments which may be 
rged that at times the whole spot-zones are surmounted by streamers, 
ith their bases lying in all longitudes along the zones. 

It was probably the considerable extension of these streamers 
irthwards, in 1882, which hid the finer special details at the poles, 
hile in 1871, the part of the sun turned towards the earth was not 
ch in streamers of sufficient extension. 

Touching these streamers, it is an important fact to be borne in 
ind, that no spots ever form on the poleward side of them. 

It is obvious, therefore, that spots are not produced by the 
mdensation of materials on their upper surfaces, for in that case the 
K>ts would be produced indifferently on either side of them, and the 
idth of the spot-zoues would be inordinately increased. 

Although in the foi*egoing I have laid stress upon the indications 
forded by the observations of 1878 of the existence of a ring, it 
Lould be remarked that, so far, the eclipse appearances on which the 
ea rests have not been observed at maximum. This, however, is 
)t a fatal objection, because precautions for shielding the eye were 
^cessary even in 1878 when the corona was dim; and if it is 
imposed merely of cooled* material it would not readily be photo- 
raphed. 



*e 



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1886.] Structure of Mucous Salivary Olands. 863 

there are 8 to 12 grannies. After a time the ontlines of the granules 

become indistinct ; this takes place mnch sooner in alkaline than in 
neutral salt solution. 

The reactions of the granules are best observed bj irrigating pieces 
of gland which have been teased out in neutral salt solution. On 
irrigating with dilute alkalis, dilute mineral acids, or with water, the 
granules disappear as if they were bubbles bursting. It is difficult, 
however, to be certain that they are completely dissolved ; after treat- 
ment with dilute mineral acids, and still more frequently after treat- 
ment with water, pale, very slightly refractive masses are seen, appa- 
rently consisting of swollen and altered granules. On irrigating 
with osmic acid the granules swell up considerably, and become less 
refractive. On irrigating with alcohol or with acetic acid they 
remain, bat are somewhat shrunken. 

The hyaline substance of the cells swells up and in part dissolves in 
3 per cent, sodium carbonate. The solution forms a viscid fluid ; on 
irrigating with acetic acid or with alcohol a membranous precipitate 
of mucin takes place. Since the granules are not, for a time at any 
rate, dissolved by sodium carbonate, it follows that the hyaline sub- 
stance gives rise to mucin. The granules also give rise to mucin ; in 
most of their reactions they resemble mucin ; on solution they form 
a viscid fluid ; further, when a gland is hardened in alcohol, and a 
section mounted in Canada balsam or in glycerine, the granules in the 
hyaline substance are usually indistinguishable, both together form 
the clear inucigen portion of the cells. 

During secretion both the hyaline substance and the granules are 
turned out of the cells ; after prolonged secretion the cells consist of 
an outer zone, chiefly of freshly formed substance, and of an inner 
zone of network, hyaline substance, and granules, as in the resting 
state. When the saliva has a high percentage of solids, both the hya- 
line substance and the granules can be seen in it ; such saliva is 
obtained from the submaxillary gland of the dog by stimulating the 
sympathetic, and often by strong stimulation of the chorda tympani. 
The hyaline substance is more soluble than are the granules, and is 
thus less commonly seen ; it is partly dissolved, partly swollen up into 
a continuous mass ; the less swollen parts appear as strings or blebs. 
The granules in saliva vary greatly in appearance ; they may be very 
slightly swollen, and have fairly sharp outlines ; or they may be more 
swollen and run together, forming pale masses of various size ; occa- 
sionally in more dilute saliva they are just visible as pale spheres : 
these are probably the spheres mentioned by Heidenhain,* as seed 
by him in the submaxillary saliva of the dog after combined stimula- 
tion of the chorda tympani and sympathetic nerves. 

• •' Studien des Physiol. Institute luBteaiaa," ^. Afc,\^^- 




364 Mr. J. K. LangleT'. OnA$ 

Henoe then, when a small amount of flnid only is ■eer e te d y Ihetf^ 
line snbstanoe and the grannies are tnmed oat of the oella withssi 
being completely dissolved, when a certain amoont more of fluid ii 
secreted the hyaline substance is completely dissolved, and with 
more fluid, the granules also are completely dissolved. Soma 
&t globules are usually turned out of the cells daring s o ero t i on. 

According to Heidenhain,* nerve stimalation causes some 
tuents of the cell to be converted into a more solable form, tiuii I 
usually expressed by saying that mucigen is converted into nuun. I 
Apart from the reasons given by Heidenhain, this is probable, siiiei / 
both hyaline substance and granules appear to be more solable ii I 
osmic acid and in chromic acid when they are in saliva than wliet 
they are in the gland cells ; but the proof does not seem to me to bi { 
conclusive. 

Eleinf has described the mucous cells as being open towards the 
lumen, in this I am inclined to agree with him ; it is not easy to see 
in all cells, but in many it is perfectly distinct. 

Although I think that the mucous cells are able to turn out bodilj 
their products, I am unable to agree with the view of Heidenhain^ 
and of Lavdowsky,§ that the cells disintegrate during secretion. As 
the decrease in the interfibrillar substance takes place, there is a 
fresh formation of substance in the outer part of the cells, i.e., as tbe 
cell secretes it also grows : the changes which take place are closely 
comparable to tbe changes which take place in the pancreas and in 
other glands, in which there is no question of the disintegration of 
cells. Moreover, in saliva I can find no evidence of broken down 
cells ; when the cells of a fresh gland are treated with osmic acid the 
cell membrane becomes very distinct, when sympathetic saliva is 
treated with osmic acid no signs of cell membrane are found; nor 
are nuclei present except those in " salivary corpuscles," which, as 
stated by Pfluger,|| are leucocytes. 

Further, there is not, I think, any satisfactory proof that the 
demilune cells multiply during secretion, and give rise to mucous 
cells. I have examined glands at various times after stimulation of 
the chorda and of the sympathetic, and have not, except extremely 
rarely, found nuclei undergoing indirect divisioti. As I have pre- 
viously said,^ I hold the demilunes to be secreting cells of a different, 
nature from that of the mucous cells, for in different glands aU 
variations are found between glands wholly " albuminous " and 

• Loe, cU., p. 108. 

t " Quart. Joum. Bficr. Science," toI. xix, p. L51, 1879. 
X Loc. cit. 

§ Max Schulfcze'a " ArchW," Bd. xlvv, ^. i^l, 1ST7. 
1/ Strieker's " Hibiology" ^tTwv%AaJLed.>a^^o^«t^,N^.\,^. ^SA. 
% " Tiane. Intemat. Ued. Oon^teaa;* \^«». 



1886.] Structure of Mucous Salivary Glands, 365 

glands wholly mncons. Glands with demilunes are simply glands in 
which the *' albuminous " element is reduced to a minimum. The 
apparent increase in size of the demilunes, described by Lavdowsky* 
as taking place in the first stage of secretory activity, I take to be 
due to the decrease in the size of the alveoli, so that the ordinarily 
flat demilunes become more spherical. Moreover, the demilune cells 
show signs of secretory activity ; in the submaxillary gland of the 
dog after prolonged secretion the demilune cells, in section of the 
gland hardened in alcohol, are smaller, they stain more readily with 
carmine, and their nuclei and nucleoli are more conspicuous. The 
"young" cells described by Heidenhain and by Lavdowsky are, I 
think, chiefly altered mucous cells. 

The network of the cell consists of two parts, one in the cell-mem- 
brane, the other stretching from this throughout the cell. The 
peripheral network is best seen in the isolated cells of the orbital 
gland of the dog after treatment with chloral hydrate, 2 per cent., for 
a week to a fortnight. It consists of very delicate fibres ; at some of 
iho nodal points there are small spherical swellings. From lumen to 
basement membrane there are twelve to fifteen meshes. In many 
cases this network is perfectly distinct, every fibre in it can be 
followed without the slightest difficulty. In such specimens, on the 
other hand, it is often difficult or impossible to make out any cell- 
membrane. That a membrane exists I conclude chiefly from observing 
cells isolated in sodium chloride, 5 per cent., and then treated with 
osmic acid. In such specimens the outline of the cells although 
beaded appears to be continuous. The beading of cell-membrane has 
been noticed by SchiefFerdecker ;t it is obvious with most methods 
of treatment, it is caused by the fibi*es of the network, seen in optical 
section. 

The internal network is connected with the peripheral network, 
but it appears to me to have much larger meshes. From basement 
membrane to lumen there are in the submaxillary gland of the dog 
four to six meshes, in the orbital gland of the dog five to seven 
meshes, i.e., the number of meshes in a given direction in the cell is 
about half that of the number of granules. This network is seen on 
treating with dilute mineral acids fresh cells which have been teased 
out in sodium chloride, 5 per cent. ; it is seen more or less distinctly 
in cells treated with the ordinary dissociating agents, and is seen after 
hardening in various reagents. The reagent which I have found to 
give most constantly satisfactory results, is a mixture containing 
0*3 per cent, of chromic acid and 0*1 per cent, of osmic acid. 

The network which I have described above as the limiting network 

• Xoc. cit. 
f Max. Schnltze'a " i^rchiV," Bd. xmi,^.^^"i,\fi&^. 



266 Simeture of Mueow Sathary Ghmdi. [Ma^ 18, 

▼eiy doselyresemblefl that described by Klein,* as shown hj unBODi 
eella after treatment with spirit or with a mixture of bhxomio aoid 
4Uid spirit. I cannot, however, find a network with snch close msshsi 
beneath the limiting membrane. The passage from the doee^meshed 
limiting network to the wide-meshed internal network can often, be 
traced with a good lens, snoh as Powell and Lealand's -^ oil-immer^ 
«ion, with angular aperture 1*45. 

With certain modes of treatment the cell network is not seen, thvi 
when a piece of gland is hardened in osmic acid and sabseqnentiij 
with alcohol, the cell usually appears to consist of faint granules 
imbedded in the cell-substance. In such cases the hyaline substance 
find the network are indistinguishable, and the two together maj 
stain and leave the granules unstained. At any one focus the stained 
substance will then appear as a close network, and the unstained 
granules as the meshes of the network. On careful focussing, how- 
ever, it can be seen that the stained substance is simply the mass of 
the cell in which the granules are imbedded. This is, I think, the 
explanation of the close network described by Schiefferdecker| and 
by Paulsen J in certain mucous cells. And that the " network " 
described by Schiefferdecker is in part the hyaline interfibrillar sub- 
stance of the cell is indicated by his account of it ; according to him 
it consists of mucigen. 

The sablingual gland differs in various respects from other mucons 
glands ; a considerable portion of it consists of " albuminous " cells. 
According to Klein§ no demilunes are present and the gland tubes 
have only one layer of cells. This is certainly true of the larger part 
of the gland; the appearance of two layers of cells in a tube is 
occasionally caused by the section passing obliquely through a spot 
where a side tube is given off or where the lumen suddenly alters its 
•calibre. But whilst none of the tubes have a complete double layer of 
cells, it is I think an open question whether demilunes are absent 
from the gland. The sublingual gland has been taken as an especially 
favourable one in which to observe the disintegration of the mucous 
cells. I do not find that there is any more evidence of disintegration 
here than there is in ordinary mucous glands. The mncQus cells 
undergo the same changes as do these in the submaxillary of the dog, 
they discharge hyaline substance and granules, and they form fresh 
cell-substance. Secretion does not cause any division of nuclei. The 
** albuminous " cells probably secrete on nerve-stimulation as do the 
mucous cells ; in speaking of these cells as '* albuminous " cells I only 
follow the ordinary usage according to which a secreting cell which is 

• " Quart. Journ. Micr. Science," vol. xix, p. 125, 1879 ; vol. xxi, p. 154, 1882. 

t Loc. cit. 

X Max Schultze'a " Archiv," Bd. xxvi, p. 307, 1885. 

^ " Quart. Journ. Micr. Science," vol. xxi, p. 175, 1882. 



SSiEH^Mai^a-tJ 



1886.] Computation of the Harmonic Components^ ^c. 367 

granular after a certain mode of treatment is said to be albaminoos. 
It is perfectly possible that such a cell should secrete a substance 
which is more allied to mucin than to albumin. We do not yet know 
enough about the chemical characters of the bodies intermediate 
between proteid and mucin to make any dogmatic statement on this 
head. 

A fuller account of the points dealt with iu this paper will shortly 
be published in the " Journal of Physiology." 



II. " On the Computation of the Harmonic Components, &c" 
By Lieui-Geueral Straohey, R.E., C.S.I., F.R.S. Received 
April 15, 1886. 

(Abstract.) 

The object of this paper is to propose a method of computing the 
harmonic components of formulae to represent the daily and yearly 
variations of atmospheric temperature and pressure, or other recur- 
ring phenomena, which is less laborious than the ordinary method, 
though practically not involving sensibly larger probable errors. 

According to the usual method the most probable values of the 
harmonic coefficients are found by solving the equations of condition 
supplied from the hourly or other periodical observations, by the 
method of least squares. The number of these equations is, however, 
much larger than the number of unknown quantities, when these are 
limited, as is usual, to the coefficients of the first four orders, and the 
numerical values of the coefficients of those quantities which depend 
on a series of sines of multiple arcs, afford peculiar facilities for the 
eliminating process, so that values of the harmonic coefficients may be 
obtained by applying certain multipliers to combinations of the original 
observations obtained by a series of additions and subtractions, the 
results giving probable errors virtually the same as those got by the 
method of least squares. These multipliers for the two first orders of 
coefficients are so nearly equal to ^, and for the third order so nearly 
0*07, that the values may readily be found without tables, though 
such tables have been calculated to facilitate computations. 

Approximate methods of determining the coefficients and of the 
components for each interval of the series, are also given, from which 
last a graphical representation of the components may easily be ob- 
tained. 

The system of computation is applicable to all cases in which the 
angular intervals between the observations are such as to make the 
circle a whole series, exactly divisible by 6 and 8, and it has been 
extended, by aid of an interpolation, to the case of the 73 five-day 
means of a yearly period, in which the calculation by thA o'cdkxAsr^ 

VOL. XL. ^ ^ 



368 Mr. 0. A. Bell. • [May 13^ ] 

luB&od ironld be wo laborioiu as to be impnctioable in most e 



Tabular forms bare been prepared by belp of whioh the oompcfi^ 
tions of ibe coeffidenti in tbe form p cos 0, q smO, may oonraniflBfljr 
be oarried out, irith a miaimnm. of arithmetical labonr ; also &r 
obtaining the ooefficients P and the angle C in the form P sin (^+0); 
and tbe method of correcting' the coeffioiente, as oompnted irom tbe 
observed qnantitnes, for any non-periodic variation between the oon^ 
menoement and end of the series is likeirise indicated. 



m. '* Od the Sympathetic Tibratibne of Jets." By CmcmESTB 
A. Bell, M.B. Commanicated by Prof. A. W. WfUjut- 
SON, F.IU3. Received April 28, 1886. 
(Abstract.) 

After a brief hiBtorical notice of the observations of Savart, 
MasBOD, SondhaaSB, Enndt, Lacoote, Barret and Tyndall, Decharme, 
and liTeyreneiif, on tbe eympatbetic vibrations of jets and flames, tbe 
anthor describeB his own experiments. Attention was directed to the 
snbject by the accidental observation that a pnlsating air-jet directed 
against a flame cansed tbe latter to emit a mnsical Boniid. The pitch 
of this sonnd depended solely on the rapidity of the jet palsBtdonB, 
bat its intensi^ was fonnd to increase in a remarkable way with the 
distance of the flame from the orifice. In order to study the pheno- 
menon, air was allowed to escape against tbe flame from a small orifice 
in the 'diaphragm of an ordinary telephone, the chamber behind the 
diaphragm being placed in commnnication with a reservoir of air 
nnder gentle presanre. Yibratoiy motions being then excited in the 
diaphragm, by means of a battery and a microphone or rheotome in a 
distant apartment, the discovery was made that speech as well as 
musical and other sounds conld be quite loudly reproduced from the 
flame. Certain observations led the author to suspect that motion of 
the orifice rather than compression of the air in the chamber was the 
chief agent in the phenomenon ; and, in fact, precisely similar resolta 
were obtained when a light glass jet-tube was cemented to a soft iron 
armatnre, mounted on a spring in front of the telephone magnet. 

Experiment also showed that an air-jet at suitable pressure directed 
against a flame repeats all sounds or words uttered in the neigh- 
bourhood. Except, however, where the impressed vibrations do not 
differ widely in pitch from the normal vibrations of the jet (dis- 
covered by Sondhanss and Masson), these effects are likely to est^pe 
notice, owing to the inabihty of the car to distinguish between the 
distnrbing sonnds and their echo-like reproduction from the flame. 



1886.] On the Sympathetic Vibrations of Jets. 369 

In these experiments the primary action of the impressed vibra- 
tions was undoubtedly exerted on the air- jet ; but a singular and per- 
plexing fact was that no sound, or at best very faint sounds, could be 
heard from the latter when the flame was removed, and the ear or the 
end of a wide tube connected with the ear, was substituted for it. 
Suspecting, finally, that the changes in the jet, effective in producing 
sound from the flame, must be relative changes of different parts of it, 
the author was led to try a very small hearing orifice, about as large 
as the jet orifice. The results were most striking. By introducing 
this little hearing orifice into the path of a vibrating air-jet, the 
vibrations can be heard over a very wide area. Close to the jet orifice 
they are so faint as to be scarcely audible; but they increase in 
intensity in a remarkable way as the hearing orifice is moved away 
along the axis of the jet, and reach their maximum at a certain 
distance. Experiments with smoked air showed that this point of 
maximum sound is that at which the jet loses its rod-like character, 
and expands rapidly ; it has been named the " breaking point," 
because just beyond it the sounds heard from the jet acquire a broken 
or rattling character, and at a greater distance are completely lost. 
The distance of the breaking point from the orifice diminishes as the 
intensity of the disturbing vibrations is increased, and also depends 
to some extent on their pitch, and on the velocity of the jet. With 
orifices of 1 to 1| mm. in diameter it usually varies from 1 to 6 cm. 
The vibrations of an air- jet may also be heard at points not situated on 
the axis ; but they are always most intense along the axis, and become 
rapidly fainter as the distance from it increases. 

With glass jet and hearing tubes, and a light gas bag to serve as 
reservoir, these experiments are easily repeated ; but simple apparatus 
for more careful experiments is described. The author's general 
conclusions from his experiments and those of others are as 
follows : — 

A jet of air at moderate pressure (below 10 mm. of water) from 
an orifice 1 to 1^ mm. in diameter, forms a continuous column for a 
certain distance, beyond which it expands and becomes confused. 

Any impulse, such as a tap on the jet support, or a short and sharp 
sound, causes a minute disturbance to start from the orifice. This 
disturbance increases in area as it progresses, and finally causes the 
jet to break. By directing the jot against a flame or a hearing orifice 
it is readily perceived that such disturbances travel along the jet 
path with a velocity which is not that of sound in air. In fact, the 
sound heard in the car- piece resembles an echo of the disturbing 
sound. 

The disturbances produced by sounds of different pitch travel 
along the jet path with the same velocity. This is evident ; since 
otherwise accurate reproduction of the complex vibrations of s^^eeScibL 



870 Mr.aA.Be1L [MftyUi 

«t a distance from the orifice would be impotnble. This TdoeUj » 
mucli less than that of sonndin air, and is probabljthe mean ydocikf 
of the stream. 

A vibrating air-jet playing into free air giyes rise to ybtj feeUs 
sounds, but these sounds are much intensified when the jet impingM 
on any obstacle which serves to divide it into two parts. Of sabk 
arrangements the best is a perforated surface, the orifice being placed 
in the axis of the jet. 

A jet of air at low pressure responds to and reprodnoea onfy 
sounds of low pitch. Sounds above a certain pitch, which dependi 
<m the pressure, either do not affect it or are only faintly repsodnoed. 

At pressures between 10 and 12 mm. of water an air-jet repm>diioes 
all the tones of the speaking voice, and those usually employed in 
music, with the exception of very shrill or hissing noises. When 
the pressure in the reservoir equals about 18 mm. of water, hisBiiig 
sounds are well reproduced, while sounds of low pitch become fainter. 
At higher pressures, up to about 25 mm. of water, shrill or hissing 
noises produce very violent disturbance, while ordinary speech tones 
have little effect. But at these pressures sounds of high pitch 
frequently cause the jet to emit lower sounds of which they are 
harmonics. 

In general a pressure of about 12 mm. of water will be found 
most suitable for reproducing speech or music. Under this condition 
the jet is very sensitive to disturbances of all kinds, and will repro- 
duce speech, music, and the irregular sounds classified as " noises." 

It must be understood that the pressures here given are only suit- 
able for jets of not too small diameter. When the diameter of the 
orifice is only a small fraction of a millimetre the above limits may be 
much exceeded ; since the velocity of efflux no longer depends solely 
on the pressure. 

A jet of air escaping from a perfectly circular orifice does not 
vibrate spontaneously so as to emit a musical sound. But musical 
vibrations may be excited in it by the passage of the air on its way 
to the orifice through a resonant cavity, or through any irregular 
constriction. 

An air-jet impinging on any obstacle, such as a flame, frequently 
vibrates spontaneously, if the obstacle is at sufficient distance and of 
such a nature as to difiEuse the disturbances produced by impact or 
throw them back on the orifice. This constitutes one of the chief 
objections to the use of a flame as a means of rendering audible the 
vibrations of a jet. The disturbances excited in the surrounding air 
by the impact of the stream upon it are so intense as easily to react 
on the orifice. When, therefore, the jet is thrown into any state of 
vibration it tends to continue in the same state, even after the excit- 
sound has ceased. 






1886.] On the Sympathetic Vxhrations of JeU. 371 

A jet of air naiially responds most energetically to some particular 
tone or set of related tones (Sondhauss). Snch a particular tone 
may be called the jet fundamental. The practical inconvenience 
arising from this may be diminished by raising the air-pressure until 
the jot fundamental is higher than any of the tones to be repro* 
duced. 

When a flame and an air- jet meet at right angles vibrations im- 
pressed upon the flame orifice also yield sound. The conditions of 
pressure, <fec., are somewhat different ; but the changes produced at 
the orifice grow in the same way as those in an air- jet The best results 
are obtained when a gentle current of air is directed from a wide 
tube just below the apex of the blue zone. 

It is difficult at first sight to account for the fact that a vibrating 
jet gives rise to sound only when it stiikes upon some object which 
divides it into two parts. The following experiments, however, in 
some sense explain this. The relative normal velocity at different 
points in the stream may be measured by introducing into its path 
the open end of a capillary tube which is connected with a water 
manometer. This velocity diminishes continuously along the axis 
from the orifice to the breaking point ; and also diminishes continu- 
ously from any point of the axis outwards towards the circumference. 
Now a sudden disturbance communicated to the air at the orifice will 
be found to produce a/aZ2 in velocity along the axis of the jet, but a 
rise in velocity along its extreme outer portions. It thus appears that 
the changes along the axis and along the circumference, produced by 
a disturbance, are of opposite character. When the jet plays into 
free air these opposing changes neutralise each other in the main ; but 
this interference is prevented when the jet strikes upon any object 
which serves to divide it. 

When a vibrating air-jet plays against a small flame, the best 
sounds are heard when the stream strikes the flame just below the 
apex of the blue zone. At the plane of contact an intensely blue 
flame ring appears, and this ring vibrates visibly when the jet is 
disturbed. The production of sound from it doubtless depends on 
changes in the rate of combustion of the gas. This may be proved 
by inserting into the ring a fine slip of platinum, connected in circuit 
with a battery and a telephone. When the jet is thrown into vibra- 
tion the consequent variations in the temperature of the platinum 
affect its conductivity, and hence a feeble reproduction of the jet 
vibration may be heard in the telephone. 

To Savart we are mainly indebted for our knowledge of the 
sympathetic vibrations of liquid jets. This physicist showed that a 
liquid jet always tends to separate into drops at a distance from the 
orifice in a regular manner; and that this tendency is so well marked^ 
that when the jet strikes upon any object^ buc\i «a «i ^Xit^V^^^Tci^sssi- 



872 Hr.aA.BeIL [IfajlS, 

braine, bo arrangdd that the diBtnrbanoefli caused b^ impaot may he 
condnoted hack to the orifice, a definite mnBical Bound is produced. 
The pitch of the Bound, or the number of drops separated in a given 
time, varies directly as the square root of the height of liquid in the 
reservoir, and inversely as the diameter of the orifice. Savart further 
showed that external vibrations impressed upon the orifice may act 
like the impact disturbances, and cause the jet to divide into drops. 
Impact on a stretched membrane may then cause the reproduction as 
sound of the impressed vibrations. The tones capable of producing 
this effect were considered to lie within the limits of an octave below 
and a fifth above the jet normal. 

The author has found, however, that jets of every mobile liquid are 
capable of responding to and reproducing all sounds whose pitch is 
below that of the jet normal, as well as some above; and that the 
timbre or quality of the impressed vibrations is also preserved, pro- 
vided that the jet is at such pressure as to be capable of responding 
to all the overtones which confer this quality. Other essential con- 
ditions for perfect reproduction are, that the receiving membrane 
should be placed at such distance from the orifice that the jet never 
breaks into drops above its surface ; and that it should be insulated 
as carefully as possible from the orifice. 

In order to assist the action of aerial sound-waves on the fluid, it is 
advisable to attach the jet-tube rigidly to a pine sound- board about 
f ths of an inch thick. The surfaces of the board should be free, 
otherwise it may be supported in any way. The receiving membrane 
is formed by a piece of thin sheet rabber, tied over the end of a brass 
tube aboat f ths of an inch in internal diameter. A wide flexible 
hearing tube furnished with an ear-piece is attached to the brass 
tabe. The jet- tube is connected with an elevated reservoir by an 
india-rubber pipe. 

With an apparatus of this kind, and a tolerably wide jet-tube 
having an orifice about 0*7 mm. in diameter, a pressure of about 
15 decimetres of water is required to bring the jet into condition to 
respond to all the tones and overtones of the speaking voice (except 
hissing sounds) and those employed in music. At a somewhat higher 
pressure it will reproduce hissing sounds. It is not easy for an un- 
trained ear to distinguish between the disturbing sounds and their 
reproduction by the jet, when both are within range of hearing. 
Vibrations may however be conveyed to a jet from a distance in a 
&irly satisfactory way, by attaching one end of a thin cord to the jet> 
support, and the other to the centre of a parchment drum. The cord 
being stretched, an assistant may speak, sing, or whistle, to the dis- 
tant drum. Other devices for conveying vibrations from a distance 
are described. 

Vow when the jet is diaiurbed. m «u^ ^«.^^ ^x^d. tha receiving mem- 



1886.] Oil the Siimpntlietic Vibrations of Jets, 373 

brane is introduced into its path close to the orifice, scarcely anj 
sonnd can be heard in the ear-piece. But .if the membrane be moved 
away from the orifice along the path of the jet the sounds become 
gradnallj louder, until at a certain distance (which varies both with 
the character of the orifice and the intensity of the impressed vibra- 
tions) a position of maximum purity and loudness is reached. At 
greater distances the reproduction by the jet becomes at first rattling 
and harsh, and finally unintelligible. In the latter case the jet will 
be seen to break above the membrane. 

From this experiment we may draw the conclusions previously 
arrived at for air-jets ; viz., that all changes produced by sound at the 
orifice grow in accordance with the same law ; and that all changes 
travel with the same velocity, which is probably the mean velocity of 
the stream. 

The mode in which the jet acts upon the membrane becomes 
apparent when instantaneous shadow photog^phs of vibrating jets 
are examined. When the jet is steady, and the orifice strictly 
circular and well insulated, the outline in the upper part of the stream 
is that of a slightly conical rod, the base of the cone being at the 
orifice. When, however, vibrations are impressed upon the support, 
swellings and constrictions appeal' on the surface of the rod, which 
become more pronounced as the fluid travels downwards. At the 
breaking point the constrictions give way, those due to the more 
energetic sound impulses being the first to break. When the im- 
pressed vibrations are complex, the outline of the jet may be very 
complicated. When the membrane is interposed, we have then a 
constantly changing mass of liquid hurled against it, and vibratory 
movements are therefore excited in it, proportional to the varying 
cross section of the jet at its surface. 

It would appear at first sight that the mode of growth of the 
vibratory changes in a liquid jet must be different from that which 
characterises the vibrations of an air-jet. It is possible, however, by 
special arrangements, to receive the impact of only a small section of 
a vibrating liquid jet, and thus to get a reproduction of its vibrations 
as sound. We are thus led to conclude that the sound effects of a 
vibrating liquid jet may not be simply due to its varying cross section, 
since actual changes occur in the translation- or rotation-velocity of 
its particles. Experiment shows that these changes are greatest 
along the axis of the jet. 

One of the most interesting and beautiful methods of studying the 
vibrations of a jet consists in placing some portion of it in circuit with 
a battery and telephone, whereby its vibrations become audible in the 
telephone. A number of forms of apparatus for this purpose have 
been constructed, but one will serve as a type. Savart in the course 
of his experiments showed that the vibrations ol V\i^ *^^\t «i^ Y^^^^^^^ 



874 Ur. a A. BelL [May 18^ 

in the ''nappe" or thin sheet of fluid formed when the jet strikes 
normallj on a small snr&oe. So far then as vibratory changes axe 
concerned, the nappe has all the properties of the main stream. 
Although the diameter of this excessively thin film is about the same 
whatever be the distance of the snrface ^m the orifice, the intensily 
of the vibratory changes propagated to it varies with this distanee, 
as for the jet itsel£ It- is simply necessary then to insert into the 
nappe two platinum electrodes in circoit with a telephone and a 
battery having an electromotive force of from 12 to 30 volts, to get an 
aconrate and ^thful reproduction of the jet vibrations. Loud sounds 
can thus be obtained from a jet which is finer than the finest needle, 
and the arrangement constitutes a highly sensitive " transmitter." 

A jet transmitter, in its simplest form, consists essentially of a glass 
jet-tube which is rigidly attached to a sound-board, and supplied from 
an elevated reservoir containing some conducting liquid (distilled 
water acidified with y^th of its volume of pure sulphuric acid is the 
best) ; and a couple of platinum electrodes, embedded in an insulator,, 
such as ebonite, against which the jet strikes. The jet may issue from 
a circular orifice, about ^th of a millimetre in diameter, in the blunt 
and thin-sided end of a small glass tube. Much smaller jets may be 
used : but for one of the given size the pressui*e required for distinct 
transmission of all kinds of sounds will not exceed 30 inches. The 
receiving surface is the rounded end of an ebonite rod, through the 
centre of which passes a platinum wire. The upper end of the rod 
should be about 1 millimetre in diameter, and should be surrounded 
by a little tube of platinum ; and the end of the central wire and the 
upper margin of the tube should form a continuous slightly convex 
surface with the ebonite, fi-ee from irregularities. The inner and 
outer platinum electrodes are joined respectively to the terminals of 
the circuit. The jet is allowed to strike on the end of the central wire, 
and thence radiatiug in the form of a nappe, comes iuto contact with 
the tube, thus completing the circuit. The dimensions of the 
apparatus may be varied to suit jets of different sizes ; it is highly 
desirable, however, that the jet nappe should well overlap the inner 
margin of the ring-shaped electrode. 

With small jets the impact disturbances are so feeble that slight 
precautions are necessary to insulate the receiving surface from the 
orifice, unless the former is placed low down in the path^ The 
strength of battery may be increased until the escape of electrolytic 
g^-bubbles causes a faint hissing noise in the telephone. The liquid 
on its way to the jet should pass downwards through a wide tube 
lightly packed with coarse clean cotton, by which minute air- bubbles 
which violently disturb the jet, and small particles of dust which 
might obstruct the orifice, are stopped. This tube should never be 
mllowed to empty itself. 



1886.] On the Sympathy V%br<aum» of JeU. 372^ 

Experiments are g^yen to show that in this instrument the jet may 
act upon the electric current in two ways : firstly, by interposing a^ 
constantly changing liquid resistance between the electrodes; and^ 
secondly, by cansiog chaoges in the so-called *' polarisation " of the 
electrodes. In one form of instrument, namely, that in which both 
jet and electrodes are entirely immersed in a mass of liquid of the 
same kind as the jet liquid, the action must be entirely at the woLviAa^ 
of the electrodes. 

In the latter case a liquid jet becomes similar in structure and 
properties to a jet of air in air, and the velocity at difEerent points, 
when it is steady and when it is disturbed varies in precisely the 
manner already described. 

The author briefly passes in review the leading facts to be accounted 
for, and lays stress upon the parallelism of the properties of gaseoua 
and liquid jets. Some shadow photographs of vibrating smoke jeta 
have shown that these also present drop-like swellings and contrac- 
tions which grow along the jet-path. The most satisfactory explana^ 
tion of the phenomena will then be one which refers the vibratory 
changes in jets of both kinds to the same origin. 

The beautiful and well-known experiments of Plateau have supplied 
a satisfactory explanation of the normal vibrations of a liquid jet in 
air. He has shown that a stationary liquid cylinder, whose length 
exceeds a certain multiple of its diameter, must break up under the 
influence of the ** forces of figure " into shorter cylinders of definite 
length, which when liberated tend to contract into drops. Now, the 
jet being regarded as such a stationary cylinder, we have a satisfactory 
explanation of the musical tone resulting when its discontinuous pari 
strikes upon a stretched membrane, and when the impact disturbances- 
may be in any way conducted back to the orifice. These disturbances- 
then accelerate the division of the jet after it leaves the orifice. 
Plateau endeavoured to show that division of the jet might take place 
at other than the normal points, thus explaining Savart's experimental 
conclusion that a jet can vibrate in sympathy with a limited range of 
tones. Lord Bajleigh, moreover, has recently shown that the inferior 
limit of this range is not so sharply defined theoretically as Savart*a 
experiments would prove it to be. 

Both Savart and Magnus, however, describe experiments in which 
a water-jet, carefully protected from impact and other disturbances,, 
does not exhibit the peculiar appearances characteristic of rhythmical 
division ; and the author's experiments conclusively prove that thia 
rhythmical division does not take place in a well insulated jet. While 
the tendency so to divide may therefore be admitted, and the normal 
rate* of vibration of the jet and its greater sensitiveness to particular 
tones may thereby be explained. Plateau's theory cannot be held to 
accoont for the uniform growth along the ^et-^tk oi ^ ^*dsi^gii^.. 



376 Mr. C. A. BelL [May Vi, 

however complei their form. For this growth takes pliice inde- 
pendently of the " forces of figure," and under conditions in which 
they are entirely absent, as when a gaseous or liquid jet plays within 
ft jhelss of fluid of its own kind. 

The author is inclined rather to refer the properties of jets of all 
kinds to conditions of motion on which hitherto little stress has beeo. 
laid, viz., the unequal velocities at different points in the stream afMr 
it has left the orifice. From the axis towards the circumference of ft 
jet near the orifice the velocity diminiihca continuously, and the 
motions of the stream may be regarded as I'CBnltants of the motions 
of an infinite series of parallel and coaxial vortei-rings. In many 
respects, in fact, the appearance of a jet resembles the appearance of 
a vortex-ring projected from the same orifice. Thus a jet from a 
■circular orifice, like a vortex-ring from a round aperture, remains 
always circular. In a frictionleas flnid a vortex-ring, uninfluenced by 
other vortices, would remain of constant diameter; a condition to 
which a horizontal liquid jet approiimates. When, however, the 
ring moves throngh a viscous fluid it esperiencca retai'dation and 
expansion, which are precisely the changes which a jet playing in a 
fluid of its own kind undergoes. The vibrating smoke-ring projected 
from an elliptical aperture changes its form in exactly the same 
manner as a jet, at sufQcientty low pressure, from an elliptical orifice. 
These analogies might be considerably extended. 

In a liquid jet in air, or in a vacuum, internal friction must 
gradually equalise the velocities. At a distance from the oi-ifice, 
therefore, depending on the viscosity of the liquid, such a jet most 
approach the condition of a cylinder at rest, and must tend to 
divide in accordance with Plateau's law. The rapidity with which 
drops are formed depends mainly on the superficial tfii^sion of the 
liquid. The length of the continuous column should therefore bear 
some inverse ratio to the viscosity and snpcrScial tension of tho 
liqnid ; a view which is in harmony with the resnlts of Savart'l 
experiments, and some of the antlior's, in this direction. 

Where tbo jet plays into a flnid of its own kind the retardation and 
expansion which it experiences are mainly due to its parting with iU 
energy to the surrounding medium. When, as a result of vibration, 
growing swellings and contractions are formed in it, this loss must be 
more rapid, and the jet therefore shows a diminution of mean velocity 
along the axis, which increases with the distance from the orifice. 

Such being the conditions, it is evident that any impulse com- 
mnniciited to the fluid, either behind or external to the orifice, or to 
the orifice itself, must alter the vorticity of the stream. That vortei- 
rings are generated by impulses of the first kind is well known ; the 
action when the orifice is moved is intelligible, if we consider that a 
trrrsrd motion of it will 'pToA.ow woftleTatioOt a backward motioi 



1886.] On the Sympathetic Vibrations of JeU. 377 

retardation, of the outer layers of the jet. As the result of a rapid 
to-and-fro motion we may then imagine two vortex-rings to be 
developed — the foremost lajer of greater energy and moving more 
slowly than the hindmost. These two rings in their onward coarse 
will then act on each other in a known maimer ; the first will grow in 
size and energy at the expense of the second, at the same time 
diminishing in velocity ; the second will contract while its velocity 
increases. The inequalities in cross-section, initiated at the orifice, 
thus tend to grow along the jet-path, and will be attended also by 
growing inequalities of the normal and rotational velocities of the 
particles. Since the stream lines of a voriex-ring are crowded 
together at its centre, the disturbances produced by impact of the jet- 
rings will be greatest along the axis, and least along the circum- 
ference. 

Indeed the sound disturbances produced by impact of a common 
vortex-ring are quite analogous to those of a vibrating jet. Let an 
air-ring be projected into a trumpet-shaped tube connected with the 
ear, and little more than a rushing noise will result. But let it be 
projected against a small orifice in the hearing-tube, and a sharp 
click will be heard at the moment of impact. This click is loud 
when the centre of the ring strikes the tube, but faint, although still 
of the same character, when produced from the circumference. 

The foregoing considerations may be extended to cases in which 
the motions of the orifice are complex vibrations. Expansions and 
contractions are then initiated in the fluid proportional at every point 
to the velocity of the orifice. The inequalities must tend to further 
diverge in the manner described. 

Similar considerations apply to cases in which the motions of the 
orifice are the result of lateral impulses. In these cases the rings 
formed in the jet will not be perpendicular to its direction, and in 
their onward coarse may possibly vibrate about a mean position. 

The author further points out how the viscosity and surface-tension 
of the fluid may influence its sensitiveness. When the surface- 
tension is very high, as in mercury, it produces a tendency in the jet 
to break easily under the influence of moderate impulses. 

The foregoing is little more than the outlines of a new theory of 
jet-vibrations. The author hopes to supply in the future further 
experimental evidence in support of it. 



878 Oaptain Abne7 and Majop-Geneial Festmg. ' [Haj 1S» 



IV. "IntenBity of Radiation throngh Turbid Media.* B7 
Captain Abnet, RE., F.R.S.» and Major-General FESTlNa, 
R.E. Reoeived May 3, 1886. 

In the Bakerian Lectiire for this year, which was deiiTered befioie 
the Royal Sociely on March ^th, on Colour Fhotometiyy we gave 
incidentally the results of some measurements we had made of the 
intensify of visible radiation which penetrated throngh a transparent 
medinm as compared with that which penetrated throngh the same 
medinm rendered tnrbid. We showed that tiae formula deduced hj 
Lord Bajleigh from the scattering of light by small particles^ waa 
confirmed by our experiments. We thought, however, that the theory 
might be more fully tested if a larger range of spectrum than that 
to which we had confined ourselyes were used, and at the same time 
it would be more satisfactory if an instrument possessing no personal 
equation could bo utilised. Our thoughts naturally turned to the 
thermopile, and more particularly to that form which we described in 
a previous communication to the Royal Society (** Proc. Roy. Soc.," 
vol. 37, p. 157, 1884), since its delicacy was extremely great. In 
the Bakerian Lecture the results we gave were obtained from water 
rendered turbid, and it appeared to us that the same medium would 
again answer our purpose — ^more especially if certain precautions 
were taken. It will be in the recollection of the Society that we 
have shown that water possesses very definite absorption-bands in- 
the infra-red of the spectrum ("Proc. Roy. Soc.,** vol. 35, p. 328^ 
1883), as also does alcohol. Now, as the turbidity of the water w^ 
desired to produce was made by adding a dilute solution of mastics 
dissolved in alcohol to the water, it was evident that in additiooA 
to the water-spectrum we should also have superposed a fainC: 
alcohol spectrum, if the addition of the latter was made in an^ 
quantity. EEad the spectrum of a definite thickness of pure an(? 
transparent water been compared with one of the same thickness 
of water rendered turbid by the mastic, it is evident that a dis- 
crepancy might have arisen owing to alcohol being present in the 
one case and not in the other. To avoid this difficulty, when great 
turbidity was to be produced, the amount of alcohol added with the 
mastic was measured, and the same quantity of pure alcohol added 
to the transparent water. By this plan the mixture of alcohol and 
water was the same in the two cases, the only difierence in the two 
being that one had extremely fine particles of mastic suspended in it 
A reference to our paper (** Proc. Roy. Soc.,** vol. 35, p. 328, 1883) will 
show that a small thickness of water cuts ofE nearly all the spectrum 



B86.] Intensity of Radiation through Turbid Media. 379 

3low XL4,000, and that 1} inches cuts off nearly e'^erything below 
L0,000. It was therefore determined to use a thickness of \ inch, as 
p to \1 4,000 in that case the deflections of the g^vanometer would be 
ifficiently large in both cases to allow the proportion of rajs trans- 
litted through the transparent and turbid media to be calculated 
ithout fear of any grave error due to inaccuracy of reading. 
The spectroscope we have described was used for this purpose, and 
36 source of light used was the crater of the positive pole of the 
lectric light. The opening of the slit was about f^ iiich, and that 
I the linear pile about 3^ inch. In the first experiment we described 
le colour of the crater of the positive pole as seen after passing 
irough the turbid medium was a lemon-yellow, and in the second a 
cep orange, nearly approaching red. It will be seen that theory 
id experiment agree within the limits that might be expected. 



X. 


1 


Thermopile readings. 


Obserred. 


Calculated.^ 






Clear. 


Clear. 






Turbid. 


GJear. 


Turbid. 


Turbid. 






First E 


xperiment. 






524 


14-03 


3-25 


14 


4*81 


4-20 


558 


10-60 


6-5 


20-5 


8-15 


8*16 


609 


7-72 


12 


29-5 


2-47 


2-42 


652 


5-29 


20 


88 


1*90 


1-91 


684 


4*58 


27 


48 


1-77 


1-77 


720 


3 72 


38-5 


63 


1-63 


1*63 


762 


2-97 


45 


68 


1-51 


1-50 


813 


2-29 


54-5 


77 


1*41 


1-41 


877 


1-68 


64 


85 


1-33 


1-33 


960 


118 


58 


78 


1-26 


1*26 


1070 


0-76 


72 


85 


119 


1-21 


1170 


0-53 


39-5 


45 


1-14 


112 






Second Experiment. 






591 


8-24 


2 35 


17-5 


17*75 


636 


610 


5 


46*5 


9-30 


9-18 


663 


4-28 


12-5 


66 


5-28 


5-25 


774 


2*82 


27-5 


89 


3-24 


3-35 


877 


1-67 


46 


108 


2-35 


2-35 


960 


118 


47-5 


99 


2-03 


2-02 


1040 


0-855 


55 


101-5 


1-84 


1-83 


1130 


0-613 


53 


89 


1-68 


1-68 


1230- 


0-437 


28 


48 


1*60 


1-62 


1320 


0-329 


13 


20 


1-54 


1-56 



* These were calculated bj the formula r«It~^^~*, uaia^ the TMitVtfi^^*lNsMMk\. 
uarefl. 



Relation of " Tramfcr-resistance " to EUctrolyUa. [May 20, 

Other nieaan'rements have been made, and wbich give results also 

in accordance with the theory. 

It may he well to remark that in order to get a proper finenesa of 
particle in SDspeiisioii in the mater, n very convenient plan is to odd 
the varnieh very gently and by very amall qnantities in a glass jar in 
■whioli the water \% automatically or otherwise stirred. Tbe water 
efaoald be of large volume to get the best reenlts. To make the 
fineness still more uniform we have prepared the turbid medium as 
above, and then rotated the glass flask in which it was placed at the 
rate of about 2500 revolutions per minute. By this means any 
particles, escept the very finest, are deposited on the sides of the flask, 
and the filtered liquid^ — if we may so call it — can be poured off ready 
for any experiments. 



May 20, 1886. 

Professor STOEGS, D.C.L., President, in the Chtur. 

The presents received were laid on the table, and thanks ordered 
for them. 

; The following Papers were read : — 

I. " Relation of ' Transfer-resistance ' to the Molecular Weight 
and CbemJca! Composition of Electrolytes." By G. GoBE, 
LL.D., FJt.S. Received May 5, 1886. 
(Abstract.) 

lo the full paper the author first describes the method he employed 
for measuring tbe " resistance," and then gives the numerical results 
oi the measurements in the form of a series of tables. 

He took a number of groups of chemically related acidB and salts 
of considerable degrees of purity, all of them in the proportions of 
their equivalent weights, and diKsolved in equal and sufficient quanti- 
ties of water to form quite dilute solutions. The number of solutions 
was about seventy, and included those of hydriodic, bydrobromic, I 
hydrochloric, hydroflaonc, nitric, and sulphuric acids ; the iodides, 
bromides, chlorides, fluorides, hydrates, carbonates, "nitrates, and 
snlpbates of ammonium, cssiam, rubidium, potassium, sodium, and 
lithium ; the chlorides, hydrates, and nitrates of barium, strontium, 
and calcium ; and a series of stronger solntions, of equivalent 
atrength to each other, of the chlorides of hydrogen, ammonium. 



1886.] On the Thermal Properties of Ethyl Oxide. 881 

mbidiam, pota498ii]in, sodium, lithium, barium, strontium, and calcium. 
A series of similar liquids to those of one of the groups of acids, of 
equal (not of equivalent) strength to each other, was also included. 

As electrodes he employed pairs of plates of zinc, cadmium, lead, 
tin, iron, nickel, copper, silver, gold, palladium, and platinum ; and 
separate ones formed of small bars of iridium. 

He took each group of solutions, and measured in each liquid 
separately at atmospheric temperature, the '* total resistance " at the 
two electrodes, and the separate "resistances" at the anode and 
cathode respectively with each metal, and thus obtaiued about seventy 
different tables, each containing about thirty-six measurements, 
including the amounts of ** total," *' anode," and *' cathode resistance" 
of each metal, and the averages of these for all the metals. 

By comparing the numbers thus obtained, and by general logical 
analysis of the whole of the results, he has arrived at various conclu- 
sions, of which the following are the most important : — The pheno- 
menon of *' transfer-resistance *' appears to be a new physical relation 
of the atomic weights, attended by inseparable electrolytic and other 
concomitants (one of which is liberation of heat, " Phil. Mag.," 1886, 
vol. xxi, p. 130). In the chemical groups of substances examined, it 
varied in m^agnitnde inversely as the atomic weights of the constituents, 
both electropositive and electronegative, of the electrolyte, independently 
of aU other circumstances; and in consequence of beiug largely 
diminished by corrosion of the electrodes it appears to be intimately 
related to " surface-tension." He suggests that corrosion may be a 
consequence and not the cause of small ''transfer-resistance." The 
strongest evidence of the existence of the above general law was 
obtained with liquids and electrodes with which there was the least 
corrosion and the least formation of undissolved films ; those liquids 
w^re dilute alkali chlorides, with electrodes of platinum. 
> The research is an ^extension of a former one on " Transfer-resist- 
\ ance in Electrolytic and Voltaic Cells," communicated to the Royal 
i Society, March 2, 1885. Further evidence on the same subject has 
I been published by the author in the " Phil. Mag.," 1886, vol. 
pp. 130, 145, 249. 



II. '* A Study of the Thennal Properties of Ethyl Oxide.'' 
I By William Ramsay, Ph.£)., and Sydney Youxg, D.Sc. 
- ; Received May 5, 188t). 

'i (Abstract.) 

^ 1 A. year ago, a paper was communicated to the Society on the 
behaviour of ethyl alcohol when heated. A similar study of the 
properties of ether has been made, in which numerical values have 

/ 



882 Me(B0i8. B. H. Boott and B. S. Cortik [MaySO^ 

been obtained exhibiting the expansion of the liqnid, the puMWUiu id 
the vaponr, and the oompreBsibiHty of the snbetanoe in the gaMooi 
and Hqnid conditions; and from theee resnlts, the densitieB of the 
saturated vaponr and the heats of vaporisation have been dednoed. 
The temperature range of these observations is from —18" to 223^ C. 
It is the anthers' intention to consider in fall the relations of the 
properties of alcohol and ether ; in the meantime it may be stated 
ihat the saturated vaponr of ether, like that of alcohol, possesses aa 
abnormal density, increasing with rise of temperature uid corre- 
sponding rise of pressure; that at 0* the vapour-density is still 
abnormal, but appears to be approaching a normal state ; and that the 
•apparent critical temperature of ether is 194*0^0. ; the critical pressure 
very nearly 27,060 mm. = 35*61 atmospheres ; and the volume of 
1 gram of the substance at 184" between 3*60 and 4 c.c. 



TIL " On the Working of the Harmonic Analyser at the Meteoro- 
logical Office." By Robert H. Scott, F.RS., and Richard 
H. Curtis, F.R. Met Soc. Received May 6, 1886. 

On the 9th of May, 1878, Sir W. Thomson exhibited to the Society 
■a model of an integrating machine, which consisted of a series of five 
of the disk, globe, and cylinder integrators, which had been devised 
two years earlier by his brother Prof. James Thomson, and a descrip- 
tion of which will be found in the " Proceedings of the Royal Society," 
vol. xxiv, p. 262. Sir W. Thomson's paper describing this model 
will be found in vol. xxvii of the " Proceedings," p. 371 ; and refer- 
ence should be made to both these papers for an explanation of the 
principle of the machine. In the communication last named it is 
stated that the machine was about to be "handed over to the 
Mefceorologpical Office, to bo brought immediately into practical work." 

The model was received at the Office in the course of the month, 
and was at once set in action ; the results of the preliminary trials, 
when obtained, being referred to a Committee consisting of the late 
Prof. H. J. S. Smith and Prof. Stokes, who, on the 5th of July fol- 
lowing, submitted to the Meteorological Council a favourable report 
on the performance of the model. 

The Council at once resolved to have a machine constructed, which 
should be specially adapted to the requirements of the work for which 
it was intended, viz., the analysis of photographic thermograms and 
barograms. 

In preparing a working design for actual execution, it was found 
necessary to make several modifications in the details of the mechani- 
cal arrangements of Sir W. Thomson's original model, and these were 



1881).] The Harmonic Analyter at the Meteorological Offxe. 383 

mainly -worked oat by Prof. Stokes and TAx. de la Rue. Plans were 
obtained from two firms of mechanical engmeers, and those of 
Mr. Hnnro being ultimately adopted, the conatmctioa of the instrn- 
ment was entrosted to him. It was considered sufficient to limit the 
action of the machine bo aa to extend only to the determination of 
the mean, and the coefficients as far aa those of the third order, in the 
expression 

£=(1+0] coB&+!iiBiiid+a,co8 20+(2'i<°^+"3<^B^ 
-|-&jBin3&+ tfec., 

and to obtain these it was necessary to have seven sets of spheres, 
disks, and cylinders. 

A description of the machine, as actnally constmcted, was published 
in "Engineering" for December 17th, 1880, and we are indebted to 
the proprietors of that journal for permission to reproduce the 
engravings which illnetrato that description, as well as a portion of 
the text, which we now proceed to quote : — 

" The machine is shown in the accompanying engravings, figs. 1 to 
3 ; figs. 2 and 3 showing details of the arrangemeute of the ball, disk, 
and cylinder. In principle it is, of coarse, precisely similar to its 
predecessor — differing from it only in constructive details intended to 
secure stability, and accuracy in its movements. Instead of being 
largely made of wood, as was the case with the model, it is entirely 
of metal ; the cast-iron frames carrying the disks being secured to a 
firm iron bed enpported by two substantial uprights ; the disks them- 
selves are of gnn-metal, and the spheres of steel carefully turned, and 
nickel-plated to prevent msting ; the horizontal bar carrying the forks 
for moving the spheres is also of steel and plated, and is carried above 
the disks npon five iron uprights or guides. The forks are provided 
with adjusting screws allowing of veiy accurate centering of the 
spheres upon the disks, and adjuxting screws are likewise provided 
for the frames carrying the recording cylinders, by which their 
parallelism to the faces of the disks can be rigidly secnred. The 
spheres are not touched by the forks themselves, bat by the fiat faces 
of two screws passing through their lower extremities, and iu this 
way a ready means of preventing looseness or tightness of the spheres 
in the forks is provided. 

" Each recording cylinder has attached to it a counter for register- 
ing the number of its complete revolutions, and to secure a maximum 
of freedom in their movements the spindles of the cylinders, as well 
as the slides carrying the racks for giving motion to the disks, and the 
horizontal steel bar, are all made to run npon friction rollers ; the slides 
have in addition counterpoises attached to them to prevent error from 
backlash. 
" The motion of the shaft at the rear of the mt>.c'h\u& Sa cA^o.-m.-o;^- 
YOL. IL. ^ i> 



1886.] The Harmonic Analtfier at t/ie Meteorological Ofice. 
Tio. 2. Fio. 3. 




cated to the eecODd and third pairs of cranks throi^h seta of toothed 
-wheels, so arranged that they maj, if desired, be changed for others 
of difTerent ratios to the cylinder carrying the cnrveB, and in this way 
the terms of other orders of the expansion may ho obtained, should 
they be required, with the same itistmtnent, merely going oror the 
cnrves afrcBh, and nsing wheels of the proper ratios in place of those 
used for the first, second, and third pairs of terms. 

" The cylinder oyer which the carves have to pass is provided with 
an ingenious arrangement by which it can be expanded or contracted 
to alter its circumferential measurement by abont fonr-tenths of an 
inch, so that within certain limits variations in the lengt.h of the time 
oi-dinates of the curves can he very readily allowed for. To effect 
this the cylinder (see figs, i, 5, and 6) is made in three sections, each 
provided with an eccentric movement ; of course, except when these 
are at their normal positions the " cylinder " is not tmly cylindrical, 
but still, even when moved to their extreme limita, the deviation is 
not so large as to cause any inconvenience in its use. AdjustmentB 
are also supplied to the pointers, of which two axe used at once, the 
one to follow the outline of the curve dealt with, and the other tho 
zero line from which the ordinatcs are measured ; and throughout tho 
machine all racks and toothed wheels are skew cut to further lessen 
thu risk of orror from backlash. 

" The height of the machine is 3 feet 8 inches, and the length of the 
steel bar, which is rather longer than the bed of the machine, 9 feet. 

" The machine has now for some time been in regular use at the 
Meteorological Of&ce, and notwithstanding the weight and solidify 
of some of its parts, the whole is so nicely balanced and fitted that ifc 
works with the ntmost case and smoothness." 

The machine was delivered at the Office in necember, 1879, and a 
lengthened series of trials was at once commenced, to determine its 
constants, and thoroughly test tho accuracy of its working, for whicli 
purpose systems of straight lines and curves, of which the values wero 
known, were firat used. A few small unforeseen difficulties were early 
met with, necessitating slight modifications iu some portions of thu 
instrument. 

The chief of these faults was a slight turning of tho cylinders upon i 
their axes, when the balls were moved to and. fro nXoii^ &a ^-v^sa. 



Messrs. R. H. Scott and R. H. Cnrtia. 



[MaySfli 




parallel to the axes of the cylinders. The movement was always io 
the same direction, namely, towards the disks, whether the ball w»g 
moved to the right or left. Aftor the trial of many expediente the 
defect was fioalty, in great measure, overcome by attaching weights to 
the spindles of the cylinders. It however still exists in the machine 
U> a slight extent, and its effect is to decreaee the readings on the 
cylinders by a very small amonnt. 

It was decided to employ the analyser, in the firat instance, in the 
determination of tempei-ature constants, and careful compariaona h&ve 
been made of the resnlts obtained by its means, with those got by 
actual meaBurement of the photographs and namerical calcnlationa, 
as Trill pr«eeiitly b« mentioned, and the accordance is ho very close as 
to prove that the machine may safely be trusted to effect rednctions 
which conld only otherwise be accomplished by the far more laborious 
process of measurement and calculation. 

It will facilitate an apprehension of the method of using the machine 
to give a somewhat detailed accotint of the operations involved in the 
treatment of the curves, 'with an example of the manner in which the 
readings of the machine are recorded and dealt with. 

The machine is furnished with three pairs of recording cylinders 
and disks, numbered consecutively 1 to 6, whicn give the coefficients 
for the first three pairs of terms of the expansion, and in addition a 
seventh cylinder and disk from which the mean is obtained. In the 
thermograms which snpply continuous photographic records of the 
march of temperature, the trace for twenty-four honrs covers a length 
of 8'75 inches, while a vertical height of about 0*7 inch* corresponds 
to a range of ten degrees in temperature; each thermograph sheet 
contains the record for for^-eight hours. 

* ThU value vaiiei jlightly for Mch obterratorj. 



1886.] The Harmonic Analyser at the Meteorological Office. 387 

Conveniently placed in the machine is a cylinder or dram, the 
circumference of which is eqnal to the length of twenty-four hoars 
upon the thermograms. Boand this cylinder the thermograms are 
rolled, the fluctuations of temperature indicated by the carves being 
followed, as the cylinder revolves, by a combination of the move- 
ment of the cylinder with that of a pointer moving in a line parallel 
to its axis. 

The handle by which the cylinder is tamed gives motion at the 
same time to the seven disks of the machine, and the operator thus 
controls by his left hand both the speed with which fche carves are 
paid through the machine and the consequent velocity of the angular 
motion of the disks, while by a suitable contrivance, the movements 
of the pointer, governed by his right hand and following the curve, 
produce on the face of the disks corresponding movements to the right 
or left of the balls by which the motion of the disks is conveyed to 
the recording cylinders. 

At the commencement of an operation all the cylinders} are set to 
zero ; the twelve months curves are then passed consecutively through 
the instrument ; the first pair of cylinders, which gives the coefficients 
of the first order, and also the mean cylinder, 7, being read for each 
day, while cylinders 3 and 4, and 5 and 6, which give the coefficients 
of the second and third orders respectively, are only read for each five 
days and at the end of each calendar month. The numbers on the 
cylinders are, however, progressive, so that the increments upon them 
for any given period could very easily be obtained. The form in which 
the readings are recorded is as follows : — 

iieadiugs of the Recording Cylinders of the Harmonic Analyser. 
Dry-bulb Thermometer Curves, from July 30 to August 3, 1882. 
Kew Observatory. 



Month and day. 


First order. 




Cylinder 1. 


Cylinder 2. 




Keading at 
midnight. 


Difference 

from last 

reading. 


Beading at 
midnignt. 


Difference 
from last 
reading. 




June 30 


+ 10-480 




-12-333 


— 








July 30 


+ 12-540 
+ 12-678 
+ 12 -773 
+ 12 -814 
+ 12 •807 


+ 103 
+ -138 
+ 095 
+ 0-041 
+ 0083 


-14-926 
-15-004 
-15-069 
-15-207 
-15-287 


-0-118 
-0-078 
-0-065 
-0-138 
-0 080 




„ 31 




AuflTUSt 1 




2 




11 ■••.••«•«..•••• 
3 




I 





MesBrs. R. H. Scott aud R. H. Curtis. fllay Hi, 



HoDtb and dav. 


Second orfer. | 


Cylinder 3. 


CjlindCT*. 


Keikdiog Bt 


DilTerence 
Irom luC 
reading. 


S^-'|H?| 




-3 053 


- 










-4 05i 


±0-000 


1 


/si:::::::::::::' 


-3-461 ^ -O-080 


T'l'^y.'•'^'.'.''.'.'. 

















JimoSO. 

July 30 . 
„ 81 . 

August 1 



June 30, 

JuIt 30. 
„ 31, 

/ "" ^ 



Cjlindar S. 



Cylinder 6. 



Re&ding &t 
midnight. 



-2-674 
-a -786 



^^f I Hiding .t 
mding. J " 



DiSoroncc 
from lut 
nsding. 



Difference 
ftoni lut 



DiSereiiK 
from lut 
reading. 



+ 62-637 
4- 64 -554 

+ 67-177 



+ 2-302 

+ 1'917 
+ 2-623 

+VMR 



+ 2-623 — . 

\ -vI'Mft \ — \ 

\ +VMR \ ~ \ 



188^).] The Harmonic Analyser at the Metcorolcxjicai Orjire, 381^ 

At present only tlie monthly increments of the readings have beeu 
dealt with, so as to obtain the coefficients of the mean daily variation 
for each month of the year. The process followed is, therefore, 
simply to divide the monthly increment by the nnmber of days in the 
month, and then to multiply the quotient by a factor which is deter- 
mined by the scale- value of the thermograms, and which will there- 
fore be different for each observatory. 

The ratios of the factors for cylinders 1 to 6 to that of No. 7 
were very carefully determined from a series of experimental curves, 
of which the values were known. The numerical factor is obtained 
for each observatory by obtaining on cylinder No. 7 the scale reading 
corresponding to a vertical movement of the pointer of 10° on the 
thermogram, which in the case of Kew is 0*75 inch. The factor for 
cylinders Nos. 1 and 2 is eight times that for cylinder No. 7 ; the 
factor for Nos. 3 and 4 is four times that quantity, and for Nos. 5 and 
6 is eight-thirds of that quantity. The signs of the factors depend on- 
the direction in which the disks and cylinders are caused to revolve. 
The constant quantity added to the reduced reading of cylinder No. 7 
corresponds to the temperature which is assumed as the zero at the 
commencement of the operation. 

As an illustration, the case of Kew for July, 1882, may be taken, 
the final readings of the cylinders for which month are above given. 
The increments for the month shown by these figures are as fol- 
lows : — 

Cylinder ...... 1. 2. 3. 4. 5. 6. 7. 

^^e7t^^..*?!^. } "*'^*^^® -2-671 -0-101 -0198 -0-797 -0*564 +66-889 
Divided by 31" 

(the number [• +0 071 -0-086 -0*003 -0006 -0*026 -0*018 + 1*834 

of dajs) .... 
Factor -53-52 +53*52 -2676 -26*76 -17*84 -17*84 + 6*69 

^^dfced'^!. . .^.t } " ^'^ " ^*^^ + ^'^^ + ^'^^ ■*• ^'^ + ^'^^ +12*27 



Add constant 48 *17 



Mean temperature 60 *44 

After some trials with the curves for the year 1871, the year 187G 
was taken up, inasmuch as for that year the records had been dis- 
cussed by Mr. H. S. Eaton, M.A., F.R. Met. Soc, who had calculated 
the hourly means of the various meteorological elements for each 
month separately, and who kindly placed his results at the disposal 
of the Council. 

The working of the machine was thus subjected to an exact test by 
comparing the results obtained by it with the coefficients in the har- , 
monic series which were calculated from IAt. 'Ek^A.otL^ TL^^-ajw^S ^xJbS 
their trustworthy character, and the adequacy o^ Wie%^ caX'c?o^aJCv3^w^ Hi 



390 Messrs. R. H. Scott aud R. H. Curtis. [May 20; 

eerve as a standard with which the coefficionls obtained hy means of 
tlie machiDe might be compar^^d, was established by calcalatang them 
from tho odd and even hours, quite independently, for aJl the aeiec 
observatories. 

The ootcome of this expci-iment was tboronghly satisfactory, lad 
the entire aeries of results obtained botii by calculation and from 
the machine was published as Appendis IV to the Quarterly Weather 
Beport for 18/6, tog*etber with a Report prepared by Prof. Stokes, 
the concluding paragraphs of which may be quoted here, since thej 
sum up in a few words the conclusions arrived at. 

" Disregai-ding now the systematic character of some of the errors, 
snd treating them as purely casual, we get as tho average diSereixH 
between the constants as got by the machine and by calcalatioa from 
the twenty-four boiu'ly means O'OeS". It may be noticed, however, 
that the numbers are unnsnally large (and at tbe same time very 
decidedly systematic) in the ease of tbe second cylinder of the fint 
order (h{), for which the average is as much as O'lSO", the serentJi 
of a degree. 

" IE (/[ be omitted, the average for the remaining cylinders of the 
machine is reduced to 0'017^. 

" We see, therefore, that with the eiception perhaps of b^, the 
constants got by the machine for tho mean of tho days constituting 
the month are as accurate ah those got by calculation, which requires 
considerably more time, inasmuch as tho hourly lines have to be 
drawn on tlie photograms, then mensured, ihen meaned, and the 
ooudtantid deduced from the means by a numerical process by no 
means very short," 

The curves for the twelve years 1871 to 1882 inclusive have now 
been passed through the machine, and the resalts obtained have been 
carefully checked so far as the arithmetical work involved is concerned, 
npon a plan approved by the Conncil. No direat check, short of 
passing the curves a second time through the machine can however 
at present be put on any portion of the results except as regards the 
means, which have been compared with the means calculated from 
the hourly readings obtained by measurement trom the curves. The 
results of this work will be published as an appendix to the " Hourly 
Readings from the Self-Recording Instrnmenta," for 1883, bat the 
general results may here be stated. 

As a rule, the monthly means yielded by the harmonic analyser 
agree well within a tenth of a degree with those obtained by calcu- 
lation from the hourly measarements of the curves ; and although in 
some exceptional cases larger differences have been found, amonnting 
in rare instances to eis much as half a degree, it is probable that 
^renerally these are leas due to defects in ik«'novt\\^.t^oCth«i.netrDmeDt 
tbaa to other caaees. In some caaea \«rg6 Vce^ita W ft«i wi.rii«&,4aj 



1886.] The Harmonic Analyser at the Meteorological Office^ 391 

to failure of photography, &c., were interpolated when the carves 
were passed throagh the machine, bat not when the means were 
TTcrked oa.t from the hourly measurements. Some di£Eerences rather 
larger than usual, and confined chiefly to the earliest years dealt 
with, have been ascertained to have arisen from the circumstance that 
w^hen the curves were first measured, to obtain hourly values, the 
method of making the measurements was not the same as that found 
by subsequent experience to be the preferable ; and also that in some 
cases the scale-values first used were less accurately determined than 
has since been found possible. 

In both these respects the two methods were on a par in the later 
years dealt with, and therefore the fairest comparison is to be had 
with their means. 

For 1880, the average difference of the monthly mean fiir all the 
seven observatories is 009'* ; for 1881 it is 005^ ; and for 1882 O-OG** ; 
and in these three years a difEerence of 0*3° between the analyser 
and calculated means occurred but once, and of 0*2^ but five 
times. 

What has been said is sufficient to show that the instrument is 
completely applicable to the analysis of thermograms. 

It has also been employed on the discussion of barograms, and the 
curves for the years 1871, 1872, and 1876 have been passed through 
the machine. 

The year 1876 was selected owing to the existing facilities for 
comparing the resulting figures with those obtained by calculation 
from Mr. Eaton's means, and the result in this case was equally 
satisfactory with that for temperature already mentioned. 

In conclusion, the Fellows may perhaps be reminded that on 
June 18th, 1874, one of us (Mr. Scott) read a paper " On the use of 
an Amsler*s Planimeter for obtaining mean values from Photographic 
Curves,'* " Proc. Roy. Soc," vol. 22, p. 435. This paper contains a 
table exhibiting the differences between the means so obtained and 
those yielded by the hourly values. 

We reproduce this table, appending to it the values obtained from 
the analyser for the same period. 

It will, of course, be remembered that the mean is the only result 
which can be got from the planimeter, while it is but a small part of 
what is yielded by the harmonic analyser ; but a comparison of the 
figures obtained by the two instruments from the same photographic 
curves may be interesting, as being got in the case of the planimeter 
from an instrument in which there is a combined ** rolling and slipping" 
movement, while the movement in the analyser is one of ''pure 
rolling contact.' 



^T> ^ 



)i 



392 Harmonic Analyner at the MeteoTOloijiral Office. [JIaj- 20; 

Comparison of Temperature Means obtained from Kew Photographic 
Tliermograms, by Amsler's Pianimeter, and Sir W. Thomson's 
Harmonic Analyser rospectively, with those obtained by Nnmerical 
Catculntion from Hourly MeaanremeptH of the Carves. 







Mmn>. 




Differenre^ 




Omupa of fire 


























. d»j«. 


TftbnUtiona. 


Flontmeter. 


Harmonic 

uulyter. 


T-P. 


T-A. 




187a. Apr. 1— B . 


44-8 


45-1 


44-8 


-0-3 







C— 10. 


43-1 


48-4 


48-1 


-0-3 







11—15. 


62 8 


52 7 


82-7 


+ 01 


+ 0-1 




16—20. 


4a-9 


44-2 


44 1 


-0-3 


-0-2 




31—25. 


4S-0 


48-1 


48 


-0-1 







2*;— 30. 


53-3 


53-5 


53-4 


-0-2 


-0 1 




M»y 1— 6 . 


53-5 


53-6 


53-5 


-01 







8-10. 


48-1 


48-5 


48-2 


-0-4 


-0 1 




11—15 . 


*i-9 


46-9 


46-7 





+ 0-8 




Itl— 20. 


47' 8 


47-4 


47-2 


-01 


+ 0-1 




21-25 . 


60-8 


50-9 


60-6 


-0-1 


+ 0-8 




SO— 30. 


69-1 


59 


69-2 


+ 0-1 


-0-1 




31— i. 


63-4 


53 'S 


53-4 


-0 1 







June 6- 9 . 


53-8 


64-0 


53-9 


-0-2 


-0-1 




10— 1*. 


68-0 


681 


68-0 


-0-1 







15—19. 


68-7 


68 '7 


68 5 





+ 0-2 




20— M. 


G2-6 


C2-7 


62 '3 


-0-1 


+ 0-3 




26—29. 


B9-6 


69-7 


S9-6 


-0-3 







30— 4. 


62iJ 


62 7 


62-6 


-0 1 







JiUy 6— 9 . 


WO 


66-3 


eti-i 


-0 8 


-0-1 




10— 14. 


62-6 


62-7 


62-5 


-01 


+ 0-1 




15—19. 


61 


61 '0 


61-1 





-0-1 




aw-ai. 


69-7 


69-8 


69-7 


-0-1 







25—29. 


70-1 


70 '2 


70-1 


-01 







80-3. 


69-8 


69-4 


69-4 


-0-1 


-0-1 




Aug. 4— 8 . 


69-9 


60 '0 


60-0 


-0 1 


-0-1 




9—13. 


59' 7 


59-8 


59-7 


-0-1 







1-1—18. 


03-4 


62-5 


62-4 


-01 







19—28. 


65-3 


651 


66-2 


+o-a 


+ 0-1 




24—28. 


60-6 


60-6 


CO-6 





+ 0-1 




29- 2. 


69-7 


59-6 


60 '7 


+ 01 







Sept. 8- 7 . 


65-7 


65-7 


65-7 










8—12. 


62-8 


62-7 


62-7 


-0-1 


-0 1 




13—17 . 


62'S 


G21 


62-3 


+ 0-1 







18—23. 


48-8 


49 


49-0 


-0-2 


-0-a 




1878. Jan. 31— 4 . 


32-9 


33-2 


33 


-0-3 


-0-1 




Feb. 5— 9 . 


34-7 


34-9 


34-8 


-0-2 


-0-1 




lft-14. 


37- a 


37-3 


37 1 


-01 


+ 01 




15—19. 


38-4 


36-7 


36-5 


-0-3 


-0-1 




a>— 2*. 


32 '9 


33 S 


32-9 


-0-8 







M— 1 . 


39 ■? 


39'B 


39-7 


-0-1 







Mqi. 2- 6 . 


44 3 


44-4 


44-4 


-01 


-O'l 




7— U. 


42-3 


42-5 


42-4 


-0-2 


-O'l 




18-13. 


37-4 


37 5 


87-4 


-0-1 





17-21 . 


39-5 


39-7 


39 6 


-0-2 


-0-1 


aa-26. 


43-e 


43'8 


43-7 


-0 2 


-0-1 


27-81. 


47-8 


47-4 


47-3 


-01 







M»nd 


iSoMmca ... 




-0 12 


-0-01 1 




Uean 


MlBTfluCB tro 


mmeim .. 




-\ 



1886,1 PresenU. 398 



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[Mar }ll, 



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401 



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Dpley (William) Report of the Committee on the Erosion of the 
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VOL. XL. 



^ ^ 



402 Mr. F.Galtoxu [UhySTf 



May 27, 1886. 
Professor STOKES, D.G.L., President, in the Chair. 

The Presents received were laid on the taUe, and thanks ordered 
for them. 

The following Papers were read : — 

I. " Family Likenees in Eye-colonr." By Frangis Galton, 

F.R.S. Received May 10, 1886. 

My inqniiy into Family Likeness in Stature {ante^ p. 42) enabled 
me to define, in respect to that particnlar qnaliiy, the relation in 
which each man's peculiarity stands to those of each of his ancestors. 
The object of the present memoir is to verify that relation with 
respect to another quality, namely, eye-colonr. 

Speaking of heritage, independently of individual variation, and 
supposing female characteristics to be transmuted to their male equi- 
valents, I showed (1) that the possession of each unit of peculiarity 
in a man [that is of difference from the average of his race] when 
the man's ancestry is unknown, implies the existence on an average 
of just one- third of a unit of that peculiarity in his '* mid-parent," 
and, consequently, in each of his parents; also just one- third of a 
unit in each of his children ; (2) that each unit of peculiarity in each 
ancestor taken singly, is reduced in transmission according to the 
following average scale : — from a parent, to ^ ; &om a grandparent, 
to -^ ; from a great-grandparent, to -g^, and so on. 

Stature and eye-colour are not only different as qualities, but they 
ai*e more contrasted in hereditary behaviour than perhaps any other 
simple qualities. Speaking broadly, parents of different statures 
transmit a blended heritage to their children, but parents of different 
eye-colours transmit an alternative heritage. If one parent is as 
much taller than the average of his or her sex as the other parent is 
shorter, the statures of their children will be distributed in much the 
same way as those of parents who were both of medium height. But 
if one parent has a light eye-colour and the other a dark eye-oolour, 
the children will be partly light and partly dark, and not medium 
eye-coloured like the children of medium eye-coloured parents. The 
blending in stature is due to its being the aggregate of the quasi- 
independent inheritances o{ many a^^«x^\jb -^"Qxts^ while eye-oolonr 



1886.] Fmnilij Likeness in Eye-colour. 403 

appears to be much less varions in its origin. If then it can be 
shown, as I shall be able to do, that notwithstanding this two-fold 
difference between the qualities of statnre and eye-colonr, the shares 
of hereditary contribution from the various ancestors are in each case 
alike, we may with some confidence expect that the law by which 
those hereditary contributions are governed will be widely, and 
perhaps even universally, applicable. 

DatdA — My data for hereditary eye- colour are drawn from the same 
collection of " Records of Family Faculties " (" R.F.F.") as those 
npon which the above-mentioned inquiries into hereditary stature were 
principally based. I then analysed the general value of these data in 
respect to stature, and showed that they were fairly trustworthy. I 
think they are somewhat more accurate in respect to eye-colour, for 
w^hich family portraits have often furnished direct information, while 
indirect information has been in other cases obtained from locks of 
hair that were preserved in the &mily as mementos. I have also 
been able to collate some of my results with those lately published by 
M. Alphonse de CandoUe,* who instituted an inquiry that has in many 
particulars, though not in the main object of the present memoir, 
covered the same ground as my own, and which was of course founded 
on an entirely different collection of data. My conclusions in respect 
to those particulars, of which only a few find place here, are generally 
corroborated by his. 

Pergistence of Eye-colour in the Population, — The first subject of our 
inquiry must be into the existence of any slow change in the statistics 
of eye-colour in the population that might have to be taken into 
account before drawing hereditary conclusions. For this purpose I 
sorted the data, not according to the year of birth, but according to 
generations, as that method of procedure best accorded with the 
particular form in which all my R.F.F. data are compiled. Those 
persons who ranked in the Family Records as the *' children " of the 
pedigree, were counted as generation I ; their parents, uncles and 
aunts, as generation II ; their grandparents, great uncles, and great 
aunts, as generation III ; their great grandparents, and so forth, as 
generation IV. No account was taken of the year of birth of the 
*' children," except to learn their age ; consequently there is much 
overlapping of dates in successive generations. "We may, however, 
safely say, that the persons in generation I are quite different from 
those in generation III, and the persons in II from those in lY. I 
had intended to exclude all children under the age of eight years, but 
in this particular branch of the inquiry, I fear that some cases of 
young children have been accidentally included. I would willingly 

* H^^t^ de la couleur des jeux dans Tesp^ce humaine/' par M. Alphonse do 
Candolle. " Arch. Sc. Phys. et Nat. Geneve," Aug. 1884, 3rd period, vol. zii^ 
p. 97. 



i 



^^^^^^^^^^^H '^^^^^^^^^^^^^^^^^^^1 


404 


Mr. F. Galtoa. 


[May«, 



'DJlLOjq ^ilVQ ' j 



■piBH iaia (j»Q -^ 



'uaaiS'Snts 'i^O '1 



■aniq ^raQ aniH "Z 



-nMoiq ni«p iiai -g 



■lutiMq imfj 'i 



TMBH -forf IJBQ -f 



-nasiS-snia 'ioiQ 'g 



■oniq ^lM(l -onia 'B 






iSs 



^ 1 

\i4 ' 



1886.] 



Family JJUeneta in ^e-colour. 



Ferceatages of the Tarioas Eje-ooloi 
Generationa. 



a Four SnoceniTe 



I I i I I . I :i 



I Oeoeration IT. 



161S 

1477 




2277 
2213 



MUO Total ctues 



406 Mr. F. GaltoiL jlfay 97, 

have taken a later limit than eight years, but could not spare the daU 
that wonld in that case have been lost to me. 

A great varieiy of terms are nsed by the yarioas compilors of iiie 
" Family Records '' to express eye-colonrs. I began by dassifyiog 
them nnder the following eight heads: — 1, light blae; 2, bine, dark 
bine; 3, grey, bine-green; 4, dark grey, hazel; 5, light brown; 
6, brown; 7, dark brown; 8, black. Then I constmcted TaUe L 

The accompanying diagram will best convey the significance of tlie 
figures in Table I. Considering that the headings for different eye- 
colonrs are eight in number, the observations are fAV'trom. being 
sufficiently numerous to justify us in expecting clean results ; ncFer- 
theless the curves come out surprisingly well, and in accordance with 
one another. There can be little doubt that the change, if any, during 
four successive generations is very small, and much smaller than men 
memory is competent to take note of. I therefore disregard a current 
popular belief in the existence of a gradual darkening of the popula- 
tion, and shall treat the eye-colours of those classes of the English 
race who have contributed the records, as statistically persistent 
during the period nnder discussion. 

The concurrence of the four curves for the four several generations 
affords some internal evidence of the trustworthiness of the data. For 
supposing we had curves that exactly represented the true eye-colonrs 
for the four generations, they would either be concurrent or they 
would not. If concurrent, the errors in the R.F.F. curves must have 
been so curiously distributed as to preserve the concurrence. If not, 
the errors must have been so curiously distributed as to neutralise the 
non-concurrence. Both of these suppositions are improbable, and we 
must conclude that the curves really agree, and that the B.F.F. errors 
are not large enough to spoil the agreement. The much closer con- 
currence of the two curves, derived respectively from the whole of the 
male and the whole of the female data, and the still more perfect 
form of the curve derived from the aggregate of all the cases, are 
additional evidences in favour of the goodness of the data on the whole. 

Fundamental Eye^colours, — It is agreed among most writers on the 
subject {cf, A. de Gandolle) that the one important division of eye- 
colours is into the light and the dark. The medium tints are not 
numerous, and they may have four distinct origins. They may be 
hereditary with no notable variation, they may be varieties of light 
parentage, they may be varieties of dark parentage, or they may be 
blends. These medium tints are classed in my list under the heading 
"4. Dark grey, hazel," and they form only 12*7 per cent, of all the 
observed cases. It is common in them to find the outer portion of 
the iris to be of a dark grey colour, and the inner of a hazel. The 
proportion between the grey an^ V^aa V^b'L^Nvictv^^ Vg. ^^^t«!\t cases, 
and the eye- colour is then. deacrVb^^ «^ ^^V ^«^ qt v>&\iaa^^vk«»»s^- 



1886.] 



Family Likeness in Eye-colour, 



407 



ing to the colonr that happens most to arrest the attention of the 
observer. For brevity, I will henceforth call all intermediate tints by 
the one name of hazel. 

I will now investigate the history of those hazel eyes that are varia- 
tions from light or from dark respectively, or that are blends between 
them. It is reasonable to suppose that the residue which were in- 
herited from hazel-eyed parents arose originally either as variations 
or as blends, and therefore the result of the investigation will enable 
ns to assort the small but troublesome group of hazel eyes in an equit- 
able proportion between light and dark, and thus to simplify our 
inquiry. 

The family records include 168 families of brothers and sisters, 
counting only those who were above eight years of age, in whom one 
member at least had hazel eyes. The total number of these brothers 
and sisters is 948, of whom 302 or about one-third have hazel eyes. 
For distinction I will describe these as ''hazel-eyed families*'; not 
meaning thereby that all the children have that peculiarity, but only 
some of them. The eye-colours of all the 336 parents are given in the 
records, but only those of 449 of the grandparents, whose number 
would be 672, were it not for a few cases of cousin marriages. Thus 
I have information concerning about only two-thirds of the grand- 
parents, but this will suffice for our purpose. The results are given 
in Table II. 



Table II. — The Descent of Hazel-eyed Families. 





Total 
cases. 


Obserred. 


Percentages. 


Light. 


Hazel. 


Dark. 


Light. 


Hazel. 


1 
Dark. 


Gkneral population . . 
Ill, Grandparents . . 

II, Parents 

I, Children 


4490 
449 
336 
948 


2746 
267 
165 
430 


569 
61 

85 
302 


1175 

121 

86 

216 


61-2 
60 
49 
45 


12-7 
13 
25 
32 


26 1 
27 
26 
28 



It will be observed that the distribution of eye-colour among the 
grandparents of the hazel-eyed families is nearly identical with that 
among the population at large. But among the parents there is a 
notable difference ; they have a decidedly smaller percentage of light 
eye-colour and a slightly smaller proportion of dark, while the hazel 
element is nearly doubled. A similar change is superadded in the 
next generation. The total result in passing from generation III 
to I, is that the percentage of the light eyea \a ^\m\TiY^"fe^ Vcotsjl^^ ^t 
61 to 45, therefore by one qnarter of its origmaX «jno\xxk\.^ ^aA >^oaK» 



408 Mr. F. Galton. [HUgrSr, 

the peroentage of the daik eyes is dimuuBhed from 26 or 27 to 2( 
ihat is to about one-eighth of its original amount, the hacel eleraeBt 
in either case absorbing the difference. It follows thai the ehanoe U 
a light-ejed parent haying hasel ofEspring, is abont twice as great ai 
that of a dark-ef ed parent. Consequently^ since hasel is twice ai 
likely to be met with in any given light-eyed fiunily as in a gtwm 
dark-eyed one, we may look npon two^thirds of the hftsel eyes ai 
being fundamentally light, and one-third of them as fpudamen tally 
dark. I shall allot them rateably in tiiat proportion between light 
and dark, as nearly as may be without using fractions, and so get 
rid of them. M. Alphonse de GandoUe has also shown from his data, 
that yeiM gris (which I take to be the equivalent of my hazet) aie 
referable to a light ancestry rather than to a dark one, but his data 
are numerically insufficient to warrant a precise estimate of the 
relative frequency of their derivation from each of these two sources. 
Heredity of Light and Dark JBye^olour. — ^In the following discnssion 
I shall desJ only with those family groups of children in which tiie ej^ 
colours are known of the two parents and of the four grandparents. 
There are altogether 211 of such groups, containing an aggregate of 
1023 children. They do not, however, belong to 211 different family 
stocks, because each stock which is complete up to the great g^rand- 
parents inclusive (and I have fourteen of these) is capable of yielding 
three such groups. Thus, group 1 contains a, the '' children ;" 5, the 
parents ; c, the grandparents. Group 2 contains a, the father of the 
'' children," his brothers and his sisters ; 5, the parents of the father ; 
c, the grandparents of the father. Group 3 contains the correspond- 
ing selections on the mother's side. Other family stocks famish two 
groups. Out of these and other data, Tables 111 and lY have been made. 
In Table III I have classified the families together whose two parents 
and four grandparents present the same combination of eye-colour, 
no class, however, being accepted that contains less than twenty 
children. These data will enable us to test the average correctness of 
the law I desire to verify, because many persons and many families 
appear in the same class, and individual peculiarities tend to dis- 
appear. In Table lY I have separately classified on the same system 
all the families, 78 in number, that consist of six or more children. 
These data will enable us to test the trustworthiness of the law as 
applied to individual families. It will be seen from my way of 
discussing them, that smaller families than these could not be ad- 
vantageously dealt with. 



1886.] 



Famify Likeness in Eye-Colour. 



409 



Table III. — Sixteen Groups of Families, those being grouped together 
in whom the distribution of Light, Hazel, and Dark Eye-colour 
among their Parents and Grandparents is alike. Each Ghroup 
contains at least Twenty Brothers or Sisters. 



Eye-colours of the 


Total 


Number of the light eye- 
coloured children. 










Parents. 


Grandparents. 


children. 


Observed. 


Calculated. 




















Light. 


Hazel. 


Dark. 


Light. 


Hazel. 


Dark. 






I. 


11. 


TTT. 


2 






4 


• • 


• • 


188 


174 


161 


163 


172 


2 






8 


1 


• • 


68 


46 


47 


44 


48 


2 






8 


• • 


1 


92 


88 


81 


67 


79 


2 






2 


1 


1 


27 


26 


24 


18 


22 


• • 




2 


2 


• • 


2 


22 


11 


6 


12 


6 








8 


1 


• • 


62 


52 


48 


51 


51 








8 


• • 


1 


42 


80 


88 


81 


32 








2 


2 


• • 


81 


28 


24 


24 


20 








2 


• • 


2 


49 


85 


88 


28 


84 








2 


1 


1 


81 


25 


24 


21 


28 








8 


. • 


1 


76 


45 


44 


55 


46 








2 


. • 


2 


66 


80 


38 


38 


86 








2 


• • 


1 


27 


15 


16 


18 


16 








1 


• • 


8 


20 


9 


12 


8 


9 








1 


1 


2 


22 


8 


18 


11 


11 


■ • 


1 




1 


1 


2 


24 


9 


14 


12 


10 


629 


623 


601 


614 



410 



Hr. F. Galton. 



|Tfcy«, 



Table lY.— 78 Separate Families, each of not leas than 6 Brothen 

or Sisters. 



EyeHsoloun of the 


IW% ^ % 


Number of the lia^t eye- 
oolooied chikuvn. 






Total 






Parents. 


Gnndparents. 


child- 
ran. 


Ob- 

aerred. 


Oftlmln^fi^, 




















Light. 


HaxeL 


DtA. 


Light. 


Hmiel. 


Dark. 






L 


IL 


IIL 


2 


• • 


• • 








6 


6 


5-8 


5-8 


5-6 


2 
















6 


6 


6-8 


5*8 


5-6 


2 












,, 




6 


6 


6-3 


6*8 


5-6 


2 
















6 


6 


5*8 


5-8 


5-6 


2 
















7 


7 


6-2 


6-2 


6-6 


2 
















7 


7 


6*2 


6-2 


6-6 


2 
















7 


7 


6-2 


6-2 


6-6 


2 
















7 


7 


6*2 


6-2 


6-6 


2 
















7 


7 


6-2 


6-2 


6-6 


2 
















8 


8 


7 


7 1 


7-6 


2 
















8 


8 


7-0 


7 1 


7-5 


2 
















8 


8 


7 


71 


7-5 


2 
















8 


8 


70 


71 


7-5 


2 
















8 


7 


70 


7-1 


7-6 


2 










4 






8 


7 


7 


71 


7-5 


2 










4 






12 


12 


10-6 


10-7 


11-3 


2 










3 


i* 




7 


7 


6-2 


5-8 


6-4 


2 










8 


1 




10 


4 


8-8 


8-8 


9 1 


2 










3 


1 




12 


12 


10-6 


10 -0 


10-9 


2 










3 




i' 


7 


6 


6-2 


5-1 


6 


2 










3 




1 


8 


8 


7 


5-8 


6-9 


2 










3 




1 


9 


9 


7-9 


6-6 


7-7 


2 










3 




1 


9 


9 


7-9 


6-6 


7-7 


2 










3 




1 


9 


7 


7-9 


6-6 


7-7 


2 










3 




1 


10 


10 


8-8 


7 3 


8-6 


2 










2 


2 


• . 


7 


7 


6-2 


5*4 


6*2 


2 










2 


2 


* • 


10 


9 


8-8 


7-7 


8-8 


2 










2 


1 


1 


6 


6 


5-8 


4 


50 


2 










2 


1 


1 


10 


10 


8-8 


6-7 


8-3 




2 






2 


1 


1 


7 


4 


6-2 


4-7 


4-6 




2 






2 




2 


8 


6 


5-4 


4-6 


4-8 








2 


3 




1 


6 


2 


1-7 


4-4 


2-2 








2 


2 




2 


9 


1 


2-5 


5 1 


2-5 




• 




2 


1 




3 


6 


1 


2-7 


2-5 


1-2 








2 


1 




3 


11 


3 


31 


4-6 


2-2 








2 


1 




2 


6 


• • 


1-7 


3 


1-5 








2 


1 


^ 


2 


7 


4 


2-0 


3-6 


1-8 












3 






6 


6 


4-7 


5 


4-9 












3 






7 


6 


5-5 


5-7 


5-7 












3 






8 


6 


6-2 


6-6 


6-6 












3 






9 


7 


7 


7-5 


7-4 












3 






11 


10 


8-6 


9 1 


9-2 


1 1 








3 


• • 


i* 


9 


6 


7 


6-6 


6-9 


^ / ^ 


• 




3 


.. 1 I 




V^ 


8-6 


8-0 


8-5 


' r 


1 • 




MM- 


\ t*'^ 


\ V^ 


i^v< 



1886.] 



FcanUy lAkmett in Eye-eolour. 



411 



Table IV — continued. 



Eye-colours of the 






Komber of the lieht eje- 
ooloored children. 






Total 
child- 
ren. 




Parents. 


Grandparents. 


Ob- 

serred. 


Children. 




















Light. 


Hazel. 


Dark. 


Light. 


Hazel. 


Dark. 








II. 


III. 






• • 


2 


2 


• • 


9 


9 


7 


6-9 


5-7 










2 


2 


• • 


11 


11 


8-6 


8-5 


6-9 










2 


. • 


2 


6 


6 


4-7 


8-4 


41 










2 


■ « 


2 


6 


4 


4-7 


8-4 


41 










2 


• • 


2 


8 


6 


6-2 


4-6 


6-5 










2 


. • 


2 


9 


7 


7 


6 1 


6-2 










2 


1 


1 


6 


6 


4-7 


4 


4*4 










2 


1 


1 


10 


9 


7-8 


6-7 


7-4 










1 


8 


. • 


9 


4 


7 


5-5 


6-8 










1 


1 


2 


8 


5 


6-2 


4 1 


5-8 










4 




. • 


7 


8 


41 


6 '2 


4-8 










8 




1 


6 


4 


8-5 


4-4 


8-7 










8 




1 


7 


8 


4 1 


6 1 


4-8 










8 




1 


8 


6 


4-6 


5-8 


4-9 










8 




1 


8 


6 


4-6 


6-8 


4-9 










3 




1 


8 


4 


4-6 


6-8 


4-9 










8 




1 


9 


6 


5-2 


6-6 


6-6 










8 




1 


9 


5 


5-2 


6-6 


6-5 










2 




2 


6 


5 


8-6 


3-4 


8-2 










2 




2 


6 


8 


8 -5 


3-4 


8-2 










2 




2 


8 


4 


4*6 


4-6 


4-2 










2 




2 


10 


2 


5-8 


6 7 


6-8 










2 




2 


14 


9 


81 


80 


7-4 










2 




1 


7 


6 


41 


4-7 


4 1 










1 




1 


7 


8 


41 


4-8 


8-9 










1 




2 


7 


4 


41 


8-6 


3-6 










1 


• • 


8 


8 


4 


4-6 


3-3 


8-6 










1 


• • 


8 


8 


3 


4-6 


3-3 


8*6 










• • 




8 


6 


3 


3 5 


21 


2-6 


• • 


i' 






2 


• • 


2 


6 


8 


4-8 


3-4 


2-6 


• • 


1 






2 




1 


9 


4 


7 


6 


4-4 


• • 


1 






1 


• • 


8 


13 


8 


10 1 


5-8 


4-7 


• • 


1 






. • 




• • 


7 


2 


6-5 


4-6 


8-4 



It will be noticed that I have not printed the number of dark-eyed 
children in either of these tables. They are implicitly given, and 
instantly to be found by subtracting the number of light-eyed 
children from the total number of children. Nothing would have 
been gained by their insertion, while compactness would have been 
sacrificed. 

The entries in the tables are classified, as I said, according to the 
various combinations oi light, hazel, and dark. Q^Q-co\cyQx^ Vdl>(X^^^'«x^sc^^ 
smd grandparents. There are 6 diSerent i^&«ab\b coTiWv'a3B^^"'5^ «BtfSB% 



412 ilr. F. Galton. [May 27. 

tbe two parents, and 15 among tbe four grandparents ; m&lcing £■(!■ po6- 
nblo classes altogethier. The number of observations are of tmnr^ bj 
no means erenlj distribnted amon^ the clauses. I have no returns at 
•11 Dnder more than half of them, vbiie the entries of two Ugbt-fij-ed 
parents and four ligbt-ejed grandparents are proporti<matelj vei; 
anmeroos. (I shall not here discass tbe question of marriage selec- 
tion in respect to ejre'Cotoar, which is a less simple statistical question 
th&n it may appear to be at first si^ht.) 

Calculation. — I have now to show how tbe eipectation of eye- 
ooloar among- the children of a gifea family ia to be calculate on the 
besia of tbe law laid down for etatnre, so that those caleulatioiiie of 
tbe probable distribution of eje-colonrs may be made, which fill the 
three last colnmns of Tables III and IV, which are beaded I, 11, and 
III, and which are placed ia jmtaposition with the observed facts as 
entered in the colnmn beaded " Observed." These three colojnns 
contain calculations based on data limited in three different ways, in 
order tbe more tboronghly to test the applicability of tbe law tbat it 
is desired to verify. Colnmn I contains calculations based on a 
knowledge of the parents only ; II contains those based on a know- 
ledge of the grandparents only ; III contains those based on a know, 
ledge both of the parents and of the grandparents, and of them only. 

I. Eye-coloaiB given of tbe two parents — 

Let tbe letter M be nsed as a symbol to signify the person for 
whom the expected herit^e is to be calcolated. Let P stand for 
tbe words " a parent of If ;" 0^ for " a grandparent of M ;" Gg for 
" a great-grandparent of M," and so on. 

Now snppose that the amonnt of the pecoliarity of stotore pos- 
sessed by P is eqnal to r, and that nothing whatever is known with 
certainty of any of the ancestors of M except P. We have seen* that 
thongh nothing may be actually known, yet that something definite 
is implied abont the anceators of P, namely, that each of his two 
parents (who stand in the order of relationship of G^ to M) will on 
the average possess ^. Similaily that each of the fonr grandparents 
of P(who stand in the order of Gg to H) will on the average poasess 
^, and so on. Again we have seen that P, on the average, transmits 
to M only \ of his peculiarity ; that G, tmnsmite only ^ ; G, only ^, 
and so on. Hence the aggregate of the heritages that may be ex- 
pected to converge throogh P upon M, is contained in the following 
•eries: — 

• -late. ¥.*a(J5o. Mai. 



1886.] 



Family Likenesa in Eye-colour* 



41S 



That is to saj, each parent miist in this case be considered as con- 
tributing 0*30 to the heritage of the child, or the two parents toge- 
ther as contribating 0*60, leaving an indeterminate residue of 0*40 due 
to the influence of ancestry about whom nothing is either known or 
implied, except that they may be taken as members of the same race 
as M. 

In applying this problem to eye-colour, we must bear in mind that 
a given fractional chance that each member of a family will inherit 
either a light or a dark eye-colour, must be taken to mean that that 
same fraction of the total number of children in the family will pro- 
bably possess it. Also, as a consequence of this view of the meaning 
of a fractional chance, it follows that the residue of 0*40 must be 
rateably assigned between light and dark eye-colour, in the propor- 
tion in which those eye-colours are found in the race generally, and 
this was seen to be (see Table II) as 61*2 : 26*1 ; so I allot 0*28 out of 
the above residue of 0*40 to the heritage of light, and 0*12 to the 
heritage of dark. When the parent is hazel-eyed I allot |> of his total 
contribution of 0*30, i.e., 0'20 to light, and J^, i.e., 0*10 to dark. 
These chances are entered in the first pair of columns headed I, in 
Table V. 



Table V. 



Contribution to the 
heritage from each. 


Data limited to the eye-colours of the 


2 parents. 


4 grandparents. 


2 parents and 
4 grandparents. 


L 


IL 


III. 


light. 


Dark. 


Light. 


Dark. 


Light. 


Dark. 


Light-eyed parent .... 
Hazel -eyed parent .... 
Dark -eyed parent 

Light-eyed grandparent. 
Hazel-eyed grandparent 
Dark-ejed grandparent. 

Residue, rateably a«- 
aifimed 


0-30 
0-20 

. . 

« . 
0*28 


0-io 

0-30 

• • 

• • 

• • 

012 


. • 

016 
10 

• • 

0-26 


• * 

0-be 

16 

oil 


0-25 
16 

. . 

08 
06 

• • 

12 


0-09 
0-25 

0-08 
08 

0-06 










414 llr. F. Galton. [Uaj 37, 

Table VI. — ^Bzample'of one Galonlation in each of the 3 Caaea. 



Ancestry and their 
eje-coloars. 


I. 


n. 


in. 


No. about whom 
data exist. 


Contribute 
to 


It 

o 

• • 

• • 

• • 
• 

1 
2 

1 


Contribute 
to 


• • 
1 
1 

1 

2 
1 


Contribute 
to 


Light. 


Dark. 


Light 


Dark. 


Light. 


Daik. 


light-^ed parents . . 
Haiel-€^ed parents • • 
Dark-eyed parents . . . 

light - eyed grand- 
parents 

Hasel - eyed grand- 
parents 

Dark • eyed grand- 
parents 


2 


00 

• • 

• • 

• • 
■ • 

0-28 


• • 

• • 

• • 

• • 

• • 

• • 

0*12 


• • 

• • 

• • 

0*16 
0*20 

• • 

0*25 


• 

• • 

• • 

• ■ 

• • 

• 

0-12 
0*16 

« 

Oil 


0*-16 

• • 

0-08 

pio 

• • 
012 


0-09 
0*25 

• • 
0-06 
0-08 

0*06 


Sesidne, rateably as- 
signed 








Total contributions . . 




0*88 


12 


0*61 


0*89 


0*46 


0*54 




; 100 

! 




100 




100 



The pair of columns headed I in Table VI shows the way of sum- 
ming the chances that are given in the columns with a similar heading 
in Table V. On the method there shown I calculated all the entries 
that appear in the columns with the heading I in Tables III and IV. 

IT. Eye-colours given of the four grandparents — 

Suppose r to be possessed by Gj and that nothing whatever is 
known with certainty of any other ancestor of M. Then it has been 
shown that the child of G^ (that is P) will possess ^ ; that each of 
the two parents of G^ (who stand in the relation of G3 to M) will 
also possess \r ; that each of the four grandparents of Gj (who stand 
in the relation of G3 to M) will possess |r, and so on. Also it has 
been shown that the shares of their several peculiarities that will on 
the average be transmitted by P, G^, Gj, &c., are J, -jig-, ^, Ac., 
respectively. Hence the aggregate of the probable heritages &om G^ 
are expressed by the following series : — 



X-+lx^+3x2x^-f^x 4 x-^-f Ac. I 



2*^3 



2«^9 



4- 
13 



1886.] 



Family Likeness in Eye-eohur. 



415 



So that each grandparent contributes on the average 0*16 (more 
exactly 0*1583) to the heritage of M, and the fonr grandparents 
contribnte between them 0*64, leaving 36 indeterminate, which when 
rateablj assigned gives 0*25 to light and O'll to dark. A hazel -ejed 
grandparent contribates, according to the ratio described in the last 
paragraph, 0*10 to light and 0*06 to dark. All this is clearly expressed 
and employed in the columns II of Tables Y and VI. 

III. Eye-colonrs given of the two parents and four grandparents — 
Suppose P to possess r, then P taken alone, and not in connexion 
with what his possession of r might imply concerning the contri- 
butions of the previous ancestry, will contribute an average of 0*25 
to the heritage of M. Suppose G^ also to possess r, then his contri- 
bution together with what his possession of r may imply concerning 
the previous ancestry, was calculated in the last paragraph as 
^'^=0*075. For the convenience of using round numbers I take this 
as 0*08. So the two parents contribute between them 0*60, the four 
grandparents together with what they imply of the previous ancestry 
contribute 0*32, being an aggregate of 0*82, leaving a residue of 0*18 
to be rateably assigned as 0*12 to light, and 0*6 to dark. A hazel- 
eyed parent is here reckoned as contributing 0*16 to light and 0*9 to 
dark ; a hazel-eyed grandparent as contributing 0*5 to light and 0*3 
to dark. All this is tabulated in Table Y, and its working explained 
by an example in the columns headed. Ill of Table YI. 

Results, — A mere glance at Tables III and lY will show how 
surprisingly accurate the predictions are, and therefore how true the 
basis of the calculations must be. Their average correctness is shown 
best by the totals in Table III, which give an aggregate of calculated 
numbers of light-eyed children under Groups I, II, and III as 623, 
601, and 614 respectively, when the observed numbers were 629 ; that 
is to say, they are correct in the ratios of 99, 96, and 98 to 100. 

Table YII. 

Number of Errors of various Amounts in the 3 Calculations of the 
Numbers of Light Eye-coloured Children in the 78 Families. 



DatA employed referring to 



I. The 2 parents only 

II. The 4 grandparents only .... 

III. The two parents and 4 grand 

parents 



Amount of Errors. 



00 

to 

0-5. 



19 
16 

41 



0-6 

to 

11. 



SO 
28 

17 



1-2 

to 

1-7. 



18 
10 

8 



1-8 

to 

2-3. 



5 
10 



2-4 

and 

aboye. 



\ 



6 
14 

8 



Total 
Cases. 



78 
78 

7a 



4lfi Mr. J. Buchanan, [5 

Their trastwortliiness when applied to individaal families ia ahonn 
BB Btrongly in Table TV, whose resalta are conveniently soEam&rised in 
Table VI. I have there classified the amounts of error in the several 
calcnlations : thus if the estimate in any one family was 3 light-eyed 
children and the observed number was 4, 1 should conn t the error as 10, 
I have worked to one place of decimals in this table, in order to bring 
ont the different shades of trustworthiness in the three sets of calcnla- 
tionfl, which thus become very apparent. It will be seen that the calcQ- 
lations in Ciasa III are by far the most precise. In more than one-ha!f 
of those calculations the error does not exceed 0'5, whereas in I and II 
more than three-quarters of them are wrong to at least that amount. 
Only one-quarter of Class III are more than I'l in error, but some- 
where about the half of Classes I and II are wrong to that amonnl. 
In comparing I with II, we lind I to be slightly, bnt I think distinctlr, 
the superior estimate. The relative accuracy of III a.s compared 
with I and II, is what we shonld have expected, supposing the basis 
of the calcnlations to be trao, because the additional knowledge 
utilised in III, over what ia turned to account in I and II, must be 
an advantage. 

Coneltuion. — The general truat worthiness of these oalonlations of 
the probable proportion of light-eyed and dark-eyed children in indi- 
vidual families, whose auceatral eye-coloar is more or lees known, is 
comparable with the chance of drawing a white or a black ball oat of 
a bag in which the relative numbers of white and black balls are the 
same as those given by the calculation. The larger the proportaou 
of data derived from a certain knowledge of ancestral eye.oolonre, 
and not from inferences about them, the more true does the oom- 
pariaon become. My retams are insufficiently nnmerona and too 
sabJBCt to uncertainty of observation to make it worth while to 
submit them to a more rigorous analysis, bnt the broad ooncloaion to 
which the present results irresistibly lead, is that the same peculiar 
hereditary relation that was shown to subsist between a man and 
each of his ancestors in respect to the quality of statnre, also 
subsists in respect to that of eye-colour. 



II. " A General Theorem in Electroatatic Induction, with Appli- 
cation of it to the Origin of Electrification by Friction." 
By John Buchanan, B.Sc, Demonstrator of Physicfl, 
Univeraity College, London. Communicated by Profeasor 
G. Caret Foster, BA., F.R.S. Received May 13, 1886. 
Paet I. 
TJiis paper containa the Teaulta of au. iiiveati^tiou into the qnestioit : 
If a dieiectrio be brought into & &«&& ol ^^ciWui Icecw., «n&. '(^m«'-^ 



1886.] A General Theorem in Electrostatic Induction, 417 

specific indnctive capacity is changed, what will be the electrical con- 
dition of the dielectric? The subject has occupied me both in its 
theoretical and experimental aspects for a considerable time, and I 
believe that the answer to the question throws light upon some 
fundamental electrical phenomena. 

This investigation has led me to a general theorem in electrostatic 
indnction which may be stated as follows : — 

When a dielectric is brought into a field of electric force and the 
specific inductive capacity is there altered, in general the dielectric 
becomes electrified. 

To give de6niteness to our notions, let us imagine a field of electric 
force to be due to an electrified conductor, which we will call the 
'* primary ;'* inclosing this primary is a conducting shell which is 
connected to earth. 

For simplicity we will assume, for the present, that the charge on 
the primary remains unchanged in magnitude during this series of 
opeiiitions : — 

(1.) The dielectric is brought into the field of force ; 
(2.) The specific inductive capacity is increased; 
(3.) The dielectric is carried out of the field. 

The state of the field is exactly the same as it was before the 
operations were performed. We can therefore fix our attention on 
the dielectric. 

Let us compare the work done by electrical forces with the work 
done against them in the operations (1), (2), (3). We have in (1) 
work done hy electrical forces in assisting to bring the dielectric into 
the field; work is also done by (say) the forces in (2). In operation 
(3) work is done against electrical forces. The question to be answered 
is this, does the following equation hold in every case ? 

Work done by electrical forces in bringing the dielectric into the 

field 
+ work done by the forces during the change of specific inductive 

capacity 
= work done against the electrical forces in carrying the dielectric 

out of the field. 

If this equation be true under all circumstances, there is no excess 
of work done by or against electrical forces. . We would have then no 
reason to expect to find an electric distribution on or in the dielectriOi 
whose energy would be the equivalent of the excess of work 
^ Now that the above equation should always hold seems to 
variance with Hound conceptions regarding the efiPect of an arl 
change in the physical state of a body. 

Take, for instance, a case such as that oi a '^OCA ol^Mib 

VOL, XL. 




418 Mr. J. Buchanan. [ilayil 

cool, and meanwhile to undergo eleotroiysie by the action of tk 
elertric forL-es of the field ; and wlen cold carried oat of the field. 

The important part here played by the element time, render* 
qnit« impossible to mainlain a priori that the above hypothotiful 
eqaation shonid hold under oil cireumatancos : the pivof wonld iiMJ 
to be experimental. 

The iiivestigatifin given below is designed to ezprc«9 in definita 
terniB the effect of the somewhat general conditions therein fpeci6ed. 

Let nB denote the potential of the primary by V, ita cbargv by j; 
the Bpecific inductive capacity of the dielectric placed in the field <d 
force by K. ; and the electrostatic capacity of the whole ayatem by C, 
Then the theorem is that the magnitude and sign of the " apparent 
electrification " of the dielectric ore given by an equation of IIh 

where k denotee the rate of change of the apparent electrifi cation 
of the dielectric with regard to the specific inductive capacity Km 
independent variable ; and w denotes the rate of change of the work 
done against electrical foi-ces with regard to the same independent 
variable. 

By translating the theorem into the language of magnetism, we 
obtain a theorem relating to magnetic induction in matter placed in a 
magnetic field of force. 

Proof. 
The dielectric being enppoBed in the field of force, let the specific 
inductive capacity be changed. The influence of this change of 
specific inductive capacity of the dielectric on the electrical state of 
the primary can be espreesed by taking a-i independent variables the 
potential V of the primary, and the specific inductive capacity K of 
the dielectric. Dne to an arbitrary change of potential aV, and an 
arbitrary change of specific indoctive capacity £K, there will be an 
augmentation tq of the charge of the primary — by oonnetittng it to 
proper sources of electricity — given by an equation of the form— ■ 

«9=C.aV+V.^.aK + A.iK (1.) 

The first term of the right hand member ezpressea tke well-jEnown 
relation between the charge, the potential, and the capaci^ of an 
electrical system ; the second term expresses the eBect of the change 
of capacity caused by the alteration of specific indnctire capacity ; 
snd the third term expresses the effect of the electrification of the 
dielectric due to the same ca^iaa. '^■W\. \ ^viv»« ^ *««» >v*ia>. 



1886.] A General Theorem in Electrostatic Induction. 419 

the quantity h need not be zero, unless under very special circum- 
stances. 

As it appears in (1), ^ . £K is clearly the quantity of electricity that 
must be given to the primary in order to maintain the potential 
constant whilst the specific inductive capacity is altered by ^K, and 
this in addition to the influence of the mere change of capacity of the 
system. 

We may assume as a well-known result that for a closed cycle of 
operations 



\- 



and Sq IB Sk perfect differenfcial.* 

Expressed in words, this is equivalent to stating that, when after 
undergoing a series of changes, the potential is brought back to any 
given value V, and the molecular condition of the dielectric in the 
field of force is brought back to its initial state, then the charge of the 
primary is the same as at first. 

The analytical statement of the condition that 6q in (1) is a perfect 
differential gives us — 

dC_ d /^ dG 

dK 






dh 
or --— 



In order to obtain another relation between the quantities, let us 
denote by Be the increment of electrical energy of the system during 
the series of operations described above as leading to (1). This is 
expressed by an equation of the form — 

a6=Vagr+«-^K (3) 

The meaning of the first term of the right hand number of (3) is 
obvious ; the other term, wBK., denotes the work done against electrical 
forces when the specific inductive capacity of the dielectric is increased 
by ^K. 

By the principle of the conservation of energy, for a closed cycle of 
operations 



1 



««:=0, 



and ^6 is a perfect difPerential. Hence,. if we express the analytical 
condition of this, after putting for Bq its value from (1), we get — 

* I would here acknowledge mj great indebtedness to a pa^r on th«*' CQ»TAKtx^> 
tion of Electrioitf,'* by M. Gt, Lippmann, " Ann&leB ^ft CVlvdca^ ^\. \<6 '^Vjix^a^i^'^V 
5— 8er., T. 24 (1881) p. 145. 




Pei-forming the differentiatio 



If (4) bo differentiated with respect to V 
we find — 

Hence, finally, the theorem 



Since as a rnle n- will probably increase with T, 



id making use of (2) we have — 

(ij 

id (2) be again applied, 

=0 (5.) 

be ezpreased in either of the 

(6) 

(6') 

will Dsnallj 



dV 



have the same sign as r. 

The form (6'), amongst other nses, enables ns to get at once 
important reanlt, viz., the circamstaDCee nnder which h is zero, 
have A = when — 

dY dV» 

Integrating twice we get sncoeBBively — 



We 



where a is an arhitrary constant ; and 

'^i-V (7.) 

The constant of the second integration will in general be sero. 

Equation (?), taken in connexion with (&), gives by differentiation, 



dC_ 
dK' 



!Conat.= — o. 



It appears therefore that in order to have no electrification of the 
dielectric when the specific inductive capacity is altered, the change 
of capacity of the Bjelem miut \i6 '(to^T^■^Qfs»l to tha change of 
speciBc inductive capacity. 



-n ■ L ■ . . 



1886.] A General Theorem in Electrostatic Induction. 421 

Remark also tliat since -j7= mnst in general be positive, the quantity 

a, and therefore also n*, most be negative, bj (7). 

It is not difficult to prove that the condition -yr^ = const, leads to 

the conclusion that the whole electric field must be occupied by an 
electrically homogeneous dielectric. 

The following proof seems to be convenient. Let us imagine the 
assumed heterogeneous medium to consist of shells of dielectric 
material whose boundaries are equipotential surfaces; each shell is 
supposed to be itself homogeneous. If the bounding equipotential 
surfaces consisted of excessively thin conducting shells, the distri- 
bution of electric force in the field would be unaltered. Each 
consecutive pair of conducting equipotential surfaces with the (homo- 
geneous) shell of dielectric between, would then form a condenser. 
And since the same quantity of electric induction crosses all the 
equipotential sui*faces in the field, the capacity of the whole system 
would be simply that of a series of condensers in " cascade.*' 

When air is the dielectric, denote the capacity of the condenser 
which consists of the primary, the first conducting equipotential 
surface, and the space between, by C^ ; the capacity of the condenser 
formed by the first and second equipotentials by C^, and so on. If, 
instead of air, the spaces be respectively filled up by dielectrics of 
specific inductive capacities K|, K^, and so on, we have for the capacity 
of the whole system C, the relation — 

l=J-+J_+ ... 

Replacing the shells of dielectric by others of different specific indue- 
tive capacity, and denoting the changed quantities by dashes, we have — 



Let now Kj — Kj^K^ — xl^^ . . . =^K, 

so that the alteration of specific inductive capacity is the same for all 
the dielectrics. 

It is evident that unless — 

and Kj ^EI^ = . . . 

it is impossible that — 

m 

should he independent oi SK, 



I 422 Mr. J. Buchanan. pfay 27, 

I The oondasion gWen above follows at once. 

' To Hum op the discnssion, the result is that the equations (5), (6), 
and (6) expreas the effect of heterogeneity in the constitntion of the 
dielectric mcdiiua. 

Note. — It may be well to notice here ao objection that might be 
raised against the validity of the above theorem. It could be urged, 
that since Dr. Hopkinson has found by eiperimont" that no change 
of specific indnotive capacity could bo detected when glass wm 
subjected to electric stress varied through a very wide I'ange o( 
luagnitudes, the quantity n- in the theorem has no exietenoo. The 
experiments jast referred to, however, only prove that the quantity r 
is very small. It is shown in Pai-t II of this paper that for mosl 
substances ir haa a value different from zero, being positive in acme 
cases, negative iu others, 

pabt n. 

Appticdlion to the Theory of Ike Origin of Eleetrijieitlion by Friction. 

The rubbing together of two boilies is tbe moat ancient means 
known of obtaining electricity. The absence of any accepted 
explanation of this historical mode of rendering a body electrified 
does not need to be enlai^ed upon. 

I have ventnred to entertain the hope that the general theorem 
proved above, together with the experimental reanlts obtained by Dr. 
Kerr in his memorable researches in the region of " electro-optica," 
may be found to prove adequate to the explanation of the fandamental 
and important sobject of electrification by friction. 

As is well known, Dr. Kerr has proved that transparent dielectrics 
become aa a rule doubly refracting when subjected to electric force. 
Under the action of electric stress, a dielectric becomes strained. 
With the electric stress different at different parts of the field of 
force, the strain varies from point to point. This space-variation of 
strain manifests itself optically by the material assuming the property 
of converting plane polarised into elliptically polarised light, when 
tbe incident light is passed transversely across the direction of the 
electric induction in the dielectric, and the plane of polarisation is 
inclined at an angle to this direction. 

Moreover, as has been pointed out and proved experimentally by 
Prof. Quincke,t the electrically -induced strain — the effect of which 
Dr. Kerr observed as double refraction — produces a change in the 
index of refraction. When the strain ia uniform, Quincke has shown 
that no double refraction ensues. Doubly refracting properties are 

• "Phil. Trans.," vol. 172, p. 556 (,\WV^. 
/ Quincke, " On Electrical Hspttnuott," ""£\ia..'».«4.;' a«. ViV v^-^- 



1886.] A General Theorem in Electroslatic Induction. 423 

assumed only Id a field of force which is not imiform from point to 
point. 

Dr. Kerr has made the remarkable discovery that some dielectrics 
become optically "positive," others "negative/* when subjected to 
electric stress. I think it may be inferred from Prof. Quincke's 
experiments just referred to, that those bodies which Dr. Kerr found 
to be " positive " have their index of refraction decreased by electric 
stress; "negative" bodies on the contrary have their index of 
refraction increased. I am not aware that this point has been decided, 
but I hope shortly to investigate it in the laboratory of University 
College, London. 

The sign of the change of index of refraction is not essential to 
the present discussion. We will assume, however, simply for con- 
venience of statement, that a "positive" dielectric experiences a 
decrease, and a " negative " dielectric experiences an increase of index 
of refraction when placed in a field of electric force. 

Now, whatever opinion may be held concerning the electro- 
magnetic theory of light, there can be no doubt that along with 
change of index of refraction of a dielectric, there goes always 
chaoge of specific inductive capacity. With the supposition we have 
made above regarding the sign of the change of index of refraction 
produced in the dielectrics examined by Dr. Kerr, his results when 
expressed in electrical terms translate into the statements that: a 
" positive " dielectric has its specific inductive capacity decreased by 
electric force; a "negative" dielectric baa its specific inductive 
capacity increased by electric force. In view of the theorem proved 
in Part I of this communication, this form of statement is very 
important. 

It means that if the specific inductive capacity of a "positive" 
body be decreased in presence of a field of force, then the electric 
forces assist this change — work is done by these forces. On the other 
hand, if the specific inductive capacity be increased, work is done 
against the forces of the field. 

We get corresponding statements for "negative" bodies by 
changing signs. 

Let us return now to equation (6). It is — 



'=-(^^^-f> 



Let us suppose that the dielectric is placed in a field of zero force. 

Then, with the disposition of apparatus that we assumed at the 

beginning of Part 1, y=0, and the second term of the right hand 

dw 
number is zerp. But the first term -r=j need, uo^ uo 



42i Mr. J. Buchanaii. [May il, 

with V. Let as denote hj- \^) the ralne of -^ when Y^O; tbeu 
aooording to the view adopted in this paper, l^j^J is a qnantitr 

which haa a valae characteristic of each material, and may be 

regarded as a property of each material in the same sense as, for 
iuataoce, the index of refraction. 

Let now the Bpeci6c inductive capacity of the dielectric be increase)} 
by IK. Thus the lendfncy is for the dielectric to become electrifieii 
with a quantity of electricity— 

This tendency being eqaal in all direoticns there ia no resnltaot 
electrification. If, howeyer, another dielectric is pat into close con- 
tact with the first, disMymmetry is introdnced. Denoting by the 
snffises (i) and (q) the qnantitiea relating to the two dielectrics, and 
by aE the electrification, we have initially. 



.E,=-aK,(^)^„K.(i^); 



1 



--.^^^--.(m 



^\iif)-"^\W.i 



These two equations express my view of the mode in which electri- 
fication begins when two dielecti-ica are put into contact and their 
specific inductive capacities are altered. The change of specific 
inductive capacity may take place either by pressure or by friction^ 
with liquids it ia probable that only the heating effect of friction can 
influence the results. 

According to what law the electrification goes on increasing when 
once started is a point still to be cleared up, the value for any 
material of the quantity w having still to bo worked oat experi- 
mcm tally. 

Before discnsaing (8) it is convenient here to notice that when two 
bodies are in very close contact, the capacity of the system that cod- 
siste of the two opposed aarfaces and the extremely small distance 
between them, most be very great indeed. If then at anv moment 
Q be the charge on either of these opposed surfaces and C denote the 
capacity of the system, then (6) becomes — 



\dV C dYL) 



1886.] A Qeneral Theorem in Electrostatic Induction, 425 

when — = and Q are finite and C is extremely large. Hence, in con- 

sidering what is happening when two bodies are rubbed together, we 
need onlj take account of the value of — -r^ for each. 

To simplify discussion of (8) we will take the second body as 
"neutral"; t.e., ( --^l =0. We shall see that boxwood appears 

nearly to fulfil this condition. Also for brevity and convenience, we 
will put -__=a. 

Two cases arise for consideration. 
Case I. 

~-—r(a) positive, i.e., work is done against electric forces by in- 
dV 

creasing the specific inductive capacity. 

(a). " Positive " liquids. If a liquid dielectric be warmed, the 

index of refraction, and therefore the specific inductive capacity, is 

decreased. Hence, by friction there is a change of specific inductive 

capacity —6K to be expected. Using AE in the same sense as 

in (8)- 

It is shown by the experimental results quoted below, that AE 
positive indicates that by friction this class of liquids tends to become 
positively electrified. And since in this particular case the sign of 
AE is the same as that of the electrification, it ought to hold in 
general. It will be seen that this is true. 

(6). " Positive" solids. Here friction, by raising the temperature 
of the surface, tends to change the specific inductive capacity by an 
amount +^K, 

.-. AE=-«o^K. 

Such bodies tend to become negatively electrified by friction. 

Case IL 

——.(a) negative. Here work is done by electrical forces when 
dV 

the specific inductive capacity is increaised. 

(c). "Negative" liquids. Friction tends to decrease the specific 

inductive capacity by an amount — ^K, 

/. AE=-«o.^^K. 

Hence " negative " liquids tend to become h^^^n^"^ ^^^\fc>S^^^\ir^ 
fiictioB, 



426 Mr. J. Buchanan. [May 27, 

{d). " Negative " solids. Friction teuda to increase tbe specific ' 
inductive capacity, I 

.-. AE = +«o.«K. 

" Negative " Hoiida tlieref ore tend to become positively electrified bj 
friction. 

The conclusions nnder (a), (6), (c), (d) are all found to be verified i 
by experiment. 

ProfesHor Foster has suggested to me that, in connexioD with tbe 
ideas expressed by equation (8), it is interesting to find the statement 
by Bccearia* that the cause of the electrical difference set np between , 
two pieces of similar silk ribbon when rubbed together lies in the j 
unequal warming of the opposed surfaces. The oft-qnoted esperi- ! 
ments of Faraday with a feather and piece of canvas fall obrionsly t 
under the same head. i 

I may perhaps be allowed to cite in addition some very old eiperi. 
ments with glaas made by Bergman. t On nibbing two similar strips , 
of glaaa togelJier, the portion of the surface of either strip nltich 
received tbe greatest amount of friction per nnit area became positive. 
This agrees perfectly with what may be deduced from (6). For the 
two strips, -j=-= — * was the same; hence by (8) — 
.-. aEi=«o(iKi-SKs). 
If iKj >2K) we get AEj positive, as Bergman found. 

Experim-entt on the Eleclrifiration of Steam by Frielion. 
The experimental results given below are far from complete ; but 
I venture to publish them as affording in s( 
mental verification of the ideas put forward ii 

Tbe method of experimenting and the arrangement of apparatus 
employed were essentially tbe same as were used by Faraday in his 
classical experimenta on this same subject.} 

It is needless for me to say how very much I am indebted to 
Faraday's observations daring the whole courae of this experimental 
enquiry. Like all that the great experimenter undertook, the record 
of his observations in the " Researches " is a treasure-house for later 
experimenters to draw supplies from. 

To generate steam, a smidl vertical copper boiler was uaed, which 
was heated by gas led to the burner by india-rubber tubiug. By 
placing tbe boiler on small blocks of shellac the insulation was found 
at all times to be excellent. The weather was very favourable. 

■ Biemii, " Beibonj^ElectricitU," S 914. 

t liM., |ftW,ag.V]6. 

J " EspeiVmenlal B*w»i«»i'»r \^til^,rt»«4. 



1886.] A General Theorem in Electrostatic Induction. 427 

The electrical condition of the boiler was the thing tested in all 
the experiments : a gold leaf electroscope connected to it served as 
indicator. 

The steam was led from the boiler throngh a straight brass tube 
aboat 1'2 cm. diameter and 120 cm. long, to a steam-globe of copper 
10 cm. in diameter. This steam-globe was always kept well supplied 
with distilled water, as Faraday points ont how essential it is to have 
the steam wet. A " feeder- tube " was nsed to contain the substance 
to be experimented npon : it was of glass 1*5 cm. internal diameter, 
and about 15 cm. long. A short length of narrow tubing, furnished 
with a glass stopcock, was fused to the main tube at the centre and at 
right angles to the axis. It was nsed to renew the supply of material 
in the wider tnbe below along which the cnrrent of steam was 
passed to sweep the material away. This arrangement was found 
convenient in working ; and it possessed the great merit of allowing 
the pieces to be easily cleaned. 

For the friction-piece that was rubbed by the cnrrent of fluid, I 
worked principally with a boxwood tnbe of as nearly as was con- 
venient the dimensions of the tube described by Faraday as an 
" excellent exciter."* 

By a fortunate chance, this tnbe was fonnd to be very nearly at 
the nentral line where Dr. Kerr's ** positive " and ** negative " snb- 
stances meet. 

In order to find out if possible what was the meaning of some 
anomalous results that appeared in the experiments, a number of 
observations were made with, amongst others, tubes of pine, haw- 
thorn, birch, sulphur, plaster- of-par is, and a tube formed out of a 
piece of carbon rod 1*2 cm. diameter, such as is used in electric 
lighting. The results obtained with the sulphur and plaster-of-paris 
tubes were interesting, but in no way decisive, as the tubes were 
found to have become very much disintegrated by the action of the 
cnrrent of steam ; they are, therefore, not recorded in what follows. 
The results with the hawthorn tnbe will illustrate the effect of 
friction-tubes of materials whose place is on the negative side of the 
neutral line ; carbon stands on the positive side. 

Between the two lies the boxwood tube. This is well shown by 
the results obtained with methylic alcohol and amylic alcohol as 
shown in the list given below. 

The wooden tubes used were always kept well soaked with distilled 
water. 

After each day's work with the apparatus, it was taken to pieces, 
and the copper steam-globe and the feeder-tube were left to steep in a 
strong solution of carbonate of soda ; then they were well rinsed out 
with distilled water before being nsed again. k« oee.^<^\oTL T^o^oxe^^ 

* " j:xperimental Researches," footnote, % ^\Q^. 



428 Sir. J. Bucliau«ii. [Maj i'.. 

methjlafed spirit was naed to give the appwatua a ttorongh cleansi 
from all tmoea of oil, ftc. 

As a valuable teat of tlio proper working of tte apparatus, oil <if 
turpentine was conafantly in use. If everjtliing was going well, the 
efiect of adding a. small quantity of the oil to the distilled wate 
the fe«der-tnbe waa to make the boiler positive, and the stoani veg^ 
tive. On continning to blow out, the boiler quickly passed or 
negative. 

This was repeated na a mle between the testing of each pair of snb- 
ntanoes. 

It will be observed in the list given below that there arc ll 
perfliafent apparent eiceptions to the rule that holds for all the Other 
Bubetances tried ; these arc turpentine, sperm oil, and chloroform. 

The extremely uncertain composition of the first and second of 
these three bodies did not allow their escepcional behaviour 
assume mnch importance in my oyes. Bat that chioroforni should 
remain an eseeption to the role appears to indicate that either 
influence of the water masks that of the chloroform (i-idn remarks bj 
Faraday on Akohol, " Exper. Res." §2115, 2116), or that ther« 1 ' 
been a change of sign in the electro-optical position of the body d 
to rise of temperature. These points, together with some others 
that have been raised in my mind in connexion with the present 
application of the theorem of Part I, I hope to be able to clear 
by experiments in a different direction from those recorded here, 
may he desirable to state also, that I began experiments in which dry 
compressed air was ased instead of ateam, but was not able to a 
tinue them. 

In conclusion 1 desire t« record my thanks to Prof, Poster, for the 
valuable criticisms with which he has favoared me during the pre- 
paration of this paper. 

Note. — In the experimental results which follow, the sign of the 
electrification is that assumed by the body to whose name it stands 
opposite when rubbed on the material whose name is at the top of 
the colamn. 



A General^ Theorem in Electrostatic Induction, 



429 



Experimental Results (November, 1884). 



dielectric. 



w&cer • • • • 
lisulphide. . 

wax 

line 

ing oil 1 
uin?) / •• 

odide 

rpentine. .. 
1 

)ucine . . . . 

5ti 

! alcohol . . . 

•Icohol . . . . 

rm 

e 

i '.','. y.y,v. 

* oil 



Sign of 
electro- 
optical 
effect. 



+ 
+ 
+ 
+ 



+ 
+ 
+ 
+ 
+ 
+ 
+ 



Hawthorn 
tube. 
Sign of 
electrifica- 
tion. 



+ 

+ 
+ 



Boxwood tube. 
Sign of electrification. 



First set 
of experi- 
ments. 



+ 
+ 
+ 
+ 

+ 

+ 



+ 
+ 
+ 



Last set 
of experi- 
ments. 



+ 
■I- 



Carbon 
tube. 
Sign of 
electrifica- 
tion. 



+ 
+ 



above maj be added a list of solids whose electro-optical 

have been determined by Dr. Kerr. The electrical position 

st two is well known. The others I examined by rubbing 

h the same boxwood tube as was employed in the experi- 

th fluids. 



ame of dielectric. 



z 

ur 

paraffin wax 

aceti 

haline 



Sign of the electro* 
optical effect. 



+ 
+ 
+ 
+ 
-I- 



Sign of electrifica- 
tion when rubbed by 
boxwood. 



+ 
+ 



\ 



^SO Mr. F. Rutley. . play 27. 

Roferancee to Dr. Kerr's papers on electro- op tics : — 

" Philosophical Magasine," Ser. 4, vol. 50, 1876 ; pp. 337 and +i6. 

Ser. 5, vol. 8, 1879; pp. 85 and 229. 

13, I8b2 ; pp. IS3 aud 248. 

Faraday gives a list of bodies with the sign of the elt^ctrificfttiaB 

they acquired by friction, which is here reproduced for companMn 

with my rcBults. 



Nrnne of dielectric. 


Sign »f the eloctni- 
optical effect. 


Sign of dectrifiBBtim 
by friction. 




+ 


: 














BewD (dieaoUed m ttlcohol) . . 













III. "Notes on Alteration induced by Heat in certain Viti-eons 
Rocks; based on the E.spenmentB of Douglas Hermau, 
F.I.C., F.C.S., and G. F. Rodwell, lato Science Master in 
Marlborough College." By Fran^k Rutlet, F.G.S.. 
Lecturer on Mineralogy lu the Royal School of Mines. 
Comniuuicatcd by ProfesBor T. G. Bonney, D.Sc, F.R.S, 
&c Received May 18, 1886. 

[Plates 3—5.] 
In this paper an endeavour is made to show the natore of the 
changes which have resulted from the action of heat upon cert«ia 
vitreons rocks. The changes which take place in snch rocka tbrongh 
natural processes may sometimes be effected by heat alone, at othen 
by heat in presence of moisture. Of these actions the latter is 
probably the more frequent, bnt, at the ontset, it seems important to 
ascertain the action simply of dry heat before stndying the more 
complicated conditions engendered by the i^resence of water and the 
j>ressare of auperincnnAeTit tocV "CQaasea. 



1886.] AUercUion by Heat in certain Vitreous Rocks. 431 

The following examples which have been operated upon are few, 
but typical, and the alterations which thej have undergone will be 
found to have a certain petrological significance. 

The first subject taken for experiment was a small fragment of the 
well-known pitchstoue of Corriegills in the Isle of Arran. This was 
kept at a temperature ranging from 500^ up to about 1100'' C, during 
a period of 216 hours. The change visible at the end of the nine dajs' 
heating is not so strongly marked as might have been expected, the 
fragment still exhibiting a resinous lustre, but the colour, originally 
a deep green, has been altered to a deep reddish-brown or chocolate 
colour. The rock in its normal condition has already been described 
by Mr. S. Allport* and others, and a section cut from the specimen 
before heating presents exactly the same characters shown in AUport's 
drawings, published in the ** Geological Magazine," in Vogelsang's 
'' Krystalliten," Plate 13, fig. 2, and in Zirkel's *' Mikroskopische 
Beschaffenheit der Mineralien und Gesteine," fig. 43. 

A section made from the specimen now described, but prepared 
prior to heating, has furnished the figs. 1, 3, and 5, on Plate 3. The 
three right-hand figures on the same plate have been drawn from a 
section made after nine days' heating at a temperature ranging from 
500** up to about 1100° C. For the sake of oomparison the figures on 
opposite sides of the plate have been drawn under the same amplifica- 
tion. 

When the artificially altered rock is examined under a power of 
25 linear it presents the general appearance shown in fig. 2, Plate 3. 
On comparing this with fig. 1 on the same plate we see that a marked 
change has taken place. The clear spaces surrounding the crystallites 
or belonites of hornblende have increased, while the dusty-looking 
matter no longer shades ofE into the clear glass but lies within more 
or less sharply defined boundaries. It also presents a coarser appear- 
ance than in the section taken from the unaltered specimen. With 
increased amplification the character of the change becomes moi'e 
clearly perceptible. 

In fig. 4, Plate 3, we find, on comparing it with fig. 2 on the same 
plate, that the hornblende belonites themselves have undergone very 
considerable alteration. They have to a great extent lost their frond- 
like appearance. Their dplicate lateral growths seem to have shri- 
velled up, and their green or greenish-brown colour has changed to a 
deep rusty brown. Their stems or central rods have become opaque, 
and the lateral fringes frequently share this opacity. They seem, in 
fact, mere withered representatives of the greenish fern-like crystallites 
which occar in the natural state of the rock, and the chaoge appears 



^'i 



* " On the liioroftcopical Structure of the FitcY&fttouA ol Xxtvar '" ^«>«^.^)&3tf|,:;' 
2872. 



432 5Ir. F. Rutlej. [May JT. 

to oonBist in the peroiidntion of the protoside of iron in the horn- 
blende. The general aspect of those crjatallites is mnch darker tbu 
that of their nnaltered represenlatires, and they stand oat in boL 
contrast to the clear glass aronnd them. 

On looking at the left-band portion of fig. 4, Plate 3, we see , 
number of coarse spiculte which onder a lower power, as in fig. i 
Plate 3, appear merely as stippling. This stippling in fig. 2 is the 
altered condition of those part« of fig, 1 which are softly shaded, is 
seem to be so under an Finiplifi cation of 25 linear. When magnified 
250 diameters this portion of the normal rock still e,py ' iite]j 
stippled, bnt contains nambcrs of very minute apicnlfe, as showi 
fig. 3, Plate 3. When we compare this stippling in fig. 3 with the 
coaree apicula; on the left of fig. 4, Plate 3, the extent of the alt^ratiun 
prodnced by the nine days' beating becomes striking. It is probable 
that these spicnlie are hornblende, and that they are eTidentlj ■ 
farther development of the much smaller ones so plentiful in ti* 
glassy ground-mass of the unaltered rock. In the dnstj looking parts 
of the unaltered glass we find, under an amplification of 1150 dia- 
meters, some indication of the source from which this wealth ol 
crystalline apiculse has been deinved, fainter and smaller apical* 
being visible, together with sparsely distributed dark specks, a few 
blant-ended colourless microUths, and a profusion of coloarlesa giobn- 
lites, as in fig. 5, Plate 3. 

The spiculw shown on the left of fig, 4 are again represented in 
fig. 6, Plate 3, under a power of H50 diameters. They are grooperf 
in a stellate manner and constitute a large proportion of the rock, 
while the fine dusty matter previously visible has almost entirely dis- 
appeared. Although, through the agency of dry heat, we have here 
an instance of further crystalline development, yet no approach to a 
felfiitic structure is discernible in the glas.sy matter of this rock ; the 
new crystallites which have been formed being certainly neither 
felspar nor quartz, bnt possibly actiuolite. 

The next specimen te be considered is a piece of black obsidian 
from Ascension, about as typical an obsidian as it would be possible 
to find, and showing a faintly banded structure. The general micro- 
scopic character of this rock is shown in figs. 1 and 3, Plate 4, 
fig. 1 being magnified 25, and fig. 3 i>70 diameters. In fig. I tie 
banded structure is well marked, and streams of colourless microliths 
lie with their longest axes in the genei'al direction of tiie banding. A 
fi-agment of this rock was kept for the same period at the same j 
range of temperature adopted in the case of the Arran piteh- 
atone. 

The rock in its normal condition is a deep black glass with a well- 
marked conchoidal fracture. In section, when not very thin, it 
appears Lr traEsmittedWgVvt. ol s-Xito-wiv ot wffisiei t(i\Q\i\,».\i\ ■oi^j.'Miffliak, 



188G.] Alteration hi/ Heat in certain Mtreon.^i Rock.^, 433 

as already stated, numerous microliths, mostly bacillar or spicnlar, 
sometimes in rectangular forms, and often shaped like a batcher's 
meat- tray. In the artificially heated specimen a remarkably vesicular 
structure has been developed, the rock, in fact, has become filled with 
vesicles, mostly spherical, or approximately so. The sand in which 
the specimen was heated has adhered firmly to its surface. Vitreous 
lustre is visible on fractures. Under the microscope between crossed 
Nicols the rock shows no sign of devitrification from its protracted 
heating, but the section is full of the large vesicles which have been 
devt>r (fig. 2, Plate 4). The glass still contains great numbers of 

microliths, a few small stellate or cruciform gronps being here and 
there visible, but it seems probable that they are fresh developments, 
and that the old ones have been dissolved, for there is no longer any 
banded structure, or only very faint indications of it, the microliths 
lying in all directions and not in streams. This view is favoured by 
the almost necessary assumption that the rock must have been 
reduced to a condition bordering on fusion to have permitted the 
development of such an extremely vesicular structure, while further 
evidence of this is seen in the firm adhesion to the surface of the 
specimen of the sand-grains in which it was embedded during the 
process of heating. In spite, however, of the great molecular chansre 
of position implied by this development of vesicles, there is no sign of 
devitrification, unless indeed the microliths be fresh ones formed 
during the heating of the specimen, or dnring two days in which it 
cooled from 800** to about 100* C. They do not probably equal those 
present in the normal condition of the rock. 

Fig. 4, Plat-e 4, represents part of a section of a piece of the same 
obsidian, which was kept for 701 hours at a temperature ranging from 
about 850° to 1100° C. The specimen has been nearly fused, and is 
pitted on the surface by the impressions of the sand-grains in which 
it was embedded, a few of the grains still adhering. There is a 
resinoas or subvitreous lustre on some parts of the specimen, but one 
face is dull. Internally it is fnll of vesicles, but a thin compact crust 
exists in which there are none, and this crust is continuous with the 
spongy vesicular portion. One or two of the cavities are nearly 
half an inch in diameter, i.e., they occupy nearly the whole thickness 
of the specimen, while others are of very small dimensions. They are 
irregalar in form, and appear as- a rule to communicate with one 
another. 

Under the microscope, with an amplification of twenty-five diameters, 
the section shows large irregular vesicles ; their walls (i.e., whai 
remains of the rock) appearing to consist of greenish-brown loaMsBlt 
traversed by opaque and approximately parallel bands. The 
lucent portions of the section seem, under tVvVa \o^ '^^«t^\ft 
of njicro-crystalline matter, the general a^pectt 'Hievn^ ^JaaJu A 

VOL. XL. 




434 Mr, F. Rut ley. [May 2T, 

mixed with a felted miurolilhie anbstance, while between crcweed 
Kicols numerous doubly refracting' graiialea and needles are visibl) 

Where the actual inarf^n or outer crust of the specimen is included 
in the section the substftcce is quite transparent and colourless by 
ordinary trausmittod light, and is seen to contain nnmeronB green 
microliths. 

By reflected light the whole eeotion appears of a greyish- white. 
except the parallel bands, which are of a lather darker prey, i 
the more vitreous portion of the outer cmst, which appears dart. 
The exlreme outer crust is seen by substage illumination to be alnKrsi 
or quite opaque. 

Under a power of 250 diameters the outer crost may be distin- 
guinhed as conNisting of three layers, the ontepmost of estreme tbii 
ness. ti'aosparent, and coSee-coloured ; the next quite opaque i 
feebly transmitting a brown or brownish -green light. It in of mn( 
greater thickneBS than the outermost glassy layer, and consists of 
greenish -brown mici'oliths matted parallel to one another, 
directed with their longest axea at an angle to the outer surface of 
the specimen, the angle being sometimeR nearly a right angle, 
seldom less than about 20° or 30°. This shades ofl" or fringes off into 
a clear colourless glass Inyei', also containing numerous greenish- 
brown spicular microHtbs, evidently identical in character with tho$e 
which, by their massing together, form the nearly opaque band last 
described. It is not easy to say what these microliths are, bot thej 
appear to be some form of amphibole or pyroxene ; they have, as a rule, 
a somewhat frayed and ragged or fibrous aspect, and it seems ocra- 
sionally that they either belong to the rhombic Byst-ecn, or eKtinguist 
at a very small angle with their longest axea. With the enception o 
the ghisay band in the thin outer crust, the remainder of the rock 
has been completely devitrified, fig. 4, Plate 4. Owing to the porous 
nature of the specimen it was scarcely possible to prepare a very thin 
section, but, judging from what can be Hcen, it consists of doubly re- 
fi-aeting mirrolitfas with an admijitare of minute crystalline grannies. 

The devitrification does not in this caae appear to be precisely of the 
same character as that met with in naturally devitrified obsidians, but 
at all events we have here a proof that the action of dry heat dnrijig 
701 hours has been capable of devitrifjing this glassy rock. 

The next specimeo, a black obsidian from the Tellowstone Dis- 
trict, Montana, U.S., was in the first instance kept at a temperatni 
ranging from 500" to about 1100° G. for 216 hours. Some of the sand J 
in which the specimen was heated adheres firmly to its surface. On 
fractures the rock is still vitreous in lustre, but it appears of a much 
paler colour than in its natural condition. This is probably due to 
the derelopmeat of great TiumVion oC am&Ll vesicles, the colour being 
now grej, where« in ttie unaWjetei »^wftm6"(i.\\.-^«»^*w3*„ 






1886.] Aheration by Heat in certain Vitreous Rocks, 435 

Microscopic, examination of a section of this obsidian in its normal 
condition shows the presence of numerous trichites, resembling small 
eyelashes, and often occurring in radial or stellate groups ; globulites 
are also plentiful, but, with the exception of these and some minute 
gas-pores, the obsidian is remarkably free from enclosures, although 
here and there a few porphyritic felspar crystals and a spherule or 
two occur. This was, therefore, regarded as a very favourable speci- 
men to experiment upon. 

The appearance of a section of this rock in its normal condition is 
represented in fig. 5, Plate 4, as seen under a magnifying power of 
570 diameters. In this drawing rather faint indications of batiding 
aj*e shown. Part of the same section is also represented in fig. 7, 
magnified 570 linear, in which some of the trichites are visible. The 
specimen which was heated for 216 hours has developed an exceed- 
ingly vesicular structure, but apart from this it appears to have 
undergone but little change. The vesicles are large, fig. 6, Plate 4. 
Their sections are nearly all circular or approximately so. The 
trichites seem to have disappeared entirely, but some small opaque 
granules are now visible, and in some instances they have distinctly 
triangular sections. These by reflected light appear black and are no 
doubt magnetite. 

In order to ascertain what change would take place by further 
heating, another fragment, taken from the same specimen as the pre- 
ceding, was heated for a period of 701 hours at a temperature of from 
850" to about 1100° C. 

The rock is still vitreous, but a marked change has occurred. The 
specimen had no sand adhering to its surface, and it perfectly pro- 
served its original external form, the conchoidal fractures and sharp 
cutting edges remaining quite distinct, but the outer surface has 
merely a dull sub-resinous or flint-like lustre, although on freshly 
fractured surfaces the lustre is quite vitreous. Here and there upon 
the surface very slight elevations occur, and these are mostly per- 
forated by a diminutive hole, as if made with a common sewing- 
needle. When a point was inserted in one of these apertares and the 
crust was prized off, a remarkably cavernous interior was exposed, 
the cavities appearing to have been formed by the coalescence of more 
or less spherical vesicles, averaging from a quarter to half an inch in 
diameter. 

In these cavities white crystalline pellets were found, for the most 
part about a third the size of the cavities in which they respectively 
occurred. 

Three of these pellets are represented in the middle line of figures on 
Plate 4. Some of them are approximately spherical, audtVve^ wc^TiKs«»i\'^ 
crystalline cmats, either empty or enveloping «b ft\x\«XVet -^^^^^ ^"^ *^^ 
SAwe kind. The walla of the cavities in wVkida. t\\^3 o^^tjlT ^x^ ^^ 



Mr. F. Riitley. [May 2", 

timed lined with crystalB apparently of the eame minentl. Tlie pellet* 
themselvefi are too friable to admit of any sections of them being cot. 
while no §alisfactory conclnsion has yet been arrived at by crnshitu; 
them and examining the f raemeuts onder the mioroscope. Small glisten- 
ing faces sometimes showing a certain p&ralleliem of growth may be 
detected with the help of alenR, and, so far as general appearnnces go, 
the mineral bearB a somewhat close resemhlftuce to rhyacoHte, Thej 
are, at all events, probably anhydroDH silicates allied to the felspar or 
nepheline groups. In some cases the pellets adhere slightly to tbc 
walls of the vesicles, yet in one or two instances they appeared to be 
loose, but may possibly have been detached by the shock in breaking 
open the specimen. Oneiaininingrmcot these pellets by reflected ligbi 
under a half-inch objective, the white crystalline snrface was seen to 
be stndded with minnte black or deep blackish-red crystals, having ■ 
brilliant metallic Inatre. One of them exhibited a six-sided face as 
shown in the bottom figure of the middle line in Plate 4. This 
was turned sufficiently well into position to enable all parts of the face 
to bo hi-ODght at once into focas, when It was found that measure- 
ment of the angle formed by adjacent edges was 60°. There is, 
therefore, little doabt that these small crystals are specular iron, 
which has separated out during the process of arti6cial heating, no 
each crystals being visible in a microscopic section of the rock in it,' 
normal condition. 

Under a power of 250 linear the section of this artificially heated 
rock etill appears as a clear glass, bnt trichites similar to those presenf 
in the unaltered obsidian are again seen; they are, however, mueb 
more nnmeroos. A vesicular etructnre still exists, and the sections of 
the vcsiclea are sometimes circular, at others oval. Two or three 
porphyritio felspar crystals occnr in this section, one of them, 
apparently twinned on the Carlsbad trpe, has a very irregular outline, 
somewhat like that of a comb with broken teeth. Felspar crystals 
with equally iiTCgnlar contonre occur, however, in the unaltered 

In thia specimen the devitrification has been confined to the tormft- 
tion of the white cryslalline pellets, the rest is glass, containing 
trichites and globnlites, which of coarse maybe regarded aa, evi- 
dences of incipient devitrification. Still they are also present in the 
unaltered rock, and between the two sections the differenoes are 
barely appreciable, even under the microacope. Figs. 7 and 8 
(Plate 4) show how close the resemblance is. 

Being auzions to ascertain the resalt of dry heat upon basic as well 

as highly silicated glassy rocks, a small fragment of the very Teaicular 

basalt-glaas from Mokna Weo Weo, Sandwich IslandB, was treated ia 

the same manner as t\L6 ^T«y\oa:^'j &«BR»r&xi&. w^ecvmflna. ^his 

came completely diBmieKM.^^4 '^^ "iiia -^.Twwna A «ft^-«sK-i»ftiasii(, 



1886.] Alteration by Heat in certain VUreovs Hocks. 437 

The specimen had, however, quite lost its vitreous lustre, and had 
changed from black to a pale brown colour. Another fragment of 
basalt-glass from Kilauea, very vesicular, but less so than the previous 
sample, was kept at a high temperature, about 750° to 1200° C, for a 
period of 960 hours. 

The effect of this heating has been to completely destroy all glassy 
lustre. The specimen is still vesicular, but the colour has, like that 
of the Mokua specimen, changed from black to purplish-grey or light 
brown. 

Fig. 1, Plate 5, shows the general character of a section of the 
unaltere