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a, 3 
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NATURE 
47 
term which I employ is his, though the fact was not known 
to him. 
I have published an article describing these experiments, 
which may be known to you, but I have since found some new 
facts. At Berlin I tested some metals which I had not tried 
before. I cannot vouch for the quantities within 50 per cent., 
but I think I can vouch for the direction of the effect. It is 
not the same for different metals under the same conditions of 
current and magnetic force. It might have been expected that 
the effect would be in the same direction in nickel as in iron ; 
but it is not, it is in the opposite direction ; nickel acts like gold, 
cobalt acts like iron. Nickel, silver, gold, platinum, and tin 
gave an effect opposite to iron. 
The most important fact that I have to bring before you is 
that in zinc the effect is in the same direction as in iron and cobalt, 
Table of effects on an arbitrary scale, 
Tron. * 2; Cee OMB YASS: (5.0 cox, con, Gemekes 
Cobalt ... + 25 | Platinumsy=-- “<-. 2 
ZU ee Mee voces Sr et) Goldeves4 (cme yn One 
Mead@es amiss: aoc — mwieliaan oad) con | te 
Tin Gall Cate ay se = @) 
| Aluminium =: - = 50 
| Magnesium cos = 12) 
Nickel —120 
The deflection of the current in those marked + is in the same 
direction in which the conductor itself tends to move in the 
magnetic field. I cannot vouch for the order of the metals. I 
have tried three specimens of nickel, and the direction was the 
same in themall. One of them was pure nickel, furnished me 
by Prof. Chandler Roberts. 
The following remarks were made by the chairman, Sir 
William Thomson :— § 
The subject of this communication is by far the greatest dis- 
covery that has been made in respect to the electric properties of 
metals since the times of Faraday—a discovery comparable with 
the greatest made by Faraday. I look upon it with special 
interest myself as so closely connected with electrodynamic 
properties of metals, which formed the subject of my Bakerian 
Lecture in 1856. I pointed out in that paper, in about § 104, 
that it was to be expected that magnetic induction would produce 
change of thermal conductivity and of electric conductivity in 
different directions in substances perfectly isotropic. I found by 
mathematical investigation rotational terms, and pointed out that 
we might expect in bodies which have rotational quality to find 
the effect of such terms exhibited. But the only influence having 
that relation to rotation which was necessary for producing the 
terms in question I pointed out to be the influence of a magnet, 
and that we might expect that the effect of a magnet upon an 
isotropic body would be to induce difference of quality in 
different directions in accordance with the rotatory term, and I 
said I thought it improbable that the rotatory terms would be 
found to be null in a body subjected to the influence of a 
magnet. I look with great delight on Prof, Hall’s discovery, as 
having verified that which I predicted as probable. I did not 
myself make any serious attempt to discover it. It is the first 
illustration ever brought out by experiment of one of the most 
curious antl interesting things in the mathematics of zolotropy. 
The previous mathematical writers dismissed these terms alto- 
gether, although they found them in the formula ;—dismissed 
them as something which we could not imagine to exist. I 
refused to dismiss them, and said there was decided reason that 
they could exist under the rotational influence which we know to 
belong to a magnet. 
Prof. Rowland said: Mr. Hall had tried the direction of rota- 
tion of the plane of polarisation when light is reflected from 
nickel and iron on Dr. Kerr’s plan. The direction was found, 
if he remembered aright, to be in opposite directions for these 
two metals. We did not yet know enough to say whether this 
investigation explains the rotation of the plane of polarisation of 
light. 
Prof, Sylvanus Thompson said he had verified Prof, Hall’s 
result by using a telephone instead of a galvanometer. 
Mr. Glazebrook said he had published a paper on the same 
subject in connection with the rotation of the plane of polarisa- 
tion of light. Maxwell said this effect (rotation of the plane of 
polarisation by reflection from a magnet) could be explained by 
molecular rotation of the particles in the field. 
Prof. Fitzgerald asked Sir William Thomson to express an 
opinion as to how it happens that different substances differ in 
the direction of this effect. He also remarked that the terms 
expressing the magnetic force on the matter were the same as 
those which would express Prof. Hall’s observed effect on the 
current. Was the action to be regarded as an action on’ the 
matter or on the current ? 
Prof. Everett asked whether the current in its deflected condi- 
tion was oblique (instead of, as usual, normal) to the equipotential 
surfaces ? 
Sir William Thomson, in reply, said that effect on matter and 
effect on the current through it went' together, and could not be 
distinguished. He could not say why the effect in any particular 
metal was in one direction rather than the other. There was 
nothing in the mathematical theory to show in which metals it 
should be in the same direction. Prof, Everett’s question might 
be answered by referring to several corresponding cases. If 
heat was flowing from end to end of a bar cut obliquely from a 
crystal, the points of equal temperature in two opposite sides 
would not in general be exactly opposite to each other. The 
foundation of the general theory of which this was an illustration 
had been laid by Prof. Stokes. 
UNIVERSITY AND EDUCATIONAL 
INTELLIGENCE 
OxrorD.—On November 3 Sir William Anson, Bart., 
D.C.L., Fellow and Sub-Warden, was elected Warden of All 
Souls’ College in succession to Dr. Leighton, deceased, Sir 
William Anson was Vinerian Reader in English Law. 
A Fellowship at University College will be offered for com- 
petition about the end of next February. The examination will 
be in biology and kindred subjects. At the last examination for 
a Biological Fellowship none of the candidates were judged ot 
sufficient merit, and the election was accordingly deferred, 
Candidates for the Brackenbury Natural Science Scholarship 
at Balliol College must communicate with the Master by letter 
on or before Friday, November 11. Papers will be set in 
Chemistry, Mechanics and Physics, and in Biology. There will 
also be an optional paper in Mathematics, and an essay. 
At Christ Church there will be one or more Natural Science 
Junior Studentships elected next March. Candidates must not 
have exceeded the age of twenty on January I, 1882. Papers 
will be set in Chemistry, Biology, and Physics, but no candi- 
date will be allowed to offer himself in more than two. of these 
subjects. 
CAMBRIDGE.—On Monday, November 7, ‘Mr. J. E. Marr, 
F.G.S., was elected to a Fellowship at St. John’s College. In 
1878 Mr. Marr obtained a First Class in the Natural Sciences 
Tripos ; in 1879 he received a grant from the University to 
enable him to travel in Bohemia and study the Cambrian and 
Silurian rocks there ; also in 1880 he went in a similar manner 
to Norway and Sweden. His paper on the Rocks of Bohemia 
was published in the Quarterly ¥ournal of the Geological Society 
for November 1880. He is at present lecturing for the University 
at Barrow, Kendal, and Lancaster. | 
=*GLascow.—Mr. John Macalister Dodds, B.A., Fellow of St. 
Peter’s College, Cambridge, 4th Wrangler, 1880, has been ap- 
pointed one of the assistants to Dr. Jack, Professor of Mathe- 
matics in the University of Glasgow. Mr. Dodds was a dis- 
tinguished Glasgow student before proceeding to Cambridge. 
All the four Professors of Mathematics and Natural Philosophy 
in the Universities of Edinburgh and Glasgow—Prof. Tait, 
Prof. Chrystal, Prof. Sir William Thomson, and Prof, Jack— 
are Peterhouse men. 
SCIENTIFIC SERIALS 
The American Naturalist for September and October, 1881, 
contains (No. 9, vol. xv.): Carl F. Gessler, variations in‘ a 
copepod crustacean (woodcuts),—A. S. Packard, jun., Scolo- 
pendrella and its position in nature (places Symphyla as a sub- 
order of Thysanura).—W. H. Dall, American work in the 
department of recent mollusca in 1880.—D, G, Brinton, notes 
on the Codex Troano and Maya chronology. 
No. 10, vol. xv.: D. H. Campbell, on the development of 
the stomata of Tradescantia and Indian corn (woodcuts).— 
Cyrus Thomas, the age of the manuscript Troano.—J. Walter 
Fewkes, the Physophoride (iii.).—R. E. Cull, the Loess in 
Central Iowa.—A. S. Packard, jun., on the early stages of the 
