142 REPORT— 1890. 
Whence, finally, ; ' 
9 (2) =a 108 “N08 # 9 (1) 
S log A/log u $ (1). 
The general form for ¢ (z) is therefore 
p (@)=Az?, ; 
where A and B are constants, the physical meanings of which are obvious from what 
recedes. 
: We see from equation (1) that the like holds for the specific resistance of every 
metal which has the property indicated by the experiment. 
Moreover, as you have pointed out, such a law of specific resistance is sufficient 
to secure the result of the experiment. 
We conclude, therefore, that what the experiment really proves is that the spe- 
cific resistance of metals varies as a power of the current intensity, which power is 
the same for all metals. This is a good deal, but not quite so much as is concluded 
in the paper in which the experiment was originally described. The deviation spoken 
of in the paper must therefore be regarded as deviations not from absolutely constant 
resistance, but from the resistance calculated according to the above simple law. 
To establish that the constant B is zero will not be quite so simple a matter. 
Many ways might be suggested, and will, doubtless, occur to you. Tbe most direct 
and satisfactory would be to get the resistance for different current-intensities, in 
Joule’s way, by measuring the heat evolved. 
Should the above sophistry be right, it is curious that you and Dr. Fison should 
each have suggested not a way, but the only possible way, in which the resistance may 
vary with the current, and Wheatstone’s bridge still remain the ideal instrument that 
electricians have always considered it to be. F 
G. CHRYSTAL. 
An important contribution to the theory of vacuum-tube discharges 
by Professor J. J. Thomson appears in the ‘ Phil. Mag.’ for August this 
year. After showing experimentally that the velocity of electric trans- 
mission through electrolytes and through vacuum tubes is at least roughly 
the same as it is along wires, viz. the speed of light, he proceeds to 
consider how this is reconcilable with the doctrine of convection by mov- 
ing molecules, without supposing the molecules themselves to be affected 
with any such extravagant velocity. He conjectures that the gas conducts 
by a series of Grotthus chains, of a length depending on the time of recom- 
bination of molecules ; that each chain propels its own current like a series 
of boys on stepping-stones; and that the junctions of the chains constitute 
the well-known striz. 
The Committee are glad to record the appearance in English of 
Professor Ostwald’s work, ‘Outlines of General Chemistry,’ wherein is 
given an account of. the work and views of Professor van ’t Hoff on solu- 
tion, and the theory of electrolysis held by Dr. Arrhenius is developed 
into a large number of consequences. They likewise cordially welcome 
Professors van ’t Hoff and Ostwald to England, and regret that Dr. 
Arrhenius has been unable to be present also. 
In preparation for a discussion on the extreme dissociation theory of 
solution supported by these recent investigations, as opposed to the more 
customary view held by chemists, and having reference also to Dr. Arm- 
strong’s views of residual affinity, Professor Fitzgerald has written the 
following article :— 
Hlectrolytic Theories. By Professor FirzGeRap. 
Electrolysis has been explained on two different theories by Grotthus and Clausius. 
As generally received they differ. Grotthus’ theory, as generally given, assumes that 
the molecules in an electrolyte are both polarised and moved by the electric forces 
