140 REPORT—1890. 
-smaller then before. The concentric rings were, however, clearly visible. (« Phys. 
Inst. der Univ. Freiburg, i. B.’) 
In connection with this deposition of metal obtained on the upper 
surface of a liquid, Professor Ostwald’s discovery of the deposition of 
copper at the boundary of a semi-permeable partition may also be called 
attention to. (See below.) 
Mr. J. Brown has communicated a paper, which appeared in the 
“Phil. Mag.’ for July 1890, ‘On the Electrification of the Effluvia from 
Chemical or from Voltaic Reactions,’ wherein he discusses and extends 
the observations of Mr. Enright on the electrification detected above a 
vessel in which chemical ebullition is occurring. He considers that the 
electrification is not due to friction or any contact effects, but that it has 
a voltaic or electrolytic significance. If so, the observations of Mr. 
Enright (‘Phil. Mag.’ January 1890, page 56) have more importance 
than a criticism by Lodge (‘ Phil. Mag.’ March 1890, page 292) was dis- 
posed to concede to them. It is to be hoped that Mr. Enright will pursue 
the subject, and obtain definite evidence as to how the spray-matter 
receives its charge. 
Mr. Brown’s summary of conclusions is as follows :-— 
When gas is evolved in a chemical or voltaic reaction, the efluvium (7.e. this gas 
or something carried up with it) is usually, as shown by Mr. Enright, electrically 
charged. So far as these present experiments show, no electrification is produced by 
simple effervescence unaccompanied by chemical changes. 
The sign of the electrification is influenced by the kind of chemical or voltaic 
action taking place, and is apparently not due to any contact effect. 
When the effluvium is that given off from zine dissolving in HCl (taken as a typical 
experiment), and consists of hydrogen accompanied by foggy matter, it is not decided 
whether the charge is given originally to the gas or the fog particles, though the 
balance of evidence inclines perhaps towards the latter view. The fog in question is 
formed apparently at, or nearly at, the same place as the gas; and the nature of its 
charge (if any) is therefore possibly influenced by the voltaic condition there 
resent. 
> The gas, or effluvium, from the decomposition of a liquid by a current from the 
poles of a separate battery immersed in it (voltameter) appears also to be elec- 
trified. 
Concerning the verification of Ohm’s law in electrolytes which has 
been carried out by members of the Committee, or rather concerning the 
wider question of the validity of the Maxwell-Chrystal method in general, 
the Committee have been favoured with a letter from Professor Chrystal, 
which is reproduced with a sufficient introduction here. 
Verification of Ohm’s Law. 
In one of the circulars issued to the Electrolysis Committee of the British Asso- 
ciation, viz. that dated June 24, 1886, Professor Fitzgerald suggested an objection to 
the complete validity of the theory of the experimental method of verifying Ohm’s ~ 
Jaw with twelve-figure accuracy, devised by Clerk Maxwell and carried out by Mr. 
Chrystal ; doing so in the following words :— 
‘There is an objection to this method that I have not seen noticed. Maxwell 
-assumes that you can expand in powers of = Now, if the law were the positive 
value of ()’ where » differs very slightly from unity, the method would fail, for 
the current would vanish both in the numerator and in the denominator of Maxwell’s 
-expansion,’ 
