770 REPORT—1885, 
a rate of travel independent of any other from which it is completely de- 
tached ; in fact, that it is difficult to see how the velocity of any given 
radicle can be controlled by the nature of the opposite radicle, which is 
travelling at its own pace in an opposite direction. 
And against this independence of the corresponding ions I have only 
to urge that it would mean that an electric current could consist of 
unequal opposite currents of positive and negative electricity, and that in 
some cases at least this is certainly not true. Thus, in a simple fused or 
homogeneous electrolyte, it is quite certain that opposite ions are travel- 
ling at the same rate, and that therefore the current in them consists of 
equal opposite streams of positive and negative electricity. Now if such 
an electrolyte is put in series with salt solutions, and the same current 
sent through all, it is difficult to suppose that in one part of the circuit 
the current consists of equal opposite streams, and in another part of 
unequal; yet this is what Kohlrausch’s theory necessitates. 
Again, when a Holtz machine or other replenisher is used to produce 
a current, half the plate is carrying positive in one direction, and the other 
half is carrying negative in the other direction, so that in the visible con- 
vective part of the circuit it is easy to ensure the existence of equal 
opposite currents; and there is no evidence that the decomposition pro- 
duced by such currents differs in any respect from that produced by 
equally strong voltaic currents. 
But whence the repugnance to admitting that a current may be at one 
place } positive and $ negative, and at another place 3 positive and + 
negative? Only from the habit of picturing positive and negative elec- 
tricity as both obeying the laws of an incompressible fluid, with identity 
or continuity of existence, and the consequent difficulty of supposing 
that + stream of negative electricity and } stream of positive can at one 
point rush towards each other, meet, and disappear, leaving no trace be- 
hind of either. For this is what must happen at the junction of a fused 
electrolyte, in which opposite ions are going at the same pace, with a dis- 
solved electrolyte, in which the positive ion is travelling three times as 
fast as the negative ion. 
If there is no validity in the objection, then Kohirausch’s theory is 
probably true pretty much as it stands ; but if any difficulty may be legi- 
timately felt in the direction indicated, some modification must be made 
in Kohlrausch’s theory. 
7. On the apparent relative velocity of opposite Ions. 
The facts of migration may, I believe, be accounted for by assuming 
that the solvent and the dissolved salt both conduct the current; but the 
result is to produce an apparently unequal velocity of ions, which has 
been mainly examined by subsequent analysis of the liquid near either 
electrode. I propose to examine it further by means of electrolytes in 
series :—e.g. noting whereabouts in the path of a current a solid pre- 
cipitate, caused by uniting ions, first forms. Iam, indeed, now engaged 
in these observations (see Question 5). 
A disobedience to Faraday’s law of electro-chemical equivalence might 
in the same way be detected, either by an escape of an excess of one ion 
past another with which it should wholly combine and become insoluble, 
or by a deposit of the excess of one ion because it finds insufficient of the 
opposite ion with which to combine and remain soluble. 
