740 REPORT—1885. 
Objections to the idea of unequal velocities of anions and cations. 
The bare notion of unequal molecular velocity has received consider- 
able and important development at the hands of Quincke, Wiedemann, 
and Kohlranusch; but they all accept the fact, and suggest modes of 
accounting for it. We will therefore defer consideration of their theories 
to a later head. What I wish to point ont is that migration data afford 
no proof that ions travel at unequal rates, because the facts can be 
accounted for without any such assumption, as has been shown at length ; 
but if I have to state what objection I feel towards considering the 
anion and cation velocity unequal, I can only answer in an unsatisfac- 
tory manner as follows :— 
1st. Electricity is known to obey the laws of an incompressible fluid ; 
and whether for positive electricity or for negative electricity, this is 
equally true. It may well be that electricity is far from being such a 
fluid, or pair of finids, but there must be some analogy or they would not 
obey so exactly the same equations. If one allows mental images of 
electric actions, the guise of an incompressible, indestructible, uncreat- 
able fluid, always flowing in closed circnits, naturally suggests itself for 
either kind of electricity. Equal quantities of opposite kinds in coin- 
cidence do indeed neutralise all electrostatic effect, but one does not. 
conceive of their annihilating each other. 
2nd. In certain cases an electric current is known to consist of equal 
opposite streams of positive and negative electricity. In a simple binary 
(fused) electrolyte this is so (see above) ; and in the convection portion 
of the circuit of a Holtz machine it is so. 
If provisionally these lemmas be granted, the argument is obvious. 
Include one or other such arrangement for insuring equal opposite 
flow in any circuit, along with many kinds of voltameters. Can one 
think of unequal rates of flow of opposite electricities in one part of a 
circuit and equal rates of flow in another? Not unless it is possible for 
equal streams of opposite electricities to meet and annihilate each other. 
And if we can thus control and make equal the electric streams without 
affecting phenomena in the slightest, must they not always be equal ? 
And it is plain that equality of the electric streams renders necessary 
the equal speed of anion and cation, since by Faraday’s laws atomic 
charge is constant. Not, indeed, that this rigidly requires that each 
anion should travel at the same rate as its corresponding cation, or that 
) = Yp 42 = Yo, &e. Allis satisfied if the anions as a whole travel as 
quick as the cations as a whole—+.e. if Xa = Sy; but it is difficult to 
think of the relation as being always: satisfied unless each individual a 
equals each individual y: the same kind of argument as that which leads 
one to ‘ equate coefficients.’ But less rigorous! Granted. I do not 
pretend that any of this is a rigorous argument ; it is little better than 
a statement of prejudice with an attempt at justification. 
To see if any definite and unambiguous experimental answer can be 
obtained to the question, ‘At what rate do ions travel?’ I propose to 
try a modification of those old experiments with electrolytes in series, 
where a precipitate is formed in the middle one of three vessels. For 
instance, use BaCl, in the anode vessel, Na,SO, in the cathode vessel, 
and in the intermediate vessel, which is to be in the form of a long tube, 
dilute HCl. Then pass a current, and observe whereabouts, how soon, 
and with what appearances, the precipitate shows itself. 
