50 PRESIDENT’S ADDRESS—SECTION A. 
of electricity and a negative quantity of electricity beyond the 
difference of sign which is included in our definition. This idea 
is familiar to everyone from the very terms “ positive electricity ” 
and ‘negative electricity.” The phrase, ‘“ Positive Quantity of 
Electricity” thus connotes much less than the by-no-means 
equivalent phrase, “Quantity of Positive Electricity.” If the 
latter phrase is legitimate, we must admit that we think we know 
more about electricity than is actually the case. For instance, in 
hydrogen chloride (possibly only in the presence of water), we 
tind that the direction of motion of the hydrogen coincides with 
the nominal direction of the current, or in our notation each 
hydrogen atom carries a positive quantity of electricity. In 
hydrogen sulphate the case is the same, and in silver chloride 
and silver sulphate it is the silver which carries the positive 
quantity. Thus, so far, all is well, and if we like to suppose that 
silver carries positive electricity nothing can be said against it. 
If we take the cases of Iodide of Potassium and Iodide of 
Bromine however, we notice that in one case the iodine goes one 
way, and that in the other it goes in the opposite way—conse- 
quently if we talk of iodine carrying a positive charge in one 
case, we must admit it carries a negative charge in the other. 
The chemical theory of Berzelius was destroyed by this and 
similar facts (not very many, by the way), but it need not 
influence us with respect to the question in hand. The only 
point we have to note is that the hypothesis of positive and 
negative electricity at once forces us to make the additional 
hypothesis that a given atom may sometimes carry one and 
sometimes the other. 
Now, from the extraordinary quantitative fixity of the charges, 
it is very difficult to escape the impression that electrification, 
regarded as a state of the ether, is a consequence of the same 
cause, whatever it may be that conditions the distinction between 
element and element. If there be anything in this view, it 
becomes difficult to understand how iodine can sometimes carry 
positive and sometimes negative electricity and be still iodine. 
The view that free atoms (at least when they are ions) are asso- 
ciated with an ether state which we call electrification has, I 
consider, been somewhat strengthened recently by the researches | 
of Ostwald. According to the Clausius-Williamson hypothesis 
(which we have tacitly assumed above in order to account for 
electrolytes obeying Ohm’s Law), every liquid is in a steady state of 
dissociation. The influence which any such liquid—say a solution 
of hydrochloric acid—has in bringing about such chemical change 
as the inversion of sugar is supposed by Ostwald, on very strong 
grounds, to depend on the amount of this dissociation. But on our 
view of electrolytic conduction, the number of free ions must be 
proportional to the conductivity, since it is only by them that 
conduction takes place. Ostwald has shown experimentally that 
