a profound effect on the pure sciences of Physics and Chemistry, and perhaps having some influence on certain aspects of Biology also.
In admitting that I am going to promulgate a speculative hypothesis, that is a hypothesis for which there is evidence but not yet conclusive evidence, I must not lead you to suppose that the whole of what I have to say is of this character. On the contrary, much of it is certain, that is to say is accepted by a consensus of opinion to-day among those who by reason of study are competent to judge. I will endeavour carefully to discriminate between what is in this sense certain and what must still be regarded as doubtful and needing further support.
To treat the subject properly, to give all the evidence as well as the results, would need a volume, or a course of lectures; and in order to be brief I must frequently be dogmatic, but I shall only intend to be so in those places where I feel sure that the physicists present will agree with me. When I have a dogma of this kind to propound I shall call it a thesis. The more speculative opinions I shall plainly denominate hypotheses.
1. My first thesis is that an electric charge possesses the most fundamental and characteristic property of matter, viz. mass or inertia; so that if any one were to speak of a milligramme or an ounce or a ton of electricity, though he would certainly be speaking inconveniently, he might not necessarily be speaking erroneously.
In order to have any appreciable mass, however, an electric charge must either be extremely great or must
