INAUGURAL ADDRESS. 7 



watch the process taking place. There is, however, no clear evidence 

 as j^'et that we can be anything more than .spectators ; and this is a 

 very important point. Sir William Ramsay does indeed describe cer- 

 tain experiments in which the radium emanation seems to have played 

 the part of the philosopher's stone, but the matter is so new that 

 science has not yet uttered her final decision on the point. It is Strang^ 

 enough, however, that the transmutation should take place at all; 

 and that we should have definite proof that the atom is not absolutely 

 stable. Up to the present we are sure of the transmutation in one 

 direction only, the break-up of larger atoms to form smaller ones. We 

 have found no instance of the reverse process, but Ave may Avell imagine 

 that it merely awaits discoveiy. Surely it must exist. 



This, then, is the second lesson — the instability of the atom. I 

 will not discuss it at greater length, because it has already received 

 such interested and full discussion in recent years; its importance has 

 been recognised from the earliest times in the histoiy of our. new 

 science. 



The third lesson which may be drawn fi-om the study of radio- 

 activity follows naturally on the previous discussion. If such trans- 

 mutations of atoms take place, there must be a certain uniformity of 

 sti'ucture, or rather of building materials. This view is strongly sup- 

 ported if we consider the character of the radiations from the various 

 radio-active substances. Wliere uranium passes through one or two 

 intermediate forms into radium, and this again disintegrates step by 

 step to polonium, and the process continues to an extent as yet not 

 wholly known, a number of substances of widely varying properties 

 have existed each for its allotted time. But the various fragments 

 which have been shed by the disintegrating atoms, and which consti- 

 tute the radiation, are found to be of two forms only, known as alpha 

 particles and beta particles. Rutherford has shoAvn clearly that the 

 former are atoms of helium, and owe their positive charge to the fact 

 that each has lost two negative electrons. The latter have long been 

 known to be negative electrons simply. Therefore, that which began 

 as an atom of uranium j^roceeds to become atoms of other substances 

 in succession, by an operation of which the main feature is the drop- 

 pting of one or more of svich particles ; we conclude that these particles 

 are integral portions of the atom — parts which go to the building of the 

 whole. The helium atom is doubtless further divisible; but for some 

 reason it seems to exist as a more or less self-contained portion of large 

 atoms. Though this principle is clear in the case of the radio-active 

 substances only, it seems illogical to deny it in the case of others. 

 Thus we are led to recooiiise a certain sameness in the materials of 



