ADDRESS. 13 
future. Now, although the conception of the decay of an element and 
its spontaneous transmutation into another element would have seemed 
absolutely repugnant to the chemist until recently, yet analogy with other 
moving systems seems to suggest that the elements are not eternal. 
At any rate it is of interest to pursue to its end the history of the 
model atom which has proved to be so successful in imitating the pro- 
perties of matter. The laws which govern electricity in motion indicate 
that such an atom must be radiating or losing energy, and therefore a 
time must come when it will run down, as a clock does. When this 
time comes it will spontaneously transmute itself into an element which 
needs less energy than was required in the former state. Thomson con- 
ceives that an atom might be constructed after his model so that its decay 
should be very slow. It might, he thinks, be made to run for a million 
years or more, but it would not be eternal. 
Such a conclusion is in absolute contradiction to all that was known 
of the elements until recently, for no symptoms of decay are perceived, 
and the elements existing in the solar system must already have lasted 
for millions of years. Nevertheless, there is good reason to believe that 
in radium, and in other elements possessing very complex atoms, we do 
actually observe that break-up and spontaneous rearrangement which 
constitute a transmutation of elements. 
It is impossible as yet to say how science will solve this difficulty, but 
future discovery in this field must surely prove deeply interesting.! It 
may well be that the train of thought which I have sketched will ulti- 
mately profoundly affect the material side of human life, however remote 
it may now seem from our experiences of daily life. 
I have not as yet made any attempt to represent the excessive minute- 
ness of the corpuscles, of whose existence we are now so confident ; but, 
as an introduction to what I have to speak of next, it is necessary to do 
so. To obtain any adequate conception of their size we must betake our- 
selves to a scheme of threefold magnification. Lord Kelvin has shown 
that, if a drop of water were magnified to the size of the earth, the mole- 
cules of water would be of a size intermediate between that of a cricket- 
ball and of a marble. Now each molecule contains three atoms, two 
being of hydrogen and one of oxygen. The molecular system probably 
presents some sort of analogy with that of a triple star ; the three atoms, 
replacing the stars, revolving about one another in some sort of dance 
which cannot be exactly described. I doubt whether it is possible to say 
how large a part of the space occupied by the whole molecule is occupied 
by the atoms ; but perhaps the atoms bear to the molecule some such 
relationship as the molecule to the drop of water referred to. Finally, 
the corpuscles may stand to the atom in a similar scale of magnitude. 
Accordingly a threefold magnification would be needed to bring these 
1 The view that the elements are not absolutely permanent seems to be gaining 
ground. See correspondence in Nature: D. Murray, December 7; Soddy and 
Campbell, December 14, 1905. 
