August 25, 1905.] 



SCIENCE. 



233 



of association in stable communities of 

 definite types. 



An infinite number of communities are 

 possible, possessing greater or lesser de- 

 grees of stability. Thus the corpuscles in 

 one such community might make thousands 

 of revolutions in their orbits before in- 

 stability declared itself; such an atom 

 might perhaps last for a long time as esti- 

 mated in millionths of seconds, but it must 

 finally break up and the corpuscles must 

 disperse or rearrange themselves after the 

 ejection of some of their number. We are 

 thus led to conjecture that the several 

 chemical elements represent those different 

 kinds of communities of corpuscles which 

 have proved by their stability to be suc- 

 cessful in the struggle for life. If this is 

 so, it is almost impossible to believe that 

 the successful species have existed for all 

 time, and we must hold that they originated 

 under conditions about which I must for- 

 bear to follow Sir Norman Lockyer in 

 speculating. 



But if the elements were not eternal in 

 the past, we must ask whether there is 

 reason to believe that they will be eternal 

 in the future. Now, although the concep- 

 tion of the decay of an element and its 

 spontaneous transmutation into another 

 element would have seemed absolutely re- 

 pugnant 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 properties 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 conceives 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, but it would not be eternal. 



Such a conclusion is an absolute contra- 

 diction to all that was known of the ele- 

 ments until recently, for no symptoms of 

 decay are perceived, and the elements exist- 

 ing in the solar system must already have 

 lasted for millions of years. Nevertheless, 

 there is good reason to believe that in ra- 

 dium, and in other elements possessing very 

 complex atoms, we do actually observe that 

 break-up and spontaneous rearrangement 

 which constitute a transmutation of ele- 

 ments. 



It is impossible as yet to say how science 

 will solve this difficulty, but future discov- 

 ery 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 minuteness 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 concep- 

 tion of their size we must betake ourselves 

 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 molecules 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 hydro- 

 gen and one of oxygen. The molecular 

 system probably presents some sort of anal- 

 ogy with that of a triple star; the three 

 atoms, replacing the stars, revolving about 

 one another in some sort of dance which 

 can not be exactly described. I doubt 



