^e SCIENCE PROGRESS 



Whereas the burning of a gramme of coal in air, by means of 

 which 2% grammes of oxygen are also consumed, evolves about 

 2,200 calories of heat energy per gramme, more than a milhon 

 times this amount is evolved by the spontaneous disintegration 

 of a gramme of radium. Sir OUver Lodge has calculated that 

 the sub-atomic energy in an ordinary stick of blackboard chalk, 

 if only it could be harnessed, is sufficient to raise three hundred 

 million tons of matter through a distance of one foot, or one ton 

 through three hundred million feet, more than twice the distance 

 round the world. 



It is probable that in the stars there is going on a transmuta- 

 tion of the elements, more complex ones being built out of the 

 atom of hydrogen, the simplest of all, whilst others are them- 

 selves disintegrating, and accompanying it is a liberation of 

 electrical energy. And what is going on spontaneously in the 

 stars has actually been accomplished artificially in the last year 

 or two by Sir Ernest Rutherford in the Cavendish Laboratory 

 at Cambridge. Although, as yet, the total amounts of sub- 

 atomic energy he has liberated have been minute, they are 

 enormous when compared with the quantities of matter 

 affected ; but it must be added that there is no evidence to 

 suggest that we shall be able to tap these stores of power for 

 human use in the near future. 



During the last few years our conception of the nature of 

 matter has entirely changed ; but before we consider it in 

 detail it will be well to summarise the situation briefly. The 

 nineteenth century dispelled the hazy ideas of the alchemists. 

 New elements were continually being discovered, and the more 

 exact investigation became the more likely did it appear that 

 these and those previously known were the ultimate materials 

 of the universe ; hence the very name " element," a collection 

 of atoms that cannot be distinguished from each other by any 

 chemical process. More than eighty were known. Mendeleeff 

 had found it possible to arrange a periodic scheme by 

 means of which undiscovered elements could be predicted to 

 fill the blank spaces in the table ; subsequent discovery showed 

 how accurately the properties of such elements had been fore- 

 told. Later on. Sir William Crookes thought of the evolution 

 of the elements from a fundamental something he called 

 " protyle," a hypothesis originally advanced by Prout in 181 5. 

 But with the advent of the twentieth century came the greatest 

 change. From many sides attacks were made on the idea of the 

 mutual independence of the elements, each of which had been 

 supposed to possess precise and exclusive characteristics. 

 It was shown that elements existed in which the atoms were not 

 all exactly alike, although the different specimens of such 

 elements were chemically indistinguishable from one another ; 



