September S, 1911] 



SCIENCE 



299 



of 15,000 tons, with engines of 15,000 horse- 

 power, at the rate of 15 knots an hour, for 

 30 years — practically the lifetime of the 

 ship. To do this actually requires a mil- 

 lion and a half tons of coal. 



It is easily seen that the virtue of the 

 energy of the radium consists in the small 

 weight in which it is contained; in other 

 words, the radium-energy is in an enor- 

 mously concentrated form. I have at- 

 tempted to apply the energy contained in 

 niton to various purposes; it decomposes 

 water, ammonia, hydrogen chloride and 

 carbon dioxide, each into its constituents; 

 further experiments on its action on salts 

 of copper appeared to show that the metal 

 copper was converted partially into lith- 

 ium, a metal of the sodium column; and 

 similar experiments, of which there is not 

 time to speak, indicate that thorium, zir- 

 conium, titanium and silicon are degraded 

 into carbon ; for solutions of compounds of 

 these, mixed with niton, invariably gener- 

 ated carbon dioxide; while cerium, silver, 

 mercury and some other metals gave none. 

 One can imagine the very atoms them- 

 selves, exposed to bombardment by enor- 

 mously quickly moving helium atoms fail- 

 ing to withstand the impacts. Indeed, the 

 argument a priori is a strong one; if we 

 know for certain that radium and its de- 

 scendants decompose spontaneously, evolv- 

 ing energy, why should not other more 

 stable elements decompose when subjected 

 to enormous strains 1 



This leads to the speculation whether, if 

 elements are capable of disintegration, the 

 world may not have at its disposal a hith- 

 erto unsuspected source of energy. If 

 radium were to evolve its stored-up energy 

 at the same rate that gun-cotton does, we 

 should have an undreamt-of explosive; 

 could we control the rate we should have a 

 useful and potent source of energy, pro- 

 vided always that a sufficient supply of 



radium were forthcoming. But the supply 

 is certainly a very limited one; and it can 

 be safely affirmed that the production will 

 never surpass half an ounce a year. If, 

 however, the elements which we have been 

 used to consider as permanent are capable 

 of changing with evolution of energy ; if 

 some form of catalyzer could be discovered 

 which would usefully increase their almost 

 inconceivably slow rate of change, then it 

 is not too much to say that the whole fu- 

 ture of our race would be altered. 



The whole progress of the human race 

 has indeed been due to individual members 

 discovering means of concentrating energy, 

 and of transforming one form into another. 

 The carnivorous animals strike with their 

 paws and crush with their teeth; the first 

 man who aided his arm with a stick in 

 striking a blow discovered how to concen- 

 trate his small supply of kinetic energy; 

 the first man who used a spear found that 

 its sharp point in motion represented a 

 still more concentrated form; the arrow 

 was a further advance, for the spear was 

 then propelled by mechanical means ; the 

 bolt of the crossbow, the bullet shot forth 

 by compressed hot gas, first derived from 

 black powder, later, from high explosives; 

 all these represent progress. To take an- 

 other sequence : the preparation of oxygen 

 by Priestley applied energy to oxide of 

 mercury in the form of heat; Davy im- 

 proved on this when he concentrated elec- 

 trical energy into the tip of a thin wire by 

 aid of a powerful battery, and isolated 

 potassium and sodium. 



Great progress has been made during the 

 past century in effecting the conversion of 

 one form of energy into others, with as 

 little useless expenditure as possible. Let 

 me illustrate by examples : A good steam 

 engine converts about one eighth of the 

 potential energy of the fuel into useful 

 work ; seven eighths are lost as unused heat 



