president's address. 15 



were available, ib would be equal to three and a half million times 

 the energy available by the explosion of an equal volume of detonating 

 gas — a mixture of one volume of oxygen with two volumes of hydrogen. 

 The major part of this energy comes, apparently, from the expulsion 

 of particles (that is, of atoms of helium) with enormous velocity. It 

 is easy to convey an idea of this magnitude in a form more realisable, 

 by giving it a somewhat mechanical turn. Suppose that the energy 

 in a ton of radium could be utilised in thirty years, instead of being 

 evolved at its invariable slow rate of 1760 years for half-disintegration, 

 it would suffice to propel a ship 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 

 million 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 enormously concentrated form. I have 

 attempted 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 lithium, a metal of the sodium column; and similar 

 experiments, of which there is not time to speak, indicate that thorium, 

 zirconium, titanium, and silicon are degraded into carbon; for solutions 

 of compounds of these, mixed with niton, invariably generated carbon 

 dioxide; while cerium, silver, mercury, and some other metals gave 

 none. One can imagine the very atoms themselves, exposed to 

 bombardment by enormously quickly moving helium atoms, failing 

 to withstand the impacts. Indeed, the argument a priori is a 

 strong one; if we know for certain that radium and its descen- 

 dants decompose spontaneously, evolving energy, why should not 

 other more stable elements decompose when subjected to enormous 

 strains ? 



This leads to the speculation whether, if elements are capable of 

 disintegration, the world may not have at its disposal a hitherto un- 

 suspected 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, provided 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 catalyser could be discovered which 

 would usefully increase their almost inconceivably slow rate of change, 



