on Radioactive Change. 583 



Hence the energy liberated in radioactive processes does not 

 disobey the law of the conservation o£ energy. 



It is not implied in this view that radioactivity, considered 

 with reference to the quantity of matter involved, is conserved 

 under all conceivable conditions, or that it will not ultimately 

 be found possible to control the processes that give rise to it. 

 The principle enunciated applies of course only to our present 

 state of experimental knowledge, which is satisfactorily 

 interpreted by its aid. 



The general evidence on which the principle is based 

 embraces the whole field of radioactivity. The experiments 

 of Becquerei and Curie have shown that the radiations from 

 uranium and radium respectively remain constant over long- 

 intervals of time. Mme. Curie put forward the view that 

 radioactivity was a specific property of the element in 

 question, and the successful separation of the element radium 

 from pitchblende was a direct result of this method of re- 

 garding the property. The possibility of separating from a 

 radio-element an intensely active constituent, although at 

 first sight contradictory, has afforded under closer examination 

 nothing but confirmation of this view. In all cases only a 

 part of the activity is removed, and this part is recovered 

 spontaneously by the radio-element in the course of time. 

 Mme. Curie's original position, that radioactivity is a specific 

 property of the element, must be considered to be beyond 

 question. Even if it should ultimately be found that uranium 

 and thorium are admixtures of these elements with a small 

 constant proportion of new radio-elements with corre- 

 spondingly intense activity, the general method of regarding 

 the subject is quite unaffected. 



In the next place, throughout the course of our investiga- 

 tions we have not observed a single instance in which radio- 

 activity has been created in an element not radioactive, or 

 destroyed or altered in one that is, and there is no case at 

 present on record in which such a creation or destruction can 

 be considered as established. It will be shown later that 

 radioactive change can onlv be of the nature of an atomic 

 disintegration, and hence this result is to be expected, from 

 the universal experience of chemistry in failing to transform 

 the elements. For the same reason it is not to be expected 

 that the rate of radioactive change would be affected by 

 known physical or chemical influences. Lastly, the principle 

 of the conservation of radioactivity is in agreement with the 

 energy relations of radioactive change. These will be con- 

 sidered more fully in § 7 , where it is shown that the energy 

 changes involved are of a much higher order of magnitude 

 than is the case in molecular change. 



