24 JBumstead — Heating Effects produced by Rontgen Bays. 



much as possible. An attempt will be made to detect the 

 effect with a thermopile as well as with the radiometer ; and 

 to ascertain whether cathode rajs produce similar effects, as 

 might be expected. If the present results are due to some 

 hitherto unsuspected source of error, it is hoped that the error 

 may reveal itself as the conditions are varied. 



It is in no perfunctory spirit that I wish to express my thanks 

 to Professor J. J. Thomson for permission to work in the 

 Cavendish Laboratory and for the help which I constantly derived 

 from his advice and suggestions, some of which were vital to 

 the success of the experiments. I take pleasure in acknowl- 

 edging my great indebtedness to him. 



Conclusions. 



The present experiments indicate that when Rontgen rays are 

 equally absorbed in lead and iu zinc, approximately twice as 

 much heat is generated in the lead as in the zinc. It does not 

 appear possible to attribute this result to errors in the meas- 

 urements or in the theory underlying the experimental 

 method. 



To account for this effect the writer has been able to think 

 of only one hypothesis which is not in more or less direct con- 

 flict with experimental facts. This hypothesis is that, by means 

 of Rontgen rays, the atoms of certain elements may be artifici- 

 ally broken up and that the energy thus liberated forms a 

 part (and perhaps the greater part) of the energy which 

 appears when the rays are absorbed by matter. 



New Haven, Conn., Oct. 20, 1905. 



