Trowbridge and Rollins — Radium and Electron Theory. 79 



and afterwards to the upper layer. The bridge was competent 

 to detect a change in resistance of one hundredth-thousandth 

 of an ohm. On account of the difficulty of distinguishing 

 between a heating effect and what may be called an electrody- 

 namic effect, the observations occupied a comparatively short 

 interval of time. JSTo instantaneous effect was observed : a 

 very slight creeping deviation of the galvanometer mirror 

 came after a considerable interval of time, which might have 

 been due to change of temperature. It could not be ascribed 

 with reason to the presence of the radium. 



The light from the radium could be seen through a slab of 

 iron an inch thick ; yet this manifestation of energy passed 

 through the aluminium without any apparent effect upon the 

 mechanism of the electric current. Should we reason, there- 

 fore, from this negative experiment that the theory of the im- 

 material electron is supported, or that a theory of dissociative 

 effect on gases between each molecule of the metallic con- 

 ductor under the effect of a current is also negatived : for the 

 radium emanations, like the X-rays, can produce this dissocia- 

 tive effect in the passage of electricity through gases ? 



Mr. McKay, graduate student working in this laboratory, has 

 endeavored to detect the effect of the X-rays in changing the 

 apparent resistance of thin films of metals. The effect, if it 

 exists, is extremely small. He, however, is still continuing his 

 work upon this subject. 



Jefferson Physical Laboratory, 

 Harvard University. 



