A HISTORY OF SCIENCE 



" Radium bromide of three hundred thousand activ- 

 ity was placed in a sealed glass tube inside a rubber 

 thermometer-holder, which was tightly screwed to 

 prevent any emanation of any kind from passing 

 through the joints. This was placed under a heavy 

 silver tureen fully one-sixteenth of an inch in thickness ; 

 upon this were placed four copper plates, such as are 

 used for engraving; upon these a heavy graduated 

 measuring-glass 10 cm. in diameter; this was filled 

 with water to a depth of six inches. A diamond was 

 suspended in the water and immediately phosphor- 

 esced. Whenever the tube of radium was drawn 

 away more than two or three feet the phosphor- 

 esce ce ceased; whenever it was placed under the 

 tureen the diamond immediately phosphoresced 

 again. This experiment proves that the active 

 power of the radium penetrated the following sub- 

 stances : 



" Glass in the form of a tube, sealed at both ends ; the 

 rubber thermometer-holder ; silver tureen ; four copper 

 plates; a glass vase or measuring-glass one-quarter of 

 an inch in thickness ; three inches of water. There is no 

 previously known substance or agent, whether it be 

 even light or electricity, that possesses such wonder- 

 fully penetrative powers." 5 



The Nature of Emanations from Radio-active Bodies 



What, then, is the nature of these radiations ? Are 

 they actually material particles hurled through the 

 ether? Or are they like light and possibly the 

 Roentgen rays simply undulations in the ether ? As 

 yet this question is an open one, although several of 



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