﻿BOVIE— SCHUMANN RAYS 



source of light was kept constant. The short waves would have 

 been absorbed by the air had it not been replaced by the more 

 transparent fluorite. 



Spores of Cephalothecium roseum were 

 not killed by an exposure of 60 seconds, 

 and spores of a species of Monilia were 

 not killed by an exposure of 420 seconds 

 when the screen of rock salt was used, 

 while the spores of both forms 

 killed by an exposure of 15 

 seconds when the screen of rock 

 salt was replaced by the screen 

 of fluorite. 



In the two other methods the 

 apparatus shown in fig. 4 was used. A 

 glass tube A, 31 cm. in diameter, was 

 closed at one end with a glass stopper 

 B which was ground in. The other end 

 was closed by a brass ring C which had 

 a fluorite disk D sealed into its center. 

 The seal was made with De Khotenski 

 cement. A side tube E connected the 

 tube A with a mercury vacuum pump 

 and a McLeod gauge. The tube was 

 used in a vertical position. An upright 

 brass tube F was cemented to the glass 

 stopper. At its upper end it carried a 

 platform H. The platform was a 

 copper disk soldered to the head of a 

 screw J which passed through a nut 

 soldered to the top of the brass tube F. 

 By turning the screw the distance be- 

 tween the platform H and the fluorite 

 window D could be regulated. A 

 hemisphere K, 5 mm. in diameter, 

 platinum plate. Its open side was brazed to a small piece of brass 



support for t 



pins N; O, discharge tube. 



