﻿i9 16] BOVIE— SCHUMANN RAYS 23 



only with the spores on the top of the hemisphere, only those which 

 had been directly exposed to the rays of light were transferred . The 

 length of exposure required to kill the spores with and without the 

 salt screen was determined. The results obtained with the spores 

 of Trichothecium roseum are given in table I. 



An unknown amount of light was reflected from the surface of 

 the salt screen. In order to avoid this source of error, the experi- 

 ments were repeated, and the length of exposure required for killing 

 was determined first with the tube containing air at atmospheric 

 pressure, and then with the tube evacuated. The distance from 

 the top of the platinum hemisphere to the fluorite window D was 

 1 cm. This gave a filtration of 1 cm. of air. Lyman (27) has 

 shown that an air filter 1 cm. thick cuts out all of the shortest 

 Schumann rays. The results obtained with Trichothecium roseum 

 are given in table II. 



TABLE II 



I was not able to kill the tan-colored spores of Penicillium 

 brevicaule or the black spores of Stemphylium sp. (probably S. 



