Mr Richardson, On an attempt, to detect radiation, etc. 175 



of the wire ff x to the testing system bg an earthed ring of tin 

 toil was put round the outside of the glass tube at d ; and inside 

 a fine steel spiral c which pressed tight against the glass was 



TJEPLER PUMP 

 MCLEOD GAUGE 

 »NO ty> r BULB. 



LErdEN 

 JAR 



supported by the stout copper wire k. The wire as passed of 

 course down the axis of this spiral. The lower part of the 

 apparatus was protected from spark gases and ultra-violet lio-ht 

 by being enclosed in the cigar-box h. It was found necessary to 

 protect also the upper part of the apparatus from ultra-violet 

 light. This was done by a cardboard arrangement p built to fit 

 it. The air was exhausted through the tube n which led by way 

 of a phosphorus pentoxide bulb to a Topler pump and McLeod 

 gauge. 



