302 Prof. R. W. Wood : Experimental Determination 



surface polished with rouge on pitch. The drop was mounted 

 on a slender stem of glass which was fused to the bottom of 

 the drawn-out portion of the bulb (PL III. fig. 2). In this 

 case the deposit began to appear in about three minutes 



Fig. 1. 



after the heat'ng-current had been started, and in ten 

 minutes it was so opaque as to be quite impervious to light. 

 As will be seen from the photograph, the deposit covers the 



