CLARK. SURFACE TENSION BETWEEN LIQUIDS AND VAPORS. 365 



later is closed with a steel plug. The chamber was filled by heating to 

 about 250° and pumping out the air at one opening and allowing clean 

 dry mercury to run in at the other. In this way all air and moisture 

 could be removed from the mercury and the chamber. When full the 

 box was allowed to cool while still connected with the mercury supply. 



Figure 2. 



Then the second hole in the cover was closed by a steel plug securely 

 screwed in. 



The windows are of glass held in place by springs of heavy steel wire 

 wound horizontally around the box. On the bottom of the box are three 

 bosses provided with conical hole, groove, and plane respectively for the 

 support of the box which rests on three pillars to be described. 



