634 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



material. It is a cylindrical glass tube of about 120 c.cm. capacity with 

 a three-way cock at the upper end and a simple cock at the lower. An 

 open glass tube is laterally and internally melted on to it and almost 

 reaches to its roof. Externally this tube bifurcates, one branch becoming 

 a manometer 80 cm. long and the other connected by a thick-walled 

 rubber tubing with a funnel B, held by a clamp on to the iron pillar of 



Fig. 106. 



a vertical stand. The whole is first filled with quicksilver, which com- 

 presses the air in A to a pressure regulated by the mercury levels in the 

 funnel and the manometer ; th.ese can be read off from the scale. In 

 order to keep this pressure constant by slow ingress of mercury from the 

 funnel, a spherical flask is inverted and fitted into the funnel neck. 

 This flask is also filled with mercury, which can only flow when the level 

 in the funnel is low enough to allow the admission of air into the neck 

 of the flask. The action of the flask is improved by the open tube 

 soldered into its neck, and the outflow of mercury takes place through a 



