30 ATTAINMENT OF VERY LOW TEMPERATURES. 



XIII. The Gasometer. 



The gasometer in use at University College, London, is of the 



simple type shown in fig. ii, A. It consists of two cylindrical tanks, 



one enclosing the other. The outer tank is 2,000 cm. high and 1,500 



cm. in diameter, the inner one is 1,800 cm. high and 1,450 cm. in 



Fig. 10. — Apparatus for generating the hydrogen. 



diameter. The outer tank is filled with water to just above the level 

 of the top of the nner tank. The supply pipe passes through the center 

 of the gasometer, and opens inside a small dome in the top of the inner 

 tank. This enables practically the whole of the gas to be easily ex- 

 pelled from the gasometer. 



