DIVING BELL 



65 



the sides of the machine. The moment then that the air, by its expansion from 

 diminished resistance, or by the introduction from above of a greater volume than can 



632 





be sustained by the water below, reaches, in its 

 downward passage, the level of these chambers, 

 following the direction of least resistance, it 

 passes through these channels and escapes into 

 the surrounding water, without of course affecting 

 the movement of the machine in the least. 



The pump for supplying air to the diving 

 bell or other suitable vessel is represented in 

 figs. 632 and 633, and is constructed as follows : 

 D is a cylinder, opening at the upper part into 

 a chamber or chambers F F, separated by a parti- 

 tion E. On the side of each of these chambers 

 there is a valve H H, opening inwards, and at 

 the upper part of the same are two valves 1 1, 

 opening outwards into the valve chamber G. 

 Outside the opening for each of the valves H, H, 

 there is a cup, into which the end of the water 

 supply pipe M passes; by this means a small 

 stream of water is supplied to the cup, and is 

 drawn from it into the chamber F to supply the 

 waste in the operation of pumping. The valve 

 chamber o is covered with a jacket k, having a 

 space between it and the valve chamber that is 

 filled with water from the water-pipe M, which 

 affords a stream of cold water to carry off the 

 heat from the condensed air which is forced into 

 the chamber. The water thus supplied circu- 

 lates through the tubes in the chamber and 

 round them in the jacket, and thus cools the air 

 in these tubes ; it is then conveyed so as to be 



Yoj,. H. F 



633 



