DIVING BELL 



nautilus gradually sinks. As soon as it is fairly under water, in order that tho 

 descent may bo quiet and without shock, the water-cock b, is closed. Tho receiver at 

 the surface being previously charged by the air-pump to a density somewhat greater 

 than that of the water at the depth proposed to attain, one of the branch-cocks on tho 

 pipe c c, connecting the chambers at top, is opened, and the air rushes into the work- 

 ing chamber, gradually condensing until a density equal to the density of the water 

 without is attained ; this is indicated by proper air and water gauges. These gauges 

 marking equal points, showing the equilibrium of forces without and within, the cover 

 to the bottom z is removed or raised, and communication is made with the under 

 water surface, on which the nautilus is resting. In order to move about in localities 

 where tides or currents do not affect operations, it is only necessary for the workman 

 to step out of the bottom of the nautilus, and placing the hands against its sides, the 

 operator may move it (by pushing) in any direction. 



Where currents or tides, however, have sway, it becomes necessary to depend upon 

 fixed points from which movements may be made in any direction. This is accom- 

 plished by placing, in the bottom of the nautilus, stuffing boxes of peculiar construc- 

 tion (M M, jig. 630), through which cables may pass over pulleys to the external sides, 



631 



2;]!!^3^ 



thence up through tubes (to prevent their being worn), to and over oscillating or 



