the diving-bell. 051 
•nrfior to keep the bell at any particular depth which the 
divers may think necessary ; or, by pulling it quite up^ tho 
descent may be continued to the very bottom. 
By another very ingenious contrivance, Mr. Spalding has 
rendered it possible for the divers to raise the bell, with all 
the weight appending to it, even to the surface of the water, 
or to stop it at any particular depth, as they think proper ; 
and thus they would still be safe, even though the rope de- 
signed for pulling up the bell should be broken. For this 
purpose the bell is divided into two cavities, both made as 
tight as possible. Just above the second bottom arc small 
slits in the sides of the bell, through which the water, enter- 
ing as the bell descends, displaces the air originally con- 
tained in its cavity, wdiich flies out at the upper orifice of a 
cock expressly fitted for that purpose. When this is done, 
the divers turn the handle which stops tlie cock ; so that it 
any more air were to get into the cavity, it could no longei 
be discharged through the orifice as before. If, therefore, 
the divers wish to raise themselves, they turn the cock, by 
Which a communication is made between the upper and 
Under cavities of the bell. The consequence is, that a 
quantity of air immediately enters the upper cavity, forces 
out a quantity of tire water coutained in it, and thus lenders 
the bell lighter by the whole weight of the water which is 
displaced. Thus, if a certain quantity of air is admitted 
into the upper cavity, the bell will descend very slowly ; it 
a greater quantity, it will neither ascend nor descend, but 
remain stationary ; and, if a larger quantity of air be still 
admitted it will rise to the top. It should be observed, 
however, that the air which is thus let out into the upper 
cavity, must immediately be replaced from the air-ban cl ; 
and the air is to be let out very slowly, or the bell will rise 
to the top with so great a velocity, that the divers will be 
in danger of being shaken out of their seats. But by fol- 
lowing these directions, every possible accident may be pre- 
vented, and persons may descend to very great depths with- 
out the smilest apprehension of danger. The bell also 
becomes so easily manageable in the water, that it may e 
conducted from one place to another, by a small boat, with 
Ihe greatest ease, and with perfect safety to those within. 
THE END. 
