880 THE OCEAN. 
manage the “ bell,” and they lower it into the wa- 
ter slowly until it reaches the bottom or until the 
diver makes a signal to stop. The diving bell sinks 
by its own weight. As it goes down, water cannot 
get into it because it is full of air which cannot 
escape. The air however becomes very dense and, at 
great depths, very oppressive. 
When the bell touches the bottom, the diver gets 
off the seat and works around inside the bell at 
whatever is undertaken. He can have a light with 
him, and various tools, and can labor for a short 
time, as though not under water. The air however 
soon becomes vitiated by his breathing and by the 
burning of his light, so that he would suffocate after 
a while, unless fresh air was supplied. Furnishing 
fresh air by the means of a pump and tube connec- 
ting with the bell was one of the first improvements. 
It has been found, in practice, however, that in 
the very best form the diving-bell is a cumbersome, 
clumsy affair. The latest and most approved model 
is constructed in three compartments, one of which 
is filled with compressed air, and one designed to 
be filled with water, to assist in sinking the machine 
while the whole apparatus is under the control of 
the diver. " But he is limited in his work to the 
small space bounded by the sides of the bell. As this 
heavy sub-marine house cannot be moved, in a later- 
al direction, without great trouble and asthe move- 
ments of the diver is so closely circumscribed as 
to render him useless in many kinds of submarine 
work, a sort of water-proof armor has been inven- 
ted which seems to answer every purpose. 
