1?G DIVING BELL. 



obstacle, the balance \voight is immediately lowered down, so that it 

 may rest upon the bottom. By this means the bell is lightened, and all 

 danger of oversetting is removed ; for being lighter without the balance 

 weight than an equal bulk of water, it is evident that the bell will rise 

 as far as the length of rope affixed to the balance weight will permit. 

 This serves therefore as a sort of anchor, to keep the bell at any desired 

 depth. Instead of wooden seats, ropes are used, suspended by hooks 

 across the bottom of the bell, and on these the diver stands; two 

 windows made of strong thick glass are fixed near the top of the bell. 



Two air casks (each will contain forty gallons) having a flexible tube, 

 are attached with a cock to discharge the hot air when needed. By 

 another very ingenious contrivance, the diver can raise the bell to the 

 surface, or stop it at any desired depth, and thus safety is preserved, 

 although the communicating rope with those above may be broken. 

 This is accomplished by affixing a second bell of smaller dimensions 

 over the large one; in the top of which is a cock, which can be opened 

 by the diver to let the air escape from the upper bell ; there is also 

 another cock in the top, which permits the air to pass out of the great 

 bell and rise into the smaller one. There is also space left between the 

 two bells, so that the water has free entrance into both, and when the 

 bell is first let down the upper cock is opened, therefore the air escapes 

 and lets in the water. In this state the bell is lighter than an equal 

 bulk of water without the balance weight, though, with the addition of it, 

 it is heavier. Now, if the divers wish to raise themselves, they turn the 

 lower cock, by which a communication is made between the bells, and 

 the quantity of air rushing from the lower to the upper bell forces the 

 water out, and this air being replaced from the air barrel, thus renders 

 the bell lighter, by the whole weight of water which is displaced. 

 Therefore, if a certain quafuity of air is admitted into the upper cavity, 

 the bell, with the balance, will descend very slowly ; if a greater quantity, 

 it will remain stationary, and if a larger quantity of air is still admitted, 

 it will rise to the top. 



The diving bell which is commonly used, resembles a large box 

 without its bottom ; it is in length six feet by five and a half, and is 

 four and a half high. It is formed of cast iron, very thick, and its own 

 weight sinks it ; it is made in one piece, air tight, and the thickness of 

 the sides prevents the possibility of its being injured by fracture in 

 descent; its weight is about four tons. In the top of this bell is a round 

 aperture, communicating by a number of small circular holes with the 

 interior, where the holes are all covered and closed by a piece of thick 



