DIVING BELL. 
air is admitted, it rises. If therefore tlie 
divers liave a mind to raise themselves, they 
turn the small cock, by which a commu- 
nication is made between the upper and 
under cavities of the bell ; the consequence 
of this is, that a quantity of air immediately 
enters the upper cavity, forces out a quan- 
tity of water contained in it, and thus ren- 
ders the bell lighter by the whole weight of 
the water which is displaced thus. If a cer- 
tain quantity of air is admitted into the 
upper cavity, the bell will descend very 
slowdy ; if a greater quantity, it will neither 
ascend nor descend, but remain stationary ; 
and if a larger quantity of air be still admit- 
ted, it will rise to the top. It is to be ob- 
.served, how ever, that the air wdiicli is thus 
let out into the nppercavity, must be imme- 
diately replaced from the air barrel, and the 
air is to be let out very slowly, or the bell 
will rise to the top with so great velocity, 
that the divers will be in danger of being 
shaken out of their seats ; but by following 
these directions, every possible accident 
may be prevented, and people may descend 
to very great depth without the least ap- 
prehension of danger, the bell also becomes 
so easily manageable in the water that it 
may be conducted from one place to an- 
other by a small boat with the greatest ease, 
and with perfect safety to those who are 
in it. 
Instead of wooden seats, used by Dr. 
Halley, Mr. Spalding made use of ropes 
suspended by hooks h, h, h, and on these 
ropes the divers may sit without any incon- 
venience, there are two windows made of 
thick strong glass for admitting light to the 
divers ; N represents an air cask with its 
tackle, and C P the flexible pipe through 
which the air is admitted to the bell, in the 
ascent and descent of this cask, the pipe is 
kept down by a small appended weight, as 
in Dr. Halley’s machine ; R is a small cock 
by which the hot air is discharged as often 
as it becomes troublesome. 
Mr. Spalding is of opinion, that one air 
barrel, capable of containing thirty gallons, 
is sufficient for an^ordinary machine. 
In tig. 1 and 2 , are shewn representations 
of a frame for supporting a diving bell, and 
transporting it from place to place upon 
the water. Fig. 1, is a side elevation, and 
fig. 2, a section of it. The same letters re- 
fer to both figures. A B, fig. 2, are sections 
of two barges, such as are used upoo the 
Thames, at London : D E F, is a frame lay- 
ing across the barges, and supporting a 
beam, G, from which hangs a strong block 
for the rope by which the bell, H, is suspend- 
ed ; the other end of the rope goes round a 
windlass, «, with a rachet wheel and click 
to raise and lower the bell as occasion re- 
quires : h d are smaller blocks, for the ropes 
to draw up the air barrels ; e f are rollers, 
turned by winches, fixed on the opposite 
barge to the windlass, a ; the ropes are 
wound round these rollers in contrary di- 
rections, and the winches come close toge- 
ther, so that one man can turn them both 
at once, and when one rope descends, the 
other ascends, so as to give a constant sup- 
ply of air to the divers under the bell, H. 
When the divers wish to come up, they give 
a signal to that purpose, and the windlass is 
turned by men until the bottom of the bell 
is brought above water; a small boat or 
raft is rowed under the bell to take the 
divers out : the same method is to be used 
to get them in, and this will be done without 
wetting them, or any other inconvenience. 
Several small bells of very different tones 
should be fixed to the beam G, and strings 
fastened to them should go into the bell for 
the divers to ring, as signals to the workmen 
in the barges above. The barges should be 
well secured together by cross beams. 
Several other machines have been con- 
trived to answer the purposes of the diving- 
bell ; one of which, fig. 4, was invented in 
1753, by Rowe, Esq. and published in 
the Universal Magazine. 
The engine is a trunk, or hollow vessel, of 
copper or brass, of sufficient strength to re- 
sist the pressures of deep waters, and di- 
mensions to contain the body of a man, 
supposed to enter therein feet foremost at 
t, bent at the bearing of his knees at I, for 
the more convenient going between rocks 
and great stones; at fc, and on the other 
side, are holes for his arms to pass through, 
and a glass for his sight at n. h represents 
a sleeve made of soft leather, lined with 
fine cloth, exactly to fit the diver, and fas- 
tened to the body of the engine at k, where 
the arms come through; which is likewise 
defended by a soft quilting, to prevent the 
arms from being hurt by pressure, and the 
sleeves from being thrust into the engine ; 
d d represents a cover to fit the head of the 
engine, fastened down with screws, and 
leatlier between the borders, so as to pre- 
vent leaking in any depth of water ; a b 
represents a plate of lead, to be fastened 
before the engine, in a straight line, passing 
between the arms, not only as a proper 
weight to sink the engine, but as a balance 
thereto ; whereby the diver will always be 
Mm2 
