540 
DIVING. 
from the lowermost parts: for which pur- 
pose a flexible leather tube, about two feet 
long, is fixed to the upper end of the copper 
tube at b ; and to the other end of this tube is 
fixed an ivory mouth-piece, by which the 
diver draws in the air. 
A great improvement in the diving-bell 
was made by the late Mr. Spalding, of 
Edinburgh. This construction seems de- 
signed to remedy some inconveniences of 
Dr. Halley’s, which are very evident, and ot 
a very dangerous tendency. These are, 1. 
By Dr. Halley’s construction the sinking or 
raising of the bell depends entirely on the 
people who are at the surface of the water ; 
and as the bell even when in the water lias a 
very considerable weight, the raising it not 
only requires a great deal ol labour, but 
there is a possibility of the rope breaking by 
which it is raised, and thus every person in 
-the bell would inevitably perish. 2. As there 
are; in many parts of the sea, rocks which 
lie at a considerable depth, the figure of which 
cannot possibly be perceived from above, 
there is danger that some of their ragged 
prominences may catch hold of one ot the 
edges of the bell in its descent, and thus 
overset it before any signal can be given to 
'these above, which would infallibly be at- 
tended with the destruction of the people in 
‘the bell ; and as it must always be unknown, 
before trial, what kind of a bottom the sea has 
m any place, it is plain, tliat without some con- 
trivance to obviate this last, danger, the de- 
scent in Dr. Halley’s diving-bell is not at all 
eligible. 
How these inconveniences are remedied 
by Mr. Spalding’s new contrivance, will be 
easily understood from the following descrip- 
tion. A B C D, fig. 52, represents a sec- 
tion of the bell, which is made of wooci ; c, e, 
are iron hooks, by means' of which it is sus- 
pended by ropes <4 BF e, and (I A E c, and 
QS, as expressed in the figure: c, c, are 
iron hooks, to which are appended leaden 
weights, that keep the mouth of the bell al- 
ways parallel to the surface of the water, 
whether the machine taken altogether is 
lighter or heavier than an equal bulk of wa- 
ter. By these weights alone, however, the 
bed would not sink: another is therefore 
added, represented at L, and which can be 
raised pr lowered at pleasure, by means of a 
rope passing over the pulley a, and fastened 
to one of the sides of the bell at M. As the 
bell descends, this weight, called by Mr. 
Spalding the balance-weight, hangs down a 
considerable way below the mouth of the 
bell. Jn case the edge of the bell is caught 
by any obstacle, the balance-weight is im- 
mediately lowered down so that it may rest 
upon the bottom. By this means the bell is 
lightened, so that all danger of oversetting is 
removed ; for being lighter, without the ba- 
lance-weight, than an equal bulk of water, 
it is evident that the bell will rise, as far as 
the length of the rope affixed to the balance- 
weight will allow it. This weight, therefore, 
will serve as a kind of anchor to keep the 
bell at any particular depth which the divers 
may think necessary ; or by pulling it quite 
up the descent may be continued to the very 
bottom. 
By another very ingenious contrivance Mr. 
Spalding rendered it possible for the divers 
to raise the bell, with all the weights append- 
ed to it, even to the surface, or to stop at any 
particular depth, as they think proper ; and 
thus they could still be safe, even though the 
rope designed for pulling up the bell was 
broken. For this purpose the bell is divided 
into two cavities, both of which are made as 
tight as possible. Just above the second bot- 
tom EF, are small slits in the sides of the heli, 
through which the water, entering as the bell 
descends, displaces the air originally contain- 
ed in its cavity, which flier, out at the upper 
orifice of the cock G H. When this is done, 
the divers turn the handle G, which stops the 
cock ; so that if any more air was to get into 
the cavity AEFB, it could no longer be 
discharged through the orifice H as before. 
When this cavity is full of water the bell 
sinks ; but when a considerable quantity of 
air is admitted it rises. If therefore the 
divers have a mind to raise themselves, they 
turn the small cockG, by which a comminu- 
tion is made between the upper and under 
cavities of the bell. The consequence of 
this is, that a quantity of air immediately en- 
ters the upper cavity, forces out a quantity 
of the water contained it, and thus renders . 
the bell lighter by the whole weight of the 
water which is displaced. Thus if a certain 
quantity of air is admitted iuto the upper ca- 
vity the bell will descend very slowly ; if 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 is to be observed, how- 
ever, that the air which is thus let out into 
the upper cavity must be immediately re- 
placed 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 beini^ shaken out of their 
seats. But by following these directions 
every possible accident may be prevented, 
and people may descend to very great depths 
without the least apprehension of danger. 
The bell also becomes so easily manageable 
in the water, that it may be conducted from 
one place to another 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. Hal- 
ley, Mr. Spalding made use of ropes suspend- 
ed by hooks bbb ; and on these ropes the 
divers may sit without any inconvenience. 
There are two windows made of thick strong 
glass, for admitting light to the divers. N 
represents an air-cask with its tackle, and 
OCP the flexible pipe through which the 
air is admitted to the bell. Jn the ascent and 
descent oflthis cask the pipe is kept down by 
a small appended weight, as in Dr. Blalley’s 
machine. R is a small cock by which the , 
hot air is discharged as often as it becomes 
troublesome. Annexed is a representation of 
the whole diving apparatus* which, no doubt, 
will be readily understood without any fur- 
ther explanation. Two ai r-barrels are repre- 
sented in this figure ; but Mr. Spalding was 
of opinion that one, capable of containing 
thirty gallons, is sufficient for an ordinary 
machine. See fig. 53. 
Mr. Adam Walker recommends, for the 
purposes of diving, a conical tub of wood 
three feet diameter at the bottom, two and a 
half feet at the top, and three feet high, so 
loaded with lead at the bottom as just to sink 
itself, with a small seat for the diver. See 
Plate, fig. 54. A bent metal tube is attach- 
ed to the outside of the bell, as abc, with a 
stop-cock a, and a flexible leathern tube to 
the other end at c; this tube terminates 
in a forcing air-pump fastened to the side 
of a ship; d is a solid piston acted upon 
by a lever e ; upon the piston being drawn 
up the air rushes in at the valve g, and 
tills ihe space n ; in its descent the valve g 
shuts, and the conical valve o opens, and 
thus the air is forced down the hose into the 
bell. The pump is kept working, while the 
diver, by opening and shutting the stop- 
cock, is abundantly supplied with fresh air, 
and that which is vitiated is forced out at the 
bottom of the bell. By a machine of this 
kind live greatest part of the wreck was saved 
from the rich ship Belgiosa. 
Mr. Smeaton’s diving-bell was a square 
chest of cast-iron, four and a half feet in 
height, four and a half feet in length, and 
three feet wide, and afforded room for two 
men to work in it. It was supplied with fresh 
air by a forcing-pump. This was used with 
great success at Ramsgate. Other contriv- 
ances as intimated before have been used 
for diving to small depths ; such as strong 
cases for the body, to keep oft' the pressure 
of the water, which were supplied with fresh 
air by pipes from live surface. 
The most effectual of this kind is a method 
put in practice by a gentleman of Devonshire. 
He has contrived a large case of si rong leather, 
perfectly water-proof, which may hold about 
half a hogshead |of air. This is so adapted, 
that, when he shuts himself up in this case, he 
may walk at the bottom of the sea, and go 
into any part of a Wrecked vessel, and deliver 
out the goods. This method, we are told, 
lie has practised for many years, and has thus 
acquired a large fortune, It would be a con- 
siderable improvement of this machine to 
condense the air in it as much as possible be- 
fore the diver descended, as he would thus be 
furnished with an atmosphere endued with 
an elasticity sufficient to resist the weight of 
water, which otherwise would squeeze his 
case into much less room than it originally 
took up. The condensed air would serve 
for respiration a much longer time than that 
which is in its ordinary slate. 
Diving-bladder, a machine invented by 
Borelli, and by him preferred, though without 
any good reason, to the diving-bell. It is a 
globular vessel of brass or copper, about two 
feet in diameter, formed to contain the 
diver’s head. It is fixed to a goat’s-skin, ha- 
bit, exactly fitted to his person. Within the 
vessel are pipes, by means of which a circu- 
lation of air is contrived ; and the person 
carries an air-pump by his side, by which lie 
can make himself heavier or lighter, as fishes 
do by contracting or dilating their air-blad- 
ders. By this means he thought all the ob- 
jections to which other diving-machines are 
liable were entirely obviated, and particu- 
larly that of want of air; the air which had 
been breathed being, as he imagined, de- 
prived of its noxious qualities by circulating 
through the pipes. These advantages, how- 
ever, it is evident, are only imaginary. The 
diver’s limbs being defended from the pres- 
sure of the water only by a goat’s skin, 
would infallibly be crushed if he descended 
to any considerable depth ; and from the 
discoveries made by Dr. Priestley and others, 
it is abundantly evident that air which is 
once rendered foul by breathing, cannot in 
any degree be restored by circulation through 
