DIVING BELL. 
kept iu a proper posture for working, and 
the more so by means of a block, or cradle, 
supposed to be fastened over the lead, by 
which means tlie diver has not only the 
power of handling what is at the bottom ; 
but may at any time rest his arms from 
work ; g is the engine-rope by which it is 
let down and hauled up again from the 
bottom; zyu is called the life-line, witli a 
knot at y, so as the handle at 2 may always 
remain at a due distance for the diver to 
take hold thereof, in order to give any no- 
tice to the persons above, as, by agreement, 
by giving a certain number of pulls, or 
sudden twitches, which is immediately felt 
by the person that holds the line. The di- 
ver can tarry under water at least half an 
hour at one time, without the help of pipes, 
or any other air than what the engine con- 
tains. At i and w are two brass screw 
caps, or plugs, both which are to be opened 
as soon as the diver gets from the bottom 
to the water’s surface, in order to give him 
fresh air by help of a pair of bellows blow- 
ing at the latter ; at which, when the engine 
leaks, we likewise pump out the water. In 
deep water the diver is forced to make use 
of a saddle on his back, with a ridge touch- 
ing the tipper part of the engine, whereby 
he can keep his arms at a due distance out 
of the engine, which otherwise would be 
thrust in by the column of water pressing 
tliereon equal to the weight tliereof. 
The subject of submarine navigation was 
largely and pleasantly discanted upon by 
Mersennus, in his “ Tractatus de Magnetis 
Proprietatibus,” and Bishop Wilkins has 
given a chapter at some length on the sub- 
ject, in his “ Mathematical Magick,” (ed. 
1648)w'herehe affirms that Cornelius Dreble 
has proved, beyond all question, that the 
contrivance is feasible, by the experiments 
he made in England. The chapter of Wil- 
kins is entertaining for a sort of visionary 
facility with which he removes the difficul- 
ties, and enumerates the benefits of these 
submarine enterprizes. For letting out 
and taking in such things as the nature of 
the voyage may require, he recommends 
bags, or flexible tubes, somewhat resemb- 
ling the scupper bags of ships. The pro- 
gressive motion may, he observes, be pro- 
duced by fins or oars, which will operate 
with ease when the vessel is truly equipois- 
ed ; and if swiftness should not be obtained, 
he supposes the observations and discoveries 
to be made at the bottom of the sea would 
abundantly recompense for the defect. The 
greatest difficulty, in his apprehension, would 
be the necessity of renovating the air for 
respiration and combustion ; tor remedying 
which, besides the probability that custom 
may render men capable of living in air of 
inferior purity, he has several philosophical 
views and projects. The conveniences and 
advantages he enumerates are, 1. Privacy ; 
as a man may thus go to any part of the 
world invisibly, without being discovered 
or prevented. 2. Safety from the uncer- 
tainty of tides and tempests, that vex the 
surfece; from pirates and robbers; and 
from the ices that so much endanger other 
voyages towards the poles. 3. It may be 
of use to undermine and blow up a navy of 
enemies : 4. Or to relieve a blockaded 
place. 5. And as the prospect enlarges in 
the mind of our author, he proceeds to con- 
template the unspeakable benefit of sub- 
marine discoveries. Experiments on the 
ascent and descent of submerged bodies ; 
the exploration of the deep caverns and 
passages, and the waters of the ocean ; ob- 
servations on the nature and kinds of fishes, 
with allurements, artifices, and treacheries 
which may successfully be practised during 
so familiar a residence in their territories ; 
the food and oil they may afford ; the pro- 
bability of fresh springs for a supply of 
water at the bottom of the sea ; the facility 
of recovering submarine treasures, whether 
lost or naturally produced beneath the 
ocean ; and last of all he adds, that 
“ All kinds of arts and manufactures may 
be exercised in this vessel. The observa- 
tion made by it may be both written, and, 
if need were, printed here likewise. Se- 
veral colonies may thus inhabit, having their 
children born and bred up without the 
knowledge of land, who could not chuse 
but be amazed with strange conceits upon 
the discovery of this upper world.” 
The only modern instance of actual sub- 
marine navigation is that of Mr. Bushnel, 
recorded in the Transactions of the Ameri- 
can Society, Vol. IV. The external shape 
of his vessel bore some resemblance to two 
upper tortoise shells of equal size joined to- 
gether ; the place of entrance into the ves- 
sel being represented by the opening made 
by the swell of the shells at the head of tho 
animal. The inside was capable of contain- 
ing the operator, and air sufficient to sup- 
port him thii’ty minutes without receiving 
fresh air. At the bottom, opposite the en- 
trance, was fixed a quantity of lead for bal- 
last. At one edge, which was directly be- 
fore the operator, who sat upright, was an 
oar for rowing forwards and backwards. At 
