1050

THEORY AND PRACTICE OF ENGINEERING.

Book II

Fig. 1617.

CEMENT MILL.

Diving Bell . — The earliest account we have of a machine similar to that now in use isgiven by John Taisner, of Hainault, who was born in 1509, and went to Toledo with theEmperor Charles V. : “ he there saw two Greeks let themselves down under water, in a largeinverted cauldron, with a burning light, and rise to the surface again without being wet."Lorini, in a work upon fortification, also describes a diving machine, consisting of a squarebox bound round with iron, and furnished with windows; but no mention is made of sucha machine in England until Dr. Halley commenced his experiments; that ingeniousphilosopher contrived means to supply the diving machine with air, and at the same time tokeep the water from rising in it; his description of the apparatus in the PhilosophicalTransactions is as follows : —

“ The bell I made use of was of wood, containing about 60 cubic feet in its concavity,and of the form of a truncated cone, whose diameter at top was S feet and at bottom5 feet; this I coated with lead, so heavy that it would sink empty, and I distributed itsweight about its bottom, so that it would go down in a perpendicular situation, and noother ; in the top I fixed a strong but clear glass, to let in the light from above, and like-wise a cock to let out the hot air that had been breathed; and below, about a yard underthe bell, I placed a stage which hung by three ropes, each of which was charged with1 cwt. to keep it steady. This machine I suspended from the mast of a ship by a spreit.which was sufficiently secured by stays to the mast-head, and was directed by braces tocarry it over-board clear of the ship’s side, and to bring it again within board.

“ To supply air to this bell when under water, I caused a couple of barrels of about 36gallons each to be cased with lead, so as to sink when empty, each having a bung-hole inits lowest part, to let in water as the air in them condensed on their descent, and to let itout again, when they were drawn up full of water from below, and to a hole in the upper-most part of these barrels I fixed a leathern trunk or hose, well liquored with bees’-waxand oil, and long enough to fall below the bung-hole, being kept down by a weightappended, so that the air in the upper part of the barrels could not escape, unless the lowerends of these hose were first lifted up : I fitted these air barrels with tackle proper to makethem rise and fall alternately, after the manner of two buckets in a well, which was donewith so much ease, that two men, with less than half their strength, could perform all thelabour ; and in their descent they were directed by lines fastened to the under edge of thebell, which passed through rings placed on both sides the leathern hose of each barrel, sothat, sliding down by those lines, they came readily to the hand of the man who stood on thestage to receive them, and to take up the end of the hose into the bell. Through thesehose, as soon as the ends of the pipes came above the surface of the water in the barrels, allthe air that was included in the upper parts of them w as blown with great force into thebell, whilst the water entered at the bung-holes below and filled them : as soon as theair of one barrel had been thus received, upon a signal given it was drawn up, and at the