Submarine Appliances And Their Uses
Deep Sea Diving, &c., &c.

We are familiar with the experiment of placing an inverted tumbler in a bowl of water, and seeing the water excluded from the tumbler by the air inside it. Perhaps it was to some such experiment as this that the conception of the diving bell was due. As is well known, the pressure of water increases with the depth. For all practical purposes, this pressure can be taken at four and a quarter pounds to every ten feet. See page 93 for further particulars. : J . Sink a diving bell to a depth of, say, 33ft., and the air inside it will be compressed to about half its original volume, and the bell itself will be about half filled with water. But keep up a supply of air at a pressure equal to the depth of water at which the bell is submerged, and you will not only keep the water down to the cutting' edge, but you will ventilate the bell and make it possible for its occupants to work lor hours at a stretch. Roger Tradition gives Roger Bacon (a.d. 1250) the credit for being the originator of the (A.D. diving bell, but actual records are lost in antiquity. 1250). Of the records preserved to us, probably one of the most trustworthy is an ac- count given in Schott’s work, Technica Curiosa, printed at Nuremberg in the year 1664, which quoted from one John Taisnier, who was in the service of Charles V. I his account describes an experiment which took place at loledo, Spain, in the year 1538, before the Emperor and some thousands of spectators, when two Greeks descended into the water in a large “ kettle,” suspended by ropes, with its mouth downwards. The “ ‘ kettle ’ was equipoised by lead fixed round its mouth.” The men came up dry, and a lighted candle, which they had taken down with them, was still burning. Sturmius. Sturmius, too, in the 16th century, introduced a diving bell, in which he carried a number of bottles of air, which were broken as the air in the bell required revivifying. Francis Bacon, in the Novum Organum, lib. 11, makes the following reference to a machine, or reservoir, of air to which labourers upon wrecks might resort whenever they required to take breath :—• “A hollow vessel., made of metal, was let down equally to the surface of the water, and thus carried with it to the bottom of the sea the whole of the air which it contained. It stood upon three feet—like a tripod—which were in length something less than the height of a man, so that the diver, when he was no longer able to contain his breath, could put his head into the vessel and, having filled his lungs again, return to his work.” i65