The divers of Astracan, employed in the fishery there, can remain only seven minutes under water280. The divers in Holland seem to have been more expert. An observer, during the time they were under water, was obliged to breathe at least ten times281. Those who collect pearl-shells in the East Indies can remain under water a quarter of an hour, though some are of opinion that it is possible to continue longer; and Mersenne mentions a diver, named John Barrinus, who could dive under water for six hours282. How far this may be true I shall leave others to judge.
[The various statements regarding the length of time during which divers can remain under water, unaided by apparatus for renewing the supply of atmospheric air, are not borne out by the experience of those who have carefully observed and noted these phænomena. The average time which human beings can remain in the water under these conditions, is one and a half or two minutes283; extraordinary cases are attested where five and even six minutes have elapsed, but these are exceedingly rare instances and far beyond the average; no instance of a longer time than this is recorded on credible authority. Some interesting remarks on this point were made not long since by a member of the Asiatic Society to Dr. Faraday. The lungs in their natural state are charged with a large quantity of impure air; this being a portion of the carbonic acid gas which is formed during respiration, but which, after each expiration, remains lodged in the involved passages of the pulmonary tubes. By breathing hard for a short time, as a person does after violent exercise, this impure air is expelled, and its place is supplied by pure atmospheric air, by which a person will be enabled to hold his breath much longer than without such precaution. Dr. Faraday states, that although he could only hold his breath, after breathing in the ordinary way, for about three-fourths of a minute, and that with great difficulty, he felt no inconvenience, after making eight or ten forced respirations to clear the lungs, until the mouth and nostrils had been closed more than a minute and a half; and that he continued to hold breath to the end of the second minute. A knowledge of this fact may enable a diver to remain under water at least twice as long as he otherwise could do. It is suggested that possibly the exertion of swimming may have the effect of occasioning the lungs to be cleared, so that persons accustomed to diving may unconsciously avail themselves of this preparatory measure.]
It is certain, however, that men began very early to contrive means for supplying divers with air under the water, and of thereby enabling them to remain under it much longer. For this purpose the diving-bell, campana urinatoria, was invented. Those who had no idea of this machine, might have easily been led to it by the following experiment. If a drinking-glass inverted be immersed in water, in such a manner that the surface of the water may rise equally around the edge of the glass, it will be found that the glass does not become filled with water, even when pressed down to the greatest depth; for where there is air no other body can enter, and by the above precaution the air cannot be expelled by the water. In like manner, if a bell of metal be constructed under which the diver can stand on a stool suspended from it so that the edge of the bell may reach to about his knee, the upper part of his body will be secured from water, and he can, even at the bottom of the sea, breathe the air enclosed in the bell.
The invention of this bell is generally assigned to the sixteenth century, and I am of opinion that it was little known before that period. We read, however, that even in the time of Aristotle divers used a kind of kettle to enable them to continue longer under water; but the manner in which it was employed is not clearly described.
The oldest information we have respecting the use of the diving-bell in Europe is that of John Taisnier, quoted by Schott284. The former, who was born at Hainault in 1509, had a place at court under Charles V., whom he attended on his voyage to Africa. He relates in what manner he saw at Toledo, in the presence of the emperor and several thousand spectators, two Greeks let themselves down under water, in a large inverted kettle, with a burning light, and rise up again without being wet. It appears that this art was then new to the emperor and the Spaniards, and that the Greeks were induced to make the experiment in order to prove the possibility of it. After this period the use of the diving-bell seems to have become still better known. It is described more than once in the works of Lord Bacon, who explains its effects, and remarks that it was invented to facilitate labour under the water285.
In the latter part of the seventeenth century the diving-bell was sometimes employed in great undertakings. When the English, in the year 1588, dispersed the Spanish fleet called the Invincible Armada, part of the ships went to the bottom near the Isle of Mull, on the western coast of Scotland; and some of these, according to the account of the Spanish prisoners, contained great riches. This information excited, from time to time, the avarice of speculators, and gave rise to several attempts to procure part of the lost treasure. In the year 1665, a person was so fortunate as to bring up some cannon, which, however, were not sufficient to defray the expenses. Of these attempts, and the kind of diving-bell used, an account has been given by a Scotsman named Sinclair286; but Paschius287, Leupold288 and others falsely ascribe the invention of this machine to that learned man. He himself does not lay claim to this honour; but says only, that he conversed with the artist and measured the machine.
Some years after attempts of the like kind were renewed. William Phipps, the son of a blacksmith, born in America in 1650, and who had been brought up as a ship-carpenter at Boston, formed a project for searching and unloading a rich Spanish ship sunk on the coast of Hispaniola, and represented his plan in such a plausible manner, that king Charles II. gave him a ship, and furnished him with every thing necessary for the undertaking. He set sail in the year 1683; but, being unsuccessful, returned again in great poverty, though with a firm conviction of the possibility of his scheme. He endeavoured, therefore, to procure another vessel from James II., who was then on the throne; but as he failed in this, he tried to find the means of executing his design by the support of private persons, and, according to the prevailing practice, opened for that purpose a subscription. At first he was laughed at; but at length the duke of Albemarle, son of the celebrated General Monk, took part in it, and advanced a considerable sum to enable him to make the necessary preparations for a new voyage. Phipps soon collected the remainder; and in 1687 set sail in a ship of two hundred tons burthen to try his fortune once more, having previously engaged to divide the profit according to the twenty shares of which the subscription consisted. At first, all his labour proved fruitless; but at last, when his patience was almost entirely exhausted, he was so lucky as to bring up, from the depth of six or seven fathoms, so much treasure, that he returned to England with the value of two hundred thousand pounds sterling. Of this sum he himself got about sixteen, others say twenty thousand, and the duke ninety thousand pounds. After he came back, some persons endeavoured to persuade the king to seize both the ship and the cargo, under a pretence that Phipps, when he solicited for his Majesty’s permission, had not given accurate information respecting the business. But the king answered, with much greatness of mind, that he knew Phipps to be an honest man, and that he and his friends should share the whole among them, had he returned with double the value. His Majesty even conferred upon him the honour of knighthood, to show how much he was satisfied with his conduct. This Phipps was afterwards high sheriff of New England, and died at London, greatly respected, in 1693. This affair was attended with such good consequences to the duke of Albemarle, that he obtained from the king the governorship of Jamaica, in order to try his fortune with other ships sunk in that neighbourhood. But whether it was that the gold had been already taken from the one before-mentioned,