A History of Inventions, Discoveries, and Origins. Johann Beckmann

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      DIVING-BELL.

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The first divers learned their art by early and adventurous experience, in trying to continue under water as long as possible without breathing; and, indeed, it must be allowed that some of them carried it to very great perfection. This art, however, excites little surprise; for, like running, throwing, and other bodily dexterities, it requires only practice; but it is certain that those nations called by us uncultivated and savage excel in it the Europeans274, who, through refinement and luxury, have become more delicate, and less fit for such laborious exercises.

In remote ages, divers were kept in ships to assist in raising anchors275, and goods thrown overboard in times of danger276; and, by the laws of the Rhodians, they were allowed a share of the wreck, proportioned to the depth to which they had gone in search of it277. In war, they were often employed to destroy the works and ships of the enemy. When Alexander was besieging Tyre, divers swam off from the city, under water, to a great distance, and with long hooks tore to pieces the mole with which the besiegers were endeavouring to block up the harbour278. The pearls of the Greek and Roman ladies were fished up by divers at the great hazard of their lives; and by the like means are procured at present those which are purchased as ornaments by our fair.

I do not know whether observations have ever been collected respecting the time that divers can continue under water. Anatomists once believed that persons in whom the oval opening of the heart (foramen ovale) was not closed up, could live longer than others without breathing, and could therefore be expert divers. Haller279, however, and others, have controverted this opinion; as people who had that opening have been soon suffocated, and as animals which have it not can live a long time under water: besides, when that opening is perceptible in grown persons, it is so small as not to be sufficient for that purpose, especially as the ductus arteriosus is scarcely ever found open.

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; СКАЧАТЬ