So far as the reasoning went, it was faultless. It only did not go far enough.
The balloon being made, he named a day for its ascent, and asked many friends to witness his triumph. At the last moment, all air was withdrawn; and everybody waited in expectation, hoping to see the novel balloon skim lightly above their heads.
But the inventor, while using strong materials, had failed to make full allowance for the tremendous pressure of the air, when counteractive pressure from within should have been done away with. As the air was drawn out, the sides of the balloon collapsed, being crushed together as an empty egg-shell may be smashed in a boy’s hand. Instead of soaring gaily upward, the would-be aeronaut stood on earth, scanning with disappointed eyes a flattened and useless shell.
A diver going down into the sea has a much increased weight upon his body; but he does not suffer from it to a serious extent, provided that he is not raised or lowered too fast. Much depends upon this. Both men and beasts can endure a good deal of alteration in the degree of pressure, whether from air or from water; but they cannot bear very abrupt changes. Hearts and lungs need time for growing accustomed to a fresh condition. In early days of diving this was not understood, and some divers lost their lives through being too hurriedly hauled up.
The same has been noticed in animals brought quickly from great depths. They have been constantly found in the net or trawl, dying or dead, their bodies swollen and even bursting from the lessening of pressure. It was natural that at first the belief should arise of Life being in those parts impossible. Now we know that animals die in the act of being drawn up, and that they live and flourish in profound depths, unaffected by the vast load of water.
The weight that a man can endure is not to be compared with what fragile sea-creatures thrive under. Beyond a depth of some two hundred feet or more, the pressure becomes too great for any human beings; yet animals are found at depths of three or four miles. But the fact that man breathes air, and that animals in the sea breathe, in a sense, water, makes an enormous difference in their power to resist pressure.
One might suppose that the terrific weight of miles of water would squeeze lower layers to a smaller bulk. Water is, however, very difficult to compress; unlike air.
At the bottom of the sea, four or five miles deep, the weight is said to be equal to about four tons upon the square inch. If this tremendous load were pressing upon a mass of air, eleven thousand cubic feet in quantity, the whole would be crushed together into only twenty-two cubic feet. But the same weight pressing upon the same quantity of sea-water, would merely reduce its size to ten thousand cubic feet. So there is not much difference between the make of sea-water near the surface and sea-water at a great depth.
Not only are ocean’s depths calm and free from storms; not only are they black with midnight darkness; not only are they heavy with the weight of miles of water overhead; but also for the most part they are cold.
Changes from season to season, like changes of weather, are superficial. At a depth of about six hundred feet, Seasons have ceased to be. There, summer and winter, autumn and spring, exist no longer. The dead level of calm and darkness is also a dead level of uniform weather and unalterable climate. Where changes of cold and heat do come about, they are very uncertain, and usually they are due to other causes than those which bring about the succession of seasons upon Earth.