my condenser, a quantity of this same atmosphere sufficiently condensed for the purposes of respiration. With this object in view I had prepared a very strong perfectly airtight, but flexible gum-elastic bag. In this bag, which was of sufficient dimensions, the entire car was in a manner placed. That is to say, it (the bag) was drawn over the whole bottom of the car, up its sides, and so on, along the outside of the ropes, to the upper rim or hoop where the net-work is attached. Having pulled the bag up in this way, and formed a complete enclosure on all sides, and at bottom, it was now necessary to fasten up its top or mouth, by passing its material over the hoop of the net-work—in other words, between the net-work and the hoop. But if the net-work were separated from the hoop to admit this passage, what was to sustain the car in the meantime? Now the net-work was not permanently fastened to the hoop, but attached by a series of running loops or nooses. I therefore undid only a few of these loops at one time, leaving the car suspended by the remainder. Having thus inserted a portion of the cloth forming the upper part of the bag, I refastened the loops—not to the hoop, for that would have been impossible, since the cloth now intervened—but to a series of large buttons, affixed to the cloth itself, about three feet below the mouth of the bag; the intervals between the buttons having been made to correspond to the intervals between the loops. This done, a few more of the loops were unfastened from the rim, a farther portion of the cloth introduced, and the disengaged loops then connected with their proper buttons. In this way it was possible to insert the whole upper part of the bag between the net-work and the hoop. It is evident that the hoop would now drop down within the car, while the whole weight of the car itself, with all its contents, would be held up merely by the strength of the buttons. This, at first sight, would seem an inadequate dependence; but it was by no means so, for the buttons were not only very strong in themselves, but so close together that a very slight portion of the whole weight was supported by any one of them. Indeed, had the car and contents been three times heavier than they were, I should not have been at all uneasy. I now raised up the hoop again within the covering of gum-elastic, and propped it at nearly its former height by means of three light poles prepared for the occasion. This was done, of course, to keep the bag distended at the top, and to preserve the lower part of the net-work in its proper situation. All that now remained was to fasten up the mouth of the enclosure; and this was readily accomplished by gathering the folds of the material together, and twisting them up very tightly on the inside by means of a kind of stationary tourniquet.
“In the sides of the covering thus adjusted round the car, had been inserted three circular panes of thick but clear glass, through which I could see without difficulty around me in every horizontal direction. In that portion of the cloth forming the bottom, was likewise, a fourth window, of the same kind, and corresponding with a small aperture in the floor of the car itself. This enabled me to see perpendicularly down, but having found it impossible to place any similar contrivance overhead, on account of the peculiar manner of closing up the opening there, and the consequent wrinkles in the cloth, I could expect to see no objects situated directly in my zenith. This, of course, was a matter of little consequence; for had I even been able to place a window at top, the balloon itself would have prevented my making any use of it.
“About a foot below one of the side windows was a circular opening, eight inches in diameter, and fitted with a brass rim adapted in its inner edge to the windings of a screw. In this rim was screwed the large tube of the condenser, the body of the machine being, of course, within the chamber of gum-elastic. Through this tube a quantity of the rare atmosphere circumjacent being drawn by means of a vacuum created in the body of the machine, was thence discharged, in a state of condensation, to mingle with the thin air already in the chamber. This operation being repeated several times, at length filled the chamber with atmosphere proper for all the purposes of respiration. But in so confined a space it would, in a short time, necessarily become foul, and unfit for use from frequent contact with the lungs. It was then ejected by a small valve at the bottom of the car—the dense air readily sinking into the thinner atmosphere below. To avoid the inconvenience of making a total vacuum at any moment within the chamber, this purification was never accomplished all at once, but in a gradual manner—the valve being opened only for a few seconds, then closed again, until one or two strokes from the pump of the condenser had supplied the place of the atmosphere ejected. For the sake of experiment I had put the cat and kittens in a small basket, and suspended it outside the car to a button at the bottom, close by the valve, through which I could feed them at any moment when necessary. I did this at some little risk, and before closing the mouth of the chamber, by reaching under the car with one of the poles before mentioned to which a hook had been attached.
“By the time I had fully completed these arrangements and filled the chamber as explained, it wanted only ten minutes of nine o’clock. During the whole period of my being thus employed, I endured
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