I was not wholly satisfied with my boat. I did not like the idea of having to dive overboard to find out where I was, as I had had to to-day, and I commenced racking my brains to overcome it; and at last I accomplished it in theory, and it may be as well to state here that it served me perfectly when put in practice on many future occasions, and in fact almost took the place of the spray-wheel. It was this. I arranged, in the first place, a sort of air-boat, in the shape of the half shell of an English walnut, but shallower, nearly four feet in length. This boat was made of very thin sheet-iron, but perfectly airtight, and upon it was lashed, in a horizontal position, a cylinder of sheet-iron, closed at one end and open at the other, a foot in diameter, and in length the same as the shallow, airtight, walnut-shaped boat that sustained it. At the end of this boat, just below the mouth of the cylinder, was affixed a solid iron ring, and to this was spliced a strong rawhide rope of great length. To utilize this machine I made two long bars of iron, which I could arrange in the interior of the boat, across its greatest diameter, in the form of the letter V, pointing downwards towards the bottom of the ocean, and at the point of contact was arranged a block through which the rope attached to the air-boat could be rove. This inverted derrick, in the form of a letter V, was still further braced by another bar, leading to one of the short diameters of the boat, in the interior, forming a tripod. To use the air-boat I had only (at any time when beneath the surface and in need of air, either to purify that surrounding me or obtain enough to force the boat out of water on the surface, after having used up the air in the tanks) to reeve the rawhide rope through the derrick, as above, and erect the same in an inverted form, pointing towards the bottom, and then put the air-boat in the water in the interior of the submarine boat, force it bodily down in a horizontal manner till the cylinder was filled with water, and then start the goats so that the rope attached to the nose of the air-boat, leading down to the inverted apex of the tripod, through the block, and thence to the drum of the treadmill, would be tautened, and cause it to erect itself in a perpendicular manner, and be forced down under the water towards the apex of the tripod. When submerged enough to clear the bottom of the tank I slackened the rope gradually, pressing it at the same time out and clear from the tank, and yet keeping enough strain upon it to prevent its touching the latter; when, as soon as it was clear, I slacked the rope wholly, to allow it to arise to the surface outside, which it rapidly did on account of the confined air in the air-tight shell. Of course immediately upon its arrival at the surface it righted itself, and presented the appearance, on a small scale, of a barrel with one head out, placed in a horizontal position upon a small sled or vessel. In this position all the water that had been in the cylinder was at once discharged, and, to get a measure of fresh air exactly equal to the dimensions of this cylinder, I had only to set the goats to work, to take the rope to the drum of the treadmill, the first effect of which was to depress the nose and open mouth of the cylinder on the air-boat, at the surface, and the next to drag it down under the water in a perpendicular position, with the cylinder charged with air, which could not escape. As soon as it appeared clear of the outside of the tank, against which it rubbed in its descent, and was brought down near to the inverted apex of the tripod, I commenced slacking the same rope till it arrived at the surface of the water within the submarine boat, when I cast off the rope and it righted itself violently, discharging at the same time the contents of the cylinder in the shape of new air, and I had only to repeat this process of conveying fresh air from the surface to obtain all I needed, taking care only, in sending the apparatus to the surface, to see that, when the air-boat was first pointed under water ready to ascend, it took back with it none of its precious freight, which was easily obviated when it was held in a semi-perpendicular state, and half submerged ready to ascend, by pushing upon the part out of water till it was forced into a horizontal position, the air from the cylinder discharged, and replaced by water, when, after descending towards the connecting points of the tripod and pushed clear of the side tank, it was allowed to ascend to the surface, discharge the water, and descend again filled with air.
With this apparatus I found that I could even compress the air in the interior, and in many future expeditions I had no trouble in making my submarine boat, at any time, self-sustaining on the surface of the water, and I could by a little labor come to the surface, open my manhole, and look about me and see where I was.
THE AIR BOAT.
CHAPTER XXII.
Manufacture glass. Build a steam yacht, and circumnavigate the island. Lay up large stores of valuable pearls obtained from the pearl oysters.
After I had perfected my submarine boat I used it often to gather the pearl oysters, and it was not difficult to steer straight to the buoy on the reef, fill the shelves of my boat, arise again to the surface, and return home. After allowing my first load to putrify, I went to work upon them and washed them out in the water of Stillwater Cove, obtaining nearly a handful of seed-pearls, some twelve of the size of peas, and four very handsome and perfectly-shaped larger ones. This induced me to keep on; for here was portable wealth such as I could take away with me when I left the island. Let it suffice to say that, during repeated trips at intervals, I ended by obtaining probably the finest private collection of pearls in the world. I had some eighteen of enormous size, nearly as large as English walnuts, but as perfect as if from the turning-lathe,—except one that had a slight blemish, and one that was irregular in form,—and I much doubted if there were more perfect and larger ones in any royal crown. They were regal in size and appearance, and were, I knew, of immense value. Besides these sixteen perfect gems without price, I had at least four hundred and sixty as large as a small filbert nut, and several hundreds as large as common peas, not to speak of vast quantities of seed-pearls, too many to enumerate. If I could escape from the island, these treasures would keep me in ease and comfort in any part of the world.