Construct a submarine boat, to be propelled by goat power and to make its own air, to examine the bottom of the ocean near the island for pearl-oysters.

Yes, as I have hinted in the preceding chapter, I had fully made up my mind to explore the bottom of the ocean that surrounded my island, and I did not intend to commence in the stupid way in which the former Crusoe went to work, and build me a boat and then be unable to launch it. Far from it. My very first care was to erect ways running down into Stillwater Cove, made out of large square timbers, placed at a considerable decline, so that I felt confident that what I should erect upon them could be launched by me into the water without difficulty or trouble. These ways I bolted strongly together, and made firm and enduring, and upon them erected a kind of raft, which I kept in place by means of upright iron bolts through the timbers of the ways, which prevented it, for the time being, from slipping into the water if it should be so inclined, but which, when the bolts were removed, and the three timbers upon which it rested well greased, I felt sure would, at the proper moment desired, slip into Stillwater Cove.

Upon this raft I commenced to construct my submarine boat. These launching-ways were erected near the smelting house, and not far below the falls, just where the water became deep enough for my purpose, and yet as near as possible of access to my forge and shop. The raft that I built and erected upon the ways was only as a cradle to support my submarine boat so that I could float the whole affair to the mouth of Stillwater Cove before allowing the latter to be submerged; for where I now was there was not water enough for my experiment, and I well knew that if my boat, which was to be of iron, was once launched, and should, by its displacement or specific gravity, go to the bottom, that I should be unable to raise it again, and that in the water directly in front of the ways it would touch the bottom even before it would be submerged. On the other hand, if I should erect my ways running into deep water at some place near the mouth of Stillwater Cove, and opposite Point Deliverance, I should have no means at hand to complete it, all my forges, iron-work, tools, and shop being too far distant for such an undertaking. I saw, therefore, that I must construct it near to my foundry, and hence I chose this method of a cradle, or raft, to carry out my plan. This raft, or cradle as I shall call it in future, was of itself quite an undertaking, for I had to make it of mortised pieces of wood, so that at the proper time I could take it to pieces, and allow its load, the submarine boat, to drop into the ocean, at some place yet to be determined, to which I should tow it, where the water would be smooth, and protected from the billows of the ocean, and not too deep for my experiment.

I had also another care in forming this cradle, and that was, that it should be buoyant enough to sustain the submarine boat, and not, when launched, go to the bottom of Stillwater Cove with its precious freight, on account of the weight of the latter. This cradle, therefore, took both time and care to make, and long hours were passed by me in figuring out the weight of the iron boat I was about to build, and how large and extensive my cradle ought to be to sustain it. By studying my book, and by experimenting in different ways with small vessels of pottery and bladders blown up with air, that I submerged, I got at what I thought would be about the weight of my submarine boat and its relation to the cradle, and I saw plainly that the latter would have to be improved in some way to sustain the necessary weight. So this is how I went to work to overcome this obstacle.

On the two long sides of the cradle running parallel to the timber ways, beyond which they extended several feet (although the ways themselves were some six feet wide from the outside of one timber to the outside of the other, by my island rule), I lashed firmly with iron bands and bolts two water-tight iron tanks, which I constructed of my rolled iron, riveted together, fully six feet long, three feet wide, and three feet deep. The dimensions of the cradle itself were about these: Ten feet wide and eighteen feet in length, resting firmly upon the three declined timbers or ways, which were six feet wide from side to side and some forty feet in length from where they commenced on the shore to their terminus under the water in Stillwater Cove, at a depth of about eight or nine feet at high water. They were kept in place by their own weight, being of as large a size as I could handle with my team of goats, and of hard-wood, the inclination they received from the shore ends forcing the outer ends to the bottom of the water. Of course these ways were not made of one piece of timber but of several, which were as large as I dared cut them with any hope of being able to handle them, and were fished together to make the required length, being first sawed out at the mill, planed upon the upper side by hand, and then let down again over the inclined planes of the mill into Rapid River, and thence thrust over the falls into the shallow water and conveyed to their place, where I pulled them on shore by means of rollers and my team of goats, till I had each in place and mounted upon short uprights of other timber, that I had placed at equal distances from each other, and higher one than the other as they were erected landward from the water.

The underpinning of my cradle was exactly like the wooden underpinning of a house, and consisted of a parallelogram, eighteen feet by ten feet, with timbers of about eight inches square. Across these timbers were placed smaller ones in sockets, exactly as slats are placed across a bed, and this was to form the foundations upon which I was to erect my boat.

When I desired to submerge it I had only to saw away each of these slats, on either side, and it would drop into the ocean, leaving the outer framework—or bedstead, if you please—floating; for my boat was to be built, of course, less than eighteen feet long and ten wide, so as to rest wholly upon these slats and not upon the framework of the cradle that supported the slats. This took me a long time to finish; but what was time to me whilst revolving the problem of my escape, which was not yet solved. Till I knew how I was to escape I should never again be in a hurry.

To build my boat I commenced by making two watertight tanks, each sixteen feet long and two feet square, and two smaller ones, each six feet long and of the same dimensions otherwise as the long ones; these, placed upon the slats of my cradle, gave me a parallelogram composed of four water-tight tanks, all made out of my rolled iron and riveted together firmly. I had to erect a derrick to hoist them into place, but once in the cradle I had only to bind the two ends of each extremity of the long tanks to the short ones placed at right angles to them and I had the foundations of my boat laid. I bound the small tanks in place, as also the large ones, by bands of iron, several in number, which I brought together on one side by means of what is called a turn buckle, such as is often seen on iron bridges, both ends of the bands being formed with a screw-thread, and fitting into this turn-buckle nut on both sides, which could be then tightened by means of a lever, so as to bring an immense binding force upon each band.

Upon the outer edge of this parallelogram of tanks I had left a sort of comb of iron, some three inches in height, already pierced, or rather punched, ready to receive the roof of the boat, also air-tight, to be bolted to it, so that when all was done my platform of tanks would be nearly two feet wide within the boat, and allow me plenty of margin to rest any kind of a movable platform upon, or deck over the space that was left open, some fourteen feet long by six feet wide.

The nearest description that I can give of this roof is, that it rose in all directions at an angle of about forty-five degrees till it was bolted to a large flat surface made up of several sheets of rolled iron, which formed the top, which was ten feet long and four feet wide. This flat roof was fitted with a manhole, somewhat large in proportion to the rest of the boat, at least two feet square, and fitted over a raised rib of iron, which was packed with greased milkweed floss, and closed on the inside by set-screws, that were worked with a short iron lever, so as to make the opening perfectly air-tight.

I commenced this chapter by saying that I did not intend to make such a fool of myself as the old Robinson Crusoe did, and that I was not going to make any errors either of judgment or figures; and yet I had not my boat completed as far as I have described before I discovered that I had been a silly ass, fully as silly as it was possible for a mechanic to be, and one day it flashed upon me that my whole cradle, with its air-tight chests, was an egregious folly; that I had not the least need in the world for it, and that I had wasted time, labor, and patience in perfecting it. Carried away, as I was, with the means I intended to employ to sink and raise my boat I had totally overlooked the fact that as now being built, and as it would be launched, that it would float itself, the size of the four air-tight tanks being sufficient to float five times the upper structure built on top of them.

As I am writing a veritable history, and no fable, it behooves me to tell the truth, and it was with feelings of both mortification and mirth that I surveyed my partially finished work. It was the mental contemplation of a series of air-cocks, weights, pumps, etc., to be hereinafter described, that had led me astray as to the buoyancy of the boat as it now stood, and it was what I was going to use the tanks for, rather than what they now were, that had led me to this error. But then there was no great harm done. I had not to change the plan of the boat in the minutest particular, and the cradle might after all be advantageous in launching it, and preserve it from any casualty. Therefore, with the exception of my loss of time, I was nothing the worse; still I was rather crestfallen to think what a mistake I had made. But after mourning for a short time I set to work with renewed ardor to complete my task.

After having strapped the four tanks together and covered them with the iron roof, as described, I went on to complete the remainder of the boat, in this manner. In the interior, which I could easily reach by getting up from underneath the ways through two of the slats of the cradle, I arranged the following: The space in which I had to work was about fourteen feet in length, six feet wide, and eight feet high from the bottom of the tanks to the flat roof, which contained the manhole, which, for the present I left open, to give me both light and air. In the first place I connected all these four tanks together by means of a half-circular arm of piping some three inches in diameter, which I placed in each of the four corners of the parallelogram formed by the interior of the boat, leading from one tank to the other, where the latter met at an angle, so that the air that each contained was put in direct communication with the others. These connecting pipes were fitted in with a flange and riveted, and were placed a few inches from the bottom of the tanks, thus making really one tank of the whole. As the roof was fastened to the outside of these tanks, I had a seat or margin running round all the sides of the interior two feet wide, from the outer or further side of which arose the roofing. I could, therefore, easily lay any kind of a movable deck over this open space of fourteen feet by six feet, resting the ends of all my planks upon the top of the tanks in any direction.

Having connected all the tanks so as virtually to form one, so far as concerned being one air-chamber, I then went to work and pierced the perpendicular side of one of the tanks quite near the bottom and inserted a similar pipe to the horizontal ones that connected the tanks at the angles. This pipe, however, was in the form of a right angle, or rather its two ends were at a right angle, the bend being of a circular form. It pierced the tank near the bottom, as I have said, extended in a horizontal line some eight inches, and then gradually turned in a circular manner till the other end, about one foot in length, pointed downward, in an exact right-angle from the end entering the tank. This was put on with a flange, and made water-tight, and in the top of it, about three inches from the tank, was fixed a stopcock, with a long rod, which arose inside the boat, parallel with the side of the tank, till it ended in a handle, situated some ten inches higher than the top of the tanks. Near this, also, I erected another piece of pipe, which entered the top of the tank and pierced the roof of the boat, which was also fitted with a stopcock. Still another pipe pierced the roof, which was fitted with a stopcock outside as well as inside, and depended down into the boat some four feet from the roof. These four pipes, with their stopcocks, were so arranged as to be all near to each other, so that I could control them all without moving in my position, and were made at about the middle of what I called the starboard side of my boat, though it would be hard to say which side starboard was, as both ends of the boat were exactly alike up to the present time. But as I was eventually to have a propeller and rudder, which would define the stern, I had already concluded that the part of the boat nearest the water should be the bows, and hence I knew which to call the starboard side and which the port side. Added to the pipes and stopcocks already enumerated was one which was simply about a foot in height, which pierced the tank on the top, some few inches from the inner edge, and near the others. It was also fitted with a stopcock, and, that my readers may fully understand the uses to which I put all these appliances at a later day, it will be well, perhaps, to name them, so that when used it will be possible to understand to which of the numerous ones I refer; and to prevent confusion, and to make myself understood, I will say that the pipes at the angles of the tanks I took no note of, they not being fitted with any cocks, and only made to connect all the tanks together, so that any action I might make with any of the stopcocks would be communicated to the whole system of tanks, of which the foundations and main part of the boat was formed.

The pipes with stopcocks I named as follows: The one leading down into what would be the water when the boat was launched, and below the bottom of the tank some inches, fitted with a long rod and handle, I called the water-pipe and stopcock; the one that connected the tank with the roof, the tank air-pipe and stopcock; the one that pierced the roof and depended into the interior, the atmospheric pipe and outer and inner stopcocks; the one that stood erect, ten inches in height, the pump-pipe and stopcock. So that I had four pipes and five stopcocks to my boat, all of which had their uses, as shall be related.

Besides all these four pipes I also made near to them an opening into the tanks, which was fitted with a screw thread, upon which I could, when occasion demanded, erect a quite large and powerful pump, that I had made for the express purpose.

One more thing remained to be done, and that was to make all around the boat inside a sort of movable step, that would ship and unship. I was well aware that, unless the centre of gravity was kept well down, my boat would capsize and spill out all the air when in use, and to prevent this I made these movable steps, which it is difficult to describe. They were made of an upright piece of wood that was over four feet in length, and on the top of which another piece of wood was nailed horizontally, some twelve inches in width, like one arm of the letter T, whilst at the other end of the upright of four feet in length was nailed another horizontal piece, some twelve inches in width, on exactly the opposite side, like the letter L; so that when the whole was done the upper horizontal board rested one foot on the top of the tanks, whilst at the other end of the upright, two feet below the bottom of the tanks, was the other horizontal board, facing in towards the centre of the boat in all directions, and forming a kind of step or shelf, upon which weights could be placed so as to prevent all chance of the capsizing of the boat, the vomiting out of its air, and perhaps the destruction of its constructor and inventor. I had this so arranged that I could speedily ship and unship it in sections, for it was of course greatly in the way, and of no use except when the boat was launched.

I then completed my deck, which I made of light planks, marked and arranged so that I could readily board over all the space in the interior or leave part of it open. Upon further thoughts, some of this deck I made permanent, leaving only a space of about six feet by four open in the forward end, which I could cover or uncover.

I then entered upon another part of the programme, namely, the motive power by which I was to move this submarine monster, but that I had long ago solved in my own mind. For some months I had been practising two fine young goats upon a treadmill fitted to their size and strength, all the time having in view the end of using them to create the motive power of my boat; and for this purpose I had left the manhole two feet square so as to be able to take them down with me into it. I now went to work and transported the treadmill to the boat, and, having fixed it in place, I each day conveyed the goats on board and set them to work, so that they might get used to it. They were already used to the motion of the mill, and I noticed that with the precision of step of their race they worked the rounds of the mill much better than horses usually do, and they soon became accustomed to the boat and worked rapidly and well, obeying the least word of command. In fact they were to me almost companions, and it would be amazing to relate, if I had time, all I have taught these really sagacious and gentle creatures since I have been on the island; not these very ones of which I am now speaking in particular, but several of their race. Perhaps before I am through with my narrative I may give an idea of the many interesting things which I taught them.

For a long time I allowed the mill to be turned daily, without making up my mind just how I would connect it with the wheel or screw that I foresaw that I should have to make to propel the boat. I at last fixed upon a propeller, to work in the open space of water in the interior of the boat, and which I readily set up with good strong gearing, that I could as readily take down by hand when needful. By means of bevelled gearing I obtained several revolutions of my propeller to one of the balance-wheel of the treadmill, and I saw, as a mechanic, that my boat would move forward, perhaps not very fast, but still at the rate of three or four knots an hour, which would answer all purposes.

I had one more necessary thing to make, and that was a rudder, which I connected to the outside of the rear tank of the boat, bringing the tiller or steering rods into the interior of the boat under the bottom of the tank. I took care to fasten the heel of the rudder, which was quite wide, above the line of the bottom of the tank, so that if the boat grounded it would not be injured or destroyed.

And now I came to the most important part of my boat, and, in fact, upon the success of which, and practical application, rested the actual consummation of all my efforts. It was to obtain a supply of air whilst under the surface of the water without connection with the atmosphere, from which I was of course debarred. This problem solved, I had, I felt, the whole matter under control,—and let it not be believed that I had proceeded thus far in my self-imposed task without seeing a way out of this difficulty. The following every-day facts were easily ascertained from my Book of Useful Arts and Sciences, and upon the following conclusions I had based my invention. It is well known that oxygen is the portion of atmospheric air which supports life, and that it composes nearly twenty-two per cent of the same, whilst nitrogen, the remaining portion, is incapable of sustaining life. It is also well known that water also contains oxygen, in the proportion of two parts to one of hydrogen, of which two gases water is composed; or, in other words whilst atmospheric air holds only twenty-two per cent of the life-giving principle, water contains about sixty-six per cent, or, by weight, eight-ninths of oxygen to one-ninth of hydrogen. I also ascertained that the specific gravity of nitrogen is 0.94, whilst that of hydrogen is only 0.0692. Now if I could release the oxygen in the water I could make new air and at the same time precipitate the nitrogen and carbonic acid in the boat, that might be in the atmosphere, that had accumulated by my repeated breathings. Now the only problem to solve was evidently how to release this oxygen with which the water was so freely impregnated, charged, or made up of, and by the breathing of which fishes sustained life. And this is how I set about to do it. I made a very light paddle-wheel, full six feet in diameter, with many, but light arms, and only six inches across the face of each paddle; this was arranged so as to ship inside the boat, upon sockets arranged so that the lower paddles would just touch the water, and was adjustable by set screws, so that the journals could be lowered or elevated as the pressure of the water in the boat might show itself, higher or lower, according to the depth the boat might be at. By this arrangement I could have the paddles, which were more like a set of large-teethed combs than paddles, dip just such distance into the water as I desired. This wheel was connected by series of light wheels to the drum of the treadmill, so that I could obtain many revolutions of the water-wheel to one of the latter. My idea was this. By violent motion of the extreme ends of my comb-paddles through the water I intended to throw up into the interior of the boat a mass of minute spray, that in that form would itself release the oxygen that it contained, or at least a large part of it, and grant to my exhausted air the vitality it needed by new oxygen, or the life-sustaining principle, and at the same time precipitate the carbonic acid that the used-up atmosphere might contain. By this simple contrivance I intended to renew my air, and thus remain just as long below the surface as I might desire. The test that I should have that my air was becoming impure would be the dimness with which the candles would burn, with which I was to furnish the boat; and if after the use of the spray-wheel they again flashed up brilliantly, I should know that my theory was correct.

I had only one more thing to make to complete the whole affair, and that was a compass, which, having finished, I took within the boat to see and note its variations from the true north on account of the attraction of the iron, and to regulate it so that I might be aware always of my true course, for upon the exactitude of this instrument rested the responsibility of my ever again reaching land should I dare to go out into the ocean, supposing that the boat should work according to my desires and theory.

For light I had nothing but the light contained in the water and my candles. I could only pass from spot to spot by compass alone, and in case of utmost disaster plunge into the water within my own boat and try to reach the surface by coming up outside. It was not my intention to propel the boat near the bottom but only when near the surface. When near the bottom a turn or two of the propeller would send me in any needed direction.

A few blocks of iron to place upon my hanging shelves, and four anchors with strong rawhide hawsers, completed the appurtenances of the boat, and it was finished. By examination of my diary I found that I had been just nine months and eleven days in completing it from the day I had started to work upon the ways.