CHAPTER XIX.
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 mymind 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 formerCrusoe went to work, and build me a boat and then be unable to launchit. Far from it. My very first care was to erect ways running downinto Stillwater Cove, made out of large square timbers, placed at aconsiderable decline, so that I felt confident that what I should erectupon them could be launched by me into the water without difficultyor trouble. These ways I bolted strongly together, and made firm andenduring, and upon them erected a kind of raft, which I kept in placeby means of upright iron bolts through the timbers of the ways, whichprevented it, for the time being, from slipping into the water if itshould be so inclined, but which, when the bolts were removed, and thethree timbers upon which it rested well greased, I felt sure would, atthe proper moment desired, slip into Stillwater Cove.
Upon this raft I commenced to construct my submarine boat. Theselaunching-ways were erected near the smelting house, and not far belowthe falls, just where the water became deep enough for my purpose, andyet as near as possible of access to my forge and shop. The raft thatI built and erected upon the ways was only as a cradle to support mysubmarine boat so that I could float the whole affair to the mouth ofStillwater Cove before allowing the latter to be submerged; for whereI now was there was not water enough for my experiment, and I wellknew that if my boat, which was to be of iron, was once launched, andshould, by its displacement or specific gravity, go to the bottom, thatI should be unable to raise it again, and that in the water directlyin front of the ways it would touch the bottom even before it wouldbe submerged. On the other hand, if I should erect my ways runninginto deep water at some place near the mouth of Stillwater Cove, andopposite Point Deliverance, I should have no means at hand to completeit, all my forges, iron-work, tools, and shop being too far distant forsuch an undertaking. I saw, therefore, that I must construct it nearto my foundry, and hence I chose this method of a cradle, or raft, tocarry 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 mortisedpieces 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 someplace yet to be determined, to which I should tow it, where the waterwould be smooth, and protected from the billows of the ocean, and nottoo deep for my experiment.
I had also another care in forming this cradle, and that was, thatit should be buoyant enough to sustain the submarine boat, and not,when launched, go to the bottom of Stillwater Cove with its preciousfreight, on account of the weight of the latter. This cradle,therefore, took both time and care to make, and long hours were passedby 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. Bystudying my book, and by experimenting in different ways with smallvessels of pottery and bladders blown up with air, that I submerged, Igot at what I thought would be about the weight of my submarine boatand its relation to the cradle, and I saw plainly that the latter wouldhave to be improved in some way to sustain the necessary weight. Sothis is how I went to work to overcome this obstacle.
On the two long sides of the cradle running parallel to the timberways, beyond which they extended several feet (although the waysthemselves were some six feet wide from the outside of one timber tothe outside of the other, by my island rule), I lashed firmly with ironbands and bolts two water-tight iron tanks, which I constructed of myrolled iron, riveted together, fully six feet long, three feet wide,and three feet deep. The dimensions of the cradle itself were aboutthese: Ten feet wide and eighteen feet in length, resting firmly uponthe three declined timbers or ways, which were six feet wide from sideto side and some forty feet in length from where they commenced on theshore to their terminus under the water in Stillwater Cove, at a depthof about eight or nine feet at high water. They were kept in place bytheir own weight, being of as large a size as I could handle with myteam of goats, and of hard-wood, the inclination they received from theshore ends forcing the outer ends to the bottom of the water. Of coursethese ways were not made of one piece of timber but of several, whichwere as large as I dared cut them with any hope of being able to handlethem, and were fished together to make the required length, being firstsawed out at the mill, planed upon the upper side by hand, and then letdown again over the inclined planes of the mill into Rapid River, andthence thrust over the falls into the shallow water and conveyed totheir place, where I pulled them on shore by means of rollers and myteam of goats, till I had each in place and mounted upon short uprightsof other timber, that I had placed at equal distances from each other,and higher one than the other as they were erected landward from thewater.
The underpinning of my cradle was exactly like the wooden underpinningof a house, and consisted of a parallelogram, eighteen feet by tenfeet, with timbers of about eight inches square. Across these timberswere placed smaller ones in sockets, exactly as slats are placedacross a bed, and this was to form the foundations upon which I was toerect my boat.
When I desired to submerge it I had only to saw away each of theseslats, on either side, and it would drop into the ocean, leaving theouter framework--or bedstead, if you please--floating; for my boat wasto be built, of course, less than eighteen feet long and ten wide, soas to rest wholly upon these slats and not upon the framework of thecradle 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 shouldnever again be in a hurry.
To build my boat I commenced by making two watertight tanks, eachsixteen feet long and two feet square, and two smaller ones, each sixfeet long and of the same dimensions otherwise as the long ones; these,placed upon the slats of my cradle, gave me a parallelogram composedof four water-tight tanks, all made out of my rolled iron and rivetedtogether firmly. I had to erect a derrick to hoist them into place, butonce in the cradle I had only to bind the two ends of each extremity ofthe long tanks to the short ones placed at right angles to them and Ihad 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 Ibrought 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 beingformed with a screw-thread, and fitting into this turn-buckle nut onboth sides, which could be then tightened by means of a lever, so as tobring an immense binding force upon each band.
Upon the outer edge of this parallelogram of tanks I had left a sort ofcomb of iron, some three inches in height, already pierced, or ratherpunched, ready to receive the roof of the boat, also air-tight, to bebolted to it, so that when all was done my platform of tanks would benearly two feet wide within the boat, and allow me plenty of margin torest any kind of a movable platform upon, or deck over the space thatwas left open, some fourteen feet long by six feet wide.
The nearest description that I can give of this roof is, that it rosein all directions at an angle of about forty-five degrees till it wasbolted to a large flat surface made up of several sheets of rollediron, which formed the top, which was ten feet long and four feet wide.This flat roof was fitted with a manhole, somewhat large in proportionto the rest of the boat, at least two feet square, and fitted over araised rib of iron, which was packed with greased milkweed floss, andclosed on the inside by set-screws, that were worked with a short ironlever, so as to make the opening perfectly air-tight.
I commenced this chapter by saying that I did not intend to make such afool of myself as the old Robinson Crusoe did, and that I was not goingto make any errors either of judgment or figures; and yet I had not myboat completed as far as I have described before I discovered that Ihad been a sill
y ass, fully as silly as it was possible for a mechanicto be, and one day it flashed upon me that my whole cradle, with itsair-tight chests, was an egregious folly; that I had not the least needin the world for it, and that I had wasted time, labor, and patiencein perfecting it. Carried away, as I was, with the means I intended toemploy to sink and raise my boat I had totally overlooked the fact thatas now being built, and as it would be launched, that it would floatitself, the size of the four air-tight tanks being sufficient to floatfive times the upper structure built on top of them.
As I am writing a veritable history, and no fable, it behooves me totell the truth, and it was with feelings of both mortification andmirth that I surveyed my partially finished work. It was the mentalcontemplation of a series of air-cocks, weights, pumps, etc., to behereinafter described, that had led me astray as to the buoyancy ofthe boat as it now stood, and it was what I was going to use the tanksfor, 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 ofthe boat in the minutest particular, and the cradle might after allbe advantageous in launching it, and preserve it from any casualty.Therefore, with the exception of my loss of time, I was nothing theworse; still I was rather crestfallen to think what a mistake I hadmade. But after mourning for a short time I set to work with renewedardor to complete my task.
After having strapped the four tanks together and covered them withthe iron roof, as described, I went on to complete the remainder ofthe boat, in this manner. In the interior, which I could easily reachby getting up from underneath the ways through two of the slats of thecradle, I arranged the following: The space in which I had to work wasabout fourteen feet in length, six feet wide, and eight feet high fromthe 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. Inthe first place I connected all these four tanks together by means ofa half-circular arm of piping some three inches in diameter, which Iplaced in each of the four corners of the parallelogram formed by theinterior of the boat, leading from one tank to the other, where thelatter met at an angle, so that the air that each contained was putin direct communication with the others. These connecting pipes werefitted in with a flange and riveted, and were placed a few inches fromthe 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 seator 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 spaceof fourteen feet by six feet, resting the ends of all my planks uponthe top of the tanks in any direction.
Having connected all the tanks so as virtually to form one, so faras concerned being one air-chamber, I then went to work and piercedthe perpendicular side of one of the tanks quite near the bottom andinserted a similar pipe to the horizontal ones that connected the tanksat the angles. This pipe, however, was in the form of a right angle, orrather its two ends were at a right angle, the bend being of a circularform. It pierced the tank near the bottom, as I have said, extended ina horizontal line some eight inches, and then gradually turned in acircular manner till the other end, about one foot in length, pointeddownward, in an exact right-angle from the end entering the tank. Thiswas 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 longrod, which arose inside the boat, parallel with the side of the tank,till it ended in a handle, situated some ten inches higher than thetop 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 theroof, which was fitted with a stopcock outside as well as inside, anddepended down into the boat some four feet from the roof. These fourpipes, with their stopcocks, were so arranged as to be all near to eachother, 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 sideof 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 woulddefine the stern, I had already concluded that the part of the boatnearest the water should be the bows, and hence I knew which to callthe starboard side and which the port side. Added to the pipes andstopcocks already enumerated was one which was simply about a foot inheight, which pierced the tank on the top, some few inches from theinner 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 allthese appliances at a later day, it will be well, perhaps, to namethem, so that when used it will be possible to understand to which ofthe numerous ones I refer; and to prevent confusion, and to make myselfunderstood, I will say that the pipes at the angles of the tanks Itook no note of, they not being fitted with any cocks, and only madeto connect all the tanks together, so that any action I might makewith any of the stopcocks would be communicated to the whole system oftanks, of which the foundations and main part of the boat was formed.
The pipes with stopcocks I named as follows: The one leading down intowhat would be the water when the boat was launched, and below thebottom of the tank some inches, fitted with a long rod and handle, Icalled the water-pipe and stopcock; the one that connected the tankwith the roof, the tank air-pipe and stopcock; the one that pierced theroof and depended into the interior, the atmospheric pipe and outerand inner stopcocks; the one that stood erect, ten inches in height,the pump-pipe and stopcock. So that I had four pipes and five stopcocksto 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 intothe tanks, which was fitted with a screw thread, upon which I could,when occasion demanded, erect a quite large and powerful pump, that Ihad made for the express purpose.
One more thing remained to be done, and that was to make all aroundthe boat inside a sort of movable step, that would ship and unship. Iwas 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 toprevent this I made these movable steps, which it is difficult todescribe. They were made of an upright piece of wood that was overfour feet in length, and on the top of which another piece of wood wasnailed horizontally, some twelve inches in width, like one arm of theletter T, whilst at the other end of the upright of four feet in lengthwas nailed another horizontal piece, some twelve inches in width, onexactly the opposite side, like the letter L; so that when the wholewas done the upper horizontal board rested one foot on the top of thetanks, whilst at the other end of the upright, two feet below thebottom of the tanks, was the other horizontal board, facing in towardsthe centre of the boat in all directions, and forming a kind of stepor shelf, upon which weights could be placed so as to prevent allchance of the capsizing of the boat, the vomiting out of its air, andperhaps the destruction of its constructor and inventor. I had this soarranged that I could speedily ship and unship it in sections, for itwas of course greatly in the way, and of no use except when the boatwas launched.
I then completed my deck, which I made of light planks, marked andarranged so that I could readily board over all the space in theinterior or leave part of it open. Upon further thoughts, some of thisdeck I made permanent, leaving only a space of about six feet by fouropen in the forward end, which I could cover or uncover.
I then entered upon another part of the programme, namely, the motivepower by which I was to move this submarine monster, but that I hadlong ago solved in my own mind. For some months I had been practisingtwo fine young goats upon a treadmill fitted to their size andstrength, all the time having in view the end of using them to createthe motive power of my boat; and for this purpose I had left themanhole two feet square so as to be able to take them down with me intoit. I now went to work and transported the treadmill to the boat, and,having fixed it in place, I each day conveyed th
e goats on board andset them to work, so that they might get used to it. They were alreadyused to the motion of the mill, and I noticed that with the precisionof step of their race they worked the rounds of the mill much betterthan horses usually do, and they soon became accustomed to the boatand worked rapidly and well, obeying the least word of command. In factthey were to me almost companions, and it would be amazing to relate,if I had time, all I have taught these really sagacious and gentlecreatures since I have been on the island; not these very ones of whichI am now speaking in particular, but several of their race. Perhapsbefore I am through with my narrative I may give an idea of the manyinteresting things which I taught them.
For a long time I allowed the mill to be turned daily, without makingup my mind just how I would connect it with the wheel or screw that Iforesaw that I should have to make to propel the boat. I at last fixedupon a propeller, to work in the open space of water in the interior ofthe boat, and which I readily set up with good strong gearing, that Icould as readily take down by hand when needful. By means of bevelledgearing I obtained several revolutions of my propeller to one of thebalance-wheel of the treadmill, and I saw, as a mechanic, that my boatwould move forward, perhaps not very fast, but still at the rate ofthree or four knots an hour, which would answer all purposes.
I had one more necessary thing to make, and that was a rudder, whichI connected to the outside of the rear tank of the boat, bringing thetiller or steering rods into the interior of the boat under the bottomof the tank. I took care to fasten the heel of the rudder, which wasquite wide, above the line of the bottom of the tank, so that if theboat 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 theactual consummation of all my efforts. It was to obtain a supply ofair whilst under the surface of the water without connection with theatmosphere, from which I was of course debarred. This problem solved,I had, I felt, the whole matter under control,--and let it not bebelieved that I had proceeded thus far in my self-imposed task withoutseeing a way out of this difficulty. The following every-day facts wereeasily ascertained from my Book of Useful Arts and Sciences, and uponthe following conclusions I had based my invention. It is well knownthat oxygen is the portion of atmospheric air which supports life,and that it composes nearly twenty-two per cent of the same, whilstnitrogen, the remaining portion, is incapable of sustaining life. Itis also well known that water also contains oxygen, in the proportionof two parts to one of hydrogen, of which two gases water is composed;or, in other words whilst atmospheric air holds only twenty-two percent of the life-giving principle, water contains about sixty-six percent, or, by weight, eight-ninths of oxygen to one-ninth of hydrogen. Ialso ascertained that the specific gravity of nitrogen is 0.94, whilstthat of hydrogen is only 0.0692. Now if I could release the oxygenin the water I could make new air and at the same time precipitatethe nitrogen and carbonic acid in the boat, that might be in theatmosphere, that had accumulated by my repeated breathings. Now theonly problem to solve was evidently how to release this oxygen withwhich the water was so freely impregnated, charged, or made up of,and by the breathing of which fishes sustained life. And this is howI set about to do it. I made a very light paddle-wheel, full six feetin diameter, with many, but light arms, and only six inches across theface of each paddle; this was arranged so as to ship inside the boat,upon sockets arranged so that the lower paddles would just touch thewater, and was adjustable by set screws, so that the journals couldbe lowered or elevated as the pressure of the water in the boat mightshow itself, higher or lower, according to the depth the boat mightbe at. By this arrangement I could have the paddles, which were morelike a set of large-teethed combs than paddles, dip just such distanceinto the water as I desired. This wheel was connected by series oflight wheels to the drum of the treadmill, so that I could obtain manyrevolutions 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 thewater I intended to throw up into the interior of the boat a mass ofminute spray, that in that form would itself release the oxygen that itcontained, or at least a large part of it, and grant to my exhaustedair the vitality it needed by new oxygen, or the life-sustainingprinciple, and at the same time precipitate the carbonic acid thatthe used-up atmosphere might contain. By this simple contrivance Iintended to renew my air, and thus remain just as long below thesurface as I might desire. The test that I should have that my airwas becoming impure would be the dimness with which the candles wouldburn, with which I was to furnish the boat; and if after the use of thespray-wheel they again flashed up brilliantly, I should know that mytheory was correct.
I had only one more thing to make to complete the whole affair, andthat was a compass, which, having finished, I took within the boatto see and note its variations from the true north on account of theattraction of the iron, and to regulate it so that I might be awarealways of my true course, for upon the exactitude of this instrumentrested the responsibility of my ever again reaching land should I dareto go out into the ocean, supposing that the boat should work accordingto my desires and theory.
For light I had nothing but the light contained in the water and mycandles. I could only pass from spot to spot by compass alone, and incase of utmost disaster plunge into the water within my own boat andtry to reach the surface by coming up outside. It was not my intentionto propel the boat near the bottom but only when near the surface. Whennear the bottom a turn or two of the propeller would send me in anyneeded direction.
A few blocks of iron to place upon my hanging shelves, and four anchorswith strong rawhide hawsers, completed the appurtenances of the boat,and it was finished. By examination of my diary I found that I had beenjust nine months and eleven days in completing it from the day I hadstarted to work upon the ways.