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hitherto. been given. Perhaps it may be this, down, and let the air pass out at E, which that great part of the force employed contri- striking forcibly against the water abaft must butes little to the motion. For instance, (fig. push the boat forward. If there is added an air 12) of the four paddles a, b, c, d, all under vessel F properly valved and placed, the force water, and turning to move a boat from X to would continue to act while a fresh stroke is Y, c has the most power, b nearly though taken with the lever. The boatman might not quite as much, their motion being nearly stand with his back to the stern, and putting horizontal; but the force employed in moving his hands behind him, work the motion by a, is consumed in pressing almost downright taking hold of the cross bar at B, while anoupon the water till it comes to the place of ther should steer; or if he had two such b; and the force employed in moving d is pumps, one on each side of the stern, with a consumed in lifting the water till d arrives at lever for each hand, he might steer himself the surface; by which means much of the la- by working occasionally more or harder with bour is lost. It is true, that by placing the either hand, as watermen now do with a pair wheels higher out of the water, this waste la- of sculls. There is no position in which the bour will be diminished in a calm, but where body of a man can exert more strength than a sea runs, the wheels must unavoidably be in pulling right upwards. To obtain more swiftoften dipt deep in the waves, and the turn- ness, greasing the bottom of a vessel is someing of them thereby rendered very laborious times used, and with good effect. I do not to little purpose.
know that any writer has hitherto attempted Among the various means of giving motion to explain this. At first sight one would imato a boat, that of M. Bernoulli appears one of gine, that though the friction of a hard body, the most singular, which was to have fixed sliding on another hard body, and the resistin the boat a tube in the form of an L, the up- ance occasioned by that friction, might be diright part to have a funnel-kind of opening at minished by putting grease between them, yet top, convenient for filling the tube with wa- that a body sliding on a fluid, such as water, ter; which, descending and passing through should have no need of, nor receive any adthe lower horizontal part, and issuing in the vantage from such greasing. But the fact is middle of the stern, but under the surface of not disputed. And the reason perhaps may be the river, should push the boat forward. this—The particles of water have a mutual There is no doubt that the force of the de- attraction, called the attraction of adhesion. scending water would have a considerable ef- Water also adheres to wood, and to many other fect, greater in proportion to the height from substances, but not to grease : on the contrary which it descended; but then it is to be con- they have a mutual repulsion, so that it is a sidered, that every bucket full pumped or question whether when oil is poured on wadipped up into the boat, from its side or through ter, they ever actually touch each other; for its bottom, must have its viz inertiæ over- a drop of oil upon water, instead of sticking come so as to receive the motion of the boat, to the spot where it falls, as it would if it fell before it can come to give motion by its de- on a looking-glass, spreads instantly to an imscent; and that will be a deduction from the mense distance in a film extremely thin, which moving power. To remedy this, I would it could not easily do if it touched and rubbed propose the addition of another such L pipe, or adhered even in a small degree to the surand that they should stand back to back in face of the water. Now the adhesive force the boat thus, figure 13, the forward one be- of water to itself, and to other substances, ing worked as a pump, and sucking in the may be estimated from the weight of it neceswater at the head of the boat, would draw it sary to separate a drop, which adheres, while forward while pushed in the same direction growing, till it has weight enough to force by the force at the stern. And after all it the separation and break the drop off. Let us should be calculated whether the labour of suppose the drop to be the size of a pea, then pumping would be less than that of rowing. there will be as many of these adhesions as A fire-engine might possibly in some cases there are drops of that size touching the botbe applied in this operation with advantage. tom of a vessel, and these must be broken by
Perhaps this labour of raising water might the moving power, every step of her motion be spared, and the whole force of a man applied that amounts to a drop's breadth : and there to the moving of a boat by the use of air in- being no such adhesions to break between the stead of water; suppose the boat construct- water and a greased bottom, may occasion the ed in this form, figure 14. A, a tube round difference. or square, of two feet diameter, in which a So much respecting the motion of vessels. piston may move up and down. The piston to But we have sometimes occasion to stop their have valves in it, opening inwards, to admit motion; and if a bottom is near enough we air when the piston rises; and shutting, when can cast anchor : where there are no soundit is forced down by means of the lever B turn- ings, we have as yet no means to prevent ing on the centre C. The tube to have a driving in a storm, but by lying-to, which still valve D, to open when the piston is forced permits driving at the rate of about two miles
an hour; so that in a storm continuing fifty | To make one of suppose fifteen feet high; hours, which is not an uncommon case, the take a small spar of that length for the backship may drive one hundred miles out of her bone, A B, figure 16, a smaller of half that course; and should she in that distance meet length C D, for the cross piece. Let these be with a lee shore, she may be lost.
united by a bolt at E, yet so as that by turning To prevent this driving to leeward in deep on the bolt they may be laid parallel to each water, a swimming anchor is wanting, which other. Then make a sail of strong canvas, in ought to have these properties.
the shape of figure 17. To form this, with1. It should have a surface so large as, be out waste of sail-cloth, sew together pieces of ing at the end of a hauser in the water, and the proper length, and for half the breadth, as placed perpendicularly, should hold so much in figure 18, then cut the whole in the diaof it, as to bring the ship’s head to the wind, gonal lines a, b, c, and turn the piece F so as in which situation the wind has least power to place its broad part opposite to that of the to drive her.
piece G, and the piece H in like manner op2. It should be able by its resistance to pre-posite to I, which when all sewed together vent the ship's receiving way.
will appear as in fig. 17. This sail is to be 3. It should be capable of being situated extended on the cross of fig. 16, the top and below the heave of the sea, but not below the bottom points well secured to the ends of the undertow.
long spar; the two side points d, e, fastened 4. It should not take up much room in the to the ends of two cords, which coming from ship.
the angle of the loop (which must be similar 5. It should be easily thrown out, and put to the loop of a kite) pass through two rings into its proper situation.
at the ends of the short spar, so as that on 6. It should be easy to take in again, and pulling upon the loop the sail will be drawn stow away.
to its extent. The whole may, when aboard, An ingenious old mariner, whom I former- be furled up, as in figure 19, having a rope ly knew, proposed, as a swimming anchor for from its broad end, to which is tied a bag of a large ship, to have a stem of wood twenty- ballast for keeping that end downwards when five feet long and four inches square, with in the water, and at the other end another four boards of 18, 16, 14 and 12 feet long, rope with an empty keg at its end to float on and one foot wide, the boards to have their the surface; this rope Jong enough to permit substance thickened several inches in the the kite's descending into the undertow, or if middle by additional wood, and to have each you please lower into still water. It should a four inch square hole through its middle, be held by a hauser. To get it home easily, to permit its being slipt on occasionally upon a small loose rope may be veered out with it, the stem, and at right angles with it; where fixed to the keg. Hauling on that rope will all being placed and fixed at four feet distance bring the kite home with small force, the refrom each other, it would have the appearance sistance being small, as it will then come end of the old mathematical instrument called a ways. forestaff. This thrown into the sea, and held It seems probable that such kite at the end by a hauser veered out at some length, he of a long hauser would keep a ship with her conceived would bring a vessel up, and pre- head to the wind, and, resisting every tug, vent her driving, and when taken in might would prevent her driving so fast as when her be stowed away by separating the boards from side is exposed to it, and nothing to hold her the stem. (Figure '15.). Probably such a back. If only half the driving is prevented, swimming, anchor would have some good so as that she moves but fifty miles instead of effect, but it is subject to this objection, that the hundred during a storm, it may be some laying on the surface of the sea, it is liable to advantage, both in holding so much distance be hove forward by every wave, and thereby as is saved, and in keeping from a lee-shore. give so much leave for the ship to drive. If single canvas should not be found strong
Two machines for this purpose have oc- enough to bear the tug without splitting, it curred to me, which, though not so simple may be doubled, or strengthened by a netting as the above, I imagine would be more ef- behind it, represented by figure 20. fectual, and more easily manageable. I will The other machine for the same purpose, is endeavour to describe them, that they may to be made more in the form of an umbrella, be submitted to your judgment, whether as represented, figure 21. The stem of the either would be serviceable; and if they umbrella, a square spar of proper length, with would, to which we should give the preference. four moveable arms, of which two are repre
The first is to be formed, and to be used in senter C, C, figure 22. These arms to be the water on almost the same principles with fixed in four joint cleats, as D, D, &c. one on those of a paper kite used in the air. Only each side of the spar, but so as that the four paper
kite rises in the air, this is to arms may open by turning on a pin in the descend in the water. Its dimensions will be joint. When open they form a cross, on which different for ships of different size.; à four-square canvas sail is to be extended,
its corners fastened to the ends of the four he added, they are carried back by the cur
Those ends are also to be stayed by rent more than they are forwarded by the ropes fastened to the stem or spar, so as to wind : and if the wind be good, the subtrackeep them short of being at right angles tion of 70 miles a day from their course is of with it: and to the end of one of the arms some importance. I then observed it was a should be hung the small bag of ballast, and pity no notice was taken of this current upon to the end of the opposite arm the empty keg: the charts, and requested him to mark it out This, on being thrown into the sea, would for me, which he readily complied with, addimmediately open; and when it had performed ing directions for avoiding it in sailing from its function, and the storm over, a small rope Europe to North America. I procured it to be from its other end being pulled on, would turn engraved by order from the general post-office, it, close it, and draw it easily home to the ship on the old chart of the Atlantic, at Mount and This machine seems more simple in its opera- Page's Tower-hill; and copies were sent tion, and more easily manageable than the down to Falmouth for the captains of the pacfirst, and perhaps may be as effectual.* kets, who slighted it however; but it is since
Vessels are sometimes retarded, and some-printed in France, of which edition I hereto times forwarded in their voyages, by currents annex a copy.* at sea, which are often not perceived. About This stream is probably generated by the the year 1769, or 70, there was an application great accumulation of water on the eastern made by the board of customs at Boston, to coast of America between the tropics, by the the lords of the treasury ir London, complain- trade-winds which constantly blow there. It ing that the packets between Falmouth and is known that a large piece of water ten miles New York, were generally a fortnight longer broad and generally only three feet deep, has in their passages, than merchant-ships from by a strong wind had its waters driven to one London to Rhode Island, and proposing that side and sustained so as to become six feet for the future they should be ordered to Řhode- deep, while the windward side was laid dry. Island instead of New York. Being then This may give some idea of the quantity concerned in the management of the Ameri- heaped up on the American coast, and the can post-office, I happened to be consulted on reason its running down in a strong current the occasion; and it appearing strange to me through the islands into the bay of Mexico, that there should be such a difference between and from thence issuing through the gulf of two places, scarce a day's run asunder, espe- Florida, and proceeding along the coast to the cially when the merchant-ships are generally banks of Newfoundland, where it turns off todeeper laden, and more weakly manned than wards and runs down through the Western the packets, and had from London the whole Islands. Having since crossed this stream length of the river and channel to run before several times in passing between America and they left the land of England, while the Europe, I have been attentive to sundry cirpackets had only to go from Falmouth, I could cumstances relating to it, by which to know not but think the fact misunderstood or mis- when one is in it; and besides the gulph weed represented. There happened then to be in with which it is interspersed, I find that it is alLondon a Nantucket sea-captain of my ac- ways warmer than the sea on each side of it, quaintance, to whom I communicated the and that it does not sparkle in the night: I affair. He told me he believed the fact might annex hereto the observations made with the be true; but the difference was owing to this, thermometer in two voyages, and possibly that the Rhode Island captains were acquaint- may add a third. It will appear from them, ed with the gulf stream, which those of the that the thermometer may be an useful inEnglish packets were not. We are well ac- strument to a navigator, since currents comquainted with that stream, says he, because in ing from the northward into southern seas, our pursuit of whales, which keep near the will probably be found colder than the water sides of it, but are not to be met with in it, we of those seas, as the currents from southern rundown along the sides, and frequently cross seas into northern are found warmer. And it it to change our side: and in crossing it have is not to be wondered that so vast a body of sometimes met and spoke with those packets, deep warm water, several leagues wide, comwho were in the middle of it, and stemming ing from between the tropics and issuing out it. We have informed them that they were of the gulph into the northern seas, should restemming a current, that was against them to tain its warmth longer than the twenty or the value of three miles an hour; and advis- thirty days required to its passing the banks ed them to cross it and get out of it; but they of Newfoundland. The quantity is too great, were too wise to be counselled by simple Ame- and it is too deep to be suddenly cooled by can fishermen. When the winds are but light, passing under a cooler air. The air immedi
* Captain Truxton, on board whose ship this was * The map in this edition has beeen constructed so as written, has executed this proposed machine ; he has to embrace in one view, the theory of the Gulf Stream giver six arms to the umbrella, they are joined to the and the theory of the migration of fish ; soule atten. stem by iron hinges, and the canvas is double. He has tion has been paid also to Volney's suggestions on the taken it with him to China. February, 1786.
subject of the Gulf Stream. See the plate.