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how useful this invention might be

on land as well as at sea. A sufficient number of soldiers, provided with these jackets, might pass a deep and rapid river in the night time, armed with pistols and sabres, and surprise a corps of the enemy. If repulsed, they could throw themselves into the water, and escape without any fear of being pursued. “During sea voyages, the sailors, while employed in dangerous manoeuvres, often fall overboard and are lost; others perish in ports and harbours by boats oversetting in consequence of a heavy swell, or some other accident; in short, some vessel or other is daily wrecked on the coasts, and it is not without difficulty that only a part of the crew are saved. If every man, who trusts himself to this perfidious element, were furnished with such a cork jacket, to put on during the

momentsof danger, it is evident that many of them might escape death.”

To construct a Boat which cannot be sunk, even if the Water should enter it on all Sides.

“ Cause a boat to be made with a false bottom, placed at such a distance from the real one, as may be proportioned to the length of the boat, and to its burthen and the number of persons it is intended to carry. According to the most accurate calculation, this distance, in our opinion, ought to be one foot, for a boat eighteen feet in length, and five or six in breadth. The vacuity between this false bottom and the real one ought to be filled up with pieces of cork, placed as near to each other as possible: and as the false bottom will lessen the sides of the boat, they may be raised proportionally; leaving large aper. tures, that the water thrown into the vessel may be able to run off. It may be proper also to make the stern higher, and to furnish it with a deck, that the people may take shelter under it, in case the boat should be thrown on its side by the

violence of the waves. “ Boats constructed in this manner might be of great utility for #. on board a vessel lying in a arbour, perhaps several miles from the shore; or for going on shore from a ship anchored at a distance from the land. Unfortunate accidents too often happen on such occasions, when there is a heavy surf, or in consequence of some sudden gust of wind; and it even appears that sometimes the greatest danger of a voyage is to be a . under circumstances of this kind. But boats constructed on the above principle would prevent such acci* Much we confess is to be added to this idea, presented here in all its simplicity; for some changes perhaps ought to be made in the form of the vessel; or heavy bodies ought to be added in certain places to increase its stability. This is a subject of research well worth attention, as the result of it might be the preservation of thousands of lives every year.

dents.

“Much

“ For this invention we are indebted to M. de Bernieres, one of the four controllers-general of bridges and causeways; who, in 1769, constructed a boat of this kind for the king. He afterwards constructed another with improvements for the duke de Chartres; and a third for the marquis de Marigny. The latter was tried by filling it with water, or endeavour.# to make it overset; but it righted as soon as left to itself; and though filled with water, was still able to carry six persons.

“By this invention the number of accidents which befal those who lead a sea-faring life, may in future be diminished ; but the indifference with which the invention of M. de Bernieres was received, shews how regardless men are of the most useful discoveries, when the general interests of humanity only are concerned, and when trouble and expence are required to render them practically useful.”

How to raise from the Bottom of the Sea a Vessel which has sunk.

“ This difficult enterprise has been several times accomplished by means of a very simple hydrostatical principle, viz. that if a boat be loaded as much as possible, and then unloaded, it tends to raise itself with a force equal to that of the weight of the volume of water

which it displaced when loaded. And hence we are furnished with the means of employing very powerful forces to raise a vessel that has been sunk. “. The number of boats employed for this purpose, must be estimated according to the size of the vessel, and by considering that the vessel weighs in water no more than the excess of its weight over an equal volume of that fluid ; unless the vessel is firmly bedded in the mud: for then she must be accounted of her full weight. The boats being arranged in two rows, one on each side of the sunk vessel, the ends of cables, by means of divers, must be made fast to different parts of the vessel, so that there shall be four on each side for each boat. The ends of these cables which remain above water, are to be fastened to the head and stern of the boat for which they are intended. Thus, if there are four boats on each side, there must be thirty-two cables, being four for each boat. “When every thing is thus arranged, the boats are to be loaded as much as they will bear without sinking, and the cables must be stretched as much as possible. The boats are then to be unloaded, two and two, and if they raise the vessel, it is a sign that there is a sufficient number of them; but, in raising the vessel, the cables affixed to the boats which remain loaded will be. come slack, and for this reason they must be again stretched as much as possible. The rest of the boats are then to be unloaded, by shifting their lading into the former. The vessel will thus be Elised a little more, and the cables of the loaded boats will become slack; these cables being again stretched, the lading of the latter boats must be shifted back into the others, which

N 4 will

will raise the vessel still a little higher; and if this operation be repeated as long as necessary, she may be brought to the surface of the water, and conveyed into port, or into dock. “An account of the manoeuvres employed to raise, in this manner, the Tojo, a Spanish ship belonging to the Indian fleet, sunk in the harbour of Vigo, during the battle on the 10th of October 1702, may be seen in the ‘Mémoirs des Academiciens étrangers,’ vol. ii. But as this vessel had remained more than thirty-six years in that state, it was imbedded in a bank of tenacious clay, so that it required incredible labour to detach it; and when brought to be surface of the water, it contained none of the valuable articles expected. It had been one of those unloaded by the Spaniards themselves, before they were sunk, to prevent them from falling into the hands of the English. “On the same principle is constructed the camel, a machine employed by the Dutch for carrying vessels heavily laden over the sand banks in the Zuyder-Zee. In that sea, opposite to the mouth of the river Y, about six miles from the city of Amsterdam, there are two sand banks, between which is a passage, called the Pampus, sufficiently deep for small vessels, but not or those which are large and heavily laden. On this account ships which are outward bound take in before the city only a small part of their cargo, receiving the rest when they have got through the Pampus; and those that are homeward bound must, in a great measure, unload before they enter it. For this reason the goods are put into lighters, and in these transported to the warehouses of the merchants in the city; and the

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large vessels are then made fast to boats, by means of ropes, and in that manner towed through the passage to their stations. “Though measures were adopted, so early as the middle of the sixteenth century, by forbidding ballast to be thrown into the Pamus, to prevent the farther accumuation of sand in this passage, that inconvenience increased so much, from other causes, as to occasion still greater obstruction to trade; and it at length became impossible for ships of war and others heavily laden to get through it. About the year 1672, no other remedy was known, than that of making fast to the bottoms of ships large chests filled with water, which was afterwards pumped out, so that the ships were buoyed up and rendered sufficiently light to pass the shallow. By this method, which was attended with the utmost difficulty, the Dutch carried out their numerous fleet to sea in the above-mentioned year. This plan however gave rise soon after to the invention of the camel, by which the labour was rendered easier. The camel consists of two half ships, constructed in such a manner that they can be applied, below water, on each side of the hull of a large vessel. On the deck of each part of the camel are a great many horizontal windlasses; from which ropes proceed through apertures in the one half, and, for. carried under the keel of the vessel, enter similar apertures in the other, from which they are conveyed to the windlasses on its deck. When they are to be used, as much water as may be necessary is suffered to run into them; all the ropes are cast loose, the vessel is conducted between them, and large beams are placed horizontally through the port-holes of the vessel, with their ends resting on the camel, on each side. When the ropes are made fast, so that the ship is secured between the two parts of the camel, the water is pumped from them, by which means they rise, and raise the ship along with them. Each half of the camel is generally one hundred and twenty-seven feet in length; the breadth at one end is twenty-two, and at the other thirteen. The hold is divided into scveral compartments, that the machine may be kept in equilibrio, while the water is flowing into it.

port

An East-India ship that draws

fifteen feet of water, can by the help of the careel be made to draw only eleven; and the heaviest ships of war, of ninety or one hundred guns, can be so lightened, as to pass, without obstruction, all the sand banks of the Zuyder-Zee. “ Leupold, in his Theatrum machinarum, says that the camel was invented by Cornelius Meyer, a Dutch engineer. But the Dutch writers, almost unanimously, ascribe this invention to a citizen of Amsterdam, called Meeuves Meindertszoon Bakker. Some make the year of the invention to have been 1688, and others 1690. However this may be, we are assured, on the testimony of Bakker himself, written in 1692, and still preserved, that in the month of June, when the water was at its usual height, he conveyed, in the course of twenty-four hours, by the help of the camel, a ship of war called the Maagt van Enkhuysen, which was one hundred and fifty-six feet in length, from Enkhuysen Hooft, to a place where there was sufficient depth ; and that this could have been done much sooner had not a rfect calm prevailed at the time. n the year 1698, he raised a ship

called the Unie six feet by the help of this machine, and conducted her to a place of safety. “As ships built in the Newa cannot be conveyed into harbour, on account of the sand banks formed by the current of that river, camels are employed also by the Russians, to carry ships over these shoals: and they have them of various sizes. Bernoulli saw one, each half of which was two hundred and seventeen feet in length. and thirty-six in breadth. Camels are used likewise at Venice.”

What is it that supports in an upright Position, a Top or Tetotum, while it is revolving P

“It is the centrifugal force of the parts of the top or tetotum, put in motion. For a body cannot move circularly without making an effort to fly off from the centre; so that if it be affixed to a string, made fast to that centre, it will stretch it, and in a greater degree according as the circular motion is more rapid. . . .

“The top then being in motion, all its parts tend to recede from the axis, and with greater force the more rapidly it revolves; hence it follows that these parts are like so many powers acting in a direction perpendicular to the axis. But as they are all equal, and as they pass all round with rapidity by the rotation, the result must be that the top is in equilibrio on its point of support, or the extremity of the axis on which it turns.

How comes it that a Stick, loaded with a Weight at the upper Extremity, can be kept in Equilibrio, on the Point of the Finger, much easier than when the Weight is near - - the

the lower Extremity; or that a Socord, for Example, can be ba

lanced on the Finger much better then the Hill is uppermost 8

“The reason of this phenomenon, so well known to all those who perform feats of balancing, is as follows. When the weight is at a considerable distance from the point of support, its centre of gravity, in deviating either on the one side or the other from a perpendieular direction, describes a larger circle, than when the weight is very near to the centre of rotation, or the point of support. But in a large circle an arc of a determinate magnitude, such as an inch, describes a curve which deviates much

less from a horizontal direction than if the radius of the circle were less. The centre of gravity of the weight then may, in the first case, deviate from the perpendicular the quantity of an inch, for example, without having a tendency or force to deviate more, than it would in the second case; for its tendency to deviate altogether from the perpendicular is greater, according as the tangent to that point of the arc where it happens to be, approaches more to a vertical direction. The greater therefore the circle described by the centre of gravity of the weight, the less is its tendency to fall, and consequently the greater the facility with which it can be kept in equilibrio.”

ANIMALcules capable of REvivification.

[From Mr. DALYELL’s TRAN slation of SPAllANZANI’s Tracts.]

44 NHE sand of tiles, the mud

T of ditches and marshes, which pass in the vulgar eye for the vilest of matter, are sources of wonder to the philosophic observer, from the rare and singular beings they contain. To the mud of ditches and marshes we owe the cluster, armed, bulb, funnel, and knotted polypus. It is there we find the fresh-water worm, the boat worm, and the dart millepede, animals that have confounded the human mind, and created a new philosophy. When the sand of tiles is not the abode of wheel animals, it is not then the less famous or remarkable. An animal which revives after death, and which, within certain limits, revives as often as we please, is a phenomenon as incredible as it seems improbable and Paradoxical. It confounds the most

received ideas of animality; it creates new ideas, and becomes an object no less interesting to the researches of the naturalist than the speculation of the profound metaphysician. But the celebrity of this sand will increase, by learning that it contains other animals, which, like the wheeler, possess the property of resurrection: so that we almost say, all the animals living in sand are immortal. There I have discovered two new species of animals, which I proceed to describe. I lament that their raremess has prevented me from extending my observations as far as I could have wished, or rather as far as the importance of the subject would have required. “. On wetting wheel animals' sand, 1 several times observed a yellowish animal three or four times

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