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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. 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, a scribe 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. How ever 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 perfect calm prevailed at the time. In 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 Rus sians, to carry ships over these shoals: and they have them of va rious sizes. Bernoulli saw one, each half of which was two hun dred 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?

"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 Scord, for Example, can be balanced on the Finger much better when the Hilt is uppermost ?

"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 are 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 TRANSLATION of SPALLANZANI'S TRACTS.]

"TH

HE sand of tiles, the mud 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 rareness 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

larger

larger than a wheeler with six legs; but I paid no particular attention to it, supposing that it was some little terrestrial insect that had casually fallen into the watch-glass where the sand was kept. My reason for thinking so, was from always having seen it move obliquely and very slowly at the bottom of the water, as if unable to walk, and often supine, making great exertions to recover its natural position, but they were in general fruitless, as happens to many aërial and terrestrial insects casually falling into water. At the same time, with more continued and careful observation, I recognised it as an animal really aquatic, and perceived that its awkward and laborious mode of progression was from the smoothness of the glass slider on which it bad been put for examination, and, when placed on sand, that it had a regular progressive motion, slow indeed, and, compared with the wheel animals' motion, like the crawling of a tortoise. Thus to design it by some descriptive name, I called it the Sloth.

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"The whole body is granulated: the anterior part obtuse: and the posterior terminated by four hooked filaments, which serve for attaching it to any particular place. The limbs have small shining claws, or nails, which, as far as one can judge, are of a corneous substance, the points turned towards the body, as we see in the recurved claws of several insects. The corpulence of the sloth, rendering it opaque, prevents us from seeing the internal organization. But we can perceive a small elliptical spot in the middle of the body, which I suspect to be the reservoir of the aliments. In the anterior part is also distinguished an internal lucid spot, smaller, narrower, and longer than

the other, which I have sometimes supposed the oesophagus. The figure of the whole is clumsy, and very much resembles the testicle of a cock.

"This animalcule forms no vortex in the water, which is not surprising, as it has neither the wheels nor fibrille of the animals that perform this operation. It appears that the wheel animal cannot advance a step without fixing the trident to some adjacent substance; it is otherwise with the sloth, for it often makes no use of its hooked filaments. It never swims; it is specifically heavier than the water; thence it always turns round on the surface of the sand, or amongst it.

"The phenomena of its death, from the want of water, and of resurrection when water is supplied, are precisely the same with those of the wheel animal. Motion gra dually ceases: the limbs are contracted and drawn entirely within the body, which diminishes very much, is completely dried, and assumes a globular figure. The reverse succeeds when the sloth is revived by supplying water. As the wheel animal can only revive a certain number of times, so it is with the sloth. And, although sand is necessary for its resurrection, it does not appear so essential as for that of the wheel animal.

"The degrees of heat, fatal to revived or dead wheel animals, are also fatal to sloths; and the same may be said of odours and liquors. Cold, however intense, docs them no harm, and in this they likewise coincide with wheel animals.

"Sloths are infinitely more rare than wheel animals: for five-andtwenty of these, four or five sloths are hardly found. All are of the

same

same figure, but not equal in size. I have isolated many in watchglasses, sometimes with sand and sometimes with pure water, intending to discover their mode of propagation; but, instead of multiplying, all perished; some sooner, some later, none ever attaining the sixth day.

"The third species of resurgent animals found in sand consists of certain minute eels, very like the anguille of vinegar. This species is much rarer, nor is it to be found on every roof. The head and adjoining part of the body are very transparent, and of a shining silver colour: the tail is the same, but the intermediate part is darkish and all granulated. The greater part of the tail is bent, and terminates in a very sharp point. The head, on the contrary, is obtuse; and a little below the extremity there is a mouth, which terminates a canal, apparently serving for an œsophagus, and traversing the whole length of the body.

"If the sand is quite dry, they are seen motionless, dried up, and generally bent into a spiral. When considerably sprinkled with water, they soon exhibit signs of life. The tail first commences a gentle motion, bending and turning in different directions; the head then moves, and afterwards the rest of the body: so that the whole animal soon becomes animated. Whence it results, that the same degree of humidity is not required to animate this species as for the wheel animal and sloth, which do not revive unless completely immersed in water. The eels do not change their place; they only extend, contract, turn, and bend. If the sand is thoroughly wet, their activity, and rapidity of course, is as great as that of the eels of vinegar. Pro

vided they have water, they live long in watch-glasses: if there is sand at the bottom, they seldom quit it, always moving about the grains, and pushing their heads among them, which would induce us to suppose that they do so in search of food, for some more minute and delicate particles are transmitted by the mouth to the esophagus. Notwithstanding they have been long kept in glasses, I never saw them propagate.

"When the water evaporates, they die; but they resist death longer than wheel animals and sloths. A small degree of motion remains several minutes after evaporation : when dead, the figure of the body is changed; the length is contracted, and the breadth is diminished. They insensibly resume their original size on humectation, and animation returns. There are conditions necessary for resurrection: when the eels are in sand, a quarter of an hour is sufficient for recalling them to life; but in pure water, there is a great difference, according to circumstances. If only the first or second time of revival, there is not much difference in the time required for resurrection; but, in proportion as the number of resurrections increases, the time necessary for revival always becomes greater: an hour at least, and sometimes more, is required for the fourth; for the fifth still longer, and so on for the rest. The frequency of resurrection in pure water, as in sand, is limited, like that of wheel animals and sloths. The eels die for ever at the seventh or the eighth, or, at most, the ninth resurrection; and, although moistened again, they revive no more. Part of their rapidity and activity is lost in each resurrec

tion, so that the last is but a simple change from immobility to languid contorsions of the members.

"Here then are three species of animals, inhabiting the sand of roofs, which nature has permitted to revive after death. These three are the only inhabitants of this sand, at least I do not think I have ever seen other animated beings there, having a permanent abode. They are not the only animals, however, that enjoy. the privilege of resurrection; others also possess it: among these, the celebrated eels of blighted corn deserve to be particularly mentioned. All the world knows that Mr. Needham is the author of this famous discovery. Examining the internal surface of blighted corn, he saw, with agreeable surprise, that it was composed of minute eels, which, on being wet, acquired motion, and gave certain indications of life. Their imme.diate resurrection, as he has observed, takes place when the ears are gathered still fresh and humid if they have been gathered some time, and have lost their humidity, maceration is necessary; nor will this always be sufficient for resurrection; it is even requisite that the eels remain a given time in the water. When allowed to dry, they become motionless, and recover life on humectation. But what chiefly surprised the author of the discovery was, after having preserved the blighted corn for two years and more, the same phenomena were observed anew when it was wet.

"The fact was too wonderful for others not to endeavour to ascertain it. It has been corroborated by several good observers, such as the illustrious translator of Mr. Needham's work, where this

discovery is spoken of; by the count Ginnani; but by Baker in particular, in his excellent treatise on the eels of blighted corn. Among other things, he has seen the resurrection of eels taken from grain that had been dry four years. This observation he made before Mr. Folkes, then president of the Royal Society, and other friends. But he witnessed a resurrection much more wonderful, which was effected after a far longer time. In 1771 he had some blighted corn, which he had got from Mr. Needham in 1744. In his experiments, resurrection succeeded perfectly at the end of twenty-seven years.

"In short, there is not at this day any professor, any amateur of natural history, particularly in Italy, who does not take pleasure in amusing himself, and gratifying the curiosity of his learned friends, with these admirable resurrections. For this reason, I judge it needless to stop and prove their reality by new facts, and to speak of the origin and generation of the eels; for we know that this, which is a most essential part of their history, has been amply elucidated by the learned labours of Italians. The result of some of my trivial observations only shall be related, which will both serve as proofs of their history, and are analogous to those we have given of other resurgent animalcula.

"The external colour of a grain of blighted corn, that has been kept some time, is like soot: if broken, the internal substance consists of a dry whitish matter, which, examined with the microscope, changes to a mass of long eel-shaped corpuscula. They are not only excessively dry, but lifeless, and so confused and confounded together, that it is ex

tremely

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