wards found in the same situation as before. It also happened, that on placing the hand on the loins of this horse, he kicked with great violence, and repeated his stroke several times. Now, during the period his hind legs were in the air, all the weight of the animal was sustained by the laminæ of two feet, and yet this extraordinary weight made not the smallest change in the situation of the foot bones."

The descent of the horny and sensible soles seems to be necessary, in order to allow the lamina to elongate and act the purpose of a spring; and that this actually does happen in the proportion that the elongation takes place, was proved by an experiment, in which

"The space between the shoe and horny sole was filled with a quantity of plaster of Paris, made of a sufficient thickness not to escape by the motions of the limb. The horse was then walked, in which action there appeared but a very trifling displacement of the plaster; but, on trotting the animal, which added force to weight, a large quantity of the plaster was displaced from under the shoe. I repeated this experiment," continues the author, "with stiff clay, and the same result followed. It has also been found, that a small stone, introduced with ease at the heels, between the shoe and horny sole, or the shoe being in contact with the sole, will frequently, while the horse is standing still, or only walking, occasion no inconvenience; but when his motions are quickened, the pain and lameness become

manifest."

The effects of pressure upon the frogs in expanding the heels of horses, will appear from the following quotation.

"The superior part of the sensible frog being received between the two side cartilages, in proportion as the horny frog receives pressure, the cartilages, when in health, expand or recede from each other; but when the cartilages, from ossification, contraction of the hoof, or any other cause, are deprived of motion, the upper part of the sensible frog is confined between two fixed points: whereas, in the natural state, when the horny frog meets the ground, the superior portion of the sensible frog ascends between the side cartilages, and the wedge-like form of that organ necessarily opens the heels of the side cartilages. The expansion of the side cartilages at every ascent of the horny

and sensible frogs, not only gives a powerful spring to the animal, and enables the frogs to complete their function, but the direction of the growth of the crust at the quarters and heels, is absolutely governed by the motion of the side cartilages.

"If the horny frog has no pressure, the cartilages are at rest, and the heat of the stable evaporates the moisture of the crust, and contracts the quarters and heels of the living hoof, as on every kind of dead or hoof. Heat produces the same effect on the living horn: catgut, leather, hair, and, I believe, all animal substances are also diminished by heat. When the water is eraporated, the solid parts contract; but the crust at the interior part is preserved from any considerable contraction, in consequence of being opposed by the coffin-bone; but the upper part of the quarters, and the heels of the hoof, being placed opposite to cartilage, a substance naturally elastic, and incapable of much resistance, the overbearing contraction of the crust presses the cartilages towards each other, and narrows the heels. So long as the frog uniformly touches the ground, this effect will not take place; for the wedge-like form of that organ being pressed upwards between the cartilages, prevents the new crust at the quarters of the cornet from contraction. The weight and action of the animal forcing the frogs ebliquely upward, laterally expands the side cartilages; and it is this expansion at the heels which puts the soft newly formed crust on the stretch, and directs its future growth obliquely outward. The crust at its origin, immediately below the hair, is very thin, and of a soft elastic nature; and, at the quarters and heels, is always governed in its growth downward by the natural ex pansion, or by the morbid contraction of the cartilages."

From the contraction which takes place in the circumstances now ailuded to, the sides of the sensible frog are pressed upon, and the inflammation and suppuration called thrush, produced.

The distribution of the blood vessels in the horse's foot, is extremely curious. It seems to the author, to be intended, not only to obviate the effects of acci dental interruptions, by the frequent anastomose which take place, but to retard the motion of the blood, and thus to prepare it for the secretion of horn.

some points of view, the plan may be useful; but, as an introduction to the veterinary art, it does not appear to possess any particular advantages over a systematic treatise on the same subject. The author seems to have availed himself of the best and latest information in the different articles which compose the first part of his work. The following quotation on the mode of ascertaining the age of horses, may be interesting to some of our readers, and will serve as a specimen of the author's style.

A

"AGE OF A HORSE.This is easily known by his mouth, till he comes eight, after which the usual marks wear out. horse, like many other brute animals, has his teeth divided into three ranks, viz. his foreteeth, which are flat and smooth, his tushes, and his back-teeth. His back-teeth, or jawteeth, are called his grinders, being those by which a horse chews and grinds his provender, and are twenty-four in number, twelve above, and twelve below: they are strong double teeth with sharp edges; but when a horse grows old, they wear much smoother.

"The first that grow are his foal teeth, which begin to appear a few months after he is foaled: they are twelve in number, six above, and six below; and are easily distinguished from the teeth that come afterwards, by their smallness and whiteness, not unlike the fore teeth of a man.

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When the colt is about two years and a half old, he casts the four middlemost of his foal teeth, viz. two above and two below; but some do not cast any of their foal teeth till they are near three years old. The new teeth are easily distinguished from the foal teeth, being much stronger, and always twice their size, and are called the INCISORS or gatherers, being those by which a horse nips off the grass, when he is feeding abroad in the fields, or, in the house, gathers his hay from the rack. When a horse has got these four teeth complete, he is reckoned three years old.

"When he is about three and a half, or in the spring before he is four years old, he casts out four more of his foal teeth, viz. two above, and two below, one on each side the nippers, or middle teeth: so that when you look into a horse's mouth, and see the two middle teeth full grown, and none of the foal teeth, except the common teeth, remaining, you may conclude he is four that year, about April or May. Some indeed are later colts, but that makes little alteration in the mouth.

"The tushes appear near the same time with the four last-mentioned teeth, sometimes sooner than these, and sometimes not till after a horse is full four years old: they are curved like the tushes of other beasts,

only in a young horse they have a sharp edge all round the top, and on both sides, the inside being somewhat grooved and flattish, inclined to a hollowness.

"When a horse's tushes do not appear for some time after the foal teeth are cast, and the new ones come in their room, it is generally owing to the foal teeth having been pulled out before their time, by the breeders or other dealers in horses, to make a colt of three years old appear like one of four, that he may be the more saleable; for when any of the foal teeth have been pulled out, the others soon come in their places; but the tushes having none that go before them, can never make their appearance till their proper time, viz. when a horse is about four, or coming four; and therefore one of the surest marks to know a four-years-old horse, is by his tushes, which are then very small, and sharp on the top and edges.

"When a horse comes five, or rather in the spring before he is tive, the corner teeth begin to appear, and at first but just equal with the guns, being filled with flesh in the middle. The tushes are also by this time grown to a more distinct size, though not very large: they likewise continue rough and sharp on the top and edges. But the corner teeth are now most to be remarked; they differ from the middle teeth in being more fleshy on the inside, and the gums generally look rawish upon their first shooting out, whereas the others do not appear discoloured. The middle teeth arrive at their full growth in less than three weeks, but the corner teeth grow leisurely, and are seldom much above the gums till a horse is full five: they differ also from the other fore teeth in this, that they somewhat resemble a shell; and thence are called the shell teeth, because they environ the flesh in the middle half way round; and as they grow, the flesh within disappears, leaving a distinct hollowness and openness on the inside. When a horse is full five, these teeth are generally about the thickness of a crown-piece above the gums. From five to five and a half they will grow about a quarter of an inch high, or more; and when a horse is full six, they will be near half an inch, and in some large horses a full half-inch, above the gums.

"The corner teeth in the upper jaw fall out before those in the under, so that the upper corner teeth are seen before those below; on the contrary, the tushes in the under gums come on before those in the upper.

When a horse is full six years old, the hollowness on the inside begins visibly to fill up, and that which was at first fleshy, grows into a brownish spot, not unlike the eye of a dried garden bean, and continues so till he is seven; with this difference only, that the tooth is more filled up, and the mark, or spot, becomes faint, and of a lighter colour. At eight, the mark in most horses

is quite worn out, though some retain the vestiges of it a long time; and those who have not had a good deal of experience, may sometimes be deceived by taking a horse of nine or ten years old for one of eight. It is at this time only, when a horse is past mark, that one can easily err in knowing the age of a horse; for what practices are used to make a very young horse or colt appear older than he is, by pulling out the foal teeth before their time, may be discovered by feeling along the edges where the tushes grow, for they may be felt in the gums before the corner teeth are put forth; whereas, if the corner teeth come in some months before the tushes rise in the gums, we may reasonably suspect that the foal teeth have been pulled out at three years old.

"It will, perhaps, be needless to mention the tricks that are used to make a false mark in a horse's mouth, by hollowing the tooth with a graver, and burning a mark with a small hot iron; because those who are acquainted with the true marks, will easily discover the cheat by the size and colour of the teeth, by the roundness and bluntness of the tushes, by the colour of the false mark, which is generally blacker, and more impressed than the true mark, and by many other visible tokens, which denote the advanced age of a horse.

"After the horse has passed his eighth year, and sometimes at seven, nothing certain can be known by the mouth. It must, however, be remembered, that some horses have but indifferent mouths when they are young, and soon lose their mark; others have their mouths good for a long time, their teeth being white, even, and regular, till they are sixteen years old and upwards,

together with many other marks of freshness and vigour; but when a horse comes to be very old, it may be discovered by several indications, the constant attendants of age, viz. his gums wear away insensibly, leaving his teeth long and naked at their roots: the teeth also grow yellow, and sometimes brownish. The bars of the mouth, which, in a young horse, are always fleshy, and form so many distinct ridges, are, in an old horse, lean, dry, and smooth, with little or no rising. The eye-pits in a young horse (except those come of old stallions) are generally filled up with flesh, look plump and smooth; whereas in an old horse, they are sunk and hollow, and make them look ghastly, and with a melancholy aspect. There are also other marks which discover a horse to be very old, viz. grey horses turn white, and many of them all over flea-bitten, except their joints. This, however, happens sometimes later, and sometimes sooner, according to the variety of colour and constitution. Black horses are apt to grow grey over their eye-brows, and very often over a good part of their face, especially those who have a star or blaze fringed round with grey when they are young. All horses when very old, sink more or less in their backs, and some horses, that are naturally long backed, grow so hollow with age, that it is scarce possible to fit them with a saddle. Of this kind are several Spanish and Barbary horses, and many of the Danish and Flanders breed. The joints also grow stiff with old age, and their knees and hocks bend so, that they are apt to trip and stumble upon the least descent, though the way be smooth, and no ways rugged. After which they can be of little use to the owner."

for the most part unacknowledged, use that has been made of it by the authors of all succeeding cyclopædias and dictionaries of science in the English language, and by the writers of the French Encyclopedié, is a striking proof of its intrinsic merit. The interval that has elapsed since the publication of Dr. Rees's edition of Chambers, has been distinguished for nothing more than the immense acceleration of the march of science and the arts: investigations on every subject have been pursued with a minuteness and comprehensiveness of which there had existed before only few examples; and no human intellect is now sufficiently capacious to admit even a very imperfect outline of the various and complicated objects of human knowledge.

The second edition of Chambers, bulky and expensive as it was, experienced and deserved a large and rapid sale; encouraged by which the proprietors have commenced the publication of a new one. Two volumes have already made their appearance; but our remarks must be at present confined to the first. The alteration in size from the cumbersome folio form of the preceding edition, to the handsome quarto of the present, is an improvement sufficiently obvious indeed, but not the less real and important. Another circumstance in its favour is, that it is superintended by the abilities and matured experience of the former editor, assisted in various departments by men of learning and eminent professional skill: the names of these coadjutors have been published, and we are justified in expecting much from a work thus supported.

Among the mathematical articles of this volume are several of considerable importance, which, in general, are drawn up with great accuracy, and manifest the hand of a master. One great excellence common to them all is, that the sources whence the knowledge required on any subject may be drawn are well pointed out; so that a student who wishes to pursue his inquiries to a greater extent than this work from its very nature affords him, is directed to a catalogue of authors which, perhaps, errs sometimes rather on the side of excess than defect.

The most laboured article is algebra; in the composition of which much assist

ance has been derived from the labours of Dr. Hutton. The history of this branch of science is well given to the days of Vieta, who understood the theory of equations, where the number of roots was equal to that of the highest index of the unknown quantity. After his time a hypothesis was admitted, for the honour of which a contest took place between the French and English writers; and Wallis is treated with a great deal of acrimony by the historian Montucla. As soon as the doctrine of the genera tion of equations had taken place of the theory and mode of investigation pointed out by Vieta, inquiries were daily made into the nature of positive, and negative, and impossible roots, and researches of this kind were carried to the greatest extent by Waring. Within the last fifty years the whole of this doctrine has been called in question; and as the innova tion after Vieta's time has been so well explained, we expected to have also found an account of the resistance opposed to it, and the attempts made to restore the ancient method of demon. stration. Here, however, we have been disappointed; for though Baron Maseres is honourably mentioned, yet his peculiar merit is forgotten, and no reference is made to the work published by him nearly fifty years ago on the nega tive signs: nor is it mentioned that he and Mr. Frend follow a system in their publications of algebra, by which every consideration of what are called nega tive or impossible roots is excluded. As Mr. Frend has laid down a different classification of equations, determining the greatest number of roots of which an equation is susceptible by the num ber of unknown terms, and not by the highest index of the unknown term, this distinction should also have been no ticed: the defect, however, may be repaired under the article equation." Sir I. Newton is said to have discovered the binomial theorem; but as particular notice is taken of "the many valuable papers" of Baron Maseres on this theorem, we trust that when we come to the particular article, a due degree of merit will be assigned to the original inventors of this curious and hitherto not sufficiently developed theorem.

Under the article acceleration reference is made to Mr. Robertson's two propositions on this subject; but though it is said that "the laws of accelerated mo