what flexible and elastic towards the heels, it assists in the action of those curious springs we have just described. The bars form two ridges, one on each side the frog, extending from the heel of the crust towards the toe of the frog. They appear to be a continuation of the crust, being, like it, composed of strong longitudinal fibres. At the part where it joins the crust, a very firm bearing is afforded for the beel of the shoe. The use of the bars is to oppose any disposition there may be in the hoof to contract, by acting as props to the heels but, in the common practice of shoeing, they are generally destroyed, for farriers have supposed that they bind the heels together, and prevent their expansionthey have therefore named them binders, and cat them away, in order to open the heels, as they term it. The internal foot is endued with great sensibility; and so nicely adapted to the coffin, or hoof, that it completely fills it, without suffering the least inconvenience from pressure; but when the foot has been improperly treated, when the frog has been mutilated, the bars destroyed, and shoes applied that are either turned up or made very thick at the heels, the hoof must necessarily contract, and its cavity become diminished; so that the nerves and blood-vessels being compressed, the circulation of the blood is impeded, and lameness will naturally follow. All the anterior and lateral surfaces of the sensible foot are covered with that membranous or laminated substance which we have before described; but it differs from those laminae which are found on the internal surface of the crust, in possessing numerous blood-vessels. At the upper part of the sensible foot, where the lamina terminate, a roundish projecting body may be observed, extending all round the coronet to the back part of the frog; this is termed the coronary ring: its surface is covered with the extremities of blood-vessels, and it is from this part that the hoof is formed. The natural frog of the horse, says Mr. Coleman, is placed in the centre of the sole, externally convex, and of a wedgelike form, pointed towards the toe, but expanded as it advances to the heels. In the centre of the broad part there is a fissure, or separation. The frog is connected internally with another frog, of a similar figure, but different in structure. The external frog is composed of soft elastic horn, and totally insensible. The internal frog has sensation, and is much more elastic than the horny frog; and at the extremity of the heels is connected with two elastic substances called cartilages. The toe of the sensible frog is united to the coffin-bone; but more than nine-tenths of both frogs are behind the coffin-bone. The toe of the sensible and horny frogs, from their connection with the coffin-bone, are fixed points, and have no motion; but the heels of the frogs being placed posterior to the coffin-bone, and in contact with movable, elastic, and not fixed or resisting substances, a very considerable lever is formed, and whenever the horny frog comes in contact with the ground, it first ascends, and then descends. The pressure of the ground also expands the horny frog, and the sensible frog expands the cartilages, and at the heels and quarters, immediately below the hair, totally governs the direction of the future growth of the crust. This ascent of the frog not only, by its wedge-like form, preserves the heels and quarters from contraction, but affords to the horse an elastic spring, and prevents the animal from slipping whenever it embraces the ground. Without any anatomical inquiry into its internal structure and union with other parts, the shape and convexity of the horny frog clearly demonstrate that it was formed to come into contact with the ground; and the more I investigate this subject, the more I am convinced that the use of the frog is to prevent the horse from slipping, to preserve the cartilages and hoof expanded, and, by its motion, to act as an elastic spring to the animal. Mr. Coleman contends, that Mr. St. Bel, and many others, who suppose that the use of the frog is merely to serve as a cushion, or guard, to the tendon of the flexor muscle of the foot, and who, on that account, were disposed rather to raise the frog from the ground by a thick-heeled shoe, have been in an error. On the contrary, he maintains it to be a law of nature, that, unless the frog perform its functions, by being allowed to press the ground, it must become diseased. Accordingly, the practice of shoeing depends very much on the functions of the frog being understood. If the opinions here advanced respecting its uses be well founded, then it must follow, that paring the frog, and raising it from the ground, annihilates its functions, and ultimately, if not immediately, produces disease; and that exposing the frog to pressure is the only proper method to keep it in health. Moreover, it has from experience been ascertained, that, unless the frog sustain an uniform pressure when at rest, the heels as well as the frog contract, but if that organ be in close contact with the ground, then it spreads and is free from thrushes and canker, and operates as a wedge to keep open the hee's of the hoof. Granite and other hard substances give no pain to a frog exposed to constant pressure in the stable; but, when above the pavement, it generally becomes contracted, and the sensible frog inflamed, and then one stroke from a projecting stone will produce pain, perhaps lameness, while perpetual perpendicular pressure is attended with salutary effects. When the hoof contracts, the frog must also become contracted, and inflammation and a suppuration follows, called a thrush. No contraction, however, takes place where the frog is made to receive constant pressure, as the standing perpetually on that wedge increases its growth, presses upward the sensible frog, and expands the cartilages of the hoof. And as the first shoot of the crust at the coronet is very thin, the direction of its fibres will be altogether regulated by the width of the cartilages immediately below the hair at the quarters and heels, and the cartilages will be always more or less expanded, and the hoof more or less circular, as the frog has more or less pressure. On that principle, continues Mr. Coleman, I long since recommended a shoe with thin heels as the best formed shoe to bring the frog on the same level; and with great truth I can assert, that, although in some instances, from a sudden misapplication of the thinheeled shoe to improper feet, I have seen the tendons affected, yet, from all the experience I have since had, and from what I have seen or heard of the practice of others, I know of no instance where the frog, from constant pressure, did not expand and receive great benefit. But the pavement, whatever shoes are employed, the hoof in the stable will be as much disposed to contract as if the frog was raised any greater distance. I wish this fact to be well considered; for it has been supposed that shoes with a flat seat, without pressure to the frog, will prevent contraction. I am fully convinced, that neither thick nor thin heeled shoes, where the frog is raised above pressure, and exposed to the heat of the stable, can prevent contraction or its effects; and, where the frog receives that pressure, the heels cannot contract even with the most common shoes. For very obvious mechanical reasons, a wedge in the centre of the heels, aided by the pressure from below, must be best calculated to preserve them expanded, or, when the heels are contracted, to force them open. The heat of the stable in all cases tends to contraction of the hoof; but, with common shoes, there is no pressure on the wedge, or other cause to counteract that tendency. The artificial frog, which is intended to cover and give any degree of pressure to the natural frog only, is made of iron. In order to fit the natural frog, it is requisite to ascertain its width, the length of the foot, and the disWhere the frog is in a morbid state, tance between the lower surface of the shoe and unnaturally deprived of a perpendicular and the frog. But if the artificial frog be pressure, it is seldom safe to lower the heels too long, the toe, which is flat and thin, at once, so as to make the frog on a level may be shortened; and if the heels of the with the shoe; and, in many cases, it is not shoe are higher than the artificial frog, possible with any shoes, or even without nothing more is requisite than to introduce shoes, to give the frog pressure on smooth a surfaces; much less is it practicable for the frog to rest on the ground when shod with common thick-heeled shoes. In the stable, therefore, while at rest, the frog is generally raised above the shoe; and as pressure is essential to its health, particularly when the hoof is exposed to heat, it appeared to me of great importance, in all cases where the heels of the shoe and the frog cannot with safety be made on the same level, to apply an artificial frog (see Plate IX.), to fit and give any degree of pressure, in the stable, to the natural frog, with any shoes. While the horse is in motion, and the hoof exposed to unequal surfaces, the artificial frog should be removed, as the natural frog, out of the stable, will receive frequent pressure with any shoes; but that period is of short duration, when compared to the length of time the horse remains at rest, and the frog raised from the ground. Artificial pressure is most particularly wanted when the heat of the stable operates powerfully to contract the hoof. In all cases, therefore, where the pavement of the stable does not touch the natural frog, an artificial frog is necessary to resist contraction of the hoof, thrushes, and canker. Sand-cracks, also, very generally arise from a contracted hoof, and may be prevented by the artificial frog does not absolutely rest on quantity of tow between the natural and artificial frog, so as to raise it equal or above the level of the shoe. I have ascertained by experience, that no inconvenience takes place by raising the artificial frog even one quarter of an inch above the shoe; but, in ordinary cases, it should not project more than one-sixth of an inch above the surface of the shoe. It may, however, be imagined, that so much perpendicular pressure to the frog would retard rather than increase its growth; but the very reverse is the fact; for as the frog, when long elevated above the ground, is very generally contracted, this unnatural lateral pressure excites inflammation of the sensible frog, and deprives, in a great degree, the blood-vessels of the power of secreting horn. When the horny frog is exposed to perpendicular pressure, it gives health, and not disease, to the sensible frog. The blood-vessels secrete their due proportion of elastic horn, and then the cavity of the frog is preserved, expanded, and fully equal to contain the sensible frog, without the smallest degree of lateral pres sure. It therefore follows, that perpendicular pres sure increases the bulk of the frog; while its absence from the ground produces contraction, and lessens its growth. The following in an explanation of Plate Ixxix. in which Mr. Coleman's PATENT ARTIFICIAL FROG is represented, with other figures that illustrate the subject. Fig. 1. exhibits a view of the natural hoof of the horse, which is of a circular shape. a a a The external surface of the sole, of a concave form, bbb The inferior edge of the crust. frost, a variety of frogs are made, to be adapted to particular feet and particular shoes. In cases of thrushes and canker of the frog, where no remedies without pressure are likely to be serviceable, an astringent ee The junction of the bars with the thrush-powder may be applied between the crust. dd The points of the bars. e e The sole between the heels of the crust and bars, the seat of corns. ff Two cavities between the sides of the bars and the sides of the crust. g The toe of the frog. i i The cleft between the heels of the frog, the seat of thrushes. Fig. 2. A view of the hoof with contracted heels, occasioned by raising the frog above the pressure of the pavement in the stable. a a a The sole. bb The original seat of the bars, but improperly removed by the farrier. ee The original seat of the cavities between the bars and crust, but now, from contraction, become solid horn. dd The heels of the frog very much compressed by the contraction of the hoof. e e The width of the hoof at the heel, not being more than one half of the length from f to g. The extremity of the heels of the frog. g The toe of the crust. Fig. 3. The patent frog, made of cast and wrought iron. a a The lower surface opposite the ground, formed of cast iron. An irregular cavity for the reception of the elastic spring, fig. 4. e The toe of the patent frog, formed of wrought iron, to be occasionally shortened and adapted to the length of the foot, and placed under the toe of the shoe, to confine the artificial frog from moving forwards. dd A hole in the heels of the iron frog for the passage of a strap to buckle at the outside quarter or coronet. Fig. 4. A flat steel spring to fix the artificial frog in its place. a An irregular projection, to be received into a corresponding concavity in the patent frog. bb The ends of the spring, to be placed under the heels of the shoe opposite è e in fig. 1. The toe of the artificial frog is intended to be inserted under the toe of the shoe. This effectually fixes the frog forwards; and to prevent backward or lateral motion, an irregular groove is made in the iron frog, to receive a corresponding piece of steel, placed under the heels of the shoe. In general, it is necessary to fix the frog more firmly; and, for that purpose, a hole is necessary, made in the heel of the artificial frog, to receive a strap, and to buckle at the outside quarter below the coronet. And that the artificial frog may give pressure in all cases, with shoes thickened, or turned up for hunting or natural and artificial frog. And in contracted hoofs (or what has improperly been termed chest-foundered), where it may not be advisible to lower the heels equal with the horny frog, the artificial frog is essentially necessary. But, indeed, in every horse where the shoe and frog on a smooth surface are not on the same level, whatever shoes may be used, the iron frog in the stable should be applied; and, in order to fix it with facility, the spring should first be laced under the shoe, and brought backward to the heels of the hoof. The toe of the iron frog should then be inserted under the centre of the spring, and pushed as far as the toe of the shoe, while the other hand confines the spring until the centre of the spring meets the centre of the groove. The strap may then be buckled: and, to dislodge the spring and iron frog, after the strap is unbuckled, nothing more is requisite than a small horse-picker introduced into a hole at the bottom of the groove of the iron frog; and the spring being raised above the groove, and carried gently forward, the frog may be withdrawn from under the shoe without the smallest difficulty. Mr. Coleman, in conclusion, wishes it to be clearly understood, that, in all cases where the frog and the heels of the shoe are placed on the same level, the patent frog is unnecessary. But where the frog is small, or the pastern joint long, or the action of the animal high, or the heels low, so as to render the application of thin-heeled shoes improper, or when the frog, from any cause, is raised above the ground in the stable, an artificial frog is useful in all such cases, and necessary to resist contraction of the hoof. To this equally ingenious and candid statement of Mr. Coleman, we are enabled to add our individual testimony as to the soundness of his reasoning, and the great practical utility of his artificial frog, which is now very generally adopted in the stables of persons of fashion in the United Kingdom, and may be had, at the small price of three shillings, at the Veterinary College, Little Moorfields, as also at a variety of other forges. Hoof, in geometry (or ungula), is a part cut off a cylinder cone, &c. by a plane passing both through the base and part of the curve surface. It has obtained its name from its resemblance to the hoof (ungula) of a horse. For the contents and surfaces of such hoofs, see Hutton's Mensuration, page 218-246, 2d Edition.-With respect to the surfaces of conical ungulas formed by planes perpendicular to the base, Fatlrer GuidoGrandi first remarked, that if a polygon be inscribed in the base of a cone, and if on each side of this polygon a plane be raised perpendicular to the base, the portion of the conical surface cut off towards the axis, is equal to a rectilineal space. The portions also of the cone cut off by the above planes, towards the base, are in the same ratio with the segments of the base on which they stand. In fact, whatever figure be inscribed in the base, if we conceive a right prismatic surface raised from the perimeter of the figure, it will cut off from the conical surface a portion which will be to it in the same ratio, namely, that of the radius of the base to the slant height of the cone. HOOFED. a. (from hoof.) Furnished with hoofs (Greeds). HOOFED or HOOF-SHAPED. In botany, ungulate. Exemplified in the silicle of the Rose of Jericho. HOOF-BOUND, in veterinary language, implies a defect in a horse's hoof, in which it becomes so tight round the instep as to turn the foot somewhat into the shape of a bell. As the disease commonly proceeds from hard and undue exercise on rough road, the remedy is best obtained by turning the animal to grass. HOOF-CASTING, in veterinary language, a complete separation of a horse's hoof. This may be produced by any cause exciting a general inflammation and abscess in the foot. If the coffin-bone remain uninjured a new hoof will commonly succeed: but the old should never be taken away forcibly, and a soft easy leathern boot or shoe should afterward be applied, interlined with emol lient ointment, and the dressing be renewed daily. HOOGEVEEN (Henry), a learned Dutchman, born at Leyden, of poor parents, in 1712. He received a good education, and at the age of fifteen became a teacher himself for the purpose of supporting his parents. In 1732, he was made under-master of the academy at Gorcum, and shortly after he was appointed to the care of the academy at Woerden, from whence, in 1738, he removed to Culembourg. In 1745 he settled at Breda, which he left in 1761 for Dort, but after a residence of three years there he went and settled at Delft, where he died in 1794. His works are, 1. An edition of Vigerus de Idiotismis Linguæ Græcæ; 2. Doctrina particularum Linguæ Græcæ, 2 vols. 4to. 3. Some Latin poems and Discourses. A posthumous piece of his, entituled, Dictionarium Analogicum Græcum, is now printing. HOOGLY, a small but ancient city of Hindustan, in Bengal. It is now nearly in ruins, but possesses many vestiges of former greatness. In the beginning of the 18th century it was the great mart of the export trade from Bengal to Europe. Lat. 32. 30. N. Lon. 88. 28 E. HOOGLY RIVER, an arm of the Ganges, formed by the union of its two western branches, named the Cassium Buzar and Yellinghy rivers. It is the port of Calcutta, and the only branch of the Ganges that is commonly navigated by ships. HOOK. s. (hoce, Saxon.) 1. Any thing bent so as to catch hold. 2. The curvated wire on which the bait is hung for fishes, and with which the fish is pierced. See ANGLING. 3. A snare; a trap (Shakspeare). 4. An iron to seize the meat in the caldron (Spenser). 5. A sickle to reap corn (Mortimer). 6. Any instrument to cut or lop with (Pope). 7. The part of the hinge fixed to the post. 8. Hook. (In husbandry.) A field sown two years running (Ainsworth). 9. Hook or Crook. One way or other; by any expedient (Hudibras). HOOKS OF A SHIP, those forked timbers which are placed directly under the keel. HOOKS (CAN), those whieh being made last to the end of a rope with a noose (like that which brewers use to sling or carry their barrels on), are made use of for slings. HOOKS (FOOT), in a ship, the same with FUTTOCKS. HOOKS (LCOF), a tackle with two hooks; one to hitch into a cringle of the main or fore-sail, in the bolt-rope at the leech of the sail by the clew; and the other is to hitch into a strap, which is spliced to the chess tree. HOOK-PINS, in architecture, are taper iron pins, only with a hook-head, to pin the frame of a roof or floor together; HOOKS (SHEER), in a ship, those hooks like sickles fixed in the ends of the yard-arms, that if a ship under sail come to board her, those sheers may cut her shrowds, and so spoil her tackling. To HOOK. v. a. (from the noun.) 1. To catch with a hook (Addison). 2. To entrap; to ensnare. 3. To draw as with a hook (Shakspeare). 4. To fasten as with a hook, 5. To draw by force or artifice (Norris). HOOKAH, among the Arabs and other nations of the East, is a pipe of a singular and complicated construction, through which tobacco is smoked. The Hindu's tobacco is made up into a paste with spices: the tobacco being lighted, is put on the upper extremity of a tube, and the lower extremity runs down into a shell or other vessel containing cold water, sometimes rose water; through which the smoke is agreeably drawn by means of another flexible tube, which is the pipe, and about 12 feet long. HOOKE (Robert), a celebrated mathematician, was born in the Isle of Wight, in 1635; and having a taste for drawing, was placed under Sir Peter Lely but the oilcolours disordering his head he soon quitted painting, and was taken by Dr. Busby into his house and under his tuition. There he gained a good knowledge of the languages, and about 1653 went to Christ Church, Oxford, and became a member of the Philoso phical Society then instituted in that univer sity. He assisted Dr. Willis in his chymical operations, and afterwards became assistant to Mr. Boyle. He was one of the first fellows of the Royal Society, the repository of which was entrusted to his care. In 1664 he was made professor of mechanics to that learned body with a salary of 501. per annum, to which was afterwards added 301. more. At the same time he was elected professor of geometry in Gresham College. After the fire of London he produced a plan of his own for rebuilding the city, which procured him the appointment of one of the city surveyors, though his plan was not carried into effect. In 1668 he had a dispute with Hevelius respecting telescopic sights, which he managed with such warmth as to give great offence to his scientific friends. In 1671 he attacked Sir Isaac Newton's Theory of Light and Colours; and when that Philosopher's Principia came out, Hooke pretended that the discovery concerning the force and action of gravity was his own, which occasioned that patient man to feel some just resentment against him. In 1691 archbishop Tillotson created him M. D. by warrant. He died at his lodgings at Gresham College in 1702. He wrote a valuable work, entituled, Micrographia, or Philosophical Descriptions of minute Bodies made by magnifying Glasses, with observations and inquiries thereupon, folio, 1665. Several of his papers are in the Philosophical Transactions, and after his death appeared his posthumous works, in folio, 1705. He was a man of great mechanical genius, and the sciences are indebted to him for several valuable instruments and improvements. The following are the inventions and discoveries to which he laid claim: 1656. Barometer, a weather glass. 1657. A scapement, for maintaining the vibration of a pendulum.-And not long after, the regulating or balance-spring for watches. 1658. The double-barrelled air-pump.-—The conical pendulum.-His first employment of the conical pendulum was no less ingenious and scientific than it was original. He employed it to represent the mutual gravitation of the planets; a fact which he had most systematically announced. He had shewn, that a force, perfectly analogous to gravity on this earth, operated on the surface of the moon and of Jupiter. Considering the numerous round pits on the surface of the moon, surrounded with a sort of wall, and having a little eminence in the middle, as the production of volcanoes, he inferred that the ejected matter fell back again to the moon, as such matter falls back again to the earth. He saw Jupiter surrounded with an atmosphere, which accompanied him; and therefore pressed on him; as our air presses on the earth-He inferred, that it was the same kind of power that maintained the sun and other planets in a round form. He inferred a force to the sun from the circulation round him, and he called it a gravitation; and said it was not the earth which described the ellipse, but the centre of gravity of the earth and moon. He therefore made a conical pendulum, whose tendency to a vertical position represented the gravitation to the sun, and which was projected at right angles to the vertical plane; and shewed, experimentally, how the different proportions of the projectile and centripetal tendencies produced various degrees of eccentricity in the orbit. He then added another pendulum, describing a cone round the first, while this described a cone round the vertical line, in order to see what point between them described the ellipse. The results of the experiments were intricate and unsatisfactory; but the thought was ingenious. He candidly acknowledged, that he had not discovered the true law of gravitation which would produce the description of an ellipse round the focus, owing to his want of due mathematical knowledge; and therefore left this investigation to his superiors. Sir Isaac Newton was the happy man who made the discovery, after having entertained the same notions of the forces which connected the bodies of the solar system, before he had any acquaintance with Dr. Hooke, or knew of his speculations. 1660. The engine for cutting clock and watch wheels. The chief phenomena of capillary attraction.-The freezing of water a fixed temperature. 1663. The method of supplying air to a diving bell.-The number of vibrations made by a musical chord, 1664. His Micrographia was, by the council of the Royal Society, ordered to be printed; but in that work are many just notions respecting respiration, the composition of the atmosphere, and the nature of light, which were afterwards attributed as discoveries to Mayow and others, who, though we are far from supposing that they stole their discoveries from Dr. Hooke, were certainly anticipated by him. 1666. A quadrant by reflection. 1667. The marine barometer.-The gage for sounding unfathomable depths. 1668. The measurement of a degree of the meridian, with a view to determine the figure of the earth, by means of a zenith sector. 1669. The fact of the conservatio virium vivarum, and that in all the productions and extinctions of motion, the accumulated forces were as the squares of the final or initial velocities. This doctrine he announces in all its generality and importance, deducing from it all the consequences which John Bernoulli values himself so highly upon, and which are the chief facts adduced by Leibnitz in support of his doctrine of the forces of bodies in motion. But Hooke was perfectly aware of their entire correspon. dence with the Cartesian, or common doctrine, and was one of the first in applying the celebrated 39th proposition of Newton's Principia to his former positions on this subject, as a mathematical demonstration of them. |