Physiology, a hard substance growing on the heads of divers animals, particularly the cloven-footed quadrupeds; and serving them both as weapons of offence and defence.

The horn of animals is of the same nature as their gelatinous matter; and is only that matter charged with a less quantity of water, and a larger quantity of earth, and sufficiently condensed to have a firm and solid consistence. By digesting horn with water in Papin's digester, it may be entirely converted into jelly.

Horn is a perfectly animalised matter, and furnishes in distillation the same principles as all animal matters; that is, at first a pure phlegm, with a degree of heat not exceeding that of boiling water; then a volatile alkaline spirit, which becomes more and more penetrating and strong; a fetid, light, and thin oil; a concrete volatile salt, which forms ramifications upon the sides of the receiver; much air; fetid oil, which becomes more and more black and thick; and lastly, it leaves in the retort a considerable quantity of almost incombustible coal, from which, after its incineration, scarcely any fixed alkali can be obtained.

Animal oil, and particularly that which is drawn first in the distillation of horn, is susceptible of acquiring great thinness and volatility by repeated distillations, and is then called the oil of dippel.

The horns of stags, and of other animals of that kind, are the most proper to furnish the animal oil to be rectified in the manner of dippel; because they yield the largest quantity. These horns also differ from the horns of other animals in this, that they contain a larger quantity of the same kind of earth which is in bones; hence they seem to possess an intermediate nature betwixt horns and bones.

Hart's-Horn. See Hart's-Horn.

Horns make a considerable article in the arts and manufactures. Bullocks horns, softened by the fire, serve to make lanthorns, combs, knives, ink-horns, tobacco-boxes, &c.

Dyeing of Horn.—Black is performed by steeping brass in aquafortis till it be returned green: with this the horn is to be washed once or twice, and then put into a warmed decoction of logwood and water. Green is begun by boiling it, &c. in alum-water; then with verdigrise, ammonia, and white-wine vinegar; keeping it hot therein till sufficiently green. Red is begun by boiling it in alum-water; and finished by decoction in a liquor compounded of quick-lime steeped in rain water, strained, and to every pint an ounce of Brazilwood added. In this decoction the bone, &c. is to be boiled till sufficiently red.

Dr Lewis informs us that horns receive a deep black stain from solution of silver. It ought to be diluted to such a degree as not sensibly to corrode the subject; and applied two or three times, if necessary, at considerable intervals, the matter being exposed as much as possible to the sun, to hasten the appearance and deepening of the colour.

Dyeing or staining Horn to imitate Tortoise-shell.—The horn to be dyed must be first pressed into proper plates, scales, or other flat form; and the following mixture prepared. Take of quick-lime two parts, and of litharge one part; temper them together to the consistence of a soft paste with soap-ley. Put this paste over all the parts of the horn, except such as are proper to be left transparent, in order to give it a nearer resemblance of the tortoise-shell. The horn must remain in this manner covered with the paste till it be thoroughly dry; when, the paste being brushed off, the horn will be found partly opaque and partly transparent, in the manner of tortoise-shell; and when put over a foil, of the kind of latten called assidue, will be scarcely distinguishable from it. It requires some degree of fancy and judgement to dispose of the paste in such a manner as to form a variety of transparent parts, of different magnitudes and figures, to look like the effect of nature: and it will be an improvement to add semitransparent parts; which may be done by mixing whiting with some of the paste to weaken its operation in particular places; by which spots of a reddish brown will be produced, which if properly interspersed, especially on the edges of the dark parts, will greatly increase both the beauty of the work, and its similitude with the real tortoise-shell. Horn is also a sort of musical instrument of the wind kind; chiefly used in hunting, to animate and bring together the dogs and the hunters. The term anciently was, wind a horn, all horns being in those times compassed; but since straight horns are come in fashion, they say blow a horn, and sometimes sound a horn.—There are various lessons on a horn; as the recheat, double recheat, royal recheat, running or farewell recheat, &c. See Recheat.

The French horn is no other than a wreathed or contorted trumpet. It labours under the same defects as the trumpet itself; but these have of late been so palliated, as to require no particular selection of keys for this instrument. In the beginning of the year 1773, a foreigner, named Spandau, played in a concert at the opera-house a concerto, part whereof was in the key of C, with the minor-third; in the performance of which all the intervals seemed to be as perfect as in any wind-instrument. This improvement was effected by putting his right hand into the bottom or bell of the instrument, and attempting the sounds by the application of his fingers to different parts of the tube.

The Hebrews made use of horns, formed of rams' horns, to proclaim the jubilee; whence the name Jubilee.

Cape-Horn. See Terra del Feugo.

Horn-Beam. See Carpinus, Botany Index.

Horn-Bill. See Buceros, Ornithology Index.

Horn-Blende, a species of mineral. See Mineralogy Index.

Human Horns. In Dr Charles Leigh's natural history of Lancashire, Cheshire, and the Peak in Derbyshire, is the print of a woman with two horns on her head. When she was 28 years of age an excrescence grew upon her head like a wen, which continued 30 years, and then grew into two horns. After four years she cast them, and in their place grew two others. After four years she cast these also; and the horns which were on her head in 1668 (the time when the account was written) were then loose. Her picture and one of her horns are in Ashmole's museum. In the university library at Edinburgh is preserved a horn which was cut from the head of Elizabeth Love, in the 50th year of her age. It grew three inches above the ear, and was growing seven years.