HOREB HORN. 



795 



Acron, Porphyrion, and the scholiast of Cruquius; 

 among his later editors and commentators, we will 

 only mention Dan. Heinsius (first 1605), John Bax- 

 ter, Bentley (first 1711), Sanadon, Gesner, Zeiuie, 

 Jani, Mitscherlich (only the odes and epodes) (first 

 edition, Leipsic, 1778 82,2 vols.; 2d edit., Leipsic, 

 1800, 2 vols.), Doering (Leipsic, 1803; 2d edit., 

 1815), Eichstadt, Preis, Heindorf, Fea (Rome, 1811, 

 2 vols). Wieland's translation of the epistles and 

 satires of Horace contains illustrations of the genius 

 of Horace and his age, and the peculiarities of his 

 works. 



HOREB (Arabic, Dsjabel Mttsa], a mountain in 

 the northern part of Arabia, of the same ridge as 

 mount Sinai, which lies not far distant from it, is 

 memorable in the history of Moses. The monks on 

 mount Sinai still point out the rock on Horeb from 

 which water issued at the blow of Moses. 



A small party of Hussites called the mountain 

 between Ledetz and Lipniza, in Bohemia, where 

 they assembled, Horeb, and themselves Horebites. 



HOREHOUND (marrubiwm vulgare); a labiate 

 plant, with whitish, cottony leaves and stem. 

 Like other plants of the same family, it possesses an 

 aromatic odour ; but, in this instance, it is strong and 

 unpleasant, and the taste is bitter and penetrating. 

 It is a popular remedy in pulmonary complaints. 



HORIZON ; the line that seems to link the land 

 or sea and sky ; and it is either rational or sensible. 

 The rational, true, or astronomical horizon, which is 

 also called simply and absolutely the horizon, is a 

 great circle, whose plane passes through the centre 

 of the earth, and whose poles are the zenith and 

 nadir. It divides the sphere into two equal parts or 

 hemispheres. The sensible, visible, or apparent 

 horizon is a lesser circle of the sphere, which divides 

 the visible part of the sphere from the invisible. Its 

 poles are likewise the zenith and nadir ; and, conse- 

 quently, the sensible horizon is parallel to the 

 rational, and it is cut at right angles, and into two 

 equal parts, by the vertical. These two horizons, 

 though distant from each other by the semi-diameter 

 of the earth, will appear to coincide, when continued 

 to the sphere of the fixed stars, because the earth, 

 compared with this sphere, is but a spot. The sen- 

 sible horizon is divided into eastern and western. 

 The eastern or ortive horizon is that part of the hori 

 zon wherein the heavenly bodies rise. The western or 

 occidual horizon is that wherein the stars set. By 

 sensible horizon is also frequently meant a circle 

 which determines the segment of the surface of the 

 earth over which the eye can reach ; called, also, the 

 physical horizon. In this sense we say, a spacious 

 horizon, a narrow, scanty horizon. It is manifest, 

 that the higher the spectator is raised above the 

 earth, the farther this visible horizon will extend. 

 On account of the refraction of the atmosphere, dis- 

 tant objects on the horizon appear higher than they 

 really are, or appear less depressed below the true 

 horizon, and may be seen at a greater distance, espe- 

 cially on the sea. Legendre says, that, from several 

 experiments, he is induced to allow for refraction a 

 14th part of the distance of the place observed, 

 expressed in degrees and minutes of a great circle. 

 Thus, if the distance be 14,000 toises, the refraction 

 will be 1000 toises, equal to the 57th part of a 

 degree, or I' 3''. 



HORIZON OF A GLOBE; the broad, wooden, 

 circular ring in which the globe is fixed. On this 

 are several concentric circles, which contain the 

 months and days of the year, the corresponding signs 

 and degrees of the ecliptic, and the thirty-two points 

 of the compass. 



HORIZONTAL DIAL is one drawn on a plane, 

 parallel to the horizon, having its gnomon o: 



elevated according to the altitude of the pole of the 

 place it is designed for. See Dial. 



HORIZONTAL RANGE of a piece of ordnance 

 is the distance at which a ball falls on or strikes a 

 horizontal plane, whatever be the angle of elevation 

 or direction of the piece. When the piece is pointed 

 parallel to the horizon, the range is then called the 

 point-blank, or point-blank range. The greatest 

 horizontal range, in the parabolic theory, or in a 

 vacuum, is that made with the piece elevated to 

 forty-five degrees, and is equal to double the height 

 from which a body must freely fall, to acquire the 

 velocity with which the shot is discharged. But in 

 a resisting medium, like the atmosphere, the eleva- 

 tion of the piece, to shoot farthest, is always below 

 forty-five degrees, and gradually the more below it 

 as the velocity is greater ; so that the greater veloci- 

 ties with which balls are discharged from cannon 

 with gunpowder, require an elevation of the gun 

 equal to but about thirty degrees, or even less. 

 And the less the size of the ball is, too, the less must 

 this angle of elevation be, to shoot the farthest with 

 a given velocity. See Gunnery. 



HORN, in physiology; a tough, flexible, semi 

 transparent substance. The hollow horns of the ox, 

 goat, &c., the hoof, the horny claw and nail, and the 

 scale of certain insects, as the shell of the tortoise, 

 resemble each other in chemical characters ; but they 

 differ very widely from stag's horn, ivory, &c. Horn 

 is distinguished from bone, in being softened very 

 completely by heat, either applied immediately or 

 through the medium of water, so as to be readily 

 bent to any shape, and to adhere to other pieces of 

 horn in the same state. It contains but a small por- 

 tion of gelatine, and in this it differs from bone, which 

 contains a great deal. Horns consist chiefly of con- 

 densed albumen, combined with a small and varying 

 portion of gelatine, with a small part of phosphate of 

 lime. The fixed alkalies readily and totally dissolve 

 horn into a yellow saponaceous liquor. With some 

 animals, the horn is an instrument of defence; with 

 others, not. In some species of animals, the males 

 only have horns ; as, for instance, the stag. Female 

 sheep seldom have horns. The female goats have 

 horns, but they are always smaller than those of the 

 male. In cattle, the horn is particularly developed. 

 The bull generally has a shorter, denser, firmer horn 

 than the cow. There are, however, hornless cattle. 

 In the case of most horned animals, the horns are not 

 entirely developed, until they have become capable 

 of continuing their species. 



Horns admit of being divided into four kinds, at 

 least: 1. those of the rhinoceros; 2. of the ox, 

 antelope, goat, and sheep ; 3. of the camelopard or 

 giraffe ; 4. of the deer kind. The horns of the 

 rhinoceros are composed entirely of a horny sub- 

 stance. They are situated not upon the os fronds, 

 but on the nasal bones, and are attached to the skull 

 only at the surface of their basis. They appear to be 

 composed of a number of fibres, resembling strong 

 hairs consolidated together. They are not deciduous, 

 but increase from the root or base in proportion 

 as they wear. Those of the second sort are most 

 common. They belong to many of the ruminating 

 quadrupeds, and some birds have similar 'processes 

 on their heads. They consist of three parts an 

 osseous substance, a vascular investment, and the 

 external sheath. The bone is first formed. It appears 

 as a knob covered with skin, and movable on the os 

 fronds. As it elongates, the skin becomes callous, 

 and appears to wear off, when the osseous process is 

 found to be clothed in a real case of horn. It then 

 becomes fixed to the os fronds by anchylosis. The 

 horny case grows from the roots, and the increase in 

 each yr:-v is marked by a circular groove near the 



