HARTSHORN, (Seim oe,) is now usually obtained by the distillation of bones, hoofs, horns, and in general the refuse of slaughter-houses. An iron still or retort is generally used with a pipe leading from it into a worm con denser. The retort is filled with bones roughly broken, or other materials, and a strong heat applied. Water, and a tar-like oil, accompanied with a foetid inflam mable gas, result; carbonic acid also comes over, but this is mostly taken up by the ammonia, which is formed at the same time, and received in the state of carbonate of ammonia. When the different substances have been condensed in the worm, they should pass into a receiver, which has no communication with the open atmosphere, (on account of the overpowering nuisance of its odour,) but which should have a pipe inserted into the upper part of it, and connected with the ash-pit of the sfill. The inflammable gas and the smell are conveyed to the fire, where the former ignites ; but care must be taken to avoid any explosion, for when the evolution of the inflammable gas becomes slow, or ceases entirely, the common air passes along the pipe into the close receiver, which is filled with the same inflammable gas ; and, under these cir ums tances, an explosion will take place, which will not only burst the receiver, but do other injury. This evil, Mr. Gray observes, may be avoided by placing a valve in the pipe opening outwards, to allow the passage of the gas; and another valve into the receiver, opening inwards ; by this means the flaming gas will be stopped in its passage to the receiver • as the valve into the receiver open ing, will admit the common air to fill up the vacuum. Thus, by means of this apparatus, if it be well constructed, and proper luting be employed, the distilla tion of hartshorn may be carried on almost without any smell, although the odour of animal oil is so remarkably offensive. The first product consists of water. animal tar, and volatile salt. A great part of the tarry oil may be sepa rated mechanically ; the rest, in a great measure, by a second distillation with a gentle heat. The liquid which conies over consists of a solution of sesqui-car bonate of ammonia, with a fetid animal oil, which gives it a peculiar odour.
This liquid is still sold in the shops under the name of spirit of hartsborn, as the alkaline liquor obtained from that substance was at one time thought to certain medical virtues, not to be found in the alkaline liquor obtained other animal matters. HATS. A well-known covering for the head, and distinguished from a cap or bonnet by a brim. They are made by various methods, according to the nature of the substance of which they are composed ; but by far the greatest number are formed of the fur of different animals, by a process called felting : this manufacture has of late years become of considerable commercial impor tance, and numerous improvements have been introduced into it. The materials for making hats are chiefly rabbits' fur, cut off from the skin, together with wool and beaver, to which may also be added mole fur, and kid hair. These are mixed in various proportions, and of different qualities, according to the value of the hats intended to be made ; but the beaver is now wholly used for facing the finer hats, and not for the main body or stuff. The first process in the manufacture of hats is termed bowing, which has for its object to separate the fibres, and break up any clots, so as to form the whole into a kind of light down : it is performed as follows—the workman is provided with a pole of ash, or white deal, about seven feet long, having a bridge at each end, over which is stretched a catgut about of an inch thick ; and a portion of the material being laid upon a hurdle of wire, he holding the bow horizontally in his left hand, nearly in contact with the material, gives the string a pluck with a wooden pin, held in his right hand. The string, in its return, strikes the fur, and causes it to spring up in the air, and fall in a light open form, at a little distance from the mass. By repeated strokes, the whole is subjected to the bow ; and having thus fallen together in all directions, it forms a thin mass or substance for the felt. The quantity thus treated at once is called a batt, and never exceeds half the quantity required to make one hat.