Tar, a thick, black, viscid, impure turpentine, procured by burning the wood of pinus palustris, P. sylvestris, and other species of pine and coniferous trees; also obtained as a product of the destructive distillation of peat, bituminous coals, and shales. It was known to the ancient Greeks, and Dr. Clarke, who describes the method of manufacturing it in the forests of Bothnia, says there is not the smallest difference between the processes there practised and those of ancient Greece. Along the whole coast of the gulf of Bothnia the inhabitants are very generally engaged in this occupation. They make use of the roots of the fir trees, with logs and billets of the same, which they arrange in a conical stack, fitted to a cavity in the ground, generally in the side of a bank. In the bottom of this cavity is placed a cast-iron. pan from which a spout leads out through the bank. The heap is covered over with turf, and is then fired, as in making charcoal. Tar collects in the latter part of the process of charring, and runs off through the spout into barrels. Tar is a product where charcoal is the chief object of the process, but is seldom obtained in quantities sufficient to render it an object to collect it, except in charring the resinous woods of the pine family.

In Sweden, where the business is also important, some peculiar methods are adopted to increase the yield of tar. Trees of no value for the saw mill are partially peeled of their bark a fathom or two up from the ground, not enough to kill them, but only to check their growth. After five or six years, when cut' down, the wood is found to be much richer in resinous matters which produce tar. It is noticed that the condition of the weather during the process of charring may make a difference of 15 or 20 per cent, in the yield of tar. In the United States tar is produced in almost all parts of the country where pitch pine and the pinus australis are found. Along the coast of the southern states, especially of North Carolina, Virginia, and Georgia, the business is carried on upon a large scale in connection with the manufacture of turpentine, rosin, and pitch. Old trees which have ceased to produce turpentine, and dead wood which is rich in resinous matter, are selected for the coal pits. The process does not materially differ from that already described.

The product is not only sufficient for home consumption, but large quantities are annually exported. - In the preparation of pyroligneous acid, tar is one of the products of the destructive distillation, settling in the bottom of the tanks in which the liquids are collected. The variety known as coal tar is obtained when bituminous matters are distilled for the production of illuminating gas. (See Gas, and Petroleum.) Both wood and coal tars are complex mixtures of a variety of liquids holding solid matters in solution or suspension; thus, wood tar contains the hydrocarbons included in the term eupion, and the benzole series of hydrocarbons, including tolu-ole, xylole, cymole, also naphthaline, etc, besides oxidized compounds, including creosote, picamar, kapnomor, etc. Rosin and paraffine are among its solid contents. When its volatile products have been driven off by distillation or boiling, the black carbonaceous residue is known as pitch. The composition of coal tar is materially different, as it contains all the great variety of products derived from the destructive distillation of bituminous coal as obtained from the gas works.

Coal tar, a refuse product of these works, may be considered in general as consisting of from 3 to 15 per cent, of light oils, from 60 to 67 per cent, of heavy oils, usually termed "dead oil," and from 18 to 35 per cent, of pitch; the best coals, as the cannel and boghead, produce tar richer in light oils, and yield least pitch. - Wood tar is thick and hard in cold weather, and softens when warm so as to flow like thick molasses. Its specific gravity is about 1.04. It is boiled down to produce pitch, is used to coat the bottoms of vessels to render them water-tight, and to cover rigging of ships to preserve it from the action of the weather, and is a useful lubricant for the journals of wheels. In medicine it is used internally in chronic catarrhs, and in some cutaneous diseases, as ichthyosis. The inhalation of its vapor is recommended in cases of bronchial disease, the air of a room being impregnated with it by moderately heating the tar placed in a cup over a lamp. It has been found beneficial as an external application to ulcers and various diseases of the skin. It is administered in pills mixed with flour, or in an electuary of tar and sugar.

It yields a portion of its properties to water with which it is stirred, and this preparation, known as tar water, is administered as a stimulant and diuretic, and is applied as a wash in chronic cutaneous affections. - Coal tar has an exceedingly repulsive odor, and was long considered of no value; but it has been found that the light oils obtained by its distillation may be made to furnish a variety of singular products, possessing rare properties, and affording the rich colors applicable to dyeing, known as the aniline colors (see Aniline, Benzole, and Mauve), and also flavors of various essences and agreeable perfumes. The dead oil is frequently burned for the production of lampblack. One of its most useful products is carbolic acid. (See Carbolic Acid.) Coal tar is now in common use as a coating for iron work exposed to the weather, and is used with asphalt and other substances to form a tight covering for roofs and the walls of vaults, etc. Its use in preparing a fuel with the dust of mineral coal is noticed in Fuel, vol. vii., p. 518.

Tar #1

Tar, a river of North Carolina, which rises in Person co. and flows S. E., passing Tarbor-ough, Greenville, and Washington, and discharges into Pamlico sound by an estuary called Pamlico river. Its length is 140 m., or including Pamlico river 180 m., and it is navi-' gable for small steamers to Tarborough, 85 m. from the sound.