Yarn, in general, denotes the manufacture of wool, hemp, flax, cotton, etc. converted into filaments or threads, which are subservient to a variety of useful purposes.

Formerly, all yarn WW spun or twisted by means of the distaff, or wheel; but lately, both the ingenuity of mechanics, and the powers of machinery, have been called in aid (see the articles Cotton, and Spinning), to facilitate that operation : and, in June, 1787, Messrs. John Kendrew and Thomas PorThouse, obtained a patent for their invention of a machine, upon new principles, designed to spin yarn from hemp, tow, flax, or wool. - As this privilege is now expired ; and such contrivance promises to be very useful in the woollen as well as other manufactures, we subjoin a concise account of its construction.

The machine consists of a frame, which supports a cylinder, three feet in diameter, and ten inches in breadth; made of dry wood or metal ; and its circumference being covered with smooth leather. On this, are placed six rollers, also covered with leather, and upheld in their situations by slits made in a piece of wood, in which the iron axes of the rollers move, at the same time suffering them to press on the principal wheel: such rollers are of different weights; the highest on the cylinder weighing two stone, while the others gradually decrease, so that the lowest is only two lbs. in weight. A cloth is placed beneath the cylinder, that revolves upon two rollers, inserted in the frame ; and by its side there is a table of an equal length and breadth, furnished with two .similar cloths.

The workman lays on this table a greater or smaller quantity of the material intended to be spun, according to the degree of fineness required; spreading it uniformly on the cloths, whence he removes and applies it to the revolving cloth. The rollers and cylinders are then put in motion by wheel-work moved by a horse, water, or any other impulsive power; the wool, etc. is drawn forward, and extended, during its passage, into a thread or sliver; which, on being submitted to the action of a similar machine, but of different dimensions, is spun into thread of various degrees of fineness: after the yarn has thus passed beneath the rollers, it falls into canisters suspended below, for its reception. - A minute specification of this useful machinery is inserted in the 16th vol. of the "Repertory of Arts" etc. where it is illustrated by an engraving.

By the 12 Geo. II. c. 21, §. 5, 6, 7; and 26 Geo.III. c. 11, Linen, Woollen, or Bay-yarn, may be imported from Ireland, in British-built vessels, duty-free, provided they be regularly entered; but, from other countries, Cable-yarn is subject to the duty of 9s. 4 1/2d. per cwt.; - Cotton-yarn pays 3d. 17-20 per lb.; though, when imported from Ireland, it is free from the customs ; - Grogram-yarn is chargeable with 8 3/4d. per lb. 5 - Raw-linen-yarn, with 1d. 7-10 per lb.; - Wick-yarn pays 1l. 15s. 1 l 1/4d. per cwt.; and Worsted-yarn, 11d. per lb.