in mechanics, a well-known instrument of common use for raising great weights of any kind.

The common kitchen-jack is a compound engine, where the weight is the power applied to overcome the friction of the parts and the weight with which the spit is charged; and a steady and uniform motion is obtained by means of the fly.

the sea-language, a sort of flag or colours, displayed from a mast erected on the outer end of a ship's bowsprit. In the British navy the jack is nothing more than a small union flag, composed of the interlacement of the red and white crosses; but in merchant-ships this union is bordered with a red field. See the article Union.

Jack is used also for a horse or wooden frame to saw timber upon; for an instrument to pull off a pair of boots; for a great leathern pitcher to carry drink in; for a small bowl that serves as a mark at the exercise of bowling; and for a young pike.

Jack-Flag, in a ship, that hoisted up at the sprit-sail topmast head.

Jack-Daw, the English name of a species of corvus. See Corvus.

This bird is very mischievous to the farmer and gardener; and is of such a thievish disposition, that he will carry away much more than he can make use of. There is a method of destroying them by a kind of springs much used in England; and is so useful, that it ought to be made universal.—A stake of about five feet long is to be driven firmly into the ground, and made so fast that it cannot move, and so sharp in the point that the bird cannot settle upon it. Within a foot of the top there must be a hole bored through it, of three quarters of an inch diameter; through this hole is to be put a stick of about eight inches long; then a horse-hair spring or noose is to be made fast to a thin hazel-wand, and this brought up to the place where the short stick is placed, and carried with it through the hole, the remainder being left open under that stick. The other end of the hazel rod is to be put through a hole in the stake near the ground, and fastened there. The stake is to be planted among the jack-daw's food, and he will naturally be led to settle on it; but finding the point too sharp, he will defend to the little cross stick. This will sink with his weight, and the spring will receive his leg, and hold him fast.