6. BORING or WOODEN PIPES, is done by means of a long auger, beginning with one of small dia meter, and proceeding to employ successively spoon formed augers of larger diameter. Notwithstand ing the frequent employment of cast-iron pipes, some wooden pipes are still used for conveying eater in London ; they are of elm, which is the kind of tree most frequent in the neighbouring country. A. pipe is bored out of one trunk of elm, and the bark is left on. When a tree is to be bored, it is fixed on a carriage, with a rack on the under part. This rack fits into a pinion, whose axis passes through Fudgeons on a fixed frame. On the axis of the pinion is a ratchet wheel, moved by two catches, which de rive their motion from the wind or water power that turns the auger; and the pinion is moved in a direc- • tion that brings the tree towards the auger. See a fi gure in the Encyclopedia Britannica,PlateCCCX1X; and in Belidor, Architecture Hyaraulique, I. 1, 341. This apparatus is the same as the one employed in saw-mills. In the boring of pipes for the water works in London, the tree is made to advance by ropes, which pass over a windlass wrought by men, whilst the auger is turned by a horse-mill. Wooden pipes are frequently bored by an auger having at its outer end a wooden drift or handle, which is put in motion by the workman. The trees are placed on tressels, and there are also tressels of a convenient height that support the auger ; there is also a lathe to turn one end aT the tree conical, so as to fit into a conical cavity in the end of the adjoining tree, and thus form a joint water-tight. The end of the tree,
which receives the adjoining pipe within it, has a surface at right angles to the axis of the pipe. Into th;s surface is driven an iron hoop, whose diameter is some inches greater than the diameter of the aper ture of the pipe. This precaution prevents the tree from splitting when the conical end of the next tree is driven home. When the tree is crooked, a bore is driven in from each end, and the two bores meet, forming an angle. ' An auger, whose stalk is formed spirally for some way up, is figured in Bailey's Ma chines V the Society of Ails. The object of this is that the chips may be delivered without taking the auger out of the hole.
There is a patent granted in 1796 to Mr Howell, Coahnaster, of Oswestry, for boring wooden pipes by a hollow cylinder, made of thin plates of iron, about an inch less in diameter than the hole to be bored. To one end of this cylinder is fixed a flange about a quarter 'of an inch in breadth, and one part of this flange is to be divided, so that, being of steel, a cut ter is formed thereby. The object of this method is to bore out a solid cylinder of wood, capable of being converted into a smaller pipe, or of being ap plied to some other use in carpentry. (Repertory 1 Arts, This kind of borer is like the trepan, which is a hollow cylinder- of steel, saw-toothed on the edge, and, when made to revolve rapidly on its axis, in the hand of the surgeon, it saws or bores out circular pieces of the fiat bones of the head. (v.)