The method of making leaden pipes has been described under the article LEAD; but we will take the opportunity of mentioning in this place, that it appears, by some recent experiments made by Mr. Jardine, of the Water Company's Works at Edinburgh, that a lead pipe of 11 inch bore, and the fifth of an inch in thickness, was found capable of sustaining a power equal to that of a column of water 1000 feet high, which is equal to 30 atmospheres, or 420 pounds per square inch of internal surface. With a pressure of 1200 feet it began to swell, and at with 1400 feet it buret. In another experiment, a pipe two inches in diameter, and one-fifth of an inch thick,, sustained 800, but burst with 1000 feet pressure.
Wooden p4ses for the conveyance of water, are bored by means of large iron augers, worked by one or two men, who commence with a small bore, and increase it as the work proceeds, by changing the auger to a larger size, which are sometimes extended to eight or nine inches in diameter. The tree in the pro cess of boring, is laid horizontally upon tressels constructed to support and hold it firmly, and the augurs are similarly supported and guided, so as to pass cen trically through the tree. The manual operation is of course slow, and extremely laborious : machinery, worked by steam, or other power, has therefore been introduced to execute the work. The piece of timber, or tree, is held down upon a frame by chains passing over it, and round two windlasses. The frame and tree, thus bound together. run upon small wheels traversing two long beams, called ground-sills, placed on each side of a pit, dug to receive the chips made by the borers. At one end they are connected by a cross-beam, bolted upon them; this supporta the bearing for a shaft, the extremity of which, beyond the bearing, is perforated at the end of a 'square hole to receive the end of the borer. The timber and carriage are made to advance towards the borer by means of ropes ; one rope being made to wind up, while the other gives out and draws the carriage and piece of timber backwards and forwards according as the wheel is turned. The weight of the borer isby a wheel between uprights fixed on a block, the end of upon the : it is moved forward by means of two iron bars, pinned to the CI cross-bar of the carriage. The distance between the wheel and the car riage may be varied by altering the iron bars and pins, so as to bring the wheel always as near as convenient to the end of the tree. The shaft nosy be turned by any first mover. When the borer is put in motion by turning the wheel, he draws the tree up to the borer that pierces it; when a few inches are bored, he draws the tree back by reversing the motion of the wheel, in order that the borer may throw out its chips ; he then returns the tree, and continues the pro cess until the work is finished : the borer, in this case, be its size what it may, is of the same shape as that of a common auger. We would suggest the employment of spiral augers instead of the common, as the former would deliver the chips as it proceeded, and not require withdrawal until the perfora tion was completed.
Some years ago Mr. Howel, of Oswestry, invented a machine for making concentric wooden pipes out of one piece of timber, the mechanism of which was on the same principle as that we have described under Mr. Murdock's patent for sawing out atone pipes, who, it appears, derived the principle of operating from Mr. Howel, and modified it so as to adapt it to the cutting of
stone.
T • &—The clay of which these are made is obtained from Purbeck, in Donets ire, and at Teignmouth, in Devonshire, in large lumps, which are purified by dissolving in water in large pits, where the solution is well stirred up, by which the stones and coarse matter are deposited ; the clayey solution is then poured off into another, where it subsides and deposits the clay. The water, when clear, is drawn off; and the clay at the bottom is left sufheiently dry for use. Thus prepared, the clay is spread on a board, and beaten with an iron bar to temper and mix it ; then it is divided into pieces of the proper sizes to form a tobacco-pipe ; each of these pieces is rolled under the hand into a long roll, with a bulb at one end to form the bowl ; and in this state they are laid up in parcels for a day or two, until they become sufficiently dry for pressing, which is the next process, and is conducted in the following manner:— The roll of clay is put between two iron moulds, each of which is impressed with the figure of one-half of the pipe ; before these are brought together a piece of wire of the size of the bore is inserted midway between them ; they are then forced together in a press by mains of a screw upon a bench. A lever is next depressed, by which a tool enters the bulb at the end, and compresses it into the form of a bowl; and the wire in the pipe is afterwards thnut backwards and forwards to carry the tube perfectly through into the bowl. The press is now opened by turning back the screw, and the mould taken out. A knife is next throat into a cleft of the mould left for the purpose, to cut the end of the bowl smooth and flat ; the wire is carefully withdrawn, and the pipe taken out of the mould. The pipes, when so far completed, are laid by two or three days, properly arranged, to let the air have access to all their parts, till they become stiff, when they are dressed with scraper's to take off the impressions of the joints of the moulds ; they are afterwards smoothed and polished with a piece of hard wood.
The next process is that of baking or burning ; and this is performed in a furnace of a peculiar construction. It is built within a cylinder of brickwork, having a dome at top, and a chimney rising from it to a considerable height, to promote the draught. Within this is a lining of fire-brick, having • fireplace at the bottom of it. The pot which contains the pipes is formed of broken pieces of pipes cemented together by fresh clay, and hardened by burning; it has a number of vertical flues surrounding it, conducting the flame from the fire-grate up to the dome, and through a hole in the dome into the chimney.
Within the pot several projecting rings are made; and upon these the bowls of the pipes are supported, the ends resting upon circular pieces of pottery, which stand on small loose pillars, rising up in the centre. By this arrangement • small pot or crucible can be made to contain fifty gross of pipes without the risk of damaging any of them. The pipes are put into the pot at one side, when the crucible is open ; but when filled, this orifice is made up with broken pipes and fresh clay. At first the fire is but gentle, but it is increased by degrees to the proper temperature, and so continued for seven or eight hours, when it is damped, and suffered to cool gradually; and when cold, the pipes are taken out ready for sale.