POTTER'S WHEEL. The wheel as used by the potter ranks among the earliest me chanical contrivances. The Egyptians classed it among the inventions of the gods and claimed that Num, the creator, fashioned man upon it. As a broad principle the wheel consists of a flat disc, on an upright axle, rotating in a horizontal plane. The primitive form was simply a turn-table. The edge of the disc was made of heavy substance to secure momentum and steady motion. It was rotated by the hand. The Chinese improved upon this by driving by a cord running in a groove. In Europe the favorite device was a lengthening of the axle of the wheel, enabling a heavy disc some three feet in diameter to be placed at the bottom. The potter seated himself at the wheel and propelled it with his foot, working on the lower disc. This was the first form of the *kick') wheel. The next improvement was the application of a crank and handle which was kept in constant motion by one foot. The in troduction of power gave rise to two forms of wheel. The special requirement is that the speed of the wheel shall be variable at the will of the workman. This is accomplished either by cones in contact or by a traveling disc, or some similar device. In the former case a
cone with a slightly curved face is fitted to the axle, so that it forms the base of the machine. In contact with this is an inverted cone faced with paper or leather and so arranged that the potter can, by pressure of his foot, bring the large end of one cone into contact with the small end of the other or vice-versa. Thus the speed of rotation is completely under con trol. In the disc wheel the power is applied to a large steel disc revolving in a vertical plane. Upon the shaft of the wheel is a small disc faced with leather and free to move up and down the shaft, but rotating with it. A treadle enables the workman to place this either at the centre or the edge of the large steel disc, thus securing any desired speed. The potter's wheel is fast disappearing. It is now used mainly for shaping blanks, which are after ward pressed into molds, or is employed by the makers of artistic pottery for the sake of the individuality of the work. Stoneware makers also use it for the Production of large jars. See POTTERY, MANUFACTURE OF.