Page:Popular Science Monthly Volume 40.djvu/180

168 which prevents the frame C from turning. E is the former or profile which shapes the interior of the vessel. The lever or pulldown, above the horizontal bar F, gives a transverse motion, and forces the former toward the side of the mold. 1 and 2 are adjustable collars which are fastened by screws; 1 regulates the distance to which the collar or frame C must be lowered to give the proper thickness to the bottom of the vessel, while 2 acts as a stop to prevent the frame from being thrown up too high.

A "jolly" is a somewhat similar contrivance, consisting of a table on which is a revolving mold with a single or double pull-down.

The construction of pottery kilns has changed but little in the past fifty years. The glaze kiln of the Tucker & Hemphill factory was made on the French plan. It possessed six fire-boxes and the same number of flues, eight inches in width, which passed through solid walls and met in the center. Besides the central space there were two circular passages, one extending around the circumference of the kiln and another midway between this and the center. Modern kilns are generally made about fifteen to sixteen and a half feet diameter inside, and measure about the same in height to the crown, with usually ten fire-boxes. In some of the Western kilns slight modifications have been made in the latter for the employment of natural gas, which is used instead of coal.