Page:The Kinematics of Machinery.djvu/235

 EG YPTTAN LA THE. 213

the bow d. The wooden cross-bar at ~b is fastened to the table e, the second cross-bar c is quite separate, and movable upon e. It is held in any required position by means of the iron bar/, which is weighted with a stone at g. The rod / is itself linked to b by means of a pin at h. The iron " centres " at I and c are simply bent nails driven into the cross-bars. In using this machine the turner squats on the ground behind it, moving the bar with his left hand, while he holds the chisel at i with his right. He presses the tool against the rest at k with the great toe of his right foot. His skill is most remarkable.* In this instrument, in which we notice a very extended use of force-closure, we cannot trace any distinct development from the potter's wheel. It is, however, im- probable that Southern Europe should have worked in any way

FIG. 164.

upon the type of lathe used in Egypt, for its construction is directly connected with the squatting position of the worker, a position which is foreign to the habits of the Western nations.

In the middle ages we find a lathe used which has beyond question developed itself from the ancient form ; its motion is received just as in the fire-drill, but with notable improvements. It still remains in use in Italy, and indeed, in various parts of Southern Europe. One man only is required to work it. A cord or band is turned round the lathe spindle, or often round the piece to be turned (this method is certainly the older), and is attached above to a spring beam of wood and below to a tread-plate, Fig. ] 65. The latter is pressed downwards with the foot, and the cord is then raised again by the elasticity of the spring, the piece to be turned receives rotary motion alternately in two directions,


 * See Descript. de VEgypte (2nd Ed. 1823) vol. xii. p. 452. Plate XV.