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KINEMATICS OF MACHINERY.

and during the forward turning the workman uses his chisel upon it.* An Italian turnery, its ceiling covered with a labyrinth of cords and wooden beams, impresses a modern engineer as something very strange ; it may be conjectured that it is a tolerably true copy of a turner's workshop in Ancient Eome.

Our continued use of the alternate rotation of the fire-drill for small turning and boring work is familiar to all. We secure the two ends of the driving cord to a bow, having given it in the middle a turn round a small drum. The simple drawing to and fro

FIG. 165*

of the bow, which, unlike the spring-beam just described, is always equally tense, causes the rotation of the drum. This bow-lathe is still used by watchmakers for turning, both with centres and bearings ; for mere boring the more primitive method of hand or breast-pressure is used. The bow-drill must be of very high an- tiquity, for it is very widely used in a homely form by the Chinese,^ by the Kalmucks it is employed in two different forms,J and it


 * Laboulaye, Cinemat. p. 463. calls this lathe "tour en fair."

t Klemm (as above) i. 385. J Bergmann (as above) ii. p. 93.