Vidius shows three arrangements for driving these drills with thongs: the first method consists simply of a thong attached to the shaft of the drill (Pl. XLII, fig. 4); the second consists of a bow with the string of the bow wound once round the shaft (Pl. XLII, fig. 5); and the third consists of a crosspiece with a hole in the centre of it through which the shaft passes, and having strings from the end of the crosspiece to the top of the shaft (Pl. XLII, fig. 3). Primitive arrangements truly, yet all three methods of producing rotary motion are to be seen in use at the present day, and be it known that some of the most delicate boring performed by the hand of man at the present day is done with drills turned by the thong stretched across a bow. The latest developments in mechanical devices for drilling have failed to displace thong-driven drills for boring the holes in which the wheel spindles of the best hand-made chronometers move, and the spindles themselves are turned in chucks rotated not by belts in continuous rotary motion, but in alternating motion by means of a thong stretched across a bow. A bow of cane with a strong but fine thread, one turn of which is taken round the drill, is drawn backwards and forwards and rotates the drill with marvellous rapidity and accuracy. The bows used by watchmakers average about a foot along the string. Similar drills are used by engineers in turning out small work. The form with the crosspiece may be seen in use by travelling crockery menders, who drill holes in broken pottery and clamp the pieces with rivets. A turn or two of the string is made round the shaft, and the point of the drill being adjusted on the spot to be bored the crosspiece is gently pressed down by the first and third fingers, causing the shaft to rotate. When the thong has nearly uncoiled itself the pressure is slightly removed, the momentum causes the shaft to overrun and coil the thong in the opposite direction to which it originally was. The crosspiece is again depressed and the alternating rotation goes on without intermission, and the drill bores through the pottery. The travelling crockery mender is, in the northern towns of England, not an unusual sight squatting at work on the kerb. On the continent the 'Rastelbinder' is a regular domestic institution. Not only crockery but glass is readily drilled by these means, and one who has seen the rapidity with which these drills rotate can readily understand the necessity for the advice given both by Hippocrates and Celsus to frequently remove the drill and dip it in cold water, in case sufficient heat be generated by the friction to cause subsequent exfoliation of the neighbouring bone.