Like most of the great inventions, it was the work of many men. In crude applications, parts of it date back to the Middle Ages. Leonardo da Vinci caught an inkling of it. French writers in the sixteenth and seventeenth centuries describe and illustrate devices which involve the parts of it. Fig. 13, reproduced from an illustration in the old work of Besson, first published in 1569,[32] shows a lead screw. The copy from which this illustration was taken is printed in Latin and is in the Astor library, New York. The upper shaft had three drums; the middle one carried the rope which was manipulated by the operator. Of the drums at the ends, the one at the left operated a lead screw and the one on the right, the piece being cut. The two outer weights held the follower up against the lead screw. The cutting was, of course, intermittent, as in all the earlier types of lathes. The idea of the lead screw occurs in other French works of the seventeenth and eighteenth centuries. In the lathe shown in Fig. 14, from a French book published in 1741,[33] gears instead of ropes were used to connect the rotation of the lead screw with that of the work, but if the idea of _change_ gears was contemplated, it was not developed. [32] “_Des Instruments Mathématiques et Méchaniques, &c., Inventées par Jacques Besson._” First Latin and French Edit., 1569. Plate 9. Two later editions were published at Lyons, one in 1578 and one in 1582. The same copper plates were used in the three editions. [33] Holtzapffel: “Turning and Mechanical Manipulation,” Vol. II, p. 618. London, 1847. [Illustration: FIGURE 13. FRENCH SCREW-CUTTING LATHE, PREVIOUS TO 1569] [Illustration: FIGURE 14. FRENCH SCREW-CUTTING LATHE, ABOUT 1740] The slide-rest was also known. An illustration of a French slide-rest, published long before Maudslay’s time, is reproduced in Fig. 3. In Bramah’s original “slide-tool,” the tail-stock and slide-rest were combined.[34] It was made about 1795 by Maudslay while still his foreman. How much of the design was Bramah’s and how much Maudslay’s we cannot tell. It was a light, flimsy affair and very different from the slide-rests Maudslay was making only a few years later. [34] Buchanan: “Practical Essays on Mill Work and Other Machinery.” London, 1841. Volume of Plates.