[169] For a detailed account of this machine and its history see _American Machinist_, Vol. XXXVI, p. 1037. [Illustration: FIGURE 28. THE FIRST MILLING MACHINE BUILT BY ELI WHITNEY ABOUT 1818. NOW IN THE MASON LABORATORY, YALE UNIVERSITY] [Illustration: FIGURE 29. BLANCHARD “GUN-STOCKING” LATHE BUILT IN 1818 FOR THE SPRINGFIELD ARMORY. IN USE OVER FIFTY YEARS] Probably no machine has had so great an influence on interchangeable manufacture as the automatic turret lathe. The turret lathe, “the first radical improvement on Maudslay’s slide-rest,” was built commercially by Robbins & Lawrence in 1854, and is said to have grown out of a revolving-head bolt cutter which Henry D. Stone saw at Hartford. The turret idea was not originated by Stone. Root and Howe had used it a number of years before, and it had been utilized by several others. All of these turrets except Howe’s seem to have had a horizontal axis instead of the vertical one which became general. Later improvements by C. M. Spencer and a long line of brilliant mechanics have increased the accuracy of the turret lathe and made it more nearly automatic than any other type of general machine tool. Today it is, with the milling machine, the main reliance for interchangeable work. In sketching the development of interchangeable methods in American shops, we have confined our attention to gun makers chiefly. They were by no means the only ones to have a part in this development, but they were its originators, they determined its methods, and developed most of the machines typical of the process. About 1830 Chauncey Jerome began the manufacture of brass clocks. Terry, Thomas and other Connecticut mechanics had been manufacturing wooden clocks, which gave way to metal clocks as the advantage of interchangeable manufacture became recognized. In 1848 A. L. Dennison founded the American Watch Company at Waltham. The interchangeable system has nowhere reached a higher development than in the work of this company and of the other great watch factories. In 1846 Elias Howe was granted his patent on sewing machines, and within four or five years their manufacture sprang up on a large scale. Both of these industries, watch and clock manufacture and the manufacture of sewing machines, utilized a system which was already well established. Since that time it has been applied to a wide variety of articles. CHAPTER XII WHITNEY AND NORTH In the last chapter we considered the rise of the interchangeable system of manufacture and saw that it started in the shops of Eli Whitney, at New Haven, and of Simeon North, at Middletown. The lives of these men are of much interest, particularly that of Whitney. His struggle in defense of his patent rights on the cotton gin is instructive for all who see a high road to fortune in the patenting of a valuable invention.