It is well to glance for a moment at the problems which were involved in building the first steam engine. Watt had been working for several years on the steam engine when the idea of the separate condenser came to him on that famous Sunday afternoon walk on the Glasgow Green, in the spring of 1765, and, to use his own words, “in the course of one or two days the invention was thus far (that is, as a pumping engine) complete in my mind.”[1] He was a skilled instrument maker and his first small model was fairly successful, but when he undertook “the practice of mechanics _in great_,” his skill and all the skill of those about him was incapable of boring satisfactorily a cylinder 6 inches in diameter and 2 feet long; and he had finally to resort to one which was hammered. For ten weary years he struggled to realize his plans in a full-sized engine, unable to find either the workmen or the tools which could make it a commercial success. His chief difficulty lay in keeping the piston tight. He “wrapped it around with cork, oiled rags, tow, old hats, paper, and other things, but still there were open spaces left, sufficient to let the air in and the steam out.”[2] Small wonder! for we find him complaining that in an 18-inch diameter cylinder, “at the worst place the long diameter exceeded the short by three-eighths of an inch.” When Smeaton first saw the engine he reported to the Society of Engineers that “neither the tools nor the workmen existed that could manufacture so complex a machine with sufficient precision.”[3] [1] Smiles: “Boulton & Watt,” pp. 97, 98. London, 1904. [2] _Ibid._, p. 114. [3] _Ibid._, p. 186. Smeaton himself had designed a boring machine in 1769 for the Carron Iron Works for machining cannon, an illustration of which is given in Fig. 1.[4] It consisted of a head with inserted cutters mounted on a long, light, overhung boring bar. The work was forced forward on a rude carriage, as shown. The method of supporting the cutter head, indicated in the section, shows an ingenious attempt to obtain a movable support from an inaccurate surface. One need hardly say that the work resulting was inaccurate. [4] “Engineer,” London, March 4, 1910; p. 217. Drawn from the description given in Farey’s “Treatise on the Steam Engine.” [Illustration: FIGURE 1. SMEATON’S BORING MACHINE CARRON IRON WORKS, 1769] [Illustration: FIGURE 2. FRENCH LATHES OF ABOUT 1772]