In calculating the former, a deduction is to be made for the quantity rounded off, amounting to one-third of the whole depth--that is, one-sixth from the top and one-sixth from the bottom of the thread. Making this deduction it will be found that the angle of 55 deg. gives for the actual depth rather more than three-fifths and less than two-thirds of the pitch. The precaution of rounding off is adopted to prevent the injury which the thread of the screw, and that of the taps and dies, might sustain from accident. [Illustration: FIGURE 25. SIR JOSEPH WHITWORTH] In 1853 Whitworth visited the United States, and in conjunction with George Wallis of the South Kensington Museum, reported on the enterprises and manufactures of the United States.[106] Nearly all the memoirs of Whitworth refer to the profound effect of this report. As one reads it today, it seems difficult to see why it should have had so much influence. It is probable that Whitworth’s own personal report to the influential men about him contained much which does not appear in the formal report. In it he takes up steam engines, railway supplies, woodworking tools, electric telegraph, textile mills, and gives brief accounts of some of the factories and methods which he found at various places in New England and the Middle States. The longest description is given to the Springfield Armory, but even this is a mere fragment, and the only detailed information is of the time necessary to finish a gun-stock. We know, however, that this armory and the various private armories they saw, made an impression upon Whitworth and the whole Commission which led to the remodeling of the British gun-making plant at Enfield. Nasmyth was also concerned in this and a fuller account of it will be given later. [106] “Report of the British Commissioners to the New York Industrial Exhibition.” London, 1854. The conclusion of Whitworth’s report shows clearly that he was deeply impressed with the extent to which the automatic principle was being applied to machine tools in America. “The labouring classes,” he says, “are comparatively few in number, but this is counterbalanced by, and indeed, may be regarded as one of the chief causes of, the eagerness with which they call in the aid of machinery in almost every department of industry. Wherever it can be introduced as a substitute for manual labour, it is universally and willingly resorted to.... It is this condition of the labour market, and this eager resort to machinery wherever it can be applied, to which, under the guidance of superior education and intelligence, the remarkable prosperity of the United States is mainly due.” Another characteristic of American manufacture attracted his attention,--the tendency toward standardization. In his address in 1856 he condemns the overmultiplication of sizes prevalent in every branch of English industry.