In 1848 Jean Laurent Palmer, a skilled mechanic in Paris, patented a “screw caliper,” shown at B, Fig. 44, and began manufacturing it under the name of “Systeme Palmer.” In this micrometer the graduations were divided, one set being on the cylinder of the frame and the other on the revolving barrel, an arrangement which permitted all the markings necessary for clearness. The importance of this tool does not seem to have been appreciated until August, 1867, when J. R. Brown and Lucian Sharpe saw one at the Paris Exposition. They at once recognized its possibilities and brought one home with them. To use Mr. Sharpe’s own words: “As a gauge was wanted for measuring sheet metal, we adopted Palmer’s plan of division, and the Bridgeport man’s size of gauge, adding the clamp for tightening the screw and the adjusting screw for compensating the wear of end of points where the metal is measured, and produced our ‘Pocket Sheet Metal Gauge.’... We should never have made such a gauge as was shown us by the Bridgeport man in 1867, to sell on our own account, as it would be too troublesome to read to be salable. If we had not happened to find the Palmer gauge, and thereby found a practical way to read thousandths of an inch, no gauges would have been made. If we had never seen the Bridgeport device we should have found the Palmer at Paris, and without doubt have made such gauges, but possibly would have made a larger one first. The immediate reason of making the ‘Pocket Sheet Metal Gauge’ was the suggestion coming from the Bridgeport Brass Company of the want of a gauge of the size of the sample shown us for the use of the brass trade.”[194] [194] From a letter of Lucian Sharpe, quoted in the _American Machinist_ of December 15, 1892, p. 10. [Illustration: A B C D FIGURE 44. EARLY MICROMETER CALIPERS A--Wilmot’s Micrometer, 1867 B--Palmer Micrometer, brought from Paris by J. R. Brown and Lucian Sharpe, 1867 C--“Pocket Sheet Metal Gauge,” Brown & Sharpe, 1868 D--One-inch Micrometer, Brown & Sharpe, 1877] This gauge, shown at C, in Fig. 44, was put on the market in 1868, and appeared in the catalog of 1869. Comparison of A, B, and C in Fig. 44 shows clearly their close relationship. The term “micrometer” caliper was first applied to the one-inch caliper (D, Fig. 44) which was brought out and illustrated in the catalog of 1877. In _Machinery_ of June, 1915, Mr. L. D. Burlingame has given an admirable and very complete account of the various improvements which have been brought out since that time. In connection with the article, a modern micrometer is shown and its various features, with the inventors of each, are clearly indicated.[195] [195] The origin and development of the present form of micrometer is further discussed in _Machinery_, August, 1915, p. 999, and September, 1915, pp. 11, 58.