MACHINERY'S REFERENCE SERIES EACH NUMBER IS ONE UNIT IN A COMPLETE LIBRARY OF MACHINE DESIGN AND SHOP PRACTICE REVISED AND REPUBLISHED FROM MACHINERY NUMBER 21 MEASURING TOOLS THIRD EDITION CONTENTS History and Development of Standard Measurements Calipers, Dividers, and Surface Gages Micrometer Measuring Instruments Miscellaneous Measuring Tools and Gages Copyright, 1910, The Industrial Press, Publishers of MACHINERY. 49-55 Lafayette Street, New York City * * * * * CHAPTER I HISTORY AND DEVELOPMENT OF STANDARD MEASUREMENTS[1] While every mechanic makes use of the standards of length every day, and uses tools graduated according to accepted standards when performing even the smallest operation in the shop, there are comparatively few who know the history of the development of the standard measurements of length, or are familiar with the methods employed in transferring the measurements from the reference standard to the working standards. We shall therefore here give a short review of the history and development of standard measurements of length, as abstracted from a paper read by Mr. W. A. Viall before the Providence Association of Mechanical Engineers. Origin of Standard Measurements By examining the ruins of the ancients it has been found that they had standard measurements, not in the sense in which we are now to consider them, but the ruins show that the buildings were constructed according to some regular unit. In many, if not all cases, the unit seems to be some part of the human body. The "foot," it is thought, first appeared in Greece, and the standard was traditionally said to have been received from the foot of Hercules, and a later tradition has it that Charlemagne established the measurement of his own foot as the standard for his country. Standards Previous to 1800