Telemeters and Range-Finders for Naval and Other Purposes
Barr, Stroud · Proceedings of the Institution of Mechanical Engineers · 1896
In this paper it is not propOsed to treat of the history of Telemeters or Range-Finders, though that subject would not be devoid of interest.Such instruments cannot be said to be at all in common use, either at sea or on land ; yet descriptions of probably some hundreds of different forms have been published, and the workers in this field of invention have included many eminent engineers and physicists, among whom it may be sufficient to name James Watt and Sir David Brewster.A mere classification of the various devices that have been proposed for determining the distances of distant objects without direct measurement would take more time than can be devoted to the present paper.Nor is it proposed to give any account of the different kinds of telemeters that have been devised by the authors themselves in the eight years during which nearly all the time at their disposal for original work has been devoted to invention and experiment in this field.The present paper will be confined to a description of two instruments:-namely (1) the range-finder which is now in use in the navies of this and many other countries ; and (2) a small hand instrument, identical in principle with that for naval use, but much more portable and much simpler in its details.Even with this restriction however, it will be necessary t o omit the discussion of many of the difficulties that have been encountered, and of the methods by which these have been surmounted.Principle of Telemeters in general.-Settingaside a few instruments devised for military range-finding, to indicate the distance of the enemy by measurement of the time-interval between the instant when J a s .1596.RAKQE-FINDEILS.37 * (1) . . . .