. Machinery and processes of the industrial arts, and apparatus of the exact sciences. toallow of this than when it is more distant, the instrument becomes atelemeter, or distance measurer. For facility in use it is more convenientin general that the edges of the plates should be horizontal than ver-tical; but either construction may be employed. The principle hereexplained is that which has been adopted in the second of the instru-ments of Mr. Lorieux mentioned above. TELEMETRICAL APPARATUS. 579 THE STADIMETER. In Mr. Brunners collection was exhibited an instrument called thestadirneter, inve
. Machinery and processes of the industrial arts, and apparatus of the exact sciences. toallow of this than when it is more distant, the instrument becomes atelemeter, or distance measurer. For facility in use it is more convenientin general that the edges of the plates should be horizontal than ver-tical; but either construction may be employed. The principle hereexplained is that which has been adopted in the second of the instru-ments of Mr. Lorieux mentioned above. TELEMETRICAL APPARATUS. 579 THE STADIMETER. In Mr. Brunners collection was exhibited an instrument called thestadirneter, invented by Messrs. Peaucellier and Wagner, of the imperialtopographical corps of France. This is a horizontal rale bearing strongly-marked divisions, which are numbered from the centre in both directions,the whole being supported by a vertical rod in the manner of a signalmark on an engineers levelling rod. The marks are in white on black,for the sake of greater distinctness, and the numbers are inverted thatthey may appear upright in an inverting telescope. This part of the Fig. X> HiiBninBMHtHBj Brunners Stadirneter. apparatus is represented in Fig. 120. In the focus of the eye-piece aretwo fixed micrometric lines, and the determination of distance is madeby observing how many divisions of the stadirneter are embraced betweenthese lines. The manner of observing is as follows: The stadirneter is fixed at thedistant station, with its support truly vertical, and the plane of its armsat right angles to the line to be measured. The observer at the tele-scope turns the instrument in azimuth by means of a tangent screw, soas to make the two lines of the micrometer cat, if possible, two simi-larly numbered divisions. Thus if these lines fall exactly on thedivisions 1, right and left, the distance is one decameter; if on thedivisions 2, it will be two decameters; if on the divisions 3, three deca-meters, and so on. But, as a general rule, the divisions will not fall exactly on t
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