. The railroad and engineering journal . all departures from uniformitj—such as a vari-able specific heat—be determined. 56 THE RAILROAD AND [February, 1888. THE PRINCIPLES OF RAILROAD LOCATION. By Professor C. D. Jameson. (Copyright, 1887, by M. N. Forney.) ijContinued from f age 14.) CHAPTER The Vernier has been referred to in several of the de-scriptions of instruments used in location. Its use is sogeneral that a special description is given below. A vernier is a contrivance by means of which smallerdivisions of distance are read than the actual divisionsmade on the scale or
. The railroad and engineering journal . all departures from uniformitj—such as a vari-able specific heat—be determined. 56 THE RAILROAD AND [February, 1888. THE PRINCIPLES OF RAILROAD LOCATION. By Professor C. D. Jameson. (Copyright, 1887, by M. N. Forney.) ijContinued from f age 14.) CHAPTER The Vernier has been referred to in several of the de-scriptions of instruments used in location. Its use is sogeneral that a special description is given below. A vernier is a contrivance by means of which smallerdivisions of distance are read than the actual divisionsmade on the scale or rule. By its use exceedingly smalldivisions can be read by the naked eye. On railroad work the vernier is used upon a level rod intaking turning-points and upon the transit in measuringangles. \ The principle of the vernier is as follows : Take anyscale, as Plate XVI, which represents a part of the level large divisions A, B, C, D, etc., are tenths of tenths of feet are divided each into 10 parts, mak- Flate XV/.. ing .01 of a foot. Now, it is desired to measure distance tothe thousandth of a foot. If the smaller divisions, or .01ft., are to be divided into 10 parts, making .001 ft., eachof these divisions would be so small as to be scarcely per-ceptible to the naked eye, and this subdivision, owing to the increased amount of work on the rod, would also in-crease the cost very much. Now, the object of the vernieris to permit the reading of .001 ft. without the necessity ofdividing each hundredth of a foot into 10 equal way in which it is accomplished is as follows ; The rod is divided into hundredths of a foot, a, b, c, etc.,then the vernier scale_) is made equal in length to nine ofthese small divisions a, b, c, and is divided into 10 equal Tlate XV/I
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