. The railroad and engineering journal . nt is then sighted through/^i^at any desired point, the magnetic needle loosened,and the bearing of the line taken. The direction of thelines being taken by their magnetic bearing, no back-sights are used. But apart from this, the method of usingthe Surveyors Compass on railroad work is the same asthat described for the use of the transit. As will be seen,under certain circumstances the compass is preferable tothe transit. The one thing to guard against is the presence of anymetal, such as a knife or bunch of keys, which might dis-turb the needle by its
. The railroad and engineering journal . nt is then sighted through/^i^at any desired point, the magnetic needle loosened,and the bearing of the line taken. The direction of thelines being taken by their magnetic bearing, no back-sights are used. But apart from this, the method of usingthe Surveyors Compass on railroad work is the same asthat described for the use of the transit. As will be seen,under certain circumstances the compass is preferable tothe transit. The one thing to guard against is the presence of anymetal, such as a knife or bunch of keys, which might dis-turb the needle by its magnetic attraction. The Wye Level, as made by different makers, variesin some of its details, but the general principles are thesame in all, and all are much like, in details, the oneshown in Plate XIII. In this plate A A is the telescope which rests on the twowyes B B. The two clamps C C shut down over the tele-scope, and are held in place by the two pins D D, whichare fastened to the instrument by means of small pieces of PlATZ XIII. cord. E is the eye-piece of the telescope, and Jis theslide of the object-glass. (7 is a milled screw by meansof which the object-glass is moved back and forth, //is along spirit-level suspended from the telescope and parallelto it, by means of which the instrument is known to belevel. / is a small brass tube covered with a dead blackon the inside, which is put on the large end of the tele-scope to protect it from the rays of the sun. AAAA arecapstan-headed screws by means of which the wyes areraised or lowered. The telescope swings freely upon thejoint L. N is a clamp by means of which the telescopecan be clamped in any horizontal position, and thus pre-vented from moving in any direction except by use of thetangent-screw My by means of this screw the telescopecan be moved veiy slightly to the right or left. 0 0 0 arelevelling screws. There are four of these in ordinary in-struments, but only three in some of the more modernones. jP P are smal
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Keywords: ., bookcentury1800, bookdecade1880, bookidrailroadengi, bookyear1887
