International Correspondence Schools · Scranton, Pa. : The Colliery engineer co. · leaf 77
e as possible. A treewith a large exposed root ischosen, the bench mark is cutinto the root in the form of apyramid, a tack is driven into the apex and the rod heldupon it. The tree is blazed smooth and the letters B. M.,together with the elevation of the mark, written with redchalk. A bench mark… … SURVEYING. 6G7 of a line of levels before their adoption as a basis for con-struction. Usually intermediate points or stations are nottaken, but only the turning points necessary to cover theline. Readings are taken at all the bench marks, and thecorrect elevations marked. The adjustments of the…
Railroad engineering
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