Identifier: treatiseonsurvey00robi (find matches)
Title: A treatise on surveying and navigation: uniting the theoretical, the practical, and the educational features of these subjects
Year: 1852 (1850s)
Authors: Robinson, Horatio N(elson), 1806-1867. (from old catalog)
Subjects: Surveying Navigation
Publisher: Cincinnati, J. Ernst
Contributing Library: The Library of Congress
Digitizing Sponsor: The Library of Congress

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ad passes.Take, for example, a railroad line, ABCDE, represented in thenext figure. The lines being all measured and marked in distancesof 100 or 200 feet, the bases are all ready where the line isstraight. Set the table as at A, and draw lines to all objects that you wishto appear on the map, both to the right and to the left,— then movethe instrument to B, drawing lines to the same object from a corres-ponding base on the paper, and also draw lines to other objects fur-ther in advance on the line that may be seen from another base. The intersections of the lines from the extremeties of any base toto the same object will locate the object. When all the objects are thus located, both to the right and tothe left, we pass on to new objects, taking care to keep at least twoof the old objects in sight, to connect one new observation with thosepreviously taken. We now commence a series of observations froma new base, which base must take its proper relative position on the SURVEYING. 151
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152 SURVEYING. paper, and if the paper on the table is not large enough, it must betaken off and new paper put on, and two of the objects on the oldpaper must appear on the new, and then these two papers can beput together so that the objects which are on both papers will coin-cide, and then the two papers will be the same as one, and thuswe may put any number of papers together and form as large a mapas we please. If the different bases are not in the same direction, the objectswhich are on two different papers on being put together will showit, and several papers put together may make a very inconvenientfigure ; but they must be put together and then a square sheet oftissue paper put over the whole, and the map taken off. From thetissue paper the map can be put on any other paper. The engineers of Napoleons army frequently made maps of thelocalities they were about to pass ; indeed it is a military principlenever to go into an unknown locality, except in cases of absolutenecessity.

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