A treatise on land-surveying; comprising the theory developed from five elementary principles; and the practice with the chain alone, the compass, the transit, the theodolite, the plane table, &cIllustrated by four hundred engravings, and a magnetic chart . 87° W. Any line is similarly changed. The proof of this is apparrent on inspecting the figure. Suppose now that a suiveyor, ignorant or neglectful of thischange, should attempt to run out a F=- -^^• farm by the old Bearuigs of thedeed, none of the old fences or cor-ners ^emaiuing. The full lines inthe figure represent the original /bounds o
A treatise on land-surveying; comprising the theory developed from five elementary principles; and the practice with the chain alone, the compass, the transit, the theodolite, the plane table, &cIllustrated by four hundred engravings, and a magnetic chart . 87° W. Any line is similarly changed. The proof of this is apparrent on inspecting the figure. Suppose now that a suiveyor, ignorant or neglectful of thischange, should attempt to run out a F=- -^^• farm by the old Bearuigs of thedeed, none of the old fences or cor-ners ^emaiuing. The full lines inthe figure represent the original /bounds of the farm, and the dotted \lines those of the new piece of landwhich, starting from A, he wouldimwittingly run out. It would be ofthe same size and the same shape aathe true one, but it would be in thewrong place. None of its lineswould agree with the true ones, andin some places it would encroach onone neighbor, and in other places would leave a gore which belongs to It, between itself and anotherneighbor. Yet this is often done, and is the source of a gi-eat partof the litigation among farmers respecting their 208 COMPASS SURVEYING. [part hi. (321) To run out old lines, To succeed in retracing oldlines, proper allowance must be made for the change in the varia-tion since the date of the original survey. That date must firstbe accurately ascertained; for the survey may be much older thanthe deed, into which its bearings may have been copied from anolder one. The amount and direction of the change is then to beascertained by the methods of Arts. (318) or (319). The bear-ings may then be corrected by the following Rules. When the North end of the needle has been moving Westerly,(as it has for about forty years), the present Bearings will be thesums of the change and the old Bearings which were North-East-erly or South-Westerly, and the differences of the change andthe old Bearings which were North-Westerly or South-Easterly. If the change have been Easterly, reverse
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectsurveying, bookyear18
