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 . (135) When one of the lines with whichan inaccessible field is surrounded, as inthe last two figures, cuts a corner of thefield, as in Fig. 84, the triangle ABC isto be deducted from the content of theenclosing figure, and the triangle CDEadded to it. The triangle DEF is alsoto be added, and the triangle FGH de-ducted. To do this directly,
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 . (135) When one of the lines with whichan inaccessible field is surrounded, as inthe last two figures, cuts a corner of thefield, as in Fig. 84, the triangle ABC isto be deducted from the content of theenclosing figure, and the triangle CDEadded to it. The triangle DEF is alsoto be added, and the triangle FGH de-ducted. To do this directly, it would benecessary to find the points of intersectionC and F. But this may be difficult, andcan be dispensed with by obtaining thedifference of each pair of triangles. Thedifference of ABC and CDE will be ob-tained at once by multiplying the differ-ence of the offsets AB and DE by half of BE; and the difierencaof DEF and FGH by multiplymg the difference of DE and GHby half of EG.*. * For, making the triangle Bmn = ABC, then mtiEG = En X h {^^ + ^^^(DE — AB) X i EB ; and so with the other pair of triangles. CHAP, IV.] Diagonals, Tie-lines and Perpendiculars. «5 (136) Roads. A winding Road may also be surveyed thas, as18 shown in Fig. 85; straight lines being measured in the road, Fig. 85.
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectsurveying, bookyear18
