A complete treatise on practical land-surveying, in seven parts; . uess-line, Section 1.) land-surveying. 283 and the quotient will be the perpendicular to be set off fromeach end of the guess-line, on one side, or the other, as above. Note 1.—When from a trapezium, approaching very nearly to a rect-angle, it is required to part off any number of acres, &c. by a line parallelto one of its sides ; it may be done as directed in Prob. XI.; and if therebe offsets upon any of the lines, they must be treated as in the last Problem. 2.—In using guess-lines, it is not necessary that the learner should
A complete treatise on practical land-surveying, in seven parts; . uess-line, Section 1.) land-surveying. 283 and the quotient will be the perpendicular to be set off fromeach end of the guess-line, on one side, or the other, as above. Note 1.—When from a trapezium, approaching very nearly to a rect-angle, it is required to part off any number of acres, &c. by a line parallelto one of its sides ; it may be done as directed in Prob. XI.; and if therebe offsets upon any of the lines, they must be treated as in the last Problem. 2.—In using guess-lines, it is not necessary that the learner should drawthem so as to coincide in measure, with those of the examples which he isperforming. It will be sufficient for him to proceed in a similar manner. EXAMPLES. 1. From a trapezium, whose dimensions are contained in thefollowing notes, part off 2a. 2r. 24p. by a line parallel to theside A B. Return Begin BD 12491000toB. 1112 1000 R. off A. D A 550R. off D. CD 979R. off C. BC557R. off B. AB 11141000at A. Diag. Diag. Range W. 284 LAND-SURVEYING. (Part Having laid down the figure, draw the guess-line m n parallelto A B ; and from n, let fall the perpendicular a n ; then, sup-pose m n = 1058 links, a n will be = 230, and A a = 1052links; therefore, Ba = 1114 -1052 = 62 links,sq. links. Then, 1055x230 = 242650 the area of the trapezoid A a n m. And, 230x 31= 7130 the area of the triangle Ban. The sum - =249780 the area of the trapezium A 2r. 15220 the difference between the quan-tity proposed, and the quantity parted off by the guess-line ;which, divided by 1058, gives links, to be set off perpen-dicularly from m and n toward D and C. Hence, E F is thetrue line of division; and the trapezium A B E F contains 24p. As A is very nearly a right-angle, measure, in the field, 230-f- = links, from A to F. Then, upon any part ofthe line A B, (toward B) as at e, erect the perpendicular e r,which make = links; stake out the line E r F
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