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Show _ II SUGGESTIONS ON USE OF TABLES. A MANUAL OF LAND SURVEYING. 1. The Table of Tangents is convenient in estimating courses of lines to be run. Example 1.--From the quarter post on the east side of Section 2 I wish to run a line for a road straight to a ' point 80 rods north of the southwest corner of Section 30. What course shall I run? Solution-Distance west, 5 miles; distance south, 4.25 miles, which divided by 5 equals the natural tangent of III 3 Then a: =-- r, see. A. If r = 100, as is common, :1: maybe taken directly from the table. If r = 100, A = 21° 40', then a: = 107.6. In laying out such lots it is generally easier and quicker to measure this distance on the street line than it is to set up the transit for each lot line and run it in. ' 3. Table of Departures.-This table has many convenient uses, of which a few examples are given. the angle which the course makes with an east and west line, = .850. Find this number in the table of natural tangents and take out the corresponding angle, = 40° 22', which is the same as S. 49° 38' W. 2. What is the course from the village of Climax, at the east quarter post of Section 3, Township 3 south, 3 Range 9 west, to the village of Richland, at the southwest corner of Section 14, Township 1 south, Range 10 west? To the village of Schoolcraft, at the southeast corner of Section 19, T. 4 S., R. 11 W., from Climax? What to Schoolcraft from Richland? Examples-1. I wish to stake out a line along an old hedge row from quarter-post to section corner. On one side is a clear field. I go to the section Corner, and make an offset of 25 links and set up a. flag. I then go to the quarter-post, and, making an equal offset, find that I cannot see the flag; so I offset until I can see it-say 37 links more. I sight to the flag, find from the table of departures the angle corresponding to 37 links at a distance of 40 chains = 32'. turn off the angle on the transit, and run the line back parallel with the section line, setting stakes on the true line, by 62 link offsets, as qften as required. 2. The Table of Secants is convenient for finding the hypothenuse of a triangle, thus simplifying many computations in the field. Secants not given in the table may be found by interpolation or by the formula: 1' 1..../ 2. To run a true half-quarter-line when one end is inaccessible. :13" Secant = "lg i2 " .7 , "'~ cosine ' " The following example indicates one of the practical applications in the field: sents the whole c ' section, and ab the line to be run. Bisect cg, setting Example-Lots in a city are laid out with /K 1" , FIG_ 81. "R."e‘». - r ' stake at a. Measure the angle acd, which we will call their lines perpendicular to N Street and running through to M Street. Required the width (x) of the lots on M Street. Call the width of the lots on N Street 7'. Measure the angle A. Fig. 82 repre« 89° 24'. By the field notes the north line of the section measures 77. .9 80.22, hence ac= 20.05%. The south" line measures |
