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How to take the Ground-plot
fany City or Corporation by the Theodolite or Degrees on the plane Table.
OR the performance of which, it will
be necessary for the young Surveyor to provide himself of a Chain that is so Foot long, containing 50 Links, and each Link a Foot; for all Cities are best laid down by a Scale of Feet: It will be convenient that he have a Rod that is 5 or 10. Foor in Length and to be subdivided into Feet: This Rod is to take the Off-sets of the Houses on both sides your Chain, as you measure along the Streets or Lanes.
Example. Let Fig. 1. be a part of some City, and you are required to take a Ground-plot thereof.
First, Cause two Men to stand, one at B, and the other at F; then placing your Instrument al A, laying the Index upon the Diameter, turn it about until through the Sights you espie the Man at F; then screw your Instrument fast, and direct your Sights to the Man at B, and note the degrees cut by the Index, which let be 95 deg. and 30 min. Note this 95 deg, and 30 mio. down in your Field-Book, as you did when you measured the Lane; then with your Rod measure your Off sets both the Right and Left, as you did in meafuring the Lane allo; which you will find to be to the Right 5 Feet; then with your Chain measure towards B, and at 6 Foot diftance from A you will have your Off-let to the Left 10 be 7 Feet; note both these down in your Feld-Book orEye-draught,which is best torepresent the thing; then measuring on toward B, you will find that at 47 Feet distance from A, you will have a Street both to the Right and Lefr, and the Off-set to the Right will be 10 Foot, and to the Left 6; note these down in your Field Book or Eyedraught, then still measuring toward B,
you will find that at 90 Foot distance trom A, you will have an Off-let to the Left that is 5 Foot; note this down in your Feld Book, and at the same time your Off-set to the Right will be ni Foot; noto this down also, then come to B, where one of your Men ftood, and by measurirg with your Chain, you will find the diftance be tween A and B to be yoo Foot; then placing your Inftrument at B (causing the Man that itood at F, to stand at A, lo soon as you took your Instrument up from A) laying your Index upon the Diameter, turis your Instrument about until you through che Sights espy the Man at A; there make your Instrument fast, and cause the Man that stood at B, to go and stand at C; then dir<ct your Sights to C, and note the deg. cut by the Index, which let be 140 deg. then with your Rod measure the Off-set both to the Right and Left, and you will find that to the Right is 11 Foot, and to the Left 8 Foot; then cause your Men to measure towards C, in as direct a Line as they can, and ab 61 Foot distance froin B, you have a Street both to the Right and Left; then measure the Off sets, and you will find it will be 9
Foot on both sides the way, viz. to the Right and Left, at 120 Foot distance from B, the Off set to the Left will be found ta be 8 Foot, and at 127 Foot distance froin B, the Oft set to the right is 8 Foot allo ;
then you will find you are come to C; then cause a Man to go and stand at B, and another to stand at D, place your Inftrument at C, and lay the Index thereof upon the Diameter, turning it about till through the Sights you espie the Man at By there (crew your Instrument faft; then direct your Sights to the Man ar D, and the Index will be found to cut too degi and if you ineasure with your Rod, the Off-set to the right at the faine time, it will be found to be 8 Foot; then measure with your Chain towards D, and at & Foot distance from C, the Off-set to the left will be found to be 9 Foot; then measure on with your Chain, and you will find that at 64 Foot diftance from C, the Off set to the left is 4 Footjat 75 Foot the distance of CD, the Of set to the right is 12 Foot; then place your lo- : strument at D, and cause a Man to stand at C, and another at E; and laying the Index of the instrument upon the Diameter, it about till through the Sghts you elpie the Man at C; there make your Instrument tast; then direct your Sights unto the Man att and you will find that the Index will cut I co deg.then with your Rod ineasure the Offfer to the right, and it will be found to be
9 Foot, and the Off-set to the left 11 Foot ; !hen with your Chain inealnire towards E, and at 41 Foot distance from D you will have a Street to the right and left; then mealuring on towards E, you will find that at