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Tom to take the Ground-plot of any City or Corporation by the Theodolite or Degrees on the plane Table.
OR the performance of which, it will
be neceffary for the young Surveyor to provide himself of a Chain that is 50 Foot long, containing 50 Links, and each Link a Foot; for all Cities are beft laid down by a Scale of Feet: It will be convenient that he have a Rod that is 5 or 10 Foot in. Length,and to be fubdivided into Feet: This Rod is to take the Off-fets of the Houfes on both fides your Chain, as you measure along : the Streets or Lanes.
Let Fig. 1. be a part of fome City, and you are required to take a Ground-plot thereof.
Firft, Caufe two Men to ftand, one at B, and the other at F; then placing your Inftrument at A, laying the Index upon the Diameter, turn it about until through the Sights you efpie the Man at F; then fcrew your Inftrument faft, 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 min. down in your Field Book, as you did when you measured the Lane; then with your Rod measure your Off fets 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 to wards B, and at 6 Foot diftance from A, you will have your Off-et to the Left to be 7 Feet; note both thefe down in your Feld-Book orEye-draught,which is beft toreprefent the thing; then meafuring on toward B, you will find that at 47 Feet diftance from A, you will have a Street both to the Right and Left, and the Off-fet to the Right. will be 10 Foot, and to the Left 6; note. thefe down in your Field Book or Eyedraught; then ftill measuring toward B,
you will find that at 90 Foot distance from A, you will have an Off-fet to the Left that is 5 Foot; note this down in your Feld Book, and at the fame time your Off fet to the Right will be 11 Foot; note this down alfo, then come to B, where one of your Men flood, and by measuring with your Chain, you will find the diftance be tween A and B to be yoo Foot; then placing your Inftrument at B (caufing the Man that stood at F, to ftand at A, fo foon as you took your Inftrument up from A) Jaying your Index upon the Diameter, turn your Inftrument about until you through the Sights efpy the Man at A; there make. your Inftrument faft, and cause the Man that flood at B, to go and ftand at C ; then direct your Sights to C, and note the deg. cut by the Index, which let be 140 deg. then with your Rod measure the Off-fet 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 meafure towards C, in as direct a Line as they can, and at 61 Foot diftance from B, you have a Street both to the Right and Left; then measure the Off fets, and you will find it will be 9 Foot on both fides the way, viz. to the Right and Left, at 120 Foot diftance from B, the Off fet to the Left will be found to be 8 Foot, and at 127 Foot distance from B, the Off fet to the right is 8 Foot alfo 3
then you will find you are come to C, then caufe a Man to go and stand at B, and another to ftand at D, place your Inftrument at C, and lay the Index thereof upon the Diameter, turning it about till through the Sights you efpie the Man at B there fcrew your Inftrument faft; then direct your Sights To the Man at D, and the Index will be found to cut too deg. and if you measure with your Rod the Off-fet to the right at the fame time, it will be found to be 8 Foot; then measure with your Chain to wards D, and at 8 Foot distance from C, the Off-fet 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 fet to the left is 4 Foot, at 75 Foot the diftance of CD, the Offset to the right is 12 Foot; then place your Inftrument at D, and caufe a Man to ftand at C, and another at E; and laying the Index of the Inftrument upon the Diameter, turn it about till through the Sghts you efpie the Man at C; there make your Inftrument faft; then direct your Sights unto the Man atE,and you will find that the Index will cut Ico deg.then with your Rod measure the Offfet to the right, and it will be found to be Foot, and the Off-fet to the left 11 Foot, then with your Chain meafire towards E, and at 41 Foot diftance from D you will have a Street to the right and left; then mesfuring on towards E, you will find that at