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under the fights of the Inftrument to the mark at F, is (as it were) the prime Diameter whence the D grees of the Argles are to be numbred, and accordingly I mark: the Angle A, in my Table hereafter to be exemplified with 360 Degrees. But to proceed, turning the Index with the fiducial Edge upon the Center, till I fee that Thread cutting the Mark at at B, the faid Edge cuts upon the Frame at 76 Degrees 15 Minutes: I note down for that Angle: The like work I do, turning the fights to C,D and E, (but not to F, for there is no Angle but only a Mark in the Boundary) and I find mine Index to cut for every Angle as I have Marked them within the pricked Circle of the laft Figure, viz. 157 deg.. 35 Minutes for C, 225 degrees 20 Minutes for D, and 278 Degrees and 50 Minutes for E.
DIMIDIL A360 004
Then I meafure (or caufe to be frictly meafured by others) the distances betwixt the place where the Inftrument ftands, and eve ry Angle, and find them to to be as I have fet them upon the pricked Lines in the little Circle, viz. A 4 Chains 20 Links, B 4 Chains 3 Links,
B 7615403 C157 35 384 D22520535 E278
C 3 Chains 84 Links, D 5. Chains 35 Links, E 4 Chains 6 Links. And now my Table both for Lines and Angles is thus perfect
ed, and the work is ready for Protraction within Doors.
Now to protract our Obfervations: I draw upon Paper a Line AF at Adventure, fo it be long enough, and ftick a pin in it at pleasure for the Center O, upon which I place the Center of the Protractor, fo that the ftreight fide of the Protractor may lye upon the Line AF, the Limb or Arched fide being upwards towards B, by the help whereof I make a prick on the Paper at 76 deg. 15 Min. for B, and at 157 deg. 35 Min. for C, according to the numbers in my Field-Book.
Then turning the Protractor about the pin, with the Limb down towards I) and E,, till the Diameter lye again juft upon the Line AF, I number downwards from the Righthand towards the Left, beginning 190, 200, &c. And ove-ragainst the place where 225: degrees 20 Minutes and 278 degrees 50 Minutes fall, I prick the Paper at the fide of the Limb, and through thofe four points. I draw fo many feveral Lines, up-on which,and alfo upon the Line A O, Imark: out by points the true mealure of every Line by a Scale trom the Center, and from thofe points drawing the Lines AB, BC, CD, DE, and EE, I have the true Plot of the Field.
How to take the plot of an Irregular Field by the Theodolite or by the Degrees on the plain Table by going round the fame, being the best M thod in Practice.
Fig. 101 Firft caufe marks to be fet up at every Station, as A, B, C, D, E, F; then making Choice of a Station at A to begin at Meafure from A, to the Hedge at a, which you'll find to be 35 Links, which note down in your Eye Draught or Field Book, likewife measure from A, to the Hedge at b,and you'll find it to be 20 Links, which Note down; then meafure from your Sation A, towards B your fecond Station. and at 6 c. 40 l you have an off-fet of 30 Links to the right at the corner c, and at 6c.50%.you have measured to your fecond Station at B, where you are to fix your Infirument and take the Angle ABC, which is found to be 126° 30' which note down, then measure from your Station B to your Station C: which contains 3c. 2;1. at Station C, measure to the Hedge at right Angles to d; which let be 35 Links,and from C to the Hedge at e, is 20 Links, fixing your Inftrument at C take the Angle: BCD, which contains 104 o'; then measure in a ftreight Line from C: towards D, and at 1 c. 701. you have an off-fet to the Corner at f, which contains 25 Links; at 2 c. 5ol.you have an off-fet to the Corner g: which is
I c. 20 l. at 3 c. 90l. you have another, at h, of 1 c 40%. then measuring on 6 c. 30 l. you are come to your Station D: measure from D to the Hedge at right Argles to i, which is 80 Links, and from D to k: which is 50 Links: Then fix your Inftrument at D: and take the Angle CDE: which is 75° 30 Measuring along the Line DE, you'll find that at 3 c. 60 1. you have an off fet of c. 50l. to the Angle at 1: and at 8 c. 151. you have an off-fet of 1 c. 50l. to the Angle at m and at 13 c. 20 1. you have measured to your Station at E: from E to the Hedge at right Angles measure to n: which is 30 Links and fromE to o, which is go Links alfo: Then fix your Inftrument faftat E, and take the Angle DEF, which is 99°: 0, then meafuring in a freight line from E towards F: you'll find that at 4 c. 10l you touch the Hedge, and at 8 c. 3cl. you have neafured to your Station at F: From F to the Cerner q, at right Angles contains 53 Links; because you have meafured to the very Corner, you have no occafion to meafure from the Station F, to the Hedge at r: Having fixt your Inftrument at F: take the Angle E FA which contains To 8° 30 then measuring from F: towards A you'll find that at 2c, 70 l. you have an offfet of 85 Links to the bend at S: and at 6c. 65. you have meafured to your firft Station at A: where you began.
How to protract these Obfervations.
Firft draw an obfcure line at pleasure, as AB,then with your thin Ruler,having 27 qual parts in an Inch placed upon the very Edge. (being the number that this Draught was protracted by) apply, the Edge of this Ruler to the Line AB, and with your protracting pin make a mark at 35 Links, from A to a, then place the Edge of your Ruler at right Angles to the line AB, and prick off 20 Links from A to b: then place the be ginning of your Scale at the point A: the Edge being laid along the Line AB, by your Field Book or Eye Draught you'll find that at 6 c.40 you have an off-fet to the Corner c: which accordingly prick off, and draw the Black-line bc, then at 6 c. 50 prick off the length of the Line AB; at the point B, with your protractor lay down the quantity of the Angle ABC 126: 3'0 and with your thin Ruler prick off upon the Line BC 3c. 25 from B to C, at the Station C: prick off 25 Links to d, and 20 Links to c: both being at right Angles ;at the point C: Protract the quantity of the Angle BCD 104 o, then with your Scale prick off upon the line CD 1 c. 70 l. and at right Angles to this point prick off 25: Links to the Hedge at f: Then draw your boundary Line through the point f and e: