your 2 Acres; then the Angle A. C. D. is the two Acres, or 320
Pole, and the Angle C. D. B. is 2 Acres 105 pole, and near ½ a
pole.
By the same Rule may you cut off what Number of poles you please,
from the Angle D. to fall upon the Line C. B. or to fall upon the Line
D. B. having but the length of the Lines given you.
But if it be Required to take off a part from a Triangle according to
any proportion given, by a Line drawn parallel to any of the sides
assigned.
As let A. B. C. be a Triangle containing 5 acres, and it is desired to
cut off 2 acres, by a Line drawn parallel to A. B. first, on the Line
A. C. draw the Semi-circle A. E. C. and the Diameter C. A. Divide
into 5 equal parts, and from the point of 3 of these parts of that
Line draw the perpendicular D. E. to cut the arch-line in E. then set
the length of C. E. from C. on the Diameter-line, and it will reach to the
point F. then from that point at F. take the nearest distance to the Line
A. B. and set that distance off from B. to G. then draw the Line F. G.
exactly parallel to A. B. so will the Triangle C. G. F. be 3 acres, and
G. B. A. F. 2 acres, the thing propounded.
(See Fig. 39.)
This Rule in it self is exact, but in a large Field or Wood it is diffi∣cult
to be done, because the Semi-circles and other Lines are very hard
to be drawn exactly.
But if your Field, or part of it, be a square, and you are to take off
some parts of it, you may do it to any Number of Rods desired, easily
and exactly, thus:
Let the Field be never so great, Measure you onely that side of the
Square whence you are to take off your part, exactly.
(See Fig. 40.)
Examp. It is Required to cut off 2 acres, or 320 Pole from a Field,
or part of one, that is in form of the Square A. B. D. C. with a Line
drawn parallel to the side A. B. Now, finding the side of the Square to
be 32 Pole; Divide 320 (the parts you are to cut off) by 32, the
side of the Square, and the Quotient will be 10; then set off 10 Pole
from A. to E. and from B. to F. and the Square A. B. F. E.
is 2 acres, as was Required.
〈 math 〉〈 math 〉
This is very Useful for several Men, and readily to be
performed; but if these sides A. C. or B. D. do not go
Square from the end A. B. then must you find the mid-line
of the Square you are to take, and Divide the Summe of Poles you are