8243. SURVEYING, Method of platting.—
You requested for the use of your
school, an explanation of a method of platting
the courses of a survey, which I mentioned to
you as of my own practice. This is so obvious
and simple, that as it occurred to myself,
so I presume it has to others, although I have
not seen it stated in any of the books. For
drawing parallel lines, I use the triangular
rule, the hypothenusal side of which being applied
to the side of a common straight rule, the
triangle slides on that, as
thus, always parallel to itself.
Instead of drawing meridians
on his paper, let the pupil
draw a parallel of latitude, or
east and west line, and note
in that a point for his first
station, then applying to it his
protractor, lay off the first
course, and distance in the
usual way to ascertain his second station. For
the second course, lay the triangular rule to the
east and west line, or first parallel, holding the
straight or guide rule firmly against its hypothenusal
side. Then slide up the triangle (for
a northerly course) to the point of his second
station, and pressing it firmly there, lay the
protractor to that, and mark off the second
course, and distance as before, for the third
station. Then lay the triangle to the first
parallel again, and sliding it as before to the
point of the third station, then apply to it the
protractor for the third course and distance,
which gives the fourth station; and so on.
When a course is southwardly, lay the protractor,
as before, to the northern edge of the
triangle, but prick its reversed course, which
reversed again in drawing, gives the true
course. When the station has got so far from
the first parallel, as to be out of the reach of
the parallel rule sliding on its hypothenuse,
another parallel must be drawn by laying the
edge, or longer leg of the triangle to the first
parallel as before, applying
the guide-rule to the end, or
short leg (instead of the hypothenuse ),
as in the margin,
and sliding the triangle up to
the point for the new parallel.
I have found this, in practice, the quickest
and most correct method of platting which I
have ever tried, and the neatest also, because it
disfigures the paper with the fewest unnecessary
lines.—
To Mr. Girardin. Washington ed. vi, 338.
(M.
1814)
