Surveyor's Instrument. Page: 2 of 3
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UNITED
STATES
PATENT OFFICE.
JOHN HI. DOLM3AN, OF ALBANY, TEXAS.
SURVEYOR'S INSTRUMENT.
SPECIFICATION forming part of Letters Patent No, 313,659, dated MIVarch 10, 1885.
Appication fled June 6, 1884. (MIodel.)To aZZ whon it 7maC/y concern:
Be it known that I, JOHN H. DOLMAN, of
Albany, in the county of Shackelford and
State of Texas, have invented a new and use-
5 ful Improvement in Instruments for the Use of
Surveyors and Others, of which the follow-
ing is a full, clear, and exact description.
My invention consists in an instrument for
the measurement of angles for use in survey-
1o ing and for plotting, constructed as herein-
after described and claimed.
Reference is to be had to the accompanying
drawings, forming a part of this specification,
in which similar letters of reference indicate
5 corresponding parts in both the figures.
Figure 1 is a face view of the instrument,
and Fig. 2 is a detail section on line x x.
The parts composing the instrument are a
protractor, A, secured by a pivot or set-screw,
20 a, at the intersection of its pole and meridian
lines, to a bar, b, a leveling-piece, B, and a
sight-piece, C, carrying a telescope, d, both
parts B and C being hung on pin a, as rep-
resented; and a piece, D, is fitted to slide on
25 piece B. The piece B is of open square form,
and in the edges of its upper and lower
sides are levels e, so as to allow its use either
side up. The inside edges of the four sides
are spaced and numbered alike, the numbers
30 running from 1 to 200 on each. The sight-
piece C is spaced and numbered to corre-
spond with the piece B, the numbers com-
mencing at pivot a and running up to 360,
and the telescope d is parallel to the marked
35 edge. The top and bottom sides of piece B
are grooved to receive the ends of piece D,
and there are side arms, f, on the latter that
fit the grooves, so as to retain the piece D al-
ways at right angles to the top and bottom of
40 the level B, and the arms are connected by a
cross-piece, g, which serves for use in sliding
the piece back and forth. The edge of this
sliding piece is marked and numbered to cor-
respond with the sides of level B.
45 On the end of the sighting-piece C is a
clamp, i, taking over the edge of the protract-
or A, for holding the piece C in place, and a
similar clamp at h serves for clamping the
piece B. The bar b will have a clamping-
50 screw at its mid-length for securing it to a
tripod or staff, with the protractor in a ver-
tical plane.In using this instrument, the inside edges of
the top and bottom of piece B always repre-
sent the base-line for a right-angled triangle. 55
The other two sides of level B and the slid-
ing piece D represent the perpendicular, and
the sighting-piece C the hypotenuse of the
triangle.
To use the instrument for plotting, paper is 6o
placed on the face of the protractor and be-
neath level B. Base-lines are then drawn
along the edge of the piece B to any distance,
representing feet, inches, or poles. Slide D is
then moved to the end of the base-line to ob- 6j
tain the perpendicular, and then the piece C
is moved to any number on piece D, and the
scale on piece C indicates the length of the
hypotenuse by the number at the intersec-
tion. From this a square or a parallelogram 70
or other shaped figure can be drawn by using
a separate rule similar to piece D.
For taking altitude and depression and hori-
zontal lines to same, or to correct measured
lines on hilly grounds, the operation is as fol- 75
lows: The instrument is placed at the top of
the hill, and fastened to the stand with the
meridian line of protractor A pointing to a
staff at foot of hill. The piece B is then to
be leveled and clamped to the protractor, So
the telescope sighted on the staff at apoint
the same distance from the ground as the
pivot of the instrument, and piece C then
clamped. Supposing the measured line to be
ten poles, slide D is tobe moved until its edge 85
coincides with 10 on piece C, and the end of
the slide at the top bar of piece B will be at
8, which will be the length of the horizontal
line.
For obtaining the length of the true line at 90
a rise, the instrument is to be set on the
stand with the protractor reversed, so as to
bring the bottom bar of level B at the top.
The method is the same as before; and the
instrument is also adapted for other purposes 95
of the same character, which it is not neces-
sary to describe. It is to be observed that
the piece B furnishes two radial lines and
right-angled lines thereto,while piece C gives
another radial line, adjustable with reference oo
to the first, so that at any part of the protract-
or right angles can be had and right-angled
triangles formed with the length of any side
i indicated. The four angles of piece B may
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Dolman, John H. Surveyor's Instrument., patent, March 10, 1885; [Washington D.C.]. (https://texashistory.unt.edu/ark:/67531/metapth170920/m1/2/: accessed July 18, 2024), University of North Texas Libraries, The Portal to Texas History, https://texashistory.unt.edu.; crediting UNT Libraries Government Documents Department.