DOI Page / Citation link:
https://doi.org/10.11588/diglit.20658#0372
358
SURVEYING.
exactly one English acre ofland ; so that the dimensions being taken in these chains, and the
contents of the field computed in square chains, they are readily turned into acres by dividing
them by 10. It is more convenient, however, in practice, to count the dimensions not in chains
and links, but in links alone; then the contents are obtained in square links; and five figures
being cut off for decimals, the rest are acres; that is, four figures are cut off, to bring the square
links to square chains, and one figure more to bring the square chains to acres, &c, In Gunter's
chain the links are each 7- 92 inches in length, or nearly two thirdsof a foot; hence any number of
chains or links are readily brought to feet or inches, or the contrary, by multiplying the number
of links by 66, (the number of feet in a chain of 100 links) and cutting off two [daces of figures
for decimals, the rest are feet; or multiply the links-by '22, and cut-off two figures, when the
others will shew the number of vards.
The Perambulator is an instrument for measuring distances; it is also called the Surveying-xcheel,
and a particular sort is named the Pedometer or Way-wiser. This wheel is fitted to measure out
a pole or l6f feet in making two revolutions; consequently, its circumference is 8 a feet, and its
diameter 2,626 feet, or two feet seven and a half inches, and a small fraction more. The
instrument is either pushed forward by a person walking and holding the handle, or it is-drawn
by a coach-wheel, &c. to which it is attached by a pole. It contains various movements, or
clock-work, as it is called, with indexes on the face, which resembles that of a clock, to point
out the distance passed over, in miles, furlongs, poles, yards, &c. The advantages of the pei am-
bulator are its readiness and expedition, being very useful for measuring roads, and great
distances on hard ground.
The second branch of surveying called plotting,.protracting, or mapping, is performed by
means of the Pr-otractor and Scale. The protractor in its simplest form, consists of a semi-
circular limb of brass, ivory, &c. divided into 180 degrees, and subtended by a diameter, having
in the middle a small notch called the centre of the protractor; and for the convenience of
counting both ways, the degrees are numbered from the left hand to the right, and from the
right to the left. This instrument is also -made- by transferring the division from the cireum-
ference of the semicircle to the edge of a ruler parallel to the diameter, and having the centre
similarly situated.
To make an angle on paper with the protractor, lay its side or diameter along the given line
which is to form one leg of the angle, and the centre at the given angular point; then make
a mark opposite to the given degree of the angle found on the limb of the instrument and re-
moving the protractor, by a plain ruler laid over this mark or point, and the centre, draw a right
line which will form the angle required. In the-same way any given angle already draw n on
paper may be measured. The protractor is useful in drawing one line perpendicular to another,
by laying it across the given line so that both its centre, and the 90th degree on the opposite
edge, fall upon the line, also one of the edges passing over the point from which the perpen-
dicular is to be let fall : a line drawn down this edge will be perpendicular to the given line.
Scales of various sorts are useful in surveying and laying down on: paper, but that principally
employed is the Plot/ingscn\e. It is-made of six, nine, or twelve inches in length, by an inch
and a half broad, and of braes, box, or ivory. This instrument contains several scales laid out
on both sides. On one are a number of plain scales, or scales of equal divisions, each of dif-
ferent size and number to one inch ; also scales of chords, for laying down angles: and sometimes
< the
SURVEYING.
exactly one English acre ofland ; so that the dimensions being taken in these chains, and the
contents of the field computed in square chains, they are readily turned into acres by dividing
them by 10. It is more convenient, however, in practice, to count the dimensions not in chains
and links, but in links alone; then the contents are obtained in square links; and five figures
being cut off for decimals, the rest are acres; that is, four figures are cut off, to bring the square
links to square chains, and one figure more to bring the square chains to acres, &c, In Gunter's
chain the links are each 7- 92 inches in length, or nearly two thirdsof a foot; hence any number of
chains or links are readily brought to feet or inches, or the contrary, by multiplying the number
of links by 66, (the number of feet in a chain of 100 links) and cutting off two [daces of figures
for decimals, the rest are feet; or multiply the links-by '22, and cut-off two figures, when the
others will shew the number of vards.
The Perambulator is an instrument for measuring distances; it is also called the Surveying-xcheel,
and a particular sort is named the Pedometer or Way-wiser. This wheel is fitted to measure out
a pole or l6f feet in making two revolutions; consequently, its circumference is 8 a feet, and its
diameter 2,626 feet, or two feet seven and a half inches, and a small fraction more. The
instrument is either pushed forward by a person walking and holding the handle, or it is-drawn
by a coach-wheel, &c. to which it is attached by a pole. It contains various movements, or
clock-work, as it is called, with indexes on the face, which resembles that of a clock, to point
out the distance passed over, in miles, furlongs, poles, yards, &c. The advantages of the pei am-
bulator are its readiness and expedition, being very useful for measuring roads, and great
distances on hard ground.
The second branch of surveying called plotting,.protracting, or mapping, is performed by
means of the Pr-otractor and Scale. The protractor in its simplest form, consists of a semi-
circular limb of brass, ivory, &c. divided into 180 degrees, and subtended by a diameter, having
in the middle a small notch called the centre of the protractor; and for the convenience of
counting both ways, the degrees are numbered from the left hand to the right, and from the
right to the left. This instrument is also -made- by transferring the division from the cireum-
ference of the semicircle to the edge of a ruler parallel to the diameter, and having the centre
similarly situated.
To make an angle on paper with the protractor, lay its side or diameter along the given line
which is to form one leg of the angle, and the centre at the given angular point; then make
a mark opposite to the given degree of the angle found on the limb of the instrument and re-
moving the protractor, by a plain ruler laid over this mark or point, and the centre, draw a right
line which will form the angle required. In the-same way any given angle already draw n on
paper may be measured. The protractor is useful in drawing one line perpendicular to another,
by laying it across the given line so that both its centre, and the 90th degree on the opposite
edge, fall upon the line, also one of the edges passing over the point from which the perpen-
dicular is to be let fall : a line drawn down this edge will be perpendicular to the given line.
Scales of various sorts are useful in surveying and laying down on: paper, but that principally
employed is the Plot/ingscn\e. It is-made of six, nine, or twelve inches in length, by an inch
and a half broad, and of braes, box, or ivory. This instrument contains several scales laid out
on both sides. On one are a number of plain scales, or scales of equal divisions, each of dif-
ferent size and number to one inch ; also scales of chords, for laying down angles: and sometimes
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