by 1 inch by
5 feet long, which we secured from one of the mills at Lumberville. Each
leg was formed of two of these strips, nailed securely together to
within 20 inches of the top. At the upper ends the strips were spread to
receive the blocks on the tripod head. In this position they were held
by headless wire nails driven into the ends of the blocks and fitting
into holes drilled in the strips. For a plumb line we tacked a cord to
the center of the tripod head, and attached a good-sized sinker to its
lower end. In connection with this plumb line we occasionally used a
protractor consisting of a semicircle of cardboard 5 inches in diameter,
on which the degrees of the circle were marked off with radiating lines,
as illustrated in Fig. 76. By holding the straight edge of this
protractor against the base of the tripod, and noting the number of
degrees between the 90 degree mark and the plumb line, we could tell at
a glance at what angle from the horizontal the instrument was tipped.

SURVEYOR'S CHAIN.

[Illustration: Fig. 77. The Surveyor's Chain.]

[Illustration: Fig. 78. Forming the Links.]

[Illustration: Fig. 79. A Double-Ringed Link.]

We made a surveyor's chain of wire links, each 12 inches long, instead
of 7.92 inches, which is the length of a standard surveyor's link. The
wire we used was No. 16 galvanized iron, which was rather stiff and
difficult to bend. In order to make all the links of exactly the same
size and shape we used a form, around which they were bent. The form
consisted of a 1-inch board in which two 1/2 inch holes were drilled,
just 11-1/2 inches apart, measured from their centers. An oak pin, 1/2
inch in diameter, was driven into each hole and projected about an inch
above the board. Two blocks of oak were secured to the baseboard, just
before each pin, as shown in Fig. 78. This form gave great satisfaction.
A groove was cut in the side of one of the pins to receive the ring of a
completed link, while the wire was passed through this ring and bent
around the peg to form the ring of the new link. After each link was
formed it was carefully measured, and, if too long, was shortened by
flattening the rings endwise, or, if too short, was lengthened by
pinching together the sides of the rings. There were fifty links in our
chain, and every tenth one was formed with a double ring at the end, so
as to distinguish it from the rest (see Fig. 79).

THE SURVEYOR'S ROD.

[Illustration: Fig. 80.