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.