That is, 29
quarter-inches for one side and 29-1/4 quarter inches for the other. As
each quarter-inch represents a foot, you will find that the tree is about
29 feet from the right end of our base line and 29 feet 3 inches from the
left hand end. Of course, our instrument is not perfect, neither is our
drawing; but if you measure it off with the chain you will see that I am
not very far from correct."
[Illustration: Fig. 84. Determining the Distance to the Tree.]
Mapping the Island.
Most of our surveying was done by actual measurement, the surveying
instrument being used only to determine the exact direction of the
measurement. However, there were some measurements which we could not make
directly with the chain. For example, we wished to know just how far it
was from our tent to the Jersey shore of the river. We measured off a base
line along our shore 400 feet long and sighted to a point directly across
the river from our tent. The angle in front of our tent was 90 degrees,
and at the other end of the base line was 73 degrees. When we drew out our
triangle on the scale of 100 feet to the inch we found that the shorter
side directly in front of the tent was almost exactly 13 inches long.
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