must first make what is called a leveling rod. Find a piece of
wood about one or two inches square and six or more feet long, mark on
it feet and inches, beginning at the bottom end, and your leveling rod
is complete.
Now to find the difference in level of two points
100 feet apart, scratch a line or insert a small stake at one point,
then pace off 100 feet and mark the second point. Now set up your level
between the two points, ask a friend to hold the rod on the ground and
upright, at the first point, sight along the water levels at the rod,
and ask your friend to move his finger, or a white card, up and down
until it is exactly in your line of sight. Now ask your friend to tell
you exactly where his finger or card is and record the height. Let us
suppose that it is 4 feet 6 inches above the ground. Now leave the level
exactly where it is, ask your friend to hold the rod upright at the second
point, and again sight along the water levels at the rod. Let us suppose
that his finger or card is now exactly 3 feet above the ground.
The difference in level at the two points is
4 feet 6 inches minus 3 feet or 1 foot 6 inches. That is, the second
point is 1½ feet above the first point or the grade is 1.5 in 100,
or 1.5 per cent.
You can now mark a third point 100 feet beyond
the second point, set up your level between the second point and third
point, place the rod at the second point, then at the third point,
and find their difference in level as above. If the third point is
1 foot above the second, the total rise in the 200 feet is 2½
feet; if, however, it is 1 foot below the second, the rise is 1½
minus 1 or ½ foot in the 200 feet.
You can repeat this with as many points as
you please.
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