Also, "The Jack of All Trades." By Dan C. Beard, Scribner's; and "Field and Forest Handy Book."
Measuring Distances[1]
The height of a tree is easily measured when on a level, place by measuring the length of its shadow, then coming that with your own shadow, or that of a ten-foot pole.
Thus, the ten-foot pole is casting a fifteen-foot shadow, and the tree's shadow is one hundred and fifty foot long, apply
15 : 150 :: 10 : x = 100
But it is seldom so easy, and the good old rue of the triangle can be safeely counted on: Get a hundred or more feet from your tree on on open ground, as nearly as possible on the level of its base. Set up a ten-foot pole (A B, page 65). Then mark the spot where the exact line from the top of the tree over the top of the pole touches the ground (C).
 | An image should appear at this position in the text. To use the entire page scan as a placeholder, edit this page and replace "{{missing image}}" with "{{raw image|Handbook for Boys.djvu/85}}". Otherwise, if you are able to provide the image then please do so. For guidance, see Wikisource:Image guidelines and Help:Adding images. |  |
Now measure the distance from that spot (C) to the foot of the ten-foot pole (B); suppose it is twenty feet. Measure also the distance from that spot (C) to the base of the tree (D); suppose it is one hundred and twenty feet, then your problem is:
20 : 10 :: 120 : x = 60
i.e., if at that angle twenty feet from the eye gives ten feet elevation, one hundred and twenty feet meet give sixty.
To make a right angle, make a triangle whose sides are exactly six, eight, and ten feet or inches each (or multiples of these). The angle opposite the ten must be a true right angle.
There are many ways of measuring distance across rivers, etc., without crossing. The simplest perhaps by the equilateral triangle. Cut three poles of exactly equal length; peg them together into a triangle. Lay
- ↑ See "Two Little Savages", 1903.
