MEASURING DISTANCES
(See " Two Little Savages," 1903) The height of a tree is easily measured when on a level, open place, by measuring the length of its shadow, then comparing that with your own shadow, or that of a 10- foot pole. r Thus, the 10- foot pole is casting a 15-foot shadow, and the tree's shadow is 150 feet long, apply the simple rule of three:.
: 150 : : 10 :x = 100
But it is seldom so easy, and the good old rule of the triangle can be safely counted on : Get a hundred or more feet from your tree, on open ground, as nearly as possible on the level of its base. Set up a 10- foot pole (AB). Then mark the spot where the exact line from the top of the tree over the top of the pole touches the ground (C). Now, measure the distance from that spot (C) to the foot of the 10- foot pole (B) ; suppose it is 20 feet. Measure also the distance from that spot (C) to the base of the tree (D) ; suppose it is 120 feet, then your problem is :
: 10 :: 120 : x = 60
i.e., if at that angle 20 feet from the eye gives 10 feet elevation, 120 feet must give 60.
