Diagram B. To Measure Height of Tree, Etc.
Diagram C. To Measure Height with a Mirror
There are other ways of determining height. As shown in the diagram C, place a mirror (M) horizontally on the ground reflector side up, some distance from the base of the object to be measured, in this case a tent. Walk backward from the mirror in a straight line until the top of the tent pole can be seen in it. The problem will read in this way: the distance from the mirror to your heels (MS) is to the distance from your heels to your eyes (GS) as the distance from the mirror to the base of the object (MT) is to the height of the object (TT'). Water in a dark pan or tray or a pool on a still day will answer for a mirror.
Diagram D. To Test a Right Angle
A right angle can be tested by measuring off 3 feet on one side of the corner and 4 feet on the other side, as shown in diagram d. If the distance between the two points is 5 feet the angle is true; if not 5 feet move one point as much as is necessary to make 5 feet.
South American natives estimate height fairly correctly by turning the back to the object, walking straight away from it to the point where the top of the object can be seen by bending over and looking between the legs. Plant a peg at this point and the distance from the peg to the base of the object is roughly equal to the height.
Sound travels at the rate of 365 yards every second, as many yards as there are days in the year. By counting the seconds between seeing the flash from a gun, or the steam puff from a locomotive and hearing the sound of the explosion or whistle it is possible to figure the length of the distance between yourself and the gun or locomotive.