. The woodsman's handbook. Fic. .).—Stiid compass. two sights hinged to its opposite sides. A removable support,:screwed into the bottom, terminates in a socket, adapting the INSTRUMENTS USEFUL TO A WOODSMAN. 97 instrument to be mounted upon a Jacob staff or upon a support also comprises a ball-and-socket joint, by which thecompass is leveled with the aid of spirit tubes on two sides, aswivelj which permits the compass to be turned in sighting it, and. FiG. 6.—Measuring the height of a tree by means of two poles. a set screw for securing it against turning after sighting. Whennot in
. The woodsman's handbook. Fic. .).—Stiid compass. two sights hinged to its opposite sides. A removable support,:screwed into the bottom, terminates in a socket, adapting the INSTRUMENTS USEFUL TO A WOODSMAN. 97 instrument to be mounted upon a Jacob staff or upon a support also comprises a ball-and-socket joint, by which thecompass is leveled with the aid of spirit tubes on two sides, aswivelj which permits the compass to be turned in sighting it, and. FiG. 6.—Measuring the height of a tree by means of two poles. a set screw for securing it against turning after sighting. Whennot in use the sights are folded down and the support taken apart the entire instrument is in compact form fortransportation, and, being made of aluminum, it is not heavy.•The price is between $20 and $25, without staff or tripod. °—Bull. 36—12 7 98 THE WOODSMAN S HANDBOOK. INSTRUMENTS FOR MEASURING HEIGHTS. There are several methods of determining the height of a stand-ing tree. One of the simplest is to measure the shadow of the treeand the shadow of a straight pole of known length set perpendicularto the earth. Multiply the length of the shadow of the tree by thelength of the pole and divide the product by the length of theshadow of the pole. The result will be the height of the tree. A method used when the sun is not shining is to set two polesin a line with the tree. (See fig. 6.) From a point on one polesight across the secon
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