FORESTRY QUARTERLY 



Vol. XII.] June, 1914. [No 2. 



LIBRARY 



DESIGN OF A RANGE FINDER. '^^^ ^^^^ 



ttOTANICAI. 



By Lincoln Crowell. oakdbn. 



Some time ago, I designed a range finder for lookout stations 

 to be constructed entirely of metal. At present the accuracy 

 and expense of such an instrument do not seem warranted. 

 Therefore I have devised another range finder, which, while 

 quite accurate, is nevertheless cheaply and easily constructed. 

 (See frontispiece.) 



It consists, first, of a wooden base frame ; second, of a disk of 

 three-ply veneer or thin boards upon which a paper azimuth 

 jircle is glued ; third, of an alidade made of scrap iron. 



The azimuth disk and alidade turn about a pivot fastened to 



the base frame. The disk is turned by means of a U-shaped 



iron rod, the ends of which fit into holes placed diagonally on the 



isk. When oriented, the azimuth disk can be secured in place 



jy clamps at the corners of the frame. 



The sights of the alidade are cut out with a hack saw. The 

 azimuth readings are made at the right hand edge of the base of 

 +he alidade adjacent to the slit sight, where a knife edge is filed 

 jn a radius with the pivot. 



The most practical diameter for the azimuth circle is 20 inches. 



Upon the circumference of such a circle graduations of 30 feet 



or 15 feet can be accurately drawn. Five degree graduations are 



obtained by measuring their natural tangents along the edge of a 



circumscribed square, and by laying off the single degrees with 



dividers along the circumference of the inscribed circle. By this 



method the azimuth circle can be quickly and accurately drawn. 



. The paper disk and alidade are covered with a heavy coat of 



^ shellac. When exposed to the weather the instrument is covered 



'"" by a box with a pitch roof. 



CO 



