100 THE WOODSMAN'S HANDBOOK. 



in which it may be set. The left-hand end bar of the frame is 

 furnished with an eyepiece, and the right-hand end bar with an 

 objective, these being made of metal and hinged so as to be folded 

 down out of the way when the device is not in use. A long, nar- 

 row mirror, hinged to the frame at a point below the objective, is 

 furnished to reflect a right-hand horizontal scale and a left-hand 

 horizontal scale engraved upon the lower bar of the frame, and 

 meeting at a zero point which is intersected by a line passing 

 through the longitudinal center of the slide. The right-hand 

 scale runs to 75 and the left-hand scale to 225, the latter scale ex- 

 tending upward on the left-hand end bar of the frame. The right- 

 hand crossbar is provided with a vertical scale running upward 

 from zero to 100, and continued on the left-hand crossbar with 

 a scale running upward to 175. These scales are divided in fifths 

 and numbered. The lines forming the scales are equally sepa- 

 rated from each other and represent units of distance under any 

 system of measurement that may be adopted. The handle of the 

 device is attached to the left-hand crossbar. 



To use the instrument, the observer measures the horizontal 

 distance in feet, yards, or in any other desirable unit, from where 

 he is to stand to the base of the tree. He then sets the slide by 

 one or the other of its two index marks, which is brought into line 

 with the graduation on the vertical scale corresponding to the 

 measurement just secured. If the distance is less than 75, the 

 slide should be set so that the upper end of the plumb line will 

 take a position opposite the required number on the portion of the 

 vertical scale on the right-hand crossbar. If the distance is more 

 than 75, the slide should be pulled out and reversed end for end 

 and adjusted until the index mark at its then lower end is brought 

 opposite the required number on that portion of the vertical scale 

 on the left-hand crossbar. The observer then looks through the 

 eyepiece and objective and brings the hair of the latter into line 

 with the top of the tree. The plumb line is allowed full play and 

 crosses the left-hand horizontal scale. As soon as the plumb line 

 is at rest the number which it crosses is read off in the mirror. 

 This number indicates the height of the tree from the level of the 

 observer's eye to its top. He then sights through the instrument 

 to the base of the tree and reads the number crossed by the plumb 



