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- © 
Y tending upward on the left-hand end bar of the frame. The right- — 
hand crossbar is provided with a vertical scale running upward ! 
Ni from zero to 100, and continued on the left-hand crossbar with ~ 
a scale running upward to 175. These scales are divided in fifths © 
ib and numbered. The lines forming the scales are equally sepa- | 
‘ rated from each other and represent units of distance under any | 
i system of measurement that may be adopted. The handle of the © 
Ki, device is attached to the left-hand crossbar. | 
To use the instrument, the observer measures the horizontal 
i 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 
a take a position opposite the required number on the portion of the 
i 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 }, 
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