444 Forestry Quarterly 



the number of feet the operator stands from the base of the 

 tree. Instead of measuring this distance with the tape, the ad- 

 justment may be made by standing a 10-foot pole against the 

 tree. Both arms of the hypsometer are sighted at the base of the 

 pole, the adjustable arm locked and released, and the fixed arm 

 sighted at the top of the pole. Then, holding the adjustable 

 arm firmly so as to preserve the angle between the fixed and mov- 

 able arms {i.e., the angle from the eye of the operator to the top 

 and bottom of the 10-foot pole), the pendulum is slid back until 

 the point on the scale corresponding to ten feet crosses the edge of 

 the adjustable arm. Special construction will make this adjust- 

 ment easy and accurate. 



The height of the tree is shown on the pendulum scale when 

 the movable arm is sighted on the base of the tree and the other 

 arm is sighted at the top. If a strip of metal is used for the fixed 

 sighting surface, independent of a board, this may be attached to 

 a stock somewhat like a gun stock, but lighter and more curved, 

 so as to bring the end of the sighting surface close to the eye. 

 A simple trigger and spring arrangement may be attached, so 

 that when the trigger is pulled a rod will grip the scale pendulum 

 and adjustable arm and hold them firmly in place until the read- 

 ing is made. 



The instrument may be made so that the scale arm of the sec- 

 ond pendulum swings upward, as in the Klausner hypsometer, 

 but it is preferable to have the pendulum scale read from the 

 pivot downward, since this saves one adjustment over the other 

 form, if the instrument is used with the 10-foot pole. So far 

 as the measurement of height is concerned, this instrument 

 operates on exactly the same plan as the Klausner. The new 

 feature is the adjustable sighting arm which automatically re- 

 mains fixed on the point to which it is set, and which permits of 

 the free movement of the principal sighting arm without affecting 

 the accuracy of measurement. In a hand instrument, this is 

 a valuable quality ; it gives us the accuracy of the Klausner 

 without the necessity of using a tripod or staff. Models which 

 have been made indicate that its use is practical. The idea is 

 presented to the readers of the Forestry Quarterly in the hope 

 that it may be used to increase efiiciency and comfort in height 

 measuring. 



