Popular Science MontJdi) 



(197 



A Simple Instrument Which Measures 

 the Height of a Tree 



EXPERIKNC"1-:L) foresters become 

 expert in jutiging oft-hand the 

 height of average timber. By merely 

 looking at a tree of medium height they 

 are able to make a guess with a degree 

 of accuracy that is sufficient for roughly 

 estimating the number of board feet of 

 lumber it contains. But in the case o 

 timber two hundred feet or more in 

 luight c\cn the most expert woodsman 

 is apt to make an error of from ten t(j 

 twenty feet in his calculations. 

 Errors of this kind greatly 

 impair the value of an estimate 

 of the amount of timber in a 

 tract that perhaps is measured 

 by hundreds of acres. 



By the use of the hypsometer, 

 however, the height of the tallest 

 of timber can be ascertained 

 with a remarkable degree of 

 accuracy. There are a number 

 of types of hypsometers, but all 

 of them operate on about the 

 same principle. 



One that has been adopted by the 

 Forest Service consists of a round 

 instrument about four or five inches in 

 diameter and an inch in thickness. To 

 one side is attached a convenient handle. 

 Within the instrument there is a device 

 which operates on the principle of a 

 pendulum. Attached to this is a celluloid 

 scale. On the outer edge of the instru- 

 ment is a small peep-hole on one side 

 and opposite it a square window-like 

 opening somewhat larger in size. There 

 is a convenient device for securing the 

 pendulum at a fixed position. 



To ascertain the height of a tree by 

 means of the hypsometer, the 

 operator takes a sight at liie wL 

 proper point on its "- 



trunk by looking 

 through the peep- 

 li o 1 e and out 

 through the open- 

 ing on the opposite 

 side of the instru- 

 ment. Three differ- 

 ent heights figure 

 in timber calcula- 

 tions. One is calk'd 

 the merchantable jhe dog is harnessed 

 length. In making structed and equipped 



The height of a triru 

 can be accurately 

 n-.easured by look- 

 ing through a slot. 

 The figures are 

 noted on a celluloid 

 scale as on the kft 



certain estimates the "clear" length is 

 ascertained, while in other instances 

 consideration is given only to the height 

 from the ground to the first limb of 

 appreciable size. 



The height of the tree governs the 

 angle at which the operator holds the 

 hypsometer in taking the sight. 



In His Merry "Dogmobile." How a 

 Cripple Gets Along in the World 



ALTHOUGH he is a cripple, R. A. 

 Burdick of Los Angeles, has traveled 

 ,^^ nearly five thousand miles 

 "^Uliil in a single year with the aid 

 ^\SK1 "^f '''^ P'-'l dog Trix. The dog 

 ^ Hf , is harnessed to a speci- 



all>' built t r i cy cle 

 eciuipped with handle- 

 bars, headlight, tail- 

 light and a scat sim- 

 ilar to that used on 

 wheel-chairs. 



He sells newspapers 

 and chewing gum. 

 When he wishes to stop 

 he presses a leather pad 

 to a specially con- to the wheel, and the 

 tricycle-whed chair dog stops immediatelj'. 



