162 A MANUAL FOR NORTHERN WOODSMEN 



who uses these methods is frequently very lame when he 

 gets into a country with which he is unfamiliar. Lastly, 

 when time consumed and training involved are considered, 

 estimates of this nature may not be the cheapest by any 

 means. 



There is a general tendency among timber estimators, 

 commendable in the main on the ground of safety and 

 conservatism, to put their figures below the mark. As for 

 the general degree of accuracy obtained, there seems to 

 be no reason founded on experience this side of the At- 

 lantic to greatly change the verdict of experience in Europe ' 

 that good and experienced men in timber with which they 

 are familiar are liable to errors up to 25 per cent. 



It is true, moreover, that the weakness of these tra- 

 ditional methods is generally recognized. More careful 

 and elaborate methods are in fact practiced in many 

 sections of the country, and the area is fast extending in 

 which the treatment demanded by the situation is not 

 really an estimate but a survey. 



SECTION II 

 INSTRUMENTAL HELPS 



The helps that may be used in the survey of standing 

 timber are as follows: 



1. FOR DIAMETER MEASUREMENT 

 Calipers for measuring the diameter of trees may be 

 constructed by the woodsman himself, or they can be 

 purchased of dealers. The best are made of light-colored 

 hard wood and have the inches plainly marked on both 

 flat sides of the bar. The jaws are detachable for con- 

 venience in transportation, and the sliding arm is so fitted 

 with adjustable metal bearings that it is truly square and 

 gives a correct diameter when pressed firmly against a 

 tree or log. 



Substitutes for the caliper, useful in some circumstances, 

 are the Circumference Tape, a steel tape so graduated 

 that when a circumference is measured a diameter is read, 

 1 Schlich's "Manual of Forestry." 



