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 1 
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.” 
