ESTIMATING STANDING TIMBER. 119 
pacing. -The cruiser passes back and forth over the strip estimat- 
ing the timber. He paces the distance when going away from the 
lineman, who guides the cruiser, when returning, by a policeman’s 
whistle. When a strip of one-half mile, or 40 acres, has been 
completed, an adjacent strip is cruised in the same manner. 

ESTIMATE BY SAMPLE PLOTS. 
Where less accurate results will answer, the estimate is made by 
determining the amount of timber on an average acre and then 
multiplying the result by the total number of acres on the tract. 
The contents of the average acre is usually determined not by the 
measurement of one acre alone, but by averaging the measure- 
ments of a number of acres representing different conditions, in 
order that the less productive portions of the forest may be in- 
cluded as well as the best. These sample acres may be laid off 
by pacing, but it is more satisfactory to measure their sides accu- 
rately with a chain or tape and to make sure that their corners 
are correct right angles by the use of such instruments as a com- 
pass or a mirror right-angle finder. (Cf. p. 132.) 
Some cruisers estimate the contents of a sample acre by standing 
still and counting the trees about them to an estimated distance 
of 7 rods in each direction. In the forests of Maine and northern 
New York, where this method is common, 7 rods is about as far 
as a person can count the trees in a forest of average density. 
Cruisers sometimes count the trees in a circle about them toa 
distance of 60 feet, which would include approximately one-quarter 
of an acre. : 
| It is, of. course, not necessary that the sample plot should be 
exactly 1 acre in size. A fraction of an acre or larger area may 
be used, provided the cruiser knows the exact area of the plot. 
The measuring of sample plots used in estimating timber is tech- 
nically known among foresters as taking valuation surveys. 

ESTIMATE BY THE EYE. 
A well-trained cruiser is able to make a fair estimate of the 
average yield per acre simply by looking over the forest. In many 
sections cruisers guess at the yield of an entire block of the forest, 
