TIMBER ESTIMATING, | Sl 
and may follow the plans described for rough sample plots under 
estimating by the eye on page 66. They will seldom be run out 
by compass, as too much time would be lost. The trees in each 
plot may be calipered, or tallied by the eye, or merely counted, 
with the selection, by eye, of an average tree, the volume of which 
can be determined either by the logs contained or from a volume 
table. 
A METHOD USED ON THE PACIFIC COAST. 
On the Pacific coast the cruiser, alone or with a compass man, 
starts from the center of one side of the forty and paces along a 
compass course across the center of the forty a distance equal to 
one-tenth of the width of the ‘‘forty.’’ Standing here, he laysout by 
the eye a circular plot containing an acre, as described on page 66, 
and counts all the trees by species; then for each species he selects 
an average tree for the plot. The breast-high diameter is measured 
or estimated, and the top diameter and number of merchantable 
logs in the tree. The middle diameter is assumed to be the arith- 
_metical mean of the breasthigh and top diameters, and the volume 
is obtained by the application of the rule of thumb given on page 
60. 
The cruiser then proceeds in the same direction a distance equal 
te one-fifth of the width of the forty, and lays off a second plot. 
Proceeding in this way he measures five circular plots, of an acre 
_ each, across the center of the ‘‘forty,’’and these contain 124 per cent 
_or one-eighth of the total area. A correction factor is applied to 
the final result if observation shows that the plots are too heavy or 
too light. 
SCATTERED OR ARBITRARY PLOTS. 
One of the most rapid methods of estimating is to locate a few 
_ plots in timber of average density of stand, run out the boundaries 
with care, and determine the volume of the stand per acre on the 
plot by some such careful method as calipering the diameters, 
measuring the heights, and using a volume table. The average 
stand thus obtained is assumed to be the stand per acre for that 
portion of the tract which has similar timber. The difficulties in 
the way of determining by inspection what constitutes an average 
stand are somewhat reduced if it is possible to divide the area into 
38850°—Bull. 36—10——6 
