138 ELEMENTARY FORESTRY. 
Putting all these trees in one class, and dividing the total 
basal area by the number of trees, the mean basal area is found 
to be .4468, which would correspond to a diameter, at breast 
height, of nine inches. Selecting a tree nine inches in diameter, 
it is felled and measured accurately, and the volume found to be 
11.63 cubic feet. This volume of the sample tree is multiplied 
by the number of trees, 317, for the total volume on the acre— 
3,686.71 cubic feet. Greater accuracy may be attained by taking 
a sample tree for each diameter size, and a forest may be meas- 
ured in miniature by felling and measuring a proportionate num- 
per of each diameter, say one per cent of each. 
The volume of a sample tree, or of sample trees, is often 
found by applying the factor of shape, which has been previously 
determined for that particular species and locality. 
The Conversion of Cubic Feet Total Volume of 
Standing Timber into Feet Board Measure may be done 
roughly by considering 1,000 cubic feet as the equivalent of from 
4,000 to 7,000 feet board measure, according to the size of the 
trees, young growths giving much less than old growths. 
The Conversion of Cubic Feet Firewood into Cords 
is accomplished by the use of the factors which experience has 
shown to be practically accurate. A cord of wood piled up occu- 
pies 128 cubic feet of space, but on account of the shape of the 
sticks much of this is air space, and the actual wood content 
much less than 128 cubic feet. In Germany a cord has been 
found to contain 83.2 cubic feet of wood. In Saxony Dr. 
Schenck says that eighty-six cubic feet make a cord of ordinary 
firewood, and that 25.73 cubic feet of branch stuff will pile up to 
acord. At the Minnesota Experiment Station, by actual meas- 
urement of round, straight sticks, a cord has been found to con- 
tain as high as 102 cubic fect. This factor of 102 cubic feet may 
apply very well to straight, well-trimmed spruce, tamarack, etc., 
free from knots and limbs, but will be too high for oak and 
similar wood, which is inclined to be more crooked, and does not 
pile so closely. A cord of small oak averaging 3.4 inches in 
diameter and ranging from 1.5 to 7.5 inches, consisting of 274 
four-foot sticks, measured 60.67 cubic feet. Averaging these two 
extremes, 85.85 cubic feet is found in a cord of mixed wood, cor- 
responding very nearly-to the figure given by Dr. Schenck. 
