TIMBER ESTIMATING, ifs 
will fit a coat pocket but not a hip pocket. The books have stiff 
board covers, which do away with the old cumbersome and 
insecure tally-sheet holders. 
The trees are tallied by dots and lines, in blocks of ten, as indi- 
cated in the following table, which shows the marks corresponding 
to different numbers: 
4 a “Sy F x Co PA fo F /0 
, oee?eeeeece es Ae ee ie VA' Xx 
eeeee ®@ | 
This method is economical of space and enables the recording of 
a large number of trees on a single sheet. 
| 
NUMBER OF STRIP SURVEYS REQUIRED. 
Usually the sample strips should comprise from 5 to 10 per cent 
of the total area. Sometimes it is possible to include 20 or 30 per 
cent, but on large tracts from 5 to 10 per cent is considered suffi- 
cient. On very large areas of 100,000 or 200,000 acres the strips 
cover 2 to 3 percent. In recent work on the National Forests the 
strips have been run one-quarter or one-half of a mile apart, and 
thus take 5 per cent or 24 per cent of the total area. 
COMPUTATION OF RESULTS. 
After the measurements are secured, the average yield per acre 
may be computed in two ways: 
(1) By computing separately the yield of each acre, and averag- 
ing all together; or (2) by constructing a model acre through the 
adding together of the number of trees of each diameter which 
occur on all the sample plots and dividing the result by the num- 
ber of plots, which gives the average number per acre of trees of 
each diameter. For example, to construct a model acre the aver- 
age number of 6-inch trees on all the acres measured is calcu- 
lated; then the average number of 7-inch trees; then of 8-inch 
trees, of 9-inch trees, etc. The result is a model acre having the 
average number oi trees of each inch diameter. Only one com- 
putation of yield is then required, and this will represent the 
average of all the sample acres. 
