112 THE BOOK OF FORESTRY 
tally man generally has charge of the party and from 
his position can oversee the work of the other men. 
These strips should always be run up and down hill 
for the reason that a better average of the timber may 
be obtained in this way. The tallest forest trees and 
best stands of timber are always found in the valley 
bottoms where the soil is deep and the wash from the 
hillsides provides plenty of moisture. Upon the 
mountaintops where the soil is thin and dry the trees 
are short, scrubby and far apart; hence to get a fair 
average of the timber in a valley a strip from one 
mountaintop down the slope to the bottom and up the 
other side must be run. ) 
_ The distance that may be covered in a day depends 
largely on how close the trees stand and how hilly the 
country is. In dense forest like the spruce forests of 
Maine two and one-half miles or twenty acres actually 
measured, is a good day’s work. If it has been decided 
to caliper one acre in ten, two hundred acres have been 
accounted for. In gently rolling country where the 
trees are far apart from five to six miles of lme may 
be run in a day. 
Sample Plot Method.—In some cases it may be more 
convenient to measure sample acres than an average 
strip. Then the contents of the entire forest is computed 
in practically the same way by laying off a number of 
one-half or one-quarter acre plots and getting the diam- 
eters of all the trees upon it. If one-twentieth of the 
forest is included in these sample plots, the sum of their 
volumes multiplied by twenty will give the total stand 
of timber. However, the total area of the forest property 
must be known. 
Forestry students often obtain summer jobs in val- 
uation survey parties, because this mechanical method 
