MEASURING THE FOREST CROP 111 
pers. From time to time the heights of trees of different 
diameters are measured by an instrument called a 
“hypsometer” and with the diameters and average 
heights known the contents of each strip may be obtained 
by consulting a table of average contents called a 
“volume table.” Since there are ten square chains to 
an acre and the strip is one chain (sixty-six feet) wide, 
every ten chains advance means that one acre has been 
measured. 
Ordinarily the making of a valuation survey of this 
kind takes a party of four men. The compass man 
runs the course, keeps track of the distance, either by 
counting his paces or by means of a surveyor’s chain 
dragging from his belt. He makes note of the character 
and condition of the timber and makes a map of the 
country indicating the slopes, benches, mountaintops, as 
well as lakes, rivers, roads or any other features bearing 
on the logging of the tract. 
The two caliper men measure the trees with calipers 
or a Biltmore stick. By practice they know about how 
far to measure out from the chain or compass lines; if 
they are not experienced it may be necessary for them 
to pace in from time to time, for a large error in the 
width of the strip, would mean an error in the estimate. 
Such errors as they do make generally average up 
pretty well. Now they may get a tree which is too far 
out but in a few minutes they miss one that is within 
the two-rod strip each man is supposed to measure. 
With care, the day’s work will turn out quite well. 
The fourth member of the crew is called the tally man. 
He carries a note book in which he puts a dot for each 
tree of a given species and diameter. He generally walks 
along behind the compass man and between the caliper 
man and checks the measurement of the trees. The 
