190 A MANUAL FOR NORTHERN WOODSMEN 
ture of highest present economy is practiced, approximate 
mill output. A peculiar feature will be noted in this 
table — that the base diameter employed is not diameter 
breast high, but diameter inside bark at the top of the 
first log length. A reduction from calipered diameters is 
required therefore, for bark thickness and for taper. 
This reduction is made either tree by tree in the field by 
estimate or in the office by classes on the basis of meas¬ 
ures taken in logging operations. Timber quality is a 
matter of importance. It is seldom or never dealt with 
in the field other than by way of general comparison and 
experience. 
The strip system was also largely employed in the 
early years of the United States Forest Service, with the 
object of ascertaining not merely the merchantable tim¬ 
ber on the tracts examined but also the number and 
kind of young trees growing there as a basis for re¬ 
commendations as to treatment. The method and cost of 
strip survey work as carried out by the Service men are 
indicated in the following extract from the “ Woodsman’s 
Handbook”: 
Sample acres are laid off in the form of strips, 10 surveyor’s 
chains long and 1 chain wide, and the diameters of all trees to be 
included in the estimate are measured at breast height with 
calipers. At least three men are required to do effective work 
under this method. One man carries a note book, or tally sheet, 
and notes the species and their diameters as they are called out 
by the men who take the measurements. The tallyman carries 
the forward end of the chain, the other end of which is carried 
by one of the men taking the measurements. The chain is first 
stretched on the ground and the trees are calipered within an 
estimated distance of 33 feet (one half chain) on each side of the 
chain. When all trees adjacent to the chain have been calipered 
the whole crew moves on the length of another chain in the direc¬ 
tion chosen (by the tallyman). The chain is again stretched on 
the ground and the trees are calipered on each side of it as before. 
This same operation is repeated until the trees have been measured 
on a strip 10 chains long. Notes are then made of the general 
character of the forest and the land, according to the requirements 
of the investigation. If heights are desired they may be taken 
by a separate crew, or as the calipering crew encounter from time 
to time trees whose heights are desired, they may stop long enough 
to take such measurements. 
In an average virgin forest a crew of three men will caliper the 
trees on from 20 to 40 acres in one day if only trees of merchant* 
