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- 



