312 JOURNAL OF FORESTRY 



tions, and the hemlock slopes and yellow pine ridges at lower altitudes. 

 Jt should be borne in mind that the object of this classification is 

 to reduce the great variety of timber on the tracts to be examined, 

 an average of which is a mere mathematical abstraction, to a number 

 of relatively homogeneous stand classes each of which can be 

 expressed by an average per acre that can be arrived at satisfactorily 

 by a sample tally and checked by judgment. In cases where it seems 

 best to make three or four "type" divisions as a basis for estimating 

 the timber, the principles and methods are the same as where only 

 two are recognized, although both field work and computation are 

 more complex. 



LOCATION OF STRIPS 



The location of the strips depends on the distribution of the 

 timber and hence on the topography. The usual plan calls for strips 

 crossing the drainage lines approximately at right angles so that 

 the tendency will be to include all gradations of timber stand. Some- 

 times it is necessary to parallel the main stream, in order to cross 

 a series of large side branches. The strips are run from base lines, 

 usually surveyed with compass and chain, and constituting a closed 

 traverse in case this is justified by the size of the tract. The base 

 lines must be located so that the strips need not exceed two to three 

 miles in length, and as nearly at right angles to their direction as the 

 ground permits. They ordinarily follow the principal divides or main. 

 valleys, taking advantage of conveniently located roads and trails. 

 Sometimes a long, straight boundary line of the tract to be estimated, 

 if not too difficult to follow on account of rough topography, under- 

 brush, or dim boundary marks, will make the most convenient base line. 



One of the most important considerations is the location of the 

 strips in such a way as to tally a sufficiently large per cent of the 

 entire stand to give a reliable average. Since two or more distinct 

 stand classes are recognized, and a separate estimate per acre for 

 each is obtained and applied to the appropriate acreage as plani- 

 nietered from the map, the necessity of locating the strips so as to 

 include an equal proportion of each type is obviated. In fact, it is 

 often advantageous purposely to vary this proportion. In some 

 localities it is best to follow the ordinary method of gridironing a 

 tract with parallel strips a fixed distance apart. This is desirajble 

 v/hen the valuable timber is distributed irregularly, as is the case 



