l62 FORESTRY IN NEW ENGLAND 



whole. In order to determine this proportion a map is necessary, 

 from which the total area of each portion or type can be obtained. 

 For example, a io,ooo-acre tract in northern New England might 

 be found to comprise 2000 acres of second-growth pine, 1000 

 acres abandoned pastures, 4000 acres mixed birch, beech, and 

 maple, and 3000 acres second-growth spruce. A knowledge of 

 the area of each of these types is necessary. There might also 

 be subdivisions according to age, which would have to be esti- 

 mated separately. Thus in the second-growth spruce and pine 

 t3qDes, certain blocks might occur containing timber twenty to 

 fifty years old, while the remainder was less than twenty years 

 of age. The only accurate way to determine these areas is to 

 map them, and consequently a map must be secured by the 

 estimator.^ In an open country, undoubtedly, it is better to 

 map the area first with a plane table and do the estimating 

 separately, but there can be no question that for those sections 

 of New England where large forests occur, the so-called "strip 

 system," or "valuation survey," devised by the United States 

 Forest Service, is unsurpassed. By this method the data for 

 making the map are secured at the same time that measurements 

 of the timber are being taken. To carry out this method a crew 

 of four men is best, although it can be done with a gmaller or a 

 larger number. The necessary equipment is a surveyor's chain, 

 a hand compass (for more accurate work a staff compass), two 

 pairs of calipers, a tally board, some record sheets or a notebook, 

 and a pencil. A hypsometer is a valuable addition as will be 

 explained later. The crew may be arranged in various ways. 

 The main object is to run a straight compass course through the 

 forest and this is done by the head man. The other two men 

 carry the calipers and measure the diameters of all trees for a 

 distance of one-half chain length, two rods on either side. At 

 first this distance should be checked frequently, by carrying the 

 chain out to the side or by pacing; but with practice the men soon 

 are able to judge very closely, and the few inaccuracies balance 



^ For methods of mapping forests, see "A Manual for Northern Woodmen," by 

 Austin Gary, published by Harvard University, Gambridge, 1909. 



