TIMBER ESTIMATING. 81 



and may follow the plans described for rough sample plots under 

 estimating by the eye on page 66. They will seldom be run out 

 by compass, as too much time would be lost. The trees in each 

 plot may be calipered, or tallied by the eye, or merely counted, 

 with the selection, by eye, of an average tree, the volume of which 

 can be determined either by the logs contained or from a volume 

 table. 



A METHOD USED ON THE PACIFIC COAST. 



On the Pacific coast the cruiser, alone or with a compass man, 

 starts from the center of one side of the forty and paces along a 

 compass course across the center of the forty a distance equal to 

 one-tenth of the width of the ' 'forty . ' ' Standing here, he lays out by 

 the eye a circular plot containing an acre, as described on page 66, 

 and counts all the trees by species; then for each species he selects 

 an average tree for the plot. The breast-high diameter is measured 

 or estimated, and the top diameter and number of merchantable 

 logs in the tree. The middle diameter is assumed to be the arith- 

 metical mean of the breasthigh and top diameters, and the volume 

 is obtained by the application of the rule of thumb given on page 

 60. 



The cruiser then proceeds in the same direction a distance equal 

 to one-fifth of the width of the forty, and lays off a second plot. 

 Proceeding in this way he measures five circular plots, of an acre 

 each, across the center of the "forty, "and these contain 12J per cent 

 or one-eighth of the total area. A correction factor is applied to 

 the final result if observation shows that the plots are too heavy or 

 too light. 



SCATTERED OR ARBITRARY PLOTS. 



One of the most rapid methods of estimating is to locate a few 

 plots in timber of average density of stand, run out the boundaries 

 with care, and determine the volume of the stand per acre on the 

 plot by some such careful method as calipering the diameters, 

 measuring the heights, and using a volume table. The average 

 stand thus obtained is assumed to be the stand per acre for that 

 portion of the tract which has similar timber. The difficulties in 

 the way of determining by inspection what constitutes an average 

 stand are somewhat reduced if it is possible to divide the area into 



38850 Bull. 3610 6 



