6 Forestry Quarterly 



study made for a stand of a given density should applj- to other 

 similar stands of the same density. 



The pathological defects of trees, such as rot, shake, and worm 

 holes, are more or less uniform throughout wide areas, sometimes 

 covering almost the entire range of a species, as is the case with 

 worm holes in Black Locust. 



Therefore, as far as the natural factors are concerned, a mill 

 scale study made for a given specips in any region ought to apply 

 more or less accurately to a large area, if the density and the 

 character of the stands are similar in this region. It must not be 

 overlooked, however, that to determine what effect the density of 

 a stand had on the shape and character of its trees, it is necessary 

 to know not only the present density, but the past history of the 

 stand. For this reason mill scales will be most accurate when 

 made for virgin stands, or for even-aged second-growth stands. 

 Still it is not impossible to make fairly accurate tables for culled 

 forests by introducing some simple classification. For example, 

 stands may be classified as having had their origin in a virgin 

 forest and culled lo to 20 )^ears ago, 20 to 30 years ago, 30 to 40 

 years ago, and so on. In fact, since virgin forests are disappear- 

 ing very rapidly, and uniform second-growth stands are rare, mill 

 scales made for such culled forests would be of the most perma- 

 nent value. 



Since, in making a mill scale, only the actual amount of 

 lumber obtained at the mill is considered, it is evident that for 

 trees of a given size, the higher the stump and the longer the 

 top left in the woods, the less lumber the tree will jdeld. The 

 skill used in cutting a tree into logs, and the care with which 

 crooks, scars, and wounds are culled may greatly affect the 

 quantity of lumber obtained. 



The efficiency of the sawyer at the mill, as well as that of the 

 edger and trimmer, wall affect not only the quantity of lumber 

 yielded, but also the grades of the boards. In fact, this is 

 probably the most disturbing factor of all, because the personal 

 equation enters so strongly into it. 



The judgment of the lumber inspector is another disturbing 

 factor. Two inspectors, equally expert, may put the same board 

 into different grades. This, however, will be only in doubtful 

 cases where a board is as near one grade as it is the next. 



Finally, the market demands may, to a certain extent, affect 



