86 



FOREST COMMISSIONER'S REPORT. 



trees like this give the history of their early growth much closer 

 than the long logs ordinarily cut in the backwoods. 



As to growth in diameter an equally full history is given. The 

 programme of field work was to lay off on the square-cut top of 

 the log a radius of average length. On this the rings were counted 

 beginning with the bark, and every tenth one marked. Then the 

 total number was recorded, and the thickness of each group of ten. 



To understand the upshot of this work, turn again to schedule 

 six, to the ''Detail of Sections " The thickness of the outer ten 

 rino-s at the first section is nine millimeters or a little over a third 

 of an inch. This is the thickness of the sheath of wood added to 

 the tree in the last ten years, and twice that amount is the increase 

 in the tree's diameter. Similarly for the next ten rings, the thick- 

 ness of which was in this case the same. From twenty to forty 

 years back, however, this tree must have been crowded or subjected 

 to some other unfavorable conditions, for the growth in diameter 

 was only a half what it was for the later decades, and much less 

 than in those previous. Passing up the trunk, by means of the 

 measuris on the second and third sections, each group of rings is 

 seen to grow thicker. 



This brings us to another main branch of the inquiry — the vol- 

 ume of the year's growth, or as was in fact ascertained, of the last 

 ten years. The figure will render the facts clear and be useful to 

 refer to. A log is represented in diagram as the frustum of a cone. 



