784 



JOURNAL OF FORESTRY 



The study of spiral was extended to cover the poorest grade of spruce 

 himber accepted in the airplane industry at the time the field-work was 



Fig. 4. — Change in direction and degree of spiral 



Graph on the left from data taken at Cranberry Lake. Graph on the right from data taken 

 at Brandreth Lake. Per cents on the horizontal co-ordinate represent the preponderance in 

 numbers of trees from each diameter class and the direction in which they spiral. Numbers 

 on the vertical co-ordinate show the diameters inside the bark at breast height. Numbers in 

 the right-hand column show the total number of trees in each diameter class and constitute the 

 basis upon which the percentages on the horizontal co-ordinate are computed. 



