BULLETIN 229, U. S. DEPARTMENT OF AGRICULTURE. 



TABLE 13. Comparison of the amount of scrape formed by the cup and box systems, 



season 1902, Georgia. 



Scrape is troublesome to collect, yields a low grade of resin, and 

 gives but 11 per cent of turpentine on distillation, while gum col- 

 lected by the cup system yields about 19 per cent of turpentine. 



RELATIVE YIELDS FROM DIFFERENT DEPTHS AND HEIGHTS OF 



CHIPPING. 



In the years 1905 to 1908 the Forest Service carried out experi- 

 ments to determine the effect of the depth and height of chipping on 

 the yield of resin. Four crops l were used in the experiment, desig- 

 nated A, B, C, and D, respectively. 



Crop A, taken as the standard, was chipped in the ordinary way, 

 the average depth of chipping being seven-tenths of an inch and the 

 average height five-tenths of an inch. 



Crop B was used to test the effect of shallow chipping, the average 

 depth being four-tenths of an inch. 



Crop C served to show the effect of narrow chipping, the average 

 height being four-tenths of an inch. 2 



Crop D was turpentined with reference to the possibility of work- 

 ing the turpentine a second time. The present method consists 

 in exhausting the tree within four years. This crop was chipped 

 in the same manner as crop A, but the minimum diameter of the 

 trees turpentined was limited to 10 inches, as compared to a mini- 

 mum diameter of 6 inches in crop A; in addition the minimum diame- 

 ter of the tree to bear two faces was raised from 13 inches in A to 

 16 inches in crop D; no tree in crop D had more than two working 

 faces. 



Table 14 shows the yields from the four crops A, B, C, and D. 



1 Crops of 8,000 faces each were used. 



* It was intended to have the height of chip in "C" half that in "A," but in spite of close supervision 

 the chippers cut wider than was desired. 



