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BULLETIN 229, U. S. DEPARTMENT OF AGRICULTURE. 



of gum, since clay does not become heated like metal when exposed 

 to the sun and thus cause evaporation of the turpentine. Clay cups 

 are three or four times as heavy as metal cups, however, and much 

 more bulky. They are also more likely to break, both in transit and 

 in handling. On the other hand, they do not rust like the galvan- 

 ized-iron cups. Rusting not only results in loss of cups, but may 

 also darken the gum. 



In shape the cups may be like a flowerpot (Plate I, fig. 2), an 

 oblong box (Plate V, fig. 1), or a flattened cone (Plate VII, fig. 2). 

 With the deep cups, it is claimed, there is less evaporation of gum, on 

 account of the smaller surface exposed. On the other hand, deep 

 cups take up more vertical height on the tree, and are generally con- 

 sidered more difficult to dip. The cone-shaped cups are similar in 

 shape to the interior of the ordinary "box," being so made for the 

 sake of economy, since only one seam is necessary. 



Within certain limitations the kind of cup used with a particular 

 gutter or apron is immaterial. Between the cups and gutters now 

 on the market, the greatest room for improvement exists in the case 

 of the latter, though improved aprons and gutters are constantly 

 put on the market. 



RELATIVE YIELDS SECURED FROM CUPS AND BOXES. 



Experiments made by the Forest Service in Georgia during 1902 

 showed conclusively that more and better turpentine and rosin can 

 be obtained by the use of cups than by the use of boxes. 



The timber studied consisted of a first, second, third, and fourth 

 year crop, one-half of each crop being turpentined by the cup sys- 

 tem and the other half by the box system, The comparative results 

 are shown in Tables 9 and 10. 



TABLE 9. Spirits of turpentine from eight half crops, season of 1902, Georgia. 



