COLORADO EXPERIMENTS ON WESTERN YELLOW PINE. 



21 



trees, ranging in size from 14 to 42 inches diameter breast high. 

 J because of adverse weather conditions, weekly chippings were skipped 

 throe times during the course of the experiment, so that instead of 

 21 chippings from June 16 to November 4 there were but 18. Con- 

 siderable rain fell while the experiment was in progress. In Durango, 

 which is some 2,500 feet lower than the turpentine area, the precipi- 

 tation from June 1 to October 31 was 17.08 inches. The greater 

 elevation and the topographic features of the experimental area tend 

 to cause a much greater precipitation there than in Durango. During 

 the last few weeks of the experiment there wore several snow flurries 

 and periods of cold weather with freezing at night. 



The method of hanging the cups and conducting the work on both 

 areas was the same as in the Arizona experiments, except that the 

 chipping was done by rangers. The trees used in the Colorado and 

 Arizona experiments were of the same species and variety. 



YIELDS. 



Table 16 shows the weights of dip obtained from western yellow 

 pine on the Montezuma and San Juan areas. 



TABLE 16. Weights of dip obtained from western yellow pine in Colorado. 



The average flow per cup per week 011 the Montezuma area was 

 0.188 pound, and on the San Juan 0.127 pound; in both cases lower 

 than the average of 0.217 pound secured from the same pine in the 

 Arizona experiments. This difference is perhaps due in part to the 

 fact that the chipping in Arizona was done by an experienced tur- 

 pentine hand. On the Montezuma area the greater regularity in 

 carrying on the experiment accounts, at least partly, for the higher 

 yield as compared with that from the San Juan area. 



SUMMARY OF RESULTS. 



The Arizona experiments show a yield of resin from western yellow 

 pine (Pinus ponderosa scopulorum) about four-fifths as great as that 

 obtained from southern yellow pines (Pinus palustris and Pinus 



