8 WESTERN PINES AS A SOUECE OF NAYAL STOEES. 



The montli of August shows the highest mean temperature (61.4° 

 F.) and, as would be expected, the greatest jield of dip was during 

 this month (see Table 3). Hardly any rain feU until July, when 

 5.71 inches was recorded. The three following months also had a 

 substantial rainfall. The total precipitation from April 1 to Novem- 

 ber 15, 15.28 inches, was above the average for previous years. The 

 mean humidity was greatest in July, and the driest weather in June. 

 The mean temperature, humidity, and rainfall during the experi- 

 ments were all below the average of similar observations made in 

 Florida in connection with experiments there. In that part of 

 Arizona in which the experiments were conducted the diurnal range of 

 temperatures is much greater than in the turpentine regions of the 

 Southeast, and a drop of from 35 to 40 degrees duriag the night is 

 not at all uncommon. These conditions cause the gum to harden 

 on the faces at night, and it takes a comparatively long period under 

 the influence of the morning sun to start the flow again. 



METHOD OF CONDUCTING EXPERIMENTS. 



All trees of 12 inches or more breast-high diameter were tapped, 

 except where they were so defective that they would not be used 

 in a commercial operation. No cups were placed on trees less than 

 12 inches in diameter. One cup was placed on trees between 12 

 and 15 inches in diameter; two cups on trees between 15 and 24 

 inches; and three cups on trees more than 24 inches in diameter; 

 but not more than three cups were hung on any one tree, no matter 

 how large. On the o.ther hand, less than the prescribed number 

 of cups were hung in some cases because of defects in the tree. 



The cups were of galvanized iron. In hanging them, the rough 

 outer bark near the base of the tree was first smoothed off, and a 

 concave-edged broadax was then driven in with a maul ia order 

 to make an incision for a galvanized-iron ''apron." The apron was 

 pushed tightly into the incision and the cup held below it by a naU 

 driven into the tree, on w^hich the weight of the cup rested. Plate 

 II shows a ''face" at the end of the season. The trees were chipped 

 once a week with an ordinary turpentine "hack." An experienced 

 turpentine hand from the Southeast was employed to do the chippuig. 

 While it was the intention to make the streaks one-half iach deep 

 and to add one-half inch to the height of the face at each chipping, 

 measurements taken at the end of the season showed the average 

 depth of the streaks to be 0.68 inch and the average height 0.77 

 inch. This excess over the measurements originall}^ plamied was 

 due to the fact that the workman had been trained to make a much 

 wider and deeper cut. The cups were dipped every three weeks. 

 Eight dippings were made on each area, the first on May 30, three 

 weeks after the first streak was put on, and the last on October 31. 



