OLEORESIN PRODUCTION. 19 
In the second year in all crops there was some decrease in total 
yield. The 1917 comparisons, using the total 1916 yields from a 
crop as 100 per cent or the criterion for judging the relative yield 
of that crop, showed that the greatest decrease occurred in the stand- 
ard tract. (Table 5.) 
DOUBLE CHIPPING. 
The special feature of this method, used for two years on this 
area at Columbia, Miss., was that the streak was cut at four-day 
intervals instead of only once each seven days. This type of chip- 
ping was used (PI. IV, figs. 3, 5, and 6) on about 3,000 faces on the 
same kind of timber as that in the standard experiment. Only as 
much wood as was cut in the standard chipping was removed by 
this double method, since the dimensions of the streak specified were 
one-half inch deep and one-fourth inch high, cut twice weekly. The 
depth in general tended to average slightly less in the double than 
in the standard. During 1916 the chipping was carried on with a 
"00" hack (PI. IV, fig. 2) and a streak averaging 0.32 inch was ob- 
tained (Table 6, footnote). In 1917 a "puller" (PI. IV, fig. 6) was 
used, and a more accurate narrow chipping or rather "pulling" 
was obtained (average 0.26 inch) as is indicated in Table 6. This 
was also more accurate chipping than was obtained in 1917 on the 
single narrow-chipped area (average height of streak 0.34 inch), 
where a hack was used. It is of considerable interest to note that 
with this narrow chipping the double showed a smaller relative re- 
duction in the second-year yield. of turpentine, when compared to 
that of its first-year yield, than was shown by the wider-chipped 
(one-half inch per streak) standard. This was true in spite of the 
fact that the vitality of the double-chipped timber had apparently 
suffered rather more severely from the process of turpentining than 
had the standard. 
In figures 3 and 4 are given the monthly observations on the five 
trees selected from the double area for 1916 and 1917, respectively 
(different sets of five each year). The same reduction as in the case 
of the standard was noted in the number of resin passages per unit 
area of the 1916 ring, as was observed in material cut at the level of 
the 1917 chipping. The tendency for fewer resin passages to be 
present at the end of the 1917 season than in midsummer was also 
observed. In 1917 practically all five trees from the double area 
showed that their wood formation had suffered as a consequence of 
that method of turpentining, and that they had not been able to 
recover, as many of the narrow-area trees had, or even been able to 
hold their own during 1917, the second year of turpentining, as some 
of the standard-area trees appeared to have done. 
The results from the examinations of the 50 specimens collected 
at the end of the season each year are given in Tables 2, 3, and 4. In 
