44 BULLETIN 1064, U. S. DEPARTMENT OE AGRICULTURE. 
6. Low rate of death of trees from turpentining and the pro- 
duction of few dry faces, hence less degrade of lumber due to pitch 
saturation or to infection at the face area. 
7. Responsive vigor not reduced, as is shown by (a) the early 
formation of wood and resiniferous tissue ; (6) the increases in diam- 
eter growth found even under turpentining; (c) the formation of 
the summer wood, which also occurred earlier in the narrow than 
in the standard and double chipped timber at Columbia, Miss.; 
and (d) a relatively very high total production during the second 
year of operation, especially since this was sustained as is shown, 
for instance, late in the season even after a severe drought, when 
neighboring crops showed a comparatively poor exudation of gum. 
8. Greater ease in operating, once the chipper becomes accus- 
tomed to the method, since less wood is removed and the chipping 
period can be prolonged and the pulling period deferred, because 
the amount of surface chipped yearly is less. 
FREQUENCY OF CHIPPING. 
From the results obtained with the double chipping at Columbia, 
Miss., it was concluded that the yield obtained did not show a suffi- 
cient increase to offset the additional cost in the case of turpentine 
operations lasting for a considerable number of years. For a very 
short operation, when it is planned to turpentine for a period of 
perhaps two years before cutting the timber, double chipping might 
possibly be practiced regularly, or perhaps with greatest advantage 
for a limited period during the height of the producing season. The 
microscopic study of the material from the double tract showed 
that this method exerted a decidedly detrimental influence on wood 
formation and on the general vitality of the timber; and that it 
used up chipping surface to the same extent as ordinary commercial 
practice. 
STANDARDS FOR ESTIMATING THE EFFECTS PRODUCED BY DIFFERENT METHODS 
OF CHIPPING. 
In estimating the responses of the timber turpentined by the va- 
rious methods of operation used at Columbia, Miss., the wood for- 
mation, especially the width of ring and the amount of summer wood 
produced by unturpentined trees growing in the same locality 
under the same conditions, was determined as a basis for judging the 
effects of turpentining on the wood structure. The best diameter 
growth and summerwood formation for the three years 1915, 1916, 
and 1917, were found in the round timber in 1916. Hence marked 
decreases in the wood formation of the turpentined timber for that 
year could be attributed directly to the effect of the wounding. De- 
