44 BULLETIN 1064, U. S. DEPARTMENT OF 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 resinif erous tissue ; ( h ) 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- 



