648 EXPERIMENT STATION RECORD. 



with 64.3 iu. in crop A. On crop D the chipping was tlie same as in crop A, 

 but the width of the unchipped surface was increased by raising the minimum 

 diameter of trees to be turpentined from 6 to 10 in., and the minimum diameter 

 of trees to carry 2 chipping faces from 13 to 16 in. No tree in crop D carried 

 more than 2 chipping faces. The shallow and narrow chippings as in crops 

 B and C were also combined and tested for one season. The results of the 

 investigation are summaiized and discussed, and detailed yield tables are 

 appended. 



The total yield for the 4-year period from the standard crop A, based on cor- 

 rected data, was 206,235 lbs. of dipi>ed turpentine and 47,742 lbs. of scraped 

 turpentine. Both shallow chipping and nari-ow chipping as in B and C gave a 

 relatively small but valuable increase in yield of dip which was only partially 

 offset by a reduced yield of scrape. Moreover, laboratory analyses showed that 

 the dip from shallow -chipped trees in the second year was about 10 per cent 

 richer in turpentine than the ordinary dip. The same increase is anticipated in 

 the dip of narrow-chipped trees also. In both B and C there was evident at 

 the end of the second year a heavy reduction in the loss from dead trees and 

 faces abandoned because of dry face. It was also found that C could be profit- 

 ably w^orked for a fifth year as a result of reducing the height of cut. The 

 " light cupping " method employed in crop D gave a 35 per cent Increase of 

 dipped turpentine and a 13 per cent increase of scraped turpentine. In addition 

 the timber was left in condition to be immediately worked again for a second 

 4-year period. In crop A a second working was entirely impracticable. 



In the 4-year experiments the principal gain from improved methods has 

 been found in the later years, due presumably to a decreased drain on the vigor 

 of the trees. The combined narrow and shallow chipping, however, tried for 

 only one year, showed an increased yield of dip of between 35 and 40 per cent in 

 the single season, and on the basis of the 4-year results it is believed that this 

 increase would have been maintained in subsequent seasons. * 



Acting on the results secured from Tschirch's studies of resinous secretions 

 and resin ducts, the report of which has been briefly noted (E. S. R., IS, p. 743), 

 it has been found that the first dipping yields from the cup system of turpen- 

 tining may be considerably increased by making a regular chipping the full 

 width of the face when the gutters are placed on the trees during the winter 

 months. Vertical secondary resin ducts, which constitute the chief source of 

 commercial crude turpentine, are thereby formed along the entire length of the 

 cut, so that iu the spring the first regular chipping will open the full number of 

 these ducts instead of only a few ducts near the center of the face where pre- 

 liminary winter chipping is not employed. 



Taken as a whole the chipping experiments appear to demonstrate conclusively 

 that the adoption by turpentine operators of the methods herein described will 

 substantially increase the yield per crop of crude turpentine obtainable in a 

 4-year period ; make possible the indefinite prolongation of the turpentine period ; 

 and cause far less sacrifice of merchantable timber. The Forest Service is to 

 undertake continued turpentine experiments in the Choctowhatchee National 

 Forest with the above aims in view. 



Australian timber. — Its strength, durability, and identification, J. Mann 

 (Melbourne, 1909, pp. XVI-\-l.'t8, figs. 19). — This treatise comprises a compi- 

 lation of the data available prior to 1900 relative to the strength and dura- 

 bility of about 50 of the best-known engineering and construction timbers of 

 Australia. The information was obtained at the engineering laboratories at 

 the Sydney and Melbourne universities, government departments, and other 

 reliable sources, lleports of subsequent timber tests in various Australian 

 colonies have been noted (E. S. R., 19, p. 950; 20, p. 243; 21, p. 47). 



