1912] The Naval Stokes Industry 121 



of these experiments is given in Bulletin No. 40 and Circular 

 No. 34 of the U. S. Bureau of Forestry. 



With the main points at issue settled, namely — improved 

 yields both in quantity and quality of the products and preser- 

 vation of the trees, other forms of apparatus were devised to 

 meet the objections of some of the operators to certain points in 

 the cup and gutter system. Many of these have never proved 

 practical, but some have been introduced on a considerable com- 

 mercial scale. 



The successful outcome of the experiments on the relative 

 yields from the " box " and the " cup " system led the United 

 States Forest Service to further experiments in more conserva- 

 tive treatment of the trees in chipping. Comparative studies 

 were made of the yield from deep and shallow chipping and the 

 latter found to give the greater yield during a period of four 

 years of operation. Other experiments showed that a less rapid 

 rate of ascent of the trunk also gave larger yields, and experi- 

 ments combining these several modifications of present practices 

 showed a largely increased yield. A final set of experiments 

 pointed clearly the rational way to a perpetuation of the naval 

 stores industry in America. The details of this investigation 

 are given in Bulletin No. 90 of the United States Forest 

 Service. 



DISTILLATION. 



In the matter of distillation, only slight advances have been 

 made in America. The uniform process consists in the use of a 

 large copper kettle and condensing worm. The charge for a 

 distillation averages nine to ten barrels of crude turpentine. 

 The kettle is heated by free flame and during the distillation a 

 small stream of hot water from the top of the condenser tub is 

 admitted through an opening in the upper part of the kettle, 

 thus facilitating the removal of the volatile oil. The condensed 

 spirits of turpentine and water separate in the receiver, owing 

 to difference in specific gravity, and the lighter spirits of tur- 

 pentine is transferred to oak barrels, well coated with glue on 

 the inside. No effort is made to redistill this product, and it 

 always comes upon the market contaminated by a small amount 



