PKRIODICAt LITERATURE 139 



spruce stands are orcharded. As the pine resin contains more turpen- 

 tine than that obtained from spruce, it is more valuable. 



Intensive experiments in the production of resin are still under way 

 in Germany. A modification of the Gilmer turpentine cup system has 

 given promising experimental results. The following specific research 

 problems are under investigation at the present time : 



1. The effect of the depth of faces and streaks. 



2. Careful measurements to determine the degree in which the production of resin 



increases during the first weeks and months after facing and to what extent 

 the failure of certain individual trees to produce sufficient amounts of resin 

 consists. 



3. Experiments to determine the most suitable number of faces on a single tree 



and the effect of a greater or lesser number of faces on the ultimate gross 

 production of resin. 



4. A continuance of experiments to determine the degree in which weather con- 



ditions influence the production of resin. 



5. A continuance of experiments to determine the proper interval between cliip- 



ping in stands of different origin and different age classes. 



6. The effect of site upon resin production. 



7. The influence of crown size upon resin production. 



The effect of turpentine orcharding upon the strength and durability 

 of the wood was determined by the bureau to be negligible. Seeds from 

 trees that have been orcharded, however, produce seedlings of inferior 

 size and vitality. 



B. L. G. 



Tysklands nuvarande fiartsiiidustri. vSkogsvardsforeningens Tidskrift. hilv- 

 August, 1917, pp. 735-762. 



The de\elopment of the flotation process for 

 Use of recovering metals from ores has given rise to new 



Wood Oils uses of wood for the production of oils to be 



in used in this process. In this connection we call 



Flotation attention to the investigations of the Canadian 



Forest Products Laboratories, carried on by Gil- 

 more and Par.sons. reported in detail, with extensive tabulations, in the 

 Monthly Bulletin of the Canadian Mining Institute, on over 40 pages. 

 The conclusions are: (i) Crude hardwood oils, the supply of which 

 is abundant, can be substituted for pine oil as a .selective frothing agent 

 in the commercial flotation of cobalt area silver ores. (2) Heavy 

 hardwood creosote oil and acid (creosote) oil give equallv satisfactory 

 results, and a mixture of these two oils in proportions as produced is 



