Other Current Literature. 8i 



(5) Returning surplus chemical to working tank, 15 " 



(6) Producing vacuum to hasten drying of ties, . . 30 " 



(7) Blowing back last remnant of chemical to 



working tank, 15 " 



(8) Opening door and discharging cylinder, 15 " 



Impregnation is considered complete when the manometer 

 shows, for at least twenty minutes, that without further pump- 

 ing the pressure has remained stationary at one hundred pounds 

 — thus showing that the chemical is no longer penetrating into 

 the wood. The duration of this phase of the operation varies 

 from one to two hours, depending upon many factors, such as 

 species of wood, its physical structures, proportion of heartwood 

 and sapwood, degree of seasoning, size, shape, mass, and many 

 other conditions, not a single one of which is sufficiently well 

 defined to make it possible or practicable to segregate timbers 

 into many groups for treatment. The treatment should in all 

 cases be carried to "refusal," which obviates the necessity for 

 sorting ties or timbers into numerous groups, and this is the only 

 way to secure complete and thorough impregnation. 



S. J. R. 



OTHER CURRENT LITERATURE. 



Forest Fire Protection under the Weeks Lazv in Co-operation- 

 imth States. By J. Girvin Peters, Circular 205 (first revision), 

 U. S. Forest Service. Washington, D. C. 1913. Pp. 14. 



Greenheart. By C. D. Mell and W. D. Brush. Circular 211, 

 U. S. Forest Service. Washington, D. C. 1913. Pp. 12. 



The wood of Greenheart (Nectandra rodiaei) a South Ameri- 

 can and West Indian tree is greatly esteemed for dock construc- 

 tion and ship-building. The circular discusses the uses and dura- 

 bility of the wood, logging and transportation methods, markets, 

 and the chief anatomical features of its structure. 



Circassian Walnut. By G. B. Sudworth and C. D. Mell. Cir- 

 cular 212, U. S. Forest Service. Washington, D. C. 1913. 

 Pp. 12. 



