Current Literature. 461 



Lumbermen commonly recognize two varieties of the timber — 

 red fir and yellow. Experiments show that they have practically 

 the same strength; the yellow variety, however, contains fewer 

 defects and is of more even grain. 



The average weight per cubic foot of Douglas Fir is, oven dry, 

 28.8 pounds; thoroughly air seasoned, 33.1 pounds; green, 38.4 

 pounds. Within limits, strength varies directly as the drv weight 

 of the wood. The greatest strength in small specimens is most 

 frequently associated with an average rate of growth of twelve 

 to sixteen rings per inch of radius. In grading structural timbers, 

 however, average rate of growth has little significance. 



The bulletin is replete with tables, figures and diagrams, show- 

 ing the relation of the physical characteristics of Douglas Fir to 

 its mechanical properties. Of special interest is the comparison of 

 different grading rules and specifications for Douglas Fir, based 

 on data secured from tests on green material, with pertinent sug- 

 gestions for their modification in order to secure the best results. 



S. J. R. 



Preservative Treatment of Poles. By William H. Kempfer. 

 Bulletin 84, U. S. Forest Service. Washington, D. C, 191 1. Pp. 

 55- 



This bulletin embodies in convenient form the results of the 

 investigations by the Forest Service of methods for prolonging 

 the life of poles. Though most of the data has been previously 

 published in separate circulars, there is included additional infor- 

 mation gained by more recent experiments. 



In treating poles it Is seldom considered practicable to impreg- 

 nate the wood throughout, an outer protective envelope around 

 the untreated interior wood proving sufficient. The antiseptic 

 should penetrate deeply enough to prevent exposure of the un- 

 treated wood by abrasion, checking or other action. It has been 

 the aim of the Forest Service to perfect cheap and simple methods 

 for applying such creosote treatments locally and without expen- 

 sive plants, thereby overcoming the chief hindrances to general 

 adoption of the practice. 



The more important conclusions from the investigations dis- 

 cussed in the bulletin are summarized as follows : 



"Seasoning poles reduces their weight, commonly from 16 to 



