5)84 JOURNAL OF FORESTRY 



Mr. Newlin's (Forest Products Laboratory) famous density- 

 strength curves are given in full, and the intrinsic strength values of 

 American timbers taken from Mr. Newlin's bulletin, "The Mechanical 

 Properties of Woods Grown in the United States," are reproduced in 

 six folded inserts. These folded tables are very clearly printed, al- 

 though of a somewhat inconvenient size for handling. 



A discussion of the grading of structural timber with a classification 

 of defects and methods used by the Forest Service in classifying de- 

 fects for knots is fully discussed and illustrated, and comparisons of 

 the common grading rules in use throughout the country are given. 



A table for the working stresses permissible for structural timbers 

 for twenty-three species is based on the tests and investigations of the 

 Forest Service. 



Tests for commercial articles such as telephone poles, cross arms, 

 packing boxes, and vehicle parts are described and tables of data given. 



It is of interest to note the statement that "there is little difiference 

 between the (southern yellow) pine and (Douglas) fir (cultivator) 

 poles for most of the qualities measured, but the range was much 

 greater in the pine poles than in the fir." 



The following conclusions are quoted: "Spoke tests show an error 

 of 50 per cent in the grading system used which is largely due to the 

 traditional prejudice . . . against red hickory." "The superi- 

 ority of hickory in toughness and shock resisting ability as compared 

 with maple is brought out in the axle tests." "Shaft tests indicate 

 that red oak may be substituted for hickory of the lower grades in 

 shaft manufacture." 



An original compilation taken from various sources showing the 

 "Life of untreated woods" in the form of ties, posts, poles, and lum- 

 ber is given in a table for 42 species. It is interesting to note that no 

 partiality is shown between redwood and cypress, both being quoted 

 with a life of ten to twelve years for ties and twelve to fifteen years 

 for all other purposes. 



Thirty-seven pages are devoted to the "Seasoning of Wood," which 

 is a compilation of Forest Service literature. The discussion has to do 

 primarily with the air seasoning of both timbers and lumber, with brief 

 remarks concerning kiln drying, giving a classification of various 

 methods used. Rules for piling lumber are given, being quoted from 

 Department of Agriculture (Forest Service) Bulletin 552, "The Sea- 

 soning of Wood." 



Considerable space is given to a discussion of the grading of lumber 

 and grading rules. There are two principal sets of rules for hardwood 



