REVIEWS 983 



on the general subject of strength of wood in relation to its com- 

 mercial uses which has yet appeared. The book is of convenient form 

 and size to use for a reference book and also for a textbook in 

 universities. 



The subject matter covers four principal topics: (1) Statistical 

 analysis of the timber supplies and cuts throughout the United 

 States; (2) the strength values and factors affecting the same, both of 

 wood intrinsically and also of manufactured products; (3) the sea- 

 soning of wood; and (4) the grading systems in use. The main part 

 of the book has to do with the subject of strength and its application 

 to commercial uses of wood. 



While there is little that can be said to be entirely new in the book, 

 wood users will nevertheless find the subject matter brought together 

 in a convenient and easy form for reference. The material has been 

 taken almost entirely from the various circulars and bulletins issued 

 by the Forest Service, including Air. Betts' own bulletin, "The Season- 

 ing of Wood." Full credit for the material is given in the preface; it 

 would have been interesting, however, to have had a biblography of 

 the works quoted. 



Mr. Betts has had long experience in the testing of yellow pine 

 timbers of all sizes, and the summary of the strength and stiffness of 

 natural and treated sizes is of special value, as it is based upon his 

 intimate knowledge and experience in this line of work. It is inter- 

 esting to note from comparative results given that Douglas fir stringers 

 show a decided loss in strength in the modulus of rupture of the 

 creosoted material, both before subsequent air seasoning and after 

 thorough seasoning. In the boiling process this loss is shown to range 

 in the unseasoned timbers from 18 to 52 per cent of the strength of 

 the natural wood and after seasoning the loss in strength (modulus of 

 rupture) is shown to range between 17 and 52 per cent for the un- 

 seasoned. In small sized pieces cut from the large beams the losses 

 are much less, namely, from 17 per cent in the unseasoned to 2 per 

 cent when air dried. The following is quoted from his deductions : 



"1. Timber may be very materially weakened by the preservative process. 



"2. Creasote in itself does not appear to weaken timber. 



"3. A preservative process which will seriously injure one timber may have 

 little or no effect on the strength of another. 



"4. A comparison of the effect of a preservative process on the strength of 

 different species should not be made unless it is one of the best adapted pro- 

 cesses for all the species compared. 



"5. The same treatment given to a timber of a particular species may have a 

 different effect upon different pieces of that species, depending upon the form of 

 the timber used, its size, and its condition when treated." 



