REVIEWS 75 



tracks. Unless combined with some other material, such as creosote, 

 these salts gradually leach out, particularly in damp climates, and 

 eventually their influence on the resistance of roadbeds disappears." 

 Accordingly the use of these salts for preservatives should be avoided 

 where the escape of stray currents is objectionable or where block 

 signals are used. 



Creosoting tends to retain what moisture is within the woods and to 

 retard air-seasoning, but otherwise has little efifect upon the electrical 

 resistance. A tie treated by the Card process with one-half pound zinc 

 chloride and two pounds coal-tar creosote per cubic foot exhibited a 

 very low resistance. 



A treating material consisting of 75 per cent gas oil and 25 per cent 

 creosote appears to increase materially the resistance of the wood. 

 Open-track construction on which ties treated in this manner were 

 employed had a leakage resistance about twice as great as similar road- 

 beds with untreated ties and about four times as great as roadbeds 

 with ties treated with chemical salts. 



S. J. R. 



forest Products: Their Manufacture and Use. Embracing the prin- 

 cipal conuncrcial features in the production, manufacture, and utilisa- 

 tion of the most important forest products other than lumber in the 

 United States. By Nelson Courtland Brown. New York. John 

 Wiley & Sons. Inc. 1919. Pp. 471, illustrated with 120 cuts. Price, 

 $3.75. 



This valuable additon to the forester's ready reference library brings 

 together into compact, readable form a vast amount of data about many 

 important industries concerning which information has been scatterefl 

 and often inaccessible. The author is more than compiler and has put 

 into his work the results of ten years' study at first hand of the various 

 industries treated. 



The book comprises 22 chapters. The first is of an introductory 

 nature, covering briefly the extent of our original forests, history of the 

 lumber cut, present forest resources, rate of consumption, annual pro- 

 duction of lumber, lumber values, u.ses of the lumber cut, wastage in 

 j/roduction, and converting factors, including those used in the inter- 

 national timber trade, with particular reference to European countries. 



Each succeeding chapter is devoted to a single industry, and con- 

 cludes with a selected bibliography. The sequence of the chapters and 

 the space given to the various subjects are as follows: Wood pulp 



