CHAPTER VIII 

 TIMBER; FORESTRY 



100. Wood as a structural material. 1 There are a few dis- 

 advantages in the use of wood for many purposes of construc- 

 tion. Wooden fences and buildings are easily destroyed by 

 fire. Wooden posts, bridges, and similar structures, and shin- 

 gled roofs, are subject to rather rapid decay. Most woods 

 will not stand long-continued friction without wearing out, 

 so that many of the working parts of machines, when made 

 of wood, as they often were by the early settlers in this 

 country, were short-lived. 



Some of the advantages of wood for constructive purposes 

 are as follows : 



1. Wood is far cheaper than metals ; bulk for bulk, it does 

 not, on the average, cost more than one thirtieth as much as 

 iron or steel. 



2. Wood is much more easily worked than metals. 



3. Weight for weight, some wood is stronger than iron or 

 steel. A bar of hickory will stand a stronger pull lengthwise 

 than one of wrought iron of equal length and weight. A block 

 of the best hickory or long-leaf pine will bear, without crush- 

 ing, a greater load than a block of wrought iron of the same 

 height and weight. 



4. Wood is light and is therefore much more convenient 

 than metals for many purposes of construction, as building 

 vehicles and making packing cases and tool handles. 



5. Wood is a poor conductor of heat and on this account is val- 

 uable in the construction of houses, railway cars, refrigerators, 



1 See Roth, First Book of Forestry, pp. 232-238. Ginn and Company, 

 Boston. 



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