162 FORESTS AND MANKIND 



example, made up of several layers of veneer are stronger and 

 less likely to warp and crack then if they were all of one piece. 



Most veneers are made by first boiling a log for some hours 

 to soften it and then revolving the log, by machinery, against 

 a sharp knife. As it turns the knife bites into the wood and 

 a long thin sheet of veneer is peeled away. Woods chiefly used 

 for this purpose are the highly-priced species, such as mahog- 

 any, Spanish cedar, and Circassian walnut. But increasing 

 numbers of woods are becoming acceptable for veneer stock 

 as our supplies of valuable hardwood species get scarcer. 



In the process of changing raw hide into leather the tannin 

 used is extracted from the wood and bark of hemlock and 

 oak. It is this extract that makes leather durable and pliable. 

 During the summer the bark is peeled from these species and 

 transported to plants where the tannin is extracted. At one 

 time the tan-bark industry was so important that in the eastern 

 United States hemlock trees were cut and stripped for the bark 

 alone, leaving the wood to rot. Today the scarcity of hemlock 

 trees and the introduction of other tannin materials have cur- 

 tailed the industry seriously. 



A great deal of wood is used for the manufacture of recep- 

 tacles such as barrels, casks, tubs, and kegs. These and similar 

 containers are bulked together under the term of cooperage 

 and for these purposes, red oak, white oak, cypress, and gum 

 are the species most frequently used. Excelsior is still another 

 valuable forest product, and is used for shipping fragile ma- 

 terial and even for mattresses and rugs. Basswood makes the 

 best excelsior and cotton wood, poplar, and white pine are 

 also used. 



The uses of wood are far from ended. Spools, box boards, 



