FUEL WOOD 



341 



power for the 30,000 sawmills in operation in this country. This is 

 made up of slabs, edgings, trimmings, sawdust and defective material. 



FUEL VALUES 



The value of equal weights of 'dry wood for fuel purposes is practically 

 the same with all species. According to this rule, therefore, specific 

 gravity may be used as a direct means of comparing the heat values of 

 the different species. This, however, does not hold with resinous woods. 



Photograph by U. S. Forest Service. 



Fig. 92. — ^Woodyard with a capacity of 5000 cords of fuel wood along the Potomac River 

 at Washington, D. C. Rivers afford cheap transportation for low-priced forest products 

 such as fuel wood. This is mixed pine and hardwoods brought by small sailboats from 

 forests along the lower Potomac. 



Aside from weight, however, other considerations often determine 

 the value of different kinds or classes of wood for fuel purposes. The 

 l-)rincipal other considerations that may be mentioned are as follows: 



1. The design, construction and regulation of furnaces, stoves 

 and fire places all have an important bearing upon the question 

 of getting the maximum fuel value out of any wood. Oak and 

 hickory burn with practically a smokeless flame, whereas others 

 often burn with more or less smoke due to improperly regu- 

 lated flues, drafts, etc. 



2. The degree of dryness. Much heat is lost in driving the re- 



