412 



ON FUEL. 



In England, coal, from its abundance and cheapness, 

 is the commonly employed fuel ; but where wood is 

 abundant, or where its value is little more than that of 

 felling it, it is used either in its original state, or in the 

 form of charcoal. It is essential to good and profitable 

 fuel that it should be free from moisture ; for unless it be 

 dry, much of the heat which it generates is consumed in 

 converting its moisture into vapor ; hence the superior 

 value of old, dense, and dry wood, to that which is porous 

 and damp. A pound of dry wood will, for instance, heat 

 thirty-five pounds of water from 32 to 212, and a pound 

 of the same wood in a moist or fresh state, will not heat 

 more than twenty-five pounds from the same to the same 

 temperature ; the value, therefore, of different woods for 

 fuel is nearly inversely as their moisture, <md this may 

 be roughly ascertained, by finding how much a given 

 weight of their shavings loses by drying them at 212. 



The following table exhibits at one view the power of 

 various species of wood in producing heat. 



The number indicates the quantity of timber in pounds 

 required to raise the temperature of a cubic foot of water 

 from 52 to 212. 



Pounds. 



Oak chips , 4.20 



Elm 3.52 



Fir 3.52 



Ash 3.50 



Hornbeam 3.37 



Cherry-tree 3.20 



Beech 3.16 



Lime-tree 3.10 



Poplar 3.10 



Maple 3.00 



Service-tree 3.00 



The value of turf and peat, as fuel, is liable to much 



