GREEX AND DRY WOOD FOE FUEL. 275 



by thorough seasoning, which is equal to about 25 cubic 

 feet in every compact cord, or 156 imperial gallons. Now 

 all this water must be evaporated before the wood is burn- 

 ed. The heat thus made latent and lost, being five times 

 as great as to heat the water to boiling, is equal to enough 

 for boiling 780 imperial gallons in burning up every cord 

 of green wood. The farmer, therefore, who burns 25 

 green cords in a winter, loses heat enough to boil more 

 than fifteen thousand gallons of water, which would be 

 saved if his wood had been previously well seasoned un- 

 der shelter. 



The loss in using green fuel is, however, sometimes 

 overrated. It has been found by experiment that one 

 pound of the best seasoned wood is sufficient to heat 27 

 lbs. of water from the freezing to the boiling point.* 

 This will be equal to heating and evaporating four pounds 

 of water by every pound of wood. The 25 cubic feet of 

 water, therefore, in every cord of green wood, weighing 

 about 1,500 pounds, would require nearly 400 pounds of 

 wood for its evaporation, or about one-seventh or one- 

 eighth of a cord. Hence we may infer that seven cords 

 of dry w^ood are about equal to eight cords of green. 

 This imperfect estimate will apply only to the best hard 

 wood, and will vary exceedingly with the different sorts 

 of fuel ; the more porous the wood becomes, the greater 

 w411 be the necessity for thorough seasoning. 



* The following results show the heathig power of several combust- 

 ibles: 

 1 lb. of wood (seasoned, but still holding 20 per cent of water) 



raised from 33 to 212 27 lbs. water. 



lib. ofalcohol 68 " 



1 lb. of charcoal 78 '* " 



1 lb. of oil or wax 90 " " 



1 lb. of hydrogen 216 " " 



It should be remembered that by ordinaiy modes of heating water, a 

 very large proportion of the heat is wasted by passing up the chimney 

 and into surrounding bodies, and the air. 



