680 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



give out heat according to the relative quantities of their carbon. 

 If all the woods used are equally dry, they will give out equal 

 degrees of heat during combustion. Wet wood contains more 

 than one-third of water, and much heat escapes up the chimney 

 while converting this into vapor. The quantity of water con- 

 tained in recently cut wood amounts frequently to fifty per cent. ; 

 wood felled a year will contain twenty-five per cent. 



Wood obtained from trees that, without passing into decay, 

 have attained their maturity, will produce greater heat than any 

 any other ; as a tree decays, its value for fuel diminishes. To 

 produce the greatest effect of fuel, it should be placed in close 

 stoves. 



Charcoal is very valuable as fuel; it is exceedingly' porous, 

 containing 5,724,000 pores in one inch in diameter, and produces 

 no flame when burned. The hardest woods make the best char- 

 coal. 



Besides its use as fuel, it possesses qualities that qualify it 

 to render service to the arts. If posts intended for fence are 

 charred, before being placed in the ground, they are rendered 

 indestructible to a certain extent. It likewise prevents putrefac- 

 tion by absorbing sundry gases. It will remove taint from meat 

 that has been kept too long ; and being non-conducting, it may 

 be used for confining heat, for freeing liquors from color, and 

 depriving them of empyreumatic flavor, &c. 



But the most important fuel now known in the world is coal ; 

 the manner in which it has been formed into such immense col- 

 lections, by the action of water, heat, compression, &c., upon 

 vegetable matter, is not precisely understood. 



By analysis it compares favorably with other vegetable matter, 

 and consists of hydrogen, carbon and oxygen, sulphur, ammonia 

 and earthy matter. 



It may now be considered for domestic, as well as other pur- 

 poses, superior to all other combustible matter, and is classed 

 thus, bituminous coals, non-bituminous and open burning. Bitu- 

 minous are those which soften when brought in contact with 

 heat, and throw out jets of flame. 



Cannel is a rarer variety of bituminous, burns with a beautiful 

 white flame, and affords light as well as heat; it is perfectly clean, 

 will not soil the fingers, and may be turned on a lathe to repre- 

 sent any desirable form or figure. I think without exception 



