HEATING-POWER, 105 



(Scotch pinewood gives more soot than sprucewood) , beech, &c. ; 

 others less, such as softwood broad-leaved trees, especially alder 

 and birch. 



Other woods crackle and send out sparks, owing to the air they 

 contain, as woods of the sweet chestnut, larch, spruce and oak ; 

 others to a less degree, as those of Scotch pine, silver-fir and 

 aspen ; whilst some woods burn without any crepitation, as those 

 of hornbeam, birch, alder, &c. 



