6 Schoiiten Island. 



As a general rule, bodies in burning heat in proportion 

 to the carbon which they contain ; but combustion may 

 be retarded by the presence of earthy matter, and one 

 coal, though containing as compared with another less 

 carbon, may yet have greater heating power, in conse- 

 quence of its containing bitumen, and its combustion 

 being more rapid and complete. 



It appears certain, for instance, that the Schouten coal 

 taken in the aggregate, from its containing so consider- 

 able a proportion of bitumen in the lower part of its seam, 

 and so large an amount of carbon in the upper portion of 

 it, possesses heating powers far superior to the coal from 

 Port Arthur, which probably contains a much larger pro- 

 portion of carbon in a given weight. 



Earthy anthracite in a state of combustion is not only 

 less powerful in emitting heat, but, in consequence of the 

 extreme difficulty with which it ignites, a great deal 

 of time, and already realized caloric, are wasted by its 

 introduction into furnaces in an unprepared state. It 

 only burns after attaining a high temperature ; and until 

 it reaches this point it absorbs heat, and reduces the 

 temperature around it. 



An owner of steam machinery here informs me, that 

 he considers the value of the Sydney bituminous coal, 

 from the greater intensity and manageableness of its 

 heating powers, as three to one compared with Port 

 Arthur coal. 



The customary articles of fuel rank as heating agents 

 in the following order : — 



Perfectly dry Wood. 



Pit Coal. 



Coke. 



Wood Charcoal. 



The Oils, &c. 

 In the preparatory roasting of metallic ores for re- 



