226 On the Rhode-Island Coal. 



ranee should prevail on this subject, and that prejudice 

 in favour of what they have been accustomed to, should 

 operate strongly against the introduction of a more eco- 

 nomical, and, in many respects, a more convenient 

 substitute. To point out, therefore, in this place, the 

 distinctions between the different species of coals, the 

 various uses for which each of them are designed, and 

 the particular purposes to which Rhode-Island coal may 

 be applied with advantage, will not, I hope, be gene- 

 rally unacceptable. 



The two points which are principally to be consi- 

 dered, with respect to pit-coal, are, first, the intensity 

 of the heat it emits, and, secondly, the duration of its 

 combustion. Coals, which abound in bitumen, maltha, or 

 pctrolium, such as Whitehaven, Newcastle, and some 

 of the Virginia coal, burn quickly, and briskly, with, 

 considerable flame and smoke. They may generally 

 be distinguished by their low specific gravity, and, 

 when bitumen or maltha prevails, a sort of semi-fusion 

 occurs, which causes them to cake and swell, produ- 

 cing a cohesion on their surface ; this interrupts a free 

 circulation of the air, and renders it necessary that the 

 substance should be broken, in order to keep up the 

 combustion. 



Common bituminous coal is certainly what is gene- 

 rally used in England. It usually contains from 30 to 

 40 per cent, of naptha or bitumen ; but, though the 

 presence of these volatile substances does not injure the 

 qualities of the coal for domestic life, yet they render it 

 unfit for v.:-*?, when in its natural state, for many ] 



