1819.] the different Species of Pit-Coal. 95 



as it does of carbon. Hence the readiness with which it burns ■ 

 the great quantity of gas which it yields ; and its unfitness 

 for the purposes of coking. 



The following table exhibits in one view the results of the 

 preceding experiments on the composition of these four different 

 species of coal. 



I. Constituents by Weight. 



II. Constituents in Atoms. 



Caking coal . 

 Splint coal . . 

 Cherry coal . 

 Cannel coal . 



Number of 

 atoms. 



48-5 

 46i 

 71 



34 



I flatter myself that these experiments, imperfect as they are, 

 wdl serve very materially to guide manufacturers in the choice of 

 their coal according to the peculiar objects which they have in 

 view. We see from them that the goodness of a coal does not 

 depend so much upon the absolute quantity of carbon which it 

 contains, as upon the proportion which exists in it between the 

 carbon and the hydrogen. When the object is to convert the 

 coal into coke, or when we wish to make it subservient to the 

 production of long, continued, and intense heat, we must make 

 choice of the species which contains the greatest proportion of 

 carbon and the smallest of hydrogen. On the other hand, when 

 the object is to procure coal gas, we must choose the species 

 which contains the greatest proportion of hydrogen compared to 

 that of the carbon. For this purpose cannel coal answers best 

 of all. It contains twice as many atoms of hydrogen as it does 

 of carbon, and seems likewise to' be destitute of oxygen, or at 

 least nearly so. Next to the cannel coal, the cherry coal 

 answers best for the preparation of coal gas. Caking coal is 

 inferior to cherry coal for this purpose. I have not tried splint 

 coal, being deterred by the great heat requisite to decompose it; 

 but it would not in all probability yield much gas, nor of the best 

 quality. 



I have made a great variety of experiments on coal gas, but 

 think it needless to state the results, as they contain but little 



