262 



circumstantial nature: which I, however, trust is of some consider- 

 able weight. 



Bitumen alone would not, however, accomplish that grand pur- 

 pose for which nature formed coal ; that of supplying future ages 

 with a substance for fuel, which, by a moderate exercise of the 

 ingenuity of man, might be made to burn with almost every degree 

 of intensity ; from that which is employed to convey to the human 

 body a grateful sensation, to that which is necessary to fuse some 

 of the untractable metals. 



The rapidity with which pure bitumen burns, would not only 

 occasion a considerable waste of it, if it were attempted to be 

 employed for the purposes to which coal is applied : but would 

 also render it so unmanageable, as entirely to prevent its useful 

 application, to even the most ordinary purposes, which coal is in- 

 tended to fulfil. 



To moderate this high degree of combustibility, and so to regu- 

 late it, that the consumption of a substance, so necessary to man, 

 should be rendered uniform and economical, was therefore required. 

 To accomplish this, the intermixture of some incombustible sub- 

 stance with the bitumen became necessary. But to produce those 

 characteristic properties, by which coal is distinguished from all 

 other substances of the same class, a particular kind of arrange- 

 ment of the particles of this heterogeneous mass was requisite. It 

 was necessary that the bituminous particles should be so involved, 

 and insulated, on every side, as to be nearly defended from the 

 action of the fire. It was also necessary that the regularity of its 

 combustion should not be disturbed, by the superadded incombus- 

 tible matter existing in the mixture, in such gross particles, or in 

 so irregular a state of diffusion, as would have been the case, if the 

 earth had remained in it, in the state in which it had subsided 

 along with the sunken vegetable mass. 



