MODE III. COAL. ,575 



last subspecies y that of Moor coal, is again a mere 

 variety of bituminous wood, but more brittle, as 

 it is mingled with reeds. 



The author must confess, that when he had 

 perused Werner's account of the coals, his ideas 

 of the subject were far more confused than ever 

 they were before ; so that he seemed with great 

 study to have learned ignorance. This effect must 

 necessarily arise, when subjects of the utmost 

 importance, and of the most trifling minuteness, 

 are presented to the mental eye, as of equal mag- 

 nitude. By the unhappy microscope of external 

 characters, an insect may appear like an ele- 

 phant; while common sense and chemistry can 

 alone present the objects as they really are. It 

 is the chief, if not the only, use of systems in 

 natural history, to assist the memory ; and for 

 this purpose, that the faculty may not be strained 

 and overpowered, it is the office of a judicious 

 arrangement, to present the chief objects in the 

 fore-ground, while the others are marked at gra- 

 dual distances, that the mental eye may repose, 

 as upon a landscape, painted by a master artist. 



But to return to a more immediate view of the 

 subject. It is not a little remarkable that dif- 

 ferent qualities of coal are found in different 

 strata of dissimilar rocks, thus confirming an 

 observation already made, that the quality of 



