O THE WONDERS OF GEOLOGY. 



advantage. Our beautiful planet is indeed worthy of our study ; 

 it was once our cradle — it will soon be our grave, — between the 

 dawn and the night of life, it is the scene of our busy action, and 

 from it we shall rise to another state of being. t 



6. Discovery of useful Minerals. — Geology discloses to us 

 the valuable minerals, and teaches us where they are likely to be 

 found, and where research would be vain. 



Coal. — Coal is, without doubt, wholly of vegetable origin : hun- 

 dreds of species of plants have been distinguished in the coal forma- 

 tion, but none of these have been found living on the earth, although 

 many of the families still exist ; the recent allied species are generally 

 of a diminutive size, in comparison with those of the coal period, 

 and those that approach the ancient in magnitude, are chiefly found 

 in tropical climates. 



Duly informed in geology, we should never look for coal in 

 granite,* nor among the most ancient rocks ; and in the wide inter- 

 vening series, a large part of the formations are excluded from the 

 association with this most important mineral. Slates, shales, and 

 limestones, charged with bitumen, afford indications of some value, 

 but not decisive, as bitumen is associated with many minerals that do 

 not belong to coal formations. The impressions of plants in the 

 rocks, especially those charged with bitumen, strengthen the pre- 

 sumption, and should we find fragments of coal scattered in the soil, 

 or mingled with gravel and sand in the banks and water courses, or 

 observe dark masses of earth, which, on close inspection, appear to 

 contain fine coaly matter, we may infer that beds of this combus- 

 tible may be near, and that it may be proper to dig or bore ; and 

 when, at last, we find the beds of coal, they will be regularly 

 arranged between a roof and floor of coal-slate or shale. But it by 

 no means follows, that beds of shale and slate necessarily indicate 

 coal ; those of the primary series would scarcely contain any com- 

 bustible, unless it were plumbago, or possibly a little anthracite. 

 The geological laws of coals are very strict, and a thorough 

 acquaintance with them is the only safeguard against fruitless 

 enterprises. 



Lignite. — It is easy to mistake beds of lignite for coal : lignite, 

 when found in sufficient abundance, is a valuable combustible, but it 



* Coal strata sometimes repose upon granite, (not in it,) as in France, and near 

 Richmond, in Virginia. 



