ON GEOLOGY, 



t o crystallize and consolidate after the formation of granite, in the order in 

 which we have already traced them ; and some of these before the whole 

 of the granite was rendered perfectly firm, whence we trac-^ beds of seve- 

 ral of them in the granite formation itself ; and as the same kind of action 

 appears to apply (o the whole, we, in like manner, trace beds of the newer 

 rocks successively in formations of those that are older ; and, at last, re- 

 mains of animal and vegetable materials, which are hence proved to have 

 had an existence coetaneous with the newer classes. 



The law of gravity appears to have operated through the whole of this 

 process : and hence, water, as the least heavy material, must have risen to 

 the surface, and purified itself by a filtration through the other materials, 

 and at length collected in such hollows as were most convenient for its 

 reception : these hollows constitute the bed of the ocean. 



Water, thus collected in the cavity of the ocean, is carried by the at- 

 mosphere over the tops of the most elevated mountains, on which it is pre- 

 cipitated in rain, and forms torrents, by which it returns with various de- 

 grees of rapidity into the common reservoir. This restless motion and 

 progress of the water in the form of rain or torrents gradually attenuate and 

 wear away the hardest rocks, and carry their detached parts to distances 

 more or less considerable ; whence we meet with limestone, clay, quartz 

 or flint, sand, and mineral ores, in places to which they do not naturally 

 belong. The influence of the air, and the varying temperature of the 

 atmosphere, facilitate the attenuation and destruction of these rocks. 

 Heat acts upon their surface, and renders it more accessible, and more 

 penetrable to the moisture, as it enters into their texture ; the limestone 

 rocks are reduced by efliorescence, and the air itself affords the acid prin- 

 ciple by which the eflilorescence is continued. Such are a few of the nu- 

 merous causes that contribute to the disunion of concrete bodies, and 

 powerfully co-operate with that wonderful fluid which alternately forms 

 and unforms ; which creates, decomposes, and regenerates all nature. 



The immediate effects of water in the shape of rain is to depress the 

 mountains. But the materials which compose them must resist in propor- 

 tion to their hardness ; and hence we ought not to be surprised at meeting 

 occasionally with peaks, which have stood firm amid the wreck of ages, 

 and still remain to attest the original level of the mountain-breadths which 

 have disappeared. These primitive rocks, alike inaccessible to the assault 

 of time and to that of the once animated beings which cover the less ele- 

 vated heights with their reUcs, may be considered as the origin of streams 

 and rivers. The water which falls on their summits flows down in torrents 

 by their lateral surfaces. In its course it wears away the soil upon which 

 it is incessantly acting. It hollows out channels of a depth proportioned 

 to its rapidity, its quantity, and the hardness of the rock over which it pass- 

 es, and at the same tide carries along with it fi-agments of such stones as 

 it loosens in its progress. 



These stones, rolled by the water, strike together, and mutually break 

 off" their projecting angles : and hence we obtain collections of rounded 

 flints which fine the beds of rivers, and of smaller pebbles which the sea is 

 perpetually throwing upon the shores, often incrusted with a gravelly or 

 calcareous edging. The powder which is produced by the rounding of 

 the flints, or is washed down from the mountains, frequently stagnates, 

 forms a paste, and agglutinates into fresh masses of the rocky matter of 

 which it consists ; often imbedding flints and other materials, and consti- 

 tuting compound substances known by the name of pudding-stones and grit- 



