AND ANALOGIES, OF ROCKS. 227 



but it is necessary here to distinguish between those 

 which are of a local and those which are of a more 

 general nature. 



These rocks are found, both in the antient and 

 recent series ; and, in both, under circumstances pre- 

 cisely similar, if differing in extent. They are pro- 

 perly divisible into general and local ; and it is only 

 indeed by thus distinguishing them, that we can 

 derive any advantage, in our reasonings on events, 

 from the evidences they afford, or avoid the confusion 

 to which, from incorrect observation, they have fre- 

 quently given rise. As, in both the secondary and 

 primary series, similar accidents have occurred, in 

 the fracture, displacement, and transference of strata, 

 it is natural to expect that the conglomerates, here 

 called local, which have resulted from these changes, 

 should be found in both. With respect to the general 

 ones, as they have been produced by that gradual 

 waste of the solid rocks which now forms our super- 

 ficial alluvia, it is natural to expect that they should 

 be found chiefly, and most extensively, at the great 

 interval which separates the primary and secondary 

 strata; and this expectation is realized by the existence 

 of that almost universal conglomerate, the first portion 

 of that red sandstone, which is, itself, the lowest and 

 first of the secondary series. 



If no revolution of so general a nature can else- 

 where be traced, yet partial ones of an analogous kind 

 are found, both in the primary and secondary series; 

 and thus, in both, there exist conglomerates which, 

 if not universal, are still, in the sense here laid down, 

 entitled to the name of general. 



The mechanical origin of all these rocks is so ob- 

 vious, that it is unnecessary to dwell on it; while it 

 is also easy to discover that the component parts have 



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