258 GENERAL REMARKS ON 



must then have been. But we may also adopt the theory 

 of aestuaries ; arid, in such a case, the deposits of ve- 

 getables in the plastic tlay, and, as the type of both, 

 the similar ones in the existing alluvia of rivers, as in 

 those of the Ganges and Mississipi, become the expla 

 nation. If any one shall prefer this as the exclusive 

 solution of that state of things, he will find arguments 

 in the community of condition, both as to the strata 

 themselves and the imbedded fossils, between the up- 

 per beds of this deposit and the lower ones of the coal 

 series. I do not think that our information is such as, 

 in almost any case, to justify our drawing the infer- 

 ences of geological philosophy too strictly; and I am 

 very sure that the hill of truth will never be reached 

 by shutting up the road which leads to it. 



I may pass over the coal series, since this has de- 

 manded a separate inquiry ; nor need I again notice 

 the revolutions connected with it ; so that the next 

 object of inquiry is the magnesian limestone. I think 

 that the characters of this deposit bespeak a very differ- 

 ent origin from that of the " mountain" or any other 

 limestone in the series ; arid can see no solution of its 

 peculiarities but the following, while I must here add 

 the essential facts on which that rests. 



It contains conglomerate beds, or fragments, mark- 

 ing its production from the degradation of former 

 rocks, thus far at least, and not, like the other lime- 

 stones, from the disintegration of animals- Excepting 

 fuci, of which the explanation under this>iew is easy, 

 it contains no fossil remains, generally at least ; and, 

 of those which have been asserted to exist, there are 

 serious doubts ; from the inaccuracy of observers, con- 

 founding with it some casually associated deposit, per- 

 haps lacustral ; while; though they were proved as to 

 certain localities, this may be explained, for those 

 which should prove terrestrial, under the theory of an 



