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geological speculations grounded on the first opinion, 

 be ultimately abandoned. 



The geographical distribution of organic remains, 

 is an exceedingly curious inquiry. If accurately pur- 

 sued, without reference to any preconceived theory, 

 it will no doubt furnish much information as to the 

 comparative ages of the different strata which com- 

 pose the external crust of our planet for that 

 these strata were deposited or formed at periods of 

 time more or less remote from each other, every one 

 knows, to be a generally admitted geological fact. 

 The occurrence of similar fossils in districts of coun- 

 try remotely situated from each other, certainly pre- 

 sents a phenomenon highly interesting to the specu- 

 lative naturalist, and apparently indicates that the 

 same powerful and general causes must have con- 

 curred to produce these isomorphous depositions. 

 No fossils have contributed more to this kind of in- 

 formation, than those of shells, and as the mineralized 

 species could not be satisfactorily studied, except by 

 accurately comparing them with those which now 

 inhabit our seas and continents; the search for shells, 

 has become, from a simple amusement, the study of 

 scientific men or, as a writer remarks, " it was only 

 after the period when it was perceived that geology 

 and ancient zoology were destined to be enlightened 

 by their fossil remains, that this research passed from 

 the hands of amateurs into those of naturalists."* 



* We have not unfrequently noticed, both in the writings and 

 conversation of some geologists, a disposition to sneer at the 

 subsidiary branches of natural history. Mineralogy and con- 



