10 Principles of Geology. 



of wide-spread formations ; and finally combining together observa- 

 tions made in distant regions, we ascend to a grand principle of uni- 

 versal analogy in the construction of our planet. If, then, such anal- 

 ogy pervades the structure of different regions, it will be necessary, 

 in stating general laws, to call in the aid of extensive research ; but 

 particular laws for each country can only be derived from local in- 

 vestigation. 



Possibly those who are accustomed to trace across our island the 

 wonderful regularity of strata, or who know the strong resemblance 

 which they exhibit in countries far removed from each other, may 

 have expected more sweeping assertions than I have thought it correct 

 to maintain. They might, perhaps, have been little surprised at a 

 bold declaration, that all our secondary rocks may be discovered 

 with their proper characters over all the continent, when the labors 

 of foreign geologists have been as successful as our own. But this 

 would be an unjust view of the matter; in several instances it is ab- 

 solutely disproved. The utmost that can be expected, is to trace a 

 general conformity and universal analogy of deposits. To what ex- 

 tent this conformity reaches, much as geologists have done, they have 

 not yet demonstrated. It is ascertained that there are certain for- 

 mations which possess a mineralogical character, and a geological 

 position so uniform in all parts of the world, as to allow no doubt of 

 their cotemporaneous origin, and even in some of their subordinate 

 beds an astonishing affinity prevails; but neither these beds, nor the 

 formations themselves, are in all places, continuous in extent, nor con- 

 stant in thickness, nor identical in chemical composition. Hence 

 arise differences in the geological structure of different countries, 

 and the more distant from each other the points of comparison, the 

 less perfect is the agreement of the rocks. Some writers, overlook- 

 ing these differences, have erroneously asserted the universality of 

 formations ; others, not understanding the simple and beautiful gra- 

 dation of nature, have absurdly denied the regular construction of 

 our planet. 



The organic fossils commonly found in the earth are plants, 

 corals, crusts of radiaria, shells of mollusca, the hard coverings of 

 Crustacea, scales and bones of fishes ; reptiles, cetacea, birds, and 

 mammiferous quadrupeds. From very early times, the wonder of 

 mankind has been excited by those fossil shells which are inclosed 



