THEIR DISTRIBUTION. 115 



entirely distinct from one another, and immediately suggest the second 

 inquiry, to which we now proceed. What is the relation between the 

 species of fossils, and the antiquity of their enveloping strata? That 

 such a connexion between the age of a rock and its organic contents 

 does certainly exist, and may plainly be recognised, will appear from a 

 few facts which any one may verify by examining a good collection of 

 Yorkshire fossils, or a sufficient suite of specimens from the same strata 

 in other parts of England. The mountain limestone of the north-western 

 dales of Yorkshire, abounds with crinoidea, productse, spiriferae, and 

 bellerophontes, of which no single individual has ever been found in 

 the strata of the eastern part of the county, which on the other hand, 

 contain echini, trigonias, cucullgeee, rostellarias, and ammonites, to which 

 there is nothing similar in the west. The partition between these groups 

 of strata and their fossils is made by the red sandstone stratum, which, 

 in Yorkshire at least, has never yielded one single organic fossil. The 

 same observation has been made in other parts of England. Again, in 

 the eastern part of Yorkshire itself, a complete partition of the same 

 kind is made by the blue clays of the vale of Pickering, between the 

 chalk on the south and the oolitic rocks on the north ; both full of 

 fossils, and those entirely different. 



I am sure that these assertions will not be disputed by any person 

 at all acquainted with geological phenomena, or accustomed to distinguish 

 the characters of fossils. The consequence flowing from them is of the 

 highest importance and interest ; for since it thus appears, that a few 

 shells brought from a quarry, are data sufficient to determine the geological 

 relations of the rock, we are entitled to conclude, that in a given district 

 the age and position of certain strata, or groups of strata, are infallibly 

 indicated by their organic contents. These researches, commenced by Mr. 

 Smith in England, have been extended with the same results over all 

 parts of Europe, and a large portion of America, and therefore it is con- 

 cluded that strata, or groups of strata, are to be discriminated in local 

 regions, and identified in distant countries, by their imbedded organic 

 remains. 



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