STUDY OF THEM INDISPENSABLE. 93 



organic remains, would be no less absurd than to undertake 

 to write the history of any ancient people,^without reference 

 to the documents afforded by their medals and inscriptions, 

 their monuments, and the ruins of their cities and temples. 

 The study of Zoology and Botany has therefore become as 

 indispensable to the progress of Geology, as a knowledge 

 of Mineralogy. Indeed the mineral character of the inor- 

 ganic matter of which the Earth's strata are composed, 

 presents so similar a succession of beds of sandstone, clay, 

 and limestone, repeated irregularly, not only in diflerent, 

 but even in the same formations,* that similarity of mineral 

 composition is but an uncertain proof of contemporaneous 

 origin, while the surest test of identity of time is afforded by 

 the correspondence of the organic remains : in fact without 

 these, the proofs of the lapse of such long periods as Geo- 

 logy shows to have been occupied in the formation of the 

 strata of the Earth, would have been comparatively few 

 and indecisive. 



The secrets of Nature, that are revealed to us, by the 

 history of fossil Organic Remains, from perhaps the most 

 striking results at which we arrive from the study of Geo- 

 logy. It must appear almost incredible to those who have 

 not minutely attended to natural phenomena, that the micro- 

 scopic examination of a mass of rude and lifeless limestone 

 should often disclose the curious fact, that large proportions 

 of its substance have once formed parts of living bodies. 

 It is surprising to consider that the walls of our houses are 

 sometimes composed of Httle else than comminuted shells, 

 that were once the domicile of other animals, at the bottom 

 of ancient seas and lakes. 



It is marvellous that mankind should have gone on for 



* The same formation which in England constitutes the argillaceous de- 

 posites of the London Clay, presents at Paris the sand and freestone of the 

 Calcaire Grossicr ; whilst the resemblance of their Organic remains proves 

 the period of their deposition to have been the same, notwithstanding the 

 difference in the character of their mineral ingredients. 



