RELATION OF BIOLOGY TO GEOLOGICAL INVESTIGATION. 285 



somewhat general among fchem that the consolidation <>f the sedimen- 

 tary rocks, and also in part their displacements, were secularly accom- 

 plished and therefore that such conditions are to that extent indicators 

 of their relative age; but these views did not long survive. 



When the fossil faunas and floras which characterize each of a given 

 series of sedimentary formations are compared with those which sev- 

 erally characterize the formations of the next preceding and suc- 

 ceeding series, and the whole are systematically compared with living 

 faunas and floras, there is to be observed among those fossil forms, when 

 studied in connection with an unbroken vertical range of formations, 

 an order of successive changes and modifications indicative of a general 

 advance in biological rank and also an indication of structural relation- 

 ship. Furthermore, when the faunas and floras of a given series of 

 formations are compared with those of other series in other parts of the 

 world, it frequently appears that there is a close similarity between 

 those of a certain portion of each series which indicates their correla- 

 tion. In such cases an order of biological rank is to be observed sim- 

 ilar to that which was observed in the original case. It also frequently 

 occurs that the range of rank is found to be greater in one or both direc- 

 tions than is to be observed in other cases. By such means a knowl- 

 edge of the order of faunal and floral, as well as of stratigraphical, suc- 

 cession far beyond that which could be obtained in anyone region, has 

 been acquired. 



It is upon such empirical facts as these that the early geologists 

 based their investigations concerning the chronological arrangement 

 of the sedimentary formations of the earth, the grand result of which 

 was the adoption of a general scheme and the construction of a corre- 

 sponding scale for their classification. This scale, which in its present 

 condition is a masterpiece of inductive reasoning, necessarily originated 

 in Europe, because it was there that geology was first systematically 

 studied, and it is there also that its adaptation is more complete than 

 elsewhere. The first of the two following tables, the one to which, for 

 the sake of convenience, the date 1840 is given, represents the scale in 

 a condensed form as it was recognized and approved by leading geolo- 

 gists at, and a few years both prior and subsequent to, the date men 

 tioned. 1 



The second table, the one bearing the date 1890, has been compiled 



ft is not my purpose to discuss historically* any of the questions referred to in 

 these essays, but it is proper to remark that Cuvier and Brongniart seem to have 

 been the first to apply paleontology to tin- study of structural geology (1800-1812), 

 and that William Smith did the same, apparently independently of the two authors 

 .just named, in 1816, 1S17. In lsli) Brongniart advanced the idea of correlating dis- 

 tinctly separated formations by means of fossils. After the latter date these ideas 

 rapidly gained acceptance, and the first steps toward the construction of a genera] 

 geological scale soon followed. 



