254 Prof. Rogers^s Address before the 



they are invaluable in establishing approximate identity of age between 

 large groups of strata, separated in all other respects from each other, 

 they fail entirely to fix the equivalency of particular members or form- 

 ations, and from their obtuseness to ordinary changes they are the least 

 instructive of all the species in respect to the special events and condi- 

 tions of their epoch. 



CAINOZOIC OR TERTIARY PERIOD. 



Our knowledge of the tertiary strata of the Atlantic seaboard has 

 been considerably advanced during the last three years, through the re- 

 searches of Mr. Conrad, Mr. Lyell, Prof. W. B. Rogers, Prof. Bailey, 

 Prof. Booth, and Mr. Henry Lea, while Prof. Emmons has made us ac- 

 quainted with the contents of the modern tertiary of Lake Champlain. 

 We may confidently anticipate further contributions to this very inter- 

 esting portion of American geology from Mr. Conrad and Mr. Tuomey, 

 who are engaged I believe at present in exploring some portions of the 

 southern strata. The plan which I have assigned to myself in this ad- 

 dress will require me to confine myself to the principal results arrived at. 



Mr. Conrad, to whom this branch of our geology is so largely in- 

 debted, has, in a neat and instructive synopsis of his own labors, printed 

 in the second bulletin of the National Institute, renewed a statement for- 

 merly made by him, that our older tertiary is linked to the newest sec- 

 ondary or cretaceous strata by the possession in common of three species 

 of organic remains. Every fact which would tend to restore any part 

 of that lost leaf in the earth's chronology, the absence of which marks 

 the abrupt transition from the secondary to the tertiary periods, would 

 be hailed with general interest ; for, although the interruption in the 

 succession of species at the close of the cretaceous epoch is hardly 

 greater than prevails in other portions of geological time ; and though 

 the discoveries of Ehrenberg have partially bridged the chasm, yet the 

 very loide extent of this horizon of discontinuity throughout Europe and 

 America, lends it much importance. It was therefore a principal object 

 with Mr. Lyell, in his visit to the tertiary strata of the Carolinas and 

 Georgia in 1842, to investigate the evidence for the alleged passage of 

 certain cretaceous species into the lower eocene strata. Having done 

 so, he mentions that he was " unable to find any beds containing an in- 

 termixture of cretaceous and tertiary fossils," and he affirms that " the 

 facts at present ascertained will not bear out the conclusion that any beds 

 of passage exist in the southern states."* It is to be observed, how- 



* See Proceed Geol. Soc. London, No. 89. 



