J. D. Dana on American Geological History. 323 



and everywhere bears evidence of having been thrown out soon 

 after the deposition of the sandstone, or in connection with the 

 formation of its later beds. Even the small sandstone region of 

 Southbury in Connecticut, has its trap. 



Thus ended in fire and violence, and probably in submergence 

 beneath the sea, the quiet plains of the Connecticut valley, where 

 lived, as we now believe, the first birds of creation ; kinds that 

 were nameless, until, some countless ages afterwards, President 

 Hitchcock tracked them out, found evidence that they were no 

 unworthy representatives of the feathered tribe, and gave them 

 and their reptile associates befitting appellations * 



Such vast regions of eruptions could not have been without 

 effusions of hot water and steam, and copious hot springs. And 

 may not these heated waters and vapors, rising through the 

 crystalline rocks below, have brought up the copper ores, that 

 are now distributed, in some places, through the sandstone? 

 The same cause, too, may have given the prevalent red color to 

 the rock, and produced changes in the adjoining granite. 



After the era of these rocks, there is no other American rec- 

 ord during the European Jurassic Period. 



In the next or Cretaceous Period, the seas once more abound 

 in animal life. The position of the cretaceous beds around the 

 Atlantic border shows that the continent then stood above the 

 sea very much as now, except at a lower level. The Mississippi 

 valley, which, from the Silurian, had generally been the region 

 of deeper waters, was even in cretaceous times occupied to a 

 considerable extent by the sea, — the Mexican Gulf then reaching 

 far north, even high up the Missouri, and covering also a con- 

 siderable part of Texas and the Eocky Mountain slope. 



An age later, the Cretaceous species had disappeared, and the 

 Mammalian Age (or the Tertiary, its first Period) begins, with a 

 wholly new Fauna, excepting, according to Professor Tuomey, 

 some half a dozen species, about which however there is much 

 doubt. The continent was now more elevated than in the pre- 

 ceding age, and the salt waters of the Mexican Gulf were with- 

 drawn from the region of Iowa and Wisconsin, so as not to 

 reach beyond the limits of Tennessee. f 



* Mr. J. Deane of Greenfield was also an early explorer of these tracks, and 

 is now engaged in publishing on the subject, illustrating his memoir with plates of 

 great beauty and perfection. 



f The recent investigations of F. B. Meek and Dr. J. V. Hayden, have shown (Proc. 

 Acad. Nat. Sci. Philad., viii, 111, 1856,) that while there is much fresh-water tertiary 

 in the Nebraska regions and beyond, there is also about the head waters of the 

 Missouri some marine tertiary. The region investigated lies between the 46th and 

 49th parallels of North latitude and the 100th and 108th degrees of longitude : but 

 it is not yet ascertained whether the body of salt water thus indicated was an isola- 

 ted area, or an arm from the Mexican Gulf. The shells, (species of Ostrea, Corbula, 

 and Cerithium) do not satisfactorily fix the age of the tertiary, but suggest, the 

 authors say, that it may be the older Eocene. They occur in the same beds with 



