Correspondence— Mr. W. H. Ball. 287 



cos-iaEsiPOisriDEisrciE. 



ELEVATION OF AMEEICA IN THE TERTIARY PERIODS. 



Sir, — I notice in recent numbers of the Geological Magazine 

 that Mr. Upham has been discussing his views on the elevation of 

 the Gulf of Mexico, etc. It seems a pity that gentlemen, who 

 desire to launch such startling hypotheses, should not devote more 

 time to settling the facts upon which these hypotheses are based, 

 before promulgating their new views. As the statements made by 

 Mr. Upham may by many be taken as properly verified, and more 

 confusion be thereby occasioned, permit me to call attention to a few 

 facts which have been verified. 



1. The late Dr. Maack when on the isthmus of Darien did not 

 collect any Pleistocene fossils fi'om the summit of the Atrato divide 

 763 feet above the sea. 2. The Pleistocene fossils collected by Dr. 

 Maack were from an elevation of only 150 feet on the Panama side, 

 ten miles from Panama city. The fossils above this height collected 

 by Dr. Maack are Eocene or Miocene exclusively, and related to 

 the Miocene fauna of Santo Domingo, as indeed was pointed out by 

 Gabb nearly twenty years ago (Proc. Am. Phil. Soc. vol. xii. p. 572). 

 3. The summit or dividing ridge is not fossiliferous, and is probably 

 not later than the Mesozoic epoch. 



I may add, from information to be shortly published, that the 

 supposed great elevation of Florida at any time since the later 

 Eocene is as improbable as any hypothesis which could well be 

 conceived. The conclusions which the facts necessitate in the case 

 of Florida may be briefly outlined as follows : — During the later 

 Eocene, west central Florida was an island, like one of the Bahamas 

 at present, composed exclusively of organic marine sediments which 

 in the Vicksburg epoch attained an unbroken thickness of more than 

 1000 feet. The whole submarine plateau above which the present 

 Florida rises may turn out to be of this age and constitution. This 

 island had a land-shell fauna derived from the south. The strait 

 between the island and the main coast north of it was more than 

 fifty miles wide at the narrowest point, and was only closed at the 

 beginning of the Pliocene. There have been gentle changes of 

 level since the Eocene, but nothing violent, and the vertical range 

 has been small. The Eocene and the old Miocene faunas were of a 

 subtropical character like the Antillean fauna at present. A change 

 took place in Mid-Miocene by which a cool, temperate, or colder 

 vpater fauna invaded the Floriclian region from the north, and about 

 200 feet of strata (Chesapeake Group) were deposited ; equivalent 

 to the well-known Miocene beds of Virginia and Maryland. With 

 the elevation which connected the Floridian islands with the con- 

 tinent a warmer era was again inaugurated in the sea, and an 

 invasion of Pliocene Vertebrates began, on the Peninsula of Florida. 



There were unquestionably great changes of level on the con- 

 tinent, increasing as one goes northward, both in Miocene and 

 Pleistocene times. In the Antilles it has been proved that great 

 changes have taken place. But the Floridian region, for some 

 unknown reason, escaped, and Yucatan, probably, also. 



