FLORIDA GEOLOGICAL SURVEY 175 



of this conjecture, and also necessitated the restriction to the extreme 

 southern end ' of the peninsula of Professor Le Conte's theory of its 

 growth. 



Dr. George W. Hawes, of the Smithsonian Institution, who had charge 

 of the building stones statistics for this Tenth Census, received from 

 Alachua County, Florida, a sample of so-called building stone, which on 

 analysis was found to contain over 16 per cent of phosphoric acid. This 

 analysis was forwarded to me and was published in the Florida Report on 

 Cotton Culture, volume VI, of the Tenth Census, and is, so far as I 

 know, the first published analysis of this phosphate, since found to be 

 extensively distributed throughout the state and now forming the basis 

 of a great industry. 



In 1884 Daniel W. Langdon, while working for the Geological Survey 

 of Alabama, made his memorable discovery of a series of Miocene forma- 

 tions, as they were then called, ^long Chattahoochee River between Chat- 

 tahoochee Landing and Alum Bluff, thus filling the gap in the knowledge 

 of the stratigraphic sequence of the post-Vicksburg marine Tertiaries of 

 the Gulf Coastal Plain. The third bed from the top of Langdon's section 

 at Alum Bluff is composed of calcareous sands, which contain well pre- 

 served shells of undoubted Miocene age (according to the present nomen- 

 clature). This bed overlies other fossiliferous sands, which Langdon 

 also considered Miocene, but which are now classed by Dall as Upper 

 Oligocene. The lowest member of the Appalachicola River section, a 

 white argillaceous limestone, somewhat resembling the Vicksburg, which, 

 however, it overlies, is seen at Chattahoochee Landing and at several 

 points farther down the river, where it passes below the basal bed of the 

 Alum Bluff section. 



In contrast to the highly fossiliferous sandy marls exposed at Alum 

 Bluff, this limestone contains relatively few fossils; but a sufficient num- 

 ber and variety have been obtained to establish its essential equivalence 

 with the fossiliferous limestone of the Tampa formation at Tampa, 

 Florida. Langdon was correct in considering it a part of the Miocene, as 

 the period name was then applied. For this limestone formation over- 

 lying the Vicksburg he proposed the name Chattahoochee. 



Later investigations have definitely fixed its age and at the same time 

 have led to some changes in the nomenclature, the Vicksburg being now 

 classed as Lower Oligocene, the Chattahoochee and the lower beds ex- 

 posed at Alum Bluff = (Alum Bluff formation) as Upper Oligocene, 

 while of the beds exposed at the bluff only some of the upper retain the 

 name of Miocene (Chesapeake)= (Choctawhatchee formation). 



It is only fair to state that the paleontologists are not yet all agreed 

 as to the necessity for these changes. 



