GEOLOGY. 309 



nearly parallel ranges, which enclose elevated valleys. The third extends 

 from Snake River on the north to the parallel of 40 degrees. Mr. Blake pro- 

 posed new names for these three ranges. The first he proposes to call the 

 Anahuacian ; the second, the California Chain ; the third, the Aztecian 

 Chain. 



OX THE AGEXCY OF THE GULF STREAM IX THE FOEMATIOX OF 

 THE PEXIXSULA AXD KEYS OF FLORIDA. 



The following paper was read before the Albany meeting of the American 

 Association for the Promotion of Science, by Mr. J. Le Conte : 



Until the explorations of Agassiz and Tuomey, the geology of Florida had 

 not been known, it being supposed to consist of a prolongation of that of 

 Georgia and Alabama; but these gentlemen made known the remarkable 

 fact that the keys and most of the Peninsula are of recent origin, and, so far 

 as they examined, are the work of corals, still living in the vicinity and still 

 at work. The object of the present paper was to show that coral agency 

 alone was not sufficient to account for the phenomena, but that another and 

 more powerful agent has been at work preparing the foundation for the 

 builders, and that this agent was the Gulf Stream. A section was drawn 

 upon the blackboard, dividing the lower part of Florida into three sections 

 the more northerly bounded by a line from Tampa Bay north-easterly to the 

 Atlantic ; a second from Charlotte's Harbor, parallel to this ; and a third, also 

 parallel, from Chatham Bay. 



These lines are also parallel to the line of coast at the extremity of the 

 peninsula. Parallel also is the line of islands, the keys, separated from the 

 shore by a ship channel, and still further outside the line of living coral reef, 

 just on the edge of the Gulf Stream. The living reef is some five to ten 

 miles from the keys, and the keys some forty miles from the coast, the water 

 here being very shoal and dotted over with small mangrove islands. The shore 

 is some twelve or thirteen feet above the sea, but inland the so called Ever- 

 glades sink, and are but a few feet above water, varied by fresh ponds and 

 hammocks. Outside the living reef the sea bottom slopes rapidly to almost 

 unfathomable depths. This description being kept in mind, the theory to be 

 presented will be clear. That the Southern coast, the keys, and the Ever- 

 glades are the work of coral agency there is no doubt. But as corals cannot 

 grow above the surface of the water, their agency alone is not sufficient the 

 violent action of the winds and waves is necessary to break off masses of the 

 coral and bear them within the line of the reef. Here these coral boulders 

 become the nuclei around which smaller pieces of coral, sand, and other sub- 

 stances collect, become cemented by the carbonate of lime in the sea water, 

 and so at length the whole becomes an island clothed with vegetation. All 

 these processes may be seen going on at the keys and reefs of Florida, There 

 is the soh'tary boulder, that already is the centre of a mass of coral debris, and 

 so on up to the inhabited island. The coral sand hi these islands is found 

 always affected by that kind of stratification caused by the action of violent 

 waves. The idea of Prof. Tuomey that the masses of coral exposed above 

 the sands and soils of some of the islands are the tops of ancient coral trees 



