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upon a topic by which the attention of the Institute was called by Mr. 

 Hyatt. This was upon the dynamics of geology, a subject to which 

 Dr. WinsloAV, in the coui'se of his extensive travels, had given special 

 attention. The Dr. stated that his views of the causes of the general 

 geographical features of the globe, as they at present existed, diflfered 

 from the common theories of geology. He was compelled by his ob- . 

 servations to believe in sudden subsidences of vast continental areas 

 rather than in the slow upheavals of hills, mountain chains and con- 

 tinents. His attention was specially called to this subject when visit- 

 ing the island of St. Paul's, in the Indian ocean. This is an island 

 many hundred feet high, constituting an extinct crater, one side of 

 which has sunk lower than the general subsidence of the land, leaving 

 a channel of seventy feet wide, through which the sea flows with a 

 depth of nine feet. The depth of water in the crater is two hundred 

 feet, and is the same depth outside the bar, and for several miles on 

 the south eastern side of the island. The ocean also pi'esented a dis- 

 colored appearance for one or two days sail to the south east, indica- 

 tive of soundings with no very great length of line. That a great 

 continent once occupied the Indian Ocean is the inference. Continu- 

 ous observation of the various coasts of continents and great islands, 

 and the various aspects of declivities and dislocated strata in high 

 mountainous regions, as of the Atlas, Sierra Nevada, Andes, and Alps, 

 and appearances even among some of the South Sea Islands, had 

 slowly but strongly convinced him that the present theory ought to be 

 carefully examined h\ geologists, with a view to its correction. He 

 had presented two memoirs on this subject to the Boston Society of 

 Natural History, in years past ; and has subsequently found his obser- 

 vations and opinions sustainefl.by those of DeLuc, a Swiss naturalist, 

 whose observations upon the appearances of the Jura, led him (about 

 the middle of the last century) to declare that these mountains re- 

 sulted from subsidences rather than from upheavals. 



This question of subsidence, however, led to other geological con- 

 siderations of a very important character. It involved the necessity 

 of vast caverns between the crust and molten nucleus of the planet, 

 into which the crust, from cycle to cycle, has been rent or plunged- 

 He had shown these to exist, as might be seen by his memoirs, under 

 the northern part of the South American continent, under the Gulf of 

 Mexico and Central America, into which all that area of the planet 

 might at any moment fall, and the oceans be changed. The planet, 

 when life first appeared, must have been five hundred miles larger in 

 all its diameters. This view would comport well with the knowl- 

 edge recently attained, relative to the consideration of physical force. 

 It would also extend this knowledge in cosmical directions. 

 [To be concluded.] 



