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Association of American Geologists and Naturalists. 161 



gales which prevail in that region of the Pacific during so large a por- 

 tion of the year, into the current setting constantly to the northward 

 along the whole west coast of South America, it might have floated to 

 the verge of the tropics ere it dissolved entirely, or perhaps been 

 stranded somewhere about the shores of the Chilean Archipelago. 



The attention of the Association was called to the fact of such large 

 masses of rock, which were undoubtedly once at the bottom of the 

 berg, being exposed on its face or sides, Mr. Couthouy conceived that 

 the dissolution below the surface by the action of the water, and above 

 it by that of the weather, being unequal in different portions of the 

 berg, especially when it was aground, and consequently one side 

 more constantly exposed to the sun's rays than the other ; the equilib- 

 rium would be occasionally destroyed, the result of which would be 

 an overturn, like that witnessed upon the Grand Banks, bringing to the 

 surface portions of the mass containing rocks and earth. The U. S. 

 ship Peacock, during her last cruise of discovery in the Antarctic Ocean, 

 while attempting to penetrate the great barrier of ice, was seriously 

 injured, and narrowly escaped utter destruction, from the separation and 

 toppling down of a huge fragment of an iceberg. Had not this latter 

 been still attached to the main body, there can be no question but that 

 one of the violent overturns referred to, would have followed such a 

 change in the proportions of the berg. Again, in the case of a drifting 

 island, where from its rotary motion it is probable the waste from expo- 

 sure would be nearly equal on all sides, it is evident that the side in 

 which the rocks were imbedded, would, owing to their specific gravity 

 being much greater than that of the ice, gradually preponderate, and 

 either produce a sudden and violent change of axis, or slowly settle 

 down once more, according as circumstances varied. In smooth, 

 still water, the latter would probably occur, while the former might be 

 expected to happen in a tempest or a heavy sea. In connection with 

 these facts, Mr. C. submitted the following supposititious case, as one 

 by no means of improbable actual occurrence, the first portion of which, 

 indeed, was merely a statement of what had really taken place in the 

 great iceberg last described. Suppose an island of ice to be detached 

 from the great southern barrier, having its base loaded with rocks, 

 &c., and after drifting several hundred miles northward, to experience 

 an overturn bringing these rocks to the surface. It then floats on for a 

 considerable distance farther, till from the equilibrium being again 

 destroyed, the rocky portion settles down and resumes its original posi- 

 tion. These alternations may occur several times. Driven landward 

 by the heavy westerly swell into the continental northern current, it is 

 at length stranded on the coast of South America, and undergoes one 

 or more overturns, bringing up at each time an additional amount of 

 Vol. xLiii, No. 1.— April-June, 1842. 21 



