AMERICAN GEOLOGISTS ANB NATURALISTS. 55 



104° 50' W., making its distance from Terra del Fuego, the nearest 

 eastern land, one thousand four hundred and fifty miles, and one 

 thousand from St. Peter's and Alexander's Islands, the proximate 

 southern land from which it could have been detached. From its 

 great magnitude, it was the opinion of Mr. C. that should this berg 

 have been driven by the westerly gales which prevail in that region 

 of the Pacific during so large a portion 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 conceiv- 

 ed that the dissolution belo\v the surface by the action of the water, 

 and above it by that of the weather, being unequal in different por- 

 tions of the berg, especially when it was aground, and consequently 

 one side more constantly exposed to ^he sun's rays than the other ; 

 the equilibrium 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 des- 

 truction, from the separation and toppling down of a huge fragment 

 of an iceberg. Had not this latter been still attached to the main 

 tody, 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 

 rotaiy motion it is probable the waste from exposure 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 circiunstances 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 supposed 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 ice- 

 berg 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 further, till from the equilibrium being again 

 destroyed, the rocky portion settles down and resumes its original 

 position. These alternations may occur several times. Driven land- 

 ward by the heavy westerly swell into the continental northern cur- 



