GEOLOGY. 



DEEP-SEA DREDGINGS. 



IN his report of the deep-sea dredgings in the Gulf Stream, Pro- 

 fessor Agassiz says : " There is one subject of scientific research, 

 the connection of which with deep-sea 'soundings cannot fail to 

 lead to unexpected results. When attempting to explain the 

 structure of the stratified rocks, and many other phenomena con- 

 nected with the general appearance of the earth's surface, geolo- 

 gists have not hesitated to ascribe, in a general way, the fact under 

 observation to the agency of water ; but they have rarely entered 

 into such specific detail as would establish a causal connection 

 between all these facts and the cause appealed to. In pro- 

 portion as the sea-bottom becomes more extensively known, and 

 the character of the materials lying beneath the water, and their 

 mode of arrangement are ascertained with great precision, more 

 accurate comparisons, in consequence of which current views 

 may have to undergo considerable modifications, will certainly be 

 made between geological formations of past ages, including all 

 their deposits of various kinds, and the materials at present scat- 

 tered in special ways over the ocean floor. 



" From what I have seen of the deep-sea bottom, I am already 

 led to infer that among the rocks forming the bulk of the strati- 

 fied crust of our globe from the oldest to the youngest formation, 

 there are probably none which have been formed in very deep 

 waters. If this be so, we shall have to admit that areas now re- 

 spectively occupied by our continents, as circumscribed by the 

 200-fathom curve or thereabout and the oceans of greater depth, 

 have from the beginning retained their relative outline and posi- 

 tion ; the continents having at all times been areas of gradual up- 

 heaval, with comparatively slight oscillations of rise and subsi- 

 dence, and the oceans at all times areas of gradual depression, 

 with equally slight oscillations. Now that the geological consti- 

 tution of our continent is satisfactorily known over the greatest 

 part of its extent, it seems to me to afford the strongest evidence 

 that this has been the case ; while there is no support whatever 

 for the assumption that any part of it has sunk again to any very 

 great depth after its rise above the surface of the ocean. The 

 fact that upon the American Continent east of the Rocky Moun- 

 tains, the geological formations crop out in their regular succes- 

 sion from the oldest azoic and primordial deposits to the cretaceous 



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