258 Address before the Association of American Geologists. 



more than two hundred feet high, which occur in Plymouth and 

 Barnstable counties in Massachusetts. I see nothuig in this the- 

 ory that will explain such astonishing accumulations in such cir- 

 cumstances ; and yet their existence may not militate against its 

 truth. For even the present mighty glaciers of the Alps, may 

 give us but a faint idea of the effects of the advance and retreat 

 of a sheet of ice thousands of feet thick. We have no evidence 

 in this country, that any of our mountains have been elevated 

 since the glacial epoch ; as seems to be proved to have been the 

 case with the Alps, and this circumstance may have produced a 

 considerable modification of glacial action on this continent. 



I do not mention these difficulties (to which I might add more,) 

 as any strong evidence against this theory. For so remarkably 

 does it solve most of the phenomena of diluvial action, that I am 

 constrained to believe its fundamental principles to be founded in 

 truth. Modifications it may require : for it would be strange 

 enough if it had already attained perfection, even in the skillful 

 hands that have thus far framed and fashioned it. But I can 

 hardly doubt that glacio-aqueous action* has been the controlling 

 power in producing the phenomena of drift. Having hovered so 

 long over the shoreless and troubled ocean of uncertainty and 

 doubt, I may be too ready to alight on what looks like terra firma. 

 But should it prove a Delos, I have only to plume my wings 

 again, when it sinks beneath the waves. 



I have dwelt long on this subject; its great importance, its in- 

 teresting aspect at this time, and its wide developement in our 

 country, must plead my apology. 



In referring to our alluvial formations I shall call your atten- 

 tion only to a single subject, and that is, microscopic palaton- 

 tology. The splendid discoveries of Ehrenberg in this depart- 

 ment, were yet fresh among us, when Prof. Bailey demonstra- 

 ted that similar relics abound in this country. They form ex- 

 tensive deposits, covering many acres, and sometimes several 

 feet thick, beneath our peat-bogs. The substance appears to be 

 the Bergmehl, ov mountain meal, ox fossil farina, of the Germans, 

 and is mostly composed of the Shields or Carapaces of the family 

 Baccillarice. Some do, indeed, yet doubt the animal origin of 



* By which I mean the joint action of ice and water, without deciding which 

 has exerted the greatest influence. 



