J. B. Dana on the Quaternary of the New Haven Region. 3 



that the unstratified drift might have been dropped over the 

 hills by icebergs ; but, as Mr. Croll has recently urged, deposi- 

 tions in water cannot be made without stratification. The 

 slightest jar of a vat of water holding sediment suspended will 

 cause that sediment to go down in a laminated state ; and so de- 

 posits of sands and gravels in the ever moving sea will always 

 manifest their aqueous origin. The stratified and unstratified 

 material about New Haven therefore mark the limit between 

 aqueous and dry-land dep<:»sition. Much has been said about 

 " modified drift^' or more or less stratified drift deposits, over 

 the hills ; but they occur no where, according to my observation, 

 except along water courses or about the sites of old lakes ; they 

 sustain the conclusion that the unstratified drift was essentially 

 a dry land deposition. 



2. The magnitude, wide distribution, and regularity of direc- 

 tion in the scratches are evidences against Icebergs. 



This is no new argument ; yet it has lost nothing of its force 

 by long use. Broad furrows, eight to ten inches in depth, made 

 in trap or granite over long distances, uniform in direction, 

 must have required prolonged abrasion for scores of yeai-s, and 

 by an abrading agent not liable to change of course through 

 tides or currents, or to changes of form and thereby of center of 

 gravity from waste in the waters over the rocks. Glacial abra- 

 sion has been found so generally wherever the soil has been 

 freshly removed that it may be safely inferred, as has been 

 done for other parts of New England, that the abrasion was 

 universal. Passing from the New Haven region westward, over 

 the high plateau of Litchfield, Warren, et€., 1000 to 1500 feet 

 in height above the sea, the scratches have the same uniformity 

 and wide distribution. Grounded icebergs would be suflicient 

 for such results only in case they spread completely over the 

 wide surface and rested firmly upon its every part,— in which 

 case they would be nothing less than partly submerged gla- 



3. The scratches are, in some cases, in such positions that only 



the Connecticut valley depression, about 750 feet in height, nine 

 miles north of New Haven— along one of the steep southern 

 valleys, the surface of trap (dolerite) is extensively abraded, 

 and marked with many large and broad north-and-south far- 

 rows. An iceberg, moving southward, which could float over 

 the top of Mount Carmel ridge would not touch bottom in this 

 southern valley, for the part eroded is at least 150 feet below 

 the level of the rido-e to the north of it. While this erosion is, 

 .v._„r_... , . ,? --^^iceb 



