44 GEOLOGY OF OHIO. 



clay, all tlie Atlantic coast north of New York has been raised, although 

 very unequally; the elevation increasing northward from fifty to sixty 

 feet in southern New England, to one thousand eight hundred feet at 

 Polaris Bay, Greenland. 



Professor K. W. Hilgard has shown that the country about the mouth 

 of the Mississippi, during the Quarternary Age, changed its level a 

 thousand feet or more, and the facts which he reports are altogether in 

 keeping with those observed higher up the valley. The manner in 

 which the Loess is spread demonstrates that the region where it occurs 

 was covered with water at the time of its deposition, and we know that 

 it was mainly the silt transported by the Missouri, arrested in its passage 

 to the Gulf — where it is now deposited — and diffused through quiet water, 

 which, at one time, apparently, occupied the whole valley as far north 

 as the Great Lakes. With these submergences, the filling of the lake- 

 basin had, perhaps, nothing to do, for, as we have shown, the water it 

 contained was fresh, and was, doubtless, derived from the melting of the 

 glaciers and snow fields of the north. 



LAKE EIDGES. 



The old beaches which encircle the lakes have been fully described in 

 our second volume, and the proof that they are what they are commonly 

 called has been given at length. The mistaken notion that they are 

 moraines is, however, still entertained by some persons who have not 

 carefully studied them, so that it is, perhaps, desirable to recapitulate 

 very briefly here the proofs that they are "raised beaches." 



First. The true lake ridges, three or four in number, are found mark- 

 ing the south shore of Lake Erie, up to the height of two hundred and 

 fifty feet above its present surface, in horizontal lines, that conform to 

 all the topography, precisely like the " Parallel roads of Glenroy." They 

 are, in fact, contour lines on the surface, and hence water-lines. No 

 glacier would give such uniformity of height and dimension, such hori- 

 zontality and parallelism to the terminal or lateral moraines, which it 

 left as it shrunk in volume. 



Second. The lake ridges are composed of beach and not moraine 

 material; that is, they consist of gravel and sand, the former water- 

 worn and rounded, with sometimes sticks, leaves, and, it is said, fresh 

 water shells. 



Third. Where the line of an old beach passes round a headland, or 

 along a steep declivity, it becomes a terrace — as at Berlin Heights, 

 Cleveland, etc. This would be necessarily true of a shore line, but never 

 of a moraine. 



Fourth. The ridges sometimes rest on stratified sands and clays — as 



