SURFACE GEOLOGY. 



63 



The bluff of the river is 250 feet above the Lake. An irregular clay ridge is a half 

 mile north of the bluff. This is 260 feet above the Lake, and is composed of bowlder 

 clay, with a surface somewhat irregular from the effects of erosion, but gently sloping 

 to the sandy ridge, D, on which Madison village stands. From this point there is a 

 rapid descent to the level of the railroad, the incline beyond being so gradual that the 

 surface appears quite level, until the gravelly ridge, 0, is reached. Between D and 

 the soil is a gravelly loam, with some clay. Near the ridge, C, it is somewhat swampy. 

 The general slope from B to is very regular, but the surface is much diversified by 

 sand dunes and stretches of marshy land. The ridge at B is made of fine, water- 

 washed and drifted sand. The north ridge, B, continues from Madison to Painesville, 

 and consists of irregular sand dunes, constantly changing in form under the influence 

 of the wind. Where undisturbed, it is from 10 to 12 rods wide, with a gentle descent 

 on each side." 



SECTION OP SOUTH EIDGE, PAINESVILLE, OHIO. 



Coarse unstratified gravel, 12 feet. 

 Fine stratified gravel, 4 feet. 





Coarse gravel, obliquely stratified, 6-12 feet. 



Fine gravel, with irregular waved lines of stratification. 



OKIGIN OF THE LAKE KIDGES. 



In the preceding notes on the lake ridges so much evidence has been 

 furnished that they are raised beaches, that little more need be said on 

 this subject. It is, however, necessary that I should make brief reference 

 to some theories that have been published in regard to the mode of forma- 

 tion of these ridges, and which are inconsistent with the views I hold. 

 Of these theories, one is that advanced by Col. Chas. Whittlesey, who has 

 gathered and published a vast number of interesting facts connected with 

 the Drift of the Western* States, that the lake ridges are sub-aqueous bars 

 which were formed in the Lake, parallel with the shore, when the water 

 stood at higher levels than now. The considerations which prevent my 

 acceptance of this view are : First, that they show too much continuity, 

 regularity of form, and uniformity of level, to have been produced in the 

 manner suggested. Sand-bars, as we know, form off the mouths of rivers, 

 and these, sometimes, have considerable linear extent ; but so far as my 

 knowledge extends, no sand-bars exhibit anything like the extent, con- 



