208 GEOLOGY OF OHIO. 



ern part of the township, and having an altitude of 200 feet. Near 

 Elyria this south ridge divides into two parallel ridges, which turn up 

 the valley of Black River and reappear in Carlisle, Eaton, and Ridge- 

 ville, there known as Chestnut Ridge and Butternut Ridge. Thence they 

 continue easterly, with some interruptions and interlocking, till they 

 reach Brooklyn, Cuyahoga county, and curve southward into the valley 

 of the Cuyahoga. In Ridgeville, which has taken its name from the 

 ridges, four distinct ridges have been identified, while another, the most 

 continuous of all, passes further north through Avon. 



The want of uniformity in the elevation of the surface in different 

 parts of these ridges is not greater than we should expect to find in the 

 circumstances. No one who will examine the composition of the ridges, 

 and trace their courses on the map, will doubt that they are contour 

 lines inscribed upon the topography by the action of shore waves. But 

 on all sea beaches we find that the materials thrown up by the shore 

 waves, or blown up by the wind, rise to somewhat different heights in 

 different localities, according to the exposure and to the abundance and 

 fineness of the material. Where this is sand, it is not generally thrown 

 up to any great height by the waves, but it is often caught by the sea 

 or lake winds, and heaped up much beyond the reach of wave action. 

 Hence the ridges were doubtless higher in some places than others when 

 first formed, and this inequality may have been exaggerated by the sur- 

 face erosion to which they have been exposed during the ages which 

 have since elapsed. By surface erosion they have also been frequently 

 cut through, and perhaps locally quite removed; and to this cause we 

 must attribute many of the gaps and interruptions which break their 

 continuity. 



The ridges parallel with the south shore of Lake Erie are sometimes 

 continuous with and run into terraces ; that is, the waves cut steps, or 

 notches, into the shore where it was abrupt and hard — washed up mate- 

 rial and formed ridges along the same line where it was low and soft. 



In the same way we now see a cliff forming at Avon Point, and a ridge 

 being raised between the mouth of Huron River and Cedar Point, Erie 

 county. In some places, also, a terrace left by the old shore waves is 

 composed of unstratified Drift clay. In such localities the declivity has 

 been mistaken for a ridge, and from the nature of the materials compos- 

 ing it some erroneous ideas have been conceived in regard to the origin 

 of the lake ridges. Precisely such terraces as I have referred to may, 

 however, be seen now forming near Cleveland, and at other points where 

 the immediate shore of the Lake is composed of Drift clay. 



Drift Deposits. — As has been mentioned, most of the surface of Lorain 



