STJKFACE GEOLOGY. 59 



unfrequently find a marsh createdby a ridge which presents a barrier to the passage 

 of water to a lower level." 



The lake ridges have not been carefully traced throughout their entire 

 extent, as this was a task which required more time and money than we 

 have felt justified in devoting to it ; but they have been carefully exam- 

 ined and mapped in many different localities, and the succession at these 

 points shows a remarkable correspondence. In some places, where the 

 topography of the lake shore has been irregular, the ridges are much 

 broken up and run into each other, in such a way that it is very difficult 

 to trace them. This has led to some confusion of identity, and has caused 

 an unwarranted variation of level to be assigned to some of them. On 

 abrupt declivities, as has been mentioned, these old shore lines are 

 represented by terraces. A very good example of this is seen at Berlin 

 Heights, Erie county, where the highlands approach nearest to the lake 

 shore and the connection of the ridges is broken. Here the base of the 

 bluff is 60 feet above the Lake, and it shows on its slope three terraces, 

 at the heights respectively of 100, 150, and 195 feet. Similar terraces 

 may be seen on the slope of the headland which bounds the valley of the 

 Cuyahoga on the east at its mouth. Here the old delta of the Cuyahoga 

 forms a plain, which surrounds the base of the declivity, and is traversed 

 by a ridge, of which the elevation is about 100 feet. Two terraces are 

 seen over it, one of which is 165 and the other 210 feet above the Lake. 

 We, therefore, have here three shore lines, which correspond to those on 

 Berlin Heights ; the slight differences of level reported in the two cases 

 being due, perhaps, to irregularities in the surface of the terraces, or differ- 

 ences in the reading of the barometers employed. The lake ridges be- 

 tween the Vermilion river and the Cuyahoga have been examined by 

 Prof. A. A. Wright and myself, and they will be found described in detail 

 in the reports on the geology of Lorain and Cuyahoga counties ; their 

 relations will also be seen at a glance by reference to the accompanying 

 map. It will be noticed that in some instances the ridges curve up into 

 the valleys of the rivers, as on the Cuyahoga at Cleveland, and the Black 

 river at Elyria, while, in other instances, they terminate abruptly at the 

 sides of the valleys, and their bearings are unchanged by these topo- 

 graphical features. This is noticeable in all the ridges which cross 

 Rocky river, and in the crossing of all the streams by the lower ridge. 

 The cause of this is to be found in the general topography of the lake 

 shore, upon which these old beaches are contour lines, marked by the 

 shore waves at the water level. The valley of the Cuyahoga was, as we 

 know, deep and broad near its mouth, and was only partially filled by 

 the Drift sediments. Hence, when the upper ridges were formed, it was an 



