SURFACE GEOLOGY. 59 
unfrequently find a marsh created by 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 Hlyria, 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 
