No. 200.] 
293 
Avon. Fragments of this rock are profusely scattered over the surface 
near Caledonia. Next in order succeed the limestone shales, extending 
south as far as Moscow. These shales are characterized by the vast 
quantity and beauty of the fossils found in them. 
In the west branch of Beard's creek the septaria appear. An exten- 
sive section of the rocky strata at the entrance of the gorge near Mt. 
Morris dam, is given, embracing two layers of septaria. A few miles 
above the dam the alternations with the grits, or thin strata of sandstone 
first occur. The strata of sandstone are but few feet in thickness, and 
the predominance of the shales is manifest for a considerable distance 
up the river. The location of the Gardow slide is given, which took 
place about 12 years since. Above the slide the occurrence of the 
shales is less frequent, though the predominance of sandstone is not 
apparent below the lower falls of Portage. It was not intended to give 
all the angles and cliffs along this portion of the river, only such as are 
important and will tend to convey a general idea of the geology of this 
section of country. The accompanying section from Lake Ontario to 
Instantur, a town a few miles south of Smithport, Pennsylvania, exhi- 
bits the relative proportion of grits and shales. 
The lower falls are 96 feet in height. The river, except in times of 
high water, is confined to the lower narrow channel given on the map. 
Between the lower and middle falls the perpendicular elevation of 
the rocky strata, in the highest point, is 351 feet. The middle falls, 
which are more generally visited, are 110 feet in height. The olive 
sandstone in the vicinity of the upper falls, is noted. Height of the 
upper falls 66 feet. 
At Portage, the river enters the gorge, from which, after passing 
three successive falls, and for most of the distance descending with 
great rapidity, it passes into the Genesee valley, near Mt. Morris. 
It will be noticed that boulders are scattered about upon the surface 
with a degree of profusion below Mt. Morris. Above this point their 
occurrence is less frequent. 
From Moscow, along the river to Rochester, very little evergreen 
timber is found, while in going south a small distance, as the subsoil is 
more and more composed of disintegrated sandstone, the pines and hem- 
locks, with their associates, are more frequent. 
A few species of fossils occurring at the different localities, have their 
names respectively set to the right of the localities in the margin. 
