EXTENT OF THE WHEAT -REGION. 181 



From the lake to the beginning of the Marcellus shale 

 — No. 6 on this section, at a height of 216 feet, the level 

 of Seneca Lake — is about thirty miles. The rise of the 

 country, therefore, is very gradual ; indeed, it is com- 

 paratively level after the first ascent over the Niagara 

 limestone till v/e reach the Marcellus shale. Beyond this 

 shale it rises more rapidly ; and at Ovid there is a bold 

 escarpment where the two bands of limestone occur. 

 In other parts of the country there are also bolder escarp- 

 ments along the out-crop of the Niagara and Helderberg 

 limestones than the section shows, forming marked and 

 successive steps as we advance into the interior. 



From the lake to the Marcellus shale is the proper 

 wheat-district, though in some places it extends to the 

 Genesee slate, and may ultimately, under a better system 

 of culture, be generally extended thus far. But the 

 rapid rise of the land, by altering the climate, will always 

 make this higher region less propitious to vegetation, 

 supposing the soil as good as those of the Onondaga and 

 more northern formations. 



No. 1. The Medina sandstone consists of layers of 

 brownish sandstone intermixed with shales. It presents 

 an interesting illustration of a fact of much importance 

 in agricultural geology, that the same formation at dif- 

 ferent parts of its extent may produce soils very different 

 in their natui'e. Towards the east, the sandstone greatly 

 predominates, forming sandy soils comparatively poor in 

 agricultural value. But towards the west, the shaley or 

 clay beds increase in number or thickness ; so that sandy 

 loams, and finally clay loams, and excellent wheat-soils, 

 are produced from it. 



No. 2. The Clinton group consists of green and blue 

 shales and limestones, the admixture of the fragments of 

 which forms an excellent wheat-soil. 



No. 3. The Niagara formation consists of the soft shales 

 below, and of the thick impure limestone beds above, 



