182 SOILS OF THE NIAGARA EOCKS. 



which give their character to the Niagara Falls, and to 

 the outline of the landscape. The shale alone forms 

 stiff clays, which, from the sloping nature of the surface, 

 are generally dry and susceptible of culture ; while the 

 limestone alone, where it is sufficiently crumbled, pro- 

 duces a surface adapted for wheat or Indian corn. But 

 where, from the washing away of the Clinton beds, 

 which are only 60 or 80 feet in thickness, the Niagara 

 shales come in contact with, or are mixed with the debris 

 of the Medina sandstone, soils are produced which are of 

 "unequalled fertility" — illustrating another important 

 principle, of which we have many examples in England, 

 that, at the junction of beds of different kinds of rock, 

 the soils are often much superior to those which are 

 produced by the fragments of either rock alone. 



No. 4. The Onondaga salt-group consists, as I have 

 already said, of red and green shales below, succeeded 

 by porous limestones, and these by beds of shale, includ- 

 ing irregular but larger deposits of gypsum, the whole 

 surmounted by other green shales or thin beds of impure 

 light-coloured limestone, containing much magnesia. 

 Calcareous matter abounds through the whole of this 

 fertile formation — and generally the soils are rich, free, 

 and easily worked. 



No. 5. The Helderberg limestones and sandstones, 

 where the surface is hard and rocky, are often covered 

 with a thin soil of less value ; but where the soil is deep, 

 it is of excellent quality. Here, however, as a wheat- 

 region, the natural quality of the surface begins to fall off. 



No. 6. The Marcellus shale is thin, varying from a 

 few feet to 60 or 80, so that its effect on the surface is 

 seen chiefly by its improving the Helderberg series at 

 the point of junction, and by forming occasional stripes 

 and patches of stiff clay. 



No. 7. The Hamilton group, when alone, forms stiff 

 dark-coloured clays, which are less rich in calcareous 



