184 INFLUENCE OF DEIFT. 



tural capabilities and early agricultural prosperity with 

 the nature of the rocks of a country, it is only neces- 

 sary to ascend from the valley of the Onondaga shales 

 to the hills of the Portage sandstones. 



But another interesting and instructive feature pre- 

 sents itself in this wheat-growing belt. The waters 

 which in former times descended this region came from 

 the north, and have drifted the materials of the more 

 northerly over the edges of the more southernly rocks. 

 Thus the materials of the Medina sandstone are made 

 to overlap the Clinton and Niagara clays, and so to 

 mingle with, lighten, and improve the soils formed from 

 them. The Niagara shale, again, bas overlapped the 

 overlying Niagara limestone, mixed with it, and deepened 

 its naturally tliln and more slowly crumbling debris. 

 So the various soft beds of the Onondaga salt-group 

 have been Intermingled, and a comparatively low, level, 

 and undulating surface been given to the whole. The 

 abundant materials derived from this easily crumbling 

 group, again, have been spread over the Helderberg 

 limestones, and the fragments of these over the Mar- 

 cellus and Hamilton shales, adding to the calcareous 

 matter of these latter rocks, and thus widening the belt 

 of wheat-growing country beyond its natural limits. 



This widening is especially visible along the north 

 and south valleys, which penetrate far into the Hamilton 

 and Portage groups of rocks, and Into which the frag- 

 ments of the Onondaga group were naturally carried by 

 the rushing water. Up the valley of the Genesee Kiver, 

 and into the outlets of the Seneca and Cayuga lakes, 

 this drift has penetrated farthest ; and to Its presence is 

 due the peculiar agricultural excellence for which the 

 soils of these localities are known, and which the rocks 

 on which they rest could not alone have imparted to 

 them. 



The first freshness of nearly all these naturally fertile 



