GENESIS OF THE SOIL AND ITS POSSIBILITIES 191 



amples of which are seen in the so-called blue-grass 

 regions of Kentucky. These soils are well known by 

 reason of their great natural fertility. 



" Throughout the Southern States, on the slopes and 

 the uplands, we have a great variety of soils produced 

 by the chemical and the mechanical disintegration of 

 rocks, possessing every variety of character, both as 

 regards chemical fertility and physical texture. Some 

 of them, particularly when produced from certain sand- 

 stones, are poor and easily exhausted, and when ex- 

 hausted do not recuperate readily, of which we have 

 examples in some of the more barren land flanking 

 several of the chains of the Appalachian system. 

 Others possess great power for rapid recuperation, as, 

 for example, the blue-grass region of Kentucky, where 

 the calcareous portions of the soil rapidly disintegrate 

 or are changed by chemical action, and where there is 

 an abundant source of the elements of fertility in the 

 rocks themselves. The state geologist of Kentucky 

 gives interesting illustrations of this power. Certain 

 areas inclosed within the region already described as 

 being occupied by drift have been modified by these 

 same influences. Professor Whitney, former state 

 geologist of Iowa, states that some of the fertile prairie 

 soils of that State those where the soil is of almost 

 impalpable fineness have been produced by the slow 

 solution of beds of limestone which formerly occupied 

 their places. In the course of ages, under the influence 

 already spoken of, the insoluble limestone has been dis- 

 solved, the solution borne away to the ocean in the 

 rivers, and the small percentage of insoluble residue is 

 left, forming the thick prairie soil of the region, which 

 has since become blackened by the decay of abundant 

 vegetation produced upon it. From the nature of the 



