4 SOILS OF THE EASTERN UNITED STATES. 



loam is, therefore, merely the surface expression, in the form of soil, 

 of deep, complex, mechanically broken soil-making material of glacial 

 origin. The soil itself has been slowly prepared through the pro- 

 cesses of the weathering of the surface portion of this material. The 

 glacial origin of the soil, insuring the commingling of earthy material 

 from a great variety of sources, the great depth of the soil-making 

 material, and the compact nature of the mass which resists exces- 

 sive erosion all tend to form a soil of medium to good fertility and 

 of a most durable quality under even fair conditions of agricultural 

 occupation. 



In many regions where the Miami clay loam is found, scattered 

 bowlders and smaller stone will be found locally over the surface of 

 the type, and in increasing quantities in the deeper subsoil and 

 underlying till. In some areas of limited extent this accumulation 

 of stone may be sufficient to interfere somewhat with cultivation. 

 In such cases the stone has usually been gathered from the field and 

 built into boundary* fences or into the walls of buildings. In general, 

 however, the surface soil is fairly free from any large masses of rock 

 or extensive accumulations of stone and gravel. The character of 

 the larger rock masses found associated with the Miami clay loam 

 roughly indicates the character of the finer-grained soil-forming 

 material. The bowlders, stone, and gravel comprise fragments of 

 practically every known variety of igneous, metamorphic, and sedi- 

 mentary rock occurring within the area occupied by the soil type or 

 found in extensive tracts to the north, from which the glacial ice 

 passed southward to deposit its load. Granites, gneisses, schists, 

 sandstone, limestone, and quartzite are all found among the glacial 

 bowlders and pebbles. The softer rocks like shale have usually been 

 so finely ground by glacial action as to prevent identification in the 

 majority of areas. Locally, however, where the rock of the region has 

 consisted of shale, considerable proportions of this material may be 

 found in the deeper subsoil. In all such areas, which are found 

 chiefly in the eastern extension of the region occupied by the Miami 

 clay loam, that type of soil is grading in its origin and in the char- 

 acter of its constituent materials toward the soils of the Volusia series 

 found in extreme northeastern Ohio, in northwestern Pennsylvania, 

 and in southwestern New York. 



The Miami clay loam and the other soils of the Miami series are 

 characterized by their derivation through surf ace weathering from deep 

 glacial till, by the presence of a diversity of crystalline and sedimentary 

 rocks hi the form of bowlders, stone, and pebbles, and, in conjunction 

 with this origin, by the light colored, either brown or yellow, surface 

 soils. The soils of the Miami series differ from those of the Carrington 

 series, similarly derived, in that the latter are marked by black surface 

 soils ; and from the soils of the Coloma series, which are light colored, 



