42 BULLETIN 142, U. S. DEPARTMENT OF AGRICULTURE. 



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 

 use. 



In many regions where the Miami clay loam is encountered, 

 scattered bowlders and small stones are found locally over the sur- 

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

 and underlying till. In some small areas this accumulation of stone 

 may be sufficient to interfere somewhat with cultivation. In such 

 cases the stone is usually gathered from the field and used in the 

 construction of fences or buildings. In general, however, the surface 

 soil is fairly free from any large masses of rock or extensive ac- 

 cumulations of stone and gravel. The larger rock masses associated 

 with the Miami clay loam roughly indicate 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 sedimentary rock occurring within the area occu- 

 pied by the type or within the 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, such as 

 shale, have usually been so finely ground by glacial action as to pre- 

 vent identification in the majority of the areas. Usually a large part 

 of the rock fragments in the deeper subsoil consists of limestone. 



Considering the wide extent of territory over which the Miami 

 >lay loam is developed and its derivation from ice-laid materials, 

 the surface configuration of the type is unusually uniform, or. at least 

 varies within reasonably narrow limits. In general, the surface of 

 the type is gently undulating or slightly rolling with local low, 

 rounded hills or steep-sided knobs in areas which include distinct 

 glacial moraines. The only other hilly or steeply sloping areas of 

 the Miami clay loam are those found where postglacial streams have 

 cut deeply below the glacial upland surface, and have extended their 

 minor branches through the upland areas occupied by the Miami 

 clay loam. 



The altitudes at which this type is developed vary from ap 

 proximately 600 feet above tide level in the vicinity of Lakes Erie 

 and Michigan to altitudes of a little more than 1.300 feet in south- 

 western Ohio and southeastern Indiana. These differences in alti- 

 tude arise chiefly from differences in the elevation of the rock floor 

 over which the glacial materials were laid down. The rolling surface 

 of the soil type itself slopes gently upward from its lower elevations 

 to the highest altitudes attained near the southern boundary of gla- 

 ciation. 



There is considerable variation in the natural drainage of the 

 Miami clay loam. The more nearly level areas, especially those some- 



