44 BULLETIN 141, U. S. DEPARTMENT OP AGRICULTURE, 



a high percentage of carbonate of lime. Analyses of numerous sam= 

 pies have shown the lime carbonate content to range from 1 or 2 

 per cent to as high as 20 or 25 per cent. This arises from the close 

 association of the largest areas of the type with areas where the 

 local limestone was first reworked into the glacial till and later rede- 

 posited as a part of the glacial lake sediments which constitute such 

 a large proportion of the total area of the type. 



In all areas where it occurs the Clyde clay occupies level or slightly 

 saucer-shaped depressions which are usually below the level not only 

 of other upland soils but even below that of other members of the 

 Clyde series occurring in the same area. In fact, the Clyde clay 

 represents the quiet-water deposition of the ancient glacial lakes, and 

 it was formed in the central portions of the basins of the larger lakes 

 and in depressions in other glacial lake sediments. In such loca- 

 tions the deposition of mineral matter was not usually as great as 

 nearer shore lines or stream deltas, and the deposits were finer 

 grained than in the case of the materials giving the other members 

 of the series. 



The surface of the Clyde clay is almost universally flat or but 

 slightly inclined, and there is abundant evidence that the areas of this 

 type constituted shallow lakes or at most swamps until about the 

 time of the pioneer occupation of the general region. The presence 

 of numerous fresh-water shells, the high organic matter content of 

 the surface soil, and manj^ historical accounts of the original aspect 

 of the country all bear out this conception of the immediate origin 

 of the Clyde clay. 



Not until artificial drainage was undertaken either by individuals 

 or by county or State authorities was the greater part of the total 

 area of the Clyde clay susceptible of agricultural occupation. It 

 has only been after the opening of large main ditches, along the 

 boundaries of land sections or along natural drainage ways through 

 which farm drainage might find an outlet, that the land has been 

 brought under even the more extensive forms of cultivation, and the 

 production of intertilled crops has frequently become profitable only 

 after the installation of tile drainage. It is certain that many 

 thousands of acres of this soil type would be very greatly benefited 

 by the extension of tile drainage. The value of this form of im- 

 provement has been abundantly demonstrated by numerous cases 

 where the value of the land has been quadrupled through the laying 

 of tile. Usually the increased value of the land has more than paid 

 for the expenditure within 5 to 10 years from the installation of 

 the drains, while it has even been the case that the increased crop 

 production for the same period of time has more than paid the total 

 cost of drainage. It is certain that the crop adaptations of the type 



