TERMINAL MORAINES. 209 



plains, which are nearly level, with a soil of fine clay, and cov- 

 ered by a heavy growth of elm, beech, ash, maple, etc. The 

 ridge, on the contrary, presents a confused series of conical 

 hills, chiefly of clay, but showing some pebbles and small 

 bowlders, and clothed by a forest-growth almost exclusively of 

 oak. Probably the only essential point in this contrast is that 

 of hill and plain, and out of this the others have grown. 

 There is good reason to believe that the clay deposit (Erie clay) 

 of the plain is continuous with that on the hills. Where its 

 surface is level, it has retained its soluble salts and accumu- 

 lated vegetable mold, so as to form a rich soil favorable to a 

 varied vegetation ; while from the steep hill-sides a great 

 amount of soluble and fine material has been washed, so as to 

 bring to the surface some of the pebbles everywhere imbedded 

 in greater or less abundance, and the character of the vegeta- 

 tion has been determined by that of the soil. 



I conceive that this ridge is the superficial representation 

 of a terminal glacial moraine, that rests directly on the rock- 

 bed, and is covered by a heavy sheet of Eric cby, a subsequent 

 aqueous and iceberg deposit. Though this formation has an 

 average depth along the upper St. Joseph of over one hundred 

 feet, and on the upper St. Mary'rj of fift\ feet, it has not suf- 

 ficed to conceal a moraine of such magnitude, but has so far 

 conformed to its contour as to leave it still visible on the face 

 of the country — doubtless in comparatively faint relief, but 

 still so bold as to exert a marked influence on the hydrography 

 of the valley. * 



When, a little later, we come to speak of glacial erosion, 

 something more will be said confirmatory of this hypotheti- 

 cal moraine of Mr. Gilbert, and of the varying movements of 

 ice in the Lake Erie Valley at different stages of the Glacial 

 epoch. We shall then see abundant reason for supposing 

 that there was, for a considerable length n>f time about the 

 close of the period, an independent movement of ice in the 

 direction of the longer axis of the lake, and that this 



* " On the Surface Geology of the Maumee Valley," in the " Geological Sur- 

 vey of Ohio," vol. i, pp. 540-542. 



