136 Agricultural Experiment Station, Ithaca, X. Y 



Compared with those of the hillside, the pebbles are found to be 

 well rounded and smoothed (Figs. 57 and 66), as if by water action. 

 There are few if any angular corners, and no grooves or scratches. 

 The clay element is practically absent, and the pebbles are bound 

 together by sand instead. The pebbles and sand are in layers, or 

 are stratified (Fig. 57), so that there are several important differ- 

 ences between the soils of the two zones. 



A comparison with the beaches of the present lake shore shows 

 a striking resemblance, not only in texture but in the surface out- 

 line. In both cases there are many rounded pebbles and much sand ; 

 and in both cases, also, the surface form is that of a flat-topped 



r>^;v;^' 



■,>2'-"'-'?' ' '■-'-«?■ -.--irfc^Ti^e??^^-.** -■>-v.-'^5^::"-'"" 



5(j. — Upper terrace southeast of Sheridan. 



terrace. However, in the beach there is almost no clay, while in 

 the gravel ridges the decay of some of the pebbles and sand par- 

 ticles has furnished some clay ; and also the action of vegetation 

 and cultivation has somewhat modified the gravel ridge soil. 

 The meaning of this resemblance will soon be shown to be similarity 

 of origin. As many who have tilled the gravel soil have conjec- 

 tured, the ridges are true lake beaches now stranded on dry land. 



The lake clay soils. — In the present lake, gravel beaches are 

 being formed along the shore line ; and each time that there are 

 strong waves, the washing action of the water moves the pebbles 

 backward and forward, rounding them by grinding off tiny particles 

 of clay. The force of the waves and currents is capable of carrying 



