226 GEOLOGY OF EASTERN WISCONSIN. 



These springs are frequently ferruginous, as are also certain bands of 

 the deposit. 



The western limit of this formation is marked by a low flat ridge, 

 usually only six or eight rods in width, and less than three feet in 

 height. At most points, this is composed of fine gravel, except near 

 the state line, where it becomes sandy. The surface between this 

 beach ridge and the lake is level and free from bowlders, but imme- 

 diately to the west of the ridge, small bowlders occur, except over 

 certain areas that are covered with lacustrine and fluviatile deposits. 

 Here and there a stream has cut a deep, sharply-defined gorge for it- 

 self, but broad, sloping valleys are wanting. 



Immediately beneath the above beach formation lies a finely lam- 

 inated compact clay. It has a prevailing reddish hue, which is at 

 some points pronounced, but at others is bluish or dark grayish. It 

 contains but few pebbles and very rarely anything that could be de- 

 nominated a bowlder. The laminations are horizontal and often ex- 

 ceedingly fine. Some arenaceous layers are usually present, especial- 

 ly toward the top. 



In the vicinity of " The Point," near Racine, this clay rests di- 

 rectly upon the Bowlder Clay. The line of junction is most sharply 

 and distinctly marked. The surface of the obdurate hard-pan, which 

 here constitutes the lower formation is sometimes planed almost like 

 a glaciated surface, and the resemblance is enhanced at some points 

 by parallel lines of white material, the significance of which was not 

 ascertained. In other cases it presents an undulatory ripple like sur- 

 face, and in still others is more irregular. These observations are 

 made possible by the distinctness of this hard-pan from the fine put- 

 ty-like red clay that rests upon it. In digging it away, the red clay 

 peels off from the surface of the lower clay, leaving it perfectly clean 

 and distinct. 



But as we trace these clays northward a stratum of yellow sand 

 develops between the two and rapidly increases in thickness, while 

 the red clay correspondingly, but somewhat less rapidly, thins out. 

 Four drift formations are well shown at this point; a beach forma- 

 tion (D), at the top, being here a stratum of yellow sand only a few 

 feet in thickness, the red clay (modified) next, and beneath this 

 another beach formation (C), resting upon the Bowlder Clay, as shown 

 in the accompanying figure. 



As we advance northward, or more strictly northwestward, the three 

 upper formations rise and disappear at the surface in succession, each 

 seeming to have been cut off above by erosion. This is not accom- 

 plished, however, until the thinning out of the red clay, and the ap- 



