90 PECULIAR STRUCTURE OF CLARK'S CLAY-BEDS. 



verted truncated cone. The base of this cone was about 

 ninety or one hundred feet above the floor which formed 

 the lowest working level in the pit, and which was itself 

 about fifteen feet above the level of the Hudson River, 

 and also somewhat above the lowest portions of the clay. 

 Of this mass about twenty feet of the upper layers were 

 of gray clay : the rest was the blue variety. The ma- 

 terial was deposited mostly in concentric and frequent 



I 



P TV 







ETTD80N KITHR 



^. ■ '■■■ : -'#A -:-_-ML 



FIG 3. FIG. 4. 



(lark's Clat-Beds. 



Fig. 1. — Vertical section through the south bed. 



Fig. .'.—Diagrammatic view, as restored, of the three clay-beds with the vertical wall in 

 front of them. 



Figs. 3 and A.— Vertical sections through the clay-bed, vertical wall, and external gravel 

 beds, on the south and north sides, respectively, of the entrance (on the river side) into the 

 southern bed. 



In the above figures, the clay-beds, for convenience, are made to appear higher propor- 

 tionally than they really are. 



In all the figures the letters have the same reference : c, clay-beds ; s., fine sand imme- 

 diately surrounding the clay beds ; w., the vertical wall ; p., coarse, pebbly drift ; 1., 

 limestone strata in place, overhanging the clay deposits. 



7-4 



