144 N. H. WINCHELL — WAS MAN IN AMEKICA IN GLACIAL PERIOD 



h. The manner in which the face of the cliffs breaks off on being ex- 

 cavated. All over the face of the cliff, sometimes, but usually scattered 

 along the fresh excavations, the spontaneous breaking down of the loess 

 is by a series of horizontal cleavages, leaving horizontal surfaces. The 

 vertical jointage of the body of the loess has often been mentioned; it 

 may be stated that at Saint Joseph the horizontal planes left by the fall- 

 ino^ of the columnar masses are also conspicuous about the fresh faces 

 of the bluffs. These horizontal surfaces are sometimes upward-facing 

 and sometimes they overhang, according as the columnar mass had 

 toppled off or fallen vertically downward without toppling. These easy 

 cleavages are all horizontal or dip uniformly parallel to each other, the 

 latter particularly in regions where it is evident that the mass has 

 moved with a sliding, slow motion toward either the river (Missouri) or 

 toward the valley of the creek which passes through the city, and has 

 thereby lost its horizontality. They can be explained, as it appears to 

 me, only on the supposition of an original stratification of the whole 

 fine mass, the breaking being coincident with the stratification because 

 of a weakness of cohesion along the stratification planes. 



c. Besides these horizontal planes of supposed stratification there is 

 visible, sometimes, on weathered areas on the face of the same cut, an 

 indistinct fine lamination coinciding in direction with the planes above 

 described, which also suggests a bedded sedimentary structure for the 

 whole mass. 



Besides these intimations of a laminated structure, on searching more 

 widely such structure luas found perfectly preserved at several places. Such 

 a lamination extends from a point but few feet above the Missouri river 

 to near the tops of the main bluffs, namely, it can be seen at the corner 

 of Dewey avenue and Main street, on a part of the main hill or spur 

 which separates the river from the creek valle}^, not much above the 

 gjade of the Chicago and Great Western railroad. The bluff rises about 

 2o feet above the point at which the stratification is evident. The same 

 shells are seen in the loess at this point, and the whole aspect is iden- 

 tical with the loess in the higher cuts. Here the visible laminations are 

 from a sixteenth to a thirty-second part of an inch in thickness, or 

 thinner, perfectly horizontal, and cannot be questioned, the laminations 

 extending several rods along the face of the bluff, facing east. On 

 weathering it stands out, but even on being cut off by the knife or spade 

 it is still evident. In cutting out a small square block from the vertical 

 wall the loess easily separates horizontally along the lamination planes 

 into sheets of varying thickness, and it was with difficulty that a block 

 8 inches square could be kept together long enough to be photographed. 

 This easy separation along the lamination planes seems to confirm the 



