CONCLUSIONS CONCERNING THE SAND MASSES 255 



2. The shape and size of the mass is such as would be expected in the 

 filling of limestone caverns. 



3. The masses often occur one above the other, more or less perfectly 

 separated by limestone beds, which is the arrangement frequently to be 

 expected in limestone caverns. 



4. The masses occur at no definite horizon, as would be the case had 

 they been deposited contemporaneously with the inclosing limestone. 



5. The writer explains the frequent occurrence of chert fragments and 

 limestone blocks in the sandstone only on the supposition that they fell in 

 from the roofs and sides of the caves while the sand was being deposited. 



6. The absence of all stratification in the sand masses. 



7. The presence, in one observed case, of stalagmitic material beneath 

 the sandstone. 



Source and Manner op Introduction of the Sand 



The source of and manner of introduction of the sand into the cav- 

 erns is one of the difficialt things to determine in connection with the 

 deposits. This is the more difficult because of the uniform cleanness of the 

 sand. As stated, it contains no argillaceous material. How is the absence 

 of this material to be accounted for? There would seem no escape from 

 the conclusion that the sand, if introduced from the surface of the land 

 area, would have clay mixed with it. Surface streams entering caverns 

 would carry all the material, both coarse and fine, that they could get 

 hold of, and this would be sorted to a greater or less extent. The cavern 

 filling would not be different from the material deposited in the beds 

 of streams, though stratification might not be so perfect. 



If, however, we conceive of the sea advancing upon the land area, the 

 material, both coarse and fine, comprising the soil would be picked up by 

 the advancing waves, assorted, the fine carried seaward and the coarse 

 deposited along the shore. With the advance of the sea, the rocks would 

 be swept clean of soil, and if they contained caverns, these would be 

 opened up to the floor of the sea, permitting the free ingress of the sand. 



Features op the Sandstone accounted por 



The one pronounced observed case of slickensides probably was pro- 

 duced by the settling down of the sandstone mass, most likely as a result 

 of solution beneath. The common occurrence of vertical or nearly verti- 

 cal cleavage planes probably is to be explained in the same way. 



The absence of stratification finds its explanation in the uniform 

 nature of the material and the probable constant rate of introduction. 

 The quiet water in the caverns would prevent the formation of false 

 bedding and ripple-marks. 



