CORRYS WITH OR WITHOUT LAKE-BASINS. 137 



softer or more easily weathered or removed than 

 the rest of the rock. Such spots, when exposed by 

 denudation to atmospheric influence, crack, and 

 subsequently weather out. Once a hollow is formed, 

 no matter how small, particles of sand find their 

 way into it, and these are whirled -round and round, 

 either by wind or the eddying of water, thereby 

 deepening and enlarging it. As the hole increases 

 in size, larger grinders are admitted, and the work 

 goes on more and more rapidly. If the maculaa are 

 situated widely apart, as is often the case, the holes 

 for the most part will be cut symmetrical ; but if the 

 weak spots are more numerous, one hole may 

 encroach on another, or, what is not uncommon, 

 holes may form in the side of one in progress, if the 

 grinding process exposes to the weather some of 

 the concealed soft spots. In other cases the 

 maculae are so numerous that the weathering is 

 quite irregular, and without marked form. Such are 

 generally passed over unnoticed, while the remark- 

 able form of the " churn-holes " always attracts 

 attention. 



Similarly, marine action might be able to excavate 

 hollows in cooses. The sea, however, in such cases, 

 could scarcely work as symmetrically ; for while, in 

 the case just mentioned, the water would begin its 

 work on the cracks in a more or less regular nodule 

 or the like, the sea in the coose would be working 



