8 The Origin of the 



other manners. A prevailing form of the smaller 

 flints is approximately spherical or ellipsoidal, but 

 generally flattened, and not unfrequently somewhat 

 indented, as if by falling, before being fully hardened, 

 on another flint of the same form. Each usually 

 bears a crust, like chalk combined with the hard 

 silex of the flint; as if the interior particles of 

 disseminated chalk had worked towards the surface, 

 and formed a skin there, in like manner (to borrow 

 the suggestion of one writer) as sandiver or glass 

 gall separates from and swims upon glass during its 

 vitrification ; though sometimes the formation of this 

 crust might be prevented by the too sudden harden- 

 ing of the matter itself. In many cases the gelatinous 

 silex, falling into soft chalk, might also absorb a 

 portion of the chalk into combination with its 

 exterior, thus forming a thicker crust. In other 

 cases falling into the sea, it might be more rapidly 

 cooled. The surface is granularly corrugated, like 

 that of some Scotch pebbles which used to be reputed 

 of igneous formation. Whether the granular cor- 

 rugation has been produced in the process of cooling, 

 by shrinking, so as to resemble the surface of a 

 shrunken apple, we cannot say. But certainly the 

 round form of these flints has not been acquired by 

 rolling among shingle on the sea beach. Where 

 this has occurred to them, as is often the case, it 

 rubs off the corrugated surfaces, and presents them 

 smooth, and semi-polished ; and the crust of flinty 

 chalk which is on them demonstrates that their form 

 has not been acquired by rolling and trituration in 

 any manner. 



Where the flints are of larger size, the spherical or 

 ellipsoidal form could not equally be taken or 

 preserved; but the rounded tendency still often 



