Mr Grimes'' Observations on the Flints in Warwickshire. 79 



There is no stage between this and the absolute cementation 

 of the two parts by means of this exudation ; and I suppose 

 that the whiteness of the substance may be occasioned by its 

 greater liability to decompose, when not completely hardened ; 

 and where the white line is of any considerable thickness, as it 

 often is, to a quarter of an inch or more, it seems probable, 

 that the interstice has been partially filled up by the abraded 

 particles produced by friction, or by the chalk falling in be- 

 tween. 



But how is this substance condensed without the aid of at- 

 mospherical air ? Very compact flints of considerable size, 

 and agate-balls, are found to contain crystals of quartz and 

 chalcedony in the interior ; and sometimes flints, which ap- 

 pear to have rent in the heart by the effect of contraction when 

 drying, have been filled up with siliceous matter, (see speci- 

 men, letter F,) none of the rents reaching to the surface. Si- 

 milar effects of drying are to be observed in balls of lime and 

 ironstone, which sometimes remain vacant, and in others are 

 filled up with calcareous matter, &c. probably by infiltration. 



The moisture above mentioned, as being found in flints, in 

 a great measure disappears when they are exposed to the at- 

 mosphere, though not entirely ; for I have found it in some 

 that have been exposed for a great length of time, and after 

 baking them too for some hours. Possibly the stones may 

 partially crack, by exposure, in a manner imperceptible to the 

 eye. They appear to contract, and to be elastic to a certain 

 degree. 



I never could induce them to re-imbibe any moisture by 

 soaking them in water. 



There is a common effect of the atmosphere upon chalk- 

 flints which is curious and interesting. It commences in lit- 

 tle white spots or rings, which appear upon the surface. After 

 a time, pieces break out in the form of a crescent, with three 

 angles, the lower angle being perpendicular to the plane of 

 the surface, so that a crescent-shaped hollow is left, the inner 

 side of which forms a half cone ; these of course multiply ; 

 and the projecting parts falling into dust, if the stone exists 

 long enough in an exposed situation, they are succeeded by 

 others. 



