134 THE FORMATION OF FLINTS 



places where it abounds ; even churches are built of 

 it. It enters into the composition of some kinds of 

 china and earthenware ; but in flint-glass, needless to 

 remark, there is no flint. 



In London and many towns in the east of England 

 we are most familiar with flint as the pebbles and gravel 

 which form our gravel walks. Let us start on our 

 investigation with this material. Its warm orange 

 colour, ill-deserving of Thackeray's jest, has nothing to 

 do with the flint, but is due to the presence of an iron 

 ochre, which may be easily removed, for the most part, 

 by washing. Examining a clean pebble, we observe its 

 round, smooth form an indication of transport by 

 water. In some cases we shall find the surface marked 

 all over by small concentric circles, the outlines of cracks 

 which extend deeper into the stone. These are the 

 result of blows, given and taken as it was hurried along 

 by stormy water. 



If we proceed to the pit whence the gravel was dug out 

 we shall find it arranged in layers, generally of very 

 irregular thickness, and of all degrees of fineness or 

 coarseness. As a rule, the gravel-pits are excavated in 

 shelving banks or terraces which run with the valley, 

 and at various heights above the level of the existing 

 river ; some form its actual banks, others are found 

 at increasing elevations of 20, 40, 100, or 300 feet or 

 more above it. These terraces evidently mark suc- 

 cessive stages in the excavation of the valley. That 

 which is now 100 feet above the river contributed at 

 the time of its deposition to form the river bed. The 

 most ancient flint implements which are found in our 

 islands have been dug out from the gravels of this 

 ledge, whence we may conclude that man was con- 

 temporaneous with its formation, which dates back to 

 the glacial period. The terraces extending along the 



