7.3 



It may probably be imagined that the Geologist, who has read with 

 such clearness the olden' rooks, tratii-.g them in successive order, and nn- 

 folding their history by an examination of their organic contents, will 

 have little difficulty in deciphering tlicse newer beds. Snob however 

 is not the case, on the contrary, no more difficnlt questions have been 

 propounded of him to explain the changes in the more recent history of 

 our globe, than those connected with the post tertiary period, but there 

 arc certain broad and well ascertained facts that we may and must esa- 

 nihie before we are capable of forming any sound conclusions on the 

 whole matter, and I propose to set them before you this evening, avoiding 

 as much as possible any dry details. 



The questions we have first to answer, may be epitomised as follows : 



1 . — Of what materials is the Gravel composed ? 



2. — Whence were the materials derived ? 



3. — By what means have they been brought into their present 

 position ? 



On the first point I would observe that all the gravels of Kent are 

 composed of materials derived from the older beds in the neighbourhood. 



The larger portion consists of flint stones. 



The hills between Canterbury and Dover are capped with flint 

 stones in clay, which Mr. Whitaker calls " Clay with Flints,''^ and these 

 flints have evidently been derived from the chalk, by the latter having 

 been dissolved and can ied away by rain water. The chalk, being soluble 

 in rain water, owing to the carbonic acid contained in it, has disappeared, 

 leaving the flints behind, together with the insoluble matter of the chalk, 

 which is the red clay, in which these flints are imbedded. The chalk 

 about Dover has also upon it the remains of some old Tertiary beds of 

 red sand, which is largely impregnated with iron. This has given the 

 clay an unusually red colour, consequently, the original white coat- 

 ing of the flints is stained correspondingly. 



Clay with flints, is not found upon these hills only, it occurs all over 

 the district, and has even been washed down into the valleys around to 

 the level of the present rivers. In such low-lying situations, the floor 

 of the valley is covered by the stones, washed and partly rounded by 

 water action into subangular gravel ; while higher up, often in terraces 

 above the level of the present valleys, arc patches of water-worn gravel, 

 often containing small rounded pebbles of iron sandstone, and chert, from 

 the Lower grccnsand. These constitute our river gravels or drift, and 

 we shall find this river drift spread out in similar thick sheets or 

 terraces corresponding with the direction of the rivers of the district, 

 but at a very considerable elevation above their present level. 



Now it is chiefly in this river drift that our Kentish gravel pits 

 are quarried ; and, moreover, it is amongst such gravel that we find the 

 remains of the extinct mammoth, and, contemporaneously the evidences 



