BEACHES, ETC., OP THE SOUTH QE ENGLAND. 



333 



ported, a more energetic movement is made manifest. Some indi- 

 cation also of the duration of the uplift is afforded by tlie mass of 

 the material moved and distance traversed. 



The effects produced by this re-elevation of the land were 

 necessarily simultaneous throughout the whole of the disturbed area, 

 but varied with the depth of water and the gradients of _ the 

 ground, so that the sweep of the Oolitic debris on the summit of 

 the Cotteswolds proceeded concurrently with the first drifting-in of 

 the Chalk-rubble at Brighton ; but while the growth of the former 

 ceased with its early emergence above the water, the latter was 

 prolonged to the last stage of the emergence, and therefore affords 

 an index of the changes going on during the whole period of 

 elevation. As the Brighton section (antea, fig. 3, p. 268) varies with 

 every fall of cliff, and all the points are rarely seen together on 

 each occasion, my meaning will be best illustrated by a diagram. 



-pig, 20. — Diagram showing the successive incitements in the forma^ 

 tion of the Head where the strata are of variable resistance, as 

 in a Chalk district. 



I 



The dark lines represent the coarser and heavier detritus of angular flint- 

 fragments mingled with Chalk-rubble — sometimes in large proportion, at 

 other times so small as to leaTe scarcely anything but a mass of sharp 

 broken flints. - The white spaces represent Ohalk-rubble with few or no 

 flints, and sometimes so fine as to pass into a pure marl, occasionally 

 laminated. 



These beds succeed one another without any definite order, and 

 it is difficult to say how many there may be — possibly not less than 

 12 or more. 



The coarser beds indicate the action of the stronger, and the finer 

 beds that of the more gentle, efiluent currents. Each of these may be 

 taken to indicate an eievatory movement more or less rapid. There 

 may have been intervals when the movement was so slow as not to 

 give rise to any effective currents, or there may have been short 

 intervals of rest. The whole series is continuous, and the beds, as 

 it were, interdigitate with one another. 



Judging from this structure, we may infer that at times the rise 

 of the land from beneath the sea proceeded with sufficient rapidity 

 to cause the efiluent waters to carry masses of flints and coarse 

 Chalk-rabble over the cliff from the slope of the hills behind, and 

 even to roll down occasionally blocks of Tertiary sandstone from 

 the higher ground at a distance of one or two miles from the 

 coast; while at other times it proceeded so slowly that only the 

 finer sediment was removed from the same surface. It is evident 



