220 GEOLOGY OF THE ISLE OF WIGHT. 



Brooh. 



The greater part of the series of gravels and brlck-eaith which 

 caps the cliff at Brook and Brixton belongs to a later group, and 

 will be described under the head of Valley Gravels, but four small 

 patches may be referred with more probability to the Plateau 

 Gravels. 



The Valley Gravels, it will be noticed, follow an old line of 

 valley, which runs nearly parallel with the coast. The encroach- 

 ments of the sea have removed the south side of this valley, 

 except for a distance of about a mile between Brook and Chilton 

 Chines, where the slight convexity of the coast leaves room for 

 just the lower slopes of some hills which formed the south side of 

 the old valley. The cliff section shows that the valley deposits 

 thin away against these slopes, leaving the Wealden Beds bare, 

 but on mounting the slopes we find another series of gravels of a 

 different character coming on at a higher level. The section is 

 similai- to that above described, where the Plateau Gravel of Blake 

 Down runs down nearly to the valley gravel of the Yar, leaving 

 only a strip of bare Lower Greensand between. The difference 

 between the two gravels at Brook consists in the comparative 

 absence of brick-earth and stratification in the higher and older 

 set, and especially in the peculiar contortions which appear both 

 in the older gravel and in the Wealden Clays on which it rests. 

 The clays have been bent and puckered, and the gravel forced 

 into the puckers so as to occur in pockets, while the beds of loam 

 or sand in the gravel are doubled up and bent, or dragged over 

 towards the west. There are four places only where the clifT rises 

 high enough to reach these older gravels, and their thickness barely 

 reaches 8 feet. The contortions are best seen in the patches at the 

 east and west ends respectively. As mentioned before, these 

 contortions are regarded as probable evidence of the action of ice 

 during the deposition of the gravels, perhaps in the form of frozen 

 soil, or of masses imbedded in the gravels. 



III. — The Valley Gravels and Brick -Earth. 

 Mode of Occurrence. 



We have already mentioned that these deposits differ from the 

 Plateau Gravels in having been distributed along the lower parts 

 of the existing valleys. They were no doubt made up principally 

 of the materials of the older gravels, redistributed after the exca- 

 vation of the valleys to nearly their present depth. 



They occur as terraces, often nearly level, bordering the modern 

 Alluvium, but at a variable height, up to 50 feet, above it, and 

 often separated from it by a steep bank. The streams having 

 lowered their beds below the base of the gravel, the greater part 

 of this bank is formed by rock in place, usually the Lower 

 Greensand. This is particularly the case along the upper part 

 of the eastern Yar, where, as may be seen on the map, a narrow 



