VALLEY GRAVELS. 223 



the gravel is derived directly from the Greensand, and not from 

 the plateau gravels, though the present stream with its slight fall 

 is incapable of transporting such coarse material. 



Near Coppin's Bridge loam comes on again, overlying the 

 gravel. 



The Westo'ii Far. 



The most remarkable fact in connection with the valley gravels 

 of this tract is the entire disappearance of the river by which they 

 were deposited. For nearly the whole of the southern side of the 

 valley of the Yar, as well as a large part of its di-ainage basin, has 

 been removed by the encroachment of the sea, so that the old 

 river gravels have come to occupy the position of a terrace of 

 gravel capping the sea cliff', Avhile the small streams, which drain 

 what is left of the basin of the old Y^ar, now find their way direct 

 to the sea by deep notches or chines cut in this cliff. The evidence 

 on which this gravel terrace is attributed to such a river was 

 first recognised by Mr. Codrington in 1870,^ and is singularly 

 impressive. 



The breach in the Chalk range at Freshwater is out of all pro- 

 portion large in comparison with the stream which now occupies 

 it. Moreover, the river gravels conclusively prove the valley to 

 have once formed the channel of a river comparable in size to the 

 Medina, or eastern Yar, The distribution of these gravels further 

 shows that this river, like the others, flowed from south to north, 

 draining lands wdiich, lying to the south of the Chalk range, have 

 since been washed away. We may further assume that some of 

 the sources of the river lay in the direction of St. Catherine's 

 Down, in the area which has formed the principal watershed of 

 the Island from a very early period. 



The gravels at Brook occur in the line which the old river 

 might have been expected to take^ and at such a height above 

 those of Freshwater Grate, as would be required to allow a gradient 

 for the stream. When we add to this that the gravels and brick- 

 earths bear every appearance in themselves of being old river 

 deposits, there is left no room for doubt that they mark the course 

 of the old Yar. 



The occurrence of teeth of Elephas iirimigeiiius in these gravels 

 at Freshwater has long been known ; remains of the same animal 

 have been recorded also from Brook Chine and Grange Chine by 

 Mr. Codrington (op. cit, p. 539). 



The continuous section afforded by the cliff gives unusual 

 opportunities for examining these gravels. In describing the 

 section, we will commence in the upper part of the valley and 

 proceed westwards to Freshwater. 



Gravel first makes its appearance on the top of the cliff between 

 Blackgang and Atherfield. It is seen as a band 2 to 4 feet thick 

 underlying a considerable depth of alluvial deposits and blown 

 sand {see p. 234), and is composed principally of chert. It may 



* Quart. Journ. Geol. Soc, vol. xxvi. p. 528. 



