some Cambridgeshire Sands and Gravels. 143 
: of the Neocomian sands of Norfolk, the Carstone and the Sand- 
ringham sands, only differing from them in their slightly more 
rounded form. The far-travelled grains on the other hand are 
largely such as might be obtained from igneous and metamorphic 
rocks, then undergoing disintegration for the first time: they are 
angular in the earlier deposits, subangular in the later, and only 
in the obviously wind-borne surface deposits are all alike reduced 
to a small size and a fairly uniform degree of roundness. Thus 
during the deposition of the Cam gravels water action was pre- 
dominant; at a later time wind asserted its power as the principal 
agent of distribution of the latest superficial accumulations of the 
drier parts of East Anglia. 
