O12 Reviews—Geology of Hungerford and Newbury. 
The beds of gravel of the district are separated upon the map into 
two divisions or classes— 
(i) Plateau Gravel (of doubtful age and origin). 
(11) River and Valley Gravel. 
Now, as the author explains, there may be some practical convenience 
in this division, though to a great extent it is a survival of the old 
theory of the marine origin of the plateau gravels. In any case, the 
result of the conclusion to which the author has come, and which has 
just been quoted, is that when he comes to speak ofthe plateau 
gravels he says: ‘‘ The ‘ Plateau Gravel’ group as defined on the sheet 
is, iN a measure, an arbitrary one, for some of its members are not 
to be distinguished from deposits classed as ‘ River and Valley Gravel’ 
by their composition, structure, mode of occurrence, or altitude, 
absolute or relative, that is to say, by any of the tests which are 
usually regarded as of chief importance for the discrimination of 
unfossiliferous, or very sparingly fossiliferous, drifts of this type, and 
further on he remarks that the Plateau and the Valley Gravels are 
very often inseparable; their more level spreads frequently appear to 
be but the higher and lower members of a single graduated series.”’ 
If it be admitted that the author is correct in his opinion, and we 
believe that he is here in agreement with many or most of his fellow- 
workers in the Thames district, then the history of our river system 
is thrown back to a vastly earlier date than could have been 
contemplated by those who looked upon the plateau gravels as of 
marine origin, and we find that the author is fully prepared to accept 
the result of his view, for he says that it seems not improbable that 
the broad outlines of the present drainage system were marked out 
in the Miocene period coincidently with the development of the 
Kingsclere fold. At the same time he considers it possible that the 
dominant surface slopes of the district, in so far as they have a tectonic 
origin, may be due less to Miocene folding than to Pliocene warping, 
and he also observes that the district may have been overflowed by 
the Diestian Sea, which, though not very probable, is no doubt 
a possibility for which we have to allow. 
If we agree in the author’s view as to the origin and antiquity of 
the gravels, the question of the age of the various deposits in relation 
to the age of the most recent earth-movements is one of great 
importance, for if earth-movement continued after the deposit of any 
part of the gravels the relative position and altitude of different gravel 
deposits may have been greatly affected thereby. The author, however, 
in suggesting a tentative grouping of the gravels, thinks it best to 
assume that the original height-relations of the sheets of gravel have 
not been significantly changed by differential earth-movements. 
He separated the plateau gravel into three stages— 
(i) Cold Ash Stage gravel, now 265 feet above the present River 
Kennet, and possibly of late Pliocene age. 
(ii) Bucklebury Stage, now 230 feet above the present river, possibly 
belonging to the earlier part of the Pleistocene period. 
(iii) Silchester or Greenham Stage, 150-160 feet above the modern 
river of rather later date. 
