506 Reviews— Codrington’s Berks and Hants, &c., Railways. 
most irregtlar ; next toit there is a thin layer of black clay, and 
the lowermost flints in the clay are often black-coated ; the Clay- 
with-flints underlies the Brickearth, and the latter often contains 
‘ Sarsen stones,’ or, as they are more generally called, ‘Greywethers.’ 
Mr. Codrington observes that the appearances of these pipes are 
just such as would be caused by the gradual dissolving away of the 
Chalk. In one case, where a tabular bed of flint was cut through 
by a pipe, ‘the fragments extended quite across the pothole, lying 
in a festoon in the clay within a few inches of the bottom’; and he 
says that ‘everything seems to indicate a quiet subsidence of the 
overlying bed into irregularities in the dissolving chalk. Hvery- 
thing here also favours the supposition that the origin of the Clay- 
with-flints is to be ascribed to the gradual dissolving away of the 
Chalk-with-flints, under a capping of drift Brickearth. Mr. Cod- 
rington has therefore come, independently, to the same conclusion 
on the formation of Clay-with-flints as the Geological Survey has 
done. The remark that ‘a covering of drift, made up of Tertiary 
materials (Brickearth ?), seems greatly to promote the formation 
of potholes and the irregular erosion of the Chalk; Tertiary beds, 
unless where they thin out, appear to protect it,’ is to the point, as 
‘also that a ‘vast time must be allowed for the formation of Clay- 
with-flints.’ 
Our author speaks of some drift older than the Boulder-clay ; 
but we do not remember having heard of any of the latter in this 
neighbourhood, except in some geological remarks published in a 
‘Flora of Marlborough’ a few years ago, in which (besides other 
mistakes) the mottled Brickearth (or the Clay-with-flints), so com- 
mon on the Chalk hills near that town, was so called. 
Mr. Codrington ends his paper with a theory of the denudation of 
the Vale of Pewsey, in which we must disagree with him. How 
the escarpments there could have been formed by the action of the 
sea passes our understanding. ‘To treat of this question here would 
take up far too much space; but we would ask—where is the beach 
that should be found at the foot of the sea-cliffs ? or where is the 
talus that should be formed by the mouldering away of the nearly 
vertical cliff to the curved escarpment? Moreover, to speak more 
eenerally, can any one give an instance of a sea-cliff that runs along 
the strike of a formation for scores of miles, as the chalk-escarp- 
ment does round the London Basin ? Surely some such long slow 
agency as that which Mr. Codrington allows to be able to dissolve 
away vast masses of Chalk-with-flints, forming therefrom the Clay- 
with-flints, over a wide-spreading tract of country, would also be 
able to dissolve away the lower beds of the Chalk into the form of 
an escarpment. It is but fair to say that Mr. Codrington allows 
that atmospheric agencies may have had something to do with the 
wearing out of valleys in the Chalk, and that, knowing well that the 
gravels of the Vale of Pewsey are river-gravels, he also allows that 
it has been deepened by river-action; though he supposes an oscilla- 
tion of the land to account for the different heights of some of the 
