1867.] DAWKINS LOWEE-BEICK EARTHS. 109 



me perfectly incredible. "Whether or not the true Bonlder-clay was 

 ever deposited in the Thames Valley proper, is an open question ; but 

 the fact that it lies in the basin of its affluent the Eoding, as well as 

 in those of the next two rivers to the north, the Blackwater and the 

 Colne, would prove that the main features of the country were 

 sketched out before the Boulder-clay period, and that it also was 

 excavated in Praeglacial times. 



Again (to test the truth of relative levels being any guide to 

 antiquity in some instances), the mammal- bearing stratum of the 

 ^Norfolk shore is proved by its fiuviatile shells to have owed its origin 

 to a river ; it lies below high-water mark, at a slightly lower level 

 than the Lower Brick-earths; and yet no one would venture to 

 call it of late PostpKocene age for that reason, because the 

 Boulder- clay happens to lie on its top. "Were it not for this acci- 

 dent, or had the Boulder-clay been lost by denudation, it would be 

 precisely in the same category as those deposits. Under these cir- 

 cumstances I cannot agree with Mr. Prestwich in considering them 

 of late Postpliocene age, but believe that the evidence adduced in 

 this paper is sufficient to relegate them to a higher antiquity than 

 any river- deposits in Britain, the Porest-bed only being excepted. 



8. Summary of Evidence as to Age. — In conclusion I will briefly 

 recapitulate the inferences which the foregoing premisses seem to me 

 to warrant. The direct relation of the Lower Brick-earths to the 

 Boulder-clay being not absolutely proved, it is very probable that 

 the "trail" may be its equivalent in point of time. The superposi- 

 tion of the " trail " over the Lower Brick-earths indicates a far lower 

 temperature at the time of the accumulation of the former de- 

 posit than at that of the latter. The mammals form a connecting 

 link between the fauna of the Forest-bed and that of Postglacial 

 times. The absence of the Arctic group of mammals implies also an 

 absence of cold such as prevailed in the Glacial and Postglacial 

 epochs, and adds to the probability of the beds in question being of 

 an age anterior to the great refrigeration of our climate. Por these 

 reasons I would suggest the insertion of the Lower Brick-earths in 

 the classified list of Pleistocene deposits as follows : — 



1. Forest-bed of Norfolk — climate temperate. 



2. Lower Brick-earths of Thames Valley — climate comparatively 



temperate. 



3. Glacial deposits — climate severe. 



4. Postglacial deposits — climate severe, but gradually becoming 



temperate. , 



Januaet 23, 1867. 



The Eev. George Deane, B.A., B.Sc. (Lend.), Harrold, Bedford- 

 shire ; Joseph Gledhill, Esq., F.M.S., King's Cross, Halifax, York- 

 shire ; and James Parker, Esq., of Oxford, were elected Fellows. 



VOL. XXIII. PAET I. 



