f 



1855.] PRESTWICH — GRAVEL AT MAIDENHEAD. 133 



which has been too frequently overlooked ; it is of essential importance 

 in considering the drift phsenomena, but its fuller discussion I must 

 reserve for a future occasion. 



With regard to the age of this gravel, it belongs doubtlessly to the 

 same period as the Kingston, Brentford, Kew, and London beds, 

 which I am inclined to consider as amongst the most recent of our 

 drift deposits, and as posterior to the period of the great Boulder Clay 

 of Norfolk and Suffolk ; but the exact relation of these deposits is 

 nowhere clearly seen, and this question of relative age depends upon 

 a variety of collateral evidence which I hope to lay before the Society 

 at a future period. 



In the meantime I may mention that although the boulder clay 

 does not approach within twenty miles* of Maidenhead, yet there is 

 another gravel in that district, distinct from the mammaliferous 

 gravel, and showing that distinctive position tolerably clearly, although 

 not so well as it is seen further westward. 



Section of part of the Valley of the Thames ^ showing the relation of 

 the high-level and the low-level gravels. , 



Railway Station 

 near Maidenhead. 



a. High-level gravel 5 to 10 feet. 



b. Valley-gravel, with mammalian remains 5 to 20 „ 



c. Mottled clays (lower tertiary). 



d. Chalk. 



Thus immediately from this plain of gravel there rises near the 

 Maidenhead station the chalk hill on which Taplow stands. This 

 hill forms a ridge connected with the hills at Beaconsfield and above 

 Wycombe. Over these hills and extending as far as Taplow is 

 another gravel very similar in many respects to that in the valley, but 

 always on a higher level, and without organic remains. It is an older 

 gravel. In the same way the hills of Bagshot and Windsor Forest 

 to the southward of the Thames Valley are capped by older gravel. 

 Both these possess some peculiar and interesting features, but the 

 description of them I will reserve until I can bring the subject before 

 you in a more complete form. My object on this occasion is merely 

 to point out the position and general relation of the gravel in which 

 the very remarkable fossil, the subject of this evening's important com- 

 munication by Prof. Owen, was found, and not at present to occupy 

 your time by any independent inquiry on the physical phsenomena 

 considered apart. 



* The nearest places to which I have yet traced it are on the Finchley Hills ; 

 and it extends probably as far as Hendon HiU. 



