210 PROF. J. E. MARR OX THE [vol. lxXV,. 



on the 3o-40-foot plateau on which the old and new Botanic 

 Gardens Site and the Downing Site are located. 



A gravel-pit on the Eoyston Road, half-a-mile south of Trump- 

 ington, close to the London & North-Western Railway, is outside 

 the limit of the tract which I am describing in detail; but, as 

 Mr. Kennard treats of the shells found there, I may notice the 

 occurrence of worked flints in this deposit, one of which, found 

 by the late Mr. St.-H. Lingwood, is apparently of Chellean tvpe. 

 The shells were collected by Miss M. E. J. Chandler, Mr. T. C. 

 Nicholas, and rnyself . 



It is important to note that the localities in which these 

 implements were found are at elevations considerably below that 

 of the Observatory Gravels to be described later, as are also the 

 Barrington Beds. 



Taking all the fossil evidence into consideration, it would appear- 

 that in Chellean (or possibly pre -Chellean) times a valley existed in 

 the vicinity of Cambridge, the bottom of which was there not more 

 than 20 feet above present sea-level, and only about 10 feet above 

 the present river. The evidence on the ground agrees with the 

 palaeontological evidence in pointing to the correlation of these 

 deposits with the Co rbicula -bearing beds containing marine fossils 

 at Bluntisham and March, although A. J. Jukes-Browne correlated 

 the latter with the gravels of the Ancient River System (Obser- 

 vatory Gravels, etc.). 



There is, then, evidence in the neighbourhood of Cambridge of" 

 deposits at 25 to -10 feet above sea-level containing Corbicala flv- 

 minalis, JJnio littoral is, Belgrandia maryinata, Hippopotamus^ 

 and implements of Chellean type. These deposits we may, after- 

 consideration of the recent discoveries in North-Western France, 

 confidently refer to an early age of Palaeolithic times, and some 

 may even be anterior to those times. 



(/>) The Observatory Gravels. 



These deposits now occupy a ridge separating the Cam Valley on 

 the east from a minor valley on the west which is drained by two 

 streamlets, one flowing northward into the Great Ouse and the other 

 southward into the Cam. The gravels reach a height of 84 feet at 

 the Observatory and of about 88 feet near the Traveller's Rest, 

 some half-a-mile north of this. 



The deposits appear to have been laid down originally in the- 

 small western valley, and not in that now occupied by the Cam : 

 for the base of the gravel is about 20 feet lower near the Madingley 

 Road than it is where it ends on the eastern side of the present ridge, 

 as shown in the section (PI. XI, fig. 1). This is recorded by the 

 Geological Surveyors, 1 who further note that a section exposed in 

 1873 showed 



' that the gravel of Gravel Hill, on which the Cambridge Observatory is built, 

 lies banked up against the S.W. side of the Chalk Marl ridge.' 



1 ' The Geology of the Neighbourhood of Cambridge ' Mem. Geol. Surv.. 

 1381, p. 89. 



