PROCEEDINGS 
OF THE 
Cambridge Bhilosopbhieal Society, 
The Minerals of some Sands and Gravels near Newmarket. 
By R. H. Rasratt, M.A., Christ’s College. 
[Read 10 February 1913.] 
In a recent communication to this Society* a brief account 
was given of the composition and characters of certain sands and 
gravels of Pleistocene and Recent age found in the neighbourhood 
of Cambridge. A few specimens have since been collected from 
deposits of the same general age in the Newmarket district, and 
the present paper embodies the results of an examination of these 
by methods similar to those previously employed, with slight 
modifications suggested by experience. 
The deposits here described are not connected with any 
streams now existing and must have been formed by rivers 
belonging to an ancient drainage system which has now totally 
disappeared, having undergone complete modification by capture 
or other processes of a like nature. For the present purpose 
however it is unnecessary to discuss in detail the origin of these 
deposits; the main object is to place on record their characters 
and composition for the guidance of future workers. It is hoped 
that a systematic investigation of the lithological characters of the 
gravels and sands of this region may eventually succeed in 
establishing the existence of definite types of deposit which may 
_be correlated with the physical conditions prevailing at different 
periods in the past. 
___ The deposits here described are referred to very briefly in the 
publication of the Geological Survey+ dealing with this district, 
and no detailed descriptions seem to exist. When mentioned at 
* Rastall, ‘‘The Mineral Composition of some Cambridgeshire Sands and 
Gravels,”” Proc. Camb. Phil. Soc., vol. xvi. 1913, pp. 132—143. 
t “The Geology of parts of Cambridgeshire and Suffolk,” Mem. Geol. Surv. 
1891, p. 72. 
VOL. XVII. PT. II. 1h: 
