116 



Level" gravels would necessarily be the most ancient, and the beds lying 

 at the lower part of the valley the most modern. What, however, may 

 be the value to be attached to these terms, ancient and modern, can only 

 be measured by a careful consideration of the physiological circumstances 

 attending the relative position of these erratic deposits, with reference to 

 the under-lying strata. A carefiil review of the evidences bearing upon 

 this interesting subject, especially those presented by the gravel-beds on 

 the Somnie, in which human works of art have been found in the " High 

 Level" drifts, associated with the remains of the Mammoth and other 

 extinct quadrupeds, have, however, afforded a standard of measurement 

 which gives reason to believe that the presence of man in Western Europe 

 dates from a period of time incalculably remote. 



Along the course of the Severn vaUey in the neighbourhood of Glou- 

 cester, it is not difficult to trace beds of gravel which may be called 

 " Upper" and "Lower" drifts. The former, occupying the summits of all 

 the rounded hills, out-liers for the most part of the Lias, which like those at 

 Hartpury, Maisemore, Apperly, &c., formed shoals in the ancient tertiary sea 

 of the Severn Straits, and are capped by gravels which represent the first 

 emergence of dry land as the river began slowly to subside into its present 

 channels. The " Lower drifls" are represented by beds of gravel at the very 

 base of the valley, but little elevated above the highest margin of the river. 

 Both sets of gravels have this feature in common, that a large portion of 

 their constituent mineral contents are derived from the degradation of the 

 Old Eed Sandstone, mixed with chalk flints, and portions of traps and 

 sienites, derived in many cases from very remote sources. But with these 

 features of agreement, this difference is observable, that whereas the more 

 ancient gravels exhibit little if any traces of oolite detritus — the lower beds 

 are largely formed, especially on the eastern side of the valley, out of the 

 constituents of the oolitic rocks. This at any rate is noticeably the case in 

 those beds examined by the Club at Highnam and Over, and those which 

 they inspected at the summit of Maisemore Hill. At the latter locality not 

 a vestige of oolite could be detected, even in the minutest grains, while at 

 the former station that mineral was seen to form one of the principal con- 

 stituents of the beds. 



This subject is still too obscure to permit of any beyond the broadest 

 generalization, and it is difficidt to lay down any canon by which to 

 determine with any degree of exactitude the relative horizons of these 

 erratic deposits, which higher up the Severn, as at Upton, present a sec- 

 tional arrangement so closely resembUng that of the same beds at Menche- 

 court and Moulin Quignon, on the Somme, even to the Lacustrine Silt 

 in the valley, that the one section may be said nearly to repeat the conditions 



