xvni. DR. KIDD. DR. BUG KL AND. 459 



part of the Thames Valley. It is not accompanied by boulder clay; 

 contains no large erratic blocks ; but a considerable variety of 

 stones of greater size than such as are commonly found in gravel. 

 Two sorts of stone are the most common : one is quartz, usually 

 in small white pebbles, the other is hard reddish gritstone or 

 quartzite, a metamorphic rock which corresponds with none in situ 

 better than with that of Hartshill, near Nuneaton, This kind of 

 stone may be collected from half the ploughed lands of Oxford- 

 shire, on the southward slopes of the oolites, on the Chiltern hills, 

 and in the Vale of the Thames about Oxford and Abingdon. I 

 have never seen a fossil in it. It is probable that the new red 

 conglomerates of Warwickshire and the midland counties may 

 with justice be credited as the immediate source of the pebbles. 

 Whence they came originally may be hard^ to determine ; though 

 such rocks as those of the Lickey Hill, and Hartshill metamorphic 

 sandstones of some palaeozoic kind, possibly destroyed in early 

 mesozoic ages are clearly indicated a . 



In the vicinity of Oxford, this high level gravel may be ob- 

 served, in the state of a coarse drift with masses several pounds in 

 weight of quartzite, felstone, and gritstone, but with little or no 

 trace of the oolite so common in the lower gravels of the Thames. 



On the clay hills at Bletchingdon and Kirtlington is a high 

 level drift, remarkable for the abundance of small fragments of 

 iron-oxide, such as occurs at the base of the oolite in several places 

 further north, and an unusual red sand. On Leafield beacon the 

 ancient tumulus is composed of white quartz pebbles, and various 

 worn fragments of small size, derived from rocks far beyond the 

 drainage of the Thames. 



From observing facts of this kind Dr. Kidd, as early as 1815, 

 while Professor of Chemistry, presented a clear division of the 

 Oxford gravels, into two groups the one a hill group, with stones 

 brought from a distance; the other a valley group, containing 

 portions of the neighbouring strata b . 



Dr. Buckland, in his celebrated work, entitled * Keliquia3 Dilu- 

 vianse c ,' gives a map of the distribution of the drift in the 

 vicinity of Oxford ; by which it appears that he had observed the 



See Brodie in Geol. Proc. 1867. 

 b Geological Essays, 1815. 1821, 4to. p. 279. 



