82 ME. B. THOMPSON ON THE GEOLOGY OF THE [Feb. 1 899, 



(iv) Sands and Gravels (Mid-Glacial). 



The gravel-beds on this raihvay in the neighbourhood of Rugby 

 are a part of the great plateaux of sand and gravel upon which 

 Eugby stands. The maximum thickness is about 25 feet, but, as 

 will be seen from the section of the line, the thickness varies 

 greatly, owing more to the irregularity of the junction of the sand- 

 and-gravel with the underlying Boulder Clay or other beds than to 

 a difference in level of the ground. 



Commencing at the beginning of the cutting, at D, 52 miles 

 40 chains (fig. 1, p. 66), the gravel terminates on the top of the 

 steep bank of the Hillinorton cutting, overlooking the Lower Lias 

 valley to the south at M, 54 miles 7 chains (fig. 2, p. 70). 



The gravel does not differ much in composition from I) to I ; it is 

 very irregularly bedded, rather coarse and dirty, of a reddish colour, 

 and sandy in places. From I to M it seems rather cleaner and 

 of a richer red, and between K and L more sandy and coherent. 



I found no fossils whatever in this gravel, though it is true that 

 I did not devote very close attention to it. It contained much 

 chalk in small pieces ; flint, mostly rather angular ; and numerous 

 well-rolled pebbles of quartzite, quartz, gritstone, etc. It will be 

 noticed that, at about 53 miles 42 chains, the Boulder Clays are cut 

 through from top to bottom by a pocket of the gravel (fig. 1, p. 66). 



For the next 7 miles there is, on the whole, a singular absence 

 of Drift of any kind, at least in quantity deserving of particular 

 record. A thin capping to the cuttings between 56 miles 20 chains 

 and 57 miles (fig. 3, p. 72) yielded : Ammonites capricornus, 

 Gryplicea, limestone, quartz, and pebbles of various kinds. 



in the cutting, between 61 miles 30 chains and 61 miles 53 chains 

 (fig. 5, p. 76), there are some sands and gravels interposed between 

 a red Boulder Clay and the Lower Lias Clay. The deposit is very 

 complicated, consisting of a red breccia or conglomerate with some 

 ironstone-fragments not much rounded, fine sand varying in colour, 

 and whitish layers of calcareous matter, all much intermingled, 

 varying in thickness up to 5 feet or more. A distinct white layer 

 of calcareous matter is interposed between the conglomerate and 

 the red marl above it. 



(v) Red Boulder Clay (Upper Boulder Clay). 



The cutting in the parish of Catesby mentioned in the foregoing 

 paragraph has, resting on the sands and gravels, a mass of red 

 Boulder Marl; it is of a red different from that of the gravels, and 

 contains green inclusions; indeed everything points to its direct 

 derivation from the New Red Marl. No doubt it represents in 

 time the Upper Chalky Boulder Clay of other parts of the railway 

 farther south. In thickness it varies up to 10 feet. No actual 

 boulders were found in this marl ; it breaks into roughly cubical 

 blocks on drying, and falls were rather frequent. 



