74 



C. MOORE ON ABNORMAL GEOLOGICAL 



around it. Its presence often puzzled me ; but there is little doubt 

 that it is due to an alluvial infilling into a small limestone cavern, 

 and is connected with one of three thin veins of alluvial material 

 ■which are present in this quarry. A cavern was many years ago 

 discovered on the Down, containing, amongst other things, the 

 remains of Hippopotamus, which are now in the Bristol Museum. 

 These three veins are filled with^ an ochreous or brown clay, which, 

 when critically examined in its natural condition, appears to differ 

 slightly in character in each, as though they might have received 

 their infilling at somewhat different times ; still, to save labour in the 

 examination of their contents, they were mixed together. Their 

 organic remains are very varied, and not less so their mineral con- 

 stituents. Their Postpliocene or still later age is indicated by the 

 presence in them of frequent portions of the incisor teeth of Arvicola, 

 and a single shell of Helix. Although all the remains are rare, those 

 from the Lower Lias are most abundant. These consist of young 

 forms of Ammonites of two species, Myacites and Astarte, Cylindrites 

 and portions of three other univalves, a Pentacrinite-stem, and a 

 single valve of an Entomostracon. There are teeth and scales of 

 fishes, and a fragment of bone which may be either Liassic or BJisetic. 

 The interesting presence of Bhsetic remains, however, is shown by 

 teeth of Saurichthys and Lophodus and a small palate identical with 

 species from Holwell. Some of the teeth are bleached and worn by 

 water-erosion. The little calcareous tubes accompany them. 



The residue of these veins, after washing, shows a great abund- 

 ance of black pisolitic granules. The following analysis of its 

 mineral contents has been obligingly made by Mr. Gatehouse, City 



Analyst of Bath : — 

 Soluble in acids : 



"Water 7'80 



Calcium carbonate 20-50 



Magnesium carbonate 0*73 



Oxide of iron , 6*50 



Zinc carbonate (calamine) 0*54 



Manganese dioxide 0*50 



Lead-sulphide (galena) . . . . „ 0'90 



Silica 8-16 



Alumina 2*60 



Potassium 0-07 



48-30 



Insoluble in acids : 



Calcium sulphate. 0*39 



Silicate of zinc 0-25 



Oxide of iron (insoluble) 6-55 



Alumina „ 10*45 



Silica „ 33-70 



Copper . , trace 



99-64 



