15 



Mountain or Carboniferous Limestone. — The bed of the Severn, 

 from the most projecting point of Aust Cliff, is composed of the 

 lower beds of the Mountain Limestone, which at low water are 

 exposed, and covered with Fuci. The Gypseous Marls of the 



High Water. . . ^ 



Low Water. — 



77^^:^ 



« 



New Eed rest upon them, the entire series of the New Red 



Sandstone being absent — indeed, were never deposited — a some- 

 what remarkable feature in this district, and clearly indicates 

 that the overHe of New Red upon the Mountain or Carboniferous 

 Limestone of the western side of the Bristol Coal Field (north) 

 is exceedingly thin and occurs in patches. The points marked 

 " TJlverstone," in the Severn at Aust and Upper Beach, are both 

 on these Limestones, and also St. Tecla's Chapel. I mention 

 this as a point not known to all, though visible at low water; 

 and as another instance of the variabiHty of level of these 

 Limestone masses, I may bring again to your notice the fact of 

 the Rhsetic beds being also upon thera in the Earl of Ducie's 

 Park. 



New Bed Marls. — These beds, the upper member of the New 

 Red series, constitute the base of the Cliff at Aust. They are 

 Gypsiferous — ^the Gypsum being of the fibrous variety — though 

 not sufficiently pure to be used as Plaster of Paris. At the base 

 of the section the beds are somewhat sandy, and rest upon the 

 upturned Carboniferous Limestones. The following measure- 

 ments may be relied upon, being numbered from the base 

 upwards ; but which in my section I will reverse, and give their 

 true order. 



