70 



LIMESTONES. 



Upper 

 Gallery. 



Wall-case 43. 



3. 



Compact bituminous freshwater limestone 



Part of the middle Purbeck limestone 



Do 



called the Feather Bed, and formed chiefly of the remains 

 of bivalve shells, Cyelas or Cyrena. — H.W.B. 



4. — Stonesfield slate ; fissile limestone, quarried ex- 

 tensively for roofing slates. — Benborough, Gloucestershire. 



" This is an exceedingly variable series of beds, bein<* 

 composed in some places of sandy flags, slates, and blue 

 limestones, and in others, of white oolite freestone, with 



false bedding, and not unlike the freestones of the 

 Inferior Oolite. Where the beds become sandy and fissile 

 as at Sevenhampton Common, Througham, Eyeford and 

 Naunton, they are capable of being split into slates, which 

 form a very suitable roofing material, especially for buildings 

 in the Tudor or other styles of Gothic architecture.' 

 ("Memoirs of 



much 



> 



of the Geological Survey" : " The Geology 

 of the Country round Cheltenham," p. 53, & Map 44. 

 Hull.) 



The rock is quarried in summer and exposed to the 

 weather in winter, when 



>/ 



it is split by the frost into thin 



which are capable of being 



dressed into slates generally of a heavy kind. The manner 

 of the formation of these slates must not be confounded with 



that produced by slaty cleavage. (See Wall-case 46, 

 and p. 118.)— A. C. R. 



5. — Carboniferous limestone, compact limestone, chiefly 

 composed of the jointed stems and detached rings of En- 

 crinites. The lower beds of the Carboniferous Limestone are 



in 



places 



Encrinites 



In 



_ 



Pembrokeshire these Encrinite beds are 500 feet thick. 



Hi 



fi 



6. — Shelly limestone, from the " freestone beds " of In- 



Bourton-on-the-Hill, Gloucestershire. 



" Above Bourton-on-the Hill, there are several quarries, 

 some of the beds are traversed by bands of pure hsematite, 

 in which the fibrous structure is apparent. There is also a 



limestone, 01 



mi ^ 



This is a 



lie jnefeic i 

 several smal 

 siliceous and 



lUWn 



Silurian lin 



kid ch('t 

 Presented to 



12—Caki 



tfon smelt 



