ON THE USE OF LIME, MARL, AND SHELL-SAND. 



15 



Composition of Great (No. I.) and Inferior Oolite Limestone 

 (Nos. II. and III.). 



99-384 



99-85 



100-065 



No. I. is a good limestone, equally useful as a building stone 

 and for burning. 



No. II. cannot be used for building, but being hard does well 

 for road mending ; less valuable it is to the lime-burner. 



Both these stones are from the neighbourhood of Cirencester. 



No. III. occurs in the neighbourhood of Combe, near Sher- 

 borne, and resembles in its general features the specimen of 

 Inferior Oolite limestone from the neighbourhood of Cirencester. 



Composition of Cornbrash (No. I.) ; Stonefield Slate (No. II.) ; and 

 Forest Marble Limestone (No. III.). 



Carbonate of lime .. 



Sulphate of lime . . 



Phosphoric acid 



(Equal to bone-earth) 



Magnesia 



Oxide of iron and alumina 



Soluble silica 



Insoluble silicious matters 



99-420 



No. II. 



84-264 



649 



177 



(244) 



454 



1-809 



582 



11-558 



99-433 



No. III. 

 81-242 

 737 

 032 

 (072) 

 372 

 1-420 

 1-210 

 15-240 



100-210 



Cornbrash limestone, it will be seen, contains most lime, and 

 likewise an appreciable quantity of phosphoric acid ; but its 

 texture is such that it cannot be conveniently used as a building 

 stone, nor does it do well for lime-burning. The soils resting 

 on Cornbrash, and formed by its degradation and decomposition, 

 are noted for their corn-growing qualities : hence the derivation 

 of the name Cornbrash. 



Stonefield slate and Forest Marble limestones are both very 

 impure forms of carbonate of lime. Stonefield slate on account 

 of its slaty structure is used as roofing slate ; and some of the 

 beds of forest marble, which separate into thin slates, furnish 

 slabs for barn-floors and pigsties. 



