BRISTOL BUILDING STONES. 



107 



Batli stone is much liglitor and less compact, the specific 

 f^ravity being from 2'4 to 2-6, and the weight per onbic foot 

 in poundavarying from 116 (Combe Down) to 123 (Box Hill). 

 I have not myself made any experiments on the crushing 

 stress which this rock is capable of resisting, but from 1,800 

 to 2,000 lbs. ('8 to '9 ton) is given as the crushing load for 

 a cubic inch of the rock. It is a very absorptive rock, taking 

 up from 10 to 15 pints per cubic foot, or from 20 to .'^0 per 

 cent, by volume. 



The following notes on. the Bath stones are kindly supplied 

 by Mr. W. Brock : 



" Coombe Down, near Bath, formerly had extensive quar- 

 ries ; but they are almost exhausted, the supply at present 

 being very uncertain. This is a first-class stone, and has 

 been used in some of the buildings in this city. Trinity 

 Church, St. Philip's, is an example. 



" Box Ground stone, if selected and cut into small scant- 

 ling, so as to get rid of the .soft places, is a good weathering 

 stone, and well adapted for plinths, sills, quoins, and copings. 

 The quarric^s are very extensive, being mostly underground. 



" Corsham stone, if thoroughly dried, is a good stone. 

 The Post Office, Small Street, was built with this. 



" Westwood and Stoko quarries are more recently opened ; 

 the stone from them is well adapted for external work." 



The fi'ccstono beds belong to the Great Oolite series, and 

 vary from ten to forty feet in thickness. They are generally 

 worked by drifts or tunnels. While it still retains the 

 "sap" or quarry water, it is soft, and may be worked with 

 (i-T'cat facility. On removal from the parent rock the blocks 

 liardcn considerably ; a process due, apparently, to evapora- 

 tion of the water with which the stone is satarated, and the 

 deposition of the calcareous salts it contains. 



The deposition being superficial forms a kind of natural 



