on certain Stony and Metalline Snbflances. 139 



Hiore rich in iron than that I have juft defcribed ; a circum- 

 ftance I think it ncedlefs to repeat in the following defcrip- 

 tions of them. The (tone now treated- of, does not, when 

 breathed upon, emit an argillaceous fmell : the fame remark 

 may be applied to all the others. 



The fpecific gravity of this ftone is 3352* 



Stone from York/hire. 



This ftone, the conftituent parts of which are exactly the 

 fame as thofe of the ftones from Benares, differs from them, , 

 however, 



Firft, In having a finer grain. 



Secondly, That the fubftance defcribed as being in the 

 form of fmall globular or elliptical bodies, is not fo con- 

 ftantly in thofe torms, but is alfo found in particles of an 

 irregular fhape; a circumftance that is not met with in the 

 other Hones : thefe bodies are likewife, in general, of a 

 i mailer fize. 



Thirdly, The proportion of martial pyrites, which has 

 precifely the fame characters as that in the ftones from Be- 

 nares, is lefs ; on the contrary, that of the iron in the me- 

 tallic ftate is much greater. The quantity I was able to fe- 

 parate by means of the magnet, appeared to me to compofe 

 about eight or nine parts, in one hundred, of the weight of, 

 the whole mafs. I obferved many pieces of this iron, of a 

 pretty confiderable fize ; one of them, taken from a portion 

 of the ftone I had powdered in order to feparate the iron, 

 weighed feveral grains. 



The part of the ftone which is in an earthy ftate, and 

 which ferves to connect the other parts together, has rather 

 more confidence than that of the preceding ftones; and its 

 appearance does not differ much from that of decompofed 

 felfpar or kaolin. The ftone itfelf, therefore, although by no 

 means hard, is rather more difficult to break with the fingers. 



The fpecific gravity of this ftone is 3508. 



Stone from Italy. 



This ftone was in a perfectly entire ftate ; confequently, its 

 whole furface was covered over with the black cruft peculiar 

 to all ftones of this kind. As the ftone was of a very fmall 

 fize, it became neceflfary to facrifice the whole of it to the 

 investigation of its nature. Its grain was coarfe, fimilar to 

 that of the ftones from Benares : in it might be perceived the 

 fame gray globular bodies, the fame kind of martial pyrites, 

 and the fame particles of iron in the metallic ftate. The 



proportion 



