Q± * ON ST ONY AND METALLINE SUBSTANCES' 



Silica - - - - 50 



Magnefia - - 15 



Oxide of iron 3 4 



Oxide of nickel * - 2\ 



101} 

 Remarks. The excefs of weight, inliead of the ufual Iofs, is owing to 



the difference of oxidizement of the iron, in the {tone and in 

 the refult of the analyns ; which v/ill be found to be the cafe 

 in all analyfes of thele fubitances ; indeed it is always necef- 

 fary to reduce the oxide to the red ftate, as oeing the only one 

 to be depended upon. To avoid future repetition, I fballalfo 

 obferve, firit, that by preliminary experiments, I could not 

 detect any other fubftance than thofe mentioned. Secondly, 

 that the earth obtained as alumina, appeared to me to be 

 moftly, if not intirely, filiceous ; becaufe, after it had been 

 ignited, and again treated with potafh and muriatic acid, I 

 found it was very nearly all precipitated by evaporation. 

 Thirdly, I examined, and judged of, the filica collected from 

 the oxide of iron, in the fame way. Fourthly, the weight of* 

 the magnefia is given,, not immediately, as obtained by eva- 

 poration, but after a fubfequent folution in an acid, and pre- 

 cipitation by potato. And, fifthly, the proportions are taken 

 from the mean of two analyfes. 

 The earthy ma- Nothing remains to be examined, of the ftone from Benares, 

 trix or cement, except the earthy matter, forming a cement or matrix for the 

 fubitances already examined. 100 grains of this matter were, 

 by mechanical means, feparated as perfectly as poffible, from 

 the pyrites, iron, and globular bodies, and analyfed as above. 

 The mean refult of two analyfes gave, 

 Its component Silica 48 



P arts » Magnefia - - - - 18 



Oxide of iron - - - 34 



Oxide of nickel 2f 



lOflf 



Stonefrom EXAMINATION OF THE STONE FROM SIENNA. 



ienna. ^ e ext( , rnu ] coa tj n g G f this ftone appeared to have the 



fame character as that of the ftone from Benares. 



The 



