DOMAIN IV. TALCOUS. 



pure. Mr. Tennant has analysed the stone em- 

 ployed in two remarkable ancient buildings. 



" STONE OF YORK 

 MINSTER. 



Carbonic acid . 47,00 



Lime 33,24 



Magnesia . . . 19,36 

 Iron and clay . 0,40 



100,00 



" STONE OF WESTMIN- 

 STER HALL.. 



Carbonic acid . 47,16 



Lime 33,48 



Magnesia . . . 17,76 

 Iron and clay . 1,60 



100,00" 



But the most remarkable stone of this kind is 

 Dolomite. Dolomite, resembling a primitive granular lime- 

 stone, but which, according to many analyses, 

 contains not less than 45 of magnesia, in the 

 form of carbonate. This stone received its name 

 from Dolomieu, who observed it among the 

 remains of ancient sculpture at Rome; arid after- 

 wards discovered it in the mountains of Tyrol. 

 It has been classed among the primitive mar- 

 bles; but the essential difference is, that the in- 

 fluence of the magnesia prevents its effervescence 

 with acids, unless previously pulverised, when 

 the calcareous particles are affected by the ex- 

 posure. It is also sometimes phosphorescent 

 when scraped in the dark, and elastic in thin 

 plates. It sometimes contains veins of green 

 mica, like the primitive marble called Cipolino. 

 In appearance it differs but little from granular 



