DOMAIN IV. TALCOUS, 



Lemnian earth, and other boles. As Theo- 

 phrastus, however, in describing the stone 

 called magnetes, says it may be turned on 

 a lathe, and has a silvery appearance, Dr. 

 Kidd agrees with Hill, that the ancient 

 Greeks called the load-stone heraclea, but 

 the more modern magueies; and Pliny's 

 description of the stone brought from Mag- 

 nesia, in Asia, seems to belong to a talcous 

 substance*. 



Hoffman, Black, and Bergman, contri- 

 buted to establish the difference between 

 magnesia and lime. It seems originally to 

 have been prepared from nitre; but sea- 

 water contains the sulphate of magnesia, 

 a salt composed of this earth and sulphuric 

 acid; and which is also found in many 

 springs, particularly at Epsom, whence it 

 was called Epsom salt. 



Magnesian or talcous earth is infusible 

 in the strongest heat. It does not form 



* Kidd, i. 91. It is singular that the modern Italians have also 

 a calamita lianca, or white magnet, which is described as fibrous, 

 and probably belongs to the same description. Ferber, Italy 88, 

 says it is a white hardened bolus, striated like asbestos. 



