DOMAIN IV. 

 TALCOUS. 



MAGNESIA. 



THIS earth seems first to have been dis- 

 covered, or at least sold as a remedy, by 

 an ecclesiastic at Rome about the begin- 

 ning of the eighteenth century. Under 

 the name of magnesia alba, it was proposed 

 as a universal medicine, while it could do 

 little more than supply the place of the 



