DURING THE MIDDLE AGE. 117 



be feparatcd from each other by acids, or, in the 

 dry way, by fulplmr, antimony, and cementa- 

 tion. The eleventh fliews the method of fepa- 

 rating filvcr from copper and iron, by cliqua- 

 tion with lead. The twelfth dcfcribcs the pre- 

 parations of common fait, nitre, alum, martial 

 vitriol, bitumen, and glafs. From all thefe ac- 

 counts, therefore, it appears, that the chcmiftsof 

 thofe days proceeded in their operations as we 

 do at prefent, except that we have learned, in a 

 a more cultivated A ate of the fciencc, to rcjed 

 many things as ufclefs, and to form (horter pro- 

 ceflcs. In his book on the nature of foflils, A- 

 gricola treats particularly on minerals. He di- 

 vides all earthy bodies into two claflcs, thofc 

 which flow out from the earth, as water and 

 fubtcrrancous air, and foflils; which he agaiu 

 arranges under five heads : i/?, Earths are en- 

 numerated according to the ufe that is made 

 of them': the earth of hufbandmcn, of pot- 

 ters, of fullers, painters, artificers, and phy- 

 ficians. 2///v, Concrete juices: fait, nitre, a- 

 him, vitriol, chryfocolla, ultramarine, Armeni- 

 an ilonc, mil, orpimcnt, fundanicha, fulphur, 

 bitumen, afphaltus, camphor, pifiafphaltus, a;n- 

 pdlites, jett, fofiil coal, and amber. 3<M 

 Stones ftriclly fo called : magnet, fchiilus, mo- 

 rochtus,gypfum, talc, amianthus, mica, the Jewilh 

 flonc, and other petrifactions ; gcodcs, urtites, 

 enhydrus, pirmex, laj)is molaris, and fluor mi- 

 neralis. Gems ^ not thofe only that are tranf- 

 H 3 



