Chap. 22.] CADMIA. 191 



tenth part of lead^* and one twentieth of silver-lead, this 

 combination being the best adapted for taking the colour 

 known as *' Grsecaaicus.""^ The last kind is that known as 

 *' ollaria/'^o from the vessels that are made of it : in this 

 combination three or four pounds of silver-lead^^ are added to 

 every hundred pounds of copper. By the addition of lead to 

 Cyprian copper, the purple tint is produced that we see upon 

 the drapery of statues. 



CHAP. 21. — THE METHOD OF PKESERVI^^G COPPER. 



Copper becomes covered with verdigris more quickly when 

 cleaned than when neglected, unless it is well rubbed with 

 oil. It is said that the best method of preserving it is 

 with a coating of tar. The custom of making use of copper 

 for monuments, which are intended to be perpetuated, is of 

 very ancient date : it is upon tablets of brass that our public 

 enactments are engraved. 



CHAP 22. (10.)— CADMIA. 



The ores of copper furnish a number of resources^^ q^^^ ^^q 

 employed in medicine ; indeed, all kinds of ulcers are healed 

 thereby with great rapidity. Of these, however, the most 

 useful is cadmia.s^ This substance is formed artificially, 



"8 "Plumbi nigri"— " black lead," hterally, but not what we mean by 

 that name. * '' 



" The " Grecian" colour. It does not appear to have been identified, 

 nor does it appear what it has to do with moulds. 



so " Pot" copper, or brass. 



81 Beckmann is of opinion that this " plumbum argentarium" was a 

 mixture of equal parts of tin and lead. Hist. Inv. Vol. II. p. 220. John's 

 Edition. 



S2 iiq^^ of ^jjggg preparations are in reality highly dangerous. Oxides 

 i however, or salts of copper, have been employed internally with success^ 

 acting by alvme evacuation and by vomiting. The Crocus Veneris of the 

 old chemists was an oxide of copper. It is still used by the peasants of 

 : bilesia, Ajassou says. 



' ..% ^^.i! ob^'o^s t'"at the "cadraia" here described must be an essen- 

 tially difrerent substance from the " cadmia " mentioned in the second 

 Chapter of this Book, that being a natural production, possibly calamine 

 or hydi-osihcate or carbonate of zinc; wliile the "cadmia" of this Chapter 

 is a furnace-calamine, a product of the fusion of the ore of copper, or 

 zmc— B. It is evident, too, that copper ores, impregnated with zinc or ca- 

 lamine, also passed under this name. See Beckmann, Hist. Inv. Vol. II. 

 pp. 33—35, BoJm's Edition^ where this subject is discussed at considerable 

 length : also the treatise by Delafosse, in Lemaire's Edition of Pliny. 



