192 PLINTHS NATTTRAL HISTOET. [Book XXXIV. 



beyond a doubt, in the furnaces, also, where they smelt silver, 

 but it is whiter and not so heavy, and by no means to be com- 

 pared with that from copper. There are several kinds of it. For, 

 as the mineral itself, from which it is prepared artificially, so 

 necessary in fusing copper ore, and so useful in medicine, has 

 the name of ''cadmia,"^^ so also is it found in the smelting- 

 furnaces, where it receives other names, according to the way in 

 which it is formed. By the action of the flame and the blast, 

 the more attenuated parts of the metal are separated, and 

 become attached, in proportion to their lightness, to the 

 arched top and sides of the furnace. These flakes are the 

 thinnest near the exterior opening of the furnace, where the 

 flame finds a vent, the substance being called " capnitis ;"®^ 

 from its burnt appearance and its extreme lightness it re- 

 sembles white ashes. The best is that which is found in the 

 interior, hanging from the arches of the chimney, and from its 

 form and position named " botryitis."^^ It is heavier than the 

 first-mentioned kind, but lighter than those which follow. It 

 is of two difi'erent colours : the least valuable is ash-coloured, 

 the better kind being red, friable, and extremely useful as a 

 remedy for affections of the eyes. 



A third kind of cadmia is that found on the sides of the 

 furnace, and which, in consequence of its weight, could not 

 reach the arched vaults of the chimney. This species is 

 called " placitis,"^'' in reference to its solid appearance, it pre- 

 senting a plane surface more like a solid crust than pumice, 

 and mottled within. Its great use is, for the cure of itch- 

 scab, and for making wounds cicatrize. Of this last there 

 are two varieties, the ** onychitis," which is almost en- 

 tirely blue on the exterior, and spotted like an onyx within ; 

 and the *' ostracitis,"^** which is quite black and more dirty 

 than the others, but particularly useful for healing wounds, 

 AH the species of cadmia are of the best quality from the 

 furnaces of Cyprus. When used in medicine it is heated a 



^* The metal known to us as " cadmium " was discovered by Professor 

 Stromeyer in 1818 : it is either associuted in its ores with zinc, or forms a 

 native sulphuret. 



*** " Smoky residue." None of these substances formed in smelting are 

 preserved for medicinal purposes at the present day. Tutty is an impure 

 oxide of zinc. 



^s " Cluster residue." From its resemblance to a bunch of grapes. 



^J " Caked residue." ^^ " Shell-formed residue." 



