278 



BOOK Will. 



into the water, but into the ground, there is created a sulphurous or a 

 bituminous substance resembling pompholyx 1 , and so light that it can be 

 blown away with a breath. Some employ a vaulted furnace, open at the 

 front and divided into two chambers. A wall built in the middle of the 

 furnace divides the lower chamber into two equal parts, in which are set pots 

 containing water, as above described. The upper chamber is again divided 

 into three parts, the middle one of which is always open, for in it the wood 

 is placed, and it is not broader than the middle wall, of which it forms the 

 topmost portion. The other two compartments have iron doors which are 

 closed, and which, together with the roof, keep in the heat when the wood 

 is lighted. In these upper compartments are iron bars which take the place 

 of a floor, and on these are arranged pots without bottoms, having in 

 place of a bottom, a grating made of iron wire, fixed to each, through 

 the openings of which the sulphurous or bituminous vapours roasted from 

 the ore run into the lower pots. Each of the upper pots holds a hundred 



A HEAP OF CUPRIFEROUS STONES. B KINDLED HEAP. 



THE BEDS OF FAGGOTS. 



C STONES BEING TAKEN TO 



'Bearing in mind that bituminous cadmia contained arsenical-cobalt minerals, this 

 substance " resembling pompholyx " would probably be arsenic oxide. In De Nalura 

 Fossilium (p. 368), Agricola discusses the pompholyx from cadmia at length and pronounces 

 it to be of remarkably " corrosive " quality. (See also note on p. 112.) 



