278

BOOK VIII.

into the water, but into the ground, there is created a sulphurous or abituminous substance resembling pompholyx 1 , and so light that it can beblown away with a breath. Some employ a vaulted furnace, open at thefront and divided into two chambers. A wall built in the middle of thefurnace divides the lower chamber into two equal parts, in which are set potscontaining water, as above described. The upper chamber is again dividedinto three parts, the middle one of which is always open, for in it the woodis placed, and it is not broader than the middle wall, of which it forms thetopmost portion. The other two compartments have iron doors which areclosed, and which, together with the roof, keep in the heat when the woodis lighted. In these upper compartments are iron bars which take the placeof a floor, and on these are arranged pots without bottoms, having inplace of a bottom, a grating made of iron wire, fixed to each, throughthe openings of which the sulphurous or bituminous vapours roasted fromthe ore run into the lower pots. Each of the upper pots holds a hundred

I

aisse

""liiilSIiil

mm

1 1\ VV' 1 .v\U«

l\\\V

>vMvV§:

A—Heap of cupriferous stones. B— Kindled heap. C— Stones being taken to

THE BEDS OF FAGGOTS.

’Bearing in mind that bituminous cadmia contained arsenical-cobalt minerals, thissubstance resembling pompholyx would probably be arsenic oxide. In De NaturaFossihum (p. 368) Agricola discusses the pompholyx from cadmia at length and pronouncesit to be of remarkably corrosive ” quality. (See also note on p 112)