BOOK XII. 



581 



A — Long wall. B — High walls. C — Low walls. D — Plates. E — Upper pots. 



F — Lower pots. 



The sulphur from such a mixture can best be extracted if the upper pots are 

 placed in a vaulted furnace, like those which I described among other 

 metallurgical subjects in Book VIII., which has no floor, but a grate inside; 

 under this the lower pots are placed in the same manner, but the plates 

 must have larger holes. 



Others bury a pot in the ground, and place over it another pot with a 

 hole at the bottom, in which pyrites or cadmia, or other sulphurous stones 

 are so enclosed that the sulphur cannot exhale. A fierce fire heats the 

 sulphur, and it drips away and flows down into the lower pot, which contains 

 water. (Illustration p. 582). 



Bitumen^* is made from bituminous waters, from liquid bitumen, and 

 from mixtures of bituminous substances. The water, bituminous as well as 



i^The substances referred to under the names bitumen, asphalt, maltha, naphtha, 

 petroleum, rock-oil, etc., have been known and used from most ancient times, and much of our 

 modern nomenclature is of actual Greek and Roman ancestry. These peoples distinguished 

 three related substances, — the Greek asphaltos and Roman bitumen for the hard material, — 

 Greek pissasphaltos and Roman maltha for the viscous, pitchy variety — and occasionally the 

 Greek naphtha and Roman naphtha for petroleum proper, although it is often enough referred 

 to as liquid bitumen or liquid asphaltos. The term petroleum apparently first appears in 

 Agricola's De Natura Fossiliiini (p. 222), where he says the " oil of bitumen . . . now 



