BOOK VIII. 273 



in a short strake, at the head of which stands the washer, who draws the water 

 upward with a wooden hoe. The water running down again, carries all 

 the light particles into a trough placed underneath. I shall deal more fully 

 with this method of washing a little later. 



Ore is burned for two reasons ; either that from being hard, it may become 

 soft and more easily broken and more readily crushed with a hammer or 

 stamps, and then can be smelted ; or that the fatty things, that is to say, 

 sulphur, bitumen, orpiment, or realgar 3 may be consumed. Sulphur is 

 frequently found in metallic ores, and, generally speaking, is more harmful 

 to the metals, except gold, than are the other things. It is most harmful of 

 all to iron, and less to tin than to bismuth, lead, silver, or copper. 

 Since very rarely gold is found in which there is not some silver, even gold 

 ores containing sulphur ought to be roasted before they are smelted, because, 

 in a very vigorous furnace fire, sulphur resolves metal into ashes and makes 

 slag of it. Bitumen acts in the same way, in fact sometimes it consumes 

 silver, which we may see in bituminous cadmia*. 



I now come to the methods of roasting, and first of all to that one which 

 is common to all ores. The earth is dug out to the required extent, and 

 thus is made a quadrangular area of fair size, open at the front, and above 

 this, firewood is laid close together, and on it other wood is laid trans- 

 versely, likewise close together, for which reason our countrymen call this 

 pile of wood a crate ; this is repeated until the pile attains a height of one 

 or two cubits. Then there is placed upon it a quantity of ore that has been 

 broken into small pieces with a hammer ; first the largest of these pieces, 

 next those of medium size, and lastly the smallest, and thus is built up a 

 gently sloping cone. To prevent it from becoming scattered, fine sand of the 



*0rpiment and realgar are the red and yellow arsenical sulphides. (See note on p. in). 



*Cadmia biiuminosa. The description of this substance by Agricola, given below, 



indicates that it was his term for the complex copper-zinc-arsenic-cobalt minerals found in 



the well-known, highly bituminous, copper schists at Mannsfeld. The later Mineralogists, 



Wallerius (Miner alogia, Stockholm, 1747), Valmont De Bomare (Mineralogie, Paris, 1762), 



and others assume Agricola's cadmia biiuminosa to be " black arsenic " or " arsenic noir," 



but we see no reason for this assumption. Agricola's statement (De Nat. Foss., p. 369) is 



. . . . the schistose stone dug up at the foot of the Melibocus Mountains, or as they are 



now called the Harz (Hercynium), near Eisleben, Mannsfeld, and near Hettstedt, is similar 



to spinos (a bituminous substance described by Theophrastus), if not identical with it. 



This is black, bituminous, and cupriferous, and when first extracted from the mine it is thrown 



out into an open space and heaped up in a mound. Then the lower part of the mound is 



surrounded by faggots, on to which are likewise thrown stones of the same kind. Then 



the faggots are kindled and the fire soon spreads to the stones placed upon them ; by 



these the fire is communicated to the next, which thus spreads to the whole heap. This 



easy reception of fire is a characteristic which bitumen possesses in common with sulphur. 



Yet the small, pure and black bituminous ore is distinguished from the stones as follows : 



when they burn they emit the kind of odour which is usually given off by burning 



bituminous coal, and besides, if while they are burning a small shower of rain should fall, they 



burn more brightly and soften more quickly. Indeed, when the wind carries the fumes 



so that they descend into nearby standing waters, there can be seen floating in it 



something like a bituminous liquid, either black, or brown, or purple, which is sufficient to 



indicate that those stones were bituminous. And that genus of stones has been recently 



found in the Harz in layers, having occasionally gold-coloured specks of pyrites adhering 



to them, representing various flat sea-fish or pike or perch or birds, and poultry cocks, 



and sometimes salamanders." 



