THE SOURCES AND USES OF IRON PYRITES. 
117 
their radiating arms, water could be raised from considerable 
depths. Ten of these wheels have been discovered at San 
Domingos ; eight of them were 1 6ft. in diameter, and the 
other two 12ft. 6in. 
The remains of another Roman contrivance for the drainage 
of water were discovered some years since in one of the Spanish 
mines near Seville. This arrangement consisted of a number 
of Archimedean screws which, one after another, raised the water 
from a series of wooden tanks lined with sheet lead. The whole 
of this apparatus, with the exception of the leaden lining of the 
cisterns, was composed of wood fastened with oaken pegs, and 
sometimes strengthened by ropes of esparto grass ; the con- 
structors thus evidently showing they were aware that iron 
was unfitted for this purpose in the presence of cupreous waters 
by which it is rapidly acted upon. 
Earthenware lamps of Roman workmanship are constantly 
found in the old workings of the mines, while vessels and imple- 
ments of copper or bronze are occasionally met with ; less 
frequently human bones are exposed, which, by the action of 
copper salts upon their calcic phosphate, have assumed an ap- 
pearance approaching that of turquoise. It may be mentioned 
also that some years since a bronze plate was found at the 
entrance of a crushed Roman gallery at Rio Tinto, which stated 
it had been begun during the reign of Cocceius Nerva, a.d. 
96-98. This plate is now in the collection of the School of 
Mines at Madrid. 
The Roman metallurgist smelted his ores in the immediate 
vicinity of the mines from which they were obtained, and the 
discovery of the foundations of blast-furnaces, as well as of frag- 
ments of earthen tuyeres , renders it probable that a blast of some 
kind was used. This is confirmed by the form assumed by the 
cakes of slag, of which vast heaps are piled up in the neigh- 
bourhood of all the principal pyrites mines of Spain ; these slag- 
heaps are usually situated above the level of the water-courses 
of the district, from which it may be inferred, either that the 
blast was obtained by manual labour, or that a furnace allied 
to the modern pavo , still used for smelting lead ores and slags 
in the neighbourhood of Carthagena, was employed. 
The extent of the mining and metallurgical operations, an- 
ciently carried out in this portion of Southern Spain, will be 
readily understood when it is stated that the slag-heaps in close 
proximity to Rio Tinto cannot weigh less than a million and a 
half tons, and that there are large, although less extensive, 
deposits at Tharsis, Buitron, and various other localities. 
That, at least, a portion of the labour of these establishments 
was performed by slaves is abundantly evident from the re- 
peated discovery of skeletons still retaining their chains. At a 
