SALT. 
443 
slaty nature. The salt is extracted from this mine 
in a very peculiar manner. The workmen pene- 
trate into the mass by forming parallel galleries ; 
into these they introduce a quantity of water, which 
is left there for several months. When the water 
is supposed to be completely saturated, they conduct 
it from the gallery through a trough, and evaporate 
the solution. The walls and lumps of salt which 
support these subterranean passages, being partly 
dissolved by the water, give way, and the earth falls 
in ; but in a few years the rubbish becomes solid, 
and the passage is again explored. 
Spain is rich in salt-mines, three of which are 
described by Bowles in his Natural History of 
Spain. The first which he mentions is situated in 
a mountainous country between the kingdoms of 
Valencia and Castile. The depth of the mine is 
unknown, since they have already penetrated three 
hundred feet below the surface, but cannot proceed 
any further on account of the expense which attends 
the extraction of the salt. 
The second mine is in Spanish Navarre, in a 
chain of hills that extend from east to west. This 
chain is more than two leagues in extent, and in 
the most elevated part is situated the village of Val- 
tierra, on one side of which we find a mine of sal 
gem. 
But the third mine which he mentions is by far 
the most curious. It is near Cardona, a town of 
Catalonia, about thirty miles from Barcelona, and is 
literally a rock of solid salt, which rises four or five 
