tons--a very heavy item when the cost of transport from Europe at about
50_l_. per ton is considered. As fast as the ore is stamped, it is
shoveled out by hand, and thrown upon inclined sieves of forty holes per
lineal inch; the stuff which will not pass through the mesh is returned to
the stamps.

Dry stamping may be said to be almost a necessity in dealing with these
rich silver ores, as with the employment of water there is a great loss of
silver, owing to the finer particles being carried away in suspension, and
thus getting mixed with the slimes, from which it is exceedingly difficult
to recover them, especially in those remote regions where the cost of
maintaining large ore-dressing establishments is very heavy. Dry stamping,
however, presents many serious drawbacks, some of which could probably be
eliminated if they received proper attention. For instance, the very fine
dust, which rises in a dense cloud during the operation of stamping, not
only settles down on all parts of the machinery, interfering with its
proper working, so that some part of the battery is nearly always stopped
for repairs, but is also the cause of serious inconvenience to the
workmen. At the Huanchaca mines, owing to the presence of galena or
sulphide of lead in the ores, this fine dust is of such an injurious
character as not unfrequently to cause the death of the workmen; as a
precautionary measure they are accustomed to stuff cotton wool into their
nostrils. This, however, is only a partial preventive; and the men find
the best method of overcoming the evil effect is to return to their homes
at intervals of a few weeks, their places being taken by others for the
same periods. In dry stamping there is also a considerable loss of silver
in the fine particles of rich ore which are carried away as dust and
irrevocably lost. To prevent this loss, the writer proposed while at
Huanchaca that a chamber should be constructed, into which all the fine
dust might be exhausted or blown by a powerful fan or ventilator.