CRANE. | Economy of Mining Operations. 363 
called ‘‘sludge’’ mills, which treat the waste product of the 
other or main concentrating mills. It is needless to state 
that they have and do pay when properly operated — this, too, 
on tailings; if, however, they could treat only the waste 
product from the jigs, especially the cleaner and sand jigs, 
unmixed with other waste, they would be still more remu- 
nerative. 
If, in connection with the regular concentrating mills, 
some form of slime-washing apparatus could be employed, 
the large percentage of waste now tolerated would be reduced 
to a trifling amount. 
Such apparatus as the concave and convex buddles (espe- 
cially the convex form), the round table with the Evans 
apron, the Wilfley shaking table, and the settling tanks or 
classifiers, as the spitz kasten and lutten, are to be recom- 
mended. 
It is to be hoped that the mill owners and operators will 
not be willing to let others reap the harvest after them, as 
has been done in the past, and, even then, not done well and 
thoroughly as if they themselves were to attempt it. 
The answer, often made to the query whether or not any 
material is sent to the sludge mill, that ‘‘The sludge mill 
will not take our waste product,’’ is rather misleading to a 
novice, but not so to one well acquainted with the methods 
and the results of the same. In most cases there is only one 
explanation ; 7. e., that the operators, either to conceal known 
wastes or otherwise, have mixed the rich slimes and sand 
with barren waste to such an extent that too much material 
must be treated to reclaim the ore, and, therefore, the re- 
fusal to attempt it. 
What is needed is not so much richer mines, but better 
and more economical methods of treatment. 
PUMPING. 
Pumping can undoubtedly be done at the least expense by 
means of the Cornish pump. In the deeper mines, where 
two lifts would be necessary, the steam-pumps would prob- 
ably be the more convenient. Some means of reducing the 
expense of repairs and replacing the pumps, pipes, etc., is 
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