CRANE. | Pumping Machinery. 317 
the engine above to the pump below; thus the pump may be 
operated at any point desired in the mine below. 
Neither this nor any other form of rotary pump has met 
with much favor in this district, due probably to the fact that 
the mine waters are very acid, and therefore any pump which 
depends upon close-fitting parts for proper working will not 
last long, and therefore not be very satisfactory. Any grit 
being drawn into the cylinder, and passing between the cogs 
and the surface of the cylinder in the course of its discharge 
from the cylinder, will tend to wear the same and the cogs rap- 
idly, which with the acid water soon incapacitate the pump. 
Plate XLV shows two of the cog wheels, one on either side 
of the pump, which operate in the double cylinder. 
Mill Pumps. 
The pumps employed about the mill are designed for lifting 
large quantities and often dirty, slimy water short distances, 
seldom exceeding thirty-five feet. These pumps are em- 
ployed for draining shallow strip pits, for pumping water, 
necessary in the concentrating works, from the mill pond to 
a tank in the upper part of the mill building, or for handling 
and transferring slime from one level to another, in the sys- 
tem of ore dressing. 
CENTRIFUGAL PUMPS. 
The centrifugal pump is the most common form of mill 
pump employed in this district, although occasionally a pul- 
someter is used for pumping water from the pond to the mill. 
Slimes are, however, seldom or never handled by a pulsom- 
eter. Rotary pumps are occasionally employed in handling 
wash and boiler water in the milling operations. 
Front and side views of the common cast iron form of 
centrifugal pump are shown in figures 84 and 85. Two forms 
made of wood, all but the revolving part, are shown in fig- 
ures 86 and 87. 
The pump consists in all cases of two hollow parts or shells, 
which, when bolted together, form an air and water tight 
cavity. ‘The cavity is spiral-shaped, increasing in size from 
about an inch near the discharge pipe at the top to the full 
size of the delivery pipe at the bottom, which is eight, nine 
