318 University Geological Survey of Kansas. 
or ten inches in diameter. The form of the cavity or spiral- 
shaped passage formed by the two hollow parts is shown in 
figure 85, which shows a corresponding enlargement on the 
outside of the casting. When wooden pumps are used, the 
spiral passage is chiseled out and is of the same shape, for 
the same capacity, as in the iron pumps. 
Fig. 84. Metal centrifugal pump. 
Water is drawn in through the pipe attached to the center 
of the side casting or part, when it is caught by a wheel pro- 
vided with curved arms or blades, which rotates in the direc- 
tion opposite the curve of the arms. By this arrangement 
the water is thrown outward by centrifugal force and is caught 
and conducted by the spiral-shaped passage to the discharge 
pipe. The spur wheel referred to above is commonly known 
as a ‘‘spider,’’ and is fastened to the end of a shaft, which is 
driven by a belt pulley. The pump, whether iron or wood, 
rests on a framework of iron or wood, which in turn is fast- 
ened to a rigid support or foundation. 
Centrifugal force and the propellent action of the blades of 
the wheel both act in raising the water from the sump to 
pump and from pump to discharge point, and the ratio of 
these two forces is in direct proportion to the ratio of speed 
of pump and height of lift. 
The different forms of iron pumps are probably easier to 
