PUMPING WATER FROM DOCKS. 



335 



The fans are 4 feet 2 inches in diameter, and when driven at 

 their usual speed of about 200 revolutions per minute, discharge 

 about 3000 cubic feet in the same time. Each pump is driven 

 by a separate high-pressure horizontal engine. 



The four lift-pumps are fixed in one large square well (Figs. 

 328, 329), and are driven by a vertical engine. These pumps 

 are each 29^ inches diameter, and 48 inches stroke. The 

 general speed at which they are worked is about 14 strokes per 

 minute, at which rate each discharges about 250 cubic feet, equal 



20 FEET 



Level of mater 



FIG. 329. 



to 1000 cubic feet discharged per minute by the four pumps 

 together. 



Figs. 331 and 332 show the arrangement of the engines and 

 pumps adopted for pumping out the Hamilton Dock, at Malta. 



The main pumping-engine is of the compound, inverted- 

 vertical type, having cylinders 26 and 44 inches in diameter, 

 and 26 inches stroke. 



The main centrifugal-pumps are driven direct from the shaft, 

 and have gun-metal fans 7 feet in diameter. The cast-iron 

 pump-casings are entirely distinct from the engine- bed, and are 

 so arranged that the upper part can be readily removed so as to 



