THE COMSTOCK MIKES. 127 



of raising the water on the downward stroke of the piston, while the lifting 

 pump does its duty on the upward stroke. The force-pumps need to be very 

 firmly set, and are therefore only employed where they can be permanently 

 and solidly established in a position easily accessible for repair and not 

 very liable to be submerged. The lifting pumps are well adapted to work 

 in the b,ottom of the shaft, their method of construction and operation fitting 

 them to draw water from the very bottom of the shaft without the use of a 

 cistern, and to be extended, foot by foot, as the sinking proceeds ; not requiring 

 to be placed with so much care as the plunger-pumps, and having also 

 the advantage of being operated as well even when the water rises above them 

 in the shaft. 



In order to extend the pump in depth as the sinking proceeds, the work- 

 ing parts of the pump, namely, the suction-pipe and working barrel, being 

 suspended by heavy chains to a winch or windlass fixed at the station above, 

 are detached, with the connecting pipe, from the bottom of the column, and 

 lowered 10 or 12 feet, sufficiently to allow of introducing another length of 

 pipe under the column, already in place ; this additional length having been 

 attached to the column, the working parts are again connected with the 

 column thus extended, and are continued in operation until the sinking has so 

 far progressed as to require the addition of another length of pipe, when the 

 above-described proceeding is repeated. In the Comstock mines the suction- 

 pipe, dipping into the pool of water at the bottom of the shaft, is usually a 

 stout hose pipe, of diameter equal to that of the short iron pipe below the 

 working barrel, to which it is closely fitted and attached. It is made of one 

 or more thicknesses of canvas, rendered water-tight by applications of tar or 

 other material of like properties. It has the advantage of flexibility and may 

 be more easily protected against injury during blasting than iron pipes, com- 

 monly used elsewhere. The lifting pump discharges into a cistern from 

 which the force-pump takes its supply to be raised to the surface or to the 

 next cistern above. 



The motion of the piston, or plunger, in its cylinder is imparted to it by 

 the pump-rod, a continuous piece of timber, which is suspended in the shaft 

 alongside of the column, extending from the surface to the bottom of the 

 mine, and to which the plungers are attached. The pump-rod is composed 



