126 MINING IKDFSTET. 



The piston or plunger of the force-pump is a smoothly-turned cylinder 

 8 to 12 inches in diameter and 10 or 12 feet long. It is cast hollow, of iron 

 about one inch in thickness. In order to attach it to the pump-rod, by which 

 it is set in motion, a suitable stick of timber, considerably longer than the 

 piston, is made to fit snugly into the inside of the cylinder or hollow piston, 

 entirely occupying the interior space ; being driven tightly in it is wedged at 

 the bottom. The top, projecting above the end of the cylinder, is then 

 attached to the main pump-rod, R, in manner shown in the figure. 



Another method, used at the Savage, Fig. 2, Plate IX, is to have the 

 plunger cast with a stout flange at the upper end, by means of which a head 

 of cast iron is bolted to it, carrying two uprights with a stout iron pin, as 

 shown in the drawing. To the end of the pump-rod is securely attached an 

 iron stub-end, which is furnished with a strap, boxes, gib and key, forming a 

 connecting link such as is commonly used in attaching the connecting rod of 

 an engine to the crank pin. By means of this link the pump-rod is attached 

 to the pin in the head that is bolted to the plunger, as just described. 



The plunger-case and valve-chambers rest upon stout timbers, which are 

 firmly established in the shaft in the most substantial manner. The column 

 rests upon the valve-chamber, and is itself further supported by timbers 

 fixed at intervals in the shaft and so arranged as to embrace the pipe 

 directly under the flanges by which the sections of the column are joined 

 together, and furnish a bearing for these to rest upon. This is illustrated by 

 Figs. 3 and 4, Plate IX. The pump-column, generally used at the more 

 important pumping works on the Comstock, is a pipe having a diameter of 

 12 or 14 inches. It is composed of sections about 10 feet long. The sections 

 are made of wrought iron or boiler-plate, usually j^ of an inch thick, strongly 

 riveted together in cylindrical form. The plate employed is little more than 

 3 feet wide, so that three cylindrical pieces riveted together form a section 

 of the column. At each end of each section a stout flange of cast iron, as 

 shown in Fig. 3, Plate IX, is riveted to the plate, by which means the sec- 

 tions are connected. In other mining regions the pump-column is usually 

 formed of cast pipe. On the Pacific coast the pipe, made as above described, 

 is preferred on account of its comparatively less weight, a consideration of 

 much importance where freights are so high. 



It will be seen from the foregoing that the force-pump performs its work 



