CHAIN-PUMP. 290 



to ball, jointed together by cross-pins, was substituted 

 for the short link chain, and passed over a revolving 

 hollow square frame at the bottom of the pump, in place 

 of the curved roller-guide in the drawing. Each of 

 the four sides of this square hollow frame was of the 

 same length as the jointed link, and the balls lay in the 

 hollow of the frame without touching it, contact . being 

 only on the links. The balls were thus guided directly 

 into the bottom of the pump on their upward course 

 with a rigid chain, and the swing and knocking was 

 avoided. This pump was in principle the traditional 

 rag-and-chain pump of a hundred years before ; yet no 

 trace of its use is met with during Trevithick's life in 

 Cornwall. The early pump had rag balls, in keeping 

 with the mechanical ignorance of the time, and suitable 

 to man's power. 



Trevithick's pump with iron balls raised "7200 

 gallons of water 10 feet high in a minute with Ii Ib. 

 of coal," 1 retaining all the original simplicity of the 

 earlier rag-pump, having uniform circular motion and 

 constant stream, without the use of a single valve. The 

 engine and pump are thus described by him : 



" The first engine that will be finished here for Holland will 

 be a 36-inch cylinder and a 36-inch water-pump, to lift water 

 about 8 feet high. On the crank-shaft there is a rag-head of 

 8 feet diameter, going 8 feet per second, with balls of 3 feet 

 diameter passing through the water-pump, which will lift about 

 100 tons of water per minute. It is in an iron boat, 14 feet 

 wide, 25 feet long, 6 feet high, so as to be portable and pass 

 from one spot to another without loss of time. This will drain 

 18 inches deep of water (the annual produce on the surface of 

 each acre of land) in about twenty minutes ; to drain each 

 acre with about a bushel of coal costing Qd. per year. The 

 engine is high pressure and condensing." 2 



1 See letter, vol. ii., p. 332. 2 See Trevithick's letter, vol. ii., p. 315. 



