18 BUHLETIN 119, U. S. NATIONAL MUSEUM. 



of the receiver which, acting as a surface condenser, condensed the 

 steam, creating a partial vacuum within the receiver. This caused 

 the water to be raised from the well or other reservoir through the 

 suction pipe and into the receiver, where it assisted in the further 

 condensation of the steam, which, in turn, resulted in the complete 

 filling of the receiver with water. Steam was then turned into 

 the receiver, and by its pressure forced the water out through the 

 delivery pipe, the suction pipe in the meantime being closed by its 

 non-return valve. Cat. No. 180,351 U.S.N.M. 



Photographic Copy of an Engraving, Published in 1719, of Newcomen's 

 Engine, Erected Near Dudley Castle, Staflfordshire, England, in 1712. 



This is believed to be the first engine constructed by Newcomen, 

 and it is interesting to note that the self-acting valve gear usually 

 ascribed to the year 1718 was in use here six years before. 



The engine consisted of a vertical open-topped cylinder fitted with a piston, 

 which by chains was connected with one end of a beam. The other end of the 

 beam was similarly connected with the vertical rods of a pump. The center 

 of the beam was fitted with trunnions so that it could oscillate, and its ends 

 were provided with arched heads so that the chains resting on them would 

 remain vertical when the beam worked. The cylinder rested on top of the 

 boiler, so that when a valve was open steam could enter the cylinder and allow 

 the piston, which was being pulled up by the weight of the pump rods at the 

 other end of the beam, to rise. When the piston had reached the top of the 

 cylinder, the steam was shut off and cold water from an overhead supply was 

 admitted in a jet at the bottom of the cylinder, which condensed the steam and 

 formed a partial vacuum, whereupon the weight of the air forced the piston 

 downwards. Upon completion of this downward stroke, the injection water 

 was cut off. Steam was then admitted for the next upward stroke, during 

 which the hot water at the bottom of the cylinder was discharged through an 

 eduction pipe, terminating in a nonreturn valve, while the air that had come 

 into the cylinder with the steam and injection water was blown out thi'ough 

 a snifting valve, so called from the noise it made. (The Science Museum.) 



The top of the cylinder was constantly flooded with water to pre- 

 vent the entrance of air into the cylinder. Soft packing was used 

 around the piston, for cylinders at that early date could not be 

 machine bored. They were made of brass, cast as thin as possible 

 to reduce the heating and cooling losses. 



The steam and injection valves of the engine were at first worked 

 by hand, but the desire of a boy, Humphrey Potter by name (so the 

 story goes), to play, rather than operate the valves, inspired liim to 

 attach cords to the oscillating beam, whereby these valves could be 

 opened and shut. The legend on the print gives the dimensions of 

 the engine's cylinder as 21 inches in diameter and 7 feet 10 inches 

 long, and of the boiler as 5 feet 6 inches in diameter and 6 feet 1 

 inch high, containing 13 hogsheads (700 gallons) of water. The 

 pump work was in two lifts, each of 75 feet. 



Cat. No. 180,596 U.S.N.M. 



I 



