QQ BULLETIN 173, U. S. NATIONAL MUSEUM 



N. Injecting cock. 



0. Lever or spanner of injecting cock. 



P. Two standards supporting the Y to work the regulator; 4 and 5 are arms 

 to work the Y by pins in the plug rod ; 6 is a strap to restrain the Y. 



Q. Working beam or plug rod. 



B. Lever, one end of which turns on a pin and the other is attached to the inter- 

 ceptor 7; the lower end of this is attached to the notched lever 2 that 

 releases the injection cock. 



S. Counterweight to lever R. 



T. Eduction pipe. 



V. Overflow pipe from top of cylinder and from shifting valve. 



W. Pipe supplying boiler with water from top of piston. 



X. Snifting valve. 



Y. Waste well. 



Z. Pipe supplying water from cistern g to top of piston. 



aaaa. Four great beams supporting the engine and the floor of the house. 



bcde. Ground floor of the house. 



f. Chimney. 



g. Cistern of cold water to supply injection, 

 h. h2. Great lever or beam. 



i. Rod and chain fixed to the outer end of the beam working pumps from the 



bottom of the mine, 

 k. Small force pump supplying cistern g. 



1. Windlass and rope, whereby men and materials are conveyed up and down 



the pit. 

 m. Pipe by which pump K supplies cistern g. 

 0000. Outline of boiler. 



[Note: Interceptor should read inceptor.] 



NEWCOMEN PUMPING ENGINE, c. 1712 



U. S. N. M. no. 308468 ; model ; made in the Museum ; not illustrated. 



This model illustrates the general arrangement of a Newcomen 

 atmospheric engine with its boiler and engine house. 



The Newcomen engine consisted of an open-top vertical cylinder 

 mounted above and connected through a valve to a steam boiler. A 

 piston within the cylinder was connected by chain to one end of an 

 oscillating overhead beam. To the other end of the beam was con- 

 nected the pump rods and plungers extending into the mine shaft. 

 The weight of the pump rods, etc., was sufficient to overbalance the 

 weight of the piston and at rest would maintain the piston at the top 

 of the cylinder. In operation, steam was admitted to the cylinder 

 to fill the space below the piston; then with all valves closed, cold 

 water was injected into the cylinder from an overhead cistern, con- 

 densing the steam to form a partial vacuum in the cylinder, with the 

 result that atmospheric pressure would force down the piston and 

 raise the pump rod. At the end of the down stroke, steam was 

 admitted, the condensed water and air were ejected, and the piston 

 was returned to the top of the cylinder. The steam and water- 

 injection valves were operated by a mechanism attached to the beam. 



