CATALOG OF THE MECHANICAL COLLECTIONS 29 



The cylinder is connected to the boiler by a short pipe at the boiler 

 end of which is the sector-plate steam valve called the regulator. The 

 lever of the regulator is attached to a Y-shaped stirrup that leads to 

 levers on a short shaft, which is hung so that two tappets on the same 

 shaft are struck by pins in the plug rod. The plug rod is a beam 

 moving up and down with the beam of the engine. The pins on the 

 plug rod are so placed that the regulator will be jerked open at the 

 end of each down stroke and closed at the end of the upstroke. The 

 injection cock, in the lower bend of the pipe connecting the cistern 

 with the cylinder, has a long sweeping handle, one end of which is 

 weighted so that the valve falls open when the handle is released from 

 its held position. In the closed position the weighted end of the 

 injection cock is held by a catch and released by a rod that projects 

 from a buoy and rises with it. The buoy floats on the surface of 

 water within a pipe connected to the pressure in the boiler. The 

 pressure within the boiler drops sharply with the upstroke of the 

 piston and then increases after the piston comes to rest at the top of 

 the stroke. The water level in the buoy pipe reacts with this change 

 in pressure, and the buoy rod at its highest point releases the injec- 

 tion cock handle. This arrangement necessitates a short pause at the 

 end of each stroke. A pin on the plug rod engages the opposite end 

 of the injection cock handle and replaces the weighted end in the catch. 



The engraving was first published in "Savery, Newcomen and the 

 Early History of the Steam Engine," by Rhys Jenkins, TransactioTis 

 of the Newcomen Society^ vol. 4, 1923-24. A supplementary note to 

 the article remarks on the similarity between this and the illustration 

 in Desaguliers' Course of Experimental Philosophy, 17 3 J^, and pre- 

 sents the following legend for this drawing as prepared with the aid 

 of the Desaguliers illustration : 



Legend of Beighton's Drawing 



A. Fireplace. 



B. Boiler and seating. 



C. Cylinder with piston. 



D. Steam pipe from boiler to cylinder. 



E. Steam cock or regulator. 



F. Puppet clack or safety valve. 



G. Gauge pipes to show when the level of the water in the boiler is too high 



or too low. 

 H. Buoy pipe; the shank of the buoy when the steam becomes strong forces 



up the lever R and interceptor 7 thereby lifting the notch from the lever 



of the injection cock which is opened by the fall of the weight 3. The tail 



1 of the lever is restored by a pin in the plug rod. 

 I. Standpipe for shank K, to indicate height of water in boiler. 

 K. Float in boiler. 

 L. Shank of the piston. 

 M. Injecting pipe bringing cold water from cistern g. 



