gg BULLETIN 173, U. S. NATIONAL MUSEUM 



springs to bow, the upper support of the springs is drawn down, 

 closing the throttle valve to which it is attached. This very simple 

 and widely used form of the ball governor was invented by Thomas 

 R. Pickering, of New York, N. Y., in 1862. 



The governor employs three balls, each attached to the center of a 

 spring. Each spring is attached at its lower end to a collar that is 

 driven by the engine and turns freely on a vertical hollow shaft. The 

 upper ends of the springs are attached to another collar supported 

 on a rod, which is free to revolve and to move up and down. As the 

 centrifugal force moves the balls out from the spindle, the upper 

 collar and rod are drawn down. The vertical rod is connected to a 

 throttle valve within the casting, which forms the support of the 

 governor. 



This specimen is a governor made in the form of the early Pickering 

 governor. 



PICKERING BALL GOVERNOR, 1931 

 U.S.N.M. no. 310290 ; original ; gift of the Pickering Governor Co. ; not illustrated. 



This is the modern form of the Pickering governor, described 

 above, and has the same spring mechanism carrying the governor 

 balls. It is provided with a speed ranger for obtaining different 

 engine speeds up to a 50 percent increase over the minimum speed, 

 and includes also an enclosure over the ball and gear mechanism. 



The principle of the Pickering governor has been very widely 

 adopted to governing the speed of practically every type of machine 

 and mechanism. It does not depend upon gravity for its proper 

 operation and can, therefore, be used in any position, while the sim- 

 plicity of its construction permits it to be made in every size. The 

 principle is employed in the governors of telephone dials, talking 

 machines, internal-combustion engines, air compressors, steam en- 

 gines, and steam turbines. 



CONDENSERS 



JAMES WATT SURFACE CONDENSER, 1769 



U.S.N.M. no. 180614 ; two photoengravings ; deposited by J. E. Watkins ; not 

 illustrated. 



These prints include a photograph of the Watt surface condenser 

 in the Science Museum of London, and a line-drawing plan and eleva- 

 tion of the condenser. 



The condenser shown is a small, tubular, surface condenser com- 

 plete with air and condensate pump. The condenser is a vertical 

 cylindrical shell with a circular tube sheet, or diaphragm, within the 

 shell near each end. The small spaces at each end of the condenser 

 are connected by some 140 tubes, which fill a large proportion of the 

 space between the tube sheets. The cold condensing water passes 



