I 



Mr. J. Preuss on a new Steam-Engine Governor. 299 



water flows out of the tank into the hot-water pan. The 

 cock can be adjusted upon the scale of the sector, so as to 

 transmit the requisite quantity of water in a given time. 



d. A float or close box of copper, or varnished sheet-iron, or 

 tin, filled with atmospheric air. 



e. Lever connected on one side to the rod at the top of the 

 float, and at its opposite extremity to the rody^ 



jf. A rod attaclied to the small lever of the throttle valve g. 

 g. Throttle valve connected with the pipe which conveys the 

 steam from the boiler to the steam cylinder. This valve being 

 turned either up or down, increases or I'educes the steam- 

 passage and affects the speed with which the piston moves 

 in the cylinder. 

 A. Index fixed against the support of the lever e, showing 

 upon the scale attached to the float-rod, such variations as 

 may occasionally take place. 



After this, it is evident that if the water-pump which sup- 

 plies the pipe a is constructed and placed so as to throw up 

 an equal quantity of water at every stroke, the cock with its 

 hand being turned upon such a figure of the index as will 

 correspond with the desired number of strokes per minute, 

 this cock will always deliver the same quantity of water in a 

 given time ; and though a greater or smaller portion may be 

 pumped into the tank b, yet neither more nor less water can 

 flow out of it (for the possible slight variation of pressure by 

 the different heights of water in the tank is too trifling to de- 

 serve any consideration in the present instance). Now let us 

 suppose the cock c were regulated upon 30 strokes per minute, 

 and that the engine happened to make 32 strokes, which 

 would certainly be so slight an increase of speed as hardly to 

 be perceptible even in very delicate work : yet this small ir- 

 regularity could not even continue for a minute ; for at the end 

 of that time there would be a surplus of water in the tank equal 

 to the bulk of two pump strokes, which would raise the float d 

 in a degree which would be the greater, the smaller the capa- 

 city of the tank had been made in proportion to the bulk of a 

 pump stroke ; and this elevation of the float d would act upon 

 the throttle valve with more efficacy, the shorter the small 

 lever g was pinned to the rod, and tne longer the right-hand 

 side of the main lever e was made in comparison with its 

 left-hand side. 



J, Pheuss. 



Pp2 LXIII. No- 



