WILLIAM SIEMENS, F.R.S. 121 



upright spindle H carrying an inverted wheel E. The axis A of 

 the regulating cup, being concentric with the spindle H, carries a 

 pinion F, and both the wheel and the pinion gear into two inter- 

 mediate or planet-wheels G and G', which latter are loose upon 

 studs and are suspended from a rocking-frame I, the latter being 

 free to turn upon its central support. The rocking-frame I is 

 connected by a rod R to a bell-crank lever 0, which is fastened 

 upon the spindle of the steam-regulating or throttle-valve V ; but 

 the horizontal arm of the lever carries a weight P which, being 

 acted upon by gravity, tends to open the valve and at the same 

 time to force the rocking-frame I, with its planet-wheels G and G', 

 round the vertical axis. This pressure is resisted, on the one 

 hand, by the teeth of the pinion F, which can only yield in the 

 ratio imposed by the rotating cup C, and on the other hand, by 

 the teeth of the inverted wheel E, which latter, being driven 

 round by the engine in the direction contrary to the effort pro- 

 duced by the weight P, causes the latter to be continually raised. 

 If the engine should succeed in raising the weight P, say 100 

 millims., while the regulating cup yields also to the extent of 

 100 millims., then the lever 0, and with it the regulating valve V, 

 will retain their relative position ; but if the engine should raise it, 

 say 95 or 105 millims., while the cup yields 100 millims., then the 

 valve will be either opened or closed by 5 millims., and the engine 

 will be urged or checked, as the case may be, to such an extent as 

 to make its revolutions coincide again absolutely with those of the 

 regulating cup. 



The driving-power of the cup is limited by the weight B, and 

 may be considered as a constant regulated quantity (although it is 

 derived indirectly from the engine) ; but whenever the valve has 

 to be opened or closed, a resistance arises which goes either in 

 diminution of or in addition to the weight P, and the power of 

 the cup must be such that its speed remains sufficiently uniform 

 under the influence of these occasional variations. 



By means of the automatic dip arrangement it would not be 

 difficult to obtain perfect uniformity, notwithstanding these irregu- 

 larities in the driving power ; but in the case of steam-engine 

 governors this arrangement is dispensed with for the sake of a 

 more immediate action upon the valve at the moment when a 

 differential velocity arises. Supposing that the greatest amount of 



