S7K WILLIAM SIEMENS, F.R.S. 115 



" reasonable limits " to this automatic adjustment are imposed by 

 the restricted orifice through \vhich the liquid has to penetrate 

 into the cup, and also by the range of action of the spring, for 

 which the law of Mariotte is applicable. Experiments, to be 

 hereafter described, have shown that the driving-power may be 

 varied between wide limits without producing any sensible varia- 

 tion of speed. The final adjustment of the instrument to the 

 normal velocity required is, moreover, easily effected by raising or 

 lowering the cup while it is running, for which purpose the lower 

 end of the upright spindle S is supported in the axis of an 

 adjusting screw E, as will be seen by inspection of Plate 20, 

 Fig. 1. 



RANGE OF POWER INCREASED. The range of power through 

 which uniform rotation can be obtained, may be further increased 

 by an arrangement which is represented in Plate 20, Fig. 2, and 

 Plate 21, Fig. 6, and which consists in arresting the liquid projected 

 over the edge of the cup by a belt of fixed vanes M, whence it drops 

 through the zone of rotating radial vanes L, which again impart 

 tangential motion to it at the expense of the superfluous driving- 

 power of the cup of which they form part. It is hardly necessary to 

 add that these fixed and rotating vanes only increase the range 

 of power of tJie instrument, ivitfwut in any way affecting its rate of 

 rotation, and that a second set of fixed and rotating vanes might be 

 added with the same effect as the first. Although the rotating cup 

 represented in Plate 20, Fig. 2, and Plate 21, Fig. G, is not pro- 

 vided with the automatic dip, it is equally evident that the fixed 

 and moveable vanes do not preclude that arrangement, which is 

 only dispensed with in such cases where great uniformity of motion 

 is not required. 



An interesting application of such a " Liquid Gyrometer," as 

 this instrument may appropriately be called, would be that of 

 obtaining synchronous motion at different places connected by a 

 telegraphic wire, for philosophical or telegraphic purposes ; but in 

 order to test its fitness for such purposes, I have constructed a 

 clock of which it constitutes the regulating principle, the moving 

 power being obtained by electro-magnetism. 



CLOCK REGULATED BY LIQUID IN ROTATION. This clock is 



represented by Plate 22, Figs. 7 and 8, and consists of three 

 principal parts : 



i 2 



