78 Royal Society, 



only the rigidity of the spring must be greater when a comparatively 

 dense liquid is employed. 



In order to test the principle of action here involved, Mr. Siemens 

 has constructed a clock consisting of a galvanic battery, an electro- 

 magnet, and his gyrometric cup, besides the necessary reducing- 

 wheels and hands upon a dial face, which proceeds at a uniform 

 rate, although the driving-power may be varied between wide limits, 

 by the introduction of artificial resistances into the electrical circuit. 

 The instrument appears, therefore, well calculated for regulating the 

 speed of all kinds of philosophical apparatus, and also for obtaining 

 synchronous rotations at different places for telegraphic purposes. 

 One of its most interesting applications is embodied in the " Gyro- 

 metric Governor" for steam-engines, of which an illustration is given. 

 This consists of a cup of 200 millimetres diameter and the same 

 height, which is fixed upon its vertical axis of rotation, and is en- 

 closed in an outer chamber, containing water in such quantity that 

 the lower extremity of the cup dips below its surface. The upper 

 edge of the rotating cup is, in this application, surrounded by a 

 stationary ring armed with vertical vanes, by which the overflowing 

 liquid is arrested and directed downward, causing it to fall through 

 a space or zone which is traversed by a number of radial and vertical 

 blades projecting from the external surface of the rotating cup, which, 

 in striking the falling liquid, project it with considerable force against 

 the sides of the outer vessel, at the expense of a corresponding retard- 

 ing effect on the cup, increasing its regulating-power. 



The cup-spindle carries at its lower extremity a pinion, which gears 

 into two planet-wheels at opposite points, which on their part gear 

 into an inverted wheel surrounding the whole, which latter is fast- 

 ened upon a vertical shaft in continuation of the cup-spindle, and is 

 driven round by the engine in the opposite direction to the motion of 

 the cup. The two intermediate or planet-wheels are attached to a 

 rocking frame supported, but not fixed, upon the central axis, which 

 wheels, in rotating upon their studs, are also free to follow the im- 

 pulse of either the pinion or the inverted wheel to the extent of 

 the differential motion arising between them. The rocking frame is 

 connected to the regulating valve of the engine, and also to a weight 

 suspended from a horizontal arm upon the valve-spindle, tending 

 to open the valve and at the same time to accelerate the cup to the 

 extent of the pressure produced between the teeth of the planet- wheels 

 and the pinion, while the engine is constantly employed to raise 

 the weight and to cut off the supply of steam. The result is that 

 the engine has to conform absolutely to the regular motion imposed 

 by the cup, which will be precisely the same when the engine is 

 charged with its maximum or its minimum of resisting load. 



The paper shows that the action upon the valve must take place 

 at the moment when the balance between the power and load of 

 the engine is disturbed, and that the readjustment will be effected 

 notwithstanding a resistance of the valve exceeding 100 kilogrammes 

 — a result tending towards the attainment of several important objects. 



