SIR WILLIAM SIEMENS, l-.R.S. I 1 3 



This cup contains upon its inner surface three or four radial ribs 

 which unite in a central boss, by which the cup is supported upon 

 the spindle S. This support is not an absolute one, but the spindle 

 is armed with a screw-thread of rapidly ascending path, into which 

 the screw-threads upon the inner surface of the boss are made to 

 fit ; a fixed connection between the driving-spindle and the cup C 

 is established by means of a spiral spring E, one end of which is 

 fastened to the projecting end of the spindle S, and the other to 

 the cup. Before this spring is fixed, it is drawn out longitudinally 

 to such an extent as to balance the weight of the cup, which latter 

 may therefore be said to float upon the screw-threads without 

 exercising any pressure upon the same. The upper support of the 

 spindle S is a boss projecting from the bottom of a cylindrical 

 vessel B of glass sides and glass-domed top, which completely 

 enclose the cup C, while it renders its action visible : this outer 

 vessel is filled with liquid to such a height as to submerge the 

 lower edge of the cup. Rotation of the liquid in the outer 

 vessel is prevented by radial ribs upon its bottom surface ; and 

 upon the external surface of the rotating cup C two concentric 

 projections are provided, one at the upper edge, and the second 

 near the surface of the outer liquid, for the purpose of throwing 

 off some liquid which would otherwise be apt to adhere to the 

 external surface of the cup, in defiance of centrifugal force, and 

 interfere slightly with its proper action. 



Rotation being imparted to the shaft S and the cup C by clock- 

 work or from any other source, the liquid at the bottom of the 

 cup will be acted upon by centrifugal force and rise upon its 

 inner sides, while additional liquid will enter from without and 

 maintain the apex of the liquid curve nearly on a level with the 

 surrounding lake. At the moment when the liquid in rotation 

 touches the upper edge of the cup, the speed should be such as is 



determined by the formula n = ~-^-, in which h may be taken 



TlT 



for the height of the brim of the cup above the lake surface ; but 

 considering that the power necessary to maintain the cup at its 

 velocity, after the liquid has been raised to its upper edge, is 

 exceedingly small, because no fresh material has to be put into 

 motion, it would be practically impossible to prevent further 

 acceleration. In order to make sure that the liquid will not fall 

 VOL. i. i 



