PERPETUAL MOTION 51 



"When I first thought of this invention, I could scarce 

 forbear, with Archimedes, to cry out 'Eureka! Eureka!' 

 it seeming so infallible a way for the effecting of a per- 

 petual motion that nothing could be so much as probably 

 objected against it; but, upon trial and experience, I find it 

 altogether insufficient for any such purpose, and that for 

 these two reasons : 



1. The water that ascends will not make any considera- 

 ble stream in the fall. 



2. This stream, though multiplied, will not be of force 

 enough to turn about the screw." 



How well it would have been for many of those inven- 

 tors, who supposed that they had discovered a successful 

 perpetual motion, if they had only given their contrivances 

 a fair and unprejudiced test as did the good old bishop! 



A modification of this device, in which mercury is used 

 instead of water, is thus described by a correspondent of 

 "The Mechanic's Magazine." (London.) 



"In Fig. u, A is the screw turning on its two pivots 

 GG; B is a cistern to be filled above the level of the lower 

 aperture of the screw with mercury, which I conceive to be 

 preferable to water on many accounts, and principally be- 

 cause it does not adhere or evaporate like water; c is a 

 reservoir, which, when the screw is turned round, receives 

 the mercury which falls from the top ; there is a pipe, which, 

 by the force of gravity, conveys the mercury from, the 

 reservoir c on to (what for want of a better term may be 

 called) the float-board E, fixed at right angles to the center 

 [axis] of the screw, and furnished at its circumference with 

 ridges or floats to intercept the mercury, the moment and 

 weight of which will cause the float-board and screw to re- 

 volve, until, by the proper inclination of the floats, the 

 mercury falls into the receiver F, from whence it again falls 

 by its spout into the cistern G, where the constant revolu- 

 tion of the screw takes it up again as before." 



