PERPETUAL MOTION 



47 



reasoned thus : A pint of water in the goblet a must more 

 than counterbalance an ounce which the tube b will con- 

 tain, and must, therefore, be constantly pushing the ounce 

 forward into the vessel again at a, and keeping up a stream 

 or circulation, which will cease only when the water dries 



Fig. 9. 



up. He was confounded when a trial showed him the 

 same level in a and in b" 



This suggestion has been adopted over and over again by 

 sanguine inventors. Dircks, in his " Perpetuum Mobile," 

 tells us that a contrivance, on precisely the same principle, 

 was proposed by the Abb6 de la Roque, in "Le Journal 

 des S^avans," Paris, 1686. The instrument was a U tube, 

 one leg longer than the other and bent over, so that any 

 liquid might drop into the top end of the short leg, which 

 he proposed to be made of wax, and the long one of iron. 

 Presuming the liquid to be more condensed in the metal 

 than the wax tube, it would flow from the end into the wax 

 tube and so continue. 



