44 THE SEVEN FOLLIES OF SCIENCE 



must roll towards the circumference. The machine ought, 

 therefore, to turn incessantly towards that side." 



In his " Course of Lectures on Natural Philosophy," 

 Dr. Thomas Young speaks of these contrivances as fol- 

 lows : 



" One of the most common fallacies, by which the super- 

 ficial projectors of machines for obtaining perpetual motion 

 have been deluded, has arisen from imagining that any 



Fig. 7- 



number of weights ascending by a certain path, on one 

 side of the center of motion and descending on the other 

 at a greater distance, must cause a constant preponderance 

 on the side of the descent: for this purpose the weights 

 have either been fixed on hinges, which allow them to fall 

 over at a certain point, so as to become more distant from 

 the center, or made to slide or roll along grooves or planes 

 which lead them to a more remote part of the wheel, from 

 whence they return as they ascend; but it will appear on 

 the inspection of such a machine, that although some of 

 the weights are more distant from the center than others, 



