PERPETUAL MOTION 37 



inventor rarely attracted much attention in ancient times, 

 while the mathematical problems were regarded as amongst 

 the highest branches of philosophy, and the search for the 

 philosopher's stone and the elixir of life appealed alike to 

 priest and layman. We have records of attempts made 

 4000 years ago to square the circle, and the history of the 

 philosopher's stone is lost in the mists of antiquity ; but it 

 is not until the eleventh or twelfth century that we find 

 any reference to perpetual motion, and it was not until 

 the close of the sixteenth and the beginning of the seven- 

 teenth century that this problem found a prominent place 

 in the writings of the day. 



By perpetual motion is meant a machine which, without 

 assistance from any external source except gravity, shall 

 continue to go on moving until the parts of which it is 

 made are worn out. Some insist that in order to be prop- 

 erly entitled to the name of a perpetual-motion machine, 

 it must evolve more power than that which is merely re- 

 quired to run it, and it is true that almost all those who 

 have attempted to solve this problem have avowed this to 

 be their object, many going so far as to claim for their 

 contrivances the ability to supply unlimited power at no 

 cost whatever, except the interest on a small investment, 

 and the trifling amount of oil required for lubrication. 

 But it is evident that a machine which would of itself 

 maintain a regular and constant motion would be of great 

 value, even if it did nothing more than move itself. And 

 this seems to have been the idea upon which those men 

 worked, who had in view the supposed reward offered for 

 such an invention as a means for finding the longitude. 

 And it is well known that it was the hope of attaining 

 such a reward that spurred on very many of those who 

 devoted their time and substance to the subject, 



