Perpetuat Motion 63 



and did not require any outside agency. In the middle ages such 

 stories were common, but the principle of motion now often 

 became a disembodied spirit, a demon or djinn, who at the com- 

 mand of a magician did mighty works. Eut a machine which 

 owed its movement to such a source was not a perpetual motion 

 in the sense in which we are going to use the words ; its power was 

 due to an outside agency just as much as in the steam engine of 

 to-day. 



We must therefore define rigidly the sense in which we shall 

 use the term and shall apply it only to a machine which moves in 

 consequence of the details of its construction, without calling upon 

 any outside agency, or, if any natural power, such as heat, the 

 winds, electricity, the tides or other phenomenon he utilized to 

 give energy to the machine, then, to be a perpetual motion the 

 action must contradict the principle of " conservation of energy,'' 

 or at least must be in disagreement with one of the settled laws 

 governing the so called " degradation of energy." 



In other words the mechanism, over and above the power 

 wasted by the friction of its parts, must return to us at least as 

 much energy as put into it. And none of the searchers after the 

 '* Perpetuum Mobile" would be satisfied without a return largely 

 exceeding this, without having a surplus of power wherewith to gain 

 a useful effect. 



The history of the search begins early, so early that according 

 to some authorities we might almost, as in the comic opera, begin 

 our seaich in " the year I." As an example, John Taisner, who 

 wrote sometime previous to 1579, is represented in the British 

 Museum Library by a blackletter translation, a tract of about eighty 

 pages. In this we are assured that " from the beginning of the 

 world, in manner all natural philoso[/hers and mathematicians, with 

 great expenses and labour, have aitempted to find out a continual 

 motion — yet unto this day few or none have atteyned to the true 

 end of their desires." The earliest reference however that we can 

 notice appears in the legend of Archimedes of Syracuse. Claudian 

 gives a poetic reference to a machine made by him, and an old 

 Chronicle tells us that " this machine did move of itself — it was a 



