26 Wilde, Evolution of the Mental Facilities. 



That the spontaneous motion of an endothermic body 

 is independent of its motion of translation, is evident from 

 its explosive power when in a state of rest, while the 

 quantitative difference between the two motions is 

 extremely great. The effective endothermic force of the 

 same weight of gunpowder as the disc of gun-metal, 

 (4-5 lbs.) is equal to 2200 foot-tons,* while the impressed 

 motion of the disc, generating yyG revolutions per minute, 

 by the fall of 2 lbs. through a space of 120 inches = 20 foot- 

 pounds, is represented by the force of less than half a grain 

 of gunpowder. 



That the electric spark would have no influence on 

 the quantity of motion generated by the explosion of an 

 endothermic body, is evident from the fact that the spark 

 does not impart motion to a heavy body at rest, its 

 function in causing the explosion being similar to that 

 of the sienal which sets a battalion or a fleet in motion.! 



Another legacy of error bequeathed by Descartes to 

 an impressionable posterity is the dogma that the quantity 

 of rest and of motion in the whole universe is at all times 

 the sa«ne. This dogma is set forth in the same paragraph 

 of his Principia as that containing his definition of the 

 quantity of motion in a body, and has since been adopted 

 by modern physicists under the term of " potential " and 

 " actual " energy. 



In his lecture on the Conservation of Force^ 



* Noble, Oil Modem Explosives. Proc. Koy. Institution, Vol. X\'I., 

 P- 330- 



t Bishop Ilorsley, the learned editor and commentator of Newton, is 

 quoted by Lord Monboddo in his "■Ancient Aletaphysics," and by Dugald 

 Stewart in his notes on '* Theories of the Activity of Matter," as saying that 

 " New talis first law of motion cannot be defended on the ptinaplcs of sound 

 philosophy." 



X Lecture delivered at Carlsruhe, 1862. 



