ch. I.] MATTER, MOTION, AND FORCE. 261 



ing many of the complex conditions in the case, the ancients 

 verbally maintained the negations of the theorems that 

 matter is indestructible and motion continuous; although, 

 if they had tried to realize in thought their crude propo- 

 sitions, they would have found it impossible. But gradually 

 it began to be perceived that in all cases where matter dis- 

 appears — as in the burning of wood or the evaporation of 

 water — the vanished matter has only undergone a mole- 

 cular change which renders it temporarily imperceptible by 

 our unaided senses. Of the manner in which quantitative 

 chemistry has demonstrated this truth, pursuing, balance 

 in hand, the vanished matter through all its protean trans- 

 formations, it is unnecessary to speak. Similar has been 

 the evidence in the case of motion. Observing that, the 

 more effectually friction, atmospheric resistance, and other 

 obstacles to the visible continuance of motion are elimi- 

 nated, the longer the motion continues, the conclusion was 

 reached, by the method of concomitant variations, that if 

 all obstacles could be eliminated the motion would con- 

 tinue for ever. Finally, when it was shown that the ap- 

 parent loss of motion caused by friction is, in fact, only a 

 transformation of a certain quantity of molar motion into 

 its equivalent quantity of that species of molecular motion 

 known as heat, it was admitted on all sides that motion is 

 indestructible, as well as matter. 



But a brief analysis will show that the twin theorems 

 which we are considering have a deductive warrant equally 

 valid with their inductive warrant. Deep as are the truths 

 that matter is indestructible and motion continuous, there 

 is a yet deeper truth implied by these two. These theorems 

 are not fundamental, but derivative ; and it therefore be- 

 comes necessary to ascertain the axiom upon which they 

 depend, since here, if anywhere, must be found the pri- 

 mordial truth which we are seeking. 



Since we cognize any portion of matter whatever only as 



