184 SPECULATIVE SCIENCE 



things are to be placed only in various separations and new associa- 

 tions and motions of these permanent particles, compound bodies 

 being apt to break, not in the midst of solid particles, but where those 

 particles are laid together and only touch in a few points. 



We confess that these arguments seem to us unanswerable, 

 as proving the existence of some unalterable basis of matter. 

 Lucretius described his atoms as small, but not infinitely small, 

 nay, having parts, yet ' strong in everlasting singleness,' im- 

 penetrably hard, indivisible, unalterable, eternal. 



Having reached his atom, before proceeding with the conse- 

 quences of his assumption, Lucretius pauses to demolish rival 

 theorists ; but though he does this very well, we prefer to follow 

 out his own propositions in their natural order, remarking, 

 however, that the next proposition occurs incidentally, as it 

 were, while refuting his antagonists, and is to the effect that the 

 differences between all bodies may be accounted for by the 

 different arrangement of the atoms, and the different way in 

 which they move ; or, more literally, ( the motions which they 

 mutually impart and receive.' Lucretius conceived matter as 

 formed by atoms in continual motion, rebounding, as it were, 

 from one another. His conception is most remarkable, as being 

 very far removed from the impression produced by inert matter 

 on our own senses, and yet almost indisputably true. Arguments 

 drawn from the laws of the elasticity of gases and from the dif- 

 fusion of fluids go far to prove the proposition. The former 

 laws may be deduced from the assumption of atoms rebounding 

 in a void : and it is hard to conceive why different fluids or 

 liquids should mix with extraordinary rapidity whenever placed 

 in contact one with its neighbour, unless molecules were con- 

 tinually fluttering as it were at the limits of each fluid, restrained 

 only from continuing their course by the opposition of other atoms. 

 If these arguments seem insufficient, we may refer to the concep- 

 tion of heat as a mode of motion. If heat be a mode of motion of 

 gross matter, then, as all bodies are more or less hot, the mole- 

 cules of all bodies will be moving with more or less speed pre- 

 cisely what Lucretius taught. Lucretius was led to his concep- 

 tion by considerations very analogous to those which lead us to 

 consider heat and other forms of energy as modes of motion. 

 Probably the reason why he does not state this seventh proposi- 



