LUCRETIUS 23 



again, though he had no conception of the modern 

 philosophical division of qualities into primary and 

 secondary, he denied to the atoms all secondary 

 qualities, such as colour, warmth, scent. The 

 sensible secondary qualities of objects, however, 

 he imagined to depend on the shape and size of 

 the atoms, and on the way in which they are fixed 

 together. Thus light is formed of very, very 

 small atoms — so small that they can pass through 

 horn. < Liquids are usually formed of round, 

 smooth atoms. Things which are hard or tough, 

 like diamonds, are formed of atoms tightly hooked 

 together, or united together by many branches. 

 A thunderbolt is formed of particles especially 

 minute and ready to move 1 The mind is composed 

 of very tiny smooth round atoms. All the atoms 

 are very hard, so that they are not crunched even 

 by the teeth of death. ! 



" Nam quid in oppressu valido durabit eorum, 

 Ut mortem efFugiat, led sub dentibus ipsis ? " 



Perhaps the most extraordinary thing about the 

 Lucretian atomic theory is the manner in which 

 it anticipated the modern theory of molecular 

 motion. To the ordinary unscientific eye, matter, 

 even if conceived as particulate, seems to consist 

 of coherent and motionless particles. Yet Lucretius 

 taught that the particles of matter were not coherent 



