302 
ON BEOWNIAN OE PEDETIC MOTION. 
two molecules varies inversely as tlie fifth power of the distance. 
If attraction at distance 2 is Ij attraction at distance 1 would he 
64. Why do not all molecules therefore coalesce? Probably^ 
because their own proper motion, of which heat represents the 
higher harmonics, causes them to fly apart again. The wave- 
length of that motion is not so minute, and although we possess 
no means of ascertaining the amplitude of such vibrations, still 
their rate is so prodigious as to give rise to an almost incredibly 
forcible impact. 
