292 EVOLUTION AND DISSOLUTION. 



istence, is a change in one or other of these two opposite 

 directions. Apparently an aggregate which has passed out 

 of some originally discrete state into a concrete state, there- 

 after remains for an indefinite period without undergoing 

 further integration, and without beginning to disintegrate. 

 But this is untrue. All things are growing or decaying, 

 accumulating matter or wearing away, integrating or disin- 

 tegrating. All things are varying in their temperatures, 

 contracting or expanding, integrating or disintegrating. 

 Both the quantity of matter contained in an aggregate, and 

 the quantity of motion contained in it, increase or decrease ; 

 and increase or decrease of either is an advance towards 

 greater diffusion or greater concentration. Continued losses 

 or gains of substance, however slow, imply ultimate disap- 

 pearance or indefinite enlargement; and losses or gains of 

 the insensible motion we call heat, will, if continued, pro- 

 duce complete integration or complete disintegration. The 

 sun's rays falling on a cold mass, augmenting the molecular 

 motions throughout it, and causing it to occupy more space, 

 are beginning a process which if carried far will disintegrate 

 the mass into liquid, and if carried farther will disintegrate 

 the liquid into gas; and the diminution of bulk which a 

 volume of gas undergoes as it parts with some of its molecu- 

 lar motion, is a diminution which, if the loss of molecular 

 motion proceeds, will presently be followed by liquefaction 

 and eventually by solidification. And since there is no such 

 thing as an absolutely constant temperature, the necessary 

 inference is that every aggregate is at every moment pro- 

 gressing towards either greater concentration or greater 

 diffusion. 



Xot only does all change consisting in the addition or 

 subtraction of matter come under this head; and not only 

 does this head include all change called thermal expansion 

 or contraction; but it is also, in a general way, comprehen- 

 sive of all change distinguished as transposition. Every in- 

 ternal redistribution which leaves the component molecules 



