(J4G DIFFUSION. 



method mar be discovered of separating them by a reversible process. If this 

 hould happen, the process of iuterdiffusion which we had formerly supposed 

 not to be an tiurtw"** of dissipation of energy would now be recognized as 

 snob an instance, 



It follows from this that the idea of dissipation of energy depends on 

 th extent of our knowledge. Available energy is energy which we can direct 

 int.. any desired channel Dissipated energy is energy which we cannot lay 

 hold of and direct at pleasure, such as the energy of the confused agitation 

 of molecules which we call heat. Now, confusion, like the correlative term 

 order, u not a property of material things in themselves, but only in relation 

 to the mind which perceives them. A memorandum-book does not, provided it 

 w neatly written, appear confused to an illiterate person, or to the owner who 

 understands it thoroughly, but to any other person able to read it appears to 

 be inextricably confused. Similarly the notion of dissipated energy could not 

 occur to a being who could not turn any of the energies of nature to his 

 own account, or to one who could trace the motion of every molecule and 

 seiae it at the right moment. It is only to a being in the intermediate si 

 who can lay hold of some forms of energy while others elude his grasp, that 

 energy appears to be passing inevitably from the available to the dissipated 



