10 Mr. J. Croll on What determines Molecular Motion ? — 



something which determined or directed the action of the forces 

 concerned in its existence. 



The vague and indefinite idea that the arrangement of the 

 molecules of matter into crystalline and organic forms is due to 

 the action of forces, appears to be implied in such terms in com- 

 mon use as " structural forces/^ ^^ formative forces,^^ " crystal- 

 building force/' &c. It is supposed that if our mental powers 

 were enlarged or strengthened so that we could perceive every 

 thing connected with the forces operating in nature, we should 

 then be able to explain the process by which the organic forms 

 of nature are built up. This, however, is evidently a mistake. 

 Though our acquaintance with the forces of nature were abso- 

 lutely perfect, the question as to how particles or molecules ar- 

 range themselves into organic forms would probably still remain 

 as deep a mystery as ever, unless we knew something more than 

 force. 



The mystery is not what are the forces which move the par- 

 ticles, but what is it that guides and directs the action of the 

 forces so that they move each particle in the particular manner 

 and direction required. Force gives motion to the particles; 

 but we are not concerned about the cause of the motion, but 

 about what directs that motion. It is replied that motion can- 

 not possibly take place without its being in some particular di- 

 rection. But this does not prove that the two things are the 

 same. It only proves that they are inseparably connected. 

 Neither does it prove that the same thing which is assigned as a 

 cause for the one will serve as a cause for the other. Two effects 

 may be inseparably conjoined and yet result from different 

 causes. But the two effects under our consideration are not in- 

 separably connected. It is true that a molecule cannot move 

 without moving in some particular direction ; and thus far the 

 two effects are inseparable ; but a molecule may move without 

 moving in the />rojoer direction. These molecular forces cannot 

 act without acting in some particular way 3 but they may act 

 without acting in the proper way. Now what is it that deter- 

 mines that they shall act in the proper way ? When a molecule 

 is to be moved, there is an infinite number of directions in which 

 force may be conceived to move it. But out of the infinite num- 

 ber of different paths, what is it that directs the force to select 

 the right path ? 



Is it asserted that force is self-directing ? This is simply 

 getting into confusion again. What conceivable idea can be 

 attached to a self-directing force ? Is force a something which 

 not only acts but determines for itself how and when it shall act ? 

 In what conceivable way can force direct its own path ? A mo- 

 lecule has to be moved into its proper place in an organic form ; 



