IIO THE REIGN OF LAW. 



form in velocity, and rectilinear in direction. Thus 

 according to this law a body moving, and not sub- 

 ject to any extraneous Force, would go on moving 

 for ever at the same rate of velocity, and in an 

 exactly straight line. 



Now, there is no such motion as this existing 

 on the earth or in the heavens. It is an Abstract 

 Idea of Motion which no man has ever, or can 

 ever, see exemplified. Yet a clear apprehension 

 of this Abstract Idea was necessary to a right 

 understanding and to the true explanation of 

 all the motions which are actually seen. It was 

 long before this idea was arrived at ; and for 

 want of it, the efforts of Science to explain the 

 visible phenomena of Motion were always taking 

 a wrong direction. There was a real difficulty in 

 conceiving it, because not only is there no such 

 motion in Nature, but there is no possibility by 

 artificial means of producing it. It is impossible to 

 release any moving body from the impulses of ex- 

 traneous Force. The First Law of Motion is there- 

 fore a purely Abstract Idea. It represents a Rule 

 which never operates as we conceive it, by itself, 

 but is always complicated with other Rules which 



