VI PREFACE. 



secondly, as possible or actual motion; and 

 thirdly, even as the result of motion. Thus the 

 attractions that start the cannon-ball, the 

 motion of the ball, and the blow it gives, have 

 each been designated by the word force. 



The indefiniteness in the use of the word 

 matter has partly originated in the assumption 

 of some stuff as the essence, or vehicle for light, 

 heat, electricity, magnetism, the interstellar 

 aether, and for life ; and these imaginary liquids, 

 or gases, have been realized as if they had been 

 proved to exist by analysis. 



As these and similar confusions pass away, 

 more and more clearness will be obtained re- 

 garding the inseparable union of matter and 

 force. 



