16 ATTRACTION AND REPULSION. 



philosophers of ancient Greece. Here is the foun- 

 dation of all physical logic, and a key to the 

 whole mechanism of nature. For as it is certain 

 that all the changes and transformations of matter 

 are the immediate effects of motion, it follows that 

 a complete knowledge of the prime mover would 

 lead to a perfect theory of physics. 



Since the time of Sir Isaac Newton, attraction 

 and repulsion have been generally regarded as 

 ultimate principles of action, for which no reason 

 can be assigned.* But if it be a fact, that the 

 elastic force of bodies is augmented by every 

 addition, and diminished by every abstraction of 

 caloric, it is obvious that the entire privation of 



* After referring to his theory of planetary motion, Newton ob- 

 serves in his Preface to the Principia, " many things induce me to 

 suspect, that all the rest of the phenomena of nature may depend 

 upon certain forces, by which the particles of bodies, by some 

 causes hitherto unknown, are mutually impelled towards each 

 other in regular figures, or are repelled and recede from one an- 

 other; which forces being unknown, philosophers have hitherto 

 attempted the investigation of nature in vain." Sir H. Davy also 

 observes, that " the various forms of matter, and the changes of 

 these forms, depend upon active powers, such as gravitation, 

 cohesion, calorific repulsion or heat, chemical attraction, and 

 electrical attraction." (Chemical Philosophy, p. 67.) Dr. Arnott 

 further states, that " attraction and repulsion are ultimate facts, 

 which admit of no explanation in the present state of science." 

 (Elements of Physics.) And Sir John Herschel adds, that " we 

 have no means of further analyzing the phenomena of cohesion 

 and elasticity, but must regard them, until we see reasons to the 

 contrary, as ultimate phenomena, referable to the direct agency 

 of an attractive and repulsive force." (Introduction to the Study 

 of Nat. Philosophy, s. 80.) 



