THEORY. 183 



All the physical researches of times gone by, 

 and all the experimental data furnished by the 

 philosophers of the present day, tend to prove the 

 reality of those admirable notions brought forward 

 by Grove in his ' Correlation of Physical Forces/ 

 The correlation theory enables us to account for 

 many hitherto unexplained phenomena, and points 

 out to us the direction in which physical science 

 may spread to greatest advantage. 



I am indeed led to believe that all those re* 

 markable phenomena classified under the heads 

 of light, heat, electricity, magnetism, etc., are in 

 reality modes of motion, or matter in motion. 

 When two bodies of a certain volume move before 

 us, we can witness and describe the motion easily 

 enough ; but when motion takes place among the 

 molecules of bodies, the most powerful microscope 

 will not allow us to detect it : we are led, how- 

 ever, by innumerable facts, to infer that such 

 motion does occur. By stating that the so-called 

 " physical forces " are different modes of motion, 

 I understand that if the molecules of any substance 

 vibrate in one direction, north- south for instance, 

 we have light; in another direction, east-west, 

 electricity ; in an intermediate direction, heat ; in 

 another direction, magnetism, etc. All these mo- 

 tions being connected to the primary rotation of 

 our planetary system, or gravitation. But we 

 have no proof that the molecules of bodies vibrato 



