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 hight, heat, electricity, magnetism, etc., are in 
reality modes of motion, or matter im 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 mnumerable 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; im another direction, east-west, 
electricity ; mm an intermediate direction, heat; in 
another direction, magnetism, etc. All these mo- 
tions bemg connected to the primary rotation of 
our planetary system, or gravitation. But we 
have no proof that the molecules of bodies vibrate 
