TRANSFORMATION AND EQUIVALENCE OF FORCES. 209 



nexions. Lastly, various experiments show that the mag- 

 netization of a body alters its internal structure; and that 

 conversely, the alteration of its internal structure, as by 

 mechanical strain, alters its magnetic condition. 



Improbable as it seemed, it is now proved that from 

 Light also may proceed the like variety of agencies. The 

 solar rays change the atomic arrangements of particular 

 crystals. Certain mixed gases, which do not otherwise com- 

 bine, combine in the sunshine. In some compounds Light 

 produces decomposition. Since the inquiries of photogra- 

 phers have drawn attention to the subject, it has been shown 

 that " a vast number of substances, both elementary and 

 compound, are notably affected by this agent, even those ap- 

 parently the most unalterable in character, such as metals." 

 And when a daguerreotype plate is connected with a proper 

 apparatus " we get chemical action on the plate, electricity 

 circulating through the wires, magnetism in the coil, heat in 

 the helix, and motion in the needles." 



The genesis of all other modes of force from Chemical 

 Action, scarcely needs pointing out. The ordinary accom- 

 paniment of chemical combination is heat ; and when the 

 affinities are intense, light also is, under fit conditions, pro- 

 duced. Chemical changes involving alteration of bulk, 

 cause motion, both in the combining elements and in adja- 

 cent masses of matter : witness the propulsion of a bullet by 

 the explosion of gun-powder. In the galvanic battery we 

 see electricity resulting from chemical composition and de- 

 composition. While through the medium of this electricity, 

 Chemical Action produces magnetism. 



These facts, the larger part of which are culled from 

 Mr. Grove's work on " The Correlation of Physical Forces," 

 show us that each force is transformable, directly or indi- 

 rectly, into the others. In every change Force undergoes 

 metamorphosis ; and from the new form or forms it assumes, 

 may subsequently result either the previous one or any of 

 the rest, in endless variety of order and combination. It is 



