THE PATH OF EVOLUTION 



tion, whether that of electricity or heat, will alter the 

 condition of the vibrating atomic combination. This 

 action may express itself as change of temperature, 

 change of state of aggregation, or as chemical changes. 

 The phenomena are always the consequence of an in- 

 crease or diminution of the active energy of the pon- 

 derable atoms, which corresponds to a diminution or 

 to an increase of the active energy of the ethereal 

 motions. Like alterations of movement occur in the 

 chemical processes of combination and of double 

 decomposition, which are produced by the force of 

 affinity; that is, by the effort of heterogeneous atoms 

 to carry out their vibrations in accord with each other. 

 The alterations in the active force of the material 

 atom must correspond to those of the active force of 

 the ethereal atoms. Usually this alteration manifests 

 itself as the development or absorbtion of heat. Thus 

 it follows that a chemical reaction is analagous in its 

 abstract nature to a change in the physical state of 

 aggregation in the molecules of a body." * 



CHEMICAL ACTION is effective at very small dis- 

 tances only. The molecules must be in actual con- 

 tact, or no changes of affinities are manifested. When 

 a plate of Zinc is placed in a dilute solution of Sul- 

 phuric or other mineral acid, a lively effervescence 

 occurs. The Zinc dissolves in the acid, the solution 



*Pierer'sKon. Lex. B. 3. S. 930. 

 18* 



