THE PATH OF EVOLUTION 



affinities of chemical attraction, at least as we know 

 them, seem to exist only within a very limited range 

 of temperature. At low* temperatures such as that 

 at which the atmospheric air liquifies (312 de- 

 grees below zero F.) chemical action almost ceases. 

 Even Fluorine, which ordinarily acts so energetically 

 upon all other substances as nearly to deserve the 

 name of the Alkahest or universal solvent the ma- 

 terial sought for by the Alchemists of old is without 

 action upon all bodies, excepting Hydrogen and some 

 of its organic compounds. Probably even this ac- 

 tion would cease with still greater cold. At a very 

 high temperature, such as a white heat, most inorganic 

 compounds are dissociated into their component atoms. 

 To effect many changes of affinities it is necessary to 

 raise the respective molecules to a higher temperature 

 than that normally existing, when the increase of heat 

 alters the pre-existing affinities. No change in 

 chemical composition takes place without a simul- 

 taneous evolution or absorption of heat, a mani- 

 festation of electrical phenomena, or of both phe- 

 nomena. 



When the change in the combination of the mo- 

 lecules begins, it is often attended with so great a de- 

 velopment of heat as to raise the surrounding mo- 

 lecules to great activity, and to propagate the action 

 throughout the mass of the molecules in contact. 



