CHEMICAL ACTION, MECHANICAL ACTION, AND HEAT. Ill 



However, to reverse the reaction or to advance it from right to left 

 requires the expenditure of a greater amount of external energy than the 

 chemical energy expended in the first reaction. In the reaction given 

 the available external energy may be from one of two sources — heat or 

 mechanical action. The ferric hydrate may be broken into ferric oxide 

 and water by heating. Also, if the pressure be very great and water have 

 a chance to escape the same transformation may take place by the 

 expenditure of mechanical energy. Doubtless in nature in many cases 

 both of these forces unite in the process, but whether the dehydration takes 

 place as a result of the expenditure of heat energy alone or mechanical 

 energy alone, or the two combined, a greater amount of energy must be 

 expended than the chemical energy expended in the hydration of the iron. 

 Hence, when hydration takes place in the zone of katamorphism energy is 

 expended. This is potential chemical energy. When dehydration takes 

 place in the zone of anamorphism, reversing the first process, energy is also 

 expended. This is either potential mechanical energy or the energy of 

 heat, or the two together. I say potential mechanical energy, for I have 

 held in another place that all earth movements, provided all the factors are 

 taken into account, result in bringing the material moved nearer the center 

 of the earth, and therefore the energy expended is the potential gravitative 

 energy of position." 



The reasoning applied to the case of hydration and dehydration of 

 ferric oxide is applicable to every other reversible reaction in metamor- 

 phism; hence, when we take all the energy factors into account, at the end 

 of the process energy has been expended. Furthermore, a part of this 

 energy during the process has been transformed to heat and dissipated; for 

 in all transformations of energy there is an inevitable tendency for some 

 of the energy to run down into the lowest form, heat, a portion of which 

 is lost. 6 



In conclusion, therefore, in the zone of katamorphism, while chemical 

 reactions frequently take place which liberate heat and expand the volume, 

 and in the zone of anamorphism chemical reactions take place which absorb 

 heat and condense the volume, in both zones alike when all of the energy 



a Van Hise, C. R., Earth movements: Trans. Wisconsin Acad. Sci., Arts, and Letters, vol. 11, 

 1898, pp. 487, 488, 512-514. 



&Daniell, Alfred, A text-book of the principles of physics, 3d ed., Macmillan Co., New York, 

 1895, p. 51. 



