Epidemics. 295 



and even death are the direct results of the unequal distri- 

 bution, at given seasons, of heat and moisture over limited 

 areas of territory. 



The famines of Persia and India will illustrate this 

 statement, and in our own land the drought of 1868 might 

 suffer feeble comparison in recent periods. 



2nd : No changes on the superficies of the globe are of 

 an extensive character, and at the same time sudden, but 

 they are slow and gradual, unless we admit those from the 

 interior which reach the surface, as earthquakes and volca- 

 noes ; but it is no infrequent thing, within 48 hours, to 

 experience a change in temperature of 30 degrees Fahr. 

 Such sudden changes are impossible to result from chemical 

 decomposition, when they range over miles of territory, and 

 much less can the regular solar heat vary so suddenly. 

 Hence the changes arising from solar heat or chemical de- 

 composition are totally insufficient to account for those 

 frequent and sudden changes of temperature and moisture 

 so commonly experienced, or for those changes of a longer 

 duration and of a more subtle nature, called epidemic 

 periods, which so materially affect the vital conditions of 

 particular districts, and of large portions of the globe 

 itself. 



3rd : Force, in some way or other, holds and binds this 

 earth together call it attraction of cohesion, aggregation, 

 or attraction of gravitation. It is force of some kind which 

 holds this earth together. But to be force, as already men- 

 tioned in the chapter upon vital physics, antagonism is 

 essential. 



And the earth itself has within itself the antagonizing 

 forces of repulsion and attraction, but in such very different 

 degrees, and manifested in such a variety of forms, that the 

 whole earth is in unceasing action throughout, in the forms 

 of magnetism, diamagnetism, internal heat, and fire, with 



