io6 POPULAR SCIENCE MONTHLY. 



of western civilization. 'Ko one can predict wliat the end of this 

 movement may be. 



Without going into detail concerning the fluctuations seen in 

 general history, we may consider those that have taken place in the 

 interior development of particular countries. In France, once busy 

 centers have declined, and their glory has been transferred to other 

 places where conditions have in some way become more advan- 

 tageous. 



In the United States, a country as of yesterday, the fluctuations 

 are sometimes very remarkable. A new region is opened to culti- 

 vation; a new lode is discovered; and railroads are built and cities 

 rise as if by magic; then the railroad is extended, the mine is ex- 

 hausted, or more fertile lands are discovered, and the new city 

 disappears while another one is built somewhere else; but if the 

 favorable conditions continue or others are found or made, it be- 

 comes permanent. 



In England, the ancient towns which owed their prominence to 

 military, ecclesiastical, or feudal conditions are declining or station- 

 ary, while places only recently of relative insignificance have be- 

 come immense manufacturing centers or commercial cities. 



There is no region which we can say will never be of importance ; 

 no country that can be supposed superior to a reverse of fortune. 

 The most arid desert will become populous if a gold mine or a 

 diamond bed is discovered in it; the most prosperous country would 

 be liable to decline if a more important source of wealth were found 

 near it. Suppose a method were discovered of applying the heat 

 of the sun directly to the production of motion. Coal would be- 

 come useless and coal lands waste. If a system of irrigation by 

 artesian wells were practically developed and conveniently applied in 

 the Great Desert, it would become populous. The future of any 

 country is at the mercy of the discovery or of a new application by 

 man of some property of matter. What seems to be a speculative 

 research may possibly result in overthrowing the material or moral 

 equilibrium of the world. 



But while the evolution of the earth is going on slowly, almost 

 imperceptibly to man, it is advancing all the time; and while man's 

 evolution is, as we have seen, vastly more rapid to appearance, it has 

 limitations. Man can never burst the bonds that subject him to 

 ^Nature, and will never be able to abstract himself from the material 

 necessities of his existence. Great as seem to be the resources now at 

 his disposal, his development is absolutely controlled by the conditions 

 of animal life. The earth is already far advanced on its course from 

 the primitive nebulous condition toward that which has been reached 

 by the moon. It, too, like the moon, will eventually lose its interior 



