214 LIGHT SCIENCE FOR LEISURE HOURS. 



indeed to show how poor and weak a creature man 

 is in presence of the grand workings of nature. The 

 mere throes which accompany her unseen subterranean 

 efforts suffice to crumble man's strongest buildings in 

 a moment into dust, while the unfortunate inhabitants 

 are either crushed to death among the ruins, or forced 

 to remain shuddering spectators of the destruction of 

 their homes. 



At first sight it may seem paradoxical to assert 

 that earthquakes, fearfully destructive as they have 

 so often proved, are yet essentially preservative and 

 restorative phenomena ; yet this is strictly the case. 

 Had no earthquakes taken place in old times, man 

 would not now be living on the face of the earth ; 

 if no earthquakes were to take place in future, the 

 term of man's existence would be limited within a 

 range of time far less than that to which it seems 

 likely, in all probability, to be extended. 



If the solid substance of the earth formed a perfect 

 sphere in ante-geologic times that is, in ages pre- 

 ceding those to which our present geologic studies 

 extend there can be no doubt that there was then 

 no visible land above the surface of the water ; the 

 ocean must have formed a uniformly deep covering to 

 the submerged surface of the solid globe. In this 

 state of things, nothing but the earth's subterranean 

 forces could tend to the production of continents and 

 islands. Let us be understood. We are not re- 

 ferring to the possibility or impossibility that lands 

 and seas should suddenly have assumed their present 



