EARTHQUAKES AND VOLCANOES. 



in parallel lines sometimes in circles. 16. Effects of the vertical 

 shock in the earthquake of Riobamba. 17. Examples of circular 

 propagation. 18. Examples of horizontal and gyratory derangement. 

 19. Strong shocks sometimes felt without overturning buildings. 

 20. Gyratory earthquakes most destructive. 21. Singular displace- 

 ment at Riobamba. 22. Earthquakes are not generally attended by 

 any peculiar atmospheric prognostics. 23. Earthquakes most frequent 

 at the equinoxes. 24. Well described by Pliny and Seneca. 25. 

 Attended by subterranean thunder. 26. Character of these sounds. 

 27. Are heard at great distances from the place of the earthquake. 

 28. Examples of this. 29. Subterranean roaring of Guanaxuato. 

 30. Their effects on the inhabitants. 31. Great extent over which 

 earthquakes spread. 32. They affect the bottom of the ocean. 33. 

 Curious examples of these effects. 



1. IT is the tendency of undisciplined ininds to refer all 

 unusual and occasional phenomena to local and accidental causes, 

 and, mistaking trivial and unimportant differences for essential 

 distinctions, to ascribe to very different physical agencies what 

 are only various effects proceeding from the operation of a 

 single principle. The tendency of science is the reverse. It 

 ignores accident in nature. It admits no contingencies. The 

 Architect of the universe operates by fixed and general laws, the 

 results of which are uniform and regular. The apparent uncer- 

 tainty of some natural phenomena arises merely from our imperfect 

 knowledge of the laws which govern them. Before the science of 

 astronomy had reached a certain degree of advancement, solar and 

 lunar eclipses were regarded as preternatural manifestations, 

 during which the common laws of nature were suspended, and as 

 the forerunners of terrible calamities to the human race. Now 

 that the laws which govern the motions of the heavenly bodies are 

 known, these phenomena have lost their terrors. They are no 

 longer regarded as either preternatural, uncertain, or accidental. 

 They are, on the contrary, as regular, periodical, and certain as 

 the seasons, or the returns of light and darkness ; and the times 

 of their occurrence, and all the circumstances attending them, are 

 predicted with the greatest conceivable certainty and the last 

 degree of precision. 



2. Nothing is more usual than to apply the term " uncertain " 

 to the weather, yet nothing can be more absurd. The causes 

 which govern its phenomena being physical agencies independent 

 of the will or interference of any being, save of HIM " who rules 

 the storm," are as fixed and as certain in their operation, and as 

 regular in the production of their effects, as those which maintain 

 and regulate the motions of the solar system. The moment of 

 the rising or setting of the sun on any given day of the ensuing 

 year, is, therefore, in .the nature of things, not more certain than 

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