CHAPTER XVIL 



TUE CAUSE OF EARTHQUAKES. 



Modern views respecting the cause of earthquakes — Earthquakes due to 

 faulting — To explosions of steam — To volcanic evisceration — To 

 chemical degradation — Attractive influence of the heavenly bodies 

 — The effect of oceanic tides — Variation in atmospheric pressure — 

 Fluctuation in temperature — Winds and earthquakes — Rain and 

 earthquakes — Conclusion. 



As the results of modern inquiries respecting the 

 cause of earthquakes, we see many investigators chiefly 

 attributing these phenomena to special causes. A few 

 attribute them to several causes. It seems to us that 

 they might be attributed to very many causes which often 

 act in a complex manner. The primary causes are telluric 

 heats, solar heat, and variations in gravitating influences. 

 These may be the principal, and sometimes the imme- 

 diate, cause of an earthquake. The secondary causes are 

 those dependent upon the primary causes, such as ex- 

 pansions and contractions of the earth's crust, variations 

 in temperature, barometrical pressure, rain, wind, the 

 attractive influences of the sun and moon in producing 

 tides in the ocean or the earth's crust, variations in the 

 distribution of stress upon the earth's surface caused by 

 processes of degradation, the alterations in the position 

 of isogeothermal surfaces, &c. 



The part which maybe played by these various causes 



