CHAPTER XXIII. 



VOLCANOES AND EARTHQUAKES. 



Another popular fallacy. The earth's internal fire. Dr. Mayer's theory. 

 Dr. Tyndall opposed to it Dr. Mayer's dogged assertion. Selfish- 

 ness of men of science. Herschell on Volcanoes. Nineveh and 

 Carthage. The earth and an egg. Objection to Ilerschell's theory. 

 Explanation of Volcanoes. Why Volcanoes become extinct. 

 Coal gas. Mount St. Helena and Sulphur Springs. Prof. Mallet on 

 Water and Volcanoes. Cause of Earthquakes. Prevention of 

 Earthquakes. Oil boring in Pennsylvania. Ilerschell's extraordin- 

 ary thedry of Earthquakes. What he knew of chemical action in 

 the interior. The necessity for scientific men not taking anything 

 for granted. 



IN this chapter we deal with a popular fallacy advocated by 

 scientific men for many years past ; but which has nothing to 

 support it, save their own assertions. This theory is, that the 

 interior of the earth is a mass of molten fire, where everything 

 is reduced to a state of " igneous fluid ;" and the crust we live 

 on is only about twenty or thirty miles thick so that taking the 

 size of the earth into account the solid substance we are sup- 

 ported on, is not so thick, by comparison, as the shell of an egg, 

 to the matter within it. Then when we fancy that the interior is 

 bubbling and boiling all the time, the wonder is that we 

 have not exploded long ago ; or that the Himalayas, the Alps, 



