EARTHQUAKES AND VOLCANOES. 



rises. 51. Also certain gases Artesian fire-wells. 52. Carbonic 

 acid its effects in former states of the globe origin of coal beds. 

 53. And marbles. 54. Mud volcanoes. 55. Those of remote 

 origin. 56. Progressive development. 57. Formation of dome- 

 shaped mountains. 58. Crater of elevation. 59. Active volcanoes. 

 60. Successive stages of their formation. 61. Not uniformly or 

 permanently active. 62. Intervals of activity and repose. 

 63. Dependent on the height. 64. Stromboli. 65. Guacamayo. 

 66. Volcanoes of the Andes. 67. Exceptions explained. 68. Erup- 

 tions often lateral. 69. Groups of small cones. 70. Remark - 

 able spectacle of Cotopaxi. 71. View of an active crater. 

 72. Remarkable permanence of the form of craters. 73. Effects of 

 snow-capped cones. 74. Cause of the fiery appearance of ejected 

 matter. 75. Islands of volcanic origin. 76. Volcanic theories. 



34. A REZtfABKAELE submarine earthquake occurred in the Gulf 

 of Mexico in 1780, during which a mass of water was carried 

 against the western coast of the island of Jamaica, which in an 

 instant submerged the entire town of Savannah la Mar. Not a 

 building nor living thing escaped this prodigious irruption of 

 water. 



The same island underwent still more extensive devastation 

 from an earthquake which occurred there in 1692. Three-fourths 

 of Port Royal, the capital of the island at that time, suddenly 

 sunk down, and with all its inhabitants was submerged by the 

 sea. Large warehouses which stood upon the quays were sub- 

 merged to such a depth, that their roofs were from 20 to 40 feet 

 below the surface of the water. The subsidence was so evenly 

 vertical and so free from any lateral displacement or rocking 

 motion, that many of the houses sunk without falling ; so that 

 after the catastrophe the chimney-tops of some of them were seen, 

 as well as the topmasts of ships wrecked in the harbour, projecting 

 from the surface of the water. A vessel of war which had been 

 under repair in one of the docks was transported over several of 

 the submerged buildings, and finally rested upon one of the 

 sunken houses, breaking through the roof. 



In the first shock of this earthquake a tract of the adjacent 

 country of the extent of above a thousand acres was instanta- 

 neously submerged. 



35. It has been calculated that in the great earthquake of 

 Lisbon, a portion of the earth's surface more than four times the 

 area of Europe was affected by the undulation, without taking 

 into account any part of the submarine disturbances which 

 attended it. 



36. As examples of shocks and tremblings of the ground which 

 have continued from hour to hour for several successive months, 

 Humboldt produces the following examples, all of which took place 

 at great distances from any active volcano. On the eastern slope 



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