230 



only when vapours and flames do not issue from 

 the crater. In the kingdom of Quito, the great 

 catastrophe of Riobamba, which we have before 

 mentioned, has led several well-informed persons 

 to think, that this unfortunate country would 

 be less often desolate, if the subterraneous fire 

 should break the porphyritic dome of Chimbo- 

 razo ; and if this colossal mountain should be- 

 come a burning volcano. At all times analogous 

 facts have led to the same hypothesis. The 

 Greeks, who, like ourselves, attributed the oscil- 

 lations of the ground to the tension of elastic 

 fluids, cited in favour of their opinion the total 

 cessation of the shocks at the island of Euboea, 

 by the opening of a crevice in the Lelantine 

 plain *. 



We have endeavoured to collect at the end of 

 this chapter the general phenomena of earth- 

 quakes under different climates. We have 

 shown, that subterraneous vapours are sub- 

 Jected to laws as uniform as the mixture of ga- 

 zeous fluids, which constitutes our atmosphere. 

 We have abstained from all discussion of the 

 nature of the chemical agents, which are the 

 causes of the great derangements that the sur- 

 face of the earth undergoes from time to time. 



* The shocks ceased only when a crevice, which ejected a 

 " river of fiery mud," opened in the plain of Lelantum, near 

 Chalcis. Strabo, lib. 1, ed. Oxon., 1807, t. i, p. 85. (See 

 also the translation by M. du Theil. t. i, p. 137, note 4.) 



