34 



buried in the entrails of the Earth; but if the 

 narrow circle, in which all certain traditions are 

 confined, do not present any of those general 

 revolutions, which have heaved up the Cordil- 

 leras, and buried myriads of pelagian animals, 

 Nature, acting under our eyes, does not less 

 exhibit tumultuous though partial changes, the 

 study of which may throw light on the most 

 remote epochs. Those mysterious powers reside 

 in the interior of the Earth, the effects of which 

 are manifested at the surface by the production 

 of vapours, of incandescent slags, of new vol- 

 canic rocks and thermal springs, by the ap- 

 pearance of new islands and mountains, by 

 commotions propagated with the rapidity of 

 an electric shock, finally by those subterranean 

 thunders *, which are heard during whole 



* Those which alarmed the inhabitants of the town of 

 Guanaxuato, in Mexico, lasted from the 9th of January till 

 the J 2th of February, 1784. This phenomenon, almost with- 

 out example among those accurately observed, will be de- 

 scribed in the sequel of this Narrative, It is sufficient here 

 to observe,, that the town is situate forty leagues Nortk of 

 the volcano of Jorullo, and sixty leagues North-West of the 

 volcano of Popocatepetl. In places nearer these two volca- 

 noes, three leagues distant from Guanaxuato, the subterra- 

 neous thunders were not heard. The noise was circumscribed 

 within a very narrow space, in the region of a primitive 

 schist, which approaches a transition schist, containing the 

 richest silver mines of the known world, and on which rest 

 trap, porphyries, slates, and diabasis (gruenstein). 



