240 COSMOS, 



also observed to exist among the volcanic mountains Oriza- 

 ba, Popocatepetl, Jorullo, and Colima ; and I have shown* 

 that they all lie in one direction between 18° 59' and 19° 12' 

 north latitude, and are situated in a transverse fissure running 

 from sea to sea. The volcano of Jorullo broke forth on the 

 29th of September, 1759, exactly in this direction, and over 

 the same transverse fissure, being elevated to a height of 1 604 

 feet above the level of the surrounding plain. The mountain 

 only once emitted an eruption of lava, in the same manner as 

 is recorded of Mount Epomeo in Ischia, in the year 1302 

 But although Jorullo, vt^hich is eighty miles from any active 

 volcano, is in the strict sense of the word a new mountain, it 

 must not be compared vrith Monte Nuovo, near Puzzuolo, 

 which first appeared on the 19th of September, 1538, and is 

 rather to be classed among craters of elevation. I believe 

 that I have furnished a more natural explanation of the erup- 

 tion of the Mexican volcano, in comparing its appearance to 

 the elevation of the Hill of Methone, now Methana, in the 

 peninsula of Troezene. The description given by Strabo and 

 Pausanias of this elevation, led one of the Roman poets, most 

 celebrated for his richness of fancy, to develop views which 

 agree in a remarkable manner with the theory of modern 

 geognosy. " Near Troezene is a tumulus, steep and devoid of 

 trees, once a plain, now a mountain. The vapors inclosed in 

 dark caverns in vain seek a passage by which they may escape. 

 The heaving earth, inflated by the force of the compressed 

 vapors, expands like a bladder filled with air, or like a goat- 

 skin. The ground has remained thus inflated, and the high 

 projecting eminence has been solidified by time into a naked 

 rock." Thus picturesquely, and, as analogous phenomena 

 justify us in beUeving, thus truly has Ovid described that 

 great natural phenomenon which occurred 282 years before 

 our era, and, consequently, 45 years before the volcanic sepa- 

 ration of Thera (Santorino) and Therasia, between Troezene 

 and Epidaurus, on the same spot where Russegger has found 

 veins of trachyte.f 



* Humboldt, Essai Politique sur la Now. Espagne, t. ii., p. 173-175. 

 t Ovid's description of the eruptioa of Methone (Meiam., xv., p. 296 

 306) : 



" Near Troezene stands a hill, exposed in air 



To winter winds, of leafy shadows bare : 



This once was level ground ; but (strange to tell) 



Th' included vapors, that in caverns dwell, 



Laboring with colic pangs, and close confined, 



In vain sought issue for the rumbhng wind : 



Yet still they heaved for vent, and heaving still, 



Enlarged the concave and shot up the hill, 



