268 REACTION OF THE INTERIOR OF THE EARTH 



and ashes on March 2, 1793. In consequence of having 

 made exact determinations of the latitudes and longi- 

 tudes of the giant Snowy Mountains and volcanoes in 

 the interior of Mexico, and while entering the culmi- 

 nating points on my large map of New Spain after my 

 return to Europe, I was led to the exceedingly re- 

 markable result, that there is there a parallel of vol- 

 canoes and of culminating points running from sea to 

 sea, and deviating only a few minutes on either side of 

 the parallel of 1 9. The only volcanoes, and at the same 

 time the only summits covered with perpetual snow, 

 therefore the only mountains exceeding 12,000 feet in 

 the country, the volcanoes of Orizaba, Popocatepetl, 

 Toluca, and Colima, lie between the parallels of latitude 

 of 18 59' and 19 20', and mark at the same time "the 

 direction of a fissure of volcanic activity "360 miles in 

 length. ( 393 ) In the same east and west line (in lat. 19 

 9'), intermediate between the volcanoes of Toluca and 

 Colima, distant 116 miles from one, and 128 miles from 

 the other, in a wide plain 2583 feet high, the new 

 volcano of Jorullo (4265 feet) was upheaved on the 

 14th of September 1759. The locality of this event, 

 viewed in relation to the situation of the other Mexican 

 volcanoes, and the circumstance that the east and west 

 fissure I have just spoken of intersects at almost right 

 angles the south south-east and north north-west direc- 

 tion of the great chain of mountains, are geological 

 phenomena no less important than are the distance from 

 the sea of the point at which Jorullo has been elevated, 

 and the evidences of its upheaval which I have repre- 

 sented in detail graphically, viz. the countless vapour- 

 exhaling hornitos which surround the volcano, and the 



