208 M. Arago on the [March, 



canos, are in a line, as if they proceeded from one fissure or vein, 

 in a direction perpendicular to that of the great chain of moun- 

 tains which traverses Mexico from the north-west to the south- 

 east. 



The volcano of Xorullo just mentioned interposed itself in 

 1759 in the line of the ancient volcanos. This curious arrange- 

 ment, which we shall observe in other places, exists also, accord- 

 ing to M. Daubuisson, in the extinct volcanos of Puy-de-D6me. 



The volcanos of Gnatimala which have most lately erupted, 

 are Los Fuegos of Guatimala, Isalco, Momotombo, Talica, and 

 Bombacho. These active volcanos, and the sixteen others 

 whose names have been mentioned, are contained between the 

 10° and 15° of north latitude, and in a line corresponding with 

 the general direction of the Cordilleras. 



The connexion of the volcano of Pasto with those of the pro- 

 vince of Quito was shown in a striking manner in 1796. A thick 

 column of smoke had existed from the month of November, 

 1796, from the volcano of Pasto ; but to the great surprise of all 

 the inhabitants of the city of that name, the smoke suddenly dis- 

 appeared on the 4th of February, 1797. This was precisely the 

 moment at which, at 65 leagues further south, the city of Rio- 

 bamba, near Tunguragua, was destroyed by a tremendous earth- 

 quake. 



Antisana is 20,000 feet high. No eruption of this volcano is 

 known to have happened since the year 1590. 



The last eruption of Rucupichincha occurred in the year 1660. 



Cotopaxi made an eruption in 1742, while the French acade- 

 micians were measuring a degree of the meridian in its neigh- 

 bourhood. The column of flames and of burning substances 

 rose 500 toises above the mountain. The snows which had been 

 heaped up during two centuries, from the summit of the mountain 

 to 500 toises below it, were melted en masse ; the torrent which 

 it occasioned rushed into the plain with impetuosity, forming 

 waves from 60 to 100 feet in height. At a distance of three or 

 four leagues from the mountain, the rapidity of the water, in the 

 opinion of Bouguer, was from 40 to 50 feet in a second. Six 

 hundred houses were destroyed, and 700 or 800 persons were 

 drowned in the torrent. The eruptions of 1743 and 1744 were 

 still more disastrous. 



Bouguer and La Condamine, having examined the remaining 

 traces of the great eruption of 1533, the memory of which is 

 preserved from generation to generation among the inhabitants, 

 they found that the volcano had ejected to a distance of more 

 than three leagues, stones containing from 70 to nearly 100 

 cubic feet, or to use the expression of La Condamine, larger than 

 the cabin of an Indian. The origin of these stones was unques- 

 tionable ; they formed lines in every direction towards the 

 volcano. It does not appear that Vesuvius has ever ejected 

 stones to more than 4,000 feet high. 



