ON ITS EXTERIOE. VOLCANOES. 301 



tion, which Burkart also saw crop out under the syenite 

 of the Eio <le las Balsas. Rose said, " the enclosure is 

 a mixture of quartz and felspar. The dark-green spots 

 appear to be not hornblende, but mica fused with some 

 felspar. The white baked-in fragment has been split by 

 volcanic heat; and in the crack, white tooth-shaped 

 molten threads run from one edge to the other." 



More to the north than the great volcano of Jorullo, 

 and than the scoriaceous lava-summit which it threw 

 out in the direction of the old basalt of the Cerro del 

 Mortero, follow the two last of the six volcanoes. They 

 appear to have been at first very active ; for the natives 

 still call the extreme one the " volcancito." A wide 

 fissure which has opened to the westward bears in this 

 part traces of a destroyed crater. The great vol- 

 cano appears, like Epomeo in Ischia, to have poured 

 forth a great stream of lava only once. There is, his- 

 torically, no reason to suppose that it continued to do 

 so beyond the immediate epoch of the great outburst ; 

 for the letter of Father Joaquin de Ansogoni, written 

 twenty days after the first eruption, speaks only of 

 the best means to be adopted for the pastoral care of 

 the dispersed country-people, who had fled from the 

 catastrophe, and for the next thirty years we are 

 entirely without documentary evidence. As tradition 

 speaks very generally of " fires covering so great a 

 space," we may suppose that all the six hills over the 

 great fissure, and all the part of the Malpais on which 

 the hornitos appeared, were burning at the same time. 

 We may in some degree infer the heat which must have 

 prevailed in the surrounding atmosphere from the tem- 

 peratures still measured by me after the lapse of forty- 



