TRUE VOLCANOES. 377 



spring of 1855) for a very instructive view of the different 

 kinds of rocks collected by him, as well as for his interesting 

 geological notices on the volcanoes of the whole Mexican 

 highlands, all of which he has personally visited. The vol- 

 cano of Toluca, whose highest summit (the Pico del Fraile), 

 though narrow and difficult to climb, I ascended on the 29th 

 of September, 1803, and found barometrically to be 15,166 

 feet high, has a totally different mineralogical composition 

 from the still active Popocatepetl and the igneous mountain 

 of Colima ; this must not, however, be confounded with an- 

 other still higher summit, called the Snow mountain. The 

 volcano of Toluca consists, like the Peak of Orizaba, the Puy 

 de Chaumont in the Auvergne and -5Cgina, of a combination 

 of oligoclase and hornblende. From this brief sketch it will 

 be seen, and it is well deserving of notice, that in the long 

 range of volcanoes which extend from ocean to ocean there 

 are not two immediately succeeding each other which are of 

 similar mineralogical composition. 



X. The Northwestern Districts of America (northward 

 of the parallel of Rio Gila.) 



In the section which treats of the volcanic action on the 

 eastern Asiatic Islands,* particular notice has been drawn 

 to the bow-like curve in the direction of the fissure of up- 

 heaval from which the Aleutian Islands have risen, and which 

 manifests an immediate connection between the Asiatic and 

 American continents — between the two volcanic peninsulas 

 Kamtschatka and Aliaska. At this point is the outlet, or 

 rather the northern boundary, of a mighty gulf of the Pacific 

 Ocean, which, from the 150 degrees of longitude embraced by 

 it under the equator, narrows itself down between the term- 

 inal points .of these two peninsulas to 37° of longitude. On 

 the American continent, near the sea-shore, a number of more 



face is vitrified without any tube-like perforation, as is the case at the 

 little Ararat and at Mont Blanc. Herr Pieschel first ascended the 

 double-peaked volcano of Colima, in October, 1852, and reached the 

 crater, from which he then saw nothinf]^ but sulphureted-hydrogen va- 

 por rising in a cloud ; but Sonneschmid, who vainly attempted to as- 

 cend Colima, in February, 1796, gives an account of an immense ejec- 

 tion of ashes in the year 1770. In the month of March, 1795, on the 

 other hand, red-hot scoria; were visibly thrown out in a column of fire 

 at night. " To the northwest of th<5 volcano of Colima a volcanic 

 branch fissure runs along the shore of the South Sea. Extinct craters 

 and ancient lava streams are recognized in what are called the Volca- 

 noes of Ahuacatlan (on the road from Guadalaxara to San Bias) and 

 Tepic." (Pieschel, Ibid., p. 529.) * See above, p. 344-349. 



