hy Alexander von Humboldt. xxxv 



what the Spaniards term Malpays, the Sicilians Sciarra 

 viva. The face of the country is covered over with boulders 

 of lava, at San Nicolas de los Ranchos, at the foot of Popo- 

 catepetl, adjoining the city of Puebla de los Angeles, after 

 which, on the road from Puebla to Vera Cruz, will be ob- 

 served two narrow strips of boulders of cooled basaltic lava, 

 rich in olivine. Similar examples will be found at Parage de 

 Garros, near Tochtilacuaja and Loma de Tablas, between 

 Cancas and the Casas de la Hoja. The mere ascension of 

 volcanic cones is geologically of far less importance, than the 

 bringing away numerous specimens, carefully selected, of 

 various trachytic rocks, which, by their oryctognostical com- 

 position, are characteristic of each volcano. I would never- 

 theless recommend that the Pico del Fraile of the Toluca 

 volcano (2372 toises) should be ascended, proper caution being 

 used. From this very sharp peak, I brought away thin 

 plates of trachyte perforated by lightning, and internally of a 

 matted texture, resembling those brought from Little Ararat. 

 Both for the miner and geologist, an interesting and useful 

 visit might be paid to the rich mines of Guanaxuato and the 

 Mines de la Biscaina and Regla, on the road from Mexico 

 to Real del Monte, so as to observe the close connection 

 subsisting between the richer silver ores, occurring in 

 trachytic porphyry without quartz, but with felspar, 

 (glassy felspar?), and the thoroughly volcanic Cerro del 

 Gacal, abounding in obsidian, and the Cerro de las Navajas 

 (Razor Range), which remind one of the environs of 



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