306 REACTION OF THE INTERIOR OF THE EARTH 



sand. The latter belongs more to the immediate vicinity 

 around Perote, to the plateau, more than 7000 feet 

 high, which lies between the two volcanic chains, run- 

 ning north and south, of Popocatepetl and Orizaba. 



When, in proceeding from Mexico to Vera Cruz, one 

 begins to descend from the heights of the non-quartz- 

 ose trachytic porphyry of Vigas towards Canoas and 

 Jalapa, one twice passes over fields of fragments of 

 scoriaceous lava, the first time between the station of 

 Parage de Garros and Canoas or Tochtlacuaya, the second 

 time between Canoas and the station of Casas de la Hoya. 

 The first is called Loma de Tablas, on account of the 

 many upright basaltic slabs of oliviniferous lava, and the 

 second simply the Malpais. A small ridge of the same 

 trachytic porphyry full of glassy felspar, which (near 

 la Cruz Blanca and Eio Frio) forms the eastern boundary 

 of the Arenal (pearlstone sand-fields), divides the 

 Loma de Tablas from the much more extensive 

 Malpais. Those among the country-people who are 

 well acquainted with the district, affirm that the lines 

 of scoriae are prolonged towards the S.S.W., therefore 

 towards the Cofre de Perote. Having myself ascended 

 the Cofre and made many measurements on it( 443 ), I 

 have been little disposed to infer, from what is indeed a 

 very probable prolongation of this stream of lava 

 (marked as such in my "Profiles," tab. 9 and 11, as 

 well in the " Nivellement barometrique "), that it had 

 actually flowed from that singularly shaped mountain. 

 The Cofre de Perote, which is indeed nearly 1400 feet 

 higher than the Peak of Teneriffe, but which yet is an 

 inconsiderable mountain compared to its colossal neigh- 

 bours Popocatepetl and Orizaba, forms, like Pichincha,, 



