414 COSMOS. 



itself, and at the same time enclose in some parts (for ex- 

 ample, between Vic and Aurillac, and at the Giou de Mamon) 

 large fragments of gneiss 59 and limestone, we find also the 

 trachyte and basalt intersecting as dykes the gneiss, and the 

 coal-beds of the tertiary and diluvial strata. Basalt and 

 phonolite, closely allied to each other, as the Auvergne and the 

 central mountains of Bohemia prove, are both of more recent 

 formation than the trachytes, which are frequently tra- 

 versed in layers by basalts. 60 The phonolites are, on the 

 other hand, more ancient than the basalts ; where they pro- 

 bably never form dykes, but on the contrary dykes of basalt 

 frequently intersect the porphyritic-schist (phonolite). In 

 the chain of the Andes belonging to Quito, I have found the 

 basalt-formation a great distance apart from the prevailing 

 trachytes ; almost solely at the Rio Pisque and in the valley 

 of Guaillabamba. 61 



As in the volcanic elevated plain of Quito everything is 

 covered with trachytes, trachytic-conglomerates, and tufas, it 

 was my most earnest endeavour to discover, if possible, some 

 point at which it might be clearly seen on which of the older 

 rocks the mighty cone and bell- shaped mountains are placed, 

 or, to speak more precisely, through which of them they 

 had broken forth. Such a point I was so fortunate as to 

 discover in the month of June 1802, on my way from Rio- 

 bamba Nuevo (9483 feet above the surface of the South 

 Pacific) when I attempted to ascend the Tunguragua on the 



59 Resembling the granitic fragments imbedded in the trachyte of 

 Jorullo. See above, p. 321. 



60 Also in the Eifel, according to the important testimony of the 

 mine-director, Von Dechen. See above, p. 237. 



61 See above, p. 333. The Rio de Guaillabamba flows into the 

 Rio de las Esmeraldas. The village of Guaillabamba, near which I 

 found the isolated oliviniferous basalt, is only 6430 feet above the level 

 of the sea. An intolerable heat prevails in the valley, which is still 

 more intense in the Valle de Chota, between Tusa and the Villa cle 

 Ibarra, the sole of which sinks to 5288 feet, and which is rather a chasm 

 than a valley, being scarcely 9600 feet wide and 4800 feet deep (Hum- 

 boldt, Rec. d' Observations Astronomiques, vol. i, p. 307), The rubbish- 

 ejecting Volcan de Ansango, on the descent of the Antisana, does not 

 belong to the basalt-formation at all ; it is an oligoclase-trachyte resem- 

 bling basalt (compare, for the distances, Antagonisme des Basalt.es et des 

 Trachytes, my Essai Geognostique sur le gisement des Roches, 1823, pp. 

 848 and 359, and generally, pp. 327336). 



