See "Geological Observations on South America" (London, 1846), Chapter VII.: "Central Chile; Structure of the Cordillera.") These islands were covered with fine trees; in the conglomerate, I found one 15 feet in circumference perfectly silicified to the very centre.

The alternations of compact crystalline rocks (I cannot doubt subaqueous lavas), and sedimentary beds, now upheaved fractured and indurated, form the main range of the Andes.

The formation was produced at the time when ammonites, gryphites, oysters, Pecten, Mytilus, etc., etc., lived.

In the central parts of Chili the structure of the lower beds is rendered very obscure by the metamorphic action which has rendered even the coarsest conglomerates porphyritic.

The Cordilleras of the Andes so worthy of admiration from the grandeur of their dimensions, rise in dignity when it is considered that since the period of ammonites, they have formed a marked feature in the geography of the globe.