From Charles San Lambert1 [c. July 1835]
You travel upwards in that dry ravine [Santandrés] for about 3 miles, where it ends, & on the summit of the hill which forms its boundary, you find large superficial beds of Sulphur & the Sulphate of Alumina.— In the ravine there are scattered about fragments of Pumice Lavas calcinèe Granite & Porphyry & other Volcanic productions.— The formation of all the country from Sant Andrès is generally of Granite & Porphyry covered by Volcanic eruptions. These substances present generally a red appearance, whilst the Granite & Porphyry formation on which they lay is black.— There are many points, where you can see the points of the Granitic hills rise in the middle of the Volcanic formation; the Lava not being in sufficient quantity to cover the whole.— All the ravines have been formed after the eruptions of the Lava.— This Volcanic formation extends from Copiapò to Atacama, forming in some places regular basaltic elevated plains. These detain the waters which flow from the Western side of the Cordilleras & cause those Salt lakes, where the inhabitants of Copiapò & Atacama provide themselves with that article.
Describes volcanic formations capping granite hills from Copiapò to Atacama [Chile]. [See South America, pp. 230–1.]
Please cite as
Darwin Correspondence Project, “Letter no. 279,” accessed on 25 July 2016, http://www.darwinproject.ac.uk/DCP-LETT-279