RECORD: Darwin, C. R. Geological diary: Salitrales (1833) CUL-DAR34.27-28 Transcribed by Kees Rookmaaker, edited by John van Wyhe (Darwin Online, http://darwin-online.org.uk/).
REVISION HISTORY: Transcribed by Kees Rookmaaker, corrected and edited by John van Wyhe 1.2011. RN1
NOTE: This document, part of the largest scientific document composed by Darwin during the voyage of the Beagle, is written mostly in ink. Marginal notes are here integrated into the text.
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Reproduced with the permission of the Syndics of Cambridge University Library and William Huxley Darwin.
1833 (41) Salitrales.—
feet above the level of the great swamp.
I also saw some on the high Tosca rock plain, it here occurred in a little valley, & coated some vegetable mould, with fragments of Tosca rock. — We have seen it in the cellars of the houses at the R. Negro; also encrusting a well in the low sandstone plain. —
It is said to occur on bare patches in the valley of the R. Negro. — & I saw it in the valley, near the Colorado; here a large swamp was covered with salt-loving plants, & in summer is white with saltpetre. —
I should imagine this plain, must occasionally be overflowed by the river, anyhow it is clearly alluvial. — there are lines of sand-dunes in the midst of these, which (& other reasons) make me believe that at some remote period the sea entered this valley or aestuary. —
In several of the above particulars, these salitrales essentially differ from the deposition of salt in the salinas. — In the almost universal occurrence in low, modern or alluvial plains (a), in contra distinction of an elevated depression, in forming only a very thin crust & this over deep mud (I
allude except in both cases, particular instances, such as salitra on the high Tosca rock plain). — in the manner of encrustation, instead of plain deposition. — From the local position & appearance of the salitrales it gives one the idea of being actually formed in the mud. — We should be obliged almost to come to some such conclusion, if the
(a) The salitrales occur in level plains, where the whole soil appears to be impregnated with salt, & a depression of an inch causes a thin coat to be seen after rain. — Salinas occur where you might expect springs. —
We may conjecture
salt in the latter case, that the salt owes its chief origin to deep seated beds; In the other case have we salts decomposed by vegetables & nitric acid formed by the mud.!!?!
1833 (42) Salitrales.—
the fact, which I believe the Gauchos asserted (a), that the salitrales were occasionally overflowed by the R. Colorado.—
To the South, at Port Desire, I found in a low muddy flat valley, in the great oyster formation an encrustation of saline matter, which I believe is of same nature with that of B. Blanca. —
At S. Cruz (1633) [crosswise]
Falkner states (P 37)1 that the saltpetre district extends from between Vinulean & St Anthony to Corriates, Rioja & Catamarca, that is in the great Tosca formation. — Now in the low plains between the Ventana & P. Salado though of same
orig geological nature, there is very little saltpetre. — I saw however one white patch about 35 miles to the south of the Salado, but I did not see it again till near B. Blanca. — Falkners southern limits are therefore wrong. —
At Corrientes & in the North it seems especially abundant & pure. — In this district we have Sulp. of Magnesia at Melincuè. (Arica). —
It is said there are saltpetre tracts near B. Ayres (b) & I heard of them in Entre Rios. — Perhaps it also occurs, (but very rarely) in the superficial Tosca of B. Oriental:
During the gran Seco, some of the smaller streams had a salt taste. —
Humboldt in Mexico2 talks of a saline efflorescence which probably is of somewhat a similar nature. —
1 Falkner 1774.
(a) Again I believe the salitrales in the valley of the R. Negro must have been overflowed during the floods & Easterly gales of (1826?). —
(b) About Rockas (71 miles W by N of Luxan) much saline efflorescence. — Miers Chili. —1
(or F. of Rosas)
1 Miers 1826, vol. 1, p. 39 describes a journey near Roccas: "There was a succession, for a considerable distance, of reedy swamps; the higher parts of them were covered with a saline efflorescence. The grass was also strongly saline."
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