The distance from the city of Cordova to that of Santiago del Estero is 110 leagues by the post-road. Portezuela is the first station beyond the jurisdiction of Cordova, shortly after which commences what is called the Travesia, a vast sandy zone thirty to forty leagues in breadth, for the most part covered with a saline efflorescence, and producing a salsola, from the ashes of which the inhabitants extract soda. It borders the Sierra de Cordova to the north, and extends west as far as La Rioja, running southward nearly to San Luis. In this arid district the sultry heat of the north wind, which is very prevalent in the summer season, is almost insufferable.
My intelligent correspondent Dr. Redhead, who has lived for more than a quarter of a century in the upper provinces, and to whom I am indebted for some of the most valuable of my information respecting them, speaking of its geological appearance, observes in one of his letters how forcibly he had been led to conjecture that the southern part of the province of Santiago must once have been a sea-coast. "Its sandy hillocks, he says, always reminded him of those on the shores of Flanders:"—certain it is, that throughout the whole extent of this sandy zone, from Ambargasta to Noria, the level of the country becomes very much depressed, and falls very nearly to that of Buenos Ayres; thus in the very heart of the continent, at a distance of 700 miles direct from the sea, we have a considerable tract of land hardly elevated above its immediate shores.
The following table of barometrical observations, taken by Dr. Redhead, will not only show the variations in the height of the country intervening between Buenos Ayres and Santiago, but also of that to the northward, along the high road, as far as Tupiza in Peru:—
Barometrical Observations, made on the road from Buenos Ayres to Potosi, by Dr. Redhead:—
| Distance from one place to another Post leagues | Point of Observation | Barometer | Thermometer | Date | Hour | |
|---|---|---|---|---|---|---|
| 134 | Rio Tercero from Buenos Ayres | 28·945 | 86 | Feb. 11 | 11 a.m. | |
| 3 | Cordova | 28·400 | 86 | 20 | 4 p.m. | |
| 14 | Sin-Sacate | 27·990 | 75 | Mar. 12 | 11 a.m. | |
| 22 | San Pedro | 26·990 | 60 | 17 | 6 a.m. | |
| 4 | Durasno | 27·300 | 73 | — | 9 a.m. | |
| 4 | Piedritas | 27·500 | 72 | — | Noon. | |
| 4 | Pozo del Tigre | 27·550 | 71 | — | 5 p.m. | |
| 6 | Portezuela | 27·860 | 69 | 18 | Noon | |
| 6 | Ambargasta | The Travesia | 28·875 | 67 | 19 | 9 a.m. |
| 6 | Punta del Monte | 29·260 | 82 | — | 4 p.m. | |
| 6 | Salinas | 29·600 | 68 | 20 | 6 a.m. | |
| 14 | Noria | 29·400 | 76 | — | 2 p.m. | |
| 24 | Santiago del Estero | |||||
| 40 | Tucuman | 27·563 | 75 | Feb. 10 | ||
| 100 | Jujuy | |||||
| 30 | Humaguaca | 21·415 | 57 | June 2 | 4 p.m. | |
| 8 | Cueba | 21·200 | 54 | 1 | ||
| 3 | Abra de Cortaderas | |||||
| 3 | Colorados | 19·350 | 50 | May 31 | 8 a.m. | |
| 6 | Cangrejos | 19·625 | 32 | 30 | 6 p.m. | |
| 9 | Quiaca | 19·300 | 50 | 29 | 4 p.m. | |
| 5 | Cumbre del Cerro de Berque | 19·100 | 60 | 28 | 11 a.m. | |
| 4 | Berque | 19·975 | 54 | 27 | 4 p.m. | |
| 5 | Talina | 20·800 | 56 | 26 | 9 a.m. | |
| 8 | Tupiza | 26·260 | 60 | 25 | 9 a.m. | |
Note.—At Buenos Ayres the mean of the barometer for the month of March, 1822, was 29·61.
In the upper parts of the Sierra de Cordova granite everywhere breaks through the surface, and innumerable fragments of it may be traced in the descent to the Travesia, whilst beyond that sandy zone there is not a vestige of it throughout the rest of the road to Potosi, the formation the whole way being of blue argillaceous schist and slate, with occasional strata of limestone and red sandstone. In the neighbourhood of Potosi, however, and on the tops of some of the highest mountains in its vicinity, Helms tells us that he fell in with a pretty thick stratum of granite pebbles rounded by the action of water. How, he says, could these masses of granite have been deposited here? Have they been rolled hither by a general deluge, or by some later partial revolution of nature? His astonishment would have been infinitely greater had he known that marine shells are to be found on the lofty mountain of Chorolque (about twelve leagues north-west from Tupiza, between Salta and Potosi), the summit of which has been determined by Dr. Redhead to be 16,530 feet above the level of the sea.
The word Chorolque is corrupted from Churucolque, signifying in the Quichua tongue that the mountain contains silver and shells. The Spaniards, however, little suspected that the latter were to be found there, till, in 1826, an enterprising Frenchman ascended the mountain and brought down specimens which established beyond doubt the fact.