“The soil for cultivation must first be prepared, and the mineral removed. The native method of doing this is very simple. The water is conducted from the Rivers Mendoza and San Juan (which take their rise in the Cordillera) through an acquia, or canal, around squares of level land, at irregular intervals of time, and, to use their own expression, they wash off the salitre (saltpetre). Then a plough, constructed of two pieces of wood, is brought into service, and it turns up from six to eight inches of the soil, which goes through the same washing process as the first.
“After two or three repetitions of this operation, a shallow soil is obtained, partially free from salitre, in which wheat, clover, pumpkins, melons, &c., are raised. The remaining salitre, according to the belief of the natives, is exhausted by successive crops, and after several years of tillage the soil is suitable for the vine. Oranges, peaches, quinces, olives, figs, &c., flourish. Within a few years large tracts of land have been made exceedingly fertile by the process above described, and could the New England plough be introduced there, the process would be far more effective.”
The following analysis of the salt was made by Dr. A. A. Hayes, of Boston, a gentleman well known in scientific circles for the care and accuracy with which he conducts all analyses:—
“The specimen was a white, crystalline solid, formed by the union of two layers of salt, as often results from the evaporation of a saline solution, when the pellicle formed on the surface falls to the bottom. Along the line of junction crystal facets are seen, but the forms are indistinct. These crystals readily scratch calc spar, and dissolve without residue in water, affording a solution, which, by evaporation at 150° Fahr., leaves the salt with some of the original physical characters. It readily parts with a portion of water by heat, and when the temperature is raised to redness, it fuses quietly into a transparent, colorless, anhydrous fluid. On cooling, an opaque, white, crystalline solid remains. In this climate the specimen attracts moisture, and therefore has not a fixed amount of water constituent.
“It consists of water, sulphuric acid, soda, magnesia, chlorine. Mixed with it are traces of crenate of iron and lime, with sandy grains of earth.
“One sample afforded—
| Water, | 16.420 |
| Sulphuric acid, | 49.658 |
| Soda, | 23.758 |
| Magnesia, | 9.904 |
| Chlorine, | .260 |
| 100.000 |
“Three fragments from different masses were taken, and the following substances found:—
| Water, | 16.42 | 18.84 | 19.60 |
| Sulphate of soda, | 48.00 | 45.82 | 45.74 |
| ” ” magnesia, | 34.20 | 33.19 | 33.31 |
| Chloride sodium, | 1.21 | 1.79 | 1.16 |
| Crenates lime and iron with silicic acid, | 0.17 | 0.30 | 0.13 |
| Sand, | 0.06 | 0.06 | |
| 100.00 | 100.00 | 100.00 |
“The varying amounts of water given are illustrative of the absorptive power of the salts in the atmosphere of this place. Dried at 90° Fahr., the amount of water was 15.20 in 100 parts, which exceeds by four parts the proportion necessary to form proto-hydrates of the two salts present.