Many theories have been advanced as to the cause of this chemical composition. The most ingenious one, perhaps, is that nitric acid is formed by a flash of lightning passing through a moist atmosphere, and electrical storms are very common in the Cordilleras. The other is that this coast was originally submerged in the ocean, and was gradually upheaved. This would leave a line of lagoons and marshes, in which seaweed and other plants flourished. As the lagoons successively dried up, the plants would be decomposed and nitric acid and iodine formed. This, united in combination with the gypsum-yielding soda found there, formed nitrate of soda. At any rate, Nature, by some mysterious process, has formed a chemical combination which has been of inestimable value to the world in general. This desert coast is not all productive of nitrate. Some sections are valueless, and some produce other chemical products. One can take a narrow-gauge train at Antofagasta and travel inland for hundreds of miles across the Andes and into the plateaus of Bolivia, and the entire distance is almost as void of green as the great Sahara Desert. Occasionally there is a scrubby tree which looks forlorn in its loneliness. There are salt plains which reach to the hills on either side. In one place there is a great salt field that is estimated to cover more than eighty thousand acres. This produces almost pure chloride of sodium in crystallized form. The thickness of the salt layer is not known, but some wells are as much as eighty feet deep and the bottom of the deposit has not been reached. It is a good quality of salt. There are borax lakes along the route, where enough borax can be secured to supply the entire world. But it is from the beds of nitrate of soda that the greatest wealth of this region is secured. To it is due the prosperity of all the ports from Pisagua to Taltal.