The deposits of this mineral are unique in geology. There is none other of the same nature on the globe. The mineral lies in horizontal beds a few feet beneath the surface. We may be riding over the flat, absolutely barren _pampa_, or plain, floored with nothing but fragments of clinkstone, eroded by the ever-drifting sand and unrestful wind, gleaming in the metallic sunlight, for no shower of rain ever visits this wilderness, a place where we might think Nature has nothing to offer of use or profit. But we should be mistaken. An excavation will reveal the sheet of white salts beneath, deposited in geological ages past by marine or lake action, under conditions not clearly understood--deposits which cover many miles of territory. The material is blasted out in open mining and conveyed to the oficinas--large establishments of elaborate machinery and appliances--where it is boiled, refined, re-crystallized and thence shipped for export. Still farther afield through the deserts here are vast areas of salt, the ground presenting the appearance of a suddenly arrested, billowy sea, over which the horseman makes his way like a lost spirit in Hades. Upon the horizon are the steely Andes, upon whose plateaux here, reached by the highest railway in the world, we find rich copper mines, such as those of Colhuahuassi, and various deposits of the salts of copper. But to return to the coast. It was upon this melancholy seaboard, the coast of Tarapacá, that a sea-fight, classic in the annals of South America, and indeed one of the very earliest of battles between ironclad ships, took place--an engagement which has rendered the names of Pratt and Grau, the Chilean and the Peruvian admirals, immortal in the memory of their respective countrymen. Peru and Chile were engaged in life and death struggle with each other on land and sea. Iquique, then a Peruvian port, was blockaded by Chile. Grau, having sailed from Callao for Arica with the _Huascar_ and _Independencia_, which vessels practically constituted the Peruvian Navy, heard of the blockade, and proceeded to Iquique to engage the enemy. The day was breaking as the Peruvian vessels arrived off the port. The approach was seen by the _Esmeralda_ and the _Covadonga_, two Chilean ships, and Captain Pratt, on board the _Esmeralda_, decided to give battle, notwithstanding that the Peruvian vessels were ironclads, whilst his own commands were unarmoured. It was a brave resolution, but the Chileans were born sea-fighters. The _Huascar_ was a turret-ship, built at Birkenhead in 1866, but of only 1,130 tons, armed with Whitworth and Armstrong guns, but with armour-plating incapable of resisting any heavy cannonade. The _Independencia_ was an older type ironclad, of 2,000 tons, built in London in 1865.