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 time being. In the Quebrada de Mani, for example, the pro- prietors emigrate in dry years to return after a flood has re- stored the amazing fertility of the valley. According to the magnitude of the flood is the length of time for which their cultivation can be continued. Attempts to increase cultiva- tion have been made, but they have met with little success. Experiments conducted in the Pampa del Tamarugal have an interest scientific rather than economic. [In the Pampa del Tamarugal there are places where the ground water is abun- dant and comparatively free from salts. In such spots wells have been sunk and small patches irrigated. Tirana is an ex- ample noted by Bollaert. Its unusual advantages gave it an early importance. It has served as a midway station between the oficinas and the oasis of Pica for Bolivian emigrants seek- ing employment in the salitreras. In 1850 another agricultural experiment was tried; the idea, it is said, being derived from the growth of corn from grain accidentally spilled by a mule- teer in a hollow of the pampa. A depression is made in the ground so that the surface is brought within a foot or two of the ground-water level. This chacra sin riego is similar to the hoyas of the coast valleys of Peru described by Garcilasso de la Vega.

The future of the piedmont and mountain valley towns is safely predictable. The small area of irrigable land, even with the maximum conservation of water supply, means definitely restricted groups of population widely separated from each other and as stagnant and self-dependent as isolated. Their limited development and the wide unproductive spaces to be overcome will always mean the absence of any improved means of communication, and no assistance can be expected in this direction. Railroads will never connect these towns except as they lie by chance upon the line of some future route