NA TURE 



\yime 20, 1889 



Passing from these generalities, we will now examine in more 

 ■detail the structure and climate of the Tamarugal Pampa, 

 between Iquique and Pisagua, in which most English people are 

 interested. Fig. 2 is a diagrammatic section from the sea across 

 the Cordillera, through the nitrate beds of Tarapaca. To the left 

 we see the barren coast range rising from the sea and falling 

 again to the level of the Tamarugal Pampa, The nitrate beds 

 are marked in their proper place at the first spring of the hill ; 

 then comes the level Pampa, sloping gently not only from the 

 Cordillera, but also slightly in a south-west direction. This 

 slope is of course enormously exaggerated in the diagram. 



Next the counterforts of the Sierra of Huatacondo rise abruptly 

 above the plain. Here and there the barren slopes of these 

 mountains are intersected by narrow valleys or quebradas, 

 each of which carries down a small stream of water that is 

 eventually lost in the sand of the Pampa. Artificial irrigation 

 at the side of each affords sustenance for a very scanty population, 

 and only one village is of sufficient importance to form anything 

 approaching to a small town. This is the town of Tarapaca, in a 

 valley of the same name, which gives its name to the province 

 in which Iquique and the nitrate beds are situated. 



A high cold upland, or Puna, some 20 miles across, separates 

 the crests of the outer Sierra of Huatacondo from the rather 

 higher range of the Cordillera Silillica, and then the mountains 

 slope steeply down to the plateau of Bolivia, some 12,000 feet 

 above the sea. None of the crests of the outer Sierra retain any 

 snow on their summits during the summer months, but a few of 

 ithe crests of the inner Cordillera are white throughout the year. 



Allusion has been already made to the Tamarugal bushes 

 which are found in places on the Pampa. These owe their 

 existence to the floods, or avcnidas as they are called locally, 

 which every few years rush down from the Sierra, and run over 

 the plain almost to the edge of the nitrate grounds. The soil of 

 the Pampa is just what might have been expected under such 

 circumstances, for the surface is not sharp sand, but really dry 

 earth with a certain proportion of sandy particles, and only 

 irrigation is required to turn the desert Pampa into a fertile plain. 

 Below ground, numerous sections which have been made in sinking 

 wells, show alternating layers of gravel, sand, mud, and as each 

 series of layers represents the sequence of a single flood, it 

 follows that the Pampa has been subject to periodical inundations 

 for a very long period. 



The laboui-s ot Signor Don Guillermo Billinghurst have made 

 us acquainted both with the regime of underground waters 

 on the Pampa, and with their chemical constitution. From his 

 researches it appears that water is found almost anywhere under 

 the Pampa, at depths varying from about 50 to 150 feet, but that 

 nowhere are the conditions necessary for artesian wells fulfilled. 

 The well water from the centre of the Pampa contains too great 

 a proportion of salts to be considered drinkable ; and that from 

 the western margin of the plain, but not in the nitrate beds, 

 belongs to the calcareo-magnesian class, which is totally unfit for 

 domestic or culinary purposes. The following examples will 

 make this very clear, and also the remarkable fact that the 

 underground waters of the Pampa do not contain the slightest trace 

 cither of nitrate of soda, or of iodine, though they contain a 



? 



10 



2,0 



4.0 



6.0 



^O 



100 



10 Mies. 



Sea 



Pampa 

 Nitrate 

 Beds 



Feet. 



- 20.000 



- 15.000 



- 10.000 



- 5.000 



CordilLeT 



Sink of 

 Titicaca 



Fig. 2. — Section across the Cordilltra, through the nitrate beds of Tarapr.ca. 



greater proportion of mineral salts the further westward they 

 Tun. 



The two subjoined analyses are those (i) of well water from 

 ■Cerro Gordo, situated 7 miles from the nitrate beds, on the open 

 plain of the Tamarugal Pampa ; and (2) of the Pozo de Almonte, 

 quite close to the nitrate beds, and from which a large proportion 

 •of the water used by the Nitrate Railway Company is derived — 



Carbonate of lime ... . 



,, magnesia 

 Sulphate of lime 



,, magnesia... 



,, potash ... , 



,, soda 



Chloride of sodium 



,, magnesium 

 Oxide of iron and alumina , 

 Silica, and insolubles ... 



I '05569 



•II36 



In connection with underground waters we may as well 

 dispel for ever the fiction so commonly believed that some of the 

 overflow from Lake Titicaca filters under the Cordillera and 

 reappears on the Tamarugal Pampa. This idea was started in 

 a pre-scientific age, more than 300 years ago, in 1550, by the 

 celebrated historian Cieza de Leon ( " La Cronica del Peru," 

 p. 445) ; but unfortunately for such a supposition the facts of the 

 case are as follows. The only outlet of Lake Titicaca is the 

 River Disaguadero (Span, drain), and the ^^ater at starting con- 

 tains about I gramme of salts in every litre. By the time the 

 river has reached the shallow lake ofPoopo or Aullagas(seemap, 

 Fig. i), the water is so salt as to be undrinkable, and then the river 

 runs out for a short distance till it is finally lost in the sail mud 

 marsh, or Cienaga de Coipasa. No doubt this marsh is due east 

 of the Pampa near Pisagua, and is marked " Sink of Titicaca" 

 in Fig. I ; but still it is impossible to believe that salt water can 

 come out fresh on the other side of the Cordillera. The water of 

 the Tamarugal Pampa must be derived from the rainfall on the 

 slopes of the Sierra, immediately above the plain. 



Ralph ABERCROMr.Y. 



(7(3 be contimicd.) 



