FEUItUAItY 10, lOU] 



SCIENCE 



209 



Detroit, Mioh., in granting pormisHion to 

 work on the islands. The assistance received 

 in tiie field will be acknowledged in the several 

 papiiPS. 



The results of the expedition will be pub- 

 lished in various journals and in the annual 

 reports of the Michigan Academy of Kcienco 

 under the common title " Itesiilts of the Mer- 

 shon Expedition to the Charity Islands, Lake 

 Huron." As most of the field work was done 

 in the late summer and fall, the survey plans 

 to continue the work in the spring and early 

 summer of 1911. 



AlkXANDEH G. IlUTIiVHN 



Univeesitv or Miohioan Mubeum 



\j' 



ABTEfllAN WATERS OF ABOENTINA 



The climate of a part of Argentina is 

 semi-arid, and the geological formations 

 which are regarded as Quaternary and Later 

 Tertiary are in the western and central dis- 

 tricts of the country saline to a degree which 

 indicates prolonged duration of aridity. 

 The region of the pampas which covers 

 the province of Buenos Aires and stretches 

 northward west of the Parana does not 

 exhibit this characteristic, it having ap- 

 parently long enjoyed a more humid climate, 

 as it docs now. The foot-hills of the Andes 

 are also well watered. But with the exception 

 of these last-named regions, a great part of 

 the country suffers from lack of good water. 

 This condition may, however, be in some 

 measure relieved by proper development of 

 artesian supplies. Many wells have been sunk 

 already, but without adequate geological in- 

 vestigation. In the pampas water is found at 

 a general depth of 20 meters more or less, and 

 is pumped to the surface b.y windmills. It 

 may be said that the development of the live- 

 stock industry of Argentina would be impos- 

 sible were it not for this supply which comes 

 from eolian, alluvial deposits of Quaternary 

 and Tertiary age. A different geological con- 

 dition exists from the Rio Colorado southward 

 in what may be best described as northern 

 Patagonia. In that region there are local 

 elevations occupying a middle position be- 

 tween the Atlantic and Pacific, composed of 



granites and older rocks possibly of Paleozoic 

 age, and rising to altitudes of 300 to 1,000 

 meters. These mountains are not represented 

 upon any map and their distribution is not 

 known, but they have been described by 

 Moreno and other explorers. Upon their 

 flanks there is an extensive formation of gray 

 sandstone which attains a thickness of several 

 hundred feet and is very porous. It slopes 

 gently toward the Atlantic and pure water 

 flows from it in outcrops near the coast. The 

 head of water in these strata is unknown. 

 Further south in Patagonia the central sierra 

 is replaced by plateau country and in Como- 

 doro Rivadavia, in latitude 4f! near the coast, 

 wells which were sunk by the government in 

 search of water developed petroleum. There 

 is a large area in this region in which the 

 geologic structure and the possibilities of ar- 

 tesian water need to be developed. In the 

 great plains east of the Andes there are 

 glacial deposits which may furnish superficial 

 supplies like those of the Dakotas, and the 

 marine Tertiary and Mesozoic strata afford 

 conditions not unlike those of southern Cali- 

 fornia. Here as well as in the valleys among 

 the spurs of the Andes from Patagonia to 

 Bolivia the geological structure is compli- 

 cated and the problem of artesian water is one 

 of peculiar difficulty as well as of great in- 

 terest. 



Our present knowledge of these conditions 

 rests upon reconnaissance work and the strati- 

 graphic and paleontologic observations of the 

 Geological Survey of Argentina. No work 

 based upon topographic maps and systematic 

 structure has as yet been undertaken. The 

 problem is therefore one whose elements are 

 as yet to be developejl. The Argentine gov- 

 ernment is using every means to encourage 

 settlement and development of the rich agri- 

 cultural regions which lie in the zone of 

 sufficient rainfall east of the Andes, and also 

 the vast grazing district of Patagonia. In 

 order to afford ready communication it is 

 building railroads at great national expense 

 and operating them. The need of pure water 

 for locomotive use as well as for other pur- 

 poses has thus been made critically evident. 



