chap, x. Saline Incmstations. 307 



of Mexico, and the Jesuit Falkner and other authors l 

 state that they occur at intervals over the vast plains 

 extending from the mouth of the Plata to Kioja and 

 Catamarca. Hence it is that during droughts, most of 

 the streams in the Pampas are saline. I nowhere met 

 with these incrustations so abundantly as near Bahia 

 Blanca : square miles of the mud-flats, which near that 

 place are raised only a few feet above the sea, just 

 enough to protect them from being overflowed, appear, 

 after dry weather, whiter than the ground after the 

 thickest hoar-frost. After rain the salts disappear, and 

 every puddle of water becomes highly saline ; as the 

 surface dries, the capillary action draws the moisture up 

 pieces of broken earth, dead sticks, and tufts of grass, 

 where the salt effloresces. The incrustation, where 

 thickest, does not exceed a quarter of an inch. M. 

 Parchappe 2 has analysed it ; and finds that the speci- 

 mens collected at the extreme head of the low plain, 

 near the R. Manuelo, consist of ninety-three per cent, 

 of sulphate of soda, and seven of common salt ; whilst 

 the specimens taken close to the coast contain only 

 sixty- three per cent, of the sulphate and thirty-seven 

 of the muriate of soda. This remarkable fact, together 

 with our knowledge that the whole of this low muddy 

 plain has been covered by the sea within the recent 

 period, must lead to the suspicion that the common 

 salt, by some unknown process, becomes in time 

 changed into the sulphate. Friable calcareous matter 

 is here abundant, and the case of the apparent double 

 decomposition of the shells and salt on S. Lorenzo, 

 should not be forgotten. 



The saline incrustations, near Bahia Blanca, are not 



1 Azara (' Travels,' vol. i. p. 55) considers that the Parana is the 

 eastern boundary of the salif erous region ; but I heard of « salitrales ' 

 in the Province of Entre Klos. 



2 M. d'Orbigny's 'Voyage,' &c. Part. Hist. torn. i. p. 664. 



