48 RIO NEGRO, [CHAP. 



those salts answer best for preserving cheese which contain most of 

 the deliquescent chlorides. 



The border of the lake is formed of mud ; and in this numerous 

 large crystals of gypsum, some of which are three inches long, lie em- 

 bedded ; whilst on the surface others of sulphate of soda lie scattered 

 about. The Gauchos call the former the " Padre del sal," and the latter 

 the " Madre ; " they state that these progenitive salts always occur on 

 the borders of the Salinas when the water begins to evaporate. The 

 mud is black, and has a fetid odour. I could not at first imagine the 

 cause of this ; but I afterwards perceived that the froth which the wind 

 drifted on shore was coloured green, as if by confervas : I attempted to 

 carry home some of this green matter, but from an accident failed. 

 Parts of the lake seen from a short distance appeared of a reddish 

 colour, and this perhaps was owing to some infusorial animalcula. 

 The mud in many places was thrown up by numbers of some kind of 

 worm, or annelidous animal. How surprising it is that any creatures 

 should be able to exist in brine, and that they should be crawling 

 among crystals of sulphate of soda and lime ! And what becomes of 

 w.ese worms when, during the long summer, the surface is hardened 

 into a solid layer of salt ? Flamingoes in considerable numbers inhabit 

 this lake, and breed here; throughout Patagonia, in Northern Chile, 

 and at the Galapagos Islands, I met with these birds wherever there 

 were lakes of brine. I saw them here wading about in search of food 

 probably for the worms which burrow in the mud ; and these latter 

 probably feed on infusoria or confervae. Thus we have a little living 

 world within itself, adapted to these inland lakes of brine. A minute 

 crustaceous animal (Cancer salinus) is said* to live in countless 

 numbers in the brine-pans at Lymington ; but only in those in which 

 the, fluid has attained, from evaporation, considerable strength namely, 

 about a quarter of a pound of salt to a pint of water. Well may we 

 affirm that every part of the world is habitable ! Whether lakes of 

 brine, or those subterranean ones hidden beneath volcanic mountains 

 warm mineral springs the wide expanse and depths of the ocean the 

 upper regions of the atmosphere, and even the surface of perpetual 

 enow all support organic beings, 



To the northward of the Rio Negro, between it and the inhabited 



* Liwiean Trans., vol. xi., p. 205. It is remarkable how all the circum- 

 stances connected with the salt-lakes in Siberia and Patagonia are similar. 

 Siberia, like Patagonia, appears to have been recently elevated above the 

 waters of the sea. In both countries the salt-lakes occupy shallow depres- 

 sions in the plains; in both the mud on the borders is black and fetid; 

 beneath the crust of common salt, sulphate of soda or of magnesia occurs, 

 imperfectly crystallized ; and in both, the muddy sand is mixed with lentils of 

 gypsum. The Siberian salt-lakes are inhabited by small crustaceous ani- 

 mals ; and flamingoes (Edt'n. New Philos. Jour., Jan. 1830) likewise frequent 

 them. As these circumstances, apparently so trifling, occur in two distant 

 Continents, we may feel sure that they are the necessary results of common 

 causes. See Pallas's "Travels," 1793 to 1794, pp. 129-134, 



