82 Mr Rose on the Composition of 



author of this article, who accompanied M. de Humboldt in his 

 journey, found crystals of gypsum in great quantities on the 

 shores of the lake ; and moreover, the whole of the specimens of 

 crystalline salts which he procured, contained, on analysis, small 

 quantities of lime, or a minute quantity of undissolved gypsum. 

 But the absence of gypsum in this water, proves, without doubt, 

 that it is insoluble in concentrated solutions of certain salts. 



The water of lake Elton, then, is nothing more than a 

 very concentrated brine, in which enormous masses of common 

 salt have been deposited during a long space of time, and in 

 which it still continues to be deposited during the summer 

 months, because the water which enters it is not sufficient 

 to replace that which it loses by evaporation. For little as 

 the temperature of the water of this lake falls, great quan- 

 tities of the crystals of sulphate of magnesia are found in 

 it. Moreover, both its composition and its specific gravity must 

 undergo great variations with the temperature. Accordingly, 

 the banks of the lake in summer present only crystals of gypsum 

 and of common salt ; but in winter there are besides many crys- 

 tals of sulphate of magnesia which are again dissolved in sum- 

 mer, so that pure common salt may be procured from the lake. 

 The composition of this water is precisely what we should 

 obtain by evaporating a very large quantity of common sea 

 water at a very moderate temperature, so long as it deposited 

 common salt. 



The water of the other salt lakes, to the north-east and east 

 of the Caspian, is somewhat similar to that of lake Elton, but 

 has not exactly the same composition. That of lake Bogda 

 is, according to Mr Erdman, altogether more like sea water. 

 But of all the salt waters which have been analyzed, that of 

 lake Elton most resembles the water of the Dead Sea. This 

 latter has an inferior specific gravity, and also contains a smaller 

 proportion of solid matter. According to the analysis of Gay- 

 Lussac, undoubtedly of all others the most accurate, its specific 

 gravity is 1.2283, at 63° Fahr. ; and it contains 26.24 per cent of 

 solid matter, which consists of metallic chlorides, viz., those of so- 

 dium, calcium, magnesium, and potassium, with some traces of 

 gypsum. The absence of the sulphate of magnesia, and the 

 presence of chloride of calcium, distinguish it from the water of 

 lake Elton. 



