203 



Geological Sociehj : 



[July 



Thermal Springs and Mineral Waters.— ki Kair (lat. 19^ 55' , long. 

 7^'^ 5G') and Urjiinah, springs having a temperature of 87°, and charged 

 with carbonic acid gas, issue through tlie limestone j and one, at the 

 former localiiy, contains also a little muriate of soda, a minute quantity 

 of sulphate of lime, and much carbonate of lime. At Byorah (lat. 17°. 

 57', long. SQo 20') is a spring, tlie temperature of which is llOo ; and 

 at Badrachelhim (lat. 17° 43', lorg. 80^ 79'), orfe possessing a tempera' 

 ture of I40o, and containing sulphuretted hydrogen, and sulphates and 

 muriates of soda and lime. 



A minuie description is given of the mineral waters of the Lonar 

 Lake, (lat. 20'^>, long, 76*^ 30') and of the natron which is deposited in 

 a layer bt'nealh its muddy bottom. The water of the lake is clear, its 

 spf'cific gravity is 1027-65, and it has no unpleasant smell ; but the 

 mud at its bottom is hiyhly charged wilh sulphuretted hydrogen. The 

 salt under I lie mud accumulates slowly, and is extracted only once in 

 several years. It consists of carbonic acid 38*, soda 40-9, water 20-6, 

 insoluble matter .5, and a trace of a sulphate ; and thus corresponds in 

 cotin)osition uiih the Trona, or striated soda from the Lakes of Fez- 

 zan, anal\zt (i hy Mr, R. Philips*, and approaches somewhat nearer to 

 the equivalent numbers of the sesquicarbonate established by that ana-, 

 lysis. The water of the Lonar lake contains, besides a little potash, 

 muriate of soda 23 irrains, sesquicarbonate of soda 4'2 nearly, and sul- 

 phate of soda i, in 1,000 grains of water. No lime was detected in it, 

 nor any ma<inesia. The absence of the former Mr- Malcolmson says, 

 is easily accounted for, as the sesquicarbonate of soda and the water it- 

 self precipitated the sulphate and muriate of lime, notwithstanding the 

 muMial decom[)osition they undergo when in a semifluid state. In ac- 

 counting for the pu-oduction of the natron, he adopts the theory of Ber- 

 ^hollet for the formation of tliat salt in the lakes of Egypt, viz., a 

 mutual decomposition of the muriate of soda and carbonate of lime, 

 when in a pasty slate ; but as the natron of Fezzan and the Lonar lake 

 contains h^Jf an equivalent more of carbonic acid than can be furnish- 

 ed l)y carbonate of lime, he i)roposes a modification of that theory, and 

 sui^uests that tlie carbonic acid by which the lime is held in solution in 

 the mud, furnishes the acid, and perhaps indicates the existence of an 

 unstable sesquicarbonate of that substance. "Wherever," adds the 

 author, " 1 have met with natron, or obtained detailed accounts of its 

 occurrence, muriate of soda and carbonate of lime existed in the soil, 



* Journal of the Roj-al Institution, vol. vii. p. 294. 



