REPORT ON MINERAL AND THERMAL WATERS. 7 



Thus, 500 grains of the water of the lake Ourmia in the pro- 

 vince of Azerbijan in Persia, contains, according to Dr. Marcet, 

 111 grains of salt *, and a similar quantity from the Dead Sea 

 192*5 grains, whereas the largest quantity present in the ocean 

 does not seem to exceed 21*3 grains. 



In quality the saline ingredients found in these lakes seem to 

 differ very little from those of sea- water, but Lake Ourmia con- 

 tained a larger proportion of sulphates, whilst the Dead Sea is 

 f jund to be entirely destitute of them. 



Prof. Henry Rose has lately examined the water of Lake Elton 

 in Asiatic Russia, and has found it to possess a specific gravity 

 of 1*27288, and to contain neai'ly 30 per cent, of saline matter, 

 which approaches nearly to the quantity present in the Lake 

 Ourmia. 



In this, muriate of magnesia was the prevailing ingrediejit, a 

 circumstance doubtless attributable to the extreme concentration 

 of the solution, which is such as to have brought about a pre- 

 cipitation of the greater part of the less soluble ingredients. 

 Hence rock salt is formed in thick beds, at the bottom and on the 

 sides of this and of several other lakes adjoining the Caspian. 

 The sea or estuary of Ohhotsk, with which are connected the 

 brine springs of Irhoutzk, in Asiatic Russia, contains an in- 

 gredient not found in the cases before alluded to, namely, mu- 

 riate of alumina, with which is associated a large quantity of 

 other deliquescent earthy muriates, ingredients which render 

 the salt obtained from them unwholesome f. 



With respect to the borax lakes of Thibet, we possess no in- 

 formation capable of throwing light on the cause of their pecu- 

 liar mineral impregnation. 



Proceeding next to the subject of mineral waters properly so , ., ,,r 

 called, I shall notice the circumstances relating, 1st, to their teiof" 

 temperature ; 2ndly, to their chemical constitution ; and 3rdly, Springs. 

 to their effects upon the animal economy. 



With respect to the first point, much confusion has arisen in Their Ten»« 

 the application of the term "thermal" to springs. By some, perature. 

 that epithet has been applied to those only, which exceed con- 

 siderably the average temperature of the springs of the country; 

 by others, to such as reach some arbitrary point in the scale. 

 It appears to me however, that the only precise mode of pro- 

 ceeding will be, to call every spring thermal which surpasses 

 ever so little the average temperature of the country in which it 

 is situated ; and in constructing a scale of temperatures with re- 

 gard to them, to calculate it, not by their actual warmth, but by 

 the degree of their excess above the mean of the climate. Thus, 



* Philosnxihkal Transactions, 1819. t -^nnales de Chhnic, vol.xli. 



