414 NOTES ON THE GEOLOGY 



ically, I find in it sulphuric acid, lime, and magnesia, in about 

 the usual quantity, but neither bromine nor iodine. 



As we go northerly from this lake, we shall find, according to 

 the researches of our countrymen, Messrs. Dwight and Smith, 

 another bed of salt, a little north of Nakchevan, east of the Aras, 

 in Georgia : a second bed, a little northeast of that place,; a third, 

 west of Erivan ; and, indeed, all along the Aras, salt is abundant 

 a little beneath the surface, as far as Kars, and perhaps further. 

 If now we look southerly from Tabreez,we are met upon the maps 

 with the great salt desert in the central parts of Persia, extending 

 almost to its southern borders ; and there can be little doubt but 

 this is a continuation southward, of the saliferous deposit in the 

 north of Persia. If so, it must be nearly one thousand miles long, 

 and of great breadth. Again, it can liardly be doubted, that this 

 formation reaches the Caspian Sea, since that is salt ; and also 

 other inland lakes in Tartary ; so that probably the formation ex- 

 tends as far northeasterly from Oroomiah, as it does northerly 

 or southerly. We catch, indeed, but glimpses of the extent of 

 this formation ; but avc see enough to make it probable, there is 

 not such another salt deposit on the globe ; enough to show us 

 what an interesting task lies before some future geologist, in trac- 

 ing out the geology of these wide regions. 



I have alluded to the deposition of marble, or alabaster, by 

 certain springs in the vicinity of lake Oroomiah. What is called 

 the Tabreez marble has been repeatedly described by travellers ; 

 but I doubt whether very definite geological ideas have yet been 

 entertained respecting the mode of its formation. With the ex- 

 ception, perhaps, of a deposit of travertin around Rome in Italy, 

 resembling statuary marble, I am not aware of any case besides 

 those around Oroomiah, in which the most beautiful marble is 

 produced by springs. The Tabreez nibble, of which Nos. 220 

 and 221 are examples, is usually of a yellowish or light blue 

 color, perfectly compact, and so translucent, that it is used in thin 

 slices for the windows of baths and other places, like the phengites 

 of the ancients. It occurs not fai* from Maraga, on the east side 

 of lake Oroomiah, and about half a mile distant from it. Im- 



