412 NOTES ON THE GEOLOGY 



dred feet high, on the plain of Oroomiah, whose central part is 

 composed of primary rocks. No. 212 is an example of this gyp- 

 sum. It occurs, also, in the hills on the west side of the plain, 

 and is extensively used in that country as a substitute for lime- 

 stone, in forming plaster for walls. The precise process for con- 

 verting it into mortar, and its comparative durability, I have not 

 been able to learn, as the natives seem to confound this with 

 limestone. 



I suspect No. 211 to be gypsum, mixed with a few per cent, of 

 carbonate of lime. Certainly it exhibits a lively effervescence 

 with an acid, but most of it remains undissolved. It is softer 

 than common gypsum. 



In passing into the mountains west of the plain, extensive de- 

 posits of coarse conglomerate arc met with, but of their nature I 

 cannot judge without a specimen. 



Finally, the prevailing rock in those mountains is granitic 

 gneiss. No. 198 is an example, nnd has the appearance of 

 granite ; but ]\L-. Perkins says, it is in strata, which have a south- 

 easterly dip from twenty to thirty degi'ees. I doubt not, therefore, 

 that the Koordish mountains are composed of primary rocks ; and 

 if we can place dependence upon the maps of that country, these 

 mountains extend northerly nearly to Ararat ; and southerly, far 

 towards the Persian Gulf. They seem to form the great water- 

 shed between the streams that flow west^vard into the Tigi'is and 

 Euphrates, and eastward into the Caspian Sea. I doubt not that 

 along that ridge will be found very extensive deposits of crys- 

 talUne rocks. 



Some of the small islands in the lake are said to be composed 

 of quartz rock. No. 199 is from near Tabreez, and is used with 

 the incinerated seaweed. No. 226, growing on the borders of the 

 lake, for making glass. It is said to be abundant in various parts 

 of Persia. Some of the islands in the lake are composed of lime- 

 stone. Petrifactions occur on some of the islands, and though I 

 have no specimen, INIr. Perkins is confident, that some of them 

 are vegetable and others animal. 



Mr. Perkins was informed by the present Prince Governor of 

 the province of Azerbijan, whose name is Malek Kasem Meerza, 



