• Notices of Memoirs — Short Notices of Scientific Papers. 121 



The central part of the principal chain of the Caucasus is com- 

 posed of igneous and metamorphic rocks, as granite, gneiss, felspar, 

 porphyry, diabase, nielaj)hyre, basalt, diorite, trachytic tufa, obsidian 

 and phonolite. The sedimentary rocks which cover the igneous 

 rocks and enter so largely into the composition of the Caucasian 

 mountains belong to the Jurassic and Cretaceous formations, including 

 the Lias and Oolite (both largely developed), the Greensand, Gault, 

 and White Chalk. The Tertiary strata representing the Eocene, 

 Miocene, and Pliocene deposits, all rich in fossils, are spread over 

 the plains bordering the great Caucasian chain. The older sedi- 

 mentary deposits are considerably folded, and the Eocene and Mio- 

 cene deposits exhibit some of the undulations of the subjacent rocks, 

 but the Pliocene and "Aralo-Caspian" deposits are nearly always 

 horizontal. This is extremely interesting as fixing the period of 

 elevation of the chain in the Miocene epoch. Argentiferous Galena 

 appears to be very widely distributed through the older rocks, and 

 to have been extensively worked from a very early date by the 

 Greeks, etc. 



"The Eussian Government now possess the mines, and, in the few 

 years that regular smelting works have been established, they have 

 yielded 1,600 kilogrammes of silver, and 1,600,000 kilogrammes 

 of lead. 



Coal of Jurassic age occurs on both slopes of the Caucasus, and 

 during the last ten years has been mined by the Eussians at Kuban 

 to the amount of 4,000,000 kilogrammes per annum. On the banks 

 of the Eion, the coal-beds have an aggregate thickness of 28 feet. 



Extensive Eock-salt mines of Tertiary age also occur, and most 

 ancient workings were seen by the author, in which he discovered 

 hundreds of stone implements, evidently used as mining tools, 

 formed with considerable skill out of a tough hornblendic rock. 

 Salt is not only procured abundantly from the Eock-salt mines but 

 also from the evaporation of the salt-lakes in the Caucasus. The 

 former yield about 24,000,000 kilogrammes, and the latter 16,000,000 

 kilogrammes, annually. Sulphur and alum also occur in abundance. 

 Abundant supplies of petroleum, varying in density from very fluid, 

 light-yellow oil to viscid, dark-brown mineral tar and asphaltum, 

 occm- in the Upper Tertiary strata, and, like the rock-salt mines, 

 some of the oil-wells are of unknown antiquity. 



On the eastern shore of the Caspian 20,000 wells have been sunk 

 with proportionate results. 



Captain Koschkull gives the estimated annual yield of three oil 

 regions in the Caucasus as follows : 



Kilogrammes. 



1. Peninsula of Abscheron 8.640.000 



2. Valley of the Kur 192,000 



3. YaUey of the Saundga 320,000 



Mud volcanoes now or recently in action occur in the peninsulas 

 of Abscheron and Taman. 



The craters of these volcanoes are from 200 to 1,000 feet in 

 height, and sometimes 700 feet in diameter. Thermal springs are 



