﻿Thos. Belt— The meppea of S. Eussia. 369 



at explosive foci," which he did not think could be carried back 

 much beyond the Tertiary epoch, the author discussed the ordinary 

 method of formation of a volcanic cone, and pointed out that the 

 effect of the piling up of material must produce a pressure on the 

 original surface commensurate with the amount of material heaped 

 up on it, and therefore increasing gradually from the circumference 

 nearly to the centre of the cone, where the loftiest column of material 

 p-resses upon the unit of sjoace. When the supporting rock is un- 

 yielding, such as the granite which bears the Puys of Auvergne, it 

 will probably maintain its original position ; but when it is of a 

 more yielding nature, as in the case of the ordinary stratified rocks, 

 the pressure of the cone will produce a saucer-shaped depression, 

 deepest in the centre where the greatest pressure occurs ; and this 

 tendency to sink will be aided materially by the honeycombing and 

 evisceration of the subjacent rock-masses exposed to the action of the 

 volcano. The consequence of this depression of the surface support- 

 ing the cone will be to diminish the original slope of the successive 

 superimposed deposits, and even in some cases cause the lowest beds 

 to slope from the circumference towards the centre. If the strata 

 upon which the volcano stands be particularly plastic, its pressure 

 may cause an uprise of the strata into protuberances round the foot 

 of the mountain. Similar phenomena may occur when the support 

 of the cone is formed by older volcanic deposits. 



2. " The Steppes of Southern Russia." By Thomas Belt, Esq., 

 F.G.S. 



The author describes sections of strata in the south of Eussia, and 

 traces the following succession of events : 



1. Deposition of marine Miocene beds when the Yienna basin and 

 the Aralo-Gaspian area were joined together, and had free commu- 

 nication with the Mediterranean. 



2. Interruption of the communication with the Mediterranean, and 

 deposition of the Sarmatic beds in a closed sea-basin. 



3. Gradual freshening of the water of this area and deposition of 

 the Congerian strata. 



4. Lowering of the water of the Vienna basin and Aralo-Caspian 

 area to below the present level of the ocean, and great denudation 

 of the preceding strata. The author thinks that the drainage was at 

 this time to the north. 



5. Interruption of drainage to the north and deposition of fluviatile 

 beds, with freshwater shells of existing species and remains of the 

 Mammoth and Irish Elk. 



6. Drainage to the north completelj'^ stopped and formation of a 

 great lake, over which floated icebergs with northern drift. Forma- 

 tion of diluvial clay of the south and boulder-clays of the north of 

 Eussia. 



7. Lake gradually lowered by the cutting through of the channel 

 of the Bosphorus. 



The author considers that the formation of the great lake was due 

 to the ice of the glacial period flowing down the beds of the Atlantic 

 and Pacific, and damming back the drainage of the continents as 



DECADE II. VOL. IV. — NO. VIII. - 24 



