132 GEOLOGY. 



the base of the Talchir group, the lowest member of the great series 

 of plaut-boaring rocka, for which the name of Gondwana series has 

 been suggested. The exact age of these beds is doubtful ; but they 

 are pre-Triassic. Dr. Oldham has observed the rock on which the 

 boulder-bed rests to be polished and grooved. It is inferred that these 

 boulders, many of wliich have come from a distance, were carried by 

 ice. W. T. 



Blanford, "VV. T. On the Physical Geography of the Deserts of Persia 

 and Central Asia. Eep. Brit. Assoc, for 1873, Sections, pp. 162, 

 163. 



The deserts of Persia consist of vast plains of Alluvium, usually 

 much longer than broad. Along the borders of the deserts are 

 remarkable slopes of coarse gravel, probably washed down from the 

 surrounding hills. It is likely that the alluvial desert-plains have 

 been formed in lakes when the rainfall was greater than now. The 

 rain which now falls is mostly evaporated or absorbed; but the 

 streams from the hills end in lakes, all but two of which are salt. 

 None of the valleys has any outlet to the sea. It is supposed that the 

 outlets were closed by the elevation of ranges of hills in the later 

 Tertiary period. W. T. 



Campbell, J. F. On Polar Glaciation, &c. Quart. Journ. Geol. Soc. 



vol. XXX. p. 450. {See post.) 

 In this paper are some remarks on subaerial denudation and on 

 glaciation in the Caucasus. 



Carpenter, Dr. "VY. B. On the Physical Geography of the Caspian 

 Sea, in its relations to Geology. Eep. Brit. Assoc, for 1873, 

 Sections, pp. 165-167. 



Gives an account of the recent report of Prof, von Baer. The 

 Caspian is from 2000 to 3000 feet deep at its southern end ; the cen- 

 tral part, on the Caucasian side, is also deep ; but the northern part 

 nowhere exceeds 50 feet in depth. The Caspian is 80 feet below the 

 level of the Black Sea. There is abundant evidence that it formerly 

 spread over a larger area than now, having been reduced to its present 

 dimensions by the excess of evaporation over supply. It would be 

 expected that the water would be salt ; but it has only one half the 

 saltness of the water of the Black Sea, and only one fourth of that 

 of the Mediterranean. Prof, von Baer has shown that this result is 

 due to the drawing off of the water into lateral bays, where it rapidly 

 evaporates. The largest bay is the Karaboghaz, which communicates 

 with the Caspian only by a channel 150 yards wide and 5 feet deep ; 

 through this a constant current of water runs from the Caspian into 

 the bay, at the rate of three miles an hour. This bay alone receives 

 350,000 tons of salt a day ; the water evaporates, and the salt remains 

 behind. The constant draining off of the salt water into these great 

 natural salt-pans, and the constant supply of fresh water by the rivers, 

 accounts for the comparative freshness of the Caspian Sea. W. T. 



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