1832.] Progress of Geological Science. 525 



From the geographical and geological chapters of this interesting report, we learn, 

 that the low hills, which rise above the Steppes of the Black Sea and Sea of Azof, 

 are composed of limestone, filled with littoral shells, the collections of which made 

 by M, Pander, on this and a former occasion, must prove of great geological im- 

 portance. On ascending from the Steppes towards the Caucasus, grits and older 

 limestones, with ammonites, occupy an undulating country, diversified by several 

 peaks of trachyte, the principal of which, the Bechtan, or five mountains, is stated 

 to be 4000 feet above the sea. The outer zone of the Caucasus is descrihed as be- 

 ing a rugged and lofty plateau from 8000 to 9000 feet above the sea, the strata of 

 which present tabular summits, chiefly composed of calcareous grit and conglome- 

 rates nearly horizontal, or rising at only a gentle angle towards the central ridge. 

 This table-land is figured by deep transverse rents, in which the rivers flow ; and 

 one of the lowest formations is a limestone, which the author compares with the 

 calcuire a gryphites. These secondary strata are separated from the central moun- 

 tains by a band of transition and old slaty rocks, which have been dislocated by 

 the contact of certain green stones and basalts. The loftiest part of the central 

 chain, culminating in the double peak of Mount Elborz, at the height of 15,400 

 French feet above the Black Sea, is entirely of igneous origin, being principally 

 composed of a dark-coloured porpbyritic trachyte. The volcanic rocks of this re- 

 gion are shown to be of considerable antiquity, because the secondary deposits rest 

 upon them in undisturbed positions, the transition formations having alone been 

 dislocated*. 



It did not come within our purpose to particularize any practical geological re- 

 searches, but we have digressed in this case, because the ground trodden is closely 

 connected with our own Asiatic field, and it may act as an useful stimulus to point 

 out what our neighbours are about. The Court of Directors have appointed to 

 Madras an eminent geologist, Dr. Turnbull Christief, of whose researches in Sicily, 

 the President of the Geological Society speaks in high terms ; to him, we look 

 with great expectation, when he enters the vast field, hitherto but partially 

 visited by Voysey and Dangerfield. 



But to continue our review of Theoretical Geology : — the phenomena of ther- 

 mal springs have been attributed by Dr. Daubeny to volcanic agency, whether 

 they issue from the neighbourhood of action and extinct foci of eruption, or upon 

 linear fissures and dislocations of the ancient strata, produced by expansive forces 

 during former periods of elevation ; in fact, the evolution of gases and increased 

 temperature of springs may be looked upon as proofs of the presence of volcanic 

 action still in force, with as much propriety as eruptions of lava and shocks of 

 earthquakes. Having detected the presence of nitrogen gas in thermal waters, 

 he concludes, that the chemical theory of the origin of volcanoes is still to be 

 maintained, as being more philosophical, and more consistent with facts and ex- 

 periments, than the hypothesis of a central ignited fluid, which has been from 

 time to time mechanically forced up to the surface of the earth. 



The question of the increase of the temperature of the ground, in descending to 

 great depths, still rests upon uncertain data. As far as experiments upon mines 

 and artesian springs have been carried (by M. Cordier in particular), the results 



* Murchison's Address, Phil. Mag. lxv. 385. 



7 Since the above was written the death of this meritorious and able officer has been 

 announced ! He was on his way to the Nilgiri Hills, which he proposed to explore with 

 care, where he was attacked by jungle fever to which he fell a victim in a few days. 



