Ill 



cumulations of rock-salt, almost mingled with lava of subsequent 

 eruption, seem to favour this hypothesis, that the accumulation of 

 this mineral may in some instances have been connected with igneous 

 agency. 



In describing the great elevation which converted the Caucasus 

 from an island into an isthmus, and desiccated large portions of 

 the adjacent seas, leaving them in the condition of steppes, M. Du- 

 bois attaches great weight to the evidences of upheaval of the 

 massas in crateriform shapes; and in tracing the succession of the 

 tertiary strata, he shows, that, as a great depression (Colchis) for- 

 merly existed between the Caucasus and Armenia, so the beds of 

 rivers which flowed into this ancient gulf, graduate into and form 

 the lowest part of such tertiary basins. 



So attractive are his descriptions, that we can actually bring be- 

 fore our mind's eye each successive mutation ; either when great 

 and irregular elevations raised up the ancient sea-beds to different 

 levels, or when volcanoes bursting forth (some submarine, and others 

 under the atmosphere) barred up these basins, forming brackish and 

 salt lakes, many of which have since been desiccated. Seeing that he 

 first establishes all the fundamental points of his work on sound 

 observation, and identifies each formation by organic remains, a 

 geologist even may revel with M. Dubois, when, after speaking of 

 the superb garland of volcanic cones, whose summits, ranging from 

 12,000 to 17,000 feet above the sea, surround the great desiccated 

 basin of Central Armenia, he allows himself to speculate on the 

 letting off of former inland seas and lakes, by the waters of which 

 our progenitors may have been destroyed. 



Receding, however, from these views, which connect our science 

 with the history of man, I specially beg to notice the very clear order 

 of the Cretaceous system, first pointed out by M. Dubois on the 

 southern shores of the Crimea ; a tract very analogous to the re- 

 gion of the Caucasus, of which, in fact, it is a prolongation. Of 

 the trachytes, trap, pumice, lava and scorite of the southern flank of 

 the Caucasus itself, we have no traces in its miniature the Crimea ; 

 but a perfect epitome of all the succession of its northern and Cir- 

 cassian slopes, showing a Jurassic series supporting a very complete 

 Cretaceous system, which the author places in perfect parallel with 

 the beds of similar age in Europe, with which he is acquainted. 



In referring you to his taWe which marks twelve distinct 

 stages in this cretaceous system, the uppermost of which contains 

 Trigonia and Ostrea gigantea, and the lowest of which is an un- 

 doubted type of what foreign geologists call the Terrain Neocomien, 

 I would here suggest that the greater part, if not the whole, of the 

 series may be paralleled in the south of England, and. that too with- 

 out consulting other sections than those described by Dr. Fitton, 

 and the natural phagnomena which he has so faithfully represented. 

 The uppermost seven divisions of the Crimea are all evidently re- 

 ferrible to our chalk and chalk marl, and contain many of our well- 

 known fossils, the only striking difi'erence consisting in the associa- 

 tion of Nummulites diaACerithium giganteum, with the Trigonice and 



