538 Geological Society: Anniversary Address, 1843. 
the region in which, if it be possible, passages may be traced, from 
rocks of plutonic or submarine igneous agency, to those of pure vol- 
canic and subaérial operation. To decipher order throughout a tu- 
multuous sea of rocks, bristling with extinct volcanoes, is no small 
effort ; and if M. Dubois should not have completely succeeded in 
neatly separating the porphyritic and later plutonic eruptions from 
those of true voleanic age, he has at all events offered proofs, that 
in many instances the former were covered by the most ancient ter- 
tiary accumulations (quasi uppermost-secondary ), in which vast ac- 
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 
masses 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 histery 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 scoriw 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 table 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- 
