110 



formerly supposed to be of primary age, are nothing more than beds 

 of Lias and other strata of the Jurassic age, often so highly altered 

 as to resemble ancient sla.ty rocks, and occasionally pierced by points 

 of granite and greenstone. These grand and strangely changed strata 

 of the Oolitic series are flanked by huge buttresses of the Cretaceous 

 system, some members of which take the form of fucoid schists 

 and greensand, whilst others are pure white chalk. Often, indeed, 

 assuming ancient lithological aspects, and broken into striking de- 

 files, covered by beauteous forests, the far-famed Circassia, from one 

 end to the other, is simply the representative, on a grand scale, of our 

 English North and South Downs, with their fringes of greensands*. 

 The explanation of the violent disturbances to which these cretaceous 

 rocks have been subjected^ is seen in numerous points of porphyry 

 and other igneous rocks ; by which agents, the strata, altered and 

 thrown into highly inclined positions, have been raised to heights of 

 10,000 feet above the sea. On each side of the flanks of these 

 gigantic mountains, essentially if not entirely composed of the 

 younger secondary rocks, are tertiary basins. To the north 

 they range into the desiccated Caspians, which form the southern 

 steppes of Russia ; and to the south they lie inclosed among 

 numerous ridges of plutonic and igneous rocks. Volcanic agency, 

 of the same extinct nature as that with which we are acquainted 

 in Central France, and with which English geologists are now 

 familiar in Asia Minor, from the descriptions of our asso^ 

 ciates "Hamilton and Strickland, abounds indeed throughout many 

 parts of this region. Of the different phases of eruption, the por- 

 phyry cone, the crater and the coulee are the evidences ; whilst 

 the continued existence of the latent and repressed fires of an- 

 tiquity is traceable in the naphtha springs of the adjacent lower 

 countries, which are still in action, upon lines running from north- 

 west to south-east, or parallel to the grand line of eruption on which 

 the Caucasus has been upheaved. M. Dubois distinctly marks the 

 great period of elevation of these tracts, when the ridges on the south 

 of the chain began to be the centres of many distinct volcanic vents ; 

 and when, by the higher and lesser elevations of districts formerly 

 submarine, the various "amphitheatres" in Georgia and Armenia 

 were formed, all of which he has personally visited. This is truly 

 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 subaerial opei'ation. To decipher order throughout a tu- 

 multuous sea of rocks, bristling with extinct volcanoes, is no small 

 eff'ort ; and if M. Dubois should not have completely succeeded in 

 neatly separating the porphyritic and later plutonic eruptions from 

 those of true volcanic age, he has at all events offered proofs, that 

 in many instances the foi'mer were covered by the most ancient ter- 

 tiary accuinulations {quasi uppermost-secondary), in which vast ac- 



;; * The botanist will find a striking analogy between the vegetation of the 

 western flanks of the Caucasus and the North Downs (Box Hill) in their 

 respective groves of Buxus. 



