SALSES. 199 



tions accompanied by flames to the subsequent condition of 

 simple eruptions of mud, form, as it were, an intermediate 

 step between hot springs and true volcanoes, which throw 

 out fused earths, either in the form of disconnected cinders 

 or as newly-formed rocks, often arranged in many beds one 

 over the other. Like all transitions and intermediate steps, 

 both in organic and inorganic nature, the salses and mud 

 volcanoes deserve a more careful consideration than was be- 

 stowed upon them by the older geognosists, from the want 

 of special knowledge of the facts. 



The salses and naphtha springs are sometimes arranged in 

 isolated close gi-oups — like the ]VI^calubi, near Girgenti, in 

 Sicily, which were mentioned even by Solinus; those near 

 Pietra Mala, Barigazzo, and on the Monte Zibio, not far 

 from Sassuolo, in the north of Italy ; or those near Turbaco, 

 in South America ; . sometimes they appear to be arranged 

 in narrow chains, and these are the most instructive and im- 

 portant. We have long known* as the outermost members 



* Humboldt, Asie Centrale, t: ii., p. 58. Upon the reasons which 

 render it probable that the Caucasus, which for five-sevenths of its 

 length, between the Kasbegk and Elburuz, runs from E.S.E. to 

 W.N.W. in the mean parallel of 42° 50', is the continuation of the 

 volcanic fissure of the Asferah (Aktagh) and Thian-schan, see the work 

 cited above, p. 54-Gl. Both the Asferah and Thian-schan oscillate 

 between the parallels of 40|° and 43°. I regard the great Aralo- 

 Caspian depression, the surface of which, according to the accurate 

 measurements of Struve, exceeds the area of the whole of France by 

 nearly 107,520 geographical square miles (Op. cit, supra, p. 309-312), 

 as more ancient than the elevations of the Altai and Thian-schan. 

 The fissure of elevation of the last-mentioned mountain chain has not 

 been continued through the great depression. It is only to the west 

 of the Caspian Sea that we again meet with it, with some alteration 

 in its direction, as the chain of the Caucasus, but associated with tra- 

 chytic and volcanic phenomena. This geognostic connection has also 

 been recognized by Abich, and confirmed by valuable observations. 

 In a treatise on the connection of the Thian-schan with the Caucasus 

 by this great geognosist, which is in my possession, he says express- 

 ly : "The frequency and decided predominance of a system of paral- 

 lel dislocations and lines of elevation (nearly from east to west) dis- 

 tributed over the whole district (between the Black Sea and the Cas- 

 pian) brings the mean axial direction of the great latitudinal central 

 Asiatic mass elevations most distinctly westward from the Kosyurt 

 and Bolar systems to the Caucasian Isthmus. The mean direction 

 of the Caucasus, S.E. — N.W., is E.S.E. — W.N.W. in the central parts 

 of the mountain chain, and sometimes even exactly E. — W., as in 

 the Thian-schan. The lines of elevation which unite Ararat with the 

 trachytic mountains Dzerlydagh and Kargabassar near Erzeroum, and 

 in the southern parallels of which Mount Argaeus, Sepandagh, and 

 Sabalan are arranged, constitute the most decided expression of a 



