VOLCANOES. 



79 



level, now a mountain ; the vapours pent up 

 in dark caverns sought in vain for a crevice of 

 escape. They swelled the expanding soil un- 

 der the force of the compressed vapour, like a 

 bladder filled with air ; it swelled like the skin 

 of a two-horned goat. The upheavement re- 

 mains upon the spot ; the high, uplifted hill be- 

 came hardened in the course of time into a 

 naked rocky mass." So picturesquely, and, 

 also, as analogous appearances lead us to be- 

 lieve, so truly, does Ovid describe the grand 

 natural incident which occurred between Trae- 

 zene and Epidaurus, 282 years before the com- 

 mencement of our era, and therefore 45 years 

 before the volcanic separation of the island of 

 Thera (Santorin) from TherasiaC^""). 



Of all the islands belonging to the series of 

 linear volcanoes, Santorin is the most impor- 

 tant. " It comprises in itself the entire history 

 of upheaved islands. For full two thousand 

 years, so long as history and tradition extend. 

 Nature has not ceased from her attempts to 

 form a volcano within the circuit of the crater 

 of elevation"(^°^)- Similar insular upheave- 

 ments, at almost regularly recurring intervals 

 of 80 or 90 years, are exhibited in the island of 

 St. Michael, one of the group of the Azores("='), 

 though here the bottom of the sea has not been 

 uplifted quite at corresponding points. The 

 island named Sabrina by Captain Tillard unfor- 

 tunately appeared at a time when the political 

 state of the maritime nations of the west of 

 Europe was little favourable to scientific inves- 

 tigations (30th Jan., 1811); so that this great 

 event did not attract the same degree of atten- 

 tion as was bestowed upon the island of Fer- 

 dinandea,* which appeared on the 2d of July, 

 1831, but soon fell to pieces again, between the 

 limestone coast of Sciacca and the purely vol- 

 canic Pantellaria in the Sicilian Sea(203). 



The geographical distribution of the volca- 

 noes which have continued active since the 

 historical epoch, their frequent situation by the 

 sea-shore, and on islands, to say nothing of the 

 recurrence, from time to time, of temporary 

 eruptions from the bottom of the sea, appears 

 at an early period to have begotten the belief, 

 that volcanic activity was connected with the 

 vicinity of the sea, and could not continue with- 

 out it. "^tna and the CEolian isles," says 

 Justin(=<'*), or, rather, Trogus Pompeius, whom 

 he copies, " have already been burning for many 

 centuries ; and how were this long continuance 

 possible, did not the neighbouring sea supply 

 food for the firel" To explain the necessity 

 for the neighbourhood of the sea, the hypothe- 

 sis of the penetration of sea- water to the hearth 

 of the volcano, i. e., to the deep-lying strata of 

 the earth, has in recent times been again pro- 

 posed. If I embrace all that occurs to me, de- 

 rived either from personal observation or from 

 carefully collected facts, it seems to me that 

 everything in this difficult inquiry depends upon 

 the way in which the following questions are 

 answered : Whether the undeniably large quan- 

 tities of watery vapour, which volcanoes emit, 

 even in their state of repose, be derived from 

 sea-water loaded with salts, or from sweet at- 

 mospheric water 1 Whether, with different 



* The Graham Island of English geologists ; vide Lyell's 

 admirable Principles of Geology, vol. ii., p. 266. Sixth edit., 

 Lond., 1840.— Th. 



K 



depths of the volcanic hearth (a depth, for ex- 

 ample, of 88,000 feet, at which the expansive 

 force of the vapour of water would be exerted 

 under a pressure of 2,800 atmospheres), the ex- 

 pansive force of the vapour engendered would 

 be competent to counterbalance the hydrostatic 

 pressure of the sea, and admit the access of its 

 water to the volcanic hearth, under certain 

 conditions ](2°^) Whether the many metallic 

 chlorides, the appearance, indeed, of common 

 salt in the fissures of craters, and the admix- 

 ture of hydrochloric acid vapours with the wa- 

 tery vapour emitted, lead necessarily to the 

 conclusion, that the sea must have access to 

 the volcano ] Whether the repose of the vol- 

 cano, be this temporary only, or final and com- 

 plete, depends on the stoppage of the channels 

 which previously c'Jnducted the sea, or the me- 

 teoric water, to the volcanic hearth 1 Whether 

 the absence of flame and of hydrogen gas — for 

 sulphuretted hydrogen belongs to the solfataras 

 rather than to the active volcanoes — is not 

 rather in open contradiction with the assump- 

 tion of any extensive decomposition of water"? 

 The discussion of physical questions of such 

 importance does not fall within the scope of a 

 Picture of Nature. Here we attach ourselves to 

 the narration of phenomena ; to facts in the geo- 

 graphical distribution of yet active volcanoes. 

 Now facts inform us, that in the New World, 

 three of these — JoruUo, Popocatepetl, and La 

 Fragua — are 20, 33, and 39 geographical miles 

 distant from the sea-shores, and that in central 

 Asia (and M. Abel-Remusat(=^''^) first directed 

 the attention of geologists to the fact), there is a 

 great volcanic mountain chain, Thian-schan, or 

 ihe Celestial Mountains, with the lava-emitting 

 Pe-schan, the solfatara of Urumtsi, and the 

 burning mountain of Turfan (Ho-tscheu), the 

 several members of which are at nearly equal 

 distances — 370 to 382 geographical miles — from 

 the shores of the Icy Sea and of the Indian 

 ocean. The distance of Pe-schan from the 

 Caspian Sea is also full 340 geographical miles ; 

 and from the great lakes, Issikul and Balkasch, 

 it is 43 and 52 miles("0- It is farther remark- 

 able, that of the four great parallel mountain 

 chains — the Altai, the Thian-schan, the Kuen- 

 luen, and the Himalaya, which cross the conti- 

 nent of Asia from east to west — it is not the 

 Himalaya, or the chain that is nearest the 

 ocean, but the two minor chains, the Thian- 

 schan and the Kuen-luen, at the distance res- 

 pectively of 400 and 180 geographical miles 

 from the sea, that are found vomiting fire like 

 ^tna and Vesuvius, and producing ammonia, 

 like the volcanoes of Guatimala. The Chinese 

 writers describe, in unmistakable terms, streams 

 of lava, 10 Li long, as occurring in the eruptions 

 of flame and smoke which took place from Pe- 

 schan, and spread far and wide, in the 1st and 

 7th centuries of our era. " Burning masses of 

 rock," say they, " flowed as thin as melted fat." 

 These few compressed facts, which have not 

 been sufficiently attended to, make it probable 

 that the vicinity of the sea, and the access of 

 sea-water to the burning focus, are not indis- 

 pensably necessary to the breaking out of sub- 

 terranean fires, and that coasts are only favour- 

 able to volcanic eruptions, because they form 

 the sides or edges of the deep sea-basin, which, 

 covered with strata of water, offers less resist- 



