HOT SPRINGS.— MUD VOLCANOES. 



67 



the interior of the earth, must probably be about 

 6700 feet (more than half a geographical mile). 

 If the cause of the heat of thermal springs, as 

 well as of active volcanoes, be the universally 

 diffused heat of the earth, then would mineral 

 species produce an effect only through their ca- 

 pacity for, and their power of conducting heat. 

 The hottest of all the permanent springs, those, 

 namely, from 95° to 97° C. (204° to 207-6° F.), 

 it is remarkable, are the purest, are those that 

 contain the smallest quantity of mineral matter 

 in solution. Their temperature appears on the 

 whole to be less permanent than that of springs 

 between 50° and 74° C, the invariableness of 

 which, both in regard to temperature and min- 

 eral impregnation, has been maintained so won- 

 derfully, within the confines of Europe at least, 

 during the last fifty or sixty years, i. e, since ac- 

 curate thermometrical observations and chem- 

 ical analyses were made. Boussingault found 

 that the thermal springs of las Trincheras had 

 risen in temperature in the course of twenty- 

 three years (from 1800, when my journey was 

 performed, to 1823), from 93-3° to 97° C.("*). 

 This very smoothly flowing spring is conse- 

 quently at this time 7° C. higher in tempera- 

 ture than the intermitting Geyser and Strokr, 

 the temperature of which has been lately very 

 carefully ascertained by Krug of Nidda. One 

 of the most remarkable proofs of the origin of 

 these hot springs being due to the percolation 

 of cold meteoric water into the interior of the 

 earth, and its contact there with a volcanic fo- 

 cus, was presented in the preceding century in 

 connection with the volcano of Jorullo in Mex- 

 ico, which was unknown to geography till after 

 my South American journey. When this mount- 

 ain suddenly made its appearance in September, 

 1759, rising to a height of 1580 feet above the 

 surrounding level, the two small streams, Rios 

 de Cuitimba y de San Pedro disappeared ; but 

 by and by they made their appearance again, 

 under the dreadful shocks of an earthquake, as 

 hot springs. In 1803 I found their temperature 

 65-8° C. 



The springs of Greece still flow apparently 

 in the same places as they did in the times of 

 Hellenic antiquity. The source of Erasinos, 

 two leagues south of Argos, on the declivity of 

 Chaon, is even mentioned by Herodotus. At 

 Delphi, the Cassotis, under its name of Stream, 

 of St. Nicholas, still rises to the south of the 

 Lesche, and flows under the Temple of Apollo ; 

 the Castalia, too, at the foot of the Phaedriadae, 

 and the Pirene at Acrocorinth, are there, as 

 well as the hot baths of ^Edepsum in Cubcea, 

 in which Sulla bathed at the time of the Mithri- 

 datic war(^^«). I gladly adduce these particu- 

 lars, because they forcibly remind us how, in a 

 country exposed to earthquakes so frequent and 

 so violent, the interior of our planet has been 

 able to preserve its fashion for 2000 years at 

 least ; the small, branching, and open fissures 

 that convey the water of these springs have not 

 altered. The Fontaine jaillissante of I.illers in 

 the department of the Pas de Calais, was bored 

 in the year 1126, and ever since then has the 

 water flowed uninterruptedly to the same height, 

 and in the same quantity ; the excellent geog- 

 rapher of the Caramanian coasts, Captain Beau- 

 fort, moreover, observed the same flame, fed by 

 a stream of inflammable gas, which escapes in 



the district of Phaselis, which Pliny(^") de- 

 scribes as the flame of Chimaera in Lycia. 



The observation made by Arago in 1821, that 

 the deeper Artesian wells are the warmer("^), 

 was the first means of throwing a great light 

 upon the origin of thermal springs, and led to 

 the discovery of the law of the increase of the 

 temperature of the earth according to the depth. 

 It is remarkable, and only noticed in very re- 

 cent times, that St. Patricius(i'^'), probably bish- 

 op of Pertusa, was led to a very correct view 

 of the phenomenon which presented itself in 

 the appearance of the hot springs near Carthage 

 at the end of the third century. When ques- 

 tioned as to the cause of the boiling hot water 

 which poured out from the earth, he answered : 

 " Fire is nourished in the clouds and in the in- 

 terior of the earth, as Etna, and another mount- 

 ain in the neighbourhood of Naples, inform you. 

 The subterranean waters rise as through sy- 

 phons ; and the cause of the heat of hot springs 

 is this : the waters that are more remote from 

 the subterraneous fire show themselves colder ; 

 those that flow in closer proximity to the fire, 

 warmed by it, bring an insupportable heat to 

 the surface which we inhabit." 



As earthquakes are frequently accompanied 

 by eruptions of water and watery vapour, so do 

 we perceive in the volcanoes that pour out mud 

 a transition from the alternating phenomena 

 presented by jets of vapour and thermal springs 

 to the grand and destructive activity of the 

 mountains that vomit lava. If these, as springs 

 of melted earths, produce volcanic rocks, so do 

 the thermal springs that are charged with car- 

 bonic acid and sulphurous gas [and earthy mat- 

 ters], produce by incessant precipitation either 

 horizontal beds of limestone (travertin), or they 

 form conical hillocks, as in the north of Africa 

 (Algeria), and the Baiios of Caxamarca, on the 

 western declivity of the Peruvian Andes. In 

 the travertin of Van Dieman's Land, not far 

 from Hobart Town, they are contained, accord- 

 ing to Mr. Charles Darwin, the remains of an 

 extinct flora. By lava and travertin, two spe- 

 cies of rock the production of which goes on 

 under our eyes, we here indicate the grand an- 

 titheses in geognostical relations. 



Mud volcanoes (Salsen) deserve a greater 

 share of attention than geologists have hitherto 

 bestowed upon them. The extent of the phe- 

 nomenon has been overlooked, because in the 

 two states in which it presents itself to us, the 

 one of repose is that which has been principal- 

 ly dwelt upon, and in this state of repose mud 

 volcanoes often continue for centuries. The 

 production of mud volcanoes is accompanied by 

 earthquakes, subterranean thunder, the eleva- 

 tion of a whole district of country, and the 

 eruption of flames, which rise high, but last only 

 for a short time. When the mud volcano of 

 Iskmali made its appearance in the peninsula of 

 Abscheron, eastward from Baku, on the Cas- 

 pian Sea (on the 27th of November, 1827), 

 flames burst forth, and blazed up to an extra- 

 ordinary height for a period of three hours ; for 

 the next succeeding twenty hours they scarcely 

 rose three feet above the surface of the crater 

 that discharged the mud. The column of flame 

 mounted to such a height near the village of 

 Baklichi, westward from Baku, that it was seen 



