TRUE VOLCANOES. 325 



nnd evidence of this activity in tho various regions of the 

 earth, the number of recognizable volcanic platforms (open, 

 conical, and dome->liapcd mountains) upheaved upon fissures. 

 Tins enumeration has been repeatedly and often very imper- 

 fectly attempted : eruptive hills and solfataras, belonging to 

 one and the same system, have been referred to as distinct 

 volcanoes. The magnitude of the space in the interior of 

 continents which has hitherto remained closed to all scien- 

 tific investigation, has not been so great an obstacle to the 

 solidity of this work as is commonly supposed, as islands and 

 regions near the coast are generally the principal seat of 

 volcanoes. In a numerical investigation, which can not be 

 brought to a full conclusion in the present state of our knowl- 

 edge, much is already gained when we attain to a result which 

 is to be regarded as a lower limit, and when we can determ- 

 ine with great probability upon how many points the fluid 

 interior of our earth has remained in active communication 

 with the atmosphere within the historical period. Such an 

 activity usually manifests itself simultaneously in eruptions 

 from volcanic platforms (conical mountains), in the increas- 

 ing heat and inflammability of thermal springs and naphtha 

 wells, and in the increased extent of circles of commotion, 

 phenomena which all stand in intimate connection and in 

 mutual dependence.* Here again, also, Leopold von Buch 

 has the great merit of having (in the supplements to the Phys- 

 ical Description of the Canary Islands) for the first time under- 

 taken to bring the volcanic system of the whole earth, after 



tbnes de Moutagnes, 1852, t. iii. The following three sections deserve 

 the particular attention of geologists : Considerations sur les Soideve- 

 ments dus a une diminution lente et progressive du volume de la Terre, p. 

 1330 ; Stir l'Ecrasement Transversal nomvie refoulement par Saussure, 

 comme une des causes de l 'elevation des Chaines de Montagues, p. 1317, 

 1333, and 1346; Sur la Contraction que les Roches fondues tprouvent en 

 cristallisant, tendant des le commencement cm refroidissement du Globe a 

 rendre sa masse interne plus petite que la capacitc de son enveloppe ext'eri- 

 eure, p. 1235. 



* " The hot springs of Saragyn at the height of fully 5G00 feet are 

 remarkable for the part played by the carbonic acid gas which trav- 

 erses them at the period of earthquakes. At this epoch the gas, like 

 the carbonated hydrogen of the peninsula of Apscheron, increases in 

 volume, and becomes heated, before and during the earthquakes in the 

 plain of Ardebil. In the peninsula of Apscheron the temperature rises 

 36°, until spontaneous inflammation occurs at the moment when and 

 the spot where an igneous eruption takes place, which is always prog- 

 nosticated by earthquakes in the provinces of Chemakhi and Apsche- 

 ron." Abich, in the Melanges Physiques et Oumiqucs, t. ii., 1855, p. 

 364-365 (see Cosjnos, vol. v., p. 169). 



