66 RICHTHOFEN NATURAL SYSTEM 



mersed, and such cones will occasionally emit currents of lava, and be in fact the rep- 

 etition on a small scale of the mother volcano. The usual and probably correct ex- 

 planation of their mode of occurrence is this : That, through crevices or by passage 

 through porous rocks, water gets access to glowing lava, and, by its action on the same, 

 causes the opening of a fracture, and, in immediate succession, the repetition of the 

 same phenomena which the mother-volcano presents when active. Just as these par- 

 asitic volcanoes have their roots in the glowing lava, volcanoes in general must, as is 

 demonstrated by their mode of occurrence, be considered as parasites on certain sub- 

 terranean portions of the material of massive eruptions, which still possess a high tem- 

 perature and are kept in a liquid state by the molecular combination with water which 

 finds access to them. This mode of origin of volcanoes, however, is only a repetition 

 on a small scale of the manner in which massive eruptions themselves originated, inas- 

 much as volcanoes bear a similar relation to the latter as these do to the primeval sub- 

 stance composing the interior of the globe, to which the fractures descend. These 

 main fissures, which are probably very few in number in every volcanic belt, form the 

 great arteries in this harmonious system. Their common origin will furnish an ex- 

 planation of the general similarity of the phenomena presented by different volcanic 

 belts ; while the varied and possibly very intricate mode of their ramifications towards 

 the surface, together with th'e different conditions of the rocks which they intersect, the 

 various rate and local diversity of the access of water, the different circumstances which 

 may determine the depth in which the expansive force of vapor can be brought into 

 action (among these may be the relative proportion in which chlorine, fluorine and sul- 

 phur are present), and other influences unknown, would give ample means for explain- 

 ing the diversity of all the phenomena of vulcanism within each separate volcanic belt: 

 such as the apparently intricate, and yet to a certain degree harmonious, mode of dis- 

 tribution of the rocks ejected ; the correlations existing among the latter in regard to 

 their composition ; the dependency of volcanic action on massive eruptions ; the mode 

 of distribution of hot springs, solfataras, geysers, and other phenomena which were ap- 

 parently associated with both modes of action ; the different phenomena connected with 

 the occurrence of earthquakes ; the small size of their area of disturbance when con- 

 nected with volcanic action, its varying, and sometimes very great extent in other 

 cases where no connection with any one distinct volcano can be discovered ; the singu- 

 lar correlations, finally, which have been observed to exist between different volcanic 

 vents situated on the same belt. Some hints may even be got in regard to the remoter 

 correlations which apparently exist between the phases of volcanic action on neighbor- 

 ing belts, though it must be conceded that in respect to the latter numerous facts have 

 been observed which cannot be satisfactorily explained in the way here proposed, and 

 rather appear to indicate the influence of the phases of magnetic currents on the 

 manifestations of vulcanism. 22 



w An extremely valuable contribution to the elucidation of these correlations respecting the phases of volcanic ac- 

 tivity waa lately given by Dr. Emil Kluge, in his work, Ueber den Synchronisms und Antaganismus von vulcanischen 

 Eruptionen, Leipzig, 1 863. The clear and able compilation of facts will be of lasting interest, though grave objections may 

 be raised against the author's views on the origin of volcanic action, which are not based on any inferences drawn from the 

 correlations demonstrated in the same book. 



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