THE ANTILLEAN VOLCANOES. 281 



a hydrostatic equilibrium and spreads out in laccolites without ever 

 reaching the surface, though normally it forces its way upward through 

 the lightest rocks (and these are those of mountains) well toward the 

 surface; and (6) that as the mass approaches the surface so closely as 

 to find relief from the subterranean pressure, its volatile constituents 

 (chiefly occluded water) flash into gas, usually with explosive violence. 

 Now if the lava column is of exceptionally viscous material, either 

 because exceptionally dry or because exceptionally acidic in composi- 

 tion, the explosively expanding steam and other gases inflate it into 

 pumice, or even blow it into dust; while if exceptionally fluent, by 

 reason either of wetness or of basic composition, the explosion is less 

 violent, the steam bubbles out as from boiling liquid, and the lava 

 flows over the crater-rim, or through some chasm rent by its own enor- 

 mous weight, in streams extending perhaps for many miles — as in 

 Kilauea in 1841, and in the New Mexican volcano near Grant shortly 

 before the Columbian discovery. Commonly it happens that the lighter 

 lavas first extruded are the more viscous, the later and heavier material 

 more fluent; so that the initial manifestation is commonly more deci- 

 dedly explosive, the action then running down to relatively quiescent 

 outflow; and their other relations depending on composition of the 

 lava, etc., too complex for ready sum m ing. 



In the light of the natural history of vulcanism, and of the mechan- 

 ism traced through the phylogeny of the volcano, the Antillean erup- 

 tions may readily be placed in the general scheme of knowledge. Both 

 Mont Pelee and La Souffriere lie in a volcanic province in which the 

 activity culminated ages ago, so that their activity may be 

 likened to the dying throes of a Vulcanean giant; and this 

 fact, while by no means to be interpreted in definite prophecy, is 

 one of some promise to future generations. Again, both volcanoes 

 approach the Krakatoan character rather than the innocent type of 

 Stromboli; this character is destructive in itself; moreover, in view 

 of the normal passage from initial explosion to final outwelling of 

 quiet lava streams, it is to be regarded as an indication either (1) that 

 the crisis of the spasm is not yet passed, or (2) that the andesitic 

 lavas thus far outcast are precursors of more completely differentiated 

 matter to be erupted during coming millenniums. In either case the 

 outlook is less roseate than the humanitarian student would wish; for 

 the fact that the region is one in which vulcanism is decadent when 

 it is measured by geologic ages is of far less immediate interest than 

 the prospect measured either in days of the single vulcanean spasm, 

 or in millenniums of the life history of particular vents. 



