228 COSMOS. 



vated strata. Occasionally not a trace of tliia iiiclosurc is 

 visible, and the volcano, w^liich is not always conical, rises 

 immediately from the neighboring plateau in an elongated 

 form, as in the case of Pichincha,* at the foot of which lies 

 the city of Quito. 



As the nature of rocks, or the mixture (gi'ouping) of simple 

 minerals into granite, gneiss, and mica slate, or into trachyte, 

 basalt, and dolorite, is independent of existing climates, and is 

 the same under the most varied latitudes of the earth, so also 

 we find every where in inorganic nature that the same laws of 

 configuration regulate the reciprocal superposition of the strata 

 of the earth's crust, cause them to penetrate one another in 

 the form of veins, and elevate them by the agency of elastic 

 forces. This constant recurrence of the same phenomena is 

 most strikingly manifested in volcanoes. When the mariner, 

 amid the islands of some distant archipelago, is no lonfjer guid- 

 ed by the light of the same stars with which he had been fa- 

 miliar in his native latitude, and sees himself surrounded by 

 palms and other forms of an exotic vegetation, he still can 

 trace, reflected in the individual characteristics of the land- 

 scape, the forms of Vesuvius, of the dome-shaped summits of 

 Auvergne, the craters of elevation in the Canaries and Azores, 

 or the fissures of eruption in Iceland, A glance at the satel- 

 lite of our planet will impart a wider generalization to this anal- 

 ogy of configuration. By means of the charts that have been 

 drawn in accordance with the observations made with large 

 telescopes, we may recognize in the moon, where water and aii 

 are both absent, vast craters of elevation surrounding or sup- 

 porting conical mountains, thus aflbrding incontrovertible evi- 

 dence of the effects produced by the reaction of the interior on 

 the surface, favored by the influence of a feebler force of grav- 

 itation. 



Although volcanoes are justly termed in many languages 

 "fire-emitting mountains," mountains of this kind are not 

 formed by the gradual accumulation of ejected currents of 

 lava, but their origin seems rather to be a general consequence 

 of the sudden elevation of soft masses of trachyte or labrador- 

 itic augite. The amount of the elevating force is manifested 



* [This mountain contains two funnel-shaped craters, apparently re 

 Bulling from two sets of eruptions: the western nearly circular, ?ncJ 

 having in its center a cone of eruption, from the summit and sides oi 

 which are no less than seventy vents, some in activity and others ex 

 tinct. It is probable that the larger number of the vents were ])r(j 

 duccd at periods anterior to history. Daubcney, op. cit., p. 488. '| — 7'/ 



