226 COSMOS. 



If the oldest formations of eruptive rock (often perfectly 

 similar to the more recent lavas in its composition), which 

 also in part occupy veins, are to be ascribed to a previous 

 fissure of the deeply shaken crust of the earth, as I have 

 long been inclined to think, both these fissures, and the less 

 simple craters of elevation subsequently produced, must be 

 regarded only as volcanic eruptive orifices, not as volcanoes 

 themselves. The principal character of these last consists 

 in a connexion of the deep-seated focus with the atmosphere, 

 which is either permanent, or at least renewed from time to 

 time. For this purpose the volcano requires a peculiar frame- 

 work ; for, as Seneca w says very appropriately, in a letter to 

 Lucilius, "ignis in ipso monte non alimentum habet, sed 

 viam." The volcanic activity exerts, therefore, a formative 

 action by elevating the soil ; and not, as was at one time uni- 

 versally and exclusively supposed, a building action by the ac- 

 cumulation of cinders, and new strata of lava, superposed one 

 upon the other. The resistance experienced in the canal of 

 eruption, by the masses in a state of igneous fluidity when 

 forced in excessive quantities towards the surface, gives rise to 

 the increase in the heaving force. A " vesicular inflation of 

 the soil " is produced, as is indicated by the regular outward 

 declination of the elevated strata. A mine-like explosion, 

 the bursting of the central and highest part of the convex 

 inflation of the soil gives origin sometimes only to what 

 Leopold von Buch has called a crater of elevation^ that is 

 nostic phantasies, alludes to these, mixing mythical matter with ob- 

 served facts, he says distinctly (in opposition to the phenomenon de- 

 scribed by Strabo) vypov rrr)\ov Trorajuot. Upon the denominations 

 TTJjXof and pua%, as volcanic emissions, I have treated on a former 

 occasion (Cosmos, vol. i, p. 236), and I shall only advert here to 

 another passage in Strabo (vi, p. 269), in which hardening lava, 

 called 71-77X6? /iifXag, is most distinctly characterised. In the description 

 of Etna we find : "The red-hot stream (pvaZ.) in the act of solidifica- 

 tion converts the surface of the earth into stone to a considerable 

 depth, so that whoever wishes to uncover it must undertake the labour 

 of quarrying. For, as in the craters, the stone is molten and then up- 

 heaved, the fluid streaming from the summit is a black excrementi- 

 tious mass (Trr/Xot.) falling down the mountain, which, afterwards har- 

 dening, becomes a millstone, and retains the same colour that it had 

 before." 



83 Cosmos, vol. i, p. 238. 



84 Leopold von Buch, On Basaltic Islands and Craters of Elevation t 

 in the Abhandl. der kvnig. Akad. der Wiss. zu Berlin, 1818 1819, s. 51; 



