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Updated: May 15, 2025
Everywhere, too, are gullies sawn in the slopes, which terminate above in deep and narrow glens, giving, especially when alternated with long lava-streams, a ridge-and- furrow look to this and most other of the Antilles. Dr.
Still more remarkable are the cases in which these lava-streams have descended into the old river channels which drained the granitic plateau. Thus the current which took its origin in the Puy Gros descended into the valley of the Dordogne, while another stream invaded the gorge of Champeix on the eastern side.
If we look at a map of the mountain showing the direction of the streams during the last three centuries, we observe that all the streams of that period flowed down on the side overlooking the Bay of Naples; on the opposite side the wall of Monte di Somma presents an unbroken front to the lava-streams.
On the 3rd and 4th November copious and splendid lava-streams coursed down the principal cone on its western side, but were soon exhausted; and in the beginning of 1872 the little cone, regaining vigour, began to discharge lava from the summit instead of the base as heretofore.
Whether the axis of the Uspallata range was injected before, or as perhaps is more probable, after that of the Portillo line, I will not pretend to decide; but it is well to remember that the highly inclined lava-streams on the eastern flank of the Portillo line, prove that its angular upheavement was not a single and sudden event; and therefore that the anticlinal elevation of the Uspallata range may have been contemporaneous with some of the later angular movements by which the gigantic Portillo range gained its present height above the adjoining plain.
These cones and craters are the most characteristic objects on the whole of the visible surface, and when highly magnified present very rugged outlines, suggestive of slag, or lava, which has consolidated on cooling, as in the case of most solidified lava-streams on our earth.
From their account we learn that the Isthmus of Auckland is one of the most remarkable volcanic districts in the world. It is characterised by a large number of extinct cinder-cones, in a greater or less perfect state of preservation, and giving origin to lava-streams which have poured down the sides of the hills on to the plains.
Its southern section, that of Mont Dore, the Cantal, and the Haute Loire, is characterised by magnificent valleys, traversing plateaux of volcanic lava, and exhibiting the results of river erosion on a grand scale; while its northern section, that of the Puy de Dôme, presents to us a varied succession of volcanic crater-cones and domes, with their extruded lava-streams, almost as fresh and unchanged in form as if they had only yesterday become extinct.
The tops of the columns are quite distinct, of the hexagonal form, like the bottom of the cells of a honeycomb, but they are not parted from each other as in the Cave of Fingal. In many parts the lava-streams may be recognized, for there the rock is rent and split in every direction, but no soil is yet found in the interstices.
We traversed the plain and mounted the foot-hills; halfway up, we observed an eruption, but we could see only the cloud, as the crater itself was hidden by hills. Through thick bush, we came to a watercourse, a narrow gully, formed by lava-streams.
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