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Above us, higher and higher, towered the crater-walls, while we journeyed on across innumerable lava-flows, turning and twisting a devious way among the adamantine billows of a petrified sea. Saw-toothed waves of lava vexed the surface of this weird ocean, while on either hand arose jagged crests and spiracles of fantastic shape.
As in the case of the Antrim district, the Island of Mull and adjoining tracts present us with the spectacle of a vast accumulation of basaltic lava-flows, piled layer upon layer, with intervening beds of bole and tuff, up to a thickness, according to Geikie, of about 3,500 feet.
Contrasted with the shining shores of Hilo, they are as dust and ashes; long reaches of black lava and miles of clinkers marking the courses of lava-flows, whose black desolation and deformity nature, as yet, has done almost nothing to clothe.
A similar group of extinct craters with lava-flows has been described and figured by a recent traveller, Mr. C. M. Doughty, in parts of Central Arabia.
And near the northern extremity of the isle, a third group of mammelated heights could be recognised under the general name of Perboewatan, from which issued several obsidian lava-flows, with a steep slope; these dated back perhaps to the period of the first known eruption of 1680.
They certainly put me on a track which could not be mistaken, for it was a narrow, straight path, cut and hammered through a broad horrible a-a stream, whose jagged spikes were the height of the horse. But beyond this lie ten miles of pahoehoe, the lava-flows of ages, with only now and then the vestige of a trail.
As Vulcan was everywhere rampant during this age, throwing out enough lava in India alone to put a lava blanket four or five feet thick over the whole surface of the globe, it was probably this fire that charred the wood. It would be interesting to know if these enormous lava-flows always followed the subsidence of some part of the earth's crust.
Professor Haughton, of Dublin University, and the author, from specimens collected by Professor Guiscardi from the lava-flows extending from 1631 to 1868, in every one of which leucite occurs, generally as the most abundant mineral, always as an essential constituent.
Before leaving Vesuvius it may be observed that throughout all the eruptions of modern times the northern side of the mountain, that is the old crater and flank of Somma, has been secure from the lava-flows, and has enjoyed an immunity which does not belong to the southern and western side.
Yet, such is the effect of atmosphere, that Mauna Loa, utterly destitute of vegetation, and with his sides scored and stained by the black lava-flows of ages, looked like a sapphire streaked with lapis lazuli.
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