Page:Transactions of the Geological Society, 1st series, vol. 2.djvu/313

From Wikisource
Jump to navigation Jump to search
This page has been validated.
Mr. Bennet on the Island of Teneriffe.

four 32°, at the bottom of the cone 36°; at the top of the Peak one hour and a half after sun-rise 38°. The descent down the cone is difficult from its extreme rapidity, and from the fall of large stones which loosen themselves from the beds of pumice. Having at last scrambled to the bottom, we pursued our march down the other course of the lava, that is to say down its westerly side, having ascended its eastern. The ravines and rents in this stream of lava are deeper and more formidable; the descent into them was always painful and troublesome, often dangerous, in some places we let ourselves down from rock to rock. I can form no opinion why there should be these strange irregularities in the surface of this lava; in places it resembles what sailors term the trough of the sea, and I can compare it to nothing but as if the sea in a storm had by some force become on a sudden stationary, the waves retaining their swell. As we again approached La Cueva there is a singular steep valley, the depth of which from its two walls cannot be less than 100 to 150 feet, the lava lying in broken ridges one upon the other similar to the masses of granite rock that time and decay have tumbled down from the top of the Alps; and, except from the scoria or what Milton calls “the Fiery Surge,” they in no degree bear the marks of having rolled as a stream of liquid matter. This current like that of the eastward branch has no resemblance to any lavas I have seen elsewhere, it is hardly at all decomposed, full of laminæ of feldspar, the fracture conchoidal, and the texture porphyritic, the colour brown like that of the other branch; it is but slightly cellular, and contains no extraneous substances.

We descended the pumice hill with great rapidity almost at a run, and arrived at La Estancia in little more than two hours. We then mounted our mules, and following the track by which we had