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Updated: May 7, 2025
Every variety of trap-rock is sometimes found in dikes, as basalt, greenstone, feldspar-porphyry, and trachyte. The amygdaloidal traps also occur, though more rarely, and even tuff and breccia, for the materials of these last may be washed down into open fissures at the bottom of the sea, or during eruption on the land may be showered into them from the air.
Towards the eastern end of this island there occur two craters composed of two kinds of tuff; one kind being friable, like slightly consolidated ashes; and the other compact, and of a different nature from anything which I have met with described.
The tract of which this celebrated district forms a part lies as it were in a bay of the Apennine limestone of Jurassic age. The floor of this bay is composed of puzzolana, a name given to beds of volcanic tuff of great thickness, and rising into considerable hills in the vicinity of the city of Naples, such as that of St. Elmo.
From the other the fine jet of water rises. On one side of the fountain a semicircular bench of tuff and terracotta. The loose, grayish white dust; the reddish, molded stone, the hewn, yellowish, porous tuff; the dark, polished porphyry, gleaming with moisture, and the living, tiny, silvery jet of water: material and colors harmonize rather well. The characters: two pages.
The lake of Albano, one of the most beautiful sheets of water in the world, is about six miles in circumference, and surrounded by beds of peperino, a variety of tuff presenting a bright, undecomposed aspect when newly broken.
Near the base of this hill, I observed beds of white tuff, intersected by numerous dikes, some of amygdaloidal basalt and others of trachyte; and beds of slaty phonolite with the planes of cleavage directed N.W. and S.E. Parts of this rock, where the crystals were scanty, closely resembled common clay-slate, altered by the contact of a trap-dike.
Bed 8, a greenish mudstone, with several layers of gypsum. Bed 9, a highly indurated, easily fusible, white tuff, thickly mottled with ferruginous matter, and including some white semi-porcellanic layers, which are interlaced with ferruginous veins. This stone closely resembles some of the commonest varieties in the Uspallata chain.
On the sides of canyons the breccia is carved by rain erosion to fantastic pinnacles. At different levels in the midst of these beds of tuff and lava are many old forest grounds.
But I didn't think she would fall. She is young and tuff, and she papered it real good, though it wuz dretful hard on her arm sockets and back. And the Secretary's wife wuz puttin' in a piece of onions. She thought she would make considerable by it, and she will, if onions keep up. But it is turrible hard on a woman's back to weed 'em.
Concluding remarks on the craters of tuff, and on the breached condition of their southern sides. Mineralogical composition of the rocks of the archipelago. Elevation of the land. Direction of the fissures of eruption. This archipelago is situated under the equator, at a distance of between five and six hundred miles from the west coast of South America.
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