Association of American Geologists and Naturalists. 223 



quarry and gravel pit — every tunnel through a mountain, and 

 every pit and gallery of a mine — every boring for coal, for salt, 

 or salt water, and every artesian perforation — furnish means of 

 perusing the interior structure. Still more, do the inland preci- 

 pices and the rocky promontories and headlands that rise along 

 the rivers, lakes, seas and oceans ; the naked mountain sides, 

 ribbed with jutting strata, that bound the defiles, gorges, and 

 valleys ; the ruins accumulated at the feet of lofty pinnacles and 

 mountain barriers, and those that have been transported far and 

 wide over the earth, present to us striking features of the interior 

 structure of the planet. 



" Most of all, do the inclined strata push up their hard edges 

 in varied succession, and thus faithfully disclose the form and 

 substance of the deep interior, as it exists — many, it may be 

 hundreds of miles and leagues, beneath the observer's feet." 



" Volcanic eruptions throw up into daylight, the foundations 

 of the fathomless deep below, either in the form of ejected or of 

 molten masses, flowing even in rivers of fluid and ignited rocks, 

 which congeal again on the surface of the ground, either inflated 

 like the scorias of furnaces or in solid forms ; often retaining no 

 visible impress of fire, and containing, occasionally, very perfect 

 and beautiful minerals, produced by heat in the bosom of the 

 volcano, or dislodged from still earlier beds from a more profound 

 igneous abyss, and impelled along by the irresistible current which 

 often ruptures the crust of the earth, and covers it with a fiery 

 deluge." 



"In addition to the products of actual volcanoes — the ignige- 

 nous rocks, the granites, the sienites, the porphyries, the serpen- 

 tines, the soapstones, and the traps — crystallized or amorphously 

 deposited from fusion — injected both in the earlier and in many 

 of the more modern epochs, among other rocks, and cutting across 

 the strata of almost all descriptions and ages, are thus assimilated 

 to the lavas, the known products of internal heat. Thus they 

 give authentic information of the unapproachable gulf of fire, 

 from which they were projected." 



" The internal waters that gush cool from the fountains on land 

 or under the sea, or those jets that spout in boiling geysers, from 

 the deep caverns, where their imprisoned vapors accumulate ex- 

 plosive force ; all these bring to the surface the materials of the 

 deep interior, and conspire with tornadoes of gas, bursting from 



