the trachyte of the Euganean Hills, where rise domes of granular trachyte, obsidian, and pearl-stone, masses connected by a common origin, which break through the lower cretaceous rock and nummulitic lime-stone, but have never flowed in narrow streams. Similar evidences of ancient revolutions of nature are found in several parts of the mainland of Greece and in Asia Minor, countries which will one day offer a rich field for geological investigation, when intellectual light shall revisit the seats from which it has radiated to the western world, and when oppressed humanity shall no longer be subject to the barbarism of Turkish rule.
I recall the geographical proximity of these various phænomena, in order to shew that the basin of the Mediterranean, with its series of islands, might have offered to an attentive observer much that has been recently discovered, under various forms, in South America, Teneriffe, and the Aleutian Islands near the polar circle. The objects to be observed were assembled within a moderate distance; yet distant voyages, and the comparison of extensive regions in and out of Europe, have been required for the clear perception and recognition of the resemblance between volcanic phænomena and their dependence on each other.
Our ordinary language, which often gives permanency and apparent authority to the first-formed erroneous views of natural phænomena, but which also often points instinctively to the truth,—our ordinary language, I repeat, applies the term "volcanic" to all eruptions of subterranean fires or molten substances; to columns of smoke and vapour rising from rocks, as at Colares after the great earthquake of Lisbon;
