Such are the evident symptoms of subterranean heat,--hot springs, jets of steam, fountains of boiling water,--which are manifested unceasingly at the surface of the Earth in every quarter of the Globe. But it is sometimes given us to behold, as it were, the subterranean fire itself, and to contemplate its power under a more striking and awful form. From time to time, in the fury of its rage, the fiery element bursts asunder the prison-house in which it is confined, and rushes forth into the light of day; then flames are seen to issue from the surface of the Earth, yawning chasms begin to appear on every side, the roaring of the furnaces is heard in the depths below, clouds of red-hot cinders are ejected high into the air, and streams of incandescent liquid rock are poured forth from every crevice, which, rolling far away through smiling fields and peaceful villages, carry destruction and desolation in their track. These are the ordinary phenomena of an active volcano during the period of eruption; and even while we write, most of them may be witnessed actually taking place for the hundredth time, on the historic ground of Mount Vesuvius. Our typical example, however, we shall take from the eruption of that mountain in the year 1779. It was not, indeed, especially remarkable for its violence or for the catastrophes by which it was attended; but it had the good fortune to be accurately recorded by an eye-witness, Sir William Hamilton, who, at that time, represented the English Government at the Court of Naples; and we are thus more minutely acquainted with all its various circumstances than with those of any other eruption of equal importance.