In addition to the solid materials thrown out by volcanoes, there are sometimes poured forth torrents of boiling water and liquid mud. More frequently, however, the water issues in the form of vast columns of steam and sulphurous vapour. These ascend to great heights in the air, and becoming gradually chilled, they form immense masses of dark heavy clouds, similar to those we observe before a thunderstorm. Nor is this resemblance apparent only. For the clouds that overhang an active volcano during an eruption of its vapours are, in reality, thunderclouds highly charged with electricity. They accordingly produce what Baron Humboldt calls the volcanic storm. It includes all the most terrible of atmospheric phenomena--lightnings of extraordinary vividness; thunders that peal and reverberate as if they would rend the echoes asunder; torrents of rain that pour down upon the mountain and its neighbourhood, hissing like thousands of serpents when they fall on the glowing lava-torrent; and whirlwinds that sweep the volcanic ashes round and round in vast eddies, and before whose violence no man of mortal mould is able for a moment to stand. Beyond and above this din of contending elements are heard the hoarse bellowings of the mountain itself, which, meanwhile, trembles to its very core. The detonations from the volcano far exceed in loudness any other earthly noise. Compared with these, the pealing of the loudest thunder is but as the report of a musket contrasted with the simultaneous discharge of a thousand pieces of heavy ordnance. The explosions of Tomboro, and the vibrations accompanying them, have been heard and felt at almost incredible distances. Judge, then, of the immensity of the forces which are thus brought into play, and the overwhelming grandeur of the scene which such an eruption, with all its accompaniments of storm and tempest, must present to the bewildered eye and ear. Even to read of it sends a thrill through the nerves: what, then, must it be to listen and behold?