The appearance of fire at the summit of a volcano is rarely ever real flame. Any who has seen the peculiar appearance occasioned by brilliant illumination on a moist or foggy evening may readily perceive the cause. The phenomenon popularly known as the “sun drawing water” is of the same character. The immense cloud of vapor ascending from the volcano glows with the light sent up from the molten mass below. So it may be seen brilliant by night, and only a dark cloud by day. Stromboli has been called the light-house of the Mediterranean. In constant action, the brilliant light at night slowly fades: then suddenly breaks out as bright as before. This alternating results from the bursting of bubbles in the crater, which expose a new, hot surface. This rapidly cools; then another bubble bursts; and so the process continues. This may have suggested the alternating light now in common use in great light-houses. In the Galapagos, and other volcanic islands of the Pacific, occurs another curious feature of volcanic action. Some places abound in seeming mounds or domes, which may be sometimes readily broken in with a heavy stone. These are produced by bubbles which partially cooled, when the lava below found some rent or outlet in another quarter and flowed away, leaving the solidified bubble. Sometimes the cavern left by the retreating lava abounds in strange beauties. A sailor, who with a comrade, explored one of these volcanic caverns, gives the following account of it: “In a sharp, deep valley of Albemarle we had broken in the roof of a bubble; and as we looked in we saw we had opened the way into a tunnel about fifteen feet in width, and extending either way as far as we could see from our position. By the lights which entered from above, we made out the floor as about twenty feet beneath us, and that the walls were curiously marked with columnar forms. My companion, who had dabbled in the sciences, proposed that we should take an underground view of volcanic action and appearances.