Having pitched their tent at the distance of about one hundred yards from the Geyser, and so arranged matters that a regular watch might be kept during the night, Sir G. S. Mackenzie took his station at eleven o’clock, and his companions lay down to sleep. About ten minutes before twelve he heard subterraneous discharges, and waked his friends. The water in the basin was greatly agitated, and flowed over, but there was not any jet. The same occurred at half past two. At five minutes past four on Saturday morning, an alarm was given by one of the company. As our traveler lay next the door of the tent, he instantly drew aside the canvas, when at the distance of little more than fifty yards, a most extraordinary and magnificent appearance presented itself. From a place they had not before noticed, they saw water thrown up, and steam issuing with a tremendous noise. There was little water; but the force with which the steam escaped, produced a white column of spray and vapor, at least sixty feet high. They enjoyed this astonishing and beautiful sight until seven o’clock, when it gradually disappeared. The remaining part of the morning was occupied in examining the environs of the Geysers; and at every step they received some new gratification. Following the channel which had been formed by the water escaping from the great basin during the eruptions, they found several beautiful and delicate petrifactions. The leaves of birch and willow were seen converted into white stone, and in the most perfect state of preservation, every minute fiber being entire. Grass and rushes were in the same state, and also masses of peat. Several of these rare and elegant specimens were brought safely to Great Britain. On the outside of the mount of the Geyser, the depositions, owing to the splashing of the water, are rough and have been justly compared to the heads of cauliflowers. They are of a yellowish brown color, and are arranged around the mount, somewhat like a circular flight of steps. The inside of the basin is comparatively smooth: and the matter forming it is more compact and dense than the exterior crust; when polished it is not devoid of beauty, being of a gray color, mottled with black and white spots and streaks. The white incrustation formed by the water of the beautiful cavity before described, had taken a very curious form at the water’s edge, very much resembling the capital of a Gothic column. THE SULPHUR MOUNTAIN. This mountain of Iceland, distant about three miles from the village of Krisuvik, presents a phenomenon very different from the one which has just been described, _viz._, that of a CALDRON OF BOILING MUD. We extract the following particulars of this singular curiosity from the relation given by Sir G. S. Mackenzie in his travels in Iceland.