After the Geysir, the most remarkable fountain of these Phlegræan fields is the great Strokkr, situated about four hundred feet from the former. Its tube, the margin of which is almost even with the general surface, the small mound and basin being hardly discernible, is funnel-shaped, or resembling the flower of a convolvulus, having a depth of forty-eight feet, and a diameter of six feet at the mouth, but contracting, at twenty-two feet from the bottom, to only eleven inches. The water stands from nine to twelve feet under the brim, and is generally in violent ebullition. A short time before the beginning of the eruptions, which are more frequent than those of the Great Geysir, an enormous mass of steam rushes from the tube, and is followed by a rapid succession of jets, sometimes rising to the height of 120 or 150 feet, and dissolving into silvery mist. A peculiarity of the Strokkr is that it can at any time be provoked to an eruption by throwing into the orifice large masses of peat or turf; thus choking the shaft, and preventing the free escape of the steam. After the lapse of about ten minutes, the boiling fluid, as if indignant at this attempt upon its liberty, heaves up a column of mud and water, with fragments of peat, as black as ink. About 150 paces from the Great Geysir are several pools of the most beautifully clear water, tinting with every shade of the purest green and blue the fantastical forms of the silicious travertin which clothes their sides. The slightest motion communicated to the surface quivers down to the bottom of these crystal grottoes, and imparts what might be called a sympathetic tremor of the water to every delicate incrustation and plant-like efflorescence. “Aladdin’s Cave could not be more beautiful,” says Preyer; and Mr. Holland remarks that neither description nor drawing is capable of giving a sufficient idea of the singularity and loveliness of this spot. In many places it is dangerous to approach within several feet of the margin, as the earth overhangs the water, and is hollow underneath, supported only by incrustations scarcely a foot thick. A plunge into waters of about 200° would be paying rather too dearly for the contemplation of their fairy-like beauty. [Illustration: 42. ENTRANCE TO THE ALMANNAGJA.] The gigantic chasm of the Almannagja is another of the volcanic wonders of Iceland. After a long and tedious ride over the vast lava-plain which extends between the Skalafell and the lake of Thingvalla, the traveller suddenly finds himself arrested in his path by an apparently insurmountable obstacle, for the enormous Almannagja, or Allman’s Rift, suddenly gapes beneath his feet--a colossal rent extending above a mile in length, and inclosed on both sides by abrupt walls of black lava, frequently upward of a hundred feet high, and separated from about fifty to seventy feet from each other. [Illustration: 43. THE ALMANNAGJA.]