GEYSERS, a name derived from an Ice landic work signifying *to burst forth with vio lence," and applied to natural springs of hot water of the kind that were first observed in Iceland, and since in Yellowstone Park in the United States and in New Zealand. They may be described as volcanoes of hot water, for they resemble volcanoes in every particular — in the vibrations of the earth and dull rumbling sounds or loud reports by which the eruptions are preceded, in the intermittence of the phe nomenon, and in the form of the opening at which the eruptions take place, like an inverted cone with a deep central throat. Natural phi losophers are not agreed as to the mode in which this phenomenon is to be explained.
Cleland gives the following explanation: ((When the [geyser] tube is so long and nar row] that the water cannot circulate with rapid ity, the water at some distance below the top of the tube will increase in temperature more rapidly than at the surface. Eventually the' water at a depth of a number of feet will reach its boiling point with the resultant formation of bubbles of steam, which, in turn, will cause the water to spill over the edge of the opening. This overflow promotes boiling by reducing the pressure upon the water deep in the tube. As a consequence a large quantity of water, which was not quite at the boiling point because of the weight of the overlying column of water, will instantly burst into steam and will eject the overlying water from the tube, sometimes to a great height." The best proof of the above theory lies in the fact that artificial geysers, constructed in conformity with the above idea, actually erupt periodically. In these the tube is of glass, and the steam action can be studied.
The geysers of Iceland lie about 30 miles west of Mount Hecla, and 16 miles north of the town of Skalholt, in a plain covered by hot-. springs and steaming apertures. They are nearly 100 in number, and are scattered over a surface scarcely more than two square miles in extent. The two most remarkable are the
Grand Geyser and the New Geyser or Strokkur (churn). The Great Geyser rises from a tun nel-shaped basin, lined and edged with silicious deposits. The pipe or throat at the bottom, from which the jet issues, is about 10 feet in diameter, and the basin at its outer edge la above 70. The emissions generally take place at intervals of six hours, and last for about five minutes at a time. The column, as meas ured by a quadrant, has been seen to rise as high as 212 feet. It is impossible to fix the age of the Great Geyser, but that its eruptions have taken place from the most remote antiquity is proved by the fact that,. although there has been no sensible increase in the depth of the silicious deposit since the earliest recorded ob servations, it is now more than 16 feet deep.
The geysers of Iceland, long the only ones known to exist, are surpassed by those which have been discovered in comparatively recent times in the Yellowstone National Park. The largest of them is called the Grand Geyser. It begins an eruption by filling its basin with boil ing water, forming a well 20 by 25 feet in dia metric measurements, and having a visible depth, when quiet, of 100 feet. The explosion is pre ceded by clouds of steam rushing up to a height of 500 feet; the great unbroken body of water succeeds, ascending in one gigantic column to a height of 90 feet; while from the apex of the column there radiate five great jets, which shoot up to the unparalleled height of 250 feet from the ground. Among the other remarkable gey sers of this district are those named Old Faith ful, the Beehive, the Giant, the Giantess, etc. The number of hot-springs in the Yellowstone is not less than 1,500, all varying in times of action, force, deposits and color of water.