# Encyclopædia Britannica, Ninth Edition/Geysers

From volume X of the work.

 .mw-parser-output .wst-fineblock{line-height:1.4;font-size:92%} Fig..mw-parser-output .nowrap,.mw-parser-output .nowrap a:before,.mw-parser-output .nowrap .selflink:before{white-space:nowrap} 1. Fig. 2. Observed. A Calculated. 186° 225° 230° 241° C 249° 251° 255° D 255° 266° 259° 278° B
GEYSERS, Geisers, or Geisirs, are fountains of a peculiar construction, in virtue of which they shoot up into the air, at more or less regular intervals of time, a column of heated water and steam or of mud. Those of Iceland have been known at least from the time of Saxo Grammaticus, who briefly mentions them in his Danorum regum historiæ; but no satisfactory explanation of the phenomena was advanced till near the middle of the present century, when Bunsen brought his scientific knowledge and power of investigation to bear on the subject. Sir George Mackenzie, in his Travels in Iceland, 1811, had written as follows:—“Let us suppose a cavity C (ﬁg. 1), communicating with the pipe PQ, filled with boiling water to the height AB, and that the steam above this line is conﬁned so that it sustains the water to the height P. If we suppose a sudden addition of heat to be applied under the cavity C, a quantity of steam will be produced which, owing to the great pressure, will be evolved in starts causing the noises like discharges of artillery, and the shaking of the ground.” He admitted that even to his own mind this could be only a partial explanation of the facts of the case, and that he was unable to account for the frequent and periodical production of the necessary heat; but he has the credit of hitting on what is certainly the proximate cause—the sudden evolution of steam. By Bunsen’s theory the whole difficulty is solved, as is beautifully demonstrated by the artificial geyser designed by Professor J. H. J. Müller of Freiburg (fig. 2). If the tube ab be filled with water and heated at two points, first at a and then at b, the following succession of changes is produced. The water at a beginning to boil, the superincumbent column is consequently raised, and the stratum of water which was on the point of boiling at b being raised to d is there subjected to a diminished pressure; a sudden evolution of steam accordingly takes place at d, and the superincumbent water is violently ejected. Received in the basin c, the air-cooled water sinks back into the tube, and the temperature of the whole column is consequently lowered; but the under strata of water are naturally those which are least affected by the cooling process; the boiling begins again at A, and the same succession of events is the result (see R. Bunsen, “Physikalische Beobachtungen über die hauptsächlichsten Gisire Islands,” in Poggendorff’s Annalen der Physik and Chemie, vol. lxxii., 1847; and J. Müller, “Ueber Bunsen’s Geysertheorie,” ibid., vol. lxxix., 1850). The principal difference between the artificial and the natural geyser-tube is that in the latter the effect is not necessarily produced by two distinct sources of heat like the two fires of the experimental apparatus, but by the continual influx of heat from the bottom of the shaft and the differences between the boiling points of the different parts of the column owing to the different pressures of the superincumbent mass. This may be thus illustrated:—AB is the column of water; on the right side the figures represent approximately the boiling points (Fahr.) calculated according to the ordinary laws, and the figures on the left the actual temperature of the same places. Both gradually increase as we descend, but the relation between the two is very different at different heights. At the top the water is still 39° from its boiling point, and even at the bottom it is 19°; but at D the deficiency is only 4°. If, then, the stratum at D be suddenly lifted as high as C, it will be 2° above the boiling point there, and will consequently expend those 2° in the formation of steam.

Any hot spring capable of depositing siliceous material by the evaporation of its water may in course of time transform itself into a geyser, a tube being gradually built up as the level of the basin is raised. And every geyser continuing to deposit siliceous material is preparing its own destruction; for as soon as the tube becomes deep enough to contain a column of water sufficiently heavy to prevent the lower strata attaining their boiling points, the whole mechanism is deranged. In geyser districts it is easy to find thermal springs busy with the construction of the tube; warm pools, or laugs, as the Icelanders call them, on the top of siliceous mounds, with the mouth of the shaft still open in the middle; and dry basins from which the water has receded with their shafts now choked with rubbish.

Geysers exist at the present time in many volcanic regions, as in the Eastern Archipelago, Japan, and South America; but the three localities where they attain their highest development are Iceland, New Zealand, and Wyoming in the United States. The very name by which we call them indicates the historical priority of the Iceland group. It is an old Icelandic word—geysir, equivalent to gusher or rager—from the verb geysa, itself a derivative of gjosa, to gush. In native usage it is the proper name of the Great Geyser, and not an appellative—the general term hver, a hot spring, making the nearest approach to the European sense of the word (see Cleasby and Vigfusson, Icelandic English Dictionary, s.v.).