The great geyser-district of New Zealand is situated in the south of the province of Auckland in or near the upper basin of the Waikato river, to the N.E. of Lake Taupo. The scene presented in various parts of the districts is far more striking and beautiful than anything of the same kind to be found in Iceland, but this is due not so much to the grandeur of the geysers proper as to the bewildering profusion of boiling springs, steam-jets and mud-volcanoes, and to the fantastic effects produced on the rocks by the siliceous deposits and by the action of the boiling water. In about 1880 the geysers were no longer active, and this condition prevailed until the Tarawera eruption of 1886, when seven gigantic geysers came into existence; water, steam, mud and stones were discharged to a height of 600 to 800 ft. for a period of about four hours, when quieter conditions set in. Waikite near Lake Rotorua throws the column to a height of 30 or 35 ft.
| Fig. 2. |
In the Yellowstone National Park, in the north-west corner of Wyoming, the various phenomena of the geysers can be observed on the most portentous scale. The geysers proper are about one hundred in number; the non-eruptive hot springs are much more numerous, there being more than 3000. The dimensions and activity of several of the geysers render those of Iceland and New Zealand almost insignificant in comparison. The principal groups are situated along the course of that tributary of the Upper Madison which bears the name of Fire Hole River. Many of the individual geysers have very distinctive characteristics in the form and colour of the mound, in the style of the eruption and in the shape of the column. The “Giantess” lifts the main column to a height of only 50 or 60 ft., but shoots a thin spire to no less than 250 ft. The “Castle” varies in height from 10 or 15 to 250 ft.; and on the occasions of greatest effort the noise is appalling, and shakes the ground like an earthquake. “Old Faithful” owes its name to the regularity of its action. Its eruptions, which raise the water to a height of 100 or 150 ft., last for about five minutes, and recur every hour or thereabouts. The “Beehive” sometimes attains a height of 219 it.; and the water, instead of falling back into the basin, is dissipated in spray and vapour. Very various accounts are given of the “Giant.” F. V. Hayden saw it playing for an hour and twenty minutes, and reaching a height of 140 ft., and Doane says it continued in action for three hours and a half, and had a maximum of 200 ft.; but at the earl of Dunraven’s visit the eruption lasted only a few minutes.
Theory of Geysers.—No satisfactory explanation of the phenomena of geysers was advanced till near the middle of the 19th century, when Bunsen elucidated their nature. Sir George Mackenzie, in his Travels in Iceland (2nd ed., 1812), submitted a theory which partially explained the phenomena met with. “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 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 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 Geisire Islands,” Pogg. Ann., 1847, vol. 72; and Müller, “Über Bunsen’s Geysertheorie,” ibid., 1850, vol. 79).
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.
GEZER (the Kazir of Tethmosis [Thothmes] III.’s list of Palestinian cities and the Gazri of the Amarna tablets), a royal Canaanite city on the boundary of Ephraim, in the maritime plain (Josh. xvi. 3-10), and near the Philistine border (2 Sam. v. 25). It was allotted to the Levites, but its original inhabitants were not driven out until the time of Solomon, when “Pharaoh, king of Egypt” took the city and gave it as a dowry to his daughter, Solomon’s wife (1 Kings ix. 16). Under the form Gazera it is mentioned (1 Macc. iv. 15) as being in the neighbourhood of Emmaus-Nicopolis (’Amwās) and Jamnia (Yebnah). Throughout the history of the Maccabean wars Gezer or Gazara plays the part of an important frontier post. It was first taken from the Syrians by Simon the Asmonean (1 Macc. xiv. 7). Josephus also mentions that the city was “naturally strong” (Antiq. viii. 6. 1). The position of Gezer is defined by Jerome (Onomasticon, s.v.) as four Roman miles north (contra septentrionem) of Nicopolis (‘Amwās). This points to the mound of debris called Tell-el-Jezari near the village of Abū Shūsheh. The site is naturally very strong, the town standing on an isolated hill, commanding the western road to Jerusalem just where it begins to enter the mountains of Judea. This identification has been confirmed by the discovery of a series of boundary inscriptions, apparently marking the limit of the city’s lands, which have been found cut in rock—outcrops partly surrounding the site. They read in every case in נור תחמ[1], “the boundary of Gezer,” with the name Alkios in Greek, probably that of the governor under whom the inscriptions were cut. The site has been partially excavated by the Palestine Exploration Fund, and an enormous mass of material for the history of Palestine recovered from it, including remains of a pre-Semitic aboriginal race, a remarkably perfect High Place, the castle built by Simon, and other remains of the first importance.
See R. A. S. Macalister’s reports in Palestine Exploration Fund Quarterly Statement (October 1902 onwards). Also Bible Sidelights from the Mound of Gezer, by the same writer.
(R. A. S. M.)