“The observations made upon these two visits led me to the following conclusions as to the phenomena accompanying the eruptions of the Great Geyser:
“The cavity of Sir George Mackenzie, or boiler, as I shall here term it, I would place from 200 to 230 yards to the south of it, not far from the little Strokkr, from which the sound of underground ‘artillery’ is heard to proceed. Here it is that the explosive force—highly superheated steam—is generated. Connected with it and the underground passage to Geyser is the reservoir of hot water.
“These underground caverns are numerous over Iceland, Surseitler being the most famous; in it the sides of the cave, a mile in length, are smooth and rounded to the ceiling, evidently formed when the lava was in a plastic state—blown out like the molten glass under the hands of the bottle-maker. From the roof large blocks had fallen, rendering the passage extremely difficult.
“It seems highly probable that the cause of the sharp rattling noise heard during eruption is due to such loose angular masses of lava rock being driven against each other with the force that propelled the rush of waters to the Geyser. The explosive force unequal at first to impel more than a portion of water up the tube, the resistance becomes less as the reservoir gets emptied by its escape up the tube, and so the water is propelled higher and higher to the last. The explosions cease by the steam in the boiler being suddenly condensed, and the vacuum thus created drawing back the water from the passage, and from the basin, and in part from the well. The premonitory thumps were probably caused by the first waves of the rushing mass of water striking against a wall of rock close to the bottom of the well.
“Numerous Geysers worthy of note are scattered all over Iceland, the joint production of water and the subterranean fires which underlie them.”
Section IV.—To Thingvellir and back to Reykjavik.
The next morning (July 16) saw our departure. The breeze had chopped round to the north, and, perhaps, this change of wind produced the general excitement which we noticed in the springs. Both yesterday and to-day several parties of Icelanders came to see the sights, the women shawled to the ears, despite the hot sun, and with bodices unpleasantly tight-laced by lines of eyelet-holes across the breast. Formerly the people “never passed the Geysir without spitting into it; or, as they say, utí Fjandans munn—into the Devil’s mouth.” We set off at eleven A.M., passing south-south-west to the Laug farm, where some travellers have slept and “lost the eruption,” and crossing the filthy swamp, where sheep graze and curlews scream, we forded the little stream which drains between the Laugarfjall and its trachytic outlier. The approach to the thermæ from the south is even meaner than the eastern, a dwarf slope of bright-coloured ground trending from the concave lump to the Túngufljót.
Most of this march is only fit for the itinerary. The path in places becomes like the hollow ways of the Brazil, whose gullies spread over a hundred yards of ground, and the “forest,” as on the Anti-Libanus, shows more root than hole, the tree hugging earth, as it were, to save itself from being blown away. The first chapel farm gives an extensive view of the coast features and of the highly picturesque formations, the Jarlhettur rampart, the twin bluffs and spines of Hagafell, and the grim, black isolated castellation of Hljóðufell, outlying the Lángjökull. At about half-past one P.M., warned by a rustling which was mistaken for that of the forest, we came “lickity, lickity, switch,” upon the planks of the Brúará or Bridgewater: in Perthshire there is also a Bruar, so called from its natural arch. Gaimard, carefully copied by later writers, shows a plank forty feet long, utterly undefended by “gardefou,” and “spanning the depths of a narrow cleft in a precipice,” where men “rush for their lives,” and where “the danger is at least a hundred feet.” Symington was reminded of the Mósi-wá-túnyá (Victoria) Falls, the Niagara of South Africa! The river, classical in Iceland story for the lynching of Jón Gerikson, the Swedish bishop, here washes over a rocky channel about 160 feet broad. There is a ferry below; higher up a gash, nearly 100 yards long, forms a wedge-shaped crevasse, opening down stream, and a drop of half-a-dozen feet in the bed combines to make a miniature horse-shoe, over which the blue water pours, foaming and mildly roaring. Over the gash is thrown a bridge of twelve planks,[113] some twelve feet broad, and well guarded by iron-cramped rails. Man must lately have suffered from “Dil. Tre.” to feel nervous in such a place, and we went our ways laughing.
Shortly after six P.M. we sighted Thingvallavatn, the “monarch of Iceland lakes,” an expanse of placid blue, ruffled by the pleasant south. Its two crater-islets are Nesjaey, small and green, near the western shore, and larger Sandey, a two-pronged lump of black stone and green turf, rising a little south of a “Lisán,” a dark foreland projected by the eastern shore. Shortly afterwards we came suddenly upon the Hrafnagjá, or Raven’s Geo,[114] whose “startling depths” extend from the snow-patched Hrafnabjörg, or Raven’s Crag, about four miles long to the Vellankatla, Bay of the Lake. This longitudinal crevasse is the facsimile of a “Ká’ah” in Hauránic Leja or the Refuge; the long parallel lines show corresponding angles, and there is little difference of level between the upper and lower lips of the barranco; in fact, it is the lateral rent to be found, in a smaller scale, upon every lava-field. The arched form is common to such streams, and where the sides find a soft and yielding foundation, and cold contracts the heated mass, it splits on both sides of the major axis, and thus forms chasms, often one or more, upon each flank. Here, at least, no “collapse theory” is wanted.
A fair causeway across the Raven’s Rift is made by the falling of many rocks. Upon the lower slopes we found “forest,” which does not exist on the sister formation. We then crossed the eastern or, as it is known in history, the “upper plain;” the surface on both sides of the path is streaked with “Geos,” mostly running parallel; we remarked one disposed obliquely to the lay, and the various names given to us were Háflagjá, Hólagjá, and Breðnigjá. At half-past nine P.M. we entered the Thingvellir church: the altar-piece, a Last Supper, is old; the pulpit dates from A.D. 1683; and the loft is not, as usual, a store-room for the farm, but a sleeping apartment for travellers, provided with pillows and mattresses, decently clean. Prófastr Bech was happily absent: his wife sent us forelles and Kaka,[115] thin rye cakes, but Icelandic modesty did not admit of our seeing the lady.