Messrs. Descloiseaux and Bunsen, who, according to Mrs. Somerville, visited Iceland in 1846, found the temperature of the Great Geyser, at the depth of seventy-two feet, to equal 260° 30’ F. prior to a great eruption, reduced, after the eruption, to 251° 30’ F.; an interval of twenty-eight hours passing in silence.
THE GREAT GEYSER.
About one hundred and forty yards distant is the Strokr (from stroka, to agitate), a circular well, forty-four feet deep, with a tube eight feet wide at its mouth, diminishing to little more than ten inches at a depth of twenty-seven feet. The surface of the water is in constant ebullition, while at the bottom the temperature exceeds that of boiling water by about twenty-four degrees. It appears, from experiments made by Donny, that water, long boiled, becomes more and more free from air, and that thus the cohesion of the particles is so much increased, that when the heat is sufficiently increased to overcome that cohesion, the production of steam is so considerable and so instantaneous as to induce an explosion. In this circumstance M. Donny finds an explanation of the phenomena of the Geysers, which are in constant ebullition for many hours, until, being almost purified from air, the intense internal or subterranean heat overcomes the cohesion of the particles, and thus an explosion takes place.
Lord Dufferin describes an eruption which he witnessed on the occasion of his visit to the Geysers, but for which he waited three days. Like pilgrims round some ancient shrine, he says, he and his friends kept patient watch; but the Great Geyser scarcely deigned to vouchsafe the slightest manifestation of its latent energies. Two or three times they heard a sound as of subterranean cannonading, and once an eruption to the height of about ten feet occurred. On the morning of the fourth day a cry from the guides made them start to their feet, and with one common impulse rush towards the basin. The usual underground thunder had already commenced. A violent agitation was disturbing the centre of the pool. Suddenly a dome of water lifted itself up to the height of eight or ten feet, then burst, and fell; immediately after which a shining liquid column, or rather a sheaf of columns, wreathed in robes of vapour, sprang into the air, and in a succession of jerking leaps, each higher than the last, flung their silver crests against the sky. For a few minutes the fountain held its own, then all at once appeared to lose its ascending power. The unstable waters faltered, drooped, fell, “like a broken purpose,” back upon themselves, and were immediately sucked down into the recesses of their pipe.
The spectacle was one of great magnificence; but no description can give an accurate idea of its most striking features. The enormous wealth of water, its vitality, its hidden power, the illimitable breadth of sunlit vapour, rolling out in exhaustless profusion,—these combine to impress the spectator with an almost painful sense of the stupendous energy of nature’s slightest movements.
The same traveller furnishes a very humorous account of the Strokr (or “churn”).
It is, he says, an unfortunate Geyser, with so little command over its temper and stomach, that you can get a rise out of it whenever you like. Nothing more is necessary than to collect a quantity of sods and throw them down its funnel. As it has no basin to protect it from these liberties, you can approach to the very edge of the pipe, which is about five feet in diameter, and look down at the boiling water perpetually seething at the bottom. In a few minutes the dose of turf just administered begins to disagree with it; it works itself up into “an awful passion;” tormented by the qualms of incipient sickness, it groans and hisses, and boils up, and spits at you with malicious vehemence, until at last, with a roar of mingled pain and rage, it throws up into the air a column of water forty feet high, carrying with it all the sods that have been thrown in, and scattering them, scalded and half-digested, at your feet. So irritated has the poor thing’s stomach become by the discipline it has undergone, that even long after all foreign matter has been thrown off, it continues retching and sputtering, until at last nature is exhausted, when, sobbing and sighing to itself, it sinks back into the bottom of its den.
The ground around the Geysers, for about a quarter of a mile, looks as if it had been “honeycombed by disease into numerous sores and orifices;” not a blade of grass grew on its hot, inflamed surface, which consisted of unwholesome-looking red livid clay, or crumpled shreds and shards of slough-like incrustations.