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An Undesirable Result of the Eruption. — Weymouth hints at Certain Pacts hitherto quite Unsuspected. — More Bode for Strokhr. — Dull. — Strokhr gets an Accidental Dose. — "Sneezing-Matches" — Try him again. — A Grand Display. — Bunsen and Tyndants Theory of the Geysers.
WHILE we were looking about the basin, Weymouth came climbing up on the other side. "What's to be done?" said he with the air of one who had just witnessed a catastrophe.
"What's to be done with what?" Kit inquired. "Why, with the tent and things!"
We looked over the rim of the basin down to where we had encamped.
"By Jude!" exclaimed Wash.
"Whew!" from Raed.
The tent looked as if an elephant had lain down on it, — crushed flat! Halgrim we could see standing off at some distance, regarding the wreck with rueful looks.
"What did that, Weymouth? Was it the geyser?"
"You bet it was! Hot water came down there like — Old Scratch! He and the Icelander was in the tent to keep out of the steam and spray. But, Lord! pretty quick hot water began to drop by the bucketful.
Wind bloomed it, ye see. When them big jets flew up, the gusts would whizzle along, — a perfect sea out. We stuck in the tent as long as we dared., and then dusted out and legged it. The Icelander got splashed. Guess it scalded him some too. He was bare-headed. Had that big hat of his in his hand when we made our break. Shouldn't wonder if it killed some of his lice!"
"Is he lousy, Weymouth?" queried Raed.
"Is he lousy! — why, didn't you know that? Lousy as a hen! I noticed you didn't give his head quite so wide a berth as I wanted to when we was all cuddled down there last night."
"I never thought of his having lice!" Raed exclaimed.
"Why, hain't ye seen him scratch?" demanded the young tar. "Well, I s'pose ye were eying these 'ere black rocks too sharp for that. But, bless ye! I knew he was full of 'em afore we'd got half a mile with him that fust morning. I never see a fellow catch at the back of his neck, right between his ears, here (illustrating it), catch and dig to it, as he does, without he's shuck-full of 'em."
After this bit of practical information, we turned our attention to the tent. The strong wind from the north-east had blown the water over it in such quantities as to prostrate it completely. The pins on the windward side were pulled out. It lay all in a heap on the pack-boxes and saddles; but the rubbers had kept the worst of the deluge off the boxes. The hay and great. coats were well soaked. The milk was washed away; but the boxes containing the biscuits, sugar, cheese, meat, &c., were comparatively dry — inside. The ground too, all about, was drenched and steaming. Puddles stood in the trenches.
We had plenty of work on hand the rest of the forenoon to move our property. The hay had to be shaken up. the boxes and saddles set upon the rocks to dry,
and the great-coats, blankets, and tent hung on a line made of the guys, and supported by the poles. Whatever vermin the pedicular Halgrim had introduced among us probably got scalded out in the shower-bath to which the Great Geyser treated our effects.
In the afternoon, before the tent and blankets were dry enough to re-organize, we cut sods again for Strokhr, — about a ton of them. These were piled in a heap around the mouth of the funnel, — piled so near, that a single push would send them toppling down the pipe.
The weather continued cold, cloudy, and windy all day. Against this we fortified strongly with hot soup, coffee, and a fresh supply of milk, cream, and skyer from the neighboring byre.
By ten o'clock (evening) it came on to rain again heavily. We were still not a little damp inside from our drenching of the morning, and, on the whole, passed a rather uncomfortable night. Too much dampness will spoil the hilarity of any party. Wet and dry have a great deal to do with the buoyancy of a fellow's spirits. It is utterly impossible to really relish a joke in a suit of wet clothes, with the rain pouring down.
An accident roused us up toward three in the morning. On a sudden, Strokhr began to growl and rumble.
"Going to heave up, sure as ye live!" said Weymouth, to whom Strokhr's symptoms of nausea had already become familiar.
"Humph!" from Kit in a great state of dissatisfaction: "it will wash away all our sods! No small job to cut a ton of sods!"
We had prepared this dose to give Strokhr at the next irruption of the Great Geyser, to have both perform at once.
Raed got up to look out.
"No wonder he's sick!" he exclaimed. "Why, Kit, half that heap of turf has tumbled into the funnel!"
"Strokhr been taking sods of his own accord!" Wash exclaimed, turning out to reconnoitre.
"That's too confounded bad!" Kit grumbled. "Another hour of good honest digging gone, — lost!"
His sleepy lamentations were cut short by the roar and dashing of the fountain. We went out to see it. Wash improved the occasion to make another sketch from the tent. As Kit had predicted, all the remaining sods were swept in with the water. The first "heave-up" was immediately followed by a second, and this by a third, and so on during the greater part of the forenoon. We took occasion to measure the height of the column, as has been previously mentioned. This irruption also settled a question which had been somewhat warmly discussed by Raed and Kit. Raed did not believe that the quantity of sods thrown into the funnel had much to do with the violence of the irruption: he contended that a hundred-weight of sods would induce as high a jet as a ton. Kit argued that the force of the jets would be somewhat in proportion to the weight of sods. The discharge, on this occasion, was seemingly far less violent than that produced by the two tons of sods on the evening of our arrival.
The rain continued all day. We began to wish that we had been content with G. G.'s first irruption, and gone back to Reykjavik. The cold and dampness were extremely uncomfortable. We had all taken "colds," and had "sneezing-matches;" object being to see which could draw the loudest echo from the side of the Langarfjal.
The next day (June 15) was fair.
More sods were cut for Strokhr, — another ton, — and heaped about the orifice.
G. G. evinced no symptoms of another irruption. Kit made a sketch of the peaks of Heels, towering grandly to the southward at a distance of twelve or thirteen miles.
The night was chilling, for a June night; though the sun was scarcely out of sight ten minutes behind the mountains. More "sneezing-matches" next morning.
A little after ten, G. G. fired his first audible gun, seemingly ten miles down in his abdomen. Wash first noticed it. For the next hour, they drew gradually nearer and heavier. By eleven, they were let off with startling loudness. Then came a lull. For over an hour there wasn't a sound, save from an occasional discharge of bubbles up the funnel. "False alarm," Wash had pronounced; but at twenty minutes past twelve the guns began again, and by one the explosions began to bulge up the water into the basin.
"Time to give Strokhr his dose!" cried Raed.
He and Kit ran down, and with the spades thrust over the heaps of clods. We then all clambered up the side of the bluff above the hvers to get a good view of the expected display. Strokhr began to growl and rumble; but, before he had got sick enough to heave; the Great Geyser went up in all its majesty. Oh, it was grand! We had eyes for nothing else. That booming, plunging, roaring pillar of steam and glittering spray — 'twas worth waiting for! I never expect to see a more magnificent spectacle. Strokhr began when Great Geyser had been playing about five minutes. The poor little churn cuts but a sorry figure beside its mighty relative. The superior height of the Great-Geyser site and its lofty mound, altogether, make it vastly overtop Strokhr. The far greater volume of its waters, too, renders the latter still more insignificant. Nevertheless, the black, inky jets of Strokhr are in startling contrast with the white and sparkling geyser-pillar. They need to be seen together; and we would respectfully advise tourists to secure a joint performance, if they can in any way manage it.
As many of our readers may, like ourselves, feel interested in the whys and wherefores of these tremen dour irruptive fountains, we subjoin Prof. Bunsen's "Theory of the Geysers " as set forth by Prof. John Tyndall, believing it to be the latest and best authority on a subject which has heretofore perplexed scientific men not a little to explain.
A THEORY OF THE GEYSERS.
In his third lecture on heat, Prof. Tyndall says, "I must now direct your attention to a natural steam-engine, which long held a place among the wonders of the world. I allude to the Great Geyser of Iceland. The surface of Iceland gradually slopes from the coast towards the centre, where the general level is about two thousand feet above the sea. On this, as a pedestal, are planted the jökull, or icy mountains, which extend both ways in a north-easterly direction. Along this chain occur the active volcanoes of the island; and the thermal springs follow the same general direction. From the ridges and chasms which diverge from the mountains enormous masses of steam issue at intervals, hissing and roaring; and, when the escape occurs at the mouth of a cavern, the resonance of the cave often raises the sound to the loudness of thunder. Lower down, in the more porous strata, we have smoking mud-pools, where a repulsive blue-black aluminous paste is boiled, rising at times in huge bubbles, which, on bursting, scatter their slimy spray to a height of fifteen or twenty feet. From the bases of the hills, upwards, extend the glaciers; and above these are the snow-fields, which crown the summits. From the arches and fissures of the glaciers vast masses of water issue, falling at times in cascades over walls of ice, and spreading for miles over the country before they find definite outlet. Extensive morasses are thus formed, which add their comfortless monotony to the dismal scene already before the traveller's eye.
Intercepted by the cracks and fissures of the land, a portion of this water finds its way to the heated rock underneath; and here, meeting with the volcanic gases which traverse these underground regions, both travel together, to issue, at the first convenient opportunity, either as an eruption of steam, or a boiling spring.
"The most famous of these springs is the Great Geyser. It consists of a tube seventy-four feet deep, and ten feet in diameter. The tube is surmounted by a basin, which measures from north to south fifty-two feet across, and from east to west sixty feet. The interior of the tube and basin is coated with a beautiful, smooth, siliceous plaster, so hard as to resist the blows of a hammer; and the first question is, How was this wonderful tube constructed? how was this perfect plaster laid on? Chemical analysis shows that the water holds silica in solution; and the conjecture might therefore arise, that the water had deposited the silica against the sides of the tube and basin. But this is not the case. The water deposits no sediments: no matter how long it may be kept, no solid substance is separated from it. It may be bottled up and preserved for years as clear as crystal, without showing the slightest tendency to form a precipitate. To answer the question in this way would, moreover, assume that the shaft was formed by some foreign agency, and that the water merely lined it. The geyser-basin, however, rests upon the summit of a mound about forty feet high; and it is evident, from mere inspection, that the mound has been deposited by the geyser. But, in building up this mound, the spring must have formed the tube which perforates the mound; and hence the conclusion that the geyser is the architect of its own tube.
"If we place a quantity of the geyser-water in an evaporating-basin, the following takes place: In the centre of the basin the liquid deposits nothing; but at the sides, where it is drawn up by capillary attraction, and thus subjected to speedy evaporation, we find silica deposited. Round the edge, a ring of silica is laid on; and not until the evaporation has continued a considerable time do we find the slightest turbidity in the middle of the water. This experiment is the microscopic representant of what occurs in Iceland. Imagine the case of a simple thermal, siliceous spring, whose waters trickle down a gentle incline: the water thus exposed evaporates speedily, and silica is deposited. This deposit gradually elevates the side over which the water passes, until finally the latter has to take another course. The same takes place here: the ground is elevated as before, and the spring has to move forward. Thus it is compelled to travel round and round, discharging its silica, and deepening the shaft in which it dwells, until finally, in the course of ages, the simple spring has produced that wonderful apparatus which has so long puzzled and astonished both the traveller and the philosopher.
"Previous to an eruption, both the tabs and basin are filled with hot water: detonations which shake the ground are heard at intervals, and each is succeeded by a violent agitation of the water in the basin. The water in the pipe is lifted up so as to form an eminence in the middle of the basin, and an overflow is the consequence. These detonations are evidently due to the production of steam in the ducts which feed the geyser-tube; which steam, escaping into the cooler water of the tube, is there suddenly condensed, and produces the explosions. Prof. Bünsen succeeded in determining the temperature of the geyser-tube, from top to bottom, a few minutes before a great eruption; and these observations revealed the extraordinary fact, that at no part of the tube did the water reach its boiling-point. In the annexed sketch I have given on one side the temperatures actually observed, and on the other side the temperatures at which water would boil, taking into account both the pressure of the atmosphere and the pressure of the super-incumbent column of water. The nearest approach to the boiling-point is at A, a height of thirty feet from the bottom; but even here the water is two degrees Centigrade, or more than three and a half degrees Fahrenheit, below the temperature at which it could boil. How, then, is it possible that an eruption could occur under such circumstances?
"Fix your attention upon the water at the point A, where the temperature is within two degrees Centigrade of the boiling-point. Call to mind the lifting of the column when the detonations are heard. Get us suppose, that, by the entrance of steam from the ducts near the bottom of the tube, the geyser-column is elevated six feet, — a height quite within the limits of actual observation: the water at A is thereby transferred to B. Its boiling-point at A is 123.8°, and its actual temperature 121.8°; but at B its boiling-point is only 120.8. Hence, when transferred from A to B, the heat which it possesses is in excess of that necessary to make it boil. This excess of heat is instantly applied to the generation of steam: the column is thus lifted higher, and the water below is further relieved.
"More steam is generated; from the middle, downwards, the mass suddenly bursts into ebullition; the water above, mixed with steam-clouds, is projected into the atmosphere; and we have the geyser-eruption in all its grandeur.
"By its contact with the air the water is cooled, falls back into the basin, partially refills the tube, in which it gradually rises, and finally fills the basin as before. Detonations are heard at intervals, and risings of the water in the basin. These are so many futile attempts at an eruption; for not until the water in the tube comes sufficiently near its boiling temperature to make the lifting of the column effective can we have a true eruption.
"To Bünsen we owe this beautiful theory. And now let us try to justify it by experiment. Here is a tabs of galvanized iron, six feet long, AB, and surmounted by this basin, CD.
"It is heated by a fire underneath; and, to imitate as far as possible the condition of the geyser, I have encircled the tube by a second fire, F, at a height of two feet from the bottom. Doubtless the high temperature of the water at the corresponding part of the geyser-tube is due to a local action of the heated rocks. I fill the tube with water, which gradually becomes heated; and regularly, every five minutes, the water is ejected from the tube into the atmosphere.
"But there is another famous spring in Iceland, called the Strokhr, which is usually forced to explode by stopping its mouth with clods. We can imitate the action of this spring by stopping the mouth of our tube, AB, with a cork. The steam below will finally attain sufficient tension to eject the cork; and the water, suddenly relieved from its pressure, will burst forth in the
atmosphere. In the following figure I have given a section of the Strokhr: —
"By stopping the tube with corks through which tubes of various lengths and widths pass, the action of many of the other eruptive springs may be accurately imitated. Here, for example, I have an intermittent action: discharges of water and impetuous steam-gashes follow each other in quick succession, the water being squirted in jets fifteen or twenty feet high. Thus it is proved, experimentally, that the geyser-tube itself is the sufficient cause of the eruptions; and we are relieved from the necessity of imagining underground caverns filled with water and steam, which were formerly regarded as necessary to the production of these wonderful phenomena.
"A moment's reflection will suggest to us that there must be a limit to the operations of the geyser. When the tube has reached such an altitude that the water in the depths below, owing to the increased pressure, cannot attain its boiling-point, the eruptions, of necessity, cease. The spring, however, continues to deposit its silica, and often forms a laug, or cistern. Some of those in Iceland are forty feet deep. Their beauty, according to Bünsen, is indescribable. Over the surface curls a light vapor: the water is of the purest azure, and tints with its lovely hue the fantastic incrustations on the cistern walls; while at the bottom is often seen the mouth of the once mighty geyser. There are in Iceland vast, but now extinct, geyser-operations. Mounds are observed whose shafts are filled with rubbish, the water having forced a passage underneath, and retired to other scenes of action. We have, in fact, the geyser in its youth, manhood, old age, and death, here presented to us, — in its youth as a simple thermal spring, in its manhood as the eruptive column, in its old age as the tranquil laug, while its death is recorded by the rained shaft and mound which testify the fact of its once active existence."