CHAPTER XXXI.
A LESSON ON VOLCANOES.--PRIMARY COLORS ARE CAPABLE OF FARTHER SUBDIVISION.
"Get into the boat," said my eyeless pilot, "and we will proceed to thefarther edge of the lake, over the barrier of which at great intervalsof time, the surface water flows, and induces the convulsion known asMount Epomeo."
We accordingly embarked, and a gentle touch of the lever enabled usrapidly to skirt the shore of the underground sea. The soft, bright,pleasant earth-light continually enveloped us, and the absence of eitherexcessive heat or cold, rendered existence delightful. The weird formstaken by the objects that successively presented themselves on the shorewere a source of continual delight to my mind. The motion of our boatwas constantly at the will of my guide. Now we would skim across a greatbay, flashing from point to point; again we wound slowly throughtortuous channels and among partly submerged stones.
"What a blessing this mode of locomotion would be to humanity," Imurmured.
"Humanity will yet attain it," he replied. "Step by step men havestumbled along towards the goal that the light of coming centuries isdestined to illuminate. They have studied, and are still engaged instudying, the properties of grosser forces, such as heat andelectricity, and they will be led by the thread they are following, tothis and other achievements yet unthought of, but which lie back ofthose more conspicuous."
"WE FINALLY REACHED A PRECIPITOUS BLUFF."]
We finally reached a precipitous bluff, that sprung to my view as bymagic, and which, with a glass-like surface, stretched upward to aheight beyond the scope of my vision, rising straight from thesurface of the lake. It was composed of a material seemingly black asjet, and yet when seen under varying spectacular conditions as weskirted its base it reflected, or emitted, most gorgeously the brillianthues of the rainbow, and also other colors hitherto unknown to me.
"There is something unique in these shades; species of color appear thatI can not identify; I seem to perceive colors utterly unlike any that Iknow as the result of deflected, or transmitted, sunlight rays, and theylook unlike the combinations of primary colors with which I amfamiliar."
"Your observations are true; some of these colors are unknown on earth."
"But on the surface of the earth we have all possible combinations ofthe seven prismatic rays," I answered. "How can there be others here?"
"Because, first, your primary colors are capable of further subdivision.
"Second, other rays, invisible to men under usual conditions, alsoemanate from the sun, and under favorable circumstances may be broughtto the sense of sight."
"Do you assert that the prism is capable of only partly analyzing thesunlight?"
"Yes; what reason have you to argue that, because a triangular bit ofglass resolves a white ray into seven fractions that are, as men say,differently colored, you could not by proper methods subdivide each ofthese so-called primary shades into others? What reason have you todoubt that rays now invisible to man accompany those capable ofimpressing his senses, and might by proper methods become perceptible asnew colors?"
"None," I answered; "only that I have no proof that such rays exist."
"But they do exist, and men will yet learn that the term 'primitive'ray, as applied to each of the seven colors of the rainbow, isincorrect. Each will yet be resolved, and as our faculties multiply andbecome more subtle, other colors will be developed, possessed of adelicacy and richness indescribable now, for as yet man can notcomprehend the possibilities of education beyond the limits of hispresent condition."
During this period of conversation we skirted the richly colored bluffwith a rapid motion, and at last shot beyond it, as with a flash, intoseeming vacancy. I was sitting with my gaze directed toward the bluff,and when it instantly disappeared, I rubbed my eyes to convince myselfof their truthfulness, and as I did so our boat came gradually to astand on the edge of what appeared to be an unfathomable abyss. Beneathme on the side where had risen the bluff that disappeared so abruptly,as far as the eye could reach, was an absolute void. To our right, andbefore and behind us, stretched the surface of that great smooth lake onwhose bosom we rested. To our left, our boat brushing its rim, a narrowledge, a continuation of the black, glass-like material, reached only afoot above the water, and beyond this narrow brink the mass descendedperpendicularly to seemingly infinite depths. Involuntarily I graspedthe sides of the boat, and recoiled from the frightful chasm, over whichI had been so suddenly suspended, and which exceeded anything of asimilar description that I had ever seen. The immeasurable depth of theabyss, in connection with the apparently frail barrier that held thegreat lake in its bounds, caused me to shudder and shrink back, and mybrain reeled in dizzy fright. An inexplicable attraction, however,notwithstanding my dread, held me spell-bound, and although I struggledto shut out that view, the endeavor failed. I seemed to be drawn by anirresistible power, and yet I shuddered at the awful majesty of thatyawning gulf which threatened to end the world on which I then existed.Fascinated, entranced, I could not help gazing, I knew not how long,down, down into that fathomless, silent profundity. Composing myself, Iturned a questioning glance on my guide.
He informed me that this hard, glass-like dam confined the waters ofthe slowly rising lake that we were sailing over, and which finallywould rise high enough to overflow the barrier.
"THE WALL DESCENDED PERPENDICULARLY TO SEEMINGLY INFINITEDEPTHS."]
"The cycle of the periodic overflow is measured by great intervals," hesaid; "centuries are required to raise the level of the lake a fractionof an inch, and thousands of years may elapse before its surface willagain reach the top of the adamantine wall. Then, governed by the lawthat attracts a liquid to itself, and heaps the teaspoon with liquid,the water of the quiet lake piles upon this narrow wall, forming aledge along its summit. Finally the superimposed surface water givesway, and a skim of water pours over into the abyss."
He paused; I leaned over and meditated, for I had now accustomed myselfto the situation.
"There is no bottom," I exclaimed.
"Upon the contrary," he answered, "the bottom is less than ten milesbeneath us, and is a great funnel-shaped orifice, the neck of the funnelreaching first down and then upward from us diagonally toward thesurface of the earth. Although the light by which we are enveloped isbright, yet it is deficient in penetrating power, and is not capable ofgiving the contour of objects even five miles away, hence the chasmseems bottomless, and the gulf measureless."
"Is it not natural to suppose that a mass of water like this great lakewould overflow the barrier immediately, as soon as the surface reachedthe upper edge, for the pressure of the immense volume must be beyondcalculation."
"No, for it is height, not expanse, which, as hydrostatic engineersunderstand, governs the pressure of water. A liquid column, one foot inwidth, would press against the retaining dam with the force of a body ofthe same liquid, the same depth, one thousand miles in extent. Then thedecrease of gravity here permits the molecular attraction of the water'smolecules to exert itself more forcibly than would be the case on thesurface of the earth, and this holds the liquid mass together morefirmly."
"See," he observed, and dipping his finger into the water he held itbefore him with a drop of water attached thereto (Figure 27), theglobule being of considerable size, and lengthened as though itconsisted of some glutinous liquid.
FIG. 27.]
"How can a thin stratum of water give rise to a volcanic eruption?" Inext queried. "There seems to be no melted rock, no evidence of intenseheat, either beneath or about us."
"I informed you some time ago that I would partially explain thesefacts. Know then, that the theories of man concerning volcaniceruptions, in connection with a molten interior of the earth, are suchas are evolved in ignorance of even the sub-surface of the globe. Theearth's interior is to mankind a sealed chamber, and the wise men whoelucidate the curious theories concerning natural phenomena occurringtherein are forced to draw entirely upon their imagination. Few personsr
ealize the paucity of data at the command of workers in science.Theories concerning the earth are formulated from so little realknowledge of that body, that our science may be said to be all theory,with scarcely a trace of actual evidence to support it. If a globe teninches in diameter be covered with a sheet of paper, such as I hold inmy hand, the thickness of that sheet will be greater in proportion tothat of such a globe than the depth men have explored within the earthis compared with the thickness of the crust of the earth. The outersurface of a pencil line represents the surface of the earth; the innersurface of the line represents the depth of man's explorations; thehighest mountain would be represented by a comma resting on the line.The geologist studies the substances that are thrust from the crater ofan active volcano, and from this makes conjectures regarding the stratabeneath, and the force that casts the excretions out. The results mustwith men, therefore, furnish evidence from which to explain the cause.It is as though an anatomist would form his idea of the anatomy of theliver by the secretion thrown out of that organ, or of the lung textureby the breath and sputum. In fact, volcanoes are of severaldescriptions, and usually are extremely superficial. This lake, thesurface of which is but one hundred and fifty miles underground, is themother of an exceptionally deep one. When the water pours over thisledge it strikes an element below us, the metallic base of salt, whichlies in great masses in some portions of the earth's crust.[9] Then animmediate chemical reaction ensues, the water is dissociated, intenseheat results, part of the water combines with the metal, part isvaporized as steam, while part escapes as an inflammable gas. The suddenliberation of these gases causes an irregular pressure of vapor on thesurface of the lake, the result being a throbbing and rebounding of theattenuated atmosphere above, which, in gigantic waves, like swellingtides, dashes great volumes of water over the ledge beside us, and intothe depth below. This water in turn reacts on fresh portions of themetallic base, and the reflex action increases the vapor discharges, andas a consequence the chamber we are in becomes a gasholder, containingvapors of unequal gas pressures, and the resultant agitation of the lakefrom the turmoil continues, and the pulsations are repeated until thesurface of the lake is lowered to such a degree as at last to preventthe water from overflowing the barrier. Finally the lake quiets itself,the gases slowly disappear by earth absorption, and by escape from thevolcanic exit, and for an unrecorded period of time thereafter thesurface of the lake continues to rise slowly as it is doing now."
[9] This view is supported in theory by a note I believe to have somewhere seen recorded. Elsewhere other bases are mentioned also.--J. U. L.
"But what has this phenomenon to do with the volcano?"
"It produces the eruption; the water that rushes down into the chasm,partly as steam, partly as gas, is forced onward and upward through acrevice that leads to the old crater of the presumed extinct butperiodically active Mount Epomeo. These gases are intensely heated, andthey move with fearful velocity. They tear off great masses of stone,which the resultant energy disturbances, pressure, gas, and friction,redden with heat. The mixture of gases from the decomposed water is inlarge amount, is burning and exploding, and in this fiery furnace amidsuch convulsions as have been described, the adjacent earth substance isfused, and even clay is melted, and carried on with the fiery blast.Finally the current reaches the earth's surface through the funnelpassage, the apex of which is a volcano--the blast described a volcaniceruption."
"One thing is still obscure in my mind," I said. "You assert that thereaction which follows the contact of the flowing water and metallicbases in the crevice below us liberates the explosive gases, and alsovolumes of vapor of water. These gases rush, you say, and produce avolcanic eruption in a distant part of the crust of the earth. I can notunderstand why they do not rush backward as well, and produce anothereruption in Kentucky. Surely the pressure of a gas in confinement is thesame in all directions, is it not?"
"Yes," he replied, "but the conditions in the different directions aredissimilar. In the direction of the Kentucky cavern, the passage istortuous, and often contracts to a narrow crevice. In one place near thecavern's mouth, as you will remember, we had to dive beneath the surfaceof a stream of water. That stratum of water as effectually closed theexit from the earth as the stopper prevents water escaping from abottle. Between the point we now occupy and that water stopper, restthousands of miles of quiescent air. The inertia of a thousand miles ofair is great beyond your comprehension. To move that column of air bypushing against this end of it, and thus shoving it instantly out of theother end, would require greater force than would burst the one hundredand fifty miles of inelastic stone above us. Then, the friction of thesides is another thing that prevents its accomplishment. While agradually applied pressure would in time overcome both the inertia ofthe air and the friction of the stone passages, it would take a supplyof energy greater than you can imagine to start into motion the elasticmass that stands as solid and immovable as a sentinel of adamant,between the cavern you entered, and the spot we now occupy. Time andenergy combined would be able to accomplish the result, but not underpresent conditions.
"In the other direction a broad open channel reaches directly to andconnects with the volcanic shaft. Through this channel the air is inmotion, moving towards the extinct crater, being supplied from anothersurface orifice. The gases liberated in the manner I have described,naturally follow the line of least resistance. They turn at once awayfrom the inert mass of air that rests behind us, and move withincreasing velocity towards the volcanic exit. Before the pressure thatmight be exerted towards the Kentucky cavern would have more thancompressed the intervening column of air enough to raise the water of awell from its usual level to the surface of the earth, the velocity inthe other direction would have augmented prodigiously, and with itsincreased rapidity a suction would follow more than sufficient toconsume the increasingly abundant gases from behind."
"Volcanoes are therefore local, and the interior of the earth is not amolten mass as I have been taught," I exclaimed.
He answered: "If men were far enough along in their thought journey (forthe evolution of the mental side of man is a journey in the world ofthought), they would avoid such theories as that which ascribes amolten interior to the earth. Volcanoes are superficial. They are as arule, when in activity but little blisters or excoriations upon thesurface of the earth, although their underground connections may beextensive. Some of them are in a continual fret with frequent eruptions,others, like the one under consideration, awaken only after greatperiods of time. The entire surface of this globe has been or will besubject to volcanic action. The phenomenon is one of the steps in theworld-making, matter-leveling process. When the deposit of substancesthat I have indicated, and of which much of the earth's interior iscomposed, the bases of salt, potash, and lime and clay is exhausted,there will be no further volcanic action from this cause, and in someplaces, this deposit has already disappeared, or is covered deeply bylayers of earth that serve as a protection."
"Is water, then, the universal cause of volcanoes?"
"Water and air together cause most of them. The action of water and itsvapor produces from metallic space dust, limestone, and clay soil,potash and soda salts. This perfectly rational and natural action mustcontinue as long as there is water above, and free elementary bases incontact with the earth bubbles. Volcanoes, earthquakes, geysers, mudsprings, and hot springs, are the natural result of that reaction.Mountains are thereby forming by upheavals from beneath, and thecorresponding surface valleys are consequently filling up, either by theslow deposit of the matter from the saline water of hot springs, or bythe sudden eruption of a new or presumably extinct volcano."
"What would happen if a crevice in the bottom of the ocean shouldconduct the waters of the ocean into a deposit of metallic bases?"
"That often occurs," was the reply; "a volcanic wave results, and avolcano may thus rise from the ocean's depths."
"Is there any danger to the earth itself? May it not be riven i
ntofragments from such a convulsion?" I hesitatingly questioned.
"No; while the configuration of continents is continually being altered,each disturbance must be practically superficial, and of limited area."
"But," I persisted, "the rigid, solid earth may be blown to fragments;in such convulsions a result like that seems not impossible."
"You argue from an erroneous hypothesis. The earth is neither rigid norsolid."
"True," I answered. "If it were solid I could not be a hundred milesbeneath its surface in conversation with another being; but there cannot be many such cavities as that which we are now traversing, and theycan not surely extend entirely through its mass; the great weight of thesuperincumbent material would crush together the strongest materials, ifa globe as large as our earth were extensively honeycombed in thismanner."
"Quite the contrary," he replied; "and here let me, for the first time,enlighten you as to the interior structure of the terrestrial globe. Theearth-forming principle consists of an invisible sphere of energy that,spinning through space, supports the space dust which collects on it, asdust on a bubble. By gradual accumulation of substance on that sphere ahollow ball has resulted, on the outer surface of which you havehitherto dwelt. The crust of the earth is comparatively thin, not morethan eight hundred miles in average thickness, and is held in positionby the central sphere of energy that now exists at a distance aboutseven hundred miles beneath the ocean level. The force inherent to thissphere manifests itself upon the matter which it supports on both sides,rendering matter the lighter the nearer it lies to the center sphere. Inother words, let me say to you: The crust, or shell, which I have justdescribed as being but about eight hundred miles in thickness, is firmand solid on both its convex and concave surface, but gradually loses inweight, whether we penetrate from the outer surface toward the center,or from any point of the inner surface towards the outside, until at thecentral sphere matter has no weight at all. Do you conceive my meaning?"
"Yes," I replied; "I understand you perfectly."
After a pause my pilot asked me abruptly:
"What do you most desire?"
The question caused my mind to revert instantly to my old home on theearth above me, and although I felt the hope of returning to it springup in my heart, the force of habit caused me involuntarily to answer,"More light!"
"More light being your desire, you shall receive it."
Obedient to his touch, the bow of the boat turned from the gulf we hadbeen considering towards the center of the lake; the responsive craftleaped forward, and in an instant the obsidian parapet disappearedbehind us. On and over the trackless waste of glass-like water we sped,until the dead silence became painfully oppressive, and I asked:
"Whither are we bound?"
"Towards the east."
The well-timed answer raised my spirits; I thought again that in thisman, despite his repulsive shape, I beheld a friend, a brother;suspicion vanished, and my courage rose. He touched the lever, and thecraft, subject to his will, nearly rose from the water, and sped withamazing velocity, as was evident from the appearance of the luminousroad behind us. So rapid was our flight that the wake of the boat seemedas if made of rigid parallel lines that disappeared in the distance, tooquick for the eye to catch the tremor.
Continuing his conversation, my companion informed me that he had nowdirected the bark toward a point east of the spot where we struck theshore, after crossing the lake, in order that we might continue ourjourney downward, diagonally to the under surface of the earth crust.
"This recent digression from our journey proper," said he, "has beenmade to acquaint you with a subject, regarding which you have exhibiteda curiosity, and about which you have heretofore been misinformed; nowyou understand more clearly part of the philosophy of volcanoes andearthquakes. You have yet much to learn in connection with alliedphenomena, but this study of the crude exhibition of force-disturbedmatter, the manipulation of which is familiar to man under the abovenames, is an introduction to the more wonderful study destined yet to bea part of your field, an investigation of quiescent matter, and puremotion."
"I can not comprehend you," I replied, "as I stated once before when youreferred to what you designated as pure motion."