LESSONS IN GEOLOGY.-VI. VOLCANOES-IGNEOUS AGENCY. THE universal action of water is to level. If the world continue for the requisite number of ages, and if no other cause interfere with the degrading and filling up which is carried on by every rain-drop, river, or ocean current, in due time our world will be a level plain. This, however, can never be the case, for there exists a force which constantly opposes the action of water. The Creator "hath set the one over against the other," and here, as in every domain of Nature, is a finely adjusted balance-the aqueous agency on the one hand, and the igneous agency on the other; the one wearing down, the other elevating; the one filling up and making the surface even, the other disrupting and throwing the existing arrangement into disorder. The action of heat is exerted in three ways—(1) in volcanoes, (2) earthquakes, and (3) the gradual upheaving or subsiding of portions of the earth's crust. We are not able to trace the action of heat so certainly as that of water, for the simple reason that we can watch the one from first to last; whereas we can only study the effects of thermal action, and thence attempt to divine the causes. Wherever there is room for speculation, no lack of speculators has been found; and upon almost every question upon which a doubt could exist-and there are many in this part of the subject-the geological world has been divided. We shall notice the prominent points of the various controversies as we discuss the subjects as they present themselves. of four groups. The Andes, which edge the western shore of the American continent, present in their chain many active, and numerous extinct, burning mountains. This is the best defined volcanic group. A second is recognised as comprising the Aleutian Islands, Japan, the Moluccas, and the volcanoes of the East Indies. The third group includes those of the Pacific Archipelago; while the fourth is represented as stretching from Central Asia to the Azores, and includes the volcanoes of the Greek islands, and those of Southern Italy. A Fig. 10. 1. Volcanoes. We shall find that rocks which owe their origin to igneous action may be safely divided into plutonic and volcanic rocks. In the former class are arranged all rocks of the primary formations, such as granites, etc., which are the offspring of a much more general and widely extended action than those igneous rocks which date from a much later period. These rocks, which are found within limited ranges, have been ejected from a crater, that is, a hole is formed from the surface to the bowels of the earth beneath, op which is thrown molten lava and ashes, or scoria. This matter is cast up and falls around the opening, forming a hillock, the top of which is a cup-like formation, at whose base is the mouth of the volcano. A mountain thus entirely formed of material ejected from the centre of action beneath, is called a crater of eruption. However, another method of construction of a volcanic mountain can be imagined, where some violent upheaving force lifts up the surface into a bubble-like mound; the apex, being naturally the weakest part, gives way, and from the opening thus formed the internal fires belch forth, and the eruption proceeds, the walls of the babble falling down from the mountain. A volcano thus produced is styled a crater of elevation. These two theories have been energetically supported by eminent geologists. Scrope, Prevost, and Lyell are B A remarkable fact will at once strike the observant reader, namely, that all volcanoes are in the immediate neighbourhood of the sea. There is no exception to this rule. In Central Asia there is said to be a volcano on the north declivity of the Thian-Shan Mountains, but its last eruption is referred to the seventh century. There are not wanting evidences that in that part of Asia large bodies of water existed, and even now the large lake Issik-Kul is in the neighbourhood of the quiescent mountain. This apparent necessity of being in immediate proximity to water, caused Bischoff to propound a theory, which is generally accepted: that the immediate cause of volcanic action is due to the fact that water percolates through fissures in the surface down to the hot regions beneath; here it is made steam at a high pressure, and thus forces for itself a passage through the superincumbent crust, urging with it molten matter, and the débris caused in the upheaval of the strata, to produce a vent. Whether water be a requisite to volcanic action or not, one thing is certain, that no volcano can exist without heat. Many geologists hold that the centre of the earth is still composed of molten matter, and that the lines traced by the volcano-chains mark the direction of vast fissures in the earth's crust up which, by the pressure of steam, the lava is forced. A grave objection at once appears to the acceptance of this assumption. If this be the case, according to the laws of hydrostatics, the pressure exerted at one point by the expanding steam must be felt by the whole liquid mass, for liquids transmit pressures equally in all directions; hence the same force which throws into action one volcano, must also Fig. 11. adherents of the eruption theory, whilst Humboldt, Elié de Beaumont, Dufrènoy, and others, maintain the theory of elevation. We shall find that there is some truth in each theory, but that no volcano owes its origin entirely to elevation or eruption, both processes having taken part in the erection of the mountain. It is supposed that all the volcanoes in the world are members VOL. III. cause all the neighbouring cones to erupt. This argument finds a remarkable example in one of the Sandwich Islands. Mauna Loa is a volcano frequently active; there is a crater near its summit, 10,000 feet above the level of the ocean; 6,000 feet up one flank is another crater, Kilauea. It often happens, that while Loa is in action, the lava in Kilauea is molten, yet undisturbed. It seems an inevitable conclusion, that if these eraters both derive their lava from the same reservoir, the force which propels the molten matter to the higher crater must cause a jet of lava to be thrown from Kilauea to a similar height. That simultaneous disturbances would take place in each crater, if their ducts led to the same reservoir, may be fairly inferred from the fact, that we have numerous accounts of volcanic action occurring at the same moment at many distant points: for example, a severe earthquake visited Chili in 1835; at the same moment the shock was felt over a wide area; the two volcanoes, Vantales and Osorno, burst into action; and at Juan Fernandez, 720 miles distant, a submarine eruption took place. Thus the commotion in some deep-seated reservoir affected a tract of country 900 miles long and 600 broad. 68 It has long been a theory pertinaciously adhered to, that the centre of the earth is now in a state of molten incandescence, and that all volcanoes derive their igneous action from the heated centre. In conjunction with the existence of burning mountains, another fact is adduced, which appears to give great weight to the supposition. It is generally found that in descending the crust of the earth the temperature increases. Numerous observations in mines and artesian wells have been made, and it is concluded that in England the thermometer rises 1° Fahr. for every 55 feet descended. The reader must not suppose that this increase is at all uniform; indeed, Kupffer, from very extensive comparisons, infers that the increase is 1° Fahr. for every 37 feet, while Cordier gives the same augment of temperature for 45 feet. English geologists, from experiments made in this country, incline to the first-mentioned figure. Admitting that the temperature increases because we descend nearer to the heated nucleus, these differences might be reconciled by taking into consideration local causes, such as the conducting power for heat of the rock in which the mine or well was sunk-which would materially affect the observation-the proximity of the ocean, and other causes. But cases are recorded where the same mine has altered its temperature very considerably: for example, the Oatfield Mine, in Cornwall, 182 fathoms deep, had a temperature of 77° Fahr. while the mine was working. After the abandonment of the workings the temperature was reduced in a few months to 66°. In many months after, the equilibrium reached was almost that of the mean temperature of the surface, 54° Fahr. It is clear that if the original high temperature were due to the central fire, the mere abandonment of the mine could not have reduced it. Presuming the increase of temperature, as we descend, be due to the approach of the central heat, at a depth of twenty-five miles a temperature sufficient to fuse such rocks as basalt and porphyry must exist. when the chemical action was exhausted. Moreover, we must remember that air in a condensed state acquires a lower specific heat, that is, its capacity for containing heat is decreased; hence an increment of heat will have a much greater effect in increas ing the temperature at the bottom of a mine than on the surface In the case of well-waters, the chemical action is induced by the gases they hold in solution acting upon the rocks through which they percolate, and on the sides of the subterranean reservoirs in which they collect. Sir Humphry Davy, Daubeny, and others. ascribe even volcanic heat to chemical action. The discoverer of the metals of the alkalies, potassium and sodium, supposed that at the base of burning mountains were vast deposits of these metals: that when water found its way to the metal it became decomposed. the metal retaining the oxygen, and the hydrogen being liberated. flamed out of the crater. The enormous scale of volcanic action, however, precludes the acceptance of this theory, and we must look for another cause of volcanic heat. Probably electricity has much to do with it; we know that electric currents traverse mineral lodes, and the Aurora Borealis proves that enormous quantities of electricity are in motion in and about the earth. If a powerful current were condensed by any cause, and forced to pass through a limited space, it would fuse the rock and supply the great necessary for the existence of a volcano. We have given a mere outline of these theories, and but very few of the facts by which they are supported. We refer the reader for further information to Lyell's "Principles of Geology," Daubeny on Volcanoes," and Scrope's "Central France.” There are 225 active volcanoes, or rather volcanoes which have been known to erupt within the last 150 years. The most remarkable European volcanoes are Vesuvius, Etna, Stromboli, one of the Lipari group, Santorin in the Greek Archipelago, and Hecla, in Iceland. The products of volcanoes are of two kinds, lava and ashes. They are not always ejected at once. In the great eruption of Vesuvius, A.D. 79, when Herculaneum and Pompeii were buried, the mountain belched forth nothing but ashes, which so completely covered the doomed cities that their very site was unknown for ages. The first authentic account of a lava current from Vesuvius is in the year 1036. The holders of this theory must, therefore, be prepared to admit that our globe has a crust of solid matter, whose thickness is represented in Fig. 10, by the breadth of the line c B; that is, if A B be the radius of the earth, 4,000 miles, the thickness of the curved line, of this, will represent the solid crust, all beneath being in a state of molten matter at a high temperature. This vast quantity of liquid cannot remain at rest, but must be traversed by currents, which would cause the temperature of the whole to be equalised; and it cannot be supposed that the mere shell would not be broken up and fused, and still more difficult is it to admit that it is possible that the proximity of such a mass at such a temperature would not affect the heat of the earth's crust, which it certainly does not. The answer given to these objections is, that we do not know the behaviour of solids under the influence of a high heat, and at the same time submitted to a great pressure; pressure may retard fusion, and that although at a high temperature, yet the rocks may not be molten; but the point of fusion must be reached a few miles further down, and therefore the objection is not removed. It is also urged that the earth's crust is a good non-conductor of heat, and instances of lava currents are adduced where the surface is In illustration of the rivers of lava which are poured out from solidified and tolerably good, and a few inches below the matter the craters, we may quote the instance given by the Rev. T. is still molten; but the cases are not parallel, the molten lava Coan, of an eruption of Mauna Loa:-"From this yawning is only a dull red, and is at rest; moreover, in due time it will fissure, from two to thirty yards wide, the molten flood rushed cool, whereas the temperature of the earth has not altered since out and spread laterally for four or five miles, filling ravines, the days of Hipparchus, who chronicled certain eclipses. Cal-flowing over plains, covering all from 10 to 200 feet deep-s culation has found that the times of those eclipses are correct, which proves that the length of the day has not altered for 2,000 years, that is, the rotation of the earth has not increased, which it must have done had the earth cooled, for then it would have contracted. Of the quantity of matter ejected by Vesuvius in the eruption of 79, history tells us that a shower of sand, lapilli, and pumice fell for eight days. Very few of the inhabitants perished ir the overwhelming of their cities. The skeletons of two soldiers in the barracks of Pompeii were found chained to the stocks, and in the cellars in a villa in the suburbs of the city seventeen skeletons were discovered. The form of a Roman lady, with an infant in her arms, was imprinted in the rock, but nothing but the bones remained, which a chain of gold encircled, and the rings still adorned the fleshless fingers. Herculaneum is buried deeper than Pompeii, but was discovered first by the sinking of a well in 1713, which came down upon the theatre. An illustration of the height to which a volcano can eject ashes was afforded by one of the Mexican mountains in 1835, ashes from which fell in Jamaica, 700 miles distant, and must have been in the air four days. The late Mr. Hopkins attempted to calculate the thickness of the earth's crust from the influence which the moon exerts upon the earth, causing what is called the precessional motion of the earth's pole. He found that, assuming the earth to be a duid nucleus enclosed by a solid shell, it was necessary that this should be at least 800 miles thick to cause the calculation to agree with observation. The heat in mines, etc., can be well accounted for, without this "central heat theory," by chemical action. Freshly exposed surfaces, especially metallic lodes, are vigorously acted on by the oxygen of the air; heat is thus developed. This will account for an abandoned mine cooling down to the ordinary temperature lava current, including windings, seventy miles long." Before leaving this part of our subject, we must allude to the peculiar phenomenon exhibited in the Geysers, in Iceland. Whatever part steam may play in a volcanic eruption, there is no doubt but that the Geysers owe their action to its agency. The springs are thirty miles from the crater of Hecla: they are springs of hot water, which rise through a bed of lava with such force as to play in the air to a height of 200 feet for five or six minutes, then the column of water subsides into the basin, which is like a volcanic crater, and is in communication with a cavern beneath. The pipe of the Great Geyser descends perpendicularly 78 feet, and is from 8 to 10 feet in diameter. The eruption commences with a distant rambling noise, which comes nearer, the water in the pool becomes agitated, and at length rises in a jet, with clouds of vapour and a loud explosion. It is remarkable that an eruption can be caused in some of the noch nichts geben und nichts springs by throwing stones into their pipes. The explanation of their action will be given by consulting Fig. 11. The water percolates through the rock, and collects in the cavern. Here it is heated by the volcanic fires; on account of the length of the pipe the water in the cavern is under great pressure, and hence its boiling point will be several degrees above 212° Fahr. When sufficient steam accumulates in the cavern it ejects the water from the pipe, and thus the liquid in the reservoir being relieved of its pressure generates a large quantity of steam suddenly, producing the eruption. When a stone is thrown into the pipe it disturbs the water, affecting the prossure, and giving an opportunity for more steam to be formed, which gives rise to the eruption. herbeikam, da nun der Geburtstag des Vaters Alss noon dair gai-bõõrts'-tac dess fah'-terss herr-by'-kahm, dah fammelten die brei jüngsten Kinder Blumen, tie allerschön zam-mel-ten dee dry yûnk'-sten kin ́-der bloo ́-men, dee al'-ler-shō'n'ften und gang heimlich, und flochten sie, daß es der Bater nicht sten ont gants hime'-lly, dont floch'-ten zee, dass ess dair fah'-ter nyt sab, zum schönen Kranze und konnten die ganze Nacht fein zah, toom sho'-nen kran'-tsai õõnt kon'-ten dee gan'-tse Auge zuthun. cu-gai teoo-toon. nacht kine alle brei in das Käm dry in dass kem'Bater nicht höre, A ter Tag erwachte, gingen fie Alss dair tad err-vach-tai, ging'-en zee al'-lai merlein mit bloßen Füßchen, daß es der mer-line mit blo'-ssen fü'ss'-yen, dass ess dair fah'-ter niyt hō'-rai, trugen den Blumenkranz alle drei, und legten ibn dont troo-ghen dain bloo'-men-krants al'-lai dry, oont ley y'-ten een auf des Baters Bett ganz leife, daß c8 der Bater nicht cuf dess fah-terss bet gants li'-zai, dass ess dair fah-ter nyt merte. Der Vater merkte es wohl, aber er that, als merr-kai. Dair fah-ter merrk'-tai ess vole, ah'-ber eyr taht, alss to et Schliefe. op eyr shlee'-fai. llat als es nun Morgen war, ba fam ter Bater und nt alss ess noon mor'-ghen vahr, dah kahm dair fah'-ter ŏŏnt batte ten schönen Blumenkranz und sagte: Wo sind die hat-tai dain sho'-nen bloo'-men-krants ŏŏnt zahdh'-tai: Vo zint dee Engelein, die mich bekränzet haben in der Nacht, da ich eng-ai-line, dee my bai-kren'-tset hah-ben in dair nacht, dah lý iche! Und die Kinder Famen und hingen an ihm, küßten sbleef! čont dee kin'-der kah'-men ŏŏnt hing'. -en an eem, küss'-ten den Bater und waren voll Freude. dain fah-ter öönt vah'-ren föll froi'-dai. fertigen, wir sind noch so klein? noch nyts ghey'-ben dönt niyts ferr'-ti-ghen, veer zint noch zo kline? Da nahm der Vater alle drei, das Mägdlein und die beiden Dah nahm dair fah'-ter al'-lai dry, dass meyýt-line dont dee bi-den Buben, und drückte fie an sein Herz und sagte: geboo'-ben, dont drück'-tai zee an zine herrts oðnt zahch'-tai: 0 gaidenket nicht, daß eure Gabe geringer sei in meinen Augen. den'-ket nyt, dass oi-rai gah'-bai gai-ring'-er zi jn mi'-nen ou ́-ghen, Klopfen doch eure kleinen Herzlein so gut wie die andern Klop-fen doch oi-rai kli'-nen herrts'-line zo goo't vee dee an ́-dern und mein Baterherz ont mine fah"-ter-herrts' fü'r oiy al'-lai. für euch alle. Angebinde, n. keep- 8. Der VOCABULARY. with wreaths. Bote, m. messenger. hungrige Dair hoong'-ri-gai Heim, home. Aus der Frembe, from Fertigen, to prepare, Drücken, to press. Araber. Ein Araber war verirrt in der Wüste. Zwei Tage harte Ine a-ra-ber vahr ferr-irrt in dair vü"-stai. Tsvi tah'-gai hat-tai er nichts zu essen und war in Gefahr, Hungers zu fter eyr niyts tsoo ess -sen oont vahr in gai-fahr, hoỡng-e -ers tsoo shterr ben, als er endlich eine von den Wassergruben antraf, Cent ben, alss eyr ent-ly i'-nai fon dain vass'-ser-groo'-ben an'-trabf, an denen die Reifenden ihre Kameele tränken. Hier sah er dey'-nen dee ri'-zen-den ee'-rai ka-mey'-lai treng'-ken. Here zab eyr auf dem Sande einen kleinen levernen Sack liegen. Gott fei ouf daim zan-dai i-nen khi-nen ley-der-nen zack lee-ghen. Got zi gelobt, sagte er, als er ihn aufhob und anfühlte; bas gai-lo'pt', zahdh'-tai eyr, alss eyr een ouf'-hope sont an'-fü'l-tai; dass er Da fam ein Mann, ein Bote, der brachte ein feines Dah kahm ine man, ine bo-tai, deyr brach'-tai ine fi'-ness runtes Fäßlein mit Reifen; darinnen war schöner Wein von roon-dess fess'-line mit ri'-fen; da-rin'-nen vahr sho'-ner vine fon Hochheim, das Herz bes Baters ju erfreuen. Ho'd-hime, dass herrts dess fah-terss tsoo err-froi'-en. der Bater erfreuet, als er sah, daß der alteste dair fah'-ter err-froi-et, alss eyr zah, dass dair el-tai-stai zone ess gefeubet, und die Kinder tanzten um den Bater und bas ga-zen'-det, dont dee kin'-der tants'-ten oom dain fah'-ter oont dass Grube, f. pit. Baflein. les' line. Da war Darnach trat ber Bater an den Tisch und fand ein fein Dahr-nahdy traht dair fah-ter an dain tish oŏnt fant ine fine grses Blatt, darauf war ein schöner und frommer Gesang gro-cess blat, dah-rouf vahr ine sho-ner oŏnt from'-mer gai-sank' stem groeiten Sohne, der aus der Fremde heimgekommen fon daim tsvi-ten zo'-nai, deyr ouss dair frem'-dai hime'-gai-kom-men Und als der Bater e8 las, da lächelte er und tie Tahr. But alss dair fah'-ter ess lahss, dah ley'-yel-tai eyr ŏŏnt dee Thränen fielen auf das Blatt. Da saben die drei Kleinen den trey-nen fee-len ouf dass blat.-Dah zah'-en dee dry kli'-nen dain Bater an und sagten : Lieber Vater, nicht wahr? wir können fah-ter an oont zahch'-ten: Lee-ber fah'-ter, nyt vahr? veer kon'-nen 3. The company 1. I am nineteen years old, and in my twenty-third year I shall go with my father to England. 2. My eldest brother had invited twentyfive persons, among whom nearly half were married. left us at a quarter to twelve. 4. Columbus discovered America in the year 1492. 5. A dozen contains twelve (pieces), and a pound contains thirty half ounces (German measure). 6. We bought three casks of oil, two pairs of shoes, and seven yards of cloth. 7. Thousands of Germans emigrate to America. 8. I have sold a hundred pens for half a dollar. 9. Shakespeare's birthday is the twenty-third of April It has long been a theory pertinaciously adhered to, that the centre of the earth is now in a state of molten incandescence, and that all volcanoes derive their igneous action from the heated centre. In conjunction with the existence of burning mountains, another fact is adduced, which appears to give great weight to the supposition. It is generally found that in descending the crust of the earth the temperature increases. Numerous observations in mines and artesian wells have been made, and it is concluded that in England the thermometer rises 1° Fahr. for every 55 feet descended. The reader must not suppose that this increase is at all uniform; indeed, Kupffer, from very extensive comparisons, infers that the increase is 1° Fahr. for every 37 feet, while Cordier gives the same augment of temperature for 45 feet. English geologists, from experiments made in this country, incline to the first-mentioned figure. Admitting that the temperature increases because we descend nearer to the heated nucleus, these differences might be reconciled by taking into consideration local causes, such as the conducting power for heat of the rock in which the mine or well was sunk-which would materially affect the observation-the proximity of the ocean, and other causes. But cases are recorded where the same mine has altered its temperature very considerably: for example, the Oatfield Mine, in Cornwall, 182 fathoms deep, had a temperature of 77° Fahr. while the mine was working. After the abandonment of the workings the temperature was reduced in a few months to 66°. In many months after, the equilibrium reached was almost that of the mean temperature of the surface, 54° Fahr. It is clear that if the original high temperature were due to the central fire, the mere abandonment of the mine could not have reduced it. Presuming the increase of temperature, as we descend, be due to the approach of the central heat, at a depth of twenty-five miles a temperature sufficient to fuse such rocks as basalt and porphyry must exist. The holders of this theory must, therefore, be prepared to admit that our globe has a crust of solid matter, whose thickness is represented in Fig. 10, by the breadth of the line c B; that is, if A B be the radius of the earth, 4,000 miles, the thickness of the curved line, of this, will represent the solid crust, all beneath being in a state of molten matter at a high temperature. This vast quantity of liquid cannot remain at rest, but must be traversed by currents, which would cause the temperature of the whole to be equalised; and it cannot be supposed that the mere shell would not be broken up and fused, and still more difficult is it to admit that it is possible that the proximity of such a mass at such a temperature would not affect the heat of the earth's crust, which it certainly does not. The answer given to these objections is, that we do not know the behaviour of solids under the influence of a high heat, and at the same time submitted to a great pressure; pressure may retard fusion, and that although at a high temperature, yet the rocks may not be molten; but the point of fusion must be reached a few miles further down, and therefore the objection is not removed. It is also urged that the earth's crust is a good non-conductor of heat, and instances of lava currents are adduced where the surface is solidified and tolerably good, and a few inches below the matter is still molten; but the cases are not parallel, the molten lava is only a dull red, and is at rest; moreover, in due time it will cool, whereas the temperature of the earth has not altered since the days of Hipparchus, who chronicled certain eclipses. Calculation has found that the times of those eclipses are correct, which proves that the length of the day has not altered for 2,000 years, that is, the rotation of the earth has not increased, which it must have done had the earth cooled, for then it would have contracted. The late Mr. Hopkins attempted to calculate the thickness of the earth's crust from the influence which the moon exerts upon the earth, causing what is called the precessional motion of the earth's pole. He found that, assuming the earth to be a fluid nucleus enclosed by a solid shell, it was necessary that this should be at least 800 miles thick to cause the calculation to agree with observation. The heat in mines, etc., can be well accounted for, without this "central heat theory," by chemical action. Freshly exposed surfaces, especially metallic lodes, are vigorously acted on by the oxygen of the air; heat is thus developed. This will account for an abandoned mine cooling down to the ordinary temperature when the chemical action was exhausted. Moreover, we must remember that air in a condensed state acquires a lower specific heat, that is, its capacity for containing heat is decreased; hence an increment of heat will have a much greater effect in increasing the temperature at the bottom of a mine than on the surface. In the case of well-waters, the chemical action is induced by the gases they hold in solution acting upon the rocks through which they percolate, and on the sides of the subterranean reservoirs in which they collect. Sir Humphry Davy, Daubeny, and others, ascribe even volcanic heat to chemical action. The discoverer of the metals of the alkalies, potassium and sodium, supposed that at the base of burning mountains were vast deposits of these metals; that when water found its way to the metal it became decomposed, the metal retaining the oxygen, and the hydrogen being liberated, flamed out of the crater. The enormous scale of volcanic action, however, precludes the acceptance of this theory, and we must look for another cause of volcanic heat. Probably electricity has much to do with it; we know that electric currents traverse mineral lodes, and the Aurora Borealis proves that enormous quantities of electricity are in motion in and about the earth. If a powerful current were condensed by any cause, and forced to pass through a limited space, it would fuse the rock and supply the great necessary for the existence of a volcano. We have given a mere outline of these theories, and but very few of the facts by which they are supported. We refer the reader for further information to Lyell's "Principles of Geology," Daubeny on 'Volcanoes," and Scrope's "Central France." There are 225 active volcanoes, or rather volcanoes which have been known to erupt within the last 150 years. The most remarkable European volcanoes are Vesuvius, Etna, Stromboli, one of the Lipari group, Santorin in the Greek Archipelago, and Hecla in Iceland. 66 The products of volcanoes are of two kinds, lava and ashes. They are not always ejected at once. In the great eruption of Vesuvius, A.D. 79, when Herculaneum and Pompeii were buried the mountain belched forth nothing but ashes, which sa com pletely covered the doomed cities that their very site was un known for ages. The first authentic account of a lava curren from Vesuvius is in the year 1036. Of the quantity of matter ejected by Vesuvius in the eruptio of 79, history tells us that a shower of sand, lapilli, and pumic fell for eight days. Very few of the inhabitants perished i the overwhelming of their cities. The skeletons of two soldier in the barracks of Pompeii were found chained to the stocks, an in the cellars in a villa in the suburbs of the city seventee skeletons were discovered. The form of a Roman lady, wit an infant in her arms, was imprinted in the rock, but nothin but the bones remained, which a chain of gold encircled, an the rings still adorned the fleshless fingers. Herculaneum buried deeper than Pompeii, but was discovered first by th sinking of a well in 1713, which came down upon the theatr An illustration of the height to which a volcano can eject ash was afforded by one of the Mexican mountains in 1835, ash from which fell in Jamaica, 700 miles distant, and must ha been in the air four days. In illustration of the rivers of lava which are poured out fro the craters, we may quote the instance given by the Rev. Coan, of an eruption of Mauna Loa :-" From this yawni fissure, from two to thirty yards wide, the molten flood rush out and spread laterally for four or five miles, filling ravin flowing over plains, covering all from 10 to 200 feet deeplava current, including windings, seventy miles long." The nature of volcanic rocks will be treated of in anoth place. Before leaving this part of our subject, we must allude to peculiar phenomenon exhibited in the Geysers, in Icela Whatever part steam may play in a volcanic eruption, th is no doubt but that the Geysers owe their action to agency. The springs are thirty miles from the crater of Hed they are springs of hot water, which rise through a bed of l with such force as to play in the air to a height of 200 feet five or six minutes, then the column of water subsides into basin, which is like a volcanic crater, and is in communicat with a cavern beneath. The pipe of the Great Geyser desce perpendicularly 78 feet, and is from 8 to 10 feet in diame The eruption commences with a distant rumbling noise, wi comes nearer, the water in the pool becomes agitated, an length rises in a jet, with clouds of vapour and a loud explo It is remarkable that an eruption can be caused in some of the noch nichts geben und nichts fertigen, wir sind noch so klein? springs by throwing stones into their pipes. noch niyts ghey'-ben oont niyts ferr'-ti-ghen, veer zint noch zo kline? Da nahm ber Bater alle drei, das Mägdlein und die beiden Dah nahm dair fah'-ter al'-lai dry, dass meyýt-line dont dee bi ́-den Buben, und drückte fie an sein Herz und sagte: Dgeboo'-ben, oont drück'-tai zee an zine herrts oont zahdy'-tai: O gaidenfet nicht, daß eure Gabe geringer sei in meinen Augen. den'-ket niyt, dass oi'-rai gah'-bai gai-ring'-er zi jn mi'-nen ou ́-ghen. Klorfen doch eure Fleinen Herzlein so gut wie die andern Klop'-fen dod oi-rai kli'-nen herrts'-line zo goo't vee dee an ́-dern ont mine fah"-ter-herrts' fü'r oiy al-lai. Baterherz für euch alle. The explanation of their action will be given by consulting Fig. 11. The water percolates through the rock, and collects in the cavern. Here it is heated by the volcanic fires; on account of the length of the pipe the water in the cavern is under great pressure, and hence its boiling point will be several degrees above 212° Fahr. When sufficient steam accumulates in the cavern it ejects the water from the pipe, and thus the liquid in the reservoir being relieved of its pressure generates a large quantity of steam suddenly, producing the eruption. When a tone is thrown into the pipe it disturbs the water, affecting the prossure, and giving an opportunity for more steam to be formed, shich gives rise to the eruption. READINGS IN GERMAN. VII. nun der 7. Das Geburtstag des Vaters herbeikam, ta Als noon dair gai-bõõrts'-tadh dess fah'-terss herr-by'-kahm, dah melten die trei jüngsten Kinder Blumen, tie allerschön ammelten dee dry yünk'-sten kin'-der bloo'-men, dee al'-ler-sho'n'len und ganz heimlich, und flechten sie, daß es der Vater nicht stenint gants hime-ly, dont floch'-ten zee, dass ess dair fah'-ter nyt ich zum schönen Kranze und fonnten die ganze zah, tom sho'-nen kran'-tsai dont kön ́-ten dee gan-tse Sage zuthun. -ai tsoo-toon. Meter Tag erwachte, gingen fie alle Alss dair tad err-vach'-tai, ging'-en zee al'-lai marlein mit bloßen Füßchen, daß mer-line mit blo-ssen fü'ss'-yen, dass e8 der Nacht kein brei in das Käm dry in dass kem'Bater nicht höre, ess dair fah'-ter niyt hō'-rai, tragen ten Blumenkranz alle trei, und legten ibn st troo-ghen dain bloo-men-krants al'-lai dry, oont ley y'-ten een aftes Baters Bett ganz leife, daß Bater nicht af dess fah-terss bet gants li'-zai, dass ess dair fah'-ter niyt arrie Der Bater merkte es wohl, aber er that, als Dair fah-ter merrk'-tai ess vole, ah'-ber eyr taht, alss mer-kai. Schliefe ablee-fai. der at als es nun Morgen war, da fam ter Bater und Wat als ess noon mor-ghen vahr, dah kahm dair fah'-ter oont Satte ten schönen Blumenkranz und sagte: Wo sind die ta dain shō-nen bloo ́-men-krants dont zahd-tai: Vo zint dee Fagerin, die mich bekränzet haben in der Nacht, da ich line, dee my bai-kren'-tset hah'-ben in dair nacht, dah lý Und die Kinder tamen und hingen an ihm, küßten doont dee kin'-der kah-men oont hing.e en an eem, küss'-ten Sater und waren voll Freude. fah-ter sont vah'-ren föll froi-dai. De fam ein Mann, ein Bote, der brachte ein feines Lah kahm ine man, ine bo'-tai, deyr brach'-tai ine fi'-ness Fäflein mit Reifen; darinnen war schöner Wein von a-dess fess'-line mit ri-fen; da-rin'-nen vahr sho'-ner vine fon Catheim, das Herz des Baters zu erfreuen. Bhume, dass herrts dess fah'-terss tsoo err-froi'-en. Da war Bater erfreuet, als er sah, daß der älteste der fan-ter err-froi'-et, alss eyr zah, dass dair el-tai-stai zone ess gard, und bie Kinder tanzten um ben Bater und bas -det, dont dee kin'-der tants'-ten oom dain fah'-ter oont dass Darnady trat ter Bater an den Tisch und fand ein fein Jahr-nahd traht dair fah'-ter an dain tish dont fant ine fine id Blatt, darauf war ein schöner und frommer Gesang blat, dah-rouf vahr ine sho'-ner dont from'-mer gai-sank' reiten Sobne, der aus ter Fremde heimgekommen in tav-ten zo-nai, deyr ouss dair frem'-dai hime'-gai-kom-men Und als ter Bater es las, ba lächelte er und bie Wat alsa dair fah'-ter ess lahss, dah ley'-yel-tai eyr dont dee Sen fielen auf das Blatt. Da sahen die drei Kleinen den a fee-len ouf dass blat.-Dah zah'-en dee dry kli'-nen dain sagten : Lieber Bater, nicht wahr? wir können ter au cont zahd-ten: Lee'-ber fah-ter, nyt vahr? veer kön ́-nen Ein Araber war verirrt in der Wüste. Zwei Tage harte Ine a-ra-ber vahr ferr-irrt in dair vü”-stai. Tsvi tah-gai hat-tai er nichts zu effen und war in Gefahr, Sungers zu fter eyr niyte tsoo ess-sen oont vahr in gai-fahr, hoong'-ers tsoo shterrben, als er endlich eine von den Wassergruben antraf, an ben, alss eyr ent-ly i'-nai fon dain vass'-ser-groo'-ben an'-trahf, an denen Die Reisenden ihre Kameele tränken. Hier sah er dey'-nen dee ri'-zen-den ee'-rai ka-mey'-lai treng'-ken. Here zah eyr auf dem Sande einen kleinen lebernen Sack liegen. Mott fei ouf daim zan-dai i-nen khi-nen ley-der-nen zack lee-ghen. Got zi gelobt, fagte er, als er ihn aufhob und anfühlte; bas gai-lo'pt', zahch'-tai eyr, alss eyr een ouf'-hope õõnt an ́-fü'l-tai; dass sind, glaube ich, Datteln oder Nüsse; wie will ich mich an ihnen zint, glou ́-bai lý, dat ́-teln o'-der nüss'-sai; vee vill lý mly an ee ́-nem erquicken und laben. In dieser füßen Hoffnung öffnete err-quick'-ken õõnt lah'-ben. In dee'-zer zü''-ssen höf′-nöönk öf′-nai-tai er den Sack, sah was er enthielt und rief voll Traurigkeit eyr dain zack, zah vass eyr ent-heelt dont reef föll trou-ry-kite aus: Ach, es sind nur Perlen. ouss: ach, ess zint noor perr'-len. KEY TO EXERCISES IN LESSONS IN GERMAN. 1. I am nineteen years old, and in my twenty-third year I shall go |
