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No. IV. Price SIXPENCE.—Published by HUNT AND CLARKE, 4, York Street, Covene Garden, London.

PROBABLE CAUSE OF VOLCANOS is obtained, we shall find twenty-five thou

lation the depth at, which that precise point AND EARTHQUAKES. sand six hundred feet, or about four miles (From Professor Silliman's American Jours and seven-eighths, equal to the pressure of nal of Science, for October.)

eight hundred atmospheres.

Thence it follows, that at the depth of

four miles and seven-eighths the air would be The air of the atmosphere at the surface of compressed in the bell 10 the same density the earth will support, in barometer tubes, with the sea water. mercury at

30 inches, But now, when arrived at this point, if we fresh water at

33 feet, plunge the bell more and more into the sea, and sea water at about 32 feet. the density will still increase, and will soon It is 828 times lighter than fresh water, exceed that of the surrounding water ; at

: : 0,00120 : 1. that moment what will become of the bubble And because fresh water is to sea water as of air contained in the bell, if even we sup1000 is to 1029, so air is 853 times lighter pose it to be upset ? than sea water, or

: :: 0,00118 : 1. W’ill it come up and break at the surface ? But for reasons to be explained in the It cannot, for, by the supposition, it is hea. course of this article, we will assume that air vier than its own volume of water ; on the is only 800 times lighter than sea water, contrary, it must descend to the bottom, with

: : 0,00125 : 1. an increased velocity ; for its density will inThis being granted, let us suppose that a crease as it sinks, and it must remain at the bell, suspended by a metallic chain, and full bottom of the sea, just as a stone itself would of atmospheric air, is plunged into the do. ocean ; the air contained in it will be com- I request the reader to stop here, and repressed more and more as it descends, and flect one moment ; the novelty of the asser. consequently its density will be increased in tion, that a bubble of air is precipitated to proportion to the depth it penetrates.

the bottom of the sea, instead of rising to its The following table will show the ratio of surface, merits to be examined with attention the condensation compared with the depth of before it is admitted ; if it can be destroyed, the immersion.

either by argument or experiment, the res mainder of this article becomes useless, for all that follows is in the form of corollaries from this first principle; but if, after a close and severe examination, the reader, as well as myself, is convinced of its truth, let us then proceed together.

If a series of bells, similar to the one just described, were constantly in operation through the whole extent of the ocean, there would soon be, under the water of the sea, a layer of compressed air of its whole extent. But bas nature provided for such an apparatus ? Yes, she has, with the simplicity, ease, grandeur, and efficacy that she shows in all her operations ; let us merely study her laws, and we shall soon discover it.

Let us take a glass of water from a running spring; let us expose it for some time to the light and heat of the sun; we shall soon observe bubbles rising from every part of the water, collecting at the surface, and breaking the one after the other. Let us put some of the same water into a convenient vessel by the fire, and we shall again observe a rising of bubbles before the moment of ebullition; and, still better, let us put some of it into a glass under the receiver of an airpump, and produce a vacuum, when the

bubbles will rise with great celerity ; let us From this table it appears that the point collect the air thus disengaged, and we shall at which the density of the atmospheric airfind its quantity a little above four per cent. would be exactly equal to 1, or equal to the in bulk of the water under experiment. density of sea water, is to be found between The water of the sea, always under full 16,352 and 32,736 feet immersion in the atmospheric pressure, is constantly agitated sea. And if we wish to determine by calcu. by the wind, and, being divided at its surVOL. I.

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No. IV.-NOVEMBER 22, 1828.

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face into waves and breakers, it so multiplies arrive at any positive result would require no its points of contact with the atmospheric air, small trouble, and meet with many difficul. that it, of course, absorbs all that its affinity ties, as the analysis should be performed at for it, under these circumstances, allows. sea, in different latitudes, and upon water Moreover, all rain water being divided into taken at various depths. It is probable, drops, the most favourable condition for its however, from what information we can col. combination, brings down water perfectly satu. lect, that the relative proportion the three rated with air, and the whole quantity of rain gases is altered ; that the absorbed air corithat falls on the globe goes ultimately to the tains nore carbonic acid, less azote, and the sea, whether it falls directly into it, or whe- same relative quantity of oxygen, which al. ther it is carried to it by rivers flowing down teration must increase its density. These and renewing constantly their surfaces, all considerations have induced us, in the forewhich circumstances unite to supply the sea going table, to represent the density of the with a new and perpetual addition of com- air and water by the numbers 800 and 1, bined atmospheric air ; it may then be ad- instead of 853 and 1. This is the explanamitted that the sea water is coinpletely satu

tion we have promised to give. rated with this fluid.

The depth of the sea water is not a varia. We have seen, in one of the preceding ble, it is an absolute quantity ; a measure paragraphs, that the affinity of the air for which will be determined to a foot by cal. water is very weak. Is it a chemical com. culation as soon as we have exactly the bination, or merely an affinity of cohesion ? relation of the three gases it contains. By It matters not which opinion we form in that our computation, which is, however, not far respect, for true it is, that the least change from the truth, we found it twenty-five in the temperature, or in the relative den- thousand six hundred feet, or four miles and sities, destroys their union. We have just seven-eighths; but whatever be the depth, seen that in spring water, by the mere sub- at the point of contact, the air must be extraction of the atmospheric pressure, the air actly of the same density with the water. It resumes its gaseous form, and then, from its cannot be more or less ; for, if it were less, relative levity, separates from the water, and it would rise to the surface ; if it were more, ascends and breaks into bubbles at its sur. a new quantity of it would shower again face. Now, below the depth of twenty-five through the water. thousand six hundred feet, the air is denser Air compressed under such an immense than the water ; and if a density different weight must have a tremendous force of from that of the water in minus has been elasticity. It is superior to any thing we sufficient to operate their disunion, a similar have as yet produced in our most powerful difference in plus must produce the same engines, not excepting Perkins's high preseffect. A bubble of air, under the pressure sure steam artillery ; so that, if we conceive of eight hundred atmospheres, small as we a tube of suflicient length and resistance to may conceive it, is still a bubble of air, and open a communication through the sea be. its density being superior to that of the me- tween that immense reservoir of compressed dium in which it is placed, it must plunge air and our atmosphere, the projectiles placed to the bottom, performing exactly what we in this tube would acquire a velocity several have ascertained to be the case with the bell. times greater than that of a cannon ball; I conceive that these bubbles collect together this air then must penetrate, under ground at in sinking, just as they do in rising, making four miles and seven-eighths below the sur. a constant shower at the bottom of the sea, face of the earth, through the crevices of the to supply the constant consumption of it, as rocks, and in all the subterranean vacuities we shall soon have occasion to state.

which communicate with each other, or with Until this moment we have called the air the general reservoir of air. And if it meets absorbed by water atmospheric air; which, there, or rather, when it meets there comaccording to the multiplied experiments bustible substances, as bitumen, sulphur, made on it, appears to be a compound of 24 coal, &c. a conflagration must ensue, which oxygen, 75 azote, and I carbonic acid gas; is constantly supplied with a new quantity of total 100. Whereas, the air absorbed by blowing air, forced by the pressure of the water, although a compound of the three sea, as if by a permanent forge bellows. The same gases, contains them in different pro. air, after having supported combustion, rareportions. The analysis of the air contained fied by the heat, opens its way, and issues by in spring water has been made at different apertures at the summit of volcanic moun. times, in different places, and by different tains, which we have called craters, as it persons, and, consequently, the results are does in common chimneys at the top of the all different and uncertain. The analysis of flues. Such is our conception of these subthe air contained in rain water, river water, terranean fires called volcanoes, considered in and particularly sea water, should be the their quiet and peaceful operation. object of our immediate researches, as going It would be difficult to conceive how more directly to our purpose ; but I could combustion should be constantly supported not find any publication on this subject. To under ground without a constant supply of

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air; and we do not perceive how that air another part decomposed : steam and hydrowould be brought into those subterranean gen gas are produced in immense abundance; cavities, except by the means just suggested; these fluids must open their passage ; water we see no hole or opening which might be is repulsed back into the sea, which rises considered as a draught for the passage of above its natural level, under the appear. air; on the contrary, all the apertures ob- ance of a huge tide or wave; another part served emit gases that may be considered as may be thrown off through the gaping the result of the conflagration of combusti. ground, and even may issue mixed with the ble bodies, and decomposition of water by Aames of the mountains.

In the meanfire. We see smoke ascending from the top while, new shocks are felt, until the weak. of volcanic mountains, and all these pheno- est point has yielded to the combined powers mena seem to speak in favour of our hypo. of the steam and gases, actuated by the thesis.

heat and a pressure of eight hundred atWe do not think it necessary to enlarge mospheres. Generally, the former crater, on the various products of these subterranean filled in part with loose stones, lava, and fires; a great deal has been said and pub- ashes of the preceding eruption, is the weak. lished on this subject; the formation of est point; all is thrown up; a column of carbonic acid ; its emission in its natural fire, produced by the burning hydrogen, is gaseous state; its combination with lime, raised to the clouds ; ashes, the result permagnesia, metallic oxides, &c. ; its abun. haps of twenty years' combustion, in suffi. dance in mineral waters ; the flowing of hot cient quantity to bury villages and cities, water springs, either simple or sulphurous; and stones of all sizes, loosened, are prothe rushing out of hydrogen gas, sulphuretted jected to an immense distance; and, finally, or carburetted : these results are the natural the lava, swept away by the steam, gases, effects of these permanent fires, considered and blowing air, is raised up to the summit in their quiet state.

of the crater, or runs on one side of the Now, it is time to present our readers mountain, after having broken open a pas. with the complement of the theory by the sage by its

mass and weight. spectacle of an eruption. A large volcano When the steam and gases are exhausted, may be considered as a whole coalery on fire, when the lava has flowed out for some time, several miles and perhaps several hundred the eruption decreases, and finally is stopped, miles in extent, five miles under ground, because the column of lava in the crater, that is to say, under the inferior level of the being of a density superior to the water of sea water; coals, bitumien, sulphur, &c. are the sea, chokes the passage, and the volcano constantly burning; minerals, sand, and must then resume its quiet operation. stones are melting, vitrifying, and running But why should I endeavour to describe at the bottom of the cavern in the shape of what must happen? Let us rather ascertain lava, of which it forms a permanent lake in what has happened, and see whether the fusion, just as melted iron is collected at the facts recorded agree with the theory here prebottom of a casting fumace. These things sented. being in this situation, if a sudden vacuum One of the first historiaris who gives an is produced, what will happen ? But I may account of Vesuvius, is, I believe, Pliny the be stopped here, and be asked, how can a younger. We read in his Epist. xx. lib. vi. sudden vacuum be produced ? I see many these remarkable words : causes why it may, but the most simple and “ Preterea mare in se resorberi et tremore natural, and consequently the least objec- terræ quasi repelli videbamus. Certè protionable one, is, that after a certain time, a cesserat littus, multa animalia maris siccis number of years that cannot be foreseen, for arenis detinebat. Ab altero latere nubes atra it is not periodical, a layer of the coal being et horrenda ignei spiritûs tortis vibratisque burnt, reduced to ashes, the mineral to lava, discursibus rupta, in longas flammarum the ground above, no longer supported, figuras dehiscebat; fulgoribus illæ et similes crumbles down, with a rumbling noise; a et majores erant.” new surface of cold ground is put in contact The retreat of the sea, and its sudden with the overheated air and vapours, and a return by the effect of the elasticity of the sudden condensation is produced ; a partial fluids, seems to be one of the best ascervacuum follows: it is so sudden, that it tained facts. communicates a tremor to the surrounding ground, which is felt as the first shock of an Eruption of Vesuvius, 1730, by Nicholas earthquake. This vacuum produces in its

Cyrillus, Phil. Trans. vol. 37. turn a violent aspiration, that brings down 66 March 8th. Vesuvius sends forth a great the water of the sea itself, and of all the smoke and stream of fire, with hollow rum. streams that may communicate with that bling. 9th. The following night Vesuvius furnace. Then, a reverse effect is produced ; thundered as it were twice. 10th, 11th, 12th. water coming in contact with the melted The clouds hide the smoke and fire. 13th. lava and the burning coals, is acted upon in Smoke lessened. 14th. In the evening, after two different ways; a part is vaporised, and eight o'clock, the fire arose to a vast height.

The sea

Pumice stones, red hot, of two or more We have expatiated with some details ounces weight, were driven several miles like upon the dreadful earthquake which was so a shower of hail."

fatal to Lisbon in 1755, destroyed whole cities The blazing flame, hollow rumbling, throw. in Europe and in Africa, cost the lives pering up of smoke, ashes, and stone, are but haps of one hundred thousand human beings, the natural results already anticipated. and was felt upon a surface of more than one Colleclion of various papers concerning We have taken into consideration particu

million square miles at the same moment. Earthquakes felt in England in 1750. larly its effects upon the water of the sea. Phil. Trans. vol. 46.

The detonation took place under ground, or " The mighty concussion was felt pre- rather under the sea, in that space which we cisely at the same instant of time, being suppose filled with condensed air, below its about half an hour after twelve at noon. inferior level. If we should wish to locate Let us reflect on the vast extent of this precisely the centre of concussion, judging trembling, one hundred miles in length, from its intensity and direction, it seems to be, and forty in breadth, which amount to four between the Azores, Madeira, and the contithousand square miles in surface. That this nent.

was swelled at the same should be put into such an agitation in one moment from the thirtieth degree of latitude moment, is such a prodigy, as we would to the fiftieth, that is to say, on the coast of never believe, did we not know it to be a Africa from Morocco up to Tangier, on the fact, from our own senses.'

coasts of Spain and Portugal, France, HamThe astonishment of the writer of this burg, the coast of England, and even to the paragraph would have ceased, if he had con- north of Scotland. However, a fact obceived, as ourselves, that the vacuum pro- served by Captain Affleck, of the Advice duced in a receiver is almost instantaneous man-of-war, then at Antigua, and recorded in all its parts, whatever be its extent, or is in the Philosophical Transactions, vol. 49, filled as instantaneously, because steam and surpasses in wonder even all this : gases rush into a vacuum at the rate of thir- " On the first of November last, you had teen hundred and five feet in a second of a remarkable Aux and reflux of the sea at time, under the pressure of one atmosphere: Portsmouth, and other parts of the coast, what then must it be under eight hundred ? which was agitated in like manner at the The following extracts will come again in same time, on the coast of America, and all support of this assertion.

these islands."

If by the words “ same time" is meant the Account of an Earthquake at Lisbon, No

same hour, it is in fact three hours later, on vember 1st, 1755. Dr. Wolfal. Phil.

account of the difference of longitude, and Trans. vol. 49.

the distance between the point of explosion “ Soon after the shock (forty minutes across the Atlantic to the Antilles, being past nine), which was near high water, the about four thousand miles, and will give a tide rose forty feet higher, in an instant, velocity of two thousand and forty feet in a than was ever known, and as suddenly sub- second of time. This velocity cannot be sided."

that of a wave of water ; it must be, it can The same at Cadiz, November 1st, 1755. fluid or gas of a greater density than atmos.

be, but a velocity of percussion in an elastic Benjamin Bewick. Phil. Trans, vol. 49.

pheric air. This fact, and similar ones, will “ Just before ten, the whole town was enable us one day to give not only a matheshaken with a violont earthquake they saw matical demonstration of the existence of rolling towards the city a tide of the sea, such a fluid under the sea, but also to calcu. which passed over the parapet of sixty feet late exactly its density. above the ordinary level of the water-the Let us proceed in our investigation. waves came in this manner four or five times, but with less force each time.”

Earthquake in Calabria, 1638. At Arzila, “ it happened about the same In Goldsmith's History of the Earth, is time.”

an account of that great convulsion of nature, Agilation of the Waters. November lst, translated from the celebrated Father Kira 1755. John Pringle.

Phil. Trans. cher, from which we extract the two follow. vol. 49.

ing observations :

i The Gulf of Charybdis, which we ap“ About ten o'clock of the forenoon, at a proached, seemed whirled round in such a seaport of the Frith or Forth, about seven manner as to form a vast hollow, verging to miles higher up than Leith, the water was a point in the centre.” observed to rise very suddenly, and return And afterwards : again with the same motion : and this con. 66 The sea itself seemed to wear a very tinued for three or four minutes, it being unusual appearance. Those who have seen then calm ; but after the second and third a lake in a violent shower of rain, covered all rush of water, it was always less."

over with bubbles, will conceive some idea of

return

its agitation ; my surprise was still increased “ The water at the great fountain at by the calmness and serenity of the weather; Torre del Greco began to decrease some days not a breeze, not a cloud

before the eruption. It was necessary in all The rushing of the sea into a subter. the other wells of the town and its neighranean abyss cannot be better demonstrated bourhood to lengthen the ropes daily to than by the first observation, and the ejec- reach the water, and some of the wells betion of gases through its water, than by the came quite dry." second.

“ Subterranean noises were heard at Resina

for two days before the eruption. Soon Earthquake in Sicily, 1692. Schenchxer. after the beginning of it, ashes fell thick Phil. Trans. vol. 33.

at the foot of the mountain-and though “ Just at the time of the second shock, there were not at that time any clouds in the the sea retired from the land, all along the air, the ashes were wet, accompanied with coast, leaving its bottom dry for a consider- large drops of water, which were to the able distance, and in a few minutes it re- taste very salt. turned again with great fury, and overflowed “ After some time, the lava ran in abun. the shores. In many places the earth gaped dance, freely and with great velocity. The prodigiously.-Out of all these openings frequent falling of the huge stones and scoriæ, sprung forth a great quantity of water, which were thrown up to an incredible height, which drowned the neighbouring places. from some of the new mouths, one of which, This last (shake) was stupendous beyond having been since measured, was ten feet imagination, the fiery eruption of the burn- high, and thirty-five in circumference, &c. ing Ætna throwing out a prodigious quan

* It is impossible that any description tity of flames, stones, and ashes, &c." can give an idea of this fiery scenie, or of the

horrid noises that attended this great ope. Earthquakes in the two Calabrias, Messina, ration of nature. It was a mixture of the

ge. 1783. By Sir Wm. Hamilton. Phil. loudest thunder with incessant reports, like Trans. vol. 73.

those from a numerous heavy artillery, ac

companied by a continual hollow murmur, “A shock had raised and agitated the like that of the roaring of the ocean during a sea so violently, that the waves went furi- violent storm ; and, added to these, was anously three miles inland, and swept off in its other blowing noise, which brought to my

two thousand four hundred and mind that noise which is produced by the seventy three of the inhabitants of Scilla, &c. action of enormous bellows at the furnace of

“ At the moment of the earthquake the the Carron iron foundry in Scotland, and river disappeared, and returning soon after, which it perfectly resembled, &c." overflowed, &c.

If this last paragraph had been written “ The officer who commanded in the with the direct intention of supporting our citadel (Messina), assured me that, on the theory, could Sir Wm. Hamilton have made fifth of February, and the three following use of other expressions ? days, the sea, about a quarter of a mile from

We will here recapitulate in a few words that fortress, rose and boiled with a most the whole of the hypothesis. We have enhorrid noise, &c."

deavoured to establish that the surface of Eruption of Mount Vesuvius, June 12th, the earth, as deep as four miles and seven

1794. Sir William Hamilton, Phil. eighths, is the domain of water ; that it canTrans. vol.

not penetrate deeper, as it there meets with

a fluid denser than itself; that either in the " The classical accounts of the eruption open sea, or between the crevices of the of Vesuvius, which destroyed Herculaneum rocks and ground at that depth, is its inand Pompei, and many of the existing ferior level, that at the surface of the earth, printed accounts of its great eruption in fresh water ascends higher than the superior 1631, might pass for an account of the level of the sea, in proportion to its relative late eruption, by only changing the date, levity, and the depth at which they come in and omitting the circumstance of the retreat contact. Below four miles and seven. of the sea from the shore, which happened eighths is condensed air which supports the in both those great eruptions, and not in combustion of inflammable bodies, and keeps this, &c."

in activity those subterranean fires, the im. The water of the sea not retiring from the mediate cause of earthquakes and volcanos; coast in this eruption seems to be an ano- that it ceases to be problematical how these maly. Whether the suction or aspiration fires under ground are not smothered for was performed too slowly, or too far from want of oxygen, and how those under the sea the shore to be observed, or whether it did are not extinguished by its water ; that we not take place at all from the sea, still we now may account for volcanic islands sud. are in no apprehension of seeing an eruption denly rising or disappearing; that it also without the presence of water; for, in the explains why carthquakes, without any outsame relation, a few lines lower, we read : ward explosion, extend to a greater distance,

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