Page images
PDF
EPUB

hano, owing to the great wave, little more than one
layer of bricks, tiles, and timber, with here and there
part of a wall left standing, could be distinguished.
From this circumstance, Concepcion, although not so
completely desolated, was a more terrible, and, if I
may so call it, picturesque sight. The first shock was
very sudden.
The invariable practice among the
residents in these provinces, of running out of doors
at the first trembling, alone saved them. The mayor-
domo of Quiriquina told me that the first notice he
received of the earthquake, was finding both the horse
he rode and himself rolling together on the ground.
Rising up, he was again thrown down. He also told
me that some cows, which were standing on the steep
sides of the island [of Quiriquina], were rolled into
the sea.
The great wave, however, was far more
destructive in this respect: on one low island near the
head of the bay seventy animals were washed off and
drowned. After viewing Concepcion, I cannot under-
stand how the greater number of inhabitants escaped
unhurt. The houses in many parts fell outwards;
thus forming in the middle of the streets little hillocks
of brickwork and rubbish. Mr. Rous, the English

consul, told us that he was at breakfast when the first
movement warned him to run out. He had scarcely
reached the middle of the courtyard when one side of
his house came thundering down. He retained pres-
ence of mind to remember that if he once got on the
top of that part which had already fallen, he should
be safe. Not being able, from the motion of the
ground, to stand, he crawled up on his hands and
knees; and no sooner had he ascended this little emi-
nence, than the other side of the house fell in, the
great beams sweeping close in front of his head.
With his eyes blinded and his mouth choked with the
cloud of dust which darkened the sky, at last he
gained the street. As shock succeeded shock, at the
interval of a few minutes, no one dared approach the
shattered ruins; and no one knew whether his dear-
est friends and relations might not be perishing from
want of help. The thatched roofs fell over the fires,
and flames burst forth in all parts. Hundreds knew
themselves to be ruined, and few had the means of
providing food for the day.

Mr. Darwin thus describes the great wave, which was estimated to have a height of from sixteen to twenty feet:

In the middle of the bay it was seen as one unbroken swell of the water; but on each side, meeting with resistance, it curled over, and tore up cottages and trees as it swept onward with overwhelming force. At the head of the bay it is easy to imagine the fearful line of white breakers which three times rushed over and almost obliterated the ruins of the former town. Pools of salt water yet remained in the streets; and children, making boats with old tables and chairs, appeared as happy as their parents were

miserable.

It is noticed by Dr. Darwin, that the walls which ran in a direction south-west by west, stood the shock much better than those which ran at right angles to them. This observation is interesting as connected with the direction of the undulatory axis, which is shown, by this and other circumstances, to have been in a north-easterly direction. It has been remarked, on other occasions of earthquakes, that all the pendulums of clocks vibrating in one direction have stopped, while all those moving in an opposite direction have continued in motion. Thus the direction of the motion given to the earth's crust by an earthquake appears to be generally determined. It has been noticed that when an earthquake reaches the junction of less with more compact strata, having first passed over the former, a sort of reaction takes place, and the

ground is torn up and twisted in an unusual and most disastrous manner.

One of the most dreadful earthquakes on record is that which, on the 1st of November, 1755, destroyed the greater part of the city of Lisbon. The only warning the inhabitants received was a noise like subterranean thunder. When the event took place they were assembled in the churches. Six minutes sufficed to destroy sixty thousand persons.

On this occasion there appeared to be a great recession of the sea, and of the water of the Tagus in connexion with it; vessels in the river having suddenly found themselves aground. Probably the general impression was incorrect, and the effects were rather due to an upheaval of the bed of the river. Shortly after, the great wave swept in, having in this instance an elevation of fifty feet. To complete the work already begun, numbers perished also, by the subsidence of a quay on which they had assembled for security. This quay, which had recently been built, vanished below the waters, and nothing was afterwards seen of it or its freight. Numerous small vessels and boats sank at the same time, but, it is said, no fragments of the wrecks appeared again at the surface.

The earthquake of Lisbon was felt over an area of 700,000 square miles, or a twelfth part of the circumference of the globe. The West Indian isles on one side were affected by it; the lakes of Scotland, Norway, and Sweden, on the other. To the south it extended at least as far as the island of Madeira, and eastward, it was felt in Italy.

A series of convulsions in Calabria, which lasted nearly four years, began in 1783, with an earthquake which is only equalled by that of Lisbon. It did not extend, like the latter, over a great extent of country, but the effects it produced within its limited sphere were even greater. It lasted only two minutes, during which brief space it destroyed all the towns and villages within a circuit of twenby the shock. ty-two miles. Messina, also, was much injured

The peninsula of Calabria Ultra, where the earthquake occurred, forms the southern extremity of Italy, is about sixty miles in length, and has a mean breadth of about twenty miles. Through the centre of the peninsula runs a chain of granite mountains, which is separated from the sea on its western side by a plain of recent strata, composed of very yielding material. The effect of the earthquake was to disconnect, throughout almost the whole length of this chain, the new with the ancient rock, leaving a chasm between them. One half of the peninsula, therefore, actually slid in the direction of the sea. From this fact alone it may be inferred what the havoc must have been. The geologist Dolomieu, who visited the district shortly after the event, says :

When I first passed over to Calabria, and first beheld Polistena, the scene of horror almost deprived me of my faculties; my mind was filled with mingled compassion and terror; nothing had escaped; all was levremained; on all sides were heaps of stones so destitute elled with the dust; not a single house or piece of wall of form, that they gave no conception of there ever having been a town on the spot. The stench of the dead bodies still rose from the ruins. I conversed with many persons who had been buried for three, four, and even for five.days.

It is stated by the Abbé Spallanzani, who visited Messina about five years after the catastrophe of

1783, that, dividing that city into four parts, two parts were levelled to the ground on that occasion, the third was half laid in ruins, and the fourth was greatly damaged. He observes that at the time of his visit, more than one half the city had been rebuilt, so that the people had left the temporary sheds in which they had been compelled to take refuge.

Earthquakes are sometimes accompanied by eruptive phenomena, but the matter ejected is generally superficial. Mud, sand, and stones, accompanied by vapor, smoke, fetid gases, and sometimes flame, are emitted from the crevices in the earth, which frequently close immediately afterwards, without leaving a trace of their existence. During an earthquake at the beginning of the last century, so much earthy matter (mixed with steam) rushed out from chasms near the town of Aquila, (at the northern extremity of the kingdom of Naples,) as to render the fields in the neighborhood unfit for cultivation for many years. Water also ascended from the same crevices to a great height. During the earthquake which destroyed Riobamba, in South America, a muddy mass containing charcoal, crystal of augite, and scales of infusoria, issued from a chasm. On another occasion, numerous hillocks resembling mud-volcanoes were thrown up, but sank again, leaving pools of water in their places.

Earthquakes are more powerful agents than volcanoes in modifying the surface of the earth. Large areas of land are raised to greater elevations or subside. Chasms are opened which are afterwards widened by rivers into large valleys. River-courses are filled up and lakes are formed. During the earthquake of Concepcion, the island of Santa Maria, seven miles long, and two miles wide, was raised eight or ten feet; and Mr. Darwin states it to be almost a certainty that it has risen

four fathoms since the convulsion of 1751. In

Cutch, a mound, fifty miles in length and several miles in width, was raised by an earthquake to a height in some places of ten feet. The mole of the harbor of Messina, which extended more than a mile in length, was entirely swallowed up in 1783, so that no vestige remained to point out

where it once was.

The following is a list, in chronological order, of the principal earthquakes on record, with the number of persons estimated to have perished :

[merged small][merged small][ocr errors][merged small][ocr errors][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][merged small][merged small][merged small]
[merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][merged small][ocr errors][ocr errors][ocr errors][merged small][ocr errors][ocr errors]

1822

1826

1827

1835

40,000

10,000

Cutch. Very few lives were lost, but a great extent of country was clevated. Aleppo destroyed.

The towns of Damascus, Acre, Tyre, and Sidon, suffered great damage, and Tiberius and afet were destroyed. In the neighborhood of Mount Ararat.

AMERICA.

[blocks in formation]

Copiapo

again destroyed;

Valparaiso, and other places in Chili greatly injured. Caraccas greatly injured. Plain of Bogota. Many towns overthrown.

Concepcion totally destroyed.

It thus appears that in the last 148 years fifteen great earthquakes have convulsed the western shores of South America, and in no case did they occur without the partial or entire destruction of at least one town. The average interval has been about ten years. Few earthquakes are recorded as having occurred in Africa, partly, perhaps, because that continent is yet but little known to Europeans. The great earthquake of Lisbon extended over the northern part of the African continent, and it is stated that a village, eight leagues distant from Morocco, was destroyed, with its inhabitants; eight or ten thousand persons having perished on the occasion.

Those who have had actual experience of earthquakes describe their sensations as being such as are given by no other events. Mr. Darwin remarks-" A bad earthquake at once destroys the oldest associations: the world, the very emblem of all that is solid, has moved beneath our feet, like a crust over a fluid; one second of time has conveyed to the mind a strange idea of insecurity, which hours of reflection would never have created.'

Basil Hall* tells an amusing anecdote, which shows the sensibility of the Chilians with respect to the slightest premonitory symptoms of these catastrophes. He relates, that while passing the evening with a family residing at Valparaiso, and when the different members of the family were busily engaged, as is customary on such occasions -suddenly," without any apparent cause, the whole party jumped up, and flew in the most frantic manner out of the house, screaming out Misericordia! Misericordia!-beating their breasts at the same time, and looking terrified beyond description.”

Travels in South America.

On reaching the street, it appeared that every one else, as if by the same impulse, had acted in a similar manner. The street was filled from end to end with persons, (some of them only half dressed,) in the same state of alarm and confusion. After standing in the street about a minute, every one entered his house, and the hubbub ceased as soon as it began.

How slight the shock which produced this strange | scene was, may be known by the fact that, until informed to the contrary, Basil Hall believed that he was witnessing a religious ceremony; and, with the view, doubtless, of complying externally with the customs of the country, did not fail (he informs us) to add his voice to those of his friends, in invoking Misericordia.

The sensibility of the inhabitants of Lisbon to slight noises is to this day a joke against them.

The number of earthquakes which occur in the course of a year is not known. In some places slight shocks are almost of daily occurrence. Slight shocks are felt occasionally in England, and, with comparative frequency, in parts of Scotland.

Sometimes an earthquake is perceived at the bottom of a mine, when it is not perceptible on the surface. This is said to have been the case in England at the time of the earthquake of Lisbon. Sometimes the converse holds good. Fourteen earthquakes, in different parts of the world, are said to have occurred in 1827. Unless parts of Africa are an exception, there is, probably, no part of the globe which has not experienced an earthquake in a slight degree.

SOLFATARAS AND HOT SPRINGS.-The phenomena of solfataras and thermal springs are attributed to the same causes as volcanoes and earthquakes. Solfatara, a word of Italian origin, is the name given to those mountains which exhale sulphureous vapors. They are considered to have formerly been active volcanoes. In one case, that of the solfatara of Puzzuoli, a volcanic eruption is said to have taken place from its crater within historical times. Solfataras are much less frequent than hot springs, and do not demand the same attention from the geologist. Their appearance, however, frequently excites attention, from the blanching nature of some of the gases evolved. The sulphuretted hydrogen and muriatic acid discharged from that of Puzzuoli, reduced the volcanic rock in contact with them to a siliceous powder. Sulphur is also deposited by the exhalations.

mentioned by Humboldt, that when the eruption of Jorullo in Mexico broke out, the waters of two rivers, which previously existed on the site of the newly formed mountain, were lost, but at some distance two thermal springs made their appearance.

Hot springs are of all degrees of temperature between that of the surrounding air and boiling water; the flow of water is generally more abundant from them than that from cold springs. They (with few exceptions) discharge at all times the same quantity of water, and their temperature and chemical constituents remain constant. There is evidence to show that the temperature of some hot springs has not diminished during the last thousand years. In Iceland, hot springs, known by the name of Geysers, are found capable of ejecting solid matter to a height of 200 feet or more. This occurs, however, only when the vents for the passage of aqueous vapor have been artificially closed. The peculiarity of the phenomena exhibited at the geysers merits a more particular description than other hot springs appear to require.

The large geyser is a nearly circular basin whose greatest diameter is fifty-six feet; its depth is about four feet. In the centre rises a tube, through which water is continually bubbling over into the basin; which process, however, is interrupted at short intervals by a sudden burst of water accompanied by a loud explosive noise. The central pipe is seventy-eight feet in depth and from eight to ten feet in diameter. The water of this geyser, when analyzed by Professor Faraday, was found to contain silica and a salt, probably of soda.

An ingenious explanation of the phenomena of the Icelandic geysers has been suggested by Sir C. Lyell. He supposes the pipe to communicate with the bottom of a reservoir into which steam also enters from crevices in the bottom, and water from the top. On this supposition, water would in the first instance collect at the bottom of the reservoir, covering both the entrance to the pipe and those which admit the steam. The steam, therefore, is condensed by contact with the water, and by parting with its heat raises the temperature of the water, which itself gives off steam, till the upper part of the reservoir is filled with steam of sufficient pressure to raise the water in the pipe. The steam, having now raised the water above itself, is enabled to escape through the water in the pipe, but should any artificial cause impede its rush through the pipe a violent explosion is the The connexion of hot springs with volcanoes is consequence. It is a common practice of travellers less evident than the similarity of solfataras and in Iceland to produce a violent movement of this the latter, for hot springs occur abundantly in coun- kind by filling up a thermal vent with solid matter. tries giving no sign at present of any volcanic It may be remarked, that the above suggestion of activity. The majority of hot springs rise either Sir C. Lyell is to be taken as indicating one of the from rocks of a volcanic nature, from mountain possible ways in which the phenomena may be chains, or from points of disruption in strata. It produced; and is not supposed to give the only exhas been remarked by Professor Forbes, who in-planation which is consistent with the observed vestigated the hot springs in the Pyrenees, (where phenomena. they are very abundant,) that they occur almost invariably at the junction of the granitic with the stratified rocks. It is strong evidence of the connexion between hot springs and volcanic phenomena, that earthquakes and volcanic eruptions are known to have affected the temperature of such springs. After the occurrence of an earthquake between Bordeaux and Narbonne, the temperature of one of the hottest of the Pyrenean springs was so much reduced as to be no longer of any value. In the year of the great earthquake of Lisbon, another There is little doubt, as we have already Pyrenean spring rose 75° in temperature. It is remarked, that the same general causes produce

Mud and air volcanoes seem to belong to the same class as solfataras and geysers. At Macalonba, in Sicily, there is a hill of dry mud, about 160 feet high. In its upper part are found a multitude of small cones not above a yard in diameter. These cones are full of soft clay, and large bubbles of gas escaping at every moment, with an exploding noise, scatter the clay around. Many similar objects occur near Modena.

volcanoes and earthquakes, smoking mountains and boiling springs. All these appearances, except earthquakes, are accompanied by heat, as one of their manifestations; they occur more frequently in volcanic regions than elsewhere; when hot springs occur in abundance in other districts, it is in those where violent earthquakes have occurred in comparatively modern times, or where much disturbance in the strata indicates such convulsions to have once been. The connection between earthquakes and volcanoes is quite certain, to the extent of slight earthquakes, and there is a general impression, as well as several striking facts, in support of a more extensive connection. It is said to be the general opinion at Naples, Messina, and Catania, that earthquakes are not to be dreaded so long as smoke escapes freely from the craters of Vesuvius and Etna. The same feeling prevails in Ecuador. The inhabitants of the elevated valleys of Quito and Hambato, residing round the bases of the volcanoes of Tungaragua and Cotopaxi, dread the visitation of an earthquake, when for any length of time no smoke has been seen rising from their craters, and they are firmly convinced that the earthquakes which have so frequently proved destructive to their country will entirely cease as soon as the porphyritic cupolas of Mount Chimborazo shall have been removed, and thus a free exit been formed for the escape of volcanic matter or vapor.

It has already been remarked that earthquakes commonly precede volcanic eruptions. There are also facts connecting volcanic eruptions with earthquakes, even when they occur at great distances from each other. Facts of this kind, too numerous and too authentic to be discredited or attributed to accident, have occurred in South America. It is stated by Humboldt, that the volcano of Pasto, which for many months had uninterruptedly emitted a column of thick smoke, ceased to do so at the very moment that the table land of Quito was convulsed by the earthquake which destroyed the town of Riobamba. The distance in this case was 220 miles.

In the years 1811 and 1812, a succession of earthquakes was felt in the islands of the Columbian sea and surrounding continent, which extended northward along the Mississippi. They did not terminate till a great eruption of the volcano of St. Vincent, which had been dormant for a century, broke out. It is supposed that these events were connected with the throwing up of the island of Sabrina, at the Azores. It was also remarked on the 1st of November, 1755, the date of the great earthquake of Lisbon, that a whirling column of smoke ascended from the crater of Vesuvius, which suddenly stopped, the smoke which had issued being even said to have reëntered the volcano. The events recorded by Mr. Darwin as having occurred simultaneously with the destruction of the town of Concepcion, in 1835, are at the same time the most striking and most indisputable on record. Mr. Darwin remarks:

Although it is known that earthquakes have been felt over enormous spaces, and strange subterranean noises likewise heard over nearly equal areas, yet few cases are on record of volcanoes very far distant from each other, bursting out at the same moment of time. In this instance, however, at the same hour when the whole country around Concepcion was permanently elevated, a train of volcanoes situated in the Andes, in front of Chiloe, instantaneously spouted out a dark column of smoke, and during the subsequent year

continued in uncommon activity. It is, moreover, very interesting circumstance, that in the immediate neighborhood these eruptions entirely relieved the trembling ground, although at a little distance, and in sight of the volcanoes, the island of Chiloe was strongly affected. To the northward, a volcano burst out at the bottom of the sea, adjoining the island of Juan Fernandez, and several of the great chimneys in the Cordillera of Central Chili commenced a fresh period of activity. We thus see a permanent eleva tion of the land, renewed activity through habitual vents, and a submarine outburst, forming parts of one great phenomenon. The extent of country throughout which the subterranean forces were thus unequivocally displayed, measures 700 by 400 geographical miles.*

From these and other considerations, Mr. Darwin is of opinion that the conclusion can scarcely be avoided, that "a vast lake of melted matter, of an area nearly doubling in extent that of the Black Sea, is spread out beneath a mere crust of solid land." Humboldt entertains a similar opinion regarding another portion of South America::-"The whole plateau of Quito must," he says, "be regarded as a single volcanic surface." These remarks naturally lead to a consideration of the different theories which have prevailed to account for volcanic phenomena.

It must be premised, that in discussing this question the geologist finds little to assist him in the truths which belong especially to his own science. It is the business of the geologist to explain the physical appearance of the globe so far as inorganic nature is concerned, and so far as it is due to mechanical causes. If he steps beyond these limits he must borrow from the astronomer, the chemist, or the naturalist, the data on which his reasonings are founded. The sciences are mutually dependent on each other, and many of the most interesting inquiries require the aid of several; but in discussing these questions it is useful to bear in mind how much of the result is due to each science, in order that the strength of each link of the chain may be separately valued. A geologist, for instance, is bound to be fully acquainted with his own science, but he is not equally answerable for the truths of other sciences. When, therefore, he undertakes to theorize beyond the pale of his science, he is bound to show clearly how many of the data rest on the independent basis of his peculiar science. this course been pursued by the many theorists who since the infancy of geology have speculated on the changes in the structure of the globe, it is probable that many rash conclusions would have been avoided. It is only when the truths of different sciences are kept apart that they can confirm each other. When no accurate distinction is made, the mind is apt to reason in a circle, by making the doubtful conclusions of one science confirm those of another, while the latter again are appealed to in support of the former.

Had

The existing theories of the internal condition of the globe have been contributed by the astronomer and chemist, but the theories which they have suggested have been scrutinized in the departments of geology and general physics, and more is being

* Mr. Darwin elsewhere remarks, that the area here given is understated. The reader may be reminded that the eruption of Coseguina, already detailed in the text, occurred on the same day as the earthquake of Concepcion. This volcano is distant 2700 miles from the sites of eruption mentioned by Mr. Darwin.

done every day in the latter sciences towards testing old theories and originating new.

The prevailing doctrine at present appears to be that which was suggested in the first instance by Leibnitz. It was remarked by that philosopher that the form of the earth is the same which it would have assumed if, with the existing laws of motion, it had originated in a fluid state.

ture of 104°. Now these facts, supposing them to be universal, clearly admit of explanation, without supposing the entire central mass of the earth to be, as some reasoning from the data have supposed, a fluid of the enormous temperature of 450,000°. It would meet the case to suppose the remainder of the earth to have that very temperature. And if the heat of fluid lava be adduced, to show that a Putting together this fact with that of the system much higher temperature exists-an evidence which of fluid rock from the interior of the earth, the cannot be denied-still we need not go beyond the hypothesis was started, that our planet was origi- facts in our theories. At the rate of 1° for every nally a burning luminous mass which has been in 45 feet, we should, at a depth of twenty-five miles, process of refrigeration since the time of its crea- attain a heat sufficient to melt almost every known tion. According to Leibnitz, a universal ocean substance. Beyond this temperature the evidence was formed, as soon as the cooling process com- does not require us to go. There remain 3975 menced, by the condensation of the vapors. Sub-miles in the earth's depth, the condition of which sequently the ocean subsided through rents in the is an open question. crust, having first deposited the matter which it held in solution.

On this hypothesis volcanoes and earthquakes are due to convulsions produced by the refrigerating process. The astronomical theory of Sir W. Herschel gave additional weight to the view of Leibnitz.

It was supposed that the gradual formation of certain heavenly bodies by the condensation of nebulous matter, could be actually seen by means of the telescope. If this nebulous matter were not itself of a high temperature, heat would necessarily be developed by its condensation. The recent discoveries by means of Lord Ross' telescope, however, have obliged astronomers to abandon the idea that nebulous matter could be distinguished as distinct from clusters of stars.

But there is strong reason for believing that throughout three fourths of the earth's superfices, the temperature does not follow any such law of increase as has been proved to take place in certain parts of Europe, and that over large areas the temperature diminishes as you descend.

From observations made by Kotzebue, Beechy, and Sir James Ross, "the extraordinary fact has been established, almost beyond a doubt, that the deep sea-water, below a certain level determined by the latitude, is of one invariable temperature throughout the globe, and that temperature a very low one; the calculations of Lenz, founded on Kotzebue's results, giving 36° Fah., and those of Ross, 39° 5'. The depth at which this temperature is attained, according to the latter authority, is 7200 feet at the equator, diminishing to 56° 26' south lat., where it attains the surface, and the sea is of equable temperature at all depths. Thence, again, the upper surface of the uniform substratum descends as the latitude increases, and at 70° has already attained a depth of 4500 feet. Similar phenomena would appear to occur in proceeding from the equator northward, the circle of constant temperature being repeated nearly in the same latitude. Thus the ocean is divided into three great regions-two polar basins, in which the surface temperature is below, and one medial one, in which it is above 39° 5."* It thus appears that the facts which have hitherto been established regarding the temperature of the earth at certain depths below the surface, afford no evidence for supposing that the interior of the globe is a fluid mass of great heat. Investigations of a profounder nature have been undertaken by M. Fourier, the well-known French philosopher, which have led him to highly interesting conclusions, some of which are now generally accepted by competent judges.

The theory of Leibnitz must, therefore, so far as astronomy is concerned, rest solely on the evidence which the earth's oblate sphericity affords. But the natural philosopher has taken the theory up at this point, and has adduced evidence both for and against the hypothesis. On the supposition that the earth is in process of refrigeration, it would follow that from the point below the surface where fluidity commences to the centre, the earth would be in all directions a hot fluid mass. Now, it has been remarked, that in descending from the surface towards the interior of the earth, the temperature gradually increases. Experiments have been made in many parts of Europe, and in all cases the increase of temperature was decided, though it varies not only in different countries, but in different parts of the same country. The mean ratio is stated by some at 1° Fahrenheit for a descent of 60 feet, and at 1° Fahrenheit for every 45 feet by others. Arguing from these facts, it has been shown that at a depth of 35,000 feet there would be a temperature of low red heat, and at a depth of twenty-four miles the melting point of iron would M. Fourier has come to the conclusion that the be attained. The hypothesis has thence been ex- actual temperature of the earth must be due to three tended to forming estimates of the temperature of causes the sun's rays, the primordial heat of the the centre of the globe, but even if it were proved earth, and the heat of the celestial spaces. "The that throughout the surface of the globe the tempera- mathematical theory of Fourier," says M. Comte,† ture increased with the depth we descend into its" has clearly shown that the temperature at the interior, and admitting that this points to the fact surface of the earth would differ extremely from that there is matter at some distance below the what it is observed to be, both in actual and relative surface more heated than the matter at the surface; amount, were not the terrestrial mass penetrated by the facts do not afford the slightest ground for a heat peculiar to itself; which heat tends to diconcluding this temperature to be a high one. If minish by radiation from the crust of the earth. we assume that the temperature has been found to This original heat contributes very little directly increase at the rate of 1° Fahrenheit for every 45 towards the actual temperature of the surface,‡ but feet as low as the bottom of the lowest mine-say *Review of Humboldt's Cosmos, in Edin. Review. 2000 feet-we attain a temperature of 44° above + Cours de Philosophie Positive. that of the atmosphere; if we reckon the latter at 60° we have at the bottom of the mine a tempera

It is calculated that it does not raise the thermometer.

« PreviousContinue »