MAY 26.

At 0h. 14m. 10s. P. M. there was a very moderate earthquake, which lasted nearly ten seconds. The wave was extremely long, and consequently its motion slow; for which reason the phenomenon escaped the attention of a large number of the population. All the city clocks were stopped by it. We learned, subsequently, that it had been very severe at the north; Copiapó and Huasco having suffered extremely from its effects. One Copiapó paper says it occurred there "about a quarter past 1 P. M.;" the other is more specific, and fixes the epoch at 1h. 20m. A number of houses were thrown down, many unroofed, and large quantities of property destroyed. Similar destruction was experienced in the mining districts, each about 50 miles distant-one to the S.E., the other to the N.W. From the fact that the injuries were greater at the former than at the latter, and also because of the estimated motion of the strong horizontal shocks, many supposed that the origin of the disturbance was to the southward. Others believed that it was in the Andes, or to the east. A great noise accompanied the vibration, which lasted nearly two minutes. It was said that a crevice, fifty yards long and eight inches wide, was opened within the city, from which water issued; but when I visited Copiapó, five weeks later, the account proved, like ten thousand other earthquake prodigies, wholly fabulous. The injury to property was not so great as at Santiago and Valparaiso, April 2; though its better preservation was evidently attributable to less elevated walls and lighter roofs. Between the time of the great shock and midnight of the 27th, more than one hundred tremors were counted; and, on the 31st, the Editor of El Pueblo says: "We have arrived at the sixth day of the earth-storm, and still the shocks cease not. Last night and this morning we have had at least six; two or three of which were of some duration and violence."

At Caldera the duration of the shock was much the same as at Copiapó, but it was not thought so violent. Afterwards, the sea ebbed and flowed in waves at intervals of seven to ten minutes, until darkness prevented its being longer observed. The height of the wave never appeared more than four feet; and when lowest, the receding volume bared the bay two feet below the lowest tide-mark.* It was estimated by W. W. Evans, Esq., resident engineer of the railroad, that 2,000,000 cubic feet of water passed through the entrance of the bay twice in every seven to ten minutes.

At Huasco, the shock was felt at 1h. 07m. P. M., when the church and many houses were irreparably injured. Shortly afterwards the sea retired from the beach with incredible velocity, until about 150 yards were left bare. Some of the vessels dragged their anchors, and one parted its cable in the rush. Of a sudden, a wave, more than ten feet higher than the highest tides, rolled to shore, inundated the custom-house, and washed out the goods deposited in its patio. This phenomenon was observed half a league out at sea, repeating itself many times and at short intervals.

An official letter to the Minister of the Interior, from the governor of Freirina, (three or four leagues east of Huasco,) says, that the earthquake occurred there about a quarter past 1 P. M., that it was more severe than the oldest persons remembered for above fifty years, and that the duration of its greatest violence was more than a minute. Some houses were prostrated, and many walls broken; but no mention is made of the supposed direction from which the disturbance came. Up to the hour of writing-at the close of the second day-the phenomenon was repeated at short intervals.

The governor says, it took place in Vallenar (thirty miles in an air-line E.S.E. from Freirina) at 1h. 42m., that the total duration of the oscillation was three minutes, and that of the greatest violence fifteen seconds. Every house was much deteriorated, and some wholly ruined. Shocks were repeated at intervals during the remainder of the day and night.

At Serena its duration was a minute and a half, and it was so sharp that all the inhabitants took to the streets, though no injury to property resulted. It occurred at 1h. 17m. P. M., and

*The rise and fall of the tide here is 5 feet.

came from the north, or is so stated to have done by the Intendente. Señor Troncoso was absent. This was the last great shock during our stay in Chile. For further details of it, and also of the April earthquakes, the reader may consult Appendix A.

There were, however, two or three lesser tremors, which merit attention. The first of these was on the night of November 15th, 1851, whilst I was looking with the equatorial telescope at the moon, whose apparent motion from north to south was through quite four minutes of arc. I was unable to detect the least diagonal displacement, other than the tremor inseparable from such disturbance of the base of the instrument. It lasted seven seconds. Owing to a strong wind blowing in at the door of the observatory, the direction of the rumbling noise accompanying it was not distinguishable. Perhaps a similar sight-the vision of terrestrial convulsion under a magnifying power of 235 times—may never occur again in all my life.

MAY 31, 1852.

There was a slight shock about 11h. 30m. A. M., which was felt at Valparaiso at the same time.

JULY 5.

Its motion was

The earth was agitated from 0h. 41m. 03s. to Oh. 41m. 38s. P. M. apparently to the southward, in the direction of the longer axis of Santa Lucia, though the meridian circle oscillated tremblingly in the transverse direction through more than a quarter of an inch. The bottle of mercury kept for nadir determinations was shaken so uniformly that it would not serve as a guide to the origin of the disturbing force. The agitation of the surface of the mercury was rather due to a succession of rapid impulses than a series of waves of much amplitude.

AUGUST 12.

A line of telegraph (magneto-electric) having been erected between Santiago and Valparaiso, the operating director very kindly consented to adopt an earthquake signal. This signal was to be struck at the commencement of a tremor at either end of the line, and the time, noted at the other end, between the receipt of the signal and arrival of the shock, was to be immediately compared by Mr. Mouat's (astronomical) or the observatory clock on Santa Lucia. This was the first we had had an opportunity to observe, and it was more than commonly severe. With an intermission of two seconds, the earth continued in motion from 11h. 58m. 32s. until 11h. 59m. 10s. A. M.; the second shock having been longest and sharpest. The noise was heard to the N.W. But that which was of most interest was the fact established by the telegraph―two cities, 64 miles apart, had been shaken at precisely the same instant—when the signal was struck in Valparaiso, the finger of the operator was on the key at Santiago for the same purpose.

Accurate record of most of the tremors that occurred from November, 1849, to September, 1852, are believed to have been kept only at Santiago and Serena; though it is well known that shocks are even more frequent in the province of Atacama than Coquimbo; and that as one travels southward they are less and less common, until at Valdivia months pass without one to startle the population. No doubt some at night escaped observers at both specified places; but when we recollect that the two are only 220 miles apart, it is a matter of surprise that of the 218 enumerated in Appendix A, only those of November 13 and 18, 1849, and December 6, 1850, were recognised at each of them. Stronger evidence of the limited districts to which the phenomenon is usually confined could not be adduced. Examination of this Appendix develops other facts also. First: That the province of Coquimbo is more liable to disturbance than that of Santiago, in the proportion of 139 to 69, these numbers of tremors having been observed during

twenty-eight corresponding months; and it is proper to remark, had not Señor Troncoso been absent from Serena on the 26th May, 1852, the disproportion would doubtless have been greater. Second: They prove that there are no permanent centres of disturbance, the apparent direction of the vibrations varying at each occurrence. Third: A large proportion of these tremors are neither undulations nor vibrations, but rather rapid vertical displacements of the crust of the earth; almost, if not absolutely, simultaneous over the whole disturbed district. Our sensations caused suspicion of the fact, the shivering of our pendulum without oscillation supported the belief, the instrument of Señor Troncoso afforded direct evidence, and the telegraph confirmed it on two occasions. The instrument alluded to consisted of an inverted pendulum within a closed glass globe from which the air had been exhausted. The pendulum is a spiral made of steel wire sensible to very slight disturbances, and he frequently remarks, "the spring is opened as far as the top of the globe will permit, but the pendulum has no lateral motion." A very experienced English gentleman wrote to me on this subject from the mining districts of Atacama: "Shocks are sometimes horizontal, sometimes vertical; but the former appear to me the more dangerous. A few days ago, we had quite a strong horizontal shake that did much damage, though a vertical shock two days after, which to our senses was of the same force, caused very little injury. At the same time the latter was so strong as to throw the water out of tumblers and jars." Fourth: So far as conclusions may be drawn from observations during thirty-five consecutive months at one place, and twenty-eight months at the other, the season of the year has influence. The numbers in each season, with the average monthly number of shocks at each city, are embodied in the subjoined table: April at Santiago, and November at Serena, embracing the extraordinary disturbances of 1849 and 1851.

Humboldt thinks we have no right to reject belief in "the influence of particular seasons, the vernal and autumnal equinox, the setting in of tropical rains after long-continued drought, and the change of monsoons, solely because we do not at present understand the causal connection which may exist between meteorological and subterranean phenomena."* Popular belief even yet associates them with peculiar meteorological conditions: many assert that the barometer is low, the thermometer high, the atmosphere calm and oppressive, and that the color of the sky changes just before the shock. The tables bear directly on all these questions; and whilst instrumental data, with other recorded evidence extracted from our meteorological journal, show that neither the pressure, the temperature, nor the hygrometric condition of the air have

*Kosmos, Vol. I.

influence, the preponderance of shocks during autumn is particularly observable. Nor is this peculiar to the tremors alone; for of the fifteen great earthquakes since 1570 which have been mentioned, two were in February, one in March, three in April, three in May, two in July, one in September, one in November, and one in December; or, distributed in seasons, there were seven in autumn, three in summer, and two each during spring and winter.

But because the earth does not evolve heat or moisture to produce sensible effect on the atmosphere, and thus announce the agitation shortly to occur, it by no means follows that the aerial strata in contact with it are not disturbed at such agitation, and that an extraordinary meteorological state does not ensue, explicable only as a consequence of the earthquake. Ordinarily rain falls in central Chile twice in nine years, between the close of October and commencement of April; yet there has been but one great earthquake not soon followed by a rainstorm, and, on that occasion, clouds and vapors (altogether unusual in December) wholly obscured the sun for days. Deluges of rain, with excessive lightning, followed also the Catania, Lisbon, and Calabria earthquakes.

The occurrence of luminous meteors about the times of the shocks seems pretty well authenticated in Chile, as well as elsewhere. They were seen before the Catania earthquake of 1693.* During the remarkable one in New England, 29th October, 1727, persons of credit affirm that they perceived flashes of light before the shock;† at Lisbon they were perceptible on the sides of the near hills at the third shock;‡ in Calabria, during the commotion; and in Chile, sometimes before, though most generally after it. We are, therefore, authorized to infer that unusual electrical disturbance is, at least, a consequence of the phenomenon. That it is the cause, has been argued by more than one philosopher, more especially at the period when our illustrious countryman established the identity of lightning and electricity. In an account of the earthquakes which occurred in England in 1750, published by Dr. Stukely in the Philosophical Transactions for that year, after referring to a discourse on electricity by Franklin, he goes on to argue that, "on the same principle, if a non-electric cloud discharges its contents on any part of the earth when it is in a highly electrified state, an earthquake must, of necessity, ensue.' This theory of its origin serves him to explain why shocks are simultaneous over such extended tracts, and also why they are most violent in rocky countries. A like hypothesis is suggested by Dr. Donati, the professor of botany at Turin. Others, as Dr. Martin Lister,§ regarded the material cause of thunder and lightning and earthquakes as the same, viz: “the inflammable breath of the pyrites; the difference is, that one is fired in the air, the other under-ground;" and when we remember that there are no electrical displays in the atmosphere west of the Andes, we need not be surprised that many in Chile and Peru, notwithstanding the mass of testimony in favor of volcanic origin, continue to believe that equilibrium is thus restored. Buffon's supposition, that they were attributable to the falling in of caverns existing in the interior of the globe, is pronounced, by geologists,|| only admissible under one of two conditions: such cavities must either have been formed at the original cooling of the earth, and, therefore, would not be likely to sink at the present day; or they could only have been created by subsequent convulsion, implying, in itself, volcanic agency. Their connection with volcanoes is shown by multitudes of isolated facts, that might be quoted from many writers; though only Humboldt and Darwin have enumerated series of events tending to establish it. The former selects the earthquakes of 1811-'12, the latter that of February, 1835; prior to recapitulating which, from their writings, three or four individual instances may be mentioned, of more than ordinary interest because of the magnitude of their consequences.

On the 29th September, 1759, after eighty days of earthquakes and subterranean thunders, the volcano of Jorullo (Mexico) burst out, increasing the height of its crater nearly 1,700 feet, and elevating 24 to 30 square miles several feet above the surrounding plain. Vesuvius exhi* Philosophical Transactions, Vol. XVII. + Ibid., Vol. XXXIX. ‡ Ibid., Vol. XLIX. || Daubeny: On volcanoes. Second edition, 1844.

§ Ibid., Vol. XIV.

bited a very uncommon appearance, in the column of smoke proceeding from it during the Lisbon earthquake; Stromboli, for the first time in the memory of man, was quiet in 1783; and the closing of the vent in Pasto was followed by the earthquake of Riobamba, in which 40,000 persons perished.* Humboldt's seriest commences with the formation of a new island in the Azores, at a spot where 40 fathoms water existed previously. In February, 1811, a volcano, accompanied by violent earthquakes, burst from the sea near the west end of St. Michael's, and in June following, after raging several days, and ejecting cinders and stones, the crater appeared above the surface. Two days after, it was 150 feet high, and ultimately it rose to more than 300, with a diameter of nearly 600 yards. From May, of the same year, until April, 1812, severe earthquake shocks were felt at St. Vincent and most of the smaller West India islands in the vicinity of that usually very active volcano. The Mississippi valley earthquakes were in December, 1811, and through the winter of 1812. One occurred at Caraccas, also, in December; the city was destroyed in March, and the earth continued shaking until the 5th of April. Finally, on the 30th April, 1812, the volcano of St. Vincent broke out, with an explosion so terrific that the shock was felt on the Apuré, more than 200 miles distant, and subterranean noises were heard at Caraccas at the same time.

Mr. Darwin's series is as follows: There was a dreadful earthquake at Sabionday, near Pasto, (latitude 1° 15′ N.,) on the 20th January, 1834. Eighty persons perished, and the town of Santiago (Peru) was swallowed up. Sixty bad shocks threw down two thirds of Santa Martha, about the 22d of May; and there was a violent shake at Jamaica on the 7th September. On the 20th January, 1835, the volcanoes of Osorno, Aconcagua, and Conseguina were in eruption, and the last continued in activity during the ensuing two months. February 12th a very strong earthquake was felt at sea, off the coast of Guyana; and eight days afterwards submarine explosions, off Juan Fernandez and Talcahuano, accompanied the destruction of Concepcion. The coast of Chile was then permanently elevated; and volcanoes were in continued eruption, for some months subsequently, along the whole length of the Andes. November 11th there was another severe earthquake at Concepcion, Osorno and Corcovado being in violent action; and on the 5th of December Osorno fell in with a grand explosion.‡

The disengagement of water, smoke, ashes, sulphurous vapors, and even flames, at times, when earthquakes occur in regions where volcanoes do not exist, must be regarded as additional proofs of the connexion of the phenomena; and the frequency and now recognised universality of tremors, has been supposed to point to the deep-seated molten strata as their origin. At one time, those tremors which manifested themselves in alluvial formations apparently very remote from igneous action, and kept the earth in vibration for months successively, as France in 1808, the United States in 1811-'13, and Asiatic Turkey in 1822, remained as exceptions seemingly inexplicable. But, as the vibrations ceased in every case with the bursting out of a volcano, and there was "scarcely room to doubt that every active volcano is in immediate communication with the whole melted matter in the interior,''§ the identity of the forces seems apparent; and it is now generally admitted that elastic fluids, subjected to enormous pressure in the interior of the earth, are not only quite sufficient to account for these harmless tremblings, but also for those terrific explosions which devastate kingdoms.

Although it is probable that the surface of the earth is almost always shaking at some point, fortunately for mankind terrific explosions are rare. Moreover, experience has shown that most of them are submarine, and so far from the habitations of man that their effects are greatly modified before reaching him. That such was the case with all the great earthquakes felt in Chile, except that of April 2, 1851, is evident from one concomitant, as we shall perceive in the explanation given of them.

*Daubeny: On volcanoes. Second edition, 1844.
+ Personal Narrative, Vol. IX.

Geological Transactions, Vol. V, second series.

§ Edinburgh New Philosophical Journal, 1838.