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down St. Michael's-on-the-Hill-without-Glastonbury, in 1274. The greatest ever known in England, November 14, 1328. A
dreadful one, accompanied with thunder and lightning, September 28, 1426. Another, 1661. Also 1683 and 1692.”
The Manchester Guardian for November 13, 1852, enumerates no fewer than eight earthquakes, experienced, more or less, in Manchester and its suburbs during the last hundred years. One in 1750, one in 1753, one in 1777, and the others in 1835, 1839, 1843 (two), and 1852.
The observations recorded with regard to the time of the occurrence were, it will be perceived, made under the circumstances with so little regard to preciseness, that it is difficult to draw any definite conclusion from them. Those made at Dublin would seem to agree in the shock having been felt at or near four o'clock in the morning, while the mass of observations made in Liverpool, Manchester, and North Wales, would give about half-past four, which, allowing for difference of longitude, would still leave a sufficient lapse of time to give priority to the coast of Ireland, and would indicate a movement between west and east, or from north-west to south-east. But then, again, the observations at Aberystwith, Birmingham, and in Oxfordshire, would indicate that this shock was felt in those places as early as four o'clock.. In the great earthquake of 1755, agitations of water were observed in various parts of Great Britain at wide intervals of time. For example, at Loch Ness and Loch Lomond at half-past nine, A.M.'; in Durham and Surrey, at half-past ten, A.M.; in Berks and Derbyshire, between eleven and twelve, A.M. The last shock of a somewhat similar description--which was experienced with various degrees of intensity in Lancashire and in the adjacent counties of Westmoreland, Cumberland, Cheshire, Flintshire, and the Isle of Man-took place a few minutes before one o'clock on the morning of Friday, March 17, 1843.
At the Royal Observatory, the mean height of the barometer during the week ending 13th November was 29.534. The mean weekly temperature, which was 54.2 deg., exceeded the average of ten years by 7.7 deg. It has not been so high since the week that ended the 25th of September; and since the beginning of October it has not been higher than 49.9 deg. In the last two weeks it has suddenly risen from 45.6 deg. to 54.2 deg. The mean daily temperature was 54.6 deg on Sunday, or 7.9 deg. above the average. It rose on Monday to 57.2 deg.; declined till Thursday, when it was 50-3 deg.; and rose again on Friday to nearly the same height as on Monday and Tuesday, when it was about 10 deg. above the average. It was higher than the average throughout the week. The wind blew generally from the south.
De Humboldt, who has seen the earth frequently and violently agitated in a clear air and a fresh wind, as well as in rain and thunderstorms, treats the general belief that a calm, an oppressive heat, and a misty horizon are forerunners of earthquakes, as a fallacious popular opinion, unsupported by the authority of inductive reasoning.
The regularity of the horary changes in the declination of the magnetic needle, and in the atmospheric pressure, as indicated by the barometer, are not also, it has been ascertained, generally or necessarily connected with earthquakes. Yet, although this may be the case, as thus strietly
and scientifically placed before us, there is no doubt, on the other hand, that a misty, oppressive air, indicative of a peculiar electric condition, and often marked by an unusual rise in the barometer, does frequently accompany earthquakes, especially in countries least exposed to volcanic influences. Volta's electrometer, for example, was strongly agitated during the protracted earthquakes of Pignerol in 1808. Humboldt himself acknowledges that, although in general the processes at work in the interior of the earth may not be announced by any meteorological phenomena, or any special appearance of the sky; it is still not improbable that some effect may be imparted to the atmosphere, in consequence of which it cannot act in a purely dynamic manner. Further, if no meteorological phenomena indicate the coming earthquake either on the morning of the shock, or a few days previously, the influence of certain periods of the year (the vernal and autumnal equinoxes), the commencement of the rainy season in the tropics after long drought, and the change of the monsoons (according to general belief) cannot be overlooked, even though what De Humboldt calls the genetic connexion of meteorological processes with those going on in the interior of our globe, is still enveloped in obscurity.
The circumstances under which the late earthquake occurred are singularly suggestive for its explanation to two of the more simple theories that have been suggested in explanation of these phenomena; the theory of electric influences, and that of the influence of water converted into steam by subterranean heat. Earthquakes, it is true, have always been of rare occurrence in these realms. Yet, historically, they date as far back as A.D. 1089, when a shock was felt throughout the country. Another shock was experienced in 1274, a partial shock having been chronicled as apparently confined to Lincoln in 1142. In 1580 a shock of such gravity was experienced in London that part of St. Paul's and the Temple churches fell. In 1690, Ireland suffered from similar causes. The inhabitants of London, who were much discomposed by a slight shock on February 8th, 1750, were still more terrified by a severer shock that occurred on the 8th of March of the same year. Till that time the absurd theories of Kircher, Descartes, and other philosophers, that there were many vast cavities under ground which have a communication with each other, some of which abound with water, others with exhalations arising from inflammable substances, as nitre, bitumen, and sulphur--the common resources of bygone chemistry-still held their ground. But at this time, Dr. Stukeley, who had been engaged in electrical experiments, began to suspect that a phenomenon of this kind ought to be attributed not to vapours or fermentations generated in the bowels of the earth, but to electricity. These ideas were advocated at the same time by Beccaria, and further illustrated by Dr. Priestley.
It is evident that the peculiar circumstances under which the late earthquake occurred were sufficient to give countenance to either of the above theories. There was quite sufficient in the electric tension, produced by the prolonged and unseasonable warmth, moisture, and stagnation of the atmosphere, to ground a theory of a contrast of a negative and positive condition established between the earth and the air, and producing tremulous vibrations like the shock of an earthquake, when an equilibrium was brought about, especially if that was, as is mostly the case with electrical phenomena, effected more or less instantaneously, just as two clouds, one negatively, the other positively, electrified, produce, according to the voltaic theory, a hailstorm in summer time, and at any time the evolution of light, accompanied by thunder. Then again, knowing positively as we do how much the temperature goes on increasing (i deg. for every 100 feet) from the surface towards the centre of the earth, those wedded to a previous theory might see enough in the great rains, and consequent inundations of the present season, to explain the late phenomenon by the supposition of large quantities of water gradually absorbed and converted into steam by subterranean heat. But while the first theory has at least something like plausibility to lend it support, the latter has not even possibility, still less probability, to recommend it.
To turn to another view of the subject. Although we have no active volcanoes in these realms, nor indeed any actual or recent igneous rocks or phenomena of any description, if we except the spontaneous combustion of certain bituminous and pyritous alum-slates, bituminous shales and coals, which certainly have nothing to do with the present inquiry ; still we have plenty of evidence of ancient (geologically speaking) igneous action, and we have further evidence that the deep-seated disturbances which have given origin to destructive earthquakes in other countries have been frequently from that very reason felt in this—in other words, that from the depth of the molten strata of the earth, strictly speaking, no portion of the earth is beyond the boundary line of these terrific natural phenomena.
For example, on the 1st of November, 1755, when Lisbon was destroyed by a great earthquake, the effects reached to an immense distance, the utmost boundaries of which, to the south, are to the present day unknown. But northwards it is well known that they were felt in the British Islands, and to the extremities of Sweden and Norway. In Great Britain and Ireland the effects were chiefly manifested by the agitation of inland waters. The waters of Loch Lomond, for example, rose suddenly without the least gust of wind against its banks, and then as suddenly retired. Loch Ness was similarly agitated. At Kinsale, the weather being very calm, and the tide nearly full, a large body of water suddenly poured into the harbour with such rapidity that it broke the cables of two sloops, and cast several boats on the shore. The agitation of the water was also observed at numerous places in Surrey, Suffolk, Durham, Berks, Kent, Oxfordshire, and Glamorganshire. The character of these agitations may be judged of from the following: -At Cobham, in Surrey, a person was watering a horse at a pond fed by springs ; whilst the animal was drinking, the water suddenly ran away from him, and moved towards the south with such swiftness that the bottom of the pond was left bare. It returned again with such impetuosity that the man had to leap backwards to secure himself from its sudden approach. It will be observed in this instance, as in all cases of earthquakes, how difficult it is to distinguish reaction from action. The shock would appear to have come from the north, whereas the seat of subterranean action being in the south, it must have been the reflex action that threw the waters to the south, after which they returned by natural causes to their own level. In the mines at the Peak of Derbyshire the same earthquake was felt as a positive shock.
It is evident from such examples that at the moment we are writing it remains to be shown whether the earthquake, which has lately so naturally alarmed her Majesty's liege subjects, may not have been the outer wave of some great earthquake which may have shaken cities or kingdoms at a distance from us ; if not so, its peculiarities, which remind us of the wet and rainy season that at Lisbon preceded the great earthquake of 1755, of the warm weather, with long continued south and south-west winds which preceded the earthquakes of 1749 and 1750 in this country, the circumstance of this shock, like so many others, chiefly affecting the sea coast and banks of rivers (averred by Priestley to be a further proof of their being electrical phenomena), will deserve some consideration, but even then they will not satisfy the inquirer. The fearful earthquake of 1783, which, according to Sir William Hamilton, caused a loss of some 40,000 lives in Italy and Sicily, was manifestly a volcanic phenomenon ; so, likewise, with many other earthquakes on record ; and it is not likely that, although the Creoles of South America distinguish the least danger ous of these phenomena as mere Temblores, or tremors, and designate the more violent as positive Terremotos, that earthquakes should originate in some countries from subterranean igneous action, and in others from electrical influence. There may be different degrees of intensity of the same phenomena: it would scarcely be suspected that there may also be different
Yet the progress of science would lead us to hesitate in effecting any such broad distinctions. “ As the internal heat of our planet,” writes De Humboldt, “ is connected on the one hand with the generation of electromagnetic currents, and the process of terrestrial light (a consequence of the magnetic storm), it on the other hand discloses to us the chief source of geognostic phonomena." The veteran physical geographer goes on to consider these in their connexion with, and their transition from, merely dynamic disturbances, from the elevation of whole continents and mountain chains to the development and effusion of gaseous and liquid fluids, of hot mud, and of those heated and molten earths which become solidified into crystalline mineral masses.
“ Modern geognosy,” continues the same philosopher, “ the mineral portion of terrestrial physics, has made no slight advance in having investigated this connexion of phenomena. This investigation has led us away from the delusive hypothesis
, by which it was customary formerly to endeavour to explain individually, every expression of force in the terrestrial globe ; it shows us the connexion of heterogeneous substances with that which only appertains to change in space (disturbances or elevations), and groups together phenomena which at first sight appeared most heterogeneous --- as thermal springs, effusion of carbonic acid, and sulphureous vapour, innocuous salses (mud eruptions), and the dreadful devastations of volcanic mountains. In a general view of nature all these phenomena are fused together in one sole idea of the reaction of the interior of a planet in its external surface. We thus recognise in the depths of the earth, and in the increase of temperature with the increase of depth from the surface, not only the germ of disturbing movements, but also of the gradual elevation of whole continents (as mountain chains in long fissures), of volcanic eruptions, and of the manifold production of mountains and mineral masses."
This is the true light in which these phenomena are to be viewed—that is to say, as having their origin in the raised temperature of the deepest molten strata, and the tension of highly compressed elastic fluids, accompanied by the generation of electro-magnetic currents, as in the formation of veins ; the existence of an active volcanic force, which although everywhere manifested, and as generally diffused as the internal heat of our planet, attains but rarely, and then only at separate points, sufficient intensity to exhibit the phenomenon of eruptions. "If,” says De Humboldt, "we could gain information regarding the daily condition of all the earth's surface, we should probably discover that the earth is almost always undergoing shocks at some point of its superficies, and is continually influenced by the reaction of the interior on the exterior. We have in these phenomena the mine-like explosion—the vertical action from below upwards, and the propagation by undulations in a linear direction, and in circles of commotion or large ellipses, in which the vibrations are propagated with decreasing intensity from a centre towards a circumference. There are even districts that are exposed to the action of two intersecting circles of commotion.'
The great depths at which earthquakes have their origin explain their independence of the superficial nature of the soil and rock. Thus, earthquakes have been felt in the loose alluvial strata of Holland, and in the tertiary basins of Paris and London. Then, again, among rocks, granite and mica slate are skaken as well as limestones or sandstones. It is not, therefore, the chemical nature of the constituents, but rather the mechanical structure of the rocks, which modifies the propagation of the motion-the wave of commotion. Where this wave proceeds along a coast, or at the foot and in the direction of a mountain chain, interruptions occur from these causes at certain points. Active volcanoes, by affording an outlet to pent-up vapours, and a means of communication between the molten interior of the globe and its outer crust and atmosphere, are everywhere safety-valves, and the danger of earthquakes increases as they are far removed from such openings in the earth.* Earthquakes, it is finally to be observed, are not as they appear, at first sight, to be, simply dynamic phenomena of motion ; it is known, from well attested facts, that they eject at times smoke, fire, and flames, steam, and hot water, noxious gases, and mud; that they are also able to elevate a whole district above its ancient level (as for instance the Ulla Bund, after the earthquake of Cutch, in June, 1819, east of the delta of the Indus, and the coast of Chili, in November, 1822). Further, earthquakes act mechanically in three different ways, either in causing disruptions, or sudden and retroversed elevations; or, finally, as was first observed in a great part of Sweden, in producing changes in the relative level of the sea and land, which, although continuous, are only appreciable at intervals of long period.
* The danger of earthquakes is well known to increase when the openings of volcanoes are closed, and deprived of free communication with the atmosphere. Thus, the late earthquake may not improbably have some connexion with the activity of Etna, which, from the last news, dated Catania, Nov. 5th, after being several days dormant, had resumed its activity, but which may either have experienced another check, or its existing state of activity may have been accompanied by an earthquake of unusual intensity.