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is depressed. When the barometer falls, Admitting an action of this description the load is removed from the area, which to take place, it would then follow that in virtue of its elasticity rises to its origi- this extra liberation of gaseous material nal position. This fall and rise of the beneath the earth's crust would result in . ground completes a single pulsation. an increased upward pressure from with:
On the assumption that the earth is ex-in, and a tendency on the part of the tremely rigid, Mr. Darwin calculates that earth's crust to elevation. If we accept if the barometer rises an inch over an this as an explanation of the increased acarea like Australia, the load is sufficient tivity of a tremor indicator, then such an to sink that continent two or three inches. instrument may be regarded as a barome
The tides which twice a day load our ter, measuring by its motions the variashores cause the land to rise and fall in a tions in the internal pressure of our similar manner. On the shores of the planet. Atlantic, Mr. Darwin has calculated that The relief of external pressure and the this rise and fall of the land may be as increase of the internal pressure, it will much as five inches. By these risings be observed both tend in the same direcand fallings of the land the inclination of tion, namely, to an elevation of the earth's the surface is so altered that the stile of crust. a plummet suspended from a rigid sup- This explanation of the increased ac. port ght not always to hang over the tivity of earth tremors, which is I believe same spot. There would be a deflection due to M. di Rossi, is here only advanced of the vertical.
as a speculation more probable perhaps In short, calculation respecting the than many others. We know how a mass effects of loads of various descriptions of sulphur which has been fused in the which we know are by natural operations presence of water, in a closed boiler, gives continually being placed upon and re- up in the form of steam the occluded mois. moved from the surface of various areas ture upon the relief of pressure. In a of the earth's surface, indicate that slow similar manner we see steam escaping pulsatory movements of the earth's sur. froin volcanic vents and cooling streams face must be taking place, causing varia- of lava. We also know how gas escapes tions in inclination of one portion of the from the pores and cavities in a seam of earth's crust relatively to another. That coal on the fall of the barometrical colpulsatory motions of this description umn. We also know that certain wells have repeatedly been observed it may be increase the height of their column under shown that there is but little doubt. . The like conditions. The latter of these phe. magnitude of these disturbances lowever nomena may be added to that which we is so great that we can hardly attribute have already mentioned, as a result contheir origin solely to the causes which sequent on diminution of atmospheric have just been indicated. Rather than pressure, which, by its tendency to renseeking an explanation from agencies ex. der an area of less weight, facilitates its ogenous to our earth we might perhaps rise. with advantage appeal to the endogenous The next question is as to whether we phenomena of our planet. When the ba- have any direct evidence of such heavings rometer falls, which we have shown cor. and sinkings in our earth's crust. responds to an upward motion of the Although some of the proofs which are earin's crust, we know from the results of brought forward to show that slow pulsaexperiment that microseismic motions are tions like these are plenomena which particularly noticeable.
have been repeatedly observed are unsatAs a pictorial illustration of what this isfactory, taking them one with another really means, we may imagine ourselves they indicate that these pulsatory phenomto be residing on the loosely fitting lid of ena have a real existence. a large cauldron, the relief of the external Pendulums for instance which have pressure over which increases the activity been suspended for the purposes of seisof its internal ebullition; the jars atten- mometrical observations, have, both by dant on this ebullition are gradually prop- observers in Italy and Japan, been seen to agated from their endogenous source to have moved a short distance out from the exterior of our planet. This travelling and then back to their normal position. outwards would take place much in the This motion has simply taken place on same way that the vibrations consequent one side of their central position, and is to the raitle and jar of a large factory slow- not due to a swing. The character of ly spread themselves farther and farther these records is such that we might imag. from the point where they were produced. line the soil on which the support of the
pendulum bad rested to have been slowly The more definite kinds of information iilted and slowly lowered. They are the which we have to bring forward, tending most marked on those pendulums pro- to prove the existence of earth pulsations vided with an index writing a record of its too slow in period to be felt, are those motions on a smoked-glass plate, which which appear to be resultant phenomena index is so arranged that it gives a multi- of great earthquakes. plied representation of the relative mo- The phenomena that we are certain of tion between it and the earth. As mo-lin connection with earth vibrations, tions of this sort inight be possibly due to whether these vibrations are produced the action of moisture in the soil tilting artificially by explosions of dynamite in the support of the pendulum, and to a bore holes, or whether they are produced variety of other accidental causes, we naturally by earthquakes, are, firstly, that cannot insist on them as being certain a disturbance as it dies out at a given indications that there are slow tips in point often shows in the diagrams obthe soil, but for the present allow them tained by seismographs a decrease in to remain as possible proofs of such phe period; and secondly, a similar decrease
in the period of the disturbance takes Evidences of displacements of the ver place as the disturbance spreads. tical which are more definite than the As examples of these actions I will refer above are those made by Bertelli, Rossi, to the diagrams which I have given in a Count Malvasi, and other Italian obser. paper on the “Systematic Observation of vers, who, whilst recording earth tremors, Earthquakes" in Vol. IV. of the Transhave spent so much time in watching the actions of the Seismological Society of vibrations of stiles of delicate pendulums Japan. by means of microscopes. As a result of In a diagram of the disturbance of these observations we are told that the March 1, 1882, it seems that the vibra. point about which the stile of a pendulum tions at the commencement of the disoscillates is variable. These displace: turbance had a period of about three per ments take place in various azimuths, and second, near the middle of the disturbthey appear to be connected with changes ance the period is about l'1, whilst near of the barometer.
the end the period has decreased to .46. From this and from the fact that it is That is to say, the back and forth motion found that a number of different pendu- of the ground at the commencement of lums differently situated on the same area the earthquake was six times as great as give similar evidence of these movements, it was near the end, when to make one it would hardly seem that this phenomena complete oscillation it took between two could be attributed to changes in temper. and three seconds. Probably the period ature, moisture, and the like. M. S. di became still less, but was not recorded Rossi lays stress on this point, especially owing to the insensibility of the instruin connection with his microseismograph, ments to such slow motions. where there are a number of pendulums We have not yet the means of compar. of unequal length which give indications ing together diagrams of two or more of a like character. The directions in earthquakes, one having been taken near which these tips of the soil take place, to the origin and the other at a distance. which phenomena are noticeable in seis. The only comparisons which I have been mic as well as microseismic motions, enabled to make have been those of dia. Rossi states are related to the direction of grams, taken of the same earthquake certain lines of faulling.
one in Tokio and the other in Yokohama. Bubbles of delicate levels when exam. As this base is only sixteen miles, and ined by a microscope change their posi- the earthquake may have originated at a tion with meteorological variations, but distance of several hundreds of miles, Rossi also tells us that they change their comparisons like these can be of but little position, sometimes not to return for a value. long time, during a microseisinic storm. The best diagrams to illustrate the Here again we have another phenomenon point I wish to bring forward are those pointing to the fact that microseismic dis- at the end of the paper just referred to. turbances are the companions of slow alterations in level.*
tween barometrical depressions and these movements. Not only are these atmospheric changes accompanied
with microseismic storms, but there are deflections in * Since my return to Japan in January, 1883, I may the stile of a pendulum, and changes in the position of Inention that I have commenced series of observations the bulbs of delicate levels, which at such times can be on earth tremors and earth pulsations, and on several seen with the naked eye to SURGB back and forb occasions have observed very marked coincidences be- | through a small range.
These are the results obtained at three and other Atlantic islands, the effests of stations in a straight line, but at differ. the disturbance which created so much ent distances from the origin, of a dis- devastation in Portugal were also more or turbance produced by exploding a charge less severely felt as violent movements of of dynainite in a bore-hole. A simple the soil. inspection of the diagrams shows that at In other countries further distant, as, the near station the disturbance consisted for instance, Great Britain, Holland, Norof back and forth motions which, com- way and Sweden, and North America, pared with the same disturbance as re- although the records are numerous, the corded at a more distant station, were only phenomena which were particularly very rapid. Further, by examining the observed were the slow oscillations of the diagram of the motions, say at the near waters in lakes, ponds, canals, ete. In station, it is clearly evident that the pe. some instances the observers especially riod of the back and forth motion rapidly remarked that there was no motion in the decreased as the motion died out.
soil. Then illustrations are given, as Pebbly Dam in Derbyshire, which is a amples out of a large series of other rec. large body of water covering some thirty ords, all showing like results.
acres, commenced to oscillate as a strong Although we must draw a distinction current from the south. between earth waves and water waves, we A canal near Godalming flowed eight yet see that in these points they present a feet over the walk on the north side. striking likeness. Let us take, for exam- Coniston Water in Cumberland, which ple, any of the large earthquake waves is about five miles long, oscillated for which have originated off the coast of about five minutes, rising a yard up its South America, and then radiated out- shores. Near Durham a pond forty yards wards, until they spread across the Pacific, long and ten yards broad rose and fell to be recorded in Japan and other coun- about one foot for six or seven minutes. tries perhaps twenty-five hours afterwards, There were four or five ebbs and flows at a distance of nearly nine thousand per minute. miles from their origin. Near this origin Loch Lomond rose and fell through they appeared as walls of water, which about two and a half feet every five minwere seen rapidly advancing towards the utes, and all other lochs in Scotland seem coast. These have been from twenty to to have been similarly agitated. two hundred feet in height, and they suc. At Shirbrun Castle in Oxfordshire, ceeded each other at rapid intervals, until where the water in some moats and poods finally they died out as gentle waves. By was very carefully observed, it was nothe time these walls of water traversed ticed that the floods began gently, the the Pacific to, let us say, Japan, they velocity then increased, till at last with broadened out to a swell so flat that it great iinpetuosity they reached their full could not be detected on the smoothest height. Here the water remained for a water excepting along shore lines, where little while, until the ebb commenced, at the water rose and fell like the tide. In- first gently but finally with great rapidity. stead of a wall of water sixty feet in At two extremities of a moat about one height we have long flat undulations per- hundred yards long it was found that the haps eight feet in height, but with a dis- sinkings and risings were almost simultatance from crest to crest of more than neous. The motions in the pond a short one hundred and twenty miles.
distance from the moat were also observed, If we turn to the effects of large earth- and it was found that the risings and sinkquakes as exhibited on the land, I thinkings of the two did not agree. that we shall find records of phenomena Durings these motions there were seve which are only to be explained on the eral maxima. assumption of an action having taken These few examples of the motions of place analogous to that which takes place waters without any record of the motions so often in the ocean, or an action similar of the ground at the time of the Lisbon to that exhibited by small earthquakes earthquake must be taken as examples of and artificially produced disturbances if a very large number of similar observagreatly exaggerated.
tions of which we have detailed accounts. As a remarkable instance of such phe- Like agitations it must also be rememnomena we may take the great earthquake bered were perceived in North America of Lisbon on November 1, 1755. In and in Scandinavia, and if the lakes of Spain, northern Italy, the south of France other distant countries had been provided and Germany, northern Africa, Madeira | with sufficiently delicate apparatus, it is
not unlikely that like disturbances would area, which may be regarded as an uncomhave been recorded.
pleted effort in the establishment of an The only explanation for these phe earthquake or a volcano. The very fact nomena appears to be that the short quick that we know that volcanoes rising from vibrations which had ruined so many cities deep oceans have in the first instance in Portugal had by the time that they had forced their way against a pressure, of at radiated io distant countries gradually be least three or four tons to the square inch, come changed into long flat waves having indicates to us the existence of internal a period of perhaps several minutes, and pressures tending to raise the crust of the in countries like England these pulse like earth, which pressures infinitely movements were too gentle to be pero greater than any of the pressures which ceived excepting in the effects produced we have upon the surface of our earth by tipping up the beds of lakes and ponds. produced by tides and variations in the
The phenomenon was not unlike that barometrical column. If we follow the of a swell produced by a distant storm. views of Mr. Mallet in considering that
At Amsterdam and other towns chande the pressures exerted on the crust of our liers in churches were observed to swing: earth may in volcanic regions be roughly At Haarlem floods rose over the sides of estimated by the height of a column of tubs, and it is expressly mentioned that lava in the volcanoes of such districts, we no motion was perceived in the ground.
see that the neighborhood of a volca At the Hague a tallow.chandler was like Cotopaxi the upward pressures must surprised at the clashing noise made by have been many times greater than the his candles, and this the more so because pressures already mentioned — sea-level no motion was felt under foot.
being taken as the line of hydrostatic equiAt Toplitz the pulsation of the ground librium. The chief point, however, is that appears to have manifested itself in effects beneath the crust of our earth enormous upon the springs. The flow of the prin pressures exist tending to cause eruption; cipal spring was greatly increased. 'Be. and farther, that these are variable. Be. fore this increase it became turbid, and at fore a volcano bursts forth we should ex. one time stopped. Subsequently it be. pect that there would be in its vicinity an came clear, and flowed as usual, but the upward bulging of the crust, and after its water was hotter and more strongly min- formation a fall. Farther, it is not disfi. eralized.
cult to conjecture other possible means At one or two places, as, for instance, by which such pressures may obtain rein Britain, slight earthquakes were experi- lief. enced. These, however, were local, and Should these pressures then find relief in every probability were secondary dis- without rupturing the surface, it is not turbances produced by the pulsations difficult to imagine them as the originacausing ground in a critical state to give tors of vast pulsations which may be reway.
corded on the surface of the earth as wave. In this earthquake I think, then, that like motions of slow period similar to the we have a clear case of the production of motions in the outer area of a tract dis. pulsations in the soil that were too slow turbed by a destructive earthquake. to be felt by ordinary observers.
That slow, undulatory motions Motions like these might be called slow changes in the vertical do occur in the earthquakes, and it does not seem un crust of the earth, whatever may be their likely that they are the resultants of all origin, we have numerous phenomena large disturlances. When they accom- which certainly admit of explanation on pany a large earthquake like that of Lis such an assumption. bon, their cause is evident. But when In Switzerland from time to time we we see the waters of lakes and ponds hear of oscillations in the waters of lakes oscillating, the bulbs of levels disturbed, known under the name of Rhussen and and the plummet line of pendulums dis- Seiches. These, it may be remarked, are placed, the reason of these phenomena common to the lakes and inland seas of are not so apparent. It would seein pos- many countries. sible that in some cases pulsations pro- Oiher examples of what may have been ducing these phenomena might have their a slow oscillating motion of the earth's origin beneath the oceans, or deep down crust are referred to by Mr. George Dar. beneath the earth's crust. Perhaps, in- win in his report to the British Associastead of commencing with the snap and tion in 1882.' One of them was made by jar of an earthquake, they may commence M. Magnus Nyrén at Pulkova, who, when as a heaving or sinking of a considerable | engaged in levelling the axis of a tele
scope, observed spontaneous oscillations pulse-like waves can, with these examples in the bulb of the level.
before us, hardly be doubted. It must, This was on May 10 (April 28), 1877. however, be noted that they are of a difThe complete period was about twenty ferent order to those phenomena which seconds, the amplitude being 15" and 2. were so carefully sought for by the DarOne hour and fourteen minutes before wins at Cambridge. JOHN MILNE. this he observes that there had been a
Tokio, Japan. severe earthquake at Iquique, the distance to wbich in a straight line was ten thousand six hundred kilometres, and on an arc of a great circle twelve thousand five hundred kilometres.
From Chambers' Journal.
UNCLAIMED MONEY. On September 20 (8) in 1867, Mr Wagner bad observed at Pulkova oscillations
agony column" of our leading of 3", seven minutes before which there papers is invariably a source of considerhad been an earthquake at Malta. able amusement to many people, by the
On April 4 (March 23), 1868, an agita. extraordinary and generally romantic tion of the level had been observed by M. character of the notices to be found there, Gromadzki, five minutes before_which amongst which may be mentioned the the had been an earthquake in Turkes curiosities of next of kin; and one and tan.
all naturally and justly arrive at the proper Similar observations had been made conclusion, that there is unquestionably a twice before. These, however, had not vast amount of property lying at the pres. been connected with any earthquakes, at ent time unclaimed in England. Perhaps least - Mr. Darwin remarks with cer- it is less difficult to find heirs, now that tainty.
communication with the colonies is so Like phenomena are mentioned by M. rapid and constant; but for all that, the S. di Rossi, in his “Meteorologica Eno number of advertisements for next of kin dogena."
proves that a difficulty still exists; and, Thus on March 20, 1881, at 9 P.M., a in fact, few people are really aware how watchmaker in Buenos Ayres observed much unclaimed cash is still lying dorthat all his clocks oscillating north and mant, and how much has been approprisouth suddenly began to increase their am-ated by goverpment. plitude, until some of them became twice In novels, people are often made to as great as before. Similar observations pick up fortunes out of a chance newspawere made in all the other shops. No per, and the incident is dismissed by the motion of the earth was detected. Sub- reader as entirely growing out of the ausequently it was learnt that this corre. thor's imagination. What ought to sursponded with an earthquake in Santiago prise us is, not that fortunes are sometimes and Mendoza.
ibus obtained, but that millions of pounds Another remarkable example illustrat- sterling should be going about begging ing the like phenomena are the observa for an owner, and advertising themselves tions which were made on December 21, to an incredulous and indifferent public, 1860, by means of a barometer in San who scarcely ever take the trouble to inFrancisco, which oscillated, with periods quire about the large sums locked up in of rest, for half an hour. No shock was chancery, not to speak of unclaimed felt, nor is it likely that it was a local dividends, etc., still awaiting their proper accident, as it could not be produced arti- owners. There are scores of people at ficially. On the following day, however, present, belonging to a circle below that a violent earthquake was experienced at of the “upper ten,” who have really Santiago.
fair grounds for expecting a change of This brings me to the end of the few fortune in the right direction some day, important illustrations of the phenomena but they lack the necessary clue on which of earth pulsations which I have at iny all their hopes turn. Others there are, disposal. With a little trouble I have no both at home and abroad, who fancy they doubt that these might be greatly multi- will in time come into something hand. plied. As they stand, however, I think some. Meanwhile, they trust to chance, that they are quite sufficient to convince without searching for themselves. us of the existence of phenomena which While it is not the writer's intention to hitherto have been almost entirely over: weary the reader's patience with an array looked. That disturbances of the vertical of dry statistical accounts, the mention of are from time to time produced by long. a few monetary items may have the effect