EFFECT OF THE GREAT EARTHQUAKE OF 1891 ON THE NAGARA GAWA RAILWAY BRIDGE, JAPAN. Milne was silent a moment, and then said: "I'll be ready, sir, on Tuesday." And so he sailed for Newfoundland and what he did there is a separate chapter. But it was all to his credit, for soon came an offer from the Japanese Government, intent upon getting the best brains in Europe to assist in the nation's development, inviting Milne to join its service, at a handsome salary, in the department of mines and public works. So it came about, twenty-five years ago, that this young Englishman took up his abode in Tokio, and in due course turned his attention to earthquakes. This happens quite naturally when one finds oneself in a country where there are two or three earthquakes a day on an average, counting small and large, throughout the year, and where in many instances a single one of these earthquakes has been a more serious matter to Japan in loss of life, and almost as serious a matter in resulting expenditure, as her recent war with China. Under such circumstances, it was not difficult for a keenly interested and scientifically-trained European to develop into an earthquake enthusiast; and Milne was soon putting forth seismic theories with the best of them, and trying experiments with roughand-ready seismoscopes and seismometers, which were sometimes rows of pins propped up in a certain way, so that in falling they would give indications as to wave direction, or sometimes bits of string with weights at the end designed to act as recording pendulums; or, again, gravestones tumbled over on their sides in the hope that by their slide or shifting they would show the line and intensity of the earthquake movement. He produced plans of earthquake-proof houses: houses with roof-timbers running down to the floor sills, which was equivalent, practically, to having the roof rest on the ground. He also showed the Japanese engineers how to build bridges with parabolic piers, so that at any horizontal section they offer equal resistance to effects of momentums applied at the base. And, as the value of his conclusions became apparent through actual tests, the Japanese Government, properly grateful, established a chair of seismology at the uni I will repeat what may have been already understood, that they are designed to record movements in the earth coming from distant, not near-by, centers of disturbance; they would be of no more service for an earthquake within a hundred miles of them versity, and picked Milne out as the one best Milne's instruments and their work at Shide, qualified to fill it; which meant that here was a young man, fresh from a country where there are no earthquakes, officially appointed to teach people who had lived among earthquakes all their lives what earthquakes are, and what measures should be taken against them in short, the whole business of seismology. Then began an interesting set of experiments, carried on for years by Professor Milne, with artificial earthquakes, which he could turn on at will by touching an electric button. Dynamite was used here, buried in the ground, and exploded when the seismographer was ready. Sometimes he would set off five or six of these little earthquakes at one time, and take the records with a like number of seismographs placed at different distances, and connected electrically, so as to show the rate of wave transmission. Once the Professor, in his eagerness to watch the seismograph at the very moment of shock, placed himself within twenty feet of a mine, his position being barricaded by earthworks, with an old door over the top to keep off falling stones. When all was ready, he waved his hand to an assistant who stood at some distance ready to send the current. Bang! went the dynamite like a broadside of heavy cannon, and the Professor had scarcely fixed his eyes upon the moving smoked-glass disk with the little recording fingers on it, when about a ton of earth came smashing down upon the door, flattening out man and instrument, and bringing that experiment to an untimely end. On another occasion, at the command of the emperor, a seismic exhibition was organized in the palace yard, where a number of miniature towns and villages had been laid out neatly for the purpose of being blown up and shaken down when his majesty should touch the button. Everything went off perfectly, and the courtiers were delighted. For twenty years Professor Milne carried on his experiments, and success seldom failed him. Then he PROFESSOR MILNE'S SENSITIVE PENDULUM, OR SEISMOGRAPH, AS THE SENSITIVE PENDULUM, OR SEISMOGRAPH, AS IT APPEARS WITH THE PROTECTING BOX REMOVED. 66 than a telescope would be at the theatre. a clock ticking here also, but no little The seismographs used all over Japan record lamp. earthquakes that can be felt; the Milne horizontal pendulums record earthquake waves that cannot be felt. After years given to the practical side of seismology, Professor Milne is now studying its theoretical side, although, as has been seen, much practical good is resulting from his investigations. "This," said the Professor, is an everyday pendulum, to let us know if anything is happening. If there is, then we look at the other pendulum for fuller details. The other one is not so easy to get at. Just glance along that paper band and you can see if there has been an earthquake anywhere in the last twenty-four hours. No, there has been nothing; the line is straight; see-that long white line the needle makes it as the band turns." 66 Suppose there had been an earthquake ?" THE EARTHQUAKE OBSERVATORY. My first view of the instruments was at night. Professor Milne walked beside me, carrying a lantern, and his Japanese assistant, Shinobo Hirota, who is nicknamed "I'll show you what would have hap"Snow" on the Isle of Wight, went ahead pened. Come around here; that's right. to open the doors of the strong-walled little Now press against the column, not hard, just houses where the pendulums were guarded. There are two of these pendulums, both constructed on the same principle, but the one more sensitive than the other. "Snow" showed us the sensitive one first; and when I saw it, I saw only a little lamp burning on a red box with steps to it. The box cov ered the pendulum. The whole place sug gested some silent altar with undying flame. I could hear a clock ticking inside the box. "What is the lamp for ?" I asked. 労 July 19 7891 RECORD MADE ON A STATIONARY SURFACE BY THE VIBRA with your hand. There it goes. See?" It was like pressing against a chimney, but the boom of the pendulum responded instantly, and the needle swerved out on the paper and then back again, marking a narrow loop. "You tipped the column and altered its level just as an earthquake wave from Japan or Borneo would have done. TIONS OF THE JAPANESE EARTHQUAKE OF JULY 19, That is the whole Showing the complicated character of the motion (common to "To photograph the end of the boom," said the Professor. "It lets a point of light down through that slit. When the earth moves, the boom swings." “Oh," said I. "And what is the clock for?" "The clock works the machinery. I'll explain it in the morning, and show you how 'Snow' develops the seismograms." "Snow" looked pleased, and led the way to the other little house. Here we found a pendulum that was not covered up. It rested on a heavy column of masonry, and one end of it pressed a tiny silver needle against a vertical band of smoked paper that moved slowly between two rollers. There was purpose of these instruments, to indicate slight changes of level. They are sensitive to a differin ten miles. That's ence in level of one inch And then he went on to tell how a pair of these pendulums, placed on two buildings at opposite sides of a city thoroughfare, would show that the buildings literally lean toward each other during the heavy traffic period of the day, dragged over from their level by the load of vehicles and people pressing down upon the pavement. "All these tons of weight make the earth's surface contract between the two rows of buildings, and that tips them together just as you tipped this column. You see the earth is so elastic that a comparatively small impetus will set it vibrating. Why, even two hills tip together when there is a heavy load of moisture in a valley between them. And then when the moisture evaporates in a hot sun, they tip away from each other. These pendulums show that." I listened in wonder, and presently we went back into the house, which is a real corner of Japan, with a Japanese servant salaaming about and bringing in pleasant things to drink, and the Professor's wife, a Japanese lady, doing the honors with all the grace of her own country. And the Professor gave some amusing reminiscences of their troubles in getting the instruments properly set up. To begin with, there were imperceptible air currents that would set the booms swinging in a most perplexing way; and when these were disposed of, there came the ghost of Charles I. out of its dungeon and blew the little lamp out, being displeased, so the neighbors declared, at their invading old Carisbrooke Castle (as they did) with such unholy contrivances. After much vain conjecture over this lamp incident, "Snow" finally discovered that it was the doing of a small beetle, which had managed to drop down the tiny glass chimney from the castle ceiling and get himself burned to ashes before extinguishing the flame. other side, and hold it there until his strength failed again. And so he would keep on for an hour or two until quite exhausted, enjoying the fun immensely, and never dreaming that he was manufacturing wonderful seismograms to upset the scientific world, since they seemed to indicate shocking earthquake disasters in all directions. Such yarns as these the Professor spun for me that evening in his charming Japanese-English home, and he showed me photographs of earthquakes in Japan, taken by himself and his friend Professor Burton, and pictures of volcanoes blowing their heads off, and he told me of exciting adventures crossing Iceland with a remarkable man named Watts, who would jump across yawning chasms just to see if he could do it. Finally, we went to bed. The next day gave me a better understanding of the instruments, and a good idea of the regular routine of work in an earthquake observatory. I followed" Snow" through his ordinary round in the little houses, saw him wind the clocks that keep the record bands moving, glance through the slit in the red box to make sure that the boom was swinging free, fill the lamp, see that the watch which marks the hours on the band was right to the second, mix some fresh deNext there appeared upon the scene or veloper for the films, and then, for my esperather made himself felt- a little gray cial benefit, draw the red window, and de"money-spinner," that managed to hide velop the accumulation of four days, a strip inside the red box and would come out nights about fifteen feet long, which might have for experiments of his own. This little on it a record of earthquake horrors, or spider knew nothing about earthquakes, but might have nothing. You can never tell took the greatest interest in the swinging of until the end of the week, when in the ordithe boom, and soon began to join in the game nary course a batch of seven days' films is himself. He would catch the end of the boom developed. In this case there was nothing, with his feelers and tug it over to one side only a straight line down the length of the as far as ever he could. Then he would band. The earth had been behaving itself. anchor himself there and hold on like grim But they showed me other films from other death until the boom slipped away. Then he weeks that indicated a very different state of would run after it, and tug it over to the things. SEISMOGRAM OF A BORNEO EARTHQUAKE THAT OCCURRED SEPTEMBER 20, 1897. As for the instruments, I saw that they are simple enough in principle, though most admirable in perfection of adjustment and delicacy of working. Beautiful devices they are, to do for our sense of level, if I may so express it, what the microscope does for our eyesight. A horizontal pendulum, or boom, poised against a knife edge at the base of a mast, that is the essential feature. A wire stay from the masthead supports the far end of the boom, and a weight hung from it keeps everything taut. Then two backscrews allow either leg of the supporting tripod to be raised or lowered by the thickness of a spider's web, and even so small a change of level as that disturbs the end of the boom. And that makes the point of light move on the band of paper, and that movement is photographed, so that the record shows a slight loop. As nothing is allowed to disturb the boom, once the pendulum is adjusted, it follows that if the record band shows loops and curves instead of a straight line, it is because the earth's surface has moved underneath the supporting column and changed its level. As a matter of fact, the earth's sur When a man finds himself in the midst of such an unfamiliar subject as earthquake shocks that cannot be felt, he naturally asks questions, and I asked a great many during my stay at Shide. For instance: "Does the ground really move, Professor, when these waves come from the other side of the earth?" "Undoubtedly; it rises and falls just as the ocean does. You see, the earth's crust is very elastic; it is constantly quivering and pulsatory, I might almost say breathing.' How much does the ground rise and fall with one of these waves?" "Oh, about three inches." "What! the solid earth comes up three inches right under us and then goes down three inches?" "Certainly, it does that very frequently." PIECES OF A SUBMARINE CABLE PICKED UP IN THE GULF OF MEXICO IN 1888. THE KINKS ARE CAUSED BY face moves very frequently with tremors like a creature of life, and with long heavings caused by distant seismic disturbances. And for each of these movements the pendulums give an individual record with characteristic waverings and loops on the band, and queer ups and downs that mean nothing to the inexperienced eye, but everything to the seismologist. When "Snow" brings in news of something on the band, there is excitement in that quiet house at Shide as among waiting tiger hunters at a crashing in the jungle. In each of these records the time is marked in hours along the edge of the band, this being done automatically by hourly passage of the long hand of the watch over the slit in the red box, that shuts off the light for an instant and makes a line on the photographic film. it "But why don't we see it or feel it?" "Because moves so slowly and evenly; fifteen seconds, perhaps, for the lift, and as many more for the descent. And then the waves are so longseveral miles between two creststhat everything about us rises and falls together; half of all London heaves up and settles down with a single breathing." And how long does it take these waves to travel around the earth, say from Japan?" They don't travel around the earththey travel through the earth; that is one of the most important discoveries we have made. If they were transmitted in the earth's crust around the circumference we should get two records for every earthquake 66 66 |