Art. 7.-THE STUDY OF EARTHQUAKES.

ON Sept. 1 last the world was shocked by the news t the cities of Tokyo and Yokohama had been destro by a great earthquake. The Greenwich time of main shock can be given within a few seconds 20h. 51m. 23s. (or nearly 4 a.m. summer time), wł is just after noon at Tokyo, so that the terrors of de ness were not in this case added to the confusion. the disaster was appalling enough without them. Ean quakes which overthrow cities generally bring both and flood in their train, and Yokohama seems to ha suffered chiefly from fire. Many survivors were gathe as quickly as possible on to relief ships sent from Ko and at one time the abandonment of the city was c templated; but the resilience of the human race is remarkable that the work of reconstruction beş almost immediately the work of succour and res was well in hand. The whole incident is still so fr in our memories that there seems scarcely any need repeat the details here. We remember the anxi inquiries for friends who might have been involv with their varying issues. Earthquakes, and especia Japanese earthquakes, are so closely associated in ms minds with the name of John Milne that it will welcome news that his widow, who returned to Jap after the war, and settled in Tokyo, was fortunat away on a visit to Hakodate. The University of Tok suffered grievously; but the observatory escaped.

On such terrible occasions it seems almost sacrile to turn from the human suffering to the scientific asp of the destruction. But the Japanese learnt thorougl the lessons inculcated by Milne and his colleagues in t last quarter of the 19th century, and we may feel co fident that scientific observation and measurement the effects of the earthquake began almost at once. is more than half a century since Robert Mallet point out the importance of losing as little time as possible instituting investigations on the spot, for reasons whi we could almost put directly into the mouth of 1 Sherlock Holmes. On Dec. 16, 1857, there was a d structive earthquake near Naples, accounts of whi 'began to arrive in England, through corresponden

and the public press, about Dec. 24.' (News travelled slowly in those days, recent though they seem.) On Dec. 28 Mallet wrote to the President of the Royal Society offering to hasten to Italy to investigate the matter, if 1507. could be found for his expenses. The urgency and novelty of the enterprise are both shown clearly by the following sentence:

'Within the last ten years only seismology has taken its place in cosmic science, and up to this time no earthquake has had its secondary or resultant phenomena sought for, observed, and discussed by a competent investigator-by one conversant with the dynamic laws of the hidden forces we are called upon to ascertain by means of the more or less permanent traces they have left. . . . Observed without such guiding light, or often passed by unnoticed and undiscovered for want of it, the facts hitherto recorded are in great part valueless.'

The appeal was successful, and Mallet spent some months collecting on the spot information which he digested in two most valuable volumes, published in 1862. In them Mallet did not neglect the general reader, who might expect the charm that belongs to tales of shipwreck, of battle or wild adventure,' but he warns him that he will find the events by which such multitudes perished and in which so many cities were overthrown,... sobered to an extent not always found in earthquake stories,' and, moreover, utilised for purposes of extracting information about such matters as the depth of the focus of the main shock, which Mallet puts at about eight miles below the earth's surface. Near the end of his work he gives us a more precise view of the exaggerations which he has thus 'sobered.' 'The well-known Jamaica earth fissures.' he writes, that were said to have opened and closed with the wave, and bit people in two, must be regarded as audacious fables.' And again:

The vulgar mind, filled from infancy with superstitions of terror as to "the things under the earth," is seized at once by the notion of these fissures of profound and fathomless depth, with "fire and vapour of smoke issuing from within their marky abysses; but they should cease to belong to science.'

The lessons taught by Mallet have not been wasted.

Destructive earthquakes have since that time genera called into being an investigating committee, which issued a voluminous report. The California earthqua April 18, 1906, for instance, prompted a State Earthqua Investigation Commission which produced a reporti 650 large quarto pages-800 words to each-with plates and maps. It would require hard work, or so effrontery, to claim even a moderate acquaintance w earthquake literature nowadays. Some of it, of cour it is not necessary to retain in the memory. 7° Californian Commission has found itself no more a than Mallet to exclude the sensational or the curio Among the pictures of destruction at Leland Stanf University, for instance, is one of a statue of Lo Agassiz which had been thrown from a lofty positi had struck the paved floor with its head so forcibly to break a large hole, and was left in an almost verti position, but with its base in the air, the body but lit damaged, and the head completely submerged to t shoulders. There is certainly a modicum of informati bearing on the earthquake to be extracted from t circumstances of this impressive fall; but the m interest of the picture, which demands its inclusion in t Report, is independent of this scientific utility.

We come now to the important difference betwe this Report and that of Mallet. In 1857 informati gathered from the ruins of a destructive earthqua was the chief stock-in-trade of the seismologist; inde he had scarcely any other; but by 1906 the records seismographs at distant stations had been added, a Part II of the California report is devoted to these nov and fertile fields of study. It should be clearly understo that they supplement and do not supplant the earli seismological work. It is still as desirable as ever note the directions in which columns have been ove thrown or the angle through which they have be twisted; or to draw contour lines of various degre of destructiveness, delimiting the areas within whic houses have been first of all demolished entirely; secondl partially damaged; and thirdly, only shaken: or th regions within which people were killed, or merely fel a slight shake, and so on. Such contour lines envelop the epicentre in a manner which is very instructive &

to the locality of the prime shock. They are, of course, liable to be somewhat indefinite. As an extreme, if we were to inquire within what region the recent Japanese disaster was felt by human beings, we might be confronted with exceptional cases at very great distances indeed; for there is some evidence that it was actually felt in England. A lady of peculiar sensitiveness has

'for many years past,' to quote a letter of Sept. 10, been able to report almost every earthquake in all parts of the world, before any news comes in. She suffers from a curious nervous tension as though under the influence of electricity. It almost incapacitates her from work while it lasts, but goes off suddenly. These Japanese earthquakes have affected her badly, and she had a bad attack yesterday. She has consulted several doctors, but none of them has been able to relieve her.'

Almost immediately the explanation of the 'bad attack yesterday' was realised. A letter dated Sept. 11 followed, saying:

'When I wrote yesterday neither my daughter nor I had any outside tidings of an earthquake-but the evening papers reported one in India-precisely at the time when she was suffering most.'

The report was, of course, quite correct: there was a considerable shock in India on Sept. 9 at 11 p.m. of our summer time (22h. 1m. 30s. Greenwich). The testimony is unexceptionable and indicates a line of inquiry which has hitherto not been explored, and may supply unsuspected information both to seismology and to physiology. It would also be applicable to all large earthquakes, and not merely to those which occurred so near a city or inhabited district as to cause damage to buildings and to life. The observations to which Mallet directed attention are practically confined to these latter instances, which have an obviously accidental and somewhat fictitious importance. The almost purely accidental character of the damage done may be illustrated from the Californian earthquake of 1906. It occurred at 5 o'clock in the morning, local time, when the greater part of the city of San Francisco was asleep. In the workmen's quarter, however, the inhabitants had risen and lit their stoves to prepare Vol. 241.-No. 478.

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early breakfast before going to work. These stove were overturned and started fires. The fires were no at first serious and might have been extinguished bu that the earthquake had burst the water mains so the no hoses could be got to work. Hence the fire slowl and steadily spread, though it was ultimately conquere by somewhat heroic measures. But we see what acc dental importance is acquired by the time of occurrenc An hour or two earlier no stoves or fires would hav been alight at all, and much damage by fire would hav been saved: an hour or two later, all the domestic fire would have been lighted, the conflagration would hav been immense, and probably nothing could have save the whole city.

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But nowadays, as already remarked, in addition t the information collected on the spot, which may b affected by what can be fairly called accidental circum stances of this kind, we have available a number o data from seismographs established at stations all ove the world. The Californian report quotes records fron seventy-six stations, the nearest being the Lick Observa tory, only seventy miles away, and the most distan Mauritius on the other side of the globe. They do no include Pulkovo, for the great Russian organisation which did so much for seismology under Prince Galitzin for a few brief years, until its famous leader died unde stress of the war, had not yet been started; and mos of the instruments were of the pioneer type devised by John Milne, which Galitzin improved almost out o recognition. But with an earthquake of sufficient in tensity the most primitive instrument will give ar accurate record. The defect of Milne's instruments was that, with a feeble earthquake, they took a little time to get going, depending for their sensitiveness on the principle of resonance'; just as a child giving a swing to another may require several well-timed pushes before the swing begins to move sensibly, whereas a strong man could start it with one vigorous effort.

Galitzin, by beautiful electro-magnetic magnification, flattered the feeble earthquakes so that though they had. been before as children, they now seemed like strong men; and he was thus able to abolish the resonance' principle; so that his records showed clearly what was happening