at any time, without inheritance from all that had gone before as was inevitable with the Milne machines. He distributed a few of his beautiful instruments over Russia and Siberia, while they found their way also to England, France, Belgium, Holland, and one or two more distant stations. He thus initiated a new accuracy in seismology. Besides this he was expert in the mathematical theory required for the discussion of the records. Altogether a wonderful and delightful man whose loss was an incalculable blow to the science. A meeting of the International Association of Academies at St Petersburg in 1913 gave us the opportunity to see his wonderful installation at Pulkovo, and he had already been to England more than once, especially to the International Congress of Mathematicians at Cambridge in September 1912, when he gave a stirring address (in English-he was master of several languages) on seismology. In May 1915 he accepted nomination as Halley Lecturer in Oxford for the following May, and for many months retained the hope of fulfilling his engagement. But the heavy work of organising the Russian Meteorological War Service broke him down, and he died in August 1916 within a few weeks of the date on which he had hoped to lecture. We can scarcely suppose that he, a member of the ruling house, would have been able to revive Russian seismology. As it was, it died a natural death when existing stores of photographic paper came to an end. They could make no more in Russia and could not afford to buy from abroad. A bright patch among the clouds is that the Petrograd Academy of Sciences managed in 1919 to print Galitzin's last two papers and have sent copies to England. They are of great importance, like all else he did. One, a searching inquiry into the possible causes of microseisms,' will be presently considered. The other is more technical, and concerns the angles at which earthquake waves from a distant station strike up to the earth's surface; but it is of fundamental importance to scientific investigation.

Since this was put in type, a letter (dated Nov. 30) has come from the Bussian Académie des Sciences saying that seismological work was recommenced during the latter half of 1923 at Pulkovo, Ekaterinburg, Irkutsk, Platigorsk, Baku, Tashkent, and Cabansk, and in 1924 will be started at Tomak, Makeyevka, and five other stations in Turkestan and the Caucasus.

The impulse to pause for a few moments to remember so great a loss to the world was well-nigh irresistible but we must now return to the point at which Galitzin's name drew us aside. He had made a vital improvement in the pioneer instruments which Milne had scattered over the world. To secure the desirable end of getting news from all directions as speedily as possible, Milne had studied simplicity and economy in his seismograph rather than the highest accuracy and efficiency: his motto had been, 'Let us have something which any one can work, even far from civilised appliances.' Stimulated by his enthusiasm cable companies, island governors. and exiles from home set up his machines and sent the records to Milne's home in the Isle of Wight for his collation and discussion. The result was a most valuable preliminary survey of the kind of information likely to be forthcoming. But Milne recognised the great instrumental advances made by his friend Galitzin, and heartily welcomed them. He hoped that his own seismograph might be improved in the same direction, and at the time of his death in 1913 Mr J. J. Shaw of West Bromwich was already at work, with Milne's cordial approval, on these improvements. They were successfully completed a year or two later, and the resulting instruments, under the name 'Milne-Shaw,' are now established in many parts of the world, giving information comparable with that from Galitzin instruments, at a much reduced cost of equipment and working. It would have been quite impossible to obtain the erection of the beautiful but expensive Galitzin instruments at more than a few of these stations, if at any.

We have as yet not given any precise idea of the form of a seismograph, though its action has been compared with that of a swing. It is indeed essentially a swing, though it is more like a swing-gate than a swing which goes with a roundabout. Perhaps the nearest analogy is the horizontal boom attached to a ship's mast, which we have seen swing idly to and fro as the vessel rolls among the billows. It requires a little effort of imagination to picture our solid earth rolling about a seismograph in a similar way; but the analogy is really very close in all but actual scale. An earthquake sends small waves rolling or shivering along the earth's surface,

and also through its interior. The solid seismograph pillar rocks like the boat, and the seismograph boom swings in miniature like that which, on a boat, is apt to injure the unwary. The miniature swings are magnified several hundred times and photographed on a drum which revolves in spiral fashion. The resulting trace usually appears as even line, though on looking closely one can see the persistent small microseisms.' But there is no mistaking a large earthquake. On developing the film it leaps to the eye,' and I well remember the experience of this kind which startled me on the morning of Sunday, Sept. 2, 1923. For the great earthquake of the preceding day we had been prepared by a telegram from Mr J. J. Shaw, as well as by the news in the morning papers. But Sunday in these postwar days obstructs papers and telegrams, and I was not only quite unprepared by outside news for anything unusual, but predisposed to expect the comparative quiescence which usually follows an exceptional shock. But immediately the developer began to work, there was a great patch on the film, so nearly like that of Saturday that my first thought was of some extraordinary mistake by which the previous day's record had become duplicated. When further scrutiny showed this view to be untenable, and that the second earthquake had really occurred, my mind at once pictured the corresponding bewilderment of Mr J. J. Shaw, whose seismograph rings a bell in his bedroom, at being wakened from sleep at almost the same early hour (4 am. summer time) on two nights running. Not till after that did my thoughts travel from the instrumental records to the ghastly possibility that the rescuers at Tokyo and Yokohama might have been themselves overwhelmed in their works of mercy by a catastrophe as appalling as that of the preceding day. For some reason, as yet not quite clear, this was happily not the case. Possibly the slight variation of locality indicated below may have made all the difference; or a greater depth of the shock. But neither of these seems quite adequate. Can it be that further destruction was practically impossible? that houses thrown flat could not be overthrown further? The official report quoted in the 'Times' of Sept. 10 says:

'Before the earthquake there were 440,548 buildings, anca of these 316,087 have been destroyed or damaged. The popula tion of Tokyo before thé disaster was 2,031,391; the number of refugees and homeless is officially given as 1,356,740. . . . There are still 135,000 persons without shelter of any kind in Tokyo.

With some hesitation I approach the attempt to give an idea of what is recorded by these beautiful seismo graphs. Much of it is too technical to interest the general reader, and yet without some illustrative figures he can scarcely visualise the interesting problems we have been able to attack by utilising these records.

There are many ways in which a disturbance can be communicated from a distance, but for the present we will limit attention to three of them, usually denoted by the letters P, S, and L. The P waves are the first to arrive (unda Prima), and though the S waves are not really second, that was the designation intended, since they follow the P waves after an interval, which is of – great importance and is denoted by S-P. In each case, by a fortunate coincidence, the designating letter is a reminder of the nature of the disturbance, as well as of its time of arrival; for P may stand for 'push' or 'pull, and S for 'shake' or screw.' When we give a pull at one end of a rope we cause an effect at the other end much more quickly than when we give a shake, which travels in a snake-like manner. The longer the rope, the greater would be S-P, the interval by which the shake follows the pull; and though the solid earth does not much resemble a rope, yet earthquake shocks are communicated through the body of the earth along definite curved paths which may be compared with ropes. The letter L signifies long waves, and represents much slower or longer fluctuations than those of P and S. But it may also stand for last waves, so that in each case the letter has a double significance, reminding us of the order of arrival (prime, second, last) and of the nature (pull, shake, long). And again the L waves arrive last because they come the longest way round,' which in this particular instance does not turn out to be the shortest way home.' They came in fact not through the earth but round it-along the surface, and are sometimes called Rayleigh waves, because the late Lord Rayleigh first explained their nature.

The following short table will give an idea of the times taken by these three kinds of waves to reach various distances from the starting-point or focus of the earthquake, supposing that point to be close to the earth's surface. The distances are measured round the surface of the earth and are given in three different ways: first of all in degrees, of which 180° take us round to the opposite point of the earth, and 90° take us round a quadrant; secondly, in kilometres, of which 20,000 take us to the opposite or antipodes, and 10,000 round a quadrant; thirdly, in miles at 5 miles to 8 kilometres, which is near enough for our purpose. The most convenient unit of the three is the first, since we can apply it to a globe of any size.

2,222

1,389

3,333

2,084

4,444

2,778

5,556

3,473

6,667

4,167

m. 8.

m.

35

The actual tables used by seismologists are, of course, much more detailed and extensive than this; but enough is given to show their nature and the way in which they can be used. Suppose, for instance, that on developing the seismograph film we find the record of a distant earthquake. We notice from the time marks on the trace that the very first disturbance of the usually quiescent trace was at 5h. 3m. 228. This is the time of arrival of P. The trace then continues to be disturbed for some little time to a moderate extent, when suddenly 8 arrives (say, at 5h. 13m. 26s.) as is shown by a much more extensive agitation of the trace, which continues till about 5h. 30m. or 31m., when the nature of the agitation changes, the movement being slower and longer (L), and gradually developing into quite extensive