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hour 47 minutes. These waves had a submarine origin about 40 miles off the N.E. corner of Yezo, in about 43° N. lat. and 146° E long., and to reach Tokio had travelled some 570 miles. I think that they have been recorded in Rome, and I have written to Dr. E. von Rebeur-Paschwitz to learn whether they were noted at Potsdam, Wilhelmshaven, and Strassburg. They ought to have reached the Birmingham instrument about midday on March 22.

While I am writing in Sapporo (Yezo), on June 20, at 2.32 P.M., a terrible earthquake has happened in Yokohama and Tokio. As we are 9 hours E. of Greenwich this should be recorded at the above stations and those in Russia at about 6.30 A.M. on the same day.

From the manner a pendulum behaves I infer that its movements are due to the fact that it is being tilted, and because the photographic records are always less than the distances through which I have seen it move, the values given for the tilting are less than those which actually happened. If a pendulum is set swinging, for example, by standing near its column, through a distance of, say, 5 mm., it will come to rest in about 5 minutes. In calculating the duration of a disturbance allowance has been made for this factor.

The point of greatest importance in connection with the foregoing remarks is the inference that the catalogue of Kamakura earthquakes represents a series of large disturbances which have travelled very great distances. Had there been any local disturbances sufficiently great to produce earth waves, then the pendulums must have recorded the same, but no such disturbances occurred. As it is not likely that earthquakes originating at a distance could in any way be connected with local tilting, if earthquakes and tilting have any connection those which might be compared with the curves already given are those of local origin which have been recorded by seismographs in the vicinity, and not those which are shown on the photographic films. Between January 24 and March 18 fifteen shocks were noted in Tokio, which cannot be seen on the photographic traces. Because nearly all these were of the nature of elastic vibrations it is probable that they were for the most part of local origin. This is a point which can only be definitely settled by analysing the reports accumulated at the Meteorological Bureau, which for various reasons cannot be done in time for the present report. These 15 shocks are indicated on the curves as black dots, and it is certainly worth observing that they chiefly occur during the seventh, eighth, and ninth weeks when tilting wast marked. Because the observations are few and because I am not yet in a position to analyse all the materials which have been accumulated, too great stress should not be laid upon this last observation. It only indicates the nature of an inquiry that is being made.

The last point to which attention must be called in connection with the Kamakura disturbances is that the greatest motion has nearly always been in the direction of the dip, that apparently being the direction of least resistance to yielding. By reference to the catalogue it will be seen that there are three instances where small disturbances have only been recorded by C, but in all other cases the records are given by both instruments, the dip record being much the larger, or the record has been given by D alone. For example on February 8 D was tilted for 30 minutes through an angle of nearly 7", while C did not show that any motion had taken place.

(f) The Observations in Tokio.

Although the observations made in Tokio were carried on at two stations, because these stations were only 1,000 feet apart, and because both were on the alluvium which here forms a layer perhaps 100 feet in thickness above the tuff rock, it was anticipated that the records would to some extent be similar in character. For this reason they are described

together.

Machine A, which is similar to those used at Kamakura, is installed on a table-like stone column in my house. The column is 4 feet square and rises clear of the floor from a concrete bed. For a few hours in the morning and in the afternoon the sun produced a marked tilting as it shone upon the column through a window on the south side; on closing this window by a shutter on the outside and by a curtain on the inside, this effect disappeared, while the diagram from a self-recording thermometer occasionally showed during 24 hours a steady rise or a steady fall of 1° or 2° C. More usually, however, the diagram showed that from 9 or 10 A.M. until 5 or 6 P.M. there had been a rise of 4° or 5° C., after which the temperature fell until next morning. This is a point to be noted, because it will be shown that the daily tilting and, in a less marked degree, the intensity of a tremor storm have a similar periodicity.

The water level beneath my house oscillates above and below 36 feet.

Machines E and F, which are underground, only differ from A in the fact that their booms are brass tubes. Machines A and F are parallel to each other, and point N.W. Machine E is at right angles to A and F. With an increase in the readings of A or F the movement corresponds to a lifting of the ground on the N.E. side of these instruments. increase in the scale readings of E corresponds to a tilting on the S.E. side.

An

The underground chamber is excavated on a flat piece of ground about 20 feet below the site of my house. It is 13 feet deep and 20 feet square. The floor is covered within. of asphalt, which rests on a bed of concrete 6 in. thick, which in turn rests on a bed of well-rammed gravel. The walls and ceiling are brick with clay puddle on the outside. Above the chamber a wooden house has been built; the entrance is by double doors, and it is fairly well ventilated by gratings for the admission of air and a short iron chimney for its exit. The daily fluctuations in temperature in this underground room are practically zero, the diagram from a selfrecording thermometer showing a straight line which at present indicates a steady rising of 1° C. per week. The water level in a well about 80 yards distant, where I have established a tide gauge, is about 25 feet below the surface. The floor of the chamber is therefore about 12 feet above water level, but it must be remembered that this level may rise and fall through 2 or 3 feet.

(g) Sensitiveness of the Instruments.

From time to time the sensitiveness of the instruments was determined, and if necessary they were readjusted.

The first column in the accompanying table indicates the number of millimetres through which the end of the boom travelled by a 1° turn of

the sensitising screw in the bed plate, the pitch of the screw being 1 mm. One complete turn of the screw attached to A tilted the bed plate of this instrument through an angle of 1 in 228. For E and F one complete turn represented an angle of 1 in 222.

The ratio of unity to the numbers in the second and fourth columns is the tangent of the angle corresponding to a deflection of the boom through a distance of 1 mm., the values of these angles expressed in seconds of arc being given in the third and fifth columns.

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To bring the points of E or F to the centre of the scale, a rough adjustment is made with the sensitising screw, after which the boom may be slightly moved to the right or left by means of a stone about 40 lb. in weight which I shift on the floor of the chamber towards or away from

the instrument.

(h) Daily Tilting.

The approximate times at which the diurnal wave reached its maximum and minimum, and the amplitudes of these waves for dates between January 24 and March 1, 1894, are given in the table, p. 97. Should it be necessary the table may be completed from December 9, 1893, up to the middle of June 1894. With but few interruptions the records have been continuous. It will be observed that the records for F, which is parallel to A, are only one or two in number. The letter s means that the diurnal wave is too small to be measurable, while blank spaces indicate that it was not visible, the photographic trace being a straight line. Had greater sensibility been given to Fit is quite possible that the daily wave would have been recorded; but this could not be done because, even with the stability it had during three days, the end of the boom often wandered through a distance greater than 1 inch, and the spot of light left the film. This wandering of the pendulums has been already referred to. On two occasions when gave measurable waves (January 31 and February 2) the times of their occurrence approximately coincided with the movements of E and A-that is, the movement of the pendulums in one direction was reached in the evening, after which they gradually returned to reach their normal position in the morning. The pendulums E and A, although at right angles to each other, have shown a marked synchronism in their movements. would seem that these two instruments have either been simultaneously acted upon by independent forces, or that they have recorded components of a common force, which has acted in different directions at the two

F

stations.

It

The latter explanation appears to be the more satisfactory, because

periods of steadiness when the diagrams were practically straight lines happened at the same time, and because the large or small movements of A have agreed in time with the large or small movements recorded by E. As illustrative of this synchronism, the movements of these instruments between February 15 and February 25 have been plotted as curves (see Plate IV.).

Once or twice it will be observed that crests of waves have been reached after midnight or in the morning, which agrees with the results published in 1893 (Thirteenth Report). In the majority of instances, however, this has been reversed, and the movement of the pendulum in one direction has been completed at any time between 4 P.M. and 10 P.M., and it has returned to its original position between 5 A.M. and 10 A.M. Because the waves on the original diagrams are long and flat it is usually difficult to determine with any accuracy the exact time at which an excursion in any one direction has been completed. Sometimes the boom has remained at rest at one of its limits for five or six hours before the return journey has been commenced. The movement from 5 or 10 A.M. until 4 or 10 P.M. has nearly always been quicker than the return motion during the night.

The amplitude of motion does not seem ever to have exceeded 3"-00. In 1893 I described movements of from 200 to 1000; but these which I now discuss are the result of observations with several instruments, although I cannot answer for any great degree of accuracy, I am inclined to consider the new determinations as being nearer the truth. The movements of E, which is underground, have usually been greater than those recorded by A in my house. In a few instances, however, the deflections of A have been the greater.

As an appendix to the table on p. 97 short abstracts from my journal are added:

(i) Extract from Journal of Records obtained in 1894.

In the following extracts the sensitiveness of the instruments means the angular tilting required to produce a deflection of one millimetre of the points at the end of the booms. These degrees of sensitiveness for the instruments E, A, and F are given in fractions of seconds of arc immediately after the date.

January 24-27 (018, 023, 0·43). From the 24th to the 25th E showed a rapid S.E. lifting of 3" when the light spot left the film. A small earthquake occurred at 10.48 A.M. on the 25th. From the 25th to the 27th there was a S.E. lifting of 1"-62. Daily waves of 1"44 and 1"-26 are well marked. All instruments showed tremors, but they are most marked underground on E, where they reach 12 mm. On A and F the daily waves are hardly visible.

January 27-30 (0"-19, 0"-23, 0"-18).-E moved 5"-32, and the light spot left the film. It shows tremors reaching 14 mm. A and F agree in showing a N.E. lifting, but the daily wave is only seen on A when the tremors reach 10 mm. The tremors are most pronounced underground.

January 30-February 2 (0-43, 0"-23, 018).-E shows similar characters to A and F, that is, the trace is at first straight, and then two daily waves and three small earthquakes. For the first day A and F are straight, but for the other two days there are daily waves. F shows a

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Diagrams showing daily movement of pendulums on the surface (A) and underground (E).

Tracings showing daily motion of water in a well.

Illustrating the Fourteenth Report of the Committee on the Earthquake and Volcanic Phenomena of Japan.

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