steady N.E. rising of 2"-70 until February 2, when at 7 P.M. there was an earthquake. Tremors are slight. February 2-5 (0-43, 0-23, 0"-23).-E shows the usual daily tilting with small tremors. After the earthquake of the 2nd F continued to rise until the 3rd, when at 8 P.M. the light left the film. February 5-7 (043, 023, 0-23). The daily waves in E and A are pronounced, and when one is large the other is large also, and vice versâ, In F the waves are not so marked. Tremors are slight on A, but underground in E and F they reach 3 mm. February 8-12 (0-43, 0"-26, 0.23).—E daily deflection (9-10) slight, but from 10-11 like A. On A the daily deflections are well marked, but on F they are very slight. F, however, falls from 84-67 (391). Tremors are greater on the surface, reaching 6 mm., than they are under ground. Н Rainfall in mm. curves. February 12-15 (0-43, 0"-25, 0"-39).-E shows well-marked daily A out of order, and therefore no record. F found to have changed its sensitiveness; therefore reset, so that 1° 0'23. From 12-13 F wandered from 75.5 to 52 (897), and again from the 14-15 it crept from 72 to 62 (230). These movements, which so often occur with F, mean a change in sensibility. Both instruments show tremors of 3 mm. February 15-19 (0-43, 0"-25, 0-26).-On E and A the daily waves are seen as a succession of symmetrical waves, gradually increasing in height and in length. Close upon the crest of the last and largest of these waves an earthquake occurs. Fonly shows the last of these daily waves, the remainder of the trace being a straight line, indicating a slight N.E. sinking (130). Tremors on all three instruments are slight. February 19-22 (0-43, 0-25, 0-25).-E and A show a continuation of the daily waves. Between the 21st and 22nd both instruments gave a straight line. F only shows the wave of 20-21, but it shows a N.E. sinking from 76 to 40 (8"·00). On the 20th, at 9.30, there was a strong shock. A shows two series of strong tremors, which are only faintly indicated by the underground instruments. February 22-26 (0-43, 0.25 0.26).—E and A show well-defined daily waves. F is nearly a straight line, but wandered about 30 mm., as if N.E. had sunk. Tremors are seen from 6 A.M. until noon on the 23rd, and again from 6 P.M. on the 24th to 4 P.M. on the 25th on A and F they reach about 5 mm. The earthquake of the 24th is not shown. The daily curves on E are marked, but they are irregular. The shock of the 27th occurs just over the crown of the daily wave, which was at 10 P.M. The crest of this tilting, both in time and amplitude, was unusual. On A and F the daily curves are slight; on A, like E, they are irregular. Tremors of 2 or 3 mm. are shown on A and F on the 26th, 6 to 7 P.M.; 27th, 6 A. to 4 P. ; and on the 28th, 6 a. to 1 p. The last are visible on E. F wanders by a N.E. sinking through 10 mm. On March 1 the direction of motion commenced to change, that is, there was a N.E. lifting. March 1-5 (0-43, 0'25, 0'26).-On E the daily curves are large, but at unusual times. A shows slight daily curves, but a N.E. lifting of 10 mm. F shows a N.E. lifting of 22 mm. Tremors are seen on A on the 2nd, 2 A. to 11 A.; and this agrees with E, but not with F, which shows slight tremors, March 1, from 9.30 a. to midnight. March 5-8 (043, 0.25, 0.25).-E shows a well-marked series of daily curves, and wanders 8 mm., as if the S.E. was rising. The daily curves on A are slight, but the trace is faint. F wanders 40 mm. as if the N.E. was rising. On March 6 small tremors are recorded, but only on A. March 8-12 (0·43, 0.25, 0"-26).-E shows slight daily curves on the 8th, 1 P. to 10 P. A sinks on N.E. side 4 mm., showing tremors of 6 mm. It then rises to the 10th, 8.30 P. 12 mm. At 8.40 an earth quake. Frises on N.E. side 40 mm. Tremors on E and F are slight. March 12-15. (0-43, 0.25, 0.26). The daily curve is barely visible on E, which shows small tremors. shows curves, but they are irregular, and the N.E. sinks 15 mm. A Frises 23 mm., that is, the direction of motion is contrary to A. Both A and F show small tremors. March 15-19 (0"-43, 0.25, 0"-26).-E clock stopped, and therefore no records until end of month. From the 15th to 16th A was steady, but from this date onwards it gave large daily curves. On the 15th, and at 3 A.M. on the 18th, there were earthquakes. During the three days A rose 9 mm. F does not show daily curves, but it rose 39 mm. The conclusions I arrive at respecting this section of the report is, that instruments on the surface and underground show diurnal movements, which closely agree in the times at which they occur. These movements are most pronounced underground by pendulum E, the excursions of which have in nearly all instances been greater than those shown by pendulum A in my house. The crest of a wave which corresponds to a N.E. lifting on A and a S.E. lifting on E has usually been reached between 4 P.M. and 10 P.M., the movement in the opposite direction being completed between 5 A.M. and 10 A.M. It does not seem that air temperature has had any measurable effect in the production of these movements, because they have been most marked beneath the surface, where the change in temperature during twenty-four hours has practically been zero. The opportunities for observing whether they hold any relationship with rainfall have been few. It is possible that the rainfali of March 16 and 17 may have been connected with the large motions of A between March 16 and 18, but the largest motions of E on March 1 and 2 occurred during a dry period. After the rainfall of January 25 and 26, and again after that of February 8 and 9, it may be noticed that the time at which E completed its N.W. excursion was delayed, while after that of March 16 and 17 pendulum A was delayed in its N.E. movement, and these are the only occasions on which rain fell in any quantity. (j) The Wandering of the Pendulums. The following table shows the daily change which has taken place in the position of the pointer of pendulum A, and for a few days that which has taken place with pendulums F and E. The numbers indicate so many millimetres of motion. The sign + prefixed indicates that the scale readings were increasing, while the sign indicates that they were becoming smaller. When the signs for A and F are similar, then these two pendulums were moving in the same direction. The difference between the readings of an instrument when a new film was put on and when it was taken off gives the distance through which a boom has been displaced during periods of three or four days: this quantity is also expressed in seconds of arc. The fifth column gives the rainfall in millimetres, and the sixth the number of hours of sunshine, but only between February 25 and April 30. These latter records were taken for me by my colleague, Prof. W. K. Burton. |