430 . SCIENTIFIC RECOKD FOR 1882. 



will allow measures to he made). This first motion was to decrease 

 the west declination and increase the horizontal force at both places. A 

 bold motion in the two Zi-ka-wei curves at 11.30 A. m. (increase of dec- 

 lination, decrease of horizontal force) has* corresponding decrease of 

 horizontal force at Greenwich, not accompanied, however, by much mo- 

 tion in declination. And of nun)erous fluctuations occurring at Green- 

 wich, between noon and midnight of the same day, some appear to 

 correspond with motions at Zi-ka-wei whilst others do not, 



A calm state follows at both i)laces until near noon of August 12. 

 Upon this day at about 11.40 A. m. the magnets at Greenwich made 

 a further start, and until 4 p. M. Ihe movements were large. A corre 

 sponding start is also shown in both the Zi-ka-wei curves, commencing, 

 according to the register, some minutes sooner than at Greenwich, the 

 movements following being similarly large. Afterwards, until C A. m. 

 of August 13, considerable oscillation was nearly contiuually shown at 

 Greenwich, there being especially a.large change of declination between 

 7 and 9 P. M. (August 12) ; but there is no strongly marked motion at 

 the latter time at Zi-ka-wei, and the changes tliroughout are much 

 smaller than at Greenwich. Later, on August 13, further oscillations 

 occur at both places, but the separate motions are in no particular 

 accordance. This j)eriod of disturbance seems to definitely come to an 

 end at both places at G A. m., August 14. 



A period of quiet is broken at Greenwich August 18, at 1.45 p. m., 

 by a sharp though small movement both in declination and horizontal 

 force (increase of both). There is a corresponding sharp increase 

 (after quietude) of horizontal force at Zika-wei, but no change of decli- 

 nation. A bold increase of declination and decrease of hoiizontal force 

 at Greenwich, 7 A. M. of August 10, is accompanied by a similar de- 

 crease of horizontal force at Zi-ka-wei, but with little change of decli- 

 nation. Bolder changes occur at the latter place at noon, but with 

 comparatively small change at Greenwich. The magnets become quiet 

 at both places at or near midnight, August 10. 



The general result of this comparison- of Greenwich and Zi-ka-wei 

 curves appears to be that, after a quiet period, the first indication of a 

 disturbance, if sudden (it need not be large), occurs simultaneously or 

 nearly so at both places, bnt that during the continuance of disturbance 

 the oscillations of the magnets seem to be so locally modified that it 

 becomes difficult to trace correspondence: some movements appear to 

 correspond and some not. A strongly marked bend in the trace at one 

 place may appear, as it were, stunted in that at the other place, or may 

 not be perceptible at all. The disturbances appear to die out at pretty 

 much the same time at both places. All this confirms very much what 

 Mr. Whipple has pointed out as regards Melbourne. {JS^iture, xxii, 

 p. 558.) 



M. Dechevrens of Zi-ka-wei, in some remarks which accompany the 

 sheet of curves, notes that the disturbance of August 11-14 is the great- 



