54 



;; ■")•_'. F.mlirst J,;r„,tls. 



Tlu' lollciwiii;^ ai-coiint of tlir rarlic.-t cMitlniiiiikc rcmiil olituiiR'd l>y tlio 

 writer is taki-n, witli little alteration, from a ]i:i|i<'r entitled "Notes on f^onie Eeeent 

 Eaithi|iiake.-.,'' |)uMi-lieil in tlie Tian.^aftion- of tiie Asiatic .Society of Japan, Vol. 

 IX, |). 40. Tiiis was notliin<r more than a feel)ie shock, which «lid no damage 

 to linildings, and was jn.st siieli as residents in Tokio ex|)eet to occur at intervals 

 of a few day.s. 



E.VRTnQi AKK OF Is'ov. ^JüD, 1 ■'^SO, •") II. -J-'ijr. A.M. — ÜKcor.i) (jivkn nv tue 

 HonzoNTAi, Pkxdi'i.im PEiSMO(;RArii. 



One jiointer rejji.stereil Kast-West motion, the other North-South motion. 

 Tiie <rla.<s ])lato of this instnimeiit was revolvinu; at the rato of one turn in thirty 

 seconds, and the record extended over three comiilete revolutions. In other 

 words, the carth(|uake lasted continuously duriiii^ one and a half minutes of time. 

 Duriiiii' this time no fewer than löO complete (double) oscillations of the earth'.s 

 surface took place. The mean period of a complete os<'illation was, as nearly as 

 possible, three-lifths of a second. The motion was almost wholly North-South ; 

 the other pointer showed a very small, thouj^h perce])tible, amount of disturbance. 

 'J'he rc<'oids ijiven by both jiointers began simultaneously, as far as can be judged, 

 but the Kast-West movement soon censed, while the North-South movement 

 lasted, as has been said, for li minutes, and consisted of more than 150 waves. 



'J"he earth(iuake did not begin suddenly. Tiie waves liegan to a|)])ear .<o 

 gradually that it was inipo.-sible to say to which side the first deviation took 

 place. The am|)1itude increa.«ed, however, ])retty rapi<llv, and reached a niaximuin 

 after about three <'oinplete waves. Allowing for the nuilti]ilication introduced iiv 

 tiic recording lever (*> to 1, in this case) the greati'st dis])laceineiit of a partich' 

 ^in the earth's surface was (l'i!!( mm. in a <lirection approximately North and 

 South, and (l-Oö mm. in a direction approximately East and M'est. The two to- 

 gether gave a motion of about ()'-">0 mm. in the direction N. 15" AV. and E. 15" S. 



Hotli in ain]ilitn<le and in jieriixl the sueee.ssive waves were far from regular. 

 The disturbance did not consist of a series of sim|)le harmonic displacements. 



After about the tliii'd wave from the begimiing ol" the distnrliance the 

 amplitude of motion ceased to iiK'icase. It then flu<'tuated consi<lerab]v, some- 

 times becoming almost inappreciable, and again increasing to a \aliie appioai'liing 

 its lirst maximum. I'efore the earthijnake ceased there were several maxinuuns 

 and minimums in the amplitude of motion, but iK'ver a complete cessation until 

 llie wliiiii- disturlianee was over. 



UlTOR}) fMVl'.N I;Y IJIi: LoXC PlCXlHT.f.M SKISMcicr.APir. 



Thi.'i record showed that the pendulum was set swinging by the shock through 

 a distance of about 1 mm : and as the swinging continued with graduallv diminish- 

 ing amplitude during many revolutions of the plates, the records we]-c nmih 

 obscured. It was, however, ea.sy to see the comparatively lapid undulations 



