63 



A record vi' tin' sinie i'artlii(iuikf, given liy tlu' iluiilcx jieiululuni (;$ 41 1 on a 

 stationary )>late, witli a nHilti|)liraticin of O.ö, is shown in tlie centre of I'late 

 XIX. Near the origin the motions are so numerous ami so various in direction 

 that a considerable area of the lanip-hlack has simply iieen cleaned off, and it is 

 only till' more ])rominent nintiiuis tliat are traceable. The jn-ominent part of 

 tiie (igure, liowever, agrees very closely with the path sliown by tlie other two 

 instruments lor the same portion of the motion, and so gives additional evidence 

 of the accuracy of the records. 



S Gl. Suinmanj of remtls. 



Tile examples whiih liave been given arc fairlv representative of a nuuli 

 preat -r niiml>er of records, obtained during two and a half year:-. In the great 

 majoiity of cases, however, tlie motions have resembled the smaller rather than 

 the larger of tlio cartlKjuakes here cited. In very many instances tlie recorded 

 di.splacements are too small to admit easily of reproduction. 



The following conclusions may be taken as estalili.-h.d, with respect to the 

 cartli'iuakes which ixcur with much frequency in the IMain of Yedo.* 



(1). In almost every iiLstance the motion of tlie ground begins verv gra- 

 dually, and at least some seconds ])ass before it reaches its maximum. This 

 makes it impossible to deti'vmiiie acturatelv thr time of occurrence of an earth- 

 quake by means of a nuchauical or electrical <-lück-stt)pi)ing or time-taking 

 aj'i aratu.s since the time so determined will be dependent on the sensiiiilitv of 

 the apparatus to disturbance. 



(lil. An eaithquake consist? of many successive movements, and there is. al- 

 most always, no single la:g' one which stands out prominently from the rest. 

 As a rule there are many movements of nearly equal range, and sometimes several 

 nia.ximunis, with intervals of comparative rest between. 



(3). The di.>-turbance ends even more gradually than it Ixgins. The motion 

 of the ground dies out in a long series of undulations with irregularly diminishing 

 amplitudes. 



(4). Tin- range, the periixl, and the direction of movement are exceedingly 

 and irregularly variable during any one earthquake. 



fö). The duration of disturbance of the ground i~ rarel\- les- than one minute, 

 and often .««-vei-al minutes. 



(6). Even in rt)mewhat destructive earthquakes tlie greatest displacement of 

 a |oint on the .Miifac<> of the .=oil is only a few millimetres, and there an- very 

 many mint»r earthquakes in which it is less than one millimetre. 



(7). In many ca.-^es the beginning of visibh' motion consists of a tremor of 



•The wrilfr'ii otifcrvnlory in «iliinlcil on one of llin IowpbI jnrts of lliv Rrcnl nlluviiil pliiin 

 which forum tin- «il.- of ihi- cily of Tokio. It Hlniidn »I a consi<li'nihli! diKtiinti.' from iiny I'lrvali-d 

 ((round. Water, in nliiiiidaiivi', in n-nchi'd alxiiil oni! mein- bi'low the xiirfncf. 'l"ho wall.^ of the 

 liiiildiiig »hicli cotiiainK Ihi» Ki-iKinoernpliK aru light woodvn «IrneliircK placnd on ihc Kiirfuci-, 

 without any foundaliuiii tu dliturh ibu continuity uftbu ground inxidu and uutoidc. 



