53 



rapid undulations of tlic oartlii)iiakc siiiK'rpoHod mi lar<;('r displaci'inonts wliiili 

 arc prcsiimalilv tliif to tlio swiiininii- of tlic pcndiilimi. ^Ir Milne also nivos 

 rosult.s obtained witii anotlier ion«^ punduliini, wliicli liad t\vi> pointers writini; 

 witliout midtiplieation on stri])sof sniokcd-i;lass, wliiili wcic -et in iiKitiini iiv tiie 

 disturl)aii<'0, and were caused ti> move under tlie pointers fur a time ('.--timated at •"> 

 seconds. l)uriii<x tliis time short portions of two uiidulatinji- curves were tra<'eil ; 

 hut the nnuiunt of displacement shown was too smaii to admit of exact measure- 

 ment, and the time included by the records was jirohalily imt nioi-e tlian a iifiielh 

 part of the whole duration of disturbance. 



A remarkable series of examples of static records ha-; been f'lii iii.-lied liy the 

 nbservati<>ns of Father Faura at jVIaniJa diiiiiiL;- the ji^reat caitlii|Uakes of July 

 14th to 2öth, 1S80. The.se records, talcen by a common jiendiilum wiitinii' in 

 lyeopodiuni dust without multiplication, will be found desci'ilied and tii^ured in 

 the ProeeedinjTs of the Royal Society of I^ondou, Vol. XXXI, ]>. 4'j(). Xotliinj;' 

 is Slid ;is to the scale of the fi}i;ures, whii-ii are probably nuicli less than full-size.'' 

 In the description which accompanies them the amplitudes of liorizontai motion 

 arc stated only in terms of the angles of inclination made by the ])endulum, but 

 its lentjth is not given. Strant^ely enoutch, the wi-iter a|)|iears to suppose that the 

 inclination of a vertical pendidum dui-in<r an cartlujuake is a measure of the i>lnp(- 

 of the surface of the ground, when tiiat is horizontal before disturbance. Tiie 

 diagrams are very complicated, and it is impossible to make out, by inspection of 

 them, how much of the recorded displacement is a true motion of the ground, and 

 how much is due to the swinging of the |)endulum. 



>! 31. Iii(-ni(h on nuitiiriiiiii^li/ iiinn'iii/ jjiiti'.<. 



I'iie |>re>cnt writer was enabled, through the liiierality of llir I'lc-ident of 

 the I'niversity of Tokio, to e.-^tablish a seismometrical ol)servatory tliere in ISSO. 

 The in.-itruments originally erected wei'c the long pendidnm with two multiplying 

 pointers (§ ."JT), and the hoi'izontnl pendulum, or rathei' pair of horizontal pendulums 

 (^ 'I'-i), also with mtdtiplyiiig point<-is. In both eases, plates driven with a con- 

 tinuous motion by cIo<'kwork were n.«c<l to receive tli<' records, llic writer liavinij 

 Ikh-u early convinced of the almost <'om|)lcte useles<ness of static records. A 

 number of the othir instruments dcs<ribed inChapteis 11, III and I \' havi' been 

 added, lint most of the reconls hitiierto obtained have been given by the horizontal 

 |M-ndulum, in one form or another, l-'rom tin; eslaidishmenl of liie observatory to 

 the present time a very large nundier of carth'jUakes have; been r<'c<irded, out of 

 which :i few typical exam|iles have l)cen selected for tieseription, and an- given 

 Ik-Iow. Plates XII to XX are far-similf re|)roduetions of |,hotographs taken 

 from the sniokcd-glass plates on whidi records were automatically iuM-ribed. 



* A «liBjcrnrii of tlm Maniln cnrtliqunko, which i« Ihn sniiir- as Iho fijt. 2 of iho Riiynl Soeioly 

 nrooiiiit, will Im: fouiiil in \\w Jiifian Werlin Mail of .\ii|;. Mlli, IHHO. If thin w (iih it n|i|i<'m'H 

 to U') a fac-fiwile of llii- im'IiiIiiIiiiii rociinl, lln- Itoyiil Smiclv (lingniiiix iiiiihI liiivi- Ih-i-ii ri'ijiici'il 

 ill the |iri>|K>rtiuii ufiilxnit 1 to 2 j. 



