58 



A i(.'in;iili!il)l<' iii^^taiiiM' nf tlii> iicctn- ilmini,' tlic sixtccutli si'onxl, wlicii tlie 

 niii|>litii(li' I'f iiiotiiiii was it its maxiiniim. 'J'lic W-K ('(imiioiR'nt was tlicii al- 

 iiKist cxa'llv a ijiiaitci- (if a ]irii(i(] on ailvaiicc of tin' N-S (•oiiipoiiciit, and licni't', 

 uli( II (Miini'iiiiiidcil, tlir two rcM'iiids >l)(i\v tiir iniitiiiii of tlie i;-romi(l to lia\'r coii- 

 .-istcd, at lliat tiini', of" rotation in a very lon^ldy ciivnlar jiatli. Tlif aimoxcd 



fitjiirc is till! patli detciiniiicd hy coni- 

 ])oimdiiiji- tlie two i-ccords dnrinir tincc 

 seconds, (fi'oni tlic tinio l^M sec. to ](i'7 

 set'., nK'asnrod from tlif l)('!L;iiniinj;' of tin' 

 i'artlii|ntd<('l. Tlic ]iatli d('scril)cd in tins 

 inlii \ ;d licuins at p and I'lids at </. 



Tlic displacements ])lotted in tins 

 sketcli arc taken witliont change of scale 

 from the record, and hence tlie scale of 

 the sketcii is six times full size. 



The jfreatost single liori/ontal dis- 

 |ilacemeiit ilinni one side to the otlnrl is ahout "Jo mm. iin the recor<l, whii'h 

 nirrcs]ioniI> to neai ly \'2 nnn. of aciiial motion. Tlu' «jreatest velucify "f hori- 

 zontal movement of a surface imrtiele was nearly lO mm. [)er sec. It is ditficidt 

 to lind the iireatest rate of acceleration from tin; record, on account of the very 

 irrei;nlar liiaracter of the motion: it appears to have heeii from 40 to 50 mm. per 

 sec. ])er xvr., or aliont -.tI„ of .'/. The period of the largest sini^le complete oscil- 

 lation (that which occurred at I.") M'dinds IVoni the heginnin":;! was 1"1 seconds. 



It may lie added that this period was unusually long, which ac<ounts for the 

 fa<'t that, nolw ilhstanding the large amplitude of motion, this earthi|nake was not 

 of a desli iicti\'<' chaiai'ter. Although alarming enough, it ditl no damage except 

 cause .•-onie i laiks in walls. 



S .").",. K,i,lli'iiiii/,r^ of Mnrh 1.4, ISS.; 



Two carthi|Uakes whi< h occuiied on Marcii 1st, li*<S:2, of which the second 

 was mmsually sharp, though not deVtructive, are shown in I'late XI \', which is 

 the record given hy a single horizontal pendidum, of the form described in § 2ö. 

 The record gives onlv the W'cst-Kast coni|ionent of the horizontal motion : the 

 ]H)inter which should have registered North-South motion was nnforttuiately out 

 of order, and failed to do more than show that a considerable amount of K-S 

 movement had also taken place. 



Here the plate made (vne revolution in So sees., and the nHilti|ilying ratio 

 was 7 to 1. Of the two ciicles which appear close together in the record, the 

 outer is the ])ath traced before the first eartiimiake, and the inner is the path 

 traced after the second. 



The earliest visible motion is a trcniur of sliort-i)eriod wave.s, which 

 ajipears on the outer circle at a. Following the record in the direction in 

 whicli it was dejwsited (the direction shown by the arrow), we see these short- 



