CHAPTER V. 



HKSri.TS UV (»liSKlMAlliiNS. 



ij 00. i%itt<- l!aiiid<. 



Previous ill tlir lirsf ]>iililic;ition of the wi-itcrV sfismoimtric oliscrvations '% 

 no olisorvcr li;ul (so iar as lie is awarul siicccfdid in ('ff(ji'tin<r a measurement of tlio 

 maijuitu<le and direetiim of tli«' ground's motion, in conjunction with the tim ', 

 (hirini^ any j)ro]onged earthijnake. Sndi measurements as luid been made weii', 

 almost witliout exception, of the static kind, into whicli the consideration of time 

 dill not enter. The information wiiich static records can yield is im])erfeet in a 

 \eiy iin])ortant particular. A knowledj^e of the direction and maguituile of 

 cartlniuake motions does not suffice to enable us to estimate the encrjjy and 

 destructive power of the disturltance, since these thinijs depend, most directly, on 

 th(; relation of displacement to time. An<l it may fairly lie added, that no static 

 i'c<'ord can determine conclusively (>ven the amplitude of an eartlKpiakc vibi'ation. 

 If the .s^'ismometer has much stability, its oseillations may become great enough 

 to exceed and altogether mask the true earthijuake motion; unless, indeed, there 

 is nuicli friction, in which case the records will be too small. On the other hand, 

 if the e(piilibrium of tiie seismometer is nearly neutral, it will be liable, during a 

 <listurbance consisting of many successive waves, to work gradually away from 

 its original («isition, and so to give a record which is gi-eatly in excess of the 

 amplitude of any single movement. 



It would be s<'arcely possilile, and not at all ])rt)titable, to give a full account 

 of the early static measurements of earthcjuakes. The observations made by 

 Wr. Kni])|)ing in Tokio with I)r. (x. AVagener's pendulum seismometer liave been 

 already alluded to (J5 •'!(( ). These, and also the earlier observations of Dr. Verbcck 

 (§.■}!), were valuable a~ showing that the amplitude of motion in ordinary earth- 

 (piakes is so excecdiugb' small that a considerable multiplication is indispensable 

 in the recoiding apparatus; and at the same lime that it is needless to let the steady 

 mass be free to move, or be in neutial e.|uilii)rium, throughout more than a very 

 small range of ])ositions. 



In an account of a somewhat destruetive earth<piake felt in Tokio and Yoko- 

 hama in Februaiy 1.SH0+, Mr. ISlilno gives some static records, which he obtained 

 by means of a long ))endiiliim, withnut multiplication. The curves arc very 

 irregular and not ea.-ily intelligilile : tiiey show pretty elearlv the com])aratively 



■■TninsaLtiuiis oI'iIk- Asiatic Society of Japiin, Vol. I.\. p. 40 (Dec. 14, 1880). 

 t I'lansai'lions of tlic Si'Isinolou'ical Sooiofy of .lajKin, \'ol. I, )iarl 2. 



