118 



F. OMORT. 



constants. This equation wliich re]')resents a rectangular liyperbola 

 may be deduced l)y tidcing terms (^dy as far as tlie first ])ower of .r 

 from either of the equations — 



and y 



1 



2) + qv + rx- + , 



where //, /,', // and p, q. r are constants. 



Equation (/>) im]>h'es that the frequency varies nearly in an 

 inverse ratio to the time. 



§ 11. 'Jlic j\flHO-Oirari EnrllKjiialt-e. 



Let us apply eqnatioii (]>) to the record of after-shocks t:ds:en at 

 the Gifu Meteorological Station. As may be seen fi'om Fig. 5, the 

 carve of actual frequency presents a series of maxima and minima, and 

 in deducing the mean values of the c<mstants /,• and // from observations, 

 the latter nmst either cover a number of such fluctuations, or betaken 

 to 1)e those at an early epoch when the rate of variation in the frequency 

 is very great and little alferted by periods of long (bu'ation. 



Taking the half-daily mimbei's of e:u'th([uakes (buang the first 

 five days, from October l^Dtli to Xovember ^nd, LSOl,' and a|)plying 

 tlie mcthoil of Least Sipiares, we obtain the equation 



440.7 



in Avliich ./: denotes successive intervals of 12 hours, l)eginning with 

 the first half of October 21)th, ISDl, and // the corresponding numbers 

 of eartlKpr.dves. Actual and calculated values of 7/ are tabulated below. 



1 Soe Fiu-. 0. 



