80 



REPORT — 1900. 



Btationa the distances corresponding to each of them from an origin ai*e 

 read from tlie curve, and by the intersection of these on a globe seismic 

 foci are determined with greater certainty. 



By the Intervals represented by Seismic Recurrences. 



a seismogram shows the interval of time between a 



(4) 

 Whenever 

 hiaximum movement and a distinct reinforcement of vibratrions which can- 

 not be accounted for as forming part of the gradually decreasing surgings 

 following the principal disturbance, this interval enables us to state the 

 distance of the origin from the station at which the seismogram was 

 obtained. Opportunities to apply this method are not frequent 

 (see p. 68). 



14. The Application of the above Methods to the Records for 1899. 



To carry into eflFect the method of determining origins by comparisons 

 of time differences, the following eleven tables have been prepared. In 

 these the 105 Shide records are referred to by their British Association 

 register number and their date. For each of these the time intervals 

 between the arrival of maximum motion at the station beneath which a 

 fcero is placed and its arrival at other stations are given in minutes.' In 

 those instances where the time at which an earthquake originated is 

 approximately known, as in Table I., the zero is placed beneath the 

 word ' origin.' So far as possible the various earthquakes have been 

 analysed according to the localities from which they originated. When 

 the time intervals in a series are less than three in number, the location 

 of an origin is sometimes doubtful. A dash beneath a station indicates 

 that an earthquake was observed, but for reasons which are various 

 the time of its maximum could not be determined. A query indicates 

 that an observation is uncertain. 



The above earthquakes were recorded by seismographs in Japan, and therefore originated in or near 

 that country. 



