106 



REPORT — 1892. 



4. Direction of Earthquakes. 



The following table shows the number of earthquakes arranged' 

 according to direction : — 



5. Nature of Earthquakes. 



The following table shows the number of earthquakes according to> 

 the nature of movement : — 



Nature 



Both vertical and liorizontal 

 Horizontal . . . . 

 Uncertain . . . . 



Eapid 



Slow 



Uncertain . . . . 



From the above we see that the number of earthquakes which were 

 felt as a horizontal movement was greater than those in which horizontal 

 and vertical motions were combined. There were 58 earthquakes the 

 movement of which was indeterminate. As regards the velocity of back 

 and forth motion, 31 out of 113 earthquakes were slow, 21 were rapid, 

 and 61 were indeterminate. 



Remarks on the above Reports. 



The above notes are based on two epitomes of the work done in 1888 

 and 1889, by the Central Meteorological Bureau, which I have recently 

 published in vol. xvi. of the 'Transactions of the Seismological Society.'^ 

 The tables are altogether the work of the officers in the Meteorological 

 Bureau. 



Laws relating to the frequency of earthquakes which are sharply 

 defined have not yet been discovered. During the winter months we 

 know that earthquakes are more numerous than they are in summer, 

 and if, instead of reckoning our earthquakes as efforts of equal value, we 

 give to each a value corresponding to the area shaken, the fact that 

 seismic energy is more intense during the winter than in summer becomes 

 more pronounced. All areas given in this and previous Reports are laMcl 

 areas. A more satisfactory method of determining earthquake intensity 

 would be to give total areas. In estimating frequency, it would seem 

 that a series of secondary shocks, which may spread over a period of 

 several months, but which are the outcome of a primary disturbance, 

 ought either to be omitted, or at least to be regarded as belonging to the 



