ON THE EARTHQUAKE AND VOLCANIC I'HENOMENA OF JAPAN. 153 



((') Object of the Catalogues. 



The principal object of the catalogues, as we have indicated, is to 

 furnisli investigators with a certain quantity of material relating to the 

 occurrence of eaithquakes, different from that which has hitherto been at 

 their disposal, on account of the want of which it has been impossible to 

 make many desirable inquiries. 



Many catalogues exist, like those of Perrey, Mallet, Kluge, de Bal- 

 lore, and Fuchs, in which the actual number of records are equal to, or 

 greater than, tlie number of earthquakes now noted, and which are 

 equally good as foundations for a particular class of investigations. 

 The incompleteness of these catalogues, however, is seen in the fact 

 that they give for the whole world a frequency less than the present 

 list gives for a small portion of it like Japan. If, for example, we take 

 Dr. C. W. C. Fuchs' ' Statistik der Erdbeben,' 1865 to 1885, giving a list of 

 some 8,000 disturbances, out of these Japan is credited with from three to 

 thirty shocks per year, while a truer estimate would have been from 500 to 

 1,000. Again, it is often difficult to distinguish between shocks which 

 have shaken a few square miles and those which have disturbed an empire. 

 Large shocks and small shocks, primary shocks and after shocks, are with 

 difficulty separable, and no data have been available enabling an investi- 

 gator to separate disturbances arising from the yielding of strata in one 

 area from those dute to fracturing which might take place in a neighbour- 

 ing region. Even when the lists of a particular observatory have been 

 examined by themselves, inasmuch as its records are those of shocks of 

 local orgin combined with those of shakings which originated at distances 

 of several hundreds of miles, all that we can expect to lind is a relation- 

 ship between earthquake occurrence and influences of a widespread 

 character. Such investigations have been made for the records of obser- 

 vatories, countries, and the world, with the result that a more or less 

 pronounced annual and semi-annual periodicity and traces of what is 

 apparently a lunar influence have been discovered. 



No doubt many and very just objections may be made as to the 

 accuracy of much of tlie material in the present list ; but because it 

 enables us to give approximate lueiglds to the different shocks, to dis- 

 tinguish between primary and secondary disturbances, and to divide the 

 country to which it refers into distinct seismic or natural districts, it is 

 to be hoped that it will open the way for investigations along new lines. 



Although the catalogues suggest several investigations hitherto impos- 

 sible, inasmuch as it so often hapj^ens that one inquiry becomes the 

 parent of another, it is impossible to indicate all the paths which may be 

 followed. A suggestion given by the list, which shows that shocks 

 originating in Japan have travelled to Europe, is that a I'ing of twelve or 

 twenty-four stations situated round our globe would in a veiy short time 

 give us valuable information, not simply about its crust, but possibly also 

 about its interior. 



One set of investigations which may possibly lead to interesting 

 results will be those relating to the frequency and periodicity of earth- 

 quake shocks which may be considered as having equal values, or receive 

 values relative to the area they have disturbed. Each of these analyses 

 may be made for Japan as a whole, or for special seismic disti'icts ; in the 

 former case the object being to determine whether the occurrence of 



