Dr. C. Davison on Earthquake- Sounds . 

 Table IV. 



47 





Number of Eecords. 



1 



2 



91 



36 



396 



3 



54 



24 



444 



4 



26 

 15 



577 



13 



8 

 615 



6 



17 



11 



64-7 



7-10 



>10 



Number of earthquakes 



K umber of earthquakes ac- 

 companied by sound 



Percentage of earthquakes 

 accompanied by sound 



595 

 124 

 20-8 



32 

 26 



812 



45 



43 



95-5 



weak earthquakes. But in Great Britain, at any rate, this is 

 not the case ; for the weaker shocks would often pass entirely 

 unnoticed if it were not for the far greater prominence of 

 the sound. The more probable interpretation is that, with 

 the larger number of records, there is the greater chance of 

 finding among the observers one or more who are capable of 

 hearing very deep sounds. Though the average observer in 

 Italy may be inferior in this respect to the average observer 

 in Great Britain, it is difficult, I think, to resist the conclusion 

 that, with a large enough number of records, every Italian 

 earthquake would be found to be accompanied by sound. 



Japan. — For this country we have Prof. Milne's valuable 

 catalogue of 8331 earthquakes recorded between 1885 and 

 1892 *. Many of the shocks originated beneath the sea, and 

 in the following estimates these have been omitted, for, in 

 some cases, it is possible that the sound-area may not have 

 reached the land. There remain 5902 earthquakes, of which 

 1562, or 26*5 per cent., were accompanied by sound. 



The percentage varies from year to year, being for the 

 eight years included in the record, 38"0 ; 42-0, 30'4, 30'0, 

 33-7, 20-4, 20-6, and 29'2 respectively. The low percent- 

 ages for the years 1890 and 1891 are due to the prepon- 

 derance of earthquakes in certain districts where the sounds 

 are somewhat rarely heard. 



In his great catalogue from which the above results are 

 obtained. Prof. Milne gives approximately the disturbed area 

 and the position of the epicentre of nearly every earthquake. 

 For the latter purpose the whole country is divided into 

 rectangles, the sides of which are a sixth of a degree of 

 latitude and longitude in length. Prof. Milne has studied 

 the distribution of earthquakes accompanied by sound by 

 placing a mark in the epicentral rectangle of each such earth- 

 quake. He has shown that the number of these earthquakes 

 * Japan Seisniol. Journ. vol. iv., 1895. 



