﻿14 



DR. CHARLES DAVISON ON THE 



[Feb. 1905, 



Clunbury (6 miles to the south-west), and Wormleighton, Wroxton, 

 and Brockworth (respectively 4, 11, and 27 miles to the south). 



Though the sound- area is greater than in 1903, owing probably 

 to the conditions at the time of occurrence, the percentage of 

 audibility is somewhat less. Within the isoseismal 7, 94 per cent, 

 of the observers heard the earthquake-sound ; in the zone between 

 the isoseismals 7 and 6, the percentage of audibility was 93 ; 

 between the isoseismals 6 and 5, 79 ; between the isoseismals 

 5 and 4, 56 ; and outside the isoseismal 4, 38. The want of 

 parallelism between the isacoustic line of percentage 80 and the 

 boundary of the sound-area is probably due to the rapid decline in 

 audibility as the latter curve is approached. 



Nature of the Sound. 



The total number of descriptions of the earthquake -sound is 812. 

 In 45 per cent, of these, the sound is compared to passing traction- 

 engines, motor-cars, etc., in 26 per cent, to thunder, in 15 to wind, 

 in 5 to loads of stones falling, in 4 to the fall of a heavy body, in 2 

 to explosions, and in 2 per cent, to miscellaneous sounds. 



The variation in the nature of the sound with the distance 

 is shown in the following table (I), in which the figures are per- 

 centages of comparison to the different types for each of the districts 

 mentioned: — 





i/5 







go 



t>> 









r o 







a 







TO 











■+2 



CO 



-a 



GO 



O 



Table I. 



a 



'w 

 m 



Ph 



S3 





c3 eg 

 O ^ 



c3 



^H O 



.2 



03 

 "a! 



CO 



Within isoseismal 7 



39 



41 







9 



2 



9 







Between isos. 7 and 6 . . . 



52 



28 



9 



8 



2 



1 







„ 6 „ 5 ... 



44 



24 



19 



3 



5 



3 



2 



„ 5 „ 4 ... 



35 



24 



25 



4 



4 



2 



6 



Outside isoseismal 4- 



40 



33 



27 



















The most noticeable variation is the increase with distance in the 

 proportion of comparisons to the smooth and monotonous type 

 of wind. 



Time-Relations of the Sound and Shock. 



In the following table (II, p. 15), the letters^?, c, and / indicate 

 the number of records per cent, in which the beginning or end of the 

 sound preceded, coincided with, or followed, the corresponding epoch 

 of the shock ; the letters g, e, and I show the number of records 

 per cent, in which the duration of the sound was greater than, 



