122 



KNOWLEDGE 



[June 1, 1899. 



places seem to be those which suffered most severely from 

 the earthquake. 



The other isoseismal lines correspond to gradually 

 lessening degrees of intensity. Within the isoseismal 7, 

 the shock was strong enough to overthrow objects such as 

 vases, picture-frames, etc. ; the isoseismal 6 bounds places 

 where chandeliers, pictures, etc., were observed to swing, 

 and some difficulty was experienced in drawing this line, 

 as so many observers seem to have slept in darkened rooms. 

 Inside the isoseismal 5, the displacement of the ground 



sea been replaced by land, but as no deductions of any 

 consequence depend upon them, except where they traverse 

 land, the errors, if they exist, cannot be of great moment. 

 Returning to the isoseismal 8, we find it to be an oval 

 curve, forty miles long and twenty-three miles broad, the 

 longer axis being directed W. 44° N. and E. 44° S. It 

 might be argued that the elongated form of the curve is 

 due to the vibrations being more readily propagated along 

 a north-west and south-east line than in the perpendicular 

 direction. But, in 18(13, another earthquake, almost as 



MAP OF THE 



HEREFORD 



EARTHQUA-KE 



OF DEC 17.1896 



Map 



Area afl'ceted by the Hereford Earthquake. 



was perceptible, and quite distinct from the quivering felt, 

 say, in a railway station when a heavy train is passing. 

 The isoseismal 4, as already mentioned, includes places 

 where the shock was strong enough to make loose objects 

 rattle, such as doors, windows, fireirons, etc. Large parts 

 of the last two isoseismals traverse the sea, and in drawing 

 them we have to be guided by the trend of the curves just 

 before they leave the coast, and also by the known intensity 

 at the nearest places on land. It is possible, of course, 

 that their paths might have been found different had the 



strong as that of 1896, originated in nearly the same 

 district, and the area in which it was most strongly felt 

 was also elongated, but along a north-east and south-west 

 line. Thus, it appears that the form of these curves must 

 be due to the focus being longer in one direction than in 

 the other ; and we may infer that, in the case of the 

 Hereford earthquake of 1896, the longer axis of the focus 

 was directed almost exactly north-west and south-east. 



If the initial impulse were uniform all over the focus, 

 the nature of the shock would be nearly the same through- 



