308 C. Davison — British Earthquakes of 1889. 



it refer to the same shock, at Radcliffe. Between this last isoseismal 

 and the boundary of the disturbed area, the following times are 

 given: 22 h. 32m,. at Rusholme, 22 h. 37m. at Greenhalgh, Preston 

 and Meltham ; 22h. 43m. at Marbury (near Northwich), and 

 22 h. 45 m. at Waterhead and Heaton Chapel. 



From this evidence, I have indicated 22 h. 36 m. as the probable 

 time of occurrence at the epicentrura. If the average surface- 

 velocity of the earth- wave wei'e ]200 feet per second, the shock 

 could be felt at the limits of the disturbed ai'ea about two minutes 

 later. But the records in all parts of the area are too discordant to 

 lead to results of any value. 



Nature of the Shock. — The descriptions I possess of the nature of 

 the shock are, with one exception, derived entirely from newspapers, 

 and cannot always be closely trusted. As a rule, they are too vague 

 and inesact to justify detailed quotation. There can be no doubt, 

 however, that the character of the shock, especially with regard to 

 the number of vibrations felt, was subject to considerable variation 

 throughout the disturbed area ; but this we should be led to expect 

 from Prof. Milne's seismic survey of an area of about nine acres in 

 Tokio.^ In the present case, it is possible that these variations may 

 in part be attributable to the form and position of the seismic focus. 



From a very large number of accounts, I select the following as 

 fairly typical of the different eifects observed : — 



Bolton : a distinct heavy rumbling for a few seconds, and, mingled 

 with it, a sharp thud like an explosion. 



Bury : a rumbling noise, lasting about four seconds, and then a 

 sort of heavy thud, as of some enormous weight dropping on the 

 floor, causing an alarming vibration and a rattling of window- 

 frames. 



Prestwich : a shock as of a heavy falling body, which caused the 

 windows to rattle loudly ; two or three seconds later, a second thud- 

 like shock of somewhat greater intensity than the first ; followed 

 by gentle, but distinct tremors, lasting, perhaps, twenty or thirty 

 seconds more. 



Chorley : a noise like the rumbling of heavy waggons on a stone 

 pavement was suddenly heard, and, along with it, a few sharp thuds 

 "were felt, accompanied by a vibratory motion of the earth. 



Bowdon : a sudden jar was felt, like that produced by a heavy 

 body falling, or by the slamming of a heavy door ; then the floor 

 vibrated three times distinctly ; and this was followed after a few 

 seconds by another slight vibration, a double one. 



Bolton and Bury, it will be seen, are close to the epicentrum of 

 the earthquake, and, at both these places, a single thud, or prominent 

 vibration, was felt. It follows, then, that the double or multiple 

 vibrations observed in other parts of the district cannot have been 

 due to a recurrence of the shock near the same spot as the first ; and 

 it seems almost impossible to suppose that they were produced by 

 repetitions of the initial disturbance in different parts of the area. 

 We must conclude, therefore, that the nature of the shock varied 

 1 Japan Seism. Soc. Trans, vol. i. pp. 1-36. 



