﻿10 DR. CHARLES DAVISON ON THE [Feb. I905, 



The isoseismal 7 is approximately circular in form, 7| miles in 

 diameter, and 41 square miles in area. Its centre lies about 

 H miles east of Ashbourne iu lat. 53° 0-4' N., long. 1° 41-6' W. 

 The next isoseismal, of intensity 6, is roughly an ellipse, 37 miles 

 long, 27 miles wide, and 804 square miles in area ; the direction of 

 its longer axis is N". 31° E, and S. 31° W., or very nearly parallel 

 to the axis of the isoseismal 7 of the earthquake of 1903. The 

 distance between the isoseismals 7 and 6 is 12 miles on the north- 

 west side and 8 miles on the south-east. The most important 

 feature in the two curves is, however, their exeentricity : the 

 distance between the centres of the two curves in the direction of 

 the longer axis being about 2 miles. In the neighbourhood of 

 Matlock Bath, there is another maximum of intensity 7 or nearly 7. 

 The observations are insufficient to draw a second isoseismal in that 

 district ; but it is clear that, if the isoseismal corresponding to an 

 intensity between 7 and 6 could be drawn, it would consist of two 

 detached portions, one concentric with the isoseismal 7, the other 

 not far from Wirksworth and Matlock Bath, their centres being 

 separated by a distance of 6 or 7 miles. Thus, the two epicentres 

 of 1904 are approximately coincident with those of the previous 

 year. 



The isoseismal 5 is the last which retains any trace of an 

 elongated form. It is 72 miles long, 65 miles wide, and contains 

 3600 square miles ; its distance from the isoseismal 6 is 21 miles on 

 the north-west and 17 miles on the south-east side. The next two 

 isoseismals are very nearly circles, the isoseismal 4 being 114 miles 

 long from north-east to south-west, 113 miles wide, and about 10,120 

 square miles in area; the isoseismal 3, -which forms the boundary of 

 the disturbed area, is 181 miles long from north-east to south-west, 

 179 miles wide, and about 25,000 square miles in area. Observa- 

 tions were also made at a few places outside the latter isoseismal, 

 at Aisgill, Appleby, Beckfoot, and Mallerstang in Westmorland ; at 

 Bridlington, on the east coast of Yorkshire ; and at Long Whittenham, 

 near Abingdon, in Berkshire. 



Comparing the dimensions just given with those for the earth- 

 quake of 1903, we see that the isoseismals 7 to 4 of that earthquake 

 are all larger than those for the earthquake of 1904 ; in 1903, a 

 few buildings sustained slight injury over an area of 112 square 

 miles, while, in 1904, there was practically no damage to property. 

 On the other hand, the earthquake of 1904, owing to its occurrence 

 on a Sunday afternoon, could be traced to a much greater distance, 

 its disturbed area being about double of that of the earthquake of 

 1903. 



Nature of the Shock. 



In 1903, the twin-character of the earthquake was clearly defined ; 

 it was recognized by two out of every three observers, and was 

 perceptible close to the boundary of the disturbed area. In 1904, 

 only one out of five observers recorded the existence of two parts or 



