﻿Vol. 6 1.] DERBY EARTHQUAKES OP 1904. 9 



July 3rd, 3.23 p.m. : Dalbury Lees. — A low distant rumbling, as of thunder. 

 July 3rd, 4.20 p.m. : Grindon. — A heavy rumbling, without any attendant 



shock. 

 July 4th, about 1.30 a.m. : Matlock Bath. — A slight shock. 

 July 4th, about 6 a.m. : Wirksworth.— A slight shock. 



II. Pore-Shock. 



a. July 3rd, 2.28 p.m. 



Intensity, 3. Number of records, 5, from 5 places. 



A slight quivering was felt at Ambergate, Cromford, Matlock 

 Bath, Mayfield, and Wirksworth (see map, p. 16). At Ambergate, a 

 noise like a loud peal of thunder accompanied the tremor. May- 

 field is about a mile south-west of Ashbourne. The other four 

 places, however, are close to the north-eastern or "Wirksworth epi- 

 centre of the principal earthquake, and the shock probably originated 

 in the corresponding focus. 



III. The Principal Earthquake. (PL II.) 



b. July 3rd, 3.21 p.m. 



Intensity, 7; centre of isoseismal 7, lat. 53° 0"4' N., long. 1° 41-6' W. 

 Number of records, 1467, from 653 places, and 46 negative records from 

 44 places. 



Time of Occurrence. 



Excluding approximate estimates, the total number of records 

 of the time is 737. Of these, 113 are regarded by their observers 

 as accurate to the nearest minute. The average of all the latter is 

 3 h 21 | m p.m., and as the averages of the different zones included 

 between successive pairs of isoseismals do not differ from this by 

 more than a minute, it is probable that the time of occurrence at 

 the epicentre was very nearly 3.21 p.m. 



Isoseismal Lines and Disturbed Area. 



The five continuous curves on the map of the earthquake (PL II) 

 are isoseismal lines of intensities 7 to 3, the broken-and-dotted 

 lines referring to the earthquake of March 24th, 1903. 



Waterhouses, near Ashbourne ; Mr.T. Gledhill, of Dronfielcl ; Mr. C. W. Groves, 

 of Eisley ; Mr. S. E. Howse, of Ambergate ; Mr. A. V. Jones, of Church 

 Broughton ; Mr. T. W. Learovd, of Eostherne, near Knutsford ; the Eev. C. 

 Price, of Denstone College ; Mr. S. Steele, of Chesterfield ; Mr. P. K Tollit, 

 headmaster of the Grammar-School, Derby ; Miss A. C. Tute, headmistress 

 of the High School for Girls, Derby; and Mr. W. M. Wilson, headmaster of 

 the Higher Grade School, Hanley. By kindly writing on my behalf to the 

 local press, Mr. Arnold-Bern rose has also prompted the communication of many 

 valuable records. The expenses of the investigation were defrayed from a grant 

 received from the Government Eesearch-Fund. 



