282 Transactions. — Geology. 



the localities must be rejected as too inaccurate. After careful 

 consideration, and from information obtained, I judge the 

 following eight places to give the most trustworthy records for 

 the purpose of discovering the epicentrum — viz., Christchurch, 

 Ashburton, Lauriston, Kaikoura, Bealey, Boatman's, West- 

 port, and Greymouth. 



I first tried to draw coseimal lines ; but found the data far 

 too meagre for any useful purpose. 



I next attempted to find the position of the epicentrum by 

 the method of straight lines,''' using three pairs — viz.. West- 

 port and Greymouth, Greymouth and Bealey, Christchurch 

 and Kaikoura. By this means, on the Government map of 

 twenty-five miles to the inch, I found the position of the 

 epicentrum to be in the Upper Grey, six or seven miles w^est 

 of Lake Christabel, or five to six miles north-west of the 

 Amuri Pass. 



I then tried the method of circles, with the following results, 

 all being taken on the twenty-five-miles-to-the-inch map. 

 Greymouth, Ashburton, and Kaikoura gave it in the Upper 

 Grey, near Lake Christabel ; Bealey, Boatman's, and Christ- 

 church gave it one mile north of Lake Christabel ; Bealey, 

 Christchurch, and Kaikoura gave it between Lake Christabel 

 and the Amuri Pass; Greymouth, Boatman's, and Kaikoura, 

 half-way between Lake Christabel and the Amuri Pass. All 

 these localities lie within a circle the radius of which is five 

 miles, and the centre about four miles N.E. of the Amuri Pass. 

 I subsequently obtained a more recent and accurate map, on a 

 scale of eight miles to the inch, and on trying on this the 

 stations Greymouth, Boatman's, and Kaikoura, I found that it 

 gave the position four miles more to the S.E. than the twenty- 

 five-miles-to-the-inch map : thus putting the position of the 

 epicentrum between three and four miles E. of the Amuri 

 Pass, or fourteen miles W.N.W. of Glynn Wye. 



Taking all these different methods into consideration, I 

 conclude that the epicentrum was not of an elongated form, 

 but more or less circular, with a radius of perhaps five miles, 

 and the centre a little east of Amuri Pass and about sixteen 

 miles W.N.W. from Glynn Wye. 



Depth of the Centrum. 



When we consider that the earthquake-wave spread for a 

 distance of three hundred miles from the epicentrum, it becomes 

 evident that the centrum was deeply seated, and this convic- 

 tion is strengthened by the fact that the wave passed below 

 high mountain-ranges, to Greymouth and Westport on the one 

 hand and to Kaikoura on the other, without any apparent effect 



* For this and tlie following methods, see Milne's " Earthquakes," 

 International Scientific Series, p. 200, 



X" 



