472 Transactions. — 2Iiscellaneous, 



The agreement (the time at the origin, of course, should 

 theoretically be the same from whatever place it is determined) 

 is remarkable. No other assumed depth gives by trial any 

 results so close. For Akaroa, in the last table, 9.26 is taken 

 as the time of the beginning of the shock ; it was, how- 

 ever, probably nearer to 9.25|- than to 9.26. Taking it as 

 9h. 25-7min., the origin of the shock felt there should be nearly 

 8 miles nearer to Akaroa. A is the nearest point to Akaroa 

 that the other data will allow. In the same way the Ash- 

 burton time may be made to agree with the rest by supposing 

 an extension of the disturbed area above the origin in the 

 direction of B. I have therefore marked A B as a possible 

 boundary of the epicentric area. I have little doubt about 

 the portion OA;'-' but the other portion, OB, is far within 

 the limits of error, and is not more, therefore, than a specula- 

 tion. 



Professor Hutton, in a letter to the Press, gave the epi- 

 centrum as H. (See PI. XLII.) He used, however, only part 

 of the above data, and, finding that I was engaged on the ques- 

 tion, did not pursue the matter further, but courteously gave 

 way to me. 



To sum up : The earthquake had its origin beneath the 

 sea at a point (O) 45 miles south-by-east from Christchurch, 

 nearly opposite Akaroa Heads and the mouth of the Eakaia ; 

 in longitude 172° 51' E., latitude 44° 10' S. ; at a depth of 

 about 24 miles. The shock took place at the origin at 

 9.24^ p.m., and was propagated with a velocity of 19i miles 

 per minute, or 1,690ft. per second. 



The chief interest connected with the determination of 

 this earthquake-origin is, that I think it will be found that 

 most of the small earthquake-shocks felt from time to time 

 in Christchurch and its neighbourhood proceed from the same 

 region. For instance, there is very little doubt that a series 

 of earthquakes on the 5th and 6th of June, 1869 — much dis- 

 cussed in the newspapers at the time — had their origin at 

 nearly, if not quite, the same spot, 



* Even the later time, 9.26 p.m. at Akaroa, requires us to suppose 

 some extension of the epicentric area towards A. By assuming further 

 that the portion of the earth's crust where the disturbance originated (or 

 the focal cavity) was nearer the earth's surface in the direction of A than 

 at 0, we may make the agreement of the data from the six best planes 

 perfect. Without complete seismographic apparatus, however, such an 

 assumption can be no more than a mere conjecture. 



