292 Transactions. — Geology. 



of them are small and local, but others are far more violent 

 than earthquakes due to explosions of steam, and, as the 

 centrum is often deeply seated, they are often felt over a very 

 Vvide area. 



The earthquake of Wellington in 1855 was one of this kind, 

 as also are, no doubt, most or all of those in the South Island. 

 The "Wellington earthquake, however, belongs to a very rare 

 class, in which the centrum extends to the surface, and surface- 

 rocks are moved. In a large majority of cases no movement 

 takes place in the surface-rocks''' except that due to the earth- 

 wave generated below by the fractures. 



Small earthquakes may not be accomjaanied by actual 

 fracture of rocks ; and when there is no fracture no noise will 

 be heard, although the shock may be felt for a considerable 

 distance : for the waves of sound in the earth are produced by 

 the fractures. 



In the earthquake we are now considering the shake was 

 of an unusual character, inasmuch as it was long and even, 

 without any violent jerks ; but, as it was accompanied by a 

 sound-wave, fractures of some kind must have taken place. 

 These fractures could not have been due to an explosion or to 

 a very sudden bre?^k or split : they appear to me to have 

 been due to a slow splitting or crushing of rocks. 



At first sight the evidence seems to favour the idea of a 

 slow splitting having taken place along an east-and-west line 

 in the valleys of the Waiau-ua and Hanmer, for it was in this 

 direction that most of the damage was done. But .this idea is 

 much weakened when we remember that this is the only line 

 which is even fairly well inhabited, and is the only line along 

 which an alluvial valley approaches the epicentrum ; and 

 when we examine the evidence attentively I think we must 

 give up the idea altogether. It is certainly in favour of it 

 that a better explanation could then be given of the destruc- 

 tion caused at Woodbank ; but this is the only favourable fact 

 that I can find, for no fault or fissure has been proved from 

 other evidence to exist in the valleys of the Waiau-ua and 

 Hanmer, and no fracture or movement of solid rock has been 

 found anywhere in the neighbourhood. On the other hand 

 this line has a distinct meizoseimal band, and if it were a line 

 of fissure reaching to the surface the shock would have com- 

 menced at this band and gone both ways, which is distinctly 

 contradicted by both an eye-witness and by time-observations. 

 Again, the Ferry Hotel stands on the very edge of this sup- 

 posed fissure, and ought to have suffered more than Leslie 

 Hills or Highfield. And, again, no explanation is in this way 

 given of the strength of the shock at Tekoa and in the Otira, 



* By the term " surface-rocks " I do not include alluvium, &c. 



