Field. — On Earthquahes at Wnnganui. 569 



■ Art. LIV. — On Earthquakes in the Vicinity of Wanganui. 



By H. C. Field. 



[Bead before the Wellington Philosophical Society, 24th February, 1S93.] 



As efforts are being made to determine the sources of earth- 

 quakes in the colony, any extended observations in a given 

 locahty may be of value. In the volume of the Transactions 

 of the Institute lately to hand I notice a paper by Mr. G. 

 Hogben on an earthquake which occurred in Wanganui on the 

 7th March, 1890, in which he fixes the source of the shock at 

 a point under the sea about three hundred miles east of Wel- 

 lington. In this he is certainly wrong, as his calculations are 

 based upon the assumption that the times and direction 

 recorded at the telegraph- stations are those not of the normal 

 wave, but of an imaginary subsequent transverse one, at right- 

 angles to it. I do not attach importance to such data, either 

 as regards time or direction, as I know that in many cases (as 

 in those quoted for this shock by Mr. Hogben) the times given 

 are very uncertain, and the points of the compass are apt to be 

 exactly reversed. That shock, like every other that has oc- 

 curred in Wanganui since 1851, came from the south-west. 



I have long been under the impression that an important 

 earth-fissure passes beneath, or very close to, Wanganui; and 

 the late Rev. Eichard Taylor, the Church missionary at Putiki, 

 who had paid considerable attention to the subject, entertained 

 a similar opinion. He believed that there was a subterranean 

 communication between Mount Erebus and Ngauruhoe, and 

 that earthquakes hereabouts were caused by vast volumes of 

 gas or superheated steam being suddenly formed in this pas- 

 sage, and rushing towards Ngauruhoe as a vent. Unfortunately, 

 Ngauruhoe is not visible from my house, so that I am unable 

 to observe whether our earthquake-shocks are succeeded by 

 any unusual discharge of vapour from the volcano. About 

 twenty years ago, however, as I was walking home from town 

 one evening about 10 p.m., I heard an earthquake-explosion, 

 and at once stopped to note the result. Before the shake had 

 well passed, there was a very bright and prolonged explosion 

 from the volcano, followed, after the usual five minutes' 

 interval, by an unusually loud and prolonged report. This 

 single observation certainly bore out the Eev. Mr. Taylor's 

 theory that Ngauruhoe is our safety-valve. 



I have paid particular attention to earthquakes for more 

 than forty years, so can speak very positively respecting them as 

 they affect this part of the colony. Slight earth-tremors often 

 occur, and are not noticed by our local papers, unless in the 



