366 Transactions. — Geology. 



The limits within which the epicentrum must almost cer- 

 tainly lie are shown by the inner circle, of 6 miles radius, 

 containing all the points D, E, E ', K, and I. The epicentrum 

 of the earthquake of the 5th July, 1891, was estimated to be 

 at A, which is 4 miles S.E. of the last-named circle. 



F is the position assigned approximately to the epicentrum 

 of the earthquake of the 20th February, 1890. (Trans. Aus. 

 Assoc. Adv. Sc, 1891, p. 46, and map.) 



The line HM is that marked as a probable continuation of 

 the line of fault No. 5 in the map of New Zealand, showing 

 faults and earthquake-rents, published in 1890 by Sir James 

 Hector and Mr. A. McKay. 



The small figures on Plate XLVI. to the S.W. of E' show 

 the soundings : it will be seen that there is a marked hollow 

 in the sea-bed in the neighbourhood in question. 



It may be as well to note the last two facts referred to, 

 though I do not propose to discuss their significance at pre- 

 sent. 



The depth of the origin may have been even greater than 

 10 miles (though that depth agrees most closely with the 

 observed times), for the shock was not stopped by the moun- 

 tains ; for the same reason it could hardly have been very 

 shallow. 



Though we are not called upon to explain all the incon- 

 sistencies 3ven of professedly good observations, yet the fol- 

 lowing hypothesis of the movements that took place removes 

 most of the discrepancies, and is supported by the remarks in 

 the fifth column of the table : — 



I. A shock, noted at White's Bay and Palmerston North, 

 occurring 3 or 4 minutes before II. 

 II. The chief shock, lasting nearly 1 minute, with three 

 chief maxima, viz. : — 



(a.) First maximum, observed at Marton (so-called 

 "first shock"), Blenheim, and New Plymouth (?). 



(/3.) Greatest maximum, observed at Wellington, 

 Masterton, Feilding, Havelock, Picton, Otaki, Fox- 

 ton, Wanganui, Opunake (4.43), and Marton (" second 

 shock "). 



(y.) A lower maximum (still considerable), Upper 



Hutt. 



III. A third shock, less severe than I. and II., 5 minutes 



later than II. — Opunake (4.48) ; and possibly Nelson 



(4.45). 



The only records remaining unexplained would, if we accept 



this hypothesis of the history of the earthquake, be Westport, 



which is evidently rough. (New Plymouth and Nelson may 



be only approximate also, but admit of explanation as above.) 



