HoGBEN. — On the Earthquake of July 5, 1891 511 



which probably includes the chief epicentrum. The roman 

 numbers under the names of the places in the table show the 

 degrees on the Rossi-Forel scale of intensity that seemed most 

 nearly to correspond to the details given. The isoseismal III., 

 it will be seen, would lead us to suppose a focus not very far 

 from N or A, and certainly would prepare us to believe that 

 there were two distmct shocks. Both these methods, Time 

 and Intensity, seem therefore to point to the same conclusion. 



3. To sum up. A possible hypothesis, which explains all 

 or nearly all the facts, is that a fault-movement began below 

 A, going northwards, was accelerated rapidly at or near B, and 

 continued for some time afterwards in minor shocks along the 

 line AB. There is no evidence of the existence of such a fault, 

 nor is there likely to be, as the region indicated lies under 

 the sea. 



4. The velocity of propagation was between twelve and 

 fifteen miles a minute. 



Akt. LVI. — Notes on the Earthquake of the 5th July, 1891, 

 in Cook Strait : an Attempt to define the Epicentrum. 



By Geoege Hogben, M.A. 



lEead before the Philosophical Institute of Canterbury, 1st October, 



1891.] 



This was a slight earthquake, without any marked effects, and 

 I do not propose to deal with it at any length. Its sole interest 

 is derived from the fact that the observations of it, though 

 not many in number, were sufficiently exact to enable us to 

 ascertain the epicentrum very nearly. The data — all obtained 

 through the Telegraph Department — are these : — 



Blenheim 



Upper Hutt 

 Masterton 

 Woodville 

 Marton . . 

 Foxton . . 

 Wellington 

 Picfcon 

 Featherston 



Time. 

 10.53 p.m. 



10.55 p.m. 



10.53 p.m. 



10.54 p.m. 

 10.53 p.m. 



10.55 p.m. 

 10.55 p.m. 

 10.52 p.m. 

 10.52 p.m. 



Direction. 

 W. to E. (but un- 

 certain) 



N.E. to S.W. 



N.E. to S.W. 

 W. to E. 



N.E. to S.W. 

 N. to S. 



S.E. to N.W. 



N. to S. 



N.W. 



Duration. 

 10 sees. 



3 sees. 

 about J min. 



5 sees. 

 8 to 10 sees. 



5 sees. 



5 sees. 

 10 to 15 sees. 



2 sees. 



The times are those of the beginning of the shock : the 



first six are stated to have been verified by New Zealand mean 



time, the last three being given to the best of the officers' 



belief to N.Z.M.T. No qualification of the times at the Upper 



37 



