EARTHQUAKES IN NEW ZEALAND. 243 



time of the shock, and therefore for ascertaining the position and 

 depth of the origin and the velocity of transit or propagation, much 

 simpler instruments -would be sufficient. They should be seismocopes, 

 all of the same type, capable of showing the time of the earthquake 

 and the particular phase of the earthquake to which the time recorded 

 belongs. They should be corrected electrically with a clock regulated 

 by some standard time. There should be as large a number of these 

 instruments as possible, and the advantage obtained by their use 

 would be that almost any earthquake felt at five or six places should 

 afford sufficient data for the determination of the epicentrum (or 

 portion of the earth's surface vertically above the real origin or 

 centrum), and of the velocity of propagation; — and any earthquake 

 felt, say at ten places, should give us the depth of centrum as well. 

 Theoretically, five good times from places favourably situated should 

 give us all these, but in practice it is better to have ten at least. 



Instruments, however, cost money, and at present there seems 

 small hope of obtaining them either from the Government or private 

 individuals. Without crying " sour grapes," we can nevertheless 

 console ourselves with the fact that, though instruments would yield 

 the required data with greater certainty, yet much may be done 

 without instruments. In fact, an observation by a careful observer, 

 who takes the necessary precautions to check his notes of the time 

 and the various facts of the movement, is worth at least as much as 

 the observation of a moderately good instrument, and far more than 

 an observation recorded by an instrument not kept in scrupulously 

 good order. 



The Charleston earthquake of August 31st, 1886, was probably 

 one of the best, if not the very best-recorded earthquake hitherto, 

 and yet Major Dutton tells us : "At the time of the earthquake there 

 was not within the United States a single seismocope or other suitable 

 instrument of precision on guard and so connected with a clock as to 

 give an accurate record of the time at which the impulses arrived. 

 Nevertheless there were several circumstances which gave hope that 



a fairly satisfactory result might be reached The 



fact which gave the highest encouragement was the existence and 

 successful working of the standard time system, whereby once each 

 day a signal is telegraphed from an astronomical clock to every 

 telegraph station in the country at an appointed hour, minute, and 

 second." And he goes on to show that the habit formed by large 

 numbers of intelligent men of daily using these facilities led to the 

 amazingly large and accurate set of returns on wbich his calculations 

 were based. (See Charleston Earthquake Report, U. S. Geological 

 Survey, 1890.) In short, the history of the Charleston earthquake 

 has taught us two things — the great value of time-observations, and 

 the rosf-ibility of obtaining fairly good time observations in any 

 country where comparison can be made with a standard time. Tbis 

 can be done in New Zealand, as any telegraph office gets, or can get 

 New Zealand Mean Time from the Head Office at Wellington ; and L 

 suppose it would be equally possible in the other colonies. 



