600 Transactions. — Chemistry and Physics. 



I have also examined the data for two of the other well- 

 known earthquakes — the 13th July, 1884, and 19th September, 

 1884 ; they are scarcely exact enough for a good determination 

 of the epicentrum, but in both cases point to an origin about 

 fifty miles north-north-west of Vss- These estimates, again, 

 rough though they may be, are not widely at variance 

 with the more exact results of the present investigation. 

 Mr. A. B. Biggs, of Launceston, has assigned a different 

 position altogether for the epicentrum of the earthquake 

 of the 27th January, 1892 — namely, a point 730 miles due 

 east of Hobart. (See Launceston Examiner, 23rd February, 

 1892.) 



This is totally inconsistent with the data, even as given 

 by Mr. Biggs himself. It is always assumed that an earth- 

 quake-wave travels with nearly the same velocity throughout ; 

 indeed, since Major Dutton's report on the Charleston earth- 

 quake, already alluded to, this is taken to be practically 

 settled. 



If, then, di, d^ be the distances of two places from the 

 supposed origin, ti, t^ the time of the same phase at those 

 places, V the velocity of propogation, evidently we have 



d'y — di 



— J =v. 



1-2 — tl 



Applying this formula to different pairs of places with Mr. 

 Biggs's origin we get the following values for v : Hobart and 

 Kiama give v = 11-4 miles per minute ; Hobart and Kiandra 

 = 24-3 miles per minute ; Hobart and Bombala — 30 miles 

 per minute ; Launceston and Kiama = 8-3 miles per minute ; 

 Launceston and Kiandra = 23-3 miles per minute ; while 

 Launceston and Bombala would agree with any velocity 

 whatever. 



When we remember, as just stated, that all these values 

 of V should be the same, or very nearly the same, we shall 

 see, I think, that it is impossible to accept Mr. Biggs's theory 

 of the origin. 



N.B. — I have used Mr. Biggs's version of the data, though 

 they differ slightly from mine. As a matter of fact, the data 

 he has used give an epicentrum within twenty miles of 

 mine — not one where he has placed it. Moreover, Mr. 

 Biggs puts the origin much nearer to New Zealand — where 

 the earthquake was not felt at all — than to Tasmania or 

 Australia. 



The maximum intensity of the earthquake of the 27th 

 January, 1892, was vii. or viii. on the Eossi-Forel scale, as 

 appears from the following summary of the observed effects, 

 which I put here for future reference, though they do not 

 seem to call for any special remarks : — 



