and the Conditions which they Indicate. 13 



second; and through solid granite at 1640 feet per second. 

 The rates of speed recorded in Europe are various, but the 

 maximum speed is S3 miles per minute. The rate of the 

 Calabrian earthquake, of 1857, was 8 miles per minute in 

 one direction, and 11 miles in another. That of Viege, 1855, 

 was 33 miles to the north, and 14 miles to the south. The 

 central European earthquake of 1872 recorded 27 miles per 

 minute, and that of Travancore, E.I., was but eight miles. 



The rates noted here at the earthquake of the 13th May 

 vary very much, and some are extraordinarily high. From 

 the east coast to Launceston the rate was 27 miles per 

 minute ; from thence to Circular Head, 36 miles per minute; 

 from Wilson's Promontory to Beech worth, 63 miles; from 

 Sale to Warragul, Q6 miles; and from Omeo to Beechworth, 

 30 miles. On the other hand, from Gabo to Bombala the 

 rate was only 7J miles per minute. It is very doubtful 

 whether all of these records can be relied upon. Nevertheless, 

 we have a mass of evidence to justify the belief that the 

 speed of the tremor in some parts may have been double 

 that of the shocks noted elsewhere. 



The direction of the wave varies with the locality : thus in 

 Tasmania it was from east to west ; in New South Wales it 

 was from south to north ; and in Victoria it was from south- 

 east to north-west. These lines all converge upon the 

 seismic centre which we have already determined. 



The duration of the shock varied from point to point, 

 being from three seconds up to three minutes. In this fact 

 we have evidence that more than one rupture occurred. 

 For, if there had been but one, the length of the resultant 

 tremor would have been everywhere proportioned to the one 

 movement. The duration of such a tremor might indeed be 

 expected to increase regularly with the distance, for an 

 earthquake is compounded of two dissimilar movements, 

 the one longitudinal and the other horizontal, and these two 

 motions travel at different rates of speed, Consequently, as 

 the distance traversed increases, the two motions straggle 

 apart, and the effect is that the vibrations are spread 

 over a period which lengthens as they travel outwards. 

 But the duration of the recent tremors varies most 

 eccentrically. It does not increase as the focus' is 

 left behind, nor does it diminish regularly in any one 

 direction. The nearest approach to uniformity is noticed 

 in the vicinity of Cape Howe ; for at Gabo, Bombala, 

 Bruthem, and Foster, the time was from fifty to sixty 



