267 



These observations may help to fix the centre of disturb- 

 ance. Thus the slight shocks, as mentioned, are confined to 

 N.E. Tasmania, while the severer shocks may reach the West 

 Coast of Tasmania, South Victoria, and New South Wales. 

 The places which appear to feel the shocks earliest are Kent's 

 Group, St. Mary's, Swan Island, and places round, later, 

 Launceston, and afterwards, Hobart, Circular Head, etc., and 

 later still, Gabo, and places on the Continent. 



Some time since an opinion was published by me that the 

 disturbances originate under the sea to the E. of Barren 

 Island, and this is confirmed by a consideration of subse- 

 quent observations, some of which are given above, as well as 

 by reports from ships at sea in that neighbourhood. 



It may be admitted, however, that there are serious dis- 

 crepancies in the times reported for many of the shocks, and 

 this is what we might expect, as such may arise from 

 various causes. For instance, it is almost certain that the 

 correct time is not in all cases reported. Clocks and watches 

 are often out of time, and again, many persons would forget 

 to look at the clock at the time of shock, and afterwards 

 guess it approximately. As one cannot tell how often such 

 mistakes occur, it is only by comparing the reports of a con- 

 siderable number of shocks that one can speak with any con- 

 fidence. Another explanation of the discrei3ancies would be 

 to suppose that the shocks emanate from different centres. 

 This is possible, but must be used with great caution in rea- 

 soning, as, imless we suppose the shocks originate about the 

 same place, the value of the observations made as yet would 

 be very small indeed. At the same time, it is very possible 

 that the centre of disturbance is not at a j^oint, but may be 

 along a line. It is also possible that all the shocks do not 

 travel at the same rate. As to this, although a subject of 

 great interest, we cannot say anything at present. 



As to the direction from which the shock seems to come, 

 few reliable reports have been received, and even those which 

 have come to hand are little more than rough approxima- 

 tions. In many cases, too, observers appear clearly to have 

 reported the shock as travelling in exactly an opposite direc- 

 tion to the real one, e.g., S. to N. instead of N. to S. How- 

 ever, the reports which seem to be tolerably rehable give 

 a direction such as we might expect if they originate about 

 the place stated. 



Of the angle of emergence of the vibration scarcely any- 

 thing is known, as the shocks are generally much too slight 

 to leave permanent traces, such as cracks in buildings, 

 from which evidence might be obtained on the point, so that 

 we are not yet in a position to calculate the depth at which 

 the disturbance takes place. Similarly we have no direct 



