'4* JChe Causes and Phenomena of EartJipuahes . 



premise, however, that I include indications of probable shocks 

 in some instances, of which I will give explanations in due order. 



But it may be useful first to explain that I so include them 

 according to the known peculiarities of earthquake shocks, which 

 may embrace three separate — though connected kinds of wave : 

 1. The earth wave ; 2. the earthquake sea wave; 3. The sound 

 waves through the earth, the sea, or the air. 



This is well explained by Mr. Mallet in the "Admiralty 

 Manual," (p. 206). He says, "If one stand upon a line of rail- 

 way, near the rail, and a heavy blow be delivered at a few hundred 

 feet distant upon the iron rail, he will almost instantly hear the wave 

 through the iron rail ; directly after he will feel another wave 

 through the ground on which he stands, and lastly he will hear 

 another through the air ; and if there were a deep side drain to the 

 railway, a person immersed in the water would hear a wave of sound 

 through it, the rate of which would be different from any of the 

 others — all these starting from the same point at the same 

 moment." 



It is very certain, therefore, that where a vibrition may be too 

 weak to be sensibly felt by an inattentive person, yet the sound 

 may be audibly felt ; and this, I think, has very often happened 

 in the interior of this country. 



I now proceed to refer to a Catalogue of all the Earthquakes in 

 Australasia of which I have obtained particulars, but which at 

 present is not iu a state for publication. For the present I must 

 be content to offer a few remarks on some of the New South 

 Wales shocks enumerated in the Catalogue, in order to compare 

 the phenomena reported with those observed during earthquakes 

 in other countries, and to obtain, if possible, some additional 

 idea of the class of earthquakes to which those felt here probably 

 belong. 



Although I have headed my list with Captain Furneaux's New 

 Zealand shock, in 1773, yet the first recorded shock in New South 

 Wales was felt within a month of the foundation of this colony. 

 It is an interesting commencement to our Catalogue. 



The duration of the disturbance agrees with that of the shocks 

 felt in 1837 and 1868. 



Respecting the noise.mentioned, "like that of a cannon," this 

 too is in agreement with the noise heard also during the two 

 later occurrences. 



Mr. Kempson, who is my authority for the shock of 28th April, 

 1868, records the same kind of noise. He says it was " like the 

 firing of ordnance." Collins' s remark has just been quoted. 

 The Rev. C. P. N. Wilton says, on 3rd August, 1837 the noise 

 was "like the distant discharge of artillery." This kind of noise 

 I consider of great importance in the identification of a probable 

 earthquake when other data cannot be obtained. For it must 



