62 The Causes and Phenomena of Earthquakes. 



Sydney. It also reached Hawaii within an hour of the time at 

 Samoa. But in all these cases the wave is propagated without 

 delay. This must have been enormously destructive, for it is 

 stated that a whale ship in 43°. 38' S., near the land, and more 

 than 250 miles to the southward of Yaldivia, was so violently 

 shaken as to lose her masts. 



"Whilst on this branch of the subject I think it right to offer 

 a few remarks on a phenomenon that excited at the time — more 

 recently than the shock of 18th June — the wonder- and curiosity 

 of many persons in the colony. 



I allude to the extraordinary fluctuations of the tides in the 

 Lower Hunter, in Port Jackson, and along the coast during the 

 15th, 16th, and 17th, and even up to 18th August, 1868 ; and 

 along the coasts from Moreton Bay to Hobart Town, Adelaide, 

 and King George's Sound. The particulars as recorded in the 

 daily journals are fresh in remembrance, and as only a few days 

 more than a fortnight have elapsed reference may be given to 

 them at once. But the official remarks of one of our members 

 who is associated with the Observatory may be read here : — 



" A remarkable phenomenon is now being recorded by the 

 tide-gauge at Fort Denison, viz. : — At 2.15 a.m. this morning, 

 August 15th, the water in the hai'bour suddenly began to fall ; 

 and in a few minutes rose again. This has been repeated at 

 intervals up to the present time (6h. 30m. p.m.) The fall at each 

 oscillation varies from 1 inch to 22 inches, and the time occupied 

 in fall and rise together from five minutes to forty-five minutes ; 

 many of them occur at regular intervals of twenty-five minutes. 

 The most remarkable .began at 6h. 55m. a.m. ; in seventeen 

 minutes the water fell 22 inches, and in the following fourteen 

 minutes rose 21 inches. The general curve of the tide is pre- 

 served, broken only by these remarkable oscillations. Similar 

 oscillations have been recorded by the tide-gauge before, espe- 

 cially during the gale of June, 1867, but never to the same 

 extent. No oscillation can be detected in the barometer." 



The rise and fall at Newcastle was even greater than at Sydney 

 — the tide-guage watched by another of our members indicating 

 a rise and fall at low water of 2 feet 4 inches in fifteen minutes, 

 which is about half what was at another hour observed by others 

 among the shipping. 



Unusual is this phenomenon, and only once, as we learn by a 

 casual notice, has it been recorded before ; but, probably, it 

 escaped detection or passed out of remembrance on other 

 occasions. 



Various surmises were offered as to the cause of the occurrence ; 

 and, naturally enough, vith the recollection of recent earth- 

 quakes in mind they come in as the supposed origin. But it 

 was also remembered that there is a storm wave as well as an 



