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Some Facts about the Great Tidal Wave, May, 1877. 
By J. P. Joszrusoy, C.E. 
[Read before the Royal Society of N.S.W., 4 December, 1878.] 
Tus tidal wave was observed at the following places, viz., 
Sydney Harbour, Newcastle Harbour, Ballina, Richmond River, 
Gn N.S.W.), Brisbane (Queensland), Napier, Wellington, Christ- 
church, Akaroa, Omaru, Kaitangata, Lyttleton ,and many other 
ports and bays in New Zealand, Sandwich Islands, South America. 
dney Harbour.—The gauge is fixed at Fort Denison. The 
tidal wave of the harbour marked on diagram made its appearance 
on the gauge at 5:20 a.m. on the 11th of May, 1877, and the oscil- 
lations gradually increased ad a maximum of 42 inches, and on the 
18th they died away. The a e interval was 34 minutes. 
may mention that the float "of ‘the gauge at Fort Denison is 
placed i in a well, and a tube, 6 inches diameter, is connected to 
it from the harbour to let the water in; diameter of well, 3 feet 
6 inches, but may perhaps be partly stopped with seaweed ; the 
gauge could not record the full force of the wave ; it came up the 
a i almost at right angles to it. (See sketch.) 
m 
SO: Fort Denison. Fal Tide-gauge. 
There are two tides in Sydney Harbour regularly every mh ; 
the extreme range from the extreme highest tide to the extrem 
faves is 6 feet 9 inches ; and the range of low water, or difference 
low water is 3 feet 4 inches. pny pene gar fee 
The establishment of the port is 8 hours 88 min 
entrance to the harbour is between two ioasia, which 
. oy called the North and South Heads, distance apart art being ote 
+ 
en earering them, no doubt the wave got partly 
broken, and then hav g to fill several large bays, and cross the 
bar, the full ange pb lost before reaching th the gauge, which 
is fixed about 3 miles up harbour from the heads 
Nore.—A man = mma a yacht in the harbour, naka a the 
shign ka recorded about 3 feet 6 in The 
—— anes "bo3- —_ was pases taken on ant AS.N. Co's 8 pa at 
and lifted her suddenly off t 
