60 PROCEEDINGS OF SECTION A. 
duced by the sun and moon are just about equal co one 
another. Investigations by the United States Geodetic 
Survey have shown that the same is true at Mazailan, on the 
Pacific Coast of Mexico; whilst Van der Stok states that, 
at a port in the Dutch East Indies, the solar wave is actually 
greater than the lunar. This is possibly caused by the 
‘partial destruction of the lunar cemponent, owing to the 
interference of two different tidal waves. | On the other 
side of Australia we have more the ordinary condition of 
things. Thus at Sydney the lunar semi-diurnal is about 
four times as great as the solar. At Melbourne, the ratio 
appears to be exceptionally great about 7-8; at Port 
Darwin it is 1-9. ‘ 
We should not, of course, expect that the short-period 
waves would travel in the same way as the long-period 
waves. Thus, if our knowledge were sufficient to enable us 
to draw co-tidal lines for the semi-diurnal waves, and also for 
the diurnal waves, we shculd-expect that the two sets of 
lines would be very different. Our knowledge is not yet 
sufficient to enable this to be done over any extensive 
regions, but Van der Stok (Wind and Weather, Currents, 
Tides, and Tidal Streams in the Indian Archipelago) has 
endeavoured to draw the co-tidal lines for the two classes of 
waves in the Indian Archipelago. The result is very inter- 
esting, showing the two sets of waves proceeding by an 
entirely different track, and even in opposite directions. 
The tidal work being done im Australia at present con- 
sists mainly in the recording of tides, and, in a few cases, of 
the preparation of tide-tables. Along the whole of the 
northern, western, and southern coasts of Australia, how- 
ever, we have at present only seven self-recording tide 
gauges. There is one at Port Darwin, there are two at Fre 
mantle, and the others are at Port Adelaide, Port Pirie, and 
Port Augusta, in South Australia, and at Williamstown, 
Victoria. On the Tasmanian coast there are two—one at 
Strahan and the other at Hobart. To the energy of Mr. 
Russell we are indebted for the publication of the records 
froma three tide-gauges in New South Wales, one at Fort 
Denison (Sydney Harbour), one at Ballina, and one at New- 
castle. To him also we owe a most interesting series of 
records of the Oscillations of Lake George. In Queensland 
there are four gauges--two on the Brisbane River and two 
on the Fitzroy. Tide-tables are published a year im advance, 
giving times and heights of high and low water, for Brisbane 
and Port Adelaide; inthe Victorian and Tasmanian Almanacs 
the times of high and low water are predicted for Mel- 
