146 PROF. W. J. DAKIN : EXPEDITION TO THE 



during the summer, the wind with a falling barometer comes away fresh 

 from the E. to N.E. at sunrise, hut it drops at noon and is followed by the 

 Southerly as usual. 



Winter Winds — During the winter the winds are variable. Southerly 

 winds are frequent though of lighter force than those during the summer. 

 N.E. winds are also of frequent occurrence in the mornings, but there is a 

 calm or Southerly during the afternoon, or perhaps a strong N.W. blow. 

 Taken altogether there is far less wind during the winter than summer. 



Now, at the Abrolhos, 30 to 50 miles away from land, the winds are much 

 the same, except that the hind breeze is not nearly so evident and often quite 

 absent. There is not much support here for a prevailing East wind blowing- 

 out the surface water. Further information may be obtained from actual 

 observations of the currents. Here again I have had to depend upon 

 information culled from the fishermen who are out at all seasons of the year. 

 They state that during the winter, a southerly current is usually experienced 

 between Geraldton and the Islands. Its velocity is about one knot per hour, 

 but this may be increased with N. winds to 2-3 knots. This is quite 

 in favour of the tropical current theory. During the summer southerly set 

 has also been experienced, but as calms are very seldom it has not been 

 noticed nearly so definitely. 



Tides. 



The tides on the West Coast of Australia present some great problems, and 

 very little is known of these phenomena at present, although the question is 

 of importance to shipping. For the greater part of the coast from the 

 Leeuwin northwards (as far as Shark's Bay), the rise and fall of the tide is 

 very small, the mean spring rise being only 2 ft. 6 ins. at Fremantle and 

 G-eraldton, and only 2 feet at Bunbury. At Carnarvon the mean spring 

 rise is 5 feet, but in the north-west the conditions are very different, and a 

 mean spring rise of 34 feet has been recorded at Derby. 



The mean neap rise at Geraldton is only 1 ft. 6 ins. 



It must not be thought, however, that tidal phenomena on this coast are 

 only peculiar in that the amplitude varies enormously along the coast, and 

 is so small at Fremantle and Greraldton as to be practically insignificant. The 

 greatest problem is associated with tidal irregularity. Thus, at Fremantle 

 the tides are usually diurnal, roughly 24 hours elapsing between the two 

 high tides. Occasionally, however, for a succession of a few days, the tides 

 become semi-diurnal. The diurnal tides are associated with irregularity, and 

 it is extremely difficult to predict them with any accuracj r . 



At the Abrolhos, as at Fremantle, there is but little rise and fall of the 

 tide, but it is of more use for collecting purposes than at the latter place, 

 and seems to be of somewhat greater amplitude. VVe should say that the 



