266 



PKOCEEDINGS OF SECTION A. 



from the west, followed on their retreating side by a sudden shift 

 of wind to south-west and a rapid fall of temperature as the 

 depression passes, the thermometer at times falling 30° or 40° in a 

 few hours. I have known a fall of 20° in almost as many minutes. 

 From what I have said you will see that we have, as weather 

 conditions : — 



1st. A continual series of anticyclonic areas, which in the winter 

 pass over the interior, covering the whole or greater 

 part (if the continent, with gradual falling gradients from 

 the centre, while in the summer they pass along or near 

 the south coast. 

 2nd. Cyclones, disturbers of the peace, but bringing fi'uitf ul rains ; 

 sometimes, alas ! disastious floods These are mostly of 

 tropical origin, and, starting on a west to south-west 

 course, they re curve south of the irade belt, and move to 

 the south-east. Some — those approaching from the 

 north-east of Avistralia — strike the east coast of Queens- 

 land : others enter by the Gulf of Carpentaria, and, passing 

 inland, shed rains over the western interior of Queensland 

 and New South Wales: others pass over the interior from 

 the north-west ; whilst others again pass to the west of 

 Australia, and ultimately, rounding the Leeuwin, appear 

 as a south coastal disturbance. 

 3rd. Northerly extensions of the antarctic low pressure, which, 

 passing along the south coast, give us our winter rains, 

 and, on their retreating side, south-westerly gales. 

 Taking the five years 1888 to 1892, Mr. Russell, in a recent paper 

 to the Koyal British Meteorological Society, states that on the 

 average about forty-three high pressure areas pass over us during 

 the year, and that they are more frequent in summer than in winter. 

 Their general movement, as with cyclones, is from west to east, 

 cin-ving to the south-east, no doubt dying out as they reach 

 higher latitudes. Mr. Russell makes their average rate of motion 

 to be about 400 miles a day, passing over Australia in seven or 

 eight days in summer anti nine or ten in winter. My own observa- 

 tions lead me to the conclusion that anticyclonic areas seldom retain 

 their general outlines and energy for any great length of time ; 

 both are continually varying, according to surrounding conditions. 

 For instance, our weather charts may show an anticyclone on the 

 west coast pushing its way inland, and in a few days covering nearly 

 the whole of the continent; but by that time it will very fre- 

 quently have greatly increased in energy, and the central pressure 

 may be 30-oin. or more, although no such pressure may have 

 passed over the west coast ; it gets built up over the land. '1 his 

 is especially noticeable when there is a deep " low " adjoining, 

 say, off the coast to the south-east, the increased pressure in the 

 anticyclone being probably due to the upper outflow of air from, 

 the neighboring "low," or cyclone. 



