440 TRANSACTIONS OF SECTION E. 
due to the indraught caused by the heating of the centre of the continent. This 
leads to the formation of a low pressure in Northern Australia, and the ascend- 
ing winds are cooled and deposit their water-vapour in heavy rainstorms and 
thunder showers. 
Tropical depressions when well developed are productive of good inland 
rains, and are evidently caused by southward flows of the atmosphere of wide 
extent and considerable depth. The ‘ Antarctic’ disturbances are, however, the 
more frequent in winter. The heaviest totals from this last-named source are 
precipitated on the west coast of Tasmania. Thus at Mount Lyell the total 
for one year exceeded 140 inches, and even the average is 116°05 inches. When 
an ‘ Antarctic’ is supplemented by a ‘ trough’ extending well into the northern 
interior, it brings much rain to the inland areas of South Australia, Victoria, 
New South Wales, and even Queensland. 
Anticyclonic rains occur at all times of the year, but more markedly from 
March to September. They benefit particularly the southern area of the 
continent, and are responsible for many of the heaviest rainfalls and floods on 
the coastal districts of New South Wales. ‘ 
Flood rains occur at infrequent intervals over various portions of the 
Commonwealth, principally in Queensland, the south-eastern parts of the 
continent, and the northern regions of West Australia. 
Typical instances of floods in South-eastern Australia are (1) the flood which 
occurred in January 1910 in the Upper Darling tributaries, consequent on 
abnormally heavy rains on the north-western plains and slopes of New South 
Wales, as well as on the Darling Downs of Queensland. 
These exceptionally heavy, continuous rains were caused by the joint action 
of an anticyclonic area over the southern regions and a monsoonal depression 
operating in the northern half of the continent. A monsoonal tongue developed 
and extended southwards over Queensland and New Scuth Wales, while at the 
same time the energy of the high pressure in the south increased. In five days 
large areas in the two States had from 5 inches to 19 inches of rain. 
The enormous amount of water which fell over approximately 86,000 square miles 
of country may be roughly estimated at thirty-one billion, six hundred and 
eighty-seven million (31,687,000,000) tons, or seven thousand one hundred 
billion (7,100,000,000,000) gallons. 
(2) A similar development occurred in March of the present year, when a 
monsoonal tongue extending southwards across the continent against an 
intensified anticyclone in the south was accompanied by severe thunderstorms 
and torrential rains. Some of the heaviest individual falls were in New South 
Wales; e.g., Taralga on the Central Tablelands 10-74 inches, Sydney 8-49 inches, 
Parramatta 16°91 inches, and Beecraft 18°84 inches in the metropolitan area, and 
Wollongong 25:34 inches, on the south coast. The barometer readings at Sydney 
ranged from 30°13 inches to 29:97 inches during the five days the storms were 
in progress, while the anticyclone to the south gradually gave way simul- 
taneously, the centre (30-4 inches) moving slowly over the southern parts of 
Victoria and Tasmania eastwards to the South Pacific Ocean. 
The wettest known place in Australia is Innisfail, on the north-east coast of 
Queensland, where the average rainfall for twenty-one years is no less than 
145 inches, the maximum yearly total being 211:24 inches, and the minimum 
69°87 inches. 
The driest region so far furnished with rain gauges lies east and north-east 
from Lake Eyre, where less than 5 inches is the average annual rainfall, and 
where a total of 10 inches is rarely recorded during the twelve months. This 
minimum rainfall is coincident with the lowest elevation, Lake Eyre being 
actually below sea-level 39 feet. 
The inland districts of Western Australia have until recent years been 
regarded as the driest part of the Commonwealth, but authentic observations 
taken during the past decade at settled districts in the east of that State show 
that the annual average is from 10 to 12 inches. 
In comparing the rainfall of the chief cities of the rest of the world! with 
1 Amsterdam, Athens, Berlin, Berne, Bombay, Brussels, Budapest, Buenos 
Ayres, Calcutta, Cape Town, Chicago, Christiania, Colombo, Constantinople, 
Copenhagen, Dublin, Edinburgh, Genoa, Hong Kong, Johannesburg, Lisbon, 
~ 
