egeson’s weather system.

21

In order to make terrestrial precipitation comparablewith sun-spots it is necessary that the rain area should bedetermined for the whole earth. Such a work it is not forany one man to do, if, indeed, it can be done at all. But ifthere are prospects of finding in the variations embracing thewhole earth’s rain area a facsimile of the sun’s maculationvariations, there should be at least some slight approximationto the same result, if only a portion of the earth’s surface betaken.

To this end I undertook the determination of the rainarea for New South Wales , a task imposing no slight amount■of labour.

The area of that part of the colony lying east of theRiver Darling I take to represent in round numbers 300,000square miles, though it is somewhat less. It represents aboutone-tenth of Australia and the six-hundredth part of thewhole earth. I have, then, to compare an area three hundredtimes less than a hemisphere of the earth, with a hemisphereof the sun. A brief description of the method of area deter-mination is necessary.

Upon a map where the area of New South Wales occupiesseveral square feet were plotted the positions of some seventystations sending daily reports of weather, etc. Symbols ofvarious colours were made to represent different states ofweather, as rain, overcast sky, scattered clouds, and clear sky,each with an arrow to show the direction of the wind. Othersymbols were used to show where rain had fallen during thetwenty-four hours. The symbols were distributed over themap according to reports received each day from the variousstations, thus giving a general graphic representation of theareas of rain, clouds, and of rainfall over the colony, as ob-served at nine a.m. each day.

The respective areas were then estimated in tenths of thewhole reporting area (there are no daily reporting stationsbeyond the Darling), just as one would estimate clouds uponthe sky in tenths of the whole. The result was noted,together with some remarks, and the general outlines and