Page:A sketch of the physical structure of Australia.djvu/98

86 showers, and during their prevalence, is the only time throughout the year when rain was known to fall at Port Essington. In the winter the trade wind that blows on the north-east coast, of course, brings much moisture with it. The summits of the eastern chain catch and precipitate much of this moisture, their peaks being frequently clothed with clouds, and a multitude of small rills and brooks run down their eastern slopes into the sea. After passing over this ridge, however, and being thus partially drained of its moisture it would appear that the south-east trade wind meets with no other range, at least of equal or greater altitude, or we should have streams like these combining to form a river that must come out upon the coast. Instead of this its behaviour exactly accords with its passing over plains and burning deserts, where it is heated and rarified instead of cooled and condensed, and thus becomes capable of taking up more moisture instead of being obliged to part with that which it possessed.

In the same manner during the summer season, if any great mountain range existed in the interior of Australia, it must attract and condense the moisture with which the north-west wind is loaded, precipitate it into rain, and send it back to the north-west or to some other coast in the shape of a