Opening Address. 11 



to 68 degs. in less than an hour." I have noticed that unless the 

 barometer fall quickly and considerably the hot wind simply dies 

 away and is followed by moderate southerly or easterly winds 

 without thunder or rain. 



Hot winds are scarcely known so far north as Brisbane. They 

 are not very frequent at Sydney ; and in a wet summer, like the 

 one just passed, they are rare, and of no great severity. At 

 Melbourne they are more frequent and more severe than at 

 Sydney. They are felt occasionally in Tasmania ; sometimes at 

 Hobart Town without being experienced at the same time at 

 Launceston, as, for example, on November 11, 1865, when a 

 north-west wind at Hobart Town raised the thei-mo meter to 95 

 dgrs., while there was no such wind at Launceston, and the 

 thermometer was only 69 dgrs. Strzelecki mentions that, on 

 one occasion, he experienced a hot wind at an altitude of 5000 

 feet on Ben Lomond in Tasmania, while it was not felt at an 

 altitude of 2000 feet on the windward side of the same mountain. 

 In this colony I have felt a hot wind on the Blue Mountains and 

 down to Penrith, while the usual sea breeze was blowing at 

 Sydnej'. Hot north-west winds occur occasionally at New 

 Zealand, but they are said to be confined to the Province of 

 Canterbury, where (at Christchurch) I experienced one on the 

 loth January, 1855. To reach that point it had to blow over the 

 snowy crests of the neighbouring mountains, and during this 

 wind nearly all the snow in sight from Christchurch disappeared. 



In searching for an explanation of hot winds, we may consider 

 that in the summer season there . will usually be a current of 

 heated air rising up from the surface of Australia, causing 

 easterly sea breezes on the east coast and southerly on the south 

 coast. But occasionally this hot upward current is overpowered 

 and beaten back by the return trade wind, the normal direction 

 of which is from N.W., and which for a time takes the place of 

 the sea breezes. As the hot wind generally blows strong, it 

 takes up impalpable dust from the earth's surface, and this dust 

 absorbing the solar heat tends to raise still farther the tempera- 

 ture. The air becoming highly rarefied, causes the barometer to 

 fall, until after a time the equilibrium is restored by a rush of cold 

 wind from the south. More extended and accurate observations 



