22^ Voyage of the Novara. 



had expected, chiefly perhaps in consequence of the influence 

 exercised by the Australian continent, the temperature of 

 which during this, the summer season of the Southern Hemi- 

 sphere, is raised to an extraordinary degree by its sandy 

 surface, that when the air has become thus warmed, it ascends 

 and becomes more rarefied in its lower strata, in consequence 

 of which its elasticity becomes so great as to drive back the 

 surrounding colder atmosphere, and only admit it to contact 

 with the heated air at its most remote limits. This occurs the 

 more readily, that the heated air, after it has risen to the more 

 rarefied tracts, expands on all sides, and at a certain distance 

 from the lower level, begins to add to the pressure of the 

 atmosphere. In this self-acting zone of increased atmospheric 

 pressure, the winds, however, are naturally more faint, and, to 

 observers who happen to be on the exterior of this zone, always 

 appear to take their rise from the further side. For this 

 reason, probably, we fell in with easterly breezes, so long as we 

 had the Northern portion of Australia to the eastward of us. 



At any rate, the equilibrium of the air seemed to be dis- 

 turbed, as we could plainly perceive from the weather and the 

 confused sea. At last on 1 8th December, the heavens seemed 

 somewhat more propitious, though the wind still continued east- 

 erly ; indeed occasionally blew from the north, and frequent 

 squalls of rain poured pitilessly down upon us. The more, 

 however, we increased our distance from the Australian conti- 

 nent, that is, from all land to the eastward, the more steadily 

 blew the south east Trade. And so we kept standing steadily 



