THE CLOUD KEGION, ETC. 265 



drenclied witli rain, as he sails througli these latitudes, he is dis- 

 pirited imder the influences of the gloomy and mui'ky weather 

 which prevades those regions. His hope in the " brave west winds " 

 and trust in the prowess of a noble ship are then his consolation 

 and his comfort. 



512. Such are the quantities of vapom- rising up from the en- 

 why there should be orirdlmo^ occau about thosc austral regions, that it 



le&5 atinospheie in P j_i n n j_i ^ l' 



the southern than in Jvceps permanently expelled thence a large portion 

 the northern hemi- ^^ ^j^^ atmospherc. The spccific gravity of dry air 

 being 1, that of aqueous vapour is 0.6 (§ 252). According to the 

 table (§ 362), the mean height of the barometer at sea, between 

 the equator and 78^ 37' north, is 30.01 ; whilst its mean height in 

 lat. 70^ S. is 29.0. To explain the great and grand phenomena 

 of nature by illustrations dra\\ai from the puny contrivances of 

 human device is often a feeble resort, but nevertheless we may^ 

 m order to explain this expulsion of air from the watery south, 

 where all is sea, be pardoned for the homely reference. We all 

 know, as the steam or vapom^ begins to form in the tea-kettle, it 

 expels au' thence, and itself occupies the space which the air occu- 

 pied. If still more heat be applied, as to the boiler of a steam- 

 engine, the au' will be entkely expelled, and we have nothing but 

 steam above the water m the boiler. Now at the south, over this, 

 gi'eat waste of circumfluent waters, we do not have as much heat 

 for evaporation as in the boiler or the tea-kettle ; but, as far as it 

 goes, it forms vapom' which has proportionally precisely the same 

 tendency that the vapour in the tea-kettle has to drive off the ah^ 

 above and occupy thei space it held. Nor is this all. This austral 

 vapour, rising up, is cooled and condensed. Thus a vast amount 

 of heat is liberated in the upper regions, which goes to heat the air 

 there, expand it, and thus, by altering the level, causing it to flow 

 off". Tliis unequal distribution of atmosphere between the two 

 halves of the globe is imperfectly represented in harometric profile 

 on Plate I. (§ 215) — the shading aroimd the periphery of the circle 

 being intended to represent the relative height, and the scales 

 standing up in it, the barometric column. 



513. This part of the southern ocean where the barometer 

 Influence of antarctic sliows diminished prossm^c is frequented by icebergs, 

 ihe^aif fim^aSstniT ^^uy of them vcry large and high, and some of 

 regions. them scudiug up towers, minarets, and steeples, 

 which give them the appearance in the distance of beautiful cities 

 afloat. Each one of them is a centre of condensation. Could an 



