4G-i PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOllOLCGY. 



the warm air to ascend, and cooling cun-ents to come down from 

 the upper sky. To this cause Dr. Franklin ascribed the cold 

 summer gusts in America that come from the west. To the 

 effect of this vapour and its heat, with the constant vertical cir- 

 culation imparted to the atmosphere, we owe those variations of 

 our climates which make an}"- given day of one year to differ 

 from its corresponding day of another. Were it not for those 

 vertical movements, our days would gradually gi'ow cooler from 

 midsummer to midwinter ; as the sun recedes in the ecliptic, 

 each day, after he reached a certain degree of south declination, 

 would grow cooler and cooler until his return towards the north 

 again ; so that were it not for this vertical circulation the tem- 

 perature of the day of the month, like the rising and the setting 

 of the sun, or the changes of the moon, might be foretold in a 

 calendar. 



871. — Aurora australis. — There is not only reason to suppose 

 that the topogi-aphical features and the climates of the antarctic 

 regions differ greatly from the topographical features and cli- 

 mates of the arctic, but there is reason to suppose a difference 

 in other physical aspects also. The aurora points to these. 

 *' On the morning of the second of September last," says Capt. 

 B. P. Howes, in his abstract log of the " Southern Cross," lat. 

 58° S., long. 70° W., "at about half-past one o'clock, the rare 

 phenomenon of the aurora australis manifested itself in a most 

 magnificent manner. Our ship was off Cape Horn in a violent 

 gale, plunging furiouslj^ into a heavy sea, flooding her decks, 

 and sometimes burjdng her whole bows beneath the waves. Tlie 

 heavens were black as death : not a star was to be seen when 

 the brilliant spectacle first appeared. I cannot describe the 

 awful grandeur of the scene ; the heavens gradually changed 

 from murky blackness till they became like vivid fire, reflecting 

 a lurid, glowing brilliancy over everything. The ocean appeared 

 like a sea of vermilion lashed into fury by the storm ; the waves, 

 dashing furiously over our sides, ever and anon rushed to lee- 

 ward in crimson torrents. Our Avhole ship, sails, spars, and all, 

 seemed to partake of the same ruddy hues. The}^ were as if 

 lighted up by some terrible conflagration. Taking all together, 

 the howling, shrieking storm, the noble ship plunging fearlessly 

 beneath the crimson-crested waves, the furious squalls of hail, 

 snow, and sleet driving over the vessel and falling to leeward in 

 ruddy showers, the mysterious balls of electric fire resting on 



