the warm air to ascend, and cooling currents 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 circulation imparted to the atmosphere, we owe those variations of our climates which make any given day of one year to differ from its corresponding day of another. Were it not for those vertical movements, our days would gradually grow 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 temperature 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 topographical features and the climates of the antarctic regions differ greatly from the topographical features and climates 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 furiously into a heavy sea, flooding her decks, and sometimes burying her whole bows beneath the waves. The 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 leeward in crimson torrents. Our whole ship, sails, spars, and all, seemed to partake of the same ruddy hues. They 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
