Page:Physical Geography of the Sea and its Meteorology.djvu/491

Rh our mast-heads, yard-arms, etc., and above all, the awful sublimity of the heavens, through which coruscations of auroral light would often shoot in spiral streaks and with meteoric brilliancy, altogether presented a scene of terrible grandeur and awful sublimity surpassing the wildest dreams of fancy. Words fail to convey any just idea of the magnificence it presented. One must see it and feel it in order to realize it. I have written this because I believe it an unusual occurrence to see the 'southern lights' at all, and also because this was far superior, and, in fact, altogether different from our northern lights, as seen from the latitude of Boston."

872.—An erroneous opinion.—Some objections to these views respecting the comparative mildness of antarctic climates are suggested by common opinion. It is an opinion which is generally received among sailors and physicists that the southern is colder than the northern hemisphere, and that the austral are more severe than the boreal climates, and that the antarctic icebergs, in the silent evidence afforded by their size and numbers, are witnesses of the fact. These objections have an apparent weight; they deserve consideration.

873.—Tropical regions of the southern hemisphere cooler, extra-tropical warmer, than those of the northern.—The answer to them is as follows : Between lat. 40° or lat. 45° and the equator, and parallel for parallel, the southern hemisphere is cooler than the northern. Reason teaches, and observations show that it is so. But beyond 45° S. observations are wanting, and we are left to reason and conjecture. That the southern hemisphere should, till within a certain distance of the pole, be warmer in winter and cooler in summer, may be explained by the fact that the southern hemisphere has more water; that water being more equable than land in its temperature, produces more equable climates; that the vapour which is taken up from trans-equatorial seas and condensed into rains for cis-equatorial rivers conveys with it a vast amount of heat which the southern hemisphere receives from the sun. It is rendered latent by evaporation on one side of the equator, and made sensible by precipitation on the other. Much of it is set free in the equatorial calm belt, and it is this liberated heat which assists mightily to maintain the thermal equator in its northern position.

874. Formation of southern icebergs,—So, in like manner, the vapour that is borne to the antarctic regions by the polar-bound