"I think you ascribed it to the interaction of the solar heat and the evaporation from the surface."
"Quite so. I assumed that when the sun is low the vapours above the edge of the crater and elsewhere cool and condense, thus bending the rays and seeming to lift the sun higher; but after a time the rays heat and rarefy the vapours, thus lowering the sun again. It seemed a plausible hypothesis and satisfied me for a time, but still not altogether, and now I believe I have made a discovery."
"That she wobbles--that she doesn't keep steady--swings from side to side. You have seen a top, how stiff and erect it is when it is spinning fast, and how it wobbles when it is spinning slow, just before it falls. Well, I think something of the kind is going on with Venus. The earth may be compared to a top that is whirling fast, and Venus to one that has slowed down. She is less able than the earth to resist the disturbing attraction of the sun on the inequalities of her figure, and therefore she wobbles. In addition to the slow swinging of her axis which produces her 'seasons,' she has a quicker nodding, which gives rise to day and night in some favoured spots like Womla."
"After all," said I, "tis a feminine trait. _Souvent femme varie._"
"Oh, she is constant to her lord the sun," rejoined Gazen. "She never turns her back upon him, but if I have not discovered a mare's nest, which is very likely, she becks and bows to him a good deal, and thus maintains her 'infinite variety.'"
The cloudy surface of Mercury now lay far beneath us, and the glowing disc of the sun, which appeared four or five times larger than it does on the earth, had taken a bluish tinge--a proof that we had reached a very great altitude.
"What a magnificent 'sun-spot!'" exclaimed the professor in a tone of admiration. "Just take a peep at it."
I placed my eye to the telescope, and saw the glowing surface of the disc resolved into a marvellous web of shining patches on a dimmer background, and in the midst a large blotch which reminded me of a quarry hole as delineated on the plan of a surveyor.
"Have you been able to throw any fresh light on these mysterious 'spots?'" I enquired.
"I am more than ever persuaded they are breaks in the photosphere caused by eruptions of heated matter, chiefly gaseous from the interior--eruptions such as might give rise to craters like that of Womla, or those of the moon, were the sun cooler. No doubt that eminent authority, Professor Sylvanus Pettifer Possil, regards them as aerial hurricanes; but the more I see, the more I am constrained to regard Sylvanus Pettifer Possil as a silly vain asteroid."