Page:Popular Science Monthly Volume 10.djvu/742

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selves!' 'Copernicus,' I replied, 'could not understand it better.'" This novel theme continues to occupy them during their return to the house, and the first evening secures her belief for the new system.

The next morning, on Fontenelle's sending to ask how the lady has passed the night, and to politely inquire whether she has been able to sleep while turning, he is assured that she has already got used to the motion, and was able to rest as soundly as Copernicus himself could have done. With so apt a scholar, progress is rapid, and, by evening, we find them discussing the habitability of the moon, and the cause of the sun's light and heat. What is the view of our author (the subsequent secretary of the Académie des Sciences, and an authority in his day) on the source of supply for this immense expenditure of the solar energy? What theory does he adopt—how was it accounted for in his time? Listen to the explanation of the man who has just satirized so happily the fallacies of the schoolmen. It shines because "it is self-luminous in its nature." And this is given in good faith by Fontenelle as a reason!

Clever as he is, he is here in the bondage of his age; but he might yet have taken a lesson from a contemporary, who, though pretending to no "philosophy," had seen and laughed at the weakness of the learned of his time in thus making words do duty for facts. We remember how the candidate for medical honors in the "Malade Imaginaire," on being asked why opium induces sleep, replies to the delighted satisfaction of the examining Faculty that it is because it possesses a soporific quality! When we see a man so acute as Fontenelle giving a precisely similar answer, with an obtuseness so plain to us, so imperceptible to him, can anything suggest more pertinently the need of watchfulness for traces of this legacy of ancient fallacies of thinking in our own modes of thought?

The third evening is occupied with a further discussion of the moon, and of Venus; on the fourth the other planets are considered, and reasons given for their possible habitability, some of which would hardly satisfy a more modern philosopher. Thus, the ingenious but scarcely satisfactory suggestion is made that, in spite of the neighborhood of Mercury to the sun, that planet may be a comfortable residence, owing to the presence there of large quantities of saltpetre, a substance which (according to our author) gives out "cold exhalations" in the sunshine. Lest this idea be unacceptable to our skeptical age, it should be added that Fontenelle takes care to fortify his position by citing the case of China, large portions of which, it appears, in spite of a southern latitude, experience extreme cold, even to the freezing up of their rivers in July, on account of the existence of this ingredient in their soil!

The "vortices" of Descartes are here introduced and offered as an explanation of the motions of the Jovian satellites about their primaries, and of the principal planets about the sun; and, in the next