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40 being only a satellite, or resorted to strained hypotheses; such as, that there may be an atmosphere at the bottom of the valleys, or that she must necessarily have appropriated, by her attraction, the matter of the tails of comets, and of the zodiacal light. A recent discovery, has, however, been made, which entirely changes the aspect of the question. In all previous speculations, astronomers proceeded on the supposition that w^hat held in reference to one side of the moon, would equally hold in reference to the other. The profound research of a continental astronomer has now shewn, that this is by no means a legitimate supposition, and that the non-existence of an atmosphere in the visible side, does not, at all, imply that the other is equally destitute.

The moon constantly turns the same side to us. She does, indeed, as if to tantalise us, shew a small portion of the other side. She turns round at one time the western edge, so as to shew us a few more mountains and craters, and then, at another, the eastern; there is a similar oscillation at the poles, but it is only a very limited region that she thus reveals. It is by this libration, as we have seen, that we are able to take stereoscopic pictures of her disc. She turns constantly the same side to us, for the simple reason, that she rotates once upon her axis, in the same time that she performs a revolution round the earth. It, at first sight, appears like a contradiction, to say that she turns round upon her axis, and yet, that she never shews us