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LUNAR CELESTIAL PHENOMENA.

In the case supposed, as the moon really passedover a star, we should see the star changing inappearance into an arc, this arc gradually increasingin length and span, until at length, when the star wascentrally behind the moon, it would appear as a ringaround her disc.

The actual circumstances of an occultation of a starby the moon are very markedly contrasted with thosehere mentioned. In nearly all cases a star disappearsinstantly, when the moon’s edge reaches the star’splace. There is no perceptible displacement of thestar, no change of colour, no effect whatever such asa refractive atmosphere would produce. In certaininstances, the brightness of a star has been observedto diminish just before disappearance; but we cannotbe sure that, where this has happened, the star maynot be really multiple, or perhaps nebulous. In thecase of the star k Cancri, according to some ob-servers, the star has seemed suddenly reduced byabout one half of its light, and almost instantly afterto vanish ; but these phenomena, only noticed in thecase of this star, may be fairly explained by sup-posing the star to be a close binary. Again, therehave been instances where a star has seemed toadvance for some distance upon the moon’s discbefore vanishing; but it is by no means unlikelythat the star has in such a case chanced to crossthe moon’s limb where a valley or ravine hascaused a notch or depression which is too smallto be indicated by any ordinary method of observa-