a pale-white semicircle based on the moon's limbs; a third figure was a red detached cloud, or balloon, of nearly circular form, separated from the moon by nearly its own breadth; a fourth appeared like a small triangle, or conical red mountain, perhaps a little white in the interior;" and the Professor proceeds to say, "I employed myself in an attempt to draw roughly the figures, and it was impossible, after witnessing the increase in height of some, and the disappearance of another, and the arrival of new forms, not to feel convinced that the phenomena belonged to the sun, and _not_ to the moon." Still the question remains unanswered, what are these "rose-coloured prominences?" If they belong to the sun, and are mountains in that luminary, they must be some thirty or forty thousand miles in height. M. Faye has formally propounded the theory, that they are caused by refraction, or a kind of mirage, or the distortion of objects caused by heated air. This phenomenon is not peculiar to any country, though most frequently observed near the margin of lakes and rivers, and on hot sandy plains. M. Monge, who accompanied Buonaparte in his [Page 30] expedition to Egypt, witnessed a remarkable example between Alexandria and Cairo, where, in all directions, green islands appeared surrounded by extensive lakes of pure, transparent water. M. Monge states that "Nothing could be conceived more lovely or picturesque than the landscape. In the tranquil surface of the lake, the trees and houses with which the islands are covered were strongly reflected with vivid and varied hues, and the party hastened forward to enjoy the refreshment apparently proffered them; but when they arrived, the lake, on whose bosom the images had floated--the trees, amongst whose foliage they arose, and the people who stood on the shore, as if inviting their approach, had all vanished, and nothing remained but the uniform and irksome desert of sand and sky, with a few naked and ragged Arabs." If M. Monge and his party had not been undeceived, by actually going to the spot, they would, one and all, have been firmly convinced that these visionary trees, lakes, and buildings had a real existence. This kind of mirage is known in Persia and Arabia by the name of "serab" or miraculous water, and in the western districts of India by that of "scheram." This illusion is the effect of unusual refraction, and M. Faye attempts to account for the rose-coloured mountains by something of a similar nature. It is right, however, to mention, that learned astronomers do not consider this theory of any value.