I have very little to say to you respecting the cause of this wonderful phenomenon. The most reasonable notion seems to be, that it is occasioned by electric fluid playing about, and diffusing itself in the upper regions of the atmosphere, where the air is very thin. A similar kind of light is produced by a very pretty experiment, which consists in sending an electric spark through a long glass vessel, from which the air has been exhausted. When the air is more compressed, as it is near the surface of the earth, the electric fluid does not so spread itself abroad, but moves in more direct lines, and in more compact masses, as you may see in lightning, or in the sparks of an electrifying machine sent into the atmosphere under ordinary circumstances of density. CHAPTER III. PARLEY TELLS OF SOME OTHER METEORS. PARHELIA OR MOCK SUNS. There are a great many very wonderful appearances in a polar sky, besides the Aurora Borealis. Perhaps the most remarkable of these are Parhelia, or "mock suns," which are often seen to shine in various parts of the sky. As many as six of them are sometimes seen at once, all shining with great brilliancy. They are generally brightest just before day-break, and fade away as the true sun ascends. Parhelia have also been seen at different times on the continent of Europe. At Marienberg, in Prussia, many years ago, towards evening, one was observed which seemed attached to a small white cloud that was situated just below the sun. It was at first of a reddish colour, but as the sun descended towards it, it assumed the aspect of the sun itself. Three at once were seen at Sudbury, in Suffolk, and two were seen in a part of Rutlandshire. There are recorded many other appearances of this remarkable phenomenon, but they do not seem to differ much from each other. There is great uncertainty as to what occasions these mock suns. Perhaps they are merely reflections of the image of the true sun upon reflecting clouds, such as I shall describe to you presently. The circumstance that seems to render this probable, is that they sometimes become brighter as the sun approaches them, which cannot easily be accounted for by supposing them to have any source of light in themselves. On the contrary, their fading away at times as he rises, may be occasioned by the clouds on which they are reflected, becoming rarified; or the effect may be only comparative, just as the moon grows paler, and at last disappears, as day comes on. Thus you see the two opposite effects of the sun's approach may be equally well accounted for, on the supposition of the Parhelia being mere reflections of the sun, and I do not think that they could on any other. IGNES FATUI.