In February 1837, two gentlemen, on whom I confidently trust, were standing on Calton Hill while a murky cloud hung over Edinburgh. Above this veil Arthur’s Seat peeped out like a rocky island beneath two white arches, like the lunar bows; and on the cloud itself, each gentleman saw the shadow of his companion magnified to gigantic proportions. The aeronaut, among other glories of his ascent, may by chance be gratified by the shadow of his balloon on the face of a cumulus cloud; thus did the Duke of Brunswick, who ascended with Mrs. Graham, in August 1836. And this is the analogous recital of Prince Puckler Muskau, in his “Tutti Frutti.” “We dipped insensibly into the sea of clouds which enveloped us like a thick veil, and through which the sun appeared like the moon in Ossian. This illumination produced a singular effect, and continued for some time, till the clouds separated, and we remained swimming about beneath the once more clear azure heavens. Shortly after we beheld, to our great astonishment, a species of ‘Fata Morgana,’ seated upon an immense mountain of clouds the colossal picture of the balloon and ourselves surrounded by myriads of variegated rainbow tints. A full half hour the spectral reflected picture hovered constantly by our side. Each slender thread of the network appeared distended to the size of a ship’s cable, and we ourselves two tremendous giants enthroned on the clouds.” The phantom, which rode side by side with Turpin, might be a mere reflected shadow in the mist; indeed, Burton writes that “Vitellio hath such another instance of a familiar acquaintance of his, that after the want of three or four nights’ sleep, as he was riding by a river-side, saw another riding with him, and using all such gestures as he did, but when _more light appeared, it vanished_.” The principles of refraction are the sources of many an illusion, which is startling even to those who are aware of them. The sea, the vessels floating on its surface, the rocks and buildings on its shores, often appear elevated far beyond their usual position: things are thus presented to the eye which, in the direct course of the rays, would be completely out of sight; and the praises bestowed on the Irish telescope may not have been a bull, although we are assured that we may _see through it round the corner_.