the inward iris, taken from its last colour, was about five degrees and a half; and that of the white arch, which circumscribed the others, not less than sixty-seven degrees. At the beginning of the phenomenon, the arches seemed of an oval or elliptical figure, like the disk of the sun, and afterwards became perfectly circular, Each of the least was of a red colour, bordered with an orange; and the last followed by a bright yellow, which degenerated into a straw colour, and this turned to a green. But, in all, the external colour remained red. On the mountains we also had frequently the pleasure of seeing arches formed by the light of the moon, particularly one on the 4th of April, 1738, about eight at night, on the plain of Turubamba. But the most singular was one seen by Don George Juan, on the mountain of Quinoa loma, on the 22d of May, 1739, at eight at night. These arches were entirely white, without the mixture of any other colour, and formed along the slope or side of a mountain. That which Don George Juan saw, consisted of three arches, touching in the same point: the diameter of the inner arch was sixty degrees, and the breadth of the white mark, or delineation, took up a space of five degrees; the two others were, in every respect, of the same dimensions. The atmosphere, and the exhalations from the soil, seem more adapted than in any other place for kindling the vapours, meteors being here more frequent, and often very large, last longer, and are nearer the earth, than the like phænomena in other parts. Ulloa's Voyage to South America. SECTION XI. Lunar Rainbow in Derbyshire. By Mr. Ralph Thoresby, F.R.S. THE iris lunaris being so rarely seen, that Dr. Plot tells us that several learned and observing men never saw one in their lives; and that even Aristotle himself observed only two in above fifty years; the ensuing account, which I had from a gentleman of great veracity and ingenuity, will be the more acceptable. He was lately in Derbyshire, where, on Christmas last, he was at Glapwell Hall; and walking towards Patterson Green, about eight in the evening, he observed with great satisfaction the bow, which the moon had fixed in the clouds: she had then passed her full about *Nat. Hist. of Oxford, cap. 1, sec. 7. 2 M TOL. IV. twenty-four hours; the evening had been rainy, but the clouds were dispersed, and the moon shone pretty clear. The iris was more remarkable than that which Dr. Plot observed at Oxford, the 23d of November, 1675; that being only of a white colour, but this had all the colours of the solar iris, exceedingly beautiful and distinct, only faint in comparison of those we see in the day; as must necessarily be the case, both from the different beams that cause it, and the disposition of the medium. What puzzled him the most, was the largeness of the arc, which was not so much less than that of the sun, as the different dimensions of their bodies, and their respective distances from the earth seem to require: but as to its entireness and beauty of its colour, it was surprising. It conti. nued about ten minutes, before the interposition of a cloud hin. dered his further observation. [Phil. Trans. 1711. SECTION XII. Description of a Glory seen on Mount Realt, near the Vale of On the 13th of February, 1780, as I was returning to Chester, and ascending, at Rhealt, the mountain, which forms the eastern boundary of the Vale of Clwyd, I observed a rare and curious phenomenon. My ingenious friend Mr. Falconer has given, from my description, an exact representation of it, in a drawing which accompanies this paper. In the road above me, I was struck with the peculiar appearance of a very white shining cloud, that lay remarkably close to the ground. The sun was nearly setting, but shone extremely bright; I walked up to the cloud, and my shadow was projected into it. The head of my shadow was surrounded, at some distance, by a circle of various colours, whose centre appeared to be near the situation of the eye, and whose circumference extended to the shoulders. This circle was complete, except what the shadow of my body intercepted. It exhibited the most vivid colours, red being outermost as far as can be recollected, all the colours appeared in the same order and proportion that the rainbow presents to our view. It resembled, very exactly, what in pictures is termed a glory, around the head of our Saviour, and of saints: not indeed that luminous radiance, which is painted close to the head, but an arch of concentric colours, which is placed separate and distinct from it. As I walked forward, this glory approached or retired, just as the inequality of the ground shortened or lengthened my shadow. The cloud being sometimes in a small valley below me, sometimes on the same level, or on higher ground, the variation of the shadow and glory became extremely striking and singular. To add to the beauty of the scene, there appeared, at a considerable distance, to the right and left, the arches of a white shining bow. These arches were in the form of, and broader than a rainbow; but were not completely joined into a semicircle above, on account of the shallowness of the cloud. When my chaise came up, I could observe no peculiar appearance round the shadows of the postillion, horses, or chaise. But the postillion was alarmed, to an uncommon degree, by this very singular apparition: which, indeed, might excite terror, or delight, in the beholder, according to the disposition of mind with which it was viewed. Several appearances have been described by philosophers, in Come respects resembling what I saw, but not exactly the same. The arch in size, situation, and colour, was most exactly the glory represented in some pictures, and is manifestly the archetype whence it had been copied by a painter. Indeed such a phenome non is well adapted to excite religious awe and reverence. When I returned into the chaise, a bright radiance appeared close to its shadow, but no separate coloured circle was formed. In order to investigate the cause of these curious appearances, on optical principles, it may be useful to note some peculiar cir. cumstances. The cloud was specifically heavier than the air of that |