over the land, obscuring every thing but the summits of the surrounding hills. He saw his shadow cast upon the mist, and round it was an arc of prismatic hues; at another time he observed a double ring surrounding, and distant about two feet from his shadow. Mr L. Agassiz' witnessed the phenomenon from the Rigi-calm in Schwyz, at sunset. A large prismatic arc, about 4-5ths of a circle, attracted his attention, in the centre of which there appeared "a small but perfect circle of faint colours, ring within ring like a target, within which we saw our own contours as clearly delineated as in a looking-glass." In 1841, a party witnessed the same phenomenon from the Faulhorn. Scoresby' witnessed this meteor in the polar regions, when sunshine and a fog coexisted. On the 23d of July 1821, four concentric circles appeared to him, of the following radii and colours :-a, nearest his head; radius, 1° 45'; hues, white, yellow, red, purple,-all very vivid: ß, next to a; radius=4° 45′; hues, blue, green, yellow, red, and purple,—all very vivid: 7, radius=6° 30′; hues, green, whitish, yellowish, red, and purple,-indistinct and sometimes invisible, radius=38° 50; hues, faint green and white. Kämtz twice witnessed a similar appearance on the Alps, the mean radius of the largest circle being 39° 48'; Bravais at Bell Sound, Spitzbergen, measured one the radius of which was 45°; and from five observations, in 1841, on the Faulhorn, he derived a mean radius of 38° 54'. The mean radius obtained from all these records equals 39° 12', while that of the primary rainbow is 41° 9′ 30′′, consequently these phenomena are distinct and cannot be accounted the same. 260. An appearance analogous to this meteor is mentioned by Mr Green as having been sometimes seen by him from his balloon, at altitudes of about two miles. It is a shadow of the balloon beautifully depicted on the upper surface of a cloud, invariably encircled by a triple iris. A similar effect was witnessed by Prince Pückler Muskau, a Silesian nobleman, the "German Prince," author of the Tour,-upon an ascent with Mr Richard from Berlin. The balloon and its 1 Jour. to Switzerland. a Kämtz et Mart. Met. 2 Journ. pp. 274-284. æronauts appeared upon the clouds of colossal magnitude, surrounded by many prismatic wreathes. 261. The immediate cause of the prismatic colours of the meteors described, is the diffraction' or inflexion' of light, dependent upon the undulatory theory of that fluid; or the different refrangibility of the solar rays suffering refraction in passing through media of unequal density. The size of the vesicles of the interposed vapour, and the diameter of the meteor, are in direct ratio; when the vesicles are of equal magnitudes, the phenomenon is perfect, but should they vary in size, it undergoes modifications according to the peculiarities of the case. Mariotte3 long since referred the halo to the refraction of light by prismatic crystals of snow floating in the higher regions of the atmosphere,-an opinion supported by observations made by Arago' on the 11th of April 1825, with an instrument invented by him for the examination of polarized light. When the phenomenon arises from the interposition of cirri, this is doubtless the case, for the altitude of these clouds is within the regions of perpetual congelation. This theory is supported by Young, Cavendish, and others. The hypotheses of Des Cartes, Huygens, and Newton, being accounted untenable, we need not dwell upon them.s 262. The Parhelion, or Mock-sun,-Nebensonne,-frequently seen in the polar circle, is one of the finest of the luminous meteors of our atmosphere. It presents the appearance of halos and luminous arcs, intersecting with mathematical precision, and studded with solar images. In the following descriptions of the phenomenon, it will be observed that there is a remarkable regularity preserved, although occasionally some parts may be wanting. The circles which most frequently appear are those which surround the true sun, and 1 Grimaldi,-Physico-Mathesis de Lumine, Coloribus et Iride. Bononiæ 1665, -Ph. Tr. 1672, No. 79. p. 3069; Fraunhofer. 2 " Newton,-Optics. 3 (Euvres, i. 272; Tr. des Couleurs, Par. 1686. Bullet. Univ. Mai 1825. Vide Des Cartes,-Meteorol. x.; Huygens,-Dissert. de Cornuis et Parhel.; Newton,-Opt. book ii. pt. iv. obs. 13; Priestley,-On Vision, &c. vol. ii.; Dr T. Young, Nat. Phil.; Wood,-Manch. Mem, vol. iii. 336; Smith,-Optics, vol. i. that one which passes through his disc parallel with the horizon. Besides these, tangental arcs are often visible. Occasionally, segments of vertical circles render the meteor more complicated. The Paraselene is a similar phenomenon occurring at night, when the moon is shining. Arago1 has observed that the circumstances favourable to these phenomena may exist over a wide extent; thus, parhelia were visible on the 13th of May 1838, in the Departments of Aisne and Nord; and upon the 29th of March 1848, in the south of England and Guernsey. 263. Aristotle records two appearances of this meteor; and Pliny mentions their occurrence at Rome. A double parhelion, which was noticed before the Christian era, is referred to by Augustine; and Zonaras mentions two seen after the death of Christ. In England the phenomenon is said to have been witnessed in the year 346, when, besides the true sun, four mock-suns were visible; two in 812, and the same number in 953. Holinshed records one in 1199 on the authority of William Paruus, an eye-witness, and he quaintly observes, -"At length when the beholders had well wearied their eyes in diligent marking the manner of this strange appearance, the counterfeit sunne vanished awaie." Matthew Paris, monk of St Albans and historian,3 mentions a meteor of this kind which was seen from sunrise till noon on the 8th of April 1233, in the 17th year of the reign of Henry III. Four mock-suns were visible in a white circle which passed through the sun, equidistant from each other and having the true luminary between two of them; where the parhelia appeared, arcs, the vertices of which turned to the centre of the large circle, cut that ring. On the 1st December 1236, the phenomenon is again recorded. Palmerius mentions three suns seen in 1466. In the year 1514, three were witnessed at Wirtemberg, on the authority of Surius; and in 1532, the same number at Venice, on that of Cardan. In 1551,—a year remarkable for earthquakes and meteors, and no less memo P. 373-501. 'Compt. Rend. tom. vi. 2 Chron. vol. iii. p. 157. adventu ad an. 43 Hen. III, Hol.-Chron. vol. iii. p. 216; 4 Hol. vol. iii. P. 220. rable for the 5th visitation of the sweating sickness,'-several parhelia were visible. Thus, on the 28th February, mocksuns were seen at Antwerp;' on the 17th of March a similar phenomenon, with two halos, was witnessed; and on the 21st, at 7 A. M., two parhelia with three halos were seen at Magdeburgh, and in the evening two paraselenæ ; at Wittemberg the mock-suns were observed, but not the other meteors. On January 2. 1586, Christopher Rotham saw at Cassel, before sunrise, an upright column of light of the breadth of the sun's disc. He rose, preceded and followed by a parhelion, which appeared in contact with his orb; they continued visible for thirty minutes, till obscured in a cloud. In 1596, Barentz, at Nova Zembla, saw the sun attended by two parhelia and three halos. In 1619, three were visible, on the authority of Fromundus. Scheiner witnessed a singular one at Rome on the 20th of March 1629: from the zenith as a centre there was seen a great white circle, having the true sun in its circumference; this was intersected by two concentric circles around his disc; where the outer of these smaller rings cut the zenithal circle two parhelia appeared, and in the great circle, nearly opposite to these, but separated by a wider arc, two others were visible. Gassendi' describes a very remarkable phenomenon of this kind, which was seen in 1630 by Scheiner. Around the sun were two concentric halos, the 'Hecker,-Epidem. Mid. Ages. 2 Chronici Chronicorum, 1614, p. 402. 4 3 Spangenberg. Ch. Chron. p. 401; Angelus-Annales Brandenburg. 1598. p. 344; Mansfeldische Chronica,-Spang. fol. 464; Hecker,-Epidem. p. 296. 5 Opera, tom. vi. 401. larger cut the horizon and consequently was incomplete; these were coloured like the rainbow, excepting that the red was internal. In the direction of the zenith, there was a tangental arc external to these halos; and with the zenith as a centre, a great white circle ran parallel with the horizon, having the true sun in its circumference. At the five intersections of these circles and arcs parhelia appeared, and a sixth was seen in the internal halo between the true sun and the zenith. Gassendi was an eye-witness of the phenomenon in 1635 and 1636. Lilly mentions two mocksuns seen on the 19th of November 1644; and two appeared on February 28. 1648. At Leyden, on January 14. 1653, between the hours of 1 and 2 P. M., Kechelius saw from the Observatory two parhelia, distant about 22° 35′ from the sun, which was the centre of the circle in which they appeared; the western was the fainter, and disappeared first; from the eastern, a tail issued 27° in length. On the 6th of April 1660, at 5.5 P.M., when the sun was nearly set, Hevelius noticed a partial circle about 22°.5 from his centre, tipped above by a tangental arc. Opposite the sun, north and south, in the circumference of the halo, two parhelia with tails were visible, and a third appeared in the intersection of the arcs. In 1666, six suns were seen at once at Arles.' 264. One of the finest meteors of this kind on record was seen by Hevelius' at Sedan on the 20th of February 1661 "A little before 11 o'clock," he says, "the sun being towards the south, and the sky very clear, there appeared seven suns 1 Coetlogon,-Univ. Hist. of Arts and Sc. vol. ii. p. 429. Mercurius in Sole Visus, p. 174. |