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HISTORY OF PHYSICAL ASTRONOMY.
moon ’s surface. He remarks that the fulminations had a serpentineappearance, causing them to resemble flashes of lightning*.
Weidler, in an account of the partial eclipse of August 4, 1739, asobserved by him at Wurtemberg, makes mention of a similar phenomenon.He states that a friend of his, well skilled in astronomical observations,having viewed the moon towards the commencement of the eclipse witha telescope 9 feet long, noticed bright lights like flashes of lightning in-terspersed here and there upon her dark surface; and that after the lapseof one hour and nineteen minutes he again saw the same appearance f.
Attempts were made during the total eclipse of 1842 to verify the fore-going observations, but it was only at Venice that any analogous corus-cations of light were discerned. Sig. Zantedeschi, who observed theeclipse at that city, states, that from time to time there were visible uponthe moon’s surface faint illuminations of an intermittent character, re-sembling flashes of phosphoric light, intermingled with black streaksA similar appearance was noticed by M. Wullerstorf J.
The phenomena above referred to have been explained in various waysby different enquirers. Louville attributed them to the prevalence ofelectric storms in the lunar atmosphere; other persons suppose them tohave been produced by volcanic energy. M. Arago is of opinion thatthey may have arisen from the occasional passage of aerolites across thefield of view of the telescope. In support of this view of their origin, hecites one or two instances in which, during the total eclipse of 1842, therewere seen meteoric lights traversing the regions of the heavens in whichthe sun and moon were then situate. From the circumstance of thephenomena having been visible only on two or three occasions, it is clearlyimpossible to arrive at any trustworthy conclusions on the subject.
At various places in France , a singular undulation of the solar light wasremarked on the occasion of the total eclipse of 1842. In a letter to M.Arago, dated July 9, 1842, M. Fauvelle gives the following account of thephenomenon as witnessed by him at Perpignan :—“At the moment whenthe eclipse was about to become total, I perceived the last rays of the sunundulate with great intensify and rapidity upon a white wall of one of themilitary establishments of the rampart of St. Dominique. The effectmight be compared with that which is observed when the light of the sunfalls upon a wall or a ceiling after having been reflected from the surfaceof a sheet of water in a state of agitation. The same phenomenon re-appeared at the instant of the emersion of the sun; the undulations whichat first were very intense gradually died away, and disappeared altogetherat the end of five or six seconds.”!
M. Arago remarks also that during the few seconds which could bedevoted by his colleagues and himself to the observation of such a pheno-menon, the facade of the great tower of the citadel of Perpignan appearedto be illuminated by a singularly-fluctuating light.
M. Lentheric thus describes the phenomenon as observed by him atMontpellier :—“ A little before the commencement of the total obscura-tion, there were seen on the ground and on walls undulating shadoivscomposed of a succession of arcs of three or four decimetres in length,but of much less breadth, which seemed to turn upon themselves. Theeffect was analogous to that produced by those moveable shadows which
* Mem. Acad, des Sciences, 1715, p. 90. + Phil. Trans., 1739, p. 228.
f Annuaire, 1846, p. 364. § Annuaire, 1846, p. 392.