the moon's light. 143 



able ; but during a total eclipse of the Moon (31st of May, 

 1848), Arago detected indubitable signs of polarization in the 

 reddened disk of the Moon, the latter being a phenomenon of 

 which we shall speak further on. (Comities Hcnclus, torn, 

 xviii., p. 119.) 



That the moonlight is capable of 'producing heat, is a dis- 

 covery which belongs, like so many others of my celebrated 

 friend Melloni, to the most important and surprising of our 

 century. After many fruitless attempts, from those of La 

 Hire to the sagacious Forbes,* Melloni was fortunate enough 

 to observe, by means of a lens {lentille a cchellons) of three 

 feet in diameter, which was destined for the meteorological 

 station on Vesuvius, the most satisfactory indications of an el- 

 evation of temperature during different changes of the Moon. 

 Mosotti-Lavagna and Belli, professors of the Universities of 

 Pisa and Pavia, were witnesses of these experiments, which 

 gave results differing in proportion to the age and altitude 

 of the Moon. It had not at that time (Summer, 1848) been 

 determined what the elevation of temperature produced by 

 Melloni's thermoscope, expressed in fractional parts of the 

 centigrade thermometer, amounted to.f 



* Forbes, On the Refraction and Polarization of Heat, in the Trans- 

 act, of the Royal Society of Edinburgh, vol. xiii., 1836, p. J31. 



t Lettre de M. Melloni a M. Arago sur la Puissance calorifique dc la 

 Lumiere de la Lune, in the Comptes Rendus, torn, xxii., 1846, p. 541-544 

 Compare also, on account of the historical data, the Jahresbericht der 

 Physicalischen Gesellschaft zu Berlin, bd. ii., p. 272. It had always 

 appeared sufficiently remarkable to me, that, from the earliest times, 

 when heat was determined only by the sense of feeling, the Moon had 

 first excited the idea that light and heat might be separated. Among 

 the Indians the Moon was called, in Sanscrit, the King of the stars of 

 cold ('sitala, hima), also the cold-radiating (himdrfsii), while the Sun 

 was called a creator of heat {niddghakara). The spots upon the Moon, 

 in which Western nations supposed they discerned a face, represent, 

 according to the Indian notion, a roebuck or a hare ; thence the San- 

 scrit name of the Moon (mrigadhara}, roebuck-bearer, or ( , sa'sabhrit), 

 hare-bearer. (Schtitz, Five Hymns of the Bhatti-Kdvya, 1837, p. 19-23.) 

 Among the Greeks it was complained " that the sunlight reflected from 

 the Moon should lose all heat, so that only feeble remains of it were 

 transmitted by her." (Plutarch, in the dialogue " De Facia quce in 

 OrbeLuna apparel, Moralia," ed. Wyttenbach, torn, iv., Oxon., 1797, p. 

 793.) In Macrobius (Comm. in Soimiium Scip., i., 19, ed. Lud. Janus, 

 1848, p. 105) it is said, " Luna speculi instar lumen cpao illustratur . . . 

 rursus emittit, nullum tamen ad nos preferentem sensum caloris : quia 

 lucis radius, cum ad nos de origine sua, id est de Sole, pervenit, natu- 

 ram secum ignis de quo nascitur devehit; cum vero in Lume corpus in- 

 funditur et inde resplendet, solam refundit claritatem, non calorem." 

 The same in Macrobius, Saturnal., lib. vii., cap. 16, ed. Bipont, torn. 

 ii., p. 277. 



