386 COSMOS. 



instance, from the obscuring (mostly organic) meteoric dust, 

 ink-, or sand-rain, such as is described by Macgowan to have 

 continued for several days together in China. The second 

 and third of these causes do not require the occurrence of a 

 diminution of the electro-magnetic light process, perhaps, 

 (of the perpetual polar light 23 ) in the solar atmosphere ; but 

 the last-named cause excludes the visibility of stars at noon, 

 of which such frequent mention is made in these mysterious 

 and vaguely described obscurations. 



Arago's discovery of chromatic polarization has not only 

 confirmed the existence of the third and outermost envelope 

 of the Sun, but has likewise added considerable weight to the 

 conjectures advanced in reference to the whole physical con- 

 sanguine perfusum comparuisse, ut etiam stellse pleraque 

 in meridie conspicerentur." Kepler, (in Stella Nova in 

 Serpentario, p. 113,) further expresses his uncertainty 

 as to the cause of the phenomenon; he asks whether the 

 diminution of the Sun's light be owing to some celestial 

 causes: '" Solis lumen ob causas quasdam sublimes hebe- 

 tari . . . ." whether it be owing to the wide diffu- 

 sion of some cometary substance " materia cometica 

 latius sparsa," for the cause cannot have originated in 

 our atmosphere, since the stars were visible at noon." 

 Schnurrer (Chronik der Seuchen, th. ii. p. 93) thinks, 

 notwithstanding the visibility of the stars, that the 

 phenomenon must have been the same as the so-called 

 "Hohenrauch;" for Charles V. complained before the 

 battle, " that the Sun was always obscured when he was 

 about to engage with the enemy." " Semper se nebula3 

 densitate infestari, quoties sibi cum hoste pugnandum 

 sit." (Lambert, Hortens. de hello german. lib. vi. p. 182.) 

 23 Horrebow (Basis Astronomic, 1735, 226) makes use of 

 the same expression. Solar light, according to him, is " a 

 perpetual Northern-light within the Sun's atmosphere ; produced 

 by the agency of powerful magnetic forces" (See Hanow, in 

 Joh. Dan. Titius' gemeinmitziye Abhandlunyen uber naturliche 

 Dinge, 1768, p. 102.) 



