S76 COSMOS. 



photosphere. 20 Arago, in putting forward this hypothesis, 

 expresses the conjecture that the intense blue colour of the 

 sky, which I have myself measured upon the loftiest part of 

 the Cordilleras, though with instruments which are certainly 

 still very imperfect, may afford a convenient opportunity for 

 frequently observing these mountain-like clouds in the outer- 

 most atmosphere of the Sun. 21 



20 " Si nous examinions de plus pres 1' explication d'apres 

 laquelle les protuberances rougeatres seraient assimilees a 

 des nuages (de la troisieme enveloppe), nous ne trouverions 

 aucun principe de physique qui nous empechat d'admettre 

 que des masses nuageuses de 25.000 a 30,000 lieues de long 

 flottent dans 1'atmosphere du Soleil ; que ces masses, comme 

 certains nuages de 1' atmosphere terrestre, ont des contours 

 arretes, qu'elles affectent, ga et la, des formes tres tour- 

 mentees, meme des forms en surplomb ; que la lumiere 

 solaire (la photosphere) les colore en rouge. Si cette 

 troisieme enveloppe existe, elle donnera peutetre la clef de 

 quelques-unes des grandes et deplorables anomalies que Ton 

 remarque dans le cours des saisons." "On examining more 

 closely the grounds on which these rose-coloured protube- 

 rances are compared to clouds (of the third atmosphere) we 

 do not find any principle in physics which would oppose the 

 assumption that masses of clouds extending from 25,000 to 

 30,000 leagues, float in the Sun's atmosphere; that these 

 masses, like some clouds in our terrestrial atmosphere, assume 

 contours exhibiting here and there much-involved forms, 

 appearing sometimes even sloping or inverted, as it were; 

 and that they are coloured red by the light of the Sun (the 

 photosphere). If this third atmosphere actually exist, it 

 may, perhaps, tend to solve some of those vast and deplo- 

 rable anomalies which we observe in the course of the 

 seasons." (Arago, in the Annuaire pour 1846, pp. 460, 467.) 



21 " Tout ce qui affaiblira sensiblement 1'intensite eclairante 

 de la portion de 1'atmosphere terrestre qui parait entourer et 

 toucher le contour circulaire du Soleil, pourra contribuer a 

 rendre les preeminences rougeatres visibles. II est done 

 permis d'esperer qu'un astronome exerce, etabli an sonimet 



