- ill ihe Vapours of the Atmofph ere, 349 



tiQularly the dodlrinc of .eonic fuiSlions, niighl be smplojed 

 fur explaining fimilar phenomena. But refpc6ting this point 

 time mud determine. 



But that the above obferved phsenomenon may in fome 

 meafure be ufeful to meteorologifts, I ftall here add a few 

 remarks. If we eftin)ate the Iranfverfe diameter of the el-, 

 lipfe at 60 , and the diameltrr of the circular ring at more 

 than '20°, it muft be admitted that the whole phseuomenoii 

 was at no great height in the atmofphere, eli'e it muft have 

 comprehended feu cr of the conllellaiions : the vapours in 

 Mhich it appeared floated therefore in a very low fituation, 

 and near the obferver's horizon. It thence follows, that this 

 phaenomenon could be vifible to no other perfon, unlels he 

 had the fame ftratum of clouds over him, and beheld the 

 moon through it; and it is probable that the phienomenon 

 might have remained unnoticed had the obferver been a 

 mile towards one fide from the poiition in which he then 

 Aood. We may admit, not without reafon, that all fuch 

 circles with which the fan and moon are fometimes fur- 

 rounded are not at a very confiderablc diftance from the fur- 

 face of the earth,, and therefore are not vifible in a greater 

 extent than 40 or 50 miles. If the highcft clouds over the 

 fea can be fecn only at the diftance of about 20 geographical 

 miles above the horizon, how much more nujft a phaeno-; 

 menon which takes place in far lower diflricls of the atnio- 

 fphere efcape the notice of different obfervers whofe pofitions 

 are at a great diltance from each other, and particularly 

 \vhen its vifibility depends on the angle under which an objcdl 

 muft be viewed to obferve that peculiar image which is pro- 

 duced ! We never fee the rainbow in a cloud, or rather in 

 the falling drops of rain, when the Tun is either too high or 

 too low. In the high Alps of SwifTerland it fometimes hapl 

 pens, that mltead or a bow there is feen a complete, circle of 

 the prifmatic colours in the drops precipitated from the at- 

 mofphei-e. In the fame manner, the vifibility of various 

 other phrcnomena in the atmofpherc depends on the point 

 of fight which is favourable for the obfervution. We there^ 

 fore cnight not to afllrt that fuch or fuch phienomcna fcldom 

 occur; we oupht rather to i'ay that they liave been feen by 

 individual obfervers, and in particular geographical points ot 

 fight. . . '. 



I (hall embrace this- opportunity of making fome obfer«alC 

 lions on an adcrtion which appeared in one of the public 

 journals of lalt year. Speaking of a rainbow produced l»y 

 moonlight, whicSi w.n5 oKfervtd on the 5tli of September i8co 

 from tiie obfervutuiy of Gulljogen, the account concluded 



with 



