MK OF PROGNOSTICS. CHAP. 4. 3. 



signs of Rain and Snow that we have ; though 

 I have even known this fail in its accustomed 

 indication. The Parhelion and other peculiar 

 refractions also forebode rainy weather.* 



The simple Corona often occurs in many 

 kinds of thin clouds, and frequently without 

 any Rain following; but we may generally 

 expect wet when it is coloured, double, or with 

 any remarkable peculiarities. We do not know 

 at present under what peculiar circumstances 

 Halones and Coronae are coloured ; but it must 

 be done by something particular in the structure 

 of the cloud which produces them. 



The Halo appears at times in a sky where 

 there appears to an inattentive observer little 

 or no visible obscuration, the interstitial space 

 between the rings seems quite blue, like the 

 sky in general. Some very fine diffused hazi- 

 ness, perhaps cirrostratus, however produces by 

 refraction the white ring of the phaenomenon. 

 We often find on such occasions the light of 

 the stars dim, and a more complete obscuration, 

 and eventually Rain to follow. Pliny has 

 noticed this obscuration of the light of the 



* Consult Arist. Meteor, lib. iv. cc. 3 6; the Dios. of 

 Aratus ; the Natural History of Pliny ; the Natural Quest, 

 of Seneca, &c. 



