104 OF THE HALO, CORONO, &c. CHAP. 2. 19. 



in the Raincloud. Lunar Rainbows are rare 

 occurrences. 



Ims DVPLEX. Duo Circuit colororati, quorum 

 centrum commune Soils centra opponitur, 

 qui quod eorum portiones tantum videantur 

 Arcus adpareant. 



Double Rainbows are not unfrequent. The 

 order of colours in the outer one is reversed.* 

 They are mentioned by Aratus.f 



IRIS VNICOLOR. Circulus maximus colorum 

 excors, in nube visus, et cujus centrum centra 

 Soils vel Lunae opponitur ; qui quod portio 

 ejus tantum videatur Arcus adpareat. 

 The Iris unicolor is more properly a colour- 

 less Rainbow, and appears in the mist. Such a 

 one appeared on 20th November, 1812, in the 

 vicinity of London. The afternoon of the 

 same day there was a shower in which the 

 Rainbow showed the usual colours4 



RABDI DIVERGENTES. Radii Soli* radiantcs 

 ob quandam specialis generis interpositam 

 nuber.i. 

 The remarkable appearance of the sun's rays, 



* Arist. Meteor, lib. iii. cap. 5. Newton's Opticks, &c. 



t Arat. Dios. 208. 



J Annals, of Philosph. by Dr. Thomson, p. 80. 



