104 



South West. The illuminated line from the western mock 

 moon was not traceable to any distance, nor did a mock moon 

 appear in the North, opposite to the moon. The red rays were 

 next the moon. The phenomenon was faint and ill-defined ; 

 the eastern and upper moons scarcely discernible. It dis- 

 appeared in about half an hour after it was first observed. 



" No observation being taken at these hours at the Mag- 

 netic Observatory, there is no record of the phenomenon as 

 observed there. But the observer at ten, p. m. has noted as 

 follows: — Sky all covered with very fine long cirrostrati, ex- 

 tending across the entire sky from North to South. Haze 

 visible about the moon. The barometer, at this hour, stood 

 at 29.978 ; the thermometer at 48.4 ; wet thermometer, 47.1. 



Professor AUman made the following observations on the 

 same phenomenon. 



Observed between the hours of 10 and 11 o'clock, p. m., 

 on the 21st May, 1845, a thin haze spreading over the sky. 

 The arm of the cross which approached more nearly to the 

 horizontal was slightly inclined to the horizon, at an angle 

 which, as far as the unassisted eye could determine, might 

 have been about 15°. The other arm was perpendicular to 

 this. The diameter of the circle included within the halo was 

 equal to about forty diameters of the moon. At the points 

 where the cross, if produced, would have intersected the halo, 

 were paraselene. The two lateral paraselene were more con- 

 stant in their appearance than the superior, which was visible 

 only two or three times during the observation. The lower 

 part of the halo was not visible. The moon itself was imme- 

 diately surrounded by an ordinary blur-like halo, which was 

 more intensely luminous than the cross, and within the mar- 

 gins of which it was wholly confined. The extremities of the 

 paraselene, which were placed upon the halo, were obscurely 

 prismatic ; but I could determine nothing satisfactory as to 

 the order of the colours. The arms of the cross were inter- 



