ad * i * 
— 
26 | Dec of a Halo or Boris 
tion of the halo. "The outer circles, however, one may of which 
appeared to be perfect, were composed of pure white-light, and 
had for their centres the circumference, or a point near it, of the 
inner ring. Consequently, their circumferences, if all the circles 
had been sorte would necessarily have passed through the ap- 
parent situation of the sun. I mentioned, however, that one only 
of these rings was perfect, the others were concentric arcs of cir- © 
cles which crossed one another, as seen in the accompanying 
diagram. i 
In the centre of the inner circle and bounded by it, a bluish 
mass of dense vapor was perceptible, which gave to the whole 
an embossed appearance, and added much to the beauty and 
brilliancy of the scene. Around and within the exterior circles 
there were also perceptible masses of vapor, though obviously 
much less dense than the mass which was nearer the sun, With 
the exception of these masses of vapor, and a large cumulus 
which lay to the south of us, and here and there a few scattered 
cirri, the sky was cloudless and the atmosphere calm and serene. 
The mercury in the thermometer stood at 86°. ‘The weather 
continued thus for thirty six hours, when we had a smart fall of 
rain, and a descent of the mercury in the thermometer to 36°, at 
which point or near this, it has remained until about three days 
since, when it rose to 66°. 
Coronas and parhelia have frequently been observed and ac- 
curately and glowingly described, by many scientific gentlemen, 
and various and conflicting opinions have been entertained re- 
specting their causes, some attributing them to the peculiar state 
of the air consequent upon intense cold, while others, probably 
more correctly, attribute them to the refraction and reflection of 
the rays of light through masses of vapor which are formed in 
such aggregations as are not heavy enough to fall in the form of 
drops. Descartes remarks, that halos never.appear when it rains. 
Coronas have frequently been observed around the moon, and 
even around Sirius and Jupiter, but, as far as my information ex- 
tends, they have been but seldom variegated, even when they 
have encircled the sun. 
I know not to what cause this phenomenon can be attributed, 
unless it be to the refraction and reflection of the sun’s rays 
- through the masses of vapor. Doubtless the first circle was thus 
formed, and if we suppose the rays of light from the circumfer- 
