_ Prof. Snell on a singular case of Parhelion, &c. 73 
Arr. VIIL—Singular case of Parhelion, with a statement of the 
Theory of ordinary Halos; by Prof. E. 8. Sneri, of Am- 
herst College. 
On the 23d of last March I witnessed an optical phenomenon 
in nature, which was to me entirely new. ‘The sun had ascend- 
ed eight or ten degrees from the horizon, and I was stepping from 
my door, which opens to the east, when I was surprised to no- 
tice a luminous curvilinear band, three or four feet wide, thickly 
studded with shining points of every prismatic hue, stretching 
over the dead grass of the wide street before me. Its form seemed 
to be that of a parabola or hyperbola ; its nearest point, which was 
the vertex of the curve, was not more than twelve or fifteen feet 
distant, and its two branches extended several rods, one to the 
_ right and the other to the left of the sun,—the axis being the in- 
tersection of the ground plane with a vertical through the sun 
and the eye. Though the band could be thus distinctly traced, 
yet the illumination was not continuous, as in the rainbow, but 
pencils of intense light were seen to come from innumerable but. 
separate points; and these exhibited, without much order of ar- 
rangement, the countless shades of the prismatic spectrum. As 
I moved, the luminous arch moved also in the same direction, 
so as to retain its relations to my eye and the sun, while the in- 
dividual points changed from hue to hue and were extinguished, 
and others started into sight, to twinkle fora moment in their 
turn, and then disappear. 
My first thought was, that it was the lower limb of a rainbow, 
such as I have often traced in dew-drops, as they rest on vege- 
table leaves and are strung upon spider lines that are stretched 
along the grass. Its form appeared the same as the rainbow 
must assume when seen in such circumstances. But it was in 
the wrong direction ; 1 stood facing the sun, and the colors plain- 
ly came from points not more than thirty degrees from it. I per- 
ceived in a moment, however, that there were no dew-drops, but 
that the spires of dead grass were feathered over with frost crys- 
tals of unusual size. The true nature of the phenomenon in- 
stantly flashed upon my mind; and I was delighted to witness a 
most interesting confirmation of the truth of the generally re- 
ceived theory respecting the large solar and lunar halos. In the 
Vol. xxix, No. 1.—April-June, 1845. 10 
