
100 NOTE ON PECULIAR AURORA.—MACGREGOR. 
ArT. III.—Nore on Precutian Auror&. By Pror. J. G, 
MacGrecor, D. Sc. 
Two auroree which I observed during the past summer exhibit- 
ed a peculiarity of form sufficiently interesting to warrant my 
drawing the attention of the members of this Society to it. 
The first was observed at Halifax on the 31st July. It had the 
form of a bow stretching across the sky from the east to the 
west point of the horizon and through a point a few degrees south 
of the zenith. The bow was about five degrees in width. No 
rayed structure could be traced in it, and its light during the 
greater part of its duration was very nearly uniform through- 
out, the whole luminous area, except at the edges of the 
bow, where the luminosity diminished rapidly outwards. The 
bow was visible from 10 to 10.30 o'clock, p.m. Towards the end 
of that time the east and west ends grew more faint, and the 
diminution of luminosity gradually extended from the ends 
towards the zenith. In about 15 minutes from the time at which 
this diminution began the bow had entirely vanished. The sky 
was quite clear and there were no clouds: Iwas unable to deter- 
mine the spectrum of the bow. 
The second aurora mentioned above I observed at New 
Glasgow, N.S., on the evening of September 5th. It had 
the form of a bow of the same width as the other, stretching 
from a point about 30° north of west to a point about 30° 
north of east through the zenith. It had at first a slightly 
marked rayed structure in the direction of its length, but 
this structure gradually vanished, and rays then appeared 
crossing the bow so as to make angles of about 45° with the 
direction of its length. It lasted also from about 10 to 11.30 
o'clock, when it faded away, the ends fading first, and the portions 
near the zenith widening before disappearing. One of Hilger’s 
larger pocket spectroscopes shewed that its spectrum consisted 
of two lines in the green, one bright, the other faint, and at times 
invisible. The sky was clear. No auroral lines were seen in the 
spectrum when the instrument was directed to other parts of 
the sky than that occupied by the bow. 
