Travels in the Mogul Empire (Bernier) 23.10

23.10

You are not to imagine that I mistake a halo for an iris, I am familiar with the former, because during the rainy season at Dehli, there is scarcely a month in which a halo is not frequently seen round the moon. But they appear only when that luminary is very high above the horizon: I have observed them three and four nights successively, and sometimes I have seen them doubled. The iris of which I speak was not a circle about the moon, but was placed in an opposite direction, in the same relative position as a solar rainbow. Whenever I have seen a night iris, the moon has been at the west and the iris at the east. The moon was also nearly complete in its orb, because otherwise the beams of light would not, I conceive, be sufficiently powerful to form the rainbow; nor was the iris so white as the halo, but more strongly marked, and a variety of colours was even discernible. Thus you see that I am more happy than the ancients, who, according to Aristotle, had observed no lunar rainbows before his time.