CORONA II. Coronary Arteries. flance of about from the centre of the moon. It was elliptical; and its long diameter was perpendicular to the horizon, verging below farthest from the moon. He was told, that the moon has sometimes three or more concentric crowns of colours encompassing one another next about her body. The more equal the globules of water or ice are to one another, the more crowns of colours will appear, and the colours will be the more lively. The halo, at the distance of degrees from the moon, is of another sort. By its being oval, and more remote from the moon below than above, he concludes that it was made by refraction in some kind of hail or snow floating in the air in an horizontal posture, the refracting angle being about or degrees. Dr Smith, however, makes it sufficiently evident, that the reason why this halo appeared oval, and more remote from the moon towards the horizon, is a deception of sight, and the same with that which makes the moon appear larger in the horizon.
Dr Kotelnihow having, like Dr Halley, made very accurate observations to determine the number of possible rainbows, considers the coloured halo which appears about a candle as the same thing with one of these bows which is formed near the body of the sun, but which is not visible on account of his excessive splendor.
Lastly, M. Muschenbroeck concludes his account of coronas with observing, that some density of vapour, or some thickness of the plates of ice, divides the light in its transmission through the small globules of water, or their interstices, into its separate colours: but what that density was, or what was the size of the particles which composed the vapour, he could not pretend to determine.