A remarkable luminous appearance in the sky, seen in the west after sunset, and in the east before sunrise, at certain seasons of the year. It is a triangle of light, of greatest intensity within the tropics, where its brilliancy sometimes rivals that of the Milky Way. It stretches through the sky nearly in the direction of the sun's equator. It is only during the spring and autumn that in our latitudes it can attain sufficient height in the sky to be distinguishable.