What is the clouds at gas

A view looking gas cloud, is very popular at gas in ancient China, judging by identifying gas state affairs and personnel good or ill luck.Clouds at gas has three methods: observation of Yin and Yang five lines of air, gas, sun, clouds around the sun, the solar eclipse and lunar eclipse, the dim light clouds, penetration, mistbow, solar halo, lunar halo, and the image of the cloud.Looking for ancient people, gas like astrology, are related to the affairs of state augury.