White and black are believed to be the origin of all colours. They are looked upon as extremes, and as the component parts of the other colours. Thus white when mixed in large proportions with an impure black, will yield yellow; and white and black, in equal proportions, will give red. White mixed with a large quantity of black, will give a bluish green. Other colours may be formed by compounding these. Besides, it must be borne in mind that cold makes a juicy body white, and a dry body black; and heat renders that which is fresh black, and white that which is dry. These two powers (heat and cold) produce, each in its place, a change in the colour of a body, because bodies are both qábil, i. e., capable of being acted upon, and muqtaza, i. e., subject to the influence of the heavenly bodies (chiefly the sun), the active origin of heat.