Sun Beams. The sunbeam is composed of three distinct and separate rays, one of heat, one of light, and one called the chemical ray. These three agencies exist in different proportions in the sunbeam, in the spring, summer, and autumn. The blue or chemical ray is greater in the spring; the light greater in the summer. The chemical ray is less in autumn, and then the heating ray predominates. The proportion of these rays varies in different seasons of the year, in order that the growing plant may arrive at maturity. It has also been ascertained that the proportions of these agents vary in different climates