Then, in late October or early November, comes a period of a few days or a week of mellow sunshiny weather called Indian summer. Supposedly it was given this name by the early settlers who knew that the blue haze at this season was smoke from prairie fires set by the Indians on their autumn hunts. This bluish haze that dims our view of distant trees and hills is a light effect caused by smoke and dust in the atmosphere. So are the glowing colors of a sunset or sunrise. When the particles are extremely small the blue rays are scattered most and produce haze because the wave length of blue light is shorter than, for instance, yellow or red rays.
Tobacco smoke furnishes a good example.
It scatters light and appears blue even though the smoke itself consists of small droplets of a yellow liquid. This can be proven by blowing tobacco smoke through a white handkerchief. Frequently, when there is little air movement, dust particles concentrate in a layer near the earth, thus reducing visibility and giving the air a slightly veiled appearance. Against a dark background, this haze appears bluish, like smoke. Against a bright background, it gives a coppery tint to the atmosphere because the blue rays as well as some of the green and yellow rays are filtered out, allowing only the red and orange rays to get through.