Dr. C.V. Raman, delivered a lecture on “Atmospheric Optics and the Theory of Mirage” on August 13 at a meeting held under the auspices of the Department of Physics of the Presidency College. He mentioned that there were two types of mirages, inferior and superior mirages, and said that a very familiar type of mirage was that seen when the light rays were nearly parallel to the heated surface of earth. The sky and objects on the horizon then appeared to be reflected by the surface or rather by the cushion of hot air in contact with it. The phenomenon was frequently observed over asphalted or concrete roads on sunny days and over firm smooth sands in warm weather.