The Chairman, in a few well chosen words introduced the lecturer. Professor Bose in going to deliver his highly interesting lecture first showed how on account of the imperfection of our senses we fail to detect various forces which play around us. We are not only deaf, but practically blind. While we perceive eleven octaves of sound, we can see only a single octave of other vibration which is called light. In order to detect the invisible light a special detector has to be devised. Prof. Bose showed his artificial retina previously exhibited at the Royal Institution which not only detected luminous radiation but also invisible lights in the intra red and ultra violet regions. In the course of his remarks illustrating the nature of electric or Hertzian waves, which gave rise to the invisible radiation he proceeded to enumerate some of the conditions necessary for experimenting with them, and to describe the apparatus he had invented for the purpose. Hertz had used waves which were about 10 metres in length. It was impossible to attempt any quantitative measurement of their optical properties on account of large waves curling round corners. The lecturer had succeeded in producing the shortest waves, with frequency of 50,000 millions of vibrations per second, the particular invisible radiation being only thirteen octaves below visible light. His generator produced the small sharp beam which alone could be employed for quantitative measurements. By means of this apparatus experiments on electric radiation could be carried on with as much certainty as could experiments with ordinary light. Prof. Bose then performed experiments illustrative of the properties possessed in common by light waves and electric waves. He exhibited the power of selective absorption to electric rays displayed by many substances pointing out that while water stopped them, pitch, coal tar, and others were quite transparent to them. He showed how the rays were reflected by mirrors, obeying the same laws as light. The hand of the experimenter was found to be a good reflector, the rays rebounding after impact. Electric rays also undergo refraction and he described an ingenious method he had devised by which the index of refraction of numerous opaque substances could be obtained with the highest exactitude. In conclusion he gave an account of his discovery of the polarisation of electric rays by crystals. He showed that these polarised the electric rays just as they did ordinary light. He further proved that substances under pressure and strain could produce double refraction in them, as did glass under the same conditions in light. Tourmaline was useless for electric rays; but a lock of human hair was extraordinarily efficient. According to this theoretical prediction, an ordinary book was shown to exhibit selective absorption in a striking manner. Thus while the Calcutta University Calendar was, usually, very