Jagadis Chandra Bose: millimetre wave research in the nineteenth century

In the last decade of the nineteenth century, many experimenters began working with the newly discovered "Hertzian waves." J.C. Bose (1897, 1907, 1927) in particular investigated the properties of waves and materials in the short cm- to mm-wave part of the spectrum. He used waveguides, horn antennas, dielectric lenses, various polarisers, and even semiconductors at frequencies as high as 60 GHz. Some of his work is surprisingly relevant today.