Radiometry before World War II: measuring infrared and millimeter-wave radiation 1800-1925

I sketch some of the highlights of the neglected early history of radiometry. The only unifying theme is the measurement of infrared and millimeter-wave radiation, with an emphasis on the personalities involved. Although there were virtually no strictly commercial applications of radiometry during the period (unless one counts the making of scientific instruments), many of the investigators also tried their hands at applied research and inventions, with mixed results. However, the first researcher we consider was a good example of the eighteenth-century "gentleman scientist:" William Herschel