Optical, chemical and capillary oscillographs

With the spread of alternating-current systems at the end of the nineteenth century, the need for a convenient and reliable method of displaying waveforms became more urgent. Certain methods were developed to a high degree of usefulness, notably the rotating contacts, the Blondel/Duddell mechanical oscillographs and eventually, of course, the cathode-ray tube. The paper recalls three other methods which seemed, for a short time, to hold out great promise but which were not successful and soon faded into obscurity.