The cathode ray oscilloscope is an instrument for the measurement of variation of electric voltage and current. It has taken 90 years to reach its present level of sophistication. Such has been the cathode ray tube's success that many scientists and engineers are largely unaware of the earlier methods which preceded it. In this book, Phillips recalls the early methods of the examination of electrical waveforms, illustrating the ingenuity and persistence which was brought to bear on the problem andlooks at some of the apparatus - sometimes crude, but often quite sophisticated and beautifully engineered - which was developed and used during the nineteenth century. This book will be of interest to physicists and electrical engineers with an interest in the history of science, historians of science, engineering, instrumentation, television and radio.