The Collected Works of Irving Langmuir, Volume 4: Electrical Discharge is a 12-chapter text that covers the fundamental and theoretical aspects of electrical discharge, with a particular emphasis on discharge in gases. The opening chapters are concerned the negative probes as being due to the random positive-ion current of the plasma and the proper space-charge with a very simple discharge tube and some miscellaneous experiments on a simple tube in which streamer type discharges were observed, as well as the effects of small amounts of tungsten in the argon discharge. These topics are followed by discussions on the verification of the Langmuir Probe-Theory; the disturbing effects of mercury vapor blast from the cathode spot on the mercury pool; and the phenomena observed in the low pressure discharges. Other chapters explore the Faraday dark space of the glow discharge and how the electrons of a beam in a plasma are given their higher velocity components. The final chapters introduce the concept of plasma oscillation. This book will be of value to electronics engineers and technical workers.