On first acquaintance the electric arc discharge appears to be both visually attractive and a relatively simple phenomena to understand. To those of us engaged in prolonged study of this discharge, it remains a constantly exciting phenomena but we become only too aware of its complex nature and the difficulties in interpreting its bulk properties. This is particu- larly true when the arc exists in a practical device and is subjected therefore to extreme conditions. In recent years the possibilities for the beginning of a fuller understanding of the complexities of the arc has arisen out of the excellent research and development work of scientists and engineers throughout the world. Much of this work has been stimulated not only by the need for the development of practical devices but also by the interest in thermonuclear fusion, mag- netohydrodynamic generation and space exploration. In much of this work, the arc discharge has been a common feature as a source of study of high temperature plasma. As a result of this increased interest in the arc, the expert and would-be expert is now faced with the problem of assessing extensive newly published information on arc properties. Thus there is the need for texts which present to the engineer and researcher a review and summary of the present situation. This book is a valuable contribution to this task.