The purpose of this study was to investigate the stability of spectrographic spark sources when controlled by the well known synchronous (Feussner) interrupter, or an auxiliary air-gap interrupter. Kaiser and Wallraff's (1) work on this subject is the most complete literature available. The work of H. Barkhausen (2), D. R. Roschansky (3), and H. T. Simon (4) also has been referred to in studying the behavior of a spark gap in an electric circuit. Wherever feasible, observations have been made upon the instantaneous events in the system by introducing a suitable pickup whose output was recorded with the aid of an oscilloscope. First the source was considered from the standpoint of what goes into the system. That is, the over-all electrical circuit for each of the two spark sources was analyzed part by part. One assumption throughout this work has been that a basic requirement for a stable source (a source giving optimum reproducible spectrographic results) is that it shall have as nearly as possible identical starting conditions for successive sparks. The sparks are the result of a charged condenser discharging through an inductance, resistance, and the several air-gaps in series. Therefore, assuming at this point that the air-gaps return to fairly identical conditions between sparks, it remains essential that the starting voltage on the condenser be the same. Also it will be assumed that events during the transient discharge be maintained consistent from spark to same. The second phase of this work was that of studying the light output from a controlled spark source. Because of the pulsating nature of the generated light signal, instantaneous light-intensity observations are possible with an oscilloscope employing a-c. amplifiers. for the most part, a study of the instantaneous shape of the characteristic light signal (5) was not attempted, but rather, observations were made on the peak values only. The fluctuation of these peak values was considered a measure of the constancy of the source output.