Abstract: The purpose of this report is to outline the work done at the Radiation Laboratory toward the development of a magnetic field measuring device using the phenomenon of nuclear resonance. While the work described here is far from complete, it has served to indicate the limitations of the method as well as some of its possibilities. For reasons which will become apparent, the project is being discontinued. It is hoped that this report will serve as a starting point should the work be continued at some later time and that some of the mistakes already made need not be repeated.