RECENT work on the time course of eye movements has led to the development of a new technique of measurement. This was required to deal, in addition to the normal static situation, with conditions where space and the rigid laboratory bench are absent; for example, in a rotating chair and the human centrifuge. A wide range of sensitivity, simplicity and robust construction were considered most important, and since recordings could only be made via a slip ring system, an electrical output signal was essential. The instrument finds additional applications in circumstances where it is advantageous to keep to a minimum the loading of a deflected member, the movement of which is to be recorded.