The National Bureau of Standardshas some new direction‐finding equipment for the study of electromagnetic waves originating in lightning discharges (“sferics”), which was developed at the NBS Boulder Laboratories and has been put into operation near Brighton, Colo. The experimental system, known as “Ephi”, obtains information about the sources of sferics by analyzing the signals and the differences in time of arrival at three 125‐foot antennas, which form an equilateral triangle four miles on a side. The precision of the equipment is such that measurements of time differences can be made with an accuracy of a small fraction of a microsecond.