This paper reports progress in the development of apparatus for the transmission of signals in times of obscured vision. Descriptions of the results of tests made almost daily from November 12, 1936 to May 20, 1937 in the transmission of signals over distances of about 480 meters and about 2400 meters using the Hayes Radiometer as the receivers and sources of radiant energy of varied power and nature are given. There was not a day in the period covered where good signals were not received from a 25‐watt source over the shorter range nor any day when good signals were not received over the longer range when a source actuated by an input of about 650 watts was used. There were but two days when the 25‐watt source failed to transmit clear signals over the longer range of about 2400 meters. On these days the air was filled with heavy wet snow.