Close-up of a Post Office Dept. mail plane equipped with the new experimental radio apparatus with which the Dept. hopes soon to make possible night flying. The little lead fish at the bottom of the picture is let out while flying and carries with it a long copper wire which serves as the antennae. A sound-proof covering over the pilot's set and transmitter is necessary and the electricity is manufactured by a generator run by a free fan. Experiments conducted at Bolling Field, Wash. Aug. 2, 1922