Secret development of an instrument, that shows the exact ground speed of an airplane promises to be a great aid to navigation in thick weather. Independent of winds and drift, the pilot would know at all times how fast he is covering ground and could figure his position and arrival time accurately without the intricate calculations now necessary. A bombing plane could take off in dense fog, and with knowledge of the ground speed could drop: bombs when the instrument indicated the. objective had been reached. A U. S. army officer invented the device. Little is known except that it operates on the electric induction from the earth’s magnetic field and thus far has shown ground speeds accurately up to 300 miles an hour. It is reported that the instrument can be applied to a map so that a needle would travel over. the map and show the position of the plane constantly. It may be used on boats as well as aircraft.