One of the lessons learned from the operation of the air mail service during the year is that the element of danger that exists in the training of aviators in military and exhibition flying is almost entirely absent from commercial flying. Second Assistant Postmaster-General Praeger, in reporting to the postmaster-general the operations for the year, says that the record of the air mail service, which includes flying at altitudes of as low as 50 feet during periods of marked invisibility, throws an interesting light on this question. During the year, more than 128,000 miles having been travelled, no aeroplane carrying the mail has ever fallen out of the sky, and there has not been a single death of an aviator in carrying the mail. The only deaths by accident which have occurred were that of an aviator who made a flight to demonstrate his qualifications as an aviator and that of a mechanic who fell against the whirling propeller of a machine on the ground. But two aviators have been injured seriously enough to be sent to a hospital. Other accidents consisted mainly of bruises and contusions sustained by planes turning over after landing. Of the three types of planes operated regularly in the mail service, one type was more given than the others to turning over on rough ground, and it was principally on planes of this type that pilots were shaken up or bruised by the plane turning turtle. One type of machine in the mail service which has performed almost half of the work has never turned turtle. The record of the air mail service with respect to accidents will compare favorably with that of any mode of mechanical transportation in the early days of its operation. One of the first studies to be taken up by the air mail service was to determine whether visibility is absolutely necessary to commercial flying. The first step necessary was the refinement of the existing radio direction-finders so as to eliminate the liability of 3 to 5 per cent of error. This has been successfully worked out by the Navy Department on an air mail testing-plane. The second problem was that of guiding the mail plane after it had left the field to the centre of the plot for landing. This problem has been solved by the Bureau of Standards in experiments conducted on the air mail testing-plane in connection with the radio directional compass. This device is effective up to an altitude of 1,500 feet, and with the further refinements of the device another thousand feet is expected to be added. Aeronautical engineers are working upon a device for the automatic landing of a mechanically flown plane which would meet the condition of absolute invisibility that could exist only in the most blinding snow-storm or impenetrable fog.