THE wireless communications of the mercantile marine are subject to regulations issued by the administrations of the maritime nations, which in turn are governed by the relevant parts of the General Radio Communication Regulations attached to the current International Telecommunication Convention which came into force on January 15, 1933. These regulations lay down the purposes for which the various bands of frequencies may be employed, certain bands being allocated exclusively to the mercantile marine, others to mobile services generally, while some are shared between mobile and other services. A certain amount of difficulty has been experienced in carrying out the communications of the mercantile marine owing to the interference which exists, especially in some areas near the coasts of Europe and the United States. In a paper read before the Wireless Section of the Institution of Electrical Engineers on May 2, Commander J. A. Slee made an analysis of the sources of this interference. Typical response curves of the average ship's receiver were given in the paper, and from these the field strengths of signals which can cause interference in the different sections of the marine communication band have been computed. The analysis dealt with both spark and valve transmitters, and also with the possible interference which might arise from the large number of fixed beacon stations now in operation for the use of ship directionfinders. Although these beacons are located in a restricted band of wave-lengths, it has proved possible to utilise different modulation note frequencies, and it is considered that as at present organised, mutual interference between beacon stations is negligible.