The lecture first deals briefly with the early history of long distance radio communication. The work carried out by the engineers and experts of the Marconi Company in England with electron tubes or triode valves shows that, according to their experience, greater efficiency can be obtained at present by a number of bulbs used in parallel than by the employment of large single unit tubes. Information is given in a general way in regard to recent practise in the design and construction of receivers with the object especially of improving selectivity, reducing interference, and concerning the possible speed of working. The lecture also deals briefly with results obtained at receiving observation stations situated in various far distant parts of the world, where it has been ascertained that radio signals arriving from high-power stations situated at or near the antipodes of the observation stations, reach the receivers by various ways around the earth, not always following the shortest great circle route, and also that at such places the electric waves coming around by different ways do in certain cases increase this effect on the receivers whilst in others interfere with each other. It has also been noticed that apparently transmission is easier from west to east than from east to west, and that it may be necessary to modify somewhat the transmission formula for long distances. It has also been ascertained that the most troublesome atmospheric disturbances or static usually come from the continents and not from the oceans. The lecture further deals with a study of short electrical waves and the results which have been obtained with such waves of a length from 1 meter to 20 meters, and describes tests which show for the first time that electric waves of under 20 meters in length, used in connection with suitable reflectors, are quite capable of providing a good and reliable point-to-point, unidirectional system of radio over quite considerable distances. The application of this system as a direction finder in aid of navigation, and as a method for preventing collisions at sea, is also dealt with.