Table 1 shows the resonant cyclotron frequencies of single ions of different forms when subject to the steady geomagnetic field. The lower frequency expressed in Hz is that of a single ion type. The presence of other ions may raise the resonant frequency by up to 50%. Table 2 shows how the power supplied to a purely resistive load is, by conventional electrical engineering analysis, divided between the lower frequency components of an unsmoothed full-wave rectified sinusoidal 50Hz voltage source. submarine cables Waves, wind and the teredo worm At a time when plans for global communications seem to rest on the semantics of international standards, Greg Grant looks back to the Victorian adventurers who conquered nature to put a communication girdle around the world. Integrated-systems digital-networks, open systems interconnections and 1992 are popular subjects of conversation at the moment. The consensus is that such technologies will require international standardisation, long-term planning and organisational coordination. But it has obviously been forgotten that a near-similar system was in place almost exactly a century ago -- the submarine