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 employed for the production of the continuous trains of waves a high frequency alternator of his own invention (see The Electrician, 1907, 58, p. 675, 701). Much work has been done on this matter by E. Ruhmer, for which the reader must be referred to his work, Drahtlose Telephonie, Berlin, 1907. There is no doubt that the transmission of articulate sounds and speech over long distances without wires by means of electric waves is not only possible as an experimental feat but may perhaps come to be commercially employed. In connexion with this part of the subject a brief reference should also be made to M. Wien’s method of impact excitation by employing a form of spark gap which quenches the primary discharge instantly and excites the free oscillations in the antenna by impact or shock.

Instruments and Appliances for making Measurements in Connexion with Wireless Telegraphy.—The scientific study of electric wave telegraphy has necessitated the introduction of many new processes and methods of electrical measurement. One important measurement is that of the wave-length emitted from an antenna. In all cases of wave motion the wave-length is connected with the velocity of propagation of the radiation by the relation v = n, where n is the frequency of the oscillations and is the wave-length. The velocity of propagation of electric waves is the same as that of light, viz., about 1000 million feet, or 300 million metres, per second. If therefore we can measure the frequency of the oscillations in an antenna we are able to tell the wave-length emitted. Instruments for doing this are called wave meters and are of two kinds, open circuit and closed circuit. Forms of open circuit wave meter have been devised by Slaby and by Fleming. Slaby’s wave meter consists of a helix of non-insulated wire wound on a glass tube. This helix is presented or held near to the antenna, and the length of it shortened until oscillations of the greatest intensity are produced in the helix as indicated by the use of an indicator of fluorescent paper.

Electric wave telegraphy has revolutionized our means of communication from place to place on the surface of the earth, making it possible to communicate instantly and certainly between places separated by several thousand miles, whilst

at the same time it has taken a position of the greatest importance in connexion with naval strategy and communication between ships and ships and the shore in time of peace. It is now generally recognized that Hertzian wave telegraphy, or radio-telegraphy, as it is sometimes called, has a special field of operations of its own, and that the anticipations which were at one time excited by uninformed persons that it would speedily annihilate all telegraphy conducted with wires have been dispersed by experience. Nevertheless, transoceanic wireless telegraphy over long distances, such as those across the Atlantic and Pacific oceans, is a matter to be reckoned with in the future but it remains to be seen whether the present means are sufficient to render possible communication to the antipodes. The fact that it has become necessary to introduce regulations for its control by national legislation and international conferences shows the supremely important position which it has taken in the short interval of one decade as a means of communicating human intelligence from place to place over the surface of the globe. An important International Conference on radio-telegraphy was held in Berlin in 1906, and as a result of its deliberations international regulations have been adopted by the chief Powers of the world. The decisions of the Conference were ratified for Great Britain by the British government on July 1, 1908.

 TELEMACHUS, in Greek legend (Odyssey i.–iv., xv.–xxiv.; Hyginus, Fab. 127), son of Odysseus and Penelope. When he reached manhood, he visited Pylos and Sparta to make inquiries about his father, who had been absent for nearly twenty years. On his return, he found that Odysseus had reached home before him. Then father and son, aided by Eumaeus and Philoetius, slew or drove out the suitors of Penelope (see ). According to later tradition, Telemachus became the husband of Circe and by her the father of Latinus and of a daughter Roma, afterwards the wife of Aeneas. In another story, he married a daughter of Circe, named Cassiphone; having slain his mother-in-law in a quarrel, he was himself killed by his wife. This is the only notice of the death of Telemachus. The foundation of Clusium in Etruria was attributed to him.

 TELEMARK, or, a district of southern Norway, wholly comprised in the amt (county) of Bratsberg. It covers the uplands and fjelds of the southward projection of the country, having its highest point in the Gaustafjeld (6200 ft.); and contains several large and beautiful lakes, as Nordsjö, Bandaksvand, Tinsjö, Mjösvand and Totakvand. The two 