This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1899 Excerpt: ...part of which was revived by him and was used, as a relic of the year of the Queen"s accession, to telegraph Her Majesty"s message to her scattered peoples on the day of her Diamond Jubilee. What that lusty infant, the telegraph, has grown to in the intervening 60 years you do not need to be told. Taking British telegraphs alone, the expansion of which owes much to our President"s fostering care, there are now considerably more than 1,000,000 miles of wire. Our distant colonies are bound to the mother country not simply by links of loyalty and mutual affection, but by material bonds of copper which have no small part to play in the building up of Empire. The suspended needle, by which Cooke and Wheatstone gave practical application to the discovery of Oersted, did not long remain the sole, or even the chief, instrument in telegraphy. It was almost at once supplemented, and soon to a great extent displaced, by the family of instruments which depend on the attraction which an electromagnet exerts on a movable armature, instruments of which the telegraph of Morse was the first to take working shape. But Oersted"s discovery met with a second great application at the hands of Lord Kelvin in 1858, when the problem of signalling at a remunerative speed through long ocean cables was solved by his invention of the mirror galvanometer, an invention which, at the same time supplied physicists with an invaluable new weapon of research. His later invention of the siphon-recorder allowed the delicate fluctuations of current, which constitute the signals in such a cable, to be registered as well as read. In the galvanometer the coil is held fixed and the magnet moves. In the Kelvin recorder the force between the two is still the operative force, but it is the coil that mo...