The cyclopędia of electrical engineering: containing a history of the discovery and application of electricity with its practice and achievements from the earliest period to the present time : the whole being a practical guide to artisans, engineers and students interested in the practice and development of electricity, electric lighting, motors, thermo-piles, the telegraph, the telephone, magnets and every other branch of electrical application, Volume 2

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The Gebbie Pub. Co., Limited, 1895 - Science
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Page 569 - How would you prove that the illumination on any surface is inversely as the square of its distance from the source of light ? 6.
Page 785 - The transmission of sound through the microphone is perfectly duplex; for if two correspondents use microphones as transmitters and telephones as receivers, each can hear the other, but his own speech is inaudible ; and if each sing a different note, no chord is heard. The experiments on the deaf have proved that they can be made to hear the tick of a watch, but not, as yet, human speech distinctly ; and my results in this direction point to the conclusion that we only hear ourselves speak through...
Page 536 - To explain the construction of the common barometer, and to shew that the mercury is sustained in it by the pressure of the air on the surface of the mercury in the basin.
Page 862 - ... outside to the centre, a series of strata in a more and more perfect crystalline condition. Light, as we know in the case of some bodies, tends to promote crystallization, and, when it falls on the surface of such a stick of selenium, probably tends to promote crystallization in the exterior layers, and therefore to produce a flow of energy from within outwards, which under certain circumstances appears, in the case of selenium, to produce an electric current. The crystallization produced in...
Page 767 - ... of these currents of induction from the innumerable working wires contiguous to it, and through some of the underground pipes of the streets of London sounds are inaudible when the wires are working. In fact, two small-sized gutta-percha wires, one foot long, were lashed side by side by Mr. Marson ; and when battery currents were sent through one, induction currents were distinctly heard on a telephone fixed on the other. Indeed this induction between wire and wire, has proved the most serious...
Page 781 - ... each having a special range of resistance. The tramp of a fly or the cry of an insect requires little range but great sensitiveness ; and two surfaces, therefore, of chosen materials under a very slight pressure, such as the mere weight of a small superposed conductor, suffice ; but it would be unsuitable for a man's voice, as the vibrations would be too powerful, and would, in "fact, go so far beyond the legitimate range that interruptions of contact amounting to the wellknown " make and break...
Page 902 - Gramme dynamos, the magnets being series-wound similar to one another ; but their usual low resistance coils had been replaced by coils of very many turns of fine wire. The resistance of each machine was consequently 470 ohms, whilst that of the line was 950 ohms. The velocity of the generator was 2,100 revolutions per minute ; that of the motor, 1,400. The difference of potential at the terminals of the generator was 2,400 volts ; at that of the motor, 1,600 volts. According to Professor von...
Page 784 - ... matter ; but as the best results as regards the human voice were obtained from two surfaces of solid gold, I am inclined to view with more favour the idea that an infinite variety of fresh contacts brought into play by the molecular pressure affords the true explanation. It has the advantage of being supported by the numerous forms of microphone I have constructed, in all of which I can fully trace the effect.
Page 783 - ... this upper piece B when pressure is removed proves that a blow, pressure, or upheaval of the lower portion takes place : that this takes place there cannot be any doubt, as the surface, considered alone (having no depth), could not bodily quit its mass. In fact, there must have been a movement to a certain depth ; and I am inclined to believe, from numerous experiments, that the whole block increases and diminishes in size at all points, in the centre as well as the surface, exactly in accordance...
Page 783 - I am inclined to believe, from numerous experiments, that the whole block increases and diminishes in size at all points, in the centre as well as the surface, exactly in accordance with the form of the sonorous wave. Confining our attention, however, to points on A and B, how can this increased molecular size or form produce a change in the electrical waves ? This may happen in two ways : first, by increased pressure on the upper surface, due to its enlargement ; or, second, the molecules themselves,...

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