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acid action acts alternating currents apparatus applications armature arrangement Bell's telephone bobbin brushes Bunsen carbon carbon pencil carbon point carbon-holder centimetres centre charge circuit communication conductor connected consists constructed continuous currents copper current passes cylinder diameter disc distance dynamo-electric machines Edison's effect electric current electric light electrical resistance electro-dynamic machines electro-magnet electro-motive force electrode elements employed experiments extremities feeble fixed Gramme's machine heat incandescent increase induced currents induction balance induction coil inductors insulated intensity interior resistance invented iron lamp lever liquid luminous point magnetic field magnetic telephones membrane mercury metallic metres microphone millimetres motion motor movable obtained placed plate poles pressure produced quantity receiver regulator rendered Reynier's ring screw secondary battery secondary couple selenium Serrin's shunt Siemens solderings solenoid sound spiral spring sulphate sulphuric acid temperature tension thermo-electric transform transmission traverses tube vessel vibrations voltaic arc zinc zinc sulphate
Page 384 - in the focus of which is placed a sensitive selenium cell, connected in a local circuit with a battery and telephone. A large number of trials of this apparatus have been made, with the transmitting and receiving instruments so far apart that sounds could not be heard directly through the air.
Page 378 - further, that when we control the form or character of the light-vibration on selenium, and probably on the other substances, we control the quality of the sound, and obtain all varieties of articulate speech. We can thus, without a conducting wire as in electric telephony, speak from station to station, wherever we can project
Page 411 - in the induction balance ; and this is so exact that if we put, say a silver coin whose value is 115°, no other degree will produce equality. Once knowing, therefore, the value of any metal or alloy, it is not necessary to know in advance what the metal is, for if its equality is 115°, it is
Page 379 - darkness, or vice versa, and that it would be advisable to intermit the light with great rapidity, so as to produce a succession of changes in the conductivity of the selenium corresponding in frequency to musical vibrations within the limits of the sense of hearing. For I had often noticed that currents of electricity, so feeble as
Page 378 - glass. We find that when a vibratory beam of light falls upon these substances they emit sounds—the pitch of which depends upon the frequency of the vibratory change in the light. We find, further, that when we control the form or character of the
Page 265 - life of the plant, from the early leaf to the ripened fruit. The latter is superior in size, in aroma, and in colour to that produced by alternating light, and the resulting seeds are not, at any rate, devoid of regerminating power. Further experiments are necessary
Page 410 - was moved through several degrees, or through more than the required amount, we should find that the sounds increase when the key is depressed ; but when the coil is moved to a degree where there is absolute equality, if the key is up or down, then the degree on scale should give the true value of the disturbance
Page 381 - to those of the diaphragm itself. " In arranging the apparatus for the purpose of reproducing sound at a distance, any powerful source of light may be used ; but we have experimented chiefly with sunlight. For this purpose a large beam is concentrated by means of a lens upon the diaphragm mirror
Page 411 - instrument gives very different values for different metals or alloys ; consequently, we cannot obtain a balance by employing two discs of different metals, and the instrument is so sensitive to any variation in mass or matter, that it instantly detects the difference by clear loud tones on the telephone. If
Page 407 - it became evident that the induced currents circulating in a metallic mass might be so acted upon either by voltaic or induced currents as to bring some new light to bear on the molecular construction of metallic bodies. " The question was particularly studied by Babbage, Sir John Herschell, and