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ly when aggregated into cities. Doubtless the old systems of lighting are destined in time to give place altogether to the splendors of the electric glow. The general effect of the change upon society must be as marked as it is salutary. Darkness, the enemy of good government and morality in great cities, will, in great measure, be dispelled by the beneficent agent, over which the genius of Davy, Gramme, Brush, Edison, and a host of other explorers in the new continents of science has so completely triumphed. The ease, happiness, comfort, and welfare of mankind must be vastly multiplied, and the future must be reminded, in the glow that dispels the night, of that splendid fact that the progress of civilization depends, in a large measure, upon a knowledge of Nature's laws, and the diffusion of that knowledge among the people. THE TELEPHONE. Perhaps no other great invention of man has been within so short a period so widely distributed as the telephone. The use of the instrument is already co-extensive with civilization. The cost at which the instruments are furnished is still so considerable that the poor of the world are not able to avail themselves of the invention; but in the so-called upper circles of society the use of the telephone is virtually universal. It has made its way from the city to the town, from the town to the village, from the village to the hamlet, and even to the country-side where the millions dwell. The telephone came by a speedy revelation. It was born of that intense scientific activity which is the peculiarity of our age. The antecedent knowledge out of which it sprang had existed in various forms for a long time. The laws of acoustics were among the first to be investigated after a true physical science began to be taught. The phenomena of sound are so universal and experimentation in sound production so easy, that the governing laws were readily discovered. Acoustics, we think, foreran somewhat the science of heat, as the science of heat preceded that of light. Electricity came last. The telephone is an instrument belonging not wholly, not chiefly, but only in part, to acoustics. It owes its existence to magnetic induction and electrical transmission as much as to the mere action of sound. One foot of the instrument, so to speak, is acoustics, and the other foot electricity. The telephone philosophically considered is an instrument for the conversion of a sound-wave into electrical
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