A History of Physics in Its Elementary Branches; Including the Evolution of Physical Laboratories - Softcover

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1899 edition. Excerpt: ... THE NINETEENTH CENTURY In physical speculation the nineteenth century has overthrown the leading theories of the previous one hundred years, and has largely built anew on the older foundations laid during the seventeenth century. The emission theory of light gave way to the wave theory; the substance called "caloric " was set aside, and the fact was established that heat is due to molecular motion. The imponderables, assumed to exist by the advocates of the one-fluid and the two-fluid theories of electricity, were discarded in favour of the view that the phenomena of electricity and magnetism are to be explained, in some way, by the existence of pulsations and strains in the luminiferous ether. The effluvia of a magnet, capable of passing through glass without resistance, are of interest now only to the historian. The chemical substance phlogiston is no more. Of the half dozen imponderables which filled space during the eighteenth century, only one remains; and this one, apparently, has proved its right of existence. By it, the two great branches of light and electromagnetism are becoming practically one. Notwithstanding the enormous multiplication of observed phenomena, we are simplifying our interpretation of them by bringing into consistent and comprehensive order that which formerly seemed to be capricious and isolated. The very fact that intimate relations are perceived to exist between wide realms of physics, once thought to be perfectly distinct, seems to show that we are moving in the right direction. Radiant energy has developed into a subject of central importance. Stimulated and aided by the progress of its sister science chemistry, physics has made marvellous progress during the past one hundred years. At the beginning of the...

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