Lessons in elementary physics / by Balfour Stewart.

  • Balfour Stewart
Date:
1895
Catalogue details

Licence: Public Domain Mark

Credit: Lessons in elementary physics / by Balfour Stewart. Source: Wellcome Collection.

    465/502 page 445
    ray of polarised light be made to traverse the glass in the line of the magnetic poles, the plane of polarisation will be twisted round to the right or left, according to the direction of the current. •Another peculiarity of the current is the stratification of the light which is given out when it traverses a gas or vapour of very small pressure. We have a series of zones alternately light and dark, which occasionally present a display of colours. These stratifications have been much studied by Gassiot and others, and are found to depend upon the nature of the substance in the tube. If, however, the vacuum be a per- fect one, Gassiot has found that the most powerful current is unable to pass through any considerable length of such a tube. Another effect produced by the passage of electricity is the production of ozone. This substance is a peculiar modifica- tion of oxygen, into which ordinary oxygen is converted by the passage of the current. It is a powerful bleaching agent, and has a very peculiar smell, which may be noticed when an electric machine is in action. Lesson LI.—Applications of Electricity. 438. Applications of Electricity.—The technical applica- tions of electricity are numerous and important, and are rapidly increasing. They may be classified as follows :—• 1. Electric Bells. 2. Telegraphy. .1. Telephony. 4. Electro-chemistry and Electro-metallurgy 5. Electric Lighting. 6. Electric Transmission of h'nergy. 7. Medical Uses. 8. Miscellaneous Uses. 439. Electric Bells.—The electric bell has two chief types—the single stroke and the vibrating hell. The single stroke bell is chiefly employed in mines and on railways. Its con- struction is seen in Fig. 139. A horse-shoe electro-magnet
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