File:The fireside university of modern invention, discovery, industry and art for home circle study and entertainment (1902) (14798792703).jpg

Identifier: firesideuniversi01mcgo (find matches)
Title: The fireside university of modern invention, discovery, industry and art for home circle study and entertainment
Year: 1902 (1900s)
Authors: McGovern, John. (from old catalog)
Subjects: Science
Publisher: Chicago, Union pub. house
Contributing Library: The Library of Congress
Digitizing Sponsor: The Library of Congress

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teen Jetscould be turned on and off separately and variously lighted,and one or many electric lights could be used. At the Fair,each fountain used one eighty-ampere light, and the jets wereassembled for collective lighting. To what other astonishing use has tlie Electric Arc-Lightbeen put ? The Search-Light has been developed, and the largestexample the world has seen was exhibited by the GeneralElectric Company at the Worlds Fair of 1893. Lights andflames which project their rays to great distances have been thestudy of all lighthouse builders for centuries. Under the oper-ations of the early reflectors of light, although the flame weresheltered and backed by brilliant reflectors, yet as the flame wasa central point, and its rays went out in all directions, it followedthat in the cone directly in front of this central point the raysthat went past the outer lips of the reflector or holder divergedinto the sky and downward into the water or earth. The appli- 60 THE FIRESIDE UNIVERSITY.
Text Appearing After Image:
Fig. 25. THE SEARCHLIGHT AND ITS ELECTRIC ARC LIGHT. ELECTRICITY. 61 cation of the glass prism—that is a three-cornered bar of glass—to the work of reflection, while it corrected all the rays thatreached it, and sent them all out in parallel lines ahead of theflame, so that they would travel to a great distance in the direc-tion where they could be useful, still did not cover the case ofthe rays that went out past the rim of the reflector, on the wayupward, downward and sidewise. So Fresnel, who had appliedthe prism adopted the ingenious plan of nearly surrounding hisflame with prisms and mirrors, and letting out his rays onlywhen they had been bent around so many times that if theywent out at all they must go out straight, at an aperture justahead of the flame. Describe the great Search-Light ? It was shaped like a bass-drum, and hung by trunnions on afork, so that if it were really a drum, the drum-head would lookforward into the sky, or any direction desired. The apparatusweigh

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