. Lighthouse construction and illumination; . mentioned, an ordinary paraboloid has about 14-| degrees ofdivergence, so that 25 reflectors were needed to light upcontinuously (though, as we have seen, not equally) thewhole horizon. If, again, the light was to be revolving, achandelier having 3 or 4 flat faces was employed (j), Figs. CATOrTEIC SYSTEM. 59 23 and 24), on each of wliich were fixed a certain number of. separate lamps and reflectors, o,having their axes parallel to eachother. When the frame wasmade to revolve, and one of thesides was turned towards thesailor, he would, when at somed
. Lighthouse construction and illumination; . mentioned, an ordinary paraboloid has about 14-| degrees ofdivergence, so that 25 reflectors were needed to light upcontinuously (though, as we have seen, not equally) thewhole horizon. If, again, the light was to be revolving, achandelier having 3 or 4 flat faces was employed (j), Figs. CATOrTEIC SYSTEM. 59 23 and 24), on each of wliich were fixed a certain number of. separate lamps and reflectors, o,having their axes parallel to eachother. When the frame wasmade to revolve, and one of thesides was turned towards thesailor, he would, when at somedistance from the shore, receivea flash at once from each of themirrors which were on that face ;but when the face was turnedaway from him, there would bea dark period until the next face came roimd. The power of theflashes in this kind of light is obviously proportional to the numberof reflectors on each side of the chandelier. If the light was to beflashing, the apparatus was made with eight sides. 9. Mr. B. Stevensons focusing arrangement, 1811.—(Accountof Bell Eock, p. 527.) It follows from the laws of reflec-tion that any angular displacement of the position of the Elevation Fig. 23. GO LIGHTHOUSE ILLUMINATION. flame in relation to the mirror, will produce a correspondingdeviation in the emergent rays. It is important, therefore,that after the lamp has been removed to be cleaned or re-wicked, means s
Size: 1928px × 1296px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1880, bookpublisherlondo, bookyear1881
