. Lighthouse construction and illumination; . lve, and by their adoption twonew characteristics are added to the lighthouse system inde-pendently of the changes which might be produced by varyingthe speed of revolution of the prisms. Any existing fixedlight can easily therefore be altered in character and increasedin power by the simple addition of the condensing prisms. Itwin be readily seen that these lights are different in characterfrom the gi-oup flashing light of Dr. Hopkinson (Chapter IV.), in which the duration ofthe flashes is dependentsolely on the natural diver-gence due to the size
. Lighthouse construction and illumination; . lve, and by their adoption twonew characteristics are added to the lighthouse system inde-pendently of the changes which might be produced by varyingthe speed of revolution of the prisms. Any existing fixedlight can easily therefore be altered in character and increasedin power by the simple addition of the condensing prisms. Itwin be readily seen that these lights are different in characterfrom the gi-oup flashing light of Dr. Hopkinson (Chapter IV.), in which the duration ofthe flashes is dependentsolely on the natural diver-gence due to the size of theJlame. The drawings willbe readily understood with-out further explanation. 3. Condensing Intermit-tent Light with DifferentialBcfractors (Figs. 96, 97).^—A still more perfect form ofthe condensing inteiTaittentlight can be produced byavailing ourselves of the pro-perty of the differential lens (6, 4), which, in this case, takesthe form of the differential refractor (6, 5). This refractor ^ Min. Ins. of Civ. Eng., vol. Iviii CONDENSING INTERMITTENT LIGHTS. 123 having its centre of inner curvature at 0, Fig. 9 7, is substi-
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Keywords: ., bookcentury1800, bookdecade1880, bookpublisherlondo, bookyear1881
