. Lighthouse construction and illumination; . V4 ?, ?y ^- SectioTV \l Fis. or horizontal axis, or may be made straight, as shown in elevation and section in These prisms were firstused at Lochindaal Light-house in Islay, and were madeby Messrs. Chance in accord-ance with Professor Swansformula, which will be foundin the Appendix, 10. Improved DioptricEoloplwte (Fig. 69). — Bycombining the back prisms, g a, h f, just described, with a semi-holophote a h c subtending. Fig. 69. MK. CHiVXCE S niPKOVEMENTS. 93 180°, and a portion of the dioptric spherical mirrov i j k,the whole rays are par
. Lighthouse construction and illumination; . V4 ?, ?y ^- SectioTV \l Fis. or horizontal axis, or may be made straight, as shown in elevation and section in These prisms were firstused at Lochindaal Light-house in Islay, and were madeby Messrs. Chance in accord-ance with Professor Swansformula, which will be foundin the Appendix, 10. Improved DioptricEoloplwte (Fig. 69). — Bycombining the back prisms, g a, h f, just described, with a semi-holophote a h c subtending. Fig. 69. MK. CHiVXCE S niPKOVEMENTS. 93 180°, and a portion of the dioptric spherical mirrov i j k,the whole rays are parallelised, and none of them are loston the burner, so that this apparatus, being all of glass, isboth geometrically and physically perfect. 31. Mr. J. T. Clianccs Improvements o/ 18 6 2 o?i StevensonsDioptric Sphcrieal Mirror.—Mr. Chance proposed (Fig. 70) togenerate the prisms of the spherical mirror round a verticalinstead of a horizontal axis, and also to arrange them insegments. He says (Min. Inst. Civ. Eng., vol. xxvi.) :— Theplan of generating the zones round the vertical axis wasintroduced by the author, who adopted it in the first com-plete catadioptric miiTor which was made, and was shownin the Exhibition of 1862 by the Commissioners of Northern Secibion^(wU/u> AB
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Keywords: ., bookcentury1800, bookdecade1880, bookpublisherlondo, bookyear1881
