A Rudimentary Treatise on the History, Construction and Illumination of LighthousesWeale, 1850 |
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Common terms and phrases
adopted angle of incidence apparatus applied Ardnamurchan Lighthouse arrangement arris Augustin Fresnel beam Bell Rock burner catadioptric catoptric centre of curvature co-ordinates colza oil concave cone construction convex course curve curved mirrors cylindric diameter dioptric lights direction ditto divergence Eddystone effect Engineer equal feet fixed lights flame flashes focal distance focus frame Fresnel frustum glass grinding height horizon illumination inches inclination instrument iron belt lantern length lens lenses Light-room Lightkeeper loss of light luminous means mètres millimètres mirror mode Northern Lighthouses observer obtained outer parabolic paraboloïdal parallel placed plane position practical prisms produced radius of curvature rays reflecting side reflecting surface reflectors refraction refractive index refractors revolving lights rings Robert Stevenson screw shadows shewn in Plate shews sin² Skerryvore spermaceti stone Tables tance tangent tion tower Triangle vertical axis whole wicks
Popular passages
Page 21 - cylinder 6 feet in diameter, and 30 inches high ; below it are six triangular rings of glass, ranged in a cylindrical form, and above a crown of thirteen rings of glass, forming by their union a hollow cage, composed of polished glass, 10 feet high and 6 feet in diameter ! I know
Page 129 - On pourrait même composer de plusieurs pièces ces loupes à échelons ; on y gagnerait plus de facilité dans la construction, une grande diminution de dépense, l'avantage de pouvoir leur donner plus d'étendue, et celui d'employer, suivant le besoin, un nombre de cercles plus ou moins grand, et d'obtenir ainsi d'un même instrument différents
Page 35 - paribus, on the lowness of its centre of gravity, the general notion of its form is that of a cone ; but that, as the forces to which its several horizontal sections are opposed decrease towards its top in a rapid ratio, the solid should be generated by the revolution of some curve line convex to the
Page 17 - the sea prevented any one going down to the rock, anxiously looking for supplies from the shore, and earnestly longing for a change of weather favourable to the recommencement of the works. For miles around nothing could be seen but white foaming breakers, and nothing heard but howling winds and lashing waves.