"Catadioptric Fixed Light.—This apparatus, in which a central burner is used, consists of a dioptric cylindric refractor with zones of silvered mirror above and below similar in profile to Bordier Marcet's reflector. By the adoption of the refractor the whole of the wasteful divergence which occurs in Marcet's reflector is prevented. We have here a geometrically perfect combination, but it is not so physically, because metallic reflexion is used. This physical defect Fresnel obviated in his next design." —The Encyclopedia Britannica, 1910

Catadiopteric Light

"Catadioptric Fixed Light.—This apparatus, in which a central burner is used, consists of a dioptric…

"Catadioptric Fixed Light.—This apparatus, in which a central burner is used, consists of a dioptric cylindric refractor with zones of silvered mirror above and below similar in profile to Bordier Marcet's reflector. By the adoption of the refractor the whole of the wasteful divergence which occurs in Marcet's reflector is prevented. We have here a geometrically perfect combination, but it is not so physically, because metallic reflexion is used. This physical defect Fresnel obviated in his next design." —The Encyclopedia Britannica, 1910

Catadiopteric Light

"Catadioptric Fixed Light.—This apparatus, in which a central burner is used, consists of a dioptric…

"Catadioptric Holophote.—Part of the anterior hemisphere of rays is intercepted and at once parallelized by the lens L, whose principal focus (i.e., for parallel rays) is in the center of the flame, while the remainder is intercepted and made parallel by the paraboloid a, and thus the double agents in Fresnel's design are dispensed with. The rays of the posterior hemisphere are reflected by the spherical mirror b back again through the foxus, whence passing onwards one portion of them falls on the lens and the rest on the paraboloid, so as finally to emerge in union with and parallel to the front rays." —The Encyclopedia Britannica, 1910

Catadioptric Holophote

"Catadioptric Holophote.—Part of the anterior hemisphere of rays is intercepted and at once parallelized…

"Catadioptric Holophote.—Part of the anterior hemisphere of rays is intercepted and at once parallelized by the lens L, whose principal focus (i.e., for parallel rays) is in the center of the flame, while the remainder is intercepted and made parallel by the paraboloid a, and thus the double agents in Fresnel's design are dispensed with. The rays of the posterior hemisphere are reflected by the spherical mirror b back again through the foxus, whence passing onwards one portion of them falls on the lens and the rest on the paraboloid, so as finally to emerge in union with and parallel to the front rays." —The Encyclopedia Britannica, 1910

Catadioptric Holophote

"Catadioptric Holophote.—Part of the anterior hemisphere of rays is intercepted and at once parallelized…

"First Application of Total Reflexion to Fixed Lights. In this apparatus Fresnel substituted his totally reflecting prism p and lens R for Marcet's reflector, and thus distributed the whole light equally over the horizon by means of dioptric agents alone. This was the first application of total reflexion to lighthouse apparatus, and this beautiful instrument continues till now in universal use." —The Encyclopedia Britannica, 1910

Dioptric Light

"First Application of Total Reflexion to Fixed Lights. In this apparatus Fresnel substituted his totally…

"Fresnel's Revolving Light. —In this form of revolving light the central burner is surrounded by annular lenses L, and a compound arrangement of inclined trapezoidal lenses L' and plane silvered mirrors M. The inclined lenses fit closely to each other and form a pyramidal dome, and the light, intercepted by them, is sent upwards in inclined beams until, falling upon the plane mirrors M, it is sent outwards in horizontal parallelized beams. All these optical agents are made to revolve round the central lamp, and the sailor receives a full flash when the axis of one of the emerging beams passes his eye, and as soon as it passes him he is in darkness until the next beam comes round." —The Encyclopedia Britannica, 1910

Fresnels Revolving Light

"Fresnel's Revolving Light. —In this form of revolving light the central burner is surrounded…

"Fresnel's Revolving Light. —In this form of revolving light the central burner is surrounded by annular lenses L, and a compound arrangement of inclined trapezoidal lenses L' and plane silvered mirrors M. The inclined lenses fit closely to each other and form a pyramidal dome, and the light, intercepted by them, is sent upwards in inclined beams until, falling upon the plane mirrors M, it is sent outwards in horizontal parallelized beams. All these optical agents are made to revolve round the central lamp, and the sailor receives a full flash when the axis of one of the emerging beams passes his eye, and as soon as it passes him he is in darkness until the next beam comes round." —The Encyclopedia Britannica, 1910

Fresnels Revolving Light

"Fresnel's Revolving Light. —In this form of revolving light the central burner is surrounded…

"Fresnel's Revolving Light. —In this form of revolving light the central burner is surrounded by annular lenses L, and a compound arrangement of inclined trapezoidal lenses L' and plane silvered mirrors M. The inclined lenses fit closely to each other and form a pyramidal dome, and the light, intercepted by them, is sent upwards in inclined beams until, falling upon the plane mirrors M, it is sent outwards in horizontal parallelized beams. All these optical agents are made to revolve round the central lamp, and the sailor receives a full flash when the axis of one of the emerging beams passes his eye, and as soon as it passes him he is in darkness until the next beam comes round." —The Encyclopedia Britannica, 1910

Fresnels Revolving Light

"Fresnel's Revolving Light. —In this form of revolving light the central burner is surrounded…

"Fresnel's Revolving Light. —In this form of revolving light the central burner is surrounded by annular lenses L, and a compound arrangement of inclined trapezoidal lenses L' and plane silvered mirrors M. The inclined lenses fit closely to each other and form a pyramidal dome, and the light, intercepted by them, is sent upwards in inclined beams until, falling upon the plane mirrors M, it is sent outwards in horizontal parallelized beams. All these optical agents are made to revolve round the central lamp, and the sailor receives a full flash when the axis of one of the emerging beams passes his eye, and as soon as it passes him he is in darkness until the next beam comes round." —The Encyclopedia Britannica, 1910

Fresnels Revolving Light

"Fresnel's Revolving Light. —In this form of revolving light the central burner is surrounded…

"Holophotal Catadioptric Apparatus Revolving round a Central Flame." —The Encyclopedia Britannica, 1910

Holophotal Catadioptric

"Holophotal Catadioptric Apparatus Revolving round a Central Flame." —The Encyclopedia Britannica,…

"Holophotal Catadioptric Apparatus Revolving round a Central Flame.—If in place of Fresnel's compound arrangement of trapezoidal lenses and plane mirrors there are substituted mirrors R, R generated by the revolution of a parabolic profile round a horizontal axis, all the light will be at once sent out in parallel beams by them and the lenses L, and the apparatus is therefore geometrically perfect, but metallic instead of glass agents are still employed." —The Encyclopedia Britannica, 1910

Holophotal Catadioptric

"Holophotal Catadioptric Apparatus Revolving round a Central Flame.—If in place of Fresnel's compound…

"Fresnel next conceived the admirable improvement of employing the principle of "total" or internal reflexion by glass prisms. The ray Fi falling on a prismoidal ring, ABC, is refracted and bent in the direction iR, and falling on the side AC, at an angle of incidence greater than the critical, is totally relfected in the direction Re, and, impinging on the side BC at e, it undergoes a second refraction, and emerges horizontally. The highest ray FA after refraction by AB and reflexion by AC must (in order to avoid superfluous glass) pass along AB, and after a second refraction at B emerge horizontally. The lowest ray FB after refraction by AC and a second refraction by BC also emerge horizontally." —The Encyclopedia Britannica, 1910

Reflecting Prism

"Fresnel next conceived the admirable improvement of employing the principle of "total" or internal…

"In 1835 Mr. Stevenson, in a report to the Northern Lighthouse Board, proposed to add fixed reflecting prisms p below the lenses of Fresnel's revolving light, and he communicated this proposal to M. L. Fresnel, who approved of his suggestion, and assisted in carrying out the design in 1843. This combination added, however, but little to the power of the flash, and produced both a periodically flashing and constantly fixed light; but it must be remembered that the prism for fixed lights was the only kind of reflecting prism then known." —The Encyclopedia Britannica, 1910

Stevensons Revolving Light

"In 1835 Mr. Stevenson, in a report to the Northern Lighthouse Board, proposed to add fixed reflecting…