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"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 by annular…

"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 by annular…

"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 by annular…

"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 by annular…

"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…

"Condensing Straight Prisms.—These, either by reflexion or refraction or both, cause a ray fr proceeding in any compass bearing from a fixed light apparatus AA to emerge in the direction, e.g., parallel to the corresponding ray fb, which proceeds in the same compass bearing from another part of the apparatus and so of any other ray fc which is bent parallel to the ray fa." —The Encyclopedia Britannica, 1910

Straight Prisms

"Condensing Straight Prisms.—These, either by reflexion or refraction or both, cause a ray fr…