Chapter IV: Part II

NOTES ON THE ILLUMINATION OF LIGHTHOUSES, WITH SHORT NOTICES OF
THEIR HISTORY, 181.

Early history, 181 -- Colossus of Rhodes, 182 -- Pharos of Alexandria,
183 -- Coruna Tower, 187 -- Lighthouse at the mouth of the
Quadalquivir, 188 -- Ancient Phari in Britain, 188 -- Tour de Corduan,
189 -- Eddystone, 189 -- Bell Rock, 192 -- Carlingford, 194 -- Iron
lighthouses, 194 -- Early modes of illumination, 195 -- Flame, 196 --
Drummond and Voltaic Lights, 199 -- Mr Gurney’s Lamp, 200 -- Argand
Burners, 200.

CATOPTRIC SYSTEM OF LIGHTS, 204.

Application of Paraboloidal Mirrors, 205 -- Reflection, 207 --
Paraboloidal Mirrors, 209 -- Divergence of Paraboloidal Mirrors, 212
-- Effect of Paraboloidal Mirrors, 217 -- Power of ditto, 218 --
Manufacture of reflectors, 218 -- Testing of mirrors, 219 -- Argand
Lamps used in reflectors, 220 -- Arrangements for raising or lowering
the Argand wick, 222 -- Flowing of the lamp, 223 -- Placing
the lamp in the focus, 226 -- Distinctions of Catoptric Lights, 227 --
Colour as a distinction for lights, 229 -- Arrangement of reflectors
on the frame, 230 -- Bordier Marcet’s reflectors, 232 -- Fanal
sidéral, 232 -- Fanal à double effet, 234 -- Fanal à double face, 236
-- Mr Barlow’s spherical mirrors, 237 -- Captain Smith’s mirrors in
the form of a parabolic spindle, 238.

DIOPTRIC SYSTEM OF LIGHTS, 239.

Early history of Lighthouse lenses, Condorcet, Buffon, Brewster,
Fresnel, 239 -- Refraction, 242 -- Lenses, 245 -- Spherical
aberration, 248 -- Fresnel’s formulæ for annular lenses, 249 --
Testing lenses, 255 -- Divergence of lenses, 256 -- Illuminating power
of lenses, 257 -- Arrangement of lenses in a Lighthouse, 258 --
Pyramidal lenses and mirrors, 259 -- Curved mirrors, 260 -- Cylindric
refractors of fixed Lights, 263 -- Application of crossed prisms to
cause flashes, 264 -- True cylindric form given to refractors, and
other improvements in their construction, 264 -- Catadioptric zones,
the mode of computing their elements, &c., 267 -- Testing of zones,
282 -- Framing of zones, 286 -- Mechanical lamp, 286 -- Height of
flame of mechanical lamp, 289 -- Position of flame in reference to
focus, 290 -- Working of the pumps, 291 -- Choice of focal point for
various parts of apparatus, 292 -- Choice of a focal point for zones,
292 -- Application of spherical mirrors to fixed Dioptric Lights, 293
-- Arrangement of Dioptric apparatus, 293 -- Arrangement of Dioptric
apparatus in Lightroom, 294 -- Power of Dioptric instruments, 298 --
Orders of French Lights, 298 -- Distinctions of Dioptric Lights, 299
-- Comparison of Dioptric and Catoptric apparatus for revolving
lights, 301 -- Comparison for fixed lights, 303 -- Summary of views as
to two systems for revolving lights, 306 -- Summary of views as to two
systems for fixed lights, 306 -- Advantages and disadvantages of both
systems under certain circumstances, 308 -- Distinctions of the
Dioptric Lights and the application of coloured media, 311 -- Captain
Basil Hall’s proposal for fixed lights, 313 -- Effects of rapid motion
on the power of lights, 315 -- Connection of experiments with
irradiation, 320.

VARIOUS GENERAL CONSIDERATIONS CONNECTED WITH LIGHTHOUSES, 320.

Masking Lights, 320 -- Double Lights, 322 -- Leading Lights, 323 --
Distribution of Lights on a coast, 325 -- Height of Lighthouse Tower,
and its relation to range of light, 328 -- Diagonal Lantern, 330 --
Glazing of Lantern, 331 -- Ventilation of Lanterns, 331 --
Arrangements and Management of a Lighthouse, 334 -- Cleansing of
apparatus, 335 -- Mode of measuring relative power of lights, 336 --
More accurate comparison of intensity of lights, 338 -- Floating
Lights, 346 -- Beacons and Buoys, 347.